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The bending actuators are designed for easy adaptation for different mirror widths and thicknesses, and are very compact in the direction of the X-ray beam, so that the whole device is only 20 mm longer than the mirror substrate. The ALBA adaptive optics device The active optics system developed by ALBA (Figure 5) is essentially a mechanical mirror bender with point force actuators along the mirror length. The development of X-ray photon science has been characterized in the last few years by the development of free electron lasers and the so-called diffraction limited storage rings. The use of helicoidal springs enables the bender for an excellent dynamic range, and it is capable of applying forces up to 1 kN, with a below 1 mN, sufficient to ensure that the bender actuators can apply is 1,000 , enough to bend a flat mirror to curvatures below 100 m, with steps corresponding to a change of height below one nanometer. [Extracted from the article]

Although the graphitic carbon contamination of synchrotron beamline optics has been an obvious problem for several decades, the basic mechanisms underlying the contamination process as well as the cleaning/remediation strategies are not understood and the corresponding cleaning procedures are still under development. In this study an analysis of remediation strategies all based on in situ low-pressure RF plasma cleaning approaches is reported, including a quantitative determination of the optimum process parameters and their influence on the chemistry as well as the morphology of optical test surfaces. It appears that optimum results are obtained for a specific pressure range as well as for specific combinations of the plasma feedstock gases, the latter depending on the chemical aspects of the optical surfaces to be cleaned. [ABSTRACT FROM AUTHOR]

Molecular orientation and strain-induced crystallization of vulcanized natural rubbers (by sulfur and peroxide) and synthetic polyisoprene rubber (by sulfur) during uniaxial deformation at 0 °C were studied by in situ synchrotron wide-angle X-ray diffraction. The high intensity of synchrotron X-rays and new image analysis methods made it possible to estimate the mass fractions of strain-induced crystals and amorphous chains in both oriented and unoriented states. Most of the polymer chains (∼75%) were found to be in the random coil state even at large strains (>5.0). Only about 5% the amorphous chains were oriented, whereas the rest of the chains (∼20%) were in the crystalline phase. Sulfur vulcanized and peroxide vulcanized natural rubbers did not exhibit notable differences in structure and property relationships. In contrast, synthetic polyisoprene rubber showed a different behavior of deformation-induced structural changes, which can be attributed to the difference in cross-link topology. Our results indicated that strain induces a network of microfibrillar crystals in both natural and synthetic polyisoprene rubbers due to the inhomogeneity of cross-link distribution that is responsible for their elastic properties. [Copyright &y& Elsevier]

The self-nucleation behaviour of isotactic poly(1-butene) in the trigonal modification was investigated. Large and isolated Form I spherulites, successfully generated via a purposely designed thermal history protocol, were self-nucleated at different temperatures and subsequently crystallized at 90 °C. The morphology that developed was analysed using polarized optical microscopy, and the polymorphic content and distribution were monitored using synchrotron IR microspectroscopy. Images of the polymorphic distribution were generated using both univariate (band ratio) and multivariate (chemometric) analyses of the spectral data. From the morphological point of view, polarised optical microscopy showed that low seeding temperatures (＜130 °C) enabled preservation of the original large spherulite that served as a seed for the growth of Form II at its periphery through cross-nucleation. However, with increasing seeding temperature, more complex morphologies arise, through progressive fading of the original morphology. Firstly, re-crystallization results in a defective large spherulite, and then at temperatures above 132 °C, it results in numerous highly-nucleated Form II spherulites. The IR microspectroscopy images generated either by univariate (band ratio) or multivariate (hierarchical cluster analysis) mappings provided concise information on the spatial distribution of the two polymorphs in the re-crystallized specimens, with a resolution in the range of several microns. It was shown that the content of Form II in the region of the self-nucleated Form I spherulite increases with increasing seeding temperature, demonstrating that the morphological changes accompany the gradual erosion of the memory of the original crystalline structure. [ABSTRACT FROM AUTHOR]

