多種金屬離子雜質對碳酸鈣薄膜晶型影響之探討

Exploring the Effects of Various Metal Ionic Impurities on the Polymorphism of CaCO3 Thin-film

鄭宇辰(Yu-Chen Cheng)

指導教授 ： 王勝仕

共同指導教授 ： 戴怡德(Clifford Yi-Der Tai)

國立臺灣大學/工學院/化學工程學研究所/碩士(2013年)

https://doi.org/10.6342/NTU.2013.00660

摘要

生物礦化(biomineralization)為自然界中生物用以製造生物礦物的重要程序，而生物礦物中之貝殼，其具有之珍珠層即以一層層的霰石板片及有機物所堆積而成，特殊的層狀結構及霰石晶型缺乏晶劈面的特性，使珍珠層擁有極佳的硬度及韌性。為了研究此種複合結構，必須先分析單層之無機/有機複合碳酸鈣薄膜，而在薄膜的製備方面，文獻中採用雙注射法、擴散法、及CO2通氣法。周哲宇(2011)及王媛婷(2012)曾採用溶液流動法配製位於介穩區之碳酸鈣過飽和溶液，並加入可溶性高分子使碳酸鈣薄膜成長於固體模板上。此方法與以往製備薄膜之方法比較，具有以下三項優點：控制操作變數較容易、溶液配置時間短(約1小時)、及將薄膜的成長時間由數天縮短至數小時。因碳酸鈣具有三種不同的多晶型，此些多晶型由於它們晶型上的結構不同，而具有不同的性質，故在發展仿生材料的過程中，晶型的控制為一極為重要的課題。
本研究首先重複王媛婷(2012)探討pH效應及添加兩種離子雜質(Mg2+、Fe2+)效應之實驗；從實驗結果發現，本研究於同樣之條件下，生成之薄膜成長量及晶型特徵峰皆較王媛婷者(2012)為低；推測成長速率下降結果之差異可能來自兩研究中所使用之藥品來源不同所致。經由提升相對過飽和度的實驗證明，不論有無雜質離子存在下成長之碳酸鈣薄膜，其薄膜覆蓋率及XRD特徵峰強度皆有明顯上升。
由本實驗群多年的經驗得知，碳酸鈣的晶型明顯地受到如磁場、溫度、雜質離子的存在與否、pH值、及相對過飽和度等操作變數之影響。而王媛婷(2012)已探討了前三種操作變數對於碳酸鈣薄膜晶型的影響，而本研究延續其雜質離子效應之實驗，探討另外三種離子雜質(Zn2+、Cu2+、Mn2+)對碳酸鈣薄膜晶型之影響。
而本研究將溶液相對過飽和度提升至12後，以在40℃下、[Ca2+]/[COO-] =55、且無雜質時之結果當作參考值，以利於與添加不同離子雜質之結果進行比較；在此情況下，霰石比例為34.82%而球型方解石比例為65.18%。當添加[Mg2+]/[Ca2+]=0.2時，霰石晶型比例由34.82%提升至60.16%，而添加[Mg2+]/[Ca2+]=0.4及0.5時，會完全抑制球型方解石的生成，並且使霰石晶型比例幾乎達到100%；在添加[Fe2+](mg/L) =0.62~1.64時，則會導致霰石晶型從無Fe2+時之34.82%些微增加至40.11~41.31%，並且產生微量的方解石晶型，其比例介於0%~7.57%；而添加Zn2+、Cu2+之組別則由於XRD特徵峰不明顯，無法計算晶型比例；添加Cu2+之結果則與添加Zn2+者類似：添加[Zn2+](mg/L)=0.11或[Cu2+](mg/L)=0.082時，薄膜由霰石及球型方解石晶型構成，但其特徵峰強度大幅下降；[Zn2+](mg/L)=0.21或[Cu2+](mg/L)=0.164時，薄膜完全由球型方解石構成；而當[Zn2+](mg/L)=0.53或[Cu2+](mg/L) =0.414時，雖然無法於XRD結果觀察到特徵峰，但在[Cu2+](mg/L) =0.414時由POM可觀察到細小之霰石薄膜；最後，添加[Mn2+](mg/L) =0.616~2.466時，會大幅抑制霰石的成長，使霰石晶型由34.82%降至1.63%，並可使球型方解石由65.18%成長至95.27%，但對於方解石晶型並無明顯促進效果。

