Niobates are promising all-climate Li^(+)-storage anode material due to their fast charge transport,large specific capacities,and resistance to electrolyte reaction.However,their moderate unit-cellvolume expansion(gen...Niobates are promising all-climate Li^(+)-storage anode material due to their fast charge transport,large specific capacities,and resistance to electrolyte reaction.However,their moderate unit-cellvolume expansion(generally 5%–10%)during Li^(+)storage causes unsatisfactory long-term cyclability.Here,“zero-strain”NiNb_(2)O_(6) fibers are explored as a new anode material with comprehensively good electrochemical properties.During Li^(+)storage,the expansion of electrochemical inactive NiO_(6) octahedra almost fully offsets the shrinkage of active NbO_(6) octahedra through reversible O movement.Such superior volume-accommodation capability of the NiO_(6) layers guarantees the“zero-strain”behavior of NiNb_(2)O_(6) in a broad temperature range(0.53%//0.51%//0.74%at 25//−10//60℃),leading to the excellent cyclability of the NiNb_(2)O_(6) fibers(92.8%//99.2%//91.1%capacity retention after 1000//2000//1000 cycles at 10C and 25//−10//60℃).This NiNb_(2)O_(6) material further exhibits a large reversible capacity(300//184//318 mAh g−1 at 0.1C and 25//−10//60℃)and outstanding rate performance(10 to 0.5C capacity percentage of 64.3%//50.0%//65.4%at 25//−10//60℃).Therefore,the NiNb_(2)O_(6) fibers are especially suitable for large-capacity,fast-charging,long-life,and all-climate lithium-ion batteries.展开更多
In SiC（f）/Ti-6Al-4V composites, the microstructure of the matrix close to the fiber was different from that of the fiber-less material. Microstructure observations show that a layer of fine grains was located adjace...In SiC（f）/Ti-6Al-4V composites, the microstructure of the matrix close to the fiber was different from that of the fiber-less material. Microstructure observations show that a layer of fine grains was located adjacent to the fiber, and more dislocations and faults were found in this region. Higher recrystallization nucleation rate due to the undeformed SiC fiber and thermal residual stress induced during cooling from the fabrication temperature caused the microstructural changes of the matrix. Hardness measurement indicates that the matrix in the fiber neighborhood was strengthened, and the strengthening effect decreased with distance away from the fiber.展开更多
Stitch welding of plate covered skeleton structure of Ti-6Al-4V titanium alloys has a variety of applications in aerospace vehicle manufacture. The laser stitch welding of Ti-6Al-4V titanium alloys was carried out by ...Stitch welding of plate covered skeleton structure of Ti-6Al-4V titanium alloys has a variety of applications in aerospace vehicle manufacture. The laser stitch welding of Ti-6Al-4V titanium alloys was carried out by a 4 kW ROFIN fiber laser. Influences of laser welding parameters on the macroscopic geometry, porosity, microstructure and mechanical properties of the stitch welded seams were investigated by digital microscope, optical microscope, scanning electron microscope and universal tensile testing machine. The results showed that the three-pipe nozzle with gas flow rate larger than 5 L/min could avoid oxidization, presenting better shielding effect in comparison with the single-pipe nozzle. Porosity formation could be suppressed with the gap between plate and skeleton less than 0.1 mm, while the existing porosity can be reduced with remelting. The maximum shear strength of stitch welding joint with minimal porosity was obtained by employing laser power of 1700 W, welding speed of 1.5 m/min and defocusing distance of ＋8 ram.展开更多
SiCf/Ti-6Al-4V composites were fabricated by the powder-coated fiber method. The precursor fiber was prepared under the optimized parameter, and the composites were made using the vacuum hot pressure method. The influ...SiCf/Ti-6Al-4V composites were fabricated by the powder-coated fiber method. The precursor fiber was prepared under the optimized parameter, and the composites were made using the vacuum hot pressure method. The influence of heat exposure time on products of thelinterfacial reaction was investigated using scanning electron microscope （SEM） and analytical transmission electron microscope （TEM） with energy dispersive spectrometer （EDS）. The main products are TiC and Ti5Si3 after vacuum exposing the samples at 700℃ for 50 h. The growth dynamics of interracial reaction products was analyzed quantitatively, which fitted the parabola rule. The activity energy of the reaction was 252 kJ·mol^-1.展开更多
