Directionally solidified eutectic and off-eutectic mullite zirconia fibres
authors Carvalho, RG; Pires, MS; Fernandes, AJS; Silva, RF; Costa, FM
nationality International
journal JOURNAL OF THE EUROPEAN CERAMIC SOCIETY
author keywords Laser floating zone (LFZ); Directional solidified eutectics; Mullite; Zirconia
keywords FLOATING-ZONE TECHNIQUE; GROWN AL2O3-ZRO2(Y2O3) EUTECTICS; MECHANICAL-PROPERTIES; RESIDUAL-STRESSES; CERAMICS; AL2O3-ZRO2-SIO2; MICROSTRUCTURE; Y2O3-ZRO2; STABILITY; COMPOSITE
abstract Eutectic and off-eutectic mullite-zirconia fibres were grown by LFZ (laser floating zone) directional solidification. The microstructure of the mullite-zirconia eutectic fibres varies from planar coupled eutectic (1 mm/h pulling rate) through mullite columnar growth with coarse zirconia inclusions (10 mm/h pulling rate) to faceted mullite eutectic dendrites, which enclose a dispersion of fine zirconia fibrils (100-500 mm/h pulling rates). Near-equilibrium conditions determine the crystallization of monoclinic zirconia and the absence of any amorphous phase, whereas for higher speeds the tetragonal structure is retained and a residual liquid is kept after the eutectic solidification. Similar structural and morphological characteristics are displayed by the mullite-rich off-eutectic composition added to the development of prismatic crystals of mullite primary phase. In opposition, heavy constitutional supercooling takes place in the case of the zirconia-rich off-eutectic fibres, where equiaxed zirconia dendrites soon form as a primary phase, leaving a non-equilibrium mixture of alumina and sillimanite as interdendritic constituent. (C) 2012 Elsevier Ltd. All rights reserved.
publisher ELSEVIER SCI LTD
issn 0955-2219
year published 2013
volume 33
issue 5
beginning page 953
ending page 963
digital object identifier (doi) 10.1016/j.jeurceramsoc.2012.09.032
web of science category Materials Science, Ceramics
subject category Materials Science
unique article identifier WOS:000314332600007
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