Xi:Irritant;7439-98-7Relevant articles and documents
Use of ionic liquids (ILs) for the IL-anion size-dependent formation of Cr, Mo and W nanoparticles from metal carbonyl M(CO)6 precursors
Redel, Engelbert,Thomann, Ralf,Janiak, Christoph
, p. 1789 - 1791 (2008)
Stable chromium, molybdenum and tungsten nanoparticles are obtained reproducibly by thermal or photolytic decomposition under argon from mononuclear metal carbonyl precursors M(CO)6 (M = Cr, Mo, W) suspended in the ionic liquids BMim+BF4-, BMim +OTf- and BtMA+Tf2N- (BMim+ = n-butyl-methyl-imidazolium, BtMA+ = n-butyl-trimethyl-ammonium, Tf2N = N(O2SCF 3)2, OTf = O3SCF3) with a very small and uniform size of 1 to 1.5 nm in BMim+BF4- which increases with the molecular volume of the ionic liquid anion to ～100 nm in BtMA+Tf2N- [characterization by transmission electron microscopy (TEM), dynamic light scattering and transmission electron diffraction (TED) analysis]. The Royal Society of Chemistry.
Phase and structural transformations in the Ni65Mo 20Cr15 alloy at changing the temperature of heat treatment
Ustinovshikov
, p. 470 - 473 (2014)
The ternary Ni65Mo20Cr15 alloy was studied using TEM after heat treatment at different temperatures. It has been shown that the tendency to phase separation which exists in the Ni/Mo diffusion couple at high temperatures leads to precipitation of crystalline particles of Mo atoms in the liquid solution. At lowering the heat treatment temperature to 1200 C, a phase transition ordering - phase separation occurs in the Ni/Mo diffusion couple, which results in dissolution of the particles of Mo atoms. At 650 C, there takes place precipitation of Ni2Mo phase particles, which can initiate intercrystalline embrittlement of Hastelloy-type alloys.
A novel growth mode of Mo on Au(111) from a Mo(CO)6 precursor: An STM study
Song, Zhen,Cai, Tanhong,Rodriguez, Jose A.,Hrbek, Jan,Chan, Ally S.Y.,Friend, Cynthia M.
, p. 1036 - 1043 (2003)
The growth of a submonolayer of metallic Mo prepared by chemical vapor deposition (CVD) of Mo(CO)6 on Au(111) was studied by scanning tunneling microscopy (STM). At low coverage, nanoscale Mo clusters grow at the elbow sites and in the fcc regions of the reconstructed Au surface. When the coverage increases, rather than decorating uniformly all elbows as found in physical vapor deposition (PVD), the Mo clusters aggregate but do not coalesce, forming ramified cluster islands. Within the islands, the clusters preferentially aggregate along the fcc troughs and the domain boundaries. At step edges, Mo clusters are found to grow at both upper and lower step edges. Differences between CVD and PVD are attributed to differences in the mobility of the nascent Mo species leading to growth. We hypothesize that the difference in mobility for the CVD process is due to the presence of CO from the precursor molecules. Oxidation of the Mo islands leads to their spreading, proving that the Mo clusters are either three-dimensional above or embedded in the surface of the gold substrate.
Visible Laser-Induced Nucleation and Growth of Cr, Mo, and W Films from the Hexacarbonyls. Reactivity of CO on Film Surfaces
Houle, F. A.,Singmaster, K. A.
, p. 10425 - 10439 (1992)
Continuous visible laser irradiation is used to deposit Cr, Mo, and W films from the hexacarbonyls by thermal excitation.Detailed analyses of the films by scanning Auger microscopy show that the Mo and Cr films are spatially inhomogeneous, having clean metal centers surrounded by contaminated metal rings.W films are completely pure.Depth profiles reveal that, prior to formation of clean Mo and Cr, an interfacial layer of contaminated material is deposited which becomes progressively metal rich as thickness increases.If such a layer is formed for W, it is very thin.The measured composition profiles are compared to calculated surface temperature distributions in order to extract information on the kinetics of CO dissociation and desorption during growth.The temperature and mechanism simulations show that CO desorption dominates above about 450 K, ensuring that pure metal is deposited.Below that temperature contamination occurs.Previous investigations of film growth from metal hexacarbonyls have led to the conclusion that film purity will only be high at temperatures exceeding 800 K, where recombinative desorption of CO is fast.The origins of the large discrepancy in temperatures are discussed.Chemical processes leading to growth of metal oxycarbide material at the film edges and film-substrate interface are explored using data from the catalysis literature.The strong parallels found between the laser-deposited material and supported catalysts formed from the hexacarbonyls suggest that the oxycarbide films may have significant Lewis acid-base character, leading to faster CO and metal-CO bond dissociation rates.Thus, formation of contaminated material appears to depend on local surface composition as well as temperature.
