• Journal of Welding and Joining
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• v.26 no.4
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• pp.50-54
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• 2008

In this research, anode for SOFC has been manufactured from two different kinds of feedstock materials through thermal spraying process and the properties of the coatings were characterized and compared. One kind of feedstock was manufactured from spray drying method which includes nano-components of NiO, YSZ (300 nm) and graphite. And the other is manufactured by blending the micron size NiO coated graphite, YSZ and graphite powders as feedstock materials. Microstructure, mechanical properties and electrical conductivity of the coatings as-sprayed, after oxidation and after hydrogen reduction containing nano composite which is prepared from spray-dried powders were evaluated and compared with the same properties of the coatings prepared from blended powder feedstock. The coatings prepared from the spray dried powders has better properties as they provide larger triple phase boundaries for hydrogen oxidation reaction and is expected to have lower polarization loss for SOFC anode applications than that of the coatings prepared from blended feedstock. A maximum electrical conductivity of 651 S/cm at $800^{\circ}C$ was achieved for the coatings from spray dried powders which much more than that of the average value.

• Elastomers and Composites
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• v.47 no.3
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• pp.238-245
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• 2012

Graphene oxide was synthesized from natural graphite, and its surface was modified using diisocyanatodicyclohexylmethane( $H_{12}MDI$). Isocyanate-graphene sheet(i-RGO) was obtained by reduction of surface modified GO. To select nanofiller having good dispersion with polyurethane, GO, i-RGO, natural graphite and thermal reduced graphite were analyzed, and then i-RGO was selected as a suitable nanofiller. PU/i-RGO nanocomposite was synthesized with various i-RGO contents to estimate effect of reinforcement on nanocomposite. Thermal stability, hardness, contact angle were increased with i-RGO contents due to i-RGO characteristic and crosslink bridge effect. But, tensile strength and elongation were decreased at i-RGO contents more than the 4 wt%. This phenomenon was interpreted by the excess formation of crosslink bridge.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.290.1-290.1
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• 2016

Grapehen, a single atomic layer of graphite, has been in the spotlight and researched in vaious fields, because its fine mechanical, electrical properties, flexibility and transparence. Synthesis methods for large-area graphene such as chemical vaper deposition (CVD) and mechanical, chemical exfoliation have been reported. In particular, chemical exfoliation method receive attention due to low cost process. Chemical exfoliation method require reduction of graphene oxide in the process of exfoliation such as chemical reduction by strong reductant, thermal reduction on high temperature, and optical reduction via ultraviolet light exposure. Among these reduction methods, optical reduction is free from damage by strong reductant and high temperature. However, optical reduction is economically infeasible because the high cost of short-wavelength ultraviolet light sorce. In this paper, we make graphene-oxide and lanthanoid ion mixture aqueous solution which has highly optical absorbency in selective wevelength region. Sequentially, we synthesize reduced graphene oxide (RGO) using the solution and visible laser beam. Concretely, graphene oxide is made by modified hummer's method and mix with 1 ml each ultraviolet ray absorbent Gd3+ ion, Green laser absorbent Tb3+ ion, Red laser absorbent Eu3+ ion. After that, we revivify graphene oxide by laser exposure of 300 ~ 800 nm layser 1mW/cm2 +. We demonstrate reproducibility and repeatability of RGO through FT-IR, UV-VIS, Low temperature PL, SEM, XPS and electrical measurement.

• Proceedings of the Korean Institute of Resources Recycling Conference
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• 2005.10a
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• pp.173-177
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• 2005

리튬이온 2차전지(Lithium ion battery, LIB)는 기존에 사용되던 전지에 비해 에너지 밀도가 높고 충방전 사이클이 우수하다. 이 때문에 휴대전화와 노트북 등에 수요가 급속하게 증가하고 있으며 1995년 LIB의 생산량은 4천만 개에서 2004년에는 약 8억 개로 20배 이상 증가하였다. 이에 따라 폐LIB도 급속하게 증가하게 되어 전국적인 재활용 시스템의 확보가 필요한 실정이다. 본 연구에서는 폐LIB에 함유되어 있는 유가금속 중에서 리튬코발트옥사이드(이하 $LiCoO_2$)를 회수하기 위하여 분쇄기(orient vertical cutting mill)와 진동 Screen을 사용하여 유기분리막, 금속류(Aluminium foil, Copper foil, case 등) 그리고 전극물질(lithium cobalt oxide와 graphite 등의 혼합 분말)로 분리하였다. 전극물질에서 $LiCoO_2$와 graphite 분리를 위한 전처리 단계로서 $500^{\circ}C$ 정도의 열처리를 하여 $LiCoO_2$의 표면 성질을 변화시켜 부유선별에 의해 $LiCoO_2$와 graphite의 분리가 가능하도록 하였다. 부유선별 실험 결과 93% 이상의 순도를 가지는 $LiCoO_2$를 92% 이상 회수할 수 있었다.

