Tungsten Ions Research Articles

Optimized Tungsten Disulfide via Pyrolytic Deposition for Improved Zn‐Ion Batteries

AbstractThe selection and optimization of cathode materials are crucial for enhancing the performance of aqueous zinc‐ion batteries. In this work, different active materials were created by combining Sulfur powder and polydopamine in four different mass ratios. The novel N‐doped carbon/WS2 is obtained. Thanks to the optimization of the dopamine‐carrying tungsten ion precursor and Sulfur powder (1 : 2, 1 : 4, 1 : 6 and 1 : 8), the four samples exhibited different morphology. The N−C/WS2‐6‐based zinc ion batteries with the highest specific capacity, 120.0 mAh/g in the first discharge at 2.0 A/g, and 78.0 mAh/g after 2500 cycles, with a capacity retention of 65 %, had a relatively good overall performance, according to the results. The reaction kinetics characteristics of the N−C/WS2‐6 cathode reveal that diffusion has a significant impact on the processes in the aqueous zinc ionic material N−C/WS2‐6.

Collisional-Radiative modeling of unresolved transition array spectra near 200 Å from W17+-W25+ emissions for diagnostics of ITER edge plasma

Tungsten (W) is one of the major impurities in ITER and future DEMO reactors. However,diagnosing the ion density, temperature, and spatial distribution of tungsten ions in intermediate charge states, such as W8+-W27+, is difficult because of the lack of spectral line data. In this study, we observed a tungsten Unresolved Transition Array (UTA) spectrum, which has a pseudo-continuum structure, around W20+ in the Extreme Ultraviolet wavelength region in the Large Helical Device (LHD). We conducted Collisional-Radiative (CR) modeling for W17+-W25+. Two pseudo-continuum peaks corresponding to 5 s-5p transition and transition between doubly excited states of 5 s2-5s5p, are strongly emitted around 200 Å for each ion. The synthesized spectrum of W17+-W25+ ions reproduced the observed LHD spectrum near 200 Å. From the electron temperature dependence of the UTA spectral shape, the UTA shifted toward longer wavelength region with several pseudo-continuum peaks appearing for ions in lower charge states, with decreasing electron temperature from 0.4 keV to 0.2 keV. This result qualitatively explained the observed time evolution of the spectrum.

Spectroscopic analysis of tungsten spectra in extreme-ultraviolet range of 10-480 Å observed from EAST tokamak with full tungsten divertor

Tungsten spectra in extreme ultraviolet (EUV) wavelength range of 10-480 Å have been observed from high-temperature plasmas in Experimental Advanced Superconducting Tokamak (EAST) with full tungsten divertor using four fast-time-response EUV spectrometers of EUV_Short (5-45 Å), EUV_Long_a (40–180 Å), EUV_Long_c (130–330 Å) and EUV_Long_b (270–480 Å) and two space-resolved EUV spectrometers of EUV_Short2_d (45–70 Å) and EUV_Long2_d (40–130 Å). The wavelength of measured spectra is accurately calibrated based on several well-known spectral lines emitted from low-Z (He, Li, C, N and O), medium-Z (Fe and Cu) and high-Z (Mo) impurity ions. Measurements of the tungsten spectra were taken from discharges accompanied with a transient tungsten burst event, which creates a pulsed influx of tungsten atoms into the EAST plasma. The tungsten spectra observed before and after the burst event are carefully analyzed with temporal behavior and radial profile distribution of the tungsten line intensity. As a result, 213 tungsten lines are successfully confirmed in the spectra observed after the tungsten burst, and the results are summarized in tables. These tungsten lines include line identifications of 78 lines of W XXIII - W XLVI (W22+ - W45+) at 10–140 Å and 88 lines of W V - W IX (W4+ - W8+) at 160–480 Å, while 47 tungsten lines at 50–380 Å could not be clarified the transition. In addition, quasi-continuum spectra called unresolved transition array (UTA) from tungsten ions in low- and high-ionization stages are also analyzed in three wavelength ranges of 18–38 Å, 45–70 Å and 150–280 Å at which W XXIII - W XXXVIII (W22+ - W37+), W XXVII - W XLVI (W26+ - W45+) and W VI—W IX (W5+ - W8+) are dominantly emitted, respectively. Through the analysis it is found that charge state distributions of tungsten UTA at 140–220 Å significantly vary with decrease in the electron temperature. Ionization stages of all observed tungsten lines including both isolated and quasi-continuum lines are experimentally reconfirmed by comparing the radial intensity profile with the electron temperature profile. Finally, spectral lines useful for tungsten diagnostic in fusion plasmas are selected and marked in the tables.

