title: Investigation of the electromagnetic absorption properties of Ni@TiO2 and Ni@SiO2 composite microspheres with core-shell structure.
abstract: In this work, amorphous TiO2 and SiO2-coated Ni composite microspheres were successfully prepared by a two-step method. The phase purity, morphology, and structure of composite microspheres are characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDS), thermogravimetric analysis (TGA), and transmission electron microscopy (TEM). Due to the presence of the insulator SiO2 shell, the core-shell Ni-SiO2 composite microspheres exhibit better antioxidation capability than that of pure Ni microspheres. The core-shell Ni-SiO2 composite microspheres show the best microwave absorption properties than those of pure Ni microspheres and Ni-TiO2 composites. For Ni-SiO2 composite microspheres, an optimal reflection loss (RL) as low as -40.0 dB (99.99% absorption) was observed at 12.6 GHz with an absorber thickness of only 1.5 mm. The effective absorption (below -10 dB, 90% microwave absorption) bandwidth can be adjusted between 3.1 GHz and 14.4 GHz by tuning the absorber thickness in the range of 1.5-4.5 mm. The excellent microwave absorption abilities of Ni-SiO2 composite microspheres are attributed to a higher attenuation constant, Debye relaxation, interface polarization of the core-shell structure and synergistic effects between high dielectric loss and high magnetic loss.
authors.affiliation: School of Materials Science and Engineering, Zhengzhou University, Zhengzhou, Henan 450001, P. R. China. gang_shao@zzu.edu.cn zhangray@zzu.edu.cn.
authors.forename: Biao
authors.initials: B
authors.lastname: Zhao
authors.forename: Gang
authors.initials: G
authors.lastname: Shao
authors.forename: Bingbing
authors.initials: B
authors.lastname: Fan
authors.forename: Wanyu
authors.initials: W
authors.lastname: Zhao
authors.forename: Rui
authors.initials: R
authors.lastname: Zhang