Superhard composites of cubic silicon nitride and diamond

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• 作者：Wendan Wang ; Duanwei He ; Mingjun Tang ; Fengjiao Li ; Lei Liu ; Yan Bi
• 关键词：Cubic silicon nitride ; Nanodiamond ; High pressure
• 刊名：Diamond and Related Materials
• 出版年：2012
• 出版时间：July-August, 2012
• 年：2012
• 卷：27-28
• 期：Complete
• 页码：49-53
• 全文大小：1439 K

文摘

Powder mixture of graphite and silicon nitride with hexagonal structure (¦Á/¦Â-Si₃N₄) was ball-milled in nitrogen and compressed under ~ 16 GPa/1800 ¡ãC and ~ 18 GPa/2000 ¡ãC, to investigate the possibility for replacing Si atoms by C atoms in cubic spinel silicon nitride (c-Si₃N₄). The sintered samples were characterized by X-ray diffraction (XRD), hardness measurement, optical microscope, scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM). The results show that the well-sintered compacts were composed of nanocrystalline c-Si₃N₄ and nanocrystalline diamond, and neither C₃N₄ and CSi₂N₄ nor other reaction products of Si₃N₄ and C were observed. Vickers hardness test shows that the average hardness of the samples is 41-42 GPa. As a comparison, phase-pure c-Si₃N₄ bulks also have been synthesized and their hardness was confirmed to be about 31 GPa. The pure c-Si₃N₄ sintered bulks exhibit a high frangibility, but their fracture toughness could be largely improved by adding carbon (nanocrystalline diamond) in the sintered compacts.