Synchrotron X-ray Diffraction Techniques Research Articles

Разложение аммиака на Co-Al2O3 /SiO2 катализаторах: влияние способов восстановления кобальта

The focus on "green" energy requires the search for environmentally friendly energy storage systems. The reason for choosing ammonia as a potential storage for hydrogen is its high energy capacity and the absence of carbon and nitrogen oxide emissions during decomposition. Herein, we tested Co-Al2O3/SiO2 ammonia decomposition catalysts that had been pre-activated via cyclic hydrogenation-carburization-hydrogenation (RCR) and reduction-oxidation-reduction (ROR) procedures versus the conventional cobalt oxides reduction with hydrogen (R). The samples were characterized by H2-TPR, TEM and synchrotron X-ray diffraction techniques, which revealed that the structural properties of the catalysts were not modified by the reaction. Since the activities of the tested catalysts and the effective reaction barriers appeared to be close, the easiest-to-prepare catalyst R was chosen for the long-term catalytic trial (500 h), and it showed excellent performance stability.

The dielectric and radiation shielding features of Zn0.9Ni0.1Co2-xFexO4 nanopowder

Nano Zn0.9Ni0.1Co2-xFexO4 (x = 0, 0.05, 0.1, 0.15) specimens were synthesized utilizing the hydrothermal method. An extensive assessment was conducted on the structure and dielectric characteristics of the fabricated specimens. The synchrotron x-ray diffraction and scanning electron microscopy techniques were employed to analyze the formed phases and the morphological characteristics of the specimens. Rietveld refinement was utilized for determining the structural and microstructural parameters of all specimens. The impact of temperature and frequency on the dielectric properties of the material is thoroughly investigated. Except for the specimen with x = 0.15, all samples exhibit ferroelectric characteristics. The electric modulus corroborated the existence of the non-Debye relaxation phenomenon and the presence of relaxation times distributed at a specific frequency. Each specimen demonstrates a singular relaxation time, which was modified by the introduction of Fe ions. Through the utilization of the Phy-X/PSD software, the radiation shielding parameters for the examined specimens were computed across a wide energy spectrum ranging from 15 KeV to 15 MeV. These parameters encompass the linear attenuation coefficients (LAC), mean free path (MFP), mass attenuation coefficient (MAC), half value length (HVL), effective nuclear number (Z eff), and fast neutron removal cross-section (FNRCS). The specimens of Zn0.9Ni0.1Co2-xFexO4 exhibit elevated FNRCS values compared to RS-253-G18, RS-360, and RS-520 commercial shielding glasses.

Enhancement the electrical and linear/nonlinear optical properties of ZnCo2O4 through Al3+doping

In this work, ZnCo2O4 samples doped with Al3+ were prepared by the hydrothermal method. Synchrotron x-ray diffraction, FTIR, SEM and EDX techniques were used to investigate the structure, microstructure, morphology, and composition of ZnCo2-xAlxO4 samples. Rietveld analysis revealed a nearly inverse structure for the undoped ZnCo2O4. The degree of inversion is increased upon increasing the Al3+ doping content. Al ions preferentially occupy the octahedral B-site. The optical band gaps of ZnCo2−xAlxO4 samples are 1.9, 1.8 and 1.91 eV for x = 0, 0.1 and 0.2, respectively. Different empirical models were used to obtain the refractive index of the different samples using their corresponding optical band gaps. The increase in non-linear optical values in the sample with x = 0.1 suggested that this sample could be used in a variety of photonic applications. The effects of frequency and temperature on the dielectric permittivity, impedance and electrical modulus of different samples were explored. All samples exhibited the non-Debye relaxation phenomenon. The relaxation time of each sample is affected with the frequency and temperature. The Cole-Cole curve is employed to reduce uncertainty regarding the electrical characteristics of these ZnCo2−xAlxO4 samples induced by grain boundaries or bulk grain. The substitution of Al3+ ions can regulate the conductivity of the ZnCo2O4 sample.

Microstructures and micromechanical behaviors of high-entropy alloys investigated by synchrotron X-ray and neutron diffraction techniques: A review

Microstructures and micromechanical behaviors of high-entropy alloys investigated by synchrotron X-ray and neutron diffraction techniques: A review

Coprecipitation Strategy for Halide-Based Solid-State Electrolytes and Atmospheric-Dependent In Situ Analysis.

