Thermal purification of detonation diamond

Detonation ultradispersed diamonds (UDDs) of different types were comparatively studied by thermogravimetric analysis (TGA) and Raman scattering (RS). The TGA method was used to determine temperature regions corresponding to oxidation of different carbon forms contained by UDD powder. In particular, it was found that heating in air at temperatures above 550°C results in oxidation and removal of nondiamond carbon, while the diamond fraction is retained. The shape of diamond lines in RS spectra of different UDDs oxidized at 550°C showed good agreement with the phonon confinement model. A comparison of the experimental data and theoretical calculations for the RS line shape allowed the determination of crystalline grain sizes in UDDs of different types. The values obtained correspond to the data of manufacturers of nanodiamond powders under study.