Time-resolved X-ray Diffraction Data Research Articles

In Situ Synchrotron X-ray Scattering Investigation of Cathodic ZIF-8 Deposition on Graphite Using 3D-Printed Cells

Electrochemical approaches provide unique means to fabricate thin films of metal-organic frameworks (MOFs). However, the kinetics of electrochemical MOF deposition has not been quantitatively investigated so far. In this study, we report the first in situ measurements of electrochemical MOF growth using transmission synchrotron X-ray scattering. Electrochemical cells based on poly(lactic acid) with two windows were fabricated using fused-deposition modeling. The resulting three-dimensional (3D)-printed cells, the surface of which was coated with paraffin wax to prevent solvent percolation through the polymer material, were used to monitor the cathodic growth of zeolitic imidazolate framework-8 (ZIF-8) on graphite in a methanol solution containing ZnCl2 and 2-methylimidazole (Hmim) at different cathodic potentials. The resulting time-resolved X-ray diffraction data showed a gradual increase in crystal size with negligible changes in crystal orientation during the cathodic ZIF-8 deposition. More importantly, the time-resolved data provided a means to quantitatively assess the kinetics of the cathodic ZIF-8 growth using the Gualtieri model, revealing that the cathodic potential and Hmim concentration affected crystal growth kinetics but not nucleation kinetics. These ZIF-8 samples exhibited changes in X-ray diffraction patterns after being washed with methanol and dried in air, indicating that in situ measurements are essential to investigate mechanisms behind MOF electrodeposition.

Room temperature crystallography and X-ray spectroscopy of metalloenzymes.

The ultrashort (10s of femtoseconds) X-ray pulses generated by X-ray free electron lasers enable the measurement of X-ray diffraction and spectroscopic data from radiation-sensitive metalloenzymes at room temperature while mostly avoiding the effects of radiation damage usually encountered when performing such experiments at synchrotron sources. Here we discuss an approach to measure both X-ray emission and X-ray crystallographic data at the same time from the same sample volume. The droplet-on-tape setup described allows for efficient sample use and the integration of different reaction triggering options in order to conduct time-resolved studies with limited sample amounts. The approach is illustrated by two examples, photosystem II that catalyzes the light-driven oxidation of water to oxygen, and isopenicillin N synthase, an enzyme that catalyzes the double ring cyclization of a tripeptide precursor into the β-lactam isopenicillin and can be activated by oxygen exposure. We describe the necessary steps to obtain microcrystals of both proteins as well as the operation procedure for the drop-on-tape setup and details of the data acquisition and processing involved in this experiment. At the end, we present how the combination of time-resolved X-ray emission spectra and diffraction data can be used to improve the knowledge about the enzyme reaction mechanism.

Millisecond time-resolved synchrotron radiation X-ray diffraction and high-pressure rapid compression device and its application

Non-equilibrium transition dynamics under high pressure depends on temperature, pressure and (de)compression rate. The studies require combination of time-resolved probe and rapid compression device on different time scales. Here we report the time-resolved X-ray diffraction (XRD) and dynamic diamond anvil cell (dDAC) system, which were recently developed at the BL15U1 beamline of Shanghai Synchrotron Radiation Facility (SSRF). There are two rapid loading methods for dDAC. One uses membrane control and the other is piezoelectric actuator driven dDAC. Both methods can dynamically compress the DAC sample chamber up to 300 GPa on millisecond scale (20 μm culet is used), and the time-resolved XRD data are obtained correspondingly. A new type of piezoelectric ceramic dDAC is designed with single-side drive or double-side drive, which allows us to realize extremely high pressure (above 300 GPa) with a fast compression rate of 13 TPa/s. During the rapid compression process, the X-ray diffraction spectra are collected continuously and simultaneously. The XRD detector is Pilatus 3X 900K, which has 2-ms resolution with 500 kHz frame rate. The millisecond time-resolved XRD and high pressure rapid compression system developed at BL15U1 of SSRF enrich the high-pressure experimental methods and enable the beamline to carry out ultra-high pressure experiments, non-equilibrium phase transition and relevant scientific researches.

