Rhenium Concentration Research Articles

Influence of tungsten and rhenium concentration on creep properties of a second generation superalloy

Creep properties at three different temperatures (1123, 1253 and 1373 K) for five single crystal alloys with varying Re and W content are presented. Tungsten content has been varied between 3.0 and 3.6 wt.%, rhenium between 2.3 and 2.9 wt.%. Creep properties, such as minimum creep rate, time to reach 1, or 2% strain and time to failure have been evaluated. For the low temperature regime, two parts of rhenium can be replaced by one part of tungsten. In the intermediate range, the ratio c W/ c Re≈1.3 has to be fulfilled with the constraint that c Re≥2.3 wt.%. At high temperature the sum of W plus Re concentration determines the time to failure.

Hydrothermal Transport and Deposition of Rhenium under Subcritical Conditions (up to 200°C) in Light of Experimental Studies

To investigate the aqueous species important for transport of rhenium under subcritical conditions, we conducted a series of solubility experiments from 100° to 200°C at vapor saturation pressures. In these experiments, oxygen fugacity was buffered by fixing the partial pressure of hydrogen gas, and pH was mainly buffered by H3PO4/H2PO4- and H2PO4/ HPO-24homogeneous aqueous buffers. These experimental solubility studies indicate that \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(Re(OH)_{4}^{0}\) \end{document} may be the predominant species over a wide range of pH from ~2.2 to ~8.8 in low-temperature solutions up to 200°C. The equilibrium constants in the temperature range from 100° to 200°C for the reaction Re(solid) O2(gas) 2H2O \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(Re(OH)_{4(aqueous)}^{0}\) \end{document} can be expressed as follows (temperature, T , is in degrees K): \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \[log K = {-}19.38 {\pm} 0.86 + \frac{29358 {\pm} 322}{\mathit{T}} (2\mathit{{\sigma}}).\] \end{document} Sandstone copper deposits and black shales are typically enriched in rhenium, and our results may shed some light on their formation. As the formation temperature of such deposits is generally below 150°C, neutral species should be important for the transport of rhenium in them. Our evaluation further demonstrates that the species ReO4 -is not important in the transport of rhenium, even under geologically relatively oxidizing conditions close to the HS-/\batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(SO_{4}^{-2}\) \end{document} boundary in low-temperature environments typical of sandstone copper deposits and black shales. Our results suggest that several processes should be effective in concentration and deposition of rhenium, including (1) mixing of the fluids containing rhenium with cooler, sulfide-rich solutions, (2) decrease in temperature, (3) change in pH, and (4) redox reactions. Application of our results to sandstone copper deposits indicates that our findings are in good agreement with field observations, and it implies that mineralizing fluids responsible for the formation of sandstone copper deposits are capable of transporting thousands of tonnes of rhenium. Extrapolation of our experimental results suggests that ReS2 is important in controlling solubility in sulfur-bearing environments. Our calculations indicate that rhenium concentrations in the sulfide stability field, even close the HS-/\batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(SO_{4}^{-2}\) \end{document} boundary, are very low (~10-6 to ~10-5 ppm) in the temperature range from 100° to 200°C. This result may have important implications for the Re-Os isotopic system, implying that as long as low-temperature hydrothermal alteration is constrained to oxygen fugacity conditions under which sulfide is stable, disturbance of Re-Os systematics will not be severe.

Production of concentrated rhenium acid by electrodialysis of rhenium salts solutions

Effects of current density, temperature, rhenium concentration in initial solution, flow rate of initial solution in the demineralization chamber on rhenium acid concentration in a seven-chambered electrodialyzer with ionite heterogeneous membranes have been studied during the process of electrodialysis. It was determined that the optimum conditions of the process of rhenium acid concentration by electrodialysis of ammonia and potassium perrhenate solutions are the following: 300 A/m 2 current density, 50°C solution temperature in the electrodialyzer, 35–40 g/L rhenium concentration in initial solution, 0.67–0.83 volume of chamber/min flow rate of initial solution in the demineralization chamber. Concentration of rhenium acid in these conditions is 300 g/L and higher.

