Tungsten Metal Research Articles

Self-tuned interfacial charges induced by protonated transition metal heterostructure for efficiently acidic hydrogen evolution reaction

The interfacial engineering provides an effective strategy to develop the noble-free catalysts. However, the long protons migration path and undesirable electrons transportation resistance at the heterointerfaces has hampered advances in highly efficient acidic hydrogen production. Herein, the self-tuned interfacial charges in NiP/HxWO3 binary catalyst are developed for the efficiently acidic water electrocatalysis. Specifically, the interfacial electrons could be automatically tuned and accelerated by a self-modulated work function via the in-situ protonation process of WO3 from the semi-conductor to metallic tungsten bronze (HxWO3) in acidic medium. Moreover, the charge redistribution in NiP/HxWO3 balances the electronic state between surficial Ni sites and P sites, bidirectionally optimizing the hydrogen binding energy over surficial NiP for the favorable H* adsorption and H2 release. A further promotion is achieved by constructing NiP/HxWO3 on carbon fiber fabric to form a hierarchically and seamlessly conductive nanostructure. Impressively, the interfacial charge coordinated NiP/HxWO3 catalyst exhibits outstanding HER activity with an overpotential of 280 mV at the high current density of 500 mA·cm−2 and an excellent long-term stability beyond 110 h in acidic medium, surpassing the most reported catalysts. This work demonstrates an protonation assisted interfacial charge regulation strategy for the development of the efficient multicomponent catalyst.

Preparation and electrochemical performance study of a self-healing electrode composite material with WSe2/liquid metal Galinstan for lithium-ion batteries

In this work, a room temperature liquid metal alloy (Galinstan) and tungsten diselenide (WSe2) composite anode (LMx@WSe2) were synthesized utilizing a one-step hydrothermal method. Through a comprehensive characterization process, including XRD, SEM, HRTEM, Raman spectroscopy, XPS, and BET, the structural and morphological properties of the synthesized composites were extensively explored. The liquid metal alloy was observed to combine effectively with WSe2 via electrostatic adsorption, coordination, and additional bonding methods. Furthermore, it displayed high fluidity, deformability, and chemical stability. Consequently, the alloy promoted the repair of cracked surface areas in the electrode material and reduced internal oxidation-reduction reactions, leading to improved electrochemical performance during repeated lithium-ion insertion and extraction cycles. After 500 cycles at a current density of 1 A g−1, this composite electrode retained a capacity of 224.5 mAh g−1. Impressively, at a low temperature of − 10 °C, it maintained a capacity of 290 mAh g−1 after 50 cycles at a current density of 0.2 A g−1. Our research may open avenues for addressing mechanical difficulties experienced in flexible electronic devices and self-healing electronic circuits exposed to chemical reaction processes.

High Temperature Flexural Strength, Microstructure, and Phase Evolution of Quartz Fiber/Boron Phenolic Resin Ceramizable Composite Modified with W and B4C

In order to investigate the effect of refractory metal on the high temperature properties of phenolic resin matrix composites, modified quartz fiber reinforced ceramizable composites were prepared by a molding process with a refractory component, tungsten, as the functional component and boron carbide as the ceramic forming agent. The effects of the tungsten and the boron carbide on the heat resistance of the composite were investigated. The results showed that the introduced refractory metal tungsten and the boron carbide can react to form tungsten borides and tungsten carbides at high temperature, and form a ceramic layer on the surface of the composite, which can fill the defects caused by pyrolysis of matrix and improve the high temperature performance of the composite. When the content of boron carbide was 10 wt% and the content of tungsten powder was 30 wt%, the flexural strength of the composite before and after heat treatment at 1200 °C were increased by 54.6% and 30.2% respectively compared with that without filler.

