• 청정기술
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• 제19권3호
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• pp.300-305
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• 2013

ZnO(산화아연)와 rGO(환원 흑연산화물, reduced graphite oxide)로 구성된 복합체를 제조하여 중저온 영역($300-500^{\circ}C$)에서 $H_2S$(황화수소) 흡착실험을 수행하였다. rGO에 붙어있는 수산화기, 에폭시기, 그리고 카르복실기와 같은 산소를 포함하는 관능기들이 $H_2S$흡착에 미치는 영향을 조사하기 위해서 다양한 특성분석(TGA, XRD, FT-IR, SEM, 그리고 XPS)을 실시하였다. GO(흑연산화물, graphite oxide)를 rGO로 환원시키기 위해서 마이크로파 조사법을 사용하였다. 마이크로파 조사법에 의한 환원공정에서는 온화한 환원분위기를 조성하여 rGO 표면에 상당량의 산소 관능기들이 남아있는 것을 확인하였다. 이러한 관능기들은 나노 크기의 ZnO가 2D rGO 표면에 균일하게 부착되도록 유도하여 고온 영역에서도 ZnO의 응집 및 소결이 일어나는 것을 방지하는 효과가 있다. 이로 인해 ZnO/rGO 복합체는 순수한 ZnO와 비교하여 3.5배 정도의 흡착량을 보여주었다.

• Carbon letters
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• 제12권3호
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• pp.138-142
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• 2011

Poly(vinyl alcohol) (PVA) composites with various graphite oxide (GO) contents (0 to 10 wt%) were prepared by sonicating the mixture of PVA and GO, followed by crosslinking with glutaraldehyde. GO was pre-treated with oxyfluorination ($O_2:F_2$ = 8:2) in order to modify the surface of GO to allow it to carry hydrophilic functional groups. PVA/GO composite hydrogels were characterized by scanning electron microscopy and Fourier-transform infrared spectrometer (FT-IR). The morphology of the PVA/GO composite hydrogels and the variations in soluble gel portion were investigated under various GO contents and UV irradiation doses. The variation in the chemical structure of photo degraded PVA/GO composite hydrogels was studied by FT-IR. The photochemical stability of PVA/GO composite hydrogels under UV irradiation was found to improve noticeably with increasing content of uniformly dispersed GO.

• 한국재료학회지
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• 제31권2호
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• pp.68-74
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• 2021

Zinc-ion Batteris (ZIBs) are recently being considered as energy storage devices due to their high specific capacity and high safety, and the abundance of zinc sources. Especially, ZIBs can overcome the drawbacks of conventional lithium ion batteris (LIBs), such as cost and safety issues. However, in spite of their advantages, the cathode materials under development are required to improve performance of ZIBs, because the capacity and cycling stability of ZIBs are mainly influenced by the cathode materials. To design optimized cathode materials for high performance ZIBs, a novel manganese oxide (MnO2) coated graphite sheet is suggested herein with improved zinc-ion diffusion capability thanks to the uniformly decorated MnO2 on the graphite sheet surface. Especially, to optimize MnO2 on the graphite sheet surface, amounts of percursors are regulated. The optimized MnO2 coated graphite sheet shows a superior zinc-ion diffusion ability and good electrochemical performance, including high specific capacity of 330.8 mAh g-1 at current density of 0.1 A g-1, high-rate performance with 109.4 mAh g-1 at a current density of 2.0 A g-1, and remarkable cycling stability (82.2 % after 200 cycles at a current density of 1.0 A g-1). The excellent electrochemical performance is due to the uniformly decorated MnO2 on the graphite sheet surface, which leads to excellent zinc-ion diffusion ability. Thus, our study can provide a promising strategy for high performance next-generation ZIBs in the near future.

