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In this study, enzymatic synthesis was conducted using cellodextrin phosphorylase (CDP), sucrose phosphorylase (SP), and sucrose with 1-azido-1-deoxy-β-glucoside (β-glucosyl azide) as the acceptor in phosphate buffer at pH 7.0. This yielded cellulose oligomers (degree of polymerization, DP ≈ 10) with azido groups at the reducing end as a white precipitate. A suspension of cellulose microcrystals with exposed azido groups on the surface was obtained via dissolution and recrystallization of the synthetic products dispersed in water by heating. The flat, ribbon-like cellulose microcrystals were a crystalline form of cellulose II and were several micrometers in length and several hundred nanometers in width. The microcrystals were 5.1–5.2 nm thick, which is equivalent to the chain length of cellulose oligomers with DP ≈ 10. When the cellulose II microcrystal suspensions were dried under a horizontal static magnetic field of 8 T, oriented films were obtained, wherein the microcrystals were aligned three-dimensionally. Synchrotron X-ray diffraction studies of the films revealed that the easy and intermediate axes (χ1 and χ2, respectively) of the cellulose II crystals corresponded approximately to the [1 1 0] and [1 1 ¯ 0] directions, respectively. [ABSTRACT FROM AUTHOR]

In this work, multi-principal element alloys (MPEAs) with the five base elements Al, Cr, Fe, Ni and Ti plus elements in minor amounts were produced by powder metallurgy and their microstructure and elastic behavior were analyzed via light and scanning electron microscopy, electron backscatter diffraction (EBSD) and synchrotron X-ray diffraction. The two studied compositions are an MPEA with Al, Cr, Fe, Ni and Ti in equimolar ratio as well as a similar composition with a concentration of Ti reduced to 10 mol%. The goal is to analyze the microstructural behavior of these compositions during macroscopic loading in dependence of chemical composition and phases present. Analysis via synchrotron X-ray diffraction predicts the presence of body-centered cubic phases, Full Heusler-phases and C14_Laves-phases in both compositions, MPEA5 and MPEA_Ti10. Synchrotron X-ray diffraction offers the possibility to monitor the deformation of these phases during macroscopic loading of specimens. Thermodynamic calculations of stable phases predicted a microstructure of MPEA5 consisting of body-centered cubic and Full Heusler-phases at room temperature. Further calculation and X-ray diffraction experiments showed the stabilization of minor amounts of C14_Laves-phase ( Fe 2 Ti ) at room temperature with a decreasing amount of Ti. MPEA5 showed the development of long and un-branched cracks during compressive testing, which resulted in a remarkable decrease in lattice-dependent elastic moduli. MPEA_Ti10 exhibited branched cracks during compression tests. Also, the lattice-dependent elastic moduli of MPEA_Ti10 did not change notably during the compression tests. In both compositions, the Full Heusler-phase showed the lowest lattice-dependent elastic moduli, hence taking the largest share of the overall deformation among all phases present in the materials under macroscopic loading. [ABSTRACT FROM AUTHOR]

Laser welding of a Ni-rich NiTi-20Zr (at.%) high temperature shape memory alloy was performed. The starting base material was aged for 3 h at 550 °C followed by air cooling prior to welding to induce H-phase precipitation. Advanced microstructure characterization encompassing scanning and transmission electron microscopy, coupled with synchrotron X-ray diffraction, were used. Defect-free welds were obtained with a conduction welding mode. The weld thermal cycle altered the microstructure across the heat affected and fusion zones of the joints. The heat affected zone exhibited partial H-phase dissolution, causing a decrease in hardness. In the fusion zone, the H-phase fully dissolved, and the non-equilibrium rapid solidification conditions prevented the H-phase from re-precipitating during cooling, leading to a microstructure resembling that of an as-cast alloy with the same material composition. Mechanical testing revealed that the laser welded samples sustained stresses in the order of 500 MPa and exhibited stress-strain responses comparable to those of the unwelded base material. Thus, this initial study shows new possibilities for using advanced laser joining methods in these alloys.

The helix‐sense reversal of poly(β‐phenylpropyl l‐aspartate) (3PLA) in the solid state was studied by synchrotron wide‐angle X‐ray diffraction and small‐angle X‐ray scattering. The direct determination of the characteristic helical pitch before and after the transition revealed that the transition takes place reversibly between the two α‐helices having opposite screw‐sense during the heating and cooling cycle. While the hexagonal packing remains unaltered, the helix‐sense inversion causes discontinuous changes in the molecular arrangement and, by extension, the crystalline dimension. In this study, another transition was detected at a higher temperature from the left‐handed α‐helix to the π‐helix, the molecular chirality being unaffected. [ABSTRACT FROM AUTHOR]

Metal tetraphosphides (MP4, M = 3d transition metals) exhibit the layered‐structure character, in which the metal atom chains are sandwiched between the P42− layers, and have attracted considerable interest due to the outstanding physical and chemical properties, such as good electrical conductivity and high lithium capacity. Herein, the CrP4 single crystal is prepared using the high‐pressure and high‐temperature method via the 2000 ton Kawai‐type multianvil apparatus at ShanghaiTech University (SHTech‐2000). The structural modification under high pressure is investigated by synchrotron X‐ray diffraction combined with diamond anvil cell techniques. CrP4 shows remarkable axial anisotropic compressibility, in which the c‐axis is more compressible than a‐ and b‐axes. The formation of infinite chains of CrCr metallic bonding in CrP4 under high pressure enhances the electrical conductivity. [ABSTRACT FROM AUTHOR]

