High-purity Metal Research Articles

Influence of the Metal Center in M–N–C Catalysts on the CO2 Reduction Reaction on Gas Diffusion Electrodes

In this work, the influences of various transition metal ions as active sites in high purity metal- and nitrogen-doped carbon catalysts (in short M–N–C), where M: Mn3+, Fe3+, Co2+, Ni2+, Cu2+, Zn2+...

Research Status of High-Purity Metals Prepared by Zone Refining.

The zone refining method is a physical method for effectively purifying metals. Increasing yield and reducing impurity content have always been the focus of its research. This article systematically summarizes the relevant research on the production of high-purity metals by zone refining, including mechanisms, parameter optimization, zone refining types, analysis methods, limitations, and future development directions, and it provides relevant theoretical foundations for the production of high-purity metals as well.

Effect of low Al 3+ doping on the structural, electrochemical performances, and thermal stability of the LiNi 1 / 3 Co 1 / 3 Co 1 / 3 O 2 electrode material for lithium‐ion batteries

A series of Al-doping Li(Ni1/3Co1/3Mn1/3)1-yAlyO2 (y = 0, 0.0001, 0.0002, 0.0003, and 0.0004) electrode materials were prepared via an optimized co-precipitation method using high-purity metal sulfates produced by Managem (Morocco), and at low-synthesis temperature of 750°C. Refinement of the X-ray diffraction patterns reveals the formation of pure layered oxides with no obvious change in the hexagonal unit-cell parameters. Li(Ni1/3Co1/3Mn1/3)1-yAlyO2 electrode materials were tested as electrode for lithium-ion batteries in the voltage range of 2.5 to 4.25 V vs Li+/Li. Discharge capacities of around 160 mAh/g were achieved with an obvious enhancement of the electrochemical performance although the rate of Al-doping is very small. 0.02% Al-doping exhibits better coulombic efficiency (98%) and a capacity retention of 98% at the 50th cycle. Safety tests were also investigated for delithiated cathode materials Liy(Ni1/3Co1/3Mn1/3)1-yAlyO2 recovered at the end of the charge process. Once again, the composition corresponding to 0.02% Al-doping shows the best safety parameters compared to the NCM(111) reference material (Tonset = 289°C; ΔH = 738 J/g).

Carbon-graphite preparation for impregnation with aluminum alloy

The possibility of increasing the efficiency of gasostat-free impregnation of porous carbon-graphite materials with aluminum alloys by applying thin high-purity metal alloying coatings by galvanic method to the surface of the pores of a carbon-graphite specimen is studied. It is shown that the preliminary application of such coatings by an electroplating method allows obtaining the effect of alloying with highly pure elements, increases the filling of pores with matrix melt and decreases the impregnation temperature (750°C). This technology makes it possible to obtain high-quality composite materials using simple technological equipment.

Three-dimensional nanoprinting via charged aerosol jets.

Three-dimensional (3D) printing1-9 has revolutionized manufacturing processes for electronics10-12, optics13-15, energy16,17, robotics18, bioengineering19-21 and sensing22. Downscaling 3D printing23 will enable applications that take advantage of the properties of micro- and nanostructures24,25. However, existing techniques for 3D nanoprinting of metals require a polymer-metal mixture, metallic salts or rheological inks, limiting the choice of material and the purity of the resulting structures. Aerosol lithography has previously been used to assemble arrays of high-purity 3D metal nanostructures on a prepatterned substrate26,27, but in limited geometries26-30. Here we introduce a technique for direct 3D printing of arrays of metal nanostructures with flexible geometry and feature sizes down to hundreds of nanometres, using various materials. The printing process occurs in a dry atmosphere, without the need for polymers or inks. Instead, ions and charged aerosol particles are directed onto a dielectric mask containing an array of holes that floats over a biased silicon substrate. The ions accumulate around each hole, generating electrostatic lenses that focus the charged aerosol particles into nanoscale jets. These jets are guided by converged electric-field lines that form under the hole-containing mask, which acts similarly to the nozzle of a conventional 3D printer, enabling 3D printing of aerosol particles onto the silicon substrate. By moving the substrate during printing, we successfully print various 3D structures, including helices, overhanging nanopillars, rings and letters. In addition, to demonstrate the potential applications of our technique, we printed an array of vertical split-ring resonator structures. In combination with other 3D-printing methods, we expect our 3D-nanoprinting technique to enable substantial advances in nanofabrication.

