Time-resolved X-ray Diffraction Measurements Research Articles

Crystalline structures formed in cream and anhydrous milk fat at 4 °C

Crystallization and polymorphic evolutions of triacylglycerols (TG), at 4 o C, in cream and anhydrous milk fat (AMF) samples were studied using high-sensitivity differential scanning cal- orimetry (DSC), time-resolved synchrotron X-ray diffraction (XRD) and density measurement, and compared as a function of time after quenching from 60 to 4 o C. The evolution of the two crystalline structures initially formed in both samples, corresponding to a metastable 2L (47 A) and a 3L (70.5 A) lamellar organization with hexagonal chain packings (α form), were monitored in isothermal condi- tions at 4 o C as a function of time t. For t > 15 min, short spacings showed the formation of a β' pack- ing of the chains in coexistence with the α form. In AMF, the occurrence of some β form was also recorded. For long spacings, a 2L (39 A) structure was formed in cream with the 3L (70.5 A) structure still being preponderant after conditioning for 30 min at 4 o C. In AMF samples, a TG polymorphic transition 3L (70.5 A) → 2L (39 A) + 3L (66 A), correlated with an exothermic peak recorded simul- taneously by DSC, was clearly visible. At t > 100 h conditioning at 4 o C, the same crystalline struc- tures were found in cream and AMF with the coexistence of at least a 2L (40.5 A) and a 3L (54.2 A) longitudinal organization, associated with α, β'2 , β'1 and β packings of the chains. The melting be- haviors of cream and AMF were monitored on heating at 2 o C.min -1 by coupled XRD as a function of temperature and DSC experiments. The absence of further structural evolution and polymorphic tran- sition until final melting demonstrates the relative stability of the structure formed. The evolution of cream density after quenching to 4 o C revealed two transitions, the amplitudes, rates and duration of which coincided with DSC and XRD experiments. All data are in agreement in demonstrating that two transitions, a fast and a slow one, occur in dairy products after fast cooling to 4 o C.

Picosecond Time-Resolved X-ray Diffraction Using Laser-Induced X-ray Pulse.

Generation of ultrashort hard X-ray pulses using laser-driven electron X-ray sources and picosecond time-resolved X-ray diffraction measurements are reviewed. Hard X-ray pulses are characterized by measurements of energy spectrum and pulse duration. Picosecond lattice dynamics of laser-irradiated silicon crystal measured by time-resolved X-ray diffraction is described.

SPring-8におけるX線放射光・短パルスレーザーの同期と時間分解測定

The combination of an intense pulsed laser and the SPring-8 X-ray synchrotron radiation (SR) pulses has enabled us to make time-resolved X-ray diffraction measurements on picosecond time scale. The laser-SR synchronization technique needed for the time-resolved measurements and the performance obtained at SPring-8, are described. By using the synchronization system, the laser-induced crystal lattice expansion with a response time of a few hundred picoseconds was observed. Application of the laser-induced lattice expansion to a fast X-ray shutter is also described.

Thermal Evolution of Carbon-Supported Pd Nanoparticles Studied by Time-Resolved X-ray Diffraction

Time-resolved X-ray diffraction measurements were performed in situ on a Pd/C catalyst during two successive thermal treatments from 300 to 873 K. Analysis of the diffraction patterns, as a function of thermal treatment, reveals anomalous features in the evolution of Pd particles. An intermediate Pd1-xCx phase (x ∼ 0.1) is observed and dissolved into pure Pd at ∼700 K. Moreover, the size of metal particles, remaining almost constant (∼10 nm) during the annealing, abruptly increases to 30 nm in close connection with the dissolution of the Pd1-xCx phase. These effects clearly point out an interaction between the metal and the support and suggest that the formation of the Pd1-xCx phase would prevent the metal-particle sintering, thus maintaining the catalyst dispersion at a high level. There is no evidence of the formation of a Pd1-xCx phase during the second temperature treatment since only metallic Pd was detected. As for the growth in particle size, a small increase to 32 nm was observed.

Simultaneous IR and time-resolved X-ray diffraction measurements for studying self-sustained reactions

Self-propagating high-temperature synthesis provides an attractive practical method for producing advanced materials such as ceramics, composites and intermetallics. This kind of reaction has been investigated in situ using time-resolved X-ray diffraction, with an X-ray synchrotron beam (D43 beamline, LURE, Orsay) coupled to simultaneous IR thermography to study structural transformations and thermal evolution. With short acquisition times (30 ms per pattern) it has been possible to observe several steps before obtaining compounds. Two different compound formations have been described: (i) the different steps of reaction, aluminium melting, subsequent temperature increase and fast reaction between Al and Ni at such temperatures that only Ni and AlNi are solid and all other compositions are liquid and well identified; (ii) the formation of FeAl. Here, a portion of the iron seems to transform into its allotropic phase and this transition stabilizes the reaction temperature at approximately 1173 K. In addition, the aluminium melting during the reaction explains why the nanostructure induced by the mechanical activation is maintained in the end product.

