Papers by Keyword: Bismuth

Abstract: Archaeometallurgical copper-artefacts contain a wide variety of metal admixtures (e.g. Pb, Bi, As, Sb, Sn) which either originate from the ores or were intentionally added. When the melt solidifies, these elements can accumulate in different structural areas and form special phases. The different alloying elements also interact with each other. In order to be able to examine these interactions, model alloys with different elements (Pb, Bi, As, Sb, Sn) and concentrations (5 or 10 wt.% each) were produced. More simple alloys show a dendritic microstructure and the added elements accumulate in the interdendritic areas. This is clearly visible for Pb and Bi additions, as both metals are not soluble in copper. As and Sb form compounds with Cu which precipitate mainly in the interdendritic regions. Sn is soluble in Cu at lower concentrations and Cu-Sn phases are formed only at higher concentrations. The resulting microstructures become very complex if more elements are involved. Finally, they enable us to have a better understanding for microstructures of ancient copper alloys.

Abstract: Currently, X-rays are extensively utilized in various fields, particularly in medical diagnostics. X-rays have played a pivotal role in diagnosing diseases in patients. To ensure the safe use of radiation, it is essential to consider the effects of radiation on the personnel involved. Radiation protection must be implemented by minimizing exposure time and increasing the distance from the radiation source, alongside the use of radiation shielding, in accordance with the principle of As Low As Reasonably Achievable (ALARA). This study employed bismuth (Bi) as the shielding material due to its high radiation protection efficiency and low toxicity. Specifically, the radiation shielding properties of bismuth-metal phosphate glass were investigated, with the following chemical formula: (70-x)P₂O₅: 15NaF: 5ZnF₂: 10AlF₃: xBi₂O₃, where x represents the mole percentage of Bi₂O₃, with values of 0, 3, 6, 9, 12, and 15. The results indicated that the glass's ability to shield against X-rays improved as the quantity of bismuth oxide increased. This was evaluated through experiments conducted with an X-ray machine, adjusting the technique to 50-120 kVp, 100 mA, and 2s. As the mole percentage of bismuth oxide increased, the measured radiation values decreased. The linear attenuation coefficient (µ) increased, while the half-value layer (HVL) and tenth-value layer (TVL) decreased, and the mean free path (MFP) also decreased. When compared to standard materials, bismuth-metal phosphate glass demonstrated superior radiation shielding effectiveness. Based on the findings of this research, bismuth-based phosphate glass is considered a promising material for safe radiation shielding in future applications.

Abstract: A series of GaAsBi/GaAs multiple quantum well p-i-n diodes was grown using molecular beam epitaxy and the opto-electrical characterisations are presented. The result shows that devices experience low carrier extractions when light is absorbed due to hole trapping in the valence band. Carrier enhancement can be achieved by applying slight reverse bias when the measurement was taken. The absorption coefficient of the devices is confirmed to be similar with other Bi-based work. GaAsBi/GaAs multiple quantum well do have a lot of room for improvement especially on growth, structure and strain level of the material. If these components can be catered, GaAsBi can be a competitive alternative for 1 eV junction in multiple junction solar cells.

Abstract: Electrical conductance of Si(111)6×6-Tl and Si(111)β√3×√3-Bi surfaces has been monitored in the course of fullerenes deposition. It has been found that dependence of surface conductivity on the adsorbed C60 dose can be understood in terms of charge transfer induced by interaction of fullerene molecules and substrate which can be explained by the acceptor-like behavior of fullerenes. For the Si(111)6×6-Tl surface decreasing of conductance is connected with depletion of metallic bands of the Tl double layer. For the Si(111)β√3×√3-Bi surface the conductivity is almost unchanged with C60 dose, but due to the fact that C60 layer on this surface form close-packed hexagonal arrays in the layer-by-layer mode, it can be used as a template for alkali-induced ultra-thin fulleride formation.

Abstract: In the present paper we demonstrate and compare different properties of Bi and Bi_1-xSb_x thin films placed on polyimide (PI) substrate in frequency range from 0.2 to 1.0 THz. Bi films with a thickness of 40, 105 and 150 nm have been studied as well as 150 nm Bi_1-xSb_x solid solutions with Sb concentration of 5, 8, 12 and 15 %. An effective refractive index and permittivity of whole substrate/film structures have been derived by using terahertz time-domain spectroscopy (THz-TDS) method. These measurements have shown the positive phase shift in PI substrate with a thickness of 42 μm and revealed that it is barely transparent in studied frequency range, but the whole substrate/film structure provides the negative phase shift of terahertz wave. It was shown that the permittivity depends on mobility of charge carriers which is driven by film thickness and antimony content.

Abstract: Bismuth nanoparticles (BiNPs) are of interest in many applications such as imaging, antimicrobial agent, biosensors and electrochemical electrodes. However, synthesis of pure bismuth is difficult as bismuth tend to oxidise and form bismuth oxide that affects its properties. In this work, BiNPs were synthesised using hydrothermal method in an autoclave at 160°C. The effect of hydrazine (N₂H₄•H₂O) volume as reducing and capping agent was studied from 1.0-2.5ml with 3.6 Bi(NO₃)₃: 4.2 Polysodium 4-Styrene-Sulfonate: 50 H₂O (mass ratio). The produced BiNPs was used to modify indium tin oxide (ITO) substrates and tested as electrochemical heavy metal sensors to detect Pb and As. Pure BiNPs were successfully produced in all hydrazine volume. However, size and crystallinity of BiNPs were influenced by volume of hydrazine. Among these changeable compositions, the mass ratio of Bi(NO₃)₃ to N₂H₄•H₂O is the most important factor to form uniform size and shape of BiNPs. The addition of the reducing agent, N₂H₄•H₂O into the precursor solution promoted the subsequent reduction of Bi(III) and enabled the growth of BiNPs. Cyclic voltammetry (CV) in 0.002 mol/L of K₃Fe(CN)₆ electrolyte showed peak current responses obtained for BiNPs/ITO modified electrodes are larger than the bare ITO electrode, which were attributed to the fact that the electrochemical activities of ITO electrode increased by BiNPs surface modification. Stripping current responses of the Differential Pulse Anodic Stripping Voltammetry measurements were recorded for the determination of Pb(II) after a 300 seconds of deposition time at −1.2 V in 0.002 mol/L of acetate buffer solution with pH 4.5. Sensitivity response for the detection of Pb(II) was achieved in the range from 2.5 to 100 μg/L. The limit of detection (LOD) is 2.5 μg/L for Pb(II).

