미립화 및 분무장치 : 고압 환경에서 극저온 제트의 분열에 대한 분석

이건웅 ( Keon Woong Lee ),김도헌 ( Do Hun Kim ),구자예 ( Ja Ye Koo ) 한국액체미립화학회 2013 한국액체미립화학회 학술강연회 논문집 Vol.2013 No.-

Cryogenic propellants are used to produce thrust in numbers of liquid rocket engines. The combustion chamber of the liquid rocket engines are at supercritical environment to the cryogenic propellants. So the phase of cryogenic propellants are changed from subcritical phase to supercritical phase while the propellants are injected to the combustion chamber. So it is necessary to study about the supercritical jet spray, but the study about the supercritical jet spray are still insufficient. For subcritical and super/near-critical jet tests, experimental system with zero-recess shear coaxial injector was constructed. LN2 and argon were selected for stimulants, shadowgraph method was used for jet visualization and the dark core length was used to discuss the experiment result. The dark core length was measured from post-processed instantaneous images. Image histogram was used to get rid of the pixel of background and injector tip, and the remains are the region of the dark core. The dark core length means the distance between injector and the first break of the jet. The dark core length of each case were averaged from over 50 instantaneous images. Because of the narrowness of the visualization area, the dark core length in the subcritical case was not observed/visualized. The measured dark core length in supercritical/near-critical cases were compared with momentum flux ratio and density ratio. The equations between the dark core length and momentum flux ratio as suggested from previous work was analysed, and the results were found in accord with the previous work.

A route to synthesis molybdenum disulfide-reduced graphene oxide (MoS₂-RGO) composites using supercritical methanol and their enhanced electrochemical performance for Li-ion batteries

Choi, Mugyeom,Koppala, Siva Kumar,Yoon, Dohyeon,Hwang, Jieun,Kim, Seung Min,Kim, Jaehoon Elsevier 2016 Journal of Power Sources Vol.309 No.-

<P><B>Abstract</B></P> <P>A simple and effective approach for the tight anchoring of molybdenum disulfide (MoS<SUB>2</SUB>) to the surface of supercritical-alcohol-reduced graphene oxide (SRGO) is developed. The MoS<SUB>2</SUB>-SRGO composites are synthesized by the one-pot deposition of MoO<SUB>2</SUB> on SRGO and simultaneous reduction of GO to SRGO in supercritical methanol followed by sulfurization. The obtained MoS<SUB>2</SUB>-SRGO composites contain a crystalline MoS<SUB>2</SUB> phase comprising 11–14 layers of MoS<SUB>2</SUB>. In addition, the composites have mesoporous structures with high porosities, ranging between 55 and 57%. In comparison with bare MoS<SUB>2</SUB> and SRGO, the MoS<SUB>2</SUB>-SRGO composites have enhanced electrochemical performances due to their mesoporous structures and the synergetic effect between MoS<SUB>2</SUB> and SRGO sheets. When tested as the anode in a secondary lithium battery, it shows high reversible capacity of 896 mAh g<SUP>−1</SUP> at 50 mA g<SUP>−1</SUP> after 50 cycles, a high rate capacity of 320 mAh g<SUP>−1</SUP> at a high charge-discharge rate of 2.5 A g<SUP>−1</SUP>, and long-term cycling of 724 mAh g<SUP>−1</SUP> at 50 mA g<SUP>−1</SUP> after 200 cycles. This unique synthetic approach effectively and tightly anchors MoS<SUB>2</SUB> nanoparticles to the SRGO surface, resulting in improved structural integrity, electron transfer efficiency between the SRGO sheets and MoS<SUB>2</SUB>, and Li-ion diffusion kinetics.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A simple supercritical methanol route is used for tight anchoring of MoS<SUB>2</SUB> to RGO. </LI> <LI> RGO prevents restacking of MoS<SUB>2</SUB> layer, resulting in mesoporous structure. </LI> <LI> The MoS<SUB>2</SUB>–RGO composite exhibits reversible capacity of 896 mA g<SUP>−1</SUP> at 50 mA g<SUP>−1</SUP>. </LI> <LI> Charge transfer kinetics of MoS<SUB>2</SUB>–RGO improved an order of magnitude than bare MoS<SUB>2</SUB>. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