Ultrafast X-ray Diffraction Study of a Shock-Compressed Iron Meteorite above 100 GPa

Natural kamacite samples (Fe92.5Ni7.5) from a fragment of the Gibeon meteorite were studied as a proxy material for terrestrial cores to examine phase transition kinetics under shock compression for a range of different pressures up to 140 GPa. In situ time-resolved X-ray diffraction (XRD) data were collected of a body-centered cubic (bcc) kamacite section that transforms to the high-pressure hexagonal close-packed (hcp) phase with sub-nanosecond temporal resolution. The coarse-grained crystal of kamacite rapidly transformed to highly oriented crystallites of the hcp phase at maximum compression. The hcp phase persisted for as long as 9.5 ns following shock release. Comparing the c/a ratio with previous static and dynamic work on Fe and Fe-rich Fe-Ni alloys, it was found that some shots exhibit a larger than ideal c/a ratio, up to nearly 1.65. This work represents the first time-resolved laser shock compression structural study of a natural iron meteorite, relevant for understanding the dynamic material properties of metallic planetary bodies during impact events and Earth’s core elasticity.

X-ray Emission Spectroscopy of Biomimetic Mn Coordination Complexes

Understanding the function of Mn ions in biological and chemical redox catalysis requires precise knowledge of their electronic structure. X-ray emission spectroscopy (XES) is an emerging technique with a growing application to biological and biomimetic systems. Here, we report an improved, cost-effective spectrometer used to analyze two biomimetic coordination compounds, [MnIV(OH)2(Me2EBC)]2+ and [MnIV(O)(OH)(Me2EBC)]+, the second of which contains a key MnIV═O structural fragment. Despite having the same formal oxidation state (MnIV) and tetradentate ligands, XES spectra from these two compounds demonstrate different electronic structures. Experimental measurements and DFT calculations yield different localized spin densities for the two complexes resulting from MnIV-OH conversion to MnIV═O. The relevance of the observed spectroscopic changes is discussed for applications in analyzing complex biological systems such as photosystem II. A model of the S3 intermediate state of photosystem II containing a MnIV═O fragment is compared to recent time-resolved X-ray diffraction data of the same state.

Application of combined multivariate techniques for the description of time-resolved powder X-ray diffraction data

In this work, multivariate statistical techniques are employed to determine patterns and conversion curves from time-resolved X-ray powder diffraction data. For these purposes, time-window statistical total correlation spectroscopy is introduced for the pattern matching of the crystalline phase and is shown to be effective even in the case of overlapping peaks. When combined with evolving factor analysis and multivariate curve resolution–alternating least squares, this technique allows a definite estimation of patterns and conversion curves. The procedure is applied to in situ synchrotron powder diffraction patterns to monitor the setting reaction of magnesium potassium phosphate ceramic (MKP) from magnesia (MgO) and potassium dihydrogen phosphate. It is shown that the phases involved in the reaction are clearly distinguished and their evolution is correctly described. The conversion curves estimated with the proposed procedure are compared with the ones determined with the peak integration method, leading to an excellent agreement (Pearson's correlation coefficient equal to 0.9995 and 0.9998 for MgO and MKP, respectively). The approach also allows for the detection and description of the evolution of amorphous phases that cannot be described through conventional analysis of powder diffraction data.

