期刊
COATINGS
卷 12, 期 12, 页码 -出版社
MDPI
DOI: 10.3390/coatings12121847
关键词
alumina; phase formation; plasma spray; dielectric properties; spray distance; coatings; microstructure
资金
- European Regional Development Fund (EFRE)
- German Research Foundation
- Open Access Publication Fund of TU Berlin
The need for new solutions for electrical insulation is increasing due to the growing electrification in industrial sectors. In this study, alumina coatings with different spray distances were prepared and analyzed to investigate their dielectric properties. The results show that decreasing spray distance reduces resistivity and enhances the formation of the metastable phase.
The need for new solutions for electrical insulation is growing due to the increased electrification in numerous industrial sectors, opening the door for innovation. Plasma spraying is a fast and efficient way to deposit various ceramics as electrical insulators, which are used in conditions where polymers are not suitable. Alumina (Al2O3) is among the most employed ceramics in the coating industry since it exhibits good dielectric properties, high hardness, and high melting point, while still being cost-effective. Various parameters (e.g., feedstock type, spray distance, plasma power) significantly influence the resulting coating in terms of microstructure, porosity, and metastable phase formation. Consequently, these parameters need to be investigated to estimate the impact on the dielectric properties of plasma-sprayed alumina coatings. In this work, alumina coatings with different spray distances have been prepared via atmospheric plasma spray (APS) on copper substrates. The microstructure, porosity, and corresponding phase formation have been analyzed with optical microscopy, X-ray diffraction (XRD), and scanning electron microscopy (SEM). Moreover, we present an in-depth analysis of the fundamental dielectric properties e.g., direct current (DC) resistance, breakdown strength, dielectric loss tangent, and permittivity. Our results show that decreasing spray distance reduces the resistivity from 6.31 x 10(9) omega m (130 mm) to 6.33 x 10(8) omega m (70 mm), while at the same time enhances the formation of the metastable delta-Al2O3 phase. Furthermore, space charge polarization is determined as the main polarization mechanism at low frequencies.
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