Strong Structural Ceramics

The removal of pores and internal cracks is also of value where functional ceramics are concerned. Dielectrics such as are used in capacitors in enormous quantities, alumina in particular, have long been made with special attention to removing any pores because these considerably lower the breakdown field and therefore the potential difference that the capacitors can withstand. 

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The application of ceramics has infiltrated almost all fields in the last 20 years, because of their advantages over metals due to their strong ionic or covalent bonding. But it is just this bonding nature of ceramics that directly results in their inherent brittleness and difficulty in machining. In other words, ceramics show hardly any macroscopic plasticity at room temperature or at low temperatures like metals. Hence, superplasticity at room temperature is a research objective for structural ceramics. In recent years, many researches have been carried out to investigate nanophase ceramic composites. 

Structural ceramics are seeing a strong growth rate due to the increased demand for ceramic armor for personal protection and military vehicles. In 2004 alone, US companies such as Ceradyne, Cercom, Armor Holdings/Simula and ArmorWorks dehvered armor worth over US 200 million to the US military. With stUl more orders expected in the future, the Business Communications Co. (BCC) forecasts that the structural advanced ceramics market will double in size, from US 650 million in 2004 to US 1.3 billion by 2009, due largely to the continued boom in armor demand (see Table 6.4). 

A great potential for new compounds is provided by structures with two carbon and two silicon atoms around the central silicon. These polysilanes with organic groups lead to silicon-carbide ceramics. A wide field of application would be opened up if one could make a polysilane as a plastic mass which could be extruded and modeled and if after pyrolysis silicon-carbide is formed without a strong contraction (this means a high ceramic yield). Polysilane fibers are only one product in a range of many... 

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