Showing papers on "Tungstate published in 1988"

Rhenium generator system and its preparation and use

Abstract: A process for preparing a tungsten-188/rhenium-188 generator having a tungstate matrix containing W-188 produced by irradiating tungsten-186 in the tungstate compound. High activity, carrier-free rhenium-188 may be obtained by elution. Substrates for further purifying the rhenium-188 eluate are also described.

Elastic and acoustic properties of ZnWO4 single crystal

Abstract: The acoustic and elastic characteristics of zinc tungstate crystals are determined. It is found that ZnWO4 has a considerable elastic anisotropy and large mechanical impedance. [Russian Text Ignored]

Activity of tungstate catalysts in the synthesis of metylmercaptane from methanol and hydrogen sulfide

Abstract: Catalysis obtained by impregnation of Al2O3 with solutions of hepta-, dodeca-, meta- and normal alkaline metal tungstates showed approximately the same activity. Most selective towards methylmercaptane were catalysts with an alkaline metal to tungsten atomic ratio equal to 2∶1.

Alkyl Transfer in the Heterodinuclear Organometallic Complex. Preparation of Organo(1,5-cyclooctadiene)platinum-tricarbonyl(cyclopentadienyl)tungsten

Abstract: Methyl(1,5-cyclooctadiene)platinum-tricarbonyl(cyclopentadienyl) tungsten has been prepared by the reaction of methylchloro(1,5-cyclooctadiene)platinum(II) with sodium tricarbonyl-(cyclopentadienyl)tungstate(0). Methyl transfer from platinum to tungsten smoothly takes place on thermolysis as well as by the reaction with tertiary phosphine ligands, CO, or olefins.

Corrosion inhibition of 304 stainless steel in H3PO4–Cl− solutions by chromium, molybdenum, nitrogen, tungsten, and boron anions: Part 1: Polarisation measurements

Abstract: Corrosion inhibition studies of 304 stainless steel in phosphoric acid–chloride solutions with chromium, molybdenum, nitrogen, tungsten, and boron anions have been undertaken. The effect of dichromate, molybdate, tungstate, borate, nitrite, and nitrate ions on the behaviour of the alloy has been studied using potentiodynamic and potentiostatic polarisation techniques. The potentiodynamic results showed that most of these additives improve the corrosion resistance of the alloy. The additives retard both active and pitting attack to an extent depending on the type and concentration of the additive. The potentiostatic (i–t curve) results showed that only nitrite and nitrate salts could achieve complete inhibition of pitting corrosion. The results have been correlated with the beneficial action of the corresponding alloying elements.

Method of treating tungsten cathodes

Abstract: A method of treating a tungsten cathode that is comprised of coating the surface of the tungsten cathode with a triple carbonate suspension. The coated tungsten cathode is placed in a heated oxidizing environment (e.g., air, oxygen, or carbon dioxide) and heated for a sufficient amount of time in order to form a diffuse coating of triple carbonates and tungsten oxide. Thereafter, the triple carbonates are reduced to their respective oxides by passing heater current through the tungsten cathode. When used in conjunction with the manufacture of a fluorescent lamp, the formation of this diffuse coating of carbonates enhances the chances of forming barium tungstate during the cathode activation process. As a result, the life of the fluorescent lamp is increased and the amount of phosphor darkening is reduced.

Process for the oxidation of organic compounds by hydrogen peroxide in the presence of a catalyst

Abstract: An improved process for the oxidation of organic compounds. The process of oxidation using aqueous hydrogen peroxide in accordance with the invention, which makes it possible to oxidise organic compounds in the presence of a catalyst, is distinguished in that the aqueous hydrogen peroxide is reacted with the organic compound in the presence of a catalyst consisting of an alkali metal molybdate or tungstate in the form of microemulsion obtained by mixing an aqueous solution of the catalyst, at least one surfactant and at least one organic solvent. Application to the oxidation of various organic compounds and to chemiluminescence.

