Showing papers on "Antimony published in 2001"

Chemical vapor deposition of antimony-doped metal oxide and the coated article made thereby

Abstract: Antimony doped tin oxide coatings on glass are prepared by providing a uniform, vaporized reactant mixture containing an organotin compound, an organoantimony compound, water and oxygen, and delivering the reactant mixture to the surface of the hot ribbon of glass, where the compounds react to form an antimony doped tin oxide coating. The antimony doped tin oxide coatings applied in accordance with the invention exhibit improved uniformity in thickness and sheet resistance over the coated surface of the glass, and increased coating/manufacturing efficiency.

Effects of bismuth and antimony additions on the microstructure and mechanical properties of AZ91 magnesium alloy

Abstract: The effects of bismuth and antimony additions on the microstructure and mechanical properties of AZ91 alloy have been studied. Results show that a small amount of bismuth or antimony additions to AZ91 increases the yield strength and creep resistance significantly at elevated temperatures up to 200°C. The highest creep resistance has been obtained from the alloy with combined additions of bismuth and antimony. The activation energies of the steady-state creep for AZ91-based alloys studied were close to that of pure magnesium self-diffusion, indicating that dislocation climb is responsible for the creep mechanism under the present conditions. Microstructural observations reveal that the additions of bismuth or antimony have the effect of refining the b (Mg17Al12) precipitates in as-cast alloys and suppressing discontinuous precipitation of the b phase effectively during the aging process. Some rod-shaped Mg3Bi2 or Mg3Sb2 particles distributed mainly at grain boundaries have been observed in the alloys with bismuth or antimony additions. Both Mg3Bi2 and Mg3Sb2 have a high thermal stability and play important roles in improving creep resistance of the alloys at elevated temperatures. © 2001 Elsevier Science B.V. All rights reserved.

Antimony and arsenic biogeochemistry in the western Atlantic Ocean

Abstract: The subtropical to equatorial Atlantic Ocean provides a unique regime in which one can examine the biogeochemical cycles of antimony and arsenic. In particular, this region is strongly affected by inputs from the Amazon River and dust from North Africa at the surface, and horizontal transport at depth from highlatitude northern (e.g., North Atlantic Deep Water) and southern waters (e.g., Antarctic Bottom and Intermediate Waters). As a part of the 1996 Intergovernmental Oceanographic Commission’s Contaminant Baseline Survey, data for dissolved As(III+V), As(III), mono- and dimethyl arsenic, Sb(III+V), Sb(III), and monomethyl antimony were obtained at six vertical profile stations and 44 sites alongthe 11,000 km transect from Montevideo, Uruguay, to Bridgetown, Barbados. The arsenic results were similar to those in other oceans, with moderate surface depletion, deep-water enrichment, a predominance of arsenate (>85% As(V)), and methylated arsenic species and As(III) in surface waters that are likely a result of phytoplankton conversions to mitigate arsenate ‘‘stress’’ (toxicity). Perhaps the most significant discovery in the arsenic results was the extremely low concentrations in the Amazon Plume (as low as 9.8 nmol/l) that appear to extend for considerable distances offshore in the equatorial region. The very low concentration of inorganic arsenic in the Amazon River (2.8 nmol/l; about half those in most rivers) is probably the result of intense iron oxyhydroxide scavenging. Dissolved antimony was also primarily in the pentavalent state (>95% antimonate), but Sb(III) and monomethyl antimony were only detected in surface waters and displayed no correlations with biotic tracers such as nutrients and chlorophyll a. Unlike As(III+V)’s nutrient-type vertical profiles, Sb(III+V) displayed surface maxima and decreased into the deep waters, exhibitingthe behavior of a scavenged element with a strongatmospheric input. While surface water Sb had a slight correlation with dissolved Al, it is likely that atmospheric Sb is delivered with combustion byproducts and not from mineral aerosols. In the Amazon Plume, antimony concentrations dropped substantially, and an Amazon River sample had a concentration (0.25 nmol/l) that was less than one-fourth those found in other major rivers. Usingthese river data, and estimates of atmospheric fluxes based on

