WO3 Content Research Articles

Improved photocatalytic oxidation of arsenic (III) with WO3/TiO2 nanomaterials synthesized by the sol-gel method

Photocatalytic oxidation of arsenite (As(III)) to arsenate (As(V)) was studied in aqueous solution using a series of WO3/TiO2 semiconductors readily synthesized through sol-gel method with WO3 content in the range of 1-5 wt%. The resulting materials showed enhanced photocatalytic activity towards As(III) photo-oxidation compared to their individual counterparts under UV radiation. The amount of As(III) and As(V) species in the irradiated solution was determined using the molybdenum blue method. The efficiency of photoinduced carriers separation was further affirmed by electrical impedance spectroscopy (EIS) and photocurrent tests. The maximum catalytic efficiency was observed when the binary oxide 3%WO3/TiO2 (TW3) was used, reaching a 99% conversion of As(III) to As(V) within the first 25 min under UV irradiation. The enhanced photocatalytic performance of the heterostructures could be explained as consequent to an improved charge separation due to the migration of photoproduced holes in TW3 photocatalyst. Based on the electric band structure of WO3 and TiO2, a reasonable mechanism for the photo-oxidation of As(III) over TW3 novel catalyst has been proposed.

Ultralow-detection limit ammonia gas sensors at room temperature based on MWCNT/WO3 nanocomposite and effect of humidity

Nanocomposite-based NH3 gas sensors working at room temperature were systematically fabricated by compositing multi-walled carbon nanotubes (MWCNTs) and tungsten oxide (WO3) nanobricks at different mass ratios. The response of the nanocomposite-based sensors increases with increasing WO3 content from 0 to 95 wt% then decreases as the WO3 content continuously increases to 100 wt%. The sensor with 95 wt% of WO3 shows a significant enhancement in NH3 gas sensing characteristics, namely, high response (~350% with 60 ppm NH3), ultralow limit of detection (6 ppb), and selectivity to NH3. The enhancement of gas sensing characteristics was attributed to the synergistic effect of the p-p junction between MWCNT and the inversion layer on the WO3 surface caused by the adsorbed oxygen gas and water vapor in ambient air. The response increases while the sensor's resistance decreases with increasing relative humidity from 25% to 65%. Hence, MWCNT/WO3 nanocomposite is a promising material for selective sub-ppm NH3 gas sensor at room temperature.

Preparation, characterisation and lubrication performances of Eu doped WO3 nanoparticle reinforce Mn3B7O13Cl as water‐based lubricant additive for laminated Cu‐Fe composite sheet during hot rolling

AbstractCitric acid‐synthesised Eu‐doped WO3 (WO3:Eu3+) and Mn3B7O13Cl nanoparticles were characterised by X‐ray diffraction and transmission electron microscopy. The tribological properties of the Eu doped WO3 and Mn3B7O13Cl prepared as anti‐wear additives for enhanced lubrication were studied using a four‐ball tester. The experiment results indicated that Eu doped WO3 nanoparticle reinforce Mn3B7O13Cl has excellent load‐carrying capacity, wear‐resistance and friction‐reducing properties in water‐based lubricant, optimum concentration of WO3:Eu3+‐Mn3B7O13Cl was 0.5 wt%. The wear scar diameter decreased from 0.62 to 0.37 mm and the coefficient of friction was reduced from 0.083 to 0.065, which reductions are attributed to the nanotribofilms composed of B2O3, WO3, Fe2O3 and Eu2O, which prevented direct contact between metals. Hot rolling experiments of laminated Cu‐Fe composite sheet were carried out to study the effect of nano‐WO3:Eu3+‐Mn3B7O13Cl on surface qualities including topography of rolled strips. Results show that the surface topography becomes smooth with the addition of nanoparticles into water‐based lubricant, which is mainly attributed to the nanoparticles increase the viscosity of water‐based lubricant and the oil film to avoid the direct contact tribopair during hot rolling, thus reducing the friction coefficient and roll wear.

