Al_(2)O_(3)–SiO_(2)sols were synthesized by using aluminum chloride hex hydrate and tetraethoxysilane(TEOS)as precursors,deionized water and ethanol mixture as the solvent,and propylene oxide as the coagulant aids.Al...Al_(2)O_(3)–SiO_(2)sols were synthesized by using aluminum chloride hex hydrate and tetraethoxysilane(TEOS)as precursors,deionized water and ethanol mixture as the solvent,and propylene oxide as the coagulant aids.Alumina coatings were prepared on the surfaces of hollow quartz filament fiber,then a new lightweight and thermal insulating material were successfully prepared by impregnatingAl_(2)O_(3)–SiO_(2)sol into a needle fabric made by coated hollow quartz filament fiber.The coated quartz fiber,aerogels and composites were characterized by Fourier transform infrared spectroscopy(FTIR),X-ray diffraction(XRD),energy dispersive spectroscopy(EDS),nitrogen adsorption-desorption(BET),scanning electron microscopy(SEM),transmission electron microscopy(TEM),and tensile tests.The effects of different fiber and calcination temperatures on the microstructures and properties ofAl_(2)O_(3)–SiO_(2)composite aerogels were investigated.The test results indicate that the mechanical properties of the aerogels are improved by introducing quartz filament fabrics and the introduction of alumina coating improves the thermal stability of the material.Compared to other fibers,Al_(2)O_(3)-coated hollow quartz fiber has significant advantages as reinforcement for composite,and their tensile strength is well retained after high temperature heat treatment.展开更多
Al 2O 3-SiO 2-TiO 2-ZrO 2 supported membranes were prepar ed by Sol-Gel method. These composite ceramic membranes are level, even and no macro crack. There exist several crystalline phases such as Al 2O 3, TiO...Al 2O 3-SiO 2-TiO 2-ZrO 2 supported membranes were prepar ed by Sol-Gel method. These composite ceramic membranes are level, even and no macro crack. There exist several crystalline phases such as Al 2O 3, TiO 2(a natase), Al 2SiO 5, and ZrO 2 in these membranes. Changing the molar ratio of Al∶Si∶Ti∶Zr,the kinds and content of crystal phases of composite membranes could be different, which may lead to a variety of microstructure of membranes. The surface nanoscale topography and microstructure of membranes were investiga ted by XRD,SEM,AFM,EPMA. The effects of additives and heat treatments on the sur face nanoscale topography and microstructure of composite ceramic membranes were also analyzed.展开更多
The cermet composites WC-20wt%Co/ZrO2（E6）with four different comtents of ZrO2（3Y）were prepared by normal vacuum sinter processing;the optical microscope and SEMwere used to characterize their microstructures.The h...The cermet composites WC-20wt%Co/ZrO2（E6）with four different comtents of ZrO2（3Y）were prepared by normal vacuum sinter processing;the optical microscope and SEMwere used to characterize their microstructures.The hardness.bending strength and impact toughness of the specimens were determined.The experimental results show that ZrO2（3Y） particles in WC-20wt%Co matrix are sphcrical particles in different sizes which are distributed uniformly in Co phases and WC phases,the bending strength and impact toughness of the WC-20wt%Co cermet composites added ZrO2（3Y）improve remarkably.but the hardness values have little change.展开更多
A lead-free solder composite was prepared by adding ZrO2 nanopowders in eutectic Sn-Ag alloy. Microstrucrural features and microhardness properties of those solders with different ZrO2 nanopowder fraction were examine...A lead-free solder composite was prepared by adding ZrO2 nanopowders in eutectic Sn-Ag alloy. Microstrucrural features and microhardness properties of those solders with different ZrO2 nanopowder fraction were examined. Results indicate that the addition of ZrO2 nanopowders reduced the size of β-Sn grains and restrained the formation of bulk Ag3Sn intermetallic compounds （IMCs） due to the adsorption effect of the ZrO2 particles. The Vicker＇s hardness of the obtained lead-free solder composites fits well with the HalI-Petch relationship. The refinement of β-Sn grains favors to improve the microhardness of composite solders.展开更多
Zircon （mesh size ≤ 44μm ） and carbon black （mesh size ≤30μm ） were used as the starting materials, weighed with re（zircon） ： re（carbon black） of 100 ： 20 and mixed fully. The specimens with the diameter...Zircon （mesh size ≤ 44μm ） and carbon black （mesh size ≤30μm ） were used as the starting materials, weighed with re（zircon） ： re（carbon black） of 100 ： 20 and mixed fully. The specimens with the diameter of 20ram and length of 5ram were prepared by pressing at 100 MPa, then dried at 120℃ for 12h, put into a furnace with 1. 5L ·min^-1 argon gas and fired at 1450℃, 1500℃, 1550℃, 1600℃ and 1650℃ for 4h, respectively. The chemical composition, phase composition and microstructure of the specimens were studied by chemical analysis, X-ray diffraction and scanning electronic microscope, and the carbothermal reduction reaction process was discussed by thermodynamic analysis. The results showed that the ZrO2-SiC composite could be synthesized by carbothermal reduction reaction using zircon and carbon black as the starting materials in argon atmosphere. The composite with different composition was obtained by controlling the firing temperature and partial pressure of CO gas. The proper temperature to synthesize ZrO2-SiC composite was 1600℃ in this experiment.展开更多
