(546f) Doping Boron with Iron for Better Combustion

Boron is a thermodynamically attractive fuel additive for propellants and explosives, however it has yet to reach its full potential because of its lengthy combustion times and ignition delays. This work focuses on increasing the rate of the heterogeneous combustion reaction on the surface of burning boron particles by introducing iron as a catalytic additive. Iron is readily oxidized and reduced, and is therefore expected to improve the surface reaction rate. Varying quantities of iron (0 – 5 wt %) are introduced as a coating on boron agglomerates using iron pentacarbonyl as the iron source. The samples are prepared using 95% pure commercial boron and higher purity, 99%, boron powders in an inert reaction batch with dodecane and an organic surfactant. The prepared samples are characterized using SEM analysis to observe surface morphology and particle size distribution. Each sample is ignited in air using a CO₂ laser. Particle emission streaks of single burning particles are collected optically to determine burn times. Correlating statistical distributions of the measured burn times with the particle size distributions, an effect of the particle size on its burn time is determined for all materials. Flame temperatures are also recovered from the optical measurements. Combustion data will be compared to boron-iron composites prepared by mechanical milling to establish the effect of the preparation technique on the effectiveness of iron additive. The effect of purity of the starting material and iron dosing will also be discussed in detail.