Showing papers on "Noble metal published in 1988"

The Use of Mantle Normalization and Metal Ratios in Discriminating between the Effects of Partial Melting, Crystal Fractionation and Sulphide Segregation on Platinum-Group Elements, Gold, Nickel and Copper: Examples from Norway

Abstract: The distribution of noble metals, Ni and Cu in mafic and ultramafic rocks is thought to be controlled by sulphides, chromite, olivine and platinum-group minerals (PGM). One method for presenting noble metal, Ni and Cu data focuses on the sulphide control by recalculating the data to 100% sulphides and presenting the data chondrite normalized. The relative importance of the influence of sulphides, chromite, olivine and PGM on the noble metals, Ni and Cu is examined here using two alternative methods.

Superconductivity in the Bi-Sr-Ca-Cu-O compounds with noble metal additions

Abstract: The Bi‐Sr‐Ca‐Cu‐O superconductors have been doped with various noble metals and their superconducting properties have been investigated. The resistivity and magnetic susceptibility measurements on sintered Bi4Sr3Ca2Cu4O16+x containing 20% by weight of Au, Ag, or Pt‐group metals indicate that Au and the Pt‐group metals significantly suppress or eliminate the superconducting transition in Bi‐Sr‐Ca‐Cu‐O. Only Ag is found to be benign, maintaining both the 115 and 85 K transitions in the compound. This nonpoisoning behavior of silver is of significant technical importance because of the need for a proper stabilizing normal metal for composite superconductor wire, nonreactive crucible materials for melt processing or crystal growth, and suitable nonpoisonous substrates or barriers for thin‐ or thick‐film superconducting devices.

The catalysed hydrogenation of carboxylic acids and their anhydrides to alcohols and/or esters

Abstract: An alcohol and/or a carboxylic acid ester is produced from a carboxylic acid or anhydride thereof by reacting the acid or anhydride with hydrogen at elevated temperature in the presence as catalyst of a composition comprising an alloy of (i) at least one noble metal of Group VIII of the Periodic Table and (ii) at least one metal capable of alloying with the Group VIII noble metal, optionally including a support and at least one of the metals rhenium, tungsten or molybdenum The process is particularly applicable to the hydrogenation of monobasic acids, for example acetic acid, and the hydrogenation of maleic acid or maleic anhydride to gamma-butyrolactone

Selectivity in Cinnamaldehyde Hydrogenation of Group-VIII Metals Supported on Graphite and Carbon

Abstract: Noble metal catalysts (Ir, Pt, Ru, Rh Pd) have been prepared with a very homogeneous dispersion on graphite (300 2 m 1 g) and carbon support (1400 m 2 g 1 ). On graphite the particles decorate the edges of the basal planes and there is an electron transfer to the metal. The cinnamaldehyde (CAL) hydrogenation into cinnamyl alcohol (COL) has been performed under 4MPa of H 2 in liquid phase. The factors affecting the selectivity to COL are: (i) the nature of the metal (0=Pd

Electrochemical Pretreatment of Thin Film Platinum Electrodes

Abstract: Thin film noble metal electrodes and electrode arrays prepared by photolithographic process suffer from contamination of the surface by the traces of transition metals and their oxides which are used as adhesion promoters at the insulating substrates. This contamination is an ongoing process as the transition metals migrate continuously along the grain boundaries through the thin (1000–4000A) layer of the noble metal. The transition metal oxide affects the electrochemical properties of the noble metal surface and also its electron work function. A simple electrochemical pretreatment has been developed which removes these contaminants from the surface and "anneals" the surface in such a way that acceptable electrochemical behavior identical with a thick noble metal electrode is obtained. It consists of electrochemical etching of the surface by pulsing it between 0 and +2V in solution containing 0.08M EDTA, 5.2% , and for 5–10 min. It is then followed by cycling of the applied potential between 0.4 and −0.4V in for 10 min. Surfaces prepared by this procedure have remained clean for a period of at least 24h.

Polyredox couples in analyte determinations

Abstract: Enzyme or substrate determinations can be achieved by employing an organic second substrate, which produces a product which may be coupled with a metal inorganic redox couple capable of interacting with and affecting the potential of a metal electrode on a semiconductor surface. Particularly, hydrogen peroxide or indoxyl phosphate are coupled with iron- or ruthenium-containing ionic redox couples for determination with a noble metal electrode.

