Influence of annealing treatment on microstructure and waves absorption of Ni/TiO2 nanocomposites

Ni/TiO2 nanocomposite was prepared by mechano- chemical synthesis. The as- milled nanocomposite consists of hexagonal-structure rutile TiO2 and face-centered cubic structure Ni. Annealing treatment decreases both the lattice defects and the internal stress, while remarkably increases the grain size of metal Ni and the saturation magnetization. After annealing treatment the intrinsic emission, free exciton emission and bound exciton emission peaks of TiO2 exhibit a red shift, for which the reason may be the distortion of the band structure. For the as-milled nanocomposite an intense nonlinear dielectric resonance occurs at 15 GHz and a clear Cole-Cole semicircle was observed. Meanwhile, a reflection loss (RL) exceeding -10 dB in a frequency range of 14-16 GHz and a maximum value of RL as large as -32 dB are obtained for an 8 mm thick absorber. After annealing treatment the intensity of the natural resonances at 2.8 and 5.2 GHz has been significantly strengthened, leading to a remarkable improvement of microwave-absorption properties in the frequency range 2-6 GHz. © Copyright.