Preparation of NiFe2O4 nanorod-graphene composites via an ionic liquid assisted one-step hydrothermal approach and their microwave absorbing properties

Novel NiFe2O4 nanorod-graphene composites were synthesized by a facile one-step hydrothermal process in the presence of 1-propyl-3-hexadecylimidazolium bromide ([PHeIm][Br]). The structure and morphology of as-prepared hybrid materials were characterized by FESEM, TEM, HRTEM, AFM, XRD, FTIR, XPS and Raman spectroscopy. The results showed that uniform NiFe2O4 nanorods with a typical length of about 400 nm and a diameter of about 50 nm were well distributed on graphene sheets. The magnetic and electromagnetic parameters were measured using a vibrating sample magnetometer and a vector network analyzer, respectively. The obtained composites exhibited a saturation magnetization of 22.5 emu g(-1) and a coercivity of 48.67 Oe at room temperature. A minimum reflection loss of -29.2 dB was observed at 16.1 GHz with a thickness of 2.0 mm, and the effective absorption frequency (RL < -10 dB) ranged from 13.6 to 18 GHz, indicating the excellent microwave absorption performance of the novel composites in the range of 13.6-18 GHz. The absorbing performance of the NiFe2O4 nanorod-graphene composites was better than that of the NiFe2O4 nanoparticle-graphene composites.