Significantly enhanced thermal conductivity of epoxy composites by in-situ growing AlN whiskers in pre-constructed Si3N4-AlN network skeleton

Polymer composites that have good thermal conductivity can be fabricated by utilizing various categories or dimensions of ceramics as fillers, which is critical for improving heat dissipation in electronic products. Herein, silicon nitride-aluminum nitride (Si 3 N 4 -AlN) ceramic powder was first synthesized from photovoltaic silicon waste (PSW) and aluminum (Al) powder, where a three-dimensional (3D) Al-containing Si 3 N 4 -AlN ceramic network skeleton was constructed by ice-templating subsequently. Next, the raw powder skeleton was transformed into Si 3 N 4 -AlN ceramic skeleton containing one-dimensional (1D) rod-like AlN whiskers based on in-situ nitriding reaction sintering. Ultimately, after epoxy (EP) was impregnated into the composite skeleton under vacuum, polymer composites could be prepared to show good thermal conductivity. The influence of the composite skeleton sintered with different combinations of sintering additives on the behavior of heat transfer in Si 3 N 4 -AlN/EP composites was investigated. The prepared Si 3 N 4 -AlN/EP composites with yttrium fluoride (YF 3 ) and lanthanum oxide (La 2 O 3 ) as primary and secondary sintering aids could achieve thermal conductivity up to 7.04 W m −1 K −1 at a ceramic volume fraction of 38.13 vol%, which was 35.2 times that of pure EP. Practical application tests on a running CPU and heating table confirmed the superior heat dissipation performance of the Si 3 N 4 -AlN/EP composite substrate. This was attributed to the large number of rod-like AlN whiskers generated in the 3D Si 3 N 4 -AlN skeleton during the in-situ nitriding reaction sintering, which could construct more continuous phonon heat transfer pathways. Overall, our work proposes a novel option in developing ceramic/polymer composites that could have outstanding thermal conductivity for potential applications in the industrial field.