Neutron Diffraction Characterization Research Articles

In-Situ Neutron Diffraction Characterization of State-of-Charge Kinetics of High-Power Battery

not Available.

Neutron diffraction characterization of Japanese artworks of Tokugawa age

Neutron time-of-flight diffraction technique has been used to characterize some Japanese historical artifacts. With this method, metal samples can be analyzed in their bulk properties without need of sampling. Results shown here were obtained at the Italian Neutron Experimental Station (INES@ISIS) located at the pulsed neutron source ISIS (UK). The parallel use of a scanning electron microscope equipped with an energy-dispersive X-ray fluorescence device (SEM-EDX) permitted a full quantitative characterization of the investigated samples, namely four hand-guards (Tsubas) of Japanese swords attributed to the Tokugawa age. In particular, we were able to obtain, in a totally non-invasive non-destructive way, a full quantitative phase characterization of the samples, a detailed Bragg peak broadening analysis, and a quantitative texture determination. These results, complemented with those obtained via the traditional analysis method of SEM-EDX, allowed a full characterization of both the bulk and the surface of the artifacts.

MeNC5H5]2[TCNE]2 (TCNE = tetracyanoethylene). Single crystal X-ray and neutron diffraction characterization of an exceptionally long 2.8 Å C–C bond

The reaction of N-methylpyridinium iodide, Mepy+I−, and tetracyanoethylene (TCNE) forms [Mepy]2[TCNE]2, which possesses [TCNE]22− with an intradimer C–C bond distance of 2.806(1) A at 50 K from X-ray diffraction, and 2.801(4) A at 50 K from neutron diffraction. In the IR it exhibits νC≡N absorptions at 2191, 2174, 2169, 2163 and a νCC absorption at 1366 cm−1, with UV/Vis absorption bands at 26,880 and 18,520 cm−1. Analysis of the cation-hydrogen to [TCNE]22− interactions do not provide evidence that the cation stabilizes formation of the [TCNE]22− dimer, which is stabilized by the intradimer 2e−-4 center C–C bonding interaction.

Simultaneous thermogravimetric and neutron diffraction characterization of hydrogen stores

Simultaneous thermogravimetric and neutron diffraction characterization of hydrogen stores

Structure and bonding configuration of hydrided ErNi3 and CeCo3

The intermetallic compounds ErNi 3 and CeCo 3 has been hydrided at low ( ≤ 0.01 GPa) and high ( up to 0.2 GPa) hydrogen pressures. X-ray and neutron diffraction characterization has shown that the resultant hydrides have structures of the same type (PuNi 3 ) as the parent intermetallics and have a larger unit- cell volume. We have identified the positions occupied by the metal and hydrogen atoms and have determined their positional parameters. The lattice anisotropy has been shown to vary little at high hydrogen concentrations. Our results indicate that the metal-hydrogen bonds in the hydrides studied are predominantly ionic for the rare- earth metals (Er and Ce) and predominantly metallic for the transition metals (Ni and Co).

Neutron scattering applied to materials problems

Neutron scattering techniques for studying materials have been applied for more than 50 years, in part led by Clifford G. Shull and Bertram N. Brockhouse, who shared the 1994 Nobel Prize in physics. The award was given for their developments in studying both the structure and dynamics of materials. The application of neutron scattering to materials has received significantly greater attention in the last few years, due to the construction of the Spallation Neutron Source (SNS) at the Oak Ridge National laboratory. The SNS will provide unprecedented access to a wide variety of instruments designed for materials research. The idea for this series of articles originated during the 2005 TMS Annual Meeting. Two symposia were devoted to neutron scattering: Neutron Scattering in Materials Research; and Neutron Diffraction Characterization of Mechanical Behavior. the goal of these articles is to introduce techniques for studying materials using neutrons, particularly to answer what are considered traditional materials problems. The first article discusses structure and phase analysis. Neutrons may be used for diffraction, similar to x-rays. However, in certain circumstances, they bring particular advantages. For example, x-rays have difficulty 'seeing' light elements, particularly when heavier elements are present, whereas neutrons may scatter effectively from elementsmore » such as hydrogen and its isotopes. The scattering strength of neutrons is sensitive to the isotopic composition. This can be used to examine the influence of a particular element. Neutrons also interact magnetically, allowing their use for studying magnetic order in materials. Because neutrons are highly penetrating, in-situ investigations under special sample environments (e.g., temperature, magnetic field, high pressure) have become routine. The second article describes applications for studying residual stress and mechanical deformation. neutrons are better able to penetrate engineering components compared to x-rays so neutron diffraction is used to examine the spatial distribution of stress and texture. In-situ loading studies have allowed for a sensitive, nondestructive study of the deformation mechanisms. More recently, neutrons have been used to analyze the dislocation and subgrain structures due to deformation. neutrons are also well suited for the study of composite materials, as diffraction peaks from each phase are separated. The author describes the fundamentals and applications of inelastic neutron scattering. By measuring not only the change in wave vector, but also the change in energy, neutrons can probe the dynamics in materials. This is used for examining elastic properties, magnetic excitations, and other dynamics that affect both the response of materials to applied driving forces and the thermodynamic properties of materials. The last article discusses facilities. The user facilitates are almost as varied as the applications, with many different instruments at each major facility. The article discusses the various facilities and instruments, as well as how to apply for access to these facilities.« less

