Ceramics-Silikáty 43 (1) 12-17 (1999)

SOL - GEL a-AL₂O₃/Fe₂O₃ ABRASIVE GRAINS

L. Bača, L. Pach, Z. Hrabě 

Boehmite derived alumina gels (grains and sticks) containing Fe₂O₃ in the range of 1 to 6 wt. % were sintered at 1350 °C for 3 hours. Relative density, strength and unexpectedly also the size of a-Al₂O₃ crystals increase with Fe₂O₃ content. A bimodal microstructure of anisotropic a-Al₂O₃ crystals is observed at and above 3 wt.% content of Fe₂O₃. Anisotropic growth of a-Al₂O₃ crystals is attributed to the presence of Fe²⁺ and to the specific nucleation effect of a-Fe₂O₃. Due to high strength and the relatively small size of a-Al₂O₃ crystals a Fe₂O₃ content of 3 wt.% seems most appropriate when applications of the material as abrasive grains are intended.

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