Silicon Carbide-Welded Boron Nitride Networks for Self-Healing Flexible Thermal Interface Materials

Boron nitride (BN) as fillers for thermal interface materials (TIMs) has attracted great attention due to its high thermal conductivity (TC) and electrical insulation. The carbon-welding strategy is demonstrated to be effective for lowering the interface thermal resistance (ITR) between the BN plates. However, the welded structure made by a conventional carbon-welding strategy is always electrically conductive, making it unsuitable for electric devices. To lower the ITR while maintaining the electrical insulation, a dual-welding strategy combined with the directional freeze-casting technique is designed to construct an out-of-plane oriented silicon carbide (SiC)-welded BN (SiC-w-BN) network for high-performance TIMs. Moreover, self-healing polydimethylsiloxane (SH-PDMS) based on hydrogen bonds between polymer chains was prepared as a polymer matrix to endow TIMs with a self-healing property. The oriented and welded filler structure endows the SiC-w-BN/SH-PDMS composite with a high out-of-plane TC of 2.137 W m^-1 K^-1 at 23.45 wt % filler loading, which is more than 10 times higher than that of pure SH-PDMS (0.19 W m^-1 K^-1). Finite element analysis and molecular dynamics simulation illustrate the advanced heat conduction and low ITR of the welded structure. Besides, the composite demonstrates 72% extensibility with 69% strain and 97% strength recovery efficiency after being completely cut off. This work provides a new strategy for manufacturing high-performance TIMs with multifunctional properties including flexibility, self-healing capability, and electrical insulation.