Showing papers on "Platinum published in 1976"
514 citations
273 citations
TL;DR: In this article, the dehydrogenation and hydrogenolysis were studied on platinum single crystal surfaces of varying atomic surface structure at low pressures (10−6 Torr) in the temperature range of 300 −723 K. The active catalyst surface was covered with a carbonaceous overlayer.
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TL;DR: In this paper, a large number of platinum-based binary catalysts have been prepared by deposition of submonolayer amounts of the second components onto the surface of platinum catalysts via an immersion method.
202 citations
TL;DR: In this article, a novel technique was developed for the preparation of platinum-tin electrodes, which consists in covering a properly pretreated platinum surface with a fraction of a monolayer of tin without the use of electrical current.
194 citations
TL;DR: In this article, the development, growth, and adhesion of α-Al2O3 scales on platinum-aluminum alloys containing between 0.5 and 6 wt.% aluminum have been studied at temperatures in the interval between 1000 and 1450°C.
Abstract: The development, growth, and adhesion of α-Al2O3 scales on platinum-aluminum alloys containing between 0.5 and 6 wt.% aluminum have been studied at temperatures in the interval between 1000 and 1450° C. The morphologies and microstructures of the α-Al2O3 scales were found to be influenced by the temperature, oxygen pressure, and the microstructures of the alloys. The oxidation rates of the alloys appeared to be controlled by transport of oxygen along grain boundaries in the α-Al2O3 scales. The α-Al2O3 scales adhered to the platinum-aluminum substrates even after extensive periods of cyclic oxidation. The good adhesion of the α-Al2O3 may result from mechanical keying of the oxide to the alloys due to the development of irregular oxide-alloy interfaces.
174 citations
TL;DR: In this paper, the authors studied the adsorption of carbon monoxide, ethene, and deuterium on platinum, Pt3Sn, PtSn, and PtSn2 and found significant differences between the surface and the bulk composition of the alloys.
163 citations
TL;DR: In this article, a ligand-stabilized platinum(II)-group IVB metal halide complexes have been found to catalyze the homogeneous hydroformylation of olefins to aldehydes.
TL;DR: A detailed mineralogical investigation was made of 25 samples from nine deposits geographically encircling the Sudbury basin this article, which resulted in the identification and characterization of 13 platinum-group minerals, as well as in a description of their textures, mode of occurrence, mineral associations, and other details relevant to improving beneficiation.
Abstract: A detailed mineralogical investigation was made of 25 samples from nine deposits geographically encircling the Sudbury basin. This study has resulted in the identification and characterization of 13 platinum-group minerals, as well as in a description of their textures, mode of occurrence, mineral associations, and other details relevant to improving beneficiation.The platinum-group minerals found are froodite, insizwaite, kotulskite, merenskyite, mertieite II, michenerite, moncheite, niggliite, sperrylite, sudburyite, unnamed Pd(Te, Sb,Bi), unnamed Pd 8 Sb 3 , and unnamed Ag 4 Pd 3 Te 4 . Most of the opaque minerals in these samples were analyzed in situ for minor substitutions of the major metals by Pd, Pt, and Rh with the following results: Pd occurs in minor, but, in some cases, significant quantities in cobaltite, gersdorffite, insizwaite, maucherite, melonite, moncheite, nickeline, and niggliite; Pt occurs in cobaltite-gersdorffite, froodite, michenerite, and nickeline; Rh was found in cobaltite-gersdorffite and sperrylite.The South Range and Offset deposits are characterized by the presence of arsenides and antimony and by the scarcity of tin-bearing platinum-group minerals; in contrast, arsenides and antimonides are sparse and tin is present in platinum-group minerals in the North Range deposits. This difference is reflected in the platinum-group mineralogy; sperrylite is the principal platinum mineral in the former deposits, whereas moncheite, insizwaite, and niggliite are the principal platinum minerals in the North Range deposits. Other differences in the geochemistry between the South and North Range deposits are reflected in the most common palladium mineral, michenerite. South Range michenerite is usually antimonian- and platinum-free, whereas North Range michenerite is platinian and contains from nil to trace amounts of antimony.Much of the Pd and Pt, now found as discrete platinum-group minerals, is considered to have been fractionated into a Cu-rich liquid upon crystallization of monosulfide solid solution from an original immiscible sulfide-silicate magma. Crystallization of an intermediate solid solution from the Cu-rich liquid resulted in further enrichment of platinum-group elements in a Pd-Pt-Te-Bi-Sb-(As?)-rich liquid. The crystallization of the platinum-group minerals, on further cooling, was subsequently controlled by the phase relations in that type of system.
