Liquid metal embrittlement to boost reactivity and combustion performance of Al in composite propellants

Abstract

Aluminum (Al) powder has been widely used in solid composite propellants (SCPs) due to its high energy density and appropriate combustion kinetics. However, the presence of a passivation shell (Al2O3) on the surface of Al would reduce its reactivity and heat release. Herein, a facile ‘one-step’ modification method was proposed for the fabrication of micron-sized Al substitutes in SCP, aiming to induce the involvement of Al cores in the reaction by letting the liquid metal embrittlement (LME) damage the homogeneous Al2O3 shell. Oxidation weight gain experiments in the air atmosphere were conducted to investigate the effect of liquid metal content on the breakthrough of the Al2O3 shell to improve ignition and combustion performance. Moreover, the composites with gallium-based liquid metal (Galinstan) addition of 3 wt% exhibited the largest oxidation weight gain and oxidation weight gain rates, which were approximately 6 and 8-fold higher than that of the raw-Al particles, respectively. Furthermore, the resulting Galinstan-modified aluminum-based powder (GLM-Al) was used as a metal fuel for the formulation of SCP to validate its thermal and combustion properties. According to the DSC results, the heat release of SCP-2 containing GLM-Al was 3321 J·g−1, which is 1.42 folds of that from the reference SCP-1(2341 J∙g−1). Furthermore, SCP-2 exhibited a 12 % increase in burning rate under 0.1 MPa air atmosphere and a much higher pressurization rate (5.4 MPa·s−1) than that of SCP-1 (2.6 MPa·s−1) under 1 MPa argon atmosphere. The resulting condensed combustion product (CCP) size of SCP-2 is much smaller than that of SCP-1.