A molecular dynamics study on oxidation of aluminum hydride (AlH3)/hydroxyl-terminated polybutadiene (HTPB) solid fuel

MY Feng and HP Li and KH Luo, PROCEEDINGS OF THE COMBUSTION INSTITUTE, 38, 4469-4476 (2021).

DOI: 10.1016/j.proci.2020.09.023

Aluminum hydride (AlH3) is a promising replacement for aluminum in hybrid and solid propellants, where hydroxyl-terminated polybutadiene (HTPB) is normally used as a binder. In this study, a reactive molecular dynamics simulation method is employed to investigate the fundamental oxidation mechanisms of AlH3/HTPB solid fuel using a core-shell nanoparticle configuration. The overall oxidation is found to proceed in three distinctive stages: (I) preheating, (II) acceleration and (III) oxidation. Furthermore, oxidation mechanisms of AlH3 and HTPB are separately studied to understand their different roles during the overall oxidation process. With respect to the oxidation of the AlH3 nanoparticle, the reaction is delayed compared with the oxidation of pure AlH3 , due to the initial coverage of the nanoparticle surface by HTPB molecules. Additionally, decomposition of HTPB/HTPB intermediates is observed to occur on the nanoparticle surface and some of the decomposed products are integrated with the nanoparticle. In the meantime, the AlH3 nanoparticle facilitates the HTPB initiation by dehydroxylation or dehydrogenation. Moreover, the primary decomposition pathway of HTPB/HTPB intermediates is the continuous scission of carbon chain to form a large amount of C-4 species, which are finally oxidized at a later stage of the reaction producing CO, CO2 and H2O. The new atomistic insights obtained from the present research could potentially benefit the design of AlH3/HTPB-based solid propellants. (C) 2020 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

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