• Applied Microscopy
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• 제45권2호
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• pp.95-100
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• 2015

The in-situ heating transmission electron microscopy experiment allows us to observe the time- and temperature-dependent dynamic processes in nanoscale materials by examining the same specimen. The temperature, which is a major experimental parameter, must be measured accurately during in-situ heating experiments. Therefore, calibrating the thermocouple readout of the heating holder prior to the experiment is essential. The calibration can be performed using reference materials whose phase-transformation (melting, oxidation, reduction, etc.) temperatures are well-established. In this study, the calibration experiment was performed with four reference materials, i.e., pure Sn, Al-95 wt%Zn eutectic alloy, NiO/carbon nanotube composite, and pure Al, and the calibration curve and formula were obtained. The thermocouple readout of the holder used in this study provided a reliable temperature value with a relative error of <4%.

• Composites Research
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• 제15권4호
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• pp.43-48
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• 2002

이 논문에는 미국 MIT에서 복합재료 관련연구를 간략하게 소개하였다. 복합재료 관련 연구는 4개의 학과에서 수행하고 있다. 즉, 기계공학과내의 Laboratory for Manufacturing & Productivity (LMP), 항공우주공학과의 Technology Laboratory for Advanced Composites(TELAC), 토목환경공학과에 있는 구조 및 재료 프로그램 (Structures & Materials Program) 그리고 건축학과 내의 Building Technology Program등에서 수행되고 있다.

• Carbon letters
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• 제14권4호
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• pp.206-209
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• 2013

Nanocomposites comprised of graphene oxide (GO) nanosheets and magnesium oxide (MgO) nanoparticles were synthesized by a sol-gel process. The synthesized samples were studied by X-ray powder diffraction, atomic force microscopy, transmission electron microscopy, and energy-dispersive X-ray analysis. The results show that the MgO nanoparticles, with an average diameter of 70 nm, are decorated uniformly on the surface of the GOs. By controlling the concentration of the MgO precursors and reaction cycles, it was possible to control the loading density and the size of the resulting MgO particles. Because the MgO particles are robustly anchored on the GO structure, the MgO/GOs nanocomposites will have future applications in the fields of adsorption and chemical sensing.

• 마이크로전자및패키징학회지
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• 제11권2호
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• pp.1-9
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• 2004

[ $BaTiO_3$ ]분말의 양과 에폭시/$BaTiO_3$ 복합 내장형 커패시터 필름의 유전상수와의 관계를 살펴보고 이에 대해 고찰하였다. 이를 위해 $BaTiO_3$ 분말의 함량에 따른 에폭시/$BaTiO_3$ 복합 내장형 커패시터 필름의 밀도 변화와 필름의 표면 및 단면 모습을 관찰하였다. 또한 $BaTiO_3$ 분말의 함량을 높이기 위한 여러 가지 bimodal 조합에 따른 에폭시/$BaTiO_3$ 복합 내장형 커패시터 필름의 유전상수 변화를 관찰하였다. 단일 입자를 이용한 unimodal의 경우 유전상수가 가장 높게 측정된 $S_4$ 분말을 이용하여 얻을 수 있었던 유전상수의 최대값은 약 60 이었다. 최대값보다 과량의 $BaTiO_3$ 분말을 첨가하였을 경우, 에폭시/$BaTiO_3$ 복합 내장형 커패시터 필름의 유전상수가 감소하는데, 이는 과량의 분말을 수용하기 위해 생성된 기공에 의한 것이었다. Bimodal 조합의 경우 가장 큰 분말과 가장 작은 분말의 조합인 $S_5+C_1$ 조합이 $75\;vol\%$의 가장 많은 양의 분말을 넣어 가장 높은 유전상수 90 을 얻는데 성공하였다.

• Carbon letters
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• 제14권2호
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• pp.110-116
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• 2013

This study investigated a developed process for producing a composite bipolar plate having excellent conductivity by using coal tar pitch and phenol resin as binders. We used a pressing method to prepare a compact of graphite powder mixed with binders. Resistivity of the impregnated compact was observed as heat treatment temperature was increased. It was observed that pore sizes of the GCTP samples increased as the heat treatment temperature increased. There was not a great difference between the flexural strengths of GCTP-IM and CPR-IM as the heat treatment temperature was increased. The resistivity of GPR700-IM, heat treated at $700^{\circ}C$ using phenolic resin as a binder, was $4829{\mu}{\Omega}{\cdot}cm$ which was best value in this study. In addition, it is expected that with the appropriate selection of carbon powder and further optimization of process we can produce a composite bipolar plate which has excellent properties.

