钙铁磷酸盐玻璃固化体包容特性研究

发布时间：2018-03-09 14:41

本文选题：钙铁磷酸盐玻璃　切入点：稀土元素　出处：《西南科技大学》2015年硕士论文　论文类型：学位论文

【摘要】：基于钙铁磷酸盐玻璃对核素包容量大、熔融温度与高温粘度、优良的化学稳定性等特点,同时考虑到稀土元素与锕系元素在化合价、核外电子排布和配位数相同时离子半径等基本相似,导致与锕系元素难于实现分离,而且部分稀土元素为高放废物的主要裂变产物。因此,本课题采用X射线衍射(XRD)、扫描电子显微镜(SEM)、傅里叶变换红外光谱(FT-IR)、拉曼光谱(Raman spectroscopy)、紫外可见光谱(UV-vis spectroscopy)和差示扫描量热法(DSC)等测试手段研究了钙铁磷酸盐玻璃及利用该基质玻璃包容钇(Y)、镧(La)、钕(Nd)、钐(Sm)、钆(Gd)五种稀土元素形成的玻璃固化体的结构、热稳定性和表面形貌。研究表明:1、该钙铁磷酸基质玻璃xCaO (32 x)Fe2O3 68P2O5有宽广的玻璃形成范围。光谱分析阐明了在该玻璃体系中CaO含量少于16 mol%时,使玻璃网络中的P O-转变为(P O-Ca2+-O P)链,从而使玻璃结构更加紧密,导致了硬度的提高和玻璃化转变温度的升高;当CaO含量大于16 mol%时,钙离子通过代替P O P和P O Fe形成了(P O-C a2+-O P)和P O C a,致使玻璃的化学稳定性下降。随着CaO代替Fe2O3,该基质玻璃由焦磷酸盐结构转变为偏磷酸盐链,从而样品平均磷酸盐链的长度增大以及非桥氧的含量降低。对玻璃样品两步的热处理后,确定了其主要析晶态随CaO含量的变化规律,仅FePO4析晶相易被酸蚀。CaO的加入导致该玻璃体系的析晶活化能增加,其析晶方式为表面析晶。2、玻璃固化体xY2O3 (100 x)(12CaO 20Fe2O3 68P2O5)能够包容10 mo l%Y2O3,其填充到玻璃网络的空隙中,玻璃固化体的网络结构更加紧密,导致了密度的增大和硬度的提高。在玻璃结构中Y2O3的加入使P O P链的键角减小,而且其可以通过P O Y键代替P O-和P=O,导致固化体主要结构单元的转变,增加了玻璃网络的交叉连接。Y2O3含量的变化导致了钇配位数(NYO)增大。随着Y2O3含量的增加,玻璃固化体热稳定性的下降。热处理后的掺杂钇玻璃固化体,由于Y2O3的加入导致析晶相的变化,影响了固化体的析晶特性。3、多种稀土氧化物的玻璃固化体展示了与钇掺杂固化体相似的包容量,过量的稀土元素导致了析晶态REPO4的产生。基质玻璃中加入RE2O3形成了RE O P,而且高电场强度的阳离子提供了更多的非桥氧来解聚玻璃网络。由于掺杂Y磷酸盐玻璃相比于La磷酸盐玻璃有更小的P O键长,导致了它们硬度的变化。更高配位数的稀土元素能够增强玻璃网络的交叉连接,从而增强了其机械性能。随着稀土离子电场强度的减小,稀土玻璃样品中非桥氧含量越少。不同稀土玻璃的热稳定性随稀土离子电场强度值的增大而增强。研究了不同稀土玻璃热处理后的主要析晶相和其形态,其主要析晶相为FePO4和REPO4,酸浸之后通过SEM观察到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.
【学位授予单位】：西南科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ171.11

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