| Electrorheological fluids (ERF) are field-controlled rheological materials consisted of dielectric nanoscale or micron-size particles dispersing in insulating liquid medium. When an electric field is applied, the ER fluid produces a rapid, continuous and reversible change in rheological properties (such as shear stress, elasticity modulus and viscosity) and a "liquid-solid" change of their macrostates. These smart properties make ER fluid have potential and value for actual production application in many fields, such as shock absorbers, machinery intelligent control, biomedical engineering and robotics. However, at present the comprehensive performance of ER fluids is still insufficient. Their poor stability, insufficient shear stress and low ER efficiency all restrict the ER fluids go to production applications from laboratory. In order to solve these problems, we prepared aniline strontium titanyl oxalate particles with chemical precipitation method based on the dielectric polarization theory and polar molecules-charge effect model, in which the aniline worked as polar molecule and morphology control agent. The urea modified strontium titanyl oxalate particles were also prepared for comparison. The main conclusions are listed as follows:First, a kind of partly crystallographic aniline strontium titanyl oxalate particles were synthesized by meanings of chemical precipitation method. Characterization results of particle structures showed that the polar molecule was doped on particles successfully. The morphology of particles is controlled by aniline content added into the reaction system. The morphology of particles is micron scale size polyhedron when the mole ratio of aniline and Ti element is naniline/nTi=2, and the morphology is the mixed system of rod and cluster if naniline/nTi=3. With the increase of addition content of aniline, the infiltration angle showed a trend of decreases, which proves the improvement of wettability.The aniline strontium titanyl oxalate ER fluids were prepared with a mass concentration of66.7%afterward. The shear stress and yield stress of aniline strontium titanyl oxalate suspensions first increase with increasing the dosage of aniline and then decrease. When the dosage of aniline is naniline/nTi=2, the aniline strontium titanyl oxalate ER fluid shows the best ER properties and yield stress achieved56.43kPa at5kV/mm, while the current density shows opposite variation law. Within a certain range, the adding amount of aniline can effectively improve the ER efficiency. The aniline strontium titanyl oxalate particles that naniline/nTi=1.5 has the highest ER efficiency which is221.2. Aniline strontium titanyl oxalate particles have a better shear stress stability and temperature stability than pure strontium titanyl oxalate (STO) particles. This means the stronger polarization of polar molecules increase the ER effect of aniline strontium titanyl oxalate particles. The microstructural changes of the ER fluids were observed by optical microscopy using a high-voltage DC source, the sample which naniline/nTi=2would form the most thick and dense column structure which is consistent with the test results of ER property. From all the result we got above, we can get the conclusion that aniline controls the particle morphology during the preparation of particles and acted as polar molecules in the ERF system. The effect to the properties of aniline strontium titanyl oxalate ERF is a result of the integrated effects of that.Finally, for contrast, a kind of urea modified strontium titanyl oxalate particles were prepared by meanings of chemical precipitation method. The particles’surface is successfully doped polar molecule and they exhibit an irregular morphology with a particle size distribution between100-300nm. The addition of urea has effectively improved the shear stress and static yield stress, but its comprehensive performance like ER efficiency and temperature stability are lower than aniline strontium titanyl oxalate particles. |
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