2022 Vol. 39, No. 10
2022, 39(10): 4509-4517.
doi: 10.13801/j.cnki.fhclxb.20211109.001
Abstract:
Due to the fast curing speed, high precision and smooth surface, UV-curing 3D printing has become one of the preferred technologies to rapidly manufacture sophisticated devices. However, the photosensitive resins for UV-curing 3D printing are still challenged by poor mechanical strength and toughness. Carbon fiber has been widely utilized in diverse structural or functional composites because of its excellent characteristics like electrical conductivity, heat conductivity, high specific strength and high specific modulus. Therefore, modified short carbon fiber (MCF) was prepared by chemical oxidation and modification with silane coupling agent (KH580). Then, the modified carbon fiber/photosensitive resin (MCF/PR) composite was prepared by compositing MCF with 3D printing photosensitive resin (PR). The UV-curing kinetics of MCF/PR composite and mechanical performances of 3D printed samples were also studied. The results indicate that when the grafted amount of KH580 is 0.5wt% and the content of MCF is 0.15wt%, the viscosity of MCF/PR composite is increased to some extent, but the curing depth and critical exposure are insignificantly influenced by MCF, which still meets the requirements of UV-curing 3D printing. A variety of devices are successfully fabricated by stereolithography (SLA) 3D printing. The tensile strength and impact strength of 3D printed samples are 70 MPa and 1.91 kJ/m2, respectively, which are increased by about 100% and 60% compared with pure PR. Moreover, the 3D printed MCF/PR composite has good thermostability below 350℃.
Due to the fast curing speed, high precision and smooth surface, UV-curing 3D printing has become one of the preferred technologies to rapidly manufacture sophisticated devices. However, the photosensitive resins for UV-curing 3D printing are still challenged by poor mechanical strength and toughness. Carbon fiber has been widely utilized in diverse structural or functional composites because of its excellent characteristics like electrical conductivity, heat conductivity, high specific strength and high specific modulus. Therefore, modified short carbon fiber (MCF) was prepared by chemical oxidation and modification with silane coupling agent (KH580). Then, the modified carbon fiber/photosensitive resin (MCF/PR) composite was prepared by compositing MCF with 3D printing photosensitive resin (PR). The UV-curing kinetics of MCF/PR composite and mechanical performances of 3D printed samples were also studied. The results indicate that when the grafted amount of KH580 is 0.5wt% and the content of MCF is 0.15wt%, the viscosity of MCF/PR composite is increased to some extent, but the curing depth and critical exposure are insignificantly influenced by MCF, which still meets the requirements of UV-curing 3D printing. A variety of devices are successfully fabricated by stereolithography (SLA) 3D printing. The tensile strength and impact strength of 3D printed samples are 70 MPa and 1.91 kJ/m2, respectively, which are increased by about 100% and 60% compared with pure PR. Moreover, the 3D printed MCF/PR composite has good thermostability below 350℃.
2022, 39(10): 4518-4530.
doi: 10.13801/j.cnki.fhclxb.20211228.001
Abstract:
In order to obtain the flame retardant epoxy resin (EP) composites with good comprehensive properties, the 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-sulfide (DOPS) derivative was applied to EP. First, maleic anhydride-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-sulfide (MAH-DOPS) was synthesized by the reaction of DOPS and maleic anhydride (MAH). The structure was determined by FTIR, 1H NMR and 31P NMR. Secondly, DOPS and MAH-DOPS were added to EP respectively, to prepare composites DOPS/EP and MAH-DOPS/EP by blending. Thirdly, the thermal stability, flame retardancy and mechanical properties of DOPS/EP and MAH-DOPS/EP were compared. Finally, the effects of MAH-DOPS on the combustion performance and thermal degradation behavior of EP were discussed, and its flame retardant mechanism was analyzed in depth. The results show that the initial decomposition temperature of flame retardant DOPS (205.4℃) is lower than that of MAH-DOPS (235.2℃), and the thermal stability of DOPS/EP is lower than that of MAH-DOPS/EP when the same mass fraction of flame retardants is added, which is consistent with the thermal stability of flame retardants. Both flame retardants DOPS and MAH-DOPS can improve the flame retardancy of EP, and MAH-DOPS/EP has better flame retardant effect. When the amount of flame retardant is 15wt%, limit oxygen index (LOI) values of MAH-DOPS/EP and DOPS/EP are 28.6% and 29.1%, reaching UL-94 V-0 and V-1 rating, respectively. The mechanical test results show that compared with EP, the bending strength of MAH-DOPS/EP increases by 45.8%, while DOPS/EP decreases by 62.5%. The mechanical properties of DOPS/EP system decrease obviously, and almost lose the use value. Cone calorimeter tests show that the average heat release rate (av-HRR) and total heat release (THR) of the composite MAH-DOPS/EP decrease significantly. The results of TG-IR show that the H•, O• or HO• free radicals are captured by the phosphorus-containing free radicals generated by the pyrolysis of MAH-DOPS/EP, and the free radicals are quenched. SEM-EDS results show that MAH-DOPS/EP can form a more complete and compact char layer, and the content of P in the char layer is higher. The study shows that MAH-DOPS plays a flame retardant role in gas phase and condensed phase through flame suppression and char formation respectively, and the gas phase flame retardant mechanism is the main one.
In order to obtain the flame retardant epoxy resin (EP) composites with good comprehensive properties, the 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-sulfide (DOPS) derivative was applied to EP. First, maleic anhydride-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-sulfide (MAH-DOPS) was synthesized by the reaction of DOPS and maleic anhydride (MAH). The structure was determined by FTIR, 1H NMR and 31P NMR. Secondly, DOPS and MAH-DOPS were added to EP respectively, to prepare composites DOPS/EP and MAH-DOPS/EP by blending. Thirdly, the thermal stability, flame retardancy and mechanical properties of DOPS/EP and MAH-DOPS/EP were compared. Finally, the effects of MAH-DOPS on the combustion performance and thermal degradation behavior of EP were discussed, and its flame retardant mechanism was analyzed in depth. The results show that the initial decomposition temperature of flame retardant DOPS (205.4℃) is lower than that of MAH-DOPS (235.2℃), and the thermal stability of DOPS/EP is lower than that of MAH-DOPS/EP when the same mass fraction of flame retardants is added, which is consistent with the thermal stability of flame retardants. Both flame retardants DOPS and MAH-DOPS can improve the flame retardancy of EP, and MAH-DOPS/EP has better flame retardant effect. When the amount of flame retardant is 15wt%, limit oxygen index (LOI) values of MAH-DOPS/EP and DOPS/EP are 28.6% and 29.1%, reaching UL-94 V-0 and V-1 rating, respectively. The mechanical test results show that compared with EP, the bending strength of MAH-DOPS/EP increases by 45.8%, while DOPS/EP decreases by 62.5%. The mechanical properties of DOPS/EP system decrease obviously, and almost lose the use value. Cone calorimeter tests show that the average heat release rate (av-HRR) and total heat release (THR) of the composite MAH-DOPS/EP decrease significantly. The results of TG-IR show that the H•, O• or HO• free radicals are captured by the phosphorus-containing free radicals generated by the pyrolysis of MAH-DOPS/EP, and the free radicals are quenched. SEM-EDS results show that MAH-DOPS/EP can form a more complete and compact char layer, and the content of P in the char layer is higher. The study shows that MAH-DOPS plays a flame retardant role in gas phase and condensed phase through flame suppression and char formation respectively, and the gas phase flame retardant mechanism is the main one.
2022, 39(10): 4531-4539.
doi: 10.13801/j.cnki.fhclxb.20211028.007
Abstract:
The development of polymer-based thermally conductive composites with low filling and high thermally conductivity remains a bottleneck problem that needs to be solved. Based on the layer-by-layer hydrogen-bond assembly, the low filling and high thermally conductive BNNS@PDA/PU composites are prepared by the dip coating-hot pressing method, using the porous polyurethane (PU) foams as template, and polydopamine functionalized nitride boron nanosheets (BNNS@PDA) as thermally conductive fillers. The microstructures, thermal conductive properties and thermal stability of BNNS@PDA and BNNS@PDA/PU composites were investigated in detail. The results show that the surface functionalization of BNNS by PDA can make it coat well on the three-dimensional skeleton of porous PU foams. After hot pressing, the highly effective double heat-conduction networks with the PU skeleton as the main heat-conduction network and BNNS@PDA on the surface of PU skeleton as the secondary heat-conduction network are constructed, leading to the decreased interfacial thermal resistance of the thermally conductive composites. When the filling amount of BNNS@PDA is 16.3wt%, the thermal conductivity of BNNS@PDA/PU composites with double heat-conduction networks reaches 0.783 W/(m·K), which is 102.3% higher than that of PU with single heat-conduction network (0.387 W/(m·K)).
The development of polymer-based thermally conductive composites with low filling and high thermally conductivity remains a bottleneck problem that needs to be solved. Based on the layer-by-layer hydrogen-bond assembly, the low filling and high thermally conductive BNNS@PDA/PU composites are prepared by the dip coating-hot pressing method, using the porous polyurethane (PU) foams as template, and polydopamine functionalized nitride boron nanosheets (BNNS@PDA) as thermally conductive fillers. The microstructures, thermal conductive properties and thermal stability of BNNS@PDA and BNNS@PDA/PU composites were investigated in detail. The results show that the surface functionalization of BNNS by PDA can make it coat well on the three-dimensional skeleton of porous PU foams. After hot pressing, the highly effective double heat-conduction networks with the PU skeleton as the main heat-conduction network and BNNS@PDA on the surface of PU skeleton as the secondary heat-conduction network are constructed, leading to the decreased interfacial thermal resistance of the thermally conductive composites. When the filling amount of BNNS@PDA is 16.3wt%, the thermal conductivity of BNNS@PDA/PU composites with double heat-conduction networks reaches 0.783 W/(m·K), which is 102.3% higher than that of PU with single heat-conduction network (0.387 W/(m·K)).
2022, 39(10): 4540-4550.
doi: 10.13801/j.cnki.fhclxb.20211119.002
Abstract:
In order to reduce the melting point of polyacrylonitrile (PAN) and improve the properties of melt-spun PAN fibers, the effects of isotropic naphthalene pitch (INP) and coal tar pitch (ICP) as plasticizers on 85∶14∶1 mole percent poly(acrylonitrile-methyl acrylate-4-acryloxy dibenzophenone) terpolymer (P(AN-MA-ABP)) were investigated in detail. The 1wt%INP/P(AN-MA-ABP) terpolymer fibers were prepared by mixing 1wt%INP with P(AN-MA-ABP), and then melting spinning and drawing. The effects of UV irradiation time on 1wt%INP/P(AN-MA-ABP) terpolymer fibers were studied. The results show that the long-chain sulfur heterocyclic INP has a better plasticizing effect than the ICP with a thick ring structure. The diameter of the 1wt%INP/P(AN-MA-ABP) terpolymer fibers is about 52 μm, and the tensile strength is about 250 MPa, which has a smooth surface and a dense structure. Delaying the UV irradiation from 0 min to 60 min, the oxygen content on the surface of 1wt%INP/P(AN-MA-ABP) terpolymer fibers increases from 17.3% to 26.0%. Under nitrogen conditions, the initial cyclization temperature decreases from 303.8℃ to 292.4℃, and the cyclization peak temperature decreases from 318.0℃ to 308.8℃. Under air conditions, the initial cyclization temperature decrease from 299.9℃ to 295.0℃, and the cyclization peak temperature decreases from 316.4℃ to 312.6℃. After UV irradiation for 20 min, the carbon yield of 1wt%INP/P(AN-MA-ABP) terpolymer fibers carbonized at 800℃ under nitrogen increases from 41.0% to 43.4%. UV irradiation decreases the initial cyclization temperature, peak temperature, and enthalpy value of 1wt%INP/P(AN-MA-ABP) terpolymer fibers and increases the carbon yield, which are beneficial to the subsequent heat-treatment process.
In order to reduce the melting point of polyacrylonitrile (PAN) and improve the properties of melt-spun PAN fibers, the effects of isotropic naphthalene pitch (INP) and coal tar pitch (ICP) as plasticizers on 85∶14∶1 mole percent poly(acrylonitrile-methyl acrylate-4-acryloxy dibenzophenone) terpolymer (P(AN-MA-ABP)) were investigated in detail. The 1wt%INP/P(AN-MA-ABP) terpolymer fibers were prepared by mixing 1wt%INP with P(AN-MA-ABP), and then melting spinning and drawing. The effects of UV irradiation time on 1wt%INP/P(AN-MA-ABP) terpolymer fibers were studied. The results show that the long-chain sulfur heterocyclic INP has a better plasticizing effect than the ICP with a thick ring structure. The diameter of the 1wt%INP/P(AN-MA-ABP) terpolymer fibers is about 52 μm, and the tensile strength is about 250 MPa, which has a smooth surface and a dense structure. Delaying the UV irradiation from 0 min to 60 min, the oxygen content on the surface of 1wt%INP/P(AN-MA-ABP) terpolymer fibers increases from 17.3% to 26.0%. Under nitrogen conditions, the initial cyclization temperature decreases from 303.8℃ to 292.4℃, and the cyclization peak temperature decreases from 318.0℃ to 308.8℃. Under air conditions, the initial cyclization temperature decrease from 299.9℃ to 295.0℃, and the cyclization peak temperature decreases from 316.4℃ to 312.6℃. After UV irradiation for 20 min, the carbon yield of 1wt%INP/P(AN-MA-ABP) terpolymer fibers carbonized at 800℃ under nitrogen increases from 41.0% to 43.4%. UV irradiation decreases the initial cyclization temperature, peak temperature, and enthalpy value of 1wt%INP/P(AN-MA-ABP) terpolymer fibers and increases the carbon yield, which are beneficial to the subsequent heat-treatment process.
2022, 39(10): 4551-4560.
doi: 10.13801/j.cnki.fhclxb.20211101.001
Abstract:
Water-assisted co-injection molding (WACIM) technology is an novel injection molding process that combines co-injection molding technology and water-assisted injection molding technology. Its special process makes the glass fiber reinforced composite used in the process have special characteristics of fiber orientation and enhancement. WACIM pipes with polypropylene (PP) as inner material and short glass fiber reinforced polypropylene (GF/PP) as outer material were prepared to investigate the effects of glass fiber mass fraction on the thicknesses of pipe inner and outer layers, glass fiber orientation and tensile strength. It is found that when the mass fraction of glass fiber is less than 30wt%, the variations of pipe inner and outer layer thicknesses are not obvious. When the mass fraction of glass fiber increases to 40wt%, both the inner and outer layer thicknesses of pipe increase. According to the distribution characteristics of glass fiber orientation, the outer layer of WACIM pipes can be divided into three layers: Near interface layer, intermediate layer and near mold wall layer. The orientation degree of glass fiber along the flow direction decreases from inside to outside. The tensile properties of pipes increased first and then decreased with the increase of glass fiber mass fraction. The highest tensile strength of pipes can be obtained when the glass fiber mass fraction is 30wt%. It is found by comparison that the influences of glass fiber mass fraction on thickness, glass fiber orientation and tensile strength of WACIM and water-assisted injection molding (WAIM) pipes are different, and the influence mechanism are different.
Water-assisted co-injection molding (WACIM) technology is an novel injection molding process that combines co-injection molding technology and water-assisted injection molding technology. Its special process makes the glass fiber reinforced composite used in the process have special characteristics of fiber orientation and enhancement. WACIM pipes with polypropylene (PP) as inner material and short glass fiber reinforced polypropylene (GF/PP) as outer material were prepared to investigate the effects of glass fiber mass fraction on the thicknesses of pipe inner and outer layers, glass fiber orientation and tensile strength. It is found that when the mass fraction of glass fiber is less than 30wt%, the variations of pipe inner and outer layer thicknesses are not obvious. When the mass fraction of glass fiber increases to 40wt%, both the inner and outer layer thicknesses of pipe increase. According to the distribution characteristics of glass fiber orientation, the outer layer of WACIM pipes can be divided into three layers: Near interface layer, intermediate layer and near mold wall layer. The orientation degree of glass fiber along the flow direction decreases from inside to outside. The tensile properties of pipes increased first and then decreased with the increase of glass fiber mass fraction. The highest tensile strength of pipes can be obtained when the glass fiber mass fraction is 30wt%. It is found by comparison that the influences of glass fiber mass fraction on thickness, glass fiber orientation and tensile strength of WACIM and water-assisted injection molding (WAIM) pipes are different, and the influence mechanism are different.