The Origin of Platinum Group Minerals from the FreetownIntrusion, Sierra Leone, Inferred from Osmium Isotope Systematics

The origin of certain alluvial platinum-group mineral (PGM) grains is controversial, with two major proposed models. One involves primary formation within ultramafic intrusions, followed by weathering into laterites with no further alteration prior to alluvial concentration. The other involves in addition, solution of the platinum-group elements (PGE) during weathering of the ultramafic source rocks, probably by organic reactions, followed by the supergene growth of the macroscopic grains within laterites. In order to provide further evidence concerning the formation of macroscopic (~ μ m in size) platinum-group mineral grains, the authors have studied the osmium isotope ratios in PGM grains from the Freetown peninsula in Sierra Leone using an ion microprobe. Indirect isotopic evidence and modeling are required to infer their origin as no PGM grains larger than ~10 mm have ever been discovered in situ within the source rocks. Unlike virtually all other alluvial PGM grains that have been studied, the Freetown ones are distinguished by 187 Os/ 188 Os ratios that are much higher than canonical mantle values and vary considerably between different grains (0.12 187 Os/ 188 Os < 0.28). The 187 Os/ 188 Os ratios are, with one exception, the same for individual osmium-rich inclusions within the platinum-iron alloy host of each grain, although different grains have significantly different 187 Os/ 188 Os ratios. In the one significant exception, there are two Os-Ru-Ir alloy inclusions within a single platinum-iron alloy host which have 187 Os/ 188 Os ratios that are different from each other. Various models are considered to explain these observations: (1) the elevated osmium isotope ratios could be primary and derived from a mantle inhomogeneity such as a mantle plume; (2) the intruded material with a canonical mantle signature may have reacted with the host rocks at the time of the intrusion or at a later stage during postulated metamorphic or hydrothermal activity, or (3) the supergene remobilization could have modified the osmium isotope signature of the PGM. Interpretation of the osmium isotopes is by no means unambiguous. The range of 187 Os/ 188 Os ratios is far higher than known mantle sources which, combined with the grain to grain variation, seems to rule out the primary formation model. Sr, Nd, and O isotope evidence indicates no reaction with the host rocks during intrusion or by metamorphic or hydrothermal activity and mixing calculations show that enhancement of the radiogenic Os during intrusion could only have been small. The evidence points to some extremely localized process which could, however, have acted in two ways: either a preexisting high concentration of rhenium and PGE (a xenolith) was incorporated into the magma chamber, remained essentially unmixed with the majority of the material in the chamber, and after extrusion of the gabbro, PGE nuggets were weathered out into laterites, or alternatively, concentration processes within the magma chamber produced a localized concentration of rhenium—possibly in copper sulfides or late magmatic iron oxides in acid intrusions—which, when chemically dissolved in the supergene environment, precipitated PGE nuggets with extremely radiogenic 187 Os/ 188 Os signatures. The data presented in this paper in conjunction with work elsewhere have been used to demonstrate that the processes producing highly radiogenic 187 Os/ 188 Os signatures cannot have resulted from large-scale processes and have been used to dismiss a number of previously proposed models. However, a resolution between the two alternative models proposed is not possible using the present data.

Controlled gas‐phase preparation and HDS activity of Re 2 (CO) 10 alumina catalysts

Re/Al2O3 catalysts were prepared from a carbonyl precursor by controlled gas‐phase deposition with all conditions accurately monitored by a computer‐programmed CVD reactor. The catalysts were made in an inert atmosphere. Growth of the rhenium concentration was studied with different preparation procedures and with different times and temperatures of deposition. Rhenium loading of the catalysts varied between 0.3 and 12.8 wt%. The activity of the catalysts was tested in thiophene hydrodesulfurization reaction and the results suggest good activity in low rhenium loading. The portion of n‐butane among the reaction products was high for the catalysts with high rhenium content.

Evaporation behavior of water and concentration of technetium and rhenium using thin film evaporator

The nuclear energy cycle requires the recycling of nuclear fuel, water, chemical reagents, and the volume reduction of radioactive liquid wastes. A fundamental technique for continuous recovery of water using a thin-film evaporator was examined. Appropriate recovery measurements were: an evaporator heat temperature of 323 K, a feed rate of 0.23 cm3s−1, a vacuum pressure of 15 mmHg (2 kPa), and impeller rotational speeds of 500–600 rpm (min−1). The concentration of trace technetium and rhenium in aqueous solutions was also studied. A decontamination factor of 105 for rhenium was obtained.

