Latest Accepted Articles
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Abstract:
In order to balance the effect of flame retardant modification and mechanical modification of polycarbonate (PC), the flame retardant toughening agent with silicone-phosphorus-containing acrylate core-shell structure (ACR) prepared by seed emulsion polymerization was used to modify PC materials in this paper. When 4wt% ACR was added to PC, the limiting oxygen index (LOI) of 4% ACR/PC could reach 31.7%, the vertical combustion test reached UL-94 V-0 level, and the cone calorimeter test showed that the combustion heat release and smoke density were reduced by 43.2% and 20.5%, respectively. At the same time, the tensile strength of 4% ACR/PC was similar to that of pure PC, and the impact strength was increased by 9.4%. Thermogravimetric-infrared spectroscopy, Raman spectroscopy and post-combustion residue scanning electron microscopy analysis showed that the flame retardant effect was mainly due to the synergistic effect of phosphorus-silicon and the catalytic charring effect of phosphorus on PC. The impact cross-section scanning electron microscope images showed that the toughening effect is reflected in the fact that the ACR core layer silicone rubber can absorb impact energy and inhibit or terminate the generation of cracks.
In order to balance the effect of flame retardant modification and mechanical modification of polycarbonate (PC), the flame retardant toughening agent with silicone-phosphorus-containing acrylate core-shell structure (ACR) prepared by seed emulsion polymerization was used to modify PC materials in this paper. When 4wt% ACR was added to PC, the limiting oxygen index (LOI) of 4% ACR/PC could reach 31.7%, the vertical combustion test reached UL-94 V-0 level, and the cone calorimeter test showed that the combustion heat release and smoke density were reduced by 43.2% and 20.5%, respectively. At the same time, the tensile strength of 4% ACR/PC was similar to that of pure PC, and the impact strength was increased by 9.4%. Thermogravimetric-infrared spectroscopy, Raman spectroscopy and post-combustion residue scanning electron microscopy analysis showed that the flame retardant effect was mainly due to the synergistic effect of phosphorus-silicon and the catalytic charring effect of phosphorus on PC. The impact cross-section scanning electron microscope images showed that the toughening effect is reflected in the fact that the ACR core layer silicone rubber can absorb impact energy and inhibit or terminate the generation of cracks.
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Abstract:
The copper-plated steel fiber has excellent electrical conductivity, corrosion resistance and good mechanical properties. Compared with cement, the ceramic waste powder has low electrical resistivity, low carbon property, pozzolanic activity and internal curing. The synergy between copper-plated steel fiber and waste ceramic powder is expected to endow concrete with excellent and stable piezoresistivity and a wide stress/strain monitoring range. Therefore, low-carbon and smart copper-plated steel fiber reinforced ultra high performance concrete with ceramic waste was prepared. Then, the effects of copper-plated steel fibers content on the slump, electrical and piezoresistivity properties under different failure load types of the ultra high performance concrete with ceramic waste were analyzed, and the stress-electricity constitutive model was established. The results show that the spread of ultra high performance concrete with waste ceramic powder reduces with increasing copper-plated steel fiber content, but still has self-leveling compacting characteristics. The copper-plated steel fiber can significantly reduce the direct current and alternating current resistivity of the ultra high performance concrete with ceramic waste. The copper-plated steel fiber greatly improves the fractional change in resistivity and stress/strain sensitivity of the ultra high performance concrete with ceramic waste under ultimate flexural and compressive loads, and the piezoresistivity properties are better under the fracture failure condition. According to the stress-electricity constitutive model, both the fractional change in resistivity and stress/strain curves basically follow the cubic polynomial function relationship. Therefore, the copper-plated steel fiber reinforced ultra high performance concrete with ceramic waste can be used to monitor the stress/strain of concrete structures through testing resistivity.
The copper-plated steel fiber has excellent electrical conductivity, corrosion resistance and good mechanical properties. Compared with cement, the ceramic waste powder has low electrical resistivity, low carbon property, pozzolanic activity and internal curing. The synergy between copper-plated steel fiber and waste ceramic powder is expected to endow concrete with excellent and stable piezoresistivity and a wide stress/strain monitoring range. Therefore, low-carbon and smart copper-plated steel fiber reinforced ultra high performance concrete with ceramic waste was prepared. Then, the effects of copper-plated steel fibers content on the slump, electrical and piezoresistivity properties under different failure load types of the ultra high performance concrete with ceramic waste were analyzed, and the stress-electricity constitutive model was established. The results show that the spread of ultra high performance concrete with waste ceramic powder reduces with increasing copper-plated steel fiber content, but still has self-leveling compacting characteristics. The copper-plated steel fiber can significantly reduce the direct current and alternating current resistivity of the ultra high performance concrete with ceramic waste. The copper-plated steel fiber greatly improves the fractional change in resistivity and stress/strain sensitivity of the ultra high performance concrete with ceramic waste under ultimate flexural and compressive loads, and the piezoresistivity properties are better under the fracture failure condition. According to the stress-electricity constitutive model, both the fractional change in resistivity and stress/strain curves basically follow the cubic polynomial function relationship. Therefore, the copper-plated steel fiber reinforced ultra high performance concrete with ceramic waste can be used to monitor the stress/strain of concrete structures through testing resistivity.
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Abstract:
The air transport environment is a low pressure environment, which will have a significant impact on the occurrence and development of fire. In order to explore the pyrolysis characteristics of civil aircraft cabin panel materials under low environmental pressure, the pyrolysis characteristics of civil aircraft cabin panels were studied by the thermogravimetric analyzer. Selecting the glass fiber/phenolic resin sandwich panel structure panel material (A panel) and the glass fiber/phenolic resin laminated panel structure panel material (B panel) of a certain type of Airbus aircraft as the research objects, and studied in Guanghan (96 kPa) and Kangding (61 kPa) of Sichuan Province, respectively. The results show that the initial reaction temperature, termination temperature and maximum mass loss rate temperature of thermal decomposition of A and B panels move slightly to high temperature with the decrease of pressure and the increase of heating rate. At the heating rate of 15℃ / min, the upper and lower resin base panel of A panel consists of two pyrolysis stages, and there is only one pyrolysis stage of aramid honeycomb core, and the initial decomposition temperature of the resin base panel is about 182℃, which is obviously lower than that of the aramid honeycomb core, while the pyrolysis temperature of B panel is divided into two stages and the initial pyrolysis temperature is about 258℃. The pyrolysis kinetics was analyzed by the Kissinger method, the Flynn-Wall-Ozawa method, the Starink method and the KAS method. The apparent activation energy obtained by the Flynn-Wall-Ozawa method, the Starink method and the KAS method is similar, and the apparent activation energy of A and B panels under low pressure increase by approximately 10.4% and 28.5% relative to that under normal pressure., respectively. And the chemical reaction rates of A panel and B panel in 96 kPa environment are about 1.9 and 1.2 times higher than that in 61 kPa environment.
The air transport environment is a low pressure environment, which will have a significant impact on the occurrence and development of fire. In order to explore the pyrolysis characteristics of civil aircraft cabin panel materials under low environmental pressure, the pyrolysis characteristics of civil aircraft cabin panels were studied by the thermogravimetric analyzer. Selecting the glass fiber/phenolic resin sandwich panel structure panel material (A panel) and the glass fiber/phenolic resin laminated panel structure panel material (B panel) of a certain type of Airbus aircraft as the research objects, and studied in Guanghan (96 kPa) and Kangding (61 kPa) of Sichuan Province, respectively. The results show that the initial reaction temperature, termination temperature and maximum mass loss rate temperature of thermal decomposition of A and B panels move slightly to high temperature with the decrease of pressure and the increase of heating rate. At the heating rate of 15℃ / min, the upper and lower resin base panel of A panel consists of two pyrolysis stages, and there is only one pyrolysis stage of aramid honeycomb core, and the initial decomposition temperature of the resin base panel is about 182℃, which is obviously lower than that of the aramid honeycomb core, while the pyrolysis temperature of B panel is divided into two stages and the initial pyrolysis temperature is about 258℃. The pyrolysis kinetics was analyzed by the Kissinger method, the Flynn-Wall-Ozawa method, the Starink method and the KAS method. The apparent activation energy obtained by the Flynn-Wall-Ozawa method, the Starink method and the KAS method is similar, and the apparent activation energy of A and B panels under low pressure increase by approximately 10.4% and 28.5% relative to that under normal pressure., respectively. And the chemical reaction rates of A panel and B panel in 96 kPa environment are about 1.9 and 1.2 times higher than that in 61 kPa environment.
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Abstract:
Buckling of metallic cylindrical shells stiffened with helical composite stripes was investigated in the current study. A mathematical relationship between area ratio and thickness ratio of composite layer for externally pressurized metallic cylinder stiffened with helical composite stripes was proposed. An analytical formula for collapse load of such hybrid structure was derived. Numerical analysis and experimental verification were conducted. Furthermore, depth chart for full-scale hybrid cylinder was designed using analytical formulae. The results indicate that the maximum and minimum difference between numerical and theoretical results obtained using interpolation method are 5.2% and 0.9%, respectively. The theoretical, numerical and experimental data for samples agree favorably. The difference between theoretical and numerical results is 3.20%; The difference between theoretical and experimental results is 3.46%. Metallic cylindrical shells stiffened with multiple helical composite stripes is satisfy for a wide range of depths. Composite stripe stiffeners have vast potential for application in installed and reusable tubes.
Buckling of metallic cylindrical shells stiffened with helical composite stripes was investigated in the current study. A mathematical relationship between area ratio and thickness ratio of composite layer for externally pressurized metallic cylinder stiffened with helical composite stripes was proposed. An analytical formula for collapse load of such hybrid structure was derived. Numerical analysis and experimental verification were conducted. Furthermore, depth chart for full-scale hybrid cylinder was designed using analytical formulae. The results indicate that the maximum and minimum difference between numerical and theoretical results obtained using interpolation method are 5.2% and 0.9%, respectively. The theoretical, numerical and experimental data for samples agree favorably. The difference between theoretical and numerical results is 3.20%; The difference between theoretical and experimental results is 3.46%. Metallic cylindrical shells stiffened with multiple helical composite stripes is satisfy for a wide range of depths. Composite stripe stiffeners have vast potential for application in installed and reusable tubes.
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Abstract:
The preparation of prepreg tape required spreading the fiber tow to facilitate resin impregnation. Traction tension is the driving force for fiber bundle spreading, but current fiber tow-spreading models rarely involve the effect of traction tension. Aiming at the spreading process of fiber tow on mechanical rollers, combining force analysis, the input work, and the friction work along the axial and lateral directions can be computed. Then the fiber tow spreading model can be established by energy conservation law. Utilizing the pre-dispersion device with mechanical rollers which was built by laboratory, contrastively validate and analyze the spreading model. The results indicate that traction tension is an important reason for fiber tow spreading. And the numbers, radius, smoothness of mechanical rollers, and the wrap angle between the fiber tow and the roller all affect the fiber tow spreading. Compared to the Wilson spreading model, the energy-balance spreading model can better predict the spreading width of fiber tow, and it can be used to guide the pre-dispersion process of fiber tow.
The preparation of prepreg tape required spreading the fiber tow to facilitate resin impregnation. Traction tension is the driving force for fiber bundle spreading, but current fiber tow-spreading models rarely involve the effect of traction tension. Aiming at the spreading process of fiber tow on mechanical rollers, combining force analysis, the input work, and the friction work along the axial and lateral directions can be computed. Then the fiber tow spreading model can be established by energy conservation law. Utilizing the pre-dispersion device with mechanical rollers which was built by laboratory, contrastively validate and analyze the spreading model. The results indicate that traction tension is an important reason for fiber tow spreading. And the numbers, radius, smoothness of mechanical rollers, and the wrap angle between the fiber tow and the roller all affect the fiber tow spreading. Compared to the Wilson spreading model, the energy-balance spreading model can better predict the spreading width of fiber tow, and it can be used to guide the pre-dispersion process of fiber tow.
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Abstract:
The development of petrochemical, textile industry, steel and other industries has produced oily wastewater that has seriously damaged the eco-logical environment of humans and has aggravated the shortage of water resources. How to effectively separate oil-water mixture has become a current research hotspot under the global consensus of carbon peaking and carbon neutral. The special infiltrating nanocellulose-based aerogel has the characteristics of different infiltration to oil and water phases and has high efficiency of oil-water separation, so it has a broad application prospect in the field of oil-water separation. This article systematically summarized several infiltration models and basic action mechanisms, focusing on detailed analysis of nanocellulose-based aerogels in oil-water separation field and preparation process. Finally, the existing problems of special infiltrating nanocellulose-based aerogels are discussed with looking forward to their future development.
The development of petrochemical, textile industry, steel and other industries has produced oily wastewater that has seriously damaged the eco-logical environment of humans and has aggravated the shortage of water resources. How to effectively separate oil-water mixture has become a current research hotspot under the global consensus of carbon peaking and carbon neutral. The special infiltrating nanocellulose-based aerogel has the characteristics of different infiltration to oil and water phases and has high efficiency of oil-water separation, so it has a broad application prospect in the field of oil-water separation. This article systematically summarized several infiltration models and basic action mechanisms, focusing on detailed analysis of nanocellulose-based aerogels in oil-water separation field and preparation process. Finally, the existing problems of special infiltrating nanocellulose-based aerogels are discussed with looking forward to their future development.
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Abstract:
To study the interface bonding and sliding performance of corrugated steel plate concrete, considering the thickness of concrete cover, concrete strength, embedded length and stirrup ratio, the push out tests of 12 corrugated steel plate concrete specimens were completed, the failure modes of the specimens were analyzed and summarized, the composition of interfacial bonding force at different stages was analyzed based on the interfacial bonding slip mechanism, and the bonding performance of corrugated steel plate concrete was studied from the perspective of interface energy consumption. The results show that the concrete cracks at the trough develop from the outside to the inside. Under the action of interfacial compressive stress and stirrup tension, the crack of concrete at wave ridge is 45° with the extension line of wave ridge. The ultimate bond strength of the interface is between 0.99 and 1.86 MPa, and the residual bond strength is between 0.25 and 0.63 MPa. Increasing the embedded length can improve the elastic deformation energy of the interface and the ultimate bond strength of the interface. Finally, considering the four influencing factors, the bond stress-slip constitutive relation expression of the interface between corrugated steel plate -concrete was proposed and verified by finite element analysis. It is found that the simulated curve is in good agreement with the experimental curve, which shows that the proposed constitutive relation expression is reasonable and accurate, and can provide a reference for the finite element analysis of corrugated steel plate concrete structure.
To study the interface bonding and sliding performance of corrugated steel plate concrete, considering the thickness of concrete cover, concrete strength, embedded length and stirrup ratio, the push out tests of 12 corrugated steel plate concrete specimens were completed, the failure modes of the specimens were analyzed and summarized, the composition of interfacial bonding force at different stages was analyzed based on the interfacial bonding slip mechanism, and the bonding performance of corrugated steel plate concrete was studied from the perspective of interface energy consumption. The results show that the concrete cracks at the trough develop from the outside to the inside. Under the action of interfacial compressive stress and stirrup tension, the crack of concrete at wave ridge is 45° with the extension line of wave ridge. The ultimate bond strength of the interface is between 0.99 and 1.86 MPa, and the residual bond strength is between 0.25 and 0.63 MPa. Increasing the embedded length can improve the elastic deformation energy of the interface and the ultimate bond strength of the interface. Finally, considering the four influencing factors, the bond stress-slip constitutive relation expression of the interface between corrugated steel plate -concrete was proposed and verified by finite element analysis. It is found that the simulated curve is in good agreement with the experimental curve, which shows that the proposed constitutive relation expression is reasonable and accurate, and can provide a reference for the finite element analysis of corrugated steel plate concrete structure.
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Abstract:
Polyacrylonitrile (PAN) separator has excellent electrochemical performance, and has been widely concerned as a lithium ion battery separator material, but its mechanical strength and heat resistance are still insufficient problems. In this paper, polymeric thermoplastic polyurethane (TPU) composed of soft segment and hard segment was blended with PAN, and the prepared fiber film was modified by Co60γ to prepare a new type of lithium-ion battery separator. Through FTIR, it was found that the irradiation-modified PAN/TPU membrane had cyclization reaction among PAN molecules, and C=N-N bond crosslinking appeared between PAN and TPU molecules. The introduction of ring and crosslinking structures both improved the mechanical and heat resistance properties of the membrane. In addition, the membrane modified by 100 kGy had excellent electrochemical properties. It has a high electrolyte uptake (552%) and porosity (68.2%), an electrochemical stability window of 5.42 V, an interface impedance of 149.44 Ω, and an ionic conductivity of 1.68×10−3S /cm, all of which are better than the separator before irradiation. After cycling 100 at 1 C, the discharge capacity retention rate is 96.53%. It also shows excellent magnification performance in cyclic test.
Polyacrylonitrile (PAN) separator has excellent electrochemical performance, and has been widely concerned as a lithium ion battery separator material, but its mechanical strength and heat resistance are still insufficient problems. In this paper, polymeric thermoplastic polyurethane (TPU) composed of soft segment and hard segment was blended with PAN, and the prepared fiber film was modified by Co60γ to prepare a new type of lithium-ion battery separator. Through FTIR, it was found that the irradiation-modified PAN/TPU membrane had cyclization reaction among PAN molecules, and C=N-N bond crosslinking appeared between PAN and TPU molecules. The introduction of ring and crosslinking structures both improved the mechanical and heat resistance properties of the membrane. In addition, the membrane modified by 100 kGy had excellent electrochemical properties. It has a high electrolyte uptake (552%) and porosity (68.2%), an electrochemical stability window of 5.42 V, an interface impedance of 149.44 Ω, and an ionic conductivity of 1.68×10−3S /cm, all of which are better than the separator before irradiation. After cycling 100 at 1 C, the discharge capacity retention rate is 96.53%. It also shows excellent magnification performance in cyclic test.
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Abstract:
Wrinkles are easily produced during the forming process of complex composite structures, which affect the forming quality and load-bearing performance of the components. It is urgent to establish the quantitative mapping relationship between forming process parameters and prepreg wrinkles to support the low-defect forming manufacturing of components. In this paper, a global sensitivity analysis method for wrinkled defects in thermoplastic prepregs coupled with multiple process parameters is proposed. A finite element simulation method based on a non-orthogonal constitutive model is developed for the wide temperature domain deformation of thermoplastic prepreg. Combining the distance between the prepreg and the mold and the curvature of the out of plane bending of the prepreg improves the reliability of quantitative characterization of crease defects. Finally, a global sensitivity analysis method was established using the Sobol global sensitivity index based on variance, which can quantitatively calculate the impact of forming process parameters on wrinkle defects. It is verified through the typical Carbon Fiber/Polycarbonate (CF/PC) material single dome forming process. The results show that in the temperature range of 200~250℃ and the pressure range of 0.2~2.0 kPa, the influence of temperature on the wrinkling defects of CF/PC prepreg is greater than that of pressure, and there is a dual parameter coupling effect of temperature and pressure during the forming process.
Wrinkles are easily produced during the forming process of complex composite structures, which affect the forming quality and load-bearing performance of the components. It is urgent to establish the quantitative mapping relationship between forming process parameters and prepreg wrinkles to support the low-defect forming manufacturing of components. In this paper, a global sensitivity analysis method for wrinkled defects in thermoplastic prepregs coupled with multiple process parameters is proposed. A finite element simulation method based on a non-orthogonal constitutive model is developed for the wide temperature domain deformation of thermoplastic prepreg. Combining the distance between the prepreg and the mold and the curvature of the out of plane bending of the prepreg improves the reliability of quantitative characterization of crease defects. Finally, a global sensitivity analysis method was established using the Sobol global sensitivity index based on variance, which can quantitatively calculate the impact of forming process parameters on wrinkle defects. It is verified through the typical Carbon Fiber/Polycarbonate (CF/PC) material single dome forming process. The results show that in the temperature range of 200~250℃ and the pressure range of 0.2~2.0 kPa, the influence of temperature on the wrinkling defects of CF/PC prepreg is greater than that of pressure, and there is a dual parameter coupling effect of temperature and pressure during the forming process.
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Abstract:
To study the impact of nucleation effect and weak interface interaction of composite materials in the presence of high content of rigid particles on the non-isothermal crystallization behavior of poly(butylene succinate) (PBS), poly(butylene succinate)/microcrystalline cellulose(PBS/MCC) composites with MCC content of 5-25wt% were prepared by melt blending. The melting behavior and non-isothermal cooling crystallization kinetics of PBS were characterized by differential scanning calorimetry. The crystallization behavior and mechanism of PBS were analyzed using Avrami method modified by Jeziorny and Friedman’s isoconversional method modified by Vyazovkin. Kinetics studies reveal that MCC can act as an efficient nucleating agent to increase the crystallization temperature and crystallization rate of PBS, and promote the growth rate of PBS crystals without changing the nucleation mechanism and crystal growth of PBS, but the weak interface interaction between PBS and MCC will significantly inhibit the nucleation ability of PBS and reduce its crystallinity which reduced from 34.8% to 28.8%. The results of this study have certain guiding significance for studying the influence of weak interface interactions on the crystallization behavior of PBS in the presence of high content rigid particles.
To study the impact of nucleation effect and weak interface interaction of composite materials in the presence of high content of rigid particles on the non-isothermal crystallization behavior of poly(butylene succinate) (PBS), poly(butylene succinate)/microcrystalline cellulose(PBS/MCC) composites with MCC content of 5-25wt% were prepared by melt blending. The melting behavior and non-isothermal cooling crystallization kinetics of PBS were characterized by differential scanning calorimetry. The crystallization behavior and mechanism of PBS were analyzed using Avrami method modified by Jeziorny and Friedman’s isoconversional method modified by Vyazovkin. Kinetics studies reveal that MCC can act as an efficient nucleating agent to increase the crystallization temperature and crystallization rate of PBS, and promote the growth rate of PBS crystals without changing the nucleation mechanism and crystal growth of PBS, but the weak interface interaction between PBS and MCC will significantly inhibit the nucleation ability of PBS and reduce its crystallinity which reduced from 34.8% to 28.8%. The results of this study have certain guiding significance for studying the influence of weak interface interactions on the crystallization behavior of PBS in the presence of high content rigid particles.
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Abstract:
To investigate the forming process of bio-based epoxy resin system with acetal structure, the rheological properties and curing behavior of the epoxy resin system with acetal structure were studied by rotating rheometer and differential scanning calorimetry (DSC). The glue injecting temperature is determined to be about 40 ℃. The curing kinetic parameters were obtained by the piecewise model combining the autocatalytic model and the n-order model. The fitting curves from the piecewise model are in good agreement with the experimental curves, indicating that the model can accurately describe the curing reaction process of epoxy resin system with acetal structure at the heating rates of 2.5-20 K/min. The curing procedure of the resin system was determined by an extrapolation method. The tensile strength and bending strength of the epoxy resin with acetal structure are 79 MPa and 130 MPa, respectively. It is found that the interfacial shear strength (IFSS) and interlaminar shear strength (ILSS) of carbon fiber/acetal epoxy resin composites are similar to those of carbon fiber/commercial epoxy resin composites, indicating that the interfacial bonding property between acetal epoxy resin and carbon fiber is similar to that of commercial epoxy resin. In addition, the tensile and flexural properties of the two composites are similar, indicating that the degradable acetal epoxy resin may replace the commercial epoxy resin and give potential competitive advantages over the applications. In addition, the carbon fiber/acetal epoxy resin composites have good degradation performance, and the single fiber tensile strength of the recovered carbon fiber is comparable to that of the original carbon fiber, indicating that high-quality carbon fiber can be effectively recycled.
To investigate the forming process of bio-based epoxy resin system with acetal structure, the rheological properties and curing behavior of the epoxy resin system with acetal structure were studied by rotating rheometer and differential scanning calorimetry (DSC). The glue injecting temperature is determined to be about 40 ℃. The curing kinetic parameters were obtained by the piecewise model combining the autocatalytic model and the n-order model. The fitting curves from the piecewise model are in good agreement with the experimental curves, indicating that the model can accurately describe the curing reaction process of epoxy resin system with acetal structure at the heating rates of 2.5-20 K/min. The curing procedure of the resin system was determined by an extrapolation method. The tensile strength and bending strength of the epoxy resin with acetal structure are 79 MPa and 130 MPa, respectively. It is found that the interfacial shear strength (IFSS) and interlaminar shear strength (ILSS) of carbon fiber/acetal epoxy resin composites are similar to those of carbon fiber/commercial epoxy resin composites, indicating that the interfacial bonding property between acetal epoxy resin and carbon fiber is similar to that of commercial epoxy resin. In addition, the tensile and flexural properties of the two composites are similar, indicating that the degradable acetal epoxy resin may replace the commercial epoxy resin and give potential competitive advantages over the applications. In addition, the carbon fiber/acetal epoxy resin composites have good degradation performance, and the single fiber tensile strength of the recovered carbon fiber is comparable to that of the original carbon fiber, indicating that high-quality carbon fiber can be effectively recycled.
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Abstract:
A high-sensitivity air-coupled ultrasonic transducer with an acoustic matching layer based on epoxy resin/hollow glass microsphere (HGM) is investigated. In order to improve the dispersion of low-density HGM in high-density epoxy resin matrix, poly(methyl vinyl ether-alt-maleic anhydride) (PVMMA) was grafted onto the HGM surface (PVMMA-g-HGM). The morphology and surface chemical characteristics of modified HGM and HGM/epoxy resin composite were analyzed. An air-coupled ultrasonic transducer was fabricated with the improved matching layer, which achieved a peak-to-peak voltage of 4.88 V. In addition, the gas ultrasonic flowmeter equipped with the improved ultrasonic transducer had better flow field adaptability, and the relative error was less than 1.0%. The purpose of this study is to propose a new technology to improve the performance of ultrasonic transducer in gas ultrasonic flowmeter.
A high-sensitivity air-coupled ultrasonic transducer with an acoustic matching layer based on epoxy resin/hollow glass microsphere (HGM) is investigated. In order to improve the dispersion of low-density HGM in high-density epoxy resin matrix, poly(methyl vinyl ether-alt-maleic anhydride) (PVMMA) was grafted onto the HGM surface (PVMMA-g-HGM). The morphology and surface chemical characteristics of modified HGM and HGM/epoxy resin composite were analyzed. An air-coupled ultrasonic transducer was fabricated with the improved matching layer, which achieved a peak-to-peak voltage of 4.88 V. In addition, the gas ultrasonic flowmeter equipped with the improved ultrasonic transducer had better flow field adaptability, and the relative error was less than 1.0%. The purpose of this study is to propose a new technology to improve the performance of ultrasonic transducer in gas ultrasonic flowmeter.
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Abstract:
Fiber reinforced polymer (FRP) composite has great potential in infrastructure construction due to the advantages of light weight and high strength, corrosion resistance and high economic benefit. However, the performance of FRP composite will decrease by more than 50% after long-term service in complex environment, which limits its application in engineering. In the paper, the enhancement methods of different FRP composites components are reviewed. The evolution law of FRP composites on long-term properties under thermal oxygen, ultraviolet and corrosive media environment were revealed, and the deterioration mechanism of FRP composites in complex environment was elucidated by the analysis of chemical structure and microstructure. In addition, the long-term performance prediction model of FRP composites under complex environments is summarized, which can provide theoretical basis for ensuring the long-term performance of FRP composites in complex environment and promote its application in practical engineering.
Fiber reinforced polymer (FRP) composite has great potential in infrastructure construction due to the advantages of light weight and high strength, corrosion resistance and high economic benefit. However, the performance of FRP composite will decrease by more than 50% after long-term service in complex environment, which limits its application in engineering. In the paper, the enhancement methods of different FRP composites components are reviewed. The evolution law of FRP composites on long-term properties under thermal oxygen, ultraviolet and corrosive media environment were revealed, and the deterioration mechanism of FRP composites in complex environment was elucidated by the analysis of chemical structure and microstructure. In addition, the long-term performance prediction model of FRP composites under complex environments is summarized, which can provide theoretical basis for ensuring the long-term performance of FRP composites in complex environment and promote its application in practical engineering.
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With the increase in the demand for carbon fiber (CF), CF scraps have increased dramatically, resulting in a great waste of resources. To solve this problem, CNTx/SCF-TPU electrothermal nanocomposite materials were prepared by using short carbon fiber (SCF) felt fabricated by CF scraps through filtration method, with carbon nanotubes (CNT) as secondary filler and TPU as the matrix, via vacuum hot pressing process. The composite materials were tested and analyzed using SEM, TGA, DSC, etc., and the optimal concentration of CNT was investigated. The mechanical and electrothermal properties of CNTx/SCF-TPU composite materials were studied. The results show that CNT1.0/SCF-TPU composite material exhibit highest electrical conductivity of 417.8 S/m using 60 g/m2 SCF felt and a CNT concentration of 1.0 g/mL, representing a 34.8% improvement compared to the SCF-TPU without CNT. CNT1.0/SCF-TPU composite exhibit significantly improved electrothermal performance at a low voltage of 3.5 V, reaching a temperature of approximately 165℃ in 240 s. It also represents advantages such as precise and stable electrothermal temperature control.
