Highly wear-resistant and low-friction Si3N4 composites by addition of graphene nanoplatelets approaching the 2D limit

TL;DR

This study demonstrates that adding highly exfoliated few-layer graphene nanoplatelets to Si3N4 ceramics significantly enhances wear resistance and reduces friction by forming a continuous tribo-film, with minimal impact on mechanical properties.

Contribution

The paper introduces an effective method to exfoliate GNPs to the few-layer range and shows that this greatly improves the tribological performance of Si3N4 composites.

Findings

Wear resistance increased by about twenty times.

Friction coefficient reduced to nearly half.

Formation of a continuous FL-GNP tribo-film at 5wt% GNP content.

Abstract

Graphene nanoplatelets (GNPs) have emerged as one of the most promising filler materials for improving the tribological performance of ceramic composites due to their outstanding solid lubricant properties as well as mechanical and thermal stability. Yet, the addition of GNPs has so far provided only a very limited improvement in the tribological properties of ceramics, particularly concerning the reduction of their friction coefficient. This is most likely due to the challenges of achieving a lubricating and protecting tribo-film through a high GNP coverage of the exposed surfaces. Here we show that this can be achieved by efficiently increasing the exfoliation degree of GNPs down to the few-layer (FL) range. By employing FL-GNPs as filler material, the wear resistance of Si3N4 composites can be increased by about twenty times, the friction coefficient reduced to nearly its half, while the other mechanical properties are also preserved or improved. Using confocal Raman microscopy, we were able to demonstrate the formation of a continuous FL- GNP tribo-film, already at 5wt% FL-GNP content.