Size-Controllable Mechanochemical Synthesis of Boron Carbide Nanoparticles and Their Surface Modification

Boron carbide nanoparticles (B₄C NPs) exhibit considerable potential across a wide range of applications such as wear-resistant coatings, neutron shielding, and cancer therapy. However, fundamental studies and practical applications of B₄C NPs with specific sizes have been limited due to the lack of size-controllable synthesis. Herein, we report a green and facile mechanochemical synthesis of B₄C NPs from boron oxide, graphite, and magnesium to control their sizes from 35 to 130 nm by adjusting the ball-milling conditions. We found a clear relationship between the ball-milling conditions and the size of B₄C NPs, which is interpreted by the nucleation and growth mechanism, enabling the rational design of the conditions for specific sizes. The synthesized NPs were subjected to surface chemical modification, such as poly(glycerol) functionalization, expanding their applicability. Overall, this size-controllable synthesis provides practical and theoretical platforms to investigate the size effects on various applications of B₄C NPs.