Sintering Mechanisms and Kinetics for Reaction Hot‐Pressed ZrB2 |
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Authors: | Jason M Lonergan William G Fahrenholtz Greg E Hilmas |
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Affiliation: | Department of Material Science and Engineering, Missouri University of Science and Technology, Rolla, Missouri |
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Abstract: | Sintering mechanisms and kinetics were investigated for ZrB2 ceramics produced using reaction hot pressing. Specimens were sintered at temperatures ranging from 1800°C to 2100°C for times up to 120 min. ZrB2 was the primary phase, although trace amounts of ZrO2 and C were also detected. Below 2000°C, the densification mechanism was grain‐boundary diffusion with an activation energy of 241 ± 41 kJ/mol. At higher temperatures, the densification mechanism was lattice diffusion with an activation energy of 695 ± 62 kJ/mol. Grain growth exponents were determined to be ~4.5, which indicated that a grain pinning mechanism was active in both temperature regimes. The diffusion coefficients for grain growth were 1.5 × 10?16 cm4/s at 1900°C and 2.1 × 10?15 cm4/s at 2100°C. This study revealed that dense ZrB2 ceramics can be produced by reactive hot pressing in shorter times and at lower temperatures than conventional hot pressing of commercial powders. |
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