Mechanochemical synthesis of mullite and mullite-silicon carbide from secondary mineral resources used as an aggregate for fireproof concretes

摘要

Mullite (3Al_2O_3 • 2SiO_2) is a promising material for modern technologies. With its melting point of 1850℃, it may be used as an aggregate for fireproof concretes. The feasibility of producing mullite by its synthesis from the industrial by-products is studied in the paper. The materials used were fireproof clay from stripping rocks of the coal cuts and spoil sludge from the abrasion works (high alumina product). To reduce the temperature of agglomeration from 1400 to 1200℃, mechanochemical activation of the mixture in planetary mills was applied. The fireproof clay was mostly kaoline with a small amount of quartz. The high alumina product contained above 80% Al_2O_3 (corundum). The initial products were mixed in the proportions corresponding to the following reaction equation: Al_2O_3 • 2SiO_2 • H_2O + 2Al_2O_3 = Al_2O_3 • 2SiO_2.