透過您的圖書館登入
IP:44.215.110.142
  • 學位論文

片狀氧化鋁及稜角狀莫來石於氧化鋁基材上生成機制之研究

Study on the Formation mechanism of Tabular Al2O3 and Prismatic Mullite Formation on Alumina Substrate

指導教授 : 韋文誠

摘要


本研究使用氧化鋁-氧化矽雙相溶膠(diphasic aluminum silicate sol)在多孔及緻密氧化鋁基材上,以低於共晶溫度(1560oC)的熱處理條件(1280oC)形成鍍膜。在多孔氧化鋁基材上,生成片狀(tabular)氧化鋁的互鎖(interlock)結構;而在緻密96%純度氧化鋁基材上,則生成針狀(acicular)莫來石的互鎖結構。 實驗中以矽酸四乙酯(TEOS,tetraethlylorthosilicate)和氫氧化鋁(boehmite)分別當作鋁、矽原子的來源,形成氧化鋁-氧化矽雙相溶膠。在固定鋁矽莫耳比為莫來石當量比3Al2O3•2SiO2的條件下,利用旋轉塗佈法(spin coating)在氧化鋁基材上生成雙相氧化鋁-氧化矽(簡稱DAS)薄膜,經過乾燥和1280oC熱處理得到具有非等向晶粒鍍膜的高溫陶瓷複合材料。所得到的複合材料經由X光繞射儀(XRD)、掃描式電子顯微鏡暨能量分析光譜儀(SEM&EDX)、與分析式穿透電子顯微鏡(AEM)及電子能量損失譜儀(EELS)來進行成分及微結構的觀察。研究中採用不同的純度、鍍膜成分或熱處理條件等製程參數,並製備多種條件的多孔陶瓷TEM樣品,針對非等向晶粒在氧化鋁基材上生成的機制進行探討。 DAS鍍膜在多孔氧化鋁基材上會形成以片狀氧化鋁為主的層狀結構。在薄膜中,片狀晶交錯生成,產生微米級的孔洞,一片狀氧化鋁晶粒中含有數個方向相同的次片狀晶(sub-tabular grain),片狀晶的最大平面為(000h)AlO。同一個片狀晶中的次片狀晶晶粒生長方向略有不同,但不論成分鑑定或晶相分析皆能証明其為氧化鋁。 在96%緻密氧化鋁基材上的DAS薄膜經燒結後會生成針狀莫來石。經過TEM的晶相分析,針狀莫來石具有的軸向(zone direction)為[001]M,長度為5-20

並列摘要


In this study, diphasic aluminum silicate sol (M) was coating on porous or dense alumina substrate to form a covering layer (DAS) and then sintered at 1280oC, which was below eutectic temperature (1560oC) of Al2O3-SiO system. A gradient, porous Al2O3 substrate was prepared with the characteristics of micro-sized tabular grains on surface, fine interlocking of Al2O3 grains in matrix. Acicular mullite grains were formed on dense Al2O3 substrate with interlocking structure. The sample was made by spin-coating alumina substrates with diphasic gel made by pseudo-boehmite (AlOOH) and hydrolyzed TEOS [Si(OC2H5)4]. After drying and sintering at different heat treatments, which at the temperature 1280oC, the crystallography and microstructure of the porous structure was investigated by analytical electron microscopy (AEM), X-ray differactometry (XRD), and scanning electron microscopy (SEM). Detailed micro-beam compositional and structural analyses were conducted in order to verify the glassy phase and abnormal Al2O3/ mullite grains. The abnormal grain growth of Al2O3 grains is possibly due to the transient SiO2-glass phase during sintering above 1250oC. The formation of tabular grains is due to a heterogeneous nucleation from faceted grain of Al2O3/Glass interface, ripening from transient Al2O3 nano-crystals through amorphous SiO2 glass. The reactions are limited to regions where the density is higher, and results in a perpendicular growth of plate-like grains on the substrate. Ostwald ripening in association with the rearrangement of small transient

參考文獻


M. G. M. U. Ismail, Z. Nakai, and S. Somiya, “Microstructure and Mechanical Properties of Mullite Prepared by Sol-Gel Method,” J. Am. Ceram. Soc., 70, C7-C8, (1987).
G.P Souza, E. Rambaldi, A. Tucci, L.Esposito, and W. E. Lee, “Microstructural Variation inPorcelain Stoneware as a Function of Flux System,” J. Am. Ceram. Soc., 87 [10] 1959-1966 (2004)
A. J. Pyzik and C. G. Li, “New Design of a Ceramic Filter for Diesel Emission Control Application,” Int. J. Applied Ceramic Technology, 2, 6, 440-51 (2005).
Phase Diagrams for Ceramists I-IIIV, printed by American Ceramic Society, Columbus, Ohio, USA (1964-
S. H. Risbud and J. A. Pask, “SiO2-Al2O3 Metastable Phase Equilibrium Diagram without Mullite,” J. Mater. Sci., 13 [11] 2449-2454 (1978).

被引用紀錄


Chen, H. Y. (2005). 分散劑於α–氧化鋁表面之吸附研究 [master's thesis, National Taiwan University]. Airiti Library. https://doi.org/10.6342%2fNTU.2005.02461

延伸閱讀