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 ϳ0.8 mm diam. The largest unipolar electric voltage and current were produced during the combustion of either a Zr or a Ti particle ͑ϳ2 V and ϳ100 mA͒. 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.

Transient electric fields of up to 1.5 V were generated during the high temperature oxidation of pure metals (Mg, Al, Ti, Zr, Hf, Cr, Mn, Fe, Co, and Ni) either by gaseous oxygen or by solid peroxides or perchlorates. These time-varying fields are most probably due to ion formation and motion in and behind the moving high temperature reaction zone, which creates an electric double layer within individual particles. The shape and magnitude of the induced temporal electric signal depends upon the reactant properties, mode of the front propagation, and mobility of the ions formed. Unsteady combustion front propagation (occurring during the oxidation of Mg, Al, and Nb) generates an oscillatory electrical signal. Metals belonging to the same group in the periodic table (Ti, Zr, and Hf; Ni and Co) and whose products have the same oxidation state generate qualitatively similar electrical signals. The sign and magnitude of the transient electric potential generated during metal oxidation by perchlorates or peroxides are dominated by the chemoionization processes involved in the decomposition of a solid oxidizer. © 2001 The Electrochemical Society. All rights reserved.

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We report here the observation of chemomagnetism, generation of a magnetic field by rapid high-temperature solid reactions producing various oxides. The low-level transient magnetic fields were measured with a high-Tc superconducting quantum interference device magnetometer during the synthesis of both nonferromagnetic and ferromagnetic (ferrite) compounds. The magnetic field was most likely produced by chemoionization processes generated by the moving high-temperature reaction zone. The permanent magnetic field formed by the synthesis of ferromagnetic materials depended on the difference between the combustion temperature and the Curie temperature of the product.