The influence of nano-SiO2 particle size on dilatant effect of shear thickening fluids
Agnieszka Idźkowska, Mikołaj Szafran
Quarterly No. 2, 2013 pages 117-121
DOI:
keywords: shear thickening fluids, nanosilica, particle size, dilatant effect, poly (propylene glycol)
abstract Recently, the shear thickening phenomenon has drawn the attention of many researchers. The ability of shear thickening fluid to resist operative force creates a possibility of applying this kind of material wherever there is a necessity to dampen and disperse energy. Therefore, dilatant slurries have found their application in dampers, devices that protect buildings against seismic shocks or military applications in so called “liquid armor”. A great deal of research has focused on investigation of the mechanism and influence of parameters such as volume fraction, polydispersity and medium viscosity of the dilatant effect, however, some fields are still unexplored. In this work, the influence of nanosilica particle size on the dilatant effect of shear thickening fluids was investigated. For the tests, nanosilica with diameters of 7 and 200 nm was chosen. The suspension was prepared by dispersing the nanosilica into poly (propylene glycol) of a molecular weight of 400 g/mol. The concentration of the ceramic powder varied from 12 to 30 vol.%. The influence of the particle size on the dilatant effect was observed by a rotational rheometer Kinexus Pro with a plate-plate system. In this case, viscosity as a function of shear rate was measured. The shear rate increased from 1 to 1000 s-1. The measurement showed that the diameter of silica particles has a significant influence on the rheological properties of the investigated suspensions. With an increase in particle size the dilatant effect increases. However, its position is shifted to a lower shear rate. The maximum volume fraction and relative viscosity of the suspension also was examined. The measurements showed that with increasing particle size, the relative viscosity of the suspension decreases, which result in an increase in the maximum volume fraction of nano-SiO2.