Determination of the purity of bismuth and bismuth oxide by atomic absorption spectrometry

To enable high-speed analyses in the preparation of high-purity bismuth and bismuth oxide, we have developed an atomic absorption technique which ensures Ag, Cr, Cu, Fe, Mg, Mn, Ni, Pb, and Te detection limits in the range 2 × 10⁻⁷ to 2 × 10⁻⁵ wt %. The technique was used to assess the purity of bismuth and bismuth oxide in metal refining and oxidation steps.     

Application of vacuum refining in copper production

Abstract

his literature review was prepared in order to determine the state of the art with respect to the vacuum refining of copper. There have been numerous reported laboratory investigations of copper refining by vacuum treatment since the 1940s. Most studies have been carried out with the aim of eliminating deleterious impurities, such as arsenic, antimony, bismuth, lead, sulphur, and oxygen, from copper to levels appropriate to marketable grades, thereby improving the quality of the copper produced. It is interesting to note that the majority of work in this area has been carried out by Japanese and Soviet researchers: Japanese authors have generally tried to explain their results by means of kinetic or thermodynamic analyses, whereas the Soviet ones have merely given experimental results. This review contains three sections. In the first, the theory of vacuum treatment is discussed. The second presents information currently available (to 1980) on vacuum refining and is divided into three subsections, based on the type of copper treated, namely: (i) treatment of blister copper (or crude copper); (ii) treatment of anode copper and/or cathode copper; and (iii) treatment of copper matte. Finally, a patent survey has been carried out, which is reported in the third section.

MST/54     

Characterization of bismuth tri-iodide single crystals for wide band-gap semiconductor radiation detectors

Bismuth tri-iodide is a wide band-gap semiconductor material that may be able to operate as a radiation detector without any cooling mechanism. This material has a higher effective atomic number than germanium and CdZnTe, and thus should have a higher gamma-ray detection efficiency, particularly for moderate and high energy gamma-rays. Unfortunately, not much is known about bismuth tri-iodide, and the general properties of the material need to be investigated. Bismuth tri-iodide does not suffer from some of the material issues, such as a solid state phase transition and dissociation in air, that mercuric iodide (another high-Z, wide band-gap semiconductor) does. Thus, bismuth tri-iodide is both easier to grow and handle than mercuric iodide. A modified vertical Bridgman growth technique is being used to grow large, single bismuth tri-iodide crystals. Zone refining is being performed to purify the starting material and increase the resistivity of the crystals. The single crystals being grown are typically several hundred mm³. The larger crystals grown are approximately 2 cm³. Initial detectors are being fabricated using both gold and palladium electrodes and palladium wire. The electron mobility measured using an alpha source was determined to be 260±50 cm²/Vs. An alpha spectrum was recorded with one of the devices; however the detector appears to suffer from polarization.     

Biosynthesis of bismuth nanoparticles using Serratia marcescens isolated from the Caspian Sea and their characterisation

Today, synthesis of nanoparticles (NPs) using micro-organisms has been receiving increasing attention. In this investigation, a bismuth-reducing bacterium was isolated from the Caspian Sea in Northern Iran and was used for intracellular biosynthesis of elemental bismuth NPs. This isolate was identified as non-pigmented Serratia marcescens using conventional identification assays and the 16s rDNA fragment amplification method and used to prepare bismuth NPs. The biogenic bismuth NPs were released by liquid nitrogen and highly purified using an n-octanol water two-phase extraction system. Different characterisations of the purified NPs such as particle shapes, size and purity were carried out with different instruments. The energy-dispersive X-ray and X-ray diffraction (XRD) patterns demonstrated that the purified NPs consisted of only bismuth and are amorphous. In addition, the transmission electron micrograph showed that the small NPs formed larger aggregated NPs around <150?nm. Although the chemical syntheses of elemental bismuth NPs have been reported in the literature, the biological synthesis of elemental bismuth NPs has not been published yet. This is the first report to demonstrate a biological method for synthesising bismuth NPs and their purification with a simple solvent partitioning method.     

In vitro cytotoxicity of surface modified bismuth nanoparticles

This paper describes in vitro cytotoxicity of bismuth nanoparticles revealed by three complementary assays (MTT, G6PD, and calcein AM/EthD-1). The results show that bismuth nanoparticles are more toxic than most previously reported bismuth compounds. Concentration dependent cytotoxicities have been observed for bismuth nanoparticles and surface modified bismuth nanoparticles. The bismuth nanoparticles are non-toxic at concentration of 0.5 nM. Nanoparticles at high concentration (50 nM) kill 45, 52, 41, 34 % HeLa cells for bare nanoparticles, amine terminated bismuth nanoparticles, silica coated bismuth nanoparticles, and polyethylene glycol (PEG) modified bismuth nanoparticles, respectively; which indicates cytotoxicity in terms of cell viability is in the descending order of amine terminated bismuth nanoparticles, bare bismuth nanoparticles, silica coated bismuth nanoparticles, and PEG modified bismuth nanoparticles. HeLa cells are more susceptible to toxicity from bismuth nanoparticles than MG-63 cells. The simultaneous use of three toxicity assays provides information on how nanoparticles interact with cells. Silica coated bismuth nanoparticles can damage cellular membrane yet keep mitochondria less influenced; while amine terminated bismuth nanoparticles can affect the metabolic functions of cells. The findings have important implications for caution of nanoparticle exposure and evaluating toxicity of bismuth nanoparticles.     

