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Mesoporous materials containing heteroelements have a huge potential for use as catalysts, exchangers, and adsorbents due to their tunable nanometer-sized pores and exceptionally large internal surfaces accessible to bulky organic molecules. In the present work, ordered mesoporous silica containing Ni atoms as active sites was synthesized by a new low-temperature method of condensation of silica precursors on a micellar template from aqueous solutions in the presence of nickel salt. The homogeneity of the resulting product was achieved by introducing ammonia and ammonium salt as a buffer to maintain a constant pH value. The obtained materials were characterized by nitrogen sorption, X-ray and neutron diffraction, scanning electron microscopy, infrared spectroscopy, and thermal analysis. Their morphology consists of polydisperse spherical particles 50–300 nm in size, with a hexagonally ordered channel structure, high specific surface area (ABET = 900–1200 m2/g), large pore volume (Vp = 0.70–0.90 cm3/g), average mesopore diameter of about 3 nm, and narrow pore size distribution. Adsorption tests for methylene blue show sorption capacities reaching 39–42 mg/g at alkaline pH. The advantages of producing nickel silicates by this method, in contrast to precipitation from silicon alkoxides, are the low cost of reagents, fire safety, room-temperature processing, and the absence of specific problems associated with the use of ethanol as a solvent, as well as the absence of the inevitable capture of organic matter in the precipitation process. [ABSTRACT FROM AUTHOR]

A 9Cr-oxide dispersion strengthened (ODS) steel was thermally aged at 873 K for up to 5000 h. The size distribution and chemical composition of the dispersed oxide nanoparticles were analyzed by small-angle neutron scattering under a magnetic field. Combined with transmission electron microscopy, Vickers micro-hardness tests and electron backscattered diffraction measurements, all the results showed that the thermal treatment had little or no effect on the size distributions and volume fractions of the oxide nanoparticles in the ferromagnetic matrix, which suggested excellent thermal stability of the 9Cr-ODS steel. [ABSTRACT FROM AUTHOR]

Inhomogeneous structure occurring in biological membranes being rich in glycosphingolipids (GSL) has been proposed as an important phenomenon involved in the cellular endocytosis process. However, little is known about the correlation between the formation of microdomains and the GSL-dependent biogenesis for tubular endocytic pits occurred on the surface of the cellular membrane. In the present work, the interaction between the bacterial Shiga toxin from Escherichia coli (STxB) and its cellular receptor GSL globotriaosylceramide (Gb3) were studied using small unilamellar vesicle (SUV). The model membrane invagination induced by STxB was determined by the contrast variation small-angle neutron scattering (SANS) and the synchrotron radiation facility based small-angle X-ray scattering (SR-SAXS). The results revealed that Gb3 molecules provided the binding sites for STxB, inducing increased membrane fluctuation. The formation of protein–lipid complex (STxB-Gb3) apparently induced the thinning of model membrane with the thickness decreased from 3.10 nm to 2.50 nm. It is the first time to successfully characterize the mesoscopic change on membrane thickness upon GSL-dependent endocytic process using a small-angle scattering technique. Overall, this paper provided a practical method to quantify the inhomogeneous biological membrane structures, which is important to understand the cellular endocytosis process. [ABSTRACT FROM AUTHOR]

A series of calibration measurements have been performed on Suanni – the first small‐angle neutron scattering spectrometer entering into routine user operation in China – aiming to characterize instrument performance and to provide a reference for user experiments. Various calibration standards were used to verify the precise association of the scattering intensity I with the scattering vector magnitude q at short and medium sample–detector distances. The measurements recorded for silver behenate powder revealed a slight shift of the neutron wavelength (λ) at the sample position as compared to the nominal λ calculated by the selector constant. The deviation was more significant with λ > 0.8 nm owing to the shape of the incoming neutron spectrum incident on the selector. The measured dead time for the entire detection system is 2.7 µs, as determined by measurements with varying fluxes. A protonated/deuterated polystyrene blend was employed as the primary standard to calibrate the secondary standard H2O. The instrument covers an effective q range between 0.013 and 5 nm−1, as demonstrated by scattering curves obtained from a monodisperse poly(methyl methacrylate) nanoparticle suspension and a glassy carbon plate. The wavelength, the scattering vector magnitude and the absolute intensity for the Suanni small‐angle neutron scattering spectrometer have been calibrated by using standard samples, providing an informative reference for users and diagnostic tools for instrument scientists. [ABSTRACT FROM AUTHOR]