Watson, I. M.,Connor, J. A.,Whyman, R.
, p. 1794 - 1796 (1989)
Carbothermic reduction of copper, nickel, and cobalt oxides and molybdates
Lebukhova,Karpovich
, p. 890 - 893 (2008)
The carbothermic reduction of NiO, CoO, CuO, MoO3, and the MMoO4 (M = Ni, Co, Cu) molybdates has been studied by thermogravimetry. The results demonstrate that the reactivity of the molybdates with solid carbon, the sequence of reduc
Electrochemical and Chemical Behavior of Extra Molybdenum Atoms into the Chevrel Phase Host Network
Kaidi,Belin,Boulanger,Lecuire,Sergent,Chevrel
, p. 199 - 210 (1999)
In this paper, we present a comparative electrochemical study of copper insertion into series of Mo6Se8-xSx phases which are obtained through different synthesis processes. We show that α-, β-, and HT-forms can reversibly accommodate copper at room temperature. The variation of the integral copper insertion rate is a function of the sulfur content and the synthesis type of pseudobinaries. While the mechanism of copper intercalation is quite similar for the different Mo6Se8-xSx for a given x, there is a drastic difference for α- and β-Mo6S8 compound. This behavior is explained on the basis of structural considerations. If the extra Mo atoms, present in the lattice channels of the β form and HT-Mo6Se8-xSx, are not displaced by this copper intercalation, they are shown to be mobile through cationic exchange reactions and chemical deinsertion at higher temperature.
Srivastava, S. K.,Avasthi, B. N.
, p. 85 - 92 (1986)
Preparation and characterization of molybdenum disulphide catalysts
Srivastava,Avasthi
, p. 5032 - 5035 (1993)
Molybdenum disulphide has been prepared by atmospheric-pressure hydrogen reduction of molybdenum trisulphide in the temperature range 400-750°C for 4 h and characterized. Chemical analysis of the product confirmed the S to Mo ratio 2.00 as desired for MoS2, consistent with its thermogravimetric analysis data in an air atmosphere. MoS2 prepared under these reducing conditions possessed a hexagonal structure with n-type diamagnetic semiconducting behavior and a lower surface area. The catalytic activity of the MoS2 was studied for liquid-phase hydrogenation of nitrobenzene. X-ray studies on MoS3 when reduced at 750°C for 48 h indicated that MoS2 so formed is unstable, resulting in the formation of its over-reduced products Mo2S3 and Mo.
High-temperature solid-vapor and liquid-vapor transitions in binary and ternary chalcogenides La2S3, MoS2, Mo2S3 and LiInSe2
Vasilyeva,Nikolaev
, p. 89 - 93 (2008)
High heating rate thermo-microscopic analysis, analytical atomic-emission technique with inductively coupled plasma and differential dissolution method have been used to investigate solid-liquid and solid-liquid-vapor transitions of refractory chalcogenides La2S3, MoS2, Mo2S3 and LiInSe2. The techniques were effective in determining the total pressure and vapor phase composition over the compounds in large temperature and pressure ranges. As a result, for compounds that evaporate incongruently, the melting points corresponding to their strict stoichiometry, the decomposition pressure-temperature relations, and other new results of the T-x phase diagrams for the La3S4-La2S3, Mo-MoS2, and Li2Se-LiInSe2 systems were obtained.
Simulation of MoS2 crystal structure and the experimental study of thermal decomposition
Liu, Dachun,Chen, Xiumin,Li, Dianjun,Wang, Fei,Luo, Xiaogang,Yang, Bin
, p. 66 - 71 (2010)
In this paper, the theoretical calculations of MoS2 crystal geometries, energy band structure, electron density, electron density difference, density of states and Mulliken overlap population were carried out by density functional theory (DFT).
Hawkins, D. T.,Worrell, W. L.
, p. 271 - 273 (1970)
A study on the kinetics of hydrogen reduction of molybdenum disulphide powders
Mehdi Afsahi,Sohrabi, Morteza,Vasant Kumar,Ale Ebrahim, Habib
, p. 61 - 67 (2008)
In order to achieve direct reduction of molybdenite in presence of a sulphur scavenger such as CaO such that SO2 emission is completely avoided, it is important to maximise the rate of the partial reaction involving molybdenite and hydrogen (without lime) given the low thermodynamic driving force for this reaction. Accordingly, reaction of molybdenum disulphide powders with hydrogen was investigated by thermogravimetric method. Effect of temperature and concentration on the reaction rate was studied under such conditions that resistance to mass transfer arising from external film, between particles and intra-grain was negligible. The operating temperature ranged between 973 and 1173 K while the hydrogen concentration was varied between 30 and 100%. The experimental data obtained under the above conditions were analyzed by applying the shrinking unreacted core model . The reduction reaction was found to be first order with respect to the gaseous reactant. Pre-exponential factor and activation energy have been determined to be 3.91 × 103 cm min-1 and 139.0 kJ mol-1, respectively. Activation energy obtained from a fitted model, agreed well with the values determined from the model-free methods using isothermal measurements.
