• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.286-286
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• 2006

We report on a fascinating morphology; giant spherical conducting polythiophene by the in-situ gamma radiation-induced chemical polymerization method. The resultant micron-size buckyball-shaped polymer structures were identified by high resolution transmission electron microscopy and scanning electron microscopy. Different characterizations e.g. Fourier transform infrared, x-ray diffraction, and x-ray photoelectron microscopy were utilized to prove that the new morphological conducting polythiophene was synthesized successfully by this novel method.

• Journal of Korea Foundry Society
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• v.24 no.3
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• pp.159-164
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• 2004

The aim of the present work is to investigate the possibility of in-situ synthesis and net-shape forming of the titanium matrix (TiC+TiB) hybrid composites using a casting route. From the scanning electron microscopy, electron probe micro-analyzer, X-ray diffraction and thermodynamic calculations, the spherical TiC and needle like TiB reinforced hybrid titanium matrix composites could be obtained in-situ by the conventional melting and casting route between titanium and $B_4C$. No melt-mold reaction occurred between the titanium matrix (TiC+TiB) hybrid composites and the SKK mold, since the mold is consisted with interstitial and substitutional metal-mold reaction products. Not only the sound in-situ synthesis but also the economic net-shape forming of the titanium matrix (TiC+TiB) hybrid composites could be possible by the conventional casting route.

• Journal of Welding and Joining
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• v.17 no.2
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• pp.36-43
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• 1999

The effect of microstructure on the fracture toughness of multi pass weld metal has been investigated. The micromechanisms of fracture process are identified by in-situ scanning electron microscopy(SEM) fracture observation using single edge notched specimen. The notches of the in-situ fracture specimens were carefully located such that the ends of the notches were in the as-deposited top bead and the reheated weld metal respectively. The observation of in-situ fracture process for as-deposited top bead indicated that as strains are applied, microcracks are formed at the interfaces between soft proeutectoid ferrite and acicular ferrite under relatively low stress intensity factor. Then, the microcracks propagate easily along the proeutectoid ferrite phase, leading to final fracture. These findings suggest that proeutectoid ferrite plays an important role in reducing the toughness of the weld metal. On the other hand, reheated regions showed that the microcrack initiated at the notch tip grows along the localized shear bands under relatively high stress intensity factor, confirming that reheated area showing momogeneous and fine microstructure would be beneficial to the fracture resistance of weld metal.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.91-91
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• 2015

반도체 공정의 발전에 의해 최근 생산되는 메모리 등은 십 수 나노미터까지 좁아진 선 폭을 갖게 되었다. 이러한 이유로, 기존에는 큰 문제를 발생시키지 않던 나노미터 영역의 입자들이 박막 증착 공정과 같은 반도체 제조공정 수율을 저감시키게 되었다. 따라서 오염입자의 유입을 막거나 제어하기 위해 transmission electron microscopy (TEM)나 scanning electron microscopy (SEM)과 같은 전자현미경을 활용한 비 실시간 입자 측정 방법 및 광원을 이용하는 in-situ particle monitor (ISPM) 및 전기적 이동도를 이용한 scanning mobility particle sizer (SMPS) 등 다양한 원리를 이용한 실시간 입자 측정방법이 현재 사용중에 있다. 이 중 진공 내 입자의 수농도를 측정하기 위해 개발된 particle beam mass spectrometer (PBMS) 기술은 박막 증착 공정 등 chemical vapor deposition (CVD) 방법을 이용하는 진공공정에서 활용 가능하여 개발이 진행되어 왔다. 본 연구에서는 PBMS의 한계점인 입자 밀도, 형상 등의 특성분석이 용이하도록 PBMS와 scanning electron microscopy (SEM), 그리고 energy dispersive spectroscopy (EDS) 기술을 결합하여 입자의 직경별 개수농도, 각 입자의 형상 및 성분을 함께 측정 가능하도록 하였다. 협소한 반도체 제조공정 내부 공간에 적용 가능하도록 기존 PBMS 대비 크기 또한 소형화 하였다. 각 구성요소인 공기역학 집속렌즈, electron gun, 편향판, 그리고 패러데이 컵의 설치 및 물리적인 교정을 진행한 후 입자발생장치를 통해 발생시킨 sodium chloride 입자를 상압 입자 측정 및 분류장치인 SMPS 장치를 이용하여 크기별로 분류시켜 압력차를 통해 PBMS로 유입시켜 측정을 진행하였다. 나노입자의 입경분포, 형상 및 성분을 측정결과를 토대로 장치의 측정정확도를 교정하였다. 교정된 장치를 이용하여 실제 박막 증착공정 챔버의 배기라인에서 발생하는 입자의 수농도, 형상 및 성분의 복합특성 측정이 가능하였으며, 최종적으로 실제 공정에 적용가능하도록 장치 교정을 완료하였다.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.257-257
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• 2011

