Effect Of WO Research Articles

Effect of WO3 on the radiation shielding ability of TeO2–TiO2–WO3 glass system

Abstract In this study, glass composition based on tungsten oxide (WO3) doped tellurium, titanium glasses: (100 − x − y) TeO2–xTiO2–yWO3: where (x = 5) and (y = 5, 10, 15, 20, 25) coded as TT5W5, TT5W10, TT5W15, TT5W20, and TT5W25 were investigated for shielding properties against ionizing radiation. Gamma radiation shielding parameters such as mass attenuation coefficients (MAC) are calculated through MCNPx code and Phy-X/PSD software in the energy range of 0.015–15 MeV. Obtained MAC values are then used to calculate other gamma radiation shielding parameters such as mean free path (MFP) and effective atomic number (Z eff). Besides this, the exposure buildup factor (EBF) was also calculated by using EXABCal software at different penetration depths (PDs) in the energy range of 0.015–15 MeV. Sample TT5W25, which has a larger WO3 content of 25 mol% shows higher values of MAC and lower values of MFP among all the examined glass samples. Our investigated TeO2–TiO2–WO3 glass samples possess the lowest MFP values in comparison with the different types of concretes and commercially available shielding glasses. In addition, fast neutron shielding characteristics in light of fast neutron removal cross-section have also been computed. Glass sample TT5W25 possesses the higher values of fast neutron removal cross-section as compared to the other glass samples. The results indicate that the adding up of WO3 improves shielding against the fast neutron and gamma radiation.

Effect of WO<sub>3</sub> on the Performances of Cordierite Ceramics Synthesized by Using Kyanite as Raw Materials

In order to synthesize cordierite ceramics with low thermal expansion coefficient and good properties, in our work, the cordierite ceramics were prepared by using talc, natural containing zirconium kyanite, common kyanite and industrial Al2O3 as raw materials, introducing the right amount of WO3 (introducing tungsten acid) as catalyst. The effects of the introduced WO3 on the phase composition, sintering characters, microstructure and thermal expansion coefficient of the cordierite ceramics were investigated. The results show that the introduction of WO3 can eliminate the intermediate phase magnesia-alumina spinel and promote the formation of cordierite; the as-prepared cordierite ceramics synthesized by using natural containing zirconium kyanite as raw materials have high densification degree and low thermal expansion coefficient (1.53×10-6/°C, Rt~1000 °C).

A study on the optical, structural, electrical conductivity and dielectric properties of a lithium bismuth germanium tungsten glasses

Glasses in the system (65 − x)Bi 2O 3–15Li 2O–20GeO 2– xWO 3 (where x = 2, 5 and 10 mol%) were prepared by normal melt quenching method. The change in density and molar volume in these glasses indicates the effect of WO 3 on the glass structure. Fourier transform infrared (FT-IR) spectra show that these glasses are made up of GeO 4, GeO 6, BiO 6, BiO 3, WO 4 and WO 6 basic structural units. The structural units of BiO 6, GeO 6 and WO 6 increase with the increasing of WO 3 content. The optical constants of these glasses are determined over a spectral range, providing the complex dielectric constant to be calculated. Higher values for the refractive index and dispersion are recorded due to the high polarizability of bismuth and tungsten ions. The values of the optical band gap E g for all types of electronic transitions and refractive index have been determined and discussed. The dc conductivity measured in the temperature range 423–623 K obeys Arrhenius law. The dielectric constant ( ɛ′), dielectric loss (tan δ) and ac conductivity over a wide range of frequency and temperature, of the glasses were investigated.

Effect of WO 3 doping on dielectric and ferroelectric properties of 0.94(Bi 0.5Na 0.5)TiO 3–0.06BaTiO 3 ceramics

WO 3(0–6 mol%)-doped 0.94Bi 0.5Na 0.5TiO 3–0.06BaTiO 3 lead-free ceramics were synthesized by conventional solid-state reaction. The effect of WO 3 addition on the structure and electrical properties were investigated. The result revealed that a small amount of WO 3 (≤1 mol%) can diffuse into the lattice and does not significantly affect the phase structure, however, more addition will result in distortion and enlargement of the unit cells. The maximum permittivity temperature ( T m) is suppressed dramatically as the dopant increasing, while the depolarization temperature ( T d) fall to the minimum with 1 mol% WO 3 additive. The remanent polarization ( P r) was enhanced and coercive field ( E c) was reduced by doping with WO 3. The strain shows the largest value for 1 mol% doped sample, which is due to a field-induced antiferroelectric–ferroelectric phase transition.

