172,888 research outputs found
Studies on Bis(imido) molybdenum complexes containing unsaturated hydrocarbon ligands
Get PDFThis thesis describes the synthesis and characterisation of molybdenum bis(imido) complexes containing unsaturated hydrocarbon ligands. A principal objective of the work was to examine the effect of various imido substituents on the coordination number of the complex and the orientations adopted by olefin and acetylene ligands. Chapter One highlights areas of transition metal chemistry relevant to the thesis, with particular emphasis on the psuedo-isolobal analogy between cyclopentadienyl and imido ligands, A convenient one-pot synthesis of molybdenum bis(imido) complexes of the type Mo(NR)(NR')Cl(_2).DME (R=R'=l-adamantyl, 2-t- BUC(_6)H(_4); R=2,6-i-Pr(_2)C(_6)H(_3), R'=t-Bu) is described in Chapter Two. Mo(N-l- adamantyl)(O)Cl(_2).DME has been synthesised, and its structure determined by single crystal X-ray diffraction.- The preparation of olefin complexes Mo(NR)(NR')(C(_2)H(_4))(PMe(_3))n (R=R'=l-adamantyl, n=l; R=R'=2-t-BuC(_6)H(_4), n=2; R=2,6-i-Pr(_2)C(_6)H(_3), R'=t- Bu, n=l) is outlined in Chapter Three. Structural information derived from NMR data has allowed comparison with metallocene-like olefin adducts. Chapter Four describes the synthesis of complexes containing σ-bound phenyl ligands (Mo(NR)(NR')(σ-C(_6)H(_5))(PMe(_3)) (R=R'=l-adamantyl, 2-t-BuC(_6)H(_4); R=2,6-i-Pr(_2)C(_6)H(_3), R'=t-Bu)) as potential precursors to benzyne complexes. Chapter Five describes the preparation of diphenylacetylene complexes Mo(NR)(NR')(PhC=CPh)(PMe(_3)), structural information derived from NMR data allows comparison with previously known metallocene-like acetylene complexes. Full experimental details for Chapters Two to Five are given in Chapter Six
Electrical, morphological and structural properties of RF magnetron sputtered Mo thin films for application in thin film photovoltaic solar cells
Get PDFMolybdenum (Mo) thin films were deposited using radio frequency magnetron sputtering, for application as a metal back contact material in ‘‘substrate configuration’’ thin film solar cells. The variations of the electrical, morphological, and structural properties of the deposited films with sputtering pressure, sputtering power and post-deposition annealing were determined. The electrical conductivity of the Mo films was found to increase with decreasing sputtering pressure and increasing sputtering power. X-ray diffraction data showed that all the films had a (110) preferred orientation that became less pronounced at higher sputtering power while being relatively insensitive to process pressure. The lattice stress within the films changed from tensile to compressive with increasing sputtering power and the tensile stress increased with increasing sputtering pressure. The surface morphology of the films changed from pyramids to cigar-shaped grains for a sputtering power between 100 and 200 W, remaining largely unchanged at higher power. These grains were also observed to decrease in size with increasing sputtering pressure. Annealing the films was found to affect the resistivity and stress of the films. The resistivity increased due to the presence of residual oxygen and the stress changed from tensile to compressive. The annealing step was not found to affect the crystallisation and grain growth of the Mo films
Roles of bulk γ(L)-Bi₂MoO₆ and surface β-Bi₂Mo₂O₉ in the selective catalytic oxidation of C₃H₆
Get PDFγ(L)-Bi₂MoO₆ (L: low temperature phase) catalysts, whose surface compositions have a Mo/Bi ratio above = 0.5, exhibited high selectivity in the partial oxidation of C₃H₆, while catalysts with Mo/Bi surface ratios near or below = 0.5 exhibited low selectivity. γ(L)-phase catalysts which have Mo/Bi surface ratios greater than = 0.5, were demonstrated to form β-Bi₂Mo₂O₉ on their surface. An interaction between the β- and γ(L)-phases was observed in these catalysts’ UV–vis spectra at 430 nm. The new β-phase material seems to grow along b-axis of γ(L)-phase, i.e., perpendicular to MoO₂–Bi₂O₂ layers. Structure visualizations revealed that the α-Bi₂Mo₃O₁₂, β-, and γ(H)-phases, which are selective catalysts, contain twin Mo tetrahedral structures, and that their Mo and Bi ions lie on the same plane. The pure γ(L)-phase does not contain this structure. A model for the very rapid transfer of oxygen between the γ(L)- and β-phases is discussed in relation to the kinetics of C₃H₆ oxidation.ArticleJournal of molecular catalysis. A, Chemical. 318(1-2):94-100 (2010)journal articl
Substituted metal carbonyls. Part 24. Heteropolymetallic oligomers [(OC)xM′(μ-L-L)M(CO)4(μ-L-L)M′(CO) x] and [(OC)5Mn-Mn(CO)4(μ-L-L)M(CO) 4(μ-L-L)(OC)4Mn-Mn(CO)5] [m = Cr, Mo or W; M′ = Cr, Mo, W (x = 5) or Fe (x = 4); L-L = Fe(C5H 4PPh2)...
