Grain Boundary Design using Ceramic Multiple Crystals and Plasticity

在这一年里，系统地制备了氧化铝和氧化锆多晶，并用高分辨电子显微镜、能谱和电子能量损失谱对其晶界结构和化学组成进行了表征。在1500℃的空气中，采用热连接技术制备了氧化铝多晶，获得了包括小角度晶界、CSL晶界和大角度晶界在内的10种倾斜晶界。结果表明，晶界能强烈地依赖于晶界特征，如在低Σ的晶界处有较大的能量尖峰。但是，晶界能的主要来源可能是晶界附近的应变能，原子组态对晶界能的贡献不大。小角度晶界由伯格斯矢量为1/3[11^-00]的部分位错阵列组成，形成位错间的层错。The BEH…通过1400℃高温蠕变试验，研究了典型晶界的晶界滑移行为。结果表明，晶界滑移的发生与晶界的几何形状和原子结构有关。在1600℃的空气中，采用热连接技术制备了氧化锆多晶，获得了10种倾斜晶界。研究发现，晶界结构和晶界能量强烈依赖于晶界性质。例如，Σ9晶界显示出特别高的能量，这是因为结构单元在晶界处应变很大，尽管偏析的Y的量很大。在Σ3边界的情况下，原子结构取决于边界平面。当边界面为(111)面时，边界沿(111)面完全笔直，而当初始边界面平行于(112)面时，则沿(111)//(115)面形成小面结构。从氧化锆中各种晶界的原子结构和偏析的角度，详细讨论了晶界特征与能量的关系。较少

In this year, alumina and zirconia multiple crystals were systematically fabricated, and the respective grain boundary structure and chemistry were characterized by high-resolution electron microscopy (HREM), energy dispersive X-ray spectroscopy (EDS) and electron energy loss spectroscopy (EELS).Alumina multiple crystals were fabricated by a hot joining technique at 1500 ℃ in air to obtain ten kinds of tilt grain boundaries which included small angle, CSL and high angle grain boundaries. It was found that grain boundary energy strongly depended on the grain boundary characters, e.g., there were large energy cusps at low Σ CSL grain boundaries. But, main part of grain boundary energy is likely to be due to the strain energy around the grain boundary, and the contribution of atomic configuration is not so large. Small angle grain boundaries were consisted of an array of partial dislocation with Burgers vector of 1/3[1 1^^- 00] to form the stacking faults between the dislocations. The beh … More avior of grain boundary sliding was also investigated for typical grain boundaries by high-temperature creep test at 1400 ℃. As the result, the occurrence of grain boundary sliding was found to depend on the grain boundary geometry and atomic structure.Zirconia multiple crystals were also fabricated by a hot joining technique at 1600 ℃ in air to obtain ten kinds of tilt grain boundaries. It was found that the grain boundary structure and energy strongly depended on the grain boundary characters. For example, Σ9 grain boundary showed particularly high energy because the structure unit is highly strained at the boundary, although the amount of segregated yttrium is very large. In the case of Σ3 boundary, the atomic structure depends on the boundary planes. When boundary plane is (111), the boundary is perfectly straight along the (111) plane, however, facet structure is formed along (111)//(115) planes when the initial boundary plane is set parallel to (112). The relationship between grain boundary characters and energy will be discussed in detail from the view point of atomic structures and segregation for all kinds of grain boundaries in zirconia. Less