Time-resolved Synchrotron X-ray Diffraction Research Articles

Isothermal Crystallization Kinetics of Palm Oil as Influenced by Addition of a Commercial Phytosterol Ester Mixture.

In literature there is good agreement on the health-promoting effects of phytosterols. However, addition of phytosterol esters (PEs) to lipid (containing food products) may influence its crystallization behavior. This study investigated the crystallization kinetics of palm oil (PO) after addition of PEs in high concentrations (≥10%). The isothermal crystallization of the PE-PO blends was analyzed at a temperature of 20 °C and at a supercooling of 18.7 °C using differential scanning calorimetry and time-resolved synchrotron X-ray diffraction. At increasing PE concentrations, PO crystallization at an isothermal temperature of 20 °C started later and was slower and a smaller amount of crystals were formed. Furthermore, a delay in polymorphic transition from α to β' was observed. When the blends were isothermally crystallized at a supercooling of 18.7 °C, only two of these effects remained: the delay in polymorphic transition and the decrease in crystalline content.

Macromol. Mater. Eng. 2/2018

Front Cover: Screw-assisted melt extrusion 3D printing has been developed for tissue engineering applications. The cover page image illustrates the in situ characterization of the polycaprolactone crystal structure evolution during the scaffold printing process via time-resolved synchrotron X-ray diffraction. This is reported by Fengyuan Liu, Cian Vyas, Gowsihan Poologasundarampillai, Ian Pape, Sri Hinduja, Wajira Mirihanage, and Paulo Bartolo in article number 1700494.

Rationalization of Hydrothermal Synthesis of NaNbO3 by Rapid in Situ Time-Resolved Synchrotron X-ray Diffraction

In situ monitoring of the formation of crystalline phases during conventional hydrothermal synthesis is experimentally challenging. Here, we report an in situ time-resolved synchrotron X-ray diffraction study during hydrothermal synthesis of NaNbO3 using a high-pressure custom-made capillary cell penetrable to X-rays. The high time resolution (0.1 s) revealed a sequence of transient intermediate phases, including several unknown phases, before the final perovskite NaNbO3 was formed. These new findings highlight the complexity of the hydrothermal synthesis of NaNbO3 and demonstrate the potential for obtaining in-depth knowledge of the reactions taking place by time-resolved in situ X-ray diffraction.

Changes in the structure of birnessite during siderophore-promoted dissolution: A time-resolved synchrotron X-ray diffraction study

We used time-resolved synchrotron X-ray diffraction to follow the complete dissolution of synthetic triclinic Na-birnessite as promoted by the trihydroxamate siderophore desferrioxamine B (DFOB). Many microorganisms employ siderophores to increase the availability of Fe, Mn, and other trace metals for metabolic processes. Our primary goal was to quantify the DFOB-assisted dissolution rate by direct, continuous observation of the solid phase. Our kinetic model indicates that the rate of dissolution is dependent on [DFOB] but not pH, and has a reaction order of 0.505 with a rate constant of 0.112wt%birnmin−1. The unit-cell dimensions of birnessite remained virtually constant within error throughout the dissolution process, showing only a 0.3% contraction along the c-axis.Despite the small changes in unit-cell volume, Rietveld analysis revealed that the occupancy of Mn within the octahedral sheets decreased from 100% to ~80%, presumably as the result of complexation of structural Mn3+ with DFOB followed by extraction of Mn3+ from the crystal structure. These observations suggest a critical lacunarity of ~20mol% Mn for triclinic Na-birnessite, below which the structure is destabilized. Moreover, this study reveals that DFOB-promoted dissolution must operate by a different mechanism from that engaged when bacterial membrane fractions directly transfer electrons to birnessite crystals. We propose that crystal structure analysis of minerals undergoing dissimilatory metal reduction can elucidate metabolic pathways employed by microorganisms.

