THE EFFECTS OF FLOCCULATION ON THE PROPAGATION OF ULTRASOUND IN DILUTE KAOLIN SLURRIES

A broadband ultrasonic spectrometer has been used to measure ultrasoni c attenuation and phase velocity dispersion as functions of frequency in kaolin suspensions over a range of solid volume fractions from phi = 0.01 to phi = 0.08 and over a pH range from 3 to 9. The Harker and T emple theory was used to simulate ultrasound propagation in the suspen sion, using measured slope viscosity, particle size, and size distribu tion. Simulated results for ultrasonic attenuation and phase velocity agree well with measured values. Both sets of results agree well and s how that for volume fractions above phi similar to 0.05 attenuation an d velocity dispersion increase for increasing flee size, whereas for v olume fractions below phi similar to 0.05 attenuation and velocity dis persion both decrease. It is proposed that the mechanism for this chan ge in behavior around phi similar to 0.05 involves changes in flee den sity and flee size distribution with phi and pH. (C) 1998 Academic Pre ss.