Detrimental Impurities Research Articles

STUDY OF THE PHASE AND IMPURITY COMPOSITION OF PD—BA AND PT—BA CATHODE ALLOYS

We have studied the phase and impurity composition of Pd—Ba and Pt—Ba cathode alloys obtained on an A 535.02TO arc melting plant using a technology developed by AO Shokin NPP Istok. The study showed that the concentration of detrimental impurities (C; Zn; Cu; Al) in the specimens is within the allowed range. Pd—Ba tapes are rich in Ba but this does not compromise their quality. We have confirmed the earlier found domination of two−phase composition in Pd—Ba and Pt—Ba alloys where one of the phase is an intermetallic compound (Pd5Ba, Pt5Ba) and the other is a noble metal(the matrix). The intermetallide is distributed in the platinum metal matrix quite inhomogeneously, this tangibly impairing the operation parameters of cathodes produced from these alloys. For the first time we have shown the high efficiency of transmission electron microscopy for studying Pd—Ba and Pt—Ba cathode alloys. We have for the first time found the Pd2О phase in Pd—Ba. It may significantly reduce the secondary electron emission coefficient and the quality of devices based on this alloy. We have determined the Pd and Pd5Ba grain size in the Pd—Ba alloys and the Pt and Pt5Ba grain size in the Pt—Ba alloys. All the Pd and Pt5Ba grains contain high densities of randomly arranged dislocations, and Pt5Ba grains contain internal stresses. Recommendations have been given concerning the improvement of the current Pd—Ba and Pt—Ba cathode alloy tape technology.

Biotechnological aspects of ethanol biosynthesis from Miscanthus

The study demonstrates that Saccharomyces cerevisiae VKPM Y-1693 yeast is resistant to the aqueous enzymatic Miscanthus hydrolysate. The good morphophysiological condition of the yeast indicates that the media contain no detrimental impurities characteristic of acidic chemical hydrolysates. It is shown that the native active acidity of the hydrolysate (pH 4.5–4.7) is optimal for ethanol biosynthesis from enzymatic Miscanthus cellulose hydrolysate. An addition of 1% yeast extract makes the aqueous enzymatic Miscanthus cellulose hydrolysate medium complete. Under the conditions of batch fermentation, it is sufficient to introduce 10% yeast inoculum in the log phase of growth. As shown by gas-liquid chromatography, the enzymatic digestion of Miscanthus cellulose produces ethanol with low contents of esters and fusel oils. Miscanthus bioethanol the contains no methanol.

Разработка стандартных образцов жаропрочных никелевых сплавов для определения вредных примесей и редкоземельных элементов спектральными методами

Разработка стандартных образцов жаропрочных никелевых сплавов для определения вредных примесей и редкоземельных элементов спектральными методами

Chemical and mineral transformation of a low grade goethite ore by dehydroxylation, reduction roasting and magnetic separation

The utilization of abundant low grade goethite (α−FeOOH) ores is potentially important to many countries in the world, especially Australia. These ores contain many detrimental impurities and are difficult to upgrade to make suitable concentrates for the blast furnace. In this paper, chemical and mineral transformations of a goethite ore were studied by dehydroxylation, reduction roasting in CO and CO2 gas mixtures, and magnetic separation. The goethite sample was taken from a reject stream at an iron ore mine from the Pilbara region, Western Australia. The roasting temperature range investigated was 400–700°C. Chemical and mineralogical analysis was conducted using XRF, XRD, optical microscope, EPMA, and SEM. Magnetic separation was conducted using a Davis tube tester and a high intensity magnetic separator.The results show that reduction roasting can remove moisture and impurities but does not significantly change the Fe content in the feed. However, reduction roasting transforms goethite to hematite and eventually maghemite which can be recovered by magnetic separation, allowing upgrading. Further studies are needed to optimize the reduction roasting and correlate it with the magnetic separation to maximize the efficiency of iron upgrading.

The effect of catalyst modification on the conversion of glycerol to allyl alcohol

Conversion of glycerol to allyl alcohol was carried out over an iron on alumina catalyst. With the aim of enhancing selectivity towards the desired product and to reduce acrolein formation (a detrimental impurity in the subsequent epoxidation of allyl alcohol) the supported iron catalyst was modified using alkali metals. It was found that lithium, sodium, potassium, rubidium and caesium deposition on the catalyst surface increased allyl alcohol yield and reduced the rate of catalyst deactivation. Coincidently, acrolein selectivity decreased by up to 75% following treatment with the alkali salt.Changes in the product distribution were determined to be associated with altering the acid/base properties of the catalyst, as confirmed by isopropanol dehydration/dehydrogenation, ammonia and carbon dioxide temperature programmed desorption. The treatment was also found to influence the physical properties of the catalyst surface. A correlation between acid to basic site concentration and allyl alcohol selectivity was established. A reduction in the former value results in an enhancement in the rate of allyl alcohol formation. A reaction mechanism was developed based on the effect of iron and alkali metals catalysing the conversion of glycerol into allyl alcohol. The proposed catalyst modification technique is a straightforward method, readily applicable at a larger scale due to the simplicity of the alkali inclusion and its striking influence on the reaction selectivity.