A novel study of tungsten oxide nanocrystallites as fuel additive for diesel oil

In this paper, a basic solvothermal synthesis using sodium tungstate as a precursor is reported to prepare tungsten oxide (WO3) particles. XRD data confirmed the highly crystalline nature. The broad peaks of XRD patterns estimated the nanocrystallites of WO3. The average crystallite size as was 95 nm. Scanning electron microscopy showed the morphologically cube-like particles with aggregation that was converted to larger brick-like particle of WO3 after calcination. WO3 was used as fuel additive in diesel oil. Fire and flash points of diesel oil were enhanced to 49°C and 54°C respectively. The calorific value was increased up to 36580 Jg−1. Thus fuel efficiency was enhanced by use of WO3 as an additive. The use of different concentrations of WO3 (20, 40, 60, 80 ppm) as fuel additive has been also explored in this paper. The observed additive properties of WO3 suggested the potential applications of such metal oxides.

Study on volatilization characteristic of vanadium and tungsten of vanadium-based selective catalytic reduction

Vanadium-based selective catalyst reduction (V-SCR) has made significant contributions to De-NOx of diesel vehicles. However, the two main catalyst components, V2O5 and WO3, are volatile and toxic. Therefore, there are some restrictions for its application on heavy duty diesel vehicles (HDDV) in the CHINA VI stage. In view of this problem, the volatilization rates of two kinds of volatiles under different inlet temperature and test duration were measured on three V-SCR samples from different catalyst manufacturers. The effects of V-SCR inlet temperature and test duration on the volatilization characteristics of the two volatiles on different samples were systematically studied and compared. The emission concentrations of V2O5 and WO3 at different temperatures were compared with the occupational exposure limits of chemical harmful factors in the workplace which is specified in the GBZ 2.1-2019. The results show that the initial temperature of volatilization of V-SCR is directly related to the technical level of the catalyst itself; whether the volatilization characteristics of V-SCR will change with the prolongation of test duration depends on its inlet temperature; V2O5 emission concentration of V-SCR at 550 C° can reach a quite high exposure level, and the exposure level of WO3 volatiles at 650 C° may be equivalent to that of V2O5 volatiles at 550 C°.

Structural, physical and radiation attenuation properties of tungsten doped zinc borate glasses

For the x WO3 (40 – x) ZnO 50B2O3 10K2O, (0 ≤ x ≤ 20 wt%) glass system. optical, structure, gamma and neutron radiation shielding aspects were examined comprehensively. The mass attenuation coefficients of gamma-rays, the mean free photon path (MFP), and the effective atomic number (Zeff) have been determined experimentally at photon energies 238, 662,911, 1173, 1332 and 2614 keV. The results obtained were compared with the corresponding theoretical data, which were found to be dependent on glass components and energy. Moreover, the calculated ƩR shows that increasing the removal cross section increases with increasing the WO3 concentration. The molar volume of the glasses has been derived from density measurements and studied as a function of composition. FTIR spectral results revealed that the glass network matrix is sequentially formed by BO3, BO4, ZnO4, WO4 and WO6 structural groups. The optical transmission was done on these glasses and the absorbance was increased as WO3 increased. Moreover, the peak shifted to a longer wavelength as WO3 increased and a decreasing behavior of the bandgap. The obtained results have been analyzed in the light of various oxidation states of tungsten ions in the glass matrix. All results pointed out that these glasses have potential applications in radiation shielding.

Lattice-water-induced acid sites in tungsten oxide hydrate for catalyzing fructose dehydration

Herein, hydrated WO3 was synthesized by hydrothermal method, and the relationship between its structure and acidity was explored. The numbers of Brønsted acid sites (BAS) and Lewis acid sites (LAS) can be modulated by adjusting the lattice water content of WO3·nH2O. Mechanism studies shown that the density of BAS and diffusion effect have a synergistic effect on the activity of dehydration reaction. The optimized WO3·0.5H2O catalyst in the presence of both high BAS density and high BAS accessibility afforded 73% 5-hydroxymethylfurfural (HMF) yield, and almost no deactivation appeared after five cycles. Nearly twice higher turnover frequency (TOF) and 50% higher HMF selectivity were observed in comparison to anhydrous WO3.

