2017 Vol. 34, No. 6
2017, 34(6): 1167-1176.
doi: 10.13801/j.cnki.fhclxb.20161018.001
Abstract:
Conducting polymers represent a promising application prospect in the field of metal corrosion control. In order to obtain a poly(o-chloroaniline) (POCl)-nano SiC/epoxy resin composite with good anticorrosion performance, hydrochloric acid doped POCl-nano SiC composite modified material was prepared by in situ polymerization method. The structure, composition and morphology of the POCl-nano SiC composite were characterized by FTIR, UV-vis, XRD, TGA, XPS and SEM. The POCl-nano SiC composite modified material was used as the filler, and epoxy resin was used as the film forming substance, hydrochloric acid doped POCl-nano SiC/epoxy resin composite coatings with 3wt%, 5wt% and 8wt% POCl-nano SiC contents were prepared on the carbon steel substrates, and the fracture surface morphologies of the coatings were observed by SEM. Its anticorrosion performances were studied by Tafel polarization curve and electrochemical impedance spectroscopy in 3.5% NaCl solution. The results demonstrates that the POCl-nano SiC/epoxy resin composite coatings whose POCl-nano SiC content is 5wt% shows better anticorrosion performance, with a corrosion rate of 2.78×10-3 mm/y and the corrosion protection efficiency up to 90.45%. It indicates that the proper amount of POCl-nano SiC as the reinforcing phase of the epoxy resin coating would reduce the pinhole defects of the coating, under the infiltration of corrosion medium, a passivation layer formed on the surface of carbon steel. Nano SiC particles act as a barrier, which was analogous to the fence structure and blocked the penetration of gas molecules and corrosion solution toward metal substrate spatial structurally.
Conducting polymers represent a promising application prospect in the field of metal corrosion control. In order to obtain a poly(o-chloroaniline) (POCl)-nano SiC/epoxy resin composite with good anticorrosion performance, hydrochloric acid doped POCl-nano SiC composite modified material was prepared by in situ polymerization method. The structure, composition and morphology of the POCl-nano SiC composite were characterized by FTIR, UV-vis, XRD, TGA, XPS and SEM. The POCl-nano SiC composite modified material was used as the filler, and epoxy resin was used as the film forming substance, hydrochloric acid doped POCl-nano SiC/epoxy resin composite coatings with 3wt%, 5wt% and 8wt% POCl-nano SiC contents were prepared on the carbon steel substrates, and the fracture surface morphologies of the coatings were observed by SEM. Its anticorrosion performances were studied by Tafel polarization curve and electrochemical impedance spectroscopy in 3.5% NaCl solution. The results demonstrates that the POCl-nano SiC/epoxy resin composite coatings whose POCl-nano SiC content is 5wt% shows better anticorrosion performance, with a corrosion rate of 2.78×10-3 mm/y and the corrosion protection efficiency up to 90.45%. It indicates that the proper amount of POCl-nano SiC as the reinforcing phase of the epoxy resin coating would reduce the pinhole defects of the coating, under the infiltration of corrosion medium, a passivation layer formed on the surface of carbon steel. Nano SiC particles act as a barrier, which was analogous to the fence structure and blocked the penetration of gas molecules and corrosion solution toward metal substrate spatial structurally.
2017, 34(6): 1177-1184.
doi: 10.13801/j.cnki.fhclxb.20160907.004
Abstract:
In order to improve the performances of ultrahigh molecular weight polyethylene (UHMWPE), surface modification of Ti3AlC2 filled UHMWPE was studied. Ti3AlC2/UHMWPE composites were prepared by hot-press moulding technique. SEM results show that Ti3AlC2 distributes homogeneously in the matrix and the modified fillers have a better boundary integrate with the polymer matrix. Thermal analysis results show that the crystallinity and enthalpy of Ti3AlC2/UHMWPE composite decreases with the addition of Ti3AlC2, while the thermal conductivity of the composites increases. DMA results show that Ti3AlC2 improves the creep performence of Ti3AlC2/UHMWPE composites effectively, which is benefited from the increase of hardness and rigidity of the polymer matrix and the capability of resistance to deform under external stress is enhanced. Additionally, tribology analysis shows that the right amount of Ti3AlC2 (mass fraction≤15wt%) filled UHMWPE can improve the anti-friction performance of the composites effectively, while the worn surface morphology analysis of Ti3AlC2/UHMWPE composites shows that the friction and wear mechanism of the composite transform from adhesive wear to abrasive wear.
In order to improve the performances of ultrahigh molecular weight polyethylene (UHMWPE), surface modification of Ti3AlC2 filled UHMWPE was studied. Ti3AlC2/UHMWPE composites were prepared by hot-press moulding technique. SEM results show that Ti3AlC2 distributes homogeneously in the matrix and the modified fillers have a better boundary integrate with the polymer matrix. Thermal analysis results show that the crystallinity and enthalpy of Ti3AlC2/UHMWPE composite decreases with the addition of Ti3AlC2, while the thermal conductivity of the composites increases. DMA results show that Ti3AlC2 improves the creep performence of Ti3AlC2/UHMWPE composites effectively, which is benefited from the increase of hardness and rigidity of the polymer matrix and the capability of resistance to deform under external stress is enhanced. Additionally, tribology analysis shows that the right amount of Ti3AlC2 (mass fraction≤15wt%) filled UHMWPE can improve the anti-friction performance of the composites effectively, while the worn surface morphology analysis of Ti3AlC2/UHMWPE composites shows that the friction and wear mechanism of the composite transform from adhesive wear to abrasive wear.
2017, 34(6): 1185-1190.
doi: 10.13801/j.cnki.fhclxb.20160919.005
Abstract:
The phase change microcapsulates containing dodecanol(DA) were fabricated using melamine-formaldehyde (MF) or polyethylene glycol 200 modified melamine-formaldehyde (PMF) resin as the shell by in situ polymerization. Wood flour/high-density polyethylene (WF/HDPE) composites filled with MF shelled microcapsules (DA@MF) or PMF shelled microcapsules (DA@PMF) were prepared, respectively. The synthesized DA@PMF and DA@PMF filled WF/HDPE composites (DA@MF-WF/HDPE, DA@PMF -WF/HDPE) were characterized by infrared thermal imaging, DSC and TG analysis. The results show that the cooling and melting enthalpy of DA@PMF is increased by 35 J/g and 21.5 J/g, respectively, and the rapid mass loss temperature is delayed to 19.9℃; The thermal properties of DA@PMF-WF/HDPE indicate that DA@PMF are successfully incorporated into the WF/HDPE composites and there is little damage during the preparation process; DA@PMF -WF/HDPE are potential thermal energy storage materials based on their appropriate phase change temperature (27.2, 11.3℃), outstanding thermal enthalpy (31.6, 20.3 J/g) and perfect thermal stability (rapid mass loss at 256.9℃).
The phase change microcapsulates containing dodecanol(DA) were fabricated using melamine-formaldehyde (MF) or polyethylene glycol 200 modified melamine-formaldehyde (PMF) resin as the shell by in situ polymerization. Wood flour/high-density polyethylene (WF/HDPE) composites filled with MF shelled microcapsules (DA@MF) or PMF shelled microcapsules (DA@PMF) were prepared, respectively. The synthesized DA@PMF and DA@PMF filled WF/HDPE composites (DA@MF-WF/HDPE, DA@PMF -WF/HDPE) were characterized by infrared thermal imaging, DSC and TG analysis. The results show that the cooling and melting enthalpy of DA@PMF is increased by 35 J/g and 21.5 J/g, respectively, and the rapid mass loss temperature is delayed to 19.9℃; The thermal properties of DA@PMF-WF/HDPE indicate that DA@PMF are successfully incorporated into the WF/HDPE composites and there is little damage during the preparation process; DA@PMF -WF/HDPE are potential thermal energy storage materials based on their appropriate phase change temperature (27.2, 11.3℃), outstanding thermal enthalpy (31.6, 20.3 J/g) and perfect thermal stability (rapid mass loss at 256.9℃).
2017, 34(6): 1191-1198.
doi: 10.13801/j.cnki.fhclxb.20160919.004
Abstract:
Carboxy-functionalized multi-walled carbon nanotubes(MWCNTs)/polyethylene glycol (PEG)-poly-vinyl alcohol (PVA) composite hydrogels were prepared by the freezing/thawing method. The microstructure, swelling property, tensile strength, thermal stability and conductivity of MWCNTs/PEG-PVA composite hydrogels with different mass ratios were studied. The results show that the MWCNTs/PEG-PVA hydrogel still has a porous 3D structure, but the pore size becomes smaller after the addition of MWCNTs. When the mass ratio of MWCNTs to PVA is larger than 1.0:100, the uniformity of the porous structure of the MWCNTs/PEG-PVA hydrogel decreases. With the increment of MWCNTs content, the swelling degree and tensile strength of the MWCNTs/PEG-PVA composite hydrogel increase first and then decrease. When the mass ratio of MWCNTs to PVA is 1.0:100, the swelling degree and porosity of the MWCNTs/PEG-PVA hydrogel reach the maximum (1450% and 75.8%, respectively). The tensile strength and elongation reach a maximum value of 0.97 MPa and 384.0%, respectively. The addition of MWCNTs improves the thermal stability of the composite hydrogel, and the initial thermal decomposition temperature of MWCNTs/PEG-PVA composite hydrogel increases from 235℃ to 260℃. With the increment of the amount of MWCNTs, the conductivity of the composite hydrogel increases from 1.10×10-6 S/cm to 6.96×10-4 S/cm.
