Synthesis high-qulity graphene oxide and temperature-dependent dielectric properties of reduced graphene oxide

Abstract

Here, High-quality graphene oxide (GO) is prepared by oxidation at 0° to avoid the loss of carbon atoms (CO2 formation) due to oxidation temperatures exceeding 50 °C during conventional oxidation. GO with a higher degree of oxidation (C:O = 1.98) corresponds to lower defect (ID: IG = 0.63), which indicates the advantage of low temperature oxidation. X-ray photoelectron spectroscopy further indicates that the C–O content of GO prepared by one-step oxidation at a lower temperature is higher than that of the conventional method, which is about 10%. After GO is in situ reduced by aluminum powder at room temperature, an extremely high ID:IG ratio of 1.82 was observed. The as-prepared reduced graphene oxide (rGO) is located in the stage 1 of Ferrari and corresponding average defect distance exceeds 6.8 nm. The dielectric properties of GO and rGO are investigated at 2.45 GHz. The dielectric parameters of GO was negatively correlated to the degree of oxidation. The dielectric constant of rGO increases from 13.3 to 118.2 as the temperature increases from room temperature to 800 °C. However, the dielectric loss of rGO is reduced from 0, 03 to 0.025 and then increased to 0.032. The theoretical reflection loss (RL) of the rGO sample suggest that the maximum microwave absorption with the reflection losses of −26.67 dB can be obtained. This work reveals the relationship between dielectric parameters and oxidation degree and temperature, which may contribute to the proper understanding of designing and synthesizing graphene-based materials by microwave.