Development of a novel electrolytic process for producing high-purity magnesium metal from magnesium oxide using a liquid tin cathode

The current electrolytic processes for magnesium (Mg) metal have several disadvantages, such as anhydrous magnesium chloride (MgCl 2 ) preparation and generation of harmful chlorine (Cl 2 ) gas. To overcome these drawbacks, a novel Mg production process to produce high-purity Mg metal directly from magnesium oxide (MgO) was investigated in this study. The electrolysis of MgO was conducted using a liquid tin (Sn) cathode and a carbon (C) anode in the eutectic composition of a magnesium fluoride (MgF 2 ) – lithium fluoride (LiF) molten salt under an applied voltage of 2.5 V at 1053 – 1113 K. Under certain conditions, the Mg – Sn alloys with Mg 2 Sn and Mg (Sn) phases were obtained with a current efficiency of 86.6 % at 1053 K. To produce high-purity Mg metal from the Mg – Sn alloy, vacuum distillation was conducted at 1200 – 1300 K for a duration of 5 – 10 h. Following the vacuum distillation, the concentration of Mg in the Mg – Sn alloy feed decreased from 34.1 to 0.17 mass%, and Mg metal with a purity of 99.999 % was obtained at 1200 K. Therefore, the electrolytic process developed here is feasible for the production of high-purity Mg metal from MgO using an efficient method.

Production of High-Purity Tantalum Metal Powder for Capacitors Using Self-Propagating High-Temperature Synthesis

Production of High-Purity Tantalum Metal Powder for Capacitors Using Self-Propagating High-Temperature Synthesis

Synthesis of colloidal silver, platinum, and mixture of silver-platinum nanoparticles using pulsed laser ablation as contrast agent in computed tomography

Introduction : Over the last seven years, the development of nanoparticles as computed tomography (CT) contrast agents has increased significantly. In this present work, syntheses of colloidal silver nanoparticles (Ag NPs), platinum nanoparticles (Pt NPs), and silver-platinum nanoparticles (Ag-Pt NPs) have been successfully performed using pulsed laser ablation method in deionized water media.Materials and Methods : Experimentally, an neodymium-doped yttrium aluminum garnet (Nd:YAG) laser (1064 nm, 45 mJ, 10 Hz) was focused on a high-purity metal plate including Ag and Pt plates, which are placed in deionized water medium. Colloidal Ag NPs has been succesfully produced with a dark brownish-yellow color with an averaged diameter of 24 nm. For colloidal Pt NPs, the liquid has transparent color with an averaged diameter of 20 nm. Both colloidal nanoparticles of Ag and Pt were then mixed to obtain a mixture composition of Ag and Pt with ratios of Ag:Pt of 75:25%, 50:50%, 25:75%, respectively, with a concentration of each of 10 part per million (ppm). The Ag NPs, Pt NPs, and Ag-Pt NPs mixture were then examined as contrast agents in computed tomography (CT) scan. The CT Scan was set at 80 kV and 100 mAs. Results: The imaging results of these agents were measured in Hounsfield Unit (HU), showing 13.5, 12.8, 13.3, 14.1, and 17.3 HUs for colloidal Ag NPs only, colloidal Ag and Pt NPs with ratios of Ag:Pt of 75:25%, 50:50%, 25:75%, and colloidal Pt NPs only, respectively.Conclusion: These findings confirmed that for colloidal solution containing high concentration of platinum (Pt NPs only and colloidal Ag and Pt NPs with ratio of 25:75%) has higher HU values compared to the case of Pt NPs. The higher HU value for platinium can be attributed to its higher density.

