2022 Vol. 39, No. 12
2022, 39(12): 5665-5677.
doi: 10.13801/j.cnki.fhclxb.20211228.004
Abstract:
In order to improve the corrosion resistance of epoxy resin (EP) coatings, both polyhedral oligomeric silsesquioxane (POSS) modified hexagonal boron nitride (h-BN) and aniline trimer (AT) were co-doped into the epoxy curing system using as functional fillers. The hydroxylated boron nitride OH-BN was obtained by peeling off the hexagonal boron nitride at high temperature. The surface of OH-BN was modified with the silane coupling agent KH-560, and then the aminopropyl heptaisobutyl POSS (APS) and octaaminophenyl POSS (OAPPS) were grafted to synthesize APS-BN and OAPPS-BN. The two modified h-BN and aniline trimer were dispersed into EP to prepare organic-inorganic hybrid coatings through π-π interactions. The coating's AC impedance spectroscopy, Tafel curve, salt spray test, and contact angle, thermal and mechanical properties were characterized by some techniques. The results show that, compared with the pure epoxy coating, the composited coating doped with 0.5wt% OAPPS-BN-AT has the largest improvement in performance with an impedance value of 1.27×1011 Ω·cm2. The corrosion potential is −0.052 V with an increasing of 0.35 V. The salt spray resistance test exhibites that no pitting or blistering occurred for 30 days. Based on the POSS surface migration effect and h-BN barrier effect, the pencil hardness of the composited coating is increased to 3H level. The surface contact angle is changed from 67.1° to 93.2°. In a word, the composited 0.5wt%OAPPS-BN-AT/EP coating has excellent adhesion, impact resistance, flexibility and heat resistance, which showed a promising potential in the field of anti-corrosion.
In order to improve the corrosion resistance of epoxy resin (EP) coatings, both polyhedral oligomeric silsesquioxane (POSS) modified hexagonal boron nitride (h-BN) and aniline trimer (AT) were co-doped into the epoxy curing system using as functional fillers. The hydroxylated boron nitride OH-BN was obtained by peeling off the hexagonal boron nitride at high temperature. The surface of OH-BN was modified with the silane coupling agent KH-560, and then the aminopropyl heptaisobutyl POSS (APS) and octaaminophenyl POSS (OAPPS) were grafted to synthesize APS-BN and OAPPS-BN. The two modified h-BN and aniline trimer were dispersed into EP to prepare organic-inorganic hybrid coatings through π-π interactions. The coating's AC impedance spectroscopy, Tafel curve, salt spray test, and contact angle, thermal and mechanical properties were characterized by some techniques. The results show that, compared with the pure epoxy coating, the composited coating doped with 0.5wt% OAPPS-BN-AT has the largest improvement in performance with an impedance value of 1.27×1011 Ω·cm2. The corrosion potential is −0.052 V with an increasing of 0.35 V. The salt spray resistance test exhibites that no pitting or blistering occurred for 30 days. Based on the POSS surface migration effect and h-BN barrier effect, the pencil hardness of the composited coating is increased to 3H level. The surface contact angle is changed from 67.1° to 93.2°. In a word, the composited 0.5wt%OAPPS-BN-AT/EP coating has excellent adhesion, impact resistance, flexibility and heat resistance, which showed a promising potential in the field of anti-corrosion.
2022, 39(12): 5678-5687.
doi: 10.13801/j.cnki.fhclxb.20211207.002
Abstract:
Polymer-based hydrated ferric oxide (HFO) composite adsorbents had attracted extensive attention because of large phosphate adsorption capacity, rapid adsorption rate and high regeneration efficiency. Nevertheless, whether the same structure and phosphate adsorption could be performed by composite adsorbents prepared at different NaOH concentration was still unclear. In order to provide evidence for optimization of polymer-based hydrated ferric oxide composite adsorbents preparation, the structure and phosphate adsorption of composite adsorbents prepared by regulating NaOH concentration were studied. The results show that when NaOH concentration increases from 1 mol·L−1 to 6 mol·L−1, there are no significantly effect on the HFO loadings (approximately 16wt%, mass fraction in Fe) and crystal structure of composite adsorbents. However, the considerable self-agglomerate of HFO nanoparticles decrease, and HFO nanoparticles distribute evenly. Moreover, phosphate adsorption capacity is increased with NaOH concentration and then remains the same (18 mg·g−1). Additionally, adsorption equilibrium times are 240 min, and the adsorption kinetic curves are fitted well with pseudo-first order kinetic model (R2 > 0.99). The optimal pH value for phosphate adsorption is 6-8, and the influence degree of phosphate adsorption by co-existing ions is SO42−>Cl−>NO3− under the same concentration. The regeneration efficiencies of composite adsorbents approach 100% during 5 continuous adsorption regeneration cycles. The experiments show that the HFO nanoparticles distribute evenly with the increase of NaOH concentration, and the phosphate adsorption capacity of composite adsorbents is increased and then remains the same, while there is no significant difference in crystal structure, adsorption equilibrium time, optimal pH, effect of coexisting anions, and elution effect.
Polymer-based hydrated ferric oxide (HFO) composite adsorbents had attracted extensive attention because of large phosphate adsorption capacity, rapid adsorption rate and high regeneration efficiency. Nevertheless, whether the same structure and phosphate adsorption could be performed by composite adsorbents prepared at different NaOH concentration was still unclear. In order to provide evidence for optimization of polymer-based hydrated ferric oxide composite adsorbents preparation, the structure and phosphate adsorption of composite adsorbents prepared by regulating NaOH concentration were studied. The results show that when NaOH concentration increases from 1 mol·L−1 to 6 mol·L−1, there are no significantly effect on the HFO loadings (approximately 16wt%, mass fraction in Fe) and crystal structure of composite adsorbents. However, the considerable self-agglomerate of HFO nanoparticles decrease, and HFO nanoparticles distribute evenly. Moreover, phosphate adsorption capacity is increased with NaOH concentration and then remains the same (18 mg·g−1). Additionally, adsorption equilibrium times are 240 min, and the adsorption kinetic curves are fitted well with pseudo-first order kinetic model (R2 > 0.99). The optimal pH value for phosphate adsorption is 6-8, and the influence degree of phosphate adsorption by co-existing ions is SO42−>Cl−>NO3− under the same concentration. The regeneration efficiencies of composite adsorbents approach 100% during 5 continuous adsorption regeneration cycles. The experiments show that the HFO nanoparticles distribute evenly with the increase of NaOH concentration, and the phosphate adsorption capacity of composite adsorbents is increased and then remains the same, while there is no significant difference in crystal structure, adsorption equilibrium time, optimal pH, effect of coexisting anions, and elution effect.
2022, 39(12): 5688-5698.
doi: 10.13801/j.cnki.fhclxb.20211213.001
Abstract:
Dry winding is an important branch of the winding forming process. The winding process has uniform glue content, high winding efficiency, low environmental pollution and easier industrial automation production. The development of prepreg yarn with good processing properties is of great significance to the promotion and application of dry winding. Through dynamic DSC and constant temperature DSC, combined with the viscosity test, the curing characteristics of the epoxy resin system used were studied. Based on the autocatalytic model, the resin curing reaction kinetic equation was established and verified by comparison with the measured curing degree. A prepreg yarn preparation platform was set up, an improved hot-melt method to prepare dry winding prepreg yarn was adopted, and the influence of different curing degrees on the surface quality of prepreg yarn during the preparation process was analyzed. On this basis, the response surface method was used to analyze the influence of different process parameters (creel tension, winding speed, drying tunnel temperature) on the glue content of the prepreg yarn. The results show that the autocatalytic model is basically consistent with the experimental results, and the best curing range for dry winding prepreg yarn is 5%-10%. The factor that has the greatest influence on the glue content is the winding rate, followed by the unwinding tension. The temperature of the drying tunnel has the least influence. Considering the influence law of various process parameters, the optimized preparation process parameters are obtained: The temperature of the drying tunnel is 180℃, the winding speed is 8 m/min, the yarn unwinding tension is 6 N, and the resin mass fraction is 30.1wt% at this time. The tensile strength of the NOL ring can reach 2536.1 MPa, the tensile modulus is 162.3 GPa, and the interlaminar shear strength is 57.3 MPa.
Dry winding is an important branch of the winding forming process. The winding process has uniform glue content, high winding efficiency, low environmental pollution and easier industrial automation production. The development of prepreg yarn with good processing properties is of great significance to the promotion and application of dry winding. Through dynamic DSC and constant temperature DSC, combined with the viscosity test, the curing characteristics of the epoxy resin system used were studied. Based on the autocatalytic model, the resin curing reaction kinetic equation was established and verified by comparison with the measured curing degree. A prepreg yarn preparation platform was set up, an improved hot-melt method to prepare dry winding prepreg yarn was adopted, and the influence of different curing degrees on the surface quality of prepreg yarn during the preparation process was analyzed. On this basis, the response surface method was used to analyze the influence of different process parameters (creel tension, winding speed, drying tunnel temperature) on the glue content of the prepreg yarn. The results show that the autocatalytic model is basically consistent with the experimental results, and the best curing range for dry winding prepreg yarn is 5%-10%. The factor that has the greatest influence on the glue content is the winding rate, followed by the unwinding tension. The temperature of the drying tunnel has the least influence. Considering the influence law of various process parameters, the optimized preparation process parameters are obtained: The temperature of the drying tunnel is 180℃, the winding speed is 8 m/min, the yarn unwinding tension is 6 N, and the resin mass fraction is 30.1wt% at this time. The tensile strength of the NOL ring can reach 2536.1 MPa, the tensile modulus is 162.3 GPa, and the interlaminar shear strength is 57.3 MPa.
2022, 39(12): 5699-5710.
doi: 10.13801/j.cnki.fhclxb.20211221.001
Abstract:
The thermal and tribological properties at high temperature of polyimide (PI) composites were improved by enhancing the heat resistance and thermal conductivity. Cage polysesquiloxane (POSS) and SiO2 were selected to improve the heat resistance, carbon nanotubes (CNTs) and Cu powder were chosen to improve the thermal conductivity. Then, molecular simulation and experiment were both used to study the effect of each component on its properties. The results show that POSS and SiO2 could improve the heat resistance and Young's modulus of PI, but reduce the thermal conductivity and impact strength. Cu improves the high temperature resistance and thermal conductivity of PI, but reduces the mechanical strength. CNTs show an excellent reinforced effect at low content, but become worse at high content. Then, PI composites modified by the multi-component were designed according to the results of single-component modification. The results show that the PI composites with 3wt% POSS, 3wt% SiO2, 0.5wt% CNTs and 3wt% Cu have the best comprehensive performance and the best friction performance at high temperature. The friction coefficient at 200℃ is 0.65, which is 27.8% lower than that of pure PI. The wear rate is 5.11×10−5 mm3/(N·m), decreasing by 19.3%.
The thermal and tribological properties at high temperature of polyimide (PI) composites were improved by enhancing the heat resistance and thermal conductivity. Cage polysesquiloxane (POSS) and SiO2 were selected to improve the heat resistance, carbon nanotubes (CNTs) and Cu powder were chosen to improve the thermal conductivity. Then, molecular simulation and experiment were both used to study the effect of each component on its properties. The results show that POSS and SiO2 could improve the heat resistance and Young's modulus of PI, but reduce the thermal conductivity and impact strength. Cu improves the high temperature resistance and thermal conductivity of PI, but reduces the mechanical strength. CNTs show an excellent reinforced effect at low content, but become worse at high content. Then, PI composites modified by the multi-component were designed according to the results of single-component modification. The results show that the PI composites with 3wt% POSS, 3wt% SiO2, 0.5wt% CNTs and 3wt% Cu have the best comprehensive performance and the best friction performance at high temperature. The friction coefficient at 200℃ is 0.65, which is 27.8% lower than that of pure PI. The wear rate is 5.11×10−5 mm3/(N·m), decreasing by 19.3%.
2022, 39(12): 5711-5726.
doi: 10.13801/j.cnki.fhclxb.20211217.002
Abstract:
In order to study the mechanical properties, thermal stability, dynamic thermomechanical properties, crystallization behavior and interfacial compatibility of hydrotalcite composites, Mg-Al hydrotalcite was prepared by coprecipitation method, and then calcined to obtain calcined Mg-Al hydrotalcite. The effects of temperature and time on the interlayer structure of hydrotalcite were investigated by variable control method. The hydrotalcite calcined at 300℃ (LDHs(300)) was characterized and tested by TG, SEM and XRD. The morphology and thermal stability confirmed that most of the interlayer water had been removed, and the layered structure was maintained without damaging its original properties. The calcined hydrotalcite was successfully intercalated with sodium dodecylbenzene sulfonate (SDBS) by FTIR and XRD. Then different surface modified hydrotalcite particles were added to polylactic acid/maleic anhydride grafted polypropylene (PLA-PP-g-MAH) by melt blending to obtain different composites. The results show that the properties of hydrotalcite composites modified by calcination are the best. The morphological analysis by SEM shows that with the addition of hydrotalcite to PLA-PP-g-MAH, the domain size of PP-g-MAH particles decreases significantly, and the PP-g-MAH phase has better wettability, resulting in higher impact strength, compared with pure PLA, it increased by 37.72%. From the rheological behavior, it is found that the rheological properties of calcined hydrotalcite composites are significantly higher than those of PLA. DMA shows that when calcined hydrotalcite is added to PLA-PP-g-MAH blend, the glass transition temperature (Tg) of PLA increased and the cold crystallization temperature (Tcc) decreased. DSC and POM show that the crystallization rate and crystallinity of calcined hydrotalcite composites are higher than those of PLA by 62.8%.
In order to study the mechanical properties, thermal stability, dynamic thermomechanical properties, crystallization behavior and interfacial compatibility of hydrotalcite composites, Mg-Al hydrotalcite was prepared by coprecipitation method, and then calcined to obtain calcined Mg-Al hydrotalcite. The effects of temperature and time on the interlayer structure of hydrotalcite were investigated by variable control method. The hydrotalcite calcined at 300℃ (LDHs(300)) was characterized and tested by TG, SEM and XRD. The morphology and thermal stability confirmed that most of the interlayer water had been removed, and the layered structure was maintained without damaging its original properties. The calcined hydrotalcite was successfully intercalated with sodium dodecylbenzene sulfonate (SDBS) by FTIR and XRD. Then different surface modified hydrotalcite particles were added to polylactic acid/maleic anhydride grafted polypropylene (PLA-PP-g-MAH) by melt blending to obtain different composites. The results show that the properties of hydrotalcite composites modified by calcination are the best. The morphological analysis by SEM shows that with the addition of hydrotalcite to PLA-PP-g-MAH, the domain size of PP-g-MAH particles decreases significantly, and the PP-g-MAH phase has better wettability, resulting in higher impact strength, compared with pure PLA, it increased by 37.72%. From the rheological behavior, it is found that the rheological properties of calcined hydrotalcite composites are significantly higher than those of PLA. DMA shows that when calcined hydrotalcite is added to PLA-PP-g-MAH blend, the glass transition temperature (Tg) of PLA increased and the cold crystallization temperature (Tcc) decreased. DSC and POM show that the crystallization rate and crystallinity of calcined hydrotalcite composites are higher than those of PLA by 62.8%.