In the continuous pursuit of an energy-efficient alternative to the energy-intensive mechanochemical process, we developed a coprecipitation strategy for synthesizing halide-based solid-state electrolytes that warrant both structural control and commercial scalability. In this study, we propose a new coprecipitation approach to synthesized Li3InCl6, exhibiting both structural and electrochemical performance stability, with a high ionic conductivity of 1.42 × 10-3 S cm-1, comparable to that of traditionally prepared counterparts. Through the in situ synchrotron X-ray diffraction technique, we unveil the stability mechanisms and rapid chemical reactions of Li3InCl6 under dry Ar, dry O2, and high-humidity atmosphere, which were not previously reported. Furthermore, the fast reversibility capability of moisture-exposed Li3InCl6 was tracked under vacuum, revealing the optimal recovery conditions at low temperatures (150-200 °C). This work addresses the critical challenges in structural engineering and sustainable mass production and provides insights into chemical reactions under real-world conditions.

Phase transformation and thermal stability of the laser powder bed fused high-strength and heat-resistant Al–Ce–Mg alloy

The coarsening of strengthening phases, phase transformations, and interface stability between these phases and the matrix play a crucial role in determining the strength, ductility, and heat resistance of aluminum alloys fabricated through additive manufacturing (AM). In this study, a heat exposure experiment at 400 °C for 1 h was conducted on the laser powder bed fused Al–Ce–Mg alloy. A comprehensive analysis of the microstructural evolution, phase composition, interfacial bonding strength, and mechanical properties before and after heat exposure was performed using synchrotron X-ray diffraction techniques, first-principles calculations, transmission electron microscopy, and mechanical testing. For the first time, a phase transformation from Al11Ce3 to Al4Ce was discovered. Some semi-coherent relationships of [301]Al11Ce3//[011]Al, (060)Al11Ce3//(00)Al were transformed into coherent relationships of [001]Al4Ce//[001]Al, (200)Al4Ce//(00)Al, and the interfacial energy was reduced by 4.385 J m−2. In-situ Al11Ce3 nano-networks after heat exposure were retained and Al4Ce nanoparticles contribute to the thermal stability of the alloy by hindering dislocation motion and grain coarsening. The strength of the heat exposure alloy reached up to 416 MPa, which is about 95 % of the strength of the as-fabricated state and the elongation increased from 9.3 % to 13.8 %. These results provide a new approach for the design of high strength-ductility synergy and heat-resistant aluminum alloys via AM.

In situ synchrotron X-ray diffraction analysis of ultrasonically assisted microstructure refinement during laser melting process

This work investigates the effect of ultrasonic treatment (UST) on the microstructure of AA4043 alloy during laser melting process. The study utilizes in situ synchrotron X-ray diffraction (SXRD) and postmortem electron backscatter diffraction (EBSD) techniques to examine the ultrasonic grain refinement mechanism. The SXRD diffraction patterns exhibit higher continuity of major diffraction rings in the UST-test pattern, indicating a more refined grain structure. The presence of new diffraction spots in the post-test diffraction pattern with UST suggests the breakdown of epitaxial growth of columnar dendrites during solidification. Thermal profiles determined by analyzing the lattice parameter evolution show a faster cooling rate with UST. The inverse pole figures and aspect ratio distribution from EBSD reveal that the UST samples exhibit a refined, more equiaxed grain structure along the weld centerline. UST sample also develops more fine-sized low angle grain boundaries (LAGBs). These features offer better hot-cracking resistance in aluminum alloys.

