Alkyl-Functionalized Boron Nitride Nanosheets as Lubricant Additives

Inorganic boron nitride (BN) nanosheets with excellent oil solubility were essential to replacing the traditional sulfur/phosphate-containing additives because of their long practical services. However, serious agglomerated BN nanosheets without proper modification hamper their application in lubricant as green oil additives. Here, we developed a simple and robust method for fabricating highly oil-dispersed ultrathin alkyl-functionalized BN nanosheets via a ball-milling process combined with surface modification. Such a chemical-assisted exfoliation process endows ultrathin BN nanosheets with a superior dispersion ability in nonpolar lubricant. Because of the ultrathin structure and good compatibility, the resulting BN nanosheets significantly display great antifriction and antiwear performance as oil additives, as well as reduced surface pitting. As a result, about 45% friction reduction and 89% wear reduction, together with 2.67 times load capacity improvement, were achieved with the help of BN nanosheets in lubricant. High lubrication performance could be attributed to the continuous delivery of BN nanosheets to the contact region and the chemical formation of a protecting boron-based tribofilm. The present work highlights the significance of designing well-dispersed functional 2D nanosheets as green additives for boosting lubrication performance as well as reducing surface pitting.