Combustion of off-Stoichiometirc Al-Moo3 Nano-Composite Powders in Dry Air

Fully dense, nano-composite Al-MoO3 powders with excess Al were prepared by Arrested Reactive Milling (ARM) as potential components for propellants, explosives, and pyrotechnics. The thermite reaction reducing MoO3 is expected to boost the Al ignition rate, and the minimum concentration of MoO3 needs to be determined that enables rapid and complete combustion of aluminum. In the first part of this project, a nanocomposite powder with the bulk composition 4Al + MoO3 was produced and its combustion was compared to that of pure aluminum powder in air. The combustion experiments were conducted in a 9.2 L volume, closed vessel. The mass load of aluminum powder was determined from thermodynamic calculations to ensure the maximum flame temperature. To maintain consistency in the experiments, the amount of the nano-composite powder loaded in the vessel was selected to match the volume of the pure Al load. Specifically, 2.79 g and 3.81 g of Al and 4Al + MoO3, respectively, were aerosolized in the explosion vessel and ignited at its center using a heated wire while monitoring the vessel pressure in real time as the flame propagated outward. The results showed that both the pressure increase and rate of pressure rise produced in the vessel by combustion of the 4Al + MoO3 powder are greater than those of Al. The project continues with producing and testing nanocomposite powders with increasingly greater concentrations of Al. A special care is taken to ensure the similarity of the particle size distributions for different powders used in the constant volume explosion tests.