2023 Vol. 40, No. 5
2023, 40(5): 2465-2479.
doi: 10.13801/j.cnki.fhclxb.20220804.005
Abstract:
Fiber reinforced resin matrix composites are widely used in aerospace, wind power and automobile industry due to the advantages of light weight, high strength, corrosion resistance, fatigue resistance etc. However, as heterogeneous anisotropic materials, fiber-reinforced composites are difficult to process. Traditional processing methods can lead to problems like excessive heat affected zone, delamination and fuzzing, which are difficult to meet the requirements of high-precision processing in the aeronautic and astronautic industry. As a new processing technique, ultrashort pulse laser processing has the advantages of micro scale, strong controllability, no material restriction and non-contact. It is expected to realize the high-precision processing of fiber composites. In this paper, on the basis of the current research on ultrafast laser processing carbon fiber reinforced polymer (CFRP) was reviewed, and the mechanisms of ultrafast laser processing CFRP and methods to improve the machining quality were discussed. Further, the research direction and content for the purpose of breaking through the bottleneck of high-precision machining technology in aerospace industry are prospected, which provides a technical route and possible solutions for precision machining meeting the high-precision and large-scale requirements of the aerospace industry.
Fiber reinforced resin matrix composites are widely used in aerospace, wind power and automobile industry due to the advantages of light weight, high strength, corrosion resistance, fatigue resistance etc. However, as heterogeneous anisotropic materials, fiber-reinforced composites are difficult to process. Traditional processing methods can lead to problems like excessive heat affected zone, delamination and fuzzing, which are difficult to meet the requirements of high-precision processing in the aeronautic and astronautic industry. As a new processing technique, ultrashort pulse laser processing has the advantages of micro scale, strong controllability, no material restriction and non-contact. It is expected to realize the high-precision processing of fiber composites. In this paper, on the basis of the current research on ultrafast laser processing carbon fiber reinforced polymer (CFRP) was reviewed, and the mechanisms of ultrafast laser processing CFRP and methods to improve the machining quality were discussed. Further, the research direction and content for the purpose of breaking through the bottleneck of high-precision machining technology in aerospace industry are prospected, which provides a technical route and possible solutions for precision machining meeting the high-precision and large-scale requirements of the aerospace industry.
2023, 40(5): 2480-2494.
doi: 10.13801/j.cnki.fhclxb.20220809.003
Abstract:
Maintaining thermal comfort is of essential significance for human normal life, but traditional heating, ventilation, and air conditioning systems are inefficient and produce large carbon footprint. Personal thermal management materials based on infrared radiation regulation provide new ways to mitigate the pressing burden of energy crisis and keep thermal comfort of humankind, which harnesses thermal management of human body and local microenvironment for personalized temperature control. Here, the latest progress on personal thermal management materials with engineered infrared radiation properties are reviewed. The regulation principles of radiative cooling and radiative heating are elucidated from both indoor and outdoor scenarios, and the bidirectional temperature regulation mode of radiative cooling/heating is discussed. The design ideas, fabrication, microstructure and temperature regulation effect of corresponding materials are elaborated, an outlook about development trend is provided as well.
Maintaining thermal comfort is of essential significance for human normal life, but traditional heating, ventilation, and air conditioning systems are inefficient and produce large carbon footprint. Personal thermal management materials based on infrared radiation regulation provide new ways to mitigate the pressing burden of energy crisis and keep thermal comfort of humankind, which harnesses thermal management of human body and local microenvironment for personalized temperature control. Here, the latest progress on personal thermal management materials with engineered infrared radiation properties are reviewed. The regulation principles of radiative cooling and radiative heating are elucidated from both indoor and outdoor scenarios, and the bidirectional temperature regulation mode of radiative cooling/heating is discussed. The design ideas, fabrication, microstructure and temperature regulation effect of corresponding materials are elaborated, an outlook about development trend is provided as well.
2023, 40(5): 2495-2506.
doi: 10.13801/j.cnki.fhclxb.20220818.001
Abstract:
Predicting the failure behavior of composite materials is of great significance to the design of composite structures. Due to the complexity of its failure mode and failure mechanism, the traditional computational fracture mechanics method and the numerical method based on damage mechanics are difficulty to model modeling its failure behavior. The phase field method combines the advantages of fracture mechanics and damage mechanics. It can accurately capture the crack initiation, propagation and kink behavior without additional criteria. Recently, it has been widely used in the failure analysis of composite materials. In this paper, the basic theory of phase field method was briefly introduced, and the fundamental fracture energy model and governing equations were given. Following that, the review focused on the research progress of composite failure analysis based on phase field method. The application ranges of phase field method on composite material field were reviewed. Finally, the damage simulations of composites under fatigue, hygrothermal environment and impact by using phase field method were discussed.
Predicting the failure behavior of composite materials is of great significance to the design of composite structures. Due to the complexity of its failure mode and failure mechanism, the traditional computational fracture mechanics method and the numerical method based on damage mechanics are difficulty to model modeling its failure behavior. The phase field method combines the advantages of fracture mechanics and damage mechanics. It can accurately capture the crack initiation, propagation and kink behavior without additional criteria. Recently, it has been widely used in the failure analysis of composite materials. In this paper, the basic theory of phase field method was briefly introduced, and the fundamental fracture energy model and governing equations were given. Following that, the review focused on the research progress of composite failure analysis based on phase field method. The application ranges of phase field method on composite material field were reviewed. Finally, the damage simulations of composites under fatigue, hygrothermal environment and impact by using phase field method were discussed.
2023, 40(5): 2507-2524.
doi: 10.13801/j.cnki.fhclxb.20220909.001
Abstract:
Fiber reinforced composites are broadly used in the vehicle industry to realize the lightweight of automobile, due to its excellent performances such as high specific strength and stiffness. However, the multiscale nature of fabric results in the extremely complicated deformation mechanism of fabric in the forming of automobile component with complex shape. Characterization of fabric deformation behavior and revealing the fabric deformation mechanism, is the foundation that accurately predicts the fabric forming in the complex shape and guides the reasonable design of process parameters. Therefore, in this paper, four key deformation modes of fabric in the forming including compaction, shearing, bending and sliding are reviewed. In addition, the draping behavior in the complex shape forming is also reviewed. The research methods and focuses of deformation and draping behavior are introduced in detail. This paper will provide guidance for the research of fabric deformation mecha-nism, accurate prediction of fabric in complex shape forming, and the reasonable design of process parameters. These will promote the large-scale application of composites in the automotive field.
Fiber reinforced composites are broadly used in the vehicle industry to realize the lightweight of automobile, due to its excellent performances such as high specific strength and stiffness. However, the multiscale nature of fabric results in the extremely complicated deformation mechanism of fabric in the forming of automobile component with complex shape. Characterization of fabric deformation behavior and revealing the fabric deformation mechanism, is the foundation that accurately predicts the fabric forming in the complex shape and guides the reasonable design of process parameters. Therefore, in this paper, four key deformation modes of fabric in the forming including compaction, shearing, bending and sliding are reviewed. In addition, the draping behavior in the complex shape forming is also reviewed. The research methods and focuses of deformation and draping behavior are introduced in detail. This paper will provide guidance for the research of fabric deformation mecha-nism, accurate prediction of fabric in complex shape forming, and the reasonable design of process parameters. These will promote the large-scale application of composites in the automotive field.
2023, 40(5): 2525-2535.
doi: 10.13801/j.cnki.fhclxb.20220907.002
Abstract:
Compared with randomly oriented cathodes, nickel-rich cathodes assembled with radially oriented primary particle, which are ideal materials for fast charging and long-life lithium ion battery, have better fracture toughness and Li+ diffusion rate. In recent years, Some researchers have reported a series of studies on morphology and accumulation regulation of primary particles for nickel-rich cathode. The performance of the cathodes developed by his group is excellent, representing the top level in the world, and the related technology has recently been transferred to the South Korean battery giant LG Chem. However, the synthesis of cathodes assembled with radially oriented primary particles is still in its infancy in China, and there is no systematic elaboration for the morphology and accumulation regulation of primary particles required to synthesize the nickel-rich cathode. In this paper, the necessity for the morphology and accumulation regulation of primary particles is first introduced. Then, the research progresses about the precipitation and high-temperature lithiation crystallization of precursor for the cathodes are summarized, and the mechanism involved in regulation of precipitation and high temperature calcination crystallization is analyzed. This pare is hoped to provide reference for relevant domestic specialist staff when developing high-end nickel-rich cathode materials.
Compared with randomly oriented cathodes, nickel-rich cathodes assembled with radially oriented primary particle, which are ideal materials for fast charging and long-life lithium ion battery, have better fracture toughness and Li+ diffusion rate. In recent years, Some researchers have reported a series of studies on morphology and accumulation regulation of primary particles for nickel-rich cathode. The performance of the cathodes developed by his group is excellent, representing the top level in the world, and the related technology has recently been transferred to the South Korean battery giant LG Chem. However, the synthesis of cathodes assembled with radially oriented primary particles is still in its infancy in China, and there is no systematic elaboration for the morphology and accumulation regulation of primary particles required to synthesize the nickel-rich cathode. In this paper, the necessity for the morphology and accumulation regulation of primary particles is first introduced. Then, the research progresses about the precipitation and high-temperature lithiation crystallization of precursor for the cathodes are summarized, and the mechanism involved in regulation of precipitation and high temperature calcination crystallization is analyzed. This pare is hoped to provide reference for relevant domestic specialist staff when developing high-end nickel-rich cathode materials.
2023, 40(5): 2536-2549.
doi: 10.13801/j.cnki.fhclxb.20221019.002
Abstract:
Microfluidic spinning technology combines the advantages of microfluidic technology and spinning technology, and can design and fabricate complex microfibers that are difficult to be realized by conventional spinning technology. Through the precise regulation of micro-scale fluid flow and the use of laminar flow characteristics of the fluid in the micro-channel, microfluidic spinning technology has a wide range of applications in biomedicine, flexible electronics, analytical chemistry and other fields. In this paper, the spinning device and curing mechanism of microfluidic spinning technology are systematically introduced, and the preparation methods, structural characteristics and applications of multi-structure fibers such as solid/porous fiber, hollow/core-shell fiber, Janus/two-component/multi-component fiber, spindle fiber and spiral fiber are reviewed. Finally, the advantages and disadvantages of microfluidic spinning technology in the preparation of microfibers are analyzed, and the application prospect of microfluidic spinning technology is forecasted.
Microfluidic spinning technology combines the advantages of microfluidic technology and spinning technology, and can design and fabricate complex microfibers that are difficult to be realized by conventional spinning technology. Through the precise regulation of micro-scale fluid flow and the use of laminar flow characteristics of the fluid in the micro-channel, microfluidic spinning technology has a wide range of applications in biomedicine, flexible electronics, analytical chemistry and other fields. In this paper, the spinning device and curing mechanism of microfluidic spinning technology are systematically introduced, and the preparation methods, structural characteristics and applications of multi-structure fibers such as solid/porous fiber, hollow/core-shell fiber, Janus/two-component/multi-component fiber, spindle fiber and spiral fiber are reviewed. Finally, the advantages and disadvantages of microfluidic spinning technology in the preparation of microfibers are analyzed, and the application prospect of microfluidic spinning technology is forecasted.
2023, 40(5): 2550-2565.
doi: 10.13801/j.cnki.fhclxb.20220929.002
Abstract:
As an important member of non-precious metal materials, cobalt-based materials have been widely used in electrochemical energy storage and conversion fields such as supercapacitors and electrocatalysis due to their high theoretical capacity, good catalytic activity, and excellent thermal/chemical stability. However, cobalt-based materials have also many shortcomings, such as low conductivity, insufficient exposure of active sites, easy agglomeration and decomposition of active components during testing, poor structural stability, etc. In recent years, many studies have reported the modification of cobalt-based materials to improve their electrochemical performance. Based on this, this review introduces the modification research of cobalt-based materials in recent years in detail, mainly including morphology control, elemental doping, heterostructure construction, defect engineering and composite with specific supports materials, etc. Then, their electrochemistry applications including supercapacitors (SCs), electrocatalytic oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER) is systematically summarized. Finally, the current problems and future development directions of cobalt-based materials are proposed.
As an important member of non-precious metal materials, cobalt-based materials have been widely used in electrochemical energy storage and conversion fields such as supercapacitors and electrocatalysis due to their high theoretical capacity, good catalytic activity, and excellent thermal/chemical stability. However, cobalt-based materials have also many shortcomings, such as low conductivity, insufficient exposure of active sites, easy agglomeration and decomposition of active components during testing, poor structural stability, etc. In recent years, many studies have reported the modification of cobalt-based materials to improve their electrochemical performance. Based on this, this review introduces the modification research of cobalt-based materials in recent years in detail, mainly including morphology control, elemental doping, heterostructure construction, defect engineering and composite with specific supports materials, etc. Then, their electrochemistry applications including supercapacitors (SCs), electrocatalytic oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER) is systematically summarized. Finally, the current problems and future development directions of cobalt-based materials are proposed.
2023, 40(5): 2566-2574.
doi: 10.13801/j.cnki.fhclxb.20221107.001
Abstract:
In recent years, plant fiber reinforced composites have been widely concerned because of their advantages of environmental protection, high specific modulus and low cost. In order to study the water absorption characteristics of flame retardant treated plant fiber reinforced composites, flax fiber reinforced phenolic composites (Flax/Phenolic, FP) were used as the research object. The flame retardant treatment of flax fiber was carried out by grafting dimethyl methylphosphonate (DMMP), and the optimal treatment process was explored. The water absorption of DMMP grafted composites and its influence on the flame retardancy and tensile properties of the composites were studied, compared with the physical impregnation method. The results show that DMMP grafting method has higher flame retardant efficiency and better water absorption resistance. Compared with physical impregnation method, the chemical bond formed by DMMP grafting is difficult to be destroyed by water molecules. After 30 days of water absorption, the limiting oxygen index (LOI), vertical combustion, heat release and smoke release of DMMP grafted composites have not changed significantly compared with those before water absorption, and the flame retardancy of DMMP grafted composites is well maintained after water absorption. On the other hand, the negative effect of grafting on the tensile properties of composites after water absorption is also lower than that of physical impregnation.
In recent years, plant fiber reinforced composites have been widely concerned because of their advantages of environmental protection, high specific modulus and low cost. In order to study the water absorption characteristics of flame retardant treated plant fiber reinforced composites, flax fiber reinforced phenolic composites (Flax/Phenolic, FP) were used as the research object. The flame retardant treatment of flax fiber was carried out by grafting dimethyl methylphosphonate (DMMP), and the optimal treatment process was explored. The water absorption of DMMP grafted composites and its influence on the flame retardancy and tensile properties of the composites were studied, compared with the physical impregnation method. The results show that DMMP grafting method has higher flame retardant efficiency and better water absorption resistance. Compared with physical impregnation method, the chemical bond formed by DMMP grafting is difficult to be destroyed by water molecules. After 30 days of water absorption, the limiting oxygen index (LOI), vertical combustion, heat release and smoke release of DMMP grafted composites have not changed significantly compared with those before water absorption, and the flame retardancy of DMMP grafted composites is well maintained after water absorption. On the other hand, the negative effect of grafting on the tensile properties of composites after water absorption is also lower than that of physical impregnation.
2023, 40(5): 2575-2586.
doi: 10.13801/j.cnki.fhclxb.20220822.002
Abstract:
High-performance carbon fiber reinforced epoxy composites have become important materials for aircraft manufacturing due to their excellent mechanical and thermal properties. The three-dimensional crosslinked network of epoxy matrix is insoluble, making degrading and recycling challenging. In engineering, to reclaim the expensive carbon fiber from composite wastes, harsh conditions such as high temperature (300-800℃), high pressure (3-27 MPa), and trenchant catalyst are usually demanded to destroy the epoxy matrix. However, the properties of carbon fibers are deteriorated simultaneously. In this work, high-performance epoxy resin was decomposed into oligomers via the bond exchange reactions between the epoxy and alcohol solvent. The epoxy resin was dissolved in the alcohol solvent at mild condition (200℃, 0 MPa). Meanwhile, the woven structure of the recycled fabric remains intact, and its tensile strength is 94% of the fresh fabric. Thereby, the recycled fabrics can be used to prepare new composites. Furthermore, the decomposed epoxy oligomer (DEO) is used as a reactant to prepare new epoxy resin. When the DEO content is 20wt%, the elongation at break of the new resin is significantly improved by 20%, while its strength is similar to the original epoxy resin. For the same DEO content, the elongation at break of re-manufactured epoxy composites increased by 50%, compared to the fresh one. To sum up, we develop a closed-loop recycling and re-manufacturing method for an epoxy resin and its composite, and a novel method for the toughening of epoxy resin that is eco-friendly, easy and efficient.
