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91.
Antonio F. Fuentes M. Garza-Garc?&#x;a G. Mendoza-Suárez U. Amador 《Journal of solid state chemistry》2003,175(2):299-305
We describe in this work the synthesis and crystal structure of five rare earth and Mo(VI) or W(VI) containing complex perovskites. The compounds studied are Ba(Dy2/3Mo1/3)O3, Ba(Dy2/3W1/3)O3, Ba(Gd2/3Mo1/3)O3, Ba(Gd2/3W1/3)O3 and Ba(Sm2/3W1/3)O3 and were prepared starting from solutions, by the polymeric precursors method. Structural characterization by HREM, SAED and powder XRD revealed the five compounds to be ordered cubic perovskites, SG Fm-3m (225), with a cell parameter double of that of a simple perovskite cell and increasing as the size of the trivalent lanthanide ion increases (Dy<Gd<Sm). 相似文献
92.
Thin films of molybdenum trioxide were deposited on glass substrates employing direct current (DC) magnetron sputtering by
sputtering of molybdenum at different oxygen partial pressures in the range 8 × 10−5–1 × 10−3 mbar and at a substrate temperature of 473 K. The glow discharge characteristics of magnetron cathode target of molybdenum
were studied. The influence of oxygen partial pressure on the structural and optical properties of molybdenum trioxide films
was investigated. The films formed at an optimum oxygen partial pressure of 2 × 10−4 mbar were polycrystalline in nature with orthorhombic α- phase and an optical band gap of 3.16 eV. The refractive index of
the films formed at an oxygen partial pressure of 2 × 10−4 mbar decreased from 2.08 to 1.89 with increase of wavelength from 450 to 1,000 nm, respectively.
Paper presented at the Third International Conference on Ionic Devices (ICID 2006), Chennai, Tamilnadu, India, Dec. 7–9, 2006. 相似文献
93.
K.L. Man 《Surface science》2007,601(16):L95
The formation and stability of Cu, Ag and Au-induced c(2 × 2) alloys at the Mo(1 0 0) and W(1 0 0) surfaces have been investigated with low-energy electron microscopy and diffraction. The ordered alloys transform to disordered overlayer structures at elevated temperature. Comparison of the transformation temperatures with energetics obtained from first principles calculations reveals the vibrational entropic contribution to the system free energy that defines alloy thermal stability. Effective Debye temperatures for metal adatoms are determined that exhibit the expected mass and bond strength dependence. 相似文献
94.
Laser cladding of copper with molybdenum for wear resistance enhancement in electrical contacts 总被引:1,自引:0,他引:1
Laser cladding of Mo on Cu has been attempted with the aim of enhancing the wear resistance and hence increasing the service life of electrical contacts made of Cu. In order to overcome the difficulties arising from the large difference in thermal properties and the low mutual solubility between Cu and Mo, Ni was introduced as an intermediate layer between Mo and Cu. The Ni and Mo layers were laser clad one after the other to form a sandwich layer of Mo/Ni/Cu. Excellent bonding between the clad layer and the Cu substrate was ensured by strong metallurgical bonding. The hardness of the surface of the clad layer is seven times higher than that of the Cu substrate. Pin-on-disc wear tests consistently showed that the abrasive wear resistance of the clad layer was also improved by a factor of seven as compared with untreated Cu substrate. The specific electrical contact resistance of the clad surface was about 5.6 × 10−7 Ω cm2. 相似文献
95.
A Mo(V) oligophosphate, built up of di and triphosphate groups, Cs(MoO)4(P2O7)2(P3O10) has been synthesized for the first time. This compound crystallizes in the triclinic P−1 space group with , , , α=94.534(6)°, β=102.520(6)°, γ=103.663(4)°. This original structure can be described by the association of MoO6 octahedra, MoP2O11 units built up of one P2O7 group sharing two apices with the same MoO6 octahedron, and triphosphates groups P3O10. The resulting tridimensional framework forms large S-shaped tunnels running along c where the Cs+ cations are located. 相似文献
96.