With the increase in the demand for carbon fiber (CF), CF scraps have increased dramatically, resulting in a great waste of resources. To solve this problem, CNTx/SCF-TPU electrothermal nanocomposite materials were prepared by using short carbon fiber (SCF) felt fabricated by CF scraps through filtration method, with carbon nanotubes (CNT) as secondary filler and TPU as the matrix, via vacuum hot pressing process. The composite materials were tested and analyzed using SEM, TGA, DSC, etc., and the optimal concentration of CNT was investigated. The mechanical and electrothermal properties of CNTx/SCF-TPU composite materials were studied. The results show that CNT1.0/SCF-TPU composite material exhibit highest electrical conductivity of 417.8 S/m using 60 g/m2 SCF felt and a CNT concentration of 1.0 g/mL, representing a 34.8% improvement compared to the SCF-TPU without CNT. CNT1.0/SCF-TPU composite exhibit significantly improved electrothermal performance at a low voltage of 3.5 V, reaching a temperature of approximately 165℃ in 240 s. It also represents advantages such as precise and stable electrothermal temperature control.
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There is an urgent need to explore new treatment technologies and biomass materials to mitigate the growing ecological problems of global warming, sea level rise and climate degradation caused by excessive carbon dioxide emissions. This paper reviews the research progress of biomass chitosan in CO2 separation, capture and resource utilization; details the mechanism of CO2 separation by chitosan membranes and methods to improve membrane separation performance; summarizes the methods to enhance the CO2 capture performance of chitosan-based activated carbon; and summarizes the research on the conversion of CO2 into value-added products such as carbonate, methane and olefin by chitosan-based catalysts. Finally, the future development trend of biomass chitosan in the process of helping to achieve the “double carbon” strategic goal is presented.
There is an urgent need to explore new treatment technologies and biomass materials to mitigate the growing ecological problems of global warming, sea level rise and climate degradation caused by excessive carbon dioxide emissions. This paper reviews the research progress of biomass chitosan in CO2 separation, capture and resource utilization; details the mechanism of CO2 separation by chitosan membranes and methods to improve membrane separation performance; summarizes the methods to enhance the CO2 capture performance of chitosan-based activated carbon; and summarizes the research on the conversion of CO2 into value-added products such as carbonate, methane and olefin by chitosan-based catalysts. Finally, the future development trend of biomass chitosan in the process of helping to achieve the “double carbon” strategic goal is presented.
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Abstract:
Due to the high porosity and high absorption characteristics, aerogel has been a promising candidate material in the field of oily wastewater treatment. However, the reported aerogels were still suffering from insufficient mechanical strength, complicated fabrication process and high preparation cost, which limited the application of aerogels in the field of oil-water separation. Bentonite (BT) has the characteristics of low price, abundant source and excellent mechanical properties, which can effectively improve the mechanical properties of aerogels. in this paper, hydrophobic nanocellulose-chitosan/exfoliated bentonite aerogels (CNC/BTex) were synthesized by introducing exfoliated bentonite (BTex) onto a cross-linked network of carboxycellulose nanofibres (CNF-C) and chitosan (CS) by a simple freeze-drying and ambient temperature impregnation method. The prepared CNC/BTex aerogel exhibited excellent hydrophobic properties (water contact angle 133°), recovered deformation within 5 s after extrusion and showed good mechanical properties. The adsorption capacities for different oils (hexane, cyclohexane, dichloromethane, cooking oil and engine oil) ranged from 18.48 ~ 40.20 g·g−1. Using dichloromethane and cyclohexane as the main research objects, the oil adsorption performance remained stable (90% of the original adsorption capacity) after five cycles of use. In summary, the present work provides a reference for the preparation of low-cost and high-performance adsorbent materials for oil-water separation.
Due to the high porosity and high absorption characteristics, aerogel has been a promising candidate material in the field of oily wastewater treatment. However, the reported aerogels were still suffering from insufficient mechanical strength, complicated fabrication process and high preparation cost, which limited the application of aerogels in the field of oil-water separation. Bentonite (BT) has the characteristics of low price, abundant source and excellent mechanical properties, which can effectively improve the mechanical properties of aerogels. in this paper, hydrophobic nanocellulose-chitosan/exfoliated bentonite aerogels (CNC/BTex) were synthesized by introducing exfoliated bentonite (BTex) onto a cross-linked network of carboxycellulose nanofibres (CNF-C) and chitosan (CS) by a simple freeze-drying and ambient temperature impregnation method. The prepared CNC/BTex aerogel exhibited excellent hydrophobic properties (water contact angle 133°), recovered deformation within 5 s after extrusion and showed good mechanical properties. The adsorption capacities for different oils (hexane, cyclohexane, dichloromethane, cooking oil and engine oil) ranged from 18.48 ~ 40.20 g·g−1. Using dichloromethane and cyclohexane as the main research objects, the oil adsorption performance remained stable (90% of the original adsorption capacity) after five cycles of use. In summary, the present work provides a reference for the preparation of low-cost and high-performance adsorbent materials for oil-water separation.
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Due to the excellent mechanical properties, good durability, and low carbon and environmental friendly synthetic characteristics, geopolymers are considered as the most promising new cementitious materials to replace Portland cement. Unfortunately, there are some defects in geopolymers: on the one hand, coal-based solid wastes with low calcium content such as fly ash and coal gangue can only obtain high strength cured at a high temperature, while the strength of geopolymers prepared at room temperature is low; on the other hand, geopolymers have disadvantages such as high brittleness and low toughness, which seriously restricts the large-scale application of geopolymers. In this study, the effects of mechanochemical effect, compounding of silicon, aluminum and calcium substances, fiber and organic matter modifications on the mechanical properties of geopolymers were reviewed, and the mechanisms of strengthening and toughening were also summarized. Finally, some suggestions were made for related studies that needs to be carried out in depth in the future.
Due to the excellent mechanical properties, good durability, and low carbon and environmental friendly synthetic characteristics, geopolymers are considered as the most promising new cementitious materials to replace Portland cement. Unfortunately, there are some defects in geopolymers: on the one hand, coal-based solid wastes with low calcium content such as fly ash and coal gangue can only obtain high strength cured at a high temperature, while the strength of geopolymers prepared at room temperature is low; on the other hand, geopolymers have disadvantages such as high brittleness and low toughness, which seriously restricts the large-scale application of geopolymers. In this study, the effects of mechanochemical effect, compounding of silicon, aluminum and calcium substances, fiber and organic matter modifications on the mechanical properties of geopolymers were reviewed, and the mechanisms of strengthening and toughening were also summarized. Finally, some suggestions were made for related studies that needs to be carried out in depth in the future.
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Laser-induced graphene (LIG) is a novel graphene preparation technique, which is a process for the rapid transformation of three-dimensional network-structured graphene by irradiating carbon-containing substrates with high-energy beams. Compared with the conventional graphene preparation process, LIG has attracted broad research interest because of its rapid preparation, designable patterning, environmental friendliness, controlled microscopic morphology, and controlled composition. This review summarizes the synthesis process of LIG, including the composition of precursors, the selection of light sources, and the structural modulation of LIG. It also explores the in-situ and non-in-situ modification methods of LIG in recent years, describes the applications of LIG in the field of flexible electrodes and sensors, and provides an outlook on the development of LIG in the direction of integrated energy, sensing, and detection devices.
Laser-induced graphene (LIG) is a novel graphene preparation technique, which is a process for the rapid transformation of three-dimensional network-structured graphene by irradiating carbon-containing substrates with high-energy beams. Compared with the conventional graphene preparation process, LIG has attracted broad research interest because of its rapid preparation, designable patterning, environmental friendliness, controlled microscopic morphology, and controlled composition. This review summarizes the synthesis process of LIG, including the composition of precursors, the selection of light sources, and the structural modulation of LIG. It also explores the in-situ and non-in-situ modification methods of LIG in recent years, describes the applications of LIG in the field of flexible electrodes and sensors, and provides an outlook on the development of LIG in the direction of integrated energy, sensing, and detection devices.
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In order to realize the accurate analysis of mechanical properties of 3D printing fiber reinforced polymer (FRP) bridge components and promote the application of 3D printing FRP technology in bridge engineering, the key mechanical properties of 3D printing FRP were explored based on theoretical and experimental methods. Firstly, the hypothesis of printing filament continuity was proposed based on the spatial geometry characteristics of the meso-structure of printing FRP. Based on the hypothesis and the in-plane stress rotation axis model, the Young’s modulus analysis and prediction model of 3D printing FRP under in-layer stress was constructed. At the same time, considering multiple failure modes of the material, a tensile strength prediction model under in-plane stress was established based on Tsai-Wu theory, and four different shear strength calculation modes were considered in this model. Secondly, considering the printing angle, filament width, and layer thickness, systematic testing and analysis of Young’s modulus and tensile strength were designed to verify the accuracy of the above two theoretical models. The results show that there is an obvious negative correlation between printing angle and the two kinds of key mechanical properties. When the printing angle increases from 0° to 90°, the decrease range of Young’s modulus is 65.48%-79.62%, and the decrease range of tensile strength is 50.99%-71.55%. The filament width has obvious influence on Young’s modulus and tensile strength. These two kinds of key mechanical properties with 0.6mm and 0.8mm filament width are similar to each other, and both are significantly bigger than those with 0.4mm filament width. The variation range of Young’s modulus is 20.18%-49.27%, and the variation range of tensile strength is 27.53%-54.55%. The macro-scale failure results show that there are two types of failure modes, namely, printing filament fracture and printing filament separation. Additionally, the mechanism of the two types of failure modes and the influence mechanism of printing parameters on the key mechanical properties are revealed from the meso-scale. In conclusion, these two models established in this study provide theoretical support for the quantitative evaluation of the key mechanical properties of 3D printing FRP bridge engineering components.
In order to realize the accurate analysis of mechanical properties of 3D printing fiber reinforced polymer (FRP) bridge components and promote the application of 3D printing FRP technology in bridge engineering, the key mechanical properties of 3D printing FRP were explored based on theoretical and experimental methods. Firstly, the hypothesis of printing filament continuity was proposed based on the spatial geometry characteristics of the meso-structure of printing FRP. Based on the hypothesis and the in-plane stress rotation axis model, the Young’s modulus analysis and prediction model of 3D printing FRP under in-layer stress was constructed. At the same time, considering multiple failure modes of the material, a tensile strength prediction model under in-plane stress was established based on Tsai-Wu theory, and four different shear strength calculation modes were considered in this model. Secondly, considering the printing angle, filament width, and layer thickness, systematic testing and analysis of Young’s modulus and tensile strength were designed to verify the accuracy of the above two theoretical models. The results show that there is an obvious negative correlation between printing angle and the two kinds of key mechanical properties. When the printing angle increases from 0° to 90°, the decrease range of Young’s modulus is 65.48%-79.62%, and the decrease range of tensile strength is 50.99%-71.55%. The filament width has obvious influence on Young’s modulus and tensile strength. These two kinds of key mechanical properties with 0.6mm and 0.8mm filament width are similar to each other, and both are significantly bigger than those with 0.4mm filament width. The variation range of Young’s modulus is 20.18%-49.27%, and the variation range of tensile strength is 27.53%-54.55%. The macro-scale failure results show that there are two types of failure modes, namely, printing filament fracture and printing filament separation. Additionally, the mechanism of the two types of failure modes and the influence mechanism of printing parameters on the key mechanical properties are revealed from the meso-scale. In conclusion, these two models established in this study provide theoretical support for the quantitative evaluation of the key mechanical properties of 3D printing FRP bridge engineering components.
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Abstract:
In order to improve the photogenerated electron/hole separation and recycling ability of single semiconductor powder material, based on the functionally synergistic effect, magnetic graphene aerogel (Fe3O4/BiOBr/graphene) modified by Fe3O4/BiOBr had been facilely prepared by one-step hydrothermal by dispersing Fe3O4/BiOBr composite in aqueous solution of graphene oxide containing lysine. The Fe3O4/BiOBr composite was synthesized in non-miscible solvent system under room-temperature, in which nano Fe3O4, firstly prepared by co-precipitation method using Fe3+/Fe2+ salt under the action of ammonia water with a certain concentration, was dispersed in n-octane containing CTAB for providing Br ion, interacting with an aqueous solution containing bismuth nitrate and citric acid adding drop by drop. The crystal structure、morphology and catalytic activity of the samples were characterized by XRD、Raman、XPS、SEM、TEM、and UV-Vis spectra. Fe3O4/BiOBr/graphene composite, in which spherical Fe3O4 with a size of 15-25 nm was evenly embedded in layered BiOBr flake, and they interact with graphene, overall, had showed a sphere-sheet-cavity structure. Fe3O4/BiOBr/graphene composite had favorable visible light absorption efficiency and Cr(Ⅵ) photocatalytic activity. The photocatalytic activity of Cr(Ⅵ) could achieve about 100% within 30 min, which was higher than that of single magnetic Fe3O4. This phenomenon maybe origin from the introduction of Fe3O4/BiOBr heterostructure and conductive graphene as well as their good interfacial interaction within them, effectively promoting the separation efficiency of photogenerated electrons and holes between Fe3O4/BiOBr/graphene composite.
In order to improve the photogenerated electron/hole separation and recycling ability of single semiconductor powder material, based on the functionally synergistic effect, magnetic graphene aerogel (Fe3O4/BiOBr/graphene) modified by Fe3O4/BiOBr had been facilely prepared by one-step hydrothermal by dispersing Fe3O4/BiOBr composite in aqueous solution of graphene oxide containing lysine. The Fe3O4/BiOBr composite was synthesized in non-miscible solvent system under room-temperature, in which nano Fe3O4, firstly prepared by co-precipitation method using Fe3+/Fe2+ salt under the action of ammonia water with a certain concentration, was dispersed in n-octane containing CTAB for providing Br ion, interacting with an aqueous solution containing bismuth nitrate and citric acid adding drop by drop. The crystal structure、morphology and catalytic activity of the samples were characterized by XRD、Raman、XPS、SEM、TEM、and UV-Vis spectra. Fe3O4/BiOBr/graphene composite, in which spherical Fe3O4 with a size of 15-25 nm was evenly embedded in layered BiOBr flake, and they interact with graphene, overall, had showed a sphere-sheet-cavity structure. Fe3O4/BiOBr/graphene composite had favorable visible light absorption efficiency and Cr(Ⅵ) photocatalytic activity. The photocatalytic activity of Cr(Ⅵ) could achieve about 100% within 30 min, which was higher than that of single magnetic Fe3O4. This phenomenon maybe origin from the introduction of Fe3O4/BiOBr heterostructure and conductive graphene as well as their good interfacial interaction within them, effectively promoting the separation efficiency of photogenerated electrons and holes between Fe3O4/BiOBr/graphene composite.
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As a low- and zero-carbon energy source, hydrogen energy is an important part of the future national energy system. The development of an efficient and inexpensive alkaline hydrogen evolution reaction (HER) electrocatalyst is of great significance for the large-scale preparation and utilization of hydrogen energy. In this paper, the MoO3/Ni-NiO/Nb2CTx was prepared by one-step co-electrodeposition method to loaded MoO3/Ni-NiO heterostructure on two-dimensional Nb2CTx MXene, and the obtained MoO3/Ni-NiO/Nb2CTx exhibited excellent HER performance. The XRD, SEM and TEM were conducted to analyze the surface morphology and structure of the catalysts. Results demonstrate that the MoO3/Ni-NiO heterostructure were successfully electrodeposited on the surface of Nb2CTx MXene nanosheets. The results of HER tests in 1.0 mol/L KOH electrolyte show that the MoO3/Ni-NiO/Nb2CTx at current densities of 10 and 100 mA·cm−2 has small overpotentials of 8 and 201 mV, respectively, and Tafel plot is 51 mV·dec−1. The MoO3/Ni-NiO/Nb2CTx also has good catalytic stability with almost no detectable activity decay after 20 h HER test at current densities of 10 and 50 mA·cm−2, respectively. Besides, the operando electrochemical impedance spectroscopy measurements were used to estimate electrocatalytic HER kinetics of different catalysts at overpotential from 0 to 220 mV (vs. RHE), which indicating the MoO3/Ni-NiO/Nb2CTx can effectively promote hydrolysis dissociation process and active hydrogen adsorption process, thus improving HER activity.
As a low- and zero-carbon energy source, hydrogen energy is an important part of the future national energy system. The development of an efficient and inexpensive alkaline hydrogen evolution reaction (HER) electrocatalyst is of great significance for the large-scale preparation and utilization of hydrogen energy. In this paper, the MoO3/Ni-NiO/Nb2CTx was prepared by one-step co-electrodeposition method to loaded MoO3/Ni-NiO heterostructure on two-dimensional Nb2CTx MXene, and the obtained MoO3/Ni-NiO/Nb2CTx exhibited excellent HER performance. The XRD, SEM and TEM were conducted to analyze the surface morphology and structure of the catalysts. Results demonstrate that the MoO3/Ni-NiO heterostructure were successfully electrodeposited on the surface of Nb2CTx MXene nanosheets. The results of HER tests in 1.0 mol/L KOH electrolyte show that the MoO3/Ni-NiO/Nb2CTx at current densities of 10 and 100 mA·cm−2 has small overpotentials of 8 and 201 mV, respectively, and Tafel plot is 51 mV·dec−1. The MoO3/Ni-NiO/Nb2CTx also has good catalytic stability with almost no detectable activity decay after 20 h HER test at current densities of 10 and 50 mA·cm−2, respectively. Besides, the operando electrochemical impedance spectroscopy measurements were used to estimate electrocatalytic HER kinetics of different catalysts at overpotential from 0 to 220 mV (vs. RHE), which indicating the MoO3/Ni-NiO/Nb2CTx can effectively promote hydrolysis dissociation process and active hydrogen adsorption process, thus improving HER activity.
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Abstract:
Fenton reaction is an oxidation process that generates hydroxyl radicals (·OH) through the decomposition of hydrogen peroxide (H2O2) catalyzed by ferrous ions (Fe2+), which is widely used for the degradation of organic pollutants in wastewater because of its fast ·OH generation rate and simple operation. In this study, the g-C3N4/CQDs/Fe2+ photo-Fenton system was constructed by adding Fe2+ activated composite photocatalyst g-C3N4/CQDs to generate H2O2 in situ, which avoids the potential risk of H2O2 during storage and transportation, and broadens the pH range of the reaction. The system showed excellent activity for the degradation of oxytetracycline (OTC) with a high degradation efficiency of 97% at a g-C3N4/CQDs dosing of 120 mg, an initial OTC concentration of 20 mg·L−1, an Fe2+ dosing of 0.36 mmol·L−1, and an initial pH of 7 for OTC solution. The excellent activity of g-C3N4/CQDs/Fe2+ photo-Fenton degradation of OTC based on experiments such as radical capture, determination of changes in the generation of ·OH and comparison with the H2O2 generation process was demonstrated to be mainly derived from the ·OH active species generated by Fe2+ activation of in situ H2O2 production. Further, the intermediate products of OTC degradation were detected and analyzed by mass spectrometry, and the possible degradation paths of OTC were inferred. In addition, by measuring the optical density (OD600) value to obtain the growth curve of bacteria, the results showed that the toxicity of the reaction solution gradually decreased with the degradation of OTC by g-C3N4/CQDs/Fe2+. Finally, compared with the conventional Fenton system with the addition of H2O2 to degrade OTC, the results showed that the photo-Fenton system can basically achieve the effect of conventional Fenton , and it is not limited by the pH range which provides a new idea for improving the application of Fenton reaction in actual wastewater treatment.
Fenton reaction is an oxidation process that generates hydroxyl radicals (·OH) through the decomposition of hydrogen peroxide (H2O2) catalyzed by ferrous ions (Fe2+), which is widely used for the degradation of organic pollutants in wastewater because of its fast ·OH generation rate and simple operation. In this study, the g-C3N4/CQDs/Fe2+ photo-Fenton system was constructed by adding Fe2+ activated composite photocatalyst g-C3N4/CQDs to generate H2O2 in situ, which avoids the potential risk of H2O2 during storage and transportation, and broadens the pH range of the reaction. The system showed excellent activity for the degradation of oxytetracycline (OTC) with a high degradation efficiency of 97% at a g-C3N4/CQDs dosing of 120 mg, an initial OTC concentration of 20 mg·L−1, an Fe2+ dosing of 0.36 mmol·L−1, and an initial pH of 7 for OTC solution. The excellent activity of g-C3N4/CQDs/Fe2+ photo-Fenton degradation of OTC based on experiments such as radical capture, determination of changes in the generation of ·OH and comparison with the H2O2 generation process was demonstrated to be mainly derived from the ·OH active species generated by Fe2+ activation of in situ H2O2 production. Further, the intermediate products of OTC degradation were detected and analyzed by mass spectrometry, and the possible degradation paths of OTC were inferred. In addition, by measuring the optical density (OD600) value to obtain the growth curve of bacteria, the results showed that the toxicity of the reaction solution gradually decreased with the degradation of OTC by g-C3N4/CQDs/Fe2+. Finally, compared with the conventional Fenton system with the addition of H2O2 to degrade OTC, the results showed that the photo-Fenton system can basically achieve the effect of conventional Fenton , and it is not limited by the pH range which provides a new idea for improving the application of Fenton reaction in actual wastewater treatment.
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The increasing use of electrical equipment at high frequencies poses greater demands on the corona aging resistance and dielectric properties of insulating materials. Therefore, it is crucial to enhance the insulation properties of insulating materials for the development of high-frequency power systems. In this study, we utilized 2,2'-Bis(trifluoromethyl)-4,4'-diaminodiphenyl ether (6FODA), 4,4'-diaminodiphenyl ether (ODA), and 1,2,4,5-Benzenetetracarboxylic anhydride (PMDA) as reactive monomers to design and synthesize block copolymerized fluoro-polyimide (FPI) trilayer films. The focus was primarily on assessing the corona-resistant and dielectric properties of these materials. Results revealed that the corona-resistant life of the block copolymerized FPI trilayer films, with varying amounts of fluorine, was higher when compared to the Pure PI trilayer films. Furthermore, the corona-resistant life of the films increased with an increase in fluorine content. When the molar ratio of ODA to 6FODA is 1∶9, the corona resistance life of the three-layer film can reach up to 4.0 h at room temperature (20℃) and 80 kV/mm, which is 2.86 times higher than that of the Pure PI three-layer film (1.4 h). Moreover, with the increase of fluorine content, the dielectric constant of FPI three-layer film shows a trend of decreasing and then increasing, and the dielectric constant of the three-layer film when the molar ratio of ODA and 6FODA is 1∶1 can be reduced to as low as 2.26 at 1 MHz, and the dielectric loss and conductivity show a trend of increasing and then decreasing. The dielectric strength decreased with the increase of fluorine content, but they were all higher than that of the Pure PI trilayer film, and the dielectric strength of the trilayer film was as high as 434 kV/mm when the molar ratio of ODA to 6FODA was 9∶1.
The increasing use of electrical equipment at high frequencies poses greater demands on the corona aging resistance and dielectric properties of insulating materials. Therefore, it is crucial to enhance the insulation properties of insulating materials for the development of high-frequency power systems. In this study, we utilized 2,2'-Bis(trifluoromethyl)-4,4'-diaminodiphenyl ether (6FODA), 4,4'-diaminodiphenyl ether (ODA), and 1,2,4,5-Benzenetetracarboxylic anhydride (PMDA) as reactive monomers to design and synthesize block copolymerized fluoro-polyimide (FPI) trilayer films. The focus was primarily on assessing the corona-resistant and dielectric properties of these materials. Results revealed that the corona-resistant life of the block copolymerized FPI trilayer films, with varying amounts of fluorine, was higher when compared to the Pure PI trilayer films. Furthermore, the corona-resistant life of the films increased with an increase in fluorine content. When the molar ratio of ODA to 6FODA is 1∶9, the corona resistance life of the three-layer film can reach up to 4.0 h at room temperature (20℃) and 80 kV/mm, which is 2.86 times higher than that of the Pure PI three-layer film (1.4 h). Moreover, with the increase of fluorine content, the dielectric constant of FPI three-layer film shows a trend of decreasing and then increasing, and the dielectric constant of the three-layer film when the molar ratio of ODA and 6FODA is 1∶1 can be reduced to as low as 2.26 at 1 MHz, and the dielectric loss and conductivity show a trend of increasing and then decreasing. The dielectric strength decreased with the increase of fluorine content, but they were all higher than that of the Pure PI trilayer film, and the dielectric strength of the trilayer film was as high as 434 kV/mm when the molar ratio of ODA to 6FODA was 9∶1.
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In order to solve the problem that the shrinkage compensation effect of expansive agent was not significant at a low water to binder ratio, this study used super-absorbent polymer (SAP) as the internal curing agent to study the influence of HCSA, SAP, HCSA and SAP together on the volume deformation (autogenous shrinkage, drying shrinkage, deformation in water) of cement paste with a low water to binder ratio (0.25), and the synergistic effect of HCSA expansive agent and SAP was discussed. The results show that both HCSA expansive agent and SAP reduce the autogenous shrinkage and dry shrinkage of cement paste, and increase the expansion deformation when immersed in water. The expansive effects of HCSA under sealed and immersed condition are more significant than that under drying condition. HCSA and SAP have synergistic effect, i.e. the pre-absorbed water by SAP could promote the effectiveness of HCSA. Under sealed condition, the synergistic effect mainly occur before about 1 day, and then it still work slowly. When immersed in water, HCSA and SAP also show synergistic effect. But under drying condition, the synergistic effect of HCSA and SAP mainly takes effect after 7 days. SAP could not promote the effectiveness of HCSA at early ages, and the addition of HCSA and SAP together increases the drying shrinkage of cement paste with low water to binder ratio.
In order to solve the problem that the shrinkage compensation effect of expansive agent was not significant at a low water to binder ratio, this study used super-absorbent polymer (SAP) as the internal curing agent to study the influence of HCSA, SAP, HCSA and SAP together on the volume deformation (autogenous shrinkage, drying shrinkage, deformation in water) of cement paste with a low water to binder ratio (0.25), and the synergistic effect of HCSA expansive agent and SAP was discussed. The results show that both HCSA expansive agent and SAP reduce the autogenous shrinkage and dry shrinkage of cement paste, and increase the expansion deformation when immersed in water. The expansive effects of HCSA under sealed and immersed condition are more significant than that under drying condition. HCSA and SAP have synergistic effect, i.e. the pre-absorbed water by SAP could promote the effectiveness of HCSA. Under sealed condition, the synergistic effect mainly occur before about 1 day, and then it still work slowly. When immersed in water, HCSA and SAP also show synergistic effect. But under drying condition, the synergistic effect of HCSA and SAP mainly takes effect after 7 days. SAP could not promote the effectiveness of HCSA at early ages, and the addition of HCSA and SAP together increases the drying shrinkage of cement paste with low water to binder ratio.
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Abstract:
To solve the problem of poor interfacial compatibility of wheat straw fiber/poly (lactic acid) (WF/PLA) composites, wheat straw was treated with hydrogen peroxide (H2O2) as oxidant, and the effects of pH, treatment temperature, and mass fraction of H2O2 on the mechanical properties of oxidized wheat straw fiber/poly (lactic acid) (OWF/PLA) composites were investigated by response surface method. The results showed that there was a significant interaction between pH and treatment temperature, pH and mass fraction, and treatment temperature and mass fraction. The optimal process parameters predicted by the regression equation are as follows: the pH of H2O2 is 8.9, the treatment temperature of H2O2 is 52.3°C, and the mass fraction of H2O2 is 2%. Under these conditions, the tensile strength and elongation at break of the composite material are 38.89 MPa and 7.85% respectively, which are 15.64% and 15.20% higher than before modification. The FT-IR results indicate that some hydroxyl groups in oxidized wheat straw fiber (OWF) are oxidized to carboxyl groups by H2O2. The SEM results indicate that OWF can better bind with PLA, and the composite materials prepared after melt blending have better interfacial compatibility. In addition, XRD and DSC results indicate that the addition of H2O2 promotes the heterogeneous nucleation process of the polymer, resulting in an increase in its crystallinity.
