Aluminum Impurities Research Articles

Research of reinforcement phase formation on the borders of sintered berillium grains

The paper presents the results of studying the effect of the state of grain boundaries (formed in the consolidation of beryllium powders by vacuum hot pressing on the strength properties of sintered beryllium. Scanning electron microscopy and X-ray spectral microanalysis were used to study the dependences of the morphology, elemental composition and structure of a dispersion hardening phase - beryllium oxide – on the content of low-melting impurities at the grain boundaries of sintered beryllium. A new hypothesis is proposed to explain the difference in the morphology and structure of reinforcing particles based on the transition features of amorphous beryllium oxide to a crystalline state (devitrification) at the grain boundaries of metallic beryllium. It is theoretically substantiated and experimentally confirmed that the devitrification mechanism can be homogeneous or heterogeneous depending on the content and ratio of silicon and aluminum impurities. This difference leads to the formation of either finely dispersed high-strength reinforcing particles of beryllium oxide or large, lower-strength oxide clusters. Changes in the morphology and structure of reinforcing oxide particles at the metallic beryllium grain boundaries, in its turn, influence the dynamics of beryllium microstructure grain growth during vacuum hot forming and, ultimately, the effect of dispersed grain-boundary hardening of sintered n beryllium. The paper provides the statistically processed results of testing the mechanical properties of industrial hot-pressed blanks produced of less than 56 μm powders to determine the effect of various factors (the content of impurities, their ratio and particle size of the initial powders) on the strength properties of hot-pressed beryllium. The adequacy of the obtained regularities was evaluated using the approximation confidence coefficients and confirmed the conclusions made in the theoretical and experimental analysis of the research problem. The statistical studies substantiated a comprehensive quality indicator of initial powders in order to predict the strength properties of hot-pressed beryllium. The results obtained substantiate new possibilities for controlling the mechanical properties of sintered beryllium for various purposes.

Green and Efficient Method for Recycling Valuable Metals from Scrapped Lithium Cobalt Oxide Cathode Materials

In this study, green and efficient method for recycling valuable metals from scrapped lithium cobalt oxide cathode materials to form lithium carbonate and cobalt powder was proposed. To this end, aluminum and iron impurities were efficiently removed from scrapped lithium cobalt oxide cathode materials through alkali dissolution and magnetic separation with removal rates of 99.9% and 98.3%, respectively. After removal of impurities, lithium cobalt oxides were reduced by hydrogen at high temperature of 650 °C for 3 h to yield Li2O, Co, and very small amounts of CoO and LiOH. Next, the mixture was subjected to water leaching and sodium carbonate precipitation to obtain lithium carbonate with purity of 99.5%. The water-leaching Co and small amounts of cobalt oxides were again reduced by hydrogen to form cobalt powder with purity of 99.4%. In sum, the proposed method looks promising in terms of efficiency, easy for implementation, environmentally-friendliness, and potential industrialization.

Demantoid from the Telyansky Klyuch deposit (Middle Urals) – is the place of the first discovery in the Urals

The relevance of the work is due to the need to study the Ural gems, including those discovered in the Urals. This is important not only from a scientific point of view, but for the history of science and the development of geological tourism in our region as well. Purpose of the work: study of the chemical composition of demantoid from the Telyansky Klyuch deposit, which is the site of the first find of this gem in the Urals. Research methodology. Demantoid (green jewelry andradite) was washed by the author in the Telyansky Klyuch gold placer; the quantitative analysis of the chemical composition of garnet was performed using the JXA-733 X-ray electron probe microanalyzer. Results. A historical study of the sites of finds of demantoids in the Middle Urals was carried out. It was established that precious garnet was found not in placers of the Bobrovka river located south of Nizhny Tagil, but in the gold placer of the Telyansky Klyuch to the north of Nizhny Tagil. Microprobe analysis of individual demantoid crystals showed that garnets with different green color saturation according to the main components are andradites with average contents: CaO – 33,18%; Fe2 O3 – 30,74%; SiO2 – 35,02% (for 6 analyzes). The feature of the chemical composition of Telyansky demantoids is the absence or insignificant amount of aluminum impurity in them – not more than 0.02% Al2 O3 , which is practically at the level of microprobe analysis sensitivity for this element. The amount of chromium varies from 0.02% Cr2 O3 in a light green demantoid to 0.5–0.74% Cr2 O3 in green and bright green andradites. Conclusions. The place of the first find of low-impurity and chromium-containing andradites in the Urals with the name of “diamantoite” (proposed by N. G. Nordenskiöld ) is the Telyansky Klyuch gold deposit on the East Tagil dunite-harzburgite massif in the Middle Urals

