Synchrotron Radiation Diffraction Experiments Research Articles

放射光回折システムの高機能化と機能性材料の開発研究

Driven by improvement of the computer speed and tremendous efforts of crystallographers and equipment manufacturers, X-ray structure analysis has recently become relatively easy and requires no specialized knowledge. On the other hand, synchrotron radiation diffraction experiments have mainly aimed at advanced structural analysis, including electron density analysis, taking advantage of stable and intense X-rays. In recent years, demand for the use of the facility in the materials field has increased, but researchers unfamiliar with synchrotron radiation experiments have felt difficulty in use. Based on my experience in developing conventional diffractometers and software at the equipment manufacturer where I worked after obtaining my degree, I have promoted the development of advanced synchrotron radiation X-ray diffraction systems at SPring-8, a large synchrotron radiation facility. In particular, I have been responsible for the single crystal structure analysis beamline（BL02B1）and the powder diffraction beamline（BL02B2）, which have a wide range of user groups and diverse requirements for instrumental performance, and engaged in instrument development. In addition, I have also worked on structural analysis of functional materials and clarified their structure-function relationships. Among them, I introduce fruitful results on generation process of magnesia cement and design of spin crossover Fe（II）complexes. I believe that such upgrading of synchrotron radiation diffraction systems and development research of functional materials could not be performed without hardware and software knowledge which I learned at the equipment manufacturer.

The effect of temperature on load partitioning evolution in magnesium metal matrix composite reinforced with Ti particles using in-situ synchrotron radiation diffraction experiments

The load partitioning between the magnesium and titanium phases in an extruded Mg-15%Ti (vol.%) composite from room temperature up to 300 °C using synchrotron radiation diffraction during in-situ compression tests. During compression, the magnesium matrix composite deforms mainly by the activation of the extension twinning system up to 200 °C. The volume fraction of twins increases with the plastic strain but decrease with the compression temperature. Hard titanium particles bear an additional load transferred by the soft magnesium matrix from room temperature up to 300 °C. This effect is amplified after yield stress during plastic deformation. Additionally, twins within magnesium grains behaves as an additional reinforcement at low temperature (below 200 °C) inducing an increase in the work hardening of the composite.

Study of solid state transformations and their effect on mechanical response in the stoichiometric Ni2Cr using in-situ synchrotron radiation diffraction experiments

A complete microstructural characterization of the stoichiometric Ni2Cr alloy after different ageing times in which different degrees of order are attained has been carried out. The study of order-disorder transformation has been done using synchrotron radiation diffraction monitoring eventual changes in high-energy X-ray diffraction (HEXRD) patterns every six seconds in the course of differential scanning calorimetry DSC experiments. According to acquired data, the onset of the order-disorder transformation occurs at 630 °C, temperature higher than that reported in previous works. In addition, the appearance of fine carbide precipitation has also been found inside the grains and at grain boundaries. Both ordering of the stoichiometric Ni2Cr and carbide precipitation seems to be responsible for the strengthening of the alloy.

Elucidation of the redox activity of Ca2MnO3.5 and CaV2O4 in calcium batteries using operando XRD: charge compensation mechanism and reversibility

Ca2MnO3.5 and CaV2O4 were found to be potentially interesting as positive electrode materials for calcium metal-based high-energy density batteries with DFT-predicted average voltages of 3.7 V and 2.5 V and energy barriers for Ca migration of 1.1 eV and 0.6 eV, respectively. Both compounds were prepared by solid state reaction under reducing atmospheres. Optimum conditions to achieve Ca2MnO3.5 comprised the reduction of Ca2MnO4 under NH3 gas at 420⁰C with a flow rate of 1200 ml/min while CaV2O4 was achieved by reduction of CaV2O6 at 700 ⁰C under H2 flow. Electrochemical oxidation of Ca2MnO3.5 in lithium or calcium cells resulted in the formation of an orthorhombic phase with cell parameter (a= 5.2891(1), b= 10.551(2), c= 12.1422(1)). Operando synchrotron radiation diffraction experiments indicate that the charge compensation mechanism is not related to Ca2+ extraction but to intercalation of F− (originated from electrolyte salt decomposition) into the anion vacancy position, as confirmed by EELS and EDS. This process was found to be irreversible. In the case of CaV2O4, oxidation induces the electrochemical extraction of calcium with the formation of an orthorhombic phase (space group Pbnm) with cell parameters a = 10.72008(9) Å, b = 9.20213(2) Å and c = 2.89418(3) Å. The process was also investigated via operando synchrotron radiation diffraction, with the oxidized phase being found to reintercalate Ca2+ ions upon reduction, with the formation of a solid solution. Preliminary cycling tests reveals a decrease in the polarization after the first cycle and call for further investigation of this system.

