Fraction Of Sb Research Articles

Bioavailability of arsenic and antimony in soils from an abandoned mining area, Glendinning (SW Scotland)

The mobility and bioavailability of As and Sb in relation to soil-biota transfer were evaluated at a former Sb mining and smelting site (Glendinning, SW Scotland, UK). The study specifically assessed the accumulation of As and Sb in different environmental components (soil, plants and earthworms) across mining area to estimate risk factors for the biota. Total concentrations and fractions of As and Sb in soils were determined. The latter using both a single solute and a non-specific stepwise sequential extraction (CISED) method. Mineralogical information was gathered from XRD and SEM analysis used to identify element distribution patterns. Pseudo-total (aqua-regia) levels of As and Sb in the soils varied between 50–17,400 mg kg− 1 and 10–1,200 mg kg− 1, respectively. Both elements are predominantly associated with Fe (or Al) oxides/hydroxides, by adsorption around silicate grains, representing a potentially bioavailable fraction. Antimony was also associated with sulphide phases. The highest values of As and Sb in biota were recorded in the earthworms (960 mg kg−1 and 27 mg kg− 1, respectively). Bioconcentration factors for both elements were below 1 and the highest for earthworms. Total and leached As levels in soils and biota were positively and significantly correlated, but only for Sb in earthworms and grass. Bioavailability of As in the biota, was shown to be limited by pH. In spite of the considerably high As and Sb contents of the soil the plant contamination remained comparably low, but still exceeded background values.

Antimony and Arsenic Uptake by Plants in an Abandoned Mining Area

The degree of antimony (Sb) and arsenic (As) pollution and their bioavailability in mining‐affected grassland soils were determined. Antimony and As concentrations in aboveground parts of plants, collected in three consecutive years, were measured to investigate their uptake capacity, food chain contamination, and ecological risks. Total Sb and As contents in soils ranged from 60 to 230 mg/kg and from 42 to 4530 mg/kg, respectively, indicating a high degree of pollution of soils. The mobile fractions of Sb (0.02–0.27% of the total Sb content) and As (0.02–0.70% of the total As content) in soils, which reflect the plant‐available portion, are extremely low compared to total Sb and As contents in soils. The Sb and As contents in plants were also very low in both study areas. This lower accumulation of Sb and As in the plants is attributed to the low bioavailability of Sb and As in mine soils. Antimony and As contents in some plants were lower than the controls, and the concentrations in some plants were slightly higher than the normal grass mean level but were less than the phytotoxic or toxic levels for human or livestock consumption. The results of this study demonstrate that the plants growing in these mining areas, which have evolved As and Sb tolerance and detoxification capacity, can be cultivated to phytostabilize the metalloid‐contaminated mining sites.

Enhanced flow injection leaching of rocks by focused microwave heating with in-line monitoring of released elements by inductively coupled plasma mass spectrometry

A focused microwave digestion system was used to heat a mini-column of sample of crushed rock (hematite) during its successive leaching by repeated 250-μL injections of water, HNO 3 1%, 10% and 30% (v/v). The mini-column was connected to the nebulizer of an inductively coupled plasma mass spectrometry instrument, which allowed a continuous monitoring of the progressive release of elements by a given leaching reagent. Quantitation of the accessible fraction of Mg, V, Cr, Mn, Co, Ni, Cu, Zn, Mo, Sb and Pb was done by calibration using 250-μL injections of standard solutions prepared in the leaching reagent matrices. Total digestion of the sample residue was also done to verify mass balance. With the exception of Mg, V and Co, where the same total amount was released with or without microwave heating, an increased release resulted from focused microwave heating, by up to an order of magnitude. Furthermore, mass balance was verified for more elements using microwave heating, presumably because of a lower relative proportion of spectroscopic interference as a result of an increased release of analytes. Using microwave energy in general resulted in the dissolution of additional phases, as evidenced by significantly different 208Pb/ 206Pb ratios as well as the increased release of elements with milder reagents. In fact, in the case of Pb, leaching with 30% HNO 3 was no longer necessary as all the Pb was released in the first three leaching reagents. Microwave heating could therefore be used advantageously in on-line leaching for exploration geochemistry and environmental monitoring.

