Electric Field-assisted Preparation of Anisotropic BNNw/SiR Composites for Thermal Management

Enhancing the thermal conductivity of insulation materials in high-capacity electrical equipment and highly integrated circuits can significantly improve the operational efficiency and lifespan of the devices. Establishing a phonon propagation pathway is a critical factor in enhancing the thermal conductivity of composite insulation materials. Traditionally, the reliance on random filler dispersion presents challenges related to a high percolation threshold and potential detrimental effects on mechanical and insulating properties. This work investigates the dielectric and thermal properties of BN nano whiskers / silicone rubber (BNNWs/SiR) composites prepared with electric field assistance. The dielectric spectrum data demonstrate the oriented self-assembly of BNNWs under the electric field. The thermal conductivity of the composites in the direction of the assisted electric field is enhanced with the filler content and assisted electric field strength. Compared to pure SiR, the out-plane thermal conductivity increased from 0.16 W/m·K to 0.37 W/m·K with only 8wt% filler and 24 V/mm/10 kHz assisted electric field lasting for 0.5h. The out-of-plane orientation of BNNWs would reduce the in-plane thermal conductivity. Therefore, for different thermal management scenarios, the degree of anisotropy of the thermal conductivity of the material should be modulated, thus optimizing the heat dissipation effect of the target device.