Construct the continuously layered structure of h-BN nanosheets in liquid phase via sonication induced gelation to achieve low friction and wear
To endow the h-BN nanosheets with gelling ability, diurea compound was decorated on the h-BN nanosheets via the designed adsorption and in-situ reaction processes. The prepared h-BN-based gelator, BTO, exhibits excellent dispersibility in non-polar liquid media, and the gelation of BTO dispersions could be readily triggered by ultrasonic treatments. The sol-gel transformation of system is found to be highly reversible through stirring and sonication. Based on the investigation into the self-assembly behavior of BTO nanosheets in liquid phase, it is proposed that a continuous and layered structure formed by BTO during sonication is the key factor for the gelling properties. The viscoelasticity of sonication induced gel was studied with rheometer. Tribological evaluations show that the prepared h-BN nanogel exhibits outstanding lubricating performances, and more importantly, it is proved that the gel state of h-BN nanosheets provide superior and more reliable lubricating performances than the corresponding dispersion state in some conditions, which could be ascribed to the formed continuous and uniform structure of modified h-BN nanosheets during gelation. The work not only clarify the key role of the assembly structure played in tribological performances of 2D nanomaterials, but also demonstrate the potential of gelation in improving the macroscopic friction reduction and wear resistance of 2D nanomaterials.