Showing papers on "Molybdenum published in 1995"
TL;DR: In this article, the infrared and Raman spectra of powder samples of MoO3 (orthorhombic and monoclinic) and MoO 3 · x H 2 O (x = 1 3, 1 2, 1 and 2) have been recorded.
437 citations
355 citations
TL;DR: In this article, a method for fabricating low-resistivity molybdenum films on soda-lime glass substrates with good adhesion was described, where 1-μm-thick films sputtered at low argon pressure were found to have low resistivity (10−15 μΩ cm), were under compressive stress, and suffered from poor adhesion.
331 citations
TL;DR: A series of moderate surface area transition metal carbides and nitrides of molybdenum, tungsten, vanadium, niobium, and titanium were prepared by temperature-programmed reaction of the oxide precursor with a reactant gas as discussed by the authors.
Abstract: A series of moderate surface area transition metal carbides and nitrides of molybdenum, tungsten, vanadium, niobium, and titanium were prepared by temperature-programmed reaction of the oxide precursor with a reactant gas (20% CH{sub 4}/H{sub 2} for the carbides and 100% NH{sub 3} for the nitrides). The phase purity and composition of the samples were established by X-ray diffraction photoelectron spectroscopy (XPS), while surface properties were determined by N{sub 2} BET and CO chemisorption measurements. The catalysts were tested in three-phase trickle-bed reactor for their activity in hydrodenitrogenation (HDN), hydrodesulfurization, and hydrodeoxygenation, with particular emphasis on HDN. The catalytic tests were carried out using a model liquid feed mixture containing 3000 ppm sulfur (dibenzothiophene), 2000 ppm nitrogen (quinoline), 500 ppm oxygen (benzofuran), 20 wt% aromatics (tetralin), and balance aliphatics (tetradecane). The carbides and nitrides were found to be active for HDN of quinoline with activity following the order group 6 > group 5 > group 4. Notably, Mo{sub 2}C showed superior areal HDN activity than a commercial sulfided Ni-Mo/Al{sub 2} O{sub 3} catalyst (shell 324). The XRD analysis of the spent catalysts indicated no change in the bulk structure, while XPS results showed little incorporation of sulfur in the surface regionmore » of the catalysts, suggesting that these materials are tolerant of sulfur. 42 refs., 11 figs., 7 tabs.« less
318 citations
TL;DR: In this paper, the structure of Mo/HZSM-5 catalysts with various molybdenum loadings were studied by means of XRD, IR, UV diffuse reflectance spectroscopy, TPR, and ammonia adsorption and desorption measurements.
205 citations
TL;DR: In this article, the lateral and depth distributions of nitrogen and molybdenum in and near the passive layer were studied with Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopic (XPS).
200 citations
184 citations
TL;DR: In this paper, a transition metal chalcogenide material based on Mo-Ru-Se for electrocatalytic reduction of molecular oxygen in acid medium was chemically prepared by reacting the transition metal carbonyl compounds and selenium powder in xylene solvent (140 °C).
182 citations
TL;DR: In this article, new amorphous molybdenum oxysulfide thin films, prepared by r.f. magnetron sputtering and which could be used as positive electrode materials in microbatteries, were analyzed by X-ray photoelectron spectroscopy.
133 citations
131 citations
TL;DR: In this article, NiMo catalysts supported on mixed TiO2Al2O3 oxides containing between 0 and 22 wt.−% have been prepared and characterized by temperature-programmed reduction (TPR), infrared (IR) and diffuse reflectance (DR) spectroscopy, and ammonia adsorption measurements.
Abstract: NiMo catalysts supported on mixed TiO2Al2O3 oxides containing between 0 and 22 wt.−% TiO2 have been prepared and characterized by temperature-programmed reduction (TPR), infrared (IR) and diffuse reflectance (DR) spectroscopy, BET and ammonia adsorption measurements. The samples have been tested in hydrodesulphurization (HDS) of thiophene. The spectral results show that the proportion of weakly bonded MoO42− groups is higher for NiMo/TiO2Al2O3 catalysts compared to catalysts contained only molybdenum. The increase in TiO2 content in the mixed supports leads to a decrease of inactive NiAl2O4 spinel. An increase of Ni2+ ions in octahedral surroundings, included in a structure analogous to NiTiO3 is observed. Acidity shows the nickel-molybdenum surface interaction to be a result of the formation of a precursor of NiMoO4-like structure. The TPR results demonstrate that addition of titania into the support facilitates the Mo6+ reduction to Mo5+ and Mo4+. The influence of nickel on the molybdenum reducibility is revealed by a decrease of the temperature of reduction of the molybdenum species. The HDS activity of NiMo/TiO2Al2O3 catalysts reaches a maximum at 17 wt.−% TiO2 due to formation of an active phase with an optimal composition of the oxidic precursors.
