SIC ENHANCED NUCLEATION OF DIAMOND UNDER HIGH-PRESSURE AND HIGH-TEMPERATURE

Three kinds of catalyst have been prepared to investigate the role of SIC in diamond nucleation under high pressure and high temperature: (1 ) a fresh Ni-SiC powder mixture; (2) a heat-treated Ni-SiC mixture at 1300 degrees C for 2 h in vacuum, and (3) a heat-treated Ni-Si mixture at 1100 degrees C for 3 h in vacuum. When carbon black was treated wi th each catalyst at 4.7 GPa, 1450 degrees C for 5 min, diamond was syn thesized only in the specimen containing the fresh mixture of Ni-SiC c atalyst. The added fresh SiC enhanced drastically diamond formation. S iC thus appears to act as direct nucleation sites of diamond under the experimental condition.