bluuebunny/crossref_metadata_2025_split huggingface dataset:
High Resolution Synchrotron X-Ray Diffraction Tomography of Polycrystalline Samples
Authors: Stock S. R. , Guvenilir A. , Piotrowski D. P. , Rek Z. U. 
Published: April 2011

AbstractThe macroscopic response of polycrystalline materials to loading depends on both the spatial distribution of strain and the variation of microtexture on the scale of 100 μm. Nondestructive measurements are needed if the three-dimensional evolution of strain is to be studied. This paper describes approaches for high resolution synchrotron polychromatic x-ray diffraction tomography of polycrystalline materials. Preliminary experiments are reported on partially cracked compact tension samples of Al-Li 2090 and on model samples of randomly-packed, millimeter-sized pieces of Si wafers. Polychromatic beams collimated to 100 μm diameter have been used, and the distribution of diffracted intensity has been collected on high resolution x-ray film as well as on image storage plates. The depths of diffracting volume elements are determined from the changes in the spatial distribution of diffracted intensity with varying sample to detector separation.
Dislocation Mobility in HCL-Doped Ice
Authors: Hu Xiaohong , Jia Kunlun , Liu Fuping , Baker Ian , Black David 
Published: April 2011

AbstractDislocation velocities have been measured in both lightly and heavily HCl-doped ice single crystals using synchrotron-based, monochromatic X-ray topography. In the temperature range −10°C to −30°C, a concentration of ˜1 × 10−6M was found not to affect the mobility of either 60° or screw basal dislocations, confirming the earlier observations of C. Shearwood and R. W. Whitworth [Philosophical Magazine A65, 1992, 85]. However, heavier doping (˜1.9 × 10−4M) increased the basal dislocation velocity, compared to pure ice, by a factor of 2.6 at −16.4°C.
Densification of Sio Gel Films by Synchrotron Radiation and its Dependence on Photon Energy
Authors: Imai Hiroaki , Awazu Koichi , Yasumori Masaru , Hirashima Hiroshi , Onuki Hideo 
Published: April 2011

AbstractThe interaction of synchrotron radiation (SR) emitted from a polarizing undulator with SiO2 gel films was investigated by ellipsometry and infrared spectroscopy. The photon energy in SR was varied in the range of 6.4−17.8 eV using an Onuki-type undulator in order to study the energy dependence of the interaction. We found that an increase of refractive index, a decrease of thickness of the films and a loss of OH groups were induced by photons with energies above ˜9 eV although any changes were not observed with photons below ˜7 eV. These results suggest that SiO2 gel films are densified through electronic processes stimulated by the energetic photons.
Magnetic X-Ray Circular Dichroism in Nickel-Gold Multilayers
Authors: Jankowski A. F. , Waddill G. D. , Tobin J. G. 
Published: April 2011

AbstractMagnetic circular dichroism in x-ray absorption is used to investigate the in-plane, remnant magnetization of well-characterized Ni0.48/Au0.52 multilayers. Large superlattice strains are found in this multilayer system for samples with a 2nm layer pair spacing. A larger dichroism is found in the Ni 2p absorption edge for a 1.8nm than for a 4.4nm layer pair sample. The larger dichroism is consistent with a larger magnitude of in-plane strain for the Ni layers and a larger total magnetic anisotropy energy as previously shown from magnetization curves.
The Paramagnetic Correlation Length of Mn Thin Films
Authors: MclLroy D. N. , Dowben P. A. 
Published: April 2011

AbstractWe have utilized Ginzberg-Landau mean field theory to analyze the branching ratio and soft X-ray magnetic circular dichroism measurements of the L3 and L2 adsorption edges of thin Mn overlayers on ferromagnetic fcc Co(001) at room temperature. We have determined a short range magnetic correlation of 4.25Å and that the long range magnetic magnetic order has a decay length of 1.29Å. These results indicate that the first monolayer of Mn ferromagnetically couple with the Co substrate. The paramagnetic Mn layer exhibits short range magnetic order, but lacks long range magnetic order. Due to the exponential decrease of both the branching ratio and dichroism signals, we have concluded that the magnetization of the Mn overlayer is substrate induced.
The Mit Specular and Diffuse Neutron Reflectometer for the Investigation of Surfaces & Interfaces
Authors: Ku Chwen-Yuan , Zhou Xiao-Lin 
Published: April 2011

