High-purity Metal Research Articles

Laser-induced breakdown spectroscopy for the quantitative analysis of metals in sediments using natural zeolite matrix

The dependence of laser-induced breakdown spectroscopy (LIBS) to the matrix of the sample remains an important consideration in performing quantitative analysis. In this study, a new matrix was introduced in the preparation of solid powder calibration curves. Heat-treated natural zeolite and KBr were mixed separately into high purity metal powders to generate calibration curves using a univariate approach. A LIBS technique was used in the detection and quantitative analysis of Cr, Cu and Pb in river sediment samples. The relative percent difference (RPD) was calculated to describe the variability measurements made using ICP/OES and LIBS as well as to evaluate the accuracy of the method. Calculated limits of detection in the matrices prepared were comparable with literature values and ranged from 0.41 to 6.1ppm. The resulting metal concentrations indicate that the natural zeolite matrix were closer to the reference values compared to the KBr matrix. By employing principal component analysis (PCA), heat treated zeolite was shown as a potential diluent or binder for generating calibration curves and could provide matrix-matched standards in identification of target metals from unknown sediment samples. The natural zeolite appeared to closely simulate the ablation behavior and property of the samples, and it is found to be a potential suitable matrix for the quantitative LIBS analysis of sediments.

Carbon nanotube/metal-sulfide composite flexible electrodes for high-performance quantum dot-sensitized solar cells and supercapacitors

Carbon nanotubes (CNT) and metal sulfides have attracted considerable attention owing to their outstanding properties and multiple application areas, such as electrochemical energy conversion and energy storage. Here we describes a cost-effective and facile solution approach to the preparation of metal sulfides (PbS, CuS, CoS, and NiS) grown directly on CNTs, such as CNT/PbS, CNT/CuS, CNT/CoS, and CNT/NiS flexible electrodes for quantum dot-sensitized solar cells (QDSSCs) and supercapacitors (SCs). X-ray photoelectron spectroscopy, X-ray diffraction, and transmission electron microscopy confirmed that the CNT network was covered with high-purity metal sulfide compounds. QDSSCs equipped with the CNT/NiS counter electrode (CE) showed an impressive energy conversion efficiency (η) of 6.41% and remarkable stability. Interestingly, the assembled symmetric CNT/NiS-based polysulfide SC device exhibited a maximal energy density of 35.39 W h kg−1 and superior cycling durability with 98.39% retention after 1,000 cycles compared to the other CNT/metal-sulfides. The elevated performance of the composites was attributed mainly to the good conductivity, high surface area with mesoporous structures and stability of the CNTs and the high electrocatalytic activity of the metal sulfides. Overall, the designed composite CNT/metal-sulfide electrodes offer an important guideline for the development of next level energy conversion and energy storage devices.

Doping effect of Ta5+ ions on microstructure and electrical properties of BaTiO3–(Bi0.5Na0.5)TiO3 ceramics with positive temperature coefficient of resistivity

Lead-free 0.912Ba0.97TiO3–0.088(Bi0.5Na0.5)TiO3–xTa2O5 (0 ≤ x ≤ 0.005) ceramics with positive temperature coefficient of resistivity (PTCR) were prepared by solid reaction sintering of high-purity metal oxides and carbonates reagents. The doping effect of Ta5+ ions on the microstructure and electrical properties of the samples was investigated. X-ray diffraction analysis indicated that all the samples were of a single tetragonal perovskite structure with the calculated c/a value first increased and then decreased with increasing x. The Raman shift at 305 cm−1 became strong firstly and then declined, and the broad band at 722 cm−1 narrowed initially and then broadened with the increase in Ta5+ content. The Curie temperature raised first and then decreased, presenting the highest value up to 170 °C for the samples with x = 0.001. Moreover, after the incorporation of Ta5+ ions, the PTCR (defined by the resistivity jump with the ratio of maximum to minimum ones) decreased first and then increased, presenting the best PTCR performance for the samples with x = 0.005. And with increasing x, the room temperature resistivity decreased first and then increased, displaying the lowest room temperature resistivity for the samples with x = 0.003.

