Mildred S. Dresselhaus

Nanotechnology: ‘Buckypaper’ from coaxial nanotubes

Double-walled carbon nanotubes are needed in a pure, highly crystalline form before features such as their electronic properties, thermal transport and mechanical behaviour can be investigated. Here we fabricate a paper-like material that consists of hexagonally packed bundles of clean, coaxial carbon nanotubes whose double walls vary little in diameter; it is prepared in high yields using chemical-vapour deposition with a conditioning catalyst and two-step purification. Our results will enable investigation of the physical properties of double-walled carbon nanotubes, which are predicted to be superior to those of both their single- and multiwalled relatives.

Intercalation of Graphite Fibers

Intercalated carbon fibers are of interest for both applications and basic science. The availability of intercalation compounds in fibrous form opens up a number of scientific opportunities, many of which exploit the favorable geometry of fibrous samples. For example, the large aspect ratio (length/diameter) greatly improves the sensitivity of transport measurements such as resistivity, magnetoresistance, thermopower, and thermal conductivity, thereby allowing systematic investigations of these properties to be made in graphite intercalation compounds (GICs). For this reason, there is a strong connection between the study of transport properties in GICs (Chap. 6) and the present review of intercalated carbon fibers. For example, with fibrous intercalation compounds it has been possible to separate the lattice and electronic contributions to the thermal conductivity of GICs by measuring the thermal and electrical conductivities on the same fiber sample and invoking the Wiedemann-Franz law [8.1]. The small fiber diameters are of particular utility for structural studies using transmission electron microscopy, where observations can be made directly without thinning of the specimens. The small fiber diameters also allow preparation of compounds not readily synthesized in bulk form, such as stage-1 NiCl2 GICs.

Graphitic cones in carbon nanofibres

High yields of graphitic conical nanofibres (5-70 nm OD; <5 µm in length) are produced by pyrolysing various palladium precursors under an Ar atmosphere at 850-1000°C. The fibres exhibit diamond-shaped Pd particles at their tips, which are responsible for the carbon aggregation and its subsequent diffusion. This carbon replication phenomenon on the Pd particles results in the formation of stacked graphene cones, which grow aligned along a common axis, thus creating graphitic nanofibres. The cones within the fibres can be either open (lamp-shade type) or closed. The material has been analysed using sophisticated electron microscopy (HRTEM, SEM, ED) and spectroscopic techniques (Raman, EELS, EDX). Due to the large number of open edges, we envisage that these novel nanofibres may find important applications in the fabrication of field emitters, gas storage devices and composites.

Microstructure of Milled Mesophase Pitch-Based Carbon Fibers as an Anode Material for Li-ion Batteries

Abstract The microstructure of milled mesophase pitch-based carbon fibers (mMPCFs) that have been developed as an anode material for Li ion batteries have been studied as a function of heat treatment temperature (HTT), by SEM, X-ray diffraction, and Raman spectroscopy. And the results obtained are compared with those by X-ray diffraction (XRD) and SEM observations, for the characterization of specific structural features of mMPCFs as a promising anode material.