Nanoenergetics as pressure generator for nontoxic impact primers: Comparison of Al/Bi2O3, Al/CuO, Al/MoO3 nanothermites and Al/PTFE

Abstract

In the last two decades, major progresses have been made in developing highly-exothermic reactive mixtures. Mixtures of metallic and oxide powders, so-called nanothermites have been used to release temperature, pressure waves and eventually new compounds through exothermic reactions. By varying the size and nature of the oxidizer, we can tune the performances of these materials and multiply the applications. For application in nanothermite-based impact primers, it is important to generate a high pressure peak with a pressurization rate as high as possible to accelerate a thin plastic or metallic foil to a few hundreds of meter per second. This paper reports on the burning rate performances and over-pressure generation for 4 kinds of nanothermite powder mixtures prepared using aluminum nanoparticles mixed with 3 different nano-sized oxidizers, Bi2O3, CuO, MoO3 and micron-sized PTFE (Polytetrafluoroethylene) and compare them to Al/CuO multilayer nanothermite. We observe that Al/Oxide reactions are very luminous with an unconfined burning rate spanning from 65 to 420m/s. The maximum value has been obtained for Al/Bi2O3 powder mixture. Al/CuO mixture generates the highest pressure peak (41.7MPa) at 50% TMD (Theoretical Maximum Density). The maximum pressurization rate is also measured for this Al/Bi2O3 mixture (∼5762kPa/μs) at 30% TMD comparatively higher than the others: 172, 35 and 33kPa/μs for Al/CuO, Al/MoO3 and Al/PTFE respectively. The shortest time needed to reach maximal pressure is obtained for Al/Bi2O3 with 225μs. It is of 360μs for Al/MoO3, 770μs for Al/CuO and 1040μs for Al/PTFE. So there is a difference of performance. Burning rates follow the same tendency: the highest velocity is obtained for Al/Bi2O3, and slowest for Al/PTFE. So the faster reaction results in a reduced ignition delay.