Carboxy-functionalized multi-walled carbon nanotubes(MWCNTs)/polyethylene glycol (PEG)-poly-vinyl alcohol (PVA) composite hydrogels were prepared by the freezing/thawing method. The microstructure, swelling property, tensile strength, thermal stability and conductivity of MWCNTs/PEG-PVA composite hydrogels with different mass ratios were studied. The results show that the MWCNTs/PEG-PVA hydrogel still has a porous 3D structure, but the pore size becomes smaller after the addition of MWCNTs. When the mass ratio of MWCNTs to PVA is larger than 1.0:100, the uniformity of the porous structure of the MWCNTs/PEG-PVA hydrogel decreases. With the increment of MWCNTs content, the swelling degree and tensile strength of the MWCNTs/PEG-PVA composite hydrogel increase first and then decrease. When the mass ratio of MWCNTs to PVA is 1.0:100, the swelling degree and porosity of the MWCNTs/PEG-PVA hydrogel reach the maximum (1450% and 75.8%, respectively). The tensile strength and elongation reach a maximum value of 0.97 MPa and 384.0%, respectively. The addition of MWCNTs improves the thermal stability of the composite hydrogel, and the initial thermal decomposition temperature of MWCNTs/PEG-PVA composite hydrogel increases from 235℃ to 260℃. With the increment of the amount of MWCNTs, the conductivity of the composite hydrogel increases from 1.10×10-6 S/cm to 6.96×10-4 S/cm.
Preparation and thermal performances of 3D graphene network/epoxy resin thermal interface composites
2017, 34(6): 1199-1204.
doi: 10.13801/j.cnki.fhclxb.20160919.002
Abstract:
Graphene modified epoxy resin, which can be used widely in the microelectronic device area, has attracted a great deal attention due to its excellent thermal conductivity and mechanical strength. However, the reported thermal conductivities of thermal interface composite (TIMs) from different research groups shows obvious discrepancy even if the adopted mass fraction of graphene is identical. After research, we found that the reduction degree is closely related to the thermal performance of resulting TIMs. Thereby, it is difficult to evaluate the RGO acting as conductive filler under uniform standard. In this study, 3D graphene network was employed as the conductive filler to prepare a series thermal interface composites with epoxy resin. The influence from mass fraction of adopted 3D graphene network on the thermal conductivity of resulting thermal interface composites was studied, and the influences on the thermal performance stability under high temperature and mechanical properties were revealed. The findings are useful to build a completed evaluation system for estimate the ability of graphene using as conductive filler.
Graphene modified epoxy resin, which can be used widely in the microelectronic device area, has attracted a great deal attention due to its excellent thermal conductivity and mechanical strength. However, the reported thermal conductivities of thermal interface composite (TIMs) from different research groups shows obvious discrepancy even if the adopted mass fraction of graphene is identical. After research, we found that the reduction degree is closely related to the thermal performance of resulting TIMs. Thereby, it is difficult to evaluate the RGO acting as conductive filler under uniform standard. In this study, 3D graphene network was employed as the conductive filler to prepare a series thermal interface composites with epoxy resin. The influence from mass fraction of adopted 3D graphene network on the thermal conductivity of resulting thermal interface composites was studied, and the influences on the thermal performance stability under high temperature and mechanical properties were revealed. The findings are useful to build a completed evaluation system for estimate the ability of graphene using as conductive filler.
2017, 34(6): 1205-1211.
doi: 10.13801/j.cnki.fhclxb.20160927.002
Abstract:
The graphene oxide/SiO2 composite (GO/SiO2) was fabricated using graphene oxide (GO), ethylsilicate (TEOS) as the raw material, oxygen polyoxyethylene-polypropylene-polyoxyethylene (P123) as the surfactant. Through a static test, different experimental parameters such as solution pH, dosing, adsorption time and initial concentration were examined to investigate their effects on adsorption of cadmium by GO/SiO2. The GO/SiO2 composite was investigated by FTIR, XRD, SEM and EDS. The experimental results show that the optimal pH, dosing, adsorption time is 8.5, 0.25 g/L, and 100 min, respectively. The equilibrium data fit well with the pseudo-second-order model(R2 ≈1) and Freundlich model(R2 ≈1). XRD indicate that SiO2 has been successfully combined with GO. FTIR and SEM indicate that GO/SiO2 structure itself keeps unchanged, and the GO/SiO2 has good adsorption effect on Cd(Ⅱ), in which ionexchange of —OH and —COOH play a major role, with the assistant of complexation reaction of Si—OH in the adsorption.
The graphene oxide/SiO2 composite (GO/SiO2) was fabricated using graphene oxide (GO), ethylsilicate (TEOS) as the raw material, oxygen polyoxyethylene-polypropylene-polyoxyethylene (P123) as the surfactant. Through a static test, different experimental parameters such as solution pH, dosing, adsorption time and initial concentration were examined to investigate their effects on adsorption of cadmium by GO/SiO2. The GO/SiO2 composite was investigated by FTIR, XRD, SEM and EDS. The experimental results show that the optimal pH, dosing, adsorption time is 8.5, 0.25 g/L, and 100 min, respectively. The equilibrium data fit well with the pseudo-second-order model(R2 ≈1) and Freundlich model(R2 ≈1). XRD indicate that SiO2 has been successfully combined with GO. FTIR and SEM indicate that GO/SiO2 structure itself keeps unchanged, and the GO/SiO2 has good adsorption effect on Cd(Ⅱ), in which ionexchange of —OH and —COOH play a major role, with the assistant of complexation reaction of Si—OH in the adsorption.
2017, 34(6): 1212-1220.
doi: 10.13801/j.cnki.fhclxb.20160831.001
Abstract:
The accelerated aging tests in mixed acid medium (H2SO4, HF, HCl and HNO3 mixed solution) of glass fiber/bromide epoxy vinylester(GF/VE) composite and carbon fiber-glass fiber/bromide epoxy vinylester(CF-GF/VE) composite used in fiber reinforced plastic chimney were carried out. The changes of mass and flexural pro-perties of GF/VE and CF-GF/VE after immersing in mixed acid medium at different temperatures (25℃, 55℃, 80℃) were studied. The dynamic thermal mechanical properties and microstructures of samples were investigated to reveal the mechanism of property decline. The experimental results show that the mass gain rate of GF/VE is higher than that of CF-GF/VE when immersed under the same conditions. The diffusion activation energy of mixed acid medium in GF/VE and CF-GF/VE are 8.798 kJ·mol-1 and 10.959 kJ·mol-1, respectively. After 2 160 h aged at 80℃, the flexural strength retention rate of CF-GF/VE is 75.29%, but GF/VE is only 58.84%. DMA study finds that the glass transition temperature (Tg) of samples under normal immersion temperature decreases slightly, and it reduces significantly when samples are immersed at higher temperature. SEM study shows that the surface of specimen appears many micropores and its fiber/matrix interface occurs obvious debonding damage after aging in mixed acid medium.
The accelerated aging tests in mixed acid medium (H2SO4, HF, HCl and HNO3 mixed solution) of glass fiber/bromide epoxy vinylester(GF/VE) composite and carbon fiber-glass fiber/bromide epoxy vinylester(CF-GF/VE) composite used in fiber reinforced plastic chimney were carried out. The changes of mass and flexural pro-perties of GF/VE and CF-GF/VE after immersing in mixed acid medium at different temperatures (25℃, 55℃, 80℃) were studied. The dynamic thermal mechanical properties and microstructures of samples were investigated to reveal the mechanism of property decline. The experimental results show that the mass gain rate of GF/VE is higher than that of CF-GF/VE when immersed under the same conditions. The diffusion activation energy of mixed acid medium in GF/VE and CF-GF/VE are 8.798 kJ·mol-1 and 10.959 kJ·mol-1, respectively. After 2 160 h aged at 80℃, the flexural strength retention rate of CF-GF/VE is 75.29%, but GF/VE is only 58.84%. DMA study finds that the glass transition temperature (Tg) of samples under normal immersion temperature decreases slightly, and it reduces significantly when samples are immersed at higher temperature. SEM study shows that the surface of specimen appears many micropores and its fiber/matrix interface occurs obvious debonding damage after aging in mixed acid medium.