Effect of WO 3 on structural and optical properties of CeO 2–PbO–B 2O 3 glasses

Pure and WO 3 doped CeO 2–PbO–B 2O 3 glasses are prepared by the melt-quench technique. The structural and optical analyses of glasses are carried out by XRD, FTIR, density and UV–vis spectroscopic measurement techniques. FTIR analysis indicates the transformation of structural units of BO 3 into BO 4 with W–O–W vibration and the presence of WO 4 and WO 6 units observed with increase in WO 3 contents. Decrease in band gap for CeO 2–PbO–B 2O 3 glasses from 2.89 to 2.30 eV and for WO 3 doped glasses from 2.89 to 1.95 eV has been observed and discussed. This decrease in band gap with WO 3 doping approaches to semiconductor behavior. It shows that the presence of WO 3 in the glass samples causes more compaction of the borate network due to the formation of BO 4 groups and the presence of WO 4 and WO 6 groups, which result in a decrease in the optical band gap energy and increase in the density.

The effect of WO 3 source stability on the properties of films deposited by electron beam deposition

This study investigates the impact of high temperature and vacuum on the properties of WO 3 powder during electron beam deposition and evaluates the consequential effects on the as-deposited films. Therein, the grain size and the crystallinity of the source were observed to increase and become non-stoichiometric tungsten oxide (WO 3− x ) due to the high temperature and vacuum during the first deposition. As a result of these changes in the source, the optical band gap, E g, of the deposited film decreased from 3.11 eV to 3.07 eV, and the absorbance was observed to increase. The coloration efficiencies of the deposited films decreased from 23 to 16 cm 2 C −1. WO 3-incorporated carbon nanotubes (WO 3/CNT) were observed in the source after electron beam deposition if there were some initial carbon impurities in the source prior to deposition.

Effect of WO 3 and MoO 3 addition on LnTiTaO 6 (Ln = Ce, Pr and Nd) microwave ceramics

The effect of dopants such as WO 3 and MoO 3 on the structural, processing and microwave dielectric properties of LnTiTaO 6 (Ln = Ce, Pr and Nd) ceramics is reported. Conventional solid-state ceramic route was used for the preparation of samples. The samples are calcined and sintered at optimized temperatures. A reduction of 50 °C in the sintering temperature was observed for all the samples. The crystal structure of the materials was analyzed using X-ray diffraction techniques and the surface morphology of the sintered samples was analyzed using scanning electron microscopy. The dielectric constant at microwave frequency range decreased on higher doping concentrations for all the samples but the quality factor is improved on small doping concentrations. The thermal stability of resonant frequency is also improved with doping on all the systems. A number of samples with improved microwave dielectric properties were obtained on all the systems and are suitable for practical applications.

Improved high Q value of MgTiO 3–CaTiO 3 microwave dielectric resonator using WO 3-doped at lower sintering temperature for microwave applications

The effect of WO 3 additive on the microstructures, the phase formation and the microwave dielectric properties of MgTiO 3–CaTiO 3 ceramics system were investigated. The sintering temperature of WO 3-doped 0.95MgTiO 3–0.05CaTiO 3 (95MCT) ceramics can be lowered to 1175 °C. The microwave dielectric properties are found strongly to correlate with the sintering temperature as well as the amount of WO 3 addition. At 1250 °C 95MCT ceramics with 0.5 wt% WO 3 addition gives a dielectric constant ɛ r of 20.3, a Q × f value of 66,000 (GHz) and a τ f value of −8.2 ppm/°C. A band-pass filter is designed and simulated using the proposed dielectric to study its performance.

Effect of WO 3 on the spectroscopic properties in Er 3+/Yb 3+ co-doped bismuth–borate glasses

The spectroscopic properties of Er 3+/Yb 3+ co-doped Bi 2O 3–B 2O 3–WO 3 (BBW) glasses were analyzed and discussed. The effect of WO 3 content on the absorption spectra, the Judd–Ofelt parameters Ω t ( t=2, 4, 6), emission spectra and the lifetime of the 4I 13/2 level and the quantum efficiency of Er 3+: 4I 13/2→ 4I 15/2 transition were also investigated. With the substitution of WO 3 for B 2O 3, the measured lifetime of the 4I 13/2 level and the quantum efficiency of Er 3+: 4I 13/2→ 4I 15/2 transition increase from 0.98 to 1.31 ms and from 38.2% to 49.2%, respectively. The effective width of emission band and the emission cross-section both decrease slightly. And the emission spectra is analyzed via the different curve ( σ e− σ a) of BBW glasses, the influence of OH − is also discussed.

