As a novel two-dimensional material possessing both high thermal conductivity and electrical insulation, boron nitride nanosheets exhibit great application potential in fields such as thermal management and dielectric composites. Efficient dispersion technology is key to unlocking their performance advantages. Among these, ultrasonic dispersion, due to its simplicity and ease of control, has become one of the mainstream techniques for preparing boron nitride nanosheet dispersions.
The core principle of ultrasonic dispersion for preparing boron nitride nanosheets lies in energy transfer and interfacial interactions. The commonly used ultrasonic disruptor generates a mechanical effect through high-frequency vibration. The resulting ultrasonic cavitation releases enormous energy, effectively disrupting the interlayer forces of the hexagonal boron nitride bulk, achieving the exfoliation from macroscopic powder to nanosheets. This top-down exfoliation method maximizes the preservation of the intrinsic properties of boron nitride and avoids structural defects caused by chemical exfoliation.
In the actual preparation process, the control of process parameters directly affects the product quality. When water is used as the dispersion medium, by optimizing the ultrasonic power and time, the diameter of boron nitride nanosheets can be controlled within the range of 80-200 nm, and the sheet thickness can be stabilized within 10-20 nm, forming a well-uniform dispersion system. This size of nanosheet ensures effective contact with the matrix material while reducing interfacial thermal resistance, laying the foundation for subsequent composite material preparation.
However, this technology still faces the challenge of dispersion stability. The surface of boron nitride nanosheets is inert, resulting in poor wettability in water and a tendency to aggregate. Experimental data show that without the addition of a dispersant, the upper limit of the stable dispersion concentration is approximately 1 mg/mL; excessively high concentrations lead to turbidity and sedimentation. This limitation restricts large-scale applications to some extent, therefore, dispersion optimization has become a key research focus.
Currently, the industry has explored various synergistic solutions. Studies have shown that introducing auxiliaries such as glucose and utilizing the hydroxyl groups generated from their decomposition to modify the surface of nanosheets significantly improves water dispersibility and exfoliation yield. Alternatively, a combination of ultrasonic and magnetic stirring can be used to prevent agglomeration through mechanical synergy, ensuring consistent particle size distribution.
From an application perspective, boron nitride dispersions prepared by ultrasonic dispersion have demonstrated practical value. In the field of thermal management, they can be combined with polymers to construct highly efficient thermally conductive networks; in functional coatings, uniformly dispersed nanosheets can impart excellent insulation and weather resistance to materials. With the continuous iteration of dispersion technology, ultrasonic methods will undoubtedly play an even more important role in the industrialization of boron nitride nanomaterials.
