Encapsulation of SiC/SiC Cladding Tubes with Excellent Mechanical Performance and Air Tightness Using a CaO-modified Y2O3-Al2O3-SiO2 Glass

Currently, the encapsulation of SiC/SiC has been a key technical challenge limiting further application, and YAS-based glass offered a possible solution. In this paper, different CaO-doped Y2O3-Al2O3-SiO2 (YAS) glass solders were prepared and employed to join SiC/SiC. The joints were all structurally dense with the room temperature shear strengths higher than or equal to ∼51.7 MPa. Notably, joints containing 3.0 wt% CaO exhibited increased shear strength of ∼57.1 MPa, and the shear strength at 1200 °C was about 15.8 MPa in an air environment, meeting the requirements of the LOCA conditions. Optimal performance was achieved by using 3.0% CaO-doped YAS glass to encapsulate SiC/SiC cladding, yielding a continuous, dense encapsulation region with predominantly small closed pores (≤1.0 mm3). Glass infiltration was found in both the end plug and cladding wall. The joints did not leak after 72h of holding pressure at 15MPa, indicating their excellent air tightness.