Metal Impurities Research Articles

Adsorption of CO2, CO, H2, and N2 on Zeolites, Activated Carbons, and Metal-Organic Frameworks with Different Surface Nonuniformities

The single-component adsorption of CO2, CO, N2, and H2 at 25 and 35 °C was studied using microporous faujasite-framework zeolites (NaY and NaX), activated carbons (GCN and MSP), and metal–organic frameworks (A100 and Z1200) as starting points for the separation of CO2 from syngases produced by gasifying biomass-based solid wastes. The indicated adsorption isotherms and uptake of the adsorbates strongly depended on the adsorbates themselves as well as on the adsorbents because of significant differences in the surface features, such as surface nonuniformity, and in the molecular properties. The selectivity of CO2 to the other gases also varied with the adsorbents due to the distinctive energetic characteristics. The surfaces of the zeolites were the most energetically heterogeneous ones, yielding higher CO2 uptake at low pressures, while the two activated carbons and A100 had moderate surface heterogeneities, and MSP showed the highest CO2 uptake at high pressures, such as 6 bar, at which the micropore volume and surface area are important. Z1200, which has highly homogeneous surfaces and no high-affinity-binding sites, exhibited the lowest CO2 adsorption capacity regardless of equilibrated pressure. The surface nonuniformities of the six sorbents were consistent with the calculated isosteric heats of CO2 adsorption. CO2 could be reversibly adsorbed on NaY and MSP but not on GCN, with some metal impurities, although all these adsorbents showed a fully reversible process for CO adsorption. The estimated working capacity for CO2 adsorption at 25 °C was 0.78–6.50 mmol/g, depending on the sorbents used. The highest value was disclosed for MSP, the surface energetic heterogeneity of which was between that of zeolites and Z1200. Such a high working capacity bodes well for use in our later applications.

Tungsten separation behavior on preparation of high-purity cerium by combined vacuum gravity sedimentation–directional solidification

In light of the difficult removal of harmful impurity tungsten (W) in Ce metal, in this paper a combined vacuum gravity sedimentation‒directional solidification method was innovatively designed and the W separation behavior was investigated. By reducing the electron beam power instantly and gradually at reduction rates of 1, 3 and 5 kW/min, it is found that W is enriched at the bottom of ingots as the melt solidifies. The enrichment effect is much better than that of single purification method and the enrichment degree increases as the beam reduction rate decreases, attributed to the k0(W) ＞ 1 and ρ(W) ＞ ρ(Ce). Overall, the minimum content of W impurity can decrease from 630 to 0.1 ppm at the top of the ingot, and the purity of Ce increases from 99.932 wt% to 99.995 wt% by this combined method. Additionally, this paper provides a new method for the removal of high density and low evaporation coefficient impurities in low vapor pressure rare earth metals.

Single-atom transition metals (Rh, Ir, Co) doped silicon carbide nanotubes (SiCNT) as nonenzymatic nitrotyrosine (NTS) sensor: Insight from theoretical calculations

Transition metals Namely Rhodium (Rh), Iridium (Ir), and Cobalt (Co) doped silicon carbide nanotube (SiCNT) surfaces were theoretically investigated using first-principles density functional theory (DFT) at the B3LYP-GD3(BJ)/def2SVP computational level of theory to understand the biological adsorption, selectivity, reactivity and trapping efficacy of Nitrotyrosine (NTS) as a biomarker for Alzheimer disease. The different parameters and studies conducted showed that there was an increase in conductivity after doping of the metal impurities on SiCNT nanotubes on adsorption of the drugs there and was increase in adsorption strength which lead to chemisorption of the drug on metal-dope-doped surfaces with adsorption energies of −90.550 kcal/mol, −84.839 kcal/mol, −81.702 kcal/mol, and −34.952 kcal/mol corresponding to NTS_Ir@SiCNT, NTS_Co@SiCNT, NTS_Rh@S,iCNT and NTS_@SiCNT systems, hereby suggesting them as a promising biomarker system for Alzheimer disease control.