Influence of Intermetallic Phases on Fracture Resistance of Silumins

Abstract In secondary aluminium alloys iron is the main detrimental impurity. It forms intermetallic phases which have lamellar shape, high brittleness and weak crystallographic conformity with the matrix. In the work the influence of intermetallic phases on the initiation and propagation of microcracks, mechanical and service properties of aluminium alloys has been investigated.

Sn(IV) anions adsorption onto ferric hydroxide: A speciation-based model

Sn is a detrimental impurity in tungsten hydrometallurgy which should be strictly controlled. Using the freshly precipitated ferric hydroxide to remove Sn impurity from tungstate solution exhibits satisfactory effects. The goal of the present research is to provide further understanding of the adsorption mechanism. The work indicates that the surface of ferric hydroxide consists of three types of surface acid sites denoted as S1, S2, and S3, each of which has a surface density (Гi) of 1.0×10−3, 3.1×10−3, and 9.6×10−3mol·g−1 and acid constant (pKH) of 3.6, 5.7, and 10.8 respectively. The pHzpc of 7.9 for the ferric hydroxide is obtained. Since Sn exists in alkaline solution as Sn(OH)5− and Sn(OH)62−, a speciation-based model is developed and data fitting to the model gives six adsorption equilibrium constants which are 26.2, 1.2×10−11 and 1.5 for Sn(OH)5−, and 4.3, 1.6×10−15 and 2.2×10−3 for Sn(OH)62− onto S1, S2, and S3 respectively. The average absolute error of the predicting results and experimental data is 5.3%. The speciation-based model can successfully describe the Sn adsorption ratio at different pH values and predict the Sn adsorption ratio with different initial Sn concentrations.

Increasing Lightning Strength of Optical Ground Conductors

In this article, testing and improvement stages of AA6101 and 6201 materials used in manufacturing of new generation optical ground conductors (OPGW) installed against lightning strike have been presented. The designed and manufactured prototype composite conductor OPGW for Turkey’s transmission lines is composed of six galvanized steel wires, one stainless steel tube with multi glass fibers and 12 aluminium alloy wires. Test samples prepared from prototype failed in first trial of lightning strike due to spot melting of conductor outer surface. The amplitude of the arc current was adjusted to 200A. The duration of the arc was 500 ms with 100C total charge. It caused breaking of excessive aluminium alloy wires at outer layer. Thus material improvement by inoculation with AlB2 compound into molten metal was applied at continuous casting line. Its aim is to obviate destroying effects of lightning strike by the increasing conductivity of the base conductive part composed of alloy AA6101 and 6201 wires. Conductivity increases were made by transforming detrimental transition impurities Ti, V, Cr and Zr into diborides as TiB2, ZrB2, CrB2, and VB2. After all OPGW composite conductor manufactured with improved aluminium alloy wires passed lightning strike tests perfectly.

Influеnce of alkaline earth metal oxides on the properties of fluor- and boron-free enamels

These days, plenty of industries widely utilize various kinds of enamelware, which must comply with State Standards, look attractive, be safe and easy-to-use. However, the production of such ware requires the enamel, containing detrimental and unhealthy impurities of fluorine as well as boron. Yet, the compounds with these elements give enamel numerous positive qualities, including fusibility, viscosity of their melt and luster of the glass coating.This article sets forth the results of analyzing the influence of alkaline earth oxides (СаО, МgO and SrO) on the fluorine- and boron-free coating enamel properties. It’s been ascertained, that the mentioned oxides have positive influence on physicochemical enamel properties (i.e. chemical resistance and the temperature coefficient of linear expansion - TCLE), as well as optical characteristics of experimental enamel coatings.The developed fluorine- and boron-free enamels can lower expenses for raw materials, preclude the lixiviation of boric oxide from enamel coatings and reduce industrial environment pollution with toxic substances (e.g. alkaline metaborates and fluorine compounds), which are emitted during the enamel melting process.The new enamels can serve as the basic materials for colored fluorine- and boron-free enamels used for coating everyday household goods.

