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Title: | 非晶態碳酸鈣相演化與含鎂方解石介晶之形成機制 Phase evolution of amorphous calcium carbonate and the formation mechanism of Mg-calcite mesocrystals |
Authors: | Chieh Tsao 曹杰 |
Advisor: | 陳振中 |
Keyword: | 非晶態含鎂碳酸鈣,高鎂方解石介晶,暗場成像,液相燒結,Rietveld analysis,非晶態碳酸鈣,XANES, magnesian amorphous calcium carbonate,mesocrystals of high-magnesium calcites,dark field image,Rietveld analysis,amorphous calcium carbonate,XANES, |
Publication Year : | 2018 |
Degree: | 碩士 |
Abstract: | 高鎂含量方解石介晶普遍存在於生物礦物中,但難以用實驗合成出來。在本實驗中,通過非晶態含鎂碳酸鈣 (MgACC) 在脂質水溶液中的相轉化,成功合成出高鎂方解石介晶。利用穿透式電子顯微鏡的選定區域電子衍射圖以及暗場推斷出MgACC利用二次成核形成了介晶的結構,除了相轉化的探討,還結合其他分析技術,如SEM、TXM、NMR、HRXRD等,探討脂質在溶液中扮演的角色以及雙半球構形的生長機制,發現脂質可能與碳酸鈣有特殊的作用力,而雙半球的形成可能與液相燒結 (LPS) 機制有關。除了溶液狀態時的相轉化探討外,本研究還涉及樣品在高濕度下的相轉化,發現部分實驗條件樣品會在此環境下長出fiber的結構,可能為後續長出spicule的中間態。
本實驗第二部分利用XANES變溫實驗在高真空以及0.4 mbar水氣的環境來研究ACC相轉過程,發現環境水的是ACC相轉的關鍵,且ACC的相轉可能為相轉帶動脫水,而非脫水帶動相轉。 Mesocrystals of high-magnesium calcites are commonly found in biominerals but are difficult to prepare in vitro under ambient conditions. In this work, mesocrystals of high-magnesium calcite were successfully synthesized through the phase transformation of magnesian amorphous calcium carbonate (Mg-ACC) in aqueous solution with lipids. From the selected area electron diffraction patterns and the dark field transmission electron microscopic images, we infer that the mesocrystals are formed via the solid-state secondary nucleation within Mg-ACC. The role of lipids in the phase transformation process was studied by 13C and 31P NMR spectroscopy. We also investigate the phase transition of ACC by X-ray absorption spectroscopy (XAS). In particular, ACC was characterized by XAS at different temperatures under either ultra high vacuum or a water atmosphere of 0.4 mbar. We found that moisture in the environment is the key for the phase transition of ACC. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/71070 |
DOI: | 10.6342/NTU201802132 |
Fulltext Rights: | 有償授權 |
Appears in Collections: | 化學系 |
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ntu-107-1.pdf Restricted Access | 7.07 MB | Adobe PDF |
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