High-performance carbon fiber reinforced epoxy composites have become important materials for aircraft manufacturing due to their excellent mechanical and thermal properties. The three-dimensional crosslinked network of epoxy matrix is insoluble, making degrading and recycling challenging. In engineering, to reclaim the expensive carbon fiber from composite wastes, harsh conditions such as high temperature (300-800℃), high pressure (3-27 MPa), and trenchant catalyst are usually demanded to destroy the epoxy matrix. However, the properties of carbon fibers are deteriorated simultaneously. In this work, high-performance epoxy resin was decomposed into oligomers via the bond exchange reactions between the epoxy and alcohol solvent. The epoxy resin was dissolved in the alcohol solvent at mild condition (200℃, 0 MPa). Meanwhile, the woven structure of the recycled fabric remains intact, and its tensile strength is 94% of the fresh fabric. Thereby, the recycled fabrics can be used to prepare new composites. Furthermore, the decomposed epoxy oligomer (DEO) is used as a reactant to prepare new epoxy resin. When the DEO content is 20wt%, the elongation at break of the new resin is significantly improved by 20%, while its strength is similar to the original epoxy resin. For the same DEO content, the elongation at break of re-manufactured epoxy composites increased by 50%, compared to the fresh one. To sum up, we develop a closed-loop recycling and re-manufacturing method for an epoxy resin and its composite, and a novel method for the toughening of epoxy resin that is eco-friendly, easy and efficient.
2023, 40(5): 2587-2597.
doi: 10.13801/j.cnki.fhclxb.20220906.002
Abstract:
High performance polyether-ether-ketone (PEEK) thermoplastic composites have the advantages of good impact and fatigue resistance, unlimited ambient temperature storage life, short molding cycles, being recyclable and good reprocessing ability, which have been widely used in aerospace and other industry domains. Powder impregnation method can realize the infiltration of resin particles into fibers by water-based suspension, which has become an effective technical route for preparing continuous fiber reinforced thermoplastic prepregs. This paper focused on the surface characterization of PEEK produced in both domestic and overseas by inverse gas chromatography (IGC) as well as the comparison of microstructure and size distribution. The results show that the dispersion surface energy value of imported PEEK (19.2 mJ/m2) is obviously lower than the domestics (41.1 mJ/m2). The driving force of the adsorption between PEEK particles and polar probe molecules is acid-base interaction in nature, while the surface of PEEK particles is generally alkaline. With higher surface polarity, imported PEEK can more easily disperse into water through the dispersant. By preparing the water-based resin slurry based on the surface characterization results, the thermoplastic prepregs produced with powder impregnation method show excellent quality. The porosity of the powder impregnation prepregs is less than 0.5% and fibers are neatly arranged, with the short beam shear strength of 109 MPa, 30% higher comparing with prepregs produced by traditional hot melt impregnation method.
High performance polyether-ether-ketone (PEEK) thermoplastic composites have the advantages of good impact and fatigue resistance, unlimited ambient temperature storage life, short molding cycles, being recyclable and good reprocessing ability, which have been widely used in aerospace and other industry domains. Powder impregnation method can realize the infiltration of resin particles into fibers by water-based suspension, which has become an effective technical route for preparing continuous fiber reinforced thermoplastic prepregs. This paper focused on the surface characterization of PEEK produced in both domestic and overseas by inverse gas chromatography (IGC) as well as the comparison of microstructure and size distribution. The results show that the dispersion surface energy value of imported PEEK (19.2 mJ/m2) is obviously lower than the domestics (41.1 mJ/m2). The driving force of the adsorption between PEEK particles and polar probe molecules is acid-base interaction in nature, while the surface of PEEK particles is generally alkaline. With higher surface polarity, imported PEEK can more easily disperse into water through the dispersant. By preparing the water-based resin slurry based on the surface characterization results, the thermoplastic prepregs produced with powder impregnation method show excellent quality. The porosity of the powder impregnation prepregs is less than 0.5% and fibers are neatly arranged, with the short beam shear strength of 109 MPa, 30% higher comparing with prepregs produced by traditional hot melt impregnation method.
2023, 40(5): 2598-2608.
doi: 10.13801/j.cnki.fhclxb.20220809.009
Abstract:
In order to study the effect of nano conductive particles with different microscopic morphologies on the direct current (DC) dielectric properties of low-density polyethylene (LDPE), polypyrrole (PPy) nanospheres and nanowires with a diameter of about 100 nm were prepared by soft template method, and melt blended with LDPE to obtain PPy/LDPE nanocomposites. The microscopic morphology of PPy nanoparticles and their dispersion structure in PPy/LDPE nanocomposites were observed by scanning electron microscopy (SEM). The crystallinity, space charge distribution, dielectric spectrum, and DC conductive current and DC breakdown strength of the composites at different temperatures were tested. The results show that the addition of PPy nanoparticles can improve the crystallinity of LDPE, inhibit the accumulation of space charges in LDPE and reduce the relative dielectric constant, DC conductive current and DC breakdown strength. The addition of PPy nanospheres can reduce the DC conductive current of LDPE by more than one order of magnitude at different temperatures, but has little effect on its DC breakdown strength, and can increase the DC breakdown strength of LDPE by 4.4% at a higher temperature. The improvement effect of PPy nanospheres on DC dielectric properties of LDPE insulation materials is better than that of PPy nanowires.
In order to study the effect of nano conductive particles with different microscopic morphologies on the direct current (DC) dielectric properties of low-density polyethylene (LDPE), polypyrrole (PPy) nanospheres and nanowires with a diameter of about 100 nm were prepared by soft template method, and melt blended with LDPE to obtain PPy/LDPE nanocomposites. The microscopic morphology of PPy nanoparticles and their dispersion structure in PPy/LDPE nanocomposites were observed by scanning electron microscopy (SEM). The crystallinity, space charge distribution, dielectric spectrum, and DC conductive current and DC breakdown strength of the composites at different temperatures were tested. The results show that the addition of PPy nanoparticles can improve the crystallinity of LDPE, inhibit the accumulation of space charges in LDPE and reduce the relative dielectric constant, DC conductive current and DC breakdown strength. The addition of PPy nanospheres can reduce the DC conductive current of LDPE by more than one order of magnitude at different temperatures, but has little effect on its DC breakdown strength, and can increase the DC breakdown strength of LDPE by 4.4% at a higher temperature. The improvement effect of PPy nanospheres on DC dielectric properties of LDPE insulation materials is better than that of PPy nanowires.
2023, 40(5): 2609-2620.
doi: 10.13801/j.cnki.fhclxb.20220705.001
Abstract:
In order to improve the problem that the process window for the size of the silicone rubber mandrel was too narrow, which led to the high sensitivity of the forming quality of the composite hat-stiffened structure, a novel mandrel pressurization method combining silicon rubber mandrel and vacuum bag airbag was proposed, and the pressure distributions in the co-curing process and the forming accuracy, microstructure and mechanical properties of the composite hat-stiffened structures formed under the combined mandrel with different adjustable apertures were studied. The results show that the internal pressure fluctuates obviously and unevenly without the opening of adjustable aperture. With the increase of aperture proportion XS, the internal pressure is uniform and stable at the required pressure of 0.6 MPa within XS=0.40-0.53. At the same time, the average differences between the component thickness and the cavity height areonly 0.046 mm and 0.40 mm. The microstructure quality of the triangular area is high, and the average pull-off performance and increase rate are 3.42 MPa and 23.02% respectively. The method proposed in this study has a wider process window of adjustable aperture, which has a certain application potential in the forming manufacturing of composite hat-stiffened structures.
In order to improve the problem that the process window for the size of the silicone rubber mandrel was too narrow, which led to the high sensitivity of the forming quality of the composite hat-stiffened structure, a novel mandrel pressurization method combining silicon rubber mandrel and vacuum bag airbag was proposed, and the pressure distributions in the co-curing process and the forming accuracy, microstructure and mechanical properties of the composite hat-stiffened structures formed under the combined mandrel with different adjustable apertures were studied. The results show that the internal pressure fluctuates obviously and unevenly without the opening of adjustable aperture. With the increase of aperture proportion XS, the internal pressure is uniform and stable at the required pressure of 0.6 MPa within XS=0.40-0.53. At the same time, the average differences between the component thickness and the cavity height areonly 0.046 mm and 0.40 mm. The microstructure quality of the triangular area is high, and the average pull-off performance and increase rate are 3.42 MPa and 23.02% respectively. The method proposed in this study has a wider process window of adjustable aperture, which has a certain application potential in the forming manufacturing of composite hat-stiffened structures.
2023, 40(5): 2621-2627.
doi: 10.13801/j.cnki.fhclxb.20220704.002
Abstract:
Thermoplastic starch (TPS) prepared from natural starch has complete biodegradability and thermoplastic processability similar to traditional plastics, but its poor mechanical properties and water resistance limit its development. Biodegradable polyvinyl alcohol fiber (PVAF) was grafted onto its surface with glycyl methacrylate (GMA) containing epoxy and vinyl groups. In the process of twin-screw extrusion, the hydroxyl group on starch macromolecule reacted with the epoxy group of PVAF surface grafted with GMA (GMA-PVAF) to form a crosslinked structure, thus improving the mechanical properties of thermoplastic starch plastics. The results shows that GMA-PVAF shows obvious coating, which has the characteristic infrared absorption peaks of ester carbonyl group and epoxy group in GMA. The crystallinity decreases significantly, and the glass transition temperature (Tg) increases from 95.8℃ to 100.7℃. Thermogravimetric analysis shows that the mass fraction of coating is about 8.77wt%. When the content of GMA-PVAF is 1.5wt%, the tensile strength of GMA-PVAF/TPS composite increases from 3.00 MPa to 4.99 MPa, the elongation at break is 146.84%, the bending strength increases from 1.82 MPa to 11.62 MPa, and the mechanical properties are significantly improved.
Thermoplastic starch (TPS) prepared from natural starch has complete biodegradability and thermoplastic processability similar to traditional plastics, but its poor mechanical properties and water resistance limit its development. Biodegradable polyvinyl alcohol fiber (PVAF) was grafted onto its surface with glycyl methacrylate (GMA) containing epoxy and vinyl groups. In the process of twin-screw extrusion, the hydroxyl group on starch macromolecule reacted with the epoxy group of PVAF surface grafted with GMA (GMA-PVAF) to form a crosslinked structure, thus improving the mechanical properties of thermoplastic starch plastics. The results shows that GMA-PVAF shows obvious coating, which has the characteristic infrared absorption peaks of ester carbonyl group and epoxy group in GMA. The crystallinity decreases significantly, and the glass transition temperature (Tg) increases from 95.8℃ to 100.7℃. Thermogravimetric analysis shows that the mass fraction of coating is about 8.77wt%. When the content of GMA-PVAF is 1.5wt%, the tensile strength of GMA-PVAF/TPS composite increases from 3.00 MPa to 4.99 MPa, the elongation at break is 146.84%, the bending strength increases from 1.82 MPa to 11.62 MPa, and the mechanical properties are significantly improved.
2023, 40(5): 2628-2638.
doi: 10.13801/j.cnki.fhclxb.20220901.001
Abstract:
A hybrid prepreg-resin transfer moulding (Prepreg-RTM) process was proposed to realize the integration manufacturing of composite cross stiffened composite cabin. The rheological properties of prepreg resin (AC631) and RTM resin (6421A) were studied. The results show that the two resin systems have good co-forming processes basis. Combined with cabin structure design, layup design and mould design, the integrated preparation process of composite cross stiffened cabin based on hybrid Prepreg-RTM technology was verified. The results show that the cabin structure has good surface quality, dimensional accuracy and internal quality. The service strength of cabin was verified by static strength tests at room temperature and high temperature, and its failure mechanism and failure mode were studied by high temperature failure test. The results of static strength test at room temperature show that the cabin maintains good structural integrity under 125% service load, and the maximum strain of the cabin is −1283×10−6 which meets the static strength design requirements. The static strength test results at 100℃ reveal that the maximum strain of the cabin is −1315 ×10−6. There is no abnormal state such as instability and failure occurred in the cabin, which meets the requirements of thermal-mechanical coupling condition design. The high temperature failure experiment results demonstrated that the cross stiffened composite cabin failed under 143.2% service load at high temperature of 150℃, caused by the fracture of the longitudinal stiffener in loading side, where the crack propagated to both sides. The failure model of the cabin is local buckling of skin due to the fracture of the longitudinal stiffener.
A hybrid prepreg-resin transfer moulding (Prepreg-RTM) process was proposed to realize the integration manufacturing of composite cross stiffened composite cabin. The rheological properties of prepreg resin (AC631) and RTM resin (6421A) were studied. The results show that the two resin systems have good co-forming processes basis. Combined with cabin structure design, layup design and mould design, the integrated preparation process of composite cross stiffened cabin based on hybrid Prepreg-RTM technology was verified. The results show that the cabin structure has good surface quality, dimensional accuracy and internal quality. The service strength of cabin was verified by static strength tests at room temperature and high temperature, and its failure mechanism and failure mode were studied by high temperature failure test. The results of static strength test at room temperature show that the cabin maintains good structural integrity under 125% service load, and the maximum strain of the cabin is −1283×10−6 which meets the static strength design requirements. The static strength test results at 100℃ reveal that the maximum strain of the cabin is −1315 ×10−6. There is no abnormal state such as instability and failure occurred in the cabin, which meets the requirements of thermal-mechanical coupling condition design. The high temperature failure experiment results demonstrated that the cross stiffened composite cabin failed under 143.2% service load at high temperature of 150℃, caused by the fracture of the longitudinal stiffener in loading side, where the crack propagated to both sides. The failure model of the cabin is local buckling of skin due to the fracture of the longitudinal stiffener.
2023, 40(5): 2639-2652.
doi: 10.13801/j.cnki.fhclxb.20220718.001
Abstract:
In order to investigate the ultimate strength of imperfect composite cylindrical shell under hydrostatic pressure, a moderate thick filament wounded glass fiber-reinforced polymer (GFRP) composite cylindrical model was fabricated, and its initial deflection was measured before hydrostatic external pressure test. Then the compo-site cylinder model was tested up to failure under hydrostatic external pressure, the ultimate bearing capacity, strain response and failure mode were analyzed comprehensively. Based on the measured initial deflection and failure mode, a nonlinear finite element model was established, which the initial geometric defects and in-plane damage of composites during the loading procedure were simultaneously considered in the numerical model. Through programming interface subroutine with ABAQUS software, the failure process and mechanism of moderate thick GFRP cylinder model were obtained, and numerical result were compared and comparative verified with the experimental results. The results show that the ultimate load of moderate thick GFRP cylinder model is almost increasing before model collapse, and the final failure mode is the compression failure of the composite material, while the global buckling failure mode is not obvious. After considering the geometrical defects and damage evolution of composites, the ultimate strength of the moderate thick composite cylindrical shell is agreed well with the experimental result. It can be used as a method to predict the ultimate strength of medium thickness composite cylindrical shells with defects. On this basis, the key parameters affecting the ultimate strength of medium thickness composite cylindrical shells were studied, which can provide reference for the design of deep-sea composite pressure shells.
