Li+离子掺杂对红色发光材料Y2(W,Mo)O6:Eu3+发光性能的影响

采用高温固相法制备了荧光粉Y2-x(W,Mo)O6:Eu3+,xLi+,利用X射线衍射仪和电子扫描显微镜对样品的结构和形貌进行了表征,并利用荧光光谱法分析了样品的光谱特性.首先在Y2WO6中掺入少量的Mo6+离子,掺入Mo6+后增加了原Y2WO6:Eu3+的激发光谱在近紫外光区的吸收,扩展了激发光谱的谱宽,但却使Y2W...     

RE2O3-Al2O3-SiO2玻璃连接氮化硅合成复相陶瓷的研究

采用Ｙ２Ｏ３－Ａｌ２Ｏ３－ＳｉＯ２－Ｘ稀土玻璃进行氮化硅复相陶瓷的连接。用四点弯曲方法测定不同连接工艺下的连接强度。并对连接界面进行ＳＥＭ、ＥＰＭＡ和ＸＲＤ分析。液相钎料玻璃在界面上与氮化硅反应，形成氮化硅／Ｓｉ２Ｎ２Ｏ／Ｙ（Ｌａ）－Ｓｉａｌｏｎ玻璃／Ｙ（Ｌａ）－Ｓｉａｌｏ玻璃的梯度层界面。接头强度随着保温时间、妆温度的增加，先增后。 在ＹＡＳ钎料中添加氧化镧，可以提高接头的高温强度。ＬａＹＯ３的     

Beiträge zur Mikrobestimmung von Kohlenstoff-14 und Tritium

Die Verwendung Con¹⁴C und Tritium zur Lösung kinetischer und analylischer Probleme erfordert zuverlässige Analysenmethoden. Es wird iiber die Herstellimg von Meβgasen durch Naβcerbrennung mil Chromsäure-Jodsäure-Gemischen, Trockenverbrennung in Gegenwart Con Katalysatoren wie Kupferoxid, Kobaltoxid und Zersetzungsprodukte des Silberpermanganats und durch Umsetziingentm geschlossenen Rohr berichtet. Die Aktivitätsniessungen erfolgten auf cerschiedene IVeise. Hier werden besonders die Ergebnisse diskutiert, die durch Ionisationskammermessungen erzielt wurden. Schlieβlich werden einfache Apparaturen zur routinemäβigen Durchfiihrung von Mikroanalysen beschrieben.     

Palladium(II) complexes of Y,C,Y‐chelated phosphines: synthesis,structure, and catalytic activity in Suzuki–Miyaura reaction

The phosphines L¹PPh₂ (1) and L²PPh₂ (2) containing different Y,C,Y‐chelating ligands, L¹ = 2,6‐(^tBuOCH₂)₂C₆H₃^? and L² = 2,6‐(Me₂NCH₂)₂C₆H₃^?, were treated with PdCl₂ and di‐µ‐chloro‐bis[2‐[(N,N‐dimethylamino)methyl]phenyl‐C,N]‐dipalladium(II) and yielded complexes trans‐{[2,6‐(^tBuOCH₂)₂C₆H₃]PPh₂}₂PdCl₂ (3), {[2,6‐(Me₂NCH₂)₂C₆H₃]PPh₂} PdCl₂ (4), {[2,6‐(^tBuOCH₂)₂C₆H₃]PPh₂}Pd(Cl)[2‐(Me₂NCH₂)C₆H₄] (5) and {[2,6‐(Me₂NCH₂)₂C₆H₃]PPh₂}Pd(Cl)[2‐(Me₂NCH₂)C₆H₄] (6) as the result of different ability of starting phosphines 1 and 2 to complex PdCl₂. Compounds 3–6 were characterized by ¹H, ¹³C, ³¹P NMR spectroscopy and ESI‐MS. The molecular structures of 3,4 and 6 were also determined by X‐ray diffraction analysis. The catalytic activity of complexes 3–6 was evaluated in the Suzuki‐Miyaura cross‐coupling reaction. Copyright © 2010 John Wiley & Sons, Ltd.     

Iron(III), cobalt(II) and copper(II) complexes bearing 8‐quinolinol encapsulated in zeolite?Y for the aerobic oxidation of styrene

A series of Fe(III), Co(II) and Cu(II) complexes of 8‐quinolinol were encapsulated into the supercages of zeolite? Y and characterized by X‐ray diffraction, SEM, N₂ adsorption/desorption, FT‐IR, UV–vis spectroscopy, elemental analysis, ICP‐AES and TG/DSC measurements. The encapsulation was achieved by a flexible ligand method in which the transition metal cations were first ion‐exchanged into zeolite Y and then complexed with 8‐quinolinol ligand. The metal‐exchanged zeolites, metal complexes encapsulated in zeolite–Y plus non‐encapsulated homogeneous counterparts were all screened as catalysts for the aerobic oxidation of styrene under mild conditions. It was found that the encapsulated complexes always showed better activity than their respective non‐encapsulated counterparts. Moreover, the encapsulated iron complex showed good recoverability without significant loss of activity and selectivity within successive runs. Heterogeneity test for this catalyst confirmed its high stability against leaching of active complex species into solution. Copyright © 2011 John Wiley & Sons, Ltd.     

Emission Mössbauer studies of the magnetoresistive compound, La0.7Sr0.3MnO3

The magnetic behavior of the Sr_0.3 manganite is studied using a local microprobe, ⁵⁷Co. In contrast with Ca substituted manganites, a much larger fraction of the material exhibits short-range order with superparamagnetic-like behavior even at 80 K. The differences in behavior are attributed to the large mismatch between the ionic radii of La⁺³ and the divalent substituent Sr⁺², which introduces anharmonicity in local vibrations. In common with all other compounds exhibiting negative bulk magnetoresistivity, the Sr_0.3 compound also exhibits very marked softening of lattice as one approaches T_c from below. Application of an external magnetic field results in coalescing of nanosized magnetic clusters to form larger ones with better alignment of spins.     

Statistical emission of electrons from nanocrystalline silicon quantum dot memory nodes in a few-electron MOSFET memory device

Operation of a short and narrow channel metal-oxide-semiconductor field-effect transistor (MOSFET) memory device with a few nanocrystalline Si (nc-Si) dots in the active region has been investigated at 300 and 30 K. The discrete shift of the threshold voltage (V_th) in the current-voltage characteristics that arises from the screening effect of the charge stored in the nc-Si dot above the FET channel, suggests memory operation. It is found that the value of V_th changes with temperature whereas the magnitude of the shift in V_th is independent of temperature. The lifetime of the electrons stored in the floating node has also been investigated at different read voltages.