Regularities of phase formation, structure and properties of chemically and thermally resistant ceramic materials
Based on the compositions of MgO—Al2O3—TiO2—SiO2 system, the chemically and thermally resistant ceramic was obtained at a firing temperature of 1250 °C by the directed synthesis of tialite and mullite phases. The influence of alternative raw materials of natural and technogenic origin on the operational properties and phase composition of porous and densely-sintered ceramic materials was studied. The using expediency of pyrophyllite containing waste of quartzite mining and ferrotitanium production wastes as the phase forming components of ceramic masses is established. The mechanism of structure- and phase formation of tialite and mullite-tialite ceramics was investigated. It was established that, stabilization of the tialite phase at a temperature of 1200—1250 oC occurs while maintaining the ratio of TiO2/Al2O3 oxides ~ 1.4 and the presence of 1.3 wt. % Fe2O3, as the mineralizing component included in the waste. The possibility of obtaining tialite containing ceramic materials at a lower firing temperature (1200 oC) due to the formation of a tialite solid solution (Mg0.3Al1.4Ti1.5O5) while maintaining the ratio of MgO : TiO2 oxides = 0.18 was proved. Technological principles of the production of chemically and thermally resistant ceramics both with the densely-sintered and with the porous structure, the total porosity of which is respectively 0.41 and 60 %, have been developed. The permeability of porous ceramic materials of mullitе-tialite composition was determined (water permeability coefficient P = 5.39∙10-5 cm2/s), as well as parameters of sorption processes (diffusion rate of Cr2O7-2 and MnO4- ions is 6.38∙10-6 and 1.06∙10-5 cm2/s respectively). This indicates the possibility of using the developed porous ceramics for the manufacture of industrial wastewater filters. Complex studies of the phase composition, structure and properties of the developed ceramic materials confirmed the promise of their use for the manufacture of parts of equipment operating in corrosive environments.