The self-nucleation behaviour of isotactic poly(1-butene) in the trigonal modification was investigated. Large and isolated Form I spherulites, successfully generated via a purposely designed thermal history protocol, were self-nucleated at different temperatures and subsequently crystallized at 90 °C. The morphology that developed was analysed using polarized optical microscopy, and the polymorphic content and distribution were monitored using synchrotron IR microspectroscopy. Images of the polymorphic distribution were generated using both univariate (band ratio) and multivariate (chemometric) analyses of the spectral data. From the morphological point of view, polarised optical microscopy showed that low seeding temperatures (＜130 °C) enabled preservation of the original large spherulite that served as a seed for the growth of Form II at its periphery through cross-nucleation. However, with increasing seeding temperature, more complex morphologies arise, through progressive fading of the original morphology. Firstly, re-crystallization results in a defective large spherulite, and then at temperatures above 132 °C, it results in numerous highly-nucleated Form II spherulites. The IR microspectroscopy images generated either by univariate (band ratio) or multivariate (hierarchical cluster analysis) mappings provided concise information on the spatial distribution of the two polymorphs in the re-crystallized specimens, with a resolution in the range of several microns. It was shown that the content of Form II in the region of the self-nucleated Form I spherulite increases with increasing seeding temperature, demonstrating that the morphological changes accompany the gradual erosion of the memory of the original crystalline structure. [ABSTRACT FROM AUTHOR]

The shear-induced crystallization behavior of isotactic polypropylene (iPP) nanocomposite melt containing modified carbon nanofibers (MCNFs) was investigated by rheo-SAXS (small-angle X-ray scattering) and rheo-WAXD (wide-angle X-ray diffraction) techniques using synchrotron radiation. Under quiescent conditions, the nucleating effect of MCNFs on crystallization of iPP was pronounced and the system exhibited a remarkably low saturation point (ca. 0.05 wt% of MCNF). In-situ SAXS and WAXD results showed the development of shear-induced crystalline structures and lamellar morphology in nanocomposite melts. Under the same shear conditions, the filled system exhibited notably faster kinetics compared with the unfilled system. The oriented crystalline fraction was found to decrease with the MCNF loading, indicating the competition between oriented crystals (induced by shear) and unoriented crystals (due to the nucleating effect of MCNF). At the early stages of crystallization, the amount of the oriented crystals increased with the MCNF concentration, suggesting that the nanofiller hindered the motion of polymer chains after the cessation of flow resulting in the delayed relaxation of stretched polymer segments. [ABSTRACT FROM AUTHOR]

Abstract: Structure and property of a nanocomposite consisting of modified carbon nanofibers (MCNFs), homogenously dispersed in an elastomeric ethylene/propylene (EP) random copolymer (84.3wt% P) matrix, were studied by in situ synchrotron X-ray diffraction during uniaxial deformation. The MCNF acted as a nucleating agent for crystallization of the α-form of isotactic polypropylene (iPP) in the matrix. During deformation at room temperature, strain-induced crystallization took place, while the transformation from the γ phase to α phase also occurred for both unfilled and 10wt% MCNF-filled samples. The tensile strength of the filled material was consistently higher than that of pure copolymer. However, when compared with pure copolymer, the highly stretched nanocomposite exhibited a higher amount of unoriented crystals, a lower degree of crystal orientation and a higher amount of γ crystals. This behavior indicated that polymer crystals in the filled nanocomposite experienced a reduced load, suggesting an effective load transfer from the matrix to MCNFs. At elevated temperatures, the presence of MCNFs resulted in a thermally stable physically cross-linked network, which facilitated strain-induced crystallization and led to a remarkable improvement in the mechanical properties. For example, the toughness of the 10wt% nanocomposite was found to increase by a factor of 150 times at 55°C. [Copyright &y& Elsevier]

