Showing papers on "Noble metal published in 1993"

Chemical processing in high-pressure aqueous environments. 2. Development of catalysts for gasification

Abstract: A liquid water processing environment was used at 20 MPa and 350 C to convert organic compounds to methane and carbon dioxide in the presence of catalysts. This paper describes the evaluation of various types of base and noble metal catalysts and numerous support compositions for the process. The feedstock used in these tests was a mixture of p-cresol and water. Nickel, ruthenium, and rhodium were identified as active metals for the reaction. Other metals from groups VIII, VIB, IB, and IIB were inactive or readily oxidized and lost activity. Stable supports in the processing environment included [alpha]-alumina and zirconia. Silica and titania did not react chemically, but the tablet forms lost their physical integrity. Alumina forms, other than [alpha]-alumina, reacted with water to form boehmite ([gamma]-AlOOH) with significant loss of surface area and physical strength.

Optical characterization of anodic aluminum oxide films containing electrochemically deposited metal particles. 1. Gold in phosphoric acid anodic aluminum oxide films

Abstract: In a previous paper (Preston, C. K.; Moskovits, M. J. Phys. Chem. 1988, 92, 2957) we presented a technique, based on the width of the surface plasmon absorption measured by reflectance spectroscopy, for determining the average size of noble metal particles electrochemically deposited in anodic aluminum oxide films. This method is expanded, here, to take into account the optical anisotropy and nonuniformity of the film which arises from nonspherical nature of the particles themselves as well as from their distribution. Equations describing the reflectance spectrum expected for such films, assumed to consist of an alumina overlayer, a metal-filled oxide layer, and an aluminum substrate, are developed

Catalyst for exhaust gas purification and process for production thereof

Abstract: A catalyst for exhaust gas purification, comprising a heat-resistant inorganic monolith carrier and a catalyst layer loaded thereon, the catalyst layer including a catalyst composition containing at least one noble metal selected from Pt, Pd and Rh, as an active catalyst component, and active alumina. The catalyst composition has a specific surface area of at least 50 m 2 /g and a porosity of at least 50%. This catalyst for exhaust gas purification contains noble metal(s) in a well dispersed state, has excellent high-temperature durability, and is low in thermal deterioration of catalyst performance. Hence, the catalyst can be suitably used as a converter installed in engine manifolds of gasoline engine automobiles, or as a heater having improved purification ability for the exhaust gases emitted from automobiles during their cold start.

Multiple layer thin films with improved corrosion resistance

Abstract: The durability of thin metal coatings and particularly substantially transparent copper and silver plus noble metal coatings and their ability to withstand corrosive environments is improved by overcoating the metal layers with a double coating of dielectric. The first coating is made up of dielectric based on indium and/or zinc. The second coating is made up of dielectric based on indium and tin. These overcoatings are more effective than a single coating based on one metal or a single coating based upon the two metals.

Method of forming electrical connections to high dielectric constant materials

Abstract: A preferred embodiment of this invention comprises an oxidizable layer (e.g. tantalum 48), an oxygen gettering layer (e.g. platinum/tantalum mixture 34) overlaying the oxidizable layer, a noble metal layer (e.g. platinum 36) overlaying the oxygen gettering layer, and a high-dielectric-constant material layer (e.g. barium strontium titanate 38) overlaying the noble metal layer. The novel structures presented provide electrical connection to high-dielectric-constant materials without the disadvantages of current structures. The oxygen gettering layer controls oxygen diffusion, minimizing the formation of a resistive layer either in the lower electrode or at the lower electrode/substrate interface. The oxygen gettering layer acts as a gettering site for oxygen, where the oxygen oxidizes the reactive metal portion of the layer, leaving the noble metal portion of the layer intact. While the oxides/suboxides (e.g. tantalum pentoxide 40) that are formed are resistive, they are dispersed within the noble metal matrix, leaving a conductive path from the top of the layer to the bottom. This invention provides a stable and electrically conductive electrode for high-dielectric-constant materials while using standard integrated circuit materials to facilitate and economize the manufacturing process.

