Effectiveness of carbon nanomaterials as lubricant additives: Recent review

Wear and friction are unavoidable in mechanical motion, leading to energy loss, low productivity, damage to machine parts, and high operating costs; therefore, the use of appropriate lubricants is essential. To solve these unwanted conditions and protect the environment, lubricants containing nano-additives could effectively perform the operations. As a result, it is imperative to understand the effectiveness trajectory of various kinds of carbon nanomaterials towards enhancing lubricating performance. Therefore, this review paper compiles the advancement and contributions of carbon nanomaterials to tribology in recent years. The development of different carbon nanotubes and nanoparticles was investigated, and studies conducted between 2010 and 2024 showed notable improvements over time. The review identified the potential influencing factors that impact the tribological responsiveness of carbon nanomaterials, including the nano-additives' dispersion in lubricants, effects of their microstructure and particle sizes. This paper provides a summary of the accomplishments of graphene, fullerene, carbon nanotubes, carbon nanodiamonds, carbon nano-onions and carbon spheres in their application as lubricant additives. A thorough analysis of graphene and carbon nanotubes on their exceptional lubricant additives was conducted. According to reports in the literature, graphene is the most well-known and extensively utilized carbon nanomaterial for exceptional tribological qualities. Significant decreases in wear and friction are facilitated by its capacity to smooth surfaces, create protective layers, and act as a third-body lubricant. To fully utilize graphene's potential in a variety of tribological applications, further research into functionalization and dispersion processes is essential thus providing insight into their synthesis and design.