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  • 學位論文

離子雜質對碳酸鈣薄膜晶型之影響

Effects of Ionic Impurity on the Polymorphism of CaCO3 Thin-Film

指導教授 : 戴怡德

摘要


生物礦物為具有極佳特性的有機/無機複合材料,如貝殼中的珍珠層係由碳酸鈣及蛋白質所構成,雖然碳酸鈣的強度低且極脆,而珍珠層卻具有極佳的硬度及韌性,其原因係珍珠層是以一層層的霰石板片及有機物所堆積而成,如此特殊的層狀結構,以及霰石晶型缺乏晶劈面的特性,使得珍珠層具有如此優異的特性。為了製備此仿生材料,文獻中採用雙注射法、擴散法和CO2通氣法,而周哲宇(2011)在本實驗室採用溶液流動法,將碳酸鈣過飽和溶液組成控制於介穩區內,並且加入可溶性高分子,使得碳酸鈣薄膜可成長於固體模板上。此方法控制變數較為容易,且配置時間短(約1小時),並且可將薄膜的成長時間由數天縮短至數小時。而碳酸鈣具有不同的多晶型,這些多晶型由於它們的晶型結構不同,而具有不同的性質,因此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。 本實驗一開始先重覆周哲宇(2011)探討pH效應的實驗,從實驗結果中發現,周哲宇(2011)在40℃下,且無磁場及雜質時,於pH=9.0~10.5間,所成長出的碳酸鈣薄膜,具有方解石、球型方解石及霰石三種晶型,而在本研究中,只出現了球型方解石及霰石兩種晶型,因此推測時間效應可能為造成方解石晶型形成的因素。然後由本實驗證明,當溶液放置時間變長,的確會形成熱力學上最為穩定的方解石晶型。 由本實驗室多年的經驗得知,磁場有無、溫度高低、以及雜質離子對於碳酸鈣的晶型皆有很大的影響,因此本研究將此三種變數視為實驗變因,探討單變因及多變因對於碳酸鈣薄膜晶型的影響。當溶液通過磁場後立即進入成長槽可有效增加霰石晶型的比例;提升溫度亦有助於霰石晶型比例的提升;而共同施予磁場作用並且提升溫度,則發現霰石晶型提升的比例有加成的效果,可得到幾乎100%的霰石薄膜。在添加雜質離子的實驗中,根據Roques和Girou (1974)對雜質的分類,本研究分別選用一類有助於霰石晶型成長(Mg2+、Fe2+),以及另一類促進方解石晶型成長的雜質(Sr2+、Ba2+),來進行添加雜質效應對碳酸鈣薄膜晶型的影響。以下添加Mg2+、Sr2+、Ba2+的效應,皆與在40℃下、[Ca2+]/[COO-] =55、未施加磁場且無雜質時之結果比較,此情況下,霰石比例為28.03%而球型方解石比例為71.46%。而添加Fe2+的效應, 則與[Ca2+]/[COO-] =35之結果比較,因為FeCO3之溶解度極低,因此吾人增加PAA的量以抑制成核,在此情況下,霰石比例為24.47%而球型方解石比例為74.70%。添加[Mg2+]/[Ca2+]= 0.2及0.4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100%,而在[Mg2+]/[Ca2+] =0.5時,無球型方解石但有方解石晶型的出現,且方解石的含量隨PAA含量而變化,當[Ca2+]/[COO-] =55變至30,方解石比例由51.62%提升至82.61%;在 [Fe2+]/[Ca2+]=2.07*10-3~4.43*10-3,則會導致霰石晶型從無Fe2+時之24.47%增加至29.91~33.70%,並且使方解石晶型從0.83%增加至5.30%~11.33%;而添加[Sr2+]/[Ca2+]=0.011~0.11,則使霰石晶型從28.03%增加至約48%;最後,添加[Ba2+]/[Ca2+]=0.121~0.141,則發現會完全抑制霰石晶型,並且使方解石晶型從0.51%增加至16.32%~20.06%,而球型方解石也從71.46%增加至79.94%~83.68%。接著探討兩個變數之交互作用。 [Mg2+]/[Ca2+] =0.5,PAA添加量為[Ca2+]/[COO-] =30~55時,在40℃及無磁場下,無球型方解石,霰石比例為17.39%~48.38%。在施加磁場下,會使霰石晶型提升至51.27%~69.77%;當溫度提升至50℃且無磁場時,能使霰石晶型比例達100%。而在[Ba2+]/[Ca2+] =0.121~0.141,40℃下及無磁場時,無霰石,且球型方解石比例為79.94%~83.68%。當溫度提升至50℃且無磁場時,會使球型方解石晶型從提升至91.25%~92.57%;而在40℃下施加磁場時,則能使球型方解石比例達100%。

