2020 Vol. 37, No. 3
2020, 37(3): 493-503.
doi: 10.13801/j.cnki.fhclxb.20190911.003
Abstract:
In order to obtain a high-performance heavy metal Cr(Ⅵ) adsorption material, the halloysite nanotubes/poly(m-phenylenediamine) (HNTs/PmPD) composite was synthesized through in situ chemical polymerization under the regulation of Na2CO3 at room temperature. The surface structure and properties of HNTs/PmPD composite were characterized by SEM, TGA, EDS, Brunauer-Emmett-Teller specific surface area analysis (BET), inductively coupled plasma mass spectrometry (ICP-MS), FTIR and Zeta potential analysis (Zeta). The effects of experimental conditions such as pH value, time, initial concentration and temperature on the removal of Cr(Ⅵ) have been also analyzed. In addition, the experimental data of Cr(Ⅵ) adsorption by HNTs/PmPD composite were fitted and evaluated by kinetic and isotherm models. The HNTs/PmPD composite shows excellent removal ability for Cr(Ⅵ), good sedimentation separation and cycle regeneration performance, moreover, the adsorption capacity can reach above 855.66 mg·g-1 at room temperature. The results show that amino and imine groups presented on the surface of the HNTs/PmPD composite are the main adsorption sites for the removal of Cr(Ⅵ). HNTs/PmPD composite has excellent performance and application prospects in the field of chromium-containing wastewater treatment.
In order to obtain a high-performance heavy metal Cr(Ⅵ) adsorption material, the halloysite nanotubes/poly(m-phenylenediamine) (HNTs/PmPD) composite was synthesized through in situ chemical polymerization under the regulation of Na2CO3 at room temperature. The surface structure and properties of HNTs/PmPD composite were characterized by SEM, TGA, EDS, Brunauer-Emmett-Teller specific surface area analysis (BET), inductively coupled plasma mass spectrometry (ICP-MS), FTIR and Zeta potential analysis (Zeta). The effects of experimental conditions such as pH value, time, initial concentration and temperature on the removal of Cr(Ⅵ) have been also analyzed. In addition, the experimental data of Cr(Ⅵ) adsorption by HNTs/PmPD composite were fitted and evaluated by kinetic and isotherm models. The HNTs/PmPD composite shows excellent removal ability for Cr(Ⅵ), good sedimentation separation and cycle regeneration performance, moreover, the adsorption capacity can reach above 855.66 mg·g-1 at room temperature. The results show that amino and imine groups presented on the surface of the HNTs/PmPD composite are the main adsorption sites for the removal of Cr(Ⅵ). HNTs/PmPD composite has excellent performance and application prospects in the field of chromium-containing wastewater treatment.
2020, 37(3): 504-511.
doi: 10.13801/j.cnki.fhclxb.20190505.001
Abstract:
The material of institute lavoisier framework (MIL-101(Cr)) was synthesized through hydrothermal synthesis. Then sulfonic groups (SO3H) were introduced into cages of MIL-101(Cr) by post sulfonation reaction to obtain MIL-101(Cr)-SO3H with proton conduction property. FTIR results confirm the successful introduction of sulfonic groups to MIL-101(Cr). SEM and XRD results indicate that the particle size of MIL-101(Cr) and MIL-101(Cr)-SO3H are in the range of nanometer scale, and no crystal structural collapse can be observed for as-prepared MIL-101(Cr)-SO3H. The elemental analysis shows that the sulfonation degree of MIL-101(Cr)-SO3H is 0.36. Then MIL-101(Cr)-SO3H is embedded into sulfonated polyarylethersulfone with cardo (SPES-C) to obtain a series of MIL-101(Cr)-SO3H/SPES-C hybrid proton exchange membranes for fuel cell application. SEM characterization demonstrates that MIL-101(Cr)-SO3H is uniformly dispersed in the MIL-101(Cr)-SO3H/SPES-C hybrid membrane. SPES-C and MIL-101(Cr)-SO3H show good compatibility and no interfacial defects appear in the MIL-101(Cr)-SO3H/SPES-C hybrid membranes. TGA analysis results show that the thermal stability of MIL-101(Cr)-SO3H/SPES-C hybrid membranes is excellent. The introduction of MIL-101(Cr)-SO3H enhances the water uptake of MIL-101(Cr)-SO3H/SPES-C hybrid membranes and reduces the methanol permeability. The proton conductivity of MIL-101(Cr)-SO3H/SPES-C hybrid membranes increases with increasing MIL-101(Cr)-SO3H mass fraction and testing temperature. When mass fraction of MIL-101(Cr)-SO3H is 5wt%, the proton conductivity of MIL-101(Cr)-SO3H/SPES-C hybrid membrane reaches to 0.162 S·cm-1 at 80℃, which is 20.1% higher than that of the commercial Nafion membrane (0.134 S·cm-1).
The material of institute lavoisier framework (MIL-101(Cr)) was synthesized through hydrothermal synthesis. Then sulfonic groups (SO3H) were introduced into cages of MIL-101(Cr) by post sulfonation reaction to obtain MIL-101(Cr)-SO3H with proton conduction property. FTIR results confirm the successful introduction of sulfonic groups to MIL-101(Cr). SEM and XRD results indicate that the particle size of MIL-101(Cr) and MIL-101(Cr)-SO3H are in the range of nanometer scale, and no crystal structural collapse can be observed for as-prepared MIL-101(Cr)-SO3H. The elemental analysis shows that the sulfonation degree of MIL-101(Cr)-SO3H is 0.36. Then MIL-101(Cr)-SO3H is embedded into sulfonated polyarylethersulfone with cardo (SPES-C) to obtain a series of MIL-101(Cr)-SO3H/SPES-C hybrid proton exchange membranes for fuel cell application. SEM characterization demonstrates that MIL-101(Cr)-SO3H is uniformly dispersed in the MIL-101(Cr)-SO3H/SPES-C hybrid membrane. SPES-C and MIL-101(Cr)-SO3H show good compatibility and no interfacial defects appear in the MIL-101(Cr)-SO3H/SPES-C hybrid membranes. TGA analysis results show that the thermal stability of MIL-101(Cr)-SO3H/SPES-C hybrid membranes is excellent. The introduction of MIL-101(Cr)-SO3H enhances the water uptake of MIL-101(Cr)-SO3H/SPES-C hybrid membranes and reduces the methanol permeability. The proton conductivity of MIL-101(Cr)-SO3H/SPES-C hybrid membranes increases with increasing MIL-101(Cr)-SO3H mass fraction and testing temperature. When mass fraction of MIL-101(Cr)-SO3H is 5wt%, the proton conductivity of MIL-101(Cr)-SO3H/SPES-C hybrid membrane reaches to 0.162 S·cm-1 at 80℃, which is 20.1% higher than that of the commercial Nafion membrane (0.134 S·cm-1).
2020, 37(3): 512-518.
doi: 10.13801/j.cnki.fhclxb.20190521.001
Abstract:
The bisphenol A type cyanate resin (CE) was modified with diglycidyloxypropyloctaphenyl double-decker silsesquioxane (EP-DDSQ) as a modifier to prepare the EP-DDSQ/CE composite. The results show that EP-DDSQ accelerates the curing reaction rate of EP-DDSQ/CE composites. When the mass fraction of EP-DDSQ is 1wt%, the impact strength, flexural strength and flexural modulus of EP-DDSQ/CE composites are 16.9 kJ/m2, 123.6 MPa and 3.37 GPa, which are 80.5%, 21.6% and 14.0% higher than the pure CE, respectively, indicating that the proper amount of EP-DDSQ can simultaneously improve the toughness and strength of EP-DDSQ/CE composites. The thermogravimetric and dynamic mechanical analysis results show that the glass transition temperature, initial decomposition temperature and residual mass of the EP-DDSQ/CE composites increases with the addition of appropriate amount of EP-DDSQ, and the maximum decomposition temperature remains basically unchanged. The dielectric performance test results show that the dielectric constant and dielectric loss of EP-DDSQ/CE composites have a tendency to decrease, indicating that the addition of EP-DDSQ gives the EP-DDSQ/CE composites better dielectric properties.
The bisphenol A type cyanate resin (CE) was modified with diglycidyloxypropyloctaphenyl double-decker silsesquioxane (EP-DDSQ) as a modifier to prepare the EP-DDSQ/CE composite. The results show that EP-DDSQ accelerates the curing reaction rate of EP-DDSQ/CE composites. When the mass fraction of EP-DDSQ is 1wt%, the impact strength, flexural strength and flexural modulus of EP-DDSQ/CE composites are 16.9 kJ/m2, 123.6 MPa and 3.37 GPa, which are 80.5%, 21.6% and 14.0% higher than the pure CE, respectively, indicating that the proper amount of EP-DDSQ can simultaneously improve the toughness and strength of EP-DDSQ/CE composites. The thermogravimetric and dynamic mechanical analysis results show that the glass transition temperature, initial decomposition temperature and residual mass of the EP-DDSQ/CE composites increases with the addition of appropriate amount of EP-DDSQ, and the maximum decomposition temperature remains basically unchanged. The dielectric performance test results show that the dielectric constant and dielectric loss of EP-DDSQ/CE composites have a tendency to decrease, indicating that the addition of EP-DDSQ gives the EP-DDSQ/CE composites better dielectric properties.
