High-purity Metal Research Articles

High-purity titanium, zirconium, and hafnium in nuclear power

The use of high-purity (iodide) titanium, zirconium, and hafnium for obtaining building and absorbing materials for use in nuclear power is examined. The possibilities for iodide refining of these metals to remove impurities and the chemical composition, microstructure, and microhardness of iodide rods are presented. Regimes for chemical decontamination of raw materials and iodide refining of metals in commercial equipment are examined. It is shown that iodide refining makes it possible to use as raw materials the wastes and recyclables from metallurgical and rolled production of titanium, zirconium, and hafnium and to obtain from them under commercial conditions high-purity metals with multiple uses, including as components of a charge for smelting alloys to be used in nuclear power. Materials based on titanium, zirconium, and hafnium of consistent quality which are obtained using metal iodides will make it possible to extend the VVER service life to 60 years.

Cross-reactivity among some metals in a murine metal allergy model

Information concerning cross-reactivity among metal allergens is scarce. We previously devised a murine metal allergy model using lipopolysaccharide (LPS) as an adjuvant. LPS reduces the minimum allergy-inducing concentration (MAIC) of metals at both the sensitization and the elicitation steps. Here, we examined allergic cross-reactivity among some metals in this murine model, and compared the effects of ultrapure (99·99% or more) and low purity (93-99%) metal salts. A mixture of a metal salt and Escherichia coli LPS was injected intraperitoneally into BALB/c mice (0·25 mL per mouse). Ten days later, metal salts (with or without LPS) were challenged to ear pinnas (20 μL per ear), and ear swelling was measured. Among the ultrapure metals tested (Ni, Pd, Co, Cr, Cu and Au), only Ni and Pd cross-reacted. In this cross-reaction, their MAICs were at the same level. Combined challenge with Ni and Pd at sub-MAICs (but not at higher concentrations) produced an additive effect. Surprisingly, mice sensitized with low purity Ni reacted to all the tested low purity metals (Ni, Pd, Co and Cr), and the low purity metals were shown to contain contaminant metals. In our model: (i) Ni and Pd (members of the same group in the periodic table of elements) cross-react with each other, (ii) this cross-reaction may depend on true and false antigens forming metal-protein complexes with similar spatial geometries, (iii) Co, Cr, Cu and Au do not cross-react with each other, (iv) in low purity materials, trace contaminant metals may be sufficient to evoke allergy, and thus (v) high purity metal salts should be considered for use in clinical patch testing.

Structural, magnetic, and magnetothermal properties of the Tb0.3Dy0.7Co2 compound

A complex investigation of the structural, magnetic, and magnetothermal properties of the Tb0.3Dy0.7Co2 compound synthesized with the use of high-purity rare-earth metals has been performed. The phase composition has been controlled using the X-ray structural analysis, and the topology of the alloy surface has been investigated using atomic-force microscopy. It has been established that the Tb0.3Dy0.7Co2 compound is single-phase, while the samples selected for measurements possess a clearly pronounced texture. The magnetization has been measured using a vibrating-sample magnetometer in the fields up to 100 kOe in a temperature range from 4.2 to 200 K. The Curie temperature of the compound is 170 K. The data on the temperature dependence of heat capacity of Tb0.3Dy0.7Co2 have been obtained. The magnetocaloric effect ΔT has been measured by a direct method in the fields up to 18 kOe applied both along and perpendicularly to the texture axis. The anisotropic behavior of the magnitude ΔT for this compound, which possesses the cubic structure, has been found. The maximum value of the magnetocaloric effect ΔT = 2.3 K (ΔH = 18 kOe) has been observed upon applying the magnetic field along the texture axis.

