飞秒脉冲激光对Ti宝石辐照作用的研究

采用波长800nm、脉冲宽度120fs的飞秒激光对温度梯度(TGT)生长的Ti宝石进行辐照后,材料呈暗黑色。通过相关数学模型计算出Ti宝石在激光辐照瞬间的热影响范围(HAZ)为1.968×10-3μm,材料最高温度达1.47×105K。样品经飞秒激光辐照后吸收增大,但没有新吸收峰出现,通过对比不同品质因数(FOM)值的Ti宝石样品在420nm处荧光谱发现,飞秒激光辐照后420nm处荧光强度增大是由于样品中Ti4+浓度增大引起的。拉曼光谱和X射线衍射(XRD)的检测结果表明,激光辐照后材料的晶格产生畸变,晶格质量明显下降。     

Characterizations of SnO2 and SnO2:Sb thin films prepared by PECVD

Structural characterizations of tin oxide (SnO₂) thin films, deposited by plasma-enhanced chemical vapor deposition (PECVD), were investigated with scanning electron microscope (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The results show that the films are porous, the crystalline structure transforms from crystalline to amorphous phase as deposition temperature changes from 500°C to 200°C, and the chemical component is non-stoichiometric (Sn:O is 1.0716 prepared at 450°C with a value of O₂ flow 3.5 l/min). Sheet resistance of the thin films decreases with increasing of deposition temperature. Whereas, sheet resistance increases with increasing of oxygen flow. Tin oxide doped with antimony (SnO₂:Sb) thin films prepared by same method have a better selectivity to alcohol than to carbon monoxide; the maximum sensitivity is about 220%. The gas-sensing mechanism of SnO₂ thin films is commentated.     

Sulfated Zirconia with Ordered Mesopores as an Active Catalyst for n-Butane Isomerization

Zirconia/surfactant composites were hydrothermally synthesized in aqueous sulfuric acid at 373 K using Zr(O-nPr)₄ as oxide precursor and hexadecyl-trimethyl-ammonium bromide as template. Mesostructural features similar to those of MCM-41 were detected by X-ray diffractometry, with d=4.6 nm. A sample obtained from a starting mixture with Zr:S:CTAB = 2:2:1 was stable enough for removal of occluded organics. After calcination at 813 K, the d-value was 3.6 nm, the surface area 200 m²/g, and the mean pore diameter estimated by the BJH method 2.2 nm. Extended X-ray absorption fine structure analysis suggests Zr to be in a short-range structure (<4 Å) similar to that of Zr in monoclinic ZrO₂. Scanning electron microscopy including energy dispersive X-ray analysis showed 1-5 m sulfur-containing ZrO₂ spheres. The material catalyzes the isomerization of n-butane to i-butane at 378 K with a steady activity in the order of magnitude of commercial sulfated ZrO₂.     

Development of Time-Resolved XAFS Instrumentation for Quick EXAFS and Energy-Dispersive EXAFS Measurements on Catalyst Systems

From its very earliest days, at which time measuring a spectrum took at least 1 h, XAFS has been used for catalysis studies. In more recent times technological advances have improved the time resolution to minutes and seconds with quick EXAFS, and subsecond to millisecond with energy-dispersive EXAFS. This paper describes the instrumentation necessary and elucidates with specific examples where this has been used. In particular the Daresbury QEXAFS monochromator will be shown and several examples of combined XAFS and diffraction, a powerful technique for in situ studies. The development of energy dispersive EXAFS at Daresbury will be described. Recent results on in situ Rh catalysis combining EDE and mass spec measurements at the ESRF are highlighted, and finally the details of the latest microstrip detector that will enable continuous measurements at 10 s time intervals is presented.     

射频磁控溅射法在玻璃基片上沉积CeO2 薄膜的研究

二氧化铈具有高折射率、介电常数和紫外吸收率,因此它广泛地应用于各种光学和电子器件.本文采用射频磁控溅射法在玻璃基片上沉积CeO2薄膜.溅射过程中,首先制备纯二氧化铈靶材,然后在不同的功率上调节不同的基片温度进行溅射.采用光电子能谱、X射线衍射、拉曼光谱和扫描电镜等测试方法表征薄膜的特性.     

