A matrix of 96 Al2O3 ceramics was implanted with Ni ion of different dosages and energies using a MEVVA implanter. Then metallic structures of copper were made on the implanted ceramics, by using selective electroless...A matrix of 96 Al2O3 ceramics was implanted with Ni ion of different dosages and energies using a MEVVA implanter. Then metallic structures of copper were made on the implanted ceramics, by using selective electroless copper plating. In addition, the characteristics and microstructure of the implanted layer were studied by using the SEM, RBS and XPS. The results show that： 1） the implanted Ni exits as Ni^2, Ni^2＋, and Ni^3＋ in the surface of Al2O3 and metal Ni particles precipitate on ceramics during implantation; 2） the concentration of Ni submits to the Gauss distribution along the direction of implantation on the surface of Al2O3 and high Ni concentration on the surface can be obtained if the Ni is implanted with low energy and a high dosage and 3） Ni ion implantation can activate the surface of Al2O3 and induce electroless copper plating on the ceramics.展开更多
Spark plasma sintering was successfully used to produce WC-Co cermets with the addition of Cr3C2and TaC grain growth inhibitors. The spark plasma sintered compacts were investigated by scanning electron microscopy, X-...Spark plasma sintering was successfully used to produce WC-Co cermets with the addition of Cr3C2and TaC grain growth inhibitors. The spark plasma sintered compacts were investigated by scanning electron microscopy, X-ray diffraction analysis, density measurements, hardness tests, fracture toughness tests and elastic modulus tests. The results were comparedwithan inhibitor-free WC-Co cermet consolidated under the same process parameters. By using Cr3C2and TaC additives, it is possible to improve the hardness and fracture toughness of WC-Co cermets, but Cr3C2has better grain growth inhibition propertythan that of TaC. The best combination of hardness （HV30（2105±38）） and fracture toughness （（8.3±0.2）MPa·m^1/2） was obtained by the WC-5Co-2Cr3C2 cermet.展开更多
The low-temperature magnetoresistance (LTMR) in hydrothermally synthesized La 0.98 Ca 0.02 MnO 3- δ / γ -Mn 2O 3 granular system was investigated. As-prepared powders are amorphous except for a small amount of cryst...The low-temperature magnetoresistance (LTMR) in hydrothermally synthesized La 0.98 Ca 0.02 MnO 3- δ / γ -Mn 2O 3 granular system was investigated. As-prepared powders are amorphous except for a small amount of crystalline phase LaCO 3OH. After sintered at 1 073 K or above, La 0.98 Ca 0.02 MnO 3- δ perovskite and secondary phase γ -Mn 2O 3 coexist. A large LTMR of ～65% at 127 K and ～50% at 0 K in the sample with mean grain size of 23 nm was observed. The observation of a large magnetoresistance over a wide temperature interval could be of importance for useful applications.展开更多
Node interpolation cell method（NICM）is a micromechanics method employing the virtual displacement principle and the representative volume element（RVE）scheme to obtain the relationship between the global and the lo...Node interpolation cell method（NICM）is a micromechanics method employing the virtual displacement principle and the representative volume element（RVE）scheme to obtain the relationship between the global and the local strain.Mechanical properties of 2-D textile fabric reinforced ceramic matrix composites are predicted by NICM.Microstructures of 2-D woven and braided fabric reinforced composite are modeled by two kinds of RVE scheme.NICM is used to predict the macroscopic mechanical properties.The fill and warp yarns are simulated with cubic B-spline and their undulating forms are approximated by sinusoid.The effect of porosity on the fiber and matrix are considered as a reduction of elastic module.The connection of microstructure parameters and fiber volume fraction is modeled to investigate the reflection on the mechanical properties.The results predicted by NICM are compared with that by the finite element method（FEM）.The comparison shows that NICM is a valid and feasible method for predicting the mechanics properties of 2-D woven and braided fabric reinforced ceramic matrix composites.展开更多
