Abstract:
Materials that pack in the form of small rod shapes are of technological interest since they can
exhibit considerable strength. In the past decade we have seen an enormous level of activity in
nanostructured materials, in particular relating to carbon nanotubes which are closed elongated
structures of pure carbon. They have application in nanoelectronics as conductors,
semiconductors and as transistors. Carbon nanotubes can also be used for hydrogen storage. In
our laboratory we have made efforts to synthesise these materials from sources other than
graphite and in particular coal. The work complements a similar program in synthesising
fullerenes from coal. Because coal is a molecular solid, and graphite is a lattice solid, there are
distinct differences in processing mechanisms between the two materials. Unlike graphite, coal
has weak bonds, and hence can proceed through a mechanism that does not involve single carbon
units. Thus the products can differ from those of graphite.
Nanotubes come in a variety of types that include multi walled and single walled forms. Each
form can have a variety of diameters or can arise from different ways of rolling the graphite
sheet from which they derive. They are called armchair, chiral and zig zag. Additives such as
naphthalene and cobalt can affect the nature of the product formed. The presence of other
elements in coal produces a different type of nanotube distribution. Both iron and sulphur are
important. Coal also produces other products such as microfilaments and polycyclic
hydrocarbons.
