Thermal and surface properties of AlZnO and surfactant-stabilized AlZnO nanofluids: Influence of sonication duration for heat transfer applications

Research into doped metal oxide nanofluids (NFs) has intensified due to recent breakthroughs in heat transfer applications. This study explores the thermophysical properties of Aluminum Zinc Oxide (AlZnO) at a 0.10 vol% concentration and surfactant-enhanced Aluminum Zinc Oxide (f@AlZnO) at concentrations of 0.05, 0.10, and 0.20 vol%. Experiments were conducted across a temperature range from 20 to 80°C. The study utilized various analytical techniques such as FT-IR, UV-visible spectroscopy, Powder XRD, SEM, and EDX to examine the effects of volume concentration and sonication duration on stability, particle size, thermophysical properties, contact angle, wettability, and surface tension. It was found that the thermal conductivity of AlZnO and f@AlZnO NFs increases with both volumetric concentration and temperature. Notably, surfactant inclusion significantly enhanced the stability of AlZnO NFs, achieving a high zeta potential after 160 minutes of sonication. The 0.10 vol% f@AlZnO NF displayed optimal stability at this sonication duration, while the 0.10 vol% AlZnO NF showed the smallest particle size distribution after just 20 minutes. Thermal conductivity enhancements of 5 %, 2.5 %, 2 %, and 1.9 % were observed for 0.10 vol% AlZnO NF and 0.05, 0.10, and 0.20 vol% f@AlZnO NFs, respectively. Additionally, at 200 minutes of sonication, the 0.05 vol% f@AlZnO NF demonstrated the lowest increase in specific heat capacity. The study also revealed that both surfactant addition and increasing volumetric concentration of AlZnO NFs reduced surface stress and contact angle values. In contrast, dynamic viscosity and density increased with higher nanoparticle concentration and decreased with rising temperature. The Mouromtseff number calculations underscore the potential of AlZnO NFs in thermal applications, meriting further investigation. This comprehensive examination provides critical insights into the effective utilization of hybrid metal oxide NFs in heat transfer applications.