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NiO/camphene 슬러리의 동결건조 및 수소환원 공정에 의한 Ni 다공체 제조
정재헌,오승탁,현창용,Jeong, Jae-Hun,Oh, Sung-Tag,Hyun, Chang-Yong 한국분말재료학회 (*구 분말야금학회) 2019 한국분말재료학회지 (KPMI) Vol.26 No.1
In this study, freeze drying of a porous Ni with unidirectionally aligned pore channels is accomplished by using a NiO powder and camphene. Camphene slurries with NiO content of 5 and 10 vol% are prepared by mixing them with a small amount of dispersant at $50^{\circ}C$. Freezing of a slurry is performed at $-25^{\circ}C$ while the growth direction of the camphene is unidirectionally controlled. Pores are generated subsequently by sublimation of the camphene during drying in air for 48 h. The green bodies are hydrogen-reduced at $400^{\circ}C$ and then sintered at $800^{\circ}C$ and $900^{\circ}C$ for 1 h. X-ray diffraction analysis reveals that the NiO powder is completely converted to the Ni phase without any reaction phases. The sintered samples show large pores that align parallel pores in the camphene growth direction as well as small pores in the internal walls of large pores. The size of large and small pores decreases with increasing powder content from 5 to 10 vol%. The influence of powder content on the pore structure is explained by the degree of powder rearrangement in slurry and the accumulation behavior of powders in the interdendritic spaces of solidified camphene.
CuO-SnO<sub>2</sub>/camphene 슬러리의 동결 및 소결조건이 Cu-Sn 다공체의 기공구조에 미치는 영향
김주형,오승탁,현창용,Kim, Joo-Hyung,Oh, Sung-Tag,Hyun, Chang-Yong 한국분말야금학회 2016 한국분말재료학회지 (KPMI) Vol.23 No.1
The present study demonstrates the effect of freezing conditions on the pore structure of porous Cu-10 wt.% Sn prepared by freeze drying of $CuO-SnO_2$/camphene slurry. Mixtures of CuO and $SnO_2$ powders are prepared by ball milling for 10 h. Camphene slurries with 10 vol.% of $CuO-SnO_2$ are unidirectionally frozen in a mold maintained at a temperature of $-30^{\circ}C$ for 1 and 24 h, respectively. Pores are generated by the sublimation of camphene at room temperature. After hydrogen reduction and sintering at $650^{\circ}C$ for 2 h, the green body of the $CuO-SnO_2$ is completely converted into porous Cu-Sn alloy. Microstructural observation reveals that the sintered samples have large pores which are aligned parallel to the camphene growth direction. The size of the large pores increases from 150 to $300{\mu}m$ with an increase in the holding time. Also, the internal walls of the large pores contain relatively small pores whose size increases with the holding time. The change in pore structure is explained by the growth behavior of the camphene crystals and rearrangement of the solid particles during the freezing process.
Cu 입자가 분산된 Al<sub>2</sub>O<sub>3</sub> 다공체의 제조 및 항균특성
유호석,김민성,오승탁,현창용,Yoo, Ho-Suk,Kim, Min-Sung,Oh, Sung-Tag,Hyun, Chang-Yong 한국분말야금학회 2014 한국분말재료학회지 (KPMI) Vol.21 No.1
In order to fabricate the porous $Al_2O_3$ with dispersion of nano-sized Cu particles, freeze-drying of camphene/$Al_2O_3$ slurry and solution chemistry process using Cu-nitrate are introduced. Camphene slurries with 10 vol% $Al_2O_3$ was frozen at $-25^{\circ}C$. Pores were generated by sublimation of the camphene during drying in air. The sintered samples at 1400 and $1500^{\circ}C$ showed the same size of large pores which were aligned parallel to the sublimable vehicles growth direction. However, the size of fine pores in the internal walls of large pores decreased with increase in sintering temperature. It was shown that Cu particles with the size of 100 nm were homogeneously dispersed on the surfaces of the large pores. Antibacterial test using fungus revealed that the porous $Al_2O_3$/1 vol% Cu composite showed antifungal property due to the dispersion of Cu particles. The results are suggested that the porous composites with required pore characteristics and functional property can be fabricated by freeze-drying process and addition of functional nano particles by chemical method.
