COPRECIPITATED NI-ALUMINA AND NI-CU-ALUMINA CATALYSTS OF METHANE DECOMPOSITION AND CARBON DEPOSITION .3. MORPHOLOGY AND SURFACE-STRUCTURE OF THE CARBON FILAMENTS

Filamentous carbons produced by the coprecipitated Ni-alumina and Ni-C u-alumina catalysts of methane decomposition were studied with high re solution transmission electron microscopy and scanning tunneling micro scopy. Graphite layers were found to orient at an angle to the filamen t axis in carbon prepared by Ni catalysts, and perpendicular to the ax is in those deposited on Ni-Cu catalysts. In both cases the surface wa s very rough and was likely represented by the misoriented edges of gr aphite crystallites. However, these graphite edges were generally bent so that at the filament surface of the carbon, deposited on Ni cataly st, the basal planes tend to be parallel to the filament axis. In prep ared by Ni-Cu one the neighbor and/or next-neighbor layers were linked , therefore, producing the closed-layers structures. This surface reco nstruction likely lowers the surface energy of the deposited carbons d uring catalytic reaction.