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The structure of calcium aluminosilicate glasses (CaO)x(Al2O3)y(SiO2)1−x−y with the near tectosilicate compositions x ≃ 0.19 and 1 − x − y ≃ 0.61 or x ≃ 0.26 and 1 − x − y ≃ 0.49 was investigated by in situ high-pressure neutron diffraction and 27Al nuclear magnetic resonance (NMR) spectroscopy. The results show three distinct pressure regimes for the transformation of the aluminum coordination environment from tetrahedral to octahedral, which map onto the deformations observed in the production of permanently densified materials. The oxygen packing fraction serves as a marker for signaling a change to the coordination number of the network forming motifs. For a wide variety of permanently densified aluminosilicates, the aluminum speciation shares a common dependence on the reduced density ρ′ = ρ/ρ0, where ρ is the density and ρ0 is its value for the uncompressed material. The observed increase in the Al–O coordination number with ρ′ originates primarily from the formation of six-coordinated aluminum Al(VI) species, the fraction of which increases rapidly beyond a threshold ρ thr ′ ∼ 1.1. The findings are combined to produce a self-consistent model for pressure-induced structural change. Provided the glass network is depolymerized, one-coordinated non-bridging oxygen atoms are consumed to produce two-coordinated bridging oxygen atoms, thus increasing the network connectivity in accordance with the results from 17O NMR experiments. Otherwise, three-coordinated oxygen atoms or triclusters appear, and their fraction is quantified by reference to the mean coordination number of the silicon plus aluminum species. The impact of treating Al(VI) as a network modifier is discussed. [ABSTRACT FROM AUTHOR]

Solid-state refrigeration using barocaloric materials is environmentally friendly and highly efficient, making it a subject of global interest over the past decade. Here, we report giant barocaloric effects in sodium hexafluorophosphate (NaPF6) and sodium hexafluoroarsenate (NaAsF6) that both undergo a cubic-to-rhombohedral phase transition near room temperature. We have determined that the low-temperature phase structure of NaPF6 is a rhombohedral structure with space group R 3 ¯ by neutron powder diffraction. There are three Raman active vibration modes in NaPF6 and NaAsF6, i.e., F2g, Eg, and A1g. The phase transition temperature varies with pressure at a rate of dTt/dP = 250 and 310 K GPa−1 for NaPF6 and NaAsF6. The pressure-induced entropy changes of NaPF6 and NaAsF6 are determined to be around 45.2 and 35.6 J kg−1 K−1, respectively. The saturation driving pressure is about 40 MPa. The pressure-dependent neutron powder diffraction suggests that the barocaloric effects are related to the pressure-induced cubic-to-rhombohedral phase transitions. [ABSTRACT FROM AUTHOR]

In this report, the high-temperature transport properties of (Dy1−xCax)(Zr0.2Hf0.2Sn0.2Ti0.2Ge0.2)O7 pyrochlore oxides with x = 0, 0.05, and 0.1 are studied in dry and humid air. The phase composition and crystal structure were determined by using x-ray and neutron diffraction. The addition of calcium to the structure caused an increase in the concentration of oxygen vacancies, indicating an ionic charge compensation mechanism. Electrical studies allowed us to determine the total electrical conductivity as a function of the synthesis atmosphere and pH2O. The electrical conductivity turned out to be at the level of ∼10−3 S/cm at 800 °C, and only a slight effect of the presence of protonic defects in the structure on the total electrical conductivity was observed. In general, the samples had a low electrical conductivity with a relatively high activation energy of conduction. [ABSTRACT FROM AUTHOR]

Here, we present a new approach for obtaining radial distribution functions (RDF) from the electron diffraction data using a regularized weighted sine least-squares spectral analysis. It allows for explicitly transferring the measured experimental uncertainties in the reduced molecular scattering function to the produced RDF. We provide a numerical demonstration, discuss the uncertainties and correlations in the RDFs, and suggest a regularization parameter choice criterion. The approach is also applicable for other diffraction data, e.g., for x-ray or neutron diffraction of liquid samples. [ABSTRACT FROM AUTHOR]

The nuclear and magnetic structures of CaxSr2−xWMnO6 (x = 0.5, 1.0, 1.5) have been investigated by neutron diffraction at 295, 30 or 40 K, and 4 or 5 K. The compounds crystallized in the monoclinic symmetry with a space group P21/n. The nuclear structure consists of ordered WO6 and Mn2+O6 octahedral frameworks, with lattice constant a decreasing more rapidly than b with increasing Ca content. No structural change was found around the magnetic transition temperature, although the Mn octahedron below the magnetic order temperature exhibited a slightly compressed Jahn–Teller distortion (0.1–0.3 Å) along the c axis. A standard magnetic model was used to solve the magnetic structure, with the Mn magnetic moments ferromagnetically coupled along the a axis and anti-ferromagnetically coupled along the b and c axes, resulting in a magnetic propagation vector of k = (0,1/2, 1/2) and a magnetic superlattice of 1a × 2b × 2c. In each crystallographic cell, the Mn1–Mn2 atoms are antiferromagnetically configurated, compensating the total moment to zero by symmetry. A layer-type magnetism along the (111) crystallographic plane was confirmed to couple antiferromagnetically between these planes and ferromagnetically within them. The magnetic structure refinement confirmed an average Mn moment of 4.5 μB. Also, it reveals that the collinear magnetic Mn configuration has three possible spin orientations, namely, (with their standard deviation) [μx = (3.3 ± 0.4) μB, μy = (2.5 ± 0.3) μB, μz = (−0.7 ± 0.7) μB], [μx = (3.0 ± 0.4) μB, μy = (0.5 ± 0.2) μB, μz = (−2.8 ± 0.2) μB, and [μx = (−1.8 ± 0.4) μB, μy = (2.9 ± 0.2) μB, μz = (−2.4 ± 0.3) μB. The first configuration is estimated to be the ground state, while the other magnetic configurations are an optimum local value derived from the refinements. Combined with the density functional theory calculations, these experimental results confirm a high-spin state Mn2+ (d5) electron configuration. [ABSTRACT FROM AUTHOR]

A comparison is made between the three principal methods for the analysis of neutron and x-ray diffraction data from noble gas fluids by direct Fourier transform. All three methods (standard Fourier transform, Lorch modification, and Soper–Barney modification) are used to analyze four different sets of diffraction data from noble gas fluids. The results are compared to the findings of a full-scale real-space structure determination, namely, Empirical Potential Structure Refinement. Conclusions are drawn on the relative merits of the three Fourier transform methods, what information can be reliably obtained using each method, and which method is most suitable for the analysis of different kinds of diffraction data. The mathematical validity of the Lorch method is critically analyzed. [ABSTRACT FROM AUTHOR]

