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ceramics(sərăm`ĭks), materials made of nonmetallic minerals that have been permanently hardened by firing at a high temperature, or objects made of such materials. Most ceramics resist heat and chemicals and are poor conductors of heat and electricity. Traditional ceramics are made of clay and other natural occurring materials, while modern high-tech ceramics use silicon carbide, alumina, and other specially purified or synthetic raw materials. Ceramic materials are used in all forms of potterypottery,
the baked-clay wares of the entire ceramics field. For a description of the nature of the material, see clay. Types of Pottery
It usually falls into three main classes—porous-bodied pottery, stoneware, and porcelain.
..... Click the link for more information. , from crude earthenwareearthenware,
form of pottery fired at relatively low temperatures, so that the clay does not vitrify (become glassy), as do stoneware and porcelain clays. Occasionally, earthenware is used as a general term for all kinds of pottery.
..... Click the link for more information. to the finest porcelainporcelain
[Ital. porcellana], white, hard, permanent, nonporous pottery having translucence which is resonant when struck. Porcelain was first made by the Chinese to withstand the great heat generated in certain parts of their kilns.
..... Click the link for more information. , and in industrial and engineering products. Ceramic products include cookware and dinnerware; art objects, such as figurines; building materials, such as brickbrick,
ceramic structural material that, in modern times, is made by pressing clay into blocks and firing them to the requisite hardness in a kiln. Bricks in their most primitive form were not fired but were hardened by being dried in the sun.
..... Click the link for more information. ; abrasivesabrasive,
material used to grind, smooth, cut, or polish another substance. Natural abrasives include sand, pumice, corundum, and ground quartz. Carborundum (silicon carbide) and alumina (aluminum oxide) are important synthetically produced abrasives.
..... Click the link for more information. , such as aluminaalumina
or aluminum oxide,
Al2O3, chemical compound with m.p. about 2,000°C; and sp. gr. about 4.0. It is insoluble in water and organic liquids and very slightly soluble in strong acids and alkalies. Alumina occurs in two crystalline forms.
..... Click the link for more information. , and specialized cutting tools; electrical equipment, such as insulators in spark plugs; refractories, such as firebrickfirebrick,
brick that can withstand high temperatures, used to line flues, stacks, furnaces, and fireplaces. In general, such bricks have high melting points that range from about 2,800°F; (1.540°C;) for fireclay to 4,000°F; (2,200°C;) for silicon carbide.
..... Click the link for more information. and the heat shield on the space shuttlespace shuttle,
reusable U.S. space vehicle (1981–2011). Developed by the National Aeronautics and Space Administration (NASA) and officially known as the Space Transportation System (STS), it was the world's first reusable spacecraft that carried human beings into earth
..... Click the link for more information. ; and artificial bones and medical devices. The oldest known fired ceramics date from the Paleolithic period some 27,000 years ago.
articles and materials obtained by sintering clays and clay mixtures with mineral additions as well as oxides and other inorganic compounds. Ceramic objects are widely used in all areas of life—everyday life (various wares), construction (brick, roof tile, pipes, tablets, tile, sculptural details), sculpture and applied art, technology, and rail, water, and air transport. The main technological kinds of ceramics are terra-cotta, majolica, faience, stoneware, and porcelain. The best examples of ceramics reflect the high achievements of the art of all times and peoples.
Historical survey. Man has made use of the plastic properties of clay since the dawn of his existence, and almost the first articles made of clay were sculptures of men and animals, known as early as the Paleolithic period. Some researchers believe that the first attempts at firing clay also date from the late Paleolithic period. However, the practice of firing clay objects to make them hard, waterproof, and fireproof became widespread only in the Neolithic period (about 5000 B.C.). Mastering ceramic production was one of the most important achievements of primitive man in his struggle for existence: the cooking of food in clay vessels made it possible to greatly expand the range of edibles. Like other similar discoveries (such as the use of fire), ceramics is not the invention of any one person or people. It was mastered independently in different parts of the world whenever a society had attained the necessary level of development. This fact did not exclude subsequent mutual influences among societies, with the result that the best achievements of peoples and individual masters became common property. Both the technology used to process the clay for obtaining ceramics and the techniques of producing articles changed and improved in keeping with the development of the people’s productive forces. The prevalence of ceramics and distinctiveness of types of ceramics among different peoples in different periods and the fact that ceramics were covered with ornamentation, marks, and often inscriptions makes them an important historical source. Ceramics played a significant role in the development of written language (cuneiform writing), early specimens of which have been preserved on ceramic tablets in Mesopotamia.
