• Title/Summary/Keyword: Graphite sheet

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Synthesis of Manganese Oxide Coated Graphite Sheet for Zinc-Ion Batteries with Improved Energy Storage Performance (아연-이온 배터리의 에너지 저장 성능 향상을 위한 망간산화물이 코팅된 흑연시트의 제조)

  • Lee, Young-Geun;An, Geon-Hyoung
    • Korean Journal of Materials Research
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    • v.31 no.2
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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.

Evaluation of Electrochemical Stability and Performance of Graphite Sheets as Current Collectors for Lead Acid Battery (납축전지 전류집전체로서 그라파이트 시트의 전기화학적 안정성과 방전성능 평가)

  • An, Sang-Yong;Kim, Eung-Jin;Yoon, Youn-Saup;Kim, Hee-Jung
    • Journal of the Korean Electrochemical Society
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    • v.13 no.2
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    • pp.128-131
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    • 2010
  • Graphite sheet electro-deposited with lead was evaluated as a possible candidate for current collectors of lead acid batteries. Cyclic voltammetry was performed on the materials to evaluate the electrochemical properties. The graphite sheet electro-deposited with lead is electrochemically stable in the cathodic potential sweep. However, in the anodic potential sweep, the graphite sheet electro-deposited with lead is electrochemically unstable due to the oxygen evolution and the intercalation of sulfuric acid. Lead acid batteries were prepared by using a graphite sheet and a cast grid as current collectors for anode and performance test using those batteries was carried out. A lead acid battery with graphite sheets showed higher capacity and energy density than a conventional lead acid battery with cast grid.

Fabrication of X-ray Mask Using Graphite Sheet (Graphite Sheet를 이용한 X-ray Mask 제작)

  • Cho, Jin-Woo;Hong, Sung-Jei;Park, Soon-Sup;Shin, Sang-Mo
    • Proceedings of the KIEE Conference
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    • pp.3276-3278
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    • 1999
  • LIGA 기술을 제품의 대량생산에 적용하기 위해서는 한번에 넓은 면적을 노광할 수 있는 X-ray 마스크가 요구된다. 기존에 널리 사용되고 있는 SiN 멤브레인 마스크는 내구성이 좋지 않고 면적을 크게하기 어렵다. 따라서 본 연구에서는 이러한 단점을 보완하기 위해 상용 graphite sheet를 이용하여 X-ray 마스크를 제작하였다. 제작된 graphite 마스크와 SiN 마스크를 이용하여 동일한 조건에서 X-ray 노광 실험을 하였고 마스크의 외형변화를 관찰하였다. 그 결과 SiN 마스크는 에너지 2.3GeV, 평균 전류 110mA에서 약 18시간 만에 파괴되었으나 graphite mask는 60시간 경과 후에도 육안상의 변화는 관찰되지 않았다. 또한 graphite 마스크를 이용하여 제작된 미세구조물의 치수측정결과 오차가 $1{\mu}m$ 미만인 정밀한 구조물 제작이 가능함을 확인하였다.

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Thick Graphene Embedded Metal Heat Spreader with Enhanced Thermal Conductivity

  • Park, Minsoo;Chun, Kukjin
    • Journal of Sensor Science and Technology
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    • v.23 no.4
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    • pp.234-237
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    • 2014
  • In this paper, a copper foil-thick grapheme (thin graphite sheet)-copper foil structure is reported to achieve mechanically strong and high thermal conductive layer suitable for heat spreading components. Since graphene provides much higher thermal conductivity than copper, thick graphene embedded copper layer can achieve higher effective thermal conductivity which is proportional to graphene/copper thickness ratio. Since copper is nonreactive with carbon material which is graphene, chromium is used as adhesion layer to achieve copper-thick graphene-copper bonding for graphene embedded copper layer. Both sides of thick graphene were coated with chromium as an adhesion layer followed by copper by sputtering. The copper foil was bonded to sputtered copper layer on thick graphene. Angstrom's method was used to measure the thermal conductivity of fabricated copper-thick graphene-copper structure. The thermal conductivity of the copper-thick graphene-copper structures is measured as $686W/m{\cdot}K$ which is 1.6 times higher than thermal conductivity of pure copper.