초임계 이산화탄소를 이용한 미세전자기계시스템의 식각, 세정, 건조 연속 공정

민선기 ( Seon Ki Min ),한갑수 ( Gap Su Han ),유성식 ( Seong-sik You ) 한국화학공학회 2015 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.53 No.5

기존의 초임계 이산화탄소를 이용하여 식각 및 건조하는 공정은 고압 건조기 외부에서 용매를 이용하여 웨이퍼를 식각한 후 고압 건조기로 이동시켜 초임계 이산화탄소를 이용하여 세정 및 건조 하는 2단계 공정으로 구성되어 있다. 이 공정을 이용하여 본 연구에서 실험을 수행한 결과 점착 없이 식각, 세정 및 건조가 가능함은 확인되었지만, 반복 실험 결과 재현성이 떨어지는 것을 확인하였다. 이것은 외부에서 식각한 후 건조기로 이동할 때 식각용 용매가 기화하여 구조물이 점착되는 문제가 발생하기 때문이었다. 본 연구에서는 이 문제를 개선하기 위하여 웨이퍼를 이동시키지않고, 고압 건조기 내에서 초임계 이산화탄소를 이용하여 미세전자기계시스템 웨이퍼의 식각, 세정 및 건조공정을 연속적으로 수행하고자 하였다. 또한, 연속공정 수행 시 식각 공정에서 사용하는 이산화탄소의 상태(기체, 액체, 초임계상태)에 따른 영향을 알아보고자 하였다. 기체 이산화탄소를 이용하여 식각하는 경우(3 MPa, 25 oC)에는 점착 없는 식각, 세정 및 건조를 할 수 있었고 반복 실험을 통하여 공정의 최적화 및 재현성을 확인하였다. 또한 기존의 2단계로 이루어진 공정에 비해 세정용 용매의 양을 절감 할 수 있었다. 액체 이산화탄소를 이용하여 식각하는 경우(3 MPa, 5 oC)액체 이산화탄소와 식각용 공 용매(아세톤)간의 층 분리가 일어나 완전한 식각이 이루어지지 않았다. 초임계 이산화탄소를 이용하여 식각 하는 경우(7.5 MPa, 40 oC) 점착 없는 식각, 세정 및 건조를 할 수 있었고 기존 2단계 공정에 비해 세정용 용매의 절감 뿐 아니라 기체 이산화탄소를 이용한 연속공정에 비하여 공정시간도 단축시킬 수 있었다. The previous etching, rinsing and drying processes of wafers for MEMS (microelectromechanical system) using SC-CO2 (supercritical-CO2) consists of two steps. Firstly, MEMS-wafers are etched by organic solvent in a separate etching equipment from the high pressure dryer and then moved to the high pressure dryer to rinse and dry them using SC-CO2. We found that the previous two step process could be applied to etch and dry wafers for MEMS but could not confirm the reproducibility through several experiments. We thought the cause of that was the stiction of structures occurring due to vaporization of the etching solvent during moving MEMS wafer to high pressure dryer after etching it outside. In order to improve the structure stiction problem, we designed a continuous process for etching, rinsing and drying MEMS-wafers using SC-CO2 without moving them. And we also wanted to know relations of states of carbon dioxide (gas, liquid, supercritical fluid) to the structure stiction problem. In the case of using gas carbon dioxide (3 MPa, 25 oC) as an etching solvent, we could obtain well-treated MEMS-wafers without stiction and confirm the reproducibility of experimental results. The quantity of rinsing solvent used could be also reduced compared with the previous technology. In the case of using liquid carbon dioxide (3 MPa, 5 oC), we could not obtain well-treated MEMS-wafers without stic- tion due to the phase separation of between liquid carbon dioxide and etching co-solvent(acetone). In the case of using SC-CO2 (7.5 Mpa, 40 oC), we had as good results as those of the case using gas-CO2. Besides the processing time was shortened compared with that of the case of using gas-CO2.

