Tribological properties and processing challenges of bulk structural ceramic nanomaterials

Abstract

With the recognition that bulk nanostructured ceramics, defined by the grain size of at least one of the constituent microstructural phases being smaller than 100 nm, possess some appealing physical, mechanical and tribological properties, they have been the subject of considerable research activities in recent years. Among the various properties of structural ceramics, the most remarkable and reproducible improvement produced by the refinement of the grain size to nanoscale levels or through reinforcement of the matrix by nanosized particles, has been in the tribological properties. This review critically analyses the effects of microstructural refinement to nanoscale levels on the wear resistance of structural ceramics and ceramic composites. This is followed by an overview of the tribological behaviour of different ceramic nanomaterials. It must be noted that although nanostructured ceramics possess superior properties with respect to their conventional counterparts, the challenges involved in the successful processing of such materials have hindered their penetration of the commercial market to any notable degree. In light of this, the review outlines the challenges involved and the techniques developed for the successful processing of bulk nanocrystalline ceramics. Finally, the review concludes with critical comments on some of the unresolved issues related to bulk nanostructured ceramics, along with a brief mention of the scope for future research.