High-purity Metal Research Articles

Pure metals for creation the nuclear structural materials

The paper presents the main results of research on the development of structural materials for equipment elements of existing and prospective nuclear power plants. The further development of nuclear energy largely depends on the development of advanced structural materials for new generation reactors and the improvement of materials for operating nuclear power plants. The high requirements for structural materials regarding the content of impurity elements can be met only when high-purity metals are used as initial components and new technologies for their production are used. The prospects of using new methods and approaches for evaluating and improving the physico-mechanical and physico-chemical properties (microhardness, corrosion resistance, radiation resistance, etc.) of structural materials for nuclear technologies were considered.

Study of the surface features of palladium-based alloys using atomic force microscopy and magnetic force microscopy

The surface state of palladium-based alloys, specifically Pd–6.0In–0.5Ru and Pd–7.0Y (the element content is given in wt.%) has been studied using magnetic force microscopy (MFM) and atomic force microscopy (AFM). The study was conducted within the framework of the current trend to enhance the safety of hydrogen separation and storage. The samples for the study were made of high-purity metals through arc alloying. They underwent reversible hydrogen alloying to investigate the impact of internal deformation of metal systems on their structure-sensitive properties. The study demonstrates the characteristics of the sample surface morphology and domain structure before and after hydrogenation. The local magnetic properties of alloy surfaces have been clarified, and their changes as a result of hydrogen exposure have been identified.

Influence of lead concentration on Debye temperature in palladium alloys and microstructure

This article is about palladium-based membrane alloys with promising characteristics. Lead concentration in samples is 5 and 20 wt%. The samples are prepared from high purity metals (99.95 wt%). The samples are characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM) techniques. Effect of the concentration of alloying components on the Debye temperature and on the mean-square displacements of atoms is determined. Influence of defects of the first class (point defect – vacancy pairs, pores, dislocation loops of small radius) found to be dominant in alloys.

Al Impurity Upcycled High-Voltage Cathodes from Spent LiCoO2 Batteries.

Al impurity is among the most likely components to enter the spent lithium-ion battery (LIB) cathode powder due to the strong adhesion between the cathode material and the Al current collector. However, high-value metal elements tend to be lost during the deep removal of Al impurities to obtain high-purity metal salt products in the conventional hydrometallurgical process. In this work, the harmful Al impurity is designed as a beneficial ingredient to upcycle high-voltage LiCoO2 by incorporating robust Al-O covalent bonds into the bulk of the cathode assisted with Ti modification. Benefiting from the strong Al-O and Ti-O bonds in the bulk, the irreversible phase transitions of the upcycled R-LCO-AT have been significantly suppressed at high voltages, as revealed by in situ XRD. Moreover, a Li+-conductive Li2TiO3 protective layer is constructed on the surface of R-LCO-AT by pinning slow-diffusion Ti on the grain boundaries, resulting in improved Li+ diffusion kinetics and restrained interface side reactions. Consequently, the cycle stability and rate performance of R-LCO-AT were significantly enhanced at a high cutoff voltage of 4.6 V, with a discharge capacity of 189.5 mAhg-1 at 1 C and capacity retention of 92.9% over 100 cycles at 4.6 V. This study utilizes the detrimental impurity element to upcycle high-voltage LCO cathodes through an elaborate bulk/surface structural design, offering a strategy for the high-value utilization of spent LIBs.

Accelerated de-chelation of EDTA-metal complexes: A novel and versatile approach for wastewater and solid waste remediation

Industrial waste, including wastewater and solid waste, often contains toxic heavy metals that necessitate extraction and separation prior to safe disposal or reusing them. Sewage sludge incineration ash (SSIA), a non-incinerable waste, holds significant amounts of heavy metals such as iron, zinc, copper, nickel, chromium, and lead. Recovery and reuse of heavy metals from SSIA and further application of treated SSIA sludge remain challenging. Ethylenediaminetetraacetic acid (EDTA) is widely used for heavy metals chelation in different applications. While its chelation with heavy metals is rapid and easy to achieve, the de-chelation of the metal complexes is otherwise slow (∼3 days) and challenging due to their high stability constants. In this study, we investigate the recovery of heavy metals from SSIA through chelation using EDTA, and develop, for the first time, a method to rapidly de-chelate the EDTA-metal complexes through the facile chilling process (1 – 3 h) that accelerates the separation of EDTA and metal ions. A sequential precipitation of high-purity heavy metals from the EDTA-metal complexes was demonstrated with and without de-chelation. This novel and versatile method allows the separation of many valuable compounds from the treated SSIA, including regenerated EDTA, potassium hexafluorosilicate, iron phosphate, iron(III) hydroxide, iron silicate, titanium phosphate, calcium phosphate, copper(I) thiocyanate, nickel bis(dimethylglyoximate), lead(II) sulfate, and zinc sulfide. This approach opens doors for more sustainable waste management and the recovery of valuable resources from industrial waste.

