• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.376.1-376.1
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• 2014

그래핀은 차세대 2차원 물질로서 지금까지 활발히 연구되어 왔으나 밴드갭이 없기 때문에 전자소자로서의 응용이 매우 제한적이다. 최근에 그래핀을 대체할 수 있는 물질로서 Transition Metal Dichalcogenides (TMDs)가 주목을 받고 있다. 특히, TMDs 중에서 $MoS_2$는 bulk일 때 indirect한 1.2 eV인 밴드 갭을 갖고 있으나, layer가 줄어들면서 direct한 1.8 eV인 밴드갭을 가진다. 국내외 여러 연구 그룹에서 $MoS_2$를 이용하여 제작한 Field Effect Transistor (FET)는 high-$\small{K}$ gate가 산입되지 않은 경우에 on-off ratio와 mobility가 각각 $10^6$와 약 $3cm^2/Vs$로 나타나고 있다. 이와 같이 아주 우수한 전기적, 광학적 특성을 갖는 소자 응용성을 가지고 있다. 최근까지의 연구결과들은 대부분 mechanical exfoliation method (MEM) 로 제작된 $MoS_2$ monolayer를 이용하였으나, 이 방법은 large scale 및 layer controllable에는 적합하지 않다. 본 연구에서는 대면적의 집적회로 응용에 적합한 chemical vapor deposition법을 이용하여 $MoS_2$를 성장하였다. 높은 결정성을 위해 sulphur (powder purity 99.99%)와 molybdenum trioxide(powder purity 99.9%)를 이용하고, Ar 가스 분위기에서 sulphur powder 및 molybdenum trioxide powder를 각각 $130^{\circ}C$ 및 $1000^{\circ}C$로 유지하며 $MoS_2$ 박막을 성장하였다. 성장된 $MoS_2$ 박막은 Atomic force Microscopy (AFM)을 통해 박막의 단차와 roughness을 확인하였다. 또한, X-ray Diffraction (XRD) pattern 분석으로 박막의 결정성을 확인하였으며, Raman Spectroscopy, X-ray Photoelectron Spectroscopy (XPS), Photoluminescence (PL) 측정으로 광학적 특성을 분석하였다.

• Analytical Science and Technology
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• v.5 no.3
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• pp.319-325
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• 1992

Plasma are melting method was used in making Mo-1.17 Ti-0.18 Zr-0.06 C ingot having over 99% of the theoretical density. Oxygen content herewith, decreased from the origin of 830ppm to 40ppm. After cold rolling of Mo alloy by 50%, the recrystallization behaviors were studied in the temperature range from $800^{\circ}C$ to $2100^{\circ}C$ for 1 hr isochronical holding time and also at $1400^{\circ}C$, $1500^{\circ}C$, $1600^{\circ}C$ for varying isothermal holding time 0 to 108000sec. The complete recrystallization temperature of Mo was $1400^{\circ}C$ but that of Mo alloy was $1700^{\circ}C$. 50%-1 hr recrystallization temperature of Mo alloy sheet was about $1500^{\circ}C$ and when compared to Mo there was an increase of over $300^{\circ}C$. The activation energy of recrystallization of Mo alloy sheet was 508kJ/mol.

• Proceedings of the Korean Society of Radiological Science
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• 2001.06a
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• pp.88.1-88.1
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• 2001

• Proceedings of the Korean Nuclear Society Conference
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• 1998.05b
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• pp.521-526
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• 1998

군분리공정의 관심대상 핵종인 잔존 U, MA인 Am, Np 및 백금족원소의 장수명핵종인 Tc을 방사성모의용액으로부터 효과적으로 분리할 수 있었다. 각 단위공정에 주입되는 용액의 농도를 기준으로 하여 볼 때 잔존 U 제거 공정에서 U, Np, 및 Tc의 회수율은 각각 99.1%. 31.9%, 및 99.5%였다. 개미산 탈질 공정에서는 탈질 용액의 총 산도를 0.4M 이하까지 감소시켰으며, 부수적으로 후속용매추출 공정 전반에 걸쳐 문제 핵종으로 작용하는 Zr, Mo, Fe 등을 각각 99.8%, 94.2%, 22.4% 침전 제거시킬 수 있었다. 마지막으로 DEHPA에 의한 AM/RE 상호분리 공정에서는 연속적인 선택적역추출에 의해 Am 및 Np 의 회수율은 각각 99.8% 및 98.2％ 정도였고, Am의 경우 7.6%읜 Fe및 81.6% 의 Mo가, Np의 경우 5.8%의 Fe이 불순물로서 여전히 존재하고 있다. 한편 RE 생성물에서는 97～99.9%의 RE가 회수 제거되었다.

