Thermal conductivity enhancement of BN/silicone composites cured under electric field: Stacking of shape, thermal conductivity, and particle packing structure anisotropies

We have prepared thermal conductive silicone rubbers filled with BN micro particles assisted with electric field assisted curing, and studied the electric field effect. The composites structure was characterized by XRD, SEM, and the results indicate that aligned conductive networks have formed between the electrodes under either AC or DC electric fields. Furthermore, the "c" axis of BN particles was found to orient along with the electric field and the orientation degree under AC was higher than that with DC. Upon increasing the filler volume fraction, the orientation decreases dramatically. In addition, we have investigated the thermal conductivity of BN/silicone composites with varying particle volume fractions and electric-field strengths. For example, under the AC electric field (50 Hz) of 11.0 kV/mm, the thermal-conductivity with 20% loading of BN increases by ca. 250% compared to that prepared without electric field. A two-level homogenization model was adopted to analyze and fit the thermal conductivity data.