Very Small Angle Neutron Scattering Research Articles

Compaction and clay content control mudrock porosity

Mudrocks, ubiquitous yet poorly understood sedimentary rocks with significant variations in composition and physical properties, form seals for geological carbon dioxide and energy (e.g., hydrogen and methane) storage, repositories for radioactive waste disposal, and reservoirs for natural gas. Understanding the controls on mudrock pore structure is essential for evaluating their porosity. The identification and quantification of controls depend on the nano-to micron scale pore network, which are the subject of this study. Small-angle (SANS) and very small-angle neutron scattering (VSANS) experiments were conducted on 13 diverse mudrock sets, characterised by differences in mineralogy, stratigraphy, maturity, and depositional environment. We performed multivariate statistics to systematically characterise the pore structure in 71 samples cross a 5 μm–2 nm pore size range. Our results indicate a multivariate approach more effectively captures the complex controls on porosity rather than single parameters. Compaction and clay content emerge as key primary and secondary controls on mudrock porosity, respectively, upon which we introduce a new porosity classification. Our complementary experimental-statistical assessment involving SANS-derived multiscale porosity sheds new light on the influence of structural controls on storage or production capacity in mudrocks.

Advanced polarization analysis capability on the very small-angle neutron scattering instrument at the NIST Center for Neutron Research

The Very Small Angle Neutron Scattering (VSANS) diffractometer at the National Institute of Standards and Technology has been commissioned and is in the user program. A large available space of nearly 2 m along the beam in the sample area not only enhances the existing SANS polarization analysis capability, but also makes it possible for implementation of other polarization analysis capabilities which would not be easily available on existing SANS instruments, including grazing-incidence small-angle neutron scattering with polarization analysis and spherical neutron polarimetry. We present two polarized setups, one for high magnetic sample fields and the other for low magnetic sample fields, together with a versatile and flexible operational platform for polarized beam experiments. The design of a magnetostatic cavity device that provides better field homogeneity and thus longer 3He polarization relaxation time is discussed. It consists of an end-compensated magnetic shielded solenoid with non-identical holes to accommodate the divergent scattered beam in a constrained distance. Significant improvement in polarized neutronic performance, 3He polarization relaxation time, and an extended momentum transfer range for polarization analysis are presented. Improved neutron polarizing devices, double V-shaped supermirror polarizer, adiabatic radio-frequency spin flipper, and a 3He spin analyzer have yielded an initial instrumental flipping ratio of 100, allowing for higher sensitivity to detection of weak magnetic features in the sample.

Further Optimized Design of a Nested Rotate Sextupole Permanent Magnet Lens for the Focusing of Pulsed Neutrons

A compact nested rotate sextupole permanent magnet (Nest-Rot-SPM) lens was designed for the focusing of pulsed neutrons. It is based on the working conditions of the Very Small Angle Neutron Scattering (VSANS) instrument at the China Spallation Neutron Source (CSNS), and is expected to focus a neutron pulse from 6 Å to 10.5 Å, without chromatic aberration. Three hurdles must be addressed, i.e., the tremendous torque, the heat deposition, and the synchronization with the neutron pulse, respectively. The bore diameter and segment length of the lens are optimized using a formula analysis of the key parameters and model simulations of the torque and heat deposition. A twin torque canceling design is used to reduce the torque to one-third of its original value, or even lower. The goal of this project is to take the device into practical use in the VSANS at the CSNS.

Combining SANS and VSANS to Extend Q-Range for Morphology Investigation of Silicon-Graphite Anodes

Silicon-based electrodes are attractive candidates as anodes for Li-ion batteries due to their high theoretical specific capacity. However, repeated lithiation/delithiation causes significant morphological changes in the silicon particles, which results in formation of highly porous silicon structures and severe side reactions at the silicon–electrolyte interface. To quantify such morphological changes on both the micrometer and nanometer scales, we combine the techniques of very small-angle neutron scattering (VSANS) and small-angle neutron scattering (SANS). While conventional and contrast-matched SANS data provide insight into the solid–electrolyte-interphase coverage around silicon particles and the filling of evolving porosity within the electrode, VSANS data provide information on the micrometer-sized graphite particles.

