掺镨铈独居石陶瓷固化体的制备及化学稳定性

发布时间：2018-04-18 01:36

  本文选题：独居石 + 镨　； 参考：《西南科技大学》2015年硕士论文

【摘要】：本文用镧系元素镨(Pr)模拟三价次锕系核素镎(Np),以Ce2(C2O4)3?10H2O、Pr6O11和NH4H2PO4为原料,通过固相反应合成了掺镨铈独居石固溶体Ce1-xPrxPO4(x=0-1),采用热压烧结制备了掺镨铈独居石陶瓷固化体(Ce0.5Pr0.5PO4),借助失重-差示扫描量热(TG-DSC)、X射线衍射(XRD)、场发射扫描电镜(FESEM)、能谱(EDS)等分析测试手段,研究了铈独居石(Ce PO4)与镨独居石(Pr PO4)的相互固溶规律,研究了Ce1-xPrxPO4(x=0-1)独居石固溶体及其陶瓷固化体的较佳制备工艺,分析了其相组成、密度及显微结构等。结果表明:采用二次研磨/煅烧工艺,制备单相独居石固溶体Ce1-xPrxPO4(x=0-1)的较佳煅烧工艺为1200oC下煅烧6h;随着Pr含量的增加,独居石固溶体Ce1-xPrxPO4(x=0-1)的晶胞参数a、b、c和晶胞体积V呈线性减小,晶胞参数?呈线性增加;热压烧结制备Ce0.5Pr0.5PO4独居石陶瓷固化体的较佳工艺为1150oC保温2h(30MPa),固化体相对密度可达到99%以上,物相为Ce0.5Pr0.5PO4独居石固溶体,其晶粒间紧密结合,晶界较模糊。采用MCC-1静态浸出实验法,通过水热反应釜装置模拟深地质处置环境,借助电感耦合等离子体发射光谱-质谱(ICP-MS),研究热压烧结Ce0.5Pr0.5PO4陶瓷固化体的化学稳定性。结果表明:热压烧结的Ce0.5Pr0.5PO4陶瓷固化体中的Ce元素和Pr元素均具有良好的化学稳定性。42d时,Ce元素的归一化浸出率≤9.93×10-6g·m-2·d-1,浸出率≤1.90×10-12g·m-1;Pr元素的归一化浸出率≤7.74×10-5g·m-2·d-1,浸出率≤1.48×10-11g·m-1。p H值对热压烧结Ce0.5Pr0.5PO4陶瓷固化体中Ce元素和Pr元素的归一化浸出率和浸出率有一定影响。Ce元素和Pr元素在弱酸性环境(p H=5)中的抗浸出性能相对较差,在中性和弱碱性环境中的化学稳定性能相对较好。
[Abstract]:In this paper, the lanthanide praseodymium praseodymium (praseodymium) is used to simulate the trivalent subactinide neptunium neptunium, using Ce2OC2O3H2O3H2O Pr6O11 and NH4H2PO4 as raw materials.Praseodymium and cerium doped cerium monazite solid solution Ce1-xPrxPO4 + 0-1N was synthesized by solid state reaction. Cerium-doped cerium-doped monazite ceramic curable Ce0.5Pr0.5PO4 was prepared by hot pressing sintering. The X-ray diffraction (XRDDX), field emission scanning electron microscope (SEM), energy spectrum (EDS), etc., were obtained by means of weightlessness and differential scanning calorimetry (TG-DSCT), X-ray diffraction (XRD) and X-ray diffraction (XRDX) of cerium monazite doped with praseodymium and cerium-doped cerium-doped monazite.The solid solution law of cerium monazite (ce PO 4) and praseodymium monazite (pr PO 4) was studied. The better preparation process of ce 1-xPrxPO 4 O 4) monazite solid solution and its ceramic solidification were studied. The phase composition, density and microstructure of cerium monazite were analyzed.The results show that the optimum calcination process for the preparation of single-phase monazite solid solution Ce1-xPrxPO4OxO0-1) is calcined under 1200oC for 6h, and the unit cell parameter abcnc and unit cell volume V decrease linearly with the increase of pr content in monazite solid solution Ce1-xPrxPO4O4x0-1), and the results show that the single phase monazite solid solution Ce1-xPrxPO4O4xPO4x0-1) has a linear decrease with the increase of pr content.Cell parameters?The optimum technology for preparing Ce0.5Pr0.5PO4 monazite ceramic solidified by hot pressing sintering is 1150oC holding for 2 h or 30 MPA / L, the relative density of the solidified body can reach more than 99%, the phase is Ce0.5Pr0.5PO4 monazite solid solution, its grain size is tightly bound and the grain boundary is rather fuzzy.The chemical stability of hot press sintered Ce0.5Pr0.5PO4 ceramics was studied by means of MCC-1 static leaching experiment, the hydrothermal reactor was used to simulate the environment of deep geological treatment, and the inductively coupled plasma-mass spectrometry (ICP-MS) was used to study the chemical stability of the solidified Ce0.5Pr0.5PO4 ceramics.The results show that the chemical stability of ce and pr elements in Ce0.5Pr0.5PO4 ceramic cured by hot pressing sintering is good. The normalized leaching rate of ce element 鈮，

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