並列摘要


Biominerals are organic / inorganic composite materials with excellent characteristics formed in nature. For example, calcium carbonate is brittle, but the nacre of the shell, which is composed of calcium carbonate and protein, has excellent hardness and toughness. Through the observation of its microstructure, the nacre of the shell is made of layered aragonite and proteins. The layered hybrid structure and the absence of cleavage planes of aragonite let the nacre have such excellent features. In order to prepare this biomimetic material, the double-jet method, diffusion method, and Kitano method have been applied. On the other hand, Chou (2011) used the technique developed in our laboratory for preparing the supersaturated CaCO3 solution stablized in the metastable region, so that a thin-film of CaCO3 had been successfully prepared on the surface of a solid matrix from the supersaturated solution in the presence of a soluble polymer. This method has several advantages, such as the ease for controlling the solution properties, the simple procedure for preparing supersaturated solution, and the shorted time (several hours) for growing the CaCO3 thin-film. The calcium carbonate has three polymorphs formed in the biominerals with different crystal structures and properties. If we intend to develop biomimetic materials, the control of polymorphism is an extremely important issue. At the beginning of this study, we tried to repeat the pH effect on the polymorphism of CaCO3 thin-film synthesized by Chou (2011) who found that the CaCO3 thin-film grown at 40 ℃, and pH between 9.0 and 10.5 contained calcite, vaterite, and aragonite. On the other hand, the CaCO3 thin-film formed under the same solution properties in this study was a mixture of vaterite and aragonite. Since calcite is the most stable form, the formation of calcite could be caused by the time effect. And then we did show that calcite would form by circulating the supersaturated solution over 20h before the start of growth. From the experience of our laboratory, we knew that the magnetic field, temperature level, and ionic impurity ions influenced the polymorphism of calcium carbonate. In this study, we took these variables into consideration in the preparation of CaCO3 thin-film; first, the individual effect of variables and then the interaction between variables. The magnetic field and higher temperature would be effective to increase the proportion of aragonite. Moreover, the magnetic field and temperature had a synergetic effect on the formation of aragonite to form a pure product. On the effect of ionic impurity, we chose from the two groups classified by Roques and Girou (1974); one for favoring aragonite (Mg2+ and Fe2+) and the other one for favoring calcite (Sr2+ and Ba2+). The effect of Mg2+, Sr2+, and Ba2+ were compared with the result of 28.03% aragonite and 71.46% vaterite obtained at 40 ℃ and [Ca2+]/[COO-]=55, with no magnetic field applied and no impurities presented. However, the effect of Fe2+ was compared with the result of [Ca2+]/[COO-]=35, which contained 24.47% aragonite and 74.70% vaterite, because the solubility of FeCO3 is low. At the ratio of [Mg2+]/[Ca2+]= 0.2 and 0.4, vaterite was inhibited completely, and the 100% aragonite film formed. At the ratio of [Mg2+]/[Ca2+]=0.5, calcite would appear. The proportion of calcite increased from 51.62% to 82.61% with increasing the PAA concentration by decreasing the [Ca2+]/[COO-] from 55 to 30. At the ratio of [Fe2+]/[Ca2+]= 2.07*10-3~4.43*10-3, the proportion of aragonite would increase from 24.47% (no Fe2+) to 29.91~33.70%, and the proportion of calcite would increase from 0.83% (no Fe2+) to 5.30%~11.33%. At the ratio of [Sr2+]/[Ca2+]= 0.011~0.11, the proportion of aragonite would increase from 28.03% (no Sr2+) to about 48%. Finally, at the ratio of [Ba2+]/[Ca2+]= 0.121~0.141, aragonite was inhibited completely, and not only increased the proportion of calcite from 0.51% (no Ba2+) to 16.32%~20.06%, but also increased the proportion of vaterite from 71.46% (no Ba2+) to 79.94%~83.68%. Next, we investigated the interaction between variables. The film contained no vaterite and the proportion of aragonite was 17.39%~48.38% measured at 40 ℃and [Ca2+]/[COO-]=30~55, with no magnetic field applied and [Mg2+]/[Ca2+]= 0.5. With magnetic field applied, the proportion of aragonite increased to 51.27%~69.77%. At 50 ℃ and with no magnetic field applied, 100% aragonite was obtained. When Ba2+ was present, for a [Ba2+]/[Ca2+]= 0.121~0.141, the film contained no aragonite and the proportion of vaterite was 79.94%~83.68% measured at 40 ℃, with no magnetic field applied. At 50 ℃, the proportion of vaterite increased to 91.25%~92.57%. At 40 ℃ and with magnetic field applied, 100% vaterite was obtained.

參考文獻


張煥杰,「磁場、溫度與雜質對於文石及方解石晶體成長之影響」,碩士學位論文,台大化工所 (2010)
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周哲宇,「操作變數對CaCO3/有機複合薄膜之影響」,碩士學位論文,台大化工所 (2011)

被引用紀錄


鄭宇辰(2013)。多種金屬離子雜質對碳酸鈣薄膜晶型影響之探討〔碩士論文,國立臺灣大學〕。華藝線上圖書館。https://doi.org/10.6342%2fNTU.2013.00660

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