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Synthesis and Mechanical Properties of Stoichiometric Aluminum Silicate (Mullite)
Author(s) -
MAZDIYASNI K. S.,
BROWN L. M.
Publication year - 1972
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.1151-2916.1972.tb13434.x
Subject(s) - mullite , materials science , microstructure , hot pressing , cristobalite , orthorhombic crystal system , mineralogy , crystallite , amorphous solid , ceramic , composite material , metallurgy , crystallography , crystal structure , chemistry , quartz
Highly dense translucent polycrystalline bodies of stoichiometric aluminum silicate (mullite) were obtained by vacuum‐hot‐pressing of high‐purity submicron mixed oxide powders. The powders were prepared by the hydrolytic decomposition of mixed metal alkoxides. X‐ray diffraction and electron microscopy indicated that the initially amorphous needlelike fine particulates transform into highly crystalline orthorhombic mullite at ∼1200°C. Optimum hot‐pressing conditions were 5 kpsi and 1500°C for 30 min. Densities within experimental error of the theoretical value of 3.19 g/cm 3 were obtained. A typical microstructure consisted of fine interlocking needlelike grains arranged in an overall mosaic or “jigsaw” pattern. Microprobe traverses across the samples indicated homogeneous dispersion of SiO 2 in the AlO 3 matrix. Room‐temperature mechanical properties were measured and correlated with the microstructure and crystal structure of the ceramic compact. A slightly higher melting temperature than has been previously reported was observed for the 3Al 2 O 3 ·2SiO 2 studied. All specimens exhibited a smooth surface finish and excellent thermal‐shock resistance from 1200°C to room temperature.