High-energy Synchrotron Radiation X-ray Research Articles

Piezoelectric Actuation Mechanism Involving Extrinsic Nanodomain Dynamics in Lead-Free Piezoelectrics.

Piezoelectric materials play a key role in applications, while there are physically open questions. The physical origin of piezoelectricity is understood as the sum of contributions from intrinsic effects on lattice dynamics and those from extrinsic effects on ferroic-domain dynamics, but there is an incomplete understanding that all but intrinsic effects are classified as extrinsic effects. Therefore, the accurate classification of extrinsic effects is important for understandingthe physical origin of piezoelectricity. In this work, high-energy synchrotron radiation X-ray diffraction is utilized to measure the response of BiFeO3 -BaTiO3 piezoelectrics and the intrinsic/extrinsic contribution to electric fields. It is found from crystal structure and intrinsic/extrinsic contribution, using the analysis involving structure refinement with various structural model and micromechanics-based calculations, that Bi3+ -ion disordering is important for realization of piezoelectricity and nanodomains. Here, an extrinsic effect on the rearrangement of nanodomains is suggested. The nanodomains, which are formed by the locally distorted structure around the A-site by Bi-ion disordering, can significantly deform the material in the BiFeO3 -BaTiO3 system, which contributes to the piezoelectric actuation mechanism apart from the extrinsic effect on ferroic-domain dynamics. Bi-ion disordering plays an important role in realizing piezoelectricity and nanodomains and can provide essential material design clues to develop next-generation Bi-based lead-free piezoelectric ceramics.

Effects of micro-alloying with lead for battery grid material

Pb-alloys are used as grid material for lead-acid batteries and have been implemented for years, and studying these Pb-alloys is critical to understanding the effects minor alloying additions on material characteristics. The current objective of this research is to evaluate the effects of minor alloying additions of Sb, As, Ca, Sn, Al, In, and Bi in Pb-alloy grid material during thermal cycling. In this study, Pb-grid material alloyed with a combination of elements mentioned above are examined using high-energy Synchrotron radiation X-ray diffraction measurements during in situ thermal cycling from RT to 75 °C to analyze grain inhibition and potential phase evolution. In addition, sulfation studies are performed in a solution of approximately 0.5 M H2SO4 and the Pb-alloys are added to an electrochemical cell to undergo cyclic voltammetry. Results show In mitigates grain growth, and, during electrochemical testing, increases passivation of Pb-alloys. Bi causes increased grain growth during thermal cycling and promotes sulfate formation. Ca refines and stabilizes grains during thermal cycling and increases corrosion resistance during cyclic voltammetry testing. Sn and Al attribute to texturing in the material and increase corrosion rates.

The effect of Ni or Co additions on the structure of Zr60Cu30Al10 bulk metallic glass revealed by high-energy synchrotron radiation

The effect of substituting Cu by elemental additions of Ni or Co on the atomic structure of the Zr60Cu30Al10 ternary bulk metallic glass (BMG) is studied using high-energy synchrotron radiation X-ray diffraction. Analyses of the structural features in reciprocal and real space using the structure factors S(Q) and pair-distribution functions (PDF) point to an increase in the structural disorder for the Ni- or Co-bearing quaternary alloys. This is consistent with the “confusion principle” since upon alloying the initially nearly identical atomic sizes of Cu, Ni and Co diversify due to local electronic interactions. In real space, the disordering is manifested by a reduced deviation from the average particle density visible in the nearest-neighbour (NN) atomic shell structure over the complete short- and medium-range order region. Despite their similar atomic size, enthalpies of mixing with the main alloy elements and apparent disordering of the structure, the additions of Ni or Co have different effects on thermal stability of the ternary “mother” alloy.