2020, 37(3): 519-529.
doi: 10.13801/j.cnki.fhclxb.20190523.001
Abstract:
Six types of telechelic polyimides with terminal alkynyl groups (API) were prepared from 3,4'-oxydiphthalic anhydride, 1,3-bis(aminopropyl)tetramethyldisiloxane and m-amino phenylacetylene or p-aminophenyl propargyl ether. The T300 carbon fiber cloth (T300 cloth) reinforced API (T300 cloth/API) composites were also prepared by hot press molding. The structure and properties of the API resins and the T300 cloth/API composites were studied by FTIR, 1H NMR, DSC, TGA, DMA and other methods. The results show that the six API resins have good solubility and good processability. The processing window of six API resins becomes wider as the molecular weight of the API resins increases. The processability of the API resins with terminal propargyloxy groups (API-e) is better than that of the API resins with terminal ethynyl groups (API-a). The thermal stability of the cured API resins decreases with the increasing of molecular weight. The temperature at 5% mass loss (Td5) and residual yield at 800℃ of the cured API-a resins are higher than that of the cured API-e resins, which are 473.7℃ and 48.8%, respectively. The glass transition temperature (Tg) of the T300 cloth/API composites can reach up to 220℃. The mechanical properties of T300 cloth/API composites increase with the increase of the molecular weight of API matrices. And the T300 cloth/API-e composites have better mechanical properties than the T300 cloth/API-a composites at room temperature and 200℃. The flexural strength, tensile strength and interlayer shear strength (ILSS) of the T300 cloth/API-e composites are 636.5 MPa, 406.1 MPa and 48.4 MPa at room temperature, respectively. The flexural strength and ILSS of T300 cloth/API-e composites at 200℃ are 381.9 MPa and 33.9 MPa, respectively.
Six types of telechelic polyimides with terminal alkynyl groups (API) were prepared from 3,4'-oxydiphthalic anhydride, 1,3-bis(aminopropyl)tetramethyldisiloxane and m-amino phenylacetylene or p-aminophenyl propargyl ether. The T300 carbon fiber cloth (T300 cloth) reinforced API (T300 cloth/API) composites were also prepared by hot press molding. The structure and properties of the API resins and the T300 cloth/API composites were studied by FTIR, 1H NMR, DSC, TGA, DMA and other methods. The results show that the six API resins have good solubility and good processability. The processing window of six API resins becomes wider as the molecular weight of the API resins increases. The processability of the API resins with terminal propargyloxy groups (API-e) is better than that of the API resins with terminal ethynyl groups (API-a). The thermal stability of the cured API resins decreases with the increasing of molecular weight. The temperature at 5% mass loss (Td5) and residual yield at 800℃ of the cured API-a resins are higher than that of the cured API-e resins, which are 473.7℃ and 48.8%, respectively. The glass transition temperature (Tg) of the T300 cloth/API composites can reach up to 220℃. The mechanical properties of T300 cloth/API composites increase with the increase of the molecular weight of API matrices. And the T300 cloth/API-e composites have better mechanical properties than the T300 cloth/API-a composites at room temperature and 200℃. The flexural strength, tensile strength and interlayer shear strength (ILSS) of the T300 cloth/API-e composites are 636.5 MPa, 406.1 MPa and 48.4 MPa at room temperature, respectively. The flexural strength and ILSS of T300 cloth/API-e composites at 200℃ are 381.9 MPa and 33.9 MPa, respectively.
2020, 37(3): 530-538.
doi: 10.13801/j.cnki.fhclxb.20190620.002
Abstract:
Lignin(Lig) and a flame retardancy of P-N-B were added to wood flour/high density polyethylene (WF/HDPE)mixture alone or in combination to prepare Lig-WF/HDPE composites by extrusion. The role of Lig in Lig-WF/HDPE composites flame retardation was investigated. The results of cone calorimeter show that Lig can effectively reduce the heat release rate of Lig-WF/HDPE composites and increase the quantity of residues. The flame retardant capacity of Lig-WF/HDPE composites is optimum when Lig is added at 15wt% level, however, the total smoke production is high. When Lig and flame retardancy of P-N-B are added together, the smoke release of (P-N-B)-Lig-WF/HDPE composites is obviously reduced and the flame retardancy is furthermore improved. When the Lig is 5wt% and flame retardancy of P-N-B is 10wt%, the limiting oxygen index of (P-N-B)-Lig-WF/HDPE composite increases from 24.3 to 27.3 when flame retardancy of (P-N-B) and Lig is not added. In addition, the combination of Lig and flame retardancy of P-N-B improves the mechanical properties of (P-N-B)-Lig-WF/HDPE composites comparing to using them separately.
Lignin(Lig) and a flame retardancy of P-N-B were added to wood flour/high density polyethylene (WF/HDPE)mixture alone or in combination to prepare Lig-WF/HDPE composites by extrusion. The role of Lig in Lig-WF/HDPE composites flame retardation was investigated. The results of cone calorimeter show that Lig can effectively reduce the heat release rate of Lig-WF/HDPE composites and increase the quantity of residues. The flame retardant capacity of Lig-WF/HDPE composites is optimum when Lig is added at 15wt% level, however, the total smoke production is high. When Lig and flame retardancy of P-N-B are added together, the smoke release of (P-N-B)-Lig-WF/HDPE composites is obviously reduced and the flame retardancy is furthermore improved. When the Lig is 5wt% and flame retardancy of P-N-B is 10wt%, the limiting oxygen index of (P-N-B)-Lig-WF/HDPE composite increases from 24.3 to 27.3 when flame retardancy of (P-N-B) and Lig is not added. In addition, the combination of Lig and flame retardancy of P-N-B improves the mechanical properties of (P-N-B)-Lig-WF/HDPE composites comparing to using them separately.
2020, 37(3): 539-545.
doi: 10.13801/j.cnki.fhclxb.20190527.002
Abstract:
In order to improve the electrical and mechanical properties of carbon fiber/epoxy (CF/EP) composite, the 12K CF was prepared into CF/EP prepreg using the integrated process of carbon fiber spreading and infiltration. The thickness of CF/EP prepreg was 0.02 mm, 0.03 mm, 0.08 mm and 0.10 mm, respectively. Then CF/EP composite unidirectional laminate was fabricated by the molding process. The influence of the microstructure structure on the resistivity of CF/EP composite laminate, the resistivity of the CF/EP composite laminate as a function of temperature and the response of the laminate resistivity under tensile load were analyzed and tested. The results show that the proportion of the resin-rich pocket with larger area in the CF/EP composite unidirectional laminate is reduced as the prepreg thickness is reduced from 0.10 mm to 0.02 mm, and the resistivity of the CF/EP composite along the thickness direction decreases from 151.3 Ω·cm to 32.1 Ω·cm. This improves the electrical conductivity of CF/EP composite by about 5 times. As the temperature increases, the resistivity of the CF/EP composite laminate decreases gradually, and the rate of resistivity declination of the thick prepreg laminate in the thickness direction is larger than that of the thin prepreg laminate. The resistivity of the CF/EP composite laminate made of thin prepreg under loading has high stability, indicating that the thin layer of prepreg helps to improve the electrical properties of CF/EP composite and the ability of load bearing, thus obtaining higher mechanical properties and electrical properties. The experimental results provide the basis for the structure-functional integration design of the CF/EP composite.
In order to improve the electrical and mechanical properties of carbon fiber/epoxy (CF/EP) composite, the 12K CF was prepared into CF/EP prepreg using the integrated process of carbon fiber spreading and infiltration. The thickness of CF/EP prepreg was 0.02 mm, 0.03 mm, 0.08 mm and 0.10 mm, respectively. Then CF/EP composite unidirectional laminate was fabricated by the molding process. The influence of the microstructure structure on the resistivity of CF/EP composite laminate, the resistivity of the CF/EP composite laminate as a function of temperature and the response of the laminate resistivity under tensile load were analyzed and tested. The results show that the proportion of the resin-rich pocket with larger area in the CF/EP composite unidirectional laminate is reduced as the prepreg thickness is reduced from 0.10 mm to 0.02 mm, and the resistivity of the CF/EP composite along the thickness direction decreases from 151.3 Ω·cm to 32.1 Ω·cm. This improves the electrical conductivity of CF/EP composite by about 5 times. As the temperature increases, the resistivity of the CF/EP composite laminate decreases gradually, and the rate of resistivity declination of the thick prepreg laminate in the thickness direction is larger than that of the thin prepreg laminate. The resistivity of the CF/EP composite laminate made of thin prepreg under loading has high stability, indicating that the thin layer of prepreg helps to improve the electrical properties of CF/EP composite and the ability of load bearing, thus obtaining higher mechanical properties and electrical properties. The experimental results provide the basis for the structure-functional integration design of the CF/EP composite.
