Abstract: As a kind of multifunctional and high porosity carbon fiber composite, carbon paper plays an important role in mass transfer, heat and electric conductivity in the fuel cell, and its micro-structure characteristics directly determine the performance and durability. In this paper, the micro-structure of carbon paper is reconstructed by micro computed tomography (CT). And the volume fraction, pore diameter distribution, carbon fiber length, tortuosity, orientation and slant angle are measured and analyzed. Results indicate that the pore diameters approximately obey normal distribution, and the average pore diameter is 30.95 μm. The carbon fiber lengths and chord lengths obey 3-parameter Weibull distribution, and the average tortuosity is 1.03, which means that the fiber linearity is well. The orientation angle is distributed in the probability range of 0°~90°, and only 1.1% of the slant angle is more than 45°, indicating that the carbon fibers are randomly distributed on the XY plane, and only a small number of fibers migrate vertically into carbon. Finally, some distinct characteristics and defects in the micro-structure of carbon paper have been pointed out. This study is helpful to improve the understanding of the role of carbon paper in fuel cell.

Key words: carbon paper, micro-CT, micro-structure, fuel cell, carbon fiber composite