Controlling shape of InAs 1−xSb x quantum structures on InP for quantum dots with 1.55-μm emission

We have investigated the effects of changing Sb fractions and misorienting InP(0 0 1) substrates on InAs 1− x Sb x quantum structures grown by metal-organic vapor-phase epitaxy (MOVPE), with the aim of obtaining small quantum dots (QDs) with 1.55-μm emission. At medium Sb content, InAsSb tended to form quantum wires (QWRs) with widths of less than 20 nm along the [ 1 1 ¯ 0 ] direction on InP(0 0 1), which was due to the surfactant effect. The [ 1 1 ¯ 0 ] size of these narrow InAsSb QWRs decreased as the miscut angles toward the [ 1 1 ¯ 0 ] direction of the vicinal InP(0 0 1) substrates was increased, and the InAsSb shapes changed from QWRs into QDs. Nearly 1.55-μm-emitting InAs 0.61Sb 0.39 QDs with lateral sizes of 20–30 nm embedded in InGaAsP barriers were fabricated on a vicinal substrate with a miscut of 5°, which will enable InP-based QD-telecom device applications.

Quantitative antimony speciation in shooting-range soils by EXAFS spectroscopy

The Sb speciation in soil samples from Swiss shooting ranges was determined using Sb K-edge X-ray absorption spectroscopy (XAS) and advanced statistical data analysis methods (iterative transformation factor analysis, ITFA). The XAS analysis was supported by a spectral data set of 13 Sb minerals and 4 sorption complexes. In spite of a high variability in geology, soil pH (3.1–7.5), Sb concentrations (1000–17,000 mg/kg) and shooting-range history, only two Sb species were identified. In the first species, Sb is surrounded solely by other Sb atoms at radial distances of 2.90, 3.35, 4.30 and 4.51 Å, indicative of metallic Sb(0). While part of this Sb(0) may be hosted by unweathered bullet fragments consisting of PbSb alloy, Pb L III-edge XAS of the soil with the highest fraction (0.75) of Sb(0) showed no metallic Pb, but only Pb 2+ bound to soil organic matter. This suggests a preferential oxidation of Pb in the alloy, driven by the higher standard reduction potential of Sb. In the second species, Sb is coordinated to 6 O-atoms at a distance of 1.98 Å, indicative of Sb(V). This oxidation state is further supported by an edge energy of 30,496–30,497 eV for the soil samples with <10% Sb(0). Iron atoms at radial distances of 3.10 and 3.56 Å from Sb atoms are in line with edge-sharing and bidentate corner-sharing linkages between Sb(O,OH) 6 and Fe(O,OH) 6 octahedra. While similar structural units exist in tripuhyite, the absence of Sb neighbors contradicts formation of this Fe antimonate. Hence the second species most likely consists of inner-sphere sorption complexes on Fe oxides, with edge and corner-sharing configuration occurring simultaneously. This pentavalent Sb species was present in all samples, suggesting that it is the prevailing species after weathering of metallic Sb(0) in oxic soils. No indication of Sb(III) was found.

MIGRATION OF SILVER, INDIUM, TIN, ANTIMONY, AND BISMUTH AND VARIATIONS IN THEIR CHEMICAL FRACTIONS ON ADDITION TO UNCONTAMINATED SOILS

