| タイトル | Kinetics of hexacelsian-to-celsian phase transformation in SrAl2Si2O8 |
| 著者（英） | Drummond, Charles H., III; Bansal, Narottam P. |
| 著者所属（英） | NASA Headquarters; NASA Lewis Research Center |
| 発行日 | 1993-05-01 |
| 言語 | eng |
| 内容記述 | The kinetics of hexacelsian to celsian phase transformation in SrAl2Si2O8 have been investigated. Phase pure hexacelsian was prepared by heat treatment of glass flakes at 990 C for 10 h. Bulk hexacelsian was isothermally heat treated at 1026, 1050, 1100, 1152, and 1200 C for various times. The amounts of monoclinic celsian formed were determined using quantitative X-ray diffraction. Values of reaction rate constant, k, at various temperatures were evaluated from the Avrami equation. The Avrami parameter was determined to be 1.1, suggesting a diffusionless, one-dimensional transformation mechanism. From the temperature dependence of k, the activation energy for this reaction was evaluated to be 527 plus or minus 50 kJ/mole (126 plus or minus 12 kcal/mole). This value is consistent with a mechanism involving the transformation of the layered hexacelsian structure to a three-dimensional network celsian structure which necessitates breaking of the strongest bonds, the Si-O bonds. |
| NASA分類 | NONMETALLIC MATERIALS |
| レポートNO | 93A40293 |
| 権利 | Copyright |
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