In order to investigate the ultimate strength of imperfect composite cylindrical shell under hydrostatic pressure, a moderate thick filament wounded glass fiber-reinforced polymer (GFRP) composite cylindrical model was fabricated, and its initial deflection was measured before hydrostatic external pressure test. Then the compo-site cylinder model was tested up to failure under hydrostatic external pressure, the ultimate bearing capacity, strain response and failure mode were analyzed comprehensively. Based on the measured initial deflection and failure mode, a nonlinear finite element model was established, which the initial geometric defects and in-plane damage of composites during the loading procedure were simultaneously considered in the numerical model. Through programming interface subroutine with ABAQUS software, the failure process and mechanism of moderate thick GFRP cylinder model were obtained, and numerical result were compared and comparative verified with the experimental results. The results show that the ultimate load of moderate thick GFRP cylinder model is almost increasing before model collapse, and the final failure mode is the compression failure of the composite material, while the global buckling failure mode is not obvious. After considering the geometrical defects and damage evolution of composites, the ultimate strength of the moderate thick composite cylindrical shell is agreed well with the experimental result. It can be used as a method to predict the ultimate strength of medium thickness composite cylindrical shells with defects. On this basis, the key parameters affecting the ultimate strength of medium thickness composite cylindrical shells were studied, which can provide reference for the design of deep-sea composite pressure shells.
2023, 40(5): 2653-2669.
doi: 10.13801/j.cnki.fhclxb.20220913.001
Abstract:
In order to improve the heat resistance, flame retardancy and mechanical properties of traditional water-based polyurethane (WPU), in this study 9,10-dihydro-9-oxo-10-phosphenanthrene-10 oxide (DOPO) and 2,2’-diallylbisphenol A (DABA) were used as starting materials, and the chemical synthesized double DOPO pendant flame retardant DDBA, the chemical structure was characterized by infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR), and a new waterborne polyurethane (DDBA/WPU) was prepared by chemically modifying waterborne polyurethane (WPU). The effects of DDBA on water resistance, heat resistance, flame retardancy and mechanical properties of DDBA/WPU film were studied. Evaluation of the films by water contact angle, water absorption, thermal weight loss (TG), cone calorimetry (CONE), scanning electron microscope (SEM), oxygen index (LOI), vertical combustion (UL-94), universal testing machine related performance. The research results show that with the increase of DDBA addition, the water resistance, heat resistance, flame retardancy and mechanical properties of the film continue to improve. When the addition mass ratio of DDBA is 20%, the water contact angle can reach 134.56°, an increase of 106.06%, and the water absorption rate is reduced by 33.29%, the temperature resistance is increased by 60°C. Its LOI value is 35.9%, the total flue gas release (TSP) and average effective heat of combustion (AEHC) decreased by 85.42% and 55.76%. The maximum heat release rate (pHRR), total heat release (THR) and CO2 release decreased by 35.40%, 51.20%, 58.49%, ignition time is prolonged by 15 s, CO release increased by 163.46%. The tensile strength can reach 25.7 MPa, which is about 9.51 times than that of WPU before modification.
In order to improve the heat resistance, flame retardancy and mechanical properties of traditional water-based polyurethane (WPU), in this study 9,10-dihydro-9-oxo-10-phosphenanthrene-10 oxide (DOPO) and 2,2’-diallylbisphenol A (DABA) were used as starting materials, and the chemical synthesized double DOPO pendant flame retardant DDBA, the chemical structure was characterized by infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR), and a new waterborne polyurethane (DDBA/WPU) was prepared by chemically modifying waterborne polyurethane (WPU). The effects of DDBA on water resistance, heat resistance, flame retardancy and mechanical properties of DDBA/WPU film were studied. Evaluation of the films by water contact angle, water absorption, thermal weight loss (TG), cone calorimetry (CONE), scanning electron microscope (SEM), oxygen index (LOI), vertical combustion (UL-94), universal testing machine related performance. The research results show that with the increase of DDBA addition, the water resistance, heat resistance, flame retardancy and mechanical properties of the film continue to improve. When the addition mass ratio of DDBA is 20%, the water contact angle can reach 134.56°, an increase of 106.06%, and the water absorption rate is reduced by 33.29%, the temperature resistance is increased by 60°C. Its LOI value is 35.9%, the total flue gas release (TSP) and average effective heat of combustion (AEHC) decreased by 85.42% and 55.76%. The maximum heat release rate (pHRR), total heat release (THR) and CO2 release decreased by 35.40%, 51.20%, 58.49%, ignition time is prolonged by 15 s, CO release increased by 163.46%. The tensile strength can reach 25.7 MPa, which is about 9.51 times than that of WPU before modification.
2023, 40(5): 2670-2679.
doi: 10.13801/j.cnki.fhclxb.20220620.001
Abstract:
The soft gripper can deform under external stimuli, and has a good application in the fields of cargo transportation. However, the current soft gripper has a slow response speed, and cannot adapt to most scenarios like a human hand to move the cargoes with various shapes and weights. Therefore, it is necessary to develop a soft gripper with fast response speed and adaptation for various cargoes. In this work, a hard magnetic material—Neodymium-Iron-Boron powder (NdFeB) was blended with a room temperature vulcanized rubber (RTV rubber) to form a printable magnetically responsive NdFeB-RTV rubber composite. Through the exploration and optimization of the manufacturing process-related parameters of the direct ink writing technology, the precursor ink of the NdFeB-RTV rubber composite could be accurately printed into various shapes. The material exhibits excellent mechanical properties after curing: The elongation at break is close to 300%, the tensile strength is 1.03 MPa, the tensile Young's modulus is 1.27 MPa, the flexural strength is 78.06 MPa, and the flexural modulus is 160.96 MPa. Finally, the direct ink writing technology was used to design and manufacture a magnetically responsive four-arm gripper robot. Using the magnetic actuation and flexibility characteristics of the robot, functions such as soft deformation, fast grasping, and smooth transportation are realized.
The soft gripper can deform under external stimuli, and has a good application in the fields of cargo transportation. However, the current soft gripper has a slow response speed, and cannot adapt to most scenarios like a human hand to move the cargoes with various shapes and weights. Therefore, it is necessary to develop a soft gripper with fast response speed and adaptation for various cargoes. In this work, a hard magnetic material—Neodymium-Iron-Boron powder (NdFeB) was blended with a room temperature vulcanized rubber (RTV rubber) to form a printable magnetically responsive NdFeB-RTV rubber composite. Through the exploration and optimization of the manufacturing process-related parameters of the direct ink writing technology, the precursor ink of the NdFeB-RTV rubber composite could be accurately printed into various shapes. The material exhibits excellent mechanical properties after curing: The elongation at break is close to 300%, the tensile strength is 1.03 MPa, the tensile Young's modulus is 1.27 MPa, the flexural strength is 78.06 MPa, and the flexural modulus is 160.96 MPa. Finally, the direct ink writing technology was used to design and manufacture a magnetically responsive four-arm gripper robot. Using the magnetic actuation and flexibility characteristics of the robot, functions such as soft deformation, fast grasping, and smooth transportation are realized.
2023, 40(5): 2680-2687.
doi: 10.13801/j.cnki.fhclxb.20220705.004
Abstract:
In recent years, flexible capacitive pressure sensors have been widely used in medical diagnosis, electronic skin, artificial intelligence and other important fields due to their excellent mechanical properties and good sensitivity. In order to improve the sensitivity of the capacitive flexible sensor, a flexible capacitive pressure sensor with a three-dimensional network cross-linked multi-wall carbon nanotubes (MWCNTs)/polydimethylsilane (PDMS) sponge as the dielectric layer was designed based on multi-directional freezing process. The manufacturing process, sensing mechanism, response performance and human suitability of the sensor were characterized. The results show that: The three-dimensional network structure of MWCNTs/PDMS sponge dielectric layer is successfully constructed by multi-direction freezing method, and the flexible capacitive is assembled by this dieletric layer. It has high sensitivity (~1.94 kPa−1), low detection limit (~4 Pa), fast response time (~250 ms), good stability and human suitability. The flexible sensor has a good application prospect in wearable electronic products.
In recent years, flexible capacitive pressure sensors have been widely used in medical diagnosis, electronic skin, artificial intelligence and other important fields due to their excellent mechanical properties and good sensitivity. In order to improve the sensitivity of the capacitive flexible sensor, a flexible capacitive pressure sensor with a three-dimensional network cross-linked multi-wall carbon nanotubes (MWCNTs)/polydimethylsilane (PDMS) sponge as the dielectric layer was designed based on multi-directional freezing process. The manufacturing process, sensing mechanism, response performance and human suitability of the sensor were characterized. The results show that: The three-dimensional network structure of MWCNTs/PDMS sponge dielectric layer is successfully constructed by multi-direction freezing method, and the flexible capacitive is assembled by this dieletric layer. It has high sensitivity (~1.94 kPa−1), low detection limit (~4 Pa), fast response time (~250 ms), good stability and human suitability. The flexible sensor has a good application prospect in wearable electronic products.
2023, 40(5): 2688-2698.
doi: 10.13801/j.cnki.fhclxb.20221207.001
Abstract:
In order to solve the electromagnetic radiation brought by 5G mm-wave, and environmental secondary pollution, high radar scattering cross section, optical opaque and difficult to conformal caused by the existing electromagnetic shielding materials. A multi-performances electromagnetic shielding material based on a metamaterial absorber was proposed in this paper, which can meet the green shielding index gs≥1 with low radar cross section (RCS), optical transparency, and flexible performances. This electromagnetic shielding material belongs to a manually designable multi-layer structure, in which the transparent conductive material indium tin oxide was used as the periodic resonant unit structure and the underlying floor material. The transparent materials polyethylene terephthalate and polyvinyl chloride were used as the dielectric layer. The consistency between simulation and experimental results shows that in the frequency range of 22-30 GHz, and un-conformal and conformal angle of 45° states, the proposed shielding material can achieve >30 dB green effective electromagnetic shielding and >5 dB RCS reduction. The equivalent circuit of theoretical derivation, and equivalent parameters, field distribution demonstrated the principle of absorption shielding. The green multi-performances electromagnetic shielding material accurately covers the 5G mm-wave n257, n258, and n261 frequency bands, which can effectively solve the electromagnetic interference problem caused by these frequency bands.
In order to solve the electromagnetic radiation brought by 5G mm-wave, and environmental secondary pollution, high radar scattering cross section, optical opaque and difficult to conformal caused by the existing electromagnetic shielding materials. A multi-performances electromagnetic shielding material based on a metamaterial absorber was proposed in this paper, which can meet the green shielding index gs≥1 with low radar cross section (RCS), optical transparency, and flexible performances. This electromagnetic shielding material belongs to a manually designable multi-layer structure, in which the transparent conductive material indium tin oxide was used as the periodic resonant unit structure and the underlying floor material. The transparent materials polyethylene terephthalate and polyvinyl chloride were used as the dielectric layer. The consistency between simulation and experimental results shows that in the frequency range of 22-30 GHz, and un-conformal and conformal angle of 45° states, the proposed shielding material can achieve >30 dB green effective electromagnetic shielding and >5 dB RCS reduction. The equivalent circuit of theoretical derivation, and equivalent parameters, field distribution demonstrated the principle of absorption shielding. The green multi-performances electromagnetic shielding material accurately covers the 5G mm-wave n257, n258, and n261 frequency bands, which can effectively solve the electromagnetic interference problem caused by these frequency bands.
2023, 40(5): 2699-2708.
doi: 10.13801/j.cnki.fhclxb.20220630.004
Abstract:
Hydroxystannate is a novel flame retardant aroused in recent years. In this study, starting from the flame retardant design, submicron calcium hydroxystannate (CSH) cubes were synthesized by chemical co-precipitation method, and then were rapidly in-situ coated by hydroxyapatite (HA) in simulated body fluid with high concentrations. Finally, the hybrid CSH@HA micro-nano particles were prepared and applied to the flame retardant flexible polyvinyl chloride (PVC). The results show that CSH@HA exhibits excellent flame retardancy on PVC. A very small amount of CSH@HA can significantly increase the limit oxygen index (LOI) value, and reduce the heat release rate, total heat release, total smoke release and CO production during combustion of PVC. By reacting with HCl generated during the degradation of PVC, CSH@HA protects the inner CSH and promotes more PVC into stable chars. The low loading of CSH@HA also improves the toughness of PVC while maintaining the mechanical properties. The CSH@HA hybrid flame retardant obtained in this paper pave a new way to the development of novel flame retardants.
Hydroxystannate is a novel flame retardant aroused in recent years. In this study, starting from the flame retardant design, submicron calcium hydroxystannate (CSH) cubes were synthesized by chemical co-precipitation method, and then were rapidly in-situ coated by hydroxyapatite (HA) in simulated body fluid with high concentrations. Finally, the hybrid CSH@HA micro-nano particles were prepared and applied to the flame retardant flexible polyvinyl chloride (PVC). The results show that CSH@HA exhibits excellent flame retardancy on PVC. A very small amount of CSH@HA can significantly increase the limit oxygen index (LOI) value, and reduce the heat release rate, total heat release, total smoke release and CO production during combustion of PVC. By reacting with HCl generated during the degradation of PVC, CSH@HA protects the inner CSH and promotes more PVC into stable chars. The low loading of CSH@HA also improves the toughness of PVC while maintaining the mechanical properties. The CSH@HA hybrid flame retardant obtained in this paper pave a new way to the development of novel flame retardants.
2023, 40(5): 2709-2721.
doi: 10.13801/j.cnki.fhclxb.20220627.001
Abstract:
Selective conversion of methane into platform molecule methanol is one of the ideal ways to effectively utilize natural gas resources. Photocatalytic technology with low carbon emission can activate and transform methane at room temperature and atmospheric pressure, whereas the methane conversion performance of aqueous photocatalytic system is still low. Oxygen defects-rich WO3-x was firstly synthesized through hydrothermal method and then triphase photocatalyst WO3-x/CFs was constructed by loading WO3-x on carbon fiber (CFs) with polytetrafluoroethylene concentrate (PTFE). Changing the addition amount of PTFE, the surface wettability of WO3-x/CFs can be regulated. The morphology, structure and surface properties of triphase catalysts were systematically characterized by XRD, SEM, water contact angle, electron paramagnetic resonance (EPR) and low temperature nitrogen adsorption-desorption. The results of visible-light photocatalytic experiments show that WO3-x/CFs triphase system can significantly improve the conversion performance of methane into methanol. Methane conversion amount of the optimal WO3-x/CFs-0.3 catalyst is 2522.20 μmol·g−1, which is 1.76 times and 2.48 times of WO3-x/Indium tin oxide conducting glass (Glas) and powder WO3-x diphase systems, respectively. Methanol yield of WO3-x/CFs-0.3 triphase system is 1918.83 μmol·g−1, which is 2.81 times and 4.69 times of WO3-x/Glas and powder WO3-x systems respectively, and meanwhile methanol selectivity of triphase WO3-x/CFs system is up to 76.76%. The enhanced photocatalytic performance of WO3-x/CFs is primarily due to the gas-liquid-solid triphase interface formed by the hydrophobic catalyst. The consumed methane can be directly transferred to the catalytic interface through gas transport channel in CFs, promoting the activation and conversion of methane molecules. Additionally, the triphase photocatalytic system shows excellent cyclic stability and the methanol yield of WO3-x/CFs-0.3 can still reach 1506.98 μmol·g−1 after 6 cycles.