Gas flow–directed growth of aligned carbon nanotubes from nonmetallic seeds

Kite growth is a process that utilizes laminar gas flow in chemical vapor deposition to grow long, well-aligned carbon nanotubes (CNTs) for electronic application. This process uses metal nanoparticles (NPs) as catalytic seeds for CNT growth. However, these NPs remain as impurities in the grown CNT. In this study, nanodiamonds (NDs) with negligible catalytic activity were utilized as nonmetallic seeds instead of metal catalysts because they are stable at high temperatures and facilitate the growth of low-defect CNTs without residual metal impurities. Results demonstrate the successful growth of over 100-μm-long CNTs by carefully controlling the growth conditions. Importantly, we developed an analysis method that utilizes secondary electron (SE) yield to distinguish whether or not CNTs grown from metal impurities. The absence of metallic NPs at the CNT tips was revealed by the SE yield mapping, whereas the presence of some kind of NPs at the same locations was confirmed by atomic force microscopy (AFM). These results suggest that most of the aligned CNTs were grown from nonmetallic seeds, most likely ND-derived NPs, via the tip-growth mode. Structural characterizations revealed the high crystallinity of CNTs, with relatively small diameters. This study presents the first successful use of nonmetallic seeds for kite growth and provides a convincing alternative for starting materials to prepare long, aligned CNTs without metal impurities. The findings of this study pave the way for more convenient fabrication of aligned CNT-based devices, potentially simplifying the production process by avoiding the need for the removal of metal impurities.

A unique sustainable chemical method for the recovery of pure silicon from waste crystalline silicon solar panels

The present work suggests a unique approach for recovering pure silicon from end-of-life silicon solar panels by a direct treatment which does not involve the use of Hydrofluoric Acid (HF). Firstly, the better alkaline treatment between NaOH and KOH was determined. Then, effects of HF etching time and concentration were studied by comparing different etching treatments. Metal impurities such as Ag, Sn, and heavy metal Pb decreased considerably during the acid leaching studies with suitable concentrations. The major impurity Aluminium was reduced significantly by a two-step chemical treatment which ensures minimal silicon loss. Although it is possible to recover 4 N pure silicon by both (with and without HF etching) methods, direct treatment is preferred since the process eliminates potential human health and environmental concerns associated with HF. The recovered silicon samples were analysed by ICP-OES to detect impurity concentration, by XRD for phase identification and SEM analysis for surface morphology. The critical doping impurities, boron and phosphorous dropped considerably to 18.7 ppm and ND in direct treatment. Thus, the study not only provides an alternative way for recovering pure silicon without the use of harmful chemicals such as HF, but it also recommends a 6 M nitric acid leaching treatment before the etching procedure to lower the concentration of metallic impurities. The results are based on treatments with commercial grade chemicals which ensures the scalability of the process at commercial batch. The profit analysis of the recoverable metals was carried out and estimated to be nearly $19 for an 18 kg c-Si module.

Corn stover‐derived porous carbon for asymmetric supercapacitors

AbstractIn this investigation, hydrothermal liquefaction‐derived hydrochar from pulverized corn stover (avg. particle size 1.12 mm and ash content 6.75 wt%) is chemically activated with aqueous KOH in the presence of Pluronic F127 surfactant and thermally treated further up to 800°C to generate porous carbon (POC) with higher specific surface area and porosity. POC obtained under different processing conditions is thoroughly characterized by Brunauer‐Emmett‐Teller surface area analyzer, Fourier transform infrared spectroscopy, Raman spectroscopy, scanning electron microscopy, and transmission electron microscopy. Metallic impurity present in POC is characterized by inductively coupled plasma mass spectrometry. Higher specific surface area POC is observed with the use of the surfactant during the activation process. Fully characterized POC is used with (Mn, Ti)‐mixed oxide electrode to fabricate asymmetric supercapacitor (ASC). Specific capacitance of ASC is measured by cyclic voltammetry (CV) technique using Gamry G‐300 potentiostat/galvanostat/ZRA. CV plots are obtained with different voltage scan rates whereas galvanostatic charge‐discharge plots are studied by varying the current density. Renewable corn stover‐derived POC prepared using Pluronic F127/KOH activation method is found to be highly suitable as an electrode material because of higher capacitance and electrochemical stability over 100 charging‐discharging cycles.