Characterization of Alloy 600 joints exposed to a high-temperature supercritical-carbon dioxide environment

Lee, Ho Jung,Kim, Sung Hwan,Jang, Changheui Elsevier 2018 Materials characterization Vol.138 No.-

<P><B>Abstract</B></P> <P>Two types of Alloy 600 joints, such as diffusion-bonded joint and Alloy 182 fusion-weld, were exposed to supercritical-CO<SUB>2</SUB> environment at 550 and 650 °C (20 MPa) for 1000 h. The diffusion-bond region showed similar oxidation characteristics as parent Alloy 600, but the migration of diffusion bond line below oxide layer was observed due to the Cr-depletion induced recrystallization. For Alloy 182 fusion-weld, outer Mn-rich oxides (Mn<SUB>3</SUB>O<SUB>4</SUB> and MnCr<SUB>2</SUB>O<SUB>4</SUB>) and a small amount of inner SiO<SUB>2</SUB> mixed with chromia were formed due to high Mn and Si contents. The presence of SiO<SUB>2</SUB> in chromia suppressed carburization at the oxide/matrix interface, which resulted in the formation of an amorphous C layer between the outer Mn-rich oxide and inner Cr-rich oxide. For Alloy 182 fusion-weld, tensile property changes after exposure to supercritical-CO<SUB>2</SUB> environment were negligible.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Diffusion-bond showed similar corrosion and carburization behavior as parent matrix. </LI> <LI> Diffusion-bond line migrated due to the Cr-depletion induced recrystallization. </LI> <LI> Alloy 182 fusion-weld showed larger weight gains with outer Mn-rich oxides. </LI> <LI> The presence of SiO<SUB>2</SUB> in chromia suppressed carburization at the oxide/matrix interface. </LI> <LI> Despite larger weight gains, Alloy 182 fusion-weld showed negligible tensile property changes. </LI> </UL> </P>

Micronization of a poorly water-soluble drug, fenofibrate, via supercritical-fluid-assisted spray-drying

Kim Jeong-Soo,Park Heejun,강규태,Ha Eun-Sol,김민수,Hwang Sung-Joo 한국약제학회 2022 Journal of Pharmaceutical Investigation Vol.52 No.3

Purpose In the present study, fenofibrate (a model drug with poor aqueous solubility) was micronized using the supercriticalfluid- assisted spray-drying (SA-SD) process to improve dissolution and biopharmaceutical property. Methods Solid-state characterizations including particle size analysis and dissolution test were carried out. To identify the main effects of SA-SD process parameters (such as pressure, temperature, concentration of drug solution, supercritical carbon dioxide (SC-CO2) injection rate, and drug solution injection rate) on the morphology and particle size distribution of micronized fenofibrate particles, a 27−3 IV fractional factorial screening design was employed. Moreover, the effect of improved dissolution rate via micronization using SA-SD technology on the biopharmaceutical properties of fenofibrate was evaluated in a pharmacokinetic (PK) study in Sprague–Dawley rats. Results The results of the screening design showed that the mean particle size and distribution can be controlled by manipulating the drug solution concentration and CO2 injection rate. The SA-SD process resulted in a significant decrease in mean particle size (1.8–8.33 μm), as compared with that of unprocessed fenofibrate (24.2 ± 0.8 μm). There was a significant enhancement in the dissolution rate of micronized fenofibrate particles smaller than 5 μm compared to that of unprocessed fenofibrate. Moreover, an in vivo PK study in Sprague–Dawley rats showed that the increased dissolution rate improved biopharmaceutical properties (larger area under the curve and maximum serum concentration) of micronized fenofibrate than those of unprocessed fenofibrate. Conclusion Therefore, the SA-SD process is a useful micronization technology for improving both physicochemical and biopharmaceutical properties of poorly water-soluble drugs.

Comparison of YAG?:?Eu phosphor synthesized by supercritical water and solid-state methods in a batch reactor

이창하,이현철,Min-Jae Yoon,Jung-Hyun In 한국화학공학회 2006 Korean Journal of Chemical Engineering Vol.23 No.5

yttrium aluminum garnet (Y3Al5O12, YAG) doped with Eu (10 at% ) was synthesized by supercrit-ical water (SCW) and solid-state methods in a batch reactor. The crystals, morphologies and luminescent propertiesof the phosphors obtained from diferent pH conditions in the SCW were studied. Pure YAG phase was successfulysynthesized at the alkaline condition in the SCW without formation of intermediate phases, while the size and lumi-nescent property of YAG : Eu were strongly affected by pH condition. The luminescent intensity of YAG : Eu by theSCW method without further thermal treatment is stronger than that by the solid-state method with thermal treatment.

