The Use of Ammonia Halides

In a general view, stoichiometric equations of obtaining of final products look as follows  

The SHS process that uses sodium azide and halides for obtaining powders of refractory compounds has been termed as SHS-Az.  

NH Cl and NH F are the most acceptable ammonia halides for the use in SHS-Az processes. The reason is that they are safe to handle and there is presently sufficient base of initial products for it. The chemical reaction equations with the use of halides of ammonia have the form  

As a result, the final synthesis product can contain the neutral halides NaCl and NaF besides the final nitride. These halides are easily removed by water cleaning of the final powder. If the transient metals of the IV group are used as a fuel, the amount of the subsidiary synthesis product in a nitride and carbonitride is 2-3% of the theoretical one in average. The remaining amount leaves the sample and can be condensed both on the reactor walls and in the purifying setups outside of the reactor. After the water cleaning operation, the amount of NaCl and NaF in the final product practically becomes to zero. 

The use of such a class of halides in SHS-Az systems does not lead to formation of fibers according to the research results. The powders are formed in a shape of asymmetric splinter particles with the specific surface being 3.5-7.5m g . The purity degree is on the average level with the main substance being 95-99%. The powders with the main substance more than 99% can only be obtained from transitive metals such as H, Zr, and Hf. Incidentally, the nitrogen of halide is not accounted for in the chemical reaction equation (see Equation 8.8). In addition to 

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