2022, 39(12): 5892-5900.
doi: 10.13801/j.cnki.fhclxb.20220105.001
Abstract:
Eucommia ulmoides gum (EUG) was blended with styrene butadiene rubber (SBR) to prepare EUG-SBR composites. The co-vulcanization was characterized by stripping experiments and tensile experiments, and the effect of EUG content on the dynamic properties of the composites was studied via tensile experiment, SEM, DMA and XRD. The results display that the prepared sulfide formula (mass ratio of accelerant N, N-dicyclohexyl-2-benzothiazole sulfonamide (DZ) 1.0% (based on the mass of EUG- SBR), accelerant tetramethylthiuram disulfide (TMTD) 0.1%, sulfur 1.5%) could achieve better co-vulcanization of the two rubbers. The stripping strength of the two rubbers reaches 4.2 kN/m and the tensile strength (mass ratio of SBR∶EUG=70∶30) could reach 6.3 MPa. The EUG phase in the composites mainly exists in β-crystalline form, and with the EUG content increasing, the crystallinity and melt temperature of the composites are significantly improved. The introduction of EUG decreases the peak loss factor tanδmax value and increases the storage modulus of the composites. At temperatures of 10 ℃, the storage modulus of EUG-SBR composites increases from 3.0×106 Pa (with 5% mass of EUG) to 1.7×107 Pa (with EUG of 35%). At the same time, the presence of crystal zone plays a role of physical crosslinking points to improve the tensile strength and fixed elongation stress of composites.
Eucommia ulmoides gum (EUG) was blended with styrene butadiene rubber (SBR) to prepare EUG-SBR composites. The co-vulcanization was characterized by stripping experiments and tensile experiments, and the effect of EUG content on the dynamic properties of the composites was studied via tensile experiment, SEM, DMA and XRD. The results display that the prepared sulfide formula (mass ratio of accelerant N, N-dicyclohexyl-2-benzothiazole sulfonamide (DZ) 1.0% (based on the mass of EUG- SBR), accelerant tetramethylthiuram disulfide (TMTD) 0.1%, sulfur 1.5%) could achieve better co-vulcanization of the two rubbers. The stripping strength of the two rubbers reaches 4.2 kN/m and the tensile strength (mass ratio of SBR∶EUG=70∶30) could reach 6.3 MPa. The EUG phase in the composites mainly exists in β-crystalline form, and with the EUG content increasing, the crystallinity and melt temperature of the composites are significantly improved. The introduction of EUG decreases the peak loss factor tanδmax value and increases the storage modulus of the composites. At temperatures of 10 ℃, the storage modulus of EUG-SBR composites increases from 3.0×106 Pa (with 5% mass of EUG) to 1.7×107 Pa (with EUG of 35%). At the same time, the presence of crystal zone plays a role of physical crosslinking points to improve the tensile strength and fixed elongation stress of composites.
2022, 39(12): 6168-6176.
doi: 10.13801/j.cnki.fhclxb.20211213.002
Abstract:
In order to investigate the influences of fiber-mat, shear plain and temperature on the shearing properties of multi-axial pultruded composite materials, the in-plain shear experiments on the traditional composites strengthened with chopped strand mats (shear plane perpendicular to or parallel to fiber direction), as well as the multi-axial pultruded composites strengthened with 90° uniaxial mat and ±45°/90° triaxial mat, were carried out at elevated temperatures. The results show that the main failure modes are diagonal micro buckling, debonding and shear failure, depending on the mat and shear plain. The shear properties significantly depend on the woven. Under ambient temperature, the average shear strength of specimens strengthened with the triaxial mat is 67.5 MPa, which is significantly greater than those of the specimens strengthened with the uniaxial mat and the chopped strand mat, which are 44.4 MPa and 45.2 MPa, respectively. The shear properties also depend on the shear plain. Under ambient temperature, the average shear strength of the chopped strand mat reinforced specimens with the shear plane perpendicular to the fiber direction is higher than that of the specimens parallel to the fiber direction (38.9 MPa). However, with the increase in temperature, the shear properties for all group specimens reduce rapidly while the difference in each group gradually becomes smaller. The calculation model for shear property of uniaxial pultruded composites based on thermal kinetic theory and parallel law is generally suitable for multi-axial pultruded composites. Finally, a formula was proposed for the calculation of shear strength and shear modulus of multi-axial pultruded composites at elevated temperatures. The research results could provide a basis for the shear design of multi-axial pultruded composites at elevated temperatures.
In order to investigate the influences of fiber-mat, shear plain and temperature on the shearing properties of multi-axial pultruded composite materials, the in-plain shear experiments on the traditional composites strengthened with chopped strand mats (shear plane perpendicular to or parallel to fiber direction), as well as the multi-axial pultruded composites strengthened with 90° uniaxial mat and ±45°/90° triaxial mat, were carried out at elevated temperatures. The results show that the main failure modes are diagonal micro buckling, debonding and shear failure, depending on the mat and shear plain. The shear properties significantly depend on the woven. Under ambient temperature, the average shear strength of specimens strengthened with the triaxial mat is 67.5 MPa, which is significantly greater than those of the specimens strengthened with the uniaxial mat and the chopped strand mat, which are 44.4 MPa and 45.2 MPa, respectively. The shear properties also depend on the shear plain. Under ambient temperature, the average shear strength of the chopped strand mat reinforced specimens with the shear plane perpendicular to the fiber direction is higher than that of the specimens parallel to the fiber direction (38.9 MPa). However, with the increase in temperature, the shear properties for all group specimens reduce rapidly while the difference in each group gradually becomes smaller. The calculation model for shear property of uniaxial pultruded composites based on thermal kinetic theory and parallel law is generally suitable for multi-axial pultruded composites. Finally, a formula was proposed for the calculation of shear strength and shear modulus of multi-axial pultruded composites at elevated temperatures. The research results could provide a basis for the shear design of multi-axial pultruded composites at elevated temperatures.
2022, 39(12): 5727-5735.
doi: 10.13801/j.cnki.fhclxb.20211221.003
Abstract:
Supercapacitor, which has a series of advantages such as fast charge and discharge, high specific capacitance as well as good cycle stability, has become an important energy storage device, whose performance mainly depends on the electrochemical properties of electrode materials. Composite nanomaterials with high specific surface area and environmental friendliness are ideal electrode materials for supercapacitors. In this paper, nickel-molybdenum nanosheets were grown on the surface of cobalt hydroxide nanowires on the carbon cloth substrate by a two-step hydrothermal method to achieve CoO@NiMo-O(P) composite nanomaterials after low temperature annealing and phosphorlation. The morphology, structure and chemical valence of the samples were characterized and analyzed by SEM, TEM and XPS. The results of electrochemical tests show that the hierarchical CoO@NiMo-O(P) composites has good capacitance performance. The specific capacitance reaches 1304.55 F/g at a low current density of 1 A/g, and a capacity retention of 87% is exhibited after 1000 charge and discharge at a current density of 10 A/g, showing good cycle stability.
Supercapacitor, which has a series of advantages such as fast charge and discharge, high specific capacitance as well as good cycle stability, has become an important energy storage device, whose performance mainly depends on the electrochemical properties of electrode materials. Composite nanomaterials with high specific surface area and environmental friendliness are ideal electrode materials for supercapacitors. In this paper, nickel-molybdenum nanosheets were grown on the surface of cobalt hydroxide nanowires on the carbon cloth substrate by a two-step hydrothermal method to achieve CoO@NiMo-O(P) composite nanomaterials after low temperature annealing and phosphorlation. The morphology, structure and chemical valence of the samples were characterized and analyzed by SEM, TEM and XPS. The results of electrochemical tests show that the hierarchical CoO@NiMo-O(P) composites has good capacitance performance. The specific capacitance reaches 1304.55 F/g at a low current density of 1 A/g, and a capacity retention of 87% is exhibited after 1000 charge and discharge at a current density of 10 A/g, showing good cycle stability.
Performance optimization of La0.65Sr0.35MnO3 oxygen electrode based on alternate infiltration method
2022, 39(12): 5736-5746.
doi: 10.13801/j.cnki.fhclxb.20211202.002
Abstract:
Hydrogen energy has become an effective substitute for fossil energy due to its advantages of high efficiency, cleanliness and renewability. Reversible solid oxide cell (RSOC) can use hydrogen to output electricity or electrolyze H2O to produce hydrogen, which has very important research significance. The performance optimization of La0.65Sr0.35MnO3 (LSM) oxygen electrode was studied in this research. Sm0.2Ce0.8O1.9 (SDC) and Sm0.5Sr0.5CoO3−δ (SSC) nanoparticles were introduced into the LSM oxygen electrode. The polarization resistance of the one-time alternate LSM-SDC-SSC1 oxygen electrode at 800°C is 0.49 Ω·cm2, which is 43% of the LSM oxygen electrode. The effect of infiltration sequence of SDC and SSC on the morphology and properties of the electrode decrease with the increase of impregnation time. The two-time alternate LSM-SDC-SSC2 oxygen electrode show the lowest polarization overpotential and polarization resistance. The Ni-(Y2O3)0.08(ZrO2)0.92 (YSZ)/YSZ/LSM-SDC-SSC2 single cell obtain a maximum power density of 870 mW·cm−2 in solid oxide fuel cell (SOFC) mode and a maximum electrolysis current density of −1150 mA·cm−2 in the solid oxide electrolytic cell (SOEC) mode at 800°C, which show good reversible cell performance.
Hydrogen energy has become an effective substitute for fossil energy due to its advantages of high efficiency, cleanliness and renewability. Reversible solid oxide cell (RSOC) can use hydrogen to output electricity or electrolyze H2O to produce hydrogen, which has very important research significance. The performance optimization of La0.65Sr0.35MnO3 (LSM) oxygen electrode was studied in this research. Sm0.2Ce0.8O1.9 (SDC) and Sm0.5Sr0.5CoO3−δ (SSC) nanoparticles were introduced into the LSM oxygen electrode. The polarization resistance of the one-time alternate LSM-SDC-SSC1 oxygen electrode at 800°C is 0.49 Ω·cm2, which is 43% of the LSM oxygen electrode. The effect of infiltration sequence of SDC and SSC on the morphology and properties of the electrode decrease with the increase of impregnation time. The two-time alternate LSM-SDC-SSC2 oxygen electrode show the lowest polarization overpotential and polarization resistance. The Ni-(Y2O3)0.08(ZrO2)0.92 (YSZ)/YSZ/LSM-SDC-SSC2 single cell obtain a maximum power density of 870 mW·cm−2 in solid oxide fuel cell (SOFC) mode and a maximum electrolysis current density of −1150 mA·cm−2 in the solid oxide electrolytic cell (SOEC) mode at 800°C, which show good reversible cell performance.
2022, 39(12): 5747-5757.
doi: 10.13801/j.cnki.fhclxb.20211231.001
Abstract:
In order to improve the irreversible sulfation and hydrogen evolution of the negative electrode of lead-acid batteries, in this study, the olypyrrole coated with conductive carbon black/indium oxide composite [PPy@(C/In2O3)] were prepared by in-situ oxidation polymerization on C/In2O3. The composite materials were characterized by SEM, FTIR, BET and XRD. The electrochemical performance of the composites was analyzed by CV and LSV. Finally, the PPy@(C/In2O3) composite materials were added in the negative active material of lead-acid batteries. The effect of composite materials on the high-rate partial-state-of-charge (HRPSoC) performance of lead-acid batteries was investigated. The results show that the PPy@(C/In2O3) retain the structural feature of C, and have larger specific surface area than PPy, and have higher hydrogen evolution over-potential and capacitance than C. When PPy@(C/In2O3) composite materials were added to the negative active material of the lead-acid batteries, it can not only reduce the internal resistance of the negative plate and inhibit the negative sulfation problem of the batteries, but also reduce the hydrogen evolution problem of the negative electrode of the batteries. At the same time, the discharge capacity significantly improves the cycle life of the lead-acid batteries under the HRPSoC operation. Finally, the lead-acid batteries containing the negative plate of PPy@(C/In2O3) show excellent HRPSoC cycle life which increased by 1.78 times compared with the cycle life of the blank battery.
In order to improve the irreversible sulfation and hydrogen evolution of the negative electrode of lead-acid batteries, in this study, the olypyrrole coated with conductive carbon black/indium oxide composite [PPy@(C/In2O3)] were prepared by in-situ oxidation polymerization on C/In2O3. The composite materials were characterized by SEM, FTIR, BET and XRD. The electrochemical performance of the composites was analyzed by CV and LSV. Finally, the PPy@(C/In2O3) composite materials were added in the negative active material of lead-acid batteries. The effect of composite materials on the high-rate partial-state-of-charge (HRPSoC) performance of lead-acid batteries was investigated. The results show that the PPy@(C/In2O3) retain the structural feature of C, and have larger specific surface area than PPy, and have higher hydrogen evolution over-potential and capacitance than C. When PPy@(C/In2O3) composite materials were added to the negative active material of the lead-acid batteries, it can not only reduce the internal resistance of the negative plate and inhibit the negative sulfation problem of the batteries, but also reduce the hydrogen evolution problem of the negative electrode of the batteries. At the same time, the discharge capacity significantly improves the cycle life of the lead-acid batteries under the HRPSoC operation. Finally, the lead-acid batteries containing the negative plate of PPy@(C/In2O3) show excellent HRPSoC cycle life which increased by 1.78 times compared with the cycle life of the blank battery.
2022, 39(12): 5758-5767.
doi: 10.13801/j.cnki.fhclxb.20211217.001
Abstract:
Treatment of oily wastewater problem of oil spills at sea and the discharge of oily wastewater have brought huge damage to the economy and the environment. This paper used polydopamine to adhere the self-made dual-scale ZIF-8/TiO2 nanoparticles to the polyurethane sponge, and prepared the superhydrophobic oil-water separation sponge by modification with octadecylamine. The structure was characterized and analyzed by FTIR, XRD, etc.. ZIF-8 and TiO2 two kinds of nano-particles constructed a two-scale rough structure, and the influence of the amount of the two kinds of particles on the surface performance of the composite coating was deeply explored. The results show that when the molar ratio of ZIF-8 and TiO2 nanoparticles is 2∶1, the contact angle reaches the maximum value of 153°.The composite sponge has good oil-water separation performance, the absorption capacity is 40 to 118 times its own weight, and the separation efficiency is on average more than 96%. The temperature can rise by 55℃ within 10 s under 808 nm laser irradiation, and it has good light-to-heat conversion performance.
Treatment of oily wastewater problem of oil spills at sea and the discharge of oily wastewater have brought huge damage to the economy and the environment. This paper used polydopamine to adhere the self-made dual-scale ZIF-8/TiO2 nanoparticles to the polyurethane sponge, and prepared the superhydrophobic oil-water separation sponge by modification with octadecylamine. The structure was characterized and analyzed by FTIR, XRD, etc.. ZIF-8 and TiO2 two kinds of nano-particles constructed a two-scale rough structure, and the influence of the amount of the two kinds of particles on the surface performance of the composite coating was deeply explored. The results show that when the molar ratio of ZIF-8 and TiO2 nanoparticles is 2∶1, the contact angle reaches the maximum value of 153°.The composite sponge has good oil-water separation performance, the absorption capacity is 40 to 118 times its own weight, and the separation efficiency is on average more than 96%. The temperature can rise by 55℃ within 10 s under 808 nm laser irradiation, and it has good light-to-heat conversion performance.
