Paul C. P. Watts

Carbon nanotubes as polymer antioxidants

The oxidation of polystyrene, polyethylene, polypropylene and poly(vinylidene fluoride) is retarded by carbon nanotubes. Incorporation of boron into the nanotubes enhances the electron affinity of the tubes and leads to a small increase in antioxidant efficiency.

Field emission from nonaligned carbon nanotubes embedded in a polystyrene matrix

Low threshold fields of 1.6 V/μm and 2.6 V/μm were obtained for field emission from multiwalled carbon nanotubes and boron-doped multiwalled carbon nanotubes embedded in polystyrene, respectively. A Fowler–Nordheim analysis of the results together with sheet resistivity data illustrate that the higher carbon nanotube concentrations in a polystyrene matrix result in larger effective emission areas, at the expense of higher operating threshold fields.

The importance of oxygen-containing defects on carbon nanotubes for the detection of polar and non-polar vapours through hydrogen bond formation

We report the electrical responses of water vapour and O2 adsorption onto macroscopic multi-walled carbon nanotube (MWCNT) ropes, and compare the results with mats of acid-treated MWCNTs on SiO2 substrates in order to investigate the importance of oxygen-containing defects on CNTs. In the outgassed state both carbon nanotube (CNT) materials exhibit rapid changes in electrical resistance when exposed to dry air, humid air or water vapour at standard temperature and pressure (STP). The measured electrical responses are highly reversible at STP when cycled between humid air, vacuum and dry air. We report a decrease in resistance for the CNT materials in dry air, attributed to O2 p-type doping of the CNTs, whereas there is an increase in resistance when exposed to a humid environment. This latter effect is attributed to the formation of hydrogen bonding from the polar water molecules with the oxygen-containing defects on the CNTs. Our observations indicate that the increase in electrical resistance upon water absorption affects a reduction of the electron-withdrawing power of the oxygen-containing defect groups, thus leading to a reduced hole carrier concentration in the p-type nanotubes.

A low resistance boron-doped carbon nanotube–polystyrene composite

A composite made from boron-doped carbon nanotubes and polystyrene exhibits relatively low electrical resistance and minor variations in conduction when mechanically loaded. Carbon nanotubes form a network within the plastic film, thereby establishing electrical conduction uniformly throughout the composite. Individual carbon nanotubes behave as intrinsic resistors, therefore the film resistance obeys Ohms law.

Non-linear current–voltage characteristics of electrically conducting carbon nanotube–polystyrene composites

Multi-walled carbon nanotube and boron-doped multi-walled carbon nanotube–polystyrene composites exhibit negative and positive temperature coefficients of resistivity respectively. When combined they exhibit non-linear current–voltage behaviour.

Fe-filled carbon nanotube-polystyrene: RCL composites

Fe-filled carbon nanotube-polystyrene composites exhibit inductive, capacitive and resistive phases, respectively, as materials were measured by the AC impedance spectrometry in the range of 1 MHz to 0.1 Hz. The presence of inductive component in composite films is novel and truly arises from carbon nanotubes associated with encapsulated ferromagnetic Fe crystals.

WS2 nanotubes containing single-walled carbon nanotube bundles

Single-walled carbon nanotubes (SWCNs) encapsulated in multiwalled WS2 nanotubes are produced by pyrolyzing a mixture of WO3−x and SWCNs in N2/H2S atmosphere.

Production of Aligned Carbon Nanotube Films and Nitrogen Doped Carbon Nanotube Films from the Pyrolysis of Styrene

Styrene is used as a carbon source in a CVD process to obtain aligned carbon nanotube films. Changing the carrier gas from argon to ammonia introduces nitrogen into the tubes. SEM, TEM and HRTEM show the well‐aligned structures, which appear to exist as macrobundles. EELS analyses have verified the existence of 3.3 wt.% nitrogen in the tube. Irradiation experiments show that this technique can be used to manipulate NCNTs.

Novel Nanostructures: from Metal-Filled Carbon Nanotubes to MgO Nanoferns

Recently, numerous advances have been achieved by the fullerene/nanotube team at Sussex. Formerly, arc discharge techniques provided a unique method for generating fullerenes and carbon nanotubes. However, the yields and dimensional uniformity of these materials were not controllable. We have made significant advances in this area by pyrolysis of selected organic precursors in order to generate: (a) aligned nanotube bundles of uniform length and diameter; (b) metal nanowires using benzene-based aerosols in conjunction with metallocenes; (c) CN x nanostructures. High-temperature methods have also been employed to produce (d) fern-like MgO nanostructures using MgO and Co mixtures. Finally, these novel materials are predicted to exhibit extraordinary physical and chemical properties and may thus prove useful, i.e. in the manufacture of (superstrong) composite materials and novel electronic or optical devices (e.g. field emission sources, ultra-thin TV displays, etc.).