2021 Vol. 38, No. 7
2021, 38(7): 1985-2000.
doi: 10.13801/j.cnki.fhclxb.20210301.004
Abstract:
The carbon fiber reinforced magnesium matrix (Cf/Mg) composites are considered as the most promising structural materials with great potential in both aerospace and automotive applications, which have high specific strength, high specific stiffness, excellent thermal conductivity, great electrical conductivity and good damping properties, as well as close to zero thermal expansion coefficient and good dimensional stability. In the present review, the craft principles and characteristics, as well as the current development status and the key technical problems of powder metallurgy, diffusion bonding, squeeze casting, etc that can be used to prepare Cf/Mg composites are discussed deeply. Then the new progresses made in the preparation of Cf/Mg composites in recent years are hackled. Furthermore, engineering application cases of Cf/Mg composite that have a significant promotion effect and potential application prospects in the fields of national defense and national economy are introduced. Additionally, the facing challenges of Cf/Mg composite are analyzed, and the future development directions are prospected.
The carbon fiber reinforced magnesium matrix (Cf/Mg) composites are considered as the most promising structural materials with great potential in both aerospace and automotive applications, which have high specific strength, high specific stiffness, excellent thermal conductivity, great electrical conductivity and good damping properties, as well as close to zero thermal expansion coefficient and good dimensional stability. In the present review, the craft principles and characteristics, as well as the current development status and the key technical problems of powder metallurgy, diffusion bonding, squeeze casting, etc that can be used to prepare Cf/Mg composites are discussed deeply. Then the new progresses made in the preparation of Cf/Mg composites in recent years are hackled. Furthermore, engineering application cases of Cf/Mg composite that have a significant promotion effect and potential application prospects in the fields of national defense and national economy are introduced. Additionally, the facing challenges of Cf/Mg composite are analyzed, and the future development directions are prospected.
2021, 38(7): 2001-2009.
doi: 10.13801/j.cnki.fhclxb.20201218.001
Abstract:
Nitrates are widely used as heat storage mediums in the concentrating solar power system due to their low costs and wide operating temperature ranges. It can significantly improve the heat transfer and storage performance of the nitrates incorporated with nano-fillers, by which the power generation efficiency of the concentrating solar power system can further be improved. In this review, the components and preparation methods of nitrate composite materials were introduced. Then, the effects of the doping concentration and size of the nano-fillers on the heat transfer and storage properties of nitrate composites were analyzed. The enhancement mechanisms of the thermal performance were also summarized. Finally, the future research directions of the nitrate composite systems were outlined.
Nitrates are widely used as heat storage mediums in the concentrating solar power system due to their low costs and wide operating temperature ranges. It can significantly improve the heat transfer and storage performance of the nitrates incorporated with nano-fillers, by which the power generation efficiency of the concentrating solar power system can further be improved. In this review, the components and preparation methods of nitrate composite materials were introduced. Then, the effects of the doping concentration and size of the nano-fillers on the heat transfer and storage properties of nitrate composites were analyzed. The enhancement mechanisms of the thermal performance were also summarized. Finally, the future research directions of the nitrate composite systems were outlined.
2021, 38(7): 2010-2024.
doi: 10.13801/j.cnki.fhclxb.20210302.004
Abstract:
The MXenes is a new type of two-dimensional nanosheets. With the rapid development of MXene materials, a new material, namely MXene-based hydrogel composites, has emerged in recent years. It has broad application prospects in biomedical, energy storage, electromagnetic interference shielding, sensors and other aspects. However, the preparation and application of MXene-based hydrogel composites are still in their infancy. This article mainly reviews the latest progress of MXene-based hydrogel composites, combs the preparation progress of MXene-based hydrogel composites in detail, and highlights its potential application prospects. Finally, the opportunities and challenges on the challenges in the field of MXene-based hydrogel composites are prospected.
The MXenes is a new type of two-dimensional nanosheets. With the rapid development of MXene materials, a new material, namely MXene-based hydrogel composites, has emerged in recent years. It has broad application prospects in biomedical, energy storage, electromagnetic interference shielding, sensors and other aspects. However, the preparation and application of MXene-based hydrogel composites are still in their infancy. This article mainly reviews the latest progress of MXene-based hydrogel composites, combs the preparation progress of MXene-based hydrogel composites in detail, and highlights its potential application prospects. Finally, the opportunities and challenges on the challenges in the field of MXene-based hydrogel composites are prospected.
2021, 38(7): 2025-2037.
doi: 10.13801/j.cnki.fhclxb.20210114.002
Abstract:
With the continuous development of lithium-ion batteries and other new energy batteries in the power/energy storage field, traditional commercial polyolefin separators can no longer meet the development needs of high-performance lithium batteries due to the disadvantages of poor wettability, ion selectivity, and low porosity. In recent years, scholars have done a lot of research on improving the ionic conductivity of separators. However, during the charging and discharging process of lithium batteries, only cations can transport to participate in the redox reaction. Lithium ions in binary electrolytes are usually surrounded by solvent molecules to form a larger solvent sheath, which causes the mobility of anions to be stronger than that of lithium ions. The low cation transmission efficiency inside the battery leads to problems such as concentration polarization and lithium dendrites in the battery, which limits the application of the battery at high rates. Therefore, the design of a new type of battery separator that inhibits the shuttle of anions and promotes the rapid migration of cations has excellent development prospects in improving the electrochemical performance of the battery. Starting from recent research hotspots, this article mainly introduces the development of new separators based on the improvement of cation migration ability in the battery field from the functional design of groups, the trapping effect of Lewis acid, and spatial screening. Finally, it concludes that the battery separator field exists challenges and future development directions.
With the continuous development of lithium-ion batteries and other new energy batteries in the power/energy storage field, traditional commercial polyolefin separators can no longer meet the development needs of high-performance lithium batteries due to the disadvantages of poor wettability, ion selectivity, and low porosity. In recent years, scholars have done a lot of research on improving the ionic conductivity of separators. However, during the charging and discharging process of lithium batteries, only cations can transport to participate in the redox reaction. Lithium ions in binary electrolytes are usually surrounded by solvent molecules to form a larger solvent sheath, which causes the mobility of anions to be stronger than that of lithium ions. The low cation transmission efficiency inside the battery leads to problems such as concentration polarization and lithium dendrites in the battery, which limits the application of the battery at high rates. Therefore, the design of a new type of battery separator that inhibits the shuttle of anions and promotes the rapid migration of cations has excellent development prospects in improving the electrochemical performance of the battery. Starting from recent research hotspots, this article mainly introduces the development of new separators based on the improvement of cation migration ability in the battery field from the functional design of groups, the trapping effect of Lewis acid, and spatial screening. Finally, it concludes that the battery separator field exists challenges and future development directions.
2021, 38(7): 2038-2055.
doi: 10.13801/j.cnki.fhclxb.20210312.001
Abstract:
Thermally conductive polymer composites have been widely applied in various industries due to lightweight, flexible design and easy-processing. However, the thermal conductivity k and dielectric breakdown strength Eb of polymer composites cannot be synergistically enhanced, thereby seriously affecting and limiting their applications in the high-voltage power equipment. The intrinsic thermally conductive polymers (ITCP) resulting from the developed ordered structures based on pristine discorded structures, not only reserve inherent excellent overall properties, but also exhibit a concurrent enhancement in both Eb and k. This paper discussed the heat conduction mechanism and analyzed the factors influencing k of intrinsic polymers, and summarized the latest advances in ITCP. Furthermore, the factors influencing k, such as polymer structure, orientation, hydrogen bonding, mesomorphic unit and curing agents, processing methods, were analyzed, as well as the strategies to improve the ordered arrangement and k of polymer microstructures. Finally, this paper summarized the existing questions in the study of ITCP and pointed out the future research direction of ITCP. The ITCP show important applications in high-density electronic packaging and high-voltage power equipment, representing the future development direction of thermally conductive polymer composites.
Thermally conductive polymer composites have been widely applied in various industries due to lightweight, flexible design and easy-processing. However, the thermal conductivity k and dielectric breakdown strength Eb of polymer composites cannot be synergistically enhanced, thereby seriously affecting and limiting their applications in the high-voltage power equipment. The intrinsic thermally conductive polymers (ITCP) resulting from the developed ordered structures based on pristine discorded structures, not only reserve inherent excellent overall properties, but also exhibit a concurrent enhancement in both Eb and k. This paper discussed the heat conduction mechanism and analyzed the factors influencing k of intrinsic polymers, and summarized the latest advances in ITCP. Furthermore, the factors influencing k, such as polymer structure, orientation, hydrogen bonding, mesomorphic unit and curing agents, processing methods, were analyzed, as well as the strategies to improve the ordered arrangement and k of polymer microstructures. Finally, this paper summarized the existing questions in the study of ITCP and pointed out the future research direction of ITCP. The ITCP show important applications in high-density electronic packaging and high-voltage power equipment, representing the future development direction of thermally conductive polymer composites.
2021, 38(7): 2056-2069.
doi: 10.13801/j.cnki.fhclxb.20210324.002
Abstract:
Aerogel composites made from organic polymer materials and inorganic fillers have excellent properties such as ultralight, heat insulation and flame retardant, which can be widely used in building energy saving and heat preservation, electronics industry, aerospace and other fields. This paper reported the preparation of organic-inorganic aerogel composite materials processes and methods, compared the advantages and disadvantages of the existing aerogel materials preparation methods, and summarizes the current research hot spots of several common aerogel composite materials, including: poly (vinyl alcohol), cellulose, alginate and pectin as organic phase, inorganic components as filler. The future development of aerogel composites is summarized: the mechanical properties and water resistance of aerogel composites need to be improved, the influence of inorganic fillers on the properties of aerogels with different matrixes should be studied, the variety of biomass degradable aerogel composites should be expanded, and the industrial application of aerogel materials needs to be realized.
Aerogel composites made from organic polymer materials and inorganic fillers have excellent properties such as ultralight, heat insulation and flame retardant, which can be widely used in building energy saving and heat preservation, electronics industry, aerospace and other fields. This paper reported the preparation of organic-inorganic aerogel composite materials processes and methods, compared the advantages and disadvantages of the existing aerogel materials preparation methods, and summarizes the current research hot spots of several common aerogel composite materials, including: poly (vinyl alcohol), cellulose, alginate and pectin as organic phase, inorganic components as filler. The future development of aerogel composites is summarized: the mechanical properties and water resistance of aerogel composites need to be improved, the influence of inorganic fillers on the properties of aerogels with different matrixes should be studied, the variety of biomass degradable aerogel composites should be expanded, and the industrial application of aerogel materials needs to be realized.