Novel characterization of lead-based micro-alloys for battery applications

Although Pb-alloy acid batteries have been incorporated in vehicles for decades, a significant gap exists in the scientific understanding of minor alloying elements in the complex Pb-alloy grid materials. The aim of this research is to close this gap by using modern analytical techniques to examine the effects associated with adding minor alloying elements, less than 100 ppm, in Pb-alloy grid materials during isothermal holds and thermal cycling at relatively high temperatures. In this study, pure Pb, Pb-Bi, and Pb-Ba foils are examined using high-energy synchrotron radiation X-ray diffraction measurements during in situ isothermal holding at 85 °C and thermal cycling from RT to 85°C to analyze the grain inhibition and phase evolution. It is observed that Ba inhibits grain growth while Bi does not, when compared to pure Pb. Furthermore, no obvious phase evolution in any of the three cases is observed. After the synchrotron radiation X-ray diffraction measurements, the three materials are examined ex situ using scanning electron microscopy to verify the results. Additionally, baseline sulfation studies were performed in a solution of approximately 5 M H2SO4 and Pb-Bi and Pb-Ba were added to the electrochemical cell to undergo cyclic voltammetry.

Shape memory effect in metallic glasses

Shape memory effect in metallic glasses

Internal Strain Distribution of Laser Lap Joints in Steel under Loading Studied by High-Energy Synchrotron Radiation X-rays

The automotive industries employ laser beam welding because it realizes a high energy density without generating irradiation marks on the opposite side of the irradiated surface. Typical measurement techniques such as strain gauges and tube X-rays cannot assess the localized strain at a joint weld. Herein high-energy synchrotron radiation X-ray diffraction was used to study the internal strain distribution of laser lap joint PNC-FMS steels (2- and 5-mm thick) under loading at a high temperature. As the tensile load increased, the local tensile and compressive strains increased near the interface. These changes agreed well with the finite element analysis results. However, it is essential to complementarily utilize internal defect observations by X-ray transmission imaging because the results depend on the defects generated by laser processing.

Current Status of the VEPP-4 Accelerator Facility

At the VEPP-4 accelerator complex experiments on high energy physics, nuclear physics, synchrotron radiation and hard X-ray are carried out. The paper presents the current status of the complex and its experimental programs. The development of the resonance depolarization method for the absolute beam energy measurement using a laser polarimeter is discussed. The results of observing the azimuthal difference of the orbits of electron and positron beams, which is a consequence of energy losses due to synchrotron radiation, are presented.

Electric-field-induced structural changes for cubic system of lead-free and lead-based perovskite-type oxides

Changes in crystal structures of lead-free BaTiO3 (BT) and lead-based 0.70Pb(Mg1/3Nb2/3)–0.30PbTiO3 (PMN–PT) single crystals with a perovskite-type structure have been investigated under applied electric field by analyzing the high-energy synchrotron radiation X-ray diffraction data. The experiment is performed within the cubic phase in the phase diagram with the range of temperatures and electric fields where no electric field-induced phase transition is caused. The crystal structure analysis demonstrates that the crystal system is change to a tetragonal system by electrostriction when the electric field is applied along the crystal axis. The atomic arrangement in BT corresponds to the displacement pattern attributed to the Slater mode where Ti and O ions are mutually shifted in the opposite directions along the electric field, while that in PMN–PT is of the Last mode where Pb ions and (Mg, Nb)O6 oxygen octahedra are mutually shifted. The electron charge density study demonstrates that the Ba–O bonding in BT is ionic, whereas the Pb–O bonding in PMN–PT is highly covalent in the cubic structure. PMN–PT is revealed to have a characteristic Pb–O covalent bond which induces the atomic displacement attributed to the Last mode under applied electric field within the cubic phase despite no phase transition.

Comparing CALPHAD predictions with high energy synchrotron radiation X-ray diffraction measurements during in situ annealing of Al0.3CoCrFeNi high entropy alloy

