Fe3C carbide was treated at a high temperature of 1630 K and a high pressur
e of 5.3 GPa (HPHT) in a cubic anvil apparatus. Diamond is found to form fr
om iron carbide at high temperature-high pressure (HPHT). The formation of
the diamond can be confirmed by laser Raman spectra. This work opens a new
way to synthesize diamond at HPHT and provides direct evidence about the di
amond formation mechanism in the presence of a transition metal catalyst us
ing graphite as the carbon source at HPHT. (C) 2002 Elsevier Science B.V. A
ll rights reserved.