RHEOLOGY AND MAGNETIZATION OF CONCENTRATED MAGNETITE COLLOIDS

The apparent viscosity and magnetization of highly concentrated magnet ite colloids based on liquid hydrocarbons and oleic acid as a stabiliz er were experimentally studied. It was shown that the concentration de pendence of viscosity is most precisely approximated by the Chong form ula with an adjustment coefficient taking into account the particle ag gregation. Ignoring the particle aggregation (i.e., interparticle inte ractions) results in about a twofold underestimation of the apparent v iscosity. A calculation procedure for saturation magnetization and ini tial magnetic susceptibility of extremely concentrated colloids was pr oposed that makes it possible to account for the particle polydispersi ty and interparticle interactions. Magnetic susceptibility was shown t o be changed by almost two orders of magnitude depending on the partic le size distribution. The results of the calculations are in good agre ement with the experimental data.