High-entropy oxides (HEOs) stabilize multiple cations in a single solid solution phase, providing a new opportunity for property engineering in almost infinite compositional space. The structural stability and tunability of HEO are of great interest and importance but has not been well understood, especially under pressure. Here, we studied the structure evolution of a rock salt phase (Co0.2Cu0.2Mg0.2Ni0.2Zn0.2)O HEO using in situ synchrotron X-ray diffraction, pair distribution function, Raman spectroscopy up to ~43 GPa, and ex situ transmission electron microscopy, a pressure-induced reversible rock salt to highly distorted cubic phase transition was observed. These results suggest highly tunable lattice distortion in HEOs under pressure, which could promote the fundamental understanding and also guide applications of HEOs.

Great interests on high temperature shape memory alloys (HTSMAs) are recently raised, driven primarily by the aerospace and automotive industries, for their potential to serve as solid state actuators at high temperatures over 373 K. Near equiatomic Ti-Ni conventional SMAs, as the most applied SMA system, were considered to possess appreciable shape memory effect and superelasticity only below 373 K, which owes to low martensitic transformation temperatures. Here we utilized the martensite stabilization effect and successfully expanded the viable zone of B19′ (monoclinic) martensite to 616 K in a 35% cold-rolled Ti-50Ni (CR35) SMA. After a training cycle, it exhibited quasi-linear superelasticity of narrow hysteresis, ~3% superelastic strain and high strength over 1.2 GPa in a wide temperature range up to 483 K. It is the first exploration of high temperature superelasticity associated with the stabilized martensite. Using transmission electron microscopy and in-situ heating/tensile synchrotron X-ray diffraction, we reveal the origin of martensite stabilization and the underlying mechanisms of unique superelasticity in the CR35. Our work provides an attractively facile approach to realize high temperature superelasticity in Ti-Ni conventional SMAs, as well as in other kinds of SMAs, for precise actuation within an expanded range of working temperature and stress.

Accurate and efficient measurements of the piezoelectric properties of AlN and AlScN films are very important for the design and simulation of micro-electro-mechanical system (MEMS) sensors and actuator devices. In this study, a process control monitor (PCM) structure compatible with the device manufacturing process is designed to achieve accurate determination of the piezoelectric coefficients of MEMS devices. Double-beam laser interferometry (DBLI) and laser Doppler vibrometry (LDV) measurements are applied and combined with finite element method (FEM) simulations, and values of the piezoelectric parameters d33 and d31 are simultaneously extracted. The accuracy of d31 is verified directly by using a cantilever structure, and the accuracy of d33 is verified by in situ synchrotron radiation X-ray diffraction; the comparisons confirm the viability of the results obtained by the novel combination of LDV, DBLI and FEM techniques in this study.

Gas adsorption by porous frameworks sometimes results in structure "breathing", "pores opening/closing", "negative gas adsorption", and other phenomena. Time‐dependent diffraction can address both kinetics of the guest uptake and structural response of the host framework. Using sub‐second in situ powder X‐ray diffraction, three intracrystalline diffusion scenarios have been evaluated from the isothermal kinetics of Ar, Kr, and Xe adsorption by nanoporous γ‐Mg(BH4)2. These scenarios are dictated by two possible simultaneous transport mechanisms: diffusion through the intra‐ (i) and interchannel apertures (ii) of γ‐Mg(BH4)2 crystal structure. The contribution of (i) and (ii) changes depending on the kinetic diameter of the noble gas molecule and temperature regime. The lowest single activation barrier for the smallest Ar suggests equal diffusion of the atoms trough both pathways. Contrary, for the medium sized Kr we resolve the contributions of two parallel transport mechanisms, which tentatively can be attributed to the smaller barrier of the migration paths via the channel like pores and the higher barrier for the diffusion via narrow aperture between these channels. The largest Xe atoms diffuse only along 1D channels and show the highest single activation barrier. [ABSTRACT FROM AUTHOR]

Thermoelastic behavior of transition metal boride Os2B3 was studied under quasi-hydrostatic and isothermal conditions in a Paris-Edinburgh cell to 5.4 GPa and 1273 K. In-situ Energy Dispersive X-ray diffraction was used to determine interplanar spacings of the hexagonal crystal structure and the P-V-T data were fitted to a 3rd Order Birch–Murnaghan equation of state with a temperature modification to determine thermal elastic constants. The bulk modulus was shown to be K0 = 402 ± 21 GPa when the first pressure derivative was held to K0' = 4.0 from the room temperature P-V curve. Under a quadratic fit α = α 0 + α 1 T − α 2 T − 2 , the thermal expansion coefficients were determined to be α 0 = 1.862 × 10 − 5 K−1, α 1 = 0.841 × 10 − 9 K−2, and α 2 = − 0.525 K. Density functional theory (DFT) with the quasi-harmonic approximation (QHA) were employed to study Os2B3, including its P-V-T curves, phonon spectra, bulk modulus, specific heat, thermal expansion, and the Grüneisen parameter. A good agreement between the first-principle theory and experimental observations was achieved, highlighting the success of the Armiento-Mattsson 2005 generalized gradient approximation functional employed in this study and QHA for describing thermodynamic properties of Os2B3. [ABSTRACT FROM AUTHOR]

