Manipulating thermal conductivity of polyimide composites by hybridizing micro- and nano-sized aluminum nitride for potential aerospace usage

Electrically insulating yet thermally conductive polymer-based composites are highly sought after in aerospace field. In this work, for the first time, electrically insulating but thermally conductive polyimide (PI) composites are fabricated by simultaneously incorporating micro- and nano-sized aluminum nitride (AlN) particles via a simple, economic, and scalable method of ball milling and subsequent hot-pressing process. The thermal conductivity, dielectric, and mechanical properties of the PI composites depend on the ratio of micro-sized AlN (m-AlN) to nano-sized AlN (n-AlN) and the total content of AlN in the PI composites. The thermal conductivity of the PI composites with 40 wt% m-AlN and 20 wt% n-AlN is 1.5 +/- 0.05 W center dot m(-1)center dot K-1, which is 10 times higher than that of bare PI. The PI composites hold a great potential in aerospace industries.