Search Results (62)

Tungsten-doped vanadium dioxide (W-VO₂) shows semiconductor-to-metal phase transition properties at room temperature, which is an ideal thermo-chromic smart window material. However, low visual transmittance and solar modulation limit its application in building energy saving. In this paper, a W-VO_2−x@AA core-shell nanoparticle is proposed to improve the thermo-chromic performance of W-VO₂. Oxygen vacancies were used to promote the connection of W-VO_2−x nanoparticles with L-ascorbic acid (AA) molecules. Oxygen vacancies were tuned in W-VO₂ nanoparticles by thermal annealing temperatures in vacuum, and W-VO_2−x@AA nanoparticles were synthesized by the hydrothermal method. A smart window was formed by dispersing W-VO_2−x@AA core-shell nanoparticles into PVP evenly and spin-coating them on the surface of glass. The visual transmittance of this smart window reaches up to 67%, and the solar modulation reaches up to 12.1%. This enhanced thermo-chromic performance is related to the electron density enhanced by the AA surface molecular coordination effect through W dopant and oxygen vacancies. This work provides a new strategy to enhance the thermo-chromic performance of W-VO₂ and its application in the building energy-saving field. Full article

Photoelectrochromic devices, which combine light-induced color change with energy-efficient optical modulation, have attracted significant attention for applications such as smart windows, displays, and optical sensors. However, achieving high optical modulation, fast switching speeds, and long-term stability remains a major challenge. In this study, we explore the structural and photoelectrochromic enhancements in tungsten oxide (WO₃) films achieved by doping with molybdenum disulfide quantum dots (MoS₂ QDs) and grapheneoxide–molybdenum disulfide quantum dots (GO–MoS₂ QDs) for advanced photoelectrochromic devices. X-ray diffraction (XRD) analysis revealed that doping with MoS₂ QDs and GO–MoS₂ QDs leads to a reduction in the crystallite size of WO₃, as evidenced by the broadening and decrease in peak intensity. Transmission Electron Microscopy (TEM) confirmed the presence of characteristic lattice fringes with interplanar spacings of 0.36 nm, 0.43 nm, and 0.34 nm, corresponding to the planes of WO₃, MoS₂, and graphene. Energy-Dispersive X-ray Spectroscopy (EDS) mapping indicated a uniform distribution of tungsten, oxygen, molybdenum, and sulfur, suggesting homogeneous doping throughout the WO₃ matrix. Scanning Electron Microscopy (SEM) analysis showed a significant decrease in film thickness from 724.3 nm for pure WO₃ to 578.8 nm for MoS₂ QD-doped WO₃ and 588.7 nm for GO–MoS₂ QD-doped WO₃, attributed to enhanced packing density and structural reorganization. These structural modifications are expected to enhance photoelectrochromic performance by improving charge transport and mechanical stability. Photoelectrochromic performance analysis showed a significant improvement in optical modulation upon incorporating MoS₂ QDs and GO–MoS₂ QDs into the WO₃ matrix, achieving a coloration depth of 56.69% and 70.28% at 630 nm, respectively, within 10 min of 1.5 AM sun illumination, with more than 90% recovery of the initial transmittance within 7 h in dark conditions. Additionally, device stability was improved by the incorporation of GO–MoS₂ QDs into the WO₃ layer. The findings demonstrate that incorporating MoS₂ QDs and GO–MoS₂ QDs effectively modifies the structural properties of WO₃, making it a promising material for high-performance photoelectrochromic applications. Full article

