Copper Nanoparticle-Decorated Boron Nitride Nanosheets for Enhancing Thermal Conductivity of Nanocellulose Films

Boron nitride nanosheets (BNNSs)-cellulose nanofibrils (CNF) nanocomposites have attracted significant interest as advanced materials for thermal management. However, their thermal conductivities are still insufficient due to the high interfacial thermal resistances (ITR) among the different components of the composites. In the present work, copper nanoparticles (CuNPs)-BNNS (Cu-BNNS) hybrid fillers were prepared by anchoring CuNPs on the BNNS surfaces using the liquid phase reduction method. Subsequently, the hybrid fillers were dispersed in a CNF matrix to produce the Cu-BNNS/CNF composite film, which exhibited high in-plane and out-of-plane thermal conductivities up to 37.5 ± 3.1 and 1.8 ± 0.026 W·m–1·K–1, respectively. The copper nanoparticles connecting the adjacent BNNSs contributed to reduced ITR and significant improvement of thermal conductivity. Specifically, CuNPs did not compromise the electrical insulation of the BNNS/CNF composites when enhancing their heat dissipation capability. The Foygel model developed for Cu-BNNS/CNF theoretically confirmed the role of copper nanoparticles. This study provides a feasible strategy for advancing the applications of BNNS and CNF in modern electronics for sustainable thermal management.