Composite powder prepared of calcium oxide stabilzed ZrO2(CSZ) and NiCr by vacuum sintering is studied,and the effect of additive TiO2 on its properties is discussed. The morphology and phases of the powder were measu...Composite powder prepared of calcium oxide stabilzed ZrO2(CSZ) and NiCr by vacuum sintering is studied,and the effect of additive TiO2 on its properties is discussed. The morphology and phases of the powder were measured and determined by SEM. EPMA, XRD methods and the testing of flowability, bulk density and microhard-ness. The results show that the metallic components in the powder are in homogeneous distribution , the flowability, bulk density and microhardness are superior to the ZrO2-NiCr powder prepared by mechanically mixing. All components in the coating made of the composite powder are well-distributed because of avoiding segregation in the middle of mixing. It proves that the composite powder is an excellent material for plasma spraying.展开更多
The Ni/ZrO2 was used as raw materials to fabricate the surface infiltrated composite layer with 1-4 mm thickness on cast steel substrate through vacuum infiltrated casting technology. The microstructure indicated that...The Ni/ZrO2 was used as raw materials to fabricate the surface infiltrated composite layer with 1-4 mm thickness on cast steel substrate through vacuum infiltrated casting technology. The microstructure indicated that the infiltrated composite layer included surface composite layer and transition layer. Wear property was investigated under room temperature and 450 ~C. The results indicated that the abrasion volume of substrate was 8 times that of the infiltrated composite layer at room temperature. The friction coefficient of infiltrated composite layer decreased with the increasing load. The wear resistance of infiltrated composite layer with different ZrO2 contents had been improved obviously under high temperature. The friction coefficient of infiltrated composite layer was decreased comparing with that at room temperature. The oxidation, abrasive and fatigue abrasion was the main wear mechanism at room temperature. Oxidation abrasion, fatigue wear and adhesive wear dominated the wearin~ process under elevated temperature.展开更多
文摘Al_(2)O_(3)–SiO_(2)sols were synthesized by using aluminum chloride hex hydrate and tetraethoxysilane(TEOS)as precursors,deionized water and ethanol mixture as the solvent,and propylene oxide as the coagulant aids.Alumina coatings were prepared on the surfaces of hollow quartz filament fiber,then a new lightweight and thermal insulating material were successfully prepared by impregnatingAl_(2)O_(3)–SiO_(2)sol into a needle fabric made by coated hollow quartz filament fiber.The coated quartz fiber,aerogels and composites were characterized by Fourier transform infrared spectroscopy(FTIR),X-ray diffraction(XRD),energy dispersive spectroscopy(EDS),nitrogen adsorption-desorption(BET),scanning electron microscopy(SEM),transmission electron microscopy(TEM),and tensile tests.The effects of different fiber and calcination temperatures on the microstructures and properties ofAl_(2)O_(3)–SiO_(2)composite aerogels were investigated.The test results indicate that the mechanical properties of the aerogels are improved by introducing quartz filament fabrics and the introduction of alumina coating improves the thermal stability of the material.Compared to other fibers,Al_(2)O_(3)-coated hollow quartz fiber has significant advantages as reinforcement for composite,and their tensile strength is well retained after high temperature heat treatment.
文摘Al 2O 3-SiO 2-TiO 2-ZrO 2 supported membranes were prepar ed by Sol-Gel method. These composite ceramic membranes are level, even and no macro crack. There exist several crystalline phases such as Al 2O 3, TiO 2(a natase), Al 2SiO 5, and ZrO 2 in these membranes. Changing the molar ratio of Al∶Si∶Ti∶Zr,the kinds and content of crystal phases of composite membranes could be different, which may lead to a variety of microstructure of membranes. The surface nanoscale topography and microstructure of membranes were investiga ted by XRD,SEM,AFM,EPMA. The effects of additives and heat treatments on the sur face nanoscale topography and microstructure of composite ceramic membranes were also analyzed.
