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Magnetically Aligned Co–C/MWCNTs Composite Derived from MWCNT-Interconnected Zeolitic Imidazolate Frameworks for a Lightweight and Highly Efficient Electromagnetic Wave Absorber

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journal contribution
posted on 18.08.2017 by Yichao Yin, Xiaofang Liu, Xiaojun Wei, Ya Li, Xiaoyu Nie, Ronghai Yu, Jianglan Shui
Developing lightweight and highly efficient electromagnetic wave (EMW) absorbing materials is crucial but challenging for anti-electromagnetic irradiation and interference. Herein, we used multiwalled carbon nanotubes (MWCNTs) as templates for growth of Co-based zeolitic imidazolate frameworks (ZIFs) and obtained a Co–C/MWCNTs composite by postpyrolysis. The MWCNTs interconnected the ZIF-derived Co–C porous particles, constructing a conductive network for electron hopping and migration. Moreover, the Co–C/MWCNTs composite was aligned in paraffin matrix under an external magnetic field, which led to a stretch of the MWCNTs along the magnetic field direction. Due to the anisotropic permittivity of MWCNTs, the magnetic alignment considerably increased the dielectric loss of the Co–C/MWCNTs composite. Benefiting from the conductive network, the orientation-enhanced dielectric loss, and the synergistic effect between magnetic and dielectric components, the magnetically aligned Co–C/MWCNTs composite exhibited extremely strong EMW absorption, with a minimum reflection loss (RL) of −48.9 dB at a filler loading as low as 15 wt %. The specific RL value (RL/filler loading) of the composite was superior to that of the previous MOF-derived composite absorbers. It is expected that the proposed strategy can be extended to the fabrication of other lightweight and high-performance EMW-absorbing materials.