Use of complex modifiers for improvement of steel R7 quality

Purpose. Stabilizing of chemical composition and properties, decrease of detrimental impurities concentrations, amount of nonmetallics, grinding down of grain of the R7 wheeled steel by treatment of multicomponent modifiers. Methodology. Probed chemical composition and mechanical properties in accordance with UIC 812-3 and EN 13262 serial melting steel R7 and treated a multicomponent deoxidizers-modifiers are researched. Processing of data is conducted by a regressive-cross-correlation analysis. Findings. Influence of operations of out-of-furnace treatment is set on detrimental impurities concentration. Using of complex modifiers has reduced the concentration of sulfur most effectively. It is shown that in the modified melting variation of both basic alloying elements and admixtures has decreased, homogeneity and dispersion of structure have increased, what mechanical properties of wheels were stabilized due to. Originality. Influence was first set each of the stages of out-of-furnace treatment steel R7 on the detrimental impurities concentration, micro hardness, structure of hard-tempered tests. Dependences of mechanical characteristics were got of the detrimental impurities concentrations. Practical value. By treatment of multicomponent deoxidizers-modifiers, stabilization of chemical composition, sulfur concentration reducing, nonmetallic inclusions amount, grain refining and improving the homogeneity of the structure are achieved, this led to stabilizing and increase of mechanical properties level. It is shown the efficiency of multicomponent deoxidizers-modifiers usage in order to improve quality of steel R7 and reliability of wheels made of it.

Preparation of High Purity Sodium 5‐Nitrotetrazolate (NaNT): An Essential Precursor to the Environmentally Acceptable Primary Explosive, DBX‐1

AbstractSodium 5‐nitrotetrazolate dihydrate (NaNT) is a useful precursor compound for the synthesis of lead‐free primary explosives; however, currently employed syntheses for the compound are tedious, dangerous, and plagued by impurities. Through comprehensive analysis, we elucidate the identity of the most detrimental impurities and further report an improved procedure for preparation of NaNT, which greatly improves the purity, while avoiding the handling of acid copper(II) nitrotetrazolate, a highly sensitive explosive intermediate. In the new procedure, 5‐aminotetrazole is diazotized with sodium nitrite, cupric sulfate, and nitric acid. Copper is precipitated as its oxide and the aqueous solution evaporated. After soxhlet extraction with acetone, large crystals of NaNT are obtained. The prepared material is suitable for preparation of lead azide replacement DBX‐1 [copper(I) 5‐nitrotetrazolate] as evidenced by successful use in M55 stab detonators.

Ore geochemistry, zircon mineralogy, and genesis of the Sakharjok Y-Zr deposit, Kola Peninsula, Russia

The Sakharjok Y-Zr deposit in Kola Peninsula is related to the fissure alkaline intrusion of the same name. The intrusion ∼7 km in extent and 4–5 km2 in area of its exposed part is composed of Neoarchean (2.68–2.61 Ma) alkali and nepheline syenites, which cut through the Archean alkali granite and gneissic granodiorite. Mineralization is localized in the nepheline syenite body as linear zones 200–1350 m in extent and 3–30 m in thickness, which strike conformably to primary magmatic banding and trachytoid texture of nepheline syenite. The ore is similar to the host rocks in petrography and chemistry and only differs from them in enrichment in zircon, britholite-(Y), and pyrochlore. Judging from geochemical attributes (high HSFE and some incompatible element contents (1000–5000 ppm Zr, 200–600 ppm Nb, 100–500 ppm Y, 0.1–0.3 wt % REE, 400–900 ppm Rb), REE pattern, Th/U, Y/Nb, and Yb/Ta ratios), nepheline syenite was derived from an enriched mantle source similar to that of contemporary OIB and was formed as an evolved product of long-term fractional crystallization of primary alkali basaltic melt. The ore concentrations are caused by unique composition of nepheline syenite magma (high Zr, Y, REE, Nb contents), which underwent subsequent intrachamber fractionation. Mineralogical features of zircon-the main ore mineral—demonstrate its long multistage crystallization. The inner zones of prismatic crystals with high ZrO2/HfO2 ratio (90, on average) grew during early magmatic stage at a temperature of 900–850°C. The inner zones of dipyramidal crystals with average ZrO2/HfO2 = 63 formed during late magmatic stage at a temperature of ∼500°C. The zircon pertaining to the postmagmatic hydrothermal stage is distinguished by the lowest ZrO2/HfO2 ratio (29, on average), porous fabric, abundant inclusions, and crystallization temperature below 500°C. The progressive decrease in ZrO2/HfO2 ratio was caused by evolution of melt and postmagmatic solution. The metamorphic zircon rims relics of earlier crystals and occurs as individual rhythmically zoned grains with an averaged ZrO2/HfO2 ratio (45, on average) similar to that of the bulk ore composition. The metamorphic zircon is depleted in uranium in comparison with magmatic zircon, owing to selective removal of U by aqueous metamorphic solutions. Zircon from the Sakharjok deposit is characterized by low concentrations of detrimental impurities, in particular, contains only 10–90 ppm U and 10–80 ppm Th, and thus can be used in various fields of application.

