Situ Small-angle Neutron Scattering Research Articles

Vortex fluidic regulated phospholipid equilibria involving liposomes down to sub-micelle size assemblies.

Conventional channel-based microfluidic platforms have gained prominence in controlling the bottom-up formation of phospholipid based nanostructures including liposomes. However, there are challenges in the production of liposomes from rapidly scalable processes. These have been overcome using a vortex fluidic device (VFD), which is a thin film microfluidic platform rather than channel-based, affording ∼110 nm diameter liposomes. The high yielding and high throughput continuous flow process has a 45° tilted rapidly rotating glass tube with an inner hydrophobic surface. Processing is also possible in the confined mode of operation which is effective for labelling pre-VFD-prepared liposomes with fluorophore tags for subsequent mechanistic studies on the fate of liposomes under shear stress in the VFD. In situ small-angle neutron scattering (SANS) established the co-existence of liposomes ∼110 nm with small rafts, micelles, distorted micelles, or sub-micelle size assemblies of phospholipid, for increasing rotation speeds. The equilibria between these smaller entities and ∼110 nm liposomes for a specific rotational speed of the tube is consistent with the spatial arrangement and dimensionality of topological fluid flow regimes in the VFD. The prevalence for the formation of ∼110 nm diameter liposomes establishes that this is typically the most stable structure from the bottom-up self-assembly of the phospholipid and is in accord with dimensions of exosomes.

In Situ Characterization of 17-4PH Stainless Steel by Small-Angle Neutron Scattering.

17-4PH martensitic steel is usually used as valve stems in nuclear power plants and it suffers from thermal aging embrittlement due to long-time service in a high-temperature and high-pressure environment. Here, we characterized the evolution of microstructures at the nano-scale in 17-4PH steel by in situ small-angle neutron scattering (SANS) with a thermo-mechanically coupled loading device. The device could set different temperatures and tensile so that an in situ SANS experiment could dynamically characterize the process of nanoscale structural changes. The results showed that with increasing thermal aging time, the ε-Cu phase precipitates and grows as the temperature is 475 °C and 590 °C, and the ε-Cu phase is spherical at 475 °C but became elongated cylinders at 590 °C. Moreover, the loading stress could aid in the growth of the ε-Cu phase at 475 °C.

The maximum-strain and strain-interval dependences of microstructural evolution underneath the Mullins effect

In situ small-angle neutron scattering (SANS) and constitutive model were combined to investigate silica filled deuterated silicone rubber (SFdSR) under strain rise path at strain rate of 0.001 s−1, with strain intervals from 0.1 to 1. It was found that, (i) The non-linear behaviors are sensitive to strain interval, cycle - number, and maximum strain, etc. (ii) SANS suggests that the cyclic orientation-relaxation of bound rubber can cause accumulative fatigue. (iii) The orientation of bound rubber tH/tV − 1 decreases from 9.9 to 3.6 with increasing the strain intervals from 0.1 to 1 for the same macroscopic maximum strain 3.0. Interestingly, the mechanical response softening (Es) and recovery hysteresis (Erh), the evolution of bound rubber, and the constitutive analysis consistently suggests a strain threshold of 1.5. Accordingly, the roles of matrix, interface, and filler networks as well as their interactions on the origin of the Mullins effect were discussed.

Correlation between the hierarchical structure evolution and Mullins effect of filled rubber under variable amplitude loading

Aiming to investigate the correlation between structure evolution and Mullins effect of filled silicone rubber, deuterated chain labeling and in situ small-angle neutron scattering (SANS) under variable amplitude loading have been conducted. The mechanical properties provide stress (σmax′) at the maximum strain (εmax), energy loss and recovery hysteresis (Es and Erh), etc. While the macrostructure such as radius of gyration Rg of aggregate covered with the bound rubber and the orientation can be obtained from SANS. All the parameters demonstrate consistently pattern in the two conditions of variable amplitude loading process. The evolution of crosslinking modulus Gc, the number of chain segment between entanglements ne/Te, amplification factors of filler X, etc. extracted from constitutive model further confirm such manners. With repeating cycles, the values reflecting mechanical properties such as σmax′ and Erh all exhibit a variation of less than 10%. Additionally, parameters related to microstructural evolution, such as X0 and Rg, also demonstrate a small variation of less than 10%. This implies that the system is in a state of stable equilibrium. With the εmax further increase, the amplitude of variation in orientation of bound rubber (th/tv-1) reaches 30%，ranging from 0.48 at S0.5C5 to 0.62 at S1.0C1, along with the variation of σmax′ around 75%, indicating the reversible deformation might transform into irreversible inelastic destruction and tend to an updated equilibrium.

