Showing papers by "Chalk River Laboratories published in 2006"
TL;DR: In this article, X-ray and neutron diffraction studies were carried out on highly ordered (2−3% Li/Ni exchange) layered Li 1-xCo1/3Ni 1/3Mn 1/ 3O2 [(1 − x) = 1.0; 0.8, 0.6, 0., 0.45, 0, 0..30, and 0.04] prepared by chemical delithiation and relithiation.
Abstract: X-ray and neutron diffraction studies were carried out on highly ordered (2−3% Li/Ni exchange) layered Li1-xCo1/3Ni1/3Mn1/3O2 [(1 − x) = 1.0; 0.8, 0.6, 0.45, 0.30, 0.04] prepared by chemical delithiation and relithiation. The studies reveal that the initial R3m phase (O3) is maintained up to extraction of 0.70−0.75 Li and exhibits only ∼1% change in volume over the range of composition. Additional extraction of Li results in the appearance of the O1 phase (trigonal; P3m1), which displays a strong contraction in the c axis by 5.3% and a volume decrease of 7.2%. Oxygen vacancies were not evident in the completely delithiated material. Re-intercalation of lithium in this phase was relatively irreversible, however, resulting in poorly defined mixtures of the O3 and O1 structures that exhibited a large fraction of stacking faults. In contrast, materials that were not delithiated beyond x = 0.30 resulted in fully reversible reformation of the original crystalline O3 phase on re-intercalation. Electrochemical ...
251 citations
TL;DR: In this article, the phase diagram of the Al2O3-Y2O 3 system has been investigated with five different compositions by XRD and in situ high temperature neutron diffractometry.
Abstract: The phase diagram of the Al2O3–Y2O3 system has been investigated with five different compositions by XRD and in situ high temperature neutron diffractometry. High purity YAG, YAP and YAM compounds have been produced successfully through a melt extraction technique. High temperature neutron diffraction has made it possible to follow, in real time, the reactions involved in this system, especially to determine the temperature range of each reaction, which would have been impossible to determine by other means. A good agreement between the experimental results and the phase diagram of the Al2O3–Y2O3 system has been observed.
114 citations
TL;DR: In this article, the structural properties of PMN-60PT were compared with pure PT and showed that the structural distortion is long-range and short-range polar correlations (polar nanoregions) are not present.
Abstract: Using neutron elastic and inelastic scattering and high-energy x-ray diffraction, we present a comparison of $40%\phantom{\rule{0.3em}{0ex}}\mathrm{Pb}({\mathrm{Mg}}_{1∕3}{\mathrm{Nb}}_{2∕3}){\mathrm{O}}_{3}\text{\ensuremath{-}}60%\phantom{\rule{0.3em}{0ex}}{\mathrm{PbTiO}}_{3}$ (PMN-60PT) with pure $\mathrm{Pb}({\mathrm{Mg}}_{1∕3}{\mathrm{Nb}}_{2∕3}){\mathrm{O}}_{3}$ (PMN) and ${\mathrm{PbTiO}}_{3}$ (PT). We measure the structural properties of PMN-60PT to be identical to pure PT, however, the lattice dynamics are exactly that previously found in relaxors PMN and $\mathrm{Pb}({\mathrm{Zn}}_{1∕3}{\mathrm{Nb}}_{2∕3}){\mathrm{O}}_{3}$ (PZN). PMN-60PT displays a well-defined macroscopic structural transition from a cubic to tetragonal unit cell at $550\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. The diffuse scattering is shown to be weak indicating that the structural distortion is long-range in PMN-60PT and short-range polar correlations (polar nanoregions) are not present. Even though polar nanoregions are absent, the soft optic mode is short-lived for wave vectors near the zone center. Therefore PMN-60PT displays the same waterfall effect as prototypical relaxors PMN and PZN. We conclude that it is random fields resulting from the intrinsic chemical disorder which is the reason for the broad transverse optic mode observed in PMN and PMN-60PT near the zone center and not due to the formation of short-ranged polar correlations. Through our comparison of PMN, PMN-60PT, and pure PT, we interpret the dynamic and static properties of the $\mathrm{PMN}\text{\ensuremath{-}}x\mathrm{PT}$ system in terms of a random field model in which the cubic anisotropy term dominates with increasing doping of ${\mathrm{PbTiO}}_{3}$.
