NanoCoCoX

Solid granular explosives are used in a large number of applications for their ability to deliver a fast and intensive mechanical work (genie civil, mining, military applications, etc.) or to synthesize materials for which the reaction path travels through pressure and temperature ranges not accessible to conventional processes. For instance, mixtures of carbon-rich and high detonation pressure explosives are used to synthesize detonation nanodiamonds for various applications [Pichot et al. Sci. Rep. 7, 14086 (2017), Pichot et al., J. Hazard. Mater. 300, 194-201 (2015)]. The detonation mechanism of these solid explosives is widely studied, both from the experimental and theoretical point of view, despite the difficulties inherent to its characteristic length and time scales, which represent a challenge both for experiments and simulations. In the course of the previous ANR-ASTRID project « ATOLE », the NS3E laboratory and CEA-DAM have built a collaboration based on theory and experiments in order to understand the impact of granularity on the pyrotechnic properties of various explosives and explosive mixtures. The objective of the project was to understand the correlation between the nanostructure of the explosives and the size distribution of the recovered detonation nanodiamonds. During this project, NS3E showed that the spray flash evaporation process used to synthesize the nanograins of explosive could lead to the formation of sub-micrometer core-shell structures, with a core of one explosive covered by a layer, or shell, of the other [T. Deckert-Gaudig et al, Chem. Phys. Chem. 18 (2), 175-178 (2017)]. Although these original structures are well known at the micrometer scale, the formation of these new nanostructures through a fully "in situ" reaction path opens new potential routes to the synthesis of granular explosives. However this discovery calls for preliminary experimental and theoretical studies in order to understand, and rationalise, their formation process and their properties. The goal of this proposal is to take advantage of the duality and complementarity of the NS3E/CEA-DAM consortium in order to investigate the formation mechanism of the nanometric core-shell explosives. Their thermodynamic stability and pyrotechnic properties will be investigated in terms of yield and safety, with a particular focus on the influence of the experimental conditions, which could be adapted to tune the performance of the explosive. NS3E will run the experimental component of the project and CEA-DAM will lead the theoretical studies.