Insights into the CO2 Capture Characteristics within the Hierarchical Pores of Carbon Nanospheres Using Small-Angle Neutron Scattering.

Understanding adsorption processes at the molecular level has transformed the discovery of engineered materials for maximizing gas storage capacity and kinetics in adsorption-based carbon capture applications. In this work, we studied the molecular mechanism of gas (CO2, H2, methane, and ethane) adsorption inside an interconnected porous network of carbon. This was achieved by synthesizing novel macro-meso-microporous carbon (M3C) nanospheres with interconnected pore structures. The M3Cs showed a CO2 capture capacity of 5.3 mmol/g at atmospheric CO2 pressure, with excellent kinetics. This was due to fast CO2 adsorption within the interconnected hierarchical macro-meso-microporous M3C. In situ small-angle neutron scattering (SANS) under various CO2 pressures indicated that the macro- and mesopores of M3C enable fast diffusion of CO2 molecules inside the micropores, where adsorbed CO2 molecules densify into a liquid-like state. This strong densification of CO2 molecules causes fast CO2 diffusion in the macro- and mesopores of M3C, restarting the adsorption cycle for fresh CO2 molecules until all pores are completely filled. Notably, M3C also showed good capture capacities for hydrogen and various hydrocarbons, with excellent selectivity toward ethane over methane.

Spatially confined protein assembly in hierarchical mesoporous metal-organic framework

Immobilization of biomolecules into porous materials could lead to significantly enhanced performance in terms of stability towards harsh reaction conditions and easier separation for their reuse. Metal-Organic Frameworks (MOFs), offering unique structural features, have emerged as a promising platform for immobilizing large biomolecules. Although many indirect methods have been used to investigate the immobilized biomolecules for diverse applications, understanding their spatial arrangement in the pores of MOFs is still preliminary due to the difficulties in directly monitoring their conformations. To gain insights into the spatial arrangement of biomolecules within the nanopores. We used in situ small-angle neutron scattering (SANS) to probe deuterated green fluorescent protein (d-GFP) entrapped in a mesoporous MOF. Our work revealed that GFP molecules are spatially arranged in adjacent nanosized cavities of MOF-919 to form “assembly” through adsorbate-adsorbate interactions across pore apertures. Our findings, therefore, lay a crucial foundation for the identification of proteins structural basics under confinement environment of MOFs.

In Situ Small-Angle Neutron Scattering Analysis of Water Evaporation from Porous Exhaust-Gas-Catalyst Supports.

Porous media as catalyst supports are key to developing automotive exhaust purification systems. In particular, the water content of these porous media is attracting research attention because catalyst supports containing condensed water vapor at the early stage of cold start require a longer warm-up period. In this regard, water isotherms and evaporation in porous Al2O3 were investigated in this study using in situ small-angle neutron scattering (SANS) experiments. Unlike conventional evaluation methods, such as weighing and X-ray tomography, SANS distinguishes water in the primary and secondary pores using a contrast-matching method. Time-resolved measurements showed that water started to evaporate from the secondary pores in tens of seconds and subsequently from the primary pores in a hundred seconds. Exhaustive experiments conducted using nine alumina-based samples revealed that the drying rate depended on the secondary pore size of the porous Al2O3. The proposed approach can enable the evaluation of controlling factors to additionally optimize the performance of automotive exhaust gas catalysts, especially during cold start.