No full textFull title: Substituted metal carbonyls. Part 24. Heteropolymetallic oligomers [(OC)xM′(μ-L-L)M(CO)4(μ-L-L)M′(CO) x] and [(OC)5Mn-Mn(CO)4(μ-L-L)M(CO) 4(μ-L-L)(OC)4Mn-Mn(CO)5] [m = Cr, Mo or W; M′ = Cr, Mo, W (x = 5) or Fe (x = 4); L-L = Fe(C5H 4PPh2)2 or Ph2P(CH2) mPPh2 (m = 2 or 3)], with metal carbonyl and diphosphine repeating units. A series of soluble oligomeric complexes of formulae [(OC) xM′(μ-L-L)M(CO)4(μ-L-L)M′(CO) x] [L-L = Fe(C5H4PPh2)2: M = Cr, M′ = Cr, Mo, W, Fe, or Mn2; M = Mo, M′ = Cr, Mo, Fe or Mn2; M = W, M′ = Cr or W. L-L = Ph2P(CH 2)mPPh2: M = Cr, M′ = Mo, m = 2 or 3. M′ = Cr, Mo, or W, x = 5; M′ = Fe, x = 4; M′ = Mn2, x = 9) has been isolated either as by-products in the syntheses of the bimetallics [(OC)xM′(μ-L-L)M(CO)x] or in a designed synthesis from cis-[M(CO)4(solv)2] (solv = solvent) (yields 1-18%). The repeating units are ferrocenyl or alkyl-chain diphosphine and metal carbonyl fragments and sometimes the oligomeric chains are supported by a M-M bond. The longest polymeric chain consists of seven metal atoms, Fe2MMn4. The linearity of the oligomeric propagation depends on the geometry of the central M(CO)4 unit, which is cis for Mo but trans for Cr or W. The geometrical preference is explained on steric and thermodynamic grounds, and the fluxionality of the five-co-ordinate intermediate. Nucleophilic attack by Me3NO on the bimetallics did not give oligomers through decarbonylation, but rather the phosphine oxide complexes [M(CO)5{Fe(C5H4PPh 2)(C5H4PPh2O)}] through dephosphination.link_to_subscribed_fulltex
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Comportamento eletroquimico e caracterização microestrutural dos aços sinterizados e nitretados por plasma contendo MO e Ni
Get PDFDissertação (Mestrado) - Universidade Federal de Santa Catarina, Centro de Ciências Físicas e Matemáticas.A fabricação de produtos via metalurgia do pó (M/P) é amplamente empregada na indústria, porém em aços sinterizados a presença de poros residuais decorrentes do processso de fabricação afeta o seu desempenho face à corrosão eletroquímica. Aplicou-se um tratamento superficial nas ligas, nitretação por plasma, visando melhorar a resistência à corrosão. Neste trabalho foram produzidas ligas na forma binária por M/P, Fe-5% Mo e Fe-10% Ni as quais foram sinterizadas a uma temperatura de 1250°C durante 2h e posteriormente nitretadas por plasma a uma temperatura de 540°C em uma mistura de 75%N2/25%H2 por 2h. O objetivo deste trabalho é avaliar o comportamento destas ligas sinterizadas, sinterizadas/nitretadas, frente à corrosão. Os ensaios eletroquímicos empregados para avaliar o comportamento das mesmas foram: Ecorr vs tempo, potenciodinâmico, potenciostático, realizados em uma solução de KNO3 1,25M, de onde derivaram os valores para os cálculos da taxa de corrosão. A Microestrutura das ligas sinterizadas e camada nitretada, foram analisadas por Microscopia Eletrônica de Varredura (MEV) e análise de energia dispersíva (EDAX). Entre as amostras de Fe-10%Ni sinterizadas e sinterizadas/nitretadas, não ocorreu diferença significativa nos ensaios potenciodinâmicos. O ensaio potenciostático revelou uma densa camada de óxido formada na liga sinterizada Fe-5%Mo, indicando a sua passivação. Em ambos os casos as amostras nitretadas não exibem uma melhora na resistência à corrosão
L. Petrazycki, Law and Mo-râlity
No full textL. Petrazycki, Law and Mo-râlity. In: Revue internationale de droit comparé. Vol. 7 N°3, Juillet-septembre 1955. pp. 672-673
L. Petrazycki, Law and Mo-râlity
No full textL. Petrazycki, Law and Mo-râlity. In: Revue internationale de droit comparé. Vol. 7 N°3, Juillet-septembre 1955. pp. 672-673
The rank of Mordell-Weil groups of surfaces
No full textMo J.-L. The rank of Mordell-Weil groups of surfaces / J.-L. Mo // Algebraic and geometric methods of analysis - 2023 : abstr. of the Intern. sci. conf., Odesa, 29 May - 1 June 2023 / [Odesa Nat. Univ. of Technology et al.] ; sci comm.: [Yu. Fedchenko, N. Konovenko et al.]. - Odesa, 2023. - P. 47-48. - Ref.: 4 ti
- …
