Research Of Bipolar Plate In Fuel Cell With Graphite Nanosheets

Expanded Graphite (abbreviated as EG) is vermiform in shape withloose and porous structure and extreme specific area. It has been put intoproducing industrialization, and with certain properties such as low priceand large production. In this study, taking graphite nanosheets and carbonnanotubes(CNTs) as the main raw materials, we prepared the compositebipolar plates by compression molding technology. The expanded graphite issynthesized by chemical intercalation of natural graphite and suddenexpansion at high temperature. With the changes of graphite nanosheets andpolyimide in the percentage, the density, electrical conductivity andmechanical properties will vary but it’s difficult to achieve the desiredconductivity and mechanical properties. The increase of resin content is notconducive to the conductivity of the bipolar plate but beneficial to thebending strength. Therefore, CNTs was added to reinforce the composite toreduce the capacity and weight of bipolar plate.In my research, graphite nanosheets/polyimide composite was preparedby low temperature and hot pressure molding formation. The effect ofpreparation technology on properties of composite was also studied, thenthe technological parameter of composite was optimized. Graphite nanosheets/polyimide composite was prepared by single-factor test at first. Theeffect of preparation technology on properties of composite was studied, too.The results show that the electrical conductivity and bending strengthincrease with the increasing of the specific volume. The electricalconductivity decreases and bending strength increases with the increasing ofpolyimide content. The effect of molding temperature, pressure and moldingtime is similar. The conductivity of composite will rise and then decline withthe molding temperature, pressure and molding time increasing. While thebending strength is not the same. With the molding temperature and pressure increasing, the bending strength increases. When the molding time increases,the bending strength appears augment and then decline. The CNT reinforcedgraphite nanosheets/polyimide composite was prepared successfully and theeffect of content on properties of composite was also studied to get theoptimal preparation technological parameters. The results show that with thecontent of CNT increasing, the density of bipolar plate decreases and thebending strength and conductivity will increase firstly and then decrease.The best conductivity and bending strength of the composite are113s/cmand54MPa when CNT content is2wt%, respectively, which improved25%and19%compared with graphite nanosheets/polyimide composite.The analysis of microstructure characteristics and chemical content wasconducted by scanning electron microscopy (SEM) quantitative X-raydiffraction (XRD) and Raman spectroscopy. The reinforcement mechanismof composite was studied by SEM. The results show that the boundarybetween CNT and polyimide is on strong bonding state. The bendingstrength forecast equation on the CNT reinforced graphite/polyimidecomposite was concluded by using composite mechanical theory. The CNTlength coefficient, and CNT oriental coefficient were considered and theiranalytic equations were also concluded.