title: Characterization of microwave-induced electric discharge phenomena in metal-solvent mixtures.
abstract: Electric discharge phenomena in metal-solvent mixtures are investigated utilizing a high field density, sealed-vessel, single-mode 2.45 GHz microwave reactor with a built-in camera. Particular emphasis is placed on studying the discharges exhibited by different metals (Mg, Zn, Cu, Fe, Ni) of varying particle sizes and morphologies in organic solvents (e.g., benzene) at different electric field strengths. Discharge phenomena for diamagnetic and paramagnetic metals (Mg, Zn, Cu) depend strongly on the size of the used particles. With small particles, short-lived corona discharges are observed that do not lead to a complete breakdown. Under high microwave power conditions or with large particles, however, bright sparks and arcs are experienced, often accompanied by solvent decomposition and formation of considerable amounts of graphitized material. Small ferromagnetic Fe and Ni powders (<40 μm) are heated very rapidly in benzene suspensions and start to glow in the microwave field, whereas larger particles exhibit extremely strong discharges. Electric discharges were also observed when Cu metal or other conductive materials such as silicon carbide were exposed to the microwave field in the absence of a solvent in an argon or nitrogen atmosphere.
authors.affiliation: Christian Doppler Laboratory for Microwave Chemistry (CDLMC), Institute of Chemistry, Karl-Franzens-University Graz Heinrichstrasse 28, 8010 Graz (Austria), E-mail: oliver.kappe@uni-graz.at ; On leave from the Shanghai Key Laboratory of Chemical Biology, East China University of Science and Technology 130 Meilong Road, Shanghai, 200237 (P. R. China).
authors.forename: Wen
authors.initials: W
authors.lastname: Chen
authors.affiliation: Christian Doppler Laboratory for Microwave Chemistry (CDLMC), Institute of Chemistry, Karl-Franzens-University Graz Heinrichstrasse 28, 8010 Graz (Austria), E-mail: oliver.kappe@uni-graz.at.
authors.forename: Bernhard
authors.initials: B
authors.lastname: Gutmann
authors.affiliation: Christian Doppler Laboratory for Microwave Chemistry (CDLMC), Institute of Chemistry, Karl-Franzens-University Graz Heinrichstrasse 28, 8010 Graz (Austria), E-mail: oliver.kappe@uni-graz.at.
authors.forename: C Oliver
authors.initials: CO
authors.lastname: Kappe
keywords: arcing; electric discharges; magnesium; microwave chemistry; particle size; thermal decomposition