Design and reflectivity analysis of high temperature wave-absorbing coatings with circular periodic structure

The electromagnetic (EM) parameters of a type of radar-absorbing materials (RAM) with periodic structure of thin aluminum circulars were simulated by HFSS software. The RAM is constructed of two layers: upper layer, a periodic array of aluminum circular and lower layer, C/Al₂O₃ ceramic coating thermal sprayed on metal substrates, were designed and prepared according to the simulated results. Both the simulated and measured results show that combination of the aluminum periodic structure to ceramic coatings improve the wave absorbing properties both in absorbing intensity and absorbing bandwidth. EM wave absorption performance enhancement is ascribed to the resonance peak of frequency selective surface (FSS). The range of absorption frequency can be easily tuned by adjusting the size of aluminum circular and the thickness of the ceramic coating. The measured reflection coefficient was -40 dB at 11 GHz and the -5 dB bandwidth was about 9 GHz. The RAM's thickness is 2.0 mm.