Showing papers on "Molybdenum published in 1973"

Strength and toughness of Fe-10ni alloys containing C, Cr, Mo, and Co

Abstract: The effects of C (0.10 to 0.20 pct), Cr (0 to 3 pct), Mo (0 to 2 pct), and Co (0 to 8 pct) on the yield strength, toughness (Charpy shelf energy), and tempering behavior of martensitic lONiCr-Mo-Co steels have been investigated. Variations in the carbon content between 0.10 and 0.20 pct result in yield strengths between 160 and 210 ksi (1.1 and 1.45 GN/m2) when these steels are tempered at 900° to 1000°F (480° to 540°C) for times of 1 to 100 h. These steels exhibit a secondary-hardening peak at 900° to 1000° F (480° to 540°C) where coarse Fe3C carbides are gradually replaced by a fine, dislocation-nucleated dispersion of (Mo, Cr)2C carbides. Maximum toughness at a given yield strength in these steels is only obtained when they are tempered for sufficiently long times so that the coarse Fe3C carbides are completely dissolved. Molybdenum is primarily responsible for the secondary-hardening peak observed in these steels. However, chromium additions do result in lower secondaryhardening temperatures and promote coarsening of the secondary-hardening carbide. Best combinations of strength and toughness are obtained with steels containing 2 pct Cr and 1 pct Mo. Cobalt increases the yield strength of these steels over the entire tempering range and results in a higher secondary-hardening peak. This effect of cobalt is attributed to 1) a retardation in the rate of recovery of the dislocation substructure of the martensite, 2) the formation of a finer dispersion of secondary-hardening carbides, and 3) solid-solution strengthening. The finer dispersion of secondary-hardening carbides in steels containing cobalt is favored by the finer dislocation substructure in these steels since the (Mo, Cr)2C carbide is dislocation-nucleated. This fine dispersion of (Mo, Cr)2C carbide combined with the high nickel content accounts for the excellent combination of strength and toughness exhibited by these steels.

Blistering of molybdenum under helium ion bombardment

Abstract: Polished molybdenum targets have been bombarded with helium ions of energy from 7 to 80 keV in ultra-high vacuum. During bombardment the release of gas was continuously monitored and after bombardment the targets were examined in a scanning electron microscope. Blister formation was observed to occur after a critical dose of ∼ 5 × 1017 ions/cm2, and the appearance of blisters coincides with gas release from the surface. The average size of the blisters increases with energy but not with ion dose. In addition to room temperature observations, blisters have also been examined following high temperature bombardment of molybdenum, and room temperature bombardments of W, Pt, Ni, Cu and Zr targets.

Proposed Molecular Mechanism for the Action of Molybdenum in Enzymes: Coupled Proton and Electron Transfer

Abstract: The reactions catalyzed by Mo enzymes each find the product differing from the substrate by two electrons and two protons (or some multiple thereof). The coordination chemistry of Mo suggests that there is a distinct relationship between acid-base and redox properties of Mo complexes, and that a coupled electron-proton transfer (to or from substrate) may be mediated by Mo in enzymes. Each of the Mo enzymes (nitrogenase, nitrate reductase, xanthine oxidase, aldehyde oxidase, and sulfite oxidase) is discussed; it is shown that a simple molecular mechanism embodying coupled proton-electron transfer can explain many key experimental observations. In view of this mechanism, the reasons for the use of Mo (from an evolutionary and chemical point of view) are discussed and other metals that may replace Mo are considered.

Process for the preparation of methacrylic acid from methacrolein

Abstract: Catalysts containing tungsten, phosphorus, vanadium, molybdenum, and promoted with at least one of the elements selected from the group selected from Sn, As, Cu, Ce, B, Cr, Fe, Ni, Co, U, Mn, Ag, Ru, Rh, Cd, Sr, In, Zn, and La have been found to be especially effective for the oxidation of unsaturated aldehydes to form the corresponding unsaturated acid.

Synthesis of bis-π-benzene-titanium and -molybdenum using metal vapours

Abstract: Bis-π-benzene-titanium and -molybdenum are formed by co-condensation of benzene vapour with the metal vapours at 77K.

