https://scholars.lib.ntu.edu.tw/handle/123456789/64943
標題: | 固化界面失穩及型態發展之非線性解析及可視化研究(3/3) | 作者: | 藍崇文 | 關鍵字: | 定量相場模擬;等拉速凝固實驗 | 公開日期: | 31-十月-2005 | 出版社: | 臺北市:國立臺灣大學化學工程學系暨研究所 | 摘要: | 我們首次以定量相場模擬琥珀腈/丙酮合金薄膜固化在接近Mullins-Sekerka 不穩定區的型態轉變過程。並做長時間/長樣品的等拉速凝固實驗比較之。模擬 結果從平整界面失穩到λ c ↔λ c/2 細 胞分歧區與古典理論相當吻合;其中λ c 為臨 界波長。在較高拉速區,我們並引入反向溶質通量來維持局部熱力學平衡,並發 現V λ 2 約為常數的區域。最後在波長接近四分之一的臨界波長時,更有巒生細胞 的出現。實驗中由於有限的溶區長度,在等拉速下有溶質累積,我們可觀察到類 似模擬中變拉速(固定濃度)的型態轉變。模擬與實驗也同樣的觀察到細胞分裂, 結合,溶質覆胞脫離,與非對秤細胞等有趣的非線性行為。 The morphological transitions of shallow cells near the onset of Mullins-Sekerka instability during the thin-film directional solidification of a succinonitrile/acetone alloy have been simulated quantitatively by means of phase field modeling for the first time. Long time/length scale experiments at a constant pulling speed were performed for the purpose of comparison. The simulation results show good agreement with classic theories in the planar and c c/2 cellular bifurcation regions, where c is the critical wavelength. At a higher pulling speed, V, an anti-trapping current was introduced to maintain the local equilibrium, and the region for V 2~constant was found. Finally, multiplets appeared when was close to c/4. In the experiments, due to slow solute accumulation in the molten zone, morphological transitions were also revealed. Some interesting nonlinear phenomena, such as tip splitting, coarsening, pinch-off, and asymmetric cells, were also confirmed through both simulations and experiments. |
URI: | http://ntur.lib.ntu.edu.tw//handle/246246/9413 | 其他識別: | 932214E002009 | Rights: | 國立臺灣大學化學工程學系暨研究所 |
顯示於: | 化學工程學系 |
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932214E002009.pdf | 2.92 MB | Adobe PDF | 檢視/開啟 |
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