Showing papers on "Molybdenum published in 1983"

Effect of Molybdenum, Niobium, and Vanadium on Static Recovery and Recrystallization and on Solute Strengthening in Microalloyed Steels

Abstract: The effect of molybdenum, niobium, and vanadium on the occurrence of static recovery and recrystallization after high temperature deformation was investigated in a series of microalloyed steels. The steels had a base composition of 0.05 pct C and 1.40 pct Mn. To this, single additions of 0.30 pct Mo, 0.035 pct Nb, and 0.115 pct V were made. Interrupted hot compression tests were performed at 900 and 1000 °C, and at a constant true strain rate of 2 s-1. The load-free time was decreased from 5000 s to 50 ms, and the degree of static softening during this period was determined. Both graphite and glass were used as lubricants. Percent softeningvs delay time curves are presented and the retarding effect of molybdenum, niobium, and vanadium addition on the rate of static recovery and recrystallization is discussed. The greatest solute retardation of static recovery and recrystallization is produced by niobium addition, followed by that of molybdenum, vanadium leading to the smallest delay. Although the rank order of this effect is the same as found under dynamic softening conditions, the relative contribution of niobium is more profound for the static condition. The solute strengthening attributable to each element was also assessed, and found to follow the same order as for the recovery and recrystallization results. At 900 °C, the onset of the static precipitation of Nb (CN) was detected at approximately 10 seconds, somewhat earlier than previously reported.

Structural, elastic, and transport anomalies in molybdenum/nickel superlattices

Abstract: Metallic superlattices of nickel and molybdenum have been synthesized for a wide range of layer thicknesses by alternate sputtering. X-ray examination shows that they are composed of layers of fcc nickel and bcc molybdenum oriented along [111] and [110] directions, respectively. Anomalies have been observed in the lattice spacings, elastic moduli, and electrical resistivity versus modulation wavelength. These anomalies occur simultaneously at the same superlattice wavelength. The anomalies have been interpreted as due to strains in the nickel lattice.

Surface Enrichment of Nitrogen during Passivation of a Highly Resistant Stainless Steel

Abstract: Nitrogen, probably in an uncharged form, is enriched on the metal side of the metal film interface after passivation of the number 30 alloy. Molybdenum is probably present in the oxide film, but is depleted compared with the bulk alloy and shows no obvious association with nitrogen. The improvement of passivity by alloying with nitrogen probably results from segregation of nitrogen to the metal surface during preferential dissolution of metal atoms, rather than from its incorporation into an oxide film.

