Azides, crystal imperfections

The central role of imperfections in mechanistic interpretations of decompositions of solids needs emphasizing. Apart from melting (which requires redistribution of all crystal-bonding forces, by a mechanism which has not yet been fully established) the decompositions of most solids involve the participation of atypical lattice constituents, structural distortions and/or surfaces. Such participants have, in particular instances, been identified with some certainty (e.g. excitons are important in the decompositions of some azides, dislocations are sites of nucleation in dissociations of a number of hydrates and carbonates). However, the... 

Gray and Waddington [57,120] examined the physico-chemical properties of silver azide and state that its melting point is 300°C. On the basis of the latest opinion that the explosive decomposition of azides results from processes involving ions and electrons caused by imperfection and deficiencies in the crystal lattice (Jacobs and Tompkins [22]), the authors incorporated silver cyanide, Ag2(CN)2,... 

The radiation-induced color changes in inorganic materials (Ref 145) led to a comprehensive study by Rosenwasser, Dreyfus and Levy (Ref 148) on Na azide, which turns to brownish yellow when subjected to radiation. Subsequently, when mechanically deformed crystals of Na and K azide were irradiated with 107R gamma radiation, Dreyfus and Levy (Ref 69) observed the formation of pyramidal etch pits which occurred mainly in regions where imperfections were located at the surface. These were also evident in ammonium perchlorate crystals (Ref 255)... 

Slow neutron irradiation caused color changes and darkening in most of the explosive crystals, indicating the formation of imperfections, which subsequently affected the thermal decomposition of the explosives. The rates of thermal decomposition of irradiated lead azide are shown in Figure 9. 

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