Operating voltage of a W-fuzz cathode arc and the mass/charge composition of the arc plasma depending on the fuzz thickness

The arc operating voltage and the mass/charge composition of the arc plasma were measured for W-fuzz samples with different fuzz thicknesses at different numbers of arc pulses. It was found that the formation of a fuzz structure led to a significant decrease in the arc operating voltage within the first few arc pulses. With an increase in the number of pulses, the operating voltage and the mean charge of tungsten ions in the arc plasma increased to values characteristic of conventional tungsten cathodes. The obtained experimental data were analyzed theoretically using an empirical cohesive energy rule and a magnetohydrodynamic model of the ionization processes occurring in a cathode plasma jet.

Observation of tungsten emission spectra up to W46+ ions in the Large Helical Device and contribution to the study of high-Z impurity transport in fusion plasmas

Spectroscopic studies of emissions released from tungsten ions combined with a pellet injection technique have been conducted in Large Helical Device for contribution to the tungsten transport study in tungsten divertor fusion devices and for expansion of the experimental database of tungsten line emissions. The spectral intensities of W5+, W24+–W28+, W37+, W38+, W41+–W43+, W45+, and W46+ emission lines were measured simultaneously over a wide wavelength range from x-ray to visible. Time evolutions of the various tungsten line spectra indicate that the tungsten confinement time depends on the electron density of the plasma and is long in high density plasmas, on the order of seconds, and short in low density plasmas, on the order of sub-seconds. When the confinement time was long, the tungsten ions remained in the plasma until the end of the discharge, changing their dominant charge with the change in electron temperature. When the confinement time was short, the tungsten ions rapidly decreased in all charge states and disappeared. Space-resolved EUV and visible spectroscopy measurements have revealed that tungsten ions stayed in the core region of the plasma with changing their dominant charge state depending on the electron temperature in the discharges with the long confinement time. Detailed analysis of soft x-ray emission suggested that the confinement time increases with density and becomes saturated when the central electron density exceeds 2 × 1013 cm−3.

Synthesis, characterization, and physico-chemical aspects of a new PVC-based quaternary triethanol ammonium chloride anionite for tungsten recovery.

The usability of polyvinyl chloride-based quaternary triethanol ammonium chloride anionite (PVC-TEAC) as a potential extractant for tungstate was investigated to recover tungstate from Gabal Qash Amir, Egypt, assaying 70.91% WO3. Structure elucidation for PVC-TEAC anionite was successfully carried out using several techniques. Experimental measurements, such as pH, agitation time, initial tungsten concentration, anionite dose, co-ions, temperature, and eluting agents, have been optimized. It was found that PVC-TEAC anionite has a maximum capacity of 63 mg per gram. From the distribution isotherm modeling, Langmuir's model fits the experimental results better than Freundlich's, with a theoretical value of 61.728 mg g-1. According to kinetic modeling, the first- and second-order modeling may be regarded as a mixed modeling for a successful adsorption system. Thermodynamic prospects reveal that the adsorption process was predicted as an exothermic, spontaneous, and preferable adsorption at low temperatures. Tungsten ions can be eluted from the loaded anionite, by 1M H2SO4 with a 97% efficiency rate. It was found that PVC-TEAC anionite reveals good separation factor (S.F.) towards most of co-ions. A successful Alkali fusion with NaOH flux followed by tungstate recovery by PVC-TEAC anionite is used to obtain a high-purity tungsten oxide concentrate (WO3), with a tungsten content of 78.3% and a purity of 98.75%.

First principles modeling of WO3 transport in molten Na2WO4 via a grotthuss-like mechanism and the kinetic characterization involved

Between the inherent difficulties associated with high temperature experiments and the inherent complexity of multi-component liquid phase systems, a Grotthuss-like transport mechanism for WO3 in molten Na2WO4 has been discovered and investigated in order to deepen the understanding of the properties of the Na2WO4-WO3 molten salt and to broaden its applications in areas such as electroplating, catalysis and energy. The research on the Grotthuss-like transport mechanism of WO3 in molten Na2WO4 shows that the mass transfer rate of this mechanism is about 1.5 times faster than the self-diffusion of tungsten ions. The bridging oxygen bond of W2O72- is longer, the Mayer bond level is lower and has a smaller ELF than that of the non-bridging oxygen bond, which makes the bridging oxygen bond more susceptible to breakage. The total energy, Pauli mutual repulsion energy and orbital interaction energy of the non-bridging oxygen bond are larger than those of the bridging oxygen bond. The transition state of the W2O72- dissociation process is the torsion of the bridging oxygen bond with a potential barrier of 42.903 kJ/mol.

