Emily M. Hunt, Department of Mathematics, Physical Sciences, and Engineering, West Texas A & M University, Box 60787, Canyon, TX 79016, Michelle Pantoya, Mechanical Engineering Department, Texas Tech University, Corner of 7th and Boston Ave, Lubbock, TX 79409, and Jason Jouet, Research and Technology Department, Naval Surface Warfare Center, Indian Head Division, Indian Head, MD 20640.
A highly porous intermetallic alloy was created through self-propagating high-temperature synthesis. The reactants are composed of nano-scale particles of nickel (Ni), micron-scale particles of aluminum (Al), and nano-scale Al particles passivated with a gasifying agent, C13F27COOH. The concentration of nano-Al particles present in the reactant matrix was controlled according to the wt % of gasifying agent. The reactant mixture was cold-pressed into cylindrical pellets with a constant density equal to 70% of the theoretical maximum density. Once ignited, flame propagation was observed to transition from normal to convectively dominant burning as more gasifying agent became present in the reactants. A critical Andreev number of 6 was determined to represent this transition. Ignition delay times were reduced by two orders of magnitude when only 2.24 wt % nm Al particles were present. The product alloy expanded by a factor of 14 in the axial direction with 1.6 wt % nm Al (corresponding to 10 wt % gasifying agent). Total porosity of the pellets was also measured and found to increase with increasing wt % of the nano-Al and gasifying agent.
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