Simultaneous measurements of Raman spectroscopy and synchrotron two-dimensional (2D) wide-angle x-ray diffraction (WAXD) have been successfully demonstrated for in situ study of an anisotropic system: isotactic polypropylene (iPP) fiber under tensile deformation. A fiber-optic probe was used to remotely deliver the incident laser beam on the sample as well as to collect the Raman signal based on the confocal arrangement, whereas high resolution 2D WAXD patterns were obtained simultaneously at the same position during deformation of polymers. The combined techniques yielded complementary information on the molecular structural evolution in both crystalline and amorphous phases. 2D WAXD results showed that the α-form iPP crystals were converted into the mesophase upon stretching at room temperature. Corresponding Raman spectra showed that characteristic bands from the crystal phase became weaker or disappeared during the transition from the crystal phase to the mesophase. However, the bands associated with the helical structure were still present, indicating the remainder of the helical conformation in the mesomorphic phase. The persistence of the Raman band at 812 cm[sup -1] in the mesophase implied that the structural difference between the crystal phase and the mesophase in iPP is due to the packing defects, rather than the conformational deviations from the (...TGTG...) sequence in chains. The variations in the Raman intensity ratio (I812/I843) indicated that the overall orientation of the fiber increased during stretching. The demonstrated techniques will be particularly useful for in situ studies of anisotropic polymers, where orientational dependent structural information from both crystalline and amorphous phases needs to be collected simultaneously. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Structure evolution during deformation of unfilled natural rubber (NR) vulcanizate and filled ones with carbon black or calcium carbonate was investigated by the synchrotron x-ray diffraction. The crystallization onset strain, α0, was found to decrease by the inclusion of the filler. However, corrected α0 values into the effective strain ratio of deformable rubber portion were almost constant between filled and unfilled samples. Accordingly, our model of strain-induced crystallization of unfilled NR vulcanizates, assuming that melting temperature is independent of network-chain length (n), was applied to the filled samples. The discrepancy between classical theories and experimental results was thought to come from the distribution of n. By the inclusion of filler, the lateral crystallite size was decreased but the orientational fluctuation increased. The lattice of the strain-induced crystallites changed almost linearly with the nominal stress. In addition, the degree of lattice deformation decreased with the filler content, especially in the carbon black-filled system. All these experimental results are consistent with the proposed model. [ABSTRACT FROM AUTHOR]

The isothermal crystallization of poly(ethylene terephthalate) (PET) homopolymers with different molecular weight was studied in a wide temperature range (140-230 °C) using different experimental techniques. Three different morphological regions, labeled r1, r2 and r3, were distinguished as a function of crystallization temperature (Tc). In r1 (low Tc) crystallized samples were characterized by a low crystalline degree with a small spherulite texture containing thin crystals. In r2 (intermediate Tc) samples showed medium size spherulites composed of two distinct crystalline families (thin and thick crystals). In this temperature range, the crystallization exhibited a maximum value and it was associated with a high content of secondary crystals. In r3 (high Tc), samples presented considerable amorphous zones and regions consisting of oversized spherulites containing only thick crystals. Time-resolved wide-angle X-ray diffraction measurements, using synchrotron radiation, indicated a rapid evolution of the crystalline degree within the second region, incontrast with the quite slow evolution observed in the third region. On the other hand, by small-angle X-ray scattering (SAXS) and time-resolved SAXS experiment, it was found that the long period (L) as well as the lamellar thickness (lc) increase as a function of Tc, corroborating the formation of the thickest crystals in the third region. From all these observations, a morphological model was proposed for each region. [ABSTRACT FROM AUTHOR]

Synchrotron small-angle X-ray scattering (SAXS) was conducted on native intramuscular shad/herring bone samples. Two-dimensional SAXS patterns were quantitatively analyzed with special consideration for preferred orientation effects, leading to new insights into the three-dimensional superstructure of mineralized collagen fibrils in shad/herring bone. [ABSTRACT FROM AUTHOR]