Tungsten disulfide (WS₂) is attractive for the development of chemiresistive sensors due to its favorable band gap, as well as its mechanical strength and chemical stability. In this work, we elaborate a procedure for the synthesis of thin films consisting of vertically and/or horizontally oriented WS₂ nanoparticles by sulfurizing nanometer-thick tungsten layers deposited on oxidized silicon substrates using magnetron sputtering. According to X-ray photoelectron spectroscopy and Raman scattering data, WS₂ films grown in an H₂-containing atmosphere at 1000 °C are almost free of tungsten oxide. The WS₂ film’s thickness is controlled by varying the tungsten sputtering duration from 10 to 90 s. The highest response to nitrogen dioxide (NO₂) at room temperature was demonstrated by the film obtained using a tungsten layer sputtered for 30 s. The increased sensitivity is attributed to the high surface-to-volume ratio provided by the horizontal and vertical orientation of the small WS₂ nanoparticles. Based on density functional calculations, we conclude that the small in-plane size of WS₂ provides many high-energy sites for NO₂ adsorption, which leads to greater charge transfer in the sensor. The detection limit of NO₂ calculated for the best sensor (WS₂-30s) is 15 ppb at room temperature and 8 ppb at 125 °C. The sensor can operate in a humid environment and is significantly less sensitive to NH₃ and a mixture of H₂, CO, and CO₂ gases. Full article

This research investigates the application of activated tungsten inert gas (A-TIG) welding on boiler grade SA516 Grade 70 carbon steel using nano titanium dioxide (TiO₂) nano flux to enhance weld penetration depth, microstructure, and mechanical properties. A unique flux application technique was devised and experiments were carried out. Response Surface Methodology (RSM) was utilized to optimize weld parameters, namely arc length, welding current, and travel speed.The selection between A-TIG and TIG welding significantly influences penetration depth, as A-TIG benefits from arc constriction and elevated current density. The welding speed is crucial for controlling heat input, whereas current and arc length enhance penetration by influencing arc force and energy distribution. Optimizing all three parameters guarantees optimal penetration and weld quality. Microstructural research revealed enhanced mechanical properties in A-TIG weldments, distinguished by acicular ferrite in the fusion zone, which augmented toughness and tensile strength (520 MPa) compared to TIG weldments (470 MPa) and the base metal (480 MPa). Although A-TIG welds exhibited reduced impact toughness (68 J) relative to the base metal (128 J), A-TIG joints had superior ductility. The findings of this research clearly demonstrate the A-TIG welding process improved the depth of penetration and mechanical strength of the weld joints. Full article

Perovksite solar cells have emerged as a promising photovoltaic technology due to their high increasing power conversion efficiency (PCE). However, challenges related to thermal instability and material toxicity, especially in lead-based perovskites, bring the need to investigate alternative materials and structural designs. This study investigated the current–voltage and power–voltage characteristics of lead-free PSCs based on tin- and germanium using a two-diode equivalent circuit model. The novelty of this work was based on the intensive evaluation of three different electron transport layers (ETLs)—titanium dioxide (TiO₂), zinc oxide (ZnO), and tungsten trioxide (WO₃)—under different ambient temperature conditions (5 °C, 25 °C, and 55 °C) to study their impacts on device performance and the thermal stability. SCAPS-1D simulations were used to model the electrical and optical behaviors of the proposed perovskite structures, and the results were validated by using the two-diode model. The main performance parameters that were considered were open-circuit voltage, short-circuit current, maximum power point, and fill factor. The results showed that TiO₂ was better than ZnO and WO₃ as an ETL, achieving a PCE of 24.83% for Sn-based perovskites, and ZnO was the better choice for Ge-based perovskites at 25 °C, with an efficiency reaching ~15.39%. The three ETL materials showed high thermal stability when analyzing them at high ambient temperatures reaching 55 °C. Full article

