PM-04Relationship between amorphous structure and radiation tolerance of silicon oxycarbide

Silicon oxycarbide (SiOC) glasses are anticipated to be utilized as a component material for nuclear reactors, because of their high thermal stability, durability, and corrosion resistance. A recent research demonstrated that the formation of He bubbles in SiOC was highly suppressed after even 90 at% He implantation [1].To clarify the origin of superior radiation tolerance of SiOC, knowledge of amorphous structures is required. In the present study, we prepared SiOC with different composition by sputtering and examined their structures as well as radiation tolerance using transmission electron microscopy (TEM). Figure 1 shows cross-sectional bright-field TEM images of 120 keV He ion irradiated SiOC: (a) SiC:SiO2= 1:2, (b) 1:1, and (c) 2:1. Electron diffraction experiments revealed that amorphous structures were maintained after irradiation. No structural changes were detected in SiO2-rich and equiatomic specimens (Figs. 1(a) and 1(b)), while remarkable He bubbles were formed in SiC-rich one (Fig. 1(c)). From a quantitative analysis of electron diffraction intensities, it was found that a first sharp diffraction peak (FSDP) appears at ~1.5 Å in SiO2-rich and equiatomic specimens. The FSDP revealed that the size of voids formed by connecting the SiOxC4-x tetrahedra in both the specimens is much larger than the diameter of He atom, suggesting that He atoms can easily migrate in the amorphous SiOC networks.