Ion exchange recovery and concentration of rhenium from salt solutions

The rhenium concentration as well as Re(VII) and Mo(VI) separation from sulphuric and nitric–sulphuric acid solutions obtained after pyrometallurgical and nitric acid processing of rhenium-containing molybdenum concentrates were investigated on weak basic anion exchangers by means of sorption–desorption method and by IR-spectroscopy. The anion exchangers with porous and non-porous structure were synthesized on the basis of styrene and divinylbenzene using amines with cyclic radical. The resins AN-82-14G and AN-105-14G were used for the selective rhenium extraction from molybdenum-containing solutions. The complete rhenium recovery from nitric–sulphuric acid solutions was reached on porous anion exchangers AN-82-10P and AN-105-10P.

Structure of granular and homogeneous Re-Co alloys and the mechanism of its formation

Films of granular and homogeneous Re-Co alloys are obtained by electrolytic deposition. The results of x-ray diffraction and electron microscope studies are analyzed. A mechanism is proposed to explain the formation of the structure of Re-Co films, taking into account the effect of the concentration of rhenium and other components of the electrolyte on the nucleation and growth of the film. It is shown that a "polycrystalline — amorphous" structural transformation is realized in accordance with the following scheme:columnar → ultradisperse → aggregate → amorphous film structure.

Electronic topological transitions in Mo-Re random alloys

Electronic spectra and bulk properties of Mo-rich bcc Mo-Re random alloys have been studied in the framework of density-functional theory. We show that the Fermi surface topology changes with rhenium concentration, i.e., so-called electronic topological transitions take place. We have found two electronic topological transitions, the formation of an electronic void at about 2 at. % of Re and a formation of a neck at about 6 at. % of Re. The influence of these transitions on the thermodynamic (lattice parameter, bulk modulus, and Gr\"uneisen constant) and kinetic (thermoelectric power) properties is analyzed.

Investigation of argon ion bombarded Re x Si 1-x thin film composites by XPS, SEM and AES

The electronic structure of argon ion bombarded RexSi1-x films (∼ 100 nm) were investigated by X-ray photoelectron spectroscopy. Argon ion bombardment leads to preferential sputtering of the silicon atoms and produces an subsurface rhenium enrichment. Changes in the core level binding energies and in the valence band structure have been studied as the rhenium concentration in the composites varies between 0 ≤ x ≤ 1 through the metal-semiconductor transition at x ≈ 0.32. The data of the multiplex spectra were subjected to factor analysis in order to determine the relevant components of the ion bombarded metal-silicon system. Four principal components are extracted and are proposed as the pure elements, a rhenium-rich phase and a component near the ReSi2 stoichiometry. Complementary investigations by SEM and AES provide further proof of the phase assignment in the rhenium-rich component. The silicon-rich component being in composition close to the metal-semiconductor transition can be correlated to the ReSi2 compound.

A study on the metallisation and stabilisation of porous silicon

Rhenium was deposited in porous silicon by Chemical Vapour Infiltration and Deposition (CVID) using a deuterium rhenium carbonyl DRe(CO) 5 precursor. The results indicate that the precursor penetrates into the pores and reaches a saturation level very quickly (in less than 2 min) to give a uniform rhenium concentration of 8–10 at% of the silicon content to a measurable depth of at least 1.5 μm. High levels of oxygen were also observed at ∼ SiO 1.5. In addition to having a high level of carbon at about one third of the oxygen level, the carbon content of the samples dropped during analysis, suggesting that it was present in a volatile form.

Discovery of a pure rhenium mineral at Kudriavy volcano

KUDRIAVY volcano on Iturup island in the Kuril arc is an active calc-alkaline volcano. It has not erupted this century; its current volcanic activity is characterized by hot (up to 910oC) gas jets which have been stable for at least 30 years. The composition of the gaseous emissions is typical of high-temperature fumaroles, but we report here the discovery of unusual subsurface sublimates associated with one gas jet—a sulphide mineral containing rhenium as the only cation. To our knowledge, this is the first reported occurrence of a pure rhenium mineral. The concentration of rhen-ium in the fumarole gas is only 2–10 p.p.b., so the condensation of pure rhenium sulphide from this gas requires both enrichment of rhenium by eight orders of magnitude and remarkable selectivity. Rhenium is generally believed to exist in only trace amounts at the Earth's surface, but our findings demonstrate that it can be readily mobilized, dispersed and concentrated by degassing magmas.

