Calculation of the Free Surface Energy of Coals from the Donets Basin and Graphites

Abstract

The methodologies of the determination of the free surface energy of solids were analyzed. It was shown that the currently available models for the calculation of free surface energy are based on the measurements of the angles of contact, and they contain an internal contradiction that consists in the fact that the surface energy is divided into two or three components: a polar component, hydrogen bonds, and a dispersion component. The free surface energy was calculated for the metamorphic series of coals from the Donets Basin (long-flame, gas, coke, and lean coals and anthracites) and graphites. Considerable differences in the values of free surface energy for different coalmine beds of anthracites were not revealed. Technical-grade and spectral graphites are insignificantly different from anthracites in terms of free surface energy, but a polar component of free surface energy has lower values of 0.0054–0.0117 J/m².