本研究之目的為設計一含鋁成份的凝聚體，用它來製造均一晶徑之50~80 nm α-Al2O3粉末。實驗利用Boehmite與θ-Al2O3為原料，藉控制漿料之pH值使其達分散-凝聚效果，進而製造平均粒徑32 nm (S4A, pH= 4) 與163 nm (S6A, pH= 6) 之θ-Al2O3-boehmite凝聚體。將兩種粒徑凝聚體之漿料分別利用直接微波烘乾與陳化 24小時後烘乾的方法獲得四種實驗用起始樣品，在透過熱處理得到α-Al2O3粉末。實驗中以粒徑分佈儀觀察製程中凝聚體的大小，以DTA觀察混合凝聚體的熱行為，並藉BET與TEM技術了解所得α-Al2O3晶粒之外型及尺寸。
研究結果顯示：(1) 經陳化處理 (平衡穩定) 後的漿料系統反應發生的時間較短且集中。也因此可獲得均一性質之α-Al2O3粉末。(2) 分散良好 (pH=4) 之系統 (30 nm凝聚體) 無論是否經過陳化處理，其熱反應皆呈類均質反應。但產出粒徑不均一粉末。而pH=6, 160 nm凝聚體凝聚系統需經陳化處理 (穩定後) 始可發生類均質反應，應可產出粒徑均一的α-Al2O3粒子。(3) 若α-生成量90 wt%以下 (產生退變) 的氧化鋁粉末較易有馬賽克構造出現。(4) α-Al2O3粒徑成長超過100 nm後，蠕蟲狀成長的現象仍難以避免。其發生應源於不均一微結構的凝聚體。(5) 在凝聚且穩定系統(pH = 6)中凝聚體之堆積密度為28%。

Fabrication of α-Al2O3 powders with uniform sizes ranging from 50- 80 nm by calcination of aluminum-based agglomerates was examined in this study. The θ-Al2O3-boehmite agglomerates with average sizes of 32 nm (designated as S4, at pH = 4) and 163 nm (designated as S6, at pH = 6) in the slurries were prepared by pH adjustment, respectively, using boehmtie and θ-Al2O3 particles as raw materials. Four dry powders prepared by microwave-drying of unaged and 24 hr-aged slurries, respectively, were obtained. And the α-Al2O3 powders were obtained through appropriate thermal treatments. During the process, the size of agglomerates and the thermal behaviors of the dry powders were examined by dynamic light scattering method and DTA techniques, respectively. Furthermore, the morphology and particle sizes of the α-Al2O3 particles were investigated by TEM and BET-N2 (Brunauer-Emmett-Teller) techniques. The results are shown as followings:
(1) The reaction of the α-Al2O3 formation can be concentrated as the powders of aged slurries were used, therefore the α-Al2O3 powders with uniform sizes could be fabricated.
(2) As long as the θ-Al2O3-boehmite slurries were well-dispersed (at pH = 4, agglomerate size ~30 nm), they could show similar outlines of exothermic peaks of θ- to α-Al2O3 phase transformation, no matter the slurry was aged or not. However, α-Al2O3 powders calcined from them show un-uniform particles sizes. The dry powders obtained from aged slurries at pH = 6(agglomerate size ~160 nm) performed qusai-homogeneous reactions, and α-Al2O3 powders with uniform particle sizes could be formed accompanied with suitable heat treatments.
(3) The α-Al2O3 crystallites with vermicular growth occurs inevitably as the size is larger than ~ 100 nm, caused by agglomerates with un-uniform microstructure.
(4) The packing density of agglomerates in sample S6A is 28%.

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