Influence Of Tungsten Research Articles

Low-temperature stabilization of rutile in W-doped Titania thin films deposited by magnetron Co-Sputtering

Tungsten doped Titania thin films were sputtered on a silicon substrate by magnetron co-sputtering. The influence of tungsten on Vickers hardness and crystallographic changes was studied in films subjected to stepped annealing treatments. Rutile is the dominant phase with crystallite size ∼ 10 nm after 500 °C annealing. The films, doped with 1.79 % W, exhibit the highest hardness (20.88 GPa), a rutile-anatase mixture (80:20) and a preferential shift in crystallographic orientation from (101) to (110). The homogeneous distribution of tungsten in TiO2 stabilizes rutile at 500 °C, providing an innovative and simple strategy for its synthesis, thus expanding the options for substrate materials.

Influence of Tungsten on the Structure and Properties of a Composite Based on Fe–30Cr Steel

Influence of Tungsten on the Structure and Properties of a Composite Based on Fe–30Cr Steel

Influence of tungsten on microstructure evolution and mechanical properties of selected novel FeCoCrMnWx high entropy alloys

A novel equiatomic FeCoCrMnW-based High Entropy Alloy system has been designed with the help of well-established thermodynamic parameters as well as a unique learning strategy based on multi-criteria decision-making tool named ‘TOPSIS’. The present study describes the effect of W addition on as-cast FeCoCrMnWx HEAs on their phase identities and mechanical properties. The results showed that the as-cast FeCoCrMnWx (molar ratio x = 0.2, 0.4, 0.6, 0.8, 1) HEAs were composed of BCC, FCC and several minor Fe–Cr and Co–Cr type σ phases. Transmission Electron Microscopy (TEM) analysis confirms the formation of potentially-embrittling intermetallic phases in minor amounts. The designed HEAs exhibit desirable compressive fracture strength of 1771 MPa and compressive plasticity of 17.1% at room temperature. Hike in Vickers microhardness and compressive strength values could be attributed to a large atomic radius of ‘W’ which further plays a crucial role in grain refinement and solid solution strengthening. This work not only provides advancement in decision making studies of HEAs with new and essential perspectives but also reveals possibly concealed relationships amongst some critical belief in the field of material science.

Crevice corrosion of solution annealed 25Cr duplex stainless steels: Effect of W on critical temperatures

In this work, the influence of tungsten on the crevice corrosion resistance of three super duplex stainless steels (SDSS) containing 0.0, 0.6, and 2.1 wt.% W was determined. The PD-GS-PD technique was used to estimate the critical crevice repassivation temperature by performing tests at different temperatures. Additionally, long-term potentiostatic experiments were conducted as a function of temperature in natural seawater to validate PD-GS-PD testing. Results showed that W improved crevice corrosion resistance as evidenced by the higher initiation and repassivation crevice temperatures, which were 7.5–15 °C higher in the 2.1 wt.% W SDSS than in the W-free case.

The Role of Tungsten on the Phase Transformation Kinetics and its Correlation with the Localized Corrosion Resistance of 25Cr Super Duplex Stainless Steels

Super Duplex Stainless Steels (SDSS) have excellent corrosion resistance due to their high concentration of alloying elements like Cr, Mo, and N. There is still, however, disagreement on the role of tungsten in the corrosion resistance of stainless steels. In this regard, the influence of tungsten on tertiary phase precipitation kinetics remains a chief source of controversy. In this study, three different SDSS with different tungsten contents have been investigated, namely, UNS S32750 (W-free), S32760 (0.6 wt% W), and S39274 (2.1 wt% W). Different isothermal aging conditions were studied, followed by microstructure characterization using scanning electron microscopy, energy dispersive X-ray spectroscopy, electron backscatter diffraction, and transmission electron microscopy to quantify the type and volume fraction of tertiary phases and intermetallic compounds. Time-Temperature-Transformation-Corrosion maps were constructed by quantifying the changes in pitting corrosion resistance caused by the precipitation of incremental amounts of deleterious phases. Results showed that 2.1 wt% W additions retarded the precipitation kinetics of all tertiary phases—including σ-phase—favoring the formation of χ-phase. Both χ- and σ-phase affected corrosion resistance, reducing the critical pitting temperature by 10 °C–20 °C at concentrations well below 1 vol%.

