Abstract
Rare earth (RE) disilicates are utilized in environmental barrier coatings to protect Si-based engine components from destructive reactions with water vapor and other combustion species. These coating materials, however, degrade when exposed to molten silicate deposits in the engine. Four RE-disilicates (RE2Si2O7, RE = Er, Dy, Gd, Nd) are analyzed herein in thermochemical interactions with glassy calcium-magnesium-aluminosilicate (CMAS) compositions at 1400°C. Crystalline reaction products included RE2Si2O7, SiO2, and a Ca2+ yRE8+ x(SiO4)6O2+3 x /2+ y apatite-type silicate. RE2Si2O7 formation was favored in interactions with CMAS having low CaO:SiO2 ratios. Increased reactivity was observed for higher CaO:SiO2 ratios in CMAS combined with larger RE3+ cation size, resulting in apatite formation of varying stoichiometry and changes in lattice parameters. The crystallization of SiO2 was dependent on both thermodynamic equilibrium at low CaO:SiO2 ratios and sequestration of silicate modifiers at higher CaO:SiO2 ratios, although residual amorphous content after CMAS exposure in both cases was still substantial.
| Original language | English (US) |
|---|---|
| Journal | Journal of the American Ceramic Society |
| DOIs | |
| State | Accepted/In press - Jan 1 2019 |
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All Science Journal Classification (ASJC) codes
- Ceramics and Composites
- Materials Chemistry
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Effects of crystal structure and cation size on molten silicate reactivity with environmental barrier coating materials. / Stokes, Jamesa L.; Harder, Bryan J.; Wiesner, Valerie L.; Wolfe, Douglas Edward.
In: Journal of the American Ceramic Society, 01.01.2019.Research output: Contribution to journal › Article
TY - JOUR
T1 - Effects of crystal structure and cation size on molten silicate reactivity with environmental barrier coating materials
AU - Stokes, Jamesa L.
AU - Harder, Bryan J.
AU - Wiesner, Valerie L.
AU - Wolfe, Douglas Edward
PY - 2019/1/1
Y1 - 2019/1/1
N2 - Rare earth (RE) disilicates are utilized in environmental barrier coatings to protect Si-based engine components from destructive reactions with water vapor and other combustion species. These coating materials, however, degrade when exposed to molten silicate deposits in the engine. Four RE-disilicates (RE2Si2O7, RE = Er, Dy, Gd, Nd) are analyzed herein in thermochemical interactions with glassy calcium-magnesium-aluminosilicate (CMAS) compositions at 1400°C. Crystalline reaction products included RE2Si2O7, SiO2, and a Ca2+ yRE8+ x(SiO4)6O2+3 x /2+ y apatite-type silicate. RE2Si2O7 formation was favored in interactions with CMAS having low CaO:SiO2 ratios. Increased reactivity was observed for higher CaO:SiO2 ratios in CMAS combined with larger RE3+ cation size, resulting in apatite formation of varying stoichiometry and changes in lattice parameters. The crystallization of SiO2 was dependent on both thermodynamic equilibrium at low CaO:SiO2 ratios and sequestration of silicate modifiers at higher CaO:SiO2 ratios, although residual amorphous content after CMAS exposure in both cases was still substantial.
AB - Rare earth (RE) disilicates are utilized in environmental barrier coatings to protect Si-based engine components from destructive reactions with water vapor and other combustion species. These coating materials, however, degrade when exposed to molten silicate deposits in the engine. Four RE-disilicates (RE2Si2O7, RE = Er, Dy, Gd, Nd) are analyzed herein in thermochemical interactions with glassy calcium-magnesium-aluminosilicate (CMAS) compositions at 1400°C. Crystalline reaction products included RE2Si2O7, SiO2, and a Ca2+ yRE8+ x(SiO4)6O2+3 x /2+ y apatite-type silicate. RE2Si2O7 formation was favored in interactions with CMAS having low CaO:SiO2 ratios. Increased reactivity was observed for higher CaO:SiO2 ratios in CMAS combined with larger RE3+ cation size, resulting in apatite formation of varying stoichiometry and changes in lattice parameters. The crystallization of SiO2 was dependent on both thermodynamic equilibrium at low CaO:SiO2 ratios and sequestration of silicate modifiers at higher CaO:SiO2 ratios, although residual amorphous content after CMAS exposure in both cases was still substantial.
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U2 - 10.1111/jace.16694
DO - 10.1111/jace.16694
M3 - Article
AN - SCOPUS:85070716492
JO - Journal of the American Ceramic Society
JF - Journal of the American Ceramic Society
SN - 0002-7820
ER -