The effect of adding a commercial phytosterol ester mixture on the phase behavior of palm oil

The objective of this study was to investigate in depth the non-isothermal crystallization and melting behavior of binary blends of palm oil (PO) with a commercial, multi-component phytosterol ester (PE) mixture. DSC and time-resolved synchrotron X-ray diffraction (XRD) experiments were conducted on blends with a PE concentration from 0 to 100% at intervals of 10% for DSC and 20% for XRD. Based on XRD, two different ordered structures were identified in pure the PEs. The structure designated as PEx was truly crystalline and needed a very high degree of supercooling for its nucleation from the melt. The structure designated PEy formed without supercooling and showed long-range order with multiple reflections at small angles but only one broad reflection at high angle, typical of liquid crystalline samples. Furthermore, PEy had a high tolerance for molecules of different chemical nature. In the PE-PO blends no other ordered structures were formed other than the ones observed in the pure PEs and PO. The peaks in the DSC runs of the PE-PO blends were linked to transitions of the different polymorphic forms. All structural information of the binary blends as a function of concentration and temperature was collected in morphology maps. The binary blends exhibited eutectic characteristics visualized in the morphology maps with a eutectic point at 40% PEs.

From Rate Measurements to Mechanistic Data for Condensed Matter Reactions: A Case Study Using the Crystallization of [Zn(OH2)6][ZnCl4

The kinetics of crystallization of the R = 3 hydrate of zinc chloride, [Zn(OH2)6][ZnCl4], is measured by time-resolved synchrotron x-ray diffraction, time-resolved neutron diffraction, and by differential scanning calorimetry. It is shown that analysis of the rate data using the classic Kolmogorov, Johnson, Mehl, Avrami (KJMA) kinetic model affords radically different rate constants for equivalent reaction conditions. Reintroducing the amount of sample measured by each method into the kinetic model, using our recently developed modified-KJMA model (M-KJMA), it is shown that each of these diverse rate measurement techniques can give the intrinsic, material specific rate constant, the velocity of the phase boundary, vpb. These data are then compared to the velocity of the crystallization front directly measured optically. The time-resolved diffraction methods uniquely monitor the loss of the liquid reactant and formation of the crystalline product demonstrating that the crystallization of this hydrate phase proceeds through no intermediate phases. The temperature dependent vpb data are then well fit to transition zone theory to extract activation parameters. These demonstrate that the rate-limiting component to this crystallization reaction is the ordering of the waters (or protons) of hydration into restricted positions of the crystalline lattice resulting in large negative entropy of activation.

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.

A kinetic analysis of the transformation from akaganeite to hematite: An in situ time-resolved X-ray diffraction study

The nucleation and growth of akaganeite and its transformation to hematite under hydrothermal conditions were monitored over a temperature range of 80 to 200°C using time-resolved synchrotron X-ray diffraction. In each experiment, akaganeite was the first phase to form and hematite was the final phase. No intermediate phases were identified. The induction time to akaganeite nucleation was ~5525s and 537s at 80°C and 100°C, respectively, yielding an activation energy of 129±15kJ/mol. However, akaganeite nucleated at a constant temperature of 123±5°C when the heater set point was 150°C or higher, suggesting an activation energy for akaganeite nucleation of 0kJ/mol between 150 and 200°C. Hematite nucleation induction times decreased with increasing temperature from 1723s to 110s between 150 and 200°C. Based on a JMAK analysis, the activation energies for the crystal growth and dissolution of akaganeite were 74±8kJ/mol and 125±7kJ/mol, respectively. Our calculated activation energies for hematite nucleation and crystal growth were 80±13kJ/mol and 110±21kJ/mol, respectively.

