Thermal Initiation of Fast Decomposition

Many inorganic azides melt before exploding, and Table I shows the melting points of various azides. 

Although the slow decomposition of the azides is a surface phenomenon, when the temperature is high, decomposition may occur within the melt because of the enhanced mobility of the azide radical [2]. Many of the parameters which affect slow decomposition are also important in fast decomposition, but the 

Cadmium azide Copper (I) azide Lead azide Mercury (II) azide Silver azide Thallium (I) azide Potassium azide 

Among parameters which need to be specified for the initiation of fast decomposition of azides by heat are the thickness (minimum dimension) of the crystal or pellet, the temperature and duration of the heat pulse, and the amount and type of impurity, in addition to the ambient geometry and conditions. 

Various studies of the effect of particle size on the critical temperature of azides have been made. Bowden and Yoffe [2] gave data for several explosives which exhibit a critical size for explosion at a particular temperature. For lead azide Hawkes and Winkler [13] and Bowden and Singh [14] showed that the smallest dimension of a crystal controls its explosion temperature and that the temperature decreases with increasing crystal thickness. A size effect was also found by Bowden and McLaren [15] for pellets of lead azide. 

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