Role of plastic deformation in tailoring ultrafine microstructure in nanotwinned diamond for enhanced hardness

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• 作者：Wentao Hu 胡文涛 ; Bin Wen 温斌 ; Quan Huang 黄权 ; Jianwei Xiao 肖建伟…
• 关键词：nanotwinned diamond ; high temperature and high pressure (HTHP) ; plastic deformation ; hardness
• 刊名：Science China Materials
• 出版年：2017
• 出版时间：February 2017
• 年：2017
• 卷：60
• 期：2
• 页码：178-185
• 全文大小：1884KB
• 刊物类别：Materials Science, general; Chemistry/Food Science, general;
• 刊物主题：Materials Science, general; Chemistry/Food Science, general;
• 出版者：Science China Press
• ISSN：2199-4501
• 卷排序：60

文摘

Nanotwinned diamond (nt-diamond), which demonstrates unprecedented hardness and stability, is synthesized through the martensitic transformation of onion carbons at high pressure and high temperature (HPHT). Its hardness and stability increase with decreasing twin thickness at the nanoscale. However, the formation mechanism of nanotwinning substructures within diamond nanograins is not well established. Here, we characterize the nanotwins in nt-diamonds synthesized under different HPHT conditions. Our observation shows that the nanotwin thickness reaches a minimum at ~ 20 GPa, below which phase-transformation twins and deformation twins coexist. Then, we use the density-functional-based tight-binding method and kinetic dislocation theory to investigate the subsequent plastic deformation mechanism in these pre-existing phase-transformation diamond twins. Our results suggest that pressure-dependent conversion of the plastic deformation mechanism occurs at a critical synthetic pressure for nt-diamond, which explains the existence of the minimum twin thickness. Our findings provide guidance on optimizing the synthetic conditions for fabricating nt-diamond with higher hardness and stability.