Nanoscale Coal Deformation and Alteration of Porosity and Pore Orientation Under Uniaxial Compression: An In Situ SANS Study

Nanoscale coal deformation affects the geomechanics response of coal structure under external stress conditions. In this study, in situ small-angle neutron scattering (SANS) is used to characterize the evolution of nanopore structures under uniaxial compression on an Illinois coal specimen. Porod invariant mapping is used to estimate apparent porosities at different azimuthal angles. Structure-free orientation factors, including the alignment factor and Hermans’ orientation factor, are used to characterize orientation degree in nanopores quantitatively. The nanoscale pore deformation and evolution with stress have not been directly measured before, and the in situ SANS technique offers the unique capability to probe the nanoscale rock deformation. From the results, higher values of apparent porosities are shown near the coal bedding direction. At different azimuthal angles, the apparent porosities increase with increasing uniaxial stress in the elastic deformation range (54–575 bar) for the measured coal. The pore-scale degree of orientation is a size-dependent parameter, and pore orientation along the coal bedding generally increases as pore size increases. The degree of orientation in nanopores on average (in a size range between ~ 2 × 103 A and ~ 15 A) tends to increase first and then decreases with increasing stress loading, although different from that of macropores, indicating higher stresses on the nanopore edges along the bedding direction and then on the nanopore body along the normal direction. There is no distinct permanent change of porosity within the measured stress range (0–575 bar) after the stress relief.

Influence of cooling rate on the precipitation kinetics of nanoscale isothermal ω-phase in metastable β-Ti alloy, Ti–5Al–5Mo–5V–3Cr

In metastable β-Ti alloys, nanoscale isothermal ω-phase (ωiso) precipitates are regarded as the nucleation sites for the α strengthening phase. Here we investigate the precipitation kinetics of the ωiso precipitates as a function of cooling rate (air cooling and water quenching) after β-solutionising. A combined in situ small-angle neutron scattering (SANS) and electrical resistivity measurement approach was used during ageing of Ti–5Al–5Mo–5V–3Cr wt% (Ti-5553) alloy at 300 °C and 325 °C up to 8 h. The SANS modelling was consistent with ellipsoid shaped particles for the ωiso precipitates, for both air-cooled and water-quenched samples. The precipitates attained a maximum size (equatorial diameter) of ∼21 nm and ∼17 nm after 2 h and 4 h of ageing the water-quenched and air-cooled samples respectively. Although the air-cooled samples showed delayed nucleation in comparison to water-quenched sample, the volume fraction became approximately the same (∼11%) after ageing for 8 h. The average value of the activation energy for ωiso nucleation from the β-phase matrix was determined as 122 kJ mol−1 from electrical resistivity data using a modified Johnson-Mehl-Avrami-Kolmogorov (JMAK) model. The hardness increased with ageing time, with water quenching leading to a higher final value of hardness than air cooling.

Anisotropic pore structure of shale and gas injection-induced nanopore alteration: A small-angle neutron scattering study

Gas transport in the shale matrix is controlled by pore structure, which can ultimately influence natural gas production potential and carbon sequestration in shale gas reservoirs. In this study, in situ small-angle neutron scattering (SANS) measurements under methane and CO2 injections were employed to investigate two Marcellus Shale thin section samples cut parallel and perpendicular to the bedding. Marcellus Shale nanopores show intrinsic anisotropy over the detected length scale of 5–2000 Å. Microscopic gas transport could be inhibited due to the decrease of accessible porosity with increasing gas pressure. The degree of inhibition may be higher for CO2 than for methane, and for the direction normal to the bedding than in the bedding direction. In addition, under the condition of liquid CO2, higher porosity reduction for the direction normal to the bedding may insight into nanoscale anisotropic wettability in the shale matrix.

In Situ Small-Angle Neutron Scattering Investigation of Adsorption-Induced Deformation in Silica with Hierarchical Porosity.