Challenges in Chemical Vapour Deposition of Graphene on Metallurgical Alloys Exemplified for NiTi Shape Memory Alloys

Atomically-thin two-dimensional (2D) materials like graphene have been suggested as ultimately thin corrosion barriers and functional coatings for modern metallurgical alloys. The challenges of chemical vapour deposition (CVD) of such 2D materials, particularly graphene, on modern metallurgical alloys are discussed and reviewed here, focusing on the key problems with the metallurgical alloys’ often limited catalytic activity towards 2D materials growth and the key need to preserve the metallurgical alloys’ bulk properties during the high temperature 2D materials CVD processes. Using graphene CVD on NiTi (Nitinol) shape memory alloys as a case study, we illustrate the constraints arising from low catalytic activity and tendency to form oxides due the Ti in the NiTi alloy in terms of graphene growth results. We show that, by using a scalable low-temperature CVD process at 650 to 750 °C, we can deposit fully covering carbon films on the NiTi, albeit at limited structural quality. Notably, we also demonstrate that our CVD process does not degrade the bulk microstructure of the NiTi during carbon deposition and, importantly, leaves the crystallographic shape memory effect evolution intact. This underscores the potential of CVD for depositing graphene films on NiTi alloys while emphasizing the necessity for further exploration of CVD conditions to achieve high-quality graphene deposits akin to those on prior widely investigated dedicated (often sacrificial) high-purity metal substrates such as Ni.

New approach to predict impurity concentration in high-purity antimony metal prepared by vacuum distillation

Previous studies have shown that there is a significant difference in impurity concentration in the distillate, resulting in an unclear average impurity concentration in the distilled product. To address this issue, a variation model of impurity average concentration in the distillate was developed based on the mass conservation of the solute during the vacuum distillation process. Five continuous distillation experiments of crude antimony (Sb) metal were carried out to obtain the variation regularity of impurity average concentration in the distillate, and two verification experiments of vacuum distillation were conducted to verify the model. The research results showed that, the concentration of As impurity in residue decreases exponentially as the distillation proceeds, whereas the concentration of Bi impurity increases exponentially; there are the increasing and decreasing concentration gradients of As and Bi impurities in the distillate along with the decreasing condensing temperature, respectively; the average concentrations of As and Bi impurities in the distillate present the linearly decreasing and exponentially increasing tendency, respectively; the calculated values of As and Bi impurities average concentrations in the distillate are in good agreement with the values of two verification experiments, confirming the efficacy of the model.

A review of preparing high-purity metals by vacuum distillation

With the development of science and technology, the high-tech industry has increasingly higher requirements for the purity of metals. However, the presence of trace impurities can have a bad effect on the properties of metals. Vacuum distillation process is widely used to prepare high-purity metals because of its advantages of high metal recovery, good environmental protection and simple equipment. In this paper, the overall progress in the preparation of high-purity metals around the principle and process research of vacuum distillation is systematically summarized. Principles of vacuum distillation, variant design of vacuum distillation, parameter optimization and simulation are covered. Based on the current status of the preparation of high-purity metals by this technology, it is pointed out that mechanistic studies and simulations are indispensable in scientific research. This research has certain reference significance for improving production efficiency, saving production cost and improving metal purity.

A Study on the Removal of Impurity Elements Silicon and Zinc from Rubidium Chloride by Vacuum Distillation.

With the rapid development of high and new technology, rubidium and its compounds show broad application prospect and market demand with their unique characteristics. At present, the production of rubidium metal is mainly prepared by calcium thermal reduction of rubidium chloride. Rubidium metal obtained by reduction requires multi-step vacuum distillation to obtain high-purity rubidium metal. The purity of rubidium metal depends on the purity of the raw material rubidium chloride. Rubidium metal is relatively active and is easy to oxidize and explode in air. Therefore, a method combining vacuum decomposition and vacuum distillation to reduce impurity elements in rubidium chloride from raw materials is proposed in this paper. The experimental results show that under the conditions of pressure of 5-10 Pa, distillation temperature of 823 K and vacuum distillation time of 60 min, the contents of Si and Zn impurities are reduced from 1206 mg/kg and 310 mg/kg to less than 0.1 mg/kg, and the removal rates are 99.99% and 99.97%, respectively. Rubidium chloride has almost no loss, and through one-step vacuum distillation, the impurity elements silicon and zinc can be deeply removed, reducing the flammability and explosiveness, high cost, long process and other problems caused by the subsequent preparation of high-purity rubidium metal.

