Showing papers on "Antimony published in 1984"

Arsenic, antimony, and germanium biogeochemistry in the Baltic Sea

Abstract: Arsenic, antimony, and germanium species concentrations have been determined from fivehydrographic stations along the central axis of the Baltic Sea from the Bornholm Basin to theGulf of Finland. Arsenic and antimony concentrations are lower than in the open oceans and inmost rivers. In the oxic waters, the pentavalent species of As and Sb predominate, while in theanoxic basins, the distribution shifts to the trivalent species and possibly some sulfo-complexes.Methylated arsenic species make up a large fraction of dissolved As in the surface waters, andmethylated species of As, Sb, and Ge are detectable throughout the water column. Germanicacid concentrations are about ten times higher than in the ocean and much higher than can beaccounted for by Ruvial input. The vertical distributions of arsenic, antimony, and germaniumwithin the Baltic Sea are controlled by biogeochemical cycling, involving biogenic uptake,particulate scavenging and partial regeneration. A mass balance including river and atmosphericinputs, exchange with the Atlantic through the Belt Sea, and removal by sediment depositionsuggests that anthropogenic inputs make a significant contribution to the budgets of all threeelements, with atmospheric fluxes dominating the input of Ge to the Baltic. DOI: 10.1111/j.1600-0889.1984.tb00232.x

Effect of antimony ion implantation on Al‐silicon Schottky diode characteristics

Abstract: Shallow (≲100 A) antimony ion implantation on n‐type silicon is shown to reduce the effective barrier height on Al Schottky diodes formed on the implanted surface irrespective of postimplant annealing. The mechanisms of barrier reduction are quite different in the two cases. In the postimplant annealed case, the antimony is activated resulting in barrier height reduction due to the surface N+ dopant charge, while in the unannealed case, lattice damage causes barrier height reduction as observed earlier for ion etched silicon surfaces.

Enthalpies of formation of liquid and solid binary alloys of lead, antimony and bismuth with rare earth elements

Abstract: The predictions of Miedema's model for the heats of formation of binary intermetallic compounds of lead, bismuth and antimony with rare earth elements and for the heats of mixing and solution of the corresponding liquid alloy systems are presented. The predicted values are compared with the existing experimental data. The differences between the experimental and the calculated values of the enthalpy are discussed.

Self-diffusion of gallium and antimony in GaSb

Abstract: Self-diffusion of gallium and antimony in GaSb has been investigated in both Ga-saturated and Sb-saturated single crystals at temperatures ranging from 867 K to the temperature of congruent melting. The radio-isotopes 72Ga and I22 Sb were diffused simultaneously to avoid composition gradients. After sputter-sectioning, the penetration profiles for both isotopes were obtained by means of a Ge(Li) spectrometer. It is found that Ga diffuses slightly faster than Sb and that the composition plays an important role: Ga and Sb diffuse faster in Sb-rich than in Ga-rich samples. The temperature dependence of both diffusivities resembles that of the Sb partial pressure over the compound. Several mechanisms of diffusion are discussed in the light of these observations. The coupled diffusion of Ga and Sb leads us to conclude that both components diffuse via the same defect. In view of the special type of defect structure in GaSb, we propose that the triple defect is the predominant diffusion vehicle for both...

Grain boundary segregation of copper, tin and antimony in C-Mn steels at 900°C

Abstract: The segregation of copper, tin and antimony to austenite grain boundaries at 900° C has been investigated in C-Mn steels using a scanning Auger microprobe (SAM). The specimens for microanalysis were prepared in a manner such that the prior austenite grain boundaries could be exposed by fracturing at room temperature in the UHV chamber of the SAM unit. Initial bulk concentrations ranged between 600 and 2600 ppm Cu, 50 and 360 ppm Sn and 8 and 35 ppm Sb. Significant enrichment of copper, tin and antimony was detected along the austenite grain boundaries. The grain boundary concentration of copper and tin was found to vary depending upon the initial bulk concentration while the average concentration of antimony at the grain boundaries was found to be approximately 1 at % for all of the heats studied. For heats in which a significant level of copper segregation was detected, a relationship of at % Cu = at % (Sn+Sb) at the austenite grain boundaries was observed. Deformation at 900° C prior to fracture in UHV was found to be necessary to promote segregation. Samples that were annealed at 900° C but not hot worked did not exhibit evidence of copper, tin or antimony segregation. These results have been interpreted in terms of the effects of deformation on segregation kinetics, and were correlated with hot ductility measurements made at 900° C.

Potentiometric stripping analysis with a thin-film gold electrode for determination of copper, bismuth, antimony, and lead

Abstract: The in situ thin-film gold electrode at glassy carbon substrate has been successfully used as a working electrode in potentiometric stripping analysis. Gold(III) present in the solution studied also serves as an oxidant. The equations for the transition time (stripping signal) and for the stripping curve of potentiometric stripping analysis have been derived and verified experimentally for copper(II), bismuth(III), antimony(III), and lead(II), in 0.1 M HCl. This method is available for the simultaneous determination of these four ions used for sample analysis.