2021, 38(7): 2070-2077.
doi: 10.13801/j.cnki.fhclxb.20210312.007
Abstract:
Ti-Ni shape memory alloys have been widely used in aerospace, mechanical, electronic, biomedical and other fields due to their excellent shape memory effect and superelasticity, good corrosion resistance and biocompatibility and so on. The interaction between the Ti-Ni matrix and the reinforcements in the Ti-Ni matrix composites can integrate excellent mechanical and functional properties. In the present paper, the latest research progress of Ti-Ni shape memory alloy composites prepared by different methods was reviewed, including the evolution of microstructure, martensitic transformation behaviors, mechanical properties and strain recovery characteristics. In addition, the existing problems and the future development direction of Ti-Ni shape memory alloy composites were analyzed and prospected.
Ti-Ni shape memory alloys have been widely used in aerospace, mechanical, electronic, biomedical and other fields due to their excellent shape memory effect and superelasticity, good corrosion resistance and biocompatibility and so on. The interaction between the Ti-Ni matrix and the reinforcements in the Ti-Ni matrix composites can integrate excellent mechanical and functional properties. In the present paper, the latest research progress of Ti-Ni shape memory alloy composites prepared by different methods was reviewed, including the evolution of microstructure, martensitic transformation behaviors, mechanical properties and strain recovery characteristics. In addition, the existing problems and the future development direction of Ti-Ni shape memory alloy composites were analyzed and prospected.
2021, 38(7): 2078-2091.
doi: 10.13801/j.cnki.fhclxb.20210330.001
Abstract:
The MXene is a group of newly emerging two-dimensional carbide/nitride layered materials, which is usually produced by selectively etching the A atomic layer from the MAX phase of the precursor. Due to its special microstructure as well as outstanding physical and chemical properties, it can be used for the construction of membranes separation material and gradually exhibits good application prospects in the fields of wastewater treatment and desalination. However, it has been limited to apply MXene in the process of actual water treatment. For example, MXene membranes are prone to swell in aqueous solution. The antifouling property of membrane should be improved and the separation mechanism of MXene membrane is not yet clear. This article summarized the preparation and modification methods of MXene nanosheets and two-dimensional MXene membrane materials as well as their latest reports of the application in water treatment. In addition, the separation mechanism of MXene membrane for pollutants from wastewater was proposed. The current urgent problems, solutions and the development of MXene membrane in the future were also prospected. This article has guiding significance for design and application of high-performance MXene based membrane material.
The MXene is a group of newly emerging two-dimensional carbide/nitride layered materials, which is usually produced by selectively etching the A atomic layer from the MAX phase of the precursor. Due to its special microstructure as well as outstanding physical and chemical properties, it can be used for the construction of membranes separation material and gradually exhibits good application prospects in the fields of wastewater treatment and desalination. However, it has been limited to apply MXene in the process of actual water treatment. For example, MXene membranes are prone to swell in aqueous solution. The antifouling property of membrane should be improved and the separation mechanism of MXene membrane is not yet clear. This article summarized the preparation and modification methods of MXene nanosheets and two-dimensional MXene membrane materials as well as their latest reports of the application in water treatment. In addition, the separation mechanism of MXene membrane for pollutants from wastewater was proposed. The current urgent problems, solutions and the development of MXene membrane in the future were also prospected. This article has guiding significance for design and application of high-performance MXene based membrane material.
2021, 38(7): 2092-2106.
doi: 10.13801/j.cnki.fhclxb.20210327.001
Abstract:
The studies on concrete structures prestressed with external fiber reinforced polymer (FRP) tendons are reviewed in the aspects of FRP tendon, key technology and structural component, in this review. The tensile properties and long-term behaviors of FRP tendon are firstly introduced. The design-oriented values of creep-rupture stress, relaxation rate and the limits of maximum fatigue stress and fatigue stress range are provided. The advantages and deficiencies of three main types of anchor for FRP tendon, and the methods of reducing the stress concentration on FRP tendon at anchor are elaborated. The newly-developed composite-wedge anchor is emphasized, which possesses an anchor efficiency coefficient exceeding 90%. Meanwhile, the curvature radius of deviator is recommended to be larger than 200 times of the radius the cross-section of FRP tendons, and the bending angle of FRP tendons should not exceed 5°, based on the experimental results on the mechanical properties of deviated FRP tendons. The experimental results of concrete beams prestressed with external FRP tendons are reviewed, including monotonic loading, sustained loading and cyclic loading. The design methodologies in the codes at home and overseas are introduced. The accuracies of the calculating methods in the codes are evaluated using the experimental data of forty-two beams, and the methods in the Chinese code GB 50608—2020 are validated to be accurate in the design calculation for concrete structures prestressed with external FRP tendons. This paper is expected to actively promote the popularization and application of concrete structures prestressed with external FRP tendons.
The studies on concrete structures prestressed with external fiber reinforced polymer (FRP) tendons are reviewed in the aspects of FRP tendon, key technology and structural component, in this review. The tensile properties and long-term behaviors of FRP tendon are firstly introduced. The design-oriented values of creep-rupture stress, relaxation rate and the limits of maximum fatigue stress and fatigue stress range are provided. The advantages and deficiencies of three main types of anchor for FRP tendon, and the methods of reducing the stress concentration on FRP tendon at anchor are elaborated. The newly-developed composite-wedge anchor is emphasized, which possesses an anchor efficiency coefficient exceeding 90%. Meanwhile, the curvature radius of deviator is recommended to be larger than 200 times of the radius the cross-section of FRP tendons, and the bending angle of FRP tendons should not exceed 5°, based on the experimental results on the mechanical properties of deviated FRP tendons. The experimental results of concrete beams prestressed with external FRP tendons are reviewed, including monotonic loading, sustained loading and cyclic loading. The design methodologies in the codes at home and overseas are introduced. The accuracies of the calculating methods in the codes are evaluated using the experimental data of forty-two beams, and the methods in the Chinese code GB 50608—2020 are validated to be accurate in the design calculation for concrete structures prestressed with external FRP tendons. This paper is expected to actively promote the popularization and application of concrete structures prestressed with external FRP tendons.
2021, 38(7): 2107-2122.
doi: 10.13801/j.cnki.fhclxb.20201030.002
Abstract:
As sustainable energy storage and convert device, dielectric capacitors play a non-substitutable role in the sustainable energy systems. The dielectrics are the core of dielectric capacitors. The polymer dielectrics have great potential to be applied in the high energy density capacitors for their high breakdown strength, fast discharge rate and excellent cyclability with self-healing property but the low dielectric constant. The mposite dielectrics combining ceramic counterparts with high dielectric constant and poly(vinylidene fluoride)(PVDF)-based copolymers with high breakdown strength have been developed, which achieved high energy density, low loss and high efficiency. This review introduces the fundamental principles of dielectrics and different types of ceramic/PVDF-based copolymers composites, their development trends are also prospected.
As sustainable energy storage and convert device, dielectric capacitors play a non-substitutable role in the sustainable energy systems. The dielectrics are the core of dielectric capacitors. The polymer dielectrics have great potential to be applied in the high energy density capacitors for their high breakdown strength, fast discharge rate and excellent cyclability with self-healing property but the low dielectric constant. The mposite dielectrics combining ceramic counterparts with high dielectric constant and poly(vinylidene fluoride)(PVDF)-based copolymers with high breakdown strength have been developed, which achieved high energy density, low loss and high efficiency. This review introduces the fundamental principles of dielectrics and different types of ceramic/PVDF-based copolymers composites, their development trends are also prospected.
2021, 38(7): 2123-2131.
doi: 10.13801/j.cnki.fhclxb.20200928.001
Abstract:
In order to improve the dimensional stability of the rubber-based foam material and realize its wide industrialization, an organic scaffold structure was constructed with crystalline ethylene vinyl acetate copolymer (EVA) to enhance the dimensional stability of styrene butadiene rubber (SBR)/EVA composite foam based on the cross-linked structure of sulfur and dicumyl peroxide through mechanical blending. The effects of different content of vinyl ester (VA) content on the crystallinity, compatibility, cell morphology, dimensional stability and mechanical properties of SBR/EVA composites were studied, and the anti-shrinkage mechanism of the EVA crystal area as an organic scaffold structure was explored. The results show that SBR/EVA composites with different VA content of EVA have good foaming behavior. The shrinkage of SBR/EVA composite foam with high crystallinity EVA (18% VA content) is reduced to 4.7% and its hardness and compression stress (60%) are increased to 70 Shore C and 22 MPa, respectively.
In order to improve the dimensional stability of the rubber-based foam material and realize its wide industrialization, an organic scaffold structure was constructed with crystalline ethylene vinyl acetate copolymer (EVA) to enhance the dimensional stability of styrene butadiene rubber (SBR)/EVA composite foam based on the cross-linked structure of sulfur and dicumyl peroxide through mechanical blending. The effects of different content of vinyl ester (VA) content on the crystallinity, compatibility, cell morphology, dimensional stability and mechanical properties of SBR/EVA composites were studied, and the anti-shrinkage mechanism of the EVA crystal area as an organic scaffold structure was explored. The results show that SBR/EVA composites with different VA content of EVA have good foaming behavior. The shrinkage of SBR/EVA composite foam with high crystallinity EVA (18% VA content) is reduced to 4.7% and its hardness and compression stress (60%) are increased to 70 Shore C and 22 MPa, respectively.
2021, 38(7): 2132-2139.
doi: 10.13801/j.cnki.fhclxb.20200928.003
Abstract:
The reduced graphene oxide (RGO) has been widely used in the treatment of oil, heavy metal ions, organic dyes and other fields due to the large specific surface area, high electron transport efficiency and fast adsorption rate. However, the poor dispersion caused by agglomeration limited the further research. In-situ polymerization was used to prepare nano core-shell polystyrene aldehyde microspheres (PS-CHO)@RGO composite microspheres. The morphology and physicochemical properties of the PS-CHO@RGO composite microspheres were characterized by TEM, Raman, XRD, XPS and insulation resistance tester. The methylene blue (MB) was selected as the target pollutant, the oxidation activity of PS-CHO@RGO composite microspheres in the presence of potassium hydrogen persulfate (PMPS) was investigated, and the degradation mechanism was proposed. The results indicate that RGO layer is uniformly coated on the surface of PS-CHO microspheres, which effectively improved the dispersion. The prepared PS-CHO@RGO composite microspheres are described as low penetration threshold and perfect conductive network. In the degradation experiment, PS-CHO@RGO composite microspheres can stimulate PMPS to generate sulfate radicals (SO4−•), over 98% of MB is catalytically degraded within 60 minutes. Meanwhile, the PS-CHO@RGO composite microspheres also show good stability and can be recycled by high-speed centrifugation.
