Preparation And Electrorheological Properties Of Polar Molecules Modified Nanoparticles

Electrorheological fluids (ERF) are suspensions of polarizable solid nanoparticles or microparticles dispersing in non-conducting liquid medium. The material parameters of ERF such as viscosity, yield stress, and shear modulus can change obviously and reversibly upon the application of an external electric field. These characteristics find practical applications in many fields, e.g. actuators, shock absorbers, active devices. But some existing ER materials due to their relatively low shear stress or poor suspension stability, are not satisfactory in engineering. ER mechanism is still not clear restricting in-depth study of the ER material.In this thesis, Ca-Ti-O particles and Ni/(TiO2+PAn) particles were prepared, and their structures, ER effect of the particles, the factors influencing ER effect and the stability of the ER fluid were characterized. Principal results are as follows:Ca-Ti-O particles of nanoscale were successfully prepared by the sol-gel method and the particles are amorphous with polar group successfully doped on the surface. Increasing the electric field and the concentration of particles and being doped with polar molecules would make the chain structure become thick and dense. The polar groups of the particle surface were changed by alcohol washing, improving ER properties of the particles. The ER properties of the particles were increased by isooctane modification, and isooctane could be used as an additive of the ER fluid. Study on SDBS and rare earth doping revealed that they both improve the ER properties of the particles. And polar molecules are the main factor influencing the ER effect. Study on the stability of the ER fluid revealed that, the particles doped with urea have good temperature stability below100℃, and the particles have good reusability.Ni/(TiO2+PAn) core-shell particles were successfully prepared by improved sol-gel method, and PAn was successfully modified,1g Ni particles dispersed in100ml ethanol, using stirring and ultrasonic vibration at the same time, coated with three layers are the optimal preparation. The results of study on the ER effect of the particle showed that doping with PAn greatly improves the ER properties of the particles, electromagnetic coupling enhances the shear strength of the ERF, and the upper working temperature limit is increased by PAn modification.