Synthesis, magnetic and microwave electromagnetic properties of dendritic iron

Iron dendritic micropines are synthesized by a hydrogen reduction, where the hematite dendritic micropines prepared by a hydrothermal method are used as starting materials. The as-obtained dendritic iron exhibits enhanced coercivity and remanent magnetization at room temperature and high complex permittivity at 2–18 GHz due to the peculiar shape anisotropy and good crystallinity. The negative imaginary permeability is observed at 14.5–18.0 GHz, suggesting it has a potential as a left-handed material. The paraffin-based composites containing 30 wt% dendritic irons show large permittivity resulting from the charge polarization and the conductivity and have a minimal reflection loss (RL) of −37.4 dB at 7.4 GHz when the thickness (d) is 2.0 mm. The RL values less than −20 dB are obtained in the frequency range of 5.5–12.9 GHz when d increases from 0.9 to 3.0 mm.