Effect of Silica Morphology on Rheological Properties and Stability of Magnetorheological Fluid

SiO 2 is commonly used as an abrasive in optical devices and magnetorheological (MR) fluid. In this study, MR fluid with composite and free-state SiO 2 were prepared. Composite magnetic particles of CIP@SiO 2 were synthesized using the sol-gel method with tetraethyl orthosilicate (TEOS) as the silicon source. Performance test results showed that CIP@SiO 2 MR fluid exhibited superior mechanical properties compared with CIP MR fluid under zero magnetic field conditions. However, under the influence of a magnetic field, the SiO 2 shell weakened the response of CIP@SiO 2 MR fluid to the magnetic field, whereas CIP MR fluid demonstrated better rheological properties. The addition of free-state SiO 2 to CIP MR fluid significantly improved its rheological performance. At a volume fraction of 6% SiO 2 , the shear stress and viscosity reached their maximum values, and further increasing the volume fraction to 8% resulted in a noticeable decrease in rheological behavior. Stability improved with an increase in magnetizable particle content. The stability of CIP MR fluid at the same concentration was superior to that of CIP@SiO 2 MR fluid, while free-state SiO 2 had a notable enhancing effect on stability. Therefore, when SiO 2 exists as a free-state abrasive, the rheological properties and stability of the MR fluid considerable improve.