Magnetic Fields Produced by the Combustion of Metals in Oxygen

Abstract

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.

Historical perspective and contribution of US researchers into the field of self-propagating high-temperature synthesis (SHS)/combustion synthesis (CS): Personal reflections

“…Another interesting activity conducted by this group is focused on spontaneous magnetization generated by solid state combustion [222][223][224][225][226][227][228]. Using a highly sensitive high-T c superconducting quantum interference device (SQUID), they were able to conduct the first measurement of the very low intensity (order of nT) transient magnetic field formed by a combustion front motion.…”

High-Temperature Combustion Synthesis: Generation of Electromagnetic Radiation and the Effect of External Electromagnetic Fields (Review)

“…High-temperature synthesis of ferrites can involve generation of rather strong residual magnetic fields (≈2 µT) under significant cooling, which reduces the temperature of products during the synthesis below the Curie point. It was also found [13][14][15] that the type of the magnetic signal arising during the synthesis depends on the combustion regime. Numerical calculations [13] validated the assumptions [13,14] about the influence of front oscillations on the shape of the signal being registered.…”

“…It was also found [13][14][15] that the type of the magnetic signal arising during the synthesis depends on the combustion regime. Numerical calculations [13] validated the assumptions [13,14] about the influence of front oscillations on the shape of the signal being registered. The maps of residual magnetic fields formed during the synthesis of ferrites were considered in [15] with the use of a magnetometer.…”

“…Owing to re-grouping of domains in the sample, a rather powerful (≈10 µT) residual field is formed, which is independent of the sample orientation in the magnetic field of the Earth. The use of a highly sensitive superconducting quantum interference device (SQID) made it possible to find [11][12][13][14] extremely weak (≈20 nT) magnetic signals directly in the course of synthesis of various oxides. The principal difference in synthesis of non-ferromagnetic and ferromagnetic materials was found [11,12,14]: the magnetic field completely disappears when the afterburning processes are completed.…”

Generation of the transient electrical and spontaneous magnetic fields by solid state combustion

“…4-8 A slowly oscillating field up to 20 nT was generated during the combustion in oxygen of various pure metals Ti, Zr, Mn, Nb, Fe, etc. 9 Different modes of combustion front motion, i.e., spin, pulsating, and planar combustion synthesis of ferrites generated qualitatively different magnetic field spatial distribution. The average magnetization vector generated by either planar or pulsating combustion was oriented at a smaller angle with respect to the pellet axis ͑ ഛ 45°͒ than those generated by spin combustion ͑60°ഛ ഛ 80°͒.…”