2020, 37(3): 546-552.
doi: 10.13801/j.cnki.fhclxb.20190917.005
Abstract:
The BN fiber-graphene nanoplatelets/polypropylene (BN fiber-GNP/PP) high thermal conductivity electrical insulation composite was prepared by melt blending. The effects of BN fiber content and length on the thermal insulation properties of BN fiber-GNP/PP composites were investigated by finite element simulation, SEM, XRD and thermal conductivity test results. The results show that the increase of BN fiber content and length in BN fiber-GNP/PP composites can increase the range of GNP distribution and the contact probability of BN fiber with GNP. At 7wt% GNP content, the addition of 100 μm BN fiber at 20wt% makes the thermal conductivity of BN fiber-GNP/PP composites 4.2 times higher than PP, while the electrical insulation is slightly improved. The simulation results show that the addition of high content of 100 μm BN fiber tends to complete the thermal network of BN fiber-GNP/PP composites and reduce the area of local heat flux. Under the influence of the "synergistic effect" of flake GNP and fibrous BN two-phase filler, GNP and BN fibers form a special "dual network" structure as "islands" and "bridges", respectively. The BN fiber acts as a high thermal conductivity "bridge" to block the formation of conductive pathways between adjacent GNP. The thermal insulation properties of the BN fiber-GNP/PP composite are improved.
The BN fiber-graphene nanoplatelets/polypropylene (BN fiber-GNP/PP) high thermal conductivity electrical insulation composite was prepared by melt blending. The effects of BN fiber content and length on the thermal insulation properties of BN fiber-GNP/PP composites were investigated by finite element simulation, SEM, XRD and thermal conductivity test results. The results show that the increase of BN fiber content and length in BN fiber-GNP/PP composites can increase the range of GNP distribution and the contact probability of BN fiber with GNP. At 7wt% GNP content, the addition of 100 μm BN fiber at 20wt% makes the thermal conductivity of BN fiber-GNP/PP composites 4.2 times higher than PP, while the electrical insulation is slightly improved. The simulation results show that the addition of high content of 100 μm BN fiber tends to complete the thermal network of BN fiber-GNP/PP composites and reduce the area of local heat flux. Under the influence of the "synergistic effect" of flake GNP and fibrous BN two-phase filler, GNP and BN fibers form a special "dual network" structure as "islands" and "bridges", respectively. The BN fiber acts as a high thermal conductivity "bridge" to block the formation of conductive pathways between adjacent GNP. The thermal insulation properties of the BN fiber-GNP/PP composite are improved.
2020, 37(3): 553-561.
doi: 10.13801/j.cnki.fhclxb.20190611.006
Abstract:
The melamine pyrophosphate (MPP) was introduced into bamboo fiber/polypropylene (BF/PP) mats as flame retardant to prepare a series of MPP-BF/PP composites. The effects of MPP mass fractions on mechanical properties, microstructures of MPP-BF/PP composites were investigated by mechanical test and SEM. The flame retardancy, thermal stability and water resistance of MPP-BF/PP composites were studied using limiting oxygen index (LOI), thermal gavimetric (TG) and water absorption as index. The results show that the bending strength and impact strength of the MPP-BF/PP composites increase firstly and then show a decreased trend when the mass fraction of MPP is less than 30wt%. As the mass fraction of MPP increases up to 5wt%, the bending strength and impact strength of MPP-BF/PP composites reach the optimal values. MPP distributes evenly in the MPP-BF/PP composites, but the surface roughness of cross section increases with the mass fraction of MPP increasing, which means the interface compatibility between MPP and PP becomes worse, reducing the mechanical properties of MPP-BF/PP composites. The results of LOI indicate that the flame retardancy of MPP-BF/PP composites is enhanced with the mass fraction of MPP increasing. When the mass fraction of MPP reaches to 30wt%, the LOI is 24.3%. TG test reveals that the addition of MPP enhances the thermal decomposition temperature and char residues of MPP-BF/PP composites, contributing to the flame retardancy. The test of water resistance of MPP-BF/PP composites indicates that the water absorption and thickness swelling values are almost not affected by the mass fraction of MPP when less than 20wt%. According to fuzzy comprehensive evaluation, the MPP-BF/PP composites will achieve the optimal properties when the mass fraction of MPP is 10wt%.
The melamine pyrophosphate (MPP) was introduced into bamboo fiber/polypropylene (BF/PP) mats as flame retardant to prepare a series of MPP-BF/PP composites. The effects of MPP mass fractions on mechanical properties, microstructures of MPP-BF/PP composites were investigated by mechanical test and SEM. The flame retardancy, thermal stability and water resistance of MPP-BF/PP composites were studied using limiting oxygen index (LOI), thermal gavimetric (TG) and water absorption as index. The results show that the bending strength and impact strength of the MPP-BF/PP composites increase firstly and then show a decreased trend when the mass fraction of MPP is less than 30wt%. As the mass fraction of MPP increases up to 5wt%, the bending strength and impact strength of MPP-BF/PP composites reach the optimal values. MPP distributes evenly in the MPP-BF/PP composites, but the surface roughness of cross section increases with the mass fraction of MPP increasing, which means the interface compatibility between MPP and PP becomes worse, reducing the mechanical properties of MPP-BF/PP composites. The results of LOI indicate that the flame retardancy of MPP-BF/PP composites is enhanced with the mass fraction of MPP increasing. When the mass fraction of MPP reaches to 30wt%, the LOI is 24.3%. TG test reveals that the addition of MPP enhances the thermal decomposition temperature and char residues of MPP-BF/PP composites, contributing to the flame retardancy. The test of water resistance of MPP-BF/PP composites indicates that the water absorption and thickness swelling values are almost not affected by the mass fraction of MPP when less than 20wt%. According to fuzzy comprehensive evaluation, the MPP-BF/PP composites will achieve the optimal properties when the mass fraction of MPP is 10wt%.
2020, 37(3): 562-572.
doi: 10.13801/j.cnki.fhclxb.20190625.002
Abstract:
Non-isothermal differential scanning calorimetry(DSC) method was used to study the curing behavior of Al2O3/epoxy (EP) composites for extra-high voltage gas insulated switchgear (GIS). The DSC curves were subjected to peak separation treatment, and the apparent activation energy of different reaction stages was studied by the equal conversion rate method. According to the Málek criterion, the model type of the curing behavior of Al2O3/EP composites was obtained, and the kinetic parameters of different reaction stages and the curing kinetic equation of the Al2O3/EP composites were obtained. The microstructure of Al2O3/EP composites was observed by SEM, dynamic thermomechanical properties and creep behavior of Al2O3/EP composites were analyzed by dynamic mechanical analysis(DMA), and the long-term creep properties were predicted by time-temperature superposition. The results indicate that DSC heat flow curves are bimodal of Al2O3/EP composites. The apparent activation energies of Al2O3/EP composites at two reaction stages are 35.3 kJ/mol and 48.1 kJ/mol, respectively. The curing behavior of Al2O3/EP composite system at different curing stages can be well described by the Sestak-Berggren model. Al2O3 particles are uniformly dispersed in the resin matrix, and the addition of Al2O3 filler causes cracks to be deflected. The storage modulus (E') of Al2O3/EP composites decreases with increasing temperature, and the peak of loss tangent (tanδ) corresponds to the glass transition temperature (Tg) is 120.03℃. Creep resistance of Al2O3/EP composites decreases with increase of tensile stress and temperature. The creep rate decreases over time.
Non-isothermal differential scanning calorimetry(DSC) method was used to study the curing behavior of Al2O3/epoxy (EP) composites for extra-high voltage gas insulated switchgear (GIS). The DSC curves were subjected to peak separation treatment, and the apparent activation energy of different reaction stages was studied by the equal conversion rate method. According to the Málek criterion, the model type of the curing behavior of Al2O3/EP composites was obtained, and the kinetic parameters of different reaction stages and the curing kinetic equation of the Al2O3/EP composites were obtained. The microstructure of Al2O3/EP composites was observed by SEM, dynamic thermomechanical properties and creep behavior of Al2O3/EP composites were analyzed by dynamic mechanical analysis(DMA), and the long-term creep properties were predicted by time-temperature superposition. The results indicate that DSC heat flow curves are bimodal of Al2O3/EP composites. The apparent activation energies of Al2O3/EP composites at two reaction stages are 35.3 kJ/mol and 48.1 kJ/mol, respectively. The curing behavior of Al2O3/EP composite system at different curing stages can be well described by the Sestak-Berggren model. Al2O3 particles are uniformly dispersed in the resin matrix, and the addition of Al2O3 filler causes cracks to be deflected. The storage modulus (E') of Al2O3/EP composites decreases with increasing temperature, and the peak of loss tangent (tanδ) corresponds to the glass transition temperature (Tg) is 120.03℃. Creep resistance of Al2O3/EP composites decreases with increase of tensile stress and temperature. The creep rate decreases over time.
2020, 37(3): 573-580.
doi: 10.13801/j.cnki.fhclxb.20190705.001
Abstract:
The interface-regulating mechanisms of atmospheric air plasma modification for ultra high molecular weight polyethylene (UHMWPE) fiber/epoxy composites were investigated from the perspective of engineering application. The influence of plasma treatment duration on UHMWPE fiber surface properties and the interfacial adhesion of UHMWPE/epoxy composites was mainly researched. The SEM and surface water absorption tests were chosen as characterization methods to study the effects on UHMWPE fiber surface morphologies and surface wettability, respectively. Furthermore, the UHMWPE/epoxy composite interfacial adhesion was characterized based on both of the fiber surface adhesion test and the interlaminar shear strength test of laminates by using the stretching load and the bending load, respectively. The results show that the UHMWPE fiber surface adhesion is increased by 84.0% after plasma treatment for only 4 s, and specially the interlaminar shear strength value of UHMWPE/epoxy composite laminates is increased from 7.01 MPa to 15.81 MPa with the increment of 125.5%. These results indicate that the interfacial properties of UHMWPE/epoxy composites can be regulated notably and effectively by UHMWPE fiber surface air-plasma treatment, providing a theoretical basis for its subsequent expanded engineering application.