Sublimed fine-grained dysprosium: Significant magnetocaloric effect

As is known, rare-earth metals (REMs) are promising magnetocaloric materials. The magnitude of the magnetocaloric effect (MCE) of REMs significantly depends on their purity. This paper presents results of studies of the magnetic and magnetocaloric properties of sublimed dysprosium, prepared in the course of the present study, with an emphasis on its impurity and structure perfection. The comprehensive analysis of the chemical composition of sublimed dysprosium, which was performed for the first time by atom probe tomography, showed that the metal corresponds to high-purity rare-earth metals (3 N+). The MCE effect was studied using direct measurements of the adiabatic temperature change (ΔTad) in pulsed (up to 50 T) and steady (up to 14 T) magnetic fields. The studies of the MCE of polycrystalline sublimed Dy by direct method showed that the high ΔTad value for sublimed Dy are comparable with those obtained for single-crystal Dy in magnetic fields up to 5 T. The vacuum sublimation, which is more economical and technologically advanced in contrast to single crystal growing, can be used to create magnetocaloric REM-based materials with high MCE values.

Evaluation Method for Technology Readiness Assessment in High-purity Metal Target

Technology readiness level is an assessment tool for technology risk control, widely used in large-scale complex engineering such as military and aerospace industries. High purity metal targets are one of the key materials required for production in fields such as semiconductors, flat panel displays, and solar cells. The technology and process are very complex, which determines the level of technological maturity and will have a significant impact on downstream applications. This article combines the needs of downstream users and establishes a technology maturity evaluation model for high-purity metal targets with "parameters-indicators-data" as the core. It develops a technology maturity evaluation method suitable for high-purity metal targets and uses high-purity cobalt targets as an example for evaluation and application practice. It diagnoses the problems existing in the industrialization process, proposes improvement suggestions, and helps target production enterprises continuously improve and enhance.

Element partitioning and stabilization for impurities removal between liquid silicon and silicate melts: Ab initio insights into electronic structure

The partitioning and stabilization of common impurity elements challenge the impurity removal process during slag refining for developing high-purity metals. The role of electronic properties remains indistinct in the stability of non-metallic, alkaline earth metal, and transition metal impurity clusters in silicon and silicate melts, impeding the advancement of separation medium and purification process. Herein, local structures of impurity atoms are explored through ab initio molecular dynamics, and notable configurations are [PSi4], [TiSi10], [MgSi12] in silicon melts and [PO4], [TiO5], [MgO5] in silicate melts. A novel partition model based on impurity coordination predicted the impurity atoms’ distribution behavior consistent with industrial experiments. Furthermore, this model proposes a critical parameter k that evaluates impurity oxidation levels in coexisting systems and establishes a quantitative link between melt structures and distribution ratio, enabling precise predictions from two-phase ab initio calculations. Innovatively, the electronic structure analysis assessed element partitioning through bonding characteristics and interactions within impurity clusters via parameters: electron density distribution, partial density of states, electron localization function, and Mayer bond order. This yields a distinctive mapping relationship between impurity distribution ratio and stability, evidenced by quantitative associations with 12 key ab initio-derived descriptors through Pearson correlation analysis. This work unveils the electronic properties governing partitioning and endows modeling approach for distribution, driven by cluster structure analysis and ab initio calculations.

Simulation and experimental study of temperature and mass distributions of indium metal in vacuum evaporation

The temperature field and spatial distribution of metal vapor (i.e., flow field) are critical for the purity and direct yield of metals. However, it is impossible to accurately determine the temperature field and distribution of the metal vapor in a vacuum furnace. This study developed a surface-to-surface thermal radiation and volume of fluid multiphase flow coupling model. The temperature distribution and mass distribution of indium vapor in the vertical vacuum furnace at different temperatures from 1423 to 1573 K under the condition of 1 Pa were obtained. The reliability of the model was verified by experimental data obtained under the same conditions as the simulation. The temperature difference between the inside and outside of the condensing plate was 30–45 K in the temperature interval of 1423–1573 K. The temperature difference between the inside wall and the center of the condensing plate was 10 K. The simulation results of indium vapor mass distribution match with the experimental values; the overall temperature error is 5%, and the volatility error is less than 15%. The model developed in this study can be used to predict the temperature field and metal vapor distribution in a vacuum furnace, which will significantly reduce experimental exploration and accurately guide the production practice of vacuum metallurgy. This will expand the application of vacuum metallurgy technology in metal purification, material preparation, waste recycling, and other industries. This can effectively reduce exploratory experiments in the process of vacuum distillation to prepare high-purity metals, reduce the consumption of resources and energy in the experiment and production process, and achieve clean production.

