The catalyst temperature was adjusted by changing the position of catalyst bed in the column reactor tube for the preparation of carbon nanotubes (CNTs) from methane using the microwave plasma technique. The maximum value of the carbon yield (80%) was obtained for a catalyst temperature of 794 K. CNTs grew at temperatures as low as 588 K with this method. CNTs prepared at temperatures above 794 K were cylindrical and that of those prepared at 588 K were herringbone type.
Stage 1 and 2 potassium-graphite intercalation compounds (GICs) suspended in N-methylpyrrolidone were ground and sonicated. After centrifuging, the supernatant solutions were analyzed photochemically. Absorption and emission spectra of the supernatant suggest that the solute is a mixture of aromatic hydrocarbons with some benzene nuclei. Graphene layers in GICs are supposed to be torn during the process including sonication. This finding is expected to provide some information on the isolation methods of graphene, which has been attracting much attention due to its fascinating physical properties.