The interface-regulating mechanisms of atmospheric air plasma modification for ultra high molecular weight polyethylene (UHMWPE) fiber/epoxy composites were investigated from the perspective of engineering application. The influence of plasma treatment duration on UHMWPE fiber surface properties and the interfacial adhesion of UHMWPE/epoxy composites was mainly researched. The SEM and surface water absorption tests were chosen as characterization methods to study the effects on UHMWPE fiber surface morphologies and surface wettability, respectively. Furthermore, the UHMWPE/epoxy composite interfacial adhesion was characterized based on both of the fiber surface adhesion test and the interlaminar shear strength test of laminates by using the stretching load and the bending load, respectively. The results show that the UHMWPE fiber surface adhesion is increased by 84.0% after plasma treatment for only 4 s, and specially the interlaminar shear strength value of UHMWPE/epoxy composite laminates is increased from 7.01 MPa to 15.81 MPa with the increment of 125.5%. These results indicate that the interfacial properties of UHMWPE/epoxy composites can be regulated notably and effectively by UHMWPE fiber surface air-plasma treatment, providing a theoretical basis for its subsequent expanded engineering application.
2020, 37(3): 581-590.
doi: 10.13801/j.cnki.fhclxb.20190611.005
Abstract:
In order to improve the bonding strength of Ti/polyimide by monomer polymerization (PMR) resin interface and improve the mechanical properties of Ti-carbon fiber(CF)/PMR super hybrid laminates, the effect of the addition of multi-walled carbon nanotubes (MWCNTs) on the mechanical properties of Ti-CF/PMR super hybrid laminates was investigated in this paper. The MWCNTs with different mass fractions (0wt%, 2.5wt%, 5.0wt% and 7.5wt%) were uniformly dispersed in PMR resin by ultrasonic dispersion. The mode Ⅰ interlaminar fracture toughness tests were experimentally conducted to explore the effect of adding MWCNTs on the interface properties of Ti-CF/PMR super hybrid laminates. Then the MWCNTs of optimized content was added to the PMR adhesive layer and CF/PMR resin to conduct bending test so as to explore the effect of adding MWCNTs on the mechanical properties of Ti-CF/PMR super hybrid laminates. SEM was used to investigate the interface morphology and enhancement mechanism of Ti-CF/PMR super hybrid laminates. The results reveal that the mode Ⅰ interlaminar fracture toughness of the PMR adhesive layer for Ti-CF/PMR super hybrid laminates is improved by 74% with 5.0wt% MWCNTs; when 5.0wt% MWCNTs are added into both the PMR adhesive layer and CF/PMR resin, the bending property of Ti-CF/PMR super hybrid laminates is improved by 42% compared with those without adding MWCNTs. This is because the MWCNTs are uniformly dispersed in the PMR adhesive layer and CF/PMR resin, and it can disperse and bear the load transferred from the interface layer to the fiber layer, using its own pull-out, fracture, bridging, debonding to absorb and consume the fracture energy to further improve the bending performance of the Ti-CF/PMR super hybrid laminates.
In order to improve the bonding strength of Ti/polyimide by monomer polymerization (PMR) resin interface and improve the mechanical properties of Ti-carbon fiber(CF)/PMR super hybrid laminates, the effect of the addition of multi-walled carbon nanotubes (MWCNTs) on the mechanical properties of Ti-CF/PMR super hybrid laminates was investigated in this paper. The MWCNTs with different mass fractions (0wt%, 2.5wt%, 5.0wt% and 7.5wt%) were uniformly dispersed in PMR resin by ultrasonic dispersion. The mode Ⅰ interlaminar fracture toughness tests were experimentally conducted to explore the effect of adding MWCNTs on the interface properties of Ti-CF/PMR super hybrid laminates. Then the MWCNTs of optimized content was added to the PMR adhesive layer and CF/PMR resin to conduct bending test so as to explore the effect of adding MWCNTs on the mechanical properties of Ti-CF/PMR super hybrid laminates. SEM was used to investigate the interface morphology and enhancement mechanism of Ti-CF/PMR super hybrid laminates. The results reveal that the mode Ⅰ interlaminar fracture toughness of the PMR adhesive layer for Ti-CF/PMR super hybrid laminates is improved by 74% with 5.0wt% MWCNTs; when 5.0wt% MWCNTs are added into both the PMR adhesive layer and CF/PMR resin, the bending property of Ti-CF/PMR super hybrid laminates is improved by 42% compared with those without adding MWCNTs. This is because the MWCNTs are uniformly dispersed in the PMR adhesive layer and CF/PMR resin, and it can disperse and bear the load transferred from the interface layer to the fiber layer, using its own pull-out, fracture, bridging, debonding to absorb and consume the fracture energy to further improve the bending performance of the Ti-CF/PMR super hybrid laminates.
2020, 37(3): 591-600.
doi: 10.13801/j.cnki.fhclxb.20190528.003
Abstract:
To improve the specific energy absorption of thin-walled structure, carbon fiber reinforced polymer(CFRP) composite-aluminum (CFRP-Al) square tube with different braiding angles were prepared by circular braiding technology. The CFRP-Al square tubes with various braiding angles, tube lengths and tube thicknesses were subjected to quasi-static axial compression test to study the effect of the braiding angle of CFRP composite layer on the deformation mode and specific energy absorption. The results show that the CFRP composite layer can decrease the flexibility and prevent Euler buckling mode. The CFRP composite layer with large braiding angle can effectively carry the transverse tension caused by the folding of tube, and sequentially prevent corner splitting. In addition, the specific energy absorption of CFRP-Al square tube improves with the increase of braiding angle.
To improve the specific energy absorption of thin-walled structure, carbon fiber reinforced polymer(CFRP) composite-aluminum (CFRP-Al) square tube with different braiding angles were prepared by circular braiding technology. The CFRP-Al square tubes with various braiding angles, tube lengths and tube thicknesses were subjected to quasi-static axial compression test to study the effect of the braiding angle of CFRP composite layer on the deformation mode and specific energy absorption. The results show that the CFRP composite layer can decrease the flexibility and prevent Euler buckling mode. The CFRP composite layer with large braiding angle can effectively carry the transverse tension caused by the folding of tube, and sequentially prevent corner splitting. In addition, the specific energy absorption of CFRP-Al square tube improves with the increase of braiding angle.
2020, 37(3): 601-608.
doi: 10.13801/j.cnki.fhclxb.20190918.001
Abstract:
To effectively predict the compressive instability load and failure mode of honeycomb sandwich composite structure, the buckling stability of the honeycomb sandwich composite structure under axial compressive loads based on the multi-scale numerical analysis model was studied. The macro-micro multiscale model of the honeycomb sandwich composite structure was established using the improved general cell model and the ABAQUS user-defined subroutine interface. The compressive instability load of the honeycomb sandwich composite structure was predicted and compared with the experimental results. The results show that the numerical model established in this paper can effectively predict the buckling load and failure mode of the honeycomb sandwich composite structure under compression load. The predicted first-order buckling load of the structure is 128.12 kN, which have an error of 4.58% compared with the experimental result. The failure modes of the sandwich structure are first buckling instability and then rapid failure.
To effectively predict the compressive instability load and failure mode of honeycomb sandwich composite structure, the buckling stability of the honeycomb sandwich composite structure under axial compressive loads based on the multi-scale numerical analysis model was studied. The macro-micro multiscale model of the honeycomb sandwich composite structure was established using the improved general cell model and the ABAQUS user-defined subroutine interface. The compressive instability load of the honeycomb sandwich composite structure was predicted and compared with the experimental results. The results show that the numerical model established in this paper can effectively predict the buckling load and failure mode of the honeycomb sandwich composite structure under compression load. The predicted first-order buckling load of the structure is 128.12 kN, which have an error of 4.58% compared with the experimental result. The failure modes of the sandwich structure are first buckling instability and then rapid failure.
2020, 37(3): 609-617.
doi: 10.13801/j.cnki.fhclxb.20190701.001
Abstract:
A novel Bi@Bi4Ti3O12/TiO2 plasmonic composite fibers was synthesized in situ by solvothermal method using electrospun titanium dioxide nanofibers as matrix and reactant, and ethylene glycol as reductant. The XRD, SEM, high power transmission electron microscope (HRTEM), XPS, UV-visible diffuse-reflectance spectrum and photoluminescence (PL) spectra were employed to explore the structural and properties of Bi@Bi4Ti3O12/TiO2 composite fiber. The results indicate that when the reaction temperature is lower than 210℃, the Bi4Ti3O12 nanosheets on the surface of Bi@Bi4Ti3O12/TiO2 composite fiber become smaller and thicker gradually with the increasing reaction temperature, and a large number of metal Bi nanoparticles are evenly formed. When the reaction temperature is higher than 210℃, not only the nanosheets accumulate and deform, but also the metal Bi on the surface is oxidized to Bi2O3. The Bi@Bi4Ti3O12/TiO2 composite fiber showed excellent photocatalytic efficiency for the degradation of Rhodamine B, with a Rhodamine B degradation rate of 97.8% after visible light irradiation for 5 h. Adjusting reaction temperature not only exerts a pivotal effect on the morphological structure and phase composition, but also affects the photocatalytic capability of the Bi@Bi4Ti3O12/TiO2 plasmonic composite fibers. The improvement of visible-light photocatalytic performance of Bi@Bi4Ti3O12/TiO2 composite fiber is mainly attributed to the formation of high-quality heterojunctions between Bi4Ti3O12 and TiO2, the plasma resonance effect of metal Bi, and the synergistic effect of plasma resonance effect and heterojunction.