Experimental electron density distribution of KZnB3O6 constructed by maximum-entropy method

The dynamic charge density of KZnB3O6, which contains edge-sharing BO4 units, has been characterized using laboratory and synchrotron X-ray diffraction techniques. The experimental electron density distribution (EDD) was constructed using the maximum-entropy method (MEM) from single crystal diffraction data obtained at 81 and 298 K. Additionally, MEM-based pattern fitting (MPF) method was employed to refine the synchrotron powder diffraction data obtained at 100 K. Both the room-temperature single crystal diffraction data and the cryogenic synchrotron powder diffraction data reveal an intriguing phenomenon: the edge-shared B2O2 ring exhibits a significant charge density accumulation between the O atoms. Further analysis of high-quality single crystal diffraction data collected at 81 K, with both high resolution and large signal-to-noise ratio, reveals no direct O–O bonding within the B2O2 ring. The experimental EDD of KZnB3O6 obtained aligns with the results obtained from ab-initio calculations. Our work underscores the importance of obtaining high-quality experimental data to accurately determine EDDs.

The asymmetric evolution of grain-scale stresses in notched specimens under cyclic loads

Engineering components are often exposed to various cyclic loading conditions. The development of microscale stresses under such conditions depends on the material texture, local microstructure, the degree of crystals elastic and plastic anisotropy, as well as the presence of geometrical irregularities. In this study, the three-dimensional synchrotron X-ray diffraction (3D-XRD) technique is used and coupled with a crystal plasticity finite element (CPFE) model to deconvolute the contribution of such parameters on the magnitude of localized stresses. Special attention is paid to the notch geometry, where two double-edge-notched α-zirconium specimens with different geometries but the same texture were deformed in-situ while grain-scale stresses were measured both in the vicinity of the notches and in the far-field zones. Deep and shallow notches were cut to the dimensions comparable with the specimens’ average grain sizes. For each specimen, the center of mass, orientation, elastic strain, stress, and relative volume of more than 6,000 grains were measured and studied. Post-deformation analysis with Electron Backscatter Diffraction (EBSD) was conducted to further validate the observed trends. It is shown that the distribution of grain-scale stresses is asymmetric within each specimen. This asymmetry develops from the early stages of the applied cyclic load and remains intact with further loading. A new method is introduced for quantifying the effects of grain neighbourhood on load sharing, where it is shown that such effects relax the stresses acting on “hard” grains, altering grain-scale stress concentration factors.

High-Pressure Vibrational and Structural Studies of the Chemically Engineered Ferroelectric Phase of Sodium Niobate

Pure NaNbO3 has an antiferroelectric phase at ambient pressure. The structural behaviour of the chemically engineered ferroelectric phase of sodium niobate, NNBT05: [(0.95) NaNbO3-(0.05) BaTiO3], under high-pressure has been studied using Raman scattering and angle-dispersive synchrotron X-ray diffraction techniques. At pressure > 1 GPa, noticeable changes in the Raman spectra can be seen in the low wavenumber modes (150–300 cm−1). Large changes in the positions and intensities of the Raman bands as a function of pressure provide evidence for structural phase transition. The results indicate significant changes in the bond-lengths and the orientation of the NbO6 octahedra at ~1 GPa, and a transition to the paraelectric phase at ~5 GPa, which are at lower pressures than previously found in pure NaNbO3. The powder X-ray diffraction pattern shows an appreciable change in the peak profile in terms of position and width on increasing pressure. The pressure dependences of the structural parameters show that the response of the lattice parameters to pressure is strongly anisotropic. By fitting the pressure–volume data using the Birch–Murnaghan equation of state, the isothermal bulk modulus was estimated. The experimental results suggest that on doping BaTiO3 in NaNbO3, the bulk modulus increases. The bulk modulus of NNBT05 has been estimated to be 164.5 GPa, which is fairly close to 157.5 GPa, as previously observed in NaNbO3.

Correlating Rate-Dependent Transition Metal Dissolution between Structure Degradation in Li-Rich Layered Oxides.

Understanding the mechanism of the rate-dependent electrochemical performance degradation in cathodes is crucial to developing fast charging/discharging cathodes for Li-ion batteries. Here, taking Li-rich layered oxide Li1.2 Ni0.13 Co0.13 Mn0.54 O2 as the model cathode, the mechanisms of performance degradation at low and high rates are comparatively investigated from two aspects, the transition metal (TM) dissolution and the structure change. Quantitative analyses combining spatial-resolved synchrotron X-ray fluorescence (XRF) imaging, synchrotron X-ray diffraction (XRD) and transmission electron microscopy (TEM) techniques reveal that low-rate cycling leads to gradient TM dissolution and severe bulk structure degradation within the individual secondary particles, and especially the latter causes lots of microcracks within secondary particles, and becomes the main reason for the fast capacity and voltage decay. In contrast, high-rate cycling leads to more TM dissolution than low-rate cycling, which concentrates at the particle surface and directly induces the more severe surface structure degradation to the electrochemically inactive rock-salt phase, eventually causing a faster capacity and voltage decay than low-rate cycling. These findings highlight the protection of the surface structure for developing fast charging/discharging cathodes for Li-ion batteries.