Al-C在机械合金化过程中的结构变化

针对C原子的扩散过程，研究了Al-石墨在机械合金化过程中的结构变化.用X射线衍射仪（XRD）、扫描电子显微镜、拉曼光谱仪及计算机模拟观察，分析了不同球磨时间的Al-C混合物的结构.结果表明，球磨初期，石墨晶粒尺寸的减小及六角石墨转变为Turbostratic 结构，使石墨的X射线衍射峰迅速减弱，以至消失.随球磨时间的增加，C原子逐渐扩散到Al的点阵中形成固溶体. 将Al-C固溶体进行退火处理，便转变为Al4C3.即使在球磨产物的XRD图中观察不到石墨的衍射峰后，继续球磨数十小时，拉曼光谱表明球磨样品中仍有未与Al反应的单质石墨.     

Tin–cobalt electrodeposition from sulfate–gluconate baths

The electrodeposition of tin + cobalt alloys from a slightly acidic sulfate–gluconate bath on both vitreous carbon and copper substrates has been studied for different [Sn(II)]/[Co(II)] ratios in the bath, varying between 1/10 and 1/2. A relationship between the electrochemical stripping analysis and the morphology of the deposits has been found. Two different types of deposit were obtained. At low [Sn(II)]/[Co(II)] ratios and relatively high deposition rates a nodular, cobalt-rich, nanocrystalline coating was obtained, while at high [Sn(II)]/[Co(II)] ratios and low deposition rates a new, well-defined tetragonal SnCo phase was obtained, with cell parameters of a = 3.087 Å and c = 5.849 Å. This structure favours hydrogen evolution.     

三种不同煤阶煤的模拟热解实验研究 (Ⅱ)固态产物分析

利用油气生成的地质历史过程中温度－时间补偿效应,运用“慢速升温＋长时间恒温”的方法,采用热重分析法和改进的封闭系统热解装置,在热解终温范围３５０℃～５５０℃,升温速率５Ｋ／ｍｉｎ,恒温时间２４ｈ等比较温和的反应条件下,研究了不同变质程度的神木煤、东山煤和阳城煤的热解过程,并运用傅立叶变换红外光谱（ＦＴＩＲ）、Ｘ－射线衍射（ＸＲＤ）、元素分析等现代仪器分析技术研究了不同温度下热解所得到的系列化固态产物．研究结果表明：采用改进的热解装里能得到较好的模拟热解实验结果,至少在上述实验条件下可以得到很好的结果;煤样的元素组成、物理和化学特性、所含官能团种类和数量等不同,使得在相同条件下所发生反应不同,尤其是高变质程度的阳城无烟煤与其它煤差异更大．所以,固态产物的组成特性和随热解温度的变化规律不同;相对高阶煤而言,选用中等变质程度的烟煤可以得到更好的模拟效果．     

Implication of the microstructure of binary Cu/ZnO catalysts for their catalytic activity in methanol synthesis

Binary Cu/ZnO catalysts with varying molar ratios (90/10 through 10/90) were studied under methanol synthesis conditions at 493 K and at atmospheric pressure. The methanol synthesis activity of the catalysts was correlated to their specific Cu surface area (N₂O reactive frontal chromatography, N₂O RFC) after reduction in 2 vol% H₂ at 513 K. Activity data were supplemented with a detailed analysis of the microstructure, i.e., crystallite size and strain of the reduced Cu and the ZnO phases after reduction using X-ray diffraction line profile analysis. The estimated copper surface area based on a spherical shape of the copper crystallites is in good agreement with data determined by N₂O RFC. A positive correlation of the turnover frequency for methanol production with the observed microstrain of copper in the Cu/ZnO system was found. The results indicate a mutual structural interaction of both components (copper and zinc oxide) in the sense that strained copper particles are stabilized by the unstrained state of the zinc oxide microcrystallites. The observed structural deformation of ZnO in samples with higher Cu loading can originate, for instance, from epitaxial bonding of the oxide lattice to the copper metal, insufficient reduction or residual carbonate due to incomplete thermal decomposition during reduction. Additional EXAFS measurements at the Cu K and the Zn K edge show that about 5% ZnO are dissolved in the CuO matrix of the calcined precursors. Furthermore, it is shown that the microstructural changes (e.g., size and strain) of copper can be traced back to the phase composition of the corresponding hydroxycarbonate precursors.