Tungsten Oxide Nanopowders Research Articles

A New Method for Tungsten Oxide Nanopowder Deposition on Carbon-Fiber-Reinforced Polymer Composites for X-ray Attenuation

A new method for the synthesis and deposition of tungsten oxide nanopowders directly on the surface of a carbon-fiber-reinforced polymer composite (CFRP) is presented. The CFRP was chosen because this material has very good thermal and mechanical properties and chemical resistance. Also, CFRPs have low melting points and are transparent under ionized radiation. The synthesis is based on the direct interaction between high-power-density microwaves and metallic wires to generate a high-temperature plasma in an oxygen-containing atmosphere, which afterward condenses as metallic oxide nanoparticles on the CFRP. During microwave discharge, the value of the electronic temperature of the plasma, estimated from Boltzmann plots, reached up to 4 eV, and tungsten oxide crystals with a size between 5 nm and 100 nm were obtained. Transmission electron microscopy (TEM) analysis of the tungsten oxide nanoparticles showed they were single crystals without any extended defects. Scanning electron microscopy (SEM) analysis showed that the surface of the CFRP sample does not degrade during microwave plasma deposition. The X-ray attenuation of CFRP samples covered with tungsten oxide nanopowder layers of 2 µm and 21 µm thickness was measured. The X-ray attenuation analysis indicated that the thin film with 2 µm thickness attenuated 10% of the photon flux with 20 to 29 KeV of energy, while the sample with 21 µm thickness attenuated 60% of the photon flux.

Tungsten oxide nanopowders: pulse alternating current electrosynthesis, structure optimization and performance in a flow photocatalytic fuel cell

Tungsten oxide nanopowders: pulse alternating current electrosynthesis, structure optimization and performance in a flow photocatalytic fuel cell

A new electrolytic process for the synthesis of tungsten oxide nanopowder from WC-6Co scrap

An improved process was developed for the synthesis of hydrated tungsten oxide nanopowder from WC-6Co scrap at room temperature. This process is relatively less expensive and energy efficient. The conventional processes used for synthesizing tungsten oxide nanopowder are performed at high temperatures. In this study, tungsten oxide nanopowders are produced via electrolysis of WC-6Co pellet using sulfuric acid as an electrolyte; followed by dehydration at 150 °C. The dehydration treatment resulted in phase transformation. High purity nanorods and nanoplates of hydrated tungsten oxide were produced. The crystal size in the range of 9.6–13.8 nm was produced. The effect of process parameters on phase, crystal size, lattice strain, and morphology of tungsten oxide nanopowder is discussed.

Effect of hydrogen treatment on the photocatalytic activity of tungsten oxide nanopowders

The results on the synthesis and study of the properties of tungsten oxide nanopowders WO3 obtained by the hydrothermal method is presented in this work. The structural features of the synthesized WO3 nanopowders were studied using X-ray phase analysis and Raman spectroscopy. The final WO3 nanopowders have a monoclinic modification of tungsten oxide. The data on the morphology of the synthesized samples obtained by scanning electron microscopy. The samples have a rectangular shape with a smooth surface in the form of nanoplates with sizes in the range of 50-150 nm. Moreover, the photocatalytic properties of nanopowders were studied for as photocatalysts for water treatment application. A significant photocatalytic activity of the synthesized materials was found during the decomposition of the test substance of the dye rhodamine B under ultraviolet illumination. A method of heat treatment of tungsten oxide nanopowders in a hydrogen atmosphere has been developed to introduce oxygen vacancies. As a result, tungsten oxide nanopowders of non-stoichiometric composition were obtained. Comparative studies on the effects of hydrogen heat treatment on photocatalytic activity have been carried out. The photocatalytic activity of the starting WO3 oxide after heat treatment in a hydrogen atmosphere at 400 °C more than doubled.

Studying the effect of monochrome light on the photocatalytic activity of tungsten oxide

The paper presents studies of the photocatalytic activity of tungsten oxide nanopowder agglomerates under the action of monochrome light in the decomposition reactions of an organic pollutant (methylene blue). It is determined that the radiation of 470 nm (blue) provides the highest values of the rate constant of phototransformation of methylene blue

Navigating the effect of tungsten oxide nano-powder on ethylene glycol surface tension by artificial neural network and response surface methodology

The quiddity of ethylene glycol (EG) surface tension is attributed to the cohesive forces between EG molecules. The presence of tungsten oxide (WO3) nanoparticles certainly affects the cohesive forces and the surface tension will be affected. In this study, SITA dynotester was utilized for measuring surface tension at 20–50°C and 0.005–5 wt%. Loading nanoparticles intensified the adhesive force between EG and WO3 molecules and simultaneously attenuated cohesive forces between EG molecules. According to the results, the positive effect of the adhesive force was overcome by the negative effect of reducing the adhesion force and therefore the surface tension was weakened. At 20 ° C the EG surface tension was attenuated up to 15.57% by adding WO3 nanoparticles (5 wt%). Performing response surface methodology and artificial neural network for navigating the surface tension was successful. The acceptable R-squared for RSM (0.982) and ANN (0.99) led to maximum error of 1.43% and 0.95%.

