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Diffraction

Distribution by Scientific Domains
Chemistry48%
Polymers and Materials Science30%
Physics and Astronomy13%
Medical Sciences2%
7 Other Domains7%
Distribution within Chemistry
Crystallography50%
General & Introductory Chemistry10%
Organic Chemistry6%
24 Other Subdomains34%

Kinds of Diffraction

  • angle x-ray diffraction
  • anomalous diffraction
  • area electron diffraction
  • coherent diffraction
  • convergent-beam electron diffraction
  • crystal diffraction
  • crystal x-ray diffraction
  • dispersive x-ray diffraction
  • electron diffraction
  • energy dispersive x-ray diffraction
  • energy electron diffraction
  • energy-dispersive x-ray diffraction
  • grazing-incidence x-ray diffraction
  • high energy electron diffraction
  • high resolution x-ray diffraction
    		•
  • high-energy electron diffraction
  • high-energy x-ray diffraction
  • high-resolution neutron powder diffraction
  • high-resolution synchrotron powder diffraction
  • high-resolution x-ray diffraction
  • high-resolution x-ray powder diffraction
  • incidence x-ray diffraction
  • laser diffraction
  • laue diffraction
  • light diffraction
  • low-energy electron diffraction
  • multiple-wavelength anomalous diffraction
  • multiwavelength anomalous diffraction
  • neutron diffraction
  • neutron powder diffraction
    		•
  • powder diffraction
  • powder neutron diffraction
  • powder x-ray diffraction
  • preliminary x-ray diffraction
  • reflection high energy electron diffraction
  • reflection high-energy electron diffraction
  • resolution x-ray diffraction
  • selected area electron diffraction
  • selected-area electron diffraction
  • single crystal diffraction
  • single crystal x-ray diffraction
  • single-crystal diffraction
  • single-crystal x-ray diffraction
  • single-wavelength anomalous diffraction
  • situ x-ray diffraction
    		•
  • small-angle x-ray diffraction
  • synchrotron powder diffraction
  • synchrotron x-ray diffraction
  • synchrotron x-ray powder diffraction
  • wave diffraction
  • wide angle x-ray diffraction
  • wide-angle x-ray diffraction
  • x-ray diffraction
  • x-ray powder diffraction
  • x-ray single crystal diffraction
  • x-ray single-crystal diffraction

    • Terms modified by Diffraction

  • diffraction analysis
  • diffraction analysis shows
  • diffraction analysis.
  • diffraction angle
  • diffraction characteristic
  • diffraction data
  • diffraction data analysis
  • diffraction data collection
  • diffraction data set
  • diffraction data show
  • diffraction effects
    		•
  • diffraction efficiency
  • diffraction experiment
  • diffraction geometry
  • diffraction grating
  • diffraction image
  • diffraction imaging
  • diffraction intensity
  • diffraction investigation
  • diffraction limit
  • diffraction line profile
  • diffraction measurement
    		•
  • diffraction method
  • diffraction methods
  • diffraction pattern
  • diffraction peak
  • diffraction profile
  • diffraction property
  • diffraction quality
  • diffraction result
  • diffraction reveal
  • diffraction shows
  • diffraction signal
    		•
  • diffraction spectroscopy
  • diffraction spectrum
  • diffraction spot
  • diffraction structure
  • diffraction studies
  • diffraction studies.
  • diffraction study
  • diffraction technique
  • diffraction techniques
  • diffraction theory

    • Selected Abstracts

    DETERMINATION OF PIGMENTS AND BINDERS IN POMPEIAN WALL PAINTINGS USING SYNCHROTRON RADIATION , HIGH-RESOLUTION X-RAY POWDER DIFFRACTION AND CONVENTIONAL SPECTROSCOPY , CHROMATOGRAPHY

