• 멤브레인
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• 제21권3호
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• pp.247-255
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• 2011

본 연구에서는 뛰어난 전도도와 물리적 강도를 가지는 그라핀의 고른 분산성을 얻기 위하여 두 가지 다른 방법으로 그라핀을 개질시켰다. 그리고 SPAES/그라핀 복합막은 각기 다른 함량을 첨가하여 제조되었으며 그라핀의 제조방법과 첨가된 그라핀의 함량에 따른 성능을 비교하였다. 복합막의 모폴로지는 SEM을 이용하여 관찰하였으며 개질된 그라핀의 화학적 구조는 FT-IR과 TGA를 사용하여 분석되었다. 그라핀의 함량변화가 0.5~3.0 wt% 일 때 복합막의 이온전도도와 메탄올 투과도를 측정하였으며 $80^{\circ}C$, 100% 가습상태에서 SPAES/그라핀 복합막의 이온전도도(0.216 S/cm)는 순수한 SPAES 전해질 막보다 높은 이온전도도(0.098 S/cm)를 나타내었으며 그라핀의 함량이 1.5 wt%까지 증가될 때 메탄올 투과도는 감소되었다.

• Carbon letters
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• 제27권
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• pp.81-89
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• 2018

The present study aimed to prepare a novel efficient flame retardant additive for polypropylene. The new flame retardant was prepared by chemical grafting of melamine to graphene oxide with the aid of thionyl chloride. Fourier-transform infrared spectroscopy and thermogravimetric analysis proved that melamine had been successfully grafted to the graphene oxide. The modified graphene oxide was incorporated into polypropylene via solution mixing followed by anti-solvent precipitatio. Homogeneous distribution as well as exfoliation of the nanoplatelets in the polymer matrix was observed using transmission electron microscopy. Thermogravimetric analysis showed a significant improvement in the thermo-oxidative stability of the polymer after incorporating 2 wt% of the modified graphene oxide. The modified graphene oxide also enhanced the limiting oxygen index of the polymer. However, the amount of improvement was not enough for the polymer to be ranked as a self-extinguishing material. Cone calorimetry showed that incorporating 2 wt% of the modified graphene oxide lowered total heat release and the average production rate of carbon monoxide during burning of the polymer by as much as 40 and 35%, respectively. Hence, it was concluded that the new flame retardant can retard burning of the polymer efficiently and profoundly reduce suffocation risk of exposure to burning polymer byproducts.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.159-159
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• 2013

Atomically thin graphene is the ideal model system for studying nanoscale friction due to its intrinsic two-dimensional anisotropy. Furthermore, modulating its tribological properties could be an important milestone for graphene-based micro and nano-mechanical devices. Here, we report that the tribological properties can be easily altered via simple chemical modifications of the graphene surface. Friction force microscopy measurements show that hydrogenated, fluorinated, and oxidized graphenes exhibit, 2-, 6-, and 7-fold enhanced nanoscale friction on their surfaces, respectively, compared to pristine graphene. The measured nanoscale friction should be associated with the adhesive and elastic properties of the chemically modified graphenes. Density functional theory calculations suggest that, while the adhesive properties of chemically modified graphenes are marginally reduced down to ~30%, the out-of-plane elastic properties are drastically increased up to 800%. Based on these findings, we propose that nanoscale friction on graphene surfaces is characteristically different from that on conventional solid surfaces; stiffer graphene exhibits higher friction, whereas a stiffer three-dimensional solid generally exhibits lower friction. The unusual friction mechanics of graphene is attributed to the intrinsic mechanical anisotropy of graphene, which is inherently stiff in plane, but remarkably flexible out of plane. The out-of-plane flexibility can be modulated up to an order of magnitude by chemical treatmentof the graphene surface. The correlation between the measured nanoscale friction and the calculated out-of-plane flexibility suggests that the frictional energy in graphene is mainly dissipated through the out-of-plane vibrations, or the flexural phonons of graphene.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
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• pp.71-71
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• 2012

Chemically modified graphene has been great interest for the application of printed electronics using solution prossesable technique. Here, we demonstrate a large area graphene exfoliation method with fewer defects on the basal plane by application of shear stress in solution to obtain high quality reduced graphene oxide (RGO). Moreover, we introduce a novel route to preparing highly concentrated and conductive RGO in various solvents by monovalent cation-${\pi}$ interaction. Noncovalent binding forces can be induced between a monopole (cation) and a quadrupole (aromatic ${\pi}$ system). The stability of this RGO dispersion was more sensitive to the strength of the cation-${\pi}$ interactions than to the cation-oxygen functional group interactions. The RGO film prepared without a post-annealing process displayed superior electrical conductivity of 97,500 S/m. Our strategy can facilitate the development of large scalable production methods for preparing printed electronics made from high-quality RGO nanosheets.

