Graphitic carbon nanotubes were synthesized by using a water-based mixture, such as equilibrated C-H-O fluid, in the presence of a catalyst, specifically Ni, at 700-800°C under 60-100 MPa pressure.@footnote 1,2@ TEM and electron diffraction analysis show that these carbon nanotubes are characterized by having high perfection of graphene layers, long and wide internal channels, Ni tips, and internal liquid inclusions trapped during the synthesis. During the growth of a tube, the synthesis fluid, which is a supercritical mixture of CO, CO@sub 2@, H@sub 2@O, H@sub 2@, and CH@sub 4@, exists inside the tube. After closure of the tube, aqueous liquid and gases are trapped inside. Closed hydrothermal nanotubes, unlike conventional nanotubes produced in vacuum or at ambient pressure, contain water and gases encapsulated under pressure. H@sub 2@O, CO and CH@sub 4@ are expected to dominate from thermodynamic calculations done using ChemSage 3.1 Gibbs energy minimization code. These nanotubes can be used as miniature pressure vessels for in-situ studies. Thus, they provide a unique opportunity for studying the behavior of fluids in nanosize channels, and for analysis of aqueous samples in TEM. The liquid inclusions were studied by using TEM, where apparent condensation and evaporation of liquid as well as a strong interaction between the liquid enclosed and the nanotube@super -@s walls were observed. These experiments demonstrate the possible use of nanotubes for in-situ study of carbon chemistry
@FootnoteText@
@footnote 1@ Y.G. Gogotsi, M.Yoshimura, Nature 367, 628-630 (1994)
and Y.G. Gogotsi, K.G. Nickel, Carbon 36, 937-942 (1998) @footnote 2@ Y.Gogotsi, J. Libera, and M. Yoshimura, J. Mater. Res., Vol. 15, No. 12, 2591-2594(2000)