文摘The cermet composites WC-20wt%Co/ZrO2（E6）with four different comtents of ZrO2（3Y）were prepared by normal vacuum sinter processing;the optical microscope and SEMwere used to characterize their microstructures.The hardness.bending strength and impact toughness of the specimens were determined.The experimental results show that ZrO2（3Y） particles in WC-20wt%Co matrix are sphcrical particles in different sizes which are distributed uniformly in Co phases and WC phases,the bending strength and impact toughness of the WC-20wt%Co cermet composites added ZrO2（3Y）improve remarkably.but the hardness values have little change.
基金The authors are grateful to the National Natural Science Foundation of China （No. 50401033）FANEDD of China （No. 200335）+1 种基金the Natural Science Foundation of Tianjin City （No. 033608811） Fok Ying Tong Education Foundation （No. 104015） for grant and financial support.
文摘A lead-free solder composite was prepared by adding ZrO2 nanopowders in eutectic Sn-Ag alloy. Microstrucrural features and microhardness properties of those solders with different ZrO2 nanopowder fraction were examined. Results indicate that the addition of ZrO2 nanopowders reduced the size of β-Sn grains and restrained the formation of bulk Ag3Sn intermetallic compounds （IMCs） due to the adsorption effect of the ZrO2 particles. The Vicker＇s hardness of the obtained lead-free solder composites fits well with the HalI-Petch relationship. The refinement of β-Sn grains favors to improve the microhardness of composite solders.
文摘Zircon （mesh size ≤ 44μm ） and carbon black （mesh size ≤30μm ） were used as the starting materials, weighed with re（zircon） ： re（carbon black） of 100 ： 20 and mixed fully. The specimens with the diameter of 20ram and length of 5ram were prepared by pressing at 100 MPa, then dried at 120℃ for 12h, put into a furnace with 1. 5L ·min^-1 argon gas and fired at 1450℃, 1500℃, 1550℃, 1600℃ and 1650℃ for 4h, respectively. The chemical composition, phase composition and microstructure of the specimens were studied by chemical analysis, X-ray diffraction and scanning electronic microscope, and the carbothermal reduction reaction process was discussed by thermodynamic analysis. The results showed that the ZrO2-SiC composite could be synthesized by carbothermal reduction reaction using zircon and carbon black as the starting materials in argon atmosphere. The composite with different composition was obtained by controlling the firing temperature and partial pressure of CO gas. The proper temperature to synthesize ZrO2-SiC composite was 1600℃ in this experiment.
文摘Composite powder prepared of calcium oxide stabilzed ZrO2(CSZ) and NiCr by vacuum sintering is studied,and the effect of additive TiO2 on its properties is discussed. The morphology and phases of the powder were measured and determined by SEM. EPMA, XRD methods and the testing of flowability, bulk density and microhard-ness. The results show that the metallic components in the powder are in homogeneous distribution , the flowability, bulk density and microhardness are superior to the ZrO2-NiCr powder prepared by mechanically mixing. All components in the coating made of the composite powder are well-distributed because of avoiding segregation in the middle of mixing. It proves that the composite powder is an excellent material for plasma spraying.
基金"Xi-Bu-Zhi-Guang" Foundation of Chinese Academy of Sciences(No.XBZG-2007-5)Gansu Natural Science Foundation of China(No.0806RJYA004)
文摘The Ni/ZrO2 was used as raw materials to fabricate the surface infiltrated composite layer with 1-4 mm thickness on cast steel substrate through vacuum infiltrated casting technology. The microstructure indicated that the infiltrated composite layer included surface composite layer and transition layer. Wear property was investigated under room temperature and 450 ~C. The results indicated that the abrasion volume of substrate was 8 times that of the infiltrated composite layer at room temperature. The friction coefficient of infiltrated composite layer decreased with the increasing load. The wear resistance of infiltrated composite layer with different ZrO2 contents had been improved obviously under high temperature. The friction coefficient of infiltrated composite layer was decreased comparing with that at room temperature. The oxidation, abrasive and fatigue abrasion was the main wear mechanism at room temperature. Oxidation abrasion, fatigue wear and adhesive wear dominated the wearin~ process under elevated temperature.
