A cobalt-coated reticulated porous alumina for radar-absorption applications

Recently, porous ceramics have received much attention because of their excellent chemical and thermal stabilities, despite their mechanical instability. Among the various types of porous ceramics, reticulated porous ceramics (RPCs) have been newly fabricated. However, there is still insufficient data on the characteristics of RPCs for radar-absorption applications. Therefore, in this study, the feasibility of using RPCs of alumina (reticulated porous alumina, RPA) is investigated. It is examined whether RPA can achieve appropriate mechanical strength, be coated by a radar-absorbing material (RAM), and have radar-absorbing properties. The compressive strength of the RPA specimens is significantly enhanced from 0.07 to 1.03 MPa by the combined effect of increasing the number of alumina coating, sintering temperature, and pore density. The measured reflection loss is less than − 3 dB over the X-band range (8.2–12.4 GHz) for an 8.46-mm-thick RPA specimen coated with 40 wt.% cobalt slurry, which corresponds to 49.9% absorption. However, the calculated reflection loss of an RPA specimen with a thickness of 38.27 mm and coated with 40 wt.% cobalt slurry approaches − 15 dB at 10.0 GHz, corresponding to a 96.8% absorption of the radar wave.