High Wo Research Articles

Nanoporous WO3 grown on a 3D tungsten mesh by electrochemical anodization for enhanced photoelectrocatalytic degradation of tetracycline in a continuous flow reactor

• A nanoporous WO 3 /W electrode was obtained via mild anodization of W mesh. • Photo-electrocatalytic (PEC) degradation of tetracycline in continuous flow reactor. • PEC was 3x times more efficient than photocatalysis alone. • Continuous flow reactor design is scalable and highly efficient. The efficient removal of organic micropollutants remains a major challenge for conventional water treatment technology. Photocatalysis, while effective, has not been widely adopted due to cost and implementation challenges. Here, an effective alternative is proposed through the integration of photocatalytic and electrochemical degradation of tetracycline (TC) in a continuous flow reactor using a WO 3 /W mesh as photo-electrode. WO 3 nanoporous structures were grown on a tungsten (W) metal mesh via one step anodization in aqueous oxalic acid electrolyte (0.05 mol/L). The prepared materials were then used as 3D array photoanode in a continuous flow photo-electrocatalytic reactor. The combined influence of anodization time and post-treatment annealing temperature on the photo-electrochemical activity of the WO 3 /W mesh was examined through morphological and structural analysis. W mesh anodized for 4 h, and subsequently annealed at 450 °C have a homogenous nanoporous structure uniformly distributed and well adhering onto the W mesh, with average pore diameter of ∼ 80 nm and pore wall thickness of ∼ 250 nm. These materials are transparent, have high conductivity and WO 3 monoclinic phase. Under optimal conditions of recirculating flow rate of 230 mL min −1 and bias potential of + 1.0 V vs Ag/AgCl/KCl (3 mol/L), the photo-electrocatalytic degradation led to a TC removal of up to 90 % after 60 min of treatment, almost 3 times higher than photocatalysis only. The excellent results by integration of photocatalysis and electrochemical degradation in a flow reactor, combined with a scalable WO 3 /W mesh, offers a useful information for upscaling and designing for practical issues in water treatment (such as costs and efficiency).

High capacity WO 3 film as efficient charge collection electrode for solar rechargeable batteries

Abstract In this work, we demonstrated the dye-sensitized solar rechargeable batteries devices sharing a structure of Dye-TiO2/electrolyte/Ni/WO3. The WO3 film was prepared by a simple sol-gel process exhibit high cavities and large surface area allowing efficient chemical/electrical reactions. The WO3 films with 2 ± 0.5 μm in thickness as charge collection electrodes exhibited a high energy density over other materials reported thus far. Under irradiation energy of 7.5 mWcm−2 in the photo-charging, the discharging time sustained 1758 s at the current density of 0.05 mA cm−2 in dark, the first specific discharge capacities of WO3 nano-film reach 40.6 mAh g−1 (0.0244 mAh cm−2). This work substantially pushes forward the easy processing solar rechargeable batteries for future potential applications.

Preparation of highly dispersed W/ZrO2–Al2O3 hydrodesulfurization catalysts at high WO3 loading via a microwave hydrothermal method

Abstract A microwave hydrothermal (MWH) method was used to deposit WO 3 onto ZrO 2 –Al 2 O 3 with various ZrO 2 contents to prepare hydrodesulfurization (HDS) catalysts with high WO 3 loading (23 wt%) close to industrial hydrotreating, for achieving high W dispersion and weak W-support interaction. The catalysts with the same WO 3 and ZrO 2 contents were prepared by a conventional impregnation (IM) method as reference. The effects of catalyst preparation methods and ZrO 2 contents on the catalyst property and dibenzothiophene HDS activity were investigated. The results show that the MWH method leads to highly dispersed octahedrally coordinated W species which are weakly linked on ZrO 2 –Al 2 O 3 and easy to be reduced; no bulk WO 3 crystallites are observed even at high ZrO 2 content (50 wt%). Therefore, it causes better sulfidation and shorter WS 2 slabs. Contrarily, the IM method induces W species to agglomerate into bulk WO 3 crystallites which are poorly dispersed and hard to be reduced, which is further aggravated by ZrO 2 . The HDS activity of the MWH-prepared catalysts significantly increases with ZrO 2 up to 40 wt% ZrO 2 . This catalyst shows 2 times higher rate constant and 1.64 times higher efficiency of HDS than the IM-prepared catalyst with the same ZrO 2 content. For the IM-prepared catalysts, the HDS activity slightly increases at small amount of ZrO 2 (10 wt%) and then decreases drastically.