2022, 39(10): 4561-4571.
doi: 10.13801/j.cnki.fhclxb.20211012.001
Abstract:
Thermoplastic polyurethane elastomer (TPU) was equipped with excellent properties, which was widely used in various fields of industry and living. However, the application scope of TPU was limited because the material was a kind of organic polymer material with high inflammability. Moreover, a large amount of CO, CO2, NOx and other toxic asphyxiating gases from TPU material were released during combustion. The design of MXene-based hybrid flame retardant based on layered titanium carbide (Ti3C2Tx) and manganese dioxide (MnO2) was proposed for preparation of MXene-based hybrid/TPU nanocomposites. The mechanisms of flame retardancy, smoke suppression and toxicity reduction of the TPU nanocomposites were studied by means of TGA, XRD, SEM and other techniques. In the case of Ti3C2Tx-MnO2/TPU systems, the total heat release (THR), the total smoke release (TSR), the total CO yield (CO TY) and the total CO2 yield (CO2 TY) of the TPU nanocomposite were maximally decreased by 28.62%, 33.41%, 34.12% and 29.77% respectively compared to those of TPU, besides 91.89% increase in residual char at 700℃. According to the analysis, Ti3C2Tx in MXene-based hybrid flame retardant was oxidized to TiO2 and co-catalyzed with MnO2 to form carbon, which not only improved the continuity and compactness of carbon layer after combustion of nanocomposite materials, but also blocked the entry of heat and oxygen and inhibit the release of flue gas.
Thermoplastic polyurethane elastomer (TPU) was equipped with excellent properties, which was widely used in various fields of industry and living. However, the application scope of TPU was limited because the material was a kind of organic polymer material with high inflammability. Moreover, a large amount of CO, CO2, NOx and other toxic asphyxiating gases from TPU material were released during combustion. The design of MXene-based hybrid flame retardant based on layered titanium carbide (Ti3C2Tx) and manganese dioxide (MnO2) was proposed for preparation of MXene-based hybrid/TPU nanocomposites. The mechanisms of flame retardancy, smoke suppression and toxicity reduction of the TPU nanocomposites were studied by means of TGA, XRD, SEM and other techniques. In the case of Ti3C2Tx-MnO2/TPU systems, the total heat release (THR), the total smoke release (TSR), the total CO yield (CO TY) and the total CO2 yield (CO2 TY) of the TPU nanocomposite were maximally decreased by 28.62%, 33.41%, 34.12% and 29.77% respectively compared to those of TPU, besides 91.89% increase in residual char at 700℃. According to the analysis, Ti3C2Tx in MXene-based hybrid flame retardant was oxidized to TiO2 and co-catalyzed with MnO2 to form carbon, which not only improved the continuity and compactness of carbon layer after combustion of nanocomposite materials, but also blocked the entry of heat and oxygen and inhibit the release of flue gas.
2022, 39(10): 4572-4579.
doi: 10.13801/j.cnki.fhclxb.20211027.002
Abstract:
According to the failure problem of the solid rocket engine insulation material caused by deformation incompatibility between the reinforced fabric and rubber matrix under impact loading, the polyimide fiber weft knitted fabric reinforced nitrile rubber (NBR) composites were designed and prepared. Based on the rib structure, two kinds of fiber fineness, three kinds of loop length and two lay-up structures were selected. The effects of reinforced structure on the low velocity impact properties of composites were investigated. Results show that the composites with large tow fiber, long loop length and orthogonal lay-up have higher peak load and absorbed energy. Profilometer and microscope observation were adapted to observe the damage modes of impacted composites. The specimens are not penetrated under 20.1 J impact loading. It is found that matrix cracking along the fiber direction and plastic deformation along the thickness direction are the main damage mode of composites.
According to the failure problem of the solid rocket engine insulation material caused by deformation incompatibility between the reinforced fabric and rubber matrix under impact loading, the polyimide fiber weft knitted fabric reinforced nitrile rubber (NBR) composites were designed and prepared. Based on the rib structure, two kinds of fiber fineness, three kinds of loop length and two lay-up structures were selected. The effects of reinforced structure on the low velocity impact properties of composites were investigated. Results show that the composites with large tow fiber, long loop length and orthogonal lay-up have higher peak load and absorbed energy. Profilometer and microscope observation were adapted to observe the damage modes of impacted composites. The specimens are not penetrated under 20.1 J impact loading. It is found that matrix cracking along the fiber direction and plastic deformation along the thickness direction are the main damage mode of composites.
2022, 39(10): 4580-4589.
doi: 10.13801/j.cnki.fhclxb.20211028.001
Abstract:
Graphene oxide (rGO) has become a leader in supercapacitors with a wide specific surface area (SSA) (2630 m2/g), high electrical conductivity and chemical stability, and excellent mechanical, thermal and optical properties. However, rGO itself has poor electrical conductivity, so in this paper, rGO is combined with Mo0.7Co0.3S2 to improve its performance. This paper was successfully synthesized different mass ratios of rGO and Mo0.7Co0.3S2 by a simple hydrothermal method. The microstructure was characterized by XRD, SEM, HRTEM, EDS. The electrode is made by using foamed nickel as the substrate, polyvinylidene chlorofluoride as the binder, and N-methyl pyrrolidone as the auxiliary agent. The electrochemical performance was tested on a three-electrode electrochemical workstation with KOH as the electrolyte. The experimental results show that all samples exhibit hexagonal system structure with good crystallization, the morphologies are flower-like microsphere shape with a certain degree of agglomeration. The surface of Mo0.7Co0.3S2 nanoparticles is wrapped by a layer of rGO like yarn. rGO/Mo0.7Co0.3S2 nanocomposite exhibits pseudo-capacitance behavior and excellent electrochemical performance, especially the Mo0.7Co0.3S2 electrode (30wt% rGO content) exhibits the largest specific capacitance and smallest impedance, and the Mo0.7Co0.3S2 electrode (30wt% rGO content) electrode reduced from 1377.00 F·g−1 to 1307.87 F·g−1 after 3000 cycles at a current density of 5 A·g−1, the coulombic efficiency is 95%, which may be due to the Coupling effect between Mo0.7Co0.3S2 and rGO.
Graphene oxide (rGO) has become a leader in supercapacitors with a wide specific surface area (SSA) (2630 m2/g), high electrical conductivity and chemical stability, and excellent mechanical, thermal and optical properties. However, rGO itself has poor electrical conductivity, so in this paper, rGO is combined with Mo0.7Co0.3S2 to improve its performance. This paper was successfully synthesized different mass ratios of rGO and Mo0.7Co0.3S2 by a simple hydrothermal method. The microstructure was characterized by XRD, SEM, HRTEM, EDS. The electrode is made by using foamed nickel as the substrate, polyvinylidene chlorofluoride as the binder, and N-methyl pyrrolidone as the auxiliary agent. The electrochemical performance was tested on a three-electrode electrochemical workstation with KOH as the electrolyte. The experimental results show that all samples exhibit hexagonal system structure with good crystallization, the morphologies are flower-like microsphere shape with a certain degree of agglomeration. The surface of Mo0.7Co0.3S2 nanoparticles is wrapped by a layer of rGO like yarn. rGO/Mo0.7Co0.3S2 nanocomposite exhibits pseudo-capacitance behavior and excellent electrochemical performance, especially the Mo0.7Co0.3S2 electrode (30wt% rGO content) exhibits the largest specific capacitance and smallest impedance, and the Mo0.7Co0.3S2 electrode (30wt% rGO content) electrode reduced from 1377.00 F·g−1 to 1307.87 F·g−1 after 3000 cycles at a current density of 5 A·g−1, the coulombic efficiency is 95%, which may be due to the Coupling effect between Mo0.7Co0.3S2 and rGO.
2022, 39(10): 4590-4601.
doi: 10.13801/j.cnki.fhclxb.20211105.001
Abstract:
In order to improve the shortages of big density and narrow absorption bandwidth of Fe3O4 absorbing material, in this study, wood-based porous charcoal (WPC)/Fe3O4 composites were prepared from fast-growing masson pine wood by delignification and high temperature in-situ growth methods. The microwave absorption properties of the composites were regulated by tailoring the carbonization temperature. The results of micromorphology, structure and electromagnetic parameters show that, the WPC/Fe3O4 composites retain the natural three-dimensional porous structure of wood with Fe3O4 particles evenly loaded in the carbon walls and channels of WPC. The increment of carbonization temperature (630-690℃) can enhance the electric conductivity and microwave attenuation capacity of the composites, but too high temperature causes the impedance mismatching. The composite prepared at 670℃ exhibits excellent microwave absorption performance with a minimum reflection loss of −49.5 dB and an effective absorption bandwidth of 6.24 GHz (9.04-15.28 GHz), due to its strong attenuation capability and good impedance matching characteristics. The main dissipation mechanism includes conductive loss, polarization relaxation, and synergistic effect of dielectric and magnetic loss. The strong reflection loss and wide effective absorption bandwidth of WPC/Fe3O4 composite suggest a good prospect in electromagnetic absorption field, which can promote the value-added and functional application of fast-growing wood.
In order to improve the shortages of big density and narrow absorption bandwidth of Fe3O4 absorbing material, in this study, wood-based porous charcoal (WPC)/Fe3O4 composites were prepared from fast-growing masson pine wood by delignification and high temperature in-situ growth methods. The microwave absorption properties of the composites were regulated by tailoring the carbonization temperature. The results of micromorphology, structure and electromagnetic parameters show that, the WPC/Fe3O4 composites retain the natural three-dimensional porous structure of wood with Fe3O4 particles evenly loaded in the carbon walls and channels of WPC. The increment of carbonization temperature (630-690℃) can enhance the electric conductivity and microwave attenuation capacity of the composites, but too high temperature causes the impedance mismatching. The composite prepared at 670℃ exhibits excellent microwave absorption performance with a minimum reflection loss of −49.5 dB and an effective absorption bandwidth of 6.24 GHz (9.04-15.28 GHz), due to its strong attenuation capability and good impedance matching characteristics. The main dissipation mechanism includes conductive loss, polarization relaxation, and synergistic effect of dielectric and magnetic loss. The strong reflection loss and wide effective absorption bandwidth of WPC/Fe3O4 composite suggest a good prospect in electromagnetic absorption field, which can promote the value-added and functional application of fast-growing wood.
2022, 39(10): 4602-4609.
doi: 10.13801/j.cnki.fhclxb.20211115.001
Abstract:
In view of the harmness and resource utilization of chlorosilane residues, the by-products are prepared into dimethyldichlorosilane with higher economic benefit through disproportionation reaction. The ZSM-5@γ-Al2O3 core-shell carrier was constructed by modifying the surface of ZSM-5 molecular sieve with Tianjing gum as the binder and γ-Al2O3 as the shell. NaAlCl4 was loaded on the surface of ZSM-5@γ-Al2O3 core-shell carrier by high-temperature impregnation loading method. The effect of ZSM-5 molecular sieve with different Si/Al molar ratios on the disproportionation preparation of dimethyldichlorosilane, the effect of different NaAlCl4 loading ratios and the impregnation time of AlCl3 solution on the reaction of disproportionation preparation of dimethyldichlorosilane were investigated comprehensively, and the samples were characterized by XRD, SEM, SEM-EDS, BET and FTIR. The results show that the catalyst activity reach the optimum with 71.81% yield when the temperature is 200°C, the silica-alumina molar ratio is 50, the compound salt NaAlCl4 ratio is 8wt%, and the AlCl3 impregnation time is 3 h. The NaAlCl4 compound salt loading on the surface of the ZSM-5@γ-Al2O3 core-shell catalyst shows the improved catalytic efficiency and enhanced performance instability compared with single catalytic component. Further redistribution chlorosilane by-products methyl trichlorosilane (M1) and trimethylchlorosilane (M3) synthesis can obtain high commercial value dimethyl dichlorosilane (M2), so as to realize the transformation of waste into treasure.
In view of the harmness and resource utilization of chlorosilane residues, the by-products are prepared into dimethyldichlorosilane with higher economic benefit through disproportionation reaction. The ZSM-5@γ-Al2O3 core-shell carrier was constructed by modifying the surface of ZSM-5 molecular sieve with Tianjing gum as the binder and γ-Al2O3 as the shell. NaAlCl4 was loaded on the surface of ZSM-5@γ-Al2O3 core-shell carrier by high-temperature impregnation loading method. The effect of ZSM-5 molecular sieve with different Si/Al molar ratios on the disproportionation preparation of dimethyldichlorosilane, the effect of different NaAlCl4 loading ratios and the impregnation time of AlCl3 solution on the reaction of disproportionation preparation of dimethyldichlorosilane were investigated comprehensively, and the samples were characterized by XRD, SEM, SEM-EDS, BET and FTIR. The results show that the catalyst activity reach the optimum with 71.81% yield when the temperature is 200°C, the silica-alumina molar ratio is 50, the compound salt NaAlCl4 ratio is 8wt%, and the AlCl3 impregnation time is 3 h. The NaAlCl4 compound salt loading on the surface of the ZSM-5@γ-Al2O3 core-shell catalyst shows the improved catalytic efficiency and enhanced performance instability compared with single catalytic component. Further redistribution chlorosilane by-products methyl trichlorosilane (M1) and trimethylchlorosilane (M3) synthesis can obtain high commercial value dimethyl dichlorosilane (M2), so as to realize the transformation of waste into treasure.
2022, 39(10): 4610-4619.
doi: 10.13801/j.cnki.fhclxb.20211108.002
Abstract:
LiNi0.5Mn1.5O4 cathode material is considered as a promising cathode material due to its advantages of high voltage, cobalt-free and high energy density. But its further application is limited by its poor cyclic stability as the decomposition of electrolyte under high voltage. In this study, LiNi0.5Mn1.5O4 was prepared by low temperature self-propagating combustion method, and then different sugars were used as carbon sources to study the coating modification. The results show that the properties of LiNi0.5Mn1.5O4 composite prepared with chitosan at 400℃/Air is improved significantly. The specific discharge capacity of LiNi0.5Mn1.5O4 composite is 113.3 mA·h/g after 400 cycles at 148 mA·h/g, and the capacity retention rate is 91.07%. This is mainly attributed to the carbon layer on the surface of the material, which improves the electrical conductivity of the material, alleviates the erosion of electrolyte, reduces the electrode reaction polarization, and improves the transport rate of lithium ions. In this study, cheap sugars are used as carbon source, and the synthesis process is simple, which provides a new idea for the application of LiNi0.5Mn1.5O4.
LiNi0.5Mn1.5O4 cathode material is considered as a promising cathode material due to its advantages of high voltage, cobalt-free and high energy density. But its further application is limited by its poor cyclic stability as the decomposition of electrolyte under high voltage. In this study, LiNi0.5Mn1.5O4 was prepared by low temperature self-propagating combustion method, and then different sugars were used as carbon sources to study the coating modification. The results show that the properties of LiNi0.5Mn1.5O4 composite prepared with chitosan at 400℃/Air is improved significantly. The specific discharge capacity of LiNi0.5Mn1.5O4 composite is 113.3 mA·h/g after 400 cycles at 148 mA·h/g, and the capacity retention rate is 91.07%. This is mainly attributed to the carbon layer on the surface of the material, which improves the electrical conductivity of the material, alleviates the erosion of electrolyte, reduces the electrode reaction polarization, and improves the transport rate of lithium ions. In this study, cheap sugars are used as carbon source, and the synthesis process is simple, which provides a new idea for the application of LiNi0.5Mn1.5O4.
2022, 39(10): 4620-4630.
doi: 10.13801/j.cnki.fhclxb.20211025.001
Abstract:
Anisotropic wettable materials have become a hot spot in oil-water separation research because of their apparently opposite absorption characteristics for oil and water. In this paper, γ-aminopropyltriethoxysilane (APTES) and hydrophilic nano TiO2 were mixed and applied to the fabric. APTES-TiO2 coated superhydrophilic underwater superoleophobic fabric (APTES-TiO2@fabric) was obtained after hydrolyzing and crosslinking. The modified fabric was characterized by contact angle measuring instrument, FTIR, XPS, FESEM, XRD and EDS. The results show that APTES-TiO2 is successfully coated on the surface of the fabric, which has a water contact angle of 0° in air and an oil contact angle of greater than 152° for the selected oil in water. In the oil-water separation test, the separation efficiency of APTES-TiO2@fabric for the several light oils is above 99%, and it still has a good separation efficiency after 5 separation cycles and soaked in acid-base salt solution. In addition, the fabric also has excellent photocatalytic performance. Under 12 h of ultraviolet irradiation, it can degrade the methylene blue in water and adsorb to itself, achieving the effect of water purification and self-cleaning. The results show that APTES-TiO2@fabric has good oil-water separation and photocatalytic performance, which can be used as a reference for water purification in practical applications.