Size Measurement of Extracellular Vesicles and Synthetic Liposomes: The Impact of the Hydration Shell and the Protein Corona

Size characterization of extracellular vesicles (EVs) and drug delivery liposomes is of great importance in their applications in diagnosis and therapy of diseases. There are many different size characterization techniques used in the field, which often report different size values. Besides technological biases, these differences originate from the fact that various methods measure different physical quantities to determine particle size. In this study, the size of synthetic liposomes with nominal diameters of 50nm and 100nm, and red blood cell-derived EVs (REVs) were measured with established optical methods, such as dynamic light scattering (DLS) and nanoparticle tracking analysis (NTA), and with emerging non-optical methods such as microfluidic resistive pulse sensing (MRPS) and very small-angle neutron scattering (VSANS). The comparison of the hydrodynamic sizes obtained by DLS and NTA with the sizes corresponding to the excluded volume of the particles by MRPS enabled the estimation of the thickness of the hydration shell of the particles. The comparison of diameter values corresponding to the boundary of the phospholipid bilayer obtained from VSANS measurements with MRPS size values revealed the thickness of the polyethylene glycol-layer in case of synthetic liposomes, and the thickness of the protein corona in case of REVs.

Very-small angle neutron scattering study on grain coarsening inhibition by V-doping of WC-Co composites

The mechanical properties of cemented carbides can be tuned by controlling WC grain coarsening and the simultaneous growth of the binder pocket size during the sintering. So far, bulk studies considering this phenomenon are scarce, but here, we report the first very-small angle neutron scattering (VSANS) study on cemented carbides. VSANS is supplemented with electron backscatter diffraction (EBSD) and the microstructural refinement by increasing V-doping (0, 0.02, 0.22, and 0.76 wt%) is quantified. The capability of VSANS as a non-destructive bulk probe for cemented carbides is shown, paving way for forthcoming in-situ studies.

Effect of grain-boundary diffusion process on the geometry of the grain microstructure of Nd−Fe−B nanocrystalline magnets

Hot-deformed anisotropic Nd$-$Fe$-$B nanocrystalline magnets have been subjected to the grain-boundary diffusion process (GBDP) using a $\mathrm{Pr}_{70}\mathrm{Cu}_{30}$ eutectic alloy. The resulting grain microstructure, consisting of shape-anisotropic Nd$-$Fe$-$B nanocrystals surrounded by a Pr$-$Cu-rich intergranular grain-boundary phase, has been investigated using unpolarized small-angle neutron scattering (SANS) and very small-angle neutron scattering (VSANS). The neutron data have been analyzed using the generalized Guinier-Porod model and by computing model-independently the distance distribution function. We find that the GBDP results in a change of the geometry of the scattering particles:~In the small-$q$ regime the scattering from the as-prepared sample exhibits a slope of about $2$, which is characteristic for the scattering from two-dimensional platelet-shaped objects, while the GBDP sample manifests a slope of about $1$, which is the scattering signature of one-dimensional elongated objects. The evolution of the Porod exponent indicates the smoothing of the grain surfaces due to the GBDP, which is accompanied by an increase of the coercivity.

Study of a multi-pinhole collimation system based small-angle neutron scattering instrument at the Compact Pulsed Hadron Source

