Microwave Absorption of α-Fe₂O₃@diatomite Composites

A neoteric round sieve diatomite (De) decorated with sea-urchin-like alpha-type iron trioxide (α-Fe₂O₃) synthetics was prepared by the hydrothermal method and further calcination. The results of the electromagnetic (EM) parameters of α-Fe₂O₃-decorated De (α-Fe₂O₃@D) showed that the minimum reflection loss (RL_min) of α-Fe₂O₃@D could reach -54.2 dB at 11.52 GHz and the matched absorber thickness was 3 mm. The frequency bandwidth corresponding to the microwave RL value below -20 dB was up to 8.24 GHz (9.76-18 GHz). This indicates that α-Fe₂O₃@D composite can be a lightweight and stable material; because of the low density of De (1.9-2.3 g/cm³), the density of α-Fe₂O₃@D composite material is lower than that of α-Fe₂O₃ (5.18 g/cm³). We found that the combination of the magnetic loss of sea-urchin-like α-Fe₂O₃ and the dielectric loss of De has the most dominant role in electromagnetic wave absorption and loss. We focused on comparing the absorbing properties before and after the formation of sea-urchin-like α-Fe₂O₃ and explain in detail the effects of the structure and crystal shape of this novel composite on the absorbing properties.