Enhanced burn rate results are presented for ammonium perchlorate/Al nanoparticle strand burners at atmospheric (and higher) pressure and for the comparative combustion in a high pressure closed vessel of a solid propellant containing 15% of either conventional micrometer-scale Al or nanometric Al. The burn rate at the smallest nanometric Al particle size appears to be asymptotically approaching an inverse particlediameter-squared dependence.Surface-Controlled Decomposition. The enhancements at nanometric particle, grain, crystal, or other unit sizes of either structural material strength properties or electronic device/circuit performances appear to be relatively mature research topics compared to the achievement of greater energy release rates at similar ultrafine particle dimensions. Such potential achievement of substantial increases in energy release rates for the chemical decomposition of ultrafine particles might be foreseen, however, because such decompositions are often surface area dependent, as welldemonstrated, for example, in the use of ultrafine particles for catalytic assistance of chemical reactions. Here, we are concerned with the achievement of enhanced propellant (and explosive) energy release rates at nanometric particle sizes, particularly, involving Al particles whose surface-controlled oxidation to alumina is strongly exothermic. 1 Burn Rate Dependence on Al Particle Diameter. Recent early indications of increasing the burn rate of solid rocket propellant materials with addition of Russian-produced "Alex" nanoscale Al powder ingredient has been credited by Baschung et al. 2 to results reported by Kuo and colleagues. 3 Baschung et al. made their own comparison at ISL, France, of the combustion behaviors exhibited by a new double-base gun propellant, at different pressures in a highpressure closed vessel of 50 cm 3 volume. The propellants employed 15% of Alex material substituted for the same amount of conventional micrometer-sized Al in otherwise the same Pechiney YX 76 propellant formulation of 55% nitrocellulose and 30% dioxyethylnitramine dinitrate (DINA). Also recently, Technanogy, LLC has produced another Al nanoparticle material and obtained experimental strand-type
The dislocation pile-up avalanche model is used to explain the crystal size dependence for hot spot-controlled initiation of chemical decomposition in cyclotrimethylenetrinitramine crystals subjected to drop-weight impact testing. Deformation-induced temperature rises, hot spot sizes, and lifetimes are related to previously reported values for direct thermal decomposition. A reasonable chemical reaction yield is estimated from available kinetic data.
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