本研究旨在探討以熱處理法球化微粒α-Al2O3之效果。採用方式有二：一、以熱處理提供活化能，藉降低表面能(積)現象使微粒α-Al2O3球化。二、在系統中製造微粒α-Al2O3，於高溫下同時藉第一種方式及Ostwald ripening觀點，使α-Al2O3晶粒球化。
　　實驗分三部分：(1)單純對微粒α-Al2O3作熱處理。(2)藉θ-Al2O3→α-Al2O3相變過程產生的小α-晶粒，依Ostwald ripening的原理產生球化。(3)在含少量θ-Al2O3的α-Al2O3粉末中添加Boehmite，經預熱處理後使粉末系統中除原有的α-微粒外，另外存在新生之小α-晶粒及θ-Al2O3。目的在瞭解依Ostwald ripening原理球化，供晶粒球化之小α-Al2O3是原有或新生(相變過來)之α-Al2O3晶粒。
　　實驗結果發現，球化過程略分為兩階段。一是α-Al2O3晶粒在單純熱處理中的自體球化。二是因微細α-Al2O3出現於系統中而由之發生的球化。後者發生於由θ- →α-Al2O3相變時產生之α-Al2O3新晶粒系統中。實驗過程也發現，α-Al2O3粉末系統的比表面積與熱處理溫度呈線性反比關係。而持溫對球化的影響小於溫度。
　　綜合而言，單純對微粒α-Al2O3作熱處理，可球化之。但若要藉Ostwald ripening現象球化，則以θ-至α-相變生成的小α-晶粒，才具效果。

The effect of thermal treatment on submicron α-Al2O3 particles’ becoming spherical is investigated in this study by two ways. The mean size of the submicron α-Al2O3 particles is about 170 nm and the two ways are described briefly as follows:
1. Owing to the tendency of the system toward decreasing in surface free energy, submicron α-Al2O3 particles may become spherical during heat treating.
2. When there exists part of relatively smaller α-Al2O3 particles, except by the first way, submicron α-Al2O3 particles may change gradually to spheres through the Ostwald ripening mechanism.
The experiment is composed of three parts:
(1) Heat treatment of submicron α-Al2O3 only.
(2) Heat treatment of submicron α-Al2O3 and θ-Al2O3.
(3) Heat treatment of θ-Al2O3 and two different sizes of α-Al2O3 (larger one: ~170 nm, smaller one: ~50 nm).
The difference between (2) and (3) is the origin of the smaller α- crystallites for the Ostwald ripening phenomena. In the second part, the smaller α- appears after θ-→α-Al2O3 phase transformation occurs. However in the third part, it has already existed in the system.
It is found that the process of becoming spherical can be separated into two parts. One is that submicron α-Al2O3 changes its grain shape progressively during heating just by itselt. And the other is that through the Ostwald ripening phenomenon. However, the part with the Ostwald ripening mechanism occurs merely at the stage of θ-→α-Al2O3 phase transformation. In addition, the specific surface area of the system shows an inverse proportion to the heating temperature. And the heating temperature has a more critical influence on the process than the heating duration.
In conclusion, submicron α-Al2O3 particles may become spherical by means of thermal treatment. But if through Ostwald ripening phenomenon, choosing θ-Al2O3 as the source of the smaller α- crystallites may then be the effective way.

1. A. Shui, Z. Kato, S. Tanaka, N. Uchida, and K. Uematsu,“Isotropic Sintering Shrinkage in Pressed Compact of Near-Spherical Alumina Particles,” Am. Ceram. Soc. Bull., 80, 29-32, 2001.
2. V. K. LaMer and R. H. Dinegar,“Theory, Production and Mechanism of Formation of Monodispersed Hydrosols,”J. Am. Chem. Soc., 72, 4847-4854, 1950.
3. P. Tartaj and J. Tartaj,“Preparation, Characterization and Sintering Behavior of Spherical Iron Oxide Doped Alumina Particles,” Acta Mater., 50, 5-12, 2002.