We report the detailed analysis of temperature dependent neutron diffraction pattern of the Cr 2 CoAl inverse Heusler alloy and unveil the magnetic structure up to the phase transition as well as its fully compensated ferrimagnetic nature. The Rietveld refinement of the diffraction pattern using the space group I 4 ¯ m2 confirms the inverse tetragonal structure over the large temperature range from 100 to 900 K. The refinement of the magnetic phase considering the wave vector k = (0, 0, 0) reveals the ferrimagnetic nature of the sample below 730 ± 5 K. This transition temperature is obtained from empirical power law fitting of the variation in the ordered net magnetic moment variation in intensity of (110) peak as a function of temperature. The spin configuration of the microscopic magnetic structure suggests the nearly fully compensated ferrimagnetic behavior where the magnetic moments of Cr2 are antiparallel with respect to the Cr1 and Co moments. Moreover, the observed anomaly in the thermal expansion and lattice parameters at 730 ± 5 K suggests that the distortion in the crystal structure may play an important role in the magnetic phase transition. [ABSTRACT FROM AUTHOR]

This study presents "K0.5Na0.5NbO3-based" Pb-free smart material 0.80(K0.5Na0.5NbO3)–0.20(Ba0.9Sr0.1TiO3) (KBST20) as exhibiting zero thermal expansion (ZTE) at low temperatures (T ≤ 100 K) with long-range cubic symmetry stable over a wide temperature range (9 K ≤ T ≤ 500 K). The linear coefficient of the thermal expansion (αl) obtained from temperature-dependent neutron diffraction data is in the range of 0.255–5.75 × 10−6 K–1 (9–500 K), which is rarely observed for Pb-free materials possessing long-range cubic symmetry. The temperature-dependent dielectric data of KBST20 exhibits a strong relaxational behavior with high frequency dispersion (Δ T ≈ 27 K), suggesting the presence of polar phased regions known as polar nano regions. The ZTE has been attributed to enhanced correlations among PNRs exhibiting ferroelectrostriction. Furthermore, temperature-dependent Raman scattering data reveal polar monoclinic distortion at short ranges rather than cubic symmetry at long ranges. In addition, the intensity of Raman modes increases with the decrease in temperature, suggesting enhancement of the polar phase at low temperatures, which consequently leads to zero thermal expansion in KBST20. [ABSTRACT FROM AUTHOR]

Polyanion rotations are often linked to cation diffusion, but the study of multiple polyanion systems is scarce due to the complexities in experimentally determining their dynamic interactions. This work focuses on BH4‐based argyrodites, synthesized to achieve a high conductivity of 11 mS cm−1. Advanced tools, including high‐resolution X‐ray diffraction, neutron pair distribution function analysis, and mutinuclear magic‐angle‐spinning nuclear magnetic resonance (NMR) spectroscopy and relaxometry, along with theoretical calculations, are employed to unravel the dynamic intricacies among the dual polyanion lattice and active charge carriers. The findings reveal that the anion sublattice of Li5.07PS4.07(BH4)1.93 affords an even temporal distribution of Li among PS43− and BH4−, suggesting minimal trapping of the charge carriers. Moreover, the NMR relaxometry unveils rapid BH4− rotation on the order of ∼GHz, affecting the slower rotation of neighboring PS43− at ∼100 MHz. The PS43− rotation synchronizes with Li+ motion and drives superionic transport. Thus, the PS43− and BH4− polyanions act as two‐staged dual motors, facilitating rapid Li+ diffusion. [ABSTRACT FROM AUTHOR]

We present calculations of interferograms (interference patterns) of one or multiple spiral phase plates that would be observed with a perfect crystal neutron interferometer of Mach–Zehnder type. A spiral phase plate (SPP) in one of the two coherent beam paths produces a twist in the phase front and thus a vortex beam with intrinsic angular momentum, which in the case of neutrons should be observed as a characteristic interference pattern that appears complementary to each other in both detectors behind the interferometer. Adding additional SPPs in one beam path of the interferometer yield interference patterns similar to that of a single SPP but only due to the cumulative step height. All simulated interferograms have been calculated on the basis of dynamical neutron diffraction without any assumption of a neutron orbital angular momentum and show very convincing agreement with experimental results from the literature, see e.g. (C. W. Clark, R. Barankov, M. G. Huber, M. Arif, D. G. Cory, and D. A. Pushin, "Controlling neutron orbital angular momentum," Nature, vol. 525, pp. 504–506, 2015). In particular, this clarifies, that the cited experiments do not give evidence of the quantization of interactions caused by a twist of the phase front of a neutron wave in the interferometer and thus no evidence for the effect of a neutron orbital angular momentum. [ABSTRACT FROM AUTHOR]

Neutron time‐of‐flight transmission spectra of mosaic crystals contain Bragg dips, i.e., minima at wavelengths corresponding to diffraction reflections. The positions of the dips are used for investigating crystal lattices. By rotating the sample around a fixed axis and recording a spectrum at each rotation step, the intensity of the transmitted beam is obtained as a function of the rotation angle and wavelength. The questions addressed in this article concern the determination of lattice parameters and orientations of centrosymmetric crystals from such data. It is shown that if the axis of sample rotation is inclined to the beam direction, the reflection positions unambiguously determine reciprocal‐lattice vectors, which is not the case when the axis is perpendicular to the beam. Having a set of such vectors, one can compute the crystal orientation or lattice parameters using existing indexing software. The considerations are applicable to arbitrary Laue symmetry. The work contributes to the automation of the analysis of diffraction data obtained in the neutron imaging mode. [ABSTRACT FROM AUTHOR]

Neutron and x‐ray diffraction measurements have been performed on CaO–MgO–Al2O3–SiO2 (CMAS) glasses doped with NiO–FeXO at room temperature, along with x‐ray measurements on aerodynamically levitated liquids at ≥2000 K. The disordered structures have been modeled using empirical potential structure refinement to investigate the relation between the aluminosilicate network and the modifying cations. The SiO4 and AlO4 tetrahedra are found to have wider Si–O and Al–O bond distance distributions in the glass, and the first Ca–On coordination shell is highly distorted, redistributing different populations of long and short bonds between the liquid and the glass. The addition of Fe and Ni at low aluminosilicate content increases the number of free oxygens not bonded to AlO4 or SiO4. Mg–O and Fe–O are both found to be predominantly fourfold and fivefold in the liquid and glassy states. Despite these low coordination numbers, their bond angle distributions indicate that they are predominantly in nontetrahedral‐type geometries, with ferrous and ferric iron possessing similar coordination environments. The Ca–O and Mg–O average coordination numbers and enthalpies of solution are consistent with their higher reactivity within relatively acidic aluminosilicate melts. [ABSTRACT FROM AUTHOR]

