bluuebunny/crossref_metadata_2025_split huggingface dataset:
X-Ray Absorption Studies of Uranium Sorption on Mineral Substrates
Authors: Hudson Eric A. , Terminello Louis J. , Viani Brian E. , Reich Tobias , Bucher Jerome J. , Shuh David K. , Edelstein Norman M. 
Published: April 2011

AbstractUraniumL3-edge x-ray absorption spectra have been measured for uranium-mineral sorption systems. An expansible layer silicate, vermiculite, was treated to obtain a collapsed phase, thereby limiting access to the interior cation exchange sites. Samples were prepared by exposing the finely powdered mineral, in the natural and modified form, to aqueous solutions of uranyl chloride. EXAFS spectra of the encapsulated samples were measured at the Stanford Synchrotron Radiation Laboratory. Results indicate that the uranyl ion possesses a more symmetric local structure for the natural vermiculite than for the collapsed form, suggesting structural differences between uranyl species within the interlayer regions of vermiculite and on the external surfaces.
Element Specific Vector Magnetometry (Esvm) Via Soft X-Ray Magnetic Circular Dichroism
Authors: Chakarian V. , Lin H.-J. , Idzerda Y. U. , Chaban E. E. , Meigs G. , Park J.-H. , Gutierrez C. J. , Prinz G. A. , Chen C. T. 
Published: April 2011

AbstractSoft X-Ray Magnetic circular dichroism (SX-MCD) can be used to obtain element-specific magnetic hysteresis curves and to elucidate the two- and three-dimensional magnetization reversal processes for each constituent magnetic element of a heteromagnetic system. As a demonstration, two systems which exhibit in-plane magnetization reversal are studied: a thin Fe (100) singlecrystal film and a Fe1-xCox/Mn/Fel-xCox trilayer. The results for both systems show that the magnetic moment vector reverses via a combination of coherent rotation toward the nearest in-plane magnetically easy axis followed by the formation of orthogonal <100> domains which rapidly sweep across the sample. In the case of the trilayer, the moment reversal process is significantly more complex due to a strong ∼90° coupling between the magnetic moments of the two FeCo layers. By using element-specific vector magnetometry (ESVM), the details of this reversal process are revealed. Furthermore, the results of the SX-MCD for Mn show that Mn possesses a ferromagnetically aligned net magnetic moment which depicts a 2D magnetization behavior different than that for either Fe or Co.
Nonlinear Neutron and X-Ray Reflectance for Surface Films
Authors: Zhou Xiao-Lin 
Published: April 2011

ABSTRACTThis paper presents an analysis of the relationship between Parratt's recurrence formula and several existing analytical formulations for the neutron and x-ray reflectance of a surface film. In particular, it was shown that the Born approximation and the weighted-superposition approximation (WSA) for the neutron and x-ray reflectance can both be derived directly from Parratt's recurrence formula. It was also shown that the well-known nonlinear differential equation for the reflectance at an arbitrary point inside a film can be obtained from Parratt's recurrence formula and the WSA was an approximate solution to this equation. Finally, the nonlinearity in the WSA was discussed through a comparison between the Born approximation and the WSA. It was pointed out that the exponential factor in the WSA correctly accounted for both the phase shift effect due to the scattering length density of the film and the amplitude attenuation effect due to evanescence.
In Situ Neutron Reflection from Electrochemically Produced Conducting Polymeric Systems
Authors: Roser Stephen J. , Hillman A.Robert , Richardson Robert M. 
Published: April 2011

ABSTRACTThe technique of neutron reflection has been developed by us to investigate a variety of thin film electrochemical systems, including polymer bilayers, matrix-trapped active biological molecules and inorganic oxides. Measurements have been made with the electrodes in contact with the electrolyte, allowing studies of structural rearrangements after polymerisation, redox cycling and solvent exchange have taken place. In this paper we demonstrate these possibilities for the technique by concentrating on thin layers of an electrochemically produced polymer. polybithiophene.
Neutron Reflection Measurement of Near-Surface Structural Change in an Oil-Water-Surfactant System
Authors: Jeng U. , Esibov L. , Crow M. L. , Steyerl A. 
Published: April 2011

