Time-sensitivity for the preparation and microwave absorption properties of core–shell structured Ni/TiO2 composite microspheres

Abstract

Core–shell Ni/TiO2 composite microspheres with different crystallinity have been prepared at various reaction times by the solvothermal method. The crystal structure and morphology of the products were investigated by X-ray diffraction, field-emission scanning electron microscopy and transmission electron microscopy. The microwave absorption properties of the core–shell Ni/TiO2 composites were investigated at 1.0–18.0 GHz. The results show that the morphology and microwave absorption performances of Ni/TiO2 composites were largely influenced by the crystallinity of TiO2 shells. The crystallinity of anatase TiO2 can be increased with increasing reaction time. Minimum peaks of Ni/TiO2 composites shift to the high frequency with increasing the crystallinity of anatase TiO2, which are due to high thermal conductivity of high crystallinity of TiO2. The Ni/TiO2 prepared at 36 h exhibits the best microwave absorption properties with minimum reflection loss of −16.9 dB at 14.1 GHz.