Debye-Scherrer Rings Research Articles

Nanostructures of polyelectrolyte gel-surfactant complexes in uniaxially stretched networks

Nanostructures of poly(acrylate) gel and dodecylpyridinium complexes equlibrated with the NaCl aqueous solution (from 5 to 100mM) and their time evolution after stretching uniaxially were investigated by means of time-resolved small-angle x-ray scattering. The scattering profile revealed the existence of the cubic nanostructure belonging to Pm3n space group in the gel before and long after the stretch. Each of the three intensive peaks was found to be resolved into two, which suggested the existence of two cubic structures with the slightly different lattice spacings. On the other hand, the splits of scattering peaks were not observed for the linear poly(acrylate) and dodecylpyridinium complexes. This indicates that the existence of the cross-linked chain is concerned in the formation of the double structure in the complex system. A series of time-resolved experiments demonstrated that the peaks corresponding to the longer lattice constant disappeared once just after stretching and regenerated to grow up, whereas the peaks corresponding to the shorter lattice constant were continuously observed. The growing rates of the peaks increased with the NaCl concentration. It was also found that a two-dimensional scattering pattern changed from the Debye-Scherrer ring type into the Laue spot type with stretching at the lower NaCl concentrations. This indicates that the single-crystal-like domains align in the stretched network due to the strong electrostatic interaction between the dodecylpyridinium cation and poly(acrylate) anion.

Performance of a synthetic diamond backing-plate for the diamond-anvil cell at ultrahigh pressures

Synthetic diamond has been successfully used as a backing-plate in the diamond-anvil cell up to 223 GPa. Use of diamond for the backing-plate has a great advantage for powder x-ray diffraction experiments at ultrahigh pressures, for it makes it possible to measure full Debye–Scherrer rings to a maximum scattering angle of 34°. The mechanical strength of the diamond backing-plate should contribute to the extension of the current pressure limit of the diamond-anvil cell. Problems and future improvements of the design are discussed.

Multichannel detector–collimator for powder diffraction measurements at energy scanning x-ray absorption spectroscopy synchrotron radiation beamlines for high-pressure and high-temperature applications

We describe a modular detector system suitable to intercept the diffracted x-ray radiation (Debye–Scherrer rings) in a transmission geometry setup at monochromatic tunable synchrotron radiation beamlines. The detector consists of several independent channels composed of a motorized front slit and a rear detector slit system which can be mounted in either a vertical or a horizontal configuration. The detectors are placed at fixed scattering angles 2θ and the diffraction scan is performed by tuning the monochromator energy. The availability of a multidetector system allows one to cover a wide range of scattering vectors with limited range energy scans. The photon sensitive elements are based on CdZnTe solid state detectors which are used at ambient temperature for high efficiency photon counting in the 10–60 keV range. In alternative, conventional NaI(Tl) scintillation detectors can be integrated in the setup. The system can be mounted in a high-resolution configuration and typical widths in the range ΔE/E≃10−3 have been obtained for Bragg peaks. In these conditions the sensitivity to changes in the lattice spacing is better than 10−4. This detector system fully complements the experimental devices usually available at x-ray absorption spectroscopy beamlines and the short range structural information obtained using the x-ray absorption fine structure technique. Typical applications include high-pressure and high-temperature investigations of condensed matter.

Application of Image Plate to X-Ray Stress Measurement of Dual Phase Stainless Steel with Cr-K.ALPHA./.ALPHA.211 and Cr-K.BETA./.GAMMA.311 Diffractions

It is possible to carry out stress measurement by single X-ray incidence using whole part of Debye-Scherrer ring. Yoshioka et al, reported that it is useful for this method to use image plate (IP) for its practical use. There is a possibility to analyze Debye-Scherrer rings of plural phases in composite materials simultaneously exposed on one image plate, as the diffraction rings have the different radius due to the different diffraction angle each other. It will be possible, in these cases, to measure phase stresses, macro- and microstresses by single X-ray exposure. Therefore, we can carry out quicker X-ray stress measurement. In case of the use of chromium Kα radiation to dual phase stainless steel, αFe211 diffraction occurs at 2θ=153.5 deg and γFe311 diffraction at 2θ=146.6 deg is also available if chromium Kβ, radiation is used. Through these diffraction experiments, the stress measurement mentioned above will be possible.

