由於二維奈米材料有極大的重要性於工業上諸多領域。本文簡介以低升溫速率熱處理，可由單水鋁石 (Boehmite，AlO(OH)，或Al2O3‧H2O) 獲得奈米級片狀氧化鋁粉末的過程。單水鋁石屬於氧化鋁水合物的一種，鋁氧氫元素結合排列成層狀結構，晶體出現完美的{010}節理面。由單水鋁石相變之過渡相氧化鋁具順構延伸特性(Topotactic transformation)，因此單水鋁石經熱處理相變成同為層狀結構的過渡相γ-Al2O3晶粒，其有{110}節理面。本實驗原料單水鋁石粉末呈2維奈米疊層狀，推測可藉由熱處理過程中，造成其晶粒沿節理面剝開，生成片狀氧化鋁粒體粉末。
本研究將單水鋁石以每分鐘0.5、1.0、及2.0oC升溫速率加熱，並以淬冷、持溫10、20分鐘進行熱處理。觀察的製程特性包含單水鋁石的失重、比表面積，及以XRD量測之單水鋁石消失量與γ-Al2O3生成量。失重包含2.1wt%吸附水及15wt%結晶水。單水鋁石比表面積的增加以40m2/g為界分兩段，先因其脫去結晶水產生的蒸汽壓力使BET上升至40m2/g，再加入結構重整之應力達BET值100m2/g。於XRD量測之Boehmite殘餘量與DTA吸熱峰溫度範圍近乎吻合，γ-Al2O3生成量則由BET值40m2/g開始。當Boehmite含量為0%時，γ-Al2O3生成完畢。單水鋁石加熱至DTA吸熱峰結束溫度，其失重約15%、BET值超過100m2/g及γ-Al2O3生成量100%。亦即生成之γ-Al2O3還帶有2%羥基。
以疊層狀單水鋁石為原料所得的片狀氧化鋁粉末，其片體截面積與原料單水鋁石的{010}面一致。雖最終所得粉末為過渡相γ-Al2O3，但外形不變，出現假型現象（Pseudomorphism）。γ-Al2O3之片體厚度可薄至約5nm，其比表面積超過100m2/g。疊層狀單水鋁石之剝片機制包含其釋出結晶水所產生之蒸汽壓力，及相變成γ-Al2O3下結構重整產生的應變應力。
關鍵詞：片狀粉末、氧化鋁、熱處理、順購延伸特性、假型現象。

Summary
Due to the importance of 2-dimensional nanomaterials, the research aims to fabricate boehmite-derived flake alumina powders with lower heating rate thermal treatments. Boehmite is a kind of alumina hydrates. Because of the layered structure, boehmite has a perfect cleavage {010}. Boehmite transforms into stable α-Al2O3 via the sequence of metastable transition aluminum oxide: AlOOH → γ → δ → θ → α-Al2O3. The transformation of boehmite to γ-Al2O3 is topotatic. Hence, γ-Al2O3 also belongs to layered structure with a perfect cleavage {110}. In this study, boehmite dehydration caused vapor stress and alumina migration resulted in strain stress are speculated the driving force that boehmite delaminates.
Heat treatments of boehmite use three different heating rates: 0.5, 1, and 2℃/min. TEM photos, specific surface, and geometric evaluation are the methods observing the cleavage {010}. Examining three different experimental data, in-cluding weight loss of boehmite, the residual amount of boehmite, and the for-mation of γ-Al2O3 realizes the driving force of delamination.
The boehmite-derived flake alumina powders have the same cross-sectional surface with boehmite. Although the flake alumina powders end up in γ-phase, it has the phenomenon called ‘pseudomorphism’ that γ-Al2O3 has the same ap-pearance as the boehmite cleavage {010}. The final thickness of γ-Al2O3 is low to approximately 5 nanometers, and its’ value of specific surface surpasses 100m2/g.
Keyword: flake-like powder, alumina, heat treatment, topotatic and pseudo-morphsim.

[1] Ewing, F., 1935. The Crystal Structure of Lepidocrocite. The Journal of Chemical Physics, 3(7), pp.420-424.
[2] Mathieu, Y., Lebeau, B. and Valtchev, V., 2007. Control of the Morphology and Particle Size of Boehmite Nanoparticles Synthesized under Hydrothermal Conditions. Langmuir, 23(18), pp.9435-9442.
