Macroporous silicon nitride (Si3N4) ceramics with high strength, uniform structure and relatively high porosity wereobtained by gelcasting and carbonthermal reaction in a two-step sintering technique. Microstructure and compositionwere investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction(XRD). Open porosity, pore size distribution and basic mechanical performance were measured by Archimedes method,mercury intrusion porosimetry and three-point bending methods, respectively. SEM and TEM results revealed thatpores were formed by elongated β-Si3N4. SADP measurement proved the formation of SiC particles. The SiCgranules were beneficial for the formation of high ratio elongated β-Si3N4, and at proper amount, they also acted asreinforcement phase. Thermodynamic analysis indicated that the mechanisms of the reactions were mainly associatedwith liquid-solid reaction and gas-liquid reaction.
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