High‐Energy X‐Rays: A tool for Advanced Bulk Investigations in Materials Science and Physics

High‐energy X‐rays between 30 keV and 1MeV, such as provided by modern synchrotron radiation sources as the ESRF and HASYLAB, bear the advantage of high penetration into most materials. Even heavy element compositions can be accessed in their volume. The range of applications is huge and spreads from nuclear spectroscopy to the characterization of metal extrusion under industrial conditions. This article compiles an overview over the most common instrumental diffraction techniques.Modern two‐dimensional detectors are used to obtain rapid overviews in reciprocal space. For example, diffuse scattering investigations benefit from the very flat Ewald sphere as compared to low energies, which allow mapping of several Brillouin zones within one single shot. Diffraction profiles from liquids or amorphous materials can be recorded easily. For materials science purposes, whole sets of Debye–Scherrer rings are registered onto the detector, their diameters and eccentricities or their intensity distribution along the rings relating to anisotropic strain or texture measurements, respectively. At this point we stress the resolution of this technique which has to be carefully taken into account when working on a second generation synchrotron source.Energy‐dispersive studies of local residual strain can be studied by a dedicated three‐circle diffractometer which allows accurately to adjust the scattering angle from a defined gauge volume.Triple axis diffractometry and reciprocal space mapping is introduced and can be employed for highest resolution purposes on single crystal characterization, even under heavy and dense sample environments. Thus, the perfection of single crystals can be mapped and strain fields and superstructures as introduced by the modulation from ultrasonic waves into crystals or epitaxially grown Si/Ge layers can be investigated in detail. Phase transitions as magnetic ordering can be studied directly or through its coupling to the crystal lattice. Time resolved studies are performed stroboscopically from a sub‐nanosecond to a second time scale.The combination of these techniques is a strong issue for the construction and development of future instruments.

A new method of Debye-Scherrer pattern integration on two-dimensional detectors, demonstrated for the new structure powder diffractometer (SPODI) at the FRM-II in Garching

The expected diffraction patterns of the new powder diffractometer SPODI, currently under construction at the FRM-II in Garching, will be smeared Debye–Scherrer rings as depicted by Monte Carlo (MC) simulations. To overcome this disadvantage, a concept based on the combination of MC simulations and empirical approximation methods is developed to reverse the smearing by deconvolution and then summing up along the rings, including corrections for different arc lengths, resulting in conventional one-dimensional diffraction patterns suitable for Rietveld-refinement programs without further processing.

A new detector system for the structure powder diffractometer SPODI at the FRM-II in Garching

This article describes the concept of one of the new technical features of the structure powder diffractometer SPODI: the array of position-sensitive detectors including the read-out electronics. 80 single-He3 detectors each with an active length of 300 mm will be arranged vertically in a detector bank. The position sensitivity enables us to evaluate larger parts of the Debye–Scherrer rings and to improve the determination of the 2θ positions of the Bragg peaks. The set-up of this detector system, which is called an individual counter array, is described. Test measurements with the prototype of the read-out electronics are presented. A software package will store the signals in a 2D matrix and allow various evaluation procedures of the data.

Separating the recrystallization and deformation texture components by high-energy X-rays

High-energy synchrotron diffraction offers great potential for experimental study of recrystallization kinetics. Measurements on partially recrystallized samples using a monochromatic high-energy synchrotron beam show that recrystallized grains generate sharp diffraction spots, whereas the intensity from the deformed matrix varies smoothly along the Debye–Scherrer rings. Based on these observations, a method has been developed to separate the recrystallization texture components from those originating from the deformation matrix. The validity of this method is demonstrated with partially recrystallized interstitial-free steel.

Powder Pattern Decomposition with the Aid of Preferred Orientation - Use of the Whole Debye-Scherrer Ring

Method of the decomposition of overlapping reflections in a powder pattern with the aid of preferred orientation is tested on magnetically aligned samples using the effect of easy magnetization direction in hexagonal SmCo5 and TbCo5. Complete Debye-Scherrer rings, measured with an image plate detector, are integrated in different radial directions. The texture aided powder pattern decomposition results in correct values of structure amplitudes

In-situ Annealing of Thin SrO Films Grown on Si(001)-2×1 by Molecular Beam Epitaxy

Thin strontium oxide films were grown at 350°C in an oxygen atmosphere of 5 ×10-8 Torr by Sr-deposition using molecular beam epitaxy (MBE). The evolution of 300-Å-thick SrO films on a Si(001)-2 ×1 substrate is studied by reflection high-energy electron diffraction (RHEED) as a function of annealing temperature in an oxygen atmosphere of around 1 ×10-6 Torr. The RHEED patterns of the SrO crystalline films show streaks with spots up to an annealing temperature of 625°C, and then Debye-Scherrer rings appear with broad spots at 650°C. Above this temperature, the patterns consist only of the rings. From the results, we find that the growth temperature for any epitaxial film on Si with a MBE-grown SrO buffer layer is restricted to be under 625°C.