The neutron flux of the Compact Pulsed Hadron Source (CPHS) is about 2–3 orders of magnitude lower than that of large neutron sources, which means that the beam intensity should be improved to achieve good statistics. Multi-pinhole collimation can be used to obtain a lower Q with an acceptable beam intensity in a very small angle neutron scattering (VSANS) instrument and a higher beam intensity for a larger sample size in a small-angle neutron scattering (SANS) instrument. A new nine-pinhole structure is used in a SANS instrument at CPHS to achieve an acceptable range and resolution of Q and a higher beam intensity compared to single-pinhole collimation. The crosstalk issue associated with multi-pinhole collimation is addressed using an optimized algorithm to achieve a higher safety margin and a larger pinhole size with a higher beam intensity at the sample. Different collimator aperture structures are compared on the basis of their noise production. Experiments are performed to verify the theory of calculating reflection noise from the inner surface of the collimator's aperture and parasitic noise from the beveled collimator structure. From a simulated SANS experiment using cold neutrons in the SANS instrument, it is clarified that multi-pinhole collimators with an opening angle on the downstream side have better performance than those with an opening angle on the upstream side and straight-cut collimators. Compared with a single-pinhole collimation system, a nine-pinhole collimation system increases the intensity at the sample by approximately sevenfold when the sample size is increased by 20-fold for CPHS-SANS, and the signal-to-noise ratio is improved by exploiting a specific collimator aperture structure. Our goal is to install a multi-pinhole collimator based SANS instrument at CPHS in the future, and it is hoped that these results will serve to promote the utilization of multi-pinhole collimation systems at other facilities.

Microstructural investigations of bulk metallic glass using small-angle neutron scattering techniques

Bulk metallic glasses (BMG) are very attractive materials exhibiting high specific strength, decent corrosion resistance and other benefiting features due to their amorphous microstructure. However, the mechanisms of mechanical properties as an issue of structure-properties relation in BMGs are not understood as well as those in polycrystalline materials. For example, the driving force for fatigue in crystalline materials is connected to grain boundary slip and the formation of dislocations i.e. to those structural elements whose existence in BMGs is still debatable. In order to find a link between the mechanical properties and the microstructure in BMG, researchers investigate structural heterogeneities i.e. clusters. The size order of the clusters and intercluster boundaries are within the resolution of small-angle neutron scattering (SANS) techniques. Here we present the results of SANS and very-small-angle neutron scattering (VSANS) studies of Zr46.75Ti8.25Cu7.5Ni10Be27.5 bulk metallic glass after deformation with and without ultrasonic vibrations. VSANS measurements revealed the creation and growth of large micropores induced by ultrasonic vibration.

New Very Small Angle Neutron Scattering (VSANS) Instrument

The design of a new Very Small Angle Neutron Scattering (VSANS) Instrument for use in National Institute of Standards And Technology (NIST) will be discussed. This instrument is similar to a shorter instrument we designed and delivered to ANSTO in Australia called the Bilby SANS instrument. The NIST VSANS and the ANSTO Bilby SANS instruments have very similar dimensions for length and diameter and have similar requirements for internal detector motion, top access port, walkway supports, and ports; however, the Bilby SANS instrument vacuum requirement was lower (7.5×10-5 Torr) and the entire (60,000 pound) vessel was required to move 1.5 meters on external rails with a repeatability of 100 um, which ADC achieved. The NIST VSANS length is 24 meter, internal diameter 2.3 meter with three internal carriages.The NIST VSANS instrument, which covers the usual SANS range will also allow configuration to cover the range between q ∼⃒ 10-4 A-1 to 10-3 A-1 with a sample beam current of (104 neutrons/s). The key requirements are a second position-sensitive detector system having a 1 mm pixel size and a longer sample-detector flight path of 20 m (i.e., a 40 m instrument).

Development and prospects of Very Small Angle Neutron Scattering (VSANS) techniques**Supported by National Natural Science Foundation of China (21474119, 11305191)

Very Small Angle Neutron Scattering (VSANS) is an upgrade of the traditional Small Angle Neutron Scattering (SANS) technique which can cover three orders of magnitude of length scale from one nanometer to one micrometer. It is a powerful tool for structure calibration in polymer science, biology, material science and condensed matter physics. Since the first VSANS instrument, D11 in Grenoble, was built in 1972, new collimation techniques, focusing optics (multi-beam converging apertures, material or magnetic lenses, and focusing mirrors) and higher resolution detectors combined with the long flight paths and long incident neutron wavelengths have been developed. In this paper, a detailed review is given of the development, principles and application conditions of various VSANS techniques. Then, beam current gain factors are calculated to evaluate those techniques. A VSANS design for the China Spallation Neutron Source (CSNS) is thereby presented.