Analytical Chemistry of Molybdenum

Abstract: 1 Introduction.- 2 Detection.- 1. Detection in the Presence of Many Ions.- 2. Spot Tests.- 3. Detection in Specific Materials.- 3 Separations.- 1. Precipitation.- 2. Extraction.- 3. Ion Exchange.- 4. Paper and Thin Layer Chromatography.- 5. Other Separation Techniques.- 6. Applications of Specific Materials.- 4 Gravimetric Methods.- 1. Precipitation with Sulfide Ion.- 2. Precipitation as Molybdate Ion.- 2.1 Lead Molybdate.- 2.2 Other Molybdates.- 3. Precipitation with Organic Reagents.- 3.1 8-Hydroxyquinoline.- 3.2 ?-Benzoinoxime.- 3.3 Other Organic Precipitating Agents.- 4. Applications to Specific Materials.- 5 Titrimetric Methods.- 1. Precipitation Titrations.- 1.1 With Various Metals.- 1.2 With Organic Reagents.- 2. Complexometric Titrations.- 3. Oxidation-Reduction Titrations.- 3.1 Reactions with Oxidizing Agents.- 3.2 Reactions with Reducing Agents.- 4. Applications to Specific Materials.- 6 Colorimetric Methods.- 1. Color Forming Reagents.- 1.1 Thiocyanate Ion.- 1.2 Toluene-3,4-dithiol.- 1.3 Other Color Forming Agents.- 2. Applications to Specific Materials.- 7 Emission Spectroscopy.- 1. General Considerations.- 2. Laboratory Procedures.- 3. Applications to Specific Materials.- 8 Atomic Absorption Spectrometry.- 1. General Considerations.- 2. Laboratory Procedures.- 3. Applications to Specific Materials.- 9 X-Ray Fluorescence.- 1. General Considerations.- 2. Laboratory Procedures.- 3. Applications to Specific Materials.- 10 Voltammetry.- 1. Polarography.- 2. Anodic Stripping Voltammetry.- 3. Applications to Specific Materials.- 11 Catalytic Methods.- 1. Hydrogen Peroxide - Iodide Reaction.- 2. Other Molybdenum Catalyzed Reactions.- 3. Applications to Specific Materials.- 12 Radiochemical and Activation Methods.- 1. Radioactive Molybdenum Isotopes.- 1.1 Determining Radioactive Molybdenum.- 1.2 Isotopic Dilution with Radioactive Molybdenum.- 2. Activation Analysis.- 3. Applications to Specific Materials.- 13 Rocks and Mineral Samples.- 14 Molybdenum and Molybdenum Based Alloys.- 15 Molybdenum in Ferrous Alloys.- 16 Molybdenum in Non-Ferrous Alloys.- 17 Molybdenum Compounds.- 18 Animal, Plant, and Soil Samples.- 1. Animal Samples.- 2. Plant Samples.- 3. Soil Samples.- 19 Environmental Samples.- 1. Water Samples.- 2. Air Samples.- 3. Fuels Samples.- 20 Miscellaneous Samples.- Author Index.

Preparation of Molybdenum Zeolites from Molybdenum Hexacarbonyl: 1. Infrared Studies

Abstract: Ir spectroscopy has been used to study the adsorption and decomposition of molybdenum hexacarbonly (Mo(CO)/sub 6/) in the hydrogen (H) and sodium (Na) forms of zeolite Y. Two forms of adsorbed Mo(CO)/sub 6/ are found in both H-Y and Na-Y: a weakly (physically) adsorbed complex and a more strongly perturbed species. On being heated in vacuo above room temperature, the adsorbed Mo(CO)/sub 6/ decomposes. In H-Y, three distinct subcarbonyl species are formed reversibly. At temperatures of 200/sup 0/C or higher, decarbonylation is irreversible, and oxidation of the molybdenum occurs, as indicated by loss of zeolite OH groups and appearance of oxomolybdenum species. Carbon monoxide (CO) chemisorbed on oxidized molybdenum sites gives a characteristic ir band at 2170 cm/sup -1/. Ir evidence is presented for interaction of ammonia with intra-zeolitic molybdenum cations. Surface area, X-ray diffraction, and low-frequency infrared measurements indicate that the zeolite crystallinity is retained on heating in vacuo up to 500/sup 0/C, but loss of structure occurs on heating in oxygen at high temperature. In Na-Y, a single subcarbonyl species is formed reversibly upon initial decomposition of adsorbed Mo(CO)/sub 6/. At higher temperatures metallic molybdenum appears to be formed which does not adsorb appreciable quantities of CO. The more » resistance of the MoNa-Y to oxidation by O/sub 2/ depends on the temperature of prior activation. « less

A spectroscopic investigation of cerium molybdenum oxides

Abstract: A detailed X-ray photoelectron, i.r., and Raman spectral study has been made of Ce2(MoO4)3 and five novel cerium molybdenum oxides (α- and β-Ce2Mo4O15, β- and γ-Ce2Mo3O13, and Ce8Mo12O49), which are of particular interest as they are closely related to the cerium molybdenum oxide species which are expected to play an active role in an industrial cerium molybdenum tellurium oxide acrylonitrile catalyst. The photoemission results add to the few existing previous data concerning cerium compounds and confirm the valence distribution in the compounds. With the exception of the tetrahedral oxomolybdenum co-ordination in Ce2(MoO4)3 the cerium molybdates consist of highly irregular or mixed polyhedral arrangements with Mo–O bond strengths (in valence units) either below 0.3 v.u or above 1.0 v.u.

