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| 題名: | 高溫高壓水熱法合成矽酸鈾、水合氫氧化氧鈾及砷酸鈾化合物的結構與性質量測;High-Temperature, High-Pressure Hydrothermal Synthesis, Crystal Structures, and Properties of Uranium Silicates, Oxyhydroxides, and Arsenates |
| 作者: | 劉信寬;Liu, Hsin-Kuan |
| 貢獻者: | 化學學系 |
| 關鍵詞: | 高溫高壓水熱法;鈾化合物;矽酸鈾;水合氫氧化氧鈾;砷酸鈾;high-temperature, high-pressure hydrothermal method;uranium compounds;uranium silicates;uranium oxyhydroxides;uranyl arsenates |
| 日期: | 2018-07-30 |
| 上傳時間: | 2018-08-31 11:33:54 (UTC+8) |
| 出版者: | 國立中央大學 |
| 摘要: | 本論文使用高溫高壓水熱法，合成十個新穎的鈾化合物，並將其分為三個系列介紹：A系列矽酸鈾化合物：包含 Cs2USi6O15 (A1) 、 Cs2USi3O9 (A2) 、 Cs2(UO2¬)Si10O22 (A3) 、 Cs2USiO6 (A4) 、 Na2(UO2)Si4O10·0.5H2O (A5) 、及 K2(UO2)Si4O10 (A6)；B系列水合氫氧化氧鈾化合物：Na5[U5O16(OH)2] (B1) 與 Na5[U5O17(OH)] (B2)；C系列砷酸鈾化合物：Na14(UO2)5(AsO4)8·2H2O (C1) 與 Rb4(UO2)3O2(AsO4)2 (C2)。所有化合物皆以單晶 X 光繞射方法收集數據並進行結構解析，利用粉末 X 光繞射進行樣品純度比對。化合物A1與B1利用 X 光光電子能譜分析結構中鈾的氧化態；化合物A5與C1利用熱重分析儀分析比對結構中結晶水的數目；化合物A3利用固態核磁共振儀分析結構中矽的配位環境與單晶數據做驗證比對；化合物A3與C1進行螢光光譜分析量測得知樣品的放光特性。
A系列化合物中，化合物A1是第一個經由人工方法合成得到具有鈾四價結構的矽酸鈾化合物。化合物A1、A3與A6的結構中具有 SiO4 四面體所構成的矽酸層；化合物A5結構中具有 SiO4 構成如同管子一般的矽酸鏈。化合物A1到A4是在相似的合成環境，藉由調整溶劑 CsOH(aq) 與 CsF(aq) 的比例獲得。pH值在化合物A5與A6的合成上扮演很重要的角色，僅能在弱鹼的環境中才能獲得化合物A5與A6。
化合物B1與B2兩者皆為層狀結構化合物。在B1化合物的合成反應中額外添加還原金屬 Zn ，使得鈾在結構產生混價態 U(V, VI) ，且其陰離子拓撲形式與文獻上的礦物 sayrite 相同。B2化合物的反應與B1的差異在不添加還原金屬 Zn 。結構上B2與B1結構有著相似的陰離子拓撲形式。
化合物C1與C2的結構均為鈾氧多面體與砷氧四面體所構成的層狀結構。C1是由 UO7 平面雙五角錐與 AsO4 四面體共點連接形成的鏈，經 UO6 構成的平面雙四角錐連接形成層；C2結構中具有2個 UO7 的平面雙五角錐共邊形成二聚體，並與 UO8 的平面雙六角錐共邊形成鈾氧直鏈，此直鏈再經由 AsO4 形成的四面體經共點與共邊的方式形成層。
;This thesis reports ten uranium compounds which are divided into three series. Series A, uranium silicates, contains six compounds. They are Cs2USi6O15 (A1), Cs2USi3O9 (A2), Cs2(UO2¬)Si10O22 (A3), Cs2USiO6 (A4), Na2(UO2)Si4O10·0.5H2O (A5), and K2(UO2)Si4O10 (A6). Series B, uranium oxyhydroxides, comprises two compounds, Na5[U5O16(OH)2] (B1) and Na5[U5O17(OH)] (B2). Series C, uranyl arsenates, holds Na14(UO2)5(AsO4)8·2H2O (C1) and Rb4(UO2)3O2(AsO4)2 (C2). All of the above compounds were synthesized by high-temperature, high-pressure hydrothermal method and their crystal structures determined by single-crystal X-ray diffraction. The purity was investigated by powder X-ray diffraction. The amounts of the lattice water of A5 and C1 were determined by thermogravimetric analysis. The oxidation states of uranium in A1 and B1 were confirmed by X-ray photoelectron spectroscopy. The solid-state 29Si NMR and photoluminescence spectra of some of the compounds were also measured.
A1 is the first synthetic U(IV) silicate in the literature. A1, A3 and A6 contain layers of silicate in their structures. A1, A2, A3 and A4 were synthesized under similar reaction conditions by adjusting the relative amounts of CsOH(aq) and CsF(aq). A5 and A6 could only be obtained from weakly alkaline solution.
Both B1 and B2 adopt layer structures. B1 is an unusual mixed-valence uranium (V, VI) oxyhydroxide which was synthesized by using zinc powder as a reducing agent. The overall anion topology of B1 is the same as that of the uranyl mineral sayrite. Under the same experimental conditions, the reaction without zinc powder yielded a uranyl oxyhydroxide, B2, which has a new sheet structure. Its sheet anion topology is closely related to that of B1.
C1 and C2 have layer structures that consist of uranyl polyhedra and arsenate tetrahedra. C1 has a double layer structure which is formed of uranyl pentagonal bipyramids, arsenate tetrahedra and discrete uranyl square bipyramids. The structure of C2 contains infinite chains which are built up from two uranyl pentagonal bipyramids and one uranyl hexagonal bipyramid by sharing their edges. These chains are linked by corner-sharing AsO4 tetrahedra to form a layer structure. |
| 顯示於類別: | [化學研究所] 博碩士論文
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