The Preparation And Study Of Properties Of Bipolar Plate Composite Material Based On Carbon Microspheres/Graphite Microchip

As an important part of proton exchange membrane fuel cell, the bipolar plate has the characteristic of good function of electrical conductivity and thermal conductivity, good function of retardant gas, low volume resistance and contact resistance, great corrosion resistance, light weight, strength, and quantity production. The composite bipolar plate based on graphite has the advantages of pure graphite bipolar plate and metal bipolar plate and it has the advantages of cheap, small volume, strength and great corrosion resistance. It also can enhance the volume ratio power and weight ratio power of the fuel cells. This is one of development tendency of bipolar plates. However, the electrical conductivity and mechanical property of composite bipolar plate should be enhanced. Thus, to develop a greater bipolar plate by studying the electrical conductivity and mechanical property is one important research direction.In this content, the graphite microchip was prepared by method of chemical oxidation insert layer and the carbon microsphere was prepared by hydrothermal method. The two raw materials were character by scanning electron microscope, infrared spectroscopy, X-ray diffraction and thermogravimetry. Set carbon microsphere as basement and mix with electric graphite microchip by ball grinding. The mixture was sintered after directly mould pressing to get bipolar plate composite material. To study the performance and change rules of carbon microsphere/graphite microchip composite material, the experiments were performed by changing the ratio of content, molding pressure, ball milling time and dwell time. Other experiments were performed to observe the surfaces and fracture surface of bipolar plate materials and to test the properties of electric conductivity, mechanical, corrosion resistance, thermostability, hydrophily and volume density. The optimal technological conditions were confirmed according to the comprehensive properties. The results show that the carbon microsphere was prepared at 190 °C for 5 hours with 0.5 mol/L concentration of glucose. The carbon microsphere/graphite microchip bipolar plate composite material was prepared by bill milling the mixture with 6:4 ratio of carbon microsphere and graphite chip for 6 hours. Then put the mixture under 20 MPa pressure and keep for 5 minutes. The electric conductivity of bipolar plate composite material was 226 S/cm.To study the modification of carbon microsphere/graphite microchip bipolar plate composite material, the iron powder and silica powder were adding to study the effect on electric conductivity and flexure strength of carbon microsphere/graphite microchip bipolar plate composite material. The results show that the adding of metal iron can enhance the electric conductivity to 249 S/cm, but had merely effect with flexure strength. Add little nonmetal silica can enhance the properties of bipolar plate composite material. In conclusion, the properties of carbon microsphere/graphite microchip modified by adding iron powder or silica powder both meet the requests of United States department of energy.