감껍질 열수 및 초임계 유체 추출물의 항아토피 효과

조병옥(Byoung Ok Cho),윤홍화(Hong Hua Yin),방숭주(Chong Zhou Fang),신재영(Jae Young Shin),하혜옥(Hye Ok Ha),김상준(Sang Jun Kim),정승일(Seung Il Jeong),장선일(Seon Il Jang) 한국식품과학회 2015 한국식품과학회지 Vol.47 No.3

본 연구에서는 고종시 감껍질을 열수 추출 및 초임계 유체 추출하여 아토피 피부염 증상 억제 효과를 밝히고, 항염 효능을 나타내는 기능성 소재로서의 이용 가능성을 알아보고자 하였다. 그 결과 육안 평가를 통해 피부의 홍반(erythema), 가려움과 피부의 건조상태(pruritus and dry skin), 부종과 혈종(edema and excoriation), 짓무름(erosion), 그리고 태선화(lichenification)와 같은 아토피 피부염 같은 증상이 AD 모델에서 증가하였지만, SPPE와 PPWE를 투여하였을 경우 완화되는 것을 확인할 수 있었으며, SPPE가 PPWE보다 더 뛰어난 효과를 나타내었다. 피부 두께와 염증 세포의 침윤은 AD 모델에서 크게 증가하였지만, SPPE와 PPWE를 투여하였을 경우 감소하는 것을 확인할 수 있었으며, SPPE가 PPWE보다 더 뛰어난 효과를 나타내었다. 혈청 중의 IgE와 IL-4의 수치를 측정한 결과, AD 모델에서 크게 증가하였으나 SPPE와 PPWE를 투여하였을 경우 감소하는 것을 확인할 수 있었으며, SPPE가 PPWE보다 더 뛰어나게 억제하는 효과를 나타내었다. 또한 RAW264.7 세포에 SPPE를 처리하였을 경우 염증매개 인자인 NO, PGE2, IL-6, IL-1β의 생성량이 유의적의로 감소하였고, PPWE의 경우 NO, PGE2, IL-1β의 생성을 억제한 반면 IL-6 생성 억제에는 영향을 나타내지 않았다. 이러한 염증 매개인자 억제 효능은 SPPE가 PPWE보다 더 뛰어나게 억제하는 것을 확인하였다. 따라서 감껍질 추출물은 아토피 피부염 증상 개선과 염증관련 질환 치료를 위한 기능성 천연물 소재로 유용하게 활용될 수 있을 것으로 판단된다. This study aimed to investigate the anti-atopic effect of hot water (PPWE) and supercritical-carbon dioxide fluid extract of persimmon peels (SPPE) on atopic dermatitis (AD)-like skin lesions in hairless mice. Histological analyses demonstrated that SPPE treatment more strongly inhibited the dermal infiltration of inflammatory cells in AD-like skin lesions than that by PPWE. Compared to PPWE, SPPE significantly decreased the dermatitis clinical score and the epidermal thickness and potently suppressed serum IgE and interleukin (IL)-4 production in hairless mice with AD. Furthermore, compared to PPWE, SPPE potently inhibited the production of nitric oxide, prostaglandin E₂, and proinflammatory cytokines such as IL-6 and IL-1β in lipopolysaccharide-stimulated RAW264.7 macrophages. These results suggested that SPPE exhibited anti-atopic dermatitis activity via the regulation of inflammatory responses.

Physicochemical characteristics and microbial safety of defatted bovine heart and its lipid extracted with supercritical-CO₂ and solvent extraction

Rahman, M. Shafiur,Seo, Jin-Kyu,Choi, Sung-Gil,Gul, Khalid,Yang, Han-Sul Elsevier 2018 FOOD SCIENCE AND TECHNOLOGY -ZURICH- Vol.97 No.-

