Oxidation behavior and chemical evolution of architecturally arranged Zr/Si multilayer at high temperature

Abstract

Multilayer structure came into focus as a potential material in nuclear environment due to the special interface effect. Here, we studied the stability and chemical evolution of sputtered Zr/Si multilayer during annealing at 600 °C and 800 °C in air to explore its potential application as protective coating for nuclear materials. At 600 °C after 20 h oxidation, only the top Zr layer was oxidized and the diffusion of Si into the buried Zr layers contributed to the formation of Zr3Si compound layer uniformly. At 800 °C, the first Zr layer and Si layer were oxidized into m-ZrO2 and amorphous SiO2 layer, respectively. Underneath these oxide capping layers, the ZrSi compound layers near surface transformed into Zr-rich silicate layers with prolonged oxidation time. The continuous incorporation of Si into silicate layer triggered a reduction reaction to form Si-rich ZrSi2. Then, some silicon particles were formed through the de-alloying process of ZrSi2 and kept coherent interface with ZrSi2. These compounds were in situ formed in the original layer position, which maintained the multi-interface character. With further oxidation, this ZrSi2&Si layer was finally oxidized with self-healing ability.