Refractory and Ceramic Materials

Common ancient ceramic materials often foxmd in archaeological excavations, such as fired brick and pottery, were made mostly from a mixture of a secondary clay and fillers. The nature, composition, and properties of clay have been already discussed the nature of the fillers, the changes undergone by the clay as well as by the fillers during their conversion to ceramics, and the xmique properties of ceramic materials, are reviewed in the following pages. Attention is drawn also to studies that provide information on the composition and characteristics of ancient ceramic materials. 

Some of these studies contribute to the understanding of ancient potterymaking techniques, others to learning about the provenance of pottery. The craft aspects of potterymaking, fascinating as they may be in themselves, are, however, outside the scope of this book (Rice 1982). 

It is possible, therefore, that early humans may have accidentally made this t)q)e of dish when making fire to warm themselves or for cooking. Could such accidentally fired objects have given prehistoric humans the idea of modeling clay by hand and then firing it into pottery Any such hypothesis 

FIGURE 52 Preceramics. Cracked loess crusts after firing in an open fire, found in a ravine (a) and (c) inside unfired (b) and (d) outside unfired. 

The generic name used to refer to ceramic objects shaped from a wet mixture of clay and fillers that is then dried and subsequently fired at high temperatures is pottery. Making pottery involves a number of working stages  

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Tables 1.8 and 1.9 and Fig. 1.21 give some reference data on the values of the thermal coefficient of linear expansion for oxides, refractory, and ceramic materials [100-102]. Crystals with a cubic lattice (CaO, MgO) have equal values of linear coefficients of expansion along aU axes. The typical linear coefficients of thermal expansion for such materials are 6-8 x 10 and increase with the temperature up to 10-15 X 10 K . Anisotropic crystals with low symmetry have different values of linear coefficients of thermal expansion along different axes, but with a temperature increase, this difference becomes smaller. Materials with strong chemical bonds (silicon carbide, titanium diboride, diamond) have low values of linear coefficients of thermal expansion. However, these materials have high values of Debye characteristic temperature (values of the linear coefficients of thermal expansion grow below the Debye temperature and are almost constant above it).

Refractories, Glass, Ceramic Materials Carbon and Graphite Products," ASTM Annual Book ofASTM Standards, Vol. 15.01, ASTM, Philadelphia, Pa., 1992. 

Materials such as metals, alloys, steels and plastics form the theme of the fourth chapter. The behavior and use of cast irons, low alloy carbon steels and their application in atmospheric corrosion, fresh waters, seawater and soils are presented. This is followed by a discussion of stainless steels, martensitic steels and duplex steels and their behavior in various media. Aluminum and its alloys and their corrosion behavior in acids, fresh water, seawater, outdoor atmospheres and soils, copper and its alloys and their corrosion resistance in various media, nickel and its alloys and their corrosion behavior in various industrial environments, titanium and its alloys and their performance in various chemical environments, cobalt alloys and their applications, corrosion behavior of lead and its alloys, magnesium and its alloys together with their corrosion behavior, zinc and its alloys, along with their corrosion behavior, zirconium, its alloys and their corrosion behavior, tin and tin plate with their applications in atmospheric corrosion are discussed. The final part of the chapter concerns refractories and ceramics and polymeric materials and their application in various corrosive media. 

T. M. Besmann, B. M. Gallois, eds., MRS Symp. Proc., Vol. 168 Chemical Vapor Deposition of Refractory Metals and Ceramics, Material Research Society, Pittsburgh, 1990. 

Chemical vapour deposition of refractory metals and ceramics. Materials Research Society, Pittsburgh, PA, ppl99-204... 

Buiting Ml, Reader AH (1990) Influence of impurityes and micro structure on the resistivity of LPCVD titanium nitride films. In Besmann TM, Gallois BM (eds) Chemical vapour deposition of refractory metals and ceramics. Materials Research Society, Pittsburgh, PA, ppl 99-204... 

Institute of Glass, Ceramics, Refractory and Construction Materials, Warsaw, Poland ... 

With the exception of glass fiber, asbestos (qv), and the specialty metallic and ceramic fibers, textile fibers are a class of soHd organic polymers distinguishable from other polymers by their physical properties and characteristic geometric dimensions (see Glass Refractory fibers). The physical properties of textile fibers, and indeed of all materials, are a reflection of molecular stmcture and intermolecular organization. The abiUty of certain polymers to form fibers can be traced to several stmctural features at different levels of organization rather than to any one particular molecular property. 

Tetraethylene glycol may be used direcdy as a plasticizer or modified by esterification with fatty acids to produce plasticizers (qv). Tetraethylene glycol is used directly to plasticize separation membranes, such as siHcone mbber, poly(vinyl acetate), and ceUulose triacetate. Ceramic materials utilize tetraethylene glycol as plasticizing agents in resistant refractory plastics and molded ceramics. It is also employed to improve the physical properties of cyanoacrylate and polyacrylonitrile adhesives, and is chemically modified to form polyisocyanate, polymethacrylate, and to contain siHcone compounds used for adhesives. 

The electrical characteristics of ceramic materials vary gteady, since the atomic processes ate different for the various conduction modes. The transport of current may be because of the motion of electrons, electron holes, or ions. Electrical ceramics ate commonly used in special situations where reftactoriness or chemical resistance ate needed, or where other environmental effects ate severe (see Refractories). Thus it is also important to understand the effects of temperature, chemical additives, gas-phase equilibration, and interfacial reactions. 

Refractories and Molds. Citric acid is used as a binder for refractory cements, imparting volume stabiUty and strength in ceramic materials for electrical condensers, foundry and glassmaking molds, and sand molds for metal castings (219—223). 

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