Combustion synthesis of tunable‐aspect‐ratio β‐Si3N4/BN composite ceramic materials

Abstract High thermally conductive β‐Si 3 N 4 is a new type of filler for thermally conductive materials. Tailoring its aspect ratio is crucial to optimize the preparation process and performance of polymer‐based thermal conductive materials. In this work, β‐Si 3 N 4 /BN thermally conductive hybrid fillers were prepared by combustion synthesis in a nitrogen atmosphere using low‐cost Si, B 2 O 3 powders as raw materials, and the aspect ratio of β‐Si 3 N 4 crystals were regulated according to the inhibiting growth strategy of second phase BN generated by in situ reaction. With the increase of B 2 O 3 , the content of BN increased slightly, while that of β‐Si 3 N 4 decreased slightly. The aspect ratio of β‐Si 3 N 4 decreased from 6.3 ± 1.9 to 1.9 ± 0.6, which might be ascribed to the inhibiting effect of BN sheets on the axial growth of rod‐like β‐Si 3 N 4 . Low‐aspect‐ratio β‐Si 3 N 4 /BN/epoxy composite exhibited high thermal conductivity of 1.04 W·m ‐1 ·K ‐1 at the solid content of 50 wt%, which was 372.7% and 30.0% higher than that of neat epoxy and 40 wt% high‐aspect‐ratio β‐Si 3 N 4 /epoxy composite, respectively. In addition, β‐Si 3 N 4 /BN/epoxy composite also had good mechanical properties.