Anhydrate to hydrate solid-state transformations of carbamazepine and nitrofurantoin in biorelevant media studied in situ using time-resolved synchrotron X-ray diffraction

Transformation of the solid-state form of a drug compound in the lumen of the gastrointestinal tract may alter the drug bioavailability and in extreme cases result in patient fatalities. The solution-mediated anhydrate-to-hydrate phase transformation was examined using an in vitro model with different biorelevant media, simulated fasted and fed state intestinal fluids containing bile salt and dioleoylphosphatidylcholine (DOPC) micelles, DOPC/sodium dodecyl sulfate (SDS) mixture, bile salt solution and water. Two anhydrate compounds (carbamazepine, CBZ and nitrofurantoin, NF) with different overall transformation time into hydrate form were used as model compounds. The transformations were monitored using direct structural information from time-resolved synchrotron X-ray diffraction. The kinetics of these transformations were estimated using multivariate data analysis (principal component analysis, PCA) and compared to those for nitrofurantoin (NF). The study showed that the solution-mediated phase transformation of CBZ anhydrate was remarkably faster in the DOPC/SDS medium compared to transformation in all the other aqueous dispersion media. The conversion time for CBZ anhydrate in water was shorter than for DOPC/SDS but still faster than the conversion seen in fed and fasted state micellar media. The conversion of CBZ anhydrate to hydrate was the slowest in the solution containing bile salt alone. In contrast, the solution-mediated phase transformations of NF did only show limited kinetic dependence on the dispersion media used, indicating the complexity of the nucleation process. Furthermore, when the CBZ and NF material was compacted into tablets the transformation times were remarkably slower. Results suggest that variations in the composition of the contents of the stomach/gut may affect the recrystallization kinetics, especially when investigating compounds with relatively fast overall transformation time, such as CBZ.

Negligible substrate clamping effect on piezoelectric response in (111)-epitaxial tetragonal Pb(Zr, Ti)O3 films

The converse piezoelectric responses of (111)- and (001)-epitaxial tetragonal Pb(Zr0.35Ti0.65)O3 [PZT] films were compared to investigate the orientation dependence of the substrate clamping effect. Synchrotron X-ray diffraction (XRD) and piezoelectric force microscopy revealed that the as-grown (111)-PZT film has a polydomain structure with normal twin boundaries that are changed by the poling process to inclined boundaries, as predicted by Romanov et al. [Phys. Status Solidi A 172, 225 (1999)]. Time-resolved synchrotron XRD under bias voltage showed the negligible impact of substrate clamping on the piezoelectric response in the (111)-PZT film, unlike the case for (001)-PZT film. The origin of the negligible clamping effect in the (111)-PZT film is discussed from the viewpoint of the elastic properties and the compensation of lattice distortion between neighboring domains.

Novel Electrothermodynamic Power Generation

To investigate how exhaust heat from automobiles can be converted to renewable energy, an innovative electrothermodynamic cycle is presented, which is based on temporal temperature variations, the pyroelectric effect, instead of spatial temperature gradient, and the Seebeck effect. A generating mechanism is investigated using operando time-resolved synchrotron X-ray diffraction. Practical energy and true energy breakeven are achieved via real engine dynamometer experiments.

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.

Dynamic Lithium Intercalation/Deintercalation in 18650 Lithium Ion Battery by Time-Resolved High Energy Synchrotron X-Ray Diffraction

A time-resolved in situ high energy synchrotron X-ray diffraction (HESXRD) technique is employed to study the lithiation/delithiation of cathode/anode in a commercial 18650 battery under real working condition (current rate is 4 C). The phases and their changes in both the cathode and anode are identified simultaneously. For the anode component, during the charge process, as well as the LixC6 phase, a lithium-rich phase close to LiC6 phase and a series of intermediate phases between the Li0.5C6 and LiC6 phases are observed. A distinct lithium intercalation/deintercalation mechanism is proposed for the cathode. The transforms of LiFePO4 into the FePO4 consists three periods with different components of phases, i.e., LiFePO4 + lithium-deficient solid solution phases (period I), FePO4 + LiFePO4 phases (period II), and FePO4 + lithium-rich solid solution phases (period III). The changes in both the andode and cathode during the discharge process are just inversed to those occurrs during the charge process. The present work indicates that dynamic lithiation/delithaition process under real working condition is different from those at the thermodynamic state, and the in situ HESXRD is one of the most promising technique to monitor such kind of dynamic lithium behavior.