Structure and method for a superbarrier to prevent diffusion between a noble and a non-noble metal

Abstract: This invention relates generally to structure and method for preventing metal diffusion between a noble metal layer and an adjoining non-noble metal layer, and more specifically to new structures and methods for providing a superbarrier structure between copper and an adjoining noble metal layer. This is achieved by sequentially deposited a layer of non-noble metal, a layer of titanium, a layer of molybdenum, and a layer of noble or relatively less noble metal as the interconnecting metallurgy. This invention also relates to an improved multilayer metallurgical pad or metallurgical structure for mating at least a portion of a pin or a connector or a wire to a substrate.

An Examination of the Electrochemical Behavior of Palladium in Base

Abstract: This survey of the electrochemistry of palladium in base is a continuation of a related investigation of the same metal in acid. Both dc and in‐phase ac cyclic voltammograms for palladized palladium in base gave even more marked indications that, as compared with the behavior at low pH, the active metal can undergo premonolayer oxidation. Incipient hydrous oxide formation (positive sweep) was assumed to occur in the same region where thick Pd(IV) hydrous oxide films reduce,i.e., in the region on the negative sweep extending from below the monolayer oxide reduction peak right into the hydrogen adsorption region. Incipient hydrous oxide species were again assumed to be involved, as mediators, in the electrocatalytic oxidation of reductants such as hydrazine. Anomalous oxidation, which was reported recently, in quite independent work, for metal cluster/oxygen gas reductions, together with super‐Nernstian potential/pH shifts, appear to be an intrinsic part of noble metal electrochemistry.

Application of poly(aniline) as an ion exchanger for the separation of palladium, iridium, platinum and gold prior to their determination by neutron activation analysis

Abstract: The distribution coefficients of PdIII, IrIV and AuIII on poly (aniline) in 0.1–10 mol l–1 HCI were determined. They are strongly adsorbed at low acidities and the extent of adsorption decreases with increase in acidity, except for AuIII. Palladium, Pt and Au are quantitatively eluted with 5% thiourea in 0.05 mol l–1 HCI whereas the recovery of lr is >90% with 1% ascorbic acid followed by 10 mol l–1 HCl. It was found that Cr, Fe, Co, Ni, Zn, Ga and Ge are not retained on poly(aniline) at low acidities. This separation procedure was applied prior to the determination of Pd, lr, Pt and Au in iron meteorite and PCC-1 standard rock by neutron activation analysis.

The Study of Surface Films Formed on Lithium and Noble Metal Electrodes in Polar Aprotic Systems By the Use of In Situ Fourier Transform Infrared Spectroscopy

Abstract: Two approaches for in situ Fourier transform infrared spectroscopy (FTIR) studies of surface films formed on lithium and noble metal electrodes at low potentials in polar aprotic systems (e.g. alkyl carbonates, ethers, and their mixtures) are presented and discussed. One is based on external reflectance mode similar to SNIFTIRS. The other method is based on single internal reflectance mode (SIRFTIRS) with working electrodes of thin metal films deposited on NaCl crystals. Both methods were found to be adequate for the study of surface species formed on the active metals in several solvent systems in spite of the strong masking effect of the solution absorption

Phase behavior of palladium-silver particles supported on silica

Abstract: In this work, the structure as a function of treatment of palladium-silver catalyst particles supported on silica is explored using X-ray diffraction, kinetic probes, calorimetry, and temperature-programmed desorption. It is shown that following oxidation at a high temperature (675 K), the particles consist of an outer shell of PdO with an inner core of metallic silver. This structure undergoes a number of transformations under reaction conditions (butadiene hydrogenation) at low (300 K) temperatures. Initially, the outer shell of PdO reduces to palladium metal, and an alloy layer begins to form at the center. After a period of several hours, the entire particle becomes a true alloy. Following oxidation at a lower temperature (475 K), the particle consists of an outer layer of silver oxide and an inner core of palladium metal. The outer shell reduces under reaction conditions, but an alloy never forms. The potential application of these findings to other noble metal/noble metal systems is discussed. 26 refs., 7 figs., 1 tab.

NOx-reduction in lean exhaust gas from automobile engines

Abstract: The invention relates to a catalyst for decreasing nitrogen oxide in the lean exhaust gas of automobile engines. On a structurally reinforcing body, it contains a first catalytic coating of a high surface area aluminium oxide and/or cerium oxide impregnated with a mixture of iridium and platinum as catalytically active noble metal components. On the first layer is applied a second catalytic coating of a zeolite which contains copper and/or iron and is of the mordenite type.