Обоснование механизма доминирующего государственного участия в освоении ресурсов высоколиквидных полезных ископаемых Арктики

For a scientific discussion the authors present proposals on the formation in Russia of a new form of effective mineral resource base development of the strategic solid mineral resources in the Arctic zone of Siberia and the Far East. The mechanism is based on the prevailing govenmental participation in projects of development and exploitation of highly liquid metals (rare earth elements, Tomtor ore cluster in Yakutia) and minerals (diamond abrasive materials, Rock Popigai meteorite crater deposit in Krasnoyarsk region) in the Siberian Arctic, carried out under conditions of high risk. Shown, that due to the unique parameters of both rare earth and diamond ores flow of hi-tech products and semi-products is formed. With the extension of the technological and value chain - delivery to the domestic and the global markets of highly liquid products (oxides of rare earth metals and high-purity metals, technical super abrasive diamond powders and products for the treatment of materials). Thus, a cluster for the production of final products based on rare-earth metals and super abrasive rough diamonds with high added value can be created. Milestones and additional exploration operations, preparations for the operation and development of deposits are carried out by the State Corporation for Mineral Resources with the joint participation, investment, technological cooperation of private companies and research organizations. The Corporation could be considered as a platform for international cooperation and foreign investment in technological chains of a presented mega-project of development of two closely located deposits. Introduced organizational and economic mechanism allows to: a) carry out public administration of complex resource projects in the Arctic and to develop them to an economically efficient level with a gradual sale of business projects to the private sector; b) to initiate and stimulate long-term scientific and technological development in conditions of high risk; c) to form a system of preferences for the development of Russian high-tech exports; d) ensure Russia’s economic presence and increased geopolitical and geo-economic interests in the Arctic.

Effect of Tb and Al substitution within the rare earth and cobalt sublattices on magnetothermal properties of Dy0.5Ho0.5Co2

The effect of Tb and Al substitution within the rare earth and cobalt sublattices on structural and magnetothermal properties of Dy0.5Ho0.5Co2 has been studied. Multicomponent Laves phase alloys Tbx(Dy0.5Ho0.5)1−xCo2−yAly (x=0, 0.3, 0.4, 0.5; y=0, 0.25) synthesized using high-purity metals have been studied using X-ray diffraction analysis, heat capacity and magnetocaloric measurements. Dy0.5Ho0.5Co2 has a first order phase transition at the Curie temperature TC≈110K. Both Tb and Al substitution leads to increase of the TC. The increasing Tb content leads to the decreases slightly the MCE and all the transitions near the Curie temperature are of the first order. As for the Al-containing compounds, MCE measurements show that the phase transition type changes from the first to the second-order. The advantage of Tbx(Dy0.5Ho0.5)1−xCo1.75Al0.25 as compared with Al-free alloys is ‘table-like’ behavior of MCE.

Solid-phase extraction microfluidic devices for matrix removal in trace element assay of actinide materials

Advances in sample nebulization and injection technology have significantly reduced the volume of solution required for trace impurity analysis in plutonium and uranium materials. Correspondingly, we have designed and tested a novel chip-based microfluidic platform, containing a 100-µL or 20-µL solid-phase microextraction column, packed by centrifugation, which supports nuclear material mass and solution volume reductions of 90% or more compared to standard methods. Quantitative recovery of 28 trace elements in uranium was demonstrated using a UTEVA chromatographic resin column, and trace element recovery from thorium (a surrogate for plutonium) was similarly demonstrated using anion exchange resin AG MP-1. Of nine materials tested, compatibility of polyvinyl chloride (PVC), polypropylene (PP), and polytetrafluoroethylene (PTFE) chips with the strong nitric acid media was highest. The microcolumns can be incorporated into a variety of devices and systems, and can be loaded with other solid-phase resins for trace element assay in high-purity metals.

