Mo(Al<sub>x</sub>Si<sub>1−</sub><sub>x</sub>)<sub>2</sub> healing particles for high temperature ceramics and encapsulation by selective oxidation of aluminium

Journal article (2023)

Authors

Z. Ding Team Marcel Hermans - Mechanical, Maritime and Materials Engineering
J.C. Brouwer Team Marcel Hermans - Mechanical, Maritime and Materials Engineering
C. Kwakernaak Team Maria Santofimia Navarro - Mechanical, Maritime and Materials Engineering
Jia-Ning Zhu Team Vera Popovich - Mechanical, Maritime and Materials Engineering
V. Popovich Team Vera Popovich - Mechanical, Maritime and Materials Engineering
M.J.M. Hermans Team Marcel Hermans - Mechanical, Maritime and Materials Engineering
W.G. Sloof Team Joris Dik - Mechanical, Maritime and Materials Engineering
Research Group
Team Marcel Hermans (Mechanical, Maritime and Materials Engineering) (TU Delft)
Copyright: © 2023 Z. Ding, J.C. Brouwer, C. Kwakernaak, Jia-Ning Zhu, V. Popovich, M.J.M. Hermans, W.G. Sloof
DOI: https://doi.org/10.1016/j.matdes.2022.111577
Oxidation Encapsulation Self-healing thermal barrier coatings Alumina scale growth Mo(Al,Si)
More Info
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Published Date

2023

Language

English

Faculty

Mechanical, Maritime and Materials Engineering

Department

Materials Science and Engineering

Research Group

Team Marcel Hermans

Abstract

To prevent premature triggering of the healing reaction in Mo-Si containing self-healing thermal barrier coating system, an oxygen impenetrable shell (α-Al2O3) around the sacrificial healing particles (MoSi2) is desired. Here an encapsulation method is presented through selective oxidation of Al in Mo(AlxSi1-x)2 particles. Healing particles of Mo(AlxSi1-x)2 is designed in terms of alumina shell thickness, particle size and fraction Al dissolved. By replacing Si by Al in MoSi2 up to the maximum solubility (x = 0.65) a strong crack healing ability is maintained (relative volume expansion ≥ 40 %). The formed exclusive α-Al2O3, featuring a two-layered structure, results from a counter-diffusion process along the grain boundaries, and its oxidation kinetics fits well with the 3D diffusion-Jander model. After 16 h exposure in gaseous ambient with a pO2 of 5 × 10-10 atm. at 1100 °C, a closed and dense shell of α-Al2O3 is formed with a thickness of about 1.3 µm. The oxide shell produced under this condition provided healing particles with significantly improved stability upon exposure to high pO2 of 0.2 atm. at 1100 °C for 50 h. The particles after exposure feature an inner core of MoSi2 with Al completely consumed and an oxide shell of α-Al2O3.