ABSTRACT
Ceramics are inorganic, nonmetallic materials that have been subjected to high temperatures (above red heat, -500°C) during manufacture and, often, during use. Although typical ceramics are metal oxides, borides, carbides, nitrides, or combinations of these, most ceramic products developed throughout history have been oxide materials, largely based on clay (which consists mostly of aluminum oxide and silicon dioxide). There is evidence that clay-derived pottery was used as long ago as 10,000 B.C., and that use in bricks and tile was practiced by 2000 B.C.[l]
The term "traditional ceramics" refers to ceramics made solely from unrefined clay or from clay in combination with other powdered or nonplastic materials. Traditional ceramic materials have found wide application in kitchenware such as plates, mugs, and cookware, in decorative articles such as vases, in socalled sanitary ware such as lavatories and toilet bowls, in decorative tile, and in "technical ceramics" such as electrical insulators for power Jines and spark plugs. Properties such as high hardness, low thermal conductivity, low thermal expansion, and ability to be brightly colored by coating with other ceramics (in the form of "glazes") have led to development of uses of these types. However, an undesirable characteristic of any of these materials is "brittleness," or susceptiblity to catastrophic cracking. Another undesirable feature is the considerable variablity in properties among apparently identical items.
