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Results for “small angle neutron scattering”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Effects of soil particles and convective transport on dispersion and aggregation of nanoplastics via small-angle neutron scattering (SANS) and ultra SANS (USANS)

Terrestrial nanoplastics (NPs) pose a serious threat to agricultural food production systems due to the potential harm of soil-born micro- and macroorganisms that promote soil fertility and ability of NPs to adsorb onto and penetrate into vegetables and other crops. Very little is known about the dispersion, fate and transport of NPs in soils. This is because of the challenges of analyzing terrestrial NPs by conventional microscopic techniques due to the low concentrations of NPs and absence of optical transparency in these systems. Herein, we investigate the potential utility of small-angle neutron scattering (SANS) and Ultra SANS (USANS) to probe the agglomeration behavior of NPs prepared from polybutyrate adipate terephthalate, a prominent biodegradable plastic used in agricultural mulching, in the presence of vermiculite, an artificial soil. SANS with the contrast matching technique was used to study the aggregation of NPs co-dispersed with vermiculite in aqueous media. We determined the contrast match point for vermiculite was 66% D 2 O / 33% H 2 O. At this condition, the signal for vermiculite was ~50–100%-fold lower that obtained using neat H 2 O or D 2 O as solvent. According to SANS and USANS, smaller-sized NPs (50 nm) remained dispersed in water and did not undergo size reduction or self-agglomeration, nor formed agglomerates with vermiculite. Larger-sized NPs (300–1000 nm) formed self-agglomerates and agglomerates with vermiculite, demonstrating their significant adhesion with soil. However, employment of convective transport (simulated by ex situ stirring of the slurries prior to SANS and USANS analyses) reduced the self-agglomeration, demonstrating weak NP-NP interactions. Convective transport also led to size reduction of the larger-sized NPs. Therefore, this study demonstrates the potential utility of SANS and USANS with contrast matching technique for investigating behavior of terrestrial NPs in complex soil systems.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2026

Characterization of volcanic tuff pores pre- and post-underground nuclear detonation using ultra-small and small angle neutron scattering

The ability to accurately model the subsurface transport of radionuclides is fundamental to the remote detection and characterization of underground nuclear explosion (UNE) events. Developing more sophisticated transport models presents a significant opportunity to enhance monitoring capabilities, particularly in the reliable prediction of signature migration. Experimentally determined characterization of geologic materials associated with transport properties is the pertinent base information for such robust model development and calibration. Here, we report results from an unprecedented study demonstrating changes to the pore and fracture network structures in geological materials in response to UNEs over nanometer to micrometer length scales. Volcanic tuffs of five different lithological formations from pre- and post-UNE environments were collected from the Nevada National Security Site. Combined ultra-small and small-angle neutron scattering techniques were used to characterize the tuff pore structure. The results demonstrate measurable differences in the specific surface area and porosity of samples pre- and post-shot from texturally similar lithological formations, indicating that pore properties can serve as a direct physical signature of a UNE. The results also provide experimentally determined transport parameters in support of advanced model development through the integration of gas migration, hydrodynamic simulations, and geologic framework models.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2024

Insight into the Competitive Adsorption Behavior of Polymer Chains in Silica Nanopores by Small-Angle Neutron Scattering

Processive hydrogenolysis catalysts, in which a metal nanoparticle (e.g., Pt) embedded at the bottom of a cylindrical silica nanopore can repeatedly cleave polymer chains and produce value-added hydrocarbon products, offer a potential solution for billions of tons of waste plastics. As the chain stays longer near the Pt catalysts, it would have a higher chance of getting cut, and therefore the molecular weight distribution of the product could be affected by the adsorption behavior of virgin chains (long polymers) versus cleaved chains (short polymers) into the nanopores. Further, this work reports a model study to understand the competitive adsorption behavior of the two different molecular weight polymers that are mixed, mimicking the reaction medium in the intermediate stage of the catalytic reaction. This study employs small-angle neutron scattering (SANS), which takes advantage of contrast differences between hydrogenous and deuterated polystyrenes to experimentally observe the relative composition of the two polymers in the silica nanopores. Our results reveal preferential adsorption of longer chains in the silica nanopores, which is consistent with the theoretical prediction in the literature for the case of the enthalpic attraction between polymers and pore walls.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Probing the Li 4 Ti 5 O 12 Interface Upon Lithium Uptake by Operando Small Angle Neutron Scattering

