LnX3型稀土卤化物闪烁晶体的闪烁性能

本文简要综述了LnX3型稀土卤化物闪烁晶体的发展历史与研究现状,对几种常见晶体(CeF3,LaF3,LuCl3,LaCl3,LuBr3,LaBr3)的物理、化学性质、晶体生长及闪烁性能等进行详细总结归纳,同时指出了当前具有优异闪烁性能的LaCl3:Ce和LaBr3:Ce晶体亟待解决的问题、未来的发展方向及其广阔的应用前景.     

Simulation by Molecular Dynamics of Erbium-Activated Silica-Titania Glasses

Rare-earth doped silicate-based glasses are widely used in telecommunication technology. A limitation in the performance of active optical devices such as amplifier comes from the rare-earth clustering. Simulation methods give complementary informations to the spectroscopic usual investigations. We present a molecular dynamics simulation of a SiO₂-TiO₂:Er³⁺ system in varying its composition. Different distribution functions have been analyzed in order to have information about the clustering of erbium. To this purpose, the titanium distribution has been studied for concentration 7.8 and 15.7% Ti/(Ti + Si). We have simulated the structure of the system doped with 1 and 2.3 mol%. A calculation of the crystal field strength for the different kinds of erbium site has been interpreted in the light of the local structure. The important trend of erbium for clustering in our modeled system has been explained by the energetic requirements of the rare-earth.     

稀土掺杂改性对Cu/ZnAl水滑石衍生催化剂甲醇水蒸气重整制氢性能的影响

采用原位合成法在γ-Al₂O₃表面合成了锌铝水滑石,再通过顺次浸渍法制备了一系列掺杂稀土改性的M（M=Y、La、Ce、Sm、Gd）/Cu/ZnAl催化材料,并将其应用于甲醇水蒸气重整制氢反应。探讨了稀土掺杂改性对Cu/ZnAl催化剂催化性能的影响,并采用XRD、SEM-EDS、BET、H₂-TPR、XPS和N₂O滴定等手段对催化剂进行了表征。结果表明,催化剂的活性与Cu比表面积和催化剂的还原性质密切相关,Cu比表面积越大,还原温度越低,催化活性越高。稀土Ce、Sm、Gd的引入能改善活性组分Cu的分散度、Cu比表面积以及催化剂的还原性质,进而提高催化剂的催化活性。其中,Ce/Cu/ZnAl催化剂表现出最佳的催化活性,在反应温度为250 ℃时,甲醇转化率达到100%,CO含量为0.39%,相比Cu/ZnAl催化剂,甲醇转化率提高了近40%。     

Low-temperature heat capacities and thermodynamic properties of rare-earth triisothiocyanate hydrates (III) —Sm(NCS)3 · 6H2O, Gd(NCS)3 · 6H20, Yb(NCS)3 · 6H20 and Y(NCS)3 · 6H20

The heat capacities of four RE isothiocyanate hydrates, Sm(NCS)₃, · 6H₂0, Gd(NCS)₃ · 6H₂0, Yb(NCS)₃, · 6H₂O and Y(NCS)₃, · 6H₂0, have been measured from 13 to 300 K with a fully-automated adiabatic calorimeter. No obvious thermal anomaly was observed for the above-mentioned compounds in the experimental temperature ranges. The polynomial equations for calculating the heat capacities of the four compounds in the range of 13–300 K were obtained by the least-squares fitting based on the experimentalC _P, data. TheC _P, values below 13 K were estimated by using the Debye-Einstein heat capacity functions. The standard molar thermodynamic functions were calculated from 0 to 300 K. Gibbs energies of formation were also calculated. Project supported by the National Natural Science Foundation of China.     

爆炸去磁脉冲功率发生器的实验和理论计算

设计了两种结构的爆炸去磁脉冲功率发生器:炸药透镜平面波冲击加载圆柱形磁体和中心装药冲击加载圆环形磁体，磁体材料都采用Nd2Fe14B永磁体。进行了爆炸冲击加载实验，测量了爆炸去磁脉冲发生器的输出电流、电压以及Nd2Fe14B永磁体中的冲击波速度。通过对爆炸去磁脉冲功率发生器基本原理的分析，建立了感生电动势的理论计算方法。用Maxwell 3D电磁场分析软件，对Nd2Fe14B永磁体进行了静磁场分析，给出了Nd2Fe14B永磁体的磁场强度分布规律。实验结果表明:爆炸去磁脉冲功率发生器每匝线圈能够产生约67 V的感生电动势,对于0.56 H的电感负载能够输出脉宽78.3 s、峰值1 212 A的脉冲电流。     

