Effects of Ambient Conditions on the Dielectric Properties of Thermally Sprayed Ceramic Coating

Abstract

<p>Thermal spraying techniques are used to manufacture insulating coatings especially for demanding applications like fuel cells where normal insulating materials cannot be used. In electrical insulation applications, the mostly used coating materials are aluminum oxide (Al2O3), magnesium oxide (MgO) and magnesium aluminate (MgAl2O4). Dielectric properties of thermally sprayed ceramic coatings are strongly affected by ambient conditions, and in addition to this they are not well documented in the literature. In this paper the effects of environmental conditions on certain dielectric properties of a thermally sprayed coating are studied. DC resistivity as well as permittivity and losses at different frequencies at relative humidities of 20 % and 45 % at temperature of 20 °C, 40 °C and 60 °C will be reported in the paper for Al2O3 samples sprayed using HVOF (High Velocity Oxygen Fuel) technique. DC dielectric breakdown strength is also studied for the HVOF alumina coating at temperature of 20 °C and relative humidity of 20 %. Effects of ambient conditions and coating material composition are also analyzed.</p>

DC Dielectric Breakdown Behavior of Thermally Sprayed Ceramic Coatings

“…space charge accumulation cannot be noticed. The breakdown strength of the studied coating (ramp rate 100 V/s) is at similar level to the strengths obtained in previous studies [4], [7], [8] for HVOF sprayed alumina coatings.…”

“…The relative permittivity is 11.7 at the frequency of 50 Hz and the loss index at the same frequency is 3.4. These values are quite typical for HVOF sprayed alumina coatings at dry ambient conditions [4], [8].…”