Showing papers on "Tungsten published in 1979"
TL;DR: In this article, hydrogenated amorphous silicon has been deposited by a new technique of thermal decomposition of silane from a hot tungsten or carbon foil heated to about 1600°C.
Abstract: Hydrogenated amorphous silicon has been deposited by a new technique of thermal decomposition of silane from a hot tungsten or carbon foil heated to about 1600 °C. Initial measurements indicate that the resulting films have a fairly high photoresponse. Introduction of ammonia along with silane is seen to enhance the photoconductivity quite significantly.
148 citations
TL;DR: In this article, a study of the contact between metal specimens in an UHV scanning electron microscope incorporating an Auger facility for characterising the surfaces in situ is described, and the results show that with clean surfaces, the loading-unloading cycle is not reversible.
124 citations
113 citations
TL;DR: In this article, it is suggested that the driving force for this process is the chemical potential difference between the equilibrium W-Ni alloy and the pure tungsten phase being dissolved.
111 citations
TL;DR: The fabrication procedure for a liquid gold ion source is described in this article, where the source consists of a tungsten needle wetted with liquid gold, and stable gold ion currents of 1 to 100 μA have been reliably obtained.
Abstract: The fabrication procedure for a liquid gold ion source is described. The source consists of a tungsten needle wetted with liquid gold. Stable gold ion currents of 1 to 100 μA have been reliably obtained. Factors affecting the ion emission characteristics including needle geometry, surface structure, and temperature are discussed.
110 citations
105 citations
TL;DR: In this article, the variations in toughness of the liquid-phase sintered heavy alloys W-Ni-Fe and WNi-Cu have been examined, and it was found that the toughness was controlled primarily by the strength of the tungsten particlematrix interfaces, which is sensitive to the rate of cooling from the sintering temperature.
Abstract: The variations in toughness of the liquid-phase sintered heavy alloys W-Ni-Fe and W-Ni-Cu have been examined. Toughness was found to be controlled primarily by the strength of the tungsten particle-matrix interfaces, which is sensitive to the rate of cooling from the sintering temperature. Furnace-cooling led to the embrittlement of these interfaces; in the case of W-Ni-Fe transmission electron microscopy identified interfacial precipitation of a W(NiFe) intermetallic compound, and in W-Ni-Cu Auger electron spectroscopy indicated interfacial segregation of the trace elements phosphorus and sulfur. This embrittlement was effectively reduced by solution treating beneath the sintering temperature and quenching
86 citations
TL;DR: In this paper, the authors presented a Kisliuk model for covering tungsten surfaces with absolute coverage, surface and gas temperature, and showed that the model is applicable over much of the temperature range for CO on (110 and (100) but not for oxygen, where adsorption and reflection coefficients on first impact vary with coverage, and surface temperature.
74 citations
TL;DR: In this paper, the electrical transport properties of hexagonal tungsten bronze were studied for the temperature range from 1.5 to 300 K and the temperature at which this transition occurs was shown to depend on the Rb concentration, exhibiting a sharp maximum near $x=0.33$ and then decreasing to less than 1 K at $x = 0.24$.
Abstract: Studies of the electrical transport properties---resistivity, Hall effect, and Seebeck coefficient---of the hexagonal tungsten bronze ${\mathrm{Rb}}_{x}\mathrm{W}{\mathrm{O}}_{3}$ for $0.16l~xl~0.33$ are reported for the temperature range from 1.5 to 300 K. In the normal state, these properties show temperature-dependent anomalies which suggest a phase transition with temperature. The temperature at which this transition occurs is shown to depend on the Rb concentration, exhibiting a sharp maximum near $x=0.25$. As the Rb concentration is decreased below $x=0.33$ the superconducting transition temperature first increases above the value of 1.94 K at $x=0.33$ and then decreases to less than 1 K at $x=0.24$. As the Rb concentration is lowered further a second increase in ${T}_{c}$ is observed. This behavior appears to be associated with a phase transition at a composition near $x=0.25$. The nature of neither the transition with temperature nor the transition with concentration could be precisely determined. The superconducting state shows a large temperature-independent 60\ifmmode^\circ\else\textdegree\fi{} anisotropy in ${H}_{c2}$ in the plane perpendicular to the hexagonal axis and positive curvature in the temperature dependence of ${H}_{c2}$ near ${T}_{c}$.