Associations between urinary heavy metals and anxiety among adults in the National Health and Nutrition Examination Survey (NHANES), 2007–2012

BackgroundFew studies have investigated the associations between heavy metals and anxiety. The purpose of this study was to examine the associations between single and combined exposure to heavy metals and anxiety. MethodsThis study employed data from the National Health and Nutrition Examination Survey (NHANES) from 2007 to 2012. Anxiety was assessed by patients self-reporting the number of anxious days per month. First, we evaluated the associations between 10 heavy metals single exposure and anxiety by multivariable logistic regression. We then selected 5 heavy metals (cadmium, antimony, cobalt, tungsten, and uranium) for further analysis by elastic net regression. Subsequently, principal component analysis (PCA), weighted quantile regression (WQS), and Bayesian kernel machine regression (BKMR) were utilized to evaluate the associations between 5 heavy metals co-exposure and anxiety. ResultsThis study included 4512 participants, among whom 1206 participants were in an anxiety state. Urinary cadmium and antimony were separately related to an increased risk of anxiety (p for trend <0.01 and < 0.01, respectively). In PCA analysis, PC1 was associated with an increased risk of anxiety (p for trend <0.001). In WQS analysis, the positive WQS index was substantially linked with the risk of anxiety (OR (95%CI): 1.23 (1.04,1.39)). In BKMR analysis, the overall effects of co-exposure to heavy metals were positively connected with anxiety. ConclusionOur study identified a positive correlation between individual exposure to cadmium and antimony and the risk of anxiety. Additionally, the co-exposure to cadmium, antimony, cobalt, tungsten, and uranium was associated with an increased risk of anxiety.

Investigation of the Effect of Vacuum and Air Annealing on the Structural, Optical and Electrical Properties of Radio Frequency Sputtered WO&lt;sub&gt;3&lt;/sub&gt; Thin Films

Thin films of tungsten oxide were deposited on glass substrates by the radio frequency (RF) reactive sputtering from a high purity tungsten metal target (99.9%) with a diameter of 10 cm. The reactive sputtering was carried out in an argon-oxygen gas mixture containing 20% of O2 and 80% of Ar. The used RF power is 200 W while fixing the deposition time at 120 min. Finally, the prepared films were annealed at different temperatures (350 °C, 400 °C, 450 °C, 500°C and 550 °C) for 1 hour under air and under vacuum. X-ray diffractograms showed that the deposited thin films crystallized in Hexagonal/Monoclinic WO3 phase. It was found that the crystallite size varies with the annealing temperature and the lattice parameters is a= 7.3064Å, b = 7.5292Å, c = 7.6875Å and a=b= 7.3242Å, c= 7.6624 Å, for h-WO3 and m-WO3 structures, respectively. Scanning Electron Microscopy (SEM), Raman spectra confirmed the formation of WO3 thin films. In addition, optical transmittance data revealed that the optical bandgap of the films decreases with increasing the annealing temperature. Electrical measurements revealed that annealing in air results in more resistive samples, which should be taken into account in future investigations, especially as buffer layers for efficient photovoltaic solar cells. Keywords: Vacuum, Tungsten oxide, Raman spectroscopy, RF Sputtering method, RF Power, Annealing temperature.

Exposure to arsenic, polycyclic aromatic hydrocarbons, metals, and association with skin cancers in the US adults.

