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Tailoring Thermal Properties of Ebcs in High Entropy Rare Earth Monosilicates

31 Pages Posted: 30 Jan 2020 Publication Status: Accepted

See all articles by Mackenzie Ridley

Mackenzie Ridley

University of Virginia - Department of Materials Science and Engineering

John Gaskins

University of Virginia - Department of Mechanical and Aerospace Engineering

Patrick E. Hopkins

University of Virginia - Department of Mechanical and Aerospace Engineering

Elizabeth Opila

University of Virginia - Department of Materials Science and Engineering

Abstract

This work explores the possibility of tailoring the thermal conductivity and thermal expansion of rare earth monosilicates through the introduction of multiple rare earth cations in solid solution. Six rare earth monosilicates are studied: Sc2SiO5, Y2SiO5, Nd2SiO5, Dy2SiO5, Er2SiO5, and Yb2SiO5. Four equimolar binary cation mixtures and a high entropy five-cation equimolar mixture were characterized. Thermal expansion was measured up to 1200 ˚C with X-Ray Diffraction (XRD) and bulk thermal conductivity was measured by Hot Disk technique. The linear coefficient of thermal expansion (CTE) of mixed-cation systems followed a rule of mixtures, with average linear CTE between 6 - 9x10-6 /˚C. Scandium monosilicate showed a lower linear CTE value as well as a notably lower degree of CTE anisotropy than other rare earth monosilicates. Thermal conductivity was found to decrease below rule of mixtures values through increasing heterogeneity in rare earth cation mass and ionic radii, as expected for the thermal conductivity of solid-solutions. The high entropy mixture RE2SiO5 (RE=Sc, Y, Dy, Er, and Yb) shows a thermal conductivity of 1.06 W/mK at room temperature, demonstrating that high entropy rare earth silicates are strong candidates for novel dual-purpose thermal and environmental barrier coatings.

Keywords: Environmental Barrier Coating, Thermal Expansion, Thermal Conductivity, Silicates, High Entropy

Suggested Citation

Ridley, Mackenzie and Gaskins, John and Hopkins, Patrick E. and Opila, Elizabeth, Tailoring Thermal Properties of Ebcs in High Entropy Rare Earth Monosilicates. Available at SSRN: https://ssrn.com/abstract=3525134 or http://dx.doi.org/10.2139/ssrn.3525134

Mackenzie Ridley (Contact Author)

University of Virginia - Department of Materials Science and Engineering ( email )

VA
United States

John Gaskins

University of Virginia - Department of Mechanical and Aerospace Engineering

United States

Patrick E. Hopkins

University of Virginia - Department of Mechanical and Aerospace Engineering ( email )

United States

Elizabeth Opila

University of Virginia - Department of Materials Science and Engineering

VA
United States

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