Er~(3+)/Tm~(3+)/Yb~(3+)共掺杂BaGa2ZnO5粉末的上转换发光

对Er~(3+)/Tm~(3+)/Yb~(3+)共掺杂BaGa_2ZnO5粉末的上转换发光特性进行了研究。首先,通过不同的制备工艺研究了BaGa2ZnO5粉末的生成条件。XRD分析表明,由于ZnO的高温分解,必须密封烧结并增加ZnO用量才能制备出BaGa2ZnO5。其次,测量了Er~(3+)/Tm~(3+)/Yb~(3+)共掺杂BaGa2ZnO5粉末在980nmLD激发下的上转换发射光谱,发现存在8个较强上转换发射峰,其中480nm和798nm对应于Tm~(3+)离子能级跃迁,其他上转换峰对应于Er~(3+)离子能级跃迁。另外,测量了980nmLD不同激发功率对应的上转换发射峰强度,并根据激发功率-上转换强度曲线拟合得到了各发射峰对应的多光子吸收过程。最后,根据上转换发射光谱和CIE1931标准数据计算了样品粉末的色坐标为(x=0.4151,y=0.4794) ,比较接近白光色坐标,说明所制备的粉末样品具有产生上转换白光的前景。     

Influence of rare-earth metal doping on the catalytic performance of CuO-CeO2 for the preferential oxidation of CO in excess hydrogen

Doping of different rare-earth metals （Pr, Nd, Y and La） had an evident influence on the catalytic performance of CuO-CeO2 for the preferential oxidation （PROX） of CO in excess hydrogen. As for Pr, the doping enhanced the catalytic activity of CuO-CeO2 for PROX. For example, the CO conversion over the above catalyst for PROX was higher than 99% at 120 °C. Especially, the doping of Pr widened the temperature window by 20 °C over CuO-CeO2 with 99% CO conversion. For Nd, Y, and La, the doping depressed the catalytic activity of CuO-CeO2 for PROX. However, the doping of transition metals markedly improved the selectivity of CuO-CeO2 for PROX.     

共掺杂效应对Y2O3∶Eu^3＋和Gd2O3∶Eu^3＋发光影响的理论研究

通过在Y2O3∶Eu3 和Gd2O3∶Eu3 发光材料中掺入Li ,Mg2 ,Al3 等离子能有效地提高材料的发光强度,根据分子动力学和密度泛函计算的结果,认为这些离子多倾向于形成C2格位附近的间隙缺陷对,导致部分Y(Gd)—O的键长增加,提高了材料的量子效率的同时使得激发峰位出现红移,是引起材料发光增强的一个原因。     

Thermal decomposition of 4,4′-dipyridyl complexes of light rare-earth thiocyanates in air atmosphere

The thermal decompositions of Ln(NCS)₃(4-dipy)₂·5H₂O were studied, whereLn=La, Pr, Nd, Sm, Eu and Y, and 4-dipy=4,4′-dipyridyl. The compounds are first dehydrated. During the thermal decomposition of Ln(NCS)₃(4-dipy)₂, deamination takes place. The transient products decompose with the formation of Ln₂O₂SO₄. The energies of activation for the first step of dehydration of the La, Pr, Nd, Sm and Eu complexes were determined.

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Zusammenfassung Es wurde die thermische Zersetzung von Ln(NCS)₃(4-dipy)₂.5H₂O mitLn=La, Pr, Nd, Sm, Eu, Y und 4-dipy=4,4′-Dipyridyl untersucht. Die Verbindungen werden zuerst dehydratiert. Bei der thermischen Zersetzung von Ln(NCS)₃(4-dipy)₂ findet eine Desaminierung statt. Die übergangsprodukte zersetzen sich unter Bildung von Ln₂O₂SO₄. Die Aktivierungsenergie für den ersten Schritt der Dehydratation der La-, Pr-, Nd-, Sm- und Eu-Komplexe wurde ermittelt.

     

将自由基转化为负离子的光催化稀土材料

设计制造了具有负离子功能的稀土-半导体氧化物组装材料，并进行了自由基的测试。测试表明，该材料不仅在紫外光照射条件下能产生大量活性氧自由基，而且在无光照条件下也能产生大量活性氧自由基，突破了常规半导体氧化物不能在可见光条件下催化的难点。同时表明，材料所产生的自由基量与负离子量有直接对应关系。这意味着，在稀土离子的光催化及变价的氧化-还原过程中存在羟基自由基转化为负离子的可能。依此提出了在光催化作用下稀土离子与材料表面吸附的H2O和O2的循环变化模型图。