Worldwide, skin cancer affects millions of people yearly and is broadly classified into melanoma and nonmelanoma types of skin cancer. The toxicity of metals to human health is a public and clinical health problem due to their widespread use in tools, machinery, and appliances as well as their widespread distribution in the air, water, and soil. Arsenic is a carcinogenic metalloid and available in the Earth's crust. Polycyclic aromatic hydrocarbons (PAHs) are toxic to humans, and incomplete combustion of fossil fuels is the main source of PAHs. Human populations exposed to metals from various sources can lead to various diseases including cancer. Limited studies are conducted to simultaneously assess the correlation of multiple arsenic, PAHs, metals with the occurrence of skin cancer. This study aimed to analyze the association between six PAHs compounds, seven types of arsenic, and fourteen metals from urine specimen with skin cancer in US adults. We performed a cross-sectional analysis using data from a total of 14,716 adults from the National Health Examination and Nutrition Survey (NHANES) database for three cycles ranging from 2011-2012 to 2015-2016. Specialized weighted complex survey logit regressions were conducted. Linear logit regression models using only main effects were performed first to identify the correlation between the selected demographic and lifestyle variables and melanoma, nonmelanoma, and unknown types of skin cancer. A second set of linear, main-effects logit regression models were constructed to examine the correlation between melanoma, nonmelanoma, and other types of skin cancers and seven types of arsenic (arsenous acid, arsenic acid, arsenobetaine, arsenocholine, dimethylarsinic acid, monomethylacrsonic acid, and total arsenic), six PAHs (1-hydroxynaphthalene, 2-hydroxynaphthalene, 3-hydroxyfluorene, 2-hydroxyfluorene, 1-hydroxyphenathrene, and 1-hydroxypyrene), and fourteen metals (barium, cadmium, cobalt, cesium, molybdenum, manganese, lead, antimony, tin, strontium, thallium, tungsten, uranium, and mercury) when adjusted for the selected covariates. The statistical analysis was conducted using R software, version 4.0.4. A marginal positive significant correlation between total arsenic and nonmelanoma was observed. This study identified a significant positive association between barium, cadmium, cesium, mercury, tin, and melanoma development. Cesium showed a significant positive statistical association for nonmelanoma, and thallium showed a borderline significant statistical association for nonmelanoma. A statistically significant positive association was found between cadmium and an unknown type of skin cancer. The findings of this study indicated a statistically significant positive association between skin cancer and barium, cadmium, cesium, tin, mercury, and thallium. Further studies are recommended in humans to refute or confirm these findings.

Behaviors of redox-sensitive tungsten and molybdenum in the northern South China Sea: From the Pearl River to the continental slope

To increase the proxy toolbox for the reconstruction of redox conditions, the transition metal tungsten (W) has been increasingly suggested as a promising new candidate during the last few years. However, compared to other trace metals such as molybdenum (Mo), studies on the redox behavior of W in the brackish/marine environment are relatively rare and mainly limited to euxinic settings. To contribute to our understanding of the behavior of W in modern aquatic ecosystems, we here present a water column W and Mo dataset that follows the salinity gradient of the Pearl River Estuary towards the adjacent coastal and offshore waters of the northern South China Sea (water depths range from 36 m to 3735 m) with the latter also including mostly anoxic porewater and rather oxic sediment surface data. Except for deviations of W in the low-salinity reaches of the Pearl River Estuary, both metals are conservatively introduced to the coastal ocean. The contribution of dissolved W via the Pearl River plume was identified in surface waters along the coastline. In line with previous open ocean studies, the conservative behavior of W proceeds towards the remote parts of the study area with surface waters that are possibly also affected by the South China Sea Warm Current. Within the short core porewater profiles, W concentrations increased with sediment depth and reached the highest levels at the more distal sites. These trends are not linked to the formation of more soluble thiotungstate species as indicated by generally non-sulfidic porewaters. Along with porewater gradients of W, the W concentrations in near-bottom waters suggest effective trapping of W at the sediment/water interface by Mn oxides especially at greater water depths and limited contribution to the open water column W inventory. In contrast to W, Mo concentrations show little variation in the reducing porewaters and remain close to or slightly above the ocean level. Enrichments of W and Mo in the surface sediments from the upper and lower continental slope reflect the known affinity of both trace metals to Mn oxides. Positive correlations of W with the heavy mineral-associated metals titanium (Ti) and zirconium (Zr) in sand-rich deposits of the outer continental shelf subjected to stronger near-bottom currents, further indicate a relation of sedimentary W abundances to the depositional environment.

