Possible mechanism of strength change of diamond depending on thermal histories based on molecular dynamics analysis

摘要

Molecular dynamics (MD) simulations of indentations and heat treatments of diamond were carried out to understand the mechanism of strength change of diamond depending on thermal histories. In the simulations, a pre-existing micro crack on diamond surface disappeared by complete healing at 1070 K for 55 ps while no crack healing took place at 590 K for 2000 ps. The length of Hertzian crack decreased and dislocations moved to the crack and vanished at 1700 K. Graphitization was also observed around the crack and the area of graphitization gradually increased. The results of the simulations suggested that the strength increased by crack healing and decreased by graphitization depending on the heating temperature.