High-entropy alloys (HEAs) offer the unique ability to tailor microstructures through thermal processing techniques. One family of alloys of interest is AlxCoCrFeNi, where x varies from 0.0 to 2.0 molar fraction which allows for a transition from face-centered cubic (FCC) to body-centered cubic (BCC) crystal structure, as well as the formation of various secondary phases, such as B2, sigma, and L12. In this study, we focus on the Al0.3CoCrFeNi HEA. Based on CALPHAD simulations, the Al0.3CoCrFeNi HEA consists of the following phases from highest to lowest temperature: a) FCC at high temperature, followed by b) B2 precipitation in an FCC matrix, c) then B2 and σ phase co-precipitation in an FCC matrix, d) then B2, σ phase, and L12 phase in an FCC matrix, and finally e) B2, σ phase, and L12 phase in a BCC matrix at low temperature. The purpose of our study is to compare phases observed using high-energy synchrotron radiation X-ray diffraction measurements during in situ annealing with the equilibrium phases predicted using CALPHAD. Phase evolution and dissolution are discussed and compared with the CALPHAD simulation predictions. Our experimental results matched well with the CALPHAD predictions of the phase evolution for the B2 phase, however, the phase dissolution of L12 and σ phases was incomplete, which is likely only observable using high resolution synchrotron radiation X-ray diffraction. Better CALPHAD models are needed as well as longer annealing times due to the complexity of achieving phase equilibrium in multi-phase HEAs.

Static and dynamic structural features of single pellets determine the release behaviors of metoprolol succinate sustained-release tablets

The multiple-unit sustained-release (MUSR) dosage forms containing numerous sustained-release subunits present a reliable choice for oral formulation of controlled release systems. As a typical MUSR, the metoprolol succinate sustained-release tablet is an advanced system with limited researches devoted to relating its structure to the drug release phase other than the preparation process and modulation to the release behaviors. This research details a three-dimension method to image the internal structure and detail drug release features of commercial metoprolol succinate sustained-release tablets and component individual single pellets. As such, a new perspective for MUSR dosage form is provided. Using high energy synchrotron radiation X-ray microcomputed tomography (SR-μCT), the in-situ structure parameters were obtained nondestructively. It was demonstrated that the average number of spherical pellets in a tablet was 853 ± 12 (n = 3). The average volume of the pellets was 0.09 ± 0.01 mm3, the diameter was 0.55 ± 0.03 mm, and the sphericity was 0.87 ± 0.06. These data reflected the numerical features of pellets in MUSR tablets, which were helpful for reverse engineering to MUSR. Based on the three dimensional model generated by image processing and analysis software, the pellet structures were divided into three layers of typical depot sustained release system: pellet core, drug-containing layer and outer film. The dynamic structural features determined refer to the changes of structures in pellets during in vitro drug release, with evidence that the coating layer on the pellets maintained a spherical morphology whilst numerous valleys appeared on the surface. The material constitution and distribution in coating layer were evaluated by synchrotron radiation-based Fourier transform infrared mapping and results indicated a composition of hydroxypropyl methylcellulose dispersed in ethyl cellulose. Knowledge of these structural characteristics confirmed that the mechanism of sustained drug release was membrane controlled and consistent with the drug release profiles. In conclusion, the structural investigation provided knowledge of the intrinsic quality of metoprolol succinate sustained-release tablets and offers guidance for reverse engineering of MUSR.

Structural fluctuation of Pb(Mg1/3Nb2/3)O3 in the cubic phase

To investigate the structural fluctuations of relaxor Pb(Mg1/3Nb2/3)O3 (PMN) in the cubic phase, the probability density function of each atom was determined by high-energy synchrotron radiation X-ray powder diffraction measurements and a Rietveld analysis with anharmonic temperature factors. A rotator-like behavior of the Pb ion was observed in the cubic phase. The off-center behavior along the 〈1 1 1〉 directions became pronounced with decreasing temperature. The ferroelectricity of PMN was attributed to a combination of the freezing of the 〈1 1 1〉-preferred rotator-like disorder and the ferroelectric distortion of the B–O6 octahedron.

