A combination of a series of epoxy coatings filled with octadecylamine (ODA)-modified graphene oxide (mGO) or commercial exfoliated graphite nanoplatelets (xGnP) was developed to boost the anticorrosion performances of mild steel substrates in acidic and NaCl aqueous solutions. The xGnP and mGO were applied successfully as fillers for the preparation of layer by layer (LBL) xGnP or mGO/epoxy coatings, respectively, which were coated on the clean steel surfaces to form LBLassembled layers. The LBL-assembled xGnP or mGO/epoxy coating-coated steel substrates exhibit excellent anticorrosion performances. The corrosion potentials (Ecorr) of xGnP-1/xGnP-2/3 and mGO-1/mGO-2/3 display at − 193 and − 150 mV, respectively, while Ecorr of the bare steel shows at − 871 mV of immersion in the 3.5 wt% NaCl solution. The most positive Ecorr values are obtained for xGnP-1/2/3 (− 117 mV) and mGO-1/2/3 (− 66 mV), showing the best anticorrosion performances compared to the bare steel (− 404 mV) in 17 wt% HCl solution.

The microstructure, flexural properties, electrical conductivity, thermal conductivity and electromagnetic interference (EMI) shielding effectiveness (SE) of epoxy composites filled with multi-walled carbon nanotubes (CNTs), exfoliated graphite nanoplatelets (xGnPs) and CNT-xGnP hybrid filler were investigated. The EMI SE of the CNT-xGnP hybrid composite was higher than 25 dB at 100 MHz while that of the xGnP based composite was almost zero. The flexural modulus of the CNT-xGnP based epoxy composite continuously increased to 3.32 GPa with combined filler content up to 10 wt% while that of the CNT based epoxy composites slightly decreased to 1.96 GPa at 4 wt% CNT, and dropped to 1.57 GPa at 5 wt% loading, which is lower than that of epoxy. The CNT and CNT-xGnP samples had the same EMI SE at the same surface resistivity, because samples with the same surface conductivity have the same amount of the charge carriers.

In the present study, exfoliated graphite nanoplatelets (xGnP) with different particle sizes were coated onto polyacrylonitrile-based carbon fibers by a direct coating method. The flexural properties, interlaminar shear strength, and the morphology of the xGnP-coated carbon fiber/phenolic matrix composites were investigated in terms of their longitudinal flexural strength and modulus, interlaminar shear strength, and by optical and scanning electron microscopic observations. The results were compared with a phenolic matrix composite counterpart prepared without xGnP. The flexural properties and interlaminar shear strength of the xGnP-coated carbon fiber/phenolic matrix composites were found to be higher than those of the uncoated composite. The flexural and interlaminar shear strengths were affected by the particle size of the xGnP, while the particle size had no significant effect on the flexural modulus. It seems that the interfacial contacts between the xGnP-coated carbon fibers and the phenolic matrix play a role in enhancing the flexural strength as well as the interlaminar shear strength of the composites.