Tracking the progression of bronze disease – A synchrotron X-ray diffraction study of nantokite hydrolysis

The hydrolysis of nantokite to form cuprite could be a reaction step in the progression of bronze disease on cupreous objects d’art. In this paper, this transformation is visualized for the first time using a time-resolved synchrotron X-ray diffraction experiment. Complete conversion of nantokite to cuprite was observed on a nantokite patina over 5h in water using time-resolved synchrotron X-ray diffraction.

Unsaturated fatty acid enriched vs. control milk triacylglycerols: Solid and liquid TAG phases examined by synchrotron radiation X-ray diffraction coupled with DSC

The fatty acid composition of milk triacylglycerols (TAGs) can be modified to improve their nutritional properties and the long-term health of consumers. However, the consequences of an increase in unsaturated fatty acid (UFA) content on the physical properties of milk TAGs remain to be elucidated. This study aimed at comparing the crystallisation properties and melting behaviour of control vs. UFA-enriched milk TAGs using the coupling of time-resolved synchrotron X-ray diffraction and differential scanning calorimetry on cooling and then heating at 3°C/min. On cooling from the melt, high crystallisation temperature (HCT) TAGs solidify from 15.8°C in α 2L (45–49Å) structures, then low crystallisation temperature (LCT) TAGs form α 3L structures with a higher thickness (75.5Å vs. 71.5Å) and a delay (8.5°C vs. 12.1°C) for UFA-enriched TAG. On heating, melting of TAGs crystals and formation of 3L2 (64.7–80.1Å) and β′ 2Lf (40–44Å) crystals associated with polymorphic reorganisations have been characterised. The organisation of TAG molecules in their liquid state revealed a higher thickness for UFA-enriched TAGs as compared to control TAGs. Such results improve the knowledge about the mechanisms of TAG crystallisation as a function of their FA composition and are important for the technological utilisation of UFA-enriched TAGs in food products.

Solidification and fcc to metastable hcp phase transition in krypton under variable compression rates

We present time-resolved synchrotron x-ray diffraction measurements to study kinetics associated with the liquid-solid and solid-solid high-pressure phase transitions in Kr under dynamic loading in a dynamic-diamond anvil cell. The results show a strong compression-rate dependence of the solidification/melting process in liquid Kr. The analysis of the compression-rate dependent melting/solidification, using an Avrami equation with the parameter $n=1$, indicates a spontaneous nucleation and one-dimensional growth mechanism. In contrast, the face-centered-cubic to metastable hexagonal close-packed transition in solid Kr occurs rapidly at \ensuremath{\sim}0.8 GPa near the melting line, which has negligible compression-rate dependence within the range of compression rates studied $(0.004--13 \mathrm{GPa}/\mathrm{s})$.

Time-resolved synchrotron X-ray diffraction study of the dehydration behavior of chalcophanite

Time-resolved synchrotron X‑ray powder diffraction data were used to investigate the dehydration behavior of the chalcophanite (ZnMn 3 O 7 ·3H 2 O) structure from 300 to 1060 K. Rietveld refinements revealed two obvious phase changes, at ∼450 and ∼950 K, corresponding to the dehydration of chalcophanite followed by transformation to a spinel structure (Mn-hetaerolite). Only small changes were observed in the chalcophanite unit cell from RT to ∼438 K; the volume increased by ∼0.8%, mostly caused by thermal expansion of ∼0.5% along c. Above ∼427 K, the interlayer water molecules were lost, resulting in a collapse of the interlayer spacing from ∼7 to ∼4.8 Å. The newly formed anhydrous phase (ZnMn 3 O 7 ) retained chalcophanite’s R3̅ space group and a dimension, but the c dimension decreased from ∼21 to 14.3 Å, and the Zn coordination changed from octahedral to tetrahedral. Above ∼775 K the anhydrous chalcophanite began to transform to a spinel structure, corresponding to a Mnrich hetaerolite [(Zn 0.75 Mn 2+ 0.25 )Mn 2 3+ O 4 ]. By ∼973 K the transformation was complete. The diffraction patterns did not show a significant increase in background during the transformation, indicating that the reaction did not involve transient amorphization. The phase change was likely triggered by loss of 1.25 of seven O atoms in the original anhydrous chalcophanite structure with a corresponding reduction of Mn 4+ to Mn 3+ and Mn 2+ .