Fabrication of High-Density Microarchitected Tungsten via DLP 3D Printing.

Current additive manufacturing (AM) techniques for tungsten, such as powder bed fusion and directed energy deposition, often generate parts with rough surfaces. Vat photopolymerization presents a promising alternative for fabricating tungsten structures with high shape fidelity and low surface roughness. However, existing vat photopolymerization approaches suffer from surface defects and low final density, leading to compromised mechanical properties. Therefore, achieving high-density tungsten structures using vat photopolymerization remains a crucial challenge. This work presents a straightforward and reliable method for fabricating complex, micro-architected tungsten structures with superior density and hardness. The approach utilizes a water-based photoresin with exceptional tungsten ion loading capacity. The photoresin is then patterned using digital light processing (DLP) to create tungsten-laden precursors. A three-step debinding and sintering process subsequently achieves 3D tungsten structures with dense surface morphology and minimal internal defects. The microstructures achieve a minimum feature size of 35µm, a low surface roughness of 2.86µm, and demonstrate exceptional mechanical properties. This new method for structuring tungsten opens doors to a broad range of applications, including micromachining, collimators, detectors, and metamaterials.

Regulation of Transition Metal Doping into Double Perovskite Structure as for a Electrocatalyst in Water Electrolysis

Applying and combining of transition metals to perovskite structure is significantly dealt for improving the electrochemical property. The introduction of transition metals in the active B-site is considered as a useful pathway to regulate the chemical and electronic properties of the perovskites. In this study, a double perovskite structure (A2BB’O6) is designed to apply large ionic radius elements such as tungsten(W) that can not be doped into the general single perovskite structure(ABO3). Tungsten is normally equilibrium in the metallic phase, but tungsten ions rapidly move from 4+ state to the 6+ state in the oxide phase, boosting the electrochemical property. The W-based double perovskite materials are synthesized by a high temperature solid-state method. With a combination of Calcium (Ca) doped in the B-site for structural stabilization, transition metals (Ni, Co, etc.) are doped together as an active site to enhance the electrochemical performance. To analyze the physical and chemical structural characteristics, XRD with Rietveld refinement, XPS and XANES/EXAFS measurements are used. Rotating Disk Electrode (RDE) system is utilized to confirm the electrochemical performance of the prepared samples. Through cyclic voltammetry (CV) and linear sweep voltammetry (LSV) measurements, oxygen involved reactions are carried out to prove possibility on our W-based double perovskite materials as a high performance oxygen electrocatalyst with low-price.

Gene sll1454 is important for growth of Synechocystis sp. PCC 6803 on nitrate as the only source of nitrogen

The gene sll1454 (narB) encodes a nitrate reductase in Synechocystis sp. PCC 6803. Deletion of sll1454 was performed by insertion of a gene coding for a neomycin phosphate transferase (npt) in both directions to the sll1454 ORF resulting in two different mutant strains named sll1454::npt direct and sll1454::npt complementary. Both strains lost the ability to grow on nitrate as the only source of nitrogen, but instead grew at the same rate as the wild type if ammonium was supplied. Trace metal replacement experiments revealed that tungsten ions inhibited the nitrate reductase in Synechocystis sp. PCC 6803, as no growth occurred with nitrate as the sole nitrogen source, if molybdenum ions were replaced equimolarly by tungsten ions. Vanadium ions, on the other hand, did not exert any negative effect under the same conditions and neither did the omission of molybdenum, tungsten or vanadium ions in the growth medium. The co-addition of molybdenum ions to cultures containing tungsten ions restored growth to the same rate as in cultures containing only molybdenum ions or none of them.Graphical abstract

