Time-resolved Synchrotron X-ray Diffraction Research Articles

Deformation of diopside single crystal at mantle pressure. 1: Mechanical data

Steady-state deformation experiments were carried out in a deformation-DIA (D-DIA) high-pressure apparatus on oriented diopside single crystals, at pressure ( P) ranging from 3.8 to 8.8 GPa, temperature ( T) from 1100 to 1400 °C, and differential stress ( σ) between 0.2 and 1.7 GPa. Three compression directions were chosen in order to test the activity of diopside dislocation slip systems, i.e., ½<1 1 0>{ 1 1 ¯ 0 } systems activated together, both [1 0 0](0 1 0) and [0 1 0](1 0 0) systems together, or [0 0 1] dislocation slip activated in (1 0 0), (0 1 0) and {1 1 0} planes. Constant applied stress and specimen strain rates ( ε ˙ ) were monitored in situ using time-resolved synchrotron X-ray diffraction and radiography, respectively. Transmission electron microscopy (TEM) investigation of the run products revealed that dislocation creep was responsible for sample deformation. Comparison of the present high- P data with those obtained at room- P by Raterron and Jaoul (1991) – on similar crystals deformed at comparable T– σ conditions – allows quantifying the effect of P on ½<1 1 0>{ 1 1 ¯ 0 } activity. This translates into the activation volume V* = 17 ± 6 cm 3/mol in the corresponding creep power law. Our data also show that both ½<1 1 0> dislocation slips and [0 0 1] have comparable slip activities at mantle P and T, while [1 0 0](0 1 0) and [0 1 0](1 0 0) slip systems remain marginal. These results show that P has a significant effect on high- T dislocation creep in diopside, the higher the pressure the harder the crystal, and that this effect is stronger on ½<1 1 0> slip than on [0 0 1] slip.

Use of Inorganic Fullerene-like WS2 to Produce New High-Performance Polyphenylene Sulfide Nanocomposites: Role of the Nanoparticle Concentration

The use of tungsten disulfide (WS2) nanoparticles offers the opportunity to produce novel and advanced polymer-based nanocomposite materials via melt blending. The developed materials, based on the high-performance engineering thermoplastic polyphenylene sulfide (PPS), display a unique nanostructure on variation of the nanoparticle concentration, as confirmed by time-resolved synchrotron X-ray diffraction. The cold-crystallization kinetics and morphology of PPS chains under confined conditions in the nanocomposite, as determined by differential scanning calorimetry (DSC) and atomic force microscopy (AFM), also manifest a dependence on the IF-WS2 concentration which are unexpected for polymer nanocomposites. The addition of IF-WS2 with concentrations greater than or equal to 0.5 wt % of IF-WS2 remarkably improves the mechanical performance of PPS with an increase in the storage modulus of 40-75%.

In situ observation of phase transformation in Fe–0.15C binary alloy

Time-resolved high resolution synchrotron X-ray diffraction has been used to conduct in situ studies of the temporal evolution of α → γ and γ → α transformations. Moreover, high temperature laser scanning confocal microscopy with an infrared imaging furnace has been used to directly observe the morphological development of γ → α transformations. It makes possible that phase transformation can be identified in real time during heating and continuously cooling process. Phase transformation process of Fe–0.15C binary alloy was analyzed as a combination of these two experimental facilities.

Microstructures, Surface Properties, and Topotactic Transitions of Manganite Nanorods