Although nitrogen in the Earth's interior has attracted significant attention recently, it remains the most enigmatic of the light elements in the Earth's core. In this work, synchrotron X-ray diffraction (XRD) and electrical conductivity experiments were conducted on iron nitrides (Fe 2 N and Fe 4 N) in diamond anvil cells (DACs) up to about 70 ​GPa ​at ambient temperature. These results show that iron nitrides are stable up to at least 70 ​GPa. From the equation of state (EOS) parameters, iron nitrides are more compressible than iron carbides. Moreover, using the van der Pauw method and Wiedemann-Franz law, the electrical and thermal conductivity of samples were determined to be much lower than that of iron carbides. The conductivities of Fe 2 N and Fe 4 N were similar at 20–70 ​GPa, suggesting no evident effects by varying the N stoichiometries in iron nitrides. Iron nitrides are less dense and conductive but more compressible than carbides at 0–70 ​GPa. This study indicates that less nitrogen than carbon can explain geophysical phenomena in the deep Earth, such as the density deficit. Image 1 • Synchrotron X-ray diffraction and electrical conductivity measurements were carried on Fe 2 N and Fe 4 N up to ~70 ​GPa. • Nitrogen effectively enhances the compressibility but lowers the density and electrical and thermal conductivity of iron. • Compared to carbides, iron nitrides exert more profound effects on geophysical properties of iron. [ABSTRACT FROM AUTHOR]

Synchrotron X-ray diffraction experiments of an icosahedral AuAlYb quasicrystal and its 1/1 crystalline approximant were performed under quasi-hydrostatic pressure up to approximately 20 GPa at room temperature. Their pressure-volume compression curves are similar to each other, and show a monotonic decrease, which indicates the structural stability of these compounds under pressure. The bulk moduli were determined to be B0 = 105.1(8) GPa for the quasicrystal and B0 = 108.1(7) GPa for the crystalline approximant. These values are explained by the composition-weighted average of the bulk moduli of each constituent element. [ABSTRACT FROM AUTHOR]

Thermoelastic behavior of transition metal boride Os2B3 was studied under quasi-hydrostatic and isothermal conditions in a Paris-Edinburgh cell to 5.4 GPa and 1273 K. In-situ Energy Dispersive X-ray diffraction was used to determine interplanar spacings of the hexagonal crystal structure and the P-V-T data were fitted to a 3rd Order Birch–Murnaghan equation of state with a temperature modification to determine thermal elastic constants. The bulk modulus was shown to be K0 = 402 ± 21 GPa when the first pressure derivative was held to K0' = 4.0 from the room temperature P-V curve. Under a quadratic fit α = α 0 + α 1 T − α 2 T − 2 , the thermal expansion coefficients were determined to be α 0 = 1.862 × 10 − 5 K−1, α 1 = 0.841 × 10 − 9 K−2, and α 2 = − 0.525 K. Density functional theory (DFT) with the quasi-harmonic approximation (QHA) were employed to study Os2B3, including its P-V-T curves, phonon spectra, bulk modulus, specific heat, thermal expansion, and the Grüneisen parameter. A good agreement between the first-principle theory and experimental observations was achieved, highlighting the success of the Armiento-Mattsson 2005 generalized gradient approximation functional employed in this study and QHA for describing thermodynamic properties of Os2B3. [ABSTRACT FROM AUTHOR]

This work investigated the impact of the thermal profile in the shift of phase transition temperature for KNNS piezoceramic, using high-resolution synchrotron x-ray powder diffraction (SXPD) and dielectric measurement. The temperature-dependent dielectric permittivity and SXPD profile showed that all phase transformations occurred at higher temperature under heating than under cooling. Moreover, under cooling from 227 °C to −163 °C and reheating to 227 °C, none of the unit-cell volumes fully recovered to their initial size. These results suggest that the change in unit-cell volume under heating/cooling plays a significant role in the shift of phase transition temperatures that was observed. [ABSTRACT FROM AUTHOR]

The thermal expansion of orthorhombic CaFe2O4-type β-CaCr2O4, ellinaite, was studied by high temperature in-situ synchrotron X-ray diffraction measurements in the temperature range of 301–973 K at atmospheric pressure. Based on the obtained data, the thermal expansion coefficients of β-CaCr2O4 were determined as 2.84(3) × 10–5 K−1, 1.08(1) × 10–5 K−1, 0.79(1) × 10–5 K−1, 0.99(1) × 10–5 K−1 for volume, a-, b- and c axis, respectively. An anisotropic behavior was observed because the axial expansivity for the b axis is smaller than those of the a- and c axis. Combined with available experimental results, the isobaric heat capacity (Cp) of β-CaCr2O4 was evaluated by using a Kieffer's model with Raman spectroscopy data and compared with previous studies. The isochoric heat capacity (Cv), standard entropy (S0298) and Debye temperature (θD) of β-CaCr2O4 were also determined. [ABSTRACT FROM AUTHOR]