    ARCHAEOMETRY, Issue 2 2010
    A. DURAN
    The employment of synchrotron techniques complemented by conventional laboratory systems has allowed us to deepen and improve our knowledge of Roman wall painting procedures. The palette identified in wall paintings from Pompeii and Herculaneum from the second century bc includes goethite, hematite, cinnabar, glauconite, Egyptian blue, and other components such as calcite and aragonite. Proof of the use of organic binders is provided by FTIR and PY,GC/MS. Therefore, the possibility of the use of ,a secco' techniques cannot be ruled out. Pigments in wall paintings are usually found in small percentages and conventional X-ray diffractometers do not detect them. Synchrotron radiation , high-resolution X-ray powder diffraction has allowed identification with only a few micrograms of sample. [source]

    Structural, electrical and optical properties of Ge implanted GaSe single crystals grown by Bridgman technique

    CRYSTAL RESEARCH AND TECHNOLOGY, Issue 12 2006
    H. Karaa
    Abstract Structural, optical and electrical properties of Ge implanted GaSe single crystal have been studied by means of X-Ray Diffraction (XRD), temperature dependent conductivity and photoconductivity (PC) measurements for different annealing temperatures. It was observed that upon implanting GaSe with Ge and applying annealing process, the resistivity is reduced from 2.1 × 109 to 6.5 × 105 ,-cm. From the temperature dependent conductivities, the activation energies have been found to be 4, 34, and 314 meV for as-grown, 36 and 472 meV for as-implanted and 39 and 647 meV for implanted and annealed GaSe single crystals at 500°C. Calculated activation energies from the conductivity measurements indicated that the transport mechanisms are dominated by thermal excitation at different temperature intervals in the implanted and unimplanted samples. By measuring photoconductivity (PC) measurement as a function of temperature and illumination intensity, the relation between photocurrent (IPC) and illumination intensity (,) was studied and it was observed that the relation obeys the power law, IPC ,,n with n between 1 and 2, which is indication of behaving as a supralinear character and existing continuous distribution of localized states in the band gap. As a result of transmission measurements, it was observed that there is almost no considerable change in optical band gap of samples with increasing annealing temperatures for as-grown GaSe; however, a slight shift of optical band gap toward higher energies for Ge-implanted sample was observed with increasing annealing temperatures. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Thermal, phase transition and spectral studies in erythromycin pseudopolymorphs: dihydrate and acetone solvate

    CRYSTAL RESEARCH AND TECHNOLOGY, Issue 12 2006
    Zhanzhong Wang
    Abstract The thermal, phase transition and spectral studies of erythromycin A dihydrate and acetone solvate were performed by Differential Scanning calorimetry (DSC), Thermo Gravimetry (TG-DTA), X-Ray Powder Diffraction (XRPD) and Fourier Transform Infra-Red (FTIR) spectrum. The non-thermal kinetic analysis of erythromycin A dihydrate was carried out by DSC at different heating rates in dynamic nitrogen atmosphere. The result showed that heating rate has substantial influence on the thermal behavior of erythromycin dihydrate. The Arrhenius parameters were estimated according to the Kissinger method. Corresponding to dehydration of dihydrate, melting of dehydrated dihydrate, phase transition from dehydrated dihydrate to anhydrate, and melting of anhydrate, the calculated activation energy were 39.60, 269.85, 261.23, and 582.16 kJmol,1, the pre-exponential factors were 3.46 × 103, 8.06 × 1032, 9.23 × 1030, and 7.29 × 1063 s,1, respectively. Ozawa method was used to compare activation energy values calculated by Kissinger method. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    An Energy Dispersive X-ray Diffraction Study of Dioxouranium(VI) in 1 M Lithium Citrate

    EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 13 2004
    Ermanno Vasca
    Abstract An Energy Dispersive X-ray Diffraction (EDXD) study of 0.3 M dioxouranium(VI) in 1 M lithium citrate at pH = 5 is reported. The data are in accordance with the existence of a predominately polynuclear complex containing four U atoms, concluded from potentiometric measurements. The uranium atoms lie at the corners of two triangles sharing one edge. Five O atoms surround each uranyl group, the uranium coordination polyhedron being a pentagonal bipyramid; four U atoms are linked through double or single O bridges. The U,U distances are 3.95 Å and 4.65 Å. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source]

    In Situ Characterization of a Nb and Mo Containing , -TiAl Based Alloy Using Neutron Diffraction and High-Temperature Microscopy,

