Magnetic Field Induced Variation in Surface Charge Accumulation Behavior on Epoxy/Al2O3 Nanocomposites under DC Stress

Surface charge accumulation on epoxy based nanocomposites under DC stress with and without the presence of a magnetic field was investigated in this work. Two mm-thick sheet samples were prepared by adding 60 nm-Al2O3 particles into epoxy with filler content of 1 to 5 wt%. A pair of finger-shaped electrodes was employed to introduce electric charges onto the sample surface under DC stress of +/- 5 and +/- 10 kV. The magnetic field was established by using a pair of permanent magnets, by which a magnetic flux density of 100 and 180 mT was achieved. Surface charge between the electrodes was measured by means of a Kelvin type electrostatic voltmeter, and the influence of nano-filler content and magnetic flux density on charge distribution as well as charge density was estimated. The results indicate that increasing nano-filler content from 0 to 5 wt%, the average charge density increased initially then decreased. The presence of a magnetic field results in a deflection of charge profile as compared with that formed without a magnetic field. The charge density increased as the magnetic flux density increased from 0 to 180 mT. It is suggested that the charge trajectory close to high voltage electrode varies by the combined electric-magnetic force, by which electric field recovery in such a region is facilitated thus more charges are encouraged to accumulate on the surface.