Time-resolved synchrotron x-ray diffraction studies of the crystallization of amorphous Co(80−x)FexB20

This paper addresses the time-dependent crystallization process occurring in “bulk” amorphous Co80−xFexB20 (x = 20, 40) metallic ribbons by means of synchrotron x-ray diffraction (SXRD) and transmission electron microscopy. Metallic ribbons, produced via melt-spinning technique, were annealed in-situ, with SXRD patterns collected every 60 s. SXRD reveals that Co40Fe40B20 alloys crystallize from an amorphous structure to a primary bcc α-(Co,Fe) phase, whereas Co60Fe20B20 initially crystallizes into the same bcc α-(Co,Fe) but exhibits cooperative growth of both stable and metastable boride phases later into the hold. Johnson-Mehl-Avrami-Kolmogorov statistics was used on post annealed samples to determine the mechanisms of growth and the activation energy (Ea) of the α-(Co,Fe) phase. Results indicate that the growth mechanisms are similar for both alloy compositions for all annealing temperatures, with the Avrami exponent of n = 1.51(1) and 2.02(6) for x = 20 and 40, respectively, suggesting one-dimensional growth, with a decreasing nucleation rate. Activation energy for α-(Co,Fe) was determined to be 2.7(1) eV and 2.4(3) eV in x = 20 and 40, respectively, suggesting that those alloys with a lower Co content have a stronger resistance to crystallization. Based on these results, fabrication of CoFeB magnetic tunnel junctions via depositing amorphous layers and subsequently annealing to induce lattice matching presents itself as a viable and efficient method, for increasing the giant magnetoresistance in magnetic tunnel junctions.

FeCoSiBNbCu bulk metallic glass with large compressive deformability studied by time-resolved synchrotron X-ray diffraction

By adding 0.5 at. % Cu to the strong but brittle [(Fe0.5Co0.5)0.75Si0.05B0.20]96Nb4 bulk metallic glass, fully amorphous rods with diameters up to 2 mm were obtained. The monolithic samples with 1 mm diameter revealed a fracture strain of 3.80% and a maximum stress of 4143 MPa upon compression, together with a slight work-hardening behavior. SEM micrographs of fractured samples did neither reveal any shear bands on the lateral surface nor the typical vein patterns which characterize ductile fracture. However, some layers appear to have flowed and this phenomenon took place before the brittle final fracture. An estimate of the temperature rise ΔT in the shear plane gives 1039 K, which is large enough to melt a layer of 120 nm. The overall performance and the macroscopic plastic strain depend on the interaction between cleavage-like and viscous flow-like features. Mechanical tests performed in-situ under synchrotron radiation allowed the calculation of the strain tensor components, using the reciprocal-space data and analyzing the shift of the first (the main) and the second broad peak positions in the X-ray diffraction patterns. The results revealed that each atomic shell may have a different stiffness, which may explain the macroscopic compressive plastic deformation. Also, there were no signs of (nano) crystallization induced by the applied stress, but the samples preserve a monolithic amorphous structure until catastrophic failure occurs.

Quantitative determination of fragmentation kinetics and thermodynamics of colloidal silver nanowires by in situ high-energy synchrotron X-ray diffraction

Colloidal silver nanowires become instable and tend to fragment into shortened nanorods and nanoparticles at elevated temperatures. Such morphological variations are associated with the transformation of crystalline structures from the body-centered tetragonal (b.c.t.) lattices into the face-centered cubic (f.c.c.) ones. The crystalline phase transformation has been probed in real time with an in situ technique based on time-resolved high-energy synchrotron X-ray diffraction. Comprehensive analysis of the in situ measurements provides, for the first time, the quantitative understanding of kinetics and thermodynamics involved in the fragmentation of the colloidal silver nanowires.