稀土氢化物的晶体结构及其可转换光学特性

稀土氢化物薄膜的可转换光学特性近年来才被发现，采用气态吸放氢或电化学充放电方法，可使稀土薄膜的光学特性产生可逆变换。本文介绍了稀土氢化物的晶体结构和热力学特性，对稀土氢化物薄膜的楞转换光学特性及其研究进展进行了概述，并分析了稀土薄膜光学特性变化的原因。     

稀土上转换发光纳米材料的制备及生物医学应用研究进展

荧光探针技术已经被广泛应用于生物成像、生物标记、生物检测、免疫分析等生物医学领域。传统荧光标记材料,如有机荧光染料、荧光蛋白和半导体量子点,目前面临诸多应用局限,如发光强度不稳定、检测灵敏度低、生物毒性高、自荧光强等。有鉴于此,人们开发了La系金属离子掺杂的稀土上转换发光纳米材料作为新型生物标记材料,该材料受近红外光激发后发出近红外或可见光范围内的高能量光子。这种带有特殊光学性质及良好生物相容性的荧光标记材料克服了传统荧光标记材料的缺点,从而成为材料科学与生物医学交叉领域的研究热点。综述了稀土纳米材料上转换功能的特殊物理机制及其制备和表面修饰方法的研究进展。在此基础上介绍了稀土上转换纳米材料在生物成像、检测、载药、即时诊断器件开发等生物医学工程中的应用。     

水热法制备纳米Fe3O4磁性颗粒

通过水热法制备了Fe3O4纳米颗粒,采用TEM、XRD和VSM等测试手段对合成的样品的形貌粒径和结构进行了表征.研究了不同反应温度、反应时间、合成比例因素对样品形貌、尺寸和结晶性的影响,探索出形成高纯度Fe3O4的最佳条件.并借助VSM对合成的样品的磁性能进行了表征,可确定产物有较理想的磁性能.     

Co掺杂ZnAl2O4纳米颗粒的制备与光学性质研究

以CTAB为表面活性剂,采用水热法成功制备了不同掺杂比例的Zn1-xCoxAl2O4（x=0,0.20,0.40和0.60）纳米晶。并对样品的晶体结构、形貌、化学成分、价态和光学性能进行表征。实验结果表明,本方法所制备的不同掺杂浓度的Zn1-xCoxAl2O4纳米颗粒为尖晶石结构,晶化程度良好。根据XRD数据计算了晶胞参数a、晶格间距dhkl、晶粒尺寸D,随着掺杂Co离子浓度的增加,均表现为减小趋势。XPS能谱显示大多数Co离子占据四面体中心位置,但有少量的Co离子占据八面体中心位置。随着掺杂Co离子浓度的增加,紫外吸收光的强度逐渐增加。     

稀土金属离子掺杂对LiFePO4结构和性能的影响

采用稀土金属离子(Er3+、Y3+、Nd3+)分别对LiFePO4的Li、Fe原子位进行掺杂,通过X射线衍射(XRD)、恒电流充放电及电化学阻抗(EIS)法系统地研究掺杂对LiFePO4结构和性能的影响。结果表明:掺杂试样的微观结构和性能与掺杂离子半径、取代位置密切相关。LiFe0.99Y0.01PO4试样具有最佳的电化学性能,在15mA.g-1放电电流密度下首次放电容量达到149.8mAh.g-1,当电流密度增加到300mA.g-1时,放电容量为134.3mAh.g-1,经过50次循环充放电后,放电容量保持率为99.1%。     

溶胶-凝胶合成Er3 和Ho3 离子掺杂的Gd2(MoO4)3上转换发光纳米晶

采用柠檬酸与乙二醇溶胶-凝胶法合成了Er3 和Ho3 离子分别掺杂的铝酸钆Gd2(MoO4)3纳米晶.用XRD证实了产物的结构,用扫描电镜与透射电镜研究了产物微观形貌与尺寸.在980nm激光泵浦下,Ho3 掺杂Gd2(MoO4)3纳米晶发出很强的位于660nm的红光,而Er3 掺杂Gd2(MoO4)3纳米晶发出很强的位于540nm左右的红光.共掺Yb3 分别对Ho3 与Er3 起着显著的敏化作用.从发光强度与激光功率变化图中可知,Ho3 与Er3 的发光均属于双子光发光过程.     

