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首页> 外文期刊>Journal of Materials Research >Structural characterization of amorphous ceramics in the system Si-B-N-(C) by means of transmission electron microscopy methods
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Structural characterization of amorphous ceramics in the system Si-B-N-(C) by means of transmission electron microscopy methods

机译：Si-B-N-（C）体系中非晶陶瓷的结构表征，采用透射电子显微镜方法

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摘要

Amorphous ceramics with the chemical composition Si_3B_3N_7 and SiBN_3C were produced from single-source molecular precursors by polymerization and pyrolysis. The powder and fiber materials were investigated by means of energy filtering transmission electron microscopy. The intensity of elastically scattered electrons is recorded to calculate the pair distribution function of these ceramics. In the pair distribution function of Si_3B_3N_7 three significant maxima at 0.l44, 0.l72, and 0.29l nm are clearly resolved and are assigned to the pair distances B-N, Si-N, and Si-Si (N-N), respectively, by comparison to crystalline materials. The predominant structural units of the ceramic are trigonal planar BN_3 and tetrahedral SiN_4 groups, which are close to their regular symmetry. The overall pair distribution function of SiBN_3C is very similar to that of Si_3B_3N_7 however, the maxima are broadened due to the incorporation of carbon into the network. High-resolution mapping of the elements Si, B, N, and C with electron spectroscopic imaging reveals a homogeneous distribution on a subnanometer scale without precipitation or separation of , for example, carbon-rich clusters. Similarly, elemental mapping of Si_3B_3N_7 reveals a random distribution of the elements Si, B, and N at the same scale. Both new ceramics consist of an amorohous network with bonds and coordinations as preformed in the precursor.
机译：化学成分为Si_3B_3N_7和SiBN_3C的非晶态陶瓷是由单源分子前驱体通过聚合和热解制得的。通过能量过滤透射电子显微镜研究了粉末和纤维材料。记录弹性散射电子的强度，以计算这些陶瓷的成对分布函数。在Si_3B_3N_7的对分布函数中，三个明显的最大值分别位于0.144、0.172和0.29l nm处，并分别分配给对距离BN，Si-N和Si-Si（NN），分别为与结晶材料的比较。陶瓷的主要结构单元是三角形平面BN_3和四面体SiN_4基团，它们接近其规则的对称性。 SiBN_3C的整体对分布函数与Si_3B_3N_7的对分布函数非常相似，但是，由于碳掺入网络中，极大值变宽了。利用电子光谱成像对元素Si，B，N和C进行的高分辨率映射揭示了亚纳米级的均匀分布，而没有沉淀或分离出例如富碳簇。类似地，Si_3B_3N_7的元素映射显示了相同比例的元素Si，B和N的随机分布。两种新陶瓷均由具有前体中预先形成的键和配位基团的无规网络组成。

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