Effect of pH on the Tribological Behavior of Eu-Doped WO3 Nanoparticle in Water-Based Fluid

Eu-doped WO3 (WO3:Eu3+) nanoparticles were prepared by Pechini method under different pH values (pH 1, 3, 5, and 7). The prepared nano-powders were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HRTEM). The results showed that the average external diameter of the prepared nano-WO3:Eu3+ powders is the smallest and reaches 50 nm at pH 5. Structural transformation matrix contained different crystals of anorthic and orthorhombic structures. Eu3+ ions are located at the center of the non-inversion symmetry of WO3:Eu3+. The tribological properties of the WO3:Eu3+ as extreme pressure and wear resistance agents in water-based lubricant were investigated by a four-ball machine. The results showed that WO3:Eu3+ displays excellent load-carrying capacity, wear resistance, and friction-reducing properties in water-based lubricant, particularly in the best concentration of WO3:Eu3+ was 0.6 wt%. WSD was reduced from 0.62 to 0.35 mm and COF was decreased from 0.083 to 0.055. This was due to the formation of tribofilms with a few tens of nanometers thick, which prevented no actual metal-to-metal contact.

The impact of γ-irradiation on Cd-B2o3 glass doped WO3: New evidences by TL and ESR spectroscopy

A well resolved Thermoluminescence (TL) glow peak at ~168 °C was observed in Cd-borate glass doped WO3. The maximum TL intensity was observed for 1.5 mol% of WO3+ doped samples and thereafter decreases. The variation of gamma exposure (0.025→2 kGy) on TL glow curves of Cd-borate glass showed linear and sub-linear behavior supported by track interaction model (TIM). Here γ-irradiated sample shows the formation of shallow trap (surface trapping) beside the formation of deep trapping. The composition dependence of the g ≈ 1.94 ESR absorption line intensity shows a decrease with increasing WO3 content, which is attributed to a fall in the ratio of the number of unpaired pentavalent ions W5+ ions to the number of W6+ ions. The effect of gamma irradiation doses on TL and ESR studies show high response with dose which indicates that these glass samples may be useful for TL dosimetry.

2,4-Dichlorophenoxyacetic acid (2,4-D) photodegradation on WO3-TiO2-SBA-15 nanostructured composite.

A current environmental problem is the uncontrolled use of various pesticides that are harmful to the environment and public health. The herbicide 2,4-D is widely used, making it a vector of contamination for aquatic bodies, air, soil, and biomass. In recent decades, researchers have studied remediation of this compound in the environment. In this work, WO3 and TiO2 were supported on SBA-15 molecular sieve by the in situ anchoring (ISA) method, with different molar percentages of WO3 in relation to the oxide content: X= 25%, 50%, and 75%. The W-Ti-S (X) samples were characterized by XDR, XRF, Raman, FTIR, diffuse reflectance of UV-vis, and adsorption and desorption of N2. SBA-15 mesoporous structure was not destroyed even after the incorporation of the oxides. XRD analyses associated with Raman result found a predominance of the anatase phase for titanium oxide, and the FRX showed low incorporation of nanoparticles. Photocatalytic tests indicated that the catalytic activity depends on WO3 and TiO2 content, although all W-Ti-S (X) samples exhibited similar TOF value. The W-Ti-S (25) sample had the highest photocatalytic activity, 76% herbicide photodegradation under ultraviolet irradiation, at 270min. The analysis of the catalytic cycles indicated that W-Ti-S (25) keeps out 70% of photocatalytic activity in the fourth catalytic cycle. In addition, the W-Ti-S (25) catalytic activity under direct sunlight irradiation was similar to that under artificial UV irradiation.

