In-situ neutron diffraction of LaCoO3 perovskite under uniaxial compression. I. Crystal structure analysis and texture development

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aman, Amjad; Chen, Yan; Lugovy, Mykola

2014-01-01

The dynamics of texture formation, changes in crystal structure and stress accommodation mechanisms are studied in R3c rhombohedral LaCoO3 perovskite during in-situ uniaxial compression experiment by neutron diffraction. The neutron diffraction revealed the complex crystallographic changes causing the texture formation and significant straining along certain crystallographic directions during in-situ compression, which are responsible for the appearance of hysteresis and non-linear ferroelastic deformation in LaCoO3 perovskite. The irreversible strain after the first loading was connected with the appearance of non-recoverable changes in the intensity ratio of certain crystallographic peaks, causing non-reversible texture formation. However in the second loading/unloading cycle the hysteresismore » loop was closed and no irreversible strain appears after deformation. The significant texture formation is responsible for increase in the Young s modulus of LaCoO3 at high compressive loads, where the reported values of Young s modulus increase from 76 GPa measured at the very beginning of the loading to 194 GPa at 900 MPa applied compressive stress measured at the beginning of the unloading curve.« less

Neutron Bragg-edge-imaging for strain mapping under in situ tensile loading

NASA Astrophysics Data System (ADS)

Woracek, R.; Penumadu, D.; Kardjilov, N.; Hilger, A.; Strobl, M.; Wimpory, R. C.; Manke, I.; Banhart, J.

2011-05-01

Wavelength selective neutron radiography at a cold neutron reactor source was used to measure strain and determine (residual) stresses in a steel sample under plane stress conditions. We present a new technique that uses an energy-resolved neutron imaging system based on a double crystal monochromator and is equipped with a specially developed (in situ) biaxial load frame to perform Bragg edge based transmission imaging. The neutron imaging technique provides a viewing area of 7 cm by 7 cm with a spatial resolution on the order of ˜ 100 μm. The stress-induced shifts of the Bragg edge corresponding to the (110) lattice plane were resolved spatially for a ferritic steel alloy A36 (ASTM international) sample. Furthermore it is demonstrated that results agree with comparative data obtained using neutron diffraction and resistance based strain-gauge rosettes.

Phase diagram of the relaxor ferroelectric (1- x )Pb(Mg 1/3Nb 2/3)O 3+ x PbTiO 3 revisited: a neutron powder diffraction study of the relaxor skin effect

DOE Office of Scientific and Technical Information (OSTI.GOV)

Phelan, D.; Rodriguez, E. E.; Gao, J.

2014-11-17

We revisit the phase diagram of the relaxor ferroelectric PMN- xPT using neutron powder diffraction to test suggestions that residual oxygen vacancies and/or strain affect the ground state crystal structure. Powdered samples of PMN- xPT were prepared with nominal compositions of x = 0:10, 0.20, 0.30, and 0.40 and divided into two identical sets, one of which was annealed in air to relieve grinding-induced strain and to promote an ideal oxygen stoichiometry. For a given composition and temperature the same structural phase is observed for each specimen. However, the distortions in all of the annealed samples are smaller than thosemore » in the as-grown samples. Further, the diffraction patterns for x = 0:10, 0.20, and 0.30 are best refined using the monoclinic Cm space group. By comparing our neutron diffraction results to those obtained on single crystals having similar compositions, we conclude that the relaxor skin effect in PMN- xPT vanishes on the Ti-rich side of the morphotropic phase boundary.« less

Thermomechanical behavior and microstructural evolution of a Ni(Pd)-rich Ni 24.3Ti 49.7Pd 26 high temperature shape memory alloy

DOE PAGES

Benafan, O.; Garg, A.; Noebe, R. D.; ...

2015-04-20

We investigated the effect of thermomechanical cycling on a slightly Ni(Pd)-rich Ni 24.3Ti 49.7Pd 26 (near stochiometric Ni–Ti basis with Pd replacing Ni) high temperature shape memory alloy. Furthermore, aged tensile specimens (400 °C/24 h/furnace cooled) were subjected to constant-stress thermal cycling in conjunction with microstructural assessment via in situ neutron diffraction and transmission electron microscopy (TEM), before and after testing. It was shown that in spite of the slightly Ni(Pd)-rich composition and heat treatment used to precipitation harden the alloy, the material exhibited dimensional instabilities with residual strain accumulation reaching 1.5% over 10 thermomechanical cycles. This was attributed tomore » insufficient strengthening of the material (insufficient volume fraction of precipitate phase) to prevent plasticity from occurring concomitant with the martensitic transformation. In situ neutron diffraction revealed the presence of retained martensite while cycling under 300 MPa stress, which was also confirmed by transmission electron microscopy of post-cycled samples. Neutron diffraction analysis of the post-thermally-cycled samples under no-load revealed residual lattice strains in the martensite and austenite phases, remnant texture in the martensite phase, and peak broadening of the austenite phase. The texture we developed in the martensite phase was composed mainly of those martensitic tensile variants observed during thermomechanical cycling. Presence of a high density of dislocations, deformation twins, and retained martensite was revealed in the austenite state via in-situ TEM in the post-cycled material, providing an explanation for the observed peak broadening in the neutron diffraction spectra. Despite the dimensional instabilities, this alloy exhibited a biased transformation strain on the order of 3% and a two-way shape memory effect (TWSME) strain of ~2%, at relatively high actuation temperatures.« less

A preliminary neutron diffraction study of rasburicase, a recombinant urate oxidase enzyme, complexed with 8-azaxanthin

DOE Office of Scientific and Technical Information (OSTI.GOV)

Budayova-Spano, Monika, E-mail: spano@embl-grenoble.fr; Institut Laue-Langevin, 6 Rue Jules Horowitz, BP 156, 38042 Grenoble; Bonneté, Françoise

2006-03-01

Neutron diffraction data of hydrogenated recombinant urate oxidase enzyme (Rasburicase), complexed with a purine-type inhibitor 8-azaxanthin, was collected to 2.1 Å resolution from a crystal grown in D{sub 2}O by careful control and optimization of crystallization conditions via knowledge of the phase diagram. Deuterium atoms were clearly seen in the neutron-scattering density map. Crystallization and preliminary neutron diffraction measurements of rasburicase, a recombinant urate oxidase enzyme expressed by a genetically modified Saccharomyces cerevisiae strain, complexed with a purine-type inhibitor (8-azaxanthin) are reported. Neutron Laue diffraction data were collected to 2.1 Å resolution using the LADI instrument from a crystal (grownmore » in D{sub 2}O) with volume 1.8 mm{sup 3}. The aim of this neutron diffraction study is to determine the protonation states of the inhibitor and residues within the active site. This will lead to improved comprehension of the enzymatic mechanism of this important enzyme, which is used as a protein drug to reduce toxic uric acid accumulation during chemotherapy. This paper illustrates the high quality of the neutron diffraction data collected, which are suitable for high-resolution structural analysis. In comparison with other neutron protein crystallography studies to date in which a hydrogenated protein has been used, the volume of the crystal was relatively small and yet the data still extend to high resolution. Furthermore, urate oxidase has one of the largest primitive unit-cell volumes (space group I222, unit-cell parameters a = 80, b = 96, c = 106 Å) and molecular weights (135 kDa for the homotetramer) so far successfully studied with neutrons.« less

Residual-stress measurement in socket welded joints by neutron diffraction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hayashi, M.; Ishiwata, M.; Minakawa, N.

1994-12-31

Neutron diffraction measurements of lattice strains provide spatial maps of residual stress near welds in ferritic steel socket joints. The highest tensile stresses in the welds are found in axial, radial and hoop direction at the weld root. However, the highest tensile stress in the axial direction is about 110MPa. Balancing compressive stresses are found near the surface of the socket weld fusion zone. Heat treatment at 600 C for 2 hours is sufficient to relieve residual stress in socket welds.

In situ high-energy X-ray diffraction study of tensile deformation of neutron-irradiated polycrystalline Fe-9%Cr alloy

DOE PAGES

Zhang, Xuan; Li, Meimei; Park, Jun -Sang; ...

2016-12-30

The effect of neutron irradiation on tensile deformation of a Fe-9wt.%Cr alloy was investigated using in situ high-energy synchrotron X-ray diffraction during room-temperature uniaxial tensile tests. New insights into the deformation mechanisms were obtained through the measurements of lattice strain evolution and the analysis of diffraction peak broadening using the modified Williamson-Hall method. Two neutron-irradiated specimens, one irradiated at 300 °C to 0.01 dpa and the other at 450 °C to 0.01dpa, were tested along with an unirradiated specimen. The macroscopic stress–strain curves of the irradiated specimens showed increased strength, reduced ductility and work-hardening exponent compared to the unirradiated specimen.more » The evolutions of the lattice strain, the dislocation density and the coherent scattering domain size in the deformation process revealed different roles of the submicroscopic defects in the 300°C/0.01 dpa specimen and the TEM-visible nanometer-sized dislocation loops in the 450°C/0.01 dpa specimen: submicroscopic defects extended the linear work hardening stage (stage II) to a higher strain, while irradiation-induced dislocation loops were more effective in dislocation pinning. Lastly, while the work hardening rate of stage II was unaffected by irradiation, significant dynamic recovery in stage III in the irradiated specimens led to the early onset of necking without stage IV as observed in the unirradiated specimen.« less

Residual strain mapping of Roman styli from Iulia Concordia, Italy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Salvemini, Filomena, E-mail: floriana.salvemini@fi.isc.cnr.it; Università degli Studi di Firenze, Dipartimento di Scienze della Terra; Grazzi, Francesco

Iulia Concordia is an important Roman settlement known for the production of iron objects and weapons during the Roman Empire. A huge number of well-preserved styli were found in the past century in the bed of an old channel. In order to shed light about the production processes used by Roman for stylus manufacturing, a neutron diffraction residual strain analysis was performed on the POLDI materials science diffractometer at the Paul Scherrer Institut in Switzerland. Here, we present results from our investigation conducted on 11 samples, allowing to define, in a non-invasive way, the residual strain map related to themore » ancient Roman working techniques. - Highlights: • We examined 11 Roman styli from the settlement of Iulia Concordia, Italy. • We performed a neutron diffraction residual strain analysis on POLDI at PSI (CH). • We identified the production processes used by Roman for stylus manufacturing. • We clarified the way and direction of working applied for different classes of styli.« less

Evolution of thermo-physical properties and annealing of fast neutron irradiated boron carbide

NASA Astrophysics Data System (ADS)

Gosset, Dominique; Kryger, Bernard; Bonal, Jean-Pierre; Verdeau, Caroline; Froment, Karine

2018-03-01

Boron carbide is widely used as a neutron absorber in most nuclear reactors, in particular in fast neutron ones. The irradiation leads to a large helium production (up to 1022/cm3) together with a strong decrease of the thermal conductivity. In this paper, we have performed thermal diffusivity measurements and X-ray diffraction analyses on boron carbide samples coming from control rods of the French Phenix LMFBR reactor. The burnups range from 1021 to 8.1021/cm3. We first confirm the strong decrease of the thermal conductivity at the low burnup, together with high microstructural modifications: swelling, large micro-strains, high defects density, and disordered-like material conductivity. We observe the microstructural parameters are highly anisotropic, with high micro-strains and flattened coherent diffracting domains along the (00l) direction of the hexagonal structure. Performing heat treatments up to high temperature (2200 °C) allows us to observe the material thermal conductivity and microstructure restoration. It then appears the thermal conductivity healing is correlated to the micro-strain relaxation. We then assume the defects responsible for most of the damage are the helium bubbles and the associated stress fields.

Numerical and neutron diffraction measurement of residual stress distribution in dissimilar weld

DOE PAGES

Eisazadeh, Hamid; Bunn, Jeffrey R.; Aidun, Daryush K.

2017-01-01

In this study, a model considering an asymmetric power heat distribution, temperature-dependent material properties, strain hardening and phase transformation was developed to predict temperature field and residual stress distribution in GTA dissimilar weld between austenitic stainless steel (304) and low carbon steel (1018). The effect of martensite formation on longitudinal and transverse residual stress distributions were investigated using both FE model and neutron diffraction measurement. The results indicate that martensitic phase has a significant influence on both residual stress components, i.e., transverse and longitudinal, and it not only can change the distribution shape of residual stress near the weld centermore » line but, also, can alter the peak value of the residual stresses. The calculated temperature and weld zone profile were in agreement with the experimental results. Favorable general agreement was also found between the calculated residual stress distribution and residual stress measurements by the neutron diffraction method.« less

Numerical and neutron diffraction measurement of residual stress distribution in dissimilar weld

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eisazadeh, Hamid; Bunn, Jeffrey R.; Aidun, Daryush K.

In this study, a model considering an asymmetric power heat distribution, temperature-dependent material properties, strain hardening and phase transformation was developed to predict temperature field and residual stress distribution in GTA dissimilar weld between austenitic stainless steel (304) and low carbon steel (1018). The effect of martensite formation on longitudinal and transverse residual stress distributions were investigated using both FE model and neutron diffraction measurement. The results indicate that martensitic phase has a significant influence on both residual stress components, i.e., transverse and longitudinal, and it not only can change the distribution shape of residual stress near the weld centermore » line but, also, can alter the peak value of the residual stresses. The calculated temperature and weld zone profile were in agreement with the experimental results. Favorable general agreement was also found between the calculated residual stress distribution and residual stress measurements by the neutron diffraction method.« less

Crystallographic texture of straight-rolled ?-uranium foils via neutron and X-ray diffraction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Einhorn, J. R.; Steiner, M. A.; Vogel, S. C.

The texture of recrystallized straight-rolled ?-uranium foils, a component in prospective irradiation target designs for medical isotope production, has been measured by neutron diffraction, as well as X-ray diffraction using both Cu and Mo sources. Variations in the penetration depth of neutron and X-ray radiation allow for determination of both the bulk and surface textures. The bulk ?-uranium foil texture is similar to the warm straight-rolled plate texture, with the addition of a notable splitting of the (001) poles along the transverse direction. The surface texture of the foils is similar to the bulk, with an additional (001) texture componentmore » that is oriented between the rolling and normal directions. Differences between the surface and bulk textures are expected to arise from shear forces during the rolling process and the influence that distinct strain histories have on subsequent texture evolution during recrystallization.« less

Crystallographic texture of straight-rolled ?-uranium foils via neutron and X-ray diffraction

DOE PAGES

Einhorn, J. R.; Steiner, M. A.; Vogel, S. C.; ...

2017-05-25

The texture of recrystallized straight-rolled ?-uranium foils, a component in prospective irradiation target designs for medical isotope production, has been measured by neutron diffraction, as well as X-ray diffraction using both Cu and Mo sources. Variations in the penetration depth of neutron and X-ray radiation allow for determination of both the bulk and surface textures. The bulk ?-uranium foil texture is similar to the warm straight-rolled plate texture, with the addition of a notable splitting of the (001) poles along the transverse direction. The surface texture of the foils is similar to the bulk, with an additional (001) texture componentmore » that is oriented between the rolling and normal directions. Differences between the surface and bulk textures are expected to arise from shear forces during the rolling process and the influence that distinct strain histories have on subsequent texture evolution during recrystallization.« less

Characterization of deformation mechanisms in zirconium alloys: effect of temperature and irradiation

NASA Astrophysics Data System (ADS)

Long, Fei

Zirconium alloys have been widely used in the CANDU (CANada Deuterium Uranium) reactor as core structural materials. Alloy such as Zircaloy-2 has been used for calandria tubes; fuel cladding; the pressure tube is manufactured from alloy Zr-2.5Nb. During in-reactor service, these alloys are exposed to a high flux of fast neutron at elevated temperatures. It is important to understand the effect of temperature and irradiation on the deformation mechanism of zirconium alloys. Aiming to provide experimental guidance for future modeling predictions on the properties of zirconium alloys this thesis describes the result of an investigation of the change of slip and twinning modes in Zircaloy-2 and Zr-2.5Nb as a function of temperature and irradiation. The aim is to provide scientific fundamentals and experimental evidences for future industry modeling in processing technique design, and in-reactor property change prediction of zirconium components. In situ neutron diffraction mechanical tests carried out on alloy Zircaloy-2 at three temperatures: 100¢ªC, 300¢ªC, and 500¢ªC, and described in Chapter 3. The evolution of the lattice strain of individual grain families in the loading and Poisson's directions during deformation, which probes the operation of slip and twinning modes at different stress levels, are described. By using the same type of in situ neutron diffraction technique, tests on Zr-2.5Nb pressure tube material samples, in either the fast-neutron irradiated or un-irradiated condition, are reported in Chapter 4. In Chapter 5, the measurement of dislocation density by means of line profile analysis of neutron diffraction patterns, as well as TEM observations of the dislocation microstructural evolution, is described. In Chapter 6 a hot-rolled Zr-2.5Nb with a larger grain size compared with the pressure tubing was used to study the development of dislocation microstructures with increasing plastic strain. In Chapter 7, in situ loading of heavy ion irradiated hot-rolled Zr-2.5Nb alloy is described, providing evidence for the interaction between moving dislocations and irradiation induced loops. Chapter 8 gives the effect on the dislocation structure of different levels of compressive strains along two directions in the hot-rolled Zr-2.5Nb alloy. By using high resolution neutron diffraction and TEM observations, the evolution of type and dislocation densities, as well as changes of dislocation microstructure with plastic strain were characterized.

Assessment of Shape Memory Alloys - From Atoms To Actuators - Via In Situ Neutron Diffraction

NASA Technical Reports Server (NTRS)

Benafan, Othmane

2014-01-01

As shape memory alloys (SMAs) become an established actuator technology, it is important to identify the fundamental mechanisms responsible for their performance by understanding microstructure performance relationships from processing to final form. Yet, microstructural examination of SMAs at stress and temperature is often a challenge since structural changes occur with stress and temperature and microstructures cannot be preserved through quenching or after stress removal, as would be the case for conventional materials. One solution to this dilemma is in situ neutron diffraction, which has been applied to the investigation of SMAs and has offered a unique approach to reveal the fundamental micromechanics and microstructural aspects of bulk SMAs in a non-destructive setting. Through this technique, it is possible to directly correlate the micromechanical responses (e.g., internal residual stresses, lattice strains), microstructural evolutions (e.g., texture, defects) and phase transformation properties (e.g., phase fractions, kinetics) to the macroscopic actuator behavior. In this work, in situ neutron diffraction was systematically employed to evaluate the deformation and transformation behavior of SMAs under typical actuator conditions. Austenite and martensite phases, yield behavior, variant selection and transformation temperatures were characterized for a polycrystalline NiTi (49.9 at. Ni). As the alloy transforms under thermomechanical loading, the measured textures and lattice plane-level variations were directly related to the cyclic actuation-strain characteristics and the dimensional instability (strain ratcheting) commonly observed in this alloy. The effect of training on the shape memory characteristics of the alloy and the development of two-way shape memory effect (TWSME) were also assessed. The final conversion from a material to a useful actuator, typically termed shape setting, was also investigated in situ during constrained heatingcooling and subsequent shape recovery experiments. Neutron diffraction techniques are also being applied to the investigation of novel high temperature SMAs with the objective of designing alloys with better stability, higher transition temperatures and ultimately superior durability.

Three-dimensional welding residual stresses evaluation based on the eigenstrain methodology via X-ray measurements at the surface

NASA Astrophysics Data System (ADS)

Ogawa, Masaru

2014-12-01

In order to assure structural integrity for operating welded structures, it is necessary to evaluate crack growth rate and crack propagation direction for each observed crack non-destructively. Here, three dimensional (3D) welding residual stresses must be evaluated to predict crack propagation. Today, X-ray diffraction is used and the ultrasonic method has been proposed as non-destructive method to measure residual stresses. However, it is impossible to determine residual stress distributions in the thickness direction. Although residual stresses through a depth of several tens of millimeters can be evaluated non-destructively by neutron diffraction, it cannot be used as an on-site measurement technique. This is because neutron diffraction is only available in special irradiation facilities. Author pays attention to the bead flush method based on the eigenstrain methodology. In this method, 3D welding residual stresses are calculated by an elastic Finite Element Method (FEM) analysis from eigenstrains which are evaluated by an inverse analysis from released strains by strain gauges in the removal of the reinforcement of the weld. Here, the removal of the excess metal can be regarded as non-destructive treatment because toe of weld which may become crack starters can be eliminated. The effectiveness of the method has been proven for welded plates and pipes even with relatively lower bead height. In actual measurements, stress evaluation accuracy becomes poorer because measured values of strain gauges are affected by processing strains on the machined surface. In the previous studies, the author has developed the bead flush method that is free from the influence of the affecting strains by using residual strains on surface by X-ray diffraction. However, stress evaluation accuracy is not good enough because of relatively poor measurement accuracy of X-ray diffraction. In this study, a method to improve the estimation accuracy of residual stresses in this method is formulated, and it is shown numerically that inner welding residual stresses can be estimated accurately from the residual strains measured by X-ray diffraction.

Magnetoelastic effect in MF2 (M = Mn, Fe, Ni) investigated by neutron powder diffraction

NASA Astrophysics Data System (ADS)

Chatterji, Tapan; Iles, Gail N.; Ouladdiaf, Bachir; Hansen, Thomas C.

2010-08-01

We have investigated the magnetoelastic effects in MF2 (M = Mn, Fe, Ni) associated with the antiferromagnetic phase transition temperature TN by neutron powder diffraction. The temperature variation of the lattice parameters and the unit cell volume has been determined accurately with small temperature steps. From the temperature variation of the lattice parameters a, c and V the lattice strains Δa, Δc and ΔV associated with the antiferromagnetic phase transition have been extracted. Rietveld refinement of the crystal and magnetic structures from the diffraction data at low temperature gave a magnetic moment of 5.12 ± 0.09 μB, 4.05 ± 0.05 μB and 1.99 ± 0.05 μB per Mn, Fe and Ni ions, respectively. The lattice strains Δa, Δc and ΔV couple linearly with the intensity of the 100 magnetic reflection, which is proportional to square of the order parameter of the antiferromagnetic phase transition. The volume strains in MF2 (M = Mn, Fe, Co, Ni) due to the magnetostriction vary smoothly along the transition metal series and seem to be correlated with the strength of the exchange interaction and the moments of the magnetic ions.

Magnetoelastic effect in MF2 (M = Mn, Fe, Ni) investigated by neutron powder diffraction.

PubMed

Chatterji, Tapan; Iles, Gail N; Ouladdiaf, Bachir; Hansen, Thomas C

2010-08-11

We have investigated the magnetoelastic effects in MF(2) (M = Mn, Fe, Ni) associated with the antiferromagnetic phase transition temperature T(N) by neutron powder diffraction. The temperature variation of the lattice parameters and the unit cell volume has been determined accurately with small temperature steps. From the temperature variation of the lattice parameters a, c and V the lattice strains Δa, Δc and ΔV associated with the antiferromagnetic phase transition have been extracted. Rietveld refinement of the crystal and magnetic structures from the diffraction data at low temperature gave a magnetic moment of 5.12 ± 0.09 μ(B), 4.05 ± 0.05 μ(B) and 1.99 ± 0.05 μ(B) per Mn, Fe and Ni ions, respectively. The lattice strains Δa, Δc and ΔV couple linearly with the intensity of the 100 magnetic reflection, which is proportional to square of the order parameter of the antiferromagnetic phase transition. The volume strains in MF(2) (M = Mn, Fe, Co, Ni) due to the magnetostriction vary smoothly along the transition metal series and seem to be correlated with the strength of the exchange interaction and the moments of the magnetic ions.

Nondestructive evaluation of loading and fatigue effects in Haynes(R) 230(R) alloy

NASA Astrophysics Data System (ADS)

Saleh, Tarik Adel

Nondestructive evaluation is a useful method for studying the effects of deformation and fatigue. In this dissertation I employed neutron and X-ray diffraction, nonlinear resonant ultrasound spectroscopy (NRUS), and infrared thermography to study the effects of deformation and fatigue on two different nickel based superalloys. The alloys studied were HAYNES 230, a solid solution strengthened alloy with 4% M6C carbides, and secondarily HASTELLOY C-2000 a similar single phase alloy. Using neutron and X-ray diffraction, the deformation behavior of HAYNES 230 was revealed to be composite-like during compression, but unusual in tension, where the carbides provide strengthening until just after the macroscopic yield strength and then they begin to debond and crack, creating a tension-compression asymmetry that is revealed clearly by in situ diffraction. In fatigue of HAYNES 230, the hkl elastic strains changed very little in tension-tension fatigue. However, in situ tension-compression studies showed large changes over the initial stages of fatigue. The HAYNES 230 samples studies had two distinct starting textures, measured by neutron diffraction. Some samples were texture free initially and deformed in tension and compression to fiber textures. Other samples started with a bimodal texture due to cross-rolling and incomplete annealing. The final texture of these bimodal samples is shown through modeling to be a superposition of the initial texture and typical FCC deformation mechanisms. The texture-free samples deformed significantly more macroscopically and in internal elastic strains than the samples with the cross-rolled texture. In contrast to the relative insensitivity of neutron diffraction to the effects of tension-tension fatigue, NRUS revealed large differences between as-received and progressively fatigued samples. This showed that microcracking and void formation are the primary mechanisms responsible for fatigue damage in tension-tension fatigue. NRUS is shown to be a useful complimentary technique to neutron diffraction to evaluate fatigue damage. Finally, infrared thermography is used to show temperature changes over the course of fatigue in HASTELLOY C-2000. Four stages of temperature are shown over the course of a single fatigue test. Both empirical and theoretical relationships between steady state temperature and fatigue life are developed and presented.

In Situ Neutron Diffraction Analyzing Stress-Induced Phase Transformation and Martensite Elasticity in [001]-Oriented Co49Ni21Ga30 Shape Memory Alloy Single Crystals

NASA Astrophysics Data System (ADS)

Reul, A.; Lauhoff, C.; Krooß, P.; Gutmann, M. J.; Kadletz, P. M.; Chumlyakov, Y. I.; Niendorf, T.; Schmahl, W. W.

2018-02-01

Recent studies demonstrated excellent pseudoelastic behavior and cyclic stability under compressive loads in [001]-oriented Co-Ni-Ga high-temperature shape memory alloys (HT-SMAs). A narrow stress hysteresis was related to suppression of detwinning at RT and low defect formation during phase transformation due to the absence of a favorable slip system. Eventually, this behavior makes Co-Ni-Ga HT-SMAs promising candidates for several industrial applications. However, deformation behavior of Co-Ni-Ga has only been studied in the range of theoretical transformation strain in depth so far. Thus, the current study focuses not only on the activity of elementary deformation mechanisms in the pseudoelastic regime up to maximum theoretical transformation strains but far beyond. It is shown that the martensite phase is able to withstand about 5% elastic strain, which significantly increases the overall deformation capability of this alloy system. In situ neutron diffraction experiments were carried out using a newly installed testing setup on Co-Ni-Ga single crystals in order to reveal the nature of the stress-strain response seen in the deformation curves up to 10% macroscopic strain.

Unraveling cyclic deformation mechanisms of a rolled magnesium alloy using in situ neutron diffraction

DOE PAGES

Wu, Wei; An, Ke; Liaw, Peter K.

2014-12-23

In the current study, the deformation mechanisms of a rolled magnesium alloy were investigated under cyclic loading using real-time in situ neutron diffraction under a continuous-loading condition. The relationship between the macroscopic cyclic deformation behavior and the microscopic response at the grain level was established. The neutron diffraction results indicate that more and more grains are involved in the twinning and detwinning deformation process with the increase of fatigue cycles. The residual twins appear in the early fatigue life, which is responsible for the cyclic hardening behavior. The asymmetric shape of the hysteresis loop is attributed to the early exhaustionmore » of the detwinning process during compression, which leads to the activation of dislocation slips and rapid strain-hardening. The critical resolved shear stress for the activation of tensile twinning closely depends on the residual strain developed during cyclic loading. In the cycle before the sample fractured, the dislocation slips became active in tension, although the sample was not fully twinned. The increased dislocation density leads to the rise of the stress concentration at weak spots, which is believed to be the main reason for the fatigue failure. Furthermore, the deformation history greatly influences the deformation mechanisms of hexagonal-close-packed-structured magnesium alloy during cyclic loading.« less

High Pressure X-Ray Diffraction Studies of Nanocrystalline Materials

NASA Technical Reports Server (NTRS)

Palosz, B.; Stel'makh, S.; Grzanka, E.; Gierlotka, S.; Palosz, W.

2004-01-01

Experimental evidence obtained for a variety of nanocrystalline materials suggest that the crystallographic structure of a very small size particle deviates from that in the bulk crystals. In this paper we show the effect of the surface of nanocrystals on their structure by the analysis of generation and distribution of macro- and micro-strains at high pressures and their dependence on the grain size in nanocrystalline powders of Sic. We studied the structure of Sic nanocrystals by in-situ high-pressure powder diffraction technique using synchrotron and neutron sources and hydrostatic or isostatic pressure conditions. The diffraction measurements were done in HASYLAB at DESY using a Diamond Anvil Cell (DAC) in the energy dispersive geometry in the diffraction vector range up to 3.5 - 4/A and under pressures up to 50 GPa at room temperature. In-situ high pressure neutron diffraction measurements were done at LANSCE in Los Alamos National Laboratory using the HIPD and HIPPO diffractometers with the Paris-Edinburgh and TAP-98 cells, respectively, in the diffraction vector range up to 26 Examination of the response of the material to external stresses requires nonstandard methodology of the materials characterization and description. Although every diffraction pattern contains a complete information on macro- and micro-strains, a high pressure experiment can reveal only those factors which contribute to the characteristic diffraction patterns of the crystalline phases present in the sample. The elastic properties of powders with the grain size from several nm to micrometers were examined using three methodologies: (l), the analysis of positions and widths of individual Bragg reflections (used for calculating macro- and micro-strains generated during densification) [I], (2). the analysis of the dependence of the experimental apparent lattice parameter, alp, on the diffraction vector Q [2], and (3), the atomic Pair Distribution Function (PDF) technique [3]. The results of our studies show, that Sic nanocrystals have the features of two phases, each with its distinct elastic properties. and under pressures up to 8 GPa.

Crystallization of a fungal lytic polysaccharide monooxygenase expressed from glycoengineered Pichia pastoris for X-ray and neutron diffraction

DOE Office of Scientific and Technical Information (OSTI.GOV)

O'Dell, William B.; Swartz, Paul D.; Weiss, Kevin L.

Lytic polysaccharide monooxygenases (LPMOs) are carbohydrate-disrupting enzymes secreted by bacteria and fungi that break glycosidic bondsviaan oxidative mechanism. Fungal LPMOs typically act on cellulose and can enhance the efficiency of cellulose-hydrolyzing enzymes that release soluble sugars for bioethanol production or other industrial uses. The enzyme PMO-2 fromNeurospora crassa(NcPMO-2) was heterologously expressed inPichia pastoristo facilitate crystallographic studies of the fungal LPMO mechanism. Diffraction resolution and crystal morphology were improved by expressingNcPMO-2 from a glycoengineered strain ofP. pastorisand by the use of crystal seeding methods, respectively. These improvements resulted in high-resolution (1.20 Å) X-ray diffraction data collection at 100 K and themore » production of a largeNcPMO-2 crystal suitable for room-temperature neutron diffraction data collection to 2.12 Å resolution.« less

In-situ neutron diffraction of a quasicrystal-containing Mg alloy interpreted using a new polycrystal plasticity model of hardening due to {10.2} tensile twinning

DOE Office of Scientific and Technical Information (OSTI.GOV)

Agnew, S. R.; Singh, A.; Calhoun, C. A.

Due to the excellent balance of strength and ductility exhibited by some Mg-Zn-RE (Y subgroup rare earth element) alloys, which contain icosahedral quasicrystalline precipitates, it is of interest to examine their deformation mechanisms. Furthermore, the internal strain evolution Mg-3at%Zn-0.5 at%Y with 4 vol% i-phase was measured using in-situ neutron diffraction. The extruded samples exhibit an initially weak <10.0> || extrusion direction “rod texture,” distinct from the normally strong texture of extruded Mg alloys, but the grain size is unexceptional (16.7 ± 2.1 μm). The initially weak texture contributes to a nearly symmetric yielding response between tension and compression. The hardeningmore » responses are asymmetric, however, since {10.2} extension twinning is significantly more active during compressive straining, despite the initially weak texture. In-situ neutron diffraction tension and compression experiments parallel to the extrusion direction, together with elasto-plastic self-consistent (EPSC) crystal plasticity modeling, reveal the strength and hardening behavior of individual slip and twinning modes. A model that was previously published about twinning-detwinning (TDT) is implemented within the EPSC framework, and it is proven effective for describing the observed, mild tension-compression asymmetry. This is not possible with previous EPSC-based models of twinning. Finally, the description of hardening within the TDT model is modified, in order to accurately describe the evolution of internal strains within the twins.« less

In-situ neutron diffraction of a quasicrystal-containing Mg alloy interpreted using a new polycrystal plasticity model of hardening due to {10.2} tensile twinning

DOE PAGES

Agnew, S. R.; Singh, A.; Calhoun, C. A.; ...

2018-09-17

Due to the excellent balance of strength and ductility exhibited by some Mg-Zn-RE (Y subgroup rare earth element) alloys, which contain icosahedral quasicrystalline precipitates, it is of interest to examine their deformation mechanisms. Furthermore, the internal strain evolution Mg-3at%Zn-0.5 at%Y with 4 vol% i-phase was measured using in-situ neutron diffraction. The extruded samples exhibit an initially weak <10.0> || extrusion direction “rod texture,” distinct from the normally strong texture of extruded Mg alloys, but the grain size is unexceptional (16.7 ± 2.1 μm). The initially weak texture contributes to a nearly symmetric yielding response between tension and compression. The hardeningmore » responses are asymmetric, however, since {10.2} extension twinning is significantly more active during compressive straining, despite the initially weak texture. In-situ neutron diffraction tension and compression experiments parallel to the extrusion direction, together with elasto-plastic self-consistent (EPSC) crystal plasticity modeling, reveal the strength and hardening behavior of individual slip and twinning modes. A model that was previously published about twinning-detwinning (TDT) is implemented within the EPSC framework, and it is proven effective for describing the observed, mild tension-compression asymmetry. This is not possible with previous EPSC-based models of twinning. Finally, the description of hardening within the TDT model is modified, in order to accurately describe the evolution of internal strains within the twins.« less

Mechanical characterization of an additively manufactured Inconel 718 theta-shaped specimen

DOE PAGES

Cakmak, Ercan; Watkins, Thomas R.; Bunn, Jeffrey R.; ...

2015-11-20

Two sets of “theta”-shaped specimens were additively manufactured with Inconel 718 powders using an electron beam melting technique with two distinct scan strategies. Light optical microscopy, mechanical testing coupled with a digital image correlation (DIC) technique, finite element modeling, and neutron diffraction with in situ loading characterizations were conducted. The cross-members of the specimens were the focus. Light optical micrographs revealed that different microstructures were formed with different scan strategies. Ex situ mechanical testing revealed each build to be stable under load until ductility was observed on the cross-members before failure. The elastic moduli were determined by forming a correlationmore » between the elastic tensile stresses determined from FEM, and the elastic strains obtained from DIC. The lattice strains were mapped with neutron diffraction during in situ elastic loading; and a good correlation between the average axial lattice strains on the cross-member and those determined from the DIC analysis was found. Lastly, the spatially resolved stresses in the elastic deformation regime are derived from the lattice strains and increased with applied load, showing a consistent distribution along the cross-member.« less

Mechanical characterization of an additively manufactured Inconel 718 theta-shaped specimen

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cakmak, Ercan; Watkins, Thomas R.; Bunn, Jeffrey R.

Two sets of “theta”-shaped specimens were additively manufactured with Inconel 718 powders using an electron beam melting technique with two distinct scan strategies. Light optical microscopy, mechanical testing coupled with a digital image correlation (DIC) technique, finite element modeling, and neutron diffraction with in situ loading characterizations were conducted. The cross-members of the specimens were the focus. Light optical micrographs revealed that different microstructures were formed with different scan strategies. Ex situ mechanical testing revealed each build to be stable under load until ductility was observed on the cross-members before failure. The elastic moduli were determined by forming a correlationmore » between the elastic tensile stresses determined from FEM, and the elastic strains obtained from DIC. The lattice strains were mapped with neutron diffraction during in situ elastic loading; and a good correlation between the average axial lattice strains on the cross-member and those determined from the DIC analysis was found. Lastly, the spatially resolved stresses in the elastic deformation regime are derived from the lattice strains and increased with applied load, showing a consistent distribution along the cross-member.« less

Microstructural and micromechanical characterization of IN718 theta shaped specimens built with electron beam melting

DOE PAGES

Cakmak, Ercan; Kirka, Michael M.; Watkins, Thomas R.; ...

2016-02-23

Theta-shaped specimens were additively manufactured out of Inconel 718 powders using an electron beam melting technique, as a model complex load bearing structure. We employed two different build strategies; producing two sets of specimens. Microstructural and micro-mechanical characterizations were performed using electron back-scatter, synchrotron x-ray and in-situ neutron diffraction techniques. In particular, the cross-members of the specimens were the focus of the synchrotron x-ray and in-situ neutron diffraction measurements. The build strategies employed resulted in the formation of distinct microstructures and crystallographic textures, signifying the importance of build-parameter manipulation for microstructural optimization. Large strain anisotropy of the different lattice planesmore » was observed during in-situ loading. Texture was concluded to have a distinct effect upon both the axial and transverse strain responses of the cross-members. In particular, the (200), (220) and (420) transverse lattice strains all showed unexpected overlapping trends in both builds. This was related to the strong {200} textures along the build/loading direction, providing agreement between the experimental and calculated results.« less

Low-dimensional ordering and fluctuations in methanol-{beta}-hydroquinone clathrate studied by x-ray and neutron diffraction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rheinstaedter, Maikel C.; Enderle, Mechthild; Kloepperpieper, Axel

2005-01-01

Methanol-{beta}-hydroquinone clathrate has been established as a model system for dielectric ordering and fluctuations and is conceptually close to magnetic spin systems. In x-ray and neutron diffraction experiments, we investigated the ordered structure, the one-dimensional (1D) and the three-dimensional critical scattering in the paraelectric phase, and the temperature dependence of the lattice constants. Our results can be explained by microscopic models of the methanol pseudospin in the hydroquinone cage network, in consistency with previous dielectric investigations. A coupling of the 1D fluctuations to local strains leads to an anomalous temperature dependence of the 1D lattice parameter in the paraelectric regime.

In-situ neutron diffraction study of martensitic variant redistribution in polycrystalline Ni-Mn-Ga alloy under cyclic thermo-mechanical treatment

NASA Astrophysics Data System (ADS)

Li, Zongbin; Zhang, Yudong; Esling, Claude; Gan, Weimin; Zou, Naifu; Zhao, Xiang; Zuo, Liang

2014-07-01

The influences of uniaxial compressive stress on martensitic transformation were studied on a polycrystalline Ni-Mn-Ga bulk alloy prepared by directional solidification. Based upon the integrated in-situ neutron diffraction measurements, direct experimental evidence was obtained on the variant redistribution of seven-layered modulated (7M) martensite, triggered by external uniaxial compression during martensitic transformation. Large anisotropic lattice strain, induced by the cyclic thermo-mechanical treatment, has led to the microstructure modification by forming martensitic variants with a strong ⟨0 1 0⟩7M preferential orientation along the loading axis. As a result, the saturation of magnetization became easier to be reached.

In-situ neutron diffraction study of martensitic variant redistribution in polycrystalline Ni-Mn-Ga alloy under cyclic thermo-mechanical treatment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Zongbin; Zou, Naifu; Zhao, Xiang

2014-07-14

The influences of uniaxial compressive stress on martensitic transformation were studied on a polycrystalline Ni-Mn-Ga bulk alloy prepared by directional solidification. Based upon the integrated in-situ neutron diffraction measurements, direct experimental evidence was obtained on the variant redistribution of seven-layered modulated (7M) martensite, triggered by external uniaxial compression during martensitic transformation. Large anisotropic lattice strain, induced by the cyclic thermo-mechanical treatment, has led to the microstructure modification by forming martensitic variants with a strong 〈0 1 0〉{sub 7M} preferential orientation along the loading axis. As a result, the saturation of magnetization became easier to be reached.

Texture analysis at neutron diffractometer STRESS-SPEC

NASA Astrophysics Data System (ADS)

Brokmeier, H.-G.; Gan, W. M.; Randau, C.; Völler, M.; Rebelo-Kornmeier, J.; Hofmann, M.

2011-06-01

In response to the development of new materials and the application of materials and components in advanced technologies, non-destructive measurement methods of textures and residual stresses have gained worldwide significance in recent years. The materials science neutron diffractometer STRESS-SPEC at FRM II (Garching, Germany) is designed to be applied equally to texture and residual stress analyses by virtue of its very flexible configuration. Due to the high penetration capabilities of neutrons and the high neutron flux of STRESS-SPEC it allows a combined analysis of global texture, local texture, strain pole figure and FWHM pole figure in a wide variety of materials including metals, alloys, composites, ceramics and geological materials. Especially, the analysis of texture gradients in bulk materials using neutron diffraction has advantages over laboratory X-rays and EBSD for many scientific cases. Moreover, neutron diffraction is favourable for coarse-grained materials, where bulk information averaged over texture inhomogeneities is needed, and also stands out due to easy sample preparation. In future, the newly developed robot system for STRESS-SPEC will allow much more flexibility than an Eulerian cradle as on standard instruments. Five recent measurements are shown to demonstrate the wide range of possible texture applications at STRESS-SPEC diffractometer.

Development of a cryogenic load frame for the neutron diffractometer at Takumi in Japan Proton Accelerator Research Complex

NASA Astrophysics Data System (ADS)

Jin, Xinzhe; Nakamoto, Tatsushi; Harjo, Stefanus; Hemmi, Tsutomu; Umeno, Takahiro; Ogitsu, Toru; Yamamoto, Akira; Sugano, Michinaka; Aizawa, Kazuya; Abe, Jun; Gong, Wu; Iwahashi, Takaaki

2013-06-01

To prepare for projects such as the Large Hadron Collider upgrade, International Thermonuclear Experimental Reactor and Demonstration reactor, it is important to form a clear understanding of stress-strain properties of the materials that make up superconducting magnets. Thus, we have been studying the mechanical properties of superconducting wires using neutron diffraction measurements. To simulate operational conditions such as temperature, stress, and strain, we developed a cryogenic load frame for stress-strain measurements of materials using a neutron diffractometer at Japan Proton Accelerator Research Complex (J-PARC) Takumi beam line. The maximum load that can be applied to a sample using an external driving machine is 50 kN. Using a Gifford-MacMahon cryocooler, samples can be measured down to temperatures below 10 K when loaded. In the present paper, we describe the details of the cryogenic load frame with its test results by using type-304 stainless steel wire.

Development of a cryogenic load frame for the neutron diffractometer at Takumi in Japan Proton Accelerator Research Complex

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jin, Xinzhe; Nakamoto, Tatsushi; Ogitsu, Toru

2013-06-15

To prepare for projects such as the Large Hadron Collider upgrade, International Thermonuclear Experimental Reactor and Demonstration reactor, it is important to form a clear understanding of stress-strain properties of the materials that make up superconducting magnets. Thus, we have been studying the mechanical properties of superconducting wires using neutron diffraction measurements. To simulate operational conditions such as temperature, stress, and strain, we developed a cryogenic load frame for stress-strain measurements of materials using a neutron diffractometer at Japan Proton Accelerator Research Complex (J-PARC) Takumi beam line. The maximum load that can be applied to a sample using an externalmore » driving machine is 50 kN. Using a Gifford-MacMahon cryocooler, samples can be measured down to temperatures below 10 K when loaded. In the present paper, we describe the details of the cryogenic load frame with its test results by using type-304 stainless steel wire.« less

Development of a cryogenic load frame for the neutron diffractometer at Takumi in Japan Proton Accelerator Research Complex.

PubMed

Jin, Xinzhe; Nakamoto, Tatsushi; Harjo, Stefanus; Hemmi, Tsutomu; Umeno, Takahiro; Ogitsu, Toru; Yamamoto, Akira; Sugano, Michinaka; Aizawa, Kazuya; Abe, Jun; Gong, Wu; Iwahashi, Takaaki

2013-06-01

To prepare for projects such as the Large Hadron Collider upgrade, International Thermonuclear Experimental Reactor and Demonstration reactor, it is important to form a clear understanding of stress-strain properties of the materials that make up superconducting magnets. Thus, we have been studying the mechanical properties of superconducting wires using neutron diffraction measurements. To simulate operational conditions such as temperature, stress, and strain, we developed a cryogenic load frame for stress-strain measurements of materials using a neutron diffractometer at Japan Proton Accelerator Research Complex (J-PARC) Takumi beam line. The maximum load that can be applied to a sample using an external driving machine is 50 kN. Using a Gifford-MacMahon cryocooler, samples can be measured down to temperatures below 10 K when loaded. In the present paper, we describe the details of the cryogenic load frame with its test results by using type-304 stainless steel wire.

A virtual laboratory for neutron and synchrotron strain scanning

NASA Astrophysics Data System (ADS)

James, J. A.; Santisteban, J. R.; Edwards, L.; Daymond, M. R.

2004-07-01

The new generation of dedicated Engineering Strain Scanners at neutron and synchrotron facilities offer considerable improvements in both counting time and spatial resolution. In order to make full use of these advances in instrumentation, the routine tasks associated with setting up measurement runs and analysing the data need to be made as efficient as possible. Such tasks include the planning of the experiment, the alignment and positioning of the specimen, the least-squares refinement of diffraction spectra, the definition of strain in the sample coordinate system, and its visualization within a 3D model of the specimen. With this aim in mind, we have written a software providing support for most of these operations. The approach is based on a virtual lab consisting of 3D models of the sample and laboratory equipment. The system has been developed for ENGIN-X, the new engineering strain scanner recently commissioned at ISIS, but it is flexible enough to be ported to other neutron or synchrotron strain scanners. The software has been designed with visiting industrial and academic researchers in mind, users who need to be able to control the instrument after only a short period of training.

In-situ TOF neutron diffraction studies of cyclic softening in superelasticity of a NiFeGaCo shape memory alloy

DOE PAGES

Yang, Hui; Yu, Dunji; Chen, Yan; ...

2016-10-24

Real-time in-situ neutron diffraction was conducted during uniaxial cycling compression of a Ni 49.3Fe 18Ga 27Co 5.7 shape memory alloy to explore the mechanism on its superelasticity at room temperature, which was manifested by the almost recoverable large strains and the apparent cyclic softening. Based on the Rietveld refinements, the real-time evolution of volume fraction of martensite was in-situ monitored, indicating the incremental amount of residual martensite with increasing load cycles. Real-time changes in intensities and lattice strains of { hkl} reflections for individual phase were obtained through fitting individual peaks, which reveal the quantitative information on phase transformation kineticsmore » as a function of grain orientation and stress/strain partitioning. Moreover, a large compressive residual stress was evidenced in the parent phase, which should be balanced by the residual martensite after the second unloading cycle. As a result, the large compressive residual stress found in the parent austenite phase may account for the cyclic effect on critical stress required for triggering the martensitic transformation in the subsequent loading.« less

Structure of Ce2RhIn8: an example of complementary use of high-resolution neutron powder diffraction and reciprocal-space mapping to study complex materials.

PubMed

Moshopoulou, E G; Ibberson, R M; Sarrao, J L; Thompson, J D; Fisk, Z

2006-04-01

The room-temperature crystal structure of the heavy fermion antiferromagnet Ce2RhIn8, dicerium rhodium octaindide, has been studied by a combination of high-resolution synchrotron X-ray reciprocal-space mapping of single crystals and high-resolution time-of-flight neutron powder diffraction. The structure is disordered, exhibiting a complex interplay of non-periodic, partially correlated planar defects, coexistence and segregation of polytypic phases (induced by periodic planar ;defects'), mosaicity (i.e. domain misalignment) and non-uniform strain. These effects evolve as a function of temperature in a complicated way, but they remain down to low temperatures. The room-temperature diffraction data are best represented by a complex mixture of two polytypic phases, which are affected by non-periodic, partially correlated planar defects, differ slightly in their tetragonal structures, and exhibit different mosaicities and strain values. Therefore, Ce2RhIn8 approaches the paracrystalline state, rather than the classic crystalline state and thus several of the concepts of conventional single-crystal crystallography are inapplicable. The structural results are discussed in the context of the role of disorder in the heavy-fermion state and in the interplay between superconductivity and magnetism.

An in situ neutron diffraction study of plastic deformation in a Cu 46.5Zr 46.5Al 7 bulk metallic glass composite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, D. M.; Chen, Yan; Mu, Juan

Micro-mechanical behaviors of a Cu 46.5Zr 46.5Al 7 bulk metallic glass composite in the plastic regime were investigated by continuous in situ neutron diffraction during compression. Three stages of the plastic deformation were observed according to the work-hardening rate. Here, the underlying natures of the work hardening, correlating with the lattice/microscopic strain evolution, are revealed for the three stages: (1) the initiation of shear bands, (2) the phase load transferring from the amorphous phase to the B2 phase and (3) the accelerated martensitic transformation and the work hardening of the polycrystalline phases promoted by the rapid propagation of the shearmore » bands.« less

An in situ neutron diffraction study of plastic deformation in a Cu 46.5Zr 46.5Al 7 bulk metallic glass composite

DOE PAGES

Wang, D. M.; Chen, Yan; Mu, Juan; ...

2018-05-21

Micro-mechanical behaviors of a Cu 46.5Zr 46.5Al 7 bulk metallic glass composite in the plastic regime were investigated by continuous in situ neutron diffraction during compression. Three stages of the plastic deformation were observed according to the work-hardening rate. Here, the underlying natures of the work hardening, correlating with the lattice/microscopic strain evolution, are revealed for the three stages: (1) the initiation of shear bands, (2) the phase load transferring from the amorphous phase to the B2 phase and (3) the accelerated martensitic transformation and the work hardening of the polycrystalline phases promoted by the rapid propagation of the shearmore » bands.« less

In situ Neutron Diffraction during Casting: Determination of Rigidity Point in Grain Refined Al-Cu Alloys

PubMed Central

Drezet, Jean-Marie; Mireux, Bastien; Szaraz, Zoltan; Pirling, Thilo

2014-01-01

The rigidity temperature of a solidifying alloy is the temperature at which the solid plus liquid phases are sufficiently coalesced to transmit long range tensile strains and stresses. It determines the point at which thermally induced deformations start to generate internal stresses in a casting. As such, it is a key parameter in numerical modelling of solidification processes and in studying casting defects such as solidification cracking. This temperature has been determined in Al-Cu alloys using in situ neutron diffraction during casting in a dog bone shaped mould. In such a setup, the thermal contraction of the solidifying material is constrained and stresses develop at a hot spot that is irradiated by neutrons. Diffraction peaks are recorded every 11 s using a large detector, and their evolution allows for the determination of the rigidity temperatures. We measured rigidity temperatures equal to 557 °C and 548 °C, depending on cooling rate, for a grain refined Al-13 wt% Cu alloy. At high cooling rate, rigidity is reached during the formation of the eutectic phase and the solid phase is not sufficiently coalesced, i.e., strong enough, to avoid hot tear formation. PMID:28788507

In situ Neutron Diffraction during Casting: Determination of Rigidity Point in Grain Refined Al-Cu Alloys.

PubMed

Drezet, Jean-Marie; Mireux, Bastien; Szaraz, Zoltan; Pirling, Thilo

2014-02-12

The rigidity temperature of a solidifying alloy is the temperature at which the solid plus liquid phases are sufficiently coalesced to transmit long range tensile strains and stresses. It determines the point at which thermally induced deformations start to generate internal stresses in a casting. As such, it is a key parameter in numerical modelling of solidification processes and in studying casting defects such as solidification cracking. This temperature has been determined in Al-Cu alloys using in situ neutron diffraction during casting in a dog bone shaped mould. In such a setup, the thermal contraction of the solidifying material is constrained and stresses develop at a hot spot that is irradiated by neutrons. Diffraction peaks are recorded every 11 s using a large detector, and their evolution allows for the determination of the rigidity temperatures. We measured rigidity temperatures equal to 557 °C and 548 °C, depending on cooling rate, for a grain refined Al-13 wt% Cu alloy. At high cooling rate, rigidity is reached during the formation of the eutectic phase and the solid phase is not sufficiently coalesced, i.e. , strong enough, to avoid hot tear formation.

Investigation of Deformation Dynamics in a Wrought Magnesium Alloy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, Wei; Qiao, Hua; An, Ke

2014-11-01

In the present research, the deformation dynamics and the effect of the deformation history on plastic deformation in a wrought magnesium alloy have been studied using real-time in-situ neutron diffraction measurements under a continuous loading condition and elastic-viscoplastic self-consistent (EVPSC) polycrystal modeling. The experimental results reveal that the pre-deformation delayed the activation of the tensile twinning during subsequent compression, mainly resulting from the residual strain. No apparent detwinning occurred during unloading and even in the elastic region during reverse loading. It is believed that the grain rotation played an important role in the elastic region during reverse loading. The EVPSCmore » model, which has been recently updated by implementing the twinning and detwinning model, was employed to characterize the deformation mechanism during the strain-path changes. The simulation result predicts well the experimental observation from the real-time in-situ neutron diffraction measurements. The present study provides a deep insight of the nature of deformation mechanisms in a hexagonal close-packed structured polycrystalline wrought magnesium alloy, which might lead to a new era of deformation-mechanism research.« less

Raw neutron scattering data for strain measurement of hydraulically loaded granite and marble samples in triaxial stress state

DOE Data Explorer

Polsky, Yarom

2014-05-23

This entry contains raw data files from experiments performed on the Vulcan beamline at the Spallation Neutron Source at Oak Ridge National Laboratory using a pressure cell. Cylindrical granite and marble samples were subjected to confining pressures of either 0 psi or approximately 2500 psi and internal pressures of either 0 psi, 1500 psi or 2500 psi through a blind axial hole at the center of one end of the sample. The sample diameters were 1.5" and the sample lengths were 6". The blind hole was 0.25" in diameter and 3" deep. One set of experiments measured strains at points located circumferentially around the center of the sample with identical radii to determine if there was strain variability (this would not be expected for a homogeneous material based on the symmetry of loading). Another set of experiments measured load variation across the radius of the sample at a fixed axial and circumferential location. Raw neutron diffraction intensity files and experimental parameter descriptions are included.

Non-Destructive Measurement of Residual Strain in Connecting Rods Using Neutrons

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ikeda, Tomohiro; Bunn, Jeffrey R.; Fancher, Christopher M.

Increasing the strength of materials is effective in reducing weight and boosting structural part performance, but there are cases in where the residual strain generated during the process of manufacturing of high-strength materials results in a decline of durability. It is therefore important to understand how the residual strain in a manufactured component changes due to processing conditions. In the case of a connecting rod, because the strain load on the connecting rod rib sections is high, it is necessary to clearly understand the distribution of strain in the ribs. However, because residual strain is generally measured by using X-raymore » diffractometers or strain gauges, measurements are limited to the surface layer of the parts. Neutron beams, however, have a higher penetration depth than X-rays, allowing for strain measurement in the bulk material. The research discussed within this paper consists of non-destructive residual strain measurements in the interior of connecting rods using the 2nd Generation Neutron Residual Stress Mapping Facility (NRSF2) at Oak Ridge National Laboratory, measuring the Fe (211) diffraction peak position of the ferrite phase. The interior strain distribution of connecting rod, which prepared under different manufacturing processes, was revealed. By the visualization of interior strains, clear understandings of differences in various processing conditions were obtained. In addition, it is known that the peak width, which is also obtained during measurement, is suggestive of the size of crystallites in the structure; however the peak width can additionally be caused by microstresses and material dislocations.« less

Clifford G. Shull, Neutron Diffraction, Hydrogen Atoms, and Neutron

Science.gov Websites

Analysis of NaH and NaD, DOE Technical Report, April 1947 The Diffraction of Neutrons by Crystalline Powders; DOE Technical Report; 1948 Neutron Diffraction Studies, DOE Technical Report, 1948 Laue Structure of Thorium and Zirconium Dihydrides by X-ray and Neutron Diffraction, DOE Technical Report, April

Neutron and X-Ray Diffraction Studies of Advanced Materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barabash, Rozaliya; Tiley, Jaimie; Wang, Yandong

2010-01-01

The selection of articles in the special topic 'Neutron and X-Ray Studies of Advanced Materials' is based on the materials presented during the TMS 2009 annual meeting in San Francisco, CA, February 15-19, 2009. The development of ultrabrilliant third-generation synchrotron X-ray sources, together with advances in X-ray optics, has created intense X-ray microbeams, which provide the best opportunities for in-depth understanding of mechanical behavior in a broad spectrum of materials. Important applications include ultrasensitive elemental detection by X-ray fluorescence/absorption and microdiffraction to identify phase and strain with submicrometer spatial resolution. X-ray microdiffraction is a particularly exciting application compared with alternativemore » probes of crystalline structure, orientation, and strain. X-ray microdiffraction is nondestructive with good strain resolution, competitive or superior spatial resolution in thick samples, and with the ability to probe below the sample surface. Moreover, the high-energy X-ray diffraction technique provides an effective tool for characterizing the mechanical and functional behavior in various environments (temperature, stress, and magnetic field). At the same time, some neutron diffraction instruments constructed mainly for the purpose of engineering applications can be found at nearly all neutron facilities. The first generation-dedicated instruments designed for studying in-situ mechanical behavior have been commissioned and used, and industrial standards for reliable and repeatable measurements have been developed. Furthermore, higher penetration of neutron beams into most engineering materials provides direct measurements on the distribution of various stresses (i.e., types I, II, and III) beneath the surface up to several millimeters, even tens of millimeters for important industrial components. With X-ray and neutron measurements, it is possible to characterize material behavior at different length scales. It is predicted that the application of these techniques, in combination with theoretical simulations and numerical modeling, will lead to major breakthroughs in materials science in the foreseeable future, which will contribute to the development of materials technology and industrial innovation. Specifically, the use of these techniques provides bulk material properties that further augment new characterization tools including the increased use of atom probe tomography and high-resolution transmission electron microscopy systems. The combination of these techniques greatly assists the material property models that address multi-length-scale mechanisms. Different applications of diffuse scattering for understanding the fundamental materials properties are illustrated in the articles of Welberry et al., Goossens and Welberry, Campbell, Abe et al., Gilles et al., and Zhang et al. Analysis of thin films and two-dimensional structures is described in the articles of Gramlich et al., Brock et al., Vigliante et al., Kuzel et al., and Davydok et al. Recent advances in the line profile analysis are represented by the the articles of Scardi et al., Ungar et al., and Woo et al. Characterization of modern alloys is presented by the articles of Wollmershauser et al., Eidenberger et al., Garlea et al., Jia et al., Soulami et al., Wilson et al., and Wang et al. The collected articles are written by different scientific X-ray and neutron research groups. They represent a general trend in the development and application of diffraction techniques all over the world.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ekkebus, Allen E

Oak Ridge National Laboratory hosted two workshops in April 2007 relevant to nuclear engineering education. In the Neutron Stress, Texture, and Phase Transformation for Industry workshop [http://neutrons.ornl.gov/workshops/nst2/], several invited speakers gave examples of neutron stress mapping for nuclear engineering applications. These included John Root of National Research Council of Canada, Mike Fitzpatrick of the UK's Open University, and Yan Gao of GE Global Research on their experiences with industrial and academic uses of neutron diffraction. Xun-Li Wang and Camden Hubbard described the new instruments at ORNL that can be used for such studies. This was preceded by the Neutrons formore » Materials Science and Engineering educational symposium [http://neutrons.ornl.gov/workshops/edsym2007]. It was directed to the broad materials science and engineering community based in universities, industry and laboratories who wish to learn what the neutron sources in the US can provide for enhancing the understanding of materials behavior, processing and joining. Of particular interest was the presentation of Donald Brown of Los Alamos about using 'Neutron diffraction measurements of strain and texture to study mechanical behavior of structural materials.' At both workshops, the ORNL neutron scattering instruments relevant to nuclear engineering studies were described. The Neutron Residual Stress Mapping Facility (NRSF2) is currently in operation at the High Flux Isotope Reactor; the VULCAN Engineering Materials Diffractometer will begin commissioning in 2008 at the Spallation Neutron Source. For characteristics of these instruments, as well as details of other workshops, meetings, capabilities, and research proposal submissions, please visit http://neutrons.ornl.gov. To submit user proposals for time on NRSF2 contact Hubbard at hubbardcr@ornl.gov.« less

Orbital glass state of the nearly metallic spinel cobalt vanadate

DOE PAGES

Koborinai, R.; Dissanayake, Sachith E.; Reehuis, M.; ...

2016-01-19

Strain, magnetization, dielectric relaxation, and unpolarized and polarized neutron diffraction measurements were performed to study the magnetic and structural properties of spinel Co 1–xV 2+xO 4. The strain measurement indicates that, upon cooling, ΔL/L in the order of ~10 –4 starts increasing below T C, becomes maximum at T max, and then decreases and changes its sign at T*. Neutron measurements indicate that a collinear ferrimagnetic order develops below T C and upon further cooling noncollinear ferrimagnetic ordering occurs below T max. At low temperatures, the dielectric constant exhibits a frequency dependence, indicating slow dynamics. Lastly, these results indicate themore » existence of an orbital glassy state at low temperatures in this nearly metallic frustrated magnet.« less

High Temperature Deformation Mechanism in Hierarchical and Single Precipitate Strengthened Ferritic Alloys by In Situ Neutron Diffraction Studies.

PubMed

Song, Gian; Sun, Zhiqian; Li, Lin; Clausen, Bjørn; Zhang, Shu Yan; Gao, Yanfei; Liaw, Peter K

2017-04-07

The ferritic Fe-Cr-Ni-Al-Ti alloys strengthened by hierarchical-Ni 2 TiAl/NiAl or single-Ni 2 TiAl precipitates have been developed and received great attentions due to their superior creep resistance, as compared to conventional ferritic steels. Although the significant improvement of the creep resistance is achieved in the hierarchical-precipitate-strengthened ferritic alloy, the in-depth understanding of its high-temperature deformation mechanisms is essential to further optimize the microstructure and mechanical properties, and advance the development of the creep resistant materials. In the present study, in-situ neutron diffraction has been used to investigate the evolution of elastic strain of constitutive phases and their interactions, such as load-transfer/load-relaxation behavior between the precipitate and matrix, during tensile deformation and stress relaxation at 973 K, which provide the key features in understanding the governing deformation mechanisms. Crystal-plasticity finite-element simulations were employed to qualitatively compare the experimental evolution of the elastic strain during tensile deformation at 973 K. It was found that the coherent elastic strain field in the matrix, created by the lattice misfit between the matrix and precipitate phases for the hierarchical-precipitate-strengthened ferritic alloy, is effective in reducing the diffusional relaxation along the interface between the precipitate and matrix phases, which leads to the strong load-transfer capability from the matrix to precipitate.

In situ neutron diffraction in quantifying deformation behaviors of nano-sized carbide strengthened UFG ferritic steel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liang, J. W.; Shen, Y. F.; Zhang, C. S.

Here, the microstructures and mechanical properties of a low-alloy medium-carbon steel with a duplex microstructure composed of nanoscale spheroidized carbides in ultrafine-grained (UFG) ferritic steel are examined. The average grain size of the studied steel is ~ 430 nm, and these grains coexist with numerous carbides. Neutron diffraction reveals that the intensity of (011) and (022) peaks for the UFG sample is significantly enhanced, suggesting that the (011)//RD texture is a result of the warm rolling process. The lattice parameter of UFG steel is smaller than that of a martensitic steel (M steel) counterpart, indicating a lower carbon concentration inmore » the lattice. The estimated dislocation densities for M steel and UFG steel are 2.59 × 10 14 cm –2 and 1.76 × 10 12 cm –2, respectively. The UFG steel reveals a nearly isotropic lattice strain response under initial tension from 0 to 450 MPa, where the lattice strains of the (110), (002), and (112) planes are identical. The increase of lattice strain of the (110) plane becomes smaller than that of the (002) and (112) planes as the stress exceeds 450 MPa, suggesting that the nanosized carbides contribute to the hardening ability by promoting the accumulation of geometrically necessary dislocations around the particles, and the (110) lattice becomes harder compared to the other two planes.« less

In situ neutron diffraction in quantifying deformation behaviors of nano-sized carbide strengthened UFG ferritic steel

DOE PAGES

Liang, J. W.; Shen, Y. F.; Zhang, C. S.; ...

2018-04-25

Here, the microstructures and mechanical properties of a low-alloy medium-carbon steel with a duplex microstructure composed of nanoscale spheroidized carbides in ultrafine-grained (UFG) ferritic steel are examined. The average grain size of the studied steel is ~ 430 nm, and these grains coexist with numerous carbides. Neutron diffraction reveals that the intensity of (011) and (022) peaks for the UFG sample is significantly enhanced, suggesting that the (011)//RD texture is a result of the warm rolling process. The lattice parameter of UFG steel is smaller than that of a martensitic steel (M steel) counterpart, indicating a lower carbon concentration inmore » the lattice. The estimated dislocation densities for M steel and UFG steel are 2.59 × 10 14 cm –2 and 1.76 × 10 12 cm –2, respectively. The UFG steel reveals a nearly isotropic lattice strain response under initial tension from 0 to 450 MPa, where the lattice strains of the (110), (002), and (112) planes are identical. The increase of lattice strain of the (110) plane becomes smaller than that of the (002) and (112) planes as the stress exceeds 450 MPa, suggesting that the nanosized carbides contribute to the hardening ability by promoting the accumulation of geometrically necessary dislocations around the particles, and the (110) lattice becomes harder compared to the other two planes.« less

Effect of Heat-Treatment on the Phases of Ni-Mn-Ga Magnetic Shape Memory Alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huq, Ashfia; Ari-Gur, Pnina; Kimmel, Giora

2009-01-01

The Heusler alloys Ni50Mn25+xGa25-x display magnetic shape memory effect (MSM) with very fast and large reversible strain under magnetic fields. This large strain and the speed of reaction make MSM alloys attractive as smart materials. Our crystallographic investigation of these alloys, focused on non-stoichiometric composition with excess of manganese. Using neutron diffraction, we revealed the necessary processing parameters to achieve and preserve the homogeneous metastable one-phase martensitic structure that is needed for an MSM effect at room temperature.

Residual Stresses in 21-6-9 Stainless Steel Warm Forgings

DOE Office of Scientific and Technical Information (OSTI.GOV)

Everhart, Wesley A.; Lee, Jordan D.; Broecker, Daniel J.

Forging residual stresses are detrimental to the production and performance of derived machined parts due to machining distortions, corrosion drivers and fatigue crack drivers. Residual strains in a 21-6-9 stainless steel warm High Energy Rate Forging (HERF) were measured via neutron diffraction. The finite element analysis (FEA) method was used to predict the residual stresses that occur during forging and water quenching. The experimentally measured residual strains were used to calibrate simulations of the three-dimensional residual stress state of the forging. ABAQUS simulation tools predicted residual strains that tend to match with experimental results when varying yield strength is considered.

High-resolution 2-D Bragg diffraction reveal heterogeneous domain transformation behavior in a bulk relaxor ferroelectric

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pramanick, Abhijit, E-mail: apramani@cityu.edu.hk; Stoica, Alexandru D.; An, Ke

2016-08-29

In-situ measurement of fine-structure of neutron Bragg diffraction peaks from a relaxor single-crystal using a time-of-flight instrument reveals highly heterogeneous mesoscale domain transformation behavior under applied electric fields. It is observed that only ∼25% of domains undergo reorientation or phase transition contributing to large average strains, while at least 40% remain invariant and exhibit microstrains. Such insights could be central for designing new relaxor materials with better performance and longevity. The current experimental technique can also be applied to resolve complex mesoscale phenomena in other functional materials.

High-resolution 2-D Bragg diffraction reveal heterogeneous domain transformation behavior in a bulk relaxor ferroelectric

DOE PAGES

Pramanick, Abhijit; Stoica, Alexandru D.; An, Ke

2016-09-02

In-situ measurement of fine-structure of neutron Bragg diffraction peaks from a relaxor single-crystal using a time-of-flight instrument reveals highly heterogeneous mesoscale domain transformation behavior under applied electric fields. We observed that only 25% of domains undergo reorienta- tion or phase transition contributing to large average strains, while at least 40% remain invariant and exhibit microstrains. Such insights could be central for designing new relaxor materials with better performance and longevity. The current experimental technique can also be applied to resolve com- plex mesoscale phenomena in other functional materials.

Novel diamond cells for neutron diffraction using multi-carat CVD anvils.

PubMed

Boehler, R; Molaison, J J; Haberl, B

2017-08-01

Traditionally, neutron diffraction at high pressure has been severely limited in pressure because low neutron flux required large sample volumes and therefore large volume presses. At the high-flux Spallation Neutron Source at the Oak Ridge National Laboratory, we have developed new, large-volume diamond anvil cells for neutron diffraction. The main features of these cells are multi-carat, single crystal chemical vapor deposition diamonds, very large diffraction apertures, and gas membranes to accommodate pressure stability, especially upon cooling. A new cell has been tested for diffraction up to 40 GPa with an unprecedented sample volume of ∼0.15 mm 3 . High quality spectra were obtained in 1 h for crystalline Ni and in ∼8 h for disordered glassy carbon. These new techniques will open the way for routine megabar neutron diffraction experiments.

Investigation of microstructure in additive manufactured Inconel 625 by spatially resolved neutron transmission spectroscopy

DOE PAGES

Tremsin, Anton S.; Gao, Yan; Dial, Laura C.; ...

