Ceramic is a hard, brittle substance that resists heat and corrosion and is made by heating a nonmetallic mineral or clay at an extremely high temperature. The word ceramic comes from the Greek word for burnt material, keramos . Ceramics are used to produce pottery, porcelain, china, and ceramic tile. They may also be found in cement, glass, plumbing and construction materials, and spacecraft components.
The basic ingredient in all forms of ceramics are silicates, the main rock-forming minerals. Most silicates are composed of at least one type of metal combined with silicon and oxygen. Feldspar and silica are example of silicates. When silicates are combined with a liquid such as water, they form a mixture that can be kneaded and shaped into any form. After shaping, the object is dried and fired in a high-temperature oven called a kiln. A glaze (a glasslike substance that makes a surface glossy and watertight) may be added between drying and firing. From ancient days to the present, this process has remained virtually the same, except for the addition of mechanical aids.
The oldest examples of pottery, found in Moravia (a region of the Czech Republic) and dating back to 25,000 B.C. , are animal shapes made of fired clay. Potter's wheels and kilns first appeared in Mesopotamia (an ancient region in southwest Asia) around 3000 B.C. Some of the most fascinating pottery in history was made by the ancient Greeks, whose vases were skillfully decorated in the methods of black figure (black paint applied to red clay) or red figure (black paint covering all but the design, which stood out in red clay). Early Islamic potters of the Middle East produced colorful, imaginatively glazed tiles and other items. Their elaborate pictorial designs have provided archaeologists with many clues to their daily lives.
Perhaps the most renowned potters of all time are the Chinese, who developed the finest form of pottery—porcelain. Made of kaolin (pronounced KA-uh-lin; a white clay free of impurities) and petuntse (a feldspar mineral that forms a glassy cement), porcelain is fired at extremely high temperatures. The result is a high-quality material that is uniformly translucent, glasslike, and white. Porcelain was first made in China during the T'ang Dynasty (618–906).
In the twentieth century, scientists and engineers acquired a much better understanding of ceramics and their properties. During World War II (1939–45), a high demand for military materials hastened the evolution of the science of ceramics. These materials are now found in a wide variety of products, including abrasives, bathroom fixtures, and electrical insulation.
During the 1960s and 1970s, the growing fields of atomic energy, electronics, communication, and space travel increased demand for more sophisticated ceramic products. Because ceramics can withstand extreme temperatures, they have been used in gas turbines and jet engines. The undersides of the space shuttles are lined by some 20,000 individually contoured silica fiber tiles that are bonded to a felt pad. The felt pad in turn is bonded to the body of a shuttle. These ceramic tiles can withstand a maximum surface temperature of 1,200 to 1,300°F (650 to 705°C).
In 1990, a team of Japanese scientists working for their government developed a stretchable material from silicon-based compounds. When made into strips and heated, this special ceramic material can be stretched to two and-a-half times its original length without losing its hardness and durability.