Hot-pressing-oriented graphene in Si3N4 composites for enhanced electromagnetic wave absorption in X and Ku bands.

In this study, the oriented graphene within graphene/Si 3 N 4 composites was successfully achieved by two-step hot-press sintering. Microstructure analysis revealed that the graphene sheets were well dispersed in the Si 3 N 4 matrix and oriented perpendicular to the applied stress. The composites exhibited effective electromagnetic wave (EMW) absorption capabilities and good mechanical properties. The effective absorption bandwidth (EAB) was 9.63 GHz, nearly covering the entire X and Ku bands (8.2–18 GHz), and the minimum reflect loss (RL) was −24.23 dB when the graphene content reached 7 wt% at a thickness of 2.02 mm. Meanwhile, the oriented graphene/Si 3 N 4 composites demonstrated a bending strength of 576.66 MPa and a fracture toughness of 8.40 MPa·m1/2. The EMW absorption in these composites should be primarily due to polarization relaxation loss and conductivity loss, and the toughening mechanism should involve the graphene pull-out, crack bridging, and crack deflection. The graphene/Si 3 N 4 composites have a promising application in structurally integrated functional materials. • The oriented graphene within graphene/Si 3 N 4 composites was successfully achieved by hot-pressing. • The graphene sheets in composites were perpendicular to the applied stress. • The composites exhibited an EAB of 9.63 GHz, nearly covering the X and Ku bands (8.2‐18 GHz), with an RLmin of ‐24.23 dB. • The composites demonstrated a bending strength of 576.66 MPa and a fracture toughness of 8.40 MPa·m1/2. [ABSTRACT FROM AUTHOR]