2016-07-08

Non-destructive testing techniques based on neutron imaging and diffraction can provide information on the internal structure of relatively thick metal samples (up to several cm), which are opaque to other conventional non-destructive methods. Spatially resolved neutron transmission spectroscopy is an extension of traditional neutron radiography, where multiple images are acquired simultaneously, each corresponding to a narrow range of energy. The analysis of transmission spectra enables studies of bulk microstructures at the spatial resolution comparable to the detector pixel. In this study we demonstrate the possibility of imaging (with ~100 μm resolution) distribution of some microstructure properties, such as residual strain,more » texture, voids and impurities in Inconel 625 samples manufactured with an additive manufacturing method called direct metal laser melting (DMLM). Although this imaging technique can be implemented only in a few large-scale facilities, it can be a valuable tool for optimization of additive manufacturing techniques and materials and for correlating bulk microstructure properties to manufacturing process parameters. Additionally, the experimental strain distribution can help validate finite element models which many industries use to predict the residual stress distributions in additive manufactured components.« less

Investigation of microstructure in additive manufactured Inconel 625 by spatially resolved neutron transmission spectroscopy.

PubMed

Tremsin, Anton S; Gao, Yan; Dial, Laura C; Grazzi, Francesco; Shinohara, Takenao

2016-01-01

Non-destructive testing techniques based on neutron imaging and diffraction can provide information on the internal structure of relatively thick metal samples (up to several cm), which are opaque to other conventional non-destructive methods. Spatially resolved neutron transmission spectroscopy is an extension of traditional neutron radiography, where multiple images are acquired simultaneously, each corresponding to a narrow range of energy. The analysis of transmission spectra enables studies of bulk microstructures at the spatial resolution comparable to the detector pixel. In this study we demonstrate the possibility of imaging (with ~100 μm resolution) distribution of some microstructure properties, such as residual strain, texture, voids and impurities in Inconel 625 samples manufactured with an additive manufacturing method called direct metal laser melting (DMLM). Although this imaging technique can be implemented only in a few large-scale facilities, it can be a valuable tool for optimization of additive manufacturing techniques and materials and for correlating bulk microstructure properties to manufacturing process parameters. In addition, the experimental strain distribution can help validate finite element models which many industries use to predict the residual stress distributions in additive manufactured components.

Investigation of microstructure in additive manufactured Inconel 625 by spatially resolved neutron transmission spectroscopy

NASA Astrophysics Data System (ADS)

Tremsin, Anton S.; Gao, Yan; Dial, Laura C.; Grazzi, Francesco; Shinohara, Takenao

2016-01-01

Non-destructive testing techniques based on neutron imaging and diffraction can provide information on the internal structure of relatively thick metal samples (up to several cm), which are opaque to other conventional non-destructive methods. Spatially resolved neutron transmission spectroscopy is an extension of traditional neutron radiography, where multiple images are acquired simultaneously, each corresponding to a narrow range of energy. The analysis of transmission spectra enables studies of bulk microstructures at the spatial resolution comparable to the detector pixel. In this study we demonstrate the possibility of imaging (with 100 μm resolution) distribution of some microstructure properties, such as residual strain, texture, voids and impurities in Inconel 625 samples manufactured with an additive manufacturing method called direct metal laser melting (DMLM). Although this imaging technique can be implemented only in a few large-scale facilities, it can be a valuable tool for optimization of additive manufacturing techniques and materials and for correlating bulk microstructure properties to manufacturing process parameters. In addition, the experimental strain distribution can help validate finite element models which many industries use to predict the residual stress distributions in additive manufactured components.

Investigation of microstructure in additive manufactured Inconel 625 by spatially resolved neutron transmission spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tremsin, Anton S.; Gao, Yan; Dial, Laura C.

Non-destructive testing techniques based on neutron imaging and diffraction can provide information on the internal structure of relatively thick metal samples (up to several cm), which are opaque to other conventional non-destructive methods. Spatially resolved neutron transmission spectroscopy is an extension of traditional neutron radiography, where multiple images are acquired simultaneously, each corresponding to a narrow range of energy. The analysis of transmission spectra enables studies of bulk microstructures at the spatial resolution comparable to the detector pixel. In this study we demonstrate the possibility of imaging (with ~100 μm resolution) distribution of some microstructure properties, such as residual strain,more » texture, voids and impurities in Inconel 625 samples manufactured with an additive manufacturing method called direct metal laser melting (DMLM). Although this imaging technique can be implemented only in a few large-scale facilities, it can be a valuable tool for optimization of additive manufacturing techniques and materials and for correlating bulk microstructure properties to manufacturing process parameters. Additionally, the experimental strain distribution can help validate finite element models which many industries use to predict the residual stress distributions in additive manufactured components.« less

Investigation of microstructure in additive manufactured Inconel 625 by spatially resolved neutron transmission spectroscopy

PubMed Central

Tremsin, Anton S.; Gao, Yan; Dial, Laura C.; Grazzi, Francesco; Shinohara, Takenao

2016-01-01

Abstract Non-destructive testing techniques based on neutron imaging and diffraction can provide information on the internal structure of relatively thick metal samples (up to several cm), which are opaque to other conventional non-destructive methods. Spatially resolved neutron transmission spectroscopy is an extension of traditional neutron radiography, where multiple images are acquired simultaneously, each corresponding to a narrow range of energy. The analysis of transmission spectra enables studies of bulk microstructures at the spatial resolution comparable to the detector pixel. In this study we demonstrate the possibility of imaging (with ~100 μm resolution) distribution of some microstructure properties, such as residual strain, texture, voids and impurities in Inconel 625 samples manufactured with an additive manufacturing method called direct metal laser melting (DMLM). Although this imaging technique can be implemented only in a few large-scale facilities, it can be a valuable tool for optimization of additive manufacturing techniques and materials and for correlating bulk microstructure properties to manufacturing process parameters. In addition, the experimental strain distribution can help validate finite element models which many industries use to predict the residual stress distributions in additive manufactured components. PMID:27877885

Experimental measurement of lattice strain pole figures using synchrotron x rays

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miller, M.P.; Bernier, J.V.; Park, J.-S.

This article describes a system for mechanically loading test specimens in situ for the determination of lattice strain pole figures and their evolution in multiphase alloys via powder diffraction. The data from these experiments provide insight into the three-dimensional mechanical response of a polycrystalline aggregate and represent an extremely powerful material model validation tool. Relatively thin (0.5 mm) iron/copper specimens were axially strained using a mechanical loading frame beyond the macroscopic yield strength of the material. The loading was halted at multiple points during the deformation to conduct a diffraction experiment using a 0.5x0.5 mm{sup 2} monochromatic (50 keV) xmore » ray beam. Entire Debye rings of data were collected for multiple lattice planes ({l_brace}hkl{r_brace}'s) in both copper and iron using an online image plate detector. Strain pole figures were constructed by rotating the loading frame about the specimen transverse direction. Ideal powder patterns were superimposed on each image for the purpose of geometric correction. The chosen reference material was cerium (IV) oxide powder, which was spread in a thin layer on the downstream face of the specimen using petroleum jelly to prevent any mechanical coupling. Implementation of the system at the A2 experimental station at the Cornell High Energy Synchrotron Source (CHESS) is described. The diffraction moduli measured at CHESS were shown to compare favorably to in situ data from neutron-diffraction experiments conducted on the same alloys.« less

Characterization of beryllium deformation using in-situ x-ray diffraction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Magnuson, Eric Alan; Brown, Donald William; Clausen, Bjorn

2015-08-24

Beryllium’s unique mechanical properties are extremely important in a number of high performance applications. Consequently, accurate models for the mechanical behavior of beryllium are required. However, current models are not sufficiently microstructure aware to accurately predict the performance of beryllium under a range of processing and loading conditions. Previous experiments conducted using the SMARTS and HIPPO instruments at the Lujan Center(LANL), have studied the relationship between strain rate and texture development, but due to the limitations of neutron diffraction studies, it was not possible to measure the response of the material in real-time. In-situ diffraction experiments conducted at the Advancedmore » Photon Source have allowed the real time measurement of the mechanical response of compressed beryllium. Samples of pre-strained beryllium were reloaded orthogonal to their original load path to show the reorientation of already twinned grains. Additionally, the in-situ experiments allowed the real time tracking of twin evolution in beryllium strained at high rates. The data gathered during these experiments will be used in the development and validation of a new, microstructure aware model of the constitutive behavior of beryllium.« less

The early development of neutron diffraction: science in the wings of the Manhattan Project

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mason, T. E., E-mail: masont@ornl.gov; Gawne, T. J.; Nagler, S. E.

2013-01-01

Early neutron diffraction experiments performed in 1944 using the first nuclear reactors are described. Although neutron diffraction was first observed using radioactive decay sources shortly after the discovery of the neutron, it was only with the availability of higher intensity neutron beams from the first nuclear reactors, constructed as part of the Manhattan Project, that systematic investigation of Bragg scattering became possible. Remarkably, at a time when the war effort was singularly focused on the development of the atomic bomb, groups working at Oak Ridge and Chicago carried out key measurements and recognized the future utility of neutron diffraction quitemore » independent of its contributions to the measurement of nuclear cross sections. Ernest O. Wollan, Lyle B. Borst and Walter H. Zinn were all able to observe neutron diffraction in 1944 using the X-10 graphite reactor and the CP-3 heavy water reactor. Subsequent work by Wollan and Clifford G. Shull, who joined Wollan’s group at Oak Ridge in 1946, laid the foundations for widespread application of neutron diffraction as an important research tool.« less

Multiscale Modeling and Process Optimization for Engineered Microstructural Complexity

DTIC Science & Technology

2007-10-26

Ferroelectric Ceramics , Materials Science Forum, 404-407, 413-418 2002. 42. R. T. Brewer, H. A. Atwater Rapid biaxial texture development during...Multiscale Study of Internal Stress and Texture in Electroceramics, 106th Annual Meeting of the American Ceramic Society, Indianapolis, Indiana, 20...Rogan, Texture and Strain Analysis of PZT by In-Situ Neutron Diffraction, MRS Spring Meeting, San Francisco, CA; April 2002. 43. E. Ustundag

Novel diamond cells for neutron diffraction using multi-carat CVD anvils

DOE PAGES

Boehler, R.; Molaison, J. J.; Haberl, B.

2017-08-17

Traditionally, neutron diffraction at high pressure has been severely limited in pressure because low neutron flux required large sample volumes and therefore large volume presses. At the high-flux Spallation Neutron Source at the Oak Ridge National Laboratory, we have developed in this paper new, large-volume diamond anvil cells for neutron diffraction. The main features of these cells are multi-carat, single crystal chemical vapor deposition diamonds, very large diffraction apertures, and gas membranes to accommodate pressure stability, especially upon cooling. A new cell has been tested for diffraction up to 40 GPa with an unprecedented sample volume of ~0.15 mm 3.more » High quality spectra were obtained in 1 h for crystalline Ni and in ~8 h for disordered glassy carbon. Finally, these new techniques will open the way for routine megabar neutron diffraction experiments.« less

Orthodontic archwire composition and phase analyses by neutron spectroscopy.

PubMed

Tian, Kun V; Festa, Giulia; Basoli, Francesco; Laganà, Giuseppina; Scherillo, Antonella; Andreani, Carla; Bollero, Patrizio; Licoccia, Silvia; Senesi, Roberto; Cozza, Paola

2017-05-31

Quantitative metallurgical and phase analyses employing neutron diffraction technique were conducted on two as-received commercial rectangular austenitic stainless steel orthodontic archwires, G&H and Azdent, 0.43×0.64 mm (0.017×0.025 inch). Results showed a bi-phase structure containing martensitic phase (45.67% for G&H and 6.62% for Azdent) in addition to the expected metastable austenite. The former may be a strain-induced phase-transformation arising during the cold working process of wire fabrication. Further neutron resonance capture analysis determinations provided atomic and isotopic compositions, including alloying elements in each sample, complementary to the results of traditional energy dispersive X-ray spectroscopy. Together, these results assist in relating commercial alloying recipes and processing histories with mechanical performance, strength and ductility in particular.

Symmetry and light stuffing of H o 2 T i 2 O 7 ,   E r 2 T i 2 O 7 , and Y b 2 T i 2 O 7 characterized by synchrotron x-ray diffraction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baroudi, Kristen; Gaulin, Bruce D.; Lapidus, Saul H.

2015-07-01

The Ho2Ti2O7, Er2Ti2O7 and Yb2Ti2O7 pyrochlores were studied by synchrotron X-ray diffraction to determine whether the (002) peak, forbidden in the pyrochlore space group Fd-3m but observed in single crystal neutron scattering measurements, is present due to a deviation of their pyrochlore structure from Fd-3m symmetry. Synchrotron diffraction measurements on precisely synthesized stoichiometric and non-stoichiometric powders and a crushed floating zone crystal of Ho2Ti2O7 revealed that the (002) reflection is absent in all cases to a sensitivity of approximately one part in 30,000 of the strongest X-ray diffraction peak. This indicates to high sensitivity that the structural space group ofmore » these rare earth titanate pyrochlores is Fd-3m, and that thus the (002) peak observed in the neutron scattering experiments has a non-structural origin. The cell parameters and internal strain for lightly stuffed Ho2+xTi2-xO7 are also presented.« less

Investigation on the Residual Stress State of Drawn Tubes by Numerical Simulation and Neutron Diffraction Analysis

PubMed Central

Palkowski, Heinz; Brück, Sebastian; Pirling, Thilo; Carradò, Adele

2013-01-01

Cold drawing is widely applied in the industrial production of seamless tubes, employed for various mechanical applications. During pre-processing, deviations in tools and their adjustment lead to inhomogeneities in the geometry of the tubes and cause a gradient in residuals. In this paper a three dimensional finite element (3D-FE)-model is presented which was developed to calculate the change in wall thickness, eccentricity, ovality and residual macro-stress state of the tubes, produced by cold drawing. The model simulates the drawing process of tubes, drawn with and without a plug. For finite element modelling, the commercial software package Abaqus was used. To validate the model, neutron strain imaging measurements were performed on the strain imaging instrument SALSA at the Institute Laue Langevin (ILL, Grenoble, France) on a series of SF-copper tubes, drawn under controlled laboratory conditions, varying the drawing angle and the plug geometry. It can be stated that there is sufficient agreement between the finite element method (FEM)-calculation and the neutron stress determination. PMID:28788380

High temperature deformation mechanism in hierarchical and single precipitate strengthened ferritic alloys by in situ neutron diffraction studies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Song, Gian; Sun, Zhiqian; Li, Lin

Here, the ferritic Fe-Cr-Ni-Al-Ti alloys strengthened by hierarchical-Ni 2TiAl/NiAl or single-Ni 2TiAl precipitates have been developed and received great attentions due to their superior creep resistance, as compared to conventional ferritic steels. Although the significant improvement of the creep resistance is achieved in the hierarchical-precipitate-strengthened ferritic alloy, the in-depth understanding of its high-temperature deformation mechanisms is essential to further optimize the microstructure and mechanical properties, and advance the development of the creep resistant materials. In the present study, in-situ neutron diffraction has been used to investigate the evolution of elastic strain of constitutive phases and their interactions, such as load-transfer/load-relaxationmore » behavior between the precipitate and matrix, during tensile deformation and stress relaxation at 973 K, which provide the key features in understanding the governing deformation mechanisms. Crystal-plasticity finite-element simulations were employed to qualitatively compare the experimental evolution of the elastic strain during tensile deformation at 973 K. It was found that the coherent elastic strain field in the matrix, created by the lattice misfit between the matrix and precipitate phases for the hierarchical-precipitate-strengthened ferritic alloy, is effective in reducing the diffusional relaxation along the interface between the precipitate and matrix phases, which leads to the strong load-transfer capability from the matrix to precipitate.« less

High Temperature Deformation Mechanism in Hierarchical and Single Precipitate Strengthened Ferritic Alloys by In Situ Neutron Diffraction Studies

PubMed Central

Song, Gian; Sun, Zhiqian; Li, Lin; Clausen, Bjørn; Zhang, Shu Yan; Gao, Yanfei; Liaw, Peter K.

2017-01-01

The ferritic Fe-Cr-Ni-Al-Ti alloys strengthened by hierarchical-Ni2TiAl/NiAl or single-Ni2TiAl precipitates have been developed and received great attentions due to their superior creep resistance, as compared to conventional ferritic steels. Although the significant improvement of the creep resistance is achieved in the hierarchical-precipitate-strengthened ferritic alloy, the in-depth understanding of its high-temperature deformation mechanisms is essential to further optimize the microstructure and mechanical properties, and advance the development of the creep resistant materials. In the present study, in-situ neutron diffraction has been used to investigate the evolution of elastic strain of constitutive phases and their interactions, such as load-transfer/load-relaxation behavior between the precipitate and matrix, during tensile deformation and stress relaxation at 973 K, which provide the key features in understanding the governing deformation mechanisms. Crystal-plasticity finite-element simulations were employed to qualitatively compare the experimental evolution of the elastic strain during tensile deformation at 973 K. It was found that the coherent elastic strain field in the matrix, created by the lattice misfit between the matrix and precipitate phases for the hierarchical-precipitate-strengthened ferritic alloy, is effective in reducing the diffusional relaxation along the interface between the precipitate and matrix phases, which leads to the strong load-transfer capability from the matrix to precipitate. PMID:28387230

High temperature deformation mechanism in hierarchical and single precipitate strengthened ferritic alloys by in situ neutron diffraction studies

DOE PAGES

Song, Gian; Sun, Zhiqian; Li, Lin; ...

2017-04-07

Here, the ferritic Fe-Cr-Ni-Al-Ti alloys strengthened by hierarchical-Ni 2TiAl/NiAl or single-Ni 2TiAl precipitates have been developed and received great attentions due to their superior creep resistance, as compared to conventional ferritic steels. Although the significant improvement of the creep resistance is achieved in the hierarchical-precipitate-strengthened ferritic alloy, the in-depth understanding of its high-temperature deformation mechanisms is essential to further optimize the microstructure and mechanical properties, and advance the development of the creep resistant materials. In the present study, in-situ neutron diffraction has been used to investigate the evolution of elastic strain of constitutive phases and their interactions, such as load-transfer/load-relaxationmore » behavior between the precipitate and matrix, during tensile deformation and stress relaxation at 973 K, which provide the key features in understanding the governing deformation mechanisms. Crystal-plasticity finite-element simulations were employed to qualitatively compare the experimental evolution of the elastic strain during tensile deformation at 973 K. It was found that the coherent elastic strain field in the matrix, created by the lattice misfit between the matrix and precipitate phases for the hierarchical-precipitate-strengthened ferritic alloy, is effective in reducing the diffusional relaxation along the interface between the precipitate and matrix phases, which leads to the strong load-transfer capability from the matrix to precipitate.« less

Deformation and Phase Transformation Processes in Polycrystalline NiTi and NiTiHf High Temperature Shape Memory Alloys

NASA Technical Reports Server (NTRS)

Benafan, Othmane

2012-01-01

The deformation and transformation mechanisms of polycrystalline Ni49.9Ti50.1 and Ni50.3Ti29.7Hf20 (in at.%) shape memory alloys were investigated by combined experimental and modeling efforts aided by an in situ neutron diffraction technique at stress and temperature. The thermomechanical response of the low temperature martensite, the high temperature austenite phases, and changes between these two states during thermomechanical cycling were probed and reported. In the cubic austenite phase, stress-induced martensite, deformation twinning and slip processes were observed which helped in constructing a deformation map that contained the limits over which each of the identified mechanisms was dominant. Deformation of the monoclinic martensitic phase was also investigated where the microstructural changes (texture, lattice strains, and phase fractions) during room-temperature deformation and subsequent thermal cycling were compared to the bulk macroscopic response. When cycling between these two phases, the evolution of inelastic strains, along with the shape setting procedures were examined and used for the optimization of the transformation properties as a function of deformation levels and temperatures. Finally, this work was extended to the development of multiaxial capabilities at elevated temperatures for the in situ neutron diffraction measurements of shape memory alloys on the VULCAN Diffractometer at Oak Ridge National Laboratory.

The early development of neutron diffraction: science in the wings of the Manhattan Project

PubMed Central

Mason, T. E.; Gawne, T. J.; Nagler, S. E.; Nestor, M. B.; Carpenter, J. M.

2013-01-01

Although neutron diffraction was first observed using radioactive decay sources shortly after the discovery of the neutron, it was only with the availability of higher intensity neutron beams from the first nuclear reactors, constructed as part of the Manhattan Project, that systematic investigation of Bragg scattering became possible. Remarkably, at a time when the war effort was singularly focused on the development of the atomic bomb, groups working at Oak Ridge and Chicago carried out key measurements and recognized the future utility of neutron diffraction quite independent of its contributions to the measurement of nuclear cross sections. Ernest O. Wollan, Lyle B. Borst and Walter H. Zinn were all able to observe neutron diffraction in 1944 using the X-10 graphite reactor and the CP-3 heavy water reactor. Subsequent work by Wollan and Clifford G. Shull, who joined Wollan’s group at Oak Ridge in 1946, laid the foundations for widespread application of neutron diffraction as an important research tool. PMID:23250059

Development of a Neutron Diffraction Based Experiemental Capability for Investigating Hydraulic Fracturing for EGS-like Conditions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Polsky, Yarom; Anovitz, Lawrence; An, Ke

2013-01-01

Hydraulic fracturing to enhance formation permeability is an established practice in the Oil & Gas (O&G) industry and is expected to be an enabler for EGS. However, it is rarely employed in conventional geothermal systems and there are significant questions regarding the translation of practice from O&G to both conventional geothermal and EGS applications. Lithological differences(sedimentary versus crystalline rocks, significantly greater formation temperatures and different desired fracture characteristics are among a number of factors that are likely to result in a gap of understanding of how to manage hydraulic fracturing practice for geothermal. Whereas the O&G community has had bothmore » the capital and the opportunity to develop its understanding of hydraulic fracturing operations empirically in the field as well through extensive R&D efforts, field testing opportunities for EGS are likely to be minimal due to the high expense of hydraulic fracturing field trials. A significant portion of the knowledge needed to guide the management of geothermal/EGS hydraulic fracturing operations will therefore likely have to come from experimental efforts and simulation. This paper describes ongoing efforts at Oak Ridge National Laboratory (ORNL) to develop an experimental capability to map the internal stresses/strains in core samples subjected to triaxial stress states and temperatures representative of EGS-like conditions using neutron diffraction based strain mapping techniques. This capability is being developed at ORNL\\'s Spallation Neutron Source, the world\\'s most powerful pulsed neutron source and is still in a proof of concept phase. A specialized pressure cell has been developed that permits independent radial and axial fluid pressurization of core samples, with axial flow through capability and a temperature rating up to 300 degrees C. This cell will ultimately be used to hydraulically pressurize EGS-representative core samples to conditions of imminent fracture and map the associated internal strain states of the sample. This will hopefully enable a more precise mapping of the rock material failure envelope, facilitate a more refined understanding of the mechanism of hydraulically induced rock fracture, particularly in crystalline rocks, and serve as a platform for validating and improving fracture simulation codes. The elements of the research program and preliminary strain mapping results of a Sierra White granite sample subjected only to compressive loading will be discussed in this paper.« less

Work Hardening, Dislocation Structure, and Load Partitioning in Lath Martensite Determined by In Situ Neutron Diffraction Line Profile Analysis

NASA Astrophysics Data System (ADS)

Harjo, Stefanus; Kawasaki, Takuro; Tomota, Yo; Gong, Wu; Aizawa, Kazuya; Tichy, Geza; Shi, Zengmin; Ungár, Tamas

2017-09-01

A lath martensite steel containing 0.22 mass pct carbon was analyzed in situ during tensile deformation by high-resolution time-of-flight neutron diffraction to clarify the large work-hardening behavior at the beginning of plastic deformation. The diffraction peaks in plastically deformed states exhibit asymmetries as the reflection of redistributions of the stress and dislocation densities/arrangements in two lath packets: soft packet, where the dislocation glides are favorable, and hard packet, where they are unfavorable. The dislocation density was as high as 1015 m-2 in the as-heat-treated state. During tensile straining, the load and dislocation density became different between the two lath packets. The dislocation character and arrangement varied in the hard packet but hardly changed in the soft packet. In the hard packet, dislocations that were mainly screw-type in the as-heat-treated state became primarily edge-type and rearranged towards a dipole character related to constructing cell walls. The hard packet played an important role in the work hardening in martensite, which could be understood by considering the increase in dislocation density along with the change in dislocation arrangement.

Future directions in high-pressure neutron diffraction

NASA Astrophysics Data System (ADS)

Guthrie, M.

2015-04-01

The ability to manipulate structure and properties using pressure has been well known for many centuries. Diffraction provides the unique ability to observe these structural changes in fine detail on lengthscales spanning atomic to nanometre dimensions. Amongst the broad suite of diffraction tools available today, neutrons provide unique capabilities of fundamental importance. However, to date, the growth of neutron diffraction under extremes of pressure has been limited by the weakness of available sources. In recent years, substantial government investments have led to the construction of a new generation of neutron sources while existing facilities have been revitalized by upgrades. The timely convergence of these bright facilities with new pressure-cell technologies suggests that the field of high-pressure (HP) neutron science is on the cusp of substantial growth. Here, the history of HP neutron research is examined with the hope of gleaning an accurate prediction of where some of these revolutionary capabilities will lead in the near future. In particular, a dramatic expansion of current pressure-temperature range is likely, with corresponding increased scope for extreme-conditions science with neutron diffraction. This increase in coverage will be matched with improvements in data quality. Furthermore, we can also expect broad new capabilities beyond diffraction, including in neutron imaging, small angle scattering and inelastic spectroscopy.

Evolution of Residual-Strain Distribution through an Overload-Induced Retardation Period during Fatigue Crack Growth

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, S. Y.; Sun, Yinan; An, Ke

2010-01-01

Neutron diffraction was employed to investigate the crack-growth retardation phenomenon after a single tensile overload by mapping both one-dimensional and two-dimensional residual-strain distributions around the crack tip in a series of compact-tension specimens representing various crack-growth stages through an overload-induced retardation period. The results clearly show a large compressive residual-strain field near the crack tip immediately after the overload. As the fatigue crack propagates through the overload-induced plastic zone, the compressive residual strains are gradually relaxed, and a new compressive residual-strain field is developed around the propagating crack tip, illustrating that the subsequent fatigue-induced plastic zone grows out of themore » large plastic zone caused by the overloading. The relationship between the overload-induced plastic zone and subsequent fatigue-induced plastic zone, and its influence on the residual-strain distributions in the perturbed plastic zone are discussed.« less

POWTEX Neutron Diffractometer at FRM II - New Perspectives in Rock Deformation and Recrystallisation Analysis

NASA Astrophysics Data System (ADS)

Walter, J. M.; Stipp, M.; Ullemeyer, K.; Klein, H.; Leiss, B.; Hansen, B.; Kuhs, W. F.

2011-12-01

Neutron diffraction has become a routine method in Geoscience for the quantitative analysis of crystallographic preferred orientations (CPOs) and for (experimental) powder diffraction. Quantitative texture analysis is a common tool for the investigation of fabric development in mono- and polyphase rocks, their deformation histories and kinematics. Furthermore the quantitative characterization of anisotropic physical properties by bulk texture measurements can be achieved due to the high penetration capabilities of neutrons. To cope with increasing needs for beam time at neutron diffraction facilities with the corresponding technical characteristics and equipment, POWTEX (POWder and TEXture Diffractometer) is designed as a high-intensity diffractometer at the neutron research reactor FRM II in Garching, Germany by groups from the RWTH Aachen, Forschungszentrum Jülich and the University of Göttingen. Complementary to existing neutron diffractometers (SKAT at Dubna, Russia; GEM at ISIS, UK; HIPPO at Los Alamos, USA; D20 at ILL, France; and the local STRESS-SPEC and SPODI at FRM II) the layout of POWTEX is focused on fast (texture) measurements for either time-resolved experiments or the measurement of larger sample series as necessary for the study of large scale geological structures. By utilizing a range of neutron wavelengths simultaneously (TOF-technique), a high flux (~1 x 107 n/cm2s) and a high detector coverage ( 9.8 sr) effective texture measurements without sample tilting and rotation are possible. Furthermore the instrument and the angular detector resolution is sufficient for strong recrystallisation textures as well as weak textures of polyphase rocks. Thereby large sample environments will be implemented at POWTEX allowing in-situ time-resolved texture measurements during deformation experiments on rocksalt, ice and other materials. Furthermore a furnace for 3D-recrystallisation analysis of single grains will be realized complementary to the furnace that already exists for fine grained materials at the synchrotron beamline BW5 at HASYLAB, Germany (e.g. Klein et al. 2009). The in-situ triaxial deformation apparatus is operated by a uniaxial spindle drive with a maximum axial load of 200 kN, which will be redesigned to minimize shadowing effects on the detector. The HT experiments will be carried out in uniaxial compression or extension and an upgrade to triaxial deformation conditions is envisaged. The load frame can alternatively be used for ice deformation by inserting a cryostat cell for temperatures down to 77 K with a triaxial apparatus allowing also simple shear experiments on ice. Strain rates range between 10-8 and 10-3 s-1 reaching to at least 50 % axial strain. The furnace for the recrystallization analysis will be a mirror furnace with temperatures up to 1500° C, which will be rotatable around a vertical axis to obtain the required stereologic orientation information.

In Situ Neutron Diffraction Study of the Influence of Microstructure on the Mechanical Response of Additively Manufactured 304L Stainless Steel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brown, D. W.; Adams, D. P.; Balogh, L.

In situ neutron diffraction measurements were completed for this study during tensile and compressive deformation of stainless steel 304L additively manufactured (AM) using a high power directed energy deposition process. Traditionally produced wrought 304L material was also studied for comparison. The AM material exhibited roughly 200 MPa higher flow stress relative to the wrought material. Crystallite size, crystallographic texture, dislocation density, and lattice strains were all characterized to understand the differences in the macroscopic mechanical behavior. The AM material’s initial dislocation density was about 10 times that of the wrought material, and the flow strength of both materials obeyed themore » Taylor equation, indicating that the AM material’s increased yield strength was primarily due to greater dislocation density. Finally, a ~50 MPa flow strength tension/compression asymmetry was observed in the AM material, and several potential causes were examined.« less

Structure of alkali tellurite glasses from neutron diffraction and molecular orbital calculations

NASA Astrophysics Data System (ADS)

Niida, Haruki; Uchino, Takashi; Jin, Jisun; Kim, Sae-Hoon; Fukunaga, Toshiharu; Yoko, Toshinobu

2001-01-01

The structure of pure TeO2 and alkali tellurite glasses has been examined by neutron diffraction and ab initio molecular orbital methods. The experimental radial distribution functions along with the calculated results have demonstrated that the basic structural units in tellurite glasses change from highly strained TeO4 trigonal bipyramids to more regular TeO3 trigonal pyramids with increasing alkali content. It has also been shown that the TeO3 trigonal pyramids do not exist in the form of isolated units in the glass network but interact with each other to form intertrigonal Te⋯O linkages. The present results suggest that nonbridging oxygen (NBO) atoms in tellurite glasses do not exist in their "pure" form; that is, all the NBO atoms in TeO3 trigonal bipyramids will interact with the first- and/or second-neighbor Te atoms, resulting in the three-dimensional continuous random network even in tellurite glasses with over 30 mol % of alkali oxides.

Residual Stress Analysis in Girth-welded Ferritic and Austenitic Steel Pipes Using Neutron and X-Ray Diffraction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hempel, Nico; Bunn, Jeffrey R; Nitschke-Pagel, Thomas

This paper is dedicated to the thorough experimental analysis of the residual stresses in the vicinity of tubular welds and the mechanisms involved in their formation. Pipes made of a ferritic-pearlitic structural steel and an austenitic stainless steel are investigated in this study. The pipes feature a similar geometry and are MAG welded with two passes and comparable parameters. Residual strain mappings are carried out using X-ray and neutron diffraction. The combined use of both techniques permits both near-surface and through-wall analyses of the residual stresses. The findings allow for a consistent interpretation of the mechanisms accounting for the formationmore » of the residual stress fields due to the welding process. Since the results are similar for both materials, it can be concluded that residual stresses induced by phase transformations, which can occur in the structural steel, play a minor role in this regard.« less

In Situ Neutron Diffraction Study of the Influence of Microstructure on the Mechanical Response of Additively Manufactured 304L Stainless Steel

DOE PAGES

Brown, D. W.; Adams, D. P.; Balogh, L.; ...

2017-10-10

In situ neutron diffraction measurements were completed for this study during tensile and compressive deformation of stainless steel 304L additively manufactured (AM) using a high power directed energy deposition process. Traditionally produced wrought 304L material was also studied for comparison. The AM material exhibited roughly 200 MPa higher flow stress relative to the wrought material. Crystallite size, crystallographic texture, dislocation density, and lattice strains were all characterized to understand the differences in the macroscopic mechanical behavior. The AM material’s initial dislocation density was about 10 times that of the wrought material, and the flow strength of both materials obeyed themore » Taylor equation, indicating that the AM material’s increased yield strength was primarily due to greater dislocation density. Finally, a ~50 MPa flow strength tension/compression asymmetry was observed in the AM material, and several potential causes were examined.« less

X-ray and neutron diffraction studies of crystallinity in hydroxyapatite coatings.

PubMed

Girardin, E; Millet, P; Lodini, A

2000-02-01

To standardize industrial implant production and make comparisons between different experimental results, we have to be able to quantify the crystallinity of hydroxyapatite. Methods of measuring crystallinity ratio were developed for various HA samples before and after plasma spraying. The first series of methods uses X-ray diffraction. The advantage of these methods is that X-ray diffraction equipment is used widely in science and industry. In the second series, a neutron diffraction method is developed and the results recorded are similar to those obtained by the modified X-ray diffraction methods. The advantage of neutron diffraction is the ability to obtain measurements deep inside a component. It is a nondestructive method, owing to the very low absorption of neutrons in most materials. Copyright 2000 John Wiley & Sons, Inc.

A history of neutrons in biology: the development of neutron protein crystallography at BNL and LANL.

PubMed

Schoenborn, Benno P

2010-11-01

The first neutron diffraction data were collected from crystals of myoglobin almost 42 years ago using a step-scan diffractometer with a single detector. Since then, major advances have been made in neutron sources, instrumentation and data collection and analysis, and in biochemistry. Fundamental discoveries about enzyme mechanisms, biological complex structures, protein hydration and H-atom positions have been and continue to be made using neutron diffraction. The promise of neutrons has not changed since the first crystal diffraction data were collected. Today, with the developments of beamlines at spallation neutron sources and the use of the Laue method for data collection, the field of neutrons in structural biology has renewed vitality.

High-Pressure Neutron Diffraction Studies for Materials Sciences and Energy Sciences

NASA Astrophysics Data System (ADS)

Zhao, Y.; Los Alamos High Pressure Materials Research Team

2013-05-01

The development of neutron diffraction under extreme pressure (P) and temperature (T) conditions is highly valuable to condensed matter physics, crystal chemistry, materials sciences, as well as earth and planetary sciences. We have incorporated a 500-ton press TAP-98 into the HiPPO diffractometer at LANSCE to conduct in situ high P-T neutron diffraction experiments. We have worked out a large gem-crystal anvil cell, ZAP, to conduct neutron diffraction experiments at high-P and low-T. The ZAP cell can be used to integrate multiple experimental techniques such as neutron diffraction, laser spectroscopy, and ultrasonic interferometery. Recently, we have developed high-P low-T gas/fluid cells in conjunction with neutron diffraction and inelastic neutron scattering instruments. These techniques enable in-situ and real-time examination of gas uptake/release processes and allow high-resolution time-dependent determination of changes in crystal structure and related reaction kinetics. We have successfully used these techniques to study the equation of state, structural phase transition, and thermo-mechanical properties of metals, ceramics, and minerals. We have conducted researches on the formation of methane and hydrogen clathrates, and hydrogen adsorption of the inclusion compounds such as the recently discovered metal-organic frameworks (MOFs). The aim of our research is to accurately map phase diagram, lattice parameters, thermal parameters, bond lengths, bond angles, neighboring atomic environments, and phase stability in P-T-X space. We are currently developing further high P-T technology with a new "true" triaxial loading press, TAP_6x, to compress cubic sample package to achieve pressures up to 20 GPa and temperatures up to 2000 K in routine experiments. The implementation of TAP_6x300 with high-pressure neutron beamlines is underway for simultaneous high P-T neutron diffraction, ultrasonic, calorimetry, radiography, and tomography studies. Studies based on high-pressure neutron diffraction are important for multidisciplinary science, particularly for the theoretical/computational modeling/simulations.;

The early development of neutron diffraction: Science in the wings of the Manhattan Project

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mason, Thom; Gawne, Timothy J; Nagler, Stephen E

2012-01-01

Although neutron diffraction was first observed using radioactive decay sources shortly after the discovery of the neutron, it was only with the availability of higher intensity neutron beams from the first nuclear reactors, constructed as part of the Manhattan project, that systematic investigation of Bragg scattering became possible. Remarkably, at a time when the war effort was singularly focused on the development of the atomic bomb, groups working at Oak Ridge and Chicago carried out key measurements and recognized the future utility of neutron diffraction quite independent of its contributions to the measurements of nuclear cross sections. Ernest O. Wollan,more » Lyle B. Borst, and Walter H. Zinn were all able to observe neutron diffraction in 1944 using the X-10 graphite reactor and the CP-3 heavy water reactor.« less

Advanced setup for high-pressure and low-temperature neutron diffraction at hydrostatic conditions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lokshin, Konstantin A.; Zhao Yusheng

2005-06-15

We describe a design of the experimental setup for neutron diffraction studies at low temperatures and hydrostatic pressure. The significant benefit of the setup, compared to the previous methods, is that it makes possible the simultaneous collection of neutrons diffracted at the 30 deg. -150 deg. range with no contamination by the primary scattering from the sample surroundings and without cutting out the incident and diffracted beams. The suggested design is most useful for third-generation time-of-flight diffractometers and constant wavelength instruments. Application of the setup expands the capabilities of high-pressure neutron diffraction, allowing time-resolved kinetics and structural studies, multihistogram Rietveld,more » and pair distribution function and texture analyses. The high efficiency of the setup was proven for the HIPPO diffractometer at Los Alamos Neutron Science Center under pressures up to 10 kbar and temperatures from 4 to 300 K.« less

Neutron diffraction study of the inverse spinels Co2TiO4 and Co2SnO4

NASA Astrophysics Data System (ADS)

Thota, S.; Reehuis, M.; Maljuk, A.; Hoser, A.; Hoffmann, J.-U.; Weise, B.; Waske, A.; Krautz, M.; Joshi, D. C.; Nayak, S.; Ghosh, S.; Suresh, P.; Dasari, K.; Wurmehl, S.; Prokhnenko, O.; Büchner, B.

2017-10-01

We report a detailed single-crystal and powder neutron diffraction study of Co2TiO4 and Co2SnO4 between the temperature 1.6 and 80 K to probe the spin structure in the ground state. For both compounds the strongest magnetic intensity was observed for the (111)M reflection due to ferrimagnetic ordering, which sets in below TN=48.6 and 41 K for Co2TiO4 and Co2SnO4 , respectively. An additional low intensity magnetic reflection (200)M was noticed in Co2TiO4 due to the presence of an additional weak antiferromagnetic component. Interestingly, from both the powder and single-crystal neutron data of Co2TiO4 , we noticed a significant broadening of the magnetic (111)M reflection, which possibly results from the disordered character of the Ti and Co atoms on the B site. Practically, the same peak broadening was found for the neutron powder data of Co2SnO4 . On the other hand, from our single-crystal neutron diffraction data of Co2TiO4 , we found a spontaneous increase of particular nuclear Bragg reflections below the magnetic ordering temperature. Our data analysis showed that this unusual effect can be ascribed to the presence of anisotropic extinction, which is associated to a change of the mosaicity of the crystal. In this case, it can be expected that competing Jahn-Teller effects acting along different crystallographic axes can induce anisotropic local strain. In fact, for both ions Ti3 + and Co3 +, the 2 tg levels split into a lower dx y level yielding a higher twofold degenerate dx z/dy z level. As a consequence, one can expect a tetragonal distortion in Co2TiO4 with c /a <1 , which we could not significantly detect in the present work.

Neutron and X-ray single-crystal diffraction from protein microcrystals via magnetically oriented microcrystal arrays in gels.

PubMed

Tsukui, Shu; Kimura, Fumiko; Kusaka, Katsuhiro; Baba, Seiki; Mizuno, Nobuhiro; Kimura, Tsunehisa

2016-07-01

Protein microcrystals magnetically aligned in D2O hydrogels were subjected to neutron diffraction measurements, and reflections were observed for the first time to a resolution of 3.4 Å from lysozyme microcrystals (∼10 × 10 × 50 µm). This result demonstrated the possibility that magnetically oriented microcrystals consolidated in D2O gels may provide a promising means to obtain single-crystal neutron diffraction from proteins that do not crystallize at the sizes required for neutron diffraction structure determination. In addition, lysozyme microcrystals aligned in H2O hydrogels allowed structure determination at a resolution of 1.76 Å at room temperature by X-ray diffraction. The use of gels has advantages since the microcrystals are measured under hydrated conditions.

Intergranular Strain Evolution During Biaxial Loading: A Multiscale FE-FFT Approach

NASA Astrophysics Data System (ADS)

Upadhyay, M. V.; Capek, J.; Van Petegem, S.; Lebensohn, R. A.; Van Swygenhoven, H.

2017-05-01

Predicting the macroscopic and microscopic mechanical response of metals and alloys subjected to complex loading conditions necessarily requires a synergistic combination of multiscale material models and characterization techniques. This article focuses on the use of a multiscale approach to study the difference between intergranular lattice strain evolution for various grain families measured during in situ neutron diffraction on dog bone and cruciform 316L samples. At the macroscale, finite element simulations capture the complex coupling between applied forces and gauge stresses in cruciform geometries. The predicted gauge stresses are used as macroscopic boundary conditions to drive a mesoscale full-field elasto-viscoplastic fast Fourier transform crystal plasticity model. The results highlight the role of grain neighborhood on the intergranular strain evolution under uniaxial and equibiaxial loading.

Low temperature nickel titanium iron shape memory alloys: Actuator engineering and investigation of deformation mechanisms using in situ neutron diffraction at Los Alamos National Laboratory

NASA Astrophysics Data System (ADS)

Krishnan, Vinu B.

Shape memory alloys are incorporated as actuator elements due to their inherent ability to sense a change in temperature and actuate against external loads by undergoing a shape change as a result of a temperature-induced phase transformation. The cubic so-called austenite to the trigonal so-called R-phase transformation in NiTiFe shape memory alloys offers a practical temperature range for actuator operation at low temperatures, as it exhibits a narrow temperature-hysteresis with a desirable fatigue response. Overall, this work is an investigation of selected science and engineering aspects of low temperature NiTiFe shape memory alloys. The scientific study was performed using in situ neutron diffraction measurements at the newly developed low temperature loading capability on the Spectrometer for Materials Research at Temperature and Stress (SMARTS) at Los Alamos National Laboratory and encompasses three aspects of the behavior of Ni46.8Ti50Fe3.2 at 92 K (the lowest steady state temperature attainable with the capability). First, in order to study deformation mechanisms in the R-phase in NiTiFe, measurements were performed at a constant temperature of 92 K under external loading. Second, with the objective of examining NiTiFe in one-time, high-stroke, actuator applications (such as in safety valves), a NiTiFe sample was strained to approximately 5% (the R-phase was transformed to B19' phase in the process) at 92 K and subsequently heated to full strain recovery under a load. Third, with the objective of examining NiTiFe in cyclic, low-stroke, actuator applications (such as in cryogenic thermal switches), a NiTiFe sample was strained to 1% at 92 K and subsequently heated to full strain recovery under load. Neutron diffraction spectra were recorded at selected time and stress intervals during these experiments. The spectra were subsequently used to obtain quantitative information related to the phase-specific strain, texture and phase fraction evolution using the Rietveld technique. The mechanical characterization of NiTiFe alloys using the cryogenic capability at SMARTS provided considerable insight into the mechanisms of phase transformation and twinning at cryogenic temperatures. Both mechanisms contribute to shape memory and pseudoelasticity phenomena. Three phases (R, B19' and B33 phases) were found to coexist at 92 K in the unloaded condition (nominal holding stress of 8 MPa). For the first time the elastic modulus of R-phase was reported from neutron diffraction experiments. Furthermore, for the first time a base-centered orthorhombic (B33) martensitic phase was identified experimentally in a NiTi-based shape memory alloy. The orthorhombic B33 phase has been theoretically predicted in NiTi from density function theory (DFT) calculations but hitherto has never been observed experimentally. The orthorhombic B33 phase was observed while observing shifting of a peak (identified to be {021}B33) between the {111}R and {100}B19' peaks in the diffraction spectra collected during loading. Given the existing ambiguity in the published literature as to whether the trigonal R-phase belongs to the P3 or P3¯ space groups, Rietveld analyses were separately carried out incorporating the symmetries associated with both space groups and the impact of this choice evaluated. The constrained recovery of the B19' phase to the R-phase recorded approximately 4% strain recovery between 150 K and 170 K, with half of that recovery occurring between 160 K and 162 K. Additionally, the aforementioned research methodology developed for Ni46.8Ti50Fe3.2 shape memory alloys was applied to experiments performed on a new high temperature Ni 29.5Ti50.5Pd20 shape memory alloys. The engineering aspect focused on the development of (i) a NiTiFe based thermal conduction switch that minimized the heat gradient across the shape memory actuator element, (ii) a NiTiFe based thermal conduction switch that incorporated the actuator element in the form of helical springs, and (iii) a NiTi based release mechanism. Patents are being filed for all the three shape memory actuators developed as a part of this work. This work was supported by grants from SRI, NASA (NAG3-2751) and NSF (CAREER DMR-0239512) to UCF. Additionally, this work benefited from the use of the Lujan Center at the Los Alamos Neutron Science Center, funded by the United States Department of Energy, Office of Basic Energy Sciences, under Contract No. W-7405-ENG-36.

Role of B19' martensite deformation in stabilizing two-way shape memory behavior in NiTi

DOE PAGES

Benafan, O.; Padula, S. A.; Noebe, R. D.; ...

2012-11-01

Deformation of a B19' martensitic, polycrystallineNi49.9Ti50.1 (at. %) shape memoryalloy and its influence on the magnitude and stability of the ensuing two-way shape memory effect (TWSME) was investigated by combined ex situ mechanical experimentation and in situneutron diffraction measurements at stress and temperature. The microstructural changes (texture, lattice strains, and phase fractions) during room-temperature deformation and subsequent thermal cycling were captured and compared to the bulk macroscopic response of the alloy. With increasing uniaxial strain, it was observed that B19' martensite deformed by reorientation and detwinning with preferred selection of the (1¯50) M and (010) M variants, (201¯) B19' deformationmore » twinning, and dislocation activity. These mechanisms were indicated by changes in bulk texture from the neutron diffraction measurements. Partial reversibility of the reoriented variants and deformation twins was also captured upon load removal and thermal cycling, which after isothermal deformation to strains between 6% and 22% resulted in a strong TWSME. Consequently, TWSME functional parameters including TWSME strain, strain reduction, and transformation temperatures were characterized and it was found that prior martensite deformation to 14% strain provided the optimum condition for the TWSME, resulting in a stable two-way shape memory strain of 2.2%. Thus, isothermal deformation of martensite was found to be a quick and efficient method for creating a strong and stable TWSME in Ni₄₉.₉Ti₅₀.₁.« less

Direct evidence for the spin cycloid in strained nanoscale bismuth ferrite thin films

PubMed Central

Bertinshaw, Joel; Maran, Ronald; Callori, Sara J.; Ramesh, Vidya; Cheung, Jeffery; Danilkin, Sergey A.; Lee, Wai Tung; Hu, Songbai; Seidel, Jan; Valanoor, Nagarajan; Ulrich, Clemens

2016-01-01

Magnonic devices that utilize electric control of spin waves mediated by complex spin textures are an emerging direction in spintronics research. Room-temperature multiferroic materials, such as bismuth ferrite (BiFeO3), would be ideal candidates for this purpose. To realize magnonic devices, a robust long-range spin cycloid with well-known direction is desired, since it is a prerequisite for the magnetoelectric coupling. Despite extensive investigation, the stabilization of a large-scale uniform spin cycloid in nanoscale (100 nm) thin BiFeO3 films has not been accomplished. Here, we demonstrate cycloidal spin order in 100 nm BiFeO3 thin films through the careful choice of crystallographic orientation, and control of the electrostatic and strain boundary conditions. Neutron diffraction, in conjunction with X-ray diffraction, reveals an incommensurate spin cycloid with a unique [11] propagation direction. While this direction is different from bulk BiFeO3, the cycloid length and Néel temperature remain equivalent to bulk at room temperature. PMID:27585637

Martensite phase stress and the strengthening mechanism in TRIP steel by neutron diffraction.

PubMed

Harjo, Stefanus; Tsuchida, Noriyuki; Abe, Jun; Gong, Wu

2017-11-09

Two TRIP-aided multiphase steels with different carbon contents (0.2 and 0.4 mass%) were analyzed in situ during tensile deformation by time-of-flight neutron diffraction to clarify the deformation induced martensitic transformation behavior and its role on the strengthening mechanism. The difference in the carbon content affected mainly the difference in the phase fractions before deformation, where the higher carbon content increased the phase fraction of retained austenite (γ). However, the changes in the relative fraction of martensitic transformation with respect to the applied strain were found to be similar in both steels since the carbon concentrations in γ were similar regardless of different carbon contents. The phase stress of martensite was found much larger than that of γ or bainitic ferrite since the martensite was generated at the beginning of plastic deformation. Stress contributions to the flow stress were evaluated by multiplying the phase stresses and their phase fractions. The stress contribution from martensite was observed increasing during plastic deformation while that from bainitic ferrite hardly changing and that from γ decreasing.

POWTEX - A new High-Intensity Powder and Texture Diffractometer at FRM II, Garching Germany

NASA Astrophysics Data System (ADS)

Walter, J. M.; Brückel, T.; Dronskowski, R.; Hansen, B. T.; Houben, A.; Klein, H.; Leiss, B.; Vollbrecht, A.; Sowa, H.

2009-05-01

In recent years, neutron diffraction has become a routine tool in Geoscience for experimental high-field (HP/HT/HH) powder diffraction and for the quantitative analysis of the crystallographic preferred orientation (CPO). Quantitative texture analysis is e.g. involved in the research fields of fabric development in mono- and polyphase rocks, deformation histories and kinematics during mountain building processes and the characterization of flow kinematics in lava flows. Secondly the quantitative characterization of anisotropic physical properties of both rock and analogue materials is conducted by bulk texture measurements of sometimes larger sample volumes. This is easily achievable by neutron diffraction due to the high penetration capabilities of the neutrons. The resulting geoscientific need for increased measuring time at neutron diffraction facilities with the corresponding technical characteristics and equipment will in future be satisfied by this high-intensity diffractometer at the neutron research reactor FRM II in Garching, Germany. It will be built by a consortium of groups from the RWTH Aachen, Forschungszentrum Jülich and the University of Göttingen, who will also operate the instrument. The diffractometer will be optimized to high intensities (flux) with an equivalent sufficient resolution for polyphase rocks. Furthermore a broad range of d-values (0.5 to 15 Å) will be measurable. The uniqueness of this instrument is the geoscientific focus on different sample environments for in situ-static and deformation experiments (stress, strain and annealing/recrystallisation) and (U)HP/(U)HT experiments. A LP/LT or atmospheric-P deformation rig for in situ-deformation experiments on ice, halite or rock analogue materials is planned, to allow in situ-measurements of the texture development during deformation and annealing. Additionally a uniaxial HT/MP deformation apparatus for salt deformation experiments and an adapted Griggs- type deformation rig are also designated. Furthermore an uniaxial stress frame for in situ stress investigations is planned to conduct simultaneous measurements of stress, elastic or plastic deformation and texture. Other sample environments for geoscientific application will be HP/HT furnaces and pressure cells for powder diffraction investigations. Furthermore the diffractometer will be built in combination with a high-pressure multi anvil up to 25 GPa and 2500 K built by the University of Bayreuth at the same beam line. The detector concept allows single shot texture measurements and therefore the measurement of larger geological sample series as necessary for the investigations of complete geological structures. This concept is complementary to the geoscience neutron texture diffractometer in Dubna, Russia and the stress diffractometer STRESS-SPEC located also at the Garching research reactor. For powder diffraction the diffractometer will be complementary to the existing high-resolution powder diffractometer SPODI at the FRM-II. It will offer the possibility of short, high-intensity parametric powder diffraction measurements in dependency of temperature, electrical, magnetic and stress fields due to the higher flux at the sample. The optimization to high-intensities and therefore short measuring times will also allow time-resolved measurements of kinetic reactions even of small sample volumes.

Intergrannular strain evolution in a zircaloy-4 alloy with Widmanstatten microstructure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Clausen, Bjorn; Vogel, Sven C; Garlea, Eena

2009-01-01

A Zircaloy-4 alloy with Widmanstatten-Basketweave microstructure and random texture has been used to study the deformation systems responsible for the polycrystalline plasticity at the grain level. The evolution of internal strain and bulk texture is investigated using neutron diffraction and an elasto-plastic self-consistent (EPSC) modeling scheme. The macroscopic stress-strain behavior and intergranular (hkil-specific) strain development, parallel and perpendicular to the loading direction, were measured in-situ during uniaxial tensile loading. Then, the EPSC model was employed to simulate the experimental results. This modeling scheme accounts for the thermal anisotropy; elastic-plastic properties of the constituent grains; and activation, reorientation, and stress relaxationmore » associated with twinning. The agreement between the experiment and the model will be discussed as well as the critical resolved shear stresses (CRSS) and the hardening coefficients obtained from the model.« less

Analysis of Short and Long Range Atomic Order in Nanocrystalline Diamonds with Application of Powder Diffractometry

NASA Technical Reports Server (NTRS)

Palosz, B.; Grzanka, E.; Stelmakh, S.; Pielaszek, R.; Bismayer, U.; Neuefiend, J.; Weber, H.-P.; Proffen, T.; VonDreele, R.; Palosz, W.;

Energy-dispersive neutron imaging and diffraction of magnetically driven twins in a Ni2MnGa single crystal magnetic shape memory alloy

NASA Astrophysics Data System (ADS)

Kabra, Saurabh; Kelleher, Joe; Kockelmann, Winfried; Gutmann, Matthias; Tremsin, Anton

2016-09-01

Single crystals of a partially twinned magnetic shape memory alloy, Ni2MnGa, were imaged using neutron diffraction and energy-resolved imaging techniques at the ISIS spallation neutron source. Single crystal neutron diffraction showed that the crystal produces two twin variants with a specific crystallographic relationship. Transmission images were captured using a time of flight MCP/Timepix neutron counting detector. The twinned and untwinned regions were clearly distinguishable in images corresponding to narrow-energy transmission images. Further, the spatially-resolved transmission spectra were used to elucidate the orientations of the crystallites in the different volumes of the crystal.

Application of Powder Diffraction Methods to the Analysis of Short- and Long-Range Atomic Order in Nanocrystalline Diamond and SiC: The Concept of the Apparent Lattice Parameter (alp)

NASA Technical Reports Server (NTRS)

Palosz, B.; Grzanka, E.; Gierlotka, S.; Stelmakh, S.; Pielaszek, R.; Bismayer, U.; Weber, H.-P.; Palosz, W.

2003-01-01

Two methods of the analysis of powder diffraction patterns of diamond and SiC nanocrystals are presented: (a) examination of changes of the lattice parameters with diffraction vector Q ('apparent lattice parameter', alp) which refers to Bragg scattering, and (b), examination of changes of inter-atomic distances based on the analysis of the atomic Pair Distribution Function, PDF. Application of these methods was studied based on the theoretical diffraction patterns computed for models of nanocrystals having (i) a perfect crystal lattice, and (ii), a core-shell structure, i.e. constituting a two-phase system. The models are defined by the lattice parameter of the grain core, thickness of the surface shell, and the magnitude and distribution of the strain field in the shell. X-ray and neutron experimental diffraction data of nanocrystalline SiC and diamond powders of the grain diameter from 4 nm up to micrometers were used. The effects of the internal pressure and strain at the grain surface on the structure are discussed based on the experimentally determined dependence of the alp values on the Q-vector, and changes of the interatomic distances with the grain size determined experimentally by the atomic Pair Distribution Function (PDF) analysis. The experimental results lend a strong support to the concept of a two-phase, core and the surface shell structure of nanocrystalline diamond and SiC.

Analysis and interpretation of diffraction data from complex, anisotropic materials

NASA Astrophysics Data System (ADS)

Tutuncu, Goknur

Most materials are elastically anisotropic and exhibit additional anisotropy beyond elastic deformation. For instance, in ferroelectric materials the main inelastic deformation mode is via domains, which are highly anisotropic crystallographic features. To quantify this anisotropy of ferroelectrics, advanced X-ray and neutron diffraction methods were employed. Extensive sets of data were collected from tetragonal BaTiO3, PZT and other ferroelectric ceramics. Data analysis was challenging due to the complex constitutive behavior of these materials. To quantify the elastic strain and texture evolution in ferroelectrics under loading, a number of data analysis techniques such as the single peak and Rietveld methods were used and their advantages and disadvantages compared. It was observed that the single peak analysis fails at low peak intensities especially after domain switching while the Rietveld method does not account for lattice strain anisotropy although it overcomes the low intensity problem via whole pattern analysis. To better account for strain anisotropy the constant stress (Reuss) approximation was employed within the Rietveld method and new formulations to estimate lattice strain were proposed. Along the way, new approaches for handling highly anisotropic lattice strain data were also developed and applied. All of the ceramics studied exhibited significant changes in their crystallographic texture after loading indicating non-180° domain switching. For a full interpretation of domain switching the spherical harmonics method was employed in Rietveld. A procedure for simultaneous refinement of multiple data sets was established for a complete texture analysis. To further interpret diffraction data, a solid mechanics model based on the self-consistent approach was used in calculating lattice strain and texture evolution during the loading of a polycrystalline ferroelectric. The model estimates both the macroscopic average response of a specimen and its hkl-dependent lattice strains for different reflections. It also tracks the number of grains (or domains) contributing to each reflection and allows for domain switching. The agreement between the model and experimental data was found to be satisfactory.

Investigation of Renal Stones by X-ray and Neutron Diffraction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baeva, M.; Boianova, A.; Beskrovnyi, A. I.

2007-04-23

Renal stones were investigated by X-ray diffraction. The obtained results showed only one crystal phase in every sample. With the aim to verify eventual availability of second phase (under 3 volume %) the same renal stones were investigated by neutron diffraction. The neutron spectra proved that additional crystal phase was absent in the renal stones. The obtained results are scientific-practical, in aid of the medicine, especially in the case of renal stone disease.

Amplified effect of mild plastic anisotropy on residual stress and strain anisotropy

DOE PAGES

Prime, Michael B.

2017-07-01

Axisymmetric indentation of a geometrically axisymmetric disk produced residual stresses by non-uniform plastic deformation. The 2024 aluminum plate used to make the disk exhibited mild plastic anisotropy with about 10% lower strength in the transverse direction compared to the rolling and through-thickness directions. Residual stresses and strains in the disk were measured with neutron diffraction, slitting, the contour method, x-ray diffraction and hole drilling. Surprisingly, the residual-stress anisotropy measured in the disk was about 40%, the residual-strain anisotropy was an impressive 100%, and the residual stresses were higher in the weaker direction. The high residual stress anisotropy relative to themore » mild plastic anisotropy and the direction of the highest stress are explained by considering the mechanics of indentation: constraint on deformation provided by the material surrounding the indentation and preferential deformation in the most compliant direction for incremental deformation. By contrast, the much larger anisotropy in residual strain compared to that in residual stress is independent of the fabrication process and is instead explained by considering Hookean elasticity. For Poisson's ratio of 1/3, the relationship simplifies to the residual strain anisotropy equaling the square of the residual stress anisotropy, which matches the observed results (2 ≈ 1.4^2). Furthermore, a lesson from this study is that to accurately predict residual stresses and strains, one must be wary of seemingly reasonable simplifying assumptions such as neglecting mild plastic anisotropy.« less

Amplified effect of mild plastic anisotropy on residual stress and strain anisotropy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Prime, Michael B.

Axisymmetric indentation of a geometrically axisymmetric disk produced residual stresses by non-uniform plastic deformation. The 2024 aluminum plate used to make the disk exhibited mild plastic anisotropy with about 10% lower strength in the transverse direction compared to the rolling and through-thickness directions. Residual stresses and strains in the disk were measured with neutron diffraction, slitting, the contour method, x-ray diffraction and hole drilling. Surprisingly, the residual-stress anisotropy measured in the disk was about 40%, the residual-strain anisotropy was an impressive 100%, and the residual stresses were higher in the weaker direction. The high residual stress anisotropy relative to themore » mild plastic anisotropy and the direction of the highest stress are explained by considering the mechanics of indentation: constraint on deformation provided by the material surrounding the indentation and preferential deformation in the most compliant direction for incremental deformation. By contrast, the much larger anisotropy in residual strain compared to that in residual stress is independent of the fabrication process and is instead explained by considering Hookean elasticity. For Poisson's ratio of 1/3, the relationship simplifies to the residual strain anisotropy equaling the square of the residual stress anisotropy, which matches the observed results (2 ≈ 1.4^2). Furthermore, a lesson from this study is that to accurately predict residual stresses and strains, one must be wary of seemingly reasonable simplifying assumptions such as neglecting mild plastic anisotropy.« less

Wavelength resolved neutron transmission analysis to identify single crystal particles in historical metallurgy

NASA Astrophysics Data System (ADS)

Barzagli, E.; Grazzi, F.; Salvemini, F.; Scherillo, A.; Sato, H.; Shinohara, T.; Kamiyama, T.; Kiyanagi, Y.; Tremsin, A.; Zoppi, Marco

2014-07-01

The phase composition and the microstructure of four ferrous Japanese arrows of the Edo period (17th-19th century) has been determined through two complementary neutron techniques: Position-sensitive wavelength-resolved neutron transmission analysis (PS-WRNTA) and time-of-flight neutron diffraction (ToF-ND). Standard ToF-ND technique has been applied by using the INES diffractometer at the ISIS pulsed neutron source in the UK, while the innovative PS-WRNTA one has been performed at the J-PARC neutron source on the BL-10 NOBORU beam line using the high spatial high time resolution neutron imaging detector. With ToF-ND we were able to reach information about the quantitative distribution of the metal and non-metal phases, the texture level, the strain level and the domain size of each of the samples, which are important parameters to gain knowledge about the technological level of the Japanese weapon. Starting from this base of data, the more complex PS-WRNTA has been applied to the same samples. This experimental technique exploits the presence of the so-called Bragg edges, in the time-of-flight spectrum of neutrons transmitted through crystalline materials, to map the microstructural properties of samples. The two techniques are non-invasive and can be easily applied to archaeometry for an accurate microstructure mapping of metal and ceramic artifacts.

Applying neutron transmission physics and 3D statistical full-field model to understand 2D Bragg-edge imaging

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xie, Qingge; Song, Gian; Gorti, Sarma B.

Bragg-edge imaging, which is also known as neutron radiography, has recently emerged as a novel crystalline characterization technique. Modelling of this novel technique by incorporating various features of the underlying microstructure (including the crystallographic texture, the morphological texture, and the grain size) of the material remains a subject of considerable research and development. In this paper, Inconel 718 samples made by additive manufacturing were investigated by neutron diffraction and neutron radiography techniques. The specimen features strong morphological and crystallographic textures and a highly heterogeneous microstructure. A 3D statistical full-field model is introduced by taking details of the microstructure into accountmore » to understand the experimental neutron radiography results. The Bragg-edge imaging and the total cross section were calculated based on the neutron transmission physics. A good match was obtained between the model predictions and experimental results at different incident beam angles with respect to the sample build direction. The current theoretical approach has the ability to incorporate 3D spatially resolved microstructural heterogeneity information and shows promise in understanding the 2D neutron radiography of bulk samples. With further development to incorporate the heterogeneity in lattice strain in the model, it can be used as a powerful tool in the future to better understand the neutron radiography data.« less

Applying neutron transmission physics and 3D statistical full-field model to understand 2D Bragg-edge imaging

DOE PAGES

Xie, Qingge; Song, Gian; Gorti, Sarma B.; ...

2018-02-21

Bragg-edge imaging, which is also known as neutron radiography, has recently emerged as a novel crystalline characterization technique. Modelling of this novel technique by incorporating various features of the underlying microstructure (including the crystallographic texture, the morphological texture, and the grain size) of the material remains a subject of considerable research and development. In this paper, Inconel 718 samples made by additive manufacturing were investigated by neutron diffraction and neutron radiography techniques. The specimen features strong morphological and crystallographic textures and a highly heterogeneous microstructure. A 3D statistical full-field model is introduced by taking details of the microstructure into accountmore » to understand the experimental neutron radiography results. The Bragg-edge imaging and the total cross section were calculated based on the neutron transmission physics. A good match was obtained between the model predictions and experimental results at different incident beam angles with respect to the sample build direction. The current theoretical approach has the ability to incorporate 3D spatially resolved microstructural heterogeneity information and shows promise in understanding the 2D neutron radiography of bulk samples. With further development to incorporate the heterogeneity in lattice strain in the model, it can be used as a powerful tool in the future to better understand the neutron radiography data.« less

High-pressure cells for study of condensed matter by diffraction and inelastic neutron scattering at low temperatures and in strong magnetic fields

NASA Astrophysics Data System (ADS)

Sadykov, R. A.; Strassle, Th; Podlesnyak, A.; Keller, L.; Fak, B.; Mesot, J.

2017-12-01

We have developed and implemented series of new original clamp high-pressure cells for neutron diffraction and inelastic neutron scattering at low temperatures. The cells design allows one to place them in the standard cryostats or cryomagnets used on neutron sources. Some results obtained for ZnCr2Se4 are demonstrated as an example.

Internal Stress Distribution Measurement of TIG Welded SUS304 Samples Using Neutron Diffraction Technique

NASA Astrophysics Data System (ADS)

Muslih, M. Refai; Sumirat, I.; Sairun; Purwanta

2008-03-01

The distribution of residual stress of SUS304 samples that were undergone TIG welding process with four different electric currents has been measured. The welding has been done in the middle part of the samples that was previously grooved by milling machine. Before they were welded the samples were annealed at 650 degree Celsius for one hour. The annealing process was done to eliminate residual stress generated by grooving process so that the residual stress within the samples was merely produced from welding process. The calculation of distribution of residual stress was carried out by measuring the strains within crystal planes of Fe(220) SUS304. Strain, Young modulus, and Poisson ratio of Fe(220) SUS304 were measured using DN1-M neutron diffractometer. Young modulus and Poisson ratio of Fe(220) SUS304 sample were measured in-situ. The result of calculations showed that distribution of residual stress of SUS304 in the vicinity of welded area is influenced both by treatments given at the samples-making process and by the electric current used during welding process.

Neutron Reflectivity and Grazing Angle Diffraction

PubMed Central

Ankner, J. F.; Majkrzak, C. F.; Satija, S. K.

1993-01-01

Over the last 10 years, neutron reflectivity has emerged as a powerful technique for the investigation of surface and interfacial phenomena in many different fields. In this paper, a short review of some of the work on neutron reflectivity and grazing-angle diffraction as well as a description of the current and planned neutron rcflectometers at NIST is presented. Specific examples of the characterization of magnetic, superconducting, and polymeric surfaces and interfaces are included. PMID:28053457

Diffraction in neutron imaging-A review

NASA Astrophysics Data System (ADS)

Woracek, Robin; Santisteban, Javier; Fedrigo, Anna; Strobl, Markus

2018-01-01

Neutron imaging is a highly successful experimental technique ever since adequate neutron sources were available. In general, neutron imaging is performed with a wide wavelength spectrum for best flux conditions in transmission geometry. Neutrons provide outstanding features in the penetration of many structural materials, which often makes them more suited for bulk sample studies than other forms of radiation, often in particular as they are also highly sensitive to some light elements, especially Hydrogen. In contrast to neutron scattering applications, imaging resolves macroscopic structures, nowadays down to, in the best case, below 10 micrometre, directly in real space. However, since more than a decade there is a growing number of techniques and applications in neutron imaging that - supported by powerful neutron sources - are taking advantage of wavelength resolved measurements. In this review we summarize and discuss this outstanding development and how wavelength resolved transmission neutron imaging is successfully exploiting diffraction mechanisms to access crystal structure information in the Angstrom regime, which conventionally is probed in reciprocal space by diffraction techniques. In particular the combination of information gained in real space and on crystallographic length scales makes this neutron imaging technique a valuable tool for a wide range of new applications, while it also qualifies neutron imaging to fully profit from the new generation of powerful pulsed neutron sources.

Characterisation of the incident beam and current diffraction capabilities on the VESUVIO spectrometer

NASA Astrophysics Data System (ADS)

Romanelli, G.; Krzystyniak, M.; Senesi, R.; Raspino, D.; Boxall, J.; Pooley, D.; Moorby, S.; Schooneveld, E.; Rhodes, N. J.; Andreani, C.; Fernandez-Alonso, F.

2017-09-01

The VESUVIO spectrometer at the ISIS pulsed neutron and muon source is a unique instrument amongst those available at neutron facilities. This is the only inverted-geometry neutron spectrometer accessing values of energy and wavevector transfer above tens of eV and {\\mathringA}-1 , respectively, and where deep inelastic neutron scattering experiments are routinely performed. As such, the procedure at the base of the technique has been previously described in an article published by this journal (Mayers and Reiter 2012 Meas. Sci. Technol. 23 045902). The instrument has recently witnessed an upsurge of interest due to a new trend to accommodate, within a single experiment, neutron diffraction and transmission measurements in addition to deep inelastic neutron scattering. This work presents a broader description of the instrument following these recent developments. In particular, we assess the absolute intensity and two-dimensional profile of the incident neutron beam and the capabilities of the backscattering diffraction banks. All results are discussed in the light of recent changes to the moderator viewed by the instrument. We find that VESUVIO has to be considered a high-resolution diffractometer as much as other diffractometers at ISIS, with a resolution as high as 2× 10-3 in backscattering. Also, we describe the extension of the wavelength range of the instrument to include lower neutron energies for diffraction measurements, an upgrade that could be readily applied to other neutron instruments as well.