Effect of 3d transition metal impurities doping on electronic and magnetic properties of CeO2

The effect of transition metal (TM) impurities, namely Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu and Zn, on the electronic and magnetic properties of Ceria dioxide is studied using the Korringa-Kohn-Rostoker method combined with the coherent potential approximation (KKR-CPA). Calculations indicate that pure CeO2 is a nonmagnetic indirect semiconductor. Doping this compound with transition metals results in three main groups based on their electromagnetic behavior. The first group involves CeO2 doped with Sc, Ti and Zn which show a lack of magnetism at low concentrations. The second group of TMs, including V, Mn, Fe and Ni, induces half-metallic character and ferromagnetic behavior. Finally, when Cr, Co and Cu are substituted in CeO2, this doping creates magnetic semiconductors with a direct band gap. The origin of the magnetic states is further discussed and the Curie temperatures are determined. The present work shows that controlling impurity type and concentration renders Cerium dioxide a potential candidate for spintronic applications.

Improving the quality of converting products by the joint smelting of high-sulfur copper concentrate with copper-lead matte

The paper presents the results of studies on the processing of copper-lead mattes with high-sulfur copper concentrate in a converter. The effect of high-sulfur copper concentrate on the quality of converting products is shown. Based on the obtained results, a comparative analysis of the technological indicators of the 1st period of converting copper-lead mattes according to the existing technology and in the joint processing of copper-lead mattes with copper concentrate was carried out. It has been established that when the high-sulfur copper concentrate is used as a sulfidizing agent, excess sulfur released as a result of the dissociation of higher sulfides is completely absorbed by the slag melt. It is shown that elemental sulfur, interacting with oxides of non-ferrous metals and impurities, has a significant effect on the equilibrium distribution of metals between the converting products and their extraction into targeted products. The influence of sulfur on the destruction of magnetite in the process of converting was also established. New data on the distribution of non-ferrous and associated metal impurities (As, Sb, etc.) were obtained during the conversion of copper-lead mattes with high-sulfur copper concentrate. High values were established for the extraction of non-ferrous metals and impurities into targeted products: copper into matte - up to 98%, lead, zinc, arsenic, and antimony into dust - 87%, 91%, 84%, and 38%, respectively. The possibility of a significant improvement in technical and economic indicators, the quality of converting products, and environmental protection during the joint smelting of high-sulfur copper concentrate with a copper-lead matte are shown. The developed technology for converting copper-lead mattes, with high-sulfur copper concentrate, is easily integrated into the plant structure of Kazzinc LLP without any special material costs.

Effect of oxygen on trace impurities in extremely pure metal ingots used for realising ITS-90 fixed point temperatures

The International Temperature Scale of 1990 (ITS-90) provides a scheme for calibrating thermometers which is largely based on the freezing points of pure metals such as indium, tin, zinc, aluminium and silver. The existence of trace impurities in pure metals results in uncertainties in the realization of these freezing points. Several methods such as the sum of individual estimates (SIE) and overall maximum estimate (OME) are used to assess the uncertainties due to the presence of impurities. However, it is becoming evident that the oxidation of impurities results in their precipitation, which means that these insoluble oxides no longer play a significant role in the elevation or depression of the freezing temperature. Hence the conventional correction techniques may overestimate the magnitude of the effect. In this study, the thermodynamic modelling software MTDATA was used to evaluate the effect of oxygen on selected impurities in In, Sn, Zn, Al and Ag by calculating the binary impurity-metal phase diagram in the presence of specific amounts of oxygen. It was found that oxygen has a significant effect on many of the systems studied. The most significant effect was observed in the Ag system, and then, in decreasing order of significance, In, Sn, Zn and Al.

INFLUENCE OF As<sub>2</sub>S<sub>3</sub> STOICHIOMETRY ON THE OPTICAL TRANSMISSION OF GLASS IN THE SPECTRAL RANGE 5–8 µm

Glassy chalcogenides AVBVI obtained by solidification of high-temperature melts inherit the polymolecular nature of the melt. The influence of this circumstance on the optical properties of glasses is important in connection with the use of optical fibers for fabrication and has not been adequately studied. Bulk samples of high-pure glasses As40 – xS60 + x (0 x 5) with the content of metal and silicon impurities less than 0.1‒0.2 ppm wt., carbon, oxygen, hydrogen compounds – no more than 0.5–1 ppm wt. and optical fibers from them were obtained. The IR spectra of bulk samples 12 cm long and optical fibers up to 15 m long were recorded in the spectral range 1000–2000 cm–1. Absorption bands with maxima near 1950, 1805, 1460, and 1320 cm–1, due to the content of superstoichiometric sulfur in glass, were found in the spectra of bulk samples and fibers, and the corresponding values of the extinction coefficients were determined. The results of the study allow us to consider the As2S3 stoichiometry as a factor that significantly affects the optical characteristics of glass.

