Changes of the near-surface chemical composition of the 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide room temperature ionic liquid under the influence of irradiation

Radiation induced degradation effects are studied for a model ionic liquid (IL)--[EMIm]Tf(2)N--in order to distinguish in which way the results of X-ray based material analysis methods can be falsified by the radiation supplied by typical X-ray sources itself. Photoelectron spectroscopy is commonly used for determining the electronic structure of ionic liquids. Degradation effects, which often occur e.g. in organic materials during X-ray or electron irradiation, are potentially critical for the interpretation of data obtained from ionic liquids. The changes of the chemical composition as well as the radiation-induced desorption of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIm]Tf(2)N) fragments are analysed by X-ray photoelectron spectroscopy (XPS) as well as quadrupole mass spectroscopy (QMS) upon exposure to monochromated or non-monochromated AlKα X-rays from typical laboratory sources. During the irradiation of [EMIm]Tf(2)N, an increasing carbon concentration is observed in both cases and especially the [Tf(2)N](-) ion is strongly altered. This observation is supported by the results from the QMS analysis which revealed a variety of different IL fragments that are desorbed during X-ray irradiation. It is shown that the decomposition rate is directly linked to the photon flux on the sample and hence has to be considered when planning an XPS experiment. However, for typical experiments on this particular IL the measurements suggest that the changes are on a larger time scale as typically required for spectra acquisition, in particular if monochromated X-ray sources are used.     

PIXE and charge-induced X-rays (CHIX): Are they complementary or competitive?

Enhanced yields from CHIX studies on non-conducting samples have demonstrated conclusively that such yields are exceptionally high when compared to PIXE at low incident particle energies. This was confirmed with low energy¹⁴N⁺,¹⁶O⁺ and²⁰Ne⁺ ions whose X-ray production crosssections are negligibly small for PIXE yields. In particular, a combination of low incident energies and high X-ray yields could be useful for XSQR investigations and elemental studies with low energy accelerators. Furthermore, extended studies on pure metal targets revealed that the PIXE yield could be improved by insulating the targets thus making them suitable to produce the CHIX yield under identical experimental conditions. This paper discusses the complementary and competitive features of PIXE and CHIX.     

Parameter study of self-absorption effects in Total Reflection X-ray Fluorescence–X-ray Absorption Near Edge Structure analysis of arsenic

Total reflection X-ray Fluorescence (TXRF) analysis in combination with X-ray Absorption Near Edge Structure (XANES) analysis is a powerful method to perform chemical speciation studies at trace element levels. However, when measuring samples with higher concentrations and in particular standards, damping of the oscillations is observed. In this study the influence of self-absorption effects on TXRF–XANES measurements was investigated by comparing measurements with theoretical calculations. As(V) standard solutions were prepared at various concentrations and dried on flat substrates. The measurements showed a correlation between the damping of the oscillations and the As mass deposited. A Monte-Carlo simulation was developed using data of the samples shapes obtained from confocal white light microscopy. The results showed good agreement with the measurements; they confirmed that the key parameters are the density of the investigated atom in the dried residues and the shape of the residue, parameters that combined define the total mass crossed by a certain portion of the incident beam. The study presents a simple approach for an a priori evaluation of the self-absorption in TXRF X-ray absorption studies. The consequences for Extended X-ray Absorption Fine Structure (EXAFS) and XANES measurements under grazing incidence conditions are discussed, leading to the conclusion that the damping of the oscillations seems to make EXAFS of concentrated samples non feasible. For XANES “fingerprint” analysis samples should be prepared with a deposited mass and sample shape leading to an acceptable absorption for the actual investigation.     

<Emphasis Type="Italic">In situ</Emphasis> high-temperature X-ray diffraction measurements: Application to the study of heterogeneous catalysts

When characterizing the phase composition and structure of catalysts, researchers are faced with the problem of reversible effects of temperature and gas medium during their preparation, activation, or operation. Therefore, particular attention is paid to the methods of their research in appropriate conditions, i.e., in situ high-temperature X-ray diffraction. The theoretical framework and experimental features of high-temperature X-ray diffraction techniques are examined. Examples are given of their effective application to the study of the structural features of oxide catalysts under close-to-real conditions.     

Radiative auger effect and extended X-ray emission fine structure (EXEFS).

