TY - JOUR
T1 - Crystal structure development during devitrification of quenched mullite
AU - Johnson, Bradley R.
AU - Kriven, Waltraud M.
AU - Schneider, Julius
N1 - Funding Information:
The authors would like to gratefully acknowledge Richard Weber and Johan Abadie from Containerless Research Inc. for supplying the quenched mullite beads used in this work; Pankaj Sam from the University of Illinois and Paul Zschack from the UNICAT facility at the APS facility at ANL for their assistance in collecting the synchrotron radiation data; and Ray Twesten from the University of Illinois, for his suggestions regarding microstructural analysis. This project was funded by the US Air Force Office of Scientific Research under Science and Technology Transfer Research (STTR) grants F49620-97-l-0427 and F49620-98-C-0050. Microstructural and crystallographic characterization was performed in part using equipment in the Center for Microanalysis of Materials (in the Materials Research Laboratory) and in the Center for Cement Composite Materials, both located at the University of Illinois at Urbana Champaign. The UNICAT facility located at the Advanced Photon Source (APS) is supported by the University of Illinois at Urbana-Champaign, Materials Research Laboratory (U.S. Department of Energy, the State of Illinois-IBHE-HECA and the National Science Foundation), the Oak Ridge National Laboratory (U.S. Department of Energy under contract with Lockheed Martin Energy Research), the National Institute of Standards and Technologies (U.S. Department of Commerce) and UOP LLC. The APS is supported by the U.S. Department of Energy, BES, Office of Energy Research under contract No. W-31-109-ENG-38.
PY - 2001
Y1 - 2001
N2 - The kinetics, microstructural changes, and crystal structure development for crystallization of amorphous, quenched, mullite composition glass (3Al2O3.2SiO2) were studied between 900 and 1400°C. The phenomena observed were characterized using nonisothermal differential scanning calorimetry (DSC), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), powder X-ray diffraction (XRD, with both a standard laboratory diffractometer, as well as with synchrotron radiation), and Rietveld analysis. Crystallization of amorphous mullite was observed to occur in two steps. The activation energy for crystallization was 892 kJ/mol for the first step and 1333 kJ/mol for the second step. From the amorphous state, first phase(s) to crystallize were alumina-rich, pseudotetragonal mullite (∼70 mol% Al2O3). These crystals were highly strained and contained numerous nanometer scale inclusions. With increasing temperature, the crystals were observed to incorporate increasing amounts of SiO2, and approach the equilibrium orthorhombic structure. By 1400°C the pseudotetragonal to orthorhombic transition was complete, the strain was eliminated, most of the inclusions had been assimilated, there was ∼67% reduction in grain size, and the crystals has attained the composition of the initial, bulk glass (∼60 mol% Al2O3).
AB - The kinetics, microstructural changes, and crystal structure development for crystallization of amorphous, quenched, mullite composition glass (3Al2O3.2SiO2) were studied between 900 and 1400°C. The phenomena observed were characterized using nonisothermal differential scanning calorimetry (DSC), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), powder X-ray diffraction (XRD, with both a standard laboratory diffractometer, as well as with synchrotron radiation), and Rietveld analysis. Crystallization of amorphous mullite was observed to occur in two steps. The activation energy for crystallization was 892 kJ/mol for the first step and 1333 kJ/mol for the second step. From the amorphous state, first phase(s) to crystallize were alumina-rich, pseudotetragonal mullite (∼70 mol% Al2O3). These crystals were highly strained and contained numerous nanometer scale inclusions. With increasing temperature, the crystals were observed to incorporate increasing amounts of SiO2, and approach the equilibrium orthorhombic structure. By 1400°C the pseudotetragonal to orthorhombic transition was complete, the strain was eliminated, most of the inclusions had been assimilated, there was ∼67% reduction in grain size, and the crystals has attained the composition of the initial, bulk glass (∼60 mol% Al2O3).
KW - Crystallization
KW - Kinetics
KW - Microstructure
KW - Mullite
KW - Rietveld
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U2 - 10.1016/S0955-2219(01)00268-0
DO - 10.1016/S0955-2219(01)00268-0
M3 - Article
AN - SCOPUS:0034826854
VL - 21
SP - 2541
EP - 2562
JO - Journal of the European Ceramic Society
JF - Journal of the European Ceramic Society
SN - 0955-2219
IS - 14
ER -