Premium
Morphologically Textured Mullite in Sintered Tape‐Cast Kaolin
Author(s) -
Yang KaiHsun,
Wu JiaHan,
Hsi ChiShiung,
Lu HongYang
Publication year - 2011
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1551-2916.2010.04172.x
Subject(s) - mullite , materials science , eutectic system , sintering , texture (cosmology) , mineralogy , kaolinite , scanning electron microscope , crystallography , composite material , metallurgy , microstructure , ceramic , chemistry , image (mathematics) , artificial intelligence , computer science
A commercial Malaysian kaolin powder made into an aqueous slurry was cast into green tapes ∼200 μm in thickness using the doctor‐blade technique. A kaolinite (001) K(aolinite) texture was found on the green tapes using X‐ray diffractometry (XRD). Subsequent sintering at 1600°C/1 h induces the preferred crystallographic orientations of (100) M(ullite) , (110) M , (120) M , and (210) M in the mullite crystals thus formed by vitrification, as determined using electron backscatter diffraction. A nonunique orientation was observed on these crystals, suggesting that the texture is morphological with the c ‐axis, i.e., [001] M lying parallel to the sample surface, rather than crystallographical. An additional preferred orientation on (100) M , a forbidden reflection of the systematic absence from XRD is detected using pole figure. Kaolin is vitrified at 1600°C into mullite when the texture is developed, and sintering is initially facilitated by an SiO 2 –Al 2 O 3 liquid formed at >1260°C, the eutectic temperature of metastable equilibrium. Further densification is promoted by additional particle rearrangement in an SiO 2 –mullite liquid formed at >1587°C, the stable equilibrium eutectic temperature. Alumina used as a substrate for the kaolin sintering does not play a significant role in developing the mullite morphological texture.