燃料电池组件的孔结构表征.pptxVIP

燃料电池组件的孔结构表征第1页/共67页 IntroductionPore structure governs kinetics of physicochemical processes Flows of reactants and products in fuel cells.Quantitative measurement of pore structure is essential for Design, development and performance evaluation. Technologies for pore structure measurement are currently being developed to characterize the complex pore structure of fuel cell components. We will discuss several innovative techniques successfully developed and applied for evaluation of pore structure of fuel cell components. 第2页/共67页 Through Pore Throat Diameters, Distribution, Gas Permeability and Surface AreaImportance of Such PropertiesThrough Pores:Fluid flowPore Diameters:Capillary forces for liquid movementThroat diameters:Separation of undesirable particlesGas permeability:Overall rate of the processesThrough pore surface area:Physicochemical processesEffects of stress, chemical environments temperature:Influence of operating conditions第3页/共67页 Suitable Characterization TechniquesAdvanced Capillary Flow PorometryCapillary Condensation Flow PorometryThrough Pore Throat Diameters, Distribution, Gas Permeability and Surface Area第4页/共67页 Advanced Capillary Flow PorometryFor wetting liquid:Wetting Liquids fill pores spontaneouslyCannot come out spontaneouslyA pressurized inert gas can displace liquid from pores provided: Work done by Gas = Increase in Interfacial Free EnergyBasic Principle第5页/共67页 Advanced Capillary Flow PorometryPressure needed to displace liquid from a pore:p = 4 γ cos θ / D p = differential gas pressure γ = surface tension of wetting liquid θ = contact angle of the liquid D = pore diameterPore diameter is defined for all pore cross-sections第6页/共67页 Advanced Capillary Flow Porometry(Perimeter/Area)pore = (Perimeter/Area)cylindrical openingPore Diameter = Diameter of Cylindrical OpeningSKETCH第7页/共67页 Advanced Capillary Flow PorometryMeasured differential pressure gas flow through dry wet sample yield pore structure第8页/共67页 The TechniqueAc