Originally, the main kind of ceramics was earthenware for storing supplies and cooking food. The vessels were usually placed between the stones of the hearth, which made an egg-shaped or rounded bottom more convenient. To make the firing easier, thick walls were covered with pressed-in ornamentation, which from the very first also had an important aesthetic and cultic significance. Beginning in the Aeneolithic period (third and second millennia B.C.) decorations began to be painted on ceramic articles. The shapes of ware developed in accordance with the needs of everyday life (for example, changing over to a settled way of life required vessels with a flat bottom fitted to the flat surface of the stove and to the table; the peculiar form of Slavic pots was due to the distinctive way of cooking food in the stove, with the vessel being heated from the side) and the artistic traditions of peoples. At different times each of them had its own favorite shapes of vessels, preferred arrangement and character of ornamentation, and methods of finishing the surface, which was either allowed to retain the natural texture and color of clay or polished, whose color was altered by means of reducing firing, and which was painted with decorations, covered with engobe, and glazed.
The beaten clay dwellings of the Tripol’e culture (fourth and third millennia B.C.), which were fired from the outside by bonfires and painted with decorations, were the first example of the use of ceramics as building material. With the development of the technology of metal extraction, ceramics also became indispensable in metallurgy (kiln nozzles, crucibles, casting molds, small pouring ladles). At first ceramic articles were shaped by hand and baked in fires built outdoors or in ovens at home. Later, in class societies, there were potter-specialists who used potter’s wheels (or impressed the articles in special molds) and potter’s kilns. The potter’s wheel was not known to the peoples of America before the arrival of the Europeans; however, they too had an original form of ceramic production. (The earliest articles date from the turn of the second millennium B.C.) Ceramic production was particularly highly developed among the Maya, the Incas, and the Aztecs, who made various kinds of household and cultic ware, masks, and figurines. Some of the articles were covered with bright painted decorations. In ancient Egypt, Babylonia, and other ancient countries of the Middle East ware for festive occasions began to be covered with colored glazes, and bricks came to be used for construction (at first raw brick and then baked brick). Glazed brick and tile were used in Egypt and ancient Iran to decorate buildings.
Ancient Indian civilizations are known to have had various kinds of decorated ware shaped very much like that of Mesopotamia, brick slabs for laying floors, figurines, and tablets covered with letters. In ancient China, in the second and first millennia B.C., glazed ware and individual vessels of high-quality white clay, kaolin, were made. Kaolin was the material used in the first millennium B.C. to make the first porcelain-like articles and later genuine porcelain.
The ceramics of ancient Greece, which had a great impact on the ceramics of many peoples, occupy an important place in the history of ceramics. Ware of various shapes (20 kinds) and of perfect form was particularly famous. Vessels used for festive occasions were usually decorated with graceful paintings in a few colors on subjects from everyday life and mythology (vases painted in the black-figure and red-figure techniques). Terracotta figurines, whose main production center was Tanagra, are a magnificent example of small-scale sculpture.
Terra-cotta architectural details, roof tile, and water pipes were manufactured both in ancient Greece and ancient Rome. The production of brick used to construct complicated structures (such as roof arches, bridge spans, and aqueducts) became especially well developed in ancient Rome. In Rome ware for festive occasions was mainly impressed in wooden or ceramic molds in which relief ornamentation had been cut out, and it was covered with red lacquer. The making of ceramic funeral urns, known also to many other peoples who observed the rite of cremation, flourished among the Romans and Etruscans. The Etruscan and Roman urns were covered with sculptured decorations (such as scenes of feasts). The ceramic production of Byzantium basically followed Roman traditions, although it also experienced the influence of the Middle East (especially in the decoration of the surface of ware and in architectural ceramics). The Byzantine masters stopped using red lacquer as early as the sixth century, and from the ninth century they began to make ware with relief ornaments depicting animals and birds and covered with a transparent glaze. The Byzantine thin square brick—the plinth—had an influence on the production of brick in ancient Rus’.