Geochemistry and petrology of komatiites of the Pioneer Ultramafic Complex of the 3.3 Ga Weltevreden Formation, Barberton greenstone belt, South Africa

The 3.3Ga Weltevreden Formation, located in the northern part of the Barberton greenstone belt, contains multiple complexes that are composed largely of well-preserved, partially serpentinized komatiitic rock. The Pioneer Ultramafic Complex is a 1-km-thick section of massive and differentiated komatiites and spinifex-textured komatiitic basalts that are interbedded with current-structured komatiitic tuffs. Most komatiites were emplaced subaqueously as large sheet flows that would on occasion pond, cool slowly and internally differentiate. Between effusive eruptions, explosive komatiitic volcanism resulted in the deposition of up to 60-m-thick sections of fine-grained ash. Massive komatiites preserve primitive olivines with a maximum Mg# of 92.9, supporting the eruption of a high temperature, high magnesian liquid. Al2O3/TiO2 (19–34) and Gd/YbN (0.84–1.15) ratios indicate that the komatiites and komatiitic basalts originated from Al-undepleted to slightly Al-enriched magma. Fresh pigeonite found in the cores of zoned pyroxenes suggests that crystallization occurred under anhydrous conditions. Similar to komatiitic augites analyzed in other areas of the Barberton greenstone belt, those in the Pioneer Complex possess both high Wo contents (0.31–0.46) and high Mg#s (75–90.2) but these features are not attributed to high dissolved water contents in the melt.

Ativação adrenérgica alterada se associa à recuperação anormal da Frequência Cardíaca?

Heart Rate Recovery (HRR) reflects the capacity of the cardiovascular system to reverse the vagal withdrawal caused by exercise. Scintigraphy with metaiodobenzylguanidine (I(123) MIBG) evaluates innervation and cardiac adrenergic activation. The association of these two methods is not well established. To evaluate the association between HRR and washout rate (WO) of I(123) MIBG in patients with heart failure (HF). Twenty-five patients with ejection fraction < 45% underwent exercise testing, and analysis of the variation of HRR from the 1st to the 8th minute after exertion. Submitted to I(123) MIBG, they were separated into groups by WO: G1) <27% and G2) ≥ 27%. For the statistical analysis Mann-Whitney's U test and Spearman's correlation coefficient were used. G2 showed a slower variation of HRR: 1st minute: G1: 21.5 (16.12 to 26.87) vs. G2: 11.00 (8.5 to 13.5) bpm, p = 0.001; 2nd minute: G1: 34 (29-39) vs. G2: 20 (14 - 26) bpm, p = 0.001; 3rd minute: G1: 46 (37.8 - 54.1) vs. G2: 30 (22 - 38) bpm, p = 0.005; 5th minute: G1: 51.5 (42 - 61) vs. G2: 39 (31.5 to 46.5) bpm, p = 0.013, and in the 8th minute: G1: 54.5 (46.5 - 62.5) vs. G2: 43 (34 - 52) bpm, p = 0.037. HRR in the 1st (r = -0.555, p = 0.004), and in the 2nd minute (r = -0.550, p = 0.004) were negatively correlated with WO. Patients with high HF and WO showed an abnormal HRR compared with patients with normal WO. These findings suggest that adrenergic activation may influence the HRR.