2017, 34(6): 1221-1229.
doi: 10.13801/j.cnki.fhclxb.20160919.003
Abstract:
A novel charring agent named as hexakis (γ-aminopropylsilanetriol) cyclotriphosphazene (HKHPCP) was synthesized by using hexachlorocyclotriphosphazene (HCCP), p-hydroxy benzaldehyde and γ-aminopropylsilanetriol (KH553). The intumescent flame retardant polypropylene (PP) matrix composites (APP-HKHPCP-NOR116/PP) was prepared using HKHPCP and ammonium polyphosphate (APP) as the anti-dripping agent and N-alkoxy hindered amine (NOR116) as the synergistic agent by the melt compounding method. The chemical structures of intermediate and HKHPCP were characterized by FTIR, 1H nuclear magnetic resonance (1H NMR) and 31P NMR. The effects of the flame retardant APP-HKHPCP-NOR116/PP on the thermal degradation, flame retardancy and char layer structure were investigated by thermogravimetric analysis (TGA), limiting oxygen index (LOI), vertical burning test (UL-94), cone calorimetric test, SEM and laser Raman spectroscopy, respectively. The TGA results show that the temperature of 5% mass loss of HKHPCP in oxygen is 300.2℃, and the residues at 1 000℃ of HKHPCP in oxygen is 34.8%. The results show that the LOI value of APP-HKHPCP-NOR116/PP is 43%, while the intumescent flame retardant loading is 30wt%. The APP-HKHPCP-NOR116/PP could reach a V-0 rating in the UL-94 tests. The cone calorimetry results indicate that heat release rate (HRR), total heat release (THR), smoke produce rate (SPR) and total smoke production (TSP) are reduced by 75.0%, 50.5%, 88.0% and 80.8%, respectively. In addition, the APP-HKHPCP-NOR116/PP can form a compact and more graphitic carbon char layer during combustion.
A novel charring agent named as hexakis (γ-aminopropylsilanetriol) cyclotriphosphazene (HKHPCP) was synthesized by using hexachlorocyclotriphosphazene (HCCP), p-hydroxy benzaldehyde and γ-aminopropylsilanetriol (KH553). The intumescent flame retardant polypropylene (PP) matrix composites (APP-HKHPCP-NOR116/PP) was prepared using HKHPCP and ammonium polyphosphate (APP) as the anti-dripping agent and N-alkoxy hindered amine (NOR116) as the synergistic agent by the melt compounding method. The chemical structures of intermediate and HKHPCP were characterized by FTIR, 1H nuclear magnetic resonance (1H NMR) and 31P NMR. The effects of the flame retardant APP-HKHPCP-NOR116/PP on the thermal degradation, flame retardancy and char layer structure were investigated by thermogravimetric analysis (TGA), limiting oxygen index (LOI), vertical burning test (UL-94), cone calorimetric test, SEM and laser Raman spectroscopy, respectively. The TGA results show that the temperature of 5% mass loss of HKHPCP in oxygen is 300.2℃, and the residues at 1 000℃ of HKHPCP in oxygen is 34.8%. The results show that the LOI value of APP-HKHPCP-NOR116/PP is 43%, while the intumescent flame retardant loading is 30wt%. The APP-HKHPCP-NOR116/PP could reach a V-0 rating in the UL-94 tests. The cone calorimetry results indicate that heat release rate (HRR), total heat release (THR), smoke produce rate (SPR) and total smoke production (TSP) are reduced by 75.0%, 50.5%, 88.0% and 80.8%, respectively. In addition, the APP-HKHPCP-NOR116/PP can form a compact and more graphitic carbon char layer during combustion.
2017, 34(6): 1230-1236.
doi: 10.13801/j.cnki.fhclxb.20160920.004
Abstract:
In order to investigate the effect of interlaminar nanofibrous membranes on permeability property of glass fiber fabrics, the super depth of field optical microscope was employed to characterize the microstructure of glass fiber fabric with different nanofiber contents. The permeability of glass-fiber preforms incorporated with interlaminar nanofibrous membranes was measured by the radial flow experiments with emphasis on the effect of the nanofiber contents on the impregnating pattern of glass-fiber preforms. The results show that the millimeter-scale regions between glass fiber bundles are filled and discretized into micron-scale regions. Both the porosity and permeability va-lues of preforms decrease with the nanofiber contents increasing. The anisotropy extent of preform was decreased as the increase of nanofiber contents. The area fraction of partially saturated regions behind resin macroscopic front increases with the nanofiber contents increasing. The area fraction of partially saturated region of preforms with the same nanofiber contents increases firstly, and then decreases with injection time increasing.
In order to investigate the effect of interlaminar nanofibrous membranes on permeability property of glass fiber fabrics, the super depth of field optical microscope was employed to characterize the microstructure of glass fiber fabric with different nanofiber contents. The permeability of glass-fiber preforms incorporated with interlaminar nanofibrous membranes was measured by the radial flow experiments with emphasis on the effect of the nanofiber contents on the impregnating pattern of glass-fiber preforms. The results show that the millimeter-scale regions between glass fiber bundles are filled and discretized into micron-scale regions. Both the porosity and permeability va-lues of preforms decrease with the nanofiber contents increasing. The anisotropy extent of preform was decreased as the increase of nanofiber contents. The area fraction of partially saturated regions behind resin macroscopic front increases with the nanofiber contents increasing. The area fraction of partially saturated region of preforms with the same nanofiber contents increases firstly, and then decreases with injection time increasing.
2017, 34(6): 1237-1244.
doi: 10.13801/j.cnki.fhclxb.20160914.002
Abstract:
The interlayer-toughed carbon fiber/epoxy resin (CF/EP) composite laminates with short ramie fiber (SRF) were made through hot press laminated molding process. The interlaminar fracture toughness, the flexsural properties and tensile properties of the CF/EP composites with different SRF lengths, surface densities and surface coupling treatment were investigated. The results indicate that the insert of SRF significantly improves the CF/EP composites' mode I and mode Ⅱ interlaminar fracture toughness (GIC and GⅡC), and the best interlaminar fracture toughness property can be obtained when the length of SRF is 6 mm and the surface density of SRF is 12 g·m-2. GIC of the composites improves from 497.48 J·m-2 to 667.54 J·m-2, which increases by 34.24%, and GⅡC of the composites improves from 508.52 J·m-2 to 862.11 J·m-2, which increases by 69.54%. In addition, the flexural pro-perties and tensile properties of the composites are also slighted improved with SRF. Through the observation of scanning electron microscope (SEM), it can be obtained that the toughening mechanism is related to SRF' bridging and pulling out and splitting in the process of crack propagation.
The interlayer-toughed carbon fiber/epoxy resin (CF/EP) composite laminates with short ramie fiber (SRF) were made through hot press laminated molding process. The interlaminar fracture toughness, the flexsural properties and tensile properties of the CF/EP composites with different SRF lengths, surface densities and surface coupling treatment were investigated. The results indicate that the insert of SRF significantly improves the CF/EP composites' mode I and mode Ⅱ interlaminar fracture toughness (GIC and GⅡC), and the best interlaminar fracture toughness property can be obtained when the length of SRF is 6 mm and the surface density of SRF is 12 g·m-2. GIC of the composites improves from 497.48 J·m-2 to 667.54 J·m-2, which increases by 34.24%, and GⅡC of the composites improves from 508.52 J·m-2 to 862.11 J·m-2, which increases by 69.54%. In addition, the flexural pro-perties and tensile properties of the composites are also slighted improved with SRF. Through the observation of scanning electron microscope (SEM), it can be obtained that the toughening mechanism is related to SRF' bridging and pulling out and splitting in the process of crack propagation.
2017, 34(6): 1245-1251.
doi: 10.13801/j.cnki.fhclxb.20160907.001
Abstract:
Aiming at inner wall prone collapse problems in the conventional pipe lining repair material construction, combined with the rapid development of current green fiber composite material, adding ramie yarn in polyester woven fabric lining material was advised, and polyester-ramie composite woven fabric was producted to improve pipeline rehabilitation lined woven fabrics resin impregnated performance, the bonding performance of inner lining materials and pipe wall was enhanced. The appearance of fiber and fracture surface after pulling experiment was observed by electron microscope. With the resin and fabric contact angle testing, bonding experiment, a comprehensive analysis of the resin penetration of polyester-ramie composite woven fabrics was made. Meanwhile, mechanical properties of polyester/ramie composite woven fabric were texted in order to meet the inner lining composite materials strength requirements. Experimental results show that the use of polyester/ramie woven composite manner as described above, can significantly improve the resin penetration, and it's beneficial for carrying more resin to improve bonding performance of resin and pipe wall, and can reduce the likelihood of collapse. While, the tensile and bursting performance of woven fabric added ramie composite can meet the repair requirements of high-pressure gas pipeline.