Quasi-steady thermal analysis of solidification of cylindrical rod in Ohno continuous casting process

The Ohno continuous casting process, associated with unidirectional crystallisation of high purity metals, is of practical importance because of its increasing applications in electronic industries. This paper deals with analytical solution of axisymmetric heat transfer during solidification of pure metals in this casting process. The two-dimensional quasi-steady heat conduction equations for solid and liquid phases along with associated interface and boundary conditions are solved by the method of separation of variables. The expressions for temperature field in the melt and the solid regions are obtained as a function of various model parameters such as Biot number, Peclet number, dimensionless latent heat of solidification and liquid to solid thermal conductivity ratio. Besides, the casting rates of three different pure metals are compared for the known operating conditions.

Characteristics of chip formation in the micro-drilling of multi-material sheets

In order to meet the requirements of electronic product miniaturisation, the use of thinner and smaller printed circuit boards (PCBs) will be required. To achieve this, many more micro-holes must be drilled in a smaller area than before. PCBs are anisotropic multi-material sheets consisting of a dielectric layer (resin/glass fibre cloth) and a high purity metal conductor (copper foil). It is difficult to achieve high machining precision, surface quality, drilling efficiency and long drill life when drilling PCB micro-holes. In this study, micro-drills with a diameter of 0.1 mm were used to drill the PCBs at rotational speeds of up to 300 krpm. The drilling process was digitally photographed. The chip morphology and the hole wall were observed. The quality of the hole wall, such as hole wall roughness and nail head and exit burr formation were observed and measured. The influence of drilling condition on the drilling process and hole quality were studied. It was found that the morphology of the chips and the hole wall surface depended on the material properties of the printed circuit board. Chips were formed normally as conical helical chips from the aluminium entry board, conical helical chips from the copper foil and discontinuous chips from the glass fibre and softened resin. The hole wall through the copper foil seemed much smoother than that of resin/glass fibre cloth layer. However, nail heads and burrs were formed at the copper foil layers, which decreased the hole quality. Chip morphology and hole quality were affected by feed rate, spindle speed and tool wear. The basic removal mechanism of the PCB micro-holes was analysed, and this study provided a firm foundation for further work in this area.

The Effect of Annealing Temperature on the Magnetic Properties of Mn x Co1−x Fe2O4 Ferrites Nanoparticles

Mn x Co1−x Fe2O4 ferrites compounds (0≤x≤0.6) have been synthesized by a glycol-thermal method from high-purity metals chlorides. Single phase spinel structure of the nanoparticles has been confirmed by X-ray diffraction (XRD) and transmission electron microscopy (TEM) measurements. The diameters of the as-prepared powders were estimated from XRD and TEM and were found to be in the range: 7 to 13 nm. Room temperature magnetizations were obtained using a vibrating sample magnetometer (VSM) on the as-prepared samples and on samples annealed at 500 and 700 °C. The variation of coercive fields, saturation and remnant magnetizations as a function of composition (x) and grain size have been investigated. 57Co Mossbauer spectra for as-prepared samples were also measured at different temperatures (27, 100, and 200 °C). Significant changes in magnetization properties and Mossbauer parameters are observed across the composition range studied. The variation of coercive fields and saturation magnetizations appear to critically depend on the particle sizes as the compounds evolve from single domain to multidomain structure.

Significance of homologous temperature in softening behavior and grain size of pure metals processed by high-pressure torsion

High purity metals with low melting temperatures such as indium (99.999%), tin (99.9%), lead (99%), zinc (99.99%) and aluminum (99.99%) were processed using high-pressure torsion (HPT). An unusual softening behavior was observed in all these metals after processing by HPT at room temperature. Pure copper (99.99%) and palladium (99.95%) were used to simulate the softening behavior due to a thermal effect by processing and subsequently holding at the temperatures equivalent to room temperature of pure Al. It is shown that a hardness peak appears in any metal by static softening after processing by HPT at a homologous temperature of 0.32 which is equivalent to room temperature of pure Al. The contribution of dynamic softening on hardness decrease becomes more important as the homologous temperature and stacking fault energy increase. Microstructural examinations indicate that, although the stacking fault energy influences the rate of the microstructural evolution, the homologous temperature appears to be a dominant parameter to determine the steady-state grain size after processing by HPT.