Metals (Ag, In, Sn, Sb, and Bi) were added to the surfaces of four soil types in columns and exposed to precipitation in a grass-covered field for 18 months. The distributions of the total concentrations and the chemical fractions of the metals were then analyzed to study the metal migration in the soils. The chemical fractionation was performed by using an eight-step sequential extraction technique. Most of the added metals were retained in the uppermost (0 to 2 cm with filter) soil layers, but small portions were moved to the sublayers. Major chemical fractions (>10% in proportion) of the added metals were residual, H2O2 extractable organic-bound (H2O2-Org), and metal-organic complex-bound (Me-Org) fractions for Ag, Me-Org, residual, carbonate-bound, and H2O2-Org fractions for In, residual, Me-Org, amorphous metal oxides-bound (am-MeOx), and crystalline Fe oxides-bound fractions for Sn, Me-Org, residual, am-MeOx, and H2O2-Org fractions for Sb, and H2O2-Org, am-MeOx, and Me-Org fractions for Bi. Metal migration in soils was mainly associated with the exchangeable, carbonate-bound, and Me-Org fractions. The capacity of soils to retain the metals was in the order Andosol > Fluvisol > Regosol ≅ Cambisol. The mobility of metals was in the order In ≅ Bi > Sb > Ag ≅ Sn.

Grain boundary segregation in Cu–Sb alloys

Equilibrium grain boundary (GB) segregation of Sb in Cu–Sb alloys was studied by the methods of Auger (AES) and X-ray photoelectron spectroscopy (XPS). On the basis of Langmuir–McLean isotherm, the atomic fraction of Sb ( X b 0) at the first layer was calculated provided that all available sites at the first layer were filled and equilibrium between the first layer and the volume was reached. The values of ( X b 0) do not exceed atomic concentration of Sb in the nearest chemical compound in equilibrium with solid solution according to the phase diagram. The segregation capacity of grain boundaries in Cu-based alloys averages between 0.38 and 0.65 of Sb monolayer. The enthalpy of Sb segregation is equal to −8.9 kJ mol −1.

Electrical and optical properties of undoped GaSb grown by molecular beam epitaxy using cracked Sb 1 and Sb 2

In this paper, we report on the electrical and optical properties of undoped GaSb samples grown by MBE using Sb 1 as well as Sb 2 produced in a conventional antimony cracker. We establish the existence of Sb 1 and then extract the mole fraction of Sb 1 in the antimony beam as a function of the cracking zone temperature based on a combined analysis of mass spectrometry data and ion gauge flux reading. We find that the Sb 1 mole fraction becomes greater than 90% for cracking zone temperature above 950°C. A series of undoped GaSb samples are grown over a wide range of substrate temperature, V/III ratio and cracking zone temperature. The undoped GaSb samples grown at 550°C show p-type conductivity with a room-temperature hole mobility and hole concentration of ∼730 cm 2 v −1 s −1 and ∼3×10 16 cm −3, respectively. The hole mobility and hole concentration are essentially independent of the V/III ratio over a range of 1.2–4. Decreasing the growth temperature to 440°C leads to a simultaneous decrease in hole mobility, residual hole concentration and photoluminescence intensity. Hole mobility and hole concentration do not depend strongly on the cracking zone temperature in the range 790–1000°C; however, the optical intensity of the samples grown using Sb 1 is approximately one order of magnitude stronger than those using Sb 2. Besides the commonly seen bound exciton transitions at 805 (BE1), 803 (BE2), 800 (BE3) and 796 meV (BE4), a free exciton transition at ∼809.4 meV (4 K) is observed in the samples grown with Sb 1 at 550°C, indicating a greatly reduced density of nonradiative recombination centers.

Dopant activation in Sb-implanted relaxed Si1?xGex alloy layers grown on compositionally graded buffers

Supersaturated solid solutions of substitutional, electrically active Sb have been obtained by ion implantation of relaxed epitaxial Si1−xGex alloy layers grown on compositionally graded buffers. Substitutional and nonsubstitutional Sb fractions in relaxed Si0.85Ge0.15, Si0.65Ge0.35 and Si0.50Ge0.50 alloy layers implanted to a dose of 5×1015 Sb cm−2 and annealed isothermally at temperatures ranging from 400 to 850°C have been studied by Rutherford backscattering/channeling, transmission electron microscopy and Hall-effect and sheet resistivity measurements. A supersaturated solution of Sb corresponding to a peak carrier concentration of 4×1020 cm−3 and an electrically active fraction of 40% of the implanted dose is observed by Hall measurements for the case of Si0.85Ge0.15 and Si0.65Ge0.35 alloys annealed at 550°C.

