Search results for "vanadium"

Proposal for a Dual Spin Filter Based on [VO(C 3 S 4 O) 2 ] 2–

2018

Polynuclear magnetic molecules often present dense electronic transmission spectra with many overlapping conduction spin channels. Single-metal complexes display a sparser density of states, which in the presence of a fixed external magnetic field makes them interesting candidates for spin filtering. Here we perform a DFT study of a family of bis- and tris-dithiolate vanadium complexes sandwiched between Au(111) electrodes and demonstrate that [VO(C3S4O)2]2– can behave as a dual spin filter. This means that an external electrical stimulus can switch between the selective transmission of spin-up and spin-down carriers. By using an electrostatic gate, we show that the onset for the spin-up co…

V-containing ZrO 2 inorganic yellow nano-pigments prepared by hydrothermal approach

2017

Abstract Recent results on the preparation, characterization and color properties of the V-containing ZrO 2 inorganic yellow nano-pigment are reported. A series of monoclinic V-ZrO 2 solid solution nanocrystals (V x Zr 1-x O 2 , being x = 0, 0.1, 0.02, 0.03, 0.04, 0.05, 0.065, 0.08 and 0.1) were prepared straightforward by hydrothermal processing of mixtures of zirconyl nitrate and ammonium metavanadate in water. Interestingly, the crystalline precipitated obtained by hydrothermal processing at 140 °C for 3 d was almost entirely V-containing ZrO 2 nanocrystals with the structure of monoclinic zirconia for the whole range of compositions. Lattice parameters changes along the series of prepar…

Changes in the local structure of nanocrystalline electrochromic films of hydrated nickel vanadium oxide upon ozone-induced coloration

2005

Hydrated thin films of nickel vanadium oxide (Ni1−xVxOy), made by reactive DC magnetron sputtering, were studied by x-ray absorption spectroscopy at the Ni and V K-edges using synchrotron radiation. The XANES signals were analysed within the full-multiple-scattering formalism, whereas EXAFS data were modelled within the multi-shell multiple-scattering approach. We found that transparent films exhibit a nanocrystalline NiO-type structure with homogeneous distribution of V ions substituting Ni ions. Exposure of the films to ozone resulted in dark brown coloration associated with an appearance of Ni3+ ions and accompanied by a modification of the local electronic and atomic structures of the V…

Mechanical activation conditions of the Fe2O3 and V2O3 mixture powders in order to obtain a nanometric vanadium spinel ferrite

1999

Abstract Co-milling of iron and vanadium oxides allows to obtain an intimate oxides mixture at a nanoscale, similar to a coprecipitate elaborated by soft chemistry. Reduction of such a mixture in the same temperature and oxygen partial pressure conditions (500°C and 10−25 Pa) as the soft chemistry products leads to a nanometric vanadium ferrite with the only spinel phase. The characterization of the powders is achieved by X-ray diffraction (XRD), scanning electron microscopy, infrared (IR) spectrometry, thermogravimetry and calorimetry. Homogeneity of grain size and chemical composition is reached if the initial oxides have similar grain size.

VS2 nanotubes containing organic-amine templates from the NT-VOx precursors and reversible copper intercalation in NT-VS2.

2004

Use of pure vanadium and niobium/copper inserts for laser welding of titanium to stainless steel

2020

Abstract Niobium and vanadium have high metallurgical compatibility with titanium and therefore can be used as inserts to avoid the accumulation of brittle intermetallic phases such as Fe2Ti during the fusion welding of titanium alloys with steels. In the present study, the continuous double pass welding of 1 mm thick Ti-6Al-4V alloy and 316 L stainless steel plates through several mm wide pure vanadium or niobium insert was studied. In case of a vanadium insert, a beam offset on the vanadium was found to produce cold crack formation in vanadium/316 L melted zones containing more than 40 wt.% V despite the absence of σ phase. Whereas a centered beam position and offset on the steel side pro…

Ethylene polymerization using vanadium catalyst supported on silica modified by pyridinium ionic liquid

2016

Nano-composite thermochromic thin films and their application in Energy-efficient glazing

2010

A hybrid atmospheric pressure and aerosol-assisted chemical vapour deposition strategy is presented as a facile route for the production of vanadium dioxide nano-composite thin films. The effect of the inclusion of gold nanoparticles and the use of a surfactant molecule, tetraoctylammonium bromide, is discussed. The films were fully characterised using a wide variety of techniques, including scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and UV/vis/NIR spectroscopy. It is shown that micro-structural changes brought about by careful control of film growth conditions, and/or the use of surfactant, lead to an enhancement of thermochromic properties. Gold nano…

Rietveld refinement study of vanadium distribution in V+4–ZrSiO4 solid solutions obtained from gels

2002

Abstract Vanadium-containing zircon gel precursors with nominal compositions Vx–ZrSiO4 with x=0.0, 0.004, 0.01, 0.04 and 0.2 were prepared by a previously reported colloidal sol-gel technique and annealed for 30 h at 1400 °C. The Rietveld refinement of the structures by X-ray powder diffraction confirms previous results concerning the limit of solubility of V+4 in the zircon structure. The new finding regarding with the entry of V+4 in the Zr+4 site for zircon doped with high contents of vanadium is in accordance with reported results.

Interactions between cells and titanium surfaces.

2002

The interaction between cells and implant materials is determined by the surface structure and/or surface composition of the material. In the past years, titanium and titanium alloys have proved their superiority over other implant materials in many clinical applications. This predominant behaviour is caused by a dense passive oxide layer which forms within milliseconds in oxidizing media. Titanium dioxide layers of 100 nm thickness were produced on the surface of cp-titanium grade 2, and on an experimental alloy of high vanadium content (Ti1.5Al25V) as a harmful control. The layers were produced by thermal and anodic oxidation and by coating by means of the sol-gel process. The resulting o…