High resolution neutron Larmor diffraction using superconducting magnetic Wollaston prisms

DOE PAGES

Li, Fankang; Feng, Hao; Thaler, Alexander N.; ...

2017-04-13

The neutron Larmor diffraction technique has been implemented using superconducting magnetic Wollaston prisms in both single-arm and double-arm configurations. Successful measurements of the coefficient of thermal expansion of a single-crystal copper sample demonstrates that the method works as expected. Our experiment involves a new method of tuning by varying the magnetic field configurations in the device and the tuning results agree well with previous measurements. The difference between single-arm and double-arm configurations has been investigated experimentally. Here, we conclude that this measurement benchmarks the applications of magnetic Wollaston prisms in Larmor diffraction and shows in principle that the setup canmore » be used for inelastic phonon line-width measurements. The achievable resolution for Larmor diffraction is comparable to that using Neutron Resonance Spin Echo (NRSE) coils. Furthermore, the use of superconducting materials in the prisms allows high neutron polarization and transmission efficiency to be achieved.« less

Maximizing Macromolecule Crystal Size for Neutron Diffraction Experiments

NASA Technical Reports Server (NTRS)

Judge, R. A.; Kephart, R.; Leardi, R.; Myles, D. A.; Snell, E. H.; vanderWoerd, M.; Curreri, Peter A. (Technical Monitor)

2002-01-01

A challenge in neutron diffraction experiments is growing large (greater than 1 cu mm) macromolecule crystals. In taking up this challenge we have used statistical experiment design techniques to quickly identify crystallization conditions under which the largest crystals grow. These techniques provide the maximum information for minimal experimental effort, allowing optimal screening of crystallization variables in a simple experimental matrix, using the minimum amount of sample. Analysis of the results quickly tells the investigator what conditions are the most important for the crystallization. These can then be used to maximize the crystallization results in terms of reducing crystal numbers and providing large crystals of suitable habit. We have used these techniques to grow large crystals of Glucose isomerase. Glucose isomerase is an industrial enzyme used extensively in the food industry for the conversion of glucose to fructose. The aim of this study is the elucidation of the enzymatic mechanism at the molecular level. The accurate determination of hydrogen positions, which is critical for this, is a requirement that neutron diffraction is uniquely suited for. Preliminary neutron diffraction experiments with these crystals conducted at the Institute Laue-Langevin (Grenoble, France) reveal diffraction to beyond 2.5 angstrom. Macromolecular crystal growth is a process involving many parameters, and statistical experimental design is naturally suited to this field. These techniques are sample independent and provide an experimental strategy to maximize crystal volume and habit for neutron diffraction studies.

Deformation mechanisms in a precipitation-strengthened ferritic superalloy revealed by in situ neutron diffraction studies at elevated temperatures

DOE PAGES

Huang, Shenyan; Gao, Yanfei; An, Ke; ...

2014-10-22

In this study, the ferritic superalloy Fe–10Ni–6.5Al–10Cr–3.4Mo strengthened by ordered (Ni,Fe)Al B2-type precipitates is a candidate material for ultra-supercritical steam turbine applications above 923 K. Despite earlier success in improving its room-temperature ductility, the creep resistance of this material at high temperatures needs to be further improved, which requires a fundamental understanding of the high-temperature deformation mechanisms at the scales of individual phases and grains. In situ neutron diffraction has been utilized to investigate the lattice strain evolution and the microscopic load-sharing mechanisms during tensile deformation of this ferritic superalloy at elevated temperatures. Finite-element simulations based on the crystal plasticitymore » theory are employed and compared with the experimental results, both qualitatively and quantitatively. Based on these interphase and intergranular load-partitioning studies, it is found that the deformation mechanisms change from dislocation slip to those related to dislocation climb, diffusional flow and possibly grain boundary sliding, below and above 873 K, respectively. Insights into microstructural design for enhancing creep resistance are also discussed.« less

Neutron Diffraction Structure of Melampodin: Its Role in the Reclassification of the Germacranolides

PubMed Central

Watkins, Steven F.; Fischer, Nikolaus H.; Bernal, Ivan

1973-01-01

The precise crystal and molecular structure of melampodin, C21H24O9, was determined from three-dimensional neutron diffraction data collected by counter techniques and phases by direct statistical methods. Crystals are orthorhombic, P212121, a = 8,990(9), b = 14.352(14), c = 16.294(16) Å, V = 2102 Å3, d(calc.) = 1.328 g·cm-3, Z = 4 molecules per unit cell. The structural model was refined by full matrix least-squares of 2303 observed independent reflections, with all 54 atoms treated anisotropically, to R(F) = 5.0%. Hydrogen bonds link melampodin molecules together in the solid state. The conformation of the cyclodeca-1,5-diene ring is such that one intraannular hydrogen atom interacts strongly with one double bond, but there is little or no transannular interaction between double bonds. Strain in the ten-membered ring and in the trans-fused lactone ring is discussed, as are chemical implications of the unsymmetric epoxide in the epoxyangelic acid side chain. The previously suggested reclassification of germacranolide sesquiterpene lactones into four subgroups is supported, and a new convention for configurational representations of the four subgroups is proposed. PMID:16592106

Quarzt Fabric Insights Across a Low P-High T Shear Zone

NASA Astrophysics Data System (ADS)

Gomez Barreiro, J.; Martinez-Catalan, J. R.; Benitez Perez, J.; Wenk, H.; Vogel, S. C.; Alcock, J. E.

2013-12-01

The evolution of mylonitic fabric in quartzites across a Low-P / High-T gradient within the Lugo Dome Extensional system (NW Spain) is analyzed. Quantitative texture measurements with TOF neutron diffraction, Shape preferred orientation (SPO) and Crystal Size Distribution (CSD) analyses were correlated with tectonothermal data to constraint the prevalence of ductile deformative fabrics exposed to cycles of dynamic and static recrystallization. Results suggest two stages in the evolution of mylonites in close correlation to thermal gradient, 1) a pervasive ductile deformation affecting most of the shear zone volume, with the development of symmetric cross girdle c-axes fabric suggesting slip on {c,r,m} and dynamically recrystallized microstructures which resulted into the refinement of the grain-size. 2) An heterogeneous deformation stage where strain partition led to the formation of relatively active and passive domains. During this late stage, at deeper levels, High T detachments show [c]{m} slip system and dynamic recrystallization activation, with monoclinic texture patterns, meanwhile, passive domains followed an static recrystallization with abnormal grain growth and minor variation of early orthogonal texture patterns Neutron diffraction data (cross) and Rietveld model obtained with MAUD (solid line) of a mylonitic quartzite. Some important planes are indicated for the major phases.

Final Technical Report: Application of in situ Neutron Diffraction to Understand the Mechanism of Phase Transitions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chandran, Ravi

In this research, phase transitions in the bulk electrodes for Li-ion batteries were investigated using neutron diffraction (ND) as well as neutron imaging techniques. The objectives of this research is to design of a novel in situ electrochemical cell to obtain Rietveld refinable neutron diffraction experiments using small volume electrodes of various laboratory/research-scale electrodes intended for Li-ion batteries. This cell is also to be used to investigate the complexity of phase transitions in Li(Mg) alloy electrodes, either by diffraction or by neutron imaging, which occur under electrochemical lithiation and delithiation, and to determine aspects of phase transition that enable/limit energymore » storage capacity. Additional objective is to investigate the phase transitions in electrodes made of etched micro-columns of silicon and investigate the effect of particle/column size on phase transitions and nonequilibrium structures. An in situ electrochemical cell was designed successfully and was used to study the phase transitions under in-situ neutron diffraction in both the electrodes (anode/cathode) simultaneously in graphite/LiCoO 2 and in graphite/LiMn 2O 4 cells each with two cells. The diffraction patterns fully validated the working of the in situ cell. Additional experimental were performed using the Si micro-columnar electrodes. The results revealed new lithiation phenomena, as evidenced by mosaicity formation in silicon electrode. These experiments were performed in Vulcan diffractometer at SNS, Oak Ridge National Laboratory. In parallel, the spatial distribution of Li during lithiation and delithiation processes in Li-battery electrodes were investigated. For this purpose, neutron tomographic imaging technique has been used for 3D mapping of Li distribution in bulk Li(Mg) alloy electrodes. It was possible to observe the phase boundary of Li(Mg) alloy indicating phase transition from Li-rich BCC β-phase to Li-lean α-phase. These experiments have been performed at CG-1D Neutron Imaging Prototype Station at SNS.« less

Non-destructive Quantitative Phase Analysis and Microstructural Characterization of Zirconium Coated U-10Mo Fuel Foils via Neutron Diffraction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cummins, Dustin Ray; Vogel, Sven C.; Hollis, Kendall Jon

2016-10-18

This report uses neutron diffraction to investigate the crystal phase composition of uranium-molybdenum alloy foils (U-10Mo) for the CONVERT MP-1 Reactor Conversion Project, and determines the effect on alpha-uranium contamination following the deposition of a Zr metal diffusion layer by various methods: plasma spray deposition of Zr powders at LANL and hot co-rolling with Zr foils at BWXT. In summary, there is minimal decomposition of the gamma phase U-10Mo foil to alpha phase contamination following both plasma spraying and hot co-rolling. The average unit cell volume, i.e. lattice spacing, of the Zr layer can be mathematically extracted from the diffractionmore » data; co-rolled Zr matches well with literature values of bulk Zr, while plasma sprayed Zr shows a slight increase in the lattice spacing, indicative of interstitial oxygen in the lattice. Neutron diffraction is a beneficial alternative to conventional methods of phase composition, i.e. x ray diffraction (XRD) and destructive metallography. XRD has minimal penetration depth in high atomic number materials, particularly uranium, and can only probe the first few microns of the fuel plate; neutrons pass completely through the foil, allowing for bulk analysis of the foil composition and no issues with addition of cladding layers, as in the final, aluminum-clad reactor fuel plates. Destructive metallography requires skilled technicians, cutting of the foil into small sections, hazardous etching conditions, long polishing and microscopy times, etc.; the neutron diffraction system has an automated sample loader and can fit larger foils, so there is minimal analysis preparation; the total spectrum acquisition time is ~ 1 hour per sample. The neutron diffraction results are limited by spectra refinement/calculation times and the availability of the neutron beam source. In the case of LANSCE at Los Alamos, the beam operates ~50% of the year. Following the lessons learned from these preliminary results, optimizations to the process and analysis can be made, and neutron diffraction can become a viable and efficient technique for gamma/alpha phase composition determination for nuclear fuels.« less

Using neutron diffraction to examine the onset of mechanical twinning in calcite rocks

NASA Astrophysics Data System (ADS)

Covey-Crump, S. J.; Schofield, P. F.; Oliver, E. C.

2017-07-01

Experimental calibration of the calcite twin piezometer is complicated by the difficulty of establishing the stresses at which the twins observed in the final deformation microstructures actually formed. In principle, this difficulty may be circumvented if the deformation experiments are performed in a polychromatic neutron beam-line because this allows the elastic strain (and hence stress) in differently oriented grains to be simultaneously monitored from diffraction patterns collected as the experiment is proceeding. To test this idea small strain (<0.3%), uniaxial compression experiments have been performed on Carrara marble (grain size 150 μm) and Solnhofen limestone (5 μm) at temperatures of 20°-600 °C using the ENGIN-X instrument at the ISIS neutron facility, UK. At the lowest temperatures (25 °C Carrara; 200 °C Solnhofen) the deformation response was purely elastic up to the greatest stresses applied (60 MPa Carrara; 175 MPa Solnhofen). The sign of the calcite elastic stiffness component c14 is confirmed to be positive when the obverse setting of the calcite rhombohedral lattice in hexagonal axes is used. In the Carrara marble samples deformed at higher temperatures, elastic twinning was initiated at small stresses (<15 MPa) in grains oriented such that the Schmid factor for twinning was positive on more than one e-twin system. At greater stresses (65 MPa at 200 °C decreasing to 41 MPa at 500 °C) there was an abrupt onset of permanent twinning in grains with large Schmid factors for twinning on any one e-twin system. No twinning was observed in the Solnhofen limestone samples deformed at 200° or 400 °C at applied stresses of <180 MPa. These results highlight the potential of this approach for detecting the onset of twinning and provide, through experiments on samples with different microstructures, a strategy for systematically investigating the effects of microstructural variables on crystallographically-controlled inelastic processes.

Absence of dynamic strain aging in an additively manufactured nickel-base superalloy.

PubMed

Beese, Allison M; Wang, Zhuqing; Stoica, Alexandru D; Ma, Dong

2018-05-25

Dynamic strain aging (DSA), observed macroscopically as serrated plastic flow, has long been seen in nickel-base superalloys when plastically deformed at elevated temperatures. Here we report the absence of DSA in Inconel 625 made by additive manufacturing (AM) at temperatures and strain rates where DSA is present in its conventionally processed counterpart. This absence is attributed to the unique AM microstructure of finely dispersed secondary phases (carbides, N-rich phases, and Laves phase) and textured grains. Based on experimental observations, we propose a dislocation-arrest model to elucidate the criterion for DSA to occur or to be absent as a competition between dislocation pipe diffusion and carbide-carbon reactions. With in situ neutron diffraction studies of lattice strain evolution, our findings provide a new perspective for mesoscale understanding of dislocation-solute interactions and their impact on work-hardening behaviors in high-temperature alloys, and have important implications for tailoring thermomechanical properties by microstructure control via AM.

Grain Orientation Dependence of the Residual Lattice Strain in a Cold Rolled Interstitial-Free Steel

DOE PAGES

Xie, Qingge; Gorti, Sarma B.; Sidor, Jurij; ...

2018-01-10

The experimentally measured grain-orientation-dependent residual lattice strains, evolved in an interstitia-free steel after 70% cold rolling reduction, are studied by means of crystal elastic visco-plastic finite element simulations, which provides a very satisfactory prediction of deformation texture. The calculated residual lattice strain pole figure matches well with the experimentally measured counterpart within the highest density regions of major texture components observed. Both experimental evidence and results of modeling clearly indicate that the residual lattice strain is orientation dependent, based on comprehensive information on the evolution of residual lattice strain in various crystallographic orientations during plastic deformation. It appears that inmore » a cold rolled material, there is a general correlation between the stresses developed just prior to unloading and the residual lattice strains in particular directions. Here, it is also shown that the cumulative plastic shear does not reveal a clear correlation with the components of residual lattice strain while presented in the normal correlation plot, however, this relationship can be better understood by means of the orientation distribution function of residual lattice strain, which can be derived from the neutron or X-ray diffraction experiments.« less

Grain Orientation Dependence of the Residual Lattice Strain in a Cold Rolled Interstitial-Free Steel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xie, Qingge; Gorti, Sarma B.; Sidor, Jurij

The experimentally measured grain-orientation-dependent residual lattice strains, evolved in an interstitia-free steel after 70% cold rolling reduction, are studied by means of crystal elastic visco-plastic finite element simulations, which provides a very satisfactory prediction of deformation texture. The calculated residual lattice strain pole figure matches well with the experimentally measured counterpart within the highest density regions of major texture components observed. Both experimental evidence and results of modeling clearly indicate that the residual lattice strain is orientation dependent, based on comprehensive information on the evolution of residual lattice strain in various crystallographic orientations during plastic deformation. It appears that inmore » a cold rolled material, there is a general correlation between the stresses developed just prior to unloading and the residual lattice strains in particular directions. Here, it is also shown that the cumulative plastic shear does not reveal a clear correlation with the components of residual lattice strain while presented in the normal correlation plot, however, this relationship can be better understood by means of the orientation distribution function of residual lattice strain, which can be derived from the neutron or X-ray diffraction experiments.« less

Combined X-ray and neutron fibre diffraction studies of biological and synthetic polymers

NASA Astrophysics Data System (ADS)

Parrot, I. M.; Urban, V.; Gardner, K. H.; Forsyth, V. T.

2005-08-01

The fibrous state is a natural one for polymer molecules which tend to assume regular helical conformations rather than the globular structures characteristic of many proteins. Fibre diffraction therefore has broad application to the study of a wide range of biological and synthetic polymers. The purpose of this paper is to illustrate the general scope of the method and in particular to demonstrate the impact of a combined approach involving both X-ray and neutron diffraction methods. While the flux of modern X-ray synchrotron radiation sources allows high quality datasets to be recorded with good resolution within a very short space of time, neutron studies can provide unique information through the ability to locate hydrogen or deuterium atoms that are often difficult or impossible to locate using X-ray methods. Furthermore, neutron fibre diffraction methods can, through the ability to selectively label specific parts of a structure, be used to highlight novel aspects of polymer structure that can not be studied using X-rays. Two examples are given. The first describes X-ray and neutron diffraction studies of conformational transitions in DNA. The second describes structural studies of the synthetic high-performance polymer poly(p-phenylene terephthalamide) (PPTA), known commercially as Kevlar® or Twaron®.

Empirically testing vaterite structural models using neutron diffraction and thermal analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chakoumakos, Bryan C.; Pracheil, Brenda M.; Koenigs, Ryan

Otoliths, calcium carbonate (CaCO 3) ear bones, are among the most commonly used age and growth structures of fishes. Most fish otoliths are comprised of the most dense CaCO 3 polymorph, aragonite. Sturgeon otoliths, in contrast, have been characterized as the rare and structurally enigmatic polymorph, vaterite a metastable polymorph of CaCO 3. Vaterite is an important material ranging from biomedical to personal care applications although its crystal structure is highly debated. We characterized the structure of sturgeon otoliths using thermal analysis and neutron powder diffraction, which is used non-destructively. We confirmed that while sturgeon otoliths are primarily composed ofmore » vaterite, they also contain the denser CaCO 3 polymorph, calcite. For the vaterite fraction, neutron diffraction data provide enhanced discrimination of the carbonate group compared to x-ray diffraction data, owing to the different relative neutron scattering lengths, and thus offer the opportunity to uniquely test the more than one dozen crystal structural models that have been proposed for vaterite. Of those, space group P6 522 model, a = 7.1443(4)Å , c = 25.350(4)Å , V = 1121.5(2)Å 3 provides the best fit to the neutron powder diffraction data, and allows for a structure refinement using rigid carbonate groups.« less

Energy research with neutrons (ErwiN) and installation of a fast neutron powder diffraction option at the MLZ, Germany1

PubMed Central

Mühlbauer, Martin J.

2018-01-01

The need for rapid data collection and studies of small sample volumes in the range of cubic millimetres are the main driving forces for the concept of a new high-throughput monochromatic diffraction instrument at the Heinz Maier-Leibnitz Zentrum (MLZ), Germany. A large region of reciprocal space will be accessed by a detector with sufficient dynamic range and microsecond time resolution, while allowing for a variety of complementary sample environments. The medium-resolution neutron powder diffraction option for ‘energy research with neutrons’ (ErwiN) at the high-flux FRM II neutron source at the MLZ is foreseen to meet future demand. ErwiN will address studies of energy-related systems and materials with respect to their structure and uniformity by means of bulk and spatially resolved neutron powder diffraction. A set of experimental options will be implemented, enabling time-resolved studies, rapid parametric measurements as a function of external parameters and studies of small samples using an adapted radial collimator. The proposed powder diffraction option ErwiN will bridge the gap in functionality between the high-resolution powder diffractometer SPODI and the time-of-flight diffractometers POWTEX and SAPHiR at the MLZ. PMID:29896055

Empirically testing vaterite structural models using neutron diffraction and thermal analysis

DOE PAGES

Chakoumakos, Bryan C.; Pracheil, Brenda M.; Koenigs, Ryan; ...

2016-11-18

Otoliths, calcium carbonate (CaCO 3) ear bones, are among the most commonly used age and growth structures of fishes. Most fish otoliths are comprised of the most dense CaCO 3 polymorph, aragonite. Sturgeon otoliths, in contrast, have been characterized as the rare and structurally enigmatic polymorph, vaterite a metastable polymorph of CaCO 3. Vaterite is an important material ranging from biomedical to personal care applications although its crystal structure is highly debated. We characterized the structure of sturgeon otoliths using thermal analysis and neutron powder diffraction, which is used non-destructively. We confirmed that while sturgeon otoliths are primarily composed ofmore » vaterite, they also contain the denser CaCO 3 polymorph, calcite. For the vaterite fraction, neutron diffraction data provide enhanced discrimination of the carbonate group compared to x-ray diffraction data, owing to the different relative neutron scattering lengths, and thus offer the opportunity to uniquely test the more than one dozen crystal structural models that have been proposed for vaterite. Of those, space group P6 522 model, a = 7.1443(4)Å , c = 25.350(4)Å , V = 1121.5(2)Å 3 provides the best fit to the neutron powder diffraction data, and allows for a structure refinement using rigid carbonate groups.« less

New test of the dynamic theory of neutron diffraction by a moving grating

NASA Astrophysics Data System (ADS)

Zakharov, Maxim; Frank, Alexander; Kulin, German; Goryunov, Semyon

2018-04-01

Recently, multiwave dynamical theory of neutron diffraction by a moving grating was developed. The theory predicts that at a certain height of the grating profile a significant suppression of the zero-order diffraction may occur. The experiment to confirm predictions of this theory was performed. The resulting diffracted UCNs spectra were measured using time-of-flight Fourier diffractometer. The experimental data were compared with the results of numerical simulation and were found in a good agreement with theoretical predictions.

Neutron Radiography, Tomography, and Diffraction of Commercial Lithium-ion Polymer Batteries

NASA Astrophysics Data System (ADS)

Butler, Leslie G.; Lehmann, Eberhard H.; Schillinger, Burkhard

Imaging an intact, commercial battery as it cycles and wears is proved possible with neutron imaging. The wavelength range of imaging neutrons corresponds nicely with crystallographic dimensions of the electrochemically active species and the metal elec- trodes are relatively transparent. The time scale of charge/discharge cycling is well matched to dynamic tomography as performed with a golden ratio based projection angle ordering. The hydrogen content does create scatter which tends to blur internal struc- ture. In this report, three neutron experiments will be described: 3D images of charged and discharged batteries were obtained with monochromatic neutrons at the FRM II reactor. 2D images (PSI) of fresh and worn batteries as a function of charge state may show a new wear pattern. In situ neutron diffraction (SNS) of the intact battery provides more information about the concentrations of electrochemical species within the battery as a function of charge state and wear. The combination of 2D imaging, 3D imaging, and diffraction data show how neutron imaging can contribute to battery development and wear monitoring.

Characterization of a neutron imaging setup at the INES facility

NASA Astrophysics Data System (ADS)

Durisi, E. A.; Visca, L.; Albertin, F.; Brancaccio, R.; Corsi, J.; Dughera, G.; Ferrarese, W.; Giovagnoli, A.; Grassi, N.; Grazzi, F.; Lo Giudice, A.; Mila, G.; Nervo, M.; Pastrone, N.; Prino, F.; Ramello, L.; Re, A.; Romero, A.; Sacchi, R.; Salvemini, F.; Scherillo, A.; Staiano, A.

2013-10-01

The Italian Neutron Experimental Station (INES) located at the ISIS pulsed neutron source (Didcot, United Kingdom) provides a thermal neutron beam mainly used for diffraction analysis. A neutron transmission imaging system was also developed for beam monitoring and for aligning the sample under investigation. Although the time-of-flight neutron diffraction is a consolidated technique, the neutron imaging setup is not yet completely characterized and optimized. In this paper the performance for neutron radiography and tomography at INES of two scintillator screens read out by two different commercial CCD cameras is compared in terms of linearity, signal-to-noise ratio, effective dynamic range and spatial resolution. In addition, the results of neutron radiographies and a tomography of metal alloy test structures are presented to better characterize the INES imaging capabilities of metal artifacts in the cultural heritage field.

Neutron Nucleic Acid Crystallography.

PubMed

Chatake, Toshiyuki

2016-01-01

The hydration shells surrounding nucleic acids and hydrogen-bonding networks involving water molecules and nucleic acids are essential interactions for the structural stability and function of nucleic acids. Water molecules in the hydration shells influence various conformations of DNA and RNA by specific hydrogen-bonding networks, which often contribute to the chemical reactivity and molecular recognition of nucleic acids. However, X-ray crystallography could not provide a complete description of structural information with respect to hydrogen bonds. Indeed, X-ray crystallography is a powerful tool for determining the locations of water molecules, i.e., the location of the oxygen atom of H2O; however, it is very difficult to determine the orientation of the water molecules, i.e., the orientation of the two hydrogen atoms of H2O, because X-ray scattering from the hydrogen atom is very small.Neutron crystallography is a specialized tool for determining the positions of hydrogen atoms. Neutrons are not diffracted by electrons, but are diffracted by atomic nuclei; accordingly, neutron scattering lengths of hydrogen and its isotopes are comparable to those of non-hydrogen atoms. Therefore, neutron crystallography can determine both of the locations and orientations of water molecules. This chapter describes the current status of neutron nucleic acid crystallographic research as well as the basic principles of neutron diffraction experiments performed on nucleic acid crystals: materials, crystallization, diffraction experiments, and structure determination.

Twinning-mediated work hardening and texture evolution in CrCoFeMnNi high entropy alloys at cryogenic temperature

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, T. K.; Wu, Z.; Stoica, A. D.

The cryogenic plastic deformation of CrCoFeMnNi high entropy alloy is characterized by three distinct stages based on the change of the work hardening rate. Microstructure and bulk texture at different strain levels were studied by electron backscatter diffraction (EBSD) and neutron diffraction. Our findings indicate that the deformation twins led to the constant work hardening rate at Stage II and resulted in the appearance of <115 >//TA texture component, while the dislocation slip was involved all though the entire plastic deformation. As a result, the twinning-mediated tensile plastic deformation at cryogenic temperature finally induced the strong {111}- < 112 >more » texture component and minor {001} < 110 > texture component accompanied with twinning-induced {115}< 552 > texture component.« less

Twinning-mediated work hardening and texture evolution in CrCoFeMnNi high entropy alloys at cryogenic temperature

DOE PAGES

Liu, T. K.; Wu, Z.; Stoica, A. D.; ...

2017-06-17

The cryogenic plastic deformation of CrCoFeMnNi high entropy alloy is characterized by three distinct stages based on the change of the work hardening rate. Microstructure and bulk texture at different strain levels were studied by electron backscatter diffraction (EBSD) and neutron diffraction. Our findings indicate that the deformation twins led to the constant work hardening rate at Stage II and resulted in the appearance of <115 >//TA texture component, while the dislocation slip was involved all though the entire plastic deformation. As a result, the twinning-mediated tensile plastic deformation at cryogenic temperature finally induced the strong {111}- < 112 >more » texture component and minor {001} < 110 > texture component accompanied with twinning-induced {115}< 552 > texture component.« less

The influence of impurities on the crystal structure and mechanical properties of additive manufactured U–14at.% Nb

DOE PAGES

Wu, Amanda S.; Brown, Donald W.; Clausen, Bjørn; ...

2017-03-01

Uranium-niobium alloys can exist with significantly different microstructures and mechanical properties, heavily influenced by thermomechanical processing history and impurities. In this study, the influence of Ti and other impurities is studied on uranium-14 at.% niobium additively manufactured using laser powder bed fusion. In two different metallic impurity levels were investigated and a Nb equivalent (Nbeq) composition is defined to represent the impurities. Furthermore, in-situ neutron diffraction during compression loading shows that increased Nbeq promotes the formation of γ°-tetragonal phase at the expense of α''-monoclinic phase, resulting in 2 × higher yield strength than water quenched α'' and a strain inducedmore » transformation to α'' with superelastic strains to 4.5%.« less

The influence of impurities on the crystal structure and mechanical properties of additive manufactured U–14at.% Nb

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, Amanda S.; Brown, Donald W.; Clausen, Bjørn

Uranium-niobium alloys can exist with significantly different microstructures and mechanical properties, heavily influenced by thermomechanical processing history and impurities. In this study, the influence of Ti and other impurities is studied on uranium-14 at.% niobium additively manufactured using laser powder bed fusion. In two different metallic impurity levels were investigated and a Nb equivalent (Nbeq) composition is defined to represent the impurities. Furthermore, in-situ neutron diffraction during compression loading shows that increased Nbeq promotes the formation of γ°-tetragonal phase at the expense of α''-monoclinic phase, resulting in 2 × higher yield strength than water quenched α'' and a strain inducedmore » transformation to α'' with superelastic strains to 4.5%.« less

Strain-induced phase transformation at the surface of an AISI-304 stainless steel irradiated to 4.4 dpa and deformed to 0.8% strain

NASA Astrophysics Data System (ADS)

Gussev, M. N.; Field, K. G.; Busby, J. T.

2014-03-01

Surface relief due to localized deformation in a 4.4-dpa neutron-irradiated AISI 304 stainless steel was investigated using scanning electron microscopy coupled with electron backscattering diffraction and scanning transmission electron microscopy. It was found a body-centered-cubic (BCC) phase (deformation-induced martensite) had formed at the surface of the deformed specimen along the steps generated from dislocation channels. Martensitic hill-like formations with widths of ˜1 μm and depths of several microns were observed at channels with heights greater than ˜150 nm above the original surface. Martensite at dislocation channels was observed in grains along the [0 0 1]-[1 1 1] orientation but not in those along the [1 0 1] orientation.

Quantitative analysis of thoria phase in Th-U alloys using diffraction studies

NASA Astrophysics Data System (ADS)

Thakur, Shital; Krishna, P. S. R.; Shinde, A. B.; Kumar, Raj; Roy, S. B.

2017-05-01

In the present study the quantitative phase analysis of Th-U alloys in bulk form namely Th-52 wt% U and Th-3wt%U has been performed over the data obtained from both X ray diffraction and neutron diffraction technique using Rietveld method of FULLPROF software. Quantifying thoria (ThO2) phase present in bulk of the sample is limited due to surface oxidation and low penetration of x rays in high Z material. Neutron diffraction study probing bulk of the samples has been presented in comparison with x-ray diffraction study.

In situ investigation of deformation mechanisms in magnesium-based metal matrix composites

NASA Astrophysics Data System (ADS)

Farkas, Gergely; Choe, Heeman; Máthis, Kristián; Száraz, Zoltán; Noh, Yoonsook; Trojanová, Zuzanka; Minárik, Peter

2015-07-01

We studied the effect of short fibers on the mechanical properties of a magnesium alloy. In particular, deformation mechanisms in a Mg-Al-Sr alloy reinforced with short alumina fibers were studied in situ using neutron diffraction and acoustic emission methods. The fibers' plane orientation with respect to the loading axis was found to be a key parameter, which influences the acting deformation processes, such as twinning or dislocation slip. Furthermore, the twinning activity was much more significant in samples with parallel fiber plane orientation, which was confirmed by both acoustic emission and electron backscattering diffraction results. Neutron diffraction was also used to assist in analyzing the acoustic emission and electron backscattering diffraction results. The simultaneous application of the two in situ methods, neutron diffraction and acoustic emission, was found to be beneficial for obtaining complementary datasets about the twinning and dislocation slip in the magnesium alloys and composites used in this study.

Determination of atomic site susceptibility tensors from neutron diffraction data on polycrystalline samples.

PubMed

Gukasov, A; Brown, P J

2010-12-22

Polarized neutron diffraction can provide information about the atomic site susceptibility tensor χ(ij) characterizing the magnetic response of individual atoms to an external magnetic field (Gukasov and Brown 2002 J. Phys.: Condens. Mater. 14 8831). The six independent atomic susceptibility parameters (ASPs) can be determined from polarized neutron flipping ratio measurements on single crystals and visualized as magnetic ellipsoids which are analogous to the thermal ellipsoids obtained from atomic displacement parameters (ADPs). We demonstrate now that the information about local magnetic susceptibility at different magnetic sites in a crystal can also be obtained from polarized and unpolarized neutron diffraction measurements on magnetized powder samples. The validity of the method is illustrated by the results of such measurements on a polycrystalline sample of Tb(2)Sn(2)O(7).

Neutron diffraction study of Tb0.5Ho0.5Mn2Si2

NASA Astrophysics Data System (ADS)

Pandey, Swati; Siruguri, Vasudeva; Rawat, Rajeev

2018-02-01

The magnetic properties of tetragonal polycrystalline intermetallic compound Tb0.5Ho0.5Mn2Si2 have been investigated using temperature dependent dc magnetic susceptibility and neutron powder diffraction studies. Results of high temperature susceptibility data shows anomaly at TN = 510 K while low temperature susceptibility data indicate two successive anomalies at T1 = 11 K and T2 = 25 K. Metamagnetic transition is observed in magnetization versus field curves. Our neutron diffraction results indicate three different magnetic regions with different magnetic structures. Neutron diffraction data shows that below T2, the intensities of some of the nuclear peaks get enhanced indicating ferromagnetic ordering, while additional magnetic reflections are observed below T1, indicating antiferromagnetic order. Ordering of rare earth sublattice at low temperature rearranges the ordering of Mn sublattice and results in reorientation of Mn spins at T1. At 2 K Tb/Ho moments are aligned along c-axis while Mn moments are aligned perpendicular to c-axis.

Dynamic theory of neutron diffraction from a moving grating

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bushuev, V. A., E-mail: vabushuev@yandex.ru; Frank, A. I.; Kulin, G. V.

2016-01-15

A multiwave dynamic theory of diffraction of ultracold neutrons from a moving phase grating has been developed in the approximation of coupled slowly varying amplitudes of wavefunctions. The effect of the velocity, period, and height of grooves of the grating, as well as the spectral angular distribution of the intensity of incident neurons, on the discrete energy spectrum and the intensity of diffraction reflections of various orders has been analyzed.

New in-situ neutron diffraction cell for electrode materials

NASA Astrophysics Data System (ADS)

Biendicho, Jordi Jacas; Roberts, Matthew; Offer, Colin; Noréus, Dag; Widenkvist, Erika; Smith, Ronald I.; Svensson, Gunnar; Edström, Kristina; Norberg, Stefan T.; Eriksson, Sten G.; Hull, Stephen

2014-02-01

A novel neutron diffraction cell has been constructed to allow in-situ studies of the structural changes in materials of relevance to battery applications during charge/discharge cycling. The new design is based on the coin cell geometry, but has larger dimensions compared to typical commercial batteries in order to maximize the amount of electrode material and thus, collect diffraction data of good statistical quality within the shortest possible time. An important aspect of the design is its modular nature, allowing flexibility in both the materials studied and the battery configuration. This paper reports electrochemical tests using a Nickel-metal-hydride battery (Ni-MH), which show that the cell is able to deliver 90% of its theoretical capacity when using deuterated components. Neutron diffraction studies performed on the Polaris diffractometer using nickel metal and a hydrogen-absorbing alloy (MH) clearly show observable changes in the neutron diffraction patterns as a function of the discharge state. Due to the high quality of the diffraction patterns collected in-situ (i.e. good peak-to-background ratio), phase analysis and peak indexing can be performed successfully using data collected in around 30 min. In addition to this, structural parameters for the β-phase (charged) MH electrode obtained by Rietveld refinement are presented.

Neutron diffraction measurements on a reference metallic sample with a high-efficiency GEM side-on 10B-based thermal neutron detector

NASA Astrophysics Data System (ADS)

Pietropaolo, A.; Claps, G.; Fedrigo, A.; Grazzi, F.; Höglund, C.; Murtas, F.; Scherillo, A.; Schmidt, S.; Schooneveld, E. M.

2018-03-01

The upgraded version of the GEM side-on thermal neutron detector was successfully tested in a neutron diffraction experiment on a reference sample using the INES diffractometer at the ISIS spallation neutron source, UK. The performance of the new 10B4C-based detector is compared to that of a standard 3He tube, operating at the instrument as a part of the detectors assembly. The results show that the upgraded detector has a better resolution and an efficiency of the same order of magnitude of a 3He-based detector.

Evidence from x-ray and neutron powder diffraction patterns that the so-called icosahedral and decagonal quasicrystals of MnAl(6) and other alloys are twinned cubic crystals.

PubMed

Pauling, L

1987-06-01

It is shown that the x-ray powder diffraction patterns of rapidly quenched MnAl(6) and Mg(32)(Al,Zn)(49) and the neutron powder diffraction pattern of MnAl(6) are compatible with the proposed 820-atom primitive cubic structure [Pauling, L. (1987) Phys. Rev. Lett. 58, 365-368]. The values found for the edge of the unit cube are 23.365 A (x-ray) and 23.416 A (neutron) for MnAl(6) and 24.313 A (x-ray) for Mg(32)(Al,Zn)(49).

Evidence from x-ray and neutron powder diffraction patterns that the so-called icosahedral and decagonal quasicrystals of MnAl6 and other alloys are twinned cubic crystals

PubMed Central

Pauling, Linus

1987-01-01

It is shown that the x-ray powder diffraction patterns of rapidly quenched MnAl6 and Mg32(Al,Zn)49 and the neutron powder diffraction pattern of MnAl6 are compatible with the proposed 820-atom primitive cubic structure [Pauling, L. (1987) Phys. Rev. Lett. 58, 365-368]. The values found for the edge of the unit cube are 23.365 Å (x-ray) and 23.416 Å (neutron) for MnAl6 and 24.313 Å (x-ray) for Mg32(Al,Zn)49. PMID:16593841

Stress Induced Charge-Ordering Process in LiMn 2O 4

DOE PAGES

Chen, Yan; Yu, Dunji; An, Ke

2016-07-25

In this letter we report the stress-induced Mn charge-ordering process in the LiMn 2O 4 spinel, evidenced by the lattice strain evolutions due to the Jahn–Teller effects. In situ neutron diffraction reveals the initial stage of this process at low stress, indicating the eg electron localization at the preferential Mn sites during the early phase transition as an underlying charge-ordering mechanism in the charge-frustrated LiMn 2O 4. The initial stage of this transition exhibits as a progressive lattice and charge evolution, without showing a first-order behavior.

The use of neutron scattering to determine the functional structure of glycoside hydrolase.

PubMed

Nakamura, Akihiko; Ishida, Takuya; Samejima, Masahiro; Igarashi, Kiyohiko

2016-10-01

Neutron diffraction provides different information from X-ray diffraction, because neutrons are scattered by atomic nuclei, whereas X-rays are scattered by electrons. One of the key advantages of neutron crystallography is the ability to visualize hydrogen and deuterium atoms, making it possible to observe the protonation state of amino acid residues, hydrogen bonds, networks of water molecules and proton relay pathways in enzymes. But, because of technical difficulties, less than 100 enzyme structures have been evaluated by neutron crystallography to date. In this review, we discuss the advantages and disadvantages of neutron crystallography as a tool to investigate the functional structure of glycoside hydrolases, with some examples. Copyright © 2016 Elsevier Ltd. All rights reserved.

Six-axis multi-anvil press for high-pressure, high-temperature neutron diffraction experiments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sano-Furukawa, A., E-mail: sano.asami@jaea.go.jp; Hattori, T.; J-PARC Center, Japan Atomic Energy Agency, Ibaraki 319-1195

2014-11-15

We developed a six-axis multi-anvil press, ATSUHIME, for high-pressure and high-temperature in situ time-of-flight neutron powder diffraction experiments. The press has six orthogonally oriented hydraulic rams that operate individually to compress a cubic sample assembly. Experiments indicate that the press can generate pressures up to 9.3 GPa and temperatures up to 2000 K using a 6-6-type cell assembly, with available sample volume of about 50 mm{sup 3}. Using a 6-8-type cell assembly, the available conditions expand to 16 GPa and 1273 K. Because the six-axis press has no guide blocks, there is sufficient space around the sample to use themore » aperture for diffraction and place an incident slit, radial collimators, and a neutron imaging camera close to the sample. Combination of the six-axis press and the collimation devices realized high-quality diffraction pattern with no contamination from the heater or the sample container surrounding the sample. This press constitutes a new tool for using neutron diffraction to study the structures of crystals and liquids under high pressures and temperatures.« less

A Novel In-situ Electrochemical Cell for Neutron Diffraction Studies of Phase Transitions in Small Volume Electrodes of Li-ion Batteries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vadlamani, Bhaskar S; An, Ke; Jagannathan, M.

2014-01-01

The design and performance of a novel in-situ electrochemical cell that greatly facilitates the neutron diffraction study of complex phase transitions in small volume electrodes of Li-ion cells, is presented in this work. Diffraction patterns that are Rietveld-refinable could be obtained simultaneously for all the electrodes, which demonstrates that the cell is best suited to explore electrode phase transitions driven by the lithiation and delithiation processes. This has been facilitated by the use of single crystal (100) Si sheets as casing material and the planar cell configuration, giving improved signal-to-noise ratio relative to other casing materials. The in-situ cell hasmore » also been designed for easy assembly and to facilitate rapid experiments. The effectiveness of cell is demonstrated by tracking the neutron diffraction patterns during the charging of graphite/LiCoO2 and graphite/LiMn2O4 cells. It is shown that good quality neutron diffraction data can be obtained and that most of the finer details of the phase transitions, and the associated changes in crystallographic parameters in these electrodes, can be captured.« less

EPICS Controlled Collimator for Controlling Beam Sizes in HIPPO

DOE Office of Scientific and Technical Information (OSTI.GOV)

Napolitano, Arthur Soriano; Vogel, Sven C.

2017-08-03

Controlling the beam spot size and shape in a diffraction experiment determines the probed sample volume. The HIPPO - High-Pressure-Preferred Orientation– neutron time-offlight diffractometer is located at the Lujan Neutron Scattering Center in Los Alamos National Laboratories. HIPPO characterizes microstructural parameters, such as phase composition, strains, grain size, or texture, of bulk (cm-sized) samples. In the current setup, the beam spot has a 10 mm diameter. Using a collimator, consisting of two pairs of neutron absorbing boron-nitride slabs, horizontal and vertical dimensions of a rectangular beam spot can be defined. Using the HIPPO robotic sample changer for sample motion, themore » collimator would enable scanning of e.g. cylindrical samples along the cylinder axis by probing slices of such samples. The project presented here describes implementation of such a collimator, in particular the motion control software. We utilized the EPICS (Experimental Physics Interface and Control System) software interface to integrate the collimator control into the HIPPO instrument control system. Using EPICS, commands are sent to commercial stepper motors that move the beam windows.« less

Time-resolved in situ neutron diffraction under supercritical hydrothermal conditions: a study of the synthesis of KTiOPO4.

PubMed

Ok, Kang Min; Lee, Dong Woo; Smith, Ronald I; O'Hare, Dermot

2012-10-31

In the first in situ neutron powder diffraction study of a supercritical hydrothermal synthesis, the crystallization of KTiOPO(4) (KTP) at 450 °C and 380 bar has been investigated. The time-resolved diffraction data suggest that the crystallization of KTP occurs by the reaction between dissolved K(+)(aq), PO(4)(3-)(aq), and [Ti(OH)(x)]((4-x)+)(aq) species.

Interpretation of small-angle diffraction experiments on opal-like photonic crystals

NASA Astrophysics Data System (ADS)

Marlow, F.; Muldarisnur, M.; Sharifi, P.; Zabel, H.

2011-08-01

Comprehensive structural information on artificial opals involving the deviations from the strongly dominating face-centered cubic structure is still missing. Recent structure investigations with neutrons and synchrotron sources have shown a high degree of order but also a number of unexpected scattering features. Here, we point out that the exclusion of the allowed 002-type diffraction peaks by a small atomic form factor is not obvious and that surface scattering has to be included as a possible source for the diffraction peaks. Our neutron diffraction data indicate that surface scattering is the main reason for the smallest-angle peaks in the diffraction patterns.

FAST TRACK COMMUNICATION Determination of atomic site susceptibility tensors from neutron diffraction data on polycrystalline samples

NASA Astrophysics Data System (ADS)

Gukasov, A.; Brown, P. J.

2010-12-01

Polarized neutron diffraction can provide information about the atomic site susceptibility tensor χij characterizing the magnetic response of individual atoms to an external magnetic field (Gukasov and Brown 2002 J. Phys.: Condens. Mater. 14 8831). The six independent atomic susceptibility parameters (ASPs) can be determined from polarized neutron flipping ratio measurements on single crystals and visualized as magnetic ellipsoids which are analogous to the thermal ellipsoids obtained from atomic displacement parameters (ADPs). We demonstrate now that the information about local magnetic susceptibility at different magnetic sites in a crystal can also be obtained from polarized and unpolarized neutron diffraction measurements on magnetized powder samples. The validity of the method is illustrated by the results of such measurements on a polycrystalline sample of Tb2Sn2O7.

Loading Path and Control Mode Effects During Thermomechanical Cycling of Polycrystalline Shape Memory NiTi

NASA Astrophysics Data System (ADS)

Nicholson, D. E.; Benafan, O.; Padula, S. A.; Clausen, B.; Vaidyanathan, R.

2018-01-01

Loading path dependencies and control mode effects in polycrystalline shape memory NiTi were investigated using in situ neutron and synchrotron X-ray diffraction performed during mechanical cycling and thermal cycling at constant strain. Strain-controlled, isothermal, reverse loading (to ± 4%) and stress-controlled, isothermal, cyclic loading (to ± 400 MPa for up to ten cycles) at room temperature demonstrated that the preferred martensite variants selected correlated directly with the macroscopic uniaxial strain and did not correlate with the compressive or tensile state of stress. During cyclic loading (up to ten cycles), no significant cycle-to-cycle evolution of the variant microstructure corresponding to a given strain was observed, despite changes in the slope of the stress-strain response with each cycle. Additionally, thermal cycling (to above and below the phase transformation) under constant strain (up to 2% tensile strain) showed that the martensite variant microstructure correlated directly with strain and did not evolve following thermal cycling, despite relaxation of stress in both martensite and austenite phases. Results are presented in the context of variant reorientation and detwinning processes in martensitic NiTi, the fundamental thermoelastic nature of such processes and the ability of the variant microstructure to accommodate irreversible deformation processes.

Loading Path and Control Mode Effects During Thermomechanical Cycling of Polycrystalline Shape Memory NiTi

NASA Astrophysics Data System (ADS)

Nicholson, D. E.; Benafan, O.; Padula, S. A.; Clausen, B.; Vaidyanathan, R.

2018-03-01

Loading path dependencies and control mode effects in polycrystalline shape memory NiTi were investigated using in situ neutron and synchrotron X-ray diffraction performed during mechanical cycling and thermal cycling at constant strain. Strain-controlled, isothermal, reverse loading (to ± 4%) and stress-controlled, isothermal, cyclic loading (to ± 400 MPa for up to ten cycles) at room temperature demonstrated that the preferred martensite variants selected correlated directly with the macroscopic uniaxial strain and did not correlate with the compressive or tensile state of stress. During cyclic loading (up to ten cycles), no significant cycle-to-cycle evolution of the variant microstructure corresponding to a given strain was observed, despite changes in the slope of the stress-strain response with each cycle. Additionally, thermal cycling (to above and below the phase transformation) under constant strain (up to 2% tensile strain) showed that the martensite variant microstructure correlated directly with strain and did not evolve following thermal cycling, despite relaxation of stress in both martensite and austenite phases. Results are presented in the context of variant reorientation and detwinning processes in martensitic NiTi, the fundamental thermoelastic nature of such processes and the ability of the variant microstructure to accommodate irreversible deformation processes.

Effect of Extrusion Temperature on the Plastic Deformation of an Mg-Y-Zn Alloy Containing LPSO Phase Using In Situ Neutron Diffraction

NASA Astrophysics Data System (ADS)

Garces, G.; Perez, P.; Cabeza, S.; Kabra, S.; Gan, W.; Adeva, P.

2017-11-01

The evolution of the internal strains during in situ tension and compression tests has been measured in an MgY2Zn1 alloy containing long-period stacking ordered (LPSO) phase using neutron diffraction. The alloy was extruded at two different temperatures to study the influence of the microstructure and texture of the magnesium and the LPSO phases on the deformation mechanisms. The alloy extruded at 623 K (350 °C) exhibits a strong fiber texture with the basal plane parallel to the extrusion direction due to the presence of areas of coarse non-recrystallised grains. However, at 723 K (450 °C), the magnesium phase is fully recrystallised with grains randomly oriented. On the other hand, at the two extrusion temperatures, the LPSO phase orients their basal plane parallel to the extrusion direction. Yield stress is always slightly higher in compression than in tension. Independently on the stress sign and the extrusion temperature, the beginning of plasticity is controlled by the activation of the basal slip system in the dynamic recrystallized grains. Therefore, the elongated fiber-shaped LPSO phase which behaves as the reinforcement in a metal matrix composite is responsible for this tension-compression asymmetry.

Absolute configuration of a chiral CHD group via neutron diffraction: confirmation of the absolute stereochemistry of the enzymatic formation of malic acid

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bau, R.; Brewer, I.; Chiang, M.Y.

Neutron diffraction has been used to monitor the absolute stereochemistry of an enzymatic reaction. (-)(2S)malic-3-d acid was prepared by the action of fumarase on fumaric acid in D/sub 2/O. After a large number of cations were screened, it was found that (+)(R)..cap alpha..-phenylethylamine forms the large crystals necessary for a neutron diffraction analysis. The subsequent structure determination showed that (+)(R)..cap alpha..-phenylethylammonium (-)(2S)malate-3-d has an absolute configuration of R at the CHD site. This result confirms the absolute stereochemistry of fumarate-to-malate transformation as catalyzed by the enzyme fumarase.

Study of residual stresses in CT test specimens welded by electron beam

NASA Astrophysics Data System (ADS)

Papushkin, I. V.; Kaisheva, D.; Bokuchava, G. D.; Angelov, V.; Petrov, P.

2018-03-01

The paper reports result of residual stress distribution studies in CT specimens reconstituted by electron beam welding (EBW). The main aim of the study is evaluation of the applicability of the welding technique for CT specimens’ reconstitution. Thus, the temperature distribution during electron beam welding of a CT specimen was calculated using Green’s functions and the residual stress distribution was determined experimentally using neutron diffraction. Time-of-flight neutron diffraction experiments were performed on a Fourier stress diffractometer at the IBR-2 fast pulsed reactor in FLNP JINR (Dubna, Russia). The neutron diffraction data estimates yielded a maximal stress level of ±180 MPa in the welded joint.

40-Tesla pulsed-field cryomagnet for single crystal neutron diffraction

NASA Astrophysics Data System (ADS)

Duc, F.; Tonon, X.; Billette, J.; Rollet, B.; Knafo, W.; Bourdarot, F.; Béard, J.; Mantegazza, F.; Longuet, B.; Lorenzo, J. E.; Lelièvre-Berna, E.; Frings, P.; Regnault, L.-P.

2018-05-01

We present the first long-duration and high duty cycle 40-T pulsed-field cryomagnet addressed to single crystal neutron diffraction experiments at temperatures down to 2 K. The magnet produces a horizontal field in a bi-conical geometry, ±15° and ±30° upstream and downstream of the sample, respectively. Using a 1.15 MJ mobile generator, magnetic field pulses of 100 ms length are generated in the magnet, with a rise time of 23 ms and a repetition rate of 6-7 pulses per hour at 40 T. The setup was validated for neutron diffraction on the CEA-CRG three-axis spectrometer IN22 at the Institut Laue Langevin.

Defect ordering in YBa 2Cu 3O 6.5 and YBa 2Cu 3O 6.6: Synthesis and characterization by neutron and electron diffraction

NASA Astrophysics Data System (ADS)

Lin, Y. P.; Greedan, J. E.; O'Reilly, A. H.; Reimers, J. N.; Stager, C. V.; Post, M. L.

1990-02-01

Polycrystalline samples of YBa 2Cu 3O 6.5 and YBa 2Cu 3O 6.6 were prepared by oxygen titration of YBa 2 Cu 3O 6.0 at 450°C followed by slow cooling to room temperature. Both samples showed evidence for the a' = 2a supercell in individual grains by electron diffraction as reported previously. In addition the superlattice was observed in neutron powder diffraction indicating that the bulk material is also well ordered. In this study the YBa 2Cu 3O 6.6 phase showed longer correlation lengths for ordering along both a* and b* than YBa 2Cu 3O 6.5. For the former compound the powder-averaged, sample-averaged a* correlation distance is 26A˚from neutron diffraction. Analysis of electron diffraction profiles on selected single crystals give correlation lengths along a*, b*, and c* of 100, 200, and 50A˚, respectively. Dark field imaging discloses the presence of striped, ordered domains elongated along b* with a distribution of sizes. Both neutron diffraction and dark field imaging indicate that the volume fraction of the ordered domains is about 50%. A correlation is noted between the Meissner Effect and the extent of defect ordering in the bulk samples of the two phases.

Neutron and X-ray powder diffraction study of skutterudite thermoelectrics

DOE PAGES

Wang, H.; Kirkham, M. J.; Watkins, T. R.; ...

2016-02-17

N- and p-type filled-skutterudite materials prepared for thermoelectric power generation modules were analyzed by neutron diffraction at the POWGEN beam line of the Spallation Neutron Source (SNS) and X-ray diffraction (XRD). The skutterudite powders were processed by melt spinning, followed by ball milling and annealing. The n-type material consists of Ba–Yb–Co–Sb and the p-type material consists of Di–Fe–Ni–Sb or Di–Fe–Co–Sb (Di = didymium, an alloy of Pr and Nd). Powders for prototype module fabrication from General Motors and Marlow Industries were analyzed in this study. XRD and neutron diffraction studies confirm that both the n- and p-type materials have cubicmore » symmetry. Structural Rietveld refinements determined the lattice parameters and atomic parameters of the framework and filler atoms. The cage filling fraction was found to depend linearly on the lattice parameter, which in turn depends on the average framework atom size. Ultimately, this knowledge may allow the filling fraction of these skutterudite materials to be purposefully adjusted, thereby tuning the thermoelectric properties.« less

In situ high-pressure measurement of crystal solubility by using neutron diffraction

NASA Astrophysics Data System (ADS)

Chen, Ji; Hu, Qiwei; Fang, Leiming; He, Duanwei; Chen, Xiping; Xie, Lei; Chen, Bo; Li, Xin; Ni, Xiaolin; Fan, Cong; Liang, Akun

2018-05-01

Crystal solubility is one of the most important thermo-physical properties and plays a key role in industrial applications, fundamental science, and geoscientific research. However, high-pressure in situ measurements of crystal solubility remain very challenging. Here, we present a method involving high-pressure neutron diffraction for making high-precision in situ measurements of crystal solubility as a function of pressure over a wide range of pressures. For these experiments, we designed a piston-cylinder cell with a large chamber volume for high-pressure neutron diffraction. The solution pressures are continuously monitored in situ based on the equation of state of the sample crystal. The solubility at a high pressure can be obtained by applying a Rietveld quantitative multiphase analysis. To evaluate the proposed method, we measured the high-pressure solubility of NaCl in water up to 610 MPa. At a low pressure, the results are consistent with the previous results measured ex situ. At a higher pressure, more reliable data could be provided by using an in situ high-pressure neutron diffraction method.

In-situ neutron diffraction and crystal plasticity finite element modeling to study the kinematic stability of retained austenite in bearing steels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Voothaluru, Rohit; Bedekar, Vikram; Xie, Qingge

This work integrates in-situ neutron diffraction and crystal plasticity finite element modeling to study the kinematic stability of retained austenite in high carbon bearing steels. The presence of a kinematically metastable retained austenite in bearing steels can significantly affect the macro-mechanical and micro-mechanical material response. Mechanical characterization of metastable austenite is a critical component in accurately capturing the micro-mechanical behavior under typical application loads. Traditional mechanical characterization techniques are unable to discretely quantify the micro-mechanical response of the austenite, and as a result, the computational predictions rely heavily on trial and error or qualitative descriptions of the austenite phase. Inmore » order to overcome this, in the present work, we use in-situ neutron diffraction of a uniaxial tension test of an A485 Grade 1 bearing steel specimen. The mechanical response determined from the neutron diffraction analysis was incorporated into a hybrid crystal plasticity finite element model that accounts for the martensite's crystal plasticity and the stress-assisted transformation from austenite to martensite in bearing steels. Here, the modeling response was used to estimate the single crystal elastic constants of the austenite and martensite phases. Finally, the results show that using in-situ neutron diffraction, coupled with a crystal plasticity model, can successfully predict both the micro-mechanical and macro-mechanical responses of bearing steels while accounting for the martensitic transformation of the retained austenite.« less

In-situ neutron diffraction and crystal plasticity finite element modeling to study the kinematic stability of retained austenite in bearing steels

DOE PAGES

Voothaluru, Rohit; Bedekar, Vikram; Xie, Qingge; ...

2018-11-21

This work integrates in-situ neutron diffraction and crystal plasticity finite element modeling to study the kinematic stability of retained austenite in high carbon bearing steels. The presence of a kinematically metastable retained austenite in bearing steels can significantly affect the macro-mechanical and micro-mechanical material response. Mechanical characterization of metastable austenite is a critical component in accurately capturing the micro-mechanical behavior under typical application loads. Traditional mechanical characterization techniques are unable to discretely quantify the micro-mechanical response of the austenite, and as a result, the computational predictions rely heavily on trial and error or qualitative descriptions of the austenite phase. Inmore » order to overcome this, in the present work, we use in-situ neutron diffraction of a uniaxial tension test of an A485 Grade 1 bearing steel specimen. The mechanical response determined from the neutron diffraction analysis was incorporated into a hybrid crystal plasticity finite element model that accounts for the martensite's crystal plasticity and the stress-assisted transformation from austenite to martensite in bearing steels. Here, the modeling response was used to estimate the single crystal elastic constants of the austenite and martensite phases. Finally, the results show that using in-situ neutron diffraction, coupled with a crystal plasticity model, can successfully predict both the micro-mechanical and macro-mechanical responses of bearing steels while accounting for the martensitic transformation of the retained austenite.« less

A comparison of dilatometry and in-situ neutron diffraction in tracking bulk phase transformations in a martensitic stainless steel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Christien, F., E-mail: frederic.christien@univ-nantes.fr; Telling, M.T.F.; Department of Materials, University of Oxford, Parks Road, Oxford

2013-08-15

Phase transformations in the 17-4PH martensitic stainless steel have been studied using different in-situ techniques, including dilatometry and high resolution neutron diffraction. Neutron diffraction patterns were quantitatively processed using the Rietveld refinement method, allowing the determination of the temperature-dependence of martensite (α′, bcc) and austenite (γ, fcc) phase fractions and lattice parameters on heating to 1000 °C and then cooling to room temperature. It is demonstrated in this work that dilatometry doesn't permit an accurate determination of the end temperature (Ac3) of the α′ → γ transformation which occurs upon heating to high temperature. The analysis of neutron diffraction datamore » has shown that the respective volumes of the two phases become very close to each other at high temperature, thus making the dilatometric technique almost insensitive in that temperature range. However, there is a very good agreement between neutron diffraction and dilatometry at lower temperature. The martensitic transformation occurring upon cooling has been analysed using the Koistinen–Marburger equation. The thermal expansion coefficients of the two phases have been determined in addition. A comparison of the results obtained in this work with data from literature is presented. - Highlights: • Martensite is still present at very high temperature (> 930 °C) upon heating. • The end of austenitisation cannot be accurately monitored by dilatometry. • The martensite and austenite volumes become similar at high temperature (> ∼ 850 °C)« less

Performance improvements of wavelength-shifting-fiber neutron detectors using high-resolution positioning algorithms

DOE PAGES

Wang, C. L.

2016-05-17

On the basis of FluoroBancroft linear-algebraic method [S.B. Andersson, Opt. Exp. 16, 18714 (2008)] three highly-resolved positioning methods were proposed for wavelength-shifting fiber (WLSF) neutron detectors. Using a Gaussian or exponential-decay light-response function (LRF), the non-linear relation of photon-number profiles vs. x-pixels was linearized and neutron positions were determined. The proposed algorithms give an average 0.03-0.08 pixel position error, much smaller than that (0.29 pixel) from a traditional maximum photon algorithm (MPA). The new algorithms result in better detector uniformity, less position misassignment (ghosting), better spatial resolution, and an equivalent or better instrument resolution in powder diffraction than the MPA.more » Moreover, these characters will facilitate broader applications of WLSF detectors at time-of-flight neutron powder diffraction beamlines, including single-crystal diffraction and texture analysis.« less

New large volume hydrothermal reaction cell for studying chemical processes under supercritical hydrothermal conditions using time-resolved in situ neutron diffraction.

PubMed

Ok, Kang Min; O'Hare, Dermot; Smith, Ronald I; Chowdhury, Mohammed; Fikremariam, Hanna

2010-12-01

The design and testing of a new large volume Inconel pressure cell for the in situ study of supercritical hydrothermal syntheses using time-resolved neutron diffraction is introduced for the first time. The commissioning of this new cell is demonstrated by the measurement of the time-of-flight neutron diffraction pattern for TiO(2) (Anatase) in supercritical D(2)O on the POLARIS diffractometer at the United Kingdom's pulsed spallation neutron source, ISIS, Rutherford Appleton Laboratory. The sample can be studied over a wide range of temperatures (25-450 °C) and pressures (1-355 bar). This novel apparatus will now enable us to study the kinetics and mechanisms of chemical syntheses under extreme environments such as supercritical water, and in particular to study the crystallization of a variety of technologically important inorganic materials.

Neutron residual stress measurements on rail sections for different production conditions

DOT National Transportation Integrated Search

2004-11-13

Rail sectioning with subsequent neutron diffraction experiments has been used to assess residual stresses in the rails. In this study we present the results of neutron stress : measurements performed at the NIST Center for Neutron Research (NCNR) on ...

Piezoelectricity and rotostriction through polar and non-polar coupled instabilities in bismuth-based piezoceramics

PubMed Central

Acosta, Matias; Schmitt, Ljubomira A.; Cazorla, Claudio; Studer, Andrew; Zintler, Alexander; Glaum, Julia; Kleebe, Hans-Joachim; Donner, Wolfgang; Hoffman, Mark; Rödel, Jürgen; Hinterstein, Manuel

2016-01-01

Coupling of order parameters provides a means to tune functionality in advanced materials including multiferroics, superconductors, and ionic conductors. We demonstrate that the response of a frustrated ferroelectric state leads to coupling between order parameters under electric field depending on grain orientation. The strain of grains oriented along a specific crystallographic direction, 〈h00〉, is caused by converse piezoelectricity originating from a ferrodistortive tetragonal phase. For 〈hhh〉 oriented grains, the strain results from converse piezoelectricity and rotostriction, as indicated by an antiferrodistortive instability that promotes octahedral tilting in a rhombohedral phase. Both strain mechanisms combined lead to a colossal local strain of (2.4 ± 0.1) % and indicate coupling between oxygen octahedral tilting and polarization, here termed “rotopolarization”. These findings were confirmed with electromechanical experiments, in situ neutron diffraction, and in situ transmission electron microscopy in 0.75Bi1/2Na1/2TiO3-0.25SrTiO3. This work demonstrates that polar and non-polar instabilities can cooperate to provide colossal functional responses. PMID:27364037

Assessment of Radiation Embrittlement in Nuclear Reactor Pressure Vessel Surrogate Materials

NASA Astrophysics Data System (ADS)

Balzar, Davor

2010-10-01

The radiation-enhanced formation of small (1-2 nm) copper-rich precipitates (CRPs) is critical for the occurrence of embrittlement in nuclear-reactor pressure vessels. Small CRPs are coherent with the bcc matrix, which causes local matrix strain and interaction with the dislocation strain fields, thus impeding dislocation mobility. As CRPs grow, there is a critical size at which a phase transformation occurs, whereby the CRPs are no longer coherent with the matrix, and the strain is relieved. Diffraction-line-broadening analysis (DLBA) and small-angle neutron scattering (SANS) were used to characterize the precipitate formation in surrogate ferritic reactor-pressure vessel steels. The materials were aged for different times at elevated temperature to produce a series of specimens with different degrees of copper precipitation. SANS measurements showed that the precipitate size distribution broadens and shifts toward larger sizes as a function of ageing time. Mechanical hardness showed an increase with ageing time, followed by a decrease, which can be associated with the reduction in the number density as well as the loss of coherency at larger sizes. Inhomogeneous strain correlated with mechanical hardness.

Texture evolution during isothermal, isostrain, and isobaric loading of polycrystalline shape memory NiTi

NASA Astrophysics Data System (ADS)

Nicholson, D. E.; Padula, S. A.; Benafan, O.; Vaidyanathan, R.

2017-06-01

In situ neutron diffraction was used to provide insights into martensite variant microstructures during isothermal, isobaric, and isostrain loading in shape memory NiTi. The results show that variant microstructures were equivalent for the corresponding strain, and more importantly, the reversibility and equivalency were immediately evident in variant microstructures that were first formed isobarically but then reoriented to near random self-accommodated microstructures following isothermal deformation. Variant microstructures formed isothermally were not significantly affected by a subsequent thermal cycle under constant strain. In all loading cases considered, the resulting variant microstructure correlated with strain and did not correlate with stress. Based on the ability to select a variant microstructure for a given strain despite thermomechanical loading history, the results demonstrated here can be obtained by following any sequence of thermomechanical loading paths over multiple cycles. Thus, for training shape memory alloys (repeating thermomechanical cycling to obtain the desired variant microstructure), optimal paths can be selected so as to minimize the number of training cycles required, thereby increasing the overall stability and fatigue life of these alloys in actuator or medical applications.

Magnetic ground state of the multiferroic hexagonal LuFe O3

NASA Astrophysics Data System (ADS)

Suresh, Pittala; Vijaya Laxmi, K.; Bera, A. K.; Yusuf, S. M.; Chittari, Bheema Lingam; Jung, Jeil; Anil Kumar, P. S.

2018-05-01

The structural, electric, and magnetic properties of bulk hexagonal LuFe O3 are investigated. Single phase hexagonal LuFe O3 has been successfully stabilized in the bulk form without any doping by sol-gel method. The hexagonal crystal structure with P 63c m space group has been confirmed by x-ray-diffraction, neutron-diffraction, and Raman spectroscopy study at room temperature. Neutron diffraction confirms the hexagonal phase of LuFe O3 persists down to 6 K. Further, the x-ray photoelectron spectroscopy established the 3+ oxidation state of Fe ions. The temperature-dependent magnetic dc susceptibility, specific heat, and neutron-diffraction studies confirm an antiferromagnetic ordering below the Néel temperature (TN)˜130 K . Analysis of magnetic neutron-diffraction patterns reveals an in-plane (a b -plane) 120∘ antiferromagnetic structure, characterized by a propagation vector k =(0 0 0 ) with an ordered moment of 2.84 μB/F e3 + at 6 K. The 120∘ antifferomagnetic ordering is further confirmed by spin-orbit coupling density functional theory calculations. The on-site coulomb interaction (U ) and Hund's parameter (JH) on Fe atoms reproduced the neutron-diffraction Γ1 spin pattern among the Fe atoms. P -E loop measurements at room temperature confirm an intrinsic ferroelectricity of the sample with remnant polarization Pr˜0.18 μ C /c m2 . A clear anomaly in the dielectric data is observed at ˜TN revealing the presence of magnetoelectric coupling. A change in the lattice constants at TN has also been found, indicating the presence of a strong magnetoelastic coupling. Thus a coupling between lattice, electric, and magnetic degrees of freedom is established in bulk hexagonal LuFe O3 .

Design and implementation of a multiaxial loading capability during heating on an engineering neutron diffractometer.

PubMed

Benafan, O; Padula, S A; Skorpenske, H D; An, K; Vaidyanathan, R

2014-10-01

A gripping capability was designed, implemented, and tested for in situ neutron diffraction measurements during multiaxial loading and heating on the VULCAN engineering materials diffractometer at the spallation neutron source at Oak Ridge National Laboratory. The proposed capability allowed for the acquisition of neutron spectra during tension, compression, torsion, and/or complex loading paths at elevated temperatures. The design consisted of age-hardened, Inconel(®) 718 grips with direct attachment to the existing MTS load frame having axial and torsional capacities of 100 kN and 400 N·m, respectively. Internal cooling passages were incorporated into the gripping system for fast cooling rates during high temperature experiments up to ∼1000 K. The specimen mounting couplers combined a threaded and hexed end-connection for ease of sample installation/removal without introducing any unwanted loads. Instrumentation of this capability is documented in this work along with various performance parameters. The gripping system was utilized to investigate deformation in NiTi shape memory alloys under various loading/control modes (e.g., isothermal, isobaric, and cyclic), and preliminary results are presented. The measurements facilitated the quantification of the texture, internal strain, and phase fraction evolution in NiTi shape memory alloys under various loading/control modes.

Design and implementation of a multiaxial loading capability during heating on an engineering neutron diffractometer

NASA Astrophysics Data System (ADS)

Benafan, O.; Padula, S. A.; Skorpenske, H. D.; An, K.; Vaidyanathan, R.

2014-10-01

A gripping capability was designed, implemented, and tested for in situ neutron diffraction measurements during multiaxial loading and heating on the VULCAN engineering materials diffractometer at the spallation neutron source at Oak Ridge National Laboratory. The proposed capability allowed for the acquisition of neutron spectra during tension, compression, torsion, and/or complex loading paths at elevated temperatures. The design consisted of age-hardened, Inconel® 718 grips with direct attachment to the existing MTS load frame having axial and torsional capacities of 100 kN and 400 N.m, respectively. Internal cooling passages were incorporated into the gripping system for fast cooling rates during high temperature experiments up to ˜1000 K. The specimen mounting couplers combined a threaded and hexed end-connection for ease of sample installation/removal without introducing any unwanted loads. Instrumentation of this capability is documented in this work along with various performance parameters. The gripping system was utilized to investigate deformation in NiTi shape memory alloys under various loading/control modes (e.g., isothermal, isobaric, and cyclic), and preliminary results are presented. The measurements facilitated the quantification of the texture, internal strain, and phase fraction evolution in NiTi shape memory alloys under various loading/control modes.

