MOF-derived porous helical carbon nanotube/doped barium ferrite composites for enhanced microwave absorption

The magnetic-dielectric composite with a metal-organic framework (MOF) structure has been verified as an ideal candidate for effective microwave absorption. Helical multi-walled carbon nanotube (h-MWCNT)/doped barium ferrite composites were prepared using the sol-gel method. A porous MOF structure, with an abundant microscopic cavity structure and an adequate conductive network, was constructed, where the doped barium ferrite particles and h-MWCNTs overlapped through sheet-line interaction, and the uniformly dispersed barium ferrite particles were anchored inside the conductive network. The composition of h-MWCNTs has a great influence on the electromagnetic parameters and absorbing performance. After optimization, the minimum reflection loss of - 56.47 dB was achieved at 4.8 GHz, with a matching thickness of 1.35 mm. At this matching thickness, the composites reached the maximum wave-absorbing bandwidth of 6.20 GHz, covering the Ku band. The excellent microwave absorption performance could be attributed to the low energy barrier of electron transfer and the great charge transfer ability according to the experimental and calculation results. Simultaneously, a special charge transfer channel and a micro-capacitor caused by electron accumulation were generated by the interaction in the heterojunction, which consequently improved the dielectric loss capability. Further, due to abundant polarization genes and multiple magnetic resonances of the composites, the magnetic-dielectric synergetic effect also leads to an evident absorption. This novel light magnetic-dielectric MOF-derived composite shows great potential in microwave absorption applications.