• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2004년도 추계학술대회 논문집
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• pp.1331-1334
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• 2004

The research on electromagnetic shielding has been advanced for military applications as well as for commercial products. Utilizing the reflective properties and absorptive properties of shielding material, the replied signal measured at the rear surface or at the signal source can be minimized. The shielding effect was obtained from materials having special absorptive properties or from structural characteristics such as stacking sequence. Recently researchers studied the electromagnetic properties of nano size particles. In this research {glass fiber}/{epoxy}/{nano particle} composites(GFR-Nano composites), was fabricated using various nano particles, and their properties in electromagnetic shielding were compared. For the visual observation of the nano composite materials, SEM(Scanning Electron Microscope) and TEM(Transmission Electron Microscope) were used. For the measurement of electromagnetic shielding, HP8719ES S-parameter Vector Network Analyser System was used on the frequency range of 8 GHz～12GHz. Among the nano particles, carbon black and Multi-Walled Carbon Nano-Tube (MWCNT) revealed outstanding electromagnetic shielding. Although silver nano particles (flake and powder) were expected to have effective electromagnetic shielding due to their excellent electric conductivities, test showed little shielding effect.

• 접착 및 계면
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• 제14권2호
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• pp.75-81
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• 2013

SiC 나노입자를 이용하여 에폭시 복합재료를 제조할 수 있다. SiC 형상에 따른 영향으로 복합재료의 계면 물성이 변화된다. SiC의 형상에 따른 계면 상태의 변화를 관찰하기 위해 베타 형태, 위스커 형태의 SiC 나노입자를 사용하였다. 나노입자에 대한 분산도를 평가하기 위해 커패시턴스를 이용한 분산도 평가방법을 활용하였다. FE-SEM을 이용하여 SiC 나노입자의 활용에 따른 나노복합재료의 파단면을 관찰하여, 그 강화 효과를 비교 분석하였다. 탄소섬유와 SiC 나노입자가 함유된 에폭시를 이용한 복합재료에 계면 물성을 비교하기 위해 층간전단강도 평가법과 계면전단강도 평가법을 이용하였다. 복합재료의 계면 물성을 강화하기 위해서는 베타 형태의 SiC 나노입자를 활용할 경우가 위스커 입자를 이용한 경우보다 높은 계면 강도를 나타냈다.

• 한국재료학회지
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• 제20권3호
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• pp.137-141
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• 2010

The $(1-x)La_{0.7}Sr_{0.3}MnO_3(LSMO)/xZnFe_2O_4$(ZFO) (x = 0, 0.01, 0.03, 0.06 and 0.09) composites were prepared by a conventional solid-state reaction method. We investigated the structural properties, magnetic properties and electrical transport properties of (1-x)LSMO/xZFO composites using X-ray diffraction (XRD), scanning electron microscopy (SEM), field-cooled dc magnetization and magnetoresistance (MR) measurements. The XRD and SEM results indicate that LSMO and ZFO coexist in the composites and the ZFO mostly segregates at the grain boundaries of LSMO, which agreed well with the results of the magnetic measurements. The resistivity of the samples increased by the increase of the ZFO doping level. A clear metal-to-insulator (M-I) transition was observed at 360K in pure LSMO. The introduction of ZFO further downshifted the transition temperature (350K-160K) while the transition disappeared in the sample (x = 0.09) and it presented insulating/semiconducting behavior in the measured temperature range (100K to 400K). The MR was measured in the presence of the 10kOe field. Compared with pure LSMO, the enhancement of low-field magnetoresistance (LFMR) was observed in the composites. It was clearly observed that the magnetoresistance effect of x = 0.03 was enhanced at room temperature range. These phenomena can be explained using the double-exchange (DE) mechanism, the grain boundary effect and the intrinsic transport properties together.

• 한국재료학회지
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• 제18권12호
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• pp.655-659
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• 2008

The NO gas sensing properties of ZnO-carbon nanotube (ZnO-CNT) composites fabricated by the coaxial coating of single-walled CNTs with ZnO were investigated using pulsed laser deposition. Upon examination, the morphology and crystallinity of the ZnO-CNT composites showed that CNTs were uniformly coated with polycrystalline ZnO with a grain size as small as 5-10 nm. Gas sensing measurements clearly indicated a remarkable enhancement of the sensitivity of ZnO-CNT composites for NO gas compared to that of ZnO films while maintaining the strong sensing stability of the composites, properties that CNT-based sensing materials do not have. The enhanced gas sensing properties of the ZnO-CNT composites are attributed to an increase in the surface adsorption area of the ZnO layer via the coating by CNTs of a high surface-to-volume ratio structure. These results suggest that the ZnO-CNT composite is a promising template for novel solid-state semiconducting gas sensors.

