Formulation and Combustion of Al/CuO Nanothermites using Flake-Shaped Al Nanoparticles

Aluminum powders are widely used as fuels in propellants or in pyrotechnic mixtures. It is now well established that size reduction of aluminum particles from the micrometric down to the nanometric scale improves the combustion rate [1,2]. In the case of Al-based nanothermites, several other factors are shown to affect the combustion properties. Among them, one can cite, the surface functionalization of Al nanoparticles [3], the use of core-shell fuel-oxidant particles [4,5], and the incorporation of porosity [6–8].<br/><br/>In this work, we highlight the influence of morphology and surface properties of aluminum nanopowders on the combustion properties of Al/CuO nanothermites prepared by physical mixing. A comparative study is performed between nanothermites formulated using commercial aluminum nanospheres and two kinds of aluminum nanoflakes synthetized using high-energy ball milling and with different surface properties.<br/><br/>We will first present a detailed characterisation of initial Al nanopowders in terms of texture and reactivity towards air and water. Secondly, we will focus on Al/CuO energetic compositions. We will demonstrate that, contrary to was is generally expected, the flake shape is not problematic for the nanothermites formulation. Then, we will show that higher sensitivity thresholds can be reached notably for friction and electrostatic discharge by modifying the surface properties. Such enhanced thresholds might be of interest for safer handling. Finally, combustion tests will be presented and correlations between flame propagation velocity, morphology and Al nanopowders reactivity will be proposed.<br/><br/><br/><i>This work received support from the Direction Générale de l’Armement (DGA), Aix-Marseille Université (AMU) and the Region Sud (AENA Project).</i><br/><br/>[1] J.R. Luman, B. Wehrman, K.K. Kuo, R.A. Yetter, N.M. Masoud, T.G. Manning, L.E. Harris, H.A. Bruck, Proceedings of the Combustion Institute. 31 (2007) 2089–2096.<br/>[2] C. Rossi, A. Estève, P. Vashishta, Journal of Physics and Chemistry of Solids. 71 (2010) 57–58.<br/>[3] K.S. Kappagantula, C. Farley, M.L. Pantoya, J. Horn, J. Phys. Chem. C. 116 (2012) 24469–24475.<br/>[4] K. Shi, X. Guo, L. Chen, S. Huang, L. Zhao, J. Ji, X. Zhou, Combustion and Flame. 228 (2021) 331–339.<br/>[5] X. Ke, X. Zhou, H. Gao, G. Hao, L. Xiao, T. Chen, J. Liu, W. Jiang, Materials & Design. 140 (2018) 179–187.<br/>[6] M. Mursalat, C. Huang, B. Julien, M. Schoenitz, A. Esteve, C. Rossi, E.L. Dreizin, ACS Appl. Nano Mater. 4 (2021) 3811–3820.<br/>[7] H. Jabraoui, A. Esteve, M. Schoenitz, E.L. Dreizin, C. Rossi, ACS Appl. Mater. Interfaces. 14 (2022) 29451–29461.<br/>[8] T. Wu, B. Julien, H. Wang, S. Pelloquin, A. Esteve, M.R. Zachariah, C. Rossi, ACS Appl. Energy Mater. 5 (2022) 3189–3198.