Transient structure of thin films based on one-dimensional chain model

Functional materials have received much attention in the development of scientific technology. Macroscopic function of material is usually linked to the microscopic properties. In order to understand the relationship between structure and function, it is necessary to observe transient structural change of material in real time. In the earlier experimental work femtosecond optical probes were used to measure associated modulation in optical properties like transmissivity or reflectivity and extract the information about structural dynamics through sophisticated theoretical modeling. Since the development of laser-based ultrafast X-ray sources, there has been extensive work on femtosecond X-ray diffraction measurements. The coupling of sensitive X-ray with time-resolved pump-probe technique provides a way to directly monitor the time-dependent lattice structural changes in condensed matter. Recent researches are devoted to the study of non-thermal melting and coherent acoustic photons. The classical continuous elastic equation can only provide a limited view of structural dynamics. So, simulation of structural dynamics at an atomic level and comparison of such simulation with time-resolved X-ray diffraction data are necessary.#br#In this paper, we use the one-dimensional chain model to study the effect of thermal stress on the lattice due to the inhomogeneity of temperature distribution after ultrafast laser heating. It is developed from the classic continuous elastic equation by considering a nanometer film as a chain of point mass connected by springs. The simulation can directly reveal the positon of each point mass (atom) as a function of time for a given temperature (stress) profile. The simulation results accord very well with experimental data obtained with femtosecond X-ray diffraction. Compared with simulation results, the ultrafast X-ray diffraction experimental results are not enough to distinguish the compression near the zero time, but the characteristic time (~123 ps) and broadening of the diffraction peak are clearly observed. The simulation and experimental study of the lattice structural response are of great help for understanding the direct relationship between the lattice responses caused by ultrafast laser excitation, the generation and propagation of strain, one-dimensional chain model has important applications in studying the recoverable ultrafast lattice dynamics of metals, semiconductors and other materials.

Anhydrous Calcium Oxalate Polymorphism: A Combined Computational and Synchrotron X-ray Diffraction Study

Four possible models for anhydrous calcium oxalate (COA) polymorphs have been investigated through ab initio quantum mechanical methods. Their structural properties, infrared and Raman spectra, and thermodynamic stability in the range of 0–800 K have been analyzed and compared. Along with the known β-COA structure, two models turn out to be possible candidates for the α- and γ-polymorphs that were observed during dehydration of weddellite (calcium oxalate dihydrate, COD) by Walter-Lévy and Laniepce (C. R. Acad. Sci. Paris 1964, 259, 4685). While the calculated vibrational frequencies show that the four COA models correspond to minimum energy structures, β-COA is the thermodynamically favored phase over the range of temperatures examined in the present study. Despite the fact that computed vibrational spectra and X-ray diffraction (XRD) patterns of these polymorphs exhibit some different features, a definitive assignment of the structures based on computational results is not possible due to the lack of accurate experimental data. In an effort to improve comparative experimental data, the structural evolution of whewellite (calcium oxalate monohydrate, COM) has been probed using time-resolved synchrotron X-ray diffraction, in order to correlate the calculated structures to the observed structures. The evolution has been shown to go through at least four phases identified as COM, α-COA (corresponding to one of the models proposed by computation), β-COA, and CaCO3. The reactions are predominantly two-phase reactions, and at 140 °C evidence of three-phase coexistence has been noted between COM, α-COA, and β-COA. The time-resolved XRD data allow estimation of the kinetics of the reactions; these indicate second-order reactions between COM and α-COA and zeroth-order reactions between α-COA and β-COA.

Ultra-fast in-situ X-ray studies of evolving columnar dendrites in solidifying steel weld pools

High-brilliance polychromatic synchrotron radiation has been used to conduct in-situ studies of the solidification microstructure evolution during simulated welding. The welding simulations were realized by rapidly fusing ∼ 5 mm spot in Fe-Cr-Ni steel. During the solid- liquid-solid phase transformations, a section of the weld pool was placed in an incident 50-150 keV polychromatic synchrotron X-ray beam, in a near-horizontal position at a very low inclination angle. Multiple high-resolution 2D detectors with very high frame rates were utilized to capture time resolved X-ray diffraction data from suitably oriented solid dendrites evolving in the weld pool. Comprehensive analysis of the diffraction data revealed individual and overall dendritic growth characteristics and relevant melt and solid flow dynamics during weld pool solidification, which was completed within 1.5 s. Columnar dendrite tip velocities were estimated from the experimental data and during early stages of solidification were exceeded 4 mm/s. The most remarkable observation revealed through the time-resolved reciprocal space observations are correlated to significant tilting of columnar type dendrites at their root during solidification, presumably caused by convective currents in the weld pool. When the columnar dendrite tilting are transformed to respective metric linear tilting velocities at the dendrite tip; tilting velocities are found to be in the same order of magnitude as the columnar tip growth velocities, suggesting a highly transient nature of growth conditions.