Adsorption and degradation of some psychiatric drugs by sol-gel synthesized titania-based photocatalysts: influence of tungsten and sodium content

Mesoporous anatase nanopowders were doped with 0.05−0.5 mol% of W6+, in order to obtain more efficient photocatalyst than TiO2 Degussa P25 in the degradation of amitriptyline (AMI) under simulated solar irradiation (SSI). Dominant XRPD peaks were ascribed to anatase phase, with additional peaks which could correspond to brookite, TiO2 bronze and sodium titanate, Na2Ti9O19. The Raman scattering measurements have confirmed anatase as dominant phase, with broad Raman feature at ~270 cm−1 possibly related to Ti–O–Na stretching vibration. All W-doped nanopowders have shown enhanced adsorption and higher efficiency in photodegradation of AMI in comparison to TiO2 Degussa P25 under the same conditions. The catalyst doped with 0.4 mol% of W6+, which has shown the highest efficiency in degradation of AMI under SSI, has also been tested in degradation of alprazolam (ALP). The effect of substrate type (AMI and ALP), catalyst loading, and initial substrate concentration on photocatalytic degradation using SSI was examined. The identification of the species responsible for the photocatalytic degradation of AMI and ALP by the catalyst doped with 0.4 mol% of W6+ was performed in the presence of various scavengers under SSI. The major role in degradation of AMI may be attributed to hydroxyl radicals, whereas superoxide anion radicals, singlet molecular oxygen and hydroxyl radicals contribute to degradation of ALP.

Influence of W and effect of loading mode on the substructural evolution of reduced activation ferritic/martensitic (RAFM) steels

Influence of tungsten (W) on the evolution of substructure during creep-fatigue interaction (CFI) and effect of loading mode in terms of continuous cycling (CC) and CFI at 823 K of reduced activation ferritic/martensitic (RAFM) steels has been investigated. Increase in W from 1.4 to 2 wt% resulted in an improvement of 1.6 times of CFI life. Electron back scatter diffraction (EBSD) analysis of CFI deformed specimens demonstrated that the subgrain size was 1.8 times smaller and boundary dislocation density was 3 times higher in case of 2 wt% W steel compared to 1.4 wt% W. It can be deduced that W addition resulted in decrease in the recovery rate and enhancing the CFI life. In context to loading mode, the subgrain size was 1.5 times higher and dislocation density was 2 times lower in case of CC tested specimen with respect to CFI tested. Under CFI, the number of cycles to failure were drastically reduced due to the synergistic damage of cyclic loading and creep deformation.

Biocompatibility evaluation and corrosion resistance of tungsten added Co-30Cr-4Mo-1Ni alloy.

Biomaterials are continuously being developed to overcome the drawbacks of existing materials and provide improved function in artificial organs. Currently Co-Cr based alloys are used in many medical applications such as hip and knee implants which still require modification to better perform. In this article, therefore, the influence of tungsten allying element on electrochemical corrosion resistance and biocompatibility behaviour of a recently developed Co-30Cr-4Mo-1Ni alloy composition were investigated. The tungsten modified alloys were prepared by using a high temperature vertical vacuum casting technique at five different weight percentages (0-4wt.% tungsten). The electrochemical corrosion behaviour of all the samples under NaCl solution was studied by using potentiodynamic scan method. The corrosion characteristics were investigated in terms of corrosion potential (Ecorr) and corrosion current density (Icorr). From the results of the analysis, it was observed that out of all samples, an alloy with 2wt.% of tungsten in composition (i.e. Co-30Cr-4Mo-1Ni-2W) exhibited better corrosion resistance. Furthermore, histopathological evaluations in subcutaneous tissue were performed in rats according to the standard ISO 10993 to examine the biocompatibility of the prepared samples. The results showed no evidence of inflammatory cell migration, no epidermal necrosis, no vacuolar degeneration of basal cell, no adnexal atrophy and vesicle formation of any samples. The obtained findings indicate that Co-30Cr-4Mo-1Ni-2W can be used in biomedical applications including femoral component of hip and knee implants.