The small-angle neutron scattering (SANS) spectrometer Suanni at the liquid hydrogen cold neutron source of the 20 MW China Mianyang Research Reactor has recently been upgraded. Ultra-thin biconcave MgF2 lenses with a central thickness down to 0.2 mm have been installed between the collimator chamber and the sample stage. The lenses are able to improve the flux without too excessive an increase in the neutron beam size on the detector. A smaller minimum Q ( Qmin) can be obtained by decreasing the beam size without changing the total length of the spectrometer. By testing the central beam profiles under different neutron wavelengths (∼0.56-1 nm) with both traditional pinhole SANS (PSANS) and focusing SANS (FSANS) geometries, the gain factor thanks to the neutron lenses is about one order of magnitude. Given the loss of intensity due to the absorption of neutrons by the lenses, the benefits of the focusing can only be realized if it is possible to increase the aperture size. With an identical source aperture, FSANS can minimize the nominal Qmin from 7.20 × 10−3 nm−1 (for PSANS) to 5.55 × 10−3 nm−1 at a neutron wavelength of 1 nm. The practical benefit provided by the lenses is verified with a solution of poly(methyl methacrylate) nanospheres, which yields a scattering intensity one order of magnitude higher and a better resolution with the FSANS geometry than with that of PSANS. [ABSTRACT FROM AUTHOR]

Small angle neutron scattering (SANS) with contrast variation was used to characterize the fractal behavior and embedded porosity of micro/nano-sized 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) crystallites, gauging the effects of particle sizes on the microstructural features. Scattering results reveal that the external surface of micro-sized TATB crystallites are continuous and smooth interfaces and their internal pores display a surface fractal structure (surface fractal dimension 2.15 < DS < 2.25), while the external surface of nano-sized TATB particles exhibit a surface fractal structure (surface fractal dimension 2.36 < DS < 2.55) and their internal pores show a two-level volume fractal structure (large voids consist of small voids). The voids volume fraction of nano-sized TATB particles are found increased distinctively when compared with micro-sized TATB particles on length scale between 1 nm and 100 nm. Specific surface areas are also estimated based on Porod law method, which are coincident with Brunauer-Emmett-Teller (BET) measurements. The contrast variation technique distinguishes the information of internal voids from external surface, suggesting SANS is a powerful tool for determining the microstructural features, which can be used to establish the relationship between microstructures and properties of micro/nano-energetic materials. [ABSTRACT FROM AUTHOR]

The characteristics of strengthening nanoparticles have a major influence on the mechanical property and irradiation resistance of oxide dispersion strengthened (ODS) steels. In situ small angle neutron scattering (SANS) experiments were performed to determine the evolution of nanoparticles in 9Cr ODS steel powders varied with temperature. Initial-added Y 2 O 3 was completely dissolved into the steel matrix after mechanical alloying. Nanoparticles emerge after annealing at 600 °C for 10 min and coarsen slightly after 12 h. The radius of nanoparticles increases from 0.73 nm at 600 °C to 1.63 nm at 1000 °C, while the volume fraction decreases with increasing annealing temperature. [ABSTRACT FROM AUTHOR]

A new pinhole small-angle neutron scattering (SANS) spectrometer, installed at the cold neutron source of the 20 MW China Mianyang Research Reactor (CMRR) in the Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, has been put into use since 2014. The spectrometer is equipped with a multi-blade mechanical velocity selector, a multi-beam collimation system, and a two-dimensional He-3 position sensitive neutron detector. The q -range of the spectrometer covers from 0.01 nm −1 to 5.0 nm −1 . In this paper, the design and characteristics of the SANS spectrometer are described. The q -resolution calculations, together with calibration measurements of silver behenate and a dispersion of nearly monodisperse poly-methyl-methacrylate nanoparticles indicate that our SANS spectrometer has a good performance and is now in routine service. [ABSTRACT FROM AUTHOR]

