• 한국추진공학회지
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• 제26권6호
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• pp.28-33
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• 2022

본 연구에서는 일반적으로 사용하는 Hydroxyl terminated polybutadiene(HTPB)계 고체 추진제의 경화 온도와 당량비 변경에 따른 경화 특성을 고찰하였다. 또한, Triphenyl bismuth(TPB), Maleic anhydride(MA) 그리고 Magnesium oxide(MgO) 촉매 시스템에서 이들의 비율 및 함량에 따른 경화 반응 영향도 확인하였다. 마지막으로 추진제 혼화 시 각 공정 별 수분을 투입하여 수분이 추진제 경화에 끼치는 영향을 확인하였다.

• JSTS:Journal of Semiconductor Technology and Science
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• 제6권2호
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• pp.119-123
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• 2006

This work presents the fabrication and characteristics of $Bi_2O_3/Si$ heterojunction prepared by rapid thermal oxidation technique without any postdeposition annealing condition. The bismuth trioxide film was deposited onto monocrystalline Si and glass substrates by rapid thermal oxidation of bismuth film with aid of halogen lamp at $500^{\circ}C/\;45$ s in static air. The structural, optical and electrical properties of $Bi_2O_3$ film were investigated and compared with other published results. The structural investigation showed that the grown films are polycrystalline and multiphase (${\alpha}-Bi_2O_3$ and ${\beta}-Bi_2O_3$). Optical properties revealed that these films having direct optical band gap of 2.55 eV at 300 K with high transparency in visible and NIR regions. Dark and illuminated I-V, CV, and spectral responsivity of $Bi_2O_3/Si$ heterojunction were investigated and discussed.

• Nuclear Engineering and Technology
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• 제54권6호
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• pp.1972-1981
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• 2022

A typical ferritic/martensitic (F/M) steel sheet was subjected to pulsed laser surface remelting (LSR) and corrosion test in lead-bismuth eutectic (LBE) at 550 ℃. There present two modification zones with distinct microstructures in the LSRed specimen: (1) remelted zone (RZ) consisting of both bulk δ-ferrite grains and martensitic plates and (2) heat-affected zone (HAZ) below the RZ, mainly composed of martensitic plates and high-density precipitates. Martensitic transformation occurs in both the RZ and the HAZ with the Kurdjumov-Sachs and Nishiyama-Wassermann orientation relationships followed concurrently, resulting in scattered orientations and specific misorientation characteristics. Hardnesses of the RZ and the HAZ are 364 ± 7 HV and 451 ± 15 HV, respectively, considerably higher than that of the matrix (267 ± 3 HV). In oxygen-saturated and oxygen-depleted LBE, thicknesses of oxide layers developed on both the as-received and the LSRed specimens increase with prolonging corrosion time (oxide layers always thinner under the oxygen-depleted condition). The corrosion resistance of the LSRed F/M steel in oxygen-saturated LBE is improved, which can be attributed to the grain-refinement accelerated formation of dense Fe-Cr spinel. In oxygen-depleted LBE, the growth of oxide layers is very low with both types of specimens showing similar corrosion resistance.

• 전기화학회지
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• 제8권1호
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• pp.17-23
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• 2005

$Bi_2O_3$를 첨가한 8M KOH용액에서 다결정 Ag전극의 전기화학적인 거동과 생성된 산화물들의 미세조직 변화를 분석하였다. $Bi_2O_3$를 첨가한 8M KOH용액에서 Ag 산화물뿐만 아니라 새로운 Ag-Bi-O화합물들이 생성되는 것을 알 수 있었다. Ag(I) 산화물 생성 전위 영역에서는 $Ag_2O$ 이외에, Ag-Bi-O 화합물이 핵 생성과 3D성장 과정에 의해서 생성되고, Ag(II)산화물 생성 전위 영역에서는 AgO뿐만 아니라 새로운 Ag-Bi-O화합물들이 핵 생성과 3D성장 과정에 의해서 생성되었다. Ag(I) 산화물 생성 전위에서 두 가지 형상의 Ag(I) 산화물이 생성되는 것을 SEM 조직에 의해 관찰하였다.