Aiming at inner wall prone collapse problems in the conventional pipe lining repair material construction, combined with the rapid development of current green fiber composite material, adding ramie yarn in polyester woven fabric lining material was advised, and polyester-ramie composite woven fabric was producted to improve pipeline rehabilitation lined woven fabrics resin impregnated performance, the bonding performance of inner lining materials and pipe wall was enhanced. The appearance of fiber and fracture surface after pulling experiment was observed by electron microscope. With the resin and fabric contact angle testing, bonding experiment, a comprehensive analysis of the resin penetration of polyester-ramie composite woven fabrics was made. Meanwhile, mechanical properties of polyester/ramie composite woven fabric were texted in order to meet the inner lining composite materials strength requirements. Experimental results show that the use of polyester/ramie woven composite manner as described above, can significantly improve the resin penetration, and it's beneficial for carrying more resin to improve bonding performance of resin and pipe wall, and can reduce the likelihood of collapse. While, the tensile and bursting performance of woven fabric added ramie composite can meet the repair requirements of high-pressure gas pipeline.
2017, 34(6): 1252-1260.
doi: 10.13801/j.cnki.fhclxb.20161024.001
Abstract:
For optimal design of the composite composed of material with different Poisson's ratios, a concurrent design method for microstructures of composites and macrostructures by considering the Poisson effect was presented, when considering the macrostructure and complicated boundary conditions. A distinctive feature lies in the interpolation of Poisson's ratios for different constituent phases. The macrostructures were supposed to be constructed by periodic base composites which contains two isotropic constituent phases with distinct Poisson's ratios. The topological optimization model was established where the system compliance was minimized in static problems or the eigenvalue was maximized in dynamic problems and the macro and micro-scale volume fraction was used as constraints. The effective properties of the composites were calculated through the homogenization theory. Sensitivities on macro-and micro-scales level were derived. Density filter and sensitivity filter schemes were adopted to eliminate the instabilities in macro-and micro-scale topology optimization, respectively. The optimality criteria method was used to update both the macro-and micro-scale densities. The effect of the micro-scale volume fraction and Poisson's ratio of the constitute phases on topological results was investigated. Several 3D illustrative examples were presented to demonstrate the effectiveness and advantage of the proposed concurrent design approach.
For optimal design of the composite composed of material with different Poisson's ratios, a concurrent design method for microstructures of composites and macrostructures by considering the Poisson effect was presented, when considering the macrostructure and complicated boundary conditions. A distinctive feature lies in the interpolation of Poisson's ratios for different constituent phases. The macrostructures were supposed to be constructed by periodic base composites which contains two isotropic constituent phases with distinct Poisson's ratios. The topological optimization model was established where the system compliance was minimized in static problems or the eigenvalue was maximized in dynamic problems and the macro and micro-scale volume fraction was used as constraints. The effective properties of the composites were calculated through the homogenization theory. Sensitivities on macro-and micro-scales level were derived. Density filter and sensitivity filter schemes were adopted to eliminate the instabilities in macro-and micro-scale topology optimization, respectively. The optimality criteria method was used to update both the macro-and micro-scale densities. The effect of the micro-scale volume fraction and Poisson's ratio of the constitute phases on topological results was investigated. Several 3D illustrative examples were presented to demonstrate the effectiveness and advantage of the proposed concurrent design approach.
2017, 34(6): 1261-1270.
doi: 10.13801/j.cnki.fhclxb.20161008.003
Abstract:
Criteria for intralaminar and delamination failures of composite laminate were developed in which transverse residual shear deformation and interfacial residual opening were modeled. A brick finite element including multiple-plies was suggested in order to decrease computing costs in ply-by-ply damage analysis of composites. Quasi-static indentation tests were conducted to a carbon fiber/epoxy matrix composite laminate. The indent depth under different contact force was measured and damage areas were obtained by C-scan. The experiments were simulated by the proposed models in the Abaqus by user-defined material subroutine (UMAT). The damage modes corresponding to the characteristic points on tested force-displacement curves were identified via numerical simulations. The proposed models are validated by experimental measurements.
Criteria for intralaminar and delamination failures of composite laminate were developed in which transverse residual shear deformation and interfacial residual opening were modeled. A brick finite element including multiple-plies was suggested in order to decrease computing costs in ply-by-ply damage analysis of composites. Quasi-static indentation tests were conducted to a carbon fiber/epoxy matrix composite laminate. The indent depth under different contact force was measured and damage areas were obtained by C-scan. The experiments were simulated by the proposed models in the Abaqus by user-defined material subroutine (UMAT). The damage modes corresponding to the characteristic points on tested force-displacement curves were identified via numerical simulations. The proposed models are validated by experimental measurements.
2017, 34(6): 1271-1277.
doi: 10.13801/j.cnki.fhclxb.20161028.002
Abstract:
The dynamic mechanical properties of shape memory epoxy polymer (SMEP) and 4-harness satin carbon fiber weave reinforced composites were tested by DMA 8000, the glass-transition temperature Tg, the storage modulus E, the tangent of loss angle tan δ were calculated. The experimental results indicate that SMEP and 4-harness satin carbon fiber weave reinforced composites have significant phase transition mechanical behavior, in which E differs beyond one-order around Tg. This prove that the SMEP and 4-harness satin carbon fiber weave reinforced composites have good shape memory capacity. The thermoset SMEP involved with three kinds of carbon fiber weave reinforced composites will lead to Tg and tan δ reduction, but E is significantly enlarged. Tg and tan δ of the same SMEP carbon fiber weave reinforced composites are almost in common, but E differs greatly in its warp direction and weft direction.
The dynamic mechanical properties of shape memory epoxy polymer (SMEP) and 4-harness satin carbon fiber weave reinforced composites were tested by DMA 8000, the glass-transition temperature Tg, the storage modulus E, the tangent of loss angle tan δ were calculated. The experimental results indicate that SMEP and 4-harness satin carbon fiber weave reinforced composites have significant phase transition mechanical behavior, in which E differs beyond one-order around Tg. This prove that the SMEP and 4-harness satin carbon fiber weave reinforced composites have good shape memory capacity. The thermoset SMEP involved with three kinds of carbon fiber weave reinforced composites will lead to Tg and tan δ reduction, but E is significantly enlarged. Tg and tan δ of the same SMEP carbon fiber weave reinforced composites are almost in common, but E differs greatly in its warp direction and weft direction.
Fabrication and anti-oxidation abilities of Cu@Ag core-shell nanoparticles by polyol-assisted method
2017, 34(6): 1278-1284.
doi: 10.13801/j.cnki.fhclxb.20160913.002
Abstract:
A simple method was introduced to prepare Cu@Ag core-shell particles at room temperatureby using ethylene glycol (EG) as the reducing agent and AgNO3 as the source of Ag atom. The effects of types of dispersing agent including gelatin, cetyltrimethylammonium bromide (CTAB) and polyvinylpyrrolidone (PVP)on the morphology of Cu@Ag core-shell particles were studied. The results show that gelatin is the best choice as dispersing agent. When the concentration of AgNO3 is 0.93 mol/L, the copper particles are completely covered with Ag nanoparticles on the surface with gelatin as dispersing agent. Because of the protection of Ag nanoparticles on the surface of Cu particles, the sheet resistance of compacted film based on Cu@Ag core-shell nanoparticles is as low as 1.6 Ω/sq. After being exposed in air for 4 months, the sheet resistance of the Cu@Ag core-shell particles is a little bit higher as 12.6 Ω/sq, which shows an enduring oxidation resistance of Cu@Ag core-shell particles.The silver can be efficiently achieved over the Cu particles under control and shows better anti-oxidation abilities than Cu particles with enduring oxidation resistance. This is a remarkable improvement for the electrical conductivity of Cu particles, which lays the foundations for the application of Cu@Ag core-shell particles in industrial production.
A simple method was introduced to prepare Cu@Ag core-shell particles at room temperatureby using ethylene glycol (EG) as the reducing agent and AgNO3 as the source of Ag atom. The effects of types of dispersing agent including gelatin, cetyltrimethylammonium bromide (CTAB) and polyvinylpyrrolidone (PVP)on the morphology of Cu@Ag core-shell particles were studied. The results show that gelatin is the best choice as dispersing agent. When the concentration of AgNO3 is 0.93 mol/L, the copper particles are completely covered with Ag nanoparticles on the surface with gelatin as dispersing agent. Because of the protection of Ag nanoparticles on the surface of Cu particles, the sheet resistance of compacted film based on Cu@Ag core-shell nanoparticles is as low as 1.6 Ω/sq. After being exposed in air for 4 months, the sheet resistance of the Cu@Ag core-shell particles is a little bit higher as 12.6 Ω/sq, which shows an enduring oxidation resistance of Cu@Ag core-shell particles.The silver can be efficiently achieved over the Cu particles under control and shows better anti-oxidation abilities than Cu particles with enduring oxidation resistance. This is a remarkable improvement for the electrical conductivity of Cu particles, which lays the foundations for the application of Cu@Ag core-shell particles in industrial production.