    ADVANCED ENGINEERING MATERIALS, Issue 11 2009
    Ian J. Watson
    Abstract In recent times, novel titanium aluminides containing the bcc , -phase at high temperatures are being developed for improved hot-working capabilities, however, predictions of the phase diagrams are merely uncertain. Here we present in-situ neutron studies, which are particularly sensitive to the atomic disorder in the ordered phases. Complementary laser scanning confocal microscopy is employed for in-situ microstructural investigations. [source]

    In situ Study of Internal Load Transfer in a Novel Metal/Ceramic Composite Exhibiting Lamellar Microstructure Using Energy Dispersive Synchrotron X-ray Diffraction,

    ADVANCED ENGINEERING MATERIALS, Issue 6 2009
    Siddhartha Roy
    Freeze casting offers a new technique to fabricate ceramic preforms for metal/ceramic composites. Internal load transfer under external compressive loading in such composites has been studied for the first time using energy dispersive synchrotron X-ray diffraction. The results show that load transfer takes place from the soft metallic alloy to the hard ceramic which has been explained in the light of generalized Hooke's law and classical laminate theory. [source]

    High-Pressure, High-Temperature Formation of Phase-Pure Monoclinic Zirconia Nanocrystals Studied by Time-Resolved in situ Synchrotron X-Ray Diffraction

    ADVANCED MATERIALS, Issue 35 2009
    Martin Bremholm
    High-pressure, high-temperature, time- resolved X-ray diffraction is used to study the gel formation of aqueous zirconium acetate, and the crystallization into phase-pure, monoclinic, anisotropic nanocrystals. [source]

    Study of Cation Ordering in Ba(Yb1/2Ta1/2)O3 by X-Ray Diffraction and Raman Spectroscopy

    INTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 5 2008
    Dibyaranjan Rout
    The complex perovskite Ba(Yb1/2Ta1/2)O3 has been prepared by the two-stage solid-state reaction method. Rietveld' refinement analysis indicates cubic perovskite phase with space group . The 1:1 cation ordering at the B-site is revealed by the presence of (111) superlattice reflection in the X-ray diffraction pattern and further evidenced by the presence of A1g and F2g vibrational modes in the Raman spectra. The dielectric constant is measured to be 29.1, the product of quality factor and resonant frequency (Q×f) is found to be 32,000 GHz and the temperature coefficient of resonant frequency (,f) is 135 (ppm/°C) in the temperature range 30,70°C. [source]

    The Microstructure of Biogenic Calcite: A View by High-Resolution Synchrotron Powder Diffraction,

    ADVANCED MATERIALS, Issue 18 2006
    B. Pokroy
    Biogenic calcite obtained from different mollusk shells is subjected to heat treatments at elevated temperatures and structurally analyzed by high-resolution synchrotron X-ray powder diffraction. Remarkable broadening of diffraction peaks in samples annealed at temperatures above 200,°C is observed (see figure), indicating heat-induced degradation of intra-crystalline proteins occluded in the mineral lattice during biomineralization. [source]

    Book Review: Reflection High Energy Electron Diffraction.

    ADVANCED MATERIALS, Issue 22 2005
    By Ayahiko Ichimiya, Philip I. Cohen.
    No abstract is available for this article. [source]

    Outcomes of the International Union of Crystallography Commission on Powder Diffraction Round Robin on Quantitative Phase Analysis: samples 2, 3, 4, synthetic bauxite, natural granodiorite and pharmaceuticals

    JOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 4 2002
    Nicola V. Y. Scarlett
    The International Union of Crystallography (IUCr) Commission on Powder Diffraction (CPD) has sponsored a round robin on the determination of quantitative phase abundance from diffraction data. The aims of the round robin have been detailed by Madsen et al. [J. Appl. Cryst. (2001), 34, 409,426]. In summary, they were (i) to document the methods and strategies commonly employed in quantitative phases analysis (QPA), especially those involving powder diffraction, (ii) to assess levels of accuracy, precision and lower limits of detection, (iii) to identify specific problem areas and develop practical solutions, (iv) to formulate recommended procedures for QPA using diffraction data, and (v) to create a standard set of samples for future reference. The first paper (Madsen et al., 2001) covered the results of sample 1 (a simple three-phase mixture of corundum, fluorite and zincite). The remaining samples used in the round robin covered a wide range of analytical complexity, and presented a series of different problems to the analysts. These problems included preferred orientation (sample 2), the analysis of amorphous content (sample 3), microabsorption (sample 4), complex synthetic and natural mineral suites, along with pharmaceutical mixtures with and without an amorphous component. This paper forms the second part of the round-robin study and reports the results of samples 2 (corundum, fluorite, zincite, brucite), 3 (corundum, fluorite, zincite, silica flour) and 4 (corundum, magnetite, zircon), synthetic bauxite, natural granodiorite and the synthetic pharmaceutical mixtures (mannitol, nizatidine, valine, sucrose, starch). The outcomes of this second part of the round robin support the findings of the initial study. The presence of increased analytical problems within these samples has only served to exacerbate the difficulties experienced by many operators with the sample 1 suite. The major difficulties are caused by lack of operator expertise, which becomes more apparent with these more complex samples. Some of these samples also introduced the requirement for skill and judgement in sample preparation techniques. This second part of the round robin concluded that the greatest physical obstacle to accurate QPA for X-ray based methods is the presence of absorption contrast between phases (microabsorption), which may prove to be insurmountable in some circumstances. [source]

    Outcomes of the International Union of Crystallography Commission on Powder Diffraction Round Robin on Quantitative Phase Analysis: samples 1a to 1h

    JOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 4 2001
    Ian C. Madsen
    The International Union of Crystallography (IUCr) Commission on Powder Diffraction (CPD) has sponsored a round robin on the determination of quantitative phase abundance from diffraction data. Specifically, the aims of the round robin were (i) to document the methods and strategies commonly employed in quantitative phase analysis (QPA), especially those involving powder diffraction, (ii) to assess levels of accuracy, precision and lower limits of detection, (iii) to identify specific problem areas and develop practical solutions, (iv) to formulate recommended procedures for QPA using diffraction data, and (v) to create a standard set of samples for future reference. Some of the analytical issues which have been addressed include (a) the type of analysis (integrated intensities or full-profile, Rietveld or full-profile, database of observed patterns) and (b) the type of instrument used, including geometry and radiation (X-ray, neutron or synchrotron). While the samples used in the round robin covered a wide range of analytical complexity, this paper reports the results for only the sample 1 mixtures. Sample 1 is a simple three-phase system prepared with eight different compositions covering a wide range of abundance for each phase. The component phases were chosen to minimize sample-related problems, such as the degree of crystallinity, preferred orientation and microabsorption. However, these were still issues that needed to be addressed by the analysts. The results returned indicate a great deal of variation in the ability of the participating laboratories to perform QPA of this simple three-component system. These differences result from such problems as (i) use of unsuitable reference intensity ratios, (ii) errors in whole-pattern refinement software operation and in interpretation of results, (iii) operator errors in the use of the Rietveld method, often arising from a lack of crystallographic understanding, and (iv) application of excessive microabsorption correction. Another major area for concern is the calculation of errors in phase abundance determination, with wide variations in reported values between participants. Few details of methodology used to derive these errors were supplied and many participants provided no measure of error at all. [source]

    X-ray diffraction analysis of stacking and twin faults in f.c.c. metals: a revision and allowance for texture and non-uniform fault probabilities

    JOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 2 2000
    L. Velterop
    A revision is presented of the original description by Warren [X-ray Diffraction, (1969), pp. 275,298. Massachusetts: Addison-Wesley] of the intensity distribution of powder-pattern reflections from f.c.c. metal samples containing stacking and twin faults. The assumptions (in many cases unrealistic) that fault probabilities need to be very small and equal for all fault planes and that the crystallites in the sample have to be randomly oriented have been removed. To elucidate the theory, a number of examples are given, showing how stacking and twin faults change the shape and position of diffraction peaks. It is seen that significant errors may arise from Warren's assumptions, especially in the peak maximum shift. Furthermore, it is explained how to describe powder-pattern reflections from textured specimens and specimens with non-uniform fault probabilities. Finally, it is discussed how stacking- and twin-fault probabilities (and crystallite sizes) can be determined from diffraction line-profile measurements. [source]

