Microwave absorption properties of oriented Sm₂Fe₁₄BH_x/polyurethane with planar anisotropy

Realization of microwave-absorbing materials with "small thickness, light weight, broad bandwidth, and low reflectivity" is an invariable topic. In this paper, Sm2Fe14BHx/polyurethane (SFBH/PU) composites with planar anisotropy were prepared by reduction-diffusion (R/D) and water bath hydrogenation (WBH) process. A minimum reflection loss (RL) value reaches -59.7 dB at the perfect matching frequency of 13.79 GHz with a thickness of only 1.035 mm. Compared with unhydrogenated SFB, the bandwidth and reflectivity are significantly improved. It is mainly attributed to the fact that introduction of hydrogen atoms effectively modulates the electromagnetic parameters and increases the Snoek limit ((u(i)-1)f(r)), which leads to the improvement of the high-frequency microwave absorption performance. In addition, the bandwidth equation is derived and simplified from the perspective of the reflected wave at the interface, which is in good agreement with the measured results.