2017, 34(6): 1285-1292.
doi: 10.13801/j.cnki.fhclxb.20161008.001
Abstract:
Besides the high cost, the preforms of Cf/Mg composites sheet-shaped components prepared by the traditional fabrication techniques own the unstable performance. To overcome these disadvantages, a new fabrication technique entitled "Profiling weave-Hoop winding-Oriented placement-Stitched reinforcement" was proposed and consequently the related experimental devices were developed. Based on the experimental investigations, the separate preparations of the circular sheet preform and protruding table preform were fabricated and then protruding table preform was stitched to the sheet preform. The circular sheet preform was fabricated through the radial weave and circumferential winding of the fibers and the combination of the non-woven fabrics and hoop fiber layers, wherein the weft insertion weft tension control in 1.7-2.3 N. The protruding table preform was fabricated through the stack of the horizontal non-woven fabrics. The fabricated sheet-shaped preform preforms have the intact morphology with the uniformly distributed circular and radial fibers. Meanwhile, the Cf/Mg composites sheet-shaped components fabricated by the liquid-solid extrusion process show that the connection between the protruding table and circular sheet preform is of good quality.
Besides the high cost, the preforms of Cf/Mg composites sheet-shaped components prepared by the traditional fabrication techniques own the unstable performance. To overcome these disadvantages, a new fabrication technique entitled "Profiling weave-Hoop winding-Oriented placement-Stitched reinforcement" was proposed and consequently the related experimental devices were developed. Based on the experimental investigations, the separate preparations of the circular sheet preform and protruding table preform were fabricated and then protruding table preform was stitched to the sheet preform. The circular sheet preform was fabricated through the radial weave and circumferential winding of the fibers and the combination of the non-woven fabrics and hoop fiber layers, wherein the weft insertion weft tension control in 1.7-2.3 N. The protruding table preform was fabricated through the stack of the horizontal non-woven fabrics. The fabricated sheet-shaped preform preforms have the intact morphology with the uniformly distributed circular and radial fibers. Meanwhile, the Cf/Mg composites sheet-shaped components fabricated by the liquid-solid extrusion process show that the connection between the protruding table and circular sheet preform is of good quality.
2017, 34(6): 1293-1299.
doi: 10.13801/j.cnki.fhclxb.20161101.001
Abstract:
In order to enhance the electrical conductivity and rate capability of NaTi2(PO4)3 (NTP)as anode materials for aqueous rechargeable Na-ion batteries, the C/NTP composites were prepared by the solvothermal strategy using CO(NH2)2 as the carbon source. The crystal structure, surface morphology and electrochemical properties of the obtained CO(NH2)2/NaTi2(PO4)3(C/NTP)composites were investigated by the XRD, SEM, TEM, Raman and constant current charge-discharge testing. The effect of heating rate at different stage on the content of carbon, the graphitization degree of coating layer and the electrochemical performance of C/NTP composites was carefully studied. The results show that below 400℃ the lower of the heating rate, the higher content of carbon remains in C/NTP, and the lower of the heating rate between 400℃ and 650℃, the higher graphitization degree of carbon coating obtained, which also can improve the electrochemical performance of C/NTP composites. The initial discharge capacity of the C/NTP composites treated at the heating rate of 2℃/min reaches 114.9 mAh·g-1 at the current of 5C and maintain as 91.9 mAh·g-1 after 30 cycles, and the discharge capacity even keeps 87 mAh·g-1 at the current of 10C and 71 mAh·g-1 at the current of 20C, which exhibites excellent cycle performance at high current rate.
In order to enhance the electrical conductivity and rate capability of NaTi2(PO4)3 (NTP)as anode materials for aqueous rechargeable Na-ion batteries, the C/NTP composites were prepared by the solvothermal strategy using CO(NH2)2 as the carbon source. The crystal structure, surface morphology and electrochemical properties of the obtained CO(NH2)2/NaTi2(PO4)3(C/NTP)composites were investigated by the XRD, SEM, TEM, Raman and constant current charge-discharge testing. The effect of heating rate at different stage on the content of carbon, the graphitization degree of coating layer and the electrochemical performance of C/NTP composites was carefully studied. The results show that below 400℃ the lower of the heating rate, the higher content of carbon remains in C/NTP, and the lower of the heating rate between 400℃ and 650℃, the higher graphitization degree of carbon coating obtained, which also can improve the electrochemical performance of C/NTP composites. The initial discharge capacity of the C/NTP composites treated at the heating rate of 2℃/min reaches 114.9 mAh·g-1 at the current of 5C and maintain as 91.9 mAh·g-1 after 30 cycles, and the discharge capacity even keeps 87 mAh·g-1 at the current of 10C and 71 mAh·g-1 at the current of 20C, which exhibites excellent cycle performance at high current rate.
2017, 34(6): 1300-1307.
doi: 10.13801/j.cnki.fhclxb.20161116.004
Abstract:
The primary Mg2Si phase of hypereutectic Mg-3.2Si alloys, in which rare earth Er and Ce were added, was studied by OM, SEM, EDS and XRD. And the metamorphic mechanism was also discussed. When 0.6% (mass ratio, the same below)Er to Mg-3.2Si alloys added, the size of the primary Mg2Si phase decreases from 150 μm to 40 μm, and its shape transformes from the bulky dendritic into the irregular polyhedron shape. Then continuely adding 1.0% Ce, the polyhedron or globular primary Mg2Si phase of 5-10 μm can be obtained. When the addition of rare earth increases higher, the primary Mg2Si phase grows into a coarse. Rare earth Er and Ce on the primary Mg2Si phase reduce the critical nucleation work and the relative growth rate between the crystallographic orientation, more primary Mg2Si crystal nucleus form, and its shape transformes into the irregular polyhedron shape. The rare earth Er and Ce form a continuous solid solution during solidification. When 0.6% Er and 1.0% Ce added, the tensile strength σ b and elongation δ of Mg-3.2Si reach to maximum value of 127 MPa and 3.7%.
The primary Mg2Si phase of hypereutectic Mg-3.2Si alloys, in which rare earth Er and Ce were added, was studied by OM, SEM, EDS and XRD. And the metamorphic mechanism was also discussed. When 0.6% (mass ratio, the same below)Er to Mg-3.2Si alloys added, the size of the primary Mg2Si phase decreases from 150 μm to 40 μm, and its shape transformes from the bulky dendritic into the irregular polyhedron shape. Then continuely adding 1.0% Ce, the polyhedron or globular primary Mg2Si phase of 5-10 μm can be obtained. When the addition of rare earth increases higher, the primary Mg2Si phase grows into a coarse. Rare earth Er and Ce on the primary Mg2Si phase reduce the critical nucleation work and the relative growth rate between the crystallographic orientation, more primary Mg2Si crystal nucleus form, and its shape transformes into the irregular polyhedron shape. The rare earth Er and Ce form a continuous solid solution during solidification. When 0.6% Er and 1.0% Ce added, the tensile strength σ b and elongation δ of Mg-3.2Si reach to maximum value of 127 MPa and 3.7%.
2017, 34(6): 1308-1315.
doi: 10.13801/j.cnki.fhclxb.20161104.001
Abstract:
30%Cr-Cu composites were prepared by spark plasma sintering process (SPS). The basic properties of the composite such as relative density, Brinell hardness and electrical conductivity were tested and the microstructures of the composites were observed. Hot simulation compression tests of the 30%Cr-Cu composites were conducted at deformation temperature of 650-950℃, strain rate of 0.001-10 s-1 and deformation amount of 60% by the Gleeble-1500D thermal-mechanical simulation test machine. The true stress-true strain data of the 30%Cr-Cu composites were fitted, calculated and analyzed, constitutive equation of the composites was constructed, and the work hardening rate θ of the 30%Cr-Cu composite was obtained at the same time. The critical conditions of dynamic recrystallization during hot deformation of the 30%Cr-Cu composites were analyzed by computing the inflection point criterion of ln θ-ε curves and the minimum value criterion of -∂(ln θ)/∂ε-ε curves. The results show that the true stress-strain curves of the 30%Cr-Cu composites are mainly characterized by dynamic recrystallization softening mechanism. The peak stress increases with the increasing strain rate and the decreasing deformation temperature. The inflection point presents in the ln θ-ε curve and a minimum value appeas in the corresponding -∂(ln θ)/∂ε-ε curve when the critical state of the 30%Cr-Cu composites is attained, in which the strain that relates to the minimum value is the critical strain ε c. The critical strain ε c decreases with the increasing deformation temperature and the decreasing strain rate. The model of the critical strain with εc and Zener-Hollomon parameter can be described by the function of ε c=2.38×10-3 Z 0.1396.