Resolving intragranular stress fields in plastically deformed titanium using point-focused high-energy diffraction microscopy

The response of a polycrystalline material to a mechanical load depends not only on the response of each individual grain, but also on the interaction with its neighbors. These interactions lead to local, intragranular stress concentrations that often dictate the initiation of plastic deformation and consequently the macroscopic stress–strain behavior. However, very few experimental studies have quantified intragranular stresses across bulk, three-dimensional volumes. In this work, a synchrotron X-ray diffraction technique called point-focused high-energy diffraction microscopy (pf-HEDM) is used to characterize intragranular deformation across a bulk, plastically deformed, polycrystalline titanium specimen. The results reveal the heterogenous stress distributions within individual grains and across grain boundaries, a stress concentration between a low and high Schmid factor grain pair, and a stress gradient near an extension twinning boundary. This work demonstrates the potential for the future use of pf-HEDM for understanding the local deformation associated with networks of grains and informing mesoscale models.Graphical abstract

Stoichiometry matters: correlation between antisite defects, microstructure and magnetic behavior in the cathode material Li1−zNi1+zO2

Using synchrotron X-ray and neutron diffraction, NMR and magnetometry techniques, this study reveals how point defects evolve and critically affect particle growth and magnetic properties in the cathode material Li1−zNi1+zO2 (−0.05 ≤ z ≤ 0.35).

In situ High-Energy Synchrotron X-ray Studies in Thermodynamics of Mg-In-Ti Hydrogen Storage System

Achieving dual regulation of the kinetics and thermodynamics of MgH 2 is essential for the practical applications. In this study, a novel nanocomposite (In@Ti-MX) architected from single-/few-layered Ti 3 C 2 MXenes and ultradispersed indium nanoparticles was prepared by a bottom-up self-assembly strategy and introduced into MgH 2 to solve the above-mentioned problems. The MgH 2 +In@Ti-MX composites demonstrate excellent hydrogen storage performance: The resultant In@Ti-MX demonstrated a positive effect on the hydrogen storage performance of MgH 2 /Mg: the dehydrogenated rate of MgH 2 +15 wt%In@Ti-MX reached the maximum at 330 °C, which was 47 °C lower than that of commercial MgH 2 ; The hydrogenation enthalpy of the dehydrided MgH 2 +15 wt%In@Ti-MX and MgH 2 +25 wt%In@Ti-MX were determined to be −66.2 ± 1.1 and −61.7 ± 1.4 kJ·mol −1 H 2 . In situ high-energy synchrotron x-ray diffraction technique together with other microstructure analyses revealed that synergistic effects from Ti 3 C 2 MXenes and In nanoparticles (NPs) contributed to the improved kinetics and thermodynamics of MgH 2 (Mg): Ti/TiH 2 derived from Ti 3 C 2 MXenes accelerated the dissociation and recombination of hydrogen molecule/atoms, while In NPs reduced the thermodynamic stability of MgH 2 by forming the Mg-In solution. Such a strategy of using dual-active hybrid structures to modify MgH 2 /Mg provides a new insight for tuning both the hydrogen storage kinetics and thermodynamics of Mg-based hydrides.