• Nanoheterogeneity response as well as the interaction with matrix in a Fe 81 Ga 19 alloy is clearly revealed. • Reorientation of nanodomains relevant to L6 0 nanoprecipitates occurs at relatively lower fields than that of magnetic domains. • Nanoheterogeneities show a larger magnetic correlation length than their size, ensuring the exchange coupling and flipping of magnetizations. • Correlation length can be effectively tuned by simple heat-treatment, which in turn significantly enhances the magnetostriction. • Physical mechanism of large heterogeneous magnetostriction is uncovered, providing a general guideline for achieving tunable magnetostriction in heterogeneous ferromagnets. The underlying mechanism of large magnetostriction in Fe-Ga alloys is obviously beyond the conventional domain rotation and twin boundary motion, but has been attributed to the nanoscale magnetic heterogeneities. However, the nanoheterogeneity response as well as the interaction with matrix during magnetization process is still an open question. Through in-situ magnetic small-angle neutron scattering (SANS) study on a Fe 81 Ga 19 alloy, the present work clearly reveals that the reorientation of nanodomains relevant to face-centered-tetragonal L6 0 nanoprecipitates occurs at relatively lower fields than that of the magnetic domains. These nanoheterogeneities show a larger magnetic correlation length than their size, ensuring the exchange coupling between nanoprecipitates and matrix as well as the flipping of their magnetizations. This process contributes to the low-field-triggered large magnetostriction, unlike that induced by non-180° domain switches in the homogeneous magnetostrictive materials (such as Terfenol-D). Further study reveals that the correlation length can be effectively tuned by simple heat-treatment, which in turn significantly enhances the magnetostriction without enlarging the triggering field. Consequently, this work contributes to uncover the physical mechanism of the large heterogeneous magnetostriction besides the typical magnetic domain theory, and may also provide a general guideline for achieving tunable magnetostriction in heterogeneous ferromagnets. [Display omitted] [ABSTRACT FROM AUTHOR]

Recently, clays have been investigated for the long-term storage of spent nuclear fuel and nanominerals have been developed for the separation of radionuclides from subsurface water, but the detailed structure relating to pillaring of the sorbent is not always easily assessable by X-ray diffraction, for example, where the shift of the basal spacing to a higher value is not distinct. The purpose of this study was to gain an insight into the correlation between nanoscale structure and macroscopic sorption performance. The time dependence of 239‑plutonium sorption to Laponite, (Ce Al)-Laponite, and (Ce Al)-bentonite was studied. (Ce Al)-Laponite was characterized by TEM, XPS, XRD, N 2 adsorption/desorption isotherms, and small-angle neutron scattering. Analysis of neutron scattering from dry powder and powder dispersed in water showed that (Ce Al)-Laponite has an open pore-fractal structure described by a fractal dimension D p = 2.5, and a radius of gyration R g = 6.5 nm. In a slightly alkaline pH condition, the strength of the sorption (K d) of 239Pu by the different sorbents, from most to least, was (Ce Al)-bentonite (104) > (Ce Al)-Laponite (~104) > Laponite (103) > bentonite (103). The time it took for Pu sorption to reach equilibrium for (Ce Al)-Laponite was almost two times faster than that observed for the starting clays and the (Ce Al)-bentonite (8 days). A pseudo-second order rate expression was applied to the time-course data to describe the kinetic behavior. The enhanced rate of sorption was attributed to the connected pore system present in (Ce Al)-Laponite. • 239Pu sorption to Laponite, Ce-Al-Laponite, and Ce-Al-bentonite is investigated. • Ce-Al-Laponite has an open pore-fractal structure based on various analyses. • K d 239Pu (mild alkalinity): Ce-Al-bentonite > Ce-Al-Laponite > Laponite > bentonite. • Enhanced sorption rate is ascribed to the connected pore system in Ce-Al-Laponite. [ABSTRACT FROM AUTHOR]