Ceramic matrix materials

The important ceramic matrix materials are glass, silicon carbide, silicon nitride, alumina, glass-ceramics, sialons, intermetallics and some elemental materials. A list of some ceramic matrix materials is given in Table 3.5. 

The characteristic high strength and brittleness of ceramic matrix materials can be judged by the types of bonding in their structure [65, 66]. In ceramic matrix materials with ionic bonding, there occurs a transfer of electrons between the atoms, and in case of covalent bonding, the electrons are shared between atoms. The properties of some ceramic matrix materials are given in Table 3.6. 

Glass-matrix materials can be considered as a non-crystalline solid with the frozen-in structure of a liquid. Characteristics of some important varieties of glass are given in Table 3.7. Glass-matrix materials are polycrystalline materials having fine ceramic crystallites in a glass matrix. Important glass-ceramic matrix materials are as follows. 

Li20-Si02 (LAS). The trade names of such glass-ceramic matrix materials are Corningware, Zerodur and Ceran. This type of glass-ceramic matrix material has nearly zero thermal expansion and high thermal shock resistance. It is used for the production of optical and telescopic mirrors. 

This review is intended to focus on ceramic matrix composite materials. However, the creep models which exist and which will be discussed are generic in the sense that they can apply to materials with polymer, metal or ceramic matrices. Only a case-by-case distinction between linear and nonlinear behavior separates the materials into classes of response. The temperature-dependent issue of whether the fibers creep or do not creep permits further classification. Therefore, in the review of the models, it is more attractive to use a classification scheme which accords with the nature of the material response rather than one which identifies the materials per se. Thus, this review could apply to polymer, metal or ceramic matrix materials equally well. 

Chemical vapor infiltration (CVI) is a CVD variant capable of internally coating porous objects, e.g., an object made out of carbon fibers, with a ceramic material. Silicon carbide (SiC) or boron carbide (B4C) are examples of ceramic matrix materials that are used in combination with carbon fibers. Strong, light, durable, wear-resistant, and biocompatible joint prostheses made of ceramic-ceramic composites are manufactured by means of CVI. Figure 6.18 shows how the degree of penetration is affected by temperature and pressure. Clearly, to get deposit deep in the interior of the porous object low temperatures are necessary for reaction limitation and low pressures for helping the diffusion. Under these conditions growth rates are low. 

Ceramic matrix materials can be classified in different ways. Structural ceramics used as matrix materials can be categorized into two main groups ... 

In the field of composite materials, inorganic-organic hybrid polymers offer great promise as precursors to ceramic matrix materials. In these applications, high purity ceramics are often not necessary and preceramic polymers allow the introduction of inorganic elements such as silicon and boron in quantities which can be directed by polymer structure and stoichiometry. 

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