Supercritical fluid processing of boron nitride nanosheets for polymeric nanocomposites of superior thermal transport properties

Abstract

In the present study, a supercritical fluid (SCF) mixture was used for the rapid and efficient exfoliation of hexagonal boron nitride (h-BN), yielding high-quality boron nitride nanosheets (BNNs) of larger aspect ratios and less defects. The essence of this exfoliation strategy lies in the advantageous properties of SCFs, including especially the ultrahigh diffusivity and near-zero surface tension, as well as the special solvation power of water and ethanol under SCF conditions. These fluid medium conditions are ideally suited for the diffusion of solvent molecules into the interlayer spacing, coupled with their enhanced interactions with the B and N sites, to facilitate more efficient interlayer expansion and separation. The BNNs thus produced exhibited good compatibility with the selected polymer matrices, with the resulting polymeric nanocomposite films mechanically flexible and of superior thermal transport performance in terms of the observed thermal diffusivities higher than those based on BNNs from other exfoliation methods.