X-ray Diffraction Measurements (x-ray + diffraction_measurement)

Distribution by Scientific Domains

Kinds of X-ray Diffraction Measurements

  • single-crystal x-ray diffraction measurement
  • wide-angle x-ray diffraction measurement

  • Selected Abstracts

    Supercooled Barium Boric Oxide Melts: X-Ray Diffraction Measurements and Glass Formation

    Seiichi Matsumura
    It is well-known that oxide melts easily form a glass state from a supercooled state; however, it is difficult for some oxides to transform to the glass state from the corresponding supercooled state. ,-BaB2O4 (,-BBO) crystals are important materials for laser applications. The ,-BBO crystal easily grows from the supercooled melt, and it is therefore difficult to form the BBO glass state. We attempted to make BBO glass by a containerless technique using the conical nozzle gas-jet levitation (CNL) method. We were successful in making BBO glass with a diameter of 2 mm from a highly supercooled melt without rapid quenching. In order to clarify the phase selection mechanism of the BBO melt, we performed high-energy X-ray (113.6 keV) diffraction experiments on the glassy and supercooled liquid BBO using the CNL technique at the BL04B2 beamline of SPring-8. From these experiments, the structure factor S(Q) of BBO glasses and supercooled melts were found to have almost the same features. From these S(Q), we obtained the radial distribution function T(r)=4,rg(r). The analysis also showed that BBO glass and the BBO-supercooled melt have the same short-range distances. For phase selection between crystalline and glassy phases, we discuss a structure model of the BBO melt, including medium range structure based on the short-range structure obtained in this experiment. [source]

    Raman spectroscopy of Bi-Te thin films

    V. Russo
    Abstract The deposition of micro- and nanocrystalline bismuth telluride thin films with tailored structure and composition is of interest in view of improving the well-known material thermoelectric properties. Only a few works exist that discuss Raman scattering of Bi2Te3 crystals and films, while a Raman characterization of other phases, i.e. other lesser known compounds of the Bi-Te system, such as tsumoite (BiTe) and pilsenite (Bi4Te3), is still completely lacking. We here present a Raman investigation of Bi-Te polycrystalline thin films with controlled structure (stoichiometry and growth orientation), morphology and phase composition, produced by nanosecond pulsed laser deposition. Interpretation of Raman spectra from Bi-Te films was supported by scanning electron microscopy, energy dispersive spectroscopy (EDS) and X-Ray diffraction measurements, together with the predictions of the group theory. In this way, the first Raman characterization of Bi-rich phases (namely BiTe and Bi4Te3) has been obtained. For Bi-Te compositions characterized by a high Bi or Te content, Raman spectra reveal that segregation of elemental Bi or Te occurs. Copyright © 2008 John Wiley & Sons, Ltd. [source]

    Effect of the different rigidity of the chiral crosslinker on phase behaviors of side-chain chiral liquid crystalline elastomers

    Bao-Yan Zhang
    Abstract In the present work, the phase behaviors of two series of side-chain liquid crystalline elastomers (PI and PII series) derived from the same nematic liquid crystalline monomer and the different rigidity of chiral bisolefinic crosslinking units have been compared and studied extensively, and the effect of the different rigidity of crosslinker on the phase behavior of elastomers has been discussed. The chemical structure of the monomers and polymers obtained were confirmed by FTIR and 1H NMR spectroscopy. The phase behaviors were investigated by differential scanning calorimetry, polarizing optical microscopy measurement, thermogravimetric analyses, and X-ray diffraction measurement. The two series of elastomers showed smectic or cholesteric phases. When the amount of different crosslinking units was less than 15 mol %, both of the elastomers displayed elasticity, reversible phase transition with wide mesophase temperature ranges, and high thermal stability. It is shown that the isotropization temperature values of PII series are higher than those of PI series, and the glass transition temperature values of PII series varied smoothly and that of PI series changed smoothly first and then abruptly with increasing the contents of crosslinkers with different rigidity. In addition, PI series showed an interesting change in LC texture near clearing point, but PII series did not. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source]

    Preparation and Optical Property of Glass Ceramics Containing Ruby Crystals

    Jumpei Ueda
    We have developed the glass ceramics containing ruby crystals by heat treatment of a Cr3+ -doped SiO2,Al2O3,Y2O3 glass at 1550°C. The shape of precipitated crystals in the glass matrix was rod type whose average width and length were around 10 and 200 ,m, respectively. From an X-ray diffraction measurement and an electron probe X-ray microanalysis, it was confirmed that the rod crystals were ,-Al2O3. Intense emission bands of Cr3+ at 694 nm, called the R -lines, were observed in the glass ceramics heat treated above 1300°C. In addition, the intense red luminescence was observed only in the ,-Al2O3 rod crystals by a photoluminescence mapping image. [source]