ABSTRACTThe interfacial characteristics of an oil-water-surfactant sample were studied using the thermal neutron reflectometer at the Rhode Island Nuclear Science Center (RINSC). The sample was a mixture of deuterated octane with H2O and non-ionic surfactant (C10E4), spread onto an H2O substrate. A mixture of low surfactant concentration was used so that it could demix into a lamellar oil-water structure, stabilized by a monolayer of surfactant intervening at each oil-water interface. The reflectivity data showed a clearly visible difference between 25.2° C and 30.2°C, indicating that the significant increase of interfacial tension between these two temperatures induced a structural transition.
Reflectivity Studies on Adsorbed Block Copolymers Under Shear
Authors: Smith Gregory S. , Wages Stephen , Baker Shenda M. , Toprakcioglu Chris , Hadziioannou George 
Published: April 2011

ABSTRACTWe report neutron reflectivity data on (poly)styrene-(poly)ethylene oxide (PS-PEO) diblock copolymers adsorbed onto quartz from the selective solvent deuterated cyclohexane (a non-solvent for PEO and a poor solvent for PS). The PEO "anchor block" adsorbs strongly to form a thin layer on the quartz substrate, while the PS chains dangle into the solvent. We find that under static conditions the density profile of the PS block in a poor solvent can be well described by a Schultz function which is indicative of a polymer "mushroom." Furthermore, we have studied the same system under shear at shear rates from 0-400s-l. We find that there is a dramatic increase in the thickness of the PS layer under shear in cyclohexane and that the relaxation time from the shear-on profile back to the static profile is on the order of several days.
Effects of Shear on the Structures in a System of Small Rodlike Micelles
Authors: Butler Paul D. , Magid L.J. , Hamilton William A. , Kreke P.J. , Hayter Johnb. 
Published: April 2011

ABSTRACTWe have used small angle neutron scattering (SANS) to study solutions of cetyltrimethylammonium 2,6-dichlorobenzoate (2,6) at rest and as a function of shear. These solutions are Newtonian, and up to a concentration of at least 100mM contain spherical micelles. Comparison with viscoelastic solutions of the closely related, and much studied, cetyltrimethylammonium 3,5-dichlorobenzoate (3,5) is made. While spheres are not expected to align under shear, a shear induced sphere to rod transition has been postulated for this system. In the results presented here, no shear induced sphere to rod transition was observed even at the highest accessible shear rate. Addition of sufficient supporting electrolyte (up to 1M NaCl) does cause such a transition in the quiescent solution. Hoffmann et al. have seen what they refer to as the formation of a shear induced structure (SIS or type II micelles) on similar systems where short rods form in the absence of supporting electrolyte. Shearing of the salted system produces rapid though not spectacular alignment, with no evidence of a SIS forming.
SANS Study of Chirality and Order in Liquid Crystalline Cellulose Suspensions
Authors: Orts W.J. , Revol J.-F. , Godbout L. , Marchessault R.H. 
Published: April 2011

ABSTRACTSmall angle neutron scattering, SANS, was used to describe the magnetic alignment and in situ shear ordering of polyelectrolytic, liquid crystalline cellulose microfibrils in aqueous (D2O) suspension. In a 2.4 Tesla magnetic field, microfibril suspensions exhibit anisotropic chiral nematic (cholesteric) ordering in which the distance between nematic planes along the cholesteric axis is shorter than between rods within a nematic plane. This is consistent with the hypothesis that cellulose microfibrils are helically twisted rods. During shear, the SANS interference peaks perpendicular to the flow direction sharpen with increasing shear rate. Yet, the highest degree of alignment (for microfibrils with axial ratios of ~45) was observed a short period after the cessation of shear flow.
Dissolution and Growth of Precipitates Under Electron Irradiation in an Al-11.8 at % Zn Alloy by Small Angle Neutron Scattering.
Authors: Baig M.R. 
Published: April 2011

ABSTRACTDissolution and growth of precipitates in a room temperature aged Al-11.8 at % Zn alloy have been studied under electron irradiation using small angle neutron scattering (SANS). A series of electron irradiations were performed on each sample and SANS measurements were made on each irradiation. In general for low doses the results show an initial decrease in the magnitude of the scattering, but associated with an increase in the precipitate size. This is followed on prolonged irradiation by an increase in the magnitude of the scattering with a continued increase in precipitate size. It is believed, that at low doses some precipitate grow in size but others may dissolve in the matrix, which then becomes supersaturated. With the enhanced rate of diffusion as a result of the irradiation, the remaining precipitates grow rapidly. As the supersaturation reduces, a coarsening mechanism takes over, via a radiation enhanced diffusion mechanism.
Internal Strains Of A Creep Deformed Single Crystal Nickel-Based Superalloy
Authors: Glatzel Uwe , MÜller Andreas 
Published: April 2011