TL;DR: In this article, the influence of humidity on the electrical properties of polyvanadium-molybdenum acid was investigated and it was shown that the conductance and capacitance of thin-film samples increase with an increase of humidity.
Abstract: The results of experimental investigations of the influence of humidity on the electrical properties of poly-vanadium-molybdenum acid are presented. The conductance and capacitance of thin-film samples increase with an increase of humidity. The results obtained are explained by the increase of the ionic part of the total conductivity of the samples.
Patent•
01 Aug 1995
TL;DR: A process for the preparatiion of an amine which comprises reacting a primary or secondary alcohol and a nitrogen compound selected from the group consisting of ammonia and primary and secondary amines, at temperatures of from 80° to 250° C and pressures of from 1 to 400 bar using hydrogen in the presence of a zirconium/copper/nickel catalyst is described in this paper.
Abstract: A process for the preparatiion of an amine which comprises reacting a primary or secondary alcohol and a nitrogen compound selected from the group consisting of ammonia and primary and secondary amines, at temperatures of from 80° to 250° C and pressures of from 1 to 400 bar using hydrogen in the presence of a zirconium/copper/nickel catalyst, wherein the catalytically active material contains from 20 to 85 wt % of oxygen-containing zirconium compounds, calculated as ZrO 2 , from 1 to 30 wt % of oxygen-containing compounds of copper, calculated as CuO, from 30 to 70 wt % of oxygen-containing compounds of nickel, calculated as NiO, from 01 to 5 wt % of oxygen-containing compounds of molybdenum, calculated as MoO 3 and from 0 to 10 wt % of oxygen-containing compounds of aluminum and/or manganese, calculated as Al 2 O 3 or MnO 2 , respectively
TL;DR: A series of molybdenum carbides were prepared by the temperature-programmed carburization of MoO3, with pure CH4 or an equimolar mixture of CH4 and H2.
TL;DR: It is concluded that dietary intakes between 22 and 1500 micrograms/d by adult men are safe for > or = 24 d and that molybdenum retention is regulated by urinary excretion.
TL;DR: In this article, a group-VI transition metal complex of heterocyclic carbene ligands is obtained in 41-45% yields through reaction of azolium precursor salts with carbonyl metallates.
01 May 1995-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, the pore volume fraction of the carbon preform is a very important parameter in determining the final composition of the reaction-formed silicon carbide and the secondary phases, and various undesirable melt infiltration results, e.g., choking-off, specimen cracking, silicon veins, and lake formation, are presented.
Abstract: Investigations on the reactive melt infiltration of silicon-1.7 and 3.2 at.% molybdenum alloys into microporous carbon preforms have been carried out by modeling, differential thermal analysis (DTA), and melt infiltration experiments. These results indicate that the pore volume fraction of the carbon preform is a very important parameter in determining the final composition of the reaction-formed silicon carbide and the secondary phases. Various undesirable melt infiltration results, e.g. choking-off, specimen cracking, silicon veins, and lake formation, and their correlation with inadequate preform properties are presented. The liquid silicon-carbon reaction exotherm temperatures are influenced by the pore and carbon particle size of the preform and the compositions of infiltrants. Room temperature flexural strength and fracture toughness of materials made by the silicon-3.2 at.% molybdenum alloy infiltration of medium pore size preforms are also discussed.
TL;DR: In this article, the synthesis and characterization of ultra-thin films of iron and iron oxides on a Mo(100) surface, have been carried out under ultrahigh vacuum conditions in the 100-1500 K substrate temperature range.
TL;DR: In this article, the influence of different amounts of boron ( x = 0.0, 0.2,0.8, 1.5 and 2.0 wt.-%B) to CoMo/Al 2 O 3 catalysts on the thiophene hydrodesulfurization catalytic activity and chemical state has been investigated by UV-vis diffuse reflectance spectroscopy, X-ray diffraction spectrograph, scanning electron microscopy, FT-IR of adsorbed nitric oxide, temperature-programmed reduction and acidity measurements.
Abstract: The influence of the incorporation of different amounts of boron ( x =0.0, 0.2, 0.8, 1.5 and 2.0 wt.-%B) to CoMo/Al 2 O 3 catalysts on the thiophene hydrodesulfurization catalytic activity and chemical state of the CoMo/Al 2 O 3 -B( x ) catalysts has been investigated by UV-vis diffuse reflectance spectroscopy, X-ray diffraction spectroscopy, scanning electron microscopy, FT-IR of adsorbed nitric oxide, temperature-programmed reduction and acidity measurements. The results indicate that boria is deposited as a monolayer on the surface of the alumina up to a loading of 0.8% B. The incorporation of boron into the catalyst supports leads to a change in the distribution of the cobalt and molybdenum oxidic species which results in a decrease in the proportion of tetrahedrally coordinated Co 2+ and Mo 6+ species in strong interaction with the alumina support. As a result of this change in species in the oxidic precursors, the number of cobalt sites probed by nitric oxide in the sulfided catalysts increases with boron contents, while the molybdenum sites remain practically unchanged. The net result is a beneficial effect on the catalytic activity of the thiophene hydrodesulfurization reaction which reaches a maximum at a boron content of 0.8 wt.-% B.