    Improvement of Mechanical Properties of Self Setting Calcium Phosphate Bone Cements Mixed With Different Metal Oxides

    U. Gbureck
    Calciumphosphat Zemente; Metalloxide; Mechanische Eigenschaften Abstract Calcium phosphate cements (CPC), based on multicomponent powder mixtures of calcium orthophosphates with medium particle sizes in the region of 1 - 20 ,m, set isothermally in an aqueous environment to form hydroxyapatite (HA). HA cement reactants include tetracalcium phosphate (TTCP), tricalcium phosphate (TCP), dicalcium phosphate anhydrate (DCPA), dicalcium phosphate dihydrate (DCPD), monocalcium phosphate (MCPA) or octacalcium phosphate (OCP). The aim of this study was to improve the mechanical performance of TTCP / DCPA cement by adding several metal oxides to tetracalcium phosphate during the fabrication process. Cements based on tetracalcium phosphate mixed with silica or titanium oxide showed significant increases in compressive strength, approximately 80 - 100 MPa, whilst no change in the mechanical behavior of CPC was observed if zirconia was added. X-ray diffraction measurement confirmed the setting reaction of doped cements was similar to that of pure CPC. Low crystalline HA was found to be the main constituant of set cement; additional phases, such as calcium titanate or calcium zirconate, were not involved in the reaction. A mechanical reinforcement effect was thought to result from changes in the thermodynamic or kinetic solubilities of doped tetracalcium phosphates, this would lead to slower HA crystal formation and a more cross-linked cement structure. Verbesserung der mechanischen Eigenschaften von Calciumphosphat-Zementen durch Modifikation mit verschiedenen Metalloxiden Calciumphosphat-Zemente, CPC, bestehen aus Pulvermischungen verschiedener Calcium orthophophate, beispielsweise Tetracalciumphosphat (TTCP), Tricalciumphosphat (TCP), Dicalciumphosphatanhydrid (DCPA), Dicalciumphosphatdihydrat (DCPD), Monocalcium phosphatanhydrid (MCPA) oder Octacalciumphosphat (OCP) mit durchschnittlichen Partikelgrößen im Bereich von 1 , 20 ,m. Die Zemente binden in wässriger Umgebung isotherm zu Hydroxylapatit ab. Das Ziel dieser Arbeit war die Verbesserung materialspezifischer Eigenschaften , wie die mechanische Festigkeit - eines TTCP / DCPA-Zementes durch die Verwendung von Metalloxiden im Syntheseprozess von Tetracalciumphosphat. Zemente, die aus mit Silicium- oder Titandioxid versetzten Tetracalciumphosphaten hergestellt wurden, zeigten eine deutliche Steigerung der Druckfestigkeit auf Werte von 80 , 100 MPa, während im Falle von Zirkoniumdioxid keine Änderung der mechanischen Stabilität erreicht werden konnte. Röntgendiffraktometrische Untersuchungen ergaben, dass die Abbindereaktion dieser Zemente ähnlich der eines reinen TTCP / DCPA-Zements verläuft. Jeweiliges Hauptprodukt war niedrigkristalliner Hydroxylapatit, die im Herstellungsprozess von Tetracalciumphosphat entstandenen Nebenprodukte Calciumtitanat bzw. ,zirkonat waren nicht an der Abbindereaktion beteiligt. Ein Grund für die Steigerung der mechanischen Stabilität ist offensichtlich die Veränderung der kinetischen und thermodynamischen Löslichkeit der synthetisierten Tetracalciumphosphate, die zu einer langsameren Abbindereaktion und somit einer besseren Vernetzung in der Hydroxylapatitstruktur führt. [source]

    Properties of Ga2O3 -based (Inx Ga1,x)2O3 alloy thin films grown by molecular beam epitaxy