Internal Stress Evolution and Subsurface Phase Transformation in Titanium Parts Manufactured by Laser Powder Bed Fusion—An In Situ X‐Ray Diffraction Study

Laser powder bed fusion (LPBF) is a metal additive manufacturing technology, which enables the manufacturing of complex geometries for various metals and alloys. Herein, parts made from commercially pure titanium are studied using in situ synchrotron radiation diffraction experiments. Both the phase transformation and the internal stress buildup are evaluated depending on the processing parameters. For this purpose, evaluation approaches for both temperature and internal stresses from in situ diffraction patterns are presented. Four different parameter sets with varying energy inputs and laser scanning strategies are investigated. A combination of a low laser power and scanning speed leads to a more homogeneous stress distribution in the observed gauge volumes. The results show that the phase transformation is triggered during the primary melting and solidification of the powder and subsurface layers. Furthermore, the stress buildup as a function of the part height during the manufacturing process is clarified. A stress maximum is formed below the part surface, extending into deeper layers with increasing laser power. A temperature evaluation approach for absolute internal stresses shows that directional stresses decrease sharply during laser impact and reach their previous magnitude again during cooling.

Pressure-induced symmetry lowering in Nb3Sn1−x superconductor

Cubic Pm-3n Nb3Sn0.92 superconductor (T c ∼ 16 K) was found to exhibit tetragonal instabilities at the superconducting state (T = 10 K). These instabilities are manifested through the appearance of reflections which are forbidden in the Pm-3n symmetry but are compatible with the P42/mmc structure which is observed in the Nb3Sn1−x system for higher Sn content at temperatures lower than ∼43 K. Nevertheless, the low-temperature structure of Nb3Sn0.92 remains metrically fully cubic, as concluded from single crystal synchrotron radiation diffraction experiments. Subsequent application of external pressure amplifies the observed instabilities with a resulting pseudo-cubic–tetragonal transformation at P = 3 GPa at 10 K and this transition is energy driven, as concluded from ab initio calculations. The electronic structures of the corresponding phases are virtually identical and, therefore, the pseudo-cubic–tetragonal transformation does not influence significantly the underlying electronic interactions. Consequently, no anomalies in the behavior of the critical temperature, T c, are expected at this pressure. However, anomalies in the upper critical field are anticipated during this transition, in analogy to the corresponding behavior observed during the cubic–tetragonal transformation in Nb3Sn1−x induced by increase in Sn content. Therefore targeted changes in composition could be used to enhance upper critical field of Nb3Sn1−x for specific extreme conditions of temperature and pressure.

Direct determination of phase stress evolution in duplex steel using synchrotron diffraction

The present work deals with the investigation of the micromechanical behaviour of a duplex steel, which consists of two phases (austenite and ferrite) exhibiting significantly different mechanical properties. The stresses in both phases were experimentally determined in the elastic and plastic ranges of deformation using synchrotron radiation diffraction experiments. The used methodology enabled to determine the values of initial stresses and to study the evolutions of the principal phase stresses and the second order stresses during the elastic, as well as the plastic range of deformation. With the help of a self-consistent model, the critical resolved shear stresses and the work hardening parameters for slip systems, active in each phase, were also estimated. Comparison of the measured phase stresses and lattice strains evolutions with the model results showed a good agreement between prediction and experiment when the initial stress state in the sample and shape of grains approximated by ellipsoidal inclusions were taken into account.The overall outcome of the work is the determination of stress partitioning between the two phases of a polycrystalline material for all deformation stages, determined directly from diffraction experiment. The results enabled analyses of von Mises, hydrostatic stresses as well as second order stresses evolutions in both phases during tensile deformation. Finally, the experimental data were successfully compared with predictions of the self-consistent deformation model.

High temperature mechanical behaviour of Mg–6Zn–1Y alloy with 1 wt.% calcium addition: Reinforcing effect due to I-(Mg3Zn6Y1) and Mg6Zn3Ca2 phases

The influence of small calcium additions on the high-temperature mechanical behaviour in an extruded Mg–6Zn–1Y (wt.%) alloy reinforced by the I-phase has been investigated. Calcium promotes the formation of the intermetallic Mg 6 Zn 3 Ca 2 phase instead of I-phase, which results in a noticeable improvement of the yield strength and ultimate tensile strength of the alloy above 100 °C. The strength of the alloys was analysed taking into account the contribution due to the grain size, the crystallographic texture and the volume fraction and nature of second phase particles. In situ synchrotron radiation diffraction experiments have been used to evaluate the load partitioning between the magnesium matrix and the second phase particles (I- and Mg 6 Zn 3 Ca 2 phases) in both alloys. The load transfer from the magnesium matrix towards the Mg 6 Zn 3 Ca 2 phase is markedly more effective than that for the I-phase over the entire temperature range, especially at 200 °C, temperature at which the reinforcement effect of the I-phase is null.

