On the Mechanism of Efficiency of Lead Azide

Abstract

AbstractThe mechanism of superior efficiency of lead azide (LA) in comparison with mercury fulminate (MF) is not understood. Indeed, both primary explosives have quite close detonation velocities and result in a large amount of condensed lead (Pb) and mercury (Hg), respectively. We explore an idea that the high efficiency of LA is due to the fact that the boiling point of lead markedly exceeds that of Hg. Then the products of LA in the detonation reaction zone could contain liquid Pb droplets, while MF products are gaseous. These lead droplets could violently impact the acceptor charge and favor its initiation. The plate dent studies of high explosives (HE) heavily loaded by metal particles provide an indirect support to the proposed mechanism. To check this hypothesis we numerically studied the donor/acceptor problem, where the donor is made of HE loaded with the inert metal particles. Pressure, velocity, and temperature relaxations of particles are taken into account. The model agrees with the experimental effect of metal addition on HE performance. However, the calculations show that the effect of particle penetration into the acceptor is late and weak in comparison with the effect of primary shock induced in the acceptor. Thus, the above hypothesis could not guide the development of green substitutes of LA. Hybrid mixtures of a nanothermite with a high explosive seem to be more promising for this purpose. A simple explanation is proposed for the superior triggering capacity of LA.