Raney nickel alloy expanded mesh hydrogenation catalysts

Abstract: Hydrogenation processes utilizing improved Raney nickel alloy catalysts are disclosed The catalyst comprises a monolithic mesh type structure of a nickel alloy having an integral Beta phase Raney Ni x M 1-x coating on its outer surfaces, where M is a catalytic activator selected from the group consisting of molybdenum, ruthenium, tantalum and titanium and where x, the weight fraction of nickel in the combined alloy, is between about 080 and about 095 The catalyst is effective in processes for hydrogenation of aromatic compounds of the type wherein K is either benzene or naphthalene, R, is a hydrogen atom or an aliphatic chain containing from about 1 to about 9 carbon atoms or a phenyl radical, R 2 is a hydrogen atom or an aliphatic chain containing from about 1 to about 3 carbon atoms, and R 3 and R 4 are hydrogen atoms, hydroxy, nitro or amine groups When this catalyst is used, substantially higher reactant flow rates and lower operating temperatures are possible as compared to conventional fluidized bed granular catalysts

Effect of additive elements on cold workability in FeCo alloys

Abstract: Addition of various elements to equiatomic FeCo alloys and changes in ratio of iron and cobalt have been examined in order to study mechanisms for the improvement of ductility in the alloy. It has been revealed that Fe30Co70, one of the alloys having a different Fe/Co ratio, and alloys having additive elements such as carbon, vanadium, chromium, nickel, niobium, molybdenum, tantalum and tungsten ranging from 0.5 to 2 at %, are effective in improving ductility; whereas aluminium, beryllium, boron, copper, gold, manganese, silver, silicon, titanium and zirconium are ineffective. A common feature is found in the effective alloying elements: the elements combine with cobalt to form an Co3X type compound that can be produced only by diffusion; for instance, Co3C, Co3V, Co3Cr, Co3Ni, Co3Nb, Co3Mo, Co3Ta and Co3W. It is suggested, as a way of explaining this common feature, that as a result of the formation of the Co3X compound, the zones, difficult to cause the order lattice may be produced around the compound particles, and thus resulting in ductility.

Absence of hepatic molybdenum cofactor: An inborn error of metabolism leading to a combined deficiency of sulphite oxidase and xanthine dehydrogenase

Abstract: Five patients with a combined deficiency of xanthine dehydrogenase, sulphite oxidase and, probably, also of aldehyde oxidase are described. This remarkable coincidence of three inborn errors of metabolism in a single individual was demonstrated to result from a deficiency of the ‘molybdenum cofactor’, an essential constituent of all three enzymes. The main biochemical findings in these patients included: hypouricaemia, xanthinuria, an increased excretion of sulphite, thiosulphate andS-sulphocysteine and a decreased excretion of inorganic sulphate. Plasma molybdenum was normal. The ultimate diagnosis was made by the measurement of ‘molybdenum cofactor’ in a liver biopsy specimen in three out of five patients.

Equilibria amongst different molybdenum (V)-containing species from sulphite oxidase. Evidence for a halide ligand of molybdenum in the low-pH species.

Abstract: The interaction of chloride, fluoride and phosphate ions with the molybdenum centre of sulphite oxidase in the pH range 6.2 to 9.6 has been studied by e.p.r. of Mo(V) in the enzyme reduced by sulphite. Detailed studies were made from e.p.r. spectra recorded at about 120K and more limited studies from spectra of liquid samples at about 295K and also from enzyme activity measurements. Interconversion between low-pH and high-pH Mo(V) e.p.r. signal-giving species [described by Lamy, Gutteridge & Bray (1980) Biochem. J. 185, 397-403] is influenced by chloride concentration, a 10-fold increase in concentration (in the range of about 1 mM to 100 mM) causing an increase of about 1 pH unit in the apparent pK for the conversion. This suggests that chloride is a constituent of the low-pH species. In support of this, high concentrations of fluoride modified the e.p.r. spectrum. Partial conversion to a Mo(V) species, in which F- has presumably replaced Cl- and showing hyperfine coupling of A(19F)av. 0.5mT, is indicated. It is proposed that interconversion between high-pH and low-pH species is of the form: (formula; see text) No evidence that Cl- is essential for enzymic activity was found. Data relating to equilibria amongst low-pH, high-pH and also the phosphate species are presented. Depending on pH and on concentrations of Cl- and H2PO4-, one, two, or all three species may be present. Qualitatively, under appropriate conditions, the phosphate species tends to replace some or all of the low-pH species. Quantitative analysis by a computer procedure permitted an appropriate scheme to be deduced and equilibrium constants to be evaluated. Studies on the e.p.r. signals at 295K indicated that similar equilibria applied in liquid solution, but with some changes in the values of the constants. The structure of the molybdenum centre in its various states and the nature of the enzymic reaction are discussed.