73 citations
TL;DR: In this article, the atomic structure of clean {001}W was reconstructed by field-ion microscopy, with a reconstruction model with periodic displacements of atoms having vertical components.
Abstract: New results have been obtained, by field-ion microscopy, relating to the atomic structure of clean {001}W. The evidence supports a reconstruction model with periodic displacements of atoms having vertical components. The reconstructed atomic configuration prevails over the entire temperature range of this investigation (\ensuremath{\sim} 15-460 K), suggesting that no phase transition may be needed to account for the structural features of {001}W.
TL;DR: In this article, it was shown that the great majority of compounds containing metal-metal triple bonds of the x3mmx3 type have perfectly, or almost perfectly, staggered ethane-like rotational conformations.
Abstract: : The great majority of compounds containing metal-metal triple bonds of the x3mmx3 type where X is a monodentate ligand (including some where the ligand atmos are not all the same) have perfectly, or almost perfectly, staggered ethane-like rotational conformations. The great majority of compounds containing metal-metal quadruple bonds are of the type X4MMX4 ( again including those where more than one type of ligand is present) and have essentially eclipsed rotational conformations. The relatively few exceptions to each of these generalizations are of interest because they provide further insight into the nature of metal-metal multiple bonds.
TL;DR: Laser-raman spectroscopy of the alumina-supported rhenium oxide metathesis catalyst was performed in this article, and it was shown that rhenia is present as a single species, consisting of tetrahedrally coordinated ReO(-1) ions which are dynamically distored by the carrier or surface hydroxyl ions.
TL;DR: A slightly revised version of the previously suggested (1976) impregnated tungsten cathode model is proposed in this paper, which assumes that the cathode surface during life has an adsorbed surface layer of a monolayer or less of both barium and oxygen on the surface.
Patent•
23 Aug 1979TL;DR: In this article, an improvement for making polycrystalline compacts containing single crystal diamonds embedded therein is disclosed, which is useful in drawing wires made of such materials as tungsten, copper coated steel, copper and nickel.
Abstract: An improvement for making polycrystalline compacts containing single crystal diamonds embedded therein is disclosed. Cracking of such compacts is minimized by isolating the diamond in a relatively compressible matrix before exposing the sample to high pressure-high temperature sintering conditions. This may be done, for example, by mixing the diamond crystals with graphite or amorphous carbon powder. Useful devices which can be made from such compacts are cutting tools and wire drawing dies. A sectional view of a wire die blank of this invention is depicted in FIG. 3. One single crystal diamond 12 is embedded in polycrystalline diamond matrix 14 which has been sintered within cemented tungsten carbide ring 16. The wire is drawn through aperture 18. It is felt that this type of die would improve the wire finish while helping to prevent the failure of the single crystal through cleavage. It is useful in drawing wires made of such materials as tungsten, copper coated steel, copper and nickel.
Patent•
30 Apr 1979TL;DR: In this article, a process for patterning regions on a semiconductor structure comprises the steps of forming a first layer of an alloy of tungsten and titanium on the semiconductor, forming a conductive layer of aluminum or chemically similar material on the surface of the Tungsten-titanium alloy, removing the undesired portions of the conductive layers by etching with a plasma and removing the thereby exposed portion of the tengsten-to-itanium Alloy layer by chemical etching.
Abstract: A process for patterning regions on a semiconductor structure comprises the steps of forming a first layer of an alloy of tungsten and titanium on the semiconductor structure, forming a conductive layer of aluminum or chemically similar material on the surface of the tungsten-titanium alloy, removing the undesired portions of the conductive layer by etching with a plasma and removing the thereby exposed portions of the tungsten-titanium alloy layer by chemical etching.
TL;DR: In this article, the authors demonstrate that small amounts of porosity, even 1 or 2%, can cause drastic reduction of the mechanical properties in tungsten heavy alloys, and large irregular pores are formed with a sharp decrease of strength and ductility.
Abstract: W–Ni–Fe heavy alloy tensile specimens were sintered at 1450°C for various times up to 44h. The W content varied between 90 and 96 wt-%, and the Ni to Fe weight ratio was 1:1. The specimens are fully densified after 15 min to 1 h of sintering and show high strength and ductility. During the tension test, cracks are formed at the interface between tungsten grains when the grain deformation reaches critical levels. The number of these intergranular cracks increases with deformation until the specimens fracture. When the specimens are over-sintered for 4 and 8 h, large irregular pores are formed with a sharp decrease of strength and ductility. Upon further sintering, the porosity decreases again with a recovery of the mechanical properties. The results demonstrate that small amounts of porosity, even 1 or 2%, can cause drastic reduction of the mechanical properties in tungsten heavy alloys.