Structural Change in the Topochemical Solid-State Polymerization Process of Diethyl cis,cis-Muconate Crystal. 1. Investigation of Polymerization Process by Means of X-ray Diffraction, Infrared/Raman Spectra, and DSC

Structural change occurring in the light-induced solid-state polymerization of diethyl cis,cis-muconate crystal has been investigated by means of the X-ray diffraction, infrared and Raman spectra, and DSC. The infrared and Raman spectral changes during this polymerization reaction could be interpreted on the basis of a simple two-component system consisting of monomer and polymer molecules. This apparent observation may originate from the high sensitivity of the vibrational spectra to the local structure. The time-resolved X-ray diffraction measurement, however, showed that the lattice spacings changed continuously in the process of polymerization, indicating that the strain to the crystal lattice, due to the coexistence of the different chemical species of monomer and polymer with various lengths or volumes, changed in this reaction. But this strain was quite small, and the crystal lattice could be maintained more or less during the polymerization reaction. It was also found that the polymerization did not occur at a low temperature below −40 °C, where the phase transition occurred and the packing structure of monomer molecules changed, as indicated by the large change in the X-ray diffraction pattern. This good correlation between the reactivity and the crystal structure indicates that the polymerization reaction is governed sensitively by the packing structure of monomer molecules; i.e., this reaction is just the lattice-controlled polymerization.

A Pixel-Array Detector for Time-Resolved X-ray Diffraction.

An integrating pixel-array detector for recording time-resolved X-ray diffraction measurements on microsecond timescales has been designed and tested as a 4 x 4 pixel prototype. Operational characteristics and radiation tolerance are discussed. A 100 x 92 array with 151.2 micro m square pixels is currently under construction.

Collagen Orientation and Molecular Spacing During Creep and Stress-Relaxation in Soft Connective Tissues

Collagen fibres form cross-helical, cross-ply or quasi-random feltworks in extensible connective tissues; strain-induced reorientation of these networks gives rise to the non-linear mechanical properties of connective tissue at finite strains. Such tissues are also generally viscoelastic (i.e. display time-dependent properties). The hypothesis that time-dependent reorientation of collagen fibres is responsible for the viscoelasticity of such tissues is examined here using time-resolved X-ray diffraction measurements during stress-relaxation and creep transients applied to rat skin and bovine intramuscular connective tissue. Differences in the intensity and angular orientation of the third and fifth orders of the 67 nm meridional D-spacing of collagen molecules were shown before and after the application of loads or displacements. However, no changes in the D-spacing or angular orientation of collagen occurred during the time course of either stress-relaxation or creep in both tissues. This indicates that collagen fibre reorientation is not a primary source of their viscoelastic properties. The non-linear (strain-dependent) nature of the stress-relaxation response in these tissues suggests that relaxation processes within the collagen fibres or at the fibre-matrix interface may be responsible for their viscoelastic nature.

Polymorphism, mesomorphism, and metastability of monoelaidin in excess water

The polymorphic and metastable phase behavior of monoelaidin dry and in excess water was studied by using high-sensitivity differential scanning calorimetry and time-resolved x-ray diffraction in the temperature range of 4 degrees C to 60 degrees C. To overcome problems associated with a pronounced thermal history-dependent phase behavior, simultaneous calorimetry and time-resolved x-ray diffraction measurements were performed on individual samples. Monoelaidin/water samples were prepared at room temperature and stored at 4 degrees C for up to 1 week before measurement. The initial heating scan from 4 degrees C to 60 degrees C showed complex phase behavior with the sample in the lamellar crystalline (Lc0) and cubic (Im3m, Q229) phases at low and high temperatures, respectively. The Lc0 phase transforms to the lamellar liquid crystalline (L alpha) phase at 38 degrees C. At 45 degrees C, multiple unresolved lines appeared that coexisted with those from the L alpha phase in the low-angle region of the diffraction pattern that have been assigned previously to the so-called X phase (Caffrey, 1987, 1989). With further heating the X phase converts to the Im3m cubic phase. Regardless of previous thermal history, cooling calorimetric scans revealed a single exotherm at 22 degrees C, which was assigned to an L alpha+cubic (Im3m, Q229)-to-lamellar gel (L beta) phase transition. The response of the sample to a cooling followed by a reheating or isothermal protocol depended on the length of time the sample was incubated at 4 degrees C. A model is proposed that reconciles the complex polymorphic, mesomorphic, and metastability interrelationships observed with this lipid/water system. Dry monoelaidin exists in the lamellar crystalline (beta) phase in the 4 degrees C to 45 degrees C range. The beta phase transforms to a second lamellar crystalline polymorph identified as beta* at 45 degrees C that subsequently melts at 57 degrees C. The beta phase observed with dry monoelaidin is identical to the LcO phase formed by monoelaidin that was dispersed in excess water and that had not been previously heated.

