• 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.

• Clean Technology
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• v.14 no.3
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• pp.184-192
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• 2008

Fluoride-type cleaning agents such as 2,2,2-trifluoroethanol (TFEA) and hydrofluoroethers (HFEs) do not destroy ozone in the stratosphere and have low global warming potential compared to hydrofluorocarbons(HFCs) and hydrochlorofluorocarbons (HCFCs). Especially, HFEs which have no flash point are paid attention as next generation type of cleaning agents for chlorofluorocarbons (CFCs) since they are safe in handling and have excellent penetration ability compared to hydrocarbon cleaning agents with low flash point. Here, the physical properties and cleaning abilities of fluoride-type cleaning agents such as TFEA, HFE-7100, HFE-7200, HFE-476mec, HFE-449mec-f, AE-3000 and AE-3100E and silicide-type cleaning agents such as trifluoroetoxytrimethylsilane (TFES) and hexamethyldisilazane (HMDS) were measured and compared with those of ozone destruction substances such as CFC-113 and 1,1,1-trichloroethane. They were also compared with toxic methylene chloride (MC) and isopropyl alcohol (IPA) which are now being used as an alternative cleaning agents. As a result, TFEA and HFEs had lower cleaning ability for removal of various soils compared to chloride-type cleaning agents, but they showed excellent cleaning ability fur fluoride-type soils. TFES and HMDS also showed excellent cleaning ability for silicide-type soils.

• 한국신재생에너지학회:학술대회논문집
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• 2007.11a
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• pp.581-584
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• 2007

(HFC(hydrofluorocarbon, 수소불화탄소)는 오존층 파괴 지수가 낮기 때문에 CFC(chlorofluorocarbon)의 대체 물질로 냉매와 발포제로 널리 사용되고 있는 물질이다. 하지만 HFC는 지구온난화 지수가 높은 기체이므로 대기중으로 방출되는 것을 막기 위해 분리/회수하여 재활용하는 것이 중요하다. 본 연구에서는 공기와 HFC의 혼합기체로부터 HFC만을 분리해 내는 방법으로 가스 하이드레이트 형성법을 제안하였다. 이 방법의 열역학적 타당성을 검증하기 위하여 질소+HFC-134a 혼합기체에 대하여 275-285 K의 온도 범위와 1-27 bar의 압력범위에 걸쳐서 가스 하이드레이트 상평형을 측정하였다. 질소는 가스 하이드레이트를 형성하기 위하여 0 $^{\circ}C$에서 150 bar 이상의 높은 압력이 필요한 반면 HFC-134a는 대기압에 가까운 낮은 압력이 필요하다. 두 기체의 평형 압력의 차가 크다는 것은 가스 하이드레이트 형성법을 이용할 경우 기체의 분리 효율이 매우 높다는 것을 나타낸다. 그리고, 본 실험을 통해서 얻어진 혼합기체의 하이드레이트상(H)-액상($L_W$)-기상(V)의 3상 평형선이 순수한 HFC-134a의 3상 평형선에 가깝게 위치하였다. 이는 가스 하이드레이트를 이용한 분리법이 낮은 압력에서 운전될 수 있음을 나타낸다. 이 분리법은 낮은 압력에서 운전되어 경제적일 뿐만 아니라 물 이외의 다른 매개체를 사용하지 않기 때문에 환경 친화적인 공정이라 할 수 있다.

• Korean Chemical Engineering Research
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• v.55 no.5
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• pp.704-710
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• 2017

Although the desalination technique using gas hydrate formation is at a development stage compared to the commercially well-established reverse osmosis (RO), it still draws attention because of its simplicity and moderate operational conditions especially when using refrigerants for guest gases. In this study, DFT (density functional theory)-based molecular modeling was employed to explain the energetics of the gas hydrate formation using HFC (hydrofluorocarbon) and HCFC (hydrochlorofluorocarbon) refrigerants. For guest gases, R-134a, R-227ea, R-236fa, and R-141b were selected and three cavity structures ($5^{12}$, $5^{12}6^2$, and $5^{12}6^4$) composed of water molecules were constructed. The geometries of guest gas, cavity, and cavity encapsulating guest gas were optimized by molecular modeling respectively and their located energies were then used for the calculation of binding energy between the guest gas and cavity. Finally, the comparison of binding energies was used to propose which refrigerant is more favorable for the gas hydrate formation energetically. In conclusion, R-236fa was the best choice in terms of thermodynamic spontaneity, less toxicity, and low solubility in water.

