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Investigation of the Sintering Behavior of Ultrapure α-Alumina Containing Low Amounts of SiO2
Samples of ultrapure alpha-alumina (particle size 0.3 micron) containing small additions of colloidal silica (particle size 22 nm) were prepared by slip casting and compacts sintered at different temperatures for 2 h in different atmospheres (vacuum, static air and flowing air). The silica additions...
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Published in: | Key Engineering Materials 2004, Vol.264-268, p.989-992 |
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Main Authors: | , , , |
Format: | Article |
Language: | English |
Citations: | Items that this one cites |
Online Access: | Get full text |
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Summary: | Samples of ultrapure alpha-alumina (particle size 0.3 micron) containing small additions of colloidal silica (particle size 22 nm) were prepared by slip casting and compacts sintered at different temperatures for 2 h in different atmospheres (vacuum, static air and flowing air). The silica additions significantly reduced the shrinkage rate during the intermediate sintering stage, when the densification rate was at a maximum and controlled by grain boundary diffusion. Abnormal grain growth was observed at the alumina-silica eutectic temperature. Below the abnormal grain growth critical temperature, silica enrichment of grain boundaries was observed without the formation of continuous, noncrystalline grain boundary films. Above the critical temperature, a glassy phase was observed at the grain boundaries, and it was concluded that anisotropic grain growth was associated with the presence of amorphous layers at the boundaries. 14 refs. |
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ISSN: | 1013-9826 1662-9795 1662-9795 |
DOI: | 10.4028/www.scientific.net/KEM.264-268.989 |