Recent progress on high temperature radar absorbing coatings (RACs): a review

Due to the high temperature oxidation resistance, corrosion resistance, and good radar waves absorption performance, the radar absorbing coatings (RACs) composed of ceramics and its composites have attracted extensive attention. The RACs is composed of dielectric absorbent and matrix. According to the absorbing mechanism, RACs can be divided into magnetic loss RACs and dielectric loss RACs. High temperature RACs is usually dielectric loss RACs. This article describes the basic principle of radar waves absorption by dielectric loss RACs, and the influence mechanism of temperature, dielectric absorbent content, coating thickness, coating structure design, and other parameters on its radar waves absorption performance. Subsequently, this article introduces the test method of radar waves absorbing performance of RACs and the process of spraying method to prepare RACs, especially the atmospheric plasma spraying method. Finally, this article summarizes the latest research progress of high temperature RACs, mainly focusing on the RACs of doped oxide ceramics (especially alumina), carbide ceramics, and MAX phase ceramics. This review suggests the possibilities of improving RACs absorbing performance through the composition optimization and structural design.