A 3D α-Fe2O3 nanoflake urchin-like structure for electromagnetic wave absorption

Abstract

An α-Fe₂O₃ nanoflake urchin-like structure is formed via the thermal oxidation of micrometre-sized iron spheres in air at temperatures of 300–400 °C. The material consists of α-Fe₂O₃ nanoflakes grown perpendicularly to the sphere surface, a layer of a mixture of α-Fe₂O₃ and Fe₃O₄ as the oxidation shell, and an iron core. The ranges of the tip diameters of the nanoflakes are 20–30 nm (300 °C), 30–50 nm (350 °C), and 60–100 nm (400 °C). A composite consisting of the α-Fe₂O₃ nanoflake urchin-like structure and an epoxy resin exhibits an excellent electromagnetic (EM) wave absorption ability. A small tip diameter (20–30 nm) and a high density (3 × 10¹³ nanoflakes m⁻²) lead to a good network structure and good EM wave absorption. A minimum reflection loss (RL) of −33.8 dB (99.93% of EM wave absorption) at 7.8 GHz can be achieved using a 70 wt% urchin-like material as the filler in the resin matrix. In addition, a composite containing 60 wt% unchin-like material exhibits dual-frequency EM wave absorption. The peaks of the minimum RL values are located at 9.7 GHz (−26.2 dB) and 25.2 GHz (−21.0 dB). The unique morphology of the α-Fe₂O₃ nanoflake urchin-like material is believed to be a key factor in the enhancement of the EM wave absorption.