In ancient Rus’ various ware was made on the potter’s wheel beginning in the tenth century; some vessels were covered with green glaze. Thin slabs for floors and toys were also glazed. The marks of masters have been discovered on ware and bricks, including the names Stefan and Iakov. After the decline caused by the Mongol-Tatar invasion, the production of ceramics was revived in the 14th and 15th centuries. Its main center became Goncharnaia Sloboda in Moscow (near present-day Volodarskii Street), where by the 17th century rather large workshops of the manufactory type had been established. They produced ware (16 varieties), toys, lamps, inkwells, musical instruments, and, from the 18th century, tobacco pipes. In addition, glazed ceramic tombstones were known in the Pskov region. The main building materials were brick, roof tile, slabs, and pipes; tsarist brickyards and the first standard “tsar’s large bricks” appeared as early as the 16th century. Terra-cotta and glazed (green and polychrome) tile was manufactured to decorate the facades of buildings and their interiors. Such masters as Petr Zaborskii, Stepan Ivanov, Ivan Semenov, and Stepan Butkeev are known to have worked in Moscow in the 17th century. Tile was also produced in Yaroslavl and other cities. Beginning in the 18th century relief tile was replaced by smooth tile. Cheap popular prints had an influence on the choice of subjects depicted.
The first state porcelain plant in Russia was founded in St. Petersburg in 1744 (now the M. V. Lomonosov Plant). The private factory of F. Ia. Gardner was opened in Verbilki in the vicinity of Moscow in 1766. Later a multitude of other private enterprises were opened. Of these, the largest in the 19th and early 20th century were the plants of M. S. Kuznetsov. Domestic production of household and artistic ceramics continued even after porcelain and construction and industrial ceramics began to be produced at plants. There were several industrial districts with their own traditions (Gzhel’ and Skopin, for example).
M. G. RABINOVICH
Artistic ceramics. An important role in the development of artistic ceramics was played by discoveries involving the selection of kinds of clay and admixtures that make up the ceramic mass, the methods used to shape and fire the mass, and the methods used to treat and decorate the surface of the articles. In their search for ways of producing the finest and most beautifully colored ceramics that would be both strong and light, the ceramists of various countries made similar discoveries (often independently of one another) both at the same time and in widely spaced historical periods. For example, the secrets of producing faience and glaze, which were known to the masters of ancient Egypt as early as the 15th century B.C., were discovered anew in the third and fourth centuries in China, in the ninth and tenth centuries in the countries of the Middle East, and in the 16th century by the French scholar B. Palissy. The secret of porcelain manufacture, which had been mastered by the Chinese as early as the sixth and seventh centuries, was discovered in the 18th century by J. F. Böttger with the help of E. W. von Tschirnhaus in Germany and by D. I. Vinogradov in Russia, and, unable to find the solution to the “Chinese secret,” the ceramists of France and England created their own varieties of porcelain-like ceramics (soft porcelain and bone china). Often inventions that helped the art of ceramics reach a high level of development were subsequently forgotten for a long time or not used at all. For example, the greatly perfected methods of terra-cotta developed by the ancient Greek masters, which became the basis for the flourishing of small sculptures in ancient Greece and the production of vessels of perfect form, which influenced the entire subsequent development of ceramic art, were forgotten for a long time. So far as the fineness of the body was concerned, only in the 16th century did the relief vessels from St. Porchaire in France (St. Porchaire faience) come anywhere near the ancient Greek terracotta wares. The formulas for preparing the very durable black and red lacquers, which are resistant to the action of acid and which were the main colors in antique vase painting, have been lost, because lacquers were permanently replaced as early as in the ceramics of Byzantium (from the ninth century) by engobe, enamel, and glaze. Continuity in techniques and artistic traditions can be traced only in the evolution of pottery-making, which is closely bound up with domestic handicrafts and the people’s everyday pattern of life. But even in pottery-making there have been periods of extreme regression (such as the shaping of vessels by hand in some European countries during the early Middle Ages). Hence the history of artistic ceramics right up to the 19th century was intermittent and its landmarks consisted of periods of the flourishing of each new variety of ceramics that was more nearly perfect than the preceding. Since a newly discovered kind of ceramic mass or a material for decorating articles is in the artists’ center of attention, it gradually forces out the others, which continue their development but only in the form of traditional