In Situ Transmission Electron Microscopy of Temperature-dependent Carbon Nanofiber and Carbon Nanotube Growth from Ethanol Vapor

30 June 2023, Version 1
This content is a preprint and has not undergone peer review at the time of posting.


We report the in situ transmission electron microscopy (TEM) experiments to directly observe Ni catalysed CNFs/CNTs growth from alcohol precursor at near atmospheric pressure using a homebuilt bubbler system for the introduction of ethanol vapor. Using real time imaging, we revealed the active state of the Ni catalyst during the temperature-dependent CNFS/CNTS growth (600–800 ℃). We observed the formation of CNFs starting from 600 °C and CNTs were formed at higher temperatures. The lattice parameter measurements pointed to an expansion of the Ni lattice as the temperature was increased, which we attribute to increased carbon solubility. The as-grown CNFs and CNTs were further characterized by XPS, Raman spectroscopy, and EELS, that allowed to have a highly reliable overall view of the structure changes with temperature. Results revealed that the change in structure with temperature was caused by the combined effects of increased carbon solubility and graphitization of the walls of the growing nanostructure. This increased carbon solubility in turn affected carbon diffusion and could be the reason for the change in structure from CNF to CNT at high temperature. We also successfully identified the transition from tip-growth to base-growth in a CNT at 800 ℃.


carbon nanofiber
carbon nanotube
active state
activation energy
growth mechanism
ethanol vapor
in situ TEM

Supplementary materials

Supporting Information
Proof of system reliability for the homebuilt bubbler system; tables showing measured gas flow rate using the bubbler system; the active phase of the catalyst during the growth of CNF and CNT; SAED analysis; tables showing lattice constants from SAED patterns; the comparison of changes in lattice constant caused by thermal expansion and that due to amount of dissolved carbon; carbon concentration of the Ni particle; deconvolution of EELS spectra; tables showing the peak positions and parameters used for the deconvolution of EELS, XPS, and Raman spectra; size-dependent growth rate changes; temperature-dependent growth rate changes; distribution of growth rates according to the catalyst size and growth temperature ; calculation on the working pressure and flow rate; details of complementary spectroscopies


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