The Influence of Initial Purity Level on the Refining Efficiency of Aluminum via Zone Refining

Zone refining is a well-known technique, usually using pure initial materials to produce high purity metals. However, the effectiveness of zone refining in the purification of different purity levels of metals as well as its feasibility for use as a recycling technique for low quality metals are rarely investigated. In this work, conducted at IME/RWTH Aachen University, three kinds of Al with different purities, i.e., three-layer electrolysis (4N), commercial pure (2N8) and recycled Al (1N7), were put on focus to address the above-mentioned issue. The experiments were conducted with an optimized zone length combination at the moving rate of 1.2 mm/min for five zone passes. The results showed that the 4N pure initial Al was improved to 5N5 after five passes, much higher than the results for commercial pure- or recycled Al, where less than 50% reduction of total impurities was achieved.

High purity metal lead recovery from zinc direct leaching residue via chloride leaching and direct electrolysis

Clean and efficient recovery of lead from zinc direct leaching residue has good environmental and economic benefits. The paper firstly developed a clean and efficient electrolysis process to prepare metal lead from solid lead chloride obtained by leaching zinc direct leaching residue with brine. The solid lead chloride pellets could be well converted into metal lead by direct electrolysis in NH3-NH4Cl electrolyte at constant voltage. Metal lead with 99.1% lead purity was finally obtained by constant voltage electrolysis, and the corresponding extent of lead conversion, current efficiency, and specific energy consumption were 99.32%, 96.75% and 0.575 kW·h/kg respectively. Furthermore, the main technical parameters were also determined, such as a voltage of 2.15 V, working temperature of 45 °C, NH4Cl concentration of 2.0 mol/L, pellet thickness of 1.5 mm and time of 70 min. In addition, the mechanism of the direct electrolysis from solid lead chloride to metal lead in NH3-NH4Cl electrolyte was also proposed, which indicated that the rapid diffusion of electrolyte formed a good conductive network was critical in promoting the direct electrolysis of solid lead chloride. Moreover, the process proposed gives a feasible alternative to recycle lead from zinc direct leaching residue with an environment-friendly method.

Magnetic and Electronic Properties of Heavy Lanthanides (Gd, Tb, Dy, Er, Ho, Tm)

Rare earth metals (REM) occupy a special and important place in our lives. This became especially noticeable during the rapid development of industry in the industrial era of the twentieth century. The tendency of development of the rare-earth metals market certainly remains in the XXI century. According to experts estimates the industry demand for chemical compounds based on them will tend to grow during the nearest years until it reaches the market balance. At the same time, the practical use of high-purity rare-earth metals requires the most accurate understanding of the physical properties of metals, especially magnetic ones. Despite a certain decline in interest in the study of high-purity REM single crystals during the last decade, a number of scientific groups (Ames Lab, Lomonosov Moscow State University (MSU), Baikov Institute of Metallurgy and Materials Science Russian Academy of Science (RAS)) are still conducting high-purity studies on high-purity metal samples. The present article is a combination of a review work covering the analysis of the main works devoted to the study of heavy REMs from gadolinium to thulium, as well as original results obtained at MSU. The paper considers the electronic properties of metals in terms of calculating the density of states, analyzes the regularities of the magnetic phase diagrams of metals, gives the original dependences of the Neel temperature and tricritical temperatures for Gd, Tb, Dy, Er, Ho, Tm, and also introduces a phenomenological parameter that would serve as an indicator of the phase transformation in heavy REMs.

Novel Applications of Ferroalloys for Manufacturing of High Entropy Alloy

Ferroalloys serve important functions during the steelmaking process and impart distinctive qualities to steel. High entropy alloy can be also produced by mixing ferroalloy elements in an equimolar ratio because of it has the advantage of low cost compared with using high purity metals. However, fundamental studies about the preparation of the high entropy alloy by using ferroalloy are scarce. Therefore, the CoCrFeMnNi high-entropy alloys (HEAs) were prepared by using ferroalloys as raw material and refined in an induction furnace with magnesia or alumina refractory under pure Ar atmosphere at 1773 K in the current study. The two different CaO-Al2O3-MgO slags saturated with MgO or Al2O3 were designed to investigate the effect of slag composition on the types of inclusions in the HEAs. The results showed that the complex inclusions MnAl2O4-MnS and Al2O3 were formed when the alloys melted in an alumina refractory, whereas MnAl2O4-MnS, MnCr2O4-MnS, as well as MgAl2O4, were found when the alloys melted in a magnesia refractory.

