Molten Salt Assisted Synthesis of Dy3Si2C2 Coated SiC Powders and Sintering Behavior of SiC Ceramics

Abstract: Silicon carbide is widely used because of its excellent physical and chemical properties. The chemical bonding characteristics of SiC make it difficult to be sintered. Therefore, preparation of high-quality SiC ceramics is one of the challenges in SiC research field. In this study, the ternary rare-earth carbide Dy3Si2C2 was proposed as a new sintering additive for SiC ceramics, through the phase transition of Dy-Si-C system at high temperatures to promote the densification of SiC. The Dy3Si2C2 coated SiC powders were synthesized via an in-situ reaction between metal Dy and SiC in high temperature molten salts. The Dy3Si2C2 coated SiC powder was sintered by spark plasma sintering (SPS), at 1800 ℃, 45 MPa. As the result, high-purity SiC ceramic with the density of 99% and thermal conductivity of 162.8 W·m–1·K–1 was obtained to form the SiC-Dy3Si2C2 raw material with n(Dy) : n(SiC)=1 : 4. Further study shows that Dy3Si2C2 and SiC undergo a eutectic reaction at high temperatures, which generates liquid phase at the grain boundaries and promotes the densification of SiC ceramics. This study shows that the ternary rare-earth carbides Re3Si2C2 (Re=La, Ce…) has great potential to be used as the sintering additive for SiC.

Key words: SiC; Dy3Si2C2; spark plasma sintering; molten salt

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