Small-angle Neutron Scattering Patterns Research Articles

Presence of a chiral soliton lattice in the chiral helimagnet MnTa3S6

Chiral helimagnetism was investigated in transition-metal intercalated dichalcogenide single crystals of MnTa3S6. Small-angle neutron scattering (SANS) experiments revealed the presence of harmonic chiral helimagnetic order, which was successfully detected as a pair of satellite peaks in the SANS pattern. The magnetization data are also supportive of the presence of chiral soliton lattice (CSL) phase in MnTa3S6. The observed features are summarized in the phase diagram of MnTa3S6, which is in strong contrast with that observed in other dichalcogenides such as CrNb3S6 and CrTa3S6. The presence of the remanent state provides tunable capability of the number of chiral solitons at zero magnetic field in the CSL system, which may be useful for memory device applications.

Protein-induced transformation of unilamellar to multilamellar vesicles triggered by a polysaccharide

We report on the morphological transitions of didodecyldimethylammonium bromide (DDAB) cationic vesicles and hybrid DDAB/hyaluronic acid (HA) vesicles upon addition of BSA at pH 7 where BSA is overall negatively charged. Small angle neutron scattering (SANS) is used to extract the size distributions of the nanovesicles, the thickness of the DDAB bilayers and their lamellarity. Although the HA-decorated DDAB vesicles contain the negatively charged polysaccharide the interaction with BSA appears to be more intense in comparison to bare vesicles. Characteristic peaks in the SANS patterns indicate the presence of multilamellar interfaces while the formation of multilamellar vesicles induced by BSA depends on the amount of added HA. Consequently, higher lamellarities are observed at higher BSA contents. This work demonstrates a simple methodology to tune the encapsulation of globular proteins in vesicular nanoassemblies by affecting their lamellarity and has direct implications on the application of vesicles and liposomes in protein delivery.

Mesoporous Silica Formation Mechanisms Probed Using Combined Spin-Echo Modulated Small-Angle Neutron Scattering (SEMSANS) and Small-Angle Neutron Scattering (SANS).

The initial formation stages of surfactant-templated silica thin films which grow at the air-water interface were studied using combined spin-echo modulated small-angle neutron scattering (SEMSANS) and small-angle neutron scattering (SANS). The films are formed from either a cationic surfactant or nonionic surfactant (C16EO8) in a dilute acidic solution by the addition of tetramethoxysilane. Previous work has suggested a two stage formation mechanism with mesostructured particle formation in the bulk solution driving film formation at the solution surface. From the SEMSANS data, it is possible to pinpoint accurately the time associated with the formation of large particles in solution that go on to form the film and to show their emergence is concomitant with the appearance of Bragg peaks in the SANS pattern, associated with the two-dimensional hexagonal order. The combination of SANS and SEMSANS allows a complete depiction of the steps of the synthesis that occur in the subphase.

Self-Similar Polymer Ring Conformations Based on Elementary Loops: A Direct Observation by SANS

We report small angle neutron scattering (SANS) results on very large polyethylene-oxide (PEO) rings in the melt. Major findings are (i) the observation of a cross over in the SANS pattern from a strong Q-dependence at intermediate Q to a Q-2 dependence at higher Q that is independent of the ring size. Summing up scattering amplitudes in a minimal model that contains the ring closure and a cross over from Gaussian statistics at short distances to more compact structures at larger distances, we identify the cross over to occur at a distance along the ring of Ne,0 = 45 ± 2.5. We consider this finding as a clear signature of the theoretically predicted elementary loops that build up the ring conformation. Their size is in the range of an entanglement strand for linear PEO melts and they are characterized by Gaussian statistics. (ii) The chain length dependence of the radius of gyration Rg follows rather closely the prediction of Obukhov's decorated ring model. (iii) Other than extracted from numerous simulations that are interpreted in terms of a cross over to mass fractal behavior around N ≅ 10Ne,0 with a fractal dimension df = 3 and exponent ν = 1/3, we do not observe such a cross over, but Rg(N) ∼ Nν=0.39 holds over the entire size range.

