The ability to identify explosives by ultrasonic spectra up to 45 kHz has been investigated for forensic and anti-terror applications. To lower the threshold for laser initiation, nontrivial and well-known azides, CTAP, HMDT, ETN, HMX and other energetic materials have been synthesized. Upon initiation of copper azide by Nd:YAG laser with 11 ns pulsewidth, a threshold of only ~80 μJ was reached, and for 50 μs pulses of laser diode it was ~300 μJ, which is consistent with the thermal initiation nature. Significant differences were found in the spectrum of high-frequency acoustic and ultrasonic vibrations for various energetic materials and bilayer structures. The effective frequency range for the dissociation of copper azide, silver azide and HMTD is limited by ~27 kHz. The spectra of bilayer structures demonstrate suppression of the characteristic lines of copper azide and enrich the spectrum in the ~27 – 45 kHz range: ETN appears in relatively wide bands, while HMX modulates the spectrum with periodic ~3 kHz bands. If successful, the discovered patterns can be used in disaster forensics.
In this study, we present the results of copper azide Cu(N3)2 initiation by pulsed lasers. The threshold energy and energy density are defined. A comparison of the obtained results shows the similarity of initiation of silver azide and copper azide. An approach to improving the safety of the use of cooper azide is proposed.