4. P. Murugavel, M. Kalaiselvam, M. K. Renganathan, and A. R. Raju,“Preparation and Characterization of Sub-Micron Spherical Particles of Al2O3, SiO2 and Mullite,” Mater. Chem. Phys., 56, 247-251, 1998.
5. M. Vallet-Regí, L. M. Rodríguez-Lorenzo, C. V. Ragel, A. J. Salinas, and
J. M. González-Calbet,“Control of Structural Type and Particle Size in Alumina Synthesized by the Spray Pyrolysis Method,”Solid State Ionics, 101, 197-203, 1997.
6. T. Hirayama,“High-Temperature Characteristics of Transition Al2O3 Powder with Ultrafine Spherical Particles,”J. Am. Ceram. Soc., 70, c122-c124, 1987.
7. M. N. Rahaman, Ceramic Processing and Sintering, M. Dekker, New York, 1995.
8. Y. M. Shiang, D. P. Birnie Ⅲ, and W. D. Kingery, Physical Ceramics- Principles for Ceramic Science and Engineering, John Wiley & Sons, New York, 1997.
9. B. Sun and Z. Suo,“A Finite Element Method for Simulating Interface Motion- Ⅱ.
Large Shape Change due to Surface Diffusion,”Acta Mater., 45, 4953-4962, 1997.
10. D. Y. Noh, K. S. Liang, Y. Hwu, and S. Chandavarkar,“Thermal Roughness
of A Si(331) Surface,” Surf. Sci., 326, L455-L459, 1995.
11. I. I. M. Tijburg, H. D. Bruin, P. A. Elberse, and W. Geus,“Sintering of Pseudo-Boehmite and α-Al2O3,”J. Mater. Sci., 26, 5945-5949, 1991.
12. M. W. Chase, Jr., C. A. Davies, J. R. Downey, Jr., Fruip, R. R. McDonald, and A. N. Syverud, JANAF Thermochemical Tables, 3rd Ed., Am. Chem. Soc., Washington, 1986.
13. H. L. Wen and F. S. Yen,“Growth Characteristics of Boehmite-Derived Ultrafine theta and alpha-Alumina particles During Phase Transformation,”J. Cryst. Growth, 208, 696-708, 2000.
14. P. L. Chang, F. S. Yen, K. C. Cheng, and H. L. Wen,“Examination on the Critical and Primary Crystallite Sizes during θ- to α-Phase Transformation on Ultrafine Alumina Powders,”Nano Letters, 5, 253-261, 2001.
15.溫惠玲，由 Boehmite製得之氧化鋁粉末的 θ-→ α-Al2O3相轉換，國立成功大學資源工程研究所，博士論文，中華民國89年1月。
16.鄭功杰，氧化鋁微粉之基礎晶徑觀察，國立成功大學資源工程研究所，碩士論文，中華民國89年6月。
17. M. Rösner-Kuhn, W. H. Hofmeister, G. Kuppermann, R. J. Bayuzick, and
M. G. Frohberg,“Investigation of the Influence of Oxygen on the Surface Tension of Zirconium by the Oscillating Drop Technique,”Surf. Sci., 443, 159-164, 1999.
18. W. D. Kingery, H. K. Bowen, and D. R. Uhlmann, Introduction to Ceramics, 2nd Ed., Wiley, New York, 1975.
19.楊榮澤，20至100nm α-Al2O3晶粒的熱力學特性 ，國立成功大學資源工程研究所，碩士論文，中華民國92年7月。
20. W. C. Krumbein,“Measurement and Geological Significance of Shape and Roundness of Sedimentary Particles,”J. Sediment. Petrol., 11, 68, 1941.
21.許宇嬋，微粒 θ與 α-Al2O3混合粉末的熱反應，國立成功大學資源工程研究所，碩士論文，中華民國90年7月。
22.羅慧珊，添加 α-Al2O3晶種對 Boehmite合成奈米級氧化鋁粉末之θ-→α-Al2O3相轉換影響之研究，國立成功大學資源工程研究所，碩士論文，中華民國88年6月。