Sensitization of Austenitic Stainless Steels II. Commercial Purity Alloys

Abstract: This paper presents a study of the effects of nitrogen and molybdenum on the sensitization of commercial purity type 304 and 316 stainless steels. The modified Strauss test (ASTM-A262-E) i...

Molybdenum chloro complexes in room-temperature chloroaluminate ionic liquids: stabilization of [MoCl6]2− and [MoCl6]3−

Abstract: Donnees electrochimiques et spectrales indiquant la formation de solutions stables des ions [MoCl 6 ] 2− et [MoCl 6 ] 3− . On observe une instabilite du Mo(V) dans la masse fondue basique

Pitting-Resistant Alloys in Highly Concentrated Chloride Media

Abstract: The pitting resistance of a series of experimental stainless steels with varying amounts of nickel, chromium, molybdenum, manganese, and nitrogen and a number of commercial stainless steel...

The adsorption of molybdenum on oxide surfaces

Abstract: Adsorption of molybdenum was measured on 12 oxides with zero points of charge (ZPC) ranging from pH 2 to 7.6. Adsorption envelopes calculated using the Bowden adsorption model agreed well with the experimental results for goethite. Oxides with low ZPC, however, showed adsorption maxima well below the predicted value of pH 3.3. It was postulated that a positively charged polycationic form of molybdenum was adsorbed at low pH by oxides with low ZPC.

Metal and sulfur composition of iron-molybdenum cofactor of nitrogenase

Abstract: The sulfur content of N-methylformamide solutions of cofactor from Clostridium pasteurianum nitrogenase has been determined to be 11.9 (+/- 0.9) mol per mol of molybdenum. This number was determined radiochemically, using iron-molybdenum cofactor isolated from molybdenum-iron protein from bacteria grown on 35SO4. A total of 3.2 (+/- 0.2) mol of sulfur per mol of molybdenum was found to be present in cysteine and methionine, probably arising from contaminating proteins not intrinsic to the cofactor. Combined with accumulated evidence that is discussed, these results lead to an updated stoichiometry of MoFe6S8 or 9, not MoFe6S4 as previously thought, for this cluster.

Catalyst for production of unsaturated aldehydes

Abstract: A catalyst for the production of unsaturated aldehydes is provided which is represented by the general formula Bia Wb Fec Mod Ae Bf Cg Dh Ox wherein Bi represents bismuth, W represents tungsten, Fe represents iron, Mo represents molybdenum, O represents oxygen, A represents nickel and/or cobalt, B represents at least one element selected from the group consisting of alkali metals, alkaline earth metals and thallium, C represents at least one element selected from the group consisting of phosphorus, arsenic, boron, antimony, tin, cerium, lead and niobium, D presents at least one element selected from the group consisting of silicon, aluminum, zirconium and titanium, a, b, c, d, e, f, g, h and x represent the atomic ratios of the individual elements, and when d is taken as 12, a=0.1-10.0, b=0.5-10.0 (provided that a/b=0.01-6.0), c=0.1-10.0, e=2.0-20.0, f=0.001-10.0, g=0-10.0, and h=0-30, and x takes a number determined by the atomic valences of the individual elements. The Bi component is introduced thereinto in the form of an oxide obtained beforehand by calcining a mixture of a bismuth compound and a tungsten compound at a temperature of 600° to 900° C.