A refined monoclinic structure for a variety of "hydrohematite"

In ferruginous soils, nano- to microscale hematite (α-Fe 2 O 3 ) plays a central role in redox processes and contaminant cycling. Hematite is known to incorporate structural OH - and water, and the requisite charge balance is achieved by iron vacancies. Prior researchers have suggested that the defective hematite structures form unique phases called “protohematite” and “hydrohematite.” Infrared and Raman spectroscopic studies have assigned a lower-symmetry space group to “hydrohematite” (R3̄c) relative to that of stoichiometric hematite (R3̄c). However, the existence and structure of these phases have been contentious, largely due to the lack of in situ X-ray diffraction data Here we present a new structure refinement for “hydrohematite” precipitated hydrothermally at 200 °C in a monoclinic space group (I2/a) using time-resolved synchrotron X-ray diffraction (TRXRD) data collected during the in situ hydrothermal precipitation of akaganeite and its transformation to stoichiometric hematite. Distinct peak splitting was observed in the “hydrohematite” diffraction patterns, indicating a violation of the threefold rotational symmetry. A monoclinic unit cell with parameters of a = 7.3951(10), b = 5.0117(5), c = 5.4417(7) Å, β = 95.666(5)° provided a good fit and significant reduction in χ 2 and R wp relative to space group R3̄c. Rietveld analyses revealed that water concentrations in the first-formed crystals of “hydrohematite” were comparable to water contents of akaganeite and goethite. Thus, the hydrothermal transformation of akaganeite to “hydrohematite” is promoted not by dehydration but by reconstruction of the oxygen framework.

Time-resolved x-ray diffraction across water-ice-VI/VII transformations using the dynamic-DAC

We present recent time-resolved x-ray diffraction data obtained across the solidification of water to ice-VI and -VII at different compression rates. The structural evolution of ice-VI to ice-VII, however, is not a sharp transition, but occurs rather coarsely. The diffraction data shows an anisotropic compression behavior for ice VI; that is, the c-axis is more compressible than the a-axis at the same compression rate. Nevertheless, the present equations of state of both ice-VI and ice-VII obtained under dynamic loadings agree well with those previously obtained under static conditions. Hence, the present study demonstrates that time-resolved x-ray diffraction coupled with the dynamic-DAC is an effective method for investigating details of the structural response of materials over a wide range of well-controlled compression rates. Finally, we found the evidence for an X-ray induced chemical reaction of water and ice-VI. The impurities, produced by the x-ray induced chemical reaction, inhibit the formation of amorphous ice.

Time-resolved structural dynamics of thin metal films heated with femtosecond optical pulses

We utilize 100fs optical pulses to induce ultrafast disorder of 35- to 150-nm thick single Au(111) crystals and observe the subsequent structural evolution using 0.6-ps, 8.04-keV X-ray pulses. Monitoring the picosecond time-dependent modulation of the X-ray diffraction intensity, width, and shift, we have measured directly electron/phonon coupling, phonon/lattice interaction, and a histogram of the lattice disorder evolution, such as lattice breath due to a pressure wave propagating at sonic velocity, lattice melting, and recrystallization, including mosaic formation. Results of theoretical simulations agree and support the experimental data of the lattice/liquid phase transition process. These time-resolved X-ray diffraction data provide a detailed description of all the significant processes induced by ultrafast laser pulses impinging on thin metallic single crystals.

<i>In Situ</i> Analysis of Effects of Transformation Strain on the Austenite Phase during Martenistic Transformation of Cr-Ni Steel

A hybrid in-situ observation system has been developed to study the phase transformation behaviour simultaneously in both real and reciprocal lattice space. This paper presents the development of the observation system. Furthermore, as an example of the application of our developed system, martensitic transformation of Cr–Ni steel along a designed thermal cycle was in-situ tracked with the developed system. As a result of analysing the time-resolved X-ray diffraction data for the observed target, our system could directly detect the effect of transformation strain on austenite during martensitic transformation.