68 citations
TL;DR: In this paper, two noncentrosymmetric borates oxides, M Bi 2 B 2 O 7 (M Ca, Sr), have been synthesized by solid-state reactions in air at temperatures in the 600-700°C range.
64 citations
10 Nov 2006-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, the authors examined both the L3 diffractometer at the NRU reactor, Chalk River, Canada and the TASS strain scanner at ANSTO's HIFAR reactor, Lucas Heights, Australia.
Abstract: Low pressure turbine blades in power stations suffer from leading edge erosion damage due to water impingement. In an effort to extend the life of these blades, repair of the eroded regions has been proposed using laser cladding with Stellite material. However, the addition of Stellite results in residual stresses being generated in the parent metal due to contraction during cooling and differences in thermal expansion between the two materials. In this work test coupons and laser clad blades were examined for residual stresses using both the L3 diffractometer at the NRU reactor, Chalk River, Canada and the TASS strain scanner at ANSTO's HIFAR reactor, Lucas Heights, Australia. In addition XRD results were used to measure residual stresses on the surface of the blade to complement the neutron measurements. An FEA model of a simplified weld was used to explain some of the results.
64 citations
TL;DR: In this paper, Kiselev et al. combined the Laplace transform approach with the separated form factor (SFF) approximation to obtain expressions for polydisperse spherical vesicles with various forms of membrane scattering length density (SLD) profile.
Abstract: Use of the Schulz or Gamma distribution in the description of particle sizes facilitates calculation of analytic polydisperse form factors using Laplace transforms, {\cal L}[f(u)]. Here, the Laplace transform approach is combined with the separated form factor (SFF) approximation [Kiselev et al. (2002). Appl. Phys. A, 74, S1654–S1656] to obtain expressions for form factors, P(q), for polydisperse spherical vesicles with various forms of membrane scattering length density (SLD) profile. The SFF approximation is tested against exact form factors that have been numerically integrated over the size distribution, and is shown to represent the vesicle form factor accurately for typical vesicle sizes and membrane thicknesses. Finally, various model SLD profiles are used with the SFF approximation to fit experimental small-angle neutron scattering (SANS) curves from extruded unilamellar vesicles.
62 citations
TL;DR: In this paper, the skin effect of perovskite relaxors has been investigated in the case of PZN-xPT and Pb(Mg1/3Nb2/3)O3-xPbTiO3 relaxors.
Abstract: X-ray and neutron scattering studies of the lead-based family of perovskite relaxors Pb(Zn1/3Nb2/3)O3–xPbTiO3 (PZN-xPT) and Pb(Mg1/3Nb2/3)O3–xPbTiO3 (PMN-xPT) have documented a highly unusual situation in which the near-surface region of a single crystal can exhibit a structure that is different from that of the bulk when cooled to low temperatures. The near-surface region, or “skin” can also display critical behavior that is absent in the crystal interior, as well as a significantly different lattice spacing. By varying the incident photon energy, and thus the effective penetration depth, X-ray measurements indicate a skin thickness of order 10–50 µm for PZN-xPT samples with 0 ≤ x ≤ 8%. Neutron residual stress measurements on a large PMN single crystal reveal a uniform lattice spacing within the bulk, but an increased strain near the surface. The presence of this skin effect has led to incorrect phase diagrams for both the PZN-xPT and PMN-xPT systems and erroneous characterizations of the nature of the r...
52 citations
TL;DR: Previously unrecognised Aβ-dependent rearrangement of the membrane sterol could have an important role in AD, as cholesterol is known to regulate membrane lipid order, and this can affect a wide range of membrane mechanisms, including intercellular signalling.
