• KSBB Journal
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• 제31권4호
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• pp.208-213
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• 2016

Recently, numerous studies have utilized graphene in biomedical applications such as drug delivery, cancer therapy, and bioimaging. In this study, graphene was eco-friendly prepared by liquid phase exfoliation of graphite using plant extracts in water. Initially, 12 different plants or plant parts were screened for the characteristic graphene peak at near 268 nm using UV-Vis spectrophotometric analyses. The ability to form stable black graphene dispersion was highest using Xanthium strumarium extract. Transmission electron microscopy images showed that about 5 layer-graphene was produced from 1 g/L of graphite, while more than 5 layers were formed from 2 g/L of graphite. The optimum X. strumarium concentration for graphene production was 2 g/100 mL.

• 한국수소및신에너지학회논문집
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• 제26권5호
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• pp.416-422
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• 2015

Lithium Ion capacitor (LIC) is a new storage device which combines high power density and high energy density compared to conventional supercapacitors. LIC is capable of storing approximately 5.10 times more energy than conventional EDLCs and also have the benefits of high power and long cycle-life. In this study, LICs are assembled with activated carbon (AC) cathode and pre-doped graphite anode. Cathode material of natural graphite and artificial graphite kinds of MAGE-E3 was selected as the experiment proceeds. Super-P as a conductive agent and PTFE was used as binder, with the graphite: conductive agent: binder of 85: 10: 5 ratio of the negative electrode was prepared. Lithium doping condition of current density of $2mA/cm^2$ to $1mA/cm^2$, and was conducted by varying the doping. Results Analysis of Inductively Coupled Plasma Spectrometer (ICP) was used and a $1mA/cm^2$ current density, $2mA/cm^2$, when more than 1.5% of lithium ions was confirmed that contained. In addition, lithium ion doping to 0.005 V at 10, 20 and $30^{\circ}C$ temperature varying the voltage variation was confirmed, $20^{\circ}C$ cell from the low internal resistance of $4.9{\Omega}$ was confirmed.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2009년도 춘계학술대회 논문집
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• pp.879-880
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• 2009

• Journal of Microbiology and Biotechnology
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• 제14권5호
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• pp.1043-1046
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• 2004

The stability and electrochemical properties of a self-assembled layer of spinach ferredoxin on a quartz substrate and on a highly oriented pyrolytic graphite electrode were investigated. To fabricate the ferredoxin self-assembly layer, dimyristoylphosphatidylcholine was first deposited onto a substrate for ferredoxin immobilization. Surface analysis of the ferredoxin layer was carried out by atomic force microscopy to verify the ferredoxin immobilization. To verify ferredoxin immobilization on the lipid layer and to confirm the maintenance of redox activity, absorption spectrum measurement was carried out. Finally, cyclic-voltammetry measurements were performed on the ferredoxin layers and the redox potentials were obtained. The redox potential of immobilized ferredoxin had a formal potential value of -540 mV. It is suggested that the redox-potential measurement of self-assembled ferredoxin molecules could be used to construct a biosensor and biodevice.

• 한국결정성장학회지
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• 제23권5호
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• pp.213-217
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• 2013

GaN는 대표적인 III-V족 질화물반도체로 주로 값싸고 다루기 쉬운 사파이어 기판 위에 성장된다. 하지만 사파이어 기판은 부도체이며, GaN과의 격자부정합을 일으키고 열전도도 또한 낮은 기판으로 알려져 있다. 본 논문에서는 방열기능과 열 전기전도도가 뛰어난 금속 화합물 탄소체 기판 위에 poly GaN epilayer를 HVPE법으로 성장시켜보았다. 비정질의 금속 화합물 탄소체 기판위에 성장되는 GaN epilayer의 성장메카니즘을 관찰하였다. GaN epilayer의 성장을 위해 HCl과 $NH_3$를 흘려주었다. 성장하기 위해 source zone과 growth zone의 온도는 각각 $850^{\circ}C$와 $1090^{\circ}C$로 설정했다. 성장이 끝난 샘플은 SEM, EDS, XRD측정을 통해 분석하였다.