We investigate the onset of detwinning in magnesium alloy Mg-3Al-1Zn under continuous loading with real-time in situ synchrotron X-ray diffraction. Detwinning of the { 10 1 ¯ 2 } extension twins activated both by tension parallel to and compression perpendicular to the c -axis fibers is explored. The experimental results reveal that detwinning of the { 10 1 ¯ 2 } extension twins occurs immediately upon unloading, regardless of whether the twins are activated by tension parallel to or compression perpendicular to the c -axis fibers. [ABSTRACT FROM AUTHOR]

Co‐crystallisation is widely explored as a route to improve the physical properties of pharmaceutical active ingredients, but little is known about the fundamental mechanisms of the process. Herein, we apply a hyphenated differential scanning calorimetry—X‐ray diffraction technique to mimic the commercial hot melt extrusion process, and explore the heat‐induced synthesis of a series of new co‐crystals containing isonicotinamide. These comprise a 1:1 co‐crystal with 4‐hydroxybenzoic acid, 2:1 and 1:2 systems with 4‐hydroxyphenylacetic acid and a 1:1 crystal with 3,4‐dihydroxyphenylactic acid. The formation of co‐crystals during heating is complex mechanistically. In addition to co‐crystallisation, conversions between polymorphs of the co‐former starting materials and co‐crystal products are also observed. A subsequent study exploring the use of inkjet printing and milling to generate co‐crystals revealed that the synthetic approach has a major effect on the co‐crystal species and polymorphs produced. [ABSTRACT FROM AUTHOR]

The effect of a high‐performance retarding additive in oil well cements was investigated under elevated temperature (165°C) and pressure (1000 psi) conditions via in situ synchrotron‐based X‐ray diffraction (XRD) and quasielastic neutron scattering (QENS) techniques. Under these temperature and pressure conditions, crystalline calcium silicate hydrates (C–S–H) are formed through the cement hydration process. From in situ XRD experiments, the retardation effect was observed by a change in the rate of the appearance of 11 Å tobermorites as well as a change in the rate of the α‐C2SH generation and depletion. QENS analysis revealed that the retardation effect was related to the non‐conversion of free water to chemical and constrained water components. A high presence of free water components was attributed to a decrease in 11 Å tobermorites along with slower consumption of the quartz and portlandite phases. Furthermore, QENS results infer that the water molecules experienced confinement in the restricted pore spaces. The retarder inhibited this initial water confinement by slowing the bulk diffusion of free water in the confined region. [ABSTRACT FROM AUTHOR]

Understanding the crystallization process for chemical solution deposition (CSD) processed thin films is key in designing the fabrication strategy for obtaining high‐quality devices. Here, an in situ sample environment is presented for studying the crystallization of CSD processed thin films under typical processing parameters using near‐grazing‐incidence synchrotron X‐ray diffraction. Typically, the pyrolysis is performed in a rapid thermal processing (RTP) unit, where high heating rates, high temperatures and atmosphere control are the main control parameters. The presented in situ setup can reach heating rates of 20°C s−1 and sample surface temperatures of 1000°C, comparable with commercial RTP units. Three examples for lead‐free ferroelectric thin films are presented to show the potential of the new experimental set‐up: high temperature, for crystallization of highly textured Sr0.4Ba0.6Nb2O6 on a SrTiO3 (001) substrate, high heating rate, revealing polycrystalline BaTiO3, and atmosphere control with 25% CO2, for crystallization of BaTiO3. The signal is sufficient to study a single deposited layer (≥10 nm for the crystallized film) which then defines the interface between the substrate and thin film for the following layers. A protocol for processing the data is developed to account for a thermal shift of the entire setup, including the sample, to allow extraction of maximum information from the refinement, e.g. texture. The simplicity of the sample environment allows for the future development of even more advanced measurements during thin‐film processing under non‐ambient conditions. [ABSTRACT FROM AUTHOR]

