Sustainable Mass Production of Ultrahigh-Aspect-Ratio Hexagonal Boron Nitride Nanosheets for High-Performance Composites

Hexagonal boron nitride nanosheets (BNNSs) show great applications in metal protection, thermal management, energy storage, and medicine fields due to their many unique properties. However, the scalable preparation of large-size ultrathin BNNSs still remains a huge challenge to date. This study develops a sustainable mechanochemical exfoliation (SMCE) approach for high-yield (74%) synthesis of BNNSs by polylactide-assisted ball milling from bulk hexagonal boron nitride (hBN). The obtained BNNSs have an ultrahigh aspect ratio of ≈1240 and a low defect degree and show superior disperse ability in liquids. Combining experimental and density functional theory (DFT) results, a reasonable mechanism of edge-selective grafting is proposed. In view of the excellent processability and self-assembly ability of such large-size ultrathin BNNSs, high-performance and transparent BNNSs/epoxy (EP) composites with greatly improved anticorrosion and mechanical properties are then fabricated. Typically, the BNNSs/EP composites show an extremely high protection efficiency of 99.9%, and the tensile strength and modulus increase by 124 and 66%, respectively. We believe that this green and efficient exfoliation route will boost the development of scalable production of large-size ultrathin BNNSs and shows huge promise for their widespread application in functional composites.