A composite material was prepared for the bipolar plates of phosphoric acid fuel cells(PAFC) by hot pressing a flake type natural graphite powder as a filler material and a fluorine resin as a binder. Average particle sizes of the powders were 610.3, 401.6, 99.5, and 37.7 μm. The density of the composite increased from 2.25 to 2.72 g/cm3 as the graphite size increased from 37.7 to 610.3 μm. The anisotropy ratio of the composite increased from 1.8 to 490.9 as the graphite size increased. The flexural strength of the composite decreased from 15.60 to 8.94MPa as the graphite size increased. The porosity and the resistivity of the composite showed the same tendencies, and decreased as the graphite size increased. The lowest resistivity and porosity of the composite were 1.99 × 10−3 Ωcm and 2.02 %, respectively, when the graphite size was 401.6 μm. The flexural strength of the composite was 10.3MPa when the graphite size was 401.6 μm. The lowest resistance to electron mobility was well correlated with the composite with lowest porosity. It was possible the flaky large graphite particles survive after the hot pressing process.

1. 서 론
 2. 실험 방법
  2.1 제조 방법
  2.2 밀도 및 기공률 측정
  2.3 배향도(Degree of Alignment)
  2.4 전기비저항 및 굽힙강도 측정
 3. 결과 및 고찰
  3.1 밀도 및 기공률광학현미경(LV150
  3.2 배향도(Degree of Alignment)
  3.3 굽힙강도 및 전기비저항
 4. 결 론
 Acknowledgements
 References

• 이상민(금오공과대학교 신소재공학과) | Sang-Min Lee (School of Materials Science and Engineering, Kumoh National Institute of Technology)
• 김태진(경북지역사업평가단) | Tae-Jin Kim (Gyeongbuk Institute For Regional Program Evaluation)
• 노재승(금오공과대학교 신소재공학과) | Jae-Seung Roh (School of Materials Science and Engineering, Kumoh National Institute of Technology) Corresponding author
• 백운경(금오공과대학교 신소재공학과) | Un-Gyeong Beak (School of Materials Science and Engineering, Kumoh National Institute of Technology)