Technical Ceramics - Composites

Ceramic Composites

Ceramic matrix composites (CMCs) combine reinforcing ceramic phases with a ceramic matrix to create materials with new and superior properties.

In ceramic matrix composites, the goal of the ceramic reinforcement is to provide toughness to an otherwise brittle ceramic matrix.

Fillers can also be added to the ceramic matrix during processing to enhance the

characteristics such as electrical conductivity, thermal conductivity, thermal expansion, and hardness.

The desirable characteristics of CMCs could include high-temperature stability, high thermal shock resistance, high hardness, high corrosion resistance, low weight, low or non-magnetic qualities and nonconductive properties.

The combination of these characteristics makes ceramic matrix composites attractive alternatives to traditional processing industrial materials such as high alloy steels and refractory metals.

For the processing industry, related benefits of using ceramic composites include increased energy efficiency, increased productivity, and regulatory compliance.

Some of the more common oxide matrices used include alumina, silica, mullite, barium aluminosilicate, lithium aluminosilicate and calcium aluminosilicate.

Of these, alumina and mullite have been the most widely used because of their in-service thermal and chemical stability and their compatibility with common reinforcements.

Some of the more common nonoxide ceramics include SiC, Si3N4, boron carbide, and

AlN. Of these, SiC has been the most widely used, with AlN of increasing interest where high thermal conductivity is required and Si3N4, where high strength is desired.

Production of ceramic composites in the United States is dominated by a few large firms while small companies are involved in the manufacture of ceramic composites for niche markets.

In 1994, U.S. company shipments for ceramic composite materials totalled about $475 million, of which a majority was for discontinuous reinforced composites.

Japanese companies are estimated to control 50% of the world market in advanced ceramics, which includes ceramic composites. Major markets for ceramic composites include cutting tools, aerospace and military, engines, wear and

industrial, bioceramics, and energy related.