• 한국재료학회지
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• 제27권5호
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• pp.255-262
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• 2017

Reactive oxygen species (ROS) can be produced by interactions between sunlight and light-absorbing substances in natural water environments and can completely destroy various organic pollutants in waste water. In this study, we used graphene oxide modified $Ag_2Se$ nanoparticles to enhance photochemically generated oxygen (PGO) species activity. Surface area and pore volumes of the $Ag_2Se-graphene$ ($Ag_2Se-G$) samples showed catastrophic decrease due to deposition of $Ag_2Se$. The generation of reactive oxygen species was detected through the oxidation reaction of DPCI to DPCO. The photocurrent density and the PGO effect increase in the case of the use of modified graphene. The PGO effect of the graphene modified with $Ag_2Se$ composites increased significantly due to a synergetic effect between graphene and the $Ag_2Se$ nanoparticles. The photocatalytic activity of sample was evaluated by measuring the degradation of organic pollutants such as methylene blue (MB) and industrial dyes such as Texbrite BA-L (TBA) under visible light.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2011년도 춘계학술대회 초록집
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• pp.95.1-95.1
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• 2011

In this work, graphene was prepared by modified Hummers method and prepared graphene was applied to electrode materials for supercapacitor. In addition, to enhance the electrochemical performance of graphene, carbon black was deposited onto graphene via chemical reduction. The effect of the carbon black content incorporated on the electrochemical properties of the graphene-based electrodes was investigated. It was found that nano-scaled carbon black aggregates were deposited and dispersed onto the graphene by the chemical reduction of acid treated carbon black and graphite oxide. From the cyclic voltammograms, carbon black-deposited graphene (CB-GR) showed improved electrochemical performance, i.e., current density, quicker response, and better specific capacitance than that of pristine graphene. This indicates that the carbon black deposited onto graphene served as an conductive materials between graphene layers, leading to reducing the contact resistance of graphene and resulted in the increase of the charge transfer between graphene layers by bridge effect.

• Bulletin of the Korean Chemical Society
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• 제35권1호
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• pp.253-256
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• 2014

Functionalization of zigzag graphene nanoribbon (ZGNR) segment containing 120 C atoms with pyridine (3NV-ZGNR) defects was investigated on the basis of density-functional theory (DFT) calculations, results show that edge-modified ZGNRs by Sc can adsorb multiple hydrogen molecules in a quasi-molecular fashion, thereby can be a potential candidate for hydrogen storage. The stability of Sc functionalization is dictated by a strong binding energy, suggesting a reduction of clustering of metal atoms over the metal-decorated ZGNR.

• Advances in materials Research
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• 제8권3호
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• pp.219-235
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• 2019

This research is devoted to analyzing mechanical-thermal post-buckling behavior of a micro-size beam reinforced with graphene platelets (GPLs) based on geometric imperfection effects. Graphene platelets have three types of dispersion within the structure including uniform-type, linear-type and nonlinear-type. The micro-size beam is considered to be perfect (ideal) or imperfect. Buckling mode shape of the micro-size beam has been assumed as geometric imperfection. Modified couple stress theory has been used for describing scale-dependent character of the beam having micro dimension. Via an analytical procedure, post-buckling path of the micro-size beam has been derived. It will be demonstrated that nonlinear buckling characteristics of the micro-size beam are dependent on geometric imperfection amplitude, thermal loading, graphene distribution and couple stress effects.

• Korean Chemical Engineering Research
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• 제60권1호
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• pp.62-69
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• 2022

그래핀은 부피에 비해 표면적이 넓고 뛰어난 기계적 물성과 전기전도성을 가지며 생체적합성이 우수하다. 본 연구에서는 전기화학적 방법을 이용하여 indium tin oxide (ITO) 글래스 슬라이드 표면에 산화그래핀을 증착·환원시킨 전극을 제작하였고 그래핀으로 표면 개질된 ITO의 전기화학적 특성을 조사하였다. 산화그래핀의 증착과 환원에 순환전압전류법을 사용하였다. 주사전자현미경과 에너지 분산형 X-선 분광법을 사용하여 그래핀이 코팅된 ITO 표면을 관찰하였다. 순환전압전류법과 전기화학 임피던스 분광법을 사용하여 제작된 전극들의 전기화학 특성을 평가하였다. 사이클 수와 주사 속도는 산화그래핀 증착과 환원도에 상당한 영향을 미쳤으며 제작된 전극의 전기화학 특성도 달랐다. ITO 전극에 비하여 그래핀으로 표면 개질된 ITO는 전극 계면에서의 전하 전달 저항이 낮았고 더 많은 전류를 생산하였다. 그래핀으로 표면 개질된 ITO 표면에 고정화된 포도당 산화효소는 포도당을 산화시키며 성공적으로 전자들을 생성하였다.

• 멤브레인
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• 제27권3호
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• pp.255-262
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• 2017

본 연구에서는 graphene oxide (GO)를 polyacrylonitrile (PAN)에 첨가하여 전기방사법을 이용해 나노섬유 복합막을 제조한 뒤 물리적 특성을 관찰하였다. GO의 제조는 개선된 Hummer's 방법을 이용하였으며, 표면처리가 되지 않은 GO의 경우 0.5 wt% 이상에서 전기방사가 이루어지지 않았다. GO의 안정성 및 분산도 증가를 개선하기 위해 계면활성제를 이용하여 GO의 표면처리를 하였다. 표면처리가 된 GO를 사용하여 나노섬유 복합막의 GO의 함량을 0.5 wt% 이상 첨가할 수 있었다. 특히, 표면처리가 된 GO가 첨가된 나노섬유 복합막은 향상된 물리적 특성을 가지며, 이는 나노섬유 분리막 내의 GO의 분산도와 상관관계가 있는 것으로 보인다.