ABSTRACTA specular and diffuse neutron reflectometer was designed at the Massachusetts Institute of Technology nuclear reactor, MITR-II, and the description of the facility is presented in this paper. This reflectometer uses a horizontal sample geometry so that both solid and liquid samples can be measured. To minimize sample or beam motion and reduce measurement time, two neutron beams are extracted from the same beam port and are incident simultaneously on the same sample surface at grazing incident angles of 0.2 and 1.5 degrees, respectively. The reflected neutrons are detected by a linear position sensitive detector and energy-analyzed by the time-of-flight method. The reflection flight path is enclosed in an evacuated chamber to reduce background counts. The reflectometer performance is estimated as 0.004-0.33 Å-1 dynamic range, 5% Q resolution, 1-10-7 measurable specular reflectivity range, and a 4 orders of magnitude range in diffuse reflectivity counts. Diffuse reflectivity can be measured as a two-dimensional function of both the wavelength and the in-plane diffuse reflection angle. The instrument can be used to investigate a wide range of surface systems of condensed and soft-condensed matters.
Real Time Neutron Diffraction Experiments Using Bragg Edges
Authors: J Trela Walter , Meggers Kay , G Priesmeyer Hans 
Published: April 2011

ABSTRACTTime resolved phase transition and strain experiments have been performed on the millisecond time scale using a Bragg-edge transmission technique that has been developed at the Los Alamos National Laboratory. The precision with which lattice parameters can be determined from edge positions is sufficient to perform high-resolution strain measurements in uniaxial stress.
Deconvolution of Neutron Scattering Data from a Pulsed Spallation Source
Authors: Richardson J. W. , Birtcher R. C. , Chan S.-K. 
Published: April 2011

ABSTRACTDiffraction peak shapes generated from high purity, low strain uranium silicide powder have been used to deconvolute diffraction peaks from radiation damaged material. The deconvolution was based on the assumption that defect scattering near a strained Bragg peak could be represented as the summation of a series of discrete peaks with the same convoluted peak shape measured for unirradiated material in the same range of d-spacing. Discrete peaks were taken to have the same density as the measured time of flight data so that a deconvoluted scattering intensity was generated at each experimental point. This deconvolution technique accounts in a natural manner for peak asymmetries arising from the time structure of the neutron pulse shape and instrument broadening without arbitrary analytical functions and fitting parameters.
The Phase of Scattering Profiles & X-Ray/Neutron Reflectivity
Authors: Pershan P.S. 
Published: April 2011

ABSTRACTThe phase problem that troubles x-ray diffraction is also a problem for x-ray and neutron reflectivity; however, there are a range of small angles just beyond the critical angle for which the reflectivity contains information on the phase of the surface scattering amplitude. In principle this phase information can be used to determine the asymmetry of the normal gradient of the scattering amplitude density. We discuss here practical conditions under which this symmetry can, or cannot, be extracted from reflectivity data.
Analyzing Specular Reflectivities with Parametric B-Splines
Authors: Berk N. F. , Majkrzak C. F. 
Published: April 2011

ABSTRACTA method of using parametric B-spline curves to interpret neutron and x-ray specular reflectivity spectra is described. The introduction of parametric curves for scattering length density profiles greatly expands the function space accessible to low-dimensional representations but also requires means to restrict the space to physically acceptable functions. A practical fitting procedure is outlined, and two examples are shown.
The Determination of the Structure and Coverage of Nonionic Surfactant Monolayers at the Air-Water Interface Using Neutron Reflection Technique
Authors: Lu Jian R. , Thomas Robert K. 
Published: April 2011

ABSTRACTThe coverage and structure of the monododecyl ethers of oligoethylene glycols, C12Em where m = 2, 4, 6 and 8, adsorbed at the air-water interface have been studied by neutron reflection. At their c.m.c.s, the area per molecule is 33 ± 3 Å2 for C12E2, 44 ± 3 Å2 for C12E4 55 ± 3 Å2 for C12E6 and 62 ± 3 Å2 for C12E8. In terms of the width of a Gaussian distribution at 1/e of its height the thicknesses of the dodecyl chains are found to be constant at 16 ± 2 Å and those of the heads to vary from 11 to 19±2Å from m = 2 to 8. There is also found to be some overlap between the two chains at the interface.
An in Situ Small Angle Neutron Scattering Investigation of AgO.7Au0.3 Dealloying
Authors: Corcoran Sean G. , Wiesler David , Barker John , Sieradzki Karl 
Published: April 2011

