The objective of this work, by Montserrat Calvo et al. at the Instituto Nacional del Carbón (INCAR) in Spain, is to study the growth of nanofilaments in carbon foams by chemical vapour deposition (CVD) based on the decomposition of ethylene over Ni catalyst. The influence of the CVD conditions on the amount and morphology of the nanostructures produced in the confinement of the foam macroporous structure was investigated.
Nanofilamentous carbon was grown on a carbon foam by catalytic 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 also observed.
Fuel, Volume 88, Issue 1, January 2009, Pages 46–53.
DOI: 10.1016/j.fuel.2008.07.026