The area density of vertically aligned carbon nanotubes forests is measured and analysed by the weight gain method. The mass density of a close packed array of single- and multi-walled nanotubes is analysed as a function of the average nanotube diameter and number of walls, and this is used to derive the area density, from which the filling factor can be extracted. Densities of order 1013 cm−2 tubes are grown from cyclic catalyst methods.

No abstract

No abstract

No abstract

We report the growth of multi-walled carbon nanotube forests employing an active-active bimetallic Fe-Co catalyst. Using this catalyst system, we observe a synergistic effect by which—in comparison to pure Fe or Co—the height of the forests increases significantly. The homogeneity in the as-grown nanotubes is also improved. By both energy dispersive spectroscopy and in-situ x-ray photoelectron spectroscopy, we show that the catalyst particles consist of Fe and Co, and this dramatically increases the growth rate of the tubes. Bimetallic catalysts are thus potentially useful for synthesising nanotube forests more efficiently.