Large Scale Synthesis of Superparamagnetic Face-centered Cubic Co/C Nanocapsules by a Facile Hydrothermal Method and their Microwave Absorbing Properties

AUTOR(ES)

Liu, Xianguo, Wu, Niandu, Zhou, Pingping, Bi, Nannan, Or, Siu Wing, Cui, Caiyun, Sun, Yuping

FONTE

Mat. Res.

DATA DE PUBLICAÇÃO

2015-08

RESUMO

A large scale direct hydrothermal method has been used to prepare face-centered cubic (FCC) Co/C nanocapsules with a core of FCC-Co nanoparticles and a shell of amorphous C. The size distribution is 5-20 nm. The TB of FCC-Co/C nanocapsules is determined as 85 K, indicating that FCC-Co/C nanocapsules are superparamagnetic at 300 K. For FCC-Co/C nanocapsules-paraffin composite, an optimal reflection losbs (RL) of -33.4 dB is observed at 9.6 GHz for the 2.6 mm thick layer. RL values exceeding –20 dB in the 7.4 –15 GHz range are obtained by choosing an appropriate absorption-layer thickness between 1.7 and 3.3 mm. The good microwave absorbing properties of FCC-Co/C nanocapsules is considered to result from the excellent synergetic effect of the multi-dielectric relaxation loss and the multi-magnetic resonance loss. Quantitative calculation demonstrated that not only RL peak position but also the number of the peaks are determined by the quarter-wavelength cancellation model.

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