Improved toughness and electromagnetic shielding-effectiveness for graphite-doped SiC ceramics with a net-like structure

The graphite-doped SiC ceramics with net-like structure was fabricated via tape casting and pressureless sintering. The ceramics exhibited a step-like fracture mode, which could be attributed to the net-like structure composed of long columnar SiC grains, layered graphite, and the three-modal pore distribution. The formation of warped epitaxial graphene and large size graphite could be attributed to the pyrolysis of organics in the tape casting system. In the net-like structure, the SiC grains provide the high strength, whereas the layered graphite and three-modal pores were used to deflect the cracks and release the stress at the tip, following the crack-tip-shielding mechanism. The sample with a net-like structure exhibited a combination of a variety of extrinsic toughening mechanisms, such as crack deflection, crack bridging, crack branching and delamination, pull-out, and rupture of layered graphite, which led to improved fracture toughness of 7 MPa m^1/2, flexural strength of 400 MPa, and (work of fracture) WOF of 3.3 kJ m⁻². When increasing the graphite content, the electrical conductivity of the graphite-doped SiC ceramics significantly increased from 7.15 × 10⁻⁴ to 216 S/m. The high shielding effectiveness of 34.1 dB was due to the multi-absorption on the various surfaces during the multi-reflection by the net-like structure.