Cel-xSmxO2 （x=0, 0.1, 0.2 and 0.3） and Sm-doped ceria＋（2%-8%）Al2O3 were synthesized through sol-gel process followed by low temperature combustion. The synthesis, structure, densification, conductivity and therma...Cel-xSmxO2 （x=0, 0.1, 0.2 and 0.3） and Sm-doped ceria＋（2%-8%）Al2O3 were synthesized through sol-gel process followed by low temperature combustion. The synthesis, structure, densification, conductivity and thermal expansion were studied, and the structure and phase were confirmed by XRD. Dense ceramics were obtained through sintering the pellets at 1300 ℃. 2% and 4% Al2O3 were added into Ce0.8Sm0.2O2 to promote the densification at 1250 ℃. The surface morphology of the sintered pellets was analyzed using SEM. A two-probe AC impedance spectroscopy was used to study the total ionic conductivity.展开更多
Nd2O3 doped BaTiO3ceramics（the additive content was respectively 0.001, 0.002, 0.003, 0.005, 0.01 molar ratio）were prepared by Sol-Gel method to study their dielectric characteristics and electric conductivities thr...Nd2O3 doped BaTiO3ceramics（the additive content was respectively 0.001, 0.002, 0.003, 0.005, 0.01 molar ratio）were prepared by Sol-Gel method to study their dielectric characteristics and electric conductivities through X-ray photoelectron spectrum （XPS）. The results showed that the dielectric characteristics of Nd2O3 doped BaTiO3 ceramics were improved by doping. When Nd2O3 content was 0.003 mol, the results were even better, the dielectric constant was increased, the dielectric loss was decreased, the Curie-temperature （Tc） was 110 ℃, and the frequency characteristic was also good. The resistivity of Nd2O3 doped BaTiO3 ceramics was lower than that of pure BaTiO3 ceramics, when Nd2O3 content was 0.001 mol,the resistivity was （2.364×）108 Ω·m, the smallest. The grain resistance of Nd2O3 doped BaTiO3 ceramics exhibited NTC effect, but the grain boundary resistance showed PTC effect, and the grain boundary resistance was larger than that of the grain resistance, so the PTC effect originated from the grain boundary. The analysis of the element binding energy through X-ray photoelectron spectrum were indicated that the quantivalence of Ba2+and Ti4+in Nd2O3 doped BaTiO3 ceramics was variable, and resulted in the improvement of the conductibility of BaTiO3 ceramics.展开更多
基金Project BK200403 supported by the Natural Science Foundation of Jiangsu Province Project 2005A046 supported by Youth Foundation of CUMT
文摘A matrix of 96 Al2O3 ceramics was implanted with Ni ion of different dosages and energies using a MEVVA implanter. Then metallic structures of copper were made on the implanted ceramics, by using selective electroless copper plating. In addition, the characteristics and microstructure of the implanted layer were studied by using the SEM, RBS and XPS. The results show that： 1） the implanted Ni exits as Ni^2, Ni^2＋, and Ni^3＋ in the surface of Al2O3 and metal Ni particles precipitate on ceramics during implantation; 2） the concentration of Ni submits to the Gauss distribution along the direction of implantation on the surface of Al2O3 and high Ni concentration on the surface can be obtained if the Ni is implanted with low energy and a high dosage and 3） Ni ion implantation can activate the surface of Al2O3 and induce electroless copper plating on the ceramics.
文摘Spark plasma sintering was successfully used to produce WC-Co cermets with the addition of Cr3C2and TaC grain growth inhibitors. The spark plasma sintered compacts were investigated by scanning electron microscopy, X-ray diffraction analysis, density measurements, hardness tests, fracture toughness tests and elastic modulus tests. The results were comparedwithan inhibitor-free WC-Co cermet consolidated under the same process parameters. By using Cr3C2and TaC additives, it is possible to improve the hardness and fracture toughness of WC-Co cermets, but Cr3C2has better grain growth inhibition propertythan that of TaC. The best combination of hardness （HV30（2105±38）） and fracture toughness （（8.3±0.2）MPa·m^1/2） was obtained by the WC-5Co-2Cr3C2 cermet.