Early-Stopping of Scattering Pattern Observation with Bayesian Modeling

This paper describes a new machine-learning application to speed up Small-angle neutron scattering (SANS) experiments, and its method based on probabilistic modeling. SANS is one of the scattering experiments to observe microstructures of materials; in it, two-dimensional patterns on a plane (SANS pattern) are obtained as measurements. It takes a long time to obtain accurate experimental results because the SANS pattern is a histogram of detected neutrons. For shortening the measurement time, we propose an earlystopping method based on Gaussian mixture modeling with a prior generated from B-spline regression results. An experiment using actual SANS data was carried out to examine the accuracy of the method. It was confirmed that the accuracy with the proposed method converged 4 minutes after starting the experiment (normal SANS takes about 20 minutes).

Decoupling the anisotropic magnetization processes for the bulk Galfenol via utilizing the entire 2D SANS patterns

Abstract Quantitative understanding of the magnetization processes (MPs) is one of the important aspects for the design and development of ferromagnetic smart materials (FSMs). The present work explores the method of decoupling the anisotropic MPs directly for bulk soft FSMs. The small-angle neutron scattering (SANS) measurements were performed on the [1 0 0]-oriented alloys Fe1-xGax (Galfenol) under a series of magnetic fields. Those two-dimensional (2D) SANS patterns were decomposed and reconstructed by the spherical harmonic approaches. The scattering intensities, which are respectively decomposed into isotropic and anisotropic components, show clearly the pathway of three types of magnetic domains. The 90° domain process is thus quantified directly in the bulk Galfenol. The evolution trend for the domain process is consistent with that for the lattice strain and magnetization responses, which has been respectively evidenced by the in-situ neutron diffraction and initial magnetization measurement. Meanwhile, the quantitatively addressed domain process agrees well with the simulated results by the energy-based domain rotation modelling. These observations indicate that the anisotropic magnetization processes correlate tightly with the lattice strain response, which are of significant importance for the understanding and design of large magnetic-field-induced strain (MFIS). The present approach provides a quantitative method for decoupling the magnetization processes, which would be also applicable to other ferromagnetic systems besides Galfenol. This may help the understanding of MFIS mechanism and development of new FSMs.

Structural Response of Imogolite–Poly(acrylic acid) Hydrogel under Deformation

The structures of imogolite–poly(acrylic acid) hydrogels were investigated using small-angle X-ray scattering (SAXS) and small-angle neutron scattering (SANS) to determine the effects of particle concentration and the magnitude of deformation. The imogolite–poly(acrylic acid) hydrogel was synthesized by using γ-ray radiation as a nanocomposite gel with chemical bonds between the particles and polymers. The SAXS measurements revealed that the imogolite network was composed of particle overlaps. Under deformation, the gel structure was rearranged to increase the dimensionality of the network, forming a relaxed structure of overlaps by changing the orientation of the imogolite. The structural response of the deformed gel depended on the imogolite concentration, which influenced the changes in dimensionality of the network and the number of overlaps. The SANS patterns indicated that the polymers wrapped the imogolite aggregates, allowing polymers to follow the imogolite behavior. These observations demonstrat...

Effect of the temperature on the structural and textural properties of a compressed K-vermiculite

K-vermiculite pellets were obtained by compression (80MPa, 25°C or 200°C) of submicrometer size vermiculite particles. The evolution of the structural and textural properties of the compressed materials was studied as a function of the annealing temperature in the 400–1000°C range. Small Angle Neutron Scattering patterns of the pressed samples suggest a preferential orientation of the vermiculite particles for which the basal planes were arranged perpendicular to the compaction axis. Thermogravimetric analyses, Scanning Electron Micrographs, density and porosity measurements show that the most significant changes occurred for annealing temperatures higher than 800°C. When heated above 800°C, the pressed vermiculite samples undergo a simultaneous increase in density and decrease in porosity concomitant to a structural evolution, leading to a more three dimensional-based structure.

Small angle neutron scattering study of complex coacervate micelles and hydrogels formed from ionic diblock and triblock copolymers.