• Journal of Electrochemical Science and Technology
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• v.8 no.4
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• pp.307-313
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• 2017

In this paper we report an electrochemical sensor based on ZnO-functionalized graphene oxide nanocomposite (ZnO-GO) for the sensitive determination of the cabergoline. Cabergoline electrochemical behaviors were investigated by cyclic voltammetry (CV), chronoamperometry (CHA) and differential pulse voltammetry (DPV). The modified electrode shows electrocatalytic activity toward cabergoline oxidation in phosphate buffer solution (PBS) (pH 7.0) with a reduction of the overpotential of about 180 mV and an increase in peak current. The DPV data showed that the obtained anodic peak currents were linearly dependent on the cabergoline concentrations in the range of $1.0-200.0{\mu}M$, with the detection limit of $0.45{\mu}M$. The prepared electrode was successfully applied for the determination of cabergoline in real samples.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.280.2-280.2
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• 2016

The graphene, a single atomic sheet of graphite, has attracted tremendous interest owing to its novel properties including high intrinsic mobility, optical transparency and flexibility. However, for more diverse application of graphene devices, it is essential to tune its transport behavior by shifting Dirac Point (DP) of graphene. So, in the following context, we suggest a method to tune structural and electronic properties of graphene using atomic layer deposition. By atomic layer deposition of zinc oxide (ZnO) on graphene using 4-mercaptophenol as linker, we can fabricate n-doped graphene. Through ${\pi}-{\pi}$ stacking between chemically inert graphene and 4-mercaptophenol, conformal deposition of ZnO on graphene was enabled. The electron mobility of graphene TFT increased more than 3 times without considerably decreasing the hole mobility, compared to the pristine graphene. Also, it has high air stability. This ZnO doping method by atomic layer deposition can be applicable to large scale array of CVD graphene TFT.

• Korean Journal of Materials Research
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• v.14 no.9
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• pp.664-669
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• 2004

Anodic aluminum oxide (AAO) with pores of various diameter, density, and thickness values was obtained through control of the anodization parameters including voltage, temperature, pore widening time, anodization time, etc. The pore diameter was controlled by a pore widening in an etchant, and alumina templates having stepped nano-channels were fabricated by repetition of anodization and pore widening processes. Stepped carbon nanotubes (CNTs) were then grown on the stepped AAO templates by pyrolysis of acetylene without using the catalyst. High-resolution transmission electron microscopy images revealed that CNTs have a multi-wall structure made of graphite flakes of several nm sizes. The current-voltage characteristic of the sloped and linear CNTs were also examined.

• Journal of the Korean Electrochemical Society
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• v.3 no.3
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• pp.173-177
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• 2000

The synthetic carbon was coated with tin oxide and copper by fluidized-bed chemical vapor deposition method. $(CH_3)_4Sn\;and\;Cu(hfac)_{2s}$ were employed as the metallic organic precursor, respectively. The modified synthetic carbons were used for lithium secondary battery anode to investigate their coating effects on electrochemical characteristics as alternative anode materials for lithium secondary batteries. The electrode which prepared by the synthetic carbons(MCMB) coated with tin oxide gave the higher capacity than that of raw material. Their capacity decreased with the progress of cycling possibly due to severe volume changes. But the cyclability was improved by coating with copper on the surface of the tin oxide coated carbon, which plays an important role as an inactive matrix buffering volume changes.

• Journal of Electrochemical Science and Technology
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• v.6 no.3
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• pp.88-94
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• 2015

In this study we investigated the electrocatalytic oxidation of saccharose on conductive polymer- Nickel oxide modified graphite electrodes based on the ability of anionic surfactants to form micelles in aqueous media. This NiO modified electrode showed higher electrocatalytic activity than Ni rode electrode in electrocatalytic oxidation of saccharose. The anodic peak currents show linear dependency with the square root of scan rate. This behavior is the characteristic of a diffusion controlled process. Under the CA regime the reaction followed a Cottrellian behavior and the diffusion coefficient of saccharose was found in agreement with the values obtained from CV measurements.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.302.1-302.1
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• 2014

We report the growth of high quality zinc oxide (ZnO) thin films on amorphous glass substrates and their structural and optical characteristics. For the growth of ZnO films, mechanically exfoliated ultrathin graphite or graphene layers were used as an intermediate layer because ZnO does not have any heteroepitaxial relationship with the amorphous substrates, which significantly improved the crystallinity of the ZnO films. Structural and optical characteristics of the films were investigated using scanning and transmission electron microscopy, x-ray diffraction, and variable temperature photoluminescence spectroscopy. High crystallinity and excellent optical characteristics such as stimulated emission were exhibited from the high quality ZnO films grown on glass substrates.