Thermally stable ultra-thin and refractory microwave absorbing coating

Abstract The thickness and thermal stability of electromagnetic (EM) wave absorbing materials greatly affect its service life and practical application. In this paper, an ultra-thin high-temperature EM wave absorbing coating composed of titanium diboride (TiB2) and alumina (Al2O3) was designed and experimentally demonstrated, which exhibits excellent absorbing performance in a wide temperature range. Atmospheric plasma spraying (APS) technique was employed to simplify the preparation of the coating, ensuring its feasibility and practicability. Due to its permittivity increases with temperature and TiB2 content, the coating can exhibit good EM impedance in a wide temperature range by adjusting the suitable ratio of the x.wtTiB2~(1-x).wtAl2O3. When the x value is equal to 0.3, with a thickness of only 1.4 mm, the reflection loss (RL) below -5 dB covered almost the whole X-band in a wide temperature range from 400 °C to 800 °C. The results of X-ray diffractometer (XRD) indicate that there are only two phases in the coating. The images of scanning electron microscope (SEM) show that TiB2 is unevenly distributed in Al2O3 matrix from the microscopic view, which causes loss of interfacial polarization and conductivity. This work illustrates the broad prospects of TiB2-based materials in high-temperature microwave absorption applications.