熔盐辅助合成Dy3Si2C2包裹SiC粉体及其陶瓷的烧结行为

碳化硅陶瓷因自身优良的物理化学性能而具有广泛的应用前景。碳化硅的化学键结合特性决定了其难以烧结成型, 因此如何制备高质量碳化硅陶瓷是领域内的难点之一。本研究以三元稀土碳化物Dy₃Si₂C₂作为新型SiC陶瓷的烧结助剂, 依据Dy-Si-C体系的高温相转变原位促进碳化硅的烧结致密化。采用放电等离子烧结技术, 利用金属Dy与SiC反应生成Dy₃Si₂C₂, 对Dy₃Si₂C₂包裹的SiC粉体进行烧结。在1800 ℃、45 MPa的烧结条件下, 得到了致密度为99%、热导率为162.8 W·m ^-1·K ^-1的高纯度碳化硅陶瓷。进一步的研究表明, 高温下Dy₃Si₂C₂与SiC发生共晶反应, 在晶界处产生的液相促进了SiC陶瓷的致密化, 表明稀土层状碳化物Re₃Si₂C₂ (Re=La, Ce…)有助于SiC的烧结致密。

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

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.