Investigation of the M1 transitions from the ground configuration of W23+

To extend the research on the atomic structure of tungsten ions with an open 4f-shell, we conducted an investigation into the M1 transitions originating from the ground configuration of W23+ using the SHHtscEBIT in the 420–600 nm range. Three different calculational methods, including the relativistic configuration interactions (RCI) and the relativistic many-body perturbation theory (RMBPT) implemented in FAC, as well as the multiconfiguration Dirac-Hartree-Fock (MCDHF) in GRASP2018, are performed to investigate the energy level structure of W23+. The excitation energies obtained through RCI and RMBPT are in good agreement, with an average difference of 0.62 %. When comparing RCI and MCDHF, this difference increases to 1.20 %. The observed 12 lines of W23+are identified using the detailed collisional-radiative model with the atomic data calculated by RCI. The average wavelength deviations from experimental results are 0.77 %, 1.38 %, and 2.02 % for RCI, RMBPT, and MCDHF, respectively.

Spectral simulation of multivalent collisional-radiative model for W25+–W28+ from EBIT to tokamak plasmas

Accurate and reliable atomic modeling of tungsten ions holds significance for both spectral data analysis and the investigation of tungsten behavior within fusion plasma. To examine the impact of various atomic processes on spectral lines, a collisional-radiative model (CRM) involving multiple charge states for tungsten ions was performed with level-to-level processes with configuration interaction, including spontaneous emission, electron collisional ionization, collisional (de)excitation, radiative recombination, charge exchange, resonant capture, and autoionization. The evolution of M1 spectral lines of W25+–W28+ in the 330–540 nm range was measured using the SH-HtscEBIT and was successfully replicated by the multivalent CRM. The photon emission coefficients (PECs) associated with these M1 transitions in fusion plasma have also been furnished, revealing their minimal sensitivity to the influence of recombination and ionization processes. The verification of these PECs’ properties holds potential for the forthcoming density diagnosis of tungsten ions in Tokamak. Subsequently, the multivalent CRM was also conducted to explore the impact of dielectronic recombination on extreme ultraviolet spectra. While resonant capture does lead to an augmentation in the population of autoionizing levels, the contribution of dielectronic recombination to spectral lines for W26+ and W27+ within the 2–8 nm range remains relatively insignificant.

Turbulent drifts of impurity ions as an explanation for anomalous radial transport in the far-SOL of DIII-D

Successful fusion reactor operation relies on minimal core contamination by impurities, otherwise too much power may be radiated and harm performance. This requires reliable predictions of impurity transport from the scrape-off layer (SOL) into the core, beyond the traditional ‘anomalous’ diffusion approach. We report a set of far-SOL tungsten transport simulations that demonstrate the role of turbulent drifts on radial impurity transport. A turbulent plasma background is simulated using the gyrokinetic SOL code Gkeyll. Tungsten ions are followed within the plasma background using only their drifts. We find that tungsten tends to travel radially outwards with velocities between v r = 300–1200 m s−1 primarily due to polarization drift. We also extract an anomalous radial diffusion coefficient that varies from Dranom = 5–20 m2 s−1. These results are compared to and agree with previous interpretive modeling results. We also show how the turbulent polarization drift can transport some tungsten ions from the wall inwards with effective pinch velocities up to 10 000 m s−1. We conclude that turbulent drifts are a likely explanation for historically anomalous radial impurity transport.

Doping Engineering To Modulate Surface Plasmon Resonance and Enzyme-like Activities for Enhancing Photoacoustic Imaging-Guided Targeted Cancer Therapy in the Second Near-Infrared Window.

Biological imaging-guided targeted tumor therapy has been a soughtafter goal in the field of cancer diagnosis and treatment. To this end, we proposed a strategy to modulate surface plasmon resonance and endow WO3-x nanoparticles (NPs) with enzyme-like catalytic properties by doping Fe2+ in the structure of the NPs. Doping of the Fe2+ introduced oxygen vacancies into the structure of the NPs, inducing a red shift of the maximum absorption wavelength into the near-infrared II (NIR-II) region and enhancing the photoacoustic (PA) and photothermal properties of the NPs for more effective imaging-guided cancer therapy. Under NIR-II laser irradiation, the Fe-WO3-x NPs produced very strong NIR-II PA and photothermal effects, which significantly enhanced the PA imaging and photothermal treatment effects. On the other hand, Fe2+ in Fe-WO3-x could undergo Fenton reactions with H2O2 in the tumor tissue to generate ·OH for chemodynamic therapy. In addition, Fe-WO3-x can also catalyze the above reactions to produce more reactive oxygen species (ROS) and induce the oxidation of NADH to interfere with intracellular adenosine triphosphate (ATP) synthesis, thereby further improving the efficiency of cancer therapy. Specific imaging of tumor tissue and targeted synergistic therapy was achieved after ligation of a MUC1 aptamer to the surface of the Fe-WO3-x NPs by the complexing of -COOH in MUC1 with tungsten ions on the surface of the NPs. These results demonstrated that Fe-WO3-x NPs could be a promising diagnosis and therapeutic agent for cancer. Such a study opens up new avenues into the rational design of nanodiagnosis and treatment agents for NIR-II PA imaging and cancer therapy.

