ABSTRACT
This chapter describes two typical pore-size characterization methods, nitrogen adsorption and mercury porosimetry with their theoretical basis and with attention to be paid especially to the nanometer range. Depending on the wettability, the porous material is immersed in freon or water. Pressurized air or nitrogen is then introduced to one side of the material. An important phenomenon that commonly applies to nitrogen adsorption and mercury porosimetry is the so-called Young–Laplace effect. Pore size distributions, as well as the specific surface area, can be estimated from nitrogen adsorption isotherms at liquid-nitrogen temperature, or the amount adsorbed against relative pressure. In general, however, the accuracy of the adsorption measurement decreases as the equilibrium pressure approaches the saturated vapor pressure, because the liquid nitrogen temperature will fluctuate following variation in atmospheric pressure. The estimation based on the Kelvin model as given by Equations works well for pores larger than 10 nm.