Prediction of Toxicity of Nanomaterials Using QSAR Approach

Abstract: Building mathematical models based on the analysis of physiochemical systems is known as computational modeling. It may be used to combine different types of data and gain a thorough grasp of how they are correlated. Computational modeling techniques cannot replace true experimental techniques or function as a real mechanism. Despite this, they showed to be highly effective at displaying the outcomes for a suggested technique. Nanotechnology is a developing field of producing cost-effective nanomaterials. The toxicity of nano-based products may be significantly affected by the presence of metal impurities and latent waste. The contaminants introduced into the nano-products during manufacturing toxicate the cells. A limited number of techniques for the precise detection of nanotoxicity in nanomaterials has created interest in scientists for the development of newer computational techniques like QSAR. QSAR gives precise results based on ligand descriptors and mathematical algorithms to create functionalized bandwidth that detects toxicity at nano-levels. Now, widespread literature revealed QSAR workflow for the precise detection of various toxicants in nano-materials. The current mini-review focused on the basic principles of QSAR in nanotoxicity predictions along with the applications and future prospects.

Influence of impurity metal doping on calcite growth: A first-principles study

To better understand the effect of impurity metal doping on the initial stage of calcite growth, the attachment of the CaCO3 molecule on anhydrous and hydrated pristine and doped (Mg-, Cu-, Zn-, Sr- and Ba-doped) calcite (101¯4) surfaces and the analysis of the interactions of the water molecule with various dopants were studied using the first-principles methods. Simulation results suggest that the adsorption ability of anhydrous calcite surfaces toward the CaCO3 molecule is determined by the size of the dopant. The adsorption behavior for water molecules is dominated by chemical bonding. For the adsorption of the CaCO3 molecule on hydrated calcite surfaces, both the dopant size and the chemical bonding factors influence its stability, resulting in the decrease of the CaCO3 adsorption on all doped surfaces. By considering synergetic effects of impurity metal doping on the water and CaCO3 adsorption, we provide new insights into the understanding of the inhibiting mechanism of Mg, Cu and Zn impurities on calcite growth. Moreover, the predicted facilitation of Sr and Ba dopants on calcite growth highlights the feasibility of applying the calcite precipitation technique in mineralizing toxic Sr and Ba from contaminated environments.

Closed-loop recycling of spent lithium-ion batteries based on selective sulfidation: An unconventional approach

The facile recycling of spent lithium-ion batteries (LIBs) has attracted considerable attention because of its great importance to environmental protection and resource utilization. A novel process is developed for cyclic utilization of spent LiNixCoyMnzO2 (NCM) batteries. The spent NCM was converted into water-soluble Li2CO3, acid-dissolved MnO, and nickel–cobalt sulfides through selective sulfidation, based on roasting condition optimization and thermodynamic calculation. More than 98 % of lithium is extracted preferentially from calcined NCM through water leaching, and over 99 % of manganese is extracted selectively from water leaching residue with H2SO4 solution of 0.4 mol/L in the absence of additional reductant. The nickel and cobalt sulfides were concentrated into the leaching residue without metal impurities. The obtained Li2CO3, MnSO4, and nickel–cobalt sulfides can be regenerated as new NCM, showing good electrochemical performance, and its discharge capacity is 169.8 mAh/g at 0.2C. After 100 cycles at 0.2C, the discharge specific capacity can still be maintained at 143.24 mAh/g, and its capacity retention ratio is as high as 92 %. An environmental assessment and economic evaluation indicate that the process is an economical and eco-friendly approach for green recycling of spent LIBs.