Modeling of tungsten impurity transport and distribution in EAST based on multi-fluid and kinetic Monte Carlo simulations

In recent years, the materials of plasma facing components, such as divertor target plates, domes, and outer walls of tokamaks, such as ASDEX Upgrade, WEST, JET, EAST, and ITER, have been changed from carbon to tungsten because of its lower erosion and tritium retention rates. Impurities are produced by interactions between the plasma and the first wall. This study provides an investigation to simulate the transport and distribution of tungsten impurities in the edge plasma on EAST. The 2D multi-fluid edge plasma transport code SOLPS-ITER and 2D kinetic Monte Carlo impurity transport code DIVIMP were used in the simulations. The multi-fluid model in SOLPS-ITER and the kinetic Monte Carlo model in DIVIMP were employed to treat tungsten impurity ions. The 2D density contour distributions in the computational region and the 1D density radial profiles at the inner and outer midplanes of tungsten impurity particles with ionization states (W0–W+74) and the total tungsten particles with all charge states were obtained. With the heating power 1.5 MW and the line-averaged plasma density 2 × 1019 m−3, the results from SOLPS-ITER and DIVIMP show that the maximum density of tungsten ion with single ionization state is about 1014 m−3 and the total density of tungsten impurities with all charge states is about 1015 m−3 at the core boundary. To the best of our knowledge, the simulation results from SOLPS-ITER and DIVIMP are compared for the first time to benchmark SOLPS-ITER with the multi-fluid mode and DIVIMP with the kinetic model for tungsten impurity transport. The density distributions of tungsten impurities with different ionization states from SOLPS-ITER and DIVIMP are highly similar, and good agreement can be found under similar conditions involved in the calculation. From the comparison benchmark between SOLPS-ITER and DIVIMP for tungsten impurity transport, it can be concluded that the impurity transport approximation used by DIVIMP is good.

Electron impact single ionization cross-section and Maxwellian rate-coefficients of L-shell of tungsten ions W64+-W71+

The cross-sections and Maxwellian rate coefficients of electron impact single ionization is theoretically investigated for tungsten ions (W64+ to W71+) for fine structure levels of configurations containing n = 2 orbitals. To check the accuracy of calculated cross-sections and rate-coefficients, detailed comparison between result from different approximations, binary encounter dipole (BED), distorted wave (DW) and coulomb born exchange (CBE) is presented. The calculations for electron impact ionization cross-sections of ground state are carried out for energy range 20 keV–1000 keV of final electron and Maxwellian rate coefficients for ground state are evaluated at the temperature range 20 keV–300 keV. We have also provided cross-sections at five different energies and rate-coefficients at five different temperatures. The present study of tungsten ions may be useful in fusion plasma modelling and in future comparison.

An NIR-II-enhanced nanozyme to promote wound healing in methicillin-resistant Staphylococcus aureus infections

