Small-angle X-ray Scattering Method Research Articles

Studies on Morphological Parameters, Radius of Gyration, Correlation Length and Invariant of HPMC Polymer Doped with Ferrous (II) Oxide Using SAXS Method

It shed light on morphological parameters which influence radius of gyration, correlation length and invariant of Hydroxy Propyl Methyl Cellulose (HPMC) polymer doped with ferrous (II) oxide (FeO) using small angle X-ray scattering (SAXS) method. SAXS patterns have been recorded for different composition and gives an information about the structure of the polymer on a scale of about 800Ǻ, in which the variation of scattered intensity with angles from 0o to 2.5o has been measured for different composition of FeO with host polymer of HPMC. Employing para-crystalline model and exponential distribution function of phase lengths (amorphous and crystalline), we find a good agreement between the measured and predicted scattering except for a very small range of angles on the low angle side of the peak intensity. The method enabled quantitative parameters describing morphology of the two phases, amorphous and crystalline, consistent with the SAXS intensity distribution. A stepping procedure has been employed to compute the final parameters which gave the best fit between the calculated and experimental data. This was done by minimizing the statistical goodness-of-fit parameter chi-square. It is observed that there are significant changes in distribution of phase lengths due to different percentage weight of FeO in HPMC contents. Additionally, SAXS data has been used to estimate (i) radius of gyration (Rg), ii) correlation length (Lcor) and (iii) invariant (Q) parameters. A functional representation of the long period and also radius of gyration at different dopant concentrations is adopted by viewing them as realizations of a continuous-time stochastic process observed with measurement error. This allows one to estimate the mean functional relationship between long period and the dopant concentration.

Микроструктура и свойства сплава Zn–1%Li–2%Mg, подвергнутого интенсивной пластической деформации

In this paper, the authors consider the mechanisms of formation of high-strength states in the Zn–1%Li–2%Mg alloy as a result of its processing by the high pressure torsion (HPT) method. For the first time, the study showed that using HPT treatment, as a result of varying the degree of deformation at room temperature, it is possible to increase the ultimate strength of a zinc alloy from 155 to 383 MPa (with an increase in the yield stress from 149 to 306 MPa) without losing its ductility. To explain the reasons for the increase in the zinc alloy mechanical properties, its microstructure was analyzed by scanning electron microscopy (SEM), X-ray phase analysis (XPA), X-ray diffraction analysis (XRD), and small-angle X-ray scattering (SAXS). Using XPA, the authors established for the first time that Zn(eutectic)+β-LiZn4(eutectic)→~LiZn3+Zn(phase)+Zn(precipitation) and MgZn2→Mg2Zn11 phase transformations occur in the zinc alloy during HPT treatment. SEM analysis showed that at the initial stages of HPT treatment, cylindrical Zn particles with a diameter of 330 nm and a length of up to 950 nm precipitate in β-LiZn3 phase. At the same time, the SAXS method showed that needle-like LiZn4 particles with a diameter of 9 nm and a length of 28 nm precipitate in the Zn phase. The study established that, only spherical Zn and LiZn4 particles precipitate at high degrees of HPT treatment. Precision analysis of the zinc alloy microstructure showed that HPT treatment leads to grain refinement, an increase in the magnitude of crystal lattice microdistortion, a growth of the density of dislocations, which are predominantly of the edge type. As a result of the analysis of hardening mechanisms, the authors concluded that the increase in the zinc alloy strength characteristics mainly occurs due to grain-boundary, dislocation, and dispersion hardening.