ABSTRACTIn situ small angle neutron scattering (SANS) was used to characterize the formation of the random 3-dimensional porous structure created during the free corrosion of a Ag0.7Au0.3 alloy in concentrated HNO3. The evolution of the porosity was followed in situ for a period of 21 hours. The average ligament width evolved from a size of approximately 6 nm following only 7 minutes of dealloying to approximately 22.5 nm after 21 hours of de-alloying. Using a model developed by N.F. Berk (Phys. Rev. Lett., 58 (1987) 2718) for the scattering properties of random porous media, we were able to characterize the average ligament width distribution as a function of time. Our results represent the first in situ nanoscale characterization of the formation of 3-dimensional porosity in a corrosion system.
Internal Strain Measurement Using Pulsed Neutron Diffraction at Lansce
Authors: Goldstone J. A. , Bourke M. A. M. , Shi N. , Lujan Manuel 
Published: April 2011

ABSTRACTThe presence of residual stress in engineering components can effect their mechanical properties and structural integrity. Neutron diffraction in the only technique that can make nondestructive measurements in the interior of components. By recording the change in crystalline lattice spacings, elastic strains can be measured for individual lattice reflections. Using a pulsed neutron source, all lattice reflections are recorded in each measurement, which allows for easy examination of heterogeneous materials such as metal matrix composites. Measurements made at the Manuel Lujan Jr. Neutron Scattering Center (LANSCE) demonstrate the potential at pulsed sources for in-situ stress measurements at ambient and elevated temperatures.
Estimation of Residual Stress in Cold Rolled Iron-Disks Using Magnetic and Ultrasonic Methods and Neutron Diffraction Technique
Authors: Aksenov V.L. , Balagurov A.M. , Bokuchava G.D , Schreiber J. , Taran Frank Yu.V. 
Published: April 2011

ABSTRACTVariation of internal stress states in cold rolled sheet metal can essentially influence the result of forming processes. Therefore it is important to control the forming process by a practicable in line testing method. For this purpose magnetic and ultrasonic nondestructive methods are available. However, it is necessary to calibrate these techniques. This paper describes a first step of such a calibration procedure making use of the neutron diffraction method. On the basis of the diffraction results an assessment of the magnetic and ultrasonic methods for the estimation of residual stress in the cold rolled iron-disks was made. Reasonable measuring concepts for practical applications to forming processes with cold rolled sheet metal are discussed.
Elevated Temperature Neutron Measurements of Thermal Residual Stresses in a Sic Fibre Reinforced Al Alloy
Authors: Ceretti Monica , Kocsis M. , Lodini A. 
Published: April 2011

ABSTRACTThe main objective of the present investigation is to determine the evolution of residual stresses by neutron powder diffraction in an Al/SiC composite (Al 7075 reinforced by 27 vol.% SiC whiskers), originating from thermal treatment and mechanical loading. The results show that residual stresses in the matrix and in the reinforcement decrease in magnitude with increasing temperature and they reach the stress free state at the 'equivalent temperature'. As the temperature further increases, these stresses increase numerically in a reverse sense for both phases. The data obtained are analysed in terms of a simple model based on Eshelby's equivalent inclusion method.
Neutron Powder Diffraction Studies of Portland Cement and Cement Compounds
Authors: Berliner R. , Ball C. , West Presbury B. 
Published: April 2011

ABSTRACTNeutron powder diffraction data from phase-pure cement compounds has been used to develop structural models suitable for profile refinement of cements. These models were then applied to the determination of cement compound phase abundance in clinkers. This paper reports on the results of clinker phase analysis by powder neutron diffraction and summarizes the results of the refinements of neutron diffraction data from phase-pure cement compounds. The profile refinements provide generally good agreement with cement compound phase abundance measurements of NIST reference clinker specimens by chemical, optical and X-ray methods.
Using Quasielastic Neutron Scattering Techniques To Quantify Freezable Water In Portland Cement Paste
Authors: Gress D.L. , El-Korchi T. , Livingston R.A. , Neumann D.A. , Rush J.J. 
Published: April 2011