Understanding the deformation mechanisms of hexagonal close-packed (HCP) polycrystals at the grain scale is crucial for developing both macro and micro scale predictive models. Slip and twinning are the two main deformation mechanisms of HCP polycrystals at room temperature. In this paper, the development of grain-level stress tensors during nucleation and growth of twins is investigated. A pure zirconium specimen with HCP crystals is deformed in-situ while the centre-of-mass, orientation, elastic strain, and stress of individual grains are measured by three-dimensional synchrotron X-ray diffraction (3D-XRD). The observed microstructure is subsequently imported into a crystal plasticity finite element (CPFE) model to simulate the deformation of the polycrystal. The evolution of stress in twin-parent pairs at the early stages of plasticity, further into plasticity zone, and unload is studied. It is shown that twins do not relax very much at the nucleation step, but the difference between the measured stress in the twin and parent increases further into plastic zone where twins relax. While at the early stages of plasticity all six twin variants are active, a slightly better estimation of active variants is obtained using the measured grain-resolved stress tensors. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Unusual secondary relaxations were revealed in metallic glasses (MGs) recently. In this paper, we explore the structural origins of secondary relaxations in La-based MGs alloyed with different species of elements. With the combination of synchrotron X-ray diffraction and ab initio molecular dynamics simulations, solute-atom-centered clusters with a string-like type of medium-range order are found in the MGs, the formation of which leaves dispersed low-electron-density regions. It is found the activation energy of fast secondary relaxation increases with the reduction of low-electron-density regions, while slow secondary relaxation relates to the distance of La in next nearest La-La atomic pairs and the size of the string-like solute-atom-centered clusters. The phenomena are interpreted within the framework of the generalized Maxell model and free volume model. Our results demonstrate fast secondary relaxation as the activation of a small concentration of liquid-like regions with extremely low viscosities preceding slow secondary relaxation, and provide evidence for the correlation of secondary relaxations with short- to medium-range electronic and atomic structure in MGs. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Self-sustaining runaway reactions in reactive multilayers exhibit heat-up with over 106 K/s to temperatures of higher than 1000 °C, which defines unprecedented kinetic regimes for metallurgical phase transformations. The latter allows for developing alternative concepts for microstructure design. In order to explore the phase transformations in these kinetic regimes, we combine nanocalorimetry with time-resolved synchrotron X-ray diffraction. Nanocalorimetry allows us to perform thermal analysis of ignition as well as the reaction runaway and to develop necessary and mandatory quantitative criterions for ignition. In order to trace the temporal phase evolution, we use time-resolved synchrotron X-ray diffraction. We heat the Al/Ni multilayers with 5000 K/s and find that Ni starts to diffuse into the Al layer at 271 °C. Ignition occurs, dependent on the bilayer thickness, at about 400 °C in the solid state and atomic diffusion is revealed as the dominating mechanism. During the runaway, samples heat up in four stages with maximal 106 K/s to 1100 °C. Ni 2 Al 3 is the first phase to form which starts to nucleate once Al melts. The majority of the intermetallic phase grows after the runaway reaction in the fourth stage and reaches its maximum during cooling. This trend of the temporal phase evolution eventually enables us to propose a mechanism exhibiting conceptual similarities with the exothermic dissolution mechanism recently suggested for self-sustaining reaction fronts in Al/Ni multilayers. Image, graphical abstract [ABSTRACT FROM AUTHOR]

The structural stability of the multiferroic four-layer Aurivillius ceramic Bi 5 FeTi 3 O 15 (BFTO) under hydrostatic pressure was investigated in situ by synchrotron X-ray powder diffraction (SXRPD) and Raman spectroscopy. Measurements performed up to 15 GPa allowed the identification of two well-defined structural phase transitions. The orthorhombic phase (at ambient conditions) transforms into a tetragonal one around 3.2 GPa and a new orthorhombic phase rises around 7.5 GPa. Both phase transitions are evidenced by the pressure dependence of the lattice parameters and vibrational mode frequencies. The analysis of the induced strain indicates that the transitions are of second-order and first-order, respectively. Subtle changes in the Raman spectra and powder patterns suggest the onset of a new phase around 10.5 GPa. [ABSTRACT FROM AUTHOR]

Topological nodal‐line semimetal SrAs3 hosts a simple nodal loop on the verge of Fermi level without distracting trivial states, providing a good platform for further investigations of electronic quantum states. Here, a report on pressure‐driven superconductivity in SrAs3 single crystal is provided and the interplay between the crystal structure, electronic state, and superconductivity is clarified therein. The comprehensive high‐pressure experiments, i.e., synchrotron X‐ray diffraction, electrical transport, and Raman spectroscopy, consistently reveal a critical pressure Pc ≈ 25 GPa. Around Pc, a superconducting transition appears, concomitant with the formation of high‐pressure cubic Pm‐3m phase. Meanwhile, the superconducting transition temperature Tc and hole carrier density increase synchronously above Pc. This finding demonstrates that the emerging superconductivity in SrAs3 stems from the high‐pressure cubic phase on the one hand, and shows that the evolution of Tc(P) is intimately correlated with the enhanced density of states near the Fermi level on the other hand. [ABSTRACT FROM AUTHOR]

High‐resolution in situ synchrotron X‐ray diffraction was applied to study a cold‐drawn and solution‐treated 56Ni–44Ti wt% alloy subjected to uniaxial cyclic loading–unloading with incremental strains. The micro‐mechanical behaviour associated with the partial and repeated B2↔B19′ phase transformation at the centre of the sample gauge length was studied with respect to the macroscopic stress–strain response. The lattice strains of the (110)B2 and different B19′ grain families are affected by (i) the transformation strain, the load‐bearing capacity of both phases and the strain continuity maintained at/near the B2–B19′ interfaces at the centre of the gauge length, and (ii) the extent of transformation along the gauge length. With cycling and incremental strains (i) the elastic lattice strain and plastic strain in the remnant (110)B2 grain family gradually saturate at early cycles, whereas the plastic strain in the B19′ phase continues to increase. This contributes to accumulation of residual strains (degradation in superelasticity), greater non‐linearity and change in the shape of the macroscopic stress–strain curve from plateau type to curvilinear elastic. (ii) The initial ⟨111⟩B2 fibre texture transforms to [120]B19′, [130]B19′, [150]B19′ and [010]B19′ orientations. Further increase in the applied strain with cycling results in the development of [130]B19′, [102]B19′, [102]B19′, [100]B19′ and [100]B19′ orientations. [ABSTRACT FROM AUTHOR]