The formation of a solid–electrolyte interphase (SEI) on the surface of Li 4 Ti 5 O 12 (LTO) has become a highly controversial topic, with arguments for it and against it. However, prior studies supporting the formation of an SEI layer have typically suggested that a layer forms upon cycling of a cell, although the layer is probed after disassembling. In this study, cubic mesostructured LTO is synthesized with crystallite domain sizes between 3 and 4 nm and uniform pores with diameters ≤8 nm. The mean pore size is controlled between 4–8 nm through the use of a triblock amphipathic copolymer with a tunable hydrophobic block as template and by thermal treatment. The LTO morphology obtained is spherical and evolves upon heat treatment. We report these materials show excellent electrochemical performance, including high rate capability and capacity retention. The LTO material is subjected to operando small-angle neutron scattering and X-ray photoelectron spectroscopy experiments, which reveal that the highly debated SEI forms at potentials as high as 2.2 V, first as a LiF-rich layer and subsequently by the growth of a carbonaceous layer. These SEI products form first on the smaller pores before forming on the mesopores.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Probing nanopore structure and confined fluid behavior in shale matrix: A review on small-angle neutron scattering studies

Although continued growth in unconventional oil and gas production is generally projected, its long-term growth potential and sustainability have significant uncertainties. A critical problem is the low hydrocarbon recovery rates from shale and other tight formations using the horizontal well drilling and hydraulic fracturing techniques: < 10% for tight oil and ~ 20% for shale gas. Moreover, the production rate for a given well typically declines rapidly within one year. The low recoveries and declining production of shale oil and gas reservoirs are apparently related to the small porosity (a few to a few hundred nm) and low permeability (10 –16 –10 –20 m 2 ) of shale matrix, which make the enclosed hydrocarbon fluids difficult to access. Furthermore, to enhance the hydrocarbon recovery from shale matrix, it is essential to study its nanopore structure and confined fluid behavior.

01 COAL, LIGNITE, AND PEAT↗
DOE OSTI2022

Effect of cholesterol on nano-structural alteration of light-activatable liposomes via laser irradiation: Small angle neutron scattering study

Although the light-activated liposomes have been extensively studied for drug delivery applications, the fundamental mechanism of the drug release based on lipid compositions has not been fully understood. Especially, despite the extensive use of cholesterol in the lipid composition, the role of cholesterol in the light-activated drug release has not been studied. Here, in this study, the influence of cholesterol on drug release from light-responsive drug-encapsulated liposomes after activated by near infrared (NIR) laser was investigated. We prepared methotrexate (MTX)-encapsulated DSPC liposomes consisting of 0 mol% (—Chol) or 35 mol% cholesterol (+Chol), with (+Au) or without gold nanorods (—Au) on the lipid bilayer to compare drug release, morphological changes, and nanostructures after laser irradiations. Transmission electron microscopy (TEM) and small angel neutron scattering (SANS) data revealed that only +Chol +Au liposomes showed partial aggregation of the liposomes after laser irradiation. Similar trends on the drug release and structural change were observed when the liposomes were heated to above chain-transition temperature. Overall, we have found that (1) inclusion of 35 mol% cholesterol enhanced the permeability of lipid bilayers above T c ; (2) the mechanism of laser-activated liposomal drug delivery is disrupting lipid bilayer membranes by the photothermal effect in the presence of plasmonic materials. By understanding the fundamentals of the technology, precise controlled drug release at a targeted site with great stability and repeatability is anticipated.

59 BASIC BIOLOGICAL SCIENCES↗