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

M Niittymäki,T Suhonen,B Rotthier,K Lahti,J Metsäjoki

doi:10.5324/nordis.v0i23.2475

Abstract

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.

Highlights

Thermal spraying techniques are used to manufacture insulating coatings especially for demanding applications like fuel cells where normal insulating materials cannot be used
Alumina coatings was studied at room temperature with relative humidity of 30 % and 95 %, but the DC dielectric breakdown measurements were documented to be performed at room conditions
In [1, 2], the DC resistivity and DC dielectric strength of plasma sprayed alumina coatings were studied at room temperature conditions

Summary

Introduction

Thermal spraying techniques are used to manufacture insulating coatings especially for demanding applications like fuel cells where normal insulating materials cannot be used. Alumina coatings was studied at room temperature (not exactly defined) with relative humidity of 30 % and 95 %, but the DC dielectric breakdown measurements were documented to be performed at room conditions. In [1, 2], the DC resistivity and DC dielectric strength of plasma sprayed alumina coatings were studied at room temperature conditions.

Results

Conclusion