Amount Of Tungsten Research Articles

Element behavior during autoclave oxidation of polymetallic sulfide flotation concentrate containing tungsten and molybdenum

In this paper, we investigate the behavior of associated elements (tungsten, molybdenum, and bismuth) contained in a sulfide gold-bearing concentrate during its autoclave oxidation. The process is studied using a sulfide flotation concentrate, crushed to a particle sieve mesh size of minus 0.045 mm and containing 22.1 g/t of gold, 133.2 g/t of silver, 2.7% of tungsten, 13% of molybdenum, and 0.7% of bismuth. The process was carried out in a 2 dm3 autoclave at a temperature of 220ºC and an oxygen partial pressure of 0.7 MPa. The concentrations of sulfuric acid and iron ions in the solution were determined by titrimetric analysis. Inductively coupled plasma atomic emission spectroscopy was used to determine the concentrations of bismuth, tungsten, molybdenum, copper, silver, and arsenic in the solution, as well as the content of bismuth, tungsten, molybdenum, copper, arsenic, lead, and iron and sulfur forms in the cake. The cake was also examined using diffraction analysis. Experiments on cyanidation of oxidized cake were carried out in the pH range of 10.0–10.5 and a NaCN concentration of 1 g/dm3 with a PuroliteS992 ion exchange resin for 24 h. Autoclave oxidation experiments showed the sulfide oxidation degree to be higher than 99%. Extraction of molybdenum into solution in the form of [MoO2(SO4)n]-(2n-2) and MoO 2+ amounted to 95%. The decrease in the solid mass led to an increase in the concentration of bismuth and tungsten in the cake, with their contents reaching 1.66% and 12.7%, respectively. The main phases in the cake were established to be scheelite, anhydrite, plumboyarosite, and bedantite. The extraction of precious metals at the subsequent cyanidation stage amounted to 97.5% of gold and 91.6% of silver. Therefore, autoclave cyanide processing of sulfide gold-containing concentrates leads to a molybdenum extraction in the autoclave oxidation solution at the level of 95%. During cyanidation, more than 90% of gold and silver are extracted. Due to the significant amount of tungsten (17%), bismuth (0.9%), lead (5.3%), and molybdenum (3.3%), the obtained cake cannot be considered a waste product.

The precipitation mechanisms of scheelite from CO2-rich hydrothermal fluids: Insight from thermodynamic modeling

Scheelite and wolframite are two main tungsten-bearing ore minerals in tungsten deposits. Compared to wolframite formed mostly by NaCl–H2O fluids, scheelite in many but not all tungsten deposits is associated with CO2–bearing hydrothermal fluids, but its precipitation mechanisms from these fluids are poorly understood. The replacement of wolframite by scheelite is common among tungsten deposits where these two tungstates coexist, but how CO2, as the pH-buffering agent, affects their replacement remains unclear. To answer these questions, we first tested the pH-buffering effect of CO2 by comparing available experimental pH values of H2O–CO2±NaCl solutions at 200–280 °C and the corresponding thermodynamic modeling results. The mean absolute errors between the calculated and experimental pH values are 0.14 log units in H2O–CO2 solutions and 0.13 log units in H2O–CO2–NaCl solutions, indicating that the calculated acitivities of H+ in CO2-bearing solutions are reliable. Then, the solubilities of scheelite, scheelite-ferberite, and scheelite-hübnerite in NaCl–H2O–CO2 systems were modeled in this study. Our modeling results suggest that scheelite solubility in CO2-rich fluids is highly dependent on fluid pressure but is insensitive to fluid temperature. A decrease in fluid pressure from lithostatic to hydrostatic levels at a depth of 3–8 km causes CO2 escape and pH rise and precipitates over 70 % of tungsten contents in fluids on average. Therefore, CO2 escape is an efficient mechanism for precipitating scheelite from CO2–rich hydrothermal fluids. The independence of scheelite solubility on temperature at high pressures and the slightly retrograde solubility at low pressures allows CO2–rich hydrothermal fluids to carry a great amount of tungsten far away from its sources. This may be one of reasons why some scheelite deposits occur at greater distances (>500 m) from the granite or extend along its strike for several kilometers. Similar to the cases in NaCl–H2O systems, two mechanisms for scheelite replacing wolframite in CO2–rich fluids are identified, a single decrease in fluid pressure or simple cooling plus an increase in the ratios of total Ca contents to total Fe (or Mn) contents in fluids.