Abstract: Soluble Alzheimer's Aβ oligomers autoinsert into neuronal cell membranes, contributing to the pathology of Alzheimer's Disease (AD), and elevated serum cholesterol is a risk factor for AD, but the reason is unknown. We investigated potential connections between these two observations at the membrane level by testing the hypothesis that Aβ(1–42) relocates membrane cholesterol. Oligomers of Aβ(1–42), but not the monomeric peptide, inserted into cholesterol-containing phosphatidylcholine monolayers with an anomalously low molecular insertion area, suggesting concurrent lipid rearrangement. Membrane neutron diffraction, including isomorphous replacement of specific lipid hydrogens with highly-scattering deuterium, showed that Aβ(1–42) insertion was accompanied by outward displacement of membrane cholesterol, towards the polar surfaces of the bilayer. Changes in the generalised polarisation of laurdan confirmed that the structural changes were associated with a functional alteration in membrane lipid order. Cholesterol is known to regulate membrane lipid order, and this can affect a wide range of membrane mechanisms, including intercellular signalling. Previously unrecognised Aβ-dependent rearrangement of the membrane sterol could have an important role in AD.
48 citations
01 Jan 2006
TL;DR: The results on heat transfer to supercritical water heated above the pseudo-critical temperature or affected by mixed convection flowing upward and downward in vertical tubes of 6.28mm and 9.50mm inside diameter are presented in this paper.
Abstract: The results on heat transfer to supercritical water heated above the pseudo-critical temperature or affected by mixed convection flowing upward and downward in vertical tubes of 6.28-mm and 9.50-mm inside diameter are presented. Supercritical water heat-transfer data were obtained at a pressure of 23.5 MPa, mass flux within the range from 250 to 2200 kg/(m{sup 2}s), inlet temperature from 100 to 415 deg. C and heat flux up to 3.2 MW/m{sup 2}. Temperature regimes of the tubes cooled with supercritical water in a gaseous state (i.e., supercritical water at temperatures beyond the pseudo-critical temperature) were stable and easily reproducible within a wide range of mass and heat fluxes. An analysis of the heat-transfer data for upward and downward flows enabled to determine a range of Gr/Re{sup 2} values corresponding to the maximum effect of free convection on the heat transfer. It was shown that: 1) the heat transfer coefficient at the downward flow of water can be higher by about 50% compared to that of the upward flow; and 2) the deteriorated heat-transfer regime is affected with the flow direction, i.e., at the same operating conditions, the deteriorated heat transfer may be delayed at the downward flow compared to thatmore » at the upward flow. These heat-transfer data are applicable as the reference dataset for future comparison with bundle data. (authors)« less
47 citations
TL;DR: In this article, the authors have mapped the neutron scattering spin spectrum at low energies in the presence of hole doping and showed that the correlations are subcritical with respect to any second-order transition to N'eel order.
Abstract: We have mapped the neutron scattering spin spectrum at low energies in $\mathrm{Y}{\mathrm{Ba}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{6.353}$ $({T}_{c}=18\phantom{\rule{0.3em}{0ex}}\mathrm{K})$, where the doping $\ensuremath{\sim}0.06$ is near the critical value $({p}_{c}=0.055)$ for superconductivity. No coexistence with long-range-ordered antiferromagnetism is found. The spins fluctuate on two energy scales: one a damped spin response with a $\ensuremath{\simeq}2\phantom{\rule{0.3em}{0ex}}\mathrm{meV}$ relaxation rate and the other a central mode with a relaxation rate that slows to less than $0.08\phantom{\rule{0.3em}{0ex}}\mathrm{meV}$ below ${T}_{c}$. The spectrum mirrors that of a soft mode driving a central mode. Extremely short correlation lengths, $42\ifmmode\pm\else\textpm\fi{}5\phantom{\rule{0.3em}{0ex}}\mathrm{\AA{}}$ in-plane and $8\ifmmode\pm\else\textpm\fi{}2\phantom{\rule{0.3em}{0ex}}\mathrm{\AA{}}$ along the $c$ direction, and isotropic spin orientations for the central mode indicate that the correlations are subcritical with respect to any second-order transition to N\'eel order. The dynamics follows a model where damped spin fluctuations are coupled to the slow fluctuations of regions with correlations shortened by the hole doping.
