Siberian Federal University (Krasnoyarsk, Russia)
Gilmanshina T. R., Associate Professor, Candidate of Engineering Sciences, Associate Professor, gtr1977@mail.ru
Dubova I. V., Associate Professor, Candidate of Engineering Sciences, Associate Professor
Koroleva G. A., Associate Professor, Candidate of Сhemical Sciences, Associate Professor
Vasilyev G. V., Postgraduate Student

Graphite is the only thermodynamically stable modification of carbon with a layered structure that promotes the formation of many intercalated compounds, which, upon thermal shock exposure, form a worm-like porous structure with a low bulk density and high thermal stability. The purpose of this work is to establish the conditions for obtaining oxidized graphite with maximum capacity for further thermal expansion at Russian deposits for subsequent use in advanced fire-retardant coatings for metal products and in foundry refractory coatings. GT-1, GO-1, and GL-1 graphite grades were selected for studying the intercalation processes. These represent natural flake-like crystalline graphite from the Taiginskoe graphite deposit. After an analysis of the available literature, the following oxidative systems were studied: 96-percent H₂SO₄ – oxidizing agent (K₂S₂O₈, K₂Cr₂O₇,Co₃O₄,HNO₃) system. In the course of the work, the following conditions were established for obtaining Taiginskoe deposit GO-1 and GT-1 grade oxidized graphite: the main graphite fraction size of 200–400 μm or larger; an oxidizing mix based on concentrated sulfuric acid and potassium dichromate mixed at 20 : 1, with an oxidizing agent to graphite ratio of 0.5 : 1.0 by weight; hydrolysis of the oxidized graphite to obtain neutral wash water conditions (pH 6–7); and air drying at 95–100 °C to obtain a constant weight. Significant expansion of intercalated GT-1 and GO-1 graphites begins at 500 °C; at temperatures over 900 °C, the degree of expansion increases from 22 to 105. An X-ray diffraction analysis has confirmed the change in the interplanar distance due to the distribution of the intercalant between the layers of the graphite matrix.

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