• Analytical Science and Technology
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• v.8 no.4
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• pp.435-442
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• 1995

A matrix modification was studied for the determination of trace bismuth in water samples by graphite furnace atomic absorption spectrophotometry. The type and quantity of modifiers as well as the use of auxiliary modifiers were investigated to realize the efficient modification. Palladium was chosen as a single modifier. By the addition of palladium($5{\mu}g/mL$) to 100 ng/mL bismuth solution, the temperatures could be raised from $500^{\circ}C$ to $1,300^{\circ}C$ for the charring and from $2,000^{\circ}C$ to $2,200^{\circ}C$ for the atomization as well as the sensitivity and reproducibility were improved. The absorbance of bismuth was maximum and not changed in the range of Pd $3-25{\mu}g/mL$. And several materials were examined as an auxiliary modifier. The mixed solution of $1{\mu}g/mL$ palladium and $200{\mu}g/mL$ nickel have raised the temperatures as with $5{\mu}g/mL$ palladium only. The maximum absorbance of bismuth was shown in the nickel concentration range of $100-300{\mu}g/mL$ in $1{\mu}g/mL$ palladium modified system. With such optimum conditions, the trace amount of bismuth in several water samples could be determined by a calibration curve method, and good recoveries were also obtained.

• Journal of radiological science and technology
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• v.44 no.3
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• pp.189-194
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• 2021

This study was conducted to reduce the exposure dose to the breast and adjacent organs as the number of Mammography increased. Therefore, it has been designed a shield in lead, bismuth + tungsten, and bismuth that does not require to be equipped by the patient, in which each type of shield was compared and analyzed of radiation exposure dose to breast, thyroid, and eye. Using a mammography machine, optically stimulated luminescent dosimeter(OSLD) was inserted to bilateral breast, thyroid, and eye of a dosimetry phantom to measure dose radiated onto the phantom. Shielding device was made in different thickness of 2mm, 3mm, and 5mm and dose evaluation was performed by measuring the dose while using lead, bismuth, and bismuth + tungsten prosthesis. When each shields combined with shielding device, were compared of dose, all showed similar does reduction in the dose to breast, thyroid, and eye in both cranialcaudal and mediolateraloblique view. Based on the current study, bismuth and bismuth + tungsten can replace conventional lead shield and it is anticipated to safely and conveniently reduce radiation exposure to breast, thyroid, and eye with the shield that does not require to be equipped.

• Advances in nano research
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• v.3 no.3
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• pp.123-131
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• 2015

The unintentionally doped and bismuth (Bi) doped zinc oxide (ZnO) films were prepared by spray pyrolysis at $450^{\circ}C$ with zinc acetate and bismuth nitrate precursor. The n-type conduction with concentration $6.13{\times}10^{16}cm^{-3}$ can be observed for the unintentionally doped ZnO. With the increasing of bismuth nitrate concentration in precursor, the p-type conduction can be observed. The p-type concentration $4.44{\times}10^{17}cm^{-3}$ can be achieved for the film with the Bi/Zn atomic ratio 5% in the precursor. The photoluminescence spectroscopy with HeCd laser light source was studied for films with different Bi doping. The photocatalytic activity for the unintentionally doped and Bi-doped ZnO films was studied through the photodegradation of Congo red under UV light illumination. The effects of different Bi contents on photocatalytic activity are studied and discussed. Results show that appropriate Bi doping in ZnO can increase photocatalytic activity.

• Journal of Powder Materials
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• v.17 no.2
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• pp.136-141
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• 2010

Bismuth-telluride based $(Bi_{0.2}Sb_{0.8})_2Te_3$ thermoelectric powders were fabricated by two-step planetary milling process which produces bimodal size distribution ranging $400\;nm\;{\sim}\;2\;{\mu}m$. The powders were reduced in hydrogen atmosphere to minimize oxygen contents which cause degradation of thermoelectric performance by decreasing electrical conductivity. Oxygen contents were decreased from 0.48% to 0.25% by the reduction process. In this study, both the as-synthesized and the reduced powders were consolidated by the spark plasma sintering process at $350^{\circ}C$ for 10 min at the heating rate of $100^{\circ}C/min$ and then their thermoelectric properties were investigated. The sintered samples using the reduced p-type thermoelectric powders show 15% lower specific electrical resistivity ($0.8\;m{\Omega}{\cdot}cm$) than those of the as-synthesized powders while Seebeck coefficient and thermal conductivity do not change a lot. The results confirmed that ZT value of thermoelectric performance at room temperature was improved by 15% due to high electric conductivity caused by the controlled oxygen contents present at bismuth telluride materials.

• Journal of Powder Materials
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• v.30 no.4
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• pp.318-323
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• 2023

The thermoelectric effect, which converts waste heat into electricity, holds promise as a renewable energy technology. Recently, bismuth telluride (Bi2Te3)-based alloys are being recognized as important materials for practical applications in the temperature range from room temperature to 500 K. However, conventional sintering processes impose limitations on shape-changeable and tailorable Bi₂Te₃ materials. To overcome these issues, three-dimensional (3D) printing (additive manufacturing) is being adopted. Although some research results have been reported, relatively few studies on 3D printed thermoelectric materials are being carried out. In this study, we utilize extrusion 3D printing to manufacture n-type Bi_1.7Sb_0.3Te₃ (N-BST). The ink is produced without using organic binders, which could negatively influence its thermoelectric properties. Furthermore, we introduce graphene oxide (GO) at the crystal interface to enhance the electrical properties. The formed N-BST composites exhibit significantly improved electrical conductivity and a higher Seebeck coefficient as the GO content increases. Therefore, we propose that the combination of the extrusion 3D printing process (Direct Ink Writing, DIW) and the incorporation of GO into N-BST offers a convenient and effective approach for achieving higher thermoelectric efficiency.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.60-60
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• 2010