High-rate tensile properties of Si-reduced TRIP sheet steels

NASA Astrophysics Data System (ADS)

Choi, Ildong; Park, Yeongdo; Son, Dongmin; Kim, Sung-Joon; Moon, Manbeen

2010-02-01

There have been efforts to develop Si-reduced TRIP steels to improve the wettability of Zn coatings, since the conventional CMnSi-TRIP steels suffer from poor galvanizability. In addition, for the development of potential applications of Si-reduced TRIP steels in vehicle crash management, a better understanding of high strain rate properties is required. In the present study, the effects of alloying elements, such as Cu, Al, Si, and P, on the high-rate tensile properties of Si-reduced TRIP sheet steels were investigated. Tensile tests were performed with a servo-hydraulic tensile testing machine at strain rates ranging from 10-2 to 6 × 102 s-1, and the ultimate tensile strength, elongation, strain rate sensitivity, and absorbed energy were evaluated. The retained austenite volume fractions and carbon content of the specimens were measured using neutron diffraction. The UTS was increased with Cu, Al, Si, and P alloying throughout the strain rate range, and the alloying effect on UTS was considerable with Cu and P. The effects of alloying on the microstructure were not significant. All the steels tested in this study exhibited positive strain rate sensitivity, and the m value at strain rates higher than 10 s-1 was at least two times higher than that at lower strain rates.

The crystal structure of paramagnetic copper(II) oxalate (CuC₂O₄): formation and thermal decomposition of randomly stacked anisotropic nano-sized crystallites.

PubMed

Christensen, Axel Nørlund; Lebech, Bente; Andersen, Niels Hessel; Grivel, Jean-Claude

2014-11-28

Synthetic copper(II) oxalate, CuC2O4, was obtained in a precipitation reaction between a copper(II) solution and an aqueous solution of oxalic acid. The product was identified from its conventional X-ray powder patterns which match that of the copper mineral Moolooite reported to have the composition CuC2O4·0.44H2O. Time resolved in situ investigations of the thermal decomposition of copper(II) oxalate using synchrotron X-ray powder diffraction showed that in air the compound converts to Cu2O at 215 °C and oxidizes to CuO at 345 °C. Thermo gravimetric analysis performed in an inert Ar-gas reveals that the material contains no crystal water and reduces to pure Cu at 295 °C. Magnetic susceptibility measurements in the temperature range from 2 K to 300 K show intriguing paramagnetic behaviour with no sign of magnetic order down to 2 K. A crystal structure investigation is made based on powder diffraction data using one neutron diffraction pattern obtained at 5 K (λ = 1.5949(1) Å) combined with one conventional and two synchrotron X-ray diffraction patterns obtained at ambient temperature using λ = 1.54056, 1.0981 and λ = 0.50483(1) Å, respectively. Based on the X-ray synchrotron data the resulting crystal structure is described in the monoclinic space group P2₁/c (#14) in the P12₁/n1 setting with unit cell parameters a = 5.9598(1) Å, b = 5.6089(1) Å, c = 5.1138 (1) Å, β = 115.320(1)°. The composition is CuC2O4 with atomic coordinates determined by FullProf refinement of the neutron diffraction data. The crystal structure consists of a random stacking of CuC2O4 micro-crystallites where half the Cu-atoms are placed at (2a) and the other half at (2b) positions with the corresponding oxalate molecules centred around the corresponding (2b) and (2a) site positions, respectively. The diffraction patterns obtained for both kinds of radiation show considerable broadening of several Bragg peaks caused by highly anisotropic microstructural size and strain effects. In contrast to the water reported to be present in Moolooite, neither thermogravimetric nor the in situ thermal decomposition investigations and crystal structure analysis of the neutron diffraction data revealed any trace of water. An appendix contains details about the profile parameters for the diffractometers used at the European Synchrotron Radiation Facility and the Institute Max von Laue-Paul Langevin.

Neutron diffraction measurements and micromechanical modelling of temperature-dependent variations in TATB lattice parameters

DOE PAGES

Yeager, John D.; Luscher, Darby J.; Vogel, Sven C.; ...

2016-02-02

Triaminotrinitrobenzene (TATB) is a highly anisotropic molecular crystal used in several plastic-bonded explosive (PBX) formulations. TATB-based explosives exhibit irreversible volume expansion (“ratchet growth”) when thermally cycled. A theoretical understanding of the relationship between anisotropy of the crystal, crystal orientation distribution (texture) of polycrystalline aggregates, and the intergranular interactions leading to this irreversible growth is necessary to accurately develop physics-based predictive models for TATB-based PBXs under various thermal environments. In this work, TATB lattice parameters were measured using neutron diffraction during thermal cycling of loose powder and a pressed pellet. The measured lattice parameters help clarify conflicting reports in the literaturemore » as these new results are more consistent with one set of previous results than another. The lattice parameters of pressed TATB were also measured as a function of temperature, showing some differences from the powder. This data is used along with anisotropic single-crystal stiffness moduli reported in the literature to model the nominal stresses associated with intergranular constraints during thermal expansion. The texture of both specimens were characterized and the pressed pellet exhibits preferential orientation of (001) poles along the pressing direction, whereas no preferred orientation was found for the loose powder. Lastly, thermal strains for single-crystal TATB computed from lattice parameter data for the powder is input to a self-consistent micromechanical model, which predicts the lattice parameters of the constrained TATB crystals within the pellet. The agreement of these model results with the diffraction data obtained from the pellet is discussed along with future directions of research.« less

Denticity and Mobility of the Carbonate Groups in AMCO 3 F Fluorocarbonates: A Study on KMnCO 3 F and High Temperature KCaCO 3 F Polymorph

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rousse, Gwenaelle; Ahouari, Hania; Pomjakushin, Vladimir

We report on a thorough structural study on two members of layered fluorocarbonates KMCO3F (M = Ca, Mn). The Ca-based member demonstrates a phase transition at ~320 °C, evidenced for the first time. The crystal structure of the high temperature phase (HT-KCaCO3F) was solved using neutron powder diffraction. A new Mn-based phase KMnCO3F was synthesized, and its crystal structure was solved from electron diffraction tomography data and refined from a combination of X-ray synchrotron and neutron powder diffraction. In contrast to other members of the fluorocarbonate family, the carbonate groups in the KMnCO3F and HT-KCaCO3F structures are not fixed tomore » two distinct orientations corresponding to mono- and bidentate coordinations of the M cation. In KMnCO3F, the carbonate group can be considered as nearly “monodentate”, forming one short (2.14 Å) and one long (3.01 Å) Mn–O contact. This topology provides more flexibility to the MCO3 layer and enables diminishing the mismatch between the MCO3 and KF layers. This conclusion is corroborated by the HT-KCaCO3F structure, in which the carbonate groups can additionally be tilted away from the layer plane thus relieving the strain arising from geometrical mismatch between the layers. The correlation between denticity of the carbonate groups, their mobility, and cation size variance is discussed. KMnCO3 orders antiferromagnetically below TN = 40 K.« less

In-situ neutron diffraction study on the tension-compression fatigue behavior of a twinning induced plasticity steel

DOE PAGES

Xie, Qingge; Liang, Jiangtao; Stoica, Alexandru Dan; ...

2017-05-17

Grain orientation dependent behavior during tension-compression type of fatigue loading in a TWIP steel was studied using in-situ neutron diffraction. Orientation zones with dominant behavior of (1) twinning-de-twinning, (2) twinning-re-twinning followed by twinning-de-twinning, (3) twinning followed by dislocation slip and (4) dislocation slip were identified. Jumps of the orientation density were evidenced in neutron diffraction peaks which explains the macroscopic asymmetric behavior. The asymmetric behavior in early stage of fatigue loading is mainly due to small volume fraction of twins in comparison with that at later stage. As a result, easy activation of the de-twin makes the macroscopically unloading behaviormore » nonlinear.« less

In-situ neutron diffraction study on the tension-compression fatigue behavior of a twinning induced plasticity steel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xie, Qingge; Liang, Jiangtao; Stoica, Alexandru Dan

Grain orientation dependent behavior during tension-compression type of fatigue loading in a TWIP steel was studied using in-situ neutron diffraction. Orientation zones with dominant behavior of (1) twinning-de-twinning, (2) twinning-re-twinning followed by twinning-de-twinning, (3) twinning followed by dislocation slip and (4) dislocation slip were identified. Jumps of the orientation density were evidenced in neutron diffraction peaks which explains the macroscopic asymmetric behavior. The asymmetric behavior in early stage of fatigue loading is mainly due to small volume fraction of twins in comparison with that at later stage. As a result, easy activation of the de-twin makes the macroscopically unloading behaviormore » nonlinear.« less

A Neutron Diffractometer for a Long Pulsed Neutron Source

NASA Astrophysics Data System (ADS)

Sokol, Paul; Wang, Cailin

Long pulsed neutron sources are being actively developed as small university based sources and are being considered for the next generation of high powered sources, such as the European Neutron Source (ESS) and the Spallation Neutron Source (SNS) second target station. New instrumentation concepts will be required to effectively utilize the full spectrum of neutrons generated by these sources. Neutron diffractometers, which utilize time-of-flight (TOF) techniques for wavelength resolution, are particularly problematic. We describe an instrument for a long pulsed source that provides resolution comparable to that obtained on short pulsed sources without the need of long incident flight paths. We accomplish this by utilizing high speed choppers to impose a time structure on the spectrum of incident neutrons. By strategically positioning these choppers the response matrix assumes a convenient form that can be deconvoluted from the measured TOF spectrum to produce the diffraction pattern of the sample. We compare the performance of this instrument to other possible diffraction instruments that could be utilized on a long pulsed source.

Neutron and high-resolution room-temperature X-ray data collection from crystallized lytic polysaccharide monooxygenase

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bacik, John -Paul; Mekasha, Sophanit; Forsberg, Zarah

Bacteria and fungi express lytic polysaccharide monooxgyenase (LPMO) enzymes that act in conjunction with canonical hydrolytic sugar-processing enzymes to rapidly convert polysaccharides such as chitin, cellulose and starch to single monosaccharide products. In order to gain a better understanding of the structure and oxidative mechanism of these enzymes, large crystals (1–3 mm 3) of a chitin-processing LPMO from the Gram-positive soil bacterium Jonesia denitrificans were grown and screened for their ability to diffract neutrons. In addition to the collection of neutron diffraction data, which were processed to 2.1 Å resolution, a high-resolution room-temperature X-ray diffraction data set was collected andmore » processed to 1.1 Å resolution in space group P2 12 12 1. To our knowledge, this work marks the first successful neutron crystallographic experiment on an LPMO. As a result, joint X-ray/neutron refinement of the resulting data will reveal new details of the structure and mechanism of this recently discovered class of enzymes.« less

Neutron and high-resolution room-temperature X-ray data collection from crystallized lytic polysaccharide monooxygenase

DOE PAGES

Bacik, John -Paul; Mekasha, Sophanit; Forsberg, Zarah; ...

2015-01-01

Bacteria and fungi express lytic polysaccharide monooxgyenase (LPMO) enzymes that act in conjunction with canonical hydrolytic sugar-processing enzymes to rapidly convert polysaccharides such as chitin, cellulose and starch to single monosaccharide products. In order to gain a better understanding of the structure and oxidative mechanism of these enzymes, large crystals (1–3 mm 3) of a chitin-processing LPMO from the Gram-positive soil bacterium Jonesia denitrificans were grown and screened for their ability to diffract neutrons. In addition to the collection of neutron diffraction data, which were processed to 2.1 Å resolution, a high-resolution room-temperature X-ray diffraction data set was collected andmore » processed to 1.1 Å resolution in space group P2 12 12 1. To our knowledge, this work marks the first successful neutron crystallographic experiment on an LPMO. As a result, joint X-ray/neutron refinement of the resulting data will reveal new details of the structure and mechanism of this recently discovered class of enzymes.« less

Structure determination of Ba5AlF13 by coupling electron, synchrotron and neutron powder diffraction, solid-state NMR and ab initio calculations.

PubMed

Martineau, Charlotte; Allix, Mathieu; Suchomel, Matthew R; Porcher, Florence; Vivet, François; Legein, Christophe; Body, Monique; Massiot, Dominique; Taulelle, Francis; Fayon, Franck

2016-10-04

The room temperature structure of Ba 5 AlF 13 has been investigated by coupling electron, synchrotron and neutron powder diffraction, solid-state high-resolution NMR ( 19 F and 27 Al) and first principles calculations. An initial structural model has been obtained from electron and synchrotron powder diffraction data, and its main features have been confirmed by one- and two-dimensional NMR measurements. However, DFT GIPAW calculations of the 19 F isotropic shieldings revealed an inaccurate location of one fluorine site (F3, site 8a), which exhibited unusual long F-Ba distances. The atomic arrangement was reinvestigated using neutron powder diffraction data. Subsequent Fourier maps showed that this fluorine atom occupies a crystallographic site of lower symmetry (32e) with partial occupancy (25%). GIPAW computations of the NMR parameters validate the refined structural model, ruling out the presence of local static disorder and indicating that the partial occupancy of this F site reflects a local motional process. Visualisation of the dynamic process was then obtained from the Rietveld refinement of neutron diffraction data using an anharmonic description of the displacement parameters to account for the thermal motion of the mobile fluorine. The whole ensemble of powder diffraction and NMR data, coupled with first principles calculations, allowed drawing an accurate structural model of Ba 5 AlF 13 , including site-specific dynamical disorder in the fluorine sub-network.

Inorganic pyrophosphatase crystals from Thermococcus thioreducens for X-ray and neutron diffraction.

PubMed

Hughes, Ronny C; Coates, Leighton; Blakeley, Matthew P; Tomanicek, Steve J; Langan, Paul; Kovalevsky, Andrey Y; García-Ruiz, Juan M; Ng, Joseph D

2012-12-01

Inorganic pyrophosphatase (IPPase) from the archaeon Thermococcus thioreducens was cloned, overexpressed in Escherichia coli, purified and crystallized in restricted geometry, resulting in large crystal volumes exceeding 5 mm3. IPPase is thermally stable and is able to resist denaturation at temperatures above 348 K. Owing to the high temperature tolerance of the enzyme, the protein was amenable to room-temperature manipulation at the level of protein preparation, crystallization and X-ray and neutron diffraction analyses. A complete synchrotron X-ray diffraction data set to 1.85 Å resolution was collected at room temperature from a single crystal of IPPase (monoclinic space group C2, unit-cell parameters a=106.11, b=95.46, c=113.68 Å, α=γ=90.0, β=98.12°). As large-volume crystals of IPPase can be obtained, preliminary neutron diffraction tests were undertaken. Consequently, Laue diffraction images were obtained, with reflections observed to 2.1 Å resolution with I/σ(I) greater than 2.5. The preliminary crystallographic results reported here set in place future structure-function and mechanism studies of IPPase.

Comparison of quartz crystallographic preferred orientations identified with optical fabric analysis, electron backscatter and neutron diffraction techniques.

PubMed

Hunter, N J R; Wilson, C J L; Luzin, V

2017-02-01

Three techniques are used to measure crystallographic preferred orientations (CPO) in a naturally deformed quartz mylonite: transmitted light cross-polarized microscopy using an automated fabric analyser, electron backscatter diffraction (EBSD) and neutron diffraction. Pole figure densities attributable to crystal-plastic deformation are variably recognizable across the techniques, particularly between fabric analyser and diffraction instruments. Although fabric analyser techniques offer rapid acquisition with minimal sample preparation, difficulties may exist when gathering orientation data parallel with the incident beam. Overall, we have found that EBSD and fabric analyser techniques are best suited for studying CPO distributions at the grain scale, where individual orientations can be linked to their source grain or nearest neighbours. Neutron diffraction serves as the best qualitative and quantitative means of estimating the bulk CPO, due to its three-dimensional data acquisition, greater sample area coverage, and larger sample size. However, a number of sampling methods can be applied to FA and EBSD data to make similar approximations. © 2016 The Authors Journal of Microscopy © 2016 Royal Microscopical Society.

Structure of Aqueous Trehalose Solution by Neutron Diffraction and Structural Modeling.

PubMed

Olsson, Christoffer; Jansson, Helén; Youngs, Tristan; Swenson, Jan

2016-12-15

The molecular structure of an aqueous solution of the disaccharide trehalose (C 12 H 22 O 11 ) has been studied by neutron diffraction and empirical potential structure refinement modeling. Six different isotope compositions with 33 wt % trehalose (corresponding to 38 water molecules per trehalose molecule) were measured to ensure that water-water, trehalose-water, and trehalose-trehalose correlations were accurately determined. In fact, this is the first neutron diffraction study of an aqueous trehalose solution in which also the nonexchangeable hydrogen atoms in trehalose are deuterated. With this approach, it was possible to determine that (1) there is a substantial hydrogen bonding between trehalose and water (∼11 hydrogen bonds per trehalose molecule), which is in contrast to previous neutron diffraction studies, and (2) there is no tendency of clustering of trehalose, in contrast to what is generally observed by molecular dynamics simulations and experimentally found for other disaccharides. Thus, the results give the structural picture that trehalose prefers to interact with water and participate in a hydrogen-bonded network. This strong network character of the solution might be one of the key reasons for its extraordinary stabilization effect on biological materials.

Martensitic transformation in a B2-containing CuZr-based BMG composite revealed by in situ neutron diffraction

DOE PAGES

Song, Gian; Lee, Chanho; Hong, Sung Hwan; ...

2017-06-27

Here, CuZr-based bulk-metallic-glass (BMG) composites reinforced by a B2-type CuZr crystalline-phase (CP) have been widely studied, and exhibit that the plastic deformation of the CP induces martensitic transformation from the B2 to B19', which plays a dominant role in the deformation behavior and mechanical properties. In the present study, 2.0% Co containing CuZr-based BMG composites were investigated using in-situ neutron-diffraction technique. The in-situ neutron-diffraction results reveal the continuous load transfer from the glass matrix to B2 CP and martensitic transformation from the B2 CP to B19' during the deformation of the composite. Moreover, it was found that the martensitic transformationmore » is initiated at the applied stress higher than 1500 MPa, and is significantly suppressed during the deformation, as compared to other 0.5% Co-containing CuZr-based BMG composites. Based on these in-situ neutron-diffraction results, the martensitic transformation is strongly affected by the amount of the addition of Co, which determines the mechanical properties of CP-reinforced BMG composites, such as ductility and hardening capability.« less

Martensitic transformation in a B2-containing CuZr-based BMG composite revealed by in situ neutron diffraction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Song, Gian; Lee, Chanho; Hong, Sung Hwan

Here, CuZr-based bulk-metallic-glass (BMG) composites reinforced by a B2-type CuZr crystalline-phase (CP) have been widely studied, and exhibit that the plastic deformation of the CP induces martensitic transformation from the B2 to B19', which plays a dominant role in the deformation behavior and mechanical properties. In the present study, 2.0% Co containing CuZr-based BMG composites were investigated using in-situ neutron-diffraction technique. The in-situ neutron-diffraction results reveal the continuous load transfer from the glass matrix to B2 CP and martensitic transformation from the B2 CP to B19' during the deformation of the composite. Moreover, it was found that the martensitic transformationmore » is initiated at the applied stress higher than 1500 MPa, and is significantly suppressed during the deformation, as compared to other 0.5% Co-containing CuZr-based BMG composites. Based on these in-situ neutron-diffraction results, the martensitic transformation is strongly affected by the amount of the addition of Co, which determines the mechanical properties of CP-reinforced BMG composites, such as ductility and hardening capability.« less

Measuring and Modeling the Effects of Mechanical Twinning on the Behavior of Magnesium Alloys

NASA Astrophysics Data System (ADS)

Agnew, Sean; Wu, Peidong; Inal, Kaan; El Kadiri, Haitham; Wang, Jian; Tome, Carlos

Our community has learned a great deal about twinning in Mg alloys over the past decade. Some of these things were known qualitatively in prior decades, but we have now developed a proficiency in characterization and computational modeling which permits a quantitative description of these twinning-induced effects over a wide range of strain rates, temperatures, loading conditions, and in a variety of alloy families. These capabilities could only be dreamed of by prior generations. This lecture will review the effects of the main twinning mode, {10.2} extension twinning (e.g., tension-compression yield asymmetry, yield plateau, anisotropy, rapid strain hardening, detwinning, etc.); characterization, primarily by diffraction-based techniques (electron, X-ray, and neutron); and modeling by crystal plasticity-based methods. Strategies to control these effects through microstructure, texture, and alloy design will be proposed. Finally, outstanding questions which merit further research will be highlighted.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eisazadeh, Hamid; Goldak, John A.; Aidun, Daryush K.

Residual strain distributions in similar and dissimilar welds were measured using neutron diffraction (ND) method. Then, using three strain components, three-dimensional stress states were calculated. The results were used to determine the effect of the martensitic phase transformation and material properties on residual stress (RS) distribution. It was observed that smaller longitudinal RS was induced in the low carbon steel side of dissimilar weld when compared to its similar weld. Also, it was found that the transverse RS near and within the weld zone (WZ) in dissimilar weld exhibited a distinctive trend, with tensile mode reaching the yield strength ofmore » the base metal (BM). In order to characterize the WZ in dissimilar weld, we deployed optical microscopy, hardness, and energy dispersive X-ray spectroscopy (EDAX). This study not only provides further insight into the RS state in similar and dissimilar welds; it also delivers important consequences of phase transformation in the latter case.« less

Residual stresses in a stainless steel - titanium alloy joint made with the explosive technique

NASA Astrophysics Data System (ADS)

Taran, Yu V.; Balagurov, A. M.; Sabirov, B. M.; Evans, A.; Davydov, V.; Venter, A. M.

2012-02-01

Joining of pipes from stainless steel (SS) and titanium (Ti) alloy still experience serious technical problems. Recently, reliable and hermetic joining of SS and Ti pipes has been achieved with the explosive bonding technique in the Russian Federal Nuclear Center. Such adapters are earmarked for use at the future International Linear Collider. The manufactured SS-Ti adapters have excellent mechanical behavior at room and liquid nitrogen temperatures, during high-pressure tests and thermal cycling. We here report the first neutron diffraction investigation of the residual stresses in a SS-Ti adapter on the POLDI instrument at the SINQ spallation source. The strain scanning across the adapter walls into the SS-SS and SS-Ti pipes sections encompassed measurement of the axial, radial and hoop strain components, which were transformed into residual stresses. The full stress information was successfully determined for the three steel pipes involved in the joint. The residual stresses do not exceed 300 MPa in magnitude. All stress components have tensile values close to the adapter internal surface, whilst they are compressive close to the outer surface. The strong incoherent and weak coherent neutron scattering cross-sections of Ti did not allow for the reliable determination of stresses inside the titanic pipe.

Neutron Diffraction Studies of the Atomic Vibrations of Bulk and Surface Atoms of Nanocrystalline SiC

NASA Technical Reports Server (NTRS)

Stelmakh, S.; Grzanka, E.; Zhao, Y.; Palosz, W.; Palosz, B.

2004-01-01

Thermal atomic motions of nanocrystalline Sic were characterized by two temperature atomic factors B(sub core), and B(sub shell). With the use of wide angle neutron diffraction data it was shown that at the diffraction vector above 15A(exp -1) the Wilson plots gives directly the temperature factor of the grain interior (B(sub core)). At lower Q values the slope of the Wilson plot provides information on the relative amplitudes of vibrations of the core and shell atoms.

Holographic Gratings for Slow-Neutron Optics

PubMed Central

Klepp, Juergen; Pruner, Christian; Tomita, Yasuo; Geltenbort, Peter; Drevenšek-Olenik, Irena; Gyergyek, Saso; Kohlbrecher, Joachim; Fally, Martin

2012-01-01

Recent progress in the development of holographic gratings for neutron-optics applications is reviewed. We summarize the properties of gratings recorded in deuterated (poly)methylmethacrylate, holographic polymer-dispersed liquid crystals and nanoparticle-polymer composites revealed by diffraction experiments with slow neutrons. Existing and anticipated neutron-optical instrumentations based on holographic gratings are discussed.

In Situ Neutron Diffraction of Rare-Earth Phosphate Proton Conductors Sr/Ca-doped LaPO4 at Elevated Temperatures

NASA Astrophysics Data System (ADS)

Al-Wahish, Amal; Al-Binni, Usama; Bridges, C. A.; Huq, A.; Bi, Z.; Paranthaman, M. P.; Tang, S.; Kaiser, H.; Mandrus, D.

Acceptor-doped lanthanum orthophosphates are potential candidate electrolytes for proton ceramic fuel cells. We combined neutron powder diffraction (NPD) at elevated temperatures up to 800° C , X-ray powder diffraction (XRD) and scanning electron microscopy (SEM) to investigate the crystal structure, defect structure, thermal stability and surface topography. NPD shows an average bond length distortion in the hydrated samples. We employed Quasi-Elastic Neutron Scattering (QENS) and electrochemical impedance spectroscopy (EIS) to study the proton dynamics of the rare-earth phosphate proton conductors 4.2% Sr/Ca-doped LaPO4. We determined the bulk diffusion and the self-diffusion coefficients. Our results show that QENS and EIS are probing fundamentally different proton diffusion processes. Supported by the U.S. Department of Energy.

Structural phase transition in d-benzil characterised by capacitance measurements and neutron powder diffraction

NASA Astrophysics Data System (ADS)

Goossens, D. J.; Wu, Xiaodong; Prior, M.

2005-12-01

The ferroelectric phase transition in deuterated benzil, C 14H 10O 2, has been studied using capacitance measurements and neutron powder diffraction. Hydrogenous benzil shows a phase transition at 83.5 K from a high temperature P3 121 phase to a cell-doubled P2 1 phase. The phase transition in d-benzil occurs at 88.1 K, a small isotope effect. Neutron powder diffraction was consistent with a low temperature phase of space group P2 1. Upon deuteration the transition remained first-order and the dynamics of the phenyl ring dominated the behaviour. The isotope effect can be attributed to the difference in mass and moment of inertia between C 6H 5 and C 6D 5.

Diffraction Correlation to Reconstruct Highly Strained Particles

NASA Astrophysics Data System (ADS)

Brown, Douglas; Harder, Ross; Clark, Jesse; Kim, J. W.; Kiefer, Boris; Fullerton, Eric; Shpyrko, Oleg; Fohtung, Edwin

2015-03-01

Through the use of coherent x-ray diffraction a three-dimensional diffraction pattern of a highly strained nano-crystal can be recorded in reciprocal space by a detector. Only the intensities are recorded, resulting in a loss of the complex phase. The recorded diffraction pattern therefore requires computational processing to reconstruct the density and complex distribution of the diffracted nano-crystal. For highly strained crystals, standard methods using HIO and ER algorithms are no longer sufficient to reconstruct the diffraction pattern. Our solution is to correlate the symmetry in reciprocal space to generate an a priori shape constraint to guide the computational reconstruction of the diffraction pattern. This approach has improved the ability to accurately reconstruct highly strained nano-crystals.

Development of Intergranular Residual Stress and Its Implication to Mechanical Behaviors at Elevated Temperatures in AL6XN Austenitic Stainless Steel

NASA Astrophysics Data System (ADS)

Hong, Yanyan; Li, Shilei; Li, Hongjia; Li, Jian; Sun, Guangai; Wang, Yan-Dong

2018-05-01

Neutron diffraction was used to investigate the residual lattice strains in AL6XN austenitic stainless steel subjected to tensile loading at different temperatures, revealing the development of large intergranular stresses after plastic deformation. Elastic-plastic self-consistent modeling was employed to simulate the micromechanical behavior at room temperature. The overall variations of the modeled lattice strains as a function of the sample direction with respect to the loading axis agree in general with the experimental values, indicating that dislocation slip is the main plastic deformation mode. At 300 °C, the serrated flow in the stress-strain curve and the great amount of slip bands indicate the appearance of dynamic strain aging. Except for promoting the local strain concentration, the long-range stress field caused by the planar slip bands near the grain boundaries is also attributed to the decrease in the experimental intergranular strains. An increase in the lattice strains localized at some specific specimen orientations for reflections at 600 °C may be explained by the segregation of solute atoms (Cr and Mo) at dislocation slip bands. The evolution of full-width at half-maximum demonstrates that the dynamic recovery indeed plays an important role in alleviating the local strain concentrations during tensile loading at 600 °C.

High-level expression and deuteration of sperm whale myoglobin: A study of its solvent structure by X-ray and neutron diffraction methods

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shu, F.; Ramakrishnan, V.; Schoenborn, B.P.

1994-12-31

Neutron diffraction has become one of the best ways to study light atoms, such as hydrogens. Hydrogen however has a negative coherent scattering factor, and a large incoherent scattering factor, while deuterium has virtually no incoherent scattering, but a large positive coherent scattering factor. Beside causing high background due to its incoherent scattering, the negative coherent scattering of hydrogen tends to cancel out the positive contribution from other atoms in a neutron density map. Therefore a fully deuterated sample will yield better diffraction data with stronger density in the hydrogen position. On this basis, a sperm whale myoglobin gene modifiedmore » to include part of the A cII protein gene has been cloned into the T7 expression system. Milligram amounts of fully deuterated holo-myoglobin have been obtained and used for crystallization. The synthetic sperm whale myoglobin crystallized in P2{sub 1} space group isomorphous with the native protein crystal. A complete X-ray diffraction dataset at 1.5{Angstrom} has been collected. This X-ray dataset, and a neutron data set collected previously on a protonated carbon-monoxymyoglobin crystal have been used for solvent structure studies. Both X-ray and neutron data have shown that there are ordered hydration layers around the protein surface. Solvent shell analysis on the neutron data further has shown that the first hydration layer behaves differently around polar and apolar regions of the protein surface. Finally, the structure of per-deuterated myoglobin has been refined using all reflections to a R factor of 17%.« less

Magnetic behaviour of synthetic Co(2)SiO(4).

PubMed

Sazonov, Andrew; Meven, Martin; Hutanu, Vladimir; Heger, Gernot; Hansen, Thomas; Gukasov, Arsen

2009-12-01

Synthetic Co(2)SiO(4) crystallizes in the olivine structure (space group Pnma) with two crystallographically non-equivalent Co positions and shows antiferromagnetic ordering below 50 K. We have investigated the temperature variation of the Co(2)SiO(4) magnetic structure by means of non-polarized and polarized neutron diffraction for single crystals. Measurements with non-polarized neutrons were made at 2.5 K (below T(N)), whereas polarized neutron diffraction experiments were carried out at 70 and 150 K (above T(N)) in an external magnetic field of 7 T parallel to the b axis. Additional accurate non-polarized powder diffraction studies were performed in a broad temperature range from 5 to 500 K with small temperature increments. Detailed symmetry analysis of the Co(2)SiO(4) magnetic structure shows that it corresponds to the magnetic (Shubnikov) group Pnma, which allows the antiferromagnetic configuration (G(x), C(y), A(z)) for the 4a site with inversion symmetry 1 (Co1 position) and (0,C(y),0) for the 4c site with mirror symmetry m (Co2 position). The temperature dependence of the Co1 and Co2 magnetic moments obtained from neutron diffraction experiments was fitted in a modified molecular-field model. The polarized neutron study of the magnetization induced by an applied field shows a non-negligible amount of magnetic moment on the oxygen positions, indicating a delocalization of the magnetic moment from Co towards neighbouring O owing to superexchange coupling. The relative strength of the exchange interactions is discussed based on the non-polarized and polarized neutron data.

Neutron and X-ray diffraction of plasma-sprayed zirconia-yttria thermal barrier coatings

NASA Technical Reports Server (NTRS)

Shankar, N. R.; Herman, H.; Singhal, S. P.; Berndt, C. C.

1984-01-01

ZrO2-7.8mol. pct. YO1.5, a fused powder, and ZrO2-8.7mol. pct. YO1.5, a prereacted powder, were plasma-sprayed onto steel substrates. Neutron diffraction and X-ray diffraction of the as-received powder, the powder plasma sprayed into water, as-sprayed coatings, and coatings heat-treated for 10 and 100 h were carried out to study phase transformations and ordering of the oxygen ions on the oxygen sublattice. The as-received fused powder has a much lower monoclinic percentage than does the pre-reacted powder, this resulting in a much lower monoclinic percentage in the coating. Heat treatment increases the percentages of the cubic and monoclinic phases, while decreasing the tetragonal content. An ordered tetragonal phase is detected by the presence of extra neutron diffraction peaks. These phase transformations and ordering will result in volume changes. The implications of these transformations on the performance of partially stabilized zirconia thermal barrier coatings is discussed.

Comparing results of X-ray diffraction, µ-Raman spectroscopy and neutron diffraction when identifying chemical phases in seized nuclear material, during a comparative nuclear forensics exercise.

PubMed

Rondahl, Stina Holmgren; Pointurier, Fabien; Ahlinder, Linnea; Ramebäck, Henrik; Marie, Olivier; Ravat, Brice; Delaunay, François; Young, Emma; Blagojevic, Ned; Hester, James R; Thorogood, Gordon; Nelwamondo, Aubrey N; Ntsoane, Tshepo P; Roberts, Sarah K; Holliday, Kiel S

2018-01-01

This work presents the results for identification of chemical phases obtained by several laboratories as a part of an international nuclear forensic round-robin exercise. In this work powder X-ray diffraction (p-XRD) is regarded as the reference technique. Neutron diffraction produced a superior high-angle diffraction pattern relative to p-XRD. Requiring only small amounts of sample, µ-Raman spectroscopy was used for the first time in this context as a potentially complementary technique to p-XRD. The chemical phases were identified as pure UO 2 in two materials, and as a mixture of UO 2 , U 3 O 8 and an intermediate species U 3 O 7 in the third material.

Suppression of ferromagnetic order by Ag-doping: A neutron scattering investigation on Ce₂(Pd_1-xAg_x)₂In (x = 0.20, 0.50).

PubMed

Martinelli, Alberto; Giovannini, Mauro; Sereni, Julian G; Ritter, Clemens

2018-05-24

The ground state magnetic behaviour of Ce2(Pd0.8Ag0.2)2In and Ce2(Pd0.5Ag0.5)2In, found in the ferromagnetic branch of Ce2Pd2In, has been investigated by neutron powder diffraction at low temperature. Ce2(Pd0.8Ag0.2)2In is characterized by a ferromagnetic structure with the Ce moments aligned along the c-axis and values of 0.96(2) μB. The compound retains the P4/mbm throughout the magnetic transition, although the magnetic ordering is accompanied by a significant decrease of the lattice strain along [00l], suggesting a magnetostructural contribution. The magnetic behaviour of Ce2(Pd0.5Ag0.5)2In is very different; this compound exhibits an extremely reduced magnetic scattering contribution in the diffraction pattern, that can be ascribed to a different kind of ferromagnetic ordering, with extremely reduced magnetic moments (~ 0.1 μB) aligned along [0l0]. These results point to a competition between different types of magnetic correlations induced by Ag-substitution, giving rise to a magnetically frustrated scenario in Ce2(Pd0.5Ag0.5)2In. © 2018 IOP Publishing Ltd.

Structural molecular biology: Recent results from neutron diffraction

NASA Astrophysics Data System (ADS)

Timmins, Peter A.

1995-02-01

Neutron diffraction is of importance in structural biology at several different levels of resolution. In most cases the unique possibility arising from deuterium labelling or contrast variation is of fundamental importance in providing information complementary to that which can be obtained from X-ray diffraction. At high resolution, neutron crystallography of proteins allows the location of hydrogen atoms in the molecule or of the hydration water, both of which may be central to biological activity. A major difficulty in this field has been the poor signal-to-noise ratio of the data arising not only from relatively low beam intensities and small crystals but, most importantly from the incoherent background due to hydrogen atoms in the sample. Modern methods of molecular biology now offer ways of producing fully deuterated proteins by cloning in bacteria grown on fully deuterated media. At a slightly lower resolution, there are a number of systems which may be ordered in one or two dimensions. This is the case in the purple membrane where neutron diffraction with deuterium labelling has complemented high resolution electron diffraction. Finally there is a class of very large macromolecular systems which can be crystallised and have been studied by X-ray diffraction but in which part of the structure is locally disordered and usually has insufficient contrast to be seen with X-rays. In this case the use of H 2O/D 2O contrast variation allows these components to be located. Examples of this are the nucleic acid in virus structures and detergent bound to membrane proteins.

Beam modulation: A novel ToF-technique for high resolution diffraction at the Beamline for European Materials Engineering Research (BEER)

NASA Astrophysics Data System (ADS)

Rouijaa, M.; Kampmann, R.; Šaroun, J.; Fenske, J.; Beran, P.; Müller, M.; Lukáš, P.; Schreyer, A.

2018-05-01

The Beamline for European Materials Engineering Research (BEER) is under construction at the European Spallation Source (ESS) in Lund, Sweden. A basic requirement on BEER is to make best use of the long ESS pulse (2.86 ms) for engineering investigations. High-resolution diffraction, however, demands timing resolution up to 0.1% corresponding to a pulse length down to about 70 μs for the case of thermal neutrons (λ ∼ 1.8 Å). Such timing resolution can be achieved by pulse shaping techniques cutting a short section out of the long pulse, and thus paying for resolution by strong loss of intensity. In contrast to this, BEER proposes a novel operation mode called pulse modulation technique based on a new chopper design, which extracts several short pulses out of the long ESS pulse, and hence leads to a remarkable gain of intensity compared to nowadays existing conventional pulse shaping techniques. The potential of the new technique can be used with full advantage for investigating strains and textures of highly symmetric materials. Due to its instrument design and the high brilliance of the ESS pulse, BEER is expected to become the European flagship for engineering research for strain mapping and texture analysis.

Probing multiscale transport and inhomogeneity in a lithium-ion cells using in-situ neutron methods

DOE PAGES

Zhou, Hui; An, Ke; Allu, Srikanth; ...

2016-01-01

Here, we demonstrate for the first time the lithiation process in graphitic anodes using insitu neutron radiography in a pouch cell format. The neutron absorption contrast shows a direct correlation between degree of lithiation and the discharge voltage plateau. Furthermore, we provide a semi-quantitative comparison between the observed spatial variations of neutron attenuation line profile across the graphite electrode and the calculated lithium concentration profiles computed under similar electrochemical discharge conditions. In conjunction, in situ neutron diffraction of a similar pouch cell under identical test protocol was carried to obtain information about the local phase changes upon lithiation. Combined in-situmore » radiography and diffraction opens up a powerful nondestructive method to understand the multi-scale nature of lithium transport and degradation in practical lithium-ion cells.« less

Grating-based holographic diffraction methods for X-rays and neutrons: phase object approximation and dynamical theory

DOE PAGES

Feng, Hao; Ashkar, Rana; Steinke, Nina; ...

2018-02-01

A method dubbed grating-based holography was recently used to determine the structure of colloidal fluids in the rectangular grooves of a diffraction grating from X-ray scattering measurements. Similar grating-based measurements have also been recently made with neutrons using a technique called spin-echo small-angle neutron scattering. The analysis of the X-ray diffraction data was done using an approximation that treats the X-ray phase change caused by the colloidal structure as a small perturbation to the overall phase pattern generated by the grating. In this paper, the adequacy of this weak phase approximation is explored for both X-ray and neutron grating holography.more » Additionally, it is found that there are several approximations hidden within the weak phase approximation that can lead to incorrect conclusions from experiments. In particular, the phase contrast for the empty grating is a critical parameter. Finally, while the approximation is found to be perfectly adequate for X-ray grating holography experiments performed to date, it cannot be applied to similar neutron experiments because the latter technique requires much deeper grating channels.« less

Neutron diffraction studies of some rare earth-transition metal deuterides

NASA Astrophysics Data System (ADS)

James, W. J.

1984-04-01

Neutron diffraction studies of the ternary alloy system Y6(Fel-xMnx)23 reveal that the unusual magnetic behavior upon substitution of Mn or Fe into the end members, is a consequence of atomic ordering wherein there is strong site preference of Mn for the f sub 2 sites and of Fe for the f sub 1 sites. In the Mn-rich compositions, Fe is found to have no spontaneous moments. Therefore, the long range magnetic ordering arises solely from Mn-Mn interactions. Upon substitution of Mn into the Fe-rich ternaries, the Fe moments are considerably reduced. Neutron diffraction studies of Y6Mn23D23 show that a transition occurs below 180K from a fcc structure to a primitive tetragonal structure, space group P4/mmm with the onset of antiferromagnetic ordering. The Mn moments are directed along the c-axis. The transition probably results from atomic ordering of the D atoms at low temperature which induces c axis magnetic ordering. The question of the appropriate space group of LaNi4.5Al0.5D4.5, P6/mmm or P3/m has been resolved by a careful refinement and analysis of neutron diffraction data. The preferred space group is P6/mmm. Neutron powder diffraction and thermal magnetization measurements on small single crystals of ErNi3, ErCo3, and ErFe3 (space group R3m) show that the magnetocrystalline properties are a consequence of competing local site anisotropies between the two non-equivalent crystallographic sites of Er and two of the three non-equivalent sites of the 3d-transition metal.

Low Temperature and Neutron Physics Studies: Final Progress Report, March 1, 1986--May 31, 1987

DOE R&D Accomplishments Database

Shull, C.G.

1989-07-27

A search for a novel coupling interaction between the Pendelloesung periodicity which is formed in a diffracting crystal and the Larmor precession of neutrons in a magnetic field has been carried out. This interaction is expected to exhibit a resonant behavior when the two spatial periodicities become matched upon scanning the magnetic field being applied to the crystal. Observations on a diffracting, perfect crystal of silicon with neutrons of wavelength 1 Angstrom show the expected resonant action but some discrepancy between the observed magnitude of the resonance effects remains for interpretation.

High-resolution neutron-diffraction measurements to 8 kbar

NASA Astrophysics Data System (ADS)

Bull, C. L.; Fortes, A. D.; Ridley, C. J.; Wood, I. G.; Dobson, D. P.; Funnell, N. P.; Gibbs, A. S.; Goodway, C. M.; Sadykov, R.; Knight, K. S.

2017-10-01

We describe the capability to measure high-resolution neutron powder diffraction data to a pressure of at least 8 kbar. We have used the HRPD instrument at the ISIS neutron source and a piston-cylinder design of pressure cell machined from a null-scattering titanium zirconium alloy. Data were collected under hydrostatic conditions from an elpasolite perovskite La?NiMnO?; by virtue of a thinner cell wall on the incident-beam side of the cell, it was possible to obtain data in the instrument's highest resolution back-scattering detector banks up to a maximum pressure of 8.5 kbar.

Neutron diffraction from aligned stacks of lipid bilayers using the WAND instrument

DOE PAGES

Marquardt, Drew; Frontzek, Matthias D.; Zhao, Yu; ...

2018-02-06

Neutron diffraction from aligned stacks of lipid bilayers is examined using the Wide-Angle Neutron Diffractometer (WAND), located at the High Flux Isotope Reactor, Oak Ridge, Tennessee, USA. Data were collected at different levels of hydration and neutron contrast by varying the relative humidity (RH) and H 2O/D 2O ratio from multi-bilayers of dioleoylphosphatidylcholine and sunflower phosphatidylcholine extract aligned on single-crystal silicon substrates. This work highlights the capabilites of a newly fabricated sample hydration cell, which allows the lipid bilayers to be hydrated with varying H/D ratios from the RH generated by saturated salt solutions, and also demonstrates WAND's capability asmore » an instrument suitable for the study of aligned lipid multi-bilayers.« less

Neutron diffraction from aligned stacks of lipid bilayers using the WAND instrument

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marquardt, Drew; Frontzek, Matthias D.; Zhao, Yu

Neutron diffraction from aligned stacks of lipid bilayers is examined using the Wide-Angle Neutron Diffractometer (WAND), located at the High Flux Isotope Reactor, Oak Ridge, Tennessee, USA. Data were collected at different levels of hydration and neutron contrast by varying the relative humidity (RH) and H 2O/D 2O ratio from multi-bilayers of dioleoylphosphatidylcholine and sunflower phosphatidylcholine extract aligned on single-crystal silicon substrates. This work highlights the capabilites of a newly fabricated sample hydration cell, which allows the lipid bilayers to be hydrated with varying H/D ratios from the RH generated by saturated salt solutions, and also demonstrates WAND's capability asmore » an instrument suitable for the study of aligned lipid multi-bilayers.« less

Influence of ceramide on the internal structure and hydration of the phospholipid bilayer studied by neutron and X-ray scattering

NASA Astrophysics Data System (ADS)

Kiselev, M. A.; Zemlyanaya, E. V.; Ryabova, N. Y.; Hauss, T.; Almasy, L.; Funari, S. S.; Zbytovska, J.; Lombardo, D.

2014-07-01

Small angle neutron scattering (SANS), neutron diffraction and X-ray powder diffraction were used to investigate influence of N-stearoyl phytosphingosine (CER[NP]) and α-hydroxy- N-stearoyl phytosphingosine (CER[AP]) on the internal structure and hydration of DMPC membrane in fully and partly hydrated states at T = 30 °C. Application of Fourier analysis for diffraction data and model calculations for the SANS data evidence that addition of both CER[NP] and CER[AP] in small concentrations promotes significant changes in the organization of DMPC bilayers, such as the increase of the hydrophobic core region. SANS data evidence a decrease in the average radius and polydispersity of the vesicles that can be ascribed to hydrogen bonds interactions that favor tight lipid packing with a compact, more rigid character.

PREFACE: Exploring surfaces and buried interfaces of functional materials by advanced x-ray and neutron techniques Exploring surfaces and buried interfaces of functional materials by advanced x-ray and neutron techniques

NASA Astrophysics Data System (ADS)

Sakurai, Kenji

2010-12-01

This special issue is devoted to describing recent applications of x-ray and neutron scattering techniques to the exploration of surfaces and buried interfaces of various functional materials. Unlike many other surface-sensitive methods, these techniques do not require ultra high vacuum, and therefore, a variety of real and complicated surfaces fall within the scope of analysis. It must be particularly emphasized that the techniques are capable of seeing even buried function interfaces as well as the surface. Furthermore, the information, which ranges from the atomic to mesoscopic scale, is highly quantitative and reproducible. The non-destructive nature of the techniques is another important advantage of using x-rays and neutrons, when compared with other atomic-scale analyses. This ensures that the same specimen can be measured by other techniques. Such features are fairly attractive when exploring multilayered materials with nanostructures (dots, tubes, wires, etc), which are finding applications in electronic, magnetic, optical and other devices. The Japan Applied Physics Society has established a group to develop the research field of studying buried function interfaces with x-rays and neutrons. As the methods can be applied to almost all types of materials, from semiconductor and electronic devices to soft materials, participants have fairly different backgrounds but share a common interest in state-of-the-art x-ray and neutron techniques and sophisticated applications. A series of workshops has been organized almost every year since 2001. Some international interactions have been continued intensively, although the community is part of a Japanese society. This special issue does not report the proceedings of the recent workshop, although all the authors are in some way involved in the activities of the above society. Initially, we intended to collect quite long overview papers, including the authors' latest and most important original results, as well as updates on recent progress and global trends in the field. We planned to cover quite a wide area of surface and buried interface science with x-rays and neutrons. Following a great deal of discussion during the editing process, we have decided to change direction. As we intend to publish similar special issues on a frequent basis, we will not insist on editing this issue as systematic and complete collections of research. Many authors decided to write an ordinary research paper rather than an article including systematic accounts. Due to this change in policy, some authors declined to contribute, and the number of papers is now just 12. However, readers will find that the special issue gives an interesting collection of new original research in surface and buried interface studies with x-rays and neutrons. The 12 papers cover the following research topics: (1) polymer analysis by diffuse scattering; (2) discussion of the electrochemical solid--liquid interface by synchrotron x-ray diffraction; (3) analysis of capped nanodots by grazing incidence small-angle x-ray scattering (GISAXS); (4) discussion of the strain distribution in silicon by high-resolution x-ray diffraction; (5) study of mesoporous structures by a combination of x-ray reflectivity and GISAXS; (6) discussion of energy-dispersive x-ray reflectometry and its applications; (7) neutron reflectivity studies on hydrogen terminated silicon interface; (8) the fabrication and performance of a special mirror for water windows; (9) depth selective analysis by total-reflection x-ray diffraction; (10) nanoparticle thin films prepared by a gas deposition technique; (11) discussion of crystal truncation rod (CTR) scattering of semiconductor nanostructures; (12) magnetic structure analysis of thin films by polarized neutron reflectivity. While not discussed in the present special issue, x-ray and neutron techniques have made great progress. The most important steps forward have been in 2D/3D real-space imaging, and realtime measurement. Advances in such technologies are bringing with them new opportunities in surface and buried interface science. In the not too distant future, we will publish a special issue or a book detailing such progress. Exploring surfaces and buried interfaces of functional materials by advanced x-ray and neutron techniques contents Lateral uniformity in chemical composition along a buried reaction front in polymers using off-specular reflectivity Kristopher A Lavery, Vivek M Prabhu, Sushil Satija and Wen-li Wu Orientation dependence of Pd growth on Au electrode surfaces M Takahasi, K Tamura, J Mizuki, T Kondo and K Uosaki A grazing incidence small-angle x-ray scattering analysis on capped Ge nanodots in layer structures Hiroshi Okuda, Masayuki Kato, Keiji Kuno, Shojiro Ochiai, Noritaka Usami, Kazuo Nakajima and Osami Sakata High resolution grazing-incidence in-plane x-ray diffraction for measuring the strain of a Si thin layer Kazuhiko Omote X-ray analysis of mesoporous silica thin films templated by Brij58 surfactant S Fall, M Kulij and A Gibaud Review of the applications of x-ray refraction and the x-ray waveguide phenomenon to estimation of film structures Kouichi Hayashi Epitaxial growth of largely mismatched crystals on H-terminated Si(111) surfaces Hidehito Asaoka Novel TiO2/ZnO multilayer mirrors at 'water-window' wavelengths fabricated by atomic layer epitaxy H Kumagai, Y Tanaka, M Murata, Y Masuda and T Shinagawa Depth-selective structural analysis of thin films using total-external-reflection x-ray diffraction Tomoaki Kawamura and Hiroo Omi Structures of Yb nanoparticle thin films grown by deposition in He and N2 gas atmospheres: AFM and x-ray reflectivity studies Martin Jerab and Kenji Sakurai Ga and As composition profiles in InP/GaInAs/InP heterostructures—x-ray CTR scattering and cross-sectional STM measurements Yoshikazu Takeda, Masao Tabuchi and Arao Nakamura Polarized neutron reflectivity study of a thermally treated MnIr/CoFe exchange bias system Naoki Awaji, Toyoo Miyajima, Shuuichi Doi and Kenji Nomura

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zarkevich, Nikolai A; Johnson, Duane D

Nitinol (NiTi), the most widely used shape-memory alloy, exhibits an austenite phase that has yet to be identified. The usually assumed austenitic structure is cubic B2, which has imaginary phonon modes, hence it is unstable. We suggest a stable austenitic structure that “on average” has B2 symmetry (observed by x-ray and neutron diffraction), but it exhibits finite atomic displacements from the ideal B2 sites. The proposed structure has a phonon spectrum that agrees with that from neutron scattering, has diffraction spectra in agreement with x-ray diffraction, and has an energy relative to the ground state that agrees with calorimetry data.

Polarized neutron scattering on HYSPEC: the HYbrid SPECtrometer at SNS

DOE PAGES

Zaliznyak, Igor A.; Savici, Andrei T.; Ovidiu Garlea, V.; ...

2017-06-20

Here, we describe some of the first polarized neutron scattering measurements performed at HYSPEC [1-4] spectrometer at the Spallation Neutron Source, Oak Ridge National Laboratory. Furthermore, we discuss details of the instrument setup and the experimental procedures in the mode with full polarization analysis. Examples of polarized neutron diffraction and polarized inelastic neutron data obtained on single crystal samples are presented.

Neutron diffraction investigation of γ manganese hydride

NASA Astrophysics Data System (ADS)

Fedotov, V. K.; Antonov, V. E.; Kolesnikov, A. I.; Beskrovnyi, A. I.; Grosse, G.; Wagner, F. E.

1998-08-01

A profile analysis of the neutron diffraction spectrum of the fcc high pressure hydride λ-MnH 0.41 measured under ambient conditions showed that hydrogen is randomly distributed over the octahedral interstices of the fcc metal lattice and that the hydride is an antiferromagnet with the same collinear spin structure as pure λ-Mn, but with a smaller magnetic moment of about 1.9 Bohr magnetons per Mn atom.

STRUCTURE OF POTASSIUM HYDROGEN MALEATE BY NEUTRON DIFFRACTION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Peterson, S.W.; Levy, H.A.

1958-10-01

The preliminary results of a neutron diffraction study are presented which confirm the existence in potassium hydrogen maleate of a short, strong, hydrogen bond and show the ion to be at least statistically symmetrical. The hydrogen is strongly linked to both neighboring oxygen atoms, and there is an existing mode of correlated motion of considerable amplitude in which the oxygen atoms are displaced but hydrogen is not. (J.R.D.)

Neutron Diffraction and Electrical Transport Studies on Magnetic Transition in Terbium at High Pressures and Low Temperatures

NASA Astrophysics Data System (ADS)

Thomas, Sarah; Montgomery, Jeffrey; Tsoi, Georgiy; Vohra, Yogesh; Weir, Samuel; Tulk, Christopher; Moreira Dos Santos, Antonio

2013-06-01

Neutron diffraction and electrical transport measurements have been carried out on the heavy rare earth metal terbium at high pressures and low temperatures in order to elucidate its transition from a helical antiferromagnetic to a ferromagnetic ordered phase as a function of pressure. The electrical resistance measurements using designer diamonds show a change in slope as the temperature is lowered through the ferromagnetic Curie temperature. The temperature of the ferromagnetic transition decreases at a rate of -16.7 K/GPa till 3.6 GPa, where terbium undergoes a structural transition from hexagonal close packed (hcp) to an α-Sm phase. Above this pressure, the electrical resistance measurements no longer exhibit a change in slope. In order to confirm the change in magnetic phase suggested by the electrical resistance measurements, neutron diffraction measurements were conducted at the SNAP beamline at the Oak Ridge National Laboratory. Measurements were made at pressures to 5.3 GPa and temperatures as low as 90 K. An abrupt increase in peak intensity in the neutron diffraction spectra signaled the onset of magnetic order below the Curie temperature. A magnetic phase diagram of rare earth metal terbium will be presented to 5.3 GPa and 90 K based on these studies.

Residual Stress Induced Mechanical Property Enhancement in Steel Encapsulated Light Metal Matrix Composites

NASA Astrophysics Data System (ADS)

Fudger, Sean James

Macro hybridized systems consisting of steel encapsulated light metal matrix composites (MMCs) were produced with the goal of creating a low cost/light weight composite system with enhanced mechanical properties. MMCs are frequently incorporated into advanced material systems due to their tailorable material properties. However, they often have insufficient ductility for many structural applications. The macro hybridized systems take advantage of the high strength, modulus, and damage tolerance of steels and high specific stiffness and low density of MMCs while mitigating the high density of steels and the poor ductility of MMCs. Furthermore, a coefficient of thermal expansion (CTE) mismatch induced residual compressive stress method is utilized as a means of improving the ductility of the MMCs and overall efficiency of the macro hybridized systems. Systems consisting of an A36, 304 stainless steel, or NitronicRTM 50 stainless steel shell filled with an Al-SiC, Al-Al2O3, or Mg-B4C MMC are evaluated in this work. Upon cooling from processing temperatures, residual strains are generated due to a CTE mismatch between each of the phases. The resulting systems offer higher specific properties and a more structurally efficient system can be attained. Mechanical testing was performed and improvements in yield stress, ultimate tensile stress, and ductility were observed. However, the combination of these dissimilar materials often results in the formation of intermetallic compounds. In certain loading situations, these typically brittle intermetallic layers can result in degraded performance. X-ray Diffraction (XRD), X-ray Energy Dispersive Spectroscopy (EDS), and Electron Backscatter Diffraction (EBSD) are utilized to characterize the intermetallic layer formation at the interface between the steel and MMC. As the residual stress condition in each phase has a large impact on the mechanical property improvement, accurate quantification of these strains/stresses is paramount. X-ray Diffraction Residual Stress Analysis (XRD-RSA) or Neutron diffraction was performed on numerous systems in multiple steel shell thickness variations. The analysis shows variation in the measured strain and stress results due to outer steel thickness, difference in CTE between materials, and relative position within the composite. Improvements in mechanical properties, namely ductility and yield stress, are a direct result of these measured strains.

Measurement of elastic constants of monoclinic nickel-titanium and validation of first principles calculations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stebner, A. P.; Brown, D. W.; Brinson, L. C.

2013-05-27

Polycrystalline, monoclinic nickel-titanium specimens were subjected to tensile and compressive deformations while neutron diffraction spectra were recorded in situ. Using these data, orientation-specific and macroscopic Young's moduli are determined from analysis of linear-elastic deformation exhibited by 13 unique orientations of monoclinic lattices and their relationships to each macroscopic stress and strain. Five of 13 elastic compliance constants are also identified: s{sub 11} = 1.15, s{sub 15} = -1.10, s{sub 22} = 1.34, s{sub 33} = 1.06, s{sub 35} = -1.54, all Multiplication-Sign 10{sup -2} GPa{sup -1}. Through these results, recent atomistic calculations of monoclinic nickel-titanium elastic constants are validated.

Magnetic anisotropy in antiferromagnetic hexagonal MnTe

NASA Astrophysics Data System (ADS)

Kriegner, D.; Reichlova, H.; Grenzer, J.; Schmidt, W.; Ressouche, E.; Godinho, J.; Wagner, T.; Martin, S. Y.; Shick, A. B.; Volobuev, V. V.; Springholz, G.; Holý, V.; Wunderlich, J.; Jungwirth, T.; Výborný, K.

2017-12-01

Antiferromagnetic hexagonal MnTe is a promising material for spintronic devices relying on the control of antiferromagnetic domain orientations. Here we report on neutron diffraction, magnetotransport, and magnetometry experiments on semiconducting epitaxial MnTe thin films together with density functional theory (DFT) calculations of the magnetic anisotropies. The easy axes of the magnetic moments within the hexagonal basal plane are determined to be along 〈1 1 ¯00 〉 directions. The spin-flop transition and concomitant repopulation of domains in strong magnetic fields is observed. Using epitaxially induced strain the onset of the spin-flop transition changes from ˜2 to ˜0.5 T for films grown on InP and SrF2 substrates, respectively.

Comparing results of X-ray diffraction, µ-Raman spectroscopy and neutron diffraction when identifying chemical phases in seized nuclear material, during a comparative nuclear forensics exercise

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rondahl, Stina Holmgren; Pointurier, Fabien; Ahlinder, Linnea

This work presents the results for identification of chemical phases obtained by several laboratories as a part of an international nuclear forensic round-robin exercise. In this work powder X-ray diffraction (p-XRD) is regarded as the reference technique. Neutron diffraction produced a superior high-angle diffraction pattern relative to p-XRD. Requiring only small amounts of sample, µ-Raman spectroscopy was used for the first time in this context as a potentially complementary technique to p-XRD. The chemical phases were identified as pure UO 2 in two materials, and as a mixture of UO 2, U 3O 8 and an intermediate species U 3Omore » 7 in the third material.« less

Comparing results of X-ray diffraction, µ-Raman spectroscopy and neutron diffraction when identifying chemical phases in seized nuclear material, during a comparative nuclear forensics exercise

DOE PAGES

Rondahl, Stina Holmgren; Pointurier, Fabien; Ahlinder, Linnea; ...

2018-01-24

This work presents the results for identification of chemical phases obtained by several laboratories as a part of an international nuclear forensic round-robin exercise. In this work powder X-ray diffraction (p-XRD) is regarded as the reference technique. Neutron diffraction produced a superior high-angle diffraction pattern relative to p-XRD. Requiring only small amounts of sample, µ-Raman spectroscopy was used for the first time in this context as a potentially complementary technique to p-XRD. The chemical phases were identified as pure UO 2 in two materials, and as a mixture of UO 2, U 3O 8 and an intermediate species U 3Omore » 7 in the third material.« less

Structural properties of barium stannate

NASA Astrophysics Data System (ADS)

Phelan, D.; Han, F.; Lopez-Bezanilla, A.; Krogstad, M. J.; Gim, Y.; Rong, Y.; Zhang, Junjie; Parshall, D.; Zheng, H.; Cooper, S. L.; Feygenson, M.; Yang, Wenge; Chen, Yu-Sheng

2018-06-01

BaSnO3 has attracted attention as a transparent conducting oxide with high room temperature carrier mobility. We report a series of measurements that were carried out to assess the structure of BaSnO3 over a variety of length scales. Measurements included single crystal neutron and x-ray diffraction, Rietveld and pair distribution analysis of neutron powder diffraction, Raman scattering, and high-pressure x-ray diffraction. Results from the various diffraction probes indicate that both the long-range and local structures are consistent with the cubic symmetry. The diffraction data under pressure was consistent with a robustly cubic phase up to 48.9 GPa, which is supported by density functional calculations. Additionally, transverse phonon velocities were determined from measured dispersion of the transverse acoustic phonon branches, the results of which are in good agreement with previous theoretical estimates and ultrasound measurements.

Quantitative phase analysis of challenging samples using neutron powder diffraction. Sample #4 from the CPD QPA round robin revisited

DOE PAGES

Whitfield, Pamela S.

2016-04-29

Here, quantitative phase analysis (QPA) using neutron powder diffraction more often than not involves non-ambient studies where no sample preparation is possible. The larger samples and penetration of neutrons versus X-rays makes neutron diffraction less susceptible to inhomogeneity and large grain sizes, but most well-characterized QPA standard samples do not have these characteristics. Sample #4 from the International Union of Crystallography Commission on Powder Diffraction QPA round robin was one such sample. Data were collected using the POWGEN time-of-flight (TOF) neutron powder diffractometer and analysed together with historical data from the C2 diffractometer at Chalk River. The presence of magneticmore » reflections from Fe 3O 4 (magnetite) in the sample was an additional consideration, and given the frequency at which iron-containing and other magnetic compounds are present during in-operando studies their possible impact on the accuracy of QPA is of interest. Additionally, scattering from thermal diffuse scattering in the high-Qregion (<0.6 Å) accessible with TOF data could impact QPA results during least-squares because of the extreme peak overlaps present in this region. Refinement of POWGEN data was largely insensitive to the modification of longer d-spacing reflections by magnetic contributions, but the constant-wavelength data were adversely impacted if the magnetic structure was not included. A robust refinement weighting was found to be effective in reducing quantification errors using the constant-wavelength neutron data both where intensities from magnetic reflections were ignored and included. Results from the TOF data were very sensitive to inadequate modelling of the high- Q (low d-spacing) background using simple polynomials.« less

Illuminating the Past: The Neutron as a Tool in Archaeology

ERIC Educational Resources Information Center

Kockelmann, W.; Kirfel, A.; Siano, S.; Frost, C. D.

2004-01-01

Neutrons can be produced in nuclear reactions and used as very versatile probes for condensed matter research. Since their introduction in the 1950s neutron scattering techniques have evolved to be very powerful tools for investigating the properties of condensed matter. Here we present the concept of neutron diffraction and how this technique can…

Negative thermal expansion and magnetoelastic coupling in the breathing pyrochlore lattice material LiGaCr4S8

NASA Astrophysics Data System (ADS)

Pokharel, G.; May, A. F.; Parker, D. S.; Calder, S.; Ehlers, G.; Huq, A.; Kimber, S. A. J.; Arachchige, H. Suriya; Poudel, L.; McGuire, M. A.; Mandrus, D.; Christianson, A. D.

2018-04-01

The physical properties of the spinel LiGaCr4S8 have been studied with neutron diffraction, x-ray diffraction, magnetic susceptibility, and heat capacity measurements. The neutron diffraction and synchrotron x-ray diffraction data reveal negative thermal expansion (NTE) below 111(4) K. The magnetic susceptibility deviates from Curie-Weiss behavior with the onset of NTE. At low temperature a broad peak in the magnetic susceptibility at 10.3(3) K is accompanied by the return of normal thermal expansion. First-principles calculations find a strong coupling between the lattice and the simulated magnetic ground state. These results indicate strong magnetoelastic coupling in LiGaCr4S8 .

Non-invasive characterisation of SIX Japanese hand-guards (tsuba)

NASA Astrophysics Data System (ADS)

Barzagli, Elisa; Grazzi, Francesco; Civita, Francesco; Scherillo, Antonella; Pietropaolo, Antonino; Festa, Giulia; Zoppi, Marco

2013-12-01

In this work we present a systematic study of Japanese sword hand-guards ( tsuba) carried out by means of non-invasive techniques using neutrons. Several tsuba from different periods, belonging to the Japanese Section of the Stibbert Museum, were analysed using an innovative approach to characterise the bulk of the samples, coupling two neutron techniques, namely Time of Flight Neutron Diffraction (ToF-ND) and Nuclear Resonance Capture Analysis (NRCA). The measurements were carried out on the same instrument: the INES beam-line at the ISIS spallation pulsed neutron source (UK). NRCA analysis allows identifying the elements present in the sample gauge volume, while neutron diffraction is exploited to quantify the phase distribution and other micro-structural parameters of the metal specimen. The results show that all samples are made of high-quality metal, either steel or copper alloy, with noticeable changes in composition and working techniques, depending on the place and time of manufacturing.

High-resolution neutron diffraction study of microstructural changes in nanocrystalline ball-milled niobium carbide NbC{sub 0.93}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Balagurov, Anatoly M.; Bobrikov, Ivan A.; Bokuchava, Gizo D.

2015-11-15

High resolution neutron diffraction was applied for elucidating of the microstructural evolution of nanocrystalline niobium carbide NbC{sub 0.93} powders subjected to high-energy ball milling. The diffraction patterns were collected with the high resolution Fourier diffractometer HRFD by using the reverse time-of-flight (RTOF) mode of data acquisition. The traditional single diffraction line analysis, the Rietveld method and more advanced Whole Powder Pattern Modeling technique were applied for the data analysis. The comparison of these techniques was performed. It is established that short-time milling produces a non-uniform powder, in which two distinct fractions with differing microstructure can be identified. Part of themore » material is in fact milled efficiently, with a reduction in grain size, an increase in the quantity of defects, and a corresponding tendency to decarburize reaching a composition NbC{sub 0.80} after 15 h of milling. The rest of the powder is less efficiently processed and preserves its composition and lower defect content. Larger milling times should have homogenized the system by increasing the efficiently milled fraction, but the material is unable to reach a uniform and homogeneous state. It is definitely shown that RTOF neutron diffraction patterns can provide the very accurate data for microstructure analysis of nanocrystalline powders. - Highlights: • The NbC{sub 0.93} powder was processed by high-energy ball milling. • The microstrain and dislocation density increase with milling time increase. • The corresponding decrease in crystallite size with milling time was observed. • The material exhibits the presence of two fractions after ball milling. • The RTOF neutron diffraction data are suitable for accurate microstructure analysis.« less

Search for memory effects in methane hydrate: structure of water before hydrate formation and after hydrate decomposition.

PubMed

Buchanan, Piers; Soper, Alan K; Thompson, Helen; Westacott, Robin E; Creek, Jefferson L; Hobson, Greg; Koh, Carolyn A

2005-10-22

Neutron diffraction with HD isotope substitution has been used to study the formation and decomposition of the methane clathrate hydrate. Using this atomistic technique coupled with simultaneous gas consumption measurements, we have successfully tracked the formation of the sI methane hydrate from a water/gas mixture and then the subsequent decomposition of the hydrate from initiation to completion. These studies demonstrate that the application of neutron diffraction with simultaneous gas consumption measurements provides a powerful method for studying the clathrate hydrate crystal growth and decomposition. We have also used neutron diffraction to examine the water structure before the hydrate growth and after the hydrate decomposition. From the neutron-scattering curves and the empirical potential structure refinement analysis of the data, we find that there is no significant difference between the structure of water before the hydrate formation and the structure of water after the hydrate decomposition. Nor is there any significant change to the methane hydration shell. These results are discussed in the context of widely held views on the existence of memory effects after the hydrate decomposition.

Magnetic and Structural Characterization of Fe-Ga Using Kerr Microscopy and Neutron Scattering

DTIC Science & Technology

2010-01-01

117 4.6 Schematic of triple axes single crystal neutron diffractometer (left). TriCS intrument at Paul Scherrer Institut, Switzerland (right...Therefore, USANS data is one-dimensional. 4.3.3 Single Crystal Neutron Diffraction The single crystal neutron diffractometer, TriCS at Paul Scherrer...crystal neutron diffractometer (left). TriCS intrument at Paul Scherrer Institut, Switzerland (right) [106] 4.4 Unpolarized SANS In this section, SANS

Neutron powder diffraction and high-pressure synchrotron x-ray diffraction study of tantalum nitrides

NASA Astrophysics Data System (ADS)

Feng, Lei-hao; Hu, Qi-wei; Lei, Li; Fang, Lei-ming; Qi, Lei; Zhang, Lei-lei; Pu, Mei-fang; Kou, Zi-li; Peng, Fang; Chen, Xi-ping; Xia, Yuan-hua; Kojima, Yohei; Ohfuji, Hiroaki; He, Duan-wei; Chen, Bo; Irifune, Tetsuo

2018-02-01

Not Available Project supported by the Research Foundation of Key Laboratory of Neutron Physics (Grant No. 2015BB03), the National Natural Science Foundation of China (Grant Nos. 11774247), the Science Foundation for Excellent Youth Scholars of Sichuan University (Grant No. 2015SCU04A04), and the Joint Usage/Research Center PRIUS (Ehime University, Japan) and Chinese Academy of Sciences (Grant No. 2017-BEPC-PT-000568).

The structural and magnetic phase transitions in a ``parent'' Fe pnictide compound

NASA Astrophysics Data System (ADS)

Ni, Ni; Allred, Jared; Cao, Huibo; Tian, Wei; Liu, Lian; Cho, Kyuil; Krogstad, Matthew; Ma, Jie; Taddei, Keith; Tanatar, Makariy; Prozorov, Ruslan; Matsuda, Masaaki; Rosenkranz, Stephan; Uemura, Yasutomo; Jiang, Shan

2015-03-01

We will present transport, thermodynamic, synchrotron X-ray, neutron diffraction, μSR, ARPES and polarized optical image measurements on the ``parent'' compound of the 112 high Tc superconducting Fe pnictide family. Structural and magnetic phase transitions are revealed. Detailed magnetic structure was solved by single crystal neutron diffraction. We will discuss the similarity and difference of these transitions comparing to the parent compounds of other Fe pnictide superconductors.

