Optimised cell design for high-pressure synthesis of diamond
Chien-Min J Sung
More than 150 t of diamond grits (China makes and uses about half of the world supply) are consumed each year in sawing constructional materials (eg concrete, granite, marble). These diamond grits are typically synthesised under high pressure and high temperature with graphite as the source material and a molten metal (eg iron, cobalt, nickel or its alloy) as the catalyst. Graphite and catalyst may be either stacked in the reaction cell as alternate layers or they can be mixed as powders. The reaction cell may be small (<50 cm3) with large gradients of pressure and temperature, as in the case of a cubic press, or they can be large (up to 500 cm3) with relatively uniform distribution of pressure and temperature, as in the case of a large (10000 t) belt press.