• 한국표면공학회지
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• 제37권4호
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• pp.226-233
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• 2004

The residual stresses on the surfaces of low carbon 12Cr steels used as a nuclear steam turbine blade material have been studied by controlling the flame hardening surface treatments. The temperature cycles on the surfaces of 12Cr steel were controlled precisely as a function of both the surface temperature and cooling rate. The final residual stress state generated by flame hardening was dominated by two opposite competitive contributions; one is tensile stress due to phase transformation and the other is compressive stress due to thermal contraction on cooling. The optimum processing temperatures required for the desirable residual stress and hardness were in the range of $850^{\circ}C$ to $960^{\circ}C$ on the basis of the specification of GE power engineering. It was also observed that the high residual tensile stress generated by flame hardening induced the cracks on the surfaces, especially across the prior austenite grain boundaries, and the material failure virtually, which might limit practical use of the surface engineered parts by flame hardening.

• 지질공학
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• 제9권2호
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• pp.89-100
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• 1999

핵폐기물 처분장 공학방벽재로서의 우리나라 제 3 기층에서 산출되는 벤토나이트와 제올라이트의 활용 가능성을 물리화학적 특성을 중심으로 평가하였다. 연일 및 감포일대 제 3 기층의 9개 대표적인 벤토나이트 광산과 6개의 제올라이트 광산에서 채취한 자연산 시료와 관련회사의 추천상품시료에 대해 X-선 회절 분석, 팽윤도 측정, 양이온교환능 측정, 비표면적 측정, 몬모릴로나이트의 함량계산, 유기탄소함량 분석, 시차 열분석(DTA), 편광현미경 관찰, 주사전자현미경(SEM)관찰 및 전자현미분석(EPMA)을 실시하여 각 분석항목을 비교 평가하였다. 연구결과를 종합하면 U-41 및 G-46의 광산에서 산출되는 벤토나이트와 대도 및 Y-1호 광산의 제올라이트가 인공방벽재료로 갖추어야할 물리화학적 특성이 최적인 것으로 평가된다.

• Biotechnology and Bioprocess Engineering:BBE
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• 제5권6호
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• pp.436-440
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• 2000

Recently, we reported an improved technology for the degradation of organophosphate nerve agents using whole cells of genetically engineered Escherichia coli that anchored and displayed the enzyme organophosphorus hydrolase on the cell surface. In this paper we report the immobilization of these cells on highly porous sintered glass beads and the subsequent application of the immobilized cell in a continuous-flow packed bed bioreactor for the biodetoxification of a widely used insecticide, coumaphos.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
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• pp.738-739
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• 2006

This paper will describe a powder and processing method that facilitates single press-single sintered densities approaching $7.5g/cm^3$. At this sintered density, mechanical properties of the powder metal (P/M) component are significantly improved over current P/M technologies and begin to approach the performance of wrought steels. High performance gears have the added requirement of rolling contact fatigue durability that is dependent upon localized density and thermal processing. Combining high density processing of engineered P/M materials with selective surface densification enables powder metal components to achieve rolling contact fatigue durability and mechanical property performance that satisfy the performance requirements of many high strength automotive transmission gears. Data will be presented that document P/M part performance in comparison to conventional wrought steel grades.

• Carbon letters
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• 제13권1호
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• pp.56-59
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• 2012

The defect sites on chemical vapor deposition grown graphene are investigated through the selective electrochemical deposition (SED) of Au nanoparticles. For SED of Au nanoparticles, an engineered potential pulse is applied to the working electrode versus the reference electrode, thereby highlighting the defect sites, which are more reactive relative to the pristine surface. Most defect sites decorated by Au nanoparticles are situated along the Cu grain boundaries, implying that the origin of the defects lies in the synthesis of uneven graphene layers on the rough Cu surface.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2012년도 춘계학술발표회 논문집
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• pp.140-140
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• 2012

박막제조 기술은 과학 기술의 기초가 되는 분야로 양질의 박막을 제조하기 위한 다양한 노력이 경주되고 있다. 박막제조는 표면개질과 함께 표면처리 기술의 한 분야이며 이중 진공증착으로 알려진 물리증착법과 화학증착법은 현대의 과학기술 연구는 물론 산업적으로 폭넓게 이용되는 박막제조 기술 중의 하나이다. 진공증착을 이용한 박막제조 기술은 나노 기술의 등장과 함께 비약적인 발전을 이루었으며 자연모사와 완전화 박막의 제조, 융복합 공정을 이용한 기능성 코팅과 Engineered Structure 구현 그리고 초고속 증착과 원가 저감 기술의 실현이 주요 이슈로 등장하고 있다. 본 논문에서는 물리증착법과 화학증착법을 중심으로 박막제조 기술의 종류와 원리를 설명하고 박막제조 기술의 최신 동향과 기술적 이슈 및 향후 전망에 대해 기술한다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
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• pp.382-382
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• 2012

