• 한국재료학회지
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• 제12권12호
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• pp.904-910
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• 2002

Surface alloying using TiC, $TiB_2$ and VC ceramic particles on carbon steel has been performed using high voltage electron beam. Each type of ceramic particles was mixed with flux of Al and $MgF_2$ in 1 to 4 ratio. The microstructures of the surface alloyed layers consisted of melted region, interface region. heat affected region and the unaffected matrix. The surface layer of the TiC surface alloyed had a cubed primary and a eutectic type of TiC. $TiB_2$ in surface layer of $TiB_2$ surface alloyed were incompletely melted with$ TiB_2$ particles as observed before the alloying. On the surface layer of the VC surface alloyed, very well defined cell structure was observed with VC on the cell boundary. In addition, ~50 nm in diameter VC particles in high density were ubiquitous in the matrix. Those fine VC particles prominently improved the hardness and wear resistance of the surface layer of the VC surface alloyed.

• 한국재료학회지
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• 제12권12호
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• pp.897-903
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• 2002

Morphological evolution and growth mechanism at the solid/liquid interface during solidification were investigated in the Ni-base superalloy GTD111M by directional soldification and quenching(DSQ) technique. The experiments were conducted by changing solidification rate(V) and thermal gradient(G) which are major solidification process variables. High thermal gradient condition could be obtained by increasing the furnace temperature and closely attaching the heating and cooling zones in the Bridgeman type furnace. The dendritic/equiaxed transition was found in the G/V value lower than $0.05$\times$10{^3}^{\circ}C$s/$\textrm{mm}^2$, and the planar interface of the MC-${\gamma}$ eutectic was found under $17 $\times$ 10{^3}^{\circ}C$ s/$\textrm{mm}^2$. It was confirmed that the dendrite spacing depended on the cooling rate(GV), and the primary spacing was affected by the thermal gradient more than solidification rate. The dendrite lengths were decreased as increasing the thermal graditne, and the dendrite tip temperature was close to the liquidus temperature at $50 \mu\textrm{m}$/s.

• 한국주조공학회지
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• 제36권1호
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• pp.1-9
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• 2016

Improvement of the mechanical properties of a commercial aluminium casting alloy, A356, was achieved through an optimised combination of alloying elements, modification, and heat treatment. 0.7 wt.% Cu and an additional 0.2 wt.% Mg were added to an Al-7Si-0.35Mg alloy for strengthening at both room and elevated temperatures, whilst a subsequent decrease in the ductility was compensated for by the modification of eutectic Si by Sr addition at a level of up to 110 ppm. It was found that the dissolution of Cu-rich or Mg-rich phases could be maximised by solid-solutionising an alloy with 40 ppm Sr at $530^{\circ}C$, increasing the tensile and yield strengths to 350 MPa and 297 MPa, respectively, with a reasonably high strain of 5% after peak-aging at $210^{\circ}C$. Further addition of Sr up to 110 ppm is, however, more likely to interfere with the dissolution of the Cu-rich or Mg-rich phases during solid solution treatment, resulting in a slight decrease in both tensile and yield strengths at room temperature. Besides the Cu addition, such undissolved phases, on the other hand, may contribute to elevated temperature strength at $200^{\circ}C$.

• Composites Research
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• 제30권6호
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• pp.350-355
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• 2017

Phenylcyclohexyl (PCH) mesogen을 diglycidyl terephthalate의 2,5 위치에 치환시킨 새로운 액정성 에폭시 수지를 설계하였다. 이 물질의 액정성은 DSC(differential scanning calorimetry)와 POM(polarized optical microscopy)으로 분석하였다. 모든 액정성 에폭시 유도체는 가열 및 냉각 시에 모두 smectic상을 나타내는 enantiotropic한 성질을 나타내었다. 액정성 에폭시의 공융 혼합물을 통하여 액정 온도구간을 확장시켰다. 경화된 신규 액정성 에폭시는 $0.4W{\cdot}m^{-1}{\cdot}K^{-1}$의 높은 열전도도를 나타냈다. 높은 열전도도를 갖는 신규 액정성 에폭시는 전자 및 디스플레이용 복합소재로 이용될 것으로 기대된다.