production. Often the new kind of ceramics, as a result of its technical superiority, quickly forces out the old kinds, and the ceramists use the new ceramics to imitate more expensive and labor-consuming materials before they have discovered its artistic characteristics. Thus, in China, where ceramics developed with greater consistency than anywhere else in the world, it is possible to trace a period in early faience in which it imitated bronze, and the first stoneware and porcelain articles were very close in color and form to vessels made of nephrite. Relief architectural ceramics began to develop in outright imitation of carving in stone, ganch (a binding material used in plastering), or stucco. Luster, whose metallic sheen imparted a special fineness to the multicolored decorated dishes and bowls of Iran and other countries of the Middle East, was initially used only to imitate expensive articles of gold and silver in ceramics. Hispano-Moresque ceramics were also initially used for this purpose. Sometimes one kind of ceramics was imitated by another. Chinese porcelain, having found its way into Samarra (in what is now Iraq) in the ninth century, brought about the discovery of faience in imitation of fine porcelain wares. White majolica painted with blue decorations, produced in Delft during the 16th through 18th centuries (known as Delft china), also began to develop in imitation of Chinese porcelain.
An important role in the world history of ceramics was played by the faience and porcelain of China, which had a marked influence on the development of artistic ceramics in many European and Asian countries. Particularly outstanding in the area of architectural ceramics were the multicolored glazed facing of buildings in Middle Asia, Iran, Azerbaijan, Turkey, and the Arabic countries (the facing was covered with complex designs) and the figured brickwork and relief terra-cotta, which also reached a high level of development there. The polychrome mosaic ceramic facing of buildings in Samarkand and Bukhara is among the highest achievements of architectural decor in the tenth through 15th centuries. The Iranian faience vessels of the 13th century and the Hispano-Moresque majolica of the 14th and 15th centuries are classic examples of the use of luster. Hispano-Moresque majolica differed from Iranian ceramics by a greater severity of color and a refinement of color combinations in the painted decorations and in the luster. Hispano-Moresque ceramics exerted some influence on the development of Italian majolica of the 15th through 17th centuries, in which paintings with a story became the dominant kind of decoration for the first time since antiquity; ceramic sculpture acquired a monumental character in the work of the della Robbia family, the Florentine ceramists. Italian majolica had a noticeable impact on majolica in Germany in the 15th century (in Nuremberg and other cities), where, however, starting in the 14th century, stoneware began to be produced, and on French majolica of the 16th through 18th centuries (in the cities of Nîmes, Lyon, and Nevers), which developed along with the production of faience and, beginning with the turn of the 18th century, also along with soft porcelain (Rouen, St. Cloud, and Sèvres).
In the 18th century porcelain as an artistic material began to force out other kinds of ceramics almost everywhere. The aesthetic principles of classicism with its cult of supremely clear forms and decor were expressed in porcelain with utmost fullness. Biscuit sculpture developed at the same time as did small sculptures with painted decorations and gilt. However, beginning in the last quarter of the 18th century, interest in the artistic possibilities of coarser kinds of ceramics, stoneware and faience, was rekindled. The Englishman J. Wedgwood played a great role in this process. The faience sets manufactured at his plant, with their somewhat softened forms and light linear painted designs, which were in harmony with the nascent sentimentalist trend of the period, as well as stoneware articles in two colors with a relief design appearing to be superimposed on the surface, became the objects of imitation by the ceramic plants of Europe until the end of the 19th century.
A special place in the history of ceramics is occupied by French “revolutionary faience”—vessels of the time of the Great French Revolution of 1789–94 with propaganda appeals and figures representing the unity of the working classes, revolutionary vigilance, and the like. During the romantic era faience was almost equal in importance to porcelain in artistic ceramics (such as the products of the Mezhgor’e faience factory in the Ukraine). But the general decline of decorative and applied art in the second half of the 19th century also had an effect on the development of artistic ceramics. The renewed artistic search of ceramists during the developmental period of the “modern” style, which was a result of their interest in handmade articles fashioned from coarse but skillfully treated materials (the works of M. A. Vrubel’ and some others), could not have a substantial effect on the overall state of artistic ceramics, which continued to make mechanical reproductions of old models by machine.
