Manufacturing ceramics

This chapter will describe some of tire basic unit processes in ceramic manufacturing, and will touch on tire pertinence of tire physical chemistry of surfaces in selected unit processes. For a more comprehensive review of ceramics and ceramic processing, tire reader is referred to otlrer sources [3, 4 and 5]. 

The most significant commercial product is barium titanate, BaTiO, used to produce the ceramic capacitors found in almost all electronic products. As electronic circuitry has been rniniaturized, demand has increased for capacitors that can store a high amount of charge in a relatively small volume. This demand led to the development of highly efficient multilayer ceramic capacitors. In these devices, several layers of ceramic, from 25—50 ]lni in thickness, are separated by even thinner layers of electrode metal. Each layer must be dense, free of pin-holes and flaws, and ideally consist of several uniform grains of fired ceramic. Manufacturers are trying to reduce the layer thickness to 10—12 ]lni. Conventionally prepared ceramic powders cannot meet the rigorous demands of these appHcations, therefore an emphasis has been placed on production of advanced powders by hydrothermal synthesis and other methods. 

Characteristics ofMlumina Powders, Alumina Ceramic Manufacturers Association, New York, 1976, pp. 1—4. 

Fig. 2. Examples of traditional ceramics manufactured usiag traditional ceramic raw materials clay, flint, Si02 and feldspar.

HBF4 (aq) and metal fluoroborates electroplating of metals, catalysts, fluxing in metal processing and surface treatment. HzSiF6 and its salts fluoridation of water, glass and ceramics manufacture, metal-ore treatment. 

Many of these properties depend upon others which may themselves be governed by yet other factors. Thus, as mentioned above, increased porosity usually gives better thermal shock resistance, but it may be necessary for reasons of watertightness to employ a body with a very low porosity. The size of an article is also closely related to the degree of thermal shock which it will withstand. For this reason it is very difficult to give accurate figures for the thermal shock resistance of stoneware bodies. In practice, if precautions are taken to heat up any stoneware articles slowly and evenly no trouble will be experienced. This is a matter on which the ceramic manufacturer should be consulted. 

CVI [Chemical Vapor Infiltration] A ceramic manufacturing process in which the pores of a matrix are filed by CVD. 

CDM 105 is a proprietary glass-ceramic, manufactured by the freeze gelation method, figures in parentheses are standard deviations. 

National Emission Standards for Hazardous Air Pollutants for Clay Ceramics Manufacturing National Emission Standards for Hazardous Air Pollutants Asphalt Processing and Asphalt Roofing Manufacturing... 

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