A giant cuboctahedron based on imidazolium-terpyridine spacer

Giant supramolecular polyhedra are fascinating because of their large cavity, with applications in enzyme-mimetic catalysis, host-guest chemistry, and drug delivery. We report a coordination-driven, cuboctahedron-shaped, imidazolium-terpyridine-based supramolecular cage structure of about 7.3 nm diameter consisting of 12 ligands, 24 Zn 2+ ions, and 60 or 72 anions. The steric hindrance effect from chains on the imidazolium group keeps it perpendicular to the central linkage, which readily undergoes endohedral or exohedral decoration in functionalization. A reversible pH-controlled ring closure and opening reaction of the imidazolium ligand leads to a supramolecular fusion process from a triangular prism to a cuboctahedron. The compounds were characterized unambiguously by NMR, ESI-TWIM-MS, gMS 2 , Cryo-EM, and synchrotron X-ray diffraction techniques. Being readily modifiable through endo and exo pathways, the cages may provide a platform for the investigation of the biological mimic systems, confined nanotechnology, and confined molecular arrangements. • Steric hindrance drives the formation of giant cuboctahedron-shaped structures • pH-induced ring closure/opening of imidazolium leads to in situ structural transformation • Anchored groups within the cage facilitate endo-/exohedral functionalization Accessing giant supramolecular cages capable of structural transformation and straightforward functionalization is a challenge. Tang et al. report a giant terpyridine-based cuboctahedron with modifiable sites pre-organized by rotatable imidazolium motifs, which undergoes structural conversion from triangular prism to cuboctahedron at low pH.

Advances in the Synthesis and Superconductivity of Lanthanide Polyhydrides Under High Pressure

Room-temperature superconductors have long been the ultimate goal of scientists. Pressure-stabilized hydrides are a new rapidly growing class of high-temperature superconductors and are believed to be a new superconducting system, undoubtedly leading to a surge in the discovery of new hydrogen-rich materials. They are the forefront of physics and material science. Lanthanide polyhydrides formed under pressure are promising conventional superconductors. Especially, both the theoretical and experimental reports on lanthanum superhydrides under pressure, exhibiting superconductivity at temperatures as high as 250 K, have further stimulated an intense search for room-temperature superconductors in hydrides. This review focuses on the recent advances of crystal structures, stabilities, and superconductivity of lanthanide polyhydrides at high pressures, including the experimental results from our group. By using in situ four-probe electrical measurements and the synchrotron X-ray diffraction technique, we have identified several high-temperature superconducting phases: a lanthanum superhydride and two cerium superhydrides. The present work indicates that superconductivity declines along the La–Ce–Pr–Nd series, while magnetism becomes more and more pronounced. These discoveries have enriched the binary system of clathrate superhydrides and provided more hints for studying the role of rare earth metal elements having high-temperature superconductivity.

Plastic anisotropy and twin distributions near the fatigue crack tip of textured Mg alloys from in situ synchrotron X-ray diffraction measurements and multiscale mechanics modeling

In spite of many potential applications due to their superior mechanical properties, magnesium alloys still find many practical restrictions primarily due to our limited knowledge of their failure mechanisms. In situ and non-destructive strain measurements on the microstructural scales are critical in understanding the fatigue crack behavior, which has greater advantages than the macroscopic measurements based on replica technique and the small-scale mechanical testing that cannot easily provide a complete view on the synergy of many scale-dependent deformation and failure mechanisms. This work exploits the state-of-the-art synchrotron X-ray diffraction technique to attain in situ strain mapping results, with high spatial resolution, near a fatigue crack tip in the highly textured ZK60 Mg alloy. The accurate measurements in the plastic zone are compared to a micromechanical modeling framework, in which the steady fatigue crack is simulated by an irreversible, hysteretic cohesive interface model and the surrounding plasticity by Hill anisotropic plasticity. The general agreement in the anisotropic deformation fields is reached down to half of the plastic zone size towards the crack tip, while the discrepancy right at the crack tip can be used to develop an inverse model to extract the material-specific fatigue damage evolution in our future work. It is surprisingly noted that twin activities are localized in a narrow band from the tip to the wake of the fatigue crack, irrespective of the crack growth direction of this textured alloy. Such twin-crack interactions are understood here by our crystal plasticity finite element simulations with several representative crystallographic orientations.

