Siberian Federal University (Krasnoyarsk, Russia):

Gilmanshina T. R., Associate Professor, Candidate of Engineering Sciences, gtr1977@mail.ru
Lytkina S. I., Associate Professor, Candidate of Engineering Sciences, svetka-lisa@mail.ru
Khudonogov S. A., Senior Lecturer, s.a.hudonogov@yandex.ru
Kritskiy D. Yu., Postgraduate Student, gtr1977@mail.ru

It is shown, that chemical activation provides for a high differentiation of graphite and impurity phases, if compared with mechanical and chemical-mechanical activation. Subsequent to chemical activation, contents of iron, magnesium and calcium in graphite are significantly decreased, while content of sulfur is increased by the factor of 1.3–1.5, and contents of other elements change insignificantly. The study of phase composition showed, that formation of iron sulfates and calcium oxide is observed in the course of chemical activation, while contents of calcite and pyrite are considerably decreased. In mechanical activation, elemental composition and phase composition change insignificantly. Natural graphite particles are composed of graphite layers and laminated host rock (clay minerals), also featuring well-faceted pyramidal forms (quartz inclusions). Two conditions of surface are characteristic for chemically activated graphite. The first condition is similar to the state of natural graphite, but surface is richly covered with oxidizing atoms. The second condition is formed on particles’ cleavage surface, representing a multi-layered system. It consists of separate complex-structured rose-shaped formations, in which graphite petals are arranged around reinforcing core. With that, graphite petals are arranged at various angles relative to one another, and have different thickness. Free spaces between these formations are filled with graphite particles with arbitrarily oriented petals. Mechanical activation does not change condition of particles’ surface. Chemical activation of cryptocrystalline graphite is an efficient method of graphite preparation for beneficiation, and in its subsequent application in antistick coating permits to considerably improve cast-iron castings surface quality.
The studies were performed with the financial aid from the Russian Foundation of Fundamental Research in the framework of the International Scientific Collaboration Project No. 16-48-243043.

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