基于稀土离子荧光特性的智能温敏涂层研究现状

智能温敏涂层是一种新兴的功能性涂层,其具有实时检测温度变化的功能,可以达到涂层使用过程中温度异常的及时发现,及时处理。减少了外部测温装置检测的误差以及测温时的不便利性。本文详细介绍了航空发动机温度检测的研究现状,并介绍了稀土离子检测温度时所利用上转换发光的原理,其测温优势在于实时检测,没有外接测温等方式对工件的形状尺寸要求,没有测温延迟。但不同稀土离子的测温温度段存在较大不同,无法兼顾所有的温度范围。还介绍了基于稀土荧光离子的温敏热障涂层的应用原理,该涂层在应用于航空发动机测温以及热障涂层性能检测等方面具有较大优势。总结了国内外学者研究的不同的材料体系及其温度检测范围,分析了温敏热障涂层目前的应用现状以及未来发展趋势。     

SnO2纳米颗粒的水热法和溶胶-凝胶法制备及其气敏特性

通过不同条件的水热法和溶胶-凝胶技术分别制备了单分散SnO2纳米粉体。利用X射线衍射、透射电子显微镜和比表面积分析仪对产物进行了检测,采用静态配气法测试了样品的气敏性能。结果表明,水热时间越长,颗粒尺寸越大,以反应时间为6 h制备的粉体比表面积最大;溶胶-凝胶产物中,以SnCl2的乙醇溶液为原料制得的颗粒克服了热处理过程中产物易团聚的问题,颗粒尺寸均匀,具有良好的分散性和较高的比表面积。两种方法制备的粉体均对酒精具有良好的灵敏度,SnCl2的乙醇溶液为原料、溶胶-凝胶技术获得的材料对酒精的灵敏度更高,并认为热处理过程中Cl-的去除是导致材料气敏性能不同的主要因素。     

V掺杂纳米ZnFe2O4的制备及气敏性研究

采用柠檬酸盐热解法制备V掺杂纳米ZnFe2O4,研究了V掺杂对ZnFe2O4的物相结构、厚膜电阻特性和对苯及其衍生物蒸汽气敏特性的影响.结果发现:V掺杂ZnFe2O4的物相单一;施主掺杂剂V大大降低了厚膜元件的电阻,并随掺杂量的增加,电阻逐渐下降;V掺杂还显著提高其对苯及其衍生物的高温敏感性.     

Gr/NiFe2O4纳米复合材料的制备与形成机理研究

以氧化石墨烯(GO)、Fe2(SO4)3和NiSO4为初始反应物,利用一步水热法合成了Gr/NiFe2O4纳米复合材料。采用X射线衍射(XRD)、透射电子显微镜(TEM)和拉曼光谱(RS)等分析手段对Gr/NiFe2O4样品进行了表征。结果表明:经过水热反应GO被还原的同时,纳米NiFe2O4成功地负载到石墨烯上,二者之间存在较强的界面相互作用,而且NiFe2O4纳米粒子增加了石墨烯片层间的距离避免了其再次堆垛,实现了石墨烯与NiFe2O4的良好复合。初步讨论了Gr/NiFe2O4纳米复合材料的形成机制,Ni2+、Fe3+在GO的含氧基团处非均相成核,在水热条件下不断长大,其生长过程遵循Ostwald熟化理论,即小尺寸的NiFe2O4粒子由于其较高的表面能而逐渐溶解,被那些尺寸较大的粒子消耗。     

Thermoelectric properties of rare earth doped SrTiO3

The thermoelectric properties of Sr_0.9R_0.1TiO₃ (R=Y, La, Sm, Gd, Dy) have been measured from room temperature to 1073 K. The electrical conductivities and Seebeck coefficients are independent of the kind of rare earth elements in the temperature range, so the figure of merits are influenced by the difference in the thermal conductivities. The thermal conductivities decrease with doping according to the rare earth atomic mass and ionic radius. Sr_0.9Dy_0.1TiO₃ shows the highest figure of merit of the investigated samples, reaching 3.84×10⁻⁴ K⁻¹ at 573 K.     

