TY - JOUR
T1 - Effects of fuel and oxidizer particle dimensions on the propagation of aluminum containing thermites
AU - Weismiller, M. R.
AU - Malchi, J. Y.
AU - Lee, J. G.
AU - Yetter, R. A.
AU - Foley, T. J.
N1 - Funding Information:
This work was sponsored by the US Army Research Office under the Multi-University Research Initiative Contract No. W911NF-04-1-0178. The support and encouragement provided by Dr. Ralph Anthenien is gratefully acknowledged. T.J.F. was supported by the Joint Munitions Program (DoD/DOE) at the Los Alamos National Laboratory (LANL). The authors would also like to acknowledge Ed Roemer of LANL for the SEM micrograph in 1a. and Maria Klimkiewicz from Penn State’s Materials Characterization Lab for her help obtaining the SEM images 1b.-f.
PY - 2011
Y1 - 2011
N2 - Results from combustion experiments, in which the fuel and oxidizer particle sizes of Al/CuO and Al/MoO3 thermites were varied between the nanometer and micrometer scale, are presented to gain further insight into the factors governing their rate of propagation. The experiments were performed with thermite mixtures loosely packed in an instrumented burn tube. Critical properties, including linear propagation rates, dynamic pressure, and spectral emission, were measured and compared to determine if the scale of one constituent had more influence over the rate of propagation than the other. It was found that, although nano-fuel/nano-oxidizer composites propagated the fastest for both the Al/CuO and Al/MoO3 thermites, composites containing micron-aluminum and a nano-scale oxidizer propagated significantly faster than a composite of nano-aluminum and a micron-scale oxidizer. The impact of nano-scale oxidizer versus nano-scale Al is twofold. Firstly, mixtures containing nano-aluminum have a greater mass percentage of Al2O 3, which reduces reaction temperatures and propagation rates. Secondly, reactions in porous nano-thermites propagate through a convective mechanism; with heat transfer being driven by flow induced by large pressure gradients. Mixtures containing nano-scale oxidizer particles show faster pressurization rates. Because the majority of gas generation is due to the decomposition or vaporization of the oxide in these reactions, and oxide particles on the nano-scale have shorter heat-up times and smaller length scales for gas diffusion than micron particles, convective burning is greatly enhanced with the nano-scale oxidizer.
AB - Results from combustion experiments, in which the fuel and oxidizer particle sizes of Al/CuO and Al/MoO3 thermites were varied between the nanometer and micrometer scale, are presented to gain further insight into the factors governing their rate of propagation. The experiments were performed with thermite mixtures loosely packed in an instrumented burn tube. Critical properties, including linear propagation rates, dynamic pressure, and spectral emission, were measured and compared to determine if the scale of one constituent had more influence over the rate of propagation than the other. It was found that, although nano-fuel/nano-oxidizer composites propagated the fastest for both the Al/CuO and Al/MoO3 thermites, composites containing micron-aluminum and a nano-scale oxidizer propagated significantly faster than a composite of nano-aluminum and a micron-scale oxidizer. The impact of nano-scale oxidizer versus nano-scale Al is twofold. Firstly, mixtures containing nano-aluminum have a greater mass percentage of Al2O 3, which reduces reaction temperatures and propagation rates. Secondly, reactions in porous nano-thermites propagate through a convective mechanism; with heat transfer being driven by flow induced by large pressure gradients. Mixtures containing nano-scale oxidizer particles show faster pressurization rates. Because the majority of gas generation is due to the decomposition or vaporization of the oxide in these reactions, and oxide particles on the nano-scale have shorter heat-up times and smaller length scales for gas diffusion than micron particles, convective burning is greatly enhanced with the nano-scale oxidizer.
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U2 - 10.1016/j.proci.2010.06.104
DO - 10.1016/j.proci.2010.06.104
M3 - Article
AN - SCOPUS:79251639727
SN - 1540-7489
VL - 33
SP - 1989
EP - 1996
JO - Proceedings of the Combustion Institute
JF - Proceedings of the Combustion Institute
IS - 2
ER -