Enhanced thermal management performance of nanofibrillated cellulose composite with highly thermally conductive boron phosphide

Polymer-based composites are in great demand in thermal management with better thermal conductivity performance because of the rapid a evolutionary performance of their application systems. Pursuing new filler materials with higher thermal conductivity is an important way to improve the performance of polymer composites. Boron phosphide (BP) has been confirmed to possess the superior characteristic of high thermal conductivity, yet it is difficult to be synthesized on a large scale and thus is rarely used as a filler in composites. In this work, BP powders were synthesized by a facile molten salt method. Afterwards, milled BP (MBP) particles containing abundant surface functional groups were first explored as a filler for nanofibrillated cellulose (NFC) to fabricate NFC/MBP composite films by the vacuum filtration technology. The high thermal conductivity of MBP and the in-plane oriented arrangement, in conjunction with its strong interface bonding with NFC, led to the high in-plane thermal conductivity (17.6 W m-1 K-1) of the composite with 15 wt% MBP. The better heat dissipation capacity than that of the NFC composite with BN nanosheets as the filler makes the NFC/BP film suitable for application in the field of thermal management.