To solve the problem of poor interfacial compatibility of wheat straw fiber/poly (lactic acid) (WF/PLA) composites, wheat straw was treated with hydrogen peroxide (H2O2) as oxidant, and the effects of pH, treatment temperature, and mass fraction of H2O2 on the mechanical properties of oxidized wheat straw fiber/poly (lactic acid) (OWF/PLA) composites were investigated by response surface method. The results showed that there was a significant interaction between pH and treatment temperature, pH and mass fraction, and treatment temperature and mass fraction. The optimal process parameters predicted by the regression equation are as follows: the pH of H2O2 is 8.9, the treatment temperature of H2O2 is 52.3°C, and the mass fraction of H2O2 is 2%. Under these conditions, the tensile strength and elongation at break of the composite material are 38.89 MPa and 7.85% respectively, which are 15.64% and 15.20% higher than before modification. The FT-IR results indicate that some hydroxyl groups in oxidized wheat straw fiber (OWF) are oxidized to carboxyl groups by H2O2. The SEM results indicate that OWF can better bind with PLA, and the composite materials prepared after melt blending have better interfacial compatibility. In addition, XRD and DSC results indicate that the addition of H2O2 promotes the heterogeneous nucleation process of the polymer, resulting in an increase in its crystallinity.
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Abstract:
The influence of tension damage on residual compression strength and failure mode of open-hole composite laminates was investigated by tests and numerical analysis. In terms of test, firstly, two degrees of tension damage were introduced through the tension test of open-hole composite laminates, and the degree of tension damage was characterized and quantified by the thermal decal method. Then, the compression test of open-hole composite laminates with tension damage was carried out, the load-displacement curve was recorded. The damage evolution characteristics were observed by DIC, strain gauge, macro camera and other means. In terms of numerical analysis, a progressive damage failure model based on LaRC failure criteria was constructed to describe the intralaminar damage evolution, and cohesive elements method was established to describe the interlaminar damage of composite materials. Based on this model, the damage expansion law of open-hole composite laminates was explored. The experimental results show that the damage caused by tensile load is mainly matrix crack and delamination damage, and the delamination damage is greater between layers with small angle between loading direction and fiber direction. Tension damage will further aggravate the strain concentration around the hole, resulting in an asymmetric strain in the neighboring region of the hole, leading to the local buckling of the structure earlier, and then inducing the overall failure of the structure. Compared with the open-hole composite laminates without tension damage, the open-hole composite laminates with tension damage can reduce the compressive bearing capacity of the structure by 25.8%. The constructed numerical calculation model can accurately predict the delamination damage caused by the shear stress around the hole under tensile load and the evolution characteristics of the strain field in the compression stage, and can also reveal the difference in the compression damage expansion mode of the open-hole composite laminates with different degrees of tension damage, and explore the effects of fiber bending failure, matrix damage and interlayer delamination on the structural bearing capacity. The work in this paper can provide support for structural design and determination of residual strength of open-hole composite laminates under varying loading.
The influence of tension damage on residual compression strength and failure mode of open-hole composite laminates was investigated by tests and numerical analysis. In terms of test, firstly, two degrees of tension damage were introduced through the tension test of open-hole composite laminates, and the degree of tension damage was characterized and quantified by the thermal decal method. Then, the compression test of open-hole composite laminates with tension damage was carried out, the load-displacement curve was recorded. The damage evolution characteristics were observed by DIC, strain gauge, macro camera and other means. In terms of numerical analysis, a progressive damage failure model based on LaRC failure criteria was constructed to describe the intralaminar damage evolution, and cohesive elements method was established to describe the interlaminar damage of composite materials. Based on this model, the damage expansion law of open-hole composite laminates was explored. The experimental results show that the damage caused by tensile load is mainly matrix crack and delamination damage, and the delamination damage is greater between layers with small angle between loading direction and fiber direction. Tension damage will further aggravate the strain concentration around the hole, resulting in an asymmetric strain in the neighboring region of the hole, leading to the local buckling of the structure earlier, and then inducing the overall failure of the structure. Compared with the open-hole composite laminates without tension damage, the open-hole composite laminates with tension damage can reduce the compressive bearing capacity of the structure by 25.8%. The constructed numerical calculation model can accurately predict the delamination damage caused by the shear stress around the hole under tensile load and the evolution characteristics of the strain field in the compression stage, and can also reveal the difference in the compression damage expansion mode of the open-hole composite laminates with different degrees of tension damage, and explore the effects of fiber bending failure, matrix damage and interlayer delamination on the structural bearing capacity. The work in this paper can provide support for structural design and determination of residual strength of open-hole composite laminates under varying loading.
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Abstract:
Glue-free straw-based fiberboard is a biomass composite material, which is nontoxic, degradable, recyclable and renewable. As it does not consume petroleum resources, it is conducive to sustainable development, and can replace some wood used in fields such as flooring, building materials, furniture and interior decoration. However, there is a lack of research on its board making mechanism and process, resulting in a still low market share. In this paper, the self-bonding mechanism and application status of glue-free straw-based fiberboard are summarized. The technological progress of glueless straw-based fiberboard in recent years is introduced. The effects of fiber pretreatment, fiber size and process parameters (such as pressing time, pressure and temperature) on the performances of glueless straw-based fiberboard are systematically discussed. The future prospect of glueless straw-based fiberboard in optimal design, industrial production and promotion on a large scale are put forward.
Glue-free straw-based fiberboard is a biomass composite material, which is nontoxic, degradable, recyclable and renewable. As it does not consume petroleum resources, it is conducive to sustainable development, and can replace some wood used in fields such as flooring, building materials, furniture and interior decoration. However, there is a lack of research on its board making mechanism and process, resulting in a still low market share. In this paper, the self-bonding mechanism and application status of glue-free straw-based fiberboard are summarized. The technological progress of glueless straw-based fiberboard in recent years is introduced. The effects of fiber pretreatment, fiber size and process parameters (such as pressing time, pressure and temperature) on the performances of glueless straw-based fiberboard are systematically discussed. The future prospect of glueless straw-based fiberboard in optimal design, industrial production and promotion on a large scale are put forward.
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Abstract:
The long glass fiber reinforced polypropylene fluid-assisted injection molding pipes were molded by four processes: Gas-assisted injection molding process(GAIM), Gas-Projectile-assisted injection molding process(G-PAIM), Water-assisted injection molding process(WAIM) and Water-Projectile-assisted injection molding process(W-PAIM). The effects of each process on the wall thickness, glass fiber fracture length and glass fiber orientation of the pipes were compared and studied. The results show that the wall thickness of the W-PAIM process pipes is the thinnest and most uniform, and the wall thickness of the GAIM process pipes is the thickest and most non-uniform. G-PAIM had better wall thickness uniformity than WAIM pipes, but WAIM pipes has thinner wall thicknesses. The glass fiber fracture lengths are unevenly distributed among the four process methods. The average glass fiber fracture length is ranked as WAIM>GAIM>W-PAIM>G-PAIM. The introduction of the projectile intensifies the glass fiber fracture effect, so that the glass fiber fracture length is shorter. In G-PAIM, WAIM and W-PAIM processes, the orientation of glass fibers along the flow direction tends to increase gradually from near the mold wall layer to the middle layer to near the runner layer, and the orientation of GAIM glass fibers is disorganized. The degree of glass fiber orientation of each process pipes is ranked as W-PAIM>WAIM>G-PAIM>GAIM.
The long glass fiber reinforced polypropylene fluid-assisted injection molding pipes were molded by four processes: Gas-assisted injection molding process(GAIM), Gas-Projectile-assisted injection molding process(G-PAIM), Water-assisted injection molding process(WAIM) and Water-Projectile-assisted injection molding process(W-PAIM). The effects of each process on the wall thickness, glass fiber fracture length and glass fiber orientation of the pipes were compared and studied. The results show that the wall thickness of the W-PAIM process pipes is the thinnest and most uniform, and the wall thickness of the GAIM process pipes is the thickest and most non-uniform. G-PAIM had better wall thickness uniformity than WAIM pipes, but WAIM pipes has thinner wall thicknesses. The glass fiber fracture lengths are unevenly distributed among the four process methods. The average glass fiber fracture length is ranked as WAIM>GAIM>W-PAIM>G-PAIM. The introduction of the projectile intensifies the glass fiber fracture effect, so that the glass fiber fracture length is shorter. In G-PAIM, WAIM and W-PAIM processes, the orientation of glass fibers along the flow direction tends to increase gradually from near the mold wall layer to the middle layer to near the runner layer, and the orientation of GAIM glass fibers is disorganized. The degree of glass fiber orientation of each process pipes is ranked as W-PAIM>WAIM>G-PAIM>GAIM.
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Abstract:
The twisted bamboo fiber (TBF) was used as the reinforcement phase and the epoxy resin-anhydride system as the matrix phase to prepare the twisted bamboo fiber/epoxy resin composite (TBF/EP composite). The effects of alkali treatment on the wettability and tensile failure of TBF/EP composites were investigated by varying the concentration of NaOH solution (1-5wt%). Nano-scale and micro-scale experimental techniques, such as SEM, surface tension testing, and in-situ loading, were employed to analyze the fiber-resin interface, wetting properties, and tensile mechanical properties of the composites. The results showed that alkali treatment reduced the surface energy and polarity of the fibers, resulting in a decrease in the wetting force between TBF and the matrix from 0.45 mN to 0.1 mN. The TBF/EP composite modified with 3wt% NaOH solution exhibited a tensile strength (TS) of 242.40 MPa, which was 146.79% higher than that of the untreated composite. In-situ analysis revealed that the failure process of TBF involved fiber fracture and fiber sliding, while the failure process of the TBF/EP composite included matrix shear yielding and fiber fracture. Moreover, as the wetting properties improved, the inhibitory effect of the fibers on matrix yielding increased. Therefore, the strength of the TBF/EP composite is mainly derived from the reinforcement of the fibers and the interface, which is influenced by the wetting properties and stress transfer effect between TBF and the matrix.
The twisted bamboo fiber (TBF) was used as the reinforcement phase and the epoxy resin-anhydride system as the matrix phase to prepare the twisted bamboo fiber/epoxy resin composite (TBF/EP composite). The effects of alkali treatment on the wettability and tensile failure of TBF/EP composites were investigated by varying the concentration of NaOH solution (1-5wt%). Nano-scale and micro-scale experimental techniques, such as SEM, surface tension testing, and in-situ loading, were employed to analyze the fiber-resin interface, wetting properties, and tensile mechanical properties of the composites. The results showed that alkali treatment reduced the surface energy and polarity of the fibers, resulting in a decrease in the wetting force between TBF and the matrix from 0.45 mN to 0.1 mN. The TBF/EP composite modified with 3wt% NaOH solution exhibited a tensile strength (TS) of 242.40 MPa, which was 146.79% higher than that of the untreated composite. In-situ analysis revealed that the failure process of TBF involved fiber fracture and fiber sliding, while the failure process of the TBF/EP composite included matrix shear yielding and fiber fracture. Moreover, as the wetting properties improved, the inhibitory effect of the fibers on matrix yielding increased. Therefore, the strength of the TBF/EP composite is mainly derived from the reinforcement of the fibers and the interface, which is influenced by the wetting properties and stress transfer effect between TBF and the matrix.
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Abstract:
CFRP aluminum alloy adhesive plate is a lightweight and high-strength material, which has been widely applied in lightweight structures, such as airplanes, cars, and high-speed trains. This research first established an RVE single cell model based on the microscale from fiber/matrix, predicted the elastic mechanical parameters of unidirectional CFRP, and calculated the macro-micro stress amplification coefficient by applying a macroscopic unit load to the RVE model. Secondly, considering the micro-failure criteria and evolution rules of fiber and matrix, the macro-micro progressive damage evolution program of CFRP unidirectional plates was developed. Then combining with the damage model of metal and adhesive interface, a multiscale damage mechanism impacted model of CFRP aluminum alloy adhesive plate was established, then the accuracy and reliability of the numerical model were verified through the experimental tests. Finally, based on the numerical simulation, the influences of fiber angle and fiber volume fraction on the impact behavior of CFRP aluminum alloy adhesive plate were studied in detail. The results show that the fiber layup direction has little effect on the impact mechanical performance of the adhesive plate, while the fiber volume fraction has a greater effect on the impact behavior of the structure.
CFRP aluminum alloy adhesive plate is a lightweight and high-strength material, which has been widely applied in lightweight structures, such as airplanes, cars, and high-speed trains. This research first established an RVE single cell model based on the microscale from fiber/matrix, predicted the elastic mechanical parameters of unidirectional CFRP, and calculated the macro-micro stress amplification coefficient by applying a macroscopic unit load to the RVE model. Secondly, considering the micro-failure criteria and evolution rules of fiber and matrix, the macro-micro progressive damage evolution program of CFRP unidirectional plates was developed. Then combining with the damage model of metal and adhesive interface, a multiscale damage mechanism impacted model of CFRP aluminum alloy adhesive plate was established, then the accuracy and reliability of the numerical model were verified through the experimental tests. Finally, based on the numerical simulation, the influences of fiber angle and fiber volume fraction on the impact behavior of CFRP aluminum alloy adhesive plate were studied in detail. The results show that the fiber layup direction has little effect on the impact mechanical performance of the adhesive plate, while the fiber volume fraction has a greater effect on the impact behavior of the structure.
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Abstract:
Anti-fog film packaging can reduce the water activity in the package and reduce the large amount of waste caused by fruit and vegetable spoilage, so it is of great research significance. In this study, SiO2 was used as the wall material, and the core material of glyceryl monostearate (GMS) was coated by emulsion polymerization and mixed with linear low-density polyethylene (LLDPE) to prepare a long-term anti-fog film. The results show that the chemical composition and crystal structure of the prepared samples were analyzed by Fourier transform spectroscopy and XRD, which proved that GMS was successfully covered. The micromorphology and cross-sectional microstructure of the sample were analyzed by SEM, and the prepared GMS@SiO2 was spherical, which was well dispersed in the film. The particle size and DSC tests showed that the GMS@SiO2 samples prepared under the condition of 1:2 using GMS and tetraethyl orthosilicate (TEOS) had good particle size uniformity, 83.05% were concentrated at 20-100 nm, and had the highest coating rate, 69.9%. The results of N2 adsorption and desorption showed that there were many mesoporous structures on the surface of the GMS@SiO2. The pore size is 17.918 nm, which can effectively delay the release of GMS; through the analysis of the thermal properties of the sample by TG, it is found that SiO2 wall material has a better protective effect on GMS, and the maximum loss temperature of GMS is increased from 298°C to 405°C, which is increased by about 107°C; through thermal anti-fog test, it is found that the prepared film can effectively extend the anti-fog time of the film and has superior anti-fog performance, in 1~11 hours, the film anti-fog grade is DE grade; within 11~60 hours, the film anti-fog grade is E grade, and the anti-fog film prepared directly added to GMS is E grade in 1~11 hours.The anti-fog grade is grade D within 11~60 hours, and the prepared anti-fog film will have broad application prospects in the fields of fruit and vegetable preservation.
Anti-fog film packaging can reduce the water activity in the package and reduce the large amount of waste caused by fruit and vegetable spoilage, so it is of great research significance. In this study, SiO2 was used as the wall material, and the core material of glyceryl monostearate (GMS) was coated by emulsion polymerization and mixed with linear low-density polyethylene (LLDPE) to prepare a long-term anti-fog film. The results show that the chemical composition and crystal structure of the prepared samples were analyzed by Fourier transform spectroscopy and XRD, which proved that GMS was successfully covered. The micromorphology and cross-sectional microstructure of the sample were analyzed by SEM, and the prepared GMS@SiO2 was spherical, which was well dispersed in the film. The particle size and DSC tests showed that the GMS@SiO2 samples prepared under the condition of 1:2 using GMS and tetraethyl orthosilicate (TEOS) had good particle size uniformity, 83.05% were concentrated at 20-100 nm, and had the highest coating rate, 69.9%. The results of N2 adsorption and desorption showed that there were many mesoporous structures on the surface of the GMS@SiO2. The pore size is 17.918 nm, which can effectively delay the release of GMS; through the analysis of the thermal properties of the sample by TG, it is found that SiO2 wall material has a better protective effect on GMS, and the maximum loss temperature of GMS is increased from 298°C to 405°C, which is increased by about 107°C; through thermal anti-fog test, it is found that the prepared film can effectively extend the anti-fog time of the film and has superior anti-fog performance, in 1~11 hours, the film anti-fog grade is DE grade; within 11~60 hours, the film anti-fog grade is E grade, and the anti-fog film prepared directly added to GMS is E grade in 1~11 hours.The anti-fog grade is grade D within 11~60 hours, and the prepared anti-fog film will have broad application prospects in the fields of fruit and vegetable preservation.
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Abstract:
Electromagnetic absorbing materials with light weight, high strength, wide absorption band, thin thickness and thermal stability are the core requirements for microwave absorption applications. In this paper, Fe3O4-MWCNTs/PLA composite wires were prepared by ball milling mixing and melt extrusion using polylactic acid (PLA) as matrix, Fe3O4 and multi-walled carbon nanotubes (MWCNTs) as fillers, and Fe3O4-MWCNTs/PLA composites were prepared by melt deposition molding (FDM). The phase structure, microstructure and electromagnetic properties of the composites were characterized by XRD, SEM and vector network analyzer, respectively. The composite absorbing material of Fe3O4-MWCNTs/PLA has light weight, good stability, and adjustable dielectric properties, which exhibits excellent broadband absorption ability due to its good impedance matching and electromagnetic wave attenuation ability. The maximum reflection loss of −48.5 dB is obtained by 25%Fe3O4-6%MWCNTs/PLA at a thickness of 1.4 mm and the effective absorption bandwidth reaches 6.78 GHz (10.38-17.16 GHz), demonstrating excellent microwave absorption performance.
Electromagnetic absorbing materials with light weight, high strength, wide absorption band, thin thickness and thermal stability are the core requirements for microwave absorption applications. In this paper, Fe3O4-MWCNTs/PLA composite wires were prepared by ball milling mixing and melt extrusion using polylactic acid (PLA) as matrix, Fe3O4 and multi-walled carbon nanotubes (MWCNTs) as fillers, and Fe3O4-MWCNTs/PLA composites were prepared by melt deposition molding (FDM). The phase structure, microstructure and electromagnetic properties of the composites were characterized by XRD, SEM and vector network analyzer, respectively. The composite absorbing material of Fe3O4-MWCNTs/PLA has light weight, good stability, and adjustable dielectric properties, which exhibits excellent broadband absorption ability due to its good impedance matching and electromagnetic wave attenuation ability. The maximum reflection loss of −48.5 dB is obtained by 25%Fe3O4-6%MWCNTs/PLA at a thickness of 1.4 mm and the effective absorption bandwidth reaches 6.78 GHz (10.38-17.16 GHz), demonstrating excellent microwave absorption performance.
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Abstract:
The use of fabrics to decorate wood plastic composites(WPC)in a variety of styles can greatly improve the practical value of WPC. In this study, a new decorative fabric veneer technique was developed, in which a thermoplastic polymer is laid on the surface of the decorative fabric. This enables the thermoplastic polymer to be in direct contact with the hot platen, thus shortening the time that the decorative fabric is exposed to high temperatures. Moreover, the heat-melted polymer fuses with the polymer on the surface of the wood-plastic substrate through the decorative fabric, which serves to fix and protect the decorative fabric. In this paper, the effects of hot-pressing temperature (140°C, 160°C and 180°C), wood/plastic ratio in the substrate (6∶4, 7∶3 and 8∶2) and the type of polymer (high density polyethylene, low density polyethylene and polylactic acid) on the properties, such as surface bonding strength, decorative effect and mechanical properties of the decorative wood flour/high-density polyethylene (WF/HDPE) composites, were investigated. The changes in the properties of WF/HDPE composites and fabrics were analyzed and characterized by FTIR and SEM. The results show that the molten polymer is able to pass through the fiber voids of the decorative fabric and fuses well with the wood-plastic substrate. The surface of the produced decorative composite material is smooth and even. The effects of hot pressing temperature, substrate wood-plastic ratio and surface polymer type were comprehensive analyzed. When the hot pressing temperature is 160℃, wood-plastic ratio is 7∶3, the mechanical strength of the WF/HDPE composite substrate with the surface layer of the fabric decorated with PLA is the best. Its surface bonding strength is up to 3.64 MPa and the bending strength reaches 82.19 MPa.
The use of fabrics to decorate wood plastic composites(WPC)in a variety of styles can greatly improve the practical value of WPC. In this study, a new decorative fabric veneer technique was developed, in which a thermoplastic polymer is laid on the surface of the decorative fabric. This enables the thermoplastic polymer to be in direct contact with the hot platen, thus shortening the time that the decorative fabric is exposed to high temperatures. Moreover, the heat-melted polymer fuses with the polymer on the surface of the wood-plastic substrate through the decorative fabric, which serves to fix and protect the decorative fabric. In this paper, the effects of hot-pressing temperature (140°C, 160°C and 180°C), wood/plastic ratio in the substrate (6∶4, 7∶3 and 8∶2) and the type of polymer (high density polyethylene, low density polyethylene and polylactic acid) on the properties, such as surface bonding strength, decorative effect and mechanical properties of the decorative wood flour/high-density polyethylene (WF/HDPE) composites, were investigated. The changes in the properties of WF/HDPE composites and fabrics were analyzed and characterized by FTIR and SEM. The results show that the molten polymer is able to pass through the fiber voids of the decorative fabric and fuses well with the wood-plastic substrate. The surface of the produced decorative composite material is smooth and even. The effects of hot pressing temperature, substrate wood-plastic ratio and surface polymer type were comprehensive analyzed. When the hot pressing temperature is 160℃, wood-plastic ratio is 7∶3, the mechanical strength of the WF/HDPE composite substrate with the surface layer of the fabric decorated with PLA is the best. Its surface bonding strength is up to 3.64 MPa and the bending strength reaches 82.19 MPa.
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Abstract:
Ultraviolet(UV) curing technology has the problem of limited curable thickness. However, the in-situ photocuring process has a unique advantage in curing large thickness composite materials by stacking and curing layer by layer. In order to achieve the goal of simultaneous curing and uniform curing degree of each layer in the in-situ photocuring process, the mathematical model of single layer UV curing was presented. Based on this model, a mathematical model was established, which could describe the entire in-situ photocuring process. The time to add each layer was then optimized, the optimal layering time was solved by genetic algorithm combined with gradient descent algorithm. In addition, the in-situ photocuring process was simulated by finite element method. The simulation results show that compare with other curing methods, after optimizing the layering time of in-situ photocuring process, each layer will complete curing when the curing end time is reaching, and the curing degree is uniformly distributed within the median of the desired curing degree. The algorithm and simulation are verified by curing experiment of glass fiber reinforced resin matrix composite laminates. The comparison between experimental results and simulation results shows that the optimized in-situ photocuring process can achieve the goal of simultaneous curing.
Ultraviolet(UV) curing technology has the problem of limited curable thickness. However, the in-situ photocuring process has a unique advantage in curing large thickness composite materials by stacking and curing layer by layer. In order to achieve the goal of simultaneous curing and uniform curing degree of each layer in the in-situ photocuring process, the mathematical model of single layer UV curing was presented. Based on this model, a mathematical model was established, which could describe the entire in-situ photocuring process. The time to add each layer was then optimized, the optimal layering time was solved by genetic algorithm combined with gradient descent algorithm. In addition, the in-situ photocuring process was simulated by finite element method. The simulation results show that compare with other curing methods, after optimizing the layering time of in-situ photocuring process, each layer will complete curing when the curing end time is reaching, and the curing degree is uniformly distributed within the median of the desired curing degree. The algorithm and simulation are verified by curing experiment of glass fiber reinforced resin matrix composite laminates. The comparison between experimental results and simulation results shows that the optimized in-situ photocuring process can achieve the goal of simultaneous curing.
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Abstract:
To remove the interference caused by endogenous substances like organic acids in food during the detection of their trace residues, magnetic adsorbent materials were developed. This was achieved by modifying acidified Fe3O4 with N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane (KH792), which acted as an amination reagent. The optimal modification condition of KH792 for acidified Fe3O4 was optimized by response surface methodology, which was 82.5℃, pH 4.9, and KH792 addition of 1.8 mL. Under the optimum conditions, the acidified Fe3O4 directly modified by KH792 has an adsorption capacity of 22.8 mg/g and shows a 188% increase in the adsorption capacity of the gallic acid compared to commercially available Fe3O4. Additionally, the modified Fe3O4 exhibits excellent performances of rapid solid-liquid separation, good stability, and dispersibility. The properties of the directly modified products were characterized by BET, Zeta potential, FTIR, and XPS. The results show that KH792 bonded on Fe3O4 surface hydroxyl group's by Fe-O-Si bonding, and acidification improved the number of hydroxyl groups on Fe3O4 surface, thus improving the KH792 modification for Fe3O4. The magnetic products prepared in this work can be used for the purification of organic acids in complex sample matrices.
To remove the interference caused by endogenous substances like organic acids in food during the detection of their trace residues, magnetic adsorbent materials were developed. This was achieved by modifying acidified Fe3O4 with N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane (KH792), which acted as an amination reagent. The optimal modification condition of KH792 for acidified Fe3O4 was optimized by response surface methodology, which was 82.5℃, pH 4.9, and KH792 addition of 1.8 mL. Under the optimum conditions, the acidified Fe3O4 directly modified by KH792 has an adsorption capacity of 22.8 mg/g and shows a 188% increase in the adsorption capacity of the gallic acid compared to commercially available Fe3O4. Additionally, the modified Fe3O4 exhibits excellent performances of rapid solid-liquid separation, good stability, and dispersibility. The properties of the directly modified products were characterized by BET, Zeta potential, FTIR, and XPS. The results show that KH792 bonded on Fe3O4 surface hydroxyl group's by Fe-O-Si bonding, and acidification improved the number of hydroxyl groups on Fe3O4 surface, thus improving the KH792 modification for Fe3O4. The magnetic products prepared in this work can be used for the purification of organic acids in complex sample matrices.
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Abstract:
This study experimentally investigated the mechanical behavior of carbon fiber reinforced polymer (CFRP) confined recycled aggregate concrete (RAC) under cyclic loading. In total, 72 CFRP-confined circular RAC specimens were tested under monotonic and cyclic axial compression, with a focus on the various loading rates and recycled aggregate (RA) replacement ratios. Test results indicate that the reinforcing effect of CFRP confinement on the ultimate condition of the concrete with 100wt% RA replacement ratio is most pronounced; however, this enhancement diminishes as the loading rate increases. In comparison to a loading rate of 3 mm/min, for two layers of CFRP-confined concrete with 100wt% RA replacement ratio, the enhancement ratio in ultimate strength is reduced by 16.2%, and the enhancement ratio in ultimate strain is reduced by 22.6% at a loading rate of 18 mm/min. Furthermore, under cyclic axial compression loading, both the unloading stiffness and reloading stiffness exhibit a negative correlation with the RA replacement ratio and loading rate. Nevertheless, the loading rate increase weakens the RA ratio's influence. Based on a regression analysis of the experimental data, a new cyclic stress-strain model for CFRP-confined recycled aggregate concrete incorporating the coupled effects of loading rate and RA replacement ratio is proposed. The proposed model exhibits excellent agreement with the experimental curves in this paper and the collected stress−strain curves from the opening literature.
This study experimentally investigated the mechanical behavior of carbon fiber reinforced polymer (CFRP) confined recycled aggregate concrete (RAC) under cyclic loading. In total, 72 CFRP-confined circular RAC specimens were tested under monotonic and cyclic axial compression, with a focus on the various loading rates and recycled aggregate (RA) replacement ratios. Test results indicate that the reinforcing effect of CFRP confinement on the ultimate condition of the concrete with 100wt% RA replacement ratio is most pronounced; however, this enhancement diminishes as the loading rate increases. In comparison to a loading rate of 3 mm/min, for two layers of CFRP-confined concrete with 100wt% RA replacement ratio, the enhancement ratio in ultimate strength is reduced by 16.2%, and the enhancement ratio in ultimate strain is reduced by 22.6% at a loading rate of 18 mm/min. Furthermore, under cyclic axial compression loading, both the unloading stiffness and reloading stiffness exhibit a negative correlation with the RA replacement ratio and loading rate. Nevertheless, the loading rate increase weakens the RA ratio's influence. Based on a regression analysis of the experimental data, a new cyclic stress-strain model for CFRP-confined recycled aggregate concrete incorporating the coupled effects of loading rate and RA replacement ratio is proposed. The proposed model exhibits excellent agreement with the experimental curves in this paper and the collected stress−strain curves from the opening literature.