Antimony-doped stannic oxide thick film gas sensor

Abstract: A method of preparing an antimony-doped stannic oxide gas detecting film device responsive to the combustible constituents in an environment of interest is disclosed. Stannic oxide is structurally doped with antimony for use as a thick film gas detecting element.

Point defect trapping in solid‐phase epitaxially grown silicon‐antimony alloys

Abstract: Supersaturated silicon alloys produced by antimony implantation followed by solid‐phase‐epitaxial growth (furnace annealing), contain a supersaturation of interstitials. This is deduced from the observation of a transient, greatly enhanced diffusion of Sb into precipitates upon heating, accompanied by the formation of interstitial loops. In similar alloys produced by liquid‐phase‐epitaxial regrowth (pulsed laser annealing) much lower diffusion coefficients were obtained and no loops were observed. These observations provide clear evidence for the diffusion of the substitutional Sb dopant by an interstitialcy mechanism. The activation energy of the enhanced diffusion was 1.8±0.2 eV, presumably corresponding to the migration enthalpy of Sb by the interstitialcy mechanism. The loop number density at the end of the transient gave an estimate of the initial interstitial concentration, which allowed the diffusivity of Sb by the interstitialcy mechanism to be estimated.

Lung retention of antimony and arsenic in hamsters after the intratracheal instillation of industrial dust.

Abstract: Airborne factory dust (with a volume median diameter of 5.0 micron and a geometric standard deviation of 2.1 micron) from a Swedish copper smeltery contained antimony (Sb) (1.6 weight %) and arsenic (As) (19 weight %). The dust was neutron activated and intratracheally instilled in hamsters. In vivo measurements of lung clearance were undertaken of the radionuclides 76As, 122Sb, and 124Sb. Comparison was made with pure substances of antimony trioxide (Sb2O3) and arsenic trioxide (As2O3). Two phases were recognized in the clearance curves. The approximate half-time for the initial phase was 13 h for As2O3, 20 h for arsenic dust, about 40 h for Sb2O3, and about 30 h for antimony dust. The second phase had an approximate half-time of 20-40 d for Sb2O3 and antimony dust. Because of the short physical half-life of 76As, the second phase of the lung clearance was not possible to follow for AS2O3 and arsenic dust. The observed differences in clearance were primarily related to the solubility of the dust particles in saline, while particle size seemed to be less important in this instillation experiment. The low solubility of antimony in factory dust combined with a long biological half-time may be of importance in explaining the observed lung accumulation of antimony in exposed workers. The greater solubility and shorter biological half-time restricted the lung retention of arsenic.

Distribution of silver in massive sulfide ores

Abstract: The distribution of silver in connection with the formation of massive sulfide ores is discussed. It is proposed: 1) The affinity between silver and galena-rich ores is only pronounced if antimony and/or bismuth are also present in significant amounts, and 2) The degree of correlation between silver and lead is partly a function of the Ag/Sb+Bi ratio in the ore and increasing with decrease in ratio at least up to Ag/Sb+Bi=1. Observations of correlated Cu/Ag ratios in complex ores indicate that some silver was solved in chalcopyrite at the time of deposition. This is often masked by the much higher silver contents associated with galena. The Bi/Sb ratio is expected to increase downwards stratigraphically in galena-rich ores, due to a larger solubility of silver-bismuth in galena as compared with silver-antimony, at a realistic deposition temperature (200–300 °C). However, such an effect will only rarely be seen, due to incomplete separation of the ore-constituents at the time of deposition, as well as to post-depositional changes.

Determination of arsenic, antimony, bismuth, cadmium, copper, lead, molybdenum, silver and zinc in geological materials by atomic-absorption spectrometry

Abstract: Arsenic, antimony, bismuth, cadmium, copper, lead, molybdenum, silver and zinc are very useful elements in geochemical exploration. In the proposed method, geological samples are fused with potassium pyrosulphate and the fusate is dissolved in a solution of hydrochloric acid, ascorbic acid and potassium iodide. When this solution is shaken with a 10%V/V Aliquat 336-isobutyl methyl ketone organic phase, the nine elements of interest are selectively partitioned in the organic phase. All nine elements can then be determined in the organic phase using flame atomic-absorption spectrometry. The method is rapid and allows the determination of Ag and Cd at levels down to 0.1 p.p.m., Cu, Mo, and Zn down to 0.5 p.p.m., Pb, Bi and Sb down to 1 p.p.m. and As down to 5 p.p.m. in geological materials.

Antimony and graphite hydrogen ion electrode and method of making such electrode

Abstract: A solid state electrode that includes a graphite core as both the internal reference and the electrical conductor that is preferably formed of graphite threads maintained as a bundle that in one embodiment, has an end thereof coated with a mixture of antimony and antimony oxide as a sensor element, the graphite junction forming the internal reference to that sensor element, and in another embodiment, the graphite core is wrapped tightly around a sensor formed from section or "shot" of a mixture antimony and antimony oxide, the graphite junction forming the internal reference thereto. The connected graphite core and antimony/antimony oxide sensor are then covered with an impermeable non-conductive plastic sheath, leaving a section of the antimony/antimony oxide sensor surface exposed, and the junction of that sheath to the antimony/antimony oxide sensor is preferably sealed as with an epoxy.