금속산화물 복합분말의 동결건조 및 수소분위기 환원처리에 의한 Cu-Sn 다공체 제조
김민성,유호석,오승탁,현창용,Kim, Min-Sung,Yoo, Ho-Suk,Oh, Sung-Tag,Hyun, Chang-Yong 한국재료학회 2013 한국재료학회지 Vol.23 No.12
Freeze drying of a porous Cu-Sn alloy with unidirectionally aligned pore channels was accomplished by using a composite powder of CuO-$SnO_2$ and camphene. Camphene slurries with CuO-$SnO_2$ content of 3, 5 and 10 vol% were prepared by mixing with a small amount of dispersant at $50^{\circ}C$. Freezing of a slurry was done at $-25^{\circ}C$ while the growth direction of the camphene was unidirectionally controlled. Pores were generated subsequently by sublimation of the camphene during drying in air for 48 h. The green bodies were hydrogen-reduced at $650^{\circ}C$ and then were sintered at $650^{\circ}C$ and $750^{\circ}C$ for 1 h. XRD analysis revealed that the CuO-$SnO_2$ powder was completely converted to Cu-Sn alloy without any reaction phases. The sintered samples showed large pores with an average size of above $100{\mu}m$ which were aligned parallel to the camphene growth direction. Also, the internal walls of the large pores had relatively small pores. The size of the large pores decreased with increasing CuO-$SnO_2$ content due to the change of the degree of powder rearrangement in the slurry. The size of the small pores decreased with increase of the sintering temperature from $650^{\circ}C$ to $750^{\circ}C$, while that of the large pores was unchanged. These results suggest that a porous alloy body with aligned large pores can be fabricated by a freeze-drying and hydrogen reduction process using oxide powders.
김효정 ( Kim Hyo-jung ),현창진 ( Hyun Chang-jin ),이병재 ( Lee Byung-jae ),오세붕 ( Oh Se-boong ),김윤용 ( Kim Yun-yong ) 한국구조물진단유지관리공학회 2021 한국구조물진단유지관리공학회 학술발표대회 논문집 Vol.25 No.2
본 연구에서는 고연성 시멘트 복합체 SHCC(Strain Hardening Cement Composites) 배합으로 3D 프린팅하여 겹침 조건에 따른 적층성능을 검토하였다. 출력결과, 겹침 조건이 1겹일 경우보다 2겹으로 증가하였을 경우, 자립성과 부착성이 매우 양호하여 적층성이 우수한 것으로 나타났다. 출력노즐 크기 6mm와 겹침 조건 2겹일 경우 총 출력 크기가 12mm가 되므로, 겸침 조건 1겹과 출력노즐 크기 12mm 일 경우와 적층성이 동일 할 것으로 사료된다. 향후 출력노즐 크기에 따른 추가적인 연구가 필요한 것으로 판단된다.
다중센서 데이터 융합 기반의 자율 관리 능력을 갖는 상황인식처리 시스템의 설계
김영균 ( Young-gyun Kim ),현창원 ( Chang-won Hyun ),오장훈 ( Jang Hun Oh ),안효철 ( Hyo-chul Ahn ),김영수 ( Young-soo Kim ) 한국정보처리학회 2008 한국정보처리학회 학술대회논문집 Vol.15 No.2
다중 센서 데이터 융합(Multi-Sensor Data Fusion)에 기반하여 자율관리 기능을 갖는 상황인식시스템에 대해 연구하였다. 다양한 형태의 센서들이 대규모의 네트워크로 연결된 환경에서 센서로부터 실시간으로 입력되는 데이터들을 융합하여 상황인식처리를 수행하는 시스템으로 노드에 설치된 소프트웨어 콤포넌트의 이상 유무를 자동 감지하고 치료하는 자율관리(Autonomic management) 기능을 갖는다. 제안한 시스템은 유비쿼터스 및 국방 무기체계의 감시·정찰, 지능형 자율 로봇, 지능형 자동차 등 다양한 상황인식 시스템에 적용가능하다.