TL;DR: Proton diffusion coefficients in hydrogen tungsten bronzes (HxWO3) were measured using a chronoamperometric technique as mentioned in this paper, and the average value of 1.4 x 1011 cm2 s1.
TL;DR: Some physical properties of tungsten filaments, when operated as cathodes in a gas discharge, are presented.
Abstract: Some physical properties of tungsten filaments, when operated as cathodes in a gas discharge, are presented. For a 0.1524‐cm‐diam tungsten wire, the initiation of a discharge is found to be dependent on the filament geometry. The effect of connecting the discharge power supply to either the positive or negative leg of the filament is examined. When the emission current becomes a sizable fraction of the filament heater current, the filament does not emit uniformly. The temperature distribution indicates that the majority of the electrons are emitted from the negative leg of the filament.
TL;DR: In this paper, the amplitude and phase transmission spectra of free-standing grids wound from 5 μm diameter tungsten wire with 100, 50 and 25 μm wire spacing are presented for the frequency range 40-300 cm−1 The case of normal incidence with the electric vector either parallel or perpendicular to the wires is examined.
TL;DR: In this paper, the crystal structures of hexagonal tungsten bronze phases, A t WO 3, with A =K and Cs and with t = 0.20 and 0.32 have been refined, using the profile refinement procedure, from X-ray powder diffraction data obtained in Guinier-Hagg focussing cameras.
Patent•
16 Aug 1979
TL;DR: Coatings for iron-, nickel- and cobalt-base superalloys are applied in order to provide good oxidation/sulfidation and thermal fatigue resistance for the substrates to which the coatings are applied.
Abstract: Coatings for iron-, nickel- and cobalt-base superalloys The coatings are applied in order to provide good oxidation/sulfidation and thermal fatigue resistance for the substrates to which the coatings are applied The coatings consist essentially of, by weight, 10 to 50% chromium, 3 to 15% aluminum, 10 to 15% metal mixture from the group consisting of tantalum, tungsten, manganese and combinations thereof, up to 5% reactive metal from the group consisting of lanthanum, yttrium and other rare earth elements, up to 5 percent of rare earth and/or refractory metal oxide particles, and the balance selected from the group consisting of nickel, cobalt and iron, and combinations thereof Additions of titanium up to 5% and noble metals up to 15% are also contemplated Tantalum makes up at least 20% of the metal mixture or 05% of the total coating weight, whichever is greater Tungsten, manganese, or a combination thereof, make up at least 05% of the total coating
LKAB1
TL;DR: In this paper, the authors give a general description of the tungsten occurrences in central Sweden and deal in greater detail with the deposits at Elgfall, Snoeaan, Laggarudden, Yxsjoeberg, and Tyfors.
Abstract: The area of Bergslagen in central Sweden comprises the most important known tungsten province in Scandinavia. Several mines have been in operation for brief periods. Currently only the deposits at Yxsjoeberg and Hoegfors are in production. Most scheelite deposits in the area are confined to skarn-limestone in the vicinity of late Svecokarelian granitic rocks. Only a few deposits of vein mineralization are known where wolframite is the principal tungsten mineral. This paper gives a general description of the tungsten occurrences in central Sweden and deals in greater detail with the deposits at Elgfall, Snoeaan, Laggarudden, Yxsjoeberg, and Tyfors.From a general point of view the tungsten deposits at Elgfall, Snoeaan, and Laggarudden are of contact metasomatic origin. However, it is proposed that not only contact metasomatic processes but also thermal metamorphism and sometimes hydrothermal processes took part in the formation of the tungsten ores. At Elgfall and Snoeaan the tungsten mineralized skarn bodies occur adjacent to a granitic rock whereas at Laggarudden the tungsten-skarn is in contact with a pegmatite. No definite interpretation of the genesis of the Yxsjoeberg deposit can be made. Most evidence suggests that the stratabound deposit at Yxsjoeberg is of epigenetic origin and formed by hydrothermal solutions originating most probably from an acid magma.For the Tyfors vein deposit a two-stage mineralization process seems likely. The first stage involved formation of wolframite at high temperature and pressure, the second stage a hydrothermal formation of sulfides.