Facile synthesis of interstitial metal nitrides with the filled β -manganese structure
Prior, Timothy J.,Battle, Peter D.
, p. 138 - 147 (2003)
A new family of nitrides, Ni2-xM′xMo3N (M′=Co or Pd; 0≤x≤1.5), has been prepared pure by nitridation of commercially available crystalline metal oxides under reducing conditions (10% H2 in N2). The simple synthesis employs standard solid-state techniques and does not require the preparation of reactive precursors. Substitution of Ni by Co or Pd leads to a linear increase of the unit cell volume with composition. The temperature, composition, and magnetic-field dependence of the molar magnetisation suggest that the introduction of Co, but not Pd, increases the degree of electron localisation in Ni2-xM′xMo3N. The same synthetic method has also lead to the formation, in mixtures, of the new phases π-Co2Mo3N and Pd2N.
Nanjundaswamy, K. S.,Gopalakrishnan, J.
, p. 188 - 192 (1987)
Koyama, Koichiro,Hashimoto, Yasuhiko,Omori, Shinichiro,Terawaki, Kazuo
, p. 223 - 232 (1986)
Relationship between pack chemistry and growth of silicide coatings on Mo-TZM alloy
Majumdar, Sanjib,Sharma, Indrakumar,Samajdar, Indradev,Bhargava, Parag
, p. D734-D741 (2008)
A theoretical model equation has been derived to relate the growth kinetics of silicide coating with the pack chemical composition and other processing conditions for siliconizing of Mo-TZM (Mo-0.5Ti-0.1Zr-0.02C) alloy to improve its oxidation resistance at high temperatures. A series of experiments conducted with varying pack Si (1-10 wt %) and N H4 F (2-20 wt %) content, time (1-25 h), and temperature (800-1200°C) confirmed the validity of the model. MoSi2 was the main coating layer formed during the siliconizing process. Optimum processing conditions were derived for doping of Al in MoSi2 to form Mo (Si,Al)2 in the outer layer of the coating.
Gupta, C. K.,Jena, P. K.
, p. 148 - 150 (1968)
SELECTIVE MOLYBDENUM DEPOSITION BY LPCVD.
Lifshitz,Williams,Capio,Brown
, p. 2061 - 2067 (1987)
Molybdenum films have been deposited by low pressure chemical vapor deposition (LPCVD) on silicon substrates by the reduction of molybdenum hexafluoride in hydrogen and argon atmospheres. The deposition is extremely selective, with no Mo observed on silic
The Metathesis of Propylene Catalyzed by Model Oxides Studied Using a High-Pressure Reactor Incorporated into an Ultrahigh Vacuum Chamber
Bartlett,Molero,Tysoe
, p. 470 - 481 (1997)
The olefin metathesis activity of a series of model catalysts consisting of metallic molybdenum, MoO2, or MoO3 is investigated using a combined high-pressure reactor/ultrahigh vacuum apparatus. The model catalysts are analyzed using X-ray and ultraviolet photoelectron, Raman, and Auger spectroscopies and it is shown that MoO2 is the most active above ～650 K. Reaction in this temperature regime proceeds with a high activation energy (～60 kcal/mol). Another, lower-activation-energy (～6 kcal/mol) regime is encountered for reaction below ～650 K and it is suggested that both reactions proceed simultaneously. In addition, the absolute rate and selectivity for the reaction on MoO2 below 650 K are similar to those found for high loadings of supported molybdenum oxide, suggesting that an oxide layer provides a good model catalyst for this reaction. It is also found that reaction proceeds in the presence of a thick carbonaceous layer where the thickness of this layer decreases with increasing oxidation state. A Raman analysis of the surface of the catalyst following reaction indicates that this layer consists predominantly of hydrocarbon species, although a small amount of graphitic carbon is detected.
