Atomic and Electronic Structure of Ceramic Bicrystals and High Temperature Strength

陶瓷材料的力学性能与晶界原子结构和化学键合状态密切相关。因此，有必要阐明性能与晶界结构之间的关系，以便为设计高强度、高可靠性陶瓷提供指导。在这项研究中，1：系统地研究了陶瓷双晶的制备，2：晶界原子和电子结构的评价，3：晶界特性和晶界滑动，以及4：晶界偏析的影响，并获得了以下结果。1：[110]倾斜晶界氧化锆双晶和[1120]氧化铝双晶陶瓷的制备通过在高温下接合两个单晶来制造倾斜边界。通过原子力显微镜观察热切槽的形貌，测量了它们的晶界能。结果表明，晶界能取决于晶界 关于我们 晶界原子和电子结构的评价结合HREM图像和图像模拟技术确定了双晶中的晶界原子结构。将所得结构与分子轨道法推导的原子结构进行了比较。实验结果与理论计算结果吻合较好。3：晶界特征与晶界滑动研究发现，晶界特征对晶界滑动有一定的影响。然而，晶界滑动主要是由晶界原子的配置，而不是晶界能量控制。4：晶界偏析的影响晶界偏析研究了EDS和EELS通过使用纳米探针在场发射电子显微镜。结果表明，偏析中的化学成分和化学键合状态强烈地依赖于晶界特征。通过比较EELS谱和用分子轨道方法计算的偏态密度，评价了晶界化学键状态。少

Mechanical properties of ceramics are closely related to the atomic structure and chemical bonding state in the grain boundaries. Therefore, the relationships between properties and grain boundary structure are needed to be clarified in order to obtain a guideline to design high strength and high reliable ceramics. In this study, 1 : Fabrication of ceramics bicrystals, 2 : Evaluation of grain boundary atomic and electronic structure, 3 : Grain boundary characteristics and grain boundary sliding, and 4 : Effect of grain boundary segregation were systematically investigated and the following results were obtained.1 : Fabrication of ceramicsZirconia bicrystals with [110] tilt boundaries and alumina bicrystals with [1120] tilt boundaries were fabricated by joining two single crystals at high temperatures. Their grain boundary energy was measured by observing the profiles of thermal grooving by an atomic force microscope. It was found that the grain boundary energy depends on the grain boun … More dary characteristics and shows the energy cusp at the tilt angles corresponding to CSL orientation.2 : Evaluation of grain boundary atomic and electronic structureGrain boundary atomic structures in the bicrystals were determined by combing HREM image and the image simulation technique. The obtained structures were compared with the atomic structures deduced by molecular orbital method. The experimental results agreed well with the theoretically obtained structures.3 : Grain boundary characteristics and grain boundary slidingIt was found that the grain boundary sliding were influenced by the grain boundary characteristics. However, grain boundary sliding is mainly controlled by the grain boundary atomistic configuration, rather than grain boundary energy.4 : Effect of grain boundary segregationGrain boundary segregation was investigated by EDS and EELS by using nano probe in a field emission electron microscope. It was found that the chemical composition and chemical bonding state in the segregation strongly depended on the grain boundary characteristics. Grain boundary chemical bonding state was evaluated by comparing the EELS spectra and partial density of state calculated by the molecular orbital method. Less