Experimental investigation on the dispersion stability of Al2O3-CuO hybrid nanofluid using ultraviolet (UV)-visible spectroscopy and Zeta potential analyzer

This paper focuses on an experimental investigation on the dispersion stability of 60:40 water and ethylene glycol based Al2O3−CuO hybrid nanofluids. The volume and concentration of hybrid nanofluids were set to be 30 ml and 0.5%. Three different surfactants (PVP, CTAB, and SLS) with different surfactant ratios (1:10 and 5:10) were used to ensure the nanofluids remained homogenous for a longer period. Dispersion stability is studied using several methods such as sedimentation observation, zeta potential, and UV-Vis. FESEM testing is conducted to study the morphological behavior of the nanoparticles powder, including particle size and structure. Visual inspection showed that only pure Al2O3-CuO and Al2O3-CuO-PVP (1:10) remained homogenous without any visible separation layer. As for UV-Vis spectroscopy, the absorbance value for all samples was below than 1%. Thus, to further investigate the stability Al2O3-CuO hybrid nanofluid, the Zeta potential test is also conducted. Analysis of Zeta potential indicated that PVP with surfactant ratio 1:10 provided better result on the nanofluid stability. The pH value for sample with the PVP dispersant is then measured to be 7.7 which is slightly further from the IEP (pH 9.7-10)