Manganese oxide suspensions were obtained in the synthesis of mesoporous manganese oxides via sol-gel method or surfactant (polyoxyethylene fatty alcohol, AEO_9) template method. Comparative Rheological investigations of manganese oxide suspensions (with or without AEO_9) have been performed. The experimental results indicate that there exist transition points in the flow curves of the suspensions. Below the point, the suspension exhibits plastic flow behavior, and over it shows dilatancy. An interesting apparent viscosity fluctuation process was found in the suspensions whether pre- sheared or not. The results of small-amplitude oscillatory shearing tests show that storage modulus G' and loss modulus G" all fluctuate with time. The fluctuation mechanism is proposed in terms of the elastic gel structure in the suspension. In this kind of gel, the dispersed particles possess "soft" property. The network structure can swell and shrink reversibly, and the fluctuation of apparent viscosity reflects this microstructure transformation in the suspension. Furthermore, the results show that aggregates of AEO_9 are packed in the gel structures because the suspension containing AEO_9 exhibits the same fluctuation behavior as inorganic gel. But after the introduction of surfactant into suspension, the great decreases in apparent viscosity and storage modulus G' indicate that there are strong interactions between aggregates of AEO_9 and inorganic precursors.

Key words: MANGANESE OXIDE, SURFACTANTS, SUSPENSION, RHEOLOGY, CHEMICAL OSCILLATIONS