[en] Action of carbone dioxide on an aqueous suspension of vanadium pentoxyde gives an acid and yellow solution. The study of the composition of the product obtained by evaporation and of the physicochemical properties by methods as thermogravimetry and determination of electronic and IR spectra, allows to assert the existence of a carboxyvanadic derivative

[en] The equilibrium oxygen partial pressure over nonstoichiometric V₂O_5-x and the related two-phase mixture has been measured by coulometric titration using yttria-stabilized zirconia (YSZ) as the solid electrolyte at temperatures between 880 and 936 K. The nonstoichiometry (x) is observed up to 0.055 at 920 K and is related to the oxygen partial pressure (P_O2) as x∝P_O2^-1/4 in the region of x<0.017. This fact suggests the formation of the defect associate between an oxygen vacancy and a tetravalent vanadium ion. The equilibrium oxygen partial pressure over the coexisting mixture of V₂O₅ and V₄O₉ and the standard free energy change of the reaction, 4V₂O₅→2V₄O₉+O₂ at temperatures between 880 and 936 K are determined. 24 refs.; 8 figs.; 1 table

[en] Energy of preference of Ti²⁺, Ti³⁺, V²⁺, V³⁺, V⁴⁺, Cr³⁺, Cr⁴⁺, Cr⁶⁺ ions to octahedral positions is calculated using the equation connecting heats of oxide atomization and characteristic distances of metal-oxygen

[en] Electron-microscopic study showed that V205 irradiation by 120 keV electron beam in rather thick crystals provided possibility of procedure of two simultaneous processes: V205->V02 phase transformation - at the boundary with carbon; V205->V409->V02 - the absence of carbon. It is shown that these phase transformations are not the result of thermal effect. (author)

[en] Short note

No abstract available

[en] The diffusion coefficient of Li⁺ in the γ-lithium vanadium bronze (Li_1+xV₃O₈) has been measured with the long-pulse galvanostatic technique. Values ranging from 1.7 X 10^-7 cm²s^-1, at x=0.3, to 2.2 X 10^-8 cm²s^-1, at x=1.4, have been measured. The thermodynamic factors, d ln a/d ln c, determined from the OCV/x curve and from voltage relaxation after the current pulse, have a mean value of ∼ 15. The pseudo two-phase region observed in the OCV/x curve at high Li⁺ concentrations seems attributable to ordering of Li⁺ in specific sites and to alteration of the unit cell. This process is reversible as shown by X-ray diffractometry. Finally, from OCV/t plots at different x, the partial molar entropy of Li⁺ was determined. The values, on account of the large dE(x)/dt measured, are higher than those found for V₆O₁₃ or TiS₂. 19 refs.; 7 figs

No abstract available

[en] A vanadium dioxide (VO₂) and Gold nanotriangle composite sandwich structure (VO₂/Au/VO₂) was fabricated via nanosphere lithography technique. It exhibits reversible localized surface plasmon resonance tunability through external thermal stimuli VO₂ phase transition by tuning the near-field permittivity of Au nanotriangle. Compared optical response to the Au/VO₂ (bottom Au top VO₂) and VO₂/Au (bottomVO₂ top Au) composite nanotriangle arrays, VO₂/Au/VO₂ structure shows a largest wavelength shift of 42 nm and a largest transmittance modulation of 13.2% between the hot-metallic and cold-insulating states. And the wavelength shift of Au/VO₂ nanotriangle array is larger than that of VO₂/Au array for the higher electric intensity on top surface of Au nanotriangle. The results suggest that this sandwich architecture is one path for designing a plasmonic structure with tunable resonance responses that can be tailored by varying the top and bottom phase materials properties of the hybrid structures. (paper)

[en] An ab-initio cluster calculation of the electronic d-states in VO₂ has been made by using the self-consistent statistical exchange multiple scattering method. VO₆^8- octaedron was used to represent the tetragonal phase, and a V₂O₁₀^12- cluster with paired vanadium atoms was used for the monoclinic phase. Our results are in conflict with an explanation of the semiconducting gap in terms of simple distortion-induced band splitting