Kinetics of liquid-liquid phase separation in protein solutions exhibiting LCST phase behavior studied by time-resolved USAXS and VSANS.

We study the kinetics of the liquid-liquid phase separation (LLPS) and its arrest in protein solutions exhibiting a lower critical solution temperature (LCST) phase behavior using the combination of ultra-small angle X-ray scattering (USAXS) and very-small angle neutron scattering (VSANS). We employ a previously established model system consisting of bovine serum albumin (BSA) solutions with YCl3. We follow the phase transition from sub-second to 104 s upon an off-critical temperature jump. After a temperature jump, the USAXS profiles exhibit a peak that grows in intensity and shifts to lower q values with time. Below 45 °C, the characteristic length scale (ξ) obtained from this scattering peak increases with time with a power of about 1/3 for different sample compositions. This is in good agreement with the theoretical prediction for the intermediate stage of spinodal decomposition where the growth is driven by interface tension. Above 45 °C, ξ follows initially the 1/3 power law growth, then undergoes a significant slowdown, and an arrested state is reached below the denaturation temperature of the protein. This growth kinetics may indicate that the final composition of the protein-rich phase is located close to the high density branch of the LLPS binodal when a kinetically arrested state is reached.

On the design and experimental realization of a multislit-based very small angle neutron scattering instrument at the European Spallation Source

This article reports the design of a versatile multislit-based very small angle neutron scattering (VSANS) instrument working either as a dedicated instrument or as an add-on for any small-angle neutron scattering machine like the proposed SANS instrument, SKADI, at the future European Spallation Source. The use of multiple slits as a VSANS collimator for the time-of-flight techniques has been validated using McStas simulations. Various instrument configurations to achieve different minimum wavevector transfers in scattering experiments are proposed. The flexibility of the multislit VSANS instrument concept is demonstrated by showing the possibility of instrument length scaling for the first time, allowing access to varying minimum wavevector transfers with the same multislit setup. These options can provide smooth access to minimum wavevector transfers lower than ∼4 × 10−5 Å−1 and an overlapping of wavevector coverage with normal SANS mode, e.g. with the SKADI wavevector range of 10−3–1.1 Å−1. Such an angularly well defined and intense neutron beam will allow faster SANS studies of objects larger than 1 µm. Calculations have also been carried out for a radial collimator as an alternative to the multislit collimator setup. This extends the SANS Q range by an order of magnitude to 1 × 10−4 Å−1 with much simpler alignment. The multislit idea has been realized experimentally by building a prototype at Laboratoire Leon Brillouin, Saclay, with cross-talk-free geometry. Feasibility studies were carried out by making VSANS measurements with single- and multislit collimators, and the results are compared with multiple-pinhole geometry using classical SANS analysis tools.

Novel multiple-beam very small angle neutron scattering (VSANS) using a conventional SANS instrument

This article demonstrates how a small-angle neutron scattering (SANS) instrument, such as D33 at the Institut Laue–Langevin, can be configured without extensive modification to produce multiple highly collimated beams for measurements at the smallest scattering angles. This extends the range of material length scales able to be studied to greater than 1 µm, almost one order of magnitude greater than that of a conventional SANS instrument. The multiple-beam configuration uses the intrinsic properties of the neutron guide system and source and sample apertures with no additional optical devices or precise aperture array alignments. Up to several hundred individual beams, separated in angle by fractions of a degree in both the horizontal and vertical directions, can be extracted, which focus at the sample and diverge towards the distant neutron detector. This is particularly useful for the study of small samples, which can be probed at the smallest scattering angles while retaining sufficient neutron flux because of the use of multiple beams. The resulting data on the area neutron detector consist of multiple scattering or diffraction images which extend over and overlap those produced by neighboring beams. While the principle of the technique is rather simple, analysis of the overlapping SANS patterns requires the development of software techniques to extract the single scattering function.

