Growth of carbon nanofilaments on coal foams

8 pages, 7 figures, 2 tables.-- Available online 19 August 2008.Nanofilamentous carbon was grown on a carbon foam by catalytic chemical vapour deposition (CVD) using the decomposition of ethylene/hydrogen mixtures over Ni. The carbon foam was obtained from a coal by a two-stage thermal process, with the first stage taking place at a temperature within the plastic region of the precursor coal. The extent of porosity and the pore size of the foam were mainly influenced by the pressure reached in the reactor during the first stage. In the CVD process, 700°C was the optimum temperature for obtaining good yields of nanofilaments. A low ethylene/hydrogen ratio (1/4) in the reactive gas gave rise to almost only short and thin carbon nanostructures. A higher proportion of C2H4 (4/1, C2H4/H2) gave better yields of nanofilaments, with good proportions of higher-length and higher-diameter (up to around 0.5 μm) structures. Among the carbon forms produced, transmission electron microscopy revealed the predominance of fishbone-type nanofibres, with some bamboo-like nanotubes being also observed.The authors thank the Fundación para el Fomento en Asturias de la Investigación Científica Aplicada y la Tecnología (FICYT, Asturias, Spain) (Project ref., PB02-132), and the Spanish Ministry of Education and Science (MEC) (project ref., NAT2005-04658) for financial support. MC acknowledges CSIC-ESF for the award of an I3P contract.Peer reviewe