39 citations
TL;DR: Neutron reflectometry was used to investigate the formation and properties of such PEO layers in situ, i.e., in contact with water, and found both chain density and PEO volume fraction in the chemisorbed layers were significantly greater when the layers were formed under low solubility conditions.
TL;DR: It is shown that male mice, adapted to radiation with a low dose priming exposure, do not pass on mutations to their offspring caused by a subsequent large radiation exposure to the adapted males, and an important gene known as p53 is investigated.
Abstract: There are a number of studies that show radiation can cause heritable mutations in the offspring of irradiated organisms. These “germ-line mutations” have been shown to occur in unique sequences of DNA called “minisatellite loci”. The high frequencies of spontaneous and induced mutations at minisatellite loci allow mutation induction to be measured at low doses of exposure in a small population, making minisatellite mutation a powerful tool to investigate radiation-induced heritable mutations. However, the biological significance of these mutations is uncertain, and their relationship to health risk or population fitness is unknown. We have adopted this mutation assay to study the role of adaptive response in protecting mice against radiation-induced heritable defects. We have shown that male mice, adapted to radiation with a low dose priming exposure, do not pass on mutations to their offspring caused by a subsequent large radiation exposure to the adapted males. This presentation and paper provide a general overview of radiation-induced mutations in offspring and explain the effect of low dose exposures and the adaptive response on these mutations.
It is also known that exposure of pregnant females to high doses of radiation can cause death or malformation (teratogenesis) in developing fetuses. Malformation can only occur during a specialized stage of organ formation known as organogenesis. Studies in rodents show that radiation-induced fetal death and malformation can be significantly reduced when a pregnant female is exposed to a prior low dose of ionizing radiation. The mechanism of this protective effect, through an adaptive response, depends on the stage of organogenesis when the low dose exposures are delivered. To better understand this process, we have investigated the role of an important gene known as p53. Therefore, this report will also discuss fetal effects of ionizing radiation and explain the critical stages of development when fetuses are at risk. Research will be explained that investigates the biological and genetic systems (p53) that protect the developing fetus and discuss the role of low dose radiation adaptive response in these processes.
01 Jan 2006
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TL;DR: In this article, the effect of axial heat flux distribution on the critical heat flux (CHF) was investigated with HFC-134a cooled vertical tubes having four non-uniform and one uniform AFD profiles.
10 Nov 2006-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, the Kirkpatrick-Baez (KB) super-mirror was used to image neutrons to small spots and the beam divergence was increased to a factor of 2.5.
Abstract: High-performance Kirkpatrick-Baez (KB) neutron supermirror optics can nondispersively image neutrons to small spots. Ray tracing finds that under many conditions, KB mirrors work near the theoretical limit set by source brilliance and can deliver orders of magnitude greater intensities than is possible with conventional (nonfocusing) neutron optics. In general, KB neutron supermirrors are preferred when the required beam size at the sample is small and when the distance between the optics and the sample is not small. Waveguides with beam definings slits are preferred for very short wavelengths, for big beams and when the slits can be placed very close to the sample. For example, for λ ∼ 0.1 nm, if the distance from the last optical element to the sample is ∼100 mm, almost two orders of magnitude greater intensity can be focused onto a 100 μm spot with M = 3 KB supermirrors than with a beam guide and symmetric slits. This is independent of whether the beam guide collimates or condenses the beam so long as without slits the beam is larger than the acceptable beam size at the sample. We describe the ray tracing and phase space arguments that support the use of KB supermirrors for producing intense small beams and describe the performance of a prototype KB device which achieved a 89 μm × 90 μm focus. We briefly describe even more advanced methods that can increase the beam divergence on the sample while maintaining a small beam.