Selective conversion of methane into platform molecule methanol is one of the ideal ways to effectively utilize natural gas resources. Photocatalytic technology with low carbon emission can activate and transform methane at room temperature and atmospheric pressure, whereas the methane conversion performance of aqueous photocatalytic system is still low. Oxygen defects-rich WO3-x was firstly synthesized through hydrothermal method and then triphase photocatalyst WO3-x/CFs was constructed by loading WO3-x on carbon fiber (CFs) with polytetrafluoroethylene concentrate (PTFE). Changing the addition amount of PTFE, the surface wettability of WO3-x/CFs can be regulated. The morphology, structure and surface properties of triphase catalysts were systematically characterized by XRD, SEM, water contact angle, electron paramagnetic resonance (EPR) and low temperature nitrogen adsorption-desorption. The results of visible-light photocatalytic experiments show that WO3-x/CFs triphase system can significantly improve the conversion performance of methane into methanol. Methane conversion amount of the optimal WO3-x/CFs-0.3 catalyst is 2522.20 μmol·g−1, which is 1.76 times and 2.48 times of WO3-x/Indium tin oxide conducting glass (Glas) and powder WO3-x diphase systems, respectively. Methanol yield of WO3-x/CFs-0.3 triphase system is 1918.83 μmol·g−1, which is 2.81 times and 4.69 times of WO3-x/Glas and powder WO3-x systems respectively, and meanwhile methanol selectivity of triphase WO3-x/CFs system is up to 76.76%. The enhanced photocatalytic performance of WO3-x/CFs is primarily due to the gas-liquid-solid triphase interface formed by the hydrophobic catalyst. The consumed methane can be directly transferred to the catalytic interface through gas transport channel in CFs, promoting the activation and conversion of methane molecules. Additionally, the triphase photocatalytic system shows excellent cyclic stability and the methanol yield of WO3-x/CFs-0.3 can still reach 1506.98 μmol·g−1 after 6 cycles.
2023, 40(5): 2722-2730.
doi: 10.13801/j.cnki.fhclxb.20220705.002
Abstract:
The urgent need for high-performance energy storage devices makes lithium-sulfur batteries (LSBs) with theoretical energy densities up to 2600 W·h/kg very attractive. However, the low capacity reversibility and the natural defect of sulfur's self-insulating property restrict its commercialization. In order to effectively improve the electrical conductivity of sulfur while suppressing the shuttle effect of polysulfides, the purpose of improving the electrochemical performance of LSBs is achieved. In this paper, a layer-by-layer coating method was used to coat the surface of the expanded graphite (EG)/sulfur (S) composite cathode with fluorinated vapor-deposited carbon fiber (FVGCF). A composite layer of LiF and FVGCF is formed on the surface of the pole piece. The electrochemical performance test and morphological characterization results show that the new cathode material using FVGCF has the best cycle life. The initial discharge specific capacity of EGS-FVGCF at 1 C current density is 691.8 mA h/g, and the remaining specific capacity after 100 cycles is 549.5 mA h/g. Compared with the EGS-coated single-layer structure, the double-layer battery coated with FVGCF on EGS has great application advantages, and the LiF generated during the discharge process can inhibit the shuttle of polysulfides from the positive electrode to the negative electrode. At the same time, the electrode morphology characterization after discharge and charge found that the addition of the FVGCF layer reduced the cracks on the surface of the pole piece, indicating that the FVGCF layer buffered the volume expansion of the sulfur cathode to a certain extent. This simple and easy-to-operate composite structure provides a certain reference for the development of high-performance LSBs.
The urgent need for high-performance energy storage devices makes lithium-sulfur batteries (LSBs) with theoretical energy densities up to 2600 W·h/kg very attractive. However, the low capacity reversibility and the natural defect of sulfur's self-insulating property restrict its commercialization. In order to effectively improve the electrical conductivity of sulfur while suppressing the shuttle effect of polysulfides, the purpose of improving the electrochemical performance of LSBs is achieved. In this paper, a layer-by-layer coating method was used to coat the surface of the expanded graphite (EG)/sulfur (S) composite cathode with fluorinated vapor-deposited carbon fiber (FVGCF). A composite layer of LiF and FVGCF is formed on the surface of the pole piece. The electrochemical performance test and morphological characterization results show that the new cathode material using FVGCF has the best cycle life. The initial discharge specific capacity of EGS-FVGCF at 1 C current density is 691.8 mA h/g, and the remaining specific capacity after 100 cycles is 549.5 mA h/g. Compared with the EGS-coated single-layer structure, the double-layer battery coated with FVGCF on EGS has great application advantages, and the LiF generated during the discharge process can inhibit the shuttle of polysulfides from the positive electrode to the negative electrode. At the same time, the electrode morphology characterization after discharge and charge found that the addition of the FVGCF layer reduced the cracks on the surface of the pole piece, indicating that the FVGCF layer buffered the volume expansion of the sulfur cathode to a certain extent. This simple and easy-to-operate composite structure provides a certain reference for the development of high-performance LSBs.
2023, 40(5): 2731-2740.
doi: 10.13801/j.cnki.fhclxb.20220728.002
Abstract:
Rechargeable water zinc-manganese battery has a wide application prospect in large-scale energy storage due to its high safety, low cost and environmental friendliness. However, due to poor conductivity of manganese oxide and dissolving in water due to disproportionation reaction during battery charging and discharging, the battery has low capacity and poor cycle stability. In this paper, the carbon nanofiber (CSCNFs) composite material with raised structure and conductive network was prepared by double-needle pair spinning electrostatic spinning technology, combined with pre-oxidation and high temperature annealing process, and the surface of carbon nanofiber was modified by doping carbon nanotube (CNTs) and conductive carbon black (Super-P). MnO2@CSCNFs cathode was prepared by loading α-MnO2 active substance on the fiber surface. CNTs and Super-P doping were modified on the surface of carbon nanofibers. Among them, CNTs and Super-P cooperated to construct conductive network channels with node structure to realize efficient electron-ion cooperative transport. With the cathode of MnO2@CSCNFs zinc ion battery kinetics and electrochemical performance is significantly improved, the initial capacity reaches 784.8 mA·h·g−1, and after 100 cycle remain discharge specific capacity of 500 mA·h·g−1. The discharge specific capacity of 290.8 mA·h·g−1 is maintained at a high current density of 2 A·g−1, and the capacity recovery rate is up to 96.33% when the current density is restored to 0.1 A·g−1.
Rechargeable water zinc-manganese battery has a wide application prospect in large-scale energy storage due to its high safety, low cost and environmental friendliness. However, due to poor conductivity of manganese oxide and dissolving in water due to disproportionation reaction during battery charging and discharging, the battery has low capacity and poor cycle stability. In this paper, the carbon nanofiber (CSCNFs) composite material with raised structure and conductive network was prepared by double-needle pair spinning electrostatic spinning technology, combined with pre-oxidation and high temperature annealing process, and the surface of carbon nanofiber was modified by doping carbon nanotube (CNTs) and conductive carbon black (Super-P). MnO2@CSCNFs cathode was prepared by loading α-MnO2 active substance on the fiber surface. CNTs and Super-P doping were modified on the surface of carbon nanofibers. Among them, CNTs and Super-P cooperated to construct conductive network channels with node structure to realize efficient electron-ion cooperative transport. With the cathode of MnO2@CSCNFs zinc ion battery kinetics and electrochemical performance is significantly improved, the initial capacity reaches 784.8 mA·h·g−1, and after 100 cycle remain discharge specific capacity of 500 mA·h·g−1. The discharge specific capacity of 290.8 mA·h·g−1 is maintained at a high current density of 2 A·g−1, and the capacity recovery rate is up to 96.33% when the current density is restored to 0.1 A·g−1.
2023, 40(5): 2741-2748.
doi: 10.13801/j.cnki.fhclxb.20220727.003
Abstract:
As a cathode material for lithium ion batteries, Co3O4 has attracted much attention due to its high theoretical specific capacity of 890 mA·h/g. In this paper, Co3O4 and expanded graphite self-assembled polyhedral composites (Co3O4-EG) were prepared by simple chemical solution method and heat treatment. When used as the anode material of lithium ion battery, the reversible capacity of Co3O4-EG composite electrode with the mass ratio of EG to Co3O4 of 1∶3 after 400 cycles at the current rate of 0.1 C is still as high as 418 mA·h/g, which is higher than that of other Co3O4-EG composite materials (The capacity is 273 mA·h/g after 190 cycles with a mass ratio of 1∶4 and 329 mA·h/g after 135 cycles with a mass ratio of 1∶5). And the discharge capacity of all Co3O4-EG composites is higher than that of pure Co3O4 (The capacity is 40 mA·h/g after 400 cycles). The nanostructure of Co3O4, the excellent electrical conductivity of expanded graphite and the synergistic effect of self-assembled polyhedron structure make Co3O4-EG composites have excellent lithium storage properties.
As a cathode material for lithium ion batteries, Co3O4 has attracted much attention due to its high theoretical specific capacity of 890 mA·h/g. In this paper, Co3O4 and expanded graphite self-assembled polyhedral composites (Co3O4-EG) were prepared by simple chemical solution method and heat treatment. When used as the anode material of lithium ion battery, the reversible capacity of Co3O4-EG composite electrode with the mass ratio of EG to Co3O4 of 1∶3 after 400 cycles at the current rate of 0.1 C is still as high as 418 mA·h/g, which is higher than that of other Co3O4-EG composite materials (The capacity is 273 mA·h/g after 190 cycles with a mass ratio of 1∶4 and 329 mA·h/g after 135 cycles with a mass ratio of 1∶5). And the discharge capacity of all Co3O4-EG composites is higher than that of pure Co3O4 (The capacity is 40 mA·h/g after 400 cycles). The nanostructure of Co3O4, the excellent electrical conductivity of expanded graphite and the synergistic effect of self-assembled polyhedron structure make Co3O4-EG composites have excellent lithium storage properties.
2023, 40(5): 2749-2758.
doi: 10.13801/j.cnki.fhclxb.20220824.001
Abstract:
Solar interface water evaporation technology has a broad application prospect in solving the shortage of energy and fresh water resources that mankind is currently facing. Water transport was a very important step in the solar steam generation process. The ideal water transport was to transport the right amount of water to maintain efficient and stable water evaporation from the solar evaporation layer. The capillary force generated by the porous structure of the evaporation layer determined its ability when transporting water. Therefore, the pore structure inside the evaporation layer was very important. In this paper, a porous carbon nanotubes-hydroxyethyl cellulose/polyvinylidene fluoride (CNTs-HEC/PVDF) composite membrane for solar interfacial water evaporation was produced, which was doped with HEC and cross-linking with glutaraldehyde on a PVDF depended on the excellent light absorption capacity of CNTs. The solar interfacial water evaporation performance was improved as the microchannels formed by the porous structure of CNTs-HEC/PVDF composite membranes enhanced water transport and vapor escape. The water evaporation rate reaches 1.81 kg·m−2·h−1 under 1 kW·m−2 of solar irradiation, and the corresponding photothermal conversion efficiency is 95%. The relevant experimental results also show that the composite membrane has excellent recycling performance, chemical stability and efficient sewage purification ability.
Solar interface water evaporation technology has a broad application prospect in solving the shortage of energy and fresh water resources that mankind is currently facing. Water transport was a very important step in the solar steam generation process. The ideal water transport was to transport the right amount of water to maintain efficient and stable water evaporation from the solar evaporation layer. The capillary force generated by the porous structure of the evaporation layer determined its ability when transporting water. Therefore, the pore structure inside the evaporation layer was very important. In this paper, a porous carbon nanotubes-hydroxyethyl cellulose/polyvinylidene fluoride (CNTs-HEC/PVDF) composite membrane for solar interfacial water evaporation was produced, which was doped with HEC and cross-linking with glutaraldehyde on a PVDF depended on the excellent light absorption capacity of CNTs. The solar interfacial water evaporation performance was improved as the microchannels formed by the porous structure of CNTs-HEC/PVDF composite membranes enhanced water transport and vapor escape. The water evaporation rate reaches 1.81 kg·m−2·h−1 under 1 kW·m−2 of solar irradiation, and the corresponding photothermal conversion efficiency is 95%. The relevant experimental results also show that the composite membrane has excellent recycling performance, chemical stability and efficient sewage purification ability.
2023, 40(5): 2759-2771.
doi: 10.13801/j.cnki.fhclxb.20220727.002
Abstract:
3D printing technology has received more and more attention in the rapid manufacturing of complex shape parts. Mn-Zn ferrite (MZF) was filled into polylactic acid (PLA) as reinforcement, the MZF/PLA composite wire was prepared by ball milling mixing and melt extrusion, and the MZF/PLA composites was prepared by fused deposition modeling (FDM). The micro morphology, mechanical properties and electromagnetic properties of MZF/PLA composites with different composite ratios were characterized by XRD, SEM and vector network analyzer, and the reflection loss of different thickness was calculated to study the effect of MZF content on the microwave absorption properties of the composites. The results show that when the MZF content is 10wt%, the tensile strength of MZF/PLA composite is 17.6% higher than that of pure PLA. With the increase of MZF content, the microwave absorption performance of the composite enhanced. When the content of MZF reaches 50wt% at 12.7 GHz, when the thickness is 7.4 mm, the reflectivity reaches the minimum value of −55.3 dB, and when the thickness is 7.9 mm, the effective microwave absorption band width is 4.5 GHz. Therefore, the 3D printed MZF/PLA composite prepared based on FDM has good microwave absorbing properties and bearing capacity, and it is a very promising microwave absorbing material for 3D printing.
3D printing technology has received more and more attention in the rapid manufacturing of complex shape parts. Mn-Zn ferrite (MZF) was filled into polylactic acid (PLA) as reinforcement, the MZF/PLA composite wire was prepared by ball milling mixing and melt extrusion, and the MZF/PLA composites was prepared by fused deposition modeling (FDM). The micro morphology, mechanical properties and electromagnetic properties of MZF/PLA composites with different composite ratios were characterized by XRD, SEM and vector network analyzer, and the reflection loss of different thickness was calculated to study the effect of MZF content on the microwave absorption properties of the composites. The results show that when the MZF content is 10wt%, the tensile strength of MZF/PLA composite is 17.6% higher than that of pure PLA. With the increase of MZF content, the microwave absorption performance of the composite enhanced. When the content of MZF reaches 50wt% at 12.7 GHz, when the thickness is 7.4 mm, the reflectivity reaches the minimum value of −55.3 dB, and when the thickness is 7.9 mm, the effective microwave absorption band width is 4.5 GHz. Therefore, the 3D printed MZF/PLA composite prepared based on FDM has good microwave absorbing properties and bearing capacity, and it is a very promising microwave absorbing material for 3D printing.
2023, 40(5): 2772-2782.
doi: 10.13801/j.cnki.fhclxb.20220616.002
Abstract:
The low mechanical strength of shape memory polymers (SMP) are insufficient to meet the standards of most commercial composites today, severely limiting their use in many advanced applications. Therefore, in order to prepare high-performance SMP composite materials, a novel nano-filler SiO2@PDA was prepared by surface modification of nano-silica (SiO2) with polydopamine (PDA), its structure and properties were characterized by SEM, XPS and FTIR, respectively. Shape memory composites based on trans-1,4-polyisoprene (TPI) were prepared by filling SiO2 and SiO2@PDA into TPI as nano-fillers. The thermal stability, comprehensive mechanical properties and shape memory properties of TPI/SiO2 and TPI/SiO2@PDA composites were systematically studied. The results show that PDA modification enhances the dispersion and interfacial interaction of SiO2 in the TPI matrix, so that the thermal stability and mechanical properties of the TPI/SiO2@PDA composites can be improved, while maintaining good shape memory performance. The impact strength and tensile strength of the composite reach the maximum values when the SiO2@PDA content is 1.5% (based on the mass of TPI, the same below), which are 43.5% and 25% higher than that of the neat TPI, respectively. Moreover, shape fixation rate (Rf) and shape recovery rate (Rr) of the composites are over 97%.
The low mechanical strength of shape memory polymers (SMP) are insufficient to meet the standards of most commercial composites today, severely limiting their use in many advanced applications. Therefore, in order to prepare high-performance SMP composite materials, a novel nano-filler SiO2@PDA was prepared by surface modification of nano-silica (SiO2) with polydopamine (PDA), its structure and properties were characterized by SEM, XPS and FTIR, respectively. Shape memory composites based on trans-1,4-polyisoprene (TPI) were prepared by filling SiO2 and SiO2@PDA into TPI as nano-fillers. The thermal stability, comprehensive mechanical properties and shape memory properties of TPI/SiO2 and TPI/SiO2@PDA composites were systematically studied. The results show that PDA modification enhances the dispersion and interfacial interaction of SiO2 in the TPI matrix, so that the thermal stability and mechanical properties of the TPI/SiO2@PDA composites can be improved, while maintaining good shape memory performance. The impact strength and tensile strength of the composite reach the maximum values when the SiO2@PDA content is 1.5% (based on the mass of TPI, the same below), which are 43.5% and 25% higher than that of the neat TPI, respectively. Moreover, shape fixation rate (Rf) and shape recovery rate (Rr) of the composites are over 97%.