A Proton-Conductive Co(II)-Polyoxometalate Acts as a Precatalyst for Efficient Electrocatalytic Water Oxidation.

A cobalt(II)-containing polyoxometalate, [H3O]5[{Co(H2O)4}3{Na(H2O)4}W12O42]·3H2O (Co-POM), has been isolated in a one-step facile aqueous synthesis and characterized unambiguously using single-crystal X-ray crystallography along with routine spectral analysis. The paratungstate cluster anion [W12O42]12- coordinates with {CoII(H2O)4}2+ and {Na(H2O)4}+ complex cations resulting in the formation of the water-insoluble Co-POM compound having three-dimensional (3-D) extended structure. Motivated by the protonated water molecules existing as the counter cations in Co-POM, herein, we demonstrate the detailed proton conductivity studies of the Co-POM, reaching a value of 1.04 × 10-2 S cm-1 at 80 °C and 98% relative humidity (RH). The temperature- and humidity-dependent proton conductivity in Co-POM is governed by Grotthus mechanism with Ea = 0.25 eV. In addition, we examined the electrochemical behavior of Co-POM, in an alkaline borate buffer where it is found to be electrochemically unstable and acts as a precatalyst (and not a true catalyst) for oxygen evolution reaction (OER). We also discuss the "post-mortem" analysis of the postelectrolysis sample to identify the active species which turns out to be a cobalt oxide material (Co3O4) incorporating small amounts of tungsten. Thus, in the present electrocatalysis work, the Co-POM molecule transforms into an efficient water oxidation catalyst (WOC).

Accelerated oxygen reduction kinetics in BaCo0.4Fe0.4Zr0.2O3-δ cathode via doping with a trace amount of tungsten for protonic ceramic fuel cells

Protonic ceramic fuel cells (PCFCs), which are based on proton conducting electrolytes, are a class of power generation devices that can efficiently operate at the intermediate (500–700 °C), even low (450 °C) temperatures, but their development is hindered by sluggish cathodic kinetics at reduced temperatures. At the PCFC cathode, the absorbed oxygen molecules react with oxygen vacancies, protons and electrons to generate water and release electrical energy. Thus, the PCFC cathode materials require percolation network for proton, oxide-ion, and electron carriers simultaneously. In this work, we developed a triple ionic-electronic conductor BaCo0.4Fe0.4Zr0.15W0.05O3-δ as a new cathode material for the PCFCs using BaZr0.1Ce0.7Y0.1Yb0.1O3-δ as the electrolyte. Anode supported cells were fabricated and the performances were investigated. Compared with the parent oxide, tungsten doping can significantly improve the electrochemical reduction kinetic of oxygen. The BaCo0.4Fe0.4Zr0.15W0.05O3-δ based PCFC obtained the peak power density of 688 mW ⋅ cm−2 at 600 °C, which is 1.29 time higher than that of BaCo0.4Fe0.4Zr0.2O3-δ based PCFC (the peak power density of 534 mW ⋅ cm−2 at 600 °C). Moreover, BaCo0.4Fe0.4Zr0.15W0.05O3-δ has a better thermal expansion matching with the electrolyte material BaZr0.1Ce0.7Y0.1Yb0.1O3-δ.

Ultrahigh Ni‐Rich (90%) Layered Oxide‐Based Cathode Active Materials: The Advantages of Tungsten (W) Incorporation in the Precursor Cathode Active Material

Minor amounts of tungsten (W) are well known to improve Ni‐rich layered oxide‐based cathode active materials (CAMs) for Li ion batteries. Herein, W impacts are validated and compared for varied concentrations and incorporation routes in aqueous media for LiNi0.90Co0.06Mn0.04O2 (NCM90‐6‐4), either via modification of a precursor NixCoyMnz(OH)2 (pCAM) within a sol–gel reaction or directly during synthesis, i.e., either via an W‐based educt or during co‐precipitation in a continuously operated Couette–Taylor reactor. In particular, the sol–gel modification is shown to be beneficial and reveals >500 cycles for ≈80% state‐of‐health NCM90‐6‐4||graphite cells. It can be related to homogeneously W‐modified surface as well as smaller and elongated primary particles, whereas the latter are suggested to better compensate anisotropic lattice stress and decrease amount of microcracks, consequently minimizing further rise in surface area and the accompanied failure cascades (e.g., phase changes, metal dissolution, and crosstalk). Moreover, the different incorporation routes are shown to reveal different outcomes and demonstrate the complexity and sensitivity of W incorporation.