The electrocatalytic reduction of nitric oxide and nitrogen dioxide (NOx) remains a significant challenge due to the need for stable, efficient, and cost-effective materials. This study presents a novel support system for NOx reduction in alkaline media, composed of ZrO₂-WO₃-C (ZWC), synthesized via coprecipitation. Platinum nanoparticles (10 wt.%) were loaded onto ZWC and Vulcan carbon support, using similar methods for comparison. Comprehensive physicochemical and electrochemical analyses (N₂ physisorption, XRD, XPS, SEM, TEM, and cyclic and linear voltammetry) revealed that PtZWC outperformed PtC and commercial PtEtek in NOx electrocatalysis. Notably, PtZWC exhibited the highest total electric charge for NOx reduction. At the same time, the hydrogen evolution reaction (HER) was shifted to more negative cathodic potentials, indicating reduced hydrogen coverage and a modified dissociative Tafel mechanism on platinum. Additionally, the combination of WO₃ and ZrO₂ in ZWC enhanced electron transfer and suppressed HER by reducing NO and hydrogen atom adsorption competition. While the incorporation of WO₃ and ZrO₂ lowered the surface area to 96 m²/g, it significantly improved pore properties, facilitating better Pt nanoparticle dispersion (3.06 ± 0.85 nm, as confirmed by SEM and TEM). XRD analysis identified graphite and Pt phases, with monoclinic WO₃ broadening PtZWC peaks (20–25°). At the same time, XPS confirmed oxidation states of Pt, W, and Zr and tungsten-related oxygen vacancies, ensuring chemical stability and enhanced catalytic activity. Full article

This study explores the surface characteristics evaluation and performance optimization of tungsten (W)-doped vanadium dioxide (VO₂) thin films. W-doped vanadium dioxide films were deposited on B270 glass substrates using an electron beam evaporation technique combined with the ion beam-assisted deposition (IAD) method. The Taguchi method was used to analyze the performance optimization of VO₂ thin films, and L₁₆ orthogonal array design and Minitab software were used for optimization calculations. The surface roughness, visible light transmittance, infrared transmittance, and residual stress of un-doped and tungsten-doped (3–5%) VO₂ thin films are set as the quality performance indicators of thin films. The goal is to identify the key factors that affect the performance of VO₂ thin films during deposition and optimize their process parameters. The experimental results showed that a VO₂ thin film with 3% tungsten doping, an oxygen flow rate of 60 sccm, a heating temperature of 280 °C, and a film thickness of 60 nm exhibited the lowest surface roughness of 2.12 nm. A VO₂ thin film with 5% tungsten doping, an oxygen flow rate of 0 sccm, a heating temperature of 280 °C, and a film thickness of 60 nm had the highest visible light transmittance at 64.33%. When the oxygen flow rate was 60 sccm, the heating temperature was 295 °C, the film thickness was 150 nm, and the tungsten doping was 5%, the VO₂ thin film showed the lowest infrared transmittance of 31.34%. A thin film with 5% tungsten doping, an oxygen flow rate of 20 sccm, a heating temperature of 265 °C, and a film thickness of 120 nm exhibited the lowest residual stress of −0.195 GPa. Full article

Imitation precious wood materials have become a research focus due to their good quality, high safety level, excellent performance, rich color, varied textures, and high utilization rates. However, their uneven dyeing, poor color stability, and lack of durability limit their further application. This study utilized a neural network model optimized with the Gray Wolf Algorithm (GWA) for color matching, using acidic dyes as raw materials and deep eutectic solvents (DESs) for modification. Functional reagents like nano tungsten trioxide (WO₃) and titanium dioxide (TiO₂) were introduced alongside polyvinyl alcohol (PVA) as a modifier. A dyeing-enhancement modification process was employed to create a poplar veneer that exhibited uniform and stable color performance with a smooth surface, mimicking that of precious wood. Computerized color matching was used to adjust the dye formulation for staining, ensuring stable colorimetric values on the veneer surface, which closely resembled natural precious wood. The average mean squared error in dye concentration prediction, after processing with the Gray Wolf Algorithm and a basic neural network algorithm, decreased from 0.13 to 0.006, ensuring repeatability and consistency in wood dyeing. Analysis and characterization using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and permeability testing revealed that nano TiO₂ and WO₃ particles were uniformly distributed within the wood cell lumens and firmly bonded. Mechanical testing on PVA-glued veneers showed that compared to untreated poplar veneers, the tensile strength of the imitation wood increased by approximately 62.5%, and the bending strength reached 809.09 MPa, significantly improving the flexibility and tensile properties of the poplar veneer. This study is the first to adopt a DES-modified dyeing-enhancement modification process to improve the dyeing performance, uniformity, durability, and structural stability of wood, showcasing its great potential in architectural decoration, high-end furniture, and artisanal crafts. Full article

