Influence research of temperature and heat treatment on the properties of corundum ceramics manufactured by slip casting from reactive alumina

Abstract

Products from extra­dense corundum ceramics are widely used in various industries. The JSC “URIR named after A. S. Berezhnoy” also developed and introduced the techno-logy of highly refractory corundum extra­dense ceramics, including those using reactive alumina. Corundum ceramics, depending on the shape and size, is made by various forming methods, including slip casting, for which various compositions of alumina slip are used. In order to study the effect of temperature and heat treatment on the properties of corundum ceramics, studies were carried out, and the effect of short­term single­stage and long­term multi­stage heat treatment in the temperature range of 200—1580 C in laboratory electric furnaces, as well as long­term single­stage heat treatment at 1580 C (in an industrial periodic furnace) on the properties of corundum ceramics made by slip casting from reactive alumina from slip with different humidity and different additives (composition 1 with a moisture content of 30 %, as well as with dispersing and hardening additives, and composition 2 with a moisture content of 20 % only with dispersing additive) was studied. It was established that, after heat treatment at 1580 C the apparent density and open porosity of the samples were practically independent of their composition and heat treatment mode (short­term single­stage or long­term multi­stage) and have high almost identical an apparent density (3.93 and 3.92 g/cm3), an open porosity (0 and 0.1 %) and a total porosity (0.76 and 1.02 %), which approximate the values of these properties to the theoretical values for corundum. It has been shown that, using reactive alumina, it is possible to obtain the samples of corundum ceramics by slip casting even with short­term one­stage heat treatment at 1500 C with an open porosity of 0.3 %, a total porosity of 5.3 % and an apparent density of 3.75 g/cm3. The appropriate heat treatment mode of corundum ceramics (single­stage or multi­stage, short­term or long­term) should be selected depending on the size, configuration and weight of the products, as well as on their service conditions.