Detection and Analytical Capabilities for Trace Level of Carbon in High-Purity Metals by Laser-Induced Breakdown Spectroscopy with a Frequency Quintupled 213 nm Nd:YAG Laser

The laser-induced breakdown spectroscopy (LIBS) with a frequency quintupled 213 nm Nd:YAG laser was examined to the analysis of trace level of carbon (C) in high-purity metals and its detection and analytical capabilities were evaluated. Though C signal in a wavelength of 247.9 nm, which showed the highest sensitivity of C, could be obtained from Cd, Ti, and Zn ca. 7000 mg kg−1 C in Fe could not be detected due to the interferences from a lot of Fe spectra. Alternative C signal in a wavelength of 193.1 nm could not be also detected from Fe due to the insufficient laser output energy of the frequency quintupled 213 nm Nd:YAG laser. The depth analysis of C by LIBS was also demonstrated and the C in Cd and Zn was found to be contaminated in only surface area whereas the C in Ti was distributed in bulk. From these results, the frequency quintupled 213 nm Nd:YAG laser, which was adopted widely as a commercial laser ablation (LA) system coupled with inductively coupled plasma mass spectrometry (ICPMS) for trace element analysis in solid materials, could be used for C analysis to achieve simultaneous measurements for both C and trace elements in metals by LIBS and LA-ICPMS, respectively.

Determination of the Secondary Neutron Flux at the Massive Natural Uranium Spallation Target

The flux of secondary neutrons generated in collisions of the 660 MeV proton beam with the massive natural uranium spallation target was investigated using a set of monoisotopic threshold activation detectors. Sandwiches made of thin high-purity Al, Co, Au, and Bi metal foils were installed in different positions across the whole spallation target. The gamma-ray activity of products of (n,xn) and other studied reactions was measured offline with germanium semiconductor detectors. Reaction yields of radionuclides with half-life exceeding 100min and with effective neutron energy thresholds between 3.6 MeV and 186 MeV provided us with information about the spectrum of spallation neutrons in this energy region and beyond. The experimental neutron flux was determined using the measured reaction yields and cross-sections calculated with the TALYS 1.8 nuclear reaction program and INCL4-ABLA event generator of MCNP6. Neutron spectra in the region of activation sandwiches were also modeled with the radiation transport code MCNPX 2.7. Neutron flux based on excitation functions from TALYS provides a reasonable description of the neutron spectrum inside the spallation target and is in good agreement with Monte-Carlo predictions. The experimental flux that uses INCL4 cross-sections rather underestimates the modeled spectrum in the whole region of interest, but the agreement within few standard deviations was reached as well. The paper summarizes basic principles of the method for determining the spectrum of high-energy neutrons without employing the spectral adjustment routines and points out to the need for model improvements and precise cross-section measurements.

Пассивация поверхности высокочистых гранулированных металлов: цинка, кадмия, свинца

For the high purity metals (99.9999%), such as zinc, cadmium, and lead, which are widely used as initial components in growing semiconductor and scintillation crystals (CdTe, CdZnTe, ZnSe, (Cd, Zn, Pb) WO4, (Cd, Zn, Pb) MoO4 et al.), it is very important to ensure reliable protection of the surface from oxidation and adsorption of impurities from the atmosphere. The specific features of surface passivation of high purity cadmium, lead and zinc are not sufficiently studied and require specific methodologies for further studies. The use of organic solutions in the schemes of chemical passivation of the investigated metals avoids hydrolysis of the obtained protective films. The use of organic solvents with pure cation and anion composition as the washing liquid prevents chemisorption of ions present in the conventionally used distilled water. This keeps the original purity of the granular metals. Novel compositions of etchants and etching scheme providing simultaneous polishing and passivation of high purity granular Zn, Cd and Pb are developed. Chemical passivation allows storing metals in the normal atmospheric conditions for more than half a year for Zn and Cd and up to 30 days for Pb without changing the state of the surface. The use of the glycerol-DMF solution in the processes for obtaining Pb granules provides self-passivation of metal surfaces and eliminates the additional chemical processing while maintaining the quality of corrosion protection.

Получение высокочистых гранулированных металлов: кадмия, цинка, свинца

Cadmium, zinc and lead are constituent components of many semiconductor compounds. The obtained high purity distillates and ingots are large-size elements, which is not always convenient to use, and thus require additional grinding, which does not always allow maintaining the purity of the original materials. For the growth of semiconductor and scintillation single crystals it is advisable to use «friable» granular high-purity distillates, which can be processed without the risk of contamination. For example, the European low-background experiment LUCIFER required more than 20 kg of high-purity granulated zinc, which was agreed to be supplied by NSC KIPT. This task was then extended to cadmium and lead. Motivated by these tasks, the authors of this paper propose complex processes of deep refining of cadmium, zinc and lead by vacuum distillation. A device producing granules has been developed. The process of granulation of high-purity metals is explored. The purity of produced granules for cadmium and zinc is >99,9999, and >99,9995% for lead granules. To prevent oxidation of metal granules during exposition to air, chemical methods of surface passivation were used. Organic solvent based on dimethylformamide used as a coolant improves the resistance of granules to atmospheric corrosion during the granulation of high purity Cd, Zn and Pb.