Вплив кінетичних параметрів на ефективність виділення водню шляхом розчинення сплаву АК7 в лужних розчинах з домішками активаторів

The aim of the article is to study the influence of the main factors on the hydrogen evolution performance, in particular, the concentration of components, the nature of the electrolyte, the composition and surface condition of the aluminum alloy. For research, a MICROmed device was used, which has a temperature control and a mixing function. Weight corrosion tests were evaluated gravimetrically using the brand scales CERTUS Balance CBA-150-0.02. pH of solutions was measured using pH - meters mark 150 MA. Processing of the results was carried out by mathematical planning of experiments using the software package Exel 2016. It proposed a low-temperature chemical synthesis method by reacting hydrogen alloys of aluminum with alkali solutions with additives activators. The basic patterns of change in the dissolution rate of the AK7 alloy and formation of hydrogen halide from the impact of ions in alkaline solutions and its influence on the process condition of the alloy surface and reaction products. In this alloy, the most influential is the admixture of silicon, which is 3–6% by weight. The influence of the kinetic parameters of dissolution of the AK7 aluminum alloy on the synthesis of hydrogen as a source of environmentally safe thermal energy is determined. The dependences of the process of hydrogen evolution in alkaline solutions by the mechanism of hydrogen depolarization on the nature of the aluminum alloy and impurities of activators in the electrolyte are established. The processes of the metal chemical cycle of hydrogen production have been studied; they create the conditions for the further development of the technological process of aluminodepolarization synthesis of hydrogen without the use of membrane electrolyzers. This method is important for the needs of small energy in small quantities.

Diffusion Mechanism in Aluminum–Silicon Structures Surface-Irradiated by Off-Electrode Plasma of a High-Voltage Gas Discharge

The mechanism of diffusion in Al–Si structures that arises during surface irradiation by off-electrode plasma of a high-voltage gas discharge (discharge current and voltage are I = 50 mA and V = 4 kV, irradiation time varies from 90 to 600 s) has been investigated. A model to calculate the aluminum impurity concentration distribution in a silicon wafer versus irradiation parameters has been suggested. Analytical relationships that are in good agreement with the experiment have been derived. It has been shown that the aluminum diffusion coefficient in the semiconductor is maximal at the electron penetration depth owing to electron-induced vacancies arising in a ~0.25-μm-thick layer. As a result, the thermal diffusion coefficient rises by two to three orders.

Особенности механизма диффузии в структуре алюминий-кремний при облучении ее поверхности внеэлектродной плазмой высоковольтного газового разряда

Features of the diffusion mechanism in Al-Si structure when its surface is irradiated by off-electrode plasma of high-voltage gas discharge at discharge current I=50 mA, accelerating voltage U=4 kV and radiation durations 90 s < t ≤ 600 s are investigated. Model for calculating the concentration profiles of aluminum impurity distribution in silicon plate as a function of Al-Si structure irradiation parameters is proposed; corresponding analytical dependences and also good consent of the theory and experiment are obtained. It is shown that the maximum values of diffusant concentration are reached at a penetration depth of electrons into the semiconductor because of forming of vacancies by them in a layer (х ≈ 0.25 μm). Specified is followed by increase at 2-3 orders of coefficient of thermal diffusion.

Calcium nitrate generating out of nitrogen-acid solutions after breaking up slurries of titanium production