2022, 39(12): 5768-5777.
doi: 10.13801/j.cnki.fhclxb.20211207.001
Abstract:
Two-dimensional layered double hydroxide (LDH) of Ni7Fe1 is the most excellent catalyst in the catalytic system for its facile preparation, abundant sources, and low-cost, which is also an ideal substitute for noble metal catalyst in photocatalytic production. In this study, we prepared composites of Ni7Fe1/PDBTSO by in-situ polymerization of Ni7Fe1 and poly(dibenzothiophene-S,S-dioxide) (PDBTSO). Furthermore, we investigated their catalytic performance. The experimental results show that 15-Ni7Fe1/PDBTSO exhibites the hydrogen generation rate of 36.8 mmol·g−1·h−1, which is 22.6% higher than that of PDBTSO with 3wt% Pt as co-catalyst. Besides, 15-Ni7Fe1/PDBTSO shows good photocatalytic stability, making it an ideal candidate for photocatalytic hydrogen production. XRD, FTIR, TEM and XPS were used to explore the mechanism of photocatalytic hydrogen production performance. The high photocatalytic efficiency and low cost of Ni7Fe1/PDBTSO provide a new idea for the field of photocatalytic hydrogen production.
Two-dimensional layered double hydroxide (LDH) of Ni7Fe1 is the most excellent catalyst in the catalytic system for its facile preparation, abundant sources, and low-cost, which is also an ideal substitute for noble metal catalyst in photocatalytic production. In this study, we prepared composites of Ni7Fe1/PDBTSO by in-situ polymerization of Ni7Fe1 and poly(dibenzothiophene-S,S-dioxide) (PDBTSO). Furthermore, we investigated their catalytic performance. The experimental results show that 15-Ni7Fe1/PDBTSO exhibites the hydrogen generation rate of 36.8 mmol·g−1·h−1, which is 22.6% higher than that of PDBTSO with 3wt% Pt as co-catalyst. Besides, 15-Ni7Fe1/PDBTSO shows good photocatalytic stability, making it an ideal candidate for photocatalytic hydrogen production. XRD, FTIR, TEM and XPS were used to explore the mechanism of photocatalytic hydrogen production performance. The high photocatalytic efficiency and low cost of Ni7Fe1/PDBTSO provide a new idea for the field of photocatalytic hydrogen production.
2022, 39(12): 5778-5791.
doi: 10.13801/j.cnki.fhclxb.20211206.001
Abstract:
Photocatalytic degradation was considered as a promising strategy for the elimination of hazardousorganic pollutants. In this work, a binary 3D/2D molybdenum disulfide supported oxygen-doped graphite carbon nitride (MoS2/O-g-C3N4) heterojunctions was successfully fabricated by using a facile hydrothermal strategy. Meanwhile, the as-prepared photocatalysts were characterized by XRD, XPS, SEM, TEM, FTIR and PL. By these characterized observed the formation of Z-type heterojunction between MoS2 and O-g-C3N4. Under visible light irradiation, when the loading of MoS2 was 0.2%, MoS2/O-g-C3N4 exhibited better photocatalytic activity, and the degradation rate of bisphenol A (BPA) is 92.6%, which is 7 times higher than that of pure g-C3N4. In addition, the close contact and mutual synergistic effect of the interface between MoS2 and O-g-C3N4 significantly enhance the photocatalytic reaction active sites and visible light absorption capacity, and effectively improve the separation of photogenerated carriers. Using liquid chromatography-mass spectrometry technology (LC-MS) and capturing experimental results, the possible photocatalytic mechanism of the 0.2%MoS2/O-g-C3N4 heterojunction composite material degrading crystal violet were proposed. This research provides a new method for the preparation of high-efficiency heterojunction photocatalysts.
Photocatalytic degradation was considered as a promising strategy for the elimination of hazardousorganic pollutants. In this work, a binary 3D/2D molybdenum disulfide supported oxygen-doped graphite carbon nitride (MoS2/O-g-C3N4) heterojunctions was successfully fabricated by using a facile hydrothermal strategy. Meanwhile, the as-prepared photocatalysts were characterized by XRD, XPS, SEM, TEM, FTIR and PL. By these characterized observed the formation of Z-type heterojunction between MoS2 and O-g-C3N4. Under visible light irradiation, when the loading of MoS2 was 0.2%, MoS2/O-g-C3N4 exhibited better photocatalytic activity, and the degradation rate of bisphenol A (BPA) is 92.6%, which is 7 times higher than that of pure g-C3N4. In addition, the close contact and mutual synergistic effect of the interface between MoS2 and O-g-C3N4 significantly enhance the photocatalytic reaction active sites and visible light absorption capacity, and effectively improve the separation of photogenerated carriers. Using liquid chromatography-mass spectrometry technology (LC-MS) and capturing experimental results, the possible photocatalytic mechanism of the 0.2%MoS2/O-g-C3N4 heterojunction composite material degrading crystal violet were proposed. This research provides a new method for the preparation of high-efficiency heterojunction photocatalysts.
2022, 39(12): 5792-5802.
doi: 10.13801/j.cnki.fhclxb.20211214.001
Abstract:
In order to supply energy for wearable smart textile microelectronic functional components, flexible energy storage devices have become the important research. The electrode is an important component of the energy storage device and determines capacitance of the device. In this paper, a conductive silver-plated nylon fabric was used as the substrate, and zinc was loaded on the fabric surface by magnetron sputtering technology, then the conductive polymer polypyrrole (PPy) was constructed by both chemical and electrochemical polymerization. The morphology, electrical and electrochemical properties of the Zn@PPy fabric electrode was evaluated, and the influence of parameters such as chemical polymerization, electrochemical polymerization and magnetron sputtering time on the performance of fabric electrodes were investigated. The results show that Zn film can be uniformly grown on the fabric surface by magnetron sputtering with a surface sheet resistance of 1.51 Ω. Zn@PPy fabric electrode has a specific capacitance of 1185 mF/cm2, which is 4.21 times higher than PPy/fabric electrode. This simple method of fabric electrode has potential applications in the field of microelectronic energy supply for wearable textiles.
In order to supply energy for wearable smart textile microelectronic functional components, flexible energy storage devices have become the important research. The electrode is an important component of the energy storage device and determines capacitance of the device. In this paper, a conductive silver-plated nylon fabric was used as the substrate, and zinc was loaded on the fabric surface by magnetron sputtering technology, then the conductive polymer polypyrrole (PPy) was constructed by both chemical and electrochemical polymerization. The morphology, electrical and electrochemical properties of the Zn@PPy fabric electrode was evaluated, and the influence of parameters such as chemical polymerization, electrochemical polymerization and magnetron sputtering time on the performance of fabric electrodes were investigated. The results show that Zn film can be uniformly grown on the fabric surface by magnetron sputtering with a surface sheet resistance of 1.51 Ω. Zn@PPy fabric electrode has a specific capacitance of 1185 mF/cm2, which is 4.21 times higher than PPy/fabric electrode. This simple method of fabric electrode has potential applications in the field of microelectronic energy supply for wearable textiles.
2022, 39(12): 5803-5815.
doi: 10.13801/j.cnki.fhclxb.20211216.003
Abstract:
In order to make full use of the structure of the rich porous structure of metal-organic frame material (MOF) and the unique doping structure of conductive polymers, the influence of dopants on the structure and electrochemical properties of MOF/conductive polymer complexes are studied to achieve stable chemical doping. 3D flower-like ZIF-67 (Z8) was firstly prepared by controlling the ratio of Co2+ and 2-methylimidazole at room temperature. 5-Sulfosalicylic acid (5-SSA) doped polypyrrole (PPy)/Z8 composites were synthesized via facile in-situ polymerization. The introduction of Z8 can reduce the agglomeration of the obtained PPy microspheres. The stable chemical doping can be achieved by the multiple bonds and the conjugation effects between 5-SSA and Z8. This will be helpful for the fast transfer of electrons and electrolyte ions and the strong support for the PPy chains. The resulted composites with 10wt% Z8 loading (PPy/10wt%Z8) achieves the highest specific capacitance of 300 F·g−1 among the PPy/Z8. The asymmetric supercapacitor assembled by PPy/10wt%Z8 and active carbon on carbon cloth as flexible electrodes demonstrates high areal capacitance (200 mF·cm−2), high energy density (71 μW·h·cm−2) and power density (800 μW·cm−2). Moreover, the flexible supercapacitor provides excellent cycle stability after 10000 cycles (80.2% capacitance retention), indicating good supercapacitive performances.
In order to make full use of the structure of the rich porous structure of metal-organic frame material (MOF) and the unique doping structure of conductive polymers, the influence of dopants on the structure and electrochemical properties of MOF/conductive polymer complexes are studied to achieve stable chemical doping. 3D flower-like ZIF-67 (Z8) was firstly prepared by controlling the ratio of Co2+ and 2-methylimidazole at room temperature. 5-Sulfosalicylic acid (5-SSA) doped polypyrrole (PPy)/Z8 composites were synthesized via facile in-situ polymerization. The introduction of Z8 can reduce the agglomeration of the obtained PPy microspheres. The stable chemical doping can be achieved by the multiple bonds and the conjugation effects between 5-SSA and Z8. This will be helpful for the fast transfer of electrons and electrolyte ions and the strong support for the PPy chains. The resulted composites with 10wt% Z8 loading (PPy/10wt%Z8) achieves the highest specific capacitance of 300 F·g−1 among the PPy/Z8. The asymmetric supercapacitor assembled by PPy/10wt%Z8 and active carbon on carbon cloth as flexible electrodes demonstrates high areal capacitance (200 mF·cm−2), high energy density (71 μW·h·cm−2) and power density (800 μW·cm−2). Moreover, the flexible supercapacitor provides excellent cycle stability after 10000 cycles (80.2% capacitance retention), indicating good supercapacitive performances.
2022, 39(12): 5816-5826.
doi: 10.13801/j.cnki.fhclxb.20220105.002
Abstract:
Photocatalytic technology, due to its green and environmental friendliness, has a certain application prospect in the fields of hydrogen energy development, pollution purification and medical care in recent years. To explore the influence of the cocatalyst on the performance of hydrogen production, the crystal structure of the cocatalyst itself is studied. The phase structure was successfully transformed by controlling the calcination conditions, and two different crystal phase structures of cobalt selenide (CoSe2) were prepared, namely orthogonal cobalt selenide (o-CoSe2) and cubic cobalt selnide (c-CoSe2). The semiconductor CdS semiconductor was chosen for recombination, and found that the two promoters both have a good promoting effect on the photocatalytic hydrogen production. Through Motschottky curve (MS), UV-vis diffuse reflectance spectra (UV-vis DRS), fluorescence (PL) and photoelectric performance characterization, c-CoSe2 has stronger conductivity and more efficient charge transport ability than o-CoSe2, which is theoretically more conducive to the photocatalytic reaction. With lactic acid as the sacrificial agent, the optimal loading of 10wt%o-CoSe2/CdS and 10wt%c-CoSe2/CdS hydrogen production efficiencies are 9006.2 μmol·g−1·h−1 and 7151.2 μmol·g−1·h−1, respectively. In general, it has been increased by 20 times and 15 times respectively, which is close to or even surpassing the hydrogen production activity supported by the precious metal platinum (Pt) under the same conditions. The degradation and hydrogen production of 10wt%o-CoSe2/CdS are achieved in photocatalytic degradation simultaneous with hydrogen evolution. Combining the steps of the photocatalytic reaction and theoretical calculation and analysis, it is found that the more suitable free energy of hydrogen adsorption on the cobalt site of o-CoSe2 is the key reason for its use as a better hydrogen production co-catalyst.
Photocatalytic technology, due to its green and environmental friendliness, has a certain application prospect in the fields of hydrogen energy development, pollution purification and medical care in recent years. To explore the influence of the cocatalyst on the performance of hydrogen production, the crystal structure of the cocatalyst itself is studied. The phase structure was successfully transformed by controlling the calcination conditions, and two different crystal phase structures of cobalt selenide (CoSe2) were prepared, namely orthogonal cobalt selenide (o-CoSe2) and cubic cobalt selnide (c-CoSe2). The semiconductor CdS semiconductor was chosen for recombination, and found that the two promoters both have a good promoting effect on the photocatalytic hydrogen production. Through Motschottky curve (MS), UV-vis diffuse reflectance spectra (UV-vis DRS), fluorescence (PL) and photoelectric performance characterization, c-CoSe2 has stronger conductivity and more efficient charge transport ability than o-CoSe2, which is theoretically more conducive to the photocatalytic reaction. With lactic acid as the sacrificial agent, the optimal loading of 10wt%o-CoSe2/CdS and 10wt%c-CoSe2/CdS hydrogen production efficiencies are 9006.2 μmol·g−1·h−1 and 7151.2 μmol·g−1·h−1, respectively. In general, it has been increased by 20 times and 15 times respectively, which is close to or even surpassing the hydrogen production activity supported by the precious metal platinum (Pt) under the same conditions. The degradation and hydrogen production of 10wt%o-CoSe2/CdS are achieved in photocatalytic degradation simultaneous with hydrogen evolution. Combining the steps of the photocatalytic reaction and theoretical calculation and analysis, it is found that the more suitable free energy of hydrogen adsorption on the cobalt site of o-CoSe2 is the key reason for its use as a better hydrogen production co-catalyst.
2022, 39(12): 5827-5834.
doi: 10.13801/j.cnki.fhclxb.20220110.001
Abstract:
In order to prepare stainless steel filter with controllable wettability and oil-water separation property, a layer of zinc oxide was grown on the surface of stainless steel by hydrothermal method to construct micro-nano roughness. Then, a stainless steel filter with controllable wettability was successfully prepared by modification of fatty acids with different chain lengths. The wettability, surface morphology and composition of the samples were analyzed by contact angle measuring instrument, FTIR, SEM and XRD, respectively. The oil-water separation efficiency and reusability of the samples were characterized by oil-water separation device. The results show that the wettability of the samples modified by fatty acids with different chain lengths varie from superhydrophilic to superhydrophobic, ranging from 0° to 158°, and the oil remain at 0°. The oil-water separation efficiency is 92%-98%, and it still has oil-water separation performance after repeated use for 50 times. Therefore, the prepared stainless steel filter has excellent oil-water separation performance and good reuse performance.
In order to prepare stainless steel filter with controllable wettability and oil-water separation property, a layer of zinc oxide was grown on the surface of stainless steel by hydrothermal method to construct micro-nano roughness. Then, a stainless steel filter with controllable wettability was successfully prepared by modification of fatty acids with different chain lengths. The wettability, surface morphology and composition of the samples were analyzed by contact angle measuring instrument, FTIR, SEM and XRD, respectively. The oil-water separation efficiency and reusability of the samples were characterized by oil-water separation device. The results show that the wettability of the samples modified by fatty acids with different chain lengths varie from superhydrophilic to superhydrophobic, ranging from 0° to 158°, and the oil remain at 0°. The oil-water separation efficiency is 92%-98%, and it still has oil-water separation performance after repeated use for 50 times. Therefore, the prepared stainless steel filter has excellent oil-water separation performance and good reuse performance.
