Synergistic Effect of Fluorine and Hydrogen on Processes of Graphite and Diamond Formation from Fluorographite-Naphthalene Mixtures at High Pressures

Abstract

Pressure–temperature-induced transformations of fluorographite CF1.1 and homogeneous mixtures of CF1.1 with naphthalene under static pressure of 8.0 GPa have been investigated by X-ray diffraction, scanning and transmission electron microscopies, and energy-dispersive X-ray analysis. It was found that carbonization of neat CF1.1 occurs at temperatures above 500 °C. Formation of graphite showing high grade of crystalline perfection has been observed already at ∼900 °C. The process of graphitization of carbon residue from CF1.1 is also characterized by high yield of planar graphite monocrystals of clear-cut polygonal shape. The formation of diamonds from CF1.1 at 8.0 GPa was not observed within all studied temperature range, up to 1500 °C. Thermal transformations of CF1.1 mixtures with naphthalene are distinguished by significantly reduced graphitization temperature threshold and a record low initiation temperature of diamond formation, 900 °C at 8.0 GPa, in comparison with various hydrocarbons. This can be...