Search

Hexagonal boron nitride (h-BN) and exfoliated nanosheets (BNNs) not only resemble their carbon counterparts graphite and graphene nanosheets in structural configurations and many excellent materials characteristics, especially the ultra-high thermal conductivity, but also offer other unique properties such as being electrically insulating and extreme chemical stability and oxidation resistance even at elevated temperatures. In fact, BNNs as a special class of 2-D nanomaterials have been widely pursued for technological applications that are beyond the reach of their carbon counterparts. Highlighted in this article are significant recent advances in the development of more effective and efficient exfoliation techniques for high-quality BNNs, the understanding of their characteristic properties, and the use of BNNs in polymeric nanocomposites for thermally conductive yet electrically insulating materials and systems. Major challenges and opportunities for further advances in the relevant research field are also discussed.

Boron nitride nanosheets (BNNs) are pursued for their high thermal conductivity yet electrical insulation and their extreme thermal and chemical stabilities for a variety of applications. For high-quality BNNs, a number of exfoliation approaches under different processing conditions were evaluated. Three more effective methods were identified, including method-A based on refluxing and vigorous sonication in isopropyl alcohol, method-B involving ball-milling in urea, and method-C with the aid of ammonia in hydrothermal processing. These methods produced BNNs of apparently different structural and morphological characteristics, with those from the first two being smaller pieces, more defective, and their polymeric nanocomposites exhibiting relatively lower thermal conductive performance. The method-C yielded BNNs of obviously better quality, as also made evident by the observed high thermal diffusivities of their corresponding polymeric nanocomposites. Correlations of exfoliation approaches and conditions w...

High-quality boron nitride nanosheets (BNNs) characterized by large aspect ratios and less defective surfaces and structures are in demand for thermal management and other uses that exploit the uniquely advantageous properties of boron nitride, such as being highly thermally conductive yet electrically insulating and extreme chemical and thermal stabilities. In this study, an ammonia-assisted exfoliation processing method was developed and applied to the preparation of high-quality BNNs. As a demonstration of the excellent potential of these nanomaterials, the BNNs were dispersed in polyethylene polymers for nanocomposite films of superior thermal transport performance at levels significantly beyond the state of the art in the literature. Effects of crosslinking in the nanocomposite film structure on thermal transport were also explored and favorable outcomes were achieved.