Synthesis of Ti1‐xWx Solid Solution MAX Phases and Derived MXenes for Sodium‐Ion Battery Anodes

AbstractA distinguishing feature of MAX phases and their MXene derivatives is their remarkable chemical diversity. This diversity, coupled with the 2D nature of MXenes, positions them as outstanding candidates for a wide range of electrochemical applications. Chemical disorder introduced by a solid solution can improve electrochemical behavior. Up to now, adding considerable amount of tungsten (W) in MAX phase and MXenes solid solutions, which can enhance electrochemical performance, proved challenging. In this study, the synthesis of M site Ti1‐xWx solid solution MAX phases are reported. The 211‐type (Ti1‐xWx)2AlC exhibits a disordered solid solution, whereas the 312‐type (Ti1‐xWx)3AlC2 displays a near‐ordered structure, resembling o‐MAX, with W atoms preferentially occupying the outer planes. Solid‐solution MXenes, Ti2.4W0.6C2Tz, and Ti1.6W0.4CTz, are synthesized via selective etching of high‐purity MAX powder precursors containing 20% W. These MXenes are evaluated as sodium‐ion battery anodes, with Ti1.6W0.4CTz showing exceptional capacity, outperforming existing multilayer MXene chemistries. This work not only demonstrates the successful integration of W in meaningful quantities into a double transition metal solid solution MAX phase, but also paves the way for the development of cost‐effective MXenes containing W. Such advancements significantly widen their application spectrum by fine‐tuning their physical, electronic, mechanical, electrochemical, and catalytic properties.

Detailed Analysis of Gamma-Shielding Characteristics of Ternary Composites Using Experimental, Theoretical and Monte Carlo Simulation Methods.

Ionizing radiation is vital in various fields but poses health risks, necessitating effective shielding. This study investigated the photon-shielding properties of polyester-based ternary composites with barite (BaSO4) and tungsten (W) using experimental methods, theoretical calculations, and Monte Carlo simulations for energies between 81 keV and 1332.5 keV. WINXCOM was utilized for the theoretical predictions, and the MCNP6 and PHITS 3.22 algorithms were employed for the simulations. According to the results, the simulation, theoretical, and experimental data all closely aligned. At 81 keV, the composite containing the highest amount of tungsten (PBaW50) had the highest mass attenuation coefficient (3.7498 cm2/g) and linear attenuation coefficient (12.9676 cm-1). Furthermore, for a sample that was 1 cm thick, PBaW50 offered 99.88% protection at 81 keV and had the lowest HVL and TVL values. PBaW50 exhibited attenuation capabilities, making it appropriate for use in industrial, medical, and aerospace settings. In summary, the findings of this study underscore the potential of polyester-based composites doped with barite and tungsten as effective materials for gamma radiation shielding. The PBaW50 sample, in particular, stands out for its attenuation performance, making it a viable option for a wide range of applications where durable and efficient radiation shielding is essential.

Efficient catalytic oxidative desulfurization of liquid fuels over tungsten oxide supported on metakaolin surface

AbstractA new high yield and inexpensive composite was fabricated by supporting tungsten oxide on metakaolin via the incipient wetness impregnation method to use in oxidative desulfurization reaction and produce ultra‐clean fuel. The prepared catalyst was characterized by various techniques like XRD, FTIR, FESEM, EDX and N2 adsorption–desorption isotherms, which indicated the catalyst was properly constructed. Initially, desulfurization was examined by loading different amounts of tungsten on the metakaolin surface. Based on the results, 15 % W/metakaolin showed high catalytic activity for the model and real fuels. Moreover, the influence of the main operating variables was studied through the Box–Behnken experimental design. The maximum sulfur removal reached to 99.3 % at a reaction temperature of 60 °C, oxidant to sulfur molar ratio12, catalyst dosage 0.04 g and oxidation time 40 min. Desulfurization from gasoline and gas oil with initial sulfur contents of 300 ppm and 7550 ppm was done under optimum conditions, which represented an efficiency of 60 % and 74 %, respectively. Performing the recycling tests proved the great durability of the catalyst after five runs. This research sheds light that the employed catalyst has excellent activity for industrial applications in the desulfurization process.