Abstract: The tensile and dynamic mechanical properties of a nanocomposite, containing modified carbon nanofibers (MCNFs) homogenously dispersed in an elastomeric ethylene/propylene (EP) copolymer semicrystalline matrix (84.3wt% P), have been correlated with the structure development. These properties were characterized by in situ synchrotron X-ray diffraction during stretching, dynamic mechanical analysis and X-ray analysis techniques over a wide temperature range. Upon sequential drawing, the tensile strength of the nanocomposite film was notably higher than that of the unfilled polymer even though both samples exhibited a similar amount of crystal fraction and the same degree of crystal orientation, revealing the effect of nanofiller reinforcement in the semicrystalline matrix. The mechanical spectra of the 10wt% MCNF filled samples in both stretched and non-stretched states showed broadening of the elastic modulus at high temperatures, where the corresponding crystallinity index also decreased. It is conceivable that a significant fraction of chain orientation is induced in the vicinity of the nanofillers during stretching, and these stretched chains with reduced mobility significantly enhance the thermal mechanical properties. [Copyright &y& Elsevier]

Abstract: A poly(ethylene oxide)-b-polystyrene (PEO-b-PS) diblock copolymer with a number average molecular weight of PEO blocks, =8.8kg/mol, and a number average molecular weight of PS blocks, =24.5kg/mol, (volume fraction of the PEO blocks, f PEO, was 0.26) exhibited a hexagonal cylinder (HC) phase structure. Small angle X-ray scattering results showed that the PEO cylinder diameter was 13.3nm, and the hexagonal lattice was a=25.1nm. The cylinder diameter of this HC phase structure was virtually the same as that in the blend system constructed by a PEO-b-PS diblock copolymer (=8.7kg/mol and =9.2kg/mol) and a PS homo-polymer (=4.6kg/mol) in which the f PEO was 0.32. The cylinder diameter in this blend sample was 13.7nm and the hexagonal lattice was a=23.1nm. Comparing crystal orientation and crystallization behaviors of this PEO-b-PS copolymer with the blend, it was found that the crystal orientation change with respect to crystallization temperature was almost identical. This is attributed to the fact that in both cases the PEO block tethering densities and confinement sizes are very similar. This indicates that when the of PS homo-polymer is lower than the PS blocks, the PS homo-polymer is located inside of the PS matrix rather than at the interface between the PEO and PS in the HC phase structure. On the other hand, a substantial difference of crystallization behaviors was observed between these two samples. The PEO-b-PS copolymer exhibited much more retarded crystallization kinetics than that of the blend. Based on the small angle X-ray scattering results, it was found that in the blend sample, the HC phase structure was not as regularly ordered as that in the PEO-b-PS copolymer, and thus, the HC phase structure contained more defects in the blend. This led to a suggestion that the primary nucleation process in the confined crystallization is a defect-controlled process. The mean crystallite sizes were estimated by the Scherer equation, and the PEO crystal sizes are on the scale of the confined size. [Copyright &y& Elsevier]

Abstract: Polyvinylidene fluoride (PVDF)–nanoclay nanocomposites were prepared by both solution casting and co-precipitation methods with the nanoclay loading of 1–6wt%. The structure and morphology of the nanocomposite were investigated by wide angle X-ray diffraction (WAXD), polarized light microscopy and transmission electron microscopy (TEM) techniques. PVDF phase transformation behavior was investigated using differential scanning calorimetry and in situ thermal WAXD. All the three typical nanoclay morphologies, namely, exfoliated, partially intercalated and phase separated morphologies, were observed in the PVDF–nanoclay nanocomposites prepared by different methods. In solution-cast samples, phase separation and intercalation occurred depending upon the organic modifiers while complete exfoliation of the nanoclays was observed in the co-precipitated nanocomposites. Furthermore, unique parallel orientation of the nanoclay layers and polymer film surface was achieved in solution-cast samples. β-form PVDF was observed in all the nanocomposites regardless of the nanoclay morphology and contents. Both crystallization and melting temperatures of PVDF were increased with the addition of nanoclay, possibly due to the formation of the β-form PVDF. [Copyright &y& Elsevier]