A novel Bi@Bi4Ti3O12/TiO2 plasmonic composite fibers was synthesized in situ by solvothermal method using electrospun titanium dioxide nanofibers as matrix and reactant, and ethylene glycol as reductant. The XRD, SEM, high power transmission electron microscope (HRTEM), XPS, UV-visible diffuse-reflectance spectrum and photoluminescence (PL) spectra were employed to explore the structural and properties of Bi@Bi4Ti3O12/TiO2 composite fiber. The results indicate that when the reaction temperature is lower than 210℃, the Bi4Ti3O12 nanosheets on the surface of Bi@Bi4Ti3O12/TiO2 composite fiber become smaller and thicker gradually with the increasing reaction temperature, and a large number of metal Bi nanoparticles are evenly formed. When the reaction temperature is higher than 210℃, not only the nanosheets accumulate and deform, but also the metal Bi on the surface is oxidized to Bi2O3. The Bi@Bi4Ti3O12/TiO2 composite fiber showed excellent photocatalytic efficiency for the degradation of Rhodamine B, with a Rhodamine B degradation rate of 97.8% after visible light irradiation for 5 h. Adjusting reaction temperature not only exerts a pivotal effect on the morphological structure and phase composition, but also affects the photocatalytic capability of the Bi@Bi4Ti3O12/TiO2 plasmonic composite fibers. The improvement of visible-light photocatalytic performance of Bi@Bi4Ti3O12/TiO2 composite fiber is mainly attributed to the formation of high-quality heterojunctions between Bi4Ti3O12 and TiO2, the plasma resonance effect of metal Bi, and the synergistic effect of plasma resonance effect and heterojunction.
2020, 37(3): 618-625.
doi: 10.13801/j.cnki.fhclxb.20190610.001
Abstract:
In order to improve the electrochemical performance of LiNi0.5Co0.2Mn0.3O2 (NCM), WO3 coated NCM (NCM@WO3) composite cathode materials were synthesized with a liquid phase evaporation process. The structure and morphology of the NCM@WO3 composite were characterized by XRD, SEM and TEM. The electrochemical performance of the NCM@WO3 composite was characterized by charge-discharge test, cyclic voltammetry and electrochemical impedance spectroscopy. The results show that the NCM@WO3 composite with 3wt% WO3 has the best performance, it delivers an initial discharge capacity of 179.9 mA·hg-1 with a low irreversible capacity loss of 42.4 mA·hg-1 at 0.5 C, and the capacity retention after 50 cycles is 98.3%. The improved electrochemical properties of the NCM@WO3 composite are mainly attributed to the WO3 coating, which improves the lithium ions diffusion rate and suppresses the interface reaction between the cathode and the electrolyte.
In order to improve the electrochemical performance of LiNi0.5Co0.2Mn0.3O2 (NCM), WO3 coated NCM (NCM@WO3) composite cathode materials were synthesized with a liquid phase evaporation process. The structure and morphology of the NCM@WO3 composite were characterized by XRD, SEM and TEM. The electrochemical performance of the NCM@WO3 composite was characterized by charge-discharge test, cyclic voltammetry and electrochemical impedance spectroscopy. The results show that the NCM@WO3 composite with 3wt% WO3 has the best performance, it delivers an initial discharge capacity of 179.9 mA·hg-1 with a low irreversible capacity loss of 42.4 mA·hg-1 at 0.5 C, and the capacity retention after 50 cycles is 98.3%. The improved electrochemical properties of the NCM@WO3 composite are mainly attributed to the WO3 coating, which improves the lithium ions diffusion rate and suppresses the interface reaction between the cathode and the electrolyte.
2020, 37(3): 626-634.
doi: 10.13801/j.cnki.fhclxb.20190715.001
Abstract:
In this paper, one novel thermosetting liquid precursor for SiC was prepared (hyperbranched polycarbosilane, Tri-ImPCS, with viscosity about 3 000 mP·as at 25℃), and fast net shaping of carbon fiber/SiC composites (CF/SiC) by high pressure injection was primarily investigated. Liquid epoxy RE1820 (viscosity about 500 mP·as at 25℃) acts as effective curing agent of Tri-ImPCS, and thermal cure could proceed at room temperature or comparably low heated conditions (<100℃); thermal pyrolysis of thermally cured precursor under atmospheric pressure results into a non-foamed and shape-changeless ceramic monolith. The ceramic yield of Tri-ImPCS under N2 atmosphere is as high as 74.8% at 900℃ (based on the cured precursor). C and Si elements are uniformly distributed at micro-scale with the atomic ratio of 1.26. Using a joint-process of prepreg molding and high-pressure injection, the fast manufacturing and rapid densification was successfully realized in CF/SiC's processing. The liquid precursor of Tri-ImPCS is an ideal candidate of SiC precursor of SiC matrixed composites.
In this paper, one novel thermosetting liquid precursor for SiC was prepared (hyperbranched polycarbosilane, Tri-ImPCS, with viscosity about 3 000 mP·as at 25℃), and fast net shaping of carbon fiber/SiC composites (CF/SiC) by high pressure injection was primarily investigated. Liquid epoxy RE1820 (viscosity about 500 mP·as at 25℃) acts as effective curing agent of Tri-ImPCS, and thermal cure could proceed at room temperature or comparably low heated conditions (<100℃); thermal pyrolysis of thermally cured precursor under atmospheric pressure results into a non-foamed and shape-changeless ceramic monolith. The ceramic yield of Tri-ImPCS under N2 atmosphere is as high as 74.8% at 900℃ (based on the cured precursor). C and Si elements are uniformly distributed at micro-scale with the atomic ratio of 1.26. Using a joint-process of prepreg molding and high-pressure injection, the fast manufacturing and rapid densification was successfully realized in CF/SiC's processing. The liquid precursor of Tri-ImPCS is an ideal candidate of SiC precursor of SiC matrixed composites.
2020, 37(3): 635-641.
doi: 10.13801/j.cnki.fhclxb.20190517.001
Abstract:
Low cost, impurity-free and low thermal conductivity Al2O3-SiO2 composite aerogel were prepared from AlCl3·6H2O derived gel through ion exchange technology and sol-gel method by dipping silicon in tetraethyl orthosilicate (TEOS), subsequently surface modification and ambient pressure drying were employed. The effects of different organosilane modifiers on the structure and thermal insulation properties of the Al2O3-SiO2 composite aerogels were explored. The results show that Al2O3-SiO2 composite aerogel shows the most uniform microstructure in the neutral (pH=7) modified environment of trimethoxy methylsilane (MTMS). The SiO2 and Al2O3 phases mainly exist in amorphous form. MTMS is more effective in reducing the -OH group on the surface of Al2O3-SiO2 wet gel to form Si-O-Si and Al-O-Si groups. The specific surface area and pore volume of Al2O3-SiO2 aerogels are as high as 574 m2/g and 2.3 cm3/g, respectively, and the thermal conductivity is as low as 0.029 W(m·K)-1. The above research provides support for the application of aerogel materials in the field of thermal insulation.
Low cost, impurity-free and low thermal conductivity Al2O3-SiO2 composite aerogel were prepared from AlCl3·6H2O derived gel through ion exchange technology and sol-gel method by dipping silicon in tetraethyl orthosilicate (TEOS), subsequently surface modification and ambient pressure drying were employed. The effects of different organosilane modifiers on the structure and thermal insulation properties of the Al2O3-SiO2 composite aerogels were explored. The results show that Al2O3-SiO2 composite aerogel shows the most uniform microstructure in the neutral (pH=7) modified environment of trimethoxy methylsilane (MTMS). The SiO2 and Al2O3 phases mainly exist in amorphous form. MTMS is more effective in reducing the -OH group on the surface of Al2O3-SiO2 wet gel to form Si-O-Si and Al-O-Si groups. The specific surface area and pore volume of Al2O3-SiO2 aerogels are as high as 574 m2/g and 2.3 cm3/g, respectively, and the thermal conductivity is as low as 0.029 W(m·K)-1. The above research provides support for the application of aerogel materials in the field of thermal insulation.
