• Journal of the Korean Institute of Telematics and Electronics A
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• v.30A no.1
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• pp.31-43
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• 1993

Thermal behavior and $O_{2}$ plasma effects on residue and penetrated impurities formed by reactive ion etching (RIE) in CHF$_{3}$/C$_{2}$F$_{6}$ have been investigated using X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS) techniques. Decomposition of polymer residue film begins between 200-300.deg. C, and above 400.deg. C carbon compound as graphite mainly forms by in-situ resistive heating. It reveals that thermal decomposition of residue can be completed by rapid thermal anneal above 800.deg. C under nitrogen atmosphere and out-diffusion of penetrated impurities is observed. The residue layer has been removed with $O_{2}$ plasma exposure of etched silicon and its chemical bonding states have been changed into F-O, C-O etc.. And $O_{2}$ plasma exposure results in the decrease of penetrated impurities.

• Proceedings of the Korean Nuclear Society Conference
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• 1999.05a
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• pp.159-159
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• 1999

Application of the macro layer dryout model has been performed to predict CHF at inclined plates. For the identification of the detachment frequency of coalesced bubble, experiments have been performed with high-speed motion analyzer and bubble behaviors at inclined plates have been investigated. Based on the observed bubble behaviors, the detachment frequency of the coalesced bubble is measured and linear relations between detachment frequency and heat flux have been developed. In the case of 60$^{\circ}$ and 90$^{\circ}$ inclined plate, the detachment frequency decreases with the increase of heat flux. However, opposite trend has been identified in $30^{\circ}$ in-clined plate: the detachment frequency increases with the increase of heat flux. Using the cor- relation of macro layer thickness suggested by Haramura & Katto and the extrapolation of the identified linear relations, CHFs at different conditions have been predicted. According to the prediction results, CHF values are well predictable.

• ETRI Journal
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• v.11 no.1
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• pp.89-96
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• 1989

$C_2F_6$/$CHF_6$ 플라즈마를 이용한 실리콘 산화막의 반응성이온 식각공정시 실리콘 표면에 형성되는 고분자 잔류막과 근표면 손상영역을 X-선 광전자분광법(x-ray photoelectron spectroscopy)과 러더포드 후방산란법(Rutherford backscattering)을 이용하여 연구하였다. 표면 잔류막은 CF, $CF_2$, $CF_3$, $C-CF_x$, 그리고 C-C/C-H 등의 결합을 가진 불화탄소 고분자로 구성되어 있으며, 또한 C 1s와 Si 2p X-선 광선자 스펙트럼으로부터 C-Si 결합이 존재함을 확인하였다. 반응성이온 식각을 거친 실리콘 표면 구조의 연구결과, 불소와 탄소로 구성된 고분자막($<20 \AA$)이 극표면에 존재하며, 식각 후 공기중에 노출됨에 따라 고분자 잔류층으로 산소가 통과하여 기판을 산화시킴으로써 실리콘 산화막( $~10\AA$)이 그 아래에 형성되었음을 알았다. 그리고 실리콘산화막 아래에 탄소-산소 결합영역이 관찰되었다. 플라즈마 가스의 조성에서 $CHF_3$의 량이 증가함에 따라 고분자 잔류막의 두께가 증가하였으며, 본 연구의 실험조건에서 2분간 overetching한 시편의 경우에도 실리콘 표면 영역의 손상정도가 매우 적음을 발견하였다.

• Journal of the Korean Solar Energy Society
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• v.35 no.2
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• pp.53-62
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• 2015

Boiling heat transfer characteristic is very important in the various industries such as solar thermal system, power generation, heat exchangers, cooling of high-power electronics components and cooling of nuclear reactors. Therefore, in this study, boiling heat transfer characteristics such as critical heat flux (CHF) and heat transfer coefficient under the pool boiling state were tested using graphene nanofluids. Graphene used in this study, which have the same thermal conductivity but with different sizes. The experimental results showed that the highest the CHF and boiling heat transfer coefficient increase ratio for graphene nanofluids was at the 0.01 vol.%. At the present juncture, the CHF and boiling heat transfer coefficient increase ratio of the small-sized graphene nanofluids was higher than the large-sized graphene nanofluids.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.7
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• pp.724-728
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• 2004

This paper describes on RIE(Reactive Ion Etching) characteristics of 3C-SiC(Silicon Carbide) grown on Si(100) wafers. In this work, CHF$_3$ gas was used to form the polymer as a function of a side-wall for excellent anisotropy etching during the RIE process. The ranges of the etch rate were obtained from 60 $\AA$/min to 980 $\AA$/min according to the conditions such as working gas pressure, RF power, distance between electrodes and the $O_2$ addition ratio in working gas pressure. Under the condition such as 100 mTorr of working gas pressure, 200 W of RF power and 30 mm of the distance between electrodes, mesa structures with about 40 of the etch angle were formed, and the vertical structures could be improved with 50 % of $O_2$ addition ratio in reactive gas during the RIE process. As a result of the investigation, we know that it is possible to apply the RIE process of 3C-SiC using CHF$_3$ for the development of electronic parts and MEMS applications in harsh environments.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.10
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• pp.790-793
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• 2011

