Fabrication of Electrically Conductive, Fluid Impermeable Direct Methanol Fuel Cell (DMFC) Graphite Bipolar Plates by Indirect Selective Laser Sintering (SLS)

摘要

Graphite bipolar plates are highly desirable due to their properties of high electrical conductivityrnand low weight but are associated with prohibitive machining costs arising from poor mechanicalrnproperties. Bipolar plates made by indirect Selective Laser Sintering (SLS) offer the advantagesrnof complex part production in shorter times at lower cost. Due to the nature of the SLS process,rnthe as-produced (green part) plates are porous and possess low electrical conductivity which canrnbe improved by carbonizing the phenolic resin binder at high temperatures (brown part). It hasrnbeen found that the electrical conductivity increases significantly (> 200 S/cm) with arncorresponding increase in pyrolyzing temperature which correlates well with literature on therncarbonization of phenol formaldehyde resins. The brown parts are subsequently infiltrated withrnlow viscosity (～5 - 10 cps) cyanoacrylate to seal up the open pores, rendering the plates fluidrnimpermeable.