H.W. Kroto

Enhanced magnetic coercivities in Fe nanowires

We describe a way of generating films (<2 mm2; <40 μm thick) of aligned Fe-filled carbon nanotubes. These Fe nanowires are usually composed of single Fe crystals, and have dimensions from 5–40 nm outer diameter and <10 μm in length. The carbon tubes, which coat the wires, have external diameters of ∼20–70 nm and are <40 μm in length. High-resolution electron energy loss spectroscopy, x-ray powder diffraction, and elemental mapping of the tubular structures reveal only characteristic metallic signals and the effective absence of oxygen (or any other nonmetallic element) within the wires. The material exhibits coercivities in the 430–1070 Oe range, i.e., greater than those reported for Ni and Co nanowires.

Metal particle catalysed production of nanoscale BN structures

Abstract Graphite-like nanostructures including nanotubes and encapsulated polyhedral particles have been obtained by arcing hexagonal boron nitride (h-BN) and tantalum in a nitrogen atmosphere. High resolution electron microscopy (HRTEM), electron energy loss spectroscopy (EELS) and X-ray diffraction studies have been used to study these new materials, which contain B:N ratios of ≈ 1:1. The observations reveal interesting new information on the dynamics of metal cluster catalysed nanostructure formation. The structures provide strong circumstantial evidence for the presence of B 2 N 2 squares at the tips, in addition to B 3 N 3 hexagons in the main body of the tubes.

Pyrolytically grown BxCyNz nanomaterials: nanofibres and nanotubes

Pyrolysis of CH3CN · BCl3 at ca. 900–1000°C over Co powder generates novel graphitic BxCyNz nanofibres and nanotubes possessing a range of morphologies (e.g. curled, branched and bent). In these experiments the metal particles play an important role in the growth since nanotube formation appears to occur at the metal surface. High resolution electron microscopy (HRTEM) and electron energy loss spectroscopy (EELS) studies suggest that the stoichiometry of the filaments is ca. [BC2Nz]n (z = 0.3−0.6). Higher relative concentrations of carbon occur at the tips where the metal particle is found. A possible growth mechanism for these new materials is proposed.

Preparation of aligned carbon nanotubes catalysed by laser-etched cobalt thin films

Abstract Pyrolysis of 2-amino-4,6-dichloro-s-triazine over laser-etched thin films of cobalt deposited on an inverted silica substrate generates aligned bundles and films of carbon nanotubes of uniform dimensions. Scanning electron microscopy, high resolution transmission electron microscopy, energy dispersive X-ray analyses, electron energy loss spectroscopy and electron diffraction studies reveal that the aligned tubes, which usually grow perpendicular to the substrate surface, are mainly straight (length ⩽100 μm; 30–50 nm OD), contain traces of nitrogen (

The photoelectron and microwave spectra of the unstable species thioacetaldehyde, CH3CHS, and thioacetone, (CH3)2CS

Abstract Combined photoelectron and microwave techniques have been used to study the unstable species thioacetaldehyde, CH 3 CHS, and thioacetone, (CH 3 ) 2 CS. These species are produced when their respective cyclic trimers, 1,3,5-trimethyl s-trithiane and hexamethyl s-trithiane, are pyrolysed. The trimer vapours are flowed at approximately 30 μ Hg pressure via a quartz tube heated to between 500 and 600°C into a photoelectron or microwave spectrometer. Under these low pressure conditions the lifetime of CH 3 CHS was about 10 seconds. The lifetime of (CH 3 ) 2 CS was much longer, of the order of several minutes. The first (vertical) ionisation potentials of thioacetaldehyde and thioacetone are 8.98 ± 0.02 eV and 8.60 ± 0.05 eV respectively. The photoelectron spectra of the parent trimers have also been studied as well as s-trithiane, the trimer of thioformaldehyde. The microwave rotational spectra show evidence of hindered internal rotation. Preliminary analyses indicate that in thioacetaldehyde the barrier is 1545 ± 20 cal per mole (6470 joule per mole) and in thioacetone it is 1300 ± 50 cal per mole (5440 joule per mole).

The photoelectron spectrum of an unstable species in the pyrolysis products of dimethyldisulphide

Abstract A new photoelectron spectrum has been observed in the pyrolysis products of dimethyldisulphide, CH 3 SSCH 3 . As the major product under these conditions is known to be the unstable species thioformaldehyde, H 2 CS, the new spectrum has been assigned to this molecule. The first ionisation potential is 9.34 ± 0.01 eV which compares well with the result obtained by other techniques. The evidence for this assignment is discussed.

Advances in the Creation of Filled Nanotubes and Novel Nanowires

Soon after the identification of carbon nanotubes, produced by arc-discharge techniques, the possibility of introducing metals into the inner core of the tubes was considered (Figure 1). This idea followed logically from the successful observation of fullerenes containing endohedral metals. The introduction of metals or metal carbides and oxides into multiwalled nanotubes [usually 2–70 nm outside diameter (OD), x , SiC, MoS 2 , WS 2 , etc.) are able to form novel nanowires and fullerene-like morphologies. This review discusses methods for generating these fascinating structures and evaluates their possible applications in materials science and engineering.

Electrochemical production of low-melting metal nanowires

Abstract The extent of nanotube formation arising from the electrolysis of molten LiCl, using graphite electrodes, is reduced by the addition of salts to the electrolyte. In certain cases (99% LiCl+

The photoelectron spectrum of thioborine, HBS

Abstract A new photoelectron spectrum has been observed in the products of a high temperature (1100°C) reaction between hydrogen sulphide and crystalline boron. This spectrum has been assigned to the transient thioborine molecule HBS. The first, second and third adiabatic ionisation potentials are 11.11 ± 0.03 eV, 13.54 ± 0.03 eV and 15.83 ± 0.1 eV, respectively. The ion is linear in all the states observed. Experiments have also been carried out to detect the HBO molecule and the results are discussed.

The photoelectron spectrum of a short-lived species in the decomposition products of CS2

Abstract A new vacuum ultraviolet photoelectron spectrum of a short-lived species has been observed in the products of a discharge through CS 2 vapour. As the major product under these conditions is known to be the unstable CS, the new spectrum has been assigned to this molecule. The first ionisation potential is found to be 11.33 ± 0.02 eV which is close to the result obtained by other techniques. The evidence for this assignment is discussed.