• Six MFI-zeolites were synthesized and compressed in silicone oil and methanol. • All the samples adsorb methanol already pressure < 2 kbar. • Different chemical compositions lead to differences in the methanol adsorption. • The MOPT was bracketed at lower pressure than that previously reported in the literature. The high-pressure behavior of six synthetic zeolites with the MFI topology, characterized by different chemical composition (framework-Si partially replaced by Al or B and counterbalanced by Na or H as extra-framework cations), has been investigated by in-situ powder synchrotron X-ray diffraction using silicone-oil and methanol as hydrostatic pressure-transmitting fluids. For each sample, the compressibility in silicone-oil has been found to be considerably higher than that in methanol. This difference in terms of bulk elasticity is due to the adsorption of methanol already at P < 0.1 GPa, with different magnitudes as a function of the sample crystal-chemistry. The high number of experimental pressure points allowed an accurate determination of the monoclinic-to-orthorhombic phase transition (MOPT), detected between 0.3 and 0.7 GPa in the samples compressed in silicone-oil , whereas the orthorhombic Pnma polymorph has been found to be stable already at ∼ 0.1 GPa in four samples compressed in methanol. This suggests that the adsorption of methanol may increase the P -stability range of the orthorhombic Pnma phase. A comparative analysis of the effect of pressure on the methanol adsorption by MFI-zeolites with different chemical composition is provided, which offers potentially useful information on their application as catalysts in the methanol-to-olefins conversion processes and in industrial high-pressure processes. [ABSTRACT FROM AUTHOR]

Reidite, a high-pressure phase of zircon, is increasingly identified at terrestrial impact sites. Despite its growing recognition, the potential applications for estimating minimum impact pressure face impediments due to existing discrepancies in the condition of zircon-reidite transformation, controversial models governing the transformation mechanism, and unclear effects of pre-existing radiation damage on reidite formation. Here, we show enhanced reidite formation by synchrotron X-ray diffraction, Raman spectroscopy, and transmission electron microscopy analyses of zircon grains that have experienced different alpha-decay doses from U and Th impurities and subsequent pressurization in diamond anvil cells. Below ∼1 × 1018 α-decay events/g, the α-decay-induced isolated point defects in the still crystalline zircon facilitate the minor atomic readjustments required for reidite formation. However, above this dose, the loss of long-range periodicity in severely damaged or even metamict zircon inhibits the transformation. The enhanced reidite formation by minor radiation damage coincides with the more common occurrence of reidite at impact sites for which the precursor zircon has a relatively lower alpha-decay-event dose before the impact event. In addition, the detailed atomic-scale structures of twinned reidite provide unambiguous evidence for a characteristic internal stress-induced martensitic transition. These findings have important implications for interpreting the formation conditions of natural reidite due to the convergence of pressure from the static, shockwave, and natural reidite samples. • Moderate radiation damage enhances atomic adjustments for reidite formation. • Reidite preferentially occurs in craters with moderately damaged zircon. • Static, shocked, and natural reidite have similar formation mechanisms. • Atomic scale twinned reidite suggests internal stress-assisted martensitic transition. • Constraining the minimum impact pressure should consider radiation damage. [ABSTRACT FROM AUTHOR]

The augmentation of mechanical properties of reduced activation ferritic martensitic steels through the introduction of creep resistant nano-oxide particles produces a class of oxide dispersion strengthened steels, which have attracted significant interest as candidates for first wall supporting structural materials in future nuclear fusion reactors. In the present work, the effect of temperature on the elastic properties and micro-mechanics of 0.3 wt% Y 2 O 3 oxide dispersion strengthened steel EUROFER97 is investigated using synchrotron high energy X-ray diffraction in-situ tensile testing at elevated temperatures, alongside the non-oxide strengthened base steel as a point of comparison. The single crystal elastic constants of both steels are experimentally determined through analysis of the diffraction peaks corresponding to specific grain families in the polycrystalline samples investigated. The effect of temperature on the evolving dislocation density and character in both materials is interrogated, providing insight into deformation mechanisms. Finally, a constitutive flow stress model is used to evaluate the factors affecting yield strength, allowing the strengthening contribution of the oxide particles to be assessed, and correlation between the thermally driven microstructural behaviour and macroscopic mechanical response to be determined. in-situ XRD tensile testing of ODS EUROFER97 steel at high temperatures. [Display omitted] [ABSTRACT FROM AUTHOR]