文摘The low-temperature magnetoresistance (LTMR) in hydrothermally synthesized La 0.98 Ca 0.02 MnO 3- δ / γ -Mn 2O 3 granular system was investigated. As-prepared powders are amorphous except for a small amount of crystalline phase LaCO 3OH. After sintered at 1 073 K or above, La 0.98 Ca 0.02 MnO 3- δ perovskite and secondary phase γ -Mn 2O 3 coexist. A large LTMR of ～65% at 127 K and ～50% at 0 K in the sample with mean grain size of 23 nm was observed. The observation of a large magnetoresistance over a wide temperature interval could be of importance for useful applications.
基金Supported by the Aviation Science Foundationof China(2009ZB5052)the Specialized Research Foundation for the Doctor Program of Higher Education(20070287039)~~
文摘Node interpolation cell method（NICM）is a micromechanics method employing the virtual displacement principle and the representative volume element（RVE）scheme to obtain the relationship between the global and the local strain.Mechanical properties of 2-D textile fabric reinforced ceramic matrix composites are predicted by NICM.Microstructures of 2-D woven and braided fabric reinforced composite are modeled by two kinds of RVE scheme.NICM is used to predict the macroscopic mechanical properties.The fill and warp yarns are simulated with cubic B-spline and their undulating forms are approximated by sinusoid.The effect of porosity on the fiber and matrix are considered as a reduction of elastic module.The connection of microstructure parameters and fiber volume fraction is modeled to investigate the reflection on the mechanical properties.The results predicted by NICM are compared with that by the finite element method（FEM）.The comparison shows that NICM is a valid and feasible method for predicting the mechanics properties of 2-D woven and braided fabric reinforced ceramic matrix composites.
文摘Cel-xSmxO2 （x=0, 0.1, 0.2 and 0.3） and Sm-doped ceria＋（2%-8%）Al2O3 were synthesized through sol-gel process followed by low temperature combustion. The synthesis, structure, densification, conductivity and thermal expansion were studied, and the structure and phase were confirmed by XRD. Dense ceramics were obtained through sintering the pellets at 1300 ℃. 2% and 4% Al2O3 were added into Ce0.8Sm0.2O2 to promote the densification at 1250 ℃. The surface morphology of the sintered pellets was analyzed using SEM. A two-probe AC impedance spectroscopy was used to study the total ionic conductivity.
文摘Nd2O3 doped BaTiO3ceramics（the additive content was respectively 0.001, 0.002, 0.003, 0.005, 0.01 molar ratio）were prepared by Sol-Gel method to study their dielectric characteristics and electric conductivities through X-ray photoelectron spectrum （XPS）. The results showed that the dielectric characteristics of Nd2O3 doped BaTiO3 ceramics were improved by doping. When Nd2O3 content was 0.003 mol, the results were even better, the dielectric constant was increased, the dielectric loss was decreased, the Curie-temperature （Tc） was 110 ℃, and the frequency characteristic was also good. The resistivity of Nd2O3 doped BaTiO3 ceramics was lower than that of pure BaTiO3 ceramics, when Nd2O3 content was 0.001 mol,the resistivity was （2.364×）108 Ω·m, the smallest. The grain resistance of Nd2O3 doped BaTiO3 ceramics exhibited NTC effect, but the grain boundary resistance showed PTC effect, and the grain boundary resistance was larger than that of the grain resistance, so the PTC effect originated from the grain boundary. The analysis of the element binding energy through X-ray photoelectron spectrum were indicated that the quantivalence of Ba2+and Ti4+in Nd2O3 doped BaTiO3 ceramics was variable, and resulted in the improvement of the conductibility of BaTiO3 ceramics.
