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.     

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。     

Cl~-,S~(2-)共掺杂氧化锌荧光粉的制备及发光性能

在空气气氛中,以NH_4Cl为助剂,通过热氧化硫化锌,制备出Cl~-,S~(2-)共掺杂氧化锌荧光粉,激发和发射光谱随氧化温度的变化而变化.在350nm激发下,氧化锌荧光粉的发射光谱只有510nm绿色峰,并有黄色区拖尾现象.绿色峰强度随煅烧温度的变化而变化.绿色峰归因与一价氧空位中的电子和价带中光生空穴的复合.氧化锌荧光粉的光致发光谱的变化是Cl~-,S~(2-)共掺杂的结果.     

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     

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.     

稀土分离高铵氮废水综合回收与利用研究

稀土分离工艺中各种浓度的铵氮废水有不同的处理方法,针对其高浓度的铵氮废水,采用加硫酸并在加热及减压条件下进行回收与利用。结果表明,在一定的加酸比n(H+)∶n(NH4Cl)下,氯化铵浓度提高,其盐酸蒸出摩尔数与加入氢离子摩尔数的比值基本不变,且减压比常压高出7%左右;盐酸蒸出浓度随氯化铵含量和原料配比的增加而提高;高酸比蒸酸残留物为硫酸氢铵,低酸比则为多种铵盐;硫酸氢铵可用作稀土碳铵沉淀母液回收的pH调节剂和铵离子的补充剂,并用于南方稀土矿的稀土浸出;蒸出盐酸可用作稀土分离工艺的洗酸。高铵氮废水得以充分回收和利用。     

硝酸铜硝化水杨酸甲酯的绿色硝化方法研究

以硝酸铜为硝化剂,在回流的乙酸乙酯溶液中硝化水杨酸甲酯来合成3-硝基水杨酸甲酯（O）和5-硝基水杨酸甲酯（P）。对比研究了在不同硝酸根和水杨酸甲酯配比条件下用硝酸铜和硝酸作硝化试剂时的硝化收率和区域选择性。结果表明：以硝酸铜作硝化剂时的硝化收率可达80％,P／O比值最高为5．4。均比用相同浓度的硝酸作硝化剂时要高。而且,硝化过程中铜以氢氧化物固体沉淀的形式析出,便于与硝基化产物分离。用红外光谱、元素分析和差热-热重分析确定了析出沉淀的组成为Cu（OH）1.46（N03）0.47（MNS）0.07 1．15H2O。该沉淀经硝酸溶解和浓缩结晶可以得到硝酸铜,其回收率为82．32％（以铜含量为基准）。     

Pr~(3+)-doped Li_2SrSiO_4 red phosphor for white LEDs

Novel red phosphors,Li2Sr1-1.5xSiO4:xPr3+(x=0.002,0.003,0.004,0.005,0.006 and 0.008),were synthesized by conventional solid state reaction and the luminescent properties were investigated.The as-prepared phosphors showed red emission at 610 nm under excitation of blue light at 452 nm,indicating that they were promising candidates for red phosphors in the fabrication of white LEDs via blue LED chips.Their excitation bands at 452,476 and 487 nm were attributed to transitions of 3H4→3P2,3H4→3P1+1I6,3H4→3P0 of Pr3+ ion.The red emissions at 606 and 610 nm were originated from the 3P0-3H6 and 1D2-3H4 transitions of Pr3+.The optimum doping concentration of Pr3+ in Li2Sr1-1.5xSiO4:xPr3+ was determined to be x=0.004.With the concentration of Pr3+ over x=0.004,the fluorescence intensity of Li2Sr1-1.5xSiO4:xPr3+ decreased,indicating the concentration quenching occurred.     

用开链冠醚萃取稀土

研究了开链冠醚1.11-=(8'-羟喹啉基)-3.6.9-三氧杂十一烷对稀土元素的萃取机理和萃取规律性,并讨论了对阴离子种类、酸度及开链醚的末端基对萃取的影响.     

RECl3与NH4HCO3的沉淀反应及伴生杂质的共沉淀行为

本文通过对沉淀过程的ｐＨ值变化特征研究和沉淀物的组成分析，确定了ＮＨ４ＨＣＯ３与ＲＥＣｌ３的沉淀反应。研究了伴生金属离子Ａｌ３＋、Ｆｅ２＋、Ｍｎ２＋、Ｃａ２＋、Ｍｇ２＋随稀土的共沉淀行为，讨论了杂质离子对产品纯度的影响。