Crystallization kinetics of calcium-magnesium aluminosilicate (CMAS) glass

The crystallization kinetics of a calcium-magnesium aluminosilicate (CMAS) glass with composition relevant for aerospace applications, like air-breathing engines, were evaluated using differential thermal analysis (DTA) in powder and bulk forms. Activation energy and frequency factor values for crystallization of the glass were evaluated. X-ray diffraction (XRD) was used to investigate the onset of crystallization and the phases that developed after heat treating bulk glass at temperatures ranging from 690 degrees C to 960 degrees C for various times. Samples annealed at temperatures below 900 degrees C remained amorphous, while specimens heat treated at and above 900 degrees C exhibited crystallinity originating at the surface. The crystalline phases were identified as wollastonite (CaSiO3) and aluminum diopside (Ca(Mg,Al)(Si,Al)(2)O-6). Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were employed to examine the microstructure and chemical compositions of crystalline phases formed after heat treatment Published by Elsevier B.V.