In 1993, it was reported that diamond could be synthesized from silicon-carbide in the presence of some metallic solvent-catalysts under high pressure and high temperature [1,2]. The conversion ratio of carbon to diamond is quite high and the diamond crystals are perfect shapes with clear facets, although the grain size is very small [3]. An optical center of 1.68 eV was observed in the diamond crystals, through cathodoluminescence, suggesting that silicon impurity could be doped into the diamond in the process [4]. In this work, fine diamond crystals were synthesized by using a system of SiC and Ni_(70)Mn_(25)Co_5 alloy under high pressure and high temperature, and the effect of the pressure on the diamond yield was investigated. Thermal stability of the crystals was appraised using thermogravimetric analysis.
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