    Takayoshi Oshima
    Abstract A series of Ga2O3 -based (Inx Ga1,x)2O3 alloy thin films have been grown on c-plane sapphire substrates with a thin Ga2O3 buffer layer by plasma-assisted molecular beam epitaxy. At growth temperatures of 700 °C and higher, even with a slight inclusion of In2O3 to Ga2O3, for example, the film of (In0.08Ga0.92)2O3, exhibited a rough surface and degraded transmission spectrum resulting from phase separation of In2O3. Due to low temperature growth at 600 °C, however, the phase separation was suppressed for the In composition up to 35%, which was confirmed by X-ray diffraction measurement, and the films exhibited high transmittance over 85% with sharp absorption edges. The bandgap could be tuned form 5.0 to 4.0 eV. The results encourage the application of (Inx Ga1,x)2O3 thin films in short-wavelength optical devices. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Terahertz time-domain spectroscopy of poly- L -lysine

    BIOPOLYMERS, Issue 8 2010
    Ohki Kambara
    Abstract Poly- L -lysine is known to have three different secondary structures depending on solvent conditions because of its flexible nature. In previous work (Kambara et al., Phys Chem Chem Phys 2008, 10, 5042-5044), we observed two different types of structural changes in poly- L -lysine. In the present study, we investigated the low-frequency spectrum of poly- L -lysine with a ,-sheet structure in the solid state by terahertz time-domain spectroscopy. On the basis of this spectroscopic analysis, we found that the low-frequency dynamics differed from those of other polypeptides. Furthermore, we performed powder X-ray diffraction measurement on poly- L -lysine, which was found to be highly amorphous compared with other polypeptides. © 2010 Wiley Periodicals, Inc. Biopolymers 93: 735,739, 2010. This article was originally published online as an accepted preprint. The "Published Online" date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com [source]

    Synthesis of highly-ordered hierarchical ZnO nanostructures and their application in dye-sensitized solar cells

    Y. F. Zhu
    Abstract In order to improve the performance of ZnO-based solar cells, highly-ordered hierarchical ZnO nanostructures were design and fabricated. The hierarchical nanostructures were grown on FTO (fluorine doped tin oxide, SnO2:F) glass substrates via a facile, low-temperature, and low-cost chemical route. The morphology and structure of the obtained products has been confirmed by field-emission scanning electron microscopy and X-ray diffraction measurements. The performance investigation of the prepared dye-sensitized solar cells (DSSCs) demonstrates that the hierarchical ZnO nanostructure-based solar cell shows a higher short-circuit current density compared with the ZnO nanowire counterpart. The enhanced current density may be due to the fact that the surface area of the hierarchical nanostructures is increased. These results indicate that hierarchical ZnO nanostructures are more suitable for the application as photoelectrode of DSSCs. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Crystal structures and isotope effect on Na5H3(SeO4)4·2H2O and Na5D3(SeO4)4·2D2O crystals

    T. Fukami
    Abstract Differential scanning calorimetry (DSC) and X-ray diffraction measurements have been performed on pentasodium trihydrogen tetraselenate dihydrate Na5H3(SeO4)4·2H2O and deuterated Na5D3(SeO4)4·2D2O crystals. Any distinct anomaly around 428 K in the DSC curves for both crystals is suggested to be caused by a chemical reaction of thermal decomposition with hydrolysis at high temperature. The space group symmetry (triclinic P) and the structure parameters are determined at room temperature. The hydrogen atom in the centrosymmetric O-H(D)-O hydrogen bond of both crystals is found to be equally distributed at two equivalent sites in the bond. The expansions of two O-H-O hydrogen bonds by the substitution of deuterium are observed to be 0.016(6) and 0.011(4) Å. The geometric isotope effect on hydrogen bonds is confirmed to be existed in Na5H3(SeO4)4·2H2O. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Synthesis and Characterization of a New Guanidine,Borane Complex and a Dinuclear Boron(II) Hydride with Bridging Guanidinate Ligands

    Oxana Ciobanu
    Abstract We report the synthesis and structural characterization of the new monomeric borane complex H3B·hppH (hppH = 1,3,4,6,7,8-hexahydro-2H -pyrimido[1,2- a]pyrimidine), which represents the first example of a structurally characterized 1:1 complex between hppH and a group 13 element hydride. Significant intramolecular and, in the crystalline phase, intermolecular H···H contacts are established in this complex. It is shown that the complex can be used as a precursor to new dinuclear boron(II) compounds featuring a B,B single bond. Thus H2 elimination followed by dimerization of H3B·hppH leads to [(hpp)BH]2 with two bridging hpp units. The structural details derived from X-ray diffraction measurements are reported.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source]

    Synthesis and Characterisation of Coordination Polymers of CuII and ZnII with 1,3-Bis(1,2,3,4-tetrazol-2-yl)propane , Rotational Freedom of the Donor Group Favours Structural Diversification

