Electrical pulse formation during high temperature reaction between Ni and Al

Abstract

An electric voltage pulse (duration of about 2ms) with an amplitude of up to 0.6V was generated during the reaction between nickel and aluminum powders by a high temperature moving reaction front. The electrical signal formed during the initial stages of the combustion was annihilated before the moving front attained its maximum temperature. The voltage amplitude and combustion temperature depended on the particle size of the reactants as well as the Al to Ni ratio in the reactant mixture, and their largest values were attained for a mixture containing 27–31.5wt% Al. The combustion temperature increased when smaller Al particles were used. The electric signals annihilated either due to the growth of the initially formed product layer and∕or as a result of the formation of a molten Al matrix as the reaction propagated. Oscillatory signals formed during unstable combustion in which the reaction front was perturbed. Unipolar and nonoscillating signals formed when the combustion front was planar. We conjecture that the electric field was generated by the different diffusion rates of charge carriers through a reaction generated thin exterior intermediate products shell of Al3Ni∕Al3Ni2.