Neutron diffraction studies of laser welding residual stresses

NASA Astrophysics Data System (ADS)

Petrov, Peter I.; Bokuchava, Gizo D.; Papushkin, Igor V.; Genchev, Gancho; Doynov, Nikolay; Michailov, Vesselin G.; Ormanova, Maria A.

2016-01-01

The residual stress and microstrain distribution induced by laser beam welding of the low-alloyed C45 steel plate was investigated using high-resolution time-of-flight (TOF) neutron diffraction. The neutron diffraction experiments were performed on FSD diffractometer at the IBR-2 pulsed reactor in FLNP JINR (Dubna, Russia). The experiments have shown that the residual stress distribution across weld seam exhibit typical alternating sign character as it was observed in our previous studies. The residual stress level is varying in the range from -60 MPa to 450 MPa. At the same time, the microstrain level exhibits sharp maxima at weld seam position with maximal level of 4.8·10-3. The obtained experimental results are in good agreement with FEM calculations according to the STAAZ model. The provided numerical model validated with measured data enables to study the influence of different conditions and process parameters on the development of residual welding stresses.

Neutron diffraction study of the formation of ordered antiphase domains in cubic titanium carbide TiC{sub 0.60}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khidirov, I., E-mail: khidirov@inp.uz; Parpiev, A. S.

2013-05-15

A series of superstructural reflections (described within the sp. gr. Fd3m) are found to be split into three symmetric parts in the neutron powder diffraction pattern of titanium carbide TiC{sub 0.60} annealed at a temperature of 600 Degree-Sign C. No splitting of superstructural reflections is observed in the neutron diffraction pattern of TiC{sub 0.60} annealed at relatively high temperatures (780 Degree-Sign C). This phenomenon can be explained by that fact that the ordering of carbon atoms at relatively high temperatures (780 Degree-Sign C) is accompanied by the formation of randomly oriented rather large antiphase domains (APDs) (450 A). At relativelymore » low temperatures (600 Degree-Sign C), stacking faults arise in the arrangement of partially ordered carbon atoms. In this case, relatively small ordered APDs (290 A) are formed, along with disordered ones.« less

Neutron and electron diffraction studies of La(Zn1/2Ti1/2)O3 perovskite.

PubMed

Ubic, Rick; Hu, Yi; Abrahams, Isaac

2006-08-01

The crystallography and microwave dielectric properties of La(Zn(1/2)Ti(1/2))O(3) (LZT) ceramics prepared via the mixed-oxide route were investigated in this study. While samples were largely single phase, small amounts of ZnO impurity were detected in sintered pellets. Observed reflections in electron and neutron diffraction patterns indicate that the symmetry of LZT is P2(1)/n. The B site is ordered on {110} or pseudocubic {111}, but the presence of the pseudocubic 1/2(111) reflection is in itself insufficient to indicate the existence of such order. Rietveld refinements of the neutron diffraction data yield an excellent fit for such a model. The structure is highly twinned, with variants related through common {211} composition planes and 90 degrees rotations about <011>. The microwave dielectric properties measured were epsilon(r) = 34, Qf = 36,090 and tau(f) = -70 MK(-1).

High-resolution neutron diffraction study of CuNCN: New evidence of structure anomalies at low temperature

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jacobs, Philipp; Houben, Andreas; Dronskowski, Richard, E-mail: drons@HAL9000.ac.rwth-aachen.de

Copper carbodiimide (CuNCN) is the nitrogen-containing analogue of cupric oxide. Based on high-resolution neutron-diffraction data, CuNCN's lattice parameters are derived as a function of the temperature. In accordance with a recent synchrotron study, a clear trend in the cell parameter a is observed accompanying the changing magnetic behavior. With decreasing temperature, a slowly decreases to a minimum at ∼100 K after which it rises again. The same trend—albeit more pronounced—is observed for the c lattice parameter at ∼35 K. The herein presented neutron powder-diffraction data also support the conjectured sequence of transitions from the high-temperature one-dimensional resonating valence-bond (RVB) statemore » to a transient two-dimensional RVB state and eventually, at lowest temperatures, into another two-dimensional RVB state, presumably the ground state.« less

Probing hydrogen positions in hydrous compounds: information from parametric neutron powder diffraction studies.

PubMed

Ting, Valeska P; Henry, Paul F; Schmidtmann, Marc; Wilson, Chick C; Weller, Mark T

2012-05-21

We demonstrate the extent to which modern detector technology, coupled with a high flux constant wavelength neutron source, can be used to obtain high quality diffraction data from short data collections, allowing the refinement of the full structures (including hydrogen positions) of hydrous compounds from in situ neutron powder diffraction measurements. The in situ thermodiffractometry and controlled humidity studies reported here reveal that important information on the reorientations of structural water molecules with changing conditions can be easily extracted, providing insight into the effects of hydrogen bonding on bulk physical properties. Using crystalline BaCl2·2H2O as an example system, we analyse the structural changes in the compound and its dehydration intermediates with changing temperature and humidity levels to demonstrate the quality of the dynamic structural information on the hydrogen atoms and associated hydrogen bonding that can be obtained without resorting to sample deuteration.

A method for the monitoring of metal recrystallization based on the in-situ measurement of the elastic energy release using neutron diffraction.

PubMed

Christien, F; Telling, M T F; Knight, K S; Le Gall, R

2015-05-01

A method is proposed for the monitoring of metal recrystallization using neutron diffraction that is based on the measurement of stored energy. Experiments were performed using deformed metal specimens heated in-situ while mounted at the sample position of the High Resolution Powder Diffractometer, HRPD (ISIS Facility), UK. Monitoring the breadth of the resulting Bragg lines during heating not only allows the time-dependence (or temperature-dependence) of the stored energy to be determined but also the recrystallized fraction. The analysis method presented here was developed using pure nickel (Ni270) specimens with different deformation levels from 0.29 to 0.94. In situ temperature ramping as well as isothermal annealing was undertaken. The method developed in this work allows accurate and quantitative monitoring of the recrystallization process. The results from neutron diffraction are satisfactorily compared to data obtained from calorimetry and hardness measurements.

Design and implementation of a multiaxial loading capability during heating on an engineering neutron diffractometer

DOE PAGES

Benafan, O.; Padula, S. A.; Skorpenske, H. D.; ...

2014-10-02

Here we discuss a gripping capability that was designed, implemented, and tested for in situ neutron diffraction measurements during multiaxial loading and heating on the VULCAN engineering materials diffractometer at the spallation neutron source at Oak Ridge National Laboratory.

Use of a miniature diamond-anvil cell in high-pressure single-crystal neutron Laue diffraction

PubMed Central

Binns, Jack; Kamenev, Konstantin V.; McIntyre, Garry J.; Moggach, Stephen A.; Parsons, Simon

2016-01-01

The first high-pressure neutron diffraction study in a miniature diamond-anvil cell of a single crystal of size typical for X-ray diffraction is reported. This is made possible by modern Laue diffraction using a large solid-angle image-plate detector. An unexpected finding is that even reflections whose diffracted beams pass through the cell body are reliably observed, albeit with some attenuation. The cell body does limit the range of usable incident angles, but the crystallographic completeness for a high-symmetry unit cell is only slightly less than for a data collection without the cell. Data collections for two sizes of hexamine single crystals, with and without the pressure cell, and at 300 and 150 K, show that sample size and temperature are the most important factors that influence data quality. Despite the smaller crystal size and dominant parasitic scattering from the diamond-anvil cell, the data collected allow a full anisotropic refinement of hexamine with bond lengths and angles that agree with literature data within experimental error. This technique is shown to be suitable for low-symmetry crystals, and in these cases the transmission of diffracted beams through the cell body results in much higher completeness values than are possible with X-rays. The way is now open for joint X-ray and neutron studies on the same sample under identical conditions. PMID:27158503

Structural Properties of Barium Stannate.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Phelan, D.; Han, F.; Lopez-Bezanilla, A.

2018-06-01

BaSnO3 has attracted attention as a transparent conducting oxide with high room temperature carrier mobility. We report a series of measurements that were carried out to assess the structure of BaSnO3 over a variety of length scales. Measurements included single crystal neutron and x-ray diffraction, Rietveld and pair distribution analysis of neutron powder diffraction, Raman scattering, and high-pressure x-ray diffraction. Results from the various diffraction probes indicate that both the long-range and local structures are consistent with the cubic symmetry. The diffraction data under pressure was consistent with a robustly cubic phase up to 48.9 GPa, which is supported bymore » density functional calculations. Additionally, transverse phonon velocities were determined from measured dispersion of the transverse acoustic phonon branches, the results of which are in good agreement with previous theoretical estimates and ultrasound measurements.« less

Unified structure theory of icosahedral quasicrystals: Evidence from neutron powder diffraction patterns that AlCrFeMnSi, AlCuLiMg, and TiNiFeSi icosahedral quasicrystals are twins of cubic crystals containing about 820 or 1012 atoms in a primitive unit cube

PubMed Central

Pauling, Linus

1988-01-01

A unified structure theory of icosahedral quasicrystals, combining the twinned-cubic-crystal theory and the Penrose-tiling-six-dimensional-projection theory, is described. Values of the primitive-cubic lattice constant for several quasicrystals are evaluated from x-ray and neutron diffraction data. The fact that the low-angle diffraction maxima can be indexed with cubic unit cells provides additional support for the twinned-cubic-crystal theory of icosahedral quasicrystals. PMID:16593990

Investigation of the dependence of deformation mechanisms on solute content in polycrystalline Mg–Al magnesium alloys by neutron diffraction and acoustic emission

DOE PAGES

Mathis, Kristian; Capek, J.; Clausen, Bjorn; ...

2015-04-20

Influence of aluminium content on the deformation mechanisms in Mg–Al binary alloys has been studied using in-situ neutron diffraction and acoustic emission technique. Here, it is shown that the addition of the solute increases the critical resolved shear stress for twinning. Further, the role of aluminium on the solid solution hardening of the basal plane and softening of non-basal planes are discussed using results of the convolutional multiple peak profile analysis of diffraction patterns. In conclusion, the results indicate that the density of both prismatic and pyramidal dislocations increases with increasing alloying content.

Instrument and method for focusing X-rays, gamma rays and neutrons

DOEpatents

Smither, Robert K.

1984-01-01

A crystal diffraction instrument or diffraction grating instrument with an improved crystalline structure or grating spacing structure having a face for receiving a beam of photons or neutrons and diffraction planar spacing or grating spacing along that face with the spacing increasing progressively along the face to provide a decreasing Bragg diffraction angle for a monochromatic radiation and thereby increasing the usable area and acceptance angle. The increased planar spacing for the diffraction crystal is provided by the use of a temperature differential across the crystalline structure, by assembling a plurality of crystalline structures with different compositions, by an individual crystalline structure with a varying composition and thereby a changing planar spacing along its face, and by combinations of these techniques. The increased diffraction grating element spacing is generated during the fabrication of the diffraction grating by controlling the cutting tool that is cutting the grooves or controlling the laser beam, electron beam or ion beam that is exposing the resist layer, etc. It is also possible to vary this variation in grating spacing by applying a thermal gradient to the diffraction grating in much the same manner as is done in the crystal diffraction case.

Instrument and method for focusing x rays, gamma rays, and neutrons

DOEpatents

Smither, R.K.

1982-03-25

A crystal-diffraction instrument or diffraction-grating instrument is described with an improved crystalline structure or grating spacing structure having a face for receiving a beam of photons or neutrons and diffraction planar spacing or grating spacing along that face with the spacing increasing progressively along the face to provide a decreasing Bragg diffraction angle for a monochromatic radiation and thereby increasing the usable area and acceptance angle. The increased planar spacing for the diffraction crystal is provided by the use of a temperature differential across the line structures with different compositions, by an individual crystalline structure with a varying composition and thereby a changing planar spacing along its face, and by combinations of these techniques. The increased diffraction grating element spacing is generated during the fabrication of the diffraction grating by controlling the cutting tool that is cutting the grooves or controlling the laser beam, electron beam, or ion beam that is exposing the resist layer, etc. It is also possible to vary this variation in grating spacing by applying a thermal gradient to the diffraction grating in much the same manner as is done in the crystal-diffraction case.

Negative thermal expansion and magnetoelastic coupling in the breathing pyrochlore lattice material LiGaCr 4 S 8

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pokharel, G.; May, A. F.; Parker, D. S.

In this paper, the physical properties of the spinel LiGaCr 4S 8 have been studied with neutron diffraction, x-ray diffraction, magnetic susceptibility, and heat capacity measurements. The neutron diffraction and synchrotron x-ray diffraction data reveal negative thermal expansion (NTE) below 111(4) K. The magnetic susceptibility deviates from Curie-Weiss behavior with the onset of NTE. At low temperature a broad peak in the magnetic susceptibility at 10.3(3) K is accompanied by the return of normal thermal expansion. First-principles calculations find a strong coupling between the lattice and the simulated magnetic ground state. Finally, these results indicate strong magnetoelastic coupling in LiGaCrmore » 4S 8.« less

Negative thermal expansion and magnetoelastic coupling in the breathing pyrochlore lattice material LiGaCr 4 S 8

DOE PAGES

Pokharel, G.; May, A. F.; Parker, D. S.; ...

2018-04-30

In this paper, the physical properties of the spinel LiGaCr 4S 8 have been studied with neutron diffraction, x-ray diffraction, magnetic susceptibility, and heat capacity measurements. The neutron diffraction and synchrotron x-ray diffraction data reveal negative thermal expansion (NTE) below 111(4) K. The magnetic susceptibility deviates from Curie-Weiss behavior with the onset of NTE. At low temperature a broad peak in the magnetic susceptibility at 10.3(3) K is accompanied by the return of normal thermal expansion. First-principles calculations find a strong coupling between the lattice and the simulated magnetic ground state. Finally, these results indicate strong magnetoelastic coupling in LiGaCrmore » 4S 8.« less

Sensitivity Analysis and Simulation of Theoretical Response of Ceramics to Strong Magnetic Fields

DTIC Science & Technology

2016-09-01

Weapons and Materials Research Directorate, ARL Approved for public release; distribution is unlimited. FOR OFFICIAL USE ONLY...Compounds. 2013;551:568–577. 4. Terada N, Suzuki HS, Suzuki TS, Kitazawa H, Sakka Y, Kaneko K, Metoki N. In situ neutron diffraction study of...TS, Kitazawa H, Sakka Y, Kaneko K, Metoki N. Neutron diffraction texture analysis for alpha-Al2O3 oriented by a high magnetic field and sintering

Neutron diffraction studies on cobalt substituted BiFeO3

NASA Astrophysics Data System (ADS)

Ray, J.; Biswal, A. K.; Acharya, S.; Babu, P. D.; Siruguri, V.; Vishwakarma, P. N.

2013-02-01

A dilute concentration of single phase Cobalt substituted Bismuth ferrite, BiFe1-XCoXO3; (x=0, 0.02) is prepared by sol-gel auto combustion method. Room temperature neutron diffraction patterns show no change in the crystal and magnetic structure upon cobalt doping. The calculation of magnetic moments shows 3.848 μB for Fe+ and 2.85 μB for Co3+. The cobalt is found to be in intermediate spin state.

Neutron Diffraction Studies of Some Rare Earth-Transition Metal Deuterides.

DTIC Science & Technology

1986-05-01

RD-A168 M NEUTRON DIFFRACTION STUDIES OF SONE RARE EARTH-TRANSITION METAL DEUTERIDES(U) MISSOURI UNIV-ROLLR MATERIALS RESEARCH CENTER N J JAMES MY 86...REPORT William J. James OTtO -il May 1986 ZLECTEJU U. S. Army Research Office DAAG29-83-K-01 59 ".;’ Graduate Center for Materials Research ...9. PERFORMING ORGANIZATION NAME AND ADDRESS 10. PROGRAM ELEMENT, PROJECT. TASK AREA & WORK UNIT NUMBERS 2* Graduate Center for Materials Research

Digital Image Correlation of 2D X-ray Powder Diffraction Data for Lattice Strain Evaluation

PubMed Central

Zhang, Hongjia; Sui, Tan; Daisenberger, Dominik; Fong, Kai Soon

2018-01-01

High energy 2D X-ray powder diffraction experiments are widely used for lattice strain measurement. The 2D to 1D conversion of diffraction patterns is a necessary step used to prepare the data for full pattern refinement, but is inefficient when only peak centre position information is required for lattice strain evaluation. The multi-step conversion process is likely to lead to increased errors associated with the ‘caking’ (radial binning) or fitting procedures. A new method is proposed here that relies on direct Digital Image Correlation analysis of 2D X-ray powder diffraction patterns (XRD-DIC, for short). As an example of using XRD-DIC, residual strain values along the central line in a Mg AZ31B alloy bar after 3-point bending are calculated by using both XRD-DIC and the conventional ‘caking’ with fitting procedures. Comparison of the results for strain values in different azimuthal angles demonstrates excellent agreement between the two methods. The principal strains and directions are calculated using multiple direction strain data, leading to full in-plane strain evaluation. It is therefore concluded that XRD-DIC provides a reliable and robust method for strain evaluation from 2D powder diffraction data. The XRD-DIC approach simplifies the analysis process by skipping 2D to 1D conversion, and opens new possibilities for robust 2D powder diffraction data analysis for full in-plane strain evaluation. PMID:29543728

A residual stress study in similar and dissimilar welds

DOE PAGES

Eisazadeh, Hamid; Goldak, John A.; Aidun, Daryush K.; ...

2016-04-01

Residual strain distributions in similar and dissimilar welds were measured using neutron diffraction (ND) method. Then, using three strain components, three-dimensional stress states were calculated. The results were used to determine the effect of the martensitic phase transformation and material properties on residual stress (RS) distribution. It was observed that smaller longitudinal RS was induced in the low carbon steel side of dissimilar weld when compared to its similar weld. Also, it was found that the transverse RS near and within the weld zone (WZ) in dissimilar weld exhibited a distinctive trend, with tensile mode reaching the yield strength ofmore » the base metal (BM). In order to characterize the WZ in dissimilar weld, we deployed optical microscopy, hardness, and energy dispersive X-ray spectroscopy (EDAX). This study not only provides further insight into the RS state in similar and dissimilar welds; it also delivers important consequences of phase transformation in the latter case.« less

High-pressure studies on Ba-doped cobalt perovskites by neutron diffraction

NASA Astrophysics Data System (ADS)

Cao, Huibo; Garlea, Vasile; Wang, Fangwei; Dos Santos, Antonio; Cheng, Zhaohua

2012-02-01

Cobalt perovskite possess rich structural, magnetic and electrical properties depending on the subtle balance of the interactions among the spin, charge, and orbital degrees of freedom. Divalent hole-doped cobalt perovskites LaA^2+CoO3 exhibit structural phase transitions, metal-insulator transitions, and multi-magnetic phase transitions. High-pressure measurement is believed to mimic the size effects of the doped ions. We performed neutron diffraction experiments on selected Ba-doped LaCoO3 under pressures up to 6.3 GPa at SNAP at Spallation Neutron Source of ORNL. This work focuses on the high-pressure effects of the selected Ba-doped samples and the change of the phase diagram with pressure.

Quantum correlations and Bell’s inequality violation in a Heisenberg spin dimer via neutron scattering

NASA Astrophysics Data System (ADS)

Cruz, C.

The characterization of quantum information quantifiers has attracted a considerable attention of the scientific community, since they are a useful tool to verify the presence of quantum correlations in a quantum system. In this context, in the present work we show a theoretical study of some quantifiers, such as entanglement witness, entanglement of formation, Bell’s inequality violation and geometric quantum discord as a function of the diffractive properties of neutron scattering. We provide one path toward identifying the presence of quantum correlations and quantum nonlocality in a molecular magnet as a Heisenberg spin-1/2 dimer, by diffractive properties typically obtained via neutron scattering experiments.

The Macromolecular Neutron Diffractometer MaNDi at the Spallation Neutron Source

DOE PAGES

Coates, Leighton; Cuneo, Matthew J.; Frost, Matthew J.; ...

2015-07-18

The Macromolecular Neutron Diffractometer (MaNDi) is located on beamline 11B of the Spallation Neutron Source at Oak Ridge National Laboratory. Moreover, the instrument is a neutron time-of-flight wavelength-resolved Laue diffractometer optimized to collect diffraction data from single crystals. Finally, the instrument has been designed to provide flexibility in several instrumental parameters, such as beam divergence and wavelength bandwidth, to allow data collection from a range of macromolecular systems.

Characterizing the Nano and Micro Structure of Concrete toImprove its Durability

DOE Office of Scientific and Technical Information (OSTI.GOV)

Monteiro, P.J.M.; Kirchheim, A.P.; Chae, S.

2009-01-13

New and advanced methodologies have been developed to characterize the nano and microstructure of cement paste and concrete exposed to aggressive environments. High resolution full-field soft X-ray imaging in the water window is providing new insight on the nano scale of the cement hydration process, which leads to a nano-optimization of cement-based systems. Hard X-ray microtomography images of ice inside cement paste and cracking caused by the alkali?silica reaction (ASR) enables three-dimensional structural identification. The potential of neutron diffraction to determine reactive aggregates by measuring their residual strains and preferred orientation is studied. Results of experiments using these tools aremore » shown on this paper.« less

Characterizing the nano and micro structure of concrete to improve its durability

DOE Office of Scientific and Technical Information (OSTI.GOV)

Monteiro, P.J.M.; Kirchheim, A.P.; Chae, S.

2008-10-22

New and advanced methodologies have been developed to characterize the nano and microstructure of cement paste and concrete exposed to aggressive environments. High resolution full-field soft X-ray imaging in the water window is providing new insight on the nano scale of the cement hydration process, which leads to a nano-optimization of cement-based systems. Hard X-ray microtomography images on ice inside cement paste and cracking caused by the alkali-silica reaction (ASR) enables three-dimensional structural identification. The potential of neutron diffraction to determine reactive aggregates by measuring their residual strains and preferred orientation is studied. Results of experiments using these tools willmore » be shown on this paper.« less

Preferred Orientation of Rare Earth (RE)-Doped Alumina Crystallites by an Applied Magnetic Field

DTIC Science & Technology

2016-06-01

Magnetic Field by Victoria L Blair, Raymond E Brennan, and Jane W Adams Weapons and Materials Research Directorate, ARL Carli A Moorehead...public release; distribution is unlimited. 16 13. Terada N, Suzuki HS, Suzuki TS, Kitazawa H, Sakka Y, Kaneko K, Metok N. In situ neutron diffraction...HS, Suzuki TS, Kitazawa H, Sakka Y, Kaneko K, Metoki N. Neutron diffraction texture analysis for alpha-Al2O3 oriented by high magnetic field and

The Crystal Structure of Thorium and Zirconium Dihydrides by X-ray and Neutron Diffraction

DOE R&D Accomplishments Database

Rundle, R.E.; Shull, C.G.; Wollan, E.O.

1951-04-20

Thorium forms a tetragonal lower hydride of composition ThH{sub 2}. The hydrides ThH{sub 2}, ThD{sub 2}, and ZrD{sub 2} have been studied by neutron diffraction in order that hydrogen positions could be determined. The hydrides are isomorphous, and have a deformed fluorite structure. Metal-hydrogen distances in thorium hydride are unusually large, as in UH{sub 3}. Thorium and zirconium scattering amplitudes and a revised scattering amplitude for deuterium are reported.

Magnetic structure of the swedenborgite CaBa (Co3Fe ) O7 derived by unpolarized neutron diffraction and spherical neutron polarimetry

NASA Astrophysics Data System (ADS)

Qureshi, N.; Díaz, M. T. Fernández; Chapon, L. C.; Senyshyn, A.; Schweika, W.; Valldor, M.

2018-02-01

We present a study that combines polarized and unpolarized neutrons to derive the magnetic structure of the swedenborgite compound CaBa (Co3Fe ) O7. Integrated intensities from a standard neutron diffraction experiment and polarization matrices from spherical neutron polarimetry have been simultaneously analyzed revealing a complex order, which differs from the usual spin configurations on a kagome lattice. We find that the magnetic structure is well described by a combination of two one-dimensional representations corresponding to the magnetic superspace symmetry P 21' , and it consists of spins rotating around an axis close to the [110] direction. Due to the propagation vector q =(1/3 00 ) , this modulation has cycloidal and helicoidal character rendering this system a potential multiferroic. The resulting spin configuration can be mapped onto the classical √{3 }×√{3 } structure of a kagome lattice, and it indicates an important interplay between the kagome and the triangular layers of the crystal structure.

High-resolution inelastic neutron scattering and neutron powder diffraction study of the adsorption of dihydrogen by the Cu(II) metal-organic framework material HKUST-1

NASA Astrophysics Data System (ADS)

Callear, Samantha K.; Ramirez-Cuesta, Anibal J.; David, William I. F.; Millange, Franck; Walton, Richard I.

2013-12-01

We present new high-resolution inelastic neutron scattering (INS) spectra (measured using the TOSCA and MARI instruments at ISIS) and powder neutron diffraction data (measured on the diffractometer WISH at ISIS) from the interaction of the prototypical metal-organic framework HKUST-1 with various dosages of dihydrogen gas. The INS spectra show direct evidence for the sequential occupation of various distinct sites for dihydrogen in the metal-organic framework, whose population is adjusted during increasing loading of the guest. The superior resolution of TOSCA reveals subtle features in the spectra, not previously reported, including evidence for split signals, while complementary spectra recorded on MARI present full information in energy and momentum transfer. The analysis of the powder neutron patterns using the Rietveld method shows a consistent picture, allowing the crystallographic indenisation of binding sites for dihydrogen, thus building a comprehensive picture of the interaction of the guest with the nanoporous host.

Hemoglobin redux: combining neutron and X-ray diffraction with mass spectrometry to analyse the quaternary state of oxidized hemoglobins

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mueser, Timothy C., E-mail: timothy.mueser@utoledo.edu; Griffith, Wendell P.; Kovalevsky, Andrey Y.

2010-11-01

X-ray and neutron diffraction studies of cyanomethemoglobin are being used to evaluate the structural waters within the dimer–dimer interface involved in quaternary-state transitions. Improvements in neutron diffraction instrumentation are affording the opportunity to re-examine the structures of vertebrate hemoglobins and to interrogate proton and solvent position changes between the different quaternary states of the protein. For hemoglobins of unknown primary sequence, structural studies of cyanomethemoglobin (CNmetHb) are being used to help to resolve sequence ambiguity in the mass spectra. These studies have also provided additional structural evidence for the involvement of oxidized hemoglobin in the process of erythrocyte senescence. X-raymore » crystal studies of Tibetan snow leopard CNmetHb have shown that this protein crystallizes in the B state, a structure with a more open dyad, which possibly has relevance to RBC band 3 protein binding and erythrocyte senescence. R-state equine CNmetHb crystal studies elaborate the solvent differences in the switch and hinge region compared with a human deoxyhemoglobin T-state neutron structure. Lastly, comparison of histidine protonation between the T and R state should enumerate the Bohr-effect protons.« less

Evolution in boron-based GEM detectors for diffraction measurements: from planar to 3D converters

NASA Astrophysics Data System (ADS)

Albani, Giorgia; Perelli Cippo, Enrico; Croci, Gabriele; Muraro, Andrea; Schooneveld, Erik; Scherillo, Antonella; Hall-Wilton, Richard; Kanaki, Kalliopi; Höglund, Carina; Hultman, Lars; Birch, Jens; Claps, Gerardo; Murtas, Fabrizio; Rebai, Marica; Tardocchi, Marco; Gorini, Giuseppe

2016-11-01

The so-called ‘3He-crisis’ has motivated the neutron detector community to undertake an intense R&D programme in order to develop technologies alternative to standard 3He tubes and suitable for neutron detection systems in future spallation sources such as the European spallation source (ESS). Boron-based GEM (gas electron multiplier) detectors are a promising ‘3He-free’ technology for thermal neutron detection in neutron scattering experiments. In this paper the evolution of boron-based GEM detectors from planar to 3D converters with an application in diffraction measurements is presented. The use of 3D converters coupled with GEMs allows for an optimization of the detector performances. Three different detectors were used for diffraction measurements on the INES instrument at the ISIS spallation source. The performances of the GEM-detectors are compared with those of conventional 3He tubes installed on the INES instrument. The conceptual detector with the 3D converter used in this paper reached a count rate per unit area of about 25% relative to the currently installed 3He tube. Its timing resolution is similar and the signal-to-background ratio (S/B) is 2 times lower.

Unraveling protein catalysis through neutron diffraction

NASA Astrophysics Data System (ADS)

Myles, Dean

Neutron scattering and diffraction are exquisitely sensitive to the location, concentration and dynamics of hydrogen atoms in materials and provide a powerful tool for the characterization of structure-function and interfacial relationships in biological systems. Modern neutron scattering facilities offer access to a sophisticated, non-destructive suite of instruments for biophysical characterization that provide spatial and dynamic information spanning from Angstroms to microns and from picoseconds to microseconds, respectively. Applications range from atomic-resolution analysis of individual hydrogen atoms in enzymes, through to multi-scale analysis of hierarchical structures and assemblies in biological complexes, membranes and in living cells. Here we describe how the precise location of protein and water hydrogen atoms using neutron diffraction provides a more complete description of the atomic and electronic structures of proteins, enabling key questions concerning enzyme reaction mechanisms, molecular recognition and binding and protein-water interactions to be addressed. Current work is focused on understanding how molecular structure and dynamics control function in photosynthetic, cell signaling and DNA repair proteins. We will highlight recent studies that provide detailed understanding of the physiochemical mechanisms through which proteins recognize ligands and catalyze reactions, and help to define and understand the key principles involved.

Structure and texture analysis of PVC foils by neutron diffraction.

PubMed

Kalvoda, L; Dlouhá, M; Vratislav, S

2010-01-01

Crystalline order of molded and then bi-axially stretched foils prepared from atactic PVC resin is investigated by means of wide-angle neutron diffraction (WAND). The observed high-resolution WAND patterns of all samples are dominated by a sharp maximum corresponding to the inter-planar distance 0.52 nm. Two weaker maxima are also resolved at 0.62 and 0.78 nm. Intensities of the peaks vary with deformation ratios of the samples and their diffraction position. Average size of the coherently scattering domains is estimated as approximately 4-8 nm. Based on the experimental data, a novel model of crystalline order of atactic PVC is proposed. Copyright 2009 Elsevier Ltd. All rights reserved.

Structure of rare-earth chalcogenide glasses by neutron and x-ray diffraction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Drewitt, James W. E.; Salmon, Philip S.; Zeidler, Anita

The method of neutron diffraction with isomorphic substitution was used to measure the structure of the rare-earth chalcogenide glasses (R 2X 3) 0.07(Ga 2X 3) 0.33(GeX 2) 0.60 with R = La or Ce and X = S or Se. X-ray diffraction was also used to measure the structure of the sulphide glass. The results are consistent with networks that are built from GeX 4 and GaX 4 tetrahedra, and give R-S and R-Se coordination numbers of 8.0(2) and 8.5(4), respectively. The minimum nearest-neighbour R-R distance associated with rare-earth clustering is discussed.

Structure of rare-earth chalcogenide glasses by neutron and x-ray diffraction

DOE PAGES

Drewitt, James W. E.; Salmon, Philip S.; Zeidler, Anita; ...

2017-04-28

The method of neutron diffraction with isomorphic substitution was used to measure the structure of the rare-earth chalcogenide glasses (R 2X 3) 0.07(Ga 2X 3) 0.33(GeX 2) 0.60 with R = La or Ce and X = S or Se. X-ray diffraction was also used to measure the structure of the sulphide glass. The results are consistent with networks that are built from GeX 4 and GaX 4 tetrahedra, and give R-S and R-Se coordination numbers of 8.0(2) and 8.5(4), respectively. The minimum nearest-neighbour R-R distance associated with rare-earth clustering is discussed.

Influence of neutron irradiation on the microstructure of nuclear graphite: An X-ray diffraction study

NASA Astrophysics Data System (ADS)

Zhou, Z.; Bouwman, W. G.; Schut, H.; van Staveren, T. O.; Heijna, M. C. R.; Pappas, C.

2017-04-01

Neutron irradiation effects on the microstructure of nuclear graphite have been investigated by X-ray diffraction on virgin and low doses (∼ 1.3 and ∼ 2.2 dpa), high temperature (750° C) irradiated samples. The diffraction patterns were interpreted using a model, which takes into account the turbostratic disorder. Besides the lattice constants, the model introduces two distinct coherent lengths in the c-axis and the basal plane, that characterise the volumes from which X-rays are scattered coherently. The methodology used in this work allows to quantify the effect of irradiation damage on the microstructure of nuclear graphite seen by X-ray diffraction. The results show that the changes of the deduced structural parameters are in agreement with previous observations from electron microscopy, but not directly related to macroscopic changes.

Kinetics of methane-ethane gas replacement in clathrate-hydrates studied by time-resolved neutron diffraction and Raman spectroscopy.

PubMed

Murshed, M Mangir; Schmidt, Burkhard C; Kuhs, Werner F

2010-01-14

The kinetics of CH(4)-C(2)H(6) replacement in gas hydrates has been studied by in situ neutron diffraction and Raman spectroscopy. Deuterated ethane structure type I (C(2)H(6) sI) hydrates were transformed in a closed volume into methane-ethane mixed structure type II (CH(4)-C(2)H(6) sII) hydrates at 5 MPa and various temperatures in the vicinity of 0 degrees C while followed by time-resolved neutron powder diffraction on D20 at ILL, Grenoble. The role of available surface area of the sI starting material on the formation kinetics of sII hydrates was studied. Ex situ Raman spectroscopic investigations were carried out to crosscheck the gas composition and the distribution of the gas species over the cages as a function of structure type and compared to the in situ neutron results. Raman micromapping on single hydrate grains showed compositional and structural gradients between the surface and core of the transformed hydrates. Moreover, the observed methane-ethane ratio is very far from the one expected for a formation from a constantly equilibrated gas phase. The results also prove that gas replacement in CH(4)-C(2)H(6) hydrates is a regrowth process involving the nucleation of new crystallites commencing at the surface of the parent C(2)H(6) sI hydrate with a progressively shrinking core of unreacted material. The time-resolved neutron diffraction results clearly indicate an increasing diffusion limitation of the exchange process. This diffusion limitation leads to a progressive slowing down of the exchange reaction and is likely to be responsible for the incomplete exchange of the gases.

Unambiguous determination of H-atom positions: comparing results from neutron and high-resolution X-ray crystallography.

PubMed

Gardberg, Anna S; Del Castillo, Alexis Rae; Weiss, Kevin L; Meilleur, Flora; Blakeley, Matthew P; Myles, Dean A A

2010-05-01

The locations of H atoms in biological structures can be difficult to determine using X-ray diffraction methods. Neutron diffraction offers a relatively greater scattering magnitude from H and D atoms. Here, 1.65 A resolution neutron diffraction studies of fully perdeuterated and selectively CH(3)-protonated perdeuterated crystals of Pyrococcus furiosus rubredoxin (D-rubredoxin and HD-rubredoxin, respectively) at room temperature (RT) are described, as well as 1.1 A resolution X-ray diffraction studies of the same protein at both RT and 100 K. The two techniques are quantitatively compared in terms of their power to directly provide atomic positions for D atoms and analyze the role played by atomic thermal motion by computing the sigma level at the D-atom coordinate in simulated-annealing composite D-OMIT maps. It is shown that 1.65 A resolution RT neutron data for perdeuterated rubredoxin are approximately 8 times more likely overall to provide high-confidence positions for D atoms than 1.1 A resolution X-ray data at 100 K or RT. At or above the 1.0sigma level, the joint X-ray/neutron (XN) structures define 342/378 (90%) and 291/365 (80%) of the D-atom positions for D-rubredoxin and HD-rubredoxin, respectively. The X-ray-only 1.1 A resolution 100 K structures determine only 19/388 (5%) and 8/388 (2%) of the D-atom positions above the 1.0sigma level for D-rubredoxin and HD-rubredoxin, respectively. Furthermore, the improved model obtained from joint XN refinement yielded improved electron-density maps, permitting the location of more D atoms than electron-density maps from models refined against X-ray data only.

Neutron diffraction study of the martensitic transformation and chemical order in Heusler alloy Ni 1.91Mn 1.29Ga 0.8

DOE PAGES

Ari-Gur, Pnina; Garlea, Vasile O.; Cao, Huibo; ...

2015-11-05

In this study, Heusler alloys of Ni-Mn-Ga compositions demonstrate ferromagnetic shape memory effect in the martensitic state. The transformation temperature and the chemical order depend strongly on the composition. In the current work, the structure and chemical order of the martensitic phase of Ni 1.91Mn 1.29Ga 0.8 were studied using neutron diffraction; the diffraction pattern was refined using the FullProf software. It was determined that the structural transition occurs around 330 K. At room temperature, 300 K, which is below the martensite transformation temperature, all the Bragg reflections can be described by a monoclinic lattice with a symmetry of spacemore » group P 1 2/m 1 and lattice constants of a = 4.23047(7) [Å], b = 5.58333(6) [Å], c = 21.0179(2) [Å], beta = 90.328(1). The chemical order is of critical importance in these alloys, and it was previously studied at 363 K. Analysis of the neutron diffraction in the monoclinic phase shows that the chemical order is maintained during the martensitic transformation.« less

Early history of neutron scattering at oak ridge

NASA Astrophysics Data System (ADS)

Wilkinson, M. K.

1986-03-01

Most of the early development of neutron scattering techniques utilizing reactor neutrons occurred at the Oak Ridge National Laboratory during the years immediately following World War II. C.G. Shull, E.O. Wollan, and their associates systematically established neutron diffraction as a quantitative research tool and then applied this technique to important problems in nuclear physics, chemical crystallography, and magnetism. This article briefly summarizes the very important research at ORNL during this period, which laid the foundation for the establishment of neutron scattering programs throughout the world.

Short-range order of undercooled melts of PdZr2 intermetallic compound studied by X-ray and neutron scattering experiments

NASA Astrophysics Data System (ADS)

Klein, S.; Holland-Moritz, D.; Herlach, D. M.; Mauro, N. A.; Kelton, K. F.

2013-05-01

The short-range order in undercooled melts of the intermetallic Zr2Pd glass-forming alloy is investigated by combining electrostatic levitation (ESL) with high-energy X-ray diffraction and neutron diffraction. Experimentally determined structure factors are measured and analyzed with respect to various structures of short-range order. The comparative X-ray and neutron scattering experiments allow for investigations of topological and chemical short-range order. Based on these studies, no preference of a specific short-range order is found for the liquid Zr2Pd glass-forming alloy, even in the metastable state of the deeply undercooled melt. This is in agreement with an earlier report from X-ray diffraction and molecular-dynamics studies of a Zr75.5Pd24.5 liquid, which showed a broad distribution of cluster types. The results for the Zr2Pd liquid are discussed with respect to the glass-forming ability of this melt.

Aging behavior of lithium iron phosphate based 18650-type cells studied by in situ neutron diffraction

NASA Astrophysics Data System (ADS)

Paul, Neelima; Wandt, Johannes; Seidlmayer, Stefan; Schebesta, Sebastian; Mühlbauer, Martin J.; Dolotko, Oleksandr; Gasteiger, Hubert A.; Gilles, Ralph

2017-03-01

The aging behavior of commercially produced 18650-type Li-ion cells consisting of a lithium iron phosphate (LFP) based cathode and a graphite anode based on either mesocarbon microbeads (MCMB) or needle coke (NC) is studied by in situ neutron diffraction and standard electrochemical techniques. While the MCMB cells showed an excellent cycle life with only 8% relative capacity loss (i.e., referenced to the capacity after formation) after 4750 cycles and showed no capacity loss on storage for two years, the needle coke cells suffered a 23% relative capacity loss after cycling and a 11% loss after storage. Based on a combination of neutron diffraction and electrochemical characterization, it is shown that the entire capacity loss for both cell types is dominated by the loss of active lithium; no other aging mechanisms like structural degradation of anode or cathode active materials or deactivation of active material could be found, highlighting the high structural stability of the active material and the excellent quality of the investigated cells.

Magnetic and neutron diffraction study on quaternary oxides MTeMoO6 (M = Mn and Zn)

NASA Astrophysics Data System (ADS)

Doi, Yoshihiro; Suzuki, Ryo; Hinatsu, Yukio; Ohoyama, Kenji

2009-01-01

Crystal structures and magnetic properties of quaternary oxides MTeMoO6 (M = Mn and Zn) were investigated. From the Rietveld analyses for the powder x-ray and neutron diffraction measurements, their detailed structures have been determined. Both compounds have orthorhombic structure with space group P 21212 and a charge configuration of M2+Te4+Mo6+O6. ZnTeMoO6 shows diamagnetic behavior. In this structure, M ions are arranged in a square-planar manner. The temperature dependence of the magnetic susceptibility for MnTeMoO6 shows a broad peak at ~33 K, which is due to a two-dimensional characteristic of the magnetic interaction. In addition, this compound shows an antiferromagnetic transition at 20 K. The magnetic structure was determined by the powder neutron diffraction measurement at 3.3 K. The magnetic moments of Mn2+ ions (4.45 μB) order in a collinear antiferromagnetic arrangement along the b axis.

α-Phase transformation kinetics of U – 8 wt% Mo established by in situ neutron diffraction

DOE PAGES

Garlea, Elena; Steiner, M. A.; Calhoun, C. A.; ...

2016-05-08

The α-phase transformation kinetics of as-cast U - 8 wt% Mo below the eutectoid temperature have been established by in situ neutron diffraction. α-phase weight fraction data acquired through Rietveld refinement at five different isothermal hold temperatures can be modeled accurately utilizing a simple Johnson-Mehl-Avrami-Kolmogorov impingement-based theory, and the results are validated by a corresponding evolution in the γ-phase lattice parameter during transformation that follows Vegard’s law. Neutron diffraction data is used to produce a detailed Time-Temperature-Transformation diagram that improves upon inconsistencies in the current literature, exhibiting a minimum transformation start time of 40 min at temperatures between 500 °Cmore » and 510 °C. Lastly, the transformation kinetics of U – 8 wt% Mo can vary significantly from as-cast conditions after extensive heat treatments, due to homogenization of the typical dendritic microstructure which possesses non-negligible solute segregation.« less

Neutron-diffraction measurement of residual stresses in Al-Cu cold-cut welding

NASA Astrophysics Data System (ADS)

Fiori, F.; Marcantoni, M.

Usually, when it is necessary to join different materials with a large difference in their melting points, welding should be avoided. To overcome this problem we designed and built a device to obtain cold-cut welding, which is able to strongly decrease oxidation problems of the surfaces to be welded. Thanks to this device it is possible to achieve good joining between different pairs of materials (Al-Ti, Cu-Al, Cu-Al alloys) without reaching the material melting point. The mechanical and microstructural characterisation of the joining and the validation of its quality were obtained using several experimental methods. In particular, in this work neutron-diffraction experiments for the evaluation of residual stresses in Cu-Al junctions are described, carried out at the G5.2 diffractometer of LLB, Saclay. Neutron-diffraction results are presented and related to other experimental tests such as microstructural characterisation (through optical and scanning electron microscopy) and mechanical characterisation (tensile-strength tests) of the welded interface.

Visualizing the chemistry and structure dynamics in lithium-ion batteries by in-situ neutron diffraction

PubMed Central

Wang, Xun-Li; An, Ke; Cai, Lu; Feng, Zhili; Nagler, Stephen E.; Daniel, Claus; Rhodes, Kevin J.; Stoica, Alexandru D.; Skorpenske, Harley D.; Liang, Chengdu; Zhang, Wei; Kim, Joon; Qi, Yue; Harris, Stephen J.

2012-01-01

We report an in-situ neutron diffraction study of a large format pouch battery cell. The succession of Li-Graphite intercalation phases was fully captured under an 1C charge-discharge condition (i.e., charge to full capacity in 1 hour). However, the lithiation and dilithiation pathways are distinctively different and, unlike in slowing charging experiments with which the Li-Graphite phase diagram was established, no LiC24 phase was found during charge at 1C rate. Approximately 75 mol. % of the graphite converts to LiC6 at full charge, and a lattice dilation as large as 4% was observed during a charge-discharge cycle. Our work demonstrates the potential of in-situ, time and spatially resolved neutron diffraction study of the dynamic chemical and structural changes in “real-world” batteries under realistic cycling conditions, which should provide microscopic insights on degradation and the important role of diffusion kinetics in energy storage materials. PMID:23087812

Diffraction des neutrons : principe, dispositifs expérimentaux et applications

NASA Astrophysics Data System (ADS)

Muller, C.

2003-02-01

La diffraction de neutrons, sur monocristal ou sur échantillon polycristallin (ou poudre), est une technique très largement utilisée, en science des matériaux comme en biologie, lorsque l'on souhaite déterminer la structure cristalline d'un composé ou d'une molécule. Toutefois, le degré de précision de la détermination structurale est très corrélé au choix de l'instrument utilisé. Il s'en suit que la question “comment choisir l'instrument le mieux adapté au composé et à la problématique ?" apparaît comme fondamentale. L'objectif de ce cours est de tenter de répondre à cette question en décrivant brièvement les caractéristiques instrumentales de différents diffractomètres, en exposant les avantages spécifiques des expériences de diffraction de neutrons et en donnant quelques exemples d'application.

Structural analysis of PrBaMn2O5+δ under SOFC anode conditions by in-situ neutron powder diffraction

NASA Astrophysics Data System (ADS)

Tomkiewicz, Alex C.; Tamimi, Mazin A.; Huq, Ashfia; McIntosh, Steven

2016-10-01

The crystal structure and oxygen stoichiometry of the proposed double perovskite solid oxide fuel cell (SOFC) anode material PrBaMn2O5+δ were determined under SOFC anode conditions via in-situ neutron diffraction. Measurements were performed in reducing atmospheres between 692 K and 984 K. The structure was fit to a tetragonal (space group P4/mmm) layered double perovskite structure with alternating Pr and Ba A-site cation layers. Under all conditions examined, the oxygen sites in the Ba and Mn layers were fully occupied, while the sites in the Pr layer were close to completely vacant. The results of the neutron diffraction experiments are compared to previous thermogravimetric analysis experiments to verify the accuracy of both experiments. PrBaMn2O5+δ was shown to be stable over a wide range of reducing atmospheres similar to anode operating conditions in solid oxide fuel cells without significant structural changes.

Hydrogenation properties of Li{sub x}Sr{sub 1−x}AlSi studied by quantum-chemical methods (0≤x≤1) and in-situ neutron powder diffraction (x=1)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kunkel, Nathalie, E-mail: nathalie.kunkel@chimie-paristech.fr; FR 8.1 Universität des Saarlandes, Postach 151150, 66041 Saarbrücken; Reichert, Christian

2015-01-15

In-situ neutron powder diffraction studies of the Half-Heusler phase LiAlSi under high deuterium pressures and first principle calculations of solid solutions of Li{sub x}Sr{sub 1−x}AlSi and their hydrides Li{sub x}Sr{sub 1−x}AlSiH were carried out. In contrast to an earlier study, there is no experimental evidence for hydrogen (deuterium) uptake up to gas pressures of 15 MPa and temperatures of 550 °C. Instead a slow decomposition reaction according to LiAlSi+1/2H{sub 2}=LiH+Al+Si was found by in-situ neutron powder diffraction. Theoretical calculations by DFT methods on hypothetical solid solutions of Li{sub x}Sr{sub 1−x}AlSi show the LiAlSi type to be the energetically most stablemore » structure for 0.7« less

In situ synthesis and characterization of uranium carbide using high temperature neutron diffraction

NASA Astrophysics Data System (ADS)

Reiche, H. Matthias; Vogel, Sven C.; Tang, Ming

2016-04-01

We investigated the formation of UCx from UO2+x and graphite in situ using neutron diffraction at high temperatures with particular focus on resolving the conflicting reports on the crystal structure of non-quenchable cubic UC2. The agents were UO2 nanopowder, which closely imitates nano grains observed in spent reactor fuels, and graphite powder. In situ neutron diffraction revealed the onset of the UO2 + 2C → UC + CO2 reaction at 1440 °C, with its completion at 1500 °C. Upon further heating, carbon diffuses into the uranium carbide forming C2 groups at the octahedral sites. This resulting high temperature cubic UC2 phase is similar to the NaCl-type structure as proposed by Bowman et al. Our novel experimental data provide insights into the mechanism and kinetics of formation of UC as well as characteristics of the high temperature cubic UC2 phase which agree with proposed rotational rehybridization found from simulations by Wen et al.

Neutron diffraction study of the in situ oxidation of UO(2).

PubMed

Desgranges, Lionel; Baldinozzi, Gianguido; Rousseau, Gurvan; Nièpce, Jean-Claude; Calvarin, Gilbert

2009-08-17

This paper discusses uranium oxide crystal structure modifications that are observed during the low-temperature oxidation which transforms UO(2) into U(3)O(8). The symmetries and the structural parameters of UO(2), beta-U(4)O(9), beta-U(3)O(7), and U(3)O(8) were determined by refining neutron diffraction patterns on pure single-phase samples. Neutron diffraction patterns were also collected during the in situ oxidation of powder samples at 483 K. The lattice parameters and relative ratios of the four pure phases were measured during the progression of the isothermal oxidation. The transformation of UO(2) into U(3)O(8) involves a complex modification of the oxygen sublattice and the onset of complex superstructures for U(4)O(9) and U(3)O(7), associated with regular stacks of complex defects known as cuboctahedra, which consist of 13 oxygen atoms. The kinetics of the oxidation process are discussed on the basis of the results of the structural analysis.

A method for the monitoring of metal recrystallization based on the in-situ measurement of the elastic energy release using neutron diffraction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Christien, F., E-mail: frederic.christien@univ-nantes.fr; Le Gall, R.; Telling, M. T. F.

2015-05-15

A method is proposed for the monitoring of metal recrystallization using neutron diffraction that is based on the measurement of stored energy. Experiments were performed using deformed metal specimens heated in-situ while mounted at the sample position of the High Resolution Powder Diffractometer, HRPD (ISIS Facility), UK. Monitoring the breadth of the resulting Bragg lines during heating not only allows the time-dependence (or temperature-dependence) of the stored energy to be determined but also the recrystallized fraction. The analysis method presented here was developed using pure nickel (Ni270) specimens with different deformation levels from 0.29 to 0.94. In situ temperature rampingmore » as well as isothermal annealing was undertaken. The method developed in this work allows accurate and quantitative monitoring of the recrystallization process. The results from neutron diffraction are satisfactorily compared to data obtained from calorimetry and hardness measurements.« less

Local nanoscale strain mapping of a metallic glass during in situ testing

NASA Astrophysics Data System (ADS)

Gammer, Christoph; Ophus, Colin; Pekin, Thomas C.; Eckert, Jürgen; Minor, Andrew M.

2018-04-01

The local elastic strains during tensile deformation in a CuZrAlAg metallic glass are obtained by fitting an elliptic shape function to the characteristic amorphous ring in electron diffraction patterns. Scanning nanobeam electron diffraction enables strain mapping with a resolution of a few nanometers. Here, a fast direct electron detector is used to acquire the diffraction patterns at a sufficient speed to map the local transient strain during continuous tensile loading in situ in the transmission electron microscope. The elastic strain in tensile direction was found to increase during loading. After catastrophic fracture, a residual elastic strain that relaxes over time was observed.

Investigation of TbMn2O5 by polarized neutron diffraction

NASA Astrophysics Data System (ADS)

Zobkalo, I. A.; Gavrilov, S. V.; Sazonov, A.; Hutanu, V.

2018-05-01

In order to make a new approach to the elucidation of the microscopic mechanisms of multiferroicity in the RMn2O5 family, experiments with different methods of polarized neutrons scattering were performed on a TbMn2O5 single crystal. We employed three different techniques of polarized neutron diffraction without the analysis after scattering, the XYZ-polarization analysis, and technique of spherical neutron polarimetry (SNP). Measurements with SNP were undertaken both with and without external electric field. A characteristic difference in the population of ‘right’ and ‘left’ helix domains in all magnetically ordered phases of TbMn2O5, was observed. This difference can be controlled by an external electric field in the field-cooled mode. The analysis of the results gives an evidence that antisymmetric Dzyaloshinsky-Moria exchange is effective in all the magnetic phases in TbMn2O5.

Investigation of TbMn2O5 by polarized neutron diffraction.

PubMed

Zobkalo, I A; Gavrilov, S V; Sazonov, A; Hutanu, V

2018-05-23

In order to make a new approach to the elucidation of the microscopic mechanisms of multiferroicity in the RMn 2 O 5 family, experiments with different methods of polarized neutrons scattering were performed on a TbMn 2 O 5 single crystal. We employed three different techniques of polarized neutron diffraction without the analysis after scattering, the XYZ-polarization analysis, and technique of spherical neutron polarimetry (SNP). Measurements with SNP were undertaken both with and without external electric field. A characteristic difference in the population of 'right' and 'left' helix domains in all magnetically ordered phases of TbMn 2 O 5 , was observed. This difference can be controlled by an external electric field in the field-cooled mode. The analysis of the results gives an evidence that antisymmetric Dzyaloshinsky-Moria exchange is effective in all the magnetic phases in TbMn 2 O 5 .

Neutron Characterization of Encapsulated ATF-1/LANL-1 Mockup Fuel Capsules

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vogel, Sven C.; Borges, Nicholas Paul; Losko, Adrian Simon

Twenty pellets of mock-up accident tolerant fuels UN-U3Si5 were produced at LANL and loaded in two rodlet/capsule assemblies. Tomographic imaging and diffraction measurements were performed to characterize these samples at the Flight-Path 5 and HIPPO beam lines at LANSCE/LANL between November 2016 and January 2017 as well as in August 2017. The entire ~10 cm long, ~1 cm diameter fuel volume could be characterized, however due to time constraints only 2 mm slices in 4mm increments were characterized with neutron diffraction and a 28mm subset of the entire sample was characterized with energy-resolved neutron imaging. The double encapsulation of themore » fuel into two steel containers does not pose a problem for the neutron analysis and the methods could be applied to enriched as well irradiated fuels.« less

POWTEX Neutron Diffractometer at FRM II - New Perspectives for In-Situ Rock Deformation Analysis

NASA Astrophysics Data System (ADS)

Walter, J. M.; Stipp, M.; Ullemeyer, K.; Klein, H.; Leiss, B.; Hansen, B. T.; Kuhs, W. F.

2012-04-01

In Geoscience quantitative texture analysis here defined as the quantitative analysis of the crystallographic preferred orientation (CPO), is a common tool for the investigation of fabric development in mono- and polyphase rocks, their deformation histories and kinematics. Bulk texture measurements also allow the quantitative characterisation of the anisotropic physical properties of rock materials. A routine tool to measure bulk sample volumes is neutron texture diffraction, as neutrons have large penetration capabilities of several cm in geological sample materials. The new POWTEX (POWder and TEXture) Diffractometer at the neutron research reactor FRM II in Garching, Germany is designed as a high-intensity diffractometer by groups from the RWTH Aachen, Forschungszentrum Jülich and the University of Göttingen. Complementary to existing neutron diffractometers (SKAT at Dubna, Russia; GEM at ISIS, UK; HIPPO at Los Alamos, USA; D20 at ILL, France; and the local STRESS-SPEC and SPODI at FRM II) the layout of POWTEX is focused on fast time-resolved experiments and the measurement of larger sample series as necessary for the study of large scale geological structures. POWTEX is a dedicated beam line for geoscientific research. Effective texture measurements without sample tilting and rotation are possible firstly by utilizing a range of neutron wavelengths simultaneously (Time-of-Flight technique) and secondly by the high detector coverage (9.8 sr) and a high flux (~1 - 107 n/cm2s) at the sample. Furthermore the instrument and the angular detector resolution is designed also for strong recrystallisation textures as well as for weak textures of polyphase rocks. These instrument characteristics allow in-situ time-resolved texture measurements during deformation experiments on rocksalt, ice and other materials as large sample environments will be implemented at POWTEX. The in-situ deformation apparatus is operated by a uniaxial spindle drive with a maximum axial load of 250 kN, which will be redesigned to minimize shadowing effects inside the cylindrical detector. The HT deformatione experiments will be carried out in uniaxial compression or extension and an upgrade to triaxial deformation conditions is envisaged. The load frame can alternatively be used for ice deformation by inserting a cryostat cell for temperatures down to 77 K with a triaxial apparatus allowing also simple shear experiments on ice. Strain rates range between 10-8 and 10-3 s-1 reaching to at least 50 % axial strain. The deformation apparatus is designed for continuous long-term deformation experiments and can be exchanged between in-situ and ex-situ placements during continuous operation inside and outside the neutron detector.

Non-destructive diagnostics of irradiated materials using neutron scattering from pulsed neutron sources

NASA Astrophysics Data System (ADS)

Korenev, Sergey; Sikolenko, Vadim

2004-09-01

The advantage of neutron-scattering studies as compared to the standard X-ray technique is the high penetration of neutrons that allow us to study volume effects. The high resolution of instrumentation on the basis neutron scattering allows measurement of the parameters of lattice structure with high precision. We suggest the use of neutron scattering from pulsed neutron sources for analysis of materials irradiated with pulsed high current electron and ion beams. The results of preliminary tests using this method for Ni foils that have been studied by neutron diffraction at the IBR-2 (Pulsed Fast Reactor at Joint Institute for Nuclear Research) are presented.

A diffraction based study of the deformation mechanisms in anomalously ductile B2 intermetallics

NASA Astrophysics Data System (ADS)

Mulay, Rupalee Prashant

For many decades, the brittle nature of most intermetallic compounds (e.g. NiAl) has been the limiting factor in their practical application. Many B2 (CsCl prototypical structure) intermetallics are known to exhibit slip on the <001>{110} slip mode, which provides only 3 independent slip systems and, hence, is unable to satisfy the von Mises (a.k.a. Taylor) criterion for polycrystalline ductility. As a result, inherent polycrystalline ductility is unexpected. Recent discovery of a number of ductile B2 intermetallics has raised questions about possible violation of the von Mises criterion by these alloys. These ductile intermetallic compounds are MR (metal (M) combined with a rare earth metal or group IV refractory metal (R)) alloys and are stoichiometric, ordered compounds. Single crystal slip trace analyses have only identified the presence of <100>{011} or <100>{010} slip systems. More than 100 other B2 MR compounds are known to exist and many of them have already been shown to be ductile (e.g., CuY, AgY, CuDy, CoZr, CoTi, etc.). Furthermore, these alloys exhibit a large Bauschinger effect. The present work uses several diffraction based techniques including electron back scattered diffraction (EBSD), X-ray diffraction (XRD) and in-situ neutron diffraction; in conjunction with scanning electron microscopy (SEM), transmission electron microscopy (TEM), mechanical testing, and crystal plasticity modeling, to elucidate the reason for ductility in select B2 alloys, explore the spread of this ductility over the B2 family, and understand the Bauschinger effect in these alloys. Several possible explanations (e.g., slip of <111> dislocations, strong texture, phase transformations and twinning) for the anomalous ductility were explored. An X-ray diffraction based analysis ruled out texture, phase purity and departure from order as explanations for the anomalous ductility in MR alloys. In-situ neutron diffraction and post deformation SEM, EBSD, and TEM were unable to detect any evidence for phase transformations in CoTi and CoZr. Also, post deformation characterization did not reveal any evidence of twinning. However, TEM based g·b analysis and EBSD based in-grain misorientation axis (IGMA) analysis showed that beyond a transition in the strain hardening behavior in CoTi, slip modes involving dislocations with <110> and <111> Burgers vectors are activated. The slip of such dislocations can reduce stress concentrations that could otherwise lead to premature fracture, thus providing a satisfying explanation for the anomalous ductility of CoTi and related compounds, like CoZr. Dislocation self-energy calculations accounting for elastic anisotropy suggest that the choice of slip direction in these alloys is mobility-, rather than source-, limited. The reach of this "ductilizing effect" over B2 alloys was explored by producing, characterizing, and testing a number of simple metal-rare earth metal compounds, namely MgY, MgNd and MgCe. MgR intermetallics with the B2 structure were found to be brittle and exhibit a cleavage type fracture indicating that the ductilizing effect is not as widespread as was initially thought. MgY and MgNd were found to primarily cleave along the {100} planes, while MgCe was found to cleave on the {111} planes. A large Bauschinger effect was observed in several of the anomalously ductile B2 compounds, such that the material actually begins to yield in the reverse direction on unloading. When only the primary slip mode <100>{011} is active in CoZr (prior to a transition in strain hardening), the buildup of intergranular stresses is large and is chiefly responsible for the observed Bauschinger effect. However, past the aforementioned transition in strain hardening, the effect of intergranular stresses diminishes. The results demonstrate that the activation of hard, secondary slip modes causes the internal strains to develop more uniformly among the grains, thus reducing the intergranular stresses which cause the Bauschinger effect. Crystal plasticity modeling, which accounts for the initial paucity of independent slip modes and allows for the activation of complementary hard slip modes, reproduces these trends in the Bauschinger effect and provides additional evidence that the experimental observations have correctly identified the cause of the anomalous ductility.

Asymmetric band flipping for time-of-flight neutron diffraction data

DOE PAGES

Whitfield, Pamela S.; Coelho, Alan A.

2016-08-24

Charge flipping with powder diffraction data is known to produce a result more reliably with high-resolution data,i.e.visible reflections at smalldspacings. This data are readily accessible with the neutron time-of-flight technique but the assumption that negative scattering density is nonphysical is no longer valid where elements with negative scattering lengths are present. The concept of band flipping was introduced in the literature, where a negative threshold is used in addition to a positive threshold during the flipping. But, it was not tested with experimental data at the time. Finallly, band flipping has been implemented inTOPAStogether with the band modification of low-densitymore » elimination and tested with experimental powder and Laue single-crystal neutron data.« less

Neutron and X-ray investigations of the Jahn–Teller switch in partially deuterated ammonium copper Tutton salt, (NH 4 ) 2 [Cu(H 2 O) 6 ](SO 4 ) 2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jørgensen, Mads R. V.; Piccoli, Paula M. B.; Hathwar, Venkatesha R.

2017-01-31

The structural phase transition accompanied by a Jahn–Teller switch has been studied over a range of H/D ratios in (NH 4) 2[Cu(H 2O) 6](SO 4) 2(ACTS). In particular, single-crystal neutron diffraction investigations of crystals with deuteration in the range 50 to 82% are shown to be consistent with previous electron paramagnetic resonance (EPR) experiments exhibiting a phase boundary at 50% deuteration under ambient pressure. Polycrystalline samples show that the two phases can co-exist. In addition, single-crystal neutron and polycrystalline X-ray diffraction pressure experiments show a shift to lower pressure at 60% deuterationversusprevious measurements at 100% deuteration.

Structure and mechanical behavior of heavily drawn pearlite and martensite in a high carbon steel

NASA Astrophysics Data System (ADS)

Shiota, Y.; Tomota, Y.; Moriai, A.; Kamiyama, T.

2005-10-01

Neutron diffraction measurements have revealed that cementite peaks disappear in a pearlite steel with drawing and that the residual intergranular stresses are generated. The diffraction profiles in a heavily drawn specimen suggest the tetoragonality with a small c/a in the ferrite matrix. Although cementite was hardly observed in the heavily drawn specimen, its c/a value determined by neutron diffraction and mechanical behavior are quite different from those of as-quenched martensite. The changes in hardness and c/a with annealing or tempering were also different between heavily drawn pearlite and marteniste. Hence, most of carbon atoms do not exist inside the ferrite lattice in the drawn pearlite and multi-scaled heterogeneous plastic deformation in pearlite seems to affect the asymmetry in the diffraction profile. Fracture behavior and hardness change with tempering is different in the two microstructures.

Three-Dimensional FIB/EBSD Characterization of Irradiated HfAl3-Al Composite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hua, Zilong; Guillen, Donna Post; Harris, William

2016-09-01

A thermal neutron absorbing material, comprised of 28.4 vol% HfAl3 in an Al matrix, was developed to serve as a conductively cooled thermal neutron filter to enable fast flux materials and fuels testing in a pressurized water reactor. In order to observe the microstructural change of the HfAl3-Al composite due to neutron irradiation, an EBSD-FIB characterization approach is developed and presented in this paper. Using the focused ion beam (FIB), the sample was fabricated to 25µm × 25µm × 20 µm and mounted on the grid. A series of operations were carried out repetitively on the sample top surface tomore » prepare it for scanning electron microscopy (SEM). First, a ~100-nm layer was removed by high voltage FIB milling. Then, several cleaning passes were performed on the newly exposed surface using low voltage FIB milling to improve the SEM image quality. Last, the surface was scanned by Electron Backscattering Diffraction (EBSD) to obtain the two-dimensional image. After 50 to 100 two-dimensional images were collected, the images were stacked to reconstruct a three-dimensional model using DREAM.3D software. Two such reconstructed three-dimensional models were obtained from samples of the original and post-irradiation HfAl3-Al composite respectively, from which the most significant microstructural change caused by neutron irradiation apparently is the size reduction of both HfAl3 and Al grains. The possible reason is the thermal expansion and related thermal strain from the thermal neutron absorption. This technique can be applied to three-dimensional microstructure characterization of irradiated materials.« less

Crystal structure of human tooth enamel studied by neutron diffraction

NASA Astrophysics Data System (ADS)

Ouladdiaf, Bachir; Rodriguez-Carvajal, Juan; Goutaudier, Christelle; Ouladdiaf, Selma; Grosgogeat, Brigitte; Pradelle, Nelly; Colon, Pierre

2015-02-01

Crystal structure of human tooth enamel was investigated using high-resolution neutron powder diffraction. Excellent agreement between observed and refined patterns is obtained, using the hexagonal hydroxyapatite model for the tooth enamel, where a large hydroxyl deficiency ˜70% is found in the 4e site. Rietveld refinements method combined with the difference Fourier maps have revealed, however, that the hydroxyl ions are not only disordered along the c-axis but also within the basal plane. Additional H ions located at the 6h site and forming HPO42- anions were found.

Study of the solid-state amorphization of (GaSb){sub 1-x}Ge{sub x} semiconductors by real-time neutron diffraction and electron microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fedotov, V. K., E-mail: fedotov@issp.ac.ru; Ponyatovsky, E. G.

2011-12-15

The spontaneous amorphization of high-pressure quenched phases of the GaSb-Ge system has been studied by neutron diffraction while slowly heating the phases at atmospheric pressure. The sequence of changes in the structural parameters of the initial crystalline phase and the final amorphous phase is established. The behavior of the phases and the correlation in the structural features of the phase transitions and anomalous thermal effects exhibit signs of the inhomogeneous model of solid-state amorphization.

On the atomic structure of liquid Ni-Si alloys: a neutron diffraction study

NASA Astrophysics Data System (ADS)

Gruner, S.; Marczinke, J.; Hennet, L.; Hoyer, W.; Cuello, G. J.

2009-09-01

The atomic structure of the liquid NiSi and NiSi2 alloys is investigated by means of neutron diffraction experiments with isotopic substitution. From experimental data-sets obtained using four Ni isotopes, partial structure factors and pair correlation functions are obtained by applying a reverse Monte Carlo modelling approach. Both alloys were found to exhibit a strong tendency to hetero-coordination within the first coordination shell. In particular, covalent Si-Si bonds with somewhat greater distances seem to influence the structure of the liquid NiSi alloy.

On the atomic structure of liquid Ni-Si alloys: a neutron diffraction study.

PubMed

Gruner, S; Marczinke, J; Hennet, L; Hoyer, W; Cuello, G J

2009-09-23

The atomic structure of the liquid NiSi and NiSi(2) alloys is investigated by means of neutron diffraction experiments with isotopic substitution. From experimental data-sets obtained using four Ni isotopes, partial structure factors and pair correlation functions are obtained by applying a reverse Monte Carlo modelling approach. Both alloys were found to exhibit a strong tendency to hetero-coordination within the first coordination shell. In particular, covalent Si-Si bonds with somewhat greater distances seem to influence the structure of the liquid NiSi alloy.

Chamber for mechanical testing in H2 with observation by neutron scattering

NASA Astrophysics Data System (ADS)

Connolly, Matthew; Bradley, Peter; Slifka, Andrew; Drexler, Elizabeth

2017-06-01

A gas-pressure chamber has been designed, constructed, and tested at a moderate pressure (3.4 MPa, 500 psi) and has the capability of mechanical loading of steel specimens for neutron scattering measurements. The chamber will allow a variety of in situ neutron scattering measurements: in particular, diffraction, quasielastic scattering, inelastic scattering, and imaging. The chamber is compatible with load frames available at the user facilities at the NIST Center for Neutron Research and Oak Ridge National Laboratory Spallation Neutron Source. A demonstration of neutron Bragg edge imaging using the chamber is presented.

A brief History of Neutron Scattering at the Oak Ridge High Flux Isotope Reactor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nagler, Stephen E; Mook Jr, Herbert A

2008-01-01

Neutron scattering at the Oak Ridge National Laboratory dates back to 1945 when Ernest Wollan installed a modified x-ray diffractometer on a beam port of the original graphite reactor. Subsequently, Wollan and Clifford Shull pioneered neutron diffraction and laid the foundation for an active neutron scattering effort that continued through the 1950s, using the Oak Ridge Research reactor after 1958, and, starting in 1966, the High Flux Isotope Reactor, or HFIR.

Phase Transition and Texture Evolution in the Ni-Mn-Ga Ferromagnetic Shape-Memory Alloys Studied by a Neutron Diffraction Technique

NASA Astrophysics Data System (ADS)

Nie, Z. H.; Wang, Y. D.; Wang, G. Y.; Richardson, J. W.; Wang, G.; Liu, Y. D.; Liaw, P. K.; Zuo, L.

