The Local Uranium Environment in Cesium Uranates: A Combined XPS, XAS, XRD, and Neutron Diffraction Analysis

The cesium uranates Cs₂UO₄, Cs₂U₂O₇, Cs₄U₅O₁₇ and Cs₂U₄O₁₂ were studied using X-ray Diffraction (XRD), neutron diffraction, X-ray Photoelectron Spectroscopy (XPS) and X-ray Absorption Spectroscopy (XAS) in an attempt to couple the crystallographic structure to the uranium valence state using the local uranium environment. The diffraction spectra were used for Rietveld refinement to determine the atomic positions and interatomic distances. These distances were subsequently used in Bond Valence Sum (BVS) calculations to determine the uranium valences. The XAS spectra give direct information on the local uranium environment regarding the U-O distances and the arrangement of the oxygen atoms around the central uranium. The difference between the monovalent uranates and the multivalent Cs₂U₄O₁₂ is clearly established in all spectra, as well as in the crystal structures. The different valences present can be assigned to individual uranium lattice sites, but some amount of disorder is required to balance the charges.     

Combined XPS and AFM study of cluster-containing polymers based on Rh

Rh₆- monomer and polymer-immobilized complexes have been characterized using XPS and AFM. Polymer-immobilized clusters were obtained by the reaction of Rh₆(CO)₁₅CH₃CN with copolymer of allyldiphenylphosphine and styrene. AFM study shows the change of surface morphology of the above copolymers. XPS data demonstrated the change of charge state of Rh atoms under monosubstitution of the CO-group for Rh₆- monomer complexes as well as in copolymer cluster complexe after the catalysis process of hydrogenation.     

Characterization of Au-Rh/TiO2 catalysts by CO adsorption; XPS, FTIR and TPD experiments

On X-ray photoelectron spectra of the Au-Rh/TiO₂ catalysts the position of Au4f peak was practically unaffected by the presence of rhodium, the peak position of Rh3d, however, shifted to lower binding energy with the increase of gold content of the catalysts. Rh enrichment in the outer layers of the bimetallic crystallites was experienced. The bands due to Au⁰-CO, Rh⁰-CO and (Rh⁰)₂-CO were observed on the IR spectra of bimetallic samples, no signs for Rh⁺-(CO)₂ were detected on these catalysts. The results were interpreted by electron donation from titania through gold to rhodium and by the higher particle size of bimetallic crystallites.     

Direct measurement of the nitrogen content by XPS in self‐passivated TaNx thin films

The nitrogen content in tantalum nitride (TaN_x) thin films, where x indicates that TaN_x is not generally stoechiometric, can be measured directly by XPS. This is the purpose of the present study. However, the XPS spectra of TaN_x present electron energy loss spectroscopy (EELS) peaks that lead to a complex peak fitting, particularly for self‐passivated thin films. A complete peak fitting procedure based upon Tougaard's background, the Doniach‐Sunjic Function and EELS peaks, is presented. It is applied to two self‐passivated TaN_x thin films elaborated by reactive sputtering and presenting a different nitrogen content. The physical properties of these surfaces are interpreted in terms of Ta 4f_7/2 chemical states directly dependent on the nitrogen content. The main results are discussed and improvements are proposed to the method. Copyright © 2008 John Wiley & Sons, Ltd.     

Monitoring the Location,Amount, and Nature of Carbonaceous Deposits on Aged Zeolite Ferrierite Crystals by Using STEM‐EELS

By the use of electron energy‐loss spectroscopy performed in a scanning transmission electron microscope (STEM‐EELS), detailed spatial information is obtained concerning the amount and nature of carbonaceous deposits formed inside the crystals of the zeolite ferrierite (FER) during the reaction of n‐butene to isobutene. In all cases, gradients in coke concentration over the crystal have been observed and quantified. An extensive accumulation of coke is observed at the entrance of the eight‐membered‐ring (MR) pores, while less coke is present at the entrances of the ten‐MR channels. At a higher coke content, further filling up of the complete micropore system occurs and the eight‐MR pores become fully blocked. The ten‐MR channels remain partially accessible for n‐butene, with alkyl‐aromatic species deposited near the inlets of these channels. With regard to the selective transformation of n‐butene into isobutene, this supports the view that the catalytic action takes place in the pore mouths of the ten‐MR channels. Overall it is demonstrated that the major benefit of STEM‐EELS is the possibility to simultaneously determine the position‐resolved amount and nature of carbonaceous deposits on intact zeolite crystals.     

