Evaluation of nanoparticles for nanoscale film fabrication harnessing tribochemistry

Tribofilms, essential for reducing friction and wear in mechanical systems, are typically formed on contact surfaces through tribochemical reactions during sliding or rolling interactions. Nanofabrication of zinc dialkyl dithiophosphate (ZDDP) tribofilm provides an alternative manufacturing technique for developing micro/nano-scale structures and devices for applications other than reducing friction and wear. While ZDDP tribofilms can be fabricated with nanometer-level precision, the application of this tribologically fabricated thin film was limited by its electrically insulating nature. Nanoparticles, with their unique thermal, electrical, and optical properties, offer the potential to enhance the capabilities of fabricated tribofilms. This study investigates the role of five nanoparticles—WS₂, Al₂O₃, CuO, BN, and TiO₂—in the fabrication of tribofilms on a steel substrate. The thickness, distribution, and composition of the fabricated tribofilms were analysed. To accurately characterise the distribution and thickness of tribofilms, an innovative methodology utilising Conductive Atomic Force Microscopy (CAFM) has been developed. The results reveal that while the addition of WS₂, Al₂O₃, and CuO not affect the tribofilm composition compared with pure base oil, BN and TiO₂ are chemically incorporated into the tribofilm, altering its composition and potentially enhancing its functional properties.