Radiative Auger spectra are weak X-ray emission spectra near the characteristic X-ray lines. Radiative Auger process is an intrinsic energy-loss process in an atom when a characteristic X-ray photon is emitted, due to an atomic many-body effect. The energy loss spectra correspond to the unoccupied conduction band structure of materials. Therefore the radiative Auger effect is an alternative tool to the X-ray absorption spectroscopy such as EXAFS (Extended X-ray Absorption Fine Structure) and XANES (X-ray Absorption Near Edge Structure), and thus it is named EXEFS (Extended X-ray Emission Fine Structure). By the use of a commercially available X-ray fluorescence spectrometer or an electron probe microanalyzer (EPMA), which are frequently used in materials industries, we can obtain an EXEFS spectrum within 20 min. The radiative Auger effect, as an example, demonstrates that the study on atomic many-body effects has become a powerful tool for crystal and electronic structure characterizations. The EXEFS method has already been used in many industries in Japan. Reviews about the applications and basic study results on the radiative Auger effect are reported in this paper.     

The influence of X-ray resonant Raman scattering effects on the detection of copper(II) tetrasulphonated phthalocyanine (CuTSPc) thin-films deposited on gold electrodes

The influence of X-ray resonant Raman scattering on the detection capabilities of copper(II) tetrasulphonated phthalocyanine (CuTSPc) thin-films on gold electrodes has been investigated by means of synchrotron radiation X-ray fluorescence. In particular the paper focuses on the influence of the excitation energy in the relative narrow energy region of 9.2 to 11.7 keV on the detection limits and the peak-to-background ratios of copper.     

In vitro effects of ultra-low and low doses of radiation produced by sources of different nature and power on enzymes

The effects of low and ultra-low doses of X-ray radiation and neutron fluxes produced by continuous-wave and pulsed sources of different nature and power on the activity of plant peroxidases and the bovine lung angiotensin-converting enzyme were studied. Certain ranges of doses (including ultra-low), the exposure to which under particular conditions causes the in vitro activation and/or inactivation of the enzymes, were found. Possible factors responsible for this phenomenon are discussed.     

Spectroscopy and Structure of Sol-Gel Systems

Sol-gel derived glasses may differ from conventional melt-quenched glasses owing to the peculiar microstructures existing at the gel state, such that, even after gel densification, some differences may remain in their composition and molecular structure.This paper discusses structural characteristics of thin film oxide gels and glasses, with a special emphasis on SiO2-TiO2 based systems, which are of particular interest for sol-gel integrated optics applications. Short range structure aspects are discussed based on infrared, X-ray photoemission and X-ray photoabsorption spectroscopies. The chemical homogeneity of sol-gel materials is evaluated, based on X-ray photoemission and nuclear magnetic resonance spectroscopies, dealing in particular with the issue of homo- vs. heterocondensation. Finally, some microstructural features of sol-gel derived films are analyzed, namely the relationship between infrared absorption and porosity and the structure of nanocrystalline sol-gel films, based on grazing incidence X-ray diffraction and micro-Raman spectroscopy. The types of structural information obtainable by each different technique are compared in detail.     

Determination of pollutants in dwellings by neutron activation analysis and X-ray fluorescence

Metallic pollutants were measured in dwellings in Mexico City by instrumental neutron activation analysis (INAA) and X-ray fluorescence techniques. Monitoring was performed in the west side of the city and in the winter season. In general the average concentration of contaminants collected, when compared with the average concentrations reported in a previous paper, have increased with time and in the particular case of lead and mercury some samples are above the indicative WHO maximum levels.     

Effect of a Nematic Liquid Crystalline Polymer as Highly Active β-Nucleator on Crystallization Structure and Morphology of Isotactic Polypropylene

The effects of nematic liquid crystalline polymer as a new β-nucleator (LCP-N) on crystallization structure and morphology of isotactic polypropylene (iPP) were investigated using wide-angle X-ray diffraction and polarized optical microscopy. The experimental results showed that LCP-N could lead to substantial changes in the crystallization structure and morphology of iPP. The nucleating activity of LCP-N mainly depended on its content, mesogenic molecules, and thermal history of processing. A high content of β-form (K _β) was obtained by the combined effect of the optimum LCP-N content and crystallization temperature. The maximum K _β reached 84% when the LCP-N content and crystallization temperature and time were 0.4 wt.%, 125°C, and 1 h, respectively. In addition, the birefringence of β spherulite was stronger than that of α spherulite; this difference is related to their particular way of growing and lamellar morphology. Due to its particular sheaf-like growth, the β spherulite was brighter and more colorful.     

