Surface functionalization for dispersing and stabilizing hexagonal boron nitride nanoparticle by bead milling

This paper presents the surface functionalization with silane coupling agents for dispersing and stabilizing hexagonal boron nitride (hBN) nanoparticle suspension in a water phase. Fine milling using 30 μm bead technology was utilized for the reduction of particle size, while dispersing agents with silane coupling agents were used for surface modification to enhance dispersion stability. A monodispersed hBN nanoparticle was obtained by controlling the processing parameters and by optimizing the dispersant dosage. The hBN nanoparticle suspension showed a high degree of dispersion stability with a zeta potential below −40 mV when (3-acryl-oxypropyl) trimethoxysilane (APMS) was used as the dispersing agent. Under optimal operation conditions for bead milling, the final average size of the particle distribution for the hBN suspension was 46 nm and 38 nm for 0.5 wt.% and 5 wt.% hBN, respectively. In addition, the surface characteristics, morphology, crystal structure and chemical composition of the hBN particles before and after bead milling were investigated to know the effect of bead milling. Finally, the surface functionalization mechanism that enhanced the stability of hBN nanoparticle dispersion by electrosteric stabilization was also proposed.