    Robert Bronisz
    Abstract The novel bidentate ligand 1,3-bis(1,2,3,4-tetrazol-2-yl)propane (pbtz), which possesses a flexible spacer, was synthesised in order to investigate the influence of the flexibility of ligand molecules on the architecture of coordination polymers. For that purpose the reactions between pbtz and M(ClO4)2·6H2O salts (M = CuII and ZnII) were performed. The complexes [{Cu(pbtz)3}(ClO4)2], and [{Zn(pbtz)3}(ClO4)2·2EtOH], were characterised by IR and UV/Vis spectroscopy and their crystal structures were determined by single-crystal X-ray diffraction measurements. In both compounds the pbtz ligand molecules act as N4,N4, connectors bridging the central atoms, and the 2-substituted tetrazole rings coordinate in a monodentate fashion to the central atoms forming M(tetrazole)6 cores. [{Cu(pbtz)3}(ClO4)2], was isolated as a 1D coordination polymer. The copper(II) ions are triply bridged by ligand molecules, leading to the formation of infinite 1D chains. A highly unusual manner of bridging, with the tethering of two neighbouring central atoms by the same kind of ligand molecules, although possessing different conformations, is observed. In [{Zn(pbtz)3}(ClO4)2·2EtOH], the six-coordinate zinc(II) ions, which are bridged by single ligand molecules, serve as topological nodes, leading to the formation of a 3D ,-polonium-type network. The crystal structure of the ZnII complex contains only one such net solvated by ethanol molecules. A conformational analysis of the ligand molecules in both compounds demonstrates that the flexibility of the pbtz and the ability of the tetrazole rings in particular to adopt various, relative orientations is responsible for the diversity of the architectures of the obtained complexes. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source]

    Temperature-Dependent Solid-State Reactions With and Without Kirkendall Effect in Al2O3/ZnO, Fe2O3/ZnO, and CoXOY/ZnO Oxide Thin Film Systems,

    Andriy Zolotaryov
    Temperature-dependent solid-state reactions and the occurrence of the Kirkendall effect are studied in thin film oxide systems applying optical reflection microscopy, X-ray reflectivity, (scanning) transmission electron microscopy, grazing-incidence X-ray diffraction measurements, and SQUID magnetometry. The efficiency of the simultaneous application of different analytical methods for the precise selection and investigation of the most interesting samples is demonstrated first on the example of the Al2O3/ZnO system, for which the spinel formation after a solid-state reaction and the formation of Kirkendall voids were already reported. The demonstrated methodology is then applied to study Fe2O3/ZnO and CoXOY/ZnO film pairs. The investigations clearly demonstrate the temperature-driven formation of a ferromagnetic spinel by a solid state reaction involving the Kirkendall effect in the Fe2O3/ZnO system, already after an annealing at 600,°C for 1,h. We also report on the solid state reaction in the CoXOY/ZnO system after annealing at 700,°C for 1,h, however without the Kirkendall effect and without any evidence of ferromagnetism of the final state. [source]

    Replication and Coating of Silica Templates by Hydrothermal Carbonization,

    M.-M. Titirici
    Abstract Hierarchical carbon materials with functional groups residing at the surface are prepared for the first time by using nanostructured silica materials as templates in combination with hydrothermal carbonization at mild temperatures (180,°C). Different carbon morphologies (e.g., macroporous casts, hollow spheres, carbon nanoparticles, and mesoporous microspheres) can be obtained by simply altering the polarity of the silica surface. The surface functionality and hydrophilicity of the resulting materials are assessed by Fourier transform IR spectroscopy, X-ray photoelectron analysis, and water porosimetry. Raman spectroscopy and X-ray diffraction measurements show that the materials are of the carbon-black type, similar to charcoal. [source]

    Bismuth,Ceramic Nanocomposites with Unusual Thermal Stability via High-Energy Ball Milling,

    M.A. Meitl
    Abstract Electrically conducting nanocomposites of bismuth metal and insulating ceramic phases of SiO2 and MgO were generated via high-energy ball milling for 24 h using zirconia milling media. The resulting nanocomposites contain Bi nanoparticles with sizes down to 5 nm in diameter. The morphology is a strong function of the oxide phase: specifically, the Bi appears to wet MgO while it forms spherical nanoparticles on the SiO2. X-ray diffraction measurements indicate a nominal bismuth grain size of 50 nm, and peak fitting to a simple bidisperse model yields a mixture of approximately 57,% bulk bismuth and 43,% 27 nm diameter crystallites. Nanoparticles as small as 5 nm are observed in transmission electron microscopy (TEM), but may not constitute a significant volume fraction of the sample. Differential scanning calorimetry reveals dramatic broadening in the temperatures over which melting and freezing occur and a surprising persistence of nanostructure after thermal cycling above the melting point of the Bi phase. [source]