Evolution of Au nanoparticles in c-plane GaN under the heavy ion implantation and their optical properties

The modification of GaN with Au nanoparticles is a promising way for manipulating optical properties in optoelectronics and enhancing the sensitivity of GaN-based substrates used in Surface Enhanced Raman Spectroscopy. Ion implantation is an attractive method for the preparation of high-purity metal nanoparticles on the surface or within the bulk of solids, although this process in crystals is not yet fully understood. Here we study the specific stages of Au nanoparticle formation in c-plane GaN crystals implanted with 1.85 MeV Au ions to the fluence range of 1.5×1016 - 7×1016 cm−2. The implanted samples were annealed at 800 °C in an ammonia atmosphere for 20 minutes to support the nucleation of Au nanoparticles and prevent surface decomposition. The structural and optical properties of the samples were investigated by a combination of Rutherford backscattering spectroscopy in channeling mode (RBS-C), Transmission Electron Microscopy (TEM), Raman spectroscopy, photoluminescence (PL) and diffuse-reflectance spectroscopy (DRS). The two damaged regions, namely at the depth and at the surface, were identified. The depth region exhibits saturation of damage, unlike the surface region reaching an amorphous state for the highest implantation fluence. RBS-C revealed multimodal Au depth profiles for higher ion fluences, which were subsequently redistributed after thermal annealing due to the formation of Au nanoparticles, as confirmed by TEM. Au nanoparticles with fcc structure have been successfully synthesized with the Au-ion implantation fluence of 5×1016 cm−2 with the sizes mostly of 4 – 20 nm resulting in increased optical scattering and absorption within the spectral range of 500 – 700 nm associated with surface plasmon resonance (SPR) and the emergence of blue (2.8 eV) and red (2 eV) photoluminescence bands linked to the combined effect of SPR and implantation-induced defects.

RECEIVING METALS FROM SECONDARY RAW MATERIALS. POWDER OF SILVER

Purpose of research. Powder of silver is one of the most widely used materials in industry. In the free or sintered (compressed) state, it is widely used in medicine as an element of antiseptics, in electronics as the basis of conductive pastes, conductive adhesives and contacts intended for closing and opening electrical circuits, in the production of multilayer ceramic capacitors, etc. Due to its high electrical conductivity, powder of silver is also used as a cathode material in solar cells. In today's conditions, the development of materials for alternative energy sources is quite relevant. Powder of silver can be used as a component of the active mass in chemical current sources. It is known that the characteristics of the active mass are influenced by the properties of the powder, namely, the size and shape of the particles. Materials and methodology. In this work, it was proposed to use boards of radio-electronic equipment as raw materials for the production of powders of silver. The reductant, recovery rate and modes of obtaining finely dispersed powders of silver after processing of secondary raw materials were identified. Results. The influence of the parameters of the reduction of powders of silver, namely, the type of reducing agent and the rate of reduction, was studied. It was established that in the process of forming powders of silver, a developed morphology and space between particles are formed, which increases the surface area, due to which the performance characteristics of various devices, in which powder of silver can be used as a component, will improve. Scientific novelty. Factors that affect the size and shape of powder of silver particles, namely, the type of reducing agent and the rate of reduction, have been established. Conclusions. It was established that the size of particles of silver depends on the speed of recovery. The stronger the reducing agent, the higher the rate of metal reduction, and the larger the particle size. Changing the speed of recovery (slowing down or speeding up) allows you to get particles of silver with the desired size. The indisputable advantage of the method of obtaining powder of silver by reduction is the formation of high-purity metal, which positively affects the properties.

