Influence of NiCrAlY content on dielectric and microwave absorption properties of NiCrAlY/Al2O3 composite coatings

Abstract

NiCrAlY/Al2O3 coatings with varying NiCrAlY content were deposited by low-power plasma spraying technology. The influence of NiCrAlY content on dielectric and microwave absorption properties have been investigated in the X-band (8.2–12.4 GHz). The results indicate that metallic NiCrAlY exhibits typically string or splat-like structure in the coatings, and the elevated NiCrAlY filling content is beneficial to the formation of conductive metallic clusters. The real and imaginary parts of complex permittivity are enhanced with increase in NiCrAlY content, which results from interfacial polarization, relaxation loss and conductance loss. Owing to the excellent impedance matching and the preferable attenuation coefficient, the coating with 20 wt.% NiCrAlY and 2.0 mm thickness possesses effective bandwidth (<-10 dB) 1.3 GHz in 8.2–9.5 GHz and minimum reflection loss −15.7 dB at 8.9 GHz, exhibiting the most favorable microwave absorption properties.