Raman spectroscopic study of structure of WO 3[sbnd]La 2O 3[sbnd]B 2O 3 glasses with no color and crystallization of LaBWO 6

Glasses with the nominal compositions of xWO 3 25La 2O 3 (75 − x)B 2O 3 (mol%) with x = 15, 25, and 50 were prepared using a conventional melt quenching method, and their structure and crystallization behavior were examined from Raman scattering spectra and X-ray diffraction analyses. The glasses are colorless in the visible light region and give the optical band gap energy of 3.49–3.61 eV. The glass transition and crystallization temperatures and the thermal stability against crystallization decrease with increasing WO 3 content. The strong Raman bands at 840 and 940–960 cm −1 suggest that the main coordination state of W 6+ ions in the glasses is isolated (WO 4) 2− tetrahedral units. The formation of WO 6 octahedral units is also suggested in the glasses with high WO 3 contents. The main crystallization mechanism in the glasses is the surface crystallization, and the glass of 50WO 3 25La 2O 3 25B 2O 3 shows the crystallization of LaBWO 6 single phase. The present study proposes that WO 3 La 2O 3 B 2O 3 glasses and crystallized glasses are very interesting as optical functional materials.

Structural effects of WO 3 incorporation on USY zeolite and application to free fatty acids esterification

Zeolites have occupied a distinguished position due to their unique properties as solid acids and catalytic results achieved in several industrial reactions. This work studied the influence of supported WO 3 on USY zeolite structure, acidity and activity towards an esterification reaction. High dispersion of WO 3 species on USY was achieved, but at higher loading (⩾11.4%), microcrystalites of WO 3 were detected below the theoretical monolayer coverage (∼32%). Tungsten species were deposited preferentially inside the zeolite structure and interacted with the Brønsted sites of USY as well as on silanol surface groups with the formation of small aggregates. In addition, dealumination took place, especially in the samples with high WO 3 loading. USY had the most and the strongest acidic sites (Brønsted type), but the incorporation of WO 3 decreased the amount and the strength of the new sites. However, all WO 3/USY catalysts were more active than USY in the esterification of oleic acid with ethanol (conversion above 74%, 2 h at 200 °C). The calculation of the TOF for a 1 h reaction demonstrated that 11.4% WO 3/USY was the most active catalyst. Furthermore, it had the lowest rate of deactivation of acid sites after the reaction (∼13% after four cycles). The better performance of the 11.4% WO 3/USY sample was also attributed to a better distribution of strength of the acidic sites and a more hydrophobic character of the synthesized material.

Glass formation and structure of glasses in the ZnO―Bi 2O 3―WO 3―MoO 3 system

The glass formation region in the ternary ZnO―Bi 2O 3―WO 3 system is determined by melt quenching technique (cooling rates 10 1–10 2 K/s). New original glasses are obtained in a narrow concentration range with high WO 3 content (60–75 mol%). Homogeneous glasses of the composition (100 − x)[0.2ZnO·0.3Bi 2O 3·0.5WO 3]xMoO 3, were obtained between 20 and 60 mol% MoO 3. Characterization of the amorphous samples was made by x-ray diffraction (XRD), differential thermal analysis (DTA) and infrared spectroscopy (IR). The thermal stability of glasses decreases with the increasing of MoO 3 content. The glass transition temperature, T g, varies between 340–480 °C, while the crystallization temperature, T x, varies between 388–531 °C. The tungstate glasses possess higher crystallization temperature (T x over 500 °C) in comparison with the other vanadate and molybdate non-traditional glasses. The glass network is realized by transformation of three-dimensional structure of WO 3 into a layered one, consisting mainly of WO 6 units. We supposed that the network of quaternary glasses is built up by MoO 4, MoO 6 and WO 6. At low concentration ZnO and Bi 2O 3 facilitate the disorder in the supercooled melts, while at high concentration stimulate crystallization processes. These oxides belong to the intermediate ones.

Influence of earth gravity on reaction engineering of tubular reactor for high concentration tungsten ion-exchange

The influence of gravity on the reaction engineering of tubular reactor is studied by analyzing the residence time distribution curves. The results show that upflow-feeding mode is more beneficial compared with downflow-feeding mode, since the flow pattern of the fluid in the reactor is closer to plug flow. The result of dynamic experiment conducted in ion-exchange of tungsten metallurgy is as good as that in reaction engineering of ion-exchange column. Whether downflow-feeding or upflow-feeding mode is adopted, breakthrough time decreases when solution concentration increases. Upflow-feeding mode has longer breakthrough time and greater improvement in adsorption capacity especially with high WO 3 concentration in ion-exchange.

