• Title/Summary/Keyword: 6불화황

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Effect of Injection Stage of SF6 Gas Incorporation on the Limitation of Carbon Coils Geometries (육불화황 기체의 주입단계에 따른 탄소코일 기하구조의 제약)

  • Kim, Sung-Hoon
    • Journal of the Korean Vacuum Society
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    • v.20 no.5
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    • pp.374-380
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    • 2011
  • Carbon coils could be synthesized on nickel catalyst layer-deposited silicon oxide substrate using $C_2H_2$ and $H_2$ as source gases and $SF_6$ as an additive gas under thermal chemical vapor deposition system. The characteristics (formation density and morphology) of as-grown carbon coils according to the injection stage of $SF_6$ gas incorporation were investigated. A continuous injecting of $SF_6$ gas flow could give rise to many types of carbon coils-related geometries, namely linear tub, micro-sized coil, nano-sized coil, and wave-like nano-sized coil. However, the limitation of the geometry as the nano-sized geometries of carbon coils could be achieved by the incorporation of $SF_6$ in a short time (1 min) during the initial deposition stage. A delayed injection of a short time $SF_6$ gas flow can deteriorate the limitation of the geometries. It confirms that the injection time and its starting point of $SF_6$ gas flow would be very important to determine the geometries of carbon coils.

Effect of Gas Phase Cycling Modulation of C2H2/SF6 Flows on the Formation of Carbon Coils (탄소 코일 생성에 대한 C2H2/SF6 기체유량의 싸이클릭 변조 효과)

  • Lee, Seok-Hee;Kim, Sung-Hoon
    • Journal of the Korean Vacuum Society
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    • v.21 no.3
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    • pp.178-184
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    • 2012
  • Carbon coils could be synthesized on nickel catalyst layer-deposited silicon oxide substrate using $C_2H_2$ and $H_2$ as source gases and $SF_6$ as an additive gas under thermal chemical vapor deposition system. The characteristics (formation density and morphology) of as-grown carbon coils were investigated as functions of additive gas flow rate and the cycling on/off modulation of $C_2H_2/SF_6$ flows. Even in the lowest $SF_6$ flow rate (5 sccm) in this work, the cycling on/off modulation injection of $SF_6$ flow for 2 minutes could give rise to the formation of nanosized carbon coils, whereas the continuous injection of $SF_6$ flow for 5 minutes could not give rise to the carbon coils formation. With increasing $SF_6$ flow rates from 5 to 30 sccm, the cycling on/off modulation injection of $SF_6$ flow confines the geometry for the carbon coils to the nanosized ones. Fluorine's role of $SF_6$ during the reaction was regarded as the main cause for the confinement of carbon coils geometries to the nano-sized ones.

Raman Spectroscopy and Molecular Modeling Study on the CH4 and SF6 Mixture Gas Hydrate Growth Behavior (라만 분광학과 분자모델링을 이용한 메탄 및 육불화황 혼합 가스 하이드레이트 성장 거동 연구)

  • Lim, Jun-Heok;Lee, Ju Dong;Park, Sung Soo;Eom, Ki Heon;Won, Yong Sun
    • Clean Technology
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    • v.19 no.4
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    • pp.476-480
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    • 2013
  • The growth behavior of $CH_4$ and $SF_6$ mixture gas hydrate has been investigated by a combined approach of Raman spectroscopy and molecular modeling. Raman spectroscopy results presented that when $CH_4$ is used only, $CH_4$ guest molecule is inserted first into the large cavity of the host structure built by $H_2O$ molecules and then into the small cavity to stabilize the whole gas hydrate structure. In the other hand, when $SF_6$ is mixed together, $SF_6$ is favored over (or competing with) $CH_4$ in being inserted into the large cavity and the small cavity still prefers $CH_4$ insertion. The calculations of binding energies clearly supported this. While $SF_6$ has a binding energy of -26.9 kcal/mol a little lower than -24.2 kcal/mol of $CH_4$ in the large cavity, $SF_6$ and $CH_4$ has 1.2 kcal/mol and -22.0 kcal/mol, respectively, in the small cavity. It indicates that the sizable $SF_6$ is not preferred in the small cavity but has a relative energetic advantage over $CH_4$ in the large cavity.

Separation and Recovery of F-gases (불화 온실 가스 저감 및 분리회수 기술의 연구개발 동향)

  • Nam, Seung-Eun;Park, Ahrumi;Park, You-In
    • Membrane Journal
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    • v.23 no.3
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    • pp.189-203
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    • 2013
  • F-gases, gases containing fluorine such as perfluorocarbons (PFCs), sulfurhexafluoride ($SF_6$), nitrogen trifluoride ($NF_3$) are known to have green house effects. Although the net emission rates of gases containing fluorine are much lower than those of $CO_2$, their contribution to global warming cannot be ignored because of their extremely high global warming potential (GWP). F-gases mainly have been used for a variaty of applications in the semiconductor/LCD processes and in the electric power distribution industry of the national key industry. One of practical solutions of controlling the emission rates of F-gases is to reuse by separation and recovery of F-gases of low concentration from the gases mixtures with nitrogen or air. This work investigates some methods for F-gases recovery and separation around the membrane-based process.