The October Revolution of 1917 brought about a sharp change in the development of artistic ceramics. Starting with the so-called propaganda porcelain, which swiftly reflected the most important events in the life of the young Soviet republic, and the efforts of a number of Soviet artist-ceramists of the late 1920’s and early 1930’s to create models of highly artistic ceramic ware for mass production (porcelain, faience, and majolica), ways were sought to upgrade the aesthetic qualities of ceramics. Artists of many countries were gradually drawn into this project. The process, interrupted by World War II (1939–45), began again in the 1950’s, when problems attendant on an efficient and expressive solution of mass ceramic articles designed for industrial production began to attract the attention of the world community. These efforts were headed by the International Academy of Ceramics in Geneva, which includes the USSR among its members. Since the 1960’s, along with a rise in the artistic level of mass-produced ceramics, interest in unique decorative ceramics has grown. These ceramic articles have been made not only from coarse varieties of ceramics but also from materials that were once considered inartistic (for example, grog). New kinds of enamels and glazes, new methods of ornamentation, and new types of decorative products have been developed (such as designs painted with ceramic glazes on a decorative article made of concrete, followed by the firing of individual areas covered by the glaze). The traditional centers of folk ceramics (for example, Gzhel’ and Oposhnia) are being revived, and its traditions are being used in the works of a number of masters of decorative ceramics.
N. V. VORONOV
Ceramic production. Ceramic products and materials are classified on the basis of purpose and properties and the main raw materials used or the phase composition of sintered ceramics (see Table 1).
Depending on the composition of the raw material and the firing temperature, ceramic products are subdivided into two classes: completely sintered, dense products with a shiny fracture surface and water absorption of not more than 0.5 percent and porous, partially sintered products with water absorption of up to 15 percent. A distinction is made between coarse ceramics, the structure of whose fracture surface is coarse-grained and nonuniform (for example, building and grog brick) and fine ceramics with a body at the fracture surface that is uniform, fine-grained, and evenly colored (for example, porcelain and faience). Clays and kaolins are the main raw materials in the ceramic industry owing to their wide availability and valuable industrial properties. The most important components of the initial mass in producing fine ceramics are feldspar (mainly microcline) and quartz. Feldspars, especially of the pure kinds, and feldspar and quartz aggregates are obtained from pegmatites. Quartz-feldspar raw materials are obtained in ever-increasing amounts from various rocks by concentration and purification from harmful mineral impurities. However, the high and sharply differentiated demands made on ceramics by metallurgy, electrical engineering, and instrument-making have resulted in the development of the production of refractory materials and other kinds of indus-
|Table 1. Classification of ceramic products|
|Purpose||Type of ceramics||Raw materials||Firing temperature °C)||Products|
|Porous, partially sintered products with water absorption of up to 15%|
|wall materials||Highly porous, coarse-grained||Clay, sand, and other nonplastic materials||950–1150||Clay brick and hollow blocks (stones)|
|roofing materials||Highly porous, coarse-grained||Clay and sand||950–1150||Tile|
|facing materials||Highly porous, coarse-grained||Plastic and pyrofusible clays, grog, quartz sand, feldspar, talc, kaolin||1000–1200||Facing tiles and blocks for facades, terra-cotta, sandstone plate, mosaic, and glazed faience tiles|
|sanitary-industrial products||Faience, semiporcelain||Clay, kaolin, quartz sand||1150–1250||Bathroom fixtures|
|Household and decorative ceramics||Faience, semiporcelain, majolica||Clay, kaolin, quartz sand, feldspar||1100–1250||Dinner and tea dishes, decorative articles|
|Fireproof ceramics||Aluminosilicate, siliceous, magnesian, chromous and zirconic||Refractory clay, kaolin, grog, quartzites, lime, dolomite, magnesite, highly refractory oxides||1350–2000||Bricks and blocks used in furnace and burner construction|
|Fully sintered, dense products with a shiny fracture surface and water absorption of not more than 0.5%|
|electrical ceramics (for industrial and high-frequency currents)||Mullite, corundum, steatite, and cordierite ceramics based on pure oxides; electrical porcelain||Clay, kaolin, andalusite, alumina, feldspar, zircon, zirconosilicates||1250–1450||Insulators, thermocouple cases, vacuum-tight flasks, heat-resistant furnace parts|
|acidproof ceramics||“Stone,” acidproof porcelain||White-firing clays and kaolin, quartz, feldspar, grog, refractory clays||1250–1300||Vessels for storing acids and alkalies, chemical plant instruments, dishes|
|Household and decorative products||Hard and soft household porcelain||White-firing clays and kaolin, quartz, feldspar||1300–1450||Dinner and tea sets, statuettes, vases|
|Sanitary-construction articles||Low-temperature porcelain||Clay, kaolin, feldspar, quartz sand||1250–1300||Washstands, toilet bowls|
trial ceramics based on pure oxides, carbides, and other compounds. The properties of some kinds of industrial ceramics are very different from the properties of products made of clays and kaolins, and this is why the unifying characteristics of ceramic products and materials are still considered to be their production by sintering at high temperatures and the use of related industrial production methods that include the processing of raw materials, the preparation of the ceramic mass, and the shaping, drying, and firing of the products.
