The wettability of polytetrafluoroethylene and polymethylmethacrylate by aqueous solutions of Triton X-100 and short chain alcohol mixtures

Measurements of advancing contact angles (θ) were carried out for aqueous solutions of Triton X-100 (TX-100) and methanol and ethanol mixtures at constant TX-100 concentration equal to 1 × 10⁻⁷, 1 × 10⁻⁶, 1 × 10⁻⁵, 1 × 10⁻⁴, 6 × 10⁻⁴ and 1 × 10⁻³ M, respectively, on polytetrafluoroethylene (PTFE) and polymethylmethacrylate (PMMA). Using measured contact angle values the relationships between cos θ, adhesion tension and surface tension of the solutions were determined, and on their basis the critical surface tension of PTFE and PMMA wetting was calculated. The obtained average value of the critical surface tension of PTFE wetting is lying in the range of the PTFE surface tension values which can be found in the literature, while for PMMA it is even lower than the Lifshitz-van der Waals component of its surface tension. From the relationship between the adhesion and surface tension and Lucassen-Reynders equation it results that in the case of PTFE the adsorption at the PTFE-solution and solution-air interfaces is the same, which was confirmed by a linear relationship between the cos θ and 1/γ_LV and intercept on cos θ axis equal to −1. However, for PMMA the adsorption of the surface active agents at solution-air interface is higher than at PMMA-solution. Using the values of the contact angle the values of the adhesion work of solution to the PTFE and PMMA surface were also determined, which are constant for PTFE, but for PMMA decrease with alcohol concentration increase. Next, using the contact angle values in the Young equation, the PTFE(PMMA)-solution interface tension was also calculated. The obtained values of PTFE-solution interface tension were compared with those evaluated from the Szyszkowski, Connors and Fainerman and Miller equations, and good agreement between these values was observed for all series of TX-100 and alcohol mixtures at a low alcohol concentration.     

Three Dimensional Angular Distributions of X‐Rays in a 4 kJ Plasma Focus Device for Different Anode Tips Using TLD‐100 Dosimeters

Time and energy integrated measurements of the 3‐D angular distribution of X‐rays emission within the chamber of a 4 kJ Mather‐type plasma focus is investigated employing four different anode shapes and using nitrogen as the filling gas by the TLD‐100 thermoluminescence dosimeters. The distributions of X‐ray radiation in the energy range of 5 keV to several hundred keV were bimodal for all of the anode tips, peaked approximately at ±15°. The intensity of X‐rays decreased abruptly along the central axis of the device where the quasi cylindrical plasma pinch was formed. High intensity of X‐ray was observed in the case of a tapered ?at‐end anode, whereas less was obtained with the cylindrical hollow‐end anode. The maximum nitrogen X‐rays were for the tapered flat‐end anode at 4.5 mbar and 13 kV. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

On aberrations in saw‐tooth refractive X‐ray lenses and on their removal

The X‐ray lens, which is composed of opposing canted saw‐tooth structures, originally assembled from cut‐out pieces from long‐playing records, is understood by recognizing that an incident plane X‐ray wave will traverse a varying number of triangular prisms in them. The refraction will deflect any beam towards the prism tips and the variation of the deflection angle, which grows linearly with the number of traversed prisms, can result in X‐ray focusing. The structure offers focusing flexibility by simply changing the taper angle. This report will discuss the aberrations arising in the saw‐tooth structure in its simplest form with identical prisms. It is found that the saw‐tooth structures in low‐Z materials with focal length below 1 m provide less flux density in the focal spot than stacks of one‐dimensionally focusing refractive lenses with identical transmission function. This is due to excessive aberrations in the regular structure, which are absent in stacks of concave lenses, and which limit the focusing to spot sizes of just submicrometre dimensions, as measured experimentally for some lenses. It will be shown that this limitation can be overcome by appropriately modifying the prism shape. Then the image size could be reduced by about an order of magnitude to the diffraction limit with competitive numbers even below 0.1 µm. Microfabrication techniques are identified as the appropriate means for producing the structures.     

