Effect of Bulk Density on Reaction Propagation in Nanothermites and Micron Thermites

The thermite reaction of nanoscale aluminum and molybdenum trioxide particles has revealed a paradoxical relationship between At particle size and mixture bulk density. Specifically, with micron-scale At particles, the thermite demonstrates tin expected growth In flame speed with increased density, hill nanoscale-Al-particle mixtures exhibit an opposing trend. This paper presents new experimental measurements of the thermal properties of this thermite its a function of At particle size and applies a new oxidation mechanism in an effort to explain the paradoxical results between At particle size and mixture bulk density. Results show that lite nanocomposite's behavior is consistent with it new melt-dispersion oxidation mechanism and convective mode of flame propagation. Compaction-induced damage of the oxide shelf and distortion of the shape of spherical particles, as well as reduced free space around Al nanoparticles suppress the melt-dispersion mechanism and reduce flame speed. An additional mode of energy transfer is proposed that is associated with molten Al clusters, front the melt-dispersion mechanism that advance faster than the flame velocity. Micron-scale particle reactions may be governed by diffusion such that increased bulk density coincides with increased thermal properties and increased flame speeds.