本文探討以θ-Al2O3粉末混合聚乙二醇 (Polyethylene glycol, PEG)，如何達成PEG完全分隔θ-Al2O3晶粒，使θ-Al2O3同步相變為α-Al2O3的作業過程，並以分散程度最好的樣品，製作出顆粒尺寸50-100 nm的α-Al2O3生坯，即70-75%之α-Al2O3生成量的坯體。並觀察以此生坯進行二階段燒結之燒結行為。
本研究採用丙酮作為PEG的溶劑再與θ-Al2O3混合。乾燥後之混合粉末以單軸加壓成型，目的是將PEG壓進混合過程未能完全進入的θ-Al2O3間隙，使PEG更完整包覆於每顆θ-Al2O3粉體之表面，製得類似θ-Al2O3＠PEG之核殼粉末壓成的圓錠，並進行DTA分析，以及煅燒後進行BET、XRD、SEM及DIL分析。
　　結果顯示θ-Al2O3與PEG的混合，可因θ-Al2O3基礎粒體的凝聚程度不同，在混合/分散作業中依序出現三階段分散，最終使粒體各自分離並去除凝聚狀態，以製作α-Al2O3晶粒粒徑50-100 nm之生坯。藉由三種類型的θ凝團顆粒，可以描述θ粉末分散程度的模型，而此粉末凝聚狀態的分散過程，可由試樣的DTA圖呈現的θ- 至α-Al2O3相轉換之放熱峰溫度及形狀清楚觀察之。
　　而經熱處理後得到均一50-100 nm粒徑晶粒的α-Al2O3生坯，利於製作高密度、微米晶粒、透光氧化鋁陶瓷，因此在製得均一50-100 nm粒徑晶粒 α-Al2O3的生坯後，接著摻雜500 ppm的Mg2+並觀察其燒結行為。於真空環境下以T1 (1600℃)- T2 (1450℃)/ 3h燒結之樣品，相對密度為99.8%，晶粒大小為2.5 μm。

The mixing model of θ-Al2O3 with PEG in preparing α-Al2O3 green compacts of 50-100 nm crystallite size is examined. The research is based on the use of core-shell technology. The θ-Al2O3 powder is mixed with PEG using acetone as a solvent. After drying, the mixed powder is pressed into cylindrical discs. The PEG is pressed into the inter-particle interstices where PEG is not fully entered. Thermal treatments were then performed for the discs. The samples were analyzed by BET, XRD, DTA/TG, SEM and DIL after calcination.
The results show that if you want to mix θ-Al2O3 uniformly with PEG, effective operation of PEG addition, mechanical force and pressure is extremely important. An appropriate amount of PEG addition, proper stirring operation and pressing pressure are required. If these conditions cannot be met at the same time, three different levels of agglomeration will be encountered. The degree of powder dispersion can be assessed by a simple method, i.e. DTA.
After the α-Al2O3 compact with a uniform grain size of 50-100 nm is prepared, it is then doped with 500 ppm Mg2+ and its sintering behavior is observed. The results show that the sample sintered at T1 (1600℃)-T2 (1450℃)/3h in a vacuum atmosphere has a relative density of 99.8% and a grain size of 2.5 μm.

[1] H. Gleiter, Advanced Structural and Functional Materials. Springer-Verlag Berlin Heidelberg, 1991.
[2] Z. Z. Fang, H. Wang, and V. Kumar, "Coarsening, densification, and grain growth during sintering of nano-sized powders—a perspective," International Journal of Refractory Metals and Hard Materials, vol. 62, pp. 110-117, 2017.
[3] G. L. Messing and M. Kumagai, "Low-temperature sintering of α-alumina-seeded boehmite gels," Journal of the American Ceramic Society, vol. 73, no. 10, pp. 88-91, 1994.
[4] G.-D. Sun, G.-H. Zhang, and K.-C. Chou, "An industrially feasible pathway for preparation of Mo nanopowder and its sintering behavior," International Journal of Refractory Metals and Hard Materials, vol. 84, p. 105039, 2019.
[5] M. N. Rittner and T. Abraham, "Nanostructured materials: An overview and commercial analysis," The Journal of The Minerals, vol. 50, no. 1, pp. 36-37, 1998.
[6] C. Won, H. Nersisyan, H. Won, and J. Lee, "Refractory metal nanopowders: synthesis and characterization," Current opinion in solid state and materials science, vol. 14, no. 3-4, pp. 53-68, 2010.
[7] C. J. Szepesi and J. H. Adair, "High Yield Hydrothermal Synthesis of Nano‐Scale Zirconia and YTZP," Journal of the American Ceramic Society, vol. 94, no. 12, pp. 4239-4246, 2011.
