Ball Milling of Hexagonal Boron Nitride Microflakes in Ammonia Fluoride Solution Gives Fluorinated Nanosheets That Serve as Effective Water-Dispersible Lubricant Additives

Herein, we demonstrate that hexagonal boron nitride nanosheets (h-BNNSs) can be used as water dispersible lubricant additive through simple fluoride modification. The fluorination of h-BNNSs (F-BNNSs) is carried out via a facile ball milling of commercial h-BN microflakes in ammonia fluoride solution. The as-obtained F-BNNSs exhibit excellent antifriction and antiwear performance as water dispersible lubricant additive with low concentration of less than 1.0 mg/mL, and their friction coefficients can be lower than 0.08, achieving low friction. This low friction originates because F-BNNSs at a sliding interface roll up to form nanoscrolls induced by the fluoride doping curling effect and subsequent shearing force. These resulting nanoscrolls can slide against the substrate, achieving a rolling/incommensurate contact, thus substantially reducing friction coefficients. The overall lubricant mechanism is further elucidated based on the first principles simulations. This finding indicates the potential of achieving low, even ultralow, friction of h-BNNSs as water dispersible lubricant additives through composition and structure designing.