Fabrication of Thick Graphite Films with Considerable Conductivity via Gas Expansion and Polyamide Acid-Assisted Low-Temperature Repair

Graphite sheets with pi-pi conjugated structures offer easy processing and scalability for large-scale films, showing excellent phonon transport properties. However, the strong oxidation and nonoxidized state of the graphite sheets are not conducive to fabricating thick graphite films, significantly limiting their potential applications in next-generation flexible electronics. To address this challenge, weakly oxidized wrinkled graphite nanosheets (WGNs) were developed, positioned between strong oxidation and nonoxidation states. The WGNs were further combined with polyamide acid (PAA) via noncovalent functional auxiliary dispersion. During the staged heating process, the defect repair mechanism facilitated by PAA enabled the restoration of the lattice structure of the graphite film (WGNF-C) at a lower temperature (1400 degrees C). As a result, the prepared thick WGNF-C film (98.01 mu m) exhibits excellent in-plane thermal conductivity (471.2 W m-1 K-1), out-plane thermal conductivity (4.5 W m-1 K-1), electrical conductivity (3790.4 S/cm), and electromagnetic interference shielding effectiveness (73.2 dB). Moreover, the film's wrinkled structure also gives it high tensile strength (32.6 MPa) and good flexibility. This bubble-mediated method, featuring controllable oxidation and enhanced by PAA-assisted dispersion and defect repair, provides new insights into the controlled processing of graphite. It also offers a novel design pathway for constructing flexible, high-conductivity thick graphite films.