ABSTRACTNeutron scattering experiments have been carried out with undeformed and creep deformed samples of the superalloy CMSX-4. From the measured constrained misfit data, obtained from different reflecting planes with respect to the external load axis, two strain tensors for horizontal and vertical matrix plates can be extracted.A careful data analysis is necessary since the technical manufactured single crystals show a mosaic spreading of 0.5° and the wavelength spreading of the incident neutron beam, Δλ/λ is about 410-3 This is in the same range as the unknown constrained misfit quantities δc. A method has been developed which allows a calculated intensity distribution to be fitted to the measured one.
Plastic Strain Estimation from Neutron Bragg Peaks
Authors: Swallowe G.M. , Osborn J.C. , Lukas P. , Mikula P. , Vrana M. 
Published: April 2011

ABSTRACTThis paper describes experiments carried out at three neutron sources in which Bragg reflection peak profiles of samples of copper, nickel and iron were investigated as a function of plastic strain. All peaks were well fitted by Gaussian functions for true strains of upto 0.25. Peak widths of all samples were found to be simple power law functions of strain and independent of measurement direction. This suggests that use could be made of data gathered in standard residual elastic stress measurements to simultaneously estimate plastic strains.
Small Angle Neutron Scattering Studies of Asphaltic Materials
Authors: Storm D. A. , Sheu E. Y. 
Published: April 2011

ABSTRACTAsphaltic materials are used as binders for road asphalts. Such materials have been found to contain a dispersed phase of colloidal particles in the size range of 50-100 Å, according to small angle X-ray scattering(SAXS) techniques. The presence of this dispersed phase has a significant influence on the rheological properties of these materials. These colloidal particles can be isolated by precipitation with heptane, and so they are associated with the well-known asphaltene solubility class in some manner. In this work we review previously published results that suggest that at least part of the asphaltenes are surface active agents in certain solvents such as toluene, or pyridine, and can form micelles in these solvents. Small angle neutron scattering (SANS) indicates the micelles are spherical with average radii in the 50-100 Å range. There is a polydispersity of sizes. The micelles do not grow in these solvents with increasing concentration in the range of 1-10 wt.%, nor do they dissociate on heating to ~ 170 °C. At higher concentrations, however, a more complicated structure develops. The micelles aggregate to form a large cluster composed of micelles. The fractal dimension of the clusters is found to be 1.8.
Application of Neutron Scattering Methods to Cementitious Materials
Authors: Livingston Richard A. , Neumann D.A. , Allen Andrew , RUSH J.J. 
Published: April 2011

ABSTRACTA major part of the infrastructure is constructed of Portland cement concrete. Nevertheless, many aspects of this material are still not well understood. The main constituent of hydrated Portland cement is a hydrous gel, with significant features on the nanometer scale, that tends to be unstable under vacuum. It is difficult to investigate with conventional instrumental methods. Neutron scattering methods possess unique capabilities to characterize cementitious materials and thus to resolve a number of long-standing issues. Among the applications, quasi-elastic neutron scattering is used to follow non-destructively the progress of the main hydration reaction and to determine the distribution of the water content among the various states: i.e. free, chemically bound, or physically trapped in the gel network. Quasi-elastic neutron scattering can also be applied to investigate the process of ice formation in the pore spaces. Neutron diffraction has been used to observe the development of hydrous phases as a function of time. Small-angle neutron scattering (SANS) proves to be well-suited to the characterization of the microstructure. This method is being used to determine the surface and volume fractal dimensions of the gel as a function of time and as a function of additives such as fly ash or silica fume. In addition, SANS has been applied to characterize silica aggregates for the potential for deleterious reactions in highly alkaline concrete. Aside from their application to specific problems, the combination of neutron scattering techniques is leading to new interpretation of the fundamental structure of the Portland cement gel.
Small-Angle Neutron Scattering from Hydrated Cement Pastes
Authors: Aldridge L.P. , Bertram W.K. , Sabine T.M. , Bukowski J , Young J.F. , Heenan R.K. 
Published: April 2011