Microstructural analysis of organic matter in shale by SAXS and WAXS methods

Characterizing the kerogen-hosted pore structures is essential to understand the adsorption, transport and storage potential in organic-rich shale reservoirs. In this paper, we first separated the organic matter (kerogen) from the mineral matrix in four different shale samples of the Bakken Formation with different thermal maturities and then analyzed their chemical compositions using the wide-angle X-ray scattering (WAXS) method. Next, we acquired small-angle X-ray scattering (SAXS) to characterize the structure of the organic matter and see how these two will relate. The WAXS results showed that the isolated kerogens have high purity (free of inorganic minerals) and retain different chemical compositions. Moreover, SAXS analysis revealed that the isolated kerogens have similar radius of gyration (Rg) which is around 90 Å and the molecules are in the compact mode. Based on the pore size distribution analysis from the SAXS data, two main peaks were found in all of these four samples with one peak less than 40 Å and the other one larger than 1000 Å. Also, the TEM images revealed that Sample 1 is abundant in pores with sizes around 20 nm while Sample 2 does not have pores of that size, which agrees with the results from the pore size distribution that was obtained from the SAXS method. Ultimately, this study exhibits how different analytical instruments can provide us with useful information from complex structures of geomaterials.

Origin of the Hierarchical Structure of Dendritic Fibrous Nanosilica: A Small-Angle X-ray Scattering Perspective.

The discovery of dendritic fibrous nanosilica (DFNS) has attracted great attention to the field of catalysis, CO2 capture, drug delivery due to its distinct morphology, and pore size distribution. Despite extensive research, the understanding of the DFNS formation process and its internal structure remains incomplete as microscopy and gas sorption techniques were not able to provide necessary in-depth structural information due to their inherent limitations. In the current work, we present a structural model of DFNS derived using small-angle X-ray scattering (SAXS) supported by 129Xe nuclear magnetic resonance (NMR), which provided intricate details of DFNS and its internal structure. Mechanistic understanding of the DFNS formation and growth process was achieved by performing time-resolved SAXS measurements during the synthesis of DFNS, which unveils the evolution of two levels of a bicontinuous microemulsion structure responsible for intricate DFNS morphology. The validity and the accuracy of the SAXS method and the model were successfully established through a direct correlation among the functionality of the DFNS scattering profile and its pore size distribution, as well as results obtained from the 129Xe NMR studies. It has been established that the DFNS structure originates from direct modulation of the bicontinuous structure controlled by a surfactant, a co-surfactant, and the silicate species formed during hydrolysis and the condensation reaction of the silica precursor.

Nanostructured Polymer Composite Electrolytes with Self-Assembled Polyoxometalate Networks for Proton Conduction

Nanostructured Polymer Composite Electrolytes with Self-Assembled Polyoxometalate Networks for Proton Conduction

Insights into the Nanostructure, Solvation, and Dynamics of Liquid Electrolytes through Small‐Angle X‐Ray Scattering

AbstractThe fundamental understanding of nanostructures of liquid electrolytes is expected to enable transformative gains in electrochemical energy storage capacities. However, the solvation structures and molecular dynamics in electrolytes are hard to probe, which limits further performance improvements in macroscopic properties such as ionic conductivity, viscosity, and stability. Small‐angle X‐ray scattering (SAXS), a non‐destructive method for nanostructures characterization in liquids, offers a unique perspective on molecular clusters, anion‐cation pairs, solvation sheath, percolating network, aggregates, and domain sizes of electrolytes. Notably, the SAXS method has excellent time‐resolution, enabling the study of molecular dynamics by operando characterization. This review focuses on the microscopic understanding of liquid electrolytes by SAXS and operando SAXS. The unique capabilities of X‐ray scattering for intra‐ and inter‐molecular relationship and nanostructure characterization of electrolytes are highlighted.

Epoxy Resin Nanocomposites: The Influence of Interface Modification on the Dispersion Structure—A Small-Angle-X-ray-Scattering Study

