Composite refractory materials

摘要

A relatively dense composite refractory material which has reasonable strength and good thermal shock resistance comprises an alumina matrix material within which are dispersed particles of polycrystalline zirconia comprises from 1.0 to 40 percent by volume of the composite material. Each particle of zirconia is an agglomerate of microcrystals which are strongly bonded together. Due to the agglomerates of the bonding together of the microcrystals at their grain boundaries. The microcrystals contain no matrix material within their agglomerates, and exhibit strong thermal expansion anisotropy. They have a size such that cracks do not form spontaneously within the agglomerates during cooling from about 1600 degrees C. to room temperature. Typically the agglomerates have a mean diameter of from 10 to 15 micrometers, while the average diameter of the microcrystals in an agglomerate is from 1 to 2 micrometers.