Development of scientific and technology basics of using of lignite char in the synthesis of silicon carbide

Metallurgy and Materials

Thermodynamics is investigated and the optimal temperature-time regimes of carbidization of the briquetted charge microsilica — lignite char are defined. In Si — O — C and Si — O — C — H systems carbide formation is the dominant process, when the stoichiometric composition of the charge the maximum content in the products of recovery of silicon carbide is achieved at 1700 K. The full carbonization of charge in conditions of heat treatment is reached at temperature of 1923 — 1973 K with duration of 20 — 15 minutes. Technological expediency, conditions and rates of chemical enrichment of carbidization products are established. The phase, chemical, granulometric compositions and morphology of silicon carbide particles are investigated. Revealed is that the carbide of the cubic structure (b-SiC) is formed during carbonization. The carbide content after enrichment is over 90 %. The silicon carbide is obtained in the form of micropowder with a specific surface area 8000 — 9000 m2/kg, the particle size range of 0.2 — 1.0 micron, having an irregular shape.