Capillary slit induced orientation and microstructure control of graphene film

Graphene film is a layered material with high thermal and electrical conductivity. Its properties depend on the alignment and packing of graphene sheets. In this work, capillary slit assisted self-assembly strategy was developed to fabricate freestanding graphene film with improved orientation and structural uniformity. A suspension of graphene oxide (GO) and commercial graphene (CG) was injected into a slit mold, where capillary forces and micro-convective flow promoted the alignment and dense stacking of graphene sheets during solvent evaporation. The resulting films were thermally reduced to produce reduced GO/CG composites, denoted as SrGO/G (with slit) and rGO/G (without slit). Structural characterization revealed that SrGO/G possesses a smoother surface, a more ordered layered structure, and a higher Herman’s orientation factor (0.91) compared to rGO/G (0.86). These structural advantages result in a higher in-plane thermal conductivity of 102.86 W m −1 K −1 for SrGO/G, compared with 26.74W m −1 K −1 for rGO/G. This enhancement is attributed to the more ordered and densely packed graphene sheets, which facilitate phonon transport along the in-plane direction. These results demonstrate that slit-assisted assembly is a simple and effective strategy to control graphene sheet alignment and enhance thermal properties.