• Journal of the Korean Applied Science and Technology
• /
• v.34 no.2
• /
• pp.280-288
• /
• 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)
• /
• v.39 no.3
• /
• pp.468-474
• /
• 2015

Electrically conductive polymer nanocomposites were prepared by the inclusion of graphene-based nanofillers. Graphene oxide (GO) and reduced graphene oxide wrapped by poly(styrene sulfonate) (PSS-RGO) were used as nanofillers to make good dispersion with the aqueous dispersion of polystyrene (PS) particles. GO sheets were synthesized by the modified Hummers' method from graphite, and PSS-RGO sheets were prepared by the reduction of GO-dispersed PSS solution with hydrazine monohydrate. Morphology and properties of PS/GO and PS/PSS-RGO nanocomposites via latex technology were investigated. Both nanofillers showed well dispersed morphology in PS matrix. Rheological and electrical percolation thresholds were 0.28 and 0.51 wt% for GO, and 0.50 and 1.01 wt% for PSS-RGO respectively. It is speculated that PS/GO nanocomposites showed better conductivity than PS/PSS-RGO counterparts due to the partial recovery of GO by thermal reduction during molding.

• Journal of the Korean Applied Science and Technology
• /
• v.36 no.1
• /
• pp.200-207
• /
• 2019

In this study, flexible supercapacitor based on the all solid state electrolyte with PVA (polyvinyl alcohol)-$H_3PO_4$, ionic liquid as a BMIMBF4 (1-buthyl-3-methylimidazolium tetrafluoroborate) and reduced graphene oxide/conductive polymer composite was fabricated and characterized electrochemical properties with function of its flexibility. In order to measure and compare that electrochemical performances (including cyclic voltammetry(CV), electrochemical impedance spectroscopy(EIS) and galvanostatic charge/discharge,after 0~100th bending test) of prepared flexible supercapacitor based on reduced graphene oxide/conducting polymer composite and all solid state electrolyte, we have conducted press machine with constant pressure ( 0.01/cm2) for $100^{th}$ bending test. As a result, specific capacitance of the flexible supercapacitor was 43.9 F/g which value decreased to 42.0 and 40.1 F/g after 50 and $100^{th}$ bending test, respectively. This result exhibited that decreased electrochemical property of the flexible supercapacitor effected on physical stress on the electrode after repeated bending test. In addition, we have measured that electrode surface morphology by SEM to prove its decreased electrochemical property of the flexible supercapacitor after prolonged bending test.

• Polymer(Korea)
• /
• v.38 no.4
• /
• pp.502-509
• /
• 2014

Carbon-based nanoplatelets such as graphene oxide (GO) sheets and graphite nanoplatelets (GNPs) are frequently used as conductive nanofillers for polymer nanocomposites. In this study, polystyrene (PS)/GO and PS/GNP nanocomposites were prepared through a latex technology and investigated to compare the effect of nanofillers on rheological and electrical properties of the PS nanocomposites. PS particles were prepared by emulsifier-free emulsion polymerization and GO was synthesized by using the modified Hummers' method from graphite. Hydrophilic GO was dispersed in aqueous PS suspension, but hydrophobic GNPs were dispersed with the help of a surfactant. In comparison with PS/GO nanocomposites, the rheological properties of PS/GNP counterparts were not too high because GNP existed in aggregates of graphene layers. Conducting pathways of PS/GO and PS/GNP nanocomposites were achieved at the electrical percolation threshold of 0.50 and 5.82 wt%, respectively. The reason for enhanced electrical conductivity in PS/GO nanocomposites is that GO was thermally reduced during molding.

• Composites Research
• /
• v.35 no.4
• /
• pp.283-287
• /
• 2022

Stretchable strain sensors have been developed for potential future applications including wearable devices and health monitoring. For practical implementation of stretchable strain sensors, their stability and repeatability are one of the important aspects to be considered. In this work, we utilized 3D printed polymer structures having kirigami patterns to improve the stretchability and reduce the hysteresis. The polymer structures were coated with graphene/carbon nanofiber hybrids to make a robust electrical network. The stretchable strain sensors showed a high gauge of 36 at a strain of 32%. Because of the kirigami structures and the robust graphene/carbon nanofiber coating, the sensors also exhibited stable resistance responses at various strains ranging from 1% to 30%.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.31 no.2
• /
• pp.69-73
• /
• 2018

The power law is very important in gas sensing for the determination of gas concentration. In this study, the resistance of a gas sensor based on poly (3, 4-ethylenedioxythiophene) polystyrene sulfonate+graphene oxide composite was found to exhibit a power law dependence on hydrogen concentration at $150^{\circ}C$. Experiments were carried out in the gas concentration range of 30~180 ppm at which the sensor showed a sensitivity of 6~9% with a response and recovery time of 30s.

• Composites Research
• /
• v.31 no.3
• /
• pp.111-116
• /
• 2018

In this paper, magnetic FeCoNi particles have been grown through electroless plating on the surface of graphene, and then this hybrid material has been dispersed by various surfactants to prepare films. The pyridine surfactant shows the highest dispersability and low surface resistance value (351 Ohm/sq) and the electromagnetic shielding ability at the frequency of 10 GHz. Specially, the evaporation of the pyridine during the drying process could be able to form the internal conductive network and high dispersion of FeCoNi on the surface of graphene.

• Membrane Journal
• /
• v.32 no.6
• /
• pp.411-426
• /
• 2022

Energy plays a significant role in modern lifestyle because of our extensive reliance over energy-operating devices. Therefore, there is a need for alternative and green energy resources that can fulfill the energy demand. For this, fuel cell (FCs) especially anion exchange membrane fuel cells (AEMFCs) have gained tremendous attention over the other (FCs) due to their fast reaction kinetics without using noble catalyst and allow to use of cheaper polymers with high performance. But lack of highly conductive, chemically, and mechanically stable anion exchange membrane (AEM) still main obstacle to the development of high performance AEMFCs. Therefore, graphene-based polymer composite membranes came into the existence as AEMs for the FCs. The exceptional properties of the graphene help to improve the performance of AEMs. Still, there are lot of challenges in the graphene derivatives based AEMs because of their high tendency of agglomeration in polymer matrix which reduced their potential. To overcome this issue surface modification of graphene derivatives is necessary to restrict their agglomeration and conserved their potential features that can help to improve the performance of AEM. Therefore, this review focus on the surface modification of graphene derivatives and their role in the fabrication of AEMs for the FCs.