جستجوی مقالات مرتبط با کلیدواژه « WO3 » در نشریات گروه « مواد و متالورژی »

Photocatalytic removal of water and air pollution has received much attention today. Many photocatalysts based on semiconductors have been developed and used. Binary and even ternary composites have been developed to solve the drawback of semiconductors, including high band gaps and short life time of charge carriers. In this study, a three-component composite of TiO2/CuO/WO3 was synthesized by adding WO3 to TiO2/CuO. Their structural properties were evaluated by analyzes X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), and diffusive reflectance spectra (DRS) and their performance by methylene orange dye removal. The results of XRD and SEM analysis showed purity and uniform distribution of elements. The combination of TiO2/10%CuO and 15%WO3 with band gap 2.66 eV showed the highest rate constant of dye removal (0.0301 min-1).

This paper presents the wet chemical synthesis of WO3/TiO2 nanocomposites using hydrothermally prepared monoclinic WO3 and anatase TiO2 nanoparticles as composite matrices and filler, respectively. The nanocomposites were prepared in different compositions, i.e. WO3:TiO2 ratio (w/w) of (1:1), (1:3), and (3:1). Physicochemical properties of the resultant WO3/TiO2 nanocomposites were evaluated by X-ray diffraction (XRD), scanning electron microscopy (SEM), BET N2 adsorption-desorption isotherms, UV/vis, and Raman spectroscopy. The resultant nanocomposites exhibited a mesoporous structure with specific surface area of up to 11.5 m2 g-1, where TiO2 constituent contributed to higher surface area, especially in (1:3) ratio, and higher number of defect sites. While there was no impurities in the investigated nanocomposites as revealed by XRD analysis and Raman spectra, the WO3:TiO2 (1:3) nanocomposites showed the highest light harvesting ability indicated by higher absorption amplitude in both UV and visible regime. Three different kinetic models including pseudo-first-order, pseudo-second order, and Langmuir-Hinshelwood were applied to experimental data. The pseudo-second-order was found to be the best representing model and the adsorption kinetic studies indicated that chemisorption initially dominated the degradation mechanism. Finally, photocatalytic activity of nanocomposites was compared for photodegradation of methylene blue (MB) aqueous medium and in a good agreement with physicochemical properties, WO3:TiO2 (1:3) nanocomposites yielded the highest MB degradation rate (k ~ 0.162 min-1) and efficiency (96%) within 120 min under UV irradiation.

Tungsten oxide (WO3) and tungsten oxide hydrate (WO3.H2O) nanoparticles were synthesized via microwave-assisted solution combustion in comparison with the acidic precipitation method. Oxalic acid was used as a surfactant and forming agent in the acidic precipitation method. In addition to oxalic acid, glycine and citric acid were also used as fuels in the microwave-assisted combustion method. The synthesis process was investigated by thermogravimetric (TG) and Differential Thermal Analysis (DTA) analysis. The obtained nanoparticles were analyzed using the scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques. The sample synthesized via the acidic precipitation method showed an orthorhombic crystal structure. One of the samples synthesized via the microwave-assisted solution combustion method was monoclinic and the two others were amorphous. The acidic precipitation method resulted in uniform plate-like structures while the combusted samples indicated irregular spherical morphology. Fourier-transform infrared (FTIR) analysis revealed stretching-vibrating bands relating to W-O bonds in the synthesized tungsten oxide nanoparticles. The bandgap energy of the nanoparticles calculated using UV-Vis spectra and Tauc plot extrapolation increased with decreasing the particle size. The data of reflectance and colorimetry had good agreement with the maximum peak position in the absorption spectra. The results indicated that the acidic precipitation method controls the particle's morphology as well as the size distribution. Although the combustion of fuels releases a lot of heat, the synthesis by solution combustion can control the size and shape of the nanoparticles, which can be an appropriate method for mass production of nanoparticles.

Methanol (CH3OH) is a colorless liquid with a mild odor. The wide ranges of applications, toxicity and clinical implications of methanol have made necessary to develop reliable and high-performance methanol sensors. In this paper, WO3 thin films were deposited on SiO2/Si substrates by e-beam evaporation technique under normal and oblique angles and then post-annealed at 500 °C with a flow of oxygen for 4h to achieve a good crystallinity. The crystalline structure of the samples was confirmed by X-ray diffraction analysis while the physical adsorption isotherm was used to measure the porosity and effective surface area. These results reveal that the deposited sample under oblique angle shows more crystallinity, and porosity relative to the sample deposited at the normal angle. The response of the samples was tested with respect to methanol vapour with different concentrations in the temperature range of 140–260 °C. Reproducibility and stability of the samples were also investigated.

In this research, WO3 and Au-WO3 thin films were prepared at different temperatures using the sol gel method. The effect of gold nanoparticles (GNPs) on the electrochromic properties of W 3 was also studied. 2.5 nm GNP was synthesized through sodium citrate reduction of gold chloride in an aqueous solution. These films were characterized by XRD, SEM, TEM, and spectrophotometer analyses. The films annealed at 200˚C were amorphous and crystallized at high temperatures. According to the scanning electron microscopy (SEM) image, the films annealed at 200˚C were dense. Moreover, the particles were uniformly distributed on them. Spectrophotometer analysis of WO3 thin films annealed at 200˚C showed high electrochromic properties (transmission modulation (ΔT) was 72% and response time was 3.25s for 80% coloring). Spectrophotometer analysis of Au-WO3 thin films annealed at 200˚C showed that their coloration properties increased (ΔT = 78%) and response duration decreased (1.65s) when gold nanoparticles were added. This enhancement is attributed to the increased conductivity caused by the addition of gold nanoparticles as well as the surface plasmon resonance based absorption of GNPs.