1-D nanostructured materials have much more attention because of their outstanding properties and wide applicability in device fabrication. Bismuth oxide($Bi_2O_3$) is an important p-type semiconductor with main crystallographic polymorphs denoted by $\alpha-$, $\beta-$, $\gamma-$, and $\delta-Bi_2O_3$[1]. Due to its unique optical and electrical properties, $Bi_2O_3$ has been extensively investigated for various applications in gas sensors, photovoltaic cells, fuel cells, supercapacitors[2-4]. In this study, $Bi_2O_3$ NWs were grown by two step annealing process: in the first step, after annealing at $270^{\circ}C$ for 10h in a vaccum($3{\times}10^{-6}$ torr), we can obtain the bismuth nanowires. In the second step, after annealing at $300^{\circ}C$ for 2h in $O_2$ ambient, we successfully fabicated $Bi_2O_3$nanowires.

• Journal of the Korea Convergence Society
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• v.9 no.7
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• pp.87-93
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• 2018

In this study, $^{99m}Tc$, $^{123}I$, $^{201}Tl$, $^{18}F$, and $^{131}I$, which are widely used in nuclear medicine, were transmitted through a bismuth shield. We investigated the shielding rates according to the type of radioisotope and the distance of measurement. For the experiment, 6 sheets of lead equivalent 0.25 mm Pb of bismuth shielding material were stacked one by one up to 1.50 mm as the thickness increased. The distance was 30 cm, 50 cm, and 100 cm, and the transmission dose was measured. As a result, the shielding rates was measured as the thickness increased, and the measured value decreased as the distance increased. The shielding rate of $^{123}I$ and $^{201}Tl$ was higher than $^{99m}Tc$, $^{18}F$ and $^{131}I$ showed lower shielding effect when there is a shielding material than when there is no shielding material due to high energy and ${\beta}$ rays. Based on the results of experiments, it would be helpful to reduce the exposure of nuclear medicine workers and to manage the exposure if bismuth shields are used depending on the type of radioisotope.

• Korean Chemical Engineering Research
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• v.58 no.3
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• pp.486-492
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• 2020

The method for preparing a perovskite-type bismuth ferrite (BFO) photocatalyst which reacts to visible LED light and the characteristics of visible light photocatalysis were investigated. BFO was prepared according to the sol-gel method. The prepared BFO consisted mainly of BiFeO₃ structure and formed a nano-sized crystal including Bi₂₄Fe₂O₃₉ structure. The BFO nano crystallines were identified from the UV-visible diffuse reflectance spectra to absorb UV and visible light up to about 600 nm. The bandgap of the BFO determined from the diffuse reflectance spectrum was about 2.2 eV. Formaldehyde was decomposed by the photoreaction of BFO photocatalysts with the visible light LED lamps with wavelengths of 585 nm and 613 nm. The narrow bandgap of BFO led to elicit BFO photocatalytic activity in visible LED light.

• Journal of the Korean Society of Radiology
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• v.16 no.3
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• pp.233-240
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• 2022

Research on the presence or absence of radiation shielding for FDM-type filaments has recently begun to be studied, but filaments with shielding capabilities are not sold in Korea, and not studies yet. Therefore, in this research, we will use HDPE (High Density Polyethylene) as a base material, select bismuth as a reinforcing material to manufacture a composite filament, evaluate the shielding ability, and provide basic data for the development of a radiation shielding composite material using 3D printing.A filament is produced by mixing Bismuth with an effective atomic number 83 with HDPE of PE series and adjusting the content of Bismuth to 20% wt, 30% wt, 40% wt. Compounded filaments were evaluated for their physical properties and shielding capabilities by ASTM evaluation methods. As the bismuth content increases, the density, weight, and tensile strength increase, and the shielding capacity is confirmed to be excellent. As a result of the radiation shielding capacity evaluation, it was confirmed that HDPE (80%) + Bi (20%) showed a shielding rate of 82% at 60 kV and a shielding rate of up to 94% or more at 40% bismuth content. In this study, we confirmed that it was possible to produce a radiation shield that is lighter than the metal particle-containing filaments. Furthermore, that have been shield radiation by using HDPE + Bi filaments, and radiation in the medical and radiation industries. The possibility of using it as a shielding complex was confirmed.

• Journal of Powder Materials
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• v.18 no.5
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• pp.423-429
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• 2011

Thermoelectric-thick films were fabricated by using a screen printing process of n and p-type bismuth-telluride-based pastes. The screen-printed thick films have approximately 30 ${\mu}m$ in thickness and show rough surfaces yielding an empty gap between an electrode and the thick film. The gap might result in an increase of an electrical resistivity of the fabricated thick-film-type thermoelectric module. In this study, we suggest a conductive metal coating onto the surfaces of the screen-printed paste in order to reduce the contact resistance in the module. As a result, the electrical resistivity of the thermoelectric module having a gold coating layer was significantly reduced up to 30% compared to that of a module without any metal coating. This result indicates that an introduction of conductive metal layers is effective to decrease the contact resistivity of a thick-film-typed thermoelectric module processed by screen printing.