Effects of addition of bismuth oxide and glass on the properties of lithium ferrite for ferrimagnetic pastes

Lithium ferrite, Li_0.5Fe_2.5O₄, has been prepared by decomposition of organometallic complexes at 800° C, and the optimization of heating schedule for conversion into ferrite has been studied. The effects of addition of glass, essential for adhesion of the ferrite film to alumina substrates, and bismuth oxide, as a sintering aid, on the properties and densification of lithium ferrite have been examined. X-ray diffraction, electron probe micro analysis (EPMA) and scanning electron microscopy (SEM) techniques have been used to study the solubility and distribution of bismuth oxide, grain growth and pore morphology. It has been found that the addition of bismuth oxide (up to 1.5 wt%) improves densification and increases resistivity of the lithium ferrite but the addition of glass causes a reduction of the resistivity. Although bismuth oxide forms a solid solution, it is not uniformly distributed throughout the ferrite phase. It is shown that the addition of bismuth oxide improves the insertion loss in microwave devices fabricated using ferrimagnetic pastes.     

The performance of a special geometry bismuth germanate escape suppressed spectrometer

The performance of a special geometry bismuth germanate escape suppressed spectrometer has been investigated. The spectrometer comprises a bismuth germanate suppression shield, a germanium detector and a bismuth germanate “catcher” detector positioned behind the germanium detector. The germanium detector is irradiated through a hole in one side of the suppression shield. The performance of the system has been measured with ²⁴¹Am, ¹³⁷Cs and ⁶⁰Co gamma-ray sources.     

The photocatalytic properties of bismuth oxide films prepared through the sol-gel method

In this research, thin bismuth oxide films were prepared through the sol-gel method. In order to study the influence of bismuth oxide crystal phases on the photocatalytic properties of bismuth oxide films, these films were annealed at different temperatures and then applied to decompose a typical textile industry pollutant (Rhodamine B). Scanning electron microscopy, X-ray diffraction and profilometry were applied to characterize these films. It has been found that different annealing temperatures cause the transformation of different bismuth oxide crystal phases, which leads to the different removals of Rhodamine B photolyzed using bismuth oxide films as photocatalyst.     

Novel solution route synthesis of low thermal conductivity nanocrystalline bismuth telluride

A novel synthesis approach based on a solution route has been developed for the fabrication of nanocrystalline bismuth telluride. The method consists of dissolving both bismuth and tellurium into the same organic solvent with the assistance of complexing agents and one-step coprecipitation of bismuth telluride. The synthesized nanocrystalline bismuth telluride powders possess rhombohedral crystal structure and are nanosheet/nanorod-like with an average size of between 30 and 40 nm. The thermal conductivity of the hot-pressed compact consolidated from the as-synthesized nanopowders is 0.39-0.45 Wm(-1)K(-1) in the temperature range of 323 to 523 K, which is at most one third of that of bulk bismuth telluride-based materials reported in the literature. Such low thermal conductivity of the investigated bismuth telluride is mainly attributed to substantially high concentration of grain boundaries provided by nanostructuring to scatter phonons intensively.     

合金熔剂精炼法制备太阳能级硅的研究进展

冶金法作为制备太阳能级硅的低成本技术,受到了光伏行业的广泛关注。其工艺主要包括酸洗、造渣、定向凝固、真空精炼、熔剂精炼等。其中,熔剂精炼由于操作温度低、杂质去除效率高,被视为最有可能实现大规模产业应用的低成本冶金技术之一。近年来,熔剂精炼法提纯太阳能级硅的研究发展迅速,科研工作者已经较系统地研究了Si-Al、Si-Sn、Si-Cu、Si-Fe、Si-Ca等不同合金熔剂体系杂质从硅中去除的行为和规律。综述了国内外学者利用不同合金体系去除冶金级硅中杂质的研究结果,特别关注了硅中杂质B、P的去除,同时也对熔剂精炼过程中熔剂金属与初晶硅的分离进行了概述。最后,指出了熔剂精炼提纯冶金级硅有待进一步深入研究的方向。     

Synthesis of opal-matrix nanocomposites containing bismuth chalcogenides

Three-dimensional opal-matrix nanocomposites containing various bismuth selenides and tellurides with a particle size from 25 to 150 nm have been produced by reducing oxygen-containing compounds with supercritical isopropanol. The bismuth: chalcogen ratio in the reduction products has been shown to correlate with that in the starting mixtures, indicating that targeted synthesis in opal pores can be used to controllably fabricate nanocomposites.     