Dielectric and magnetic studies of 0.5Bi2/3Cu3Ti4O12 - 0.5Bi3LaTi3O12 nano-composite ceramic synthesized by semi-wet route

A nano-composite electro ceramic with the chemical composition of 0.5Bi2/3Cu3Ti4O12 - 0.5Bi3LaTi3O12 was synthesized by a semi-wet route using high purity metal nitrate and solid TiO2 in a stoichiometric ratio. X-ray diffraction (XRD) analysis showed the presence of Bi3LaTi3O12 (BLTO) and Bi2/3Cu3Ti4O12 (BCTO) phases in the composites sintered at 900°C for 8h. Transmission electron microscope (TEM) analysis of the composite shows the presence of nanoparticles in the range of 55±3nm. Atomic force microscopy (AFM) study also substantiates the presence of nanoparticles in the composite. Scanning electron microscope (SEM) images show that the surface morphology consists of plates like and spherical grains. The study of PE hysteresis loop revealed no saturation polarization which suggested lossy capacitor behavior of the composite. Magnetic behavior of the composite shows the weak ferromagnetic nature in M-T and M-H curve. The High observed value of dielectric constant (ε’=13.94×103) of the composite may be due to the presence of space charge polarization.

Environment-Friendly Technology of Recovering Full Resources of Waste Capacitors

High quantities of waste printed circuit boards (PCBs) have been produced along with the generation of e-waste in the world. High purity metals were contained in waste PCBs. Recovery of waste PCBs caused serious pollution in China. With the view of environment protection, new technologies have been proposed to recover resources from basal boards of waste PCBs. Besides basal boards, waste PCBs contain many electronic components. However, little recovery technology was reported for electronic components. An environmental-friendly technology was proposed to recover waste capacitors of waste PCBs. The materials comprising waste capacitors were liberated by crushing. Then, ferrous metals (nickel alloy) and nonferrous metals (aluminum) were separated from crushed waste capacitors by magnetic/eddy current separation. Nickel alloy particles and aluminum particles can be sent to smelting plants. The optimized operation parameters of magnetic/eddy current separation were fed at speeds of 0.5 m/s, and the rotation s...

Progress in preparation of rare earth metals and alloys by electrodeposition in molten salts

Rare earth (RE) metals and their alloys have attracted considerable practical interests due to their functional properties. Because of their negative deposition potentials, RE metals cannot be electrochemically deposited from aqueous media. Using molten salt as medium provides a unique opportunity for the electrowinning and electrorefining of high-purity RE metals, as well as for the electrochemical formation of their alloys and intermetallic compounds. Certainly, the electrochemical behaviors of RE metals and their alloys have been investigated in a number of different molten salts comprising all-fluorides, all-chlorides and mixed chloride-fluoride media. Based on the results, RE and their alloys were produced by molten salt electrolysis. In this paper, the developments of preparation of RE metals and their alloys by electrolysis in molten salts in recent years were systematically summarized on both the local and international levels. Attention was paid mainly to the electrodeposition of RE metals and their alloys, including RE–Mg, RE–Al, RE–Ni, RE–Co, RE–Cu, RE–Fe and RE–Zn alloys.

Cross section measurement of alpha particle induced nuclear reactions on natural cadmium up to 52 MeV

Cross sections of alpha particle induced nuclear reactions have been measured on thin natural cadmium targets foils in the energy range from 11 to 51.2MeV. This work was a part of our systematic study on excitation functions of light ion induced nuclear reactions on different target materials. Regarding the cross sections, the alpha induced reactions are not deeply enough investigated. Some of the produced isotopes are of medical interest, others have application in research and industry. The radioisotope 117mSn is a very important theranostic (therapeutic + diagnostic) radioisotope, so special care was taken to the results for that isotope. The well-established stacked foil technique followed by gamma-spectrometry with HPGe gamma spectrometers were used. The target and monitor foils in the stack were commercial high purity metal foils. From the irradiated targets 117mSn, 113Sn, 110Sn, 117m,gIn, 116mIn, 115mIn, 114mIn, 113mIn, 111In, 110m,gIn, 109mIn, 108m,gIn, 115gCd and 111mCd were identified and their excitation functions were derived. The results were compared with the data of the previous measurements from the literature and with the results of the theoretical nuclear reaction model code calculations TALYS 1.8 (TENDL-2015) and EMPIRE 3.2 (Malta). From the cross section curves thick target yields were calculated and compared with the available literature data.

