Easy gas-flow-induced CVD synthesis and tunable electromagnetic characteristics of centipede-shaped iron/cementite/multiwalled carbon nanotube (Fe/Fe3C/MWCNT) heterostructures

Centipede-shaped iron/cementite/multiwalled carbon nanotube (Fe/Fe3C/MWCNT) heterostructures were synthesized via a novel and easy gas-flow-induced in situ two-step chemical vapour deposition (CVD) method for the first time. The formation mechanism was studied via X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and Raman spectroscopy. The cooperation between the carrier gas flow and the spontaneous magnetization caused the assembly of Fe nanocrystals from the pyrolysis of Fe(CO)(5) into Fe nanofibers, which subsequently functioned as substrates and catalyst precursors for Fe3C-catalyzed MWCNT growth. The aspect ratio and the MWCNT content of the products were easily controlled by changing the feeding ratio of Fe(CO)(5) volume to polyethylene glycol 20 000 (PEG 20 000) mass. The electromagnetic property study revealed that increasing the aspect ratio and length can improve the material's dielectric properties. Simulation studies show that 40 wt.% of Fe/Fe3C/MWCNT heterostructures in a wax matrix exhibits high values of reflection loss (<-20 dB) over a wide frequency range 33 to 7.5 GHz with the minimum reflection loss value of 32.3 dB at 42 GHz. (C) 2015 Elsevier B.V. All rights reserved.