Electromagnetic wave absorbing properties of Cr <sub>2</sub> AlB <sub>2</sub> powders and the effect of high‐temperature oxidation
Haiming Zhang, Biao Zhao, Huimin Xiang, Fu‐Zhi Dai, Zhili Zhang, Yanchun Zhou
Abstract
Abstract The electromagnetic (EM) wave absorbing properties of Cr 2 AlB 2 powders and those after high‐temperature oxidation were investigated. Coupling of magnetic and dielectric loss enables Cr 2 AlB 2 with good absorption properties. The minimum reflection loss (RL) value is −44.9 dB at 8.5 GHz with a thickness of 2.7 mm, and the optimized effective absorption bandwidth ( E AB ) is 4.4 GHz (13.0‐17.4 GHz) with a thickness of 1.6 mm. After oxidation at 750, 900, and 1000°C for 2 h, the minimum RL values, respectively, are −23.9 dB (17.5 GHz, 1.5 mm), −41.4 dB (16.5 GHz, 1.5 mm), and −39.5 dB (8.0 GHz, 3.0 mm); and the corresponding E AB values, respectively, are 3.8 GHz (13.6‐17.4 GHz, 1.7 mm), 4.1 GHz (13.5‐17.6 GHz, 1.6 mm), and 4.4 GHz (13.0‐17.4 GHz, 1.7 mm). With an absorber thickness of 1.5‐4.0 mm, the E AB with a RL value of less than −10 dB can be tuned in a broad‐frequency range 5.0‐18.0 GHz, which basically covers C (4‐8 GHz), X (8‐12 GHz), and Ku (12‐18 GHz) bands. These results demonstrate that Cr 2 AlB 2 , as a high‐efficient and oxidation‐resistant absorber, is a promising candidate for microwave absorption applications and can retain good EM wave absorbing properties after high‐temperature oxidation.