Experimental Observation of Carbon and Carbon-Metal Nanotoroids and New Carbon-Metal Superstructures at Nanoscale
V. Kislov, B. Medvedev and I. Taranov
Russian Academy of Sciences, RU
carbon, nanotoroid, nanotube
We report experimental observation (by AFM, STM and HRTEM methods) of nanotoroids for both carbon and carbon-metal superstructures produced by methods of arc discharge and laser ablation. Size of superstructures is ~ 10 nm for carbon and ~ 30 nm for carbon-metal (outer diameter), with inner diameter ~ 1/3 of the total. Initial observation of toroids were made for pure carbon, but gradual increase of metal to some optimal concentration dramatically increased the yield of toroidal structures. The influence of pressure, humidity and temperature was also investigated. Also effects of reversible transition of topology (sphere - toroid) on the same sample were observed depending on external parameters. The possibility of such structures was discussed earlier, but we also discovered carbon-metal nanocapsules among toroids, with shapes like nanodiscs, reminiscent of human erithrocites. Changing concentrations and metals (Mo, Cr, etc.) leads to differences in shapes and sizes of superstructures. Therefore, new types of topologically closed carbon and carbon-metal nanostructures are discovered, with the theoretical model presented elsewhere. We also discuss some technological aspects of the growth of such toroidal nanostructures.
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Nanotech 2005 Conference Program Abstract