本文選題：鈣鐵磷酸鹽玻璃　切入點(diǎn)：稀土元素　出處：《西南科技大學(xué)》2015年碩士論文　論文類(lèi)型：學(xué)位論文

【摘要】：基于鈣鐵磷酸鹽玻璃對(duì)核素包容量大、熔融溫度與高溫粘度、優(yōu)良的化學(xué)穩(wěn)定性等特點(diǎn),同時(shí)考慮到稀土元素與錒系元素在化合價(jià)、核外電子排布和配位數(shù)相同時(shí)離子半徑等基本相似,導(dǎo)致與錒系元素難于實(shí)現(xiàn)分離,而且部分稀土元素為高放廢物的主要裂變產(chǎn)物。因此,本課題采用X射線(xiàn)衍射(XRD)、掃描電子顯微鏡(SEM)、傅里葉變換紅外光譜(FT-IR)、拉曼光譜(Raman spectroscopy)、紫外可見(jiàn)光譜(UV-vis spectroscopy)和差示掃描量熱法(DSC)等測(cè)試手段研究了鈣鐵磷酸鹽玻璃及利用該基質(zhì)玻璃包容釔(Y)、鑭(La)、釹(Nd)、釤(Sm)、釓(Gd)五種稀土元素形成的玻璃固化體的結(jié)構(gòu)、熱穩(wěn)定性和表面形貌。研究表明:1、該鈣鐵磷酸基質(zhì)玻璃xCaO (32 x)Fe2O3 68P2O5有寬廣的玻璃形成范圍。光譜分析闡明了在該玻璃體系中CaO含量少于16 mol%時(shí),使玻璃網(wǎng)絡(luò)中的P O-轉(zhuǎn)變?yōu)?P O-Ca2+-O P)鏈,從而使玻璃結(jié)構(gòu)更加緊密,導(dǎo)致了硬度的提高和玻璃化轉(zhuǎn)變溫度的升高;當(dāng)CaO含量大于16 mol%時(shí),鈣離子通過(guò)代替P O P和P O Fe形成了(P O-C a2+-O P)和P O C a,致使玻璃的化學(xué)穩(wěn)定性下降。隨著CaO代替Fe2O3,該基質(zhì)玻璃由焦磷酸鹽結(jié)構(gòu)轉(zhuǎn)變?yōu)槠姿猁}鏈,從而樣品平均磷酸鹽鏈的長(zhǎng)度增大以及非橋氧的含量降低。對(duì)玻璃樣品兩步的熱處理后,確定了其主要析晶態(tài)隨CaO含量的變化規(guī)律,僅FePO4析晶相易被酸蝕。CaO的加入導(dǎo)致該玻璃體系的析晶活化能增加,其析晶方式為表面析晶。2、玻璃固化體xY2O3 (100 x)(12CaO 20Fe2O3 68P2O5)能夠包容10 mo l%Y2O3,其填充到玻璃網(wǎng)絡(luò)的空隙中,玻璃固化體的網(wǎng)絡(luò)結(jié)構(gòu)更加緊密,導(dǎo)致了密度的增大和硬度的提高。在玻璃結(jié)構(gòu)中Y2O3的加入使P O P鏈的鍵角減小,而且其可以通過(guò)P O Y鍵代替P O-和P=O,導(dǎo)致固化體主要結(jié)構(gòu)單元的轉(zhuǎn)變,增加了玻璃網(wǎng)絡(luò)的交叉連接。Y2O3含量的變化導(dǎo)致了釔配位數(shù)(NYO)增大。隨著Y2O3含量的增加,玻璃固化體熱穩(wěn)定性的下降。熱處理后的摻雜釔玻璃固化體,由于Y2O3的加入導(dǎo)致析晶相的變化,影響了固化體的析晶特性。3、多種稀土氧化物的玻璃固化體展示了與釔摻雜固化體相似的包容量,過(guò)量的稀土元素導(dǎo)致了析晶態(tài)REPO4的產(chǎn)生�；|(zhì)玻璃中加入RE2O3形成了RE O P,而且高電場(chǎng)強(qiáng)度的陽(yáng)離子提供了更多的非橋氧來(lái)解聚玻璃網(wǎng)絡(luò)。由于摻雜Y磷酸鹽玻璃相比于La磷酸鹽玻璃有更小的P O鍵長(zhǎng),導(dǎo)致了它們硬度的變化。更高配位數(shù)的稀土元素能夠增強(qiáng)玻璃網(wǎng)絡(luò)的交叉連接,從而增強(qiáng)了其機(jī)械性能。隨著稀土離子電場(chǎng)強(qiáng)度的減小,稀土玻璃樣品中非橋氧含量越少。不同稀土玻璃的熱穩(wěn)定性隨稀土離子電場(chǎng)強(qiáng)度值的增大而增強(qiáng)。研究了不同稀土玻璃熱處理后的主要析晶相和其形態(tài),其主要析晶相為FePO4和REPO4,酸浸之后通過(guò)SEM觀(guān)察到REPO4析晶形貌。
[Abstract]:Based on the characteristics of large inclusion capacity of calcium iron phosphate glass to nuclide, melting temperature and viscosity at high temperature, excellent chemical stability, and taking into account the valence of rare earth elements and actinides, When the electron distribution and coordination number are the same, the ion radius is similar, which makes it difficult to separate from actinides, and some rare earth elements are the main fission products of high-level radioactive waste. In this paper, X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy (Raman spectroscopy), UV-vis spectroscopy (UV-vis spectroscopy) and differential scanning calorimetry (DSCS) were used to study the calcium ferric phosphate glass and its utilization. The matrix glass contains the structure of glass solidified by five kinds of rare earth elements: yttrium yttrium, lanthanum, lanthanum, neodymium, neodymium, Sm, and gadolinium. Thermal stability and surface morphologies. The results show that the glass of the calcium ferric phosphate matrix glass xCaO has a wide range of glass formation. The spectral analysis shows that the content of CaO in the glass system is less than 16 mol%, and the content of CaO in the glass system is less than 16 mol%, and the content of CaO in the glass system is less than 16 mol%. The structure of the glass is more compact, which leads to the increase of hardness and the increase of the glass transition temperature when the content of CaO is more than 16 mol%. The chemical stability of the glass was decreased by