Blast wave and contraction in Au(111) thin film induced by femtosecond laser pulses. A time resolved x-ray diffraction study.

We utilize 100 fs optical pulses as a means of heating 150 nm thick single Au (111) crystals, below the melting point and monitor the subsequent structural evolution with subpicosecond time resolution using 0.6 ps, 8.04 KeV x-ray pulses. By monitoring the energy and time dependent modulation of the width and shift of the x-ray diffraction rocking curve, we have obtained information on electron-phonon coupling, photon-lattice interaction, and time resolved kinetics of the crystal disorder. The data show that during the first couple picoseconds after optical excitation, the formation of a “blast force” and lattice contraction, followed by a pressure wave formed 10-20 ps later. Both the blast and pressure wave propagate through the crystal with sonic velocities. These time resolved x-ray diffraction data provide a detail description of the processes induced by ultrafast laser pulses impinging on very thin metallic crystals.

Direct observation of catalyst behaviour under real working conditions with X-ray diffraction: Comparing SAPO-18 and SAPO-34 methanol to olefin catalysts

We have made direct observations of the behaviour of the silicoaluminophosphate framework of the SAPO-18 catalyst under working conditions in the methanol to olefin conversion process. Time-resolved synchrotron powder X-ray diffraction data for the process at 450 °C show that the unit cell of the catalyst expands by around 0.9%, significantly less than the structurally similar SAPO-34. The smaller expansion is explained in terms of the cage volume and the rigidity of the structure compared with SAPO-34. Expansion is caused by the build-up of “hydrocarbon pool” intermediates in the cages. The lack of expansion and hence slower build-up of large hydrocarbons is linked to the slower deactivation of SAPO-18 compared with that of SAPO-34. The mechanism for suppressing the formation of the large polycyclic aromatics associated with the deactivation of SAPO MTO catalysts remains open.

Multiscale Model Predictions of X-Ray Diffraction Patterns in Contracting Skeletal Muscle

In order to explain time-resolved x-ray diffraction data, enabled by recent advances in synchrotron small-angle diffraction instruments, we explored the feasibility of using dynamic 3D models of muscle contraction to predict x-ray diffraction patterns. This approach differs radically from previous attempts, which merely aimed to provide a “best fit” structure for defined quasi-static states, by providing a tool to generate families of structures that evolve in time that explains both the structural (x-ray) and the mechanical data simultaneously. Specifically, we exploit the computational platform MUSICO which was developed originally to model muscle mechanics data, by extending this framework to simulate x-ray diffraction patterns using 3D multiscale models. These models take into account (i) biochemical states of myosin interacting with actin; (ii) rate constants in the actomyosin ATP hydrolysis cycle; (iii) function of myosin molecular motors in a 3D sarcomere lattice; (iv) Ca2+ regulation of myosin binding to actin; (v) extensibility of actin and myosin filaments; and (vi) multiple sarcomeres in series and in parallel. The platform is conceived primarily as a hypothesis-testing tool in which model predictions are tested against the best available mechanical and x-ray diffraction data on the same system. Our preliminary simulations provided dynamic x-ray diffraction patterns during force development and relaxation in skeletal muscle. The simulated patterns generally predicted well changes in repetitive molecular spacings and displayed similarity with experimental data. Once fully developed, this tool will enable extraction of maximum information from the x-ray patterns, in combination with the physiological data, and therefore provide a template to test hypotheses concerning crossbridge and regulatory protein action in working muscle. Our approach can be extended to any muscle system, and it could ultimately provide an interpretive framework for studying the mechanisms of inherited or acquired diseases.

The application of statistical methodology to the analysis of time-resolved X-ray diffraction data

We demonstrate for the first time the application of Principal Component Analysis (PCA) to the analysis of time-resolved energy-dispersive X-ray diffraction data. Previously well-characterised model systems are studied. PCA is shown to offer significant advantages over traditional curve-fitting methods in terms of speed and lack of potential user bias.