[8] M. A. Meyers, A. Mishra, and D. J. Benson, "Mechanical properties of nanocrystalline materials," Progress in materials science, vol. 51, no. 4, pp. 427-556, 2006.
[9] K. Wefers and C. Misra, Oxides and hydroxides of aluminum. America: Alcoa Research Laboratories, 1987.
[10] P.-L. Chang, F.-S. Yen, K.-C. Cheng, and H.-L. Wen, "Examinations on the critical and primary crystallite sizes during θ-to α-phase transformation of ultrafine alumina powders," Nano Letters, vol. 1, no. 5, pp. 253-261, 2001.
[11] 楊榮澤（2009）。奈米α-Al2O3晶粒之成長熱力學。國立成功大學資源工程學系博士論文，台南市。
[12] H.-L. Wen and F.-S. Yen, "Growth characteristics of boehmite-derived ultrafine theta and alpha-alumina particles during phase transformation," Journal of Crystal Growth, vol. 208, no. 1-4, pp. 696-708, 2000.
[13] 黃姵文（2002）。模擬θ-Al2O3@PEG核殼技術製作高密度細粒徑α-Al2O3生坯。國立成功大學資源工程學系博士論文，台南市。
[14] 郝成偉、吳伯麟、李繼彥（2007）。聚乙二醇分散劑對高純超細α-Al2O3製備的影響。材料導報，5，163-164。
[15] A. C. O. Lopes et al., "Microstructural, mechanical, and optical characterization of an experimental aging-resistant zirconia-toughened alumina (ZTA) composite," Dental Materials, vol. 36, no. 12, pp. 365-374, 2020.
[16] W. H. Gitzen, Alumina as a Ceramic Material. America: Wiley, 1970.
[17] H. W. Takashi Shirai, Masayoshi Fuji, Minoru Takahashi, "Structural Properties and Surface Characteristics on Aluminum Oxide Powders," Annual report of the Ceramics Research Laboratory Nagoya Institute of Technology, vol. 9, pp. 23-31, 2010.
[18] I. L. a. D. Brandon, "Metastable Alumina Polymorphs: Crystal Structures and Transition Sequences," Journal of the American Ceramic Society, vol. 81, no. 8, pp. 1995-2012, 1998.
[19] L. D. Hart, Alumina Chemicals: Science and Technology Handbook. America: Wiley-American Ceramic Society, 1990.
[20] S. Geller, "Crystal Structure of β‐Ga2O3," The Journal of Chemical Physics, vol. 33, no. 3, 1960.
[21] E. Dörre and H. Hübner, Alumina. Berlin: Springer-Verlag Berlin Heidelberg, 1984.
[22] J. A. K. G. K. J. D. Broder, "Characterization of β-Ga2O3 and its Alumina Isomorph, θ-Al2O3," American Mineralogist, vol. 42, no. 5-6, pp. 398-407, 1957.
[23] 張俊龍（2002）。奈米級氧化鋁粉末θ至α的相轉換活化能研究。國立成功大學資源工程學系碩士論文，台南市。
[24] P. Badkar and J. Bailey, "The mechanism of simultaneous sintering and phase transformation in alumina," Journal of Materials Science, vol. 11, no. 10, pp. 1794-1806, 1976.
[25] H.-L. Wen, Y.-Y. Chen, F.-S. Yen, and C.-Y. Huang, "Size characterization of θ- and α-Al2O3 crystallites during phase transformation," Nanostructured materials, vol. 11, no. 1, pp. 89-101, 1999.
[26] R. Apetz and M. P. Van Bruggen, "Transparent alumina: a light‐scattering model," Journal of the American Ceramic Society, vol. 86, no. 3, pp. 480-486, 2003.
[27] 謝佳真（2018）。以液相前驅物滲透法摻雜助燒結劑製備透光氧化鋁。國立成功大學資源工程學系碩士論文，台南市。
[28] 賴岳淵（2016）。以注漿成形法製備透光氧化鋁陶瓷。國立成功大學資源工程學系碩士論文，台南市。
[29] G. Wei, "Transparent ceramic lamp envelope materials," Journal of Physics D: Applied Physics, vol. 38, no. 17, pp. 3057-3064, 2005.
[30] J. Koo, K. Hong, J. Park, and D. Shin, "Effect of grain size on transmittance and mechanical strength of sintered alumina," Materials Science and Engineering: A, vol. 374, no. 1-2, pp. 191-195, 2004.
[31] W. Tan and M. A. Bakar, "The effect of additives on the size of Fe3O4 particles," Journal of Physical Science, vol. 17, no. 2, pp. 37-50, 2006.