Synthesis and characterization of Er doped CaF2 nanoparticles

Er³⁺ doped CaF₂ nanoparticles were synthesized by a chemical co-precipitation method. Effect of the dopant concentrations on the structure and optical properties of the CaF₂ nanoparticles was investigated. The X-ray powder diffraction and transmission electron microscopy analysis was used to characterize the structure and morphology of the nanoparticles. The nanoparticles with different dopant concentration exhibited a sphere-like morphology with diameters of about 8-36 nm. The incorporation of Er³⁺ ions into CaF₂ resulted in the decrease in grain size and deterioration of crystallinity, but enlarged the lattice constants of CaF₂. Additional annealing treatment at 400 °C to the prepared CaF₂ removed the NO₃⁻ and OH⁻ groups adsorbed on the particles’ surfaces, and improved the optical properties of the nanoparticles. The fluorescence intensity, with a maximum at approximately 0.4 mol%, decreased with the increase in doping concentration because of concentration quenching.     

Luminescence and energy migration in the oxyapatite Ca2Gd8(SiO4)6O2 doped with several rare earth and mercury-like ions

Energy transfer phenomena have been observed by activating the oxyapatite host-lattice Ca₂Gd₈(SiO₄)₆O₂ with Eu³⁺, Tb³⁺, Dy³⁺, Sm³⁺. This is based on the energy migration in the Gd³⁺ sublattice and trapping by the activators. The trapping efficiency for Gd³⁺ excitation energy increases in the sequence of Sm³⁺ < Dy³⁺ < Tb³⁺ < Eu³⁺. It is supposed that the activator ions are incorporated on both Gd³⁺ sites in Ca₂Gd₈(SiO₄)₆O₂. The Gd³⁺ sublattice in Ca₂Gd₈(SiO₄)₆O₂ can be sensitized by Pb²⁺ but not by Ce³⁺, Pr³⁺ and Bi³⁺.     

Crystal structures of new ternary rare earth silicides Sc3Pr2Si4, Sc1.26Pr3.74Si4 and Sc3.96Nd1.04Si4 with ordered and partially ordered rare earth sites

The crystal structures of three new ternary silicides Sc₃Pr₂Si₄, Sc_1.26Pr_3.74Si₄ and Sc_3.96Nd_1.04Si₄ were determined by single crystal X-ray diffraction. The title compounds crystallize with three different substitution derivatives of the Sm₅Ge₄ structure type (orthorhombic space group Pnma) containing various distributions of rare earth atoms on the three Sm sites. Crystal chemistry analysis shows that these distributions are controlled by the atomic size factor.     

Water-soluble Yb, Tm codoped NaYF4 nanoparticles: Synthesis, characteristics and bioimaging

Water soluble NaYF₄ nanocrystals codoped with 20 mol% Yb³⁺, 0.5 mol% Tm³⁺ were prepared by a facile solvothermal approach using polyvinylpyrrolidone (PVP) as a surfactant. The upconversion NaYF₄ nanocrystals were pure cubic phase with an average size of ∼40 nm. They could be well redispersed in water to form a clearly transparent solution without obvious precipitation. With the excitation of a 980-nm diode laser, the nanocrystal solution presents bright violet and blue upconversion luminescence. These upconversion nanoparticles (UCNPs) were incubated with HeLa cells at 37 °C for 24 h, and bright blue upconversion luminescence were observed from the UCNPs endocytosed into the HeLa cells on a microscope equipped with a 980-nm fiber laser. These results indicated that the UCNPs had potential applications for biological imaging as luminescent probes.     

