Identification of Thermal Barrier Areas in Graphene Oxide/Boron Nitride Membranes by Scanning Thermal Microscopy: Thermal Conductivity Improvement through Membrane Assembling

Two-dimensional (2D) materials are widely accepted as ideal candidates for thermal management materials due to their high intrinsic thermal conductivity and unique anisotropic heat conduction. Theoretical research on the thermal conductivity of 2D materials has developed rapidly in recent years, but experimental characterization on the practical level is relatively weak, especially at the micro/nanoscale. In this work, scanning thermal microscopy (SThM) was used to study the influence of the surface geometry on the in-plane thermal conductivity of practical graphene oxide (GO) membranes at the micro/nanoscale. Experiments revealed that the wrinkled structure prevented efficient heat flow. A 2D amino-modified boron nitride (a-BN) was used as a laminar cross-link to provide the edge–edge covalent bonds that reduced the wrinkles and increased the thermal conductivity. This facilitated the formation of a tightly packed GO/a-BN/GO hybrid structure, identified by the improved stiffness value characterized by force–displacement (F–D) characterization. Heat loss at the wrinkles was reduced, and the overall thermal conductivity increased with a lower loading percent of BN in the GO/BN hybrid membranes. Further increase of the BN loading generated an anabatic wrinkle effect, which prevented heat conduction and decreased the overall thermal conductivity. This provides a basic understanding of the structure–thermal relationship in practical 2D membranes and proposes an effective method to improve in-plane thermal transport through assembling 2D materials.