Molybdenum Disulfide in Oils and Greases Under Boundary Conditions

Abstract: A mineral oil and a lithium-based mineral oil grease containing molybdenum disulfide are tested under boundary conditions on the Shell Four Ball Testing Machine and on a modified Reichert Wear Balance The investigation of the wear tracks by scanning electron microscopy and microprobe analysis shows that a continuous MoS1 film is formed on the metal surface under mild friction conditions Under extremely severe conditions, however, the MoS2 reacts chemically It is found that molybdenum diffuses into the steel surface forming intermetallic compounds and carbides which improve the quality of the steel surface The effect of time and pressure on the thickness of the molybdenum disulfide is determined and the amount of wear reduction by chemical reaction of molybdenum disulfide with the steel surface is compared to that of a traditional EP-additive

Determination of Néel Temperatures of Binary Chromium Alloys from Electrical Resistivity Data

Abstract: The Neel temperatures, TN, of binary chromium alloys containing aluminium, cobalt, germanium, iridium, iron, molybdenum, nickel, niobium, osmium, ruthenium, silicon, tantalum, titanium, and vanadium have been determined from the electrical resistivity data using the d/dT minima method The composition dependence of TN is discussed in view of the existing theories of itinerant-electron antiferromagnetism

The effect of molybdenum on γ′ coarsening and on elevated-temperature hardness in some experimental nickel-base superalloys

Abstract: The coarsening of γ′ and the elevated-temperature hardness have been studied as a function of molybdenum content, time, and temperature in experimental wrought nickel-base superalloys. The alloys were selected from a systematic series containing 3, 4 1/2, and 6 wt pct Al and 1 wt pct Al plus 3 1/2 wt pct Ti. Each of the aluminum (plus titanium) series consisted of four alloys containing 0, 2, 5, and 8 wt pct Mo. The alloys were solution-treated plus aged up to 112 h at 1700°F (925°C) and up to 1000 h at 1400°F (760°C). Molybdenum retards the coarsening of γ′ on aging; this retarding effect is most pronounced in alloys containing 6 wt pct Al. The coarsening of γ′ particles follows Ostwald ripening kinetics. Hardness testingin vacuo at temperatures up to 1750°F (955°C) shows that molybdenum also increases the elevated-temperature hardness significantly. The relation of elevated-temperature hardness to the volume fraction of γ′ is considered, and the influence of aluminum and titanium contents is discussed.

Carbon-13 nuclear magnetic resonance spectra of some carbonyl complexes of chromium, molybdenum, and tungsten

Abstract: 13 C N.m.r. spectra and some i.r. (carbonyl) stretching frequencies of the complexes [M(CO)6], [W(CO)nL6–n], [M′(CO)4(norbornadiene)], and [M(CO)3L′][M = Cr, Mo, or W; M′= Cr or Mo; and n= 1, 2, or 3; L = PEt3 and P(OMe)3, and n= 1; L′= mesitylene, 1,2,4,5-tetramethylbenzene, hexamethyibenzene, or cyclo-hepta-1,3,5-triene] are reported. The work includes the first reported measurement of 1J(95Mo–13C).

Carbon-13 nuclear magnetic resonance spectra of tungsten and molybdenum carbonyl derivatives

Abstract: 13 C N.m.r. data are presented for the series of complexes (CO)6–nMLn(where M = Mo or W; L = alkylphosphine, alkyl phosphite, bisdiphenylphosphinoethane, bisdiphenylphosphinomethane, and n= 1 or 2) and for the corresponding free ligands. Chemical shifts and coupling constants for the co-ordinated carbon monoxide and ligand carbons are compared with results from other spectroscopic techniques. The chemical shift of co-ordinated carbon monoxide is found to reflect the charge donor ability of L. The phosphorus to carbon monoxide coupling constants vary in a similar way to phosphorus–phosphorus coupling constants in this class of compounds and a dependence of 1J M–13CO on s-electron density at the metal atom is suggested.

Metal-coated diamonds in a metal alloy matrix

Abstract: A compact comprising substantially graphite-free diamond particles having a continuous coating of titanium or molybdenum held in a matrix into which the titanium or molybdenum can diffuse. The matrix may for example, be an alloy selected from the group of Fe/Ni, Ni/Co/Cr/Fe, Fe/Si and Ti/Si alloys. The invention also provides a method of making such a compact by mixing the desired metal powders in suitable proportions with the coated diamond particles and compacting the mixture under pressure and temperature conditions in the diamond stable zone.