Complexation effect of antimony compounds with citric acid and its application to the speciation of antimony(III) and antimony(V) using HPLC-ICP-MS

Abstract: In this work, a complexation effect of Sb compounds with citric acid was observed using electrospray mass spectrometry (ES-MS). It was found that both Sb(III) and Sb(V) could form complexes readily with citric acid in an aqueous solution at room temperature. These complexes were found to be very stable in various matrices (moat water and aqueous extracts of airborne particulate matter), therefore, a novel HPLC-ICP-MS analytical method for the speciation of Sb(III) and Sb(V) in environmental samples was developed by using the observed complexation effect. Sb(III)- and Sb(V)-citrate complexes were separated on a PRP-X100 anion-exchange column with 10 mmol l−1 EDTA–1 mmol l−1 phthalic acid (pH 4.5) as a mobile phase. All complexes were retained on the separation column, and none of them eluted in the solvent front. Low detection limits of 0.05 µg l−1 and 0.07 µg l−1 were achieved for Sb(III) and Sb(V), respectively. The calibration curves were linear over the range of 1.0–250 µg l−1 for the investigated Sb species. The precisions, evaluated by using the relative standard deviation (%RSD) with a 2 µg l−1 standard solution, were 1.8% and 3.3% for Sb(III) and Sb(V), respectively. Several advantages of the developed method, such as improving chromatographic separation, stabilizing Sb compounds in a water sample, and preventing Sb(III) from oxidizing to Sb(V) during the ultrasonic-assisted and microwave-assisted extraction of an airborne particulate matter (APM) sample using 26 mmol l−1 citric acid as an extraction solvent, and alleviating the adsorption of Sb compounds on the sample surface, were observed. The developed method enabled us to detect the most toxic Sb specie, Sb(III), in an APM sample for the first time.

Antimony oxide based glasses

Abstract: Glass formation has been investigated in binary systems based on antimony oxide as the main glass former: (100 - x)Sb 2 O 3-x WO 3 , (5 < x < 65), (100 - x)Sb 2 O 3-x SbPO 4 , (5 < x < 80) and (100 - x)Sb 2 O 3-x [Sb(PO 3 ) 3 ] n , (10 < x < 40). Ternary systems derived from the Sb 2 O 3 -WO 3 binary glass have also been studied: Sb 2 O 3 -WO 3 -BaF 2 , Sb 2 O 3 -WO 3 -NaF and Sb 2 O 3 -WO 3 -[Sb(PO 3 ) 3 ] n . Glass transition temperature ranges from 280°C to 380°C. It increases as the concentration in tungsten oxide or antimony phosphate increases. Refractive index is larger than 2. Tungsten-containing glasses are yellow in transmission and turn green at the largest WO 3 content. Optical transmission and temperatures of glass transition, T g , onset of the crystallization, T x , and maximum of crystallization, T p , have been measured using differential scanning calorimetry (DSC). These glasses have potential photonic applications.

Surface morphologies and electrical properties of antimony-doped tin oxide films deposited by plasma-enhanced chemical vapor deposition

Abstract: Antimony-doped tin oxide (ATO) films were deposited on Corning glass 1737 substrates by a plasma-enhanced chemical vapor deposition (PE-CVD) technique using a gas mixture of SnCl4–SbCl5–O2–Ar. Electrical properties and surface morphologies of these films were studied by varying the deposition temperature, input gas ratio, R[=(PSbCl5/PSnCl4)], and RF power. The PE-CVD method effectively enhanced the deposition rate and also improved the surface roughness of the deposit compared with thermal CVD. The antimony doped tin oxide films which had relatively good electrical properties were obtained at a deposition temperature of 450°C, an input gas ratio of R=1.12, and a RF power of 30 W. In addition, the studies on the morphological development of the films by AFM analysis suggested that higher input gas ratio and lower deposition temperature led to a decrease in the surface roughness of the deposited films.

