• 한국재료학회:학술대회논문집
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• 한국재료학회 2011년도 추계학술발표대회
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• pp.43.2-43.2
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• 2011

Single-walled carbon nanotubes (SWCNT) are transparent in the visible and show conductivity comparable to copper, and are environmentally stable. SWCNT films have high flexibility, conductivity and transparency approaching that indium tin oxide (ITO), and can be prepared inexpensively without vacuum equipment. Transparent conducting Films (TCF) of SWCNTs has the potential to replace conventional transparent conducting oxides (TCO, e.g. ITO) in a wide variety of optoelectronic devices, energy conversion and photovoltaic industry. However, the sheet resistance of SWCNT films is still higher than ITO films. A decreased in the resistivity of SWCNT-TCFs would be beneficial for such an application. We fabricated SWCNT sheet with $KAuBr_4$ on PET substrate. Arc-discharge SWCNTs were dispersed in deionized water by adding sodum dodecyl sulfate (SDS) as surfactant and sonicated, followed by the centrifugation. The dispersed SWCNT was spray-coated on PET substrate and dried on a hotplate at $100^{\circ}C$. When the spray process was terminated, the TCF was immersed into deionized water to remove the surfactant and then it was dried on hotplate. The TCF film was then treated with AuBr4-, rinsed with deionized water and dried. The surface morphology of TCF was characterized by field emission scanning electron microscopy. The sheet resistance and optical transmission properties of the TCF were measured with a four-point probe method and a UV-visible spectrometry, respectively. $HNO_3$ treated SWCNT films with Au nano-particles have the lowest 61 ${\Omega}$/< sheet resistance in the 80% transmittance. Sheet resistance was decreased due to the increase of the hole concentration at the washed SWCNT surface by p-type doping of $AuBr_4{^-}$.

• 한국산학기술학회논문지
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• 제19권1호
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• pp.63-68
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• 2018

본 논문은 이산화탄소 고정 과정이 포함된 인공 광합성 과정을 모사하기 위하여 지구상에 흔히 존재하는 촉매 재료를 이용해 개발한 광화학 반응 시스템(인공나뭇잎)과 시스템 에너지 포집 및 변환 능력에 대한 성능을 조사하기 위한 기초 연구 결과를 제시한다. 본 연구에서 개발한 시스템은 태양광 전지의 전면부에 산화코발트를 도핑 하여 물의 전기분해로 인한 산소 발생이 태양전지 표면에서 직접 발생하도록 하였고, 후면 기판 표면에는 이산화탄소 변환 반응을 위한 효율적인 촉매로 $MoS_2$를 도핑 하여, 전선이 없는 구조로 구성하였다. 직접 태양광 연료 변환 시스템은 약4.5%로 이산화탄소를 일산화탄소와 수소로 변환하여 지속 가능한 연료(합성가스)의 형태로 생산하며, 이는 음극에서 촉매 변환 효율이 75%이상이 될 수 있음을 의미한다. 본 연구는 물의 광분해뿐만 아니라 태양광에 의해 유도된 이산화탄소 전환 과정을 하나의 시스템에서 동시에 실현하여 자연적 광합성 과정을 좀 더 성공적으로 모사할 수 있는 시스템 개발에 기여하였다.

• Composites Research
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• 제31권5호
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• pp.282-287
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• 2018

본 연구는 광물화된 탄소나노튜브를 고분자 기지재료의 강화재로 사용할 때, 계면 결합력이 기존 탄소나노튜브 강화재에 비해 어떤 차이를 보이는지 분자동역학 시뮬레이션을 통해 탐구한다. 최근 탄소나노튜브에 질소를 도핑한 후 표면을 광물화 하는 실험 연구가 보고되고 있다. 하지만 복합재료의 강화제로 첨가되었을 때 보일 수 있는 물성 증가 현상에 대한 연구는 아직 부족하다. 광물질로는 실리카($SiO_2$)를 사용했고 고분자 기지재료로는 열 가소성 수지인 poly(methyl metacrylate) (PMMA)를 사용했다. 계면 결합력과 계면 전단 응력을 계산하기 위해 강화재를 기지재료로부터 빼내는 pull-out 시뮬레이션이 진행되었다. 계산 결과, 실리카 광물화된 탄소나노튜브가 고분자 기지재료와 향상된 계면 상호작용을 가지는 것으로 조사되었다. 본 연구진은 향후 광물화된 탄소나노튜브 강화재가 첨가된 나노 복합재료의 열 기계적 물성을 분석하여 다양한 분야에서의 활용 가능성을 제시할 계획이다.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2003년도 하계학술연구발표회 및 한.일 공동심포지엄
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• pp.220-221
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• 2003