Nanostructures have a larger surface/volume ratio as well as unique mechanical, physical, chemical properties compared to existing bulk materials. Materials for biomedical implants require a good biocompatibility to provide a rapid recovery following surgical procedure and a stabilization of the region where the implants have been inserted. The biocompatibility is evaluated by the degree of the interaction between the implant materials and the cells around the implants. Recent researches on this topic focus on utilizing the characteristics of the nanostructures to improve the biocompatibility. Several studies suggest that the degree of the interaction is varied by the relative size of the nanostructures and cells, and the morphology of the surface of the implant [1, 2]. In this paper, we fabricate the nanowires on the Ti substrate for better biocompatible implants and other biomedical applications such as artificial internal organ, tissue engineered biomaterials, or implantable nano-medical devices. Nanowires are fabricated with two methods: first, nanowire arrays are patterned on the surface using e-beam lithography. Then, the nanowires are further defined with deep reactive ion etching (RIE). The other method is self-assembly based on vapor-liquid-solid (VLS) mechanism using Sn as metal-catalyst. Sn nanoparticle solutions are used in various concentrations to fabricate the nanowires with different pitches. Fabricated nanowries are characterized using scanning electron microscopy (SEM), x-ray diffraction (XRD), and high resolution transmission electron microscopy (TEM). Tthe biocompatibility of the nanowires will further be investigated.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2017년도 춘계학술대회 논문집
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• pp.3-23
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• 2017

The achievement of tissue engineering can be highly depending on the capability to generate complicated, cell seeded three dimensional (3D) micro/nano-structures. So, various fabrication techniques that can be used to precisely design the architecture and topography of scaffolding materials will signify a key aspect of multi-functional tissue engineering. Previous methods for obtaining scaffolds based on top-down are often not satisfactory to produce complex micro/nano-structures due to the lack of control on scaffold architecture, porosity, and cellular interactions. However, a bioprinting method can be used to design sophisticated 3D tissue scaffolds that can be engineered to mimic the tissue architecture using computer aided approach. Also, in recent, the method has been modified and optimized to fabricate scaffolds using various natural biopolymers (collagen, alginate, and chitosan etc.). Variation of the topological structure and polymer concentration allowed tailoring the physical and biological properties of the scaffolds. In this presentation, the 3D bioprinting supplemented with a newly designed plasma treatment for attaining highly bioactive and functional scaffolds for tissue engineering applications will be introduced. Moreover, various in vivo and in vitro results will show that the fabricated scaffolds can carry out their structural and biological functionality.

• Journal of Microbiology and Biotechnology
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• 제22권2호
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• pp.234-238
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• 2012

Recombinant Escherichia coli displaying organophosphorus hydrolase (OPH) was used to overcome the diffusion barrier limitation of organophosphorus pesticides. A new anchor system derived from the N-terminal domain of ice-nucleation protein from Pseudomonas syringae InaV (InaV-N) was used to display OPH onto the surface. The designed sequence was cloned in the vector pET-28a(+) and then was expressed in E. coli. Tracing of the expression location of the recombinant protein using SDS-PAGE showed the presentation of OPH by InaV-N on the outer membrane, and the ability of recombinant E. coli to utilize diazinon as the sole source of energy, without growth inhibition, indicated its significant activity. The location of OPH was detected by comparing the activity of the outer membrane fraction with the inner membrane and cytoplasm fractions. Studies revealed that recombinant E. coli can degrade 50% of 2 mM chlorpyrifos in 2 min. It can be concluded that InaV-N can be used efficiently to display foreign functional protein, and these results highlight the high potential of an engineered bacterium to be used in bioremediation of pesticide-contaminated sources in the environment.

• 센서학회지
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• 제31권6호
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• pp.383-388
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• 2022

Currently, photodetectors are being extensively studied and developed for next-generation applications, such as in autonomous vehicles and image sensors. In this regard, all-inorganic metal halide perovskite (CsPbX₃; X = Cl, Br, and I) nanocrystals (NCs) have emerged as promising building blocks for various applications owing to their high absorption coefficients, tunable bandgaps, high defect tolerances, and solution processability. These features, which are typically required for the development of advanced optoelectronics, can be engineered by modifying the chemical compositions and surface chemistry of the NCs. Herein, we briefly review various strategies adopted for the application of CsPbX₃ perovskite NCs in photodetectors and for improving device performance. First, modifications of the chemical compositions of CsPbX₃ NCs to tune their optical bandgaps and improve the charge-transport mechanism are discussed. Second, the application of surface chemistry to improve oxidation resistance and carrier mobility is described. In the future, perovskite NCs with prospective features, such as non-toxicity and high resistance to external stimuli, are expected to be developed for practical applications.