Cu-Cu<sub>2</sub>O계 공융액상을 활용한 Cu/AlN 직접접합
홍준성,이정훈,오유나,조광준,류도형,오승탁,현창용,Hong, Junsung,Lee, Jung-Hoon,Oh, You-Na,Cho, Kwang-Jun,Riu, Doh-Hyung,Oh, Sung-Tag,Hyun, Chang-Yong 한국분말야금학회 2013 한국분말재료학회지 (KPMI) Vol.20 No.2
In the DBC (direct bonding of copper) process the oxygen partial pressure surrounding the AlN/Cu bonding pairs has been controlled by Ar gas mixed with oxygen. However, the direct bonding of Cu with sound interface and good adhesion strength is complicated process due to the difficulty in the exact control of oxygen partial pressure by using Ar gas. In this study, we have utilized the in-situ equilibrium established during the reaction of $2CuO{\rightarrow}Cu_2O$ + 1/2 $O_2$ by placing powder bed of CuO or $Cu_2O$ around the Cu/AlN bonding pair at $1065{\sim}1085^{\circ}C$. The adhesion strength was relatively better in case of using CuO powder than when $Cu_2O$ powder was used. Microstructural analysis by optical microscopy and XRD revealed that the interface of bonding pair was composed of $Cu_2O$, Cu and small amount of CuO phase. Thus, it is explained that the good adhesion between Cu and AlN is attributed to the wetting of eutectic liquid formed by reaction of Cu and $Cu_2O$.
분말야금 및 주조형 니켈기 초내열합금 크리프 신뢰성의 초음파 모니터링
최찬양,송진헌,오세웅,김정석,권숙인,오승탁,현창용,변재원,Choi, Chan-Yang,Song, Jin-Hun,Oh, Se-Ung,Kim, Chung-Seok,Kwun, Sook-In,Oh, Sung-Tag,Hyun, Chang-Yong,Byeon, Jai-Won 한국분말야금학회 2012 한국분말재료학회지 (KPMI) Vol.19 No.3
An attempt was made to evaluate creep reliability of two commercial Ni-based superalloys by using ultrasonic wave. The materials include fine-grained PM alloy fabricated by mechanical alloying and subsequent hot isostatic pressing, and IN738LC cast alloy with a grain size of a few cm. Microstructural parameters (fraction of creep cavity and size of ${\gamma}^{\prime}$ precipitates) and ultrasonic parameters (velocity, attenuation) were measured to try to find relationships between them. Ultrasonic velocity decreased with creep cavity formation in PM alloy. On the other hand, no distinct changing trend of ultrasonic velocity was observed for IN738LC alloy. Ultrasonic attenuation was found to have a linear correlation with the size of ${\gamma}^{\prime}$ precipitates and was suggested as a potential parameter for monitoring creep reliability of IN738LC alloy.
고현창 ( Hyun Chang Ko ),장봉석 ( Bong Seok Jang ),김문범 ( Moon Bum Kim ),오창근 ( Chang Keun Oh ),권경술 ( Kyung Sool Kwon ) 대한피부과학회 2006 대한피부과학회지 Vol.44 No.9
Dermatofibrosarcoma protuberans is a tumor of intermediate malignancy, characterized by its aggressive local growth and marked propensity to recur after surgical excision. Dermatofibrosarcoma protuberans is most frequently located on the trunk or proximal extremities and rarely occurs on the face. In most cases, the tumor initially occurs as an asymptomatic, indurated plaque that slowly increases in size, and then develops multiple firm nodules. We report a case of a 39-year-old female who presented with a 10-year history of asymptomatic, brownish and hypopigmented plaques on the right side of her upper forehead. They gradually extended downwards and erythematous nodules appeared on the superior border of pre-existing brownish plaques 8 months ago. Histopathological examination of a nodule showed spindle-shaped cells with a storiform pattern in the dermis, and that of the plaques showed a parallel pattern. The tumor cells were stained positive for CD 34 upon immunohistochemical staining. (Korean J Dermatol 2006;44(9):1122~1125)