Potential of Graphene Doping Towards Superlubric Performance of Additively Manufactured Structures.

Significant improvements in the tribological performance of graphene-doped additively manufactured structures are reported, with absolute values of friction coefficients reaching 0.09 corresponding to ca. 70% decreases from plain/un-doped samples. The findings highlight an impressive potential of the nanocarbon variant, to endow superior tribological performance to polymers, bringing them a step closer to the ideal superlubric regime. Such structures of intrinsic superlubric performance are envisioned as viable candidates for the containment of great amounts of energy, currently wasted as friction in a plethora of applications, hence also promoting an ecologically sustainable development. Indications that superlubricity is greatly promoted by nanocarbons, especially by the two-dimensional variant of graphene with excellent response in shear action, are investigated in combination with the effect of surface topography, for the investigation of the tribological performance of three-dimensional structures with geometric surface patterning, additively manufactured from graphene-doped polymers. Spectroscopic, mechanical, and microstructural characterization of plain polymer-based samples and their graphene-enhanced nanocomposite counterparts was followed by tribometric measurements for the establishment of the evolution of the friction coefficient on a certified commercial tribometer operating under the ball-on-disk configuration as well as on a conceptual purpose-built setup. The individual and combined effects of nanomaterial presence and patterning are reported, and the influence of manufacturing-prone micropatterning is examined.