(Digital Presentation) Electrochemical Reduction of Pressed Tungsten (VI) Oxide on a Solid Electrode in a Melt of Calcium and Sodium Chlorides

This report presents the results of research on the electrochemical reduction of tungsten (VI) oxide in a molten electrolytic mixture of CaCl2-NaCl of eutectic composition. The electrochemical behavior of tableted WO3 on a solid tungsten electrode was studied by voltammetry. Analysis of the obtained products was carried out by X-Ray diffraction and electron microscopy.During the electrochemical reduction, pressed cylindrical samples were placed on a tungsten disk, which served as a cathode. A silica cloth impregnated with a CaCl2-NaCl eutectic melt was placed on top of the tableted sample in order to prevent a short circuit in the cell. The silica cloth and tableted tungsten oxide were pressed to the cathode by the anode. The anode was made of low-porous graphite, and the current was supplied to it with a molybdenum wire. The electrode assembly prepared in this way was placed in a crucible with molten chlorides of calcium and sodium.Analysis of the obtained results indicates that reduction processes occur in pressed tungsten oxide (Fig. 1, a). According to the results of X-Ray phase analysis, in the surface layer of pressed tungsten (VI) oxide, which was in contact with the cathode, when the amount of electricity (Q) twice greater than that required for the complete recovery of loaded tungsten trioxide was passed, the following phases were detected: W, CaWO4 and a small amount of NaxWO3. Having studied the entire volume of the tableted sample, the following phases were recorded: NaxWO3 (main phase) and CaWO4, W (Fig. 1, b). The formation of phases of sodium and calcium tungstates is explained by the interaction of tungsten trioxide with the components of the melt. Passing electricity through the pressed sample causes electrochemical reactions to occur with the formation of tungsten metal, which grows from the cathode/WO3/electrolyte interface into the sample volume.During galvanostatic electrolysis (i=0.4 A/cm2) of a pressed sample of tungsten (VI) oxide with a mass of 0.43 g (r=0.4 cm, h=0.174 cm) and a duration of 6 hours (Qpractical/Qtheoretical = 6), the degree of extraction of tungsten from tungsten trioxide is not less than 97.48%, and the current yield is about 29.06%. The X-Ray diffraction pattern of the obtained product under such conditions confirms the presence of only a monophase of crystalline tungsten (Fig. 1, b). Figure 1

Tungsten dopant incorporation for bandgap and type engineering of perovskite crystals

Organic–inorganic hybrid halide perovskites have shown to be viable semiconductor materials, as the absorber layer of solar cells. Unfortunately, the polycrystalline qualities of perovskite films result in nonuniform coverage or a high recombination rate, which weakens the photoelectric capabilities of thin films. Here, the pure and tungsten (W)-doped methylammonium lead bromide (CH3NH3PbBr3 or MAPbBr3) films are deposited to FTO-glass substrates using the sol–gel spin coating method. The W-doping causes the nucleation and crystallization processes, which then have an impact on the film’s characteristics. It is discovered that the introduction of tungsten metal significantly enhances the quality of the perovskite film, resulting in larger grain sizes, lower band gap energy, and shorter recombination lifetimes, increasing the power conversion efficiency of perovskite thin film solar cells.

Progress in Sustainable Recycling and Circular Economy of Tungsten Carbide Hard Metal Scraps for Industry 5.0 and Onwards

In spite of the critical environmental impacts of mining and the associated geopolitical supply risk, the strategic importance of rare metal tungsten is escalated by rapid expansions in industrialization, particularly in the ongoing low-carbon/energy era, which requires technologies that allow an economic, social, and ecologically friendly tungsten recovery from primary and secondary resources. The current recycling practices of tungsten carbide (WC)-based scraps have been accepted as economically and partially environmentally beneficial and can promote tungsten closed-loop recycling; however, low functional recycling rates and significant metal losses at varied stages hinder the economic recovery of metals. The current review presents the global situation of tungsten and WC flow with a focus on various sustainable methods to recycle spent tungsten and related metals. A detailed discussion of establishing a highly resilient circular economy with sustainable development goals is highlighted by juxtaposing the philosophy of the circular economy, integrated sustainability, and the metal life cycle approach. The article also discusses Industry 5.0 trends, such as sustainable digitalization and twin transition, to overcome the barriers associated with achieving efficient circular recycling. It is shown that cross-disciplinary methodologies, the integration of diverse technologies (digital/green), and the incorporation of state-of-the-art recycling techniques open up the future potential in the recycling sector.

