Efficient Preparation of BNNSs and Their Performance Study of Reinforced Porous Si₃N₄ Composites by Gel Casting

Abstract

The preparation of boron nitride nanosheets (BNNSs) with high efficiency and low cost has consistently been a primary obstacle, limiting their large-scale applications. In this study, BNNSs with well crystallization were efficiently synthesized at 1000 °C, by using solid state method to efficiently synthesize blocky ZnB 2 O 4 with low melting point as the precursors. This preparation method can achieve a boron source utilization of up to 76% and a single batch yield up to the gram level. In addition, BNNS/Si 3 N 4 microwave-transparent composites were prepared to investigate the potential for large-scale applications of the BNNSs produced by this method. The composite with the addition of 0.5% BNNSs exhibits low bulk density as well as excellent mechanical and microwave-transparent properties, with bulk density, bending strength, fracture toughness, dielectric constant, and loss angle tangent at 18 GHz reaching 2.015 g/cm 3 , 249.61 MPa, 2.89 MPa• m 1/2 , 4.06, and 2.9 × 10 −4 , respectively. Therefore, the low-temperature and high-efficiency preparation of BNNSs by this method provides a simple and dependable method for large-scale application in the field of microwave-transparent materials.