Importance of tungstate species for the transport of tungsten in hydrothermal solution

Abstract: Thermodynamic calculations on the stability relations among various tungsten species are performed in order to elucidate the possible form of tungsten during the transportation in hydrothermal solution, using the knowledge of the fluoride and chloride concentrations. Based on the fluorine contents in micas and topaz and the fluid inclusion data, it is calculated that HF/H2O and HC1/H2O fugacity ratios in the natural hydrothermal solutions responsible for major Japanese tungsten deposits at the Kaneuchi, Ohtani, Takatori, Fujigatani, Kiwada, and Kuga range from 10-3.15 to 10-5.91 and are less than 10-3.33, respectively. Pressure and temperature conditions for the formation of the studied deposits are summarized and calculated to be from 1 to 2 kbars, and from 300° to 600°C, respectively. Oxygen fugacities are assumed to be those defined by the C-CO-CO2 buffer as the most reducing condition encountered. Based on the pressure, temperature, f(O2), f(HF)/f(H2O), and f(HCl)/f(H2O) conditions evaluated for the studied deposits, thermodynamic calculations are performed to compare the stabilities of halogen-bearing species with those of tungstates. Calculated results show that H2WO4 may be a predominant species in the natural hydrothermal solutions responsible for the formation of major Japanese tungsten deposits.

Radiation stability of some thermally stable inorganic ion exchangers

Abstract: The effect of γ-irradiation on the ion-exchange capacity, distribution coefficient and the efficiency for binary separations of some thermally stable inorganic ion exchangers have been studied. Irradiation upto 100 Mrad, has no effect on these substances, except thorium tungstate which showed changes in ion-exchange capacity, distribution behaviour and in binary separations.

Intermediate product of tungsten and production thereof

Abstract: PURPOSE:To obtain the titled intermediate consisting of ammonium paratungstate crystal having uniform particle size and free from corrosive component, by heating a solution of ammonium tungstate, adding and dissolving tungstic acid or tungsten trioxide in the solution and cooling the mixture to precipitate crystals of the objective intermediate. CONSTITUTION:Tungsten trioxide is dissolved in ammonia water and the obtained ammonium tungstate solution is boiled. Tungstic acid or tungsten trioxide is dissolved in the above solution under agitation to obtain an alkaline solution of 10-7.5pH. The solution is cooled and the precipitated ammonium paratungstate crystal is separated by filtration to obtain the objective intermediate product of tungsten consisting of ammonium paratungstate crystal. An intermediate product of tungsten having high doping accuracy, crystal yield, etc., can be produced by this process.

The Chemistry and Catalytic Properties of Transition Metal Oxyanions in Sodalite Cages

Abstract: The loading of zeolite cages with catalytically active species provides a strategy for the modification of zeolite properties and the preparation of multifunctional catalysts. Hydroxy-sodalite has been used to study the loading of sodalite cages with chromate, molybdate and tungstate ions by a dry salt high temperature reaction. The resulting noseans were used as model systems for examining some of the properties of the occluded oxyanions.

Process for the electroless plating of ternary alloys containing nickel and phosphor

Abstract: The invention relates to a process for electroless chemically reductive deposition of ternary, nickel and phosphorus-containing alloys from aqueous, nickel ions and containing sodium hypophosphite or other reducing agent aqueous solutions in the presence of organic compounds, which is characterized ge that one metallic or nichtme-metallic materials after appropriate pretreatment ternary for depositing Ni-WP alloys lung at a pH value in the range from 4.5 to 9.5 immersed in an aq membered solution containing nickel ions, tungstate ions and sodium hypophosphite or other reducing agent and optionally buffer substances, or deposition of ternary Ni-Co-P alloys appeared at a pH in the range of 4.5 to 9.5 into an aqueous solution containing nickel ions, cobalt ions and sodium hypochlorite phosphite or other reducing agent and, where appropriate, buffer substances containing membered the respective aq solutions in addition organ to sets ic carboxylic acids as complexing agents, stabilizers and accelerators and, optionally, organic carboxylic acids or 8-hydroxyquinoline as a wetting agent and a brightener, and the materials then optionally heat treated.