• Bulletin of the Korean Chemical Society
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• 제30권4호
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• pp.817-820
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• 2009

To meet the high current load requirement from the high energy density realized by metal oxide and high power density graphite, we propose a novel hybrid supercapacitor consisting of Nb2O5 and KS6 graphite in 1.0 M LiPF6-EC:DEC (1:2). This new system exhibits a sloping voltage profile from 2.7 to 3.5 V during charging and presents a high operating voltage plateau between 1.5 and 3.5 V during discharging. The cell was tested at a current density of 100 mA/g with a cut-off voltage between 3.0 and 1.0 V. This novel energy storage system delivers the highest initial discharge capacity of 55 mAh/g and exhibits a good cycle performance.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2011년도 춘계학술발표대회
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• pp.240.2-240.2
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• 2011

그라파이트 산화물(graphite oxide;G.O)는 그라파이트와는 다르게 물에서의 분산 능력이 뛰어나고 다양한 기판상에 단일 G.O layer를 형성할 수 있는 특성을 가지고 있으며, 유연(flexible)하고 투명(transparent)하기 때문에 다양한 전 자기 디바이스에 적용 가능하다. 특히, 최근 자성산화물 나노입자(magnetic oxide nanoparticles)에 대한 연구가 집중되고 있는데, 이러한 자성 나노입자와 G.O와의 복합체에 대한 연구는 다양한 분야로의 적용성에 대한 새로운 길을 열어주고 있다. 본 연구에서는 화학적 처리법을 적용하여 자성 나노입자(Co 나노입자)와 G.O 복합체를 제조하였다. Natural Graphite powder (N.G)에 $H_2O_4$ (98%) 및 $(NH_4)_2SO_4$를 적정 몰비로 첨가하여 반응 시킨 후 공기 중에서 열처리 공정을 수행하여 expanded graphite (E.G)를 제조 하였다. 열처리된 E.G를 $1,050^{\circ}C$ 온도에서 15~30초 및 30~60초 동안 공기 중에서 열처리 하여 expanded graphite oxide (E.G.O)를 제조하였으며, E.G.O와 $Co(acac)_3$의 화학적 반응을 통하여 Co 자성나노입자-G.O 복합체를 제조하였다. N.G, E.G, E.G.O 및 E.G.O+Co입자의 결정구조 분석을 위하여 XRD 측정을 수행하였으며, FTIR을 이용하여 각 단계에서의 반응성에 대한 연구를 수행하였다. 각 단계에서 표면 및 내부 미세구조 특성 분석을 위하여 SEM, TEM, 및 EDX 분석을 수행하였으며, E.G.O+Co 복합체의 자기적 특성 평가를 위하여VSM (vibrating sample magnetometer) 측정을 수행하였다. 이러한 연구 결과는 향후 자성나노입자와 그라핀과의 복합화를 위한 기저 기술로 활용가능하리라 판단된다.

• 공업화학
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• 제24권1호
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• pp.87-92
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• 2013

광촉매 혼성 저온 플라즈마는 폐수에 함유된 유기물을 분해시키는 효과적인 기술이다. 본 연구에서는 광촉매가 결합된 특별히 설계된 유전체 방전 시스템을 골프장이나 감귤농가에서 흔히 살포되는 디크로보스, 카보퓨란 및 메치다치온 살충제의 분해에 적용하였다. 단독 및 병합 시스템에서 살충제의 분해를 평가하였다. 단독 시스템은 UV의 차폐 유무 및 산소기체와 공기에 의한 오존(각종 반응 활성종들 포함) 플라즈마를 이용하였다. 혼성 시스템은 UV로 활성화된 산화아연, 이산화티타늄과 그래파이트 옥사이드와 결합하여 공기에 의한 플라즈마 반응에 적용하였다. 그래파이트 옥사이드는 모사 허머스 법으로 제조하여 FT-IR 분광기로 성능을 측정하였다. 반응시간 60 min에서 UV를 차폐하고 공기를 이용한 플라즈마 반응에 의한 분해성능과 비교하였으며, UV로 활성화된 그래파이트 옥사이드(0.01 g/L)와 결합된 플라즈마 반응은 디크로보스와 카보퓨란의 각각 100% 분해도를 보였다. UV를 활용한 광촉매 혼성 플라즈마는 살충제를 분해시키는 효과적인 대안으로 입증되었다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제45회 하계 정기학술대회 초록집
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• pp.138.2-138.2
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• 2013