准“原位”XPS技术研究加氢精制催化剂的硫化过程

用准“原位”XPS技术研究了Mo/Al_2O_3、Mo/TiO_2-Al_2O_3、CO/Al_2O_3、CO/TiO_2-Al_2O_3、Co-Mo-Al_2O_3和Co-Mo/TiO_2-Al_2O_3等催化剂的硫化过程．结果表明：对以Al_2O_3为载体的催化剂，当Mo或Co载量较低(分别低于0.05 gMoO_3/gAl_2O_3或0.03gCoO/gAl_2O_3)时，没有Mo或Co硫化物的生成，而以TiO_2改性的Al_2O_3为载体的催化剂，Mo/TiO_2-Al_2O_3催化剂的硫化较Mo/Al_2O_3容易得多, 表现为在较低温度下，负载在TiO_2改性Al_2O_3载体上的MoO_3，能很快硫化并达到相当大的硫化度, 对Co/Al_2O_3催化剂而言，即使在较高温度400 ℃时，载体上高分散的CoO物种仍难以硫化；而Co_3O_4微晶的硫化却容易得多, 载体用TiO_2改性，并不影响高分散形态的CoO催化剂的硫化，却明显地影响Co_3O_4微晶的硫化．噻吩加氢脱硫(HDS)的活性测量指出，对Co-Mo/Al_2O_3和Co-Mo/TiO_2-Al_2O_3催化剂而言，HDS活性和硫化度之间存在着良好的相关性．并用TiO_2改性载体，可以增加Co-Mo催化剂的HDS活性和硫化度.     

Investigation into the surface selective oxidation of dual‐phase steels by XPS,SAM and SIMS

Surface selective oxides created during continuous annealing (MnO, SiO₂, etc.) can have a deleterious effect on coating adhesion after hot‐dip galvanizing. Earlier research works have made it clear that increasing the annealing atmosphere oxidizing potential can alleviate the problem by reducing external surface selective oxidation. In the present study, increasing the water vapour content of the nitrogen–hydrogen protective gas mixture was used to raise its oxidizing potential. The technique was applied to a classical dual‐phase steel (0.15% C, 1.5% Mn, 0.45% Si, 0.05% Al…) that was annealed for 60 s at 800–810°C in protective atmospheres of nitrogen and 5% hydrogen with water vapour contents ranging from 10 to 6000 ppm. Post‐annealing surfaces were characterized by x‐ray photoelectron spectroscopy (XPS), secondary ion mass spectroscopy (SIMS) and scanning Auger microscopy (SAM). In situ XPS analyses were carried out right after simulation annealing in the preparation chamber connected to the spectrometer, never returning the specimens to air. This made it possible to identify in a reliable way the elements that segregated to the surface during the treatment, and to determine their corresponding oxidation states. On the other hand, the high sensitivity of SIMS was taken advantage of to assess oxide in‐depth concentration profiles (SiO₂, Al₂O₃, FeO) as a function of the annealing conditions, and SAM was used to characterize the corresponding oxide particle morphology. External selective oxidation was thus shown to decrease with increasing water vapour contents in the atmosphere (from 80 to 6000 ppm), whereas internal oxidation increases drastically to ～4 μm below the free surface. At 10 ppm of H₂O the oxygen partial pressure is very low and the external selective oxidation results in a thin, but almost complete, coverage of the steel surface. Consequently, metallic iron cannot be observed at the surface, thus hampering hot‐dip galvanizability, unless the water vapour content is raised to 6000 ppm. Various surface morphologies were observed and discussed. In the authors' opinion, basic investigations of this type are an indispensable first step to improving the response of highly alloyed steels (dual‐phase, TRIP) to hot‐dip galvanizing. Copyright © 2003 John Wiley & Sons, Ltd.     

Surface chemistry of selected supported metallocene catalysts studied by DR‐FTIR,CPMAS NMR,and XPS techniques

Two supported metallocene catalysts (CS 1: PQ 3030/MAO/Cp₂ZrCl₂ and CS 2: PQ 3030‐BuGeCl₃/MAO/Cp₂ ZrCl₂) were prepared by sequentially loading MAO and Cp₂ZrCl₂ on partially dehydroxylated silica PQ 3030. In catalyst CS 2, ⁿBuGeCl₃ was used to functionalize the silica. These catalysts were characterized by DR‐FTIR spectroscopy, CPMAS NMR spectroscopy, and XPS. Their catalytic performance was evaluated by polymerizing ethylene using the MAO cocatalyst and characterizing the resulting polymers by GPC. Both catalysts produced two metallocenium cations (Cation 1: [Cp₂ZrCl]⁺ and Cation 2: [Cp₂ZrMe]⁺) with comparable equilibrium concentrations and showed varying solid‐state electronic environments. The modified supports (PQ 3030/MAO and PQ 3030‐BuGeCl₃/MAO) acted as weakly coordinating polyanions and stabilized the above cations. BuGeCl₃ did not affect the solid‐state electronic environment. However, it increased the surface cocatalyst to catalyst molar ratio (Al:Zr), acted as a spacer, increased catalyst activity, and enhanced chain‐transfer reactions. The separately fed MAO cocatalyst shifted the equilibrium between Cation 1 and Cation 2 toward the right. Consequently, more Cation 2 was generated, which acted as the effective and active single‐site catalytic species producing monomodal PDI. Copyright © 2006 John Wiley & Sons, Ltd.     