30%Cr-Cu composites were prepared by spark plasma sintering process (SPS). The basic properties of the composite such as relative density, Brinell hardness and electrical conductivity were tested and the microstructures of the composites were observed. Hot simulation compression tests of the 30%Cr-Cu composites were conducted at deformation temperature of 650-950℃, strain rate of 0.001-10 s-1 and deformation amount of 60% by the Gleeble-1500D thermal-mechanical simulation test machine. The true stress-true strain data of the 30%Cr-Cu composites were fitted, calculated and analyzed, constitutive equation of the composites was constructed, and the work hardening rate θ of the 30%Cr-Cu composite was obtained at the same time. The critical conditions of dynamic recrystallization during hot deformation of the 30%Cr-Cu composites were analyzed by computing the inflection point criterion of ln θ-ε curves and the minimum value criterion of -∂(ln θ)/∂ε-ε curves. The results show that the true stress-strain curves of the 30%Cr-Cu composites are mainly characterized by dynamic recrystallization softening mechanism. The peak stress increases with the increasing strain rate and the decreasing deformation temperature. The inflection point presents in the ln θ-ε curve and a minimum value appeas in the corresponding -∂(ln θ)/∂ε-ε curve when the critical state of the 30%Cr-Cu composites is attained, in which the strain that relates to the minimum value is the critical strain ε c. The critical strain ε c decreases with the increasing deformation temperature and the decreasing strain rate. The model of the critical strain with εc and Zener-Hollomon parameter can be described by the function of ε c=2.38×10-3 Z 0.1396.
2017, 34(6): 1316-1324.
doi: 10.13801/j.cnki.fhclxb.20160920.001
Abstract:
Based on the free volume theory and Ramberg-Osgood model, a representative volume element model with particles random distribution was established, and the microstructure effect of Ti64.5Zr14.5V18.5Cu2.5 particles toughening Ti-base metallic glass matrix composites under the uniaxial tension, was simulated by ABAQUS code. The effects of particles volume fraction, the number of reunion and aspect ratio, along with particles orientation and interface on the ductility of metallic glass were discussed. Results show that increasing particles volume fraction can improve the plasticity of composites significantly, but at the expense of the part strength of the composites. Increasing particles aspect ratio can enhance the plasticity and yield strength of composite materials. Making the orientation of particles and the load direction into 90 ° or 0°not only enhances the plasticity, but also improves the strength of composites compared with the other configuration. Reducing the number of reunion to below two can significantly reduce loss of the plasticity and strength of metallic glass composites, and the particles of reunions and the load at 90°, can improve the plasticity and strength of composites. In particles toughening metallic glass matrix composites with zero interface, particles and matrix debonding in interface in the main shear belt can be observed, according with the experimental phenomena more. The results help to well understand the microstructure effect of the composite materials which is beneficial to the design of the material.
Based on the free volume theory and Ramberg-Osgood model, a representative volume element model with particles random distribution was established, and the microstructure effect of Ti64.5Zr14.5V18.5Cu2.5 particles toughening Ti-base metallic glass matrix composites under the uniaxial tension, was simulated by ABAQUS code. The effects of particles volume fraction, the number of reunion and aspect ratio, along with particles orientation and interface on the ductility of metallic glass were discussed. Results show that increasing particles volume fraction can improve the plasticity of composites significantly, but at the expense of the part strength of the composites. Increasing particles aspect ratio can enhance the plasticity and yield strength of composite materials. Making the orientation of particles and the load direction into 90 ° or 0°not only enhances the plasticity, but also improves the strength of composites compared with the other configuration. Reducing the number of reunion to below two can significantly reduce loss of the plasticity and strength of metallic glass composites, and the particles of reunions and the load at 90°, can improve the plasticity and strength of composites. In particles toughening metallic glass matrix composites with zero interface, particles and matrix debonding in interface in the main shear belt can be observed, according with the experimental phenomena more. The results help to well understand the microstructure effect of the composite materials which is beneficial to the design of the material.
2017, 34(6): 1325-1333.
doi: 10.13801/j.cnki.fhclxb.20160919.001
Abstract:
Carbon nanotubes (CNTs) were directly and uniformly deposited on Ni foam by a simple chemical vapor deposition (CVD) method, and then the selected epoxy resin system was induced into Ni foam supported CNTs to prepare Ni foam/epoxy resin composites modified with CNTs by vacuum infusion molding process (VIMP). Surface morphology of Ni foam and morphology, structure and graphitization of as-formed CNTs were characterized by FE-SEM, TEM and Raman at different reaction temperatures. Meanwhile, the effect of CNTs on damping properties of composites was investigated by dynamic mechanical analysis (DMA). The results show that the CNTs with uniform diameter, high graphitization and purity can be well deposited on Ni foam at 680 ℃. Compared with Ni foam/epoxy resin composites modified without CNTs, the maximum loss factor tan δ max of Ni foam/epoxy resin composites modified with CNTs increases from 0.69 to 0.78, the glass transition temperature Tg shifts from 60℃ to 68℃, the effective damping temperature range ΔT extends from 39℃ to 44℃, and the damping property increases by 18.9%.
Carbon nanotubes (CNTs) were directly and uniformly deposited on Ni foam by a simple chemical vapor deposition (CVD) method, and then the selected epoxy resin system was induced into Ni foam supported CNTs to prepare Ni foam/epoxy resin composites modified with CNTs by vacuum infusion molding process (VIMP). Surface morphology of Ni foam and morphology, structure and graphitization of as-formed CNTs were characterized by FE-SEM, TEM and Raman at different reaction temperatures. Meanwhile, the effect of CNTs on damping properties of composites was investigated by dynamic mechanical analysis (DMA). The results show that the CNTs with uniform diameter, high graphitization and purity can be well deposited on Ni foam at 680 ℃. Compared with Ni foam/epoxy resin composites modified without CNTs, the maximum loss factor tan δ max of Ni foam/epoxy resin composites modified with CNTs increases from 0.69 to 0.78, the glass transition temperature Tg shifts from 60℃ to 68℃, the effective damping temperature range ΔT extends from 39℃ to 44℃, and the damping property increases by 18.9%.
2017, 34(6): 1334-1339.
doi: 10.13801/j.cnki.fhclxb.20161110.001
Abstract:
TiC/Al(7075) composites were fabricated by in situ reaction. The influence of in situ TiC particles form, distribution state and content on the microstructure and mechanical properties of the TiC/Al(7075) compo-sites were discussed. The results show that most spherical in situ TiC particles with aggregate exists in 7075 matrix, the cluster of grain size is about 1 μm. When the mass fraction of in situ TiC particles is less than 6%, the TiC distribution is more uniform. With the increase of in situ TiC particles, the grain sizes of the TiC/Al(7075) composites decrease significantly. But the porosity appear in the microstrcuture when the mass fraction of in situ TiC particles is more than 6%. Hardness and toughness of composite material testing shows that with the increase of the TiC particle concentration, the highest hardness of the surface reaches HB 108, the composites with 6% TiC have the best toughness, the toughness increases by 31.55% compared with the 7075 matrix.
TiC/Al(7075) composites were fabricated by in situ reaction. The influence of in situ TiC particles form, distribution state and content on the microstructure and mechanical properties of the TiC/Al(7075) compo-sites were discussed. The results show that most spherical in situ TiC particles with aggregate exists in 7075 matrix, the cluster of grain size is about 1 μm. When the mass fraction of in situ TiC particles is less than 6%, the TiC distribution is more uniform. With the increase of in situ TiC particles, the grain sizes of the TiC/Al(7075) composites decrease significantly. But the porosity appear in the microstrcuture when the mass fraction of in situ TiC particles is more than 6%. Hardness and toughness of composite material testing shows that with the increase of the TiC particle concentration, the highest hardness of the surface reaches HB 108, the composites with 6% TiC have the best toughness, the toughness increases by 31.55% compared with the 7075 matrix.
2017, 34(6): 1340-1346.
doi: 10.13801/j.cnki.fhclxb.20160926.004
Abstract:
The crystallite size of the three different carbon fibers (K223HE, HTA40 and T700SC) was characterized by Raman spectroscopy. The transverse elastic modulus and hardness of the carbon fibers were measured by nano indentation technique, and the data scatter was analyzed by two-parameter Weibull function. The results show that the crystallite length of the mesophase pitch based carbon fiber K223HE is the longest, about 39.43 nm±2.63 nm, and that of HTA40 and T700SC PAN based carbon fiber is almost the same, about 4.63 nm±0.09 nm and 4.89 nm±0.06 nm, respectively. In the nano indentation load-depth curve, the residual deformation of K223HE is the biggest (75.34 nm±17.07 nm), indicating the lowest recovery ratio of indentation work (65.89%). The characteristic transverse elastic modulus of the three carbon fibers is 19.52 GPa, 11.99 GPa and 17.92 GPa. The Weibull modulus of the transverse elastic modulus of the three different carbon fibers (HTA40, K223HE and T700SC) is 25.26, 6.85 and 8.07, which displays the consistence in the properties of HTA40 is the best. The differences in the nano indentation behavior of the three carbon fibers are attributed to the differences in the integrity and preferred orientation of the crystallite of carbon fibers.