Manganite (gamma-MnOOH) nanorods with typical diameters of 20-500 nm and lengths of several micrometers were prepared by reacting KMnO(4) and ethanol under hydrothermal conditions. Synchrotron X-ray diffraction (XRD) reveal that the gamma-MnOOH nanorods crystallize in the monoclinic space group P2(1)/c with unit cell dimensions a = 5.2983(3) A, b = 5.2782(2) A, c = 5.3067(3) A, and beta = 114.401(2) degrees . Transmission electron microscopy shows that the gamma-MnOOH nanorods are single crystalline and that lateral attachment occurs for primary rods elongated along 101. X-ray photoelectron spectroscopy studies indicate that the surfaces of the gamma-MnOOH nanorods are hydrogen deficient and compensated by surface complexation. The Raman scattering spectrum features five main contributions at 360, 389, 530, 558, and 623 cm(-1) along with four weak ones at 266, 453, 492, and 734 cm(-1), attributed to Mn-O vibrations within MnO(6) octahedral frameworks. The structural stability of the gamma-MnOOH nanorods was discussed by means of in situ time-resolved synchrotron XRD. The monoclinic gamma-MnOOH nanorods transform into tetragonal beta-MnO(2) upon heating in air at about 200 degrees C. The reaction is topotactic and shows distinctive differences from those seen for bulk counterparts. A metastable, intermediate phase is observed, possibly connected with hydrogen release via the interstitial (1 x 1) tunnels of the gamma-MnOOH nanorods.

Cs-exchange in birnessite: Reaction mechanisms inferred from time-resolved X-ray diffraction and transmission electron microscopy

We have explored the exchange of Cs for interlayer Na in birnessite using several techniques, including transmission electron microscopy (TEM) and time-resolved synchrotron X-ray diffraction (XRD). Our goal was to test which of two possible exchange mechanisms is operative during the reaction: (1) diffusion of cations in and out of the interlayer or (2) dissolution of Na-birnessite and reprecipitation of Cs-birnessite. The appearance of distinct XRD peaks for Na- and Cs-rich phases in partially exchanged samples offered support for a simple diffusion model, but it was inconsistent with the compositional and crystallographic homogeneity of (Na,Cs)-birnessite platelets from core to rim as ascertained by TEM. Time-resolved XRD revealed systematic changes in the structure of the emergent Cs-rich birnessite phase during exchange, in conflict with a dissolution and reprecipitation model. Instead, we propose that exchange occurred by sequential delamination of Mn oxide octahedral sheets. Exfoliation of a given interlayer region allowed for wholesale replacement of Na by Cs and was rapidly followed by reassembly. This model accounts for the rapidity of metal exchange in birnessite, the co-existence of distinct Na- and Cs-birnessite phases during the process of exchange, and the uniformly mixed Na- and Cs-compositions ascertained from point analyses by selected area electron diffraction and energy dispersive spectroscopy of partially exchanged grains.

Unique Nucleation Activity of Inorganic Fullerene-like WS2 Nanoparticles in Polyphenylene Sulfide Nanocomposites: Isokinetic and Isoconversional Study of Dynamic Crystallization Kinetics

The dynamic crystallization kinetics of polyphenylene sulfide (PPS) nanocomposites with inorganic fullerene WS2 nanopartices (IF-WS2) content varying from 0.05 to 8 wt % has been studied using differential scanning calorimetry (DSC). The analysis of the crystallization at different cooling rates demonstrates that the completely isokinetic description of the crystallization process is not possible. However, the isoconversional methods in combination with the JMAEK equation provide a better understanding of the kinetics of the dynamic crystallization process. The addition of IF-WS2 influences the crystallization kinetics of PPS but in ways unexpected for polymer nanocomposites. A drastic change from retardation to promotion of crystallization is observed with increasing nanoparticle content. In the same way, the results of the nucleation activity and the effective energy barrier confirmed the unique dependence of the crystallization behavior of PPS on composition. In addition, the morphological data obtained from the polarized optical microscopy (POM) and time-resolved synchrotron X-ray diffraction is consistent with results of the crystallization kinetics of PPS/IF-WS2 nanocomposites.