TL;DR: The results show that the allergy‐eliciting compounds are confined to a very small group of ionic complexes containing reactive halogen ligands and neutral complexes and those containing more strongly bound ligands are totally inactive.
Abstract: A series of platinum complexes has been used for allergy tests in a number of platinum refinery workers who are known to be sensitive to hexachloroplatinate ([PtCl6]2-) salts. The results show that the allergy-eliciting compounds are confined to a very small group of ionic complexes containing reactive halogen ligands. Neutral complexes and those containing more strongly bound ligands are totally inactive. These variations in activity are interpreted in terms of established kinetic and thermodynamic parameters.
TL;DR: In this paper, the effect of various liquids on the growth of platinum crystallites dispersed on graphitized carbon has been determined from electrochemical surface area measurements, and it is concluded that the evidence strongly suggests that two-dimensional Ostwald ripening (the migration of platinum atoms on the carbon surface) is the process whereby platinum is transferred from one crystallite to another, producing a decrease in the Pt crystallite density and surface area.
TL;DR: In this article, the activity of PtRe catalysts on α- or γ-alumina has been determined for various reactions such as benzene hydrogenation, benzene-deuterium exchange, cyclopentane, and butane hydrogenolysis.
TL;DR: In this paper, the degree of dispersion of platinum supported on a graphitized carbon black, subjected to varying levels of carbon burn-off in air, was found to increase with the extent of prior gasification of the carbon support.
TL;DR: In this article, the effects of precious metals on the adherence of Al2O3 to Ni-8Cr-6Al alloy were evaluated in cyclic oxidation testing between 800 and 1200° C.
Abstract: The effects of precious metals on the adherence of Al2O3 to a Ni-8Cr-6Al alloy were evaluated in cyclic oxidation testing between 800 and 1200° C. Additions of platinum between 2.5 and 10 wt.% and rhodium (5 wt.%) were found to improve oxide adherence at 1100 and 1200° C, but were less effective at 800 and 1000° C. Additions of 5 wt.% gold did not improve oxide adherence.
TL;DR: Two percent (Pt + Re ) Al 2 O 3 catalysts prepared by co-impregnation of Al2O3 with H2PtCl6 and Re2O7 and generally reduced by hydrogen at 500 °C were mainly investigated by thermogravimetry (H2O2 cycles at 25 °C), electron microscopy, and infrared spectroscopy (chemisorption of CO at 25°C) as mentioned in this paper.
TL;DR: In this paper, the rates and extents of hydrogen sorption by platinised tungsten trioxide and molybdenum trioxide have been measured between 273 and 363 K and between 3 and 101 kN m-2.
Abstract: The rates and extents of hydrogen sorption by platinised tungsten trioxide and molybdenum trioxide have been measured between 273 and 363 K and between 3 and 101 kN m–2. Maximum diffusion coefficients for hydrogen spilling-over from platinum to the trioxide supports have been estimated. X-Ray diffraction, differential thermal analysis and thermogravimetric analysis, e.s.r. and i.r. spectroscopy indicate that the products of this spillover are hydrogen bronzes of tungsten and molybdenum. These may be represented as HxWO3, where x has a maximum value of 0.46, and HxMoO3, where x has a maximum value of 1.63. The latter violates the ranges of composition previously accepted for bronzes. The chemical and thermal stability of these bronzes is discussed in terms of their structures.
TL;DR: The potential sweep method has enabled the quantitative monitoring of materials injected into mammalian brain, thereby providing new insights into the mode of action of intracerebrally injected 6-hydroxydopamineZL Carbon paste 1 was the electrode material of choice in those studies.