    Preparation and fluorescence properties of poly(o -methyl-acrylamideyl-benzoic acid)-ZnS composites

    JOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2010
    Qing-Feng Xu
    Abstract Poly(o -methyl-acrylamideyl-benzoic acid)-ZnS (P(o -MAABA)-ZnS) nanocomposites have been prepared and characterized. The resultant P(o -MAABA)-ZnS nanocomposites in solution show two emissions in the purple-light area (370 nm) and in the blue-light area (425 nm), which are assigned to the polymer and ZnS nanoparticles, respectively. The coordination between the polymer and Zn2+ and the surface chemical composition has been studied by Infrared spectroscopy and X-ray photoelectron spectroscopy (XPS). The particle size of ZnS nanoparticles was homogeneous and the average size was 3.8 nm, which were characterized by UV absorption spectrum and X-ray Diffraction. The P(o -MAABA)-ZnS composites displays good film formability and the films also show two emissions in 370 and 425 nm. After doped with Tb3+, there was effective energy transfer from ZnS nanoparticles to Tb3+. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source]

    Polypropylene nanocomposite film: A critical evaluation on the effect of nanoclay on the mechanical, thermal, and morphological behavior

    JOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2010
    S. K. Sharma
    Abstract Polypropylene (PP)/clay nanocomposites prepared by melt blending technique using different percentages of clay with and without maleic anhydride grafted PP (MA-PP) were studied. The intercalated and exfoliated structure of nanocomposites was characterized by X-Ray Diffraction (XRD) and transmission electron microscopy (TEM). Because of the typical intercalated and exfoliated structure, the tensile modulus of the nanocomposites were improved significantly as compared to virgin PP. The viscoelastic behavior of the nanocomposites was studied by dynamical mechanical analysis (DMA) and the results showed that with the addition of treated clay to PP there was substantial improvement in storage modulus increases. The thermal stability and crystallization of the PP nanocomposites as studied by differential scanning calorimeter (DSC) and thermo gravimetric analysis (TGA) were also improved significantly compared to PP. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source]

    Crystallization Kinetics and X-ray Diffraction of Crystals Formed in Amorphous Lactose, Trehalose, and Lactose/Trehalose Mixtures

    JOURNAL OF FOOD SCIENCE, Issue 5 2005
    Song Miao
    ABSTRACT: Effects of storage time and relative humidity on crystallization kinetics and crystal forms produced from freeze-dried amorphous lactose, trehalose, and a lactose/trehalose mixture were compared. Samples were exposed to 4 different relative water vapor pressure (RVP) (44.1%, 54.5%, 65.6%, 76.1%) environments at room temperature. Crystallization was observed from time-dependent loss of sorbed water and increasing intensities of peaks in X-ray diffraction patterns. The rate of crystallization increased with increasing storage humidity. Lactose crystallized as ,-lactose monohydrate, ,-anhydrous, and anhydrous forms of ,- and ,-lactose in molar ratios of 5:3 and 4:1 in lactose and lactose/trehalose systems. Trehalose seemed to crystallize as a mixture of trehalose dihydrate and anhydrate in trehalose and lactose/trehalose systems. The crystal forms in a mixture of lactose and trehalose did not seem to be affected by the component sugars, but crystallization of the component sugars was delayed. Time-dependent crystallization of lactose and trehalose in the lactose-trehalose mixture could be modeled using the Avrami equation. The results indicated that crystallization data are important in modeling of crystallization phenomena and predicting stability of lactose and trehalose-containing food and pharmaceutical materials. Keywords: crystallization, lactose, trehalose, crystal form, X-ray diffraction [source]

