Investigating the effect of zinc oxide nanoparticle coverings in reducing frictional wear and tear in tribological systems

Tribological systems, which are important in most industrial and consumer applications, dissipate energy in the form of friction and material wear. In this study, we examine the efficiency of zinc oxide (ZnO) nanoparticles—synthesized via the sol-gel method and applied via airbrush spraying—in reducing friction and wear on tribological surfaces. The synthesized ZnO nanoparticles were characterized through X-ray diffraction (XRD) and transmission electron microscopy (TEM), which confirmed their wurtzite crystalline phase and uniform size distribution (20–50 nm). The coatings were applied on ASTM A36 steel substrates and evaluated on a pin-on-disc tribometer under varying loads (5–20 N) and sliding velocities (0.1–0.5 m/s). Surface and wear track morphology were examined using scanning electron microscopy (SEM) and atomic force microscopy (AFM). As well, wear track cross-sectional profiles were obtained using a surface profiler. Experimental results exhibited 40–60% reduction in the COF of coated samples compared to uncoated. This is attributed to the high hardness (~5 GPa) of ZnO nanoparticles and their capability of forming a hard boundary layer that minimizes asperity contact. 50–70% decrease in wear volume was also verified through SEM analysis of decreased wear tracks and decreased adhesive wear. Cross-sectional energy-dispersive X-ray spectroscopy (EDS) mapping confirmed uniform coating adhesion with no damage to the substrate. In addition, cyclic loading endurance tests (1,000 cycles) demonstrated stable frictional behavior, pointing toward the potential for long-term application of the coating. The findings validate the potential of ZnO nanoparticles developed through the sol-gel process to be cost-effective and scalable solutions to enhance tribological durability in automotive, aerospace, and manufacturing applications. The future can examine synergy between the coatings and lubricants and also evaluate environmental sustainability under extreme conditions.