Initiation of high explosives by nanothermites: application of this concept to high energy ammunitions for the homeland security services – SUPREMATIE

Two configurations were studied: the external and the internal initiation. In the external initiation, the nanothermite and the explosive are separated and react successively. In the internal initiation, the explosive is mixed with the nanothermite; both energetics react at the same time.

1. The external initiation was studied on RDX/wax pellets (93,1 wt-%), which have been submitted to the effects produced by the reaction of several confined nanothermites. An underlying metal plate was used for performing the qualitative diagnosis (deflagration or detonation). The propagation rates of the explosive reaction were measured by using shortcut probes.

2. The internal initiation was studied with composite materials comprising a nanothermite and a high explosive. The composition were put in transparent tubes and the propagation of the reactions was observed by high speed video. This technique gives valuable information not only on the combustion rates and accelerations, but also on the phenomena involved and their mechanisms.

1. Preparation of WO3/Al et CuO/Al nanothermites insensitive to impact (> 49,6 J) and friction (> 360 N) by playing on the size of oxide particles. These insensitive nanothermites have, however, relatively high combustion rates of 100 and 450 m/s, respectively.

2. Experimental determination of the thermal conductivity of the nanothermites and of their components (metallic oxide and aluminium).

3. Study of the morphological and the reactive properties of a new thermite family (Bi2O3/B et CuO/B), prepared from boron nanoparticles.

4. Experimental demonstration of the fact, that the shock produced by the nanothermites studied in the external initiation tests, is not high enough to initiate the detonation of the explosive.

5. A low detonation rate phenomenon (1260 m/s) was observed by the internal initiation of hexogen by nanothermites.

The research on the development of more reactive nanothermites, prepared by adding high explosives will be continued. Energetic systems {nanothermite + explosive}, based on internal initiation, will be embedded in ammunition bullets. This research will involve the chemical and morphological optimization of the compositions, the study of their embedding in the bullet and the characterization of the effects produced by the impact, in order to maximize the desired effect. The high energy ammunitions will be finally tested in weapons.
The modeling of the nanothermite reactivity and of their influence on explosives will be continued in the light of the experimental results achieved by the external/internal initiation tests.

1. Publication in a journal of the American Chemical Society (ACS) :

M. Comet, F. Schnell, V. Pichot, J. Mory, B. Risse, and D. Spitzer, Boron as Fuel for Ceramic Thermites, Energy & Fuels, 28 (2014) 4139-4148.
dx.doi.org/10.1021/ef500221p


2. Communications at international conferences:

M. Comet, D. Hassler, B. Khasainov, F. Schnell, A. Bach, V. Pichot, D. Spitzer, Reactive properties of some nanothermites, 40th International Pyrotechnics Seminar, July 13-18, 2014, Colorado Springs, CO, USA.

M. Comet, B. Khasainov, B. Baschung, V. Pichot, D. Spitzer, The nanothermites: functional nanocomposites for fast energy release, XII International Conference on Nanostructured Materials (NANO 2014), July 13-18, 2014, Moscow, Russia.


3. Presentations at scientific symposia:

M. Comet, F. Schnell, B. Risse, D. Spitzer, Oxides for reactive nanothermites, ISL Scientific Symposium, March 17-21, 2014, Saint-Louis, France.

M. Comet, Nanothermites: versatile energetic materials for high power applications, Séminaire scientifique «Nanodual« ISL-CNRS-UdS, 2 juin 2014, Saint-Louis, France.

The goal of the SUPREMATIE project consists in investigating the possibility of priming high explosives by the decomposition of nanothermites. Nanothermites are versatile energetic compositions which are prepared by mixing nanoparticles of metallic oxides and a reducing metal. The mixture can be performed either by dispersing nanopowders in a liquid or by a chemical coating process. The energy released per unit volume by the combustion of thermites is higher than the one of most explosives. Classical thermites are made of micrometric particles. Their decomposition rates are slow and are responsible for their small combustion power. Conversely, nanothermites possess decomposition rates which are close to those of explosives. The power released by the combustion of nanothermites seems to be high enough to induce the deflagration -or even the detonation- of high explosives. The explosives that will be studied to validate the concept are: the pentrite (PETN), the hexogen (RDX) and the hexanitrohexaazaisowurtzitane (CL-20). The priming of the explosives will be studied by using the aluminothermic reaction of nanothermites which have been identified by the experimental characterization as the most reactive (e.g. WO3/Al; CuO/Al; Bi2O3/Al…) Up to now, the priming of high explosives is performed by the detonation of primary explosives such as metallic azides or fulminates (Ag, Pb, Hg), or the perchlorates of nitrogen complexes of transition metals (BNCP). The use of nanothermites for this purpose is a novel concept. Nanothermites have the advantage of being very stable along time and far less sensitive to thermal and impact stresses than primary explosives. Furthermore, nanothermites have extremely reproducible reactive properties and can be activated by mixing processes just before being ignited. The demonstration of the fact that high explosives could be primed by nanothermites should open new horizons in the field of pyrotechnic security, due to the relative -or absolute- flegmatisation of the most sensitive components of pyrotechnic chains. In addition, the chemicals used to formulate nanothermites can be chosen in order to minimize the toxicity of the nanothermite and of its combustion products. These aspects are all the more important as the use of explosives for civilian purposes will considerably increase in the coming years. Many fields of human activity are concerned: civilian security; spatial, automotive pyrotechnics; fireworks; demolition of concrete structures; natural resources extraction; treatment of nuclear waste and novel applications in electronics or medicine. The validation of the concept proposed in this project could lead to dual applications corresponding to well-defined needs. The last step of the project will consist to study the integration of {nanothermite + explosive} systems in 9 mm bullets used by homeland security services. These high energy ammunitions will significantly improve the defensive response ability of the law enforcement officers against criminals armed with assault weapons.