TL;DR: It is demonstrated that the Porod invariant, Q, is related to the scattering length density contrast between compositionally distinct regions in a heterogeneous membrane and the formation of domains and the concomitant identification of phase boundaries as a function of either membrane composition or temperature.
Abstract: This is the first of a series of papers considering the scattering from laterally heterogeneous vesicles. Here, it is shown that contrast variation studies on unilamellar vesicles can be analyzed in a model-independent manner to detect lateral segregation in model membranes. In particular, it is demonstrated that the Porod invariant, Q = \textstyle\int q^{2}I (q )\,{\rm d}q, is related to the scattering length density contrast between compositionally distinct regions in a heterogeneous membrane. The formation of domains and the concomitant identification of phase boundaries as a function of either membrane composition or temperature can therefore be detected in the changes taking place in Q.
TL;DR: In this paper, a synthese de l'hydrure de magnesium par broyage reactif mene a la formation d'une phase orthorhombique metastable (γ-MgH 2 ) en plus de la phase quadratique β-H 2.
Abstract: Changement de phase induit par broyage mecanique dans l'hydrure de magnesium. La synthese de l'hydrure de magnesium par broyage reactif mene a la formation d'une phase orthorhombique metastable (γ-MgH 2 ) en plus de la phase quadratique β-MgH 2 . Les structures des phases β-MgD 2 et γ-MgD 2 du MgD 2 nanocristallin broye ont ete etudiees par diffraction de neutrons sur poudre. Les structures de β-MgD 2 et γ-MgD 2 prepares par broyage mecanique sont deformees par rapport aux memes phases synthetisees par haute pression et haute temperature. Dans la phase β-MgD 2 les liaisons Mg-D sont symetriquement deformes alors que dans la phase γ-MgD 2 seule une liaison est deformee. Les microcontraintes associees aux champs de deformation et aux defauts causes par le broyage a billes sont vraisemblablement la force motrice de cette transformation de phase.
TL;DR: In this article, the propagation of fatigue cracks under constant amplitude cyclic loading was studied in welded stiffened steel plates using the neutron diffraction strain-scanning technique, and the residual stresses in the stiffened plates were measured using the NCS technique.
TL;DR: In this article, the first synthesis and high-temperature in situ X-ray diffraction study of InVO3 was performed using a carbon monoxide/carbon dioxide buffer gas.
TL;DR: In this article, a new zeolite overgrowth was synthesized by adding an amount of as-synthesised EMT crystals to a synthesis gel of mazzite (MAZ).
TL;DR: In this paper, the spin reorientation, from perpendicular to parallel to the rhombohedral [1, 1/1] direction, was observed at room temperature at the highest pressure.
Abstract: Neutron powder scattering studies of hematite to a pressure ( P ) of 6.2 GPa in a Paris–Edinburgh (PE) cell with Fluorinert ® as a P -transmitting medium, reveal different behavior to previous investigations that used solid pressure-transmitting media. The P equivalent of the Morin transition is closely approached at room temperature at the highest P . In the present study the spin reorientation, from perpendicular to parallel to the rhombohedral [1 1 1] direction, begins at some 3 GPa higher and goes 25° beyond what was previously observed at high P .
TL;DR: Direct irradiations with N, Ar and Kr charged particles at HIMAC confirm that bubble nucleation is not a simple function of particle LET and that an analysis based on track-structure appears warranted.
