2008/05/01 by H. Sumiya, K. Harano, T. Irifune
paper · doi:10.1063/1.2918985
Knoop indenters were prepared from nanopolycrystalline diamonds (NPDs) synthesized by direct conversion sintering from graphite under high pressure and high temperature. Owing to the fine structure (grain size: 10–100nm) of NPD, high-accuracy sharp edges could be formed at the indenter tips. The indentation tests demonstrated that the NPD indenter can form normal (measurable) indentations on NPD samples without fracture or chipping even at high temperatures of up to 1000°C, while conventional indenters made of single-crystal diamonds break easily above 600°C. This suggests that the NPD indenter has greater potential in high-temperature hardness tests than the conventional single-crystal diamond indenters.