Shock-Compaction of Nano-Sized Diamond Powder, as Examined by Microstructural Analysis

Nano-sized diamond powder, shock-compacted in the present study, showed neither grain growth nor graphitization, but the compact was fragmented and not strongly consolidated. In contrast, a mixture of the nano-sized powder and submicrometer-sized diamond powder consolidated into a disk with 93 % of theoretical density and a Vickers micro-hardness of 25 GPa also exhibited no grain growth and showed interparticle bonds only among large particles. Although the samples obtained were neither hard nor strong, microstructural analyses and considerations based on the shock-compaction theories and models clarified issues surrounding the shock-compaction method of producing nanocrystalline materials. Both the propriety and the limitation of these theories and models are discussed in this paper.