Hard outer coatings deposited on titanium or titanium alloys

Abstract: The invention discloses a coated substrate product comprised of a titanium of titanium alloy substrate, at least one thin interlayer composed of a non-reactive noble metal and a hard outer coating selected from the group comprised of a ceramic, a hard metal, a hard metal compound and a diamond-like carbon, wherein at least the non-reactive noble metal interlayer which is immediately adjacent to the titanium or titanium alloy substrate is deposited onto the substrate by means of an electroless plating procedure, and the hard outer coating is deposited onto the non-reactive interlayer(s) by means of known chemical and physical vapor deposition techniques. The invention also discloses a method for making these coated substrate products.

Laminated layers of a substrate, noble metal, and interlayer underneath an oxide superconductor

Abstract: This invention discloses an oxide superconductor shaped body including a noble metal layer formed on at least one surface of an oxide superconductor layer formed on a substrate, and a method of manufacturing oxide superconductor shaped body.

Pretreatment for electroplating process

Abstract: A method for metal plating the surface of an article formed from an organic plastic. The method includes a step of passing a current between two electrodes immersed in an electrolyte containing dissolved plating metal. One of the electrodes is the article to be plated and is provided with a surface having areas of a catalytic metal chalcogenide conversion coating adjacent to and in contact with conductive areas. In a preferred embodiment, the catalytic metal chalcogenide conversion coating is formed by treating the article with an acid colloidal solution of a tin-noble metal electroless metal plating catalyst and, subsequently, treating with a solution containing a dissolved sulfide to form a sulfide of the noble metal. The conversion coating allows the article to be directly electroplated. The method is especially useful for the formation of printed circuit boards and is sufficiently versatile to permit formation of a printed circuit board by a process that involves pattern plating.

High temperature combuster

Abstract: There has thus been provided a highly efficient metal-ceramic catalytic combustor for a gas turbine/catalytic combustor assembly. The catalyst zone is formed of a high temperature resistant metal wire mesh, e.g., palladium coated tungsten or ferritic stainless steel screen, e.g., 40 mesh, which is aluminized with metallic aluminum, and heated to convert the outermost layer of aluminum to aluminum oxide and encourage the diffusion of the inner layer of aluminum into the body of the metal wire, desirably forming a thin metal/aluminum alloy layer. The outer surface because of the Kerkendall Effect is porous and readily accepts and strongly bonds to a metal oxide coat, e.g., a magnesia/alumina, or magnesia/alumina/yttria, or barium oxide/alumina, or barium oxide/alumina/yttria wash coat. There may also be included a catalyst deposited on the ceramic outer coat, e.g., a noble metal catalyst, for enhancement of the combustion of an air/fuel mixture. Because the metals from which the wire mesh is formed all have melting points above the maximum temperature of operation, i.e., 2700° F., the screen itself has significant tensile strength at temperature.

Laminated substrate for catalytic combustor reactor bed

Abstract: A laminated oxidation resistant catalyst element includes a metal alloy substrate such as a steel foil coated with a noble metal such as platinum. A ceramic washcoat such as alumina is applied over the noble metal and a catalyst is applied with the washcoat or individually during a subsequent application step. The noble metal prevents oxygen from contacting the metal substrate thereby preventing its degradation by oxidation reactions. The catalyst element is particularly suited for use in a catalytic reactor bed of an industrial gas turbine.

Method of regenerating a deactivated catalyst

Abstract: A deactivated reforming catalyst comprising a type L zeolite containing a Group VIII noble metal may be regenerated and have enhanced dispersion by a method involving contacting the catalyst with oxygen and water at elevated temperatures, contacting the catalyst at elevated temperatures with a source of chlorine such as HCl or Cl2, and preferably oxygen and water, contacting the catalyst at elevated temperatures with oxygen and optionally water, and contacting the catalyst at elevated temperatures with hydrogen and optionally water to reduce the catalyst. Preferably the noble metal is platinum.

Catalytic washcoat and method of preparation of the same

Abstract: The invention is concerned with a method of adsorbing uniformly onto preformed high surface area crystalline alumina one or more catalytically active non-noble (doping) oxide(s) and preferably alumina-stablilizing non-noble doping oxide(s), both from substantially neutral aqueous colloidal solutions thereof, drying and calcining the doped alumina to form an improved washcoating composition for receiving additionally catalytic noble metal particles.

