Surface functionalization of boron nitride platelets via a catalytic oxidation/silanization process and thermomechanical properties of boron nitride-epoxy composites

Surfaces of hexagonal boron nitride (BN) platelets (with an average platelet diameter of 1 μm) were oxidized in sulfuric acid solution under the presence of a sodium nitrate catalyst, followed by silanization in aqueous ethanol solution. Based on Fourier-transform infrared spectroscopy, catalytic oxidation of BN surfaces in this way resulted in a very successful degree of silanization thereafter compared with other non-catalytic surface-oxidation processes reported in the literature. After silanization, both the width and thickness of the catalytically oxidized BN platelets notably increased, suggesting the possibility of silanization of not only the edge but also the basal planes. When the epoxy matrix was reinforced with the surface-silanized BN platelets, prepared composites demonstrated notably improved thermal and mechanical properties compared with those of raw BN-epoxy composites. Such improvement of thermal and mechanical properties is ascribed to successful surface silanization of BN platelets, yielding enhanced interfacial bonding and dispersion in the epoxy matrix.