Time-Resolved X-Ray Diffraction Measurement of Silicon Surface during Laser Irradiation under Grazing-Incidence Conditions

The time-resolved X-ray diffraction measurement under frequency-doubled Nd:YAG laser (λ=0.53 µ m) irradiation was carried out using the “out of plane” reflections at the BL-16 (MPW-beamline) in the Photon Factory (KEK). The “out of plane” 333 reflection showed that the lattice expansion in the lateral direction due to the present pulsed-laser irradiation was negligible. From the skew 422 reflection at a glancing angle of 2.3 mrad, which was near the critical angle for the total reflection, the temperature rise in silicon thin surface layers (less than 75 nm) was estimated to be 210° C from the shift of peak position at 50 ns after laser irradiation at a laser power density of 160 mJ/cm2.

Investigations on the physical state of lipid nanoparticles by synchrotron radiation X-ray diffraction

Submicron-sized parenteral drug carrier systems based on lipids solid at room temperature in the bulk phase were prepared by high pressure homogenization of an emulsion of molten lipids in an aqueous phase. Phospholipids, bile salts and block copolymers of polyoxyethylene and polyoxypropylene were used as emulsifiers. The mean diameters obtained under standardized homogenization conditions determined by photon correlation spectroscopy lie between 70 and 300 nm, and depend on the amount and type of emulsifier. The present study describes the results of an investigation on the physical state, the melting behaviour and the recrystallization of the lipids in these colloidal carrier systems using X-ray diffraction. Debye-Scherrer diffraction patterns were first obtained on a conventional X-ray source, but the long exposure times (8–24 h) precluded a systematic investigation. Therefore, simultaneous small and wide angle diffraction measurements were made using synchrotron radiation with exposure times around 3 min. All investigated carrier systems were in the β-crystalline modification at room temperature. At body temperature the carriers were either β-crystalline or amorphous liquids depending on the matrix constituent. Incorporation of coenzyme Q 10 into the lipid particles did not significantly alter the recrystallization tendency of the nanoparticles. Time-resolved X-ray diffraction measurements during temperature scans demonstrated that the recrystallization of the lipid nanodispersions is different from that of bulk material. After heating above the bulk melting temperature and cooling down under controlled conditions the dispersed lipids recrystallize in the α-form whereas the bulk lipids recrystallize in the β′-modification and transform rapidly into the β-form.

The effects of glycerol on the phase behaviour of hydrated distearoylphosphatidylethanolamine and its possible relation to the mode of action of cryoprotectants

A phase diagram for 1,2-distearoylphosphatidylethanolamine (DSPE) dispersed in glycerol/water mixtures was constructed using data obtained from differential scanning calorimetry and time-resolved X-ray diffraction measurements. The phase sequence seen on heating the lipid remains the same for samples containing up to 70 wt% glycerol. Depending on the hydration conditions, the samples are either in a metastable lamellar gel (L β) or one or other of two possible sub-gel phases (L c and L c′) at low temperatures. These phases convert first to a lamellar liquid crystalline (L α) and then to an inverted hexagonal (H II) phase on heating. On cooling, the samples revert first to the L α and then to the L β phase. Although the phase sequence is preserved, marked changes are seen in the transition temperatures between the different phases. The temperature of the transition between the L α and the H II phases decreases strongly with increasing glycerol concentration while that of the L c and L c′ phases to L α, and to a lesser extent that of the L β to L α transition, increases. Substantial changes in phase behaviour are seen if the glycerol concentration is increased above 70 wt%. Under these conditions, the L c and L c′ phases transform directly into the H II phase on heating (a similar direct transition from the L β to the H II phase is seen above 80 wt% glycerol). An exothermic transition from the L β phase to the L c′ phase is observed and there is also an increasing tendency for the samples to revert to the L c or L c′ phases on storage. These changes in relative stability of the different phases are discussed in terms of a possible membrane Hofmeister effect and their relevance to the mode of action of cryoprotectants is explored.

