Nanoparticles encapsulated carbon nanotubes dispersed lubricants for enhanced tribology through particle-phase variation

Nanostructures as an inert additive to the lubricant act as a tiny friction reduction element by providing asperity filling, polishing, and film formation mechanism at the nanoscale dimension under the boundary layer regime. Here, we explore the synthesis and tribology application of iron-carbon-based nanoparticles encapsulated multiwall carbon nanotubes (Fe-C-CNTs). Three Fe-C nanoparticles phase that is, Fe₃C-CNTs, Fe₃C-Fe-CNTs, and Fe-CNTs are synthesised. In particular, the emphasis here is on the effect of nanoparticle phase variation on the tribology property. The tribology property of the prepared nanomaterials is studied by dispersing it in commercially used Servo gearbox oil. The coefficient of friction and wear is found reduced in all dispersions compared to the base gearbox oil confirming the manifestation of nanoscale mechanisms at the tribo-interface. It is revealed that the phase variation shows more impact on the alteration of friction coefficient compared to the dispersion concentration variation analysed using ANOVA two-way technique. Further, the diameter and composition analysis of the wear scar is used to comprehend the underlying mechanism of the encapsulated particle phase variation. The findings suggest that the Fe-CNTs dispersions are efficient in reducing friction to a larger extent but also promote the interface oxidation leading to enhanced wear and roughness whereas, Fe₃C-CNTs and Fe₃C-Fe-CNTs are chemically stable providing smooth sliding and less wear.