• Journal of the Korean Applied Science and Technology
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• v.35 no.4
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• pp.1088-1095
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• 2018

In this study, reduced graphene oxide/polyaniline composite was fabricated tomaximize their advantages with electrochemical performances and use as a electrodematerial for supercapcaitor. Polyaniline as an electrode material was synthesized bychemical polymerization of aniline monomer and reduced graphene oxide wasintroduced to prepare composite with polyaniline without any pre-treatment. Thereduced graphene oxide, polyaniline and their composite electrodes were fabricatedon gold coated PET(polyethylene terephthalate) substrate through spray coatingmethod which can also apply to industrial scale. we have also prepared reducedgraphene oxide and polyaniline single material electrode to compare theirelectrochemical properties with reduced graphene oxide/polyaniline composite electrode. We have analyzed and compared electrochemical properties of eachelectrodes by using cyclic voltammetry(CV), galvanostaticcharge-discharge(GCD) and electrochemical impedancespectroscopy(EIS) at same condition. As a result, reduced graphene oxide /polyaniline composite electrode showed higher capacitance value more thanpolyaniline and reduced graphene oxide electrode, respectively. Internal resistanceof reduce graphene oxide/polyaniline composite electrode was 24% and 58% lessthan polaniline and reduced graphene oxide electrode respectively. These resultsconsidered that reduced graphene oxide/polyaniline composite electrode has potential ability and enable to apply flexible energy storage and wearable devices.

• Applied Chemistry for Engineering
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• v.30 no.1
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• pp.23-28
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• 2019

We report a supercapacitor cable, which consists of three-dimensional (3D) porous graphene coated onto the surface of carbon thread. The 3D porous framework of graphene was constructed by microwave-activated process using a graphene oxide-coated carbon thread. The use of microwave irradiation enabled to convert graphene oxide into reduced graphene oxide without any reducing agents and activate graphene sheets into exfoliated and porous graphene sheets. Combining two wire electrodes with a polymer gel electrolyte successfully completed supercapacitor device in a form of cable construction. The supercapacitor cables were highly flexible, and thus can be transformed into various shapes of devices and be integrated into textile items. A high area-capacitance of 38.1 mF/cm was obtained at a scan rate of 10 mV/s. This capacitance was retained 88% of its original value at 500 mV/s. The cycle life was also demonstrated by repeating a charge/discharge process during 10,000 cycles even under bent states, showing a high capacitance retention of 96.5%.

• Composites Research
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• v.36 no.3
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• pp.167-172
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• 2023

The manufacturing technology of composite material is applicable with filler characteristics maintaining low cost, flexibility, and easy process to develope the various functional composite materials. To realize functional composites, various researches on the high performance of composite materials using graphene as a filler is being actively conducted. In this study, physical and chemical properties were investigated using graphene to improve high functional properties. Graphene oxide (GO) was prepared using graphane nanoplatelet (GNP), and reduced graphene oxide (R-GO) was formed by reducing GO. The physical properties of GO and R-GO were analyzed, and the reliability of the manufactured method was reviewed by comparing that of GNP results. As a result of analysis by Raman spectroscopy, in the case of R-GO, it was confirmed that the intensity of D-peak and G-peak decreased compared to GO, and an increase of 0.08 was observed through the ratio of ID/IG. For the FTIR results, GO and RGO has a repeating C-C and C=C connection structure unlike GNP. GO and R-GO show clear peaks for C-O bond, C=C bond, C=O bond, and O-H bonding. As a result of X-ray diffraction analysis, GNP showed a wide diffraction peak at 25.86° of (002) plane characteristics, whereas GO and R-GO showed peaks corresponding to (001) and (100) planes. It was also found that the interlayer distance of GO increased by about 2.6 times compared to GNP.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.422.1-422.1
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• 2014

E-textile과 같은 웨어러블 전자소자는 휴대용 전자소자, 의료센서 및 디스플레이 등을 포함하는 다기능 직물등의 적용가능 응용분야에서의 잠재력으로 인하여 많은 관심을 가지고 있다. 따라서 본 논문에서는 이같은 응용분야에 적용하기 위하여 전기방사를 이용한 나노크기의 나일론 섬유를 제작하고 reduced graphene oxide를 섬유에 코팅하여 전도성을 가지는 나노섬유를 제작하였다. 나일론 알갱이를 포름산에 녹인 용액을 이용하여 전기방사를 통해 약 100 nm 두께를 가지는 나노섬유를 제작하였다. 제작된 나일론 섬유와 그래핀 옥사이드 사이의 결합력을 향상시키기 위하여 BSA(bovine serum albumin)으로 표면 처리를 하였다. 마지막으로 나일론 섬유에 코팅된 그래핀 옥사이드를 hydrazine을 이용하여 환원하여 전도성을 가지는 섬유를 제작하였다. 제작된 전도성을 가지는 섬유는 약 10 kohm 정도의 저항을 가지는 것을 확인하였으며, 물리적인 외부 변형에서도 안정적으로 전도성을 가지는 것을 확인하였다. 이러한 전도성을 가지는 나노섬유는 웨어러블 전자소자를 제작하는데 응용 가능할 뿐만 아니라, 전기방사를 통한 나노구조물 제작 기술을 가스센서, 바이오센서, 태양전지, 나노소자등 다양한 분야에 적용 가능한 우수한 기술이라고 생각한다.