Prepration and Properties of Blue Tungsten Oxide Nanopowders by High Energy Ball-Mill

The purpose of this study is to prepare WO3 nanopowders by high-energy milling in mixture gas (7 % H2+Ar) with various milling times (10, 30, and 60 min). The phase transformation, particle size and light absorption properties of WO3 nanopowders during reduction via high-energy milling are studied. It is found that the particle size of the WO3 decreases from about 30 μm to 20 nm, and the grain size of WO3 decreases rapidly with increasing milling time. Furthermore, the surface of the particles due to the pulverization process is observed to change to an amorphous structure. UV/Vis spectrophotometry shows that WO3 powder with increasing milling times (10, 30, 60 min) effectively extends the light absorption properties to the visible region. WO3 powder changes from yellow to gray and can be seen as a phenomenon in which the progress of the color changes to blue. The characterization of WO3 is performed by high resolution X-ray diffractometry, Field emission scanning electron microscopy, Transmission electron microscopy, UV/Vis spectrophotometry and Particle size analysis.

Investigations of the influence of tungsten carbide and tungsten oxide nanopowders on the radiation protection properties of cement matrix-based composite materials

The influence of tungsten carbide and tungsten oxide nanopowders on radiation-protective properties of a composite material based on a cement matrix has been studied. These powders are obtained from carbide scrap production. In the radiation energy range of 0.06…1.408 MeV the gamma radiation attenuation coefficients at various concentrations of nanopowders WC and WO3 (3.6%, 6.4%, 9.6% of the material mass) have been considered. The mass attenuation coefficient and the multiple of attenuation of radiation of investigated materials are calculated. It is shown that nanomodified composite material has high radiation protection characteristics and can find wide application as a radio protection material.

Fabrication and Characterization of Hexagonal Tungsten Oxide Nanopowders for High Performance Gas Sensing Application

Fabrication and Characterization of Hexagonal Tungsten Oxide Nanopowders for High Performance Gas Sensing Application

On the issue of the techniques to produce mass and low–price tungsten oxide nanopowder

There’s proposed an environmentally safe and cost-effective way to produce tungsten oxide nanopowders which allows obtaining it on an industrial scale. Below here there are presented the results of the elemental and particle-size analysis of tungsten oxide powder particles in the form of agglomerates.

Research of the effect of tungsten oxide nanopowders on the limit duration of concrete, plaster and ceramics

Abstract The effect of the addition of submicron powders obtained during the processing of carbide tungsten-containing waste on the strength characteristics of concrete, ceramics and gypsum is considered.

Electrospun tungsten oxide NPs/PVA nanofibers: A study on the morphology and Kramers–Kronig analysis of infrared reflectance spectra

The major objective of this work is focused on the preparation and characterization of poly (vinyl alcohol) (PVA) embedding tungsten oxide nanoparticles based on electrospinning technique. A surfactant (CTAB) was introduced to incorporate tungsten oxide nanoparticles into the PVA nanofibers homogeneously. To prepare a viscous solution of PVA nanofiber containing tungsten oxide nanoparticles, the distance between the tip of the needle and the surface of the foil was chosen as 10 and 15cm. The tungsten oxide NPs/PVA composite nanofibers have been characterized using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and reflectance spectrum in the wave length range of 200–1200nm. Fiber diameters decrease with increasing of tip-to-collector distance from 10 to 15cm. The average diameters were estimated about 165±30nm and 145±30nm from scanning electron microscopy at 10 and 15cm, respectively. The optical properties of the electrospun nanofibers were examined by the Kramers–Kronig model. The optical results show that tungsten oxide nanopowder show almost five times higher conductivity, lower absorbance and zero band gap energy.

Production of WO3 tungsten oxide nanopowders by evaporation-condensation process using focused 24-GHz microwave radiation

Fabrication of WO3 tungsten oxide nanoparticles by evaporation of the initial oxide material with a focused beam of 24-GHz electromagnetic radiation generated in a 5-kW gyrotron complex at a design microwave power density of 10 kW/cm2 has been experimentally studied. Tungsten oxide powders consisting of particles, which sizes are in range of 20 nm up to 1 μm, have been obtained. The particles have different shapes, close to spherical or octahedral, suggesting their formation via both the “vapor-liquid-crystal” and the “vapor-crystal” mechanism. The maximal evaporation rate was 100 g/h. The feasibility of powder dispersity controlling by varying the flow rate of cooling air has been revealed.

