The thermal expansion, shrinkage and formation of crystalline phases in early dense fired hydromica containing ceramic body

摘要

The thermal expansion, shrinkage and formation of crystalline phases were investigated to characterize the sensibility of firing and cooling processes in hydromica clays. In the range of temperature 700-1100 deg C the following new crystalline phases were formed: hematite, spinel, anorthite, diopside, akermanite, gehlenite. The primary thermal expansion (600-800 deg C) is connected with the formation of hematite and secondary quartz (>650 deg C) phases. The shrinkage interval (approx approx 800-1100 deg C) is characterized with the formation of spinel, diopside, anorthite and akermanite. The intensity of gehlenite and diopside formation increased in the presence of CaCO_3. The pretreatment with cold ("frost memory effect") resulted in the rise of hematite content at 850-950 deg C.