Zirconium compounds physical

The present study focused on the structure elucidation of heteropolyacid salts named Zirconium Antimonoarsanotungstate Zr[SbAsW] salt synthesised at variable pH using sol-gel route. Instrumental technique, IR was used to assign the structural aspects to the compound. Physical characterisation... 

Previously we reported the preparation of all members of zirconium compounds of (Mef,-C5H5 j )2ZrCl2 and their use in propylene polymerizations. The number and the position of methyl groups on cyclopentadienyl(Cp) rings were confirmed to exert great influence on the physical properties of atactic polypropylene. ... 

Kroll process, 13 84-85 15 337 17 140 in titanium manufacture, 24 851-853 Kroll zirconium reduction process, 26 631 KRW gasifier, 6 797-798, 828 Krypton (Kr), 17 344 commercial, 17 368t complex salts of, 17 333-334 doubly ionized, 14 685 hydroquinone clathrate of, 14 183 in light sources, 17 371-372 from nuclear power plants, 17 362 physical properties of, 17 350 Krypton-85, 17 375, 376 Krypton compounds, 17 333-334 Krypton derivatives, 17 334 Krypton difluoride, 17 333, 336 uses for, 17 336... 

A C2-symmetric ansa metallocene is a racemic mixture of an enantiomeric pair—an example is rac-(dimethylsilyl)bis(l-indenyl)zirconium dichloride (XXXIV), abbreviated as rac-(CH3)2SiInd2ZrCl2. The enantiomers are designated as (R, R) and (S, S) to describe the two coordination sites in each enantiomer. Actually, the synthesis of a C2 ansa metallocene usually produces a mixture of the racemic pair plus the meso compound (R, S). The meso compound, which is a diastereomer of the racemic pair, can be separated from the racemic mixture by physical techniques such as recrystallization. The meso stereoisomer possesses Cs symmetry, and its stereoselectivity is very different from that of the enantiomeric pair (Sec. 8-5a-3). 

Chapters S, 6, and 7 take up uranium, thorium, and zirconium in that order. Each chapter discusses the physical and chemical properties of the element and its compounds, its natural occurrence, and the processes used to extract the element from its ores, purify it, and convert it to the forms most useful in nuclear technology. 

In the 1980s, reports from Corbett s and Simon s laboratories presented a then-new chemistry based on interstitially stabilized clusters of zirconium and the rare-earth elements. " Coincident with those discoveries, molecular orbital schemes were offered to aid in understanding the electronic factors that exert influence on the stability of these cluster-based compounds. Nevertheless, direct physical measurements that supported the schemes were relatively scarce, and were almost entirely restricted to magnetic susceptibilities. " " ... 

The term upconversion describes an effect [1] related to the emission of anti-Stokes fluorescence in the visible spectral range following excitation of certain (doped) luminophores in the near infrared (NIR). It mainly occurs with rare-earth doped solids, but also with doped transition-metal systems and combinations of both [2, 3], and relies on the sequential absorption of two or more NIR photons by the dopants. Following its discovery [1] it has been extensively studied for bulk materials both theoretically and in context with uses in solid-state lasers, infrared quantum counters, lighting or displays, and physical sensors, for example [4, 5]. Substantial efforts also have been made to prepare nanoscale materials that show more efficient upconversion emission. Meanwhile, numerous protocols are available for making nanoparticles, nanorods, nanoplates, and nanotubes. These include thermal decomposition, co-precipitation, solvothermal synthesis, combustion, and sol-gel processes [6], synthesis in liquid-solid-solutions [7, 8], and ionothermal synthesis [9]. Nanocrystal materials include oxides of zirconium and titanium, the fluorides, oxides, phosphates, oxysulfates, and oxyfluoiides of the trivalent lanthanides (Ln ), and similar compounds that may additionally contain alkaline earth ions. Wang and Liu [6] have recently reviewed the theory of upconversion and the common materials and methods used. 

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