Ultra-low thermal conductivity thermal barrier coatings from recycled fly-ash cenospheres

• Published in: Acta materialia Vol. 59; no. 6; pp. 2556 - 2562
• Main Authors: Chávez-Valdez, A., Arizmendi-Morquecho, A., Vargas, G., Almanza, J.M., Alvarez-Quintana, J.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01-04-2011
• Subjects: Cenospheres; Coating; Coatings; Fly ash; Heat transfer; Microstructure; Recycling; Reduction; Sintering (powder metallurgy); Thermal barrier coatings; Thermal Conductivity; Thermal Conductivity; Recycling; Coating
• ISSN: 1359-6454; 1873-2453
• DOI: 10.1016/j.actamat.2011.01.011

► Recycled fly ash cenospheres (FAC) as ultra-low thermal conductivity coatings. ► Coating’s thermal conductivity reduction is related to cenosphere’s air-filled core. ► Sintering process slightly boosts heat conduction due to changes in microstructure. ► Results suggest a route to get thermal barriers for high-temperature applications.
Thermal conductivity of electrophoretically deposited fly ash (FA) and fly-ash cenosphere (FAC) coatings was measured in the range 100–500
K by the 3
ω method. The room temperature thermal conductivity in FAC coatings is found to be as low as 0.08
W
m
K
−1 and slightly higher for FA coatings. The reduction in the thermal conductivity is related mainly to the air-filled core of the cenospheres and the coating’s porosity, which produces a strong heat barrier. The sintering process of the FAC and FA coatings at 1000, 1100 and 1200
°C slightly increases the thermal conductivity as a result of changes in microstructure. The temperature dependence of the effective thermal conductivity of the coatings was modeled within the framework of the self-consistent field concept and a modified Maxwell equation. These results suggest a route for obtaining suitable thermal barrier coatings for high-temperature applications.