resumo
Mullite-based multilayered structures have been suggested as promising environmental barrier coatings for Si3N4 and SiC ceramics. Mullite has been used as bottom layer because its thermal expansion coefficient closely matches those of the Si-based substrates, whereas Y-ZrO2 has been tried as top layer due to its stability in combustion environments. In addition, mullite/ZrO2 compositions may work as middle layers to reduce the thermal expansion coefficient mismatch between the ZrO2 and mullite layers. Present work studies the thermal behaviour of a flame sprayed mullite/ZrO2, (75/25, v/v) composite coating. The changes in crystallinity, microstructure and thermal conductivity of free-standing coatings heat treated at two different temperatures (1000 and 1300 degrees C) are comparatively discussed. The as-sprayed and 1000 degrees C treated coatings showed an almost constant thermal conductivity (K) of 1.5 W m(-1) K-1. The K of the 1300 degrees C treated specimen increased up to twice due to the extensive mullite crystallization without any cracking. (C) 2010 Elsevier Ltd and Techna Group S.r.l. All rights reserved.
palavras-chave
ENVIRONMENTAL BARRIER COATINGS; SIO2 SCALE VOLATILITY; SILICON-CARBIDE; RECESSION BEHAVIOR; CERAMICS; MICROSTRUCTURE; CORROSION; NITRIDE; SYSTEM; LIMIT
categoria
Materials Science
autores
Garcia, E; Mesquita-Guimaraes, J; Osendi, MI; Miranzo, P
Grupos
agradecimentos
This work has been supported by MICINN (Spain) under Grant No. MAT2006-07118 and by CSIC under NRC (Canada) CSIC (Spain) Joint Project. Eugenio Garcia acknowledges the