calcium ions instead of P O O O P and P O O O Fe), and the structure of the matrix glass changed from pyrophosphate structure to metaphosphate chain with the substitution of CaO for Fe 2O 3, and the chemical stability of the glass decreased with the substitution of CaO for Fe 2O 3, and the structure of the matrix glass was changed from pyrophosphate structure to metaphosphate chain. As a result, the average length of phosphate chain increases and the content of unbridged oxygen decreases. After two-step heat treatment of glass samples, the variation of the main crystallization state with CaO content is determined. The crystallization activation energy of the glass system is increased by the addition of FePO4 crystallization phase easily by acid etching. The crystallization mode of the glass system is surface crystallization. The glass-solidified xY2O3 can contain 10 mo Y _ 2O _ 3, and is filled into the glass network, and the glass solidified xY2O3 is 100% Cao 20 Fe _ 2O _ 3 20 Fe _ 2O _ 3 / 68P _ 2O _ 5), and the crystallization activation energy of the glass system can be increased by the addition of the crystallization phase of the glass system, and the crystallization mode of the glass system is as follows: surface crystallization. The network structure of the glass solidified body is more compact, which leads to the increase of density and hardness. The addition of Y _ 2O _ 3 in the glass structure reduces the bond angle of P _ 2O _ 3 chain. In addition, it can replace P O O and P O O O by P O O Y bond, which leads to the transformation of the main structural units of the solidified body, and increases the content of yttrium coordination number nyttrium with the increase of yttrium coordination number with the increase of Y 2O 3 content in the glass network, and the increase of Y 2O 3 content leads to the increase of yttrium coordination number (Y 2O 3). The decrease of the thermal stability of the glass solidified body. After heat treatment, the crystalline phase of the doped yttrium glass solidified body changes due to the addition of Y _ 2O _ 3. The crystallization characteristics of the solidified materials. 3. The glass solidified bodies of various rare earth oxides exhibit similar encapsulation capacity as the yttrium doped solidified bodies. Excess rare earth elements lead to the crystallization of REPO4. The addition of RE2O3 to the matrix glass forms RE O O P, and the cation with high electric field strength provides more unbridged oxygen to depolymerize the glass network. Compared with La phosphate glass, it has a smaller P / O bond length. The higher coordination number of rare earth elements enhances the cross-connection of glass networks, thereby enhancing their mechanical properties. As the electric field strength of rare earth ions decreases, The less the unbridged oxygen content of rare earth glass sample is, the more the thermal stability of different rare earth glass increases with the increase of electric field intensity of rare earth ions. The main crystallization phase and morphology of different rare earth glass after heat treatment are studied. The main crystallization phases were FePO4 and REPO4, and the morphology of REPO4 was observed by SEM after acid leaching.
【學(xué)位授予單位】：西南科技大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類(lèi)號(hào)】：TQ171.11

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