Composition and structure of tungsten antimony acid

Tungsten antimony acids (TAA) with the composition H(2)Sb(2)WXO6·nH2O (0 < x ≤ 1.45; 0 < n ≤ 2.0) have been synthesized by hydrolysis of antimony trichloride pre-oxidized with nitric acid in the presence of varying amounts of Na2WO4. To obtain TAA protonated forms, the samples were kept in a 96% solution of sulphuric acid, the precipitate was washed until reaction became neutral and dried in air. The amount of tungsten, antimony, and silver ions in TAA was determined using energy dispersive analysis. Changes in structural parameters upon doping of AA with tungsten ions were studied using a Bruker D8 ADVANCE X-ray diffractometer (CuKa1-radiation). The number of oxonium ions in TAA was determined by the substitutionof these ions by silver ions in equivalent amounts (Ag+-TAA forms). All obtained TAA samples and Ag+ TAA forms had a pyrochlore-type structure, space group symmetry Fd3m. Refinement of the arrangement of atoms in the structure using the Rietveld method showed that tungsten ions replace antimony ions and are statistically located in 16c, oxygen anions in 48f, and oxonium ions and water molecules in 16d and 8b positions, respectively. When tungsten ions were introduced into samples, the structural parameters of the resulting phases changed. There was a decrease in the unit cell parameter and the distance between antimony ions and oxygen anions, while an increase in the distance between oxonium ions and oxygen anions located in 48f positions was observed. This allowed the removal of a proton from oxonium molecules and its transport via a system of hydrogen bonds formed by water molecules

Non‐oxidative Methane Activation over Molybdenum and Tungsten Nitride Catalysts

AbstractIn this study, molybdenum (Mo), tungsten (W), and mixed metal oxide and ‐nitride catalysts are synthesized via incipient wetness impregnation on silica support (SBA‐15) with a total target metal loading of 4 wt %. The effect of the Mo : W ratio on the non‐oxidative methane conversion, product selectivity, and coke formation is evaluated. The reduced Mo/SBA‐15 and MoW/SBA‐15 catalysts show higher CH4 conversion activity to benzene (selectivity of ~75.5 %) than for ethylene (selectivity of ~9.5 %) with a rather fast coke formation rate of 19–24 mgCoke gCat−1 h−1 without a clear influence of the Mo : W ratio. In contrast, the metal nitrides have a much smaller coke formation rate. The smallest rate of 0.45 mgCoke gCat−1 h−1 is achieved for the WN/SBA‐15 sample, which increases with the molybdenum content to 4.7 and 8.6 mgCoke gCat−1 h−1 for the MoWN(5 : 1) and MoN/SBA‐15 catalysts, respectively. There seems to be a yet unknown but negative correlation between the coke formation rate and the number of silanamine functional groups formed during the catalyst nitridation (Si−OH→≡Si−NH2→≡Si−NH−Si≡). The C2H4 selectivity is significantly increased with the relative amount of tungsten, with the highest C2H4 selectivity of 63 % for mixed‐metal nitride catalyst containing Mo : W ratio of 1 : 5. While the Mo/SBA‐15 the MoN/SBA‐15 achieve a C2H4 selectivity of less than 10 %.

Surface oxidation behavior of spark plasma sintered AlCrCuFeMnWx high entropy alloys at an elevated isothermal temperature

The high-temperature surface oxidation behavior of high-entropy alloys (HEAs) with compositions of AlCrCuFeMnWx (x = 0, 0.05, 0.1, and 0.5) was studied at 800 °C as an isothermal temperature for 50 h. The high entropy alloys (HEAs) were synthesized by mechanical alloying (MA) followed by spark plasma sintering (SPS). This study focused on the effect of oxidation resistance properties with different elevated temperatures on the high entropy alloy over the surfaces. The XRD and Raman analysis confirmed the formation of various oxides like Al2O3, Cr2O3, Fe2O3, and CrO2 mainly. The HEAs follow the single-stage parabolic law at 800 °C. To achieve better resistance against the heat, rather than adding more amount of refractory elements. Consequently, AlCrCuFeMnWx HEAs showed excellent oxidation resistance at elevated temperatures in a specific amount of tungsten. Different values of mass gain, loss, and complex oxidation kinetics were observed for the varying W-containing HEAs. These alloys formed inhomogeneous oxide scales possessing different regions with porous oxide layers and some areas revealed thin oxide scales due to the formation of discontinuous Mn, Cr, and Al-rich scales evidence found through the SEM images. It is noted that complicated oxides formed considerably more frequently on the W0 alloy than on other alloys, indicating that the addition of tungsten in the presence of Cr may inhibit the growth of certain types of multiphasic oxides and prevent spallation.