Experience and Recognition of Fluorides for Caries Prevention: Focusing on One University (일개 대학 재학생의 치아우식예방 불소이용법에 관한 경험과 인식)

  • Kim, Soo-Ryeon;Kim, Su-Hyun;Kim, Cho-Rong;Park, Jee-Won;Hwang, Soo-Jeong
    • Journal of dental hygiene science
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    • v.14 no.4
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    • pp.580-588
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    • 2014
  • Fluoride use is the best and widespread method for dental caries prevention. The aim of this study was to investigate experience and recognition of fluoride for caries prevention focusing on majors in one university. Four hundred twenty-four university students were selected by convenience sampling with informed consent and answered the questionnaire by self recording type. The subjects except dental hygiene students knew about purpose of fluoride use (84.6%), over the count fluoride rinse (63.2%), fluoride toothpaste (61.5%), professional fluoride application (56.4%) and water fluoridation (43.6%). They experienced over the count fluoride rinse (67.5%), school fluoride rinse (45.3%), professional fluoride application (30.8%), fluoride toothpaste (28.2%) and water fluoridation (12.0%). The main information paths about fluoride were university lectures among dental hygiene students and internet and mass media, followed by nurse-teachers among non dental hygiene students. The ratios of intention to use fluoride were: 67.8% in dental hygiene, 34.9% in health, 51.4% in non-health in case of professional fluoride application for oneself, 93.1% in dental hygiene, 48.0% in health, 50.4% in non-health in case of professional fluoride application for their children, 79.0% in dental hygiene, 51.3% in health, 55.8% in non-health in case of water fluoridation. The subjects to experience and recognize fluoride for caries prevention had more positive intention to use fluoride. The answers of students majoring in health or medical care were not different from non-health, except dental hygiene. Dental professionals should try to let the public know about fluoride use for caries prevention through mass media and internet as well as individual education in dental clinics.

A finite Element Analysis on the discharge characteristics of $SF_6$ gas ($SF_6$ 가스 방전 특성의 유한요소해석)

  • 최승길;심재학;강형부
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.13 no.3
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    • pp.265-272
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    • 2000
  • In this paper the corona discharge in SF$_{6}$ gas used as insulating material in lots o high voltage equipment, is simulated by finite element method with Flux-Corrected Transport(FCT) method. By application of proposed method the negative corona discharge characteristics in needle to plane electrode is analyzed with time step. For the accuracy of analysis the secondary electron emission by photon and ion are also considered as well as the accuracy of analysis the secondary electron emission by photon and ion are also considered as well as townsend first ionization and electron attachment. The calculated results show that the electric field intensity between anode and ion group is decreased as times go-by according to field distortion by those space charge. Accordingly the electron density is decreased strongly by the attatchment effect of SF6 gas so that the corona discharge becomes extinguished abruptly.y.

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A study on the discharge characteristics of $SF_6$ gas by Finite Element Methods in needle to plane electrode (유한요소법을 이용한 침대 평판 전극에서의 $SF_6$ 가스 방전 특성 해석)

  • 현정수;박필용;최승길;심재학;강형부
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 1999.05a
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    • pp.700-703
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    • 1999
  • Thls paper describes the process of corona discharge in $SF_6$ gas. The discharge characteristm such as electric field distribution, electron density, ion density and current denslty distribution are considered as time go by, The result show that difference between electronegative gas and nonelectronegative gas.

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Separation of $SF_6$ from $SF_6/N_2$ Mixtures Using Polymeric Membranes (고분자 분리막을 이용하여 $SF_6/N_2$ 혼합 기체에서 $SF_6$ 분리)

  • Ko, Young-deok;Lee, Hyung-Keun;Hong, Seong-Uk
    • Membrane Journal
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    • v.22 no.1
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    • pp.72-76
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    • 2012
  • $SF_6$ has an extremely high global worming potential (GWP). Therefore, there has been an effort to reduce the use of $SF_6$ and its emission into atmosphere. One possible solution for minimizing the use of $SF_6$ in electrical equipments is utilization of gas mixtures such as $SF_6/N_2$. The $SF_6$ concentration in the gas mixture varies from 10 to 60%. However, when the apparatus is repaired or dismantled, we have to recover $SF_6$ from the gas mixture. Since the boiling point of $SF_6$is low (${\sim}-60^{\circ}C$), the liquefaction method is difficult to apply. One possible alternative is the membrane separation technology. In this study, we investigated the $SF_6$ and $N_2$ permeation properties of 5 polymeric membranes. For example, permeability of $N_2$ in BOPP membrane at $25^{\circ}C$was 0.19 barrer, whereas that of $SF_6$ was only 0.0012 barrer, resulting in the selectivity of 158. An upper bound for $SF_6/N_2$ gas pair was suggested for the first time with n = -1.33 and k = 160 (barrer).

Effect of Reaction Temperature on the Geometry of Carbon Coils Formed by SF6 Flow Incorporation in C2H2 and H2 Source Gases (SF6-C2H2-H2 기체에 의해 생성된 탄소 코일 기하구조의 반응온도 효과)

  • Kim, Sung-Hoon
    • Journal of the Korean Vacuum Society
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    • v.21 no.1
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    • pp.48-54
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    • 2012
  • Carbon coils could be synthesized on nickel catalyst layer-deposited silicon oxide substrate using $C_2H_2$ and $H_2$ as source gases and SF6 as an additive gas under thermal chemical vapor deposition system. The geometries of as-grown carbon materials were investigated with increasing the reaction temperature as the increment of $25^{\circ}C$ from $650^{\circ}C$ up to $800^{\circ}C$. At $650^{\circ}C$, the embryos for carbon coils were formed. With increasing the reaction temperature to $700^{\circ}C$, the coil-type geometries were developed. Further increasing the reaction temperature to $775^{\circ}C$, the development of wave-like nano-sized coils, instead of nano-sized coils, and occasional appearance of micro-sized carbon coils could be observed. Fluorine in $SF_6$ additive may shrink the micro-sized coil diameter via the reduction of Ni catalyst size by fluorine's etching role. Finally, the preparation of the micro-sized carbon coils having the smaller coil diameters, compared with the previously reported ones, could be possible using $SF_6$ additive.