Process Economics Program Report 196
Advanced Structural Ceramics
Published: September 1989
Advanced ceramics are a group of high performance materials that possess exceptional hardness, high-temperature strengths, low thermal conductivity, and low thermal coefficient of expansion. These properties are employed to serve the needs of many engineering functions. They can be used in load-bearing structures, wear resistance parts, electronic components, high temperature sensors, biomedics, catalyst supports, etc. The basic raw materials for advanced ceramics are powders of inorganic oxides, carbides, nitrides, and various derivatives thereof. Most of these materials have been used in industry for decades, but the new types are produced by modern chemical and material science techniques. These new powders are purer, finer grained, and more homogeneous. As a result, their end products are stronger and more resistant to mechanical and thermal shocks.
For structural applications, the most important raw materials for advanced ceramics are high purity silicon nitride, alumina, silicon carbide, zirconia, and sialons. Sialons are derivatives of silicon nitride containing silicon-aluminum oxynitride to improve the sintering characteristics of silicon nitride. These advanced powders are used in making monolithic ceramic parts, spray coatings, ceramic fibers, and ceramic composites. In Section 3 of this report, we discuss in more detail the market demand and forecast for these powders and the advanced ceramic parts derived from them.
In Sections 4 through 7, we review the numerous techniques that have been developed by industry and academics to manufacture these powders. From an array of those processes, we have selected the following representative systems to estimate the investments and production costs for making advanced ceramic powders:
- Silicon nitride from silicon tetrachloride by an ammonolysis process
- High purity alumina by an aluminum chloride hexahydrate process
- b -silicon carbide by a continuous carbothermic process
- High purity zirconia by a caustic fusion-oxychloride process.