Ultrasonic attenuation by nanoporous particles : Part II: Experimental

Abstract

In Part I of this paper O'Brien presented a new theory that describes the dissipation of ultrasonic energy by porous colloidal particles in suspension. In this paper we present experimental measurements on several such suspensions and compare the resulting ultrasonic attenuation spectra with O'Brien's theory. We find that microporous colloids (e.g. zeolites) and mesoporous colloids (e.g. porous silicas) both show greater attenuation of ultrasound than would solid particles of the same size and effective density, as predicted by O'Brien. Fitting theoretical spectra to the experimental data provides information about the porosity and pore diameters in the particles. This makes the technique potentially suitable as a convenient method of characterizing nanoporous materials, especially those already in suspension.