Multiple relaxation behavior of Cf/mullite composites and their electromagnetic wave performance at high temperatures

Abstract

Reliability and stability of electromagnetic wave absorption (EMA) materials used in high-temperature fields such as aircraft and aero-engines are of great interest. In this regard, the Cf/mullite composites with an opportune heterogeneous interface were fabricated using gel-casting and pressureless sintering techniques. The as-prepared composites exhibited excellent EMA performance with multiple relaxation behavior upon increasing testing temperature ranging from 25 °C to 800 °C (the minimum reflection loss (RLmin) of −62.67 dB with a thin thickness of 2 mm at 600 °C). The results demonstrated that the temperature-dependence complex permittivity with multiple relaxation characteristics plays a key role for the EMA performance evolution. The newly generated Cole-Cole semicircle and κ curves with an increasing number of intersections at zero values suggest that the polarization relaxation is enhanced with rising temperatures, thus improving the EMA capacity. It is believed that the Cf/mullite composite could be a new promising EMA material at high temperatures.