Optimization of Size Effect of Boron Nitride on Thermoelectric Properties of Silicone Resin

Traction motors are continuously advancing toward higher power density and miniaturization, leading to increasingly critical heat dissipation challenges. To mitigate the degradation of insulation materials caused by elevated temperatures, stricter requirements have been imposed on the thermal conductivity ( λ ) of silicone resin (SR) used in stator insulation systems. In this study, composite is fabricated by incorporating boron nitride (BN) particles of varying sizes into a SR matrix. The influence of BN particle size and filler loading on the microstructure, thermal conductivity, and electrical properties of the composites is systematically investigated. At identical filler concentrations, micron‐sized BN enhances the thermal conductivity of the composites more effectively than nano‐sized BN. Specifically, when 20 wt.% of 5 μm BN is incorporated, the composite achieves a maximum thermal conductivity of 0.73 W/(m K), representing a 247% improvement over pure SR. Finite element simulations further demonstrate that larger BN particles facilitate the formation of efficient thermal conduction pathways within the matrix. Importantly, the sample with the best λ retains excellent electrical insulation properties, which with a breakdown field strength ( E b ) of 25.25 kV/mm and superior dielectric characteristics. This study presents a promising strategy for the design of advanced insulation materials tailored for high‐voltage traction motors.