Reduced Anisotropic in Thermal Conductivity of Polymer Composites via Chemically Bonded BN–SiC Hybrid Fillers

The growing demand for efficient thermal management in power electronics and high-density optoelectronic systems necessitates thermal interface materials (TIMs) with high through-plane thermal conductivity and minimal anisotropy. However, conventional polymer composites filled with platelet-type fillers such as hexagonal boron nitride (h-BN) suffer from strong directional thermal transport and interfacial resistance, limiting their practical effectiveness. To address this limitation, we present a hybrid filler strategy wherein h-BN and silicon carbide (SiC) nanoparticles interact via hydroxylated surfaces, forming a three-dimensional thermally conductive network. The resulting BN–SiC composite exhibits enhanced through-plane thermal conductivity (1.61 W/mK at 70 vol%) and lower anisotropy ratios (<2.0 at 30 vol%), all while maintaining mechanical integrity and processability. These results demonstrate that chemical bonding at the filler interface can reduce interfacial thermal resistance and extend thermal conduction paths three-dimensionally, providing insights into interface-based heat transfer mechanisms. This strategy presents a scalable and practical approach for next-generation thermal management solutions in electronic packaging and high-power device platforms.