The Use of Halides for Obtaining Refractory Compositions

It was established that the use of two different combustible elements in SHS-Az systems makes it possible to form composite powders. In this case, the portion of titanium, for example, in the initial mixture (see Equation 8.9) is replaced by an adequate portion of different combustible elements, for example, zirconium (see Equation 8.23). The composition TiN-ZrN is formed as result of synthesis. By varying the contents of combustible elements in the initial mixture, one can obtain the final compositions with different content of final refractory components of nitride-nitride type. 

As it was pointed out, halide may contain the element to be nitrided in a number of cases. This fact laid the basis for obtaining refractory compositions from SHS-Az systems in which only one initial combustible element is present. The second one is formed because of halide decomposition which is contained in the same initial mixture. This is rather efficient both for economical reasons (for example, boron appears more effective in the formation of halide in initial mixtures) and 

For illustration, let us introduce some stoichiometric equations for refractory powders obtaining in SHS-Az regime  

The quality of final powder compositions is analogous to the quality of individual refractory compounds obtained from similar systems. Besides that, the fibrous structure is preserved when using complexing halides of ammonia and elements to be nitrided. 

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