• 전기화학회지
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• 제5권2호
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• pp.62-67
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• 2002

용융탄산염 연료전지의 성능 저하와 수명 감소의 원인이 되는 부식 현상을 규명하고자 분리판 재료로 가장 널리 사용되고 있는 AISI-type 316L stainless steel을 대상으로 62Li/38K계 용융탄산염 내에서의 부식 실험을 수행하였다. 부식의 형태 및 속도는 환경에 의하여 다양하게 변화하게 되며, 용융탄산염 내에서 AISI-type 316L stainless steel의 부식 속도는 부식 반응에 의하여 형성되는 부동태 산화막의 안정성에 의하여 크게 영향을 받는다. 전기화학적 분극 거동을 분석한 결과 용융탄산염 연료전지의 anode가슨 분위기에서는 안정한 부동태 산화막이 형성되지 않았다. 순환 전압전류법과 정전위법을 이용한 부식 생성물의 X-ray분석을 통하여 특정한 전기화학적 전위 영역에서 반응기구와의 인과관계를 규명하고 다양한 형태의 부식 반응들을 분리해 내었다.

• Archives of Plastic Surgery
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• 제36권1호
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• pp.113-117
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• 2009

Purpose: Although Hydrofluoric acid(HF) is not a strong acid when compared to other hydrogen halides, it is a feared corrosive and is particularly dangerous at higher concentrations. HF burns are characterized by symptoms, often delayed and localized with diluted HF solutions, to include erythema, edema and severe pain. Pain, a well known symptom following exposure to calcium binding. And, EMLA$^{(R)}$ cream is a topical formulation based upon the eutectic mixture of lidocaine and prilocaine and is used in clinical settings to provide pain relief undergoing superficial surgical procedures. The aim of this study is to evaluate effects of EMLA$^{(R)}$ cream, pain - control dressing on the treatment for HF injury wound. Methods: From June 2007 to June 2008, this study was carried out with 10 patients who had HF partial thickness burns. We were applied topically EMLA$^{(R)}$ cream to injured wound with vaseline gauze and 10% calcium gluconate wet gauze dressings. As a principle, in the emergency treatment, partial or complete removal of the bullae along with copious washing with normal saline was done, depending on the degree of HF invasion of the distal digital extremities. The effect of dressing was investigated by visual analogue pain scale. Results: We therefore reviewed 10 cases of HF - induced pain and pain relief treatment principle. The 10 cases who came to the hospital nearly immediately after the injury healed completely without sequelae and EMLA$^{(R)}$ related complications. Conclusion: Proper initial treatment of HF burns are important, if not promptly recognized and properly treated, for produce serious injury. Topical EMLA$^{(R)}$ cream remain a powerful, new advancement for minimizing HF - related pain during dressing procedures. When used appropriately, topical EMLA$^{(R)}$ cream can provide a safe and effective alternative to other forms of HF - pain control treatment.

• 한국진공학회지
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• 제13권3호
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• pp.127-131
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• 2004

BGA(ball grid array) package에서 솔더볼의 피로강도에 대한 솔더 조성에 대한 영향을 조사하기 위하여 패키지 신뢰성 시험을 실시하였다. 공정조성 솔더 63Sn/37Pb, 62Sn/36Pb/2Ag, 63Sn/34.4Pb/2Ag/0.5Sb 솔더를 이용하여 제조된 시편을 MRT Lv3 (moisture resistance test level) 조건에서 전처리 후 T/C(temperature cycle test) 실험을 수행하였다. 각각의 신뢰성 시험에 대하여 전단강도를 측정하였으며, 미세 조직 사진을 얻었다. 또한, SEM (scanning electron microscope)과 EDX (energy dispersive X-ray)를 이용하여 파괴 기구에 대한 분석을 실시하였다. Sn63Pb34.5Ag2Sb0.5 솔더에서 Au-Sn 성장비는 63Sn/37Pb, 62Sn/36Pb/2Ag 솔더에 비해 느리다 솔더 조성에 따른 솔더볼의 전단응력 저하에 대하여 논의하였다.

