Nacre-inspired copper nanowires/graphene oxide films with excellent thermal conductivity, flame retardancy and electrical performance

Inspired by the hierarchical microstructure of nacre, via the surface modification of polydopamine (PDA), nacre-mimicking composite films containing graphene oxide (GO) and different mass ratio (5, 15, 25, 35 wt%) of copper nanowires (CuNWs) were prepared with a solvent-induced assembly strategy. The introduction of PDA not only reduced GO, but also protected the CuNWs from oxidation. 1D CuNWs, as a thermal bridge, was introduced into 2D GO nanosheets to construct an interconnected thermal conduction network. This structure can provide an effective thermal conductive pathway. The CuNWs/GO-PDA film containing 25 wt% CuNWs (25CuNWs/GO-PDA) exhibits excellent in-plane thermal conductivity of 6.841 W/mK and cross-plane thermal conductivity of 0.202 W/mK. A high anisotropy index of about 34 for 25CuNWs/GO-PDA film was obtained. Due to the char forming ability of PDA, and unique nanosheets structure of GO, films exhibit excellent flame retardancy. Micro combustion calorimeter tests confirm dramatically reduced 80.9% of peak heat release rate compared with pristine GO. More importantly, electrical conductivity of composites improved with the increase of CuNWs loading. With the addition of 35 wt% CuNWs, the electrical conductivity reaches 6.43 x 10(6) S/m. This type of bioinspired film with multifunctional properties is expected to be used as a promising candidate for electronic materials.