Silicon carbide ceramic

The history and development of polysilane chemistry is described. The polysilanes (polysilylenes) are linear polymers based on chains of silicon atoms, which show unique properties resulting from easy delocalization of sigma electrons in the silicon-silicon bonds. Polysilanes may be useful as precursors to silicon carbide ceramics, as photoresists in microelectronics, as photoinitiators for radical reactions, and as photoconductors. 

Possible ways in which polysilanes may be useful include, 1. As precursors to silicon carbide ceramics 2. As photoinitiators in radical reactions 3. As photoconductive materials, and 4. As photoresists in microelectronics. The last of these uses will be treated in the chapter by Miller,(31) and so will not be covered here. 

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... 

Polysilanes can be regarded as one-dimensional analogues to elemental silicon, on which nearly all of modern electronics is based. They have enormous potential for technological uses [1-3]. Nonlinear optical and semiconductive properties, such as high hole mobility, photoconductivity, and electrical conductivity, have been investigated in some detail. However, their most important commercial use, at present, is as precursors to silicon carbide ceramics, an application which takes no advantage of their electronic properties. 

For some uses it is important to form bonds that link different polysilane chains, to transform soluble, meltable polysilanes into insoluble resins. This process is vital if the polysilanes are to be used as precursors to silicon carbide ceramics, since, if cross-linking is not carried out, most of the polymer is volatilized before thermolysis to silicon carbide can take place. Several methods have therefore been developed to bring about cross-linking of polysilanes.109 110... 

Wang, C.M., Mitomo, M., and Emoto, H., Microstructure of liquid phase sintered superplastic silicon carbide ceramics , J. Mater. Res. 1997, 12, 3266-70. 

There are several reports of the condensation of bis-silanes of the type H3Si-X-SiH3 (primary silanes) and H2RSi-X-SiR H2 (secondary silanes) principally with the aim of producing polymers that would be precursors to silicon carbide ceramic material. The polymers would, in principle,... 

Ersoy, D.A., McNallan, M.J., and Gogotsi, Y. Carbon coatings produced by high temperature chlorination of silicon carbide ceramics. Mater. Res. Innov. 5, 2001 55-62. 

Formation of Iron Silicon Carbide Ceramics via Pyrolysis... 

Silicon nitride (SN) ceramics po.s.sess similar properties to silicon carbide ceramics and can be utilized in the same application sectors. 

Y.F. Shi, Y. Meng, D.H. Chen, SJ. Cheng, P. Chen, T.F. Yang, Y. Wan, and D.Y. Zhao, Highly Ordered Mesoporous Silicon Carbide Ceramics with Large Surface Areas and High Stability. 

Broekaert J. A. C., Brandt R., Leis F., PlLGER C., POLLMANN D., Tschopel P. and Tolg G. (1994) Analysis of aluminium oxide and silicon carbide ceramic materials by inductively coupled plasma mass spectrometry, J Anal At Spectrom 9 1063-1070. 

PROPERTIES OF SILICON CARBIDE CERAMIC FROM GELCASTING AND PRESSURELESS SINTERING... 

Properties of Silicon Carbide Ceramic from Gelcasting and Pressureless Sintering... 

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