Electromagnetic Fields Produced by Self-Propagating High-Temperature Synthesis (SHS)

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Recent experiments have shown that a transient electrical voltage ( electrochemical effect) and a weak magnetic field ( chemomagnetism) form during self-propagating high-temperature synthesis (SHS). This is a combined experimental and theoretical study of the electrochemical effect and chemomagnetism induced by combustion processes with the goals of elucidating their origin, sign, magnitude, and shape, and providing a means to predict them and their impact. Similar reactions, such as oxidation or nitridation of a metal, are done with metals from a row or group of the periodic table to give possible correlations with electronic structure, oxygen affinity, and oxidation state. Experiments are conducted at various gas pressures, sample compositions, porosities and particle sizes to determine the effects of these factors as well as the relationships between the induced signals and reaction temperature and combustion wave velocity. The small magnetic fields are measured with a high-Tc superconducting quantum interface device (SQUID). A model to predict the electrical potential formation is developed, initially based on the assumption that an electrical change is formed in individual particles due to a gradient of ions across a product layer formed during combustion. The model predicts combustion wave velocity and profiles of voltage, temperature, oxygen concentration, and metal conversion in the combustion and post-combustion zones. The predicted voltage profile is then used to calculate the induced magnetic signal. The model in revised on the basis of the experimental results.