Effect of Thermal-Vacuum Dispertion of Graphite

Abstract

A scientific and technical development of a high-performance thermal-vacuum method, which is an environmentally friendly process based on combination of vacuuming and high-speed thermal heating, was carried out with non-stop production of nanodispersed carbon. A review of physical processes that affect a powder material has been carried out. Thermal-vacuum treatment of C1 grade graphite 1…2 mm of size was carried out. To study the structural composition of the material in initial state and processed in a thermal-vacuum installation, X-ray diffraction analysis and electron microscopy were used. According to results of X-ray analysis, the original C1 grade graphite has two known structural modifications: hexagonal one with lattice periods a_o = 0.2461 nm, c_o = 0.6705 nm, and rhombohedral structure about 30% – with a = 0.2461 nm and c = (3/2)c_o = 1.003 nm. In graphite treated in a thermal-vacuum installation, these components have been detected as the main composition. Additionally, a super-structural rhombohedral phase with periods a = 2a_o = 0.492 nm and c = (3/2)c_o = 1.003 nm has been detected. A monoclinic phase with parameters a = 0.6075  nm, b = 0.4477 nm, c = 0.4913 nm, and β = 99.6° has also been detected, probably with the presence of iron atoms in structure. The results of analysis and calculations are generally consistent with TEM images of the reciprocal lattice of processed graphite. As a result, it was noted that the initial graphite powder was crushed to 2…40 nm with a partial change in the structure, formation of objects like multilayer nanotubes and fullerenes. It was noted that thermal deformations are involved in this effect, what can significantly accelerate the process of obtaining nanodispersed carbon material with new physicochemical and mechanical properties. The results could be widely used for industrial production of nanosized materials.