TL;DR: In this article, the authors used potential step techniques to study the mechanism of the anodic oxidation of carbon monoxide adsorbed onto a smooth platinum surface and showed that the experimental data are consistent with a "reactant pair" mechanism similar to that proposed by Gilman.
TL;DR: Fiber x-ray diffraction patterns of the two metallointeracalators indicate that the binding is governed by the neighbor exclusion principle, as shown by their ability to unwind closed circular duplex DNA.
Abstract: The complexes 1,10-phenanthrolineethylenediamineplatinum(II) and 2,2'-bipyridineethylenediamineplatinum(II) have a planar, aromatic ligand system that facilitates intercalation, as shown by their ability to unwind closed circular duplex DNA. Nonbonded steric interactions can rotate the pryidine ligands out of the coordination plane in bis(pyridine)ethylenediamineplatinum(II), thus preventing intercalation. Fiber x-ray diffraction patterns of the two metallointeracalators indicate that the binding is governed by the neighbor exclusion principle.
TL;DR: In this paper, the behavior of metal crystallites supported on thin films of alumina was observed in the transmission electron microscope. Butler et al. used a sputtering technique to deposit platinum crystallites on the anodized aluminum foil and the remaining aluminum was dissolved by amalgamation.
TL;DR: In this paper, the adsorption of CO and CO 2 on platinum, nickel and copper was studied by X-ray and UV photoelectron spectroscopy, and the results indicated that CO 2 is physisorbed on platinum and copper and that the bonding of CO on all three metals involves the metal d-electrons and particularly the 5σ level of CO.
TL;DR: The influence of externally located platinum on the isothermal stability of α-Al2O3 scales formed at high temperatures has been examined in this paper, where it has been observed that platinum, as the volatile species PtO2, is incorporated into the growing α 2 O3 scale where it either influences the stress relief mechanism at temperature or reduces oxidation growth stress generation.
Abstract: The influence of externally located platinum on the isothermal stability of α-Al2O3 scales formed at high temperatures has been examined. It has been observed that a nickel-base alloy forms an external scale of α-Al2O3 during oxidation at 1200°C, but this scale breaks down isothermally, enabling a faster-growing Cr2O3-rich scale to develop. However, in the presence of platinum metal alongside the specimen in the furnace hot zone, the breakdown of the α-Al2O3 scale is postponed for a substantial period of time. It appears that platinum, as the volatile species PtO2, is incorporated into the growing α-Al2O3 scale where it either influences the stress relief mechanism at temperature or reduces oxidation growth stress generation and thus significantly enhances the isothermal stability of the scale.
TL;DR: In this article, the catalytic influence of small particles of platinum and palladium on the graphite-oxygen reaction has been investigated by controlled atmosphere electron microscopy, and it was shown that all active particles, irrespective of their size, gasify the same amount of carbon per unit time under given experimental conditions.
TL;DR: In this paper, the electron transfer rate of 1,4-benzoquinone in DMF at platinum, gold and mercury electrodes was measured by cyclic voltammetry and found to be much larger than reported earlier.
01 Dec 1976
TL;DR: In this article, the electrochemical behavior of semiconductor electrodes on which a very small amount of metal is electrodeposited have been studied, and the cathodic photocurrent-potential curve for the p-type GaP or Si electrode is shifted to the 0.2-0.3V more positive potential by the deposition of platinum.
Abstract: The electrochemical behaviors of semiconductor electrodes on which a very small amount of metal is electrodeposited have been studied. The cathodic photocurrent-potential curve for the p-type GaP or Si electrode is shifted to the 0.2–0.3V more positive potential by the deposition of platinum. The cathodic current-potential curve for the n-type GaP electrode is also shifted similarly, but the anodic current-potential curves and the flat band potentials for both the p- and n-GaP electrodes are not changed. From these results and those on the effects of other metals (Pd, Ni or Cu), it is concluded that the above-mentioned shifts are due to the catalytic actions of the deposited metals on the hydrogen evolution reaction at the semiconductor electrodes. A tentative model explaining this effect is presented.
TL;DR: In this paper, the photoelectron spectra of platinum were studied for photon energies of 21.2 and 10.2 eV, in conjunction with thermal desorption experiments, for coverages of carbon monoxide and oxygen of up to 0.25 monolayer.