Radiation shielding properties of tellurite-lead-tungsten glasses against gamma and beta radiations

Tellurite-lead-tungsten glasses with the chemical composition of (80-x)TeO2-20PbO-xWO3 (where x = 0, 5, 10, 15 and 20 mol%) were reported as high-performance shields for gamma and beta applications. Geant4 toolkit and XCOM program were used to simulate and calculate the gamma attenuation factors. Beta shielding behaviour of the investigated glasses was explored by determining the CSDA range and stopping power (ψe) via ESTAR program. The results showed that the addition of WO3 has a positive influence on density, and as a result, in the shielding capability of the glass against gamma and beta radiations. This influence, however, is much stronger in the case of the shielding against gamma radiation. TPW5 glass with the highest contents of WO3 has the highest MAC, Zeff and the lowest HVL. Moreover, the glasses with low concentrations of WO3 content show the same gamma shielding properties of commercial glasses and concretes.

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.

Incorporation mechanism of tungsten in W-Fe-Cr-V-bearing rutile

Abstract Rutile is a common mineral in many types of ore deposits and can carry chemical or isotopic information about the ore formation. For closer understanding of this information, the mechanisms of incorporation of minor elements should be known. In this work, we have investigated natural rutile crystals with elevated concentrations of WO3 (up to 17.7 wt%), Cr2O3,tot (7.5), V2O3,tot (4.1), FeOtot (7.3), and other metals. X-ray absorption spectroscopy (XAS) of rutile at the Fe K, Cr K, V K, and W L1 and L3 edges shows that all cations are coordinated octahedrally. The average oxidation state of V is +3.8, and that of Cr is near +4. Shell-by-shell fitting of the W L3 EXAFS data shows that W resides in the rutile structure. Raman spectroscopy excludes the possibility of hydrogen as a charge-compensating species. High-resolution TEM and electron diffraction confirm this conclusion as the entire inspected area consists of rutile single crystal with variable amounts of metals other than Ti. Our results show that rutile or its precursors can be efficient vehicles for tungsten in sedimentary rocks, leading to their enrichment in W and possibly later fertility with respect to igneous ore deposits. Leucoxene, a nanocrystalline mixture of Ti and Fe oxides, is an especially suitable candidate for such a vehicle.

Radiation Shielding Investigation of Lead Borophosphate Glasses Modified by Tungsten Oxide

Abstract The effect of tungsten trioxide (WO3) on the shielding properties of the lead(II) oxide–boron trioxide–phosphorus pentoxide–WO3 system was investigated. The mass attenuation coefficients (μ/ρ) were evaluated using the XCOM program (National Institute of Standards and Technology, Gaithersburg, MD) in the energy range of 0.015–10 MeV. The μ/ρ values were then used to calculate the mean free path (MFP) and half value layer (HVL). In addition, the macroscopic effective removal cross section for fast neutrons (ΣR) was calculated for the present glass system. It was found that the μ/ρ values increase with increasing WO3 concentration, while HVL and MFP values decrease with increasing WO3 content. The present glass system showed good radiation shielding properties by providing shorter MFP than some glass systems, such as 70TeO2-30V2O5 and 80TeO2-20MoO3 glasses. In addition, it was found that the ΣR values for the present glasses lie within the range of 0.1100–0.1132 cm−1.

Features of the phase composition, acidity, and isomerization activity of Pt/WO3/ZrO2 catalysts

Textural characteristics, phase composition, and acidic properties of Pt/WO3/ZrO2 catalysts for C7-alkanes isomerization were studied. It was shown that the most active and selective catalysts are samples with WO3 content of 15–25 wt.% with a fraction of the active tetragonal phase of ZrO2 of 73–94 wt.%. It was found that an increase in the number of Bronsted acid sites contributes to an increase in the activity of tungstated zirconia catalysts in the isomerization of n-heptane.