Simultaneous Measurement of Plural Pole Figures Using Imaging Plate.

The purpose of this study is simultaneously to obtain plural pole figures using imaging plate (IP) which is a a two-dimensional X-ray area detector. Since more than one Debye-Scherrer rings are simultaneously recorded on an IP, plural pole figures are drawn from one X-ray measurement. Diffraction data recorded on IP are also detected as digital data, so that it is easy to analyze them by a computer. In the present paper. this method was applied to a textured dual phase stainless steel sheet which consists of coarse grains. Results are summarized as follows : (1) Plural pole figures are simultaneously obtained. (2) By applying a computer smoothing process to diffraction data containing spotty Debye-Scherrer rings, pole figures which elearly show the state of preferred orientation are obtained.

Observation of Oriented Close-Packed Lattice Planes in Polycrystalline Hard-Sphere Solids

We report time-resolved Bragg scattering experiments on solidifying colloidal suspensions of hard spheres. The polar angle-averaged, integrated intensity of the (111) and (311) reflections show a transient, two-step behavior below melting, which depends in a complex way on the volume fraction and is not present for (200) or (220). Detailed analysis of the full two-dimensional scattering pattern reveals intensity maxima of sixfold symmetry close to the position of the (111) and (311) Debye–Scherrer rings. These can be explained assuming oriented crystals with close-packed planes parallel to the container walls. We show that the observed temporal behavior is due to competing homogeneous and heterogeneous nucleation and growth scenarios.

Energy loss spectroscopy for Li/Si by energy filtered RHEED

While depositing Li atoms on a Si(111) 7×7 clean surface being kept at about 170°C, energy loss spectra of specularly reflected electron beam from the growing surface have been measured by recently developed energy filtered RHEED apparatus. AES measurements and RHEED observations were also pursued to obtain information on the amount of deposited Li and on the surface structural change, respectively. At the beginning of the deposition, Auger intensity ratio, Li(KLL)/Si(LVV), increases in proportion to the deposition time, and thereafter the ratio is saturated at nearly the same time Debye–Scherrer ring of Li appears in the RHEED pattern, that is, Stranski–Krastanov growth mode. For the series of Li depositions, energy loss spectra of the specular beam showed interesting change. It has been found that a new peak appears at about 19 eV in addition to surface plasmon loss peaks of Si when Li islands begin to grow. This new peak is supposed to be a coupled loss peak of the surface plasmon of Si (12 eV) with the bulk plasmon of Li (7 eV).

Structural Regularity of Poly(phenylsilsesquioxane) Prepared from the Low Molecular Weight Hydrolysates of Trichlorophenylsilane

Various hydrolysates of trichlorophenylsilane (TCP) and their polycondensates were reacted with trichlorosilane for capping the silanol groups formed in defect points of the ladder structure. The 1H NMR spectra of the capping products obtained showed several signals due to the Me3Si groups in different environment. Particularly, the polycondensate prepared from the TCP hydrolysate having higher molecular weight showed both sharp and broad Me3Si signals, suggesting a core-shell type branched structure. No Me3Si signal was shown in the polycondensate prepared from the hydrolysate with low molecular weight, supporting an almost perfect ladder structure with few bonding defects. The wide angle X-ray scattering (WAXS) of this polycondensate showed clear Debye-Scherrer rings due to the crystallization of the polymer chains having the regular ladder structure. The structural regularity of this polycondensate was also supported by the 29Si NMR spectrum. This polymer, having a stable double-strand structure, was found to undergo no base-catalyzed depolymerization in solution. A stepwise polycondensation is proposed for the formation of the ladder polymer in which the trivalent (T0: PhSi(O−)3) or divalent (T1: PhSi(OSi)(O−)2) siloxyl units should be involved in the reaction, leaving the monovalent siloxyl (T2: PhSi(OSi)2(O−)) units unreacted.

