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The boron nitride nanosheets (BNNSs)/aluminum nitride (AlN) composites were prepared by hot press sintering at 1600°C. The microstructure, mechanical properties, and thermal conductivity of the samples were measured, and the effect of adding BNNSs to AlN ceramics on the properties was studied. It is found that the addition of BNNSs can effectively improve the mechanical properties of AlN. When the additional amount is 1 wt%, the bending strength of the sample reaches the maximum value of 456.6 MPa, which is 23.1% higher than that of the AlN sample without BNNSs. The fracture toughness of the sample is 4.47 MPa m1/2, a 68.7% improvement over the sample without BNNSs. The composites obtained in the experiment have brilliant mechanical properties. [ABSTRACT FROM AUTHOR]

Due to their intriguing properties, boron nitride nanosheets (BNNSs) with large lateral size and high crystallinity have great promise for many applications. However, the quantitative exfoliation of hexagonal boron nitride (h-BN) into good quality BNNSs still remains a key challenge. Herein, we report a scalable method to exfoliate BNNSs in ionic liquids (ILs) via shear-assisted thermal treatment. Few-layer BNNSs with well-preserved structural integrity are successfully prepared by this method. The synergistic effects of strong physical adsorption and intercalation of IL molecules, chemical interactions between hydrogen fluoride (HF) and h-BN, activation energy provided by heat treatment, and shear forces generated by repetitive stirring effect contribute to the exfoliation of BNNSs. [ABSTRACT FROM AUTHOR]

In this study, Zn 8 B 3 H 3 O 14 nanosheets were synthesized through a one-step coprecipitation process and employed as both a boron source and substrate templates for the fabrication of boron nitride nanosheets (BNNSs), which were synthesized efficiently at low temperatures by the borate nitration method using ammonia as the nitrogen source. The thickness of the synthesized BNNSs ranged from 3 to 10 nm with a flake dimension of about 2.56 μm. The prepared BNNSs using this method realized 98.8% boron source utilization and single batch yields up to gram level. In addition, BNNSs/SiO 2 microwave-transparent composites were prepared to investigate the potential for large-scale applications of the BNNSs produced by using this method. The composites demonstrated a remarkable increase in bending strength and fracture toughness, reaching 122.02 MPa and 2.31 MPa·m1/2, respectively, with the addition of only 0.5 wt% BNNSs. Compared with SiO 2 without BNNSs, the fracture toughness of the composites is increased by 106%. A novel crack plugging strong toughening mechanism of BNNSs is proposed. Simultaneously, the composites exhibit exceptional microwave-transparent properties, with dielectric constants below 4 in the real part and below 0.03 in the imaginary part. Therefore, this study has successfully achieved the low-temperature and efficient synthesis of micron-scale BNNSs, laying the groundwork for their large-scale application. [Display omitted] • Zn 8 B 3 H 3 O 14 nanosheets were used as substrate templates for the synthesis of BNNSs. • BNNSs were synthesized with high efficiency at low temperatures (900 °C). • The single batch yield of BNNSs reached up to the gram level. • The BNNSs/SiO 2 wave-transparent composites with ultrahigh toughness were obtained. • A novel mechanism for strengthening and toughening (BNNSs plugging) is proposed. [ABSTRACT FROM AUTHOR]