    A method for the non-destructive analysis of gradients of mechanical stresses by X-ray diffraction measurements at fixed penetration/information depths

    A. Kumar
    A rigorous measurement strategy for (X-ray) diffraction stress measurements at fixed penetration/information depths has been developed. Thereby errors caused by lack of penetration-depth control in traditional (X-ray) diffraction (sin2,) measurements have been annulled. The range of accessible penetration/information depths and experimental aspects have been discussed. As a practical example, the depth gradient of the state of residual stress in a sputter-deposited nickel layer of 2,µm thickness has been investigated by diffraction stress measurements with uncontrolled penetration/information depth and two controlled penetration/information depths corresponding to about one quarter and one tenth of the layer thickness, respectively. The decrease of the planar tensile stress in the direction towards the surface could be well established quantitatively. [source]

    Effects of cryoprotectant concentration and cooling rate on vitrification of aqueous solutions

    Naji S. Husseini
    Vitrification of aqueous cryoprotectant mixtures is essential in cryopreservation of proteins and other biological samples. Systematic measurements of critical cryoprotective agent (CPA) concentrations required for vitrification during plunge-cooling from T = 295,K to T = 77,K in liquid nitrogen are reported. Measurements on fourteen common CPAs, including alcohols (glycerol, methanol, 2-propanol), sugars (sucrose, xylitol, dextrose, trehalose), polyethylene glycols (ethylene glycol, PEG 200, PEG 2000, PEG 20000), glycols [dimethyl sulfoxide (DMSO), 2-methyl-2,4-pentanediol (MPD)], and salt (NaCl), were performed for volumes ranging over four orders of magnitude from ,1,nl to 20,µl, and covering the range of interest in protein crystallography. X-ray diffraction measurements on aqueous glycerol mixtures confirm that the polycrystalline-to-vitreous transition occurs within a span of less than 2% w/v in CPA concentration, and that the form of polycrystalline ice (hexagonal or cubic) depends on CPA concentration and cooling rate. For most of the studied cryoprotectants, the critical concentration decreases strongly with volume in the range from ,5,µl to ,0.1,µl, typically by a factor of two. By combining measurements of the critical concentration versus volume with cooling time versus volume, the function of greatest intrinsic physical interest is obtained: the critical CPA concentration versus cooling rate during flash-cooling. These results provide a basis for more rational design of cryoprotective protocols, and should yield insight into the physics of glass formation in aqueous mixtures. [source]

    X-ray diffraction analysis of GaInNAs double-quantum-well structures

    Kiichi Nakashima
    The structures of GaInNAs/GaAs double-quantum-well (DQW) samples with various well-layer thicknesses were analysed by X-ray diffraction measurements. Two types of rocking-curve analysis were applied with different scanning configurations: a conventional configuration without a receiving slit and one with an analyser crystal placed in front of the receiving detector (the latter is the same as that usually used in reciprocal-space mapping measurements). It was found that systematic combination of both types of analysis is essential for the characterization of the sample structures. The two types of X-ray profiles obtained using the different scanning configurations exhibit a considerable difference in intensity as the thickness of the well layers increases. The increasing difference clearly indicates deterioration of the DQW structures. The two profiles exhibit little difference in terms of shape, merely showing that the DQW layers are coherently strained relative to the substrate. This implies that measurement in only one of the configurations is insensitive to the deterioration and leads to the wrong conclusion that a sample has a perfect structure without dislocations and defects. Photoluminescence and transmission electron microscope analyses both reveal that defects really do exist in the DQW structures, which is consistent with the difference in intensity observed in the X-ray measurements. From these results, a clear picture that consistently explains the sensitivity of X-ray diffraction analysis to the deterioration of samples is presented. In addition, based on this picture, it is proposed that the procedure of comparing the two types of profiles represents a new type of analysis method for the precise characterization of samples. [source]

    A new method for analysing peak broadening caused by compositional fluctuation in X-ray diffraction measurements