The reduced graphene oxide (RGO) has been widely used in the treatment of oil, heavy metal ions, organic dyes and other fields due to the large specific surface area, high electron transport efficiency and fast adsorption rate. However, the poor dispersion caused by agglomeration limited the further research. In-situ polymerization was used to prepare nano core-shell polystyrene aldehyde microspheres (PS-CHO)@RGO composite microspheres. The morphology and physicochemical properties of the PS-CHO@RGO composite microspheres were characterized by TEM, Raman, XRD, XPS and insulation resistance tester. The methylene blue (MB) was selected as the target pollutant, the oxidation activity of PS-CHO@RGO composite microspheres in the presence of potassium hydrogen persulfate (PMPS) was investigated, and the degradation mechanism was proposed. The results indicate that RGO layer is uniformly coated on the surface of PS-CHO microspheres, which effectively improved the dispersion. The prepared PS-CHO@RGO composite microspheres are described as low penetration threshold and perfect conductive network. In the degradation experiment, PS-CHO@RGO composite microspheres can stimulate PMPS to generate sulfate radicals (SO4−•), over 98% of MB is catalytically degraded within 60 minutes. Meanwhile, the PS-CHO@RGO composite microspheres also show good stability and can be recycled by high-speed centrifugation.
2021, 38(7): 2140-2151.
doi: 10.13801/j.cnki.fhclxb.20201015.003
Abstract:
The sodium alginate (SA) is a biomass material which is abundant and can be easily acquired. It is currently used by many scientific researchers in laboratory research to prepare adsorbents to remove metal ions from aqueous solutions. However, SA based adsorbents generally exist as hydrogels, which are low in specific surface areas, slow in adsorption rates and have low adsorption capacities. In this study, calcium carbonate and polyethyleneimine (PEI) were added to SA matrix, and glutaraldehyde was used as a crosslinking agent to prepare porous SA/PEI beads via freeze-drying. The adsorption characteristics of synthesized adsorbent for Cr(Ⅵ) in aqueous solution were studied. The adsorption behaviors of Cr(Ⅵ) ions were evaluated by varying the experimental conditions including pH values, initial metal ion concentrations, adsorption temperature and adsorption time. Adsorption kinetics and thermodynamic models were applied to analyze the adsorption process. Characterization methods, including FTIR, Zeta potential, SEM, and XPS were comprehensively used to analyze the synthesis mechanism of SA/PEI beads and the mechanism of Cr(Ⅵ) adsorption. The results show that the removal rate of Cr(Ⅵ) by SA/PEI beads is negatively related to the initial concentration; the adsorption process conforms to the pseudo-second-order kinetics and Langmuir isotherm adsorption model, and the adsorption reaction is a spontaneous endothermic process. When the temperature is 318.15 K and the pH value is 2, the Langmuir isotherm adsorption fitting shows that the maximum adsorption capacity is 262.83 mg/g. The adsorption mechanism of SA/PEI beads on Cr(Ⅵ) is mainly physical adsorption dominated by electrostatic interactions.
The sodium alginate (SA) is a biomass material which is abundant and can be easily acquired. It is currently used by many scientific researchers in laboratory research to prepare adsorbents to remove metal ions from aqueous solutions. However, SA based adsorbents generally exist as hydrogels, which are low in specific surface areas, slow in adsorption rates and have low adsorption capacities. In this study, calcium carbonate and polyethyleneimine (PEI) were added to SA matrix, and glutaraldehyde was used as a crosslinking agent to prepare porous SA/PEI beads via freeze-drying. The adsorption characteristics of synthesized adsorbent for Cr(Ⅵ) in aqueous solution were studied. The adsorption behaviors of Cr(Ⅵ) ions were evaluated by varying the experimental conditions including pH values, initial metal ion concentrations, adsorption temperature and adsorption time. Adsorption kinetics and thermodynamic models were applied to analyze the adsorption process. Characterization methods, including FTIR, Zeta potential, SEM, and XPS were comprehensively used to analyze the synthesis mechanism of SA/PEI beads and the mechanism of Cr(Ⅵ) adsorption. The results show that the removal rate of Cr(Ⅵ) by SA/PEI beads is negatively related to the initial concentration; the adsorption process conforms to the pseudo-second-order kinetics and Langmuir isotherm adsorption model, and the adsorption reaction is a spontaneous endothermic process. When the temperature is 318.15 K and the pH value is 2, the Langmuir isotherm adsorption fitting shows that the maximum adsorption capacity is 262.83 mg/g. The adsorption mechanism of SA/PEI beads on Cr(Ⅵ) is mainly physical adsorption dominated by electrostatic interactions.
2021, 38(7): 2152-2161.
doi: 10.13801/j.cnki.fhclxb.20201110.005
Abstract:
In order to solve the problem of narrow working pressure range of microstructured flexible capacitive pressure sensors, a flexible “sandwich” structure capacitive pressure sensor based on expandable microsphere/polydimethylsiloxane (PDMS) dielectric layer was designed in this paper. Then the structure and morphology of the expandable microsphere/PDMS dielectric layer were characterized. The mechanical and electrical properties of the expandable microsphere/PDMS dielectric layer sensor based on expandable microsphere/PDMS dielectric layer were tested by self-built pressure and capacitance acquisition equipment. The results show that the Young’s modulus of the expandable microsphere/PDMS dielectric layer is significantly reduced due to the addition of expandable microsphere into PDMS, and the dielectric constant of the expandable microsphere/PDMS dielectric layer is increased under pressure. The working pressure range of the expandable microsphere/PDMS dielectric layer sensor is up to 400 kPa, and the maximum sensitivity reaches 0.06 kPa−1. The expandable microsphere/PDMS dielectric layer sensor has good repeatability and stability under the load cycle of 100 kPa, and low hysteresis (4.7%). It can detect fingertip pressure accurately and rapidly, which has potential applications in areas of life and health.
In order to solve the problem of narrow working pressure range of microstructured flexible capacitive pressure sensors, a flexible “sandwich” structure capacitive pressure sensor based on expandable microsphere/polydimethylsiloxane (PDMS) dielectric layer was designed in this paper. Then the structure and morphology of the expandable microsphere/PDMS dielectric layer were characterized. The mechanical and electrical properties of the expandable microsphere/PDMS dielectric layer sensor based on expandable microsphere/PDMS dielectric layer were tested by self-built pressure and capacitance acquisition equipment. The results show that the Young’s modulus of the expandable microsphere/PDMS dielectric layer is significantly reduced due to the addition of expandable microsphere into PDMS, and the dielectric constant of the expandable microsphere/PDMS dielectric layer is increased under pressure. The working pressure range of the expandable microsphere/PDMS dielectric layer sensor is up to 400 kPa, and the maximum sensitivity reaches 0.06 kPa−1. The expandable microsphere/PDMS dielectric layer sensor has good repeatability and stability under the load cycle of 100 kPa, and low hysteresis (4.7%). It can detect fingertip pressure accurately and rapidly, which has potential applications in areas of life and health.
2021, 38(7): 2162-2171.
doi: 10.13801/j.cnki.fhclxb.20201016.002
Abstract:
In this paper, the bonding surface of domestic T800 carbon fiber/high toughness epoxy composites was modified by grinding, sandblasting and plasma treatment. The test pieces of J-116B and J-375 adhesive films on floating roller peeling and tensile shear properties were prepared, respectively. The peel and shear properties of the J-116B and J-375 adhesive films were tested under different treatment conditions. The morphology of the samples before and after aging, without etching and after etching were observed by SEM. The contact angle tester was used to test the influence of different surface treatment methods on the wettability of the domestic T800 carbon fiber/high toughness epoxy composites bonding surface, and XPS was used to study the surface physicophysication performance of domestic T800 carbon fiber/high toughness epoxy composites before and after plasma treatment. The results show that J-375 film has better hygrothermal aging property although its room temperature peeling property is not as good as that of J-116B film. The failure mode of plasma treated domestic T800 carbon fiber/high toughness epoxy composites changed from adhesion failure to cohesive failure, so that the tensile shear and peel properties of the two films are significantly improved. This is because plasma treatment can recombine the molecular chain on the surface of the composite and form new active groups on the bonding surface.
In this paper, the bonding surface of domestic T800 carbon fiber/high toughness epoxy composites was modified by grinding, sandblasting and plasma treatment. The test pieces of J-116B and J-375 adhesive films on floating roller peeling and tensile shear properties were prepared, respectively. The peel and shear properties of the J-116B and J-375 adhesive films were tested under different treatment conditions. The morphology of the samples before and after aging, without etching and after etching were observed by SEM. The contact angle tester was used to test the influence of different surface treatment methods on the wettability of the domestic T800 carbon fiber/high toughness epoxy composites bonding surface, and XPS was used to study the surface physicophysication performance of domestic T800 carbon fiber/high toughness epoxy composites before and after plasma treatment. The results show that J-375 film has better hygrothermal aging property although its room temperature peeling property is not as good as that of J-116B film. The failure mode of plasma treated domestic T800 carbon fiber/high toughness epoxy composites changed from adhesion failure to cohesive failure, so that the tensile shear and peel properties of the two films are significantly improved. This is because plasma treatment can recombine the molecular chain on the surface of the composite and form new active groups on the bonding surface.
