SAPO-34分子筛骨架稳定性的研究

利用差热分析，原位ＸＲＤ技术，高温条件下的焙烧和水蒸气处理并关联其催化性能变化，研究了ＳＡＰＯ－３４分子筛的热及水热稳定性，差热分析结果表明，ＳＡＰＯ－３４的骨架破坏温度高于１３００Ｋ，原位ＸＲＤ跟踪研究证实，ＳＡＰＯ－３４分子筛原粉在高温焙烧以除掉有机胺及随后的降温过程中无明显的骨架破坏；而焙烧型ＳＡＰＯ－３４在空气中放置一定时间后，水分子吸附微孔中明业降低样品的ＸＲＤ峰强度，且降低幅度随放置时     

The initial oxidation of magnesium: an in situ study with XPS,HERDA and ellipsometry

The initial oxidation of magnesium at oxygen partial pressures between 1.3 × 10^?8 and 1.3 × 10^?5 Pa and at temperatures ranging from 273 to 550 K has been investigated in situ with X‐ray photoelectron spectroscopy (XPS), ellipsometry and high resolution elastic recoil detection analysis (HERDA). Quantitative analysis of the XPS spectra showed a clear oxygen deficiency with respect to MgO for the initial oxide. HERDA measurements confirmed this relatively low oxygen content in the thin oxide layers formed. Ellipsometry measurements showed that the electronic structure of the initially formed oxide differs significantly from that of bulk MgO. The band gap values at room temperature for the oxide layers investigated are clearly smaller than the value for bulk MgO. Copyright © 2006 John Wiley & Sons, Ltd.     

聚合物微晶尺寸和晶格畸变

聚合物微晶尺寸和晶格畸变是对聚合物材料性能有着重要影响的结构参数。本文介绍了应用Ｘ射线衍射方法测定聚合物微晶尺寸和结构畸变的几种方法：近似函数、次晶模型法、方差法、矩法。     

Elastic scattering of gamma rays and X-rays

Studies of elastic gamma ray scattering were pursued independently by the groups of Prof. Ghose and the author for several decades in spite of somewhat meagre support. Several techniques for such studies developed by the two groups and some of the results obtained in the energy range from tens of keV to about 1.5 MeV are described briefly. The theoretical background necessary for understanding these results is also outlined. The results showed the importance of Modified Relativistic Form Factor (MRFF) approximation in the explanation of atomic Rayleigh scattering cross sections in the small angle regime and the necessity for an inclusion of real Delbrück scattering amplitudes at large scattering angles. Dispersion corrections to form factor amplitudes or the so-called anomalous scattering factors are shown to be needed at photon energies close to electron binding energy thresholds. A few promising future extensions of such studies are indicated at the end.     

The Reactivity of Cr‐Te Superlattice Reactants and of Co‐deposited Cr‐Te Films: Studies with in‐situ X‐ray Diffractometry

The reactivity of a Cr‐Te multilayer film consisting of 326 Cr/Te double‐layers with about 88(3) at% Te was investigated with in‐situ X‐ray diffraction. The occurrence of a superstructure reflection caused by the multilayer system is observed. During the annealing procedure between 80 and 90 °C the layer‐by‐layer arrangement is destroyed and elemental Te crystallizes. After 6 h isothermal annealing at 140 °C CrTe₃ starts to crystallize. The amount and the crystal size of CrTe₃ increase with raising temperature and Te is consumed during the growth process. At 220 °C the formation of crystalline Cr₂Te₃ is observed and between 220 and 260 °C CrTe₃ is completely decomposed into Cr₂Te₃. The two Cr tellurides grow as highly textured materials. The size of CrTe₃ crystals is significantly larger than that of Cr₂Te₃. For a co‐deposited Cr‐Te film with composition 77(3) at% Te the tri‐telluride and elemental Te crystallize simultaneously. The texture of CrTe₃ is less pronounced and different reflections of the tri‐telluride occur besides the (h00)‐reflections. Up to 160 °C a pronounced increase of the crystallite size is observed and the crystals are significantly larger than those obtained with the multifilm sample. At 130 °C the crystallization kinetics seem to be controlled by nucleation.     

表面修饰二氧化锡纳米微晶的制备与表征

制备了硅烷偶联剂KH-570表面修饰的SnO2纳米微晶，通过FT-IR、XPS、TEM和TG-DTA对其结构和表面特性进行表征和研究. FT-IR和XPS分析结果确证了KH-570与SnO2表面是以化学键合或物理吸附方式相结合,粒子表面存在酯基等有机官能团的红外吸收特征；观测到KH-570中Si原子的Si2s和Si2p谱线. TEM分析表明，表面修饰反应增强了SnO2纳米微晶的疏水性和分散性.由XPS和TG的实测数据探讨了纳米粒子具有较低包覆量的可能原因.     

Two‐ and Three‐Dimensional Molecular Organization of Schiff‐Base Derivatives

We have designed and synthesized a series of Schiff base derivatives, and studied their structural features in two‐dimensional (2D) and three‐dimensional (3D) states by combining scanning tunneling microscopy (STM) and X‐ray diffraction experiments. The Schiff‐base derivatives with short alkyl chains crystallize easily, which allows a detailed structural analysis by X‐ray diffraction. Due to the strong adsorbate–substrate interactions, those bases with long alkyl chains easily form 2D assemblies on highly oriented pyrolytic graphite (HOPG). The STM images indicate also that the introduction of two methoxy groups into the molecule can change the structure of these 2D assemblies as a result of the increased steric hindrances, for example: the Schiff‐base derivative, bearing both methoxy groups and C₁₆H₃₃ tails, forms 2D Moiré patterns, and an alignment of pairing Schiff‐base molecules may be easily resolved. Conversely, the Schiff base derivative, bearing solely C₁₆H₃₃ tails, forms 2D non‐Moiré patterns. It is demonstrated that the 3D structural features result from the compromise of intermolecular interactions of different molecular moieties. However, there is one more factor, which also governs the 2D structure: the adsorbate‐substrate interaction. The 3D crystal structure may thus help to understand many factors involved in the formation of 2D structures, and would be helpful for designing new molecular assemblies with tailoring functions.     