Fluid-bed synthesis of tungsten carbide/cobalt nanocomposite powders. Final technical report on Phase 1

Abstract: A solution of CoC12 was mixed with a solution of tungstic acid in ethylenediamine to immediately precipitate the desired precursor, cobalt trisethylenediamine tungstate. Low concentrations of the reactants produced hexagonal rods, while high concentrations produced flat plates. The rods were readily fluidized using standard fluidization velocities but the plates could be fluidized only by using a fluidization aid. Conversion of the powder aggregate into the desired two-phase Co-WC composite was accomplished by hydrogen reduction followed by carburization with CO/CO2. After conversion, all of the particles had the same morphology as the original precursor powder but were porous and approximately 40% smaller. Examination by SEM and EDAX showed chemical homogeneity at the microscopic scale and phase separation at the submicron scale. X-ray diffraction analysis showed a two phase mixture of Co-WC, with grain size approximately 3000 A. The two phases are in intimate contact, with the Co wetting the WC in the partially sintered porous particle aggregate.

Preparating of secondary ammonium tungstate with high purity using two-steption exchange method

Abstract: The present invention relates to the preparation of secondary ammonium tungstate with high purity using two-step ion exchange method. Firstly, the tungsten is absorbed from an alkaline solution by the porous strong alkaline negative ion exchange resin and the desorption solution is acidized to PH 2.5-4. Then,the tungsten is absorbed again by the acrylic acid type weak alkaline negative ion exchange resin and is desorbed by ammonia water. The secondary ammonium tungstate with high purity is obtained by evaporating and crystallizing the desorption solution.During the desorption by ammonia water, an ion exchange column with a drainage tube in the interface between resin layers is used. It can rapidly evade the secondary ammonium tungsten crystalline region with PH 6-8 so as to avoid the separation of crystal and to realize the desorption by fixed bed ammonia water. The density of WO3 in the desorption solution may reach 250-300 g/1. The said process can remove P,As, Si and other.......

Manufacture of cathode for electric discharge lamp

Abstract: PURPOSE:To make electron radiation property good and increase life of a cathode by contacting fused liquid or the like of barrium hydroxide with porous electrode material formed by sintering tungsten particles for impregnation, and heat processing it in non-oxidizing atmosphere to produce barrium tungstate. CONSTITUTION:Tungsten particles are formed, by press work or the like, into a porous moulded matter, which is sintered in vacuum, and the electrode material consisting of the sintered body is immersed in heated and fused liquid of 8-hydrate of barrium hydroxide, so barrium hydroxide is impregnated. Obtained electrode material is baked in a hydrogen furnace at a predetermined temperature so as to produce barrium tungstate by reaction of barrium hydroxide and tungsten, and a cathode carrying emitter material for electric discharge is formed. A cathode for an electric discharge lamp with good electron radiation property and a long service life can thus be formed.

Production of thin transparent tungsten oxide film

Abstract: PURPOSE:To easily and quickly form a thin transparent tungsten oxide film having a uniform film thickness by coating a soln prepd by dissolving tungstate into a solvent essentially consisting of an alcohol on a substrate, drying the coating and decomposing the org matter CONSTITUTION:The solvent prepd by adding 01-10ptswt polyhydric ketones such as acetyl acetone or org carboxylic acid such as acetic acid or oxalic acid to 100ptswt alcohol of 1-8C is used The tungstate such as methoxide, ethoxide or propoxide of W or phenoxide tungstate is added at 10ptswt to 100ptswt such solvent and is dissolved therein After the soln is coated on the desired substrate surface, the coating is dried for >=1hr at 10-40 degC room temp Since the film on the substrate is the film of the tungstate, the org matter is decomposed away and oxidized by calcining the film at >=350 degC in air or oxygen or treating the same with the oxygen plasma, by which the thin transparent film of the tungsten oxide having the uniform thickness is obtd

Realbau und Infrarotspektren von BaWO4 und SrWO4

Abstract: BaWO4 and SrWO4 powders with various degrees of imperfection are prepared by precipitation from aqueous solution, heat treatment and mechanical deformation. Samples are characterized as to the degree of imperfection by nitrogen sorption measurements and X-ray methods. The forbidden symmetric stretching mode v 1 of the tungstate ions is activated in the infrared spectra of highly imperfect samples due to lowering of the symmetry of the anions in the surface. A correlation between the intensity of the v 1 absorption band and the BET-surface area is established.