Near-seamless joining of C_f/SiC composites using Y₃Si₂C₂ via electric field-assisted sintering technique

A novel Y₃Si₂C₂ material was synthesized at a relatively low temperature (900 ℃) using a molten salt method for the first time, and subsequently used as the joining material for carbon fiber reinforced SiC (C_f/SiC) composites. The sound near-seamless joints with no obvious remaining interlayer were obtained at 1600 ℃ using an electric field-assisted sintering technique (FAST). During joining, a liquid phase was formed by the eutectic reaction among Y₃Si₂C₂, γ(Y-C) phase, and SiC, followed by the precipitation of SiC particles. The presence of the liquid promoted the sintering of newly formed SiC particles, leading to their complete consolidation with the C_f/SiC matrix. On the other hand, the excess of the liquid was pushed away from the joining area under the effect of a uniaxial pressure of 30 MPa, leading to the formation of the near-seamless joints. The highest shear strength (τ) of 17.2±2.9 MPa was obtained after being joined at 1600 ℃ for 10 min. The failure of the joints occurred in the C_f/SiC matrix, indicating that the interface was stronger than that of the C_f/SiC matrix. The formation of a near-seamless joint minimizes the mismatch of thermal expansion coefficients and also irradiation-induced swelling, suggesting that the proposed joining strategy can be potentially applied to SiC-based ceramic matrix composites (CMCs) for extreme environmental applications.