This article provides the results of studies of qualitative, quantitative and material composition of titanium production slurry, which is man-made waste. The leaching of slurry parameters by nitric acid are studied: concentration, solid to liquid ratio, temperature and time. The effective leaching parameters were determined: 1.7 mol/l of nitric acid concentration, solid to liquid ratio = 1:8, pH<1, temperature 20±5 ºС, leaching time is 30 minutes. The rate of filtration was 0.035-0.044 m3/ m2×h. A gradual leaching method was used to improve the solutions filtration. At the beginning, the slurry was leached with a 0.5 mol/l HNO3 solution at room temperature for 10 min at solid to liquid ratio = 1:10, the filtration rate was 0.062 m3/ m2×h. Then the cake was again leached with 3.5 mol / l HNO3 at room temperature for 30 min at solid to liquid ratio = 1:10, the filtration rate was 0.094 m3/ m2×h. Calcium hydroxide or lime milk was selected as the reagent to precipitate impurities out of solutions. The content of impurities of iron, titanium and aluminum is significantly reduced when 2.8-5 pH values. The best purification of calcium nitrate solutions by lime milk was at pH 8. Calcium nitrate crystals were obtained by evaporation of a purified solution of 8 pH value out of a slurry leaching when 5% ammonium nitrate was added to it by weight of Ca(NO3)2. The dehydrated calcium nitrate was obtained by granulating 92-95% of the melt in the form of flakes at 90 °C of a surface temperature of the granulator plate.

Simulation of AlGaAs-heterostructures CVC kinetic due to degradation

A model of degradation of AlGaAs-heterostructures has been developed. Parasitic resistance growth and diffusion of aluminum and donor impurities are considered as the main reasons of degradation of the structure. Current transfer models are generalized to the case of structures with continuous impurity distribution profiles. Algorithms based on numerical methods with reduced time complexity have been developed. RTS CVC was calculated before and after the annealing operation in order to verify the models. According to the results of the calculation, it was concluded that the developed algorithms are advisable for reliability prediction applications.

Physical and chemical characterization of McIntyre Powder: An aluminum dust inhaled by miners to combat silicosis

McIntyre Powder (MP) is a finely ground aluminum powder that was used between 1943 and 1979 as a prophylaxis for silicosis. Silicosis is a chronic lung disease caused by the inhalation of crystalline silica dust and was prevalent in the Canadian mining industry during this time period. The McIntyre Research Foundation developed, patented, and produced the MP and distributed it to licensees in Canada, the United States, Mexico, Chile, Belgian Congo, and Western Australia. In the province of Ontario, Canada it is estimated that at least 27,500 miners between 1943 and 1979 were exposed to MP. The present study was undertaken to examine the chemical and physical characteristics of two variations of MP (light grey and black). Chemical analyses (using X-ray Fluorescence and Inductively Coupled Plasma approaches) indicate that the black MP contains significantly higher concentrations of aluminum and metal impurities than the light grey MP (p < 0.001). X-ray diffractometry shows that while aluminum hydroxide dominates the aluminum speciation in both variations, the higher total aluminum content in the black MP is attributable to a greater proportion of elemental aluminum. Physical characterization (using electron microscopy, light microscopy, and dynamic light scattering) indicates that the light grey MP consists of particles ranging from 5 nm to 5 µm in diameter. Atomic Force Microscopy shows that the light grey MP particles in the nanoparticle range (<100 nm) have a mode between 5 and 10 nm. Consequently, it is possible that inhaled smaller MP nanoparticles may be transported via blood and lymph fluid circulation to many different organs including the brain. It is also possible for inhaled larger MP particles to deposit onto lung tissue and for potential health effects to arise from inflammatory responses through immune activation. This MP characterization will provide crucial data to help inform future toxicological, epidemiological, and biological studies of any long-term effects related to the inhalation of aluminum dust and nanomaterials.

Influence of Oxidation on Estimation of Long-Term Creep Rupture Strength of 2.25Cr–1Mo Steel by Larson–Miller Method

AbstractThe influence of oxidation on the estimation of long-term creep rupture strength is investigated for 2.25% chromium (Cr)–1% molybdenum (Mo) steel specified as JIS STBA 24, JIS SCMV 4 NT, and ASTM A542/A542M by the Larson–Miller method using creep rupture data in the National Institute for Materials Science (NIMS) Creep Data Sheets at 450–650 °C for up to 313,000 h. The creep rupture data exhibit a change in slope of the stress versus time to rupture curves due to oxidation in air during 600 °C creep tests at 15,000–40,000 h and 650 °C tests at 2000–3500 h for different size specimens, which indicates degradation in creep life by the oxidation. The estimated 100,000 h creep rupture strength using regression analysis is increased by the elimination of long-term data degraded by the oxidation. Several metallurgical factors, such as the initial strength represented by the 0.2% proof stress at the creep test temperature and the concentration of aluminum (Al) impurity, also affect the creep life of the tested steel.

