title: Magnetic and microwave absorption properties of self-assemblies composed of core-shell cobalt-cobalt oxide nanocrystals.
abstract: Core-shell structure cobalt-cobalt oxide nanocomposites were directly synthesized via annealing Co nanocrystals in air at 300 °C. Their microstructure and magnetic properties were characterized by XRD, TEM, XPS and VSM, respectively. The microwave absorbing properties of the nanocomposite powders by dispersing them in wax were investigated in the 2-18 GHz frequency range. The sample that was annealed for 1 h exhibits the maximum reflection loss of -30.5 dB and a bandwidth of less than -10 dB covering the 12.6-17.3 GHz range with the coating thickness of only 1.7 mm. At the same thickness, the sample annealed for 3 h exhibits the maximum reflection loss of -24 dB and a bandwidth that almost covers the whole X-band (8-11.5 GHz). With increase in the insulating cobalt oxide shell, the enhanced permeability could contribute to the decrease of eddy current loss, and the permittivity could be easily adjusted; thus, the microwave absorption properties of the cobalt oxide nanocrystals could be easily adjusted.
authors.affiliation: Engineering Technology Research Center of Magnetic Materials of Anhui Province, School of Physics & Materials Science, Anhui University, Hefei 230601, China. wangzz@ahu.edu.cn.
authors.forename: Zhongzhu
authors.initials: Z
authors.lastname: Wang
authors.forename: Hong
authors.initials: H
authors.lastname: Bi
authors.forename: Peihong
authors.initials: P
authors.lastname: Wang
authors.forename: Min
authors.initials: M
authors.lastname: Wang
authors.forename: Zhiwei
authors.initials: Z
authors.lastname: Liu
authors.forename: Lei
authors.initials: L
authors.lastname: Shen
authors.forename: Xiansong
authors.initials: X
authors.lastname: Liu