机械合金化Fe-Cu系统的EXAFS研究

ＥＸＡＦＳ研究Ｆｅ－Ｃｕ系二元金属的Ｆｅ和Ｃｕ配位环境随球磨时间及组成的变化情况，结果表明机械合金化方法能扩展Ｆｅ和Ｃｕ金属的固溶范围并形成纳米尺寸的非平衡亚稳态合金晶粒，Ｆｅ₈₀Ｃｕ₂₀（１６０ｂ）中Ｃｎ的Ｋ吸收谱和ＲＳＦ出现ｂｃｃ结构的特征，其Ｆｅ－Ｃｕ的合金晶粒为ｂｃｃ结构；Ｆｅ₆₀Ｃｕ₄₀（１６０ｋ）中Ｃｕ和Ｆｅ的ＲＳＦ都为ｆｃｃ结构，其合金晶粒的结构与Ｆｅ₈₀Ｃｕ₂₀的不同，为ｆｃｃ结构，但合金晶粒中未形成均匀分散的Ｆｅ－Ｃｕ合金相是Ｃｕ略富积于核，Ｆｅ偏析于表面的亚稳态结构。     

在纯水中高能球磨稀土氧化物制备超细纳米悬浮液

通过在纯水中对稀土氧化物进行高能球磨制备出超细纳米悬浮液,考察了球磨时间、转速等制备条件对悬浮液稳定性以及粒子结构的影响.结果表明，球磨时间和转速的增加有利于提高悬浮液的稳定性,粒子尺寸的大小，分布的均匀性以及表面电荷性质是决定悬浮液稳定性的重要因素.利用这种方法制备的悬浮液具有良好的稳定性和较高的浓度,同时不含分散剂和稳定剂,因而具有表面张力高、粘度低等特点.     

Strain Induced Metastable Phase and Phase Revolution in PbTiO3-CoFe204 Nanocomposite Film

An inter-component epitaxial strain-induced PbTiOa metastable phase is observed in a PbTiO3-GoFe2O4 epitaxial composite film, corresponding to the dielectric anomaly reported previously. High-resolution synchrotron radiation X-ray diffraction and first principles calculation demonstrate the coexistence of different PbTi03 phases, even a possible morphotropie phase boundary in the film, elucidating the underlying microscopic rneehanism of the formation of Pb TiO3 metastable phase. This sheds light on the design and manipulation of electromechanical properties of epitaxial films, through the strain engineering.     

PbS量子点在荧光集光太阳能光伏器件上的应用

荧光集光太阳能光伏器件在平面光波导效应的作用下实现等效聚光,可以减少太阳能电池的用量,有效降低光伏发电的成本。将胶体化学法制备的吸收和发射在近红外波段的单分散球状PbS量子点荧光材料封装于两片光伏超白玻璃间的正己烷溶液中,构成溶液夹层封装的平面光波导,并和效率为17%的单晶硅太阳能电池耦合,制作出了吸收在700～1000nm,效率约为1.31%的近红外荧光集光太阳能光伏器件。     

[CuO-ZnO-Al2O3]/[HZSM-5]核壳双功能催化剂的制备、结构及其CO2+H2直接合成二甲醚反应性能

利用水热合成法制备了一系列不同晶化时间的核壳结构双功能催化剂[CuO-ZnO-Al₂O₃]/[HZSM-5],通过X射线衍射(XRD)、扫描电镜(SEM)和能量分散谱(EDS)对催化剂结构进行了表征,并考察了核壳催化剂CO₂加氢直接合成二甲醚的反应性能。结果表明,通过水热合成法可在甲醇合成催化剂CuO-ZnO-Al₂O₃表面包覆一层完整的HZSM-5分子筛膜,形成核壳结构,并且调节晶化时间可以控制分子筛晶粒尺寸及膜厚。与物理混合法制备的传统双功能催化剂相比,核壳结构催化剂合成二甲醚的选择性显著提高,其中晶化时间为3d的催化剂反应性能最为理想,CO₂转化率为38.9%,二甲醚选择性达到77.0%。     

活化气氛对钼基合成醇催化剂的结构和性能的影响

Activated carbon supported Mo-based catalysts were prepared and reduced under different activation atmospheres, including pure H₂, syngas (H₂/CO=2/1), and pure CO. The catalysts structures were characterized by X-ray diffraction, X-ray absorption fine structure, and in situ diffuse reflectance infrared Fourier transform spectroscopy. The catalytic performance for the higher alcohol synthesis from syngas was tested. The pure H₂ treatment showed a high reduction capacity. The presence of a large amount of metallic Co⁰. and low valence state Mo^φ+ (0<φ<2) on the surface suggested a super activity for the CO dissociation and hydrogenation, which promoted hydrocarbons formation and reduced the alcohol selectivity. In contrast, the pure CO-reduced catalyst had a low reduction degree. The Mo and Co species at the catalyst mainly existed in the form of Mo⁴⁺ and Co²⁺. The syngas-reduced catalyst showed the highest activity and selectivity for the higher alcohols synthesis. We suggest that the syngas treatment had an appropriate reduction capacity that is between those of pure H₂ and pure CO and led to the coexistence of multivalent Co species as well as the enrichment of Mo^δ+ on the catalyst''s surface. The synergistic effects between these active species provided a better cooperativity and equilibrium between the CO dissociation, hydrogenation and CO insertion and thus contributed beneficially to the formation of higher alcohols.     

探索物质世界的利器——同步辐射

当近光速的带电粒子在磁场中转向时,沿运动轨迹的切线方向将会发出很窄的电磁辐射,这种高亮度的"光"称为同步辐射.同步辐射的波段范围从THz到远红外/红外,一直扩展到X射线/γ射线,其卓越的性能已经成为探索物质世界强有力的工具,在物理、化学、材料科学、生命科学、医学、纳米科技等领域获得了广泛的应用.本文就同步辐射的发光机制、特点及其应用作了简单的介绍,并结合我们课题组的两个研究实例展示了同步辐射的巨大潜力.     

SIMULATION OF X-RAY DIFFRACTION OF MULTILAYER FILM WITH INTERFACIAL ROUGHNESS

In this paper, the X-ray diffraction profiles of multilayer with uncorrelated rough interfaces are directly simulated using kinematic theory of X-ray diffraction. The result shows that the decrease of the reflective intensity caused by the interracial roughness is more severe than that caused by random fluctuation of period of the same degree, and the decrease of the reflective intensity of high order Bragg deffraction is more rapid than that of low order ones. So it is very important to reduce the interracial roughness in the deposition and in the annealing of multilayer films.     

直接Z型CdO-CdS纳米棒阵列的制备及其光电催化性能研究

本文通过简单的水热法制备了一种CdO-CdS一维纳米棒阵列,并系统地研究了材料的结构、形貌及其光电化学性质和产氢活性. 所得纳米棒为直径100至200 nm的六方柱. 通过优化煅烧温度和时间得到了该实验条件下光电催化性能最优的样品. 在0 V vs. Ag/AgCl偏压下,CdO-CdS光电流密度为6.5 mA/cm²,光电催化产氢活性为240 μmol·cm^-2·h^-1,几乎是纯CdS的2倍. 该体系的光电催化性能超过了许多已报道的相似体系. 根据材料结构和光电化学性能表征结果,提出了直接z型光催化机理,该机理可以很好地解释光致载流子的高分离效率和优异的氧化还原性能.