Amorphous liquid phase induced synthesis of boron nitride nanospheres for improving sintering property of h-BN/ZrO2 composites

Abstract

Hexagonal boron nitride (BN) nanospheres with large quantities and high crystallinity have been successfully synthesized from BxCyNzOkHl precursors without any catalyst. The uniform size of the obtained BN nanospheres is about 20 nm. The structure, morphology and surface chemical property of the products were characterized using XRD, FTIR, SEM, HRTEM and XPS. The results show that BN nanospheres with good crystallinity are prepared by heat treatment of amorphous BxCyNzOkHl precursor at 1100 °C in flowing N2. The urea content has great influence on the crystallinity and morphology of BN nanospheres. The diameter and morphology of BN nanospheres dramatically vary at different temperature. Based on the amorphous liquid phase encapsulated induce model, the reaction mechanism and morphological evolution mechanism were described. The viscous liquid containing B and N amorphous phase plays a crucial role in the formation of BN nanospheres. The BN nanospheres improved the density of h-BN/ZrO2 composites from 94.43% to 97.02%.