Characterization of silica–water nanofluids dispersed with an ultrasound probe: A study of their physical properties and stability

The stability and agglomeration state of nanofluids are key parameters for their use in different applications. Silica nanofluids were prepared by dispersing the nanoparticles in distilled water using an ultrasonic probe, which has proved to be the most effective system and gives the best results when compared with previous works. Results were obtained concerning the influence of the solid content, pH and salt concentration on the zeta potential, electrical double layer, viscosity, elastic and viscous moduli, particle size and light backscattering. Measurement of all these properties provides information about the colloidal state of nanofluids. The most important variable is the solid content. Despite the agglomeration due to high concentration, nanofluids with low viscosity and behaving like liquid were prepared at 20% of mass load thanks to the good dispersion achieved with the ultrasonic treatment. The pH of the medium can be used to control the stability, since the nanofluids are more stable under basic conditions far from the isoelectric point (IEP) and settle at pH = 2. Therefore, stable nanofluids for at least 48 h, with high solid content, can be prepared at high pH value (pH > 7) due to the electrostatic repulsion between particles.

In this work silica nanoparticles were dispersed by using an ultrasound probe. A complete characterization of the well-dispersed nanofluids was carried out. The influence of the solid content, the pH and the presence of salt on the viscosity, the elastic and viscous moduli, the particle size, the zeta potential, the Debye length and the light backscattering was studied.Figure optionsDownload as PowerPoint slideHighlights
► Analysis of nanofluids properties: zeta potential, rheology, light backscattering….
► Influence of variables on the stability and agglomeration of nanofluids.
► Obtaining of nanofluids with high solid content and like liquid behaviour.
► Changes in pH modify surface charges, interparticle forces and stability.