2023, 40(5): 2783-2793.
doi: 10.13801/j.cnki.fhclxb.20220628.001
Abstract:
TiO2/Bi2WO6 heterojunction composite is one of the most promising visible-light derived photocatalysts. Its photocatalytic performance mainly depends on the interface structure and micro-morphology. However, it is a great challenge to control and tailor the micro-morphology and interface structure of TiO2/Bi2WO6 heterojunction. Herein, TiO2/Bi2WO6 heterojunction was synthesized by defect induced hetero-growth method. The influences of the defect size and distribution density, located on TiO2 nanobelts substrate, on the microstructure and photocatalytic activity of the TiO2/Bi2WO6 composites was further investigated. The results indicate that the corroding temperature and retention time are the key to modify the defect size and distribution density on the substrates. The defect size and distribution density are 26 nm and 12 per μm2 respectively, which facilitate to construct TiO2/Bi2WO6 heterojunction composites with well interface structure. With the as-prepared TiO2/Bi2WO6 heterojunction as photocatalyst under visible light, rhodamine B (RhB) and methylene blue (MB) can be completely photodegraded after irradiation for 12 min and 20 min respectively, and the degradation percentage of phenol also is reached 43.8% after 70 min of irradiation.
TiO2/Bi2WO6 heterojunction composite is one of the most promising visible-light derived photocatalysts. Its photocatalytic performance mainly depends on the interface structure and micro-morphology. However, it is a great challenge to control and tailor the micro-morphology and interface structure of TiO2/Bi2WO6 heterojunction. Herein, TiO2/Bi2WO6 heterojunction was synthesized by defect induced hetero-growth method. The influences of the defect size and distribution density, located on TiO2 nanobelts substrate, on the microstructure and photocatalytic activity of the TiO2/Bi2WO6 composites was further investigated. The results indicate that the corroding temperature and retention time are the key to modify the defect size and distribution density on the substrates. The defect size and distribution density are 26 nm and 12 per μm2 respectively, which facilitate to construct TiO2/Bi2WO6 heterojunction composites with well interface structure. With the as-prepared TiO2/Bi2WO6 heterojunction as photocatalyst under visible light, rhodamine B (RhB) and methylene blue (MB) can be completely photodegraded after irradiation for 12 min and 20 min respectively, and the degradation percentage of phenol also is reached 43.8% after 70 min of irradiation.
2023, 40(5): 2794-2803.
doi: 10.13801/j.cnki.fhclxb.20220705.003
Abstract:
To solve easy photocorrosion of Cd0.5Zn0.5S, palygorskite (PGS) supported Cd0.5Zn0.5S/Zn-Fe layered double hydroxides (LDH) composites (PGS-Cd0.5Zn0.5S/Zn-Fe LDH) were prepared by a two-step hydrothermal method. The aim is to improve the separation efficiency of photogenerated carriers using Zn-Fe LDH and PGS. Its crystal phase, micromorphology and optical properties were characterized by XRD, SEM, TEM, UV-Vis DRS and PL. The electron microscope images show that the needle-like PGS and graininess Cd0.5Zn0.5S are attached on the surface of Zn-Fe LDH. UV-visible diffuse reflectance spectroscopies confirm that the PGS-Cd0.5Zn0.5S/Zn-Fe LDH has a wider absorption range than Cd0.5Zn0.5S. That absorption range has a red shift from 560 nm to 605 nm. The photocatalytic activity of PGS-Cd0.5Zn0.5S/Zn-Fe LDH is higher than those of Cd0.5Zn0.5S and Zn-Fe LDH in the degradation of crystal violet. The photocatalyst with mass ratio of PGS to Cd0.5Zn0.5S/Zn-Fe LDH of 50%, the removal rate of 20 mg/L crystal violet is 97.5% by 20 mg of PGS-Cd0.5Zn0.5S/Zn-Fe LDH for 60 min.\begin{document}${\text{•}}{\rm{O}}_2^{-} $\end{document} ![]()
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To solve easy photocorrosion of Cd0.5Zn0.5S, palygorskite (PGS) supported Cd0.5Zn0.5S/Zn-Fe layered double hydroxides (LDH) composites (PGS-Cd0.5Zn0.5S/Zn-Fe LDH) were prepared by a two-step hydrothermal method. The aim is to improve the separation efficiency of photogenerated carriers using Zn-Fe LDH and PGS. Its crystal phase, micromorphology and optical properties were characterized by XRD, SEM, TEM, UV-Vis DRS and PL. The electron microscope images show that the needle-like PGS and graininess Cd0.5Zn0.5S are attached on the surface of Zn-Fe LDH. UV-visible diffuse reflectance spectroscopies confirm that the PGS-Cd0.5Zn0.5S/Zn-Fe LDH has a wider absorption range than Cd0.5Zn0.5S. That absorption range has a red shift from 560 nm to 605 nm. The photocatalytic activity of PGS-Cd0.5Zn0.5S/Zn-Fe LDH is higher than those of Cd0.5Zn0.5S and Zn-Fe LDH in the degradation of crystal violet. The photocatalyst with mass ratio of PGS to Cd0.5Zn0.5S/Zn-Fe LDH of 50%, the removal rate of 20 mg/L crystal violet is 97.5% by 20 mg of PGS-Cd0.5Zn0.5S/Zn-Fe LDH for 60 min.
2023, 40(5): 2804-2817.
doi: 10.13801/j.cnki.fhclxb.20220729.001
Abstract:
In order to enrich and recover rare earth resources in low-concentration mine tail water, a fibrous shell magnetic titanium dioxide composite Fe3O4@fTiO2 was prepared by using sol-gel method and hydrothermal methods. The material was analyzed by SEM, TEM, XPS, FTIR and XRD. The adsorption behavior of Fe3O4@fTiO2 for rare earth La3+ was investigated. The results show that Fe3O4@fTiO2 is a core-shell magnetic composite with a fibrous shell. The adsorbent has good superparamagnetic properties, and the saturation magnetization is as high as 30.81 emu·g−1. At pH=5 and 15℃, Fe3O4@fTiO2 reaches the adsorption equilibrium for rare earth La3+ within 15 min, and conformes to the pseudo-first-order kinetic model. The Langmuir isotherm adsorption model can describe the adsorption process of La3+ well, with the theoretical adsorption capacity of 142.88 mg·g−1. With NaOH solution as the regeneration reagent, the adsorption capacity of Fe3O4@fTiO2 is 110 mg·g−1 after cyclic adsorption/desorption for 5 times, which is 73.8% of the initial value, showing the good cyclic utilization.
In order to enrich and recover rare earth resources in low-concentration mine tail water, a fibrous shell magnetic titanium dioxide composite Fe3O4@fTiO2 was prepared by using sol-gel method and hydrothermal methods. The material was analyzed by SEM, TEM, XPS, FTIR and XRD. The adsorption behavior of Fe3O4@fTiO2 for rare earth La3+ was investigated. The results show that Fe3O4@fTiO2 is a core-shell magnetic composite with a fibrous shell. The adsorbent has good superparamagnetic properties, and the saturation magnetization is as high as 30.81 emu·g−1. At pH=5 and 15℃, Fe3O4@fTiO2 reaches the adsorption equilibrium for rare earth La3+ within 15 min, and conformes to the pseudo-first-order kinetic model. The Langmuir isotherm adsorption model can describe the adsorption process of La3+ well, with the theoretical adsorption capacity of 142.88 mg·g−1. With NaOH solution as the regeneration reagent, the adsorption capacity of Fe3O4@fTiO2 is 110 mg·g−1 after cyclic adsorption/desorption for 5 times, which is 73.8% of the initial value, showing the good cyclic utilization.
2023, 40(5): 2818-2826.
doi: 10.13801/j.cnki.fhclxb.20221213.002
Abstract:
All inorganic carbon-based CsPbI2Br perovskite solar cells (C-PSCs) have lower photoelectric conversion efficiency due to poor contact performance and mismatch of energy band between carbon electrode and perovskite laye. In this paper, two kinds of regular octahedral CuxO with different morphologies and structures were prepared by a simple glucose reduction method combined with calcination technology. As inorganic hole transport materials, C-PSCs with the structure of conductive glass (FTO)/SnO2/CsPbI2Br/CuO/C were prepared and the influence of morphologies and structures on the photoelectric performance was studied. The results show that CuxO has good chemical stability and p-type carrier transport characteristics, which can effectively enhance the interface contact between CsPbI2Br and carbon electrode, improve the carrier transport performance, reduce charge recombination, and extend the photoelectron life. The highest photoelectric conversion efficiency of CsPbI2Br based C-PSCs devices based on Cu2O and CuO is 11.62% and 13.22%, respectively, which is 19.5% and 36.0% higher than that of blank devices. In addition, by adding Cu2O and CuO, the long-term stability of the device in the air is also significantly improved. This work has a certain significance for improving the performance of CsPbI2Br based C-PSCs.
All inorganic carbon-based CsPbI2Br perovskite solar cells (C-PSCs) have lower photoelectric conversion efficiency due to poor contact performance and mismatch of energy band between carbon electrode and perovskite laye. In this paper, two kinds of regular octahedral CuxO with different morphologies and structures were prepared by a simple glucose reduction method combined with calcination technology. As inorganic hole transport materials, C-PSCs with the structure of conductive glass (FTO)/SnO2/CsPbI2Br/CuO/C were prepared and the influence of morphologies and structures on the photoelectric performance was studied. The results show that CuxO has good chemical stability and p-type carrier transport characteristics, which can effectively enhance the interface contact between CsPbI2Br and carbon electrode, improve the carrier transport performance, reduce charge recombination, and extend the photoelectron life. The highest photoelectric conversion efficiency of CsPbI2Br based C-PSCs devices based on Cu2O and CuO is 11.62% and 13.22%, respectively, which is 19.5% and 36.0% higher than that of blank devices. In addition, by adding Cu2O and CuO, the long-term stability of the device in the air is also significantly improved. This work has a certain significance for improving the performance of CsPbI2Br based C-PSCs.
2023, 40(5): 2827-2835.
doi: 10.13801/j.cnki.fhclxb.20220704.003
Abstract:
Hydrogen generation by water electrolysis is an environmentally sound approach, it may become a significant breakthrough direction for the increasingly tense energy problems and carbon neutrality strategy. At present, precious metals are scarce, and precious metal hydrogen evolution (HER) catalysts represented by Pt/C are not suitable for long-term use. Iron foam (IF) is stable in structure and widely available. Based on IF, the simple soaking method was adopted to grow needle-shaped flaky ferric hydroxide (FeOOH/IF) on IF in situ, and then ferroferric oxide (Ov-Fe3O4/IF) containing oxygen vacancies (Ovs) was prepared by vacuum treatment, finally, phosphorization was carried out to prepare the Fe3O4 nanoneedle which was coordinated and controlled by Ovs and P atom doping (P-Ov-Fe3O4/IF). The doping of P atom can optimize the electronic environment around Fe atom and activate the catalytic activity of Fe3O4; Ovs can enhance the conductivity of the material and provide defects, which are more conducive to doping of P atoms. The results show that P-Ov-Fe3O4/IF has excellent HER performance. At −10 mA·cm−2, the overpotential is only 40.96 mV, and the Tafel slope is 70.93 mV·dec−1, which is similar to that of Pt/C. And after 96 hours of continuous operation under different currents, the voltage change is basically negligible and the stability is excellent. Ovs and P atom doping can jointly promote the electrocatalytic HER performance of iron-based materials. This study provides new ideas and strategies for the preparation of non-precious metal electrocatalytic materials.
Hydrogen generation by water electrolysis is an environmentally sound approach, it may become a significant breakthrough direction for the increasingly tense energy problems and carbon neutrality strategy. At present, precious metals are scarce, and precious metal hydrogen evolution (HER) catalysts represented by Pt/C are not suitable for long-term use. Iron foam (IF) is stable in structure and widely available. Based on IF, the simple soaking method was adopted to grow needle-shaped flaky ferric hydroxide (FeOOH/IF) on IF in situ, and then ferroferric oxide (Ov-Fe3O4/IF) containing oxygen vacancies (Ovs) was prepared by vacuum treatment, finally, phosphorization was carried out to prepare the Fe3O4 nanoneedle which was coordinated and controlled by Ovs and P atom doping (P-Ov-Fe3O4/IF). The doping of P atom can optimize the electronic environment around Fe atom and activate the catalytic activity of Fe3O4; Ovs can enhance the conductivity of the material and provide defects, which are more conducive to doping of P atoms. The results show that P-Ov-Fe3O4/IF has excellent HER performance. At −10 mA·cm−2, the overpotential is only 40.96 mV, and the Tafel slope is 70.93 mV·dec−1, which is similar to that of Pt/C. And after 96 hours of continuous operation under different currents, the voltage change is basically negligible and the stability is excellent. Ovs and P atom doping can jointly promote the electrocatalytic HER performance of iron-based materials. This study provides new ideas and strategies for the preparation of non-precious metal electrocatalytic materials.
2023, 40(5): 2836-2846.
doi: 10.13801/j.cnki.fhclxb.20220803.005
Abstract:
A three-dimensional cross-linked graphene (G) supported CoO nano composite (3D G/CoO) was prepared by solvothermal reaction followed by annealing at high temperature using graphene oxide and metal organic framework (ZIF-67) as precursors. The structures and morphologies of 3D G/CoO were characterized by XRD, XPS, UV-vis diffuse reflectance spectrum, SEM and TEM. The results show that CoO particles with an average particle size of ~34.5 nm are uniformly loaded on the graphene sheets. Based on the unique hot electron emission properties of 3D G, as well as the synergetic effect between the two components, 3D G/CoO nano composites exhibit excellent photocatalytic properties for hydrogen evolution from water splitting under the irradiation. Under 300 W Xenon lamp, the hydrogen production rate is 10.1 mmol·gcat−1·h−1. The apparent quantum efficiency of 7.77% is obtained at 520 nm visible light. After recycling for 5 times, the hydrogen production rate is maintained at 88%. This high-performance visible light responsive 3D photocatalyst is of great significance to the development of highly efficient catalysts in the field of photocatalysis.
A three-dimensional cross-linked graphene (G) supported CoO nano composite (3D G/CoO) was prepared by solvothermal reaction followed by annealing at high temperature using graphene oxide and metal organic framework (ZIF-67) as precursors. The structures and morphologies of 3D G/CoO were characterized by XRD, XPS, UV-vis diffuse reflectance spectrum, SEM and TEM. The results show that CoO particles with an average particle size of ~34.5 nm are uniformly loaded on the graphene sheets. Based on the unique hot electron emission properties of 3D G, as well as the synergetic effect between the two components, 3D G/CoO nano composites exhibit excellent photocatalytic properties for hydrogen evolution from water splitting under the irradiation. Under 300 W Xenon lamp, the hydrogen production rate is 10.1 mmol·gcat−1·h−1. The apparent quantum efficiency of 7.77% is obtained at 520 nm visible light. After recycling for 5 times, the hydrogen production rate is maintained at 88%. This high-performance visible light responsive 3D photocatalyst is of great significance to the development of highly efficient catalysts in the field of photocatalysis.
2023, 40(5): 2847-2858.
doi: 10.13801/j.cnki.fhclxb.20220826.001
Abstract:
Construction of heterojunction materials with efficient charge transfer pathways is the key to photocatalytic degradation of composite pollutants in water. CdS QDs@MOX(Al) heterojunction photocatalyst was prepared by dispersion of CdS quantum dots (CdS QDs) in metal-organic gel MOX(Al) using the gel-confinement-method. The compositional structure and interfacial charge transfer efficiency of the samples were characterized and analyzed by XRD, TEM, XPS, N2 adsorption-desorption, UV-Vis DRS, transient photocurrent (TPC) response and electrochemical impedance spectroscopy (EIS), and the catalytic activity and mechanism for the synergistic degradation of norfloxacin (NF) and reduction Cr(VI) under visible light were investigated. The results show that 1.0-CdS QDs@MOX(Al) exhibite excellent photocatalytic activity for the NF/Cr(VI) complex pollutant system, the degradation process conforms to the pseudo-first-order kinetic model, and the apparent rate constants k are 6.1 (8.5) and 5.3 (3.5) times higher than those of pure MOX(Al) and CdS, respectively. Compared with the single pollutant system, the photocatalytic efficiency of CdS QDs@MOX(Al) for the NF/Cr(VI) complex pollutant system is significantly improved. The combination of active species capture experiments confirm that h+ and •O2− are the main active species. The enhanced photocatalytic activity is mainly attributed to the Type-II heterostructure formed between MOX(Al) and CdS QDs, which accelerates the effective separation and transfer of photogenerated charges at the interface of the heterostructure.
