Preparation And Comparison Of Properties Of TiO₂/Urea And TiO₂/Graphene Oxide Core-shell Electrorheological Fluid

Electorheological fluids (ERF) is a new type of smart materials, consisting of microparticles or nanoparticles dispersed in insulating oil. Its viscosity, viscoelastic modulus or shear strength are changed continuously, re versibly or rapidly with the applied electric field. The comprehensive performance of the single inorganic or organic ER materials is not high and it is too difficult to meet the high demands of engineering. To obtain ER fluids with better comprehensive performance, the fabrication of core/shell structured ER particles have been proposed and they can combine the advantages of different components. It reported the core/shell structured ER particles mainly formed with inorganic materials as the core and polar molecules or graphene oxide as the shell. However, little studies reported the comparison between the core-shell structured ER fluids with polar molecules or graphene oxide as shell and also lack of mechanism analysis. In this study, we used both urea and GO as the coating materials to prepare TiO/Urea and TiO2/GO core-shell structured nanoparticles. Then we compared the two kind of core-shell structured ER fluids and analyzed its related mechanism. The main conclusions are as follows:1. Alkoxide hydrolysis method was used to prepared amorphous titanium dioxide particles. And, we discussed the influence of the two kinds of reaction conditions for the size of particle and reaction time. The microstructure of the particles were observed by scanning electron microscope (SEM), which indicated that the particles are monodispersed sphere (400-500nm). FTIR results further proved that the surface of the TiO2 particles is coated with urea. X-ray diffrantion (XRD) results indicated that the particles present amorphous structure. Their ER properties were tested and the results indicated that amorphous TiO2 particles-based ER fluid presents higher yield stress.2.’Core-shell-structured TiO2/Urea nanoparticles were synthesized with tetrabutyl titanate and urea by using a hydrolysis method and solution deposition SEM, TEM, FT-IR, XRD and so on were used to characterize the TiO3/Urea particles. The result showed that the particles are monodispersed sphere (400-500nm) with complete core-shell structure and the urea molecule was coated on the surface of TiO2 particles successfully. Their ER properties were tested and compared. The results indicated that the TiO2/urea particles-based ER fluid presents much higher yield stress than the pure TiO2 particles-based material. Besides, the shear stress of the TiO2/urea particles-based ER fluid keeps stable within a wide range of shear rate.3. Core-shell-structured TiO2/GO nanoparticles were prepared by APTES-grafted. The nanoparticles were characterized by SEM, TEM, XPS, XRD FT-IR, and so on, which were showed that graphene oxide sheets wrapped on the surface of TiO2 particles successfully. It is found that the TiO2/GO ERF has higher shear stress, lower leakage current density, better stable within a wide range of shear rate and excellent anti-sedimentation stability.