2022, 39(12): 5835-5845.
doi: 10.13801/j.cnki.fhclxb.20211223.003
Abstract:
Since flexible strain sensors require high sensitivity and a wide strain range in healthcare, soft robotics and human-computer interaction, this work designed a flexible strain sensor based on silver nanoparticles-polydopamine-carbon nanotubes (AgNPs-PDA-CNT) sensitive material system, and prepared a layer coated sandwich structure flexible strain sensor. The results of material characterization and property test showed that AgNPs were uniformly dispersed and fixed on the surface of PDA-CNT by virtue of PDA adhesion and reducibility. The AgNPs-PDA-CNT conductive material is closely bonded to the inner wall of silicone rubber capillary tube and polydimethylsiloxane (PDMS). AgNPs-PDA-CNT penetrates into PDMS and the concentration is in gradient distribution. The sensor has high sensitivity coefficient (GF) and wide strain range (69.04 when 0%-44%, 253.13 when 44%-66%, 1253.8 when 66%-76%), fast response (75 ms) and recovery (90 ms), good stability and repeatability. The sensor is applied to human motion monitoring, soft finger ontology sensing and soft grasping behavior monitoring, and good application results are achieved.
Since flexible strain sensors require high sensitivity and a wide strain range in healthcare, soft robotics and human-computer interaction, this work designed a flexible strain sensor based on silver nanoparticles-polydopamine-carbon nanotubes (AgNPs-PDA-CNT) sensitive material system, and prepared a layer coated sandwich structure flexible strain sensor. The results of material characterization and property test showed that AgNPs were uniformly dispersed and fixed on the surface of PDA-CNT by virtue of PDA adhesion and reducibility. The AgNPs-PDA-CNT conductive material is closely bonded to the inner wall of silicone rubber capillary tube and polydimethylsiloxane (PDMS). AgNPs-PDA-CNT penetrates into PDMS and the concentration is in gradient distribution. The sensor has high sensitivity coefficient (GF) and wide strain range (69.04 when 0%-44%, 253.13 when 44%-66%, 1253.8 when 66%-76%), fast response (75 ms) and recovery (90 ms), good stability and repeatability. The sensor is applied to human motion monitoring, soft finger ontology sensing and soft grasping behavior monitoring, and good application results are achieved.
2022, 39(12): 5846-5855.
doi: 10.13801/j.cnki.fhclxb.20211216.004
Abstract:
CO-releasing materials are valuable for CO medicinal applications. Herein, by using an iron complex, [Fe(η5-Cp)(CO)2I] as iron-based carbon monoxide-releasing molecule (FeCORM), cellulose acetate (CA) and polyvinylpyrrolidone (PVP) as matrix polymers, CA-PVP-based composite fibers with various amounts of FeCORM were prepared via electrospinning technology in a mixture solution of dimethylacetamide/acetone. The composite fibers were characterized by means of ATR-FTIR, UV-vis DRS, SEM techniques. CO-releasing performance of the composite fibers was then investigated upon irradiation of blue/green/red lights, and their corresponding kinetic data were obtained, respectively. The amounts of CO released by the composite fibers were further quantified. Our results demonstrate that the rates of CO-release for the composite fibers are depending on both the contents of FeCORM and the wavelengths of the light sources. Generally, the lower the content and the shorter the wavelength, the faster the release rate should be. Additionally, first-order kinetics are assigned to the CO-release process of the composite fibers, with a rate constant kobs between 1.59-0.11 min−1, and a half-life t1/2 between 0.4-6.3 min, respectively. Furthermore, a satisfied linear-relationship is estimated between the dose of released CO for the composite fibers y and the mass percentage of FeCORM x with the equation following: y=0.0284x−0.0158.
CO-releasing materials are valuable for CO medicinal applications. Herein, by using an iron complex, [Fe(η5-Cp)(CO)2I] as iron-based carbon monoxide-releasing molecule (FeCORM), cellulose acetate (CA) and polyvinylpyrrolidone (PVP) as matrix polymers, CA-PVP-based composite fibers with various amounts of FeCORM were prepared via electrospinning technology in a mixture solution of dimethylacetamide/acetone. The composite fibers were characterized by means of ATR-FTIR, UV-vis DRS, SEM techniques. CO-releasing performance of the composite fibers was then investigated upon irradiation of blue/green/red lights, and their corresponding kinetic data were obtained, respectively. The amounts of CO released by the composite fibers were further quantified. Our results demonstrate that the rates of CO-release for the composite fibers are depending on both the contents of FeCORM and the wavelengths of the light sources. Generally, the lower the content and the shorter the wavelength, the faster the release rate should be. Additionally, first-order kinetics are assigned to the CO-release process of the composite fibers, with a rate constant kobs between 1.59-0.11 min−1, and a half-life t1/2 between 0.4-6.3 min, respectively. Furthermore, a satisfied linear-relationship is estimated between the dose of released CO for the composite fibers y and the mass percentage of FeCORM x with the equation following: y=0.0284x−0.0158.
2022, 39(12): 5856-5867.
doi: 10.13801/j.cnki.fhclxb.20211116.002
Abstract:
The design and construction of functional nanomaterials with excellent properties is very important for photocatalytic applications. The ZnO@SnO2 heterojunction domed nanotubes (HDNs) were successfully prepared without additional acid etching step using one-dimensional ZnO nanorods as templates by two-step solvothermal technology based on the template self-etching mechanism. The built-in electric field which can promote carrier separation can be formed at the nanotube interface owing to the matching energy level structure between ZnO and SnO2, endowing the material excellent photocatalytic and stability properties. By controlling the intensity of self-generated alkaline during the experimental processes, the amphoteric oxide ZnO can be etched, achieving the controllable regulation of the thickness of tubes and their photocatalytic performance. The morphology, element composition, growth mechanism and properties of the ZnO@SnO2 HDNs were investigated by means of SEM, TEM, STEM and PL. Taking methyl orange, methylene blue and eosin as pollutant models, the experimental results of photocatalytic pollutant degradation showed that ZnO@SnO2 HDNs had excellent photocatalytic performance, and the degradation rate of methylene blue and eosin can reach 95% within 60 min. These results indicate that the constructed one-dimensional heterojunction can greatly promote the separation of carriers and inhibit their recombination, thereby improving the photocatalytic performance. At the same time, the cycle stability test showes that the heterojunction nanotube photocatalyst has great stability and broad application prospects in dye degradation.
2022, 39(12): 5868-5878.
doi: 10.13801/j.cnki.fhclxb.20220117.003
Abstract:
In order to solve the defects in the structure and performance of single-phase photocatalytic materials, the 2D graphitic carbon nitride (g-C3N4) was synthesized by secondary calcining, and Ag/g-C3N4 was prepared via photodeposition method. SnS2-Ag/g-C3N4 with n-n type heterojunction structure was prepared through simple ultrasonic and solvent evaporation methods. The microstructure, phase structure, light response ability and pore structure of the materials were characterized. The results showed that the lamellar structure and the spray shape coexist in the composite. The 2D-0D-2D morphology similar to sandwich structure is formed. The composite has high crystallinity and well-constructed interface, which give it a higher specific surface area and stronger visible light response performance. When the mass fraction of SnS2 is 10wt%, the photocatalytic degradation efficiency of the SnS2-Ag/g-C3N4 composite is up to 95.6%, and the degradation rate is 3.5 times as that of g-C3N4. After 4 cycles, the photocatalytic efficiency remained above 85.3%.
In order to solve the defects in the structure and performance of single-phase photocatalytic materials, the 2D graphitic carbon nitride (g-C3N4) was synthesized by secondary calcining, and Ag/g-C3N4 was prepared via photodeposition method. SnS2-Ag/g-C3N4 with n-n type heterojunction structure was prepared through simple ultrasonic and solvent evaporation methods. The microstructure, phase structure, light response ability and pore structure of the materials were characterized. The results showed that the lamellar structure and the spray shape coexist in the composite. The 2D-0D-2D morphology similar to sandwich structure is formed. The composite has high crystallinity and well-constructed interface, which give it a higher specific surface area and stronger visible light response performance. When the mass fraction of SnS2 is 10wt%, the photocatalytic degradation efficiency of the SnS2-Ag/g-C3N4 composite is up to 95.6%, and the degradation rate is 3.5 times as that of g-C3N4. After 4 cycles, the photocatalytic efficiency remained above 85.3%.
2022, 39(12): 5879-5891.
doi: 10.13801/j.cnki.fhclxb.20220120.010
Abstract:
In order to design a new type of wound dressing that does not damage the wound, has good antibacterial effect, and promotes wound healing, polyvinyl alcohol (PVA), carboxymethyl chitosan (CMCS) and sodium alginate (SA) were selected as raw materials. Silver was compounded into the PVA-CMCS-SA hydrogel, and the silver-loaded PVA-CMCS-SA hydrogel wound dressing was constructed based on 3D printing. The micro-morphology, mechanical properties, water absorption and moisture retention, biocompatibility, antibacterial properties and in vitro coagulation properties of hydrogel wound dressings were then studied. The results show that the hydrogel wound dressing prepared by 3D printing has good dimensional structural stability, good mechanical properties, and the tensile strength can reach about 1000 kPa, and both the cyclic stretching and cyclic compression properties are good. Because of the 3D printed grid structure, the 3D printed hydrogel wound dressing has good water absorption, moisture retention, in vitro clotting, air permeability and antibacterial properties. The highest antibacterial rate against Escherichia coli and Staphylococcus aureus can reach 64% and 54%. It has low cytotoxicity and good biocompatibility. The 3D printing method can combine the hydrogel with the band-aid, ensuring the practicability of the wound dressing. Studies have shown that 3D printed silver-loaded hydrogel PVA-CMCS-SA can be used as a good wound dressing material.
In order to design a new type of wound dressing that does not damage the wound, has good antibacterial effect, and promotes wound healing, polyvinyl alcohol (PVA), carboxymethyl chitosan (CMCS) and sodium alginate (SA) were selected as raw materials. Silver was compounded into the PVA-CMCS-SA hydrogel, and the silver-loaded PVA-CMCS-SA hydrogel wound dressing was constructed based on 3D printing. The micro-morphology, mechanical properties, water absorption and moisture retention, biocompatibility, antibacterial properties and in vitro coagulation properties of hydrogel wound dressings were then studied. The results show that the hydrogel wound dressing prepared by 3D printing has good dimensional structural stability, good mechanical properties, and the tensile strength can reach about 1000 kPa, and both the cyclic stretching and cyclic compression properties are good. Because of the 3D printed grid structure, the 3D printed hydrogel wound dressing has good water absorption, moisture retention, in vitro clotting, air permeability and antibacterial properties. The highest antibacterial rate against Escherichia coli and Staphylococcus aureus can reach 64% and 54%. It has low cytotoxicity and good biocompatibility. The 3D printing method can combine the hydrogel with the band-aid, ensuring the practicability of the wound dressing. Studies have shown that 3D printed silver-loaded hydrogel PVA-CMCS-SA can be used as a good wound dressing material.
2022, 39(12): 5901-5911.
doi: 10.13801/j.cnki.fhclxb.20211119.004
Abstract:
Hydrogel materials are widely used in wearable strain sensors due to they have unique biomimetic structure, performances and biocompatibility. However, it is still a big challenge to prepare a hydrogel sensor with good mechanical properties and high conductivity. In this paper, a fully physically crosslinked, high-strength and sensitive polyacrylic acid-Al3+/chitosan composite double network hydrogel sensor was prepared by a simple two-step method. Firstly, chitosan (CS), polyacrylic acid (PAA) and ionic crosslinker Al3+ were physically mixed in water to form a pre-gel, and then the pre-gel was immersed in NaCl solution to prepare the target hydrogel sensor. The obtained ionized hydrogel sensor shows excellent mechanical properties (tensile strength as high as 765.4 kPa, elongation at break to 1025%, and toughness of 4.13 MJ/m³). At the same time, the strain sensor based on the hydrogel exhibits excellent tensile sensitivity (sensitivity factor is about 1.54). The hydrogel sensor can repeatedly and stably detect large and small strains of human body. Therefore, the introduction of physical cross-linking network through the action of metal salts can improve the performances of hydrogels, which providing a new perspective for the design of multifunctional materials and their applications in electronic skins, wearable devices, and biosensors.
Hydrogel materials are widely used in wearable strain sensors due to they have unique biomimetic structure, performances and biocompatibility. However, it is still a big challenge to prepare a hydrogel sensor with good mechanical properties and high conductivity. In this paper, a fully physically crosslinked, high-strength and sensitive polyacrylic acid-Al3+/chitosan composite double network hydrogel sensor was prepared by a simple two-step method. Firstly, chitosan (CS), polyacrylic acid (PAA) and ionic crosslinker Al3+ were physically mixed in water to form a pre-gel, and then the pre-gel was immersed in NaCl solution to prepare the target hydrogel sensor. The obtained ionized hydrogel sensor shows excellent mechanical properties (tensile strength as high as 765.4 kPa, elongation at break to 1025%, and toughness of 4.13 MJ/m³). At the same time, the strain sensor based on the hydrogel exhibits excellent tensile sensitivity (sensitivity factor is about 1.54). The hydrogel sensor can repeatedly and stably detect large and small strains of human body. Therefore, the introduction of physical cross-linking network through the action of metal salts can improve the performances of hydrogels, which providing a new perspective for the design of multifunctional materials and their applications in electronic skins, wearable devices, and biosensors.
2022, 39(12): 5912-5921.
doi: 10.13801/j.cnki.fhclxb.20220105.003
Abstract:
In order to improve the bioactivity and osteogenic induction ability of porous hydroxyapatite (HA) biocomposites, porous ZnO-MgO/HA biocomposites with the mass fraction of ZnO 1.3wt% and MgO 8.4wt% were prepared by spark plasma sintering (SPS). The changes of microstructure, pore characteristics, in vitro mineralization and degradation behavior of porous composites at different sintering temperatures were studied. The effect of active ceramic phase addition on biological properties of porous HA materials in vitro and its mechanism were analyzed. The results show that the sintered porous composites are mainly composed of HA, ZnO and MgO phase. When the sintering temperature exceeds 950℃, a small amount of HA decomposition product Ca3(PO4)2 phase appears. With the increase of sintering temperature, the porosity of porous composites decreases slowly, and the pore size decreases gradually. The porous composites have good osteoapatite formation ability in simulated body fluid at different sintering temperatures, and the degradation rate increases first and then decreases with the increase of sintering temperature. Comprehensive analysis shows that the porous ZnO-MgO/HA composites prepared at 950℃ have suitable pore characteristics (porosity (34.7±0.2)%, pore size between 150-400 μm accounts for 65.5%). Moreover, the porous HA material has excellent osteogenic ability, high degradation rate ((11.3±0.2)%), high cell proliferation rate ((91.7±2.1)%) and low cell apoptosis rate ((2.3±0.2)%), indicating that the addition of ZnO and MgO active ceramic phase significantly improves the osteogenic induction ability and biocompatibility of porous HA material.
