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91.
We studied the Y–Ba–Cu–O/Ag equilibrium diagram in oxygen atmosphere around the composition YBa2Cu3Ox/Ag35 mass%. We found a high thermal effect: the peritectic decomposition temperature of Y-123 phase is lowered from 1040
to 940°C. We demonstrate here that the nature of the phenomenon is not chemical. We explained it as the result of a mechanical
segregation of Y-123 decomposition products from Y-123 phase, performed by silver.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
92.
选择水杨基荧光酮-乳化剂OP-盐酸为显色体系,应用双波长分光光度法扣除硫酸锌的基体干扰,不分离直接测定了湿法炼锌过程中硫酸锌净化液中的痕量锗。测定范围在0-40mg/L。本法应用于株洲冶炼厂锌净化液中锗的测定,结果与该厂长期的萃取-比色法结果相吻合,而测定速度较萃取-比色法至少提高了一倍。 相似文献
93.
Shape-controlled synthesis of metal nanostructures: the case of silver 总被引:19,自引:0,他引:19
The concept of shape-controlled synthesis is discussed by investigating the growth mechanisms for silver nanocubes, nanowires, and nanospheres produced through a polymer-mediated polyol process. Experimental parameters, such as the concentration of AgNO(3) (the precursor to silver), the molar ratio between poly(vinylpyrrolidone) (PVP, the capping agent) and AgNO(3), and the strength of chemical interaction between PVP and various crystallographic planes of silver, were found to determine the crystallinity of seeds (e.g., single crystal versus decahedral multiply twinned particles). In turn, the crystallinity of a seed and the extent of the PVP coverage on the seed were both instrumental in controlling the morphology of final product. The ability to generate silver nanostructures with well-defined morphologies provides a great opportunity to experimentally and systematically study the relationship between their properties and geometric shapes. 相似文献
94.
用超高真空程序升温反应谱和瞬时应答方法研究了乙二醇在电解银表面的氧化,实验表明,室温下乙二醇吸附在电解银表面,并在343K分解给出一组产物群,预吸附氧与乙二醇反应时,在343K,433K和612K处给出三组产物群,它们分别对应于不同的表面反应,并给出了电解银催化乙二醇制乙二醛的活性结果。 相似文献
95.
Jason R McCarthyPatricia J Melfi Steven H CapettaChristian Brückner 《Tetrahedron》2003,59(46):9137-9146
The use of AgII as a removable template in synthetic porphyrin chemistry is described. Mild procedures for the insertion of AgII into chlorins and the demetallation of the [chlorinato]AgII complexes are delineated. The UV-vis spectra of the novel [chlorinato]AgII complexes are discussed. The diol cleavage products of [meso-tetraphenyl-2,3-diolchlorinato]silver(II) under a number of conditions are characterized and compared to those resulting from the cleavage of the corresponding free base diol chlorin or its NiII complex, highlighting the unique templating effect of AgII. The scopes and limits of electrospray ionization mass spectrometry (ESI-MS) for the analysis of AgII chlorins is described. The use of AgII as a templating metal is superior over NiII or ZnII for the preparation of free base pyrrole-modified porphyrins along metal templated pathways. 相似文献
96.
Takeuchi Y Nishikawa M Hachiya H Yamamoto H 《Magnetic resonance in chemistry : MRC》2005,43(8):662-664
High-resolution solid-state magic angle spinning (73)Ge NMR spectra of some organogermanium compounds were measured. Most tetrasubstituted germanes with identical substituents exhibited signals except for one case. Tetrasubstituted germanes with two kinds of different but somewhat similar substituents exhibited broad peaks. Trisubstituted germanes failed to show signals, indicating the importance of symmetry around germanium. 相似文献
97.