High-energy synchrotron radiation X-ray diffraction measurements during in situ aging of a NiTi-15 at. % Hf high temperature shape memory alloy

NiTiHf high temperature shape memory alloys (HTSMAs) have begun to show considerable progress in their ability to be manufactured and are now on the cusp of becoming viable alloys for use in the aerospace industry, mainly as actuation devices. By aging the alloys at intermediate temperatures between 450 and up to 700 °C, Ni-rich NiTiHf HTSMAs form the H-phase, a Ni-rich nanoscale precipitate which can be used to strengthen the alloy and improve the shape memory response; however, precipitate phase evolution and growth has not yet been studied in-situ nor have the effects of previous thermo-mechanical processing on their formation. In this study, H-phase precipitate formation is observed experimentally in situ during aging of a Ni-rich NiTiHf alloy using high energy synchrotron radiation X-ray diffraction (SR-XRD) measurements. The effects of prior thermo-mechanical treatments, i.e. hot and cold rolling, on its formation rate and coarsening rate are compared. It is shown that growth of the H-phase can be observed in situ using SR-XRD and the H-phase formation rate seems to exhibit linear growth when aging at 550 °C, while increasing the temperature to 650 °C shows a logarithmic trend that plateaus after approximately 1 h of aging. Other properties such as incubation time, austenite lattice strains, texture evolution, and overall comparison between hot and cold rolling are discussed. New potential peak age conditions are suggested based on the diffraction data and evaluated using three-point bending and TEM imaging.

In Situ Synchrotron Radiation X-ray Diffraction Study on Phase and Oxide Growth during a High Temperature Cycle of a NiTi-20 at.% Zr High Temperature Shape Memory Alloy

Ternary additions to binary NiTi shape memory alloys are known to significantly affect the characteristic martensite-to-austenite phase transformation, i.e., decrease or increase transformation temperatures. High temperature shape memory alloys can be created by adding Au, Pt, Pd, Hf, or Zr to binary NiTi in appropriate amounts; however, the majority of these ternary additions are exceedingly expensive, unfortunately making them impractical for most commercial applications. Zr is the exception of the group, but it is often disregarded because of its poor workability and thermal stability. In an effort to find a temperature range that allows for the potential workability of NiTiZr alloys in normal atmosphere environments and to gain understanding as to the cause of failure during processing, a NiTi-20 at.% Zr was subjected to a thermal cycle ranging from RT to 1000 °C with short 15 min holds at select temperatures during both heating and cooling while simultaneously collecting high-energy synchrotron radiation X-ray diffraction measurements. This study provides valuable insight into the kinetics of precipitation and oxide formation and its relationship to processing. In addition, scanning electron microscopy was performed on five samples, each isothermally held to examine precipitation and oxide structure and growth.

Effect of Ni-Content on the Transformation Temperatures in NiTi-20 at. % Zr High Temperature Shape Memory Alloys

The effect of Ni-content on phase transformation behavior of NiTi-20 at. % Zr high temperature shape memory alloy (HTSMA) is investigated over a small composition range, i.e., 49.8, 50.0 and 50.2 at. % Ni, by differential scanning calorimetry (DSC), high-energy synchrotron radiation X-ray diffraction (SR-XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). All samples show a monoclinic B19′ martensitic structure at room temperature. It is shown that even with these small variations in Ni-content, the alloy shows vastly different transformation temperatures and responds in a drastically different manner to aging treatments at 550 and 600 °C. Lastly, a discussion on H-phase composition with respect to bulk composition is presented.

Structure fluctuation in Gd- and Mg-substituted BaTiO3 with cubic structure

Gd- and Mg-substituted barium titanate crystals (Ba1−xGdx)(Ti1−x/2Mgx/2)O3 with the Gd composition range of x > 0.1 show no ferroelectric phase transition. To discuss atomic thermal fluctuations in such unusual barium titanate crystals with cubic symmetry, accurate crystal structure analyses were performed by the maximum entropy method (MEM)/Rietveld method with the split-atom model and anharmonic temperature factor model using high-energy synchrotron radiation X-ray diffraction data. The off-centered positions of Gd ions at the Ba site in the probability density function were clearly observed at a low temperature but smeared in the high-temperature region by the over-barrier motion of Gd ions.

Pair distribution functions of amorphous organic thin films from synchrotron X-ray scattering in transmission mode.

Using high-brilliance high-energy synchrotron X-ray radiation, for the first time the total scattering of a thin organic glass film deposited on a strongly scattering inorganic substrate has been measured in transmission mode. The organic thin film was composed of the weakly scattering pharmaceutical substance indomethacin in the amorphous state. The film was 130 µm thick atop a borosilicate glass substrate of equal thickness. The atomic pair distribution function derived from the thin-film measurement is in excellent agreement with that from bulk measurements. This ability to measure the total scattering of amorphous organic thin films in transmission will enable accurate in situ structural studies for a wide range of materials.