    Kiichi Nakashima
    A new method for analysing X-ray peak broadening caused by compositional fluctuation is proposed. The method is applicable to epitaxial layers with diamond or zinc-blende structure on (001) substrates. In the new method, a rescaling procedure with a difference variable ,A is applied to measured X-ray profiles and the dependence of the profiles on various reflection indices hkl is analysed. The theoretical formula reveals that X-ray peak profiles become independent of hkl after the rescaling. A new criterion is proposed; an experimental examination based on the criterion makes it possible simply to judge whether or not X-ray peak broadening is caused by compositional fluctuation. The method is verified experimentally and demonstrated by applying it to an InGaAs multilayer sample having artificial compositional fluctuation. [source]

    Corrections for surface X-ray diffraction measurements using the Z -axis geometry: finite size effects in direct and reciprocal space

    O. Robach
    X-ray diffraction data have to be corrected by geometrical correction factors prior to any quantitative analysis. Here the case of grazing incidence X-ray diffraction measurements is considered, including the case of high exit angles. First, an approach taking into account the evolution of the diffracting area during an , scan is presented. From the calculation of the effective part of the sample surface that participates in the diffraction phenomena at each step of the scan, a more accurate correction factor than those commonly used is derived and the evolution of the line shape along a zero-width rod is explained. Secondly, the case of finite-width rods, under the point-like sample approximation, is considered: the influence of the partial integration, as a result of the detector in-plane acceptance, of a rod with an anisotropic in-plane shape, is studied and leads to an analytical expression for the corresponding correction factor. Finally, a full numerical simulation is presented, which provides an alternative method for correcting the experimental intensities and shows in which conditions the previous formulae are no longer valid. [source]

    Synthesis and properties of homopolyamide and copolyamides fibers based on 2,6-bis(p -aminophenyl)benzo[1,2-d;5,4- d,]bisoxazole

    Xiangqun Chen
    Abstract A novel aromatic homopolyamide with benzobisoxazole units in the main chain was synthesized with 2,6-bis(p -aminophenyl)benzo[1,2- d;5,4- d,]bisoxazole and terephthaloyl chloride by low temperature solution polycondensation, the inherent viscosity of which was 1.98 dL/g. The diamine and p -phenylendiamine with terephthaloyl chloride were used to synthesize the copolyamides. The structures of homopolyamide and copolyamides were characterized by IR spectra, elemental analysis, and wide-angle X-ray diffraction. Wide-angle X-ray diffraction measurements showed that homopolyamide and copolyamides were predominantly crystallinity. The results of thermal analysis indicated that the thermal stabilities of the copolymer increased with an increase of the molar fraction of benzobisoxazole in the copolymers. The thermal stability of the copolyamides with decomposition temperatures (at 10% weight loss) above 570°C was better than that of poly(p -phenylene terephthalamide) (PPTA). Fibers of homopolyamide and copolyterephthalamides were spun from lyotropic liquid crystal dope in 100% H2SO4. When compared with PPTA fibers prepared under the same conditions, the tensile strengths of copolyamides fibers improved by 20,33% with tensile strengths of 1.81 GPa, tensile moduli of 76 GPa, and elongations at break of 3.8,4.1%, which indicated that copolyamides fibers had outstanding mechanical properties. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source]

    Effect of ,-nucleating agents on crystallization and melting behavior of isotactic polypropylene

    Wenchang Xiao
    Abstract Two kinds of ,-nucleating agents, named a rare earth complex (WBG) and a N,N,-dicyclohexylterephthalamide (TMB5), were introduced into isotactic polypropylene (iPP), and their effect on crystallization and melting behavior of iPP was comparatively investigated. Wide angle X-ray diffraction measurements revealed that both the two additives were highly effective in inducing , modification. At their respective optimum concentrations of 0.08 wt % for WBG and 0.06 wt % for TMB5, the relative amount of ,-form calculated by Turner-Jones equation both exceeds 92%. However, the isothermal crystallization kinetics investigated by differential scanning calorimetry demonstrated that WBG had more pronounced effect than TMB5 in accelerating the overall crystallization rate. The Lauritzen,Hoffman theory analysis also revealed that WBG was more effective not only in increasing the nucleus number but also in accelerating the growth rate of crystallization. After completing isothermal crystallization process, the subsequent melting behavior examination suggested that the addition of WBG expanded the upper limit temperature of forming , modification, and therefore was more effective in delaying the ,-, transformation than TMB5. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source]

    Supramolecular control of spin-crossover phenomena in lipophilic Fe(II)-1,2,4-triazole complexes