A novel thermal bus architecture for large cryogenic space telescopes utilizing helium pulsating heat pipes

Future space telescopes, such as those proposed for the Far-infrared Surveyor Mission, are expected to employ actively cooled optical arrays with a similar overall surface area compared to the James Webb Space Telescope. Therefore, there is a need for a cryogenic cooling system with a thermal bus architecture that can distribute cooling to these large optical arrays. Recent experimental research of helium Pulsating Heat Pipes (PHPs) has shown that helium PHPs can transfer heat over long distances (on the order of 2 m) with high efficiency, and also have the ability to act as a passive thermal switch upon the removal of the cooling source. PHPs’ high thermal performance, passive switching capability, low mass, and ease of manufacturing make them an appealing option compared to high-purity metal straps for a thermal bus architecture on large cryogenic space telescopes. A novel architecture for the thermal control of optical arrays is proposed utilizing unique configurations of helium pulsating heat pipes that minimize mass, maximize thermal performance, and reduce the risk of mission failure.

Study on microstructures, properties and mechanisms of sinter-joining refractory metal W[sbnd]30Si powders and sputtering targets by spark plasma sintering technique

The development of semiconductor integrated circuits has been limited by the low utilization rate of refractory metal sputtering targets. Spark plasma sintering (SPS) technology has shown great superiority in the sintering and joining of materials, which can be applied to the repair of waste targets and improve the utilization rate. In this study, SPS technology was used to sinter-join the high-purity refractory metal W30Si sputtering powder and the target for integrated circuits to determine the optimal repair process and repair mechanism. The morphological characteristics, grain size, relative density, and Vickers hardness of the repair layer (powder-sintered body) and the target under different joining times were analyzed, and the interface structure and properties of the W30Si joint were also studied. It was found that the W30Si joint was composed of WSi2 and Si phases. The grain size, relative density, and Vickers hardness of the W30Si powder-sintered body and targets increased with the joining time. When the joining time was 10 min (1200 °C), the W30Si joint formed a “zigzag” joining interface, and the bending strength, relative density, grain size, Vickers hardness, and thermal conductivity of the joint were similar to those of the pristine target. In addition, the physical model of SPS sintered and joined refractory metal powders and targets was constructed. Studies have shown that the sinter-joining consists of three stages: early stage, middle stage, and late stage. Among them, the middle stage included two steps that may occur simultaneously, namely the sintering of refractory metal powders and the joining of refractory metal powders with the target, involving pressure welding, micro-arc welding, resistance welding, and diffusion welding mechanisms. This work can provide theoretical guidance for the optimal design of the SPS repair process for refractory metal W30Si sputtering targets.

OBTAINING AND APPLICATION OF SOME HIGH-PURE METALS

The results of systematic research on the complex refining of some chemical-activity and rare metals, and some applications of these are represented. Methods of melting, crystallisation, distillation and electrotransport in high vacuum and different combinations of these methods were mainly used for the refining of metals. Complex refining based on the use of complementary physical-chemical, physical methods and wide use ultrahigh vacuum technology, achieves the highest degrees of purification and obtaining metals in its purest form.

Study of physicochemical properties of secondary electroerosive molybdenum powder obtained in isopropyl alcohol

The results of obtaining and studying the physicochemical properties of powdered molybdenum obtained by electrodispersing molybdenum waste in isopropyl alcohol are presented. It is shown that the use of electrodispersion to obtain powdered molybdenum in isopropyl alcohol provides a high level of physico-chemical properties, corresponds to TU 48-19-69—80 for high purity metal molybdenum and exceeds industrial powders obtained by mechanical grinding and reduction in molybdenum content, while the composition of the new powdered molybdenum contains fewer impurities.

Калориметрия фазовых переходов «ферромагнетик ↔ парамагнетик» в железе, кобальте, никеле

There are some special features in calorimetry signal introduced by the ferromagnetic ↔ paramagnetic phase transitions in magnetic materials. The purpose of this study was to investigate, by means of high-resolution differential scanning calorimetry, the effects of heat flux change during direct and reverse second-order phase transformations of the type ferromagnetic ↔ paramagnetic in some high-purity metals possessing natural ferromagnetism: iron, cobalt, and nickel. The literature review indicates that so far there has been no research describing such phase transitions with the help of differential scanning calorimetry. Our study detected anomalies in the dependences of heat flux intensity on temperature. There was noted a shift to the region of higher temperatures during heating in the range of thermocycling rates of 5-10-20-40 K/min. A shift to the region of lower temperatures during cooling in the same range of thermocycling rates was observed in the area of registration of second-order phase transition. The possibility of using calorimetric measurements for estimating the Curie temperature at ferromagnetic ↔ paramagnetic transitions in the metals is shown. The authors highlight that, when conducting high-resolution calorimetric measurements, it is essential to take into consideration in the total heat flux balance the possible contribution from the effects associated with second-order phase transitions, including, in particular, ferromagnetic ↔ paramagnetic transitions.