High-Performance Microwave Absorption Properties of Pyramid-Shaped Metamaterials Based on Ni-Foam@Fe₃O₄

A broadband pyramid-shaped nickel and ferric oxide (Ni-foam@Fe₃O₄) metamaterial is developed in this work. The optimal metamaterial structure with 1.3 g of Fe₃O₄ and a pyramid height of 20 mm shows a broad absorption band in the frequency range of 7.84–30 GHz, with absorbance exceeding 90%. The absorbance of transverse electric (TE) waves at incident angles up to 60° remains above 90% in the frequency range of 7.5–30 GHz. In terms of the transverse magnetic (TM) waves, the absorbance at 0°–45° exceeds 90% in the frequency range of 9.5–30 GHz. The mechanism of physical absorption is systematically investigated based on the electric/magnetic (E/H) field distribution and power energy loss. The results suggest the high potential of the as-fabricated metamaterial for practical application in ultra-broadband and polarization-insensitive microwave absorption (MA).