摘要：用化学共沉淀法合成了纳米Fe₃O₄粒子,平均二次粒径为51.2nm,比表面积为109.6m²/g。以合成的纳米Fe₃O₄粒子与羰基铁粉复合配制了纳米复合磁流变(MR)液,并测定了其流变性。结果显示:纳米复合MR液对温度比较稳定;复合MR液在接近零场的低磁场强度下表现为牛顿流体,随着磁场强度提高转变为非牛顿流体;反复加载或撤除磁场,具有"开/关"特性,响应迅速,施加磁场时的响应时间Δt约为50～100ms,撤退磁场时约为100～150ms。

关键词： 磁流变液;纳米Fe₃O₄粒子;磁致剪切应力;响应时间

Abstract： T he Fe₃O₄ nanoparticles are synthesized with the method of coprecipitation its average second particle size is about 51．2 nm its surface area is about 109．6 m²／g．A series of magnetorheological （MR） suspension based Fe／Fe₃O₄ nanocomposites is prepared and the rheological characteristics are measured．T he results show that the MR suspension is not sensitive to temperature and has a characteristics of “on／off ” responded to external magnetic field but responds to external magnetic field a little lower at “switching off ” than at “switching on”． T he MR suspension changed from Newtonian fluids into non Newtonian fluids． 

Keywords：magnetorheological fluid； Fe₃O₄nanoparticles；shear stress；response time