In order to improve the bioactivity and osteogenic induction ability of porous hydroxyapatite (HA) biocomposites, porous ZnO-MgO/HA biocomposites with the mass fraction of ZnO 1.3wt% and MgO 8.4wt% were prepared by spark plasma sintering (SPS). The changes of microstructure, pore characteristics, in vitro mineralization and degradation behavior of porous composites at different sintering temperatures were studied. The effect of active ceramic phase addition on biological properties of porous HA materials in vitro and its mechanism were analyzed. The results show that the sintered porous composites are mainly composed of HA, ZnO and MgO phase. When the sintering temperature exceeds 950℃, a small amount of HA decomposition product Ca3(PO4)2 phase appears. With the increase of sintering temperature, the porosity of porous composites decreases slowly, and the pore size decreases gradually. The porous composites have good osteoapatite formation ability in simulated body fluid at different sintering temperatures, and the degradation rate increases first and then decreases with the increase of sintering temperature. Comprehensive analysis shows that the porous ZnO-MgO/HA composites prepared at 950℃ have suitable pore characteristics (porosity (34.7±0.2)%, pore size between 150-400 μm accounts for 65.5%). Moreover, the porous HA material has excellent osteogenic ability, high degradation rate ((11.3±0.2)%), high cell proliferation rate ((91.7±2.1)%) and low cell apoptosis rate ((2.3±0.2)%), indicating that the addition of ZnO and MgO active ceramic phase significantly improves the osteogenic induction ability and biocompatibility of porous HA material.
2022, 39(12): 5922-5933.
doi: 10.13801/j.cnki.fhclxb.20211217.003
Abstract:
In order to employ the high-efficiency, low-power-consumption ultraviolet light technology for the cross-linking of the ethylene propylene diene monomer (EPDM) rubber cable insulation layer and achieve the goal of energy conservation, pollution reduction and efficient production, it is necessary to develop EPDM insulation formulation with low content of solid fillers. In this paper, EPDM was reinforced by adding linear low density polyethylene (LLDPE) and a small amount of nano SiO2. The formula of photo crosslinkable EPDM insulating material was designed, and the mechanical, crosslinking and electrical properties of UV crosslinked EPDM were systematically studied. The results show that, with the irradiation time increasing, the mechanical properties of EPDM are significantly decreased, and the crosslinking degree is rapidly increased. Compared with EPDM, the crosslinking degree and mechanical properties of LLDPE/EPDM materials are significantly higher. When the LLDPE content is 10wt%, the elongation at break of the LLDPE/EPDM material is 539%, the tensile strength is 12 MPa, and the Shore hardness is 80 A, which can meet the requirements of use. For SiO2/EPDM composite, when the SiO2 content is 4% (mass ratio to rubber), the mechanical properties are the best, the elongation at break is 596% and the tensile strength is 14 MPa. Compared with EPDM, the hardness of SiO2/EPDM composite is almost unchanged, but the crosslinking degree is reduced. When the irradiation time is 12 s, the loading elongation of SiO2/EPDM is 40%, which still meets the requirements of use. The degradation of the material during irradiation can be suppressed after 0.5% mass ratio of Irganox1010 is added, and the mechanical properties of the composite material are improved. Moreover, Irganox1010 can improve the thermo-oxidative aging resistance of the composite. Both two kinds of modified EPDM composites which are designed for UV cross-linking technology can meet the requirements of cable insulation. The blending of LLDPE increases the crosslinking degree and electrical properties of the material, but bring the negative impact on the hardness of EPAM, while the doping of SiO2 has almost no effect on the hardness of the composite, but the crosslinking degree and electrical properties are slightly weakened.
In order to employ the high-efficiency, low-power-consumption ultraviolet light technology for the cross-linking of the ethylene propylene diene monomer (EPDM) rubber cable insulation layer and achieve the goal of energy conservation, pollution reduction and efficient production, it is necessary to develop EPDM insulation formulation with low content of solid fillers. In this paper, EPDM was reinforced by adding linear low density polyethylene (LLDPE) and a small amount of nano SiO2. The formula of photo crosslinkable EPDM insulating material was designed, and the mechanical, crosslinking and electrical properties of UV crosslinked EPDM were systematically studied. The results show that, with the irradiation time increasing, the mechanical properties of EPDM are significantly decreased, and the crosslinking degree is rapidly increased. Compared with EPDM, the crosslinking degree and mechanical properties of LLDPE/EPDM materials are significantly higher. When the LLDPE content is 10wt%, the elongation at break of the LLDPE/EPDM material is 539%, the tensile strength is 12 MPa, and the Shore hardness is 80 A, which can meet the requirements of use. For SiO2/EPDM composite, when the SiO2 content is 4% (mass ratio to rubber), the mechanical properties are the best, the elongation at break is 596% and the tensile strength is 14 MPa. Compared with EPDM, the hardness of SiO2/EPDM composite is almost unchanged, but the crosslinking degree is reduced. When the irradiation time is 12 s, the loading elongation of SiO2/EPDM is 40%, which still meets the requirements of use. The degradation of the material during irradiation can be suppressed after 0.5% mass ratio of Irganox1010 is added, and the mechanical properties of the composite material are improved. Moreover, Irganox1010 can improve the thermo-oxidative aging resistance of the composite. Both two kinds of modified EPDM composites which are designed for UV cross-linking technology can meet the requirements of cable insulation. The blending of LLDPE increases the crosslinking degree and electrical properties of the material, but bring the negative impact on the hardness of EPAM, while the doping of SiO2 has almost no effect on the hardness of the composite, but the crosslinking degree and electrical properties are slightly weakened.
2022, 39(12): 5934-5945.
doi: 10.13801/j.cnki.fhclxb.20211129.004
Abstract:
Uranium mining and hydrometallurgy produce a large amount of uranium wastewater, which causes pollution to the surrounding ecological environment. Therefore, efficient and green treatment is an important basis to guarantee the sustainable development and ecological security of nuclear industry. In this study, sunflower leaves were used as raw materials for green synthesis of biochar-loaded nano-iron particles (GN-FeNPs/BC) that used to remove U(VI) in water. Sunflower leaves were used to prepare plant extract, and then the residue was pyrolyzed to prepare biochar. Finally, ferrous sulfate heptahydrate solution, biochar and plant extract were mixed to successfully prepare a green nano-iron composite material. The effects of biochar carbonization temperature, iron-to-carbon ratio, pH value, temperature, time and U(VI) concentration on uranium removal were explored. When the pH is 5 at 298 K, the maximum adsorption capacity is 96.43 mg·g−1. The kinetics and thermodynamics are studied. The results show that the pseudo-second order model and Langmuir model fit well. The thermodynamic constants indicate that the adsorption of U(VI) by GN-FeNPs/BC is a spontaneous endothermic process. XPS analysis shows that the removal mechanism includes adsorption and reduction.
Uranium mining and hydrometallurgy produce a large amount of uranium wastewater, which causes pollution to the surrounding ecological environment. Therefore, efficient and green treatment is an important basis to guarantee the sustainable development and ecological security of nuclear industry. In this study, sunflower leaves were used as raw materials for green synthesis of biochar-loaded nano-iron particles (GN-FeNPs/BC) that used to remove U(VI) in water. Sunflower leaves were used to prepare plant extract, and then the residue was pyrolyzed to prepare biochar. Finally, ferrous sulfate heptahydrate solution, biochar and plant extract were mixed to successfully prepare a green nano-iron composite material. The effects of biochar carbonization temperature, iron-to-carbon ratio, pH value, temperature, time and U(VI) concentration on uranium removal were explored. When the pH is 5 at 298 K, the maximum adsorption capacity is 96.43 mg·g−1. The kinetics and thermodynamics are studied. The results show that the pseudo-second order model and Langmuir model fit well. The thermodynamic constants indicate that the adsorption of U(VI) by GN-FeNPs/BC is a spontaneous endothermic process. XPS analysis shows that the removal mechanism includes adsorption and reduction.
2022, 39(12): 5946-5957.
doi: 10.13801/j.cnki.fhclxb.20220506.002
Abstract:
In this paper, based on the two-layer design, a self-healing superhydrophobic coating self-healing shape memory epoxy resin (SMEP)/polydimethylsiloxane (PDMS)@ZnO@SiO2 (SMEP/PZS) that could quickly repair physical damages and durably corrosion resistance of stainless steel was prepared. Aiming to solve the slow physical damage repair of epoxy-based superhydrophobic anti-corrosion coatings, and inegrate with the practical application requirements of high efficiency anticorrosion and protection of stainless steel in high humidity and high salt environment for a long time. The double-layer coating was designed by combination of a SMEP and a superhydrophobic material PDMS@ZnO@SiO2 (PZS). Furthermore, the wettability, corrosion resistance, self-healing and corrosion resistance mechanism of SMEP/PZS coating before and after repairing were discussed in detail. The results show that SMEP/PZS coating has excellent superhydrophobicity and self-cleaning properties, and its superhydrophobicity increases with the increase of perfluorodecyltrimethoxysilane (PFDTMS) content, its optimal water contact angle and rolling angle are 157.6° and 2.6°. Secondly, SMEP/PZS coating has a faster self-healing ability, the best mechanical scratches of SMEP/PZS coating are reduced from 45 μm to 1.0 μm in a shorter time of 20 min at 85℃, and the repair rate reaches 97.8%. In addition, the SMEP/PZS coating shows good corrosion resistance, and after the repaired coating is immersed in 3.5wt% NaCl solution for 14 days, its corrosion resistance is closed to the original coating. When the SMEP/PZS coating is coated on the stainless steel substrate, the pitting corrosion potential Eb measured in 3.5wt% NaCl solution has increased by nearly 10 times compared with that of the bare stainless steel, and the passive current density Ip has decreased by 2 orders of magnitude, showing relatively longer corrosion resistance and protection for 304 stainless steel substrate. Finally, the self-healing and anti-corrosion mechanism of SMEP/PZS coating is further discussed.
In this paper, based on the two-layer design, a self-healing superhydrophobic coating self-healing shape memory epoxy resin (SMEP)/polydimethylsiloxane (PDMS)@ZnO@SiO2 (SMEP/PZS) that could quickly repair physical damages and durably corrosion resistance of stainless steel was prepared. Aiming to solve the slow physical damage repair of epoxy-based superhydrophobic anti-corrosion coatings, and inegrate with the practical application requirements of high efficiency anticorrosion and protection of stainless steel in high humidity and high salt environment for a long time. The double-layer coating was designed by combination of a SMEP and a superhydrophobic material PDMS@ZnO@SiO2 (PZS). Furthermore, the wettability, corrosion resistance, self-healing and corrosion resistance mechanism of SMEP/PZS coating before and after repairing were discussed in detail. The results show that SMEP/PZS coating has excellent superhydrophobicity and self-cleaning properties, and its superhydrophobicity increases with the increase of perfluorodecyltrimethoxysilane (PFDTMS) content, its optimal water contact angle and rolling angle are 157.6° and 2.6°. Secondly, SMEP/PZS coating has a faster self-healing ability, the best mechanical scratches of SMEP/PZS coating are reduced from 45 μm to 1.0 μm in a shorter time of 20 min at 85℃, and the repair rate reaches 97.8%. In addition, the SMEP/PZS coating shows good corrosion resistance, and after the repaired coating is immersed in 3.5wt% NaCl solution for 14 days, its corrosion resistance is closed to the original coating. When the SMEP/PZS coating is coated on the stainless steel substrate, the pitting corrosion potential Eb measured in 3.5wt% NaCl solution has increased by nearly 10 times compared with that of the bare stainless steel, and the passive current density Ip has decreased by 2 orders of magnitude, showing relatively longer corrosion resistance and protection for 304 stainless steel substrate. Finally, the self-healing and anti-corrosion mechanism of SMEP/PZS coating is further discussed.
2022, 39(12): 5958-5965.
doi: 10.13801/j.cnki.fhclxb.20220105.004
Abstract:
In this study, a novel double-layer flexible protective gear was proposed based on the multi-level structure of the bony fish scale and the concept of soft and hard composite protection. The upper layer of this protective gear is a scale-like layer which consists of periodically overlapping composite scales, the lower layer consists of multiple layers of ultra-high molecular weight polyethylene (UHMWPE) sheets as the backing layer. In accordance with the Level III requirements of the standard GJB 4300A—2012, the protection performance of the protective gear has been tested and simulated with finite element models, and the results verified the good protection performance of the gear against the armor-piercing incendiary bullet, and also confirmed the reliability of the numerical simulations. The results indicate that the thickness of the ceramic layer of the composite scale is one of the key factors that affect the anti-penetration performance of the protective gear. When the total thickness is unchanged, the layer thickness ratio of the composite scale is 2∶1 to meet the protection requirements. Some key mechanisms take effect to determine the anti-penetration performance of the protective gear, including the blunting and lateral deflection of bullets by composite scales, the overall synergistic energy dissipation of the overlapping scales, and the energy dispersion of the UHMWPE backing layer.
In this study, a novel double-layer flexible protective gear was proposed based on the multi-level structure of the bony fish scale and the concept of soft and hard composite protection. The upper layer of this protective gear is a scale-like layer which consists of periodically overlapping composite scales, the lower layer consists of multiple layers of ultra-high molecular weight polyethylene (UHMWPE) sheets as the backing layer. In accordance with the Level III requirements of the standard GJB 4300A—2012, the protection performance of the protective gear has been tested and simulated with finite element models, and the results verified the good protection performance of the gear against the armor-piercing incendiary bullet, and also confirmed the reliability of the numerical simulations. The results indicate that the thickness of the ceramic layer of the composite scale is one of the key factors that affect the anti-penetration performance of the protective gear. When the total thickness is unchanged, the layer thickness ratio of the composite scale is 2∶1 to meet the protection requirements. Some key mechanisms take effect to determine the anti-penetration performance of the protective gear, including the blunting and lateral deflection of bullets by composite scales, the overall synergistic energy dissipation of the overlapping scales, and the energy dispersion of the UHMWPE backing layer.
2022, 39(12): 5966-5972.
doi: 10.13801/j.cnki.fhclxb.20211230.002
Abstract:
The dynamic transparent-opaque transition behavior of the stimuli-chromic materials makes themselves have the ability to modulate the sunlight, which can reduce the energy consumption of the building. However, these materials usually involved some weak points such as high manufacturing costs, complex operation, and additional power consumption. Herein, a low-cost composite gel (KCA/PNIPAM) with excellent solar modulation ability and high stability was prepared by dispersing poly(N-isopropylacrylamide) (PNIPAM) gel microspheres into a carrageenan (KCA) matrix. In this hydrogel. KCA has a porous 3D network structure, which can effectively support PNIPAM particles, realizing the uniform dispersion and inhibiting the agglomeration and sedimentation of PNIPAM. KCA/PNIPAM gel exhibits the excellent solar modulation ability (ΔT=86%, difference in transmittance at different temperatures), when exposed to xenon lamp and sunlight, KCA/PNIPAM smart windows can lower the temperature by 5°C and 4°C respectively compared with ordinary glass windows. In conclusion, KCA/PNIPAM has the advantages of low response temperature (31.7°C), excellent solar modulation ability, long-term stability, low cost and simple manufacturing, making it a potential candidate for energy-saving materials of building.
