Electric field of a single burning magnesium particle

Ritchie

Filimonov

et al. 2002

J. Electrochem. Soc.

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.

Section: Methodssupporting

confidence: 88%

mentioning

confidence: 99%

Electric Fields Produced by High-Temperature Metal Oxidation

Ritchie

Filimonov

et al. 2002

J. Electrochem. Soc.

“…Almost all previous investigators measured the electric voltage between two electrodes separated by a distance much larger than the particle size. The only reported single particle experiment 17 is of thermoionic emission of electrons and charged MgO ϩ particles around a burning magnesium pellet.…”

mentioning

confidence: 99%

Electric Field Formation during Combustion of Single Metal Particles

Martirosyan

Filimonov

et al. 2003

J. Electrochem. Soc.

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.

“…Fluctuating electric fields may also be due to the formation and movement of negatively and positively charged ions in and around the sample. For example, negatively and positively charged electric fields were observed during the burning of Mg particles by thermo-ionic emission of electrons (negative potential) and charged (MgO') particles from condensed MgO (positive potential) (Golovko et al, 1986). Similar emission of charged ions and electrons may have occurred in our experiments.…”

Section: Discussionmentioning

confidence: 73%

“…Experiments reveal that a transient electrical field (chemi-ionization) may form during hightemperature gas-phase oxidation of several metals (Fontijn, 1974;Shaw et al, 1994). For example, an electric field was generated around a burning magnesium particle by thermoionic emission of electrons (negative potential) and charged (MgO+) particles from the condensed MgO (positive potential) (Golovko et al, 1986). A gas-phase cloud of charged ions, such as TiO+ and SiO+, was observed during the hightemperature synthesis of some binary systems: Ti-C, Ti-N2, and Mo-Si (Kudryashov et al, 1996).…”

Section: Introductionmentioning

confidence: 99%

Magnetic Fields Produced by the Combustion of Metals in Oxygen

Combustion Science and Technology

Luss

Claycomb³

et al. 2001

Weak magnetic fields produced by the combustion of pure metal and metal/metal-oxide powders in Rowing oxygen were measured by High-Tc Superconducting Quantum Interference Devices (SQUIDS). Two qualilatively different types of magnetic signals were observed for various reactions. The combustion of Nb, Cr, and Co generates a slowly oscillating field, while the combustion of Zr, Hf, Mn, Ti, Mg, and Fe generates a slowly oscillating field on which rapid oscillations are superimposed. The magnetic power spectra for these reactions scales as a power-law up to I00 Hz with an exponent between 0.64 and 0.96. This suggests that the magnetic field oscillations are generated by stochastic current fluctuations over a wide range of time scales. This may result from fluctuations in either the instantaneous shape and/or the velocity of the reaction zone. A simple electromagnetic model is used to predict the qualitative features observed in our experiments.