Experimental studies on the stability of CuO nanoparticles dispersed in different base fluids: influence of stirring, sonication and surface active agents

The main aim of this work is to investigate the influence of different parameters on the stability of spherical CuO nanoparticles dispersed in water, ethylene glycol and 50:50 water/ethylene glycol binary mixture as different base fluids for heat transfer applications. Nano-fluids were prepared using two-step method at weight concentration of 0.1-0.4 %. Time-settlement experiments were established to examine the stability of nano-fluids. Quality tests were also performed to investigate the morphology, purity and size of nanoparticles. In order to stabilize the nano-fluids, stirring, pH control and sonication were utilized. The criteria for assessing the stability of nano-fluids were zeta potential and time-settlement experiments. Results demonstrated that the ethylene glycol can be the best medium for dispersing the CuO nanoparticle in comparison with water and water/EG binary mixture. The best condition for achieving the most stable nano-fluid was also introduced. Role of sonication time, stirring time and addition of surfactant on the stability of nano-fluids were investigated and briefly discussed.