<P><B>Abstract</B></P> <P>The demand for healthier meat and meat products with low fat is increasing rapidly to reduce cardiovascular and other chronic diseases. Bovine heart was defatted using supercritical-CO<SUB>2</SUB> (SC-CO<SUB>2</SUB>) at a constant temperature (40 °C) with three different pressures (20, 30, and 40 MPa) and using solvent extraction. The objective of this study was to produce a low-fat meat ingredient such as defatted bovine heart (DBH), and investigate its physicochemical characteristics and microbial safety, including the extraction yield and fatty acid composition of bovine heart lipid. SC-CO<SUB>2</SUB> treatment at high pressure results in higher removal of fat i.e. a higher extraction yield (93.60%). The DBH prepared using SC-CO<SUB>2</SUB> at 30 and 40 MPa had significantly higher proteins (82.07 and 82.67 g/100 g DBH, respectively), amino acids (80.39 and 79.05 g/100 g DBH, respectively), and minerals (2910 and 2901 mg/100 g DBH, respectively) and with lower microbial contents compared to those of the control and other DBHs. SC-CO<SUB>2</SUB>-extracted lipid had significantly higher unsaturated fatty acids (53.09 g/100 g fatty acids) than the control (45.62) and hexane-extracted lipid (44.65). SC-CO<SUB>2</SUB>-treatment leads to higher fat removal without deterioration of nutritional quality and significantly reduces the microbial content in defatted meals.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Bovine heart was defatted by SC-CO<SUB>2</SUB> and hexane to produce a low-fat meat ingredient. </LI> <LI> SC-CO<SUB>2</SUB> treatment at high pressure resulted in higher removal of fat. </LI> <LI> Protein, amino acid and mineral contents of bovine heart increased after SC-CO<SUB>2</SUB> treatment. </LI> <LI> SC-CO<SUB>2</SUB> process significantly reduced microbial contamination in defatted samples. </LI> <LI> SC-CO<SUB>2</SUB>–extracted lipids had significantly higher unsaturated fatty acids. </LI> </UL> </P>

초임계 이산화탄소 처리된 저지방 대두분말로 제조한 식물성 대체육의 이화학적 품질 특성 및 저장 안정성

표민정,이교연,한채연,박채은,최성길 한국식품영양학회 2023 韓國食品營養學會誌 Vol.36 No.4

Physicochemical properties and storage stability of plant-based alternative meat prepared with low-fat soybean powder (LPAM) treated by supercritical-CO2 and those of full-fat soybean powder (FPAM) were compared. Ash and crude protein contents were higher in LPAM than in FRAM. Water absorption capacity and oil absorption capacity were significantly higher in LPAM than in FPAM. Water binding capacity was higher in LPAM than in FPAM during a 20 days storage period at 5℃ and pH was significantly lower in LPAM than in FPAM after a 5~10 days storage period. Hardness, gumminess and chewiness significantly increased with the increase in the storage period, and the three were significantly higher in LPAM than in FPAM after 10 days and 20 days of storage. The acid value showed no remarkable difference according to the storage period in LPAM; however, it was significantly higher in FPAM than in LPAM after 20 days of storage. The peroxide value and TBA value were significantly increased according to the storage period, and were significantly lower iin LPAM than in FPAM during all the storage periods. Therefore, the use of low-fat soybean powder may be effective in improving oxidative stability during storage in the production of plant-based alternative meat.

초임계 함침법을 이용한 PEMFC용 Pt/Nafion 자가가습막의 제조 연구

신우균(Synn, Woo-Kyun),김화용(Kim, Hwa-Yong) 한국신재생에너지학회 2006 한국신재생에너지학회 학술대회논문집 Vol.2006 No.11

Pt/Nafion self-humidifying membranes for Polymer Electrolyte Membrane Fuel Cell(PEMFC) were synthesized via supercritical-impregnation methods. The Nafion 112 membranes were impregnated with Pt(II)(acetylacetonate)₂ from a supercritical carbon dioxide (scCO₂) solution at 80?C and 30MPa. After the impregnation, the pressure decreased slowly by releasing CO₂. And the Pt-impregnated Nafion membrane was converted Pt deposited Nafion membrane by reducing agent, sodium borohydride (NaBH₄) with various concentrations under 50?C and 2 hours. The prepared Pt-impregnated Nafion (Pt/Nafion) composite membrane were investigated by Electron Prove Micro analysis (EPMA) and X-rat Diffraction analysis (XRD) which showed distribution of Pt particle and Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) a which revealed morphology of surface of Pt/Nafion composite membrane. The performance of the Pt/Nafion 112 membranes was examined in PEMFC as aself-humidifyin membranes using purpose-built equipment.