The Effect of Added Al₂O₃ on the Propagation Behavior of an Al/CuO Nanoscale Thermite

Abstract

Three types of experiments were performed on an Al/CuO nanoscale thermite to understand the effect of adding a diluent (40 nm Al₂O₃ particles) to the mixture: the constant volume pressure cell, the unconfined burn tray, and the instrumented burn tube. The addition of Al₂O₃ decreased the pressure output and reaction velocity in all three experiments. Burn tube measurements showed three reaction velocity regimes: constant velocity observed when 0% (633 m/s) and 5% (570 m/s) of the total weight is Al₂O₃, constant acceleration observed at 10% (146 m/s to 544 m/s over a distance of 6 cm) and 15% (69 m/s to 112 m/s over a distance of 6 cm) Al₂O₃, and an unstable, spiraling combustion wave at 20% Al₂O₃. The pressure measurements correlated to these three regimes showing a dropoff in peak pressure as Al₂O₃ was added to the system, with relatively no pressure increase observed when 20% of the total weight was Al₂O₃. Equilibrium calculations showed that the addition of Al₂O₃ to an Al/CuO mixture lowered the flame temperature, reducing the amount of combustion products in the gas phase, thus, hindering the presumed primary mode of forward heat transfer, convection.

Keywords:

• Burning rate
• Diluent
• Nano-aluminum
• Thermite

Authors are supported by Los Alamos National Laboratory (LANL), which is operated for the U.S. Department of Energy under the contract DE-AC52-06NA25396. Work was supported by the Joint DoD/DOE Munitions Program under the supervision of Sherri Bingert and the U.S. Army Research Office under the Multi-University Research Initiative under Contract No. W911NF-04-1-0178. The authors give a special thank you to Adam Pacheco and Dave Oschwald for their help setting up and running the equipment that made this study possible. For his help interpreting pressure transducer results, Dr. Patrick Walter of Texas Christian University is thanked as well. This work has been assigned LA-UR #07-7888.