Strain-induced ε-martensitic transformation and hydrogen embrittlement of SUS304 stainless steel

ABSTRACTWe examined the hydrogen embrittlement mechanism in SUS304 stainless steel by conducting synchrotron radiation diffraction experiments and high-resolution TEM observations. It was found that the strength of SUS304 was lowered by adding hydrogen and that brittle fracture occurred with elongation of approximately 20%. Synchrotron radiation diffraction experiments revealed that the formation of the ε phase having a hexagonal close-packed structure was promoted by hydrogen addition to SUS304. In addition, high-resolution TEM observations revealed the presence of the ε phase with a width of up to approximately 5 nm at the twin boundary in the twin structure due to the γ phase. Furthermore, a large number of stacking faults were formed in the ε phase. These results imply that the strain-induced martensitic phase transformation from the γ phase to the α′ one was suppressed by hydrogen addition to SUS304 and that the ε phase having a large number of stacking faults was stabilised as an intermediate phase during the α′ martensitic phase transformation. The formation of the ε phase having a large number of stacking faults should presumably originate in hydrogen embrittlement.

Lithium/Oxygen Incorporation-Induced Structural Transformation during Synthesis of Cobalt-Free Li-Mn-Rich Oxides

Cobalt-free Li-Mn-rich layered oxides (LMLOs) are regarded as promising cathode materials for advanced lithium ion batteries (LIBs) because of their high discharge specific capacities (> 250 mAh g-1). However, the formation mechanism during the synthesis of these oxides has not been fully understood, i.e. how are lithium and oxygen incorporated into the matrix architecture of the Li-free precursor on the process of high-temperature solid-state reaction? Herein, in situ high-temperature synchrotron radiation diffraction experiments were performed to monitor the structural evolution of the precursor combined with lithium source during thermal treatment. The in situ high-temperature diffraction results show that, with an increase in heating temperature, lithium and oxygen continuously enter into the spinel host matrix (Fd-3m) formed from the Li-free precursor, thus gradually causing the production of a halite-type phase (Fm-3m) and eventually results in the formation of a monoclinic layered phase (C2/m). These findings not only provides valuable information for industrial operation, but also contributes to a deeper understanding of the correlation between the synthesis, structure and electrochemical performances in LMLOs.

New Occurrence of Rusinovite, Ca10(Si2O7)3Cl2: Composition, Structure and Raman Data of Rusinovite from Shadil-Khokh Volcano, South Ossetia and Bellerberg Volcano, Germany

Rusinovite, Ca10(Si2O7)3Cl2, was found at two new localities, including Shadil-Khokh volcano, South Ossetia and Bellerberg volcano, Caspar quarry, Germany. At both of these localities, rusinovite occurs in altered carbonate-silicate xenoliths embedded in volcanic rocks. The occurrence of this mineral is connected to specific zones of the xenolith characterized by a defined Ca:Si < 2 ratio. Chemical compositions, as well as the Raman spectra of the investigated rusinovite samples, correspond to the data from the locality of rusinovite holotype—Upper Chegem Caldera, Northern Caucasus, Russia. The most intense bands of the Raman spectra are related to vibrations of (Si2O7) groups. Unit cell parameters of rusinovite from South Ossetia are: a = 3.76330(4) Å, b = 16.9423(3) Å, c = 17.3325(2) Å, V = 1105.10(4) Å3, Z = 2. The performed synchrotron radiation diffraction experiments did not confirm a doubling of c as reported for the synthetic phase, Ca10(Si2O7)3Cl2. However, one-dimensional diffuse scattering parallel to b* has been observed. This can be interpreted with an ordered arrangement of Si2O7 groups creating layers with a doubled a parameter. Consequently, the two different displacements of neighbouring layers allow random stacking faults to occur.