Investigation of thermal stability and spectroscopic properties in Er 3+/Yb 3+ co-doped niobic tungsten tellurite glasses

A series of novel Er 3+/Yb 3+ co-doped 75TeO 2–(25 − x)Nb 2O 5– xWO 3 (TNW: x = 0, 3, 6, 9, 12, and 15 mol%) glasses have been prepared. Effect of WO 3 on the thermal stability and spectroscopic properties of Er 3+/Yb 3+ co-doped niobic tellurite glasses have been investigated. With WO 3 content increasing from 0 to 15 mol%, the fluorescence full width at half maximum (FWHM), the peak of stimulated emission cross-section ( σ e peak ), the measured lifetime ( τ m), and quantum efficiency ( η) change from 71 nm, 8.47 × 10 −21 cm 2, 2.86 ms, 84.1% to 76 nm, 7.22 × 10 −21 cm 2, 3.14 ms, 88.9%, respectively. The FWHM and σ e peak of Er 3+ ions in different glass hosts were compared; the obtained data reveals that this new TNW4 glass may be a potentially useful candidate material host for broadband amplifiers.

Highly sensitive SnO 2 thin film NO 2 gas sensor operating at low temperature

Thin films of pure nano-crystalline SnO 2 and WO 3-doped SnO 2 in different concentrations (3 wt.% and 5 wt.%) are deposited using sol–gel spin coating technique on glass substrates. The structural and morphological properties of these films are investigated using XRD, TEM and AFM. The sensitivity and selectivity of these films are tested to different reducing and oxidizing gases such as SO 2, NH 3, NO 2 and ethanol. A SnO 2 thin film with 5 wt.% WO 3 shows very high responses to NO 2 (four orders of magnitude in the value of ( R g − R a)/ R a; R g and R a are the resistance in NO 2 and in air, respectively) and excellent selectivity for NO 2 gas at a low operating temperature of 150 °C. The effect of WO 3 on the sensing characteristics of these films towards NO 2 is discussed.

Effect of ZnO additives and acid treatment on catalytic performance of Pt/WO 3/ZrO 2 for n-C 7 hydroisomerization

The effect of WO 3 (5–50 wt%) and ZnO (0.7–22 wt%) on the catalytic properties of Pt/WO 3/(ZnO)–ZrO 2 for n-heptane ( n-C 7) hydroisomerization was investigated. The optimized WO 3 and ZnO contents are 20 wt% and 3.4 wt%, respectively. The catalytic performance is achieved at 81% n-C 7 conversion and 89% C 7 isomer selectivity at 250 °C, which is reproducible and can be kept constant over 82 h under reaction conditions. Both WO 3 and ZnO can stabilize the tetragonal phase of ZrO 2. The Brønsted acid-to-Lewis acid ratio should be optimized to achieve high catalytic performance. The activity for Pt/WO 3/ZrO 2 using Zr(OH) 4 as the catalyst support ( n-C 7 conversion, 88% at 250 °C) is much higher than that for Pt/WO 3/ZrO 2 with ZrO 2 as the support ( n-C 7 conversion, 9% at 250 °C) with the same Pt and WO 3 loadings. BET, SEM-EDX, and pyridine-FTIR analyses show that acid treatment can successfully enhance the surface area (from 73 to 91 m 2/g), increase the number of Brønsted acid sites, and lower the surface Zn:Zr ratio (from 0.43 to 0.15) for ZnO–ZrO 2 with 22 wt% ZnO. The yield of C 7 isomers is increased from nil to 47% at 300 °C on Pt/WO 3/ZnO–ZrO 2 catalyst after acid treatment. It is suggested that n-heptane hydroisomerization activity is related to acidity, surface area, and crystalline phase of ZrO 2.

Laser-induced photo-catalytic removal of phenol using n-type WO 3 semiconductor catalyst

Laser-induced photo-catalytic degradation of phenol using WO 3 was investigated for the first time. Effect of WO 3 concentrations and laser energy on photo-catalytic removal of phenol from waste water was studied. Laser enhanced Photo-degradation can be an efficient method for the removal of phenol present in waste waters. The phenol removal process obeyed the first-order kinetics.

Electrochemical behavior of tin in sodium borate solutions and the effect of halide ions and some inorganic inhibitors

The corrosion of tin electrode in sodium borate (Na 2B 4O 7) solutions was investigated using cyclic voltammetry and potentiostatic current transient techniques. In absence of halide ions, the E/ j response exhibits active/passive transition. The active region involves one anodic peak corresponding to the formation of Sn(OH) 2 and/or SnO. Addition of Cl −, Br − or I − (C ⩽ 0.01 M) ions inhibits the active dissolution of tin, but higher concentrations enhance the active dissolution and tend to breakdown the passive film and induce pitting attack. The effect of WO 4 2 - , MoO 4 2 - , NO 2 - and NO 3 - as inorganic inhibitors on the pitting corrosion of tin in (0.1 M Na 2B 4O 7 + 0.1 M NaCl) solution has also been studied. The presence of these anions (except NO 3 - ) inhibits pitting corrosion. Chronoamperometry measurements showed that nucleation of pit takes place after an incubation time ( t i). The rate of pit nucleation ( t i - 1 ) increases with increasing halide ions concentration and applied potentials, but decreases with increasing the concentration of the inorganic inhibitors (except NO 3 - ). The inhibition efficiency of these inhibitors decreases in the order: WO 4 2 − > MoO 4 2 − > NO 2 −