• Applied Chemistry for Engineering
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• v.26 no.1
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• pp.99-103
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• 2015

We conducted reduction reactions of graphene oxide (GO) using three selected reductants. The conductivity and solubility of three kinds of the reduced graphene oxides (RGOs) were examined based on the degree of reduction. When the ethylene glycol (EG) was used as a reductant, the reduction reaction did not sufficiently progress and as a result the conductivity of RGOs was observed to be relatively low. For RGOs made by hydrazine (HZ) and thiourea dioxide (TU), we observed no significant differences in the degree of the reduction, conductivity and dispersity in water. However, RGO prepared by TU showed an exceptionally good solubility in N-methylpyrrolidone, and the solution was stable for more than 4 months.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2016.11a
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• pp.192.1-192.1
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• 2016

타이타늄은 밸브 메탈의 일종으로, 다양한 전해질 조건에서 양극산화되어 이산화 타이타늄($TiO_2$)을 형성한다. 이산화 타이타늄은 저렴한 가격, 풍부함, 무독성, 높은 안정성 등 다양한 장점을 지닌다. 또한 리튬 이온의 삽입/탈리 이후에도 구조적인 변화가 적은 성질과 비교적 높은 방전 전압(1.0-2.5 V vs Li/Li+)으로 인해 그래파이트를 대체할 리튬이온 전지의 전극재료로써 연구되어 왔다. 하지만 낮은 이온 및 전기 전도도로 인해 다양한 분야에서의 활용에 한계가 있어왔다. 이러한 한계 극복을 위해, 이산화 타이타늄에 전도성이 높은 탄소 계열의 물질을 코팅하는 방법이 고려되었다. 그래핀 산화물은 강한 산을 이용하여 그래파이트를 산화시킨 물질로, 많은 산소작용기를 함유하고 있어 탄소 고유의 전기전도성을 갖지 못한다. 환원 그래핀 산화물(reduced graphene oxide)는 빛, 열, 화학 작용울 통해 그래핀 옥사이드를 환원시켜 산소작용기를 없앤 물질로, 환원과정에서 전기전도성을 회복한다. 이에 본 연구에서는 이산화 타이타늄에 환원 그래핀 산화물(reduced graphene oxide)를 코팅하여 전기 전도도를 향상시키고. 이에 대한 활용 분야를 연구하고자 하였다.

• Journal of the Korean Applied Science and Technology
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• v.34 no.2
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• pp.280-288
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• 2017

Nanocarbon base materials such as, graphene and graphene hybrid with high electrochemical performances have great deal of attention to investigate flexible, stretchable display and wearable electronics in order to develop portable and high efficient energy storage devices. Battery, fuel cell and supercapacitor are able to achieve those properties for flexible, stretchable and wearable electronics, especially the supercapacitor is a promise energy storage device due to their remarkable properties including high power and energy density, environment friendly, fast charge-discharge and high stability. In this study, we have fabricated flexible supercapacitor composed of graphene/conductive polymer composite which could improve its electrochemical performance. As a result, specific capacitance value of the flexible supercapacitor (unbent) was $198.5F\;g^{-1}$ which decreased to $128.3F\;g^{-1}$ (65% retention) after $500^{th}$ bending cycle.

• Polymer(Korea)
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• v.35 no.3
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• pp.265-271
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• 2011

Graphene oxide (GO) was prepared by the Hummers and Offeman method from graphite. Reduced graphene oxide (EGO) and functionalized graphenes were synthesized from GO by using hydrazine hydrate and amine-functionalized alkyl groups, respectively. The structures of the GO, EGO, and functionalized graphenes were identified by FTIR and $^{13}C$ NMR. In addition, we examined the thermal stability, morphology and dispersibility of the materials in various organic solvents. AFM disclosed that GO and RGO consisted of one- or two-layer graphene regions throughout the film. However, the functionalized graphene films showed average thicknesses of 2.26~3.30 nm, The thermal stability of the functionalized graphenes was poorer than that of the EGO. The functionalized graphenes were well dispersed in toluene or chloroform, as evidenced by the lack of the characteristic graphite reflection in the solutions.

• Journal of Adhesion and Interface
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• v.12 no.4
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• pp.133-137
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• 2011

Exfoliated graphite oxide (EGO) was prepared by graphite oxide in an aqueous solution of TMAOH. The hybrid graphene/Zn-Al LDH material was fabricated by the hydrothermal reduction of the solution of EGO, $Zn(NO_3)_2{\cdot}6H_2O$, $Al(NO_3)_3{\cdot}9H_2O$, urea, and trisodium citrate. That is, metal ions were absorbed on the surface of EGO, and Zn-Al LDH material was randomly dispersed on the surface of graphene along with a reduction process of EGO to graphene by hydrothermal treatment. The composition, morphology, and thermal property of the obtained graphene-based hybrid material were studied by FE-SEM, EDX, TEM, FT-IR, XRD, TGA, and DSC.

• Polymer(Korea)
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• v.37 no.4
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• pp.513-517
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• 2013

A novel conductive composite thin film was prepared for the first time by hybridization between polybenzoxazine (PBZ) having high heat resistance property and conductive graphene. Mechanically robust conductive graphene/PBZ composite thin films could effectively be prepared by a simple thermal treatment, which simultaneously induces reduction of graphene oxide (GO) and crosslinking reaction of benzoxazine monomer. Graphene sheets seem to be uniformly dispersed up to 3 wt% graphene content in the composite thin film as shown in the results of chemical/crystal structural and morphological analyses. This efficient route for making graphene/PBZ composite thin film would provide simultaneous improvement of mechanical property as well as electrical conductivity.