通过Sol-Gel法制备出Ni颗粒表面均匀包覆尿素掺杂二氧化钛涂层的纳米核壳颗粒Ni/(TiO_2+Urea),对其电流变行为进行了研究.结果表明颗粒热处理温度和尿素加入量对其电流变活性有较大影响,热处理温度高于320℃以后剪切强度明显降低;尿素与Ti的质量比为30%时,剪切强度达到40kPa(4kV/mm直流电场),是无尿素时的10倍,但过量的尿素使强度下降.显微镜观察直流电场下电流变液的结构显示,尿素与Ti的质量比为30%时核壳颗粒电流变液形成的柱粗壮、致密,尿素过量时柱产生断裂,无尿素时柱纤细、疏松.尿素中的极性分子是影响Ni/(TiO_2+Urea)颗粒电流变行为的重要因素.
The Ni/(TiO_2 + Urea)core-shell nano particles composed of nano Ni particles and urea-doped TiO_2 coating, were synthesized by using Sol-Gel method, and their electrorheological (ER) behaviors were investigated. The results show that ER activity of the particles are closely associated with heat-treatment tem-perature and urea content. The shear stress decreases when the particles is heat-treated above 320℃. When the mass ratio of urea to Ti is 30%, the shear stress of the ER fluid made from Ni/(TiO_2 + Urea) particles reaches 40kPa (the DC electric field is 4kV/mm), which is 10 times as high as that made from particles without urea. However, the shear stress decreases when excessive urea is added. The microstructure obser-vation of the ER fluids under DC electric field shows that the particles aggregate to form thicker and dense column structure when the mass ratio of urea to Ti is 30%, while the column structure is broken when exces-sive urea (> 30%) is added. A thin and loose column structure is formed in ER fluid without urea added.It is suggested that the ER behaviors is substantially correlated with the polar molecules in urea.
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