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

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 C f /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 (RL min ) 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 C f /mullite composite could be a new promising EMA material at high temperatures.