Thin films based on tungsten oxide (WO₃) were grown by nanosecond pulsed laser deposition on alumina printed-circuit boards to fabricate electrochemical sensors for nitrogen dioxide (NO₂) detection. Samples exposed to thermal annealing (400 °C for 3 h) were also produced to compare the main properties and the sensor performance. Before gas testing, the morphology and structural properties were investigated. Scanning electron microscopy and atomic force microscopy showed the formation of granular films with a more compact structure before the thermal treatment. Features of the main WO₃ phases were identified for both as-deposited and annealed samples by Raman spectroscopy, whereas X-ray diffraction evidenced the amorphous nature of the as-deposited samples and the formation of crystalline phases after thermal annealing. The as-deposited samples showed a higher W/O ratio, as displayed by energy-dispersive X-ray spectroscopy. An Arrhenius plot revealed a lower activation energy (0.11 eV) for the as-deposited thin films, which are the most electrically conductive samples, presenting a better gas response (30% higher than the response of the annealed ones) in the investigated NO₂ concentration range of 5–20 ppm at the moderate device operating temperature of 75 °C. This behavior is explained by a larger quantity of oxygen vacancies, which enhances the sensing mechanism. Full article

Tungsten-doped TiO₂ thin films were prepared by sol–gel method on fluorine-doped tin oxide-coated substrates as working electrodes of dye-sensitized solar cells. The influences of different W doping (0, 2, 4, 6, and 8 at%) on the microstructure, optical, and photovoltaic properties of the W-TiO₂ thin-film DSSCs were studied by the measurement of X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Brunauer–Emmett–Teller (BET) analysis, and electrochemical impedance spectroscopy (EIS). An optimal DSSCs performance was observed with a 6 at% W-doped TiO₂ thin film, resulting in a Voc of 0.68 V, a Jsc of 20.2 mA/cm², an FF of 68.6%, and an efficiency (η) of 9.42%. The efficiency of DSSCs with 6 at% W-doped TiO₂ photoanode improved by 75%. This is because the 6 at% W-doped TiO₂ thin film increases the specific surface area and electron transfer rate. Full article

The undoped and tungsten (W)-doped vanadium dioxide (VO₂) thin films were prepared by electron beam evaporation associated with ion-beam-assisted deposition (IAD). The influence of different W-doped contents (3–5%) on the electrical, optical, structural, and thermo-mechanical properties of VO₂ thin films was investigated experimentally. Spectral transmittance results showed that with the increase in W-doped contents, the transmittance in the visible light range (400–750 nm) decreases from 60.2% to 53.9%, and the transmittance in the infrared wavelength range (2.5 μm to 5.5 μm) drops from 55.8% to 15.4%. As the W-doped content increases, the residual stress in the VO₂ thin film decreases from −0.276 GPa to −0.238 GPa, but the surface roughness increases. For temperature-dependent spectroscopic measurements, heating the VO₂ thin films from 30 °C to 100 °C showed the most significant change in transmittance for the 5% W-doped VO₂ thin film. When the heating temperature exceeds 55 °C, the optical transmittance drops significantly, and the visible light transmittance drops by about 11%. Finally, X-ray diffraction (XRD) and scanning electron microscope (SEM) were used to evaluate the microstructure characteristics of VO₂ thin films. Full article

Pulse-magnetron-sputtered long-term superhydrophilic coatings have been synthesized to functionalize the surfaces of solid-state cooling devices, e.g., electrocaloric heat pumps, where not only a complete wetting of the surface by a fluid is intended, but also fast wetting and dewetting processes are required. The coatings consist of a (Ti,Si)O₂ outer layer that provides lasting hydrophilicity thanks to the mesoporous structure, followed by an intermediate WO₃ film that enables the reactivation of the wettability through visible light irradiation, and a W underlayer which can work as a top electrode of the electrocaloric components thanks to its suitable electrical and thermal conductivity properties. Process parameter optimization for each layer of the stack as well as the influence of the microstructure and composition on the wetting properties are presented. Finally, water contact angle measurements, surface energy evaluations, and a contact line dynamics assessment of evaporating drops on the coatings demonstrate that their enhanced wetting performance is attributed not only to their intrinsic hydrophilic nature but also to their porous microstructure, which promotes wicking and spreading at the nanometric scale. Full article

