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Studies the effect of annealing on the microstructure of co-sputtered thin films consisting of cobalt nanograins embedded in carbon. Control of the particle size; Variation in carbon concentration; Deposition chamber geometry.

Very different types of straight and long multiwalled carbon nanotubes, ranging from semi-crystalline to highly crystalline, are obtained using a floating reactant method, by merely changing the flow rate of the carrier gas. Graphitization behaviors of these nanotubes are studied comparatively in terms of their microstructure and morphology, showing a large change in structure for the semi-crystalline nanotubes, but little change in the highly crystalline nanotubes with heat treatment. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Arrays of aligned nanotubes of large diameter (100-250 nm) are synthesized by pyrolyzing a jet (spray) solution of Fe(C[sub 5]H[sub 5])[sub 2] and C[sub 6]H[sub 6] in an Ar atmosphere at relatively low temperatures (850 °C). The tubular structures consist of highly crystalline nested graphene cylinders (<200 concentric tubes) with tips that are usually open. Raman studies confirm the high degree of perfection of these "thick" structures. Tube diameter, degree of alignment, and crystallinity can be controlled by varying the Ar flow rate and the Fe:C ratio within the precursor solution. Based on these observations a possible growth mechanism is suggested. This low cost route for the synthesis of carbon nanotubes is advantageous due to the absence of H[sub 2] as a carrier gas and the low pyrolytic temperature. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]