Tungsten

Abstract: The successful synthesis of pure boron nitride (BN) nanotubes is reported here. Multi-walled tubes with inner diameters on the order of 1 to 3 nanometers and with lengths up to 200 nanometers were produced in a carbon-free plasma discharge between a BN-packed tungsten rod and a cooled copper electrode. Electron energy-loss spectroscopy on individual tubes yielded B:N ratios of approximately 1, which is consistent with theoretical predictions of stable BN tube structures.

Abstract: T ensile tests at a variety of temperatures have been carried out on composites consisting of tungsten or molybdenum wires, uniaxially aligned in a copper matrix. Both continuous and discontinuous wires have been used, and both brittle and ductile tungsten wires. It is found that the breaking strength is a linear function of the wire content. A simple theory to explain this is developed and auxiliary experiments to check the theory are described. Some simple predictions about the behaviour of fibre reinforced metals are made from the results.

Abstract: Part 1 Case study on tungsten oxide: bulk crystalline tungsten oxide tungsten oxide films - preparation, structure, and composition of evaporated films tungsten oxide films - preparation, structure, and composition of sputter-deposited films tungsten oxide films - preparation, structure, and composition of electrochemically and chemically prepared films tungsten oxide films - ion intercalation/deintercalation studied by electrochemical techniques tungsten oxide films - ion intercalation/deintercalation studied by physical techniques tungsten oxide films -ultraviolet absorption and semiconductor bandgap tungsten oxide films - optical properties in the luminous and near-infrared range tungsten oxide films - theoretical models for the optical properties tungsten oxide films - electrical properties. Part 2 Electrochromism among the oxides (except tungsten oxide): molybdenum oxide films miscellaneous tungsten- and molybdenum-oxide-containing films iridium oxide films titanium oxide films manganese oxide films vanadium dioxide films vanadium pentoxide films nickel oxide films cobalt oxide films niobium oxide films miscellaneous oxide films systematics for the electrochromism in transition metal oxides inorganic non-oxide electrochromic materials. Part 3 Electrochromic devices: transparent electrical conductors electrolytes and ion conductors ion storage materials - brief overview devices with liquid electrolytes devices with solid inorganic electrolytes and ion conductors devices with polymer electrolytes time-dependent device performance - a unified treatment.

Abstract: FOLLOWING the discovery of C60(ref. 1) and the advent of fullerene chemistry, considerable attention has been directed towards the associated cylindrical2,3 and polyhedral4,5 forms of graphite. To date, however, observations of such closed structures have been limited to the carbon system. Here we report the formation of equivalent stable structures in the layered semiconductor tungsten disulphide. After the heating of thin tungsten films in an atmosphere of hydrogen sulphide, transmission electron microscopy reveals a variety of concentric polyhedral and cylindrical structures (ranging in size from 100 nm) growing from the amorphous tungsten matrix. The closed nature of the structures is verified by electron diffraction and lattice imaging. As with the carbon system, complete closure of the tungsten disulphide layers requires the presence of structural defects (for example, edge dislocations), or the arrangement of atoms in polyhedra other than a planar hexagonal geometry.

Abstract: Tungsten carbide catalyzes the formation of water from hydrogen and oxygen at room temperature, the reduction of tungsten trioxide by hydrogen in the presence of water, and the isomerization of 2,2-dimethylpropane to 2-methylbutane. This catalytic behavior, which is typical of platinum, is not exhibited at all by tungsten. The surface electronic properties of the latter are therefore modified by carbon in such a way that they resemble those of platinum.