Abstract
The preparation of yolk–shell microwave absorption materials with low density and excellent microwave absorption property requires reasonable design and economical manufacture. In this study, an efficient strategy without any templates or reducing gases has been designed to fabricate multi-core yolk–shell Co@C nanospheres by high temperature carbonization. The results showed that Co3O4 was completely reduced by the carbon shell to metal cobalt at temperatures above 750 °C. This unique multi-core yolk–shell structure with shell of 600 nm and multiple cores of tens of nanometers can provide sufficient interface and space to reflect and scatter electromagnetic waves. At the same time, the metal cobalt layer and carbon layer provide magnetic loss ability and dielectric loss ability, respectively, making the composite show good wave absorption performance. The minimal RL value of samples carbonized at 750 °C reaches −40 dB and the efficient absorption band reaches 9 GHz with the thickness ranges from 2–9 mm. Therefore, this is a facile, effective and economical strategy to prepare yolk–shell structure, which provides a new idea for the preparation of microwave absorption materials.
Highlights
With the rapid development of electronic devices, the microwave with a frequency in the 2~18 GHz ranges has become a main part of electromagnetic pollution, so it is urgent to investigate the microwave absorbing materials (MAM) [1,2,3,4]
Transition magnetic metals (Fe, Co, Ni) with high specific magnetism, outstanding electric conductivity and low cost has attracted a lot of attention as MAM because of its excellent magnetic loss capability endowed by natural resonance and eddy current effects [5,6,7,8]
All reagents applied in this experiment were analytical grade
Summary
With the rapid development of electronic devices, the microwave with a frequency in the 2~18 GHz ranges has become a main part of electromagnetic pollution, so it is urgent to investigate the microwave absorbing materials (MAM) [1,2,3,4]. Among these materials, transition magnetic metals (Fe, Co, Ni) with high specific magnetism, outstanding electric conductivity and low cost has attracted a lot of attention as MAM because of its excellent magnetic loss capability endowed by natural resonance and eddy current effects [5,6,7,8]. The poor impedance matching which causes an undesirable microwave absorption capacity is still a great challenge to transition metals
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