On the basis of production methods, ceramic masses are subdivided into powder-like, plastic, and liquid. The powder-like ceramic masses are a mixture of crushed initial mineral components mixed while in a dry state and moistened or with organic binders and plasticizers added. By mixing clays and kaolins in a moist state (18–26 percent of the mass is water) with hardening additives, plastic molding masses are obtained, which, after the water content has been further increased and electrolytes (peptizers) added, become liquid ceramic masses (suspensions) or casting slips. In producing porcelain, faience, and some other kinds of ceramics, the plastic molding mass is obtained from the slip by partially dehydrating it in filter presses and then homogenizing it in vacuum kneaders and screw presses. In producing some kinds of industrial ceramics, the casting slip is prepared without clays or kaolins; instead, thermoplastic and surface-active agents (such as paraffin, wax, and oleic acid) are added to the finely ground mixture of the original raw materials. The surface-active agents are subsequently removed by the preliminary low-temperature firing of the articles.
The choice of the method for shaping ceramics is determined mainly by the shape of the articles. Articles of a simple shape, such as refractory brick and facing tile, are pressed from powder-like masses in steel molds on mechanical and hydraulic automatic presses. Wall construction materials, for example, brick, hollow and facing tile, roof tile, sewer pipes, and drainpipes, are formed from plastic masses in screw vacuum presses by forcing the block through shaped dies. Articles or intermediate products of the required length are cut from the block by automatic machines synchronized with the work of the presses. Porcelain and faience for household needs are shaped primarily from plastic masses in plaster molds on semiautomatic or automatic machines. Sanitary-construction ceramics of a complex configuration are cast in plaster molds from ceramic slips on mechanized conveyor lines. Radioceramics and piezoceramics, cermets, and other kinds of industrial ceramics, depending on their sizes and shapes, are made mainly by pressing from powder-like masses or by casting from paraffin slips in steel molds.
Articles shaped by any method are dried in chamber, tunnel, or conveyor dryers.
The firing of ceramics is the most important technological process ensuring the necessary degree of sintering. Close observance of the firing conditions ensures the necessary phase composition and all the most important properties of ceramics. With rare exceptions, the sintering of crystalline phases occurs with the participation of liquid phases formed from eutectic melts. Depending on the composition of the ceramic mass and the firing temperature, the liquid phase during the sintering process in porcelain, steatite, and other densely sintered articles reaches 40–50 percent of the mass and more. The forces of surface tension that arise at the interface of the liquid and solid phases cause the grains of the crystalline phases (for example, of quartz in porcelain) to move closer together and the gases distributed between them to be forced out of the capillaries. As a result of the sintering, the dimensions of the articles are reduced and their mechanical strength and density increase. The sintering of some kinds of industrial ceramics (for example, corundum, beryllium, and zirconium) occurs without a liquid phase and is the result of volume diffusion and plastic flow, which are accompanied by the growth of crystals. Sintering occurs in solid phases when very pure materials are used and at higher temperatures than sintering with the participation of the liquid phase; hence it is common only in the production of industrial ceramics based on pure oxides and similar raw materials. In accordance with the complex of demands made on it, the degree of sintering of various ceramics varies within a broad range. Products made of electric porcelain, porcelain, faience, and other kinds of fine ceramics are glazed prior to firing. The glaze melts at high firing temperatures (1000°–1400°C), forming a vitreous layer that is impervious to water and gas. The industrial and decorative and artistic properties of ceramics are increased by glaze. Large articles are glazed after drying and fired in one operation. Thin-walled articles are subjected to preliminary firing before glazing to prevent their being macerated in the glaze suspension. In some ceramic enterprises the unglazed surface of fired articles is polished with abrasive powders or abrasive instruments. Household ceramics are decorated with ceramic paints, decalcomania, and gold.