SCS-6 SiC continuous fiber-reinforced Ti-Al intermetallics-matrix composites were fabricated by HIP method and then heat-treated in vacuum under different conditions. The interfacial reaction kinetics and mechanism we...SCS-6 SiC continuous fiber-reinforced Ti-Al intermetallics-matrix composites were fabricated by HIP method and then heat-treated in vacuum under different conditions. The interfacial reaction kinetics and mechanism were studied by using SEM, EDS and XRD. The results show that the content fluctuation of reactive elements such as C, Ti and Si appears in interfacial reaction layers, and multi-layer interfacial reaction compounds form. Alloying element Nb in matrix remarkably diffuses into interfacial reaction zone and changes the activation energy for the interfacial reaction layer growth following a role of parabolic rate. The activation energy (Qk) and (k0) of SCS-6 SiC/super α2 and SCS-6 SiC/Ti2AlNb are 317.664 kJ/mol, 175.709 kJ/mol and 5.4438×10-2 m/s1/2, 1.44×10-5 m/s1/2; respectively, and the diffusion coefficient (DC) is about 10-18—10-20 m2/s. It is confirmed that the SCS-6 SiC/Ti-Al intermetallic composites have higher interface compatibility and stability. Furthermore, compared with SCS-6 SiC/super α2, the interface compatibility and stability of SCS-6 SiC/Ti2AlNb are even higher.展开更多
尼龙6(PA6)树脂具有优异的性能,其连续纤维复合材料在汽车、航空航天领域具有广泛应用。但是PA6树脂熔融后黏度较高,不易对连续纤维充分浸渍,并且连续纤维与PA6的复合材料界面黏附性较差,限制了其复合材料的性能和应用。针对这些问题,...尼龙6(PA6)树脂具有优异的性能,其连续纤维复合材料在汽车、航空航天领域具有广泛应用。但是PA6树脂熔融后黏度较高,不易对连续纤维充分浸渍,并且连续纤维与PA6的复合材料界面黏附性较差,限制了其复合材料的性能和应用。针对这些问题,文中对连续玻璃纤维增强尼龙6(CGF/PA6)复合材料开展了研究。首先,采用阴离子开环聚合制备PA6,确定了其最佳制备工艺;其次,用硅烷偶联剂KH550(AP)对连续玻璃纤维(CGF)进行改性,并对其进行了红外光谱表征;最后,通过原位聚合法制备了CGF/PA6复合材料,研究了AP改性对CGF/PA6复合材料力学性能的影响,并对CGF/PA6复合材料的拉伸断口进行了扫描电镜分析。结果表明,AP被键合到了CGF表面,AP改性可以增强CGF/PA6复合材料的界面黏附性,从而使CGF/PA6复合材料的拉伸强度得到改善,当AP用量为2%时,CGF/PA6复合材料的拉伸强度高达88.52 MPa,此时,复合材料的断裂伸长率最低,为4.90%。CGF/PA6复合材料的冲击强度变化不大,均在50 k J/m2左右,说明复合材料的韧性受CGF表面改性影响较小。展开更多
In situ, compatibilization of low density polyethylene (LDPE) (30%) and nylon-6 (70%) blends through one-step reactive extrusion using t-BuOOH as an initiator and low molecular weight interfacial agents as compatibili...In situ, compatibilization of low density polyethylene (LDPE) (30%) and nylon-6 (70%) blends through one-step reactive extrusion using t-BuOOH as an initiator and low molecular weight interfacial agents as compatibilizers was studied. The compatibilizer contained a long chain hydrocarbon, double bond and two polar functional groups which was capable of reacting with both LDPE and nylon-6 in the presence of initiator to form a copolymer at the interface of the two polymer phases. The extruded blends exhibited significant enhancement in their compatibility based on morphological, thermal analysis and mechanical studies. The effect of the hydrocarbon chain length and structure of the functional group of the compatibilizer was also examined. It was found that blends prepared by using the compatibilizer containing longer hydrocarbon chain and amide group had better mechanical properties.展开更多
A combined system consisting of hydrolysis acidification, denitrification and nitrification reactors was used to remove carbon and nitrogen from the nylon - 6 production wastewater, which was characterized by good bio...A combined system consisting of hydrolysis acidification, denitrification and nitrification reactors was used to remove carbon and nitrogen from the nylon - 6 production wastewater, which was characterized by good biodegradability and high nitrogen concentration. The influences of Chemical Oxygen Demand （COD） in the influent, recirculation ratio, Hydraulic Residence Time （HRT） and Dissolved Oxygen （DO） concentration on the system performances were investigated. From results it could be seen that good performances have been achieved during the overall experiments periods, and COD, Total Nitrogen （TN）, NH^＋ -N and Suspended Solids （SS） in the effluent were 53, 16, 2 and 24 mg· L^-1, respectively, which has satisfied the first standard of wastewater discharge established by Environmental Protection Agency （EPA） of China. Furthermore, results showed that operation factors, viz. COD in the influent, recirculation ratio, HRT and DO concentration, all had important influences on the system performances.展开更多
PA6/PET bicomponent fiber at different spinning speedswere produced. Influences of cross blowing, spinning speed, PA6 and PET component ratio, drawing condition etc. on the mechanical properties, heat shrinkage,orient...PA6/PET bicomponent fiber at different spinning speedswere produced. Influences of cross blowing, spinning speed, PA6 and PET component ratio, drawing condition etc. on the mechanical properties, heat shrinkage,orientation and crystallization of the fiber were investigated. Also the rules among these influencing parameters were obtained. The splitting property of the fiber and its influence on the textile processing are discussed, which offers a base for the production of PA6/PET bicomponent fiber using splitting technology.展开更多
基金supported by the National Natural Science Foundation of China(51762014,52231007,12327804,T2321003,22088101)in part by the National Key Research Program of China under Grant 2021YFA1200600.