Nanoscale electropolishing of high-purity silver with a deep eutectic solvent

Samples of high-purity (>99.9% composition) silver metal were used in electropolishing treatments with an acid-free ionic liquid deep eutectic solvent prepared from quaternary ammonium salts as an eco-friendly electrochemical polishing solution. Linear sweep voltammetry tests were utilized to determine the optimum conditions for electrochemical polishing, which exposed that relatively stable electropolishing for pure silver metals can achieved at 3.75V with a current density of 0.064A/cm2. Atomic force microscopy was used for surface morphology comparisons while summarizing electrochemical polishing efficiency by providing root mean square roughness averages before and after electrochemical polishing to reveal an average decrease of 150.433nm in RMS surface roughness, resulting in a surface eight times smoother than the original unpolished silver specimens. Digital microscopy provided an overall observation of the material interface between the treated and unpolished regions, and indicated that the high and electrical conductivity in silver specimens at conditions above steady state current densities could result in vigorous pitting on the silver anode surface, and result in a less smooth surface.

Predictive Control of Catalyst Selectivity in the Electroreduction of Carbon Dioxide

The direct electrocatalytic reduction of carbon dioxide to fuel-type chemicals remains a promising utilization pathway to mitigate rising carbon dioxide concentrations in the atmosphere. Copper metal is the most widely studied catalyst used in the reaction due to its unique ability to produce hydrocarbon species. While a lot of focus has been improving the catalysts, the experimental parameters that affect the reaction have not been fully understood. A variety of factors have been shown to affect the activity and selectivity of the CO2 electroreduction reaction. Pre-electrolyzing the electrolyte is a common practice after Hori et al. 1 determined that trace impurities in the salts used to make the electrolyte solutions can deposit on the electrode surface and inhibit the reaction. High purity metal electrodes (ex. Cu 99.999+ %) are used for a similar reason. The identity of the electrolyte also has an effect, leading to different product distributions even by simply using a salt with a different alkali metal cation2. Electrolyte concentration has also been shown to alter the product selectivity3. Hori et al. concluded that the cationic species and electrolyte concentration affect the local pH at the electrode surface, which plays a major role in regulating the reaction. Other researchers have also demonstrated the importance of local pH and its effect on the reaction. Gattrell et al. 4 calculated the surface concentrations of several important species in the electroreduction of CO2 in KHCO3 solutions, showing that local concentrations are drastically different from the bulk. Factors such as current density and boundary layer thickness play a role. To optimize our electrochemical set-up, we investigated how the CO2 bubbling rate and the solution flow rate within an electrochemical flow cell affected the reaction. We found that the selectivity between CH4 and C2H4 can be predictively controlled by varying the bubbling rate and solution flow rate, and that the two are inversely related. A combination of mass transport processes and local pH affects can be used to explain our observations. This work highlights the importance of controlling parameters in the electroreduction of CO2 and demonstrates predictive control of hydrocarbon selectivity. 1. Y. Hori, H. Konishi, T. Futamura, A. Murata, O. Koga, H. Sakurai and K. Oguma, Electrochimica Acta, 2005, 50, 5354-5369. 2. A. Murata and Y. Hori, Bulletin of the Chemical Society of Japan, 1991, 64, 123-127. 3. Y. Hori, R. Takahashi, Y. Yoshinami and A. Murata, Journal of Physical Chemistry B, 1997, 101, 7075-7081. 4. N. Gupta, M. Gattrell and B. MacDougall, Journal of Applied Electrochemistry, 2006, 36, 161-172.

