Effect of Mo‐Containing Additives on Combustion of Al‐B Fuels

Abstract

In this study, the Al-B-Mo alloy powders with a boron content of 7 wt % and Molybdenum content of 0.5-3 wt % were prepared by the close-coupled gas atomization. The powder morphology, phase composition, oxidation, and exothermic behavior of combustion were characterized. The results show that the addition of Mo effectively improves the energetic properties of the alloy powder, with the mass-burning enthalpy of Al-7B-1Mo reaching 31111 J/g, exceeding the theoretical mass-burning enthalpy of monolithic Al (31000 J/g). Al-7B-1Mo underwent a violent exothermic process at around 1000 °C, and the oxidation weight gain ratio and oxidation efficiency reached 46.16 % and 48.05 % respectively, an increase of 19.75 % and 21.08 % compared to Al-7B. The mesh structure formed by the AlB 2 phase on the particle surface positively promoted the particles' thermal oxidation. Mechanical mixtures of AlB 2 /Mo and AlB 2 /MoO 3 were prepared and the catalytic promotion of the combustion of AlB 2 by Mo and MoO 3 was confirmed by thermal tests of combustion. The mechanism by which Mo/MoO 3 promotes the combustion of AlB 2 was investigated through the phase composition characterization of the composite powder after heat treatment in argon and air atmosphere. It was confirmed that MoO 3 promotes the oxidation and combustion of AlB 2 by supplying oxygen to B in AlB 2 , while Mo is first oxidized to MoO 3 , which then promotes the combustion of AlB 2 .