Thermal stability of highly Sb-doped molecular beam epitaxy silicon grown at low temperatures: Structural and electrical characterization

The structural and electrical properties of highly Sb-doped molecular beam epitaxy grown silicon have been investigated as function of rapid thermal annealing (RTA) temperature. Doping levels of 3×1020 cm−3 were obtained using low temperature epitaxy (LTE) performed at a growth temperature of 300 °C. Ion channeling and transmission electron microscopy (TEM) measurements showed that the as-grown samples were of very high quality. The combination of Hall-effect profiling and Rutherford backscattering spectroscopy revealed an electrically active Sb fraction of 0.8. Short time RTA processing improved the electron mobility and the activation: RTA at 600 °C for 10 s yielded unity activation and RTA at 800 °C gave mobilities matching phosphorus doped bulk values, thus significantly exceeding previously reported values for highly doped LTE material. A degradation of the crystalline quality was observed for higher RTA temperatures: RTA at 1000 °C for 10 s reduced both the Sb-substitutional fraction and electrical activation to 0.6 due to precipitation of Sb, and lead to the formation of a high density of dislocation loops as observed by TEM. A large fraction of the precipitates decorated these dislocation loops. Mesa isolated diodes were fabricated to evaluate the use of LTE material for device production. Current–voltage measurements on these diodes revealed high quality junctions with low reverse currents and near-ideal forward characteristic.

121-Sb Mössbauer study of insulating and ion-conducting antimony chalcogenide-based glasses

The local environment of antimony in As 2S 3Sb 2S 3, AgISb 2S 3, AsSbSe and A AgAsSbSe glasses, glassy/crystalline alloys and crystals is investigated using 121-Sb Mössbauer spectroscopy. The isomer shift both for sulfide and selenide vitreous alloys is 1.2–2.0 mm/s more positive than that for corresponding crystalline parents. The smaller s-electron density at the 121Sb nucleus for glasses indicates a decrease of the antimony-chalcogen interatomic distances in comparison with those for crystalline materials. The isomer shift systematics and composition dependencies of the electric-quadrupole coupling constant, eQV zz , and the asymmetry parameter, ν, shows that in As 2S 3Sb 2S 3 and AsSbSe insulating glasses an isomorphous substitution of arsenic by antimony occurs accompanied by an increase of interatomic distances. In the case of Ag + ion-conducting vitreous alloys, however, the antimony-chalcogen distances are governed by the silver content and do not depend on the Sb fraction of the glass. Geometric and topological disorder in the glass network is correlated with an increase of the electric-quadrupole coupling constants and values of the asymmetry parameter ν between 0.4 and 1.0.

微細中空ガラス球／Ａｌ‐１２％Ｓｉ合金複合材料の引張強さに及ぼす基地金属と中空ガラス殻壁の有効断面積率の影響

A low density composite (Shirasu Balloons Aluminum Composites: SBAC) of volcano glass micro-balloons (Shirasu Balloons: SB) and an aluminum alloy (Al-12%Si) was investigated in terms of tensile strength. SBAC fractures abruptly at a critical tensile stress, that is a typical brittle material. The fractured surface propagates through the equatorial section of SB and the constricted parts of matrix metal where SB is in contact with together. The effective area fractions of metal and SB wall (SG) sections in the fractured surface are respectively AM=0.363-0.282 VSB and ASG=(1.28+0.556 VSB) h/R, where h and R are the wall thickness and the mean radius of SB, and VSB is the volume fraction of SB in SBAC. The tensile strength of SBAC is proportional to the summation of AM and ASG since SB wall has Young's modulus nearly equal to that of the aluminum alloy. The sphericity of SB changes the stress concentration around the cavitation in SB and affects the tensile strength of SBAC.