Recent research into sodium zirconate as a high-temperature CO2 sorbent has been extensive, but detailed knowledge of the material's crystal structure during synthesis and carbon dioxide uptake remains limited. This study employs neutron diffraction (ND), thermogravimetric analysis (TGA), and X-ray diffraction (XRD) to explore these aspects. An improved synthesis method, involving the pre-drying and ball milling of raw materials, produced pure samples with average crystal sizes of 37–48 nm in the monoclinic phase. However, using a slower heating rate (1 °C/min) decreased the purity. Despite this, the 1 °C/min rate resulted in the highest CO2 uptake capacity (4.32 mmol CO2/g Na2ZrO3) and CO2 sorption rate (0.0017 mmol CO2/g) after 5 min at 700 °C. This was attributed to a larger presence of microstructure defects that facilitate Na diffusion from the core to the shell of the particles. An ND analysis showed that the conversion of Na2ZrO3 was complete under the studied conditions and that CO2 concentration significantly impacts the rate of CO2 absorption. The TGA results indicated that the reaction rate during CO2 sorption remained steady until full conversion due to the absorptive nature of the chemisorption process. During the sorbent reforming step, ND revealed the disappearance of Na2O and ZrO2 as the zirconate phase reformed. However, trace amounts of Na2CO3 and ZrO2 remained after the cycles. [ABSTRACT FROM AUTHOR]

Neutron diffraction beamlines have traditionally relied on deploying large detector arrays of 3He tubes or neutron‐sensitive scintillators coupled with photomultipliers to efficiently probe crystallographic and microstructure information of a given material. Given the large upfront cost of custom‐made data acquisition systems and the recent scarcity of 3He, new diffraction beamlines or upgrades to existing ones demand innovative approaches. This paper introduces a novel Timepix3‐based event‐mode imaging neutron diffraction detector system as well as first results of a silicon powder diffraction measurement made at the HIPPO neutron powder diffractometer at the Los Alamos Neutron Science Center. Notably, these initial measurements were conducted simultaneously with the 3He array on HIPPO, enabling direct comparison. Data reduction for this type of data was implemented in the MAUD code, enabling Rietveld analysis. Results from the Timepix3‐based setup and HIPPO were benchmarked against McStas simulations, showing good agreement for peak resolution. With further development, systems such as the one presented here may substantially reduce the cost of detector systems for new neutron instrumentation as well as for upgrades of existing beamlines. [ABSTRACT FROM AUTHOR]

The systematic studies of composition and spatial distribution of main phases inside volume of 25 fragments of Byzantine ceramic obtained in archeological works in the Dobrudja region, Romania, have been performed using neutron diffraction and tomography, and Raman spectroscopy. The obtained structural data on the content of phases, the presence of calcite grains and pores, and the uniformity of phase spatial distribution made it possible to systematize the studied fragments and correlate them with clay sources or pottery workshop. The experimental possibilities of neutron methods of nondestructive structural diagnostics as well as the structural markers provided by them in the studies of ceramic samples are discussed. [ABSTRACT FROM AUTHOR]

Stabilization of a tetragonal perovskite structure in the SrCoO 3-δ system at room temperature has been achieved through wet chemical techniques, and it has been successfully tested in Solid Oxide Fuel Cells (SOFCs). Chemical substitutions at the Co position were carried out by introducing different amounts of zirconium (SrCo 1-x Zr x O 3−δ ; x = 0.05, 0.08 and 0.11) to destabilize the columns of CoO 6 octahedra sharing faces in the competitive 2H-hexagonal phase. The crystal structure was studied by X-ray diffraction (XRD) and neutron powder diffraction (NPD) at 25 °C and correlated with mechanical and electrical properties. Chemical compatibility studies between the samples and the La 0.8 Sr 0.2 Ga 0.83 Mg 0.17 O 3-δ (LSGM) electrolyte revealed not interaction at high temperatures. Dilatometric analysis measurements showed a compatible thermal expansion with the LSGM electrolyte over the entire temperature range, demonstrating good mechanical compatibility. Furthermore, the relatively high conductivity values (∼83 S cm-1 at 850 °C) indicated their suitability as cathodes in SOFCs. Finally, test cells prepared with an electrolyte (LSGM) supported configuration provided a maximum output power exceeding 600 mW/cm2 using pure H 2 as fuel at 850 °C. Importantly, the performance of the cathode materials did not degrade after extended operation at this temperature. [ABSTRACT FROM AUTHOR]

Results of the neutron powder diffraction measurements carried out for R5Pt2In4 (R = Tb–Tm) are reported. The compounds crystallize in an orthorhombic crystal structure of the Lu5Ni2In4‐type with the rare earth atoms occupying three different sublattices. Neutron diffraction data reveal that at low temperatures the rare earth magnetic moments order below the critical temperature equal to 105, 93, 28, 12 and 3.8 K for R = Tb, Dy, Ho, Er and Tm, respectively. With decreasing temperature the rare earth magnetic moments at the 2a and 4g2 sites order first, while the moments at the 4g1 site order at lower temperatures. Ferrimagnetic order along the c axis, described by the propagation vector k1 = [0, 0, 0], develops in Tb5Pt2In4 below the Curie temperature (TC = 105 K). At lower temperatures, an antiferromagnetic component in the ab plane appears. The component is incommensurate with the crystal structure (k2 = [0,0.66,½]), but it turns into a commensurate one (k3 = [0,0,½]) with decreasing temperature. Antiferromagnetic order along the c axis, described by k4 = [½,0,0], is found in Dy5Pt2In4 below the Néel temperature (TN = 93 K). The k4‐related component disappears below 80 K and the magnetic structure transforms into a ferro/ferrimagnetic one described by k1 = [0, 0, 0]. Further decrease in temperature leads to the appearance of an incommensurate antiferromagnetic component within the ab plane below 10 K (k2 = [0,0.45,½]), which finally turns into a commensurate one (k5 = [0,½,½]). In Ho5Pt2In4, a sine‐modulated magnetic structure with moments parallel to the c axis (k6 = [⅓,0,0]) is observed below 28 K. With a decrease in temperature, new components, related to k1 = [0, 0, 0] (bc plane) and k4 = [½,0,0] (c axis), appear. The coexistence of two orderings – in the ab plane (k1 = [0, 0, 0]) and a modulated one with moments along the b axis (k7 = [kx, 0, 0]) – is found in Er5Pt2In4 below 12 K. Decreasing temperature leads to the order–order transformation of the k1‐related component to another one with magnetic moments still constrained to the ab plane and preserved value of the propagation vector (i.e.k1 = [0, 0, 0]). Tm5Pt2In4 orders antiferromagnetically below TN = 3.8 K. Thulium magnetic moments lie in the ab plane, while the magnetic structure is described by k5 = [0,½,½]. The direction of magnetic moments depends on the rare earth element involved and indicates an influence of single ion anisotropy resulting from interaction with the crystalline electric field. [ABSTRACT FROM AUTHOR]