2008-12-01

The phase transition and influence of the applied stress on the texture evolution in the as-cast Ni-Mn-Ga ferromagnetic shape-memory alloys were studied by the time-of-flight (TOF) neutron diffraction technique. The neutron diffraction experiments were performed on the General Purpose Powder Diffractometer (Argonne National Laboratory). Inverse pole figures were determined from the neutron data for characterizing the orientation distributions and variant selections of polycrystalline Ni-Mn-Ga alloys subjected to different uniaxial compression deformations. Texture analyses reveal that the initial texture for the parent phase in the as-cast specimen was composed of {left\\{ {{text{001}}} right\\}}{left< {{text{100}}} rightrangle } , {left\\{ {{text{001}}} right\\}}{left< {{text{110}}} rightrangle } , {left\\{ {{text{011}}} right\\}}{left< {{text{100}}} rightrangle } , and {left\\{ {{text{011}}} right\\}}{left< {{text{110}}} rightrangle } , which was weakened after the compression deformation. Moreover, a strong preferred selection of martensitic-twin variants ( {left\\{ {{text{110}}} right\\}}{left< {{text{001}}} rightrangle } and {left\\{ {{text{100}}} right\\}}{left< {{text{001}}} rightrangle } ) was observed in the transformed martensite after a compression stress applied on the parent phase along the cyclindrical axis of the specimens. The preferred selection of variants can be well explained by considering the grain/variant-orientation-dependent Bain-distortion energy.

Crystal structure studies with the Paris-Edinburgh cell: Neutron scattering aspects

NASA Astrophysics Data System (ADS)

Loveday, J. S.; Wilson, R. M.; Nelmes, R. J.; Besson, J. M.; Klotz, S.; Hamel, G.; Hull, S.

1994-07-01

The count rates achieved in neutron powder diffraction experiments create difficulties for high-pressure experiments because large sample volumes (˜100 mm3) must be used. Until recently it has been difficult to build suitable pressure cells with such large volumes and hence the maximum pressure for neutron diffraction has remained at the relatively low value of 3 GPa. We have now developed a pressure cell (the Paris-Edinburgh cell) which is capable of exceeding 10 GPa with a sample volume of ˜100 mm3 for use at the U.K. spallation source ISIS. Considerable effort has been devoted to the opimization of the cell, shielding, and detector geometry to enable the best possible data to be recorded. Finite-element calculations to correct for the systematic errors introduced by the attenuation of the pressure-cell materials have been developed and tested. As a result of this work we are now able to obtain accurate structural data to ˜12 GPa and recent studies of phase IV of ND3, the behaviour of the O-D bondlength in D2O ice VIII, and the structural pressure dependence of B4C illustrate the importance of the extension of neutron-diffraction studies to such pressures.

Advanced sample environments for in situ neutron diffraction studies of nuclear materials

NASA Astrophysics Data System (ADS)

Reiche, Helmut Matthias

Generation IV nuclear reactor concepts, such as the supercritical-water-cooled nuclear reactor (SCWR), are actively researched internationally. Operating conditions above the critical point of water (374°C, 22.1 MPa) and fuel core temperature that potentially exceed 1850°C put a high demand on the surrounding materials. For their safe application, it is essential to characterize and understand the material properties on an atomic scale such as crystal structure and grain orientation (texture) changes as a function of temperature and stress. This permits the refinement of models predicting the macroscopic behavior of the material. Neutron diffraction is a powerful tool in characterizing such crystallographic properties due to their deep penetration depth into condensed matter. This leads to the ability to study bulk material properties, as opposed to surface effects, and allows for complex sample environments to study e.g. the individual contributions of thermo-mechanical processing steps during manufacturing, operating or accident scenarios. I present three sample environments for in situ neutron diffraction studies that provide such crystallographic information and have been successfully commissioned and integrated into the user program of the High Pressure -- Preferred Orientation (HIPPO) diffractometer at the Los Alamos Neutron Science Center (LANSCE) user facility. I adapted a sample changer for reliable and fast automated texture measurements of multiple specimens. I built a creep furnace combining a 2700 N load frame with a resistive vanadium furnace, capable of temperatures up to 1000°C, and manipulated by a pair of synchronized rotation stages. This combination allows following deformation and temperature dependent texture and strain evolutions in situ. Utilizing the presented sample changer and creep furnace we studied pressure tubes made of Zr-2.5wt%Nb currently employed in CANDURTM nuclear reactors and proposed for future SCWRs, acting as the primary containment vessel of high temperature heavy water (D2O) inside the reactor core. The measured sample texture shows that upon traversing the phase transition, which proceeded according to the Burger orientation relationship, variant selection occurred during heating and cooling of the zirconium alloy. Experimental results of lattice strains depending on the crystallographic orientation can be used to calculate strain pole figures which grant insight into the three-dimensional mechanical response of a polycrystalline aggregate and represent an extremely powerful material model validation tool. Lastly, I developed a resistive graphite high-temperature furnace with sample motion for in situ crystal structure and texture measurements of nuclear materials at steady-state temperatures up to at least 2200°C. This permits in situ observation of e.g. phase transitions and coefficients of thermal expansion, as well as phase formation and texture development during solidification. Utilizing this apparatus, I investigated the carbothermic reduction of UO2 nanopowder forming uranium carbide, a promising Generation IV reactor fuel. The onset of the UO2 + 2C → UC + CO2 reaction was observed at 1440°C with the bulk portion being complete at 1500°C. I describe the novel synthesis for this nanoparticle UO2 powder, which closely imitates observed nano grains in partially burnt reactor fuels. Of the three opposing structure models reported for the non-quenchable cubic UC2 phase, stable between 1769°C and 2560°C, the NaCl-type structure according to Bowman is found to be correct. This is deemed major progress as the CaF2-type structure was used for recent thermal modeling of safety critical factors in nuclear reactors. A temperature dependent increase in density due to carbon diffusion has been observed and quantified. I provide first experimental data of an unspecified, reversible order-disorder transition in this delta-phase with its onset at ˜1800°C which is likely due to rotating C2 molecules in the sublattice.

Determination of Coherency and Rigidity Temperatures in Al-Cu Alloys Using In Situ Neutron Diffraction During Casting

NASA Astrophysics Data System (ADS)

Drezet, Jean-Marie; Mireux, Bastien; Szaraz, Zoltan; Pirling, Thilo

2014-08-01

The rigidity temperature of a solidifying alloy is the temperature at which the solid phase is sufficiently coalesced to transmit tensile stress. It is a major input parameter in numerical modeling of solidification processes as it defines the point at which thermally induced deformations start to generate internal stresses in a casting. This temperature has been determined for an Al-13 wt.% Cu alloy using in situ neutron diffraction during casting in a dog-bone-shaped mold. This setup allows the sample to build up internal stress naturally as its contraction is not possible. The cooling on both sides of the mold induces a hot spot at the middle of the sample that is irradiated by neutrons. Diffraction patterns are recorded every 11 s using a large detector, and the very first change of diffraction angles allows for the determination of the rigidity temperature. We measured rigidity temperatures equal to 557°C and 548°C depending on the cooling rate for grain refined Al-13 wt.% Cu alloys. At a high cooling rate, rigidity is reached during the formation of the eutectic phase. In this case, the solid phase is not sufficiently coalesced to sustain tensile load and thus cannot avoid hot tear formation.

Locating active-site hydrogen atoms in d-xylose isomerase: Time-of-flight neutron diffraction

PubMed Central

Katz, Amy K.; Li, Xinmin; Carrell, H. L.; Hanson, B. Leif; Langan, Paul; Coates, Leighton; Schoenborn, Benno P.; Glusker, Jenny P.; Bunick, Gerard J.

2006-01-01

Time-of-flight neutron diffraction has been used to locate hydrogen atoms that define the ionization states of amino acids in crystals of d-xylose isomerase. This enzyme, from Streptomyces rubiginosus, is one of the largest enzymes studied to date at high resolution (1.8 Å) by this method. We have determined the position and orientation of a metal ion-bound water molecule that is located in the active site of the enzyme; this water has been thought to be involved in the isomerization step in which d-xylose is converted to d-xylulose or d-glucose to d-fructose. It is shown to be water (rather than a hydroxyl group) under the conditions of measurement (pH 8.0). Our analyses also reveal that one lysine probably has an −NH2-terminal group (rather than NH3+). The ionization state of each histidine residue also was determined. High-resolution x-ray studies (at 0.94 Å) indicate disorder in some side chains when a truncated substrate is bound and suggest how some side chains might move during catalysis. This combination of time-of-flight neutron diffraction and x-ray diffraction can contribute greatly to the elucidation of enzyme mechanisms. PMID:16707576

Simultaneous multiscale measurements on dynamic deformation of a magnesium alloy with synchrotron x-ray imaging and diffraction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lu, L.; Sun, T.; Fezzaa, K.

Dynamic split Hopkinson pressure bar experiments with in situ synchrotron x-ray imaging and diffraction are conducted on a rolled magnesium alloy at high strain rates of ~5500 s-1. High speed multiscale measurements including stress–strain curves (macroscale), strain fields (mesoscale), and diffraction patterns (microscale) are obtained simultaneously, revealing strong anisotropy in deformation across different length scales. {1012} extension twinning induces homogenized strain fields and gives rise to rapid increase in strain hardening rate, while dislocation motion leads to inhomogeneous deformation and a decrease in strain hardening rate. During the early stage of plastic deformation, twinning is dominant in dynamic compression, whilemore » dislocation motion prevails in quasi-static loading, manifesting a strain-rate dependence of deformation.« less

Phase Transformation Temperatures and Solute Redistribution in a Quaternary Zirconium Alloy

NASA Astrophysics Data System (ADS)

Cochrane, C.; Daymond, M. R.

2018-05-01

This study investigates the phase stability and redistribution of solute during heating and cooling of a quaternary zirconium alloy, Excel (Zr-3.2Sn-0.8Mo-0.8Nb). Time-of-flight neutron diffraction data are analyzed using a novel Vegard's law-based approach to determine the phase fractions and location of substitutional solute atoms in situ during heating from room temperature up to 1050 °C. It is seen that this alloy exhibits direct nucleation of the β Zr phase from martensite during tempering, and stable retention of the β Zr phase to high temperatures, unlike other two-phase zirconium alloys. The transformation strains resulting from the α \\leftrightarrow β transformation are shown to have a direct impact on the development of microstructure and crystallographic texture.

The unusual magnetism of nanoparticle LaCoO3.

PubMed

Durand, A M; Belanger, D P; Hamil, T J; Ye, F; Chi, S; Fernandez-Baca, J A; Booth, C H; Abdollahian, Y; Bhat, M

2015-05-08

Bulk and nanoparticle powders of LaCoO3 (LCO) were synthesized and their magnetic and structural properties were studied using SQUID magnetometry and neutron diffraction. The bulk and large nanoparticles exhibit weak ferromagnetism (FM) below T ≈ 85 K and a crossover from strong to weak antiferromagnetic (AFM) correlations near a transition expressed in the lattice parameters, To≈40 K. This crossover does not occur in the smallest nanoparticles; instead, the magnetic behavior is predominantly ferromagnetic. The amount of FM in the nanoparticles depends on the amount of Co3O4 impurity phase, which induces tensile strain on the LCO lattice. A core-interface model is introduced, with the core region exhibiting the AFM crossover and with FM in the interface region near surfaces and impurity phases.

The unusual magnetism of nanoparticle LaCoO 3

DOE PAGES

Durand, A. M.; Belanger, D. P.; Hamil, T. J.; ...

2015-04-15

Bulk and nanoparticle powders of LaCoO 3 (LCO) were synthesized and their magnetic and structural properties were studied using SQUID magnetometry and neutron diffraction. The bulk and large nanoparticles exhibit weak ferromagnetism (FM) below T≈85K and a crossover from strong to weak antiferromagnetic (AFM) correlations near a transition expressed in the lattice parameters, To ≈ 40 K. This crossover does not occur in the smallest nanoparticles; instead, the magnetic behavior is predominantly ferromagnetic. The amount of FM in the nanoparticles depends on the amount of Co 3O 4 impurity phase, which induces tensile strain on the LCO lattice. A core-interfacemore » model is introduced, with the core region exhibiting the AFM crossover and with FM in the interface region near surfaces and impurity phases.« less

The unusual magnetism of nanoparticle LaCoO3

NASA Astrophysics Data System (ADS)

Durand, A. M.; Belanger, D. P.; Hamil, T. J.; Ye, F.; Chi, S.; Fernandez-Baca, J. A.; Booth, C. H.; Abdollahian, Y.; Bhat, M.

2015-05-01

Bulk and nanoparticle powders of LaCoO3 (LCO) were synthesized and their magnetic and structural properties were studied using SQUID magnetometry and neutron diffraction. The bulk and large nanoparticles exhibit weak ferromagnetism (FM) below T ≈ 85 K and a crossover from strong to weak antiferromagnetic (AFM) correlations near a transition expressed in the lattice parameters, To≈40 K. This crossover does not occur in the smallest nanoparticles; instead, the magnetic behavior is predominantly ferromagnetic. The amount of FM in the nanoparticles depends on the amount of Co3O4 impurity phase, which induces tensile strain on the LCO lattice. A core-interface model is introduced, with the core region exhibiting the AFM crossover and with FM in the interface region near surfaces and impurity phases.

Neutron diffraction determination of the cell dimensions and thermal expansion of the fluoroperovskite KMgF3 from 293 to 3.6 K

NASA Astrophysics Data System (ADS)

Mitchell, Roger H.; Cranswick, Lachlan M. D.; Swainson, Ian

2006-11-01

The cell dimensions of the fluoroperovskite KMgF3 synthesized by solid state methods have been determined by powder neutron diffraction and Rietveld refinement over the temperature range 293 3.6 K using Pt metal as an internal standard for calibration of the neutron wavelength. These data demonstrate conclusively that cubic Pmoverline{3} m KMgF3 does not undergo any phase transitions to structures of lower symmetry with decreasing temperature. Cell dimensions range from 3.9924(2) Å at 293 K to 3.9800(2) Å at 3.6 K, and are essentially constant within experimental error from 50 to 3.6 K. The thermal expansion data are described using a fourth order polynomial function.

Magnetic order in the frustrated Ising-like chain compound Sr3NiIrO6

NASA Astrophysics Data System (ADS)

Lefrançois, E.; Chapon, L. C.; Simonet, V.; Lejay, P.; Khalyavin, D.; Rayaprol, S.; Sampathkumaran, E. V.; Ballou, R.; Adroja, D. T.

2014-07-01

We have studied the field and temperature dependencies of the magnetization of single crystals of Sr3NiIrO6. These measurements evidence the presence of an easy axis of anisotropy and two anomalies in the magnetic susceptibility. Neutron powder diffraction realized on a polycrystalline sample reveals the emergence of magnetic reflections below 75 K with magnetic propagation vector k ˜ (0, 0, 1), undetected in previous neutron studies [T. N. Nguyen and H.-C. zur Loye, J. Solid State Chem. 117, 300 (1995), 10.1006/jssc.1995.1277]. The nature of the magnetic ground state, and the presence of two anomalies common to this family of material, are discussed on the basis of the results obtained by neutron diffraction, magnetization measurements, and symmetry arguments.

Hydrogen atoms can be located accurately and precisely by x-ray crystallography.

PubMed

Woińska, Magdalena; Grabowsky, Simon; Dominiak, Paulina M; Woźniak, Krzysztof; Jayatilaka, Dylan

2016-05-01

Precise and accurate structural information on hydrogen atoms is crucial to the study of energies of interactions important for crystal engineering, materials science, medicine, and pharmacy, and to the estimation of physical and chemical properties in solids. However, hydrogen atoms only scatter x-radiation weakly, so x-rays have not been used routinely to locate them accurately. Textbooks and teaching classes still emphasize that hydrogen atoms cannot be located with x-rays close to heavy elements; instead, neutron diffraction is needed. We show that, contrary to widespread expectation, hydrogen atoms can be located very accurately using x-ray diffraction, yielding bond lengths involving hydrogen atoms (A-H) that are in agreement with results from neutron diffraction mostly within a single standard deviation. The precision of the determination is also comparable between x-ray and neutron diffraction results. This has been achieved at resolutions as low as 0.8 Å using Hirshfeld atom refinement (HAR). We have applied HAR to 81 crystal structures of organic molecules and compared the A-H bond lengths with those from neutron measurements for A-H bonds sorted into bonds of the same class. We further show in a selection of inorganic compounds that hydrogen atoms can be located in bridging positions and close to heavy transition metals accurately and precisely. We anticipate that, in the future, conventional x-radiation sources at in-house diffractometers can be used routinely for locating hydrogen atoms in small molecules accurately instead of large-scale facilities such as spallation sources or nuclear reactors.

Hydrogen atoms can be located accurately and precisely by x-ray crystallography

PubMed Central

Woińska, Magdalena; Grabowsky, Simon; Dominiak, Paulina M.; Woźniak, Krzysztof; Jayatilaka, Dylan

2016-01-01

Precise and accurate structural information on hydrogen atoms is crucial to the study of energies of interactions important for crystal engineering, materials science, medicine, and pharmacy, and to the estimation of physical and chemical properties in solids. However, hydrogen atoms only scatter x-radiation weakly, so x-rays have not been used routinely to locate them accurately. Textbooks and teaching classes still emphasize that hydrogen atoms cannot be located with x-rays close to heavy elements; instead, neutron diffraction is needed. We show that, contrary to widespread expectation, hydrogen atoms can be located very accurately using x-ray diffraction, yielding bond lengths involving hydrogen atoms (A–H) that are in agreement with results from neutron diffraction mostly within a single standard deviation. The precision of the determination is also comparable between x-ray and neutron diffraction results. This has been achieved at resolutions as low as 0.8 Å using Hirshfeld atom refinement (HAR). We have applied HAR to 81 crystal structures of organic molecules and compared the A–H bond lengths with those from neutron measurements for A–H bonds sorted into bonds of the same class. We further show in a selection of inorganic compounds that hydrogen atoms can be located in bridging positions and close to heavy transition metals accurately and precisely. We anticipate that, in the future, conventional x-radiation sources at in-house diffractometers can be used routinely for locating hydrogen atoms in small molecules accurately instead of large-scale facilities such as spallation sources or nuclear reactors. PMID:27386545

Non-destructive detection of cross-sectional strain and defect structure in an individual Ag five-fold twinned nanowire by 3D electron diffraction mapping.

PubMed

Fu, Xin; Yuan, Jun

2017-07-24

Coherent x-ray diffraction investigations on Ag five-fold twinned nanowires (FTNWs) have drawn controversial conclusions concerning whether the intrinsic 7.35° angular gap could be compensated homogeneously through phase transformation or inhomogeneously by forming disclination strain field. In those studies, the x-ray techniques only provided an ensemble average of the structural information from all the Ag nanowires. Here, using three-dimensional (3D) electron diffraction mapping approach, we non-destructively explore the cross-sectional strain and the related strain-relief defect structures of an individual Ag FTNW with diameter about 30 nm. The quantitative analysis of the fine structure of intensity distribution combining with kinematic electron diffraction simulation confirms that for such a Ag FTNW, the intrinsic 7.35° angular deficiency results in an inhomogeneous strain field within each single crystalline segment consistent with the disclination model of stress-relief. Moreover, the five crystalline segments are found to be strained differently. Modeling analysis in combination with system energy calculation further indicates that the elastic strain energy within some crystalline segments, could be partially relieved by the creation of stacking fault layers near the twin boundaries. Our study demonstrates that 3D electron diffraction mapping is a powerful tool for the cross-sectional strain analysis of complex 1D nanostructures.

Neutron detectors for the ESS diffractometers

NASA Astrophysics Data System (ADS)

Stefanescu, I.; Christensen, M.; Fenske, J.; Hall-Wilton, R.; Henry, P. F.; Kirstein, O.; Müller, M.; Nowak, G.; Pooley, D.; Raspino, D.; Rhodes, N.; Šaroun, J.; Schefer, J.; Schooneveld, E.; Sykora, J.; Schweika, W.

2017-01-01

The ambitious instrument suite for the future European Spallation Source whose civil construction started recently in Lund, Sweden, demands a set of diverse and challenging requirements for the neutron detectors. For instance, the unprecedented high flux expected on the samples to be investigated in neutron diffraction or reflectometry experiments requires detectors that can handle high counting rates, while the investigation of sub-millimeter protein crystals will only be possible with large-area detectors that can achieve a position resolution as low as 200 μm. This has motivated an extensive research and development campaign to advance the state-of-the-art detector and to find new technologies that can reach maturity by the time the ESS will operate at full potential. This paper presents the key detector requirements for three of the Time-of-Flight (TOF) diffraction instrument concepts selected by the Scientific Advisory Committee to advance into the phase of preliminary engineering design. We discuss the detector technologies commonly employed at the existing similar instruments and their major challenges for ESS. The detector technologies selected by the instrument teams to collect the diffraction patterns are also presented. Analytical calculations, Monte-Carlo simulations, and real experimental data are used to develop a generic method to estimate the event rate in the diffraction detectors. We apply this method to make predictions for the future diffraction instruments, and thus provide additional information that can help the instrument teams with the optimisation of the detector designs.

Neutron apparatus for measuring strain in composites

DOEpatents

Kupperman, David S.; Majumdar, Saurindranath; Faber, Jr., John F.; Singh, J. P.

1990-01-01

A method and apparatus for orienting a pulsed neutron source and a multi-angle diffractometer toward a sample of a ceramic-matrix or metal-matrix composite so that the measurement of internal strain (from which stress is calculated) is reduced to uncomplicated time-of-flight measurements.

Neutron diffraction and ferromagnetic resonance studies on plasma-sprayed MnZn ferrite films

NASA Astrophysics Data System (ADS)

Yan, Q. Y.; Gambino, R. J.; Sampath, S.; Huang, Q.

2005-02-01

The magnetic properties of MnZn ferrites are affected by the plasma spray process. It is found that improvements can be made by annealing the ferrite films at 500°C-800°C. The annealing induced magnetic property changes are studied by neutron diffraction and ferromagnetic resonance techniques. The increase of the saturation magnetization is attributed to the cation ordering within the spinel lattice, which increases the magnetic moment per ferrite formula. The refinements on the neutron diffraction data suggest that the redistribution of the cation during annealing neither starts from a fully disordered state nor ends to a fully ordered state. The decrease of the coercivity is analyzed with the domain wall pinning model. The measurements on the magnetostriction and residual stress indicate that coercive mechanisms arising from the magnetoelastic energy term are not dominant in these ferrite films. The decrease of the coercivity for annealed ferrite films is mainly attributed to the decrease of the effective anisotropic field, which may result from the homogenization of the film composition and the reduction of the microstructural discontinuity (e.g., cracks, voids, and splat boundaries).

Evidence for monoclinic distortion in the ground state phase of underdoped La 1.95Sr 0.05CuO 4: A single crystal neutron diffraction study

DOE PAGES

Singh, Anar; Schefer, Jurg; Sura, Ravi; ...

2016-03-24

The existing controversy about the symmetry of the crystal structure of the ground state of the critical doped La 1.95Sr 0.05CuO 4 has been resolved by analyzing the single crystal neutron diffraction data collected between 5 and 730 K. We observed small but significant intensities for "forbidden" reflections given by extinction rules of the orthorhombic Bmab space group at low temperatures. A careful investigation of neutron diffraction data reveals that the crystal structure of La 1.95Sr 0.05CuO 4 at 5 K is monoclinic with B2/m (2/m 1 1) space group. The monoclinic structure emerges from the orthorhombic structure in amore » continuous way; however, the structure is stable below similar to 120K which agrees with other observed phenomena. Lastly, our results on symmetry changes are crucial for the interpretation of physical properties also in other high temperature superconductors with similar structures.« less

Low temperature magnetic properties of Nd2Ru2O7

NASA Astrophysics Data System (ADS)

Ku, S. T.; Kumar, D.; Lees, M. R.; Lee, W.-T.; Aldus, R.; Studer, A.; Imperia, P.; Asai, S.; Masuda, T.; Chen, S. W.; Chen, J. M.; Chang, L. J.

2018-04-01

We present magnetic susceptibility, heat capacity, and neutron diffraction measurements of polycrystalline Nd2Ru2O7 down to 0.4 K. Three anomalies in the magnetic susceptibility measurements at 146, 21 and 1.8 K are associated with an antiferromagnetic ordering of the Ru4+ moments, a weak ferromagnetic signal attributed to a canting of the Ru4+ and Nd3+ moments, and a long-range-ordering of the Nd3+ moments, respectively. The long-range order of the Nd3+ moments was observed in all the measurements, indicating that the ground state of the compound is not a spin glass. The magnetic entropy of Rln2 accumulated up to 5 K, suggests the Nd3+ has a doublet ground state. Lattice distortions accompany the transitions, as revealed by neutron diffraction measurements, and in agreement with earlier synchrotron x-ray studies. The magnetic moment of the Nd3+ ion at 0.4 K is estimated to be 1.54(2)µ B and the magnetic structure is all-in all-out as determined by our neutron diffraction measurements.

Evidence for monoclinic distortion in the ground state phase of underdoped La{sub 1.95}Sr{sub 0.05}CuO{sub 4}: A single crystal neutron diffraction study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Singh, Anar, E-mail: singhanar@gmail.com; Schefer, Jürg; Frontzek, Matthias

2016-03-28

The existing controversy about the symmetry of the crystal structure of the ground state of the critical doped La{sub 1.95}Sr{sub 0.05}CuO{sub 4} has been resolved by analyzing the single crystal neutron diffraction data collected between 5 and 730 K. We observed small but significant intensities for “forbidden” reflections given by extinction rules of the orthorhombic Bmab space group at low temperatures. A careful investigation of neutron diffraction data reveals that the crystal structure of La{sub 1.95}Sr{sub 0.05}CuO{sub 4} at 5 K is monoclinic with B2/m (2/m 1 1) space group. The monoclinic structure emerges from the orthorhombic structure in a continuous way;more » however, the structure is stable below ∼120 K which agrees with other observed phenomena. Our results on symmetry changes are crucial for the interpretation of physical properties also in other high temperature superconductors with similar structures.« less

Pressure dependence of the magnetic order in CrAs: a neutron diffraction investigation

DOE PAGES

Keller, L.; White, J. S.; Babkevich, P.; ...

2015-01-29

The suppression of magnetic order with pressure concomitant with the appearance of pressure-induced superconductivity was recently discovered in CrAs. Here we present a neutron diffraction study of the pressure evolution of the helimagnetic ground-state towards and in the vicinity of the superconducting phase. Neutron diffraction on polycrystalline CrAs was employed from zero pressure to 0.65 GPa and at various temperatures. The helimagnetic long-range order is sustained under pressure and the magnetic propagation vector does not show any considerable change. The average ordered magnetic moment is reduced from 1.73(2) μ B at ambient pressure to 0.4(1) μ B close to themore » critical pressure P c ≈ 0.7 GPa, at which magnetic order is completely suppressed. The width of the magnetic Bragg peaks strongly depends on temperature and pressure, showing a maximum in the region of the onset of superconductivity. In conclusion, we interpret this as associated with competing ground-states in the vicinity of the superconducting phase.« less

Pressure dependence of the magnetic order in CrAs: a neutron diffraction investigation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Keller, L.; White, J. S.; Babkevich, P.

The suppression of magnetic order with pressure concomitant with the appearance of pressure-induced superconductivity was recently discovered in CrAs. Here we present a neutron diffraction study of the pressure evolution of the helimagnetic ground-state towards and in the vicinity of the superconducting phase. Neutron diffraction on polycrystalline CrAs was employed from zero pressure to 0.65 GPa and at various temperatures. The helimagnetic long-range order is sustained under pressure and the magnetic propagation vector does not show any considerable change. The average ordered magnetic moment is reduced from 1.73(2) μ B at ambient pressure to 0.4(1) μ B close to themore » critical pressure P c ≈ 0.7 GPa, at which magnetic order is completely suppressed. The width of the magnetic Bragg peaks strongly depends on temperature and pressure, showing a maximum in the region of the onset of superconductivity. In conclusion, we interpret this as associated with competing ground-states in the vicinity of the superconducting phase.« less

Growing Larger Crystals for Neutron Diffraction

NASA Technical Reports Server (NTRS)

Pusey, Marc

2003-01-01

Obtaining crystals of suitable size and high quality has been a major bottleneck in macromolecular crystallography. With the advent of advanced X-ray sources and methods the question of size has rapidly dwindled, almost to the point where if one can see the crystal then it was big enough. Quality is another issue, and major national and commercial efforts were established to take advantage of the microgravity environment in an effort to obtain higher quality crystals. Studies of the macromolecule crystallization process were carried out in many labs in an effort to understand what affected the resultant crystal quality on Earth, and how microgravity improved the process. While technological improvements are resulting in a diminishing of the minimum crystal size required, neutron diffraction structural studies still require considerably larger crystals, by several orders of magnitude, than X-ray studies. From a crystal growth physics perspective there is no reason why these 'large' crystals cannot be obtained: the question is generally more one of supply than limitations mechanism. This talk will discuss our laboratory s current model for macromolecule crystal growth, with highlights pertaining to the growth of crystals suitable for neutron diffraction studies.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Song, Gian; Lee, Chanho; Hong, Sung Hwan

Here, CuZr-based bulk-metallic-glass (BMG) composites reinforced by a B2-type CuZr crystalline-phase (CP) have been widely studied, and exhibit that the plastic deformation of the CP induces martensitic transformation from the B2 to B19', which plays a dominant role in the deformation behavior and mechanical properties. In the present study, 2.0% Co containing CuZr-based BMG composites were investigated using in-situ neutron-diffraction technique. The in-situ neutron-diffraction results reveal the continuous load transfer from the glass matrix to B2 CP and martensitic transformation from the B2 CP to B19' during the deformation of the composite. Moreover, it was found that the martensitic transformationmore » is initiated at the applied stress higher than 1500 MPa, and is significantly suppressed during the deformation, as compared to other 0.5% Co-containing CuZr-based BMG composites. Based on these in-situ neutron-diffraction results, the martensitic transformation is strongly affected by the amount of the addition of Co, which determines the mechanical properties of CP-reinforced BMG composites, such as ductility and hardening capability.« less

Acute Lethality after Fast-Neutron and X-Irradiation of Tribolium confusum

DOE Office of Scientific and Technical Information (OSTI.GOV)

Glenn, Norman D.; Ducoff, Howard S.

1976-01-01

The acute lethal effects of fast neutrons and of X-rays on adults and larvae of T. confusum are compared. The time course of mortality of adults of the Oklahoma strain was the same after midlethal doses of neutrons and X-rays, although the neutrons were about twice as effective as X-rays in producing lethality, based on LD 50(35). The neutron RBE for adults of the Ebony mutant strain was also about 2, but that for Oklahoma larvae was about 3.85. Larvae surviving midlethal doses of neutrons showed a tendency toward wing abnormalities and delayed pupation. Dose-fractionation recovery with neutron doses inmore » the midlethal range was not detectable in the adults or in the larvae. A considerable sparing effect of dose fractionation was found in X-irradiated adults. Finally, also presented are techniques for using a beam port of a Triga research reactor for fast-neutron irradiation and a method of neutron and gamma dosimetry.« less

Reintroducing electrostatics into macromolecular crystallographic refinement: application to neutron crystallography and DNA hydration.

PubMed

Fenn, Timothy D; Schnieders, Michael J; Mustyakimov, Marat; Wu, Chuanjie; Langan, Paul; Pande, Vijay S; Brunger, Axel T

2011-04-13

Most current crystallographic structure refinements augment the diffraction data with a priori information consisting of bond, angle, dihedral, planarity restraints, and atomic repulsion based on the Pauli exclusion principle. Yet, electrostatics and van der Waals attraction are physical forces that provide additional a priori information. Here, we assess the inclusion of electrostatics for the force field used for all-atom (including hydrogen) joint neutron/X-ray refinement. Two DNA and a protein crystal structure were refined against joint neutron/X-ray diffraction data sets using force fields without electrostatics or with electrostatics. Hydrogen-bond orientation/geometry favors the inclusion of electrostatics. Refinement of Z-DNA with electrostatics leads to a hypothesis for the entropic stabilization of Z-DNA that may partly explain the thermodynamics of converting the B form of DNA to its Z form. Thus, inclusion of electrostatics assists joint neutron/X-ray refinements, especially for placing and orienting hydrogen atoms. Copyright © 2011 Elsevier Ltd. All rights reserved.

Reintroducing Electrostatics into Macromolecular Crystallographic Refinement: Application to Neutron Crystallography and DNA Hydration

PubMed Central

Fenn, Timothy D.; Schnieders, Michael J.; Mustyakimov, Marat; Wu, Chuanjie; Langan, Paul; Pande, Vijay S.; Brunger, Axel T.

2011-01-01

Summary Most current crystallographic structure refinements augment the diffraction data with a priori information consisting of bond, angle, dihedral, planarity restraints and atomic repulsion based on the Pauli exclusion principle. Yet, electrostatics and van der Waals attraction are physical forces that provide additional a priori information. Here we assess the inclusion of electrostatics for the force field used for all-atom (including hydrogen) joint neutron/X-ray refinement. Two DNA and a protein crystal structure were refined against joint neutron/X-ray diffraction data sets using force fields without electrostatics or with electrostatics. Hydrogen bond orientation/geometry favors the inclusion of electrostatics. Refinement of Z-DNA with electrostatics leads to a hypothesis for the entropic stabilization of Z-DNA that may partly explain the thermodynamics of converting the B form of DNA to its Z form. Thus, inclusion of electrostatics assists joint neutron/X-ray refinements, especially for placing and orienting hydrogen atoms. PMID:21481775

A furnace with rotating load frame for in situ high temperature deformation and creep experiments in a neutron diffraction beam line

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reiche, H. M.; New Mexico State University, Las Cruces, New Mexico 88003; Vogel, S. C.

2012-05-15

A resistive furnace combined with a load frame was built that allows for in situ neutron diffraction studies of high temperature deformation, in particular, creep. A maximum force of 2700 N can be applied at temperatures up to 1000 deg. C. A load control mode permits studies of, e.g., creep or phase transformations under applied uni-axial stress. In position control, a range of high temperature deformation experiments can be achieved. The examined specimen can be rotated up to 80 deg. around the vertical compression axis allowing texture measurements in the neutron time-of-flight diffractometer HIPPO (High Pressure - Preferred Orientation). Wemore » present results from the successful commissioning, deforming a Zr-2.5 wt.% Nb cylinder at 975 deg. C. The device is now available for the user program of the HIPPO diffractometer at the LANSCE (Los Alamos Neutron Science Center) user facility.« less

Neutron diffraction studies of a four-coordinated hydride in near square-planar geometry

DOE PAGES

Liao, Jian -Hong; Dhayal, Rajendra Singh; Wang, Xiaoping; ...

2014-10-07

The structure of a nanospheric polyhydrido copper cluster, [Cu 20(H) 11{S 2P(O iPr) 2} 9], was determined by single-crystal neutron diffraction. Cu 20 cluster consists of an elongated triangular orthobicupola constructed from 18 Cu atoms that encapsulate a [Cu 2H 5} 3- ion in the center with an exceptionally short Cu-Cu distance. The eleven hydrides in the cluster display three different coordination modes to the Cu atoms: Six μ 3-hydrides in pyramidal geometry, two μ 4-hydrides in tetrahedral cavity, and three μ 4-hydrides in an unprecedented near square-planar geometry. The neutron data set was collected on a small crystal ofmore » the size 0.20 mm x 0.50 mm x 0.65 mm for seven days using the Spallation Neutron Source TOPAZ single-crystal time-of-flight Laue diffractometer at the Oak Ridge National Laboratory. Furthermore, the final R-factor is 8.64% for 16014 reflections.« less

Strain and lattice orientation distribution in SiN/Ge complementary metal–oxide–semiconductor compatible light emitting microstructures by quick x-ray nano-diffraction microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chahine, G. A.; Schülli, T. U.; Zoellner, M. H.

2015-02-16

This paper presents a study of the spatial distribution of strain and lattice orientation in CMOS-fabricated strained Ge microstripes using high resolution x-ray micro-diffraction. The recently developed model-free characterization tool, based on a quick scanning x-ray diffraction microscopy technique can image strain down to levels of 10{sup −5} (Δa/a) with a spatial resolution of ∼0.5 μm. Strain and lattice tilt are extracted using the strain and orientation calculation software package X-SOCS. The obtained results are compared with the biaxial strain distribution obtained by lattice parameter-sensitive μ-Raman and μ-photoluminescence measurements. The experimental data are interpreted with the help of finite element modelingmore » of the strain relaxation dynamics in the investigated structures.« less

Idealized powder diffraction patterns for cellulose polymorphs

USDA-ARS?s Scientific Manuscript database

Cellulose samples are routinely analyzed by X-ray diffraction to determine their crystal type (polymorph) and crystallinity. However, the connection is seldom made between those efforts and the crystal structures of cellulose that have been determined with synchrotron X-radiation and neutron diffrac...

Neutron powder diffraction studies as a function of temperature of structure II hydrate formed from propane

USGS Publications Warehouse

Rawn, C.J.; Rondinone, A.J.; Chakoumakos, B.C.; Circone, S.; Stern, L.A.; Kirby, S.H.; Ishii, Y.

2003-01-01

Neutron powder diffraction data confirm that hydrate samples synthesized with propane crystallize as structure type II hydrate. The structure has been modeled using rigid-body constraints to describe C3H8 molecules located in the eight larger polyhedral cavities of a deuterated host lattice. Data were collected at 12, 40, 100, 130, 160, 190, 220, and 250 K and used to calculate the thermal expansivity from the temperature dependence of the lattice parameters. The data collected allowed for full structural refinement of atomic coordinates and the atomic-displacement parameters.

Neutron diffraction, specific heat and magnetization studies on Nd{sub 2}CuTiO{sub 6}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rayaprol, S., E-mail: sudhindra@csr.res.in; Kaushik, S. D.; Kumar, Naresh

2016-05-23

Structural and physical properties of a double-perovskite compound, Nd{sub 2}CuTiO{sub 6} have been studied using neutron diffraction, magnetization and specific heat measurements. The compound crystallizes in an orthorhombic structure in space group Pnma. The interesting observation we make here is that, though no long range magnetic order is observed between 2 and 300 K, the low temperature specific heat and magnetic susceptibility behavior exhibits non-Fermi liquid like behavior in this insulating compound. The magnetization and specific heat data are presented and discussed in light of these observations.

X-ray absorption spectroscopy and neutron diffraction study of the perovskite-type rare-earth cobaltites

NASA Astrophysics Data System (ADS)

Sikolenko, V.; Efimova, E.; Franz, A.; Ritter, C.; Troyanchuk, I. O.; Karpinsky, D.; Zubavichus, Y.; Veligzhanin, A.; Tiutiunnikov, S. I.; Sazonov, A.; Efimov, V.

2018-05-01

Correlations between local and long-range structure distortions in the perovskite-type RE1-xSrxCoO3-δ (RE = La, Pr, Nd; x = 0.0 and 0.5) compounds have been studied at room temperature by extended X-ray absorption fine structure (EXAFS) at the Co K-edge and high-resolution neutron powder diffraction (NPD). The use of two complementary experimental techniques allowed us to explore the influence of the type of rare-earth element and strontium substitution on unusual behavior of static and dynamic features of both the Co-O bond lengths.

Neutron diffraction and μ SR studies of two polymorphs of nickel niobate NiNb 2 O 6

DOE PAGES

Munsie, T. J. S.; Wilson, M. N.; Millington, A.; ...

2017-10-13

Neutron diffraction and muon spin relaxation (μSR) studies are presented in this paper for the newly characterized polymorph of NiNb 2O 6 (β-NiNb 2O 6) with space group P4 2/n and μSR data only for the previously known columbite structure polymorph with space group Pbcn. The magnetic structure of the P4 2/n form was determined from neutron diffraction using both powder and single-crystal data. Powder neutron diffraction determined an ordering wave vector →k=( 1/ 2, 1/ 2, 1/ 2). Single-crystal data confirmed the same →k vector and showed that the correct magnetic structure consists of antiferromagnetically coupled chains running alongmore » the a or b axis in adjacent Ni 2+ layers perpendicular to the c axis, which is consistent with the expected exchange interaction hierarchy in this system. The refined magnetic structure is compared with the known magnetic structures of the closely related trirutile phases, NiSb 2O 6 and NiTa 2O 6. μSR data finds a transition temperature of T N~15K for this system, while the columbite polymorph exhibits a lower T N=5.7(3) K. Our μSR measurements also allowed us to estimate the critical exponent of the order parameter β for each polymorph. We found β =0.25(3) and 0.16(2) for the β and columbite polymorphs, respectively. The single-crystal neutron scattering data give a value for the critical exponent β =0.28(3) for β-NiNb 2O 6, in agreement with the μSR value. While both systems have β values less than 0.3, which is indicative of reduced dimensionality, this effect appears to be much stronger for the columbite system. Finally, in other words, although both systems appear to be well described by S=1 spin chains, the interchain interactions in the β polymorph are likely much larger.« less

Neutron diffraction and μ SR studies of two polymorphs of nickel niobate NiNb2O6

NASA Astrophysics Data System (ADS)

Munsie, T. J. S.; Wilson, M. N.; Millington, A.; Thompson, C. M.; Flacau, R.; Ding, C.; Guo, S.; Gong, Z.; Aczel, A. A.; Cao, H. B.; Williams, T. J.; Dabkowska, H. A.; Ning, F.; Greedan, J. E.; Luke, G. M.

2017-10-01

Neutron diffraction and muon spin relaxation (μ SR ) studies are presented for the newly characterized polymorph of NiNb2O6 (β -NiNb2O6) with space group P4 2/n and μ SR data only for the previously known columbite structure polymorph with space group P b c n . The magnetic structure of the P4 2/n form was determined from neutron diffraction using both powder and single-crystal data. Powder neutron diffraction determined an ordering wave vector k ⃗=(1/2 ,1/2 ,1/2 ) . Single-crystal data confirmed the same k ⃗ vector and showed that the correct magnetic structure consists of antiferromagnetically coupled chains running along the a or b axis in adjacent Ni2 + layers perpendicular to the c axis, which is consistent with the expected exchange interaction hierarchy in this system. The refined magnetic structure is compared with the known magnetic structures of the closely related trirutile phases, NiSb2O6 and NiTa2O6 . μ SR data finds a transition temperature of TN˜15 K for this system, while the columbite polymorph exhibits a lower TN=5.7 (3 ) K. Our μ SR measurements also allowed us to estimate the critical exponent of the order parameter β for each polymorph. We found β =0.25 (3 ) and 0.16(2) for the β and columbite polymorphs, respectively. The single-crystal neutron scattering data give a value for the critical exponent β =0.28 (3 ) for β -NiNb2O6 , in agreement with the μ SR value. While both systems have β values less than 0.3, which is indicative of reduced dimensionality, this effect appears to be much stronger for the columbite system. In other words, although both systems appear to be well described by S =1 spin chains, the interchain interactions in the β polymorph are likely much larger.

Neutron diffraction and μ SR studies of two polymorphs of nickel niobate NiNb 2 O 6

DOE Office of Scientific and Technical Information (OSTI.GOV)

Munsie, T. J. S.; Wilson, M. N.; Millington, A.

Neutron diffraction and muon spin relaxation (μSR) studies are presented in this paper for the newly characterized polymorph of NiNb 2O 6 (β-NiNb 2O 6) with space group P4 2/n and μSR data only for the previously known columbite structure polymorph with space group Pbcn. The magnetic structure of the P4 2/n form was determined from neutron diffraction using both powder and single-crystal data. Powder neutron diffraction determined an ordering wave vector →k=( 1/ 2, 1/ 2, 1/ 2). Single-crystal data confirmed the same →k vector and showed that the correct magnetic structure consists of antiferromagnetically coupled chains running alongmore » the a or b axis in adjacent Ni 2+ layers perpendicular to the c axis, which is consistent with the expected exchange interaction hierarchy in this system. The refined magnetic structure is compared with the known magnetic structures of the closely related trirutile phases, NiSb 2O 6 and NiTa 2O 6. μSR data finds a transition temperature of T N~15K for this system, while the columbite polymorph exhibits a lower T N=5.7(3) K. Our μSR measurements also allowed us to estimate the critical exponent of the order parameter β for each polymorph. We found β =0.25(3) and 0.16(2) for the β and columbite polymorphs, respectively. The single-crystal neutron scattering data give a value for the critical exponent β =0.28(3) for β-NiNb 2O 6, in agreement with the μSR value. While both systems have β values less than 0.3, which is indicative of reduced dimensionality, this effect appears to be much stronger for the columbite system. Finally, in other words, although both systems appear to be well described by S=1 spin chains, the interchain interactions in the β polymorph are likely much larger.« less

Reversible piezomagnetoelectric switching in bulk polycrystalline ceramics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stevenson, T., E-mail: t.j.stevenson@leeds.ac.uk; Bennett, J.; Brown, A. P.

2014-08-01

Magnetoelectric (ME) coupling in materials offer tremendous advantages in device functionality enabling technologies including advanced electronic memory, combining electronic speed, and efficiency with magnetic robustness. However, low cost polycrystalline ME materials are excluded from most commercial applications, operating only at cryogenic temperatures, impractically large electric/magnetic fields, or with low ME coefficients (1-100 mV/cm Oe). Despite this, the technological potential of single compound ME coupling has continued to drive research into multiferroics over the last two decades. Here we show that by manipulating the large induced atomic strain within the polycrystalline, room temperature multiferroic compound 0.7BiFeO{sub 3}–0.3PbTiO{sub 3}, we can induce amore » reversible, piezoelectric strain controlled ME effect. Employing an in situ neutron diffraction experiment, we have demonstrated that this piezomagnetoelectric effect manifests with an applied electric field >8 kV/mm at the onset of piezoelectric strain, engineered in to the compound by crystallographic phase mixing. This produces a remarkable intrinsic ME coefficient of 1276 mV/cm Oe, due to a strain driven modification to the oxygen sub-lattice, inducing an increase in magnetic moment per Fe{sup 3+} ion of +0.142 μ{sub B}. This work provides a framework for investigations into strain engineered nanostructures to realize low-cost ME devices designed from the atoms up, as well as contributing to the deeper understanding of single phase ME coupling mechanisms.« less

Neutron resonance spin-echo upgrade at the three-axis spectrometer FLEXX

DOE Office of Scientific and Technical Information (OSTI.GOV)

Groitl, F., E-mail: felix.groitl@psi.ch; Quintero-Castro, D. L.; Habicht, K.

2015-02-15

We describe the upgrade of the neutron resonance spin-echo setup at the cold neutron triple-axis spectrometer FLEXX at the BER II neutron source at the Helmholtz-Zentrum Berlin. The parameters of redesigned key components are discussed, including the radio frequency (RF) spin-flip coils, the magnetic shield, and the zero field coupling coils. The RF-flippers with larger beam windows allow for an improved neutron flux transfer from the source to the sample and further to the analyzer. The larger beam cross sections permit higher coil inclination angles and enable measurements on dispersive excitations with a larger slope of the dispersion. Due tomore » the compact design of the spin-echo units in combination with the increased coil tilt angles, the accessible momentum-range in the Larmor diffraction mode is substantially enlarged. In combination with the redesigned components of the FLEXX spectrometer, including the guide, the S-bender polarizer, the double focusing monochromator, and a Heusler crystal analyzer, the count rate increased by a factor of 15.5, and the neutron beam polarization is enhanced. The improved performance extends the range of feasible experiments, both for inelastic scattering on excitation lifetimes in single crystals, and for high-resolution Larmor diffraction. The experimental characterization of the instrument components demonstrates the reliable performance of the new neutron resonance spin-echo option, now available for the scientific community at FLEXX.« less

Energy-selective Neutron Imaging for Three-dimensional Non-destructive Probing of Crystalline Structures

NASA Astrophysics Data System (ADS)

Peetermans, S.; Bopp, M.; Vontobel, P.; Lehmann, E. H.

Common neutron imaging uses the full polychromatic neutron beam spectrum to reveal the material distribution in a non-destructive way. Performing it with a reduced energy band, i.e. energy-selective neutron imaging, allows access to local variation in sample crystallographic properties. Two sample categories can be discerned with different energy responses. Polycrystalline materials have an energy-dependent cross-section featuring Bragg edges. Energy-selective neutron imaging can be used to distinguish be- tween crystallographic phases, increase material sensitivity or penetration, improve quantification etc. An example of the latter is shown by the examination of copper discs prior to machining them into linear accelerator cavity structures. The cross-section of single crystals features distinct Bragg peaks. Based on their pattern, one can determine the orientation of the crystal, as in a Laue pattern, but with the tremendous advantage that the operation can be performed for each pixel, yielding crystal orientation maps at high spatial resolution. A wholly different method to investigate such samples is also introduced: neutron diffraction imaging. It is based on projections formed by neutrons diffracted from the crystal lattice out of the direct beam. The position of these projections on the detector gives information on the crystal orientation. The projection itself can be used to reconstruct the crystal shape. A three-dimensional mapping of local Bragg reflectivity or a grain orientation mapping can thus be obtained.

Deformation fields near a steady fatigue crack with anisotropic plasticity

DOE PAGES

Gao, Yanfei

2015-11-30

In this work, from finite element simulations based on an irreversible, hysteretic cohesive interface model, a steady fatigue crack can be realized if the crack extension exceeds about twice the plastic zone size, and both the crack increment per loading cycle and the crack bridging zone size are smaller than the plastic zone size. The corresponding deformation fields develop a plastic wake behind the crack tip and a compressive residual stress field ahead of the crack tip. In addition, the Hill’s plasticity model is used to study the role of plastic anisotropy on the retardation of fatigue crack growth andmore » the elastic strain fields. It is found that for Mode-I cyclic loading, an enhanced yield stress in directions that are inclined from the crack plane will lead to slower crack growth rate, but this retardation is insignificant for typical degrees of plastic anisotropy. Furthermore, these results provide key inputs for future comparisons to neutron and synchrotron diffraction measurements that provide full-field lattice strain mapping near fracture and fatigue crack tips, especially in textured materials such as wrought or rolled Mg alloys.« less

Deformation fields near a steady fatigue crack with anisotropic plasticity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gao, Yanfei

In this work, from finite element simulations based on an irreversible, hysteretic cohesive interface model, a steady fatigue crack can be realized if the crack extension exceeds about twice the plastic zone size, and both the crack increment per loading cycle and the crack bridging zone size are smaller than the plastic zone size. The corresponding deformation fields develop a plastic wake behind the crack tip and a compressive residual stress field ahead of the crack tip. In addition, the Hill’s plasticity model is used to study the role of plastic anisotropy on the retardation of fatigue crack growth andmore » the elastic strain fields. It is found that for Mode-I cyclic loading, an enhanced yield stress in directions that are inclined from the crack plane will lead to slower crack growth rate, but this retardation is insignificant for typical degrees of plastic anisotropy. Furthermore, these results provide key inputs for future comparisons to neutron and synchrotron diffraction measurements that provide full-field lattice strain mapping near fracture and fatigue crack tips, especially in textured materials such as wrought or rolled Mg alloys.« less

Structure of Se-Te glasses studied using neutron, X-ray diffraction and reverse Monte Carlo modelling

DOE Office of Scientific and Technical Information (OSTI.GOV)

Itoh, Keiji, E-mail: itoh@okayama-u.ac.jp; Research Reactor Institute, Kyoto University, Kumatori, Osaka 590-0494

Pulsed neutron diffraction and synchrotron X-ray diffraction measurements were performed on Se{sub 100-x}Te{sub x} bulk glasses with x=10, 20, 30 and 40. The coordination numbers obtained from the diffraction results demonstrate that Se and Te atoms are twofold coordinated and the glass structure is formed by the chain network. The three-dimensional structure model for Se{sub 60}Te{sub 40} glass obtained by using reverse Monte Carlo modelling shows that the alternating arrangements of Se and Te atoms compose the major part of the chain clusters but several other fragments such as Se{sub n} chains and Te-Te dimers are also present in largemore » numbers. The chain clusters have geometrically disordered forms and the interchain atomic order is different from those in the crystal structures of trigonal Se and trigonal Te. - Graphical abstract: Coordination environment in Se{sub 60}Te{sub 40} glass.« less

Residual stress determination in an overlay dissimilar welded pipe by neutron diffraction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Woo, Wan Chuck; Em, Vyacheslav; Hubbard, Camden R

2011-01-01

Residual stresses were determined through the thickness of a dissimilar weld overlay pipe using neutron diffraction. The specimen has a complex joining structure consisting of a ferritic steel (SA508), austenitic steel (F316L), Ni-based consumable (Alloy 182), and overlay of Ni-base superalloy (Alloy 52M). It simulates pressurized nozzle components, which have been a critical issue under the severe crack condition of nuclear power reactors. Two neutron diffractometers with different spatial resolutions have been utilized on the identical specimen for comparison. The macroscopic 'stress-free' lattice spacing (d{sub o}) was also obtained from both using a 2-mm width comb-like coupon. The results showmore » significant changes in residual stresses from tension (300-400 MPa) to compression (-600 MPa) through the thickness of the dissimilar weld overlay pipe specimen.« less

Investigating the Defect Structures in Transparent Conducting Oxides Using X-ray and Neutron Scattering Techniques

PubMed Central

González, Gabriela B.

2012-01-01

Transparent conducting oxide (TCO) materials are implemented into a wide variety of commercial devices because they possess a unique combination of high optical transparency and high electrical conductivity. Created during the processing of the TCOs, defects within the atomic-scale structure are responsible for their desirable optical and electrical properties. Therefore, studying the defect structure is essential to a better understanding of the behavior of transparent conductors. X-ray and neutron scattering techniques are powerful tools to investigate the atomic lattice structural defects in these materials. This review paper presents some of the current developments in the study of structural defects in n-type TCOs using x-ray diffraction (XRD), neutron diffraction, extended x-ray absorption fine structure (EXAFS), pair distribution functions (PDFs), and x-ray fluorescence (XRF). PMID:28817010

Optimizing disk registration algorithms for nanobeam electron diffraction strain mapping

DOE PAGES

Pekin, Thomas C.; Gammer, Christoph; Ciston, Jim; ...

2017-01-28

Scanning nanobeam electron diffraction strain mapping is a technique by which the positions of diffracted disks sampled at the nanoscale over a crystalline sample can be used to reconstruct a strain map over a large area. However, it is important that the disk positions are measured accurately, as their positions relative to a reference are directly used to calculate strain. Here in this study, we compare several correlation methods using both simulated and experimental data in order to directly probe susceptibility to measurement error due to non-uniform diffracted disk illumination structure. We found that prefiltering the diffraction patterns with amore » Sobel filter before performing cross correlation or performing a square-root magnitude weighted phase correlation returned the best results when inner disk structure was present. Lastly, we have tested these methods both on simulated datasets, and experimental data from unstrained silicon as well as a twin grain boundary in 304 stainless steel.« less

Calculation of Debye-Scherrer diffraction patterns from highly stressed polycrystalline materials

DOE PAGES

MacDonald, M. J.; Vorberger, J.; Gamboa, E. J.; ...

2016-06-07

Calculations of Debye-Scherrer diffraction patterns from polycrystalline materials have typically been done in the limit of small deviatoric stresses. Although these methods are well suited for experiments conducted near hydrostatic conditions, more robust models are required to diagnose the large strain anisotropies present in dynamic compression experiments. A method to predict Debye-Scherrer diffraction patterns for arbitrary strains has been presented in the Voigt (iso-strain) limit. Here, we present a method to calculate Debye-Scherrer diffraction patterns from highly stressed polycrystalline samples in the Reuss (iso-stress) limit. This analysis uses elastic constants to calculate lattice strains for all initial crystallite orientations, enablingmore » elastic anisotropy and sample texture effects to be modeled directly. Furthermore, the effects of probing geometry, deviatoric stresses, and sample texture are demonstrated and compared to Voigt limit predictions. An example of shock-compressed polycrystalline diamond is presented to illustrate how this model can be applied and demonstrates the importance of including material strength when interpreting diffraction in dynamic compression experiments.« less

Monochromatic neutron beam production at Brazilian nuclear research reactors

NASA Astrophysics Data System (ADS)

Stasiulevicius, Roberto; Rodrigues, Claudio; Parente, Carlos B. R.; Voi, Dante L.; Rogers, John D.

2000-12-01

Monochomatic beams of neutrons are obtained form a nuclear reactor polychromatic beam by the diffraction process, suing a single crystal energy selector. In Brazil, two nuclear research reactors, the swimming pool model IEA-R1 and the Argonaut type IEN-R1 have been used to carry out measurements with this technique. Neutron spectra have been measured using crystal spectrometers installed on the main beam lines of each reactor. The performance of conventional- artificial and natural selected crystals has been verified by the multipurpose neutron diffractometers installed at IEA-R1 and simple crystal spectrometer in operator at IEN- R1. A practical figure of merit formula was introduced to evaluate the performance and relative reflectivity of the selected planes of a single crystal. The total of 16 natural crystals were selected for use in the neutron monochromator, including a total of 24 families of planes. Twelve of these natural crystal types and respective best family of planes were measured directly with the multipurpose neutron diffractometers. The neutron spectrometer installed at IEN- R1 was used to confirm test results of the better specimens. The usually conventional-artificial crystal spacing distance range is limited to 3.4 angstrom. The interplane distance range has now been increased to approximately 10 angstrom by use of naturally occurring crystals. The neutron diffraction technique with conventional and natural crystals for energy selection and filtering can be utilized to obtain monochromatic sub and thermal neutrons with energies in the range of 0.001 to 10 eV. The thermal neutron is considered a good tool or probe for general applications in various fields, such as condensed matter, chemistry, biology, industrial applications and others.

Neutron Scattering Studies on Large Length Scale Sample Structures

NASA Astrophysics Data System (ADS)

Feng, Hao

Neutron scattering can be used to study structures of matter. Depending on the interested sample properties, different scattering techniques can be chosen. Neutron reflectivity is more often used to detect in-depth profile of layered structures and the interfacial roughness while transmission is more sensitive to sample bulk properties. Neutron Reflectometry (NR) technique, one technique in neutron reflectivity, is first discussed in this thesis. Both specular reflectivity and the first order Bragg intensity were measured in the NR experiment with a diffraction grating in order to study the in-depth and the lateral structure of a sample (polymer) deposited on the grating. However, the first order Bragg intensity solely is sometimes inadequate to determine the lateral structure and high order Bragg intensities are difficult to measure using traditional neutron scattering techniques due to the low brightness of the current neutron sources. Spin Echo Small Angle Neutron Scattering (SESANS) technique overcomes this resolution problem by measuring the Fourier transforms of all the Bragg intensities, resulting in measuring the real-space density correlations of samples and allowing the accessible length scale from few-tens of nanometers to several microns. SESANS can be implemented by using two pairs of magnetic Wollaston prims (WP) and the accessible length scale is proportional to the magnetic field intensity in WPs. To increase the magnetic field and thus increase the accessible length scale, an apparatus named Superconducting Wollaston Prisms (SWP) which has a series of strong, well-defined shaped magnetic fields created by superconducting coils was developed in Indiana University in 2016. Since then, various kinds of optimization have been implemented, which are addressed in this thesis. Finally, applications of SWPs in other neutron scattering techniques like Neutron Larmor Diffraction (NLD) are discussed.

Rheology, microstructure and crystallographic preferred orientation of matrix containing a dispersed second phase: Insight from experimentally deformed ice

NASA Astrophysics Data System (ADS)

Cyprych, Daria; Piazolo, Sandra; Wilson, Christopher J. L.; Luzin, Vladimir; Prior, David J.

2016-09-01

We utilize in situ neutron diffraction to continuously track the average grain size and crystal preferred orientation (CPO) development in ice, during uniaxial compression of two-phase and pure ice samples. Two-phase samples are composed of ice matrix and 20 vol.% of second phases of two types: (1) rheologically soft, platy graphite, and (2) rigid, rhomb-shaped calcite. The samples were tested at 10 °C below the ice melting point, ambient pressures, and two strain rates (1 ×10-5 and 2.5 ×10-6 s-1), to 10 and 20% strain. The final CPO in the ice matrix, where second phases are present, is significantly weaker, and ice grain size is smaller than in an ice-only sample. The microstructural and rheological data point to dislocation creep as the dominant deformation regime. The evolution and final strength of the CPO in ice depend on the efficiency of the recrystallization processes, namely grain boundary migration and nucleation. These processes are markedly influenced by the strength, shape, and grain size of the second phase. In addition, CPO development in ice is further accentuated by strain partitioning into the soft second phase, and the transfer of stress onto the rigid second phase.

Compositional Tuning, Crystal Growth, and Magnetic Properties of Iron Phosphate Oxide

NASA Astrophysics Data System (ADS)

Tarne, Michael

Iron phosphate oxide, Fe3PO4O 3, is a crystalline solid featuring magnetic Fe3+ ions on a complex lattice composed of closely-spaced triangles. Previous work from our research group on this compound has proposed a helical magnetic structure below T = 163 K attributed to J1 - J2 competing interactions between nearest-neighbor and next-nearest-neighbor iron atoms. This was based on neutron powder diffraction featuring unique broad, flat-topped magnetic reflections due to needle-like magnetic domains. In order to confirm the magnetic structure and origins of frustration, this thesis will expand upon the research focused on this compound. The first chapter focuses on single crystal growth of Fe3PO 4O3. While neutron powder diffraction provides insight to the magnetic structure, powder and domain averaging obfuscate a conclusive structure for Fe3PO4O3 and single crystal neutron scattering is necessary. Due to the incongruency of melting, single crystal growth has proven challenging. A number of techniques including flux growth, slow cooling, and optical floating zone growth were attempted and success has been achieved via heterogenous chemical vapor transport from FePO 4 using ZrCl4 as a transport agent. These crystals are of sufficient size for single crystal measurements on modern neutron diffractometers. Dilution of the magnetic sublattice in frustrated magnets can also provide insight into the nature of competing spin interactions. Dilution of the Fe 3+ lattice in Fe3PO4O3 is accomplished by substituting non-magnetic Ga3+ to form the solid solution series Fe3-xGaxPO4O3 with x = 0, 0.012, 0.06, 0.25, 0.5, 1.0, 1.5. The magnetic susceptibility and neutron powder diffraction data of these compounds are presented. A dramatic decrease of the both the helical pitch length and the domain size is observed with increasing x; for x > 0.5, the compounds lack long range magnetic order. The phases that do exhibit magnetic order show a decrease in helical pitch with increasing x as determined from the magnitude of the magnetic propagation vector. This trend can be qualitatively reproduced by increasing the ratio of J2/ J1 in the Heisenberg model. Intriguingly, the domain size extracted from peak broadening of the magnetic reflections is nearly equal to the pitch length for each value of x, which suggests that the two qualities are linked in this unusual antiferromagnet. The last chapter focuses on the oxyfluoride Fe3PO7-x Fx. Through fluorination using low-temperature chimie douce reactions with polytetrafluoroethylene, the magnetic properties show changes in the magnetic susceptibility, isothermal magnetization, and neutron powder diffraction. The magnetic susceptibility shows a peak near T = 13 K and a zero field cooled/field cooled splitting at T = 78 K. The broad, flat-topped magnetic reflections in the powder neutron diffraction exhibit a decrease in width and increase in intensity. The changes in the neutron powder diffraction suggest an increase in correlation length in the ab plane of the fluorinated compound. Iron phosphate oxide is a unique lattice showing a rich magnetic phase diagram in both the gallium-substituted and fluorinated species. While mean-field interactions are sufficient to describe interactions in the solid solution series Fe3-xGaxPO4O3, the additional magnetic transitions in Fe3PO7-xFx suggest a more complicated set of interactions.

Evaluation of Residual Stress Measurements Before and After Post-Weld Heat Treatment in the Weld Repairs

NASA Astrophysics Data System (ADS)

Pardowska, Anna M.; Price, John W. H.; Finlayson, Trevor R.; Ibrahim, R.

2010-11-01

Welding repairs are increasingly a structural integrity concern for aging pressure vessel and piping components. It has been demonstrated that the residual stress distribution near repair welds can be drastically different from that of the original weld. Residual stresses have a significant effect on the lifetime performance of a weld, and a reduction of these stresses is normally desirable. The aim of this paper is to investigate residual stresses in various weld repair arrangements using the non-destructive neutron diffraction technique. This research is focused on characterization of the residual stress distribution: (i) in the original weld; (ii) in a shallow toe weld repair; and (iii) after conventional post-weld heat treatment. The focus of the measurements is on the values of the subsurface strain/stress variations across the weld.

Effect of electrical and mechanical poling history on domain orientation and piezoelectric properties of soft and hard PZT ceramics

NASA Astrophysics Data System (ADS)

Marsilius, Mie; Granzow, Torsten; Jones, Jacob L.

2011-02-01

The superior piezoelectric properties of all polycrystalline ferroelectrics are based on the extent of non-180° domain wall motion under electrical and mechanical poling loads. To distinguish between 180° and non-180° domain wall motion in a soft-doped and a hard-doped lead zirconate titanate (PZT) ceramic, domain texture measurements were performed using x-ray and neutron diffraction after different loading procedures. Comparing the results to measurements of the remanent strain and piezoelectric coefficient allowed the differentiation between different microstructural contributions to the macroscopic parameters. Both types of ceramic showed similar behavior under electric field, but the hard-doped material was more susceptible to mechanical load. A considerable fraction of the piezoelectric coefficient originated from poling by the preferred orientation of 180° domains.

Characterization of the new neutron imaging and materials science facility IMAT

NASA Astrophysics Data System (ADS)

Minniti, Triestino; Watanabe, Kenichi; Burca, Genoveva; Pooley, Daniel E.; Kockelmann, Winfried

2018-04-01

IMAT is a new cold neutron imaging and diffraction instrument located at the second target station of the pulsed neutron spallation source ISIS, UK. A broad range of materials science and materials testing areas will be covered by IMAT. We present the characterization of the imaging part, including the energy-selective and energy-dispersive imaging options, and provide the basic parameters of the radiography and tomography instrument. In particular, detailed studies on mono and bi-dimensional neutron beam flux profiles, neutron flux as a function of the neutron wavelength, spatial and energy dependent neutron beam uniformities, guide artifacts, divergence and spatial resolution, and neutron pulse widths are provided. An accurate characterization of the neutron beam at the sample position, located 56 m from the source, is required to optimize collection of radiographic and tomographic data sets and for performing energy-dispersive neutron imaging via time-of-flight methods in particular.

Beyond the structure-property relationship paradigm: influence of the crystal structure and microstructure on the Li+ conductivity of La2/3Li(x)Ti(1-x)Al(x)O3 Oxides.

PubMed

García-Martín, Susana; Morata-Orrantía, Ainhoa; Alario-Franco, Miguel A; Rodríguez-Carvajal, Juan; Amador, Ulises

2007-01-01

The crystal structures of several oxides of the La(2/3)Li(x)Ti(1-x)Al(x)O(3) system have been studied by selected-area electron diffraction, high-resolution transmission electron microscopy, and powder neutron diffraction, and their lithium conductivity has been by complex impedance spectroscopy. The compounds have a perovskite-related structure with a unit cell radical2 a(p)x2 a(p)x radical2 a(p) (a(p)=perovskite lattice parameter) due to the tilting of the (Ti/Al)O(6) octahedra and the ordering of lanthanum and lithium ions and vacancies along the 2 a(p) axis. The Li(+) ions present a distorted square-planar coordination and are located in interstitial positions of the structure, which could explain the very high ionic conductivity of this type of material. The lithium conductivity depends on the oxide composition and its crystal microstructure, which varies with the thermal treatment of the sample. The microstructure of these titanates is complex due to formation of domains of ordering and other defects such as strains and compositional fluctuations.

Neutron diffraction as a tool to monitor the establishment of the electro-osmotic flux during realkalisation of carbonated concrete

NASA Astrophysics Data System (ADS)

Castellote, Marta; Llorente, I.; Andrade, Carmen; Turrillas, X.; Alonso, Cruz; Campo, Javier

2006-11-01

Realkalisation is an electrochemical technique for repairing concrete structures damaged by rebar corrosion due to carbonation. The treatment aims at restoring alkalinity of the concrete by application of a continuous current between the rebar, acting as a cathode, and an external auxiliary electrode placed in a carbonate solution and connected to a positive pole of a power supply. Here we report the application of neutron diffraction in the in situ monitoring of a realkalisation treatment, analysing at the same time the development of the electro-osmotic flux and the microstructural variations in the surroundings of the rebar.

Instrument and method for focusing x rays, gamma rays, and neutrons

DOEpatents

Smither, R.K.

1981-04-20

A crystal diffraction instrument is described which has an improved crystalline structure having a face for receiving a beam of photons or neutrons and diffraction planar spacing along that face with the spacing increasing progressively along the face to provide a decreasing Bragg angle and thereby increasing the usable area and acceptance angle. The increased planar spacing is provided by the use of a temperature differential across the crystalline structure, by assembling a plurality of crystalline structure with different compositions, by an individual crystalline structure with a varying composition and thereby a changing planar spacing along its face, and by combinations of these techniques.

NEUTRON DIFFRACTION INVESTIGATIONS OF FERROMAGNETIC PALLADIUM AND IRON GROUP ALLOYS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cable, J.W.; Wollan, E.O.; Koehler, W.C.

1962-03-01

In order to account for the magnetic properties of alloys It becomes important to determine the individual magnetic moments of the constituent atoms. This determination can be accomplished by means of neutron diffraction and magnetic induction measurements. Such measurements are made on the ferromagnetic alloys Pd/sub 3/Fe, PdFe, Pd/sub 3/Co, PdCo, Ni/sub 3/Co, and NiCo. The average moment values are obtained from magnetic induction measurements while the differences in the atomic moments are determined from either the ferromagnetic diffuse scattering by the disordered alloys or the superlattice reflections by the ordered alloys. (auth)

Change in the magnetic structure of (Bi,Sm)FeO3 thin films at the morphotropic phase boundary probed by neutron diffraction

NASA Astrophysics Data System (ADS)

Maruyama, Shingo; Anbusathaiah, Varatharajan; Fennell, Amy; Enderle, Mechthild; Takeuchi, Ichiro; Ratcliff, William D.

