MECHANICAL AND THERMAL PROPERTIES OF ADVANCED OXIDE MATERIALS FOR HIGHER-TEMPERATURE COATINGS APPLICATIONS

摘要

Advanced oxide material systems are being developed for higher-temperature thermal/environmental barrier coatings (T/EBCs) in advanced gas turbine engine applications. Four pyrochlore oxide (La{sub}2Zr{sub}2O{sub}7, Nd{sub}2Zr{sub}2O{sub}7, Gd{sub}2Zr{sub}2O{sub}7, and La{sub}2Hf{sub}2O{sub}7) and three magnetoplumbite oxide (LaMnAl{sub}11O{sub}19, LaMgAl{sub}11O{sub}19, and LaZnAl{sub}11O{sub}19) powders were hot pressed. Ambient-temperature mechanical properties of these oxides including flexure strength, fracture toughness, elastic modulus, and hardness were determined. Thermal properties such as thermal conductivity, coefficient of thermal expansion, and environmental durability were also determined. LaMgAl{sub}11O{sub}19 and LaZnAl{sub}11O{sub}19 exhibited higher strength (>300 MPa) and higher fracture toughness (≥ 3 MPa√m) than the other oxides that exhibited strength of 40-150 MPa and fracture toughness of 1-2 MPa√m. Despite their poor ambient-temperature mechanical properties, certain pyrochlore oxides showed promising results over other oxides as coating materials in view of low thermal conductivity, good creep resistance and good water vapor stability in combustion environments.