本研究以 gibbsite (Al(OH)3) 為原料，經熱水法製備單一粒徑的 boehmite (AlOOH) 粉末，以期作為製備單一粒徑 α-Al2O3 的原料。Boehmite 為工業上最常用來生產 α-Al2O3 粉末的原料之一，然以此為原料，經熱處理獲得之 α-Al2O3 粉末常具有粒徑分佈寬且不易具單離外型 (即易具指狀外型) 的缺點。造成此現象的主要原因之一可能是起始 boehmite 原料粒子大小分佈不均，相轉換發生時間前後不一，導致先生成的 α-Al2O3 粒子在後續熱處理中繼續成長所致。
研究首先改變熱水處理溫度，觀察溫度改變對製備粉末之影響，接著再從中選取一適當處理溫度作為後續實驗條件。探討以 (1) 先將 gibbsite 以熱水法製備 boehmite 後，再球磨處理成特定粒徑粉末，及 (2) 先球磨縮減 gibbsite 粒徑至特定大小後，再以熱水法製備 boehmite 粉末，分析和比較兩種製程製備單一粒徑 boehmite 粉末的可能性。實驗以 XRD 觀察 boehmite 的生成情形，以粒徑分佈儀、BET 比表面積儀、SEM 及 TEM 觀察製備之 boehmite 粉末的粒徑分佈、大小及外型。結果顯示：(1) 提高熱水系統處理的溫度與縮減 gibbsite 粉末的粒徑皆有助於加快轉換為boehmite 的速度 (縮短轉換為純相 boehmite 粉末的時間)。(2) 先以熱水法製備 boehmite 再研磨的製程，其粉末粒子大小與外型不易均勻；而先球磨縮減 gibbsite 粉末粒徑至 1 μm 以下，再以熱水製備 boehmite 的製程較有機會獲得單離且粒徑及外型均一的粉末。(3) gibbsite 粉末經球磨使粉末粒徑縮減至 250 nm-1 μm，再經 230 °C 熱水處理 48 小時，可獲得單一粒徑 (~200-500 nm) boehmite 粉末。

In this study, monodispersed boehmite (AlOOH) powders which were looking forward to be the precursors for the production of monodispersed α-Al2O3 powders were prepared hydrothermally using gibbsite (Al(OH)3) as raw materials. Boehmite is one of the most used precursors for producing α-Al2O3 powders in industry. However, α-Al2O3 powders obtained through the calcination of boehmite are usually characterized by vermicular outward and broad particle size distribution. One of the major reasons for this phenomenon may be due to the broad particle size distribution of boehmite. Boehmite with non-uniform sizes would result in the distraction of θ- to α-Al2O3 phase transformation. α-Al2O3 crystallites formed earlier would grow to behave as vermiculated outward during the subsequent thermal treatment.
The effect of reaction temperature on fabrication of boehmite was examined firstly. Then, an appropriate reaction temperature among them was chose as the following experimental condition. Two processes were adopted to prepare monodispersed boehmite in this study. (1) Boehmite was prepared hydrothermally from gibbsite firstly, and then ball-milled to a specific size. (2) Gibbsite was ball-milled to a specific size firstly, and then the pre-treated gibbsite was used as staring materials to produce boehmite hydrothermally. The XRD technique was used to examine the formation of boehmite. And the PSD, BET, SEM, and TEM techniques were used to examine the particle size distribution, particles size, and morphology of the boehmite, respectively. The results showed that:
(1) The rate of gibbsite to boehmite transformation can be facilitated by higher reaction temperature of hydrothermal treatment as well as smaller size of gibbsite. Furthermore, the duration of formation of pure boehmite can be shortened.
(2) It is not easy to obtain boehmite powders with uniform particle size and outward using the former process. Alternatively, the latter process seems to be a practicable one to fabricate boehmite powders with uniform particle size and outward.
(3) Monodispersed boehmite powders with particle size ranging from 200-500 nm can be fabricated by hydrothermal treatment of the pre-milled gibbsite (250 nm-1 μm) at 230 °C for 48h.

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