Yan Wang,Jin Wang,Junxia Wang,Long Kang,Tongming Zhang,Xusheng Li,Yijie Tang
In this work, the helium irradiation effects were systematically investigated on MgO-Nd 2 Zr 2 O 7 (hereafter M-NZO) composite ceramics used for inert matrix fuel, in which the ion fluences range from 5 × 10 16 to 3 × 10 17 ions/cm 2 at room temperature. It was demonstrated that M-NZO composite ceramic shows superior radiation tolerance after He implantation. Specifically, MgO had almost no phase transition and extensive amorphization . And Nd 2 Zr 2 O 7 phase possessed slightly pyrochlore-fluorite-amorphization structural transformation, while part of Nd 2 Zr 2 O 7 maintained the ordered pyrochlore structure and co-existed with the irradiation-induced disordered fluorite structure. Importantly, GIXRD results indicated that MgO phase presents higher resistance to radiated damage than Nd 2 Zr 2 O 7 phase. Besides, SEM images illustrated that MgO particles have substantially less fragmentation than Nd 2 Zr 2 O 7 particles due to the higher thermal conductivity of MgO. It reconfirmed that MgO phase resists irradiation damage better than Nd 2 Zr 2 O 7 phase in post-irradiated M-NZO composite ceramics.
Ceramic composites are promising candidates as structural materials for future fission and fusion reactors. In present work, Al 2 O 3 -ZrO 2 -SiC ternary ceramic composites were irradiated with 2.0 MeV He-ions at 300 and 800 ℃. Grazing incidence X-ray diffraction results confirmed that there was irradiation induced shift and broadening of diffraction peaks, but no amorphization of Al 2 O 3 -ZrO 2 -SiC composite were observed up to fluence of 1.72 × 10 18 ions/cm 2 . Transmission electron microscopy observations showed that throughout the entire irradiation region, nano-sized helium bubbles are mostly distributed in Al 2 O 3 grains and partly in ZrO 2 grains, while no detectable bubbles are observed in SiC grains. No obvious agglomeration of bubbles was found at grain/phase boundaries. By using nanoindentation technique, slight hardening or softening was confirmed for the samples irradiated at 300 and 800 ℃ respectively. The absence of amorphization and surface exfoliation indicating the Al 2 O 3 -ZrO 2 -SiC composite exhibits remarkable resistance to He-ions irradiation.
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