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Abstract:
Peridynamic (PD) theory has been proven to be of advantages in low-velocity impact modeling of composite laminate. Based on ordinary state-based peridynamic composite spherical-horizon model, energy-based failure criteria was established, which considered mixed-mode fracture in each time step. Peridynamic modeling of composite laminate under low-velocity impact was conducted using the established energy-based criteria. Firstly, the modeling stiffness was validated. Peridynamic modeling impact load, impact velocity and impact displacement agree well with FEM results. Then, peridynamic damage modeling of composite laminate under low-velocity impact was conducted, and the fiber breakage, matrix crack and delamination damage process were illustrated. Compared with test results, peridynamic modeling delamination area and shape are in good accordance, which validates the conducted peridynamic modeling of composite laminate under low-velocity impact using energy-based criteria.
Peridynamic (PD) theory has been proven to be of advantages in low-velocity impact modeling of composite laminate. Based on ordinary state-based peridynamic composite spherical-horizon model, energy-based failure criteria was established, which considered mixed-mode fracture in each time step. Peridynamic modeling of composite laminate under low-velocity impact was conducted using the established energy-based criteria. Firstly, the modeling stiffness was validated. Peridynamic modeling impact load, impact velocity and impact displacement agree well with FEM results. Then, peridynamic damage modeling of composite laminate under low-velocity impact was conducted, and the fiber breakage, matrix crack and delamination damage process were illustrated. Compared with test results, peridynamic modeling delamination area and shape are in good accordance, which validates the conducted peridynamic modeling of composite laminate under low-velocity impact using energy-based criteria.
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Abstract:
In order to solve the problems of high preparation cost, poor toughness and heat resistance of polylactic acid (PLA) -based wood-plastic composites, biodegradable resin polybutylene succinate (PBS) was used as a modified resin, which was blended with Salix powder (WF) and polylactic acid (PLA) to prepare environmentally friendly PBS-WF/PLA ternary degradable wood-plastic composites by compression molding. The results show that the addition of PBS can improve the toughness, heat resistance and thermal stability of the composites, but the strength and stiffness decrease. When the addition amount of PBS was 50wt% of the total resin, the comprehensive properties of PBS-WF/PLA composites were relatively better. Compared with WF/PLA, the production cost was reduced by about 20%. The retention rates of static bending strength, elastic modulus and tensile strength of PBS-WF/PLA were 86.5%, 63.8% and 73.1%, respectively. The impact strength was increased by 40.1%, and the vicat softening temperature, thermal deformation temperature and the initial temperature of the second stage of thermal decomposition were increased by 37.1°C, 53.7°C and 4.1°C, respectively.
In order to solve the problems of high preparation cost, poor toughness and heat resistance of polylactic acid (PLA) -based wood-plastic composites, biodegradable resin polybutylene succinate (PBS) was used as a modified resin, which was blended with Salix powder (WF) and polylactic acid (PLA) to prepare environmentally friendly PBS-WF/PLA ternary degradable wood-plastic composites by compression molding. The results show that the addition of PBS can improve the toughness, heat resistance and thermal stability of the composites, but the strength and stiffness decrease. When the addition amount of PBS was 50wt% of the total resin, the comprehensive properties of PBS-WF/PLA composites were relatively better. Compared with WF/PLA, the production cost was reduced by about 20%. The retention rates of static bending strength, elastic modulus and tensile strength of PBS-WF/PLA were 86.5%, 63.8% and 73.1%, respectively. The impact strength was increased by 40.1%, and the vicat softening temperature, thermal deformation temperature and the initial temperature of the second stage of thermal decomposition were increased by 37.1°C, 53.7°C and 4.1°C, respectively.
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Abstract:
A kind of strong and fluorescent hybrid hydrogel polyacrylamide-GQDs-TiO2 (PAM-GQDs-TiO2) hydrogel was prepared via a simultaneous in-situ sol-gel method and free radical polymerization. In the hybrid hydrogel, TiO2, and GQDs particles, which served as multifunctional crosslinkers and nano-fillers, were firmly bound to hydrophilic groups in the hydrogel network through noncovalent bonds such as hydrogen bonds. The strong non-covalent interactions among PAM, TiO2 and GQDs endowed the gel with excellent mechanical properties. The elongation at break and tensile strength of PAM-GQDs-TiO2 (0.5wt % GQDs) hybrid hydrogels were 2412% and 181 kPa, respectively, which were 1.78 and 1.13 times that of PAM-TiO2 hydrogels. In addition, the introduction of GQDs also endowed the hybrid hydrogels with special fluorescence properties, which could emit obvious blue fluorescence under 365 nm ultraviolet light. Therefore, the hydrogel has great development potential in biomedicine, heavy metal ion detection, fluorescence probes, and other fields.
A kind of strong and fluorescent hybrid hydrogel polyacrylamide-GQDs-TiO2 (PAM-GQDs-TiO2) hydrogel was prepared via a simultaneous in-situ sol-gel method and free radical polymerization. In the hybrid hydrogel, TiO2, and GQDs particles, which served as multifunctional crosslinkers and nano-fillers, were firmly bound to hydrophilic groups in the hydrogel network through noncovalent bonds such as hydrogen bonds. The strong non-covalent interactions among PAM, TiO2 and GQDs endowed the gel with excellent mechanical properties. The elongation at break and tensile strength of PAM-GQDs-TiO2 (0.5wt % GQDs) hybrid hydrogels were 2412% and 181 kPa, respectively, which were 1.78 and 1.13 times that of PAM-TiO2 hydrogels. In addition, the introduction of GQDs also endowed the hybrid hydrogels with special fluorescence properties, which could emit obvious blue fluorescence under 365 nm ultraviolet light. Therefore, the hydrogel has great development potential in biomedicine, heavy metal ion detection, fluorescence probes, and other fields.
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Abstract:
In order to study the mechanical behavior of lap-spliced CFRP-steel composite bars (referred to as "composite bars") in coral sea-sand seawater concrete (CSSC) and determine the splice length of composite bars reasonably, tensile tests were conducted on 27 sets of 81 lap-spliced specimens and test variables included the composite bar diameter, splice length, cover thickness, concrete strength, clear space between the lap-spliced bars, stirrup ratio, concrete type, and reinforcement type. The influence of various test variables on the behavior of lap-spliced composite bars in CSSC was obtained. The results indicate that pull-out failure accompanied by concrete splitting is found for specimens with a splice length less than 17 times the diameter of the composite bar (dc), while tensile fracture failure is found for specimens with a splice length greater than 17dc. After the specimen undergoing pull-out failure, severe shear damage is formed on the surface of the composite bars. When the splice length is less than 14dc, the splice strength of the specimen is about 7.2 MPa. When the splice length is greater than 14dc, the splice strength of the specimen gradually decreases with the increase of the splice length. After the cover thickness is greater than 4dc or the axial compressive strength of CSSC is greater than 30 MPa, the change in the splice strength of the specimen can be basically ignored. Increasing the stirrup ratio gradually increases the splice strength and significantly reduces the width of the splitting crack. Compared with the lap-spliced specimens of steel bars, the decrease in splice strength of the lap-spliced specimens of composite bars exceeds 25%. Based on the experimental results, the equations for calculating the splice strength and splice length of composite bars in CSSC were established, and the calculation results are consistent with the experimental results. Then, referring to the "Code for Design of Concrete Structures", the equation for calculating the splice length was simplified.
In order to study the mechanical behavior of lap-spliced CFRP-steel composite bars (referred to as "composite bars") in coral sea-sand seawater concrete (CSSC) and determine the splice length of composite bars reasonably, tensile tests were conducted on 27 sets of 81 lap-spliced specimens and test variables included the composite bar diameter, splice length, cover thickness, concrete strength, clear space between the lap-spliced bars, stirrup ratio, concrete type, and reinforcement type. The influence of various test variables on the behavior of lap-spliced composite bars in CSSC was obtained. The results indicate that pull-out failure accompanied by concrete splitting is found for specimens with a splice length less than 17 times the diameter of the composite bar (dc), while tensile fracture failure is found for specimens with a splice length greater than 17dc. After the specimen undergoing pull-out failure, severe shear damage is formed on the surface of the composite bars. When the splice length is less than 14dc, the splice strength of the specimen is about 7.2 MPa. When the splice length is greater than 14dc, the splice strength of the specimen gradually decreases with the increase of the splice length. After the cover thickness is greater than 4dc or the axial compressive strength of CSSC is greater than 30 MPa, the change in the splice strength of the specimen can be basically ignored. Increasing the stirrup ratio gradually increases the splice strength and significantly reduces the width of the splitting crack. Compared with the lap-spliced specimens of steel bars, the decrease in splice strength of the lap-spliced specimens of composite bars exceeds 25%. Based on the experimental results, the equations for calculating the splice strength and splice length of composite bars in CSSC were established, and the calculation results are consistent with the experimental results. Then, referring to the "Code for Design of Concrete Structures", the equation for calculating the splice length was simplified.
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Abstract:
It is important to increase the retention time of pesticides on the leaf surface of target crops for improving pesticide utilization and reducing the impact of pesticides on the environment. In this paper, we used abamectin as a model pesticide and mesoporous silica nanoparticles coated with tannic acid as a carrier material to construct a nano-pesticide delivery system. Based on the structural and morphological characterization of the nano-pesticide delivery system, we investigated the release performance and foliar adhesion of the nano-pesticide delivery system through simulated release experiments, comparison of contact angle and retention amount on plant foliage and UV photolysis resistance experiments. It was found that tannic acid-coated abamectin-loaded mesoporous silica nanospheres (Aba/MSNs@TA) significantly improved drug wettability on the foliage of green, maize and horsetail pine, and foliar retention was also improved compared to abamectin-loaded mesoporous silica nanoparticles. Aba/MSNs@TA exhibited significant pH-responsive release performance, with lower pH environments accelerating the release rate of Aba. In addition, the coating of tannic acid further improved the UV photolytic resistance of the drug in the drug-loaded system.
It is important to increase the retention time of pesticides on the leaf surface of target crops for improving pesticide utilization and reducing the impact of pesticides on the environment. In this paper, we used abamectin as a model pesticide and mesoporous silica nanoparticles coated with tannic acid as a carrier material to construct a nano-pesticide delivery system. Based on the structural and morphological characterization of the nano-pesticide delivery system, we investigated the release performance and foliar adhesion of the nano-pesticide delivery system through simulated release experiments, comparison of contact angle and retention amount on plant foliage and UV photolysis resistance experiments. It was found that tannic acid-coated abamectin-loaded mesoporous silica nanospheres (Aba/MSNs@TA) significantly improved drug wettability on the foliage of green, maize and horsetail pine, and foliar retention was also improved compared to abamectin-loaded mesoporous silica nanoparticles. Aba/MSNs@TA exhibited significant pH-responsive release performance, with lower pH environments accelerating the release rate of Aba. In addition, the coating of tannic acid further improved the UV photolytic resistance of the drug in the drug-loaded system.
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Abstract:
Copper has a wide application prospect in brush and contact materials because of its high conductivity and high ductility. With the rapid development of power transmission industry, the disadvantage of low strength of copper itself cannot meet the demand, and it is urgent to develop a high-strength and high-toughness copper matrix composite material (CMCs) to make up for the defects of copper materials. Boron nitride nanosheets (BNNSs) is expected to be used as good reinforcements for copper matrix composites due to its excellent mechanical properties and high temperature structural stability. In this study, BNNSs reinforced copper matrix composites (BNNSs/Cu) with high comprehensive properties were prepared by powder metallurgy. Microstructure and interface evolution characteristics of composites at different heat treatment temperatures, as well as the changes of mechanical, electrical and tribological properties were studied. The results show that by matrix microalloying (adding 1wt%Ti) and heat treatment, the dense and uniform TiN interfacial transition layer and nano-TiB whisker are formed at the interface of BNNSs, which improve the interfacial bonding between BNNSs and matrix. Ultimate tensile strength (UTS) of BNNSs/Cu-(Ti)-900℃ is 408 MPa, the elongation (EL) is 15.5% and the conductivity remains high level of 91 %IACS and the friction coefficient is 0.58 (pure Cu is 0.8). BNNSs/Cu-(Ti) prepared in this study display excellent mechanical properties and wear resistance while maintaining good conductivity, which provide the technical guidance for high performance electrical materials.
Copper has a wide application prospect in brush and contact materials because of its high conductivity and high ductility. With the rapid development of power transmission industry, the disadvantage of low strength of copper itself cannot meet the demand, and it is urgent to develop a high-strength and high-toughness copper matrix composite material (CMCs) to make up for the defects of copper materials. Boron nitride nanosheets (BNNSs) is expected to be used as good reinforcements for copper matrix composites due to its excellent mechanical properties and high temperature structural stability. In this study, BNNSs reinforced copper matrix composites (BNNSs/Cu) with high comprehensive properties were prepared by powder metallurgy. Microstructure and interface evolution characteristics of composites at different heat treatment temperatures, as well as the changes of mechanical, electrical and tribological properties were studied. The results show that by matrix microalloying (adding 1wt%Ti) and heat treatment, the dense and uniform TiN interfacial transition layer and nano-TiB whisker are formed at the interface of BNNSs, which improve the interfacial bonding between BNNSs and matrix. Ultimate tensile strength (UTS) of BNNSs/Cu-(Ti)-900℃ is 408 MPa, the elongation (EL) is 15.5% and the conductivity remains high level of 91 %IACS and the friction coefficient is 0.58 (pure Cu is 0.8). BNNSs/Cu-(Ti) prepared in this study display excellent mechanical properties and wear resistance while maintaining good conductivity, which provide the technical guidance for high performance electrical materials.
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Abstract:
A high degree of sulfonation is necessary for sulfonated aromatic polymer proton exchange membranes to achieve high proton conductivity. Nevertheless, an elevated sulfonation level will give rise to a range of complications, including heightened swelling ratio, reduced dimensional stability, and greater methanol permeability. To address this challenge, the poly(aryl ether ketone) containing carboxyl group (PAEK-x) was synthesized using the direct condensation method. Subsequently, the sulfonated poly (vinyl alcohol)(SPVA)/crosslinked sulfonated poly (aryl ether ketone) proton exchange membranes were prepared with congo red as the crosslinking agent. The crosslinked composite membranes were characterized by infrared spectroscopy. It is found that these series of crosslinked composite membranes show excellent thermal properties, mechanical properties, oxidation stability and appropriate water absorption. The crosslinked structure formed between the carboxyl group of PAEK-x and the amidogen of Congo red, along with the hydroxyl of SPVA. Notably, the Crosslinking reaction does not consume the sulfonic acid groups in the crosslinked composite membrane. Therefore, these series of crosslinked composite membranes show a high proton conductivity. The Cr-SPAEK-100 membrane demonstrated a proton conductivity of 0.053 S·cm−1 at 25℃ and 0.109 S·cm−1 at 80℃.The crosslinked network structure effectively inhibits the water swelling of the membrane and improves the dimensional stability of the crosslinked composite membrane. At 20℃, the Cr-SPAEK-100 membrane with the highest water uptake exhibits a minimal swelling ratio of only 5.26%. Moreover, the dense crosslinked network structure and the inclusion of SPVA with excellent methanol barrier properties significantly reduce the methanol diffusion coefficients in the crosslinked membranes, with the highest methanol diffusion coefficients being only 3.92×10−7 cm2·s−1. These series crosslinked composite membranes hold promise for applications in direct methanol fuel cells.
A high degree of sulfonation is necessary for sulfonated aromatic polymer proton exchange membranes to achieve high proton conductivity. Nevertheless, an elevated sulfonation level will give rise to a range of complications, including heightened swelling ratio, reduced dimensional stability, and greater methanol permeability. To address this challenge, the poly(aryl ether ketone) containing carboxyl group (PAEK-x) was synthesized using the direct condensation method. Subsequently, the sulfonated poly (vinyl alcohol)(SPVA)/crosslinked sulfonated poly (aryl ether ketone) proton exchange membranes were prepared with congo red as the crosslinking agent. The crosslinked composite membranes were characterized by infrared spectroscopy. It is found that these series of crosslinked composite membranes show excellent thermal properties, mechanical properties, oxidation stability and appropriate water absorption. The crosslinked structure formed between the carboxyl group of PAEK-x and the amidogen of Congo red, along with the hydroxyl of SPVA. Notably, the Crosslinking reaction does not consume the sulfonic acid groups in the crosslinked composite membrane. Therefore, these series of crosslinked composite membranes show a high proton conductivity. The Cr-SPAEK-100 membrane demonstrated a proton conductivity of 0.053 S·cm−1 at 25℃ and 0.109 S·cm−1 at 80℃.The crosslinked network structure effectively inhibits the water swelling of the membrane and improves the dimensional stability of the crosslinked composite membrane. At 20℃, the Cr-SPAEK-100 membrane with the highest water uptake exhibits a minimal swelling ratio of only 5.26%. Moreover, the dense crosslinked network structure and the inclusion of SPVA with excellent methanol barrier properties significantly reduce the methanol diffusion coefficients in the crosslinked membranes, with the highest methanol diffusion coefficients being only 3.92×10−7 cm2·s−1. These series crosslinked composite membranes hold promise for applications in direct methanol fuel cells.
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Abstract:
The development of nanocomposites with high dispersion and good adsorption properties is important for the removal of heavy metal ions from water bodies. Fluorine/carbon-doped hydroxyapatite (FCHAP) was prepared stepwise by microwave/light-wave assisted chemical precipitation using mixed-acid oxidized multi-walled carbon nanotubes (AO-MWCNTs) as the matrix and hydroxyapatite (HAP) was introduced and loaded onto AO-MWCNTs to synthesize fluorine/carbon-doped hydroxyapatite/mixed-acid oxidized multi-walled carbon nanotubes (FCH/AO-MWCNTs) composites. The results show that the theoretical maximum adsorption capacity of FCH/AO-MWCNTs for Mn(II) is 317.5 mg/g, which is higher than that of AO-MWCNTs and each preparation intermediate. Combined with the characterization results of SEM-EDS, FT-IR, XPS, Zeta, and BET, it is speculated that the new material FCH/AO-MWCNTs form more abundant pore structure and adsorption sites, and their dispersion and stability performance are excellent, and at the same time, the new material has broad application prospects in the removal of other heavy metals and recycling.
The development of nanocomposites with high dispersion and good adsorption properties is important for the removal of heavy metal ions from water bodies. Fluorine/carbon-doped hydroxyapatite (FCHAP) was prepared stepwise by microwave/light-wave assisted chemical precipitation using mixed-acid oxidized multi-walled carbon nanotubes (AO-MWCNTs) as the matrix and hydroxyapatite (HAP) was introduced and loaded onto AO-MWCNTs to synthesize fluorine/carbon-doped hydroxyapatite/mixed-acid oxidized multi-walled carbon nanotubes (FCH/AO-MWCNTs) composites. The results show that the theoretical maximum adsorption capacity of FCH/AO-MWCNTs for Mn(II) is 317.5 mg/g, which is higher than that of AO-MWCNTs and each preparation intermediate. Combined with the characterization results of SEM-EDS, FT-IR, XPS, Zeta, and BET, it is speculated that the new material FCH/AO-MWCNTs form more abundant pore structure and adsorption sites, and their dispersion and stability performance are excellent, and at the same time, the new material has broad application prospects in the removal of other heavy metals and recycling.
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Abstract:
The surface modification of basalt fiber (BF) was carried out by using a wetting and penetrating agent in conjunction with a silane coupling agent, followed by winding and molding to prepare basalt fiber/epoxy resin (BF/EP) composite materials. The bending performance of BF/EP was determined using a universal material testing machine, and the creep properties of BF/EP composite materials were measured at different stress levels for 240 min. The surface morphology of the fiber and the bending fracture surface were observed by field emission scanning electron microscopy (FESEM), and the effect of fiber surface modification on various mechanical properties was analyzed. The results show that the surface modification of basalt fiber (BF) using a wetting and penetrating agent in combination with a silane coupling agent is an effective approach to enhance the bending performance and interlaminar shear strength of BF/EP composites. The FESEM morphology analysis reveals that this synergistic modification of BF enhances the interfacial properties between the fiber and the resin, which contributes to the improved mechanical properties of the composite material. Moreover, the short-term creep experiments conducted at various stress levels indicate a significant reduction in creep compliance increment, which suggests that the modified BF/EP composite material has better creep resistance. The improved Findley model provides a useful tool to predict the creep properties of BF/EP composites at different stress levels, which can help optimize their design and performance in practical applications.
The surface modification of basalt fiber (BF) was carried out by using a wetting and penetrating agent in conjunction with a silane coupling agent, followed by winding and molding to prepare basalt fiber/epoxy resin (BF/EP) composite materials. The bending performance of BF/EP was determined using a universal material testing machine, and the creep properties of BF/EP composite materials were measured at different stress levels for 240 min. The surface morphology of the fiber and the bending fracture surface were observed by field emission scanning electron microscopy (FESEM), and the effect of fiber surface modification on various mechanical properties was analyzed. The results show that the surface modification of basalt fiber (BF) using a wetting and penetrating agent in combination with a silane coupling agent is an effective approach to enhance the bending performance and interlaminar shear strength of BF/EP composites. The FESEM morphology analysis reveals that this synergistic modification of BF enhances the interfacial properties between the fiber and the resin, which contributes to the improved mechanical properties of the composite material. Moreover, the short-term creep experiments conducted at various stress levels indicate a significant reduction in creep compliance increment, which suggests that the modified BF/EP composite material has better creep resistance. The improved Findley model provides a useful tool to predict the creep properties of BF/EP composites at different stress levels, which can help optimize their design and performance in practical applications.
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Abstract:
The dendrite formation and growth during Li plating/stripping process, as well as the reduced coulomb efficiency, result in a shortened cycle life of lithium metal batterie (LMB), restricting its commercial application. 2D Zn(Bim)OAc MOF functionalized polyacrylonitrile (Zn(Bim)OAc-PAN) composite separator with regulating Li+ flux and increasing Li+ migration number was successfully prepared by electrospinning combined with vacuum filtration technology. The introduction of Zn(Bim)OAc nanosheets can fix the anion, improve the ionic conductivity (2.13 mS/cm) and Li+ migration number (0.67). Meanwhile, the pores on Zn(Bim)OAc nanosheets and the nanofluid channels between the stacked nanosheets synergistically construct a micro/nano pore structure, reducing the pore size, resulting in uniform Li+ flux distribution and promoting uniform Li+ deposition on the lithium metal surface. Therefore, as-prepared Zn(Bim)OAc-PAN separator assembled Li|LiFePO4 cells can also exhibit higher initial capacity (146.6 mA·h/g) and better cycle stability (96.3% capacity retention after 300 cycles) at 2 C. Besides, as-prepared Zn(Bim)OAc-PAN separator based Li|Li achieves a stable cycle up to 1000 h under 1 mA/cm2, and there was no obvious lithium dendrite growth on the Li anode surface after cycling. The reported approach provides a feasible strategy to improve the LMB performance by regulating the Li+ flux through separators.
The dendrite formation and growth during Li plating/stripping process, as well as the reduced coulomb efficiency, result in a shortened cycle life of lithium metal batterie (LMB), restricting its commercial application. 2D Zn(Bim)OAc MOF functionalized polyacrylonitrile (Zn(Bim)OAc-PAN) composite separator with regulating Li+ flux and increasing Li+ migration number was successfully prepared by electrospinning combined with vacuum filtration technology. The introduction of Zn(Bim)OAc nanosheets can fix the anion, improve the ionic conductivity (2.13 mS/cm) and Li+ migration number (0.67). Meanwhile, the pores on Zn(Bim)OAc nanosheets and the nanofluid channels between the stacked nanosheets synergistically construct a micro/nano pore structure, reducing the pore size, resulting in uniform Li+ flux distribution and promoting uniform Li+ deposition on the lithium metal surface. Therefore, as-prepared Zn(Bim)OAc-PAN separator assembled Li|LiFePO4 cells can also exhibit higher initial capacity (146.6 mA·h/g) and better cycle stability (96.3% capacity retention after 300 cycles) at 2 C. Besides, as-prepared Zn(Bim)OAc-PAN separator based Li|Li achieves a stable cycle up to 1000 h under 1 mA/cm2, and there was no obvious lithium dendrite growth on the Li anode surface after cycling. The reported approach provides a feasible strategy to improve the LMB performance by regulating the Li+ flux through separators.
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Abstract:
In order to prepare a physically cross-linked thermo-sensitive hydrogel, in this paper, water-soluble glycol chitosan (GC) was selected as the matrix, the heptanoylated glycol chitosan (HAGC) with different degrees of heptanoylation (DS) were synthesized by acylation modification through amide coupling reaction between heptanoic anhydride and amino groups on the molecular chain of GC. The results showed that the feed molar ratio of heptanoic anhydride to the amino group on GC was between 0.2 and 0.25, and DS was modulated from 26.4% to 31.5%. By the introduction of hydrophobic acetyl groups on the backbone of GC, it was not only found that such derivatization would improve the solubility in organic solvents and in vitro biodegradability of GC, but also import new attractive properties such as thermo-sensitive sol-gel transition properties. HAGC was physically cross-linked through intermolecular interactions, including hydrogen bonding and hydrophilic and hydrophobic interactions. Thus, HAGC could undergo sol-gel phase transition in response to ambient temperature changes. By changing the DS and solution concentration of HAGC, the sol-gel transition temperature of HAGC hydrogel was effectively adjusted between room temperature and human body temperature (25~37℃) . The HAGC hydrogel had the three-dimensional porous structure. As the DS increase, the crosslink density of the HAGC hydrogel increased, the swelling ratio decreased, and the drug release rate slowed down. The HAGC hydrogel had a slow-release effect on the drug gemcitabine, and the drug release time could reach 5 days, and the drug release rate was up to 70%~91%. Therefore, HAGC hydrogel has important application value in biomedical fields such as drug injection and sustained-release carrier due to its excellent thermo-sensitive properties.
In order to prepare a physically cross-linked thermo-sensitive hydrogel, in this paper, water-soluble glycol chitosan (GC) was selected as the matrix, the heptanoylated glycol chitosan (HAGC) with different degrees of heptanoylation (DS) were synthesized by acylation modification through amide coupling reaction between heptanoic anhydride and amino groups on the molecular chain of GC. The results showed that the feed molar ratio of heptanoic anhydride to the amino group on GC was between 0.2 and 0.25, and DS was modulated from 26.4% to 31.5%. By the introduction of hydrophobic acetyl groups on the backbone of GC, it was not only found that such derivatization would improve the solubility in organic solvents and in vitro biodegradability of GC, but also import new attractive properties such as thermo-sensitive sol-gel transition properties. HAGC was physically cross-linked through intermolecular interactions, including hydrogen bonding and hydrophilic and hydrophobic interactions. Thus, HAGC could undergo sol-gel phase transition in response to ambient temperature changes. By changing the DS and solution concentration of HAGC, the sol-gel transition temperature of HAGC hydrogel was effectively adjusted between room temperature and human body temperature (25~37℃) . The HAGC hydrogel had the three-dimensional porous structure. As the DS increase, the crosslink density of the HAGC hydrogel increased, the swelling ratio decreased, and the drug release rate slowed down. The HAGC hydrogel had a slow-release effect on the drug gemcitabine, and the drug release time could reach 5 days, and the drug release rate was up to 70%~91%. Therefore, HAGC hydrogel has important application value in biomedical fields such as drug injection and sustained-release carrier due to its excellent thermo-sensitive properties.
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Abstract:
Corona discharge can adversely affect the stable operation and service life of electrical equipment. Therefore, it is crucial to enhance the corona resistance of insulation materials to ensure the normal functioning of electrical equipment. In this study, modified BN (fBN) was synthesized by treating boron nitride (BN) with a silane coupling agent, and subsequently blended with dispersant (organosilicon boron composite oxide (Si-B)) to modify epoxy resin. The fBN-Si-B/EP composites with different fBN contents were prepared by blending and thermosetting methods. The corona resistance life of epoxy resin was significantly enhanced. The experimental findings revealed that the corona resistance life of fBN-Si-B/EP composites at an electric field strength of 30 kV·mm−1 and temperature of 30℃ was up to 114.8 h, which was 5.01 times greater than that of pure epoxy resin. The dielectric constant of the fBN-Si-B/EP composite shows an increasing trend with the increase of the fBN doping. At the same time, the volume resistivity and breakdown strength of the composites show a trend of decreasing and then increasing. The addition of a small amount of fBN can reduce the relative dielectric constant of the composite and suppress the increase of dielectric loss. While the breakdown strength and volume resistivity of fBN-Si-B/EP composites are slightly reduced with the addition of fBN particles, with a minimum volume resistivity of 6.65×1014 Ω·cm and a minimum breakdown strength of 24.04 kV·mm−1, they still exhibit good insulation properties.
