A novel negative thermal expansion ceramic network interlayer for releasing high residual stress of C_f/SiC heterogeneous brazed joint

Negative thermal expansion (NTE) ceramics have been widely concerned in adjusting the coefficient of thermal expansion (CTE) to release the high residual stress of heterogeneous joint. However, one major problem that needs to be solved is the agglomeration problem caused by excessive ceramic particles addition. In this work, a novel NTE ceramic Sc₂W₃O₁₂ network interlayer is prepared by the polyurethane template method. The Sc₂W₃O₁₂ network interlayer with a single NTE phase presents a three-dimensional network structure. The NTE Sc₂W₃O₁₂ ceramic is uniformly distributed in brazing seam without agglomeration with the help of unique network structure. The active Ti elements play an important role in the interface bonding, reacted with Sc₂W₃O₁₂ network interlayer and C_f/SiC composites to form Cu₃Ti₃O and TiC/Ti₅Si₃ reaction layer, respectively. After introducing Sc₂W₃O₁₂ network interlayer, the CTE of the composite filler is reduced from 16.6 × 10⁻⁶ K⁻¹ to 11.9 × 10⁻⁶ K⁻¹, a decrease of 29 %. The highest shear strength of the C_f/SiC heterogeneous joint is reached 130 MPa, which is 5.4 times than that without Sc₂W₃O₁₂ network interlayer.