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Crystallization kinetics of BaO-Al2O3-SiO2 glassesBarium aluminosilicate glasses are being investigated as matrix materials in high-temperature ceramic composites for structural applications. Kinetics of crystallization of two refractory glass compositions in the barium aluminosilicate system were studied by differential thermal analysis (DTA), X-ray diffraction (XRD), and scanning electron microscopy (SEM). From variable heating rate DTA, the crystallization activation energies for glass compositions (wt percent) 10BaO-38Al2O3-51SiO2-1MoO3 (glass A) and 39BaO-25Al2O3-35SiO2-1MoO3 (glass B) were determined to be 553 and 558 kJ/mol, respectively. On thermal treatment, the crystalline phases in glasses A and B were identified as mullite (3Al2O3-2SiO2) and hexacelsian (BaO-Al2O3-2SiO2), respectively. Hexacelsian is a high-temperature polymorph which is metastable below 1590 C. It undergoes structural transformation into the orthorhombic form at approximately 300 C accompanied by a large volume change which is undesirable for structural applications. A process needs to be developed where stable monoclinic celsian, rather than hexacelsian, precipitates out as the crystal phase in glass B.
Document ID
19900034120
Document Type
Reprint (Version printed in journal)
Authors
Bansal, Narottam P. (NASA Lewis Research Center Cleveland, OH, United States)
Hyatt, Mark J. (NASA Lewis Research Center Cleveland, OH, United States)
Date Acquired
August 14, 2013
Publication Date
October 1, 1989
Publication Information
Publication: Journal of Materials Research
Volume: 4
ISSN: 0884-2914
Subject Category
NONMETALLIC MATERIALS
Distribution Limits
Public
Copyright
Other