Pyrolysis behavior of polysilazane and polysilazane-coated-boron nitride for high thermal conductive composite

A thermally conductive composite was fabricated using a BN filler and an epoxy matrix. Because of electrostatic repulsion force, the BN/epoxy composite had poor interfacial affinity, which led to a decrease in the thermal conductivity. To enhance the interfacial affinity, pre-ceramic polysilazane (PSZ) was introduced onto the BN surface and it was sintered in various conditions. PSZ was converted to different structure depended on pyrolysis conditions. After the pyrolysis, the PSZ was converted into a SiOC ceramic in nitrogen atmosphere, and to SiO2 and ash in air atmosphere. The thermal conductivity of the BN-PSZ/epoxy composite decreased as the pyrolysis temperature was increased because of the decomposition of polar functional groups. Pyrolysis at 300 °C in nitrogen atmosphere yielded the highest performance, resulting in an increase in the thermal conductivity to 3.521 W m−1K−1 at 70 wt% of filler, which was a 1.35-fold increase compared with the raw BN/epoxy composite.