Niobates Reduction

Niobium Tetrachloride is reported to have been obtained in solution by the electrolytic reduction of a solution of sodium niobate in hydrochloric acid.7... 

Numerous complexes of niobium(IV) and niobium(V) halides with various nitrogen-donor ligands have been reported in the literature. The products obtained from these reactions are critically dependent upon the reaction conditions. " Tetrakis(isothiocyanato)bis(2,2 -bipyridine)niobium(IV) can be prepared directly from the hexakis(isothiocyanato)niobate(IV) complex or by the reduction of the hexakis(isothiocyanato)niobate(V) ion according to the published method. This method can also be extended to the preparation of other analogous complexes. 

Tetrakis(isothiocyanato)bis(2,2 -bipyridine)niobium(IV) is a medium-brown crystalline solid. It is only very slightly soluble in 1,2-dichloroethane, dichlo-romethane, and acetonitrile. These extremely dilute solutions of the complex readily decompose in the presence of oxygen or moisture however, in the solid state the complex appears to be air-stable. It does not melt or decompose below ca. 275°. The infrared spectrum, ultraviolet spectrum, magnetic moment, and x-ray powder diffraction pattern of the product obtained by this procedure are essentially identical to those obtained for the product prepared by the reduction of the hexakis(isothiocyanate)niobate(V) complex. ... 

Kameyama et al. [27] reported on UV light-assisted reduction of MV + in water and in aqueous alcohols, in the presence of partially exchanged niobate, H2.4Ki,6Nb60]7. Figure 14 shows the concentration of MV+ produced as a function of time in water and various aqueous alcohol solutions. It is found that methanol is the best reductant for MV + reduction. 

A sensitizer concentration of 5 x 10 mol g , at which a monolayer of the sensitizer molecules on the external surface of the niobate would be formed, was found to be ideal for efficient photocatalysis. At higher concentrations, the activity diminished. Also, an initial Pt loading of 0.05 wt. /) and a reduction temperature [for reducing Pt(NH3)4 + to Pt] of 450 °C were found to be optimum for this system. 

The poled and cured film of the polyimide/ASD has NLO coefficient, d33, of 28 pmAf-This d33 value is comparable to that of lithium niobate. The temporal stability at 25 and 120 °C of the second-order nonlinearity after poling and curing of the polyimide/ASD is demonstrated in Figure 3. The sample shows excellent temporal stability at room temperature. In contrast to the stability of a poled/cured ASD sample which showed a rapid decay of the d33 value at 100 °C,20 the poled/cured polyimide/ASD sample shows a stable d33, after an initial reduction of 27%, as it is subjected to a thermal treatment at 120 °C for over 168 h. The existence of polyimide in the ASD network shows a tremendous improvement in the temporal stability. This synergistic property is a result of high Tg of polyimide and the chain entanglement between the two polymers in the composite. 

Typically, fibers having diameters up to 100 (jm are readily possible fibers with diameters above 2()0 pm are technically speaking no longer fibers but rods. This includes the niobate fibers [46] and the superconducting fibers [14] [50] [33] [63] discussed below. In principle, the float zone method is a containerless process. There is a nominal diameter reduction in the float zone from that of the preform rod to that of the final fiber. Zone (or overall process) stability for the growth of oxide and fluoride fibers is usually achieved with diameter reductions in the range of 1/2 to 1/3 [14]. 

Strontium cobalt ferrites are good mixed conductors but are more suitable to be used as cathodes due to their p-type conduction. Pervoskite gaUates/niobates/barium cerate and chromium-doped lanthanum-strontium ferrite have also been studied as the anode material. Although the gaUates and niobates exhibit low conductivity, they exhibit good compatibihty with the LSGM electrolytes. The conductivity of yttrium-doped barium cerates increases by increasing yttrium content. For barium cerates, the increase in electronic conduction due to the reduction of cerium at low... 

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