Effect of pressure on membranes

Besides temperature, hydrostatic pressure has been used as a physical-chemical parameter for studying the energetics and phase behavior of membrane systems. First we review some theoretical aspects of lipid self-assembly. Then, the temperature and pressure dependent structure and phase behavior of lipid bilayers, differing in chain configuration, headgroup structure and composition as revealed by using thermodynamic, spectroscopic and scattering experiments is discussed. We also report on the lateral organization of phase-separated lipid membranes and model raft mixtures as well as the influence of peptide and protein incorporation on membrane structure and dynamics upon pressurization. Also the effect of other additives, such as ions, cholesterol, and anaesthetics is discussed. Furthermore, we introduce pressure as a kinetic variable. Applying the pressure-jump relaxation technique in combination with time-resolved synchrotron X-ray diffraction, the kinetics of various lipid phase transformations was investigated. Finally, also new data on pressure effects on membrane mimetics, such as surfactants and microemulsions, are presented.

Supramolecular organization of S12363-liposomes prepared with two different remote loading processes

The S12363 anticancer drug was encapsulated into liposomes in an attempt to increase its therapeutic index. Loading of S12363 was achieved using two different processes based on the formation of either a pH gradient or an ammonium gradient between the acidic inner liposomal compartment and the basic outer phase. High encapsulation yields (> 90%) were obtained using both processes for sphingomyelin/cholesterol/cholesterol-PEG vesicles. Spectrofluorimetry measurements have shown that liposomes were characterized by an internal pH around 4 for both loading processes. This internal pH was stable over a period of at least 20 days. Differential scanning calorimetry coupled with time-resolved synchrotron X-ray diffraction was used to study the drug/carrier supramolecular organization. In ammonium sulfate, S12363 was inserted into the bilayer in the vicinity of the polar headgroup. In citrate buffer, S12363 was mainly adsorbed at the water–lipid interface. The drug partitioning into the membrane was inhomogeneous and led to the formation of drug-rich and drug-poor domains. This effect was enhanced in the presence of cholesterol, especially in ammonium sulfate. To conclude, for both processes, the encapsulated drug was found inside the liposome aqueous core but strongly interacting with the membrane.

Time-resolved studies of the order–disorder phase transformations in rare-earth–transition metal intermetallics with 2-17 stoichiometry

High-temperature order–disorder transformations in R2T17 and R2T17-M-C intermetallics with R = Pr, Sm, Dy, Tb; T = Co, Fe; and M = Zr, Nb were studied utilizing time-resolved synchrotron x-ray diffraction at the Advanced Photon Source (APS) at the U.S. Department of Energy’s Argonne National Laboratory (Argonne, IL). High-energy synchrotron radiation provides intense, highly penetrating x-rays, which are ideal for in situ studies of phase transformations. Alloying additions are used to stabilize formation of metastable phases; their influence on order recovery was investigated. The experimental setup utilized Debye–Scherrer geometry; specimens were heated at a rate of 10 K/min. Full-profile diffraction patterns collected every 10 s were refined in sequence using the Rietveld method to track changes of lattice parameters and phase assemblages during heating. Sharp changes observed in the evolution of temperature-dependent lattice parameters suggested formation of ordered structure via nucleation and growth. Both 2-17 polymorphs co-existed in light and heavy rare-earth systems at high temperatures. The presence of alloying additions in the solid solution greatly influenced long-range order formation.

Unique Isothermal Crystallization Behavior of Novel Polyphenylene Sulfide/Inorganic Fullerene-like WS2 Nanocomposites

The isothermal crystallization of polyphenylene sulfide (PPS) nanocomposites with inorganic fullerene-like tungsten disulfide nanoparticles (IF-WS2) has been studied from a thermal and morphological point of view, using differential scanning calorimetry (DSC), scanning electron microscopy (SEM), polarized optical microscopy (POM) and time-resolved synchrotron X-ray diffraction. All the analyses revealed that the incorporation of the IF-WS2 altered significantly the crystallization behavior of PPS, in a way strongly dependent with the nanocomposite composition. The addition of IF-WS2 in 0.1 wt % proportion retarded the crystallization of PPS by increasing its fold surface free energy in a 10%. However, addition of the nanoparticles in excess of 1 wt % results in a promotion of the crystallization rate with reduction of the fold surface free energy to half the value of pure PPS.