放射光X線分析による北海道地方の法科学土砂データベースの構築

The purpose of the present study is to construct a nation-wide forensic soil database, which allows for the identification of soil evidence based on heavy element and heavy mineral signatures determined by two synchrotron radiation (SR) X-ray techniques, i.e., a high-energy synchrotron radiation X-ray fluorescence analysis and a synchrotron-radiation X-ray powder diffraction analysis, respectively. The heavy element and heavy mineral compositions of the stream sediments collected at 3024 points located all over Japan were measured by the two SR X-ray techniques. The present paper focuses on a regional characterization of the sediments collected from the Hokkaido areas. The concentrations of heavy elements and heavy minerals in the Hokkaido areas were visualized as maps that enable us to compare the heavy element and heavy mineral compositions with the geological context of the samples. Based on a hierarchical cluster analysis using the semi-quantitative compositions of the heavy minerals, we could successfully classify the sediments into six groups corresponding to their background geologies. A Bonferroni multiple comparison demonstrated that these six groups also have significant differences in the heavy element composition. From these examinations, we could demonstrate that detailed regional identification of unknown samples is possible by analyzing both heavy element and heavy mineral compositions of each sample.

Off-centering of rare-earth ion in (Ba,R)(Ti,Mg)O3 (R = Gd, Dy)

To investigate the off-centering behavior of rare-earth ions that were partially substituted for A site ions in ABO3-type crystals, accurate crystal structure analyses of (Ba,R)(Ti,Mg)O3 (R = Gd, Dy) were performed by high-energy synchrotron radiation X-ray powder diffraction analysis and the maximum entropy method (MEM)/Rietveld method. The R ions were observed at the six equivalent off-center sites in the 〈100〉 directions from the corner of a unit cell in the cubic phase. In the tetragonal phase, the R ions occupied one off-center site along the [001] direction. The R off-centering can be attributed to the covalent nature of the bond between the R and O ions in (Ba,R)(Ti,Mg)O3 crystals.

Structural evolution and strength change of a metallic glass at different temperatures.

The structural evolution of a Zr64.13Cu15.75Ni10.12Al10 metallic glass is investigated in-situ by high-energy synchrotron X-ray radiation upon heating up to crystallization. The structural rearrangements on the atomic scale during the heating process are analysed as a function of temperature, focusing on shift of the peaks of the structure factor in reciprocal space and the pair distribution function and radial distribution function in real space which are correlated with atomic rearrangements and progressing nanocrystallization. Thermal expansion and contraction of the coordination shells is measured and correlated with the bulk coefficient of thermal expansion. The characteristics of the microstructure and the yield strength of the metallic glass at high temperature are discussed aiming to elucidate the correlation between the atomic arrangement and the mechanical properties.

Texture and Strain Measurements from Bending of NiTi Shape Memory Alloy Wires

Shape memory alloys (SMAs) are a new generation of materials that exhibit unique nonlinear deformations due to a phase transformation which allows the material to return to its original shape after removal of stress or a change in temperature. These unique properties are the result of a martensitic/austenitic phase transformation through the application of temperature changes or applied stress. Many technological applications of austenitic SMAs involve cyclical mechanical loading and unloading in order to take advantage of pseudoelasticity, but are limited due to poor fatigue life. In this paper, commercial pseudoelastic NiTi SMA wires (50.7 at.% Ni) were placed under different bending strains and examined using scanning electron microscopy and high-energy synchrotron radiation X-ray diffraction (SR-XRD). By observing the microstructure, phase transformation temperatures, surface texture and diffraction patterns along the wire, it is shown that the wire exhibits a strong anisotropic behavior whether on the tensile or compressive side of the bending axis and that the initiation of micro-cracks in the wires is localized on the compression side, but that crack propagation will still happen if the wire is reloaded in the opposite direction. In addition, lattice strains are examined for both the austenite and martensite phases.