Effects of AlF3 and calcination temperature on preparation of hexagonal-shaped α-Al2O3
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摘要: 以一水軟鋁石作為前驅體,AlF3晶種為添加劑,在較低煅燒溫度下制備結晶度好和形貌規整的六邊形片狀α-Al2O3.在晶種系數為2%的條件下,對煅燒產物的差熱-熱重-質荷(DSC-TG-MS)分析驗證了氣固反應的成核機理,結果表明:Al-O-F氣體通過氣固反應促進α-Al2O3成核相變,同時釋放出HF.實驗同時研究了AlF3晶種和煅燒溫度對煅燒產物物相、形貌、粒度和比表面的影響.結果表明:微量AlF3晶種(晶種系數為0.5%)即可促進α-Al2O3相變成核,隨著晶種系數的增加,這種效果越明顯,但同時也會增大其粒度,減少比表面積;煅燒最佳條件為:溫度850℃,晶種系數2%,煅燒時間4 h,在此條件下,一水軟鋁石可以全部轉化為結晶度良好的α-Al2O3,其形貌為規整的六邊形片狀結構.
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關鍵詞:
- 六邊形片狀α-Al2O3 /
- AlF3晶種系數 /
- DSC-TG-MS分析 /
- 成核機理 /
- 煅燒溫度
Abstract: A hexagonal α-Al2O3 with good crystallinity and regular morphology was prepared at lower calcination temperature by using boehmite (AlOOH) as precursor and AlF3 seed as additive.The possible mechanisms were investigated by DSC-TG-MS analysis under the condition of AlF3 seed coefficient 2%, which indicates that a transition compound (Al-O-F) promotes the nucleation phase transition of α-Al2O3 through gas-solid reaction, and releases HF simultaneously. Furthermore, the effects of AlF3 coefficient and calcination temperature (T) on the phase, morphology, size, and specific surface area were investigated. Results show that light AlF3 seeds can enhance the crystallinity of α-Al2O3. When the AlF3 coefficient increases from 0.5% to 10%, the hexagonal-shaped structure becomes clear, but its size increases and its specific surface area decreases. Boehmite can completely change into high-crystallinity, hexagonal-shaped α-Al2O3 under the best condition of T=850℃, AlF3 seed coefficient 2%, and constant calcination time of 4 h. -
參考文獻
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