ABSTRACTSmall angle neutron scattering (SANS) has been used to examine hydrated cement pastes with water-to-cement ratios between 0.25 and 0.8 and cured for 28 days. Various methods of data analysis are applied to the pastes.Fitting the entire SANS spectra of the hydrated cement paste has suggested that there are two scattering entities in the paste. There is some evidence to suggest that one scattering entity is globules of calcium silicate hydrate formed in the hydrated paste.
A Method for Interpreting Small Angle Neutron Scattering Data from Quasi-Spherical Objects
Authors: Sabine T.M. , Bertram W.K. , Aldridge L.P. 
Published: April 2011

ABSTRACTSmall angle scattering data are traditionally interpreted in terms of scattering patterns at the Porod and the Guinier limits. It is difficult to fit the entire scattering pattern to account for scattering from spheres because Rayleigh's formula contains oscillatory terms which are smeared out in practice by perturbations in the sizes of the scattering agents.It is proposed that a Lorenztian type function be used instead of Rayleigh's function. By using this equation it is possible to fit the entire small angle scattering pattern and obtain the correct forms of the Guinier and Porod limits.The effects of correlation and multiple scattering are also explored.
Neutron scattering of H.T.S.C. Materials : Zn substituted Versus Pure YBCO, Nuclear and Magnetic Structures, Spin Excitations.
Authors: Collin G. , Villeneuve R. , Sidis Y. , Bourges Ph. , Hennion B. , Onufrieva F. , Gillon B. , Bouree F. , Mirebeau I. , Mendels P. , Alloul H. , Marucco F. , Schweiss P. 
Published: April 2011

ABSTRACTThe Zn substitution on Cu(2) sites in YBa2(Cu1-yZny)3O6+x materials is most probably limited to yzn ≈ 0.04. Results of neutron diffraction associated with NMR and μ+SR results reveal ; i) a lowering of TN in the pure AF region x≤0.20 due to a dilution effect of the antiferromagnetic lattice by a static non magnetic impurity, ii) the existence of a non conventionnal magnetic behavior within the intermediate region x≥0.35 characterized by an unusual temperature dependance of magnetic intensities, a reentrancy and the existence of diffuse magnetic scattering (this region is much broader in oxygen composition for Zn-doped than for pure YBCO),iii) an unusual spin dynamics in the "doped A-F phase" which corresponds to a coupling of magnetic excitations to the hole dynamics.
Small-Angle Neutron Scattering from YBa2Cu3O7 and Bi2Sr2CaCu2O8 Near the Critical Temperature
Authors: Frost C. D. , Squires G.L. 
Published: April 2011

ABSTRACTOne of the 30 meter small-angle neutron scattering spectrometers at NIST has been used to measure the scattering from YBa2Cu3O7 and Bi2Sr2CaCu2O8 at a range of temperatures from 35 K to 135 K with wavevector transfers Q from 0.01 Å-1 to 0.08 Å-1. Considerable attention was paid to sample preparation in order to reduce the background scattering from crystalline defects and stoichiometric variations in the sample. For both materials, the difference in the differential scattering cross-sections at the critical temperature Tc and at temperatures of Tc ± 20 K showed considerable structure in Q, corresponding to spatial variations in the neutron scattering potential with Fourier components of wavelength of the order of 100 Å.
The Oxidation State and Magnetic Behaviour of Tb in High-Tc Related Materials
Authors: Soderholm L. , Staub U. , Skanthakumar S. , Antonio M. R. 
Published: April 2011

ABSTRACTL3-x-ray absorption spectroscopy is used together with inelastic neutron scattering and magnetic susceptibility measurements to characterize the Tb oxidation state and bonding in the high-Tc related materials Y1-xTbxBa2Cu3O7 and Pb2Sr2TbCu3O8. The Tb is found to be essentially trivalent in both compounds with no indications of significant hybridization. However, there is evidence of significant Tb-Tb magnetic interactions in Pb2Sr2TbCu3O8 that persist to temperatures much higher than the Tb long-range ordering temperature.
Structural Chemistry of Some Phases in The YC-Ni-B System
Authors: Chakoumakos B. C. 
Published: April 2011

