The Role of Interfaces in Ceramics Exposed to Extreme Environments

In order to increase efficiency of next generation nuclear energy systems, it is important to design materials that are stable at high temperatures as well as when exposed to radiation and chemically aggressive environments. Ceramics are attractive in this regard because of their typically higher thermal stability than that of metals, but studies of radiation effects in ceramics have been scarcer. In this talk, I will discuss radiation effects in carbides and borides, with a specific focus on the role of interfaces on material’s performance. In metals, increasing the density of interfaces has been shown to be a promising strategy for increasing radiation tolerance. The role of interfaces during irradiation of ceramics is more unclear because of the complex defect energy landscape in these materials. Here, I will demonstrate that in ceramics interfaces can be a boon or a bane with respect to radiation resistance, using a multi-layer SiC/ Ti₃SiC₂ /TiC system as an example. In addition, in both metals and ceramics, the atomic structure of interfaces is not static during irradiation. I will demonstrate that radiation-induced segregation (RIS) of constituent elements is possible in ceramics, even when they form line compounds. I will also discuss the impact of RIS on corrosion of ceramics, since it is now recognized that radiation effects can be coupled in non-trivial ways to the effects of the other extreme environments. Finally, I will introduce our recent studies of radiation effects in 3D layered borides known as MAB phases (M=transition metal, A = aluminum, B = boron). We haves shown that MAB phases can exhibit superior radiation tolerance and therefore they are a promising class of materials for nuclear applications. I will show how radiation tolerant MAB phases can be designed by introducing different types of boron networks and different transition metals. Our results reveal new pathways for improving the properties of ceramics (or more generally covalently bonded materials) under extreme conditions.