Self-decontaminating layer-by-layer functionalized textiles based on WO 3-modified titanate nanotubes. Application to the solar photocatalytic removal of chemical warfare agents

Self-decontaminating photocatalytic textiles functionalized by the layer-by-layer approach with high aspect ratio WO 3-modified titanate nanotubes have been developed and successfully used under solar light illumination for the photocatalytic degradation of organophosphorous and organosulfide chemical weapon agents. This multilayer building method, unlike both dipping and spray techniques, has been efficiently applied to textile substrates using polyethyleneimine as counter polyelectrolyte for homogeneously functionalizing textiles by a thin layer of a dense network of entangled WO 3-modified titanate nanotubes, and preparing self-decontaminating photocatalytic textiles highly efficient toward the removal under solar light of the yperite blister live agent and of dimethylmethylphosphonate as neurotoxic agent simulant. Solar light responsive high surface WO 3-modified titanate nanotubes were synthesized by hydro-thermally treating TiO 2 powder, with tungstate salt impregnation prior to the final calcination step.

Structure and geochemistry of an Alaskan-type ultramafic–mafic complex in the Eastern Pontides, NE Turkey

The Karayasmak ultramafic–mafic association (KUMA) in NE Turkey represents an Alaskan-type, pre-Liassic intrusion in the Pulur metamorphic massif and is one of many such intrusive complexes that were emplaced into the continental basement of the Eastern Pontides belt during the pre-Liassic. Its main lithological units include plagioclase peridotite, melagabbronorite, banded gabbro and anorthosite (Phase-I), gabbro-pegmatite dikes (Phase-II), unmetamorphosed banded gabbro (Phase-III), cumulate olivine gabbronorite (Phase-IV), and non-cumulate gabbroic dikes and stocks (Phase-V). The contact relations between these units are gradational or intrusive, with the peridotites (Phase-I) enveloping the cumulate gabbronorites (Phase-IV) in the center of the elliptical body, displaying a concentric reverse-zoning pattern. Cr–Al spinel, plagioclase, and olivine are the first crystallizing phases in all cumulate rocks, whereas pyroxene, hornblende, phlogopite, magnetite, and ilmenite represent the intercumulus phases. The existence of hornblende and phlogopite, the high Wo and Cr 2O 3 contents of clinopyroxene, and the high Fo and NiO contents of olivine indicate that the KUMA units were the near-liquidus fractional crystallization products of hydrous basaltic magma. The Phase-I and Phase-III cumulates are slightly enriched in LILE and LREE, depleted in HFSE and HREE with respect to chondrite and primitive mantle, and show negative Nb, Zr, Hf and Ti anomalies. The Phase-IV cumulate gabbronorites are even more enriched in LILE and LREE and show less depletion in HFSE and HREE in comparison to the earlier phases. The KUMA units formed from high-Al hydrous basaltic magmas, which were derived from partial melting of a previously subduction-metasomatized subcontinental-lithospheric mantle. These magmas underwent crystal fractionation and mineral concentration processes in small magma chamber(s) at shallow crustal levels (< 5 kbar).

Crystallochemistry and origin of pyroxenes in komatiites

We present a detailed mineralogical and major- and trace-element study of pyroxenes in two Archean komatiitic flows in Alexo, Canada. The pyroxenes in spinifex-textured lavas commonly are zoned with cores of magnesian pigeonite and rims of augite. Concentrations of incompatible trace elements are low in pigeonite and jump to higher values in the augite mantles, a variation that can be modelled using accepted partition coefficients and assuming crystallization from komatiitic liquids. Crystallization sequences are very different in different parts of both flows. In the flow top, the sequence is olivine followed by augite: deeper in the spinifex sequence, pigeonite crystallizes after olivine, followed by augite; in lower cumulates, orthopyroxene or augite accompany olivine. In spinifex lavas, pigeonite crystallizes sooner than would be predicted on the basis of equilibrium phase relations. We propose that contrasting crystallization sequences depend on the position in the flow and on the conditions of crystal growth. In the flowtop, rapid cooling causes quench crystallization. Deeper in the spinifex layer, constrained growth in a thermal gradient, perhaps augmented by Soret differentiation, accounts for the early crystallization of pigeonite. The cumulus minerals represent a near-equilibrium assemblage. Augites in Al-undepleted Archean komatiites in various localities in Canada and Zimbabwe have high moderate to high Wo contents but their Mg# (Mg/(Mg + Fe) are lower than in augites in komatiites from Barberton, South Africa. We attribute the combination of high Wo and high Mg# in Barberton rocks to the unusually high CaO/Al2O3 of these Al-depleted komatiites.

