Kinetics of diamond spontaneous crystallization from the melt of the Fe-Al-C system at 6.5 GPa

摘要

Kinetics of diamond spontaneous crystallization from the Fe-Al-C system melt in equilibrium with graphite has been studied in situ at 6.5 GPa in the range 1720-1920 K using diffraction of synchrotron radiation. The process under consideration is controlled by carbon diffusion in the melt at 1720 and 1820 K. Kinetics data might be best fitted by a model that assumes instantaneous nucleation. At 1920 K the mechanism of diamond crystallization changes; during growth, continuous nucleation is observed and the kinetics of the processes on the surface of growing crystals becomes the stage that controls the crystallization. The rate of spontaneous crystallization in the Fe-Al-C system decreases with increasing temperature as the graphite-diamond equilibrium line is approached.