Corona discharge can adversely affect the stable operation and service life of electrical equipment. Therefore, it is crucial to enhance the corona resistance of insulation materials to ensure the normal functioning of electrical equipment. In this study, modified BN (fBN) was synthesized by treating boron nitride (BN) with a silane coupling agent, and subsequently blended with dispersant (organosilicon boron composite oxide (Si-B)) to modify epoxy resin. The fBN-Si-B/EP composites with different fBN contents were prepared by blending and thermosetting methods. The corona resistance life of epoxy resin was significantly enhanced. The experimental findings revealed that the corona resistance life of fBN-Si-B/EP composites at an electric field strength of 30 kV·mm−1 and temperature of 30℃ was up to 114.8 h, which was 5.01 times greater than that of pure epoxy resin. The dielectric constant of the fBN-Si-B/EP composite shows an increasing trend with the increase of the fBN doping. At the same time, the volume resistivity and breakdown strength of the composites show a trend of decreasing and then increasing. The addition of a small amount of fBN can reduce the relative dielectric constant of the composite and suppress the increase of dielectric loss. While the breakdown strength and volume resistivity of fBN-Si-B/EP composites are slightly reduced with the addition of fBN particles, with a minimum volume resistivity of 6.65×1014 Ω·cm and a minimum breakdown strength of 24.04 kV·mm−1, they still exhibit good insulation properties.
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Abstract:
Hydrogen energy has the advantages of wide source, clean and carbon-free. With the wide application of hydrogen energy, hydrogen energy storage and transportation has gradually become a research hotspot. At present, the carbon fiber reinforced resin matrix composite material gas cylinder vigorously developed by the country has been widely used in the field of hydrogen energy storage and transportation, but the gas cylinder is prone to fiber breakage and scratches during use and transportation, which seriously affects the safety of use, so it is urgent to develop the carbon fiber reinforced resin matrix composite material gas cylinder online monitoring technology. In order to solve the problem that fiber fracture and scratch defects of composite material gas cylinders will expand during long-term and multiple filling and venting, an online monitoring method using Electromagnetic Acoustic Transducer (EMAT) was adopted. Combined with the 90TJ3-140 MPa hydraulic pressure fatigue system, the influence of fiber damage on the amplitude of guided wave was analyzed by ultrasonic guided wave reflection method and ultrasonic guided wave transmission method, and the variation of guided wave signal characteristics of gas cylinders with fiber damage under different fatigue conditions was studied. The results show that fiber damage can reduce the amplitude of transmission wave, and the amplitude reduction is determined by the degree of fiber damage. With the increase of the pressure inside the cylinder, the sound velocity and center frequency of ultrasonic guided wave decrease gradually. For cracks with length 20 mm, width 0.5 mm and depth 1 mm, the amplitude of the defect wave increases first and then decreases. After 110 MPa and 80 cycles, the amplitude of the defect wave decreases from 19.33 mV to 8.02 mV, the sound velocity decreases by 6.6%, and the center frequency decreases from 0.24 MHz to 0.17 MHz, the fibers are completely layered; For cracks with a length of 20 mm, a width of 0.5 mm and a depth of 0.5 mm, when the internal pressure of the cylinder increases from 0 MPa to 105 MPa, the direct wave amplitude decreases from 80.17 mV to 20.08 mV, which decreases by 75%. The electromagnetic ultrasonic technology adopted can solve the difficult problem of on-line monitoring of carbon fiber reinforced resin matrix composite material gas cylinder.
Hydrogen energy has the advantages of wide source, clean and carbon-free. With the wide application of hydrogen energy, hydrogen energy storage and transportation has gradually become a research hotspot. At present, the carbon fiber reinforced resin matrix composite material gas cylinder vigorously developed by the country has been widely used in the field of hydrogen energy storage and transportation, but the gas cylinder is prone to fiber breakage and scratches during use and transportation, which seriously affects the safety of use, so it is urgent to develop the carbon fiber reinforced resin matrix composite material gas cylinder online monitoring technology. In order to solve the problem that fiber fracture and scratch defects of composite material gas cylinders will expand during long-term and multiple filling and venting, an online monitoring method using Electromagnetic Acoustic Transducer (EMAT) was adopted. Combined with the 90TJ3-140 MPa hydraulic pressure fatigue system, the influence of fiber damage on the amplitude of guided wave was analyzed by ultrasonic guided wave reflection method and ultrasonic guided wave transmission method, and the variation of guided wave signal characteristics of gas cylinders with fiber damage under different fatigue conditions was studied. The results show that fiber damage can reduce the amplitude of transmission wave, and the amplitude reduction is determined by the degree of fiber damage. With the increase of the pressure inside the cylinder, the sound velocity and center frequency of ultrasonic guided wave decrease gradually. For cracks with length 20 mm, width 0.5 mm and depth 1 mm, the amplitude of the defect wave increases first and then decreases. After 110 MPa and 80 cycles, the amplitude of the defect wave decreases from 19.33 mV to 8.02 mV, the sound velocity decreases by 6.6%, and the center frequency decreases from 0.24 MHz to 0.17 MHz, the fibers are completely layered; For cracks with a length of 20 mm, a width of 0.5 mm and a depth of 0.5 mm, when the internal pressure of the cylinder increases from 0 MPa to 105 MPa, the direct wave amplitude decreases from 80.17 mV to 20.08 mV, which decreases by 75%. The electromagnetic ultrasonic technology adopted can solve the difficult problem of on-line monitoring of carbon fiber reinforced resin matrix composite material gas cylinder.
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Abstract:
Natural spider silk has superior mechanical properties, and its various forms have excellent antibacterial activity, biocompatibility, and good thermal conductivity. It is of great significance to develop natural biological drug-loaded materials with good biocompatibility for reducing the strong immunogenicity reaction of patients. By exploring the dissolution and membrane-forming methods of spider silk in different solvents, the reaction conditions were optimized, hexafluoroisopropanol was used as the dissolution solvent, the material ratio was 1∶1 (mg∶mL), the spider silk was dissolved at 60℃ for 8 h, and the membrane was formed by solvent casting, and the drug release in vitro of RhB as the model drug was explored with the correlation characterization. The cytotoxicity of the material was tested by extraction method. The spider fibroin membrane extract co-culture with cells showed that the material had no potential cytotoxicity to mouse embryonic osteoblasts cells. The drug-loaded spider silk fibroin membrane prepared by this method has high yield, uniform thickness and simple operation, which provides a simple and feasible technology for the dissolution of natural spider silk protein and the preparation of membrane agent.
Natural spider silk has superior mechanical properties, and its various forms have excellent antibacterial activity, biocompatibility, and good thermal conductivity. It is of great significance to develop natural biological drug-loaded materials with good biocompatibility for reducing the strong immunogenicity reaction of patients. By exploring the dissolution and membrane-forming methods of spider silk in different solvents, the reaction conditions were optimized, hexafluoroisopropanol was used as the dissolution solvent, the material ratio was 1∶1 (mg∶mL), the spider silk was dissolved at 60℃ for 8 h, and the membrane was formed by solvent casting, and the drug release in vitro of RhB as the model drug was explored with the correlation characterization. The cytotoxicity of the material was tested by extraction method. The spider fibroin membrane extract co-culture with cells showed that the material had no potential cytotoxicity to mouse embryonic osteoblasts cells. The drug-loaded spider silk fibroin membrane prepared by this method has high yield, uniform thickness and simple operation, which provides a simple and feasible technology for the dissolution of natural spider silk protein and the preparation of membrane agent.
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Abstract:
Strain hardening cement-based composite (SHCC) owning to its advantages of high ductility and controllable crack width has been widely used in the strengthening and repairing of concrete structures exposed to severe marine corrosion zones. Based on this, a convection-diffusion model of chloride transport in SHCC subjected to marine drying-wetting cycles was proposed, and a two -dimensional mesoscopic model considering the chaotic distribution of fibers was established by COMSOL simulation software. The spatial and temporal distribution of chloride content under different drying-wetting ratios (3.0∶1, 11.0∶1 and 85.4∶1) and exposure durations (30 d, 90 d and 180 d) was analyzed by conducting a simulated indoor test of chloride ingress into SHCC. The effectiveness of the mesoscopic numerical model to simulate chloride ingress behavior was contrastively verified. The results show that the peak chloride concentration inside SHCC increases with the extension of exposure time, and similarly increases with the increase of drying-wetting ratio. However, with the increase of penetration depth, the chloride concentration rapidly decreases and tends to be stable eventually, which make the chloride content as a whole show a higher peak concentration and a smaller penetration depth. According to the analytical solution to Fick’s second law and considering the effect of convection zone, both the surface chloride concentration (Cs) and apparent chloride diffusion coefficient (Dapp) of SHCC show obvious time-varying characteristics. At a given drying-wetting cycle ratio, the Cs and Dapp increase and decrease as the exposure time increases, respectively. When the drying-wetting cycle ratio is 85.4∶1, compared to 30 d, the Cs of SHCC for exposure to 90 d and 180 d increase by 51.72% and 83.45%, and the Dapp decreases by 27.71% and 48.50%, respectively. At the same exposure time, as the drying-wetting cycle ratio increases, both the Cs and Dapp first increase and then decrease. Finally, the comparison between the measured data and calculated results of the chloride content distribution indicates the feasibility of the proposed convection-diffusion model under the cyclic drying-wetting action to depict the chloride transport behavior in SHCC.
Strain hardening cement-based composite (SHCC) owning to its advantages of high ductility and controllable crack width has been widely used in the strengthening and repairing of concrete structures exposed to severe marine corrosion zones. Based on this, a convection-diffusion model of chloride transport in SHCC subjected to marine drying-wetting cycles was proposed, and a two -dimensional mesoscopic model considering the chaotic distribution of fibers was established by COMSOL simulation software. The spatial and temporal distribution of chloride content under different drying-wetting ratios (3.0∶1, 11.0∶1 and 85.4∶1) and exposure durations (30 d, 90 d and 180 d) was analyzed by conducting a simulated indoor test of chloride ingress into SHCC. The effectiveness of the mesoscopic numerical model to simulate chloride ingress behavior was contrastively verified. The results show that the peak chloride concentration inside SHCC increases with the extension of exposure time, and similarly increases with the increase of drying-wetting ratio. However, with the increase of penetration depth, the chloride concentration rapidly decreases and tends to be stable eventually, which make the chloride content as a whole show a higher peak concentration and a smaller penetration depth. According to the analytical solution to Fick’s second law and considering the effect of convection zone, both the surface chloride concentration (Cs) and apparent chloride diffusion coefficient (Dapp) of SHCC show obvious time-varying characteristics. At a given drying-wetting cycle ratio, the Cs and Dapp increase and decrease as the exposure time increases, respectively. When the drying-wetting cycle ratio is 85.4∶1, compared to 30 d, the Cs of SHCC for exposure to 90 d and 180 d increase by 51.72% and 83.45%, and the Dapp decreases by 27.71% and 48.50%, respectively. At the same exposure time, as the drying-wetting cycle ratio increases, both the Cs and Dapp first increase and then decrease. Finally, the comparison between the measured data and calculated results of the chloride content distribution indicates the feasibility of the proposed convection-diffusion model under the cyclic drying-wetting action to depict the chloride transport behavior in SHCC.
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Abstract:
In this paper, the performance deterioration of basalt-, glass- and carbon-fiber reinforced polymer (BFRP, GFRP and CFRP) bars in five kinds of corrosive solution environments, i.e., water, strong alkali solution (pH=12.8), weak alkali solution (pH=11), simulated seawater and acid solution (pH=1.5), was investigated. The deterioration patterns of fiber-resin interfacial bonding properties, microstructure and chemical composition of FRP bars at different aging temperatures (20, 40 and 55°C) and corrosion periods (1, 2, 3, 6 and 9 months) were investigated by interlaminar shear strength, water absorption, DMA, FTIR and SEM tests. The test results show that the interlaminar shear strength of FRP bars is significantly affected by the corrosive environment, and the deterioration rate of FRP specimen in the strong alkali solution is much higher than the other four solutions. The reason is that the high concentration of OH- ions accelerates the hydrolysis and etching reaction of FRP bars, causing a large number of fibers and resin debonding, which eventually leads to the reduction of interlaminar shear strength. Compared with BFRP bars and GFRP bars, CFRP bars have relatively excellent durability and higher interlaminar shear strength retention ratio under the same aging conditions.
In this paper, the performance deterioration of basalt-, glass- and carbon-fiber reinforced polymer (BFRP, GFRP and CFRP) bars in five kinds of corrosive solution environments, i.e., water, strong alkali solution (pH=12.8), weak alkali solution (pH=11), simulated seawater and acid solution (pH=1.5), was investigated. The deterioration patterns of fiber-resin interfacial bonding properties, microstructure and chemical composition of FRP bars at different aging temperatures (20, 40 and 55°C) and corrosion periods (1, 2, 3, 6 and 9 months) were investigated by interlaminar shear strength, water absorption, DMA, FTIR and SEM tests. The test results show that the interlaminar shear strength of FRP bars is significantly affected by the corrosive environment, and the deterioration rate of FRP specimen in the strong alkali solution is much higher than the other four solutions. The reason is that the high concentration of OH- ions accelerates the hydrolysis and etching reaction of FRP bars, causing a large number of fibers and resin debonding, which eventually leads to the reduction of interlaminar shear strength. Compared with BFRP bars and GFRP bars, CFRP bars have relatively excellent durability and higher interlaminar shear strength retention ratio under the same aging conditions.
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Carbon fibers with a carbon content of over 90% have the characteristic of strong surface inertness, so surface activation treatment is an essential process in their preparation. The effect of current intensity on the physicochemical structure and properties of electrochemically activated carbon fiber surface under dilute H2SO4 electrolyte were explored by XPS, Raman, dynamic contact angle, monofilament tensile strength and interfacial shear strength, and non-contact anodizing device was used. The results showed that the content of oxygen-containing functional groups increased by the attack of reactive oxygen [O] on the surface of carbon fibers, and the activation effect was significant with increasing current within the scope of this study. Carbon fibers near the anode were affected by static electricity and diffusion. SO4 2− and S2O8 2− entered the internal gap of carbon structure, so the surface S/C and diameter of carbon fibers increased. Under the action of SO4 2− etching, the disordered carbon structure on the surface of carbon fiber fell off, the Degree of graphitization (R) decreased. SO4 2− and S2O8 2− were intercalated into the carbon structures, forming an associated structure through electrostatic interaction. Under the combined effect of etching and intercalation, the monofilament tensile strength of carbon fibers had been improved, with a maximum increase of 16.77%. After 0.5 A current treatment, the surface roughness of carbon fiber was improved, the content of hydroxyl and carboxyl functional groups on the carbon fiber surface that can react with the epoxy resin matrix was the highest, the surface polarity of carbon fiber was the strongest, the dynamic contact angle with deionized water was reduced from 89.9° of untreated to 50.6°, and the corresponding interfacial shear strength (IFSS) of the composite was increased by 47.70%.
Carbon fibers with a carbon content of over 90% have the characteristic of strong surface inertness, so surface activation treatment is an essential process in their preparation. The effect of current intensity on the physicochemical structure and properties of electrochemically activated carbon fiber surface under dilute H2SO4 electrolyte were explored by XPS, Raman, dynamic contact angle, monofilament tensile strength and interfacial shear strength, and non-contact anodizing device was used. The results showed that the content of oxygen-containing functional groups increased by the attack of reactive oxygen [O] on the surface of carbon fibers, and the activation effect was significant with increasing current within the scope of this study. Carbon fibers near the anode were affected by static electricity and diffusion. SO4 2− and S2O8 2− entered the internal gap of carbon structure, so the surface S/C and diameter of carbon fibers increased. Under the action of SO4 2− etching, the disordered carbon structure on the surface of carbon fiber fell off, the Degree of graphitization (R) decreased. SO4 2− and S2O8 2− were intercalated into the carbon structures, forming an associated structure through electrostatic interaction. Under the combined effect of etching and intercalation, the monofilament tensile strength of carbon fibers had been improved, with a maximum increase of 16.77%. After 0.5 A current treatment, the surface roughness of carbon fiber was improved, the content of hydroxyl and carboxyl functional groups on the carbon fiber surface that can react with the epoxy resin matrix was the highest, the surface polarity of carbon fiber was the strongest, the dynamic contact angle with deionized water was reduced from 89.9° of untreated to 50.6°, and the corresponding interfacial shear strength (IFSS) of the composite was increased by 47.70%.
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Abstract:
Stretchable strain sensors have broad application prospects in the field of vibration reduction and isolation, however, developing low-cost and high stability stretchable strain sensors remains a huge challenge. This article uses the open melt method to prepare multi walled carbon nanotubes (MWCNT) - conductive carbon black (CB)/methyl vinyl silicone rubber (VMQ) conductive nanocomposites. The effects of the synergistic effect between MWCNT and CB on the dispersion, conductivity, mechanical properties and resistance-strain response of the composites were investigated.The results showed that the mechanical properties of the composite material were improved after adding CB, with a lower percolation threshold (1.24wt%), and excellent resistance strain response stability was demonstrated during 5000 cycles of loading unloading. In addition, compared to MWCNT/VMQ and CB/VMQ composites, the MWCNT-CB/VMQ composite did not exhibit shoulder peak phenomenon in the resistance strain response performance, and explained the mechanism of shoulder peak phenomenon. Through SEM, it was found that the uniform distribution and synergistic effect of MWCNT and CB in the composite material are important reasons for the low threshold and stable resistance strain response performance. The mechanism of resistance strain response was explained through the tunnel effect theory model. This composite material has great potential for strain monitoring of seismic isolation structures.
Stretchable strain sensors have broad application prospects in the field of vibration reduction and isolation, however, developing low-cost and high stability stretchable strain sensors remains a huge challenge. This article uses the open melt method to prepare multi walled carbon nanotubes (MWCNT) - conductive carbon black (CB)/methyl vinyl silicone rubber (VMQ) conductive nanocomposites. The effects of the synergistic effect between MWCNT and CB on the dispersion, conductivity, mechanical properties and resistance-strain response of the composites were investigated.The results showed that the mechanical properties of the composite material were improved after adding CB, with a lower percolation threshold (1.24wt%), and excellent resistance strain response stability was demonstrated during 5000 cycles of loading unloading. In addition, compared to MWCNT/VMQ and CB/VMQ composites, the MWCNT-CB/VMQ composite did not exhibit shoulder peak phenomenon in the resistance strain response performance, and explained the mechanism of shoulder peak phenomenon. Through SEM, it was found that the uniform distribution and synergistic effect of MWCNT and CB in the composite material are important reasons for the low threshold and stable resistance strain response performance. The mechanism of resistance strain response was explained through the tunnel effect theory model. This composite material has great potential for strain monitoring of seismic isolation structures.
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The electrical aging life of polypropylene (PP) insulation, a new environmentally friendly material, and its nano-SiO2 composites are investigated to provide theoretical support for the reliability of PP-insulated cables in later applications. Based on the electric aging life formula-inverse power method, the life model parameters of PP insulation and SiO2/PP composites were estimated by constant voltage accelerated aging test, and then the reliability of life index n was evaluated by stepwise accelerated aging test. The SiO2/PP composites were also structurally characterized and performance tested. The results show that the lifetime index n of SiO2/PP6 is 14.61, which is enhanced by 16.51% compared with that of PP6 of 12.52. It is found in the experimental stage that the doping of SiO2 has a significant effect on the enhancement of PP6's time to failure at lower aging field strengths, and it is predicted that the long-term electrical aging lifetime of SiO2/PP6 is more than five times that of PP6 below the aging field strength of 25 kV mm−1. Meanwhile, the doping of nano-SiO2 reduced the industrial frequency dielectric loss factor and lowered the loss peak height of PP insulation. Based on the electrical aging cavity theory, it is proposed that SiO2 enhances the electrical aging life of PP insulation by limiting the chain segment breakage by consuming hot electron energy.
The electrical aging life of polypropylene (PP) insulation, a new environmentally friendly material, and its nano-SiO2 composites are investigated to provide theoretical support for the reliability of PP-insulated cables in later applications. Based on the electric aging life formula-inverse power method, the life model parameters of PP insulation and SiO2/PP composites were estimated by constant voltage accelerated aging test, and then the reliability of life index n was evaluated by stepwise accelerated aging test. The SiO2/PP composites were also structurally characterized and performance tested. The results show that the lifetime index n of SiO2/PP6 is 14.61, which is enhanced by 16.51% compared with that of PP6 of 12.52. It is found in the experimental stage that the doping of SiO2 has a significant effect on the enhancement of PP6's time to failure at lower aging field strengths, and it is predicted that the long-term electrical aging lifetime of SiO2/PP6 is more than five times that of PP6 below the aging field strength of 25 kV mm−1. Meanwhile, the doping of nano-SiO2 reduced the industrial frequency dielectric loss factor and lowered the loss peak height of PP insulation. Based on the electrical aging cavity theory, it is proposed that SiO2 enhances the electrical aging life of PP insulation by limiting the chain segment breakage by consuming hot electron energy.
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In order to achieve the goal of green and efficient energy utilization, how to deal with uranium-containing waste generated during the development of nuclear energy has become an increasingly prominent environmental problem. The CaTiO3 materials were initially prepared using the solvent-thermal method. Subsequently, the carbon material was synthesized by grinding a mixture of CaTiO3 and pomegranate peel carbon material, resulting in the formation of carbon-loaded CaTiO3 (C@CaTiO3). Modern characterization techniques were employed to analyze the morphological and compositional changes of C@CaTiO3 before and after its reaction with U(VI). The performance of the material in removing uranium from the solution was evaluated using a static experimental method. The research findings revealed that, under the conditions of pH=3.5, an initial concentration of U(VI) of 25 mg·L−1, a reaction time of 40 min, and a temperature of 25℃, the material exhibited a U(VI) removal rate of 96.26% with a corresponding removal capacity of 119.21 mg·g−1. The reaction mechanism between C@CaTiO3 and U(VI) was investigated using adsorption kinetics models, isothermal adsorption models, and thermodynamic models. The results demonstrated that the adsorption process of U(VI) by C@CaTiO3 was a spontaneous endothermic reaction. The removal of U(VI) from the solution using C@CaTiO3 involved both adsorption and reduction, with physical and chemical adsorption coexisting and surface monolayer chemical adsorption being the predominant mechanism. Photocatalytic reduction played a major role in the reduction process.
In order to achieve the goal of green and efficient energy utilization, how to deal with uranium-containing waste generated during the development of nuclear energy has become an increasingly prominent environmental problem. The CaTiO3 materials were initially prepared using the solvent-thermal method. Subsequently, the carbon material was synthesized by grinding a mixture of CaTiO3 and pomegranate peel carbon material, resulting in the formation of carbon-loaded CaTiO3 (C@CaTiO3). Modern characterization techniques were employed to analyze the morphological and compositional changes of C@CaTiO3 before and after its reaction with U(VI). The performance of the material in removing uranium from the solution was evaluated using a static experimental method. The research findings revealed that, under the conditions of pH=3.5, an initial concentration of U(VI) of 25 mg·L−1, a reaction time of 40 min, and a temperature of 25℃, the material exhibited a U(VI) removal rate of 96.26% with a corresponding removal capacity of 119.21 mg·g−1. The reaction mechanism between C@CaTiO3 and U(VI) was investigated using adsorption kinetics models, isothermal adsorption models, and thermodynamic models. The results demonstrated that the adsorption process of U(VI) by C@CaTiO3 was a spontaneous endothermic reaction. The removal of U(VI) from the solution using C@CaTiO3 involved both adsorption and reduction, with physical and chemical adsorption coexisting and surface monolayer chemical adsorption being the predominant mechanism. Photocatalytic reduction played a major role in the reduction process.
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Abstract:
The phase-field method can automatically capture crack initiation and propagation, which has obvious advantages in simulating complex fracture behaviors in composites. To distinguish different fracture modes in fiber-reinforced composites (FRC), two phase-field variables were introduced to represent the damage evolution of fiber and matrix, respectively. An adaptive mesh refinement scheme based on the quadtree decomposition was incorporated into the anisotropic double phase-field formulations using the phase-field variables as the error indicators. The corresponding Matlab programs were designed and developed to study the fracture behaviors of the unidirectional and variable stiffness fiber-reinforced composite single layer laminate under tensile load. The results show that: the numerical results are in good agreement with the experimental results; and the adaptive double phase-field method can not only guarantee high computational accuracy but also refine the mesh along the crack paths with the evolution of phase-field parameters automatically and accurately. Moreover, this method can simplify the mesh pre-processing process, greatly reduce the number of unnecessary elements and the calculation cost, improve the calculation efficiency.
The phase-field method can automatically capture crack initiation and propagation, which has obvious advantages in simulating complex fracture behaviors in composites. To distinguish different fracture modes in fiber-reinforced composites (FRC), two phase-field variables were introduced to represent the damage evolution of fiber and matrix, respectively. An adaptive mesh refinement scheme based on the quadtree decomposition was incorporated into the anisotropic double phase-field formulations using the phase-field variables as the error indicators. The corresponding Matlab programs were designed and developed to study the fracture behaviors of the unidirectional and variable stiffness fiber-reinforced composite single layer laminate under tensile load. The results show that: the numerical results are in good agreement with the experimental results; and the adaptive double phase-field method can not only guarantee high computational accuracy but also refine the mesh along the crack paths with the evolution of phase-field parameters automatically and accurately. Moreover, this method can simplify the mesh pre-processing process, greatly reduce the number of unnecessary elements and the calculation cost, improve the calculation efficiency.
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Two reactive acrylate triblock copolymers including poly(methyl methacrylate-co-glycidyl methacrylate)-b- poly (butyl acrylate)-b-poly (methyl methacrylate-co-glycidyl methacrylate)(PMGBMG) and poly(methyl methacrylate)-b-poly (butyl acrylate-co-glycidyl methacrylate)-b-poly(methyl methacrylate) (PMBGM) were synthesized via initiator for continuous activator regeneration atom transfer radical polymerization (ICAR-ATRP). Nano silica (SiO2) modified by 3-ainopropyltriethoxysilane was grafted on block copolymer to prepare PMGBMG-SiO2 and PMBGM-SiO2 as tougheners for epoxy resin. Results show that addition of 5wt% PMGBMG-SiO2 in E-51 epoxy resin can increase the critical stress intensity factor (KIC) by145% compared with pure epoxy matrix. Meanwhile, the tensile strength and modulus are increased by 8% and 31% respectively, which are superior to the resins modified by pure copolymer and PMBGM-SiO2. The toughness and rigidity are improved simultaneously, while heat resistance is also well maintained.
Two reactive acrylate triblock copolymers including poly(methyl methacrylate-co-glycidyl methacrylate)-b- poly (butyl acrylate)-b-poly (methyl methacrylate-co-glycidyl methacrylate)(PMGBMG) and poly(methyl methacrylate)-b-poly (butyl acrylate-co-glycidyl methacrylate)-b-poly(methyl methacrylate) (PMBGM) were synthesized via initiator for continuous activator regeneration atom transfer radical polymerization (ICAR-ATRP). Nano silica (SiO2) modified by 3-ainopropyltriethoxysilane was grafted on block copolymer to prepare PMGBMG-SiO2 and PMBGM-SiO2 as tougheners for epoxy resin. Results show that addition of 5wt% PMGBMG-SiO2 in E-51 epoxy resin can increase the critical stress intensity factor (KIC) by145% compared with pure epoxy matrix. Meanwhile, the tensile strength and modulus are increased by 8% and 31% respectively, which are superior to the resins modified by pure copolymer and PMBGM-SiO2. The toughness and rigidity are improved simultaneously, while heat resistance is also well maintained.
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In order to develop a new way of efficient utilization of corrosion inhibitors, a corrosion inhibited polyo-toluidine - graphene oxide-based anticorrosive materials was prepared by using graphene oxide as the substrate, polyo-toluidine microcapsules as the wall material and 2-mercaptobenzothiazole as the corrosion inhibitor as the core material, and it was used as the filler for the modification of waterborne epoxy resin coating (WEP). The structure and morphology of the coating were characterized by FTIR, XRD, XPS and SEM. The release behavior of the corrosion inhibitor was analyzed by UV-Vis spectroscopy. The tensile property and anti-corrosion properties of the coating were evaluated by universal testing machine, electrochemical test and salt spray test. The results showed that the corrosion inhibitor was successfully coated inside polyo-toluidine microcapsules, and the microcapsules were connected to the surface of the modified graphene oxide by covalent bond, so that the corrosion inhibitor was fully utilized, and the tensile property, self-healing properties and shielding properties of the coating against corrosive media were improved. UV-vis spectrum test results showed that the release of corrosion inhibitor in microcapsules reached 78% after 96 h of artificial damage. The tensile property test results show that, compared with pure WEP, the coating stress increases from 14.281 MPa to 24.25 MPa when the filler content is 0.3%. SEM results show that the scratched coating self-healing after 10 h at room temperature. The electrochemical test and salt spray test results show that the corrosion potential of the coating increases from −0.6216 V to −0.1554 V, the corrosion current density decreases from 4.271×10−7 A·cm−2 to 1.016×10−11 A·cm−2, and the impedance modulus can reach 1.5757×109 Ω·cm2. After 500 h of salt spray, the corrosion resistance is still good.