• 한국전기전자재료학회논문지
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• 제29권9호
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• pp.565-570
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• 2016

In this work, the complex permittivity of epoxy resins is measured. Epoxy resins, epoxy with micro size fillers and epoxy with micro+nano alumina composites have been evaluated for dielectric properties according to frequency variation. The dielectric spectroscopy measurement and analyses are carried out in the frequency range of $10^{-2}Hz$ to 1MHz and constant to room temperature. The results of dielectric loss suggest that significant improvement in the electrical performance can be expected by using samples containing nano and micro fillers mixture when compared to materials containing only microfillers. As the result, we verified the specific characteristics of dielectric permittivity and dielectric loss namely, relative permittivity become low with improving dispersibility of nano+micro mixture composites and become rise with agglomerate of nano particles.

• Transactions on Electrical and Electronic Materials
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• 제15권4호
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• pp.193-197
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• 2014

Si-carbon composites as anode materials for lithium rechargeable batteries were prepared simply by mixing Si nanoparticles with carbon black and/or graphite through a solution process. Si nanoparticles were well dispersed and deposited on the surface of the carbon in a tetrahydrofuran solution. Si-carbon composites showed more than 700 mAh/g of initial capacity under less than 20% loading of Si nanoparticle in the composites. While the electrode with only Si nanoparticles showed fast capacity fading during continuous cycling, Si-carbon composite electrodes showed higher capacities. The cycle performances of Si nanoparticles in composites containing graphite were improved due to the role of the graphite as a matrix.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2001년도 추계학술발표대회 논문집
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• pp.137-140
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• 2001

Oragnic/inorganic hybrid materials prepared by sol-gel method have rapidly become a fasci nating research field in materials science. In this study, Polyimide/$\textrm{TiO}_2$ composites were synthesized from nano-sized anatase $\textrm{TiO}_2$ and two types of Polyimide (BTDA-PPD, PMDA-ODA) by Sol-gel method. Nano-sized $\textrm{TiO}_2$ particles were prepared from $\textrm{TiOEt}_4$ solution. The composites were charcaterized by using XRD, TGA, IR, TEM, and Atomic Force Microscope(AFM). $\textrm{TiO}_2$ nano particles were dispersed well in polyimide matrix and the thermal stability of polyimide was improved with $\textrm{TiO}_2$ nano-sized particles.

• Advances in nano research
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• 제13권3호
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• pp.247-257
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• 2022

Extraordinary properties of nanocomposites make them a primary replacement for many conventional materials. Anterior cruciate ligament (ACL) reconstruction, which is a frequent surgery in sport activities, is one of the fields in which nanocomposites could be utilized. In the present study, the mechanical properties of different porous scaffolds made from graphene nano-composites are presented ad load bearing capacity of these materials is calculated using finite element method. The numerical results are further compared with experimental published data. In addition, several geometrical and material parameters are analyzed to find the best configuration of nanocomposite scaffolds in reconstruction of ACL. Moreover, coating of detoxification chemicals are extremely easier on the nano-structured materials than conventional one. Detoxification potential of nano-composites in the injured body are also discussed in detail. The results indicated that nano-composite could be successfully used in place of auto- and allografts and also instead of conventional metallic screws in reconstruction of ACL.

• 폴리머
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• 제35권1호
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• pp.60-65
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• 2011

고분자 나노복합재의 성능을 극대화 하기 위해서는 나노업자 분산도의 향상과 더불어 분산상태가 물성 변화에 미치는 영향을 정확히 이해하는 것이 매우 중요하다. 본 연구에서는 탄소나노튜브 첨가 고분자 복합재의 분산상태를 정량적으로 평가할 수 있는 방법을 제시하고자 하였다. 자외선-가시광선 분광광도법을 이용하여 탄소나노튜브의 분산상태에 따른 투과도를 측정하였으며, 동일 농도에서 분산상태가 향상됨에 띠라 투과도가 감소하는 것을 확인하였다. 이러한 결과를 바탕으로 기존의 Beer-Lambert 투과도 법칙에 분산상태의 변화를 포함할 수 있는 새로운 분산도 평가인자인 유효 농도 인자를 제시하였다. 이를 통해 탄소나노튜브의 분산상태의 변화와 함께 다양한 탄소나노튜브의 농도 및 시편 두께에 따른 투과도 결과를 분석함으로써 제시한 분산도 평가방법과 유효 농도 인자의 유효성을 확인하였다.

• Bulletin of the Korean Chemical Society
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• 제35권6호
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• pp.1659-1664
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• 2014

A porous metal-organic framework (MOF), MIL-101, was synthesized in the presence of sulfated zirconia (SZ) to produce acidic SZ/MIL-101 composites for the first time. The composites were characterized with XRD, nitrogen adsorption, FT-IR, scanning electron microscope, chemical analysis and so on. The composites (SZ/MIL-101s) were successfully applied in a liquid-phase esterification for a high yield of ester. This catalytic result of SZ/MIL-101, compared with that of pure SZ or MIL-101 (showing a negligible yield of ester), suggests that the SZ in the composite is highly active in the acid catalysis probably because of the well-dispersed active species of SZ. Moreover, the esterification is catalyzed in heterogeneous mode as confirmed by negligible esterification after filtration of the catalyst. Finally, microwaves can be efficiently applied both in the synthesis of the composites and the esterification reaction to accelerate the two processes of synthesis and esterification by about 5 times.