Physical Properties and Effect of Helium-Vacancy Pair on Tungsten/Graphene Composite as Plasma-Facing Materials from First Principles

Tungsten/graphene composite was developed and demonstrated to have good mechanical and thermal properties. Density functional theory calculations were performed to investigate elastic constants, elastic anisotropies and isotropic elastic moduli, thermodynamic properties and minimum thermal conductivity of tungsten/graphene with and without a helium-vacancy pair, and tungsten/graphane and tungsten/ditungsten carbide (tungsten/W2C) composites. The results show that tungsten/graphene composite has more toughness when compared with pure tungsten metal. It is noticed that the minimum thermal conductivity of tungsten/graphene composite is higher, introducing a potential application in heat dissipation at high temperatures. We give an honest appraisal of the anisotropic and isotropic (polycrystalline) elastic properties of tungsten/graphene, tungsten/graphane, and tungsten/W2C carbide composites. In addition, the results show that the graphene layer is a strong trap for the He atom, while He affinity to the graphene layer is weaker to a single vacancy. The formation of the He-vacancy pair due to trapping effects near the W/graphene interface will help to reduce the concentration of impurities and defects in the tungsten matrix and maintain the inherent heat dissipation properties under irradiation.

ELECTROLYTIC CATALYSTS BASED ON TUNGSTEN AND CARBON COMPOUNDS FOR THE HYDROGEN EVOLUTION REACTION

The hydrogen evolution reaction (HER) is one of the most promising methods of obtaining high-purity hydrogen. However, the high cost and limited resources of materials with low cathodic hydrogen evolution overvoltage values, such as platinum group metals, are the main obstacles to the use HER for obtaining hydrogen on an industrial scale. Therefore, it is necessary to develop new alternative materials and methods of their production. One of the promising materials are catalysts based on refractory metals, in particular tungsten carbides. Metal tungsten can also be used for these purposes. In our opinion, high-temperature electrochemical synthesis (HTES) in molten salts can be a promising method of obtaining materials with properties that meet the requirements for effective catalysts, namely: ultra-dispersity, high specific surface area, mesoporosity and defective structure, high chemical and electrochemical stability. Therefore, the purpose of this work is to evaluate the electrocatalytic activity of a group of materials for HER, which are obtained by HTES in melts. Four samples of electrolytic materials were chosen for the study: tungsten, carbon, tungsten mono- and semi-carbides (WC and W2С). All samples were characterized in detail using X-ray diffraction (phase composition), SEM (morphology), Raman spectroscopy (structure of carbon phases), DTG (free carbon content).&#x0D; Based on the analysis of the obtained data, it was established that all samples can be used as catalysts: crystallites have a nanometer size and a large number of structural defects; morpho­logy provides increased surface area; tungsten carbide particles are covered with a layer of free carbon, which prevents oxidation of carbide to WO3, which has a lower catalytic acti­vity; carbon particles are nanosized (20–30 nm) and contain a large number of structural defects; tungsten carbide-based samples contain free carbon, which increases the specific surface area, but does not cause clogging of pores.&#x0D; Polarization measurements were carried out at room temperature at a polarization rate of 5 mV/s in a standard three-electrode cell with an Ag|AgCl reference electrode. 1N H2SO4 was used as a base solution, which was bubbled with high-purity argon. Onset potentials for all samples are -0.05 – -0.25 V (in order WC/C – W2C/WC/C – C – W). The overvoltage and Tafel slope were calculated and WC/C composite was shown to have the lowest values of -0.2 V and -75 mV, respectively.&#x0D; Electrolytic composite of tungsten carbide/carbon have demonstrated the best characteristics, so we plan to continue the development of synthesis method of carbide compounds, which will allow us to reveal even greater potential of carbide catalysts and pave the way for their wide application in catalytic processes.

