The Study On The Shear Thickening Behaviors Of Nanosilica Fluids

Shear thickening fluid is a very common non-Newtonian fluid.It is a viscous liquid under normal conditions,but its viscosity will increase rapidly after impact and this shear thickening performance is reversible.In this study,a series of suspensions containing silica?SiO₂?particles and polyethylene glycol?PEG?were prepared,and the influences of particle size,particle concentration,temperature and shear mode on the shear thickening effect of these SiO₂ fluids were investigated systematically by rheological measurements.It was observed that with the increase of silica concentration,the viscosity and critical shear rate of the fluid become higher,and the shear thickening phenomenon becomes more obvious.Under the same particle concentration,higher shear thickening effect and lower critical shear thickening concentration appear for smaller nanoparticles but for larger micro particles.As the temperature increases,the enhanced Brownian motion leads to the rising of critical shear rate and the strengthening of shear thickening effect.The rheological properties of these fluids are very sensitive to the shear rate with fast viscosity change for response,and smaller nanoparticles can recover their network structures more easily after shear breakage.In addition,three modifiers of silane coupling agent,stearic acid and titanate were utilized to modify the surface of 15nm SiO₂ nanoparticles that show stronger shear thickening effect,and the effects of particle modification on the shear thickening behaviors of nanosilica fluids were investigated.It can be found that the modification obviously decreases the particle agglomeration,improves the particle dispersion property,and increases the maximum particle concentration in fluid,but leads to the reduction of the viscosity and shear thickening effect of the fluids due to the decrease of particle interactions.The modified silica fluids exhibit stronger structural recovery ability and shear thickening reversibility even after multiple shear breakage.