• 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.

• Journal of Korean Society of Environmental Engineers
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• v.34 no.10
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• pp.702-708
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• 2012

Tetrafluoromethane ($CF_4$) has been used as etching and Chemical Vapor Deposition (CVD) gases for semiconductor manufacturing processes. These gases need to be removed efficiently because of their strong absorption of infrared radiation and long atmospheric lifetimes which cause the global warming effect. Also, the wastewater including the fluorine is caused by of the ground water pollution. Long-term consumption of water containing excessive fluoride can lead to fluorosis of the teeth and bones. The wastewater including the fluorine among the by-product which is generated by using the waterjet plasma after destroying $CF_4$ by HF is generated. The system which can remove the hydrogen fluoride among the wastewater by using the electrocoagulation using this wastewater the aluminum electrode was developed. The operating condition such as initial pH, electrocoagulation time, wastewater flow rate, current density were investigated experimentally using a electrocoagulation. Through the parametric studies, the highest hydrogen fluoride destruction of 85% was achieved at 3.5 initial pH, 10 min electrocoagulation time, 10 mL/min wastewater flow rate and $159A/m^2$ current density.

• Journal of the Korean Vacuum Society
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• v.22 no.6
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• pp.277-284
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• 2013

Carbon coils could be synthesized using $C_2H_2/H_2$ as source gases and $SF_6$ as an incorporated additive gas under thermal chemical vapor deposition system. The Ni layer on the $SiO_2$ substrate was used as a catalyst for the formation of the carbon coils. The characteristics (formation densities, morphologies, and geometries) of the as-grown carbon coils on the substrate with or without the $H_2$ plasma pretreatment process were investigated. By the relatively short time (1 minute) $H_2$ plasma pretreatment on the Ni catalyst layered-substrate prior to the carbon coils synthesis reaction, the dominant formation of the carbon microcoils on the substrate could be achieved. After the relatively long time (30 minutes) $H_2$ plasma pretreatment process, on the other hand, we could obtain the noble-shaped geometrical nanostructures, namely the formation of the numerous carbon nanocoils along the growth of the carbon microcoils. This noble-shaped geometrical nanostructure seemed to play a promising role as the good catalyst support for holding the very tiny Ni catalyst grains.

• 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.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
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• 2007.06a
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• pp.39-42
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• 2007

최근 C-H 수소결합의 강한 상한 상호작용에 의하여 blue shift를 나타내는 현상이 보고 되고 있다. 비정질 불화탄소의 화학적 이동유기 절연막의 경우, 화학적 이동의 원인은 매우 서로 다른 원인에 발생하지만 이러한 물질의 상호작용은 친핵성 첨가반응에 의한 것임을 확인하였다. a-C:F 박막의 화학적 이동은 XRD 패턴에 의해서 결합 구조와 연관이 있으며, C-H 결합이 불소에 의한 끌림현상으로부터 발생되면서 비정질 구조로 변하는 것을 확인하였다.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.1276-1281
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• 2004

Nowadays CFCs and HCFCs refrigerants are restricted because it cause depletion of ozone layer. Accordingly, this experiment apply the ammonia gas and not CFCs and HCFCs for refrigerant to study the performance characteristic from the superheat control and improve the energy efficiency from the high performance. The condensing pressure of refrigeration system is increased from 15.0bar to 16bar by 0.5bar and superheat temperature is increased from $0^{\circ}C$ to $10^{\circ}C$ by $1^{\circ}C$ at each condensing pressure. As the result of experiment, when the superheat temperature is $0^{\circ}C$ at each condensing pressure, the refrigeration system has the high performance.