Dry sintering of refractory oxides at elevated temperatures

Abstract

Recent efforts to explore the possibility of extending the service of alumina-based refractories into basic steelmaking operations have involved the application of a basic oxide veneer to both fireclay and high-alumina substrates. Because these investigations used a mineralogically complex system consisting of mixtures of commercial refractories and coatings, the nature of the chemical/mineralogical changes that occurred due to the presence of various metal oxides was often difficult to determine. Thus, the present work was undertaken to establish the extent of chemical/mineralogical reaction that might be expected when dissimilar pellets of high-purity single oxides were placed in pressureless contact for known reaction times at known temperatures. Results for the systems , and MgO-Fe showed significant diffusion of chromium into both Fe, as well as iron into MgO after 3 h at 1450 °C. Also, for mixtures of Al and MgO, over 29% spinel formation was evident, even at 1200 °C for 3 h. However, because most couples in the solid state did not remain joined on cooling in spite of the extensive reaction, it would appear that to achieve good bonding, liquid or transient liquid sintering is a prerequisite to the formation of an adherent oxide veneer on a commercial refractory.