Construction of layered double hydroxide composites derived from tungsten tailing particles for simultaneously enhancing fire protection and anti-ageing properties of intumescent fire-resistant coatings applied in wood surface

Tungsten tailing is a great deal of solid waste produced in the production process of tungsten metal, for which there is no simple and effective treatment method in the world. The success synthesis of layered double hydroxide composites (TTF-LDH) by co-precipitation method from tungsten tailing is a feasible way to solve this problem. The structure and properties of TTF-LDH were confirmed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The obtained TTF-LDH was in combination with intumescent flame retardants (IFR) to achieve a series of intumescent fire resistance coatings. The effects of TTF-LDH on the fire protection, smoke suppression and anti-ageing performances of coatings were evaluated by fire resistance test, smoke density test, cone calorimeter test and accelerated ageing test, while the flame-retardant mechanism of TTF-LDH in coatings was revealed. The results illustrate that an appropriate amount of TTF-LDH can remarkably enhance smoke suppression and fire-resistant abilities of coatings, among which the coating containing 3 wt % TTF-LDH (IFRC-LDH3) exhibits the optimal synergistic effect, revealing a smoke density rating value of 17.3%, a total heat release of 7.0 MJ/m2 and an equilibrium backside temperature of 146.2 °C at 900 s. Meanwhile, the addition of TTF-LDH can strengthen the char formation and thermal stability abilities of the coatings, and the residual weight of IFRC-LDH3 rises to 35.7% at 800 °C, as supported by thermogravimetric (TG) analysis. The results of accelerated ageing test demonstrate that the presence of TTF-LDH can strengthen structural stability of coating, decrease migration and decomposition of IFR, thus giving the coating better integrity and durability of fire-resistant and smoke suppression properties.

Estimation of Particle Emission Rates and Calculation of Human Dose from Arc Welding and Cutting of Stainless Steel in a Simulated Confined Workspace

The objective of this study was to estimate the particle emission rates, human dose and retention from two arc welding processes and cutting of stainless steel. The two arc welding processes were Shielded Metal Arc Welding (SMAW) and Tungsten Inert Gas (TIG). In a simulated confined workspace of experimental chamber under controlled conditions, four different scenarios were considered, including the use of filtering face piece respirator (FFR), leaving or staying in the workspace after the emission. Deposited and retained dose in the respiratory tract was assessed for the different regions of the human respiratory tract using a dosimetry model (ExDoM2). The three investigated processes generated high particle number concentrations ranging from 2.4 to 3.6 × 106 particles/cm3 and were the highest during TIG. Among all three processes, PM10 concentrations from cutting reached the highest levels [11 and 22 (× 103) μg/m3], while SMAW had the highest contribution of fine particles [~ 4.1 (× 103) μg/m3], consisting mostly of PM1–2.5. The examination of different scenarios revealed that there is only a slight difference in respect to deposited dose while staying in the workspace for the entire investigated time period (4 h) with or without use of Filtering Facepiece Respirator (FFR). It would be more beneficial in respect to deposited dose if the exposed subject was not wearing a FFR during the emission process and would leave the polluted workspace immediately after the emission period. In the first two scenarios (staying 4 h in the polluted workspace with and without FFR), both welding processes had higher cumulative deposited (~ 23%) and retained dose (~ 20%) in thoracic region compared to cutting (~ 9% and ~ 7%). These results demonstrate that even a short emission period can cause a considerable increase in concentrations of harmful respirable particles, thus increasing the human dose. The approach applied in this study could be used for the determination of personal exposure and dose to particles of known composition particularly in confined workspaces.

Investigation on welding defects of alloys using TIG and MIG welding

This study is to look at the welding procedures of tungsten inert gas (TIG) and metal inert gas (MIG). This study focuses on welding flaws with different types of welding joints for AISI-1020 mild steel when welding with tungsten inert gas (TIG) and metal inert gas (MIG). The effects of various process factors on weld mild steel were investigated. The primary process parameters were modified in this research, and the influence on impact strength and hardness was investigated using destructive tests (tensile test). In a tensile test, the yield stress, elastic stress, breaking stress, and breaking force were all measured. Non-destructive (NDT) testing was also carried out. The ultrasonic and liquid penetration tests were carried out without causing any damage. Additionally, non-destructive testing (NDT) was done. The liquid penetration and ultrasonic tests were conducted using non-destructive testing. A comparison of the two testing approaches also brought attention to the need of outstanding weld quality. Fig. 12 shows the stresses in the tensile test for MIG welding, which are 204.793 N/mm2 for yield, 27688 N/mm2 for elastic behavior, and 180 N/mm2 for breaking behavior. The welding link was severed at 180 N/mm2 for MIG welding. The stresses for TIG welding are depicted in Fig. 13 as 313.633 N/mm2 (yield), 16506.2 N/mm2 (elastic), and 257.890 N/mm2 (breaking). The welding connection has failed at 257.890 N/mm2. Before welding, AISI-1020 mild steel had a breaking stress of 420 N/mm2. After welding, the breaking stress was reduced and is now 257.890 N/mm2.