關鍵字

仿生材料 ； CaCO3/有機複合薄膜 ； 相對過飽和度 ； 離子雜質

並列摘要

Biomineralization is an important process which organisms use to produce biominerals in nature. One of the biominerals, for example, the nacre of the shell in the ocean is made of layered aragonite and proteins. The layered hybrid structure and the absence of cleavage planes of aragonite allow the nacre to acquire certain excellent properties such as hardness and toughness. To investigate this composite structure, we have to analyze the single-layered organic / inorganic composite calcium-carbonate thin-film first. In order to prepare this biomimetic material, serveral method including double-jet method, diffusion method, and Kitano method have been employed. In addition, Chou (2011) and Wang (2012) used the technique developed in Professor Tai’s laboratory to prepare the supersaturated CaCO3 solution stabilized in the metastable region, and a thin-film of CaCO3 was successfully prepared on the surface of a solid matrix from the supersaturated solution in the presence of a soluble polymer. This method has three advantages over the others: the ease for controlling the solution properties, the simple procedure for preparing supersaturated solution, and the time-effectiveness for growing the CaCO3 thin-film. The calcium carbonate has been found to exhibit three polymorphs formed in the biominerals. Given that the difference in crystal structures between polymorphs results in their property distinction, the control of polymorphism is of primary importance in developing biomimetic materials.
In the first part of this research work, efforts were directed toward exploring how the polymorphism of CaCO3 thin-film was affected by pH and ionic impurity (Mg2+、Fe2+) in the experimental conditions which were identical to the ones used in Wang (2012). A lower growth rate of CaCO3 thin-film formation and smaller characteristic peaks of associated XRD spectrum were observed in this work, as compared with the results reported in Wang (2012). We speculated that the difference between the results of this and Wang’s studies might be attributed to the batch-to-batch variation of the chemicals used. We found that the growth rate and the intensities of characteristic peaks of XRD spectrum could be raised by increasing the relative supersaturation of the supersaturated CaCO3 solution.
Results of our group, indicates that the polymorphism of calcium carbonate can be profoundly affected by several operating variables, including the magnetic field intensity, temperature, type of ionic impurity, pH value, and relative supersaturation. Wang (2012) have explored the effects of the first three operating variables. As a continuation, we examined the effects of three ionic impurities (Zn2+、Cu2+、Mn2+) on the polymorphism of CaCO3 thin-film in this thesis.
Our results showed that, when no ionic impurity was present (the control group), 34.82% aragonite and 65.18% vaterite were observed at the relative supersaturation of 12, 40 ℃ and [Ca2+]/[COO-]=55. At the [Mg2+]/[Ca2+] ratio of 0.2, the composition of aragonite increased from 34.82% to 60.16%. When the [Mg2+]/[Ca2+] ratios=0.4 and 0.5, the formation of vaterite was completely suppressed, and the 100% aragonite film was formed. When [Fe2+] was increased from 0 to 0.62-1.64 mg/L, the proportion of aragonite was found to increase from 34.82% (with no Fe2+) to 40.11~41.31%, whereas the proportion of calcite rose from 0% (with no Fe2+) to 0%~7.57%. However, the composition of polymorphism of CaCO3 thin-film in the presence of Zn2+ and Cu2+ due to the insignificant characteristic peaks of XRD spectrum. Similar results were obtained in the groups with the treatment of Cu2+ and Zn2+. At [Zn2+]=0.11 mg/L or [Cu2+]=0.082 mg/L, the polymorphism was composed of vaterite and aragonite, but the intensity of characteristic peaks of XRD spectrum considerably decreased. At [Zn2+]=0.21 mg/L or [Cu2+]=0.164 mg/L, the polymorphism was only composed of vaterite. At [Zn2+]=0.53 mg/L or [Cu2+]=0.414 mg/L, no characteristic peaks were observed in the XRD spctrum, whereas tiny aragonite thin-films were found at the surface of solid matrix of Cu2+ sample through POM. Moreover, while no change in the composition of calcite was detected, the proportion of aragonite was significantly decreased from 34.82% in the control group (with no Mn2+) to 1.63% when the concentration of Mn2+ was increased from 0 to 0.616~2.466 mg/L.

並列關鍵字

biomimetic material ； CaCO3/organic hybrid thin-film ； supersaturation effect ； ionic impurity effect

參考文獻

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