The microstructure and 650 °C tensile properties of a compositionally graded IN718-René41 (718-R41) superalloy fabricated by laser blown-powder directed energy deposition (DED-LB/M) are investigated to understand structure–property relationships and baseline tensile properties. Digital Image Correlation (DIC), in situ neutron diffraction, and conventional characterization techniques are performed to study the as-built and heat-treated states. The applied heat treatment generates static recrystallization and equiaxed grains in 718-rich compositions, while R41-rich compositions remain partially or un-recrystallized possibly influenced by a higher MC carbide fraction (>0.5%). The yield strengths of the 718 and R41 sections in the heat-treated state are comparable to wrought forms but the graded compositions show weakness due to unoptimized heat treatment. Diffraction elastic constants first decrease and then increase along the 718-R41 composition gradient, while a small difference is observed between the as-built and heat-treated states and γ, γ′ phases. Overall, the compositionally graded region shows a smooth transition in the elastic properties. Grain-level load transfer from the (220) to (200) grains shows compositional dependence, and qualitatively agrees with DIC-measured macroscopic yield strength. Within the (200) grains, the γ/γ′ phases deform elastically until the γ phase yields and afterwards, the γ′ phase takes load from the γ phase. [ABSTRACT FROM AUTHOR]

Alloy 693 is a precipitation hardenable nickel base superalloy containing about 30% Cr, 4% Fe, 4% Al, 1.5% Nb and 0.3% Ti (in wt.%). At elevated temperatures, alloy precipitates out particles of an ordered γ′ phase (L12 crystal structure) with Ni3(Al,Ti,Nb) stoichiometry. These particles remain coherent and maintain a cube-to-cube orientation relationship with the face-centered cubic matrix. The alloy also has a tendency to form chromium-rich α phase (body-centered cubic crystal structure) particles at temperatures above 800 °C. The α phase particles maintain a Kurdjumov–Sachs orientation relationship with the matrix. This paper reports the effect of the precipitation of γ′ and α phases on the residual stresses developed in the alloy, and correlates them with the misfit strains due to the precipitation of the two phases. Residual stresses have been measured using the blind hole drilling method, while the misfit strains have been calculated based on the lattice parameters of matrix, γ′ and α phases determined using neutron diffraction. The precipitation of the γ′ phase introduces tensile nature of stresses in the matrix, while that of the α phase introduces compressive stresses. The overall nature of the residual stresses in the alloy is governed by the volume fraction of the two precipitates. [ABSTRACT FROM AUTHOR]

This study employs neutron diffraction to investigate the relationship between residual stress and coating thickness in cold sprayed 304L austenitic stainless steel. Results show that shot peening predominantly impacts the residual stress profile, leading to substantial in-plane compressive force. The impact of laser heating, a widely used method to alter cold spray's microstructural properties, on the coating's residual stress is also analyzed. The findings indicate that the maximum compressive residual stress in the in-plane component is mainly independent of coating thickness, which suggests that the material properties determine the maximum residual stress. The cold sprayed deposits possessed compressive, nearly biaxial strain and stresses. After laser heating, these stresses were replaced by tensile residual stresses. Two analytical models, the Tsui and Clyne and the Boruah models, for predicting residual stresses are also evaluated, and both models provide reasonable fits to the experimental data. At this point, the deviations between the experimental results and the models are principally caused by the inability of the current models to address plastic deformation and relaxation, and the residual stresses generated by thermal gradients. [ABSTRACT FROM AUTHOR]

The Parameter Space Concept (PSC) is an alternative approach to solving and refining (partial) crystal structures from very few pre-chosen X-ray or neutron diffraction amplitudes without the use of Fourier inversion. PSC interprets those amplitudes as piecewise analytic hyper-surfaces, so-called isosurfaces, in the Parameter Space, which is spanned by the spatial coordinates of all atoms of interest. The intersections of all isosurfaces constitute the (possibly degenerate) structure solution. The present feasibility study investigates the La and Sr split position of the potential high-temperature super-conductor (La0.5Sr1.5)MnO4, I 4 /mmm, with a postulated total displacement between La and Sr of a few p m by theoretical amplitudes of pre-selected 0 0 l reflections ( l = 2 , 4 , ... , 20 ). The revision of 15-year-old results with state-of-the-art computing equipment enhances the former simplified model by varying the scattering power ratio f La / f Sr , as exploitable by means of resonant scattering contrast at synchrotron facilities, and irrevocably reveals one of the two originally proposed solutions as being a "blurred" pseudo-solution. Finally, studying the resolution limits of PSC as a function of intensity errors by means of Monte-Carlo simulations shows both that the split can only be resolved for sufficiently low errors and, particularly for the resonant scattering contrast, a theoretical precision down to ± 0.19   p m can be achieved for this specific structural problem. [ABSTRACT FROM AUTHOR]

In this study, we conducted in-situ tensile deformation tests using synchrotron X-ray and neutron diffraction techniques on Nb-bearing AISI 201 austenitic stainless steel specimens with varying grain sizes, including ultrafine (UFG, 0.28 μm), fine (FG, 1.75 μm), and coarse (CG, 110 μm) grains. The primary objective was to investigate the effect of grain size on the evolution of lattice strains and deformation mechanisms. Our findings reveal that grain size significantly impacts the evolution of lattice strains, peak broadening, and the distribution of load between the austenite and martensite phases. Notably, the average lattice strain and peak broadening were found to be higher in the CG specimen compared to the UFG and FG counterparts. While the lattice strains in the UFG and FG steels are all compressive, a tensile manner can be seen for the CG steel as deformation proceeds. The strain-induced martensite transformation kinetics for the reversion-annealed UFG and FG steels was higher than that of the solution-annealed CG one. A soft behavior from reflection (200) was found compared to other reflections in all UFG, FG, and CG specimens, showing anisotropic elastic properties. The analysis of lattice strain and peak broadening evolutions indicated that dislocation slip predominantly governs the deformation mechanism in the CG steel, while strain-induced martensitic transformation and twinning are more prominent in the UFG and FG specimens. [ABSTRACT FROM AUTHOR]

High pressure high temperature treatments of the composition CaMnMnTeO6 are found to yield only an A2BB'O6‐type double perovskite (Ca0.5Mn0.5)2MnTeO6, rather than a AA'BB'O6 double double perovskite with A‐ and B‐ site cation order as found in analogs CaMnMnReO6 and CaMnMnWO6 with similar cation sizes. Double perovskite (Ca0.5Mn0.5)2MnTeO6 adopts a monoclinic structure in space group P21/n with a framework of highly tilted MnO6 and TeO6 octahedra enclosing disordered Ca2+ and Mn2+ cations. Magnetic measurements show that (Ca0.5Mn0.5)2MnTeO6 is a highly frustrated spin glass with a freezing transition at 5 K, and no long‐range spin order is apparent by neutron diffraction at 1.6 K. [ABSTRACT FROM AUTHOR]

Three new nitrides La3MN5 (M=Cr, Mn, and Mo) have been synthesized using a high pressure azide route. These are the first examples of ternary Cs3CoCl5‐type nitrides, and show that this (MN4)NLa3 antiperovskite structure type may be used to stabilise high oxidation‐state transition metals in tetrahedral molecular [MN4]n− nitridometallate anions. Magnetic measurements confirm that Cr and Mo are in the M6+ state, but the M=Mn phase has an anomalously small paramagnetic moment and large cell volume. Neutron powder diffraction data are fitted using an anion‐excess La3MnN5.30 model (space group I4/mcm, a=6.81587(9) Å and c=11.22664(18) Å at 200 K) in which Mn is close to the +7 state. Excess‐anion incorporation into Cs3CoCl5‐type materials has not been previously reported, and this or other substitution mechanisms may enable many other high oxidation state transition metal nitrides to be prepared. [ABSTRACT FROM AUTHOR]

