The production of single-walled carbon nanotubes by a CVD method and their characterisation by various techniques

Seifi, M

Abstract

In this work, Chemical Vapour Deposition (CVD) was used to prepared Single-
Walled carbon nanorube (SWNT) samples. In developing the production techniques a
large number of parameters were varied during the course of work resulting in the
successful repeatible growth of single-walled carbon nanotubes. Methane was used as
a carbon-carrier gas decomposed at 950°C over a catalyst material consisting of 1.5%
and 2% by wt Fe chemically deposited on a MgO support. The activity of the catalyst
and the surround atmosphere were controlled by varying the flow ratio of Ar and H2
gases as well as the flow of the carrier gas. Metallic catalyst particles together with
the support material were treated by consecutive acid treatments in HNOs and HC1 at
50°C to reduce their concentration.
Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM)
were used to show the presence of nanotubes and also to measure the diameter of
SWNT bundles and the size of carboneous materials. Images of SEM and TEM show
a large number of nanotubes in the samples.
Raman scattering was used to probe the electronic properties and hence derive the
diameters of the SWNT. For this reason, Raman spectra of SWNT samples were
measured in the radial breathing mode (RBM) and Tangential mode (TM) ranges
using three different laser lines. Raman spectra show a diameter distribution of
nanotubes ranging from 0.97 to 1.45 nm.
Microgravimetric measurements of nitrogen and hydrogen adsorption were then
applied to these samples to evaluate the specific surface areas Brunauer, Emmett and
Teller (BET) and HT storage capacities of the samples and also derive information
about the diameter of the pores in the samples by analysing the hysteresis loop in the N2 isotherm. The BET measurements show a different surface area for samples 350
m2/g for sample 1 and 227 m2/g for sample 2. Because there is a direct relationship
between the surface area and hydrogen adsorption so the different storage capacity are
shown for samples 0.5wt% for sample 1 and 0.25wt% for sample 2.

Citation

Seifi, M. The production of single-walled carbon nanotubes by a CVD method and their characterisation by various techniques. (Thesis). Salford : University of Salford

• Thesis Type: Thesis
• Deposit Date: Oct 3, 2012
• Award Date: Jan 1, 2007