ZrO2/Ni nanocomposite was produced by pulse electrodeposition and its superplastic properties were investigated by the tensile and bulging tests.The as-deposited nickel matrix has a narrow grain size distribution with...ZrO2/Ni nanocomposite was produced by pulse electrodeposition and its superplastic properties were investigated by the tensile and bulging tests.The as-deposited nickel matrix has a narrow grain size distribution with a mean grain size of 45 nm.A maximum elongation of 605%was observed at 723 K and a strain rate of 1.67×10-3s-1 by tensile test.Superplastic bulging tests were subsequently performed using dies with diameters of 1 mm and 5 mm respectively based on the optimal superplastic forming temperature.The effects of forming temperature and gas pressure on bulging process were experimentally investigated.The results indicated that ZrO2/Ni nanocomposite samples can be readily bulged at 723 K with H/d value(defined as dome apex height over the die diameter)larger than 0.5,indicating that the nanocomposite has good bulging ability.SEM and TEM were used to examine the microstructure of the as-deposited and bulged samples.The observations showed that significant grain coarsening occurs during superplastic bulging,and the microstructure is found to depend on the forming temperature.展开更多
The influences of CeO2-ZrO2 and γ-Al2O3 mixing methods on the catalytic activity and stability of partial oxidation of methane (POM) were investigated over Ni/Ce0.7Zr0.3O2-Al2O3 catalysts. The catalysts were charac...The influences of CeO2-ZrO2 and γ-Al2O3 mixing methods on the catalytic activity and stability of partial oxidation of methane (POM) were investigated over Ni/Ce0.7Zr0.3O2-Al2O3 catalysts. The catalysts were characterized by XRD, TPR, H2-chemsorption, and TG-DTA. For fresh catalysts, the results showed that the salt precursor mixing catalyst (ATOM) presented better performance than the catalysts prepared by the precipitator mixing method (MOL) and the powder mechanically mixing method (MECH). The result of XRD suggested that the interaction between CeO2-ZrO2 and Al2O3 in ATOM sample was stronger than the others, which led to more lattice defects and thereby better initial activity. Moreover, the MECH sample had the best stability and the least coke deposition in 24 h stability tests. The results of TPR and H2-chemsorption indicated that the intimate contact of Ni-Al in MECH sample enhanced the ability of resisting coke deposition and metal sintering.展开更多
基金Funded by the National Natural Science Foundation of China(No.50575049)
摘要ZrO2/Ni nanocomposite was produced by pulse electrodeposition and its superplastic properties were investigated by the tensile and bulging tests.The as-deposited nickel matrix has a narrow grain size distribution with a mean grain size of 45 nm.A maximum elongation of 605%was observed at 723 K and a strain rate of 1.67×10-3s-1 by tensile test.Superplastic bulging tests were subsequently performed using dies with diameters of 1 mm and 5 mm respectively based on the optimal superplastic forming temperature.The effects of forming temperature and gas pressure on bulging process were experimentally investigated.The results indicated that ZrO2/Ni nanocomposite samples can be readily bulged at 723 K with H/d value(defined as dome apex height over the die diameter)larger than 0.5,indicating that the nanocomposite has good bulging ability.SEM and TEM were used to examine the microstructure of the as-deposited and bulged samples.The observations showed that significant grain coarsening occurs during superplastic bulging,and the microstructure is found to depend on the forming temperature.
基金973 Program (2004CB719503)Key Program of Natural Science Foundation of Tianjin (07JCZDJC01600)Program for New Century Excellent Talents in University (NCET-06-0243)
摘要The influences of CeO2-ZrO2 and γ-Al2O3 mixing methods on the catalytic activity and stability of partial oxidation of methane (POM) were investigated over Ni/Ce0.7Zr0.3O2-Al2O3 catalysts. The catalysts were characterized by XRD, TPR, H2-chemsorption, and TG-DTA. For fresh catalysts, the results showed that the salt precursor mixing catalyst (ATOM) presented better performance than the catalysts prepared by the precipitator mixing method (MOL) and the powder mechanically mixing method (MECH). The result of XRD suggested that the interaction between CeO2-ZrO2 and Al2O3 in ATOM sample was stronger than the others, which led to more lattice defects and thereby better initial activity. Moreover, the MECH sample had the best stability and the least coke deposition in 24 h stability tests. The results of TPR and H2-chemsorption indicated that the intimate contact of Ni-Al in MECH sample enhanced the ability of resisting coke deposition and metal sintering.