In Ukrainian

Investigating the formation of inversion layers (IL) at the Si-SiO2 interface in the manufacturing technology of silicon photodetectors, some dynamics of dislocations after isothermal annealing were revealed, which were absent in samples without inversion. After selective etching of samples with inversion layers, localization of dislocations on the periphery of responsive elements (RE) with accumulation of guard rings (GR) or other elements of n+-type topology outside the RE was observed. This testified to the movement of dislocations on the surface of the Si-SiO2 structures with IL in the direction of the periphery of the crystal during isothermal annealing, which contributed to a significant decrease in the density of structural defects in RE. The described phenomenon can be used to obtain highly doped defect-free silicon structures. Since the presence of dislocations or other violations of the crystal lattice negatively affect the parameters of the products. In the case of using the described phenomenon as a technological method of “cleaning” the surface of silicon structures, there is a need for controlled formation of IL. One of the methods of forming inversion layers can be thermal oxidation in hydrochloric acid vapors according to the principle of dry-wet-dry oxidation (for p-type silicon). Another method that does not require additional materials is the annealing of Si-SiO2 structures at a temperature of 900–950 Celsium degrees in a nitrogen atmosphere for ≥ 240 minutes. Inversion channels, in this case, will be formed due to the redistribution and diffusion of metal impurities in the oxide (which were introduced during previous thermal operations) to the Si-SiO2 interface. In the described case, these structural defects after annealing were localized in the GR, which is also an active element of the phododiodes, as it limits the dark current of the RE, accordingly, the dark current of the GR should also be low. To be able to implement this method, it is necessary to create passive n+-regions on the periphery of the crystals, limited by oxide, which will be the locations of defects after annealing. It can be both separate areas of arbitrary shape and a concentric ring outside the GR. Elements that will be the locations of defects on the periphery can be cut off at the stage of separating the substrates into crystals. After annealing, it is necessary to remove the IL and form an anti-reflective coating by any known method, since the presence of inversion channels contributes to the growth of dark currents. When examining the morphology of defect localization areas after annealing under high-magnification microscopes and with the help of an atomic force microscope, the formation of hexagonal and round defects, which are partial marginal Frank dislocation loops, was observed. The mechanism of dislocation movement described in this article has not been thoroughly studied by us and requires additional research, but it may be related to Cottrell atmospheres and their interaction with IL

Effects of Impurity Barrier Layer on the Red Zone at the Bottom of Cast Monocrystalline Si Ingot for Solar Cells

A technique to prepare low‐cost high‐purity quartz sheets as impurity barrier layers between the crucible and the seed crystal is proposed herein to improve the casting process of monocrystalline Si (mono‐Si) ingots. The results show that the diffusion of metal impurities from the crucible toward a cast mono‐Si ingot can be hindered, increasing the minority carrier lifetime of Si crystals and reducing the height of the red zone at the bottom of the ingot. Solar cell devices assembled from cast mono‐Si ingots exhibit the enhancement in their overall photoelectric conversion efficiency (η) by 0.76% in comparison to those based on conventional mono‐Si ingots. Therefore, high‐purity quartz sheets as impurity barrier layers for the casting of mono‐Si ingots have great application potential in the photovoltaic industry.

Vliyanie primesey na adsorbtsiyu kisloroda na poverkhnosti Ti5Si3(0001)

The influence of simple and transition metal impurities, as well as interstitial impurities (B, C, and N), on the oxygen adsorption on the Ti5Si3 titanium silicide surface has been studied using the of projector augmented wave method within the electron density functional theory. It has been shown that titanium-substituting impurities belonging to the latter halves of the 3d–5d periods cause most significant changes in the adsorption energy. In addition, simple metals and interstitial impurities reduce the oxygen–surface interaction. By analyzing local electron densities of states, charge density difference distribution, charge transfer, and the overlap population of oxygen bonds to nearest-neighbor atoms, we have revealed special aspects of impurity influence on chemical bonding between the titanium silicide surface and oxygen. Factors responsible for an increase/decrease in the adsorption energy of oxygen on the doped surface are discussed. A correlation between the change in adsorption energy and the electronegativity of impurities has been found.