Achievement of High Heat Removal Characteristics of Superconducting Magnets With Imbedded Oscillating Heat Pipes

Oscillating heat pipes (OHP) for cryogenic use are being developed to improve the heat removal characteristics of high-temperature superconducting (HTS) magnets. It is generally difficult to remove the heat generated in HTS windings, because the thermal diffusivities of component materials decrease with an increase of the operating temperature. Therefore, a local hot-spot can be rather easily generated in HTS magnets, and there are possibilities of observing degradation of superconducting properties and/or mechanical damages by thermal stresses. As a new cooling technology to enhance the heat removal characteristics in HTS magnets, the cryogenic OHP is proposed to be imbedded in magnet windings. The feasibility of cryogenic OHP has been confirmed by fabricating proto-types and by observing stable operations using hydrogen, neon and nitrogen as the working fluid. A high thermal conductivity was achieved that surpasses those of high-purity metals. We also propose a modified-type OHP to mitigate the orientation dependence.

Effect of Y substitution for Nb in Li5La3Nb2O12 on Li ion conductivity of garnet-type solid electrolytes

We report the effect of Y substitution for Nb on Li ion conductivity in the well-known garnet-type Li5La3Nb2O12. Garnet-type Li5La3Nb2−xYxO12−δ (0≤x≤1) was prepared by ceramic method using the high purity metal oxides and salts. Powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), 7Li nuclear magnetic resonance (Li NMR) and AC impedance spectroscopy were employed for characterization. PXRD showed formation of single-phase cubic garnet-like structure for x up to 0.25 and above x=0.25 showed impurity in addition to the garnet-type phases. The cubic lattice constant increases with increasing Y content up to x=0.25 in Li5La3Nb2−xYxO12−δ and is consistent with expected ionic radius trend. 7Li MAS NMR showed single peak, which could be attributed to fast migration of ions between various sites in the garnet structure, close to chemical shift 0ppm with respect to solid LiCl and which confirmed that Li ions are distributed at an average octahedral coordination in Li5La3Nb2−xYxO12−δ. Y-doped compounds showed comparable electrical conductivity to that of the parent compound Li5La3Nb2O12. The x=0.1 member of Li5La3Nb2−xYxO12−δ showed total (bulk + grain-boundary) ionic conductivity of 1.44×10−5Scm−1 at 23°C in air.

Preparation of high purity metals for advanced devices

The purity is one of the essential factors of the materials for preparing well controlled materials and devices, because the existence of ppm or sub-ppm level impurities leads to a significant and sometimes critical influence on the material properties and devise performance. Since the development of high technology depends strongly on the availability of high purity metals required for fabricating a new functional device, and furthermore, the purity of commercial pure materials for exploratory material researches is insufficient, the purification process that meets any requirements should be developed. In this article, based on our experience, we will describe how to construct the purification process, purification methods, and the purification of iron as an example.

The producing of lead and elemental sulfur by new technologies from galenite ores

These investigations have developed an effective hydrometallurgical method to recover high-purity lead metal and elemental sulfur from simulated galena synthetic mixures eliminating sulfur gases and lead emissions, in contrast to the current high-temperature smelting technology. The method consists of different operations: oxidative leaching with production of solution with residue containing elemental sulfur., electrowinning by the solution with metal production. The obtained results determined the optimal parameters for possible processing of natural domestic galena ores.

Separation of Sn, Sb, Bi, As, Cu, Pb and Zn from Hydrochloric Acid Solution by Solvent Extraction Process Using TBP (tri-n-Butylphosphate) as an Extractant