The crystallite size of the three different carbon fibers (K223HE, HTA40 and T700SC) was characterized by Raman spectroscopy. The transverse elastic modulus and hardness of the carbon fibers were measured by nano indentation technique, and the data scatter was analyzed by two-parameter Weibull function. The results show that the crystallite length of the mesophase pitch based carbon fiber K223HE is the longest, about 39.43 nm±2.63 nm, and that of HTA40 and T700SC PAN based carbon fiber is almost the same, about 4.63 nm±0.09 nm and 4.89 nm±0.06 nm, respectively. In the nano indentation load-depth curve, the residual deformation of K223HE is the biggest (75.34 nm±17.07 nm), indicating the lowest recovery ratio of indentation work (65.89%). The characteristic transverse elastic modulus of the three carbon fibers is 19.52 GPa, 11.99 GPa and 17.92 GPa. The Weibull modulus of the transverse elastic modulus of the three different carbon fibers (HTA40, K223HE and T700SC) is 25.26, 6.85 and 8.07, which displays the consistence in the properties of HTA40 is the best. The differences in the nano indentation behavior of the three carbon fibers are attributed to the differences in the integrity and preferred orientation of the crystallite of carbon fibers.
2017, 34(6): 1347-1353.
doi: 10.13801/j.cnki.fhclxb.20160913.004
Abstract:
The SiCW/Si3N4 composite ceramics were prepared by gel-casting using α-Si3N4 powder and β-SiCW as the raw materials and Al2O3 and Y2O3 as the sintering aids at 1 650℃ and kept 1.5 h. The effects of the content variation of SiCW on the microstructure, mechanical and room/high temperature microwave absorbing properties of the SiCW/Si3N4 composite ceramics were investigated. The results show that the flexural strength and fracture toughness of the SiCW/Si3N4 composite ceramics have a trend of decrease after an initial increase with increasing SiCW content. It possesses the most excellent flexural strength and fracture toughness (505 MPa and 9.515 MPa·m1/2) when the content is 10wt%. The real part of the dielectric constant at room temperature reaches the maximum 12 with the 10wt% SiCW. The maximum absorption is -21 dB at 12 GHz. And the high temperature permittivity has a trend of decrease after an initial increase with increasing SiCW content. The real permittivity reaches 12.5 when the content is 10wt%. Compared with the pure Si3N4 ceramic, when the SiCW content is 10wt%, the lowest reflectivity of the SiCW/Si3N4 composite ceramic reduces to -27 dB at around 11.7 GHz, and the effective absorption band (less than -5 dB) ranges from 11.2 to 12.3 GHz.
The SiCW/Si3N4 composite ceramics were prepared by gel-casting using α-Si3N4 powder and β-SiCW as the raw materials and Al2O3 and Y2O3 as the sintering aids at 1 650℃ and kept 1.5 h. The effects of the content variation of SiCW on the microstructure, mechanical and room/high temperature microwave absorbing properties of the SiCW/Si3N4 composite ceramics were investigated. The results show that the flexural strength and fracture toughness of the SiCW/Si3N4 composite ceramics have a trend of decrease after an initial increase with increasing SiCW content. It possesses the most excellent flexural strength and fracture toughness (505 MPa and 9.515 MPa·m1/2) when the content is 10wt%. The real part of the dielectric constant at room temperature reaches the maximum 12 with the 10wt% SiCW. The maximum absorption is -21 dB at 12 GHz. And the high temperature permittivity has a trend of decrease after an initial increase with increasing SiCW content. The real permittivity reaches 12.5 when the content is 10wt%. Compared with the pure Si3N4 ceramic, when the SiCW content is 10wt%, the lowest reflectivity of the SiCW/Si3N4 composite ceramic reduces to -27 dB at around 11.7 GHz, and the effective absorption band (less than -5 dB) ranges from 11.2 to 12.3 GHz.
2017, 34(6): 1354-1359.
doi: 10.13801/j.cnki.fhclxb.20161018.006
Abstract:
Aiming at the problem that stiffness coefficient of bonding interface is difficult to be accurately measured under the condition of nondestructive, a method using ultrasonic to test stiffness coefficient have been proposed. Mathematical model of the ultrasonic testing stiffness coefficient for multilayer medium has been established by the reflection and transmission of acoustic wave propagation in layered medium and the bonding interface spring model. Ultrasonic reflection spectra under different bonding interface have been obtained when the substrate material is steel, cast iron, aluminum alloy, and the coating material is Al2O3 ceramic obtained by different spraying processes. The simulation results show that the resonant frequency is periodic on the condition of the debonded or perfectly bonding interface, but the periodicity is different. When the interface is weakly bonded, many resonant frequencies emerge and move to high frequency with the increment of stiffness coefficient. The lower resonance frequencies move faster than the higher ones. The relations between resonance frequency and stiffness coefficient have been established. The variation rules of resonance frequency with the substrate and coating impedance are as follow: the resonance frequencies increase with the increasing of the substrate impedance, and decrease with the increasing of the coating impedance in the same stiffness coefficient. The relation between stiffness coefficient and resonance frequency is fitted using the exponential function. The function including the substrate and coating impedance, stiffness coefficient and resonance frequency was obtained in weakly bonded interfaces. The results will provide theoretical support to ultrasonic testing of the coating composites with weakly bonded interfaces.
Aiming at the problem that stiffness coefficient of bonding interface is difficult to be accurately measured under the condition of nondestructive, a method using ultrasonic to test stiffness coefficient have been proposed. Mathematical model of the ultrasonic testing stiffness coefficient for multilayer medium has been established by the reflection and transmission of acoustic wave propagation in layered medium and the bonding interface spring model. Ultrasonic reflection spectra under different bonding interface have been obtained when the substrate material is steel, cast iron, aluminum alloy, and the coating material is Al2O3 ceramic obtained by different spraying processes. The simulation results show that the resonant frequency is periodic on the condition of the debonded or perfectly bonding interface, but the periodicity is different. When the interface is weakly bonded, many resonant frequencies emerge and move to high frequency with the increment of stiffness coefficient. The lower resonance frequencies move faster than the higher ones. The relations between resonance frequency and stiffness coefficient have been established. The variation rules of resonance frequency with the substrate and coating impedance are as follow: the resonance frequencies increase with the increasing of the substrate impedance, and decrease with the increasing of the coating impedance in the same stiffness coefficient. The relation between stiffness coefficient and resonance frequency is fitted using the exponential function. The function including the substrate and coating impedance, stiffness coefficient and resonance frequency was obtained in weakly bonded interfaces. The results will provide theoretical support to ultrasonic testing of the coating composites with weakly bonded interfaces.
2017, 34(6): 1360-1366.
doi: 10.13801/j.cnki.fhclxb.20160905.003
Abstract:
Diluted magnetic semiconductors Zn1-xMnxS with different consistency ratios (x =0, 0.02, 0.05, 0.07) have been synthesized by hydrothermal method using ethylenediamine as a modifier. The crystal microstructure, morphology and optical and magnetic properties of the samples were characterized by XRD, FESEM, HRTEM and XEDS, photoluminescence spectra (PL) and the vibrating sample magnetometer (VSM). The experiment results show that all samples synthesized by this method possess wurtzite structure with good crystallization, and no other impurity phase appears. The morphology of the samples is one-dimensional nanorods and well dispersed. Mn2+ enters into the ZnS lattice to substitute for the lattice site of Zn2+, and the lattice constant decreases with the increase of Mn content. The PL spectra of the samples have obvious ultraviolet emission peak, blue emission peak and green emission peak, and the luminescence peak has a blue-shift. At the same time, a certain amount of Mn doped ZnS nanocrystals have ferromagnetic properties at room temperature.
Diluted magnetic semiconductors Zn1-xMnxS with different consistency ratios (x =0, 0.02, 0.05, 0.07) have been synthesized by hydrothermal method using ethylenediamine as a modifier. The crystal microstructure, morphology and optical and magnetic properties of the samples were characterized by XRD, FESEM, HRTEM and XEDS, photoluminescence spectra (PL) and the vibrating sample magnetometer (VSM). The experiment results show that all samples synthesized by this method possess wurtzite structure with good crystallization, and no other impurity phase appears. The morphology of the samples is one-dimensional nanorods and well dispersed. Mn2+ enters into the ZnS lattice to substitute for the lattice site of Zn2+, and the lattice constant decreases with the increase of Mn content. The PL spectra of the samples have obvious ultraviolet emission peak, blue emission peak and green emission peak, and the luminescence peak has a blue-shift. At the same time, a certain amount of Mn doped ZnS nanocrystals have ferromagnetic properties at room temperature.
