Abstract
The conditions and mechanism of formation of nano-polycrystalline diamonds directly from graphite and non-graphitic carbon (carbon black, glassy carbon, C 60 and carbon nanotubes) at high pressure and high temperature have been investigated. The onset temperature for diamond formation at P ≥ q 15 GPa is 1500-1600 °C for all carbon materials, although the required temperature conditions for pure polycrystalline diamond are T ≥ q 2200 °C for graphite and T ≥ q 1600 °C for non-graphitic carbon. Polycrystalline diamond forms as a result of simultaneous diffusion and two-step martensitic processes from graphite, whereas it forms only due to diffusion without graphitization or formation of intermediate phases from non-graphitic carbon. Nano-polycrystalline diamonds consisting only of very fine particles(<10nm in size) can be obtained from non-graphitic carbon at T ∼ 1600-2000 °C under pressures ≥15 GPa.
Original language | English |
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Pages (from-to) | 63-69 |
Number of pages | 7 |
Journal | High Pressure Research |
Volume | 26 |
Issue number | 2 |
DOIs | |
Publication status | Published - 2006 Jun 1 |
Externally published | Yes |
Keywords
- Diamond
- Direct conversion
- High pressure
- Nano-polycrystalline
ASJC Scopus subject areas
- Condensed Matter Physics