表面活性剂对氧化锰悬浮体系流变学振荡行为的影响

Influence of Surfactant on the Rheological Fluctuation Behavior of Manganese O xide Suspensions

对介孔氧化锰的溶胶 -凝胶法合成和用表面活性剂 (脂肪醇聚氧乙烯醚 ,AEO9)的模板合成过程中所得的悬浮体系的流变性质进行了对比研究 .结果表明 :上述体系均具有触变性 ,且无论是否预剪切 ,其表观粘度均随时间作周期性振荡 ;同时上述体系的储能模量G′和损耗模量G″亦具有周期性的振荡行为 .但表面活性剂AEO9的引入使体系的触变性大为减弱 ,屈服值明显降低 ,凝胶结构强度减弱 .同时还发现引入AEO9的模板合成过程中 ,不仅体系的表观粘度及G′大幅度下降 ,且G′与G″的振荡周期显著增大 ,振幅亦明显减小 .这说明体系中两亲分子与无机物存在较强的相互作用 。

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.