Photochromic properties of tungstate-based glasses

Vitreous samples were prepared in the NaPO 3–BaF 2–WO 3 ternary system with high WO 3 concentrations. These glasses exhibit a strong absorption in the visible due to the presence of reduced tungsten species and the use of oxidizing species is required. The couple Sb 2O 3/NaNO 3 was introduced in the composition and allowed to obtain transparent glasses. These oxidized samples were illuminated by visible laser radiation and showed an efficient volumetric photochromic effect. The photosensitive effect appeared as a dark spot throughout the entire volume of the glasses. The effect was investigated by several techniques such as, UV-visible absorption, Raman and XANES at the L 1 and L 3 tungsten absorption edges. The results suggest a photoreduction of tungsten atoms without structural changes of the viteous network. Finally, the photochromic effect can be erased by thermal treatment at 200 °C for a few minutes.

The reduction of isomerisation activity on a WO 3/SiO 2 metathesis catalyst

By increasing the WO 3 loading on WO 3/SiO 2 metathesis catalysts it was observed that metathesis activity is closely related to the tungsten surface compound and not to the crystalline WO 3. It was observed that metathesis activity reached a maximum while WO 3 crystalline material continued to increase with increasing WO 3 loading. At high WO 3 loadings the formation of crystalline material also protected the active tungsten surface compound from deactivation by being the preferred species for over-reduction. The occurrence of branched metathesis products was attributed to an increase in Brønsted acidity indicating an alkoxide (carbenium ion) mechanism responsible for skeletal isomerisation. Reduction of branched metathesis products were achieved with the addition of small amounts of an alkali-metal ion. Large amounts of the alkali-metal ion resulted in a sharp decline in conversion indicating destruction of the Lewis acidity necessary for metathesis activity. Preparation of WO 3/SiO 2 catalysts at a pH above the iso-electric point of silica also had a significant effect on catalyst selectivity.

Low pressure into high pressure won't go

Low pressure into high pressure won't go

Cross sensitivity and stability of NO 2 sensors from WO 3 thin film

The H 2O, C 2H 5OH, CO, CH 4, NO and SO 2 cross sensitivity to NO 2 gas, as well as the long term stability of the electrical response of WO 3 thin films have been evaluated and discussed in the light of different preparation conditions and working temperatures. Thin films have been obtained by evaporating high purity WO 3 powder at 5 × 10 −4 Pa on sapphire substrates provided with Pt interdigital sputtered electrodes and annealed at 500°C for 6, 12 and 24 h. The film morphology, crystalline phase and chemical composition have been characterized through AFM, glancing angle XRD and XPS. The as-deposited film is amorphous with WO 3 stoichiometry on the surface, after annealing at 500°C the films are well crystallised but with preferential orientation of WO 3 along the (200) plane. The increasing of the annealing time shows a positive effect on the crystallite and grain size of the film, while the mean roughness and surface area difference slightly decrease. The binding energies of the annealed films are close to that of WO 3 and small downshifts from the characteristic binding energy of W 4 f 7 2 reflects the formation of oxygen vacancies on the longer time annealed films. All the films show the highest sensitivity to NO 2 gas (0.7–5 ppm concentration range), at 250°C working temperature. At this temperature and 1.7 ppm NO 2 the calculated sensitivities yield S = 12, S = 43 and S = 45 for 6, 12 and 24 h annealed films, respectively. No cross sensitivity has been found by exposing the WO 3 films to CO and CH 4. Negligible H 2O cross to NO 2 has resulted for the 24 h annealed film in the 40–80% relative humidity range, as well as to 300 ppm SO 2 and 10 ppm NO. Only 1000 ppm C 2H 5OH has resulted in a significant cross to the NO 2 measure. The increase in the annealing time had positive effects on the sensitivity, cross sensitivity and long term stability properties. The 45-fold increase in the resistance of the 24 h annealed on exposure to 1.7 ppm of NO 2, as well as the good long term stability properties of its electrical response, suggest the possibility of utilising the sensor for air-quality monitoring.