Aqueous coating composition for thermal imaging film

Abstract: A heat-sensitive coating composition, and heat-sensitive material for thermal imaging containing the heat sensitive composition. The composition comprises a color-forming amount of a finely divided, solid, colorless noble metal salt of an organic acid; a color-developing amount of an organic reducing agent which at thermal copy and printing temperatures is capable of a color-forming reaction with the noble metal salt; an image toning agent; and a carrier composition in which the noble metal salt, organic reducing agent, and toning agent are distributed. The carrier composition requires no organic solvents and comprises one or more substantially water-soluble polymeric carrier materials and a solubility-enhancing amount of a dispersing agent. A protective, clarifying, radiation-cured overcoat is provided. Methods of forming the heat-sensitive composition and the overcoat are also disclosed.

Acid electrolyte solution and process for the electrodeposition of copper-rich alloys exploiting the phenomenon of underpotential deposition

Abstract: An acidic electrolytic solution for use in the electrodeposition of copper-rich alloys on a substrate, the less noble component being incorporated by underpotential deposition. The solution includes a first salt containing copper cations; a second salt containing cations of a metal less noble than copper; and an acid electrolyte (e.g., methane sulfonic acid) such that at typical current densities the potential is in the range of underpotential deposition of the less noble metal on the copper. Also provided is a process for using the acidic electrolytic solution. The process includes the following steps: (1) selecting a copper-rich alloy having, as the minor component, a metal that is less noble than copper and can form an underpotential deposition layer on copper; (2) selecting an acid electrolyte such that at typical current densities the potential is in the range of underpotential deposition of the metal on the copper; (3) providing in the acid solution simple salts of copper and of the less noble metal; and 4) applying a current between a cathode and an anode placed in the plating solution to plate the alloy on the cathode.

Thermoanalytical investigation on the formation of IrO2-based mixed oxide coatings

Abstract: The formation reactions of IrO2/TiO2 mixed oxide films supported on titanium metal plate were followed by thermoanalytical (simultaneous TGA, DTG, DTA) and combined thermoanalyticalmass spectrometric (TGA-MS) techniques. The electrochemical characterization of the fired coatings was made by cyclic voltammetry. The thermal decomposition of the titanium precursor salt, titanium diisopropoxide bis-2,4-pentanedionate, shows a major change in the presence of hydrated iridium (iii) chloride. Due to the catalytic effect of the added noble metal, an almost complete conversion of the organic components of the precursor mixture to CO2 and H2O is observed in the combustion stage. Chlorine, from thermal decomposition of the iridium salt, is produced in a separate stage at higher temperatures, indicating that a sequence of steps occurs prior to the oxide formation. For iridium chloride alone a complexation between the metal ion and the solvent (isopropanol) is observed, leading eventually to H2O and CO2 production (combustion step) between 300 and 500° C. The cyclic voltammetry results indicate that the features of the precursor reaction affect the charge storage capacity of the oxide films.

Metal-coated polyimide

Abstract: Electroless deposition-catalyzing film-forming solutions comprising polyamic acid and noble metal, eg palladium complexed with ammonia, in an aprotic solvent, eg N-methyl-2-pyrrolidone with a surfactant Such solutions are used to provide articles having a coating or patterned image of a electrolessly-depositable element such as copper, nickel and the like on high heat resistant substrates, eg metals, ceramics, glass, silicon, high heat polymers and thermoset polymers In the methods of this invention a polyamic acid/noble metal solution is applied as a coating or patterned image to provide a coherent polyamic acid film which can be imidized, eg by heat treatment at 250° C or higher, providing a tough, adhesive polyimide film that can catalyze electroless deposition

Group VIII metal containing tungsten oxide silica modified zirconia as acid catalyst

Abstract: The invention is directed to a catalyst composition comprising a Group VIII metal, preferably a Group VIII noble metal, and a zirconia support impregnated with silica and tungsten oxide and its use in an isomerization process.

Long life spark plug having minimum noble metal amount

Abstract: An economical spark plug for an internal combustion engine which has a long service life and by which a reduction in the discharge voltage and the use of the minimum amount of a noble metal can be achieved. The spark plug has an insulator, a center electrode supported by the insulator, and an earth electrode facing to the center electrode. A narrowed portion is arranged on a tip of an electrode material of at least one of the center electrode and the earth electrode. The narrowed portion includes a projection formed by extending the electrode material and a noble metal chip firmly connected to a terminal end of the projection. The electrode material is a nickel-base heat-resisting alloy. The noble metal chip is made of a Pt--Ir alloy essentially consisting of 90-100% by weight Pt and 0-10% by weight Ir. A diameter D of the narrowed portion is in a range of 0.6-1.2 mm. A thickness t of the noble metal chip is in a range of 0.16-0.8 mm. A length L of the narrowed portion including the thickness t of the noble metal chip is in a range of 0.8-1.5 mm.