Adsorption-induced deformation of a series of silica samples with hierarchical porosity has been studied by in situ small-angle neutron scattering (SANS) and in situ dilatometry. Monolithic samples consisted of a disordered macroporous network of struts formed by a 2D lattice of hexagonally ordered cylindrical mesopores and disordered micropores within the mesopore walls. Strain isotherms were obtained at the mesopore level by analyzing the shift of the Bragg reflections from the ordered mesopore lattice in SANS data. Thus, SANS essentially measured the radial strain of the cylindrical mesopores including the volume changes of the mesopore walls due to micropore deformation. A H2O/D2O adsorbate with net zero coherent neutron scattering length density was employed in order to avoid apparent strain effects due to intensity changes during pore filling. In contrast to SANS, the strain isotherms obtained from in situ dilatometry result from a combination of axial and radial mesopore deformation together with micropore deformation. Strain data were quantitatively analyzed with a theoretical model for micro-/mesopore deformation by combining information from nitrogen and water adsorption isotherms to estimate the water–silica interaction. It was shown that in situ SANS provides complementary information to dilatometry and allows for a quantitative estimate of the elastic properties of the mesopore walls from water adsorption.

An in situ SANS study of nanoparticles formation in 9Cr ODS steel powders

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 Y2O3 was completely dissolved into the steel matrix after mechanical alloying. Nanoparticles emerge after annealing at 600°C for 10min and coarsen slightly after 12h. The radius of nanoparticles increases from 0.73nm at 600°C to 1.63nm at 1000°C, while the volume fraction decreases with increasing annealing temperature.

Tracking Solvent Distribution in Block Polymer Thin Films during Solvent Vapor Annealing with in Situ Neutron Scattering

Herein, we employed in situ small-angle neutron scattering (SANS) and neutron reflectivity (NR) to elucidate the importance of polymer–solvent interactions on morphology development during solvent vapor annealing (SVA) of block polymer (BP) thin films. Judicious choice of nanostructure orientation (parallel to the substrate) permitted measurement of the preferential segregation of solvent (d6-benzene) into our cylinder-forming poly(styrene-b-isoprene-b-styrene) (SIS) films. A distinguishing feature of this work is the simultaneous tracking of nanostructure evolution and solvent segregation, enabled through the combination of SANS (in-plane features), NR (out-of-plane features), and solvent deuteration, which directly related polymer–solvent interactions to morphology reorganization. We found that at higher d6-benzene partial pressures (p/psat) the number of cylinder layers (domains) increased or decreased to accommodate overall film thickness changes upon swelling/deswelling, while the SIS domain spacing remained nearly constant. However, at lower p/psat values, the SIS domain spacing changed to accommodate similar swelling/deswelling variations, while the number of layers remained invariant. The threshold for this p/psat transition was directly related to plasticization of the polystyrene (PS) block, which has significant implications on the size of the domains, degree of ordering, and interfacial roughness. Thus, by linking polymer–solvent interactions to morphology evolution, we have developed an improved understanding of the interplay between the kinetic and thermodynamic effects that can direct the self-assembly and through-film periodicity of nanostructured thin films.

Small-Angle Neutron Scattering Investigation of Core-Shell Carbon-Coated Silicon Nanoparticles for Lithium-Ion Anodes

