Fabrication of zirconium nitride-zirconia toughened alumina core-shell ceramics as surrogate for the uranium nitride-uranium dioxide core-shell ceramic fuel

The zirconium nitride-zirconia toughened alumina (ZrN-ZTA) core-shell ceramics, whose shell was the ZTA and core was the ZrN-ZTA with ZrN content between 0 and 88 vol.% were successfully fabricated by powder metallurgy method combined with spark plasma sintering in order to improve the oxidation and corrosion resistance of ZrN ceramics used as a surrogate fuel of uranium nitride. Experimental results showed that the core-shell ceramics fabricated were intact and crack-free, and the interfaces between the shell and the core were well-defined and coherent without apparent defects. Also, all of the ZTA ceramic shells exhibited similar dense microstructure and mechanical properties. When ZrN content in the core increased from 0 to 88 vol.%, the Vickers hardness of the core was increased and then decreased, and fracture toughness was also increased to 5.42 ± 0.31 MPa·m^1/2 and then decreased to 4.32 ± 0.25 MPa·m^1/2. The core-shell ceramics fabricated in this study with the high nitride content have demonstrated reliable microstructure and mechanical properties, which can be potential candidates for application as accident-tolerant fuel in nuclear energy systems.