A complex coacervate is a fluid phase that results from the electrostatic interactions between two oppositely charged macromolecules. The nature of the coacervate core structure of hydrogels and micelles formed from complexation between pairs of diblock or triblock copolymers containing oppositely charged end-blocks as a function of polymer and salt concentration was investigated. Both ABA triblock copolymers of poly[(allyl glycidyl ether)-b-(ethylene oxide)-b-(allyl glycidyl ether)] and analogous poly[(allyl glycidyl ether)-b-(ethylene oxide)] diblock copolymers, which were synthesized to be nearly one-half of the symmetrical triblock copolymers, were studied. The poly(allyl glycidyl ether) blocks were functionalized with either guanidinium or sulfonate groups via postpolymerization modification. Mixing of oppositely charged block copolymers resulted in the formation of nanometer-scale coacervate domains. Small angle neutron scattering (SANS) experiments were used to investigate the size and spacing of the coacervate domains. The SANS patterns were fit using a previously vetted, detailed model consisting of polydisperse core-shell micelles with a randomly distributed sphere or body-centered cubic (BCC) structure factor. For increasing polymer concentration, the size of the coacervate domains remained constant while the spatial extent of the poly(ethylene oxide) (PEO) corona decreased. However, increasing salt concentration resulted in a decrease in both the coacervate domain size and the corona size due to a combination of the electrostatic interactions being screened and the shrinkage of the neutral PEO blocks. Additionally, for the triblock copolymers that formed BCC ordered domains, the water content in the coacervate domains was calculated to increase from approximately 16.8% to 27.5% as the polymer concentration decreased from 20 to 15 wt %.

Small-Angle Neutron Scattering Studies of Hemoglobin Confined Inside Silica Tubes of Varying Sizes

In addition to the chemical nature of the surface, the dimensions of the confining host exert a significant influence on confined protein structures; this results in immense biological implications, especially those concerning the enzymatic activities of the protein. This study probes the structure of hemoglobin (Hb), a model protein, confined inside silica tubes with pore diameters that vary by one order of magnitude (≈20-200 nm). The effect of confinement on the protein structure is probed by comparison with the structure of the protein in solution. Small-angle neutron scattering (SANS), which provides information on protein tertiary and quaternary structures, is employed to study the influence of the tube pore diameter on the structure and configuration of the confined protein in detail. Confinement significantly influences the structural stability of Hb and the structure depends on the Si-tube pore diameter. The high radius of gyration (Rg) and polydispersity of Hb in the 20 nm diameter Si-tube indicates that Hb undergoes a significant amount of aggregation. However, for Si-tube diameters greater or equal to 100 nm, the Rg of Hb is found to be in very close proximity to that obtained from the protein data bank (PDB) reported structure (Rg of native Hb=23.8 Å). This strongly indicates that the protein has a preference for the more native-like non-aggregated state if confined inside tubes of diameter greater or equal to 100 nm. Further insight into the Hb structure is obtained from the distance distribution function, p(r), and ab initio models calculated from the SANS patterns. These also suggest that the Si-tube size is a key parameter for protein stability and structure.

Heat-induced structural transitions of alpha-crystallin studied by small-angle neutron scattering

Alpha-crystallin from the bovine eye lens was studied by small-angle neutron scattering (SANS) in 90% D2O buffer solution at 20, 50, 60, 65, 75, 85 and 95°C. The temperature points for this study were specified on the basis of differential scanning calorimetric analysis of alpha-crystallin solutions which has shown two endothermic transitions with midpoints at 64.5 and 86°C. The SANS study revealed no significant alpha-crystallin quaternary structure alterations at 50°C as compared with 20°C. At 60-65°C the SANS data confirmed substantial alpha-crystallin quaternary structure rearrangements which resulted in the formation of alpha-crystallin oligomers with a similar shape but approximately twofold increased molecular weight as compared to the native state at 20°C. At higher temperatures (75, 85 and 95°C) the SANS patterns were very similar and were consistent with the scattering by rod-like particles with a cross-section radius of gyration ∼55 This transformation of alpha-crystallin to the rod-like particles was evidently irreversible as these particles remained in solution after cooling to 20°C. Ab initio shape models of the native and high-temperature alpha-crystallin were retrieved with DAMMIN and DAMAVER software. Schematic model of alpha-crystallin heat-induced quaternary structure transitions was considered.

Distinguishing the monomer to cluster phase transition in concentrated lysozyme solutions by studying the temperature dependence of the short-time dynamics

Recent combined experiments by small angle neutron scattering (SANS) and neutron spin echo (NSE) have demonstrated that dynamic clusters can form in concentrated lysozyme solutions when the right combination of a short-ranged attraction and a long-ranged electrostatic repulsion exists. In this paper, we investigate the temperature effect on the dynamic cluster formation and try to pinpoint the transition concentration from a monomeric protein phase to a cluster phase. Interestingly, even at a relatively high concentration (10% mass fraction), despite the significant change in the SANS patterns that are associated with the change of the short-ranged attraction among proteins, the normalized short-time self-diffusion coefficient is not affected between 5 and 40 °C. This is interpreted as a lack of cluster formation in this condition. However, at larger concentrations such as 17.5% and 22.5% mass fraction, we show that the average hydrodynamic radius increases significantly and causes a large decrease of the normalized self-diffusion coefficient as a result of cluster formation when the temperature is changed from 25 to 5 °C.