Anisotropic wettable materials have become a hot spot in oil-water separation research because of their apparently opposite absorption characteristics for oil and water. In this paper, γ-aminopropyltriethoxysilane (APTES) and hydrophilic nano TiO2 were mixed and applied to the fabric. APTES-TiO2 coated superhydrophilic underwater superoleophobic fabric (APTES-TiO2@fabric) was obtained after hydrolyzing and crosslinking. The modified fabric was characterized by contact angle measuring instrument, FTIR, XPS, FESEM, XRD and EDS. The results show that APTES-TiO2 is successfully coated on the surface of the fabric, which has a water contact angle of 0° in air and an oil contact angle of greater than 152° for the selected oil in water. In the oil-water separation test, the separation efficiency of APTES-TiO2@fabric for the several light oils is above 99%, and it still has a good separation efficiency after 5 separation cycles and soaked in acid-base salt solution. In addition, the fabric also has excellent photocatalytic performance. Under 12 h of ultraviolet irradiation, it can degrade the methylene blue in water and adsorb to itself, achieving the effect of water purification and self-cleaning. The results show that APTES-TiO2@fabric has good oil-water separation and photocatalytic performance, which can be used as a reference for water purification in practical applications.
2022, 39(10): 4631-4641.
doi: 10.13801/j.cnki.fhclxb.20211123.002
Abstract:
Due to the low cost, high safety and easy assembly, rechargeable aqueous zinc-manganese oxide (Zn-MnOx) batteries are the best devices for energy storage. However, poor conductivity of MnOx results in the bad cycle performance. Herein, highly conductive and layered Ti3C2Tx MXene with rich terminations (Tx, for example, =O, —F, —OH) were used as carriers for MnOx particles. Due to the electronegativity of the terminations, Mn2+ was intercalated into the layers and adsorbed on the surface of Ti3C2Tx MXene, making the generated Mn3O4 particles can firmly anchored, forming the Ti3C2@Mn3O4 composites. As for the cathode of zinc-ion batteries, Ti3C2@Mn3O4 was fully converted to Ti3C2@ε-MnO2 during the 1st charge process. Thanks to the excellent conductivity and layered structure of Ti3C2Tx MXene, Ti3C2@ε-MnO2 cathode presents excellent kinetic properties and electrochemical performance with a high specific capacity of 440 mA·h·g−1 and high energy density (607 W·h·kg−1) at 0.2 C (1 C=308 mA·h·g−1), and the capacities increase from 270 mA·h·g−1 to 480 mA·h·g−1 after 150 cycles at 1 C. Excellent electrochemical performance, simple material preparation methods, combined with the low cost, high safety and easy assembly characteristics, enable the possible application of rechargeable aqueous Zn-MnOx batteries in large-scale energy storage.
Due to the low cost, high safety and easy assembly, rechargeable aqueous zinc-manganese oxide (Zn-MnOx) batteries are the best devices for energy storage. However, poor conductivity of MnOx results in the bad cycle performance. Herein, highly conductive and layered Ti3C2Tx MXene with rich terminations (Tx, for example, =O, —F, —OH) were used as carriers for MnOx particles. Due to the electronegativity of the terminations, Mn2+ was intercalated into the layers and adsorbed on the surface of Ti3C2Tx MXene, making the generated Mn3O4 particles can firmly anchored, forming the Ti3C2@Mn3O4 composites. As for the cathode of zinc-ion batteries, Ti3C2@Mn3O4 was fully converted to Ti3C2@ε-MnO2 during the 1st charge process. Thanks to the excellent conductivity and layered structure of Ti3C2Tx MXene, Ti3C2@ε-MnO2 cathode presents excellent kinetic properties and electrochemical performance with a high specific capacity of 440 mA·h·g−1 and high energy density (607 W·h·kg−1) at 0.2 C (1 C=308 mA·h·g−1), and the capacities increase from 270 mA·h·g−1 to 480 mA·h·g−1 after 150 cycles at 1 C. Excellent electrochemical performance, simple material preparation methods, combined with the low cost, high safety and easy assembly characteristics, enable the possible application of rechargeable aqueous Zn-MnOx batteries in large-scale energy storage.
2022, 39(10): 4642-4651.
doi: 10.13801/j.cnki.fhclxb.20210927.003
Abstract:
Z-scheme BiVO4−x/g-C3N4−x heterostructure mediated by double defects were prepared by solid phase sintering and hydrothermal methods to acquire an efficient photocatalytic system for full water splitting. The microstructure and optoelectronic properties of the heterostructure were characterized, and the photocatalytic properties of BiVO4−x/g-C3N4−x heterostructure for hydrogen and oxygen production by overall photocatalytic water splitting were tested. The results show that the introduction of abundant oxygen vacancy and nitrogen vacancy, the tightly connected interface and the construction of direct Z-scheme heterojunction improve the visible light absorption and accelerate the separation and transfer of photogenerated charge. As a result, the material has highly efficient photocatalytic activity. The Z-scheme BiVO4−x/g-C3N4−x heterojunction mediated by double defects show excellent photocatalytic activity and stability. Under visible light irradiation, the hydrogen and oxygen evolution rate reach 654 μmol·h−1·g−1, which is 6.5 times as high as that of g-C3N4−x precursor, and the oxygen evolution rate reach 302 μmol·h−1·g−1. After 20 h of visible light irradiation, the photocatalytic activity of the sample doesn’t decrease.
Z-scheme BiVO4−x/g-C3N4−x heterostructure mediated by double defects were prepared by solid phase sintering and hydrothermal methods to acquire an efficient photocatalytic system for full water splitting. The microstructure and optoelectronic properties of the heterostructure were characterized, and the photocatalytic properties of BiVO4−x/g-C3N4−x heterostructure for hydrogen and oxygen production by overall photocatalytic water splitting were tested. The results show that the introduction of abundant oxygen vacancy and nitrogen vacancy, the tightly connected interface and the construction of direct Z-scheme heterojunction improve the visible light absorption and accelerate the separation and transfer of photogenerated charge. As a result, the material has highly efficient photocatalytic activity. The Z-scheme BiVO4−x/g-C3N4−x heterojunction mediated by double defects show excellent photocatalytic activity and stability. Under visible light irradiation, the hydrogen and oxygen evolution rate reach 654 μmol·h−1·g−1, which is 6.5 times as high as that of g-C3N4−x precursor, and the oxygen evolution rate reach 302 μmol·h−1·g−1. After 20 h of visible light irradiation, the photocatalytic activity of the sample doesn’t decrease.
2022, 39(10): 4652-4663.
doi: 10.13801/j.cnki.fhclxb.20220506.001
Abstract:
In order to develop a multi-functional oil-water separation sponge that is rich in raw materials, environmentally friendly, easy to operate in complex environment, and of good reusability, superhydrophobic collagen-based composite sponge (Fe3O4/PDMS-COL) was prepared by impregnating collagen sponge with polydimethylsiloxane (PDMS)/ferroferric oxide nanoparticles (Fe3O4). The changes of chemical structure and microstructure after modification were characterized, and the oil-water separation performance was studied. According to the measurement of contact angle, when the concentration of collagen (COL) is 10 mg/mL and the concentration of PDMS is 15vol%, the water contact angle of the composite sponge reaches 150.3°. The results from FTIR, XPS, XRD and TG show that Fe3O4/PDMS compounds with collagen sponge successfully. FE-SEM observation shows that the addition of Fe3O4 nanoparticles construct rough surface structures effectively. Fe3O4/PDMS-COL can adsorb a variety of oil phases, including benzene, n-hexane, ethyl acetate, vacuum pump oil, peanut oil, among which the adsorption capacity (47 g/g) toward ethyl acetate is the highest, meanwhile the separation efficiency towards various oil phases reaches no less than 99%. After recycling for 20 times for absorbing benzene, both of the contact angle and magnetism of the sponge do not reduce significantly. Moreover, Fe3O4/PDMS-COL has a desirable emulsion separation ability and can effectively separate oil-in-water emulsion. Oil-water separation experiments were carried out in various scenarios under the action of external magnetic field, demonstrating the favourable magnetic responsiveness and manipulation. In addition, Fe3O4/PDMS-COL exhibits a good flame retardant performance. Furthermore, Fe3O4/PDMS-COL possesses an excellent separation capacity toward solid oil/water system in a complex environment, due to its near infrared photothermal effect.
In order to develop a multi-functional oil-water separation sponge that is rich in raw materials, environmentally friendly, easy to operate in complex environment, and of good reusability, superhydrophobic collagen-based composite sponge (Fe3O4/PDMS-COL) was prepared by impregnating collagen sponge with polydimethylsiloxane (PDMS)/ferroferric oxide nanoparticles (Fe3O4). The changes of chemical structure and microstructure after modification were characterized, and the oil-water separation performance was studied. According to the measurement of contact angle, when the concentration of collagen (COL) is 10 mg/mL and the concentration of PDMS is 15vol%, the water contact angle of the composite sponge reaches 150.3°. The results from FTIR, XPS, XRD and TG show that Fe3O4/PDMS compounds with collagen sponge successfully. FE-SEM observation shows that the addition of Fe3O4 nanoparticles construct rough surface structures effectively. Fe3O4/PDMS-COL can adsorb a variety of oil phases, including benzene, n-hexane, ethyl acetate, vacuum pump oil, peanut oil, among which the adsorption capacity (47 g/g) toward ethyl acetate is the highest, meanwhile the separation efficiency towards various oil phases reaches no less than 99%. After recycling for 20 times for absorbing benzene, both of the contact angle and magnetism of the sponge do not reduce significantly. Moreover, Fe3O4/PDMS-COL has a desirable emulsion separation ability and can effectively separate oil-in-water emulsion. Oil-water separation experiments were carried out in various scenarios under the action of external magnetic field, demonstrating the favourable magnetic responsiveness and manipulation. In addition, Fe3O4/PDMS-COL exhibits a good flame retardant performance. Furthermore, Fe3O4/PDMS-COL possesses an excellent separation capacity toward solid oil/water system in a complex environment, due to its near infrared photothermal effect.
2022, 39(10): 4664-4673.
doi: 10.13801/j.cnki.fhclxb.20211129.003
Abstract:
Biomass porous carbon materials are widely used in lithium ion batteries due to their wide sources and high cost performance, while activators used in the preparation process have a great influence on the lithium storage performance of materials. Therefore, using soybean shell as carbon source, porous carbon materials were prepared under different technological conditions, and the effect of activator on lithium storage performance of porous carbon materials was investigated through structural characterization and electrochemical performance tests. It may be shown as follows: (1) When the current density is 185 mA·g−1, the initial discharge and charge specific capacity of CaCl2-activated porous carbon (DK-CaCl2) is 639.0/269.5 mA·h·g−1, while that of KOH activated porous carbon (DK-KOH) is 986.7/307.5 mA·h·g−1; (2) When the mass ratios of soybean shell to KOH are 1∶2, 1∶4 and 1∶8, the first specific capacities of the obtained porous carbon are 544.9/136.8, 986.7/307.5 and 375.1/93.4 mA·h·g−1, after 200 cycles, their discharges retain 88.8, 318.9 and 94.7 mA·h·g−1, respectively. This indicates that the lithium storage performance of porous carbon materials prepared with different activators and activation ratios are different, which is due to the different specific surface area of materials, resulting in different electrochemical performance.
Biomass porous carbon materials are widely used in lithium ion batteries due to their wide sources and high cost performance, while activators used in the preparation process have a great influence on the lithium storage performance of materials. Therefore, using soybean shell as carbon source, porous carbon materials were prepared under different technological conditions, and the effect of activator on lithium storage performance of porous carbon materials was investigated through structural characterization and electrochemical performance tests. It may be shown as follows: (1) When the current density is 185 mA·g−1, the initial discharge and charge specific capacity of CaCl2-activated porous carbon (DK-CaCl2) is 639.0/269.5 mA·h·g−1, while that of KOH activated porous carbon (DK-KOH) is 986.7/307.5 mA·h·g−1; (2) When the mass ratios of soybean shell to KOH are 1∶2, 1∶4 and 1∶8, the first specific capacities of the obtained porous carbon are 544.9/136.8, 986.7/307.5 and 375.1/93.4 mA·h·g−1, after 200 cycles, their discharges retain 88.8, 318.9 and 94.7 mA·h·g−1, respectively. This indicates that the lithium storage performance of porous carbon materials prepared with different activators and activation ratios are different, which is due to the different specific surface area of materials, resulting in different electrochemical performance.
2022, 39(10): 4674-4684.
doi: 10.13801/j.cnki.fhclxb.20211018.004
Abstract:
Lignin and its derivatives have broad application prospects in the fields of extraction of valuable metals and removal of toxic metal ions because of the characteristics of economical, efficient and friendly. Platinum was adsorbed by thiosemicarbazide/quaternary ammonium lignin in this study. The mechanism of adsorption was revealed by FTIR and the influence factors such as initial concentration of Pt(IV), hydrochloric acid concentration, adsorption time and adsorbent dosage on adsorption were optimized. The results show that the modified lignin contains a large number of phenolic hydroxyl, amino and quaternary ammonium functional groups. PtCl62− is reduced to PtCl42− by phenolic hydroxyl and then reacts with amino group by coordination reaction and chloride by ion exchange reaction. Using the optimum conditions, which include hydrochloric acid of 0.5 mol·L−1, Pt(IV) of 1 170 mg·L−1, adsorption time of 120 min and thiosemicarbazide/quaternary ammonium lignin addition of 1 g·L−1, the maximum adsorption capacity is 267.80 mg·g−1. Under the same conditions besides 7 g·L−1 thiosemicarbazide/quaternary ammonium lignin, the maximum adsorption ratio is 88.50%. The adsorption process can be simulated by Freundlich model and quasi-second-order kinetic model, which indicates that adsorption is chemisorptions of monolayer heterogeneous.
Lignin and its derivatives have broad application prospects in the fields of extraction of valuable metals and removal of toxic metal ions because of the characteristics of economical, efficient and friendly. Platinum was adsorbed by thiosemicarbazide/quaternary ammonium lignin in this study. The mechanism of adsorption was revealed by FTIR and the influence factors such as initial concentration of Pt(IV), hydrochloric acid concentration, adsorption time and adsorbent dosage on adsorption were optimized. The results show that the modified lignin contains a large number of phenolic hydroxyl, amino and quaternary ammonium functional groups. PtCl62− is reduced to PtCl42− by phenolic hydroxyl and then reacts with amino group by coordination reaction and chloride by ion exchange reaction. Using the optimum conditions, which include hydrochloric acid of 0.5 mol·L−1, Pt(IV) of 1 170 mg·L−1, adsorption time of 120 min and thiosemicarbazide/quaternary ammonium lignin addition of 1 g·L−1, the maximum adsorption capacity is 267.80 mg·g−1. Under the same conditions besides 7 g·L−1 thiosemicarbazide/quaternary ammonium lignin, the maximum adsorption ratio is 88.50%. The adsorption process can be simulated by Freundlich model and quasi-second-order kinetic model, which indicates that adsorption is chemisorptions of monolayer heterogeneous.