取代3H-吲哚分子在Triton X-100反胶束中的光谱性质和存在状态研究

用光谱法研究了荧光分子2-(对-己基胺基)苯基-3, 3-二甲基-5-乙酯基-3H-吲哚基-甲基-二-十八烷基碘化铵(A)与Triton X-100/正庚烷/正己醇/水反胶束间的相互作用。分别测定了A在Triton X-100反胶束体系中所处环境的微极性、各向异性参数和pH效应,此外还通过红外吸收光谱考察了水在反胶束中的状态。由以上实验结果得到了有关Triton X-100反胶束的结构信息,初步推测了A在该体系中的大致位置。     

X‐ray Raman spectroscopy of lithium‐ion battery electrolyte solutions in a flow cell

The effects of varying LiPF₆ salt concentration and the presence of lithium bis(oxalate)borate additive on the electronic structure of commonly used lithium‐ion battery electrolyte solvents (ethylene carbonate–dimethyl carbonate and propylene carbonate) have been investigated. X‐ray Raman scattering spectroscopy (a non‐resonant inelastic X‐ray scattering method) was utilized together with a closed‐circle flow cell. Carbon and oxygen K‐edges provide characteristic information on the electronic structure of the electrolyte solutions, which are sensitive to local chemistry. Higher Li⁺ ion concentration in the solvent manifests itself as a blue‐shift of both the π* feature in the carbon edge and the carbonyl π* feature in the oxygen edge. While these oxygen K‐edge results agree with previous soft X‐ray absorption studies on LiBF₄ salt concentration in propylene carbonate, carbon K‐edge spectra reveal a shift in energy, which can be explained with differing ionic conductivities of the electrolyte solutions.     

Optical performance of materials for X‐ray refractive optics in the energy range 8–100 keV

A quantitative analysis of the crucial characteristics of currently used and promising materials for X‐ray refractive optics is performed in the extended energy range 8–100 keV. According to the examined parameters, beryllium is the material of choice for X‐ray compound refractive lenses (CRLs) in the energy range 8–25 keV. At higher energies the use of CRLs made of diamond and the cubic phase of boron nitride (c‐BN) is beneficial. It was demonstrated that the presence of the elements of the fourth (or higher) period has a fatal effect on the functional X‐ray properties even if low‐Z elements dominate in the compound, like in YB₆₆. Macroscopic properties are discussed: much higher melting points and thermal conductivities of C and c‐BN enable them to be used at the new generation of synchrotron radiation sources and X‐ray free‐electron lasers. The role of crystal and internal structure is discussed: materials with high density are preferable for refractive applications while less dense phases are suitable for X‐ray windows. Single‐crystal or amorphous glass‐like materials based on Li, Be, B or C that are free of diffuse scattering from grain boundaries, voids and inclusions are the best candidates for applications of highly coherent X‐ray beams.     

Transmission of an X‐ray beam through a two‐dimensional photonic crystal and the Talbot effect

Results of computer simulations of the transmission of an X‐ray beam through a two‐dimensional photonic crystal as well as the propagation of an X‐ray beam in free space behind the photonic crystal are reported. The photonic crystal consists of a square lattice of silicon cylinders of diameter 0.5 µm. The amount of matter in the path of the X‐ray beam rapidly decreases at the sides of the cylinder projections. Therefore the transmission is localized near the boundaries, and appears like a channeling effect. The iterative method of computer simulations is applied. This method is similar to the multi‐slice method that is widely used in electron microscopy. It allows a solution to be obtained with acceptable accuracy. A peculiarity in the intensity distribution inside the Talbot period z_T in free space was found when the intensity is approximately equal to the initial value at a distance 0.46z_T, and it is shifted by half a period at distance 0.5z_T. The reason for this effect is the existence of a periodic phase of the wavefunction of radiation inside the intensity peaks. Simulations with zero phase do not show this effect. Symmetry rules for the Talbot effect are discussed.     

