refractory ceramic is a class of high-temperature resistant materials used in a variety of manufacturing applications. The essential properties of these materials vary, but all offer a degree of resistance to thermal shock and oxidation at temperatures over 1000degC.
Alumina, Zirconia and Other Refractory Oxides
The most commonly available refractory oxides are alumina (Al2O3) and zirconia. These materials are largely used to make the refractory ceramic fibers, boards and bricks that form the basis of most refractory systems.
These are also a key part of the refractory material that is often used to coat the substrate materials of a high-temperature process. These coatings are usually applied for protective purposes, but they can also serve as a means to enhance the performance of substrate materials.
Non-Oxide refractory ceramics
There are a number of nonoxide ceramics that can exceed 2000degC with minimal sensitivity to oxygen. Examples include calcium carbonate and dolomite.
Fireclays are a popular class of refractory clays that have very low levels of common fluxing oxides. They typically have a combination of kaolin (K2O) and calcined ball clays, sometimes mixed with bentonite.
These fireclays have a serviceable refractory character, high plasticity, support for the addition of grog and are relatively inexpensive. They are particularly popular as a low-cost alternative to alumina and other high-purity refractory materials. They are also favored because they have lower alkali contents than most other refractory clays. They do have a small amount of crystalline silica as a byproduct after firing. This can be a health concern for workers who are exposed to it.