A. Weidenkaff a, ) , S.G. Ebbinghaus a , Ph. Mauron b, A. Reller a , Y. Zhang a , A. Zuttel b
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a
Institute of Solid State Chemistry, UniÕersitat Augsburg, UniÕersitatsstr. 1, D-86159 Augsburg, Germany
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¨ b Physics Department, UniÕersite de Fribourg, Perolles, CH-1700 Fribourg, Switzerland
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Abstract
Carbon nanotube composite materials were produced by catalytic decomposition of gaseous carbon sources Žsuch as carbon monoxide or hydrocarbons. on nanometer-size metal clusters of iron, cobalt and nickel embedded in matrices of inert metal oxide particles. The resulting multiwalled carbon nanotubes are several micrometers long with tube diameters ranging from 5 to 20 nm. A fluidised bed reactor was developed for a large-scale synthesis of the carbon nanotubermetal oxide composite ŽCMC. material. Hydrogen storage capacities of these materials were tested by volumetric and electrochemical methods. q 2002 Elsevier Science B.V. All rights reserved.
Keywords: Carbon nanotubes; Functional materials; Hydrogen storage; Electron microscopy
1. Introduction
Carbon nanotubes have interesting physical properties such as high mechanical stability, large surface area, novel electronic properties Ž1D band structure., and very good thermal and chemical stability w1–3x. There are many publications on the production of nanotubes, but commercially available material is still expensive and often of poor quality. The reason is a difficult purification process to separate the carbonaceous material from the metallic or ceramic catalyst. The hydrogen storage capability of pure carbon nanotubes is in contrast to what has been published before Ž- 2 wt.%.. In combination with transition metals, hydrogen storage capacities of more than 6 wt.% can be
References: Rousset, Acta Mater. 48 Ž2000. 3803. Heben, Adv. Mater. 11 Ž1999. 1354.