• 한국재료학회지
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• 제1권1호
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• pp.37-45
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• 1991

$BaTiO_3$세라믹에서 미세구조를 조절하기 위하여 Ba/Ti비 변화에 따른 소결거동 및 비정상 입자성장에 대하여 연구하였다. 본 연구에서 사용한 $BaTiO_3$분말은 $BaCO_3$와 $TiO_2$를 이용하여 일반적인 고상반응법으로 제조하였다. Ba/Ti비가 감소할수록(과잉 $TiO_2$가 증가할수록)소결 시작온도가 낮아졌으며 치밀화가 증진되었다. 이것은 과잉 $TiO_2$양이 증가할수록 하소된 분말의 크기가 감소되었기 때문으로 판단되며, 공융액상 형성으로 인한 액상소결에 의한 것이 아님을 알 수 있었다. 또한 과잉 $TiO_2$양이 증가할수록 입자성장이 강력하게 억제되었으며, 이는 Ti-rich 이차상이 입자성장을 억제시킴을 의미한다. 따라서 이러한 이차상의 불균일한 분포로 인하여 비정상 입자성장이 일어나는 것으로 판단되었다.

• 한국분말재료학회지
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• 제4권3호
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• pp.170-178
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• 1997

An investigation was performed to apply the M3/2 grade high speed steel for metal injection molding using both prealloyed and elementally blended powders. The injected samples were subjected to a debinding step in $H_2/N_2$ gas atmosphere at a ratio that affected the carbon content of the material. The carbon content ranged from 1.4wt.% to 1.43wt%. with increasing $H_2$ content up to 80% $H_2$ in $H_2/N_2$ atmosphere for the prealloyed powders. The carbon contents of the elementally blended powders exhibited 1.44wt.% and 1.62wt.% at 10% $H_2/N_2$ and 20% $H_2/N_2$ gas, respectively. This level decreased to 0.17wt.% upon increasing the $H_2$ content. The sintered density of both powders increased rapidly as the temperature reached the liquid phase forming temperature. After forming the liquid phase, the density rapidly increased to the optimum sintering temperature for the prealloyed powders, whereas the density of mixed elemental powders goes up slowly to the optimum sintering temperature. The optimum sintering temperature and density are 126$0^{\circ}C$ and 97.3% for the prealloyed powders and 128$0^{\circ}C$ and 96.9% for the elementally blended powders, respectively. The microstructure of the specimen at the optimum sintering temperature consisted of fine grains with primary carbides of MC and $M_6C$ type for the prealloyed powders. The elementally blended powders exhibited coarse grains with eutectic carbides of MC, $M_2C$ and $M_6C$ type.

• 한국방사성폐기물학회:학술대회논문집
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• 한국방사성폐기물학회 2003년도 가을 학술논문집
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• pp.180-185
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• 2003

원자력연구소에서 개발 중인 현재의 건식처리공정에서 발생될 용융염폐기물로 인한 최종 고화체의 발생량을 재생/재순환 공정을 도입할 경우와 비교하여 최종 고화체 발생량 감소와 이로 인한 재료비 절감액을 계산하였다. 현재까지 확보된 자료와 가정 하에 계산한 결과 1 ton HM을 처리하는 것을 기준으로 차세대관리공정 발생 LiCl염폐기물의 최종 고화체는 5.4 톤에서 1.7 톤으로 약 3.7 톤 (부피로는 $1.6m^3$) 줄게 되고, 1 ton U 규모의 전해정련공정 발생 LiCl-KCl 공융염폐기물의 최종 고화체는 2.7 톤에서 0.4 톤으로 약 2.3 톤 (부피로는 $1.0m^3$)이 줄어드는 것으로 계산되었다. 본 추정으로부터 건식처리공정이 보다 더 경제성을 높이기 위해서는 재생처리공정의 도입이 꼭 필요한 것으로 판단되었다.