Electric Field Formation during Combustion of Single Metal Particles

Abstract

A strong electric field formed during the initial stage of the combustion of single Zr, Ti, Fe, and Ni particles. The electric field lasted for 20-400 ms and decayed before the particle temperature reached its maximum. A low voltage was generated during the combustion of particles initially surrounded by a thick oxide film or when the ambient oxygen concentration was low. A decrease in the rate of oxygen transport to the reaction zone generated a bipolar signal during the combustion of Zr and Ti and/or electric oscillations of 0.5-10 Hz. Melting of either the reactants, or intermediate or final products annihilated the electrical field. The maximum voltage and current were attained for particles of ∼0.8 mm diam. The largest unipolar electric voltage and current were produced during the combustion of either a Zr or a Ti particle (∼2 V and ∼100 mA). A rapid increase in the rate of temperature rise in Zr and Ti particles followed the annihilation of the electric field. It may have been caused by Joule heating following electric breakdown through the oxide film. A shift from homogeneous to relay-race combustion occurred upon increasing the distance between particles in a row. This shift affected the qualitative features of the generated electric field as well as the temperature at which it formed. © 2003 The Electrochemical Society. All rights reserved.