• Nuclear Engineering and Technology
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• v.55 no.1
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• pp.304-309
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• 2023

In the last decade, nuclear medicine appears to be a good choice of medicine. ⁵⁸Co, ⁹⁹Mo, ⁹⁹Tc, ⁹⁹Re, ¹³³Xe and ¹⁸⁶Re are very important radionuclides for nuclear medicine. In this study, the excitation functions of ⁵⁸Ni (n, p) ⁵⁸Co, ⁹⁹Tc (n, p) ⁹⁹Mo, ⁹⁹Ru (n, p) ⁹⁹Tc, ¹³¹Xe (n, p) ¹³¹I, ¹³³Cs (n, p) ¹³³Xe and ¹⁸⁶Os (n, p) ¹⁸⁶Re nuclear reactions were calculated at neutron energies between 1 and 20 MeV using TALYS 1.95 and EMPIRE 3.2 nuclear codes. Furthermore, the cross sections were calculated with the empirical formula derived in our past study at 14-15 MeV. The obtained results were compared with the measured values in EXFOR library, and with the evaluated data of (JENDL-4.0/HE, JEFF-3.3, TENDL-2019, ENDF/B-VIII.0, IRDFF-II, JENDL/ImPACT-18). The results are in good agreement with those of the evaluated data libraries and experimental results and indicates that these radioisotopes can be produced by smaller cyclotrons.

• Journal of Radiation Protection and Research
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• v.9 no.2
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• pp.103-111
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• 1984

A convenient method of $^{99m}Tc$-methyl-ethyl-ketone (MEK) extraction technique was developed and a mobile $^{99m}Tc$-extraction generator was designed. The MEK extraction and the phase separation of $^{99m}TcO^-{_4}$ were carried out with a simple procedure in the same container. The shielding of $^{99}Mo$ radioactivity was made with one lead container. The system was simplified by shielding $^{99m}TcO_4{^-}({\gamma}_e=0.14\;MeV)$ separately. $^{99m}TcO^-{_4}\;in\;^{99m}Tc-MEK$ extract was recovered by adsorption and elution only, and therefore, the possibility of volatilization was reduced. The volume of $^{99m}TcO^{-}{_4}$-saline product was reduced to 1 ml by using a small alumina column and the column operation time was shortened. The separation time of $^{99m}Tc$ was reduced to 30 minutes, and the operation was carried out at the outside of the shielding. The system was designed to operate under the condition of bacteria-free.

• Journal of Korea Foundry Society
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• v.31 no.5
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• pp.288-292
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• 2011

In order to complement the drawbacks of quartz crucible such as fragile-like break and melt-leakage through open slit nozzle, a new PFC system has been developed using a common graphite crucible and plugging system. The u melt is fed on to the rotating a roll through slit nozzle by self-gravity. The new equipment was designed and manufactured successfully. An effort for optimizing all related parameter has been made. Then using the optimized parameters about 10 meters u foil having very thin thickness, which meets the target thickness of 130 ${\mu}m$ and enough width more than 60 mm could be made. The thickness homogeneity set improved, due to the lower eddy flowing of the melt flow the self-gravity feeding system.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 1998.05a
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• pp.99-100
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• 1998

• Journal of Radiopharmaceuticals and Molecular Probes
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• v.5 no.1
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• pp.3-10
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• 2019

The activities per volume of $^{188}Re$ and $^{99m}Tc$ from their generators are dependent on the specific activity of their mother nuclides $^{188}W$ and $^{99}Mo$ respectively. After a particular lapse of time, the eluted RI activity is exponentially reduced and thus cannot satisfy the needs of clinical application. The purpose of this study is to develop a $^{188}Re$ and $^{99m}Tc$ concentration device with a compact size that can extend the period of use as well as conveniently concentrate the RI. We designed the concentration module by including two-different check valves that do not required any manual on-off operations. In these concentration process, cation exchange resin embedded with Ag and anion exchange resins were used. After completing the concentrating step, the recovering yield was identified to be more than 93% for $^{188}Re$ generators and 88% for $^{99m}Tc$ generators. Moreover, all these procedures were done within 5 min.

• Nuclear Engineering and Technology
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• v.31 no.4
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• pp.365-374
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• 1999

A nuclear design of fission moly production targets for a research reactor, HANARO was peformed. It was found that the use of MCNP-4A, ORIGEN-2 code was reliable for the analysis of production characteristics of $^{99}$ Mo in a target fuel at an irradiation holes. A parametric study was done for the optimization of target location, target dimension, target shape and fuel materials. It was shown that a fuel thickness was the most sensitive parameters and electro-deposited target gave the highest 99Mo yield ratio. A pellet target with vibro-compaction powder, however, showed the largest production capacity and better engineering feasibility even with less yield ratio. Ten kinds of optimized target design for both LEU and HEU satisfied all the given design constraints. The most favorable design was the HEU ring-shaped electro-deposited target, considered the safety limit, production yield, chemical process easiness, yield ratio, and amount of radioactive waste.