Некоторые особенности ударного внедрения пенетраторов в грунт небесных тел

The article discusses the features of the inertial explosion of metal products and the prevention of its occurrence during its impact introduction of a metal penetrator into the ground of celestial bodies. The possibility of an inertial explosion in metal penetrators is determined when calculating the critical overload of the Gcr that exceeds a certain threshold value for each metal. These values are determined for a number of alloys and high-purity metals widely used in rocket and space technology for Earth and space temperatures. The features of reducing the critical overload threshold of the Gcr for space conditions at cryogenic temperatures and ways to prevent an inertial explosion are discussed

Efficiency Improvements of the Use of Electromagnetic Induction

The paper describes the results of the experiment about efficiency improvements of the use of high frequency current and сonfirmation that the devices are working better with this type of current. The results indicate the feasibility of further experiments using better installation,in comparison with the installation that was used in the described stages of the experiment below. This installation and method of using high-frequency current will help to use all devices (but not those with an electric circuit, since electronic devices are not adapted to high frequencies, through which they fail) at the power at which they should work, because in general, at a normal frequency of 50-60 Hz there are unnecessary and unprofitable losses.To achieve this goal, the following tasks were defined:Determine how the power changes depending on the frequency of the current in the receiving coil;Is it really possible to increase the efficiency of devices due to high-frequency current;Conduct experiments and draw conclusions based on them.Hypothesis: if you add two or more flat coils together, you will get a high level of frequency savings in electricity consumptionSo the experiment was conducted in the laboratory of cryogenic technology of NTUU "Igor Sikorsky KPI". Instead of an induction plate, we used a frequency generator and an ordinary flat coil (the results of the experiment are not affected by the type of flat coil: either bifilar or ordinary (from a single wire), the dependence has been established in any way). Based on the data taken from the oscilloscope and generator, a graph of the voltage dependence on the current frequency was constructed. Since the dependence of voltage and power is linear, and the current value does not change: with the increase in voltage, there is an increase in power.High-frequency current gives advantages in that it is possible to use conductors of a smaller cross-section and even then we do not get any losses.This kind of current is distributed in the layers of the conductor that are close to the surface, which is called skin effect. Eddy currents passing along the wire, directed so as to weaken the current as much as possible in the middle of the conductor and amplify it near the surface. As a result, the so called “quick-change” current is distributed unevenly-it seems like as if it is trying to be displaced to the surface of the conductor.In a conventional transformer with a core, which is designed to convert alternating current from one voltage to alternating current from another voltage at the same frequency, the resistance can be so small that eddy currents, or Fuko currents, occured. In such massive conductors, they are useless and ony interfere with the work through heating the transformer itself. But there are cases when people on the contrary use a heated property: an induction cooker.Examples of using electromagnetic induction are placing a conductor body in the middle of the coil, in which eddy currents will occur that can warm the body up to melting. In this way, metals are melted in a vacuum, which helps to obtain high-purity metals. Another example is an induction cooker, where you do not need to get rid of eddy currents, but on the contrary, use them as much as possible.

Use of hybrid renewable energy system with organic photovoltaic cells in zinc electrowinning

This work evaluates the use of customized hybrid renewable energy system (HRES) with organic photovoltaic (OPV) cells for producing a high-purity metal by electrowinning. This process usually represents the most energy intensive step in the mining industry. A key advantage about the developed system is that the electric charge is inherently generated as direct current (DC), which can be directly supplied to the electrowinning cells without using intermediate rectifiers. This approach eliminates the energy losses associated, thus increasing the overall efficiency of the power system, and decreases the carbon footprint of the industrial facility. In this context, the main purpose of this first work was to evaluate the energy saving performance of the technology and its application to produce a quality product, which was characterized by morphology, crystal structure and bending behavior. The electrowinning of zinc was selected as case study. Thus, zinc electrodeposition tests were conducted under conditions practiced in industrial operations. The results demonstrated the proper functioning of the HRES system, since constant DC current was supplied to the process. The zinc cathodes exhibited morphology and structure typically described in the literature, which were ductile enough to allow bending without fracturing. On days with global horizontal irradiances in the range from 100 W m−2 to 1200 W m−2, 26 ± 4% of the total current supplied to the electrowinning cell was generated by the OPV cells used in this work. In Brazil, this performance corresponds to carbon mitigation of about 6.4 × 10−2 tons of carbon dioxide equivalents (CO2 eq) per ton of zinc produced. These findings indicate that hybrid systems with photovoltaic cells represent an alternative to save energy and increase the sustainability of electrowinning processes.