Structure and Chemistry of Basal-Plane Inversion Boundaries in Antimony Oxide-Doped Zinc Oxide

Abstract: The atomic structure and the chemistry of basal-plane inversion boundaries in Sb2O3-doped ZnO were investigated using quantitative transmission electron microscopy techniques. Electron microdiffraction and high-resolution transmission electron microscopy were used to determine the orientation of the polar c-axis on both sides of the inversion boundary and the translation state between the inverted ZnO domains. Quantitative energy-dispersive X-ray spectroscopy combined with high-resolution transmission electron microscopy allowed us to determine the exact amount and the arrangement of antimony in the boundary layer. Inversion boundaries are head-to-head oriented with a displacement vector of the oxygen sublattice of RIB=⅓[01[Onemacr]0] – 0.102[0001]. The boundary plane consists of a highly ordered SbZn2 monolayer in which the cations occupy the octahedral interstices of the structure. In the octahedral boundary layer, zinc and antimony atoms constitute a honeycomb superstructure with a threefold (3m) in-plane symmetry.

Uptake of 85Sr, 134Cs and 57Co by antimony silicates doped with Ti4+, Nb5+, Mo6+ and W6+

Abstract: Antimony silicate ion exchangers were prepared by precipitation using two different procedures. A crystalline product with a pyrochlore structure (SbSi) was obtained by mixing SbCl5 in HCl with sodium silicate solution (pHfinal < 1) and heating it at 60 °C overnight. An amorphous material (KSbSi) formed when KSb(OH)6 was mixed with tetraethylorthosilicate (TEOS) in acidic conditions and heated overnight at 77 °C. In both cases the Sb∶Si molar ratio was 1∶1 in the starting mixture. The products showed high 85Sr selectivity in acidic conditions, distribution coefficients (KD) being 35 500 mL g−1 for SbSi and 19 700 mL g−1 for amorphous KSbSi in 0.1 M HNO3. They are very selective for 85Sr over a wide pH range, making them superior to other strontium selective ion exchangers such as zeolites, sodium titanates and silicotitanates, which function effectively only in neutral or alkaline conditions. The antimony silicate products had also a high or reasonable selectivity for 57Co, 59Fe and 63Ni, but the selectivity for 134Cs was low. An attempt was made to increase the selectivity for 134Cs by doping the antimony silicates with Ti4+, Nb5+, Mo6+ or W6+. The best results were obtained by doping SbSi with W, which resulted in a 10-fold increase in caesium selectivity. The original pyrochlore structure was retained in the W-doped SbSi.

Heterocyclopentadienyl Complexes of Group‐3 Metals

Abstract: Heterocyclopentadienyl complexes of group-3 metals (scandium, yttrium, lanthanum and the lanthanides, and uranium) are compounds in which one or more −CH units of a cyclopentadienyl-like ligand have been replaced by a heteroelement (nitrogen, phosphorus, arsenic, or antimony). These ligands can have very diverse substitution patterns, notably with bridged and cavitand-like structures. In addition to the classical η5-coordination behaviour, the heterocyclopentadienyl ligand can adopt a very large array of coordination patterns. Some complexes have a very promising chemistry since they have been found to activate small molecules such as nitrogen and ethylene.

N-type buried layer drive-in recipe to reduce pits over buried antimony layer

Abstract: A method of driving-in antimony into a wafer, including the following steps. A wafer is loaded into an annealing furnace/tool. The wafer having an area of implanted antimony ions. The wafer is annealed a first time at a first temperature in the presence of only a first nitrogen gas flow rate. The wafer is ramped-down from the first temperature to a second temperature in the presence of only an oxygen gas flow rate. The wafer is maintained in the presence of the of oxygen gas flow rate at the second temperature. The wafer is ramped-up from the second temperature to a third temperature in the presence of only the oxygen gas flow rate. The wafer is annealed a second time at the third temperature in the presence of only a second nitrogen gas flow rate to drive-in the antimony ions within the area of implanted antimony.

