镧在TiO2薄膜中的非均匀掺杂对光催化性能的影响

采用溶胶-凝胶法制备了La^3＋非均匀掺杂的TiO2薄膜。通过对甲基橙的光催化降解实验来评价催化剂薄膜的催化活性，结果表明：La^3＋的掺杂方式对TiO2的催化活性有很大的影响，采用非均匀掺杂方式可以明显提高TiO2的催化活性，掺杂浓度以0．5％（原子分数）为最佳。紫外-可见漫反射光谱鼎示其吸收带边明显红移；电化学行为表明其光生空穴一电子对的形成能力和分离效率得到提高。通过比较太阳能光电池异质结的“窗口效应”理论，初步探讨了La^3＋非均匀掺杂对TiO2的光催化活性的影响机制。     

过渡金属离子的掺杂对TiO2光催化活性的影响

考察了过渡金属离子对TiO₂ 光催化性能的影响,结果发现:第二过渡系列金属离子对TiO₂ 膜的修饰作用比第一过渡系列金属离子的修饰作用更加明显;第二、六副族的金属离子对TiO₂ 膜的修饰效果较好.通过X射线衍射(XRD)、电镜分析 (SEM)、光电能谱分析 (XPS)及差热分析 (DTA)对催化剂表面进行了表征,结果表明:TiO₂ 的晶型为锐钛矿型,粒子半径为 32.58nm.     

钒离子掺杂对TiO2光催化剂薄膜催化活性的影响

采用溶胶凝胶工艺在普通玻璃表面制备了钒离子非均匀掺杂的TiO2薄膜,运用XRD研究了其光催化复合薄膜的表面特征.以光催化降解甲基橙溶液为模型反应,表征薄膜的光催化活性,结果表明,将钒离子富集在TiO2薄膜内部时,最佳掺杂浓度为1.0%(V/Ti原子百分比),最佳降解表观速率常数为7.44×10-3min-1,约是纯TiO2的2.3倍,有效地提高了TiO2半导体的光催化效率.通过XPS与电化学方法进行分析,说明将钒离子富集在TiO2薄膜内部十分有利于电子-空穴的分离,增强了光生电子与空穴的分离效率.     

稀土元素掺杂对TiO2薄膜光催化性能的影响

采用Sol-Gel法、浸渍-提拉法制备了RE(Sm, Dy, Lu) 掺杂TiO2的锐钛矿晶型薄膜. 用X射线衍射分析、 UV-Vis透射光谱及电化学实验对其进行了表征, 通过对紫外光照射下甲基橙溶液的光催化降解评价了其光催化性能. 结果表明, RE掺杂的TiO2薄膜的吸收光向长波方向移动; 掺杂浓度是影响光催化活性的重要因素; 适量RE掺杂可以明显提高TiO2薄膜的光催化性能; 最佳掺杂浓度是0.5%. 其中掺杂Sm样品的光催化活性最好. 分别讨论了RE不同浓度及不同元素掺杂对TiO2光催化性能的影响机制.     

掺杂金属离子改性的TiO2薄膜光催化剂的研制

采用溶胶-凝胶法制备TiO2薄膜光催化剂，着重考察了掺杂铈、镧、钨等金属离子改性的TiO2薄膜的光催化活性，研究了其紫外-可见光透过性能，甲基橙水溶液的光催化降解实验表明：掺杂铈、镧、钨三种金属离子后，TiO2薄膜的光催化活性均有不同程度的提高，最佳掺杂浓度分别为3．0％、1．0％、0．5％，其中掺杂铈的TiO2薄膜光催化活性最高。     

Ce3+掺杂对纳米TiO2/SiO2镀膜玻璃性能的影响

在TiO2/SiO2溶胶中按不同比例掺杂Ce3+得到复合溶胶,将溶胶喷涂在浮法玻璃原片上,105～300 ℃烘干得到镀有纳米TiO2膜的透明玻璃.AFM图像表明 掺杂Ce3+的TiO2/SiO2镀膜玻璃表面的颗粒小于没有掺杂Ce3+的TiO2/SiO2镀膜玻璃表面颗粒.掺杂Ce3+与TiO2 摩尔比为0.01∶1时,镀膜玻璃可见光透射比为85.3%,紫外线透射比39.7%、可见光反射比7.3%、太阳光直接透射比83.5%、太阳光直接反射比6.6%; 水接触角θ为0°; 在可见光照射下,分解甲基橙的时间为48 h; 膜表面电阻率为5.9×107 Ω·cm.在400～700 ℃对镀膜玻璃进行高温处理,其光学性能明显提高,可见光透射比为91.7%,紫外线透射比39.1%、可见光反射比6.4%、太阳光直接透射比92.0%、太阳光直接反射比5.9%; θ角为0°,亲水性明显提高; 在可见光照射下,甲基橙分解时间为28 h; 膜表面电阻率为5.5×107 Ω·cm,玻璃在可见光条件下就具有自清洁能力.     