    Keita Kuroiwa
    Abstract The spin-crossover properties of lipophilic, supramolecular Fe(II) complexes bridged by 4-(3-dodecyloxy)propyl-1,2,4-triazole [Fe(II)(1)3Cl2] were investigated in chloroform and cast films. A purple low-spin (LS) complex in a powdery form was transformed into pale yellow high-spin (HS) polymers by dissolution in chloroform. The formation of lipophilic molecular wires in chloroform was observed with transmission electron microscopy. The casting of chloroform solutions onto solid supports produced purple, transparent films (LS state). The cast films exhibited sluggish spin-crossover (LS , HS) behavior without thermal hysteresis. On the other hand, the cocasting of equimolar dodecanol or tetradecanol with Fe(II)(1)3Cl2 produced composite films in which alcohol molecules were bound to the complex by ionic hydrogen bonding (ROH···Cl,) and van der Waals interactions. At room temperature, the cast films exhibited regular lamellar structures before and after alcohol doping; this was confirmed by wide-angle X-ray diffraction measurements. Interestingly, the Fe(II)(1)3Cl2/CnOH (n = 12 or 14) ternary films showed a reversible abrupt spin crossover accompanied by thermal hysteresis. The observed bistability was related to dynamic structural transformations between lamellar and hexagonal structures. This study provides a novel supramolecular approach to designing spin-crossover polymer films with controlled thermal bistability. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5192,5202, 2006 [source]

    Synthesis, structure, and characterization of nematic liquid-crystalline thermosets based on bisacrylates

    Jian-She Hu
    Abstract Four bisacrylate mesogenic monomers and the corresponding liquid-crystalline thermosets were synthesized. The chemical structures of the intermediate compounds and monomers obtained were confirmed by elemental analyses, Fourier transform infrared, and 1H NMR and 13C NMR spectra. The mesomorphic properties and thermal stability were investigated with differential scanning calorimetry, thermogravimetric analysis, polarized optical microscopy, and X-ray diffraction measurements. The influence of the curing temperatures and time on the phase behavior and thermal stability of the thermosets was discussed. All the monomers and thermosets exhibited a nematic schlieren texture. However, the monomers only showed the melting transition, and the thermosets displayed the glass transition. The experimental results demonstrated that the monomer structures strongly affected the phase behavior and the curing reaction rate, and the glass-transition temperatures and thermal stability of the thermosets increased with the curing temperature and time. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4478,4485, 2005 [source]

    Synthesis of soluble branched polyimides derived from an ABB, monomer

    Kun-Li Wang
    Abstract A novel ABB, monomer, an isomeric mixture of 4-[4-(2,4-diaminophenoxy)phenoxy]phthalic acid 2-methyl ester, was successfully prepared. The direct polycondensation of the ABB, monomer was carried out to form polyamic acid monomethyl ester as a precursor with an inherent viscosity of 0.30 dL/g and a number-average molecular weight of 12,000. The degree of branching of the precursor, determined by 1H NMR, was 0.07. The low degree of branching was caused by the differences in the reactivities of the amino groups. The shape factor was calculated to be 0.72. End-modified reactions with acetyl chloride, benzoyl chloride, and phthalic anhydride were carried out. After the chemical imidization of the end-modified precursors, end-modified polyimides were successfully prepared. The end-modified polyimides were soluble in dimethyl sulfoxide, dimethylformamide (DMF), and N -methyl-2-pyrrolidinone. On the basis of thermogravimetry and differential scanning calorimetry measurements of the polyimides, the 5 wt % thermal loss temperatures were determined to be 400,520 °C, and the glass-transition temperatures were determined to be 200,258 °C. According to the X-ray diffraction measurements, the end-modified polyimides were amorphous. A strong but brittle film was prepared from an acetamide end-modified polyimide solution, via casting from a DMF solution, with a tensile strength of 46 MPa, an elongation at break of 4%, and a modulus of 1.3 GPa. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3200,3211, 2004 [source]

    Low-wavenumber Raman scattering spectroscopy in studies of new gallium-doped silica glass-based transparent vitroceramic medium

    R. Ceccato
    Optically transparent, silica glass-based vitroceramic material doped with gallium oxide was obtained by standard glass fusion and appropriate thermal treatments. Low-wavenumber Raman scattering spectroscopy allowed the determination of the microstructure and in particular the size distribution of nanoparticles embedded in the amorphous matrix. The nanocrystal growth was accurately controlled by heat treatment conditions. Transmission electron microscopy and X-ray diffraction measurements revealed the presence of a single crystalline phase, spherical-shaped nanoaggregates, homogeneously distributed in the transparent composite medium. Copyright © 2001 John Wiley & Sons, Ltd. [source]

