Kinetics of β-Si3N4 Grain Growth in Si3N4 Ceramics Sintered under High Nitrogen Pressure |
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Authors: | Kou-Rueh Lai Tseng-Ying Tien |
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Affiliation: | Materials Science and Engineering, The University of Michigan, Ann Arbor, Michigan 48109 |
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Abstract: | The kinetics of anisotropic β-Si3N4 grain growth in silicon nitride ceramics were studied. Specimens were sintered at temperatures ranging from 1600° to 1900°C under 10 atm of nitrogen pressure for various lengths of time. The results demonstrate that the grain growth behavior of β-Si3N4 grains follows the empirical growth law Dn– D0n = kt , with the exponents equaling 3 and 5 for length 001] and width 210] directions, respectively. Activation energies for grain growth were 686 kJ/mol for length and 772 kJ/mol for width. These differences in growth rate constants and exponents for length and width directions are responsible for the anisotropy of β-Si3N4 growth during isothermal grain growth. The resultant aspect ratio of these elongated grains increases with sintering temperature and time. |
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