The amorphous indium-gallium-zinc-oxide (a-IGZO) materials for use in high performance display research fields are strongly investigated due to its good performance, such as high mobility and better transparency. However, the stability of a-IGZO materials is increasingly becoming one of critical issues due to the sub-gap electron trap sites induced by rough interfaces during deposition processing. It is well-known that the threshold voltage shift is related to interface roughness and oxygen vacancy formed by breaking weak chemical bonds. Here, we report the better properties of transparent oxide transistors by reducing the threshold voltage shift with an external rf plasma supported magnetron sputtering system. Mainly, our sputtering method causes the surface of sample to be sleek, so that it prevents the formation of various defects, such as shallow electron trap sites in the interface. External rf power was applied from 0 to 50W during RF sputtering process to enhance the stability of our oxide transistor without having a large voltage shift. To observe the effects of external rf-plasma source on the properties of our devices, Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), Transmission Electron Microscopy (TEM) are carried out to observe surface roughness and morphology of sputtered thin film. In addition, typical electrical properties, such as I-V characteristics are analyzed.

• Korean Journal of Metals and Materials
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• v.49 no.2
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• pp.145-152
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• 2011

Mechanical and property corrosion resistance of Mg-Zn-Y alloys with an atomic ratio of Zn/Y of 6.8 are investigated using optical microscopy, scanning electron microscopy, transmission electron microscopy, uniaxial tensile test and corrosion test with immersion and dynamic potentiometric tests. The alloys showed an in-situ composite microstructure consisting of ${\alpha}$-Mg and icosahedral phase (I-phase) as a strengthening phase. As the volume fraction of the I-phase increases, the yield and tensile strengths of the alloys increase while maintaining large elongation (26~30%), indicating that I-phase is effective for strengthening and forms a stable interface with surrounding ${\alpha}$-Mg matrix. The presence of I-phase having higher corrosion potential than ${\alpha}$-Mg, decreased the corrosion rate of the cast alloy up to I-phase volume fraction of 3.7%. However further increase in the volume fraction of the I-phase deteriorates the corrosion resistance due to enhanced internal galvanic corrosion cell between ${\alpha}$-Mg and I-phase.

• Applied Chemistry for Engineering
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• v.8 no.1
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• pp.76-83
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• 1997

Blends of thermotropic liquid crystalline polymer(TLCP) with poly(ethylene terephthalate) (PET) were prepared by the coprecipitation from a common solvent. The blends were processed through a capillary die at $287^{\circ}C$ to produce a monofilament. Morphology and mechanical, thermal properties of blends and composites were examined by differential scanning calorimetry(DSC), tensile test, optical microscopy and scanning electron microscopy. Crystallization kinetics of the blends were investigated by the isothermal DSC method. The Avrami analyses were applied to obtain the information on the crystal growth geometry and factors controlling the rate of crystallization. In the blends, liquid crystalline phase did not reveal any significant macrophase separation and thermal degradation at the processing temperature. From scanning electron micrographs of cryogenic fracture surfaces of extruded fibers, the TLCP domains were found to be more or less finely dispersed with $0.1{\mu}m$ to $0.2{\mu}m$ in size. Interfacial adhesion between the TLCP and matrix polymer was excellent. Tensile strength and modulus of TLCP/PET in-situ fiber composites were enhanced with increasing draw ratio and LCP content.