In order to develop a new way of efficient utilization of corrosion inhibitors, a corrosion inhibited polyo-toluidine - graphene oxide-based anticorrosive materials was prepared by using graphene oxide as the substrate, polyo-toluidine microcapsules as the wall material and 2-mercaptobenzothiazole as the corrosion inhibitor as the core material, and it was used as the filler for the modification of waterborne epoxy resin coating (WEP). The structure and morphology of the coating were characterized by FTIR, XRD, XPS and SEM. The release behavior of the corrosion inhibitor was analyzed by UV-Vis spectroscopy. The tensile property and anti-corrosion properties of the coating were evaluated by universal testing machine, electrochemical test and salt spray test. The results showed that the corrosion inhibitor was successfully coated inside polyo-toluidine microcapsules, and the microcapsules were connected to the surface of the modified graphene oxide by covalent bond, so that the corrosion inhibitor was fully utilized, and the tensile property, self-healing properties and shielding properties of the coating against corrosive media were improved. UV-vis spectrum test results showed that the release of corrosion inhibitor in microcapsules reached 78% after 96 h of artificial damage. The tensile property test results show that, compared with pure WEP, the coating stress increases from 14.281 MPa to 24.25 MPa when the filler content is 0.3%. SEM results show that the scratched coating self-healing after 10 h at room temperature. The electrochemical test and salt spray test results show that the corrosion potential of the coating increases from −0.6216 V to −0.1554 V, the corrosion current density decreases from 4.271×10−7 A·cm−2 to 1.016×10−11 A·cm−2, and the impedance modulus can reach 1.5757×109 Ω·cm2. After 500 h of salt spray, the corrosion resistance is still good.
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Alkali-activated foam concrete is a type of green, low-carbon and energy-saving material which combines the advantages of alkali-activated materials and foam concrete. The application and development of alkali-activated foam concrete are limited by its complex drying shrinkage values which affected by its complicated pores structure and hydration products that unlike cement. In this review, the capillary tension theory, the surface tension theory, the separation pressure theory and the interlayer water transfer theory were analyzed. Contrast the similarities and differences of contraction mechanism between alkali-activated foam concrete, cement base material and alkali-activated material. Meanwhile, the latest research progress of inhibiting drying shrinkage of alkali-activated foam concrete is summarized. Compared with cement-based materials, alkali-activated materials have larger drying shrinkage because of the different hydration products. The drying shrinkage of alkali-activated foam concrete is mainly related to the amount of foam, and the less slurry, the smaller the drying shrinkage value. Finally, this review points out the research and application of alkali-activated foam concrete and provides an effective way for its development economically and environmentally.
Alkali-activated foam concrete is a type of green, low-carbon and energy-saving material which combines the advantages of alkali-activated materials and foam concrete. The application and development of alkali-activated foam concrete are limited by its complex drying shrinkage values which affected by its complicated pores structure and hydration products that unlike cement. In this review, the capillary tension theory, the surface tension theory, the separation pressure theory and the interlayer water transfer theory were analyzed. Contrast the similarities and differences of contraction mechanism between alkali-activated foam concrete, cement base material and alkali-activated material. Meanwhile, the latest research progress of inhibiting drying shrinkage of alkali-activated foam concrete is summarized. Compared with cement-based materials, alkali-activated materials have larger drying shrinkage because of the different hydration products. The drying shrinkage of alkali-activated foam concrete is mainly related to the amount of foam, and the less slurry, the smaller the drying shrinkage value. Finally, this review points out the research and application of alkali-activated foam concrete and provides an effective way for its development economically and environmentally.
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The line type polyurethane containing furan rings was prepared by diisocyanate (MDI), polyether polyols (PTMG) and 2,5-furandimethanol. The cured thermoreversible polyurethane was synthesized by Diels-Alder reaction between bismaleimide (BMI) and the line type polyurethane containing furan rings, and the unidirectional carbon fiber composite was prepared. The thermal reversible behavior of the cured thermoreversible polyurethane was analyzed through high-temperature FTIR and DSC. The solubility, melt reprocessing ability and mechanical properties of the cured thermoreversible polyurethane were studied, the mechanical properties and dynamic mechanical properties of carbon fiber composites were also analyzed. The results show that the cured thermoreversible polyurethane has a repeated behavior of bond breaking and cross-linking during thermal cycling, and the reversible reaction is completed about 160℃. Both high-temperature dissolution process and hot-melt process can be used for reprocessing. After being reprocessed three times, the original mechanical properties of the cured thermoreversible polyurethane can still be maintained. The interlaminar shear of unidirectional carbon fiber composites was characterized by secondary failure, and the interlaminar shear strength is 34.85MPa. The glass transition temperature of thermoreversible polyurethane is 93.73℃.
The line type polyurethane containing furan rings was prepared by diisocyanate (MDI), polyether polyols (PTMG) and 2,5-furandimethanol. The cured thermoreversible polyurethane was synthesized by Diels-Alder reaction between bismaleimide (BMI) and the line type polyurethane containing furan rings, and the unidirectional carbon fiber composite was prepared. The thermal reversible behavior of the cured thermoreversible polyurethane was analyzed through high-temperature FTIR and DSC. The solubility, melt reprocessing ability and mechanical properties of the cured thermoreversible polyurethane were studied, the mechanical properties and dynamic mechanical properties of carbon fiber composites were also analyzed. The results show that the cured thermoreversible polyurethane has a repeated behavior of bond breaking and cross-linking during thermal cycling, and the reversible reaction is completed about 160℃. Both high-temperature dissolution process and hot-melt process can be used for reprocessing. After being reprocessed three times, the original mechanical properties of the cured thermoreversible polyurethane can still be maintained. The interlaminar shear of unidirectional carbon fiber composites was characterized by secondary failure, and the interlaminar shear strength is 34.85MPa. The glass transition temperature of thermoreversible polyurethane is 93.73℃.
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Abstract:
With the development of information technology, electromagnetic pollution has become increasingly severe. Therefore, the development of high-performance microwave absorbing materials with "thin, light, wide, and strong" characteristics has become a top priority. Graphene's excellent properties, such as high conductivity, high specific surface area, and low density, have attracted widespread attention from researchers. To solve the problem of impedance mismatch and single loss mechanism caused by single graphene material, other components are introduced to prepare multi-component composite materials, which improve impedance matching and create diverse loss mechanisms, making it a common design solution. This paper briefly discusses the absorption mechanism, describing four categories: dielectric type, magnetic composite type, ordered type, and pressure-induced type. Through material selection (metals, ceramics, ferrites, conductive polymers, biomass materials, etc.), structural design, mechanism analysis, and combining with recent research results in the field, the research progress of graphene aerogel based microwave absorbing materials is summarized, and future research directions are also proposed.
With the development of information technology, electromagnetic pollution has become increasingly severe. Therefore, the development of high-performance microwave absorbing materials with "thin, light, wide, and strong" characteristics has become a top priority. Graphene's excellent properties, such as high conductivity, high specific surface area, and low density, have attracted widespread attention from researchers. To solve the problem of impedance mismatch and single loss mechanism caused by single graphene material, other components are introduced to prepare multi-component composite materials, which improve impedance matching and create diverse loss mechanisms, making it a common design solution. This paper briefly discusses the absorption mechanism, describing four categories: dielectric type, magnetic composite type, ordered type, and pressure-induced type. Through material selection (metals, ceramics, ferrites, conductive polymers, biomass materials, etc.), structural design, mechanism analysis, and combining with recent research results in the field, the research progress of graphene aerogel based microwave absorbing materials is summarized, and future research directions are also proposed.
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Copper-based nanomaterials have received much attention in electrocatalysis, but they suffer from low catalytic activity, unstable structures, and poor stability, and it is of great practical importance to explore simple and efficient strategies to solve these problems. In this study, a Co-MOF material was used to successfully construct cobalt-doped Cu2Cl(OH)3/CuCl composite materials on a nickel foam substrate through a hydrolysis-etching strategy in a CuCl2 solution at room temperature. By varying the hydrolysis-etching time of Co-MOF in the CuCl2 solution, the morphology and structure of the species and composites were controlled. The optimized catalyst only requires an overpotential of 238 mV to drive a current density of 100 mA·cm−2. After 50 hours of stability testing, the current density hardly decreased, indicating excellent stability. The excellent electrocatalytic oxygen evolution reaction (OER) performance can be attributed to the cobalt atom doping, which optimizes the electronic environment around the copper atoms, activating the catalytic activity of Cu2Cl(OH)3 and CuCl, as well as the CuCl2 etching of the nickel foam, which increases the active sites. This study provides new ideas and strategies for the preparation of copper-based electrocatalytic materials and enhancing their electrocatalytic OER activity.
Copper-based nanomaterials have received much attention in electrocatalysis, but they suffer from low catalytic activity, unstable structures, and poor stability, and it is of great practical importance to explore simple and efficient strategies to solve these problems. In this study, a Co-MOF material was used to successfully construct cobalt-doped Cu2Cl(OH)3/CuCl composite materials on a nickel foam substrate through a hydrolysis-etching strategy in a CuCl2 solution at room temperature. By varying the hydrolysis-etching time of Co-MOF in the CuCl2 solution, the morphology and structure of the species and composites were controlled. The optimized catalyst only requires an overpotential of 238 mV to drive a current density of 100 mA·cm−2. After 50 hours of stability testing, the current density hardly decreased, indicating excellent stability. The excellent electrocatalytic oxygen evolution reaction (OER) performance can be attributed to the cobalt atom doping, which optimizes the electronic environment around the copper atoms, activating the catalytic activity of Cu2Cl(OH)3 and CuCl, as well as the CuCl2 etching of the nickel foam, which increases the active sites. This study provides new ideas and strategies for the preparation of copper-based electrocatalytic materials and enhancing their electrocatalytic OER activity.
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Abstract:
In view of the wide frequency noise characteristics of turbofan engine with large bypass ratio at present, traditional single-degree-of-freedom honeycomb sandwich acoustic lining material was optimized to improve its sound absorption performance. Under the premise of keeping the basic form of single-degree-of-freedom honeycomb structure of sound liner unchanged, in order to broaden the sound absorption spectrum and reach two or more characteristic frequencies, carbon nanotube film was compounded at a specific position inside the single-layer honeycomb core. At the same time, in order to improve the sound absorption effect, metal wire mesh and flexible porous materials were introduced between perforated plate and honeycomb core, and they were assembled through a rapid process. The influences of placement position and parameters of the introduced material on the sound absorption performance of the sound absorption composite were also investigated. The experimental results show that the structure with the best sound absorption performance is the introduction of 37 μm hole diameter wire mesh placed behind the porous panel, the placement of 15 mm thick melamine sponge between the porous panel and the honeycomb, and the placement of carbon nanotube film with a porosity of 2% and 4% in the middle of the honeycomb sandwich structure. The sound liner prepared based on this result has excellent sound absorption performance, and shows good sound absorption performance in the range of 800 Hz to 4500 Hz. The peak sound absorption coefficients of the two characteristic frequencies reach 0.98 and 0.99 respectively, and the average sound absorption coefficient reaches 0.89, which is 61.8% higher than that before optimization. At the same time, the half-peak width can fully cover the frequency range of 800 Hz to 4500 Hz tested, which indicates good broadband noise reduction characteristics.
In view of the wide frequency noise characteristics of turbofan engine with large bypass ratio at present, traditional single-degree-of-freedom honeycomb sandwich acoustic lining material was optimized to improve its sound absorption performance. Under the premise of keeping the basic form of single-degree-of-freedom honeycomb structure of sound liner unchanged, in order to broaden the sound absorption spectrum and reach two or more characteristic frequencies, carbon nanotube film was compounded at a specific position inside the single-layer honeycomb core. At the same time, in order to improve the sound absorption effect, metal wire mesh and flexible porous materials were introduced between perforated plate and honeycomb core, and they were assembled through a rapid process. The influences of placement position and parameters of the introduced material on the sound absorption performance of the sound absorption composite were also investigated. The experimental results show that the structure with the best sound absorption performance is the introduction of 37 μm hole diameter wire mesh placed behind the porous panel, the placement of 15 mm thick melamine sponge between the porous panel and the honeycomb, and the placement of carbon nanotube film with a porosity of 2% and 4% in the middle of the honeycomb sandwich structure. The sound liner prepared based on this result has excellent sound absorption performance, and shows good sound absorption performance in the range of 800 Hz to 4500 Hz. The peak sound absorption coefficients of the two characteristic frequencies reach 0.98 and 0.99 respectively, and the average sound absorption coefficient reaches 0.89, which is 61.8% higher than that before optimization. At the same time, the half-peak width can fully cover the frequency range of 800 Hz to 4500 Hz tested, which indicates good broadband noise reduction characteristics.
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Abstract:
Improving the separation efficiency of photogenerated carriers is an effective way to improve the protection performance of photoelectrochemical cathode. In order to make up for the shortcomings of SrTiO3, such as large band gap and low separation efficiency of photogenerated carriers, BaTiO3/SrTiO3 composite films were prepared on fluorine-doped tin oxide conductive glass (FTO) by two-step ultrasonic spray pyrolysis process. The phase composition, surface morphology and optical properties of the samples were observed by XRD, SEM, UV-Vis DRS and PL. Then, 304 stainless steel (304 SS) was used as the protected metal, and the photoelectrochemical cathodic protection performance of BaTiO3/SrTiO3 composite film was observed under the condition of shading light. The relative position of BaTiO3/SrTiO3 is determined by Mott-Schottky curve. The results show that the light absorption range of BaTiO3/SrTiO3 composite films prepared by two-step ultrasonic spray pyrolysis process is broadened to 400 nm; . Compared with SrTiO3 film, BaTiO3/SrTiO3 composite film has better light absorption performance. The separation efficiency of photo-generated carriers is improved; In 3.5wt.% NaCl solution, BaTiO3/SrTiO3 composite film negatively shifts the open circuit potential of 304 SS to -0.38 V, with a negative shift degree of about 230 mV, while pure SrTiO3 film can only negatively shift by 80 mV. The performance improvement is mainly attributed to the heterojunction formed by BaTiO3 and SrTiO3, which promotes the separation of photogenerated carriers.
Improving the separation efficiency of photogenerated carriers is an effective way to improve the protection performance of photoelectrochemical cathode. In order to make up for the shortcomings of SrTiO3, such as large band gap and low separation efficiency of photogenerated carriers, BaTiO3/SrTiO3 composite films were prepared on fluorine-doped tin oxide conductive glass (FTO) by two-step ultrasonic spray pyrolysis process. The phase composition, surface morphology and optical properties of the samples were observed by XRD, SEM, UV-Vis DRS and PL. Then, 304 stainless steel (304 SS) was used as the protected metal, and the photoelectrochemical cathodic protection performance of BaTiO3/SrTiO3 composite film was observed under the condition of shading light. The relative position of BaTiO3/SrTiO3 is determined by Mott-Schottky curve. The results show that the light absorption range of BaTiO3/SrTiO3 composite films prepared by two-step ultrasonic spray pyrolysis process is broadened to 400 nm; . Compared with SrTiO3 film, BaTiO3/SrTiO3 composite film has better light absorption performance. The separation efficiency of photo-generated carriers is improved; In 3.5wt.% NaCl solution, BaTiO3/SrTiO3 composite film negatively shifts the open circuit potential of 304 SS to -0.38 V, with a negative shift degree of about 230 mV, while pure SrTiO3 film can only negatively shift by 80 mV. The performance improvement is mainly attributed to the heterojunction formed by BaTiO3 and SrTiO3, which promotes the separation of photogenerated carriers.
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Abstract:
3D woven composites are widely used in the aerospace field. As a reinforcement structure, the geometry of fiber preform has a decisive influence on the mechanical properties of composites. However, a preform is a flexible structure that is prone to significant geometric variation during the molding process, including yarn path changes and compressive deformations of cross-sections. Achieving refined and high-fidelity modeling of preforms is an important prerequisite for performance prediction and structural design of composite materials. Aiming at modeling of the complex fiber structure for carbon fiber 3D woven preforms, a quasi-fiber scale modeling method based on the concept of virtual fiber was proposed. Movements and deformations of yarn in the weaving process were simulated, and high precision model of 3D woven preform was constructed. The Micro-CT technology was used to analyze the unit cell structure inside the preform sample, which verified the reliability of the model.
3D woven composites are widely used in the aerospace field. As a reinforcement structure, the geometry of fiber preform has a decisive influence on the mechanical properties of composites. However, a preform is a flexible structure that is prone to significant geometric variation during the molding process, including yarn path changes and compressive deformations of cross-sections. Achieving refined and high-fidelity modeling of preforms is an important prerequisite for performance prediction and structural design of composite materials. Aiming at modeling of the complex fiber structure for carbon fiber 3D woven preforms, a quasi-fiber scale modeling method based on the concept of virtual fiber was proposed. Movements and deformations of yarn in the weaving process were simulated, and high precision model of 3D woven preform was constructed. The Micro-CT technology was used to analyze the unit cell structure inside the preform sample, which verified the reliability of the model.
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Abstract:
In recent years, the structure-function integrated CFRP composites have attracted extensive attention, and the interlayer reinforcing and stiffening based on CNT films with high strength, high modulus and high thermal conductivity provided an innovative idea. In this paper, the S-CNTF, E-CNTF and S-E-CNTF were prepared by wet stretching and epoxidation reaction based on P-CNTF, and used for interlayer reinforcing and stiffening CFRP composites (CFRP/S-CNTF, CFRP/E-CNTF and CFRP/S-E-CNTF), respectively. The physicochemical characteristics and tensile properties of CNT films were analyzed, and the effects of S-E-CNTF on longitudinal compressive strength and failure mechanism of composites were studied by combining with Jumahat’s combined model and experimental verification. Meanwhile, the in-plane thermal conductivity and corresponding mechanism of composites was discussed. In contrast with P-CNTF, the CNTs in S-E-CNTF present highly oriented bunching morphology and the surface chemical activity of S-E-CNTF was observably improved, so that the tensile strength and modulus of S-E-CNTF are enhanced to 116 MPa and 6.3 GPa, respectively. In comparison with CFRP, the in-plane shear modulus and interlaminar shear strength of CFRP/S-E-CNTF are increased by 28.3% and 34.2%, respectively, implying that the S-E-CNTF can effectively inhibit delamination and enhance resistance of shear deformation of CFRP. The model prediction also shows that the theoretically elastic and plastic compressive stress of CFRP/S-E-CNTF are increased by 30.7% and 32.3%, respectively, which is in accord with experimental values. Meanwhile, based on the three-dimensional thermal conductivity network constructed by S-E-CNTF in the interlaminar region of CFRP, the in-plane thermal conductivity of CFRP/S-E-CNTF is improved to 7.8 W/(m·K).
In recent years, the structure-function integrated CFRP composites have attracted extensive attention, and the interlayer reinforcing and stiffening based on CNT films with high strength, high modulus and high thermal conductivity provided an innovative idea. In this paper, the S-CNTF, E-CNTF and S-E-CNTF were prepared by wet stretching and epoxidation reaction based on P-CNTF, and used for interlayer reinforcing and stiffening CFRP composites (CFRP/S-CNTF, CFRP/E-CNTF and CFRP/S-E-CNTF), respectively. The physicochemical characteristics and tensile properties of CNT films were analyzed, and the effects of S-E-CNTF on longitudinal compressive strength and failure mechanism of composites were studied by combining with Jumahat’s combined model and experimental verification. Meanwhile, the in-plane thermal conductivity and corresponding mechanism of composites was discussed. In contrast with P-CNTF, the CNTs in S-E-CNTF present highly oriented bunching morphology and the surface chemical activity of S-E-CNTF was observably improved, so that the tensile strength and modulus of S-E-CNTF are enhanced to 116 MPa and 6.3 GPa, respectively. In comparison with CFRP, the in-plane shear modulus and interlaminar shear strength of CFRP/S-E-CNTF are increased by 28.3% and 34.2%, respectively, implying that the S-E-CNTF can effectively inhibit delamination and enhance resistance of shear deformation of CFRP. The model prediction also shows that the theoretically elastic and plastic compressive stress of CFRP/S-E-CNTF are increased by 30.7% and 32.3%, respectively, which is in accord with experimental values. Meanwhile, based on the three-dimensional thermal conductivity network constructed by S-E-CNTF in the interlaminar region of CFRP, the in-plane thermal conductivity of CFRP/S-E-CNTF is improved to 7.8 W/(m·K).
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Abstract:
Metal-organic framework (MOF), as a new type of porous crystal material, can be used as nanoparticle and carrier because of its high porosity, diverse structure and controllable chemical structure. Functional coatings prepared based on MOF materials can combine the advantages of MOF and have a wide range of applications, but there are not many papers on the application and mechanism of coatings based on MOF materials.The research status of MOF-based coatings at home and abroad was introduced, focusing on the anti-icing/de-icing applications of MOF-based coatings (superhydrophobic surfaces and smooth liquid-injected porous surfaces (SLIPS)), anti-corrosion applications (MOF materials as nanoparticles and carriers) and antibacterial applications (based on metal ion release, photodynamic therapy (PDT) and photothermal therapy (PTT)), and the anti-icing mechanisms of different coatings (reducing the solidification temperature of water and reducing ice adhesion) were summarized. Antiseptic mechanism (direct physical blocking or chemical formation to achieve the blocking effect) and antibacterial mechanism (metal ions with weak toxicity to eukaryotic cells achieve antibacterial effect, reactive oxygen species (ROS) are activated under light irradiation to achieve antibacterial effect, and heat is generated by absorbing external light, and antibacterial effect is achieved with increasing temperature). The key challenges, potential applications and development prospects of MOF-based coatings are prospected.
Metal-organic framework (MOF), as a new type of porous crystal material, can be used as nanoparticle and carrier because of its high porosity, diverse structure and controllable chemical structure. Functional coatings prepared based on MOF materials can combine the advantages of MOF and have a wide range of applications, but there are not many papers on the application and mechanism of coatings based on MOF materials.The research status of MOF-based coatings at home and abroad was introduced, focusing on the anti-icing/de-icing applications of MOF-based coatings (superhydrophobic surfaces and smooth liquid-injected porous surfaces (SLIPS)), anti-corrosion applications (MOF materials as nanoparticles and carriers) and antibacterial applications (based on metal ion release, photodynamic therapy (PDT) and photothermal therapy (PTT)), and the anti-icing mechanisms of different coatings (reducing the solidification temperature of water and reducing ice adhesion) were summarized. Antiseptic mechanism (direct physical blocking or chemical formation to achieve the blocking effect) and antibacterial mechanism (metal ions with weak toxicity to eukaryotic cells achieve antibacterial effect, reactive oxygen species (ROS) are activated under light irradiation to achieve antibacterial effect, and heat is generated by absorbing external light, and antibacterial effect is achieved with increasing temperature). The key challenges, potential applications and development prospects of MOF-based coatings are prospected.
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Abstract:
In order to explore the effects of different vulcanization systems on the thermal aging properties of silicone rubber used for enhanced insulation of cable accessories, this paper took silicone rubber used for enhanced insulation of 35 kV cable accessories as the research object, and used peroxide and hydrosilane addition vulcanization systems to produce vulcanized silicone rubber samples and carry out thermal aging tests to compare and analyze the mechanical and electrical properties of the rubber. In the early stage of thermal aging, the oxidative cross-linking reaction of molecular side chains and the re-cross-linking reaction between molecular chains occurred in both silicone rubber vulcanization systems, and the cross-linking degree increased. In the later stage of thermal aging, the cross-linking system structure and molecular chain were destroyed, and the cross-linking degree decreased. The research and test results show that the tensile strength and elongation at break of silicone rubber samples gradually decrease with the increase of thermal aging time, the conductivity decreases first and then increases with the increase of temperature, the relative dielectric constant increases gradually and decreases with the increase of temperature, the tangent of dielectric loss Angle increases gradually and increases with the increase of temperature, and the breakdown field strength increases first and then decreases. The silicone rubber under the hydrosilane addition vulcanization system has always maintained high crosslinking degree and has better mechanical and electrical properties after thermal aging, while the silicone rubber under the peroxide vulcanization system produces strong acidic by-products during vulcanization and produces strong polar groups after thermal aging, resulting in the deterioration of the thermal aging performance of the silicone rubber.
In order to explore the effects of different vulcanization systems on the thermal aging properties of silicone rubber used for enhanced insulation of cable accessories, this paper took silicone rubber used for enhanced insulation of 35 kV cable accessories as the research object, and used peroxide and hydrosilane addition vulcanization systems to produce vulcanized silicone rubber samples and carry out thermal aging tests to compare and analyze the mechanical and electrical properties of the rubber. In the early stage of thermal aging, the oxidative cross-linking reaction of molecular side chains and the re-cross-linking reaction between molecular chains occurred in both silicone rubber vulcanization systems, and the cross-linking degree increased. In the later stage of thermal aging, the cross-linking system structure and molecular chain were destroyed, and the cross-linking degree decreased. The research and test results show that the tensile strength and elongation at break of silicone rubber samples gradually decrease with the increase of thermal aging time, the conductivity decreases first and then increases with the increase of temperature, the relative dielectric constant increases gradually and decreases with the increase of temperature, the tangent of dielectric loss Angle increases gradually and increases with the increase of temperature, and the breakdown field strength increases first and then decreases. The silicone rubber under the hydrosilane addition vulcanization system has always maintained high crosslinking degree and has better mechanical and electrical properties after thermal aging, while the silicone rubber under the peroxide vulcanization system produces strong acidic by-products during vulcanization and produces strong polar groups after thermal aging, resulting in the deterioration of the thermal aging performance of the silicone rubber.
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Abstract:
With the rapid development of ultra-large-scale integrated circuits, micro-integrated high-density semiconductor components urgently require low dielectric materials. In this work, epoxy sesquisiloxane (EOVS) with cage structure was synthesized and blended with epoxy resin E51 to obtain the nanoporous EOVS/E51composite. As shown by SEM, EOVS nanoparticles are uniformly dispersed in the E51 matrix. With the increase of EOVS, the nanopores introduced by its cage structure make the free volume of EOVS/E51 composite increase and the density of polarized molecules per unit volume decrease, so that the dielectric constant decreases from 4.21 to 2.51 (1 MHz) when the EOVS content is 15wt%. However, the epoxy groups on EOVS provide new reaction sites, so the crosslink density of the EOVS/E51 composite system increases with the increase of EOVS, and the free volume of the composite decreases and the dielectric constant turns to increase when the EOVS content reaches 20wt%. In addition, the hydrophobicity of the Si—O—Si bond of EOVS enhances the moisture resistance of EOVS/E51 composites, while the thermal stability of the inorganic backbone and the nano-toughening effect lead to a significant increase in the heat and impact resistance of the composite, which is promising for applications in microelectronics.
With the rapid development of ultra-large-scale integrated circuits, micro-integrated high-density semiconductor components urgently require low dielectric materials. In this work, epoxy sesquisiloxane (EOVS) with cage structure was synthesized and blended with epoxy resin E51 to obtain the nanoporous EOVS/E51composite. As shown by SEM, EOVS nanoparticles are uniformly dispersed in the E51 matrix. With the increase of EOVS, the nanopores introduced by its cage structure make the free volume of EOVS/E51 composite increase and the density of polarized molecules per unit volume decrease, so that the dielectric constant decreases from 4.21 to 2.51 (1 MHz) when the EOVS content is 15wt%. However, the epoxy groups on EOVS provide new reaction sites, so the crosslink density of the EOVS/E51 composite system increases with the increase of EOVS, and the free volume of the composite decreases and the dielectric constant turns to increase when the EOVS content reaches 20wt%. In addition, the hydrophobicity of the Si—O—Si bond of EOVS enhances the moisture resistance of EOVS/E51 composites, while the thermal stability of the inorganic backbone and the nano-toughening effect lead to a significant increase in the heat and impact resistance of the composite, which is promising for applications in microelectronics.