Notes. An X-ray photoelectron spectroscopic study of the surface properties of vanadium antimonate and β-antimony tetroxide

Abstract: X-Ray photoelectron spectroscopy shows that non-stoicheiometric rutile-type vanadium antimonates prepared by solid-state reactions between antimony(III) oxide and vanadium(V) oxide are enriched at the surface in antimony. The observations are discussed and related to the superficial enrichment in antimony which occurs in other solids with rutile-type structures but prepared by different methods. The spectra from β-antimony tetroxide containing low concentrations of vanadium are consistent with the incorporation of vanadium within the bulk and associated with the low-temperature stabilisation of this phase. The thermally induced outgrowth from ‘β-antimony tetroxide’ formed by decomposition of vanadium antimonate is related to a surface reaction with vanadium(V) oxide and the subsequent development of a crystalline vanadium antimonate outgrowth.

Equilibria between silica-saturated iron silicate slags and molten Cu-As, Cu-Sb, and Cu-Bi Alloys

Abstract: The solubilities of copper, arsenic, antimony, and bismuth in silica-saturated iron silicate slag, equilibrated with molten copper which included the corresponding element, were measured at temperatures 1473 and 1523 K under oxygen pressures ranging from 10−1 to 10−7 atm. The results confirm that copper is dissolved as CuO0.5 in silica-saturated fayalite slag. Dissolution of As, Sb, and Bi was found to be dependent upon the oxygen potential, suggesting oxidic rather than atomic dissolution. The data obtained also support models in which these elements exist in the slag mainly as two different types of oxides, but occasionally these oxides coexist with neutral atoms. Based on these models, equations were obtained that related the solubilities of these elements in the slags to the oxygen potential in them. The knowledge obtained in this investigation will be helpful in eliminating deleterious minor elements in copper smelting.

Phase transitions in antimony at hydrostatic pressure up to 9 GPa

Abstract: Melting and solid-solid phase transitions in antimony are studied at hydrostatic pressure up to 9 GPa and at temperatures of 20 to 620 °C by means of thermopower and electrical resistance measurements and differential thermal analysis (DTA). The P-T diagram based on the precise measurement of pressure at high temperature is presented. The polymorphic transition of antimony from the rhombohedral (Sb I) to the simple cubic (Sb II) phase observed earlier under nonhydro-static pressure is not found at hydrostatic pressure. The rhombohedral phase (Sb I) transforms directly to the high pressure phase (Sb III) in the range from the room temperature up to the melting of Sb. The kinetics of the Sb I III transition is specific to thermally activated nucleation and growth transformation, with a pressure hysteresis of the transition increasing exponentially as the temperature decreases. The triple point Sb I-Sb III-liquid is found at 5.03 GPa and 559 °C. [Russian Text Ignored].

Direct catalytic synthesis of dimethyldichlorosilane from methyl chloride and silicon

Abstract: Dimethyldichlorosilane is directly prepared from methyl chloride and silicon, in high productivity, selectivity and degree of silicon conversion, by reacting methyl chloride with a solid contact mass comprising silicon and a catalytically effective amount of a catalyst which includes (1) elemental copper or a copper compound, (2) from about 30 to 1,000 ppm (calculated as metallic tin and/or antimony) of at least one of the metals tin and antimony, or at least one compound of at least one of the metals tin and antimony, and (3) from about 0.05 to 2% by weight, (calculated as alkali metal) of at least one of the alkali metals lithium, sodium, potassium and rubidium, or compound thereof, the amounts of said components (2) and (3) being based upon the total weight of said solid contact mass.

A method for processing copper smelting materials and the like containing high percentages of arsenic and/or antimony

Abstract: The invention relates to a method for preparing a sulphidic concentrate which is intended for further processing to copper and/or precious metals and which contains high percentages of arsenic and/or antimony, and possibly also bismuth in quantities likely to disturb subsequent processing stages, by partially roasting the concentrate in a fluidized bed, so as to eliminate substantially all the arsenic present and a major part of the antimony and/or bismuth. According to the invention, the concentrate and gas are supplied to a fluidized-bed reactor, and are there heated to a minimum temperature above the splitting or decomposition temperatures of the complex minerals containing arsenic and/or antimony and bismuth present in the concentrate. The oxygen potential in the reactor is regulated, so as to prevent the formation of non-volatile compounds of said impurities. The residence time of the concentrate in the reactor is controlled in a manner to ensure a given minimum elimination of the impurities. The gas and solids are withdrawn from the reactor and passed to a separating means, in which substantially impurity-free solids can be separated from the gas. The aforesaid minimum temperature and said regulated oxygen potential are maintained while the solids are in contact with said gas, and at least a part of the separated solids is returned to the reactor, for controlling the residence time, and an end product is removed from the fluidized bed and/or the separating means. The method is suitably carried out in one stage in a fluidized-bed reactor having a circulatory fluidized bed, although in certain cases the method can be carried out in two stages, in mutually separate reactors.