Preparation and microwave absorption properties of Ni-Co nanoferrites

NixCo1-xFe2O4 (x = 0.2, 0.5, 0.8) particles were prepared by a self-designed method, i.e., microwave assisted ball milling. A series of characterizations were carried out on the prepared powders, including X-ray Diffraction (XRD), transmission electron microscopy (TEM), vibrating sample magnetometer (VSM) and vector network analyzer (VNA). XRD and TEM results indicated that the particles are well-crystallized and the average size is about 15 nm. According to VSM results, the M-s values are 76 emu/gm, 61 emu/gm and 46 emu/gm respectively, which obviously presented higher saturation magnetization values compared with other existing methods. Complex permittivity and permeability of Ni-Co ferrites were explored by VNA in the frequency of 2-18 GHz, and the reflection loss (RL) was also calculated. The results illustrated that the minimum reflection loss values of the three ferrites all emerged in the range of 9-12 GHz, and the Ni0.8Co0.2Fe2O4 with a thickness of 2.5 mm could achieve -36.2 dB at 11.52 GHz, which indicated that the Ni-Co ferrite nanoparticles possessed great potential in microwave absorption applications. (C) 2014 Elsevier B.V. All rights reserved.