Vapour growth of nanocrystalline diamond and tubular nanographites

A series of synthetic routes which make use of chemical vapor deposition techniques (Hot Filament CVD and Micro-Wave CVD) are being used for the growth of non-planar graphitic nanostructures and of nanocrystalline diamonds. By varying the type and concentration of the reactants (hydrocarbons, carbon and graphite nanopowders, diesel exhaust soot, atomic H) and the process conditions (temperature, MW power, catalyst concentration, substrate pre-treatments etc.) it is possible to generate a wide range of C-sp2 nanostructures, such as single-walled and multiwalled nanotubes, onion-like carbons; of C-sp3 lattices, such as diamond nanocrystallites; as well as a new class of hybrid structures consisting of nanotubes coated bynanodiamond. We present a review of the nanostructures obtained along with comments on the reaction pathways that can favour the selective production of specific carbon nanophases or of hybrid two-phase nanostructures.