Abstract: A series of experiments have been recently performed at the Heavy Ion Medical Accelerator in Chiba (HIMAC) laboratory to study the response of bubble detectors to high-mass high-energy (HZE) particles. The motivation for this study was to improve our ability to interpret measurements of neutron energy spectra in space. A recent analysis showed that emulsions of light halocarbons display common properties when they are characterised by a quantity called 'reduced superheat'. This quantity evolved from the examination of neutron and gamma responses of many types of detectors. In this study, we describe direct irradiations with N, Ar and Kr charged particles at HIMAC. It was observed that when the linear energy transfer (LET) corresponding to bubble formation was plotted vs. reduced superheat, different curves were obtained for a particular ion for detectors at different temperatures. Different curves were also obtained when data from different ions were plotted. These results confirm that bubble nucleation is not a simple function of particle LET and that an analysis based on track-structure appears warranted.
TL;DR: A method to estimate the average radiation dose equivalent delivered to the patient's hand during irradiation using the Monte Carlo simulation of hand irradiation facility using MCNP4B is described.
TL;DR: The magnetic properties of the hole(x) doped Mott-Hubbard, antiferromagnetic insulator, NdTiO{sub 3}, have been investigated in this article.
Abstract: The magnetic properties of the hole(x) doped Mott-Hubbard, antiferromagnetic insulator, NdTiO{sub 3}, have been investigated in Nd{sub 1-x}TiO{sub 3}. For the materials in 0.010(6){ =}0.098(10), all magnetic ordering is destroyed.
TL;DR: In this article, inelastic neutron scattering measurements on the intermetallic compounds were performed on the heavy-fermion system and showed that at high temperatures the spin fluctuations in the critical composition are given by non-Fermi-liquid dynamics.
Abstract: We present inelastic neutron scattering measurements on the intermetallic compounds $\mathrm{Ce}{({\mathrm{Ru}}_{1\ensuremath{-}x}{\mathrm{Fe}}_{x})}_{2}{\mathrm{Ge}}_{2}$ ($x=0.65$, 0.76, and 0.87). These compounds represent samples in a magnetically ordered phase, at a quantum critical point, and in the heavy-fermion phase, respectively. We show that at high temperatures the three compositions have the identical response of a local moment system. However, at low temperatures the spin fluctuations in the critical composition are given by non-Fermi-liquid dynamics, while the spin fluctuations in the heavy-fermion system show a simple exponential decay in time. In both compositions, the lifetime of the fluctuations is determined solely by the distance to the quantum critical point. We discuss the implications of these observations regarding the possible origins of non-Fermi-liquid behavior in this system.
TL;DR: Chi et al. as mentioned in this paper studied the properties of a series of Re-based perovskites, including La5Re3CoO16 and La5 Re3NiO16, and showed that the Re5+ and Ni2+ moments are ordered ferrimagnetically within the corner-shared octahedral layers.
TL;DR: In this paper, the chain length dependence of the magnetism in the Mossbauer spectrograms has been studied and it has been shown that shorter chain lengths exhibit faster fluctuations at any given temperature.
Abstract: The ${\mathrm{Ni}}^{2+}$ ions in ${\mathrm{Eu}}_{2}{\mathrm{BaNiO}}_{5}$ form antiferromagnetic Heisenberg $S=1$ chains with a Haldane gap. Replacing ${\mathrm{Ni}}^{2+}$ with ${\mathrm{Zn}}^{2+}$ decreases the average ${\mathrm{Ni}}^{2+}$ chain length. $^{151}\mathrm{Eu}$ and $^{153}\mathrm{Eu}$ M\"ossbauer spectroscopy have been used to study the chain length dependence of the magnetism in ${\mathrm{Eu}}_{2}{\mathrm{BaZn}}_{x}{\mathrm{Ni}}_{1\ensuremath{-}x}{\mathrm{O}}_{5}$ with $x=0,0.05$, and 0.1. Using exchange-induced ${\mathrm{Eu}}^{3+}$ moments these independent and complementary local probes of the magnetism reveal that the chain moments undergo temperature dependent fluctuations where shorter chain lengths exhibit faster fluctuations at any given temperature. The ${\mathrm{Eu}}^{3+}$ antiferromagnetic order is established at ${T}_{N}\ensuremath{\sim}5\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, independent of the ${\mathrm{Ni}}^{2+}$ chain length. Thermally activated moment fluctuations are observed above ${T}_{N}$. Chain cutting increases the molecular exchange field of the ${\mathrm{Ni}}^{2+}$ on the ${\mathrm{Eu}}^{3+}$ and indicates a polarization of ${\mathrm{Ni}}^{2+}$ interdimer coupling in the quantum spin chains.