Eutectic growth mode in strontium, antimony and phosphorus modified hypoeutectic Al-Si foundry alloys

Abstract: The effect of strontium (Sr), antimony (Sb) and phosphorus (P) on nucleation and growth mode of the eutectic in hypoeutectic Al-10 mass%Si alloys has been investigated by electron back-scattering diffraction (EBSD) mapping. Specimens were prepared from a hypoeutectic Al-10 mass%Si base alloy, adding different levels of strontium, antimony and phosphorus for modification of eutectic silicon. By comparing the orientation of the aluminium in the eutectic to that of the surrounding primary aluminium dendrites, the solidification mode of the eutectic could be determined. The results of these studies show that the eutectic nucleation mode, and subsequent growth mode, is strongly dependent on additive elements. The EBSD mapping results indicate that the eutectic grew from the primary phase in unmodified and phosphorus-containing alloys. When the eutectic was modified by strontium or antimony, eutectic grains nucleated and grew separately from the primary dendrites.

Electrolytic hydride generation atomic absorption spectrometry for the determination of antimony, arsenic, selenium, and tin--mechanistic aspects and figures of merit.

Abstract: This article deals with the electrocatalytic and electrochemical mechanisms of hydride formation and their dependence on hydrogen overvoltage. A three-electrode-arrangement was used to determine the hydrogen overvoltage of different cathode materials (Pt, Au, Ag, glassy carbon, Cd, Pb, amalgamated Ag). The applicability of these cathode materials was tested for hydride formation using As(III), As(V), Sb(III), Sb(V), Se(IV), and Sn(IV). Glassy carbon is the most suitable cathode material for hydride generation with As(III), Sb(III), Se(IV), and Sn(IV). Hg–Ag is well suited for the production of stibine and arsine. As(III), As(V), Sb(III), and Sb(V) were all converted into their hydrides with efficiencies > 90%. A detection limit in the range of 0.11–0.13 μg L–1 for As and Sb (sample volume 200 μL) was obtained for cathode materials with a high hydrogen overvoltage. The precision of replicate measurements was better than 5% calculated as variation coefficient. The accuracy of the presented method was verified by analysis of certified reference materials and tissues of cancer patients. The recovery rates for As and Se were calculated to be 93–108%.

Determination of antimony in soils and vegetables by hydride generation atomic fluorescence spectrometry and electrothermal atomic absorption spectrometry. Optimization and comparison of both analytical techniques

Abstract: Two sensitive analytical atomic spectrometry methods, electrothermal atomic absorption spectrometry (ET-AAS) and hydride generation coupled to atomic fluorescence spectroscopy (HG-AFS), were optimized for determining total antimony in soils and plant (alfalfa) matrices. The dry soils were digested with HNO3–HCl–HF mixture, while, for the freeze dry alfalfa samples, HNO3–H2SO4–H2O2 or HNO3–H2O2 mixtures were used. The microwave oven digestion procedures chosen allowed the total dissolution of the matrices. The experimental parameters of both spectrometric techniques were optimized using standard solutions of Sb(III) and/or Sb(V), and digested solutions of soil and alfalfa samples. Since in the antimony determination by HG-AFS the kinetic of the hydride generation is dependent on the antimony oxidation state, a chemical reduction of Sb(V) to Sb(III) was carried out prior to the stibine generation. For this purpose, KI and L-cysteine were used as reducing agents, assaying different experimental conditions. The reduction of Sb(V) in plant solutions by a KI–ascorbic acid mixture can be performed at room temperature, while the Sb(V) reduction from soils solutions was quantitative when the procedure was accomplished in a microwave oven or at 90 °C in a water bath. For antimony determination by HG-AFS, the simple calibration mode was used, because this technique is less sensitive to interferences. For antimony determination by ET-AAS the use of a chemical modifier is unavoidable. Similar amounts of nickel or palladium were effective in stabilizing the antimony species present in soils and plant solutions; however, the best analytical signals were obtained using mixtures of this metals with NH4H2PO4 and citric acid. Due to the matrix interference for determining antimony by ET-AAS, the standard additions method was used. The accuracy of the proposed methods were assessed by analyzing two certified reference soils (CRM) from NIST, San Joaquin soil (SRM 2709) and Montana soil (SRM 2710) and a reference vegetal material, Virginia tobacco leaves (CTA-VTL-2). In allcases the results obtained by both techniques agreed with the certified values. Under the optimized conditions, a detection limit of 0.08 µg l−1 of Sb(III) was achieved by HG-AFS, with a precision of 4.3% for0.5 µg l−1Sb(III); the calibration graph was linear from 0.25 to 250 µg l−1. The detection limit obtained by ET-AAS, [injecting 20 µl Sb(III) solution and 10 µl chemical modifier mixture (2 µg Ni + 100 µg NH4H2PO4 + 50 µg citric acid)] was 9 pg Sb, with a precision of 4.7% for 100 pg Sb. The proposed methods were successfully applied to the Sb determination in soils and alfalfa samples, from the Valparaiso region in Chile. In all samples the antimony concentrations found were higher than the average reported for Sb concentration in soils and vegetable.