Indigenous heat flux differential scanning calorimeter (HF-DSC)

As part of the programme to develop low-cost instruments for use in educational institutions, we have developed a heat-flux differential scanning calorimeter (HF-DSC). We have used low cost components for building the parts of the calorimeter and they were fabricated by the local industries. The paper describes the design and construction of the calorimeter and measurement electronics in detail. The calorimeter was calibrated for temperature and enthalpy measurements using high purity metal standards. The results indicate that the on-set temperatures of thermal events can be measured with an accuracy of ± 0.7 °C and the enthalpy values within ± 3%. The sensitivity of the instrument is about 4 to 5 times lower than that obtained in a typical commercial DSC unit.

Study of Refining and Purification Processing of Gallium Metal As a Raw Materials for Compound Semiconductor

Gallium is used in III-V compound semiconductors according to the development of the semiconductor industry, and increasingly requires high purity gallium metal, and the amount of use is also increasing. The rare earth metal, gallium, has low reserves, which makes it difficult to supply raw materials. Therefore, process waste containing gallium is used to secure raw materials. In this study, high-purity gallium metal was fabricated from process wastes by electrolytic refining and Czochralski(CZ). The CZ device was operated in a clean room of 400 class or less for a high purity environment, and the source crucible was controlled with oxidation of metal using sodium hydroxide and mineral oil. Gallium has a low melting point of 303 K, so the seed portion was cooled to 260 K to make an ingot. The impurity elements in the highly purified gallium metal of about 8N grade was quantitatively analyzed using a glow discharge mass spectrometer(GD-MS). In quantitative analysis using GD-MS, relative sensitivity factors(RSF) are used. For RSF of each element, a standard sample containing gallium as an impurity in an aluminum matrix was used. By analyzing the aluminum matrix CRM, quantitative analysis is possible for a total of 17 elements: Mg, Si, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Ag, Cd, Sn, Pb, Bi, etc. Lastly, in the analysis of gallium crystallized using the CZ method, four of impurity elements were detected: Al, Si, Cr, and Fe, and all other elements were below the detection limit. In the quantitative analysis of impurities in the gallium metal, the total impurity element was 5.58 ppbw, and the final purity of gallium was about 99.9999994% (8N).

Surface Characterization of High-Purity Copper Electropolishing and Electrodeposition Treatments in an Ionic Liquid