匀胶铬版表面界面微观构成的X射线光电子能谱表征

用Ｘ射线光电子能谱（ＸＰＳ）研究了几种不同工艺制备的匀胶铬版表面、铬膜内部以及各层之间界面处的微观化学组成和化学状态，讨论了不同工艺对铬版材料微观构成及宏观特性的影响。     

原位XPS技术研究碳化铀的表面氧化

采用X射线光电子能谱(XPS)原位分析研究了298 K时烧结UC的清洁表面在O₂气氛中的初始氧化过程. UC试样清洁表面通过氩离子束长时间溅射获取. 初始反应各阶段U4f, O1s和C1s芯能级谱的变化显示样品表面的氧化产物为UO₂和自由碳. 当O₂饱和吸附后, UC表面氧化膜的增长呈抛物线型, 氧透过氧化膜的扩散为UC进一步氧化的速率控制步骤. 定量分析表明, 反应过程中U, C原子均未出现明显的表面偏析.     

Quantitative analysis of an organic thin film by XPS,AFM and FT‐IR

We report the characterization of Firpic (iridium(III)bis[4,6‐di‐fluorophenyl]‐pyridinato‐N,C²,]picolinate) organic thin film prepared by vacuum deposition to provide a systematic route to organic film quantification. To analyze the characteristics of thin Firpic films on a Si substrate, various techniques such as XPS, Fourier transform infra‐red (FT‐IR) spectrometer, and atomic force microscopy (AFM) are utilized. The Firpic films remain stable without surface morphological or compositional change during deposition and after exposure to X‐ray irradiation or atmospheric environment, for which qualities these films are believed to be an ideal platform as a pure organic thin film. The monotonic increases in FT‐IR and XPS intensities with film thickness are matching well with each other. In particular, from the XPS intensity analysis, the relative atomic sensitivity factors of the present system, electron attenuation length, and molecular density in the organic thin film can be evaluated. Copyright © 2011 John Wiley & Sons, Ltd.     

Titanium Defective Sites in TS‐1: Structural Insights by Combining Spectroscopy and Simulation

Ti silicates, and in particular, titanium silicalite‐1 (TS‐1), are nowadays important catalysts for several partial oxidation reactions in the presence of aqueous H₂O₂ as an oxidant. Despite the numerous studies dealing with this material, some fundamental aspects are still unclear. In particular, the structure and the catalytic role of defective Ti sites, other than perfect tetrahedral sites recognized as the main active species, has not been quantitatively discussed in the literature. We assess the structural features of defective Ti sites on the basis of outcomes of electronic spectroscopies, as interpreted through quantum mechanical simulation. Strong evidence is disclosed to support the fact that the most common defective Ti sites, often reported in the TS‐1 literature, are monomeric Ti centers that are embedded in the zeolite framework, and which have a distorted octahedral local symmetry.     

Surface studies of halloysite nanotubes by XPS and ToF‐SIMS

This report provides detailed experimental results of thermal and surface characterization on untreated and surface‐treated halloysite nanotubes (HNTs) obtained from two geographic areas. Surface characterization techniques, including XPS and time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) were used. ToF‐SIMS surface analysis experiments were performed with both atomic and cluster ion beams. Higher ion yields and more high‐mass ions were obtained with the cluster ion beams. Static ToF‐SIMS spectra were analyzed with principal component analysis (PCA). Morphological diversities were observed in the samples although they mainly contained tubular structures. Thermogravimetric data indicated that aqueous hydrogen peroxide solution could remove inorganic salt impurities, such as alkali metal salts. The amount of grafting of benzalkonium chloride of HNT surface was determined by thermogravimetic analysis. PCA of ToF‐SIMS spectra could distinguish the samples mined from different geographical locations as well as among surface‐treated and untreated samples. Copyright © 2010 John Wiley & Sons, Ltd.     