2022, 39(10): 4685-4693.
doi: 10.13801/j.cnki.fhclxb.20211101.003
Abstract:
In order to improve the photocatalytic performance of BiOI under visible light, the O-terminated Ti3C2 was prepared by etching Ti3AlC2 with NH4HF2, Ti3C2/BiOI composite materials were prepared by precipitation under ultrasonic radiation, using bismuth nitrate pentahydrate as bismuth source, potassium iodide as iodine source. The composition, morphology, structure, light absorption, transient photocurrent response and spectral response of Ti3C2/BiOI composite materials were characterized and measured by XRD, SEM, UV-vis, FTIR, EIS, I-t and PL. The photocatalytic degradation property of Ti3C2/BiOI composite material was carried out using methyl orange (MO) as targeted pollutant under simulated visible light. The results show that BiOI is successfully loaded on Ti3C2, the Ti3C2/BiOI composite material exhibits an appreciable photocatalytic activity under simulated visible light. The 6wt%Ti3C2/BiOI composite material shows the highest efficiency of 91.6% within 0.5 h, which is nearly 4.5 times higher than that of the BiOI. The O-terminated Ti3C2 as a cocatalyst to transfer photogenerated electrons in time, the charge separation is maintained in the charge depletion layer, which is helpful to improve the photocatalytic activity.
In order to improve the photocatalytic performance of BiOI under visible light, the O-terminated Ti3C2 was prepared by etching Ti3AlC2 with NH4HF2, Ti3C2/BiOI composite materials were prepared by precipitation under ultrasonic radiation, using bismuth nitrate pentahydrate as bismuth source, potassium iodide as iodine source. The composition, morphology, structure, light absorption, transient photocurrent response and spectral response of Ti3C2/BiOI composite materials were characterized and measured by XRD, SEM, UV-vis, FTIR, EIS, I-t and PL. The photocatalytic degradation property of Ti3C2/BiOI composite material was carried out using methyl orange (MO) as targeted pollutant under simulated visible light. The results show that BiOI is successfully loaded on Ti3C2, the Ti3C2/BiOI composite material exhibits an appreciable photocatalytic activity under simulated visible light. The 6wt%Ti3C2/BiOI composite material shows the highest efficiency of 91.6% within 0.5 h, which is nearly 4.5 times higher than that of the BiOI. The O-terminated Ti3C2 as a cocatalyst to transfer photogenerated electrons in time, the charge separation is maintained in the charge depletion layer, which is helpful to improve the photocatalytic activity.
2022, 39(10): 4694-4700.
doi: 10.13801/j.cnki.fhclxb.20211028.002
Abstract:
The anisotropic conductive polymer composites (ACPCs) have been applied in many fields owing to their unique anisotropic conductive property. In this article, a three-layer composite membrane with conductive middle layer and insulative inner and outer layers was prepared by three-layer film blowing technique, using high-density polyethylene (HDPE), polypropylene (PP) and multi-walled carbon nanotubes (MWCNTs) as raw materials. PP-MWCNTs/HDPE composite with anisotropic conductivity and alternating microlayers were then fabricated by hot-compression molding technique. A combination of DSC, POM, SEM, TEM, tensile and conductivity test was performed to provide a comprehensive analysis of structure and properties. The results show that the alternating arrangement of insulative PP layers and conductive MWCNTs/HDPE layers is successfully fabricated, and there is no structural defect (layer breakup or interlayer connection) in the microlayers, which indicates good adhesion in such multilayered structure. The PP-MWCNTs/HDPE composites exhibit excellent electrical conductivity in X and Y direction with electrical resistivity as low as 1.6 Ω·m, that almost 6-9 orders of magnitude lower than that in Z direction. The composites also demonstrate enhanced mechanical property, broadening the application field of conductive composite materials.
The anisotropic conductive polymer composites (ACPCs) have been applied in many fields owing to their unique anisotropic conductive property. In this article, a three-layer composite membrane with conductive middle layer and insulative inner and outer layers was prepared by three-layer film blowing technique, using high-density polyethylene (HDPE), polypropylene (PP) and multi-walled carbon nanotubes (MWCNTs) as raw materials. PP-MWCNTs/HDPE composite with anisotropic conductivity and alternating microlayers were then fabricated by hot-compression molding technique. A combination of DSC, POM, SEM, TEM, tensile and conductivity test was performed to provide a comprehensive analysis of structure and properties. The results show that the alternating arrangement of insulative PP layers and conductive MWCNTs/HDPE layers is successfully fabricated, and there is no structural defect (layer breakup or interlayer connection) in the microlayers, which indicates good adhesion in such multilayered structure. The PP-MWCNTs/HDPE composites exhibit excellent electrical conductivity in X and Y direction with electrical resistivity as low as 1.6 Ω·m, that almost 6-9 orders of magnitude lower than that in Z direction. The composites also demonstrate enhanced mechanical property, broadening the application field of conductive composite materials.
2022, 39(10): 4701-4708.
doi: 10.13801/j.cnki.fhclxb.20211108.003
Abstract:
Epoxide is an important organic synthesis intermediate and chemical raw material that is mainly prepared from the olefin epoxidation. It is a very interesting work to prepare efficient catalysts with stability and recyclability for aerobic olefins epoxidation. Composite PCuMo11/PC was prepared by using the nitrogen rich covalent organic framework material (PC) as support and the polyoxometalate PCuMo11 as active substance. The materials were characterized by FT-IR, N2 adsorption and desorption, XPS, TEM and EDS. The application of PCuMo11/PC for heterogeneous catalytic epoxidation of olefins (styrene, 1-octene, cyclooctene, cyclododecene) with molecular oxygen oxidant has obtained high catalytic activity and selectivity. There is no significant decrease in catalytic activity after recycling over five times. The experimental results show that large surface area and rich nitrogen content in the skeleton of the two-dimensional layered nitrogen rich covalent organic framework material are benefit to disperse the catalytic active substance polyoxometalate uniformly and establish a relatively stable chemical link, so as to improve the catalytic activity and stability of the composite.
Epoxide is an important organic synthesis intermediate and chemical raw material that is mainly prepared from the olefin epoxidation. It is a very interesting work to prepare efficient catalysts with stability and recyclability for aerobic olefins epoxidation. Composite PCuMo11/PC was prepared by using the nitrogen rich covalent organic framework material (PC) as support and the polyoxometalate PCuMo11 as active substance. The materials were characterized by FT-IR, N2 adsorption and desorption, XPS, TEM and EDS. The application of PCuMo11/PC for heterogeneous catalytic epoxidation of olefins (styrene, 1-octene, cyclooctene, cyclododecene) with molecular oxygen oxidant has obtained high catalytic activity and selectivity. There is no significant decrease in catalytic activity after recycling over five times. The experimental results show that large surface area and rich nitrogen content in the skeleton of the two-dimensional layered nitrogen rich covalent organic framework material are benefit to disperse the catalytic active substance polyoxometalate uniformly and establish a relatively stable chemical link, so as to improve the catalytic activity and stability of the composite.
2022, 39(10): 4709-4717.
doi: 10.13801/j.cnki.fhclxb.20211103.001
Abstract:
Because of the unique structure and function of zeolitic imidazolate frameworks (ZIFs), the utilization of ZIFs to enhance the properties of polymer and prepare new functional composites have attracted growing attention. To clarify the reinforcing effects of ZIFs on poly(vinyl alcohol) (PVA), zeolitic imidazolate framework ZIF-L was used as reinforcer and series of PVA composite films with different concentrations of ZIF-L were prepared by solution casting process. The structure, optical properties, mechanical properties, color, barrier performance and thermostability of the composite films were analyzed. The results indicate that the composite films show an enhanced anti-ultraviolet property with the addition of ZIF-L. The tensile strength initially increases and then decreases with increasing content of ZIF-L while the water vapor permeability and thermal degradation temperature show an opposite tendency. In addition, the incorporation of ZIF-L increases the oxygen permeability of the films gradually. When the ZIF-L content is 1wt%, the tensile strength of the composite film is increased by about 15%, while the water vapor permeability is reduced by 1.8%, ZIF-L significantly enhances the properties of PVA and the composite film show good comprehensive performance. When the ZIF-L content is larger than 5wt%, the maximum decomposition temperature begins to increase and reaches up to 297.84℃. The ZIF-L reinforced PVA composites in the present work will advance the development of new functional packaging composite films.
Because of the unique structure and function of zeolitic imidazolate frameworks (ZIFs), the utilization of ZIFs to enhance the properties of polymer and prepare new functional composites have attracted growing attention. To clarify the reinforcing effects of ZIFs on poly(vinyl alcohol) (PVA), zeolitic imidazolate framework ZIF-L was used as reinforcer and series of PVA composite films with different concentrations of ZIF-L were prepared by solution casting process. The structure, optical properties, mechanical properties, color, barrier performance and thermostability of the composite films were analyzed. The results indicate that the composite films show an enhanced anti-ultraviolet property with the addition of ZIF-L. The tensile strength initially increases and then decreases with increasing content of ZIF-L while the water vapor permeability and thermal degradation temperature show an opposite tendency. In addition, the incorporation of ZIF-L increases the oxygen permeability of the films gradually. When the ZIF-L content is 1wt%, the tensile strength of the composite film is increased by about 15%, while the water vapor permeability is reduced by 1.8%, ZIF-L significantly enhances the properties of PVA and the composite film show good comprehensive performance. When the ZIF-L content is larger than 5wt%, the maximum decomposition temperature begins to increase and reaches up to 297.84℃. The ZIF-L reinforced PVA composites in the present work will advance the development of new functional packaging composite films.
2022, 39(10): 4718-4731.
doi: 10.13801/j.cnki.fhclxb.20211011.002
Abstract:
In order to study the hydration development law of cement with different molding temperatures under continuous −5°C and 20°C curing environment, the hydration heat tests of cement paste with different molding temperatures of 5°C, 10°C, 15°C and 20°C were carried out under two curing systems. The hydration heat mechanism of cement paste with different curing systems and molding temperatures was analyzed. The effect of free water phase transformation on the performance of cement under negative temperature was explored. The hydration heat prediction model considering molding temperature ( 5~20°C ) under two curing systems was established. The results show that when the curing system is fixed, the hydration heat and hydration degree of cement paste increase gradually with the increase of curing age and mold temperature. The peak value of hydration heat difference and the equivalent age of hydration rate of 20°C curing and continuous −5°C curing are advanced by the molding temperature. Both negative temperature and low molding temperature will cause the age ' lag ' phenomenon in the hydration process. By analyzing the development law of hydration heat and its microscopic mechanism of action on cement paste, it is suggested that the molding temperature can be appropriately increased within a reasonable range to optimize the macro-micro performance of concrete under the negative temperature environment.
In order to study the hydration development law of cement with different molding temperatures under continuous −5°C and 20°C curing environment, the hydration heat tests of cement paste with different molding temperatures of 5°C, 10°C, 15°C and 20°C were carried out under two curing systems. The hydration heat mechanism of cement paste with different curing systems and molding temperatures was analyzed. The effect of free water phase transformation on the performance of cement under negative temperature was explored. The hydration heat prediction model considering molding temperature ( 5~20°C ) under two curing systems was established. The results show that when the curing system is fixed, the hydration heat and hydration degree of cement paste increase gradually with the increase of curing age and mold temperature. The peak value of hydration heat difference and the equivalent age of hydration rate of 20°C curing and continuous −5°C curing are advanced by the molding temperature. Both negative temperature and low molding temperature will cause the age ' lag ' phenomenon in the hydration process. By analyzing the development law of hydration heat and its microscopic mechanism of action on cement paste, it is suggested that the molding temperature can be appropriately increased within a reasonable range to optimize the macro-micro performance of concrete under the negative temperature environment.
2022, 39(10): 4732-4745.
doi: 10.13801/j.cnki.fhclxb.20211019.002
Abstract:
Large-rupture-strain fiber reinforced polymers (LRS FRPs) have the large tensile rupture strain value of more than 5%. This characteristic might enhance the load-bearing capacity and ductility and provide a new choice for seismic strengthening of reinforced concrete (RC) columns. The FRPs provide lateral support for the longitudinal bars through the cover concrete, which might prevent or delay the buckling of longitudinal steel bars. However, the buckling of the longitudinal reinforcement might still be observed when the stirrup spacing is relatively large. Especially, for the FRP-confined rectangular columns, the ununiform confinement provided by the external FRP for the specimen might result in the buckling of longitudinal bars and reduce the load-bearing capacity of the specimen. In order to study the buckling behavior of longitudinal bars in rectangular RC columns confined by FRP, a total of 28 polyethylene terephthalate (PET) FRP-confined rectangular columns, comprising 16 RC columns and 12 plain concrete (PC) columns, were prepared and tested under monotonic axial compression. The effects of the thickness of external FRP jackets, stirrup spacing and section aspect ratio on the load-bearing capacity of FRP-confined RC columns were studied. To carry out a quantitative study on the buckling behavior of longitudinal steel bars in FRP-confined RC columns, the average axial stress-strain curve of a single longitudinal bar was obtained from the test results. The experimental results show that the application of PET FRP jackets can effectively improve the load-bearing capacity and ductility of RC columns. A large confinement stiffness and a low section aspect ratio close to 1 lead to a high confinement level for RC columns. And the lateral support of FRP can delay the buckling of the steel bars to a higher deformation level.
Large-rupture-strain fiber reinforced polymers (LRS FRPs) have the large tensile rupture strain value of more than 5%. This characteristic might enhance the load-bearing capacity and ductility and provide a new choice for seismic strengthening of reinforced concrete (RC) columns. The FRPs provide lateral support for the longitudinal bars through the cover concrete, which might prevent or delay the buckling of longitudinal steel bars. However, the buckling of the longitudinal reinforcement might still be observed when the stirrup spacing is relatively large. Especially, for the FRP-confined rectangular columns, the ununiform confinement provided by the external FRP for the specimen might result in the buckling of longitudinal bars and reduce the load-bearing capacity of the specimen. In order to study the buckling behavior of longitudinal bars in rectangular RC columns confined by FRP, a total of 28 polyethylene terephthalate (PET) FRP-confined rectangular columns, comprising 16 RC columns and 12 plain concrete (PC) columns, were prepared and tested under monotonic axial compression. The effects of the thickness of external FRP jackets, stirrup spacing and section aspect ratio on the load-bearing capacity of FRP-confined RC columns were studied. To carry out a quantitative study on the buckling behavior of longitudinal steel bars in FRP-confined RC columns, the average axial stress-strain curve of a single longitudinal bar was obtained from the test results. The experimental results show that the application of PET FRP jackets can effectively improve the load-bearing capacity and ductility of RC columns. A large confinement stiffness and a low section aspect ratio close to 1 lead to a high confinement level for RC columns. And the lateral support of FRP can delay the buckling of the steel bars to a higher deformation level.
2022, 39(10): 4746-4756.
doi: 10.13801/j.cnki.fhclxb.20211214.002
Abstract:
In order to evaluate the dispersion method and dispersion degree of graphene in pure cement mud, different anionic surfactants were used as dispersion graphene materials, and graphene dispersion was prepared by high-speed physical mixing and ultrasonic dispersion methods.Their dispersion uniformity was analyzed by UV-visible spectrophotometry, static settlement, resistivity, SEM and energy spectroscopy test to observe the distribution of graphene in alkaline solutions, pure cement mud, and its pure cement mud hydrochemical hardening products.The results show that in the pure cement mud alkaline environment, the introduction of bubble microbeads helps to improve the dispersion uniformity of graphene and the stability for time and weaken the floating effect of graphene in pure cement mud. At the same time, the cross-section graphene dispersion uniformity can be improved by 30%. The dispersion effect of graphene in alkaline solution was evaluated by visible spectrophotometry, static settlement and resistivity, which is simple and effective.
In order to evaluate the dispersion method and dispersion degree of graphene in pure cement mud, different anionic surfactants were used as dispersion graphene materials, and graphene dispersion was prepared by high-speed physical mixing and ultrasonic dispersion methods.Their dispersion uniformity was analyzed by UV-visible spectrophotometry, static settlement, resistivity, SEM and energy spectroscopy test to observe the distribution of graphene in alkaline solutions, pure cement mud, and its pure cement mud hydrochemical hardening products.The results show that in the pure cement mud alkaline environment, the introduction of bubble microbeads helps to improve the dispersion uniformity of graphene and the stability for time and weaken the floating effect of graphene in pure cement mud. At the same time, the cross-section graphene dispersion uniformity can be improved by 30%. The dispersion effect of graphene in alkaline solution was evaluated by visible spectrophotometry, static settlement and resistivity, which is simple and effective.
