以單水鋁石（Boehmite）製造α-氧化鋁微粒粉末的研究

Fabricating Nano-scaled α-Alumina Powders Using Boehmite as the Raw Material

顏富士(F. S. Yen) ； 楊榮澤(R. J. Yang) ； 游佩青(P. C. Yu)

《鑛冶：中國鑛冶工程學會會刊》 54卷3期 (2010/09) Pp. 66-72

https://doi.org/10.30069/MM.201009.0006

摘要

以Boehmite為原料經熱處理法生產α-氧化鋁微粒粉末時，Boehmite會循boehmite→γ→δ→θ而→α的相變步驟生成α-氧化鋁微粒。此過程中，因θ→α的相變有相變臨界晶徑（dθс＝~30 nm）的現象，由boehmite生成的θ-氧化鋁晶粒之大小也即小於或大於相變臨界晶徑，會直接影響生成之α-氧化鋁微粒的熱力學穩定性。前者θ-在相變前需先粗化至相變臨界晶徑α核晶才得生成。此核晶為其相穩定必須再粗化至晶粒超過穩定晶徑大小（ds），約80~100 nm。因此所得的α晶粒最小會在80~100 nm。如由後者，即θ-晶粒粗於dθс（＝~30-50 nm），則可得到與θ-晶粒粒徑相當的α-氧化鋁晶粒。由於粒徑如此小的晶粒會再藉粗化或凝聚以降低表面能，因此80-100 nm的α-氧化鋁晶粒會再粗化，發生蠕蟲狀外型單晶粒體。30 nm α-氧化鋁則會凝聚產生多晶粒體。二者因此都難維持生成時之大小。如欲保有原生大小則需在其熱處理過程維持均質的反應條件。也即至少在θ→α相變過程促成所有θ-晶粒同時發生相變及同時停止粗化。此為生產高品質α-氧化鋁微粒粉末的基礎工作。

關鍵字

氧化鋁粉末 ； 奈米粉末 ； 相變 ； 臨界晶徑

並列摘要

This report elucidates three important information of fabricating specified nano-scaled α-phase alumina (a-Al2O3) powders using θ-phase alumina (q-Al2O3) as the starting material. 1. The θ-to a-phase alumina phase transformation (θ-→α-Al2O3) encounters the critical size of phase transformation, being ~30 nm (dθc). Then θ-Al2O3 particles with sizes smaller and larger than ~30 nm would lead to different thermodynamic growth routes after α-Al2O3 nuclei are formed. The former performs stable sizes by the coalescence mechanism. α-crystallites behave stable as the size exceeds 80 to 100 nm. While the latter can be stable as the sizes are larger than ~30 nm. 2. A quasi homogeneous phase transformation is required to avoid the occurrence of first come and first coarsen phenomena. 3. Domain restriction or limiting the size growth in a pre-set mass will be the appropriate techniques to obtain α-Al2O3 powders with narrow particle size distribution. Thus preparing a θ-Al2O3 powder of similar size will be another requirement.The report also provides some well-prepared powders as the examples confirming the listed important information.

並列關鍵字

alumina powder ； nano-powders ； phase transformation ； critical size