Recent developments and projects in SANS instrumentation at LLB-Orphée

This article presents an overview of the recent developments in SANS and GISANS instrumentation at LLB-Orphee. SANS is a well-known technique, especially well adapted for research in material sciences, soft matter and nanosciences, which has proved to be particularly powerful to study complex systems, from nm to μm, taking full advantage of isotopic labelling and contrast variation methods. In this article, two instruments will be described in some details: TPA, the new VSANS (Very-Small Angle Neutron Scattering) instrument which is now fully functional and PA20, the new SANS spectrometer under construction, which will extend LLB’s capabilities in terms of SANS for magnetism with a polarized neutron option and Grazing Incidence SANS (GISANS).

Morphology of Ni-base superalloys via very small-angle neutron scattering technique

Very small-angle neutron scattering (VSANS) was used to develop a nondestructive inspecting technique for predicting the residual life time of turbine blades made from single crystal Ni-base superalloy. The VSANS curves, obtained from single crystalline CMSX-4 samples with the various degrees of damage, clearly show the first order peak of the lamellar structure created by a sequence of γ and γ' phases in this material. The peak shifts in the direction of lower scattering vector magnitudes when the creep damage increases, which reflects a corresponding increase of the period of the lamellar structure. According to the VSANS data, the interphase distance in the samples increases gradually (but does not grow rapidly) with increasing creep damage when the latter is < 54% of the creep leading to rupture. Thus, the interphase distance is a sensitive parameter which can be used to describe the morphological changes in Ni-base superalloys related to creep damage. The results are consistent with those obtained from scanning electron microscopy.

Study on the entrapment of mercury in porous glasses by neutron scattering in conjunction with mercury porosimetry

A series of controlled porous glasses (CPGs) with pore sizes from 17 to 300 nm has been examined by very-small-angle neutron scattering (VSANS). The scattering curves show a peak in a range of Q values, depending on the particle size to the average pore size ratio. The entrapment of mercury in CPGs having undergone a complete intrusion–extrusion cycle has also been examined by VSANS. The peak positions do not vary for the mercury-loaded samples suggesting no structural changes due to the high intrusion pressures involved (60,000 psi). It was concluded that an amount of mercury blobs is trapped within the cavities of the glasses.

A study on structural and diffusion properties of porcine stratum corneum based on very small angle neutron scattering data.

Generation of valuable information about the biphasic geometrical configuration of porcine stratum corneum from Very Small Angle Neutron Scattering (VSANS) data and investigation of its effect on the corresponding effective diffusivity. Spectra of porcine stratum corneum are mathematically transformed in order to obtain the corresponding auto-correlation function (ACF). Model stratum corneum structures, matching this experimentally determined ACF, are then produced based on the "brick-and-mortar" configuration. The effective diffusivity through these model domains is calculated using an appropriate numerical method. The most appropriate geometry of porcine stratum corneum's lipid and protein phases in a "brick-and-mortar" configuration is quantitatively determined and correlated with the barrier properties (diffusivity) of the stratum corneum model structures. The ACF analysis indicates the most appropriate values for the dimensions of the corneocyte thickness and the surrounding lipid gap, while the corneocyte length is estimated from the diffusion study.

Design and use of a double crystal diffractometer for very small angle neutron scattering at JRR-3M

The double crystal diffractometer (DCD) for very small angle neutron scattering (VSANS) in the precise neutron optics (PNO) apparatus on a 3G beam hole at JRR-3M is described. The DCD consists of a nondispersive (1, − 1) setting of 111 reflection of silicon single crystals with a sample between two crystals and is set on a vibration isolator table in a constant temperature chamber. The peak intensity of a rocking curve without a sample is 2200 cps at a detector position and the signal to noise ratio is 1.6 × 10 4 in a typical experiment. VSANS measurements for silica powder samples reveal that the q-range is available between 2 × 10 −4 and 6 × 10 −2 nm −1.