Experimental investigation on the surface tension and contact angle of Al2O3-oil and SiO2-oil nanofluids

The experimental results regarding the surface tension and contact angle of Al2O3-oil and SiO2-oil nanofluids with 0.1%~1.0% volume fraction at the temperature of 25°C~65°C are presented. The measurements illustrate that the surface tension is improved and the contact angle is reduced compared with oil based liquid. At the temperature of 25°C, for 0.5% volume fraction with 60 nm nanoparticles size, the enhancement of the surface tension is about 4.11% for Al2O3-oil nanofluids and 6.79% for SiO2-oil nanofluids. Corresponding, the weakening of the contact angle is 37.93% and 27.59%. In addition, the experimental profiles of the surface tension of Al2O3-oil and SiO2-oil nanofluids indicate that they fall with temperature, and inversely rise with the increasing of volume fraction and nanoparticles size. And the contact angle of the two kinds of nanofluids increase with nanoparticles size, whereas decrease with the increase in volume fraction. All demonstrate that the wetting properties are modified when Al2O3 and SiO2 nanoparticles are added into oil based liquid. Furthermore, the experimental phenomena are thoroughly analysed.