Spin-lattice-charge coupling in quasi-one-dimensional spin-chain NiTe2O5

A high-quality ${\mathrm{NiTe}}_{2}{\mathrm{O}}_{5}$ single crystal was grown via the flux method and characterized using synchrotron x-ray diffraction (XRD) and electron probe microscopy techniques. The dc magnetization $(M)$ confirms the antiferromagnetic long-range ordering temperature $({T}_{\mathrm{N}})$ at 28.5 K. An apparent domelike dielectric anomaly near ${T}_{\mathrm{N}}$, with scaling of magnetodielectric (MD) coupling with magnetization $(\mathrm{MD}%\ensuremath{\propto}{M}^{2})$, signifies higher-order magnetoelectric (ME) coupling. The critical finding is that magnetoelastic coupling plays a pivotal role in bridging the electrical and magnetic dipoles, which was further confirmed by temperature-dependent XRD. In addition, the theoretical charge density difference maps indicate that the emergence of electrical dipoles between the Ni and O atoms below ${T}_{\mathrm{N}}$ originates through $p\text{\ensuremath{-}}d$ hybridization. Thus, the $p\text{\ensuremath{-}}d$ hybridization-induced magnetoelastic coupling is considered a possible mechanism for the higher-order ME effect in this quasi-one-dimensional spin-chain ${\mathrm{NiTe}}_{2}{\mathrm{O}}_{5}$.

Stable hexagonal ternary alloy phase in Fe-Si-H at 28.6–42.2 GPa and 3000 K

Hydrogen (H) and silicon (Si) are considered as important light elements for the planetary cores. A large amount of H is able to alloy with pure Fe metal at high pressures. Si can also alloy well with Fe. However, it remains uncertain how much H can alloy with iron silicides and if it alloys how H can alter the crystal structures of Fe-Si alloys at high pressures-temperatures ($P\text{\ensuremath{-}}T$). We performed experiments on Fe-9Si and Fe-16Si alloys (9 and 16 wt % Si, respectively) in a H medium up to 42.2 GPa and 3000 K in diamond-anvil cells coupled with pulsed laser heating and gated synchrotron x-ray diffraction techniques. We found conversion of the Fe-Si alloys into Fe-rich (fcc and dhcp $\mathrm{Fe}{\mathrm{H}}_{x}$), Si-rich (B20 and B2 FeSi), and intermediate (${\mathrm{Fe}}_{5}{\mathrm{Si}}_{3}{\mathrm{H}}_{x}$) phases. The new ${\mathrm{Fe}}_{5}{\mathrm{Si}}_{3}{\mathrm{H}}_{x}$ phase has a structure similar to the hexagonal ${\mathrm{Fe}}_{5}{\mathrm{Si}}_{3}$ phase but with expanded volumes, and thus, possible H incorporation. Both the observed volume expansion and the H content estimated by density-functional theory calculations support a significant amount of H with H/Fe \ensuremath{\approx} 0.6 in the crystal structure. Because ${\mathrm{Fe}}_{5}{\mathrm{Si}}_{3}$ is known to break down above \ensuremath{\sim}1300 K at \ensuremath{\sim}18 GPa, our results suggest that hydrogen stabilizes the hexagonal structure at high $P\text{\ensuremath{-}}T$. These results have implications for the crystallization of Fe-rich liquid at the solid-to-liquid boundary of planetary cores and possible existence of chemical heterogeneities in the solid cores.

An intriguing canting dipole configuration and its evolution under an electric field in La-doped Pb(Zr,Sn,Ti)O3 perovskites

Despite the fact that electric dipole ordering plays a key role in the unique physical properties of dielectric materials, electric dipole configurations mostly appear simply as either parallel or antiparallel. Here, we report a canting electric dipole configuration in La-doped Pb(Zr,Sn,Ti)O3 perovskites based on advanced neutron, synchrotron X-ray and three-dimensional electron diffraction techniques. It is revealed that, arising from the coupling between the atomic displacement and oxygen octahedral tilting, this unique electric dipole configuration displays a canting arrangement aligned in the (110)p plane that possesses an antiparallel component along the [110]P direction and a parallel component along the [001]P direction. Remarkably, under an in-situ electric field, the electric dipoles continuously rotate with a gradually reduced canting angle, as confirmed by phase-field simulations, and ultimately evolve into a ferroelectric ordering. Such an evolution gives rises to a small hysteresis and an equivalent lattice strain to the macroscopic strain. These findings enrich the current understanding of the types of electric dipole configurations in dielectric materials and are expected to aid the design of new dielectric materials with emergent properties.