Oleophilicity and the strong electrorheological effect of surface-modified titanium oxide nano-particles

Surface-modified titanium oxide nano-particles with sodium dodecyl sulfate (SDS) were prepared by means of hydrolyzation. The size distribution shows that the average size of the modified particles is about 120nm. The energy dispersive spectrometry and spectrometry photo-electron spectra indicate that the SDS does exist on the surface of particles. It is demonstrated that the slope of the wettability curve of modified particles of about 120nm in size is almost five times larger than that of unmodified particles. Rheological measurement shows that the yield stress of the electrorheological (ER) fluid with the modified particles can reach about 130kPa under 4kVmm^-1 DC electric field when the volume fraction is 56vol%; this is greatly enhanced in comparison with that of an unmodified TiO₂ ER fluid. It is further considered that the enhancements in wettability, proper dielectric constant and dielectric loss due to the SDS modification make an important contribution to the strong ER effect. Furthermore, this modified TiO₂ ER fluid also shows excellent suspended stability compared with the unmodified TiO₂ ER fluid.