An NMR-guided procedure for refining crystal structures has recently been introduced and shown to produce unusually high resolution structures. Herein, this procedure, is modified to include 15N shift tensors instead of the 13C values employed previously. This refinement involves six benchmark structures and 45 15N tensors. All refined structures show a statistically significant improvement in NMR fit over energy based refinements. Metrics other than NMR agreement indicate that NMR refinement does not introduce errors with no significant changes observed in atom positions or diffraction patterns. However, refinement does change bond lengths by more than experimental uncertainty with most bond types become shorter than diffraction values. Although this decrease is small (1–4 pm), it significantly alters computed 15N tensors. The NMR refinement was further evaluated by refining two tripeptides. These structures rapidly converged and achieved an NMR agreement equivalent to benchmark values. To ensure accurate comparisons, a complete atomic structure of the tripeptide AGG was determined by single crystal neutron diffraction at 0.58 Å resolution, allowing unambiguous determination of all hydrogen positions. To verify that all NMR refinements represent genuine improvements rather than artifacts of DFT methods, an independent approach was included to evaluate the final NMR refined coordinates. This analysis employs cluster methods and the PBE0 functional. The unusually small 15N NMR root-mean-square error of the final refined structures (3.6 ppm) supports the conclusion that the changes made represent improvements over both diffraction coordinates and lattice-including DFT energy refined coordinates. [ABSTRACT FROM AUTHOR]

Structure and magnetism of CoCr2 − xFexO4 (x = 0, 1 and 2) samples have been studied using room temperature X-ray and neutron diffraction; temperature and magnetic field dependent magnetization measurements. With increasing Fe content, it is observed that the magnetic ordering temperature increases while the nature of magnetic ordering undergoes drastic changes. The highlight of the work is that the equiatomic composition CoFeCrO4 (i.e., for x = 1 sample) exhibits lowest coercivity thus making it attractive for device applications. The present study shows control of magnetic properties through substitution, making it possible to prepare materials suitable for desired applications. [ABSTRACT FROM AUTHOR]

The crystal chemistry of inderborite, a B-rich mineral (B2O3 ~41 wt%) with ideal formula CaMg[B3O3(OH)5]2·6H2O or CaMg[B3O3(OH)5]2(H2O)4(H2O)4·2H2O from the Inder Deposit, Kazakhstan, was re-investigated by a multi-methodological approach (single-crystal X-ray and neutron diffraction, electron probe micro-analysis in wavelength-dispersive mode, laser ablation multi-collector inductively mass spectrometry). The experimental findings show that the real chemical formula of inderborite from the Inder Deposit is virtually identical to the ideal one: the fraction of potential isomorphic substituents is insignificant. Boron is, therefore, the only industrially relevant element occurring in this mineral. The in situ B isotope composition of the Inder inderborite shows enrichment in the heavy 11B isotope, giving a weighted mean δ11BNIST951 of +35.15 ± 0.49 ‰ (2σ, N = 6). Such a positive δ11B value falls within the range of values in which the source of boron is ascribable to marine reservoirs rather than to terrestrial ones. X-ray (at 293 K) and neutron (at 20 K) structure refinements confirm that the principal building block unit of the structure is a [B3O3(OH)5]2– ring, consisting of two BO2(OH)2 tetrahedra (B-ion in sp3 electronic configuration) and one planar-triangular BO2OH group (B-ion in sp2 electronic configuration). In the [B3O3(OH)5]2– ring, all the oxygen atoms that are not shared between two boron atoms are protonated. The building units share corners with the CaO2(OH)4(OH2)2 polyhedra and Mg(OH)4(OH2)2 octahedra, forming hetero-polyhedral sheets parallel to (100). Subsequent hetero-polyhedral sheets are mutually connected only by H-bonding interactions, even mediated by the zeolitic ("interstitial") H2O molecules. Ten out of 11 independent oxygen sites in the structure of inderborite are involved in H-bonds as donors or acceptors, and this reflects the pervasive effect of the H-bonding network. The role played by the complex H-bond network is expected to be substantial on the stability of the crystalline edifice, having effects within the single hetero-polyhedral sheet, between subsequent sheets, and in the bonding with the interstitial zeolitic H2O molecules. Finally, the potential utilizations of inderborite, as a B-bearing mineral, are discussed. [ABSTRACT FROM AUTHOR]

High-speed railway S38C axles undergo surface induction hardening for durability, but are susceptible to fatigue cracks from foreign object impact. The neutron diffraction method was employed to measure the residual strain in S38C axles, obtaining microscopic lattice distortion data, for the gradient layer at a depth of 8 mm under the surface. The results showed that after induction-hardening, the microscopic lattice distortion had a gradient distribution, decreasing with the distance from the surface. However, in the case of impacting speed of 600 km/m, the average microscopic lattice distortion increased with the distance from the surface, reaching a maximum augmentation of 55 pct. These findings indicate a strong experimental basis, and improve our understanding of the relationship between macroscopic residual stress and decision-making, in regard to operation and maintenance. [ABSTRACT FROM AUTHOR]

Structure and magnetism of CoCr2 − xFexO4 (x = 0, 1 and 2) samples have been studied using room temperature X-ray and neutron diffraction; temperature and magnetic field dependent magnetization measurements. With increasing Fe content, it is observed that the magnetic ordering temperature increases while the nature of magnetic ordering undergoes drastic changes. The highlight of the work is that the equiatomic composition CoFeCrO4 (i.e., for x = 1 sample) exhibits lowest coercivity thus making it attractive for device applications. The present study shows control of magnetic properties through substitution, making it possible to prepare materials suitable for desired applications. [ABSTRACT FROM AUTHOR]

This study investigated the anisotropy of the tensile properties in a duplex stainless steel of 24Cr-5Ni-0.18N based on in situ neutron diffraction experiments. The 24Cr-5Ni-0.18N steel showed a better balance of tensile strength (TS) and uniform elongation (U.El) compared with 329J4L and 329J1 steels. The Lankford value (r-value) of the 24Cr-5Ni-0.18N steel was comparable to other duplex stainless steels while showing a larger TS. Regarding the anisotropy of the mechanical properties, the results for a test specimen oriented at 45° showed a low yield strength (YS) and TS, but a better U.El and r-value. The hard phase of ferrite (α) played an essential role in the YS and TS. The austenite (γ) phase, which exhibited a large difference in the lattice strain related to the work hardening, contributed to the U.El, and its effect was further enhanced by the volume fraction of γ. The r-value increased with an increase in the lattice strain of {200}γ or a decrease in that of {200}α in the transverse direction. The lattice strain in the loading and transverse directions obtained by in situ neutron diffraction experiments also helped clarify the excellent r-values of duplex stainless steels. [ABSTRACT FROM AUTHOR]