2021, 38(7): 2172-2183.
doi: 10.13801/j.cnki.fhclxb.20201017.001
Abstract:
Based on Donnell-Mushtali approximate theory, combined with thermal elasticity theory, the axial load-bearing capability of MT300/KH420 carbon fiber/polyimide resin composite shell at ambient temperature, 420℃ and circumferential temperature distribution of 210–420℃ were evaluated by analytical methods, taking into consideration of the thermal deformation of structure, material’s degradation and other terms at high temperatures. In addition, the FEM analysis model was established by ABAQUS, which introduced the 1st buckling mode generated by buckle analysis as the original imperfection, and then studied the axial stability characteristics of MT300/KH420 composite shells by non-linear explicit dynamic method. The instability load and buckling mode are both presented which agree with the results obtained by analytical method. Furthermore, a thermal-mechanical joint axial compression test was designed and implemented, thus the failure loads and modes were obtained at above thermal fields. The results indicate that the material’s degradation and asymmetry deformation caused by non-uniform thermal fields are principal factors which impact the load-bearing capability of MT300/KH420 composite shells at high temperatures.
Based on Donnell-Mushtali approximate theory, combined with thermal elasticity theory, the axial load-bearing capability of MT300/KH420 carbon fiber/polyimide resin composite shell at ambient temperature, 420℃ and circumferential temperature distribution of 210–420℃ were evaluated by analytical methods, taking into consideration of the thermal deformation of structure, material’s degradation and other terms at high temperatures. In addition, the FEM analysis model was established by ABAQUS, which introduced the 1st buckling mode generated by buckle analysis as the original imperfection, and then studied the axial stability characteristics of MT300/KH420 composite shells by non-linear explicit dynamic method. The instability load and buckling mode are both presented which agree with the results obtained by analytical method. Furthermore, a thermal-mechanical joint axial compression test was designed and implemented, thus the failure loads and modes were obtained at above thermal fields. The results indicate that the material’s degradation and asymmetry deformation caused by non-uniform thermal fields are principal factors which impact the load-bearing capability of MT300/KH420 composite shells at high temperatures.
2021, 38(7): 2184-2195.
doi: 10.13801/j.cnki.fhclxb.20210326.001
Abstract:
Based on the high-temperature aerodynamic load environment of aero-engines, the high temperature resistant TG800 carbon fiber/polyimide resin composite cylindrical casing test piece, which with flanges for installation and window openings on the casing wall, prepared by the resin transfer molding (RTM) process was carried out simulation analysis and load-bearing performance test under room temperature, 200℃ and 260℃ high-temperature aerodynamic load. The simulation results show that the high stress level of the composite casing occurs at the installation flange and the window of the shell wall. In the load-bearing test, the designed special test device and the composite casing test piece are combined to form a test chamber structure that can decouple the internal pressure and the axial force during loading. By applying high-temperature gas pressure and mechanical static load to the designed special test cavity to simulate the high-temperature aerodynamic load of the aero-engine, compared with the traditional pressurization method of stamping capsule, it can achieve more realistic assessment of the casing flange and window. The non-destructive testing on the window of the casing after the load-bearing test at room temperature, 200℃ and 260℃ shows that the delamination damage area at the window expands towards a larger square and circular shape as the load increases. The failure mode of the TG800 carbon fiber/polyimide resin composite casing obtained by the 260℃ destruction test is installation flanging fracture, which is different from the failure mode of the traditional metal casing cylinder rupture. The results indicate that the mechanical properties of TG800 carbon fiber/polyimide resin composite structural components prepared by RTM process have good temperature stability within 200℃. The installation flanging is the weak area of the composite casing under the high temperature aerodynamic load of the aero engine, which is an important optimization part for the weight reduction design of the casing.
Based on the high-temperature aerodynamic load environment of aero-engines, the high temperature resistant TG800 carbon fiber/polyimide resin composite cylindrical casing test piece, which with flanges for installation and window openings on the casing wall, prepared by the resin transfer molding (RTM) process was carried out simulation analysis and load-bearing performance test under room temperature, 200℃ and 260℃ high-temperature aerodynamic load. The simulation results show that the high stress level of the composite casing occurs at the installation flange and the window of the shell wall. In the load-bearing test, the designed special test device and the composite casing test piece are combined to form a test chamber structure that can decouple the internal pressure and the axial force during loading. By applying high-temperature gas pressure and mechanical static load to the designed special test cavity to simulate the high-temperature aerodynamic load of the aero-engine, compared with the traditional pressurization method of stamping capsule, it can achieve more realistic assessment of the casing flange and window. The non-destructive testing on the window of the casing after the load-bearing test at room temperature, 200℃ and 260℃ shows that the delamination damage area at the window expands towards a larger square and circular shape as the load increases. The failure mode of the TG800 carbon fiber/polyimide resin composite casing obtained by the 260℃ destruction test is installation flanging fracture, which is different from the failure mode of the traditional metal casing cylinder rupture. The results indicate that the mechanical properties of TG800 carbon fiber/polyimide resin composite structural components prepared by RTM process have good temperature stability within 200℃. The installation flanging is the weak area of the composite casing under the high temperature aerodynamic load of the aero engine, which is an important optimization part for the weight reduction design of the casing.
2021, 38(7): 2196-2206.
doi: 10.13801/j.cnki.fhclxb.20200811.001
Abstract:
Based on the stress distribution in representative volume element (RVE) for Hsueh model, the explicit expression of Poisson’s ratio ν12, which can be reduced to the Halpin-Tsai model, was derived from average approximation method, and it basically coincides with the Bridging model. The modified Halpin-Tsai model for transverse modulus E22 was developed by introducing an exponential decay function of l/a related to the Fu and Giner models, and coincides with the self-consistent model. Based on the assumption of Poisson’s ratio properties, the deduced results better than the Halpin-Tsai model are close to the finite element results for Poisson’s ratio ν23, and then the underestimation of shear modulus G23 was corrected by the modified Halpin-Tsai model for ν23 based on reverse engineering. Based on the laminate analogy approach (LAA) in conjunction with fiber length distribution (FLD) and generalized fiber orientation distribution (FOD) functions, the elastic moduli for two kinds of injection molded short glass fiber reinforced thermoplastics (FRT) composite were predicted. The results show that the four combined micromechanical models all predict the elastic moduli of the composites well, but the prediction results of weight distribution of fiber lengths are more reasonable than that of number distribution of fiber lengths, especially more than 5% in the improvement effect of longitudinal Young’s modulus EL.
Based on the stress distribution in representative volume element (RVE) for Hsueh model, the explicit expression of Poisson’s ratio ν12, which can be reduced to the Halpin-Tsai model, was derived from average approximation method, and it basically coincides with the Bridging model. The modified Halpin-Tsai model for transverse modulus E22 was developed by introducing an exponential decay function of l/a related to the Fu and Giner models, and coincides with the self-consistent model. Based on the assumption of Poisson’s ratio properties, the deduced results better than the Halpin-Tsai model are close to the finite element results for Poisson’s ratio ν23, and then the underestimation of shear modulus G23 was corrected by the modified Halpin-Tsai model for ν23 based on reverse engineering. Based on the laminate analogy approach (LAA) in conjunction with fiber length distribution (FLD) and generalized fiber orientation distribution (FOD) functions, the elastic moduli for two kinds of injection molded short glass fiber reinforced thermoplastics (FRT) composite were predicted. The results show that the four combined micromechanical models all predict the elastic moduli of the composites well, but the prediction results of weight distribution of fiber lengths are more reasonable than that of number distribution of fiber lengths, especially more than 5% in the improvement effect of longitudinal Young’s modulus EL.
2021, 38(7): 2207-2217.
doi: 10.13801/j.cnki.fhclxb.20201111.003
Abstract:
In the drilling process of carbon fiber reinforced polymer (CFRP) composite, the thrust force gradually increases with the accumulation of tool wear. Excessive thrust force can cause a series of machining defects in CFRP composite. In order to realize the finite element analysis and prediction of the thrust force changing with the accumulation of tool wear in the process of CFRP composite drilling, the simulation model of CFRP composite drilling was established. Through the secondary development of the ABAQUS simulation software, the thrust force prediction model considering the wear accumulation was imported into the simulation software by using the Python language development subroutine. The thrust force in the CFRP composite drilling was studied by using the ABAQUS software, and the prediction function of thrust force change with tool wear was realized. Then, through CFRP composite drilling experiments, the changes in thrust force with the number of drilling holes were analyzed to verify the prediction results of the model. The results show that the 3D finite element model of drilling without considering the change of wear can well predict the thrust force in the actual machining process, with the error of 9.10%. After considering the wear accumulation, the thrust force prediction model can predict the thrust force in the actual machining process, with the maximum error less than 10%.
In the drilling process of carbon fiber reinforced polymer (CFRP) composite, the thrust force gradually increases with the accumulation of tool wear. Excessive thrust force can cause a series of machining defects in CFRP composite. In order to realize the finite element analysis and prediction of the thrust force changing with the accumulation of tool wear in the process of CFRP composite drilling, the simulation model of CFRP composite drilling was established. Through the secondary development of the ABAQUS simulation software, the thrust force prediction model considering the wear accumulation was imported into the simulation software by using the Python language development subroutine. The thrust force in the CFRP composite drilling was studied by using the ABAQUS software, and the prediction function of thrust force change with tool wear was realized. Then, through CFRP composite drilling experiments, the changes in thrust force with the number of drilling holes were analyzed to verify the prediction results of the model. The results show that the 3D finite element model of drilling without considering the change of wear can well predict the thrust force in the actual machining process, with the error of 9.10%. After considering the wear accumulation, the thrust force prediction model can predict the thrust force in the actual machining process, with the maximum error less than 10%.
2021, 38(7): 2218-2223.
doi: 10.13801/j.cnki.fhclxb.20200902.002
Abstract:
The polyamide 6 (PA6) modified by LiCl was compounded with wood powder in the molten state to prepare wood powder/low melting point PA6 composites. The non-isothermal crystallization kinetics of the wood powder/low melting point PA6 composites was investigated via DSC. The results show that LiCl reduces the melting point, crystallization temperature, crystallinity and crystallization rate of PA6, while increases the crystallization activation energy. As a nucleating agent, the wood powder increases the crystallization rate of PA6, but decreases the crystallinity. The non-isothermal crystallization kinetics of the wood powder/low melting point PA6 composites were analyzed by Mo equation. The results show that F(T) value (the parameters of crystallization rate) of the low melting point PA6 is higher than that of pure PA6 and the wood powder/PA6 composites. LiCl increases the cooling rate required for PA6 to reach a relative crystallinity in unit time. On the contrary, wood powder reduces the cooling rate.