Photocatalytic degradation of diazinon by illuminated WO3 nanopowder

In this study, photocatalytic degradation of diazinon as a model phosphorothioate insecticide by tungsten oxide nanopowder under UV irradiation was investigated. Effect of operational parameters including WO3 dosage, pH, initial diazinon concentration, and organic compounds (humic acid, oxalic acid, phenol, ethylenediaminetetraacetic acid (EDTA)) on the photocatalytic degradation of diazinon was studied. Degradation efficiency of diazinon by WO3/UV process was more effective than WO3-alone and UV-alone. As the nanocatalyst dosage increased, the photocatalytic degradation of the diazinon decreased. Removal efficiency was decreased by increasing pH and initial diazinon concentration. The reaction rate constant (kobs) was decreased from 0.1233 to 0.0001/min, and the value of electrical energy per order (EEo) was increased from 38.93 to 48,000 (kWh/m3) with increasing initial diazinon concentration from 5 to 50 mg/L, respectively. The photocatalytic degradation of diazinon was increased in the presence of oxalic acid and EDTA, while different trend was observed in the presence of phenol and humic acid. Proper photocatalytic activity was observed even after five successive cycles. Finally, UV/WO3 is identified as a promising technique for the removal of diazinon with high efficiency in a short reaction time.

Photocatalytic Degradation of a Textile Dye by Illuminated Tungsten Oxide Nanopowder

AbstractIn this study, photocatalytic degradation of Acid Orange 7 (AO7) by tungsten oxide nanopowder under UV irradiation was investigated with variation of pH, WO

Processing and sintering of yttrium-doped tungsten oxide nanopowders to tungsten-based composites

Innovative chemical methods are capable of fabricating nanoscale tungsten oxide compounds doped with various rare-earth elements with high purity and homogeneity, which can be processed under hydrogen into nanostructured oxide-dispersed tungsten composite powders having several potential applications. However, hydrogen reduction of doped tungsten oxide compounds is rather complex, affecting the morphology and composition of the final powder. In this study, we have investigated the reduction of tungstic acid in the presence of Y and we provide the experimental evidence that Y2O3 can be separated from Y-doped tungstic acid via hydrogen reduction to produce Y2O3-W powders. The processed powders were further consolidated by spark plasma sintering at different temperatures and holding times at 75 MPa pressure and characterized. The optimized SPS conditions suggest sintering at 1400 °C for 3 min holding time to achieve higher density composites with an optimum finer grain size (3 µm) and a hardness value up to 420 H V. Major grain growth takes place at temperatures above 1300 °C during sintering. From the density values obtained, it is recommend to apply higher pressure before 900 °C to obtain maximum density. Oxides inclusions present in the matrix were identified as Y2O3·3WO3 and Y2O3·WO3 during high resolution microscopic investigations.

Effect of Hexagonal WO3 Morphology on NH3 Sensing

Abstract Tungsten oxide nano-powders were prepared by acidic precipitation from sodium tungstate solution. The alternative processes of the applied hydrothermal method resulted in different structure and morphology of hexagonal WO 3 nano-crystals. Micro-hotplates with gold electrodes on top to measure sensing layer conductivity were fabricated. WO 3 layers of the two morphologies were deposited using capillary dropping technique. Sensor responses were measured up to 220 °C operation temperature for NH3 diluted in synthetic air in the 10-100 ppm range. Test results are compared in terms of conductivity, sensitivity and response time.

Tungsten Oxide Nanopowders and Nanorods Prepared by a Modified Plasma Arc Gas Condensation Technique

Tungsten oxide nanopowders and nanorods were synthesized by using a modified plasma arc gas condensation technique that involved the introduction of a mixed gas with controllable partial O2 pressure into a gas condensation system. Experimental results showed that yellow and blue tungsten oxide nanopowders, prepared under an Ar to O2 ratios of 1:1 and 100:1, exhibited a major WO3 phase and W19O55 phase, respectively. The nanopowders grew into W5O14-phase nanorods along the [001] direction when H2 was used as the reduction gas.

Oxygen partial pressure effect on the preparation of nanocrystalline tungsten oxide powders by a plasma arc gas condensation technique

Abstract In the present study, nanocrystalline tungsten oxide powders were prepared by a plasma arc gas condensation technique under a controlled oxygen environment with Ar/O 2 ratio ranged from 1/1 to 100/1. It is noted that stoichiometric tungsten oxide nanocrystalline powders (WO 3 ) can be prepared under an Ar/O 2 ratio ranged from 1/1 to 99/1, while nonstoichiometric tungsten oxide nanopowders (WO 3− x ) were synthesized under an Ar/O 2 ratio of 100/1. The as-prepared WO 3 powders were examined by X-ray diffraction (XRD), Raman scattering, thermal gravimetric analysis (TGA), and high-resolution transmission electron microscope (HRTEM). Experimental results showed that yellowish WO 3 nanopowders prepared using different Ar/O 2 ratio exhibited slight differences.