    Micro-Raman spectroscopic study of El Gasco pumice, western Spain

    JOURNAL OF RAMAN SPECTROSCOPY, Issue 2 2007
    F. Rull
    Abstract A micro-Raman spectroscopic study of pumice materials from El Gasco (Sierra de Gata, Spain) has been performed for the first time. The obtained spectra allow the precise identification of the minerals, quartz, haematite, magnetite, ilmenite, rutile and anatase, in general agreement with results obtained by complementary techniques of X-Ray Diffraction (XRD) and Electron Microprobe. Also, fayalite and ferroan ringwoodite have been identified. The presence of high-pressure polymorphs indicates that the pumice rocks were subjected to high-pressure conditions quite similar to those observed in shock-induced molten and recrystallised materials, such as some meteorites and impact-related rocks. Copyright © 2006 John Wiley & Sons, Ltd. [source]

    Diffraction-based automated crystal centering

    JOURNAL OF SYNCHROTRON RADIATION, Issue 2 2007
    Jinhu Song
    A fully automated procedure for detecting and centering protein crystals in the X-ray beam of a macromolecular crystallography beamline has been developed. A cryo-loop centering routine that analyzes video images with an edge detection algorithm is first used to determine the dimensions of the loop holding the sample; then low-dose X-rays are used to record diffraction images in a grid over the edge and face plane of the loop. A three-dimensional profile of the crystal based on the number of diffraction spots in each image is constructed. The derived center of mass is then used to align the crystal to the X-ray beam. Typical samples can be accurately aligned in ,2,3,min. Because the procedure is based on the number of `good' spots as determined by the program Spotfinder, the best diffracting part of the crystal is aligned to the X-ray beam. [source]

    Subcoercive Cyclic Electrical Loading of Lead Zirconate Titanate Ceramics II: Time-Resolved X-Ray Diffraction

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 10 2009
    Abhijit Pramanick
    Structural changes such as non-180° domain wall motion and lattice strains in Pb(Zr,Ti)O3 ceramics are measured during the application of subcoercive cyclic electric fields using time-resolved high-energy X-ray diffraction with a stroboscopic data collection technique. The contributions to the electric-field-induced strains from non-180° domain wall motion and lattice distortions are determined as a function of material composition and type of dopant. For the different compositions studied, the largest strains due to non-180° domain wall motion are measured for La-doped tetragonal ceramics with a composition close to the morphotropic phase boundary. It is further observed that strain contributions from both non-180° domain wall motion and lattice distortions can be nonlinear with respect to the applied electric field. The correlation between the electric-field-induced structural changes and the macroscopic piezoelectric properties is discussed. [source]

    The Structure of Yttrialite and Its Identification Using Laboratory and Synchrotron-Based Powder X-Ray Diffraction

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 2 2009
    William J. Heward
    A highly crystalline sample of the impurity stabilized phase y -Y2Si2O7, generally known as yttrialite, has been formed from the melt of a glass with a nominal composition of 62(SiO2),10(Al2O3),28(Y2O3) mol%. Powder X-ray diffraction patterns were collected using in-house instrumentation and the 11-BM diffractometer at the Advanced Photon Source, Argonne National Laboratory, Argonne, IL. Rietveld refinements were carried out on the patterns using two structural models. On patterns collected using in-house instrumentation the correct structure assignment was difficult to determine; however, the extremely high-quality data afforded by the 11-BM instrument showed conclusively that the sample was found to crystallize in the monoclinic system (SG=P21/m) with lattice parameters a=5.03032(6), b=8.06892(6), c=7.33620(6) Å, and ,=108.673(1). Furthermore, simulations have shown that it is likely that this structure model can be used to describe natural yttrialite or yttrialite that is formed at low temperatures, though the possibility that such materials are paracrystalline is also discussed. [source]

    Neutron Diffraction of Zirconia-Dispersed Alumina with Increasing Stress and Temperature