La3+-SiO2掺杂纳米TiO2的合成及其光催化降解甲基橙的研究

以三嵌段非离子表面活性剂P123为模板,采用水热法合成了La3+-SiO2掺杂纳米TiO2,通过X射线衍射(XRD)、红外光谱(FT-IR)、紫外-可见漫反射吸收光谱(DRS)等手段,考察了La3+-SiO2掺杂纳米TiO2的结构与光学特性.实验结果表明,La3+和SiO2掺杂使TiO2的晶粒在生长过程中受到阻碍.Ti-O-Si键和Ti-O-La键的形成抑制了金红石相的形成和晶粒长大,提高了TiO2的热稳定性,有利于获得高纯度锐钛矿相纳米TiO2.La3+-SiO2掺杂将TiO2的光响应范围拓宽至可见光区,提高了纳米TiO2的光催化性能.与纯纳米TiO2相比,La3+-SiO2掺杂纳米TiO2光催化降解甲基橙的性能显著提高.     

钴前驱体对掺杂TiO2微结构和可见光催化性能的影响

In order to develop photoactive cobalt-doped TiO2 for the degradation of organic pollutants using visible light irradiation, the effects of cobalt precursor on TiO2 microstructure were investigated. Three cobaltprecursors, i.e. CoCl2, Co(NO3)2 and CoSO4 with two doping levels (nominally 1% and 10%), and two annealing temperatures (400 and 800 ℃) were adopted to prepare the doped titania through the sol-gel method. The powder samples were characterized with XRD, SEM, BET surface area analysis and UV-Vis absorption spectroscopy, and their photocatalytic activities were evaluated by the degradation of aniline under visible light irradiation. The results showed that the distribution of titania phases, particle size,morphology, surface area and the optical absorption of the catalysts were greatly dependent on the cobalt precursors. Samples prepared from Co(NO3)2, especially for those doped at 1% and calcined at 400 ℃,showed the highest photocatalytic activity towards the degradation of aniline, and the possible reasons are discussed briefly.     

Au掺杂方式对锐钛矿TiO2光催化性能的影响

结合超临界乙醇干燥技术, 采用沉积-沉淀(DP)和共沉淀(CP)法分别制备了具有单一锐钛矿晶相的Au/TiO2和Au(0.2%, 原子分数)-TiO2光催化剂, 通过XRD、BET、TEM、XPS和Raman手段表征样品中Au的掺杂形态, 以光催化降解甲基橙为模型反应考察了样品的光催化活性. 结果表明, DP法制备的Au/TiO2在110 ℃干燥处理后, 表面存在的Au3+能有效地促进锐钛矿TiO2光催化性能, 其一级反应速率常数比纯锐钛矿TiO2提高了3.2倍, 比商用光催化剂Degussa-P25提高了4.1倍, 而当Au3+被还原为Au0后光催化活性下降. 用CP法制备的Au-TiO2并没有较大地提高锐钛矿TiO2光催化性能, 在焙烧温度达到800 ℃时, Au向表面迁移聚集, 造成锐钛矿TiO2晶格氧空位和缺陷位增加, 使光催化活性下降.     

Study of phase transition and volume thermal expansion in a rare-earth (RE) oxyfluoride system by high-temperature XRD (RE=La, Nd, Sm, Eu and Gd)

Volume thermal expansion behaviour of a number of rare-earth oxyfluorides (REOF) have been studied using high-temperature X-Ray diffractometry (HT-XRD) in the 298–1075 K range in air. The studies revealed an anomalous expansion for each compound associated with phase transition. The phase transition temperature and the coefficient of volume thermal expansion of five compounds in REOF series determined by this method are reported and compared with our earlier results obtained by dilatometry.     

Synthesis of nanocrystalline REBO3 (RE=Y, Nd, Sm, Eu, Gd, Ho) and YBO3:Eu using a borohydride-based solution precursor route

A solution precursor route has been used to synthesize a series of nanocrystalline rare-earth borates. Amorphous precursor powders are precipitated during an aqueous reaction between RE³⁺ and NaBH₄, and the isolated powders can be annealed in air at 700 °C to form YBO₃, NdBO₃, SmBO₃, EuBO₃, GdBO₃, and HoBO₃. YBO₃:Eu formed using this strategy shows red-orange emission properties that are similar to high-quality nanocrystals prepared by other methods. The materials have been characterized by FTIR spectroscopy, powder XRD, SEM, DSC, UV-Vis fluorimetry, and TEM with EDS and element mapping.     

