Synergetic and alone influence of graphite platelet and SiC on the oxidation resistance of ZrB2 ceramics

This study investigates how adding graphite platelets (G_P), with and without SiC, affects the oxidation resistance of ZrB₂ ceramics. The specimens-ZrB₂-10G_P, ZrB₂-15G_P, ZrB₂-15SiC, ZrB₂-30SiC, ZrB₂-30SiC-10G_P, and ZrB₂-30SiC-15G_P-were sintered at 1850 °C for 8 min via spark plasma sintering (SPS). For oxidation evaluation, the samples were exposed to air in the furnace at a temperature of 1450 °C for different times (30, 60, 90, 120, 180, 300 min). Also, the simultaneous thermogravimetric analysis (TGA) and differential thermal analysis (DTA) up to 1200 °C were applied to investigate the in situ oxidation. FESEM and EDS were utilized to perform microstructural and elemental analyses on the cross-sections of various oxide layers. It was disclosed that the G_P and SiC both improve the oxidation resistance. The best oxidation resistances were obtained in the ZrB₂-30SiC and ZrB₂-30SiC-10G_P with the lowest oxidation layer thicknesses of 38 ± 3 µm and 40 ± 4 µm, respectively. Also, the lowest oxidation resistance was obtained in pure ZrB₂ with the highest oxide layer thickness of 129 ± 5 µm. The formation of an adherent oxide layer is the dominant factor for improving the oxidation resistance. The oxidation mechanism of all samples except ZrB₂ was diffusion oxygen-controlled with a parabolic behavior. Also, TGA and DTA analysis showed a mass loss at the initial stage (∼ 200°C ), followed by mass gain at 709 °C and 1065°C.