CATALYST-FREE GAN NANOWIRES AS NANOSCALE LIGHT EMITTERS

Catalyst-free growth of GaN nanowires with molecular beam epitaxy produces material of exceptionally high quality with long minority-carrier lifetimes and low surface recombination velocity. The nanowires grow by thermodynamic driving forces that enhance the sticking coefficient of incoming reagents to the end facets of the nanowire while inhibiting growth on the m-plane sidewalls. Photoluminescence (PL) studies confirm that the material is essentially free of detrimental chemical impurities and crystalline defects. The nanowires are readily excited to lasing with modest optical pump power. Recent progress in methods for selective epitaxy has made it possible to control both the diameter and placement of the nanowires. Despite the high material quality, the energy-conversion efficiency of single nanowire LEDs remains low. The primary limitation appears to be optimizing the p-type doping with Mg , which is both a growth and a measurement problem.

Effect of intensive melt shearing on the formation of Fe-containing intermetallics in LM24 Al-alloy

Fe is one of the inevitable and detrimental impurities in aluminium alloys that degrade the mechanical performance of castings. In the present work, intensive melt shearing has been demonstrated to modify the morphology of Fe-containing intermetallic compounds by promoting the formation of compact α-Al(Fe,Mn)Si at the expense of needle-shaped β-AlFeSi, leading to an improved mechanical properties of LM24 alloy processed by MC-HPDC process. The promotion of the formation of α -Al(Fe, Mn)Si phase is resulted from the enhanced nucleation on the well dispersed MgAl2O4 particles in the melt. The Fe tolerance of LM24 alloy can be effectively improved by combining Mn alloying and intensive melt shearing.

Electronic properties of Cu(In,Ga)Se2 solar cells on stainless steel foils without diffusion barrier

ABSTRACTCompared with rigid glass, manufacturing of Cu(In,Ga)Se2 (CIGS) solar cells on flexible stainless steel (SS) substrates has potential to reduce production cost because of the application of roll‐to‐roll processing. Up to now, high‐efficiency cells on SS could only be achieved when the substrate is coated with a barrier layer (e.g. SiOx or Si3N4) for hindering the diffusion of impurities, especially Fe, into the CIGS layer. In this paper, the effect of these impurities on the electronic transport properties of the device is investigated. Using admittance spectroscopy, the presence of a deep defect level at around 320 meV is observed, which deteriorates the efficiency of the solar cells. Furthermore, it is shown that reducing substrate temperature during CIGS deposition is an effective alternative to a barrier layer for reducing diffusion of detrimental Fe impurities into the absorber layer. By applying a CIGS growth process for deposition at low substrate temperatures, an efficiency of 17.7%, certified by Fraunhofer Institute ISE, Freiburg, was achieved on Mo/Ti‐coated SS substrate without an additional metal‐oxide or metal‐nitride impurity diffusion barrier layer. Copyright © 2012 John Wiley & Sons, Ltd.

ALD-Grown Al2O3 as a Diffusion Barrier for Stainless Steel Substrates for Flexible Cu(InGa)Se2 Solar Cells

Al2O3 layer deposited by atomic layer deposition was successfully used as a diffusion barrier and insulator for the stainless steel substrate of a Cu(InGa)Se2 thin film solar cell. The 100–300 nm-thick Al2O3 coating on stainless steel improved the surface smoothness and presented reliable resistance. More importantly, the diffusion of detrimental impurities, such as Fe and Ni, was significantly reduced during CuInSe2 deposition at the substrate temperature of 550°C.

