Preparation And Application Of High-performance SiO₂ Shear Thickening Fluids

The shear thickening fluids prepared by silica particles can change into solid with high hardness by outside impact.Therefore,shear thickening fluids have wide application prospects in stab-resistant field.In this article,the effect of particle size,size distribution,solvent,surface modification of particles and concentration of nitric acid on the rheological properties of shear thickening fluids have been characterized and evaluated.In this article,the effect of the ratio of ethanol and shear thickening fluids and temperature on the stab-resistance of composites of shear thickening fluids and Kevlar fabrics was investigated.The results were significant on promoting the application of shear thickening fluids in stab-resistant field.Firstly,silica particles were synthesized by sol-gel methods with two and three steps.The effect of the concentration of ammonium hydroxide,the concentration of deionized water et al.on the morphology of silica particles and the process of formation of silica particles were characterized.The results indicate that the process of the formation of particlesfor the sol-gel method with two steps and the sol-gel method with three steps is identical.Moreover,the results indicate that the well dispersed silica particles in narrow size distribution can be synthesized by well controlling the reaction conditions.Then,the silica particles with different particle size and surface properties were prepared by the sol-gel method with three steps.The morphology and the chemical composition of these particles were characterized as well.Since the sol-gel method with three steps can greatly increase the concentration of TEOS,it can raise the efficiency of synthesizing silica particle.Therefore,this method has giant potential economic value.Secondly,the suspensions comprising silica particles with different particle diameter and different size distribution were prepared.The rheological test and analysis results indicate that the intensity of shear thickening of suspensions and the critical shear rate for shear thickening occurring have much to do with the size and the polydisperse index of particles.Additionally,the suspensions comprising silica particles with different surface chemical composition and PEG200 were prepared and evaluated.The results demonstrate that the surface properties of particles can greatly affect the shear thickening behavior of silica particle suspensions.Moreover,the rheological properties of suspensions of TPM modified silica particles dispersed in PEG200 and deionized water were characterized and evaluated.The results indicate that the silica particles dispersed in a suitable medium can be in favour of improving the shear thickening performance of suspensions.The results shown in this section were very important for preparing high-performance shear thickening fluids.Lastly,in this article,the effect of the concentration of nitric acid on the rheological properties of shear thickening fluids was investigated.The results show that the intensity of shear thickening reached to a maximum value as the concentration of nitric acid was about 8.50 mmol/L.After that,the effect of temperature and mass ratio of ethanol and shear thickening fluids on the stab-resistance performance of the composites of shear thickening fluids and Kevlar fabrics was investigated.The results of stab-resistance test indicate that the mass ration of ethanol and shear thickening fluids and temperature has much to do with the stab-resistance performance of composites.The composites have great stab-resistance performance when the mass ratio of ethanol and shear thickening fluids is about 1: 1.Additionally,the composites can show high-performance stab-resistance and excellent flexibility at low temperature.The results shown in this part is very significant for promoting the application of shear thickening fluids in stab-resistance field.