Synthesis, Stability, and Tribological Performance of TiO2 Nanomaterials for Advanced Applications

The enhancement of tribological properties represents a pivotal strategy for achieving energy efficiency and environmental protection. Titanium dioxide (TiO2) nanomaterials have been garnering significant attention due to their exemplary tribological properties and due to the abundance of titanium reserves. The present review is concerned with the study of TiO2 nanomaterials in lubricants. The properties and various synthesis methods of TiO2 nanomaterials are presented. The dispersion stability of these TiO2 nanomaterials in lubricating oils is discussed in depth, as well as strategies to improve their dispersion stability, such as enhancing compatibility with base oils, reducing the dynamic light scattering (DLS) particle size, modulating the zeta potential, and optimizing the drying step. Aggregation and dispersion instability remain key challenges for TiO2 nanomaterials, especially bare TiO2 nanoparticles (NPs). In contrast, in situ surface-modified TiO2 NPs show improved stability and tribological performance, offering promise for further research. The tribological performance of lubricants has been demonstrated to be enhanced by TiO2 nanomaterials, with the observed enhancement attributed to the synergistic effect of multiple mechanisms, including rolling, patching, polishing, and the formation of a protective film. Furthermore, future research suggestions are proposed to provide a reference for the design and synthesis of high-performance TiO2 nano-lubricants and promote their wide application.