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Graphene films are accepted as excellent heat dissipation materials due to their ultrahigh thermal conductivity. In general, the graphene film uses graphene oxide (GO) as the raw material through self-assembly, carbonization, and graphitization processes. However, the production and accumulation of a large amount of gas during the carbonization can produce high gas pressure, which causes damage to the ordered stacking structure and seriously affects the thermal conductivity of the graphene film. In this work, we propose a strategy of diamine reagents to crosslink and reduce GO for constraining volume expansion during carbonization. The amine group undergoes nucleophilic substitution and condensation reactions with oxygen-containing functional groups (−COOH, – C–O–C) to form – C–N bonds, which broaden the temperature range of gas production by changing the chemical structure. Compared to dimethylaminopropylamine and N-isopropylethylenediamine, ethylenediamine with symmetrical primary amines can react sufficiently with GO to form a robust structure. Based on these observations, the ethylenediamine-modified film shows a lower expansion rate (115.2%) and higher in-plane thermal conductivity (∼1180 W m–1 K–1) than the pure graphene film (152.6% and ∼980 W m–1 K–1, respectively). This work could be significant in the preparation of graphene films with high thermal conductivity. [ABSTRACT FROM AUTHOR]

Reduced graphene films have attracted widespread commercial interest due to high electrical conductivity toward (EMI) shielding. At present, the preparation path of reduced graphene film is to use graphene oxide (GO) as the raw material through self-assembly and high-temperature heat treatment. However, the thickness of reduced graphene films is not high and uniform because of the higher mobility of the graphene oxide slurry, which destroys the reliability of the membrane in the field of electromagnetic interference shielding. Here, we propose the use of sodium carboxymethyl cellulose (CMC) to increase the viscosity of graphene oxide to prepare reduced graphene films with high and uniform thickness. After modification with sodium carboxymethyl cellulose, the EMI shielding effectiveness (EMI SE) of reduced graphene oxide films stabilized at 91–96 dB at 8–12 GHz, which is higher than pure graphene films. Meanwhile, the addition of CMC does not affect the structure of reduced graphene films. This work broadens the application of reduced graphene films in electromagnetic shielding. [ABSTRACT FROM AUTHOR]