Enhanced Tribological and Thermal Performance of CNC–Al₂O₃ Hybrid Nanolubricant for Internal Combustion Engines: A Comprehensive Stability–Thermophysical–Tribological Assessment

Abstract

This experiment investigates the stability, thermophysical, and tribological characteristics of cellulose nanocrystal (CNC), aluminum oxide (Al2O3), and hybrid CNC-Al2O3 nanolubricants as additives in SAE 40 engine oil for internal combustion engine applications. Stability assessments were conducted through zeta potential analysis at various concentrations (0.01% to 0.05%) and temperatures (30°C to 90°C). The hybrid CNC-Al2O3 nanolubricants demonstrated excellent dispersion stability with zeta potential values exceeding 150 mV at optimal concentrations. Thermophysical property analysis revealed that dynamic viscosity increased significantly, with the hybrid system showing a 56% enhancement at 0.03% concentration and 30°C. The tribological testing revealed a remarkable 78.6% reduction in the coefficient of friction at a 0.01% concentration and an optimal specific wear rate of 0.016 mm³/Nm at a 0.05% concentration. These synergistic improvements in stability, thermophysical, and tribological properties demonstrate the CNC–Al₂O₃ hybrid’s significant potential to enhance efficiency, durability, and heat management in internal combustion engines, offering a novel, high-performance alternative to conventional lubricant additives.