Synthesis and significantly enhanced microwave absorption properties of hematite dendrites/polyaniline nanocomposite

Hematite dendrites/polyaniline (HDs/PANI) nanocomposite, i.e. coating HDs with conductive PANI, has been successfully synthesized through a two-step polymerization of aniline monomers on the surface of pre-synthesized HDs for the first time. It is discovered that a lower concentration of HCl (0.02 mol∈L^-1) has only a slight adverse effect on the dendritic structures of the coated HDs, while a higher concentration of HCl (0.04 mol∈L^-1) results in severe damage to the sub-branches of the HDs. The morphology, composition, structure, static magnetic, and spectral properties of the as-prepared pristine HDs and HDs/PANI composites were thoroughly characterized by various physicochemical techniques. Moreover, the electromagnetic and microwave absorbing properties of the HDs and HDs/PANI wax composites were compared in detail. It was found that the frequency of absorption obeys a quarter-wavelength model for both of them, and the HDs/PANI wax composite exhibits far superior microwave absorption properties. This phenomenon can be attributed to the improved dielectric loss abilities and the complementary behaviors resulting from the PANI coatings and fractal-structured HDs.