This paper presents the results of tribological tests on WE43 and WE54 magnesium alloys with rare earth metals performed in linear reciprocating motion for four different material couples (AISI 316-L steel, silicon nitride—Si₃N₄, WC tungsten carbide, and zirconium dioxide—ZrO₂). Additionally, magnesium alloys were subjected to a complex heat treatment consisting of precipitation hardening combined with a deep cryogenic treatment. The study presents the effect of deep cryogenic treatment combined with precipitation hardening on the tribological properties of WE43 and WE54 alloys. Tribological tests revealed the most advantageous results for the magnesium alloy—AISI 316-L steel friction node. For both alloys tested after heat treatment, a nearly 2-fold reduction in specific wear rate has been achieved. Furthermore, microscopic examinations of the wear track areas and wear products were performed, and the wear mechanisms and types of wear products occurring in linear reciprocating friction were determined. Wear measurements were taken using the 3D profilometric method and compared with the results obtained from calculations performed in accordance with ASTM G133 and ASTM D7755, which were modified to improve the accuracy of the calculation results (the number of measured profiles was increased from four to eight). Appropriately selected calculation methods allow for obtaining reliable tribological test results and enabling the verification of both the most advantageous heat treatment variant and material couple, which results in an increase in the durability of the tested alloys. Full article

The synergetic effects of electromagnetic and chemical enhancements via the combination of semiconductor nanomaterials with noble metal nanoparticles is crucial to the performance of surface-enhanced Raman scattering (SERS). Here, WO₃/TiO₂ photonic crystal films in the form of three-dimensional inverse opals were fabricated via the co-assembly of polymer colloidal templates with water-soluble precursors in order to simultaneously grow both constituent metal oxides with tailored electronic properties and photonic band gaps. The surface modification of compositionally tuned WO₃/TiO₂ inverse opals by Ag nanoparticles is demonstrated to be an efficient method to boost SERS efficiency in the detection of 4−mercaptobenzoic acid via the synergy of plasmonic effects with charge transfer and slow-light trapping. Full article

In this research, a life cycle inventory (LCI) is developed for tungsten carbide–cobalt (WC-Co) coatings deposited via atmospheric plasma spray (APS), high-velocity oxy-fuel (HVOF), and cold gas spray (CGS) techniques. For the APS process, a mixture of Ar/H₂ was used, while the HVOF process was fueled by H₂. The carrier gas for CGS was N₂. This study aims to determine and quantify the inputs (consumption of inputs and materials) and outputs (emissions to air, soil, water, and waste generation) that could be used in the life cycle analysis (LCA) of these processes. The dataset produced will allow users to estimate the environmental impacts of these processes using WC-Co feedstock powder. To obtain a complete and detailed LCI, measurements of electrical energy, gas, WC-CO powder, and alumina powder consumption were performed (the use of alumina was for sandblasting). Furthermore, emissions like carbon dioxide (CO₂), carbon monoxide (CO), and noise were also measured. This practice allowed us to determine the input/output process quantities. For the first time, it was possible to obtain LCI data for the APS, HVOF, and CGS deposition processes using WC-12Co as a feedstock powder, allowing access to the LCI data to a broader audience. Comparisons were made between APS, HVOF, and CGS processes in terms of consumption and emissions. It was determined that the APS process consumes more electrical energy and that its deposition efficiency is higher than the other processes, while the HVOF process consumes a large amount of H₂, which makes the process costlier. CGS has comparatively low electricity consumption, high N₂ consumption, and low deposition efficiency. The APS, HVOF, and CGS processes analyzed in this study do not emit CO, and CO₂ emissions are negligible. Full article