中性子小角散乱法で見るネオジム系焼結磁石の平均内部構造

Small-angle neutron scattering (SANS) method is applied for the investigation of average internal structures of Neodymium-Iron-Boron (Nd-Fe-B) sintered magnets. The information obtained using SANS is average structure of the magnet and sometimes complementary to the microstructural information using the scanning electron microscopy. The SANS patterns were sensitive to internal structural changes introduced by the sintering process and the formation of magnetic domains, and we found a correlation between the SANS intensity and the coercivity. These observations indicate that SANS is a promising tool to investigate the origin of the coercivity of Nd-Fe-B sintered magnets. This article is a brief introduction to SANS and gives several examples of its application to investigation of Nd-Fe-B sintered magnets in the viewpoint of the correlation between the average structure and the coercivity.

Small-angle neutron scattering characterization of the structure of nanoporous carbons for energy-related applications

We used small-angle neutron scattering (SANS) and neutron contrast variation to study the structure of four nanoporous carbons prepared by thermo-chemical etching of titanium carbide TiC in chlorine at 300, 400, 600, and 800 °C with pore diameters ranging between ∼4 and ∼11 Å. SANS patterns were obtained from dry samples and samples saturated with deuterium oxide (D 2O) in order to delineate origin of the power law scattering in the low Q domain as well as to evaluate pore accessibility for D 2O molecules. SANS cross section of all samples was fitted to Debye–Anderson–Brumberger (DAB), DAB–Kirste–Porod models as well as to the Guinier and modified Guinier formulae for cylindrical objects, which allowed for evaluating the radii of gyration as well as the radii and lengths of the pores under cylindrical shape approximation. SANS data from D 2O-saturated samples indicate that strong upturn in the low Q limit usually observed in the scattering patterns from microporous carbon powders is due to the scattering from outer surface of the powder particles. Micropores are only partially filled with D 2O molecules due to geometrical constraints and or partial hydrophobicity of the carbon matrix. Structural parameters of the dry carbons obtained using SANS are compared with the results of the gas sorption measurements and the values agree for carbide-derived carbons (CDCs) obtained at high chlorination temperatures (>600 °C). For lower chlorination temperatures, pore radii obtained from gas sorption overestimate the actual pore size as calculated from SANS for two reasons: inaccessible small pores are present and the model-dependent fitting based on density functional theory models assumes non-spherical pores, whereas SANS clearly indicates that the pore shape in microporous CDC obtained at low chlorination temperatures is nearly spherical.

Growth, Shrinking, and Breaking of Pluronic Micelles in the Presence of Drugs and/or β-Cyclodextrin, a Study by Small-Angle Neutron Scattering and Fluorescence Spectroscopy

The associative structures between F127 Pluronic micelles and four drugs, namely, lidocaine (LD), pentobarbital sodium salt (PB), sodium naproxen (NP), and sodium salicylate (SAL), were studied by small-angle neutron scattering (SANS). Different outcomes for the micellar aggregates are observed, which are dependent on the chemical nature of the drug and the presence of charge or otherwise: the micelles grow with LD, are hardly modified with PB, and decrease in size with both NP and SAL. The partition coefficient, determined by fluorescence spectroscopy, is directly correlated to the amount of charge, following NP approximately SAL < PB < LD. All drugs are found to lie at the interfacial layer, with a slightly deeper localization of LD and more superficial for PB. All drugs can form inclusion complexes with heptakis(2,6-di-O-methyl) beta-cyclodextrin (hep2,6 beta-CD). Hep2,6 beta-CD, as shown in previous studies (Joseph, J.; Dreiss, C. A.; Cosgrove, T. Langmuir, 2008, 24, 10005-10010; Dreiss, C. A.; Nwabunwanne, E.; Liu, R.; Brooks, N. J. Soft Matter, 2009, 5, 1888-1896), is also able to form a complex with F127, resulting in micellar breakup. In the ternary mixtures, a fine balance of forces is involved, which results in drastic micellar changes, as observed from the SANS patterns. Depending on the ratio of drug, polymer, and hep2,6 beta-CD and the nature of the interactions (which is directly linked to the drug chemical structure), the presence of drug either hinders micellar breakup by beta-CD (at high enough concentration of LD or PB) or leads to micellar growth (NP). These effects are mainly attributed to a preferential drug/beta-CD interaction (except for PB), which, at least in the conditions studied here, explains the higher beta-CD concentration needed for micellar breakup to occur.