微細中空ガラス球／Ａｌ―１２％Ｓｉ合金複合材料の特性に及ぼす体積分率の影響

A low density composite (Shirasu Balloons Aluminum Composite: SBAC) of volcano glass microballoons (Shirasu Balloons: SB) and aluminum alloy (Al-12%Si) was investigated in terms of the effect of volume fraction (VSB) of SB on tensile strength (σT), compressive strength (σC), shear modulus (G), internal friction coefficient (Q-1) and specific conductivity (C) of SBAC. The value of G decreased exponentially and monotonously with the increase in VSB and showed good agreement with logarithmic mixture rule. The values of σT, σC and C also decreased exponentially with the increase in VSB, but their curves inflected sharply toward low values at about 50vol% of SB. On the other hand, Q-1 value increased linearly with the increase in VSB and the curve inflected sharply toward high value at about 50vol% of SB. The VSB of their knee points (about 50vol%) seemed to be the volume fraction above which contact points of SB in SBAC markedly increased.

Spatially resolved measurement of substitutional dopant concentrations in semiconductors

It is shown that a simple ratio technique based on the electron channeling phenomenon can be used to measure substitutional fractions of dopants in submicron-sized regions of semiconductors. Samples were made from 121Sb+ implanted Si, solid-phase-epitaxially regrown, and analyzed by ion channeling. One sample was sequentially annealed so as to precipitate out various fractions of the dopant in excess of the solubility limit. In the fully annealed sample electron channeling measurements could quantitatively determine the fraction of Sb in precipitate form since it was randomly located with respect to the matrix. In the partially annealed sample electron channeling indicated a larger nonsubstitutional fraction than could be accounted for by observed precipitates.

Kinetics of Antimony Doping in Silicon Molecular Beam Epitaxy

A new kinetic model for Sb doping into the Si MBE layer is proposed. In this model, Sb doping steps are assumed as follows: a fraction of impinging Sb4 molecules adsorbs on the growing Si surface (adlayer) and monoatomic Sb desorbs from the adlayer into vapor; a fraction of monoatomic Sb in the adlayer is incorporated into the bulk, so that surface-concentration of Sb atoms may be in equilibrium with bulk-concentration of Sb. According to this model, calculated results successfully represent the present experimental data on relations between incident Sb4 flux, Sb concentration in the adlayer and that in bulk. As a result, it is indicated that doping levels in MBE layers are uniquely determined by Sb concentration in the adlayer, and not by Sb4 flux/Si flux ratio, when Si growth rate is lower than 1 Å/s.

Subcellular structure of bovine thyroid gland. The localization of the peroxidase activity in bovine thyroid

1. After differential pelleting of bovine thyroid tissue the highest relative specific activities for plasma membrane markers are found in the L fraction whereas those for peroxidase activities (p-phenylenediamine, guaiacol and 3,3'-diaminobenizidine tetrachloride peroxidases) are found in the M fraction. 2. When M + L fractions were subjected to buoyant-density equilibration in a HS zonal rotor all peroxidases show different profiles. The guaiacol peroxidase activity always follows the distribution of glucose 6-phosphatase. 3. When a Sb fraction is subjected to Sepharose 2B chromatography three major peaks are obtained. The first, eluted at the void volume, consists of membranous material and contains most of the guaiacol peroxidase activity. Most of the protein (probably thyroglobulin) is eluted with the second peak. Solubilized enzymes are recovered in the third peak. 4. p-Phenylenediamine peroxidase activity penetrates into the gel on polyacrylamidegel electrophoresis, whereas guaiacol peroxidase activity remains at the sample zone. 5. DEAE-Sephadex A-50 chromatography resolves the peroxidase activities into two peaks, displaying different relative amounts of the different enzymic activities in each peak. 6. The peroxidase activities may be due to the presence of different proteins. A localization of guaiacol peroxidase in rough-endoplasmic-reticulum membranes (or in membranes related to them) seems very likely.