Thin-film capacitor and manufacture thereof

Abstract: PURPOSE: To prevent formation of a low dielectric constant layer while forming a thin film capacitor of high dielectric constant by forming a film consisting of a specific compound and a conductive layer consisting of a high melting point noble metal film between a silicon electrode and a dielectric film. CONSTITUTION: In a thin film capacitor of the structure where a conductive layer, a dielectric layer and an upper electrode are by turns formed on a silicon electrode, the conductive layer is composed of the first layers 5, 9, 6 to be formed on the silicon electrode and a second layer to be formed thereon, and the first layer consists of at least one kind or more of material to be selected from ruthenium, ruthenium silicide, ruthenium oxide, and a second layer 7 consists of at least one or more kinds of materials selected from the high melting point noble metals of platinum, palladium, rhodium. On the silicon electrode, ruthenium or ruthenium silicide is formed on the first layers 5, 9, 6 of the conductive layer followed by heat treatment in an oxygen atmosphere at above 400°C to under 700°C to oxidize one part or the whole of the first conductor layer, thereafter, one or more kinds of materials to be selected from the high melting point noble metals of platinum, palladium and rhodium are formed on the second conductive layer 7, whereon the dielectric and the upper electrode are by turns formed. COPYRIGHT: (C)1991,JPO&Japio

Method to retard catalyst recrystallization

Abstract: The rate of noble metal crystallite recrystallization on a carbon-supported noble metal catalyst is reduced by dispersing two or more different kinds of noble metal-containing crystallites onto the surface of the carbon support. The crystallites have either different unit cell configurations or different unit cell sizes. The reduced rate of noble metal crystallite recrystallization results, over a period of time, in higher crystallite surface area and therefore, better catalyst performance compared to conventional carbon-supported noble metal catalysts. Fuel cells which incorporate such improved catalysts as cathode catalysts are capable of operating at maximum power production for longer periods of time than fuel cells which use conventional catalysts as cathode catalysts.

Catalyst and process for its preparation

Abstract: A process for the preparation of catalysts, in particular for the purification of exhaust gases from internal combustion engines, is described, which makes it possible to use supports stable up to at least 1,200° C. which are free of gamma-aluminium oxide and transition aluminium oxide and nevertheless have a high catalytic activity. The catalytically active noble metal as the constituent of a composite powder is attached to the support, which in addition to the noble metal contains a thermally stable metal oxide and is prepared by the spray pyrolysis process.

Catalyst for treatment of exhaust gases from internal combustion engines

Abstract: This invention relates to a catalytic composite for treating an exhaust gas comprising a support which is a refractory inorganic oxide having dispersed thereon lanthanum, at least one other rare earth component and at least one noble metal component selected from the group consisting of platinum, palladium, rhodium, ruthenium and iridium. An essential feature of said catalytic composite is that the lanthanum be present as crystalline particles of lanthanum oxide which have an average crystallite size of less than about 25 Angstroms. The support may be selected from the group consisting of alumina, silica, titania, zirconia, aluminosilicates and mixtures thereof with alumina being preferred. Illustrative of the other rare earth components are cerium, neodymium, praeseodymium, dysprosium, europium, holmium and ytterbium. An important feature in manufacturing the catalytic composite is the dispersion of lanthanum oxide onto said refractory inorganic oxide support. In a specific example, lanthanum may be dispersed on alumina as follows. A solution of a lanthanum salt is mixed with a hydrosol of aluminum, particles are formed from said lanthanum containing hydrosol, calcined to form an inorganic oxide particle containing lanthanum oxide, ground to give a powder of alumina containing finely dispersed lanthanum oxide. This powder in turn can be mixed with another rare earth oxide such as cerium oxide to a slurry which in turn is used to coat a solid monolithic carrier. Finally, at least one noble metal component is dispersed on said coated solid monolithic carrier.

