Salts silicon nitrides/carbides

The Badische AniKn- und Soda-Fabrik prepared a nitride of undetermined composition by heating a mixture of silica and carbon in an atm. of nitrogen. The reaction proceeds at a relatively low temp, if a hydroxide or salt of a metal be added. The product contains silicon nitride mixed with the nitride of the metal. The Badische Anilin- und Soda-Fabrik also removed many of the impurities—iron, carbon, silicates, carbides, silicides, and phosphides—by treatment with acids or mild oxidizing agents which do not affect the silicon nitride. A. S. Larsen and O. J. Storm prepared the nitride by the action of nitrogen on molten silicides—e.g. ferrosilicon. 

Some ceramic materials are not found widely or at all in nature, and thus are synthesized for use. To prepare more complex ceramic compositions such as perovskites of general structural formula ABO3, and ferrites, of formula MFc204, the individual oxides or salts of the cations A, B, and M are often combined as powders and then reacted at high temperature by a solid-state diffusion mechanism. Silicon nitride (Si3N4) can be manufactured from either the nitridation of silicon metal or from the reaction of silicon tetrachloride with ammonia. Silicon carbide (SiC) is obtained from the reduction of silica with a carbon containing source. 

Density is 1.9 to 2.3 kg/1 and flexural strength 30 to 90 mPa. Silicon oxynitride is used as a lining for cells for the electrolysis of AICI3 to A1 and ZnCl2 to Zn, and as crucibles and tubes for molten salts. It occurs as a constituent of nitride bonds (see silicon nitride, SILICON carbide) and has been used to strengthen silica optical fibres by surface coating. 

PZCs/IEPs of sparingly soluble salts (other than combination of two or more sparingly soluble oxides) are presented in Tables 3.1568 through 3.1910. PZCs/IEPs of silicon carbide and nitride are also presented in this section. Salt-type compounds composed entirely of sparingly soluble oxides are discussed in Section 3.3. In the studies devoted to the effect of water-soluble salts with an anion or cation in common with the sparingly soluble salt of interest, the IEP has been defined in terms of concentration of these salts (ions) in addition to (or rather than) pH. 

Sintering processes are known particularly in the area of the formation of metal salts from two solid oxides, the preparation of of silicon carbide from silicon dioxide and carbon. In some processes there is also a gaseous reactant, such as nitrogen in the formation of nitrides, e.g., ceramics of the SiAlON type. 

Methods of preparation for silicides and aluminides are very similar to those used for carbides, nitrides and borides (1) synthesis by fusion or sintering, (2) reduction of the metal oxide by silicon or aluminum, (3) reaction of the metal oxide with SiOj and carbon, (4) reaction of the metal with silicon halide or (5) fused salt electrolysis. The simplest preparation method consists of... 

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