• International Journal of Korean Welding Society
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• v.3 no.2
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• pp.29-39
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• 2003

The durability and reliability of thermal barrier coatings (TBCs) play an important role in the service reliability, availability and maintainability (RAM) of hot­section components in advanced turbine engines for aero and utility applications. Photostimulated luminescence spectroscopy (PSLS) and electrochemical impedance spectroscopy (EIS) are being concurrently developed as complimentary non­destructive evaluation (NDE) techniques for quality control and life­remain assessment of TBCs. This paper overviews the governing principles and applications of the luminescence and the impedance examined in the light of residual stress, phase constituents and resistance (or capacitance) in TBC constituents including the thermally grown oxide (TGO) scale. Results from NDE by PSLS and EIS are discussed and related to the microstructural development during high temperature thermal cycling, examined by using a variety of microscopic techniques including focused ion beam (FIB) in­situ lift­out (INLO), transmission and scanning transmission electron microscopy (TEM and STEM).

• Korean Journal of Metals and Materials
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• v.48 no.7
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• pp.683-689
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• 2010

In this study, FeAl based intermetallic matrix composites reinforced with in-situ synthesized TiC particles were fabricated by an in-situ liquid mixing process. The microstructures, mechanical properties and fracture behaviors of the in-situ liquid mixing processed composite were investigated and compared with the vacuum suction casting processed composite. The results showed that the in-situ formed TiC particles exhibited fine and uniform dispersion in the liquid mixing processed composite, while significant grain boundary clustering and coarsening of TiC particles were obtained by the vacuum suction process. It was also shown in both types of composites that the hardness and bending strength were increased with the increase of the TiC volume fractions. Through the study of fractography in the bending test, it was considered that the TiC particles prohibited brittle intergranular fracture of FeAl intermetallic matrix by crack deflections. Because of the uniformly distributed fine TiC particles, the bending strength of the liquid mixing processed composite was superior to that of the casting processed composite.

• Bulletin of the Korean Chemical Society
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• v.35 no.8
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• pp.2391-2399
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• 2014

Novel dual responsive pectin hydrogels composed from poly(acrylamidoglycolic acid-co-vinylcaprolactam)/Pectin (PAV-PC) and also PAV-PC hydrogels are used as templates for the production of silver nanoparticles. 5-Fluorouracil is an anticancer drug and has been loaded in situ into PAV-PC hydrogels. Structure and morphology characterization of PAV-PC hydrogels were investigated by fourier transform infrared spectroscopy, differential scanning calorimetry, thermo gravimetric analysis, X-ray diffraction studies, scanning electron microscopy and transmission electron microscopy. The results revealed a molecular level dispersion of the drug in PAV-PC hydrogels. In vitro release of 5-fluorouracil from the PAV-PC hydrogels has been carried out in GIT fluids as well as in various temperatures. 5-Fluorouracil released from PAV-PC hydrogels was 50% at pH 1.2, and 85% at pH 7.4 within 24 h. The release profile was characterized with PAV-PC hydrogels and initial burst effect was significantly reduced in two buffer media (1.2 and 7.4), followed by a continuous and controlled release phase, the drug release mechanism from polymer was due to Fickian diffusion. In situ fabrication of silver nanoparticles inside the hydrogel network via the reduction of sodium borohydrate by PAV-PC chains led to hydrogel nanocomposites. The diameter of the nanocomposites was about 50-100 nm, suitable for uptake within the gastrointestinal tract due to their nanosize range and mucoadhesive properties. These nanocomposite PAV-PC hydrogels showed strong antimicrobial activity towards Bacillus subtilis (G+ve) and Escherichia coli (G-ve).