Thermal expansion of CaAl_4O_7-based refractory compositions containing MgO and CaO additions

摘要

Various compositions of recently developed CaAl_4O_7-based ceramics are mentioned with special reference to those called "nonexpansive refractories" (=NER). The observed effect of deep depression of their thermal expansion is mainly ascribed to the creation of a specific microstructure resulting from high temperature reactions of CaAl_4O_7 with MgO or CaO additives yielding a CaAl_2O_4-based liquid. Some details characterizing the phase composition of the reaction zone are given. The effect of the calculated approximate content of CaAl_2O_4 in the specimens is interpreted graphically. Basing on the results of changes in the CaAl_4O_7 single crystal dimensions presented in comparison with some other expansion data, the presumable nature of the specific behavior of NER bodies on heating up to 500 deg C is discussed. The NER products fired at 1620 deg C are characterized by high strength and low open porosity.