Silicon-containing ceramics, classes

Silicon-containing ceramics include the oxide materials, silica and the silicates the binary compounds of silicon with non-metals, principally silicon carbide and silicon nitride silicon oxynitride and the sialons main group and transition metal silicides, and, finally, elemental silicon itself. There is a vigorous research activity throughout the world on the preparation of all of these classes of solid silicon compounds by the newer preparative techniques. In this report, we will focus on silicon carbide and silicon nitride. 

The first type of polycarbosilane synthesized by using ADMET methodology was a poly[carbo(dimethyl)silane].14c Linear poly(carbosilanes) are an important class of silicon-containing polymers due to their thermal, electronic, and optical properties.41 They are also ceramic precursors to silicon carbide after pyrolysis. ADMET opens up a new route to synthesize poly(carbosilanes), one that avoids many of the limitations found in earlier synthetic methods.41... 

And now another important question is Should these Venus sculptures be classed as ceramic materials Initial analyses proved that they were made of silicon-containing ash and mammoth bone and possibly also mammoth fat, but no aluminium oxide or potassium oxide - which are always present in clay - were found. A later analysis of the Venus of Vestonice led to the concusion that a mixture of mammoth fat and bone, mixed with bone ash and local loess had been used but still no traces of potassium nor of aluminium. In the eighties the Venus was examined using more sophisticated equipment and the result was no bone or other organic components and no stone fragments. In the period 1955-1965 some researchers concluded that the animal statues of Dolni Vestonice were made of clay, and they called this terra cotta which means burned soil . Present studies indicate that the loess of Dolni Vestonice was used as raw material for the animal figurines. 

The silicates, made up of base units of silicon and oxygen, are an important class of ceramic compounds that can take on many structures, including some of those we have already described. They are complex structures that can contain several additional atoms such as Mg, Na, K. What makes the silicates so important is that they can be either crystalline or amorphous (glassy) and provide an excellent opportunity to compare these two disparate types of structure. Let us first examine the crystalline state, which will lead us into the amorphous state. 

The so-called solvent-based binder systems contain polymers which solvate or swell in a solvent (e.g. water, alcohol). Typical polymers used in extrusion are PEG, PVA, agar agar and cellulose. Thermoplastic materials are polymers which when heated, soften, melt or become more pliable, and harden during cooling in a reversible physical process. Materials in this class which are used quite often for ceramic processing are PE, PP, EVA, POM and PMMA. Thermosetting materials are polymers which can be melted only once and which, after melting, harden as more heat is added. Thermoset plastics which are used in the ceramic industry are phenolic resins and different silicon resins like polysiloxane. 

The data base now contains 5497 test results on over 320 different batches of ceramic materials. Approximately 46% of these are on zirconia-based ceramics, 9% are on silicon carbides, 21% are on silicon nitrides, 6.7% are on whisker-reinforced silicon nitrides, 16.3% are on alumina-based ceramics (including whisker-reinforced aluminas and mullites), and 2% are on other ceramics. Table 1 gives a detailed breakdown, by material class, of the data stored in the system, A list of materials within a material class Is available on request. 

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