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Microstructure and Mechanical Behaviors of Nano-polycrystalline Diamonds Synthesized by Direct Conversion Sintering under HPHT

Published online by Cambridge University Press:  26 February 2011

Hitoshi Sumiya  and
Tetsuo Irifune
Hitoshi Sumiya
Affiliation:
[email protected], Sumitomo Electric Industries, Electronics & Materials R&D Laboratories, 1-1-1, Koyakita, Itami, Hyogo, 664-0016, Japan, +81-72-772-4804, +81-72-770-6727
Tetsuo Irifune
Affiliation:
[email protected], Ehime University, Geodynamics Research Center, 2-5, Bunkyo-cho, Matsuyama, 790-8577, Japan
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Abstract

High-purity nano-polycrystalline diamonds have been synthesized by direct conversion from graphite and various non-graphitic carbons under static high pressures and high temperatures. The polycrystalline diamond synthesized from graphite at ≥15 GPa and 2300-2600 °C has a mixed texture comprising a homogeneous fine structure (particle size: 10-30 nm, formed in a diffusion process) and a lamellar structure (formed in a martensitic process), and has a very high Knoop hardness of 120-145 GPa. In contrast, the polycrystalline diamonds made from the non-graphitic carbons at ≥15 GPa and 1600-2000 °C have a single texture consisting of a very fine homogeneous structure (5-10 nm, formed in a diffusion process) without a lamellar structure. The hardness values of the nano-polycrystalline diamonds made from non-graphitic carbons (70-90 GPa) are significantly lower than that of polycrystalline diamond made from graphite. The investigation of the microstructure beneath the indentation of these nano-polycrystalline diamonds revealed that the existence of the lamellar structure and the bonding strength of the grain boundary have a decisive effect on the hardness.

Keywords

diamondmicrostructurehardness
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 987: Symposium PP – Materials Research at High Pressure , 2006 , 0987-PP03-01
Copyright
Copyright © Materials Research Society 2007

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References

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