CCVD synthesis of carbon nanotubes from (Mg, Co, Mo)O catalysts: influence of the proportions of cobalt and molybdenum

• Published in: Journal of materials chemistry 2004, Vol.14 (4), p.646-653
• Main Authors: FLAHAUT, Emmanuel, PEIGNEY, Alain, BACSA, Wolfgang S, BACSA, Revathi R, LAURENT, Christophe
• Format: Article
• Language: English
• Subjects: Chemical Sciences; Cross-disciplinary physics: materials science; rheology; Engineering Sciences; Exact sciences and technology; Material chemistry; Materials; Materials science; Physics
• ISSN: 0959-9428; 1364-5501
• DOI: 10.1039/b312367g

Carbon nanotubes have been synthesised by catalytic chemical vapour deposition of a H2-CH4 mixture (18 mol% CH4) over (Mg,Co,Mo)O catalysts. The total amount of cobalt and molybdenum has been kept constant at 1 cat% and the proportion of molybdenum with respect to cobalt has been varied from x(Mo) = 0.25-1.0. This variation has important effects on both the yield and the nature (number of walls, straight walls or bamboo-like structures) of the carbon nanotubes. It also has an influence on the purity of the samples (amount of encapsulated metal particles, presence or not of amorphous carbon deposits). For x = 0.25, the nanotubes were mainly double- and triple-walled (inner diameter less than 3 nm); samples prepared from catalysts with higher molybdenum ratios contained larger multi-walled carbon nanotubes (inner diameter up to 9 nm), having up to 13 concentric walls. It is proposed that different growth mechanisms may occur depending on the initial composition of the catalyst.