Transport processes and surface transformation at the CaWO 4∣WO 3 interface

The effect of WO 3 activity ( a WO 3 ) in the surrounding gas phase on spontaneous processes at the CaWO 4∣WO 3 interface was examined in experiments performed in a chamber open to the ambient air (i) and in a closed chamber (ii), where the samples were brought to an equilibrium with the WO 3 vapor. The processes in both types of the chambers exhibited a bilateral behavior: spreading of WO 3 into the CaWO 4 ceramic and, simultaneously, penetration of CaWO 4 components into the WO 3 ceramic. The mass of the CaWO 4 pellets was found to change to a significantly different degree. The conductivity of the CaWO 4 ceramic increased with growing a WO 3 . The obtained results were discussed using a model of formation of the CW-s intermediate surface phase. When a WO 3 increased, the CW-s film became thicker and the degree of the film continuity was enhanced.

Improved high-Q microwave dielectric resonator using ZnO and WO 3-doped Zr 0.8Sn 0.2TiO 4 ceramics

The effect of WO 3 addition on the microstructures and the microwave dielectric properties of Zr 0.8Sn 0.2TiO 4 ceramics have been investigated. It is found that low-level doping of ZnO (1 wt%) and WO 3 (up to 1 wt%) can significantly improve the density and dielectric properties of Zr 0.8Sn 0.2TiO 4 ceramics. Zr 0.8Sn 0.2TiO 4 ceramics with additives could be sintered to a theoretical density higher than 98% at 1340°C. Second phases were not observed at the level of 0.25–1 wt% WO 3 addition. The dielectric constant (ϵ r ) and the temperature coefficient of resonant frequency (τ f ) were not significantly affected, while the unloaded quality factors Q were effectively promoted by WO 3 addition. An ϵ r value of 37.8, Q· f value of 61,000 (at 7 GHz), and τ f value of −3.9 ppm/°C were obtained for 1 wt% ZnO-doped Zr 0.8Sn 0.2TiO 4 ceramics with 0.25 wt% WO 3 addition sintered at 1340°C.

Effect of WO 3 doping on dielectric temperature characteristics of lead complex perovskite ferroelectric ceramics

The effect of WO 3 doping on the dielectric temperature characteristics and the microstructure of a ternary ceramic system were investigated. Both the increase of WO 3 doping level and the increase of sintering temperature led to a decrease in dielectric constant and the flatting of dielectric curves. The presence of a liquid phase and the pyrochlore phase cause this decrease. Also, microstructural and elemental analyses of the ceramics revealed the structure within one grain consists of three parts: the core, the shell and in-between one. This inhomogeneous composition distribution contributes to flat dielectric temperature dependence.

Magnetic properties of NiCuZn ferrites with addition of tungsten trioxide

The effect of WO 3 addition on the properties of NiCuZn ferrite, (Ni 0.2Cu 0.2Zn 0.6O) 1.02(Fe 2O 3) 0.98, has been investigated in this study. The enhanced electrical and magnetic properties obtained from WO 3 addition into NiCuZn ferrites were also shown in this study. Q-factor at 10 MHz of NiCuZn ferrites increased at higher electrical resistivity, but no significant change in initial permeability. The resonance frequency of those NiCuZn ferrites was shifted to a higher range, which means relaxation time was also decreased over 0.6 wt% of WO 3 content.

Effect of n-WO 3 thin film deposition on the photoelectrochemical properties of the textured p-Si electrode

The effect of WO 3 thin film deposition on the photoelectrochemical properties of the textured p-Si electrodes, which were prepared by anisotropic etching of (100) p-Si in alkaline solution, have been investigated. The textured p-Si surface was covered with small pyramids having (111) planes, which led to decrease in surface reflectance and to increase in effective surface area. The photocurrents of both textured p-Si and WO 3/textured p-Si electrodes tended to increase with increasing etching time up to 40 min and then slightly decreased with further etching. But the WO 3/textured p-Si electrode showed relatively higher photocurrent at a less cathodic potential compared to the textured p-Si electrode without WO 3 layer. These results were explained in terms of a degree of surface texturing, an intrinsic property of WO 3 thin film on the surface reflectance and a charge transfer behavior due to the p-n heterojunction.

Effect of WO<sub>3</sub> Addition on the Electrical and Magnetic Properties of NiCuZn Ferrites

Effect of WO<sub>3</sub> Addition on the Electrical and Magnetic Properties of NiCuZn Ferrites