REFERENCESArtsikhovskii, A. V. Vvedenie v arkheologiiu, 3rd ed. Moscow, 1947.
Avgustinik, A. I. Keramika. Moscow, 1957.
Tekhnologiia keramiki i ogneuporov, 3rd ed. Edited by P. P. Budnikov. Moscow, 1962.
Saltykov, A. B. Izbr. trudy. Moscow, 1962.
Cherepanov, A. M., and S. G. Tresviatskii. Vysokoogneupornye materialy i izdeliia iz okislov, 2nd ed. Moscow, 1964.
Kingery, W. D. Vvedenie v keramiku, 2nd ed. Moscow, 1967. (Translated from English.)
Iskusstvo keramiki. Collection edited by N. S. Stepanian. Moscow, 1970.
Encyclopedia of World Art, vol. 3. New York-Toronto-London, 1960.
I. A. BULAVIN
Inorganic, nonmetallic materials processed or consolidated at high temperature. This definition includes a wide range of materials known as advanced ceramics and is much broader than the common dictionary definition, which includes only pottery, tile, porcelain, and so forth. The classes of materials generally considered to be ceramics are oxides, nitrides, borides, carbides, silicides, and sulfides. Intermetallic compounds such as aluminides and beryllides are also considered ceramics, as are phosphides, antimonides, and arsenides. See Intermetallic compounds
Ceramic materials can be subdivided into traditional and advanced ceramics. Traditional ceramics include clay-base materials such as brick, tile, sanitary ware, dinnerware, clay pipe, and electrical porcelain. Common-usage glass, cement, abrasives, and refractories are also important classes of traditional ceramics.
Advanced materials technology is often cited as an enabling technology, enabling engineers to design and build advanced systems for applications in fields such as aerospace, automotive, and electronics. Advanced ceramics are tailored to have premium properties through application of advanced materials science and technology to control composition and internal structure. Examples of advanced ceramic materials are silicon nitride, silicon carbide, toughened zirconia, zirconia-toughened alumina, aluminum nitride, lead magnesium niobate, lead lanthanum zirconate titanate, silicon-carbide-whisker-reinforced alumina, carbon-fiber-reinforced glass ceramic, silicon-carbide-fiber-reinforced silicon carbide, and high-temperature superconductors. Advanced ceramics can be viewed as a class of the broader field of advanced materials, which can be divided into ceramics, metals, polymers, composites, and electronic materials. There is considerable overlap among these classes of materials. See Cermet, Composite material, Glass
|Flexure strength, MPa||350||850||450||790|
|Modulus of elasticity, GPa||407||310||400||205|
|Fracture toughness (KIC),||5||5||4||12|
|MPa · m1/2|
|Mean coefficient of thermal||7.7||2.6||4.4||10.2|
|expansion (× 10-6/°C)|
The general advantages of advanced structural ceramics over metals and polymers are high-temperature strength, wear resistance, and chemical stability, in addition to the enabling functions the ceramics can perform. Typical properties for some engineering ceramics are shown in the table.
Advanced ceramics are used in systems such as automotive engines, aerospace hardware, and electronics. The primary disadvantages of most advanced ceramics are in the areas of reliability, reproducibility, and cost. Major advances in reliability are being made through development of tougher materials such as partially stabilized zirconia and ceramic whiskers; and reinforced ceramics such as silicon-carbide-whisker-reinforced alumina used for cutting tools, and silicon-carbide-fiber-reinforced silicon carbide for high-temperature engine applications.