Synthesis and oxidation chemistry of highly energetic boron/aluminum/magnesium composites

Abstract

The limited use of boron (B) in energetic applications is due to the presence of a native oxide layer on its surface, which acts as a thermodynamic barrier and adds to the dead weight that does not contribute to the oxidation energy release. To extract maximum energy from B oxidation, its native oxide must be chemically reduced or modified. In this paper, we report the synthesis of a new energetic material via solid-state reactions, a composite of boron (B), aluminum (Al), and magnesium (Mg), which we call BAM. We use Al and Mg to induce cyclic thermite reactions in parallel to metal oxidation: Al and Mg reduce B2O3 to form B and oxides of Al and Mg, while Mg reduces Al2O3 to form MgO along with Al, which further reduces B2O3. The result is a material that registers higher energy release than its constituents. Specifically, BAM composites show enhanced gravimetric heat release by 40% and improved oxidation by 25% than B alone under identical conditions. The sequence and synergy of oxidation and thermite reactions are illustrated by integrating XRD with thermal analysis in the air for different exothermic peaks and temperature stages. The results demonstrate that the proper selection of metallic additives can enhance the oxidation and energetic performance of B.

Keywords

• Energetic materials
• Solid fuels
• Reactive metals
• Oxidation
• Thermite reaction
• Combustion