S. Francis Amevor Hans-Ulrich Hund Albrecht Salzer 《Journal of organometallic chemistry》1996,520(1-2):79-84
A series of heterodimetallic complexes of general formula (C5R5)M(μ-CO)3RuC5Me5 (M = Cr, Mo, W; R = Me, Et) has been prepared in good yields by the reaction of [C5R5M(CO)3]− with [C5Me5Ru(CH3CN)3]+. (C5Me4Et)W(μ-CO)3Ru(C5Me5) was characterized by a crystal structure determination. The W---Ru bond length of 2.41 Å is consistent with the formulation of a metal-metal triple bond, while the unsymmetrical bonding mode of the three bridging carbonyl groups reflects the inherent non-equivalence of the two different C5R5M-units. Using [CpRu(CH3CN)3]+ or [CpRu(CO)2(CH3CN)]+ as the cationic precursor leads to the formation of dimetallic species (C5R5)M(CO)5RuC5H5 with both bridging and terminal carbonyl groups. 相似文献
97.
Vladimir L. Kolesnichenko Victor B. Rybakov Leonid A. Aslanov Sergei V. Volkov 《Journal of Cluster Science》1997,8(1):27-45
Thioselenohalide complexes Mo2(μ-S2)2Cl6(SeCl2)2 (I), Mo2(μ-S2)2Br6(SeBr2)2 (II), and W2(μ-S2)2Br6(SeBr2)2 (III) were synthesized by the reactions of corresponding metal halides or carbonyls or molybdenum metal with excesses of S2 X 2+Se2 X 2 mixtures. The complex W2(μ-S2)2Cl6(SeCl2)2 (IV) was obtained by an exchange reaction between (III) and excess of Se2Cl2. Coordination of the neutral SeX 2 ligands to thiohalidesM 2(μ-S2)2 X 6 results in higher thermal stability, and suggests the possibility to synthesize SeX 2 complexes of the unstable parent tungsten thiohalides. An unusual oxidative addition reaction of (I) was detected: {fx27-1} Both (I) and (IV) were characterized by X-ray crystal structure analysis. They are isostructural and form discrete molecules. Bridging S 2 2? ligands are coordinated perpendicularly to the metal-metal bond;d(M?M)=2.8066 Å and 2.793 Å for I and IV, respectively. Nonequivalence of chlorine atoms which are bound to the metal atom, relate to nonequivalence of halogen atoms in the complexesM 2(μ?S2)2 X 8 2? . Chlorine atomstrans to SeCl2 ligands form short bonds with the metal; the corresponding35Cl NQR frequency is increased. The selenium dichloride ligand is ambidentate. The selenium atom binds as a donor to the metal and as an acceptor to two chlorine atoms which are also bound covalently to the same metal atom. 相似文献
98.
含钼化合物及其配合物的抗癌抗肿瘤活性 总被引:4,自引:0,他引:4
钼是生命体所必需的微量元素。本文介绍了钼在人体中的作用,钼缺乏和钼过量对人体的影响,并介绍了含钼化合物以及配合物的抗癌抗肿瘤研究情况。 相似文献
99.
催化极谱法连续测定岩石中钨和钼 总被引:2,自引:0,他引:2
本文提出了在二苯基乙醇酸-二苯胍-氯酸钠催化极谱体系测钨后,加入少许钛铁试剂,使钼产生一个极灵敏的导数波。谊波形尖锐、对称,便于测量钼。建立的连测体系简便灵敏,用于岩石样品中钨和钼的测定,取得了满意的效果。 相似文献
100.
本文应用x-射线衍射(XRD)、X-射线光电子能谱(XPS)、俄歇电子能谱(AES)、扫描电子显微技术(SEM)研究了钼酸铵在石墨炉内石墨探针表面上的原子化机理。实验结果表明,在温度<1350K时,钼酸铵经历MoO_3和Mo_4O_(11)中间产物转变为MoO_2(s)。在更高温度下,MoO_2(s)首先还原为Mo_2C,而后进一步转变为MoC(s)。MoC再分解为Mo(s)。钼的原子化起源于Mo的升华。 相似文献