Nanocellulose domain-limit fluorinated graphite to achieve efficient lubrication of engineered steel surfaces

Abstract

Nowadays, almost all research in friction testing has been devoted to exfoliateing fluorinated graphite (FGi) into thinner, less layered structures to increase its lubricating properties. The development of an exfoliating-free technology to achieve the efficient tribological performance of FGi would greatly avoid energy consumption and additional experimental operations. Herein, nanocellulose (NC) liquid-phase assisted ball-milling and freeze-induced self-assembly processes were used to achieve further refinement of crushed FGi and the construction of NC@FG large-sized interwoven lamellar structures. This process involves the further fragmentation of FGi and the disordered in-situ self-assembly of NC around FG particles, leading to the constriction of FGi into the NC-built interwoven layers. Without the need for additional separation and functionalization steps, NC@FG/sunflower oil (SFO) exhibits long-lasting stable lubricating properties. NC@FG reduced the friction coefficient and wear track width on the engineered steel surface by 32.67 % and 66.27 % as compared to pure SFO, and showing excellent lubricating properties on different substrates at the same time. The systematic wear tests and lubrication theory calculations reveal that the lubrication mechanism of NC@FG originates from the domain-limiting effect of NC on FG nanoparticles, which hinders the disordered movement and agglomeration of the nanocomponents, and improves the deconstruction of NC@FG at the friction interface. They were sequentially adsorbed at the friction interface, forming a continuous tribofilm to resist friction and wear.