Diffraction of X‐ray free‐electron laser femtosecond pulses on single crystals in the Bragg and Laue geometry

A solution of the problem of dynamical diffraction for X‐ray pulses with arbitrary dimensions in the Bragg and Laue cases in a crystal of any thickness and asymmetry coefficient of reflection is presented. Analysis of pulse form and duration transformation in the process of diffraction and propagation in a vacuum is conducted. It is shown that only the symmetrical Bragg case can be used to avoid smearing of reflected pulses.     

Third‐order nonlinear and linear time‐dependent dynamical diffraction of X‐rays in crystals

For the first time the third‐order nonlinear time‐dependent Takagi's equations of X‐rays in crystals are obtained and investigated. The third‐order nonlinear and linear time‐dependent dynamical diffraction of X‐rays spatially restricted in the diffraction plane pulses in crystals is investigated theoretically. A method of solving the linear and the third‐order nonlinear time‐dependent Takagi's equations is proposed. Based on this method, results of analytical and numerical calculations for both linear and nonlinear diffraction cases are presented and compared.     

X‐ray fluorescence induced by standing waves in the grazing‐incidence and grazing‐exit modes: study of the Mg–Co–Zr system

The characterization of Mg–Co–Zr tri‐layer stacks using X‐ray fluorescence induced by X‐ray standing waves, in both the grazing‐incidence (GI) and the grazing‐exit (GE) modes, is presented. The introduction of a slit in the direction of the detector improves the angular resolution by a factor of two and significantly improves the sensitivity of the technique for the chemical characterization of the buried interfaces. By observing the intensity variations of the Mg Kα and Co Lα characteristic emissions as a function of the incident (GI mode) or detection (GE mode) angle, it is shown that the interfaces of the Si/[Mg/Co/Zr]_×30 multilayer are abrupt, whereas in the Si/[Mg/Zr/Co]_×30 multilayer a strong intermixing occurs at the Co‐on‐Zr interfaces. An explanation of this opposite behavior of the Co‐on‐Zr and Zr‐on‐Co interfaces is given by the calculation of the mixing enthalpies of the Co–Mg, Co–Zr and Mg–Zr systems, which shows that the Co–Zr system presents a negative value and the other two systems present positive values. Together with the difference of the surface free energies of Zr and Co, this leads to the Mg/Zr/Co system being considered as a Mg/Co_xZr_y bi‐layer stack, with x/y estimated around 3.5.     

Zr and Ba edge phenomena in the scintillation intensity of fluorozirconate‐based glass‐ceramic X‐ray detectors

The energy‐dependent scintillation intensity of Eu‐doped fluorozirconate glass‐ceramic X‐ray detectors has been investigated in the energy range from 10 to 40 keV. The experiments were performed at the Advanced Photon Source, Argonne National Laboratory, USA. The glass ceramics are based on Eu‐doped fluorozirconate glasses, which were additionally doped with chlorine to initiate the nucleation of BaCl₂ nanocrystals therein. The X‐ray excited scintillation is mainly due to the 5d–4f transition of Eu²⁺ embedded in the BaCl₂ nanocrystals; Eu²⁺ in the glass does not luminesce. Upon appropriate annealing the nanocrystals grow and undergo a phase transition from a hexagonal to an orthorhombic phase of BaCl₂. The scintillation intensity is investigated as a function of the X‐ray energy, particle size and structure of the embedded nanocrystals. The scintillation intensity versus X‐ray energy dependence shows that the intensity is inversely proportional to the photoelectric absorption of the material, i.e. the more photoelectric absorption the less scintillation. At 18 and 37.4 keV a significant decrease in the scintillation intensity can be observed; this energy corresponds to the K‐edge of Zr and Ba, respectively. The glass matrix as well as the structure and size of the embedded nanocrystals have an influence on the scintillation properties of the glass ceramics.     