Proposal of Method to Make Pole Figure using Imaging Plate.

The state of texture in polycrystalline materials can be understood through a pole figure, which is measured by the X-ray diffraction technique. In this study, a method to measure the pole figure with imaging plate (IP) was proposed. IP as a two dimensional detector can measure the entire Debye-Scherrer ring, and pole density distribution of multi direction can be recorded on the Debye-Scherrer ring at the same time. Moreover, if two or more Debye-Scherrer rings are recorded on an IP, two or more pole figures can be obtained at one measurement. The measurement of the pole figure using IP has the possibility to become more efficient than the measurement by conventional method. In conventional method, X-ray device which equipped with Schulz's goniometer and a pulse-counter is used. The measurement device which adopted this method was made, and the pole figure of a textured rolled aluminum sheet was measured. Finally, the measurement accuracy of this method was proven by comparing pole figures which had been obtained by this method and a conventional method.

A new single-crystal mounting technique for low-background high-temperature X-ray diffraction

A new single-crystal mounting technique for high-temperature X-ray diffraction up to 1700 K on an imaging plate scanner has been developed. The crystal is clamped mechanically by three to six very thin alumina fibres. Besides the cheap and easy manufacturing procedure, its major advantage is the resultant very low background; it consists mainly of weak, smooth Debye–Scherrer rings which can be easily removed by image-processing methods.

Study on Structure and Properties of Polypropylene/Polyamide 6 Blend Fiber. (Part V). The Changes of Structure and Tensile Strength and Elongation Characteristics for the Polypropylene/Polyamide 6 Blend Fibers upon Drawing.

The changes of structure and tensile strength and elongation characteristics of polypropylene/polyamide 6 (hereafter “PP/PA6”) blend fibers upon drawing were investigated. Two melting peaks appeared, probably caused by the drawing of the PA6 component. The peak temperature of the PA6 component situated on the lower temperature side increased with increasing drawing ratio and with the PP content. Such melting behavior might be closely related to the crystal perfection and size developed in the PA6 component.In respect to the crystallinity of the blend fibers, the PA6 component was hardly affected by draw ratio and blend ratio. On the other hand, the PP component exhibited a higher crystallinity by draw. The X-ray diffraction patterns were examined. The undrawn blend fibers exhibited an orientation of PP crystals. However, the DebyeScherrer ring from PP crystals did not disappear even at draw ratio until 4.8. This indicates that the increment of PP crystalline orientation in the blend fibers with draw was smaller than that of the PP fibers.The tensile strength and elongation characteristics for the blend fibers depended largely on the blend ratios. At a given draw ratio, the strength increased with PA6 content. It was shown that the strength of the blend fibers was largely governed by the content of PA6 component rendering a high strength. The elongation decreased with increasing PA6 content.

２次元的Ｘ線検出器イメージングプレートを用いた全平面応力成分の単一入射Ｘ線応力測定

This study was performed to examine the possibility of X-ray measurement by analyzing the whole part of Debye-Scherrer ring. An imaging plate (IP) was used for the detection of X-ray in order to obtain a high degree of accuracy and efficiency. Through the investigation on the Tanaka's method, we proposed new equations for σy and τxy. We also found that the Tanaka's method involved an assumption that the angle η is constant. So we proposed a new method for the determination of stress from Debye-Scherrer ring without the above approximation on angle η. For the experiment, a new system of processing image data, calculating stresses and a back-reflection Laue camera for IP with a four-point-bending-device was manufactured. The stress applied mechanically with this device was compared to that obtained from the present method. The result showed that it was possible to obtain the stress with the same accuracy as that obtained by the sin2φ method. The advantage of this method is that one can obtain all three components of the stress in a plane stress state from one diffraction ring with single incidence of X-ray beam.