Metal and metal oxide catalysed electrodes for electrochemical cells, and methods of making same

Abstract: Porous electrodes for use in fuel cells and other electrochemical cells are disclosed. Principally, the electrodes a catalytically active layer on a porous conductive substrate, which catalytically active layer is derived from non-noble metals. The loading of the catalytically active layer is lower in terms of weight of catalyst per unit area of geometrical electrode surface than heretofore. Several alternative methods of forming the electrode are taught, including impregnating a porous conductive substrate with a metal salt solution, followed by chemical or thermal formation of the porous catalytically active layer; or mixing the catalytically active material with the material of the porous conductive substrate, followed by fabrication of the electrode; or depositing pyrolitic carbon from the gas phase onto a porous conductive substrate, at elevated temperatures in a gas atmosphere. The electrode may also have a porous metallic current collector, and also a further gas diffusion layer. If used as a fuel cell anode, a further small amount of noble metal is included in the porous catalytically active layer. Porous electrodes of this invention have particular utility in alkaline primary or secondary cells as auxiliary gas recombining electrodes, especially as oxygen consuming auxiliary transfer electrodes.

Magnetostriction of 3d‐transition metal/noble metal compositionally modulated multilayer films

Abstract: Young’s modulus (Ef), magnetostriction (λf), stress (σ), and stress‐induced anisotropy (Ks) were measured in Co/Cu, Fe/Cu, Co/Ag, Co/Pd, and Co/Au compositionally modulated multilayer films (CMF) prepared by rf sputtering method. The measured values of Ef are almost equivalent to those of noble metals of Cu, Ag, Pd, and Au, respectively. The values of λf have an order of 10−5–10−6 which is the same order of the values in Co and Fe films. The calculated values of Ks from these results are about 10 to 100 times smaller than the measured values of perpendicular anisotropy (Ku) in the CMFs. Consequently, these results suggest that Ku of transition metal/noble metal CMFs cannot be explained only in terms of the stress‐induced anisotropy.

Catalyst and process for high selectivity reforming with PT/RE on BA-K-L zeolite

Abstract: This invention comprises a reforming catalyst and process with an unsulfided catalyst comprising Zeolite L, in which the cationic sites have been exchanged to contain potassium or barium or both; a Group VIII noble metal and rhenium, where the ratio of noble metal to rhenium is from about 0.1:1 to about 10:0. This catalyst gives improved selectivity toward aromatics formation and has improved sulfur tolerance compared to other L zeolite reforming catalysts.

Catalytic reforming with improved zeolite catalysts

Abstract: An improved zeolite catalyst containing at least one noble metal and at least one alkali metal wherein the amount of the latter component exceeds the cationic exchange capacity of the zeolite has been found to be highly useful for catalytic reforming.

Multicomponent redox catalysts for reduction of large biological molecules using molecular hydrogen as the reductant

Abstract: One-electron reduction of the large biological molecules horse heart cytochrome c, sperm whale myoglobin, and horseradish peroxidase using H/sub 2/ as the reductant can be catalyzed by two-component, high surface area heterogeneous catalysts. The catalysts can be prepared by first functionalizing high surface area SiO/sub 2/ with a polycationic polymer into which is dispersed MCl/sub 4//sup 2 -/ (M = Pd, Pt). Reduction with H/sub 2/ yields elemental Pd or Pt dispersed in the polymer. The particles are finally functionalized with a redox polymer derived from hydrolysis of Si(OR)/sub 3/ groups of an N,N'-dialkyl-4,4'-bipyridinium- or from a cobalticenium-based monomer. The two components of the heterogeneous catalysts are the buried noble metal capable of activating the H/sub 2/ and the redox polymer, which can equilibrate both with the noble metal and with the large biological molecule. Reduction of the large biological molecules in aqueous solution can be effected at room temperature and 1 atm H/sub 2/ using the catalysts under conditions where the biological materials would not be reducible with H/sub 2/ alone or when the noble metal alone would be used as the catalyst.

Electrochemical Behavior of Several Metal Ion Solutions at Ba[sub 2]YCu[sub 3]O[sub 7] and CuO Electrodes

Abstract: The electrodeposition of metallic coatings onto Ba/sub 2/YCu/sub 3/O/sub 7/ is desirable for the environmental protection of the underlying superconductor and for providing a parallel current path when the superconductor is in the normal state. Investigations with various voltammetric techniques have been made with simple metal ions in neutral salt media where electrolyte attack of the highly oxidizing substrate can be minimized. Easily reducible metals such as silver and mercury can be plated; the transition to extensive surface reduction of the substrate and failure to plate occurs in the region of potentials required for copper reduction. Ba/sub 2/YCu/sub 3/O/sub 7/ is attacked by most buffer acids - cathodically generated local pH increases in unbuffered salts can lead to precipitation processes. Parallel studies at CuO pellet electrodes and noble metal electrodes have been carried out as models.