Detonation of Ultrafine Explosives

Detonation of PETN and HMX with a particle size of about 1  $$\mu$$ m was investigated by an electromagnetic method. At an initial density of 0.9–1.2 g/cm3, the von Neumann spike was either weak or not observed at all. This indicates a fast reaction whose time is outside the experimental resolution (about 5 ns). Electrical conductivity measurements provided only a rather rough upper-bound estimate of the reaction time (less than tens of nanoseconds). Density measurements using synchrotron radiation showed that the initiation of PETN with an air shock wave led to an almost instantaneous initiation of detonation, without an acceleration stage. In general, the results of the study confirm that the chemical reaction rate in ultrafine explosives is increased.