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.

The Bridge Safety Department of Seoul Metropolitan Government has regularly conducted precise inspection and precision safety inspection to maintain the bridge's function and safety. During a precise safety inspection in 2015, oil leakage progression was found on the cable anchorage system within the stiffened girder of Nilsen Arch bridge and as a follow-up measure, the cable replacement for the cable ACD11 was carried out in order to identify the relevant cause of the oil leakage and evaluate the integrity of the existing cable. The mechanical properties and fatigue performance tests of the cable strands of bridge inservice for about 20 years and comprehensive analysis of oil leakage were carried out. They were described hereby.