Stability and thermal conductivity of water-based hybrid nanofluids using oil palm biomass cellulose nanoparticles and metal oxide nanoparticles

Hybrid nanofluids based on surface-modified anionic cellulose nanoparticles (ACNPs) and metal oxide nanoparticles (Al₂O₃, ZnO, TiO₂, MgO) were developed to improve the dispersion stability and thermal conductivity of aqueous systems. The hybrid nanocomposites were synthesized using ACNPs and then introduced into water (1 wt%) with added polyvinylpyrrolidone (PVP) using a two-step method. The stability of the aqueous systems was assessed based on visual observations and zeta potential measurements. Density, viscosity, thermal conductivity, and specific heat were also determined. The ZnO-based nanofluid demonstrated the most favorable properties, remaining stable for over 60 days and exhibiting thermal conductivity 109% and 81% higher at 45°C and 65°C compared to water, respectively. In contrast, the MgO system was characterized by high viscosity and long-term visual stability, but there was a smaller increase in thermal conductivity.