The dynamic transparent-opaque transition behavior of the stimuli-chromic materials makes themselves have the ability to modulate the sunlight, which can reduce the energy consumption of the building. However, these materials usually involved some weak points such as high manufacturing costs, complex operation, and additional power consumption. Herein, a low-cost composite gel (KCA/PNIPAM) with excellent solar modulation ability and high stability was prepared by dispersing poly(N-isopropylacrylamide) (PNIPAM) gel microspheres into a carrageenan (KCA) matrix. In this hydrogel. KCA has a porous 3D network structure, which can effectively support PNIPAM particles, realizing the uniform dispersion and inhibiting the agglomeration and sedimentation of PNIPAM. KCA/PNIPAM gel exhibits the excellent solar modulation ability (ΔT=86%, difference in transmittance at different temperatures), when exposed to xenon lamp and sunlight, KCA/PNIPAM smart windows can lower the temperature by 5°C and 4°C respectively compared with ordinary glass windows. In conclusion, KCA/PNIPAM has the advantages of low response temperature (31.7°C), excellent solar modulation ability, long-term stability, low cost and simple manufacturing, making it a potential candidate for energy-saving materials of building.
2022, 39(12): 5973-5983.
doi: 10.13801/j.cnki.fhclxb.20211129.002
Abstract:
In order to obtain excellent properties of poly (lactic acid) based biodegradable composite, organic modified montmorillonite (OMMT) with dimethyl dioctadecyl ammonium chloride was used as a non-reactive compatibilizer. The organic modified montmorillonite/poly(lactic acid)-poly(butylene succinate) (OMMT/PLA-PBS) composites were prepared by direct melt blending method. The effect of OMMT contents on compatibility between PLA and PBS, and mechanical properties of the composites were investigated in this work. Morphological analyses reveal that OMMT can significantly reduce the particle size and result in uniform distribution of the dispersed phase PBS. The OMMT distributes in the interface between PLA and PBS can act as compatibilizer similar to block copolymer and increases interface adhesion between PLA and PBS. The dynamic rheological results indicate that OMMT forms a three-dimensional network structure at 3wt% OMMT. From dynamic thermo-mechanical analysis, glass transition temperatures of PLA and PBS in the composites get closer with the addition of OMMT. At 1wt%, the degree of glass transition temperature convergence is maximum, corresponding to the best compatibilization. Thermal data show that the crystallinity of PLA in composites first increases and then decreases by addition of OMMT. The crystallinity of PLA reaches maximum of 12.7% at 1wt%. The results of mechanical properties show that the comprehensive mechanical properties of OMMT/PLA-PBS composites reach the best when the OMMT content is 1wt%. The tensile strength and impact strength are 62.5 MPa and 12.6 kJ/m2, respectively, which are 32.1% and 80% higher than those of the PLA-PBS blend.
In order to obtain excellent properties of poly (lactic acid) based biodegradable composite, organic modified montmorillonite (OMMT) with dimethyl dioctadecyl ammonium chloride was used as a non-reactive compatibilizer. The organic modified montmorillonite/poly(lactic acid)-poly(butylene succinate) (OMMT/PLA-PBS) composites were prepared by direct melt blending method. The effect of OMMT contents on compatibility between PLA and PBS, and mechanical properties of the composites were investigated in this work. Morphological analyses reveal that OMMT can significantly reduce the particle size and result in uniform distribution of the dispersed phase PBS. The OMMT distributes in the interface between PLA and PBS can act as compatibilizer similar to block copolymer and increases interface adhesion between PLA and PBS. The dynamic rheological results indicate that OMMT forms a three-dimensional network structure at 3wt% OMMT. From dynamic thermo-mechanical analysis, glass transition temperatures of PLA and PBS in the composites get closer with the addition of OMMT. At 1wt%, the degree of glass transition temperature convergence is maximum, corresponding to the best compatibilization. Thermal data show that the crystallinity of PLA in composites first increases and then decreases by addition of OMMT. The crystallinity of PLA reaches maximum of 12.7% at 1wt%. The results of mechanical properties show that the comprehensive mechanical properties of OMMT/PLA-PBS composites reach the best when the OMMT content is 1wt%. The tensile strength and impact strength are 62.5 MPa and 12.6 kJ/m2, respectively, which are 32.1% and 80% higher than those of the PLA-PBS blend.
2022, 39(12): 5984-5995.
doi: 10.13801/j.cnki.fhclxb.20211201.003
Abstract:
In order to research the effect of substrate on microstructure and properties of laser cladding self-lubricating coating, laser cladding was carried out on the surface of Ti811 alloy and TC4 alloy by coaxial powder-feeding laser cladding technology using TC4, Ni45, Al2O3, MoS2 and rare earth oxide Y2O3 powder mixture as cladding material. The surface crack distribution of cladding layer was observed by penetration test. The elemental distribution and microstructure of coatings were analyzed by SEM, EDS and XRD. Microhardness and tribological properties of the coatings were examined. The results show that the element composition on the substrate can cause the difference of cladding layer phases. Because of the high content of element V, the precipitation of α-Ti on TC4 alloy is less than that of the laser cladding layer on Ti811 alloy. The thermal conductivity of substrates has a significantly impact on the microstructure and performance of the coatings. Because of low thermal conductivity and high density, TC4 alloy has low temperature gradient during laser cladding. As a result, the coating on TC4 alloy has less cracks, higher dilution rate, and coarser microstructure. The average hardness of coating on Ti811 substrate reaches up to 1303.5 HV0.5 attributes to its good conductivity and high cooling rate. The wear mass losing of the cladding coatings on two alloys is significantly reduced, and the average friction coefficient drops to below 0.3. Due to the reinforcement of hard phase and anti-fiction of soft phase, laser cladding coatings on different substrates both have excellent wear resistance property.
In order to research the effect of substrate on microstructure and properties of laser cladding self-lubricating coating, laser cladding was carried out on the surface of Ti811 alloy and TC4 alloy by coaxial powder-feeding laser cladding technology using TC4, Ni45, Al2O3, MoS2 and rare earth oxide Y2O3 powder mixture as cladding material. The surface crack distribution of cladding layer was observed by penetration test. The elemental distribution and microstructure of coatings were analyzed by SEM, EDS and XRD. Microhardness and tribological properties of the coatings were examined. The results show that the element composition on the substrate can cause the difference of cladding layer phases. Because of the high content of element V, the precipitation of α-Ti on TC4 alloy is less than that of the laser cladding layer on Ti811 alloy. The thermal conductivity of substrates has a significantly impact on the microstructure and performance of the coatings. Because of low thermal conductivity and high density, TC4 alloy has low temperature gradient during laser cladding. As a result, the coating on TC4 alloy has less cracks, higher dilution rate, and coarser microstructure. The average hardness of coating on Ti811 substrate reaches up to 1303.5 HV0.5 attributes to its good conductivity and high cooling rate. The wear mass losing of the cladding coatings on two alloys is significantly reduced, and the average friction coefficient drops to below 0.3. Due to the reinforcement of hard phase and anti-fiction of soft phase, laser cladding coatings on different substrates both have excellent wear resistance property.
2022, 39(12): 5996-6003.
doi: 10.13801/j.cnki.fhclxb.20211026.001
Abstract:
Whisker is able to enhance remarkably the hardness of ceramics while strengthening their strength and toughness, and has outstanding advantages in solving the lack of hardness. Aiming at the problems of high blindness of component design and time-consuming of specimen preparation in the current experimental method to investigate whisker-reinforced ceramics, a bidirectional stochastic modeling method to calculate the whisker Poisson’s ratio was proposed taking β-Si3N4w-reinforced Si3N4 ceramic as the object. Based on the plane super-soft pseudopotential method under the framework of density functional theory (DFT) and Perdew-Wang 91 (PW-91) function in the generalized gradient approximation (GGA), the β-Si3N4 supercell Poisson’s ratio was calculated. Further, an approach to establish the two-dimensional microstructure of β-Si3N4w-reinforced Si3N4 ceramics was presented by using Delaunay triangulation rule and pseudo-random function method. Then, the model hardness was predicted and the hardening mechanism of β-Si3N4w was discussed. Results show that the Poisson’s ratio of β-Si3N4w is about 0.27. The predicted hardness values of β-Si3N4w-reinforced Si3N4 ceramics are in good consistent with the related experimental test values, which demonstrates the validity of whisker Poisson’s ratio calculation model and whisker-reinforced ceramic microstructure modeling method. The hardness of Si3N4-based ceramics reaches the maximum value of 22.80 GPa at 3wt% β-Si3N4w content. Stress analysis shows that the anisotropic distribution of β-Si3N4w disperses the stress concentration area and with stands a large amount of stress depending on its high strength characteristics, which is the main reason for the increase in hardness.
Whisker is able to enhance remarkably the hardness of ceramics while strengthening their strength and toughness, and has outstanding advantages in solving the lack of hardness. Aiming at the problems of high blindness of component design and time-consuming of specimen preparation in the current experimental method to investigate whisker-reinforced ceramics, a bidirectional stochastic modeling method to calculate the whisker Poisson’s ratio was proposed taking β-Si3N4w-reinforced Si3N4 ceramic as the object. Based on the plane super-soft pseudopotential method under the framework of density functional theory (DFT) and Perdew-Wang 91 (PW-91) function in the generalized gradient approximation (GGA), the β-Si3N4 supercell Poisson’s ratio was calculated. Further, an approach to establish the two-dimensional microstructure of β-Si3N4w-reinforced Si3N4 ceramics was presented by using Delaunay triangulation rule and pseudo-random function method. Then, the model hardness was predicted and the hardening mechanism of β-Si3N4w was discussed. Results show that the Poisson’s ratio of β-Si3N4w is about 0.27. The predicted hardness values of β-Si3N4w-reinforced Si3N4 ceramics are in good consistent with the related experimental test values, which demonstrates the validity of whisker Poisson’s ratio calculation model and whisker-reinforced ceramic microstructure modeling method. The hardness of Si3N4-based ceramics reaches the maximum value of 22.80 GPa at 3wt% β-Si3N4w content. Stress analysis shows that the anisotropic distribution of β-Si3N4w disperses the stress concentration area and with stands a large amount of stress depending on its high strength characteristics, which is the main reason for the increase in hardness.
2022, 39(12): 6004-6016.
doi: 10.13801/j.cnki.fhclxb.20211228.002
Abstract:
Diamond/Cu composites have the advantage of low density, high thermal conductivity and tailorable coefficient of thermal expansion (CTE), then possess a good thermal matching performance with core chips. Therefore, it has a widespread application prospect in electronic packaging with high heat flux density and other fields. However, due to the poor wettability between diamond and Cu, which restricts its application. To improve the wettability between diamond and copper, tungsten-coated diamond particles as the reinforcement particles, which were coated on diamond particles by vacuum micro-evaporation method, and diamond/copper composites were prepared by Spark plasma sintering (SPS) technique. The formation and structure of tungsten coating on diamond (100) and (111) facets, fracture morphology, relative density (RD) and thermal conductivity (TC) of the compo-sites were studied. The results show that the coating surface is uniform, smooth and compact at the high tempera-ture of 1050oC for 60 min, and the formation of diamond coating on (100) surface is preferentially compared with that on (111) surface, the gradient structure of WC-W2C-W grows epitaxial on the diamond surface. The fracture mode of the composites is composed of debonding diamond particles from copper matrix and the ductile fracture of copper, and tight interface bonding between diamond and copper are formed. The coat thickness of tungsten-coated diamond particles is 331.46 nm at 1050℃ for 50 min, and the maximum RD and TC of diamond/copper composites are 99.71% and 459 W/(m·K), respectively.
Diamond/Cu composites have the advantage of low density, high thermal conductivity and tailorable coefficient of thermal expansion (CTE), then possess a good thermal matching performance with core chips. Therefore, it has a widespread application prospect in electronic packaging with high heat flux density and other fields. However, due to the poor wettability between diamond and Cu, which restricts its application. To improve the wettability between diamond and copper, tungsten-coated diamond particles as the reinforcement particles, which were coated on diamond particles by vacuum micro-evaporation method, and diamond/copper composites were prepared by Spark plasma sintering (SPS) technique. The formation and structure of tungsten coating on diamond (100) and (111) facets, fracture morphology, relative density (RD) and thermal conductivity (TC) of the compo-sites were studied. The results show that the coating surface is uniform, smooth and compact at the high tempera-ture of 1050oC for 60 min, and the formation of diamond coating on (100) surface is preferentially compared with that on (111) surface, the gradient structure of WC-W2C-W grows epitaxial on the diamond surface. The fracture mode of the composites is composed of debonding diamond particles from copper matrix and the ductile fracture of copper, and tight interface bonding between diamond and copper are formed. The coat thickness of tungsten-coated diamond particles is 331.46 nm at 1050℃ for 50 min, and the maximum RD and TC of diamond/copper composites are 99.71% and 459 W/(m·K), respectively.
2022, 39(12): 6017-6027.
doi: 10.13801/j.cnki.fhclxb.20220711.001
Abstract:
The additive manufacturing of heterogeneous layered titanium alloy is realized by the alternating deposition of TC4 and TA2 using a double wire plasma system. The components have good deposition morphology and mechanical properties. OM, SEM, backscattered electron diffraction technique (EBSD), XRD etc. were used to analyze the microstructure, mechanical properties were tested with microhardness and compression properties. The results show that TA2 and TC4 regions are mainly composed of lamellae α phase and α+β phase of basketweave and colonies structure. The grains in each region grow in the opposite direction of heat flow. The grain boundary characteristics and crystal orientation of TC4 region and TA2 region have similar laws, but due to the differences of phase growth of heterogeneous materials, the growth direction of β phase has changed between different layers, and the original β phase growth direction of TC4 region will grow along a preferred orientation of the deposited TA2 region, which limits the phenomenon of continuous growth of β phase into coarsened columnar crystal. In the layered structure, the hardness of TC4 region is significantly higher than that of TA2 region, and the hardness increases along the deposited direction. The component has close compressive strength along different directions, nearly 2.0 GPa, but the special layered structure formed alternately by TC4 and TA2 has high fracture strain (0.33) along the deposited direction and high yield strength (1133 MPa) along the travel direction.
The additive manufacturing of heterogeneous layered titanium alloy is realized by the alternating deposition of TC4 and TA2 using a double wire plasma system. The components have good deposition morphology and mechanical properties. OM, SEM, backscattered electron diffraction technique (EBSD), XRD etc. were used to analyze the microstructure, mechanical properties were tested with microhardness and compression properties. The results show that TA2 and TC4 regions are mainly composed of lamellae α phase and α+β phase of basketweave and colonies structure. The grains in each region grow in the opposite direction of heat flow. The grain boundary characteristics and crystal orientation of TC4 region and TA2 region have similar laws, but due to the differences of phase growth of heterogeneous materials, the growth direction of β phase has changed between different layers, and the original β phase growth direction of TC4 region will grow along a preferred orientation of the deposited TA2 region, which limits the phenomenon of continuous growth of β phase into coarsened columnar crystal. In the layered structure, the hardness of TC4 region is significantly higher than that of TA2 region, and the hardness increases along the deposited direction. The component has close compressive strength along different directions, nearly 2.0 GPa, but the special layered structure formed alternately by TC4 and TA2 has high fracture strain (0.33) along the deposited direction and high yield strength (1133 MPa) along the travel direction.