Observation of reduced-turbulence regime with tungsten injection in HL-2A edge plasmas

A reduced-turbulence regime has been observed in HL-2A NBI-heated deuterium plasmas. The transition to this regime is achieved by injecting a certain amount of tungsten into the plasma based on the laser blow-off technique. It has been found that the amplitude of geodesic acoustic mode (GAM) zonal flow and turbulent vortex size together with eddy tilting angle are all significantly increased in the edge region after tungsten injection. However, the frequency of GAM zonal flow remains nearly unchanged. Measurement shows the nonlinear coupling degree of turbulence dramatically increases while the collisional damping of GAM zonal flow drops slightly. We conclude that the increased nonlinear coupling is the main cause of the excitation of GAM zonal flow, which consequently results in the reduction in turbulent transport as observed in this experiment. These results indicate that tungsten ions play an active role in turbulence-GAM dynamics through a symmetry-breaking mechanism, which could help us to better understand the inherent physical mechanisms governing turbulent transport in the presence of high-Z impurity ions in fusion plasmas.

Spectroscopic diagnosis and simulation analysis of tungsten cathode erosion during the start-up process for a magnetoplasmadynamic thruster

Measurement of tungsten density during the start-up process plays a vital role in monitoring real-time cathode mass loss in the study of plasma discharge instrument structure optimization. The relative intensity of the W II 239.71 nm spectral line, collected at the exit by the monochromator, is used to estimate the W II density in combination with the collision radiative model. The model of a small amount of tungsten in high-density plasma takes into account the main kinetic processes including the electron impact excitation process, electron impact de-excitation process, and electron impact ionization process. Additionally, A two-dimensional axisymmetric quasi-neutral fluid model, coupled with a thermal model of the cathode into a self-consistent model, is also constructed to analyze the mass loss mechanism of tungsten cathode during the start-up process. In the initial stage, the cold-state cathode has a large potential drop in the sheath region to accelerate the ion bombardment of the cathode for the requirement of electron emission, and a large number of tungsten atoms removal from the cathode surface due to sputtering and evaporation. In the steady-state operating phase, the primary reason for the mass loss of tungsten cathodes is attributed to thermal evaporation. Both experimental and simulation results indicate that the mass loss rate during the start-up phase is higher than that during steady-state operation phase by 1 to 2 orders of magnitude.

Effects of added tungsten on the microstructure and mechanical properties of laser-directed energy deposited Inconel 625 alloys

To satisfy the extreme operational requirements of Inconel 625 alloys, the development of novel approaches for improving their strength and compensating for the corresponding loss in toughness/plasticity is critical. This study employed laser-directed energy deposition to fabricate Inconel 625 alloys containing different amounts of tungsten (W) (6.0–16.5 wt%) and investigated the effects of added W (based on the quantity) on the microstructure and mechanical properties of the samples. The moderate addition of W reduced the size of γ-Ni grains and increased the GND density, which can improve the sample strength. Adding W can increase the density of nano-stacking faults (nano-SFs) and promote the Lomer-Cottrell (L-C) locks production, thus improving the work-hardening capacity and balancing the strength and plasticity of the alloys. As the amount of W increased from 0.0 to 16.5 wt%, the elongation of the samples increased and then decreased, whereas the strength increased monotonously. In the prepared samples, the one containing 6.0 wt% W exhibited the highest elongation (51.8 ± 3.2%), 1.38 times higher than the sample without W. Furthermore, the sample containing 16.5 wt% W exhibited the highest strength: 1167.2 ± 16.5 MPa, 289 MPa greater than that without W. The theoretical yield strengths of all samples were also calculated considering the strengthening mechanisms of the grain boundary, dislocation, solid solution, and precipitation; the results agreed with the experimental data.