Texture evolution during multi-pass equal channel angular extrusion of copper: Neutron diffraction characterization and polycrystal modeling

Experimental characterization and polycrystal modeling of texture evolution in pure copper during equal channel angular extrusion (ECAE) via routes B C (1, 2, 4, 8 and 16 passes) and C (1–4 passes) are conducted. Rigorous analysis of bulk textures measured by neutron diffraction is performed for the two routes. Textures in route B C show orientation concentrations along fibers that consist of the {1 1 1} θ and 〈1 1 0〉 θ partial fibers, yet the locations and orientation densities of the main texture components vary significantly with pass number. For route C, the first pass texture is retained in subsequent passes, apart from slight variations in the strengths of the main texture components. Quantitatively good texture predictions for all passes in route B C and odd-numbered passes in route C are obtained using a viscoplastic self-consistent model with a grain co-rotation scheme and a simple shear deformation history though they are further improved when the deformation is provided by finite element (FE) simulations. For the even-numbered passes in route C, however, the simple shear deformation is not sufficient; the complex and inhomogeneous deformation captured by FE simulations is important for reproducing the retained shear texture. Regardless of the deformation history used, the full constraints Taylor model is shown to be insufficient for texture predictions in multi-pass ECAE.

Synthesis, X-ray and Neutron Diffraction Characterization, and Ionic Conduction Properties of a New Oxothiomolybdate Li3[Mo8S8O8(OH)8{HWO5(H2O)}]⋅18 H2O

The new oxothiomolybdate anion [Mo8S8O8(OH)8{HWO5(H2O)}]3− (denoted HMo8W3−) has been synthesized in aqueous solution by an acido–basic condensation reaction. Four {MoV2S2O2} building blocks are connected through hydroxo bridges around a central {WVIO6} octahedron. X-ray and neutron diffraction studies have been performed on single crystals of the lithium salt Li3[Mo8S8O8(OH)8{HWO5(H2O)}]⋅18 H2O (Li3HMo8W⋅18 H2O) grown from HMo8W3− in an aqueous solution of LiCl (1 M). The neutron diffraction experiment enabled us to locate both the protons and the lithium ions. In the structure of Li3HMo8W⋅18 H2O, ring-shaped anions interleaved by a cluster of disordered hydrogen-bonded water molecules stack on top of each other along lithium pillars. The lithium columns are formed by alternating edge-sharing octahedra and tetrahedra, with one lithium site in four being totally vacant. Ionic conductivity measurements on pressed pellets have shown that Li3HMo8W⋅18 H2O is a good ionic conductor at room temperature (σ=10−5 S cm−1), but the ionic conductivity on single crystals is smaller by two orders of magnitude and is isotropic; this suggests the main path of conduction involves surface protons rather than lithium ions of the bulk.

Synthesis, X-ray and neutron diffraction characterization, and ionic conduction properties of a new oxothiomolybdate Li3[Mo8S8O8(OH)8[HWO5(H2O)]] x 18H2O.

The new oxothiomolybdate anion [Mo8S8O8(OH)8[HWO5(H2O)]]3- (denoted HMo8W3-) has been synthesized in aqueous solution by an acido-basic condensation reaction. Four (Mo(V)2S2O2) building blocks are connected through hydroxo bridges around a central [W(VI)O6] octahedron. X-ray and neutron diffraction studies have been performed on single crystals of the lithium salt Li3[Mo8S8O8(OH)8[HWO5(H2O)]] x 18H2O (Li3HMo8W x 18H2O) in an aqueous grown from HMo8W3- solution of LiCl (1 M). The neutron diffraction experiment enabled us to locate both the protons and the lithium ions. In the structure of Li3HMo8W x 18H20, ring-shaped anions interleaved by a cluster of disordered hydrogen-bonded water molecules stack on top of each other along lithium pillars. The lithium columns are formed by alternating edge-sharing octahedra and tetrahedra, with one lithium site in four being totally vacant. Ionic conductivity measurements on pressed pellets have shown that Li3HMo8W x 18H2O is a good ionic conductor at room temperature (sigma = 10(-5) S cm(-1)), but the ionic conductivity on single crystals is smaller by two orders of magnitude and is isotropic; this suggests the main path of conduction involves surface protons rather than lithium ions of the bulk.