Deuterium analysis in zircaloy using ps laser-induced low pressure plasma

An experimental study on picosecond laser induced plasma spectroscopy of a zircaloy sample with low-pressure surrounding helium gas has been carried out to demonstrate its potential applicability to three-dimensional quantitative micro-analysis of deuterium impurities in zircaloy. This was achieved by adopting the optimal experimental condition ascertained in this study, which is specified as 7 mJ laser energy, 1.3 kPa helium pressure, and 50 μs measurement window, and which was found to result in consistent D emission enhancement. Employing these operational parameters, a linear calibration line exhibiting a zero intercept was obtained from zircaloy-4 samples doped with various concentrations of D impurity, regarded as surrogates for H impurity. An additional measurement also yielded a detection limit of about 10 μg/g for D impurity, well below the acceptable threshold of damaging H concentration in zircaloy. Each of these measurements was found to produce a crater size of only 25 μm in diameter, promising its application for performing less-destructive measurements. The result of this study has thus paved the way for conducting a further experiment with hydrogen-doped zircaloy samples and the further technical development of a three-dimensional quantitative micro-analysis of detrimental hydrogen impurity in zircaloy vessels used in nuclear power plants.

Neptunium(III) application in extraction chromatography

This paper describes a novel strategy for actinide separation by extraction chromatography with Np(III) valence adjustment. Neptunium(IV) was reduced to Np(III) using Cr(II) and then selectively separated from uranium (IV) on a TEVA resin. After elution, Np(III) was retained on a DGA resin in order to remove any detrimental chromium impurities. Neptunium(III) formation was demonstrated by the complete and selective elution of Np from TEVA resin (99±7%) in less than 12mL of 9M HCl from U(IV) (0.7±0.7%). It was determined by UV–visible and kinetic studies that Cr(II) was the only species responsible for the elution of Np(IV) as Np(III) and that the Cr(II) solution could be prepared from 2 to 30min before its use without the need of complex degassing systems to prevent the oxidation of Np(III) by oxygen. The methodology proposed here with TEVA/DGA resins provides removal of Cr(III) impurities produced at high decontamination factors (2.8×103 and 7.3×104 respectively).

Ultrapurification of archaeological lead

Based on purification efficiency calculations for lead distillation, we developed a combined process for the ultrapurification of archaeological lead. We obtained pilot amounts of high-purity archaeological lead and PbO with the following contents of detrimental impurities: U, <2 ppb; Th, <1 ppb; Ni, Cu, Fe, Si, Ti, Mg, Al, Mn, Cr, V, Co, < 0.1 ppm; K, Ca, Zn, Cd, Ag, Sb, < 1 ppm. Lead of such purity can be used in low-background experiments as a protective shield material and in the growth of low-background PbWO4 and PbMoO4 scintillator crystals. From an isotope ratio, we were able to identify the origin of the archaeological lead.

Effects of alloying elements (Mn, Co, Al, W, Sn, B, C and S) on biodegradability and in vitro biocompatibility of pure iron

Pure iron was determined to be a valid candidate material for biodegradable metallic stents in recent animal tests; however, a much faster degradation rate in physiological environments was desired. C, Mn, Si, P, S, B, Cr, Ni, Pb, Mo, Al, Ti, Cu, Co, V and W are common alloying elements in industrial steels, with Cr, Ni, Mo, Cu, Ti, V and Si being acknowledged as beneficial in enhancing the corrosion resistance of iron. The purpose of the present work (using Fe–X binary alloy models) is to explore the effect of the remaining alloying elements (Mn, Co, Al, W, B, C and S) and one detrimental impurity element Sn on the biodegradability and biocompatibility of pure iron by scanning electron microscopy, X-ray diffraction, metallographic observation, tensile testing, microhardness testing, electrochemical testing, static (for 6months) and dynamic (for 1month with various dissolved oxygen concentrations) immersion testing, cytotoxicity testing, hemolysis and platelet adhesion testing. The results showed that the addition of all alloying elements except for Sn improved the mechanical properties of iron after rolling. Localized corrosion of Fe–X binary alloys was observed in both static and dynamic immersion tests. Except for the Fe–Mn alloy, which showed a significant decrease in corrosion rate, the other Fe–X binary alloy corrosion rates were close to that of pure iron. It was found that compared with pure iron all Fe–X binary alloys decreased the viability of the L929 cell line, none of experimental alloying elements significantly reduced the viability of vascular smooth muscle cells and all the elements except for Mn increased the viability of the ECV304 cell line. The hemolysis percentage of all Fe-X binary alloy models were less than 5%, and no sign of thrombogenicity was observed. In vitro corrosion and the biological behavior of these Fe–X binary alloys are discussed and a corresponding mechanism of corrosion of Fe–X binary alloys in Hank’s solution proposed. As a concluding remark, Co, W, C and S are recommended as alloying elements for biodegradable iron-based biomaterials.