Papers by Keyword: Vanadium Pentoxide

Abstract: In the present work, vanadium pentoxide (V₂O₅) nanoparticles have been investigated for monitoring ethanol (C₂H₅OH) at ppm levels in air. A one-step flame spray pyrolysis (FSP) process has been applied for the synthesis of vanadium pentoxide (V₂O₅) and platinum-loaded vanadium pentoxide (Pt-V₂O₅) nanoparticles. The samples have been studied to characterize their morphological and microstructural properties by X-ray diffraction and transmission electron microscopy. Pt addition to V₂O₅ samples were verified by energy dispersive X-ray spectrometry mode. The specific surface area of the nanoparticles was measured by nitrogen adsorption method. The application of the produced nanoparticles as sensitive and selective ethanol resistive sensor has been demonstrated. The Pt-loaded V₂O₅ sensor has shown higher response towards ethanol at ppm-level concentrations compared to unloaded one.

Abstract: Comparative work of erbium doped vanadium pentoxide and titanium dioxide thin films were carried out via sol gel technique by dissolving erbium (III) nitrate pentahydrate in vanadium (V) oxoisopropoxide and titanium (IV) isopropoxide. Fourier Transform IR and thermogravimetric/differential thermal measurements were performed to find out erbium substitution. UV-Vis. spectroscopy indicated a blue shift upon Er doping in V₂O₅ film due to the softening of V=O bond. The similar behavior was expected in TiO₂ film and the prediction shall be shown only if annealing of the film above 600°C, resulting oxygen deficiency in anatase TiO₂ while Ti deficiency in rutile TiO₂ film. Due to such impact of erbium on structure, granule size of the films, determined by AFM, increased yielding more space for intercalation of ion in host materials and monitored through cyclic voltammetry measurements.

Abstract: Keywords: vanadium pentoxide；carbon black；reduction and nitridation；vanadium nitrogen alloy. Abstract. The V₂O₅ extracted from low vanadium shale and carbon black are used as raw materials to prepare briquetting samples through mixing, grinding and pressing. The samples are prereduced, final reduced and nitrated to produce vanadium nitrogen alloy with high nitrogen content. Thermodynamic analysis and experiment results show that：（1）In order to avoid V₂O₅ volatilization loss during reduction, the briquetting samples should be pre-reduced for 4 hours below the melting point 670°C of V₂O₅, which can transform V₂O₅ into low valence vanadium oxide.（2）During V₂O₅ being self-reduction under N₂ atmosphere, if the final reduction temperature is below 1271°C, the VN is preferential formation; if more than 1271°C, the reduced product forms V₄C₃.（3）To make a product with high nitrogen and low carbon content, the final reduction and nitride temperature should be controlled below 1300°C.

Abstract: Laminated thin films composed of V2O5 and Pd (or Pt-Pd) layers were deposited on glass substrates and the end faces of multimode optical fibers, and the sensitive behaviors of the thin films to hydrogen gas were studied using a UV-visible spectrophotometer and an optical fiber sensor’s experimental setup. Both the thickness of the V2O5 layer and that of the Pd layer have obvious influences on the sensitivity performance of the Pd/V2O5 films. The Pd (30 nm)/V2O5 (280 nm) film deposited on a glass substrate is sensitive to 0.1% hydrogen and the highest change in relative transmittance is about 25% when exposed to 4% hydrogen. Pd/V2O5 films were coated onto the end faces of multimode fibers to form optical fiber sensors. The response time of the Pd (20 nm)/V2O5 (280 nm) sensor is about 50 s and the change in relative reflected light intensity is about 18% upon exposure to 4% hydrogen. Deposition of Pt-Pd double layer instead of Pd signal layer over V2O5 can reduce the response time of the sensor. The response time of the Pd (20 nm)/V2O5 (280 nm) sensor is about 50 s, while that of the Pt (10 nm)-Pd (10 nm)/V2O5 (280 nm) sensor is about 25 s.

Abstract: A novel coordinated nano-material containing vanadium with regular helical chains has been prepared via a hydrothermal procedure by using 2,3-Diaminephenazine (2,3-DAP) and vanadium pentoxide (V2O5) as starting materials without the aid of any surfactants and templates. Then the products of V2O5 nanohelix complexes were characterized by using XRD, SEM, FT-IR, NMR, and TEM. Furthermore, the electrochemical property of the V2O5 nanohelixes was determined by the voltammetric technique.

Abstract: Vanadium pentoxide xerogel films intercalated by poly (ethylene oxide), PEO, were prepared using direct intercalation method via a sol-gel route. The electrical and electrochromic characterization of the films were conducted. The electrical properties along and across V-O layers have been evaluated. The results indicate that the proper amount of PEO can increase the electrical conductivity and charge density of the films. The electrochromism of the films upon lithium intercalation was investigated by ex-situ transmittance measurement. The films display a reversible multichromism (orange
green
blue) upon Li+ ion insertion/extraction.

Abstract: V2O5 microparticles of 0.3-0.6 μm in diameter were prepared from VO(O-C3H7 i)3 in an ethanol solution by the sol-gel method. The addition of poly(ethylene glycol) and acetyl acetone into the sols was effective to control the size and spherical shape of V2O5 particles. The particles thus obtained were amorphous having a layered structure with hydrated water, and transformed into an orthorhombic phase at 500°C through a glassy state. The microparticles were positively charged in I2-containing acetone, so that they were electrophoretically deposited on the cathode with applied DC voltage. The prepared particles were used as a cathode in an electrochemical cell with a lithium metal as an anode. Discharge capacity of a rechargeable cell of Li / LiPF6 (ethylene carbonate + diethylene carbonate) / V2O5 -based composite was 110-180 mAh g-1 when the potential range and current density were 2-4 V and 0.1 mAcm-2, respectively.