Multifunctional Si3N4-skeleton-reinforced graphite flake composites with preferred orientation integrate excellent mechanical, thermophysical, and electromagnetic shielding properties

Si 3 N 4 -skeleton-reinforced graphite flake (GF/Si 3 N 4 ) composites with preferred orientation were fabricated using a combination of vacuum infiltration and plasma-activated sintering to produce highly oriented graphite-based composites with excellent strength, favorable thermal conductivity, low thermal expansion, and effective electromagnetic shielding properties. The impact of Si 3 N 4 content on the microstructure, bending strength, thermophysical properties, and electromagnetic shielding effectiveness of the composites was systematically examined. The composites exhibited reasonable anisotropy (Lotgering factor f  > 93 %), endowing them with high thermal conductivity in the basal plane direction of the GF. The formation of SiC at the Si 3 N 4 /GF interface increased the interfacial bonding and effectively suppressed the thermal expansion of GF perpendicular to the basal plane from ∼28 × 10 −6 /K to ∼8 × 10 −6 /K. The composite with 21 vol.% Si 3 N 4 exhibited the optimal properties, including a satisfactory bending strength of 128 MPa, good thermal conductivity of 247 W/m/K, a suitable thermal expansion of 9.4 × 10 −6 /K, and good electromagnetic interference shielding effectiveness of 30 dB. Hence, the fabricated GF/Si 3 N 4 composites demonstrate significant potential as high-orientation graphite-based composites for multifunctional thermal management.