We report a novel observation of the tetragonal perforated layer structures in a series of rod—coil liquid crystalline block copolymers (BCPs), poly(styrene-block-(2,5-bis(4-methoxyphenyl]oxycarbonyl)-styrene) (PS-b-PMPCS). PMPCS forms rigid rods while PS forms the coil block. Differential scanning calorimetry (DSC), polarized light microscopy (PLM), small-angle X-ray scattering (SAXS), wide-angle X-ray diffraction (WAXD), and transmission electron microscopy (TEM) techniques were used to investigate these rod—coil molecules, and a perforated layer structure was observed at fPMPCS ≈ 0.37 in relatively low molecular weight (MW) samples and ∼0.5 in high MW PS-b-PMPCS. This substantial phase boundary shift was attributed to the rod—coil nature of the BCP. The perforation obeys a tetragonal instead of hexagonal symmetry. The "onset" of perforation was also observed in real space in sample PS272-b-PMPCS93 (fPMPCS ≈ 0.52), in which few PS chains punctuate PMPCS layers. A slight increase in fPS, by blending with PS homopolymer, led to a dramatic change in the BCP morphology, and uniform tetragonal perforations were observed at fPMPCS ≈ 0.48. [ABSTRACT FROM AUTHOR]

Phase morphological effect on crystallization kinetics in various nanoconfined spaces in a polystyrene-block-poly(ethylene oxide) (PS-b-PEO) diblock copolymer with a PEO volume fraction of 37 vol% was investigated. The phase morphology was characterized by small-angle X-ray scattering and transmission electron microscopy techniques. When the sample was cast from chloroform solution and annealed at 150 °C, a double gyroid (DG) phase was obtained. After it was subjected to a large-amplitude reciprocating shear, the sample transformed to an oriented hexagonal cylinder (Hex) phase. To obtain a lamellar confined geometry, lamellar single crystals were grown from dilute solutions. The crystallization in the lamellar (Lam) phase was one-dimensionally (1D) confined, while it was two-dimensionally (2D) confined in the DG and Hex phases, although they had different structures. Differential scanning calorimetry (DSC) was employed to study the crystallization kinetics using the Avrami analysis for these three nanoconfined geometries. Heterogeneous nucleation was found in all three samples in the crystallization temperature (Tc) regions studied. DSC results indicated that the crystallization kinetics in the Lam phase was the fastest, and the PEO crystals possessed higher thermodynamic stability than in the DG and Hex phases. For the crystallization kinetics in two 2D-confined phases, at low Tc (<35 °C) the PEO crystallization rates in the DG and Hex phases were similar, while at high Tc (>35 °C) the PEO crystallization was slower in the DG phase than in the Hex phase. The Avrami exponent n-values for the DG and the Hex samples were similar (∼1.8), yet the values of lnK in the DG phase were smaller than those in the Hex phase. This suggested that the linear growth rate was slower in the DG phase than in the Hex phase due to continuous curved channels in the DG phase. [Copyright &y& Elsevier]

An in situ study of structural formation of amorphous poly(ethylene terephthalate) (PET) during uniaxial deformation above its Tg (at 90 °C) was carried out by wide-angle X-ray diffraction (WAXD) with synchrotron radiations. Results indicate that the relationships between structure and mechanical property can be divided into three zones: I, II and III. In Zone I, oriented mesophase is induced by strain, where the applied load remains about constant but the amount of mesophase increases with strain. In Zone II, crystallization is initiated from the mesophase through nucleation and growth, where the load starts to increase marking the beginning of the strain-hardening region. The initial crystallites are defective but they form an effective three-dimensional network to enhance the mechanical property. The perfection of the crystal structure and the orientation of the crystals all increase with strain in this zone. In Zone III, the ratio between load and strain is about constant, while the stable crystal growth process takes place until the breaking of the sample. The sample damage is probably dominated by the chain pull-out mechanism from the crystal amorphous interface. The increase in molecular weight was found to enhance the overall mechanical properties such as the load to induce the mesophase and the ultimate tensile strength before breakage. [Copyright &y& Elsevier]