ABSTRACTNiB, monoclinic Ni4B3, Ni2B and Ni3B were prepared by arc-melting and their roomtemperature crystal structures were refined by Rietveld analysis of neutron powder diffraction data. The NiB refinement is altogether new data. Although the B atoms in NiB form characteristic zigzag chains, the primary coordination of each atom by atoms of the other kind is similar and distinctively sevenfold, with one short (2.117 Å), two intermediate (2.152 Å), and four long (2.163 Å) bonds. Other samples with stoichiometries (YC)nNi2B2, n = 3, 4, did not yield single-phase material, but both x-ray and neutron powder diffraction suggest that the n = 4 structure is present in both of these samples. Phase-pure samples of these homologues may require non-stoichiometry and a more controlled thermal history than is attainable by arc melting.
The Ferroelastic Transformation in Yttria- and Ceria-Stabilised Tetragonal Zirconia Via Neutron Diffraction
Authors: Cain Markys G. , Lewis Mike H. , Backshall Matthew , Bennington Stephen M. , Hull Steve 
Published: April 2011

ABSTRACTNeutron diffraction studies of tetragonal zirconia polycrystals (TZP) subjected to a varying applied uniaxial stress indicates that a ferroelastic crystalline transformation occurs within the bulk of the material. The critical coercive stress was determined to be (1.65±0.03) GPa for yttria stabilised TZP and (0.70±0.05) GPa for ceria stabilised TZP. The results agree well with previous reports concerning the ferroelasticity of tetragonal zirconia, and provide direct evidence indicating that the anomalies observed using the first X-ray diffraction studies originate from the bulk of the ceramic and not solely from the surface. The preferred orientation observed in the tetragonal crystallites was measured as a function of applied uniaxial stress and interpreted via a resolved stress criterion. It is believed that the ferroelastic transformation can act as an energy absorbing mechanism and hence toughen zirconia or ceramics containing dispersed zirconia.
Static and Dynamic Displacements in α-Phase FeCr
Authors: Robertson J. L. , Reinhard L. , Neumann+* D. A. , Moss#* S. C. 
Published: April 2011

ABSTRACTA single crystal of α-Fe0.47Cr0.53 was annealed at 1100K, 5K above the a-phase transition temperature, for four days and then water quenched. A detailed investigation using X-ray synchrotron radiation was previously carried out to study the short-range order and static displacements in this alloy. The phonon dispersion curves, studied here by inelastic neutron scattering, appear typical of bcc alloys and the phonon groups are observed to be significantly broadened in the vicinity of the dip at ξ=2/3 in the longitudinal [ξ ξ ξ] phonon dispersion. In this paper we explore the possibility that nearly random concentration fluctuations and an extremely small difference in the atomic sizes, together with an appropriate lattice response function, can nonetheless produce elastic diffuse scattering indicative of a new phase.
Preparation of Long-Alkane Monola Yers Adsorbed On Exfoliated Graphite For Neutron Diffraction Studies
Authors: Herwig K. W. , Matthies B. , Taub H. 
Published: April 2011

ABSTRACTA classic problem in polymer science is the preferential adsorption at a solid interface of one polymer species from a multi-component fluid mixture. Prototype systems for studying this selective adsorption process are solutions consisting of alkane molecules of two different lengths in the presence of a solid interface. Before neutron diffraction could be used to probe structural questions related to the selective adsorption process in such systems, a significant effort was required to develop methods for fabricating suitable samples. We describe techniques for preparing samples of long-alkane monolayers adsorbed on exfoliated graphite by adsorption from solution and by deposition from the vapor phase.
Polarized Cathodoluminescence Study of (InP)2/(GaP)2 Bilayer Superlattice Structures
Authors: Tang Y. , Rammohan K. , Lin H.T. , Rich D.H. , Colter P. , Vernon S.M. 
Published: April 2011

ABSTRACTLinearly polarized cathodoluminescence (LPCL) imaging and spectroscopy techniques have been employed to examine the optical properties and homogeneity of (InP)2/(GaP)2 bilayer superlattice (BSL) structures which exhibit a lateral composition modulation that leads to the formation of quantum wires. LPCL spectra were measured for various temperature and electron beam excitation densities. The magnitude of the polarization anisotropy and spectral lineshape are found to depend sensitively on the excitation conditions, revealing large nonlinear optical effects in these samples. CL images reveal that defects in the bilayer superlattice structure originate from the GaAs substrate or the initial stages of InGaP growth.