The polyamide 6 (PA6) modified by LiCl was compounded with wood powder in the molten state to prepare wood powder/low melting point PA6 composites. The non-isothermal crystallization kinetics of the wood powder/low melting point PA6 composites was investigated via DSC. The results show that LiCl reduces the melting point, crystallization temperature, crystallinity and crystallization rate of PA6, while increases the crystallization activation energy. As a nucleating agent, the wood powder increases the crystallization rate of PA6, but decreases the crystallinity. The non-isothermal crystallization kinetics of the wood powder/low melting point PA6 composites were analyzed by Mo equation. The results show that F(T) value (the parameters of crystallization rate) of the low melting point PA6 is higher than that of pure PA6 and the wood powder/PA6 composites. LiCl increases the cooling rate required for PA6 to reach a relative crystallinity in unit time. On the contrary, wood powder reduces the cooling rate.
2021, 38(7): 2224-2233.
doi: 10.13801/j.cnki.fhclxb.20200927.002
Abstract:
The significant influence of the hygrothermal environment on the failure of the carbon fiber reinforced polymer (CFRP) composite-aluminum alloy bolted joints has threatened the safety of the overall structures. In order to accurately assess the influence of hygrothermal environment on the quasi-static failure of CFRP composite-metal bolted joints, a quasi-static failure prediction model of composite-metal bolted joints considering hygrothermal effects was established, based on the existing progressive damage analysis of composites and Ductile damage criteria of metal. This model is validated by good consistency between the numerical and experimental results of CFRP composite-aluminum alloy single-bolt double-lap joints under 23℃/dry and 70℃/wet conditions, respectively. The proposed model was further used to reveal the influence laws of different hygrothermal environments on the quasi-static tensile failure of CFRP composite-aluminum alloy single-bolt double-lap and multi-bolt double-lap joints. The research shows that the failure loads of the single-bolt double-lap joints under 23℃/wet condition, 70℃/dry condition and 70℃/wet condition are reduced by 4.5%, 7.2% and 13.9%, respectively, compared with 23℃/dry condition. The high temperature condition is the main factor that leads to the increase of the failure area above the CFRP composite laminate under hygrothermal environments. As the number of the bolt increases, the declining degree of the quasi-static failure strength under 70℃/wet condition decreases gradually compared with 23℃/dry condition.
The significant influence of the hygrothermal environment on the failure of the carbon fiber reinforced polymer (CFRP) composite-aluminum alloy bolted joints has threatened the safety of the overall structures. In order to accurately assess the influence of hygrothermal environment on the quasi-static failure of CFRP composite-metal bolted joints, a quasi-static failure prediction model of composite-metal bolted joints considering hygrothermal effects was established, based on the existing progressive damage analysis of composites and Ductile damage criteria of metal. This model is validated by good consistency between the numerical and experimental results of CFRP composite-aluminum alloy single-bolt double-lap joints under 23℃/dry and 70℃/wet conditions, respectively. The proposed model was further used to reveal the influence laws of different hygrothermal environments on the quasi-static tensile failure of CFRP composite-aluminum alloy single-bolt double-lap and multi-bolt double-lap joints. The research shows that the failure loads of the single-bolt double-lap joints under 23℃/wet condition, 70℃/dry condition and 70℃/wet condition are reduced by 4.5%, 7.2% and 13.9%, respectively, compared with 23℃/dry condition. The high temperature condition is the main factor that leads to the increase of the failure area above the CFRP composite laminate under hygrothermal environments. As the number of the bolt increases, the declining degree of the quasi-static failure strength under 70℃/wet condition decreases gradually compared with 23℃/dry condition.
2021, 38(7): 2234-2243.
doi: 10.13801/j.cnki.fhclxb.20200910.001
Abstract:
The high content B4C (B4C≥30wt%) particle reinforced Al matrix (B4CP/Al) composites have excellent structural and functional properties, especially excellent neutron absorption performance, and are used as shielding materials in the field of nuclear protection. However, due to the addition of the high content B4C particles, the deformation of the B4CP/Al composites is difficult. ABAQUS numerical simulation method was used to simulate the hot rolling process of B4CP/Al composites under different deformations. The B4CP/Al composites fabricated by hot pressing sintering were rolled at 480℃ and its microstructure and mechanical properties were analyzed. The numerical simulation results show that when the hot rolling deformation reaches more than 60%, the stress in the middle area of the B4CP/Al composite plate surface is small, while the stress in the side is large, and the residual stress is easily generated at the edge of the plate. The results show that B4C particles in B4CP/Al composites distribute uniformly and the dislocation density increases with the increase of rolling deformation. When the rolling deformation reaches 70%, the yield strength of the B4CP/Al composite increases to 249.46 MPa and the ultimate tensile strength increases to 299.56 MPa. In the tensile process, the B4C particles have the priority to fracture without the desorbed interface with the matrix. The B4C particles bear the main stress, and the Al matrix has plastic flow, thus improving the strength of the B4CP/Al composites.
The high content B4C (B4C≥30wt%) particle reinforced Al matrix (B4CP/Al) composites have excellent structural and functional properties, especially excellent neutron absorption performance, and are used as shielding materials in the field of nuclear protection. However, due to the addition of the high content B4C particles, the deformation of the B4CP/Al composites is difficult. ABAQUS numerical simulation method was used to simulate the hot rolling process of B4CP/Al composites under different deformations. The B4CP/Al composites fabricated by hot pressing sintering were rolled at 480℃ and its microstructure and mechanical properties were analyzed. The numerical simulation results show that when the hot rolling deformation reaches more than 60%, the stress in the middle area of the B4CP/Al composite plate surface is small, while the stress in the side is large, and the residual stress is easily generated at the edge of the plate. The results show that B4C particles in B4CP/Al composites distribute uniformly and the dislocation density increases with the increase of rolling deformation. When the rolling deformation reaches 70%, the yield strength of the B4CP/Al composite increases to 249.46 MPa and the ultimate tensile strength increases to 299.56 MPa. In the tensile process, the B4C particles have the priority to fracture without the desorbed interface with the matrix. The B4C particles bear the main stress, and the Al matrix has plastic flow, thus improving the strength of the B4CP/Al composites.
2021, 38(7): 2244-2253.
doi: 10.13801/j.cnki.fhclxb.20201020.001
Abstract:
The combination of conductive carbon nanotubes (CNTs) and non-conductive flax fibers (CEL) can produce flexible conductive composites. Stretching or bending the material greatly affects its electrical conductivity. According to the resistance change rate(ΔR/R0), the change in the shape of the material can be sensitively detected, so the material is suitable for deformation sensors. The flax fiber pulp was obtained using sodium hydroxide/urea water system to treat flax fibers, which is then mixed with different concentrations CNTs suspensions, filtered, and dried to prepare conductive CNTs/CEL composite. The structure and morphology of the CNTs/CEL composites were evaluated withXRD, FTIR and SEM. The CNTs/CEL composite materials were made into deformation sensors, and the tensile conductivity was used to test the effect of stretching on the conductivity of the sensors; the optimized sensor was used to monitor the finger joints bent movement on the bases of the resistance change to test the deformation sensitivity of the sensor. The results show that with the increase of tensile strain, ΔR/R0 of CNTs/CEL sensor increases gradually. Under 50% strain, ΔR/R0 reaches over 980 and could be sensitively sensed shape changes. As the degree of bending of the finger joint increases, the resistance of the CNTs/CEL sensor increases as well. When the finger is bent to the greatest extent, the resistance of the CNTs/CEL sensor can reach more than 12000 Ω, and the repeatability is good.
The combination of conductive carbon nanotubes (CNTs) and non-conductive flax fibers (CEL) can produce flexible conductive composites. Stretching or bending the material greatly affects its electrical conductivity. According to the resistance change rate(ΔR/R0), the change in the shape of the material can be sensitively detected, so the material is suitable for deformation sensors. The flax fiber pulp was obtained using sodium hydroxide/urea water system to treat flax fibers, which is then mixed with different concentrations CNTs suspensions, filtered, and dried to prepare conductive CNTs/CEL composite. The structure and morphology of the CNTs/CEL composites were evaluated withXRD, FTIR and SEM. The CNTs/CEL composite materials were made into deformation sensors, and the tensile conductivity was used to test the effect of stretching on the conductivity of the sensors; the optimized sensor was used to monitor the finger joints bent movement on the bases of the resistance change to test the deformation sensitivity of the sensor. The results show that with the increase of tensile strain, ΔR/R0 of CNTs/CEL sensor increases gradually. Under 50% strain, ΔR/R0 reaches over 980 and could be sensitively sensed shape changes. As the degree of bending of the finger joint increases, the resistance of the CNTs/CEL sensor increases as well. When the finger is bent to the greatest extent, the resistance of the CNTs/CEL sensor can reach more than 12000 Ω, and the repeatability is good.
2021, 38(7): 2254-2264.
doi: 10.13801/j.cnki.fhclxb.20200909.001
Abstract:
Graphene-bridged ZnO/Ag3PO4 composite photocatalytic material, with excellent visible light catalytic performance, was prepared with the method of precipitation and deposition. Some characterization methods, includingXRD, XPS, SEM, EDS, BET, FTIR, UV-Vis DRS, PLand ESR were adopted to characterize and analyze the crystal structure, morphology, and optical properties of ZnO/Ag3PO4 composite photocatalytic material. Meanwhile, the photocatalytic degradation performance of GO-ZnO/Ag3PO4 with different ratios of graphene oxideto simulation antibiotics wastewater ciprofloxacin (CIP) was explored. The introduction of GO and ZnO enhances the visible light absorption of GO-ZnO/Ag3PO4, and makes GO-ZnO/Ag3PO4 have better separation efficiency of electron-hole pairs. When the mass fraction of GO is 1wt%, GO-ZnO/Ag3PO4 displays the best photocatalytic activity, and the degradation rate of CIP can reach 85.3% after 60 minutes of visible light. The capture experimentprove that, in the reaction process, superoxide radical (·O2–) is the main active substance, and a heterojunction is formed between ZnO and Ag3PO4, which conforms to the Z-scheme electron transfer mechanism. The introduction of GO furtherly improves the rapid transfer of electrons and makes the Z-scheme system more stable. After six photocatalytic cycles, the degradation rate remained above 70%, indicating that the GO-ZnO/Ag3PO4 composite material has excellent stability.