Influence of quasicrystal I-phase on twinning of extruded Mg-Zn-Y alloys under compression

The interaction of the I-phase with twins during compression has been studied in a Mg-6Zn-1Y (wt.%) alloy using the combination of Synchrotron Radiation Diffraction and Acoustic Emission experiments during compression tests. The I-phase occurs as coarse particles at grain boundaries and nanosized precipitates within magnesium grains. Their interaction with twins depends on their shape and size. The presence of coarse I-phase particles with higher Young Modulus requires an additional stress for the activation of twinning since they induce tensile residual stresses in the magnesium matrix. Besides twinning, the basal and non-basal slip systems are also activated. Non-basal slip is observed after macroscopic yield stress within twins. The fine I-phase precipitates within grains interacts with the dislocations and the twins. In the latter case a back-stress arises, which acts against the compressive applied stress. This back stress hinders the twin growth more than the effect of the coarse particles.

Temperature- and Pressure-Induced Spin Crossover in Co1+xCr2-xSe4 (x = 0.24): A Diffraction Study.

The Co(2+) ions of the Co1+xCr2-xSe4 phase (Co1.24Cr1.76Se4 composition with x = 0.24, C2/m space group, Cr3S4-type structure) undergo a high- to low-spin-state transition around 230 K, as concluded from the temperature-dependent single-crystal synchrotron radiation diffraction experiments and the previously reported physical property studies. The change of the spin state is not instantaneous and goes through a wide spin-crossover (SCO) region of 75 K. A similar Co(2+) high- to low-spin-state transition is suggested at a pressure of 14.5 GPa, as is evident from the pressure-dependent single-crystal synchrotron radiation diffraction experiments. The corresponding SCO region is equal to 5 GPa, and the structural behavior is different from the one observed during the temperature-dependent transition. Coupling between the spin-conversion process in Co1+xCr2-xSe4 and the concomitant changes in the physical properties opens a way for a controlled tuning of the observed physical response through compositional and structural modifications.

Thermal oxidation of medical Ti6Al4V blasted with ceramic particles: Effects on the microstructure, residual stresses and mechanical properties

Roughening of Ti6Al4V by blasting with alumina or zirconia particles improves the mechanical fixation of implants by increasing the surface area available for bone/implant apposition. Additional thermal oxidation treatments of the blasted alloy have already shown to be a complementary low-cost solution to enhancing the in vitro biocompatibility and corrosion resistance of the alloy. In this work, the effects of oxidation treatment on a grit blasted Ti6Al4V biomedical alloy have been analysed in order to understand the net effect of the combined treatments on the alloy fatigue properties. Synchrotron radiation diffraction experiments have been performed to measure residual stresses before and after the treatments and microstructural and hardness changes have been determined. Although blasting of Ti6Al4V with small spherical zirconia particles increases the alloy fatigue resistance with respect to unblasted specimens, fatigue strength after oxidation decreases below the unblasted value, irrespective of the type of particle used for blasting. Moreover, at 700°C the as-blasted compressive residual stresses (700MPa) are not only fully relaxed but even moderate tensile residual stresses, of about 120MPa, are found beneath the blasted surfaces. Contrary to expectations, a moderate increase in hardness occurs towards the blasted surface after oxidation treatments. This can be attributed to the fact that grit blasting modifies the crystallographic texture of the Ti6Al4V shifting it to a random texture, which affects the hardness values as shown by additional experiments on cold rolled samples. The results indicate that the oxidation treatment performed to improve biocompatibility and corrosion resistance of grit blasted Ti6Al4V should be carried out with caution since the alloy fatigue strength can be critically diminished below the value required for high load-bearing components.

Lithium Alanates as Negative Electrodes in Lithium‐Ion Batteries

AbstractHydride conversion reactions have been recently proposed and verified experimentally on simple binary and ternary H‐containing materials. Herein, we show for the first time the incorporation of lithium alanates, that is, LiAlH4 and Li3AlH6, as active materials in negative electrodes in rechargeable lithium cells. Samples were prepared by mechanochemical treatment. Characterization of the samples was performed by X‐ray diffraction, transmission electron microscopy, and Fourier‐transform infrared spectroscopy. Analysis of the electrochemical features of the conversion process was performed by potentiodynamic cycling with galvanostatic acceleration in close comparison with computational data obtained by density functional theory with the use of pseudopotentials and planewaves. The occurrence of the conversion reactions was proved by ex situ synchrotron radiation diffraction experiments. As a final point, the stability of the electrolyte/electrode interface over time was evaluated by impendence spectroscopy and attenuated total reflectance Fourier‐transform infrared spectroscopy.

