| Title | Morphology Evolution of α-Al2O3 from milled γ-Al2O3 Precursor with NH4F Additive |
| Thematic area | Raw Materials |
| Presenter | Dr. lingling zhu |
| Authors | Mr. Chunhui Sun, Zhengzhou University, Zhengzhou - China Dr. Lingling Zhu, Zhengzhou University, Zhengzhou - China Mr. Sai Li, Zhengzhou University, Zhengzhou - China Mr. Liugang Chen, Zhengzhou University, Zhengzhou - China Mr. Guotian Ye, Zhengzhou University, Zhengzhou - China Mr. Luoqiang Liu, Zhengzhou University, Zhengzhou - China |
|
Abstract
Influences of precursor milling treatment, NH4F addition and calcination time on the morphology of α-Al2O3 formed from commercial γ-Al2O3 precursor have been studied. The neck growth of α-Al2O3 nuclei formed from milled precursor has been partially suppressed by the morphological change of commercial γ-Al2O3 precursor, oval-like shape alumina with about 500nm in grain size appeared in the sample obtained by a 1450°C calcination of milled γ-Al2O3 precursor without NH4F, coexisting with vermicular-alumina aggregates in the size range of 2~10 μm. Furthermore, the morphology of α-Al2O3 was significantly changed by the introduction of NH4F addition and calcination time. Square like α-Al2O3 powders with an average primary crystal size of ~200 nm were formed from milled γ-Al2O3 precursor with 1wt% NH4F, while cake-like α-Al2O3 powders in the size range of 0.2~1 μm were synthesized from milled γ-Al2O3 precursor with 20%NH4F addition, and the particle size distribution of α-Al2O3 were further improved by increasing the calcination time from 2h to 5h.The gas intermediate compound, such as AlOF, AlO2-1 etc, produced from the reaction of Al2O3 precursor and NH4F addition at high temperature, may lead to an alteration of α-Al2O3 growth process by a change in the scale of the developing microstructure.
|
|