Large-scale synthesis and outstanding microwave absorption properties of carbon nanotubes coated by extremely small FeCo-C core-shell nanoparticles

Carbon nanotubes (CNTs) coated by extremely small FeCo-C core-shell nanoparticles (NPs) were synthesized by a facile method based on one-step metal-organic chemical vapor deposition (MOCVD). The CNTs have diameters of 10-50 nm, while the coated FeCo-C NPs have an extremely small average diameter of similar to 5 nm and an average shell thickness of similar to 1 nm. The as-synthesized nanotube-nanoparticle (CNT-NP) composite is stable in air up to similar to 190 degrees C. When blended with 80 wt% paraffin wax, the CNT-NP composite exhibits a low optimal minimum reflection loss (RLmin) value of -79.2 dB and a large effective microwave absorption bandwidth (BWeff) value of 6.3 GHz at a single thickness of 2.0 mm. Equivalent circuit modeling results reveal that CNTs can effectively regulate and optimize the dielectric loss properties of the as-synthesized CNT-NP composites. The outstanding microwave absorption performance of the composite can be attributed to the synergetic effects between the extremely small FeCo-C core-shell NPs and CNTs. This may provide a new strategy for the design of high-performance absorbers. The facile MOCVD-based method developed in this work is expected to be a universal route for the large-scale fabrication of CNT-NP composites. (C) 2019 Elsevier Ltd. All rights reserved.