Low blank rhenium isotope ratio determinations by V 2O 5 coated nickel filaments using negative thermal ionization mass spectrometry

Thenium isotope ratio determinations are, in principle, possible by negative thermal ionization mass spectrometry (NTI-MS). Relatively high rhenium blanks from the commonly-used filament materials prevent accurate isotope ratio determinations, especially for small rhenium sample amounts which are of importance, for example, in geochronology in connection with the Re/Os dating method. Platinum and nickel filaments were tested by different preparation techniques to reduce the rhenium blank contribution from the filament material. The lowest rhenium blank of less than 1 pg was achieved by coating nickel filaments with V 2O 5 prior to degassing under high vacuum conditions at 850°C. Obviously, the vanadium—nickel oxide layer formed on the surface of the filament during this process prevents further emission of rhenium ions from the filament material. Using Ba(OH) 2 for the enhancement of negative thermal ions, 1 ng of rhenium resulted in ion currents at the detector side of about 10 −11 A with an ionization efficiency of up to 20%. The 185Re/ 187Re isotope ratio of a sample of natural isotopic composition could be determined to be 0.59818 ± 0.00026 with a relative precision of 0.04%. The isotope ratio determination for an 187Re spike was comparable in precision but the relative standard deviation of an 185Re spike was significantly higher, which could be explained by mass fractionations of oxygen in the measured ReO − 4 ion. The ReO − 4 ion is about 200 to 2500 times more abundant than the only other detectable rhenium ion in NTI-MSReO − 3. The ReO − 4/ReO − 4 ratio decreases with increasing temperature. By the low blank NTI-MS technique described in this work, more precise and accurate determinations of the rhenium isotope ratio and the rhenium concentration by isotope dilution analysis from nanogramme samples are possible.

Recovery of rhenium from acidic aqueous solutions by pressure reduction with gaseous reducers

AbstractProcess of rhenium removal from acidic industrial effluents by pressure reduction with gaseous hydrogen and sulphur dioxide was examined. Solutions from two sources were investigated, namely: circulating wash liquors originated from a wet dedusting of converter gases, and from dedusting of Dörschel furnace gases at a copper smelter. The effects of temperature, sulphuric acid concentration, and addition of an activated charcoal carrier were determined on rhenium recovery. Complete removal of rhenium from the solution has been achieved with both hydrogen and sulphur dioxide and the concentration of rhenium in the resultant concentrate reached 3%. The technological process for recovering rhenium from acidic industrial effluents was suggested.

Tensile properties of tungsten-3.6% rhenium-0.4% hafnium carbide above 0.5 T m

In recent years, there has been a renewal of interest in the development of tungsten-base alloys and fibers as future aerospace propulsion and space power systems place over increasing demands on materials with high-temperature capability. For example, tungsten-base alloys are expected to be used as emitter materials in a future space power system and tungsten fiber-reinforced composites are being developed for future aerospace systems. Among various alloying elements for tungsten, rhenium has been found to be one of the most effective alloying elements because the addition of rhenium to tungsten increases not only high-temperature strength but low-temperature ductility. It has been reported that the optimum concentration of rhenium in tungsten is about 4 at.% or greater than 20 at.% to provide optimum ductilizing effect. In order to improve high-temperature strength, second-phase strengthening has also been utilized in the development of tungsten-base alloys. Among various potential second-phase particles, hafnium carbide (HfC) was found to be one of the most effective particles to improve high-temperature strength of tungsten because of its high melting temperature and thermodynamic stability. The main objective of the present paper is to report the tensile properties of a W-3.6 at.% Re-0.4 mol % HfC alloy for a widemore » temperature range above 0.5 T/sub m/ (melting temperature in Kelvin) and examine the strengthening effect of HfC.« less

Heavy metal analyses in the marine environment - approaches to quality control

The validity of analyses of elements in the femto- and picomolar ranges in waters and sediments can be assessed on the basis of several criteria: an evaluation of the chemical technique; the use of primary standards and intercalibration exercises; and chemical and geochemical coherence of the results. Herein are reported analyses of ruthenium, platinum, palladium, rhenium, iridium and gold in oceanic samples. The gold concentrations in surface seawaters, at least 25 times less than those previously reported, are in accord with the concentrations of their periodic table neighbors as well as with crustal and sedimentary contents. The remarkable concentration of rhenium in seawater, in relation to its very low crustal abundance, can be explained by the inertness of the perrhenate ion.

