• Carbon letters
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• 제14권1호
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• pp.40-44
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• 2013

The bipolar plate is the most important and most costly component of proton exchange membrane fuel cells. The development of a suitable low density bipolar plate is scientifically and technically challenging due to the need to maintain high electrical conductivity and mechanical properties. Here, bipolar plates were developed from different particle sizes of natural and expanded graphite with phenolic resin as a polymeric matrix. It was observed that the particle size of the reinforcement significantly influences the mechanical and electrical properties of a composite bipolar plate. The composite bipolar plate based on expanded graphite gives the desired mechanical and electrical properties as per the US Department of Energy target, with a bulk density of 1.55 $g.cm^{-3}$ as compared to that of ~1.87 $g.cm^{-3}$ for a composite plate based on natural graphite (NG). Although the bulk density of the expanded-graphite-based composite plate is ~20% less than that of the NG-based plate, the I-V performance of the expanded graphite plate is superior to that of the NG plate as a consequence of the higher conductivity. The expanded graphite plate can thus be used as an electromagnetic interference shielding material.

• Bulletin of the Korean Chemical Society
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• 제33권11호
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• pp.3589-3592
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• 2012

Carbon composite bipolar plates with various carbon black contents were prepared by a compression molding method. The electrical conductivity and electrochemical stability of the bipolar plates have been evaluated. It is found that the electrical conductivity increases with increasing carbon black contents up to 15 wt %. When the carbon black contents are greater than 15 wt %, the electrical conductivity decreases because of a poor compatibility between epoxy resin and carbon black, and a weakening of compaction in the carbon composite bipolar plate. Based on the results, it could be concluded that there are optimum carbon black contents when preparing the carbon composite bipolar plate. Corrosion tests show that the carbon composite bipolar plate with 15 wt % carbon black exhibits better electrochemical stability than a graphite bipolar plate under a highly acidic condition. When the optimized carbon composite bipolar plate is applied to vanadium redox flow cells, the performance of flow cells with the carbon composite bipolar plate is comparable to that of flow cells with the graphite bipolar plate.

• Composites Research
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• 제34권6호
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• pp.406-411
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• 2021

PEM(양성자 교환막) 연료 전지는 부산물로 물 만을 생성하여 친환경 에너지원으로 각광받고 있다. 이러한 연료전지의 스택을 이루는 여러 부품들 중 연료전지의 효율을 결정짓는 분리판에 관한 연구가 활발히 진행되고 있다. 복합재료 분리판은 높은 강도와 강성 및 내식성을 갖지만 상대적으로 낮은 전기 전도도를 갖는 단점이 있다. 본 연구에서는 이러한 단점을 극복하고자 가스확산층(GDL)-복합재료 분리판 조합체를 개발하고 그 성능을 실험적으로 확인하였다. 선행 연구에서 개발된 흑연 포일 코팅법을 분리판과 GDL 간의 접촉 저항을 줄이기 위해 적용하였다. 또한, 스택 내의 전자 이동경로를 향상시키고 GDL과 분리판 사이의 접촉저항을 최소화하기 위하여 금속 박막을 이용하여 GDL-분리판 조합체를 제작하였다. 실험 결과 개발된 GDL-분리판 조합체는 기존의 복합재료 분리판과 비교하여 98% 낮은 전기저항을 갖는 것을 확인하였다.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2009년도 추계학술대회 논문집
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• pp.180-183
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• 2009

Composite bipolar plates offer several advantages of low cost, light weight, and ease of manufacturing compared to traditional graphite plate. However, it is difficult to achieve both high electrical conductivity and high flexural strength. In this study, the hybrid carbons filled epoxy composite bipolar plates were fabricated to test electrical conductivity and flexural properties. Graphite powders were used as the main conducting filler and continuous carbon fiber fabrics were inserted to improve the mechanical properties of the composite. This hybrid composite showed improved in-plane electrical conductivity and flexural property. The moldability of the hybrid composite was also improved comparing to the continuous prepreg composite. This study suggested that the continuous carbon fiber inserted graphite/epoxy composites can be a potential candidate material to overcome the disadvantages of conventional graphite composite or continuous prepreg composite bipolar plates.

• 한국수소및신에너지학회논문집
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• 제23권2호
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• pp.134-142
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• 2012

A bipolar plate is a major component of a fuel cell stack, which occupies 50~60% of the total weight and over 50% of the total cost of a typical fuel cell stack. In this study, a composite bipolar plate is designed and fabricated to develop a compact and light-weight direct methanol fuel cell (DMFC) stack for a small-scale Unmanned Aerial Vehicle (UAV) application. The composite bipolar plates for DMFCs are prepared by a compression molding method using resole type phenol resin as a binder and natural graphite and carbon black as a conductor filler and tested in terms of electrical conductivity, mechanical strength and hydrogen permeability. The flexural strength of 63 MPa and the in-plane electrical conductivities of 191 S $cm^{-1}$ are achieved under the optimum bipolar plate composition of phenol : 18%; natural graphite : 82%; carbon black : 3%, indicating that the composite bipolar plates exhibit sufficient mechanical strength, electrical conductivity and hydrogen permeability to be applied in a DMFC stack. A DMFC with the composite bipolar plate is tested and shows a similar cell performance with a conventional DMFC with graphite-based bipolar plate.

