Using thermal CVD, the synthesis of multi-walled carbon nanotubes exhibiting roots anchored directly onto ␣-alumina supports, rather than the catalyst particle, is reported. At such roots, the alignment of the graphitic planes with the support lattice fringes depends on the support crystal structure and orientation.Surface defects may alter the reactivity of the surface or control the anchoring of supported atoms or nanoparticles.We argue this surface defect is provided by the catalyst particle's edge interaction with the support, in other words its circumference. The development of oxide-based catalysts is attractive in that they potentially provide an appropriate solution to directly integrate the synthesis of carbon nanotubes and graphene into silicon-based technology.

The influence of amorphous carbon on FePt catalyst particles under chemical vapor deposition conditions typically applied for CNT growth is examined through two routes. In the first, FePt catalyst particles supported on alumina are exposed to a well-established cyclohexane thermal CVD reaction at various temperatures. At higher temperatures where self-pyrolysis leads to copious amorphous carbon and carbon tar formation, carbon nanotubes are still able to form. In the second route, an amorphous carbon film is first deposited over the catalyst particles prior to the CVD reaction. Even for reactions where further amorphous carbon is deposited due to self-pyrolysis, graphitization is still demonstrated. Our findings reveal that the presence of amorphous carbon does not prevent catalytic hydrocarbon decomposition and graphitization processes. We also show an additional catalytic reaction to be present, catalytic hydrogenation, a process in which carbon in contact with the catalyst surface reacts with H(2) to form CH(4).

Y2O3 nanoparticles prepared by an inert gas phase condensation process were used to introduce artificial pinning centres in YBa2Cu3O7−δ thin films. The areal density of the particles was varied between 120 and 4200 particles µm−2 without changing the mean particle diameter of approximately 9 nm. Y2O3 particles were deposited on TiO2 terminated SrTiO3 (100) single-crystal substrates with areal densities up to 1654 particles µm−2 and subsequently covered with YBa2Cu3O7−δ by off-axis pulsed laser deposition (PLD). The areal density of the room temperature deposited particles is not changed by the substrate heating during PLD although their height on the substrate decreases. An influence on Jc is demonstrated for particle densities above 1588 particles µm−2, indicating that the substrate decoration with Y2O3 nanoparticles from the gas phase affects the formation of artificial pinning centres in the YBa2Cu3O7−δ films and can be applied to further study of the effect of particle size and areal density on defect formation in YBa2Cu3O7−δ.

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