Construction of heterojunction materials with efficient charge transfer pathways is the key to photocatalytic degradation of composite pollutants in water. CdS QDs@MOX(Al) heterojunction photocatalyst was prepared by dispersion of CdS quantum dots (CdS QDs) in metal-organic gel MOX(Al) using the gel-confinement-method. The compositional structure and interfacial charge transfer efficiency of the samples were characterized and analyzed by XRD, TEM, XPS, N2 adsorption-desorption, UV-Vis DRS, transient photocurrent (TPC) response and electrochemical impedance spectroscopy (EIS), and the catalytic activity and mechanism for the synergistic degradation of norfloxacin (NF) and reduction Cr(VI) under visible light were investigated. The results show that 1.0-CdS QDs@MOX(Al) exhibite excellent photocatalytic activity for the NF/Cr(VI) complex pollutant system, the degradation process conforms to the pseudo-first-order kinetic model, and the apparent rate constants k are 6.1 (8.5) and 5.3 (3.5) times higher than those of pure MOX(Al) and CdS, respectively. Compared with the single pollutant system, the photocatalytic efficiency of CdS QDs@MOX(Al) for the NF/Cr(VI) complex pollutant system is significantly improved. The combination of active species capture experiments confirm that h+ and •O2− are the main active species. The enhanced photocatalytic activity is mainly attributed to the Type-II heterostructure formed between MOX(Al) and CdS QDs, which accelerates the effective separation and transfer of photogenerated charges at the interface of the heterostructure.
2023, 40(5): 2859-2875.
doi: 10.13801/j.cnki.fhclxb.20220706.001
Abstract:
The bond-slip constitutive model is often used to describe the interface behavior of glass fiber reinforced polymer (GFRP) bars to engineered cementitious composite (ECC). Although significant efforts have been made on the bond-slip relation of GFRP bar to normal concrete, few studies have focused on GFRP bar/ECC interface, particularly in the exposure of some special environments, including alkaline-saline conditions or freeze-thaw cycling. Therefore, this study aims to derive the bond-slip model for GFRP bar to ECC material in these environments through experimental and analytical study. 66 GFRP bar/concrete specimens were designed to gain an understanding of critical factors, including surface treatment of GFRP bars, matrix types and concrete strength, under three different conditions (i.e., ambient environment, alkaline-saline solution, and freeze-thaw cycles), on how to affect the failure modes, bond mechanism and bond-slip curves. The test results show that the pullout failures with cracks mainly occur on ribbed GFRP bar/ECC specimens. After freeze-thaw cycles, ribbed GFRP bar/normal concrete specimens change from splitting failure to pullout failure with cracks; The slope of bond-slip curves decreases. The residual branch curves of the specimens destroyed by pullout failure or pullout failure with crack attenuate in wave mode, and the difference of slips between the peak residual stresses is about a rib spacing of GFRP bar. And the difference of slips between the peak residual stresses is about a rib spacing of GFRP bar. In addition, the bond-slip curves were fitted with the existing bond-slip models. According to the fitting results and the actual bond-slip characteristics of GFRP bar/ECC interface under three different environments, a bond-slip model containing parameters A, B and α was proposed, and the fitting correlation coefficient R2 was above 0.9, and the values of parameters A, B and α were concentrated in the range of −0.6-0.2, −0.1-0.1 and −0.6-−0.3, respectively. In addition, the accuracy and effectiveness of the proposed model were further verified using previous data from the literature.
The bond-slip constitutive model is often used to describe the interface behavior of glass fiber reinforced polymer (GFRP) bars to engineered cementitious composite (ECC). Although significant efforts have been made on the bond-slip relation of GFRP bar to normal concrete, few studies have focused on GFRP bar/ECC interface, particularly in the exposure of some special environments, including alkaline-saline conditions or freeze-thaw cycling. Therefore, this study aims to derive the bond-slip model for GFRP bar to ECC material in these environments through experimental and analytical study. 66 GFRP bar/concrete specimens were designed to gain an understanding of critical factors, including surface treatment of GFRP bars, matrix types and concrete strength, under three different conditions (i.e., ambient environment, alkaline-saline solution, and freeze-thaw cycles), on how to affect the failure modes, bond mechanism and bond-slip curves. The test results show that the pullout failures with cracks mainly occur on ribbed GFRP bar/ECC specimens. After freeze-thaw cycles, ribbed GFRP bar/normal concrete specimens change from splitting failure to pullout failure with cracks; The slope of bond-slip curves decreases. The residual branch curves of the specimens destroyed by pullout failure or pullout failure with crack attenuate in wave mode, and the difference of slips between the peak residual stresses is about a rib spacing of GFRP bar. And the difference of slips between the peak residual stresses is about a rib spacing of GFRP bar. In addition, the bond-slip curves were fitted with the existing bond-slip models. According to the fitting results and the actual bond-slip characteristics of GFRP bar/ECC interface under three different environments, a bond-slip model containing parameters A, B and α was proposed, and the fitting correlation coefficient R2 was above 0.9, and the values of parameters A, B and α were concentrated in the range of −0.6-0.2, −0.1-0.1 and −0.6-−0.3, respectively. In addition, the accuracy and effectiveness of the proposed model were further verified using previous data from the literature.
2023, 40(5): 2876-2884.
doi: 10.13801/j.cnki.fhclxb.20220726.001
Abstract:
Recycled aggregate concrete is regarded as a kind of heterogeneous composite material composed of mortar matrix phase, recycled aggregate phase and the interfacial transition zone (ITZ-2) phase between new and old mortars. Among them, mortar matrix phase is composed of fine aggregate, hardened cement pastes and the interfacial transition zone (ITZ-1) between them, while the recycled aggregate phase is composed of old aggregate, attached old mortar, old interfacial transition zone (ITZ-3) between them. Based on the N-layer spherical inclusion theory with considering the influence of microscale phase, a five-phase multiscale model of effective chloride diffusion coefficient of recycled aggregate concrete was established. The accuracy and validity of the proposed model were verified by comparing between the experimental and predicted results of steady-state chloride diffusion coefficient of hardened cement paste, mortar and recycled aggregate concrete, respectively. Finally, the influence of the key parameters including the chloride ingress time, the volume fraction of recycled coarse aggregate and the attached mortar content on effective chloride diffusion coefficient was further discussed. The results show that the predicted effective diffusion coefficient agrees well with the experimental results obtained in the literature. It indicates that the proposed model can be universally used to predict the effective chloride diffusion coefficient of recycled aggregate concrete, which provides a theoretical basis for durability evaluation and service life prediction of recycled aggregate concrete exposed to chloride salt environment.
Recycled aggregate concrete is regarded as a kind of heterogeneous composite material composed of mortar matrix phase, recycled aggregate phase and the interfacial transition zone (ITZ-2) phase between new and old mortars. Among them, mortar matrix phase is composed of fine aggregate, hardened cement pastes and the interfacial transition zone (ITZ-1) between them, while the recycled aggregate phase is composed of old aggregate, attached old mortar, old interfacial transition zone (ITZ-3) between them. Based on the N-layer spherical inclusion theory with considering the influence of microscale phase, a five-phase multiscale model of effective chloride diffusion coefficient of recycled aggregate concrete was established. The accuracy and validity of the proposed model were verified by comparing between the experimental and predicted results of steady-state chloride diffusion coefficient of hardened cement paste, mortar and recycled aggregate concrete, respectively. Finally, the influence of the key parameters including the chloride ingress time, the volume fraction of recycled coarse aggregate and the attached mortar content on effective chloride diffusion coefficient was further discussed. The results show that the predicted effective diffusion coefficient agrees well with the experimental results obtained in the literature. It indicates that the proposed model can be universally used to predict the effective chloride diffusion coefficient of recycled aggregate concrete, which provides a theoretical basis for durability evaluation and service life prediction of recycled aggregate concrete exposed to chloride salt environment.
2023, 40(5): 2885-2896.
doi: 10.13801/j.cnki.fhclxb.20220811.004
Abstract:
To improve the energy absorption performance of metal circular tube composite cladding, foam concrete filled aluminum tube composite cladding was proposed in the present study. With consideration of different foam concrete densities of 300 kg/m3, 700 kg/m3 and 1100 kg/m3, the deformation mode, mechanical properties and energy absorption performance of single foam concrete filled aluminum tube, as well as foam concrete filled aluminum tube composite cladding under quasi-static compression, were experimentally investigated. The results show that the energy absorption of the aluminum tube filled with 300 kg/m3 foam concrete is slightly inferior to that of the hollow aluminum tube. With increasing the foam concrete density to 700 kg/m3 and 1100 kg/m3, the energy absorption performance of the filled aluminum tube is significantly improved with the increased total energy absorption by 286% and 815%, respectively. Compared to the single aluminum tube, the mutual extrusion among tubes would greatly improve the specific energy absorption of the hollow aluminum tube and 300 kg/m3 foam concrete filled composite claddings, which are increased by 28.6% and 68.9%, respectively. Nevertheless, the specific energy absorptions of 700 kg/m3 and 1100 kg/m3 foam concrete filled aluminum tube composite cladding decrease by 42.7% and 38.1% due to the mutual extrusion effect of aluminum tubes. Therefore, from the point view of the practical application of the proposed foam concrete filled aluminum tube composite cladding, a small aluminum tube spacing is suggested with the low density of foam concrete filler, meanwhile, a large aluminum tube spacing is recommended to prevent the extrusion of aluminum tube with the high density of foam concrete filler.
To improve the energy absorption performance of metal circular tube composite cladding, foam concrete filled aluminum tube composite cladding was proposed in the present study. With consideration of different foam concrete densities of 300 kg/m3, 700 kg/m3 and 1100 kg/m3, the deformation mode, mechanical properties and energy absorption performance of single foam concrete filled aluminum tube, as well as foam concrete filled aluminum tube composite cladding under quasi-static compression, were experimentally investigated. The results show that the energy absorption of the aluminum tube filled with 300 kg/m3 foam concrete is slightly inferior to that of the hollow aluminum tube. With increasing the foam concrete density to 700 kg/m3 and 1100 kg/m3, the energy absorption performance of the filled aluminum tube is significantly improved with the increased total energy absorption by 286% and 815%, respectively. Compared to the single aluminum tube, the mutual extrusion among tubes would greatly improve the specific energy absorption of the hollow aluminum tube and 300 kg/m3 foam concrete filled composite claddings, which are increased by 28.6% and 68.9%, respectively. Nevertheless, the specific energy absorptions of 700 kg/m3 and 1100 kg/m3 foam concrete filled aluminum tube composite cladding decrease by 42.7% and 38.1% due to the mutual extrusion effect of aluminum tubes. Therefore, from the point view of the practical application of the proposed foam concrete filled aluminum tube composite cladding, a small aluminum tube spacing is suggested with the low density of foam concrete filler, meanwhile, a large aluminum tube spacing is recommended to prevent the extrusion of aluminum tube with the high density of foam concrete filler.
2023, 40(5): 2897-2912.
doi: 10.13801/j.cnki.fhclxb.20220706.003
Abstract:
Considering the two main factors of basalt fiber volume fraction and aspect ratio, the axial tensile failure mode, full stress-strain curve, tensile load deformation performance and toughness of basalt fiber concrete reinforced were studied through direct tensile test. The results show that the uniaxial tensile failure of basalt fiber reinforced concrete shows obvious plastic characteristics, and basalt fiber significantly enhances the toughness of concrete under axial tensile load. Compared with ordinary concrete, with the increase of basalt fiber reinforcement factor, the characteristic points and fracture energy of the full axial tensile stress-strain curve increase first and then decrease. Based on the full axial tensile stress-strain curve analysis, the axial tensile stress-strain constitutive model of basalt fiber reinforced concrete about fiber volume fraction and length diameter ratio was proposed, which can be used as a reference for nonlinear analysis and engineering design of basalt fiber reinforced concrete structures and components. The tensile compression ratio, flexural compression ratio and uniaxial tensile failure fracture energy were compared and analyzed. It is found that fracture energy can accurately evaluate the tensile toughness of basalt fiber reinforced concrete (BFRC), and the maximum increase rate of BFRC toughness compared with normal concrete (NC) is 43.0%.
Considering the two main factors of basalt fiber volume fraction and aspect ratio, the axial tensile failure mode, full stress-strain curve, tensile load deformation performance and toughness of basalt fiber concrete reinforced were studied through direct tensile test. The results show that the uniaxial tensile failure of basalt fiber reinforced concrete shows obvious plastic characteristics, and basalt fiber significantly enhances the toughness of concrete under axial tensile load. Compared with ordinary concrete, with the increase of basalt fiber reinforcement factor, the characteristic points and fracture energy of the full axial tensile stress-strain curve increase first and then decrease. Based on the full axial tensile stress-strain curve analysis, the axial tensile stress-strain constitutive model of basalt fiber reinforced concrete about fiber volume fraction and length diameter ratio was proposed, which can be used as a reference for nonlinear analysis and engineering design of basalt fiber reinforced concrete structures and components. The tensile compression ratio, flexural compression ratio and uniaxial tensile failure fracture energy were compared and analyzed. It is found that fracture energy can accurately evaluate the tensile toughness of basalt fiber reinforced concrete (BFRC), and the maximum increase rate of BFRC toughness compared with normal concrete (NC) is 43.0%.
2023, 40(5): 2913-2925.
doi: 10.13801/j.cnki.fhclxb.20220721.001
Abstract:
In order to study the effect of grooved interface on the bonding properties of high-strength steel wire mesh reinforced engineered cementitious composites (HSSWM-ECC) and concrete, a total of 36 specimens in 12 sets were designed and fabricated for beam tests, considering the effect of the number of grooves, depth of grooves, steel strand diameter, longitudinal strand ratio and tensile strength of ECC. The results show that the damage patterns include interfacial peeling failure and strand fracture damage. Within the range of the total grooves involved width of 20 mm and the groove depth of 5 mm, the bond behavior between HSSWM-ECC and concrete can be effectively improved by increasing the number or depth of grooves. The longitudinal strand ratio and ECC tensile strength are linearly correlated with the interface bond performance indicators (bond stress and its corresponding slip). Based on the analysis of the bonding mechanism of the grooved interface, a prediction model of the shear bearing capacity considering the groove features (number of grooves, depth of grooves) and the strength characteristics of the HSSWM-ECC layer (longitudinal strand ratio, strand diameter, ECC tensile strength) is established, which is in good agreement with the test results.
In order to study the effect of grooved interface on the bonding properties of high-strength steel wire mesh reinforced engineered cementitious composites (HSSWM-ECC) and concrete, a total of 36 specimens in 12 sets were designed and fabricated for beam tests, considering the effect of the number of grooves, depth of grooves, steel strand diameter, longitudinal strand ratio and tensile strength of ECC. The results show that the damage patterns include interfacial peeling failure and strand fracture damage. Within the range of the total grooves involved width of 20 mm and the groove depth of 5 mm, the bond behavior between HSSWM-ECC and concrete can be effectively improved by increasing the number or depth of grooves. The longitudinal strand ratio and ECC tensile strength are linearly correlated with the interface bond performance indicators (bond stress and its corresponding slip). Based on the analysis of the bonding mechanism of the grooved interface, a prediction model of the shear bearing capacity considering the groove features (number of grooves, depth of grooves) and the strength characteristics of the HSSWM-ECC layer (longitudinal strand ratio, strand diameter, ECC tensile strength) is established, which is in good agreement with the test results.