Flexural properties of ultra high performance concrete reinforced with steel wire mesh or fiber mesh
2022, 39(10): 4757-4768.
doi: 10.13801/j.cnki.fhclxb.20211022.002
Abstract:
To study the influence of steel wire mesh on the bending properties of ultra-high performance concrete (UHPC) slabs, a bending test of simply supported two-way slabs with four sides was carried out. The chopped fibers in UHPC ware: Steel fiber and steel fiber were mixed with polyvinyl alcohol fiber, glass fiber and basalt fiber, respectively. The research parameters were: Number of layers of wire mesh and glass fiber mesh, pore size and proportion of blended fibers. The results show that when UHPC is single-doped with 1.5vol% steel fiber, the ultimate bearing capacity and energy absorption at 25 mm deflection of UHPC slabs with 3 layers and 4 layers are increased by 14.9%, 32.3% and 14.1%, 25.2%, respectively compared with UHPC slabs with 2 layers of steel wire mesh. When the total volume fraction of hybrid fibers is 1.5vol% and the steel wire mesh is 2 layers, the blending of 1.0vol% steel fiber and 0.5vol% polyvinyl alcohol fiber has better reinforcing and toughening effect on UHPC slabs, and the UHPC slab mixed with 0.5vol% steel fiber and 1.0vol% glass fiber or basalt fiber has a stronger ability to maintain load after peak load than 1.0vol% polyvinyl alcohol fiber, namely the mixing of steel fiber with higher modulus of elasticity non-metallic fiber is advantageous to increase the post-cracking bearing capacity. Compared with glass fiber mesh, UHPC slabs with steel mesh have better ductility after peak load. A method for evaluating the flexibility of UHPC slabs with peak load deflection as initial cracking parameter was proposed, which can characterize the contribution of mesh and fibers to the post-crack toughness of UHPC slabs. Based on the concept of effective utilization of mesh, the theoretical value is in good agreement with the experimental value by calculating the bending capacity.
To study the influence of steel wire mesh on the bending properties of ultra-high performance concrete (UHPC) slabs, a bending test of simply supported two-way slabs with four sides was carried out. The chopped fibers in UHPC ware: Steel fiber and steel fiber were mixed with polyvinyl alcohol fiber, glass fiber and basalt fiber, respectively. The research parameters were: Number of layers of wire mesh and glass fiber mesh, pore size and proportion of blended fibers. The results show that when UHPC is single-doped with 1.5vol% steel fiber, the ultimate bearing capacity and energy absorption at 25 mm deflection of UHPC slabs with 3 layers and 4 layers are increased by 14.9%, 32.3% and 14.1%, 25.2%, respectively compared with UHPC slabs with 2 layers of steel wire mesh. When the total volume fraction of hybrid fibers is 1.5vol% and the steel wire mesh is 2 layers, the blending of 1.0vol% steel fiber and 0.5vol% polyvinyl alcohol fiber has better reinforcing and toughening effect on UHPC slabs, and the UHPC slab mixed with 0.5vol% steel fiber and 1.0vol% glass fiber or basalt fiber has a stronger ability to maintain load after peak load than 1.0vol% polyvinyl alcohol fiber, namely the mixing of steel fiber with higher modulus of elasticity non-metallic fiber is advantageous to increase the post-cracking bearing capacity. Compared with glass fiber mesh, UHPC slabs with steel mesh have better ductility after peak load. A method for evaluating the flexibility of UHPC slabs with peak load deflection as initial cracking parameter was proposed, which can characterize the contribution of mesh and fibers to the post-crack toughness of UHPC slabs. Based on the concept of effective utilization of mesh, the theoretical value is in good agreement with the experimental value by calculating the bending capacity.
2022, 39(10): 4769-4777.
doi: 10.13801/j.cnki.fhclxb.20211014.001
Abstract:
The rapid chloride migration coefficient (RCM) method and the natural immersion method were used to study the chloride ion penetration resistance of multi-walled carbon nanotubes (MWCNTs) reinforced concrete. The chloride ion diffusion depth on the longitudinal section of the concrete specimen was measured, and the chloride ion diffusion coefficient was calculated based on this. The test results show that when the content of MWCNTs is 0.15wt%, the chloride ion diffusion depth and chloride ion diffusion coefficient of concrete at 28 days are reduced by 25.7% and 19.1%, respectively. Under four different erosion ages of natural soaking, mixing in the concrete of MWCNTs, the internal chloride ion concentration is always lower than that of the control group. Combining the analysis of the two methods, it is concluded that the free chloride ion concentration at each depth of the concrete decreases with the increase of the MWCNTs content, so that the chloride diffusion coefficient decreases with the increase of the MWCNTs content, and the incorporation of MWCNTs improves the resistance of concrete to chloride ion penetration. In addition, through SEM and mercury intrusion (MIP) tests, the microscopic enhancement mechanism of MWCNTs on the anti-chloride ion permeability of concrete was further explored. The analysis results show that MWCNTs have a certain bridging and filling effect, which may cause concrete crack propagation to be affected, inhibit and refine the pores, thereby improving the microstructure of concrete and improving the resistance of concrete to chloride ion penetration.
The rapid chloride migration coefficient (RCM) method and the natural immersion method were used to study the chloride ion penetration resistance of multi-walled carbon nanotubes (MWCNTs) reinforced concrete. The chloride ion diffusion depth on the longitudinal section of the concrete specimen was measured, and the chloride ion diffusion coefficient was calculated based on this. The test results show that when the content of MWCNTs is 0.15wt%, the chloride ion diffusion depth and chloride ion diffusion coefficient of concrete at 28 days are reduced by 25.7% and 19.1%, respectively. Under four different erosion ages of natural soaking, mixing in the concrete of MWCNTs, the internal chloride ion concentration is always lower than that of the control group. Combining the analysis of the two methods, it is concluded that the free chloride ion concentration at each depth of the concrete decreases with the increase of the MWCNTs content, so that the chloride diffusion coefficient decreases with the increase of the MWCNTs content, and the incorporation of MWCNTs improves the resistance of concrete to chloride ion penetration. In addition, through SEM and mercury intrusion (MIP) tests, the microscopic enhancement mechanism of MWCNTs on the anti-chloride ion permeability of concrete was further explored. The analysis results show that MWCNTs have a certain bridging and filling effect, which may cause concrete crack propagation to be affected, inhibit and refine the pores, thereby improving the microstructure of concrete and improving the resistance of concrete to chloride ion penetration.
2022, 39(10): 4778-4787.
doi: 10.13801/j.cnki.fhclxb.20220104.002
Abstract:
At high temperature, the microstructure of strain hardening cementitious composites (SHCC) was damaged, which leaded to the deterioration of mechanical properties, impermeability and microstructure. The evolution of mechanical properties and capillary water absorption law of SHCC specimens with different fiber contents exposed to 20℃ (normal temperature), 105℃, 200℃, 400℃, 600℃ and 800℃ were studied, and the degradation mechanism of macroscopic properties of materials was analyzed from the perspective of microstructure by using low-field nuclear magnetic technology. The results show that when the heating temperature increases from 20℃ to 105℃, the dynamic elastic modulus decreases, but the compressive strength and flexural strength increase. When the heating temperature rises to 200℃, the compressive strength and dynamic elastic modulus of SHCC change little, but when the temperature is higher than 400℃, both of them decrease rapidly. When the heating temperature is increased from 105℃ to 200℃, the flexural strength of SHCC specimen decreases significantly, and when the heating temperature is higher than 400℃, the flexural strength further deteriorates. The fiber content has no obvious regular effect on the residual mechanical properties of SHCC specimen after high temperature. In addition, when the heating temperature is lower than 200℃, SHCC has poor capillary water absorption performance and has a certain capillary infiltration resistance. Above 400℃, the high temperature damage can significantly promote the capillary water absorption rate and the water absorption capacity of SHCC specimen. When the temperature is lower than 200℃, the initial capillary water absorption coefficient of SHCC specimen with higher fiber content increases more rapidly, and the capillary water absorption capacity is stronger. The microstructure of SHCC specimen is relatively dense when the heating temperature is lower than 200℃. When the temperature exceeds 400℃, the melting of fibers inside the SHCC specimen and the generation and propagation of cacks lead to significant deterioration of mechanical properties and improvement of capillary water absorption. In the meantime, the volume fraction of cracks in SHCC specimens increases with the increase of fiber content after high temperature.
At high temperature, the microstructure of strain hardening cementitious composites (SHCC) was damaged, which leaded to the deterioration of mechanical properties, impermeability and microstructure. The evolution of mechanical properties and capillary water absorption law of SHCC specimens with different fiber contents exposed to 20℃ (normal temperature), 105℃, 200℃, 400℃, 600℃ and 800℃ were studied, and the degradation mechanism of macroscopic properties of materials was analyzed from the perspective of microstructure by using low-field nuclear magnetic technology. The results show that when the heating temperature increases from 20℃ to 105℃, the dynamic elastic modulus decreases, but the compressive strength and flexural strength increase. When the heating temperature rises to 200℃, the compressive strength and dynamic elastic modulus of SHCC change little, but when the temperature is higher than 400℃, both of them decrease rapidly. When the heating temperature is increased from 105℃ to 200℃, the flexural strength of SHCC specimen decreases significantly, and when the heating temperature is higher than 400℃, the flexural strength further deteriorates. The fiber content has no obvious regular effect on the residual mechanical properties of SHCC specimen after high temperature. In addition, when the heating temperature is lower than 200℃, SHCC has poor capillary water absorption performance and has a certain capillary infiltration resistance. Above 400℃, the high temperature damage can significantly promote the capillary water absorption rate and the water absorption capacity of SHCC specimen. When the temperature is lower than 200℃, the initial capillary water absorption coefficient of SHCC specimen with higher fiber content increases more rapidly, and the capillary water absorption capacity is stronger. The microstructure of SHCC specimen is relatively dense when the heating temperature is lower than 200℃. When the temperature exceeds 400℃, the melting of fibers inside the SHCC specimen and the generation and propagation of cacks lead to significant deterioration of mechanical properties and improvement of capillary water absorption. In the meantime, the volume fraction of cracks in SHCC specimens increases with the increase of fiber content after high temperature.
2022, 39(10): 4788-4800.
doi: 10.13801/j.cnki.fhclxb.20210928.003
Abstract:
Based on the experiment results of drying shrinkage and internal humidity of recycled aggregate thermal insulation concrete (RATIC) with different contents of glazed hollow beads (GHBs), a theoretical model considering the influence of GHBs on the internal curing effect of concrete for the development of internal humidity and drying shrinkage of RATIC was proposed by regression analysis which provided a theoretical basis and experimental basis for revealing the mechanism of the shrinkage and cracking phenomenon of RATIC. Based on the above analysis, the model of the interaction relationship between drying shrinkage, internal humidity, and GHBs contents was established. Studies indicate that the incorporation of GHBs is beneficial to delay the decline of internal humidity resulting in delaying the development of drying shrinkage. Compared with recycled aggregate concrete (RAC), the internal humidity decrease rate of 40GHBs/RAC, 65GHBs/RAC, 90GHBs/RAC and 130GHBs/RAC (GHBs content of 40, 65, 90 and 130 kg/m3) reduce by 19.57%, 26.09%, 30.43% and 32.61% and the drying shrinkage reduce by 3.13%, 4.69%, 6.56% and 10.31%, respectively. The theoretical model is in good agreement with the experimental results which shows accurate prediction of theoretical model on the development of drying shrinkage and internal humidity of RATIC. There is a good correlation between internal humidity and drying shrinkage and the development of drying shrinkage can be evaluated based on changes in internal humidity.
Based on the experiment results of drying shrinkage and internal humidity of recycled aggregate thermal insulation concrete (RATIC) with different contents of glazed hollow beads (GHBs), a theoretical model considering the influence of GHBs on the internal curing effect of concrete for the development of internal humidity and drying shrinkage of RATIC was proposed by regression analysis which provided a theoretical basis and experimental basis for revealing the mechanism of the shrinkage and cracking phenomenon of RATIC. Based on the above analysis, the model of the interaction relationship between drying shrinkage, internal humidity, and GHBs contents was established. Studies indicate that the incorporation of GHBs is beneficial to delay the decline of internal humidity resulting in delaying the development of drying shrinkage. Compared with recycled aggregate concrete (RAC), the internal humidity decrease rate of 40GHBs/RAC, 65GHBs/RAC, 90GHBs/RAC and 130GHBs/RAC (GHBs content of 40, 65, 90 and 130 kg/m3) reduce by 19.57%, 26.09%, 30.43% and 32.61% and the drying shrinkage reduce by 3.13%, 4.69%, 6.56% and 10.31%, respectively. The theoretical model is in good agreement with the experimental results which shows accurate prediction of theoretical model on the development of drying shrinkage and internal humidity of RATIC. There is a good correlation between internal humidity and drying shrinkage and the development of drying shrinkage can be evaluated based on changes in internal humidity.
2022, 39(10): 4801-4812.
doi: 10.13801/j.cnki.fhclxb.20211028.005
Abstract:
A total of 120 specimens of fly ash ceramsite lightweight aggregate concrete were designed for conventional triaxial compression tests in order to reveal the mechanical properties and behavior under complex stress conditions with ceramsite soaking time, strength level and lateral confining pressure as the changing parameters. The failure process and final failure behavior of fly ash ceramsite lightweight aggregate concrete under triaxial compression were observed, the stress-strain curves of specimens were obtained, and the influence of changing parameters on the mechanical performances was analyzed. The experimental results show that with the increase of the confining pressure, the failure behavior of fly ash ceramsite lightweight aggregate concrete changes from vertical splitting failure to oblique shear failure. When the confining pressure value is greater than 12 MPa, the specimen shows bulging failure without obvious cracks. The stress-strain curve is greatly affected by the value of confining pressure, but less affected by the immersion time and strength grade of the concrete. And after the confining pressure is greater than 12 MPa, the curve no longer has a descending section. The peak stress increases with the increase of ceramsite immersion time, strength grade and lateral confining pressure. The peak strain is not greatly affected by the soaking time of the ceramsite, it decreases with the increase of the strength grade, and increases with the increase of the confining pressure value. The elastic modulus increases with the increase of the strength grade and the confining pressure value, and is not significantly affected by the soaking time of the ceramsite.
A total of 120 specimens of fly ash ceramsite lightweight aggregate concrete were designed for conventional triaxial compression tests in order to reveal the mechanical properties and behavior under complex stress conditions with ceramsite soaking time, strength level and lateral confining pressure as the changing parameters. The failure process and final failure behavior of fly ash ceramsite lightweight aggregate concrete under triaxial compression were observed, the stress-strain curves of specimens were obtained, and the influence of changing parameters on the mechanical performances was analyzed. The experimental results show that with the increase of the confining pressure, the failure behavior of fly ash ceramsite lightweight aggregate concrete changes from vertical splitting failure to oblique shear failure. When the confining pressure value is greater than 12 MPa, the specimen shows bulging failure without obvious cracks. The stress-strain curve is greatly affected by the value of confining pressure, but less affected by the immersion time and strength grade of the concrete. And after the confining pressure is greater than 12 MPa, the curve no longer has a descending section. The peak stress increases with the increase of ceramsite immersion time, strength grade and lateral confining pressure. The peak strain is not greatly affected by the soaking time of the ceramsite, it decreases with the increase of the strength grade, and increases with the increase of the confining pressure value. The elastic modulus increases with the increase of the strength grade and the confining pressure value, and is not significantly affected by the soaking time of the ceramsite.
2022, 39(10): 4813-4823.
doi: 10.13801/j.cnki.fhclxb.20210923.001
Abstract:
To prove the improvement of rice husk ash (RHA) on sulfate erosion performance of concrete, the ratio of RHA concrete was optimized and compared with normal concrete (NC). The performance degradation progresses of concrete specimens within 270 days under solution attack with 5wt%Na2SO4 were studied, which included changes of apparent phenomenon, compressive strength, tensile strength, effective porosity and dynamic elasticity modulus. The micro-structure changes of concrete specimens under sulfate attack were observed by SEM. The results show that the concrete specimens gradually appear local spalling and expansion with the increase of corrosion time. The compressive and tensile strength increase and then decrease sharply, the effective porosity decreases and then increases, and the relative dynamic elasticity modulus increases and then decreases. Microscopic analysis shows that the ettringite and gypsum are formed from the hydration products of concrete react with the corrosive medium, which fill pores of concrete. Whereas, with the increase of corrosion time, the expansion of the ettringite and gypsum exceeds the internal tensile strength, resulting structural expansion failure and deterioration of mechanical properties. However, RHA mixing with concrete can produce calcium silicate hydrate, which improves the strength and sulfate resistance of concrete. In each stage, the deterioration degree of RHA concrete is better than that of NC. Finally, the damage constitutive models are established, and have higher accuracy compared with the measured value.