Small-angle neutron scattering study on the cold rolled steel sheets

The effect of cold rolling on the small-angle neutron scattering (SANS) pattern was investigated for low-carbon steels. Several cold rolled steel samples with different reduction ratios and annealed samples after cold rolling were respectively measured by SANS. The cold rolled samples presented anisotropic two-dimensional (2D) SANS patterns. From the 2D SANS patterns two kinds of 1D pattern were calculated: one was for the Q⊥RD (rolling direction), the other for the Q//RD. The scatterer sizes calculated from the 1D patterns by using a model fitting increased with the reduction ratio, for the Q⊥RD section only. The annealed sample presented an isotropic SANS pattern. It can be concluded that the dislocations produced during the cold rolling process accumulated around the precipitates and then caused anisotropic 2D SANS patterns.

In situ small-angle neutron scattering investigation of theγ′ precipitation and growth in the nickel-based single-crystal alloy SC16

The precipitation of γ′ particles in the SC16 single-crystal nickel-based superalloy has been studied by insitu small-angle neutron scattering (SANS). On cooling from the one-phase fieldγ (temperaturesabove 1250 °C), the γ′ precipitates develop in different sizes and shapes at each temperature. Samples underwentsolutionizing and different ageing treatments below the solutionizing point in a saw-toothtemperature profile. Microstructural information, as well as relative volume fraction andsize of the particles, could be deduced from SANS patterns at each ageing temperature.They indirectly show that the precipitates have a cuboidal shape and are arranged(periodically) along the [100] crystallographic direction, only at temperatures below1180 °C. Between1180 and 1120 °C the transition from spherical to cuboidal shape seems to take place, driven by theprevalence of the strain energy over the other driving mechanisms of the reaction.More than one particle population is necessary to interpret the scattering profilesat each temperature. Nucleation of small particles seems to take place down to1050 °C. Morphology evolutions as a function of temperature as well as possible splitting of theprecipitates are discussed.

Time-Resolved SANS Study of Slow Dynamics in the Spin-Glass Alloy Fe0.70Al0.30

In order to probe the microscopic mechanism of slow dynamics in spin-glass materials, a time-resolved small angle neutron scattering (SANS) experiment has been made. Time-resolved SANS patterns from a concentrated spin-glass alloy Fe 0.70 Al 0.30 have been taken up to 20 h under various temperature and magnetic field with a typical time window of 10–30 min. We discuss the temperature and magnetic field dependence of the time evolution of the scattering pattern based on a magnetic cluster model.

SANS study of slow dynamics in reentrant spin glass Fe 0.70 Al 0.30

Time-resolved small angle neutron scattering (SANS) measurements have been made to probe the microscopic mechanism of slow dynamics in spin glass. SANS patterns from a reentrant spin glass alloy Fe0.70Al0.30 have been traced in real time after rapidly cooling the sample to the spin-glass phase. Diffuse-scattering patterns arising from magnetic clusters continue to change for up to 20 h, as was expected from low-field susceptibility measurements. The time evolution of the magnetic clusters in the spin-glass phase was directly observed.

Light Scattering and Small-Angle Neutron Scattering Studies of Structures in a Semidilute Polymer Solution Induced under Oscillatory Shear Flow

Oscillatory-shear-flow-induced structures of a semidilute polymer solution of ultrahigh molecular weight deuterated polystyrene in dioctyl phthalate were investigated by using the small-angle light scattering (SALS) and the small-angle neutron scattering (SANS). Under a fixed strain amplitude of oscillatory shear flow at 4.8, we observed the shear-induced structures as a function of the angular frequency (ω) and the strain-phase. At low ω, butterfly patterns, which are the scattering patterns unique to the shear-induced structures formed in semidilute polymer solution, were observed by SALS and isotropic patterns with weak scattered intensities were obtained by SANS. At high ω, on the other hand, SANS showed butterfly patterns and SALS showed almost isotropic patterns. These results indicate that the anisotropic structures developed under oscillatory shear flow become smaller with increasing ω. From the SALS and SANS patterns, we obtained scattering profiles parallel and perpendicular to the flow directio...