Neutron diffraction instruments offer a platform for materials science and engineering studies at extended temperature ranges far from ambient. As one of the widely used neutron sample environment types, cryogenic furnaces are usually bulky and complex, and they may need hours of beamtime overhead for installation, configuration, cooling, and sample change, etc. To reduce the overhead time and expedite experiments at the state-of-the-art high-flux neutron source, we developed a low-cost, miniature, and easy-to-use cryogenic environment (77–473 K) for in situ neutron diffraction. A travel-size mug serves for the environment where the samples sit inside. Immediate cooling and an isothermal dwell at 77 K are realized on the sample by direct contact with liquid N2 in the mug. The designed Al inserts serve as the holder of samples and heating elements, alleviate the thermal gradient, and clear neutron pathways. Both a single-sample continuous measurement and multi-sample high-throughput measurements are demonstrated in this environment. High-quality and refinable in situ neutron diffraction patterns are acquired on model materials. The results quantify the orthorhombic-to-cubic phase transformation process in LiMn2O4 and differentiate the anisotropic lattice thermal expansions and bond length evolutions between rhombohedral perovskite oxides with composition variation. [ABSTRACT FROM AUTHOR]

Copyright of Atomic Energy Science & Technology is the property of Editorial Board of Atomic Energy Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Neutron diffraction is one of the three crystallographic techniques (X-ray, neutron and electron diffraction) used to determine the atomic structures of molecules. Its particular strengths derive from the fact that H (and D) atoms are strong neutron scatterers, meaning that their positions, and thus protonation states, can be derived from crystallographic maps. However, because of technical limitations and experimental obstacles, the quality of neutron diffraction data is typically much poorer (completeness, resolution and signal to noise) than that of X-ray diffraction data for the same sample. Further, refinement is more complex as it usually requires additional parameters to describe the H (and D) atoms. The increase in the number of parameters may be mitigated by using the `riding hydrogen' refinement strategy, in which the positions of H atoms without a rotational degree of freedom are inferred from their neighboring heavy atoms. However, this does not address the issues related to poor data quality. Therefore, neutron structure determination often relies on the presence of an X-ray data set for joint X-ray and neutron (XN) refinement. In this approach, the X-ray data serve to compensate for the deficiencies of the neutron diffraction data by refining one model simultaneously against the X-ray and neutron data sets. To be applicable, it is assumed that both data sets are highly isomorphous, and preferably collected from the same crystals and at the same temperature. However, the approach has a number of limitations that are discussed in this work by comparing four separately re-refined neutron models. To address the limitations, a new method for joint XN refinement is introduced that optimizes two different models against the different data sets. This approach is tested using neutron models and data deposited in the Protein Data Bank. The efficacy of refining models with H atoms as riding or as individual atoms is also investigated.

This study investigates the mechanical properties of a friction-stir-welded (FSW) AA6061-T6 aluminum alloy at ultra-low temperature (ULT) of 20 K. In-situ neutron diffraction and orientation imaging microscopy were employed to compare the tensile deformation behavior of the base metal (BM) and heat-affected zone (HAZ) in the FSW aluminum plate. The results demonstrate that compared to room-temperature (RT), ULT induces a significant improvement in tensile strength and ductility in both the BM and HAZ. The enhanced mechanical properties in BM at ULT result from a more homogeneous deformation than occurs at RT. On the other hand, HAZ at ULT exhibits an even lower yield strength than at RT, but the strain hardening rate (SHR) is the most significant among the alloys, leading to a tensile strength of 346 MPa and the highest ductility of 46.8%. The lowest yield strength corresponds to the lowest-hardness zones in HAZ, caused by dissolved/coarsened precipitates during the FSW process. The highest SHR in HAZ at ULT is attributed to the hardening of the {111} grain families and finer dislocation cell structures. The dislocation densities of both the BM and HAZ increased considerably during tensile deformation at ULT, which accounts for the improvement in tensile strength. Revealing the mechanism behind the remarkable improvement in the mechanical properties of FSW AA6061-T6 at ULT suggests its applicability for cryogenic applications.

High-energy x-ray diffraction from molten and glassy BaB2O4 and BaB4O7 has been performed using aerodynamic levitation and laser heating over a wide range of temperatures. Remarkably, even in the presence of a heavy metal modifier dominating x-ray scattering, it was possible to extract accurate values for the tetrahedral, sp3, boron fraction, N4, which declines with increasing temperature, using bond valence-based mapping from the measured mean B–O bond lengths while accounting for vibrational thermal expansion. These are used within a boron-coordination-change model to extract enthalpies, ΔH, and entropies, ΔS, of isomerization between sp2 and sp3 boron. The results for BaB4O7, ΔH = 22(3) kJ mol−1 boron, ΔS = 19(2) J mol−1 boron K−1, agree quantitatively with those found previously for Na2B4O7. Analytical expressions for N4(J, T) and associated configurational heat capacity, C P conf (J, T), and entropy, Sconf(J, T), contributions are extended to cover a wide composition range 0 ≤ J = BaO/B2O3 ≤ 3 using a model for ΔH(J) and ΔS(J) derived empirically for lithium borates. Maxima in the C P conf (J, Tg) and fragility index contributions are thereby predicted for J ≲ 1, higher than the maximum observed and predicted in N4(J, Tg) at J ≃ 0.6. We discuss the utility of the boron-coordination-change isomerization model in the context of borate liquids containing other modifiers and the prospect of neutron diffraction to aid in empirical determinations of modifier-dependent effects, illustrated by new neutron diffraction data on Ba11B4O7 glass, its well-known α-polymorph, and lesser-known δ-phase. [ABSTRACT FROM AUTHOR]

The development of multi-doped oxides based on the La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3–δ (LSCF) and La 1–x Sr x MnO 3+δ perovskites would help to achieve the improved electrochemical activity of air electrodes in protonic ceramic cells due to the formation of the single-phase triple-conducting material. The search for prospective medium-entropy and high-entropy oxides based on (La,Sr)(Co,Fe,Mn)O 3–δ could provide the electrode material with advanced hydration ability. In the present work, the formation and stability of new La 0.6 Sr 0.4 Co x Fe 1–x–y Mn y O 3–δ phases are estimated by thermodynamic calculations and the structure factors. Experimentally obtained La 0.6 Sr 0.4 Co x Fe 1–x–y Mn y O 3–δ powder samples are characterized by X-ray and neutron powder diffraction. The refined crystal structure parameters of the medium-entropy single-phase La 0.6 Sr 0.4 Co 0.33 Fe 0.33 Mn 0.33 O 3–δ (LSCFM333) oxide with the trigonal structure (space group R 3 ‾ c) and the cell parameters of a = 5.4642(1) Å and c = 13.284(4) Å in hexagonal axes are used to design of a supercell simulation for density functional theory (DFT) calculations. The first-principles results are proposed to evaluate the thermodynamic parameters of proton uptake to assess future applications of Mn-doped LSCF in proton-conducting ceramic cells. The calculated values of the hydration enthalpy Δ H h y d r for the LSCF and LSCFM333 derivatives are equal to 4.5 kJ mol−1 and –3.5 kJ mol−1, respectively, which are supported by the thermogravimetric analysis (TGA). The present study shows that the modeling techniques, including the thermodynamic and DFT calculations, can be successfully applied to the design of the related oxide materials for applications in solid oxide cells. [Display omitted] • Formation of La 0.6 Sr 0.4 Co x Fe 1–x–y Mn y O 3–δ phases was estimated and approved. • Crystal structure of Mn-doped LSCF was determined from neutron diffraction data. • Decrease in hydration enthalpies with Mn-doping was demonstrated by DFT and TGA. • Proton shift was found to affect the hydration enthalpy value. [ABSTRACT FROM AUTHOR]