[3] Zhu, H., Gao, X., Song, D., Bai, Y., Ringer, S., Gao, Z., Xi, Y., Martens, W., Riches, J. and Frost, R., 2004. Growth of Boehmite Nanofibers by Assembling Nanoparticles with Surfactant Micelles. The Journal of Physical Chemistry B, 108(14), pp.4245-4247.
[4] Wang, Z., Tian, Y., Fan, H., Gong, J., Yang, S., Ma, J. and Xu, J., 2014. Facile seed-assisted hydrothermal fabrication of γ-AlOOH nanoflake films with su-perhydrophobicity. New Journal of Chemistry, 38(3), p.1321.
[5] Wu, X., Zhang, B. and Hu, Z., 2013. Large-scale and additive-free hydro-thermal synthesis of lamellar morphology boehmite. Powder Technology, 239, pp.155-161.
[6] Lippens, B. and de Boer, J., 1964. Study of phase transformations during cal-cination of aluminum hydroxides by selected area electron diffraction. Acta Crystallographica, 17(10), pp.1312-1321.
[7] Yanagida, H. and Yamaguchi, G., 1964. Thermal Effects on the Lattices of η- and γ-Aluminum Oxide. Bulletin of the Chemical Society of Japan, 37(8), pp.1229-1231.
[8] Vidal, O. and Dubacq, B., 2009. Thermodynamic modelling of clay dehydra-tion, stability and compositional evolution with temperature, pressure and H2O activity. Geochimica et Cosmochimica Acta, 73(21), pp.6544-6564.
[9] Paglia, G., Buckley, C., Rohl, A., Hart, R., Winter, K., Studer, A., Hunter, B. and Hanna, J., 2004. Boehmite Derived γ-Alumina System. Part 1. Structural Evolution with Temperature, with the Identification and Structural Determina-tion of a New Transition Phase, γ′-Alumina. ChemInform, 35(14).
[10] Paglia, G., Buckley, C., Udovic, T., Rohl, A., Jones, F., Maitland, C. and Connolly, J., 2004. Boehmite-Derived γ-Alumina System. 2. Consideration of Hydrogen and Surface Effects. Chemistry of Materials, 16(10), pp.1914-1923.
[11] Krokidis, X., Raybaud, P., Gobichon, A., Rebours, B., Euzen, P. and Toulhoat, H., 2001. Theoretical Study of the Dehydration Process of Boehmite to γ-Alumina. The Journal of Physical Chemistry B, 105(22), pp.5121-5130.
[12] Santos, P., Coelho, A., Santos, H. and Kiyohara, P., 2009. Hydrothermal synthesis of well-crystallised boehmite crystals of various shapes. Materials Research, 12(4), pp.437-445.
[13] Hill, R., 1981. Hydrogen Atoms in Boehmite: A Single Crystal X-Ray Dif-fraction and Molecular Orbital Study. Clays and Clay Minerals, 29(6), pp.435-445.
[14] Sahama, T., Lehtinen, M. and Rehtijrvi, P., 1973. Natural boehmite single crystals from Ceylon. Contributions to Mineralogy and Petrology, 39(2), pp.171-174.
[15] Xu, B. and Smith, P., 2012. Dehydration kinetics of boehmite in the temper-ature range 723–873K. Thermochimica Acta, 531, pp.46-53.
[16] Wilson, S., 1979. The dehydration of boehmite, γ-AlOOH, to γ-Al2O3. Journal of Solid State Chemistry, 30(2), pp.247-255.
[17] Sohlberg, K., Pennycook, S. and Pantelides, S., 1999. Hydrogen and the Structure of the Transition Aluminas. Journal of the American Chemical Soci-ety, 121(33), pp.7493-7499.
[18] Decleer, J., 2010. TG/XRD/Sem Study of the Conversion of Gibbsite to (Pseudo) Boehmite. Bulletin des Sociétés Chimiques Belges, 98(7), pp.449-462.
[19] Cai, S., Rashkeev, S., Pantelides, S. and Sohlberg, K., 2003. Phase transfor-mation mechanism between γ- and θ-alumina. Physical Review B, 67(22).
[20] Karouia, F., Boualleg, M., Digne, M. and Alphonse, P., 2016. The impact of nanocrystallite size and shape on phase transformation: Application to the boehmite/alumina transformation. Advanced Powder Technology, 27(4), pp.1814-1820.
