Boosting the thermal conductivity of CNF-based composites by cross-linked lignin nanoparticle and BN-OH: Dual construction of 3D thermally conductive pathways

The construction of thermally conductive pathways to improve the thermal conductivity of the thermal interface materials (TIMs) is highly demanded due to the expanding trend of miniaturization, integration, and high-power of microelectronics, whereas the present TIMs could hardly provide the satisfying heat management performance. Herein, we report a progressive 3D self-assembly strategy for the fabrication of a composite film with excellent flexibility and thermally conductivity. Hexagonal boron nitride (BN)-OH is cross-linked with lignin nanoparticle (LNP) by borax and assembled onto cellulose nanofibrils (CNF), after further freeze-drying and pressing the composite film is thus formed. SEM analysis revealed that the BN-LNP thermally conductive pathways were successfully formed, and LNP acted as the cross-linking point of BN-OH. The 50 wt% filler loaded BN-LNP/CNF composite (BN-LNP50) exhibited a through-plane thermal conductivity of 2.577 W/mK, while this feature for the pure CNF film was only 0.413 W/mK, revealing an improvement of similar to 524%. It is worth noting that at the same filler content, the composite loaded with non-cross-linked BN/LNP mixture presented a much lower thermal conductivity (1.224 W/mK) compared to that was loaded with BN-LNP (2.084 W/mK). Particularly, the BN-LNP50 was thermally decomposed at 230 degrees C, demonstrating an increasement of 30% compared with the pure CNF film. Overall, this study provides an effective approach to fabricate BN-related thermally conductive materials with improved thermal management capacity.