Presented three-axis neutron diffractometer performance documents the feasibility of using it in special cases high-resolution powder diffraction studies, namely, for elastic and plastic deformation studies of bulk polycrystalline samples when the whole powder diffraction spectrum is not required. Contrary to the conventional double-axis setting the suggested alternative consists of an unconventional three axis set-up employing a bent perfect crystal (BPC) monochromator and analyzer with a polycrystalline sample in between. The analysis of the profile of the beam diffracted by a sample is carried out by rocking the BPC-analyzer and the neutron signal is registered by a point detector. Though the diffractometer alternative is, for measurements, much more time consuming, its resolution is, however, substantially higher and permits also plastic deformation studies on the basis of analysis of the sample diffraction profiles. The so-called analyzer rocking curve then provides a sample diffraction profile and could reflect the lattice or structural changes. Moreover, much larger widths (up to 10 mm) of the irradiated gauge volumes can be investigated when just slightly affecting the resolution of the experimental setting. [ABSTRACT FROM AUTHOR]

Hydrogen bond symmetrisation is the phenomenon where a hydrogen atom is located at the centre of a hydrogen bond. Theoretical studies predict that hydrogen bonds in ice VII eventually undergo symmetrisation upon increasing pressure, involving nuclear quantum effect with significant isotope effect and drastic changes in the elastic properties through several intermediate states with varying hydrogen distribution. Despite numerous experimental studies conducted, the location of hydrogen and hence the transition pressures reported up to date remain inconsistent. Here we report the atomic distribution of deuterium in D2O ice using neutron diffraction above 100 GPa and observe the transition from a bimodal to a unimodal distribution of deuterium at around 80 GPa. At the transition pressure, a significant narrowing of the peak widths of 110 is also observed, attributed to the structural relaxation by the change of elastic properties. Atomic distribution in high-pressure water ice are directly observed, via neutron powder structure analysis, found hydrogen bonds become symmetric at pressures about 80 GPa, marking the transition from ice VII to ice X. [ABSTRACT FROM AUTHOR]

Eliminating cobalt from high‐nickel layered oxide cathodes lowers the cost of lithium‐ion batteries for electric vehicles. However, cobalt‐free cathodes with high Mn4+ and Ni2+ contents are prone to Li/Ni mixing after synthesis, potentially compromising battery energy density, rate capability, and cycling stability. Without cobalt facilitating cation ordering in the layered structure, the degree of Li/Ni mixing in cobalt‐free cathodes depends heavily on the calcination conditions. In this study, a systematic exploration of calcination temperatures and LiOH ratio for LiNi0.9Mn0.1O2 (NM‐90) provides detailed insights into the optimal synthesis conditions for high‐capacity cobalt‐free cathodes with extended cycle life. Surprisingly, high Li/Ni mixing does not necessarily lead to poor cycling stability whereas low Li/Ni mixing does not guarantee a long cycle life. More importantly, although excessive calcination temperature can further decrease Li/Ni mixing, it does not necessarily enhance capacity. Instead, the pernicious effects from the H2 → H3 phase transition are amplified due to a pronounced two‐phase reaction. An extensive suite of chemical and structural characterization methods uncovers a correlation between elevated calcination temperature, phase transformation, cation ordering, and capacity fading behavior: "overcooking" high‐nickel, cobalt‐free cathodes induce structural arrangement toward that of LiNiO2, with exacerbated lattice distortion and surface instability accelerating capacity fade. [ABSTRACT FROM AUTHOR]

We report the high adsorption of NH3 in a titanium-based metal–organic framework, MFM-300(Ti), comprising extended [TiO6] ∞ chains linked by biphenyl-3,3′,5,5′ -tetracarboxylate ligands. At 273 K and 1 bar, MFM300(Ti) shows an exceptional NH3 uptake of 23.4 mmol g-1 with a record-high packing density of 0.84 g cm-3. Dynamic breakthrough experiments confirm the excellent uptake and separation of NH3 at low concentration (1000 ppm). The combination of in situ neutron powder diffraction and spectroscopic studies reveal strong, yet reversible binding interactions of NH3 to the framework oxygen sites. [ABSTRACT FROM AUTHOR]

Scintillator‐based ZnS:Ag/6LiF neutron detectors have been under development at ISIS for more than three decades. Continuous research and development aim to improve detector capabilities, achieve better performance and meet the increasingly demanding requirements set by neutron instruments. As part of this program, a high‐efficiency 2D position‐sensitive scintillator detector with wavelength‐shifting fibres has been developed for neutron‐diffraction applications. The detector consists of a double scintillator‐fibre layer to improve detection efficiency. Each layer is made up of two orthogonal fibre planes placed between two ZnS:Ag/6LiF scintillator screens. Thin reflective foils are attached to the front and back scintillators of each layer to minimize light cross‐talk between layers. The detector has an active area of 192 × 192 mm with a square pixel size of 3 × 3 mm. As part of the development process of the double‐layer detector, a single‐layer detector was built, together with a prototype detector in which the two layers of the detector could be read out separately. Efficiency calculations and measurements of all three detectors are discussed. The novel double‐layer detector has been installed and tested on the SXD diffractometer at ISIS. The detector performance is compared with the current scintillator detectors employed on SXD by studying reference crystal samples. More than a factor of 3 improvement in efficiency is achieved with the double‐layer wavelength‐shifting‐fibre detector. Software routines for further optimizations in spatial resolution and uniformity of response have been implemented and tested for 2D detectors. The methods and results are discussed in this manuscript. [ABSTRACT FROM AUTHOR]

Because of the neutron's special properties, neutron diffraction may be considered one of the most powerful techniques for structure determination of crystalline and related matter. Neutrons can be released from nuclear fission, from spallation processes, and also from low-energy nuclear reactions, and they can then be used in powder, time-of-flight, texture, single crystal, and other techniques, all of which are perfectly suited to clarify crystal and magnetic structures. With high neutron flux and sufficient brilliance, neutron diffraction also excels for diffuse scattering, for in situ and operando studies as well as for high-pressure experiments of today's materials. For these, the wave-like neutron's infinite advantage (isotope specific, magnetic) is crucial to answering important scientific questions, for example, on the structure and dynamics of light atoms in energy conversion and storage materials, magnetic matter, or protein structures. In this primer, we summarize the current state of neutron diffraction (and how it came to be), but also look at recent advances and new ideas, e.g., the design of new instruments, and what follows from that. [ABSTRACT FROM AUTHOR]

