Interdiffusion in SiC–AlN and AlN–Al2OC Systems |
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Authors: | Qiang Tian Anil V Virkar |
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Affiliation: | Department of Materials Science and Engineering, University of Utah, Salt Lake City, Utah 84112 |
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Abstract: | AlN, Al2OC, and the 2 H form of SiC are isostructural. Both SiC–AlN and AlN–Al2OC form homogeneous solid solutions above 2000° and 1950°C, respectively. The kinetics of phase separation in the two systems, however, are quite different. Interdiffusion in both SiC–AlN and AlN-Al2OC systems was examined in the solid-solution regime in an attempt to elucidate differences in the kinetics of phase separation that occur in the two systems when annealed at lower temperatures. Diffusion couples of (SiC)0.3(AlN)0.7/(SiC)0.7(AlN)0.3 and (AlN)0.7(Al2OC)0.3/(AlN)0.3(Al2OC)0.7 were fabricated by hot pressing and were annealed at high temperatures by encapsulating them in sealed SiC crucibles to suppress loss due to evaporation. Interdiffusion coefficients in (SiC)0.3-(AlN)0.7/(SiC)0.7(AlN)0.3 diffusion couples were measured at 2373, 2473, and 2573 K, and the corresponding activation energy was determined to be 632 kJ/mol. (AlN)0.7(Al2OC)0.3/ (AlN)0.3(Al2OC)0.7 samples were annealed at 2273 K. The interdiffusion coefficient measured in the AlN–Al2OC system was much larger than that in the SiC–AlN system. |
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