Development of eutectic high entropy alloy by addition of W to CoCrFeNi HEA

High entropy alloys have shown a remarkable combination of physical and mechanical properties. The introduction of eutectic microstructure, consisting of a tough fcc phase, and a hard-intermetallic phase, can help in obtaining even better synergy of strength and ductility. The presence of multiple principal alloying elements in HEAs and absence of corresponding multicomponent phase diagrams makes designing of eutectic high entropy alloys a tedious task. In the present study, systematic investigation of CoCrFeNi-Wx system has been carried out for the development of eutectic microstructure. Experimental results validated the presence of eutectic reaction in the calculated phase diagram. CoCrFeNi-Wx HEAs remained single fcc phase alloys at smaller amount of W (x = 0.1) but changed to hypoeutectic (x = 0.25, 0.5, 0.75) and hypereutectic alloys (x = 1.0) with increase in the amount of tungsten. It has been shown that calculated pseudo binary phase diagrams can provide a very good starting point for the development of eutectic HEAs. Mechanical characterization of the developed HEAs revealed that development of eutectic mixture of a soft (fcc) and a hard phase (intermetallic/bcc) can help in obtaining outstanding combination of mechanical properties.

The Feasibility of Tungsten-Doped VO2 Films on Soda-Lime Glass with Low Thermal Budget by High Density Plasma Source for Smart Windows

Thermochromic W-doped VO2 thin films on soda-lime glass are successfully fabricated by co-sputtering technique using a high density plasma source, which is equipped by high power impulse magnetron sputtering (HIPIMS). A post-rapid thermal annealing of 500 °C is performed for the purpose of low thermal budget. The effect of doping amount of tungsten on thermochromic properties such as transmittance and transition temperature are addressed. The transition temperature can be lower down to 30 °C with a small amount of 4.5% tungsten added in VO2 nanocrystals. A solar regulation efficiency, ΔTsol = 10% is achieved at thicker TiO2 thickness. The competition of secondary phase of V2WO7.5 and oxygen-rich phase of V2O5 under different O2/Ar ratio is studied. The crystalline behavior of monoclinic phase is examined by X-ray diffraction (XRD) pattern and high resolution transmission electron microscope (HR-TEM). The good endurance property ensures the feasible use for the energy-saving applications.

Factors controlling tungsten mobility in W[sbnd]Cu skarn tailings

Few studies have addressed the mobility of tungsten in mine waste, which could act as a point source for metal leaching of this potentially toxic metal. This study examines the behavior of tungsten in acidic floodplain tailings and circumneutral impoundment tailings at the Cantung Mine in the Northwest Territories, Canada. In the Cantung deposit, tungsten is present as scheelite (CaWO4), copper is hosted in chalcopyrite (CuFeS2), and gangue mineralogy consists of abundant pyrrhotite (Fe1-xS), silicate minerals, and carbonate minerals. Samples of surface waters, tailings porewaters, and solid tailings samples were collected from Cantung Mine. For surface waters, both filtered (0.45 μm) and unfiltered aliquots were collected to compare dissolved and particulate element concentrations.Tungsten concentrations range from 5.8 to 30.0 μg/L in water samples with pH values between 7.1 and 8.1, whereas samples below pH 7.1 have concentrations below the detection limit of 0.1 μg/L. Tungsten and iron concentrations are both on average 1.7 times higher in unfiltered aliquots compared to filtered aliquots, suggesting that tungsten is transported as dissolved species but is also adsorbed to suspended Fe-oxyhydroxide minerals at neutral pH. Tailings were analyzed by scanning electron microscopy (SEM) paired with automated mineralogy software (MLA), synchrotron-based μX-ray diffraction and fluorescence (μXRD-XRF), and partial leach digestions with inductively coupled plasma mass spectrometry (cold and hot hydroxylamine hydrochloride, aqua regia, Li-metaborate fusion, and 4-acid digestion with HNO3-HClO4-HF-HCl). Samples from the impounded tailings and the highly oxidized Flat River Tailings distributed on the floodplain (FRT) have similar scheelite content (0.15 wt% and 0.21 wt%, respectively), and scheelite shows no evidence of alteration. Synchrotron-based μXRD of Fe-oxyhydroxide minerals in the FRT identified goethite (FeOOH) and lepidocrocite (γ-FeOOH) as products of pyrrhotite oxidation. Rare rims on pyrrhotite from the tailings impoundment have μXRD spectra consistent with hematite (Fe2O3) and maghemite (γ-Fe2O3). The μXRF maps of the hematite-maghemite rims have prominent tungsten peaks, which represent included scheelite grains and possibly structurally incorporated tungsten. The hydroxylamine leaches yield higher tungsten concentrations in tailings samples from the circumneutral impoundments than samples from the acidic FRT, suggesting the tailings impoundments have more tungsten that is associated with poorly crystalline and amorphous Fe-oxyhydroxide phases than the FRT. Over time, labile-hosted tungsten in the FRT may have been washed down the Flat River during Fe-oxyhydroxide recrystallization and high energy flooding events. These results indicate that scheelite has limited solubility in neutral or acid mine waters, and the mobility of the small amount of tungsten released is governed by the present of iron oxyhydroxide minerals, the transport of colloidal material in surface water, and the stability of the depositional environment.