• Advanced Composite Materials
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• 제16권3호
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• pp.223-244
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• 2007

This study experimentally and numerically investigated the tensile damage progress in stitched laminates. In particular, it focused on the effects of stitching on the damage progress. First, we experimentally confirmed that ply cracks and delamination appeared under load regardless of stitching. We then performed damage-extension simulation for stitched laminates using a layer-wise finite element model with stitch threads as beam elements, in which the damage (ply cracks and delamination) was represented by cohesive elements. A detailed comparison between observation and the simulated results confirmed that stitching had little effect on the onset and accumulation of ply cracks. Furthermore, we demonstrated that the stitch threads significantly suppressed the extension of the delamination.

• 복합신소재구조학회 논문집
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• 제1권1호
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• pp.34-45
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• 2010

This paper describes the design, manufacturing process, testing, application, and assessment of capacity-ratings of the first all advanced composites bridge on a public highway system. In order to verify the bridge design prior to the field application, a sub-scale bridge superstructure was built and tested in the laboratory. The field load test results were compared with those of the finite element analysis for the verification of validity. To investigate its in-service performance, field load testing and visual inspections were conducted under an actual service environment. The paper includes the presentation and discussion for advanced composites bridge capacity rating based on the stress modification coefficients obtained from the test results. The test result indicates that the advanced composites bridge has no structural problems and is structurally performing well in-service as expected. Since these composite materials are new to bridge applications, reliable data is not available for their in-service performance. The results may provide a baseline data for future field advanced composites bridge capacity rating assessments and also serve as part of a long-term performance of advanced composites bridge.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2006년도 6th International Meeting on Information Display
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• pp.1119-1121
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• 2006

Using a chemical radical we modified the surface property of PET substrates. The chemically treated substrate surface improved dispersion of CNTs on substrate and provides suitable adhesion of CNTs to substrate. In addition, an ink-jet printed patterning technique effectively improved the transparency of transparent conductive CNT composite films.

• 한국막학회:학술대회논문집
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• 한국막학회 2003년도 추계 총회 및 학술발표회
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• pp.219-222
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• 2003

• 한국마이크로전자및패키징학회:학술대회논문집
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• 한국마이크로전자및패키징학회 2005년도 ISMP
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• pp.201-212
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• 2005

[ $Epoxy/BaTiO_3$ ] composite embedded capacitor films (ECFs) were newly designed fur high dielectric constant and low tolerance (less than ${\pm}15\%$) embedded capacitor fabrication for organic substrates. In terms of material formulation, ECFs are composed of specially formulated epoxy resin and latent curing agent, and in terms of coating process, a comma roll coating method is used for uniform film thickness in large area. Dielectric constant of $BaTiO_3\;&\;SrTiO_3$ composite ECF is measured with MIM capacitor at 100 kHz using LCR meter. Dielectric constant of $BaTiO_3$ ECF is bigger than that of $SrTiO_3$ ECF, and it is due to difference of permittivity of $BaTiO_3\;and\;SrTiO_3$ particles. Dielectric constant of $BaTiO_3\;&\;SrTiO_3$ ECF in high frequency range $(0.5\~10GHz)$ is measured using cavity resonance method. In order to estimate dielectric constant, the reflection coefficient is measured with a network analyzer. Dielectric constant is calculated by observing the frequencies of the resonant cavity modes. About both powders, calculated dielectric constants in this frequency range are about 3/4 of the dielectric constants at 1 MHz. This difference is due to the decrease of the dielectric constant of epoxy matrix. For $BaTiO_3$ ECF, there is the dielectric relaxation at $5\~9GHz$. It is due to changing of polarization mode of $BaTiO_3$ powder. In the case of $SrTiO_3$ ECF, there is no relaxation up to 10GHz. Alternative material for embedded capacitor fabrication is $epoxy/BaTiO_3$ composite embedded capacitor paste (ECP). It uses similar materials formulation like ECF and a screen printing method for film coating. The screen printing method has the advantage of forming capacitor partially in desired part. But the screen printing makes surface irregularity during mask peel-off, Surface flatness is significantly improved by adding some additives and by applying pressure during curing. As a result, dielectric layer with improved thickness uniformity is successfully demonstrated. Using $epoxy/BaTiO_3$ composite ECP, dielectric constant of 63 and specific capacitance of 5.1nF/cm2 were achieved.