Natural graphitization of anthracite: Experimental considerations

An anthracite coal (Romax = 5.27%, fixed carbon = 95.5%) was deformed in the steady state at various pressures, temperatures, and experimental configurations to assess the effects of stress, strain, and strain energy on graphitization. In simple shear tests, graphite first appears at temperatures as low as 600 °C and samples tested at 900 °C are predominately graphitized, as evident from optical microscopy, XRD, and transmission electron microscopy. The graphite is lamellar, has punctual hkl reflections or DebyeScherrer (hkl) rings (triperiodic order), and long stiff and stacked lattice fringes typical of well-crystallized graphite. No graphite was formed in either hydrostatic or coaxial tests (they remain porous and turbostratic), although increased orientation of the basic structural units (BSUs) and increase in size of molecular orientation domains (MOD), attributed to the coalescence of neighboring pore walls, is evident in some coaxial deformed samples. Micro-Raman spectroscopy of deformed samples indicates the ongoing presence of defects (band at 1350 cm −), even in samples that by XRD and TEM prove to be mainly graphite. Results of our experiments indicate the independence of stress and the dependence on strain and strain energy in the formation of graphite. Samples deformed in simple shear at 900 °C are more highly graphitized than a sample heated to 2800 °C (HTT) at ambient pressure. Simple shear tests, in particular, haveimparted strain energy resulting in rupturing of pore walls, flattening of pores, and mechanical rotation of stacks of basic structural units (BSUs). These processes facilitate preferred parallel orientation of pore walls, coalescence of pores and, thus, growth of aromatic sheets leading to the formation of graphite. We propose that a major component of the activation energy required for graphitization in our experiments and, by analogy in nature, is provided by strain energy. The occurrence of natural graphite in rocks that have never been subjected to temperatures in excess of about 300 °C may be accounted for by strain energy imparted during tectonic deformation.

Comment on ?effect of phosphorus content on the relative proportions of crystalline and amorphous phases in electroless NiP deposits?

In a recent paper, Kumar and Nair [1] presented a quantitative analysis of electroless Ni-P deposits with phosphorus concentrations between 4.35 and 9.10 wt %. They performed X-ray diffraction (XRD) experiments on their deposits and analysed the XRD profiles on the basis of a mixture of an amorphous Ni-P phase and fcc nickel. It is the aim of this paper to show that their analysis based only on these two phases is incomplete and incorrect. To show the presence of amorphous Ni-P and fcc nickel Kumar and Nair presented selected area electron diffraction (SAED) patterns of a crystalline phase and an amorphous phase. While the diffuse halo ring pattern shown in one of their micrographs is typical for an amorphous alloy, the spot pattern shown in the other micrograph was reported to indicate a [1 1 1] orientation of fcc nickel. There is, however, strong evidence .that the diffraction spot pattern shown by Kumar and Nair [1] does not show the [1 1 1] orientation of nickel but the [0 0 1] orientation of a well-known metastable hexagonal Ni3P phase. The diffraction pattern shown by Kumar and Nair [1] consists of strong diffraction spots and two weak Debye-Scherrer rings. The ratio of the spacings of these rings is identical to the ratio of the lattice spacings of the {1 11} and {200} lattice planes of an fcc lattice. If we assign these diffraction rings to nickel and use them to calibrate the micrograph, the d-values of the spot pattern can be determined. The d-values of some spots determined in this way and the corresponding values of the a-axis of a hexagonal crystal are listed in Table I. Within the uncertainty of our measurements, all d-values result in the same lattice parameter. Hexagonal Ni-P phases with nearly the same lattice parameter were found for chemically and electrolytically deposited amorphous Ni-P alloys after heat treatment between 270 and 400°C (a =0.672nm) [2], in crystallized thin (20-50nm) films of amorphous NislPx9 (a = 0.656 nm) [3], in the thin ( < 5 0 n m ) regions of melt-spun NislP19 , and in thin regions (< 50 nm) of a crystallized Ni69Cr14P17 alloy (a = 0.690 nm) [4]. Further evidence that the diffraction pattern shown by Kumar and Nair represents a hexagonal phase is given by a comparison with our own measurements on Ni69Cr14P17 , an alloy of similar composition. Selected area electron diffraction patterns of this material in the amorphous state and in thinned regions after heat treatment to 305 °C are shown in Fig. 1 and Fig. 2, respectively. Both patterns were taken with the same camera length printed at identical magnifications. By tilting of the specimen, the lattice parameters of this crystalline phase were determined to be a = 0.690 nm and c = 1.04 nm [4]. The similarity of these two micrographs with those published by Kumar and Nair for Ni-P alloys is evident and supports our assertion that the electron diffraction pattern in [1] represents that of a hexagonal Ni-P phase together with the