To prove the improvement of rice husk ash (RHA) on sulfate erosion performance of concrete, the ratio of RHA concrete was optimized and compared with normal concrete (NC). The performance degradation progresses of concrete specimens within 270 days under solution attack with 5wt%Na2SO4 were studied, which included changes of apparent phenomenon, compressive strength, tensile strength, effective porosity and dynamic elasticity modulus. The micro-structure changes of concrete specimens under sulfate attack were observed by SEM. The results show that the concrete specimens gradually appear local spalling and expansion with the increase of corrosion time. The compressive and tensile strength increase and then decrease sharply, the effective porosity decreases and then increases, and the relative dynamic elasticity modulus increases and then decreases. Microscopic analysis shows that the ettringite and gypsum are formed from the hydration products of concrete react with the corrosive medium, which fill pores of concrete. Whereas, with the increase of corrosion time, the expansion of the ettringite and gypsum exceeds the internal tensile strength, resulting structural expansion failure and deterioration of mechanical properties. However, RHA mixing with concrete can produce calcium silicate hydrate, which improves the strength and sulfate resistance of concrete. In each stage, the deterioration degree of RHA concrete is better than that of NC. Finally, the damage constitutive models are established, and have higher accuracy compared with the measured value.
2022, 39(10): 4824-4838.
doi: 10.13801/j.cnki.fhclxb.20211115.006
Abstract:
Through the axial compression test of concrete square columns which strengthened by concrete canvas (CC) and carbon fiber reinforced polymer (CFRP) strips, the influences of restraint rate, width and spacing of CFRP, and number of layers on the mechanical property of the concrete square column were studied. The failure form, bearing capacity, energy consumption capacity and deformation capacity of the reinforced concrete square column were analyzed. The research results show that the addition of CC can alleviate the stress concentration at the corners, significantly increase the deformation ability of the specimen, and improve the failure form of the column. The influence of width and spacing of the strips on the bearing capacity and energy dissipation capacity of the specimen is attributed to the restraint rate of the fiber strips. With the increase of the strip restraint rate and the number of CFRP layers, the load-bearing capacity and energy consumption capacity of the specimens continue to increase. When the fiber restraint ratio is 0.5, the bearing capacity is the largest when the width and spacing are 50 mm. Based on the experimental research, a theoretical analysis of the effective constrained area change was carried out, and the role of CC in joint reinforcement was obtained, and the axial compression bearing capacity model was established. The error analysis shows that the model has high prediction accuracy.
Through the axial compression test of concrete square columns which strengthened by concrete canvas (CC) and carbon fiber reinforced polymer (CFRP) strips, the influences of restraint rate, width and spacing of CFRP, and number of layers on the mechanical property of the concrete square column were studied. The failure form, bearing capacity, energy consumption capacity and deformation capacity of the reinforced concrete square column were analyzed. The research results show that the addition of CC can alleviate the stress concentration at the corners, significantly increase the deformation ability of the specimen, and improve the failure form of the column. The influence of width and spacing of the strips on the bearing capacity and energy dissipation capacity of the specimen is attributed to the restraint rate of the fiber strips. With the increase of the strip restraint rate and the number of CFRP layers, the load-bearing capacity and energy consumption capacity of the specimens continue to increase. When the fiber restraint ratio is 0.5, the bearing capacity is the largest when the width and spacing are 50 mm. Based on the experimental research, a theoretical analysis of the effective constrained area change was carried out, and the role of CC in joint reinforcement was obtained, and the axial compression bearing capacity model was established. The error analysis shows that the model has high prediction accuracy.
2022, 39(10): 4839-4846.
doi: 10.13801/j.cnki.fhclxb.20211101.004
Abstract:
In order to explore the creep regulation mechanism of graphene oxide (GO) on cement-based composites, the creep of cement mortar with different GO contents was tested by using creep loading frame. Starting from the hydration and microstructure of cement-based composites, the effect of GO on the creep of cement mortar was studied by SEM, XRD and FTIR, and the regulation mechanism was explained. The results show that GO can regulate the shape and aggregation state of hydration products of cement-based composites and reduce macro creep. When the content (mass ratio to cement) of GO is greater than 0.02%, the creep of cement mortar is greatly reduced. The addition of GO promotes the adsorption and diffusion of water molecules by hydrated calcium silicate (CSH), increases the internal CSH content and makes the structure of hydration products more compact. The hydrogen bond formed by GO and CSH can enhance the bonding force between the two and enhance the adsorption of water molecules between the CSH-GO layers, thus realizing the regulation of creep of cement mortar. The results have important theoretical value for the design of cement-based composites according to end use, and are expected to be applied in prestressed concrete structures.
In order to explore the creep regulation mechanism of graphene oxide (GO) on cement-based composites, the creep of cement mortar with different GO contents was tested by using creep loading frame. Starting from the hydration and microstructure of cement-based composites, the effect of GO on the creep of cement mortar was studied by SEM, XRD and FTIR, and the regulation mechanism was explained. The results show that GO can regulate the shape and aggregation state of hydration products of cement-based composites and reduce macro creep. When the content (mass ratio to cement) of GO is greater than 0.02%, the creep of cement mortar is greatly reduced. The addition of GO promotes the adsorption and diffusion of water molecules by hydrated calcium silicate (CSH), increases the internal CSH content and makes the structure of hydration products more compact. The hydrogen bond formed by GO and CSH can enhance the bonding force between the two and enhance the adsorption of water molecules between the CSH-GO layers, thus realizing the regulation of creep of cement mortar. The results have important theoretical value for the design of cement-based composites according to end use, and are expected to be applied in prestressed concrete structures.
2022, 39(10): 4847-4855.
doi: 10.13801/j.cnki.fhclxb.20211012.004
Abstract:
In order to study the mechanical behavior of CFRP confined concrete square columns under different strain rates, CFRP confined square concrete square columns with corner radius of 15 mm, 45 mm and 60 mm were test with the strain rate of 3.3×10−5 s−1 and 3.3×10−3 s−1, respectively. The effect of corner radius of the specimen and strain rate on the stress-strain curve, axial strain-lateral strain curve and compressive strength of CFRP confined concrete square columns were analyzed. The results show that the slope of the second segment of the stress-strain curve and the compressive strength increase with the increase of the corner radius and strain rate. As the strain rate increases and the number of CFRP layers thickness decreases, the slope of the axial strain-lateral strain curve increases. Finally, the existing literature models were evaluated based on the experimental data. The evaluation results show that the prediction results of Lin et al are in good agreement with the axial strain-lateral strain relationship of FRP confined square concrete under quasi-static condition, Wei et al model can predict the harden and soften confinement of FRP, and Cao et al model can be used to predict the compressive strength of CFRP confined concrete square columns under different strain rates. The experimental results provide experimental and theoretical basis for the further application of CFRP confined concrete square columns.
In order to study the mechanical behavior of CFRP confined concrete square columns under different strain rates, CFRP confined square concrete square columns with corner radius of 15 mm, 45 mm and 60 mm were test with the strain rate of 3.3×10−5 s−1 and 3.3×10−3 s−1, respectively. The effect of corner radius of the specimen and strain rate on the stress-strain curve, axial strain-lateral strain curve and compressive strength of CFRP confined concrete square columns were analyzed. The results show that the slope of the second segment of the stress-strain curve and the compressive strength increase with the increase of the corner radius and strain rate. As the strain rate increases and the number of CFRP layers thickness decreases, the slope of the axial strain-lateral strain curve increases. Finally, the existing literature models were evaluated based on the experimental data. The evaluation results show that the prediction results of Lin et al are in good agreement with the axial strain-lateral strain relationship of FRP confined square concrete under quasi-static condition, Wei et al model can predict the harden and soften confinement of FRP, and Cao et al model can be used to predict the compressive strength of CFRP confined concrete square columns under different strain rates. The experimental results provide experimental and theoretical basis for the further application of CFRP confined concrete square columns.
2022, 39(10): 4856-4867.
doi: 10.13801/j.cnki.fhclxb.20211115.005
Abstract:
Biomass-derived fillers reinforced composites have always been considered as potential substitutes for petroleum-based products. In this work, high content of bleached pulp fibers (10wt% to 50wt%) were adopted to modify polylactic acid (PLA) with maleic anhydride grafted polypropylene (MA-g-PP) as the compatibilizer. Two pre-melting processes of fiber/PLA composites were tried, i.e., roll-grinding plus extruding as well as internal mixing process. Tensile test, SEM, FTIR、DMA and TGA were employed to comprehensively investigate the effects of processing methods and fiber content on the mechanical and thermal properties, and microstructure of fiber/PLA composites. The results showed that, internal mixing process (IM process) is more effective than grinding and extruding process (GE process) to achieve good dispersion and almost oriented-arrangement of the fibers in the matrix. IM-processed composites with fiber content up to 50wt% acquired the maximum tensile strength (50.49 MPa, slightly higher than PLA) and Young's modulus (2.56 GPa, 45.8% higher than PLA). Damping capacity and loss factor of composites are reduced by the rigid filled pulp fibers, while the peak temperature is positively migrated. Pulp fibers added have no adversely effect on thermal stability and improve the residues content of PLA composites. It can be concluded that bleached pulp fiber is an effective filler for PLA-based composites.
Biomass-derived fillers reinforced composites have always been considered as potential substitutes for petroleum-based products. In this work, high content of bleached pulp fibers (10wt% to 50wt%) were adopted to modify polylactic acid (PLA) with maleic anhydride grafted polypropylene (MA-g-PP) as the compatibilizer. Two pre-melting processes of fiber/PLA composites were tried, i.e., roll-grinding plus extruding as well as internal mixing process. Tensile test, SEM, FTIR、DMA and TGA were employed to comprehensively investigate the effects of processing methods and fiber content on the mechanical and thermal properties, and microstructure of fiber/PLA composites. The results showed that, internal mixing process (IM process) is more effective than grinding and extruding process (GE process) to achieve good dispersion and almost oriented-arrangement of the fibers in the matrix. IM-processed composites with fiber content up to 50wt% acquired the maximum tensile strength (50.49 MPa, slightly higher than PLA) and Young's modulus (2.56 GPa, 45.8% higher than PLA). Damping capacity and loss factor of composites are reduced by the rigid filled pulp fibers, while the peak temperature is positively migrated. Pulp fibers added have no adversely effect on thermal stability and improve the residues content of PLA composites. It can be concluded that bleached pulp fiber is an effective filler for PLA-based composites.
2022, 39(10): 4868-4878.
doi: 10.13801/j.cnki.fhclxb.20211116.003
Abstract:
In order to improve the adsorption capacity and recyclability of the nanomaterial MXene, sodium alginate (SA) and MXene were mixed by ion cross-linking method to fix the Ti3C2Tx MXene nanomaterial on the SA aerogel matrix. After freeze-drying, MXene/SA gel microspheres was prepared. The structure of the gel microspheres was characterized by SEM-EDS, FTIR and XPS, and the adsorption characteristics of MXene/SA gel microspheres to uranium (VI) in aqueous solution were investigated under the influence of different factors, and its recycling ability was explored. The results show that the adsorption of uranium by MXene/SA gel microspheres follows the pseudo-second-order kinetics and Langmuir isotherm adsorption model, indicating that the adsorption is mainly monolayer chemical adsorption, and the thermodynamic parameters indicate that the adsorption process is a spontaneous endothermic. When the pH is 4 and the temperature is 298 K, the maximum adsorption capacity of MXene/SA gel microspheres for uranium is 126.82 mg·g−1. The main adsorption mechanism is ion exchange and complexation. More importantly, after 5 cycles of the gel microspheres, the removal rate remains above 90%, indicating that the adsorbent has the performance of recycling and reuse and will not cause secondary pollution to the water environment. Therefore, MXene/SA gel microsphere adsorbent has shown great potential in repairing the pollution of radionuclide uranium wastewater.
In order to improve the adsorption capacity and recyclability of the nanomaterial MXene, sodium alginate (SA) and MXene were mixed by ion cross-linking method to fix the Ti3C2Tx MXene nanomaterial on the SA aerogel matrix. After freeze-drying, MXene/SA gel microspheres was prepared. The structure of the gel microspheres was characterized by SEM-EDS, FTIR and XPS, and the adsorption characteristics of MXene/SA gel microspheres to uranium (VI) in aqueous solution were investigated under the influence of different factors, and its recycling ability was explored. The results show that the adsorption of uranium by MXene/SA gel microspheres follows the pseudo-second-order kinetics and Langmuir isotherm adsorption model, indicating that the adsorption is mainly monolayer chemical adsorption, and the thermodynamic parameters indicate that the adsorption process is a spontaneous endothermic. When the pH is 4 and the temperature is 298 K, the maximum adsorption capacity of MXene/SA gel microspheres for uranium is 126.82 mg·g−1. The main adsorption mechanism is ion exchange and complexation. More importantly, after 5 cycles of the gel microspheres, the removal rate remains above 90%, indicating that the adsorbent has the performance of recycling and reuse and will not cause secondary pollution to the water environment. Therefore, MXene/SA gel microsphere adsorbent has shown great potential in repairing the pollution of radionuclide uranium wastewater.
2022, 39(10): 4879-4888.
doi: 10.13801/j.cnki.fhclxb.20211025.002
Abstract:
Uranium mining and smelting processes produce a large amount of low-concentration uranium wastewater, which endangers the ecological environment and human health. It is urgent to remove uranium(VI) from uranium-containing wastewater. In this work, UiO-66 and chitosan (CS) were used as raw materials to prepare UiO-66/CS new composite materials by cross-linking method. Through static adsorption experiments, different pH values, adsorbent dosage, adsorption time and initial uranium concentration were investigated of the influence of external factors on U(VI) removal rate. The UiO-66/CS material was characterized and analyzed by SEM, FTIR, XPS, etc., revealing the mechanism of adsorbent removal of U(VI). The results show that when the initial uranium concentration is 5 mg/L, the temperature is 298 K, the pH is 5, the dosage is 0.15 g/L, and the adsorption time is 120 min, the removal rate of U(VI) by UiO-66/CS can reach 90.24%. The adsorption process conforms to the quasi-second-order kinetic model and Freundlich isotherm adsorption model. The adsorption and removal mechanism of U(VI) is mainly the complexation of —NH, —COOH, Zr—O,—OH and other functional groups with U(VI).
Uranium mining and smelting processes produce a large amount of low-concentration uranium wastewater, which endangers the ecological environment and human health. It is urgent to remove uranium(VI) from uranium-containing wastewater. In this work, UiO-66 and chitosan (CS) were used as raw materials to prepare UiO-66/CS new composite materials by cross-linking method. Through static adsorption experiments, different pH values, adsorbent dosage, adsorption time and initial uranium concentration were investigated of the influence of external factors on U(VI) removal rate. The UiO-66/CS material was characterized and analyzed by SEM, FTIR, XPS, etc., revealing the mechanism of adsorbent removal of U(VI). The results show that when the initial uranium concentration is 5 mg/L, the temperature is 298 K, the pH is 5, the dosage is 0.15 g/L, and the adsorption time is 120 min, the removal rate of U(VI) by UiO-66/CS can reach 90.24%. The adsorption process conforms to the quasi-second-order kinetic model and Freundlich isotherm adsorption model. The adsorption and removal mechanism of U(VI) is mainly the complexation of —NH, —COOH, Zr—O,—OH and other functional groups with U(VI).