Due to their great success for portable electronic devices, lithium-based batteries are becoming increasingly important for powering (hybrid) electric vehicles. Yet, in order to achieve driving ranges comparable to those provided by combustion engines, substantial improvements regarding their energy density are required. Concerning the anode side, most commercial lithium-ion batteries use carbonaceous materials and silicon material seems promising due to its high theoretical specific capacity (up to 3580 mAh.g-1) and its relatively low operational potential. However, the huge volume expansion of silicon alloys upon lithiation (up to 300%) leads to electrical contact loss and pulverization of the material, as well as a continuous consumption of lithium due to the decomposition of the electrolyte on the renewed fresh surface of Si exposed by the cracks of the particles volume expansion. Thus, it leads to poor cycling stability and rapid capacity fading. These effects can be partially counteracted by using nanometer sized Si particles (Si-NPs) that can better sustain the mechanical strains induced by the heterogeneous volume changes. In addition, the particle expansion could be limited by carbon shell coating onto the nanoparticles, which can enhance the electronic conductivity and stabilize the initially formed solid-electrolyte interphase (SEI). In an attempt to combine both approaches, we have synthetized using a laser pyrolysis technique carbon-coated (Si@C-NPs) or non-coated Si nanoparticles (Si-NPs) [1] [2]. As it was shown that both surface state and crystallinity of the Si-NPs govern the electrochemical behavior of the materials [1] [2], both amorphous and crystalline cores were prepared. Transmission electron microscopy (TEM) was performed on native NPs (see figure 2c and d for illustration on crystalline Si NPs) and revealed the core-shell structure. Electrodes with the various NPs samples (see table 1) were processed and tested in coin cell configuration versus lithium foil. The electrochemical behavior was monitored and it was shown that carbon coating leads to improved capacity upon cycling (see figure 1). To characterize the morphology of the various electrodes upon cycling and its impact on performances, we have carried out in-depth microstructural investigation of NPs (shape, size, core-shell structure) using ex situ small-angle neutron scattering (SANS) at the Institut Laue-Langevin (Neutron reactor-Grenoble). The SANS technique is particularly suited to investigate such complex systems, because neutrons are highly sensitive to lithium (by contrast to X-rays) and can provide detailed chemical/microstructural information hardly attainable using TEM on cycled electrodes. Taking advantage of the contrast variation method (i.e. use of specific isotopic mixtures of solvent to selectively match a compound in multicomponent systems) we were able to unravel the effect of carbon coating on the NPS morphology at different (de-)lithiation stages (see figure 2a and b for results on electrodes with crystalline Si NPs). In particular, we show that Si@C NPs exhibit a different mechanism of Li insertion compared to non-coated NPs. This work elucidates the microstructural evolution of NPs used in battery electrodes and therefore helps in designing innovative nanomaterials for high density Si-based anodes.

Structural origins of mechanical properties and hysteresis in SIS triblock copolymers/polystyrene blends with spherical morphology

The mechanical response and the corresponding microstructure of polymer blends composed of styrene-isoprene-styrene block copolymer and deuterated polystyrene are studied via in situ small-angle neutron scattering (SANS) measurements during intermittent uniaxial extension. The initial blend morphologies consist of spherical PS glassy domains arranged in body-centered cubic (BCC) lattices. The spheres rearrange affinely with the macroscopic deformation up to Hencky strains ~0.35. Larger deformation is mechanically characterized by yield and strain hardening. In this regime, SANS measurements reveal a transition from a BCC crystal lattice to chevron-like patterns. Using electron microscopy, we found that the chevrons arise from a real-space structure described as spheres that have been stretched along one axis and aligned parallel to one another. Such configuration is unstable and reverts to BCC structure after stress release. After unloading the blends, remnant nano-deformation is observed, which is fully relaxed only in the transverse direction after more than 10 h. Permanent damage of the internal structure along the stretching direction impedes the full recovery of the initial sphere configuration.

In Situ Small Angle Neutron Scattering Revealing Ion Sorption in Microporous Carbon Electrical Double Layer Capacitors

Experimental studies showed the impact of the electrolyte solvents on both the ion transport and the specific capacitance of microporous carbons. However, the related structure-property relationships remain largely unclear and the reported results are inconsistent. The details of the interactions of the charged carbon pore walls with electrolyte ions and solvent molecules at a subnanometer scale are still largely unknown. Here for the first time we utilize in situ small angle neutron scattering (SANS) to reveal the electroadsorption of organic electrolyte ions in carbon pores of different sizes. A 1 M solution of tetraethylammonium tetrafluoroborate (TEATFB) salt in deuterated acetonitrile (d-AN) was used in an activated carbon with the pore size distribution similar to that of the carbons used in commercial double layer capacitors. In spite of the incomplete wetting of the smallest carbon pores by the d-AN, we observed enhanced ion sorption in subnanometer pores under the applied potential. Such results suggest the visible impact of electrowetting phenomena counterbalancing the high energy of the carbon/electrolyte interface in small pores. This behavior may explain the characteristic butterfly wing shape of the cyclic voltammetry curve that demonstrates higher specific capacitance at higher applied potentials, when the smallest pores become more accessible to electrolyte. Our study outlines a general methodology for studying various organic salts-solvent-carbon combinations.

