Acoustic spectroscopy as a technique for the particle sizing of high concentration colloids, emulsions and suspensions

The particle size distribution of particles in liquid-based suspensions and emulsions is an important parameter in a wide variety of industrial applications. Many particle-sizing methods require the transmission of light through a sample of the system, and therefore these particulate systems must be severely diluted. Many systems are unstable on dilution and therefore have to be measured at high volume concentration. Sound waves interact with both the suspending medium and the dispersed phase and are able to propagate through concentrated systems. The development of new ultrasonic transducer technology together with advances in digital signal processing has opened the way for a powerful new analysis termed acoustic attenuation spectroscopy. The technique consists of propagating ultrasonic waves of a range of frequencies through the particulate system and accurately measuring the attenuation at each frequency. This attenuation spectrum can be converted to a particle size distribution and a measure of the concentration of the dispersed phase. It offers the particle technologist the means to monitor and control particle formation and reduction processes. (C) 1999 Elsevier Science B.V. All rights reserved.