Kosmas Prassides

Controlled production of aligned-nanotube bundles

Carbon nanotubes might be usefully employed in nanometre-scale engineering and electronics. Electrical conductivity measurements on the bulk material, on individual multi-walled and single-walled nanotubes and on bundles of single-walled nanotubes have revealed that they may behave as metallic, insulating or semiconducting nanowires, depending on the method of production—which controls the degree of graphitization, the helicity and the diameter. Measurements of Youngs modulus show that single nanotubes are stiffer than commercial carbon fibres. Methods commonly used to generate nanotubes—carbon-arc discharge techniques, catalytic pyrolysis of hydrocarbons and condensed-phase electrolysis—generally suffer from the drawbacks that polyhedral particles are also formed and that the dimensions of the nanotubes are highly variable. Here we describe a method for generating aligned carbon nanotubes by pyrolysis of 2-amino-4,6-dichloro-s-triazine over thin films of a cobalt catalyst patterned on a silica substrate by laser etching. The use of a patterned catalyst apparently encourages the formation of aligned nanotubes. The method offers control over length (up to about 50 μm) and fairly uniform diameters (30–50 nm), as well as producing nanotubes in high yield, uncontaminated by polyhedral particles.

Structural Phase Transitions in the Fullerene C60

High-resolution powder neutron diffraction has been used to study the crystal structure of the fullerence C60 in the temperature range 5 K to 320 K. Solid C60 adopts a cubic structure at all temperatures. The experimental data provide clear evidence of a continuous phase transition at ca. 90 K and confirm the existence of a first-order phase transition at 260 K. In the high-temperature face-centred-cubic phase (T > 260 K), the C60 molecules are completely orientationally disordered, undergoing continuous reorientation. Below 260 K, interpretation of the diffraction data is consistent with uniaxial jump reorientation principally about a single 111 direction. In the lowest-temperature phase (T < 90 K), rotational motion is frozen although a small amount of static disorder still persists.

Metal particle catalysed production of nanoscale BN structures

\ensuremath{\alpha}\text{-FeSe}

Pyrolytically grown BxCyNz nanomaterials: nanofibres and nanotubes

with the PbO structure is a key member of the family of high-

Bulk superconductivity at 38 K in a molecular system

{T}_{c}

Crystal structure of the new FeSe1−x superconductor

iron pnictide and chalcogenide superconductors, as while it possesses the basic layered structural motif of edge-sharing distorted

Intralayer carbon substitution in the MgB 2 superconductor

{\text{FeSe}}_{4}

The disorder-free non-BCS superconductor Cs3C60 emerges from an antiferromagnetic insulator parent state.

tetrahedra, it lacks interleaved ion spacers or charge-reservoir layers. We find that the application of hydrostatic pressure first rapidly increases

Mixed valency systems : applications in chemistry, physics, and biology

{T}_{c}