Wide-angle X-ray Scattering Studies Research Articles

Tracking the Catalyst Layer Depth-Dependent Electrochemical Degradation of a Bimodal Pt/C Fuel Cell Catalyst: A Combined Operando Small- and Wide-Angle X-ray Scattering Study

Tracking the Catalyst Layer Depth-Dependent Electrochemical Degradation of a Bimodal Pt/C Fuel Cell Catalyst: A Combined <i>Operando</i> Small- and Wide-Angle X-ray Scattering Study

Small- and Wide-Angle X-ray Scattering Studies of Liquid–Liquid Phase Separation in Silicate Melts

Incongruent liquid–liquid phase separation is a common phenomenon in molten oxides, but there are few structural studies as a result of the high temperatures involved, ca. >1600 °C. Here, we presen...

Perovskite Crystallization Dynamics during Spin-Casting: An In Situ Wide-Angle X-ray Scattering Study.

In situ wide-angle X-ray scattering (WAXS) has been measured during the spin coating process used to make the precursor films required for the formation of thin films of perovskite. A customized hollow axis spin coater was developed to permit the scattered X-rays to be collected in transmission geometry during the deposition process. Spin coating is the technique most commonly used in laboratories to make thin perovskite films. The dynamics of spin-casting MAPbI3–xClx and FAPbI3–xClx films have been investigated and compared to investigate the differences between the dynamics of MAPbI3–xClx and FAPbI3–xClx film formation. In particular, we focus on the crystallization dynamics of the precursor film formation. When casting MAPbI3–xClx, we observed relatively fast 1D crystallization of the intermediate product MA2PbI3Cl. There was an absence of the desired perovskite phase formed directly; it only appeared after an annealing step that converted the MA2PbI3Cl to MAPbI3. In contrast, slower crystallization via a 3D precursor was observed for FAPbI3–xClx film formation compared to MAPbI3–xClx. Another important finding was that some FAPbI3–xClx perovskite was generated directly during spin-casting before annealing. These findings indicate that there are significant differences between the crystallization pathways for these two perovskite materials. These are likely to explain the differences in the lifetimes of the resulting perovskite solar cell devices produced using FA and MA cations.

Structure Development in Polymers during Fused Filament Fabrication (FFF): An in Situ Small- and Wide-Angle X-ray Scattering Study Using Synchrotron Radiation

Microstructure formation in individual layers during fused filament fabrication (FFF) of a Π-shaped multilayer single-walled polymer sample was studied by simultaneous measurement of small- and wide-angle X-ray scattering (SAXS and WAXS, respectively) methods employing synchrotron radiation. We investigated individual layers and the welding zone between individual layers. As a model material, we used isotactic polypropylene (iPP), which is a commodity semicrystalline polymer and has a strong potential as a feedstock material for additive manufacturing. The layers were deposited by an FFF three-dimensional (3D) printer that was custom-built to fit into the synchrotron beamline. WAXS data were utilized to determine the temperature of the irradiated volume. The polymer microstructure was characterized in terms of crystallinity and long-spacing. Avrami analysis indicates that the crystallization behavior of iPP in thin layers is rather similar to that observed in quiescent crystallization of bulk iPP, suggest...

From Molecular Entanglement Network to Crystal-Cross-Linked Network and Crystal Scaffold during Film Blowing of Polyethylene: An in Situ Synchrotron Radiation Small- and Wide-Angle X-ray Scattering Study

Combining a homemade film blowing machine and an in situ synchrotron radiation source with small- and wide-angle X-ray scattering (SAXS and WAXS) capability, an investigation of film blowing of pol...

Microbeam Wide-Angle X-ray Scattering Study on Precursor of Shish Kebab. Effects of Shear Rate and Annealing on Inner Structure

We have investigated the inner structure of shear-induced precursor of shish kebab of isotactic polystyrene (iPS) above the nominal melting temperature Tm using microbeam wide-angle X-ray scattering. We first studied the effects of the shear rate on the inner structure and found that the crystallinity in the precursor increased with the shear rate while the crystallite size was independent of that. This was explained in terms of effects of chain entanglements on shear-induced crystallization. We also studied effects of annealing below the nominal melting temperature Tm and found no changes in the crystallites size before and after the annealing, suggesting that the crystallites did not grow into shishs during the annealing below Tm although the kebabs grew.