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Abstract:
In order to further study the effect of Cr(VI) on the photodegradation of xanthate and its synergistic mechanism in the co-existing system of xanthate and Cr(VI), the photocatalyst of coal gangue/bismuth vanadate (CG/BiVO4) was used, xanthate and Cr(VI) coexisting systems were studied by photocatalytic activity test, UV, FTIR, ion chromatography and quenching experiments, the photooxidation of xanthate and photoreduction of Cr(VI) and their synergistic mechanism were explored. The results showed that there was a significant synergistic effect between the photo-oxidation of xanthate and photo-reduction of Cr(VI) in the co-existence system of xanthate and Cr(VI). Then, at the xanthate of 25 mg/L and the pH value of 7, with the dosage of catalyst being 1. 5 g/L, at the Cr(VI) of 2.0 mg/L, the removal rate of xanthate and Cr(VI) by CG/BiVO4 were the best during a period of 480 min, reaching 98.81% and 88.80% respectively. The predicted degradation rate of xanthate was 94.79% by response surface methodology, lower 3.82% than the actual degradation rate, which indicated that the model can be used to predict the degradation of xanthate in the co-existing system. In the co-existing system, the vibration of C=S was changed first, followed by C—O—C, S—H, S—C—S, butyl, and the intermediate product peroxy xanthate (ROCSSO−) was formed after the visible light illumination 3 h , the highest conversion of sulfur was reached 97.94% after the visible light illumination 7 h. The synergistic mechanism analysis showed that the photogenerated e− were rapidly captured in the photo-reduction of Cr(VI) and photogenerated h+ were consumed by xanthate photodegradation. The photogenic electron and hole pairs were consumed,on the one hand, due to the inhibition of photogenerated electrons and holes recombination, the lifetime of photogenerated electron and hole pairs were prolonged, on the other hand, the rapid consumption of photogenerated electron-hole pairs accelerates the conversion of light energy to chemical energy, generating a large number of photogenerated electron -hole pairs, therefor promoting the synergistic removal of xanthate and Cr(VI) .
In order to further study the effect of Cr(VI) on the photodegradation of xanthate and its synergistic mechanism in the co-existing system of xanthate and Cr(VI), the photocatalyst of coal gangue/bismuth vanadate (CG/BiVO4) was used, xanthate and Cr(VI) coexisting systems were studied by photocatalytic activity test, UV, FTIR, ion chromatography and quenching experiments, the photooxidation of xanthate and photoreduction of Cr(VI) and their synergistic mechanism were explored. The results showed that there was a significant synergistic effect between the photo-oxidation of xanthate and photo-reduction of Cr(VI) in the co-existence system of xanthate and Cr(VI). Then, at the xanthate of 25 mg/L and the pH value of 7, with the dosage of catalyst being 1. 5 g/L, at the Cr(VI) of 2.0 mg/L, the removal rate of xanthate and Cr(VI) by CG/BiVO4 were the best during a period of 480 min, reaching 98.81% and 88.80% respectively. The predicted degradation rate of xanthate was 94.79% by response surface methodology, lower 3.82% than the actual degradation rate, which indicated that the model can be used to predict the degradation of xanthate in the co-existing system. In the co-existing system, the vibration of C=S was changed first, followed by C—O—C, S—H, S—C—S, butyl, and the intermediate product peroxy xanthate (ROCSSO−) was formed after the visible light illumination 3 h , the highest conversion of sulfur was reached 97.94% after the visible light illumination 7 h. The synergistic mechanism analysis showed that the photogenerated e− were rapidly captured in the photo-reduction of Cr(VI) and photogenerated h+ were consumed by xanthate photodegradation. The photogenic electron and hole pairs were consumed,on the one hand, due to the inhibition of photogenerated electrons and holes recombination, the lifetime of photogenerated electron and hole pairs were prolonged, on the other hand, the rapid consumption of photogenerated electron-hole pairs accelerates the conversion of light energy to chemical energy, generating a large number of photogenerated electron -hole pairs, therefor promoting the synergistic removal of xanthate and Cr(VI) .
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Abstract:
Thermal conductive composites have a wide range of applications in the fields of electronic packaging, motor materials, batteries and heat exchange equipment. Polyvinylidene fluoride (PVDF) has excellent electrical properties, good mechanical strength and high temperature resistance. It is one of the ideal materials for applications in electronics, aerospace and other industries. However, the low thermal conductivity restricts its further development. It is urgent to develop PVDF-based high thermal conductivity composites. The key to its preparation is how to select high thermal conductivity fillers, design thermal conduction pathways, and regulate interface thermal resistance. Based on the theoretical knowledge of the mechanism, model, equation and numerical simulation of polymer-based thermal conductive composites, combined with the crystal structure of PVDF, this paper introduces the current development level of thermal conductivity of PVDF-based thermal conductive composites, and the different effects of various fillers and preparation processes on their thermal conductivity. The latest research progress of high thermal conductivity PVDF composites is reviewed from the perspectives of composite strategy, network structure and interface bonding. In addition, its future development is also prospected.
Thermal conductive composites have a wide range of applications in the fields of electronic packaging, motor materials, batteries and heat exchange equipment. Polyvinylidene fluoride (PVDF) has excellent electrical properties, good mechanical strength and high temperature resistance. It is one of the ideal materials for applications in electronics, aerospace and other industries. However, the low thermal conductivity restricts its further development. It is urgent to develop PVDF-based high thermal conductivity composites. The key to its preparation is how to select high thermal conductivity fillers, design thermal conduction pathways, and regulate interface thermal resistance. Based on the theoretical knowledge of the mechanism, model, equation and numerical simulation of polymer-based thermal conductive composites, combined with the crystal structure of PVDF, this paper introduces the current development level of thermal conductivity of PVDF-based thermal conductive composites, and the different effects of various fillers and preparation processes on their thermal conductivity. The latest research progress of high thermal conductivity PVDF composites is reviewed from the perspectives of composite strategy, network structure and interface bonding. In addition, its future development is also prospected.
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Abstract:
Carbon fiber reinforced thermoplastic resin matrix composites (CFRTP) are sensitive to temperature change. A composite heat source model for the peripheral milling process of CF/PEEK thermoplastic composites was established, which included the plastic deformation of anisotropic materials and the multi-faceted friction from tool-workpiece and tool-chip. The cutting heat distribution ratio of tool-chip-workpiece was solved when cutting thermoplastic composites in different fiber orientations. Finally, a prediction model for the peripheral milling temperature of thermoplastic composite materials was constructed, and the effects of process parameters such as fiber orientations, cutting speed and feed rate were analyzed. Through experimental verification, the average prediction error of the model is less than 11.5%. The results show that a higher proportion of heat flows into the workpiece when performing machining with a large cutting angle, resulting in higher milling temperatures. With the increase of cutting speed, the milling temperature first increases and then decreases, and the critical value is around v=100 m/min; As the feed rate increases, the overall milling temperature shows a downward trend. When the feed rate increases from 0.01 mm/r to 0.1 mm/r, the milling temperature decreases by more than 40%.
Carbon fiber reinforced thermoplastic resin matrix composites (CFRTP) are sensitive to temperature change. A composite heat source model for the peripheral milling process of CF/PEEK thermoplastic composites was established, which included the plastic deformation of anisotropic materials and the multi-faceted friction from tool-workpiece and tool-chip. The cutting heat distribution ratio of tool-chip-workpiece was solved when cutting thermoplastic composites in different fiber orientations. Finally, a prediction model for the peripheral milling temperature of thermoplastic composite materials was constructed, and the effects of process parameters such as fiber orientations, cutting speed and feed rate were analyzed. Through experimental verification, the average prediction error of the model is less than 11.5%. The results show that a higher proportion of heat flows into the workpiece when performing machining with a large cutting angle, resulting in higher milling temperatures. With the increase of cutting speed, the milling temperature first increases and then decreases, and the critical value is around v=100 m/min; As the feed rate increases, the overall milling temperature shows a downward trend. When the feed rate increases from 0.01 mm/r to 0.1 mm/r, the milling temperature decreases by more than 40%.
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Abstract:
Thermal expansion coefficient (TEC) is an important thermodynamic parameter of high-temperature resistant composites. The evolution behavior of the TEC of damaged 2D-C/SiC composites with ambient temperature was studied by theoretical model and experimental tests for the phenomenon of matrix cracking and interface debonding, which affects the thermal expansion deformation of the material under service condition. Firstly, the three-dimensional thermal mismatch stress calculation model of constituents was given based on minicomposite model. Secondly, matrix cracking and interface debonding were introduced, and the analytical expressions for axial and radial TECs of minicomposite were derived by considering thermal expansion difference between the fibers and matrix, transverse isotropy of fibers and the Poisson effect. Thirdly, based on the [0/90] cross-ply laminate model and the macro-strain consistency assumption, a predictive model was established towards the apparent TEC of damaged 2D-C/SiC composites. Finally, the present model was compared with the classical Schapery model and experimental data, and the main influencing factors of TEC were analyzed. Parameter analysis indicate that the apparent TEC of the material is affected by matrix crack spacing, interface debonding ratio, porosity, elastic modulus and TEC of the constituents, among which the influence of the matrix expansion coefficient is particularly significant; the verification results show that the proposed model is reasonable and correct, and the predicted results are in good agreement with the classical model and experimental curve.
Thermal expansion coefficient (TEC) is an important thermodynamic parameter of high-temperature resistant composites. The evolution behavior of the TEC of damaged 2D-C/SiC composites with ambient temperature was studied by theoretical model and experimental tests for the phenomenon of matrix cracking and interface debonding, which affects the thermal expansion deformation of the material under service condition. Firstly, the three-dimensional thermal mismatch stress calculation model of constituents was given based on minicomposite model. Secondly, matrix cracking and interface debonding were introduced, and the analytical expressions for axial and radial TECs of minicomposite were derived by considering thermal expansion difference between the fibers and matrix, transverse isotropy of fibers and the Poisson effect. Thirdly, based on the [0/90] cross-ply laminate model and the macro-strain consistency assumption, a predictive model was established towards the apparent TEC of damaged 2D-C/SiC composites. Finally, the present model was compared with the classical Schapery model and experimental data, and the main influencing factors of TEC were analyzed. Parameter analysis indicate that the apparent TEC of the material is affected by matrix crack spacing, interface debonding ratio, porosity, elastic modulus and TEC of the constituents, among which the influence of the matrix expansion coefficient is particularly significant; the verification results show that the proposed model is reasonable and correct, and the predicted results are in good agreement with the classical model and experimental curve.
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Abstract:
In order to study the mechanical properties of ultra-high toughness cementitious composites (UHTCC) after temperatures of 200-−100℃, UHTCC with different fiber volume content was designed. The basic mechanical properties of UHTCC after medium-high temperatures and cryogenic temperatures were tested, and the mechanical properties of UHTCC after medium-high temperatures and cryogenic temperatures were evaluated by parameters such as strength and deformation of UHTCC. The results show that the incorporation of fibers can effectively improve the brittleness of the material and enhance the toughness of the material. The temperature effect makes the initial defects appear inside the material, which has a significant effect on the mechanical properties of UHTCC, and the effect of low temperature is significantly higher than that of high temperature. When the temperature is reduced to -100℃, the strength of UHTCC is reduced by about 71% at most, and the deformation is reduced by about 92% at most, but the temperature has no significant effect on the Poisson 's ratio of UHTCC. On this basis, the regression model of axial compression and axial tensile stress-strain relationship of UHTCC after medium-high temperatures and cryogenic temperatures is proposed, which provides a reference for the performance design and engineering application of UHTCC materials at extreme temperatures.
In order to study the mechanical properties of ultra-high toughness cementitious composites (UHTCC) after temperatures of 200-−100℃, UHTCC with different fiber volume content was designed. The basic mechanical properties of UHTCC after medium-high temperatures and cryogenic temperatures were tested, and the mechanical properties of UHTCC after medium-high temperatures and cryogenic temperatures were evaluated by parameters such as strength and deformation of UHTCC. The results show that the incorporation of fibers can effectively improve the brittleness of the material and enhance the toughness of the material. The temperature effect makes the initial defects appear inside the material, which has a significant effect on the mechanical properties of UHTCC, and the effect of low temperature is significantly higher than that of high temperature. When the temperature is reduced to -100℃, the strength of UHTCC is reduced by about 71% at most, and the deformation is reduced by about 92% at most, but the temperature has no significant effect on the Poisson 's ratio of UHTCC. On this basis, the regression model of axial compression and axial tensile stress-strain relationship of UHTCC after medium-high temperatures and cryogenic temperatures is proposed, which provides a reference for the performance design and engineering application of UHTCC materials at extreme temperatures.
Effect of graphene quantum dots on fluidity, strength and salt corrosion resistance of cement mortar
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Abstract:
The effect of dispersion of graphene quantum dost (GQDs) in saturated calcium hydroxide solution (CH) simulating cement hydration pore fluid was investigated by absorbance test and static settlement test, and the effect of workability, mechanical properties and durability of GQDs blended mortar was studied. The absorbance test and static settling test show that GQDs has excellent dispersion stability in saturated CH solution, and the workability test shows that GQDs has almost no negative effect on the flowability of cement mortar. Mechanical performance tests shows that the 28d flexural and compressive strength of GQDs increase by 12.3% and 12.5%, respectively, compared with ordinary cement mortar at the optimum dose of 0.04wt%, the seepage pressure increases by 175%, and the 120d compressive corrosion resistance coefficient increases by 14.3%. Microstructure tests show that GQDs could improve pore size distribution, fill nano-pores and improve the compactness of cement mortar.
The effect of dispersion of graphene quantum dost (GQDs) in saturated calcium hydroxide solution (CH) simulating cement hydration pore fluid was investigated by absorbance test and static settlement test, and the effect of workability, mechanical properties and durability of GQDs blended mortar was studied. The absorbance test and static settling test show that GQDs has excellent dispersion stability in saturated CH solution, and the workability test shows that GQDs has almost no negative effect on the flowability of cement mortar. Mechanical performance tests shows that the 28d flexural and compressive strength of GQDs increase by 12.3% and 12.5%, respectively, compared with ordinary cement mortar at the optimum dose of 0.04wt%, the seepage pressure increases by 175%, and the 120d compressive corrosion resistance coefficient increases by 14.3%. Microstructure tests show that GQDs could improve pore size distribution, fill nano-pores and improve the compactness of cement mortar.
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The integrally formed GFRP connection is the key structural component of the transmission tower's GFRP line-suspension module, requiring investigation into its capacities. Initially, two typical connections were examined experimentally, yielding mechanical properties including load-displacement curves and failure modes. Subsequently, a finite element model based on progressive damage evolution was established. Using the experimentally validated model, sensitivity analyses on the flexural capacity in relation to parameters such as the ratio of tensile strength Yt in the direction of the fiber to shear strength SL, the ratio of main tube diameter D to thickness T, the connection beam width B, and thickness w were conducted. Based on Hashin's failure criterion and regression analysis, an approximating equation for the connection's flexural capacity was derived, followed by a reliability analysis. The results indicate a good consistency between the experimental and the finite element analysis (FEA) results. The primary failure mode is the tension fracture of the matrix of the GFRP main tube near the connection. With increasing Yt/SL, the location of failure moves from the connection to the middle of the main tube gradually, showing a corresponding decrease in load-bearing capacity. The mean value and the coefficient of variation of the ratio of approximated capacity to FEA result are 1.032 and 6.80% respectively, and the flexural capacity derived for design has an assurance rate of 99.9%.
The integrally formed GFRP connection is the key structural component of the transmission tower's GFRP line-suspension module, requiring investigation into its capacities. Initially, two typical connections were examined experimentally, yielding mechanical properties including load-displacement curves and failure modes. Subsequently, a finite element model based on progressive damage evolution was established. Using the experimentally validated model, sensitivity analyses on the flexural capacity in relation to parameters such as the ratio of tensile strength Yt in the direction of the fiber to shear strength SL, the ratio of main tube diameter D to thickness T, the connection beam width B, and thickness w were conducted. Based on Hashin's failure criterion and regression analysis, an approximating equation for the connection's flexural capacity was derived, followed by a reliability analysis. The results indicate a good consistency between the experimental and the finite element analysis (FEA) results. The primary failure mode is the tension fracture of the matrix of the GFRP main tube near the connection. With increasing Yt/SL, the location of failure moves from the connection to the middle of the main tube gradually, showing a corresponding decrease in load-bearing capacity. The mean value and the coefficient of variation of the ratio of approximated capacity to FEA result are 1.032 and 6.80% respectively, and the flexural capacity derived for design has an assurance rate of 99.9%.
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To study the sulfate resistance performance of hybrid fiber reinforced rubber concrete (HF/RC), the apparent phenomena, mass loss, ultrasonic parameters and compressive strength of normal concrete (NC) and HF/RC were analyzed during 240 dry-wet cycles under sulfate environment. SEM and XRD were used to analyze the microstructure and phase composition of the specimen under sulfate attack. The results show that with the increase of dry-wet cycles, the mass and compressive strength of NC and HF/RC specimens increase firstly and then decrease. Ultrasonic parameters are closely related to compressive strength and corrosion resistance coefficient. In the early stage of erosion, SO4 2− reacts with the cementitious material to fill the original pores, and the compactness of the matrix is improved. With the continuous consumption of cementitious materials, voids and pores appear in the matrix due to the physical erosion caused by repeated crystallization of sodium sulfate and the chemical erosion caused by sulfate. Rubber particles and hybrid fibers delay the emergence and development of crack and slow down SO4 2− diffusion. The generation of expansive products is inhibited, and the development of surface cracks induced by crystallization stress is delayed. The damage degree of HF/RC in each stages of sulfate erosion is better than that of NC. After 240 dry-wet cycles, the compressive strength loss rate of NC is 31.0% while that of HF/RC is 21.13%.
To study the sulfate resistance performance of hybrid fiber reinforced rubber concrete (HF/RC), the apparent phenomena, mass loss, ultrasonic parameters and compressive strength of normal concrete (NC) and HF/RC were analyzed during 240 dry-wet cycles under sulfate environment. SEM and XRD were used to analyze the microstructure and phase composition of the specimen under sulfate attack. The results show that with the increase of dry-wet cycles, the mass and compressive strength of NC and HF/RC specimens increase firstly and then decrease. Ultrasonic parameters are closely related to compressive strength and corrosion resistance coefficient. In the early stage of erosion, SO4 2− reacts with the cementitious material to fill the original pores, and the compactness of the matrix is improved. With the continuous consumption of cementitious materials, voids and pores appear in the matrix due to the physical erosion caused by repeated crystallization of sodium sulfate and the chemical erosion caused by sulfate. Rubber particles and hybrid fibers delay the emergence and development of crack and slow down SO4 2− diffusion. The generation of expansive products is inhibited, and the development of surface cracks induced by crystallization stress is delayed. The damage degree of HF/RC in each stages of sulfate erosion is better than that of NC. After 240 dry-wet cycles, the compressive strength loss rate of NC is 31.0% while that of HF/RC is 21.13%.
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Textiles are widely used for drug loading because of their large specific surface area, good flexibility, wide applicability, good loading of drugs and slow release and controlled release ability. The preparation methods of drug-loaded textiles mainly include spinning method, finishing method and composite method. The preparation methods of drug-loaded textiles were used as the starting point to classify the drug-loaded textiles, the preparation methods, drug release characteristics, applicability and current research status of each type of drug-loaded textiles were described, the preparation characteristics, advantages and disadvantages of preparation methods of each type of drug-loaded textiles were summarized, and finally the future research directions of drug-loaded textiles were proposed, to provide reference for further research on drug-loaded textiles and their preparation methods.
Textiles are widely used for drug loading because of their large specific surface area, good flexibility, wide applicability, good loading of drugs and slow release and controlled release ability. The preparation methods of drug-loaded textiles mainly include spinning method, finishing method and composite method. The preparation methods of drug-loaded textiles were used as the starting point to classify the drug-loaded textiles, the preparation methods, drug release characteristics, applicability and current research status of each type of drug-loaded textiles were described, the preparation characteristics, advantages and disadvantages of preparation methods of each type of drug-loaded textiles were summarized, and finally the future research directions of drug-loaded textiles were proposed, to provide reference for further research on drug-loaded textiles and their preparation methods.
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Microencapsulated phase change materials (MPCM) can effectively prevent leakage and corrosion of phase change materials, which are widely utilized in the fields of solar energy utilization, thermo-regulated fibers and fabrics, energy saving buildings and heat transfer fluids. However, there is a problem that the core-shell structure of conventional microencapsulated phase change materials weakens the photothermal conversion performance. The poor performance can be effectively improved by modifying microencapsulated phase change materials with the addition of photothermal materials. In this paper, the materials of MPCM’s core and shell and their characteristics are summarized. The characteristics and photothermal conversion mechanisms of photothermal materials, including organic photothermal materials, carbon-based materials, semiconductor materials, metal-based materials and other photothermal materials, are illustrated. Additionally, photothermal conversion efficiency η is introduced to evaluate the enhancement of photothermal properties of modified MPCM with different modified photothermal materials. Finally, future trend of modified MPCM with photothermal conversion is prospected.
Microencapsulated phase change materials (MPCM) can effectively prevent leakage and corrosion of phase change materials, which are widely utilized in the fields of solar energy utilization, thermo-regulated fibers and fabrics, energy saving buildings and heat transfer fluids. However, there is a problem that the core-shell structure of conventional microencapsulated phase change materials weakens the photothermal conversion performance. The poor performance can be effectively improved by modifying microencapsulated phase change materials with the addition of photothermal materials. In this paper, the materials of MPCM’s core and shell and their characteristics are summarized. The characteristics and photothermal conversion mechanisms of photothermal materials, including organic photothermal materials, carbon-based materials, semiconductor materials, metal-based materials and other photothermal materials, are illustrated. Additionally, photothermal conversion efficiency η is introduced to evaluate the enhancement of photothermal properties of modified MPCM with different modified photothermal materials. Finally, future trend of modified MPCM with photothermal conversion is prospected.
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MXene materials have been widely used in many fields, such as electromagnetic shielding, sensing, and wastewater treatment. The excellent electrochemical properties of MXene makes it demonstrate broad application prospects in the field of energy storage as well. However, the self-stacking and easy oxidation characteristics of MXene limit its further development. The assembly of MXene into three-dimensional (3D) structural composites is one of the effective way to solve the above problems. The 3D porous structure can provide more channels and active sites for ion transport or storage, which can effectively improve the electrochemical performance. This article reviews the recent researches of MXene composite aerogels. The preparation methods and applications of MXene composite aerogels in energy storage, such as batteries and supercapacitors, are discussed in detail. Finally, the prospects for its future development direction were also presented.
MXene materials have been widely used in many fields, such as electromagnetic shielding, sensing, and wastewater treatment. The excellent electrochemical properties of MXene makes it demonstrate broad application prospects in the field of energy storage as well. However, the self-stacking and easy oxidation characteristics of MXene limit its further development. The assembly of MXene into three-dimensional (3D) structural composites is one of the effective way to solve the above problems. The 3D porous structure can provide more channels and active sites for ion transport or storage, which can effectively improve the electrochemical performance. This article reviews the recent researches of MXene composite aerogels. The preparation methods and applications of MXene composite aerogels in energy storage, such as batteries and supercapacitors, are discussed in detail. Finally, the prospects for its future development direction were also presented.
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Waste corrugated paper (WCP) was used as raw material, gelatin (G) and phytic acid (PA) were used as modifiers,and high energy absorption aerogel was prepared by sol-gel method.The effects of gelatin dosage, phytic acid dosage, and reaction temperature on the mechanical properties of dual-crosslinked modified waste paper-based aerogels were investigated. The structural and performance changes of aerogels before and after single modification with gelatin and dual modification with gelatin and phytic acid were characterized using SEM, FTIR, XRD, and TGA..The results showed that the modified monomer was successfully crosslinked onto the waste paper fiber,and the double crosslinked waste paper based aerogel presented a three-dimensional network structure.Compared with the unmodified and single modified waste paper based aerogel,it had higher thermal stability,excellent thermal insulation (0.045W·m−1·K−1) and super energy absorption (absorption energy per unit volume was 253.45 kJ/m3 at 70% strain),The energy absorption capacity is 11.26 and 2.7 times higher than that of expanded polyethylene (EPE) and ethylene vinyl acetate (EVA),respectively.As a green cushioning material in the packaging and transportation process,it has broad application prospects.
Waste corrugated paper (WCP) was used as raw material, gelatin (G) and phytic acid (PA) were used as modifiers,and high energy absorption aerogel was prepared by sol-gel method.The effects of gelatin dosage, phytic acid dosage, and reaction temperature on the mechanical properties of dual-crosslinked modified waste paper-based aerogels were investigated. The structural and performance changes of aerogels before and after single modification with gelatin and dual modification with gelatin and phytic acid were characterized using SEM, FTIR, XRD, and TGA..The results showed that the modified monomer was successfully crosslinked onto the waste paper fiber,and the double crosslinked waste paper based aerogel presented a three-dimensional network structure.Compared with the unmodified and single modified waste paper based aerogel,it had higher thermal stability,excellent thermal insulation (0.045W·m−1·K−1) and super energy absorption (absorption energy per unit volume was 253.45 kJ/m3 at 70% strain),The energy absorption capacity is 11.26 and 2.7 times higher than that of expanded polyethylene (EPE) and ethylene vinyl acetate (EVA),respectively.As a green cushioning material in the packaging and transportation process,it has broad application prospects.
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Thermal insulation of buildings plays an important role to reduce energy consumption for maintaining an optimal atmosphere inside the building. Hence, it is crucial to improve the thermal insulation performance of the building materials, especially to achieve energy savings through the reduction of energy losses for heating–cooling purposes. Therefore, the research on building materials with excellent thermal insulation properties has become one of the focuses of current thermal insulation research. Compared with traditional thermal insulation building materials, biomass-based cellulose thermal insulation aerogel has superior physical and chemical properties, such as low thermal conductivity, high specific surface area, renewable, cost-effective and environment-friendly. It is an ideal new building material for future building energy saving technology. In this paper, the preparation technology, research status, existing problems and application of biomass-based cellulose thermal insulation aerogel in building materials (roof, interior and exterior walls and glass, etc.) in recent years are reviewed. Finally, the challenges faced by biomass-based cellulose aerogel in the application of thermal insulation materials are briefly discussed, and its future development direction is prospected.
Thermal insulation of buildings plays an important role to reduce energy consumption for maintaining an optimal atmosphere inside the building. Hence, it is crucial to improve the thermal insulation performance of the building materials, especially to achieve energy savings through the reduction of energy losses for heating–cooling purposes. Therefore, the research on building materials with excellent thermal insulation properties has become one of the focuses of current thermal insulation research. Compared with traditional thermal insulation building materials, biomass-based cellulose thermal insulation aerogel has superior physical and chemical properties, such as low thermal conductivity, high specific surface area, renewable, cost-effective and environment-friendly. It is an ideal new building material for future building energy saving technology. In this paper, the preparation technology, research status, existing problems and application of biomass-based cellulose thermal insulation aerogel in building materials (roof, interior and exterior walls and glass, etc.) in recent years are reviewed. Finally, the challenges faced by biomass-based cellulose aerogel in the application of thermal insulation materials are briefly discussed, and its future development direction is prospected.
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A large amount of industrial solid waste phosphogypsum has caused serious pollution to the environment. At the same time, the contradiction between the traditional cement industry with high energy consumption and the realization of the “double carbon” target has become increasingly prominent. Some studies have shown that the cementitious material based on phosphogypsum can replace part of ordinary Portland cement, but its working and mechanical properties are poor when using raw materials without treatment. In this paper, the green and high strength phosphogypsum based cementitious materials were prepared by using common industrial solid wastes such as original phosphogypsum, slag, steel slag and limestone. The results show that chelates are formed by mixing 0.5% plant protein with Ca2+ in the gelling system to produce a coordination compound covering the surface of gypsum nucleus, which not only delays the setting time of the gelling material, promotes the hydration reaction degree, but also improves its mechanical properties. The microstructure and composition analysis show that phosphogypsum is mainly used as a filler in the cementitious material, the slag is activated by the alkali of steel slag, and the limestone promotes the hydration reaction while providing Ca2+. Based on the original solid waste phosphogypsum, using the mixture ratio of mphosphogypsum∶mslag∶msteel slag∶mlimestone = 0.45∶0.35∶0.1∶0.1, 28 d flexural strength of mortar specimen is 7.0 MPa, compressive strength is 39.1 MPa, and softening coefficient is 0.91, which is very close to the performance of P·O 42.5 grade ordinary Portland cement.
A large amount of industrial solid waste phosphogypsum has caused serious pollution to the environment. At the same time, the contradiction between the traditional cement industry with high energy consumption and the realization of the “double carbon” target has become increasingly prominent. Some studies have shown that the cementitious material based on phosphogypsum can replace part of ordinary Portland cement, but its working and mechanical properties are poor when using raw materials without treatment. In this paper, the green and high strength phosphogypsum based cementitious materials were prepared by using common industrial solid wastes such as original phosphogypsum, slag, steel slag and limestone. The results show that chelates are formed by mixing 0.5% plant protein with Ca2+ in the gelling system to produce a coordination compound covering the surface of gypsum nucleus, which not only delays the setting time of the gelling material, promotes the hydration reaction degree, but also improves its mechanical properties. The microstructure and composition analysis show that phosphogypsum is mainly used as a filler in the cementitious material, the slag is activated by the alkali of steel slag, and the limestone promotes the hydration reaction while providing Ca2+. Based on the original solid waste phosphogypsum, using the mixture ratio of mphosphogypsum∶mslag∶msteel slag∶mlimestone = 0.45∶0.35∶0.1∶0.1, 28 d flexural strength of mortar specimen is 7.0 MPa, compressive strength is 39.1 MPa, and softening coefficient is 0.91, which is very close to the performance of P·O 42.5 grade ordinary Portland cement.
