Mechanochemical Reaction of Lanthanum Carbonate with Sodium Hydroxide and Preparation of Lanthanum Oxide Nanoparticle

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天然高岭石类粘土矿物对Sc~（3＋）、Th~（4＋）的吸附

研究了两种天然高岭石类粘土矿物样品对Ｓｃ３＋、Ｔｈ~４＋离子的吸附等温线，用最小二乘法的关联结果表明，可以用Ｌａｎｇｍｕｉｒ、Ｆｒｅｕｎｄｌｉｃｈ和Ｔｅｍｋｉｎ吸附等温线方程来描述。粘土对Ｓｃ~３＋、Ｔｈ~４＋的吸附表现出典型的电性交换吸附特征。且对Ｓｃ~３＋具有更强的吸附能力。证明该类粘土不仅可以用来吸附富集Ｓｃ~３＋、Ｔｈ~４＋，而且可以选择适当浓度的酸溶液作淋洗剂来进行Ｓｃ~３＋、Ｔｈ~４＋的离子交换分离。     

单分散球形超细氧化铈的机械化学反应制备法

采用湿固相机械化学反应法制备单分散球形超细氧化铈粉体，化学分析和XRD物相分析结果表明球磨作用不仅改善了反应的热力学和动力学条件，使反应能在较短的时间内完成，而且还促进了产物的结晶化，得到了结晶性良好的新物相，有利于球磨产物的后续处理。随着球磨反应的进行，颗粒粒度减小，直至亚微米级时球磨反应使颗粒的减小趋势与晶粒生长导致颗粒长大的趋势达到平衡，粒度降低幅度减小。球磨产物在后续煅烧过程中，其粒度随温度的升高是先减小而后增大，但在1050℃之前的增大不够明显。XRD、粒度分布及扫描电镜分析结果表明煅烧产物为球形的单分散的超细氧化铈。     

南方离子型稀土的资源和环境保护性开采模式

南方离子型稀土是我国独有的一类宝贵的中重稀土资源。其保护性开发及其环境影响一直是人们关注的问题。在分析和总结近四十年来该类矿床开采过程与资源和环境保护相关的技术进步和存在问题的基础上,提出了实现资源和环境保护性开采的环境工程模式,并对其主要内涵进行了讨论。目的是为了规范离子型稀土资源的开采提供技术和政策支持。     

以碳酸铈为前驱体制备超细氧化铈及其抛光性能

研究了以水合碳酸铈为前驱体,采用直接球磨和煅烧的方法制备了中位粒径小于3μm的超细氧化铈。结果表明:所得产物均具有立方萤石型结构,随着煅烧温度的升高,产物粒径呈下降趋势,粒度分布也越来越窄,结晶度提高。但对三种不同玻璃的抛光能力均在900℃~1000℃之间呈现出极大值。因此认为抛光过程中玻璃表面物质的去除速率受抛光粉粒度、结晶度和表面活性的影响较大。     

Synthesis of YAG：Ce^3＋ Phosphor by Polyacrylamide Gel Method and Promoting Action of α-Al2O3 Seed Crystal on Phase Formation

YAG： Ce^3 ＋ phosphor particles were prepared using polyacrylamide gel method. The structure evolution of powders during annealing process was followed by X-ray diffraction determination. It is found that some intermediate phases, including θ-Al2O3, YAM and YAP, are formed when calcining polyacrylamide gel, however, the pure YAG phase can be formed directly when calcining polyacrylamide gel with α-Al2O3 as seed crystal. These facts show that the existence of α- Al2O3 seed crystal can block the formation of θ-Al2O3, YAM and YAP, and accelerate its reaction with Y2O3 to form YAG phase directly at lower temperature. The emission peak of prepared YAG ： Ce^3 ＋ phosphor is wide with maximum at 550 nm and the exitation band has two peaks, the major one is around at 460 nm, which matches the blue emission of GaN LED and is suitable for the assemble of white LED. Some fluxes can enhance the photoluminescence intensity of phosphor particles, that can be attributed both to the improvement of crystallization processes of YAG and to the stabilization of trivalence cerium ion in YAG：Ce^3 ＋.     