Low-Frequency Ultrawide Band Gap Study of Symmetric Conical Scatterer Phononic Crystal

PurposeOne of the key challenges in the research of phononic crystals is achieving small-size control of large wavelengths, which means obtaining low-frequency band gaps with relatively small lattice dimensions. Previous studies have mostly been unsatisfactory in this regard. To obtain lower starting frequencies and more satisfactory band gap widths, this work presents a novel design for a phononic crystal structure.Design ApproachThe proposed phononic crystal consists of a silicon rubber connecting plate, an epoxy resin substrate, and tungsten metal cone scatterers. Through finite element method (FEM) calculations and analysis, we have successfully achieved an ultrawide band gap. To delve further into the origin of the ultra-wideband gap in a newly conceived phononic crystal, the vibrational modes of this crystal were carefully studied.FindingsThis work has successfully achieved an ultrawide band gap with a width ranging from 122.47 to 4360.2 in the case of a lattice constant of a = 8.5 mm. It was found that the low-frequency ultra-wideband gap cannot be obtained without the presence of silicone rubber. Furthermore, an equivalent spring model was developed, and the accuracy of this model was successfully validated through meticulous calculations. At last, It is found that d1, d4, h1, and h3 have the most pronounced effect on the ultrawide bandgap, and the intrinsic reason is the fact that they determine the geometric structure of the silicone rubber connection plate.Research Limitations/implicationsDue to the chosen research method of finite element analysis, the study results may vary depending on the different mesh discretizations, but this type of error is small and can be ignored.Practical ImplicationsThis work provides a new design solution for phononic crystal miniaturization.Originality/valueCompared with previous reports, the new phonon crystals designed in this paper have smaller size, lower starting frequency, and wider band gap.

Combustion behavior of electrically controlled solid propellant with tungsten additive

In recent times, there is a growing interest in utilizing the controllable solid propellant combustion that facilitates multiple start and stop bits of the electrically controlled solid propellant (ECSP) combustion at will. This paper is an attempt to understand the effect of tungsten metal additive in the ECSP. The tungsten metal powder (1 μm size) is blended with the lithium perchlorate (LP) and polyvinyl alcohol (PVA) along with other ingredients. LP and PVA form the baseline composition, and metal content is added between 5 and 15% by weight. Thermal analysis of the ECSP samples were conducted at 5 °C/min utilizing differential scanning calorimetry (DSC) and thermogravimetry (TGA) in the temperature range of 30 °C–600 °C, and the results showed that the dominant exothermic peaks occur around 260 °C. High speed imaging facilitates in understanding the combustion characteristics of the ECSP samples. The ignition is achieved by applying 300 V DC supply across the molybdenum electrodes. ECSP combustion can be divided into two distinct phases of burning that can be designated as the transient burning and the steady phase burning. It is found that the burning rate was 38.2% faster for 15%-metalized ECSP than 5%-metalized. In addition, multi-wavelength pyrometry was used to obtain the average flame temperature, and it was observed that the flame temperature was 9% lower for 15%-metalized than 5%-metalized. Hence, this study enunciates the burning characteristics of tungsten based ECSP and helps in realizing the potential use of tungsten as a metal additive in the ECSP for micro thrust generation.