Luminescence of natural α-quartz crystal with aluminum, alkali and noble ions impurities

Photoluminescence and thermally stimulated luminescence of synthetic and natural (morion and smoky) α-quartz crystals doped with aluminum and alkali ions were studied. The samples were examined both untreated and subjected to substitution of alkali ions for copper or silver ions. The photoluminescence spectrum of the untreated crystals is characterized with the main blue band around 400 nm (~3.1 eV). The corresponding luminescence center is based on a defect containing aluminum and alkali as compensators in natural and synthetic quartz crystals. Photoluminescence is subjected to thermal quenching and can be detected at high temperatures above 700 K, however the main intensity decay takes place at 200 K. The thermal quenching activation energy is 0.15 ± 0.05 eV and the frequency factor is 3·107 s−1. In the samples with silver ions the main luminescence band is located at ~260 nm (~4.7 eV) with a time constant of ~37 μs at 80 K, and in the samples with copper ions the PL band is at ~ 360 nm (~3.4 eV) with a time constant ~ 50 μs at 80 K. The initial luminescence of crystals is greatly reduced after introduction of noble ions. The luminescence of noble ions quenches at 700 K without drop in intensity at 200 K. For luminescence associated with silver the energy of thermal quenching is 0.7 ± 0.1 eV with a frequency coefficient of 1 · 1013 s−1, and for the luminescence related to copper, these parameters are 0.55 ± 0.1 eV and 1 · 1012 s−1. The differences in intra-center luminescence properties of the same defect containing alkali ions or noble ions are based on differences in electronic transitions. In the case of alkali ions the charge transfer transitions between oxygen and alkali ions. In the case of noble ions absorption – luminescence corresponds to intra ion transitions. Radiation properties are related to trapping of an electron on one valence ion. Created atom moves out of aluminum containing defect. The hole remains on aluminum-oxygen defect. Thermally stimulated luminescence is related to release of atom, it diffusion to aluminum defect with the hole on oxygen and following radiative recombination. Optically stimulated luminescence is explained by the similar process of optical release of excited atom and movement to aluminum defect and recombination of electron with hole.

Origin of acceptor diffusion into silicon substrate during GaN growth by metal organic chemical vapor deposition

This study investigated the change in carrier concentration near the surface of a silicon substrate during gallium nitride (GaN) growth with an aluminum nitride (AlN) buffer layer. It was observed that aluminum, gallium, and carbon diffused into the silicon substrate during the growth process and that the carrier concentration increased with increasing concentration of aluminum and gallium impurities. The gallium that diffused into the silicon substrate was identified as having originated from the gallium that decomposed on the reactor wall during the growth process and the gallium introduced onto the silicon substrate during GaN growth. In contrast, the amount of aluminum that diffused into the substrate was influenced by the duration of the trimethylaluminum (TMAl) flow: a long duration of the TMAl flow step before AlN growth led to a high aluminum concentration near the substrate surface.

Induced rectification behavior in armchair SiC nanoribbon by Al and P doping

The rectification behavior of the armchair SiC nanoribbons devices with the substitutional aluminum (Al) and phosphorus (P) impurities are investigated using density functional theory (DFT) and non-equilibrium Green’s function (NEGF) frameworks. The band structures of electrodes, molecular energy spectrum, transmission spectrum and projected device density of states are considered to analyze the results. The devices include two armchair SiC nanoribbons with the 7 and 9 atoms widths (named 7ASiCNR and 9ASiCNR, respectively) and the impurities in the center or edge of the electrodes. From the results, we found that the impurities change the electrical behavior and induce rectification of the devices whether the position of the impurities is in the center or edge of the electrodes. Among these devices, the highest rectification ratio has occurred for the 7ASiCNR device with simultaneous Al and P impurities located in the center of electrodes with the value of 2.29 × 1013. Moreover, in this device, the forward bias threshold voltage is near to zero. From the band structure analysis, it is found that by doping of Al (P) atoms in the ASiCNRs, the bands shift upward (downward) so that the electrode became a p-type (n-type) semiconductor. Therefore, the bands became well-matched and the high density of states in the central region is provided. This cause the electrons can be allowed to transport.For both Al and P atoms impurities, the rectification is obtained but the rectification ratio in the case of simultaneous Al and P impurities is more than Al or P doping due to the better matching of energy bands. For example, in the 7ASiCNR devices, the rectification ratio increases from 1.65 × 104 (P-doped) to 2.29 × 1013 (P- and Al-doped).

