On the high temperature oxidation of MoSi&lt;sub&gt;2&lt;/sub&gt; particles with boron addition

Ding, Z.; Brouwer, J.C.; Yao, Xiyu; Zhu, Jia-Ning; Hermans, M.J.M.; Popovich, V.; Sloof, W.G.

doi:10.1016/j.jeurceramsoc.2024.05.002

On the high temperature oxidation of MoSi₂ particles with boron addition

Title

On the high temperature oxidation of MoSi₂ particles with boron addition

Author

Ding, Z. (TU Delft Team Marcel Hermans)
Brouwer, J.C. (TU Delft Team Marcel Hermans)
Yao, Xiyu (Southern University of Science and Technology)
Zhu, Jia-Ning (TU Delft Team Vera Popovich)
Hermans, M.J.M. (TU Delft Team Marcel Hermans)
Popovich, V. (TU Delft Team Vera Popovich)
Sloof, W.G. (TU Delft Team Joris Dik)

Date

2024

Abstract

Boron doped MoSi₂ particles have been envisioned as sacrificial particles for self-healing thermal barrier coatings (TBCs) but their oxidation behaviour is yet not well understood. In this work, oxidation of MoSi₂ based particle is studied in the temperature range of 1050–1200 °C. The oxidation proceeds from a transient to a steady-state oxidation stage. The kinetics during steady-state oxidation is captured with a thermal diffusion-based model. As compared to the oxidation of pure MoSi₂ particles, the addition of boron strongly enhances the silica formation. Also, a finer dispersion of MoB_x in the MoSi₂ matrix accelerates the formation of silica. The oxide growth rate constant increases proportional with the boron content of the MoSi₂ particles. This enhanced oxidation is related to the microstructure of the oxide scale. Upon oxidation, boron yields B₂O₃, which promptly merge with SiO₂ to form amorphous borosilicate, hindering the formation of crystalline SiO₂. Consequently, the migration of oxygen in the borosilicate oxide scale is faster than in the silica oxide scale on pure MoSi₂ particles.