High Purity Analysis of Low Melting Point Such As Gallium By Glow Discharge Mass Spectrometry

Recently, the market demand for high-purity metal is increased and purification method of the gallium high productivity is required. Gallium have low melting point (29.76 °C) and super cooling properties and that property was not applied to zone refining method of the ordinary. Therefore, we produced zone refining system for low melting metal by using Direct Cooling and Indirect heating. Purification of 4N gallium was carried out zone refining process. Depending on the refining process up to 5pass, the trace metal impurities such as B, Al, S, Cr, Fe, Ni and Si decrease 4N to 6N. We adopted GD90(MSI, UK) to the measurement of impurities in high purity Gallium metal for prevent gallium melt. GDMS, especially GD 90 is a powerful analytical method capable of analyzing solid samples without chemical decomposition step and analyzing a low-melting metal by adopting liquid nitrogen cooling and slow sputter method.

The effect of distribution of second phase on dynamic damage

For ductile metals, dynamic fracture occurs principally through void nucleation, growth, and coalescence at heterogeneities in the microstructure. Previous experimental research on high purity metals has shown that microstructural features, such as grain boundaries, inclusions, vacancies, and heterogeneities, can act as initial void nucleation sites. In addition, other research on two-phase materials has also highlighted the importance of the properties of a second phase itself in determining the dynamic response of the overall material. However, previous research has not investigated the effects of the distribution of a second phase on damage nucleation and evolution. To approach this problem in a systematic manner, two copper alloys with 1% lead materials, with the same Pb concentration but different Pb distributions, have been investigated. A new CuPb alloy was cast with a more homogeneous distribution of Pb as compared to a CuPb where the Pb congregated in large “stringer” type configurations. These materials were shock loaded at ∼1.2 GPa and soft recovered. In-situ free surface velocity information, and post mortem metallography, reveals that even though the spall strength of both the materials were similar, the total extent and details of damage in the materials varied by 15%. This suggests that altering the distribution of Pb in the Cu matrix leads to the creation of more void nucleation sites and also changed the rate of void growth.

Magnetostructural phase transitions and magnetocaloric effect in Tb-Dy-Ho-Co-Al alloys with a Laves phase structure

The influence of simultaneous substitution within the rare earth (R) and Co sublattices on the structural, magnetic, and magnetocaloric properties of the Laves phase RCo2-type compounds is studied. Main attention is devoted to the studies of the magnetostructural phase transitions and the transition types with respect to the alloy composition. Multicomponent alloys Tbx(Dy0.5Ho0.5)1−xCo2 and Tbx(Dy0.5Ho0.5)1−xCo1.75Al0.25 were prepared with the use of high purity metals. Majority of the Tbx(Dy0.5Ho0.5)1−xCo2 alloys exhibit magnetic transitions of the first-order type and a large magnetocaloric effect. The substitution of Al for Co in Tbx(Dy0.5Ho0.5)1−xCo2 increases the Curie temperature (TC) but changes the transition type from first-to the second-order. The discussion of the physical mechanisms behind the observed phenomena is given on the basis of the first principles electronic-structure calculations taking into account both the atomic disorder and the magnetic disorder effects at finite temperatures. The advantage of Al-containing materials is that sufficiently high magnetocaloric effect values are preserved at T > TC.

A simple, reliable and cost-effective, high temperature dilatometer for bulk thermal expansion studies on solids

Abstract A simplified, highly reliable, cost effective high temperature (RT-1373 K) vertical dilatometer system, based on linear variable differential transformer (LVDT) has been designed, fabricated and tested for measurement of linear thermal dilation of solid samples. Unique features of this fully automated PC-controlled system are: simple design, fabrication from locally available components, ease of operation and maintenance, good temperature resolution (1 K), wide measurement range (±1 mm, with 100 nm resolution), microcontroller-based data acquisition hardware and a simple windows-based software. The system has been tested for its performance using NIST sapphire reference and high purity metals including aluminum and nickel. Overall accuracy of the system for measurement of linear thermal dilation is within 3% of the reported values for NIST sapphire. The system is a good example of a simple experimental facility for routine thermal expansion characterization of solids. Combination of simplified design, automation and reliable performance without using sophisticated instrumentation/control systems makes it a novel cost effective thermo-analytical equipment, which can be put to widespread routine usage for researchers, academy and small/medium-scale industries.