Group IA azides

Torkar et al. [702,706—708] identified nucleation as an autocatalytic process at the (hk0) planes of hexagonal platelets of NaN3. The decelera-tory reaction fitted the first-order equation [eqn. (15)]. Values of E tended to be irreproducible for the pure salt E was about 180 kJ mole 1 but this was reduced to about half by doping. This influence of an additive and the observed similarities in magnitudes of E for decomposition and for diffusion were interpreted as indicating that growth of nuclei was controlled by a diffusion process. 

The kinetics of NaN3 decomposition are sensitive to both pressure and composition of the surrounding atmosphere. The influence of an inert gas in suppressing sublimation of product metal has been mentioned already. The reaction of NaN3 at 623 K was strongly inhibited [711] by NO and by H2. The possible formation of transient decomposition intermediates could not, however, be distinguished from the direct interaction of added gas and azide. 

An initial deceleratory process ( 1%) in KN3 decomposition is ascribed to reaction at superficial imperfections [712]. The subsequent constant rate of product evolution corresponds to an interface process but this is not a nucleation and growth mechanism since the product metal is volatile (as in NaN3). The catalytic properties of potassium vapour are attributed 

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