One-pot low temperature solution synthesis, magnetic and microwave electromagnetic properties of single-crystal iron submicron cubes

Abstract

Large quantities of single-crystal iron submicron cubes with controllable dimensions and surface structures were synthesized by a facile low-temperature solution reduction approach under normal atmosphere. The influence of kinetic parameters such as NaOH concentration, reaction temperature, reaction time, species of solvents and reducing agents, etc. on the morphology, size and crystal structure of the as-synthesized products were investigated in detail. The resultant products experience multistep phase transformations and morphology evolutions from Fe(OH)₂ nanosheets, to weak crystalline Fe₃O₄ ultrafine particles and to high crystalline Fe cubes. It is believed that both the control over the quasi-equilibrium crystal nucleation and growth rate by adjusting kinetic parameters, and the selective interaction between ethylenediamine and various crystallographic planes of bcc iron play crucial roles in the formation of the slightly truncated cubes with {100} planes at the sides and small {111} planes on the corners. The as-synthesized iron cubes exhibit a strong and wide resonance behavior for the imaginary permittivity and imaginary permeability over the frequency range of 2–14 GHz as a result of the submicron size and anisotropy morphology. The paraffin-based composites containing 26 vol% iron submicron cubes show good electromagnetic wave absorbing characteristics and the reflection loss values less than −20 dB are obtained in the frequency range of 6.5–18.0 GHz when the thickness of the composites is 1.0–2.5 mm, suggesting that the iron submicron cubes synthesized here are promising as a strong-absorption, thin-thickness, light-weight and low-cost microwave absorber.