A method for pore size and porosity analysis of porous materials using electroacoustics and high frequency conductivity

摘要

Electroacoustic measurement of the seismoelectric current generated by ultrasound in wetted porous materials yields information on pore size in certain situations. This occurs when electric double layers inside the pore overlap or when the pore size is sufficiently large that for a given frequency the hydrodynamic flow cannot achieve a steady Pousille profile inside of the pores. Indeed, we show experimentally that magnitude and phase of the seismoelectric current become pore size dependent in such systems. Calculations of pore size from such experimental raw data requires information concerning the porosity of the material. We suggest using high frequency conductivity measurement of the porous material to determine a formation factor'', which is the ratio of the wetted porous material conductivity to the conductivity of a equilibrium supernate. Porosity calculations from the formation factor can be done by applying the Maxwell-Wagner theory. We provide experimental verification that this theory can be applied for porous materials.