[32] C. Vidyasagar and Y. A. Naik, "Surfactant (PEG 400) effects on crystallinity of ZnO nanoparticles," Arabian Journal of Chemistry, vol. 9, no. 4, pp. 507-510, 2016.
[33] C.-W. Kwon, T.-S. Yoon, S.-S. Yim, S.-H. Park, and K.-B. Kim, "The effect of excess surfactants on the adsorption of iron oxide nanoparticles during a dip-coating process," Journal of Nanoparticle Research, vol. 11, no. 4, pp. 831-839, 2009.
[34] M. Xu, H. Xue, W. Y. Tin, H. Wang, Z. Yong, and Q. Wang, "Synergistic Effect by Polyethylene Glycol as Interfacial Modifier in Silane-Modified Silica-Reinforced Composites," Polymers, vol. 13, no. 5, p. 788, 2021.
[35] G.-W. Liu, Z.-P. Xie, and Y. Wu, "Application of doping ceramics via infiltration on translucent alumina ceramics," Journal of Inorganic Materials, vol. 28, no. 4, pp. 375-380, 2013.
[36] G.-W. Liu, Z.-P. Xie, and Y. Wu, "Research progress of manipulating composition and properties of ceramics via liquid precursor infiltration technique," Journal of Inorganic Materials, vol. 26, no. 11, pp. 1121-1128, 2011.
[37] B. R. Marple and D. J. Green, "Mullite/alumina particulate composites by infiltration processing," Journal of the American Ceramic Society, vol. 72, no. 11, pp. 2043-2048, 1989.
[38] D. D. L. Chung, Carbon Composites: Composites With Carbon Fibers, Nanofibers, and Nanotubes. America: Butterworth-Heinemann, 2017.
[39] G. Tari, J. Ferreira, and O. Lyckfeldt, "Influence of magnesia on colloidal processing of alumina," Journal of the European Ceramic Society, vol. 17, no. 11, pp. 1341-1350, 1997.
[40] W. C. Tu and F. F. Lange, "Liquid precursor infiltration processing of powder compacts: I, kinetic studies and microstructure development," Journal of the American Ceramic Society, vol. 78, no. 12, pp. 3277-3282, 1995.
[41] R. L. Coble, "Transparent alumina and method of preparation," ed: Google Patents, 1962.
[42] K. A. Berry and M. P. Harmer, "Effect of MgO Solute on Microstructure Development in Al2O3," Journal of the American Ceramic Society, vol. 69, no. 2, pp. 143-149, 1986.
[43] J. D. Powers and A. M. Glaeser, "Grain boundary migration in ceramics," Interface Sci, vol. 6, no. 1-2, pp. 23-39, 1998.
[44] K. Soni, A. Thompson, M. Harmer, D. Williams, J. Chabala, and R. Levi‐Setti, "Solute segregation to grain boundaries in MgO‐doped alumina," Applied physics letters, vol. 66, no. 21, pp. 2795-2797, 1995.
[45] R. M. German, Sintering theory and practice. Wiley-VCH, 1996.
[46] M. W. Barsoum, Fundamentals of ceramics. Routledge, 2003.
[47] M. N. Rahaman, Ceramic processing and sintering. Marcel Dekker, 1995.
[48] R. L. Coble, "Sintering crystalline solids. I. Intermediate and final state diffusion models," Journal of applied physics, vol. 32, no. 5, pp. 787-792, 1961.
[49] L. C. D. J. Frank J. T. Lin, "Microstructure Refinement of Sintered Alumina by a Two-Step Sintering Technique," Journal of the American Ceramic Society, vol. 80, no. 9, pp. 2269-2277, 1997.
[50] L. S. N.J. Lóh, C.A. Faller, A. De Noni Jr, O.R.K. Montedo, "A review of two-step sintering for ceramics," Journal of the European Ceramic Society, vol. 42, pp. 12556-12572, 2016.
[51] C. J. Chirayil, J. Abraham, R. K. Mishra, S. C. George, and S. Thomas, Thermal and Rheological Measurement Techniques for Nanomaterials Characterization. Elsevier, 2017.
[52] M. C. Tanzi, S. Farè, and G. Candiani, Foundations of Biomaterials Engineering. Academic Press, 2019.
[53] C. S. Nordahl and G. L. Messing, "Thermal analysis of phase transformation kinetics in α-Al2O3 seeded boehmite and γ-Al2O3," Thermochimica acta, vol. 318, no. 1-2, pp. 187-199, 1998.
[54] 游佩青（2008）。類均質條件下奈米θ-Al2O3微粒之晶粒成長現象觀察。國立成功大學資源工程學系博士論文，台南市。
[55] A. F. Rawle, Pharmaceutical Suspensions. America: Springer, 2010.