Method of making a ground electrode for a spark plug

Abstract: In a method of making a spark plug electrode, an electrode blank is prepared to have a firing portion at one end of the electrode blank. A recess is provided at the firing portion of the electrode blank. A noble metal material is placed in the recess. Laser beams are applied on the noble metal material in the recess to melt 70%˜100% by weight of the noble metal material to form a noble metal tip. A component of the electrode blank is formed from a clad metal wherein the clad metal is thermally fused to the noble metal tip to form a fused portion, such that the clad metal comprises 0.5%˜80% of the total weight of the fused portion.

Ring opening process

Abstract: There is provided a ring opening process using a catalyst comprising a hydrogenation/dehydrogenation component, such as a noble metal, and an acidic solid component comprising a Group IVB metal oxide modified with an oxyanion of a Group VIB metal. An example of this catalyst is zirconia, modified with tungstate and platinum. This catalyst is used to convert cyclic hydrocarbons, such as cyclohexane and benzene, to paraffins, especially branched paraffins.

Spark plug and the method of manufacturing the same

Abstract: A spark plug for internal combustion engines provided with a noble metal tip on the pointed top of a spark plug center electrode. The noble metal tip is welded to the center electrode top end by heating and pressing the portion to be welded. After the welding, the center electrode is shaped to provide the pointed top. The noble metal tip is a platinum alloy consisting of platinum of 85 through 70 in weight percentage and iridium of 15 through 30 in weight percentage.

Chlorine capture by catalyst—sorbents for the oxidation of air pollutants

Abstract: Catalytic oxidation can be an effecitve and economic alternative to thermal oxidation for the destruction of halogenated hydrocarbons (HHC) which are known to deplete stratospheric ozone. Existing oxidation catalysts, noble metal and metal oxides are expensive and can deactivate when treating pollutants containing halogens. Current operation of thermal and catalytic processes require downstream gas scrubbing to remove acidic by-products HCl and Cl2 as well as corrosion resistant materials of construction. In response to the need for a better treatment process, a catalyst—sorbent that simultaneously destroys the HHCs and captures the halogens is being developed, and our initial results are presented in this paper. In this catalyst—sorbent, copper and manganese oxides are supported on sodium carbonate. The metal oxides are responsible for catalyzing the oxidation reactions and sodium carbonate captures the chlorine by forming NaCl and releasing carbon dioxide. Powder X-ray diffraction results show a significant conversion of the carbonate occurs as chlorine is captured. X-ray photoelectron spectroscopy has verified that the change between fresh and used catalyst also occurs near the surface. Trichloroethylene (TCE), trichlorofluoromethane and toluene are shown to be completely converted at a space velocity of 6700 h−1, temperatures 250°–400°C, and feed concentrations 30–350 ppm of pollutants in moist air. A chlorine balance shows that more than 98% of the chlorine from converted TCE remains in the catalyst—sorbent. Comparisons of this catalyst with others in the literature show it is a viable catalyst for the treatment of low concentrations of air pollutants.

Preparation and characterisation of noble metal solid sols in poly(methyl methacrylate)

Abstract: Novel solid sols of palladium, platinum, silver and gold in poly(methyl methacrylate) have been prepared and characterised by both visible spectroscopy and transmission electron microscopy.

Pulsed electrochemical detection at noble metal electrodes in high performance liquid chromatography

Abstract: The direct detection of numerous polar aliphatic compounds is achieved with pulsed electrochemical detection (PED). This technique exploits the electrocatalytic activity of «clean», noble metal electrode surfaces to oxidize various polar functional groups. In PED, multi-step potential-time waveforms at Au and Pt electrodes realize amperometric detection while maintaining uniform and reproducible electrode activity. The response mechanisms in PED are dominated by surface properties of the electrodes, and, as a consequence, members of each chemical class of compounds produce virtually identical voltammetric responses. Thus, PED requires a priori separation of complex mixtures via high performance liquid chromatography (HPLC)