Reaction sintering of zircon–dolomite mixtures

Dolomite–zircon mixtures have become interesting for finding alternate sources to improve the production of high magnesia refractories. To asses this option, two minerals, dolomite and zircon were selected, as economically raw materials, to produce MgO–CaZrO3–Ca2SiO4 materials. The reaction sintering mechanism of zircon–dolomite mixtures were investigated using finely ground Spanish dolomite and zircon powders as starting materials. During the heat treatment decomposed dolomite (CaO+MgO) reacts with zircon, from 1000 to 1200°C, through a series of reactions before the final stable compounds are formed. From the results obtained the reaction occurs prior to sintering in the presence of an amorphous transitory phase, magnesium calcium silicate phase and the limiting process during the reaction is the formation of Ca2SiO4. The sintering occurs after the end of the reaction so by controlling the whole process it is possible to obtain materials with controlled porosity. In the present work it is shown that reaction sintering of zircon–dolomite mixtures is a feasible route to obtain MgO–CaZrO3–β-Ca2SiO4 porous materials for refractory insulators or as filters applications.