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Nanostructured catalytic materials are considered to be a favorable design concept for various energy conversion and storage systems. Nanosized metal catalysts supported on oxide scaffolds have been adopted in numerous fields, including fuel cells, gas sensors, and chemical reforming devices. Nevertheless, nanometal catalysts often suffer from durability issues. Although surface-decorated nanometal catalysts can deliver sufficient catalytic activity, some of them still exhibit durability issues in severe operating environments. Recently, nanocatalysts produced by in situ exsolution have been demonstrated to overcome the practical limitations of conventional nanometal catalysts. The exsolution is defined as a process in which a catalytically active dopant in perovskite oxide is exsolved on its surface as highly dispersed nanometal catalysts. In particular, exsolution nanocatalysts embedded on perovskite oxides exhibit higher nanoparticle densities and greater resistance to particle agglomeration than conventional nanometal catalysts. This perspective presents an overview of recent advances in exsolution materials for energy applications including fundamental mechanisms, design strategies for host oxides, and practical applications. The future prospects of these materials and the scope for further optimization are also discussed.
Nanostructured catalytic materials are considered to be a favorable design concept for various energy conversion and storage systems. Nanosized metal catalysts supported on oxide scaffolds have been adopted in numerous fields, including fuel cells, gas sensors, and chemical reforming devices. Nevertheless, nanometal catalysts often suffer from durability issues. Although surface-decorated nanometal catalysts can deliver sufficient catalytic activity, some of them still exhibit durability issues in severe operating environments. Recently, nanocatalysts produced by in situ exsolution have been demonstrated to overcome the practical limitations of conventional nanometal catalysts. The exsolution is defined as a process in which a catalytically active dopant in perovskite oxide is exsolved on its surface as highly dispersed nanometal catalysts. In particular, exsolution nanocatalysts embedded on perovskite oxides exhibit higher nanoparticle densities and greater resistance to particle agglomeration than conventional nanometal catalysts. This perspective presents an overview of recent advances in exsolution materials for energy applications including fundamental mechanisms, design strategies for host oxides, and practical applications. The future prospects of these materials and the scope for further optimization are also discussed.
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Carbon dots (CDs) have advantages such as low toxicity, water tolerance, good biocompatibility, easy modification, excellent electrochemical activity, and optical properties. CDs can be used for the modification of polymer materials, endowing them with good optical properties and various other functionalities. Adding CDs to polyvinyl alcohol (PVA) not only effectively improves the mechanical properties and thermal stability of PVA, but also endows PVA with new properties, such as improved conductivity, dielectric properties, thermoelectric properties, and other electrical parameters, optical properties such as fluorescence, phosphorescence, and UV resistance, antibacterial, antioxidant, and water resistance, which make PVA stand out in the fields of electromagnetic shielding, storage devices, capacitors, sensors, optical devices and functional packaging bags. This article focuses on the latest research progress in the properties of PVA modified with CDs (CDs/PVA), and prospects the future application of CDs/PVA, which is of great significance for expanding its application fields.
Carbon dots (CDs) have advantages such as low toxicity, water tolerance, good biocompatibility, easy modification, excellent electrochemical activity, and optical properties. CDs can be used for the modification of polymer materials, endowing them with good optical properties and various other functionalities. Adding CDs to polyvinyl alcohol (PVA) not only effectively improves the mechanical properties and thermal stability of PVA, but also endows PVA with new properties, such as improved conductivity, dielectric properties, thermoelectric properties, and other electrical parameters, optical properties such as fluorescence, phosphorescence, and UV resistance, antibacterial, antioxidant, and water resistance, which make PVA stand out in the fields of electromagnetic shielding, storage devices, capacitors, sensors, optical devices and functional packaging bags. This article focuses on the latest research progress in the properties of PVA modified with CDs (CDs/PVA), and prospects the future application of CDs/PVA, which is of great significance for expanding its application fields.
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In this paper, it is proposed to prepare a high hardness wear-resistant layer on the surface of 17-4PH stainless steel, and in order to alleviate the problem of cracking between the high hardness cladding layer and the substrate, it is proposed to prepare a bionic gradient hardness surface cladding structure. The use of manual electric arc welding in the 17-4PH stainless steel surface preparation of bionic gradient hardness high strength layer, the choice of D322 electrode and D707 electrode were used as a transition layer and high strength layer in the 17-4PH stainless steel surface for the preparation of the bionic gradient hardness high strength layer, the use of optical microscopy, Vickers hardness tester, X-ray diffractometer, impact testing machine on the high strength layer of the microstructure, microhardness and other properties were Characterization. The results show that the bionic gradient hardness high-strength layer prepared on the surface of 17-4PH stainless steel has a uniform organization and good interfacial metallurgical bonding; the organization of the bionic gradient hardness high-strength layer mainly consists of martensite, austenite, WC and carbide; the bionic gradient hardness high-strength layer mainly consists of Fe-Cr, WC, γ-Fe, with an average hardness of 726.5 HV0.5, which is a significant improvement compared with that of the substrate; the bionic gradient hardness high-strength layer on the surface of 17-4PH stainless steel is also a good example of a bionic gradient hardness layer. 4PH stainless steel surface bionic gradient hardness high-strength layer average impact absorption power Akv is 12.9J, the main reason for the reduction of its impact absorption power is due to the different properties between the layers.
In this paper, it is proposed to prepare a high hardness wear-resistant layer on the surface of 17-4PH stainless steel, and in order to alleviate the problem of cracking between the high hardness cladding layer and the substrate, it is proposed to prepare a bionic gradient hardness surface cladding structure. The use of manual electric arc welding in the 17-4PH stainless steel surface preparation of bionic gradient hardness high strength layer, the choice of D322 electrode and D707 electrode were used as a transition layer and high strength layer in the 17-4PH stainless steel surface for the preparation of the bionic gradient hardness high strength layer, the use of optical microscopy, Vickers hardness tester, X-ray diffractometer, impact testing machine on the high strength layer of the microstructure, microhardness and other properties were Characterization. The results show that the bionic gradient hardness high-strength layer prepared on the surface of 17-4PH stainless steel has a uniform organization and good interfacial metallurgical bonding; the organization of the bionic gradient hardness high-strength layer mainly consists of martensite, austenite, WC and carbide; the bionic gradient hardness high-strength layer mainly consists of Fe-Cr, WC, γ-Fe, with an average hardness of 726.5 HV0.5, which is a significant improvement compared with that of the substrate; the bionic gradient hardness high-strength layer on the surface of 17-4PH stainless steel is also a good example of a bionic gradient hardness layer. 4PH stainless steel surface bionic gradient hardness high-strength layer average impact absorption power Akv is 12.9J, the main reason for the reduction of its impact absorption power is due to the different properties between the layers.
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The specific aerogel geometry has a crucial impact on the function of aerogel materials in application scenarios. However, conventional manufacturing technology remains challenging in the customized shaping of aerogels due to the fragility of aerogels, time-consuming manufacturing cycles, and poor designability of molds. Direct-write 3D printing technology has been applied to achieve the on-demand shaping of aerogels, imparting aerogels with compatible material composition and functional characteristics. In this work, a direct-write 3D printing strategy based on dual-channel intermixing extrusion was proposed to prepare polyimide-silica (OBS) aerogel composites. Benefiting from the efficient fluid diffusion intermixing between inks and catalysts during extrusion processes, chemical imidization solidification can be successfully achieved, and 3D-printed OBS aerogel composites show high structural integrity and high shape fidelity. Depending on the advantages of the spatial assembly of direct-write 3D printing technology, OBS aerogel composites have formed multi-scale morphologies of millimeters, micrometers, and nanometers. In micron scale, the composite structure enables 3D-printed OBS aerogel composites to display excellent mechanical properties (Young’s modulus up to 14.4 MPa). Meanwhile, nanoscale pore structure features, such as low density (0.207 g·cm−3), high surface area (373 m2·g−1), and concentrated pore diameter distribution (20~30 nm), impart 3D-printed OBS aerogel composites with excellent thermal insulation performance (thermal conductivity as low as 21.25 mW·m−1·K−1). Although our work only focuses on OBS aerogel composites, the successful implementation of this 3D printing strategy would provide guidelines for additive manufacturing of other aerogel composites.
The specific aerogel geometry has a crucial impact on the function of aerogel materials in application scenarios. However, conventional manufacturing technology remains challenging in the customized shaping of aerogels due to the fragility of aerogels, time-consuming manufacturing cycles, and poor designability of molds. Direct-write 3D printing technology has been applied to achieve the on-demand shaping of aerogels, imparting aerogels with compatible material composition and functional characteristics. In this work, a direct-write 3D printing strategy based on dual-channel intermixing extrusion was proposed to prepare polyimide-silica (OBS) aerogel composites. Benefiting from the efficient fluid diffusion intermixing between inks and catalysts during extrusion processes, chemical imidization solidification can be successfully achieved, and 3D-printed OBS aerogel composites show high structural integrity and high shape fidelity. Depending on the advantages of the spatial assembly of direct-write 3D printing technology, OBS aerogel composites have formed multi-scale morphologies of millimeters, micrometers, and nanometers. In micron scale, the composite structure enables 3D-printed OBS aerogel composites to display excellent mechanical properties (Young’s modulus up to 14.4 MPa). Meanwhile, nanoscale pore structure features, such as low density (0.207 g·cm−3), high surface area (373 m2·g−1), and concentrated pore diameter distribution (20~30 nm), impart 3D-printed OBS aerogel composites with excellent thermal insulation performance (thermal conductivity as low as 21.25 mW·m−1·K−1). Although our work only focuses on OBS aerogel composites, the successful implementation of this 3D printing strategy would provide guidelines for additive manufacturing of other aerogel composites.
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Thermoplastic polyester elastomer (TPEE) is extremely flammable, which seriously hinders its application in the fields of electronics and electrical, wire sheath, charging station, etc. TPEE composites with high flame retardancy were prepared by adding aluminum diethylphosphinate (AlPi) and melamine polyphosphate (MPP) flame retardant into TPEE matrix through internal mixing and hot pressing process. The flame retardancy of the TPEE composites was studied by limiting oxygen index (LOI), vertical burning (UL-94) and cone calorimeter (CONE) tests. The results showed that AlPi combined with MPP can achieve high-efficiency flame retardancy of TPEE composites. In addition, the TPEE composite with 22wt% AlPi and MPP passed the UL-94 V-0 rating and its LOI value increased from 19.3% to 31.5%, accompanied with 27.6% reduction in the total heat release and 64.8% reduction of the peak heat release rate compared to pure TPEE. The thermal stabilities, mechanical properties, and electrical properties of the TPEE composites, as well as the microscopic morphology of the composites before and after ablation were studied by thermogravimetric analyzer (TGA), SEM, universal testing machine and electrical insulation test. The results indicated that the flame retardant mechanism of the composite flame retardant system is the barrier action of intumescent char layer in the condense phase. The composite flame retardant system can promote the decomposition of TPEE into carbon. The mechanical properties, electrical insulation properties and microtopography tests showed that the combination of AlPi and MPP can improve the electrical insulation performance, but reduce the mechanical properties of TPEE composites due to their poor compatibility with TPEE matrix.
Thermoplastic polyester elastomer (TPEE) is extremely flammable, which seriously hinders its application in the fields of electronics and electrical, wire sheath, charging station, etc. TPEE composites with high flame retardancy were prepared by adding aluminum diethylphosphinate (AlPi) and melamine polyphosphate (MPP) flame retardant into TPEE matrix through internal mixing and hot pressing process. The flame retardancy of the TPEE composites was studied by limiting oxygen index (LOI), vertical burning (UL-94) and cone calorimeter (CONE) tests. The results showed that AlPi combined with MPP can achieve high-efficiency flame retardancy of TPEE composites. In addition, the TPEE composite with 22wt% AlPi and MPP passed the UL-94 V-0 rating and its LOI value increased from 19.3% to 31.5%, accompanied with 27.6% reduction in the total heat release and 64.8% reduction of the peak heat release rate compared to pure TPEE. The thermal stabilities, mechanical properties, and electrical properties of the TPEE composites, as well as the microscopic morphology of the composites before and after ablation were studied by thermogravimetric analyzer (TGA), SEM, universal testing machine and electrical insulation test. The results indicated that the flame retardant mechanism of the composite flame retardant system is the barrier action of intumescent char layer in the condense phase. The composite flame retardant system can promote the decomposition of TPEE into carbon. The mechanical properties, electrical insulation properties and microtopography tests showed that the combination of AlPi and MPP can improve the electrical insulation performance, but reduce the mechanical properties of TPEE composites due to their poor compatibility with TPEE matrix.
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Under the background of the “dual carbon” strategy, the research progress of bio-based fluorescent intelligent materials and their multifunctional applications have attracted much attention. Cellulose is the most abundant natural polymer material in nature. Cellulose-based solid-state fluorescence sensors not only have the advantages of green, low cost, biodegradability, good hydrophilicity, good biocompatibility, and non-toxicity, but also have advantages such as portability, efficiency, long lifespan, high stability, and wide applicability compared to traditional fluorescent molecular probes. The research progress of cellulose-based solid-state fluorescent sensors prepared by chemical modification in recent years was reviewed. The mechanism of the combination of cellulose with different fluorescent molecules was clarified. Fluorescent molecules were introduced to the surface of cellulose by covalent crosslinking or introduction of functional groups. Various types of cellulose-based solid-state fluorescence sensors, including cationic, anionic, pH-type, nitroaromatic, gas-type and double (multi) re-responsive types, were introduced. The advantages of cellulose-based solid-state fluorescence sensors in environmental detection, bioimaging, food safety, fluorescence printing and anti-counterfeiting applications were also introduced. Finally, the relevant research on cellulose-based fluorescent smart sensors is discussed in detail, and their development opportunities and future challenges are prospected.
Under the background of the “dual carbon” strategy, the research progress of bio-based fluorescent intelligent materials and their multifunctional applications have attracted much attention. Cellulose is the most abundant natural polymer material in nature. Cellulose-based solid-state fluorescence sensors not only have the advantages of green, low cost, biodegradability, good hydrophilicity, good biocompatibility, and non-toxicity, but also have advantages such as portability, efficiency, long lifespan, high stability, and wide applicability compared to traditional fluorescent molecular probes. The research progress of cellulose-based solid-state fluorescent sensors prepared by chemical modification in recent years was reviewed. The mechanism of the combination of cellulose with different fluorescent molecules was clarified. Fluorescent molecules were introduced to the surface of cellulose by covalent crosslinking or introduction of functional groups. Various types of cellulose-based solid-state fluorescence sensors, including cationic, anionic, pH-type, nitroaromatic, gas-type and double (multi) re-responsive types, were introduced. The advantages of cellulose-based solid-state fluorescence sensors in environmental detection, bioimaging, food safety, fluorescence printing and anti-counterfeiting applications were also introduced. Finally, the relevant research on cellulose-based fluorescent smart sensors is discussed in detail, and their development opportunities and future challenges are prospected.
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Abstract:
Four-dimensional (4D) printing is an emerging technology that aims to endow objects produced by additive manufacturing with the ability to change shape or function over time. By converting planar precursor patterns into three-dimensional (3D) structures with complex geometric shapes, 4D printing provides a flexible and efficient manufacturing method for the field. The design of the precursor structure is a crucial factor that affects the deformation effect of 4D printing. In this article, we aim to review the development of 4D printing based on strain mismatch from the perspective of precursor structure design. Firstly, we provided a brief overview of the current research situation on 4D printing. Then, we classified research related to structural design from the perspective of precursor structures in different dimensions, providing a comprehensive overview of 4D printing by different dimensions of precursor structures. Additionally, we discussed several auxiliary design methods for the precursor structure, including theoretical calculation models and simulation analysis to predict shape transformation, as well as reverse design tools to accurately design the precursor structure. Finally, we summarized and prospected the application prospects and challenges faced by 4D printing.
Four-dimensional (4D) printing is an emerging technology that aims to endow objects produced by additive manufacturing with the ability to change shape or function over time. By converting planar precursor patterns into three-dimensional (3D) structures with complex geometric shapes, 4D printing provides a flexible and efficient manufacturing method for the field. The design of the precursor structure is a crucial factor that affects the deformation effect of 4D printing. In this article, we aim to review the development of 4D printing based on strain mismatch from the perspective of precursor structure design. Firstly, we provided a brief overview of the current research situation on 4D printing. Then, we classified research related to structural design from the perspective of precursor structures in different dimensions, providing a comprehensive overview of 4D printing by different dimensions of precursor structures. Additionally, we discussed several auxiliary design methods for the precursor structure, including theoretical calculation models and simulation analysis to predict shape transformation, as well as reverse design tools to accurately design the precursor structure. Finally, we summarized and prospected the application prospects and challenges faced by 4D printing.
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Abstract:
To improve the compression resistance and energy absorption performance of circular honeycomb (CH), two improved honeycomb, single enhanced circular honeycomb (SEH) and double enhanced circular honeycomb (DEH) were designed on the basis of CH structure, and leaf shaped supports were added horizontally and vertically. Using carbon fiber (CF) as reinforcement and polylactic acid (PLA) as matrix, continuous fiber 3D printing technology was used to manufacture test parts, and the forming path of CF bundle inside the structure was designed, PLA control group was set. The in-plane compression properties, energy absorption characteristics and deformation failure modes of the honeycomb structures were investigated by quasi-static compression tests. The results show that the specific energy absorption(SEA) of CF enhanced DEH-CF is improved by 168% compared with CH-CF. The SEA are increased by 43%, 63% and 162% and mean crushing force are increased by 52%, 62% and 96% compared with the PLA control group, respectively. The results indicate that the fiber path planning inside the CF reinforced structure would affect the stiffness and deformation behavior of the structure. The dynamic Poisson's ratio of the DEH-CF using the "strut integrated molding path" during compression remains 35% lower than that of the PLA control group.
To improve the compression resistance and energy absorption performance of circular honeycomb (CH), two improved honeycomb, single enhanced circular honeycomb (SEH) and double enhanced circular honeycomb (DEH) were designed on the basis of CH structure, and leaf shaped supports were added horizontally and vertically. Using carbon fiber (CF) as reinforcement and polylactic acid (PLA) as matrix, continuous fiber 3D printing technology was used to manufacture test parts, and the forming path of CF bundle inside the structure was designed, PLA control group was set. The in-plane compression properties, energy absorption characteristics and deformation failure modes of the honeycomb structures were investigated by quasi-static compression tests. The results show that the specific energy absorption(SEA) of CF enhanced DEH-CF is improved by 168% compared with CH-CF. The SEA are increased by 43%, 63% and 162% and mean crushing force are increased by 52%, 62% and 96% compared with the PLA control group, respectively. The results indicate that the fiber path planning inside the CF reinforced structure would affect the stiffness and deformation behavior of the structure. The dynamic Poisson's ratio of the DEH-CF using the "strut integrated molding path" during compression remains 35% lower than that of the PLA control group.
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Abstract:
In this paper, the progress made by researchers in improving the thermal conductivity of Carbon Fiber-reinforced Polymer (CFRP) composites in the past decade is summarized. Based on the principle of thermal conductivity of polymer composites, this paper focuses on the analysis of the influence of CFs on the thermal conductivity of CFRP composites, including content, length, and orientation. In addition, four methods to improve the thermal conductivity of CFRP composites are summarized, including surface modification of CFs, directional treatment of CFs, adding thermal conductive fillers and designing three-dimensional continuous thermal channels, which have an impact on the thermal conductivity of CFRP composites. Finally, the prospect of carbon fibers arranged in the same direction and combined with high thermal conductivity fillers with different shapes and sizes to construct continuous thermal conduction channels is prospected. The preparation of CFRP composites with low filling content and high thermal conductivity will become the research direction in the future, which will provide guidance for the development and optimization of the next generation of thermal conductivity materials.
In this paper, the progress made by researchers in improving the thermal conductivity of Carbon Fiber-reinforced Polymer (CFRP) composites in the past decade is summarized. Based on the principle of thermal conductivity of polymer composites, this paper focuses on the analysis of the influence of CFs on the thermal conductivity of CFRP composites, including content, length, and orientation. In addition, four methods to improve the thermal conductivity of CFRP composites are summarized, including surface modification of CFs, directional treatment of CFs, adding thermal conductive fillers and designing three-dimensional continuous thermal channels, which have an impact on the thermal conductivity of CFRP composites. Finally, the prospect of carbon fibers arranged in the same direction and combined with high thermal conductivity fillers with different shapes and sizes to construct continuous thermal conduction channels is prospected. The preparation of CFRP composites with low filling content and high thermal conductivity will become the research direction in the future, which will provide guidance for the development and optimization of the next generation of thermal conductivity materials.
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Abstract:
AGO/WEP and KGO/WEP anti-corrosion coating was prepared, using epoxy resin E-44 and three acrylic monomers as raw materials, modified by different dosages of graphene oxide (KGO: KH560/GO, AGO: A151/GO) under in-situ polymerization method. The results show that: the addition of KGO or AGO can both improve the thermal performance of the composite coating; the comprehensive performance of 0.05wt% KGO/WEP is better, the pencil hardness of the composite coating is 5 H, the impact strength is more than 50 cm, the bonding strength is 1.79 MPa, the water absorption rate is 1.06%, the contact angle is 78.05°, the color difference ΔE after 1000h UV aging is 0.75, the gloss GU is maintained well at 9.7, the coating morphology is maintained well after 240 h of chemical resistance, and the chloride ion permeability of the coating is 0.34×10−3 mg/(cm2·d). The results show that the 0.05wt% KGO/WEP coating has good comprehensive performance and a maximum bond strength is 1.91 MPa after 40 salt freeze cycles; the mass growth rate is 1.46%; the chloride ion flux at 6h is 532 C; the compressive strength loss is 18.2%. The composite coating can effectively improve the corrosion resistance of snow melting salt on the surface of concrete substrate, and has important research significance for improving the maintenance level of roads.
AGO/WEP and KGO/WEP anti-corrosion coating was prepared, using epoxy resin E-44 and three acrylic monomers as raw materials, modified by different dosages of graphene oxide (KGO: KH560/GO, AGO: A151/GO) under in-situ polymerization method. The results show that: the addition of KGO or AGO can both improve the thermal performance of the composite coating; the comprehensive performance of 0.05wt% KGO/WEP is better, the pencil hardness of the composite coating is 5 H, the impact strength is more than 50 cm, the bonding strength is 1.79 MPa, the water absorption rate is 1.06%, the contact angle is 78.05°, the color difference ΔE after 1000h UV aging is 0.75, the gloss GU is maintained well at 9.7, the coating morphology is maintained well after 240 h of chemical resistance, and the chloride ion permeability of the coating is 0.34×10−3 mg/(cm2·d). The results show that the 0.05wt% KGO/WEP coating has good comprehensive performance and a maximum bond strength is 1.91 MPa after 40 salt freeze cycles; the mass growth rate is 1.46%; the chloride ion flux at 6h is 532 C; the compressive strength loss is 18.2%. The composite coating can effectively improve the corrosion resistance of snow melting salt on the surface of concrete substrate, and has important research significance for improving the maintenance level of roads.
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Abstract:
Coal gangue as industrial solid waste, replacing all aggregates to produce concrete, is an effective way to reuse coal gangue. In this paper, all the coarse and fine aggregates of concrete were replaced by crushed coal gangue aggregate, and modified by different amounts of nano-SiO2 and polypropylene fiber (PPF). Based on the combination of macro mechanics and micro analysis, the effects of the single and combined action of nano-SiO2 and PPF on the mechanical properties and microstructure of concrete were studied. The results show that the performance of concrete is the best when the mixture of nano-SiO2 and PPF is 1.5% and 0.6 kg·m−3, respectively. Compared with the control group, the compressive strength, flexural strength and splitting strength of the concrete at 7 days increase by 21.8%, 43.5% and 44.4%, respectively. Besides, the compressive strength, flexural strength and splitting strength at 28 days increase by 20%, 44.9% and 43.6%, respectively. The microstructure analysis shows that the porosity of coal gangue concrete decreases, the hydration process is accelerated, the fractal dimension of large holes of the concrete increases from 2.9975 to 2.9990, while that of small holes decreases from 2.9852 to 2.9827, the fractal dimension of small holes decreases, and the fractal dimension of large holes increases, so that the stronger the space filling capacity, the fewer internal pores.
Coal gangue as industrial solid waste, replacing all aggregates to produce concrete, is an effective way to reuse coal gangue. In this paper, all the coarse and fine aggregates of concrete were replaced by crushed coal gangue aggregate, and modified by different amounts of nano-SiO2 and polypropylene fiber (PPF). Based on the combination of macro mechanics and micro analysis, the effects of the single and combined action of nano-SiO2 and PPF on the mechanical properties and microstructure of concrete were studied. The results show that the performance of concrete is the best when the mixture of nano-SiO2 and PPF is 1.5% and 0.6 kg·m−3, respectively. Compared with the control group, the compressive strength, flexural strength and splitting strength of the concrete at 7 days increase by 21.8%, 43.5% and 44.4%, respectively. Besides, the compressive strength, flexural strength and splitting strength at 28 days increase by 20%, 44.9% and 43.6%, respectively. The microstructure analysis shows that the porosity of coal gangue concrete decreases, the hydration process is accelerated, the fractal dimension of large holes of the concrete increases from 2.9975 to 2.9990, while that of small holes decreases from 2.9852 to 2.9827, the fractal dimension of small holes decreases, and the fractal dimension of large holes increases, so that the stronger the space filling capacity, the fewer internal pores.
Preparation and properties of 4D printed magnetoresponsive shape memory epoxy resin-based composites
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Abstract:
Ni-ACB/EP51 composites were prepared by using direct-write 3D printer with ink that was blended from epoxy resin (EP51) as the matrix, acetylene black (ACB) and nickel powder (Ni) as fillers, and polyether polyol (PPG) as toughening agent. Rheological properties and printability of ink were characterized by rheometer and direct-write 3D printer, mechanical properties, microscopic morphology, thermal properties, and shape memory properties of the material were characterized by universal tensile testing machine (UTM), scanning electron microscope (SEM), dynamic thermomechanical analyzer (DMA), and differential scanning calorimeter (DSC). The effects of fillers on properties of the ink and material were investigated. The results show that the ink can be printed well when the ACB content reaches 12%. Clogging of the printer nozzle causes discontinuous and uneven printing when Ni content reaches 16%. The toughened structure of the "island" formed after solidification significantly improves the tensile strength of the material (above 60 MPa). As Ni content increases, the effect of Ni on tensile strength changes from promoting to weakening. The shape fixation rate (Rf) decreases from 99.4% to 94.2% when Ni content increases 6% increases to 14%. Under the action of a 300KHz alternating magnetic field, the shape recovery occurs, and an increase in Ni content results in higher shape recovery rate (Rr) and recovery rate, Rr increases from 94.8% to 99.1%, and the recovery time shortens from 39 s to 17 s. The Ni-ACB/EP51 composites exhibits excellent shape memory performance and has promising application prospects in areas such as deployable structures in space, actuators, and 4D printing.
Ni-ACB/EP51 composites were prepared by using direct-write 3D printer with ink that was blended from epoxy resin (EP51) as the matrix, acetylene black (ACB) and nickel powder (Ni) as fillers, and polyether polyol (PPG) as toughening agent. Rheological properties and printability of ink were characterized by rheometer and direct-write 3D printer, mechanical properties, microscopic morphology, thermal properties, and shape memory properties of the material were characterized by universal tensile testing machine (UTM), scanning electron microscope (SEM), dynamic thermomechanical analyzer (DMA), and differential scanning calorimeter (DSC). The effects of fillers on properties of the ink and material were investigated. The results show that the ink can be printed well when the ACB content reaches 12%. Clogging of the printer nozzle causes discontinuous and uneven printing when Ni content reaches 16%. The toughened structure of the "island" formed after solidification significantly improves the tensile strength of the material (above 60 MPa). As Ni content increases, the effect of Ni on tensile strength changes from promoting to weakening. The shape fixation rate (Rf) decreases from 99.4% to 94.2% when Ni content increases 6% increases to 14%. Under the action of a 300KHz alternating magnetic field, the shape recovery occurs, and an increase in Ni content results in higher shape recovery rate (Rr) and recovery rate, Rr increases from 94.8% to 99.1%, and the recovery time shortens from 39 s to 17 s. The Ni-ACB/EP51 composites exhibits excellent shape memory performance and has promising application prospects in areas such as deployable structures in space, actuators, and 4D printing.