Effects of shear rate and particle concentration on rheological propertiesof magnetic particle suspensions

Rheological characterizations were made for various types of magnetic parti cles (rod-like gamma-Fe2O3, CrO2, and plate-like Ba-ferrite) and nonmagneti c (rod-like alpha-Fe2O3) suspensions, in terms of particle concentration an d shear rate. Shear rate dependence on viscosity was accurately described b y the Casson equation. The highest yield stress for Ba-ferrite among the fo ur types of particles represents the sensitive flocculation characteristics of Ba-ferrite with respect to concentration. The effect of non-magnetic al pha-Fe2O3 and magnetic gamma-Fe2O3 particle mixtures on suspension viscosit y was also examined, and a negative deviation from the tie line of individu al particle viscosities was observed. (C) 2000 Kluwer Academic Publishers.