[21] Bokhimi, X., Toledo-Antonio, J., Guzmán-Castillo, M., Mar-Mar, B., Her-nández-Beltrán, F. and Navarrete, J., 2001. Dependence of Boehmite Thermal Evolution on Its Atom Bond Lengths and Crystallite Size. Journal of Solid State Chemistry, 161(2), pp.319-326.
[22] SOLED, S., 1983. $γ-Al2O3 viewed as a defect oxyhydroxide. Journal of Catalysis, 81(1), pp.252-257.
[23] Fankhänel, J., Silbernagl, D., Ghasem Zadeh Khorasani, M., Daum, B., Kempe, A., Sturm, H. and Rolfes, R., 2016. Mechanical Properties of Boehm-ite Evaluated by Atomic Force Microscopy Experiments and Molecular Dy-namic Finite Element Simulations. Journal of Nanomaterials, pp.1-13.
[24] Rudolph, M., Motylenko, M. and Rafaja, D., 2019. Structure model of γ-Al2O3 based on planar defects. IUCrJ, 6(1), pp.116-127.
[25] Chen, G., Hao, G., Guo, T., Song, M. and Zhang, B., 2004. Crystallization kinetics of poly(3-hydroxybutyrate-co-3-hydroxyvalerate)/clay nanocompo-sites. Journal of Applied Polymer Science, 93(2), pp.655-661.
[26] An, A., Lu, A., Sun, Q., Wang, J. and Li, W., 2011. Gold nanoparticles stabi-lized by a flake-like Al2O3 support. Gold Bulletin, 44(4), pp.217-222.
[27] Cao, M., Yan, Q., Li, X. and Mi, Y., 2014. Effect of plate-like alumina on the properties of alumina ceramics prepared by gel-casting. Materials Science and Engineering: A, 589, pp.97-100.
[28] Farhan, A., 2020. Effect of Alumina Contents on the Some Mechanical Prop-erties of Alumina (Al2O3) Reinforced Polymer Composites. Neuroquantology, 18(5), pp.35-42.
[29] Jadhav, N., Vetter, C. and Gelling, V., 2019. Characterization and Electro-chemical Investigations of Polypyrrole/Aluminum Flake Composite Pigments on AA 2024-T3 Substrate. ECS Transactions, 41(15), pp.75-89.
[30] Inoue, M., 1989. Alcohothermal Treatments of Gibbsite: Mechanisms for the Formation of Boehmite. Clays and Clay Minerals, 37(1), pp.71-80.
[31] Liu, W., Ullah, B., Kuo, C. and Cai, X., 2019. Two-Dimensional Nano-materials-Based Polymer Composites: Fabrication and Energy Storage Appli-cations. Advances in Polymer Technology, pp.1-15.
[32] Tan, C., Cao, X., Wu, X., He, Q., Yang, J., Zhang, X., Chen, J., Zhao, W., Han, S., Nam, G., Sindoro, M. and Zhang, H., 2017. Recent Advances in Ul-trathin Two-Dimensional Nanomaterials. Chemical Reviews, 117(9), pp.6225-6331.
[33] Jung, Y., Zhou, Y. and Cha, J., 2016. ChemInform Abstract: Intercalation in Two-Dimensional Transition Metal Chalcogenides. ChemInform, 47(26).
[34] Nicolosi, V., Chhowalla, M., Kanatzidis, M., Strano, M. and Coleman, J., 2013. Liquid Exfoliation of Layered Materials. Science, 340(6139), pp.1226419-1226419.
[35] Singh, B., Jena, B., Bhattacharjee, S. and Besra, L., 2013. Development of oxidation and corrosion resistance hydrophobic graphene oxide-polymer composite coating on copper. Surface and Coatings Technology, 232, pp.475-481.
[36] Spitalsky, Z., Tasis, D., Papagelis, K. and Galiotis, C., 2010. Carbon nano-tube–polymer composites: Chemistry, processing, mechanical and electrical properties. Progress in Polymer Science, 35(3), pp.357-401.
[37] Bigg, D., 1979. Mechanical, thermal, and electrical properties of metal fi-ber-filled polymer composites. Polymer Engineering and Science, 19(16), pp.1188-1192.