A basic study for the recovery of tin(Sn) from the scraps or plating sludges by a hydrometallurgical process was carried out. Tin was leached out by hydrochloric acid solutions and then separated from the mixed solution of co-leached miner metals such as, As, Sb, Bi, Cu, Zn and Pb for making high purity metal. A solvent extraction process was followed for the separation of tin and other minor metals from hydrochloric acid solution using TBP (tri-n-Butylphosphate) as the extracting reagent. Optimum conditions for the separation process were obtained using separation factors of tin versus each metal impurities derived at various concentrations of hydrochloric acid and sodium chloride in aqueous solution, and TBP in the organic solution. Scrubbing for metal impurities from the loaded organic solution was studied with different HCl concentrations. The study showed that Pb, Bi, Cu, Zn and Sb were quantitatively removed by scrubbing with 8.0 mol/L HCl from the organic phase after extracted in 6.0–7.0 mol/L HCl solution; As with 4.0 mol/L HCl solution from the organic phase after extracted in 3.0 mol/L HCl solution. From the integrated separation experiment by the simulate solution at 25 � C, 1.0 of O/A, and one stage contact at each extraction and purification step, the purity of finial Sn strip solution was 98.9% and the recovery of Sn was 67.9%. [doi:10.2320/matertrans.M2011142]

Selected Ion Exchange Applications in the Hydrometallurgical Industry

Ion exchange is increasingly used in hydrometallurgical applications for the recovery or purification of metal solutions or for effluent treatment. This article reviews some recent applications, including the primary recovery of gold, uranium, and rhenium, and the purification of cobalt electrolyte to ensure high-purity metal by the removal of nickel, copper, zinc, and cadmium. Improved recoveries and adherence to environmental regulations can be achieved by treating barren slurry streams in a resin-in-pulp process. Ion exchange is also positioned to play an important role in the treatment of process water to enable recycling of such waters and reduce the demand on freshwater resources.

Effects of dislocations on thermal helium desorption from nickel and iron

Helium atoms in metals have a strong tendency to accumulate at defects. Unfortunately, the experimental identification of the trapping sites of helium atoms is difficult. In this paper, the effects of dislocations on the trapping and desorption of helium atoms in nickel and iron were studied by thermal desorption spectroscopy. Defects were introduced in well-annealed high-purity metals by cold rolling. Positron annihilation spectroscopy was carried out to identify defects by measuring the positron lifetime before annihilation with various defects. The trapping and desorption of helium atoms at dislocations were investigated by implantation with low-energy He+ ions, both without irradiation damage (0.1keV or 0.15keV) and with irradiation damage (5.0keV).

Effect of Impurities on the Microstructure of HPT Deformed Nickel

Basic research considering the minimum achievable grain size of severe plastic deformation (SPD) materials is often performed with high purity metals. However, a literature study reveals large discrepancies in the microstructural size of high purity nickel processed by SPD. The focus of this work is the influence of small impurity concentrations on the resulting saturation microstructure. The microstructure of SPD nickel was systematically investigated using different purities ranging from 99.79 wt% up to 99.99 wt%. The materials were deformed by high pressure torsion (HPT) at different temperatures from liquid nitrogen temperature (-196°C) up to 400°C. It was found that carbon concentration is the governing element in achieving the finest microstructures and the highest strength. Therefore, further experiments with well defined carbon doped samples were performed. By changing the carbon content from 0.008 wt% up to 0.06 wt% tensile strength in the saturation regime increases by more than 700 MPa. It will be shown that even small variations (<0.01 wt%) lead to significant changes in ductility and tensile strength values.

Effect of La<sub>2</sub>O<sub>3</sub> Additions on Microstructure, Morphology and Pressure Sensing Behaviour of PZT Based Ceramics Sintered in Al<sub>2</sub>O<sub>3</sub> Environment

Effect of La2O3 addition on microstructure, morphology and pressure sensing behaviour of (Pb1-x, Lax)(Zr0.52, Ti0.48)O3 based ceramics was studied in three different compositions of La2O3, namely x = 0.10, 0.12 and 0.15. The samples were prepared through a conventional solid-state reaction method using high purity metal oxides powders. In order to control the PbO losses due to high sintering temperature, a novel approach was explored whereby the samples were sintered in Al2O3 environment. Structural investigation using XRD revealed that all samples exhibited a tetragonal crystal structure. However the c/a ratios exhibited a decreasing trend as the La2O3 content increased, indicating that (Pb1-x, Lax)(Zr0.52, Ti0.48)O3 crystals gradually evolved towards pseudocubic structure. SEM micrographs showed that in all samples the grains have uniform pebble stone morphology. The average grain size reduced from ~ 4.5 µm to ~ 3.0 µm with the increment of La¬2O3 content. The performance of pressure sensing behaviour which was investigated using custom-made pressure chamber showed that sample with composition of x = 0.10 exhibited the best piezoelectric properties with high pressure sensitivity, good stability and repeatability.

