National University of Science and Technology ‘MISIS’, Moscow, Russia:

E. L Kossovich, Senior Researcher, Scientific-educational laboratory of physics and chemistry of coals, Candidate of Physico-mathematical Sciences, e.kossovich@misis.ru
S. A. Epshtein, Head of scientific-educational laboratory of physics and chemistry of coals, Doctor of Engineering Sciences
N. N. Dobryakova, Researcher of scientific-educational laboratory of physics and chemistry of coals, Candidate of Engineering Sciences

Ural federal university named after the first President of Russia B.N. Yeltsin, Ekaterinburg, Russia:
M. G. Minin, Junior Researcher of Department of physical techniques and devices for quality control, Institute of Physics and Technology

The results are presented on the studies of mechanical properties of anthracite, metaanthracite and graphite samples of the Omsukchan coal basin (Magadan region) by nanoindentation are presented. It was found that at the micro level, the mechanical properties in the series of anthracite-metaanthracitegraphite undergo qualitative and quantitative changes. This is manifested, first of all, in a sequential increase in the stiffness of the material (established by the modulus of elasticity). It was shown that the damage coefficient, reflecting the ability the studied objects to be crushed, varies ambiguously, which is reflected in a slight decrease during the transition from anthracite to metaanthracite, and a significant increase in the series of metaanthracite-graphite. It was established that the mechanical properties in the series of anthracite-metaanthracite-graphite are determined by the structural features of the studied geomaterials. The elastic modulus and hardness of the geomaterials increase proportionally with an increase in the optical anisotropy index. It is shown that graphite differs significantly in its mechanical properties from anthracite and metaanthracite. This is expressed in the presence of anisotropy of its mechanical properties with respect to bedding, high stiffness and a pronounced ability to fracturing.
This work was supported by the Russian Science Foundation (grant No. 18–77–10052).

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