Effect of sulfidation atmosphere on the hydrodesulfurization activity of SiO2-supported Co-Mo sulfide catalysts: Local structure and intrinsic activity of the active sites
Okamoto, Yasuaki,Hioka, Kazuya,Arakawa, Kenichi,Fujikawa, Takashi,Ebihara, Takeshi,Kubota, Takeshi
, p. 49 - 59 (2009)
The effects of the sulfidation atmosphere on the local structure and intrinsic activity of the active sites, Co-Mo-S, are studied with SiO2-supported Co-Mo sulfide catalysts prepared by a chemical vapor deposition method using Co(CO)3/sub
Electrodeposition of metallic molybdenum films in ZnCl2-NaCl-KCl-MoCl3 systems at 250 °C
Nakajima, Hironori,Nohira, Toshiyuki,Hagiwara, Rika
, p. 3776 - 3780 (2006)
Molybdenum metal film has been electrodeposited in ZnCl2-NaCl-KCl (0.60:0.20:0.20, in mole fraction) melt containing MoCl3 at 250 °C. In this melt, a dense film was obtained by potentiostatic electrolysis at 0.15 V versus Zn(II)/Zn for 3 h. However, the film had a thickness of smaller than 0.5 μm and was not adhesive. On the other hand, addition of 4 mol% of KF to the melt led to larger cathodic current in cyclic voltammogram, and gave a dense, adhesive and thicker metal film of ca. 3 μm thickness in the same electrolysis condition as above. The present process is promising as a new method for molybdenum coating at low temperatures.
The influence of phase and morphology of molybdenum nitrides on ammonia synthesis activity and reduction characteristics
Mckay,Hargreaves,Rico,Rivera,Sun
, p. 325 - 333 (2008)
The reactivities of a series of ternary and binary molybdenum nitrides have been compared. Data have been obtained for the catalytic synthesis of ammonia at 400 °C and ambient pressure using a 3:1 H2:N2 mixture. Amongst the ternary nitrides, the mass normalised activity is in the order Co3Mo3N>Fe3Mo3N?Ni2Mo3N. For the binary molybdenum nitrides, the ammonia synthesis activity is significantly lower than that of Co3Mo3N and Fe3Mo3N and varies in the order γ-Mo2N～β-Mo2N0.78?δ-MoN. Nanorod forms of β-Mo2N0.78 and γ-Mo2N exhibit generally similar activities to conventional polycrystalline samples, demonstrating that the influence of catalyst morphology is limited for these two materials. In order to characterise the reactivity of the lattice nitrogen species of the nitrides, temperature programmed reactions with a 3:1 H2:Ar mixture at temperatures up to 700 °C have been performed. For all materials studied, the predominant form of nitrogen lost was N2, with smaller amounts of NH3 being formed. Post-reaction powder diffraction analyses demonstrated lattice shifts in the case of Co3Mo3N and Ni2Mo3N upon temperature programmed reaction with H2/Ar. Incomplete decomposition yielding mixtures of Mo metal and the original phase were observed for Fe3Mo3N and γ-Mo2N, whilst β-Mo2N0.78 transforms completely to Mo metal and δ-MoN is converted to γ-Mo2N.
Densification behavior of Mo nanopowders prepared by mechanochemical processing
Kim, Gil-Su,Kim, Hai Gon,Kim, Dae-Gun,Oh, Sung-Tag,Suk, Myung-Jin,Kim, Young Do
, p. 401 - 405 (2009)
The sintering behavior of molybdenum (Mo) nanopowder was investigated in comparison to that of commercial Mo powder. At a sintering temperature of 1400 °C, the relative density of Mo nanopowder (94%) was found to be higher than that of commercial powder (
FLUORESCENCE ANALYSIS OF LASER PRODUCED RADICALS AND ATOMS
Hohmann, H.,Radloff, W.
, p. 273 - 278 (1990)
The IR-MPD of C2H4 and C2H5Cl leads to C2-radicals in electronic excited states (d3 ? g) and electronic ground state (a3 ? u).Treating the measured fluorescence of the C2-radicals in the visible range as a measure for the radical concentration, we have found that the radical concentration depends quadratically on the laser fluence and with the power of 2 on the parent gas pressure.The addition of buffer gas Xe leads to an enhancement of the radical concentration due to rotational relaxation. --- By UV-photolysis of Mo(CO)6 neutral Mo-atoms are produced (at 308 nm as well as 248 nm). --- The intensity dependences of the fluorescence of the excited Mo-atoms indicate direct 2-photon absorption at 248 nm and 3- or 4-photon absorption at 308 nm.An upper limit of the dissociation energy is estimated to be Ediss = 5.6 eV.
Synthesis of Molybdenum Nitrides
Kuznetsov, V. Ya.,Orlov, V. M.,Osaulenko, R. N.
, p. 1113 - 1121 (2020/11/20)
Abstract—: We have studied the effect of precursors on the synthesis conditions and characteristics of molybdenum nitrides. Mo, MoO3, and MgMoO4 powders were nitrided in flowing ammonia at temperatures in the range 500–800°C. The use of molybdenum nanopowder as a precursor has made it possible to reduce the synthesis temperature and time. We have demonstrated the possibility of direct ammonolysis of the double oxide MgMoO4. Using this molybdate, we have obtained a material with a specific surface area up to 29 m2/g, which is a factor of 2 to 3 larger than that reached by nitriding MoO3. In all cases, the synthesis products consisted of the γ- and β-phases of Mo2N, with cubic and tetragonal lattices, respectively.
