The activation mechanism of oxalic acid on γ-alumina and the formation of α-alumina
| Autor: | Ya-Ling Yu, Shao-Min Lin, Yu-Chun Qiu, Zhijie Zhang, Wei Xu, Chenyang Zhang, Mingfeng Zhong, Huan Yang, Jiong-Yan Xie |
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| Rok vydání: | 2021 |
| Předmět: |
010302 applied physics
Materials science Process Chemistry and Technology Oxalic acid chemistry.chemical_element 02 engineering and technology Surface reaction 021001 nanoscience & nanotechnology 01 natural sciences Surfaces Coatings and Films Electronic Optical and Magnetic Materials γ alumina chemistry.chemical_compound chemistry Octahedron Aluminium Phase (matter) 0103 physical sciences Peak intensity Materials Chemistry Ceramics and Composites 0210 nano-technology Dissolution Nuclear chemistry |
| Zdroj: | Ceramics International. 47:26869-26876 |
| ISSN: | 0272-8842 |
| Popis: | Converting the γ phase into the α phase completely is necessary in the presintering stage of industrial alumina (Al2O3), which requires high temperature and energy consumption. To reduce the presintering temperature, γ-Al2O3 was activated by oxalic acid. XRD, 27Al-MAS-NMR and TG-DSC were used to characterize the γ - alumina before and after activation, and the phase transformation was studied. The formation temperature of α-Al2O3 decreased to 1029 °C for oxalic acid activated γ-Al2O3, and the α-fraction was 100% for activated γ-Al2O3 at 1300 °C. After oxalic acid activation, the diffraction peak intensity of γ-Al2O3 decreased significantly; the results of 27Al-MAS-NMR suggested that octahedral [AlO6] in γ-Al2O3 was easier than tetrahedral [AlO4] to be attacked by oxalic acid, and the formation of pentavalent [AlO5] with higher reaction activity, which was in favour of the lowering formation temperature of α-Al2O3. The dissolution concentration of Al increased after oxalic acid activation, and the dissolution process was controlled by surface reactions. Oxalic acid mainly attacked the octahedral aluminium in γ-Al2O3 and extracted Al as three complexes of [Al(C2O4)]+, [Al(C2O4)2]- and [Al(C2O4)3]3-. Oxalic acid activated γ - Al2O3 with a lower phase transformation temperature has broad application prospects in the alumina industry. |
| Databáze: | OpenAIRE |
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