TL;DR: The perovskites PbFeO 2 F and 0.5PbTiO 3 were synthesized at high temperatures (1000°C) and high pressures (4-6 GPa) using powder neutron diffraction as discussed by the authors.
Abstract: The perovskites PbFeO 2 F and 0.5PbFeO 2 F-0.5PbTiO 3 were synthesized at high temperatures (1000°C) and high pressures (4 – 6 GPa). The crystal and magnetic structures were determined using powder neutron diffraction. Quenched PbFeO 2 F has the cubic perovskite-type, P m3m, structure in which the Pb ion shifts from ideal A-site along the directions, which is in good accordance with a previous report. The magnetic structure is antiferromagnetic G-type with propagation vector k = (1/2 1/2 1/2) and an Fe 3+ ordered moment of 3.83 μ B at 283K. The Neel temperature is 655(5) K. Annealed PbFeO 2 F has a tetragonal perovskite-type structure at room temperature and transforms reversibly from tetragonal to cubic at approximately 470 K. A superlattice with dimensions a × a × 5 c is observed both in electron and x-ray diffraction. The solid solution 0.5PbFeO 2 F-0.5PbTiO 3 belongs to the non-centrosymmetric space group P 4mm. The magnetic structure is G-type antiferromagnetic and shows a weak ferromagnetic moment at 4 K. Consequently, 0.5PbFeO 2 F-0.5PbTiO 3 is simultaneously ferroelectric and a weak ferromagnet at low temperature. The Neel temperature is 450 K but the temperature dependence of the ordered Fe moment is anomalous.
10 Nov 2006-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, the accumulated strain and texture changes within Ni grains over the sampling volume were measured by neutron diffraction as a function of ( h k l ) reflections and sample orientations with respect to the tensile axis.
Abstract: Experiments on 99% pure Ni samples have been carried out to investigate the dependence of deformation on grain size. The accumulated strains and texture changes within the grains over the sampling volume were measured by neutron diffraction as a function of ( h k l ) reflections and sample orientations with respect to the tensile axis. Inhomogeneous developments of strain are found. Large tensile lattice strain was found for reflection (2 0 0) in the direction parallel to the loading axis. Sample of smaller grain size displays larger strain magnitude. The overall trend of the lattice strain development predicted by the elasto-plastic self-consistent model agrees with the experiment to within 30% and 50% for the small grain and large grain samples, respectively.
TL;DR: In this article, the structure and dynamics associated with Li + 8 in bulk crystalline GaAs and Ge were studied and it was shown that a large fraction of the Li end up in locations with cubic symmetry (i.e. the tetrahedral interstitial and substitutional sites).
Abstract: In this paper, we describe initial studies of the structure and dynamics associated with Li + 8 in bulk crystalline GaAs and Ge. At low temperatures in GaAs, the amplitude of the Li + 8 resonance signal at ≈ 3 T indicates that a large fraction (at least 70 % ) of the Li end up in locations with cubic symmetry (i.e. the tetrahedral interstitial and substitutional sites). The linewidth of the β -NMR Li + 8 resonance increases dramatically above 150 K, reaches a maximum at about 290 K, and decreases again. This suggests that the Li starts to change its location, probably from an interstitial to a substitutional site, at ≈ 150 K . Experiments in Ge are also described. In this sample, a narrow resonance is seen at low temperatures that is likely due to Li located at an interstitial site. Near room temperature, it appears that Li is converting to another site.