The crystal structure of superprotonic conductor caesium hydrogen sulfate phosphate [Cs4(HSO4)3(H2PO4)] have been analyzed using neutron diffraction methods. Additionally, its structure and surface layers have been investigated using atomic force microscopy. From the diffraction data obtained, Fourier syntheses of neutron scattering densities were calculated, and the localization of hydrogen atoms and the parameters of three types of hydrogen bonds in the crystal structure were accurately determined. Correlation of surface characteristics of samples obtained by atomic force microscopy with their crystal structure is shown. [ABSTRACT FROM AUTHOR]

Bridgmanite, the most abundant mineral in the lower mantle, can play an essential role in deep-Earth hydrogen storage and circulation processes. To better evaluate the hydrogen storage capacity and its substitution mechanism in bridgmanite occurring in nature, we have synthesized high-quality single-crystal bridgmanite with a composition of (M g 0.88 F e 0.05 2 + F e 0.05 3 + A l 0.03) (S i 0.88 A l 0.11 H 0.01) O 3 at nearly water-saturated environments relevant to topmost lower mantle pressure and temperature conditions. The crystallographic site position of hydrogen in the synthetic (Fe,Al)-bearing bridgmanite is evaluated by a time-of-flight single-crystal neutron diffraction scheme, together with supporting evidence from polarized infrared spectroscopy. Analysis of the results shows that the primary hydrogen site has an OH bond direction nearly parallel to the crystallographic b axis of the orthorhombic bridgmanite lattice, where hydrogen is located along the line between two oxygen anions to form a straight geometry of covalent and hydrogen bonds. Our modeled results show that hydrogen is incorporated into the crystal structure via coupled substitution of Al3+ and H+ simultaneously exchanging for Si4+, which does not require any cation vacancy. The concentration of hydrogen evaluated by secondary-ion mass spectrometry and neutron diffraction is ~0.1 wt% H2O and consistent with each other, showing that neutron diffraction can be an alternative quantitative means for the characterization of trace amounts of hydrogen and its site occupancy in nominally anhydrous minerals. [ABSTRACT FROM AUTHOR]

The maximum thickness for ferritic steel specimens' residual stress measurements using neutron diffraction is known to be about 80 mm. This paper proposes a new neutron diffraction configuration of residual stress measurements for cases that are over 80 mm thick. The configuration utilizes a neutron beam with a wavelength of 1.55 Å diffracted from the (220) plane with a diffraction angle (2θ) of 99.4°. The reason for the deep penetration capability is attributed to the chosen wavelength having enough intensities due to the low cross-section near the Bragg edge and the reduced beam path length (~16 mm) reflected by the large diffraction angle. Neutron diffraction experiments with this configuration can decrease strain errors up to ±150 με, corresponding to a stress of about ±30 MPa. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of High Pressure Physics is the property of Chinese Journal of High Pressure Physics Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

High-entropy alloys (HEAs) possess outstanding features such as corrosion resistance, irradiation resistance, and good mechanical properties. A few HEAs have found applications in the fields of aerospace and defense. Extensive studies on the deformation mechanisms of HEAs can guide microstructure control and toughness design, which is vital for understanding and studying state-of-the-art structural materials. Synchrotron X-ray and neutron diffraction are necessary techniques for materials science research, especially for in situ coupling of physical/chemical fields and for resolving macro/microcrystallographic information on materials. Recently, several researchers have applied synchrotron X-ray and neutron diffraction methods to study the deformation mechanisms, phase transformations, stress behaviors, and in situ processes of HEAs, such as variable-temperature, high-pressure, and hydrogenation processes. In this review, the principles and development of synchrotron X-ray and neutron diffraction are presented, and their applications in the deformation mechanisms of HEAs are discussed. The factors that influence the deformation mechanisms of HEAs are also outlined. This review focuses on the microstructures and micromechanical behaviors during tension/compression or creep/fatigue deformation and the application of synchrotron X-ray and neutron diffraction methods to the characterization of dislocations, stacking faults, twins, phases, and intergrain/interphase stress changes. Perspectives on future developments of synchrotron X-ray and neutron diffraction and on research directions on the deformation mechanisms of novel metals are discussed. [ABSTRACT FROM AUTHOR]

Doubly substituted Ti 2 CrV alloy with composition Ti 1.5 Sc 0.3 CrVNi 0.2 was prepared by arc melting method followed by annealing. The annealed alloy exists in body centred cubic (BCC) structure and shows fast kinetics for hydrogen absorption and desorption at room temperature. BCC phase of the alloy undergoes phase transformation to face centred cubic (FCC) hydride phase with H atoms occupying tetrahedral sites in the lattice, reaching an overall H/M ratio >2.2 (storage capacity ∼ 4 wt%). Storage capacity decreases by 40% in the 2nd cycle and then stabilizes at a value of ∼2.5 wt% for the subsequent 10 cycles. A drastic reduction in hydride desorption temperature upon double substitution (Sc and Ni substitution in Ti 2 CrV alloy) has been confirmed by DSC studies. Furthermore, the change in isotope effect in doubly substituted Ti 2 CrV alloy is discussed in light of thermal stabilities of the hydrides and deuterides. [Display omitted] • Ti 2 CrV alloy doubly substituted by Sc and Ni has been prepared via arc melting method. • The hydrogen uptake of Ti 1.5 Sc 0.3 CrVNi 0.2 alloy is > 2.2H/M at room temperature. • Neutron diffraction studies confirmed occupancy of H atoms in tetrahedral sites. • Synergistic effect of Sc and Ni double substitution causes remarkable decrease in desorption temperature of Ti 2 CrV alloy. • Isotope effects in Ti 2 CrV–H 2 /D 2 and Ti 1.5 Sc 0.3 CrVNi 0.2 -H 2 /D 2 systems have been studied. [ABSTRACT FROM AUTHOR]

Owing to geometrical frustration in the kagome lattice, Mn3Sn displays a 120° in-plane triangular antiferromagnetic order, a manifestation of exchange interaction within the Heisenberg model. Here, we show the formation of a tunable noncoplanar magnetic ground state stabilized by higher-order exchange interactions in electron-doped Mn3Sn samples. Our density Functional Theory calculations reveal that the higher-order exchange induces a partial out-of-plane alignment of the Mn moments, resulting in a canted magnetic state, further experimentally confirmed by neutron diffraction study along with 60 T magnetic and Hall resistivity measurements. Interestingly, we find a large scalar spin chirality-induced Hall signal depending on the degree of non-coplanarity of the Mn moments. Additionally, we demonstrate simultaneous manipulation of two-component order-parameter in the system, where the two Hall signals can be independently manipulated. The present study explores the quantum phenomena associated with the coexistence of multiple magnetic orders and their prospective use in spintronic devices. [ABSTRACT FROM AUTHOR]