Ceramic materials developments

This chapter deals with the preparation of ceramic materials such as pigments by sol-gel methods. Ceramics include a wide range of materials - from pottery to electronic materials. Accordingly, it can be classified into traditional ceramics - materials developed since the early civilizations until 1940 - and advanced ceramics - materials technically developed post-1940. Clay, refractories, glasses, cements, and concretes are considered traditional ceramics, whereas ceramics used in electrical, magnetic, electronic, and optical applications as well as in structural applications at elevated temperatures are called advanced ceramics. Traditional ceramics still constitute a major part of the ceramics industry [1]. 

Development of practical and low cost separators has been an active area of ceU development. CeU separators must be compatible with molten lithium, restricting the choice to ceramic materials. Early work employed boron nitride [10043-11-5] BN, but a more desirable separator has been developed using magnesium oxide [1309-48-4], MgO, or a composite ofMgO powder—BN fibers. Corrosion studies have shown that low carbon steel or... 

The piopeities of a ceramic material that make it suitable for a given electronic appHcation are intimately related to such physical properties as crystal stmcture, crystallographic defects, grain boundaries, domain stmcture, microstmcture, and macrostmcture. The development of ceramics that possess desirable electronic properties requires an understanding of the relationship between material stmctural characteristics and electronic properties and how processing conditions maybe manipulated to control stmctural features. 

The most widely used development in HTS wire production is tlie powder-in-tube procedure with BSCCO ceramic materials. In this procedure very fine HTS powder, placed inside of a hollow silver tube, is fused as the tube lengtn is mechanically increased to form a wire. Very high magnetic fields with this wire have been reported at 4 K however, the performance degrades substantially above 20 to 30 K. 

Calcination is performed in crucibles made of platinum or related metals. Tantalum or niobium oxide can be successfully used in the manufacturing of such crucibles. Frolov et al. [505, 506] developed a method for coating various ceramic materials with tantalum or niobium oxide using an optical furnace. 

The number of oxides is large since most metallic elements form stable compounds with oxygen, either as single or mixed oxides. However, the CVD of many of these materials has yet to be investigated and generally this area of CVD has lagged behind the CVD of other ceramic materials, such as metals, carbides, or nitrides. The CVD of oxides has been slower to develop than other thin-film processes, particularly in optical applications where evaporation. 

We have described new routes to useful preceramic organosilicon polymers and have demonstrated that their design is an exercise in functional group chemistry. Furthermore, we have shown that an organosilicon polymer which seemed quite unpromising as far as application is concerned could, through further chemistry, be incorporated into new polymers whose properties in terms of ceramic yield and elemental composition were quite acceptable for use as precursors for ceramic materials. It is obvious that the chemist can make a significant impact on this area of ceramics. However, it should be stressed that the useful applications of this chemistry can only be developed by close collaboration between the chemist and the ceramist. 

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