Assessment of Trace Elements in Plantago holosteum Scop. (Plantaginaceae) from Abandoned Tungsten Mine Works Using Inductively Coupled Plasma–Mass Spectrometry

ABSTRACTThe influence of tungsten on the uptake and translocation of essential elements (B, Bi, Cd, Co, Cr, Cu, Fe, Mn, Mo, Pb, Zn, and W) of Plantago holosteum around the abandoned tungsten mine works on Uludağ Mountain, Turkey was evaluated. Open-wet and Kjeldahl digestion procedures were applied to the samples before elements were determined by inductively coupled plasma–mass spectrometry. Accuracy was evaluated using standard tea and spinach leaf and soil-certified reference materials. The novel approach of this work identified P. holosteum as a possible candidate bioaccumulator species, which was widespread in the tungsten mining area and provided overall, realistic evaluations for many elements, particularly W. Thus, the specific behavior of the selected species separated this species from the others in this damaged ecosystem. The W concentrations in soils and plants were in the range from 6 to 2591 mg kg−1 dry weight and 0.6 to 85.3 mg kg−1 dry weight, respectively. The concentrations of elements in soil samples from the waste removal pool were higher than those from the unpolluted sites, and all elements except manganese increased in plant samples.

Studying the Influence of Tungsten and Chromium Additives in Flux Cored Wire System Fe-C-Si-Mn-Mo-Ni-V-Co on Surfaced Metal Properties

In the laboratory conditions were manufactured flux cored wire system Fe-C-Si-Mn-Mo-Ni-V-Co samples, studied the influence of tungsten and chromium appending in surfacing wire charge. Conducted metallographic researches of surfaced metal: microstructure evaluate, grain size, nonmetallic oxides inclusions impurity. Defined hardness and wearout speed of the deposited layers. Conducted evaluation of the chemical composition influence on surfaced metal wearout and hardness.

Impact of tungsten doping on the dynamics of the photo-induced insulator-metal phase transition in VO2 thin film investigated by optical pump-terahertz probe spectroscopy

The influence of tungsten (W) doping on the ultrafast dynamics of the photo-induced insulator-metal phase transition (IMT) is investigated at room temperature in epitaxially grown vanadium dioxide (VO2) thin films by means of optical pump-terahertz (THz) probe spectroscopy. It is observed that the THz transmission variation of the films across the IMT follows a bi-exponential decrease characterized by two time constants, one corresponding to a fast process and the other to a slower process. W-doping (i) reduces the photo-excitation fluence threshold required for triggering the IMT, (ii) accelerates the slow process, and (iii) increases the THz transient transmission variation for corresponding fluences. From the Drude-Smith model, it is deduced that a strong carrier confinement and an enhancement of the transient conductivity occur across the IMT. The IMT is also accompanied by an increase in the carrier concentration in the films, which is enhanced by W-doping. Our results suggest that W-doped VO2 could be advantageously exploited in applications such as ultrafast THz optical switching and modulation devices.

Influence of Tungsten on Dry Sliding Wear Behaviour of Sintered/Hot Extruded P/M Alloy Steels (Fe-C-W-Ti)