In this study, the surface modification for a silicon(Si) mold using $CHF_3$ inductively coupled plasma(ICP). The conditions under that plasma was treated a input ICP power 600 W, an operating gas pressure of 10 mTorr and plasma exposure time of 30 sec. The Si mold surface became hydrophobic after plasma treatment in order to $CF_x$(X= 1,2,3) polymer. However, as the de-molding process repeated, it was investigated that the contact angle of Si surface was decreased. So, we attempted to investigate the degradation mechanism of the accurate pattern transfer with increasing the count of the de-molding process using scanning electron microscope (SEM), contact angle, and x-ray photoelectron spectroscopy (XPS) analysis of Si mold surface.

• Journal of the Korea Safety Management & Science
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• v.19 no.4
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• pp.317-322
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• 2017

When the heat flux on the heating surface following changing heat condition in the boiling heat transfer system exceeds critical heat flux, the critical heat flux phenomenon is going over to immediately the film boiling area and then it is occurred the physical destruction phenomenon of various heat transfer systems. In order to maximize the safe operation and performance of the heat transfer system, it is essential to improve the CHF(Critical Heat Flux) of the system. Therefore, we have analysis the effect of improving CHF and characteristics of heat transfer following the nanoparticle coating thickness. As the results, copper nanocoating time are increased to CHF, and in case of nano-coatings are increased spray-deposited coating times more than in the fure water; copper nanopowder is increased up to 6.40%. The boiling heat transfer coefficients of the pure water are increased up to 5.79% respectively. Also, the contact angle is decreased and surface roughness is increased when nano-coating time is increasingly going up.

• Journal of Magnetics
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• v.12 no.2
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• pp.81-83
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• 2007

Etching of NiFe films covered with an organic photo-resist or Ti was successfully performed by an inductively coupled plasma-reactive ion etching (ICP-RIE) system using $CHF_3/O_2/NH_3$ discharges exchanging $CHF_3$ for $CH_4$ gas gradually. Experimental results showed that the organic photo-resist mask can be applied to the NiFe etching. In the case of the Ti metal mask, it was found that the etching-selectivity Ti against NiFe was significantly varied from 7.3 to ${\sim}0$ by changing $CHF_3/CH_4/O_2/NH_3$ to $CH_4/O_2/NH_3$ discharges used in the ICP-RIE system. These results show that the present RIE of NiFe was dominated by a chemical reaction rather than a physical sputtering.

• Journal of the Korean Society of Systems Engineering
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• v.16 no.2
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• pp.38-46
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• 2020

The accurate measurement of critical heat flux (CHF) in flow boiling is important for the safety requirement of the nuclear power plant to prevent sharp degradation of the convective heat transfer between the surface of the fuel rod cladding and the reactor coolant. In this paper, a System Engineering approach is used to develop a model that predicts the CHF using machine learning. The model is built using artificial neural network (ANN). The model is then trained, tested and validated using pre-existing database for different flow conditions. The Talos library is used to tune the model by optimizing the hyper parameters and selecting the best network architecture. Once developed, the ANN model can predict the CHF based solely on a set of input parameters (pressure, mass flux, quality and hydraulic diameter) without resorting to any physics-based model. It is intended to use the developed model to predict the DNBR under a large break loss of coolant accident (LBLOCA) in APR1400. The System Engineering approach proved very helpful in facilitating the planning and management of the current work both efficiently and effectively.

• Nuclear Engineering and Technology
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• v.54 no.10
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• pp.3962-3973
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• 2022

Several critical heat flux (CHF) correlations including the look-up table in the MARS code have been assessed for the prediction of CHF in a downward-flow narrow rectangular channel. For the assessment, we built an experiment database that covers pressures between 1.01 and 39.0 bar, gap sizes between 1.09 and 6.53 mm, mass fluxes up to 25,772 kg/m²s, and under one-sided and two-sided heating conditions. The results of the assessment showed that the Kaminaga correlation has the best overall prediction compared to others. However, because the correlation uses global variables, such as inlet and outlet subcooling and total heat transfer area, it is difficult to use in a system code. A new CHF correlation is then proposed by replacing the global variables in the Kaminaga correlation with local ones and adding correction factors to consider the effect of gap size, mass flux, and the number of heating walls. Additional correction factor is added to consider the effect of inlet subcooling. It is shown that the new one is better than the Kaminaga correlation and it is easy to implement to any system code.