Temperature dependence of the electromagnetic properties of graphene nanosheet reinforced alumina ceramics in the X-band

Graphene nanosheet (GN)/Al₂O₃ ceramics were prepared by hot press sintering with a significant improvement in both mechanical and electromagnetic properties. The excellent mechanical properties and electrical conductivity of the GN/Al₂O₃ ceramics contributed to the outstanding advantage of GNs as the reinforcing phase. The effects of GN content and temperature on complex permittivity, microwave absorption and electromagnetic interference (EMI) shielding performance of such ceramics have been studied in the frequency range of 8.2-12.4 GHz (X-band) and temperature range from 25 to 400 °C. Negative permittivity of the GN/Al₂O₃ ceramics with 2.0 vol% GNs appears throughout the whole X-band at 400 °C, and the mechanism was also investigated. The GN/Al₂O₃ ceramics show high mechanical properties, tunable electromagnetic properties, good microwave absorption and EMI shielding performance demonstrating their great potential to be applied in microwave applications.