Cold sintering of SiC ceramics with the assistance of amorphous SiO2 surface layer

The cold sintering process (CSP) densifies ceramics powder at lower temperatures (<300 degrees C) than conventional sintering by applying a small amount of solvent such as water and a uniaxial pressure of several hundred megapascals. However, this method can only be applied to materials with high solubility in solvents, and direct hardening of low solubility materials such as SiC is difficult. In this study, hardened SiC/SiO2 bodies were fabricated by CSP from SiC particles whose surface was oxidized by preheating, using NaOH solution as a solvent. The compressive strength and relative density of the hardened SiC/SiO2 bodies fabricated from a mixture of SiC particles with 15.3 mass% SiO2 and 5 mol/L NaOH solution were 520 MPa and 80%, respectively. These values were considerably higher than those of hardened SiC/SiO2 bodies fabricated by CSP from a mixed powder consisting of untreated SiC particles and amorphous SiO2 particles. When the surface-oxidized SiC particles were used as a starting material, the mismatch in chemical bonding between SiC and SiO2 and uneven distribution of the binder were reduced, resulting in high mechanical strength for the hardened SiC/SiO2 bodies.

Automated summary

The cold sintering process (CSP) was used to fabricate hardened SiC/SiO2 bodies by preheating and oxidizing the surface of SiC particles with NaOH solution as a solvent. The resulting SiC/SiO2 bodies showed high mechanical strength.