2022, 39(12): 6028-6041.
doi: 10.13801/j.cnki.fhclxb.20220223.003
Abstract:
There were many problems after 2.5 dimensional carbon fiber reinforced SiC ceramic matrix (C/SiC) composite processed by nanosecond lasers, such as ablative oxide layer, sidewall slope, uneven bottom surface, and many problems also remained in grinding processing, breakage of fiber and matrix, fiber fracture, tool wear, low shape accuracy, low efficiency and so on, the laser-grinding compound processing method was proposed. To explore the feasibility of laser-grinding compound processing of 2.5 dimensional C/SiC composite grooves, the grooves experiment of laser processing, grinding processing and laser-grinding composite processing were carried out. The results show that the slope of the side wall of the groove by laser processing is about 23°, the surface quality of the bottom and side wall is poor, but the processing efficiency is high. To a certain extent, the surface quality of the grooves by grinding is improved, but the shape precision of the grooves after grinding is extremely poor and the processing efficiency is lower because of the severe wear of the grinding wheel. However, after laser-grinding compound processing, slope of groove sidewall is removed, the grinding wheel wear is greatly reduced, and the surface quality is significantly improved, roughness of the groove surface is 1.27-1.96 times higher than that after grinding, the processing time is about 0.3 of that of grinding. Therefore, the laser-grinding compound processing can not only overcome the shortcomings of laser processing and grinding processing, but also give play to the characteristics of high laser processing efficiency and grinding accuracy, and take into account the quality and efficiency of groove processing of 2.5 dimensional C/SiC composites. The results can provide theoretical support for efficient, precise and low damage processing of 2.5 dimensional C/SiC composite grooves.
There were many problems after 2.5 dimensional carbon fiber reinforced SiC ceramic matrix (C/SiC) composite processed by nanosecond lasers, such as ablative oxide layer, sidewall slope, uneven bottom surface, and many problems also remained in grinding processing, breakage of fiber and matrix, fiber fracture, tool wear, low shape accuracy, low efficiency and so on, the laser-grinding compound processing method was proposed. To explore the feasibility of laser-grinding compound processing of 2.5 dimensional C/SiC composite grooves, the grooves experiment of laser processing, grinding processing and laser-grinding composite processing were carried out. The results show that the slope of the side wall of the groove by laser processing is about 23°, the surface quality of the bottom and side wall is poor, but the processing efficiency is high. To a certain extent, the surface quality of the grooves by grinding is improved, but the shape precision of the grooves after grinding is extremely poor and the processing efficiency is lower because of the severe wear of the grinding wheel. However, after laser-grinding compound processing, slope of groove sidewall is removed, the grinding wheel wear is greatly reduced, and the surface quality is significantly improved, roughness of the groove surface is 1.27-1.96 times higher than that after grinding, the processing time is about 0.3 of that of grinding. Therefore, the laser-grinding compound processing can not only overcome the shortcomings of laser processing and grinding processing, but also give play to the characteristics of high laser processing efficiency and grinding accuracy, and take into account the quality and efficiency of groove processing of 2.5 dimensional C/SiC composites. The results can provide theoretical support for efficient, precise and low damage processing of 2.5 dimensional C/SiC composite grooves.
2022, 39(12): 6042-6053.
doi: 10.13801/j.cnki.fhclxb.20211228.003
Abstract:
Based on the theory of non-geodesic winding and fiber slippage, it was proposed to use non-geodesic winding to form integrated composite drive shafts. Multiple groups of variable-angle composite drive shafts with different proportions of transition zone were designed, and the torsion performance and failure mechanism of the drive shafts were deeply studied by finite element analysis and torsional experiment. The results show that the greater the proportion of the transition zone with variable angles, the better the torsional performance of the drive shafts. The transition zone increases from 20% to 80%, the failure load of the drive shafts increases by 111%, and the peak load increases by 90.7%. With the increase in the proportion of the transition zone, the damage failure caused by buckling deformation is effectively alleviated, and the damage angle is reduced by 54.5%. According to the finite element simulation and torsional experiment analysis, it can be concluded that the increase of the fiber angle in the transition zone suppresses the buckling deformation and reduces mechanical conduction failure on the interface caused by delamination damage. As a result, it improves the bearing capacity of the drive shafts.
Based on the theory of non-geodesic winding and fiber slippage, it was proposed to use non-geodesic winding to form integrated composite drive shafts. Multiple groups of variable-angle composite drive shafts with different proportions of transition zone were designed, and the torsion performance and failure mechanism of the drive shafts were deeply studied by finite element analysis and torsional experiment. The results show that the greater the proportion of the transition zone with variable angles, the better the torsional performance of the drive shafts. The transition zone increases from 20% to 80%, the failure load of the drive shafts increases by 111%, and the peak load increases by 90.7%. With the increase in the proportion of the transition zone, the damage failure caused by buckling deformation is effectively alleviated, and the damage angle is reduced by 54.5%. According to the finite element simulation and torsional experiment analysis, it can be concluded that the increase of the fiber angle in the transition zone suppresses the buckling deformation and reduces mechanical conduction failure on the interface caused by delamination damage. As a result, it improves the bearing capacity of the drive shafts.
2022, 39(12): 6054-6064.
doi: 10.13801/j.cnki.fhclxb.20211213.003
Abstract:
The deformation and fracture behaviors of ductile materials under complex stress states are usually quite different from those under uniaxial loading conditions. In recent years, the development of fracture criteria and their application in numerical simulation have attracted great attention in many engineering fields. So, it is quite important to analyze the applicability of different fracture criteria over a wide range of stress states and select an appropriate model to accurately predict the fracture behavior. The fracture behavior of in-situ TiB2/2024 Al composite was investigated systematically over stress triaxialities ranging from −0.82 to 1.03, and lode angel parameters ranging from −1 to 1 by using an experimental approach. The fracture characteristics and underlying mechanisms are closely related to stress state, and both of the stress triaxiality and lode angle parameter should be included in the fracture criterion to predict fracture over a wide range of stress states. Based on the experimental data, five existing fracture criteria were calibrated, and their ability to describe and predict the fracture behavior was evaluated. The result shows that the fracture criteria which consider comprehensively the effects of the stress triaxiality, lode angle parameter and cut-off value can more accurately predict the fracture behavior of in-situ TiB2/2024 Al composite over a wide range of stress states.
The deformation and fracture behaviors of ductile materials under complex stress states are usually quite different from those under uniaxial loading conditions. In recent years, the development of fracture criteria and their application in numerical simulation have attracted great attention in many engineering fields. So, it is quite important to analyze the applicability of different fracture criteria over a wide range of stress states and select an appropriate model to accurately predict the fracture behavior. The fracture behavior of in-situ TiB2/2024 Al composite was investigated systematically over stress triaxialities ranging from −0.82 to 1.03, and lode angel parameters ranging from −1 to 1 by using an experimental approach. The fracture characteristics and underlying mechanisms are closely related to stress state, and both of the stress triaxiality and lode angle parameter should be included in the fracture criterion to predict fracture over a wide range of stress states. Based on the experimental data, five existing fracture criteria were calibrated, and their ability to describe and predict the fracture behavior was evaluated. The result shows that the fracture criteria which consider comprehensively the effects of the stress triaxiality, lode angle parameter and cut-off value can more accurately predict the fracture behavior of in-situ TiB2/2024 Al composite over a wide range of stress states.
2022, 39(12): 6065-6077.
doi: 10.13801/j.cnki.fhclxb.20211125.001
Abstract:
To investigate the failure modes and load-bearing performance of pre-tightened tooth connections of carbon fiber reinforced polymer (CFRP) in the bridge engineering, a total of 68 tensile specimens were carried out with transverse pre-tightened force (23 MPa, 34.6 MPa, 53 MPa, 64.5 MPa), tooth depth (0.5 mm, 1 mm, 2 mm), tooth length (8 mm, 16 mm, 24 mm) and tooth number (one tooth, three teeth and six teeth) as variable parameters. According to the test results of load displacement curve, strain and failure mode, the effects of various parameters on the mechanical properties of the joint were analyzed. The results show that there are four failure modes for CFRP pre-tightened tooth joints: Shear failure, crushing failure, longitudinal splitting failure and fiber breaking failure. There are two characteristics of the load-displacement curves of the joint: The load drops suddenly after reaching the extreme value and the load decreases slowly after reaching the extreme value. The former joints are subjected to shear failure or fiber breaking failure, while the latter joint is subjected to crushing failure or splitting failure. The load distribution ratio of pre-tightened multi-tooth joints is uneven, the load distribution ratio of the joint with crushing failure is more uniform than that of joint with shear failure. Whether the joint is crushing or shear failure, the load distribution ratio of the first tooth is the largest. The more the number of joint teeth, the smaller the maximum load distribution ratio of the joint. When the pre-tightened force, tooth depth and tooth length are less than 53 MPa, 2 mm and 16 mm respectively, the joint strength increases with the increase of pre-tightened force, tooth depth and tooth length. When the pre-tightened force and tooth length exceed a certain value of 53 MPa and 16mm respectively, the joint connection strength changes little. In the range of 6 teeth, the joint strength increases with the increase of the number of teeth.
To investigate the failure modes and load-bearing performance of pre-tightened tooth connections of carbon fiber reinforced polymer (CFRP) in the bridge engineering, a total of 68 tensile specimens were carried out with transverse pre-tightened force (23 MPa, 34.6 MPa, 53 MPa, 64.5 MPa), tooth depth (0.5 mm, 1 mm, 2 mm), tooth length (8 mm, 16 mm, 24 mm) and tooth number (one tooth, three teeth and six teeth) as variable parameters. According to the test results of load displacement curve, strain and failure mode, the effects of various parameters on the mechanical properties of the joint were analyzed. The results show that there are four failure modes for CFRP pre-tightened tooth joints: Shear failure, crushing failure, longitudinal splitting failure and fiber breaking failure. There are two characteristics of the load-displacement curves of the joint: The load drops suddenly after reaching the extreme value and the load decreases slowly after reaching the extreme value. The former joints are subjected to shear failure or fiber breaking failure, while the latter joint is subjected to crushing failure or splitting failure. The load distribution ratio of pre-tightened multi-tooth joints is uneven, the load distribution ratio of the joint with crushing failure is more uniform than that of joint with shear failure. Whether the joint is crushing or shear failure, the load distribution ratio of the first tooth is the largest. The more the number of joint teeth, the smaller the maximum load distribution ratio of the joint. When the pre-tightened force, tooth depth and tooth length are less than 53 MPa, 2 mm and 16 mm respectively, the joint strength increases with the increase of pre-tightened force, tooth depth and tooth length. When the pre-tightened force and tooth length exceed a certain value of 53 MPa and 16mm respectively, the joint connection strength changes little. In the range of 6 teeth, the joint strength increases with the increase of the number of teeth.
2022, 39(12): 6078-6087.
doi: 10.13801/j.cnki.fhclxb.20211126.002
Abstract:
Carbon fiber reinforced polymer (CFRP)-Al single-lap adhesive joints were made at room temperature. Firstly, a universal testing machine as well as an electro-hydraulic servo fatigue testing machine were used for quasi-static tensile tests and tensile-tension fatigue tests, respectively. Based upon the fatigue test results and two-parameter Weibull distribution methods, multiple function models were applied to fit the stress-life (S-N) curves of joints. Meanwhile, 3D digital image correlation (3D-DIC) and SEM were used respectively to obtain the strain field distribution and failure morphology of joints, revealing the failure mechanism of joints under cyclic load. According to the test results, the power function has the highest fitting degree for the S-N curves of the joints, with the correlation coefficient R2 of 0.987. Besides, with the load level decreasing, the fatigue life and the coefficient of variation of the joints gradually increase. When the load levels are 25% and 35% of the failure load, the failure modes of joints are mainly cohesive failure and interface failure. And the cohesive failure area increases correspondingly with the increase of the load level. Even when the load level is up to 75% of the failure load, only cohesive failure occurs. Moreover, when the load level is 25% of the failure load, ductile fracture occurs due to the increase of the internal temperature of the joints. And when the load level rises to 75% of the failure load, the joints gradually change to brittle fracture as a result of large tensile stress.
Carbon fiber reinforced polymer (CFRP)-Al single-lap adhesive joints were made at room temperature. Firstly, a universal testing machine as well as an electro-hydraulic servo fatigue testing machine were used for quasi-static tensile tests and tensile-tension fatigue tests, respectively. Based upon the fatigue test results and two-parameter Weibull distribution methods, multiple function models were applied to fit the stress-life (S-N) curves of joints. Meanwhile, 3D digital image correlation (3D-DIC) and SEM were used respectively to obtain the strain field distribution and failure morphology of joints, revealing the failure mechanism of joints under cyclic load. According to the test results, the power function has the highest fitting degree for the S-N curves of the joints, with the correlation coefficient R2 of 0.987. Besides, with the load level decreasing, the fatigue life and the coefficient of variation of the joints gradually increase. When the load levels are 25% and 35% of the failure load, the failure modes of joints are mainly cohesive failure and interface failure. And the cohesive failure area increases correspondingly with the increase of the load level. Even when the load level is up to 75% of the failure load, only cohesive failure occurs. Moreover, when the load level is 25% of the failure load, ductile fracture occurs due to the increase of the internal temperature of the joints. And when the load level rises to 75% of the failure load, the joints gradually change to brittle fracture as a result of large tensile stress.
2022, 39(12): 6088-6095.
doi: 10.13801/j.cnki.fhclxb.20211208.001
Abstract:
The composite hull is mainly composed of longitudinally or transversely stiffened laminates. The design of composite stiffened laminates can be approximated as an orthogonal anisotropic plate and the equivalent stiffness of stiffened composite plates needs to be calculated quantitatively. The longitudinal and transverse bending stiffness of hat-stiffened panel were derived using the Castigliano's theorem. The analytical expressions for the equivalent bending stiffness were provided. The longitudinal and transverse three-point bending tests of the hat-stiffened laminates were designed to measure the mid-span deflection of the beam and the obtained test data were compared with the analytical solution corresponding to the equivalent bending stiffness. The deflection at the center point of longitudinally and transversely hat-stiffened composite beam in three-point bending and the four-sided simply-supported hat-stiffened composite laminates was calculated by ABAQUS and compared with the analytical solution corresponding to the equivalent bending stiffness. The results show that the analytical solutions are in good agreement with the numerical calculations and the experimental results, which verifies the correctness of the analytical expression of the equivalent bending stiffness. It can be used confidently in the design of the hat-stiffened panel.