In the present scenario, Powder Metallurgy (P/M) is an established manufacturing process used to make components of complex geometries with high strength and tolerances by using incredible materials which are difficult to melt or form by other processes. The mechanical properties and microstructures will determine the component characteristic dependent on the final obtained density of sintered P/M alloy steels. An attempt has been made to investigate the dry sliding wear behaviour of sintered/hot extruded P/M alloy steels with Fe-1C as base material, W (Tungsten) and Ti (Titanium) as an alloying element. The wear test was carried out by using a pin-on-disc tribometer (ASTM G99) against EN 38 steel disc (HRC 60) with a constant sliding speed of 2m/s at normal loads of 30, 50 and 70N respectively. The microstructure of the as-sintered P/M alloy steels reveals the ferritic-pearlite structure whereas for hot extruded alloy steels the microstructure shows a combination of Widmanstatten type ferrite, pearlite and bainite. From the microstructure the presence of WC (tungsten carbide) embedded with Ti in the grain boundaries offers greater wear resistance of the hot extruded P/M alloy steels. The common wear mechanism observed for hot extruded alloy steels is Delamination wear.

Influence of Tungsten and Tantalum Content on Evolution of Secondary Phases in 9Cr RAFM Steels: An Experimental and Computational Study

This paper presents the results of a systematic study on the role of alloying elements W and Ta on the microstructural evolution in 9Cr-W-Ta-V-C Reduced Activation Ferritic/Martensitic steels during long-term thermal exposure in the temperature range of 773 K to 923 K (500 °C to 650 °C). The kinetics of evolution of secondary phases like M23C6, MX, and Laves phase crucially depend upon the W and Ta content of the steel in addition to temperature and time, which has been studied in detail using analytical transmission electron microscopy as well as predictive methods. The steel with 1 wt pct W and 0.06 wt pct Ta showed slow recovery below 873 K (600 °C) and no evidence for Laves phase at any temperature. Significant change in microstructure was observed after 10,000 hours of exposure at 923 K (650 °C), while recovery at short durations was retarded by nucleation of MX precipitates. Increase in both W and Ta content of the steel enhanced the tendency for the formation of Laves phase.

Influence of tungsten doping on dielectric, electrical and ferroelectric behavior of BaBi4Ti4O15 ceramics

The effect of tungsten (W6+) doping on modification of the structure, dielectric, ferroelectric and electrical properties of BaBi4Ti4-xWxO15 (BBTWx, x = 0, 0.03, 0.05 and 0.07) was investigated. The ceramic samples were synthesized by the conventional solid state reaction method. XRD data indicated the formation of single-phase layered crystalline structure that confirmed orthorhombic structure type of all compositions with space group A21am. SEM micrographs suggest that the grain size slightly decreases with W doping. The temperature dependent dielectric study revealed that the dielectric constant decreases with W doping while transition temperature slightly increases. Influence of tungsten on relaxor behavior and diffuseness of phase transition is also discussed. Effect of W doping on the dielectric and electrical properties were investigated in terms of ion doping and defect mechanism. The ferroelectric properties were studied by P-E hysteresis loop and it was observed that the remanent polarization increases with a small level of W doping.

Methane dehydroaromatization over modified Mn/H-ZSM-5 zeolite catalysts: Effect of tungsten as a secondary metal

The influence of tungsten (0.5–1.5wt.%) on the MDA reaction was investigated at 800°C. Addition of W to a 2Mn/H-ZSM-5 catalyst led to a decrease in methane conversion from 6 to 4%. An aromatic selectivity of 74% was obtained with the unpromoted catalyst but this decreased (i.e. from 41 to 12%) with increase in tungsten loading. Addition of Pt or Ru to a 1.5W/2Mn/H-ZSM-5 catalyst led to an increase in aromatic selectivity from 12 to 55% (Pt) or 46% (Ru) while the coke selectivity decreased from 78 to 37% (Pt) or 42% (Ru) due to the hydrogenating activity of Pt and Ru.

Carbothermal reduction of SiO2 promoted with tungsten and morphology of WC-W2C-β-SiC nanostructured composite material

This paper presents the results of a study on the influence of tungsten as a structure promoter in the carbothermal reduction of silica. The morphology and surface structure of the obtained materials were analyzed using XRD, SEM-EDS, TEM and FTIR techniques. Surface area and porosity were evaluated on the basis of low temperature adsorption of nitrogen. The WC-W2C-β-SiC nanostructured composite material formed from the carbothermal reduction of SiO2 promoted with tungsten had a larger surface area (25.8m2g−1) in comparison to that measured for a β-SiC sample obtained by the simple carbothermal reduction of silica. Based on the results of this research, tungsten promoted carbothermal reduction of silica appears as a relatively simple procedure for obtaining valuable materials with a sufficiently high surface area to be used in catalysis.