Behaviour of Redeposited Tungsten Layers with Varying Impurity Content during Thermal and Radiation Loads

Tungsten is going to be implemented as a material for plasma-facing divertor tiles in an ITER tokamak. Accumulation of dust particles due to exfoliation of redeposited tungsten layers can severely affect the operation of a fusion devices. Behaviour of tungsten films deposited on tungsten, including layers with added impurities of iron (0,2 at.% and 2 at.% concentration), as well as dust particles with Al impurity, has been studied. It is shown that a film with 2 at.% impurity of iron exhibits exfoliation and blistering when exposed to thermal and radiation loads, while tungsten dust particles with aluminium impurity undergo various structural changes depending on their Al content when heated.

Preparation and characterisation of carboxymethyl-chitosan/sodium phytate composite membranes for adsorption in transformer oil.

Adsorption of metal impurities from transformer oil was studied using a novel porous membrane. A solution of N, O‑carboxymethyl‑chitosan (CMC) and sodium phytate (SP) was blended to prepare a novel porous membrane for the metal impurities adsorption from transformer oil. The chemical structure of the membranes was characterised by their FTIR spectra, scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and video camera observations. The effects of the SP content of the membrane, contact time, and contact temperature on adsorption of copper, iron, and aluminium impurities were studied. The FTIR spectra and thermogravimetric curves of the membranes indicated good compatibility between CMC and SP. The SEM and video camera observations suggested that CMC-SP composite membranes had a mature, porous structure. The experimental results showed that the SP content significantly affected the adsorption capacity of a CMC membrane. The maximum adsorption percentages of elemental copper, iron, and aluminium were 88.12%, 82.35%, and 80.36% when the SP ratio was 80% at 60 °C.

Non-equilibrium Spin-Hall effect in irregularly shaped aluminum and tungsten samples

The method proposed by us in Ref. [1], which eliminates obstacles in the application of electrical methods for studying the spin-Hall effect (SHE) by creating a spin unbalance, which generates a charge unbalance, using the form effect without using polarized injected current, is used in this work to study and compare SHE of different origin - internal (band) and external (structural and impurity). The internal SHE (ISHE) was studied on ultrapure single crystal samples of uncompensated (aluminum) and compensated (tungsten) metals. The influence of external factors on SHE was studied on polycrystalline and impurity aluminum samples. The investigations were carried out in the region of small magnetic fields, which ensure the symmetry of the conventional Hall effect (CHE), which makes it possible to study the chiral behavior of the spin Hall effect.

Role of Vanadium in Aluminum Electrolyzer Melts

The article provides results of testing excess introduction of vanadium into a molten aluminum cell through baked anodes. This stage of special technology is preliminary and required before the boriding heavy metal impurities in molten aluminum. The requirement of a preliminary stage is dictated by the presence of an insulating aluminum carbide layer on the surface of the carbon hearth that reduces the efficiency of aluminum boriding technology. The specific properties of vanadium and its compounds make it possible to organize chemical cleaning of the cathode from an Al4C3 layer, replacing it with a VC substrate. It is shown that with constant introduction of vanadium into melt dynamic equilibrium is established between vanadium and its compounds entering the cell and removed from it. Stabilization of a VC-coating requires organization of boriding technology for molten electrolyte and aluminum, creating a viscous low-mobility layer of a metal-boride Me–B suspension wetted with aluminum on the hearth.