文摘Niobates are promising all-climate Li^(+)-storage anode material due to their fast charge transport,large specific capacities,and resistance to electrolyte reaction.However,their moderate unit-cellvolume expansion(generally 5%–10%)during Li^(+)storage causes unsatisfactory long-term cyclability.Here,“zero-strain”NiNb_(2)O_(6) fibers are explored as a new anode material with comprehensively good electrochemical properties.During Li^(+)storage,the expansion of electrochemical inactive NiO_(6) octahedra almost fully offsets the shrinkage of active NbO_(6) octahedra through reversible O movement.Such superior volume-accommodation capability of the NiO_(6) layers guarantees the“zero-strain”behavior of NiNb_(2)O_(6) in a broad temperature range(0.53%//0.51%//0.74%at 25//−10//60℃),leading to the excellent cyclability of the NiNb_(2)O_(6) fibers(92.8%//99.2%//91.1%capacity retention after 1000//2000//1000 cycles at 10C and 25//−10//60℃).This NiNb_(2)O_(6) material further exhibits a large reversible capacity(300//184//318 mAh g−1 at 0.1C and 25//−10//60℃)and outstanding rate performance(10 to 0.5C capacity percentage of 64.3%//50.0%//65.4%at 25//−10//60℃).Therefore,the NiNb_(2)O_(6) fibers are especially suitable for large-capacity,fast-charging,long-life,and all-climate lithium-ion batteries.
文摘In SiC（f）/Ti-6Al-4V composites, the microstructure of the matrix close to the fiber was different from that of the fiber-less material. Microstructure observations show that a layer of fine grains was located adjacent to the fiber, and more dislocations and faults were found in this region. Higher recrystallization nucleation rate due to the undeformed SiC fiber and thermal residual stress induced during cooling from the fabrication temperature caused the microstructural changes of the matrix. Hardness measurement indicates that the matrix in the fiber neighborhood was strengthened, and the strengthening effect decreased with distance away from the fiber.
基金Project(2012BAF08B02)supported by Key Project in the National Science and Technology Pillar Program During the Twelfth Five-year Plan Period,China
文摘Stitch welding of plate covered skeleton structure of Ti-6Al-4V titanium alloys has a variety of applications in aerospace vehicle manufacture. The laser stitch welding of Ti-6Al-4V titanium alloys was carried out by a 4 kW ROFIN fiber laser. Influences of laser welding parameters on the macroscopic geometry, porosity, microstructure and mechanical properties of the stitch welded seams were investigated by digital microscope, optical microscope, scanning electron microscope and universal tensile testing machine. The results showed that the three-pipe nozzle with gas flow rate larger than 5 L/min could avoid oxidization, presenting better shielding effect in comparison with the single-pipe nozzle. Porosity formation could be suppressed with the gap between plate and skeleton less than 0.1 mm, while the existing porosity can be reduced with remelting. The maximum shear strength of stitch welding joint with minimal porosity was obtained by employing laser power of 1700 W, welding speed of 1.5 m/min and defocusing distance of ＋8 ram.
文摘SiCf/Ti-6Al-4V composites were fabricated by the powder-coated fiber method. The precursor fiber was prepared under the optimized parameter, and the composites were made using the vacuum hot pressure method. The influence of heat exposure time on products of thelinterfacial reaction was investigated using scanning electron microscope （SEM） and analytical transmission electron microscope （TEM） with energy dispersive spectrometer （EDS）. The main products are TiC and Ti5Si3 after vacuum exposing the samples at 700℃ for 50 h. The growth dynamics of interracial reaction products was analyzed quantitatively, which fitted the parabola rule. The activity energy of the reaction was 252 kJ·mol^-1.
