Phase Formation and Structure of Mullite –Alumina - Zirconia and Spinel-Enstatite Ceramics Developed from Synthetic and Mineral Raw Materials

摘要

New dense and porous ceramics in the alumina-silica-zirconia system are developed using two formulation approaches. These are ceramics with remarkable content of mullite, corundum and ZrO2 - tetragonal and monoclynic in crystalline phase and porous (average size of pores is up to 150-350mm) spinel-enstatite/forsterite ceramics with presence up to 25 vol. % of glassy phase and 25-28 vol.% of pores. To promote the phase development by high-temperature synthesis of these ceramics the mineral raw materials – illite clay and illite clay together with dolomite are used. Bulk density for mullite (corundum) – zirconia ceramics is increased by equal addition of illite clay (8.2 wt.%) and ZrO2 and especially ZrO2 +Y2O3 to starting mixtures. Contrary the addition of different kind and amount of illite clay together with dolomite to starting mixture for cordierite ceramics trends to formation of spinel – enstatite (forsterite) ceramics and decrease the bulk density to the value up to 0.35 g/cm3. The XRD results indicate that ZrO2 monoclinic/tetragonal incorporation in mullite (corundum) structure realizes through the liquid phase. Development of the spinel MgAl2O4 and enstatite MgSiO3 crystalline phases along with the sufficient amount of glassy phase in microstructure and even distributed pores are proper for spinel-enstatite (forsterite) ceramic samples.