Random Samples

Random Samples

NO 2 sensitivity of WO 3 thin film obtained by high vacuum thermal evaporation

The gas sensitivity, selectivity and stability properties of WO 3 thin films for the detection of NO 2 gas in the concentration range 0.2–5 ppm, have been evaluated and discussed in the light of the preparation conditions and working temperature. Thin films were obtained by evaporating high purity WO 3 powder by an electrically heated crucible at about 5 × 10 −4 Pa on sapphire substrates provided with Pt interdigital type sputtered electrodes and annealed for 1 h at 400, 500 and 600°C. The film morphology, crystalline phase and chemical composition were characterised through AFM, low angle XRD and XPS. The electrical response was measured by means of DC current mode. The annealed films showed crystallographic orientation belonging to the triclinic structure of WO 3, while the as-deposited films were found to be amorphous. The binding energies of O 1s and W 4f confirmed the existence of the WO 3 phase, with a stoichiometric ratio close to the theoretical one. All the films showed the highest sensitivity to NO 2 at a working temperature of 200°C. The 500°C annealed film was found to be the most sensitive to NO 2 gas, compared to those annealed at 400 and 600°C. No cross sensitivity effects were found by exposing the sensors to CO, CH 4. WO 3 films showed strong sensitivity to C 2H 5OH and H 2O. Long term stability test at a working temperature of 350°C, performed by cycling the films in dry air and 5 ppm NO 2 revealed no substantial change in the electrical properties in terms of drift and sensitivity.

Effective Purification Method of Large Molecular Weight Proteins Using Conventional AOT Reverse Micelles.

Hydrophilic bulky proteins with molecular weights larger than 60 kDa, such as catalase, β-galactosidase, BSA and hemoglobin, can be easily solubilized into a micro water pool of AOT reverse micelles by the injection method. Those proteins and enzymes solubilized into reverse micelles maintain their activities and native structures, and can be back-extracted effectively to a new aqueous phase when the system pH is kept higher than their isoelectric points, pI, with low salt concentration, i.e. high water content. The back-extraction of hemoglobin is also partially achieved under these conditions. The efficiency of back-extraction is strongly influenced by the pH values in the feed protein solution and in the aqueous solution used for back-extraction, as well as KCl concentration in the solution. The pH values of both solutions should be higher than the protein pI together with high Wo or low salt concentration to preserve native structures and activities, since monomers and oligomers with relatively large molecular weight are likely to be denatured by association with ionic surfactant mediated by salt. In this case, both steric and electrostatic interactions between bulky proteins and micelles play dominant roles in the separation. By reducing interactions with micelles or surfactants, proteins solubitized in micelles can be effectively stabilized, and easily back-extracted to the aqueous phase without inactivation. The present method suggests an another way for the effective bioseparation of bulky proteins with high yields of activity.

Heat transfer from a fully-developed pulsating flow in a curved pipe

Numerical studies are made of the flow and heat transfer characteristics of a fully-developed pulsating flow in a strongly curved pipe. Emphasis is placed on delineating the effects of the Reynolds number, and pulsation amplitude and frequency. By using a toroidal coordinate system, the complete, time-dependent incompressible Navier—Stokes equations are formulated. The peripherally-uniform temperature condition is imposed on the pipe wall. Particular attention is given to heat transfer properties over substantially extended parameter ranges of the Reynolds number Re and the Womersley number Wo. Use is made of a well-established numerical solution procedure, with minor amendments. The computed results on the flow field are in close agreement with the existing data in the overlapping parameter ranges. The spatial distributions of axial and secondary flows are depicted. The time variations of flow structure are displayed. The numerical results on the spatial and temporal variations of the thermal field are presented. The circumferential profiles of local Nusselt number are plotted at selected instants. When Wo is small, the time- and space-averaged Nusselt numbers, Num, is lower for a pulsating flow than for a corresponding non-pulsating flow. At moderate and high Wo, however, the difference in Num between a pulsating and a non-pulsating flow is insignificant.