Clay Ceramic Products

These process steps are illustrated below in the context of the manufacturing processes of industrially important clay ceramic products. 

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Quantitywise clay ceramic products are the industrially more important. 

The properties of the different clay ceramic products is critically influenced by the relative concentrations of the three main components in their pastes, these being clay (kaolin), quartz and feldspar. Fig. 5.5-2 shows a three component diagram of these ingredients for typical batches of clay ceramic pastes for the manufacture of a number of industrially important products. 

Kaolin and clay minerals belong to the large group of layer silicates. Their ability to form plastic pastes with water, endows the batches of clay ceramic products with the plasticity important for their processing. 

The properties of the clay ceramic products vary with the particle size distribution of the raw materials. 

During the firing of clay ceramic products the following physicochemical processes take place ... 

Porous clay ceramic products can absorb more than 2% of their weight of water. This group of products includes colored earthenware (pottery) and the, generally white, fine earthenware (see Table 5.5-2). Due to its liquid and gas permeability, fine earthenware can be utilized in the manufacture of ceramic filters and diaphragms. Glazing renders it impermeable and suitable for the manufacture of household utensils, sanitary ware, wall panels and tiles (majolica, faience). 

So-called dental porcelains produced with particularly feldspar-rich mixtures (70 to 90% feldspar, 15 to 25% quartz, 2 to 8% calcite or kaolin) are not really clay ceramic products. Due to the high flux content, a glossy surface is formed upon firing and no glazing is necessary. 

Table 5.5-3. Produclion Statistics for Clay Ceramic Products in the Period 1991 to 1994.

In contrast with clay ceramic products, oxide ceramics consist essentially of a single crystalline phase of a pure high melting point metal oxide. Oxide ceramics are... 

The manufacture of such materials proceeds according to the process steps described in Section 5.5.3. However, in comparison with clay ceramic products a few characteristic chemically determined process modifications have to be taken into consideration ... 

Table 3 Clay ceramic products used in technical applications in the early years...

As solid wastes are becoming a matter of increased world concern due to their amoimt as well as difficulty and cost of final disposal, ceramic products can well supply as matrices for industrial residues incorporation snch as giving an option for the solid waste disposal with a possible increase in the properties of the clay ceramic products. The incorporation of wastes from several industrial activities is a technological alternative to reduce the environmental impact due to their indiscriminate disposal. One such measure is the waste incorporation into intensive-produced clay ceramics like bricks and tiles (Parsons et al., 1997). This incorporation is now a common practice and benefits both, the industry... 

Any product that depends on aesthetics for consideration for purchase and use will be improved by the use of color. Hence, many ceramic products, such as tile, sanitary ware, porcelain enameled appHances, tableware, and some stmctural clay products and glasses, contain colorants. 

CERAMICS. Derived from the Creek word ketamos ("burnt stuff t, ceramics comprise a wide variety of materials that constitute a major industry. The principal facets of the ceramic industry, in order of increasing value of annual production, are (I) abrasives (2i porcelain enamel coalings (3) refractories (4) whilewares l5) structural clay products (6) electronic and technical ceramic products and (7) glass. Class accuunls for about 43 1 of all ceramics produced. Sec also Glass... 

Applications The most important utilization sector for barium carbonate is the manufacture of clay tiles and ceramic products, the addition of barium carbonate hindering the bleeding of salts (sodium and calcium sulfate). In the USA 30% of the consumption is devoted to this use. A further 30% is consumed in the glass industry (e.g. for the manufacture of optically special glasses and television screens). About 20%i is used in the manufacture of other barium compounds. Other uses are in special... 

The clay products used in the construction industry are so-called coarse ceramic products. They include bricks, roofing tiles, clinkers (hard bricks), drainpipes and protection covers for cables. The manufacture of such products hardly differs from that described in Section 5.5.3 for the general manufacture of ceramic products. 

Loam, marl, tile clay, clay stone and shaly clay are used as raw materials in the manufacture of tiles. The chemical composition of the raw materials is similar to that for the manufacture of fine ceramic products (see Section 5.5). The quantities of impurities can, however, be higher. 

Plastic forming is based on the plasticity of water-containing clay ceramic pastes and, in the form of the potter s wheel, is the oldest known sort of forming. This turning of ceramic products can be automated on a large scale using the roller process. 

A survey of the fine ceramic clay-containing products will be given in this section, the coarse ceramic products having been for the most part dealt with in the sections concerned with construction materials (see Section 5.3.5) and refractory products (see Section 5.5.5.3). 

The term stoneware includes a range of different ceramic-products, whose pastes mainly consi.st of presintered, generally illitic, clay and are fired to a nonporous product. 

According to their chemical composition, fireclay products belong to the clay ceramic materials. However, their preferred utilization for refractory furnace linings makes it more reasonable to discuss them with the other refractory products. 

Despite its comparatively high price, silicon carbide is a significant refractory product due to its exceptional properties, such as its high thermal conductivity, high hardness and mechanical strength. It is used in zinc distillation kilns and in the manufacture of muffles, capsules and kiln furniture for the clay ceramic industry (see Section 5.5.4.7.2). In recent years silicon carbide has also been used in the refractory linings of blast furnaces and utilization in other sectors of the steel producing industry is in evaluation. 

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