Monte Carlo studies of a novel X-ray tube anode design

When energetic electrons are incident on high atomic number absorbers, a substantial fraction is back-scattered. This phenomenon is responsible for several undesirable effects in X-ray tubes, in particular a reduction in the X-ray output. The extent of this shortfall has been estimated by using Monte Carlo simulation to start electrons at increasing depth inside the anode, the results indicating that an output enhancement of nearly 50% could be achieved in principle if the electrons wasted in back-scatter events could be trapped inside a tungsten anode. To test this idea a further set of simulations were done for a novel anode geometry. Results showed that X-ray tube efficiencies might be substantially enhanced by this approach.     

Structure effects of weak interactions in heterodesmicπ-complexes of copper(I)

Structural effects: disordering, twinning, polymorphism, and morphotropism due to substitution of halide atoms are considered using the results of X-ray diffraction analysis of 18 olefinic π-complexes of Cu(I). These effects are associated with the heterodesmic character of compounds, in particular, with weak interactions such as lengthened coordination bonds and hydrogen contacts. Ukrainian State Wood Technology Institute. Translated fromZhurnal Strukturnoi Khimii, Vol. 39, No. 1, pp. 98–107, January–February, 1998.     

Electrochemical and structural characterization of sputter-deposited Mg–Nb and Mg–Nb–Al–Zn alloy films

Nanocrystalline Mg–Nb and Mg–Nb–Al–Zn alloy films were deposited by dc magnetron sputtering on glass and quartz substrates in a wide range of niobium concentrations from 6 to 80 at.%. Structural, electrochemical and corrosion properties of the films were studied by X-ray diffraction, dc voltammetry, electrochemical impedance spectroscopy and electrochemical quartz crystal microbalance. Development of body-centred cubic Nb structure in the Mg–Nb alloy matrix yielded the effects of lattice contraction, grain refining and electrochemical passivity. The measurements showed high corrosion resistance of the films in alkaline solutions when niobium content was one third or more. An increased corrosion resistance was achieved by introducing minor amounts of Al (ca. 2 at.%). In particular, such Al effect was pronounced at lower Nb concentrations (20 to 30 at.%). Semiconductor properties of spontaneously formed oxide on Mg–Nb alloy were studied by Mott–Schottky plots, which indicated highly doped n-type oxide structures on Mg–Nb surface. The paper fills some gap in understanding of niobium–magnesium systems, which show potential for applications in hydrogen storage, switchable mirrors and corrosion protection.     

How to determine structures when single crystals cannot be grown: opportunities for structure determination of molecular materials using powder diffraction data

Many crystalline solids cannot be prepared as single crystals of sufficient size and/or quality for structure determination to be carried out using single crystal X-ray diffraction techniques. In such cases, when only polycrystalline powders of a material are available, it is necessary instead to tackle structure determination using powder X-ray diffraction. This article highlights recent developments in the opportunities for determining crystal structures directly from powder diffraction data, focusing on the case of molecular solids and giving particular attention to the most challenging stage of the structure determination process, namely the structure solution stage. In particular, the direct-space strategy for structure solution is highlighted, as this approach has opened up new opportunities for the structure determination of molecular solids. The article gives an overview of the current state-of-the-art in structure determination of molecular solids from powder diffraction data. Relevant fundamental aspects of the techniques in this field are described, and examples are given to highlight the application of these techniques to determine crystal structures of molecular materials.     

About the dependence of the intensity of X-ray spectra of elements on their concentrations expressed in atomic and mass percents

The consideration of the classical physical fundamentals of X-ray spectrometry suggests that the properties of X-ray spectra of elements are determined by their atomic number rather than atomic weight. The intensity of X-ray spectra is determined by the number of excited atoms rather by their mass. However, in the middle of the 20th century, the dependence of intensity on the mass concentration of elements was introduced without any physical grounds. The paper presents physical, analytical, and metrological evidences for the idea that this dependence does not correspond to a real physical process. It results in distorted calibration characteristics and extra errors and hinders the development of a method of universal (for all element systems) quantitative X-ray fluorescence analysis instead of specific procedures with empirical parameters for each particular system. The dependence on atomic concentrations eliminates these difficulties.     