湿固相机械化学法制备蓝粉前驱体过程中的物相转变

采用湿固相机械化学法制备稀土铝酸盐蓝色荧光粉前驱体，用XRD和DTA－TG分析技术研究了湿固相球磨过程和后续煅烧过程中的物相转变。结果表明：在球磨过程中反应原料经历了无定型化与水热结晶两个主要阶段，观察到了MgAl2O4尖晶石结构相的形成和BaMg(CO3）2及BaCO3的再结晶现象，这些晶相在640℃之前仍保持稳定。在烧成过程，首先发生无定型Al(OH)3的分解，而后是分两个阶段的BaMg(CO3)2和BaCO3分解过程，到900℃时，碳酸盐的分解才基本结束，但没有形成高温固相反应所得到的BaMgAl10O16晶相。扫描电镜观察和粒度分析结果表明所得前驱体为粒度1－3μm,分散性良好的亚球形蓝色荧光粉前驱体。     

碳酸氢铵沉淀钇基重稀土时共存铁、铝杂质离子的行为研究

本文对钇基重稀土碳酸盐沉淀过程中杂质铁、铝离子的共沉淀行为以及对碳酸稀土的结晶性能和结晶效果的影响进行了研究。结果表明 :用碳酸氢铵沉淀稀土时 ,杂质铝可沉淀完全 ,但在上清液中仍存在微量铁。同时在碳酸稀土的陈化结晶过程中有少量铁溶出 ;常温下钇基重稀土碳酸盐在低配比区域的结晶活性差 ,而在高配比区域结晶速度较快。杂质的存在会显著影响碳酸稀土的结晶 ,使结晶速度明显减小 ,结晶过程的值下降不明显 ,结晶产品的沉降性能变差     

Synthesis of Nano-sized Yttria via a Sol-Gel Process Based on Hydrated Yttrium Nitrate and Ethylene Glycol and Its Catalytic Performance for Thermal Decomposition of NH4ClO4

Nano-sized yttria particles were synthesized via a non-aqueous sol-gel process based on hydrated yttrium nitrate and ethylene glycol. The effects of the molar ratio of ethylene glycol to yttrium ion and calcination temperature on crystallite size of the products were studied. The catalytic performance of the as-prepared yttria for the ammonium perchlorate (AP) decomposition was investigated by differential scanning calorimetry (DSC). The results indicate that the nano-sized cubic yttria particles with less than 20 nm in average crystallite size can be obtained after 2 h reflux at 70 ℃, dried at 90 ℃, forming xerogel, and followed by annealing of xerogel for 2 h, and that the addition of the nano-sized yttria to AP incorporates two small exothermic peaks of AP in the temperature ranges of 310 ～ 350 ℃ and 400 ～ 470 ℃ into a strong exothermic peak of AP and increases the apparent decomposition heat from 515 to over 1110 J·g-1. It is also clear that the temperature of AP decomposition exothermic peak decreases and the apparent decomposition heat of AP increases with the increase of the amount of nano-sized yttria. The fact that the addition of the 5 % nano-sized yttria to AP decreases the temperature of AP exothermic peak to 337.7 ℃ by reduction of 114.6 ℃ and increases the apparent decomposition heat from 515 to 1240 J·g-1, reveals that nano-sized yttria shows strong catalytic property for AP thermal decomposition.     

阴离子掺杂ZnO的荧光光谱和X光电子能谱特征

以溴化铵为助熔剂,在较低温度(-800℃)下的空气气氛中煅烧硫化锌合成了S~(2-)和Br~-共掺杂ZnO绿色荧光粉.采用XPS技术对该类ZnO荧光粉绿光发射的原因进行探讨,认为S~(2-)和Br~-共掺杂将促进ZnO中氧空穴和锌空穴的形成,使光生电子从禁带中的这些局域缺陷中心跃迁至深陷阱的空穴而产生强的绿色发射.