Laser additive manufacturing (AM) of reaction-based metal matrix composites (MMCs) involves highly complex and non-equilibrium material transformation behavior, including melting, dissolution, precipitation, and solidification. Yet, the dynamics and interplay of these phase transformation processes remain poorly understood, posing substantial challenges in identifying the microstructure formation mechanism, and predicting and controlling the microstructure in the printed parts. Here we performed the in-situ X-ray diffraction experiment to characterize the phase evolution dynamics of the 316L + 10 vol.%TiC system during laser melting, which provides direct and quantitative insights of the complex phase reaction and evolution dynamics under rapid heating and cooling conditions relevant to additive manufacturing of reaction-based MMCs. Further in-depth thermodynamic and kinetic calculations revealed that most of the phase evolution behavior observed in the in-situ X-ray diffraction experiment cannot be solely explained by widely used equilibrium thermodynamic models, and diffusion-controlled nonequilibrium dissolution and precipitation kinetics must be considered to elucidate the complex phase evolution behavior, including incomplete TiC dissolution, and three-step TiC precipitation. The three distinct types of precipitates generate unique hierarchical TiC micro- and nanostructures, which enhances the yield strength from 513 MPa to 877 MPa by 71 %, tensile strength from 628 MPa to 1054 MPa by 68 %, and Young's modulus from 193 GPa to 221 GPa by 14 %. The findings of our research provide the knowledge foundation for the design of unique microstructures and advanced MMC materials through laser AM. [Display omitted] [ABSTRACT FROM AUTHOR]

In this work , in - situ high-energy X-ray diffraction was used to analyze the effects of strain rate and austenite (γ) grain orientation on the strain-induced martensitic transformation in metastable austenitic stainless steel 301LN. The diffraction measurements were carried out at strain rates ranging from 10−3 s−1 to 1 s−1 continuously without interrupting the experiment and thus creating nearly adiabatic conditions at the highest studied strain rate. The results indicate that <100>γ fiber-oriented grains preferentially transform at the strain rate of 10−3 s−1 when the true strain is above 0.10, whereas the <111>γ fiber-oriented grains transform only at later stages of plastic deformation. The phase transformation rate of the <111>γ and <100>γ fiber-oriented grains decreases with increase in strain rate. A theoretical model based on stacking fault width as a function of external stress and temperature (stacking fault energy) was used to predict lower-bound estimates for the critical tensile stress needed to start ε-martensite and α'-martensite phase transformations. The model can predict the experimentally observed phase transformation behavior of the <111>γ fiber orientations at all strain rates but is unable to predict the decrease of phase transformation rate of <100> fiber-oriented γ grains with increase in strain rate, which could be related to change in dislocation structure. • The α'-martensite volume fraction decreases from 0.86 to 0.26 when strain rate is increased from 10−3 s−1 to 1 s−1. • The development of <111> and <100> double fiber texture parallel to the tensile direction was observed in parent austenite (γ) grains. • The phase transformation rate, especially in the <111>γ fiber, is sensitive to changes in SFE. • The calculated macroscopic critical stress levels required for formation of wide stacking faults at different SFE values were compared with experimental observations. [ABSTRACT FROM AUTHOR]

Rare-earth RTX 3 compounds (T stands for a transition d-metal and X is a p-metal) form a large family of intermetallics, revealing a variety of intriguing physical properties. Among them, Ce TX 3 compounds represent a particularly studied group, due to their frequently complex magnetic structures, Kondo physics, pressure-induced superconductivity, or recently highlighted quantum quasi-bound states. We report on the structural properties and their systematics within the CeCuAl 3 -related intermetallics crystallising in the tetragonal structure of the BaNiSn 3 -type. Our synchrotron X-ray diffraction data of 14 selected alloys allow us to follow the evolution of crystallographic parameters of the CeCuAl 3 -based substitution series. Substitutions of R , T and X elements are shown to have significant impact on the unit cell volume, virtual lattice expansion and free fraction coordinates of individual Wyckoff sites. Structural parameters are discussed within the framework of physical properties of investigated compounds. [Display omitted] • Crystallographic parameters of CeCuAl3-related intermetallics revealed. • Systematics followed based on data measured using single synchrotron X-ray beamline. • Evolution of parameters discussed in framework of physical properties of compounds. [ABSTRACT FROM AUTHOR]

This study delves into the frequent surface cracking observed in severely damaged pearlitic carbon steel rails, a phenomenon often attributed to the challenging characteristics of the white etching layer (WEL) formed during railway operations. To explore this issue, a severely damaged rail cross-section featuring a substantial WEL layer measuring 600 μm in depth was analyzed. The WEL's size was initially determined through optical microscopy and characterized via nano-hardness testing, which revealed an impressive hardness of up to 12 GPa. High-energy synchrotron X-ray diffraction (HESXRD) analysis was employed to uncover the crystalline structure diversity gradient that resulted from railway use. The results unveiled that cumulative high-temperature surface damage leads to the formation of both the WEL and a transitional layer. Within this transitional layer, a gradual reduction in retained austenite is observed, coupled with an increase in the presence of cementite and ferrite as one approaches the base metal. Remarkably, very shallow depths from the surface display tempered martensite characteristics, characterized by high nanohardness, lower dislocation density, and an initially smaller, then increasing austenite fraction. The use of site-resolved synchrotron radiation diffraction at different depths from the surface to the interior of the damaged rail cross-section allowed a unique insight into the phase transformations, microstrain developments, and compositional evolution. • Examined a railway damage sample for microstructural insights using SXRD. • Revealed complex phase changes in the WEL, impacting damage resistance. • Explored post-WEL formation, linking RA fraction and LP to α' stress relief. • Described pronounced changes in the TL, detailing phase transformations, and ρ. [ABSTRACT FROM AUTHOR]