High purity (>99.9% composition) copper metal specimens were used in electropolishing treatments with an acid-free ionic liquid electrolyte prepared from quaternary ammonium salts as a green polishing solution. A prominent ionic liquid composed of ethylene glycol (HOCH2CH2OH) and choline chloride (HOC2H4N(CH3)3 +Cl−), sometimes abbreviated as 2EG:1VB4, has been used in other studies to successfully electropolish various metal alloys, but has only been used in limited capacity to polish pure rare earth metals (1-5), like copper, the focus of this study. Voltammetry and chronoamperometry tests were conducted to determine the optimum conditions for electrochemical polishing, while Atomic Force Microscopy (AFM) revealed nanoscale effectiveness of the ionic liquid relative to an industry standard acid polishing treatment of 1 Mol Phosphoric Acid (H3PO4). Surface morphology comparisons summarized electrochemical polishing efficiency of these relative treatments by providing root mean square roughness prior to and post-electrochemical polishing.Electropolishing using the ionic liquid revealed a mirror finish >10 times smoother than the same copper metal surface prior to electropolishing. This transition manifested in a marked change in root mean squared roughness from 167.15 nm to 14.744 nm and resulted in a mass loss of 0.0535 g for an electropolishing rate of 59.444 µg/s when subjected to a 900 second treatment with an average voltage of 1.5 V. By comparison, the phosphoric acid electropolishing treatment yielded an improvement in root mean squared roughness of 85.019 nm, resulted in a mass loss of 0.067 g for a higher electropolishing rate of 74.444 µg/s when subjected to the same treatment conditions. However, the it can be noted that while the elctropolishing rate via the acid solutionis greater, there are extreme peaks and troughs etched on the smoothed surface due to pitting at low current densities (Figure 1). Hydrogen contamination can be observed to affect the overall root mean square average of the region, which may be remedied via a relatively costly degassing treatment at temperatures up to 800 deg C to achieve more comparable results to the ionic liquid solution.After these electropolishing pretreatments, the resulting copper surfaces were subsequently electroplated during a 1 hour treatment at 2 V with an 2EG:1VB4 ionic liquid solution that had previously been used to electropolish high-purity niobium metal. A thin film of niobium metal coated the polished copper during electrodeposition resulting in an average mass gain of 0.002 g, and a root mean squared roughness of increase of -2.101 nm for the ionic liquid pretreated sample, compared to the -2.417 nm resulting roughness from the phosphoric acid pretreatment.As a result, pretreatments revealed a cheaper, recyclable, and environmentally-friendly approach to electopolishing pure copper was demonstrated to be more effective than an acidic industry standard electrolyte. Additionally, electrodeposition of niobium metals on each pretreatment sample provides a reasonably cost-effective method to combine the electroconductivity benefits of copper and ferroelasticity attributes of niobium metals. References Derek Lofis and Tarek M Abdel-Fattah, International Journal of Minerals, Metallurgy and Materials, 26(5), 649–656 (2019)Derek Lofts and Tarek M. Abdel-Fattah, Colloids and Surfaces A: Physicochemical and Engineering Aspects, 511C, 113-119 (2016)Tarek M. Abdel-Fattah, Derek Loftis and Anil Mahapatro, Nanoscience and Nanotechnology, 5(2), 36-44 (2015)Tarek M. Abdel-Fattah, Derek Loftis and Anil Mahapatro, Journal of Surfaces and Interfaces of Materials, 3, 67-74 (2015)Tarek M. Abdel-Fattah, Derek Loftis and Anil Mahapatro, Journal of Biomedical Nanotechnology, 7(6) 794-800 (2011) Figure 1

The manufacturing technology of grade 6 N high-purity indium metal for compound semiconductor

Abstract This study prepared high-purity indium metal using raw materials recovered from process chips (Cu-Chip) in the electronics industry, and designed and modified a pilot device based on the Czochralski (CZ) method. The crystallinity of indium metal, which is crystallized at the reaction temperature of 180-230 ℃, was lowered since its rotation speed and pulling speed were faster than the crystal growth rate. Next, surface oxidation and corrosion during the CZ process were solved in a relatively simple manner. Only C, Al, and In were detected from the crystallized indium metal surface, while no O was detected. The study showed that the impurity content before and after the CZ process decreased and detected very small amounts of Sn, Fe, Si, Pb, etc. in several ppb with the purity of grade 6N (99.99996%).

Defect-related photoluminescence of gallium nitride/silicon nanoporous pillar array modulated by ammonia gas flow rate

The structural and physical properties of silicon nanoporous pillar array (Si-NPA) make it an ideal template for preparing Si-based gallium nitride (GaN) optoelectronic devices with promising performances. For satisfying the spectral requirements in different devices, the control of the luminescence is of key importance. Here we report that utilizing Si-NPA as substrates, high-purity metal gallium as gallium source and ammonia gas as nitrogen source, GaN nanostructures were grown on Si-NPA by a chemical vapor deposition method. It was demonstrated that the photoluminescence (PL) properties of GaN/Si-NPA can be tuned effectively by changing the ammonia flow rate used during the growing process. Through analyzing the evolution of the PL spectra of GaN/Si-NPA with ammonia flow rate, the origins of the observed ultraviolet and visible PL were attributed to the near band edge emission and the emissions from Ga vacancy and N interstitial point defects, respectively. Therefore the variation of the PL spectra of GaN/Si-NPA with ammonia flow rate is actually a reflection of the change of the types and concentrations of point defects. The results might provide an efficient path for preparing Si-based GaN with controlled properties.