Shock compression of graphite materials bearing different microtextures and their relations to diamond transition

Abstract

Microtexture dependence of diamond transition in starting graphite materials under shock compression was examined, taking account of two critical points. (i) As the starting materials, several different graphite materials, each of which possesses homogeneous microtexture throughout the material, were used. (ii) In order to distinguish the effect of the microtexture from that of other external conditions, an advanced technique that made the pressure-temperature condition common for the individual materials was developed. Four graphite materials, a glassy carbon, two types of carbon black, and artificial graphite foil, were selected and characterized in detail by x-ray diffractometry, Raman spectroscopy, transmission electron microscopy (TEM), and electron energy-loss spectroscopy (EELS) prior to the shock loading. Shock compressions were performed for the materials, changes in the microtexture and transformed products of the recovered samples were characterized by TEM and EELS, and the effect of the microtexture on the transition to diamond was also discussed.