The title compound, C25H27NO4 (I), the product of the unusual thermolysis of azacyclic allene methyl 10,11-dimethoxy-3,8-dimethyl-6-phenyl-3-azabenzo[d]cyclodeca-4,6,7-triene-5-carboxylate, represents a bicyclic heterosystem and crystallizes in the monoclinic space group P21/c with three crystallographically independent molecules in the unit cell. These independent molecules adopt very similar geometries and differ only in the conformations of the two methoxy substituents on the benzene ring. In two of the three independent molecules, both methoxy groups are almost coplanar with the benzene ring [the C—C—O—Me torsion angles are 10.8 (2), 12.3 (2), 9.1 (2) and 13.6 (3)°], whereas in the third molecule, one of the methoxy groups is practically coplanar to and the other methoxy group is roughly perpendicular to the benzene ring, the C—C—O—Me torsion angles being 14.1 (2) and 76.5 (2)°. The molecule of (I) comprises a fused tetracyclic system containing two five-membered rings (cyclopentenes) and two six-membered rings (piperidine and benzene). The five-membered rings have the usual envelope conformation, with the methyl-subsituted C atom as the flap in each molecule, and the six-membered piperidine ring has a chair conformation. The methyl substituent at the N atom occupies the sterically favourable equatorial position. The carboxylate group lies almost within the basal plane of the parent cyclopentene ring [making dihedral angle of 11.68 (8), 18.94 (9) and 15.16 (9)° in the three independent molecules], while the phenyl substituent is twisted by 48.26 (6), 42.04 (6) and 41.28 (6)° (for the three independent molecules) relative to this plane. In the crystal, molecules of (I) form stacks along the b-axis direction. The molecules are arranged at van der Waals distances.

CoCr2O4 nanoceramics are prepared by sol–gel auto combustion method. Synchrotron X-ray diffraction analysis affirms the single-phase pristine cubic structure with space group Fd3m. Debye–Scherrer method estimates the crystallite size of main intense peak to be ∼27.15nm. Prominent bands obtained in infrared spectra at 448 and 599cm−1 are due to metal–oxygen stretching bond present at tetrahedral and octahedral sites. Dielectric parameters decrease as frequency increases from 103 to 106Hz that can be interpreted by Maxwell–Wagner-type interfacial polarization. Complex impedance spectra (Nyquist plot) reveal arc like behavior, which is mainly due to intergrain (grain boundary) resistance that also exhibits conducting nature of the nanoceramics. Weak ferroelectricity is mainly associated with the partial reversal of the polarization. Leakage current behavior follows the Ohmic and Child square law. Electron conduction process was interpreted by space-charge limited current (SCLC) mechanism. Leakage current behavior observed in cobalt chromite nanoceramics is mainly attributed to the oxygen vacancies.

MCrAlY (M = Ni and/or Co) metallic coatings are essential for the protection of hot-end components against thermal and corrosion damage. Increasing the Al content is considered a feasible solution to improve the high-temperature performance of MCrAlY coatings. In this paper, the effects of high Al contents (12-20 wt.%) on the phase constituents and cast microstructures in MCrAlY alloys were studied by high-energy X-ray diffraction and electron microscopy techniques combined with phase equilibria calculations. High Al content improved the stability of β, σ, and α phases. Meanwhile, an evolution of the cast microstructure morphology from a dendrite structure to an equiaxed grain structure was observed. The thermal properties were analyzed, which were closely related to the phase constituents and solid-to-solid phase transitions at evaluated temperatures. This work is instructive for developing high-Al-content MCrAlY coatings for next-generation thermal barrier applications.

In this work, the performance of the carbon doped compositionally complex alloy (CCA) MoNbTaW was studied under ambient and high pressure and high temperature conditions. TaC and NbC carbides were formed when a large concentration of carbon was introduced while synthesizing the MoNbTaW alloy. Both FCC carbides and BCC CCA phases were detected in the sample compound at room temperature, in which the BCC phase was believed to have only refractory elements MoNbTaW while FCC carbide came from TaC and NbC. Carbides in the carbon doped MoNbTaW alloy were very stable since no phase transition was obtained even under 3.1 GPa and 870 °C by employing the resistor-heating diamond anvil cell (DAC) synchrotron X-ray diffraction technique. Via in situ examination, this study confirms the stability of carbides and MoNbTaW in the carbon doped CCA even under high pressure and high temperature.

Synchrotron X-ray diffraction was applied to measure the dislocation density of two twinning-induced plasticity (TWIP) steels with different carbon content but comparable stacking fault energy (SFE). We found that the dislocation density of the carbon-alloyed TWIP is much higher than that of the carbon-free TWIP steel, though these two steels possess similar twin volume fraction. It indicates that the excellent tensile and strain-hardening properties of the carbon-alloyed TWIP steels are mainly caused by the high dislocation density induced by the carbon-dislocation interaction. Carbon-free TWIP steels are conventional low SFE fcc alloys similar to 316L stainless steel. Image, graphical abstract [ABSTRACT FROM AUTHOR]