Kinetics of the first-order transition in stage 1 rubidium graphite intercalation compound

The kinetic properties of first-order stacking transition between α β γ δ and α β solid in stage 1 Rubidium graphite intercalation compound was studied by time-resolved synchrotron radiation X-ray diffraction measurements. The volume of the growing phase shows scaling phenomena for various excess pressures of Rb, Δ P Rb, and the function is in quite good agreement with the 1D case of phenomenological nucleation growth (NG) theory by Avrami except for small Δ P Rb. The peak width of the (104) Bragg reflection of α β solid shows remarkable change, which indicates the NG of the stable phase. However α β γ δ phase shows no change because of the stacking fault effect.

The rate process of the field-induced modulated-ferroelectric phase transition in thiourea

Time-resolved X-ray diffraction measurements of the electric-field-induced modulated-ferroelectric phase transition in thiourea (SC(NH2)2) have been made. When the phase changes at the transition point around Tc=169 K, scaling phenomena are seen in the time evolution of the integrated intensity. In addition, the phase change proceeds along the valley of free energy in the order parameter space. This phase change of the modulated-ferroelectric transition is explained in terms of a well known nucleation and growth mechanism.

Applications of multiwire proportional chambers to time resolved X-ray studies on muscle

Multiwire proportional chambers have been used for making time resolved X-ray diffraction measurements from skeletal muscle. The most useful properties are low noise, high efficiency and fast readout. A number of applications from measurements on skeletal muscle are described.

Time-resolved X-ray diffraction measurements of phosphatidylcholine-phosphatidylethanolamine mixtures: Effect of phosphatidylethanolamine acyl chain length

Phase transitions in 1:1 molar mixtures of DLPE:DPPC, DMPE:DPPC, DPPE:DPPC, and DSPE: DPPC have been examined using time-resolved X-ray diffraction techniques. A model of the gel-to-liquid crystal phase transition observed upon heating for these lipid mixtures in which the mixing of domains of gel and liquid crystal phase lipids is the rate-limiting step can be formulated. Upon cooling, it is inferred that small domains of gel state lipid are nucleated from the L α phase. The miscibility of components and domains is also related to the types of proposed phase diagrams.

Crystallization of amorphous NiZr 2

Using a wide bandpass monochromator and a fast position-sensitive detector at the IBM-MIT beamline X20C at the National Synchrotron Light Source we have been able to perform time-resolved X-ray diffraction measurements much faster than previously possible. Using this ability we have studied the polymorphic crystallization of amorphous NiZr 2. At low anneal temperatures, isothermal crystallization behavior follows closely the expected dependencies from differential scanning calorimetry measurements. At high anneal temperatures, the crystallization occurs so fast that the latent heat cannot be conducted away fast enough to maintain isothermal conditions. The temperature rise causes an increase in the rate of further crystallization. Analysis of the diffraction patterns shows that for this rapid crystallization the crystallites are initially highly deformed with the deformation annealing away with a time scale comparable with the time for crystallization.

Time-resolved X-ray diffraction from silicon during pulsed laser annealing

The pulsed X-ray line emission at 4.44 Å from a laser produced plasma has been used to make time-resolved X-ray diffraction measurements on silicon during pulsed laser annealing. This was done by varying the time delay between the annealing and plasma producing laser pulses. Preliminary results show that this technique is well suited to the study of laser heated crystals and is capable of giving single shot recording of the thermal strain profile with nanosecond time resolution.

Overheating In Silicon During Pulsed-Laser Irradiation?

ABSTRACTNanosecond resolution time-resolved x-ray diffraction measurements of thermal strain have been used to measure the interface temperatures in silicon during pulsed-laser irradiation. The pulsed-time-structure of the Cornell High Energy Synchrotron Source (CHESS) was used to measure the temperature of the liquid-solid interface of <111> silicon during melting with an interface velocity of 11 m/s, at a time of near zero velocity, and at a regrowth velocity of 6 m/s. The results of these measurements indicate 110 K difference between the temperature of the interface during melting and regrowth, and the measurement at zero velocity shows that most of the difference is associated with undercooling during the regrowth phase.

Calculation of single-crystal electrostrictive coefficients from time-resolved X-ray diffraction measurements

Calculation of single-crystal electrostrictive coefficients from time-resolved X-ray diffraction measurements