Water-Soluble PAM-Assisted Ball Milling: A Scalable Route to High-Yield BN Nanosheets for Enhanced Lubrication and Solar Thermal Conversion

We demonstrate an ecofriendly and scalable strategy for high-yield production of boron nitride nanosheets (BNNSs) via water-soluble polyacrylamide (PAM)-assisted ball milling. This method achieves a remarkable 97.6% exfoliation yield of ultrathin BNNSs (average thickness ≈3.0 nm, ≈9 layers) within 20 h, while preserving crystalline integrity and inducing surface hydroxylation. The hydroxylated BNNSs exhibit exceptional aqueous dispersion stability (zeta potential: +1.14 mV) and dual-functional enhancements: (1) superior lubrication with a friction coefficient of 0.370 at 0.3 mg/mL (20% lower than bulk h-BN), attributed to interlayer sliding facilitation and (2) efficient solar thermal conversion reaching 27.7 °C under solar irradiation (3.1 °C higher than bulk h-BN), driven by enhanced light absorption and surface resonance. The universality of this approach is validated by the successful exfoliation of mica and graphite into high-quality nanosheets. By eliminating organic solvents and post-treatment, this PAM-enabled process sets a new benchmark for sustainable, high-performance nanomaterial production toward energy-efficient tribological and solar thermal applications.