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 2 2008
    Geoffrey A. Carter
    Neutron and X-ray diffraction were used to investigate changes in the phase composition and lattice parameters with temperature and pressure of a 20-wt% zirconia-dispersed alumina composite. Neutron diffraction was used to determine the variation of tetragonal/monoclinic zirconia phase abundance for the bulk with stress. The bulk tetragonal/monoclinic ratio decreased by 40% for a stress of 550 MPa. A difference in the tetragonal/monoclinic ratio between the near-surface and the bulk of the processed samples is believed to contribute to observed variations in nonuniform strain in the matrix, which has the effect of prestressing the sample. Placing a stress on the sample initially releases this prestressing. [source]

    Tricalcium Silicate T1 and T2 Polymorphic Investigations: Rietveld Refinement at Various Temperatures Using Synchrotron Powder Diffraction

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 9 2004
    Vanessa K. Peterson
    The lattice parameters, cell volume, and structure of a sample of phase pure triclinic tricalcium silicate were determined using in situ, high-temperature synchrotron powder diffraction and full-profile Rietveld refinement. The temperature range covered was from ambient to 740°C. Evidence of superstructure was found. The T2 type structure with disordered SiO4 tetrahedra was observed, and an average structure for the subcell (P, a= 11.7416(2) Å, b= 14.2785(2) Å, c= 13.7732(2) Å, ,= 105.129(1)°, ,= 94.415(1)°, and ,= 89.889(1)°) is presented. Differential thermal analysis and X-ray fluorescence was also performed. [source]

    Hydrolysis of Pure and Sodium Substituted Calcium Aluminates and Cement Clinker Components Investigated by in Situ Synchrotron X-ray Powder Diffraction

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2004
    Axel Nørlund Christensen
    The hydrolysis of pure and sodium-substituted calcium aluminates and cement clinker phases was investigated in situ in the temperature range 25°,170°C, using the angle dispersive powder synchrotron powder X-ray diffraction technique. The final hydrolysis product in all cases was Ca3Al2(OH)12. The intermediate phase Ca4Al2O7·19H2O was formed from the pure calcium aluminates, and the intermediate phases Ca4Al2O7·xH2O, x= 11, 13, or 19, were formed from the cement clinker phases. [source]

    Raman Scattering Characterization of Polytype in Silicon Carbide Ceramics: Comparison with X-ray Diffraction

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 5 2003
    Shin-ichi Nakashima
    Raman scattering measurements have been made on SiC ceramics prepared from two powdered by sintering at different temperatures. The Raman spectra of starting powders have also been measured. The volume contents of the 4H and 15R polytype phases relative to that of the 6H phase in the ceramics are inferred from the Raman intensity of folded modes of the acoustic branches and compared with those determined from X-ray diffraction (XRD) analysis. A strong correlation is found between the results obtained from the two analyses. The 4H polytype contents estimated by Raman measurement for specimens prepared from one powder show a good agreement with those obtained by the XRD analysis. For the 15R polytype component there is a correlation between the contents inferred by the two techniques when the content is not very small. The results obtained by the two techniques demonstrate that the Raman spectroscopy as well as the XRD analysis is useful to study the natures and preparation conditions of SiC ceramics. [source]

    Light diffraction by a subwavelength circular aperture

    LASER PHYSICS LETTERS, Issue 7 2005
    Che-Wei Chang
    Abstract Diffraction of normally incident light by a subwavelength circular aperture is calculated analytically. The aperture is opened on a perfectly conducting planar screen with infinitesimal thickness. In our model, the aperture is replaced by uniform magnetic currents and charges. The model allows one to obtain the normalized cross section for the aperture radius up to half of the wavelength, which exceeds the 0.2 wavelength limit of the Bethe-Bouwkamp's dipole model [1,3]. Also, in addition to reproducing the (ka)4 dependence, which is characteristic of the dipole mode, our uniform field model explains the transmission enhancement obtained in Abajo's numerical simulation [4]. (© 2005 by Astro, Ltd. Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source]

    Submicron Polymer Gratings: Optical Diffraction and Spontaneous Brillouin Scattering

    MACROMOLECULAR RAPID COMMUNICATIONS, Issue 9 2006
    Wei Cheng
    Abstract Summary: Brillouin light scattering (BLS) from submicron-size patterned polyurethane (PU) films was found to display rich spectral features. Their identification allows the determination of the mechanical properties of the PU and the characterization of the periodicity and the coherence of the structure. A temperature-dependent study demonstrates that BLS is a sensitive tool to monitor changes of the mechanical properties and/or of the morphology. (a) Scheme of the sample structure and the scattering geometry, (b) SEM top view of the PU features. [source]