基金Project(50371069) suppported by the National Natural Science Foundation of China Project(20030699013) suported by the State Educational Ministry Doctoral Foundation+1 种基金 Project(04G53044) supported by the Foundation of Aviation Science Project(ZX200301014) supported by the Materials Engineering Center Foundation of Jiangxi Province, China
文摘SCS-6 SiC continuous fiber-reinforced Ti-Al intermetallics-matrix composites were fabricated by HIP method and then heat-treated in vacuum under different conditions. The interfacial reaction kinetics and mechanism were studied by using SEM, EDS and XRD. The results show that the content fluctuation of reactive elements such as C, Ti and Si appears in interfacial reaction layers, and multi-layer interfacial reaction compounds form. Alloying element Nb in matrix remarkably diffuses into interfacial reaction zone and changes the activation energy for the interfacial reaction layer growth following a role of parabolic rate. The activation energy (Qk) and (k0) of SCS-6 SiC/super α2 and SCS-6 SiC/Ti2AlNb are 317.664 kJ/mol, 175.709 kJ/mol and 5.4438×10-2 m/s1/2, 1.44×10-5 m/s1/2; respectively, and the diffusion coefficient (DC) is about 10-18—10-20 m2/s. It is confirmed that the SCS-6 SiC/Ti-Al intermetallic composites have higher interface compatibility and stability. Furthermore, compared with SCS-6 SiC/super α2, the interface compatibility and stability of SCS-6 SiC/Ti2AlNb are even higher.
文摘尼龙6(PA6)树脂具有优异的性能,其连续纤维复合材料在汽车、航空航天领域具有广泛应用。但是PA6树脂熔融后黏度较高,不易对连续纤维充分浸渍,并且连续纤维与PA6的复合材料界面黏附性较差,限制了其复合材料的性能和应用。针对这些问题,文中对连续玻璃纤维增强尼龙6(CGF/PA6)复合材料开展了研究。首先,采用阴离子开环聚合制备PA6,确定了其最佳制备工艺;其次,用硅烷偶联剂KH550(AP)对连续玻璃纤维(CGF)进行改性,并对其进行了红外光谱表征;最后,通过原位聚合法制备了CGF/PA6复合材料,研究了AP改性对CGF/PA6复合材料力学性能的影响,并对CGF/PA6复合材料的拉伸断口进行了扫描电镜分析。结果表明,AP被键合到了CGF表面,AP改性可以增强CGF/PA6复合材料的界面黏附性,从而使CGF/PA6复合材料的拉伸强度得到改善,当AP用量为2%时,CGF/PA6复合材料的拉伸强度高达88.52 MPa,此时,复合材料的断裂伸长率最低,为4.90%。CGF/PA6复合材料的冲击强度变化不大,均在50 k J/m2左右,说明复合材料的韧性受CGF表面改性影响较小。
文摘In situ, compatibilization of low density polyethylene (LDPE) (30%) and nylon-6 (70%) blends through one-step reactive extrusion using t-BuOOH as an initiator and low molecular weight interfacial agents as compatibilizers was studied. The compatibilizer contained a long chain hydrocarbon, double bond and two polar functional groups which was capable of reacting with both LDPE and nylon-6 in the presence of initiator to form a copolymer at the interface of the two polymer phases. The extruded blends exhibited significant enhancement in their compatibility based on morphological, thermal analysis and mechanical studies. The effect of the hydrocarbon chain length and structure of the functional group of the compatibilizer was also examined. It was found that blends prepared by using the compatibilizer containing longer hydrocarbon chain and amide group had better mechanical properties.
基金Shanghai Science and Technology Committee(No.042312045)Shanghai Post-doctor Fund
文摘A combined system consisting of hydrolysis acidification, denitrification and nitrification reactors was used to remove carbon and nitrogen from the nylon - 6 production wastewater, which was characterized by good biodegradability and high nitrogen concentration. The influences of Chemical Oxygen Demand （COD） in the influent, recirculation ratio, Hydraulic Residence Time （HRT） and Dissolved Oxygen （DO） concentration on the system performances were investigated. From results it could be seen that good performances have been achieved during the overall experiments periods, and COD, Total Nitrogen （TN）, NH^＋ -N and Suspended Solids （SS） in the effluent were 53, 16, 2 and 24 mg· L^-1, respectively, which has satisfied the first standard of wastewater discharge established by Environmental Protection Agency （EPA） of China. Furthermore, results showed that operation factors, viz. COD in the influent, recirculation ratio, HRT and DO concentration, all had important influences on the system performances.
文摘PA6/PET bicomponent fiber at different spinning speedswere produced. Influences of cross blowing, spinning speed, PA6 and PET component ratio, drawing condition etc. on the mechanical properties, heat shrinkage,orientation and crystallization of the fiber were investigated. Also the rules among these influencing parameters were obtained. The splitting property of the fiber and its influence on the textile processing are discussed, which offers a base for the production of PA6/PET bicomponent fiber using splitting technology.
