709 research outputs found
Thermodynamic calculations on the catalytic growth of multiwall carbon nanotubes
We have developed a thermodynamic model of the catalytic growth of multiwall
carbon nanotubes from hydrocarbon precursors at elevated temperature. Using
this model we have computed the heat distribution, and carbon concentration in
the catalyst. Calculations delivered a analytical formula for the growth time
and growth rate. We find that the growth is mainly driven by a concentration
gradient within the catalyst, rather than a temperature gradient.Comment: 9 pages, 3 figures, 1 tabl
Raman spectroscopy and field emission measurements on catalytically grown carbon nanotubes
We used microcontact printing to pattern a silicon surface with an
iron-containing catalytic solution. Multi-wall carbon nanotubes were
subsequently grown on the patterned areas by chemical vapor deposition at
temperatures between 650 and 1000C. We demonstrate that the diameter of the
catalytically grown multi-wall nanotubes increases with the deposition
temperature. Raman spectroscopy has been used to investigate the crystalline
character of the obtained structures and it is found that the fraction of the
nano-crystalline shell increases with the temperatures. The measurement of the
field emission properties shows a correlation between the tube diameter and the
emission field values.Comment: 6 pages, 6 figures, 1 tabl
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