Achieving high performance electromagnetic wave attenuation: a rational design of silica coated mesoporous iron microcubes

Abstract

Silica coated mesoporous Fe (Fe@SiO₂) microcubes were designed for high performance electromagnetic wave attenuation. Silica coating lowered the permittivity significantly compared to that for bare Fe cubes. Most importantly, even with the silica coating the iron particles kept their shape which ensured a mesoporous structure. The synthetic approach consists of three steps. α-Fe₂O₃ microcubes were first synthesized by a hydrothermal method. Then, the cubes were coated with silica. The silica coated α-Fe₂O₃ microcubes were finally reduced under hydrogen gas at 500 °C. The reduction of iron oxide resulted in a removal of oxygen atoms and subsequently left the empty space as pores inside the silica coated iron cubes. The silicon resin composites containing Fe@SiO₂ microcubes exhibited impressive electromagnetic wave attenuation characteristics. The reflection loss value of −54 dB could be obtained at 3.2 GHz with a thickness of 4.5 mm. In addition, the mesoporous characteristic offered a low density of Fe@SiO₂ mesoporous microcubes. The microcubes enabled a reflection loss of −15 dB with a film thickness as thin as 3 mm. The silica coated mesoporous iron microcubes significantly reduced the usage/thickness of silicon resin composite. They are very promising as a strong attenuation and lightweight electromagnetic wave attenuation material.