Indophenine Reaction as a Method for Synthesizing Conjugated Polymers with Sub-1 eV Optical Bandgaps

Traditionally, conjugated polymer syntheses have relied heavily on metal-catalyzed cross-coupling reactions. These cross-couplings require appropriately functionalized monomers, increasing the length and complexity of the overall synthesis; in addition, some of the commonly used reagents (e.g., trialkyltin chlorides) are highly toxic. Even after a polymer has been successfully prepared, residual metal impurities can also compromise its optoelectronic properties and performance in devices. As such, there is a demand for metal-free approaches to conjugated polymer synthesis. In this work, the indophenine reaction was used to polymerize thiophene and bifunctional isatin comonomers, with only sulfuric acid used as the catalyst. The structural influence of the comonomers was evaluated using different thiophenes and bifunctional isatins. The resulting polymers have very wide absorption bands that span the UV/vis/NIR regions, with optical bandgaps as low as 0.76 eV. The polymers show electrochromic behavior, as determined through spectroelectrochemical measurements.

Forensic Mass Spectrometry: Scientific and Legal Precedents.

Mass spectrometry has made profound contributions to the criminal justice system by providing an instrumental method of analysis that delivers exquisite analytical figures of merit for a wide variety of samples and analytes. Applications include the characterization of trace metal impurities in hair and glass to the identification of drugs, explosives, polymers, and ignitable liquids. This review describes major historical developments and, where possible, relates the developed capabilities to casework and legal precedents. This review also provides insight into how historical applications have evolved into, and out of, modern consensus standards. Unlike many pattern-based techniques and physical-matching methods, mass spectrometry has strong scientific foundations and a long history of successful applications that have made it one of the most reliable and respected sources of scientific evidence in criminal and civil cases. That said, in several appellate decisions in which mass spectrometric evidence was challenged but admitted, decisions sometimes still went against the mass spectrometric data anyway, which goes to show that mass spectrometric evidence is always just one piece of the larger legal puzzle.

Determination of burn rate affecting elements in composite solid propellant and its ingredients by microwave-induced plasma optical emission spectrometry.

A study of trace metallic elements in solid propellant and its ingredients is important and critical as they affect ballistic properties of solid rocket motor during combustion. In the present study, an attempt is made to develop a rapid, single run and cost-effective analytical technique for the routine and direct analysis of multi elements. Trace level metallic impurities (burn rate affecting elements) present in premix, cured propellant slab and propellant ingredients such as ammonium perchlorate, aluminium, aluminium oxide, dioctyladipate, hydroxy terminated polybutadiene and toluene diisoycanate sourced from different suppliers and propellant slag are determined based on a relatively recent analytical technique, microwave-induced plasma optical emission spectrometry (MIP-OES). Analytical wavelengths are selected based on the sensitivity and interference effects. Precision and accuracy of the developed test procedure for the metallic impurities are demonstrated using replicate analyses of certified calibration standards. The limit of quantification and detection of elements studied is determined. Linear regression coefficients are greater than 0.995. The results obtained demonstrate the potential of MIP-OES technique for the determination of metallic impurities of solid propellant ingredients, pre-mix, cured slab and slag of solid propellants with shortened analysis time which achieved lower detection limits, higher accuracy and better repeatability.

Charging Characteristics of Micrometer-Sized Metal Particles and Their Effects on Partial Discharge of Insulating Oil in Flowing

In this study, the motion behavior of micron-sized metal particle swarm in case of flow-electric field coupling is observed in a non-contact manner based on the experiments. According to the results of observation, the charging characteristics of metal particle swarm in insulating oil flow under DC electric field are analyzed in detail, and the effects of electric field intensity, voltage type and oil flow velocity on the charging process and motion of particle swarm are studied. The obtained results show that the applied electric field will cause the streamlines of velocity of the metal particles to oscillate along its direction, where such effect becomes more obvious as the electric field intensity increases. The increase of oil flow velocity can weaken the influence of electric field and make the streamlines of velocity tend to be flat. The oscillation effect of streamlines of velocity under AC electric field is much weaker than that of DC electric field. In addition, based on the measured kinetic parameters of particles, it is found that the charge quantity of the moving particles in the gap of electrodes has the characteristics of temporal and spatial variations, and the particles have a variety of charging modes, including collisional charging, charge transfer, neutralization and accumulation. High velocity of flow and the alternating electric field hinder the charge transfer between particles, resulting in a decrease in the overall charge of the particle swarm. Finally, from the perspective of micro-discharge and electric field distortion, we explain the influence mechanism of flow velocity and voltage type on the discharge characteristics of oil flow containing metal impurities.