Certain aspects of the reduction of Re/?-al2O3 and Re/SiO2 catalysts by hydrogen

1. Below 500°C, hydrogen at 100 torr pressure will not reduce Re(VII) to metallic rhenium on the aluminum oxide surface; on the silica gel surface, the reduction to metallic rhenium is complete under these same conditions. 2. The degree of reduction of the rhenium catalyst depends on the nature of the rhenium compound used in its preparation, the concentration of the rhenium in the catalyst, and the pressure of the hydrogen. Raising the rhenium concentration and increasing the hydrogen pressure reduces the temperature required for rhenium reduction, and increases the degree of reduction, on the aluminum oxide surface.

Carbonyl halides of the Group VII transition metals. I. Halocarbonyls and halocarbonyl anions of rhenium(I)

The rhenium(1) halocarbonyls Re(CO)5X (X = Cl, Br, I) may be readily prepared by refluxing a solution of the free hexahalorhenate(1V) acid in hydrohalic acid with formic acid. Visible absorption spectral studies indicate that formation of the halocarbonyls takes place following an initial reduction to rhenium(111), but no halocarbonyls of this intermediate oxidation state were isolated. The concentration of rhenium, as well as the relative amounts of hydrohalic and formic acids in the reaction mixture, are important factors for efficient production of the halocarbonyls. If the halocarbonyls are refluxed in formic acid containing a decreased proportion of hydrohalic acid, decarbonylation occurs giving the halocarbonyl anions [Re(CO)4X]2- which can be isolated as their caesium salts or as the parent halocarbonyls [Re(CO)4X]2. Continued refluxing of the formic acid solution causes still further decarbonylation giving the halocarbonyl anions [Re(CO)3X3]2- (X = Cl, Br) which may also be isolated as their caesium salts. Alternatively, evaporation to dryness of these solutions without addition of cations gives the new rhenium(1) halocarbonyl aquo complexes Re(CO)3(H2O)2X (X = Cl, Br). In the case of the iodo system, decarbonylation did not proceed to the tricarbonyl stage.

Rhenium concentration in Australian molybdenites by stable isotope dilution

A method for the determination of rhenium in molybdenite is described for concentrations down to 10 −7 g/g. Separation of microgram quantities of rhenium from molybdenite is effected by a pyridine solvent extraction and the rhenium concentration determined by stable isotope dilution. Rhenium determinations were made on molybdenite specimens sampled at various localities throughout the Australian continent. Their rhenium concentration cannot be correlated to geographical distribution, geological age, or the geology of the deposit. Within restricted regions, however, pipe deposits are demonstrably lower in rhenium concentration than are vein type occurrences. The hypothesized enhancement of rhenium in molybdenites associated with copper mineralization is substantiated in general although one remarkable exception to this relation is noted.

Reduction of rhenium(VII) at the dropping mercury electrode

The reduction of rhenium(VII), potassium perrhenate, at the dropping mercury electrode has been studied in sodium perchlorate, potassium oxalate, potassium iodide, potassium thiocyanate and potassium cyanide media. In the first four cases reduction begins at ca. −1·4 V vs. the saturated calomel electrode, but the limiting current in each case is even higher than that expected for the change from Re(VII) to Re(−I) and the waves appear to be catalytic in nature. In a cyanide medium (0·5 to at least 2 M potassium cyanide) a well-defined wave is obtained which appears to be diffusion-controlled, involving the reduction of Re(VII) to Re(O). In this medium the limiting current (diffusion current) is proportional to the concentration of rhenium(VII) from 0·3 at least 2 mM. Evidence has also been obtained as to the existence in solution of a cyano complex of rhenium(O).