Innsbruckite, Mn33(Si2O5)14(OH)38 – a new mineral from the Tyrol, Austria

AbstractA description of the new mineral innsbruckite, Mn33(Si2O5)14(OH)38, a hydrous manganese phyllosilicate found in Tyrol, Austria is given. The crystal structure was determined by singlecrystal synchrotron radiation diffraction experiments at the X06DA beamline at the Swiss Light Source (Paul Scherrer Institute, Villigen, Switzerland). The space group is Cm and lattice parameters are a = 17.2760(19), b = 35.957(5), c = 7.2560(8) Å , β = 91.359(7)º, V = 4506.1(10) Å3, Z = 2. Innsbruckite belongs to the group of modulated 1:1 layer silicates and is chemically and structurally quite closely related to bementite, Mn7(Si2O5)3(OH)8. The chemical analysis revealed a close to ideal composition with only minor amounts of Al, Fe and Mg. Using Liebau’s nomenclature for silicate classification the silicate anion can be described as an unbranched siebener single layer. Innsbruckite shows a complex topology of the silicate sheet, exhibiting 4-, 5-, 6- and 8-membered rings. The silicate sheet is fully characterized using vertex symbols, and its topology is compared to those in other complex sheet silicates. Furthermore, the structural investigation is complemented with Raman spectroscopic studies.

A rational approach to screen for hydrated forms of the pharmaceutical derivative magnesium naproxen using liquid-assisted grinding

Variation of water content in liquid-assisted grinding was utilised to mechanochemically screen for different hydrated forms of magnesium naproxen directly from a mixture of magnesium oxide and naproxen. Structure determination from powder and single crystal X-ray diffraction data, supported by solid-state NMR and synchrotron radiation diffraction experiments, revealed a monohydrate coordination polymer, a discrete tetrahydrate complex, and provided a preliminary structural model for a highly hydrated salt.

Oxidation characteristics of Ti 3AlC 2 over the temperature range 500–900 °C

Titanium aluminium carbide (Ti 3AlC 2) displays a unique combination of characteristics of both metals and ceramics coupled with an unusual combination of mechanical, electrical and thermal properties. In this research, the oxidation characteristics of Ti 3AlC 2 over the temperature range 500–900 °C were studied by synchrotron radiation diffraction (SRD) and secondary-ion mass spectrometry (SIMS) experiments which provided elemental and phase compositional depth profiles over this range. Evidence for the outward diffusion of Al during oxidation was shown for the first time by the complementary SIMS results, which suggested the existence of amorphous Al or aluminium oxide at low temperature oxidation. At 500 °C, only anatase-TiO 2 was detected by SRD in addition to the parent Ti 3AlC 2. Transformation of anatase to rutile was observed at 600 °C and was completed by 900 °C. The crystalline phase α-Al 2O 3 was detected at 900 °C but not at lower temperatures.

High-temperature and high-pressurein situSCC device for synchrotron radiation diffraction experiments and application using an austenitic stainless steel

Suppressing the stress corrosion cracking (SCC) by reducing the carbon content in austenitic stainless steels is apparently not effective on core shrouds used in boiling water reactors in Japan: trans-granular cracking was found in the shrouds. To clarify the mechanism of the cracking, in situ stress measurements on specimens under stretched conditions in hot water have been attempted in the present study. An in situ device for diffraction measurements at synchrotron radiation facilities has been developed, and in situ experiments have been carried out at SPring-8. The SUS316L steel specimen was solution heat-treated, surface-ground and then placed in the in situ device. Sapphire windows were used for the light path in the device. A sufficient diffracted beam intensity was obtained through two sapphire windows and water. The side-inclination method was used for measuring the stress exerted on the specimen. A 2theta-sin2psi plot showed that a tensile stress was induced. The measured stress value is considered to be the summation of stresses owing to pre-straining, in situ loading and residual stress owing to surface grinding.

Pseudoamorphization ofCs2HgBr4

Synchrotron-radiation diffraction experiments have revealed the critical role of nonhydrostatic stresses in the pressure-induced long-range order dissipation in ${\mathrm{Cs}}_{2}{\mathrm{HgBr}}_{4}$ crystals. With nonhydrostatic loading, the samples lose, reversibly, long-range order on the scale observable with x-ray diffraction above 11 GPa while hydrostatic conditions preserve long-range order up to 40 GPa, the limit achieved experimentally. The phenomenon is interpreted in terms of inhomogeneous lattice deformations induced in the sample by deviatoric stresses. Diffraction patterns of synthetic grains with chaotic distribution of deformations were computed, which displayed a sufficiently good agreement between calculated and observed diffraction patterns as to support the model.