Graphene-bridged ZnO/Ag3PO4 composite photocatalytic material, with excellent visible light catalytic performance, was prepared with the method of precipitation and deposition. Some characterization methods, includingXRD, XPS, SEM, EDS, BET, FTIR, UV-Vis DRS, PLand ESR were adopted to characterize and analyze the crystal structure, morphology, and optical properties of ZnO/Ag3PO4 composite photocatalytic material. Meanwhile, the photocatalytic degradation performance of GO-ZnO/Ag3PO4 with different ratios of graphene oxideto simulation antibiotics wastewater ciprofloxacin (CIP) was explored. The introduction of GO and ZnO enhances the visible light absorption of GO-ZnO/Ag3PO4, and makes GO-ZnO/Ag3PO4 have better separation efficiency of electron-hole pairs. When the mass fraction of GO is 1wt%, GO-ZnO/Ag3PO4 displays the best photocatalytic activity, and the degradation rate of CIP can reach 85.3% after 60 minutes of visible light. The capture experimentprove that, in the reaction process, superoxide radical (·O2–) is the main active substance, and a heterojunction is formed between ZnO and Ag3PO4, which conforms to the Z-scheme electron transfer mechanism. The introduction of GO furtherly improves the rapid transfer of electrons and makes the Z-scheme system more stable. After six photocatalytic cycles, the degradation rate remained above 70%, indicating that the GO-ZnO/Ag3PO4 composite material has excellent stability.
2021, 38(7): 2265-2273.
doi: 10.13801/j.cnki.fhclxb.20201014.001
Abstract:
Amorphous cobalt boride alloy-reduced graphene (CoB-RGO)/cotton fabric flexible composite electrodes were prepared by impregnation-drying method and chemical reduction method at room temperature and atmospheric pressure. The effects of Co2+ concentrations on the structural morphology and electrochemical properties of CoB-RGO/cotton fabric flexible composite electrodes were studied. The results show that amorphous CoB presents an open 3D sheet structure interlaced with each other when the concentration of Co2+ is 0.14 mol/L. Compared with amorphous CoB/fabric and RGO/fabric composite electrodes, amorphous CoB-RGO/fabric composite electrodes show the better electrochemical properties. With the current density of 0.25 mA/cm2, the specific capacitance of amorphous CoB-RGO/cotton fabric composite electrodes is up to 218.8 F/g. There is no obvious effect of folding times and folding angles on the electrochemical performance of CoB-RGO/cotton fabric composite electrodes, which indicates their good flexibility.
Amorphous cobalt boride alloy-reduced graphene (CoB-RGO)/cotton fabric flexible composite electrodes were prepared by impregnation-drying method and chemical reduction method at room temperature and atmospheric pressure. The effects of Co2+ concentrations on the structural morphology and electrochemical properties of CoB-RGO/cotton fabric flexible composite electrodes were studied. The results show that amorphous CoB presents an open 3D sheet structure interlaced with each other when the concentration of Co2+ is 0.14 mol/L. Compared with amorphous CoB/fabric and RGO/fabric composite electrodes, amorphous CoB-RGO/fabric composite electrodes show the better electrochemical properties. With the current density of 0.25 mA/cm2, the specific capacitance of amorphous CoB-RGO/cotton fabric composite electrodes is up to 218.8 F/g. There is no obvious effect of folding times and folding angles on the electrochemical performance of CoB-RGO/cotton fabric composite electrodes, which indicates their good flexibility.
2021, 38(7): 2274-2283.
doi: 10.13801/j.cnki.fhclxb.20200928.005
Abstract:
The graphene and metal nano-materials are excellent conductive nanomaterials. In order to construct an electrochemical sensing interface with high-efficiency active surface area, glassy carbon electrode was used as a conductive substrate, and Au-Pt nano particles/reduced graphene oxide-cellulose microfiber (Au-Pt NPs/RGO-CMF) composites were successfully prepared by drip coating combined with one-step electrodeposition. The SEM, atomic force microscopy (AFM), EDS and Raman spectroscopy analysis show that Au-Pt nanoparticles are uniformly distributed on the thin layer of RGO-CMF, and at the same time, graphene oxide (GO) reduce to RGO. Using potassium ferricyanide as a redox probe to study the electrochemical properties of the interface, under optimized experimental conditions (cyclic voltammetry electrodeposition: Potential is −1.2-0 V, period is 20, electrolyte pH value is 6, drops coated GO-CMF volume is 8 μL), the high-efficiency active surface area of Au-Pt NPs/RGO-CMF composites (3.54 cm2) is much better than that of bare glassy carbon electrode (1.52 cm2). It shows that the constructed interface has high electrocatalytic activity, which provides theoretical support for the further application of the sensor.
The graphene and metal nano-materials are excellent conductive nanomaterials. In order to construct an electrochemical sensing interface with high-efficiency active surface area, glassy carbon electrode was used as a conductive substrate, and Au-Pt nano particles/reduced graphene oxide-cellulose microfiber (Au-Pt NPs/RGO-CMF) composites were successfully prepared by drip coating combined with one-step electrodeposition. The SEM, atomic force microscopy (AFM), EDS and Raman spectroscopy analysis show that Au-Pt nanoparticles are uniformly distributed on the thin layer of RGO-CMF, and at the same time, graphene oxide (GO) reduce to RGO. Using potassium ferricyanide as a redox probe to study the electrochemical properties of the interface, under optimized experimental conditions (cyclic voltammetry electrodeposition: Potential is −1.2-0 V, period is 20, electrolyte pH value is 6, drops coated GO-CMF volume is 8 μL), the high-efficiency active surface area of Au-Pt NPs/RGO-CMF composites (3.54 cm2) is much better than that of bare glassy carbon electrode (1.52 cm2). It shows that the constructed interface has high electrocatalytic activity, which provides theoretical support for the further application of the sensor.
2021, 38(7): 2284-2294.
doi: 10.13801/j.cnki.fhclxb.20210312.003
Abstract:
The poly(3,4-ethyl-enedioxythiophene): polystyrenesulfonate functionalized Te nanowires (Te@PEDOT:PSS) composite films were in situ synthesized using a one-step thermal reduction process. Then the Te@PEDOT:PSS composite films were immersed into AgNO3 solutions with different concentration to prepare Ag2Te@PEDOT:PSS composite films. By introducing Ag+ into the Te@PEDOT:PSS composite films, P type Te@PEDOT:PSS composite films was transformed to N type Ag2Te@PEDOT:PSS composite films. FESEM, TEM, XPS, and XRD were used to analysis the reaction mechanism between AgNO3 and Te@PEDOT:PSS composite films. Also, the thermoelectric properties of the Ag2Te@PEDOT:PSS composite films as a function of AgNO3 concentration were measured. The electrical conductivity of Ag2Te@PEDOT:PSS composite films first increases as the increasing AgNO3 concentration, and then decreases due to the formation of TeO2. The Seebeck coefficient of the Ag2Te@PEDOT:PSS composite films decreases significantly with the increasing concentration of AgNO3. The phenomenon can be contributed to the N type conduction of Ag2Te, and when the amount of electron provided by Ag2Te is larger than the amount of hole from Te, the conduction mechanism changes from P type to N type. As the further increasing concentration of AgNO3, the absolute value of Seebeck coefficient of the Ag2Te@PEDOT:PSS composite films increases. And the value reaches (−55.9±3.3) μV/K when the concentration of AgNO3 is 10 mmol. The N type Ag2Te@PEDOT:PSS composite film shows a maximum power factor of (8.4±0.7) μW/(m·K2) with 20 mmol AgNO3.
The poly(3,4-ethyl-enedioxythiophene): polystyrenesulfonate functionalized Te nanowires (Te@PEDOT:PSS) composite films were in situ synthesized using a one-step thermal reduction process. Then the Te@PEDOT:PSS composite films were immersed into AgNO3 solutions with different concentration to prepare Ag2Te@PEDOT:PSS composite films. By introducing Ag+ into the Te@PEDOT:PSS composite films, P type Te@PEDOT:PSS composite films was transformed to N type Ag2Te@PEDOT:PSS composite films. FESEM, TEM, XPS, and XRD were used to analysis the reaction mechanism between AgNO3 and Te@PEDOT:PSS composite films. Also, the thermoelectric properties of the Ag2Te@PEDOT:PSS composite films as a function of AgNO3 concentration were measured. The electrical conductivity of Ag2Te@PEDOT:PSS composite films first increases as the increasing AgNO3 concentration, and then decreases due to the formation of TeO2. The Seebeck coefficient of the Ag2Te@PEDOT:PSS composite films decreases significantly with the increasing concentration of AgNO3. The phenomenon can be contributed to the N type conduction of Ag2Te, and when the amount of electron provided by Ag2Te is larger than the amount of hole from Te, the conduction mechanism changes from P type to N type. As the further increasing concentration of AgNO3, the absolute value of Seebeck coefficient of the Ag2Te@PEDOT:PSS composite films increases. And the value reaches (−55.9±3.3) μV/K when the concentration of AgNO3 is 10 mmol. The N type Ag2Te@PEDOT:PSS composite film shows a maximum power factor of (8.4±0.7) μW/(m·K2) with 20 mmol AgNO3.
2021, 38(7): 2295-2304.
doi: 10.13801/j.cnki.fhclxb.20200928.004
Abstract:
The Ag@AgCl-Fe3O4/reduced graphene oxide (rGO) composites were obtained by solvothermal and in-situ precipitation method. The structure and morphology of the Ag@AgCl-Fe3O4/rGO composites were characterized. The effects of rGO content, other organic dyes (such as methylene blue (MB)) and heavy metal ions (such as Cd2+) co-existing with Rhodamine B (RhB) on the degradation of RhB were investigated, and the effects of initial pH value and other organic dyes (such as MB) co-existing with Cd2+ on the adsorption of Cd2+ were also studied. The results show that about 47% of RhB can be absorbed to Ag@AgCl-Fe3O4/rGO composites in the dark and the degradation of RhB could reach 98% within 50 min visible-light irradiation, and the adsorption-photocatalytic activity of the Ag@AgCl-Fe3O4/rGO composites increases with the increasing rGO content. The degradation efficiency on RhB and the good cycle performance of the catalyst will be suppressed by the coexisted MB, but are almost unaffected by the coexisted Cd2+. For the Cd2+ solution system, the adsorption amount of Cd2+ on Ag@AgCl-Fe3O4/rGO composites varies with the pH value and the adsorption capacity at pH=5 can be up to 68 mg/g. However, the adsorption of Cd2+ will be restrained by the presence of MB in wastewater.