2014-11-01

We report on the evolution of the magnetic structure of BiFeO3 thin films grown on SrTiO3 substrates as a function of Sm doping. We determined the magnetic structure using neutron diffraction. We found that as Sm increases, the magnetic structure evolves from a cycloid to a G-type antiferromagnet at the morphotropic phase boundary, where there is a large piezoelectric response due to an electric-field induced structural transition. The occurrence of the magnetic structural transition at the morphotropic phase boundary offers another route towards room temperature multiferroic devices.

Neutron powder diffraction study on the iron-based nitride superconductor ThFeAsN

NASA Astrophysics Data System (ADS)

Mao, Huican; Wang, Cao; Maynard-Casely, Helen E.; Huang, Qingzhen; Wang, Zhicheng; Cao, Guanghan; Li, Shiliang; Luo, Huiqian

2017-03-01

We report neutron diffraction and transport results on the newly discovered superconducting nitride ThFeAsN with T_c= 30 \\text{K} . No magnetic transition, but a weak structural distortion around 160 K, is observed by cooling from 300 K to 6 K. Analysis on the resistivity, Hall transport and crystal structure suggests that this material behaves as an electron optimally doped pnictide superconductor due to extra electrons from nitrogen deficiency or oxygen occupancy at the nitrogen site, which, together with the low arsenic height, may enhance the electron itinerancy and reduce the electron correlations, thus suppressing the static magnetic order.

Magnetic structure of Ho0.5Y0.5Mn6Sn6 compound studied by powder neutron diffraction

NASA Astrophysics Data System (ADS)

Li, X.-Y.; Peng, L.-C.; He, L.-H.; Zhang, S.-Y.; Yao, J.-L.; Zhang, Y.; Wang, F.-W.

2018-05-01

The crystallographic and magnetic structures of the HfFe6Ge6-type compound Ho0.5Y0.5Mn6Sn6 have been studied by powder neutron diffraction and in-situ Lorentz transmission electron microscopy. Besides the nonlinear thermal expansion of lattice parameters, an incommensurate conical spiral magnetic structure was determined in the temperature interval of 2-340 K. A spin reorientation transition has been observed from 50 to 300 K, where the alignment of the c-axis component of magnetic moments of the Ho sublattice and the Mn sublattice transfers from ferrimagnetic to ferromagnetic.

Residual stress characterization of steel TIG welds by neutron diffraction and by residual magnetic stray field mappings

NASA Astrophysics Data System (ADS)

Stegemann, Robert; Cabeza, Sandra; Lyamkin, Viktor; Bruno, Giovanni; Pittner, Andreas; Wimpory, Robert; Boin, Mirko; Kreutzbruck, Marc

2017-03-01

The residual stress distribution of tungsten inert gas welded S235JRC+C plates was determined by means of neutron diffraction (ND). Large longitudinal residual stresses with maxima around 600 MPa were found. With these results as reference, the evaluation of residual stress with high spatial resolution GMR (giant magneto resistance) sensors was discussed. The experiments performed indicate a correlation between changes in residual stresses (ND) and the normal component of local residual magnetic stray fields (GMR). Spatial variations in the magnetic field strength perpendicular to the welds are in the order of the magnetic field of the earth.

Spin-liquid ground state in the frustrated J 1 - J 2 zigzag chain system BaTb 2 O 4

DOE PAGES

Aczel, A. A.; Li, L.; Garlea, V. O.; ...

2015-07-13

We have investigated polycrystalline samples of the zigzag chain system BaTb 2O 4 with magnetic susceptibility, heat capacity, neutron powder diffraction, and muon spin relaxation measurements. No magnetic transitions are observed in the bulk measurements, while neutron diffraction reveals low-temperature, short-range, intrachain magnetic correlations between Tb 3+ ions. Muon spin relaxation measurements indicate that these correlations are dynamic, as the technique detects no signatures of static magnetism down to 0.095 K. Altogether these findings provide strong evidence for a spin liquid ground state in BaTb 2O 4.

Neutron diffraction study of water freezing on aircraft engine combustor soot.

PubMed

Tishkova, V; Demirdjian, B; Ferry, D; Johnson, M

2011-12-14

The study of the formation of condensation trails and cirrus clouds on aircraft emitted soot particles is important because of its possible effects on climate. In the present work we studied the freezing of water on aircraft engine combustor (AEC) soot particles under conditions of pressure and temperature similar to the upper troposphere. The microstructure of the AEC soot was found to be heterogeneous containing both primary particles of soot and metallic impurities (Fe, Cu, and Al). We also observed various surface functional groups such as oxygen-containing groups, including sulfate ions, that can act as active sites for water adsorption. Here we studied the formation of ice on the AEC soot particles by using neutron diffraction. We found that for low amount of adsorbed water, cooling even up to 215 K did not lead to the formation of hexagonal ice. Whereas, larger amount of adsorbed water led to the coexistence of liquid water (or amorphous ice) and hexagonal ice (I(h)); 60% of the adsorbed water was in the form of ice I(h) at 255 K. Annealing of the system led to the improvement of the crystal quality of hexagonal ice crystals as demonstrated from neutron diffraction.

Neutron diffraction and electrical transport studies on magnetic ordering in terbium at high pressures and low temperatures

DOE PAGES

Thomas, Sarah A.; Montgomery, Jeffrey M.; Tsoi, Georgiy M.; ...

2013-06-11

Neutron diffraction and electrical transport measurements have been carried out on the heavy rare earth metal terbium at high pressures and low temperatures in order to elucidate the onset of ferromagnetic order as a function of pressure. The electrical resistance measurements show a change in slope as the temperature is lowered through the ferromagnetic Curie temperature. The temperature of this ferromagnetic transition decreases from approximately 240 K at ambient pressure at a rate of –16.7 K/GPa up to a pressure of 3.6 GPa, at which point the onset of ferromagnetic order is suppressed. Neutron diffraction measurements as a function ofmore » pressure at temperatures ranging from 90 K to 290 K confirm that the change of slope in the resistance is associated with the ferromagnetic ordering, since this occurs at pressures similar to those determined from the resistance results at these temperatures. Furthermore, a change in ferromagnetic ordering as the pressure is increased above 3.6 GPa is correlated with the phase transition from the ambient hexagonal close packed (hcp) structure to an α-Sm type structure at high pressures.« less

A study of stress-induced phase transformation and micromechanical behavior of CuZr-based alloy by in-situ neutron diffraction

DOE PAGES

Wang, Dongmei; Mu, Juan; Chen, Yan; ...

2017-03-01

The stress-induced phase transformation and micromechanical behavior of CuZr-based alloy were investigated by in-situ neutron diffraction. The pseudoelastic behavior with a pronounced strain-hardening effect is observed. The retained martensite nuclei and the residual stress obtained from the 1st cycle reduce the stress threshold for the martensitic transformation. A critical stress level is required for the reverse martensitic transformation from martensite to B2 phase. An increase of intensity for the B2 (110) plane in the 1st cycle is caused by the twinning along the {112}<111> twinning system. The convoluted stress partitioning influenced by the elastic and transformation anisotropy along with themore » newly formed martensite determines the microstress partitioning of the studied CuZr-based alloy. The reversible martensitic transformation is responsible for the pseudoelasticity. The macro mechanical behavior of the pure B2 phase can be divided into 3 stages, which are mediated by the evolvement of the martensitic transformation. This manuscript has been authored by UT-Battelle, LLC under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy.gov/downloads/doe-public-access-plan).« less

A study of stress-induced phase transformation and micromechanical behavior of CuZr-based alloy by in-situ neutron diffraction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Dongmei; Mu, Juan; Chen, Yan

The stress-induced phase transformation and micromechanical behavior of CuZr-based alloy were investigated by in-situ neutron diffraction. The pseudoelastic behavior with a pronounced strain-hardening effect is observed. The retained martensite nuclei and the residual stress obtained from the 1st cycle reduce the stress threshold for the martensitic transformation. A critical stress level is required for the reverse martensitic transformation from martensite to B2 phase. An increase of intensity for the B2 (110) plane in the 1st cycle is caused by the twinning along the {112}<111> twinning system. The convoluted stress partitioning influenced by the elastic and transformation anisotropy along with themore » newly formed martensite determines the microstress partitioning of the studied CuZr-based alloy. The reversible martensitic transformation is responsible for the pseudoelasticity. The macro mechanical behavior of the pure B2 phase can be divided into 3 stages, which are mediated by the evolvement of the martensitic transformation. This manuscript has been authored by UT-Battelle, LLC under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy.gov/downloads/doe-public-access-plan).« less

Anisotropic deformation of extruded magnesium alloy AZ31 under uniaxial compression: A study with simultaneous in situ synchrotron x-ray imaging and diffraction

DOE PAGES

Lu, L.; Huang, J. W.; Fan, D.; ...

2016-08-29

In situ synchrotron x-ray imaging and diffraction are used to investigate anisotropic deformation of an extruded magnesium alloy AZ31 under uniaxial compression along two different directions, with the loading axis (LA) either parallel or perpendicular to the extrusion direction (ED), referred to as LA∥ED and LAED, respectively. Multiscale measurements including stress–strain curves (macroscale), x-ray digital image correlation (mesoscale), and diffraction (microscale) are obtained simultaneously. Electron backscatter diffraction is performed on samples collected at various strains to characterize deformation twins. The rapid increase in strain hardening rate for the LA∥ED loading is attributed to marked {101¯2} extension twinning and subsequent homogenizationmore » of deformation, while dislocation motion leads to inhomogeneous deformation and a decrease in strain hardening rate.« less

Extracting grain-orientation-dependent data from in situ time-of-flight neutron diffraction. I. Inverse pole figures

DOE PAGES

Stoica, Grigoreta M.; Stoica, Alexandru Dan; An, Ke; ...

2014-11-28

The problem of calculating the inverse pole figure (IPF) is analyzed from the perspective of the application of time-of flight neutron diffraction toin situmonitoring of the thermomechanical behavior of engineering materials. On the basis of a quasi-Monte Carlo (QMC) method, a consistent set of grain orientations is generated and used to compute the weighting factors for IPF normalization. The weighting factors are instrument dependent and were calculated for the engineering materials diffractometer VULCAN (Spallation Neutron Source, Oak Ridge National Laboratory). The QMC method is applied to face-centered cubic structures and can be easily extended to other crystallographic symmetries. Examples includemore » 316LN stainless steelin situloaded in tension at room temperature and an Al–2%Mg alloy, substantially deformed by cold rolling and in situannealed up to 653 K.« less

SMA texture and reorientation: simulations and neutron diffraction studies

NASA Astrophysics Data System (ADS)

Gao, Xiujie; Brown, Donald W.; Brinson, L. Catherine

2005-05-01

With increased usage of shape memory alloys (SMA) for applications in various fields, it is important to understand how the material behavior is affected by factors such as texture, stress state and loading history, especially for complex multiaxial loading states. Using the in-situ neutron diffraction loading facility (SMARTS diffractometer) and ex situ inverse pole figure measurement facility (HIPPO diffractometer) at the Los Alamos Neutron Science Center (LANCE), the macroscopic mechanical behavior and texture evolution of Nickel-Titanium (Nitinol) SMAs under sequential compression in alternating directions were studied. The simplified multivariant model developed at Northwestern University was then used to simulate the macroscopic behavior and the microstructural change of Nitinol under this sequential loading. Pole figures were obtained via post-processing of the multivariant results for volume fraction evolution and compared quantitatively well to the experimental results. The experimental results can also be used to test or verify other SMA constitutive models.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Feng, Hao; Ashkar, Rana; Steinke, Nina

A method dubbed grating-based holography was recently used to determine the structure of colloidal fluids in the rectangular grooves of a diffraction grating from X-ray scattering measurements. Similar grating-based measurements have also been recently made with neutrons using a technique called spin-echo small-angle neutron scattering. The analysis of the X-ray diffraction data was done using an approximation that treats the X-ray phase change caused by the colloidal structure as a small perturbation to the overall phase pattern generated by the grating. In this paper, the adequacy of this weak phase approximation is explored for both X-ray and neutron grating holography.more » Additionally, it is found that there are several approximations hidden within the weak phase approximation that can lead to incorrect conclusions from experiments. In particular, the phase contrast for the empty grating is a critical parameter. Finally, while the approximation is found to be perfectly adequate for X-ray grating holography experiments performed to date, it cannot be applied to similar neutron experiments because the latter technique requires much deeper grating channels.« less

Neutron diffraction of acetazolamide-bound human carbonic anhydrase II reveals atomic details of drug binding

PubMed Central

Fisher, S. Zoë; Aggarwal, Mayank; Kovalevsky, Andrey Y.; Silverman, David N.; McKenna, Robert

2012-01-01

Carbonic anhydrases (CAs) catalyze the hydration of CO2 forming HCO3− and a proton, an important reaction for many physiological processes including respiration, fluid secretion, and pH regulation. As such, CA isoforms are prominent clinical targets for treating various diseases. The clinically used acetazolamide (AZM) is a sulfonamide that binds with high affinity to human CA isoform II (HCA II). There are several X-ray structures available of AZM bound to various CA isoforms, but these complexes do not show the charged state of AZM, or hydrogen (H) atom positions of the protein and solvent. Neutron diffraction is a useful technique for directly observing H atoms and the mapping of H-bonding networks that can greatly contribute to rational drug design. To this end the neutron structure of H/D exchanged HCA II crystals in complex with AZM was determined. The structure reveals the molecular details of AZM binding and the charged state of the bound drug. This represents the first determined neutron structure of a clinically used drug bound to its target. PMID:22928733

First spin-resolved electron distributions in crystals from combined polarized neutron and X-ray diffraction experiments.

PubMed

Deutsch, Maxime; Gillon, Béatrice; Claiser, Nicolas; Gillet, Jean-Michel; Lecomte, Claude; Souhassou, Mohamed

2014-05-01

Since the 1980s it has been possible to probe crystallized matter, thanks to X-ray or neutron scattering techniques, to obtain an accurate charge density or spin distribution at the atomic scale. Despite the description of the same physical quantity (electron density) and tremendous development of sources, detectors, data treatment software etc., these different techniques evolved separately with one model per experiment. However, a breakthrough was recently made by the development of a common model in order to combine information coming from all these different experiments. Here we report the first experimental determination of spin-resolved electron density obtained by a combined treatment of X-ray, neutron and polarized neutron diffraction data. These experimental spin up and spin down densities compare very well with density functional theory (DFT) calculations and also confirm a theoretical prediction made in 1985 which claims that majority spin electrons should have a more contracted distribution around the nucleus than minority spin electrons. Topological analysis of the resulting experimental spin-resolved electron density is also briefly discussed.

The structure of liquid water by polarized neutron diffraction and reverse Monte Carlo modelling.

PubMed

Temleitner, László; Pusztai, László; Schweika, Werner

2007-08-22

The coherent static structure factor of water has been investigated by polarized neutron diffraction. Polarization analysis allows us to separate the huge incoherent scattering background from hydrogen and to obtain high quality data of the coherent scattering from four different mixtures of liquid H(2)O and D(2)O. The information obtained by the variation of the scattering contrast confines the configurational space of water and is used by the reverse Monte Carlo technique to model the total structure factors. Structural characteristics have been calculated directly from the resulting sets of particle coordinates. Consistency with existing partial pair correlation functions, derived without the application of polarized neutrons, was checked by incorporating them into our reverse Monte Carlo calculations. We also performed Monte Carlo simulations of a hard sphere system, which provides an accurate estimate of the information content of the measured data. It is shown that the present combination of polarized neutron scattering and reverse Monte Carlo structural modelling is a promising approach towards a detailed understanding of the microscopic structure of water.

Electrostatic levitation facility optimized for neutron diffraction studies of high temperature liquids at a spallation neutron source

DOE PAGES

Mauro, N. A.; Vogt, A. J.; Derendorf, K. S.; ...

2016-01-01

Neutron diffraction studies of metallic liquids provide valuable information about inherent topological and chemical ordering on multiple length scales as well as insight into dynamical processes at the level of a few atoms. But, there exist very few facilities in the world that allow such studies to be made of reactive metallic liquids in a containerless environment, and these are designed for use at reactor-based neutron sources. We present an electrostatic levitation facility, NESL (for Neutron ElectroStatic Levitator), which takes advantage of the enhanced capabilities and increased neutron flux available at spallation neutron sources (SNSs). NESL enables high quality elasticmore » and inelastic neutron scattering experiments to be made of reactive metallic and other liquids in the equilibrium and supercooled temperature regime. The apparatus is comprised of a high vacuum chamber, external and internal neutron collimation optics, and a sample exchange mechanism that allows up to 30 samples to be processed between chamber openings. Two heating lasers allow excellent sample temperature homogeneity, even for samples approaching 500 mg, and an automated temperature control system allows isothermal measurements to be conducted for times approaching 2 h in the liquid state, with variations in the average sample temperature of less than 0.5%. Furthermore, to demonstrate the capabilities of the facility for elastic scattering studies of liquids, a high quality total structure factor for Zr 64Ni 36 measured slightly above the liquidus temperature is presented from experiments conducted on the nanoscale-ordered materials diffractometer (NOMAD) beam line at the SNS after only 30 min of acquisition time for a small sample ( 100 mg).« less

Electrostatic levitation facility optimized for neutron diffraction studies of high temperature liquids at a spallation neutron source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mauro, N. A., E-mail: namauro@noctrl.edu; Vogt, A. J.; Derendorf, K. S.

2016-01-15

Neutron diffraction studies of metallic liquids provide valuable information about inherent topological and chemical ordering on multiple length scales as well as insight into dynamical processes at the level of a few atoms. However, there exist very few facilities in the world that allow such studies to be made of reactive metallic liquids in a containerless environment, and these are designed for use at reactor-based neutron sources. We present an electrostatic levitation facility, NESL (for Neutron ElectroStatic Levitator), which takes advantage of the enhanced capabilities and increased neutron flux available at spallation neutron sources (SNSs). NESL enables high quality elasticmore » and inelastic neutron scattering experiments to be made of reactive metallic and other liquids in the equilibrium and supercooled temperature regime. The apparatus is comprised of a high vacuum chamber, external and internal neutron collimation optics, and a sample exchange mechanism that allows up to 30 samples to be processed between chamber openings. Two heating lasers allow excellent sample temperature homogeneity, even for samples approaching 500 mg, and an automated temperature control system allows isothermal measurements to be conducted for times approaching 2 h in the liquid state, with variations in the average sample temperature of less than 0.5%. To demonstrate the capabilities of the facility for elastic scattering studies of liquids, a high quality total structure factor for Zr{sub 64}Ni{sub 36} measured slightly above the liquidus temperature is presented from experiments conducted on the nanoscale-ordered materials diffractometer (NOMAD) beam line at the SNS after only 30 min of acquisition time for a small sample (∼100 mg)« less

Real-time observations of lithium battery reactions-operando neutron diffraction analysis during practical operation.

PubMed

Taminato, Sou; Yonemura, Masao; Shiotani, Shinya; Kamiyama, Takashi; Torii, Shuki; Nagao, Miki; Ishikawa, Yoshihisa; Mori, Kazuhiro; Fukunaga, Toshiharu; Onodera, Yohei; Naka, Takahiro; Morishima, Makoto; Ukyo, Yoshio; Adipranoto, Dyah Sulistyanintyas; Arai, Hajime; Uchimoto, Yoshiharu; Ogumi, Zempachi; Suzuki, Kota; Hirayama, Masaaki; Kanno, Ryoji

2016-06-30

Among the energy storage devices for applications in electric vehicles and stationary uses, lithium batteries typically deliver high performance. However, there is still a missing link between the engineering developments for large-scale batteries and the fundamental science of each battery component. Elucidating reaction mechanisms under practical operation is crucial for future battery technology. Here, we report an operando diffraction technique that uses high-intensity neutrons to detect reactions in non-equilibrium states driven by high-current operation in commercial 18650 cells. The experimental system comprising a time-of-flight diffractometer with automated Rietveld analysis was developed to collect and analyse diffraction data produced by sequential charge and discharge processes. Furthermore, observations under high current drain revealed inhomogeneous reactions, a structural relaxation after discharge, and a shift in the lithium concentration ranges with cycling in the electrode matrix. The technique provides valuable information required for the development of advanced batteries.

Real-time observations of lithium battery reactions—operando neutron diffraction analysis during practical operation

PubMed Central

Taminato, Sou; Yonemura, Masao; Shiotani, Shinya; Kamiyama, Takashi; Torii, Shuki; Nagao, Miki; Ishikawa, Yoshihisa; Mori, Kazuhiro; Fukunaga, Toshiharu; Onodera, Yohei; Naka, Takahiro; Morishima, Makoto; Ukyo, Yoshio; Adipranoto, Dyah Sulistyanintyas; Arai, Hajime; Uchimoto, Yoshiharu; Ogumi, Zempachi; Suzuki, Kota; Hirayama, Masaaki; Kanno, Ryoji

2016-01-01

Among the energy storage devices for applications in electric vehicles and stationary uses, lithium batteries typically deliver high performance. However, there is still a missing link between the engineering developments for large-scale batteries and the fundamental science of each battery component. Elucidating reaction mechanisms under practical operation is crucial for future battery technology. Here, we report an operando diffraction technique that uses high-intensity neutrons to detect reactions in non-equilibrium states driven by high-current operation in commercial 18650 cells. The experimental system comprising a time-of-flight diffractometer with automated Rietveld analysis was developed to collect and analyse diffraction data produced by sequential charge and discharge processes. Furthermore, observations under high current drain revealed inhomogeneous reactions, a structural relaxation after discharge, and a shift in the lithium concentration ranges with cycling in the electrode matrix. The technique provides valuable information required for the development of advanced batteries. PMID:27357605

Experimental determination of spin-dependent electron density by joint refinement of X-ray and polarized neutron diffraction data.

PubMed

Deutsch, Maxime; Claiser, Nicolas; Pillet, Sébastien; Chumakov, Yurii; Becker, Pierre; Gillet, Jean Michel; Gillon, Béatrice; Lecomte, Claude; Souhassou, Mohamed

2012-11-01

New crystallographic tools were developed to access a more precise description of the spin-dependent electron density of magnetic crystals. The method combines experimental information coming from high-resolution X-ray diffraction (XRD) and polarized neutron diffraction (PND) in a unified model. A new algorithm that allows for a simultaneous refinement of the charge- and spin-density parameters against XRD and PND data is described. The resulting software MOLLYNX is based on the well known Hansen-Coppens multipolar model, and makes it possible to differentiate the electron spins. This algorithm is validated and demonstrated with a molecular crystal formed by a bimetallic chain, MnCu(pba)(H(2)O)(3)·2H(2)O, for which XRD and PND data are available. The joint refinement provides a more detailed description of the spin density than the refinement from PND data alone.

The new HMI beamline MAGS: an instrument for hard X-ray diffraction at BESSY.

PubMed

Dudzik, Esther; Feyerherm, Ralf; Diete, Wolfgang; Signorato, Riccardo; Zilkens, Christopher

2006-11-01

The Hahn-Meitner-Institute Berlin is operating the new hard X-ray diffraction beamline MAGS at the Berlin synchrotron radiation source BESSY. The beamline is intended to complement the existing neutron instrumentation at the Berlin Neutron Scattering Centre. The new beamline uses a 7 T multipole wiggler to produce photon fluxes in the 10(11)-10(12) photons s(-1) (100 mA)(-1) (0.1% bandwidth)(-1) range at energies from 4 to 30 keV at the experiment. It has active bendable optics to provide flexible horizontal and vertical focusing and to compensate the large heat load from the wiggler source. The experimental end-station consists of a six-circle Huber diffractometer which can be used with an additional (polarization) analyser and different sample environments. The beamline is intended for single-crystal diffraction and resonant magnetic scattering experiments for the study of ordering phenomena, phase transitions and materials science.

Calculation of Debye-Scherrer diffraction patterns from highly stressed polycrystalline materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

MacDonald, M. J., E-mail: macdonm@umich.edu; SLAC National Accelerator Laboratory, Menlo Park, California 94025; Vorberger, J.

2016-06-07

Calculations of Debye-Scherrer diffraction patterns from polycrystalline materials have typically been done in the limit of small deviatoric stresses. Although these methods are well suited for experiments conducted near hydrostatic conditions, more robust models are required to diagnose the large strain anisotropies present in dynamic compression experiments. A method to predict Debye-Scherrer diffraction patterns for arbitrary strains has been presented in the Voigt (iso-strain) limit [Higginbotham, J. Appl. Phys. 115, 174906 (2014)]. Here, we present a method to calculate Debye-Scherrer diffraction patterns from highly stressed polycrystalline samples in the Reuss (iso-stress) limit. This analysis uses elastic constants to calculate latticemore » strains for all initial crystallite orientations, enabling elastic anisotropy and sample texture effects to be modeled directly. The effects of probing geometry, deviatoric stresses, and sample texture are demonstrated and compared to Voigt limit predictions. An example of shock-compressed polycrystalline diamond is presented to illustrate how this model can be applied and demonstrates the importance of including material strength when interpreting diffraction in dynamic compression experiments.« less

Reentrant cluster glass and stability of ferromagnetism in the Ga2MnCo Heusler alloy

NASA Astrophysics Data System (ADS)

Samanta, Tamalika; Bhobe, P. A.; Das, A.; Kumar, A.; Nigam, A. K.

2018-05-01

We present here a detailed investigation into the magnetic ordering of a full Heusler alloy Ga2MnCo using dc and ac magnetization measurements, neutron diffraction, and neutron depolarization experiments. The crystal structure at room temperature was first confirmed to be L 21 using the highly intense synchrotron x-ray diffraction technique. Temperature-dependent magnetization reveals that Ga2MnCo enters a ferromagnetic (FM) state at TC=154 K, characterized by a sharp increase in magnetization and a plateaulike region hereafter. As the temperature is decreased further, a sharp drop in magnetization is observed at Tf=50 K, hinting toward an antiferromagnetic (AFM) phase change. Neutron diffraction (ND) recorded over the range of temperature from 6 to 300 K provides combined information regarding crystal as well as magnetic structure. Accordingly, an increase in the intensity of the ND pattern is seen at 150 K, signaling the onset of long-range FM order. However, there is no sign of the appearance of superlattice reflections corresponding to the AFM phase in the patterns recorded below 50 K. An unusual discontinuity in the unit-cell volume is seen around Tf, indicating a coupling of this second transition with the contraction of the lattice. Attempts to unravel this interesting magnetic behavior using ac susceptibility measurements led to the existence of glassy magnetism below Tf. Systematic analysis of the susceptibility results along with neutron depolarization measurement identifies the low-temperature phase as a reentrant cluster glass.

Preliminary neutron diffraction studies of Escherichia coli dihydrofolate reductase bound to the anticancer drug methotrexate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bennett, Brad C.; Meilleur, Flora; Myles, Dean A A

2005-01-01

The contribution of H atoms in noncovalent interactions and enzymatic reactions underlies virtually all aspects of biology at the molecular level, yet their 'visualization' is quite difficult. To better understand the catalytic mechanism of Escherichia coli dihydrofolate reductase (ecDHFR), a neutron diffraction study is under way to directly determine the accurate positions of H atoms within its active site. Despite exhaustive investigation of the catalytic mechanism of DHFR, controversy persists over the exact pathway associated with proton donation in reduction of the substrate, dihydrofolate. As the initial step in a proof-of-principle experiment which will identify ligand and residue protonation statesmore » as well as precise solvent structures, a neutron diffraction data set has been collected on a 0.3 mm{sup 3} D{sub 2}O-soaked crystal of ecDHFR bound to the anticancer drug methotrexate (MTX) using the LADI instrument at ILL. The completeness in individual resolution shells dropped to below 50% between 3.11 and 3.48 {angstrom} and the I/{sigma}(I) in individual shells dropped to below 2 at around 2.46 {angstrom}. However, reflections with I/{sigma}(I) greater than 2 were observed beyond these limits (as far out as 2.2 {angstrom}). To our knowledge, these crystals possess one of the largest primitive unit cells (P6{sub 1}, a = b = 92, c = 73 {angstrom}) and one of the smallest crystal volumes so far tested successfully with neutrons.« less

Synchrotron X-ray diffraction investigations on strains in the oxide layer of an irradiated Zircaloy fuel cladding

NASA Astrophysics Data System (ADS)

Chollet, Mélanie; Valance, Stéphane; Abolhassani, Sousan; Stein, Gene; Grolimund, Daniel; Martin, Matthias; Bertsch, Johannes

2017-05-01

For the first time the microstructure of the oxide layer of a Zircaloy-2 cladding after 9 cycles of irradiation in a boiling water reactor has been analyzed with synchrotron micro-X-ray diffraction. Crystallographic strains of the monoclinic and to some extent of the tetragonal ZrO2 are depicted through the thick oxide layer. Thin layers of sub-oxide at the oxide-metal interface as found for autoclave-tested samples and described in the literature, have not been observed in this material maybe resulting from irradiation damage. Shifts of selected diffraction peaks of the monoclinic oxide show that the uniform strain produced during oxidation is orientated in the lattice and displays variations along the oxide layer. Diffraction peaks and their shifts from families of diffracting planes could be translated into a virtual tensor. This virtual tensor exhibits changes through the oxide layer passing by tensile or compressive components.

Simultaneous, single-pulse, synchrotron x-ray imaging and diffraction under gas gun loading

DOE PAGES

Fan, D.; Huang, J. W.; Zeng, X. L.; ...

2016-05-23

We develop a mini gas gun system for simultaneous, single-pulse, x-ray diffraction and imaging under high strain-rate loading at the beamline 32-ID of the Advanced Photon Source. In order to increase the reciprocal space covered by a small-area detector, a conventional target chamber is split into two chambers: a narrowed measurement chamber and a relief chamber. The gas gun impact is synchronized with synchrotron x-ray pulses and high-speed cameras. Depending on a camera’s capability, multiframe imaging and diffraction can be achieved. The proof-of-principle experiments are performed on single-crystal sapphire. The diffraction spots and images during impact are analyzed to quantifymore » lattice deformation and fracture; diffraction peak broadening is largely caused by fracture-induced strain inhomogeneity. Finally, our results demonstrate the potential of such multiscale measurements for revealing and understanding high strain-rate phenomena at dynamic extremes.« less

Simultaneous, single-pulse, synchrotron x-ray imaging and diffraction under gas gun loading

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fan, D.; Huang, J. W.; Zeng, X. L.

We develop a mini gas gun system for simultaneous, single-pulse, x-ray diffraction and imaging under high strain-rate loading at the beamline 32-ID of the Advanced Photon Source. In order to increase the reciprocal space covered by a small-area detector, a conventional target chamber is split into two chambers: a narrowed measurement chamber and a relief chamber. The gas gun impact is synchronized with synchrotron x-ray pulses and high-speed cameras. Depending on a camera’s capability, multiframe imaging and diffraction can be achieved. The proof-of-principle experiments are performed on single-crystal sapphire. The diffraction spots and images during impact are analyzed to quantifymore » lattice deformation and fracture; diffraction peak broadening is largely caused by fracture-induced strain inhomogeneity. Finally, our results demonstrate the potential of such multiscale measurements for revealing and understanding high strain-rate phenomena at dynamic extremes.« less

The Investigation of Strain-Induced Martensite Reverse Transformation in AISI 304 Austenitic Stainless Steel

NASA Astrophysics Data System (ADS)

Cios, G.; Tokarski, T.; Żywczak, A.; Dziurka, R.; Stępień, M.; Gondek, Ł.; Marciszko, M.; Pawłowski, B.; Wieczerzak, K.; Bała, P.

2017-10-01

This paper presents a comprehensive study on the strain-induced martensitic transformation and reversion transformation of the strain-induced martensite in AISI 304 stainless steel using a number of complementary techniques such as dilatometry, calorimetry, magnetometry, and in-situ X-ray diffraction, coupled with high-resolution microstructural transmission Kikuchi diffraction analysis. Tensile deformation was applied at temperatures between room temperature and 213 K (-60 °C) in order to obtain a different volume fraction of strain-induced martensite (up to 70 pct). The volume fraction of the strain-induced martensite, measured by the magnetometric method, was correlated with the total elongation, hardness, and linear thermal expansion coefficient. The thermal expansion coefficient, as well as the hardness of the strain-induced martensitic phase was evaluated. The in-situ thermal treatment experiments showed unusual changes in the kinetics of the reverse transformation (α' → γ). The X-ray diffraction analysis revealed that the reverse transformation may be stress assisted—strains inherited from the martensitic transformation may increase its kinetics at the lower annealing temperature range. More importantly, the transmission Kikuchi diffraction measurements showed that the reverse transformation of the strain-induced martensite proceeds through a displacive, diffusionless mechanism, maintaining the Kurdjumov-Sachs crystallographic relationship between the martensite and the reverted austenite. This finding is in contradiction to the results reported by other researchers for a similar alloy composition.

Inelastic neutron scattering

NASA Astrophysics Data System (ADS)

Petit, Sylvain

2017-10-01

The goal of the JDN22 school was to propose a progressive teaching eager to improve the expertise of students in neutron diffraction. Neutron-based techniques have indeed proved for decades to be essential tools in the investigation of condensed matter. This lecture is however concerned with inelastic neutron scattering and is thus somehow apart. In the context of this school, it should then only be considered as a brief introduction. We give simple examples along with the basics of the spectrometers, and finally useful formula for the inelastic cross sections in different situations. We strongly encourage interested readers to refer to the bibliography for more detailed information.

Probing the Hydrogen Sublattice of FeHx with High-Pressure Neutron Diffraction

NASA Astrophysics Data System (ADS)

Murphy, C. A.; Guthrie, M.; Boehler, R.; Somayazulu, M.; Fei, Y.; Molaison, J.; dos Santos, A. M.

2013-12-01

The combination of seismic, cosmochemical, and mineral physics observations have revealed that Earth's iron-rich core must contain some light elements, such as hydrogen, carbon, oxygen, silicon, and/or sulfur. Therefore, understanding the influence of these light elements on the structural, thermoelastic, and electronic properties of iron is important for constraining the composition of this remote layer of the Earth and, in turn, providing constraints on planetary differentiation and core formation models. The high-pressure structural and magnetic properties of iron hydride (FeHx) have previously been studied using synchrotron x-ray diffraction and Mössbauer spectroscopy. Such experiments revealed that the double hexagonal close-packed (dhcp) structure of FeHx is stable above a pressure of ~5 GPa and up to at least 80 GPa at 300 K [1]. In addition, dhcp-FeHx is ferromagnetic at low-pressures, but undergoes a magnetic collapse around 22 GPa [2]. X-ray experiments provide valuable insight into the properties of FeHx, but such techniques are largely sensitive to the iron component because it is difficult to detect the hydrogen sublattice with x-rays. Therefore, neutron diffraction has been used to investigate metastable FeHx, which is formed by quenching the high-pressure phase to liquid nitrogen temperatures and probing the sample at ambient pressure [3]. However, such neutron experiments have been limited to formation pressures below 10 GPa, and cannot be performed at ambient temperature. Here we present the first in-situ investigation of FeHx at 300 K using high-pressure neutron diffraction experiments performed at the Spallation Neutrons and Pressure Diffractometer (SNAP) instrument at the Spallation Neutron Source, Oak Ridge National Laboratory. In order to achieve pressures of ~50 GPa, we loaded iron samples with a hydrogen gas pressure medium into newly designed large-volume panoramic diamond-anvil cells (DACs) for neutron diffraction experiments [4; 5]. We will present the details of our DAC preparations and results of our in-situ structural refinements of dhcp-FeHx up to ~50 GPa. Together with previous investigations of the thermoelastic and electronic properties of FeHx [2; 6], we will discuss implications for the composition of Earth's iron-rich core. References: 1. N. Hirao et al. (2004), Geophys. Res. Lett., 31, L06616, doi:10.1029/2003GL019380. 2. W.L. Mao et al. (2004), Geophys. Res. Lett., 31, L15618, doi:10.1029/2004GL020541. 3. V.E. Antonov et al. (2002), J. Phys.: Condens. Matter, 14, 6427-6445, doi:10.1088/0953-8984/14/25/311. 4. M. Guthrie et al. (2013), ACA Transactions, 44, in press. 5. R. Boehler et al. (2013), High Press. Res., in press, doi:10.1080/08957959.2013.823197. 6. Y. Shibazaki et al. (2012), Earth Planet. Sci. Lett., 313-314, 79-85, doi:10.1016/j.epsl.2011.11.002.

Daniel Shechtman and Quasicrystals

Science.gov Websites

toolbox that included transmission electron microscopy, X-ray diffraction and neutron diffraction. The searchQuery x Find DOE R&D Acccomplishments Navigation dropdown arrow The Basics dropdown arrow Home About Letters, Vol. 53, Issue 20: 1951-1953; November 12, 1984 Nuclear γ-ray resonance observations in an

Radiation attenuation by single-crystal diamond windows

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guthrie, M.; Pruteanu, C. G.; Donnelly, M. -E.

As artificial diamond becomes more cost effective it is likely to see increasing use as a window for sample environment equipment used in diffraction experiments. Such windows are particularly useful as they exhibit exceptional mechanical properties in addition to being highly transparent to both X-ray and neutron radiation. A key application is in high-pressure studies, where diamond anvil cells (DACs) are used to access extreme sample conditions. However, despite their utility, an important consideration when using single-crystal diamond windows is their interaction with the incident beam. In particular, the Bragg condition will be satisfied for specific angles and wavelengths, leadingmore » to the appearance of diamond Bragg spots on the diffraction detectors but also, unavoidably, to loss of transmitted intensity of the beam that interacts with the sample. This effect can be particularly significant for energy-dispersive measurements, for example, in time-of-flight neutron diffraction work using DACs. This article presents a semi-empirical approach that can be used to correct for this effect, which is a prerequisite for the accurate determination of diffraction intensities.« less

Radiation attenuation by single-crystal diamond windows

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guthrie, Malcolm; Pruteanu, Ciprian G.; Donnelly, Mary -Ellen

As artificial diamond becomes more cost effective it is likely to see increasing use as a window for sample environment equipment used in diffraction experiments. Such windows are particularly useful as they exhibit exceptional mechanical properties in addition to being highly transparent to both X-ray and neutron radiation. A key application is in high-pressure studies, where diamond anvil cells (DACs) are used to access extreme sample conditions. However, despite their utility, an important consideration when using single-crystal diamond windows is their interaction with the incident beam. In particular, the Bragg condition will be satisfied for specific angles and wavelengths, leadingmore » to the appearance of diamond Bragg spots on the diffraction detectors but also, unavoidably, to loss of transmitted intensity of the beam that interacts with the sample. This effect can be particularly significant for energy-dispersive measurements, for example, in time-of-flight neutron diffraction work using DACs. Furthermore, this article presents a semi-empirical approach that can be used to correct for this effect, which is a prerequisite for the accurate determination of diffraction intensities.« less

Radiation attenuation by single-crystal diamond windows

DOE PAGES

Guthrie, Malcolm; Pruteanu, Ciprian G.; Donnelly, Mary -Ellen; ...

2017-02-01

As artificial diamond becomes more cost effective it is likely to see increasing use as a window for sample environment equipment used in diffraction experiments. Such windows are particularly useful as they exhibit exceptional mechanical properties in addition to being highly transparent to both X-ray and neutron radiation. A key application is in high-pressure studies, where diamond anvil cells (DACs) are used to access extreme sample conditions. However, despite their utility, an important consideration when using single-crystal diamond windows is their interaction with the incident beam. In particular, the Bragg condition will be satisfied for specific angles and wavelengths, leadingmore » to the appearance of diamond Bragg spots on the diffraction detectors but also, unavoidably, to loss of transmitted intensity of the beam that interacts with the sample. This effect can be particularly significant for energy-dispersive measurements, for example, in time-of-flight neutron diffraction work using DACs. Furthermore, this article presents a semi-empirical approach that can be used to correct for this effect, which is a prerequisite for the accurate determination of diffraction intensities.« less

Suppression of magnetic order in CaCo1.86As2 with Fe substitution: Magnetization, neutron diffraction, and x-ray diffraction studies of Ca (Co1-xFex) yAs2

NASA Astrophysics Data System (ADS)

Jayasekara, W. T.; Pandey, Abhishek; Kreyssig, A.; Sangeetha, N. S.; Sapkota, A.; Kothapalli, K.; Anand, V. K.; Tian, W.; Vaknin, D.; Johnston, D. C.; McQueeney, R. J.; Goldman, A. I.; Ueland, B. G.

2017-02-01

Magnetization, neutron diffraction, and high-energy x-ray diffraction results for Sn-flux grown single-crystal samples of Ca (Co1-xFex) yAs2 , 0 ≤x ≤1 , 1.86 ≤y ≤2 , are presented and reveal that A-type antiferromagnetic order, with ordered moments lying along the c axis, persists for x ≲0.12 (1 ) . The antiferromagnetic order is smoothly suppressed with increasing x , with both the ordered moment and Néel temperature linearly decreasing. Stripe-type antiferromagnetic order does not occur for x ≤0.25 , nor does ferromagnetic order for x up to at least x =0.104 , and a smooth crossover from the collapsed-tetragonal (cT) phase of CaCo1.86As2 to the tetragonal (T) phase of CaFe2As2 occurs. These results suggest that hole doping CaCo1.86As2 has a less dramatic effect on the magnetism and structure than steric effects due to substituting Sr for Ca.

New neutron imaging techniques to close the gap to scattering applications

NASA Astrophysics Data System (ADS)

Lehmann, Eberhard H.; Peetermans, S.; Trtik, P.; Betz, B.; Grünzweig, C.

2017-01-01

Neutron scattering and neutron imaging are activities at the strong neutron sources which have been developed rather independently. However, there are similarities and overlaps in the research topics to which both methods can contribute and thus useful synergies can be found. In particular, the spatial resolution of neutron imaging has improved recently, which - together with the enhancement of the efficiency in data acquisition- can be exploited to narrow the energy band and to implement more sophisticated methods like neutron grating interferometry. This paper provides a report about the current options in neutron imaging and describes how the gap to neutron scattering data can be closed in the future, e.g. by diffractive imaging, the use of polarized neutrons and the dark-field imagining of relevant materials. This overview is focused onto the interaction between neutron imaging and neutron scattering with the aim of synergy. It reflects mainly the authors’ experiences at their PSI facilities without ignoring the activities at the different other labs world-wide.

Kinetic studies of methane-ethane mixed gas hydrates by neutron diffraction and Raman spectroscopy.

PubMed

Murshed, M Mangir; Kuhs, Werner F

2009-04-16

In situ formations of CH(4)-C(2)H(6) mixed gas hydrates were made using high flux neutron diffraction at 270 K and 5 MPa. For this purpose, a feed gas composition of CH(4) and C(2)H(6) (95 mol% CH(4)) was employed. The rates of transformation of spherical grains of deuterated ice Ih into hydrates were measured by time-resolved neutron powder diffraction on D20 at ILL, Grenoble. Phase fractions of the crystalline constituents were obtained from Rietveld refinements. A concomitant formation of structure type I (sI) and structure type II (sII) hydrates were observed soon after the gas pressure was applied. The initial fast formation of sII hydrate reached its maximum volume and started declining very slowly. The formation of sI hydrate followed a sigmoid growth kinetics that slowed down due to diffusion limitation. This observation has been interpreted in terms of a kinetically favored nucleation of the sII hydrate along with a slow transformation into sI. Both powder diffraction and Raman spectroscopic results suggest that a C(2)H(6)-rich sII hydrate was formed at the early part of the clathration, which slowly decreased to approximately 3% after a reaction of 158 days as confirmed by synchrotron XRD. The final persistence of a small portion of sII hydrate points to a miscibility gap between CH(4)-rich sI and C(2)H(6)-rich sII hydrates.

Studies of cavitation and ice nucleation in 'doubly-metastable' water: time-lapse photography and neutron diffraction.

PubMed

Barrow, Matthew S; Williams, P Rhodri; Chan, Hoi-Houng; Dore, John C; Bellissent-Funel, Marie-Claire

2012-10-14

High-speed photographic studies and neutron diffraction measurements have been made of water under tension in a Berthelot tube. Liquid water was cooled below the normal ice-nucleation temperature and was in a doubly-metastable state prior to a collapse of the liquid state. This transition was accompanied by an exothermic heat release corresponding with the rapid production of a solid phase nucleated by cavitation. Photographic techniques have been used to observe the phase transition over short time scales in which a solidification front is observed to propagate through the sample. Significantly, other images at a shorter time interval reveal the prior formation of cavitation bubbles at the beginning of the process. The ice-nucleation process is explained in terms of a mechanism involving hydrodynamically-induced changes in tension in supercooled water in the near vicinity of an expanding cavitation bubble. Previous explanations have attributed the nucleation of the solid phase to the production of high positive pressures. Corresponding results are presented which show the initial neutron diffraction pattern after ice-nucleation. The observed pattern does not exhibit the usual crystalline pattern of hexagonal ice [I(h)] that is formed under ambient conditions, but indicates the presence of other ice forms. The composite features can be attributed to a mixture of amorphous ice, ice-I(h)/I(c) and the high-pressure form, ice-III, and the diffraction pattern continues to evolve over a time period of about an hour.

An In-situ method for the study of strain broadening usingsynchrotronx-ray diffraction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tang, Chiu C.; Lynch, Peter A.; Cheary, Robert W.

2006-12-15

A tensonometer for stretching metal foils has beenconstructed for the study of strain broadening in x-ray diffraction lineprofiles. This device, which is designed for use on the powderdiffractometer in Station 2.3 at Daresbury Laboratory, allows in-situmeasurements to be performed on samples under stress. It can be used fordata collection in either transmission or reflection modes using eithersymmetric or asymmetric diffraction geometries. As a test case,measurements were carried out on a 18mum thick copper foil experiencingstrain levels of up to 5 percent using both symmetric reflection andsymmetric transmission diffraction. All the diffraction profilesdisplayed peak broadening and asymmetry which increased with strain.more » Themeasured profiles were analysed by the fundamental parameters approachusing the TOPAS peak fitting software. All the observed broadenedprofiles were modelled by convoluting a refineable diffraction profile,representing the dislocation and crystallite size broadening, with afixed instrumental profile pre-determined usinghigh quality LaB6reference powder. The de-convolution process yielded "pure" sampleintegral breadths and asymmetry results which displayed a strongdependence on applied strain and increased almost linearly with appliedstrain. Assuming crystallite size broadening in combination withdislocation broadening arising from fcc a/2<110>111 dislocations,we have extracted the variation of mechanic al property with strain. Theobservation of both peak asymmetry and broadening has been interpreted asa manifestation of a cellular structure with cell walls and cellinteriors possessing high and low dislocation densities.« less

AND/R: Advanced neutron diffractometer/reflectometer for investigation of thin films and multilayers for the life sciences

PubMed Central

Dura, Joseph A.; Pierce, Donald J.; Majkrzak, Charles F.; Maliszewskyj, Nicholas C.; McGillivray, Duncan J.; Lösche, Mathias; O'Donovan, Kevin V.; Mihailescu, Mihaela; Perez-Salas, Ursula; Worcester, David L.; White, Stephen H.

2011-01-01

An elastic neutron scattering instrument, the advanced neutron diffractometer/reflectometer (AND/R), has recently been commissioned at the National Institute of Standards and Technology Center for Neutron Research. The AND/R is the centerpiece of the Cold Neutrons for Biology and Technology partnership, which is dedicated to the structural characterization of thin films and multilayers of biological interest. The instrument is capable of measuring both specular and nonspecular reflectivity, as well as crystalline or semicrystalline diffraction at wave-vector transfers up to approximately 2.20 Å−1. A detailed description of this flexible instrument and its performance characteristics in various operating modes are given. PMID:21892232

Pulsed Neutron Powder Diffraction for Materials Science

NASA Astrophysics Data System (ADS)

Kamiyama, T.

2008-03-01

The accelerator-based neutron diffraction began in the end of 60's at Tohoku University which was succeeded by the four spallation neutron facilities with proton accelerators at the High Energy Accelerator Research Organization (Japan), Argonne National Laboratory and Los Alamos Laboratory (USA), and Rutherford Appleton Laboratory (UK). Since then, the next generation source has been pursued for 20 years, and 1MW-class spallation neutron sources will be appeared in about three years at the three parts of the world: Japan, UK and USA. The joint proton accelerator project (J-PARC), a collaborative project between KEK and JAEA, is one of them. The aim of the talk is to describe about J-PARC and the neutron diffractometers being installed at the materials and life science facility of J-PARC. The materials and life science facility of J-PARC has 23 neutron beam ports and will start delivering the first neutron beam of 25 Hz from 2008 May. Until now, more than 20 proposals have been reviewed by the review committee, and accepted proposal groups have started to get fund. Those proposals include five polycrystalline diffractometers: a super high resolution powder diffractometer (SHRPD), a 0.2%-resolution powder diffractometer of Ibaraki prefecture (IPD), an engineering diffractometers (Takumi), a high intensity S(Q) diffractometer (VSD), and a high-pressure dedicated diffractometer. SHRPD, Takumi and IPD are being designed and constructed by the joint team of KEK, JAEA and Ibaraki University, whose member are originally from the KEK powder group. These three instruments are expected to start in 2008. VSD is a super high intensity diffractometer with the highest resolution of Δd/d = 0.3%. VSD can measure rapid time-dependent phenomena of crystalline materials as well as glass, liquid and amorphous materials. The pair distribution function will be routinely obtained by the Fourier transiformation of S(Q) data. Q range of VSD will be as wide as 0.01 Å-1

Real time neutron diffraction and NMR of the Empress II glass-ceramic system.

PubMed

O'Donnell, M D; Hill, R G; Karpukhina, N; Law, R V

2011-10-01

This study reports real time neutron diffraction on the Empress II glass-ceramic system. The commercial glass-ceramics was characterized by real time neutron diffraction, ³¹P and ²⁹Si solid-state MAS-NMR, DSC and XRD. On heating, the as-received glass ceramic contained lithium disilicate (Li₂Si₂O₅), which melted with increasing temperature. This was revealed by neutron diffraction which showed the Bragg peaks for this phase had disappeared by 958°C in agreement with thermal analysis. On cooling lithium metasilicate (Li₂SiO₃) started to form at around 916°C and a minor phase of cristobalite at around 852°C. The unit cell volume of both Li-silicate phases increased linearly with temperature at a rate of +17×10⁻³ ų.°C⁻¹. Room temperature powder X-ray diffraction (XRD) of the material after cooling confirms presence of the lithium metasilicate and cristobalite as the main phases and shows, in addition, small amount of lithium disilicate and orthophosphate. ³¹P MAS-NMR reveals presence of the lithiorthophosphate (Li₃PO₄) before and after heat treatment. The melting of lithium disilicate on heating and crystallisation of lithium metasilicate on cooling agree with endothermic and exotermic features respectively observed by DSC. ²⁹Si MAS-NMR shows presence of lithium disilicate phase in the as-received glass-ceramic, though not in the major proportion, and lithium metasilicate in the material after heat treatment. Both phases have significantly long T₁ relaxation time, especially the lithium metasilicate, therefore, a quantitative analysis of the ²⁹Si MAS-NMR spectra was not attempted. Significance. The findings of the present work demonstrate importance of the commercially designed processing parameters in order to preserve desired characteristics of the material. Processing the Empress II at a rate slower than recommended 60°C min⁻¹ or long isothermal hold at the maximal processing temperature 920°C can cause crystallization of lithium metasilicate and cristobalite instead of lithium disilicate as major phase. Copyright © 2011 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Effect of Upper-Cycle Temperature on the Load-Biased, Strain-Temperature Response of NiTi

NASA Technical Reports Server (NTRS)

Padula, Santo, II; Noebe, Ronald; Bigelow, Glen; Qiu, Shipeng; Vaidyanathan, Raj; Gaydosh, Darrell; Garg, Anita

2011-01-01

Over the past decade, interest in shape memory alloy based actuators has increased as the primary benefits of these solid-state devices have become more apparent. However, much is still unknown about the characteristic behavior of these materials when used in actuator applications. Recently we have shown that the maximum temperature reached during thermal cycling under isobaric conditions could significantly affect the observed mechanical response of NiTi (55 wt% Ni), especially the amount of transformation strain available for actuation and thus work output. The investigation we report here extends that original work to ascertain whether further increases in the upper-cycle temperature would produce additional changes in the work output of the material, which has a stress-free austenite finish temperature of 113 C, and to determine the optimum cyclic conditions. Thus, isobaric, thermal-cycle experiments were conducted on the aforementioned alloy at various stresses from 50-300 MPa using upper-cycle temperatures of 165, 200, 230, 260, 290, 320 and 350 C. The data indicated that the amount of applied stress influenced the transformation strain, as would be expected. However, the maximum temperature reached during the thermal excursion also plays an equally significant role in determining the transformation strain, with the maximum transformation strain observed during thermal cycling to 290 C. In situ neutron diffraction at stress and temperature showed that the differences in transformation strain were mostly related to changes in martensite texture when cycling to different upper-cycle temperatures. Hence, understanding this effect is important to optimizing the operation of SMA-based actuators and could lead to new methods for processing and training shape memory alloys for optimal performance.

Effect of Upper-Cycle Temperature on the Load-Biased, Strain-Temperature Response of NiTi

NASA Technical Reports Server (NTRS)

Padula, Santo, II; Vaidyanathan, Raj; Gaydosh, Darrell; Noebe, Ronald; Bigelow, Glen; Garg, Anita

2008-01-01

Over the past decade, interest in shape memory alloy based actuators has increased as the primary benefits of these solid-state devices have become more apparent. However, much is still unknown about the characteristic behavior of these materials when used in actuator applications. Recently we have shown that the maximum temperature reached during thermal cycling under isobaric conditions could significantly affect the observed mechanical response of NiTi (55 wt% Ni), especially the amount of transformation strain available for actuation and thus work output. This investigation extends that original work to ascertain whether further increases in the upper-cycle temperature would produce additional improvement in the work output of the material, which has a stress-free Af of 113 oC, and to determine the optimum cyclic conditions. Thus, isobaric, thermal-cycle experiments were conducted in the aforementioned alloy at various stress levels from 50-300 MPa using upper-cycle temperatures of 165, 200, 230, 260, 290, 320 and 350 oC. The data indicated that the amount of applied stress influenced the transformation strain available in the system, as would be expected. However, the maximum temperature reached during the thermal excursion also plays a role in determining the transformation strain, with the maximum transformation strain being developed by thermal cycling to 290 oC. In situ, neutron diffraction showed that the differences in transformation strain were related to differences in martensite texture within the microstructure when cycling to different upper-cycle temperatures. Hence, understanding this effect is important to optimizing the operation of SMA-based actuators and could lead to new methods for processing and training shape memory alloys for optimal performance.

Crystal Structure of Hydrazinium Iodide by Neutron Diffraction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Campbell, Eric V.; Wang, Xiaoping; Miller, Joel S.

The structure of hydrazinium iodide, [H 5N 2] +·I -, at 100 K has monoclinic (P2 1/n) symmetry from single crystal neutron diffraction with a = 7.4599(7) Å, b = 5.3185(6) Å, c = 10.1628(11) Å, β = 103.150(10)°, V = 392.64(7) Å 3, Z = 4. The refinement converged to R = 0.0575, wR 2 = 0.1602, S = 1.022. Data for the crystal structure was collected on the SNS TOPAZ single-crystal time-of-flight Laue diffractometer. The compound has a one-dimensional structure which displays N–H···N hydrogen bonding. Finally, accurate intra- and intermolecular N–H distances have been determined.

Crystal Structure of Hydrazinium Iodide by Neutron Diffraction

DOE PAGES

Campbell, Eric V.; Wang, Xiaoping; Miller, Joel S.

2017-10-31

The structure of hydrazinium iodide, [H 5N 2] +·I -, at 100 K has monoclinic (P2 1/n) symmetry from single crystal neutron diffraction with a = 7.4599(7) Å, b = 5.3185(6) Å, c = 10.1628(11) Å, β = 103.150(10)°, V = 392.64(7) Å 3, Z = 4. The refinement converged to R = 0.0575, wR 2 = 0.1602, S = 1.022. Data for the crystal structure was collected on the SNS TOPAZ single-crystal time-of-flight Laue diffractometer. The compound has a one-dimensional structure which displays N–H···N hydrogen bonding. Finally, accurate intra- and intermolecular N–H distances have been determined.

When combined X-ray and polarized neutron diffraction data challenge high-level calculations: spin-resolved electron density of an organic radical.

PubMed

Voufack, Ariste Bolivard; Claiser, Nicolas; Lecomte, Claude; Pillet, Sébastien; Pontillon, Yves; Gillon, Béatrice; Yan, Zeyin; Gillet, Jean Michel; Marazzi, Marco; Genoni, Alessandro; Souhassou, Mohamed

2017-08-01

Joint refinement of X-ray and polarized neutron diffraction data has been carried out in order to determine charge and spin density distributions simultaneously in the nitronyl nitroxide (NN) free radical Nit(SMe)Ph. For comparison purposes, density functional theory (DFT) and complete active-space self-consistent field (CASSCF) theoretical calculations were also performed. Experimentally derived charge and spin densities show significant differences between the two NO groups of the NN function that are not observed from DFT theoretical calculations. On the contrary, CASSCF calculations exhibit the same fine details as observed in spin-resolved joint refinement and a clear asymmetry between the two NO groups.

Neutron Diffraction Study On Gamma To Alpha Phase Transition In Ce0.9th0.1 Alloy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lashley, Jason C1; Heffner, Robert H; Llobet, A

2008-01-01

Comprehensive neutron diffraction measurements were performed to study the isostructural {gamma} {leftrightarrow} {alpha} phase transition in Ce{sub 0.9}Th{sub 0.1} alloy. Using Rietveld refinements, we obtained lattice and thermal parameters as a function of temperature. From the temperature slope of the thermal parameters, we determined Debye temperatures {Theta}{sup {gamma}}{sub D} = 133(1) K and {Theta}{sup {alpha}}{sub D} = 140(1) K for the {gamma} phase and the {alpha} phase, respectively. This result implies that the vibrational entropy change is not significant at the {gamma} {leftrightarrow} {alpha} transition, contrary to that from elemental Cerium [Phys. Rev. Lett. 92, 105702, 2004].

Electron Diffraction Using Transmission Electron Microscopy

PubMed Central

Bendersky, Leonid A.; Gayle, Frank W.

2001-01-01

Electron diffraction via the transmission electron microscope is a powerful method for characterizing the structure of materials, including perfect crystals and defect structures. The advantages of electron diffraction over other methods, e.g., x-ray or neutron, arise from the extremely short wavelength (≈2 pm), the strong atomic scattering, and the ability to examine tiny volumes of matter (≈10 nm3). The NIST Materials Science and Engineering Laboratory has a history of discovery and characterization of new structures through electron diffraction, alone or in combination with other diffraction methods. This paper provides a survey of some of this work enabled through electron microscopy. PMID:27500060

Nondestructive strain depth profiling with high energy X-ray diffraction: System capabilities and limitations

NASA Astrophysics Data System (ADS)

Zhang, Zhan; Wendt, Scott; Cosentino, Nicholas; Bond, Leonard J.

2018-04-01

Limited by photon energy, and penetration capability, traditional X-ray diffraction (XRD) strain measurements are only capable of achieving a few microns depth due to the use of copper (Cu Kα1) or molybdenum (Mo Kα1) characteristic radiation. For deeper strain depth profiling, destructive methods are commonly necessary to access layers of interest by removing material. To investigate deeper depth profiles nondestructively, a laboratory bench-top high-energy X-ray diffraction (HEXRD) system was previously developed. This HEXRD method uses an industrial 320 kVp X-Ray tube and the Kα1 characteristic peak of tungsten, to produces a higher intensity X-ray beam which enables depth profiling measurement of lattice strain. An aluminum sample was investigated with deformation/load provided using a bending rig. It was shown that the HEXRD method is capable of strain depth profiling to 2.5 mm. The method was validated using an aluminum sample where both the HEXRD method and the traditional X-ray diffraction method gave data compared with that obtained using destructive etching layer removal, performed by a commercial provider. The results demonstrate comparable accuracy up to 0.8 mm depth. Nevertheless, higher attenuation capabilities in heavier metals limit the applications in other materials. Simulations predict that HEXRD works for steel and nickel in material up to 200 µm, but experiment results indicate that the HEXRD strain profile is not practical for steel and nickel material, and the measured diffraction signals are undetectable when compared to the noise.

Structure and magnetism of epitaxially strained Pd(001) films on Fe(001): Experiment and theory

NASA Astrophysics Data System (ADS)

Fullerton, Eric E.; Stoeffler, D.; Ounadjela, K.; Heinrich, B.; Celinski, Z.; Bland, J. A. C.

1995-03-01

We present an experimental and theoretical description of the structure and magnetism of epitaxially strained Pd(001) films on Fe(001) and in Fe/Pd/Fe(001) trilayers. The structure is determined by combining reflection high-energy electron diffraction and x-ray diffraction. For Fe/Au(001) bilayers and Fe/Pd/Au(001) trilayers grown by molecular-beam epitaxy on Ag(001), the Fe and Au layers are well represented by their bulk structure, whereas, thin Pd layers have a face-centered tetragonal structure with an in-plane expansion of 4.2% and an out-of-plane contraction of 7.2% (c/a=0.89). Theoretical ab initio studies of the interfacial structure indicate that the structural ground state of the epitaxially strained Pd layer is well described by a fct structure which maintains the bulk Pd atomic volume with small deviations at the interface. For Fe/Pd/Fe trilayers, the interlayer coupling oscillates with a period of 4 monolayers (ML) on a ferromagnetic background that crosses to weak antiferromagnetic coupling for thicknesses >12 ML of Pd. Strong ferromagnetic coupling observed below 5 ML of Pd indicates that 2 ML of Pd at each interface are ferromagnetically ordered. Theoretical studies of Fe3Pdn superlattices (where n is the number of Pd atomic layers) determine the polarization of the Pd layer and the interlayer magnetic coupling to depend strongly on the c/a ratio of the Pd layers. Modeling of a Pd layer with a constant-volume fct structure and one monolayer interfacial roughness find that the first 2 ML of the Pd is polarized in close agreement with the experimental results. Polarized neutron reflectivity results on an Fe(5.6 ML)/Pd(7 ML)/Au(20 ML) sample determine the average moment per Fe atom of 2.66+/-0.05μB. Calculations for the same structure show that this value is consistent with the induced Pd polarization.

Gradual pressure-induced change in the magnetic structure of the noncollinear antiferromagnet Mn3Ge

NASA Astrophysics Data System (ADS)

Sukhanov, A. S.; Singh, Sanjay; Caron, L.; Hansen, Th.; Hoser, A.; Kumar, V.; Borrmann, H.; Fitch, A.; Devi, P.; Manna, K.; Felser, C.; Inosov, D. S.

2018-06-01

By means of powder neutron diffraction we investigate changes in the magnetic structure of the coplanar noncollinear antiferromagnet Mn3Ge caused by an application of hydrostatic pressure up to 5 GPa. At ambient conditions the kagomé layers of Mn atoms in Mn3Ge order in a triangular 120∘ spin structure. Under high pressure the spins acquire a uniform out-of-plane canting, gradually transforming the magnetic texture to a noncoplanar configuration. With increasing pressure the canted structure fully transforms into the collinear ferromagnetic one. We observed that magnetic order is accompanied by a noticeable magnetoelastic effect, namely, spontaneous magnetostriction. The latter induces an in-plane magnetostrain of the hexagonal unit cell at ambient pressure and flips to an out-of-plane strain at high pressures in accordance with the change of the magnetic structure.

Coherent X-Ray Diffraction Imaging and Characterization of Strain in Silicon-on-Insulator Nanostructures

PubMed Central

Xiong, Gang; Moutanabbir, Oussama; Reiche, Manfred; Harder, Ross; Robinson, Ian

2014-01-01

Coherent X-ray diffraction imaging (CDI) has emerged in the last decade as a promising high resolution lens-less imaging approach for the characterization of various samples. It has made significant technical progress through developments in source, algorithm and imaging methodologies thus enabling important scientific breakthroughs in a broad range of disciplines. In this report, we will introduce the principles of forward scattering CDI and Bragg geometry CDI (BCDI), with an emphasis on the latter. BCDI exploits the ultra-high sensitivity of the diffraction pattern to the distortions of crystalline lattice. Its ability of imaging strain on the nanometer scale in three dimensions is highly novel. We will present the latest progress on the application of BCDI in investigating the strain relaxation behavior in nanoscale patterned strained silicon-on-insulator (sSOI) materials, aiming to understand and engineer strain for the design and implementation of new generation semiconductor devices. PMID:24955950

Thermal neutron radiative capture on cadmium as a counting technique at the INES beam line at ISIS: A preliminary investigation of detector cross-talk.

PubMed

Festa, G; Grazzi, F; Pietropaolo, A; Scherillo, A; Schooneveld, E M

2017-12-01

Experimental tests are presented that assess the cross-talk level among three scintillation detectors used as neutron counters exploiting the thermal neutron radiative capture on Cd. The measurements were done at the INES diffractometer operating at the ISIS spallation neutron source (Rutherford Appleton Laboratory, UK). These tests follow a preliminary set of measurements performed on the same instrument to study the effectiveness of this thermal neutron counting strategy in neutron diffraction measurements, typically performed on INES using squashed 3 He filled gas tubes. The experimental data were collected in two different geometrical configurations of the detectors and compared to results of Monte Carlo simulations, performed using the MCNP code. Copyright © 2017 Elsevier Ltd. All rights reserved.

Comparative study of the magnetic properties of La3Ni2B‧O9 for B‧ = Nb, Taor Sb

NASA Astrophysics Data System (ADS)

Chin, Chun-Mann; Battle, Peter D.; Blundell, Stephen J.; Hunter, Emily; Lang, Franz; Hendrickx, Mylène; Paria Sena, Robert; Hadermann, Joke

2018-02-01

Polycrystalline samples of La3Ni2NbO9 and La3Ni2TaO9 have been characterised by X-ray and neutron diffraction, electron microscopy, magnetometry and muon spin relaxation (μSR); the latter technique was also applied to La3Ni2SbO9. On the length scale of a neutron diffraction experiment, the six-coordinate sites of the monoclinic perovskite structure are occupied in a 1:1 ordered manner by Ni and a random ⅓Ni/⅔B‧ mixture. Electron microscopy demonstrated that this 1:1 ordering is maintained over microscopic distances, although diffuse scattering indicative of short-range ordering on the mixed site was observed. No magnetic Bragg scattering was observed in neutron diffraction patterns collected from La3Ni2B‧O9 (B‧ = Nb or Ta) at 5 K although in each case μSR identified the presence of static spins below 30 K. Magnetometry showed that La3Ni2NbO9 behaves as a spin glass below 29 K but significant short-range interactions are present in La3Ni2TaO9 below 85 K. The contrasting properties of these compounds are discussed in terms of their microstructure.

Multidataset Refinement Resonant Diffraction, and Magnetic Structures

PubMed Central

Attfield, J. Paul

2004-01-01

The scope of Rietveld and other powder diffraction refinements continues to expand, driven by improvements in instrumentation, methodology and software. This will be illustrated by examples from our research in recent years. Multidataset refinement is now commonplace; the datasets may be from different detectors, e.g., in a time-of-flight experiment, or from separate experiments, such as at several x-ray energies giving resonant information. The complementary use of x rays and neutrons is exemplified by a recent combined refinement of the monoclinic superstructure of magnetite, Fe3O4, below the 122 K Verwey transition, which reveals evidence for Fe2+/Fe3+ charge ordering. Powder neutron diffraction data continue to be used for the solution and Rietveld refinement of magnetic structures. Time-of-flight instruments on cold neutron sources can produce data that have a high intensity and good resolution at high d-spacings. Such profiles have been used to study incommensurate magnetic structures such as FeAsO4 and β–CrPO4. A multiphase, multidataset refinement of the phase-separated perovskite (Pr0.35Y0.07Th0.04Ca0.04Sr0.5)MnO3 has been used to fit three components with different crystal and magnetic structures at low temperatures. PMID:27366599

Structure, magnetic properties, polarized neutron diffraction, and theoretical study of a copper(II) cubane.

PubMed

Aronica, Christophe; Chumakov, Yurii; Jeanneau, Erwann; Luneau, Dominique; Neugebauer, Petr; Barra, Anne-Laure; Gillon, Béatrice; Goujon, Antoine; Cousson, Alain; Tercero, Javier; Ruiz, Eliseo

2008-01-01

The paper reports the synthesis, X-ray and neutron diffraction crystal structures, magnetic properties, high field-high frequency EPR (HF-EPR), spin density and theoretical description of the tetranuclear CuII complex [Cu4L4] with cubane-like structure (LH2=1,1,1-trifluoro-7-hydroxy-4-methyl-5-aza-hept-3-en-2-one). The simulation of the magnetic behavior gives a predominant ferromagnetic interaction J1 (+30.5 cm(-1)) and a weak antiferromagnetic interaction J2 (-5.5 cm(-1)), which correspond to short and long Cu-Cu distances, respectively, as evidence from the crystal structure [see formulate in text]. It is in agreement with DFT calculations and with the saturation magnetization value of an S=2 ground spin state. HF-EPR measurements at low temperatures (5 to 30 K) provide evidence for a negative axial zero-field splitting parameter D (-0.25+/-0.01 cm(-1)) plus a small rhombic term E (0.025+/-0.001 cm(-1), E/D = 0.1). The experimental spin distribution from polarized neutron diffraction is mainly located in the basal plane of the CuII ion with a distortion of yz-type for one CuII ion. Delocalization on the ligand (L) is observed but to a smaller extent than expected from DFT calculations.