Deep tissue bacterial infections, especially methicillin-resistant Staphylococcus aureus (MRSA) infections, pose challenges to clinical therapy due to their low debridement efficiency and relapsing. Molybdenum disulfide (MoS2) is used in the antibacterial field as a classic photothermal agent (NIR-I) with good biocompatibility. However, due to its limited NIR-I tissue penetration ability and single treatment mode, MoS2 has poor therapeutic effects on deep tissue infection. Herein, we prepared a defect-type hybrid 2H-MoS2 nanozyme (MoWS2) using hydrothermal method fabricate the MoWS2 composite, which is a new antibacterial strategy involving photothermal and enzyme catalysis, and further enhances the activity of the nanozyme through overheating. The regulation of 2H-MoS2 defects through tungsten ion doping endows MoWS2 with better near-infrared two-region absorption (NIR-II) and enzyme catalytic performance. Antibacterial activity experiments in vitro have shown that MoWS2 can achieve efficient bactericidal activity and biofilm clearance through hyperthermia and reactive oxygen species (ROS). Deep MRSA infection experiments have shown that MoWS2 rapidly removes bacteria from subcutaneous infected tissues through photothermal therapy (PTT) and chemodynamic therapy (CDT), accelerates the dissipation of abscesses, and promotes the healing of infected wounds. Additionally, the versatile treatment mode of MoWS2 was further confirmed through tissue sectioning and immunofluorescence staining analysis. Overall, these results provide a feasible approach for achieving efficient treatment of deep tissue infections through tungsten ion doping to regulate defective 2H-MoS2. Statement of significanceThe photothermal effect of MoS2 nanosheets in the NIR-I (650-900 nm) window in anti-MRSA therapy is considered to be highly reliable and efficient in PTA. However, most of the developed PPT therapies or antimicrobial systems based on PTT therapies developed with 1T-MoS2 have in vivo sterilization temperatures of more than 55°C, which have the risk of damaging the normal tissues of the skin. In this study, we prepared W@MoS2 with a good photothermal effect (36.9%) in the NIR-II window and good peroxidase-like activity. The combined effect of PTT and CDT has a stronger bactericidal effect while avoiding high-temperature damage, which makes the W@MoS2 material more advantageous in terms of antimicrobial effect.

Extensive research into the structure, elasticity, optical, and radiation-shielding properties of zinc phosphate glasses doped with tungsten ions

Extensive research into the structure, elasticity, optical, and radiation-shielding properties of zinc phosphate glasses doped with tungsten ions

Effects of heterovalent ions doping-induced oxygen octahedral distortion and defect chemical change on piezoelectric characteristics and thermal stability of PHT-PIN ceramics

Electromechanical devices require functional materials possessing excellent piezoelectric properties, good thermal stability, and high electromechanical coupling coefficients. To modulate the piezoelectric, dielectric, and electromechanical characteristics of 0.89Pb(Hf0.47Ti0.53)O3-0.11Pb(In1/2Nb1/2)O3 (PHT-PIN) piezoelectric ceramics, heterovalent ions of lithium (Li) and tungsten (W) were doped through a traditional solid-phase reaction approach. On the one hand, large lattice distortions caused by the doped W6+ resulted in the shortening of BO bonds while an increase in the local displacement of B-site ions. Moreover, a mismatch occurred for the oxygen octahedral dimensions, and a subsequent disruption of the long-ranged ordered ferroelectric domains was observed, which resulted in the formation of microdomains. On the other hand, the changes in the concentration of oxygen vacancy defects induced by the Li and W doping inside the ceramic were comprehensively analyzed. The decrease in the concentration of oxygen vacancies was found to be accompanied by the enhancement of piezoelectric properties of the material. Excellent comprehensive performance (piezoelectric coefficient d33 = 655 pC N−1, Curie temperature Tc = 321.1 °C, dielectric constantεr = 3352.31, electromechanical coupling coefficient kp = 0.67, and residual polarization strength Pr = 55 μC cm−2) was obtained for 0.2 mol % doping amount of Li+ and W6+ ions. This work, therefore, proposes a novel strategy for the origin of piezoelectric properties and inspires doping of other heterovalent ions to improve the piezoelectric properties of ceramics. It further promotes the development of Pb-based piezoelectric ceramics for electromechanical devices that can efficiently operate under high-temperature environments.

Neoclassical transport of tungsten ion bundles in total-f neoclassical gyrokinetic simulations of a whole-volume JET-like plasma

The application of a bundling technique to model the diverse charge states of tungsten impurity species in total-f gyrokinetic simulations is demonstrated. The gyrokinetic bundling method strategically groups tungsten ions of similar charge, optimizing computational efficiency. The initial radial configuration of these bundles and their respective charges are derived from a coronal approximation and the quasi-neutrality of the plasma. A low-density JET H-mode like plasma is simulated using the neoclassical version of XGC across the entire plasma volume, spanning from the magnetic axis to the divertor. An accumulation of tungsten is observed at the pedestal top, as a result of low-Z tungsten ions moving inward from the scrape-off-layer into the core region and high-Z tungsten ions moving outward from the core into the pedestal. This organization of the fluxes cannot be captured by a single tungsten-ion simulation. Large up-down poloidal asymmetries of tungsten form in the pedestal and strongly influence the direction of neoclassical fluxes. The temperature screening effect and its correlation with asymmetries are analyzed.