Ion liquids derived from Lewis acid based on titanium, niobium, tantalum, tin or antimony, and uses thereof

Abstract: The invention concerns ion liquids derived from the reaction of at least a halogenated or oxyhalogenated Lewis acid based on titanium, niobium, tantalum, tin or antimony with an organic salt of formula X+A- wherein A- is a halide or hexafluoroantimoniate anion and X+ a quaternary ammonium, quaternary phosphonium or ternary sulphonium cation. Said liquids are in particular useful for liquid phase HF fluorination of saturated or unsaturated compounds with C-CI bonds.

Pulsed laser deposition of skutterudite thin films

Abstract: Skutterudite (CoSb3 and IrSb3) thin films of high phase purity and crystallinity have been prepared by pulsed laser deposition. It is found that while the crystallinity of the films increases with increasing temperature, the phase purity decreases due to antimony volatility. The skutterudite phase can be stabilized to higher temperature by addition of excess antimony to the pulsed laser deposition target. Target-to-substrate distance must be optimized to obtain stoichiometric skutterudite films with low stress. A decrease in the flux of energetic particles and changes in particle stoichiometry with increasing distance caused by plume tilting results in lower film stress, but the diantimonide phase is nucleated if the distance is too large. It is possible to further reduce compressive stress by growing films in an inert background gas to decrease the flux of energetic particles. Overall, the highest quality films are grown from targets with excess antimony at a temperature of 270 °C with a target-to-substrate distance of 7 cm and a background argon gas pressure of 10 mTorr. The resistivity, mobility, and carrier concentration of these films are indicative of a degenerate p-type semiconductor with hole concentrations in the range of previously measured bulk values.

Two successive single crystal phase transitions involving the coordination sphere of antimony in PhSb(dmit), the first organo-antimony(III) dithiolene complex.

Abstract: PhSb(dmit) (dmit2-, 4,5-dithiolato-1,3-dithiole-2-thione), the first neutral organo-antimony dithiolene complex, has been synthesized by addition of PhSbCl2 on a suspension of Na2(dmit). The complex was characterized by spectroscopic (1H and 13C NMR and IR) methods and elemental analysis. Its crystal structure was determined by X-ray diffraction at room temperature in the monoclinic P21/c space group, with a = 12.580(3), b = 8.9756(18), c = 15.905(3) A, β = 109.06(3)°, V = 1697.5(6) A3, Z = 4. A coordinating THF molecule was found in the structure and the coordination geometry around the antimony atom is of distorted pseudopentagonal bipyramid type, if taking into account the Sb···O and secondary Sb···S interactions, as well as the stereochemically active 5s2 lone pair. The intermolecular Sb···S and S···S contacts, shorter than the sum of van der Waals radii of corresponding atoms, lead to the formation of a three-dimensional polymeric network in the solid state. A second X-ray diffraction experiment, per...