Thermotropic Liquid Crystals Based on Extended 2,5‐Disubstituted‐1,3,4‐Oxadiazoles: Structure–Property Relationships,Variable‐Temperature Powder X‐ray Diffraction,and Small‐Angle X‐ray Scattering Studies

A class of extended 2,5‐disubstituted‐1,3,4‐oxadiazoles R¹‐C₆H₄‐{OC₂N₂}‐C₆H₄‐R² (R¹=R²=C₁₀H₂₁O 1 a , p‐C₁₀H₂₁O‐C₆H₄‐C?C 3 a , p‐CH₃O‐C₆H₄‐C?C 3 b ; R¹=C₁₀H₂₁O, R²=CH₃O 1 b , (CH₃)₂N 1 c ; F 1 d ; R¹=C₁₀H₂₁O‐C₆H₄‐C?C, R²=C₁₀H₂₁O 2 a , CH₃O 2 b , (CH₃)₂N 2 c , F 2 d ) were prepared, and their liquid‐crystalline properties were examined. In CH₂Cl₂ solution, these compounds displayed a room‐temperature emission with λ_max at 340–471 nm and quantum yields of 0.73–0.97. Compounds 1 d , 2 a – 2 d , and 3 a exhibited various thermotropic mesophases (monotropic, enantiotropic nematic/smectic), which were examined by polarized‐light optical microscopy and differential scanning calorimetry. Structure determination by a direct‐space approach using simulated annealing or parallel tempering of the powder X‐ray diffraction data revealed distinctive crystal‐packing arrangements for mesogenic molecules 2 b and 3 a , leading to different nematic mesophase behavior, with 2 b being monotropic and 3 a enantiotropic in the narrow temperature range of 200–210 °C. The structural transitions associated with these crystalline solids and their mesophases were studied by variable‐temperature X‐ray diffractometry. Nondestructive phase transitions (crystal‐to‐crystal, crystal‐to‐mesophase, mesophase‐to‐liquid) were observed in the diffractograms of 1 b, 1 d , 2 b, 2 d , and 3 a measured at 25–200 °C. Powder X‐ray diffraction and small‐angle X‐ray scattering data revealed that the structure of the annealed solid residue 2 b reverted to its original crystal/molecular packing when the isotropic liquid was cooled to room temperature. Structure–property relationships within these mesomorphic solids are discussed in the context of their molecular structures and intermolecular interactions.     

Capillary flow behavior of worm‐like micelles studied by small‐angle X‐ray scattering and small angle light scattering

A novel capillary flow device has been developed and applied to study the orientation of worm‐like micelles, among other systems. Small‐angle X‐ray scattering (SAXS) data from micelles formed by a Pluronic block copolymer in aqueous salt solution provides evidence for the formation of worm‐like micelles, which align under flow. A transition from a rod‐like form factor to a less persistent conformation is observed under flow. Flow alignment of worm‐like micelles formed by the low molar mass amphiphile system cetyl pyridinium chloride+sodium salicylate is studied for comparative purposes. Here, inhomogenous flow at the micron scale is revealed by streaks in the small‐angle light scattering pattern perpendicular to the flow direction. Copyright © 2006 John Wiley & Sons, Ltd.     

Synthesis, solid-state structure, and bonding analysis of the beryllocenes [Be(C5Me4H)2], [Be(C5Me5)2], and [Be(C5Me5)(C5Me4H)

The beryllocenes [Be(C(5)Me(4)H)(2)] (1), [Be(C(5)Me(5))(2)] (2), and [Be(C(5)Me(5))(C(5)Me(4)H)] (3) have been prepared from BeCl(2) and the appropriate KCp' reagent in toluene/diethyl ether solvent mixtures. The synthesis of 1 is facile (20 degrees C, overnight), but generation of decamethylberyllocene 2 demands high temperatures (ca. 115 degrees C) and extended reaction times (3-4 days). The mixed-ring beryllocene 3 is obtained when the known [(eta(5)-C(5)Me(5))BeCl] is allowed to react with K[C(5)Me(4)H], once more under somewhat forcing conditions (115 degrees C, 36 h). The structures of the three metallocenes have been determined by low-temperature X-ray studies. Both 1 and 3 present eta5/eta1 geometries of the slip-sandwich type, whereas 2 exhibits an almost regular, ferrocene-like, sandwich structure. In the mixed-ring compound 3, C(5)Me(5) is centrally bound to beryllium and the eta(1)-C(5)Me(4)H ring bonds to the metal through the unique CH carbon atom. This is also the binding mode of the eta(1)-ring of 1. To analyze the nature of the bonding in these molecules, theoretical calculations at different levels of theory have been performed on compounds 2 and 3, and a comparison with the bonding in [Be(C(5)H(5))(2)] has been made. As for the latter molecule, energy differences between the eta5/eta5 and the eta5/eta1 structures of 2 are very small, being of the order of a few kcal mol(-1). Constrained space orbital variations (CSOV) calculations show that the covalent character in the bonding is larger for [Be(C(5)Me(5))(2)] than for [Be(C(5)H(5))(2)] due to larger charge delocalization and to increased polarizability of the C(5)Me(5) fragment.