Coagulation of Na-Montmorillonite by Inorganic Cations at Neutral pH. A Combined Transmission X-ray Microscopy, Small Angle and Wide Angle X-ray Scattering Study

The coagulation of sodium montmorillonite by inorganic salts (NaNO3, Ca(NO3)2 and La(NO3)3) was studied by combining classical turbidity measurements with wide-angle-X-ray scattering (WAXS), small-angle-X-ray scattering (SAXS), and transmission X-ray microscopy (TXM). Using size-selected samples, such a combination, associated with an original quantitative treatment of TXM images, provides a true multiscale investigation of the formed structures in a spatial range extending from a few ångstroms to a few micrometers. We then show that, at neutral pH and starting with fully Na-exchanged samples, coagulation proceeds via the formation of stacks of particles with a slight mismatch between layers. These stacks arrange themselves into larger porous anisotropic particles, the porosity of which depends on the valence of the cation used for coagulation experiments. Face-face coagulation is clearly dominant under those conditions, and no evidence for significant face-edge coagulation was found. These structures appear to arrange as larger clusters, the organization of which should control the mechanical properties of the flocs.

Small and Wide Angle X-Ray Scattering Studies of Biological Macromolecules in Solution

In this paper, Small and Wide Angle X-ray Scattering (SWAXS) analysis of macromolecules is demonstrated through experimentation. SWAXS is a technique where X-rays are elastically scattered by an inhomogeneous sample in the nm-range at small angles (typically 0.1 - 5°) and wide angles (typically > 5°). This technique provides information about the shape, size, and distribution of macromolecules, characteristic distances of partially ordered materials, pore sizes, and surface-to-volume ratio. Small Angle X-ray Scattering (SAXS) is capable of delivering structural information of macromolecules between 1 and 200 nm, whereas Wide Angle X-ray Scattering (WAXS) can resolve even smaller Bragg spacing of samples between 0.33 nm and 0.49 nm based on the specific system setup and detector. The spacing is determined from Bragg's law and is dependent on the wavelength and incident angle. In a SWAXS experiment, the materials can be solid or liquid and may contain solid, liquid or gaseous domains (so-called particles) of the same or another material in any combination. SWAXS applications are very broad and include colloids of all types: metals, composites, cement, oil, polymers, plastics, proteins, foods, and pharmaceuticals. For solid samples, the thickness is limited to approximately 5 mm. Usage of a lab-based SWAXS instrument is detailed in this paper. With the available software (e.g., GNOM-ATSAS 2.3 package by D. Svergun EMBL-Hamburg and EasySWAXS software) for the SWAXS system, an experiment can be conducted to determine certain parameters of interest for the given sample. One example of a biological macromolecule experiment is the analysis of 2 wt% lysozyme in a water-based aqueous buffer which can be chosen and prepared through numerous methods. The preparation of the sample follows the guidelines below in the Preparation of the Sample section. Through SWAXS experimentation, important structural parameters of lysozyme, e.g. the radius of gyration, can be analyzed.

Small and Wide Angle X-Ray Scattering Studies of Biological Macromolecules in Solution

Small and Wide Angle X-Ray Scattering Studies of Biological Macromolecules in Solution

Microstructural Parameters in Electron Irradiated PVA Films by Wide Angle X-Ray Scattering Studies (WAXS)

The radiation-induced changes in Poly (vinyl alcohol) (PVA) polymer films exposed to electron irradiation were investigated for different radiation dose. Polymer film samples were irradiated in air at room temperature by an electron beam accelerator at different doses: 0, 100, 150 and 200 kGy. The microstructural and surface properties of the irradiated PVA films were characterized by X-ray diffraction (XRD) and Atomic force microscopy (AFM). An unirradiated PVA film was used as reference. Electron irradiation was found to induce changes in structural and surface properties of polymer films and such changes vary depending on the radiation dose.

Wide-Angle X-ray Scattering Study on Shear-Induced Crystallization of Propylene-1-Butylene Random Copolymer: Experiment and Diffraction Pattern Simulation

Shear-induced crystallization of a propylene-1-butylene random copolymer with low butylene content (5.7 mol %) was studied using time-resolved wide-angle X-ray scattering (WAXS) techniques. Polymor...

Microcrystalline parameters of polyurethane/polymethyl methacrylate semi interpenetrating polymer networks by WAXS

A series of polyurethane (PU) and polymethyl methacrylate (PMMA) semi interpenetrating polymer networks (SIPNs) in the weight percent ratios of 90/10, 70/30, 60/40 and 50/50 were synthesized. The obtained SIPNs were characterized for physico-mechanical properties. Wide angle X-ray scattering studies (WAXS) were made to know microcrystalline parameters such as crystal size (〈 N〉), lattice disorder ( g), surface ( D s ) and volume ( D v ) weighted crystal size of SIPNs. These parameters were expressed using exponential, lognormal and Reinhold asymmetric column length distribution functions and results are compared.