The surface functionalization of inorganic nanoparticles is an important tool for the production of homogeneous nanocomposites. The chemical adaptation of the nano-filler surface can lead to effective weak to strong interactions between the fillers and the organic matrix. Here we present a detailed systematic study of different surface-functionalized particles in combination with a SAXS method for the systematic investigation of the interface interaction in the development of epoxy nanocomposites. We investigated the effect of surface modification of spherical SiO2 nanoparticles with 9 nm and 72 nm diameter and crystalline ZrO2 nanoparticles with 22 nm diameter on the homogeneous distribution of the fillers in diethylenetriamine (DETA) cured bisphenol-F-diglycidylether epoxy resin nanocomposites. Unmodified nanoparticles were compared with surface-modified oxides having diethylene glycol monomethyl ethers (DEG), 1,2-diols, or epoxy groups attached to the surface. The influence of surface modification on dispersion quality was investigated by transmission electron microscopy (TEM) and small angle X-ray scattering (SAXS) for inorganic filler contents of 3, 5 and 10 wt%. It was shown that the dispersion quality can be optimized by varying the coupling agent end group to obtain homogeneous and transparent nanomaterials. UV/VIS measurements confirmed the transparency/translucency of the obtained materials. The relationship between particle–matrix interaction and particle–particle interaction plays a decisive role in homogeneity and is controlled by the surface groups as well as by the type, size, and morphology of the nanoparticles themselves.

Evaluation and comparison of bentonite surface fractal dimension and prediction of swelling deformation: Synchrotron radiation SAXS and N2-adsorption isotherms method

A key parameter for calculating the swelling deformation using fractal model is the fractal dimension. Small angle X-ray scattering (SAXS) and liquid nitrogen adsorption method (Frenkel-Halsey-Hill (FHH) and Neimark thermodynamic method) were employed to determine fractal dimension of four Chinese bentonite. Based on SAXS and the FHH method, fractal swelling deformation model was adopted to predict mechanical behavior. The result suggested that the fractal dimensions of #1, #2, #3 and #4 calculated by SAXS were 2.600, 2.650, 2.530 and 2.780, respectively. The fractal dimensions determined by FHH model were 2.636, 2.579, 2.612, and 2.892, respectively. These minor variations can be associcated with the different the test scales, difference between the open hole, closed hole and interlayer hole, and the different test mechanism. The SAXS method was based on the difference in electron density and can reach the interlayer pores of montmorillonite. It seemed that the reliability and stability of the Neimark thermodynamic method need to be further improved. Swelling deformation calculated by SAXS and FHH method was roughly in accordance with the experimental data. Compared with the liquid nitrogen adsorption method, the predicted value of the SAXS method was closer to the experimental value, which confirm that the fractal dimension calculated by SAXS was more accurate. This fills the gap of using SAXS to predict the swelling deformation of Gaomiaozi CaGMZ bentonite.

Investigation of the microporous organization of 1,2-disubstituted polyacetylenes using low-temperature argon sorption and small-angle X-ray scattering

The extra free volume of glassy, highly permeable 1,2-disubstituted polyacetylenes is associated with the microporous organization of these polymers. In this work, the microporosity of poly(1-trimethylsilyl-1-propyne) (PTMSP) and poly(4-methyl-2-pentyne) (PMP) is investigated by two independent methods—convenient low-temperature Ar sorption and less commonly used small-angle X-ray scattering (SAXS). The Ar sorption data were analyzed in connection with the specific surface area, pore volume, and micropore size distribution. It is shown that the higher specific surface area, total pore volume, and micropore volume of PTMSP than those of PMP are associated with higher gas permeability coefficients. It was found that the Brunauer–Emmett–Teller-specific surface values obtained for PTMSP and PMP from argon sorption isotherms correlate with the specific surface values obtained from the SAXS method. The correlation of the specific surface values obtained from fundamentally different methods makes it possible to evaluate the small-angle scattering method as adequate for assessing the microporosity of polymeric materials. The microporosity of poly(1-trimethylsilyl-1-propyne) (PTMSP) and poly(4-methyl-2-pentyne) (PMP) is investigated by two independent methods—convenient low-temperature Ar sorption and less commonly used small-angle X-ray scattering (SAXS). The Brunauer–Emmett–Teller-specific surface values obtained for PTMSP and PMP from Ar sorption isotherms correlate with the specific surface values obtained from the SAXS method. The correlation of the specific surface values obtained from fundamentally different methods makes it possible to evaluate the small-angle scattering method as adequate for assessing the microporosity of polymeric materials.

