球磨Si,C混合粉末合成纳米SiC的高分辨电镜观察

HREM OBSERVATION OF THE SYNTHESIZED PROCESS OF NANO-SIZED SiC BY BALL MILLING OF Si AND C MIXED POWDERS

在室温条件下，球磨Ｓｉ，Ｃ混合粉末合成纳米尺寸ＳｉＣ．采用高分辨电子显微术在原子尺度上详尽地表征了该反应过程．高分辨像表明，在球磨过程中首先形成非晶 Ｃ（ａ－Ｃ）、非晶 Ｓｉ（ａ－Ｓｉ）以及纳米晶 Ｓｉ（ｃ－Ｓｉ），为合成 ＳｉＣ提供了适宜条件 ＳｉＣ的合成主要是通过 Ｃ原子向 ａ－Ｓｉ及 ｃ－Ｓｉ的扩散对于前者，形成非晶 ａ－Ｓｉ（Ｃ），然后机械力诱使非晶 ａ－Ｓｉ（Ｃ）晶化；对于后者， Ｃ原子直接取代 Ｓｉ原子形成 ＳｉＣ，具有取向关系（１１１）ＳｉＣ ／／（１１１）Ｓｉ．在一些区域内，还发生局域自蔓延反应，形成稍大尺寸的

Synthesis of nano-sized SiC through ball milling of elemelltal Si and graphite mixed powders at room temperature has been reported. Detailed reaction process has been characterized by high-resolution electronic microscopy (HREM). HREM observations presented herein suggest that amorphous graphite (a-graphite), amorphous silicon (a-Si) and nano-sized crystalline Si (c-Si) with many defects have been produced under ball milling (BM), which is favorable for the reaction. SiC is synthesized mainly through diffusion of C atoms into a-Si and c-Si. For the former case, a-Si (C) forms, and then mechanically driven crystallization of the a-Si (C) occurs to render the formation of SiC; for the latter case, C atoms directly replace Si atoms to form SiC with the orientation relationship (1ll)siC // (111)si In some regions, localized self-sustained reaction occurs to render the formation of slightly larger SiC grain.