Influence of Particle Size and Mixing Technology on Combustion of HMX/Al Compositions

In this work, two widely used components of high-energy condensed systems - HMX and aluminium were studied. Morphology, thermal behaviour, chemical purity and combustion parameters of HMX as a monopropellant and Al/HMX as a binary system were investigated using particles of different sizes. It was shown that in spite of the differences in composition and particle size, combustion velocities are almost identical for micrometer-sized HMX (m-HMX) and ultrafine HMX (u-HMX) monopropellants under pressure from 2 to 10 MPa. Replacement of the micrometer-sized aluminium with ultrafine one in the system with m-HMX leads to a burning rate increase by a factor of 2.5 and the combustion completeness raise by a factor of 4. Two mixing techniques to prepare binary Al/HMX compositions were applied: conventional and 'wet' technique with ultrasonic processing in liquid. Applying wet mixing results in a burning rate increase of 18% compared to the conventional mixing for systems with ultrafine metal. The influence of the component's particle size and the composition microstructure on the burning rate of energetic systems is discussed and analysed.