Equiatomic FePt and CoPt alloy thin films have received considerable attention as possible magnetic and magneto-optic recording because of their high magnetic anisotropy energy and high coercivity. The high coercivity in these thin films is due to the presence of finely dispersed ordered FePt phase mixed with disordered FePt phase. However, a high temperature treatment, either substrate heating during deposition or post annealing, is needed to obtain the ordered L1$\_$0/ phase with high value of magneto crystalline anisotropy. Recent microstructural studies on these films suggest that the average grain size ranges from 10-50 nm and the grains are magnetically coupled between each other. On the other hand, the ultrahigh-density magnetic recording media with low media noise imposes the need of a material, which consists of magnetically isolated grains with size below 10 nm. The magnetic grain isolation can be controlled by the amount of additional non-magnetic element in the system which determines the interparticle separation and therefore the interparticle interactions. Recently, much research work has been done on various non-magnetic matrices. Preliminary studies showed that the samples prepared in B$_2$O$_3$ and Carbon matrices have shown strong perpendicular anisotropy and fine grain size down to 4nm, which suggest these nanocomposite films are very promising and may lead to the realization of a magnetic medium capable of recording densities beyond 1 Tb/in$^2$. So, in this work, the effect of Carbon doping on the magnetic properties of FePt nanoparticles were investigated.

• 한국초전도ㆍ저온공학회논문지
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• 제16권1호
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• pp.9-13
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• 2014

Effects of neutron irradiation on the superconducting properties of the undoped $MgB_2$ and the carbon(C)-doped $MgB_2$ bulk superconductors, prepared by an in situ reaction process using Mg and B powder, were investigated. The prepared $MgB_2$ samples were neutron-irradiated at the neutron fluence of $10^{16}-10^{18}n/cm^2$ in a Hanaro nuclear reactor of KAERI involving both fast and thermal neutron. The magnetic moment-temperature (M-T) and magnetization-magnetic field (M-H) curves before/after irradiation were obtained using magnetic property measurement system (MPMS). The superconducting critical temperature ($T_c$) and transition width were estimated from the M-T curves and critical current density ($J_c$) was estimated from the M-H curves using a Bean's critical model. The $T_cs$ of the undoped $MgB_2$ and C-doped $MgB_2$ before irradiation were 36.9-37.0 K and 36.6-36.8 K, respectively. The $T_cs$ decreased to 33.2 K and 31.6 K, respectively after irradiation at neutron fluence of $7.16{\times}10^{17}n/cm^2$, and decreased to 22.6 K and 24.0 K, respectively, at $3.13{\times}10^{18}n/cm^2$. The $J_c$ cross-over was observed at the high magnetic field of 5.2 T for the undoped $MgB_2$ irradiated at $7.16{\times}10^{17}n/cm^2$. The $T_c$ and $J_c$ variation after the neutron irradiation at various neutron fluences were explained in terms of the defect formation in the superconducting matrix by neutron irradiation.

• 한국재료학회지
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• 제30권11호
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• pp.581-588
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• 2020

Reducing CO₂ into high value fuels and chemicals is considered a great challenge in the 21st century. Efficiently activating CO₂ will lead to an important way to utilize it as a resource. This article reviews the latest progress of g-C₃N₄ based catalysts for CO₂ reduction. The different synthetic methods of g-C₃N₄ are briefly discussed. Article mainly introduces methods of g-C₃N₄ shape control, element doping, and use of oxide compounds to modify g-C₃N₄. Modified g-C₃N₄ has more reactive sites, which can significantly reduce the probability of photogenerated electron hole recombination and improve the performance of photocatalytic CO₂ reduction. Considering the literature, the hydrothermal method is widely used because of its simple equipment and process and easy control of reaction conditions. It is foreseeable that hydrothermal technology will continue to innovate and usher in a new period of development. Finally, the prospect of a future reduction of CO₂ by g-C₃N₄-based catalysts is predicted.

