%P 32-43
%T Parametric study on vapor-solid-solid growth mechanism of multiwalled carbon nanotubes
%A S. Shukrullah
%A N.M. Mohamed
%A M.S. Shaharun
%A M.Y. Naz
%I Elsevier Ltd
%V 176
%O cited By 24
%L scholars6982
%J Materials Chemistry and Physics
%D 2016
%R 10.1016/j.matchemphys.2016.03.013
%X This study aimed at investigating the effect of the fluidized bed chemical vapor deposition (FBCVD) process parameters on growth mechanism, morphology and purity of the multiwalled carbon nanotubes (MWCNTs). Nanotubes were produced in a vertical FBCVD reactor by catalytic decomposition of ethylene over Al2O3 supported nano-iron catalyst buds at different flow rates. FESEM, TEM, Raman spectroscopy and TGA thermograms were used to elaborate the growth parameters of the as grown MWCNTs. As the growth process was driven by the process temperatures well below the iron-carbon eutectic temperature (1147 °C), the appearance of graphite platelets from the crystallographic faces of the catalyst particles suggested a solid form of the catalyst during CNT nucleation. A vapor-solid-solid (VSS) growth mechanism was predicted for nucleation of MWCNTs with very low activation energy. The nanotubes grown at optimized temperature and ethylene flow rate posed high graphitic symmetry, purity, narrow diameter distribution and shorter inter-layer spacing. In Raman and TGA analyses, small ID/IG ratio and residual mass revealed negligible ratios of structural defects and amorphous carbon in the product. However, several structural defects and impurity elements were spotted in the nanotubes grown under unoptimized process parameters. © 2016 Elsevier B.V.
%K Activation energy; Amorphous carbon; Carbon nanotubes; Catalysts; Chemical analysis; Chemical vapor deposition; Crystal growth; Crystal impurities; Defects; Deposition; Electron microscopy; Ethylene; Fluidized bed process; Fluidized beds; Nanostructures; Nanotubes; Nucleation; Thermogravimetric analysis; Vapor deposition; Yarn, Catalytic decomposition; Chemical vapor depositions (CVD); Diameter distributions; Fluidized bed chemical vapor deposition; Iron carbon eutectic temperature; Low-activation energy; Multiwalled carbon nanotube (MWCNTs); Process temperature, Multiwalled carbon nanotubes (MWCN)