2017, 34(6): 1367-1373.
doi: 10.13801/j.cnki.fhclxb.20161114.002
Abstract:
With Span-80 as controlling agent, tetrabutyl orthotitanate (TBOT) as titanium source, Fe and F co-doped TiO2 composite (Fe-F/TiO2) microsphere was fabricated by hydrolysis-reflux method at low temperature. The structure and properties of as-prepared Fe-F/TiO2 samples were characterized using XRD, FTIR, SEM, TG-DTA, BJH and UV-Vis DRS. The photocatalytic performance was evaluated by degrading partially hydrolyzed polyacrylamide (HPAM). The results show that mesoporous anatase Fe-F/TiO2 microsphere is assembled with nanoparticles of which the diameter is 10-15 nm; Fe3+ can effectively promote the formation of anatase and inhibit the generation of rutile phase, which can result in high thermal stability; the specific surface area, pore volume, average pore diameter of catalyst are 145.11 m2/g, 0.26 cm3/g and 6.23 nm, respectively. In the process of photodegradation of HPAM, the synergistic effect of Fe3+ and F- can enhance the photocatalytic performance which makes Fe-F/TiO2 have the highest photocatalytic activity. The COD removal rate of HPAM (initial concentration of 500 mg/L) can be up to 81% and 74% when illuminated under ultraviolet (UV) and visible light for 120 min using 0.1 g of catalyst.
With Span-80 as controlling agent, tetrabutyl orthotitanate (TBOT) as titanium source, Fe and F co-doped TiO2 composite (Fe-F/TiO2) microsphere was fabricated by hydrolysis-reflux method at low temperature. The structure and properties of as-prepared Fe-F/TiO2 samples were characterized using XRD, FTIR, SEM, TG-DTA, BJH and UV-Vis DRS. The photocatalytic performance was evaluated by degrading partially hydrolyzed polyacrylamide (HPAM). The results show that mesoporous anatase Fe-F/TiO2 microsphere is assembled with nanoparticles of which the diameter is 10-15 nm; Fe3+ can effectively promote the formation of anatase and inhibit the generation of rutile phase, which can result in high thermal stability; the specific surface area, pore volume, average pore diameter of catalyst are 145.11 m2/g, 0.26 cm3/g and 6.23 nm, respectively. In the process of photodegradation of HPAM, the synergistic effect of Fe3+ and F- can enhance the photocatalytic performance which makes Fe-F/TiO2 have the highest photocatalytic activity. The COD removal rate of HPAM (initial concentration of 500 mg/L) can be up to 81% and 74% when illuminated under ultraviolet (UV) and visible light for 120 min using 0.1 g of catalyst.
2017, 34(6): 1374-1380.
doi: 10.13801/j.cnki.fhclxb.20160905.002
Abstract:
In order to study the microstructure and modification mechanisms of polyphosphoric acid (PPA) and styrene-butadiene-styrene block copolymer (SBS) on asphalt, fractionation tests, infrared spectrum tests, fluorescence microscopy tests and differential scanning calorimetry tests were conducted on asphalt binders modified with various dosages (by mass) of PPA and SBS. The results show that the asphaltene content and micelle interaction increase with increasing dosage of PPA, and sol structure of binder gradually changes to sol-gel structure, so that the viscosity is improved. The cross-linking, grafting actions and space mesh structure are strengthened with the addition of PPA, and thus the high temperature storage stability is enhanced. The SBS is reduced to smaller particles and the swelling is improved, so that the modification effectiveness of SBS is further exploited. The mesh structure formed in binder modified with PPA and low dosage of SBS is better than that modified with SBS of high dosage. The glass transition temperature is not significantly influenced by the addition of PPA and it indicates that PPA has little effect on the low temperature performance of binders modified with SBS.
In order to study the microstructure and modification mechanisms of polyphosphoric acid (PPA) and styrene-butadiene-styrene block copolymer (SBS) on asphalt, fractionation tests, infrared spectrum tests, fluorescence microscopy tests and differential scanning calorimetry tests were conducted on asphalt binders modified with various dosages (by mass) of PPA and SBS. The results show that the asphaltene content and micelle interaction increase with increasing dosage of PPA, and sol structure of binder gradually changes to sol-gel structure, so that the viscosity is improved. The cross-linking, grafting actions and space mesh structure are strengthened with the addition of PPA, and thus the high temperature storage stability is enhanced. The SBS is reduced to smaller particles and the swelling is improved, so that the modification effectiveness of SBS is further exploited. The mesh structure formed in binder modified with PPA and low dosage of SBS is better than that modified with SBS of high dosage. The glass transition temperature is not significantly influenced by the addition of PPA and it indicates that PPA has little effect on the low temperature performance of binders modified with SBS.
2017, 34(6): 1381-1387.
doi: 10.13801/j.cnki.fhclxb.20170121.002
Abstract:
Various content ratios of the hollow fly ash, ferrite and carbon black were used to analyze the main factors and the influencing mechanisms on absorbing properties of cement based composites. The results indicate that hollow fly ash is the main factor on absorbing property. The best absorbing bandwidth of less than -10 dB was achieved by the specimen comprised of 20wt% ferrite, 20wt% hollow fly ash and 10vol% carbon black as exhibiting 10 GHz, which is obviously better than none hollow fly ash samples. Improving material surface transmission performance and dielectric loss are the main effect mechanisms of fly ash.
Various content ratios of the hollow fly ash, ferrite and carbon black were used to analyze the main factors and the influencing mechanisms on absorbing properties of cement based composites. The results indicate that hollow fly ash is the main factor on absorbing property. The best absorbing bandwidth of less than -10 dB was achieved by the specimen comprised of 20wt% ferrite, 20wt% hollow fly ash and 10vol% carbon black as exhibiting 10 GHz, which is obviously better than none hollow fly ash samples. Improving material surface transmission performance and dielectric loss are the main effect mechanisms of fly ash.
2017, 34(6): 1388-1393.
doi: 10.13801/j.cnki.fhclxb.20160825.001
Abstract:
Based on continuum mechanics for fiber reinforced composites, an anisotropic hyperelastic constitutive model considering shear-tension coupling was developed to characterize the nonlinear and large deformation behavior of textile fabrics. The unit-volume strain energy was decomposed into two parts which represent the fiber stretches and fiber-fiber interaction considering shear-tension coupling, respectively. Experimental data were used to identify material parameters of the proposed model. The developed model was validated by comparing numerical results with experiment data of picture frame tests under tension. The proposed model establishes a foundation for more accurate finite element forming simulation of two-dimensional woven fabrics.
Based on continuum mechanics for fiber reinforced composites, an anisotropic hyperelastic constitutive model considering shear-tension coupling was developed to characterize the nonlinear and large deformation behavior of textile fabrics. The unit-volume strain energy was decomposed into two parts which represent the fiber stretches and fiber-fiber interaction considering shear-tension coupling, respectively. Experimental data were used to identify material parameters of the proposed model. The developed model was validated by comparing numerical results with experiment data of picture frame tests under tension. The proposed model establishes a foundation for more accurate finite element forming simulation of two-dimensional woven fabrics.
2017, 34(6): 1394-1399.
doi: 10.13801/j.cnki.fhclxb.20160923.001
Abstract:
The theoretical form of shear buckling strength of honeycomb core was shown based on the principle of minimum complementary energy and shear buckling theory of thin plate. By regarding the cell wall as a beam with elastic supports, the shear buckling strength of honeycomb core considering elastic supports was got from interpolating the strengths of clamped and simple supports. Then, three point short beam bending tests were performed to obtain shear buckling strength of Nomex honeycomb core. The tests' results were compared with theoretical results and agree well with theoretical solutions, which verified our theory. Finally, the anisotropy of shear buckling strength and the influence of honeycomb height on shear buckling strength were investigated. The results show that there is no influence of honeycomb height on the anisotropy of shear buckling strength, while both the longitudinal and transverse shear buckling strengths decrease with the increasing height of honeycomb and the decreasing ratio drops gradually.
The theoretical form of shear buckling strength of honeycomb core was shown based on the principle of minimum complementary energy and shear buckling theory of thin plate. By regarding the cell wall as a beam with elastic supports, the shear buckling strength of honeycomb core considering elastic supports was got from interpolating the strengths of clamped and simple supports. Then, three point short beam bending tests were performed to obtain shear buckling strength of Nomex honeycomb core. The tests' results were compared with theoretical results and agree well with theoretical solutions, which verified our theory. Finally, the anisotropy of shear buckling strength and the influence of honeycomb height on shear buckling strength were investigated. The results show that there is no influence of honeycomb height on the anisotropy of shear buckling strength, while both the longitudinal and transverse shear buckling strengths decrease with the increasing height of honeycomb and the decreasing ratio drops gradually.