The Ag@AgCl-Fe3O4/reduced graphene oxide (rGO) composites were obtained by solvothermal and in-situ precipitation method. The structure and morphology of the Ag@AgCl-Fe3O4/rGO composites were characterized. The effects of rGO content, other organic dyes (such as methylene blue (MB)) and heavy metal ions (such as Cd2+) co-existing with Rhodamine B (RhB) on the degradation of RhB were investigated, and the effects of initial pH value and other organic dyes (such as MB) co-existing with Cd2+ on the adsorption of Cd2+ were also studied. The results show that about 47% of RhB can be absorbed to Ag@AgCl-Fe3O4/rGO composites in the dark and the degradation of RhB could reach 98% within 50 min visible-light irradiation, and the adsorption-photocatalytic activity of the Ag@AgCl-Fe3O4/rGO composites increases with the increasing rGO content. The degradation efficiency on RhB and the good cycle performance of the catalyst will be suppressed by the coexisted MB, but are almost unaffected by the coexisted Cd2+. For the Cd2+ solution system, the adsorption amount of Cd2+ on Ag@AgCl-Fe3O4/rGO composites varies with the pH value and the adsorption capacity at pH=5 can be up to 68 mg/g. However, the adsorption of Cd2+ will be restrained by the presence of MB in wastewater.
2021, 38(7): 2305-2312.
doi: 10.13801/j.cnki.fhclxb.20201030.006
Abstract:
Porous Co3O4 nanofibers (Co3O4 NFs) composed with nanoparticles were fabricated by combining electrostatic spinning with subsequent calcination technology adopting Co(C5H7O2)3 as the precursor. The prepared porous Co3O4 NFs with specific surface area is up to 83 m2·g−1, which can be successfully used as an efficient catalyst in Li-air battery. Porous Co3O4 NFs provide sufficient active sites and transport channels for the battery reaction, which is favorable for the battery reaction and greatly improves the discharge capacity of the battery. In addition, the addition of Co3O4 catalyst also greatly promotes the catalytic activity of the cathode and reduces the over-potential of the Li-air battery. Significantly, with the addition of Co3O4 catalyst, the morphology of discharge product Li2O2 can also be regulated. Li2O2 with smaller size are uniformly distributed on the surface of cathode, which is more likely to be decomposed during the subsequent charging process. Additionally, the volume effect of the electrode is greatly alleviated. Because of the above-mentioned advantages, the electrochemical performances of porous Co3O4 NFs/Super P carbon (Co3O4 NFs/SP)-based Li-air battery have been greatly improved. The discharge capacity of Co3O4 NFs/SP is up to 10600 mA·h·g−1 at the current density of 50 mA·g−1, and 100 continuous discharge-charge cycles can be achieved.
Porous Co3O4 nanofibers (Co3O4 NFs) composed with nanoparticles were fabricated by combining electrostatic spinning with subsequent calcination technology adopting Co(C5H7O2)3 as the precursor. The prepared porous Co3O4 NFs with specific surface area is up to 83 m2·g−1, which can be successfully used as an efficient catalyst in Li-air battery. Porous Co3O4 NFs provide sufficient active sites and transport channels for the battery reaction, which is favorable for the battery reaction and greatly improves the discharge capacity of the battery. In addition, the addition of Co3O4 catalyst also greatly promotes the catalytic activity of the cathode and reduces the over-potential of the Li-air battery. Significantly, with the addition of Co3O4 catalyst, the morphology of discharge product Li2O2 can also be regulated. Li2O2 with smaller size are uniformly distributed on the surface of cathode, which is more likely to be decomposed during the subsequent charging process. Additionally, the volume effect of the electrode is greatly alleviated. Because of the above-mentioned advantages, the electrochemical performances of porous Co3O4 NFs/Super P carbon (Co3O4 NFs/SP)-based Li-air battery have been greatly improved. The discharge capacity of Co3O4 NFs/SP is up to 10600 mA·h·g−1 at the current density of 50 mA·g−1, and 100 continuous discharge-charge cycles can be achieved.
2021, 38(7): 2313-2325.
doi: 10.13801/j.cnki.fhclxb.20201126.003
Abstract:
Since poly(3, 4-ethylenedioxythiophene) (PEDOT) has advantages of flexible stretchable, high biocompatibility, and controllable conductivity and work function, it has emerged extensive application prospects in the flexible wearable electronic devices. In recent years, as the increasingly resources crisis, research and development of the high efficient, green, and sustainable bio-based dopant for PEDOT: PSS (polystyrene sulfonate) system has attracted serious concerns of the relevant researchers. For the first time, this work reported a new approach to prepare high-performance PEDOT conductive film using biomass-derived aromatic weak acid, i.e., gallic acid (GA, pKa of 4.41). Its special structure of adjacent multiple phenolic hydroxyl groups created a stable dual-hydrogen bonds combination with PSSH. The binding energy of GA-PEDOT is significantly higher than that of its petroleum-based strong acidic isomer (2, 4, 6-trihydroxybenzoic acid with pKa of 1.68, ) with PEDOT. GA doping not only realized the high efficient phase separation of PEDOT-PSS, but also optimized the conformational of PEDOT molecular chain, the optimal morphology and orientation of aggregation structure. This endowed GA with high doping efficiency, and the conductivity of PEDOT conductive film can be upgraded by three orders of magnitude to 1050 S/cm, only with 1.2% of doping amount of GA. That has reached the highest conductive feature in all reported bio-based dopants, and the doping efficiency of GA is significantly higher than that of bio-based dopant and its petroleum-based strong acidic isomer.
Since poly(3, 4-ethylenedioxythiophene) (PEDOT) has advantages of flexible stretchable, high biocompatibility, and controllable conductivity and work function, it has emerged extensive application prospects in the flexible wearable electronic devices. In recent years, as the increasingly resources crisis, research and development of the high efficient, green, and sustainable bio-based dopant for PEDOT: PSS (polystyrene sulfonate) system has attracted serious concerns of the relevant researchers. For the first time, this work reported a new approach to prepare high-performance PEDOT conductive film using biomass-derived aromatic weak acid, i.e., gallic acid (GA, pKa of 4.41). Its special structure of adjacent multiple phenolic hydroxyl groups created a stable dual-hydrogen bonds combination with PSSH. The binding energy of GA-PEDOT is significantly higher than that of its petroleum-based strong acidic isomer (2, 4, 6-trihydroxybenzoic acid with pKa of 1.68, ) with PEDOT. GA doping not only realized the high efficient phase separation of PEDOT-PSS, but also optimized the conformational of PEDOT molecular chain, the optimal morphology and orientation of aggregation structure. This endowed GA with high doping efficiency, and the conductivity of PEDOT conductive film can be upgraded by three orders of magnitude to 1050 S/cm, only with 1.2% of doping amount of GA. That has reached the highest conductive feature in all reported bio-based dopants, and the doping efficiency of GA is significantly higher than that of bio-based dopant and its petroleum-based strong acidic isomer.
2021, 38(7): 2326-2335.
doi: 10.13801/j.cnki.fhclxb.20200907.001
Abstract:
In order to promote the engineering application of steel fiber (SF)-polyvinyl alcohol (PVA) fiber-CaCO3 whisker (CW) multi-scale fibers/cement composite, and investigate its fire resistance and high temperature resistance, the flexural properties and microstructure of the SF-PVA-CW multi-scale fibers/cement composite after high temperature were studied. The results show that with the increase of temperature, the residual flexural strength of the SF-PVA-CW multi-scale fibers/cement composite decreases overall, but decreases slowly below 500℃ and the the SF-PVA-CW multi-scale fibers/cement composite with 3vol% CW still increase. The flexural strength decreases sharply at 800℃ and above. The equivalent flexural strength based on JSCE SF4 was used to evaluate the flexural toughness. With the increase of temperature, the equivalent flexural strength of the SF-PVA-CW multi-scale fibers/cement composite decreases gradually. At the temperature up to 500℃, the addition of CW significantly enhances the crack restricting of SF, and the effect of small deflection stage is better than that of large deflection stage. The equivalent flexural strength decreases sharply at 800℃ or above, especially at large deflection stage. With the help of digital camera, optical microscope and SEM, the micro mechanism of the influence of high temperature on the flexural properties of the SF-PVA-CW multi-scale fibers/cement composite was revealed.
In order to promote the engineering application of steel fiber (SF)-polyvinyl alcohol (PVA) fiber-CaCO3 whisker (CW) multi-scale fibers/cement composite, and investigate its fire resistance and high temperature resistance, the flexural properties and microstructure of the SF-PVA-CW multi-scale fibers/cement composite after high temperature were studied. The results show that with the increase of temperature, the residual flexural strength of the SF-PVA-CW multi-scale fibers/cement composite decreases overall, but decreases slowly below 500℃ and the the SF-PVA-CW multi-scale fibers/cement composite with 3vol% CW still increase. The flexural strength decreases sharply at 800℃ and above. The equivalent flexural strength based on JSCE SF4 was used to evaluate the flexural toughness. With the increase of temperature, the equivalent flexural strength of the SF-PVA-CW multi-scale fibers/cement composite decreases gradually. At the temperature up to 500℃, the addition of CW significantly enhances the crack restricting of SF, and the effect of small deflection stage is better than that of large deflection stage. The equivalent flexural strength decreases sharply at 800℃ or above, especially at large deflection stage. With the help of digital camera, optical microscope and SEM, the micro mechanism of the influence of high temperature on the flexural properties of the SF-PVA-CW multi-scale fibers/cement composite was revealed.