Copper oxide is a multi-functional material being used in various research areas including catalysis, electrochemical materials, oxidizing agents etc. Among these areas, we have synthesized and utilized graphene based copper oxide nanocomposites (CuOx/Graphene) for the catalytic applications (C-N cross coupling reaction). Briefly, Cu precursors were anchored on the graphite oxide(GO) sheets being exfoliated and oxidized from graphite powder. Two different crystalline structures of Cu2O and CuO on graphene and GO were prepared by annealing them in Ar and O2 environments, respectively. The morphological and electronic structures were systemically investigated using FT-IR, XRD, XPS, XAFS, and TEM. Here, we demonstrate that the catalytic performance was found to depend on oxidative states and morphological structures of CuOx graphene nanocomposites. The relationship between the structure of copper oxides and catalytic efficiency toward C-N cross coupling reaction will be discussed.

• 한국세라믹학회지
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• 제47권3호
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• pp.210-215
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• 2010

In this study, an expanded graphite-titanium oxide composite is developed from expanded graphite (EG) and titanium n-butoxide (TNB). EG is synthesized by chemical intercalation of natural graphite (NG) and rapid expansion at high temperature. TNB is used as the titanium source. The performances of the prepared EG-$TiO_2$ composite are characterized by BET surface area measurements, scan electron microscope (SEM), X-ray diffraction patterns (XRD) and energy dispersive X-ray analysis (EDX). The catalytic activities of the EG-$TiO_2$ composite are investigated by analysis of the degradation of methylene blue (MB) in aqueous solution under irradiation of UV light. Compared with the pristine $TiO_2$ and activity carbon-$TiO_2$ (AC-$TiO_2$) composite, the EG-$TiO_2$ composite shows very high efficiency against MB solution, and the EG could improve the photocatalytic effect of $TiO_2$ in the MB degradation reaction under the irradiation of UV light.

• 한국수소및신에너지학회논문집
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• 제22권5호
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• pp.592-598
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• 2011

Electrode of solid oxide fuel cell must have sufficient porosity to allow gas transport to the interface with electrolyte effectively but high porosity has a negative impact on structural stability in electrode support. Thus, the upper limit of porosity is based on consideration of mechanical strength of electrode. In this study, the effect of microstructure of Ni-YSZ anode supported SOFC on the mechanical and electrical property was investigated. LSCF composite cathode and 8YSZ electrolyte were used. The porosity of the anode was modified by the amount of graphite powder and added graphite contents were 24, 18, 12 vol%, respectively. The higher the porosity, the better the electrical performance, $P_{max}$. While the flexural strength decreased with increasing the amount of graphite. But the rate of increase in electrical performance and the rate of decrease in mechanical strength were not directly proportional to amount of graphite. The optimum graphite content incorporating both electrical and mechanical performance was 18 vol%.

• Bulletin of the Korean Chemical Society
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• 제33권2호
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• pp.449-452
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• 2012

A polyaniline-gold composite was prepared via the polymerization of aniline hydrochloride with or without water-soluble graphite oxide using auric acid as an oxidant. The reaction products were characterized using Xray photoelectron spectroscopy. The thermal stability and embedded crystallinity of the composites were also investigated using thermogravimetric and X-ray diffraction analyses. The electrical properties of the composites were examined using cyclic voltammetric measurements at room temperature and temperature-dependent DC conductivity within 300-500 K. Compared to pure graphene oxide and polyaniline-gold composite, the polyaniline-gold-graphene composite exhibited higher crystallinity and thermal stability, and higher current density response under equivalent conditions.