Nanosized boron nitride-incorporated polyvinyl alcohol composites with TEMPO-oxidized cellulose nanofibers as ultrathin thermal interface materials

Abstract

With the miniaturization and dense packing of electrical devices and mobility platforms, the effective thermal management at the interfaces of components in compact form factors is essential to overcome the performance limits and ensure the stability. Herein, we report the development of assembly of nanosized boron nitrides (BN) and TEMPO-oxidized cellulose nanofibers (T-CNFs) in polyvinyl alcohol (PVA) composites as ultrathin thermal interface materials (TIMs). BN nanoparticles (average thickness of 3.8–4.0 nm, lateral size of 90–100 nm, and aspect ratio of 25) were produced with a yield exceeding 80 % from the chemical treatment of hexagonal BN with NaOH and subsequent ball milling. TEMPO-oxidized cellulose nanofibers (T-CNFs) were added to mechanically reinforce the PVA-based matrix, while by the functionalization with OH– groups, the BN particles dispersed readily in the PVA solution, obtaining ultrathin nanosized BN/PVA/T-CNF composite films (∼50 µm). In contrast to the expected low thermal conductivity due to surface defects and high contact resistances typical of nanosized BN, composite films containing 50 wt% nanosized BN exhibited significantly high in-plane and through-plane thermal conductivities of 11.13 and 1.22 W/mK, respectively. Comparative analysis based on the Lewis–Nielsen model revealed that the size, shape, and agglomeration state of the BN particles could highly influence the thermal conductivity of composite films. Furthermore, heat dissipation experiments reflecting practical conditions demonstrated the outstanding performance and thermal stability of nanosized BN/PVA/T-CNF films as TIMs. This study will inspire rational strategies to facilely incorporate nanosized BN to diverse composites, offering advanced thermal characteristics with mechanical robustness.