2021, 38(7): 2336-2347.
doi: 10.13801/j.cnki.fhclxb.20201029.001
Abstract:
By designing the circular arc edge griping scheme and dog bone type tensile specimen, the in-plane tensile property tests of ceramic fiber reinforced SiO2 aerogel composites at room temperature were conducted. The full field deformation of ceramic fiber reinforced SiO2 aerogel composites surface was measured and analyzed based on digital image correlation method. The non-uniform strain distribution results were obtained and discussed. The mechanical behavior characteristics and deformation and fracture mechanisms were further discussed. The results show that the in-plane tensile behavior of the ceramic fiber reinforced SiO2 aerogel composites exhibits some nonlinear and ductile characteristics due to fiber reinforced and toughened mechanisms. Under certain load level, the strain distribution on the ceramic fiber reinforced SiO2 aerogel composites surface shows significantly non-uniform. This is related to the internal random fiber arrangements and the different force transferring situations. In the mechanical tests, larger calculation areas can be selected for averaging treatment to reduce the non-uniform influence on the strain measurement. In the process of loading and fracture, the local strain concentration phenomenon exists on the ceramic fiber reinforced SiO2 aerogel composites surface and evolves with the crack propagation. The fracture appearance under the in-plane tensile load has a serrated feature. It is mainly caused by the matrix fracture dominated by shear stress and the constraint effect of normal needling on the fiber layers. Results can point out the direction to improve the strengthening and toughening of thermal insulation composites.
By designing the circular arc edge griping scheme and dog bone type tensile specimen, the in-plane tensile property tests of ceramic fiber reinforced SiO2 aerogel composites at room temperature were conducted. The full field deformation of ceramic fiber reinforced SiO2 aerogel composites surface was measured and analyzed based on digital image correlation method. The non-uniform strain distribution results were obtained and discussed. The mechanical behavior characteristics and deformation and fracture mechanisms were further discussed. The results show that the in-plane tensile behavior of the ceramic fiber reinforced SiO2 aerogel composites exhibits some nonlinear and ductile characteristics due to fiber reinforced and toughened mechanisms. Under certain load level, the strain distribution on the ceramic fiber reinforced SiO2 aerogel composites surface shows significantly non-uniform. This is related to the internal random fiber arrangements and the different force transferring situations. In the mechanical tests, larger calculation areas can be selected for averaging treatment to reduce the non-uniform influence on the strain measurement. In the process of loading and fracture, the local strain concentration phenomenon exists on the ceramic fiber reinforced SiO2 aerogel composites surface and evolves with the crack propagation. The fracture appearance under the in-plane tensile load has a serrated feature. It is mainly caused by the matrix fracture dominated by shear stress and the constraint effect of normal needling on the fiber layers. Results can point out the direction to improve the strengthening and toughening of thermal insulation composites.
2021, 38(7): 2348-2358.
doi: 10.13801/j.cnki.fhclxb.20201115.001
Abstract:
The macro steel fiber and nano carbon black as conductive materials were added into the concrete to make smart concrete. A new type of concrete beam with double layers combined with the smart concrete and plain concrete was produced. In addition, the effect of the steel fiber content and the depth of the steel fiber-nano carbon black/concrete smart layer on the post-crack toughness and self-monitoring performance were studied in this paper. In order to monitor the concrete crack, four-probe method was used to measure the electrical resistance of the specimens. The results show that the toughness of the concrete beams is increased with the increasing of fiber content and the depth of the smart concrete layer. The crack self-monitoring of the concrete can be realized by analyzing the characteristics of the fraction change in resistance-time (ρFCR-t) curve. Furthermore, the ρFCR value is nearby zero before cracking, then a significant increase of ρFCR can be found after the crack appearing. If more than one crack happens on the smart concrete beam due to the deflection hardening behavior, new turning points where the slope of ρFCR-t curve changes can be observed. Additionally, the self sensing behavior decreases with the increasing of the steel fiber content and the depth of the smart concrete layer. The ρFCR value of the specimen increases rapidly after crack happening, after that it increases slowly gradually. However, the fractional change in resistance value at a certain crack width (ωCOD) decreases with the increasing of the fiber content and the height of the smart concrete layer. The proposed first order exponential decay function fits well with the ρFCR-ωCOD curves.
The macro steel fiber and nano carbon black as conductive materials were added into the concrete to make smart concrete. A new type of concrete beam with double layers combined with the smart concrete and plain concrete was produced. In addition, the effect of the steel fiber content and the depth of the steel fiber-nano carbon black/concrete smart layer on the post-crack toughness and self-monitoring performance were studied in this paper. In order to monitor the concrete crack, four-probe method was used to measure the electrical resistance of the specimens. The results show that the toughness of the concrete beams is increased with the increasing of fiber content and the depth of the smart concrete layer. The crack self-monitoring of the concrete can be realized by analyzing the characteristics of the fraction change in resistance-time (ρFCR-t) curve. Furthermore, the ρFCR value is nearby zero before cracking, then a significant increase of ρFCR can be found after the crack appearing. If more than one crack happens on the smart concrete beam due to the deflection hardening behavior, new turning points where the slope of ρFCR-t curve changes can be observed. Additionally, the self sensing behavior decreases with the increasing of the steel fiber content and the depth of the smart concrete layer. The ρFCR value of the specimen increases rapidly after crack happening, after that it increases slowly gradually. However, the fractional change in resistance value at a certain crack width (ωCOD) decreases with the increasing of the fiber content and the height of the smart concrete layer. The proposed first order exponential decay function fits well with the ρFCR-ωCOD curves.
2021, 38(7): 2359-2369.
doi: 10.13801/j.cnki.fhclxb.20200916.001
Abstract:
Adding steel fiber (SF) into rubber concrete can improve the strength reduction caused by the incorporation of rubber particles, and further increase the ductility. Ten groups of SF-rubber/concrete under uniaxial compression were conducted in order to study the compressive properties. The crumb rubber particles were incorporated at different percentages of 0%, 10% and 20% by volume substation of sand, and SF with volume fraction of 0vol%, 0.5vol%, 1.0vol%, and 1.5vol% were added to the concrete mixture. The results show that the bridging action of SF and its positive synergy with rubber particles in SF-rubber/concrete can improve the compressive behavior of concrete. The failure process of SF-rubber/concrete specimens is mild and slow, and the failure mode is obviously ductile. After adding SF, the compressive strength and elastic modulus of the SF-rubber/concrete increase obviously, and the strains at the peak stress and the post-peak ductility increase. With the increase of rubber particles, the strain at the peak stress and the post-peak ductility of SF-rubber/concrete further increase. But the compressive strength and elastic modulus of SF-rubber/concrete are reduced by adding rubber particles. Based on the test data and the literature of stress-strain curve expression, a more suitable analytical model was proposed to generate the stress-strain curve of SF-rubber/concrete, which can be applied in the analysis and design of SF-rubber/concrete structural members.
Adding steel fiber (SF) into rubber concrete can improve the strength reduction caused by the incorporation of rubber particles, and further increase the ductility. Ten groups of SF-rubber/concrete under uniaxial compression were conducted in order to study the compressive properties. The crumb rubber particles were incorporated at different percentages of 0%, 10% and 20% by volume substation of sand, and SF with volume fraction of 0vol%, 0.5vol%, 1.0vol%, and 1.5vol% were added to the concrete mixture. The results show that the bridging action of SF and its positive synergy with rubber particles in SF-rubber/concrete can improve the compressive behavior of concrete. The failure process of SF-rubber/concrete specimens is mild and slow, and the failure mode is obviously ductile. After adding SF, the compressive strength and elastic modulus of the SF-rubber/concrete increase obviously, and the strains at the peak stress and the post-peak ductility increase. With the increase of rubber particles, the strain at the peak stress and the post-peak ductility of SF-rubber/concrete further increase. But the compressive strength and elastic modulus of SF-rubber/concrete are reduced by adding rubber particles. Based on the test data and the literature of stress-strain curve expression, a more suitable analytical model was proposed to generate the stress-strain curve of SF-rubber/concrete, which can be applied in the analysis and design of SF-rubber/concrete structural members.
2021, 38(7): 2370-2382.
doi: 10.13801/j.cnki.fhclxb.20201021.001
Abstract:
According to the service environment of the platform along Lanzhou Metro Line, coupled salt solutions containing SO42−, Cl− and Mg2+ were allocated. The reinforced concrete specimens were placed in a coupled salt solution for nondestructive testing every 90 days. Weibull distribution model was selected. Fixed and dynamic parameter estimates of the degradation distribution were obtained by least square method and BLUE method. The results show that the corrosion ions in coupled salt solution reach the surface of steel bar by diffusion, permeation and electrochemical migration. The pH value near the steel bar decreases, and the passivation film transits from undamaged state to partial damaged state. The polarization curve moves towards the direction of negative potential and increasing corrosion current density, and the AC impedance graph shows a double capacitive reactance arc, while the low-frequency impedance arc radius gradually decreases and contracts to the real part of the impedance. The reliability curves show three-stage variation characteristics. Among the dynamic parameter estimates, the reliability life of the cubic scale parameter is the closest to that of the fixed parameter value, the failure rate is the largest, the reliability life of the exponential scale parameter is the shortest, the failure rate is the smallest, the power type is between the two, and the dynamic parameter function must be between them. The first derivative and the value of the function must be positive. Otherwise, the result of the reliability calculation is complex. The influence of the scale parameter function form on reliability curve is greater than that of the shape parameter function form on reliability curve. When the scale parameter function type is fixed, the shape parameter function type has great influence on the life result. However, the reliability curve changes obviously with the scale parameter function type altering.
According to the service environment of the platform along Lanzhou Metro Line, coupled salt solutions containing SO42−, Cl− and Mg2+ were allocated. The reinforced concrete specimens were placed in a coupled salt solution for nondestructive testing every 90 days. Weibull distribution model was selected. Fixed and dynamic parameter estimates of the degradation distribution were obtained by least square method and BLUE method. The results show that the corrosion ions in coupled salt solution reach the surface of steel bar by diffusion, permeation and electrochemical migration. The pH value near the steel bar decreases, and the passivation film transits from undamaged state to partial damaged state. The polarization curve moves towards the direction of negative potential and increasing corrosion current density, and the AC impedance graph shows a double capacitive reactance arc, while the low-frequency impedance arc radius gradually decreases and contracts to the real part of the impedance. The reliability curves show three-stage variation characteristics. Among the dynamic parameter estimates, the reliability life of the cubic scale parameter is the closest to that of the fixed parameter value, the failure rate is the largest, the reliability life of the exponential scale parameter is the shortest, the failure rate is the smallest, the power type is between the two, and the dynamic parameter function must be between them. The first derivative and the value of the function must be positive. Otherwise, the result of the reliability calculation is complex. The influence of the scale parameter function form on reliability curve is greater than that of the shape parameter function form on reliability curve. When the scale parameter function type is fixed, the shape parameter function type has great influence on the life result. However, the reliability curve changes obviously with the scale parameter function type altering.