The effectiveness of D2 pellet injection in reducing intra-ELM and inter-ELM tungsten divertor erosion rates in DIII-D during the Metal Rings Campaign

Edge localized modes (ELMs) in H-mode plasmas erode plasma-facing components (PFCs) and lead to impurities in the core, reducing confinement. This study analyzes D2 pellet injection on the DIII-D fusion experiment used as an ELM mitigation technique applied during the 2016 tungsten Metal Rings Campaign to reduce W erosion during ELMs. The 400.9 nm photon wavelength line emission intensity of tungsten atoms (WI) filterscope channels and Langmuir probes were used to infer the gross erosion rate of tungsten-coated tiles installed in the divertor of DIII-D. D2 mass injection rates ranging from 34 to 41 arbitrary units (A.U.) and no D2 injection resulted in a similar total W erosion rate during ELMs (intra-ELM). On average, results show a 29% increase in the total gross W erosion rate with intermediate mass injection rates (∼13–23 A.U.) compared to the no pellets and the highest injection rate cases. On average, the fast D2 mass injection rate cases had 15% less erosion in the inter-ELM phase than the case with no pellets. Generally, higher D2 mass injection rates increased the ELM frequency, and the highest injection rates reduced the average erosion per ELM and fractional carbon impurities at the top of the pedestal by nearly 40% when compared to the no-pellet case. As expected, a higher D2 pellet injection rate led to a higher plasma density and lower plasma temperature in the divertor. Additionally, an increasing divertor inter-ELM plasma electron density directly correlated to more frequent pellet injection and a decrease in both the average gross intra-ELM W erosion and the total gross intra-ELM W erosion rate. Simulations of intra-ELM erosion using the ‘free-streaming plus recycling model’ (FSRM) underestimate W erosion during pellet injection by about 30% on average. The discrepancies between the experimental measurements and the FSRM intra-ELM W erosion predictions are postulated to be due to C/W material mixing. A simple analytic mixed-material model is presented and results in better agreement with the experimental data. These results highlight the importance of incorporating the effects of a mixed-material layer in the analysis of PFC erosion.

Humidity-resistant ethanol gas sensors based on electrospun tungsten-doped cerium oxide hollow nanofibers

Serious interference of humidity limits the wide application of ethanol gas sensors. The transition metal tungsten (W) doped cerium dioxide (CeO2), possessing a hydrophobic nature and rich oxygen vacancies, will tackle the humidity issue. Herein, the pristine and W-doped CeO2 hollow nanofibers were successfully fabricated by electrospinning. Oxygen vacancy content increases first and then decreases with the doping tungsten, and the 1 mol% W-doped CeO2 sample presents the largest content. Further, the 1 mol% W-doped CeO2 sensor exhibits an excellent response of 10.2 to 100 ppm ethanol at 200° C, 3.5 times higher than the pure CeO2 sensor, good selectivity, repeatability, and long-term stability. In addition, the responses of the W-CeO2 sensors are almost humidity independent. The resistances in air and ethanol decrease gradually with the humidity increases, leading to the humidity-resistant response, mainly attributed to the hindered carrier migration by the type-I CeO2/WO3 heterojunction. These results indicate that the appropriate W-doped CeO2 is a potential humidity-resistant gas-sensing material for ethanol sensing.

The mechanism study of TIG-MIG hybrid welding process based on simulation

Tungsten inert gas-metal inert gas (TIG-MIG) hybrid welding combines the advantages of tungsten inert gas (TIG) welding and metal inert gas (MIG) welding. Due to the benefits of the two welding techniques, it is an effective strategy to enhance welding quality and productivity. To investigate the mechanism of arcs interaction in TIG-MIG hybrid welding, a three-dimensional transient model for arc-droplet-weld pool behavior was established. The temperature field, metal vapor content, flow fluid, current density and electromagnetic force in the arc space and weld pool were simulated and analyzed. The calculation results showed that the introduction of the TIG arc decreased the content of metal vapor and increased the arc temperature. Compared with single MIG welding, the amplitudes of maximum arc temperature and plasma velocity in TIG-MIG hybrid welding were lower. Experimental results demonstrated that the droplet deflection angle, droplet transfer frequency, weld bead cross-section, and arc temperature distribution all agreed well with calculated values.