Synthesis and characterization of TiO2-water nanofluids with different surfactants

A comprehensive characterization of viscosity, thermal conductivity, surface tension and pH of TiO2-water nanofluid is carried out to investigate the effects of both temperature and solid volume fraction on these thermo-physical properties-nanoparticle solid volume fraction has been varied between 0.1%-2.0% while the temperature ranged from 20 to 60°C. Stability of the synthesized nanoparticle suspension has been investigated with four major surfactants, e.g., cetyl trimethyl ammonium bromide (CTAB), acetic acid (AA), oleic acid (OA) and sodium dodecyl sulfate (SDS) when only CTAB and AA are found to provide stable suspensions. Transmission electron microscopy (TEM) and dynamic light scattering (DLS) measurements indicate particle size ranging between 10 and 40 nm and average cluster size of 147 nm and 207 nm, respectively. The experimental results show that viscosity of TiO2-water based nanofluids increases with solid volume fraction and decreases with temperature. The nanofluids also show slight shear thickening behavior for shear rates ranging between 76 and 760 s− 1. Thermal conductivity of the nanofluid increases with the increase of both solid volume fraction and temperature. Surface tension of both the AA and CTAB-stabilized nanofluids decreases with solid volume fraction and temperature. The pH of nanofluid is found to remain relatively insensitive to particle loading and temperature.