    Processing of a Strong Biodegradable Poly[(R)-3-hydroxybutyrate] Fiber and a New Fiber Structure Revealed by Micro-Beam X-Ray Diffraction with Synchrotron Radiation

    MACROMOLECULAR RAPID COMMUNICATIONS, Issue 11 2004
    Tadahisa Iwata
    Abstract Summary: Biodegradable poly[(R)-3-hydroxybutyrate] (P(3HB)) fibers with high tensile strength of 1.32 GPa were processed from ultra-high-molecular-weight P(3HB) by a method combining cold-drawing and two-step-drawing procedures at room temperature. The distribution of molecular structures in a mono-filament was analyzed by micro-beam X-ray diffraction with synchrotron radiation. It was revealed that the P(3HB) fiber has a new core-sheath structure consistent with two types of molecular conformations: a 21 helix conformation in the sheath region and a planar zigzag conformation in the core region. P(3HB) fiber processed by cold-drawing in ice water and two-step drawing at room temperature, and subsequently annealing at 50,°C. [source]

    Metastable alumina formation during oxidation of FeCrAl and its suppression by surface treatments

    MATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 12 2005
    E. N'Dah
    Abstract The influence of various surface treatments of industrial FeCrAl grades was investigated in order to reduce the formation of transition aluminas during thermal oxidation in the 800,950°C temperature range. High temperature gas phase annealing in H2 -H2O mixtures promoted the initial formation of an alpha thin film and no transition alumina formed during subsequent oxidation at lower temperatures, showing very low weight gains compared to non-treated grades. Such a treatment was shown to be efficient for isothermal oxidation in oxygen of laboratory foil specimens but also for cyclic air exposure of fiber mats in near-real operating conditions. Surface modification by application of a slurry TiO2 coating before oxidation was also shown to greatly reduce the amount of transition alumina, observed by X-Ray Diffraction and Laser Induced Optical Spectroscopy. For both treatments, the optimal conditions were determined and the influence on oxidation rate was assessed. [source]

    EBSD investigation of intergranular corrosion attack on low interstitial stainless steel

    MATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 6 2004
    T. Kuníková
    Abstract Grain boundary effect on corrosion behaviour of low interstitial AISI 316LN austenitic stainless steel after homogenization and heat treatment at 700 and 800°C was investigated by means of Electron Backscattered Diffraction (EBSD) technique. Rapid oxalic acid etch test (ASTM A262- practice A) was used to determine steel susceptibility to intergranular corrosion. An attempt to quantify oxalic acid etch test results was also made. Beneficial effect of low carbon and nitrogen content on grain boundary precipitation and corrosion was observed. No changes neither in grain orientations nor in grain boundary types between sensitised and non-sensitised steel states using orientation measurements were recorded. Twin boundaries were found in all samples with highest amount and only small occurrence changes. CSL categorizations showed only little increase of special boundary fractions with increasing time and temperature of heat treatment. Irrespective to annealing conditions a continued network of random boundaries was retained. Additionally, based on misorientation measurement of 50 grooved grain boundaries, a tendency for preferred attack of high angle boundaries (30,55°) was noted. [source]

    Diffraction of light revisited

    MATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 7 2008
    Matthias Kunik
    Abstract The diffraction of monochromatic light is considered for a plane screen with an open infinite slit by solving the vectorial Maxwell,Helmholtz system in the upper half-space with the Fourier method. With this approach we can represent each solution satisfying an appropriate energy condition by its boundary fields in the Sobolev spaces H±1/2. We show that Sommerfeld's theory using a boundary integral equation with Hankel kernels for the so-called B-polarization is covered by our approach, but in general it violates a necessary energy condition. Our representation includes also solutions which are not covered by Sommerfeld's theory. Copyright © 2007 John Wiley & Sons, Ltd. [source]