Nano Titania Grafted Polysiloxane Er Fluid Preparation And Performance Research

Electrorheological fluid (ERF) is a kind of suspension system with solid particles of high dielectric constant and low electrical conductivity dispersed in the liquid matrix of low dielectric constant. When the ERF is subjected to high electric field, its apparent viscosity, shear strength and viscoelastic modulus are changed rapidly in the milliseconds level, thus the ERF undergoes a transition from Newtonian fluid to the solid-like state. Moreover, this change is reversible, continuous and can be controlled as well. Owing to these excellent properties, ERF has been received much attention of the construction machinery field. However, the suspension system is easy to phase separation, which can not fully meet the requirements of engineering applications. Therefore, how to improve the stability of the anti-settlement of the current multi-phase fluid becomes interested by many researches. In recent years, the studies are focused on preparing nano-scaled solid particles, surface modification of solid particles and the polymer shell package, or adding surfactants in the suspension system.Nano-titanium dioxide (TiO2) is a hotspot of the ERF due to its higher dielectric constant and easy synthesis. In this paper, therefore, nano-TiO2 is selected as the basic material, and modified through rare earth doping, surface modification and so on, aiming to prepare a higher stability and higher electrorheological response of ERF. The detailed contents are mainly engaged in the following three aspects.(1) Preparation and the Properties of Nano-TiO2 Electrorheological FluidSol-gel combined hydrothermal method was used to prepare anatase nano-TiO2 successfully which is characterized by Fourier transform infrared (FT-IR), X-ray diffraction (XRD), transmission electron microscopy (TEM) and so on. Then the solution pH, the concentration of tetrabutyl titanate, hydrothermal reaction time and reaction temperature and other conditions were investigated on the morphology and crystalline behavior of nano-TiO2. The results show that all the above factors have little impact on the anatase crystal structure of nano-TiO2, only when the value of solution pH is 1, the brookite crystal structure occurred. With the decreasing pH value, prolonging the hydrothermal reaction time and hoisting reaction temperature, the grain size TiO2 becomes larger, while the concentration of tetrabutyl titanate almost does not affect the grain size of TiO2. On this basis, rotating rheometer was used to test the electrorheological properties of the ERF, and the formation mechanism of solid-particle chain was explained by polarization theory. Moreover, the electric field intensity and the concentration of solid particles on the electrorheological properties were also discussed. The results show that this ERF presents shear-thinning behavior, and the shear stress and shear viscosity of the ERF are enhanced with the electric field strength increases. With increasing the concentration of solid particles, the shear stress enhances significantly with the electric field strength increased.(2) Preparation and the Properties of Rare Earth Doped Nano-TiO2 Electrorheological FluidRare earth was selected to dope nano-TiO2 which is also characterized by FT-IR, XRD, TEM and so on. The kind of rare earth and its concentration on the morphology and crystalline behavior of rare earth doped nano-TiO2 were further studied. The results show that the incorporation of rare earth ions makes diffraction peak for the (101) crystal plane shift to smaller angle, but it does not change the anatase crystalline of TiO2. While, it leads to the crystalline cell expansion and lattice distortion which restrains the growth of grain size of TiO2. The dynamic electrorheological responses tested by rotary rheometer showed that the linear viscoelastic zone of this ERF increases with increasing electric field strength, and the storage modulus and loss modulus also increase correspondingly. Moreover, the type and the concentration of the rare earth significantly impact on the electrorheological properties of the ERF, and when the concentration of samarium ion (Sm3+) is close to 0.05 the ERF shows the highest electrorheological properties.(3) Preparation and the Properties of Novel Grafting Electrorheological FluidSilane coupling agent KH-570 was used for the surface modification of nano-TiO2 and rare earth doped nano-TiO2 which makes the surfaces have a vinyl chain. And then they can further react with the vinyl functioned siloxane oligomer to form the novel grafting ERF. FT-IR, XRD, TEM were used to characterize the surface modified solid particles. It is found that the novel grafting ERF has excellent anti-sedimentation stability owing to the internal tangled three-dimensional network which is formed by the directional arrangement of the solid particles. When the ERF is subjected to the electric field, the tangled three-dimensional network becomes more ordered, which improve the ER effect significantly. Moreover, the incorporation of rare earth ions makes this grafting ERF has a higher electrorheological effect.