Search

Sequential ultra-small-angle and small-angle and X-ray scattering (USAXS and SAXS) measurements of hierarchical microstructure of a common energetic material, the high explosive 2,4,6-Triamino-1,3,5-trinitrobenzene (TATB), were performed to follow the microstructure evolution upon applied pressure. The pellets were prepared by two different routes—die pressed from a nanoparticle form and a nano-network form of TATB powder. The derived structural parameters, such as void size, porosity, and the interface area, reflected the response of TATB under compaction. Three populations of voids were observed in the probed q range from 0.007 to 7 nm−1. The inter-granular voids with size larger than 50 nm were sensitive to low pressures and had a smooth interface with the TATB matrix. The inter-granular voids with size of ~10 nm exhibited a less volume-filling ratio at high pressures (>15 kN) as indicated by a decrease of the volume fractal exponent. The response of these structural parameters to external pressures implied that the main densification mechanisms under die compaction were the flow, fracture, and plastic deformation of the TATB granules. Compared to the nanoparticle TATB, the applied pressure strongly influenced the nano-network TATB due to its more uniform structure. The findings and research methods of this work provide insights into the structural evolution of TATB during densification. [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]

Stable actinide colloids and nanoparticles are of interest because of their potential to affect the transportation of radionuclides in the near‐field of a nuclear waste repository. At high concentrations, thorium(IV) can precipitate to form intrinsic colloids. In the present study, polynuclear thorium colloids and thorium dioxide crystallites, formed by the condensation of hydrolyzed Th4+ solutions (3 mM; initial pH 5.5) aged for up to 18 months, were studied using small‐angle X‐ray scattering. Scattering profiles were fitted using a unified Guinier/power‐law model (Beaucage model) to extract the radii of gyration and Porod exponents. Analysis of the scattering profiles from a dispersion aged for 5 months indicated that both polymer coils and more compacted structures (radius of gyration Rg ≃ 10 nm) were present, which translated in the Kratky plots as a plateau and a peak maximum, respectively. After 18 months, the SAXS data were consistent with the presence of agglomerates of ThO2 particles suspended in aqueous solution (pH 3.2; [Th] = 1.45 mM). The measured radius of gyration (Rg) of the agglomerates was 5.8 nm, whereas the radius of the ThO2 particles was 2.5 nm. [ABSTRACT FROM AUTHOR]

• The design strategies of NPCSPs were systematically summarized. • The representative progresses for the synthesis of NPCSPs were presented. • A series of typical applications in bio-adsorption and bio-catalysis were highlighted. • The current challenges and perspectives on the future research directions were proposed. Core@shell particles with controlled structure and morphology are gradually attracting attention due to their unique properties and potential applications related to electronics, catalysis, sustainability and biomedicine. In particular, the design of nanoporous core@shell particles has emerged as a key focus in recent years because of their ultra-high surface area, tunable porous structure and orientation, which play vital roles in bioadsorption and biocatalysis. In this review, we start with a brief introduction of the structures and properties of nanoporous core@shell particles, followed by a summary of their application in bioadsorption and biocatalysis. Then, we surveyed the design and preparation of these core@shell particles, including the structure and surface chemistry that will affect the particles function in bioadsorption and biocatalysis which is then correlated with the synthesis methods. Finally, we highlight the bioadsorption and biocatalysis application of nanoporous core@shell particles, how they benefit from their physical characteristics (i.e. porosity and size) before concluding with perspectives on the future directions for this topic. There is great potential for nanoporous core@shell particles to reach high biomolecular loading capacities for bioadsorption applications as well as improved catalytic efficiencies as biocatalytic materials due to their unique nanostructure, composition and biocompatibility. This review aims to guide researchers towards understanding the latest research progress in these fields, with the ultimate goal being to influence future developments in these areas. [ABSTRACT FROM AUTHOR]

Uranyl peroxide nanoparticles (NPs) with spherical cage structure form in aqueous medium by the assembly of uranyl hexagonal bipyramids. Morphological evolution of uranyl peroxide NPs prepared with different LiOH/UO 2 molar ratios is studied by small-angle X-ray scattering. Guinier analysis indicated that the overall size of the uranyl peroxide NPs increased with storage time. Their structure is further analyzed by model fitting to a spherical shell particle. Analysis of the particle size shows that U24 particles containing 24 uranium atoms are formed in dispersion with Li/U = 7.7, and U28 particles are generated in dispersion with Li/U = 3.1. With increasing storage time, the interactions between uranyl peroxide NPs changes from repulsion to attraction for samples with Li/U ratio 5.5 and 7.7, leading to their agglomeration and precipitation. Certain amount of large aggregates remained in the dispersions in ambient condition for over one year, as confirmed by dynamic light scattering. This study gives insight into the structural evolution and interactions of uranyl peroxide NPs. • Lithium–Uranium nanoparticles of different types were synthesized in aqueous medium. • Evolution of morphology and interactions was followed by scattering techniques. • Spherical Li - uranyl cages form in the first days, and agglomerate within weeks. [ABSTRACT FROM AUTHOR]

Superparamagnetic γ -Fe 2 O 3 nanoparticles (5 nm diameter) were synthesized in water. The bare particles exhibit good colloidal stability at ∼pH 2 because of the strong electrostatic repulsion with a surface charge of +25 mV. The polyacrylic acid (PAA)-coated particles exhibit remarkable colloidal stability at ∼pH 7 with abundant free carboxyl groups as reactive sites for subsequent functionalization. In this work, we used zeta potential analysis, transmission electron microscopy, small angle X-ray scattering, and Inductively coupled plasma mass spectrometry to investigate the adsorption behavior of U (VI) on bare and coated colloidal superparamagnetic nanoparticles at pH 2 and pH 7. At pH 2, uranyl ion (UO 2 2+ ) absorbed on the surface of the bare particles with decreasing particle surface charge. This induced particle agglomeration. At pH 7, uranyl ion (UO 2 2+ ) hydrolyzed and formed plate-like particles of uranium hydroxide that were ∼50 nm in diameter. The PAA-coated iron oxide nanoparticles absorbed on the surface of these U (VI) hydroxide plates to form large aggregates that precipitate to the bottom of the dispersion. At both pH 2 and pH 7, the resulting U (VI)/nanoparticle complex can be easily collected and extracted from the aqueous environment via an external magnetic field. The results show that both bare and polymer-coated superparamagnetic γ -Fe 2 O 3 nanoparticles are potential absorbents for removing U (VI) from water. [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]