Diamond Synthesis from a System of Silicon-Carbide and Iron

In order to ascertain the mechanism of the effect of catalysts on the process of diamond formation from SiC, it is necessary to investigate the behaviour of the SiC admixed with different metallic catalysts under high pressure and high temperature. In this work, SiC and iron powders were mixed in weight ratio of 1∶6, and then treated at high pressure of 5.4～6.0 GPa and temperature of 1 300～1 500 ℃ for 20 min. X-ray diffraction of the samples showed that SiC decomposed, and Fe3C and Fe3Si formed respectively in the all experiments. The decomposition of SiC carried more thoroughly under higher temperature. Diamond and graphite prectipitated clearly above 1 375 ℃ with the decrease of Fe3C. Observation in a scanning electron microscope showed that diamond crystals obtained at 6.0 GPa and 1 500 ℃ have perfect octahedron shape, the average grain size is about 50 m.