| dc.description.abstract | The purpose of this study is to investigate the effects of various
carbon materials on the mechanical, thermal and electrical properties of
polymer composites. These composites materials are potential
replacements for graphite bipolar plates currently used in proton
exchange membrane fuel cells (PEMFC).
Polymer composites are fabricated by the hot press method using
different mixing ratios of conductive fillers and HTPR. In this work,
acetylene black (AB), carbon black (XC-72), carbon fiber, and graphite
are used as the conductive fillers. The results show that as the content of
the conductive fillers increases, the mechanical strength, the hardness,
and the vibration-absorption ability of the composite increase. The
thermal conductivity also increases. The electrical resistance decreases as
the filling ratio of the conductive fillers is increased. Of the four fillers,
carbon fibers and XC-72 carbon black samples have the lowest
resistance.
The Taguchi method is used to study the optimal content of the
conductive fillers and process parameters. The best mixing speed and
time are found to be 50rpm and 4 minutes, respectively. The optimal
filling content is 30wt% ofcarbon fiber plus 25wt% of XC-72. This best
sample shows a slightly positive temperature coefficient of the resistance.
It increases from 0.35Ω-cm at 25°C to 0.40Ω-cm at 90°C .
Finally serpentine flow channel bipolar plates are fabricated using
the optimal design and are assembled with a Gore MEA to a single cell
PEMFC. NO gaskets are used between the MEA and the bipolar plate.
Gas tight is achieved with a torque of 2N-m. For cell temperature of 40°C
and humidification temperature of 55°C , the current density reaches 550
mA/cm2 at voltage 0.6 V. | en_US |