聚酰亚胺辅助制备高定向石墨烯基全炭泡沫及其在导热聚合物复合材料中的应用OA北大核心CSTPCD

Graphene and its derivatives are often preferentially oriented horizontally during processing because of their two-di-mensional(2D)layer structure.As a result,thermal interface materials(TIMs)composed of a polymer matrix and graphene-derived fillers often have a high in-plane(IP)thermal conductivity(K),however,the low through-plane(TP)K makes them unsuitable for practical use.We report the development of high-quality polyimide/graphite nanosheets(PG)perpendicular to the plane using a dir-ectional freezing technique that increase the TP K of polymer-based composites.Graphene-derived nanosheets(GNs)were obtained by the crushing of scraps of highly thermally conductive graphene films.A water-soluble polyamic acid salt solution was used to dis-perse the hydrophobic GNs filler to achieve directional freezing.The polyimide,which facilitated the directional alignment of the GNs,was then graphitized.The introduction of the GNs increases the order and density of the PG,thus improving the strength and heat transfer performance of its polydimethylsiloxane(PDMS)composite.The obtained PG/PDMS composite(21.1％PG,mass frac-tion)has an impressive TP K of14.56 W·m-1·K-1,81 times that of pure PDMS.This simple polyimide-assisted 2D hydrophobic fillers alignment method provides ideas for the widespread fabrication of anisotropic TIMs and enables the reuse of scraps of graphene films.