Sm2（Zr1-xCex）2O7 （x=0.1, 0.2, and 0.3） ceramics were prepared by solid reaction method at 1600°C for 10 h using Sm2O3, ZrO2, and CeO2 as starting reactants. The phase compositions, microstructures, thermal ex...Sm2（Zr1-xCex）2O7 （x=0.1, 0.2, and 0.3） ceramics were prepared by solid reaction method at 1600°C for 10 h using Sm2O3, ZrO2, and CeO2 as starting reactants. The phase compositions, microstructures, thermal expansion coefficients, and partial thermal conductivities of these materials were investigated. X-ray diffraction （XRD） results reveal that Sm2（Zr0.9Ce0.1）2O7 with pyrochlore structure and Sm2（Zr1-xCex）2O7 （x=0.2 and 0.3） with fluorite structure were synthesized, and scanning electrical microscopy （SEM） images show that the microstructures of these products are very dense. The linear thermal expansion coefficients increase with increasing temperature in the temperature range from ambient to 1200°C, and the thermal expansion coefficients increase with increasing content of doped CeO2. The thermal conductivities of Sm2（Zr0.8Ce0.2）2O7 and Sm2（Zr0.7Ce0.3）2O7 decrease gradually with an increase in temperature. These results show that the synthesized ceramic materials can be explored as novel prospective candidate materials for use in new thermal barrier coating systems in the future.展开更多
Resonant-cavity technique was introduced to measure the permittivity and loss tangent of low-loss dielectrics. The dielectric properties at 9-10 GHz are measured accurately at the temperature up to 800 ℃ by the reson...Resonant-cavity technique was introduced to measure the permittivity and loss tangent of low-loss dielectrics. The dielectric properties at 9-10 GHz are measured accurately at the temperature up to 800 ℃ by the resonant cavity technique. The only electrical parameters that need to be measured are quality factors （Q） and resonant length （L） of resonant cavity loaded and unloaded with dielectric sample. Moreover, the error caused by thermal expansion effect was resolved by error analysis and experimental calibration.展开更多
The maximum work principle of Bishop-Hill was developed to analyze the axisymmetric co-deformation in face-centered cubic crystals(f.c.c.)for twinning on{111}112 and slip on{111}110 systems.The influence ofξ,the rati...The maximum work principle of Bishop-Hill was developed to analyze the axisymmetric co-deformation in face-centered cubic crystals(f.c.c.)for twinning on{111}112 and slip on{111}110 systems.The influence ofξ,the ratio of critical re-solved shear stress for twinning to slip,on the yield stress states and corresponding active slip or/and twinning systems for orientations in the standard stereographic triangle of cubic crystal was investigated systematically.The Taylor factors and the anisotropy of yield strength for three important orientations[100],[110]and[111]in orientation space were analyzed.It is found that the yield strength asymmetry for the case of axisymmetric de-formation of tension and compression can be explained based on the microscopic theory of crystal plasticity.The concept of orientation factor for twinning ability was proposed and the deformation mechanism map in the orientation space was established for the case of axisymmetric deformation.The deformation texture formation and development of f.c.c.crystals with low stacking fault energy for axisymmetric tension can be explained qualita-tively on the basis of analyzed results.展开更多
基金supported by the Doctor Research Fund of Henan Institute of Engineering (No. D2007012)
文摘Sm2（Zr1-xCex）2O7 （x=0.1, 0.2, and 0.3） ceramics were prepared by solid reaction method at 1600°C for 10 h using Sm2O3, ZrO2, and CeO2 as starting reactants. The phase compositions, microstructures, thermal expansion coefficients, and partial thermal conductivities of these materials were investigated. X-ray diffraction （XRD） results reveal that Sm2（Zr0.9Ce0.1）2O7 with pyrochlore structure and Sm2（Zr1-xCex）2O7 （x=0.2 and 0.3） with fluorite structure were synthesized, and scanning electrical microscopy （SEM） images show that the microstructures of these products are very dense. The linear thermal expansion coefficients increase with increasing temperature in the temperature range from ambient to 1200°C, and the thermal expansion coefficients increase with increasing content of doped CeO2. The thermal conductivities of Sm2（Zr0.8Ce0.2）2O7 and Sm2（Zr0.7Ce0.3）2O7 decrease gradually with an increase in temperature. These results show that the synthesized ceramic materials can be explored as novel prospective candidate materials for use in new thermal barrier coating systems in the future.
文摘Resonant-cavity technique was introduced to measure the permittivity and loss tangent of low-loss dielectrics. The dielectric properties at 9-10 GHz are measured accurately at the temperature up to 800 ℃ by the resonant cavity technique. The only electrical parameters that need to be measured are quality factors （Q） and resonant length （L） of resonant cavity loaded and unloaded with dielectric sample. Moreover, the error caused by thermal expansion effect was resolved by error analysis and experimental calibration.
基金supported by the National Natural Science Foundation of China(Grant Nos.50301016 and 59971067)the China Postdoctoral Science Foundation(Grant No.2005037003).
文摘The maximum work principle of Bishop-Hill was developed to analyze the axisymmetric co-deformation in face-centered cubic crystals(f.c.c.)for twinning on{111}112 and slip on{111}110 systems.The influence ofξ,the ratio of critical re-solved shear stress for twinning to slip,on the yield stress states and corresponding active slip or/and twinning systems for orientations in the standard stereographic triangle of cubic crystal was investigated systematically.The Taylor factors and the anisotropy of yield strength for three important orientations[100],[110]and[111]in orientation space were analyzed.It is found that the yield strength asymmetry for the case of axisymmetric de-formation of tension and compression can be explained based on the microscopic theory of crystal plasticity.The concept of orientation factor for twinning ability was proposed and the deformation mechanism map in the orientation space was established for the case of axisymmetric deformation.The deformation texture formation and development of f.c.c.crystals with low stacking fault energy for axisymmetric tension can be explained qualita-tively on the basis of analyzed results.