Controllable synthesis of bifunctional NaYF4:Yb/Ho@SiO2/Au nanoparticles with upconversion luminescence and high X-ray attenuation

A novel type of bifunctional water-soluble NaYF₄:Yb³⁺/Ho³⁺@SiO₂/Au nanocomposite is fabricated by a facile layer-by-layer technology in which the mercapto-silica shell is used as the functional layer coating on the central NaYF₄:Yb³⁺/Ho³⁺ nanocrystals. Then by adjusting the mole ratio of the Au nanoparticles to the NaYF₄:Yb³⁺/Ho³⁺@SiO₂ nanoparticles, control of the gold loading on the upconversion nanocrystal surface is achieved. The fabricated nanocomposites inherit the excellent physical and chemical properties from their building blocks, simultaneously exhibiting upconversion luminescence and high X-ray attenuation and as well are easily modified with various molecules. These properties render the synthesized NaYF₄:Yb³⁺/Ho³⁺@SiO₂/Au nanocomposite not only useful as a multimodality contrast agent to increase the efficiency of molecular imaging but also has the potential of in situ curing of diseases.     

Structural and luminescent properties of nano-sized NaGdF4:Eu synthesised by wet-chemistry route

Hexagonal Eu³⁺:NaGdF₄ fluoride with average grains size of 20 nm was obtained from solution by a co-precipitation method. Morphology of the obtained powder was examined by XRD and TEM methods. Absence of the Eu³⁺-O²⁻ charge-transfer band, expected in excitation spectrum at 260 nm indicates, that oxygen ions are not incorporated into a fluoride lattice. As-received fluoride contains considerable amounts of the water molecules, adsorbed at the surface of the material, which may be relatively easily removed by heating the powder at 300 °C. Thermal treatment at 650 °C is sufficient for removing of the OH⁻ groups built into fluoride lattice. Influence of method of synthesis as well as oxygen, water molecules and OH⁻ groups content on optical properties of the obtained phosphors is investigated and discussed by comparison with optical properties of the Eu³⁺:NaGdF₄ fluoride synthesised by a solid-state reaction.     

掺铝氧化锌包覆LiFePO4的合成与性能（英文）

以简单的固相法合成了橄榄石结构LiFePO4,并以导电掺铝氧化锌材料(AZO)对其表面进行包覆。充放电结果显示,表面包覆大幅度改善了LiFePO4材料的倍率和低温性能。在20C高倍率条件下,AZO包覆LiFePO4的放电比容量可达100.9mA·h/g;在低温20°C时进行0.2C充放电,未包覆LiFePO4和AZO包覆LiFePO4的放电比容量分别为50.3mA·h/g和119.4mA·h/g。经分析,这可能是由于采用导电AZO包覆措施而增加了LiFePO4材料的电导率,从而极大地提高了其比容量。另外,导电AZO包覆措施还增加了LiFePO4材料的振实密度。这些结果表明AZO包覆LiFePO4材料是一种很好的适用于锂离子动力电池的正极材料。     

TiO2掺杂SmTaO4陶瓷热物理性能研究

热障涂层是燃气轮机高温部件保护的重要材料之一,SmTaO4陶瓷具有优异的高温相稳定性和力学性能,有望成为新型热障涂层材料。本研究采用固相法制备TiO2掺杂SmTaO4陶瓷,研究结果表明：掺杂TiO2未改变SmTaO4陶瓷晶体结构,样品均为单斜相,掺杂2% mol TiO2的SmTaO4陶瓷烧结过程中出现的第二相为Sm0.33TaO3;随着TiO2含量增加,SmTaO4陶瓷的热导率先下降后上升,当TiO2掺杂含量为2%时,热导率最低为1.42W?m?1?K?1,低于SmTaO4（1.59W?m-1?K-1,900℃）,与7-8YSZ相比（2.1~2.7 W?m?1?K?1,100~900℃）下降了近30%。掺杂2%TiO2的SmTaO4陶瓷热膨胀性系数最大值为10.8×10-6K-1,大于YSZ（~10.0×10-6K-1）和SmTaO4（9.62×10-6K-1,1200℃）,与纯SmTaO4相比,TiO2掺杂提高了SmTaO4陶瓷的热膨胀系数。因此,TiO2掺杂SmTaO4陶瓷有望作为新型热障涂层材料使用。