2020, 37(3): 642-649.
doi: 10.13801/j.cnki.fhclxb.20190722.001
Abstract:
To investigate the effects of fiber directionality and interface types on the tensile properties, 3D 4-directional and 3D 5-directional braided SiC/SiC composites were prepared by polymer infiltration and pyrolysis (PIP) process, and combined interface of PyC/SiC composite was introduced to the braided SiC preform surface for modification. The results indicate that 3D 5-directional SiC/SiC composite shows great advantages in tensile properties over 3D 4-directional SiC/SiC composite. The tensile strength, modulus and fracture strain of 3D 5-directional SiC/SiC composite are respectively 1.22 times, 1.25 times and 1.43 times of the corresponding properties of the 3D 4-directional SiC/SiC composite. Furthermore, 3D 5-directional SiC/SiC composites have better strength reliability than that of 3D 4-directional SiC/SiC composite. This is due to the increase of fiber content in the stress direction of the 3D 5-directional SiC/SiC composites, which limits the rotation and deformation of the fiber under the external force, resulting in shaping and stabilizing. With the interface of PyC/SiC, the tensile strength, tensile modulus and fracture strain of 3D 5-directional SiC/SiC composite increase by 21.7%, 15.0% and 11.0%, respectively. The interface can protect the fiber and adjust the thermal stress between the fiber and the matrix, which can induce the deflection and bifurcation of cracks and consume energy, resulting in the improvement of tensile properties of the 3D 5-directional SiC/SiC composites.
To investigate the effects of fiber directionality and interface types on the tensile properties, 3D 4-directional and 3D 5-directional braided SiC/SiC composites were prepared by polymer infiltration and pyrolysis (PIP) process, and combined interface of PyC/SiC composite was introduced to the braided SiC preform surface for modification. The results indicate that 3D 5-directional SiC/SiC composite shows great advantages in tensile properties over 3D 4-directional SiC/SiC composite. The tensile strength, modulus and fracture strain of 3D 5-directional SiC/SiC composite are respectively 1.22 times, 1.25 times and 1.43 times of the corresponding properties of the 3D 4-directional SiC/SiC composite. Furthermore, 3D 5-directional SiC/SiC composites have better strength reliability than that of 3D 4-directional SiC/SiC composite. This is due to the increase of fiber content in the stress direction of the 3D 5-directional SiC/SiC composites, which limits the rotation and deformation of the fiber under the external force, resulting in shaping and stabilizing. With the interface of PyC/SiC, the tensile strength, tensile modulus and fracture strain of 3D 5-directional SiC/SiC composite increase by 21.7%, 15.0% and 11.0%, respectively. The interface can protect the fiber and adjust the thermal stress between the fiber and the matrix, which can induce the deflection and bifurcation of cracks and consume energy, resulting in the improvement of tensile properties of the 3D 5-directional SiC/SiC composites.
2020, 37(3): 650-661.
doi: 10.13801/j.cnki.fhclxb.20190529.004
Abstract:
The 1-butyl-3-methylimidazolium phosphotungstic acid ionic liquid([BMIM]3PW12O40), was prepared from N-methylimidazole, bromo-n-butane and phosphotungstic acid. It was loaded on amino-functionalized Fe3O4(Fe3O4-NH2) by ultrasonic impregnation method. A jujube-like structure[BMIM]3PW12O40/Fe3O4-NH2 magnetic composite was obtained. The[BMIM]3PW12O40/Fe3O4-NH2 magnetic composite was characterized by FTIR, XRD, XPS, TEM, vibrating sample magnetometer (VSM) and SEM. The[BMIM]3PW12O40/Fe3O4-NH2 magnetic composite was used as catalyst for the oxidation of n-octane simulated oil samples with dibenzothiophene (DBT) as sulfur source, via hydrogen peroxide as oxidant. The effects of ultrasonic time, H2O2 usage amount, reactive temperature and catalyst dosage on desulfurization were investigated. The catalytic desulfurization mechanism was discussed. The results showed that the optimized catalytic degradation rate reached 88.13% with the H2O2 to DBT n(O):n(S) molar ratio of 8:1 at 323 K when 0.5 g/L[BMIM]3PW12O40/Fe3O4-NH2 was used for the desulfurization of simulated oil sample with the concentration of dibenzothiophene at 500 mg/g for 10 mins. After reused for 5 times, the catalytic degradation rate decreased only 2.51%, which indicated that the[BMIM]3PW12O40/Fe3O4-NH2 magnetic composite was of good catalytic desulfurization performance and can be reused. The primary desulfurization mechanism study shows that the catalytic active center might be the heteropoly acid anion of the[BMIM]3PW12O40/Fe3O4-NH2 magnetic composite, with the Fe3O4-NH2 serving as a supporter and the ionic liquid as a cooperative compatibilizer, respectively.
The 1-butyl-3-methylimidazolium phosphotungstic acid ionic liquid([BMIM]3PW12O40), was prepared from N-methylimidazole, bromo-n-butane and phosphotungstic acid. It was loaded on amino-functionalized Fe3O4(Fe3O4-NH2) by ultrasonic impregnation method. A jujube-like structure[BMIM]3PW12O40/Fe3O4-NH2 magnetic composite was obtained. The[BMIM]3PW12O40/Fe3O4-NH2 magnetic composite was characterized by FTIR, XRD, XPS, TEM, vibrating sample magnetometer (VSM) and SEM. The[BMIM]3PW12O40/Fe3O4-NH2 magnetic composite was used as catalyst for the oxidation of n-octane simulated oil samples with dibenzothiophene (DBT) as sulfur source, via hydrogen peroxide as oxidant. The effects of ultrasonic time, H2O2 usage amount, reactive temperature and catalyst dosage on desulfurization were investigated. The catalytic desulfurization mechanism was discussed. The results showed that the optimized catalytic degradation rate reached 88.13% with the H2O2 to DBT n(O):n(S) molar ratio of 8:1 at 323 K when 0.5 g/L[BMIM]3PW12O40/Fe3O4-NH2 was used for the desulfurization of simulated oil sample with the concentration of dibenzothiophene at 500 mg/g for 10 mins. After reused for 5 times, the catalytic degradation rate decreased only 2.51%, which indicated that the[BMIM]3PW12O40/Fe3O4-NH2 magnetic composite was of good catalytic desulfurization performance and can be reused. The primary desulfurization mechanism study shows that the catalytic active center might be the heteropoly acid anion of the[BMIM]3PW12O40/Fe3O4-NH2 magnetic composite, with the Fe3O4-NH2 serving as a supporter and the ionic liquid as a cooperative compatibilizer, respectively.
2020, 37(3): 662-673.
doi: 10.13801/j.cnki.fhclxb.20190529.001
Abstract:
Using thiourea and cadmium nitrate tetrahydrate as precursors, the mass ratios of graphite phase carbon nitride(g-C3N4) and CdS with low ratio and high ratio were designed in this experiment. The CdS-g-C3N4 composite photocatalysts were prepared by simple soft chemical method. Their structures and properties were characterized by SEM, XRD, UV-visible diffuse-reflectance spectrum (UV-Vis DRS), FTIR and physical adsorption. The photocatalytic activity of the CdS-g-C3N4 composite photocatalyst under visible light was investigated by photocatalytic degradation experiments of NO. The results show that CdS-g-C3N4 composite photocatalyst with low CdS mass ratio has the best degradation effect when mass ratio of CdS to g-C3N4 is 7%, and the degradation rate is 31%; among the CdS-g-C3N4 composite photocatalysts with low g-C3N4 mass ratio, the sample with 5% mass ratio of g-C3N4 to CdS has the best degradation performance of 36%. When the mass ratio of CdS to g-C3N4 is 4:1 in a large proportion range, the degradation efficiency is the highest, reaching 33%. Moreover, when the mass ratio of g-C3N4 to CdS is 5%, the CdS-g-C3N4 composite photocatalyst has good stability and best degradation effect.
Using thiourea and cadmium nitrate tetrahydrate as precursors, the mass ratios of graphite phase carbon nitride(g-C3N4) and CdS with low ratio and high ratio were designed in this experiment. The CdS-g-C3N4 composite photocatalysts were prepared by simple soft chemical method. Their structures and properties were characterized by SEM, XRD, UV-visible diffuse-reflectance spectrum (UV-Vis DRS), FTIR and physical adsorption. The photocatalytic activity of the CdS-g-C3N4 composite photocatalyst under visible light was investigated by photocatalytic degradation experiments of NO. The results show that CdS-g-C3N4 composite photocatalyst with low CdS mass ratio has the best degradation effect when mass ratio of CdS to g-C3N4 is 7%, and the degradation rate is 31%; among the CdS-g-C3N4 composite photocatalysts with low g-C3N4 mass ratio, the sample with 5% mass ratio of g-C3N4 to CdS has the best degradation performance of 36%. When the mass ratio of CdS to g-C3N4 is 4:1 in a large proportion range, the degradation efficiency is the highest, reaching 33%. Moreover, when the mass ratio of g-C3N4 to CdS is 5%, the CdS-g-C3N4 composite photocatalyst has good stability and best degradation effect.