Time-resolved X-ray diffraction analysis of the experimental dehydration of serpentine at high pressure

Time-resolved, in situ X-ray diffraction analysis was used to determine the dehydration rate and kinetics of serpentine during experimental dehydration at high pressures. The capsule used comprises a diamond sleeve fitted with Au or Pt lids in order to provide high-quality, time-resolved X-ray diffraction data. Antigorite quickly dehydrated to enstatite + forsterite + fluid within 2 h at 650 °C below ∼ 6 GPa. Avrami modeling of the results and SEM observations of the partially dehydrated sample revealed that the nucleation rate was quite high for enstatite but low for forsterite, showing incubation periods of ∼ 10 min before appearing. The crystallization of these minerals is controlled largely by the composition of the fluid generated from serpentine dehydration. The dehydration boundary determined below 6 GPa in the present study is consistent with the results of previous phase equilibrium studies. This study indicates that serpentine in a subducting slab dehydrates rapidly below 6 GPa when the slab intersects the dehydration boundary conditions.

Time and position resolved in situ X-ray diffraction study of the hydrothermal conversion of gypsum monoliths to hydroxyapatite

Time-resolved energy dispersive X-ray diffraction (EDXRD) data have been measured in situ from cast blocks of gypsum, CaSO(4) x 2 H(2)O, in the presence of reactive phosphate solutions under hydrothermal conditions (100 < or = T < or = 180 degrees C) in order to understand the formation of hydroxyapatite monoliths, for applications such as in artificial bone or dental materials. Measurement of data in short (60 s) intervals has thus permitted information about the kinetics and mechanism of transformation of gypsum to hydroxyapatite to be obtained in a non-invasive way, avoiding the irreversible conversion of hydrous intermediate phases that would occur on quenching. At the lower temperatures used gypsum first converts to an amorphous intermediate phase during reaction, but as the temperature is raised to 130 degrees C and above, hydrothermal dehydration to the subhydrate CaSO(4) x 1/2 H(2)O always occurs before hydroxyapatite crystallises. The final crystal size of the hydroxyapatite is estimated from the peak broadening of the EDXRD data and this reveals an increase in crystal dimension with increasing reaction temperature. Comparing measurements from the surface and from the core of the blocks shows that an additional phosphate phase, CaHPO(4), is observed in the core at two temperatures and also that the crystal growth of hydroxyapatite does not penetrate the core of the block on the time scales we have investigated (up to 6 hours). The observations have important implications in the fabrication of hydroxyapatite monoliths from cast gypsum for applications, since the conversion via several intermediate phases may compromise the integrity and mechanical properties of the monoliths.

Time resolved X-ray diffraction observations of phase transformations in transient arc welds

In situ X-ray diffraction methods have been developed at Lawrence Livermore National Laboratory for direct observation of microstructural evolution under quasi-steady state and transient welding conditions. Using intense highly collimated synchrotron radiation, the crystal structures in the weld heat affected and fusion zones are probed in real time to monitor solidification and solid state phase transformations during welding. Here the authors review recent work on the development and use of the time resolved X-ray diffraction (TRXRD) technique during transient welding and illustrate its unique capabilities to: directly observe the solidification mode; discover, in real time, the definitive sequence of phase transformations that lead to the final microstructure; and provide quantitative kinetic data of phase transformations through synthesis of TRXRD data with the temperature history obtained through heat transfer modelling. The TRXRD technique has been used to investigate welding induced phase transformations in titanium alloys, low alloy steels, and stainless steel alloys. The results show some of the first real time observations of the weld solidification mode and the evolution of equilibrium and non-equilibrium phases during rapid heating and cooling. When combined with numerical modelling, quantitative phase transformation kinetic data are obtained, allowing for its use in a wide variety of isothermal and non-isothermal processing. The potential for future applications of this and similar techniques is also addressed.