Joining of SiC by Li₂O-Y₂O₃-Al₂O₃-SiO₂ glass with nanosized glassy phase separation

The performance degradation caused by amorphization of crystals under irradiation is a critical challenge for glass-sealing joints applied in nuclear components. In this work, the behavior of phase separation of the Li₂O-modified YAS glass was firstly used to join SiC ceramics. It’s found that the addition of Li₂O promotes the separation of nanosized spherical quartz glass from the base glass above the softening temperature. Benefited from the “rigid-plastic” nanostructure, the glass with nanophase separation exhibit better indentation fracture toughness (1.1 MPa·m^1/2) than the original glass (0.8 MPa·m^1/2). The nanophase separation glass was successfully fabricated in the SiC brazing seam by pre-oxidizing proper thickness of SiO₂ layer on SiC as well as applying a fast-cooling process, and the joint shear strength reached 129.8 ± 16.4 MPa, 44 % higher than the traditional joint with the same brazing glass. The possible toughing and formation mechanism of nanophase separation glass was discussed.