We have investigated the microwave heating characteristics of non-magnetic conductive multi-particle systems using spatially separated electric and magnetic fields (Emax and Hmax, respectively) to determine the effects of the multi-particle structure on microwave heating. Pure carbon, carbon black, and artificial graphite multi-particle systems exhibited peak microwave absorption at specific relative densities only under Hmax. These absorptions can be categorized into two types: one originates from coupling between metal spheres, while the other originates from a heterogeneous distribution of particles.

We determine the mechanism of rapid and selective heating of nonmagnetic conductive particles by the electric and magnetic fields of microwaves. We investigated the dependencies of the heating behaviors of carbon powders on the radius and electrical conductivity for various relative densities. In these experiments, strong microwave absorption was observed in magnetic field at certain radii and ratios of the crystallite size to the radius. Mie theory for a single particle could account for the high heating rates generated by the microwave magnetic field in sintering experiments. In the dependence of the heating behavior on the relative density, that H field exhibited the maximum absorption at certain relative densities of the graphite powders. These surface plasmon-like modes were observed in graphite, but were not observed when an E field was applied. Multiparticle systems such as graphite powder were found to have significantly different heating behaviors from a single particle. Microwave heating of metal particles is expected to be affected by the structure and shape of the particles.

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We developed a new measurement method for surface charge distribution on an insulating film by Pockels effect of BSO single-crystal cell. The cell has only one transparent metal plate electrode which is located at the rear surface of the cell and is grounded. The insulating film of PET is placed on the other surface. Electrical surface charges are placed on the film by a high-voltage discharge between the rear plate electrode and a point electrode. The applied AC voltage (50Hz) on a alternately obtained using a reflection light from the BSO crystal cell. Using circular polarized incident light, the polarity of the surface charge was determined. These results are closely related to the charge densities obtained by other methods.