• Structural Engineering and Mechanics
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• 제85권1호
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• pp.29-53
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• 2023

High-strength shielding concrete against gamma radiation is a priority for many medical and industrial facilities. This paper aimed to investigate the gamma-ray shielding properties of high-strength hematite concrete mixed with silica fume (SF) with nanoparticles of lead dioxide (PbO₂), tungsten oxide (WO₃), and bismuth oxide (Bi₂O₃). The effect of mixing steel fibres with the aforementioned binders was also investigated. The reference mixture was prepared for high-strength concrete (HSCC) containing 100% hematite coarse and fine aggregate. Thirteen mixtures containing 5% SF and nanoparticles of PbO₂, WO₃, and Bi₂O₃ (2%, 5%, and 7% of the cement mass, respectively) were prepared. Steel fibres were added at a volume ratio of 0.28% of the volume of concrete with 5% of nanoparticles. The slump test was conducted to workability of fresh concrete Unit weight water permeability, compressive strength, splitting tensile strength, flexural strength, and modulus of elasticity tests were conducted to assess concrete's engineering properties at 28 days. Gamma-ray radiation of 137Cs emits photons with an energy of 662 keV, and that of 60Co emits two photons with energies of 1173 and 1332 keV were applied on concrete specimens to assess radiation shielding properties. Nanoparticles partially replacing cement reduced slump in workability of fresh concrete. The compressive strength of mixtures, including nanoparticles was shown to be greater, achieving 94.5 MPa for the mixture consisting of 7.5 PbO2. In contrast, the mixture (5PbO₂-F) containing steel fibres achieved the highest values for splitting tensile, flexural strength, and modulus of elasticity (11.71, 15.97, and 42,840 MPa, respectively). High-strength shielded concrete (7.5PbO2) showed the best radiation protection. It also showed the minimum concrete thickness required to prevent the transmission of radiation.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2006년도 동계학술연구발표회 및 자성 스핀트로닉스 국제학술대회
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• pp.116-117
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• 2006

• 한국세라믹학회:학술대회논문집
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• 한국세라믹학회 2003년도 추계총회 및 연구발표회 초록집
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• pp.189.1-189
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• 2003

• 한국표면공학회지
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• 제50권2호
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• pp.114-118
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• 2017

Bismuth telluride ($Bi_2Te_3$) and its alloys are well-known thermoelectric materials for ambient temperature applications. In this study, the dissolved Bi-Te precursor solution was used to synthesis metallic $Bi_2Te_3$ powder via ultrasonic spray pyrolysis and reduction process. The droplets of the Bi-Te precursor solution were decomposed to Bi-Te oxide powders by ultrasonic spray pyrolysis. The spherical $Bi_2Te_3$ powders were synthesized by reduction reaction in atmosphere of hydrogen gas at the temperature above $375^{\circ}C$ for 6h. The reduced $Bi_2Te_3$ powders have a mean particle size of $1.5{\mu}m$. The crystal structure of the powder was evaluated by X-Ray diffraction(XRD), and the microstructure with size and shape powders was observed by fieldemission scanning electron microscope(FE-SEM) and transmission electron microscope(TEM).

• Nuclear Engineering and Technology
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• 제55권5호
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• pp.1783-1790
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• 2023

Barium Bismuth Oxide Borate (BBOB) has been synthesized for the first time using solution combustion technique. SEM analysis reveal flower shape of the nanoparticles. The formation of the nanoparticles has been confirmed through XRD & FTIR studies which gives the physical and chemical structure of the novel material. The UV light absorption is observed in the range 200-300 nm. The present study highlights the radiation shielding ability of BBOB for different radiations like X/Gamma rays, Bremsstrauhlung and neutrons. The gamma shielding efficiency is comparable to that of lead in lower energy range and lesser than lead in the higher energy range. The bremsstrauhlung exposure constant is comparably larger for BBOB NPs than that of concrete and steel however it is lesser than that of lead. The beauty of BBOB nanoparticles lies in, high absorption of radiations and low emission of secondary radiations when compared to lead. In addition, the neutron shielding parameters like scattering length, absorption and scattering cross sections of BBOB are found to be much better than lead, steel and concrete. Thus, BBOB nanoparticles are highly efficient in absorbing X/Gamma rays, neutrons and bremsstrauhlung radiations.

• 한국결정성장학회지
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• 제19권2호
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• pp.66-69
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• 2009

The compositional dependence of bismuth iron oxides and effect of La-substitutions in the structure of $BiFeO_3$ compounds were investigated, which compounds were synthesized by conventional ceramic processing. It is shown that some of bismuth iron oxides including $BiFeO_3$ show the narrow single phase region. The effect of La-doping in $BiFeO_3$ was presented as disappearance of many impurity phases of Bi-Fe-O compounds. The lower electrical resistivity was obtained as those compositions of Fe deficient region and La-doped $BiFeO_3$. The saturation magnetization of La-doped $BiFeO_3$ was increased with La content. The dielectric dispersion was also observed for those Bi-Fe-O compounds with Fe deficient and La-doped $BiFeO_3$ at low frequencies under 1 kHz.