    Radiation driven collapse of protein crystals

    Sébastien Boutet
    During coherent X-ray diffraction measurements on crystals of ferritin at room temperature using monochromatic undulator radiation from the Advanced Photon Source, a sudden lattice contraction was observed following a characteristic latent period and ultimately leading to the collapse of the crystal. The progression of this collapse is analysed using a two-state Hendricks,Teller model. It reveals that 55% of the layers collapse by 1.6% before the crystal completely stops diffracting. [source]

    The new diffractometer for surface X-ray diffraction at beamline BL9 of DELTA

    Christof Krywka
    The experimental endstation of the hard X-ray beamline BL9 of the Dortmund Electron Accelerator is equipped with a Huber six-circle diffractometer. It is dedicated to grazing-incidence X-ray diffraction and X-ray reflectivity experiments on solid surfaces and thin films as well as to powder diffraction measurements. A new set-up for grazing-incidence X-ray scattering of liquids has been built up using a silicon mirror to reflect the incident X-ray to the liquid surface at angles of incidence around the critical angle of total reflection of the sample. X-ray reflectivity measurements of a polymer film and grazing-incidence X-ray diffraction measurements of an epitaxically grown Gd40Y60 film, an oxidized surface of Fe-15at.%Al alloy and aqueous salt solutions are presented and discussed. [source]

    Morphotropic Phase Boundary in the Pb(Zn1/3Nb2/3O3)-BaTiO3 -PbTiO3 System

    Weizhong Zhu
    The morphotropic phase boundary (MPB) in the relaxor ferroelectric system Pb(Zn1/3Nb2/3O3)-BaTiO3 -PbTiO3 (PZN-BT-PT) with 15 mol% BT was investigated through dielectric permittivity and high-temperature X-ray diffraction measurements. It was revealed that MPB is a broad composition region extending from 12 to 18 mol% PT, within which the temperatures of the permittivity maximum are close to the ending temperatures for the phase transformation from coexisting rhombohedral and tetragonal phases to cubic phase on heating. When the specimen is cooled, the starting temperatures for the rhombohedral-to-tetragonal phase transition increase with increasing PT content. The large thermal hysteresis observed by X-ray diffraction is caused by the phase transformation between rhombohedral and tetragonal phases. On cooling, the MPB curves toward the PT-rich side, so that ceramics within this composition range undergoe successive phase transitions from cubic to rhombohedral and from rhombohedral to tetragonal phase. The diffuseness of the paraelectric-to-ferroelectric phase transition is remarkably decreased by the addition of PT. The enhanced dielectric permittivity peak values for the MPB compositions are correlated with the reduced lattice distortion and phase coexistence. [source]

    Bismuth containing III,V quaternary alloy InGaAsBi grown by MBE

    G. Feng
    Abstract InGaAsBi epilayers were created on InP substrates by molecular beam epitaxy for the first time. The high crystalline quality of the InGaAsBi epilayer with smooth interface was confirmed by high resolution X-ray diffraction measurements. Up to 2.5% Bi was incorporated in the film based on Rutherford back scattering (RBS) results. The RBS channeling spectra give clear evidence that the Bi atoms were substitutionally located in the InGaAs zinc-blende lattice sites. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Growth and cathodoluminescent characteristics of blue emitting cerium-doped zinc aluminate layers synthesized by spray pyrolysis technique

    M. García-Hipólito
    Abstract Cerium doped ZnAl2O4 cathodoluminescent films have been deposited by ultrasonic spray pyrolysis deposition technique. X-ray diffraction measurements on these layers have shown that their crystalline structure depends on the substrate temperature. Cerium ions have been introduced into zinc aluminate films for produce violet-blue cathodoluminescence emissions. The behavior of cathodoluminescence emission intensity has been studied, as a function of the variations on doping concentrations, in the start spraying solution, substrate temperatures and the electron accelerating voltage. Concentration quenching of the cathodoluminescence occurs at about 0.8 percent of activator (Ce) concentrations inside the synthesized films. The surface morphology characteristics of these films, as a function of the substrate temperature, and the chemical composition, as measured by energy dispersive X-ray spectroscopy, are also exhibited. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]