• 청정기술
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• 제30권1호
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• pp.23-27
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• 2024

Bismuth는 적절한 작동 전압(0.8 V)과 높은 체적 용량(3,765 mAh cm^-3) 때문에 Li-ion battery (LIBs)의 유망한 음극소재로 여겨진다. 그럼에도 불구하고 Bi의 Li과의 합금화 반응 중 필연적인 부피 팽창은 심각한 용량 손실과 셀 파괴를 초래한다. 이를 해결하기 위해 본 논문에서는 N이 도핑된 탄소에 내장된 비스무트 합금 나노 입자(Bi@NC)의 복합체를 간단한 열분해 방법을 통해 제조하였다. 나노 크기의 Bismuth 합금은 단축된 Li⁺ 이온 확산 경로를 통해 반응 동역학을 향상시킬 수 있다. 또한, N 도핑된 탄소 코팅은 Li⁺ 이온과의 확장된 합금/탈 합금 반응 동안 Bismuth의 부피 변화를 효과적으로 완충하고 효과적인 전도성 네트워크를 유지한다. 열 중량 분석한 결과 매우 높은 Bismuth 합금 로딩(80.9 wt%)을 보여줬음에도 불구하고 100 cycles까지 315 mAh g^-1 용량을 유지하였다.

• 센서학회지
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• 제29권2호
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• pp.112-117
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• 2020

Xylene is a hazardous volatile organic compound that should be precisely measured to monitor indoor air quality. However, the selective and sensitive detection of ppm-level xylene using oxide-semiconductor gas sensors remains a challenge. In this study, pure and Cr-doped Co₃O₄ nanoparticles (NPs) were prepared using flame spray pyrolysis, and their gas-sensing characteristics to 5-ppm xylene at 250 ℃ were investigated. The 4 at% Cr-doped Co₃O₄ NPs exhibited a high gas response to 5-ppm xylene (resistance ratio to gas and air = 39.1) and negligible cross-responses to other representative and ubiquitous indoor pollutants such as ethanol, benzene, formaldehyde, carbon monoxide, and ammonia. In this paper, the enhancement of the gas response and selectivity of Co₃O₄ NPs to xylene by Cr doping was discussed in relation to the catalytic promotion of the gas-sensing reaction. This sensor can be used to monitor indoor xylene.

• Bulletin of the Korean Chemical Society
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• 제35권6호
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• pp.1799-1805
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• 2014

In this article, we described about the preparation and electrochemical properties of a flexible energy storage system based on a plastic polyethylene terephthalate (PET) substrate. The PET treated with UV/ozone was fabricated with multilayer films composed of 30 polyaniline (PANi)/graphene oxide (GO) bilayers using layer-by-layer assembly of positively charged PANi and negatively charged GO. The conversion of GO to the reduced graphene oxide (RGO) in the multilayer film was achieved using hydroiodic acid vapor at $100^{\circ}C$, whereby PANi structure remained nearly unchanged except a little reduction of doping state. Cyclic voltammetry and charge/discharge curves of 30 PANi/RGO bilayers on PET substrate (shorten to PANi-$RGO_{30}$/PET) exhibited an excellent volumetric capacitance, good cycling stability, and rapid charge/discharge rates despite no use of any metal current collectors. The specific capacitance from charge/discharge curve of the PANi-$RGO_{30}$/PET electrode was found to be $529F/cm^3$ at a current density of $3A/cm^3$, which is one of the best values yet achieved among carbon-based materials including conducting polymers. Furthermore, the intrinsic electrical resistance of the PANi-$RGO_{30}$/PET electrodes varied within 20% range during 200 bending cycles at a fixed bend radius of 2.2 mm, indicating the increase in their flexibility by a factor of 225 compared with the ITO/PET electrode.

• Journal of Information Display
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• 제11권1호
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• pp.1-7
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• 2010

The intermediate connectors play crucial roles in the performance of tandem organic light-emitting diodes (OLEDs) because they are required to facilitate charge carrier transport and to guarantee transparency for light transmission and deposition compatibility. Understanding the physical properties of the intermediate connector is not only fundamentally important but is also crucial to developing high-efficiency organic devices with a tandem structure. In this study, several effective intermediate connectors in tandem OLEDs using a doped or non-doped organic p-n heterojunction were systematically investigated by studying their interfacial electronic structures and corresponding device characteristics. The working mechanisms of the intermediate connectors are discussed herein by referring to their relevant energy levels with respect to those of the neighboring organic layers. The factors affecting the operation of the intermediate connectors in tandem OLEDs, as demonstrated herein, provide guidance for the identification of new materials and device architectures for high-performance devices.