In situ observation of water distribution and behaviour in a polymer electrolyte fuel cell by synchrotron X‐ray imaging

In situ visualization of the distribution and behaviour of water in a polymer electrolyte fuel cell during power generation has been demonstrated using a synchrotron X‐ray imaging technique. Images were recorded using a CCD detector combined with a scintillator (Gd₂O₂S:Tb) and relay lens system, which were placed at 2.0 m or 2.5 m from the fuel cell. The images were measured continuously before and during power generation, and data on cell performance was recorded. The change of water distribution during power generation was obtained from X‐ray images normalized with the initial state of the fuel cell. Compared with other techniques for visualizing the water in fuel cells, this technique enables the water distribution and behaviour in the fuel cell to be visualized during power generation with high spatial resolution. In particular, the effects of the specifications of the gas diffusion layer on the cathode side of the fuel cell on the distribution of water were efficiently identified. This is a very powerful technique for investigating the mechanism of water flow within the fuel cell and the relationship between water behaviour and cell performance.     

Concept of a spectrometer for resonant inelastic X‐ray scattering with parallel detection in incoming and outgoing photon energies

A spectrometer for resonant inelastic X‐ray scattering (RIXS) is proposed where imaging and dispersion actions in two orthogonal planes are combined to deliver a full two‐dimensional map of RIXS intensity in one shot with parallel detection at incoming hv_in and outgoing hv_out photon energies. Preliminary ray‐tracing simulations with a typical undulator beamline demonstrate a resolving power well above 11000 with both hv_in and hv_out near 930 eV, with a vast potential for improvement. Combining this instrument – nicknamed hv² spectrometer – with an X‐ray free‐electron laser source simplifies its technical implementation and enables efficient time‐resolved RIXS experiments.     

Refraction and ultra‐small‐angle scattering of X‐rays in a single‐crystal diamond compound refractive lens

In this work a double‐crystal setup is employed to study compound refractive lenses made of single‐crystal diamond. The point spread function of the lens is calculated taking into account the lens transmission, the wavefront aberrations, and the ultra‐small‐angle broadening of the X‐ray beam. It is shown that, similarly to the wavefront aberrations, the ultra‐small‐angle scattering effects can significantly reduce the intensity gain and increase the focal spot size. The suggested approach can be particularly useful for the characterization of refractive X‐ray lenses composed of many tens of unit lenses.     

Image contrast in X‐ray reflection interface microscopy: comparison of data with model calculations and simulations

The contrast mechanism for imaging molecular‐scale features on solid surfaces is described for X‐ray reflection interface microscopy (XRIM) through comparison of experimental images with model calculations and simulated measurements. Images of elementary steps show that image contrast is controlled by changes in the incident angle of the X‐ray beam with respect to the sample surface. Systematic changes in the magnitude and sign of image contrast are asymmetric for angular deviations of the sample from the specular reflection condition. No changes in image contrast are observed when defocusing the condenser or objective lenses. These data are explained with model structure‐factor calculations that reproduce all of the qualitative features observed in the experimental data. These results provide new insights into the image contrast mechanism, including contrast reversal as a function of incident angle, the sensitivity of image contrast to step direction (i.e. up versus down), and the ability to maximize image contrast at almost any scattering condition defined by the vertical momentum transfer, Q_z. The full surface topography can then, in principle, be recovered by a series of images as a function of incident angle at fixed momentum transfer. Inclusion of relevant experimental details shows that the image contrast magnitude is controlled by the intersection of the reciprocal‐space resolution function (i.e. controlled by numerical aperture of the condenser and objective lenses) and the spatially resolved interfacial structure factor of the object being imaged. Together these factors reduce the nominal contrast for a step near the specular reflection condition to a value similar to that observed experimentally. This formalism demonstrates that the XRIM images derive from limited aperture contrast, and explains how non‐zero image contrast can be obtained when imaging a pure phase object corresponding to the interfacial topography.     

Design and application of a high‐temperature microfurnace for an in situ X‐ray diffraction study of phase transformation

Thermal treatment of mineral ores such as ilmenite can initiate phase transformations that could affect their activation or deactivation, subsequently influencing their ability to dissolve in a leaching agent. Most laboratory‐based X‐ray diffraction (XRD) studies were carried out ex situ in which realistic diffraction patterns could not be obtained simultaneously with occurring reactions and were time‐consuming. The availability of synchrotron‐radiation‐based XRD not only allows in situ analysis, but significantly shortens the data recording time. The present study details the design of a robust high‐temperature microfurnace which allows thermal processing of mineral ore samples and the simultaneous collection of high‐resolution synchrotron XRD data. In addition, the application of the manufactured microfurnace for in situ study of phase transformations of ilmenite ore under reducing conditions is demonstrated.     

