TY - JOUR
T1 - High-Temperature thermochemical interactions of molten silicates with Yb2Si2O7 and Y2Si2O7 environmental barrier coating materials
AU - Stokes, Jamesa L.
AU - Harder, Bryan J.
AU - Wiesner, Valerie L.
AU - Wolfe, Douglas E.
N1 - Funding Information:
The authors would like to thank Dr. Gustavo Costa and Dr. Benjamin Kowalski for helpful discussions and Dr. Richard Rogers for XRD assistance. This work was supported under the NASA Aeronautics Scholarship and Advanced STEM Training and Research (AS&ASTAR) Graduate Fellowship [Grant Number NNX16AT27H ].
Publisher Copyright:
© 2019 Elsevier Ltd
PY - 2019/12
Y1 - 2019/12
N2 - The thermochemical behavior of EBC candidate materials yttrium disilicate (Y2Si2O7) and ytterbium disilicate (Yb2Si2O7) was evaluated with three calcium-magnesium-aluminosilicate (CMAS) glasses possessing CaO:SiO2 ratios relevant to gas turbine systems. Pellet mixtures of 50 mol% EBC powder to 50 mol% CMAS glass powder were heat treated at 1200°C, 1300°C, and 1400°C. The products of these interactions were evaluated using X-ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy. Above glass melting temperatures, exposure of the disilicates primarily resulted in dissolution into the molten glass followed by precipitation of a Ca2RE8(SiO4)6O2 (RE = Yb3+, Y3+) apatite-type silicate and/or rare earth disilicate. In glasses with high CaO concentrations, apatite readily forms while the disilicate material is consumed by the reaction. As CaO content decreases, the disilicate phase becomes the main reaction product. Overall, reactions with yttrium disilicate favored more apatite crystallization than ytterbium disilicate. The viability of using these disilicates in various operating environments is discussed.
AB - The thermochemical behavior of EBC candidate materials yttrium disilicate (Y2Si2O7) and ytterbium disilicate (Yb2Si2O7) was evaluated with three calcium-magnesium-aluminosilicate (CMAS) glasses possessing CaO:SiO2 ratios relevant to gas turbine systems. Pellet mixtures of 50 mol% EBC powder to 50 mol% CMAS glass powder were heat treated at 1200°C, 1300°C, and 1400°C. The products of these interactions were evaluated using X-ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy. Above glass melting temperatures, exposure of the disilicates primarily resulted in dissolution into the molten glass followed by precipitation of a Ca2RE8(SiO4)6O2 (RE = Yb3+, Y3+) apatite-type silicate and/or rare earth disilicate. In glasses with high CaO concentrations, apatite readily forms while the disilicate material is consumed by the reaction. As CaO content decreases, the disilicate phase becomes the main reaction product. Overall, reactions with yttrium disilicate favored more apatite crystallization than ytterbium disilicate. The viability of using these disilicates in various operating environments is discussed.
UR - http://www.scopus.com/inward/record.url?scp=85068453272&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85068453272&partnerID=8YFLogxK
U2 - 10.1016/j.jeurceramsoc.2019.06.051
DO - 10.1016/j.jeurceramsoc.2019.06.051
M3 - Article
AN - SCOPUS:85068453272
SN - 0955-2219
VL - 39
SP - 5059
EP - 5067
JO - Journal of the European Ceramic Society
JF - Journal of the European Ceramic Society
IS - 15
ER -