Step-scheme WO3/CdIn2S4 hybrid system with high visible light activity for tetracycline hydrochloride photodegradation

Photocatalytic degradation is an ideal choice for the treatment of antibiotic contaminant in water environment because of the characters of environmental-benign and sustainable. In this work, the visible-light-driven WO3/CdIn2S4 hybrid photocatalysts with different WO3 content were successfully fabricated by hydrothermal method. The phase structure, surface composition, optical properties, specific surface areas and charge separation were systematically by a series of measurements. The photocatalytic activity of resultant WO3/CdIn2S4 hybrid photocatalysts was evaluated by photocatalytic degradation for removal of tetracycline hydrochloride (TCH) and the results reveal that optimized photocatalytic efficiency in WO3/CdIn2S4 hybrid photocatalysts can be achieved by modulating the weight ratio of WO3 to CdIn2S4. The 70 wt% WO3/CdIn2S4 hybrid photocatalyst exhibited the best photodegradation activity. Significant enhancement of photocatalytic activity in WO3/CdIn2S4 hybrid photocatalysts is ascribed to effective charge separation due to the construction of step-scheme heterojunction. The photocatalytic mechanism involving charge transfer and separation, and degradation path using step-scheme WO3/CdIn2S4 hybrid photocatalysts were in-depth investigated and discussed. It is anticipated that our current investigation could open an avenue for design and preparation of step-scheme hybrid photocatalysts for environmental remediation.

Physical, Optical, Structural and Thermal Studies of xWO3 + (30 − x)As2O3 + 70TeO2 (where x = 10, 20, 30 mol%) glasses by UV–vis, Raman, IR and DSC Studies

Optical, Structural and Thermal properties of xWO3 + (30 − x)As2O3 + 70TeO2 glass system (where x = 10, 20, & 30 mol%) have been investigated by Optical absorption, Raman & FT-IR, and DSC studies respectively. Physical properties such as, density (ρ), molar volume (Vm), oxygen packing density (OPD), and oxygen molar volume (Vo) are determined for all the glass samples. Density and oxygen packing density (OPD) of glasses have been increasing monotonically with increase in WO3 content in the range 6.52–6.99 g m/cc, and 85.951–88.690 mol/l respectively. These values are correlated with molar volume and oxygen molar volume that are decreasing linearly with increase in WO3 content (10–30 mol%) falling in the range 26.745–25.932 cm3/mol and 11.628–11.274 cm3/mol respectively. The optical transitions and electronic band structure has also been investigated through optical absorption spectra. The fundamental absorption edge is measured in the short wavelength of the visible region, that shows, glasses exhibits the redshift (449 → 483 nm), at photon energy in the range 2.89–2.70 eV for direct allowed transitions. Raman and IR spectral studies reveals that the glass network consists of TeO4 (tbp), TeO3/TeO3+1 (tp), WO6 (octahedral), WO4 (tetrahedra) and AsO3 groups as basic structural units. Thermal behavior of the glasses was studied in terms of glass transition temperature (Tg), onset crystallization (To), peak crystallization (Tp) temperatures, and the thermal stability (ΔT) from DSC thermogrms. In the present glass system, it is found that the glass transition temperature (Tg = 331 → 341 → 353 °C) and thermal stability (ΔT = 56 → 93 → 120 °C) both increases linearly with increase in concentration of WO3 (10, 20, & 30 mol%).

Raman, FTIR studies and optical absorption of zinc borate glasses containing WO3

Glasses with composition [xWO3–(25−x)–ZnO–20Na2O–55B2O3 where x = 0, 5, 10, 15 and 20 mol. %] were prepared by melt quenching method. The amorphous state of the current glass samples was checked by X-ray diffraction (XRD). The measured density and calculated molar volume of all prepared samples were found to increase with the replacement of the lighter ZnO by the heavier of WO3. The network structure of the present glasses was studied using the infrared (IR) and Raman spectroscopic techniques. IR and Raman results show that the structure of the samples is BO3 and BO4 units located in several structural groups with W–O–W units. The decreasing of the band gap energy values by the introducing of WO3 showed that the creation increases of the number of non-bridging oxygens in the structure of glass. All results showed that the parameters were dependent upon the dopant concentration of WO3 in the prepared glasses.

