Radar absorption characteristics of ceramic oxide fiber/aluminosilicate-sendust composite structure at ultrahigh temperatures

This study proposes a novel radar-absorption structure (RAS) composed of Nextel 601 fiber and a geopolymer-based aluminosilicate matrix for withstanding high temperatures and providing effective electromagnetic (EM) absorption performance. To measure its complex permittivity and permeability in the X-band frequency range, we dispersed flake-type sendust particles with different sizes and contents in the matrix. The complex permittivity increased with increasing size and content of the sendust particles, which was attributed to the increase in dielectric polarizations and electrical conductivity of the composites. Furthermore, the simulation studies of the designed RAS showed excellent EM absorption performance, with a thickness of 4.25 mm, revealed a maximum return loss (RLmax) of −24 dB with a broad absorption bandwidth (BW @ −10 dB) of 8.3 GHz at room temperature (RT). Similarly, the measurement of fabricated RAS exhibited a RLmax of −19.2 dB and a broad absorption BW of 5.45 GHz at RT in the S- and X-band frequency range (6.95–12.4 GHz). However, in X-band measurements conducted at elevated temperatures, the RLmax values declined, reaching −8.04 dB at 9.87 GHz and −10.97 dB at 9.45 GHz observed at 900 °C and 1200 °C, respectively. This decrease in EM absorption performance can be ascribed to variations in impedance matching conditions arising from factors such as dielectric and magnetic losses, as well as shifts in frequency. In addition, the significant RCS reduction of the proposed RAS indicates its applicability to hypersonic aircraft.