Patent•
08 Feb 1995
TL;DR: A titanium matrix composite is a composite having eutectically formed titanium alloy reinforcement containing at least two elements of silicon, aluminum, zirconium, manganese, chromium, molybdenum, carbon, iron, boron, cobalt, nickel, germanium and copper.
Abstract: A titanium matrix composite having eutectically formed titanium alloy reinforcement containing at least two of the elements of silicon, aluminum, zirconium, manganese, chromium, molybdenum, carbon, iron, boron, cobalt, nickel, germanium and copper.
TL;DR: The role of defect and transport properties of transition metal sulfides on the kinetics and mechanism of high-temperature sulfide corrosion of metals and alloys is discussed in this paper.
Abstract: The role of defect and transport properties of transition metal sulfides on the kinetics and mechanism of high-temperature sulfide corrosion of metals and alloys is discussed. It has been shown, that due to the very high concentration of defects in common metal sulfides, not only pure metals but also conventional high-temperature alloys (chromia and alumina formers) undergo very rapid degradation in highly sulfidizing environments. Refractory metals, on the other hand, are highly resistant to sulfide corrosion, their sulfidation rates being comparable with the oxidation rate of chromium. Pioneering work of Douglass et al. has shown that alloying of common metals by niobium or molybdenum, and in particular combined alloying by molybdenum and aluminum, dramatically decreases the sulfidation rate. A novel Fe-30Mo-9Al alloy has been proved to be highly resistant to sulfide corrosion, its sulfidation rate being comparable with that of pure molybdenum. Even better resistance to highly-sulfidizing environments show new amorphous Al-Mo and Al-Mo-Si alloys, these materials also being simultaneously oxidation resistant. Thus, new prospects have been created for the development of a new generation of coating materials, resistant to multicomponent sulfidizing-oxidizing atmospheres, often encountered in many branches of modern technology.
TL;DR: The minimum dietary molybdenum requirement of healthy young men is estimated to be approximately 25 micrograms/d or possibly less, which suggests that the lower end of the recommended range could be less than the current recommended amount of 75 microgramS/d.
Patent•
28 Mar 1995TL;DR: In this paper, the authors describe a superalloy component with a ductile brittle transition temperature below 500° C. The composite component and the coating applied thereon have a similar property.
Abstract: A protective coating resistant to corrosion at medium and high temperatures is applied on a nickel-based or cobalt-based superalloy component. The protective coating essentially consists of the following elements (in percent by weight): 25 to 40% nickel, 28 to 32% chromium, 7 to 9% aluminum, 1 to 2% silicon, 0.3 to 1% of at least one reactive element of the rare earths, at least 5% cobalt; and impurities, as well as selectively from 0 to 15% of at least one of the elements of the group consisting of rhenium, platinum, palladium, zirconium, manganese, tungsten, titanium, molybdenum, niobium, iron, hafnium, and tantalum. The total share of the elements of the group is from 0 to a maximum of 15% and a remainder of at least 5% cobalt. The component and the coating applied thereon have a ductile brittle transition temperature below 500° C.
TL;DR: In this article, it was shown that the addition of more than 2 at% molybdenum is effective in promoting spontaneous passivation of amorphous Fe-8Cr-13P-7C alloy in 1 M HCl open to air.
TL;DR: In this paper, the properties of electrochromic molybdenum oxide (as a thin film) has been adjusted by incorporating the oxides of Co, Cr, Fe, Ni, W or Zn; films were made by cathodic electrodeposition.
TL;DR: In this article, a coprecipitation method was used to obtain a 1:1 mole ratio for the support of molybdenum oxide overlayers in the presence and absence of water vapour.
Abstract: TiO 2 ZrO 2 support containing 1:1 mole ratio was prepared by the coprecipitation method. TiO 2 and ZrO 2 were also prepared separately. After calcination at 823 K, the mixed oxide was found to be amorphous. These solids were impregnated with molybdenum and examined by laser Raman spectroscopy. Physical mixtures of MoO 3 with the same supports were also studied. It is shown that monolayer structures of the molybdenum oxide overlayers are formed in the presence and absence of water vapour.