Anomalous high-pressure behavior of amorphous selenium from synchrotron x-ray diffraction and microtomography

The high-pressure behavior of amorphous selenium has been investigated with time-resolved diamond anvil cell synchrotron x-ray diffraction and computed microtomography techniques. A two-step dynamic crystallization process is observed in which the monoclinic phase crystallized from the amorphous selenium and gradually converted to the trigonal phase, thereby explaining previously observed anomalous changes in electrical conductivity of the material under pressure. The crystallization of this elemental system involves local topological fluctuations and results in an unusual pressure-induced volume expansion. The metastability of the phases involved in the transition accounts for this phenomenon. The results demonstrate the use of pressure to control and directly monitor the relative densities and energetics of phases to create new phases from highly metastable states. The microtomographic technique developed here represents a method for determination of the equations of state of amorphous materials at extreme pressures and temperatures.

Applications of time-resolved synchrotron X-ray diffraction to cation exchange, crystal growth and biomineralization reactions

AbstractAdvances in the design of environmental reaction cells and in the collection of X-ray diffraction data are transforming our ability to study mineral-fluid interactions. The resulting increase in time resolution now allows for the determination of rate laws for mineral reactions that are coupled to atomic-scale changes in crystal structure. Here we address the extension of time-resolved synchrotron diffraction techniques to four areas of critical importance to the cycling of metals in soils: (1) cation exchange; (2) biomineralization; (3) stable isotope fractionation during redox reactions; and (4) nucleation and growth of nanoscale oxyhydroxides.

Thermal Imidization and Structural Evolution of Thin Films of Poly(4,4‘-oxydiphenylene p-pyromellitamic diethyl ester)

The evolution of chemical composition and structure during the thermal imidization of an ester-type polyimide precursor, poly(4,4'-oxydiphenylene p-pyromellitamic diethyl ester), in micrometer scale films were studied for a heating rate of 2.0 degrees C/min with time-resolved synchrotron X-ray diffraction, in-situ infrared spectroscopy, and modulated differential scanning calorimetry. Our analyses show that the precursor polymer undergoes imidization in a two-step process. In the first step, the precursor polymer is decomplexed from the residual solvent molecules, and in the second step, it undergoes imide ring formation with the release of ethanol as a byproduct. The imidization reaction starts around 210 degrees C and continues up to 320 degrees C. The thermal imidization reaction induces the structural evolution of the film. As the imidization reaction proceeds, the coherent length along the polymer chain axis increases. This imidization-induced structural evolution was found to occur via three steps: (i) initiation, (ii) the first crystallization, and (iii) the second crystallization. The initiation step is necessary prior to the evolution of the crystalline structure to increase the chain mobility of the precursor polymer chains, and it requires thermal heating up to at least 238 degrees C at which point 22.5% of the imidization is complete. Thereafter, the first crystallization occurs up to 310 degrees C, at which point 98.3% of the imidization is complete. In the range 310-380 degrees C, the second crystallization occurs and produces almost complete imidization of the polymer chains.

Coupling of time-resolved synchrotron X-ray diffraction and DSC to elucidate the crystallisation properties and polymorphism of triglycerides in milk fat globules

