Fabrication of hollow Fe ₃ O ₄ microspheres coated with SiO ₂ and SWCNHs through the solvothermal method and modified Stöber process for microwave absorption

In this work, hollow Fe 3 O 4 microspheres coated with SiO 2 and single-walled carbon nanohorns (H-Fe 3 O 4 @SiO 2 /SWCNHs) have been fabricated through the solvothermal method and modified Stöber process. The obtained H-Fe 3 O 4 @SiO 2 /SWCNHs composite exhibits a unique hollow core–shell structure and excellent microwave absorption properties. When the matching thickness is 2.0[Formula: see text]mm, the optimum reflection loss is −59.6[Formula: see text]dB at the frequency of 14.64[Formula: see text]GHz and the corresponding maximum effective absorption bandwidth is 5.12[Formula: see text]GHz, covering from 12.56[Formula: see text]GHz to 17.68[Formula: see text]GHz. The outstanding microwave absorption properties of the H-Fe 3 O 4 @SiO 2 /SWCNHs composite can be attributed to the unique hollow core–shell structure, optimal impedance matching and multiple electromagnetic loss mechanisms. Therefore, the as-prepared H-Fe 3 O 4 @SiO 2 /SWCNHs composite can be used as a promising candidate for high-performance microwave absorption.