Degradation of Mater-Bi/wood flour biocomposites in active sewage sludge

The mechanical properties of Mater-Bi^® are, in general, not adequate for certain applications and the addition of a filler is therefore necessary. Among the different fillers, natural fibres are particularly interesting because they potentially allow improving the performance of the material without compromising its biodegradability.In order to improve the basic mechanical properties of a Mater-Bi grade and to obtain a new, fully biodegradable material, wood flour based composites were prepared by different processing methods. To simulate actual and not laboratory bacterial attack on the prepared materials, in this work we studied the biodegradation of the composites in a real active sewage sludge reactor. In particular, the biodegradation rates were investigated with reference to different pre-treatments of the materials and different environmental conditions (summer and winter). The results showed that wood flour enhances the biodegradability of the materials. The results indicated also strong relationships between the surface roughness and the biodegradation rates (in particular, higher roughness leads to wider bacterial attack). The different processing techniques had direct effects on the overall biodegradation rates. In particular, when higher smoothness and packing is achieved, the biodegradation rate is lower. The mechanical analysis indicated that adding wood flour to Mater-Bi has positive effects on the elastic modulus, but when the bacterial attack becomes critical, a general sudden drop of the mechanical properties is observed.     

XPS分析中使用样品磁透镜引起的谱峰位移和峰形畸变

发现当使用Mg/Al双阳极和样品磁透镜进行非导电样品（或与样品托绝缘的导电样品）的X射线光电子能谱分析时，谱峰出现异常大的位移和谱形出现畸变；在同时使用电子中和枪时谱峰位移变小，当导电样品与样品托有良好的电接触时谱峰位移消失；作者提出这种异常大的位移来自样品荷电效应，后者是由于样品磁透镜的磁场与来自X射线枪A1窗的低能杂散电子发生了相互作用并使这些杂散电子不能到达样品表面起中和作用所致。     

Effects of oxygen plasma on cellulose surface

These studies aimed to investigate in detail changes on cellulose surfaces treated with low pressure oxygen plasma at various exposure times. Modifications of cellulose films were studied in respect to topography effects by means of atomic force microscopy and scanning electron microscopy. Chemical effects of plasma treatment were studied using X-ray photoelectron spectroscopy and X-ray diffractometry. Results show that the topographical evolution of the surfaces to rougher ones is not at all gradual. Local maxima of fractionation and the surface size regularity were investigated using surface fractal analysis and Wenzel roughness factors, respectively. It was shown, that plasma treatments decompose the cellulose material by formation of highly functionalized molecules. Such plasma-initiated and supported reactions taking place on the sample surface. The bulk phase and in particular, the crystalline domains are not influenced by plasma treatments. The studies provide useful information to understand the plasma reaction on amorphous and crystalline regions of cellulose surfaces and allow to predict effects of the plasma treatment on physical and chemical properties of much more complex cellulose systems such as cotton fibres and fabrics.     

Self-organization in the chitosan-clay nanoparticles system regulated through polysaccharide macromolecule charging. 2. Films

Formation conditions are studied for bionanocomposite films prepared by mixing cationic chitosan with negatively charged nanoparticles of a synthetic clay (saponite) followed by gradual increasing of the charge of macromolecules by decreasing the pH of a medium. The data on the swelling of the bionanocomposite films in water are used to determine the stoichiometric ratio between the concentrations of macromolecules and nanoparticles that provides the most intense electrostatic interactions stabilizing the films. Their properties and structure are investigated by means of scanning electron microscopy, dynamic thermomechanical analysis, and small-angle X-ray scattering. The films are shown to occur in a glassy state and undergo a number of phase transitions, the temperatures of which depend on the chitosan-to-saponite concentration ratio. In particular, their glass transition temperature increases from 62 to 175°C when passing to the stoichiometric composition. The bionanocomposite films are found to have a layered structure. The layers are, in turn, composed of highly uniform microsized plates 20?C30 nm thick. Small-angle X-ray scattering shows a structural order with a periodicity of 1.78 nm. The structure of the bionanocomposite films is discussed.     

A smoothing method for X-ray spectrum based on best beamforming

X-ray spectrum is widely used in the field of analysis and measurement. Due to the effect of electronic noise and statistical fluctuation of particle, the measurement spectrum is unsmoothed. In order to improve the signal-to-noise ratio of the spectrum, many smoothing methods were applied to process spectrum. The conventional smoothing algorithms regard the spectra as time series. In fact, X-ray spectrum is an angle series, and its essential is spatial spectrum. So the conventional smoothing algorithms are not fit for smoothing X-ray spectrum. In this paper, a new measuring model for X-ray spectrum is built up, and a new smoothing method based on best beam forming is proposed for X-ray spectrum. It regards the measured X-ray spectrum as the classic spectrum estimation result of array signal. The spatial spectrum is re-estimated to smooth the spectrum by best beam forming. The relationship between cross-correlation coefficient and number of array cell is applied to choose parameter q. The experimental results show that the method is effective to smooth X-ray spectrum with high resolution when q is larger than 200.