Tuning the Electronic Properties of Hexagonal Two-Dimensional GaN Monolayers via Doping for Enhanced Optoelectronic Applications

We explore structural, electronic, and magnetic properties of two-dimensional (2D) gallium nitride (GaN) monolayer (ML) doped with different elements belonging to the groups III–VI, using density functional theory (DFT) with the Perdew–Burke–Ernzerhof (PBE) functional and the screened hybrid functional (HSE06) approaches as well as molecular dynamics (MD) simulations. Dopant interactions in Ga- and N-rich environments are investigated by varying their concentrations from 1.38 to 5.5%. Our calculations reveal that oxygen and aluminum impurities are the most preferred candidates under Ga- and N-rich conditions, respectively. The electronic structure studies indicate that dopants containing an even number of valence electrons introduce magnetic behavior with spin-polarized properties, or n-type conductivity with nonmagnetic features, depending on the stoichiometric III/V ratio during growth. Dopants with an odd number of valence electrons modify the GaN ML band structure from indirect to direct bandgap at the Γ point, depending on dopant types at different III/V ratios as well as substitutional site. The calculated charge transfer explains the dopants’ influence on the band structure and bond nature. The HSE calculations of doped g-GaN MLs show a 0.23–1.48 eV increase in the band gaps including the spin-polarized band structures when compared with their PBE values. MD calculations suggest high structural stability at high growth temperatures. Such dopant-induced modifications in structural and physical properties of 2D GaN ML could potentially allow use of this material in diverse electronic, optoelectronic, and spintronic applications.

APPLICATION OF THERMOMIGRATION FOR TECHNOLOGY OF POWERFUL SEMICONDUCTORS APPLIANCES

Contex. The conducted researches allow to improve technological processes of manufacture of semiconductor devices and control of their quality. Objective is to investigate the relief of silicon etching in the area of p + -Si isolation and using of Al-thermigration processes for further develop and improve technology of the power devises. The task of the work is to optimize these technology.Method. The object of the study was the technological features of the processes of forming structures on different routes, differing in the manner of carrying out processes of annealing structures and processes of thermomigration Al. The influence of the annealing time on the features of the microrelief of etching grooves in the region of thermomigration has been studied. Results. The causes of change of breakdown voltage of vertical p-n- junctions formed by thermomigration vs post-migration annealing time and thermomigration process optimization are discussed. On these samples is observed minimal microrelief of the groove etching of various types of conductivity silicon in the area under the insulation of the crystals. Such a minimal microrelief determines the minimum of residual mechanical stresses. The control of changes in the kinetics of etching layers of monocrystalline silicon in the field of thermal migration of aluminum impurities helps in determining the modes of technology for the formation of semiconductor structures with high breakdown electrical voltages. At the same time, two conditions are fulfilled: the first one is the excess of the lateral length of aluminum diffusion over the lateral length of the region of mechanical stresses along the perimeter of the thermo-migration region; and the second, it is a reduction and stabilization of changes in the rate of etching of the thermo-migration layers by minimizing the elasticmechanical, deformation component of the activation energy of the etching process of p+-Si. It is shown that in the manufacture of chips of larger power devices with a larger area and a reverse voltage of up to 2000 V, the optimal variant is the route variant, when the processes of impounding impurities of deep active layers are first carried out, then the processes of thermomigration during the formation of insulation layers. Then there are annealing of isolation and active layers. This combination of annealing processes improves the characteristics of structures. Conclusions. The optimum route, the annealing mode of the structures are determined in the work, and it is shown that monitoring the changes in the etching kinetics of silicon layers in the region of thermal immigration of aluminum impurities helps in determining optimal regimes.

Purification of Metallurgical-Grade Silicon by Acid Leaching

Purification of metallurgical-grade silicon (MG-Si), used in many applications such as the medical industry, polymer industry and the solar cells manufacturing. Removal of impurities from MG-Si is critical in these applications. The MG-Si studied in the present research contained various iron, calcium, and aluminum impurities. The hydrometallurgical purification method with different types of acids as solvents was chosen to refine MG-Si. Effects of hydrochloric acid, hydrofluoric acid, sulfuric acid, nitric acid in combination with each other as a solvent for purification of MG-Si were investigated. Additionally, the effects of temperature and particle size of MG-Si were evaluated. In this study, in comparison with previous studies, samples with a larger particle size (in the range of 53 to 300 microns), less refining time (1 to 6 h) and relatively higher temperatures (30 to 70 ∘C) were studied. The results indicated that the highest purity of MG-Si was achieved by HCl (25%) + HF (5%) and followed by HCl (25%) + H2SO4 (30%), HNO3 (25%) + HCl (25%), HNO3 (5%) and H2SO4 (25%), respectively. It was also found that with particle size 53μm, applying a temperature of 50 ∘C for 6 h resulted in high efficiency and purity (99.96%) of MG-Si.