Influence of tungsten on the activity of a Mn/Ce/W/Ti catalyst for the selective catalytic reduction of NO with NH3 at low temperatures

The influence of tungsten in the Mn/Ce/W/Ti catalyst system on the activity and SO2 induced deactivation of the catalyst was evaluated. The properties of the catalyst were evaluated using physicochemical measurements, including Brunauer–Emmett–Teller (BET) surface area, X-ray photoelectron spectroscopy (XPS), NH3 temperature-programmed desorption (TPD), X-ray diffraction (XRD), and H2 temperature-programmed reduction (H2-TPR) analyses. The Mn4+ ratio increased with the addition of Ce and W to the Mn/Ti system. The Mn/Ce/W/Ti catalyst, prepared by controlling the Mn4+ ratio through the addition of Ce and W to Mn/Ti, exhibited excellent activity in the range of 120–200°C. The catalyst efficiency was positively correlated with NH3 adsorption. The catalytic activity and surface area of the Mn/Ce/5W/Ti catalyst (containing 5wt% tungsten) were optimal, but decreased at higher tungsten loadings. Increasing the Ce3+ ratio in Mn/Ce/W/Ti increased the selective catalytic reduction (SCR) activity. Mn/Ti and Mn/Ce/Ti were rapidly deactivated upon the injection of SO2 in the SCR reaction. However, the Mn/Ce/5W/Ti catalyst exhibited excellent resistance to SO2 induced deactivation. Thus, the addition of tungsten to Mn/Ce/Ti resulted in excellent NOx conversion and SO2 resistance.

Influence of Nanopowders on Corrosion Resistance of Welded Joints

The paper presents experimental results on influence of tungsten, molybdenum nanopowders and aluminum oxyhydroxide phase introduced into the molten pool on the corrosion resistance of welded joints. It was shown that the nature of nanopowders significantly impacts intercrystalline corrosion of the welding joint.

Photocatalytic and Antistain Properties of Ceramic Tiles Functionalized with Tungsten-doped Tio2

Tiles functionalized with W-doped TiO2 film has been prepared and tested in the discoloration of aqueous solution of methylene blue (MB) used as model pollutants, in presence of UV light. The influence of tungsten and its loading on tiles surface were evaluated. Photocatalytic tests, performed at controlled temperature and atmospheric pressure, have shown that the increase in the tungsten loading strongly influences the photocatalytic activity; higher content of tungsten induces an increase of the discolouration rate. Moreover, the addition of tungsten modifies the structure of titania determining a remarkably photocatalytic activity.

Influence of tungsten on microstructure and wear resistance of iron base hardfacing alloy

A series of iron based hardfacing alloys with varying tungsten contents were fabricated using slag free self-shielded flux cored wire, and the effects of tungsten addition on microstructure and wear performance were investigated. The experimental results showed that the iron base tungsten free hardfacing alloy has a typical hypereutectic microstructure, which consists of primary hexagonal M7(C, B)3 carbides and eutectic long bar-like M3(C, B) carbides in the austenite and martensite matrix. The addition of tungsten increases the size of primary hexagonal M7(C, B)3 carbides and promotes the formation of martensite, as well as changes the morphology of eutectic carbides. It was found that the eutectic carbides change from the long bar-like shape to the scattered web shape with the increase in tungsten content to 9 wt-%, and subsequently change to the plate shape with further increasing the tungsten content to 12 wt-%. For the all tungsten containing hardfacing alloys, tungsten exists in both the carbides and matrix uniformly. Results also showed that the wear loss of the sample with 9 wt-% tungsten was the smallest among all the samples owing to the higher hardness and reinforced microstructure.