Reversible rearrangement of magnetic nanoparticles in solution studied using time-resolved SAXS method.

Superparamagnetic nanoparticles have broad applications in biology and medicines. Quantitative measurements of magnetic beads in solution are essential in gaining comprehensive understanding of their dynamics and developing applications. Here, using synchrotron X-ray sources combined with well controlled magnetic fields, the results from small-angle X-ray scattering (SAXS) experiments on superparamagnetic particles in solution under the influence of external magnetic fields are reported. The particles mostly remain in monodispersed states and the linear aggregates tend to be aligned with the external magnetic field. After removing the magnetic fields, the superparamagnetic nanoparticles quickly recover to their original states indicating high reversibility of the rearrangement under the control of a magnetic field. The external magnetic field instrument composed of paired permanent magnets is integrated into the SAXS beamline at the Shanghai Synchrotron Radiation Facility providing a platform for studying time-resolved dynamics induced by magnetic fields.

INFLUENCE OF DIFFERENT SPECIFIC SURFACE AREA OF HIGHLY DISPERSIBLE SILICA AND INTERFACIAL CHARACTERISTICS OF GREEN ELASTOMER COMPOSITES

ABSTRACT Epoxidized natural rubber (ENR) is a modified form of NR bearing polar epoxy groups. The focus is on dispersion of highly dispersible silica (HDS) filler with three different specific surface areas in ENR 25/ENR 50 composites. The effect of three different specific surface areas of HDS on bound rubber content, Payne effect, physicomechanical properties, and viscoelastic properties of the green composites was studied in detail. Also, the influences of epoxide content in ENRs in the absence of silane coupling agent are evaluated on the overall properties of green composites. The highest level of reinforcement was obtained for the intermediate specific surface area of HDS due to the homogenous dispersion in the ENR matrix. Small-angle X-ray scattering (SAXS) has been used to analyze the particle network and cluster establishment in the green composites. The present SAXS method provides a unique insight into the aggregate formation according to the Beaucage model. On the other hand, SAXS results demonstrate that the particle network can be efficiently suppressed by increasing the specific surface area of HDS.

Studies on Interfacial Characteristics of Highly Dispersible Silica Reinforced Epoxidized Natural Rubber Compounds

ABSTRACTThe present work examines the effect of two different specific surface areas of highly dispersible silica (HDS)-reinforced epoxidized natural rubber (ENR) composites. The influences of different blend ratio between ENRs consisting 25 and 50 mol% of epoxidation-based (ENR-25/ENR-50) composites was studied in detail. The primary objective is to investigate the interfacial area of HDS surface involved in filler-to-rubber interaction mechanisms for the better reinforcement. Notable improvement in overall properties of these green composites are corroborated with various meticulous characterization including cure characteristics, specific bound rubber content, physicomechanical, dynamic mechanical properties, etc. Increasing the specific surface area of HDS and their subsequent interface with ENR matrix invokes its superior dispersion. Small angle X-ray scattering (SAXS) has been used to analyze the particles network and clusters establishment in green composites. The present SAXS method provides a unique insight into the cluster formation according to the Beaucage model. However, SAXS results demonstrate that particles networks can be effectively suppressed by increasing specific surface area of HDS.

WAXD/SAXS study and 2D fitting (SAXS) of the microstructural evolution of PAN-based carbon fibers during the pre-oxidation and carbonization process

Microstructural evolution in polyacrylonitrile (PAN) fibers at different temperatures during pre-oxidation and carbonization under stretching was studied by synchrotron wide-angle X-ray diffraction (WAXD) and small-angle X-ray scattering (SAXS). Microvoids were characterized by the classical SAXS method, and were compared with simulation results obtained by fitting 2D SAXS patterns to a model based on a dilute system of cylindrical microvoids randomly distributed and preferentially orientated along the fiber axis and having a log-normal size distribution. The WAXD results showed that the crystal size, d-spacing and preferred orientation decreased during pre-oxidation, and increased during carbonization. A diffraction peak for PAN fibers at 2θ=13.6° disappeared during the final stage of pre-oxidation, meanwhile a new peak at 2θ=23.6° appeared, whose intensity increased during carbonization, indicating the formation of the graphite structure. The average length of the microvoids increased, and new microvoids were formed, which became oriented along the fiber axis as the fiber manufacturing process proceeded. The length of microvoids from simulation results is consistent with that from the classical method, indicating that the model is valid to describe the microvoid structure of fibers.

