Complementary nano- and atomic-scale data from SEM, FIB, HRTEM, and EELS observations of after-coal impact diamonds from the giant Kara astrobleme are described, presenting their particular nano-sized porous polycrystalline structure, which consists of well-shaped single 20-30 nm nanocrystals that are free of deformation defects and do not contain lonsdaleite. The porous micro- and nanostructure is a special typomorphic feature of after-coal diamonds that suggests a crystallisation mechanism through short distance diffusion. The data for the after-coal impact diamonds presented here demonstrate their distinguishing characteristics from after-graphite impact diamonds, and have some similarity with the enigmatic carbonado, providing new insights to the origin of the latter.

中文翻译：

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纳米多孔纳米晶冲击金刚石

描述了来自 SEM、FIB、HRTEM 和 EELS 对来自巨型 Kara astrobleme 的煤后冲击钻石的补充纳米级和原子级数据，展示了它们特殊的纳米级多孔多晶结构，该结构由形状良好的单 20 -30 nm 纳米晶体，无变形缺陷且不含 lonsdaleite。多孔的微米和纳米结构是煤后金刚石的特殊类型特征，表明通过短距离扩散的结晶机制。这里展示的煤后冲击钻石的数据显示了它们与石墨后冲击钻石的区别特征，并且与神秘的碳粉有一些相似之处，为后者的起源提供了新的见解。