• 신재생에너지
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• 제3권4호
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• pp.3-7
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• 2007

Graphite/polymer composite bipolar plates for PEMFC are successfully developed, and their typical properties are superior to commercially available ones. Thermal property of the developed bipolar plate was evaluated by dynamic mechanical analyzer, and the results were compared to commercial ones. The specimens were immersed into the deionized water bath at $80^{\circ}$... for 1500hrs to evaluate dimensional stability and durability. Dimension, weight of the specimens as well as extraction conductivity was measured as each 500hrs. Fully molded bipolar plates without any machining or milling were also prepared using a specially developed mold, and they were applied to the fuel cell performance test. Results were compared to the machined commercial bipolar plate.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2007년도 추계학술대회 논문집
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• pp.5-7
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• 2007

Graphite/polymer composite bipolar plates for PEMFC are successfully developed, and their typical properties are superior to commercially available ones. Thermal property of the developed bipolar plate was evaluated by dynamic mechanical analyzer, and the results were compared to commercial ones. The specimens were immersed into the deionized water bath at $80^{\circ}C$ for 1500hrs to evaluate dimensional stability and durability. Dimension, weight of the specimens as well as extraction conductivity was measured as each 500hrs. Fully molded bipolar plates without any machining or milling were also prepared using a specially developed mold, and they were applied to the fuel cell performance test. Results were compared to the machined commercial bipolar plate.

• 한국수소및신에너지학회논문집
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• 제22권3호
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• pp.409-414
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• 2011

건물용 고분자연료전지는 저탄소 녹색산업화에 기여할 수 있는 대표적인 신재생에너지원으로, 정부 주도의 보급사업을 통해 초기 시장창출이 이루어지고 있다. 고분자연료전지 산업화 촉진을 위해서는 분리판을 비롯한 구성 부품의 상용화 기술개발과 저가화가 필수적이다. 탄소복합체 몰딩분리판의 적용은 고분자연료전지 상용화를 앞당기는데 기여할 것이다. 한국타이어에서 개발한 복합체 몰딩분리판은 고분자연료전지 스택 부품으로서의 요구 특성과 성능을 모두 만족시키는 것으로 나타났다. 한국타이어는 분리판 상용화 기술개발과 지속적인 생산능력 확보를 통해 국산 연료전지의 가격 및 성능 경쟁력 향상을 위해 최선의 노력을 다하고 있다.

• Carbon letters
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• 제8권4호
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• pp.326-334
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• 2007

In this study, graphite composites were fabricated by warm press molding method to realize commercialization of PEM fuel cells. Graphite composites have been considered as alternative economic materials for bipolar plate of PEM fuel cells. Graphite powder that enables to provide electrical conductivity was selected as the main substance. The graphite powder was mixed with phenolic resin and the mixture was pressed using a warm press method. First of all, the graphite powder was pulverized with a ball mill for the dense packing of composite. As the ball milling time increases, the average size of particles decreases and the size distribution becomes narrow. This allows for improvement of the uniformity of graphite composite. However, the surface electrical resistivity of graphite composite increases as the ball milling time increases. It is due to that graphite particles with amorphous phase are generated on the surface due to the friction and collision of particles during pulverizing. We found that the contact electrical resistivity of graphite particles increases as the particle size decreases. The contact electrical resistivity of graphite powders was reduced due to high molding pressure by warm press molding. This leads to improvement of the mechanical properties of graphite composite. Hydrogen gas impermeability was measured with the graphite composite, showing a possibility of the application for bipolar plate in fuel cell. And, I-V curves of the graphite composite bipolar plate exhibit a similar performance to the graphite bipolar plate.

• Carbon letters
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• 제14권2호
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• pp.110-116
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• 2013

This study investigated a developed process for producing a composite bipolar plate having excellent conductivity by using coal tar pitch and phenol resin as binders. We used a pressing method to prepare a compact of graphite powder mixed with binders. Resistivity of the impregnated compact was observed as heat treatment temperature was increased. It was observed that pore sizes of the GCTP samples increased as the heat treatment temperature increased. There was not a great difference between the flexural strengths of GCTP-IM and CPR-IM as the heat treatment temperature was increased. The resistivity of GPR700-IM, heat treated at $700^{\circ}C$ using phenolic resin as a binder, was $4829{\mu}{\Omega}{\cdot}cm$ which was best value in this study. In addition, it is expected that with the appropriate selection of carbon powder and further optimization of process we can produce a composite bipolar plate which has excellent properties.