Abstract: Surface finish is coating layer plated on a bare copper board of printed circuit board (PCB). Among PCB surface finishes, Electroless Nickel/Immersion Gold (ENIG) finish is a top choice among electronic packaging manufacturer due to its excellent properties for PCB. However, the use of gold element in ENIG is very high cost and the black pad issue have not been resolved. Thus, by introducing an Electroless Nickel/Immersion Silver (ENImAg) as alternative surface finish hopefully can reduce the cost and offer better properties. The aim of this study is to investigate the effect of bismuth on interfacial reaction during reflow soldering between Sn-2.5Ag (SA25), Sn-3.4Ag-4.8Bi (SAB3448) and ENIMAG surface finish. Solder balls with sizes of 500μm diameters were used. The characteristics of intermetallic compound (IMC) were analyzed by using scanning electron microscopy (SEM), optical microscope and energy dispersive x-ray (EDX). After reflow soldering, the result revealed that only the irregular circle-shape of (Cu,Ni)₆Sn₅ IMC layer was formed at the interface and change to an irregular rod-like shape meanwhile the irregular needle-shape (Ni,Cu)₃Sn₄ was appeared after aging treatment. The result also indicated that, the grain size and thickness of IMC for SAB3448 is smaller and thinner compared to the SA25. The IMC thickness is proportional to the aging duration and IMC morphology for both solder are became thicker, larger and coarser after isothermal aging. No bismuth particle has been detected on SAB3448 solder during top surface examination. In addition, the Bi has been observed can reduce the grain size and the growth rate of IMC. Keywords: ENIMAG, reflow soldering, lead-free solder, intermetallic compound, bismuth

Abstract: The microstructures, mechanical properties, deformation mechanism, and recrystallization behavior of Cu-Zn-Bi alloys for cartridge case application have been investigated in this research. Cu-28Zn-1.1Bi wt. % alloys were produced by gravity casting and subjected to a homogenization – cold rolling – annealing sequences with variations on reduction level and annealing temperature. Samples characterizations were done through optical emission spectroscopy, optical microscopy, SEM-EDS imaging, and X-ray mapping modes, while hardness measurements were performed using micro Vickers method. The presence of Bi was found to increase cartridge brass hardness through a dispersoid strengthening mechanism in which dislocation movements are rendered by Bi particles. Higher deformation levels resulted in higher microhardness of the alloy. Recrystallization took place at grain boundaries and areas surrounding Bi dispersoid at 400 °C, while further heating resulted in grain growth phenomenon. Bismuth addition accelerated the recrystallization process in cartridge brass by a particles stimulated nucleation (PSN) mechanism.

Abstract: Bulk β-PdBi₂ layered material is known as a low-temperature superconductor. Recently, ultrathin films of this material consisting of dozens of triple layers were grown by molecular beam epitaxy and demonstrated structural, electronic and superconducting properties similar to those of bulk crystals. In this paper, we showed that thin film of β-PdBi₂ can be grown by alternative palladium and bismuth deposition and its electrical conductance was investigated at room temperature in comparison with the conductivity of bulk β - PdBi₂.

Abstract: The growth mechanisms of the nanomaterials such as Bismuth (Bi) are investigated since the understanding of the factors that affect the kinetics is fundamental to tune the crystal growth and thus to achieve new types of nanostructures and new material properties. It is concluded that Bi nano/microparticles are grown in following: classical nucleation growth theory and then most possibly unclassical oriented attachment via two kinds of effective and noneffective collisions with mass transfer. Polycrystalline Bi nano/micropowders having variety forms such as nanocrystal, nanoplate, and nano/microparticle have been synthesized successfully in a non-coordinating solvent by using hot-injection method. The X-ray powder diffraction (XRD), scanning and transmission electron microscopies (SEM and TEM), Fourier transform infrared (FTIR) spectroscopy, and energy dispersive X-ray (EDX) techniques are used to characterize the nanopowders. It is achieved that Bi particles synthesized during the reaction are accumulated via hit and stick mechanism and taken out of the solution as a conglomerate wet powder without need to centrifuge the solution. The Bi is formed in hexagonal phase with preferred orientation of (012) plane along with the XRD peak shape factor of ~0.44 which indicates more Lorentzian than Gaussian character. The average diameter of the synthesized nanocrystals is about 1.86 nm. The unit cell parameters calculated by Rietveld refinement are a=4.5474 Å and c=11.8612 Å in hexagonal phase. It is observed that hexagonal nanoplates are completely surrounded by nanocrystals. Twinkling of the spherical Bi nano/microparticles attached by nanoplates is observed under a white light illumination. All the steps from nucleation to the conglomerate structure formed are visualized and respectively proved experimentally.