2023, 40(5): 2926-2937.
doi: 10.13801/j.cnki.fhclxb.20220707.003
Abstract:
High ductile fiber-reinforced concrete (HDC) is characterized by its excellent deformation ability. The utilization ratio of high-strength steel bars (HSS) can be effectively increased when HSS is applied in reinforced HDC members. Based on the analytical model for the flexural capacity of reinforced concrete members in code GB/T 50010—2010, the flexural capacities of the HSS reinforced concrete members and HSS reinforced HDC members were derived, respectively. Besides, some key parameters such as the relative depth of compression zone for balanced failure, maximum and minimum reinforcement ratios, the range of compression zone height and the limitation of the axial load ratio of the HSS reinforced HDC members were derived, respectively. The effect of strength grade of the steel bars, strength grade of concrete and HDC on each parameter aforementioned were investigated, respectively. A calculation method for the bearing capacity of the HSS reinforced HDC members was proposed, and the average error between the calculated results and the experimental results is less than 12.5%.
High ductile fiber-reinforced concrete (HDC) is characterized by its excellent deformation ability. The utilization ratio of high-strength steel bars (HSS) can be effectively increased when HSS is applied in reinforced HDC members. Based on the analytical model for the flexural capacity of reinforced concrete members in code GB/T 50010—2010, the flexural capacities of the HSS reinforced concrete members and HSS reinforced HDC members were derived, respectively. Besides, some key parameters such as the relative depth of compression zone for balanced failure, maximum and minimum reinforcement ratios, the range of compression zone height and the limitation of the axial load ratio of the HSS reinforced HDC members were derived, respectively. The effect of strength grade of the steel bars, strength grade of concrete and HDC on each parameter aforementioned were investigated, respectively. A calculation method for the bearing capacity of the HSS reinforced HDC members was proposed, and the average error between the calculated results and the experimental results is less than 12.5%.
2023, 40(5): 2938-2950.
doi: 10.13801/j.cnki.fhclxb.20220804.004
Abstract:
Four working conditions of room temperature (25℃), 200℃, 400℃ and 600℃ were designed. The failure modes and mechanical properties of steel-concrete composite beams reinforced with basalt fiber reinforced polymer (BFRP) bars after high temperature were studied by the model experiment method. The failure modes and bearing capacity of steel-concrete composite beams reinforced with BFRP bars and steel bars were studied by analyzing the test beam’s crack development, deflection deformation, temperature field and failure process. The results show that the mechanical properties of BFRP bars are significantly reduced after a high temperature of 400℃. The mechanical properties of composite beams are significantly reduced after the high temperature of 400℃ due to the deterioration of BFRP bars. The expansion of BFRP bars leads to the cracking of concrete slab, and the crack development is obviously different from that of steel-concrete composite beams reinforced with steel bars. The main cracks regularly develop along with the transverse reinforcements, and the cracks are wider. When the temperature is lower than 400℃, BFRP bars do not reach the deterioration temperature due to the wrapping of concrete, and the bearing capacity and appearance of the two steel-concrete composite beams have little difference. After 600℃, the deterioration of BFRP bars weakens the stiffness and strength of concrete slabs, resulting in a decrease in the bearing capacity of steel-concrete composite beams reinforced with BFRP bars more than steel bars. The steel-concrete composite beams reinforced with BFRP bars have larger deformation after loading due to the small overall stiffness. After high temperature, the failure modes of the two steel-concrete composite beams are similar, which are shear failure with evident elastic, elastoplastic and failure stages. At 600℃, the ductility of the two steel-concrete composite beams is significantly reduced, the plastic deformation is reduced, and the failure is more sudden. The research results can provide a reference for applying BFRP bars in steel-concrete composite beams.
Four working conditions of room temperature (25℃), 200℃, 400℃ and 600℃ were designed. The failure modes and mechanical properties of steel-concrete composite beams reinforced with basalt fiber reinforced polymer (BFRP) bars after high temperature were studied by the model experiment method. The failure modes and bearing capacity of steel-concrete composite beams reinforced with BFRP bars and steel bars were studied by analyzing the test beam’s crack development, deflection deformation, temperature field and failure process. The results show that the mechanical properties of BFRP bars are significantly reduced after a high temperature of 400℃. The mechanical properties of composite beams are significantly reduced after the high temperature of 400℃ due to the deterioration of BFRP bars. The expansion of BFRP bars leads to the cracking of concrete slab, and the crack development is obviously different from that of steel-concrete composite beams reinforced with steel bars. The main cracks regularly develop along with the transverse reinforcements, and the cracks are wider. When the temperature is lower than 400℃, BFRP bars do not reach the deterioration temperature due to the wrapping of concrete, and the bearing capacity and appearance of the two steel-concrete composite beams have little difference. After 600℃, the deterioration of BFRP bars weakens the stiffness and strength of concrete slabs, resulting in a decrease in the bearing capacity of steel-concrete composite beams reinforced with BFRP bars more than steel bars. The steel-concrete composite beams reinforced with BFRP bars have larger deformation after loading due to the small overall stiffness. After high temperature, the failure modes of the two steel-concrete composite beams are similar, which are shear failure with evident elastic, elastoplastic and failure stages. At 600℃, the ductility of the two steel-concrete composite beams is significantly reduced, the plastic deformation is reduced, and the failure is more sudden. The research results can provide a reference for applying BFRP bars in steel-concrete composite beams.
2023, 40(5): 2951-2959.
doi: 10.13801/j.cnki.fhclxb.20220712.002
Abstract:
In order to study the freeze-thaw resistance of rice husk ash rubber concrete (RRC), the mass loss, relative dynamic modulus loss, strength loss and microstructure characteristics of normal concrete (NC) and RRC after freeze-thaw cycles in chloride environment were compared and analyzed, and the relationship between relative dynamic modulus and relative compressive strength was fitted and analyzed. The results show that with the increase of freeze-thaw cycles, the pit erosion on the concrete surface becomes more obvious, the internal pores increase, microcracks develop and penetrate, and the macroscopic strength decreases significantly. The relative dynamic modulus has a good correlation with the compressive strength, and the fitting structure is better. The high elasticity of rubber and high pozzolanic effect of rice husk ash effectively alleviate the damage caused by frost heaving force, and the damage degree of RRC in each freeze-thaw stage is significantly better than that of NC. When the content of rice husk ash (mass ratio to cementitious materials) is 10% and the content of rubber (volume replacement of sand) is 10%, the comprehensive optimum of mechanical properties and freeze-thawing resistance of RRC is the best. After 120 freeze-thaw cycles, the loss rate of compressive strength is 18% lower than that of NC.
In order to study the freeze-thaw resistance of rice husk ash rubber concrete (RRC), the mass loss, relative dynamic modulus loss, strength loss and microstructure characteristics of normal concrete (NC) and RRC after freeze-thaw cycles in chloride environment were compared and analyzed, and the relationship between relative dynamic modulus and relative compressive strength was fitted and analyzed. The results show that with the increase of freeze-thaw cycles, the pit erosion on the concrete surface becomes more obvious, the internal pores increase, microcracks develop and penetrate, and the macroscopic strength decreases significantly. The relative dynamic modulus has a good correlation with the compressive strength, and the fitting structure is better. The high elasticity of rubber and high pozzolanic effect of rice husk ash effectively alleviate the damage caused by frost heaving force, and the damage degree of RRC in each freeze-thaw stage is significantly better than that of NC. When the content of rice husk ash (mass ratio to cementitious materials) is 10% and the content of rubber (volume replacement of sand) is 10%, the comprehensive optimum of mechanical properties and freeze-thawing resistance of RRC is the best. After 120 freeze-thaw cycles, the loss rate of compressive strength is 18% lower than that of NC.
2023, 40(5): 2960-2971.
doi: 10.13801/j.cnki.fhclxb.20220707.002
Abstract:
The heat damage of steam-curing concrete was restrained by adding rubber particles into steam-curing concrete to prepare steam-curing rubber concrete. The compressive strength of steam-curing rubber concrete was tested through experiments. A random aggregate model of rubber concrete considering interface transition zone was established based on ABAQUS simulation. The influence of rubber particles on the temperature damage stress of concrete in the cooling stage was studied. The influence of rubber particles on the temperature damage stress of concrete at the cooling stage was studied. The development of microcracks in steam-curing concrete inhibited by rubber particles was studied from a microscopical point of view, and taking the temperature damage stress as the initial defect, the compressive property of rubber concrete was studied, and the reliability of the simulation results was verified. The effect of rubber particles on the pore structure of steam-curing concrete was studied by mercury intrusion porosimetry (MIP) test. The bond between rubber and cement was studied by an ultra-depth-of-field microscope. The results show that the addition of rubber particles can restrain heat damage and reduce the strength loss of steam-curing concrete. Rubber particles can effectively reduce the total porosity of steam-curing concrete specimens, and the harmful pore size of steam-curing rubber concrete decreases by 3.1% compared with that ordi-nary steam-curing concrete without adding rubber particles. Meanwhile, the bond between rubber and cement matrix is improved.
The heat damage of steam-curing concrete was restrained by adding rubber particles into steam-curing concrete to prepare steam-curing rubber concrete. The compressive strength of steam-curing rubber concrete was tested through experiments. A random aggregate model of rubber concrete considering interface transition zone was established based on ABAQUS simulation. The influence of rubber particles on the temperature damage stress of concrete in the cooling stage was studied. The influence of rubber particles on the temperature damage stress of concrete at the cooling stage was studied. The development of microcracks in steam-curing concrete inhibited by rubber particles was studied from a microscopical point of view, and taking the temperature damage stress as the initial defect, the compressive property of rubber concrete was studied, and the reliability of the simulation results was verified. The effect of rubber particles on the pore structure of steam-curing concrete was studied by mercury intrusion porosimetry (MIP) test. The bond between rubber and cement was studied by an ultra-depth-of-field microscope. The results show that the addition of rubber particles can restrain heat damage and reduce the strength loss of steam-curing concrete. Rubber particles can effectively reduce the total porosity of steam-curing concrete specimens, and the harmful pore size of steam-curing rubber concrete decreases by 3.1% compared with that ordi-nary steam-curing concrete without adding rubber particles. Meanwhile, the bond between rubber and cement matrix is improved.
2023, 40(5): 2972-2987.
doi: 10.13801/j.cnki.fhclxb.20220629.003
Abstract:
In order to explore the effect of highland barley straw ash (HBSA) on the durability and pore structure of magnesium oxychloride cement (MOC), HBSA was used to improve the durability of MOC, and highland barley straw ash–magnesium oxychloride cement composites were prepared. The durability of magnesium oxychloride cement mortar (MOCM) with different HBSA contents were studied under the conditions of salt lake brine erosion, freeze-thaw cycle erosion and salt–frozen coupling erosion. Three durability evaluation indexes: Relative mass evaluation parameters, relative dynamic elastic modulus evaluation parameters and relative compressive strength evaluation parameters were used to reflect the durability deterioration law of MOCM, and determine the optimal content of HBSA. Through the analysis of apparent morphology and pore structure test, the durability damage degree and pore structure characteristics of MOCM under different erosion conditions were revealed. The results show that the durability damage of MOCM caused by freeze-thaw cycle erosion is more serious than salt brine erosion and salt-frozen coupling erosion, and more macro cracks are produced on the surface of MOCM specimens. The addition of HBSA can significantly improve the durability of MOCM. When the content of HBSA is 10wt%, the durability of MOCM under salt lake brine erosion, freeze-thaw cycle erosion and salt–frozen coupling erosion is 21.24%, 23.48% and 18.91% higher than that without HBSA, respectively. The opening porosity of MOCM added with 10wt%HBSA decreases, the specific surface area increases, and the most probable pore diameter and average pore diameter decrease, which refines the pore structure of MOCM and improves the durability.
In order to explore the effect of highland barley straw ash (HBSA) on the durability and pore structure of magnesium oxychloride cement (MOC), HBSA was used to improve the durability of MOC, and highland barley straw ash–magnesium oxychloride cement composites were prepared. The durability of magnesium oxychloride cement mortar (MOCM) with different HBSA contents were studied under the conditions of salt lake brine erosion, freeze-thaw cycle erosion and salt–frozen coupling erosion. Three durability evaluation indexes: Relative mass evaluation parameters, relative dynamic elastic modulus evaluation parameters and relative compressive strength evaluation parameters were used to reflect the durability deterioration law of MOCM, and determine the optimal content of HBSA. Through the analysis of apparent morphology and pore structure test, the durability damage degree and pore structure characteristics of MOCM under different erosion conditions were revealed. The results show that the durability damage of MOCM caused by freeze-thaw cycle erosion is more serious than salt brine erosion and salt-frozen coupling erosion, and more macro cracks are produced on the surface of MOCM specimens. The addition of HBSA can significantly improve the durability of MOCM. When the content of HBSA is 10wt%, the durability of MOCM under salt lake brine erosion, freeze-thaw cycle erosion and salt–frozen coupling erosion is 21.24%, 23.48% and 18.91% higher than that without HBSA, respectively. The opening porosity of MOCM added with 10wt%HBSA decreases, the specific surface area increases, and the most probable pore diameter and average pore diameter decrease, which refines the pore structure of MOCM and improves the durability.
2023, 40(5): 2988-3001.
doi: 10.13801/j.cnki.fhclxb.20220809.005
Abstract:
The influences of inorganic mineral on the properties of waterborne fluorocarbon coating were studied, and the variation in adhesion of fluorocarbon composite coatings under the salt freezing environment was studied, and the influence of fluorocarbon composite coatings on the amount of spalling per unit area of concrete was analyzed, by surface hydrophobic property test, mechanical property test, interface bonding property test and salt freezing test of concrete. The improvement mechanism of salt freezing resistance of concrete was analyzed, combining the changes of microscopic appearance and pore structure. The results show that the water contact angle of the fluorocarbon composite coating with single doped silica sol increases by 10.2%, compared with fluorocarbon coating, and the pencil hardness is up to 3 H. The pencil hardness of the fluorocarbon composite coating with triple adding of silica sol, sepiolite powder and iron tailing powder is up to 3 H, and the adhesion increases by 44.2%. The properties of the fluorocarbon composite coating with double adding of silica sol and sepiolite powder lie between both coatings. The residual adhesion of the fluorocarbon composite coating with single doped silica sol is the largest. Inorganic mineral fluorocarbon composite coatings can significantly improve the exfoliation resistance of concrete, but the improvement effect is not significant compared with fluorocarbon coating. Some micropores are generated in the waterborne fluorocarbon coating under the salt freezing environment, and the pore structure is coarsened. However, the microstructure of the fluorocarbon composite coating with single doped silica sol is still denser, and the most probable pore diameter increases slightly, and the coating is only slightly damaged. The microstructure of concrete under the protection of the fluorocarbon composite coating with single doped silica sol is denser, and the spalling amount per unit area decreases by 81.2%, compared with that without protection. Research results provide experimental and theoretical bases for the design of concrete protective coating under the salt freezing environment in cold areas.
The influences of inorganic mineral on the properties of waterborne fluorocarbon coating were studied, and the variation in adhesion of fluorocarbon composite coatings under the salt freezing environment was studied, and the influence of fluorocarbon composite coatings on the amount of spalling per unit area of concrete was analyzed, by surface hydrophobic property test, mechanical property test, interface bonding property test and salt freezing test of concrete. The improvement mechanism of salt freezing resistance of concrete was analyzed, combining the changes of microscopic appearance and pore structure. The results show that the water contact angle of the fluorocarbon composite coating with single doped silica sol increases by 10.2%, compared with fluorocarbon coating, and the pencil hardness is up to 3 H. The pencil hardness of the fluorocarbon composite coating with triple adding of silica sol, sepiolite powder and iron tailing powder is up to 3 H, and the adhesion increases by 44.2%. The properties of the fluorocarbon composite coating with double adding of silica sol and sepiolite powder lie between both coatings. The residual adhesion of the fluorocarbon composite coating with single doped silica sol is the largest. Inorganic mineral fluorocarbon composite coatings can significantly improve the exfoliation resistance of concrete, but the improvement effect is not significant compared with fluorocarbon coating. Some micropores are generated in the waterborne fluorocarbon coating under the salt freezing environment, and the pore structure is coarsened. However, the microstructure of the fluorocarbon composite coating with single doped silica sol is still denser, and the most probable pore diameter increases slightly, and the coating is only slightly damaged. The microstructure of concrete under the protection of the fluorocarbon composite coating with single doped silica sol is denser, and the spalling amount per unit area decreases by 81.2%, compared with that without protection. Research results provide experimental and theoretical bases for the design of concrete protective coating under the salt freezing environment in cold areas.