Reactivity in the solid state between CoWO4 and RE2WO6 where RE = Sm, Eu, Gd

Reactivity in the solid state between CoWO₄ and some rare-earth metal tungstates RE₂WO₆ (RE = Sm, Eu, Gd) was investigated by the XRD method. Two families of new isostructural cobalt and rare-earth metal tungstates, Co₂RE₂W₃O₁₄ and CoRE₄W₃O₁₆, were synthesized. The Co₂RE₂W₃O₁₄ phases are formed by heating in air the CoWO₄ and RE₂WO₆ compounds mixed at the molar ratio 2:1, while the CoRE₄W₃O₁₆ phases are synthesized at the molar ratio of CoWO₄/RE₂WO₆ equals to 1:2. The Co₂RE₂W₃O₁₄ phases as well as the CoRE₄W₃O₁₆ compounds crystallize in the orthorhombic system. The Co₂RE₂W₃O₁₄ and CoRE₄W₃O₁₆ compound melt above 1150 °C. A melting manner of the Co₂RE₂W₃O₁₄ and CoRE₄W₃O₁₆ compounds was determined in an inert atmosphere. The formation of CoWO_4−x phase was observed during heating in an inert atmosphere.     

Separating Ag, B, Cd, Dy, Eu, and Sm in a Gd matrix using 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester extraction chromatography for ICP-AES analysis

The separation procedure for Ag, B, Cd, Dy, Eu and Sm as impurities in Gd matrix using ICP-AES technique with an extraction chromatographic column has been developed. The spectral interference of the Gd matrix on the elements was eliminated using a chromatography technique with 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester (PC-88A) as the mobile phase and XAD-16 resin as the stationary phase. Ag⁺, B₄O₇²⁻, and Cd²⁺ were eluted with 0.1 M HNO₃, while rare earth ions were not. The best eluent for separating Eu and Sm in the Gd matrix was 0.3 M HNO₃. The limit of quantitation for these elements was 0.6-3.0 ng mL⁻¹. The recovery of Ag, B, and Cd was 90-104% using 0.1 M HNO₃ as the eluent, while that of Eu, Gd, and Sm ranged from 100 to 102% with 0.3 M HNO₃. Dy was recovered quantitatively with 4 M HNO₃. The relative standard deviation of the methods for a set of three replicates was between 1.0 and 15.4% for the synthetic and standard Gd solutions. The proposed separation procedure was used to measure Ag, B, Cd, Dy, Eu, and Sm in a standard Gd solution.     

SO2－4 表面修饰对TiO2结构及其光催化性能的影响

采用溶胶 凝胶法制备了TiO2和/TiO2催化剂.运用XRD、BET比表面测定、IR和DRS光谱等技术对催化剂进行了表征,并以光催化氧化分解溴代甲烷作为模型反应,考察了上述催化剂的光催化反应性能及其反应条件对光催化活性的影响.结果表明,表面修饰使得催化剂的结构和光催化性能显著改善,催化剂表面形成具有超强酸性质的L酸和B酸协同中心.与TiO2相比,/TiO2光催化剂的锐钛矿含量高、晶粒小、BET比表面积大、孔径分布集中、光谱吸收边蓝移,具有优异的光催化氧化活性、稳定性及抗湿性能.     

超声雾化电感耦合等离子体发射光谱法测定二氧化铀中痕量钐、铕、钆、镝

二氧化铀样品用HCl溶解，经过阴离子交换树脂和CL-PMBP萃淋树脂两步分离，超声雾化ICP-AES法同时测定其中的钐、铕、钆、镝含量。方法回收率在90％～113％之间，相对标准偏差小于5％。     

NH4H2PO4掺杂改性纳米TiO2的光催化性能

利用钛酸丁酯水解浸渍方法制备了几种不同浓度NH4H2PO4掺杂改性的TiO2纳米复合粉体材料并作了XRD、BET等表征。以正己烷的气相光催化氧化降解为探针反应研究了NH4H2PO4掺杂TiO2催化剂的光催化活性。并和未掺杂TiO2及商品TiO2 Degussa P-25作了比较．结果表明。掺杂NH4H2PO4能够显著地细化TiO2的晶粒度。增大TiO2的比表面积。同时，适量掺杂NH4H2PO4对TiO2的光催化活性也有较大的促进作用。     

原子吸收光谱测定Sm-Eu-Gd富集物中Sm、Eu、Gd

本文制定了N_2O-C_2H_2焰原子吸收光谱直接测定Sm-Eu-Gd富集物中Sm、Eu和Gd的分析方法。采用氧化镧溶液作为缓冲剂消除干扰提高灵敏度。此法不需要复杂的分离过程。方法简便、快速、成本低、适合工厂采用。     

BaLiF3∶Eu,Gd中Gd3+→Eu2+的能量传递

研究了BaLiF3中Gd3+和Eu2+的光谱性质及Gd3+对Eu2+的能量传递过程,讨论了传递机理.Gd3+的含量(物质的量分数)为0.3%时,传递效率最高,传递几率PSA＝1.35×105 s-1.当Gd3+的含量高于0.3%时,由于Gd3+和Eu2+竞争吸收Gd3+占优势,增加Gd3+含量,竞争吸收比相应增加,Eu2+自身吸收光子数目减少,发射强度降低.