Thermal expansion of ceramics containing aluminum titanate

Abstract

The investigation of the thermal expansion hysteresis facilitates, by relatively simple and available means, the obtaining of information about the presence in the ceramic material of active microcracks, that is, those capable of reverse collapse, and about their behavior during thermal cycling of the specimen. The presence of the expansion hysteresis in ceramics containing aluminum titanate exerts a considerable influence on their thermal behavior in working conditions. During thermal cycling of such ceramics in a relatively narrow temperature range (for example, from 700 to 900°C) no changes occur in the microcracked structure, and in this case the ceramic operates in the region of elastic deformations. However, with the expansion of the thermal cycling range brittle failure occurs in the intergrain bonds established at the higher temperature, which leads to the formation, after each cycle of heating and cooling, of a new system of microcracks, which reduce the strength of the bonds between the grains of the ceramic, and in the final account break it up.