Papers by Keyword: Neutron Scattering

Abstract: This paper presents a small angle neutron scattering (SANS) study of a novel porous gehlenite-based ceramic, synthesised from a homogeneous powder mixture of soda-lime-silicate (SLS) glass, α-alumina, calcite and calcium fluoride via solid-state sintering at 1200 °C. The products of sintering at single temperatures from 600 to 1200 °C are examined by X-ray diffraction (XRD). Sintering of the mixture below 1200 °C forms two intermediate phases (Na₂CaSi₃O₈ and Ca₄Si₂O₇F₂). Nepheline and α-alumina are minor phases in the gehlenite-based ceramic fabricated through sintering at 1200 °C. The microstructure of the gehlenite-based ceramic is investigated using field-emission scanning electron microscopy (FESEM) and SANS at the Australian Centre for Neutron Scattering. This study also evaluated the specific surface area of the gehlenite-based ceramic (~3.0 m² cm^–3) from quantitative analysis of SANS data.

Abstract: The difficulty of materials inner stress detection is a barrier to engineering equipment research. And neutron scattering techniques is now recognized as the most precise method for mapping of inner residual stresses in materials or even components. Nine neutron scattering spectrometers of China Advanced Research Reactor (CARR) has been carried out thermal debugging, another five spectrometers are under construction. The thermal neutron spectrometer mentioned in this paper is one of the five spectrometers to be built in the neutron guide hall. It is anticipated that the instrument will be accomplished and available to users in 2018. The design of the hardware is mentioned. The function of positioning and control of the spectrometer can be carried out by the software. This spectrometer is available for material scientists to accomplish further studies with its function, and provides a good reference for spectrometer designing experts.

Abstract: The recent discovery of topological Kondo insulating behaviour in strongly correlated electron systems has generated considerable interest in Kondo insulators both experimentally and theoretically. The Kondo semiconductors CeT₂Al₁₀ (T=Fe, Ru and Os) possessing a c-f hybridization gap have received considerable attention recently because of the unexpected high magnetic ordering temperature of CeRu₂Al₁₀ (T_N=27 K) and CeOs₂Al₁₀ (T_N=28.5 K) and the Kondo insulating behaviour observed in the valence fluctuating compound CeFe₂Al₁₀ with a paramagnetic ground state down to 50 mK. We are investigating this family of compounds, both in polycrystalline and single crystal form, using inelastic neutron scattering to understand the role of anisotropic c-f hybridization on the spin gap formation as well as on their magnetic properties. We have observed a clear sign of a spin gap in all three compounds from our polycrystalline study as well as the existence of a spin gap above the magnetic ordering temperature in T=Ru and Os. Our inelastic neutron scattering studies on single crystals of CeRu₂Al₁₀ and CeOs₂Al₁₀ revealed dispersive gapped spin wave excitations below T_N. Analysis of the spin wave spectrum reveals the presence of strong anisotropic exchange, along the c-axis (or z-axis) stronger than in the ab-plane. These anisotropic exchange interactions force the magnetic moment to align along the c-axis, competing with the single ion crystal field anisotropy, which prefers moments along the a-axis. In the paramagnetic state (below 50 K) of the Kondo insulator CeFe₂Al₁₀, we have also observed dispersive gapped magnetic excitations which transform into quasi-elastic scattering on heating to 100 K. We will discuss the origin of the anisotropic hybridization gap in CeFe₂Al₁₀ based on theoretical models of heavy-fermion semiconductors.

Abstract: Magnetic state of epitaxial heterostructures La_0.7Sr_0.3MnO₃/LaMnO₃/SrRuO₃ (LSMO/LMO/SRO) was studied by SQUID magnetometer, ferromagnetic resonance (FMR) and polarized neutron reflectometry (PNR) techniques. The fit of PNR and FMR data give us the magnetization of each layer, while the SQUID gives the total magnetization of our structures. The magnetic moment of the LMO layer has the magnetization 4πM_LMO=4.2kGs (2.4 m_B/Mn) at T=140K according to our PNR data fitting.

Abstract: Small Angle Neutron Scattering (SANS) technique allows characterizing the nanomicrostructure of the ferritic Oxide Dispersion Strengthened (ODS) steels which are candidates for the structure material of fusion reactor and fast reactor. A SANS study of domestic ferritic ODS alloys are presented. The main objective is to study the evolution of the oxide dispersion nanoparticle during the different stages of the fabrication and different content.

Abstract: Neutron Texture Diffractometer at CARR is the first neutron instrument for texture measurement in China. It was built through modifying a Four-Circle Diffractometer relocated from Juelich Center for Neutron Science and equipping with some necessary new components. Currently, the adjustment and calibration with neutrons for this instrument has been finished. The detailed characteristics of this instrument are described and the preliminary results of quantitative texture analysis for a warm-rolled Zircaloy-4 plate are presented. The results show good quality and small statistical errors.

Abstract: Density Functional Theory (DFT) calculations were performed. They were firstly implemented to optimize the structure and refine the stoichiometry of the only ternary compound, CuLi_0.08Mg_1.92 of the Cu-Li-Mg system. Furthermore using DFT, several possible structures of CuMg₂H_x were optimized. Since most of the hydrides are cubic structures or can be considered as distortions of a cubic structure, we have started calculations for CuMg₂H_x (x = 4 - 6) with tetragonal and monoclinic structures, similar to those of the hydrides formed by the nearest neighbors of Cu and Mg in the periodic table: NiMg₂H₄ and CoMg₂H₅ (e.g. monoclinic C2/c and tetragonal P4/nmm, respectively). It can be concluded that the most stable configuration corresponds to CuMg₂H₅ with C2/c structure. We have performed several neutron scattering experiments that are in agreement with the first principles calculations.

Abstract: In this work we have performed a systematic study of blends of [6,-phenyl C61 butyric acid methyl ester (PCBM) with the following amorphous and semi-crystalline polymers: atactic polystyrene (PS), syndiotactic polystyrene (syn-PS), poly (2-vinyl-naphthalene) (P2VN), poly (9-vinyl-phenanthrene) (P9VPh), poly (vinylidene-fluoride) (PVdF) and poly (3-hexyl-thiophene) (P3HT). Experimental measurements using DSC, x-ray and neutron scattering coupled with molecular modeling (MD and DFT) have been utilized to determine the solubility and phase morphology of these model polymer-fullerene blends.

Abstract: Single crystal Ni-base superalloys based on the  /  system are widely used in gas turbine applications. To understand the formation of  precipitates, including size distribution and growth, we performed in situ small-angle neutron scattering (SANS) measurements at elevated temperatures and - together with TEM as well as , SEM imaging - studied changes in the precipitates in short and long time scale. In the early stages, a bimodal precipitate size distribution of precipitate is observed, which (depending on the annealing temperature) changes to a cuboidal or nearly spherical morphology with almostmore or less uniform ( unimodal) size distribution. [Note: The term "more or less" is several times repeated in the text. I cannot imagine what it in fact means. Could you change it or explain in a more clear way]

Abstract: This paper compares proton diffusion through plasma-polymerised proton-exchange membranes (PEMs) produced using traditional wet-chemical methods (Nafion®) and those produced using plasma-polymerisation. Using quasielastic neutron scattering and a simple model of proton motion we find the measured diffusion-rate of protons in the plasma-polymerised material and Nafion® is the same (within 1 standard error) even though the plasma-polymerised membrane has 80 % less water than the Nafion®. We attribute this result to the highly cross-linked structure of the plasma-polymerised membrane.