The composite hull is mainly composed of longitudinally or transversely stiffened laminates. The design of composite stiffened laminates can be approximated as an orthogonal anisotropic plate and the equivalent stiffness of stiffened composite plates needs to be calculated quantitatively. The longitudinal and transverse bending stiffness of hat-stiffened panel were derived using the Castigliano's theorem. The analytical expressions for the equivalent bending stiffness were provided. The longitudinal and transverse three-point bending tests of the hat-stiffened laminates were designed to measure the mid-span deflection of the beam and the obtained test data were compared with the analytical solution corresponding to the equivalent bending stiffness. The deflection at the center point of longitudinally and transversely hat-stiffened composite beam in three-point bending and the four-sided simply-supported hat-stiffened composite laminates was calculated by ABAQUS and compared with the analytical solution corresponding to the equivalent bending stiffness. The results show that the analytical solutions are in good agreement with the numerical calculations and the experimental results, which verifies the correctness of the analytical expression of the equivalent bending stiffness. It can be used confidently in the design of the hat-stiffened panel.
2022, 39(12): 6096-6108.
doi: 10.13801/j.cnki.fhclxb.20211108.001
Abstract:
In the hot press molding process of metal-composite hybrid structures, various defects including fracture, spring-back, delamination, thickness thinning and wrinkle will inevitably occur. Meanwhile fiber yarns in fabric reinforced composites will undergo significant shear deformations with restrictions of blank holding force. The above defects and shear deformations will lead to a significant impact on subsequent structural performances. However, these forming defects of hybrid structures cannot be observed directly during the forming process, and the mechanical cutting method might cause secondary damage to explore these forming defects. More importantly, the damaged specimen cannot be continuously investigated in the subsequent structural performance test, which causes the isolated analysis between forming performance and structural performance and greatly increases the risk of failure. In this study, the hot press molding and three-point bending characteristics of Al-carbon fiber reinforced polypropylene (CF/PP) hybrid hat-shaped rail were studied experimentally. The X-ray computed tomography (X-ray CT) non-destructive test technology was used to investigate the formability of Al-CF/PP hybrid structure on the fiber angle variations, thickness variations, delamination and spring-back deformations, respectively. Moreover, the static three-point bending test was carried out to explore the bending characteristics of the hybrid structure. The results show that the fiber angles convert from orthogonal configurations to non-orthogonal configuration; both thickness increase and thickness reduction occur; delamination occurs significantly around the fillet transition areas; spring-back deformations are unapparent; significant plastic deformations can be found in the bending test and fracturing failures occur in both Al and CF/PP in the end of the test.
In the hot press molding process of metal-composite hybrid structures, various defects including fracture, spring-back, delamination, thickness thinning and wrinkle will inevitably occur. Meanwhile fiber yarns in fabric reinforced composites will undergo significant shear deformations with restrictions of blank holding force. The above defects and shear deformations will lead to a significant impact on subsequent structural performances. However, these forming defects of hybrid structures cannot be observed directly during the forming process, and the mechanical cutting method might cause secondary damage to explore these forming defects. More importantly, the damaged specimen cannot be continuously investigated in the subsequent structural performance test, which causes the isolated analysis between forming performance and structural performance and greatly increases the risk of failure. In this study, the hot press molding and three-point bending characteristics of Al-carbon fiber reinforced polypropylene (CF/PP) hybrid hat-shaped rail were studied experimentally. The X-ray computed tomography (X-ray CT) non-destructive test technology was used to investigate the formability of Al-CF/PP hybrid structure on the fiber angle variations, thickness variations, delamination and spring-back deformations, respectively. Moreover, the static three-point bending test was carried out to explore the bending characteristics of the hybrid structure. The results show that the fiber angles convert from orthogonal configurations to non-orthogonal configuration; both thickness increase and thickness reduction occur; delamination occurs significantly around the fillet transition areas; spring-back deformations are unapparent; significant plastic deformations can be found in the bending test and fracturing failures occur in both Al and CF/PP in the end of the test.
2022, 39(12): 6109-6118.
doi: 10.13801/j.cnki.fhclxb.20211216.001
Abstract:
In order to improve the accuracy of local buckling engineering method of hat-stiffened composite panel, the stability experiment of typical panels under axial compression was first carried out, and then an updating engineering method for local buckling of hat-stiffened composite panel based on flexural stiffness ratio was proposed. The predicted buckling loads differ less than 3% from experimental results. The buckling analysis of two kinds of hat-stiffened panels with bottom flange was carried out by finite element model (FEM) method and the updating method this paper proposed comparatively. The error of compared results is within 10%, which verifies the reasonableness of the proposed method and satisfies the engineering accuracy. Experimental data recorded in public literature were analyzed by engineering simplified method, energy method and the updating method this paper proposed comparatively. Results show that the error by engineering simply and fixedly supported boundary conditions can be reduced from 41.5% and 5.3% to 3.8% respectively, which provides a new rapid analytical method for preliminary design of hat-stiffened composite panel.
In order to improve the accuracy of local buckling engineering method of hat-stiffened composite panel, the stability experiment of typical panels under axial compression was first carried out, and then an updating engineering method for local buckling of hat-stiffened composite panel based on flexural stiffness ratio was proposed. The predicted buckling loads differ less than 3% from experimental results. The buckling analysis of two kinds of hat-stiffened panels with bottom flange was carried out by finite element model (FEM) method and the updating method this paper proposed comparatively. The error of compared results is within 10%, which verifies the reasonableness of the proposed method and satisfies the engineering accuracy. Experimental data recorded in public literature were analyzed by engineering simplified method, energy method and the updating method this paper proposed comparatively. Results show that the error by engineering simply and fixedly supported boundary conditions can be reduced from 41.5% and 5.3% to 3.8% respectively, which provides a new rapid analytical method for preliminary design of hat-stiffened composite panel.
2022, 39(12): 6119-6129.
doi: 10.13801/j.cnki.fhclxb.20211125.002
Abstract:
The out-plane shear behavior and mechanical properties of aluminum honeycomb sandwich panel were studied by experiment and numerical simulation. The failure modes were discussed, and the typical load-displacement curves were obtained. The effects of face sheet thickness, cell size and core height on the pick load and energy absorption capacity of the sandwich panel were analyzed. The results show that the out-plane shear failure process of aluminum honeycomb sandwich panel goes through four stages: Elastic-plastic deformation, upper sheet damage failure, core layer density and lower sheet damage failure, and presents two failure modes: Integral failure and phased failure. The type of failure mode is mainly determined by the relative relationship between face sheet thickness and cell size. Increasing face sheet thickness or cell size will transform the failure mode from integral failure to phased failure, and the energy absorption capacity of phased failure mode is higher than integral failure mode. The shear strength and energy absorption capacity increase with the increase of face sheet thickness, but decrease with the increase of cell size. The shear strength is slightly affected by the core height, but the energy absorption capacity of sandwich panel increases with the increase of core height. The simulation results are in good agreement with the experimental results, which fully verifies the reliability of the finite element model.
The out-plane shear behavior and mechanical properties of aluminum honeycomb sandwich panel were studied by experiment and numerical simulation. The failure modes were discussed, and the typical load-displacement curves were obtained. The effects of face sheet thickness, cell size and core height on the pick load and energy absorption capacity of the sandwich panel were analyzed. The results show that the out-plane shear failure process of aluminum honeycomb sandwich panel goes through four stages: Elastic-plastic deformation, upper sheet damage failure, core layer density and lower sheet damage failure, and presents two failure modes: Integral failure and phased failure. The type of failure mode is mainly determined by the relative relationship between face sheet thickness and cell size. Increasing face sheet thickness or cell size will transform the failure mode from integral failure to phased failure, and the energy absorption capacity of phased failure mode is higher than integral failure mode. The shear strength and energy absorption capacity increase with the increase of face sheet thickness, but decrease with the increase of cell size. The shear strength is slightly affected by the core height, but the energy absorption capacity of sandwich panel increases with the increase of core height. The simulation results are in good agreement with the experimental results, which fully verifies the reliability of the finite element model.
2022, 39(12): 6130-6138.
doi: 10.13801/j.cnki.fhclxb.20211116.005
Abstract:
The surface bonding ability of poly-p-phenylene benzobisoxazole (PBO) fibers is weak, and its interface strength after being compounded with resin is low, which affects the mechanical properties of composite materials. This research coated the PBO plain weave fabric with a layer of polyacrylonitrile (PAN) nanofiber membrane by electrospinning. The composite material was subsequently obtained by layering and curing, which formed a gradient interface between the PBO fibers and the epoxy resin to improve the interface strength of composite materials. The short beam shear test of composites was carried out by universal testing machine, and the best interlayer performance enhancement effect was determined by changing the spinning voltage. The relative stiffness image in interface was obtained with atomic force microscope (AFM) to investigate the enhancing mechanism of interface strength. The results show that when the spinning voltage is 20 kV, the interlaminar performance of the composite is most obvious under the condition that the pushing speed of the syringe pump and the rotating speed of the collecting roller remain unchanged. Compared with the pure PBO fibers reinforced composites, the interlaminar shear strength of the PBO fiber reinforced composites coated with film is increased by 40.1%. The gradient interface structure helps to transfer the stress evenly from the resin matrix to the fiber reinforcement and improve the mechanical properties of the composites.
The surface bonding ability of poly-p-phenylene benzobisoxazole (PBO) fibers is weak, and its interface strength after being compounded with resin is low, which affects the mechanical properties of composite materials. This research coated the PBO plain weave fabric with a layer of polyacrylonitrile (PAN) nanofiber membrane by electrospinning. The composite material was subsequently obtained by layering and curing, which formed a gradient interface between the PBO fibers and the epoxy resin to improve the interface strength of composite materials. The short beam shear test of composites was carried out by universal testing machine, and the best interlayer performance enhancement effect was determined by changing the spinning voltage. The relative stiffness image in interface was obtained with atomic force microscope (AFM) to investigate the enhancing mechanism of interface strength. The results show that when the spinning voltage is 20 kV, the interlaminar performance of the composite is most obvious under the condition that the pushing speed of the syringe pump and the rotating speed of the collecting roller remain unchanged. Compared with the pure PBO fibers reinforced composites, the interlaminar shear strength of the PBO fiber reinforced composites coated with film is increased by 40.1%. The gradient interface structure helps to transfer the stress evenly from the resin matrix to the fiber reinforcement and improve the mechanical properties of the composites.
2022, 39(12): 6139-6156.
doi: 10.13801/j.cnki.fhclxb.20211222.002
Abstract:
In order to solve the problems of thermal deformation and thermal residual stress of fiber reinforced polymer (FRP) circular pipe in engineering, a calculation method of equivalent thermal expansion coefficient and thermal residual stress of FRP tube with arbitrary ply was proposed. This method is a three-dimensional elastic theory considering lamination effect and three-dimensional constitutive relationship of anisotropic material. The correctness of the theory was verified by comparing and analyzing with multiple groups of data of the test and ANSYS numerical model in this paper. Based on this theoretical model, firstly, the equivalent thermal expansion coefficients of many kinds of laminated FRP circular pipes were studied. Secondly, combined with the strength ratio equation of Hashin failure criterion, the strength failure of FRP tube caused by thermal residual stress was analyzed. The results show that the influence of FRP tube ply angle on the equivalent thermal expansion coefficient is different in the thermal shrinkage stage and thermal expansion stage, and there is a laminated mode with zero equivalent thermal expansion coefficient; The diameter thickness ratio only has a great influence on the equivalent radial thermal expansion coefficient, but has no influence on the equivalent axial thermal expansion coefficient; Temperature difference and direction affect the failure mode and location of FRP tubes. The strength failure of FRP tubes caused by thermal residual stress is matrix failure.
In order to solve the problems of thermal deformation and thermal residual stress of fiber reinforced polymer (FRP) circular pipe in engineering, a calculation method of equivalent thermal expansion coefficient and thermal residual stress of FRP tube with arbitrary ply was proposed. This method is a three-dimensional elastic theory considering lamination effect and three-dimensional constitutive relationship of anisotropic material. The correctness of the theory was verified by comparing and analyzing with multiple groups of data of the test and ANSYS numerical model in this paper. Based on this theoretical model, firstly, the equivalent thermal expansion coefficients of many kinds of laminated FRP circular pipes were studied. Secondly, combined with the strength ratio equation of Hashin failure criterion, the strength failure of FRP tube caused by thermal residual stress was analyzed. The results show that the influence of FRP tube ply angle on the equivalent thermal expansion coefficient is different in the thermal shrinkage stage and thermal expansion stage, and there is a laminated mode with zero equivalent thermal expansion coefficient; The diameter thickness ratio only has a great influence on the equivalent radial thermal expansion coefficient, but has no influence on the equivalent axial thermal expansion coefficient; Temperature difference and direction affect the failure mode and location of FRP tubes. The strength failure of FRP tubes caused by thermal residual stress is matrix failure.
2022, 39(12): 6157-6167.
doi: 10.13801/j.cnki.fhclxb.20220112.003
Abstract:
The dynamic fracture toughness of the bionic spiral structured composite material was studied through three-point bending dynamic impact experiment and numerical simulation. The structure is a bionic composite structure based on the Bouligand structure design. Firstly, 8 groups of specimens with different angles were prepared by 3D printing technology using two kinds of substrates, soft and stiff, and the dynamic three-point bending impact tests were completed by using an improved split Hopkinson bar. The displacement-load curve, fracture time and fracture energy were obtained, and the final fracture morphology of the sample was analyzed. Then, the numerical simulation of the whole process of specimen fracture was completed in ABAQUS software, and the crack initiation and propagation process were analyzed. Both the experimental and numerical simulation results show that the helix angle has a great influence on the fracture toughness of the specimen, in the range of the helix angle of 0°-75°, the fracture toughness of the specimen increases with the increase of the angle, while when the helix angle is 90°, the fracture toughness of the sample drops sharply. In the process of experiment, it is observed that there is a crack deflection phenomenon during the dynamic fracture process of the sample. Finally, the influence mechanism of the crack deflection on the dynamic fracture was investigated. The results show that the crack deflection changes the local fracture mode of the composite material, increases the fracture area, and therefore improves the fracture toughness of the material.
The dynamic fracture toughness of the bionic spiral structured composite material was studied through three-point bending dynamic impact experiment and numerical simulation. The structure is a bionic composite structure based on the Bouligand structure design. Firstly, 8 groups of specimens with different angles were prepared by 3D printing technology using two kinds of substrates, soft and stiff, and the dynamic three-point bending impact tests were completed by using an improved split Hopkinson bar. The displacement-load curve, fracture time and fracture energy were obtained, and the final fracture morphology of the sample was analyzed. Then, the numerical simulation of the whole process of specimen fracture was completed in ABAQUS software, and the crack initiation and propagation process were analyzed. Both the experimental and numerical simulation results show that the helix angle has a great influence on the fracture toughness of the specimen, in the range of the helix angle of 0°-75°, the fracture toughness of the specimen increases with the increase of the angle, while when the helix angle is 90°, the fracture toughness of the sample drops sharply. In the process of experiment, it is observed that there is a crack deflection phenomenon during the dynamic fracture process of the sample. Finally, the influence mechanism of the crack deflection on the dynamic fracture was investigated. The results show that the crack deflection changes the local fracture mode of the composite material, increases the fracture area, and therefore improves the fracture toughness of the material.
