【摘要】 在利用高分辨电子显微术研究 Si₃N₄结构过程中,有了新的发现。这些发现包括纳米级裂纹、超结构、纳米畴和辐射损伤等。纳米级裂纹是晶粒中纳米大小的裂纹,它可能是导致穿晶断裂的裂纹。超结构可能影响Si₃N₄晶粒的力学性能,我们在研究中发现了三种超结构。纳米畴是晶粒中一种新的结构缺陷,在研究中我们发现了两种这类畴。也研究了辐射损伤,发现 α-Si₃N₄比β-Si₃N₄更易于受到辐射损伤,这说明β-Si₃N₄比α-Si₃N₄结构更稳定。还仔细地研究了 Si₃N₄陶瓷的晶界,结果指出,晶界工程对于改善 Si₃N₄陶瓷的力学性能是强有力的手段。更多还原

【Abstract】 During the investigation of Si₃N₄ structure by HREM,new discoveries have beensuccessively developed.These discoveries include nanocrack,superstructure,nanodo-main,radiation damage and so on.The nanocrack is a crack in nano size withingrain and it may cause transcrystalline fracture.The superstructure may effect themechanical properties of Si₃N₄ grains and three kinds of superstructures have beenfound in our research.Nanodomain is a new kind of structure defect within grain andtwo kinds of new nanodomains have been found by us.The radiation damage werealso studied and the fact that radiation damage in α-Si₃N₄ is easier to be producedthan that in β-Si₃N₄ may indicate that β-Si₃N₄ is much stronger than α-Si₃N₄.Grainboundary in Si₃N₄ ceramics were studied in detail;the results show that grain boun-dary engineering is much powerful for improving mechanical properties of Si₃N₄ cera-mics.更多还原