2020, 37(3): 674-680.
doi: 10.13801/j.cnki.fhclxb.20190729.002
Abstract:
The poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P(3HB-co-4HB)) was dissolved by chloroform and N,N-dimethyl formamide (DMF) to prepare the spinning solution, and then P(3HB-co-4HB) nanofiber scaffold was fabricated by electrospinning. The P(3HB-co-4HB) nanofiber scaffold was coated with sodium alginate (SA) to obtain the P(3HB-co-4HB)@SA composite fiber membrane. SEM, specific surface area meter and atomic absorption spectroscopy were used to characterize fiber morphology, specific surface area, and residual ion concentration of P(3HB-co-4HB)@SA composite fiber membrane. The results show that when the spinning solution concentration is 12%, P(3HB-co-4HB) nanofibers exhibit a uniform morphology. With the static voltage increasing, the diameter of P(3HB-co-4HB) fiber decreases first and then increases. The P(3HB-co-4HB) scaffold material can increase the specific surface area of SA by 3.9 times. P(3HB-co-4HB)@SA composite fiber membrane has a maximum adsorption capacity of 26.25 mg/g and 36.25 mg/g for Cu2+ ions and Pb2+ ions, respectively, which is converted into SA adsorption capacity of 364.58 mg/g and 503.47 mg/g, respectively.
The poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P(3HB-co-4HB)) was dissolved by chloroform and N,N-dimethyl formamide (DMF) to prepare the spinning solution, and then P(3HB-co-4HB) nanofiber scaffold was fabricated by electrospinning. The P(3HB-co-4HB) nanofiber scaffold was coated with sodium alginate (SA) to obtain the P(3HB-co-4HB)@SA composite fiber membrane. SEM, specific surface area meter and atomic absorption spectroscopy were used to characterize fiber morphology, specific surface area, and residual ion concentration of P(3HB-co-4HB)@SA composite fiber membrane. The results show that when the spinning solution concentration is 12%, P(3HB-co-4HB) nanofibers exhibit a uniform morphology. With the static voltage increasing, the diameter of P(3HB-co-4HB) fiber decreases first and then increases. The P(3HB-co-4HB) scaffold material can increase the specific surface area of SA by 3.9 times. P(3HB-co-4HB)@SA composite fiber membrane has a maximum adsorption capacity of 26.25 mg/g and 36.25 mg/g for Cu2+ ions and Pb2+ ions, respectively, which is converted into SA adsorption capacity of 364.58 mg/g and 503.47 mg/g, respectively.
2020, 37(3): 681-689.
doi: 10.13801/j.cnki.fhclxb.20190719.002
Abstract:
The sodium alginate (SA)-based filtration membrane is an ideal membrane separation material for wastewater containing Pb(Ⅱ). It is very valuable but lacking to study the effect of adsorption behavior on membrane filtration. The graphene oxide (GO) and urea were added into SA and crosslinked with CaCl2 solution to prepare GO/SA composite membrane to investigate its adsorption performance for Pb(Ⅱ) in aqueous solution. The effects of Pb(Ⅱ) initial concentration, GO mass fraction, initial pH value, adsorption time, adsorption-desorption times and other conditions on the adsorption effect were investigated by static adsorption experiments. The adsorption kinetics and adsorption thermodynamics analysis were also carried out on the adsorption process. The adsorption mechanism of Pb(Ⅱ) on GO/SA composite membrane was analyzed by FTIR-ATR and XPS. The experimental results show that the adsorption amount of Pb(Ⅱ) is positively correlated with the initial concentration of Pb(Ⅱ), the adsorption effect is optimal at pH=5, and GO mass fraction of 0.3wt% is the optimal ratio; the adsorption process conforms to the pseudo second-order kinetic model; The thermodynamic isotherm adsorption process accords with the Langmuir isotherm adsorption model. At temperature of 318 K, the adsorption capacity of GO/SA composite membrane obtained by the Langmuir model is 320.51 mg·g-1. The adsorption mechanism of GO/SA alginate composite membrane on Pb(Ⅱ) is mainly physical adsorption.
The sodium alginate (SA)-based filtration membrane is an ideal membrane separation material for wastewater containing Pb(Ⅱ). It is very valuable but lacking to study the effect of adsorption behavior on membrane filtration. The graphene oxide (GO) and urea were added into SA and crosslinked with CaCl2 solution to prepare GO/SA composite membrane to investigate its adsorption performance for Pb(Ⅱ) in aqueous solution. The effects of Pb(Ⅱ) initial concentration, GO mass fraction, initial pH value, adsorption time, adsorption-desorption times and other conditions on the adsorption effect were investigated by static adsorption experiments. The adsorption kinetics and adsorption thermodynamics analysis were also carried out on the adsorption process. The adsorption mechanism of Pb(Ⅱ) on GO/SA composite membrane was analyzed by FTIR-ATR and XPS. The experimental results show that the adsorption amount of Pb(Ⅱ) is positively correlated with the initial concentration of Pb(Ⅱ), the adsorption effect is optimal at pH=5, and GO mass fraction of 0.3wt% is the optimal ratio; the adsorption process conforms to the pseudo second-order kinetic model; The thermodynamic isotherm adsorption process accords with the Langmuir isotherm adsorption model. At temperature of 318 K, the adsorption capacity of GO/SA composite membrane obtained by the Langmuir model is 320.51 mg·g-1. The adsorption mechanism of GO/SA alginate composite membrane on Pb(Ⅱ) is mainly physical adsorption.
2020, 37(3): 690-695.
doi: 10.13801/j.cnki.fhclxb.20190611.004
Abstract:
The tribology behavior of nano ZnO/nitrile-butadiene rubber (NBR) composites was studied by molecular simulation. The investigation was conducted using molecular simulation to examine the radius of gyration, relative concentration of atom and shear behavior of nano ZnO/NBR composites. The microscopic mechanism of tribology behavior of nano ZnO/NBR composites was discussed. The results show that compared with the pure NBR, the nano ZnO/NBR composites owns a smaller radius of gyration and the flexibility of rubber molecular chain is decreased. Compared with the nano ZnO/NBR composites, the pure NBR owns a higher relative concentration of atom at the frictional interface. The peak value of relative concentration of atom at the top and bottom friction surface of pure NBR is 6.4% and 4.3% greater than that of nano ZnO/NBR composites, respectively. The rigidity of molecular chain in nano ZnO/NBR composites is enhanced and the energy dissipation is decreased. The improved tribology property is achieved in the nano ZnO/NBR composites.
The tribology behavior of nano ZnO/nitrile-butadiene rubber (NBR) composites was studied by molecular simulation. The investigation was conducted using molecular simulation to examine the radius of gyration, relative concentration of atom and shear behavior of nano ZnO/NBR composites. The microscopic mechanism of tribology behavior of nano ZnO/NBR composites was discussed. The results show that compared with the pure NBR, the nano ZnO/NBR composites owns a smaller radius of gyration and the flexibility of rubber molecular chain is decreased. Compared with the nano ZnO/NBR composites, the pure NBR owns a higher relative concentration of atom at the frictional interface. The peak value of relative concentration of atom at the top and bottom friction surface of pure NBR is 6.4% and 4.3% greater than that of nano ZnO/NBR composites, respectively. The rigidity of molecular chain in nano ZnO/NBR composites is enhanced and the energy dissipation is decreased. The improved tribology property is achieved in the nano ZnO/NBR composites.
2020, 37(3): 696-706.
doi: 10.13801/j.cnki.fhclxb.20190729.001
Abstract:
In order to study the influence factors of bonding properties of glass fiber reinforced polymer (GFRP) composite bars and engineered cementitious composites (ECC), pull-out tests on forty-two GFRP/ECC testing specimens were designed and carried out. The influences of the surface form of GFRP composite bar, the diameter of GFRP composite bar, the strength of ECC matrix, and the thickness of the concrete cover on the bonding properties of the interface between GFRP composite bars and ECC were analyzed. The results show that there are mainly three failure modes, namely pull-out failure, peeling off of resin, and splitting failure. The bonding strength at the interface of GFRP composite bars with ribbed surface form is about 66% higher than those plain round GFRP composite bars. When the thickness of ECC concrete cover increases from 1.5D to 4D, the bonding strength of GFRP/ECC increases by about 58% (D is diameter of GFRP composite bars). When the diameter of CFRP composite varies between 12~18 mm, the bonding strength of GFRP/ECC decreases with the increase of CFRP composite bar diameter. When the strength of ECC increases from 33.7 MPa to 73.3 MPa, the bonding strength of GFRP/ECC increases about 3 times. Increasing the complexity of the surface form of GFRP composite bars, or to some extent increasing the thickness of ECC matrix protective layer and the strength of ECC can help to improve the bonding strength between GFRP composite bars and ECC.
In order to study the influence factors of bonding properties of glass fiber reinforced polymer (GFRP) composite bars and engineered cementitious composites (ECC), pull-out tests on forty-two GFRP/ECC testing specimens were designed and carried out. The influences of the surface form of GFRP composite bar, the diameter of GFRP composite bar, the strength of ECC matrix, and the thickness of the concrete cover on the bonding properties of the interface between GFRP composite bars and ECC were analyzed. The results show that there are mainly three failure modes, namely pull-out failure, peeling off of resin, and splitting failure. The bonding strength at the interface of GFRP composite bars with ribbed surface form is about 66% higher than those plain round GFRP composite bars. When the thickness of ECC concrete cover increases from 1.5D to 4D, the bonding strength of GFRP/ECC increases by about 58% (D is diameter of GFRP composite bars). When the diameter of CFRP composite varies between 12~18 mm, the bonding strength of GFRP/ECC decreases with the increase of CFRP composite bar diameter. When the strength of ECC increases from 33.7 MPa to 73.3 MPa, the bonding strength of GFRP/ECC increases about 3 times. Increasing the complexity of the surface form of GFRP composite bars, or to some extent increasing the thickness of ECC matrix protective layer and the strength of ECC can help to improve the bonding strength between GFRP composite bars and ECC.