Cluster effects on optical properties of glass-metal nanocomposites

Optical absorption characteristics in a glass-metal nanocomposite system involving bismuth metal have been analysed using effective medium theories with a model incorporating single strand chains andfcc clusters of metallic bismuth particles. The computed values show fair agreement with experimental data.     

Compositional distributions in classical and lead-free brasses

Compositional distributions in a classical brass and a lead-free, brass, containing bismuth, have been measured. Bismuth segregates strongly to the grain boundaries in pure copper but was not observed at the boundaries in the brass. An excess concentration of tin at the grain boundaries, due to coring, was observed and prevents the segregation of bismuth.     

A facile water-based process for preparation of stabilized Bi nanoparticles

Stabilized bismuth nanoparticles have been prepared by reducing bismuth chloride with hydrazine hydrate in the presence of sodium oleate under a facile water-based process. The obtained samples are investigated by X-ray diffraction, transmission electron microscopy (TEM) and differential thermal analysis and thermogravimetry (DTA/TG). The present results indicate that the bismuth nanoparticles are spherical, small diameter and in a high purity. In addition, measurement of water contact angle indicates that Bi samples are hydrophobic, which gives defense to samples from further oxidation, samples are steady in 6 months without obvious oxidation.     

Modeling shock loading of multicomponent materials including bismuth

The behavior of multicomponent mixtures and alloys, including bismuth, under high dynamic loads is described by the thermodynamically equilibrium (TEC) model. For condensed phases, the Mie–Grüneisen-type equation of state with regard to the Grüneisen coefficient depending on temperature is used, and gas in pores is among the main environmental components. The model used makes it possible to calculate the behavior of bismuth and materials based on this element (mixtures and alloys) for pressures higher than 6 GPa in one-velocity and one-temperature approximations on the assumption that the pressure is identical for all phases. The calculation results have been compared with the known experimental data and the model calculations performed by different researchers for porosity values varying from 1 to 3. It has been indicated that the model reliably describes shock loading of solid and porous bismuth as well as multicomponent alloys containing bismuth.     

Synthesis of single-crystalline bismuth nanobelts and nanosheets

Single-crystalline bismuth nanobelts have been synthesized successfully by solution-phase route, using ethylene glycol as reductant and solvent. It was speculated that the final morphology resulted from the layered structure of rhombohedral bismuth.     

Strong blue photoluminescence from single-crystalline bismuth oxychloride nanoplates

Single-crystalline bismuth oxychloride (BiOCl) nanoplates with in-plane sizes of 200-500?nm and a thickness of 15-25?nm are synthesized by a simple solution route. Strong blue photoluminescence centred at 455?nm (～2.72?eV) with very high quantum yields (Φ(PL)～0.4) has been observed at room temperature, representing the first report of strong room temperature photoluminescence from bismuth oxyhalide nanomaterials. It is envisaged that bismuth oxychloride could join the family of non-cadmium based high-efficiency emitters; it has promising applications in various fields, especially in light emitting diodes, lasers and solar cells.     

Features of the spectra of optical emission from high-frequency discharge plasma during bismuth ferrite sputtering

he spectra of optical emission from plasma of the RF discharge in oxygen during the sputtering of bismuth ferrite (BiFeO₃) and iron-containing alloy targets have been studied. Two anomalously intense lines of emission from iron atoms at 613.6 and 306.7 nm have been observed during the sputtering of bismuth ferrite, which are much less pronounced in the case of metal targets. The lines of emission from bismuth atoms are completely absent. A mechanism responsible for excitation of the anomalous emission lines during the sputtering of BiFeO₃ is proposed.

     

Effect of bismuth on the properties of Mn ferrite nanoparticles prepared by co-precipitation method

Nanoparticles of MnBi_xFe_2−xO₄(x = 0.0, 0.02, 0.04, 0.06) have been synthesized by a chemical co-precipitation method. X-ray diffraction analysis (XRD) reveals that bismuth exits in its Bi³⁺ and Bi⁵⁺ state. It was also observed that bismuth substitution enhances the grain growth and density. The dielectric constant (ε′) and the loss tangent (tan δ) increases with increase in bismuth content. Resistivity (ρ) and maximum magnetization (M) was found to decrease with increasing bismuth content.     

Specific features of high-power nanosecond ion beam action on polycrystalline bismuth

Specific features of surface relief formation on a polycrystalline bismuth target under the action of a high-power proton-carbon ion beam of nanosecond duration have been studied. Local melt extrusion from subsurface layers and its crystallization on the surface is observed, which is explained by a significant (3.35%) thermal expansion of bismuth during the transition from liquid to solid state.