Title: Thermal-sprayed dielectric coating e.m. properties evaluation via free-space measurements at microwave frequencies

Authors: F. Nanni, F. Cipri, F. Casadei, T. Valente

Addresses: Department of Chemical Sciences and Technologies, INSTM Research Unit of University of Rome, 'Tor Vergata', Via della Ricerca Scientifica, s.n.c., 00133 Rome, Italy. ' Department of Chemical and Materials Engineering, University of Rome, 'La Sapienza', Via Eudossiana, 18, 00184 Rome, Italy. ' Surface Engineering and Ceramic, CSM Centro Sviluppo Materiali S.p.A., Via Castel Romano 100/102, 00129 Rome, Italy. ' Department of Chemical and Materials Engineering, INSTM Research Unit of University of Rome, 'La Sapienza', Via Eudossiana, 18, 00184 Rome, Italy

Abstract: At present, there is a lack of knowledge about the electromagnetic (e.m.) properties of alumina coatings in a wide microwave frequency range. In this paper, complex permittivity of thermal sprayed alumina coatings were evaluated via free-space measurements. XRD, microstructural and microhardness characterisations were performed too. The results showed that the real part of permittivity is consistent with that found for bulk alumina, being the difference due to the complexity of the coating, which is composed by multiple phases originated during the deposition process. The bond coat measurements showed that it is possible to recognise an anisotropic texture of the coating.

Keywords: plasma spraying; free-space measurements; dielectric constant; alumina coatings; electromagnetic properties; microwave frequencies; microstructure; microhardness.

DOI: 10.1504/IJSURFSE.2008.021350

International Journal of Surface Science and Engineering, 2008 Vol.2 No.5, pp.385 - 399

Published online: 20 Nov 2008 *

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