Polyimide (PI) has become one of the most promising thermal conductive carbon film precursors due to its simple preparation process, low cost, high carbon yield, and easy control of the carbonization and graphitization process. The addition of inorganic fillers to the PI film can improve the mechanical and thermal properties of the composite film, while further improving the thermal conductivity of the prepared carbon film and flexible graphite film.

Recently, researchers converted graphene (GN) into graphene with carboxylic acid groups (GO-COOH) through acidification, and then prepared carboxylated graphene/polyimide composite film (GO-COOH/ PI). On this basis, the composite film is transformed into thermally conductive carbon film and flexible graphite film through carbonization and graphitization.

Studies have found that the addition of GO-COOH has a great effect on reducing carbonization and graphitization temperatures and improving film properties.

The GO-COOH/PI composite film will be carbonized at low temperature, medium temperature and ultra-high temperature. The graphite film prepared by the 2wt% GO-COOH/PI composite film treated at 2500℃ has a smoother and relatively uniform surface without too many wrinkles. And the color of the graphite film is dark gray, reflecting a higher degree of graphitization. The graphite film can maintain overall integrity and achieve a certain degree of bending, which indicates that the flexibility of the graphite film is improved.

In addition, the graphite film prepared by the 2wt% GO-COOH/PI composite film exhibits excellent thermal conductivity (760.386 W/m∙K), which is 128% higher than the graphite film prepared by the PI film.

The research results were published in the international academic journal Ceramics International (2021, 47: 1076). The first author and corresponding author are L.R. Ma and Y.X. Wang of Shandong University.