On the temperature dependence of H-U{sub iso} in the riding hydrogen model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lübben, Jens; Volkmann, Christian; Grabowsky, Simon

The temperature dependence of hydrogen U{sub iso} and parent U{sub eq} in the riding hydrogen model is investigated by neutron diffraction, aspherical-atom refinements and QM/MM and MO/MO cluster calculations. Fixed values of 1.2 or 1.5 appear to be underestimated, especially at temperatures below 100 K. The temperature dependence of H-U{sub iso} in N-acetyl-l-4-hydroxyproline monohydrate is investigated. Imposing a constant temperature-independent multiplier of 1.2 or 1.5 for the riding hydrogen model is found to be inaccurate, and severely underestimates H-U{sub iso} below 100 K. Neutron diffraction data at temperatures of 9, 150, 200 and 250 K provide benchmark results for thismore » study. X-ray diffraction data to high resolution, collected at temperatures of 9, 30, 50, 75, 100, 150, 200 and 250 K (synchrotron and home source), reproduce neutron results only when evaluated by aspherical-atom refinement models, since these take into account bonding and lone-pair electron density; both invariom and Hirshfeld-atom refinement models enable a more precise determination of the magnitude of H-atom displacements than independent-atom model refinements. Experimental efforts are complemented by computing displacement parameters following the TLS+ONIOM approach. A satisfactory agreement between all approaches is found.« less

Strain analysis from nano-beam electron diffraction: Influence of specimen tilt and beam convergence.

PubMed

Grieb, Tim; Krause, Florian F; Schowalter, Marco; Zillmann, Dennis; Sellin, Roman; Müller-Caspary, Knut; Mahr, Christoph; Mehrtens, Thorsten; Bimberg, Dieter; Rosenauer, Andreas

2018-07-01

Strain analyses from experimental series of nano-beam electron diffraction (NBED) patterns in scanning transmission electron microscopy are performed for different specimen tilts. Simulations of NBED series are presented for which strain analysis gives results that are in accordance with experiment. This consequently allows to study the relation between measured strain and actual underlying strain. A two-tilt method which can be seen as lowest-order electron beam precession is suggested and experimentally implemented. Strain determination from NBED series with increasing beam convergence is performed in combination with the experimental realization of a probe-forming aperture with a cross inside. It is shown that using standard evaluation techniques, the influence of beam convergence on spatial resolution is lower than the influence of sharp rings around the diffraction disc which occur at interfaces and which are caused by the tails of the intensity distribution of the electron probe. Copyright © 2018 Elsevier B.V. All rights reserved.

Micro-beam Laue alignment of multi-reflection Bragg coherent diffraction imaging measurements

DOE PAGES

Hofmann, Felix; Phillips, Nicholas W.; Harder, Ross J.; ...

2017-08-08

Multi-reflection Bragg coherent diffraction imaging has the potential to allow three-dimensional (3D) resolved measurements of the full lattice strain tensor in specific micro-crystals. Until now such measurements were hampered by the need for laborious, time-intensive alignment procedures. Here, in this paper, a different approach is demonstrated, using micro-beam Laue X-ray diffraction to first determine the lattice orientation of the micro-crystal. This information is then used to rapidly align coherent diffraction measurements of three or more reflections from the crystal. Based on these, 3D strain and stress fields in the crystal are successfully determined. This approach is demonstrated on a focusedmore » ion beam milled micro-crystal from which six reflections could be measured. Since information from more than three independent reflections is available, the reliability of the phases retrieved from the coherent diffraction data can be assessed. Lastly, our results show that rapid, reliable 3D coherent diffraction measurements of the full lattice strain tensor in specific micro-crystals are now feasible and can be successfully carried out even in heavily distorted samples.« less

Micro-beam Laue alignment of multi-reflection Bragg coherent diffraction imaging measurements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hofmann, Felix; Phillips, Nicholas W.; Harder, Ross J.

Multi-reflection Bragg coherent diffraction imaging has the potential to allow three-dimensional (3D) resolved measurements of the full lattice strain tensor in specific micro-crystals. Until now such measurements were hampered by the need for laborious, time-intensive alignment procedures. Here, in this paper, a different approach is demonstrated, using micro-beam Laue X-ray diffraction to first determine the lattice orientation of the micro-crystal. This information is then used to rapidly align coherent diffraction measurements of three or more reflections from the crystal. Based on these, 3D strain and stress fields in the crystal are successfully determined. This approach is demonstrated on a focusedmore » ion beam milled micro-crystal from which six reflections could be measured. Since information from more than three independent reflections is available, the reliability of the phases retrieved from the coherent diffraction data can be assessed. Lastly, our results show that rapid, reliable 3D coherent diffraction measurements of the full lattice strain tensor in specific micro-crystals are now feasible and can be successfully carried out even in heavily distorted samples.« less

Micro-beam Laue alignment of multi-reflection Bragg coherent diffraction imaging measurements.

PubMed

Hofmann, Felix; Phillips, Nicholas W; Harder, Ross J; Liu, Wenjun; Clark, Jesse N; Robinson, Ian K; Abbey, Brian

2017-09-01

Multi-reflection Bragg coherent diffraction imaging has the potential to allow three-dimensional (3D) resolved measurements of the full lattice strain tensor in specific micro-crystals. Until now such measurements were hampered by the need for laborious, time-intensive alignment procedures. Here a different approach is demonstrated, using micro-beam Laue X-ray diffraction to first determine the lattice orientation of the micro-crystal. This information is then used to rapidly align coherent diffraction measurements of three or more reflections from the crystal. Based on these, 3D strain and stress fields in the crystal are successfully determined. This approach is demonstrated on a focused ion beam milled micro-crystal from which six reflections could be measured. Since information from more than three independent reflections is available, the reliability of the phases retrieved from the coherent diffraction data can be assessed. Our results show that rapid, reliable 3D coherent diffraction measurements of the full lattice strain tensor in specific micro-crystals are now feasible and can be successfully carried out even in heavily distorted samples.

Micro-beam Laue Alignment of Multi-Reflection Bragg Coherent Diffraction Imaging Measurements

PubMed Central

Hofmann, Felix; Phillips, Nicholas W.; Harder, Ross J.; Liu, Wenjun; Clark, Jesse N.; Robinson, Ian K.; Abbey, Brian

2017-01-01

Multi-reflection Bragg coherent diffraction imaging has the potential to allow 3D resolved measurements of the full lattice strain tensor in specific micro-crystals. Until now such measurements were hampered by the need for laborious, time-intensive alignment procedures. Here we demonstrate a different approach, using micro-beam Laue X-ray diffraction to first determine the lattice orientation of the micro-crystal. This information is then used to rapidly align coherent diffraction measurements of three or more reflections from the crystal. Based on these, 3D strain and stress fields in the crystal are successfully determined. This approach is demonstrated on a focussed ion beam milled micro-crystal from which six reflections could be measured. Since information from more than three independent reflections is available, the reliability of the phases retrieved from the coherent diffraction data can be assessed. Our results show that rapid, reliable 3D coherent diffraction measurements of the full lattice strain tensor in specific micro-crystals are now feasible and can be successfully carried out even in heavily distorted samples. PMID:28862628

Crystallization and preliminary X-ray diffraction analysis of the amidase domain of allophanate hydrolase from Pseudomonas sp. strain ADP

DOE Office of Scientific and Technical Information (OSTI.GOV)

Balotra, Sahil; Newman, Janet; French, Nigel G.

2014-02-19

The amidase domain of the allophanate hydrolase AtzF from Pseudomonas sp. strain ADP has been crystallized and preliminary X-ray diffraction data have been collected. The allophanate hydrolase from Pseudomonas sp. strain ADP was expressed and purified, and a tryptic digest fragment was subsequently identified, expressed and purified. This 50 kDa construct retained amidase activity and was crystallized. The crystals diffracted to 2.5 Å resolution and adopted space group P2{sub 1}, with unit-cell parameters a = 82.4, b = 179.2, c = 112.6 Å, β = 106.6°.

The magnetic structure of Co(NCNH)₂ as determined by (spin-polarized) neutron diffraction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jacobs, Philipp; Houben, Andreas; Senyshyn, Anatoliy

The magnetic structure of Co(NCNH)₂ has been studied by neutron diffraction data below 10 K using the SPODI and DNS instruments at FRM II, Munich. There is an intensity change in the (1 1 0) and (0 2 0) reflections around 4 K, to be attributed to the onset of a magnetic ordering of the Co²⁺ spins. Four different spin orientations have been evaluated on the basis of Rietveld refinements, comprising antiferromagnetic as well as ferromagnetic ordering along all three crystallographic axes. Both residual values and supplementary susceptibility measurements evidence that only a ferromagnetic ordering with all Co²⁺ spins parallelmore » to the c axis is a suitable description of the low-temperature magnetic ground state of Co(NCNH)₂. The deviation of the magnetic moment derived by the Rietveld refinement from the expectancy value may be explained either by an incomplete saturation of the moment at temperatures slightly below the Curie temperature or by a small Jahn–Teller distortion. - Graphical abstract: The magnetic ground state of Co(NCNH)₂ has been clarified by (spin-polarized) neutron diffraction data at low temperatures. Intensity changes below 4 K arise due to the onset of ferromagnetic ordering of the Co²⁺ spins parallel to the c axis, corroborated by various (magnetic) Rietveld refinements. Highlights: • Powderous Co(NCNH)₂ has been subjected to (spin-polarized) neutron diffraction. • Magnetic susceptibility data of Co(NCNH)₂ have been collected. • Below 4 K, the magnetic moments align ferromagnetically with all Co²⁺ spins parallel to the c axis. • The magnetic susceptibility data yield an effective magnetic moment of 4.68 and a Weiss constant of -13(2) K. • The ferromagnetic Rietveld refinement leads to a magnetic moment of 2.6 which is close to the expectancy value of 3.« less

Understanding Low-cycle Fatigue Life Improvement Mechanisms in a Pre-twinned Magnesium Alloy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, Wei; An, Ke

The mechanisms of fatigue life improvement by pre-twinning process in a commercial rolled magnesium (Mg) alloy have been investigated using real-time in situ neutron diffraction under a continuous-loading condition. It is found that by introducing the excess twinned grains through pre-compression along the rolling direction the fatigue life was enhanced approximately 50%, mainly resulting from the prolonged detwinning process and inhibited dislocation slip during reverse tension. Moreover, after pre-twinning process, the removal of the rapid strain hardening during reverse tension leads to a compressive mean stress value and more symmetric shape of stress-strain hysteresis loop. The pre-twinning has significant impactsmore » on the twinning-detwinning characteristics and deformation modes during cyclic loading and greatly facilitates the twinning-detwinning activities in plastic deformation. The cyclic straining leads to the increase of contribution of tensile twinning deformation in overall plastic deformation in both the as-received and pre-deformed sample. The mechanisms of load partitioning in different groups of grains are closely related to the deformation modes in each deformation stage, while the fatigue cycling has little influence on the load sharing. The pre-twinning process provides an easy and cost-effective route to improve the low-cycle fatigue life through manufacturing and processing, which would advance the wide application of light-weight wrought Mg alloys as structural materials.« less

Understanding Low-cycle Fatigue Life Improvement Mechanisms in a Pre-twinned Magnesium Alloy

DOE PAGES

Wu, Wei; An, Ke

2015-10-03

The mechanisms of fatigue life improvement by pre-twinning process in a commercial rolled magnesium (Mg) alloy have been investigated using real-time in situ neutron diffraction under a continuous-loading condition. It is found that by introducing the excess twinned grains through pre-compression along the rolling direction the fatigue life was enhanced approximately 50%, mainly resulting from the prolonged detwinning process and inhibited dislocation slip during reverse tension. Moreover, after pre-twinning process, the removal of the rapid strain hardening during reverse tension leads to a compressive mean stress value and more symmetric shape of stress-strain hysteresis loop. The pre-twinning has significant impactsmore » on the twinning-detwinning characteristics and deformation modes during cyclic loading and greatly facilitates the twinning-detwinning activities in plastic deformation. The cyclic straining leads to the increase of contribution of tensile twinning deformation in overall plastic deformation in both the as-received and pre-deformed sample. The mechanisms of load partitioning in different groups of grains are closely related to the deformation modes in each deformation stage, while the fatigue cycling has little influence on the load sharing. The pre-twinning process provides an easy and cost-effective route to improve the low-cycle fatigue life through manufacturing and processing, which would advance the wide application of light-weight wrought Mg alloys as structural materials.« less

Refinement of the crystal structure of the high-temperature phase G0 in (NH4)2WO2F4 (powder, x-ray, and neutron scattering)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Novak, D. M.; Smirnov, Lev S; Kolesnikov, Alexander I

2013-01-01

The (NH4)2WO2F4 compound undergoes a series of phase transitions: G0 -> 201 K -> G1 -> 160 K -> G2, with a significant change in entropy ( S1 ~ Rln10 at the G0 -> G1 transition), which indicates significant orientational disordering in the G0 phase and the order disorder type of the phase transition. X-ray diffraction is used to identify the crystal structure of the G0 phase as rhombohedral (sp. gr. Cmcm, Z = 4), determine the lattice parameters and the positions of all atoms (except hydrogen), and show that [WO2F4]2 ions can form a superposition of dynamic and staticmore » orientational disorders in the anionic sublattice. A determination of the orientational position of [NH4]+ ions calls for the combined method of elastic and inelastic neutron scattering. Inelastic neutron scattering is used to determine the state of hindered rotation for ammonium ions in the G0 phase. Powder neutron diffraction shows that the orientational disorder of NH4 ions can adequately be described within the free rotation approximation.« less

Small-angle neutron scattering study of the short-range organization of dispersed CsNi[Cr(CN){sub 6}] nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ridier, Karl; Gillon, Béatrice; André, Gilles

2015-09-21

Prussian blue analogues magnetic nanoparticles (of radius R{sub 0} = 2.4–8.6 nm) embedded in PVP (polyvinylpyrrolidone) or CTA{sup +} (cetyltrimethylammonium) matrices have been studied using neutron diffraction and small angle neutron scattering (SANS) at several concentrations. For the most diluted particles in neutral PVP, the SANS signal is fully accounted for by a “single-particle” spherical form factor with no structural correlations between the nanoparticles and with radii comparable to those inferred from neutron diffraction. For higher concentration in PVP, structural correlations modify the SANS signal with the appearance of a structure factor peak, which is described using an effective “mean-field” model. A newmore » length scale R{sup * }≈ 3R{sub 0}, corresponding to an effective repulsive interaction radius, is evidenced in PVP samples. In CTA{sup +}, electrostatic interactions play a crucial role and lead to a dense layer of CTA{sup +} around the nanoparticles, which considerably alter the SANS patterns as compared to PVP. The SANS data of nanoparticles in CTA{sup +} are best described by a core-shell model without visible inter-particle structure factor.« less

Single Hit Energy-resolved Laue Diffraction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Patel, Shamim; Suggit, Matthew J.; Stubley, Paul G.

2015-05-15

In situ white light Laue diffraction has been successfully used to interrogate the structure of single crystal materials undergoing rapid (nanosecond) dynamic compression up to megabar pressures. However, information on strain state accessible via this technique is limited, reducing its applicability for a range of applications. We present an extension to the existing Laue diffraction platform in which we record the photon energy of a subset of diffraction peaks. This allows for a measurement of the longitudinal and transverse strains in situ during compression. Consequently, we demonstrate measurement of volumetric compression of the unit cell, in addition to the limitedmore » aspect ratio information accessible in conventional white light Laue. We present preliminary results for silicon, where only an elastic strain is observed. VISAR measurements show the presence of a two wave structure and measurements show that material downstream of the second wave does not contribute to the observed diffraction peaks, supporting the idea that this material may be highly disordered, or has undergone large scale rotation.« less

Debye temperatures and magnetic structures of UFe xAl 12- x (3.6⩽ x⩽5) intermetallic alloys

NASA Astrophysics Data System (ADS)

Rećko, K.; Dobrzyński, L.; Szymański, K.; Hoser, A.

2000-03-01

Uranium ternary compounds UFe xAl 12- x crystallize in a body-centred tetragonal structure ThMn 12 (I 4/mmm No.139). The neutron powder diffraction, magnetization measurements as well as Mössbauer investigations clearly indicate the magnetic ordering within the iron sites. The rearrangement of iron magnetic moments from uncompensated antiferromagnetic system in UFe xAl 12- x with x<4, through coexistence of antiferro- and ferromagnetic iron components (4⩽ x<5) to pure ferromagnetic ordering for alloy with x=5 is observed. The neutron diffraction studies of magnetic structures of the aforementioned powder samples show a very rich world of possible uranium-iron magnetic interactions. For all these alloys the magnetic neutron scattering is generally weak in comparison to the nuclear one. Because of identical chemical and magnetic unit cells there are no pure magnetic reflections. Therefore, in order to extract magnetic part of the scattering one should be particularly careful in taking proper account of the thermal vibration effects.

A neutron-X-ray, NMR and calorimetric study of glassy Probucol synthesized using containerless techniques

NASA Astrophysics Data System (ADS)

Weber, J. K. R.; Benmore, C. J.; Tailor, A. N.; Tumber, S. K.; Neuefeind, J.; Cherry, B.; Yarger, J. L.; Mou, Q.; Weber, W.; Byrn, S. R.

2013-10-01

Acoustic levitation was used to trap 1-3 mm diameter drops of Probucol and other pharmaceutical materials in containerless conditions. Samples were studied in situ using X-ray diffraction and ex situ using neutron diffraction, NMR and DSC techniques. The materials were brought into non-equilibrium states by supersaturating solutions or by supercooling melts. The glass transition and crystallization temperatures of glassy Probucol were 29 ± 1 and 71 ± 1 °C respectively. The glassy form was stable with a shelf life of at least 8 months. A neutron/X-ray difference function of the glass showed that while molecular sub-groups remain rigid, many of the hydrogen correlations observed in the crystal become smeared out in the disordered material. The glass is principally comprised of slightly distorted Form I Probucol molecules with disordered packing rather than large changes in the individual molecular structure. Avoiding surface contact-induced nucleation provided access to highly non-equilibrium phases and enabled synthesis of phase-pure glasses.

Neutron absorption of Al-Si-Mg-B{sub 4}C composite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abdullah, Yusof, E-mail: yusofabd@nuclearmalaysia.gov.my; Yusof, Mohd Reusmaazran; Ibrahim, Anis Syukriah

2016-01-22

Al-Si-Mg-B{sub 4}C composites containing 2-8 wt% of B{sub 4}C were prepared by stir casting technique. Homogenization treatment was carried out at temperatures of 540°C for 4 houra and followed by ageing at 180°C for 2 houra. Microstructure and phase identification were studied by scanning electron microscopy (SEM) and X-ray diffraction (XRD) respectively. Neutron absorption study was investigated using neutron source Am/Be{sup 241}. The result indicated that higher B{sub 4}C content improved the neutron absorption property. Meanwhile homogeneity of the composite was increased by ageing processes. This composite is potential to be used as neutron shielding material especially for nuclear reactormore » application.« less

THE EFFECT OF SATELLITE LINES FROM THE X-RAY SOURCE ON X-RAY DIFFRACTION PEAKS

EPA Science Inventory

The article discusses the development of a method for relating reactivity to crystallite size and strain parameters obtained by the Warren-Averbach technique. EPA has been using crystallite size and strain data obtained from x-ray diffraction (XRD) peak profile analysis to predic...

Determining Individual Phase Flow Properties in a Quench and Partitioning Steel with In Situ High-Energy X-Ray Diffraction and Multiphase Elasto-Plastic Self-Consistent Method

NASA Astrophysics Data System (ADS)

Hu, Xiaohua; Choi, Kyoo Sil; Sun, Xin; Ren, Yang; Wang, Yangdong

2016-12-01

The micromechanical properties of the constituent phases were characterized for advanced high-strength steels (AHSS) produced by a quenching and partitioning (Q&P) process with in situ tensile loading under synchrotron-based, high-energy X-ray diffraction. The constituent phases present are retained austenite and three martensites (tempered, untampered, and freshly formed martensites). For the material investigated, the 200 and 220 lattice strains of the retained austenite phase were calculated by examining the changes of the X-ray diffraction peak positions during deformation. The 200 and 211 lattice strains of the various martensitic phases with similar crystal structures were determined by separating their overlapped diffraction peaks. Apart from tempered and untempered martensite, the diffraction peaks of freshly formed martensite as a result of austenite-to-martensite transformation can also be separated due to a high initial austenite volume fraction. The phase stresses are first estimated with an empirical relationship through the X-ray diffraction elastic constants. A multiphase elasto-plastic self-consistent model is next used for more accurate determination of the constitutive behaviors of the various phases by comparing the predicted lattice strain distributions and global stress-strain curves with the measured ones. The determined constitutive laws will be used for microstructure-based modeling for sheet formability of the Q&P AHSS steel.

Zigzag spin structure in layered honeycomb L i3N i2Sb O6 : A combined diffraction and antiferromagnetic resonance study

NASA Astrophysics Data System (ADS)

Kurbakov, A. I.; Korshunov, A. N.; Podchezertsev, S. Yu.; Malyshev, A. L.; Evstigneeva, M. A.; Damay, F.; Park, J.; Koo, C.; Klingeler, R.; Zvereva, E. A.; Nalbandyan, V. B.

2017-07-01

The magnetic structure of L i3N i2Sb O6 has been determined by low-temperature neutron diffraction, and the crystal structure has been refined by a combination of synchrotron and neutron powder diffraction. The monoclinic (C 2 /m ) symmetry, assigned previously to this pseudohexagonal layered structure, has been unambiguously proven by peak splitting in the synchrotron diffraction pattern. The structure is based on essentially hexagonal honeycomb-ordered N i2Sb O6 layers alternating with L i3 layers, all cations and anions being in an octahedral environment. The compound orders antiferromagnetically below TN=15 K , with the magnetic supercell being a 2 a ×2 b multiple of the crystal cell. The magnetic structure within the honeycomb layer consists of zigzag ferromagnetic spin chains coupled antiferromagnetically. The ordered magnetic moment amounts to 1.62 (2 ) μB/Ni , which is slightly lower than the full theoretical value. Upon cooling below TN, the spins tilt from the c axis, with a maximum tilting angle of 15 .6∘ at T =1.5 K . Our data imply non-negligible ferromagnetic interactions between the honeycomb layers. The observed antiferromagnetic resonance modes are in agreement with the two-sublattice model derived from the neutron data. Orthorhombic anisotropy shows up in zero-field splitting of Δ =198 ±4 and 218 ±4 GHz . Above TN, the electron spin resonance data imply short-range antiferromagnetic order up to about 80 K.

A structural investigation of the alkali metal site distribution within bioactive glass using neutron diffraction and multinuclear solid state NMR.

PubMed

Martin, Richard A; Twyman, Helen L; Rees, Gregory J; Smith, Jodie M; Barney, Emma R; Smith, Mark E; Hanna, John V; Newport, Robert J

2012-09-21

The atomic-scale structure of Bioglass and the effect of substituting lithium for sodium within these glasses have been investigated using neutron diffraction and solid state magic angle spinning (MAS) NMR. Applying an effective isomorphic substitution difference function to the neutron diffraction data has enabled the Na-O and Li-O nearest-neighbour correlations to be isolated from the overlapping Ca-O, O-(P)-O and O-(Si)-O correlations. These results reveal that Na and Li behave in a similar manner within the glassy matrix and do not disrupt the short range order of the network former. Residual differences are attributed solely to the variation in ionic radius between the two species. Successful simplification of the 2 < r (Å) < 3 region via the difference method has enabled all the nearest neighbour correlations to be deconvolved. The diffraction data provides the first direct experimental evidence of split Na-O nearest-neighbour correlations in these melt quench bioactive glasses, and an analogous splitting of the Li-O correlations. The observed correlations are attributed to the metal ions bonded either to bridging or to non-bridging oxygen atoms. (23)Na triple quantum MAS (3QMAS) NMR data corroborates the split Na-O correlations. The structural sites present will be intimately related to the release properties of the glass system in physiological fluids such as plasma and saliva, and hence to the bioactivity of the material. Detailed structural knowledge is therefore a prerequisite for optimizing material design.

The microstructure-processing-property relationships in an aluminum matrix composite system reinforced by aluminum-copper-iron alloy particles

NASA Astrophysics Data System (ADS)

Tang, Fei

Solid state vacuum sintering was studied in tap densified Al powder and in hot quasi-isostatically forged samples composed of commercial inert gas atomized or high purity Al powder, generated by a gas atomization reaction synthesis (GARS) technique. The GARS process results in spherical Al powder with a far thinner surface oxide. The overall results indicated the enhanced ability of GARS-processed Al and Al alloy powders for solid state sintering, which may lead to simplification of current Al powder consolidation processing methods. Elemental Al-based composites reinforced with spherical Al-Cu-Fe alloy powders were produced by quasi-isostatic forging and vacuum hot pressing (VHP) consolidation methods. It was proved that spherical Al-Cu-Fe alloy powders can serve as an effective reinforcement particulate for elemental Al-based composites, because of their high hardness and a preferred type of matrix/reinforcement interfacial bonding, with reduced strain concentration around the particles. Ultimate tensile strength and yield strength of the composites were increased over the corresponding Al matrix values, far beyond typical observations. This remarkable strengthening was achieved without precipitation hardening and without severe strain hardening during consolidation because of the matrix choice (elemental Al) and the "low shear" consolidation methods utilized. This reinforcement effectiveness is further evidenced by elastic modulus measurements of the composites that are very close to the upper bound predictions of the rule of mixtures. The load partitioning measurements by neutron diffraction showed that composite samples made from GARS powders present significantly higher load transfer efficiency than the composites made from commercially atomized powders. Further analysis of the load sharing measurements and the calculated values of the mismatch of coefficient of thermal expansion (CTE) and the geometrically necessary dislocation (GND) effects suggest that these strengthening mechanisms can be combined to predict accurately the strength of the composites. By neutron diffraction measurements, it also was found that the composites consolidated from Al and Al63Cu25Fe12 quasicrystal alloy reinforcement powders have compressive residual stress in the Al matrix, contrary to the tensile residual stress in typical Al/SiC composites. The composites made by the quasi-isostatic forging process exhibited higher tensile strengths and much higher compressive residual stresses than the composites made by the VHP process.

Vectorial strain gauge method using single flexible orthogonal polydimethylsiloxane gratings

NASA Astrophysics Data System (ADS)

Guo, Hao; Tang, Jun; Qian, Kun; Tsoukalas, Dimitris; Zhao, Miaomiao; Yang, Jiangtao; Zhang, Binzhen; Chou, Xiujian; Liu, Jun; Xue, Chenyang; Zhang, Wendong

2016-03-01

A vectorial strain gauge method using a single sensing element is reported based on the double-sided polydimethylsiloxane (PDMS) Fraunhofer diffraction gratings structures. Using O2 plasma treatment steps, orthogonal wrinkled gratings were fabricated on both sides of a pre-strained PDMS film. Diffracted laser spots from this structure have been used to experimentally demonstrate, that any applied strain can be quantitatively characterized in both the x and y directions with an error of less than 0.6% and with a gauge factor of approximately 10. This simple and low cost technology which is completely different from the traditional vectorial strain gauge method, can be applied to surface vectorial strain measurement and multi-axis integrated mechanical sensors.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kalsi, Deepti; Rayaprol, S.; Siruguri, V.

We report the crystallographic properties of RE{sub 2}NiGe{sub 3} (RE=La, Ce) synthesized by arc melting. Rietveld refinement on the powder neutron diffraction (ND) data suggest both compounds are isostructural and crystallize in the non-centrosymmetric Er{sub 2}RhSi{sub 3} type structure having hexagonal space group P6{sup ¯}2c. In the crystal structure of RE{sub 2}NiGe{sub 3}, two dimensional arrangements of nickel and germanium atoms lead to the formation of hexagonal layers with rare earth atoms sandwiched between them. Magnetic susceptibility measurements performed in low fields exhibit antiferromagnetic ordering in cerium compound around (T{sub o}=) 3.2 K. Neutron diffraction measurements at 2.8 K (i.e.,more » at T« less

Neutron scattering investigation of a macroscopic single crystal of a lyotropic Lα phase

NASA Astrophysics Data System (ADS)

Goecking, K. D.; Monkenbusch, M.

1998-07-01

Water-rich lamellar samples of the quaternary microemulsion SDS-pentanol-water-dodecane have been prepared in form of 1 mm×10 mm×20 mm macroscopic mono domains. The shape is given by the quartz cuvette containing the sample, the layer planes are parallel to the cuvette walls. Diffraction patterns and "rocking curves" have been obtained by neutron diffraction using a triple-axis spectrometer. Three "pseudo-Bragg peaks" have been observed, their (relative) intensities yield a new experimental access to estimate the product of the elastic constants η-2 propto Bκ resulting in a lower value than obtained from synchrotron investigation using peak shape fitting (Roux D. et al., Micelles, Membranes, Microemulsions and Monolayers (Springer, New York, Berlin) 1994).

The magnetic order of GdMn₂Ge₂ studied by neutron diffraction and x-ray resonant magnetic scattering.

PubMed

Granovsky, S A; Kreyssig, A; Doerr, M; Ritter, C; Dudzik, E; Feyerherm, R; Canfield, P C; Loewenhaupt, M

2010-06-09

The magnetic structure of GdMn₂Ge₂ (tetragonal I4/mmm) has been studied by hot neutron powder diffraction and x-ray resonant magnetic scattering techniques. These measurements, along with the results of bulk experiments, confirm the collinear ferrimagnetic structure with moment direction parallel to the c-axis below T(C) = 96 K and the collinear antiferromagnetic phase in the temperature region T(C) < T < T(N) = 365 K. In the antiferromagnetic phase, x-ray resonant magnetic scattering has been detected at Mn K and Gd L₂ absorption edges. The Gd contribution is a result of an induced Gd 5d electron polarization caused by the antiferromagnetic order of Mn-moments.

Preliminary neutron diffraction analysis of challenging human manganese superoxide dismutase crystals

DOE PAGES

Azadmanesh, Jahaun; Trickel, Scott R.; Weiss, Kevin L.; ...

2017-03-29

Superoxide dismutases (SODs) are enzymes that protect against oxidative stress by dismutation of superoxide into oxygen and hydrogen peroxide through cyclic reduction and oxidation of the active-site metal. The complete enzymatic mechanisms of SODs are unknown since data on the positions of hydrogen are limited. Here, we present, methods for large crystal growth and neutron data collection of human manganese SOD (MnSOD) using perdeuteration and the MaNDi beamline at Oak Ridge National Laboratory. Furthermore, The crystal from which the human MnSOD data set was obtained is the crystal with the largest unit-cell edge (240 Å) from which data have beenmore » collectedvianeutron diffraction to sufficient resolution (2.30 Å) where hydrogen positions can be observed.« less

Preliminary neutron diffraction analysis of challenging human manganese superoxide dismutase crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Azadmanesh, Jahaun; Trickel, Scott R.; Weiss, Kevin L.

Superoxide dismutases (SODs) are enzymes that protect against oxidative stress by dismutation of superoxide into oxygen and hydrogen peroxide through cyclic reduction and oxidation of the active-site metal. The complete enzymatic mechanisms of SODs are unknown since data on the positions of hydrogen are limited. Here, we present, methods for large crystal growth and neutron data collection of human manganese SOD (MnSOD) using perdeuteration and the MaNDi beamline at Oak Ridge National Laboratory. Furthermore, The crystal from which the human MnSOD data set was obtained is the crystal with the largest unit-cell edge (240 Å) from which data have beenmore » collectedvianeutron diffraction to sufficient resolution (2.30 Å) where hydrogen positions can be observed.« less

In situ neutron scattering study of nanoscale phase evolution in PbTe-PbS thermoelectric material

DOE PAGES

Ren, Fei; Schmidt, Robert; Keum, Jong K.; ...

2016-08-24

Introducing nanostructural second phases has been proved to be an effective approach to reduce the lattice thermal conductivity and thus enhance the figure of merit for many thermoelectric materials. Furthermore studies of the formation and evolution of these second phases are central to understanding temperature dependent material behavior, improving thermal stabilities, as well as designing new materials. We examined powder samples of PbTe-PbS thermoelectric material using in situ neutron diffraction and small angle neutron scattering (SANS) techniques from room temperature to elevated temperature up to 663 K, to explore quantitative information on the structure, weight fraction, and size of themore » second phase. Neutron diffraction data showed the as-milled powder was primarily solid solution before heat treatment. During heating, PbS second phase precipitated out of the PbTe matrix around 480 K, while re-dissolution started around 570 K. The second phase remained separated from the matrix upon cooling. Furthermore, SANS data indicated there are two populations of nanostructures. The size of the smaller nanostructure increased from initially 5 nm to approximately 25 nm after annealing at 650 K, while the size of the larger nanostructure remained unchanged. Our study demonstrated that in situ neutron techniques are effective means to obtain quantitative information to study temperature dependent nanostructural behavior of thermoelectrics and likely other high-temperature materials.« less

Neutron diffraction studies of viral fusion peptides

NASA Astrophysics Data System (ADS)

Bradshaw, Jeremy P.; J. M. Darkes, Malcolm; Katsaras, John; Epand, Richard M.

2000-03-01

Membrane fusion plays a vital role in a large and diverse number of essential biological processes. Despite this fact, the precise molecular events that occur during fusion are still not known. We are currently engaged on a study of membrane fusion as mediated by viral fusion peptides. These peptides are the N-terminal regions of certain viral envelope proteins that mediate the process of fusion between the viral envelope and the membranes of the host cell during the infection process. As part of this study, we have carried out neutron diffraction measurements at the ILL, BeNSC and Chalk River, on a range of viral fusion peptides. The peptides, from simian immunodeficiency virus (SIV), influenza A and feline leukaemia virus (FeLV), were incorporated into stacked phospholipid bilayers. Some of the peptides had been specifically deuterated at key amino acids. Lamellar diffraction data were collected and analysed to yield information on the peptide conformation, location and orientation relative to the bilayer.

Neutron diffraction study of a non-strichiometric Ni-Mn-Ga MSM alloy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ari-Gur, Pnina; Garlea, Vasile O

2013-01-01

The structure and chemical order of a Heusler alloy of non-stoichiometric composition Ni-Mn-Ga were studied using constant-wavelength (1.538 ) neutron diffraction at 363K and the diffraction pattern was refined using the FullProf software. At this temperature the structure is austenite (cubic) with Fm-3m space group and lattice constant of a = 5.83913(4) [ ]. The chemical order is of critical importance in these alloys, as Mn becomes antiferromagnetic when the atoms are closer than the radius of the 3d shell. In the studied alloy the refinement of the site occupancy showed that the 4b (Ga site) contained as much asmore » 22% Mn; that significantly alters the distances between the Mn atoms in the crystal and, as a result, also the exchange energy between some of the Mn atoms. Based on the refinement, the composition was determined to be Ni1.91Mn1.29Ga0.8« less

Structure of Nano-sized CeO 2 Materials: Combined Scattering and Spectroscopic Investigations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marchbank, Huw R.; Clark, Adam H.; Hyde, Timothy I.

Here, the nature of nano-sized ceria, CeO 2, systems were investigated using neutron and X-ray diffraction and X-ray absorption spectroscopy. Whilst both diffraction andtotal pair distribution functions (PDFs) revealed that in all the samples the occupancy of both Ce 4+ and O 2- are very close to the ideal stoichiometry, the analysis using reverse Monte Carlo technique revealedsignificant disorder around oxygen atoms in the nano sized ceria samples in comparison to the highly crystalline NIST standard.In addition, the analysis reveal that the main differences observed in the pair correlations from various X-ray and neutron diffraction techniques were attributed to themore » particle size of the CeO 2 prepared by the reported three methods. Furthermore, detailed analysis of the Ce L 3– and K-edge EXAFS data support this finding; in particular the decrease in higher shell coordination numbers with respect to the NIST standard, are attributed to differences in particle size.« less

Structure of Nano-sized CeO 2 Materials: Combined Scattering and Spectroscopic Investigations

DOE PAGES

Marchbank, Huw R.; Clark, Adam H.; Hyde, Timothy I.; ...

2016-08-29

Here, the nature of nano-sized ceria, CeO 2, systems were investigated using neutron and X-ray diffraction and X-ray absorption spectroscopy. Whilst both diffraction andtotal pair distribution functions (PDFs) revealed that in all the samples the occupancy of both Ce 4+ and O 2- are very close to the ideal stoichiometry, the analysis using reverse Monte Carlo technique revealedsignificant disorder around oxygen atoms in the nano sized ceria samples in comparison to the highly crystalline NIST standard.In addition, the analysis reveal that the main differences observed in the pair correlations from various X-ray and neutron diffraction techniques were attributed to themore » particle size of the CeO 2 prepared by the reported three methods. Furthermore, detailed analysis of the Ce L 3– and K-edge EXAFS data support this finding; in particular the decrease in higher shell coordination numbers with respect to the NIST standard, are attributed to differences in particle size.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ari-Gur, Pnina; Garlea, Vasile O.; Cao, Huibo

In this study, Heusler alloys of Ni-Mn-Ga compositions demonstrate ferromagnetic shape memory effect in the martensitic state. The transformation temperature and the chemical order depend strongly on the composition. In the current work, the structure and chemical order of the martensitic phase of Ni 1.91Mn 1.29Ga 0.8 were studied using neutron diffraction; the diffraction pattern was refined using the FullProf software. It was determined that the structural transition occurs around 330 K. At room temperature, 300 K, which is below the martensite transformation temperature, all the Bragg reflections can be described by a monoclinic lattice with a symmetry of spacemore » group P 1 2/m 1 and lattice constants of a = 4.23047(7) [Å], b = 5.58333(6) [Å], c = 21.0179(2) [Å], beta = 90.328(1). The chemical order is of critical importance in these alloys, and it was previously studied at 363 K. Analysis of the neutron diffraction in the monoclinic phase shows that the chemical order is maintained during the martensitic transformation.« less

Diffraction Studies of the Atomic Vibrations of Bulk and Surface Atoms in the Reciprocal and Real Spaces of Nanocrystalline SiC

NASA Technical Reports Server (NTRS)

Stelmakh, S.; Grzanka, E.; Weber, H.-P.; Vogel, S.; Palosz, B.; Palosz, B.

2004-01-01

To describe and evaluate the vibrational properties of nanoparticles it is necessary to distinguish between the surface and the core of the particles. Theoretical calculations show that vibrational density of states of the inner atoms of nanograins is similar to bulk material but shifted to higher energies which can be explained by the fact that the gain core is stressed (hardened) due to the presence of internal pressure. Theoretical calculations also show that there is a difference between vibrational properties of a crystal lattice of the grain interior in isolated particles and in a dense (sintered) nanocrystalline material. This is probably due to a coupling of the modes inside the grains via the grain boundaries in dense nanocrystalline bodies. We examined strains present in the surface shell based on examination of diamond and Sic nanocrystals in reciprocal (Bragg-type scattering) and real (PDF analysis) space analysis of neutron diffraction data. Recently we examined the atomic thermal motions in nanocrystalline Sic based on the assumption of a simple Einstein model for uncorrelated atomic notions. According to this model, the Bragg intensity is attenuated as a function of scattering angle by the Debye-Waller factor. Based on this assumption overall temperature factors were determined from the Wilson plots.

Development of a Neural Network Simulator for Studying the Constitutive Behavior of Structural Composite Materials

DOE PAGES

Na, Hyuntae; Lee, Seung-Yub; Üstündag, Ersan; ...

2013-01-01

This paper introduces a recent development and application of a noncommercial artificial neural network (ANN) simulator with graphical user interface (GUI) to assist in rapid data modeling and analysis in the engineering diffraction field. The real-time network training/simulation monitoring tool has been customized for the study of constitutive behavior of engineering materials, and it has improved data mining and forecasting capabilities of neural networks. This software has been used to train and simulate the finite element modeling (FEM) data for a fiber composite system, both forward and inverse. The forward neural network simulation precisely reduplicates FEM results several orders ofmore » magnitude faster than the slow original FEM. The inverse simulation is more challenging; yet, material parameters can be meaningfully determined with the aid of parameter sensitivity information. The simulator GUI also reveals that output node size for materials parameter and input normalization method for strain data are critical train conditions in inverse network. The successful use of ANN modeling and simulator GUI has been validated through engineering neutron diffraction experimental data by determining constitutive laws of the real fiber composite materials via a mathematically rigorous and physically meaningful parameter search process, once the networks are successfully trained from the FEM database.« less

Design and Characterisation of Metallic Glassy Alloys of High Neutron Shielding Capability

NASA Astrophysics Data System (ADS)

Khong, J. C.; Daisenberger, D.; Burca, G.; Kockelmann, W.; Tremsin, A. S.; Mi, J.

2016-11-01

This paper reports the design, making and characterisation of a series of Fe-based bulk metallic glass alloys with the aim of achieving the combined properties of high neutron absorption capability and sufficient glass forming ability. Synchrotron X-ray diffraction and pair distribution function methods were used to characterise the crystalline or amorphous states of the samples. Neutron transmission and macroscopic attenuation coefficients of the designed alloys were measured using energy resolved neutron imaging method and the very recently developed microchannel plate detector. The study found that the newly designed alloy (Fe48Cr15Mo14C15B6Gd2 with a glass forming ability of Ø5.8 mm) has the highest neutron absorption capability among all Fe-based bulk metallic glasses so far reported. It is a promising material for neutron shielding applications.

Design and Characterisation of Metallic Glassy Alloys of High Neutron Shielding Capability.

PubMed

Khong, J C; Daisenberger, D; Burca, G; Kockelmann, W; Tremsin, A S; Mi, J

2016-11-16

This paper reports the design, making and characterisation of a series of Fe-based bulk metallic glass alloys with the aim of achieving the combined properties of high neutron absorption capability and sufficient glass forming ability. Synchrotron X-ray diffraction and pair distribution function methods were used to characterise the crystalline or amorphous states of the samples. Neutron transmission and macroscopic attenuation coefficients of the designed alloys were measured using energy resolved neutron imaging method and the very recently developed microchannel plate detector. The study found that the newly designed alloy (Fe 48 Cr 15 Mo 14 C 15 B 6 Gd 2 with a glass forming ability of Ø5.8 mm) has the highest neutron absorption capability among all Fe-based bulk metallic glasses so far reported. It is a promising material for neutron shielding applications.

Suppression of magnetic order in CaCo 1.86 As 2 with Fe substitution: Magnetization, neutron diffraction, and x-ray diffraction studies of Ca ( Co 1 – x Fe x ) y As 2

DOE PAGES

Jayasekara, W. T.; Pandey, Abhishek; Kreyssig, A.; ...

2017-02-23

Magnetization, neutron diffraction, and high-energy x-ray diffraction results for Sn-flux grown single-crystal samples of Ca(Co 1–xFe x) yAs 2, 0 ≤ x ≤ 1, 1.86 ≤ y ≤ 2, are presented and reveal that A-type antiferromagnetic order, with ordered moments lying along the c axis, persists for x ≲ 0.12(1). The antiferromagnetic order is smoothly suppressed with increasing x, with both the ordered moment and Néel temperature linearly decreasing. Stripe-type antiferromagnetic order does not occur for x ≤ 0.25, nor does ferromagnetic order for x up to at least x = 0.104, and a smooth crossover from the collapsed-tetragonal (cT)more » phase of CaCo 1.86As 2 to the tetragonal (T) phase of CaFe 2As 2 occurs. Furthermore, these results suggest that hole doping CaCo 1.86As 2 has a less dramatic effect on the magnetism and structure than steric effects due to substituting Sr for Ca.« less

Suppression of magnetic order in CaCo 1.86 As 2 with Fe substitution: Magnetization, neutron diffraction, and x-ray diffraction studies of Ca ( Co 1 – x Fe x ) y As 2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jayasekara, W. T.; Pandey, Abhishek; Kreyssig, A.

Magnetization, neutron diffraction, and high-energy x-ray diffraction results for Sn-flux grown single-crystal samples of Ca(Co 1–xFe x) yAs 2, 0 ≤ x ≤ 1, 1.86 ≤ y ≤ 2, are presented and reveal that A-type antiferromagnetic order, with ordered moments lying along the c axis, persists for x ≲ 0.12(1). The antiferromagnetic order is smoothly suppressed with increasing x, with both the ordered moment and Néel temperature linearly decreasing. Stripe-type antiferromagnetic order does not occur for x ≤ 0.25, nor does ferromagnetic order for x up to at least x = 0.104, and a smooth crossover from the collapsed-tetragonal (cT)more » phase of CaCo 1.86As 2 to the tetragonal (T) phase of CaFe 2As 2 occurs. Furthermore, these results suggest that hole doping CaCo 1.86As 2 has a less dramatic effect on the magnetism and structure than steric effects due to substituting Sr for Ca.« less

Precision determination of absolute neutron flux

DOE PAGES

Yue, A. T.; Anderson, E. S.; Dewey, M. S.; ...

2018-06-08

A technique for establishing the total neutron rate of a highly-collimated monochromatic cold neutron beam was demonstrated using an alpha–gamma counter. The method involves only the counting of measured rates and is independent of neutron cross sections, decay chain branching ratios, and neutron beam energy. For the measurement, a target of 10B-enriched boron carbide totally absorbed the neutrons in a monochromatic beam, and the rate of absorbed neutrons was determined by counting 478 keV gamma rays from neutron capture on 10B with calibrated high-purity germanium detectors. A second measurement based on Bragg diffraction from a perfect silicon crystal was performedmore » to determine the mean de Broglie wavelength of the beam to a precision of 0.024%. With these measurements, the detection efficiency of a neutron monitor based on neutron absorption on 6Li was determined to an overall uncertainty of 0.058%. We discuss the principle of the alpha–gamma method and present details of how the measurement was performed including the systematic effects. We further describe how this method may be used for applications in neutron dosimetry and metrology, fundamental neutron physics, and neutron cross section measurements.« less

Precision determination of absolute neutron flux

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yue, A. T.; Anderson, E. S.; Dewey, M. S.

A technique for establishing the total neutron rate of a highly-collimated monochromatic cold neutron beam was demonstrated using an alpha–gamma counter. The method involves only the counting of measured rates and is independent of neutron cross sections, decay chain branching ratios, and neutron beam energy. For the measurement, a target of 10B-enriched boron carbide totally absorbed the neutrons in a monochromatic beam, and the rate of absorbed neutrons was determined by counting 478 keV gamma rays from neutron capture on 10B with calibrated high-purity germanium detectors. A second measurement based on Bragg diffraction from a perfect silicon crystal was performedmore » to determine the mean de Broglie wavelength of the beam to a precision of 0.024%. With these measurements, the detection efficiency of a neutron monitor based on neutron absorption on 6Li was determined to an overall uncertainty of 0.058%. We discuss the principle of the alpha–gamma method and present details of how the measurement was performed including the systematic effects. We further describe how this method may be used for applications in neutron dosimetry and metrology, fundamental neutron physics, and neutron cross section measurements.« less

Hard X-ray polarizer to enable simultaneous three-dimensional nanoscale imaging of magnetic structure and lattice strain

DOE PAGES

Logan, Jonathan; Harder, Ross; Li, Luxi; ...

2016-01-01

Recent progress in the development of dichroic Bragg coherent diffractive imaging, a new technique for simultaneous three-dimensional imaging of strain and magnetization at the nanoscale, is reported. This progress includes the installation of a diamond X-ray phase retarder at beamline 34-ID-C of the Advanced Photon Source. Here, the performance of the phase retarder for tuning X-ray polarization is demonstrated with temperature-dependent X-ray magnetic circular dichroism measurements on a gadolinium foil in transmission and on a Gd 5Si 2Ge 2crystal in diffraction geometry with a partially coherent, focused X-ray beam. Feasibility tests for dichroic Bragg coherent diffractive imaging are presented. Thesemore » tests include (1) using conventional Bragg coherent diffractive imaging to determine whether the phase retarder introduces aberrations using a nonmagnetic gold nanocrystal as a control sample, and (2) collecting coherent diffraction patterns of a magnetic Gd 5Si 2Ge 2nanocrystal with left- and right-circularly polarized X-rays. Future applications of dichroic Bragg coherent diffractive imaging for the correlation of strain and lattice defects with magnetic ordering and inhomogeneities are considered.« less

Diffraction contrast near heterostructure boundaries--its nature and its application.

PubMed

Bangert, U; Harvey, A J

1993-03-01

Two phenomena of diffraction contrast arising at or near III-V compound heterostructure boundaries are described and quantitatively analyzed. In the first observation alpha/delta-fringe contrast at boundaries inclined to the electron beam is discussed. Theoretical fringe profiles are generated according to the theory by Gevers et al. in 1964, which are then compared with experimental profiles. Applications to the characterization of AlGaAs/GaAs and InGaAsP/InP interfaces regarding composition, abruptness, and lattice tilt are presented. In the second study a new and very sensitive characterization technique for the direct determination of the strain in strained-layer structures is described. The method uses electron microscope images of 90 degrees-wedges, which exhibit a shift in the thickness contours due to strain relaxation at the edge, and compares these to images which are obtained theoretically by implementing finite element strain calculations in wedges in the dynamical theory of diffraction contrast. The considerable potential of this method is demonstrated on the strain analysis of strained GaInAs/GaAs structures.

Coherent X-ray diffraction imaging and characterization of strain in silicon-on-insulator nanostructures

DOE PAGES

Xiong, Gang; Moutanabbir, Oussama; Reiche, Manfred; ...

2014-12-06

Coherent X-ray diffraction imaging (CDI) has emerged in the last decade as a promising high resolution lens-less imaging approach for the characterization of various samples. It has made significant technical progress through developments in source, algorithm and imaging methodologies thus enabling important scientific breakthroughs in a broad range of disciplines. In this report, we will introduce the principles of forward scattering CDI and Bragg geometry CDI (BCDI), with an emphasis on the latter. BCDI exploits the ultra-high sensitivity of the diffraction pattern to the distortions of crystalline lattice. Its ability of imaging strain on the nanometer scale in three dimensionsmore » is highly novel. In this study, we will present the latest progress on the application of BCDI in investigating the strain relaxation behavior in nanoscale patterned strained silicon-on-insulator (sSOI) materials, aiming to understand and engineer strain for the design and implementation of new generation semiconductor devices.« less

Coherent X-ray diffraction imaging and characterization of strain in silicon-on-insulator nanostructures.

PubMed

Xiong, Gang; Moutanabbir, Oussama; Reiche, Manfred; Harder, Ross; Robinson, Ian

2014-12-10

Coherent X-ray diffraction imaging (CDI) has emerged in the last decade as a promising high resolution lens-less imaging approach for the characterization of various samples. It has made significant technical progress through developments in source, algorithm and imaging methodologies thus enabling important scientific breakthroughs in a broad range of disciplines. In this report, we will introduce the principles of forward scattering CDI and Bragg geometry CDI (BCDI), with an emphasis on the latter. BCDI exploits the ultra-high sensitivity of the diffraction pattern to the distortions of crystalline lattice. Its ability of imaging strain on the nanometer scale in three dimensions is highly novel. We will present the latest progress on the application of BCDI in investigating the strain relaxation behavior in nanoscale patterned strained silicon-on-insulator (sSOI) materials, aiming to understand and engineer strain for the design and implementation of new generation semiconductor devices. © 2014 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

TRACE ELEMENT DISTRIBUTION IN SEDIMENTS OF THE MID-ATLANTIC RIDGE.

DTIC Science & Technology

MARINE GEOLOGY, ATLANTIC OCEAN), (*OCEAN BOTTOM, MINERALS), SEDIMENTATION, IRON, COBALT, MANGANESE, STRONTIUM, CHLORITES, NEUTRON ACTIVATION, GEOCHEMISTRY, CALCITE , CARBONATES, X RAY DIFFRACTION, CLAY MINERALS, THESES

Using Neutron Diffraction to Determine the Low-Temperature Behavior of Pb2+ in Lead Feldspar

NASA Astrophysics Data System (ADS)

Kolbus, L. M.; Anovitz, L. M.; Chakoumackos, B. C.; Wesolowski, D. J.

2014-12-01

Feldspar minerals comprise 60% of the Earth's crust, so it imperative that the properties of feldspar be well understood for seismic modeling. The structure of feldspar consists of a three-dimensional framework of strongly-bonded TO4 tetrahedra formed by the sharing of oxygen atoms between tetrahedra. The main solid solution series found in natural feldspars are alkali NaAlSi3O8 -KAlSi3O8 and plagioclase CaAl2Si2O8-NaAlSi3O8. Recently, efforts have been made to systematically quantify feldspars structural change at non-ambient temperatures by considering only the relative tilts of the tetrahedral framework [1]. This serves as a tool to predict various behaviors of the structure such as the relative anisotropy of unit cell parameters and volume evolution with composition and temperature. Monoclinic feldspars are well predicted by the model [1], but discrepancies still remain between the model predictions and real structures with respect to absolute values of the unit cell parameters. To improve the existing model, a modification must be made to account for the M-cation interaction with its surrounding oxygen atoms. We have, therefore, chosen to study the structure of Pb-feldspar (PbAl2Si2O8), which provides the opportunity to characterize a monoclinic Al2Si2 feldspar containing a large M-site divalent cation using neutron diffraction. Neutron diffraction allows for the characterization of the M-site cation interaction between the oxygen atoms in the polyhedral cage by providing information to accurately determine the atomic displacement parameters.. Lead feldspar was synthesized for this study using the method described in [2], and confirmed to have a monoclinic C2/m space group. In this talk we will present structural determinations and atomic displacement parameters of Pb-feldspar from 10 - 300K generated from Neutron diffraction at the POWGEN beamline at the Spallation Neutron Source at Oak Ridge National lab, and compare our results to those predicted by the tetrahedral tilting model. [1] Angel, R.J. Ross, N.L, Zhao, J, Sochalski-Kolbus, L., Kruger, H., Schmidt, B.C. (2013) European Journal of Mineralogy, 25: 597-614. [2] Benna, P., Tribaudino, M., Bruno, E. (1996) American Mineralogist, 81: 1337-1343.

Aerodynamic laser-heated contactless furnace for neutron scattering experiments at elevated temperatures

NASA Astrophysics Data System (ADS)

Landron, Claude; Hennet, Louis; Coutures, Jean-Pierre; Jenkins, Tudor; Alétru, Chantal; Greaves, Neville; Soper, Alan; Derbyshire, Gareth

2000-04-01

Conventional radiative furnaces require sample containment that encourages contamination at elevated temperatures and generally need windows which restrict the entrance and exit solid angles required for diffraction and scattering measurements. We describe a contactless windowless furnace based on aerodynamic levitation and laser heating which has been designed for high temperature neutron scattering experiments. Data from initial experiments are reported for crystalline and amorphous oxides at temperatures up to 1900 °C, using the spallation neutron source ISIS together with our laser-heated aerodynamic levitator. Accurate reproduction of thermal expansion coefficients and radial distribution functions have been obtained, demonstrating the utility of aerodynamic levitation methods for neutron scattering methods.

Neutron and positron techniques for fluid transfer system analysis and remote temperature and stress measurement

NASA Astrophysics Data System (ADS)

Stewart, P. A. E.

1987-05-01

Present and projected applications of penetrating radiation techniques to gas turbine research and development are considered. Approaches discussed include the visualization and measurement of metal component movement using high energy X-rays, the measurement of metal temperatures using epithermal neutrons, the measurement of metal stresses using thermal neutron diffraction, and the visualization and measurement of oil and fuel systems using either cold neutron radiography or emitting isotope tomography. By selecting the radiation appropriate to the problem, the desired data can be probed for and obtained through imaging or signal acquisition, and the necessary information can then be extracted with digital image processing or knowledge based image manipulation and pattern recognition.

In operando X-ray diffraction strain measurement in Ni3Sn2 - Coated inverse opal nanoscaffold anodes for Li-ion batteries

NASA Astrophysics Data System (ADS)

Glazer, Matthew P. B.; Wang, Junjie; Cho, Jiung; Almer, Jonathan D.; Okasinski, John S.; Braun, Paul V.; Dunand, David C.

2017-11-01

Volume changes associated with the (de)lithiation of a nanostructured Ni3Sn2 coated nickel inverse opal scaffold anode create mismatch stresses and strains between the Ni3Sn2 anode material and its mechanically supporting Ni scaffold. Using in operando synchrotron x-ray diffraction measurements, elastic strains in the Ni scaffold are determined during cyclic (dis)charging of the Ni3Sn2 anode. These strains are characterized using both the center position of the Ni diffraction peaks, to quantify the average strain, and the peak breadth, which describes the distribution of strain in the measured volume. Upon lithiation (half-cell discharging) or delithiation (half-cell charging), compressive strains and peak breadth linearly increase or decrease, respectively, with charge. The evolution of the average strains and peak breadths suggests that some irreversible plastic deformation and/or delamination occurs during cycling, which can result in capacity fade in the anode. The strain behavior associated with cycling of the Ni3Sn2 anode is similar to that observed in recent studies on a Ni inverse-opal supported amorphous Si anode and demonstrates that the (de)lithiation-induced deformation and damage mechanisms are likely equivalent in both anodes, even though the magnitude of mismatch strain in the Ni3Sn2 is lower due to the lower (de)lithiation-induced contraction/expansion.

CO 2 Sorption to Subsingle Hydration Layer Montmorillonite Clay Studied by Excess Sorption and Neutron Diffraction Measurements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rother, Gernot; Ilton, Eugene S.; Wallacher, Dirk

2013-01-02

Geologic storage of CO 2 requires that the caprock sealing the storage rock is highly impermeable to CO 2. Swelling clays, which are important components of caprocks, may interact with CO 2 leading to volume change and potentially impacting the seal quality. The interactions of supercritical (sc) CO 2 with Na saturated montmorillonite clay containing a subsingle layer of water in the interlayer region have been studied by sorption and neutron diffraction techniques. The excess sorption isotherms show maxima at bulk CO2 densities of ≈0.15 g/cm 3, followed by an approximately linear decrease of excess sorption to zero and negativemore » values with increasing CO 2 bulk density. Neutron diffraction experiments on the same clay sample measured interlayer spacing and composition. The results show that limited amounts of CO 2 are sorbed into the interlayer region, leading to depression of the interlayer peak intensity and an increase of the d(001) spacing by ca. 0.5 Å. The density of CO 2 in the clay pores is relatively stable over a wide range of CO 2 pressures at a given temperature, indicating the formation of a clay-CO 2 phase. Finally, at the excess sorption maximum, increasing CO 2 sorption with decreasing temperature is observed while the high-pressure sorption properties exhibit weak temperature dependence.« less

On the crystal structure of Cr2N precipitates in high-nitrogen austenitic stainless steel. III. Neutron diffraction study on the ordered Cr2N superstructure.

PubMed

Lee, Tae-Ho; Kim, Sung-Joon; Shin, Eunjoo; Takaki, Setsuo

2006-12-01

The ordered structure of Cr(2)N precipitates in high-nitrogen austenitic steel was investigated utilizing high-resolution neutron powder diffractometry (HRPD). On the basis of the Rietveld refinement of neutron diffraction patterns, the ordered Cr2N superstructure was confirmed to be trigonal (space group P31m), with lattice parameters a=4.800 (4) and c=4.472 (5) A, as suggested in previous transmission electron microscopy studies [Lee, Oh, Han, Lee, Kim & Takaki (2005). Acta Cryst. B61, 137-144; Lee, Kim & Takaki (2006). Acta Cryst. B62, 190-196]. The occupancies of the N atoms in four crystallographic sites [1(a), 1(b), 2(d) and 2(c) Wyckoff sites] were determined to be 1.00 (5), 0.0, 0.74 (9) and 0.12 (3), respectively, reflecting a partial disordering of N atoms along the c axis. The position of the metal atom was specified to be x=0.346 (8) and z=0.244 (6), corresponding to a deviation from the ideal position (x=0.333 and z=0.250). This deviation caused the ((1/3 1/3)(0))-type superlattice reflection to appear. A comparison between the ideal and measured crystal structures of Cr2N was performed using a computer simulation of selected-area diffraction patterns.

Phase diagram of multiferroic KCu3As2O7(OD ) 3

NASA Astrophysics Data System (ADS)

Nilsen, Gøran J.; Simonet, Virginie; Colin, Claire V.; Okuma, Ryutaro; Okamoto, Yoshihiko; Tokunaga, Masashi; Hansen, Thomas C.; Khalyavin, Dmitry D.; Hiroi, Zenji

2017-06-01

The layered compound KCu3As2O7(OD ) 3 , comprising distorted kagome planes of S =1 /2 Cu2 + ions, is a recent addition to the family of type-II multiferroics. Previous zero-field neutron diffraction work has found two helically ordered regimes in KCu3As2O7(OD ) 3 , each showing a distinct coupling between the magnetic and ferroelectric order parameters. Here, we extend this work to magnetic fields up to 20 T using neutron powder diffraction, capacitance, polarization, and high-field magnetization measurements, hence determining the H -T phase diagram. We find metamagnetic transitions in both low-temperature phases around μ0Hc˜3.7 T, which neutron powder diffraction reveals to correspond to rotations of the helix plane away from the easy plane, as well as a small change in the propagation vector. Furthermore, we show that the sign of the ferroelectric polarization is reversible in a magnetic field, although no change is observed (or expected on the basis of the magnetic structure) due to the transition at 3.7 T. We finally justify the temperature dependence of the polarization in both zero-field ordered phases by a symmetry analysis of the free energy expansion, and attempt to account for the metamagnetic transition by adding anisotropic exchange interactions to our existing model for KCu3As2O7(OD ) 3 .

Neutron diffraction study and theoretical analysis of the antiferromagnetic order and the diffuse scattering in the layered kagome system CaBaCo2Fe2O7

NASA Astrophysics Data System (ADS)

Reim, J. D.; Rosén, E.; Zaharko, O.; Mostovoy, M.; Robert, J.; Valldor, M.; Schweika, W.

2018-04-01

The hexagonal swedenborgite, CaBaCo2Fe2O7 , is a chiral frustrated antiferromagnet, in which magnetic ions form alternating kagome and triangular layers. We observe a long-range √{3 }×√{3 } antiferromagnetic order setting in below TN=160 K by neutron diffraction on single crystals of CaBaCo2Fe2O7 . Both magnetization and polarized neutron single crystal diffraction measurements show that close to TN spins lie predominantly in the a b plane, while upon cooling the spin structure becomes increasingly canted due to Dzyaloshinskii-Moriya interactions. The ordered structure can be described and refined within the magnetic space group P 31 m' . Diffuse scattering between the magnetic peaks reveals that the spin order is partial. Monte Carlo simulations based on a Heisenberg model with two nearest-neighbor exchange interactions show a similar diffuse scattering and coexistence of the √{3 }×√{3 } order with disorder. The coexistence can be explained by the freedom to vary spins without affecting the long-range order, which gives rise to ground-state degeneracy. Polarization analysis of the magnetic peaks indicates the presence of long-period cycloidal spin correlations resulting from the broken inversion symmetry of the lattice, in agreement with our symmetry analysis.

Mott localization in a pure stripe antiferromagnet Rb 1 - δ Fe 1.5 - σ S 2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Meng; Yi, Ming; Cao, Huibo

A combination of neutron diffraction and angle-resolved photoemission spectroscopy measurements on a pure antiferromagnetic stripe Rb 1-δFe 1.5-σS 2 is reported. A neutron diffraction experiment on a powder sample shows that a 98% volume fraction of the sample is in the antiferromagnetic stripe phase with rhombic iron vacancy order and a refined composition of Rb 0.66Fe 1.36S 2, and that only 2% of the sample is in the block antiferromagnetic phase with √5×√5 iron vacancy order. Furthermore, a neutron diffraction experiment on a single crystal shows that there is only a single phase with the stripe antiferromagnetic order with themore » refined composition of Rb 0.78Fe 1.35S 2, while the phase with block antiferromagnetic order is absent. Angle-resolved photoemission spectroscopy measurements on the same crystal with the pure stripe phase reveal that the electronic structure is gapped at the Fermi level with a gap larger than 0.325 eV. The data collectively demonstrate that the extra 10% iron vacancies in addition to the rhombic iron vacancy order effectively impede the formation of the block antiferromagnetic phase; the data also suggest that the stripe antiferromagnetic phase with rhombic iron vacancy order is a Mott insulator.« less

A neutron diffraction study of the magnetic phases of CsCuCl3 for in-plane fields up to 17 T

NASA Astrophysics Data System (ADS)

Stüßer, N.; Schotte, U.; Hoser, A.; Meschke, M.; Meißner, M.; Wosnitza, J.

2002-05-01

Neutron diffraction investigations have been performed to study the magnetization process of CsCuCl3 with the magnetic field aligned within the ab-plane. In zero field the stacked, triangular-lattice antiferromagnet (TLA) CsCuCl3 has a helical structure incommensurate in the chain direction normal to the ab-plane. The magnetic phase diagram was investigated from 2 K up to TN in fields up to 17 T. The phase line for the expected incommensurate-commensurate (IC-C) phase transition could be determined throughout the whole phase diagram. At low temperature the IC-C transition is roughly at half the saturation field HS. The neutron diffraction patterns were found to be well described by a sinusoidally modulated spiral in fields up to HS/3. The initial increase of the scattering intensity in rising field indicates a continuous reduction of the spin frustration on the triangular lattice. Between HS/3 and HS/2 a new phase occurs where the spiral vector has a plateau in its field dependence. Close to the IC-C transition a growing asymmetry of magnetic satellite-peak intensities indicates domain effects which are related to the lifting of the chiral degeneracy in the ab-plane in rising field. The phase diagram obtained has some similarities with those calculated for stacked TLAs by considering the effects of quantum and thermal fluctuations.

Improved sample manipulation at the STRESS-SPEC neutron diffractometer using an industrial 6-axis robot for texture and strain analyses

NASA Astrophysics Data System (ADS)

Randau, C.; Brokmeier, H. G.; Gan, W. M.; Hofmann, M.; Voeller, M.; Tekouo, W.; Al-hamdany, N.; Seidl, G.; Schreyer, A.

2015-09-01

The materials science neutron diffractometer STRESS-SPEC located at FRM II is a dedicated instrument for strain and pole figure measurements. Both methods make complementary demands on sample handling. On one hand pole figure measurements need a high degree of freedom to orient small samples and on the other hand in strain investigations it is often necessary to handle large and heavy components. Therefore a robot based sample positioning system was developed, which has the capability to provide both possibilities. Based on this new robot system further developments like a full automated sample changer system for texture measurements were accomplished. Moreover this system opens the door for combined strain and texture analysis at STRESS-SPEC.

Local and average structures of BaTiO 3-Bi(Zn 1/2Ti 1/2)O 3

DOE Office of Scientific and Technical Information (OSTI.GOV)

Usher, Tedi-Marie; Iamsasri, Thanakorn; Forrester, Jennifer S.

The complex crystallographic structures of (1-x)BaTiO 3-xBi(Zn 1/2Ti 1/2)O 3 (BT-xBZT) are examined using high resolution synchrotron X-ray diffraction, neutron diffraction, and neutron pair distribution function (PDF) analyses. The short-range structures are characterized from the PDFs, and a combined analysis of the X-ray and neutron diffraction patterns is used to determine the long-range structures. Our results demonstrate that the structure appears different when averaged over different length scales. In all compositions, the local structures determined from the PDFs show local tetragonal distortions (i.e., c/a > 1). But, a box-car fitting analysis of the PDFs reveals variations at different length scales.more » For 0.80BT-0.20BZT and 0.90BT-0.10BZT, the tetragonal distortions decrease at longer atom-atom distances (e.g., 30 vs. 5 ). When the longest distances are evaluated (r > 40 ), the lattice parameters approach cubic. Neutron and X-ray diffraction yield further information about the long-range structure. Compositions 0.80BT-0.20BZT and 0.90BT-0.10BZT appear cubic by Bragg diffraction (no peak splitting), consistent with the PDFs at long distances. However, these patterns cannot be adequately fit using a cubic lattice model; modeling their structures with the P4mm space group allows for a better fit to the patterns because the space group allows for c-axis atomic displacements that occur at the local scale. Furthermore, for the compositions 0.92BT-0.08BZT and 0.94BT-0.06BZT, strong tetragonal distortions are observed at the local scale and a less-distorted tetragonal structure is observed at longer length scales. In Rietveld refinements, the latter is modeled using a tetragonal phase. Since the peak overlap in these two-phase compositions limits the ability to model the local-scale structures as tetragonal, it is approximated in the refinements as a cubic phase. These results demonstrate that alloying BT with BZT results in increased disorder and disrupts the long-range ferroelectric symmetry present in BT, while the large tetragonal distortion present in BZT persists at the local scale.« less

Local and average structures of BaTiO 3-Bi(Zn 1/2Ti 1/2)O 3

DOE PAGES

Usher, Tedi-Marie; Iamsasri, Thanakorn; Forrester, Jennifer S.; ...

2016-11-11

The complex crystallographic structures of (1-x)BaTiO 3-xBi(Zn 1/2Ti 1/2)O 3 (BT-xBZT) are examined using high resolution synchrotron X-ray diffraction, neutron diffraction, and neutron pair distribution function (PDF) analyses. The short-range structures are characterized from the PDFs, and a combined analysis of the X-ray and neutron diffraction patterns is used to determine the long-range structures. Our results demonstrate that the structure appears different when averaged over different length scales. In all compositions, the local structures determined from the PDFs show local tetragonal distortions (i.e., c/a > 1). But, a box-car fitting analysis of the PDFs reveals variations at different length scales.more » For 0.80BT-0.20BZT and 0.90BT-0.10BZT, the tetragonal distortions decrease at longer atom-atom distances (e.g., 30 vs. 5 ). When the longest distances are evaluated (r > 40 ), the lattice parameters approach cubic. Neutron and X-ray diffraction yield further information about the long-range structure. Compositions 0.80BT-0.20BZT and 0.90BT-0.10BZT appear cubic by Bragg diffraction (no peak splitting), consistent with the PDFs at long distances. However, these patterns cannot be adequately fit using a cubic lattice model; modeling their structures with the P4mm space group allows for a better fit to the patterns because the space group allows for c-axis atomic displacements that occur at the local scale. Furthermore, for the compositions 0.92BT-0.08BZT and 0.94BT-0.06BZT, strong tetragonal distortions are observed at the local scale and a less-distorted tetragonal structure is observed at longer length scales. In Rietveld refinements, the latter is modeled using a tetragonal phase. Since the peak overlap in these two-phase compositions limits the ability to model the local-scale structures as tetragonal, it is approximated in the refinements as a cubic phase. These results demonstrate that alloying BT with BZT results in increased disorder and disrupts the long-range ferroelectric symmetry present in BT, while the large tetragonal distortion present in BZT persists at the local scale.« less