Structure–Property Relationship of Castor Oil-Based PU–PBMA Interpenetrating Polymer Networks

Castor oil-based polyurethane (PU) and polybutyl methacrylate (PBMA) interpenetrating polymer networks (IPNs) (PU/PBMA; 80/20, 60/40, 50/50, 40/60 and 20/80) have been prepared by sequential polymerization. The prepared IPNs have been characterized by physico-mechanical and optical properties. The thermal behaviour of IPNs were performed using thermo gravimetric analyzer (TGA). TGA thermogram shows that the thermal degradation of PU–PBMA IPN was found to proceed in three different steps. The microcrystalline parameters such as crystal size (hNi) and lattice disorder (g) of IPNs have been estimated using wide angle X-ray scattering studies (WAXS), and quantification of the polymer network has been carried on the basis of these parameters.

Structure and Phase Transitions of Poly(heptamethylene p,p′‐bibenzoate): Time‐Resolved Synchrotron WAXS and DSC Studies

AbstractTime‐resolved wide‐angle X‐ray scattering (WAXS), as well as differential scanning calorimetry (DSC) and polarisation microscopy studies, were applied to investigate the structure and phase transitions of poly(heptamethylene p,p′‐bibenzoate). Temperature dependencies of several structural parameters were determined. Complete transformation from an isotropic melt to a smectic phase was suggested whereas the transition from a smectic to crystalline phase is only partial (around 30%), although it takes place from the ordered SCA phase. Crystals are formed within the SCA domains with nearly the same coherent length. On the basis of the analysis of the position and the profile of the diffuse wide‐angle X‐ray scattering and mesogenic layer spacing, it was assumed that either crystallisation modifies the smectic structure, or mesophase losses its positional order because of the lack of mobility of the spacers at low temperatures.WAXS scattering profiles corresponding to P7MB: a) cooling from the isotropic melt at 2 °C · min−1; b) subsequent melting at 12 °C · min−1.magnified imageWAXS scattering profiles corresponding to P7MB: a) cooling from the isotropic melt at 2 °C · min−1; b) subsequent melting at 12 °C · min−1.

In-Situ Simultaneous Small- and Wide-Angle X-ray Scattering Study of Poly(ether ester) during Cold Drawing

The cold drawing of a poly(ether ester) block copolymer was studied by in-situ simultaneous small- and wide-angle X-ray scattering techniques in combination with a tensile stretching apparatus. The results obtained revealed three distinct regions in the stress−strain relationship. At low strains (0 < ε < 18%), the applied stress caused extension of the amorphous regions, formed by PTMO and some noncrystallizable segments of PBT, and subsequently reorientation of PBT crystalline lamellae. At slightly higher strains the lamellae become perpendicularly aligned to the drawing direction. At intermediate strains (18% < ε < 80%), the elongation gradually leads to breakage of the lamellae into smaller pieces, which eventually formed microfibrils containing linear assembly of layered lamellae. At large strains (ε > 80%), a further extension of the PTMO amorphous chains resulted in the fracture of the sample. The pathway of the structural changes by deformation in the present study was slightly different than those observed in the predrawn samples.

Crystalline Structure and Morphology in Nylon-12: A Small- and Wide-Angle X-ray Scattering Study

Simultaneous small- and wide-angle X-ray scattering has been employed to monitor the temperature dependence of the crystalline structure and morphology of nylon-12. Wide-angle measurements reveal that the α‘-phase is a stable high-temperature crystalline phase. Upon cooling, a crystalline transition takes place from the α‘-form into the hexagonal γ-phase. The small-angle data indicate at this point a discontinuous change in the density. At low temperatures, two crystal reflections occur at wide angles. This is interpreted as a monoclinic or an orthorhombic structure, which evolves from the hexagonal structure of the γ-form by an anisotropic thermal expansion. The evolution of the crystalline thickness during cooling and heating suggests the occurrences of partial surface crystallization and melting. This effect is superimposed on the transition α‘ ↔ γ and leads to crystal thickening and thinning during cooling and heating, respectively. The transition from γ to α‘ with increasing temperature arises from a “one-dimensional-melting” type of rupture between the hydrogen-bonded sheets. Finally, fast quenching from the melt results in the γ‘-phase, which transforms upon annealing into either the γ- or the α‘-polymorph. This process proceeds most probably through a melting and recrystallization process.

A gas microstrip wide angle X-ray detector for application in synchrotron radiation experiments

The Gas Microstrip Detector has counting rate capabilities several orders of magnitude higher than conventional wire proportional counters while providing the same (or better) energy resolution for X-rays. In addition the geometric flexibility provided by the lithographic process combined with the self-supporting properties of the substrate offers many exciting possibilities for X-ray detectors, particularly for the demanding experiments carried out on Synchrotron Radiation Sources. Using experience obtained in designing detectors for Particle Physics we have developed a detector for Wide Angle X-ray Scattering studies. The detector has a fan geometry which makes possible a gas detector with high detection efficiency, sub-millimetre spatial resolution and good energy resolution over a wide range of X-ray energy. The detector is described together with results of experiments carried out at the Daresbury Laboratory Synchrotron Radiation Source.