Quantifying electrochemical promotion of induced bipolar Pt particles supported on YSZ

Electrochemical promotion (EP) of CO oxidation is shown for the first time on induced bipolar Pt particles supported on yttria-stabilized zirconia (YSZ). These Pt particles are formed by sputter deposition of high-purity Pt metal followed by sintering. Conditions were chosen to stay below the percolation threshold of Pt particles. In-plane polarization of Pt particles results in a bipolar system and leads to the formation of a large number of galvanic cells partially or completely polarized. We have defined an equivalent number of active cells ( n cell) which has been estimated from the oxygen evolution reaction as a function of the applied current on the two feed electrodes. The CO oxidation rate is measured under high vacuum conditions as a function of applied current. The use of isotopically labeled oxygen allows the discrimination of the faradaic process ( 16O from YSZ) from the non-faradaic process ( 18O from 18O 2) and to determine the faradaic efficiency ( Λ) and the rate enhancement ( ρ) parameters in this bipolar system. These results mark an important step in the realization of electrochemical promotion on highly dispersed catalysts.

Characterization and magnetic properties of nanocrystalline CuFe 2O 4, NiFe 2O 4, ZnFe 2O 4 powders prepared by the Aloe vera extract solution

This study reports the simple synthesis of MFe 2O 4 (where M = Cu, Ni, and Zn) nanoparticles by a modified sol-gel method using high purity metal nitrates and aloe vera plant extracted solution. Using of aloe vera extract simplifies the process and provides an alternative process for a simple and economical synthesis of nanocrystalline ferrites. The obtained precursors were characterized by TG/DTA to determine the thermal decomposition and subsequently were cc at different temperatures in the range of 600–900 °C for 2 h to obtain the ferrite nanoparticles. The calcined samples were characterized by XRD, FT-IR, SEM, and TEM. All the prepared samples are polycrystalline and have spinel structure with crystallite sizes of 15–70 nm. The crystallite size increases with increasing the calcination temperature. Magnetic properties of the prepared ferrite samples were measured using Vibrating sample magnetometer (VSM). The room temperature magnetic behavior of as-prepared ferrite powders can be explained as the results of the three important factors: impurity phase of a-Fe 2O 3, cationic distribution in spinel structure, and the surface spin structure of nanoparticles.

Surface Characterization of High Purity Metals of Silver and Nickel Electropolished with an Ionic Liquid

Samples of high purity (>99.9% composition) silver and nickel were used in electropolishing treatments with an acid-free ionic liquid electrolyte prepared from vitamin-B4 as an eco-friendlily polishing solution. Voltammetry tests were utilized to determine the optimum conditions for electrochemical polishing. Digital microscopy provided an overall observation of the material interface between the treated and unpolished regions. Atomic force microscopy (AFM) revealed microscale effectiveness of each polishing treatment after chronoamperometry tests.

Preparation of High-Purity Alumina by Hydrolyzing High-Purity Metal Aluminum

This paper puts forward a new method for the preparation of 99.999% high-purity alumina used for the LED underlay sapphire, which has above 99.999% high-purity aluminum atomized the active aluminum powder by the supersonic multistage cooling way, then makes the powder form the hydrate of the alumina through the hydrolyzing reaction, and finally gets 99.999% high-purity alumina by means of the calcinations and the follow-up granularity treatment. By the processing way, the reactant is only aluminum and water, and there is no other additive, which profitably keeps the product pure and completely satisfies the requirements of synthetic crystals while tested.