Preparation of α-Al2O3 by low-temperature calcining γ-Al2O3 with α-phase seed in-situ obtained by ball milling
Materials Today Communications(2023)
Abstract
Due to the high activation energy barrier and the sporadic nature of nucleation, the temperature required for the transition from cubic dense γ-Al2O3 to tripartite α-Al2O3 is as high as 1100–1200 °C. In this work, a two-step strategy was employed to reduce the phase transformation temperature, and prepare α-Al2O3 particles with good dispersion. As the first step, 10 nm sheet γ-Al2O3 was obtained by ammonium aluminum carbonate (AACH) decomposition, which was more favorable to the crystal transformation in the next ball-milling processing. In the second step, γ-Al2O3 powder with partial α-Al2O3 produced in situ by ball-milling γ-Al2O3 was calcined, and α-Al2O3 nanoparticles were obtained at just 850 °C. The content of the α-Al2O3 is determined by the Rietveld Refine method. The relationship between ball-milling time and α-Al2O3 content was clarified, and the effect of α-Al2O3 content on the transformation temperature and morphology of γ-Al2O3 was discussed. The results showed that the α-Al2O3 content rises with the increase of ball milling time, and spherical α-Al2O3 nanoparticles can be obtained when the α-Al2O3 content is 5 %. The addition of α-Al2O3 seeds reduces the phase transition temperature but agglomeration exists. Our proposed two-step low-temperature calcination strategy is an important method for the preparation of alumina nanoparticles
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Key words
α-Al2O3,High energy ball-milling,Reduce,Phase transformation temperature
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