2023, 40(5): 3002-3017.
doi: 10.13801/j.cnki.fhclxb.20220622.002
Abstract:
The superhydrophobic phenomenon in nature has attracted more attention due to its unique wettability. It is urgent that the preparation and application of superhydrophobic coating. Cerium dioxide (CeO2) was in situ synthesized on the surface of cellulose nanofibers (CNFs) by co-precipitation method using cerium nitrate hexahydrate (Ce(NO3)3·6H2O), following modified by octadecyltrimethoxysilane (OTMS) and the coating was constructed by spraying method. It investigated the effects of different mass ratios of CNFs, Ce(NO3)3·6H2O, and OTMS on coating morphology and hydrophobicity. The results show that the coatings consisting of CNFs, and Ce(NO3)3·6H2O with the mass ratios of 1∶5 and 1∶7 can construct the micro/nanostructure contributing to achieving superhydrophobic properties. When the mass ratios of CNFs, Ce(NO3)3·6H2O, and OTMS is 1∶5∶10, the coating static contact angle is (159.7±1.1)° and the sliding angle is (5.7±1.8)°. Its static contact angle can remain greater than 150° after the 150°C heating for 3 h and UV illumination for 36 h, meanwhile, possesses excellent pH stability and certain mecha-nical durability. When applied to glass, paper, wood, sponge, and other substrates, superhydrophobic surfaces can be constructed with excellent self-cleaning performance. The UV transmittance of superhydrophobic glass coating to UV-A and UV-B is 12.6% and 0.1%, respectively. The oil absorption efficiency of the superhydrophobic sponge is about 94%. This superhydrophobic coating is expected to use as a protective material and extends the application of rare earth metal oxidate in the cellulose-based superhydrophobic coating field.
The superhydrophobic phenomenon in nature has attracted more attention due to its unique wettability. It is urgent that the preparation and application of superhydrophobic coating. Cerium dioxide (CeO2) was in situ synthesized on the surface of cellulose nanofibers (CNFs) by co-precipitation method using cerium nitrate hexahydrate (Ce(NO3)3·6H2O), following modified by octadecyltrimethoxysilane (OTMS) and the coating was constructed by spraying method. It investigated the effects of different mass ratios of CNFs, Ce(NO3)3·6H2O, and OTMS on coating morphology and hydrophobicity. The results show that the coatings consisting of CNFs, and Ce(NO3)3·6H2O with the mass ratios of 1∶5 and 1∶7 can construct the micro/nanostructure contributing to achieving superhydrophobic properties. When the mass ratios of CNFs, Ce(NO3)3·6H2O, and OTMS is 1∶5∶10, the coating static contact angle is (159.7±1.1)° and the sliding angle is (5.7±1.8)°. Its static contact angle can remain greater than 150° after the 150°C heating for 3 h and UV illumination for 36 h, meanwhile, possesses excellent pH stability and certain mecha-nical durability. When applied to glass, paper, wood, sponge, and other substrates, superhydrophobic surfaces can be constructed with excellent self-cleaning performance. The UV transmittance of superhydrophobic glass coating to UV-A and UV-B is 12.6% and 0.1%, respectively. The oil absorption efficiency of the superhydrophobic sponge is about 94%. This superhydrophobic coating is expected to use as a protective material and extends the application of rare earth metal oxidate in the cellulose-based superhydrophobic coating field.
2023, 40(5): 3018-3025.
doi: 10.13801/j.cnki.fhclxb.20220804.006
Abstract:
Thermosetting composites have been widely applied in many fields due to their excellent mechanical properties, heat resistance, and chemical resistance. However, the drawbacks including non-renewable raw materials, non-recyclability after service, and non-degradability of fibers and resins largely limit their further application. In this work, two bamboo fibers, i.e., micrometer-scale bamboo powders (BP) and centimeter-scale bamboo fibers (BF) were respectively used as reinforcements for the resin matrix from epoxidized soybean oil (ESO), and meanwhile, a dithiol monomer containing dynamic borate esters was used as a curing agent. The recyclable bamboo fibers reinforced soybean oil-based vitrimer (ESOBV) biocomposites were prepared via a compression molding technique. The tensile properties, dynamic mechanical properties, stress relaxation, interfacial bonding, recyclability, and degradability of the composites were investigated. The results show that the tensile strength and tensile modulus of the composites decreased with the increase of BP content, while increased with the increase of BF content, indicating a significant effect of fiber morphology on the mechanical properties of the composites. Due to the presence of dynamic covalent bonds, the composites showed a stress relaxation behavior at high temperature, and their stress relaxation times increased with the fiber contents. The BP-reinforced composites can be remolded at high temperature, and the remolded composites have 91.0% tensile strength, 96.3% tensile modulus, and 110.7% elongation at break of the original composites. The dynamic borate esters in ESOBV can exchange with glycerol at 100℃ and atmospheric pressure, and thus the matrix can be degraded in glycerol to recover the fibers without any damage in morphology.
Thermosetting composites have been widely applied in many fields due to their excellent mechanical properties, heat resistance, and chemical resistance. However, the drawbacks including non-renewable raw materials, non-recyclability after service, and non-degradability of fibers and resins largely limit their further application. In this work, two bamboo fibers, i.e., micrometer-scale bamboo powders (BP) and centimeter-scale bamboo fibers (BF) were respectively used as reinforcements for the resin matrix from epoxidized soybean oil (ESO), and meanwhile, a dithiol monomer containing dynamic borate esters was used as a curing agent. The recyclable bamboo fibers reinforced soybean oil-based vitrimer (ESOBV) biocomposites were prepared via a compression molding technique. The tensile properties, dynamic mechanical properties, stress relaxation, interfacial bonding, recyclability, and degradability of the composites were investigated. The results show that the tensile strength and tensile modulus of the composites decreased with the increase of BP content, while increased with the increase of BF content, indicating a significant effect of fiber morphology on the mechanical properties of the composites. Due to the presence of dynamic covalent bonds, the composites showed a stress relaxation behavior at high temperature, and their stress relaxation times increased with the fiber contents. The BP-reinforced composites can be remolded at high temperature, and the remolded composites have 91.0% tensile strength, 96.3% tensile modulus, and 110.7% elongation at break of the original composites. The dynamic borate esters in ESOBV can exchange with glycerol at 100℃ and atmospheric pressure, and thus the matrix can be degraded in glycerol to recover the fibers without any damage in morphology.
2023, 40(5): 3026-3036.
doi: 10.13801/j.cnki.fhclxb.20220830.001
Abstract:
To solve the defects of low thermal conductivity and leakage of organic solid-liquid phase change materials (PCMs), ZIF-67 was etched by tannin acid to obtain the carbon-based supports (HX-C), stearic acid (SA) was the phase change material and then used to prepare the enhanced thermal conductivity PCMs (SA/HX-C) via vacuum melting adsorption method. In detail, thermal stability, heat storage property, thermal conductivity, shape stability and photo-thermal conversion were investigated to evaluate the thermal storage performance. Meanwhile, characterizations of nitrogen isothermal adsorption-desorption, FTIR, XRD and SEM were conducted. Results revealed that tannic acid can expand the pore size of carbonized ZIF-67 derivatives, thus enhancing the shape stability. The obtained SA/HX-C own favorable heat storage property, thermal conductivity, and photo-thermal conversion. Among them, etching time of 6 min for PCMs (SA/H6-C) exhibits high thermal storage efficiency of 80.84% and photo-thermal conversion of 76.29%. Thermal conductivity is strengthened to 0.461 W/(m·K), which is 156.11% higher than that of SA. No leakage and shape change are observed for SA/H6-C during phase transition, it still shows good thermal storage performance even after recycling 100 times.
To solve the defects of low thermal conductivity and leakage of organic solid-liquid phase change materials (PCMs), ZIF-67 was etched by tannin acid to obtain the carbon-based supports (HX-C), stearic acid (SA) was the phase change material and then used to prepare the enhanced thermal conductivity PCMs (SA/HX-C) via vacuum melting adsorption method. In detail, thermal stability, heat storage property, thermal conductivity, shape stability and photo-thermal conversion were investigated to evaluate the thermal storage performance. Meanwhile, characterizations of nitrogen isothermal adsorption-desorption, FTIR, XRD and SEM were conducted. Results revealed that tannic acid can expand the pore size of carbonized ZIF-67 derivatives, thus enhancing the shape stability. The obtained SA/HX-C own favorable heat storage property, thermal conductivity, and photo-thermal conversion. Among them, etching time of 6 min for PCMs (SA/H6-C) exhibits high thermal storage efficiency of 80.84% and photo-thermal conversion of 76.29%. Thermal conductivity is strengthened to 0.461 W/(m·K), which is 156.11% higher than that of SA. No leakage and shape change are observed for SA/H6-C during phase transition, it still shows good thermal storage performance even after recycling 100 times.
2023, 40(5): 3037-3046.
doi: 10.13801/j.cnki.fhclxb.20220809.004
Abstract:
To investigate effect of flux on properties and microstructure of resin matrix composites at elevated temperature, glass frit (GF) and Si3N4 modified high silica glass fiber reinforced boron phenolic resin composites (GF-Si3N4/BPR) were prepared via a compression molding technique using low melting point GF as flux and Si3N4 particles as high temperature resistant fillers. The influence of GF on the high temperature properties and dielectric properties of composites was studied. The results show that the introduced GF promotes the formation of liquid phase on the surface of composites and the densification of the ceramic layer, inhibiting erosion of composites by oxygen at elevated temperatures and significantly improving the high temperature performance of composites. The flexural strength of GF-Si3N4/BPR treated at 1200℃ was increased by 81.3% and 14.9%, respectively, compared with high silica glass fiber reinforced boron phenolic resin composites (BPR) and Si3N4 modified high silica glass fiber reinforced boron phenolic resin composites (Si3N4/BPR), while the mass ablation rate was reduced by 73.1% and 55.1%, respectively, compared with BPR and Si3N4/BPR. Furthermore, at 8.2 GHz, the dielectric constant (ε) and loss tangent (tanδ) of the composites gradually increased with increasing temperature. At temperatures above 800°C, the resulting glass phase effectively restrains the adverse effects of free carbon, pores, and cracks generated by resin cracking on the dielectric properties of the material. The prepared composite material has excellent high temperature properties and dielectric properties, and is expected to be applied in the field of high temperature wave transmission.
To investigate effect of flux on properties and microstructure of resin matrix composites at elevated temperature, glass frit (GF) and Si3N4 modified high silica glass fiber reinforced boron phenolic resin composites (GF-Si3N4/BPR) were prepared via a compression molding technique using low melting point GF as flux and Si3N4 particles as high temperature resistant fillers. The influence of GF on the high temperature properties and dielectric properties of composites was studied. The results show that the introduced GF promotes the formation of liquid phase on the surface of composites and the densification of the ceramic layer, inhibiting erosion of composites by oxygen at elevated temperatures and significantly improving the high temperature performance of composites. The flexural strength of GF-Si3N4/BPR treated at 1200℃ was increased by 81.3% and 14.9%, respectively, compared with high silica glass fiber reinforced boron phenolic resin composites (BPR) and Si3N4 modified high silica glass fiber reinforced boron phenolic resin composites (Si3N4/BPR), while the mass ablation rate was reduced by 73.1% and 55.1%, respectively, compared with BPR and Si3N4/BPR. Furthermore, at 8.2 GHz, the dielectric constant (ε) and loss tangent (tanδ) of the composites gradually increased with increasing temperature. At temperatures above 800°C, the resulting glass phase effectively restrains the adverse effects of free carbon, pores, and cracks generated by resin cracking on the dielectric properties of the material. The prepared composite material has excellent high temperature properties and dielectric properties, and is expected to be applied in the field of high temperature wave transmission.
2023, 40(5): 3047-3059.
doi: 10.13801/j.cnki.fhclxb.20220617.001
Abstract:
The emergence of new high-entropy alloys has broadened the selection range of metal matrix compo-sites. In this study, carbide ceramic particles doped in Fe49.5Mn30Co10Cr10X0.5 (X=B4C, ZrC and TiC) high-entropy alloy composites are prepared by using arc melting technology, and the effects of three carbide ceramic particles on the microstructure and mechanical properties of composite materials were systematically studied. The results show that the doped carbide ceramic particles can refine the matrix grains, stabilize the fcc phase, and inhibit the formation of the hcp phase. Among them, B4C ceramic particles have the most significant effect on refining grains and stabilizing fcc phase. The mechanical properties of the samples doped with ZrC and B4C ceramic particles are lower than the matrix samples, which is attributed to the poor bonding between the ceramic particles and the matrix, and the appearing void defects at the interface. But TiC doped sample, the strengthening and toughening effect is significant, which is attributed to good interface bonding, fine grain strengthening, Orowan strengthening, and load bearing strengthening.
The emergence of new high-entropy alloys has broadened the selection range of metal matrix compo-sites. In this study, carbide ceramic particles doped in Fe49.5Mn30Co10Cr10X0.5 (X=B4C, ZrC and TiC) high-entropy alloy composites are prepared by using arc melting technology, and the effects of three carbide ceramic particles on the microstructure and mechanical properties of composite materials were systematically studied. The results show that the doped carbide ceramic particles can refine the matrix grains, stabilize the fcc phase, and inhibit the formation of the hcp phase. Among them, B4C ceramic particles have the most significant effect on refining grains and stabilizing fcc phase. The mechanical properties of the samples doped with ZrC and B4C ceramic particles are lower than the matrix samples, which is attributed to the poor bonding between the ceramic particles and the matrix, and the appearing void defects at the interface. But TiC doped sample, the strengthening and toughening effect is significant, which is attributed to good interface bonding, fine grain strengthening, Orowan strengthening, and load bearing strengthening.
2023, 40(5): 3060-3074.
doi: 10.13801/j.cnki.fhclxb.20220706.002
Abstract:
Taking the aluminum honeycomb sandwich panel as the object, through the low-speed drop weight test and the detailed simulation model including the panel, the adhesive layer and the honeycomb, the changes of low-speed impact response curve and damage mode under the influence of the honeycomb cell diameter, honeycomb wall thickness, panel thickness and punch radius parameters were studied. Three damage modes under the test conditions were determined: Core buckling, core shear and sandwich panel penetration, among which the core shear mode has better energy absorption distribution. The results show that the honeycomb cell diameter and the honeycomb wall thickness have similar effects on the impact response and damage mode. The increase of the panel thickness can greatly improve the impact resistance, and the size of the punch radius will significantly affect the damage mode. On this basis, the damage mode limit load formula related to the above parameters was established, and the corresponding damage mode diagram was drawn to provide a reference for the impact resistance design of aluminum honeycomb sandwich panels.
Taking the aluminum honeycomb sandwich panel as the object, through the low-speed drop weight test and the detailed simulation model including the panel, the adhesive layer and the honeycomb, the changes of low-speed impact response curve and damage mode under the influence of the honeycomb cell diameter, honeycomb wall thickness, panel thickness and punch radius parameters were studied. Three damage modes under the test conditions were determined: Core buckling, core shear and sandwich panel penetration, among which the core shear mode has better energy absorption distribution. The results show that the honeycomb cell diameter and the honeycomb wall thickness have similar effects on the impact response and damage mode. The increase of the panel thickness can greatly improve the impact resistance, and the size of the punch radius will significantly affect the damage mode. On this basis, the damage mode limit load formula related to the above parameters was established, and the corresponding damage mode diagram was drawn to provide a reference for the impact resistance design of aluminum honeycomb sandwich panels.