TPR and XPS characterization of chromia–lanthana–zirconia catalyst prepared by impregnation and microwave plasma enhanced chemical vapour deposition methods

Chromia–lanthana–zirconia catalysts prepared by wet impregnation and microwave plasma enhanced chemical vapour deposition methods have been characterized by temperature-programmed reduction (TPR) and X-ray photoelectron spectroscopy (XPS). The impregnation procedure requires large amounts of solvent and calcination at high temperatures producing Cr⁶⁺ species. Unlike this, it is found that the microwave plasma enhanced chemical vapour deposition (PECVD) method predominantly produces Cr³⁺ species on zirconia-based supports. Moreover, it has been shown that the dispersion of chromium species deposited on zirconia-based support by the PECVD method is higher than the dispersion of those prepared by wet impregnation. Thus, the advantages of PECVD over the impregnation method consist in this case in preventing the use of large amounts of solvent and avoiding the primary formation of poisonous Cr⁶⁺ species as well as in enabling the deposition of chromium species with high dispersion on zirconia-based supports.     

Investigations on PECVD boron carbonitride layers by means of ERDA, XPS and nano-indentation measurements

The deposition of boron carbonitride layers on silicon substrates by a microwave plasma enhanced chemical vapour deposition (MW-PECVD) process using N-trimethylborazine (TMB) and benzene as precursors is presented. As plasma gases argon and nitrogen were used. In this investigation we focus on the influence of the gas composition, substrate temperature and -bias on the layer composition, layer structure as well as the thermal stability. The films were analyzed with respect to their composition and bonding structure using elastic recoil detection analysis (ERDA) and X-ray photoelectron spectroscopy (XPS). Furthermore, nano-indentation measurements before and after annealing tests at 500 and 700 °C were performed. The measurements show a strong dependence of the structure and mechanical properties on the substrate temperature. The hydrogen content strongly decreases to 8 at.% with higher substrate temperatures. Simultaneously, the layer hardness and Young’s modulus increase up to 21 and 173 GPa, respectively. The hardness does not decrease after annealing for 1 hour at 700 °C.     

EFTEM and EELS Analysis of a Pt/NiO Interface

 Energy-filtering transmission electron microscopy (EFTEM) is more and more becoming an important nanoanalytical technique in both materials science and biology. The main advantage of the method lies in the possibility to obtain two-dimensional chemical information from large specimen areas as well as from features on a nanometer scale. Due to its excellent lateral resolution it is perfectly suited for the investigation of nanometer sized features (e.g. interfaces). In this paper we will show how EFTEM can be used to characterize the interface between a Pt layer and a NiO crystal as part of a coulometric titration cell. In addition to elemental distribution maps electron energy-loss spectra (EELS) across the interface (EELS linescans) have been acquired to obtain quantitative compositional profiles. By employing these methods the following interfacial layers could be identified, all of which containing Pt, Ni and O in different proportions: 13 nm Pt-rich, 32 nm Ni-rich and 29 nm Pt-rich. The origin of these is discussed in terms of displacement reactions.     

Quantitative analysis of styrene‐pentafluorostyrene random copolymers by ToF‐SIMS and XPS

Poly(styrene) (PS), poly(2,3,4,5,6‐pentafluorostyrene) (5FPS) and their random copolymers were prepared by bulk radical polymerization. The spin‐cast polymer films of these polymers were analyzed using X‐ray photoelectron spectroscopy (XPS) and time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS). The surface and bulk compositions of these copolymers were found to be same, implying that surface segregation did not occur. The detailed analysis of ToF‐SIMS spectra indicated that the ion fragmentation mechanism is similar for both PS and 5FPS. ToF‐SIMS quantitative analysis using absolute peak intensity showed that the SIMS intensities of positive styrene fragments, particularly C₇H₇⁺, in the copolymers are higher than the intensities expected from a linear combination of PS and 5FPS, while the SIMS intensities of positive pentafluorostyrene fragments are smaller than expected. These results indicated the presence of matrix effects in ion formation process. However, the quantitative approach using relative peak intensity showed that ion intensity ratios are linearly proportional to the copolymer mole ratio when the characteristic ions of PS and 5FPS are selected. This suggests that quantitative analysis is still possible in this copolymer system. Copyright © 2005 John Wiley & Sons, Ltd.     

2—乙烯吡啶—丁烯酮共聚物及其羰基铑配合物的XPS研究

本文用X-射线光电子能谱(XPS)研究了2-乙烯吡啶-丁烯酮共聚物及其与四羰基二氯二铑形成的配合物的结构特征.由反映在共聚物Cls光电子伴峰和(?)基Cls峰的消失,以及共聚物Nls和Ols结合能在配合物中的降低,即从施受两方面确证N→Rh和O→Rh配位键的形成.对催化性能的探讨表明,丁烯酮含量的增加导致催化活性的升高,这是由于O→Rh配位键比例的增加和键强较弱所致     

多组分氧化物Ag－Bi－V－Mo－O催化作用的光电子能谱研究

对于烃类选择氧化反应中复合氧化物的催化作用,普遍认为是Redox机理.迄今对于含有钥、秘复合氧化物催化剂的活性中心和作用机理还存在不同的看法.