2022, 39(10): 4889-4897.
doi: 10.13801/j.cnki.fhclxb.20211018.002
Abstract:
Wheat straw was used as raw material to prepare lignin containing 2,3-dialdehyde cellulose (DAC) through sequential treatment of p-toluenesulfonic acid (p-TsOH), ultrasonication, sodium periodate oxidation. DAC was used as crosslinker to prepare 2,3-dialdehyde cellulose/polyvinyl alcohol (DAC/PVA) composite hydrogel through aldol condensation reaction. The microstructures, swelling properties, compression resistance and thermal stability of hydrogels were studied. Ampicillin (AP) was introduced to DAC/PVA composite hydrogel by embedding method to prepare DAC/PVA-AP hydrogel. Drug release process, release mechanism and antibacterial effect were studied as well. The results show that the microstructures of DAC/PVA composite hydrogels show a porous 3D network structure, and the crosslinking density increases with the increase of DAC. The water content and swelling property of composite hydrogel decrease with the increase of DAC. When the DAC concentration increases from 0.8wt% to 2.0wt%, the water absorption swelling rate decreases from 1823.54%±13.89% to 1105.41%±7.06%. The initial compressive strength of 1.0wt%DAC/PVA hydrogel reaches 5.765 MPa under 70% compression strain and present strong compression resistance. After sterilization at 121℃, the composite hydrogels can keep intact morphology, indicating that they have excellent high temperature resistance. The release model of DAC/PVA-AP hydrogel conforms to the Korsmeyer-Peppas model, and the sustained-release solution has a good antibacterial effect on the test bacteria. The DAC/PVA composite hydrogel prepared from wheat straw has a three-dimensional network structure, good mechanical properties and high temperature resistance, and has potential application the field of wound dressings.
Wheat straw was used as raw material to prepare lignin containing 2,3-dialdehyde cellulose (DAC) through sequential treatment of p-toluenesulfonic acid (p-TsOH), ultrasonication, sodium periodate oxidation. DAC was used as crosslinker to prepare 2,3-dialdehyde cellulose/polyvinyl alcohol (DAC/PVA) composite hydrogel through aldol condensation reaction. The microstructures, swelling properties, compression resistance and thermal stability of hydrogels were studied. Ampicillin (AP) was introduced to DAC/PVA composite hydrogel by embedding method to prepare DAC/PVA-AP hydrogel. Drug release process, release mechanism and antibacterial effect were studied as well. The results show that the microstructures of DAC/PVA composite hydrogels show a porous 3D network structure, and the crosslinking density increases with the increase of DAC. The water content and swelling property of composite hydrogel decrease with the increase of DAC. When the DAC concentration increases from 0.8wt% to 2.0wt%, the water absorption swelling rate decreases from 1823.54%±13.89% to 1105.41%±7.06%. The initial compressive strength of 1.0wt%DAC/PVA hydrogel reaches 5.765 MPa under 70% compression strain and present strong compression resistance. After sterilization at 121℃, the composite hydrogels can keep intact morphology, indicating that they have excellent high temperature resistance. The release model of DAC/PVA-AP hydrogel conforms to the Korsmeyer-Peppas model, and the sustained-release solution has a good antibacterial effect on the test bacteria. The DAC/PVA composite hydrogel prepared from wheat straw has a three-dimensional network structure, good mechanical properties and high temperature resistance, and has potential application the field of wound dressings.
2022, 39(10): 4898-4907.
doi: 10.13801/j.cnki.fhclxb.20211124.001
Abstract:
With the development of nuclear energy, the radionuclide uranium flows into the environment through various channels, posing a potential threat to human health. Using waste corn stalks as raw materials, self-made corn stalk starch (CSS) was used, and magnetic γ-Fe2O3 was wrapped on the surface of CSS by co-precipitation method to synthesize magnetic γ-Fe2O3/CSS, which was used to adsorb U(VI) in the solution. The effects of factors such as initial pH value, dosage, time, initial concentration, temperature and coexisting ions on the adsorption performance of γ-Fe2O3/CSS for U(VI) were investigated and analyzed. The SEM, FTIR, XPS were used to characterize and analyze the magnetic γ-Fe2O3/CSS before and after adsorption, and the technical mechanism of adsorption of U(VI) was deeply studied. The results show that the maximum adsorption capacity of γ-Fe2O3/CSS for U(VI) reaches 214.1 mg/g in certain conditions. The quasi-second-order kinetic model describes the adsorption process more accurately, that is, chemical adsorption is the main. The adsorption of magnetic γ-Fe2O3/CSS on U(VI) satisfies Langmuir model and Freundlich model. The adsorption mechanism is mainly complex reaction and ion exchange between U(VI) and the hydroxyl and carboxyl groups of γ-Fe2O3/CSS. Four adsorption and desorption experiments show that the U(VI) adsorption rate is still above 78.60%, indicating that the magnetic γ-Fe2O3/CSS has a certain regeneration ability.
With the development of nuclear energy, the radionuclide uranium flows into the environment through various channels, posing a potential threat to human health. Using waste corn stalks as raw materials, self-made corn stalk starch (CSS) was used, and magnetic γ-Fe2O3 was wrapped on the surface of CSS by co-precipitation method to synthesize magnetic γ-Fe2O3/CSS, which was used to adsorb U(VI) in the solution. The effects of factors such as initial pH value, dosage, time, initial concentration, temperature and coexisting ions on the adsorption performance of γ-Fe2O3/CSS for U(VI) were investigated and analyzed. The SEM, FTIR, XPS were used to characterize and analyze the magnetic γ-Fe2O3/CSS before and after adsorption, and the technical mechanism of adsorption of U(VI) was deeply studied. The results show that the maximum adsorption capacity of γ-Fe2O3/CSS for U(VI) reaches 214.1 mg/g in certain conditions. The quasi-second-order kinetic model describes the adsorption process more accurately, that is, chemical adsorption is the main. The adsorption of magnetic γ-Fe2O3/CSS on U(VI) satisfies Langmuir model and Freundlich model. The adsorption mechanism is mainly complex reaction and ion exchange between U(VI) and the hydroxyl and carboxyl groups of γ-Fe2O3/CSS. Four adsorption and desorption experiments show that the U(VI) adsorption rate is still above 78.60%, indicating that the magnetic γ-Fe2O3/CSS has a certain regeneration ability.
2022, 39(10): 4908-4917.
doi: 10.13801/j.cnki.fhclxb.20210928.002
Abstract:
The silicon carbide ceramics (SiC) and ultra-high molecular weight polyethylene fiber reinforced waterborne polyurethane composite laminate (UHMWPE/WPU) were used to prepare SiC-UHMWPE/WPU composite armor plate by resin film infusion. Based on ballistic impact test, the influence of structural parameters of the composite armor plate on the anti-penetration performance of armor-piercing projectile was investigated. The damage mode of the post-impact SiC-UHMWPE/WPU composite armor plate, which was repeatedly impacted by type-53 and 7.62 mm armor piercing projectile at a velocity of\begin{document}$ {(808}_{-8}^{+7}) $\end{document} ![]()
![]()
The silicon carbide ceramics (SiC) and ultra-high molecular weight polyethylene fiber reinforced waterborne polyurethane composite laminate (UHMWPE/WPU) were used to prepare SiC-UHMWPE/WPU composite armor plate by resin film infusion. Based on ballistic impact test, the influence of structural parameters of the composite armor plate on the anti-penetration performance of armor-piercing projectile was investigated. The damage mode of the post-impact SiC-UHMWPE/WPU composite armor plate, which was repeatedly impacted by type-53 and 7.62 mm armor piercing projectile at a velocity of
2022, 39(10): 4918-4926.
doi: 10.13801/j.cnki.fhclxb.20211103.004
Abstract:
The graphite flakes/Al composite has the advantages of low density and high thermal conductivity, but it cannot be used as a kind of commercial electronic packaging material due to its poor mechanical properties at present. In order to improve the thermophysical properties of graphite flakes/Al composite, the SiC particles reinforced graphite flakes/Al composites were prepared via vacuum hot-pressing process. The effect of the different content of SiC on the thermal conductivity, coefficient of thermal expansion, and flexure strength of the SiC-graphite flakes/Al composites were studied. The result shows that the high-frequency vibration process contributes to the good orientation of graphite flakes in the composites. The SiC particles can significantly reduce the coefficient of thermal expansion, increase the flexure strength, and slightly decrease the thermal conductivity of the composites. However, as the volume fraction of SiC particles increases, many pores and defects are gradually foamed in the SiC-graphite flakes/Al composites, causing the decrease of the relative density. When the volume fraction of SiC and graphite flakes are 15vol% and 50vol%, respectively, the thermal conductivity in x-y plane, coefficient of thermal expansion and flexure strength of the SiC-graphite flakes/Al composite are 536 W/(m·K) and 6.4×10-6 m/K and 102 MPa, respectively, exhibiting the best comprehensive thermophysical properties, which can be a kind of electronic packaging material with very commercial prospect.
The graphite flakes/Al composite has the advantages of low density and high thermal conductivity, but it cannot be used as a kind of commercial electronic packaging material due to its poor mechanical properties at present. In order to improve the thermophysical properties of graphite flakes/Al composite, the SiC particles reinforced graphite flakes/Al composites were prepared via vacuum hot-pressing process. The effect of the different content of SiC on the thermal conductivity, coefficient of thermal expansion, and flexure strength of the SiC-graphite flakes/Al composites were studied. The result shows that the high-frequency vibration process contributes to the good orientation of graphite flakes in the composites. The SiC particles can significantly reduce the coefficient of thermal expansion, increase the flexure strength, and slightly decrease the thermal conductivity of the composites. However, as the volume fraction of SiC particles increases, many pores and defects are gradually foamed in the SiC-graphite flakes/Al composites, causing the decrease of the relative density. When the volume fraction of SiC and graphite flakes are 15vol% and 50vol%, respectively, the thermal conductivity in x-y plane, coefficient of thermal expansion and flexure strength of the SiC-graphite flakes/Al composite are 536 W/(m·K) and 6.4×10-6 m/K and 102 MPa, respectively, exhibiting the best comprehensive thermophysical properties, which can be a kind of electronic packaging material with very commercial prospect.
2022, 39(10): 4927-4934.
doi: 10.13801/j.cnki.fhclxb.20211115.004
Abstract:
In order to prepare Ti(C0.7N0.3)-based cermets with high hardness and high toughness, Ti(C0.7N0.3)-WC-Mo2C-VC-AlN-Ni/Co cermets containing TaC were prepared by vacuum pressureless sintering at 1600℃. The effects of different TaC content (0wt%, 5wt%, 10wt%, 15wt%) on the phase, microstructure and mechanical properties of cermets were investigated. The results show that with the increase of TaC content, the main peak of Ti(C0.7N0.3) (200) gradually shifts to a lower angle, the thickness of rim phase increase gradually and the Vickers hardness and fracture toughness of cermet firstly increased and then decreased. When 10wt% TaC is added, the core phase size of cermets is refined with the smallest, and the rim phase is more complete and uniform, leading to the maximum Vickers hardness ((17.79±0.15) GPa) and fracture toughness ((10.20±0.39) MPa·m1/2) of cermet.
In order to prepare Ti(C0.7N0.3)-based cermets with high hardness and high toughness, Ti(C0.7N0.3)-WC-Mo2C-VC-AlN-Ni/Co cermets containing TaC were prepared by vacuum pressureless sintering at 1600℃. The effects of different TaC content (0wt%, 5wt%, 10wt%, 15wt%) on the phase, microstructure and mechanical properties of cermets were investigated. The results show that with the increase of TaC content, the main peak of Ti(C0.7N0.3) (200) gradually shifts to a lower angle, the thickness of rim phase increase gradually and the Vickers hardness and fracture toughness of cermet firstly increased and then decreased. When 10wt% TaC is added, the core phase size of cermets is refined with the smallest, and the rim phase is more complete and uniform, leading to the maximum Vickers hardness ((17.79±0.15) GPa) and fracture toughness ((10.20±0.39) MPa·m1/2) of cermet.
2022, 39(10): 4935-4948.
doi: 10.13801/j.cnki.fhclxb.20211103.003
Abstract:
This paper is aimed to perform a numerical simulation study on the high-velocity impact failure behavior of hybrid fiber reinforced epoxy composite laminates based on the finite element model. Firstly, quasi-static mechanical tests of pure carbon fiber reinforced epoxy composites and pure aramid fiber reinforced epoxy composites were carried out to obtain their basic mechanical properties. Then, high-velocity impact tests were conducted to determine the critical penetration velocity and explore the influence of hybrid ratio on the impact resistance of hybrid composite reinforced composite laminates. The finite element model of high-velocity impact for hybrid fiber laminates was established, and the progressive damage constitutive of composite laminates was developed on the basis of the Murakami-Ohno damage evolution theory. The strain rate effect coefficient was introduced to consider strain rate dependency, and the element deletion was co-controlled by damage variable and element distortion in parallel. Then the high-velocity impact simulation for different hybrid ratio laminates was carried out and the corresponding critical penetration velocity was obtained respectively. The experimental results of high-velocity impact show that the critical penetration velocity increases with the increasing hybrid ratio, exhibiting a positive hybrid effect. Compared with the experimental results, the proposed model can accurately predict the quasi-static mechanical response and high-velocity impact response for the hybrid fiber reinforced epoxy composites, and the difference of the critical penetration velocity is less than 4.5%.
This paper is aimed to perform a numerical simulation study on the high-velocity impact failure behavior of hybrid fiber reinforced epoxy composite laminates based on the finite element model. Firstly, quasi-static mechanical tests of pure carbon fiber reinforced epoxy composites and pure aramid fiber reinforced epoxy composites were carried out to obtain their basic mechanical properties. Then, high-velocity impact tests were conducted to determine the critical penetration velocity and explore the influence of hybrid ratio on the impact resistance of hybrid composite reinforced composite laminates. The finite element model of high-velocity impact for hybrid fiber laminates was established, and the progressive damage constitutive of composite laminates was developed on the basis of the Murakami-Ohno damage evolution theory. The strain rate effect coefficient was introduced to consider strain rate dependency, and the element deletion was co-controlled by damage variable and element distortion in parallel. Then the high-velocity impact simulation for different hybrid ratio laminates was carried out and the corresponding critical penetration velocity was obtained respectively. The experimental results of high-velocity impact show that the critical penetration velocity increases with the increasing hybrid ratio, exhibiting a positive hybrid effect. Compared with the experimental results, the proposed model can accurately predict the quasi-static mechanical response and high-velocity impact response for the hybrid fiber reinforced epoxy composites, and the difference of the critical penetration velocity is less than 4.5%.
2022, 39(10): 4949-4960.
doi: 10.13801/j.cnki.fhclxb.20211108.004
Abstract:
In order to explore the dynamic response and failure behaviors of fiber fabrics under blast load, quasi-static and high strain rate tensile tests were carried out on three plain fabrics, the mechanical properties of the fabrics were obtained, and the constitutive model of the fabric was established. Using the Arbitrary Lagrangian-Eulerian (ALE) algorithm, a numerical analysis model of the fabric under blast was established, and the dynamic response process and failure modes of the fabric under blast load were studied. The results were compared with the test to verify the validity of the model. The relationship between the deformation peak value and the scaled distance and the energy absorption of each fabric in the hybrid stacked fabrics were obtained that can evaluate the anti-blast ability of the fabrics. The results show that the three kinds of fabrics exhibit different degrees of strain rate sensitivity. The failure strain and ultimate strength of aramid and ultra-high molecular weight polyethylene (UHMWPE) fiber fabrics under high strain rate load increase with the increase of strain rate, showing obvious strain rate effect. The ultimate strength of carbon fiber fabric increases slightly, and the strain rate effect is not obvious. The numerical analysis has obtained the same failure modes of the fiber fabric as the test: Central hole and simply supported boundary tearing. In the studied working conditions, the deformation peak value of the fabric is inversely proportional to the proportional distance, and the back burst surface fabric fails when the deformation peak value exceeds 39 mm. The specific energy absorption of the UHMWPE fiber fabric reaches 24.7 J/g, which is 4.3 times and 8.5 times that of aramid fabric and carbon fiber fabric.
In order to explore the dynamic response and failure behaviors of fiber fabrics under blast load, quasi-static and high strain rate tensile tests were carried out on three plain fabrics, the mechanical properties of the fabrics were obtained, and the constitutive model of the fabric was established. Using the Arbitrary Lagrangian-Eulerian (ALE) algorithm, a numerical analysis model of the fabric under blast was established, and the dynamic response process and failure modes of the fabric under blast load were studied. The results were compared with the test to verify the validity of the model. The relationship between the deformation peak value and the scaled distance and the energy absorption of each fabric in the hybrid stacked fabrics were obtained that can evaluate the anti-blast ability of the fabrics. The results show that the three kinds of fabrics exhibit different degrees of strain rate sensitivity. The failure strain and ultimate strength of aramid and ultra-high molecular weight polyethylene (UHMWPE) fiber fabrics under high strain rate load increase with the increase of strain rate, showing obvious strain rate effect. The ultimate strength of carbon fiber fabric increases slightly, and the strain rate effect is not obvious. The numerical analysis has obtained the same failure modes of the fiber fabric as the test: Central hole and simply supported boundary tearing. In the studied working conditions, the deformation peak value of the fabric is inversely proportional to the proportional distance, and the back burst surface fabric fails when the deformation peak value exceeds 39 mm. The specific energy absorption of the UHMWPE fiber fabric reaches 24.7 J/g, which is 4.3 times and 8.5 times that of aramid fabric and carbon fiber fabric.