Les proprietes de cristallisation et le polymorphisme des triglycerides (TG) dans les globules gras naturels du lait sont etudies avec un appareil permettant le couplage de la diffraction des rayons X (DRX) resolue en temps et de la microcalorimetrie differentielle (DSC), pour des vitesses de refroidissement comprises entre 0,1 et 1000 °C.min -1 . Nous avons montre que la phase lipidique des produits laitiers possede un polymorphisme complexe. Pour la premiere fois, six types differents de cristaux ont ete identifies, plusieurs d'entre eux etant en coexistence, et leurs evolutions ont ete caracterisees de maniere quantitative, en fonction du temps et de la temperature. Elles correspondent a des structures lamellaires avec des structures a deux longueurs de chaine (2L: 40,5-48 A) et a trois longueurs de chaine (3L: 54-72 A). En fonction des vitesses de refroidissement, au moins cinq sous-cellules cristallines ont ete identifiees aux grands angles: a, sub-a, deux β' et β. Toutes ces structures cristallines coexistent avec une phase liquide, meme a basse temperature. Les evenements thermiques enregistres par DSC ont ete relies aux informations structurales de l'organisation des TG obtenues par DRX. Nous avons montre egalement que la cristallisation dans les globules gras induit un plus grand desordre et une plus petite taille des cristaux qu'en milieu anhydre. De plus, la DRX a permis d'identifier differents comportements de cristallisation dans les globules gras de differentes tailles, qui pourraient intervenir lors de la fabrication de produits laitiers necessitant des periodes de temperage (par exemple le beurre, la creme glacee, les produits foisonnes). L'augmentation des connaissances sur la cristallisation de la matiere grasse du lait dans les systemes disperses et dans les produits alimentaires complexes contribuera aux innovations technologiques ainsi qu'au developpement de nouveaux produits.

Water-Induced Morphology Changes in BaO/γ-Al2O3 NOx Storage Materials: an FTIR, TPD, and Time-Resolved Synchrotron XRD Study

The effect of water on the morphology of BaO/Al2O3-based NOx storage materials was investigated using Fourier transform infrared spectroscopy, temperature programmed desorption, and time-resolved synchrotron X-ray diffraction techniques. The results of this multispectroscopy study reveal that in the presence of water surface Ba-nitrates convert to bulk nitrates and water facilitates the formation of large Ba(NO3)2 particles. The conversion of surface to bulk Ba-nitrates is completely reversible (i.e., after the removal of water from the storage material a significant fraction of the bulk nitrates reconverts to surface nitrates). NO2 exposure of a H2O-containing (wet) BaO/Al2O3 sample results in the formation of nitrites and bulk nitrates exclusively (i.e., no surface nitrates form). After further exposure to NO2, the nitrites completely convert to bulk nitrates. The amount of NOx taken up by the storage material, however, is essentially unaffected by the presence of water regardless of whether the water was dosed prior to or after NO2 exposure. On the basis of the results of this study, we are now able to explain most of the observations reported in the literature on the effect of water on NOx uptake on similar storage materials.

Towards an Understanding of the Temperature/ Pressure Configurational and Free-Energy Landscape of Biomolecules

Besides temperature, we used hydrostatic pressure as a physical parameter for studying the stability and energetics of biomolecular systems. High pressure is also an important feature of certain natural environments, and the high-pressure phase behaviour of biomolecules is of increasing biotechnological interest. By using thermodynamic, spectroscopic, and scattering techniques, the temperature and pressure-dependent structure and phase behaviour of model biomembrane systems and proteins have been studied. The results demonstrate that combined temperature–pressure-dependent studies can help delineate the conformational and free-energy landscape of biomolecules and hence help to elucidate which features and thermodynamic parameters are essential in determining their stability. Moreover, we present data on the effect of various types of cosolvents on the temperature- and pressure-dependent structure and stability of proteins. We also introduce pressure as a kinetic variable. Applying the pressure-jump relaxation technique in combination with time-resolved synchrotron X-ray diffraction and spectroscopic techniques, the kinetics of lipid phase transitions and un/refolding reactions of proteins have been studied. Finally, recent advances in using the pressure axis for studying misfolding, aggregation, and amyloid fibril formation of proteins and its potential biotechnological and biomedical relevance will be discussed. We conclude with an outlook of the perspectives of high pressure research.