Effect of Various Silicone Oil And Tungsten Levels on the Stability of a Monoclonal Antibody in Nine Commercially Available Prefilled Syringes

Prefilled syringes are widely used as a primary container for therapeutic proteins because they are more convenient than glass vials. The stability of biologic molecules can be affected by different syringe materials and techniques, such as silicone oil levels and coating method, amount of tungsten remaining in the glass barrel after using a tungsten pin to create the needle hole, and end of the syringe, which can be Luer locked or pre-staked with a needle. We investigated the impact of these parameters by using a monoclonal antibody to collect the antibody's stability profile and the prefilled syringes’ functionality data. Silicone oil levels had no impact on aggregation levels, and particle counts were lowest for silicone oil–free syringes. Functionality performance was similar and did not change throughout all stability time points for all syringe configurations. The break-loose force for Ompi syringes was initially lower and increased over time to align with those of the other configurations, all of which remained well below 25 N. Tungsten contaminants and agitation stress from shipping studies did not impact quality attributes. This work can help guide the development of similar products in prefilled syringes to ensure selection of the primary container that provides adequate stability for the protein, as well as maintain the desired functionality features over the shelf life of the drug product.

Probing the Mysterious Behavior of Tungsten as a Dopant Inside Pristine Cobalt‐Free Nickel‐Rich Cathode Materials

AbstractNickel‐rich cathode materials with small amounts of tungsten (W) dopants have attracted extensive attention in recent years. However, the chemical state, crystalline form, compound chemistry, and location of W in these layered cathodes are still not well‐understood. In this study, these missing structural properties are determined through a combination of macro‐, to atomic‐sensitive characterization techniques and density functional theory (DFT). W‐doped LiNiO2 (LNO) particles, prepared with mechanofusion and coprecipitation methods, are used to probe changes in the structure and location of W‐species. The results indicate that W is mainly distributed on the surfaces and inside grain boundaries of the secondary particles, regardless of the doping method. Electron energy loss spectroscopy (EELS) mapping confirms the simultaneous presence of W, O, with and without Ni in the grain boundaries as well as W‐ and O‐rich regions on the very surface. The W‐rich areas inside the grain boundaries are found to be in two forms, crystalline and amorphous. This paper suggests the presence of kinetically stabilized‐Li4+xNi1‐xWO6 (x = 0, 0.1) with the possibility of LixWyOz phases in LNO which are consistent with the electron microscopy, X‐ray absorption and diffraction data. The multiple roles of W in this complex microstructure are discussed considering the W distribution.

Identification of radiopure tungsten for low background applications

In this article we explore the availability of radiopure tungsten and its potential as high density shield material for low background applications. For compact shield designs, conventionally, lead is used. Metallic tungsten and tungsten pseudo-alloys reach higher densities up to 19.3 g cm−3 and do not exhibit a significant 210Pb activity, which is a typical intrinsic contamination in lead. Within several γ-ray screening campaigns we were able to identify tungsten samples with activities similar or better than 1 mBq kg−1 in 232Th, 40K, 60Co and the second part of the 238U decay chain. In cooperation with a manufacturer we further reduced a persisting contamination in the first part of the 238U decay chain by a factor of ∼2.5 down to (305 ± 30) mBq kg−1. With Monte Carlo simulations, the construction of prototype tungsten-based setups and dedicated measurements, the shield capability of tungsten in comparison to lead was extensively studied. Specifically, the impact of cosmogenic radiation on the background at shallow depth was investigated. We showed that a 6%–40% reduction (depending on the exact shield configuration) in the muon-induced neutron fluence is achievable by replacing lead with an equivalent amount of tungsten regarding the suppression of external γ-radiation. Overall, many benefits using tungsten especially for low energy applications below a few 100 keV are found. The pseudo-tungsten alloy presented in this work paves the way for several applications especially regarding background suppression in particle and astroparticle physics search programs.