Investigation of the process of diamond formation from SiC under high pressure and high temperature
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SiC powder or graphite in contact with cobalt, nickel or a Ni70Mn25Co5 alloy was treated at high pressure and high temperature in stable region of diamond. It was found that Ni70Mn25Co5 alloy is more effective in the process of diamond formation from SiC than the others, but the difference was not apparent when graphite was used instead of SiC. Using the Ni70Mn25Co5 alloy, diamond formed rapidly with the decomposition of SiC at a pressure of 5.4–6.0 GPa and temperature 1350–1570°C, and the growth tended to stagnate after 6 min, when SiC was completely exhausted. X-ray diffraction showed that the relative intensity of the diffraction lines of diamond and graphite was nearly constant in the samples synthesized under the same conditions for 2, 4 and 6 min. The results suggest that diamond and graphite may be formed directly and respectively from separated carbon atoms in a short time.
KeywordsPolymer Nickel Graphite Cobalt High Pressure
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