Structural and thermal characterization of glyceryl behenate by X-ray diffraction coupled to differential calorimetry and infrared spectroscopy

Physical and thermal properties of glyceryl behenate (Compritol ® 888 ATO) used as sustained-release matrix in pharmaceutical applications are studied by coupled time-resolved synchrotron X-ray diffraction and Differential Scanning Calorimetry combined with Infrared Spectroscopy. With these techniques, all polymorphs formed in glyceryl behenate, analyzed as received and after various thermal treatments from quenching to slow crystallization, are characterized. By using different well-controlled mixtures of mono-, di- and tribehenate, we identify each lamellar phase observed in the glyceryl behenate. Finally the influence of the crystallization rate on the formation of preferential conformations was also analyzed in order to bring insights into the polymorphism of glyceryl behenate. By changing the crystallization rate of the sample, it was shown that one can favor the formation of preferential polymorphs in the sample. In particular the crystallization at 10 °C/min seems to be well adapted for producing a single lamellar phase with a period of 60.9 Å while a crystallization rate of 0.4 °C/min produces three different lamellar phases.

DSC and high resolution X-ray diffraction coupling

Abstract Coupling of time-resolved synchrotron X-ray diffraction at both small and wide angles with differential scanning calorimetry is a new technique that allows simultaneous characterization of thermal and structural properties of a sample. The apparatus, called Microcalix, works between –30 and +230C at scanning rates comprised between 0.01 and 20C min–1 with a high sensitivity in both measurements using a single sample of small volume (from about 1 to 20 μL). The last version of the instrument is designed for laboratory bench and conventional source but preferably with rotating anode or multilayered mirrors. Measurements under low pressure or under shear as well as recordings of isothermal evolution are also possible. The example of the study of polymorphism of a monounsaturated triglyceride (PPO) will be presented as an application.

Milk fat and primary fractions obtained by dry fractionation: 1. Chemical composition and crystallisation properties

The chemical composition and crystallisation properties of milk fat and its primary fractions, obtained by dry fractionation at 21 °C, were investigated. The solid fraction (stearin) and the liquid fraction (olein) displayed a different triacylglycerol (TG) composition. Stearin fraction was enriched in long-chain fatty acids, whereas olein fraction was enriched in short-chain and unsaturated fatty acids. Crystallisation properties of milk fat, and both the stearin and olein fractions were studied on cooling at |d T/d t| = 1 °C min −1 by differential scanning calorimetry and time-resolved synchrotron X-ray diffraction (XRD) at small and wide angles. Two main types of crystals corresponding to double chain length structures were characterised in the stearin fraction: α 2 L 1 (47.5 Å) and β′ 2 L 2 (41.7 Å). A triple chain length structure was formed in the olein fraction: α 3 L (72.1 Å). Crystallisaton of milk fat showed the formation of two 2 L (47.3 and 41.6 Å) and one 3 L (72.1 Å) lamellar structures with an hexagonal packing (α form). A schematic representation of the 3 L packing of olein fraction was proposed to explain how a wide diversity of TG can accommodate to form a lamellar structure with a thickness of 72 Å. Furthermore, the sharpness of the small-angle XRD lines associated to the α form was explained by the formation of liquid crystals of smectic type.

Isothermal crystallization kinetics of PEEK/Vectra® blends by DSC and time-resolved synchrotron X-ray diffraction

Thermal properties of blends of poly(aryl ether ether ketone), PEEK, with a thermotropic liquid crystalline polymer, Vectra®, were investigated by differential scanning calorimetry and X-ray diffraction techniques. Isothermal crystallization experiments were performed over a wide range of crystallization temperatures and compositions to follow the effect of Vectra® content on the crystallization kinetics of PEEK. A reduction in the crystallization rate of PEEK was related to a change in the mechanism of crystallization of PEEK, controlled in turn by the concentration of Vectra® in the blend. The addition of Vectra® resulted in a significant enhancement in the crystallization rate of PEEK. In addition, a reduction in this parameter is shown at a blend of 30% of Vectra®. Differences in the crystallization behavior of PEEK are related to structural properties of these systems measured by simultaneous real time WAXS and SAXS experiments using synchrotron radiation. Results of melting behavior of PEEK, subsequent to isothermal crystallization, were interpreted based on the effects of Vectra® on the formation of two crystal families of PEEK. Melting temperatures of PEEK and crystallinity calculated from double endotherm are influenced by blending. POLYM. ENG. SCI., 46:1411–1418, 2006. © 2006 Society of Plastics Engineers