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.