2020, 37(3): 707-715.
doi: 10.13801/j.cnki.fhclxb.20190624.003
Abstract:
In order to study the flexural capacity of corroded prestressed concrete beams under chloride environment, five pretensioned prestressed concrete beams were manufactured, and subjected to accelerated corrosion for 0 d, 7 d, 14 d, 28 d and 42 d by electrochemical method, then four points bending tests were carried out on all beams. The influence of different corrosion level on the natural frequency of prestressed concrete beams, the slip of steel strands, the structural deformation, crack propagation, failure mode and ultimate bearing capacity were researched. The results indicate that corrosion in chloride environment affects slightly the high-order frequency of prestressed concrete beams, and increases the first natural frequency of prestressed concrete beams. After 28 d, the corrosion cracks are large and part of the concrete falls off, the first natural frequency decreases rapidly. Slight corrosion has little effects on flexural behavior of prestressed concrete beams, and the flexural behavior decreases significantly with the increase of corrosion level. After 42 d corrosion, the ultimate deflection decreases by 18.7%, the flexural capacity decreases by 17.3%, and the ductility decreases by 19%. The slip rate between the corroded steel strand and concrete increases, and the ultimate slip value increases from 5 μm to 11.4 μm. Corrosion affects slightly the development of crack height, and promotes the expansion of crack width. After yielding, the cracking rate of bottom cracks increase from 0.0062 mm/kN to 0.0252 mm/kN. Based on the test, the loading process of corroded beam was simulated through finite element software ANSYS, the errors of ultimate load and ultimate slip value between the simulated value and the experimental value are less than 5% and 10%, respectively, the simulated values are in good agreement with the experimental data.
In order to study the flexural capacity of corroded prestressed concrete beams under chloride environment, five pretensioned prestressed concrete beams were manufactured, and subjected to accelerated corrosion for 0 d, 7 d, 14 d, 28 d and 42 d by electrochemical method, then four points bending tests were carried out on all beams. The influence of different corrosion level on the natural frequency of prestressed concrete beams, the slip of steel strands, the structural deformation, crack propagation, failure mode and ultimate bearing capacity were researched. The results indicate that corrosion in chloride environment affects slightly the high-order frequency of prestressed concrete beams, and increases the first natural frequency of prestressed concrete beams. After 28 d, the corrosion cracks are large and part of the concrete falls off, the first natural frequency decreases rapidly. Slight corrosion has little effects on flexural behavior of prestressed concrete beams, and the flexural behavior decreases significantly with the increase of corrosion level. After 42 d corrosion, the ultimate deflection decreases by 18.7%, the flexural capacity decreases by 17.3%, and the ductility decreases by 19%. The slip rate between the corroded steel strand and concrete increases, and the ultimate slip value increases from 5 μm to 11.4 μm. Corrosion affects slightly the development of crack height, and promotes the expansion of crack width. After yielding, the cracking rate of bottom cracks increase from 0.0062 mm/kN to 0.0252 mm/kN. Based on the test, the loading process of corroded beam was simulated through finite element software ANSYS, the errors of ultimate load and ultimate slip value between the simulated value and the experimental value are less than 5% and 10%, respectively, the simulated values are in good agreement with the experimental data.
2020, 37(3): 716-723.
doi: 10.13801/j.cnki.fhclxb.20190624.002
Abstract:
As a non-metallic mineral with a wide range of sources, coal is an ideal raw material for the preparation of porous carbon. A porous carbon was prepared by 1/3 coking coal as raw material using NaOH and KOH as activators, and the specific electrochemical properties of sulfur/porous carbon composite cathode material were analyzed. The results show that the porous carbon prepared by the activation of NaOH or KOH alone has a specific surface area of 1 649 m2/g and 1 867 m2/g, respectively. The specific surface area of porous carbon activated by the mixture of NaOH and KOH is greatly reduced. When the mass ratio of NaOH to KOH is 1:1, the specific surface area of porous carbon is least which is 290 m2/g. The electrical properties of sulfur/porous carbon composite cathode material activated by 1:1 mass fraction of NaOH to KOH mixed activation are better than other cathode materials activated by NaOH and KOH respectively. The first discharge capacity is 790 mA·h/g at 0.2 C and the coulombic efficiency is 93.16%. The discharge capacity is as high as 740 mA·h/g after 100 cycles. The effect of coal-based porous carbon pore size distribution on electrochemical performance was also analyzed.
As a non-metallic mineral with a wide range of sources, coal is an ideal raw material for the preparation of porous carbon. A porous carbon was prepared by 1/3 coking coal as raw material using NaOH and KOH as activators, and the specific electrochemical properties of sulfur/porous carbon composite cathode material were analyzed. The results show that the porous carbon prepared by the activation of NaOH or KOH alone has a specific surface area of 1 649 m2/g and 1 867 m2/g, respectively. The specific surface area of porous carbon activated by the mixture of NaOH and KOH is greatly reduced. When the mass ratio of NaOH to KOH is 1:1, the specific surface area of porous carbon is least which is 290 m2/g. The electrical properties of sulfur/porous carbon composite cathode material activated by 1:1 mass fraction of NaOH to KOH mixed activation are better than other cathode materials activated by NaOH and KOH respectively. The first discharge capacity is 790 mA·h/g at 0.2 C and the coulombic efficiency is 93.16%. The discharge capacity is as high as 740 mA·h/g after 100 cycles. The effect of coal-based porous carbon pore size distribution on electrochemical performance was also analyzed.
2020, 37(3): 724-730.
doi: 10.13801/j.cnki.fhclxb.20190612.002
Abstract:
Selective surface dissolution (SSD) method was utilized to partially dissolve the surfaces of cellulose fibers and consolidate into porous structure. After carbonization under Ar, a highly porous carbon by SSD (HPC-SSD) material was obtained, which exhibits high specific surface area (SSA) and 3D porous structure. Through SEM, BET, FTIR, XRD and electrochemical tests, the effects of two different activation pretreatment methods on the morphology, chemical composition, SSA and capacitive performance of HPC-SSD material were systematically studied. As compared with HPC carbonized directly from cellulose fibers, HPC-SSD material exhibits more stable pore-forming process, which facilitates to create a large number of micropores. The specific capacitance of HPC-SSD material pretreated by H2O→acetone→N, N-dimethylacetamide is as high as 226 F·g-1 (in a two-electrode configuation), which is 4.5 times that of HPC, and 40% higher than that of HPC-SSD material without any activation pretreatment.
Selective surface dissolution (SSD) method was utilized to partially dissolve the surfaces of cellulose fibers and consolidate into porous structure. After carbonization under Ar, a highly porous carbon by SSD (HPC-SSD) material was obtained, which exhibits high specific surface area (SSA) and 3D porous structure. Through SEM, BET, FTIR, XRD and electrochemical tests, the effects of two different activation pretreatment methods on the morphology, chemical composition, SSA and capacitive performance of HPC-SSD material were systematically studied. As compared with HPC carbonized directly from cellulose fibers, HPC-SSD material exhibits more stable pore-forming process, which facilitates to create a large number of micropores. The specific capacitance of HPC-SSD material pretreated by H2O→acetone→N, N-dimethylacetamide is as high as 226 F·g-1 (in a two-electrode configuation), which is 4.5 times that of HPC, and 40% higher than that of HPC-SSD material without any activation pretreatment.
2020, 37(3): 731-739.
doi: 10.13801/j.cnki.fhclxb.20190624.001
Abstract:
The polyaniline coated CoFe Prussian blue analogue(CoFePBA@PANI) composites were synthesized to seek high electrochemical performance. The structure and morphology of CoFePBA@PANI composite were characterized by XRD, FTIR, SEM and TEM. The electrochemical properties of CoFePBA@PANI composite were investigated by cyclic voltammetry (CV), galvanostatic charge-discharge test and electrochemical impedance spectroscopy (EIS). By using phytic acid (PA) as a chelating agent, the PANI is coated on the surface of CoFePBA to form the CoFePBA@PANI composite with core-shell structures. In the mixed acidic electrolyte of 0.5 mol/L Na2SO4 and H2SO4, the CoFePBA@PANI composite exhibits specific capacitances as high as 401.2 F/g and 367.3 F/g at the current density of 1 A/g and 10 A/g, respectively.
The polyaniline coated CoFe Prussian blue analogue(CoFePBA@PANI) composites were synthesized to seek high electrochemical performance. The structure and morphology of CoFePBA@PANI composite were characterized by XRD, FTIR, SEM and TEM. The electrochemical properties of CoFePBA@PANI composite were investigated by cyclic voltammetry (CV), galvanostatic charge-discharge test and electrochemical impedance spectroscopy (EIS). By using phytic acid (PA) as a chelating agent, the PANI is coated on the surface of CoFePBA to form the CoFePBA@PANI composite with core-shell structures. In the mixed acidic electrolyte of 0.5 mol/L Na2SO4 and H2SO4, the CoFePBA@PANI composite exhibits specific capacitances as high as 401.2 F/g and 367.3 F/g at the current density of 1 A/g and 10 A/g, respectively.