Mechanical properties and microstructure changes of proton exchange membrane under immersed conditions

In this study, mechanical tensile stress–strain response and microstructure changes of proton exchange membranes (PEM) in immersed conditions are studied. The effects of water pretreatment and immersion time on stress–strain responses of Nafion®−212 membranes are discussed. It is found that in the water immersion it took 24 h for the membrane to reach saturation equilibrium. Compared with dry membrane, immersed Nafion membrane shows a lower stress level at 30°C, but a higher stress level at 70°C. In situ small angle neutron scattering (SANS) experiments show that with the increase of temperature and water uptake, domains of the membrane become ordered and stay stable at around 60°C. Based on the observation, the relationship between the microstructure and mechanical properties is explained. POLYM. ENG. SCI. 54:2215–2221, 2014. © 2013 Society of Plastics Engineers

A portable hydro-thermo-mechanical loading cell for in situ small angle neutron scattering studies of proton exchange membranes

A portable hydro-thermo-mechanical loading cell has been designed to enable in situ small angle neutron scattering (SANS) studies of proton exchange membranes (PEMs) under immersed tensile loadings at different temperatures. The cell consists of three main parts as follows: a letter-paper-size motor-driven mechanical load frame, a SANS friendly reservoir that provides stable immersed and thermal sample conditions, and a data acquisition and control system. The ex situ tensile tests of Nafion 212 membranes demonstrated a satisfactory thermo-mechanical testing performance of the cell for either dry or immersed conditions at elevated temperatures. The in situ SANS tensile measurements on the Nafion 212 membranes immersed in D2O at 70 °C proved the feasibility and capability of the cell for small angle scattering study on deformation behaviors of PEM and other polymer materials under hydro-thermo-mechanical loading.

In Situ Observation of Solid Electrolyte Interphase Formation in Ordered Mesoporous Hard Carbon by Small-Angle Neutron Scattering

The aim of this work was to better understand the electrochemical processes occurring during the cycling of a lithium half-cell based on ordered mesoporous hard carbon with time-resolved in situ small-angle neutron scattering (SANS). Utilizing electrolytes containing mixtures of deuterated (2H) and nondeuterated (1H) carbonates, we have addressed the challenging task of monitoring the formation and evolution of the solid–electrolyte interphase (SEI) layer. An evolution occurs in the SEI layer during discharge from a composition dominated by a higher scattering length density (SLD) lithium salt to a lower SLD lithium salt for the ethylene carbonate/dimethyl carbonate (EC/DMC) mixture employed. By comparing half-cells containing different solvent deuteration levels, we show that it is possible to observe both SEI formation and lithium intercalation occurring concurrently at the low voltage region in which lithium intercalates into the hard carbon. These results demonstrate that SANS can be employed to bette...

Nucleation and Growth of Nanocrystals in Glass‐Ceramics: An In Situ SANS Perspective

We studied the nucleation and growth of nano‐sized crystals on two glass‐ceramic systems: a conventional lithium‐aluminosilicate (LAS) and a (Mg,Zn) spinel. We combined several techniques: in situ Small Angle Neutron Scattering (SANS), Differential Scanning Calorimetry (DSC), Scanning Electron Microscopy (SEM), and laboratory X‐ray diffraction (XRD). We observed by SANS, and confirmed by DSC, that during a temperature ramp, transient phenomena occur between the regions of nucleation and growth in the LAS, which do not follow classic kinetic theories. In contrast, the spinel material shows a smooth transition during the temperature ramp between the nucleation and the growth stages, and follows a more conventional growth pattern. In the spinel system the initial phase separation plays a very important role in determining the crystalline phase distribution in the glassy matrix, as crystallites are confined only in one phase.