Near net-shape manufacturing of Nafion and Nafion/ceramic membranes for fuel cell applications

NafionRTM/ceramic nanocomposite membranes are prepared by a solid state method for fuel cell applications. Nanocomposite powders from NafionRTM pellets and a zirconium phosphate ceramic are formed by mechanical attrition. The powders are consolidated into membrane form by mechanical pressing and hot isostatic pressing. Cross-sectional analysis by scanning electron microscopy (SEM) indicates that the ceramic particles exist in agglomerates that are evenly dispersed across the membrane. Dynamic mechanical analysis (DMA) and tensile testing found the membranes to be mechanically equivalent, and in some cases superior, to a commercial extruded membrane. Increasing ceramic content is accompanied by an increase in modulus and shift in the alpha transition to higher temperature. Evaluation of membrane hydration by thermal gravimetric analysis (TGA) indicates that the prepared membranes have increased water uptake when compared to a commercially available membrane. However, as distribution of the ceramic is improved, the hydration of the sample is reduced. Low temperature differential scanning calorimetry (DSC) indicates that the additional water contributes to an increase in both freezing and nonfreezing water contents in the membranes. Proton conductivity, measured by the 4-probe method at 60°C in water as well as with varying relative humidity and temperature, revealed that the prepared membranes have conductivities that are comparable to but somewhat lower than the commercial membranes. An increase in conductivity is seen with decreased particle size and improved dispersion of the ceramic.