A Study of Mechanical Properties in Compression on High density Graphite Products with Expanded Graphite (고밀도 팽창흑연 성형품의 압축 특성에 관한 연구)

  • Shin, Y.W.
    • Journal of Power System Engineering
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    • v.10 no.1
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    • pp.52-59
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    • 2006
  • Graphite is well known as a material which has high-temperature thermostable property, chemical resistance against acid and alkaline state also is very easy to environment. Nowadays the need of graphite product is increasing rapidly because of its advantages. In this paper, the mechanical property of newly developed graphite products with high density is investigated with especially in compression test. I introduced the graphite specimens for this study by NGF method with two expandable graphite and compared to the specimens of commercial graphite sheet from expanded graphite which made by the rolling process. I investigated the characteristics of these materials by measuring specific weight, hardness, compressive strength and investigating structures by SEM, It is verified that the graphite products with NGF method has superior properties for using gasket materials than that of commercial graphite sheet.

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A Study of Mechanical Properties on High Density Graphite Products with Expanded Graphite(1) (고밀도 팽창흑연 성형품의 기계적 특성에 관한 연구(1))

  • Shin, Y.W.
    • Journal of Power System Engineering
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    • v.9 no.4
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    • pp.143-147
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    • 2005
  • Graphites is well known to have superior advantages to high-temperature, high-pressured, and strong acid-state gas or liquid because it is very stable and chemical structure. Nowadays the new plant with high performance is developed in field of chemical industries, so the need of graphites is increasing rapidly. In this paper, newly developed graphite products with high density is investigated by the mechanical properties of that. I introduced the graphite material which developed for this experiment by the forming process in order to compare to the commercial graphite sheet from expanded graphite which made by the rolling process. Through measuring density and hardness test also tensile test, I investigated the characteristics of these materials. It is verified that the newly developed graphite products forming method is able to make graphite products which have superior mechanical properties than that of commercial graphite sheet.

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A Study on Thermostable Property of High Density Graphites Products with Expanded Graphite(1) (고밀도 팽창흑연 성형품의 내열 특성에 관한 연구(1))

  • Shin, Y.W.
    • Journal of Power System Engineering
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    • v.9 no.4
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    • pp.148-154
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    • 2005
  • Thermostable property is one of most important characteristics of graphite. Commercial graphites sheet from expanded graphite is using for high-temperature elements. Nowadays the new plant with high performance is developed in field of chemical industries, so the need of graphites is increasing rapidly. In this paper, the thermostable properties of newly developed graphite products with high density is investigated. I introduced the graphite material which developed for these heat tests by NGF method in order to test thermostable properties by comparing to the results of the commercial graphite sheet from expanded graphite in same condition. Through measuring the weight reducing ratio with various specimens in some conditions, I investigated the thermostable characteristics of these materials. It is verified that the graphite products by NGF method has almost same or superior thermostable properties comparing with that of commercial graphite sheet. Also the graphite products by NGF method have possibility of being better in thermostable properties.

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Performance Improvement of Flexible Thin Film Si Solar Cells using Graphite Substrate (그라파이트 기판을 이용한 유연 박막 실리콘 태양전지 특성 향상)

  • Lim, Gyeong-yeol;Cho, Jun-sik;Chang, Hyo Sik
    • Korean Journal of Materials Research
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    • v.29 no.5
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    • pp.317-321
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    • 2019
  • We investigated the characteristics of nano crystalline silicon(nc-Si) thin-film solar cells on graphite substrates. Amorphous silicon(a-Si) thin-film solar cells on graphite plates show low conversion efficiency due to high surface roughness, and many recombination by dangling bonds. In previous studies, we deposited barrier films by plasma enhanced chemical vapor deposition(PECVD) on graphite plate to reduce surface roughness and achieved ~7.8 % cell efficiency. In this study, we fabricated nc-Si thin film solar cell on graphite in order to increase the efficiency of solar cells. We achieved 8.45 % efficiency on graphite plate and applied this to nc-Si on graphite sheet for flexible solar cell applications. The characterization of the cell is performed with external quantum efficiency(EQE) and current density-voltage measurements(J-V). As a result, we obtain ~8.42 % cell efficiency in a flexible solar cell fabricated on a graphite sheet, which performance is similar to that of cells fabricated on graphite plates.