• 한국결정성장학회지
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• 제15권1호
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• pp.10-15
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• 2005

Microwave plasma CVD 다이아몬드/Ti 박막 성장 시 CH₄/H₂ 가스의 유량비율, chuck bias, microwave power 등이 다이아몬드 박막의 구조적 특성과 입자밀도에 미치는 영향에 대하여 조사하였다. 2∼3 CH₄ Vol.% 조건일 때 sp³-결합성의 탄소 neutral 들이 우선적으로 형성되고 sp²-결합성의 탄소 neutral 들이 선택적으로 제거됨에 따라 양질의 다이아몬드 박막을 얻을 수 있었으며, 다이아몬드 입자 증착 기구를 해석하였다. Ti 기판에 걸어준 negative chuck bias가 증가함에 따라 다이아몬드 핵생성이 증진되어 다이아몬드 입자 밀도가 증가하였고, 임계 전압은 약 -50V 임을 확인하였다. 또한, microwave power가 증가함에 따라 미세결정질(micro-crystalline) graphite 층 생성이 제어되고 다이아몬드 층이 형성됨을 확인하였다.

• 한국결정성장학회지
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• 제4권4호
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• pp.395-404
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• 1994

니켈.흑연 복합분말은 수소가스를 사용하여 ammoniacal 황산니켈염 수용액으로 부터 니켈이온을 흑연입자표면에 석출시켜 제조하였으며, SEM, 광학현미경, 입도 및 화학분석등을 이용하여 니켈이오느이 환원속도 및 코팅층의 특서에 미치는 여러 반응인자의 영향을 조사 하엿다. 반응온도 및 교반속도 변화에 따라 수소가스 주입 후 환원반응이 시작되기 까지 필요한 잠복기는 20~110분 정도이었으며 흑연코어 표면의 니켈코팅층은 포도송이 모양(botryoidal)인 니켈 nodule로 형성되었다. 또한 반응 온도 및 교반속도가 높아짐에 따라 코팅용액중 니켈이 온의 환원속도는 증가하였으며 $130^{\circ}C $, 600~800 rpm 조건에서는 $4.5g/{\ell}/min$를 나타내었다.

• 한국세라믹학회지
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• 제48권2호
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• pp.141-146
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• 2011

Successful coating of high quality glassy carbon is introduced by applying high pressure during the curing process of dip-coated phenol resin on graphite. The dependence of the applied pressure on the quality of the glassy carbon layer has not been reported so far. Pressure was changed from 0 to 400 psi during curing at $200^{\circ}C$. After carbonized at $1100^{\circ}C$ in inert atmosphere for the 400 psicured sample, as a promising result, a thick (~ 3 mm) and smooth glassy carbon layer could be obtained without any breakage, and the yield of carbonization was remarkably increased. It is believed that the cross-linking of resins results in decreasing volatile contents and, thus, increasing the yield of the glassy carbon. The origin of the improvement is discussed on the basis of several analytical results including FE-SEM, FT-IT and Raman spectrum.

• Applied Microscopy
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• 제48권3호
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• pp.73-80
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• 2018

Ductile cast iron is widely used for many automotive components due to its high wear resistance and fatigue resistance in addition to the low cost of fabrication. The improvement of wear resistance and fatigue properties is key to the life time extension and performance increase of the automobile parts. Surface nanocrystallization is a very efficient way of improving the performance of materials including the wear- and fatigue-resistance. Shot peening treatment, as one of the popular and economic surface modification methods, has been widely applied to various materials. In this study, ductile cast iron specimens were ultrasonic shot peening (USP) treated for 5 to 30 min using different ball size. The microstructures were then microscopically analyzed for determination of the microstructural evolution. After the USP treatment, the hardness of pearlite and ferrite increased, in which ball size is more effective than treatment time. With USP treatment, the graphite nodule count near the surface was decreased with grain refinement. The lager balls resulted in an increased deformation, whereas the smaller balls induced more homogenously refined grains in the deformation layer. In addition, formation of nanoparticles was formed in the surface layer upon USP.

• 동력기계공학회지
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• 제17권4호
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• pp.109-114
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• 2013

In this study, the microstructure, mechanical properties and high temperature oxidation characteristics of HiSiMo and HiSiMoM ductile iron for exhaust manifold were investigated. The HiSiMoM ductile iron was developed by optimization of alloying element addition and casting design. The exhaust manifold prototype was fabricated using the HiSiMoM iron and this resulted in the weight saving of 0.73kg. The microstructures of the HiSiMo and HiSiMoM irons were similar each other and graphite nodularity was 89% and 93% respectively. Tensile strengths of them were 663.5 and 674.4 MPa and Brinell hardness were 235.3 and 243.9 respectively. Both irons showed parabolic weight gain behavior in high temperature oxidation atmosphere. Oxidation layer was divided into external and internal layers. The weight gain of the HiSiMoM iron was lower than that of the HiSiMo iron after isothermal oxidation test at $900^{\circ}C$. This should be rationalized by higher Si enrichment at the interface of the matrix and internal layer of the HiSiMoM iron.