Insight to Nanoparticle Size Analysis-Novel and Convenient Image Analysis Method Versus Conventional Techniques.

The aim of this paper is to introduce a new image analysis program “Nanoannotator” particularly developed for analyzing individual nanoparticles in transmission electron microscopy images. This paper describes the usefulness and efficiency of the program when analyzing nanoparticles, and at the same time, we compare it to more conventional nanoparticle analysis techniques. The techniques which we are concentrating here are transmission electron microscopy (TEM) linked with different image analysis methods and X-ray diffraction techniques. The developed program appeared as a good supplement to the field of particle analysis techniques, since the traditional image analysis programs suffer from the inability to separate the individual particles from agglomerates in the TEM images. The program is more efficient, and it offers more detailed morphological information of the particles than the manual technique. However, particle shapes that are very different from spherical proved to be problematic also for the novel program. When compared to X-ray techniques, the main advantage of the small-angle X-ray scattering (SAXS) method is the average data it provides from a very large amount of particles. However, the SAXS method does not provide any data about the shape or appearance of the sample.

Comparison of Nanometric Particle Size Distributions as Determined by SAXS, TEM and Analytical Ultracentrifuge

AbstractIn this paper the particle size distribution of SiO2 spherical nanoparticles is determined by small angle X‐ray scattering (SAXS). The experimental scattering intensity data were compared with theoretical intensities based on different numeric procedures and different assumptions for the distribution of the particles. Hereby two fixed shapes of distribution, Gauss and log normal, were used and compared to a free particle distribution which is determined with the maximum entropy method (MEM). The results were further compared with the particle size distributions obtained from the transmission electron microscopy (TEM) and analytical ultracentrifuge (AUC). The comparison demonstrated SAXS to be a generally reliable method for determining size distributions of spherical particles in the nanometer range. Assuming a fixed distribution in the SAXS method, reliable data can be obtained even in the case of bad statistical data or higher concentrations. The MEM procedure allows shape determination but is restricted to scattering data of dilute samples and high statistical quality if one wishes to avoid artefacts in the resulting size distribution.

Small-angle X-ray scattering study of modified porous suspension-poly(vinyl chloride) particles

Small-angle X-ray scattering (SAXS) was ap- plied to investigate the microstructure of unmodified and modified porous commercial suspension-type poly(vinyl chloride) (PVC) particles. The modified PVC particles were prepared by an in situ stabilizer-free polymerization/ crosslinking of particles absorbed with a monomer/ crosslinker/peroxide solution. The modifying polymers in- clude styrene with or without divinyl benzene (DVB) as a crosslinker and methyl methacrylate (MMA) with or with- out ethylene glycol dimethacrylate (EGDMA) as a crosslinker. The SAXS method was used to highlight the effect of polystyrene (PS) on the microstructure of PVC particles and to evaluate the characteristic lengths, both in the PVC/PS and the PVC/XPS (PS crosslinked with 0 and 5% DVB, respectively) systems. A model is suggested, where during the synthesis modification process, swelling of PVC by styrene and styrene polymerization occur simulta- neously. PVC swelling by styrene causes destruction of the PVC subprimary particles, whereas styrene polymerization leads to phase separation resulting from incompatibility of the polymers. It was further suggested that because of PVC swelling by styrene, structure of the subprimary particles is lost. Therefore the characteristic lengths of PVC/PS and PVC/XPS, as calculated from the SAXS measurements, were attributed to the size of the phase-separated PS and XPS inclusions, respectively. The SAXS method also shows that PMMA and XPMMA do not influence the PVC microstruc- ture. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 95: 1024 -1031, 2005

Investigation of the staling process of bread using the small-angle X-ray scattering (SAXS) method

The bread staling process was studied using the SAXS method, data from which indicated that bread staling occurs with significant electron density changes. Two kinds of SAXS measurements were made, on dry and water suspension samples. The SAXS results indicate that dry samples show electron density changes mainly in the gluten phase, while for water suspension samples the changes are mainly in the starch matrix. Copyright © 2006 John Wiley & Sons, Ltd.

