使用模具并采用磁控溅射法在铁电陶瓷PZT基体上沉积具有条形分布结构的Ni Ti SMA薄膜。显微组织结构观察发现,以条形分布结构方式沉积的Ni Ti SMA薄膜晶化处理后具有等轴晶结构。比较所制备PZT/Ni-Ti SMA薄膜复合材料与纯PZT的介电常数...使用模具并采用磁控溅射法在铁电陶瓷PZT基体上沉积具有条形分布结构的Ni Ti SMA薄膜。显微组织结构观察发现,以条形分布结构方式沉积的Ni Ti SMA薄膜晶化处理后具有等轴晶结构。比较所制备PZT/Ni-Ti SMA薄膜复合材料与纯PZT的介电常数及介电损耗发现,两者的介电损耗水平接近;复合材料的介电常数比纯PZT的提高约18%。Ni Ti SMA的沉积使基体中靠近薄膜区域的Zr/Ti物质的量比恰好落在准同型相界区内,致使所制备复合材料的介电性能优于纯PZT。展开更多
The incremental constitutive relation and governing equations with combined stresses for phase transition wave propagation in a thin-walled tube are established based on the phase transition criterion considering both...The incremental constitutive relation and governing equations with combined stresses for phase transition wave propagation in a thin-walled tube are established based on the phase transition criterion considering both the hydrostatic pressure and the deviatoric stress. It is found that the centers of the initial and subsequent phase transition ellipses are shifted along the sigma-axis in the sigma tau-plane due to the tension-compression asymmetry induced by the hydrostatic pressure. The wave solution offers the 'fast' and 'slow' phase transition waves under combined longitudinal and torsional stresses in the phase transition region. The results show some new stress paths and wave structures in a thin-walled tube with phase transition, differing from those of conventional elastic-plastic materials.展开更多
Thin film of Ti-Ni alloy has a potential to perform the microactuation functions required in the microelectromechanical system (MEMS). It is essential, however, to have good uniformity in both chemical composition and...Thin film of Ti-Ni alloy has a potential to perform the microactuation functions required in the microelectromechanical system (MEMS). It is essential, however, to have good uniformity in both chemical composition and thickness to realize its full potential as an active component of MEMS devices. Electron beam evaporation technique was employed in this study to fabricate the thin films of Ti-Ni alloy on different substrates. The targets used for the evaporation were first prepared by electron beam melting. The uniformity of composition and microstructure of the thin films were characterized by electron probe microanalysis (EPMA), Auger electron spectroscopy (AES), X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) and transmission electron microscopy (TEM). The mechanical property of the thin films was evaluated by the nano-indentation test. The martensitic transformation temperature was measured by differential scanning calorimetry (DSC). It is confirmed that the chemical composition of deposited thin films is identical to that of the target materials. Furthermore, results from depth profiling of the chemical composition variation reveal that the electron beam evaporation process yields better compositional homogeneity than other conventional methods such as sputtering and thermal evaporation. Microstructural observation by TEM shows that nanometer size precipitates are preferentially distributed along the grain boundaries of a few micron size grains. The hardness and elastic modulus of thin films decreases with an increase in Ti contents.展开更多
文摘使用模具并采用磁控溅射法在铁电陶瓷PZT基体上沉积具有条形分布结构的Ni Ti SMA薄膜。显微组织结构观察发现,以条形分布结构方式沉积的Ni Ti SMA薄膜晶化处理后具有等轴晶结构。比较所制备PZT/Ni-Ti SMA薄膜复合材料与纯PZT的介电常数及介电损耗发现,两者的介电损耗水平接近;复合材料的介电常数比纯PZT的提高约18%。Ni Ti SMA的沉积使基体中靠近薄膜区域的Zr/Ti物质的量比恰好落在准同型相界区内,致使所制备复合材料的介电性能优于纯PZT。
基金Project supported by the National Natural Science Foundation of China(No.11072240)
文摘The incremental constitutive relation and governing equations with combined stresses for phase transition wave propagation in a thin-walled tube are established based on the phase transition criterion considering both the hydrostatic pressure and the deviatoric stress. It is found that the centers of the initial and subsequent phase transition ellipses are shifted along the sigma-axis in the sigma tau-plane due to the tension-compression asymmetry induced by the hydrostatic pressure. The wave solution offers the 'fast' and 'slow' phase transition waves under combined longitudinal and torsional stresses in the phase transition region. The results show some new stress paths and wave structures in a thin-walled tube with phase transition, differing from those of conventional elastic-plastic materials.
文摘Thin film of Ti-Ni alloy has a potential to perform the microactuation functions required in the microelectromechanical system (MEMS). It is essential, however, to have good uniformity in both chemical composition and thickness to realize its full potential as an active component of MEMS devices. Electron beam evaporation technique was employed in this study to fabricate the thin films of Ti-Ni alloy on different substrates. The targets used for the evaporation were first prepared by electron beam melting. The uniformity of composition and microstructure of the thin films were characterized by electron probe microanalysis (EPMA), Auger electron spectroscopy (AES), X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) and transmission electron microscopy (TEM). The mechanical property of the thin films was evaluated by the nano-indentation test. The martensitic transformation temperature was measured by differential scanning calorimetry (DSC). It is confirmed that the chemical composition of deposited thin films is identical to that of the target materials. Furthermore, results from depth profiling of the chemical composition variation reveal that the electron beam evaporation process yields better compositional homogeneity than other conventional methods such as sputtering and thermal evaporation. Microstructural observation by TEM shows that nanometer size precipitates are preferentially distributed along the grain boundaries of a few micron size grains. The hardness and elastic modulus of thin films decreases with an increase in Ti contents.