Rui M. Almeida Ana C. Marques Maurizio Ferrari 《Journal of Sol-Gel Science and Technology》2003,26(1-3):891-896
The present paper is focused on multilayer Er3+-doped silica-titania planar waveguides, co-doped with silver, which were prepared by spin-coating on silica glass, or buffered single crystal silicon substrates. The single layer thickness (0.4 m) and refractive index (1.60–1.63) were measured by spectroscopic ellipsometry at 715 nm. The thickness of the waveguides (measured by mechanical profilometry) was 1 m and their optical propagation losses were measured at different laser wavelengths (488 nm, 514 nm and 633 nm), exhibiting an approximately Rayleigh-like behavior. The thermal precipitation of silver nanocrystallites was achieved, both in air and under a controlled atmosphere (dry nitrogen) and these were characterized by visible absorption spectroscopy, which clearly showed the development of a plasmon absorption band near 415 nm, by X-ray diffraction (XRD) and Transmission Electron Microscopy (TEM). The Er3+ metastable level lifetimes for the emission at ca. 1.54 m were found to be ca. 4–6 ms, for Er3+ concentrations varying between 0.2–2.0 mol% (or (0.4–4.4) × 1020 ions/cm3), but no significant variation was observed with the Ag concentration added (up to 2.5 mol%). 相似文献
98.
Maksymilian Ignaczak Andrzej Grzejdziak Barbara Olejniczak 《Monatshefte für Chemie / Chemical Monthly》1989,120(6-7):515-527
Summary The conditional protonation constants (=0.1) for 2,2:6,2-terpyridine, logK
1=4.93, logK
2=3.69, were determined by thepH-metric method. The compositions of complexes of Ag2+ and Ag+ ions with 2,2:6,2-terpyridine (tp) were studied and equilibria of the complex formation process were described. The values of conditional complex formation constants are as follows: for Ag(tp)
2
+
:log01=5.79, log02=9.68, for Ag(tp)
2
2+
:log02=25.31, while the conditional constant of the Ag(tp)NO3 precipitate formation is:K
SO=2.45·104. Using coulometric and chronovoltamperometric measurements, the redox systems being formed in the complex solutions of Ag(II) and Ag(I) were determined and described including their formal potentials.
Komplexibildungsgleichgewichte und Redoxpotentiale des Systems Ag(II)/Ag(I) in Gegenwart von 2,2:6,2-Terpyridin in Wasser
Zusammenfassung Mit Hilfe derpH-metrischen Methode wurden die konditionalen Protonationskonstanten (=0.1) von 2,2:6,2-Terpyridin bestimmt: logK 1=4.93, logK 2=3.69. Es wurde auch die Zusammensetzung der Komplexe von Ag(II) und Ag(I) mit 2,2:6,2-Terpyridin(tp) bestimmt sowie die Gleichgewichte der komplexbildung beschrieben. Die Werte der Konditionalkomplexbildungskonstanten sind: für Ag(tp) 2 + :log01=5.79, log02=9.68, für Ag(tp) 2 2+ :log02=25.31 und für das Löslichkeitsprodukt Ag(tp)NO3:K SO –1 =4.08·10–5. Die in Komplexlösungen von Ag(II) und Ag(I) vorliegenden Redoxsysteme wurden mittels cyclischer Voltametrie und Coulometrie untersucht und die Formalpotentialwerte dieser Systeme in Wasser bestimmt.相似文献
99.
100.
《Surface and interface analysis : SIA》2003,35(2):174-178
Effective energy‐loss functions for Al, Cu, Ag and Au were derived from the reflection electron energy‐loss spectroscopy (REELS) spectra for 1 keV electrons using extended Landau theory. Features of the obtained effective energy‐loss functions are close to those of optical surface energy‐loss functions, revealing the significant contribution of the low energy loss below a few tens of electron‐volts in the REELS spectrum for Cu, Ag and Au. The REELS spectra were reproduced using the newly derived effective energy‐loss functions, leading to the confirmation that this type of database of the effective energy‐loss function is very useful not only for more comprehensive understanding of the measured spectrum of surface electron spectroscopies but also for practical background subtraction in surface electron spectroscopy. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献