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탄소나노섬유 표면 구리 무전해 도금에 미치는 분산제와 도금 전처리의 영향
한준현,석현광,이상수,지광구,Han, Jun-Hyun,Seok, Hyun-Kwang,Lee, Sang-Soo,Jee, Kwang-Koo 한국분말야금학회 2009 한국분말재료학회지 (KPMI) Vol.16 No.2
This paper deals with the effects of the surfactant and preplate process (sensitization and activation) on electroless copper plating on carbon nano-fiber (CNF). Ultrasonic irradiation was applied both during dispersion of CNF and during electroless plating containing preplate process. The dispersion of CNF and flatness of the plated copper film were discussed based on the changes in surfactant concentration and preplate process time. It was clearly shown that high concentration of surfactant and long time of preplate process could promote the agglomeration of CNF and uneven copper plating on CNF.
논문 : 제조공정 ; 분무성형에서의 공정변수의 최적화 (1) -초기분무온도의 제어에 관하여
이재철 ( Jae Chul Lee ),석현광 ( Hyun Kwang Seok ),신돈수 ( Don Soo Shin ),이호인 ( Ho In Lee ) 대한금속재료학회 ( 구 대한금속학회 ) 1998 대한금속·재료학회지 Vol.36 No.6
Effect of the initial melt temperature on the microstructure of the sprayformed 2014 Al billet was studied with particular emphasis on the effect of superheating on the liquid fraction(FL) in the sprayed droplets. In order to determine the average liquid fraction within the sprayed droplets, the cooling rate and the flight time of droplets were calculated. The measured cooling rate of droplets was in the vicinity of ~104℃/sec and the flight time before impinging the preform ranges from 6 to 9 msec depending on the size of droplets. The obtained results from the experiments were in good agrement with those of theoretical models by P. Grant et al. and/or Lee et al. The liquid fraction of droplets did not vary significantly with the initial melt temperature such that FL was calculated to be 24% when Ti = 800℃ while FL = 19.5% when Ti = 720℃, resulting in considerable amount of porosity within the preform. Such a result indicates that the initial melt temperature control may not be effective for fabricating preforms with a minimal amount of porosity.
가스분무성형 Cu-10Cr 합금의 열적응고거동 및 미세조직
백경호 ( Kyeong Ho Baik ),강희수 ( Hee Soo Kang ),석현광 ( Hyun Kwang Seok ) 대한금속재료학회 ( 구 대한금속학회 ) 2006 대한금속·재료학회지 Vol.44 No.5
The application of spray forming process to the fabrication of highly alloyed Cu-Cr materials has been considered in this study, in order to achieve a fine scale microstructure. Solidification and microstructural evolution of Cu-10Cr alloy during spray forming have been rationalized by quantitative analyses of average enthalpy and liquid fraction in the preform surface layer. The results gave an insight to establish quantitative guidelines for process optimization and to understand microstructural evolution during spray forming. The microstructure of spray formed Cu-10Cr alloy was characterized by an equiaxed cell structure in which smaller sized Cr particles were formed at Cu cell boundaries. In contrast, the ingot-cast billet had a dendritic microstructure comprising coarse primary Cr dendrites and fine Cu-Cr eutectic. The Cr particles had a good thermal stability in the Cu matrix because no significant growth occurred after exposure at elevated temperatures up to 900℃. After hot extrusion, the spray formed Cu-10Cr alloy had a good combination of strength and ductility.
높은 자장하에서 자기공명 영상 왜곡이 완화된 생체용 Ti 복합재료
김성철 ( Sung Chul Kim ),김유찬 ( Yu Chan Kim ),석현광 ( Hyun Kwang Seok ),양석조 ( Seok Jo Yang ),손인진 ( In Jin Shon ),이강식 ( Kang Sik Lee ),이재철 ( Jae Chul Lee ) 대한금속재료학회 ( 구 대한금속학회 ) 2012 대한금속·재료학회지 Vol.50 No.5
When viewed using a magnetic resonance imaging (MRI) system, invasive materials inside the human body, in many cases, severely distort the MR image of human tissues. The degree of the MR image distortion increases in proportion not only to the difference in the susceptibility between the invasive material and the human tissue, but also to the intensity of the magnetic field induced by the MRI system. In this study, by blending paramagnetic Ti particles with diamagnetic graphite, we synthesized Ti100-xCx composites that can reduce the artifact in the MR image under the high-strength magnetic field. Of the developed composites, Ti70C30 showed the magnetic susceptibility of χ=67.6×10-6, which corresponds to 30% of those of commercially available Ti alloys, the lowest reported in the literature. The level of the MR image distortion in the vicinity of the Ti70C30 composite insert was nearly negligible even under the high magnetic field of 4.7 T. In this paper, we reported on a methodology of designing new structural materials for bio-applications, their synthesis, experimental confirmation and measurement of MR images.
펨토초 레이저 절삭 공정을 이용한 생분해성 나노섬유 표면 미세 패터닝 공정
정용우(Yongwoo Chung),전인동(Indong Jun),김유찬(Yu-Chan Kim),석현광(Hyun-Kwang Seok),정석(Seok Chung),전호정(Hojeong Jeon) 한국표면공학회 2016 한국표면공학회지 Vol.49 No.6
A biodegradable nanofiber scaffolds using electrospining provide fibrous guidance cues for controlling cell fate that mimic the native extracellular matrix (ECM). It can create a pattern using conventional electrospining method, but has a difficulty to generate one or more pattern structures. Femtosecond(fs) laser ablation has much interested in patterning on biomaterials in order to distinguish the fundamental or systemic interaction between cell and material surface. The ablated materials with a short pulse duration using femtosecond laser that allows for precise removal of materials without transition of the inherent material properties. In this study, linear grooves and circular craters were fabricated on electrospun nanofiber scaffolds (poly-L-lactide(PLLA)) by femtosecond laser patterning processes. As parametric studies, pulse energy and beam spot size were varied to determine the effects of the laser pulse on groove size. We confirmed controlling pulse energy to 5μJ-20μJ and variation of lens maginfication of 2X, 5X, 10X, 20X created grooves of width to approximately 5㎛-50㎛. Our results demonstrate that femtosecond laser processing is an effective means for flexibly structuring the surface of electrospun PLLA nanofibers.