First experiments on the Australian Synchrotron Imaging and Medical beamline,including investigations of the effective source size in respect of X‐ray imaging

The Imaging and Medical beamline at the Australian Synchrotron achieved `first light' in December 2008. Here, the first experiments performed on the beamline are reported, which involved both X‐ray imaging and tomography studies for a range of samples. The use of a plastic‐edge phantom for quantitative measurements of contrast and resolution proved to be very instructive and helped to confirm certain parameter values such as the effective horizontal source size, detector resolution and average X‐ray energy for the polychromatic beam.     

Investigation of the multiplet features of SrTiO3 in X‐ray absorption spectra based on configuration interaction calculations

Synchrotron‐based L_2,3‐edge absorption spectra show strong sensitivities to the local electronic structure and chemical environment. However, detailed physical information cannot be extracted easily without computational aids. Here, using the experimental Ti L_2,3‐edges absorption spectrum of SrTiO₃ as a fingerprint and considering full multiplet effects, calculations yield different energy parameters characterizing local ground state properties. The peak splitting and intensity ratios of the L₃ and L₂ set of peaks are carefully analyzed quantitatively, giving rise to a small hybridization energy around 1.2 eV, and the different hybridization energy values reported in the literature are further addressed. Finally, absorption spectra with different linearly polarized photons under various tetragonal crystal fields are investigated, revealing a non‐linear orbital–lattice interaction, and a theoretical guidance for material engineering of SrTiO₃‐based thin films and heterostructures is offered. Detailed analysis of spectrum shifts with different tetragonal crystal fields suggests that the e_g crystal field splitting is a necessary parameter for a thorough analysis of the spectra, even though it is not relevant for the ground state properties.     

Simultaneous measurement of bubble size,velocity and void fraction in two‐phase bubbly flows with time‐resolved X‐ray imaging

Key parameters of two‐phase flows, such as void fraction and microscale bubble size, shape and velocity, were simultaneously measured using time‐resolved X‐ray imaging. X‐ray phase‐contrast imaging was employed to obtain those parameters on microbubbles. The void fraction was estimated from X‐ray absorption. The radii of the measured microbubbles were mostly smaller than 20 µm, and the maximum velocity was 39.442 mm s^?1, much higher than that in previous studies. The spatial variations of the void fraction were consecutively obtained with a small time interval. This technique would be useful in the experimental analysis of bubbly flows in which microbubbles move at high speed.     

A flow‐through reaction cell for in situ X‐ray diffraction and absorption studies of heterogeneous powder–liquid reactions and phase transformations

A portable powder–liquid high‐corrosion‐resistant reaction cell has been designed to follow in situ reactions by X‐ray powder diffraction (XRD) and X‐ray absorption spectroscopy (XAS) techniques. The cell has been conceived to be mounted on the experimental stations for diffraction and absorption of the Spanish CRG SpLine‐BM25 beamline at the European Synchrotron Radiation Facility. Powder reactants and/or products are kept at a fixed position in a vertical geometry in the X‐ray pathway by a porous membrane, under forced liquid reflux circulation. Owing to the short pathway of the X‐ray beam through the cell, XRD and XAS measurements can be carried out in transmission configuration/mode. In the case of the diffraction technique, data can be collected with either a point detector or a two‐dimensional CCD detector, depending on specific experimental requirements in terms of space or time resolution. Crystallization processes, heterogeneous catalytic processes and several varieties of experiments can be followed by these techniques with this cell. Two experiments were carried out to demonstrate the cell feasibility: the phase transformations of layered titanium phosphates in boiling aqueous solutions of phosphoric acid, and the reaction of copper carbonate and l ‐isoleucine amino acid powders in boiling aqueous solution. In this last case the shrinking of the solid reactants and the formation of Cu(isoleucine)₂ is observed. The crystallization processes and several phase transitions have been observed during the experiments, as well as an unexpected reaction pathway.