Graphene oxide (GO) was successfully prepared by a modified Hummer's method. The reduction effect and mechanism of the as-prepared GO reduced with hydrazine hydrate at different temperatures and time were characterized by x-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), elemental analysis (EA), x-ray diffractions (XRD), Raman spectroscopy and thermo-gravimetric analysis (TGA). The results showed that the reduction effect of GO mainly depended on treatment temperature instead of treatment time. Desirable reduction of GO can only be obtained at high treatment temperature. Reduced at 95 °C for 3 h, the C/O atomic ratio of GO increased from 3.1 to 15.1, which was impossible to obtain at low temperatures, such as 80, 60 or 15 °C, even for longer reduction time. XPS, 13C NMR and FTIR results show that most of the epoxide groups bonded to graphite during the oxidation were removed from GO and form the sp(2) structure after being reduced by hydrazine hydrate at high temperature (>60 °C), leading to the electric conductivity of GO increasing from 1.5 × 10(-6) to 5 S cm(-1), while the hydroxyls on the surface of GO were not removed by hydrazine hydrate even at high temperature. Additionally, the FTIR, XRD and Raman spectrum indicate that the GO reduced by hydrazine hydrate can not be entirely restored to the pristine graphite structures. XPS and FTIR data also suggest that carbonyl and carboxyl groups can be reduced by hydrazine hydrate and possibly form hydrazone, but not a C = C structure.

In this study, a promising cyanate ester nanocomposite with an excellent electromagnetic interference shielding effectiveness (EMI SE) and high thermal conductivity was fabricated by compounding graphene nanosheets (GNSs) and magnetic carbonyl iron–nickel alloy powder (CINAP) via a solution blending method and subsequent hot-pressing. The obtained 5 wt% GNSs/cyanate ester (CE) nanocomposite possesses the outstanding EMI SE of 38 dB and this property was synergistically enhanced to attain the value of 55 dB with the presence of 20 wt% CINAP. In addition, the GNSs/CINAP/CE nanocomposite with 5 wt% GNSs and 15 wt% CINAP exhibits high thermal conductivity (K = 4.13 W m⁻¹ K⁻¹). This synergistic enhancement is significantly affected by the formation of the efficient 3D electric and thermally conductive pathways as well as the dispersion of the incorporated fillers. This highly thermally conducting CE nanocomposite with the efficient EMI shielding properties has a potential to be used in advanced electronic packaging.