2022, 39(10): 4961-4971.
doi: 10.13801/j.cnki.fhclxb.20211116.004
Abstract:
The tensile properties of carbon fiber reinforced epoxy composite with resin rich defects caused by local fiber fracture were studied. The corresponding relationship between defect location and tensile properties was analyzed. It is found that the maximum and minimum tensile strength are observed when the defect is located at 1/3 of the sample and 1/2 of the edge of the sample, respectively whilst the intermediate strength is seen at geometric center of the sample provided the same defect size. When the defect is in the same position, the tensile strength decreases with the increase of defect size. The actual size and location of defects are detected by computed tomography (CT), and the tensile strength prediction model of carbon fiber reinforced epoxy composite with defects is established by using finite element simulation. The error between the simulation values and the experimental values is less than 10%, which shows the reliability of the finite element model. Moreover, the failure mechanism of the composites is analyzed with the simulation results.
The tensile properties of carbon fiber reinforced epoxy composite with resin rich defects caused by local fiber fracture were studied. The corresponding relationship between defect location and tensile properties was analyzed. It is found that the maximum and minimum tensile strength are observed when the defect is located at 1/3 of the sample and 1/2 of the edge of the sample, respectively whilst the intermediate strength is seen at geometric center of the sample provided the same defect size. When the defect is in the same position, the tensile strength decreases with the increase of defect size. The actual size and location of defects are detected by computed tomography (CT), and the tensile strength prediction model of carbon fiber reinforced epoxy composite with defects is established by using finite element simulation. The error between the simulation values and the experimental values is less than 10%, which shows the reliability of the finite element model. Moreover, the failure mechanism of the composites is analyzed with the simulation results.
2022, 39(10): 4972-4987.
doi: 10.13801/j.cnki.fhclxb.20211022.003
Abstract:
The toughening mechanism of concrete with different aggregate volume fractions was investigated, and the meso-mechanical model of mode II fracture toughness KIIC was developed. The wedge splitting tests and mode II fracture tests for non-notched specimens were carried out simultaneously for concrete specimens which were prepared with aggregates in different volume fractions of 19vol%, 25vol%, 31vol% and 37vol%. The meso-scale simulations of corresponding mode II fracture tests were also performed by the cohesive zone model combined with the dot matrix method. The results show that as the aggregate volume fraction increases, the mode I fracture toughness KIC, mode II fracture toughness KIIC and the values of KIIC/KIC increase significantly. It was further found that the relationship between the values of KIIC/KIC and aggregate volume fraction can be described by a logarithmic function. The trapping-bridging of aggregate plays a leading role in the toughening of concrete, and its toughening effect is much greater than that caused by crack deflection or crack shielding. The meso-mechanical relation between KIIC and aggregate volume fraction was developed, and its prediction agrees well with the experimental data. The mechanical response and fracture morphology from meso-scale simulation of mode II fracture of concrete are in good agreement with those of experimental tests. Furthermore, the scalar stiffness degradation (SDEG) development of the cohesive element can be utilized to characterize the damage evolution of concrete at meso-level, which is valuable to the prediction of macro performance.
The toughening mechanism of concrete with different aggregate volume fractions was investigated, and the meso-mechanical model of mode II fracture toughness KIIC was developed. The wedge splitting tests and mode II fracture tests for non-notched specimens were carried out simultaneously for concrete specimens which were prepared with aggregates in different volume fractions of 19vol%, 25vol%, 31vol% and 37vol%. The meso-scale simulations of corresponding mode II fracture tests were also performed by the cohesive zone model combined with the dot matrix method. The results show that as the aggregate volume fraction increases, the mode I fracture toughness KIC, mode II fracture toughness KIIC and the values of KIIC/KIC increase significantly. It was further found that the relationship between the values of KIIC/KIC and aggregate volume fraction can be described by a logarithmic function. The trapping-bridging of aggregate plays a leading role in the toughening of concrete, and its toughening effect is much greater than that caused by crack deflection or crack shielding. The meso-mechanical relation between KIIC and aggregate volume fraction was developed, and its prediction agrees well with the experimental data. The mechanical response and fracture morphology from meso-scale simulation of mode II fracture of concrete are in good agreement with those of experimental tests. Furthermore, the scalar stiffness degradation (SDEG) development of the cohesive element can be utilized to characterize the damage evolution of concrete at meso-level, which is valuable to the prediction of macro performance.
2022, 39(10): 4988-4996.
doi: 10.13801/j.cnki.fhclxb.20211025.004
Abstract:
The finite element model was used to predict the tensile strength of the self-lubricating fabric composites, and the wear rate prediction model of the composites was obtained. The unit cell finite element model of self-lubricating fabric composites was established by TexGen, and ABAQUS was used to perform finite element simulation of composites stretching, the tensile strength of the composites was verified by experiments lastly. The results show that the difference rate between the simulated value of the composites in the warp direction and the experimental value is 6.71%, and the rate of difference in the weft direction is 5.51%, indicating that finite element model of the composites has high reliability. From the tensile stress cloud diagram, it can be seen that the tensile strength of the composites is determined by the elastic modulus of the fiber in the tensile direction. On this basis, analysis of the wear rate and friction and wear mechanism of self-lubricating fabric composites, the mapping relationship between the tensile strength and the wear rate of the composites was studied. The difference rate between the predicted value of the wear rate obtained by the prediction model and the experimental result is 8.43% on average, indicating reliability of the volume wear rate prediction model.
The finite element model was used to predict the tensile strength of the self-lubricating fabric composites, and the wear rate prediction model of the composites was obtained. The unit cell finite element model of self-lubricating fabric composites was established by TexGen, and ABAQUS was used to perform finite element simulation of composites stretching, the tensile strength of the composites was verified by experiments lastly. The results show that the difference rate between the simulated value of the composites in the warp direction and the experimental value is 6.71%, and the rate of difference in the weft direction is 5.51%, indicating that finite element model of the composites has high reliability. From the tensile stress cloud diagram, it can be seen that the tensile strength of the composites is determined by the elastic modulus of the fiber in the tensile direction. On this basis, analysis of the wear rate and friction and wear mechanism of self-lubricating fabric composites, the mapping relationship between the tensile strength and the wear rate of the composites was studied. The difference rate between the predicted value of the wear rate obtained by the prediction model and the experimental result is 8.43% on average, indicating reliability of the volume wear rate prediction model.
2022, 39(10): 4997-5007.
doi: 10.13801/j.cnki.fhclxb.20211105.002
Abstract:
In order to better understand the short-term and long-term deformation behaviors of carbon fiber reinforced epoxy (CF/EP) composite materials, a series of tensile creep tests of a type of CF/EP laminated composite material under constant loads, typically, 20%, 30% and 40% of ultimate tensile strength and constant temperatures (25°C and 50°C) were conducted. The material deforms in a remarkable time-dependent way, and behaves both clearly creep temperature effect and physical aging phenomena. Specifically, the tensile strains increase during the short time duration after the tests begin, similar to creep deformation. When the testing time exceeds physical aging characteristic time, the tensile strains start to decrease during the most of loading period. To characterize reasonably this particular deformation behavior, a linear viscoelastic model was developed to describe both creep temperature effect and physical ageing effect. The related viscoelastic constitutive relations of this composite material were derived, and further numerically implemented using the Prony series. In addition, its numerical algorithm was proposed within a finite element framework, and numerical analysis was performed via UMAT subroutine. The new theoretical model is then verified by a comparison of experimental results to numerical ones.
In order to better understand the short-term and long-term deformation behaviors of carbon fiber reinforced epoxy (CF/EP) composite materials, a series of tensile creep tests of a type of CF/EP laminated composite material under constant loads, typically, 20%, 30% and 40% of ultimate tensile strength and constant temperatures (25°C and 50°C) were conducted. The material deforms in a remarkable time-dependent way, and behaves both clearly creep temperature effect and physical aging phenomena. Specifically, the tensile strains increase during the short time duration after the tests begin, similar to creep deformation. When the testing time exceeds physical aging characteristic time, the tensile strains start to decrease during the most of loading period. To characterize reasonably this particular deformation behavior, a linear viscoelastic model was developed to describe both creep temperature effect and physical ageing effect. The related viscoelastic constitutive relations of this composite material were derived, and further numerically implemented using the Prony series. In addition, its numerical algorithm was proposed within a finite element framework, and numerical analysis was performed via UMAT subroutine. The new theoretical model is then verified by a comparison of experimental results to numerical ones.
2022, 39(10): 5008-5019.
doi: 10.13801/j.cnki.fhclxb.20211028.006
Abstract:
To satisfy the requirements of eddy current testing in detecting defects of carbon fiber reinforced polymer (CFRP) composites, the numerical simulation and experiment were employed to study the electromagnetic field (EMF) diffusion and attenuation in CFRP structures. A homogeneous anisotropic 3D EMF model was built to study the influence of the two different conductive behaviors at the interlaminar interface on eddy currents distribution in CFRP, and to compare the EMF attenuation under the different conductive behaviors and its relation to frequency. The results show that the behavior affects the currents in multidirectional CFRP significantly, not only changes the currents distribution, but also reduces the currents intensity, while it has little effect on the currents in unidirectional CFRP, and its distribution form is unitary. Under the two behaviors, the EMF attenuation of unidirectional plate is independent of frequency, and the currents decay quickly, while the attenuation in the other plate is proportional to the frequency variation, and the currents decay slowly. According to the law of energy conservation of EMF, it is found that resistive loss is the dominant factor affecting the currents attenuation of unidirectional plate. Finally, the eddy current experiment was used to semi-quantitatively verify the numerical simulation results and physical phenomena.
To satisfy the requirements of eddy current testing in detecting defects of carbon fiber reinforced polymer (CFRP) composites, the numerical simulation and experiment were employed to study the electromagnetic field (EMF) diffusion and attenuation in CFRP structures. A homogeneous anisotropic 3D EMF model was built to study the influence of the two different conductive behaviors at the interlaminar interface on eddy currents distribution in CFRP, and to compare the EMF attenuation under the different conductive behaviors and its relation to frequency. The results show that the behavior affects the currents in multidirectional CFRP significantly, not only changes the currents distribution, but also reduces the currents intensity, while it has little effect on the currents in unidirectional CFRP, and its distribution form is unitary. Under the two behaviors, the EMF attenuation of unidirectional plate is independent of frequency, and the currents decay quickly, while the attenuation in the other plate is proportional to the frequency variation, and the currents decay slowly. According to the law of energy conservation of EMF, it is found that resistive loss is the dominant factor affecting the currents attenuation of unidirectional plate. Finally, the eddy current experiment was used to semi-quantitatively verify the numerical simulation results and physical phenomena.
2022, 39(10): 5020-5031.
doi: 10.13801/j.cnki.fhclxb.20210920.001
Abstract:
To reveal energy absorption mechanism and improve crashworthiness of aluminum (Al)/carbon fiber reinforced plastic (CFRP) hybrid front rails, firstly, the dynamic axial impact tests of net aluminum rails and Al/CFRP hybrid rails with carbon fiber sheets embedded into aluminum hollow were carried out. The experimental results show that the energy absorption\begin{document}$ {W_{\text{e}}} $\end{document} ![]()
![]()
\begin{document}$ {W_{\text{s}}} $\end{document} ![]()
![]()
\begin{document}$ {W_{\text{e}}} $\end{document} ![]()
![]()
\begin{document}$ {P_{\text{c}}} $\end{document} ![]()
![]()
To reveal energy absorption mechanism and improve crashworthiness of aluminum (Al)/carbon fiber reinforced plastic (CFRP) hybrid front rails, firstly, the dynamic axial impact tests of net aluminum rails and Al/CFRP hybrid rails with carbon fiber sheets embedded into aluminum hollow were carried out. The experimental results show that the energy absorption
2022, 39(10): 5032-5040.
doi: 10.13801/j.cnki.fhclxb.20211015.002
Abstract:
A buckling reliability analysis method for the metal liner of composite pressure vessel was established. Based on the analytical model of influence of the depression on the pressure and residual moment of the liner interface, the local buckling analysis of the metal liner was carried out by combining the finite element numerical simulation analysis method. Based on Monte Carlo algorithm, sampling methods for design variables of composite pressure vessel liner and winding layer were established, respectively. The radial basic function (RBF) surrogate model was used to replace the finite element analysis model for the buckling calculation of the inner liner, and a fast analysis method for the reliability of the local buckling of the pressure vessel with metal liner after autofrettage was established. Taking a 30 L cylindrical fiber wound composite pressure vessel with metal liner as an example, the influence of the uncertainties of the design parameters of the inner liner and the winding layer on the buckling reliability of the inner liner was analyzed. The results show that the buckling probability of the liner is positively correlated with the autofrettage pressure within the calculated range. The influence of the liner thickness on the buckling probability of the liner increases approximately linearly with the increase of the autofrettage pressure. Considering the liner radius, the thickness of the winding layer and the modulus of the winding layer separately, the variation trend of the buckling probability with the autofrettage pressure is an increasing curve from slow to fast and then to gentle.
A buckling reliability analysis method for the metal liner of composite pressure vessel was established. Based on the analytical model of influence of the depression on the pressure and residual moment of the liner interface, the local buckling analysis of the metal liner was carried out by combining the finite element numerical simulation analysis method. Based on Monte Carlo algorithm, sampling methods for design variables of composite pressure vessel liner and winding layer were established, respectively. The radial basic function (RBF) surrogate model was used to replace the finite element analysis model for the buckling calculation of the inner liner, and a fast analysis method for the reliability of the local buckling of the pressure vessel with metal liner after autofrettage was established. Taking a 30 L cylindrical fiber wound composite pressure vessel with metal liner as an example, the influence of the uncertainties of the design parameters of the inner liner and the winding layer on the buckling reliability of the inner liner was analyzed. The results show that the buckling probability of the liner is positively correlated with the autofrettage pressure within the calculated range. The influence of the liner thickness on the buckling probability of the liner increases approximately linearly with the increase of the autofrettage pressure. Considering the liner radius, the thickness of the winding layer and the modulus of the winding layer separately, the variation trend of the buckling probability with the autofrettage pressure is an increasing curve from slow to fast and then to gentle.
2022, 39(10): 5041-5048.
doi: 10.13801/j.cnki.fhclxb.20211116.001
Abstract:
Polyester fabrics are often used for airship structures because of their light-weight, high-strength and environmental resistance properties, their creep failure behavior under high stress levels determines the long-term safety performance of airship structures, but there is no relevant test standard or research at present. In order to study the creep properties of polyester fabrics, a membrane material composed of Vectran fibers was selected to carry out uniaxial tensile creep tests at 4 high stress levels: 85%, 80%, 75% and 70% of ultimate stress. The variation laws of creep strain, creep modulus and creep failure time with respect to stress level were summarized, and the fitting formulas of creep rupture envelopes were given through Newton iterative calculation. When the stress level is lower than 63% of the ultimate stress, the fabrics will not reach the creep rupture point. Based on the experimental data, the parametric four element creep model and creep failure criterions are established. It is found that the fitting model can generally reflect the creep failure reactions under high stress levels.
Polyester fabrics are often used for airship structures because of their light-weight, high-strength and environmental resistance properties, their creep failure behavior under high stress levels determines the long-term safety performance of airship structures, but there is no relevant test standard or research at present. In order to study the creep properties of polyester fabrics, a membrane material composed of Vectran fibers was selected to carry out uniaxial tensile creep tests at 4 high stress levels: 85%, 80%, 75% and 70% of ultimate stress. The variation laws of creep strain, creep modulus and creep failure time with respect to stress level were summarized, and the fitting formulas of creep rupture envelopes were given through Newton iterative calculation. When the stress level is lower than 63% of the ultimate stress, the fabrics will not reach the creep rupture point. Based on the experimental data, the parametric four element creep model and creep failure criterions are established. It is found that the fitting model can generally reflect the creep failure reactions under high stress levels.