Investigation of physical and spectroscopic properties of WO3 doped zinc-lithium-dysprosium borotellurite glasses

Abstract A set of WO3 doped zinc-lithium-dysprosium-borotellurite glasses in the compositions, (B2O3)0.2–(TeO2)0.3-x–(ZnO)0.28 –(Li2CO3)0.2 –(Dy2O3)0.02–(WO3)x; x = 0.02 to 0.12 (labeled as W1, W2, W3, W4, W5 and W6 respectively) have been synthesized. Amorphous nature of the samples has been confirmed and density measured. Molar volume, oxygen packing density and field strength were determined. Optical absorption spectra were recorded. Band gap values are found to increase with WO3 content up to 0.08 mol fractions and decreases for further amounts of WO3. Urbach energy behaved in the opposite fashion to that of band gap with WO3 content. These results are attributed to bonding defects and the number of non-bridging oxygen. Refractive index, molar refractivity, molar electronic polarizability, reflection loss, metallization ratio, oscillator strengths and Judd-Ofelt (J-O) intensity parameters have been determined. Based on the observed trends of JO intensity parameters, lasing ability of the glasses and their optical quality has been discussed. Photoluminescence (PL) spectra have been recorded and they exhibited three bands namely, 4F9/2 → 6H15/2 (blue), 6H13/2 (yellow) and 6H11/2 (red). The observed ratio of intensity of yellow to blue band inferred that asymmetry around rare earth ions decreases with increase of WO3 content. Using PL decay profiles, the lifetime (τexp) for yellow emission has been determined. Using the values of τexp and estimated radiative lifetime (τR), the quantum efficiency (η) has been determined and for 4F9/2 → 6H13/2 transition and, it is found to be in the range from 43% to 67% for the present glasses. Based on JO parameters, quantum efficiency and other radiative parameters, W4 glass is proposed for lasing in yellow region. For the first time, effect of WO3 on the optical properties of zinc-lithium-dysprosium-borotellurite glasses has been thoroughly investigated.

X-ray/proton and photoluminescence behaviors of Sm3+ doped high-density tungsten gadolinium borate scintillating glass

Sm-activated scintillating glasses with high WO3 concentration up to 42.5 mol% were studied in this work. The effects of Sm2O3 concentration on the density, absorption and various (photo-, X-ray induced-, proton- and temperature dependent-) luminescence properties have been monitored. The glasses possess a high density with maximum value around 6.18 g/cm3. The glass samples show the several absorption peaks of visible light and near-infrared wavelength those confirm the Sm3+ ion existence in glass matrices. The Gd3+→ Sm3+ energy transfer took place in glasses which resulted to the strongest emission around 600 nm (4G5/2 → 6H7/2) of Sm3+ in the photo-, X-ray induced- and proton luminescence spectra. The optimal doping concentration of Sm2O3 in WO3-Gd2O3˗B2O3 glass is 1.0 mol% that performed the highest emission intensity in these three types of luminescence spectra. In 1.0 mol% doped glass, the decay time under pulse X-ray excitation was analyzed and found to be 0.27 ms. The temperature dependent luminescence in a range of 10 K–300 K of 1.0 mol% doped glass was measured via UV-laser excitation. The emission intensity of glass increased 3.76 times with the temperature decrease. In this work, the fabricated WO3-Gd2O3˗B2O3 glasses doped with Sm2O3 show the strong visible luminescence under visible light, X-ray and proton excitation. The developed glass performs the potential for X-ray scintillator applications with integration mode using in the medical, industrial and security imaging inspection system.