ISSN 0862-5468 (Print), ISSN 1804-5847 (online) 

Ceramics-Silikáty 61, (4) 357 - 366 (2017)


THE INFLUENCES OF FLUORIDES ON THE TRANSFORMATION OF α -ALUMINA CRYSTALS
 
Tian Qingbo 1,2, Yang Xiaojie 3, Wang Yue 2, Lv Zhijie 2
 
1 Co-innivation Center of Green Buliding, Shandong Jianzhu University, Jinan 250101, P. R. China
2 School of Material Science and Engineering, Shandong Jianzhu University, Jinan 250101, P. R. China
3 Shandong Institute for Product Quality Inspection, Jinan 250100, P. R. China

Keywords: α- Al₂O₃, Morphology, Platelet-like Al₂O₃, Fluorides
 

Influence of addition of aluminum fluoride (AlF₃) and ammonium fluoride (NH₄F) on transformation of α-Al₂O₃ from boehmite was investigated. Transformation of α-Al₂O₃ occurred at about 1050°C and 950°C, when boehmite contained AlF₃ and NH₄F additives respectively, which was 150°C and 300°C lower than that without any additives. The formed α-Al₂O₃ consisted of clear, hexagonal plate-like particles about 2-3 μm in diameter and 200 nm in thickness. However, the formed hexagonal platelet particles gradually became blunt at edges and decreased in sizes at the higher calcinating temperatures. The transfer of α-Al₂O₃ morphology was due to the diminution and disappearance of fluorine. The fluoride coated on the surfaces were firstly decomposed and then fluorine entered the lattices of crystals was volatilized. The fluoride with tiny particles attached on the surface had a same chemical bonding of F-Al-O with that in the lattices of crystals.


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doi: 10.13168/cs.2017.0035
 
 
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