Analysis of collagen fibril diameter distribution in connective tissues using small-angle X-ray scattering

Analysis of the diameters of collagen fibrils provides insight into the structure and physical processes occurring in the tissue. This paper describes a method for analyzing the frequency distribution of the diameters of collagen fibrils from small-angle X-ray scattering (SAXS) patterns. Frequency values of fibril diameters were input into a mathematical model of the form factor to calculate the equatorial intensity which best fits the experimentally derived data from SAXS patterns. A minimization algorithm utilizing simulated annealing (SA) was used in the fitting procedure. The SA algorithm allowed for random sampling of the frequency values, and was run iteratively to build up an optimized frequency distribution of fibril diameters. Results were obtained for collagen samples from sheep spine ligaments. The mean fibril diameter value obtained from this data-fitting method was 73 nm+/-20 nm (S.D.). From scanning transmission electron microscopy, the mean diameter was found to be 69 nm+/-14 nm (S.D.). The good agreement between the two methods demonstrates the reliability of the SAXS method for the tissue examined. The non-destructive nature of this technique, as well as its statistical robusticity and capacity for large sampling, means that this method is both quick and effective.

Application of the SAXS method and viscometry for determination of the thickness of adsorbed polymer layers at the ZrO 2–polymer solution interface

The authors studied the influence of the molecular weight of polyacrylic acid (PAA) and polyacrylamide (PAM), solution pH and ionic strength, and the background electrolyte type on adsorption and the thickness of polyelectrolyte adsorption layers formed on ZrO 2 surface. Carboxyl groups distributed along PAA and PAM chains were shown to be responsible for their interface conformation, which directly influences the thickness of the adsorbed polyelectrolyte layers. Bonding of macromolecules with solid surface occurs through the hydrogen bridges of these groups. Two methods were applied to determine the PAA and PAM adsorption layer thickness on ZrO 2, i.e., SAXS (small angle X-ray scattering) and viscometry. Despite some limitations of the SAXS method resulting from the relationship between the size of solid pores, polymer molecular weight, and conformation of the adsorbed macromolecule, all obtained SAXS results were very close to those calculated from viscometry data.

Direct detection of the protein quaternary structure and denatured entity by small-angle scattering: guanidine hydrochloride denaturation of chaperonin protein GroEL

A change in the higher-order structure of an oligomeric protein is directly detectable by small-angle scattering. A small-angle X-ray scattering (SAXS) study of the denaturation process of the chaperonin protein GroEL by guanidine hydrochloride (GdnHCl) showed that the disappearance of the quaternary structure can be monitored by using a Kratky plot of the scattered intensities, demonstrating the advantage of the SAXS method over other indirect methods, such as light scattering, circular dichroism (CD), fluorescence and sedimentation. The collapse of the quaternary structure was detected at a GdnHCl concentration of 0.8 Mfor a solution containing ADP (adenosine diphosphate)/Mg2+(2 mM)/K+. From pairwise plots of the change in forward scattering intensityJ(0)/C(weight-average molecular weight) and thez-average (root mean square) radius of gyration against the GdnHCl concentration, the stability and nature of the denatured protein can be determined. The SAXS results suggest that the GroEL tetradecamer directly dissociates to the unfolded coil without going through a globular monomer state. The denatured ensemble is not a single unfolded monomer coil particle, but some mixture of entangled aggregates and a monomer of the coil molecules. Small-angle scattering is a powerful method for the detection and study of changes in quaternary and higher-order structures of oligomeric proteins.