Neutron Diffraction Characterization of Permanent Magnet Phases

ABSTRACTNeutron diffraction has been invaluable in the characterization of intermetallic magnetic phases due to the unique properties of the neutron and the availability of high performance powder diffractometers that allow large numbers of samples to be investigated. The structural data derived from these studies serves as fundamental input for theory, and constraints on analyses of data from other methods, such as Mossbauer spectroscopy. The empirical structure-property relations derived from these studies serves to guide synthesis of new compounds and may help to define the next generation of high performance permanent magnets.

Neutron diffraction refinement and characterization of (R = La, Pr, Nd, Gd)

From stoichiometric mixtures of analytical grade , or and , polycrystalline samples of four iron rare-earth germanates (R = La, Pr, Nd, Gd) have been prepared. They are monoclinic, S.G. (No 14) and Z = 4, isotypic with AlR. Results of the refinements from neutron ( R = La, Pr) powder diffraction data by the Rietveld method of profile analysis as well as x-ray (R = Nd, Gd) powder diffraction data are given. The four x-ray diffraction powder patterns are included together with lattice dimensions, which decrease from a (Å) = 7.308(1), b (Å) = 6.667(1), c (Å) = 13.065(2), and for R = La to a (Å) = 7.141(1), b (Å) = 6.5903(7), c (Å) = 12.833(2), and for R = Gd. Magnetic susceptibility measurements between 350 and 1.7 K confirm the existence of antiferro-magnetic ordering and Néel temperatures of 4.3, 3.7 and 5.8 K for R = Pr, Nd and Gd, respectively. IR spectra up to are included and briefly discussed.

Ultrasonic and neutron diffraction characterization of texture in an inhomogeneously rolled titanium plate

Deviations from orthotropic symmetry have been reported (R. B. Thompson, J. F. Smith and S. S. Lee, J. Acoust. Soc. Am., 80 (1986) 921) in the angular variation of the apparent velocities of ultrasonic guided modes propagating in a rolled titanium sheet. Additional ultrasonic and neutron diffraction measurements are presented which reveal those results to be a consequence of a subtle textural inhomogeneity, apparently developed as a result of non-uniform rolling across the sheet width. Ultrasonic and neutron diffraction measurements in material representative of the two sides of the sheet are reported which quantify the differences in the structure of the two sides. A theory is then presented which predicts the apparent angular dependence of the ultrasonic velocity in such a sheet, modeled as two adjacent homogeneous regions with slightly different properties. When the texture parameters in that theory are set equal to the values deduced from the neutron diffraction measurements, good agreement with the observed apparent velocities is obtained. These results illustrate the importance of sample homogeneity in ultrasonic texture analysis and the high sensitivity of the ultrasonic technique to small changes in texture.

New K 2NiF 4-type superconductors obtained by Cl 2 treatment: synthesis, neutron diffraction and X-ray absorption spectroscopy characterization

Chlorine gas treatment of La 2CuO 4 leads to an oxygen-doped material which is superconducting below T c = 32 K. The structural properties of this oxygen-doped La 2CuO 4+8 have been investigated by Rietveld refinement of the powder neutron diffraction data and analysis of the X-ray absorption spectra obtained in the La L III edge (LaO) region. The extra oxygen atoms occupy the ( 1 4 , 1 4 , y ) positions (O4) with y = 0.2629 at room temperature. Their occupancy factor n = 0.042 leads to the formula La 2CuO 4.08. These atoms are located between two successive (LaO) planes of a rock salt layer and are surrounded by four La and four O1 atoms, both groups of atoms forming tetrahedra. The four O1 atoms are located at 2.035 and 2.176 Å from the interstitial oxygen. Such short distances have also been found in other oxygen-excess phases, e.g. La 2CuO 4.048 and La 2NiO 4.25. The X-ray absorption spectroscopy results show that the local environment of La atoms is disturbed by the presence of anion excess. The thermal stability of this compound has been compared with that of La 2Cu(O,F) 4+ y oxyfluoride. Cl 2 − gas treatment has also been used to obtain superconducting phases in the La 2− x Ba x CuO 4 system with x⩽0.05.

Study of the low-temperature resistivity behavior in Co-Si-B metallic glasses: magnetic and neutron diffraction characterization

The origin of the minima in the electrical resistivity ϱ( T) curves in some Co-fixed Si-B metallic glasses in analyzed by means of neutron diffraction and magnetization measurements. An explanation of the minima shifts is proposed considering structural and magnetic effects.