ABSTRACTQuasi-elastic neutron scattering provides detailed information of the atomic and molecular interactions responsible for a material's properties and is a direct and nondestructive method of measuring the motion of hydrogen. This technique was utilized to evaluate the state of water in a cementitious material. The relative amount of freezable water that existed in a saturated type I portland cement paste with water/cement ratios of 0.3, 0.4, and 0.5 was determined over a temperature ranging from +3 C to - 40 C. The amount of frozen water relative to the total water content was related to the water filled pore size predicted to be freezable at each temperature. The proportion of immobilized water increased for all water cement ratios gradually with decreasing temperatures below 0 C until most of the water was immobile at -40 C. The relative proportion of immobile water at 3 C was found to be inversely related to the water/cement ratio, which suggested a smaller fraction of large pores for small water/cement ratios. The findings also suggested the immobilization water was independent of water/cement ratio for pores smaller than 15nm.
Anisotropic Magnetization of HoNi2B2C
Authors: Canfield P.C. , Cho B.K. , Johnston D.C. , Hundley M.F. 
Published: April 2011

ABSTRACTAnisotropic, temperature dependent magnetization measurements on single crystals of HoNi2B2C indicate that there is a cascade of magnetic transitions in zero and low applied magnetic fields. Comparison of the temperature dependence of the specific heat and d(χT)/dT data shows a remarkable agreement in the low field limit, supporting the use of d(χT)/dT as a method of determining the magnetic transition temperatures as a function of applied field. The magnetic transition temperatures determined by this analysis are remarkably sensitive to the applied field and highly anisotropic. Comparison to similar data for ErNi2B2C show that the sensitivity and anisotropy are common features. These data emphasize the importance of anisotropic measurements of field dependent properties on single crystal samples, since the application of a magnetic field to a polycrystalline sample will effectively broaden the transition temperatures.
Polarized Neutron Glancing-Angle Diffraction Study of Magnetic Structure at the Y/Gd(0001) Interface
Authors: Ankner J.F. , Gallagher P.D. , Schreyer A. , Zhang H. , Majkrzak C.F. , Satija S.K. , Zabel H. , Matheny A. , Flynn C.P. 
Published: April 2011

ABSTRACTBy exciting diffraction in the Laue geometry by specularly reflected beams, penetrating x-rays and neutrons can be used to probe surface and interfacial atomic structure. We present the first such measurement utilizing polarized neutrons with both incident- and exit-angle resolution. We have observed the evolution of magnetic order by monitoring the in-plane (1010) Bragg peak from an epitaxially grown film consisting of 150 Å Y(0001) on 5000 Å Gd(0001). Magnetic scattering increases as the film is cooled from the Gd bulk Curie temperature (293K) to 100 K. The gross features of the data can be captured by a simple two-layer model, but sufficient disagreement remains that one may yet hope to extract non-trivial structure at the Y/Gd interface.
Field-Induced Decoupling of NiO-Magnetite Multilayers
Authors: Erwin R.W. , Borchers J.A. , Berry S.D. , Lind D.M. , Lochner E. , Shaw K.A. 
Published: April 2011

ABSTRACTNiO-magnetite multilayers exhibit long range antiferromagnetic order with the magnetite ferrimagnetic correlations confined to a single layer due to stacking faults of the spinel structure at the interfaces[l, 2, 3, 4]. A systematic study of the field-dependence of the interlayer coupling in a series of NiO-magnetite multilayers has been made using neutron diffraction. Both NiO and magnetite single thin films were included in the measurements for comparison. In the magnetite film, intensity changes with magnetic field are consistent with domain reorientation of the net ferrimagnetic moments, while in the NiO film there are essentially no intensity changes. There is no significant field dependence of the magnetic correlation lengths in either film. For multilayers where the ratio of NiO to magnetite layer thickness is far from unity, the field dependence approximates that of the bulk films. However, for a Fe3O4(68Å)|NiO(34Å) multilayer the NiO antiferromagnetic intensity decreases with increasing field, and there is a broadening of the NiO peak on the order of 30 percent. Concomitantly, the magnetite spins rotate collinear with the field, as expected, due to the net 4.2 μB moment per unit-cell. The NiO moments appear to rotate into domains where the direction of propagation of the ferromagnetic sheets is closer to the field direction.
Neutron Scattering at the High Flux Isotope Reactor at Oak Ridge National Laboratory
Authors: Yethiraj Mohana , Fernandez-Baca Jaime A. 
Published: April 2011

ABSTRACTSince its beginnings in Oak Ridge and Argonne in the late 1940's, neutron scattering has been established as the premier tool to study matter in its various states. Since the thermal neutron wavelength is of the same order of magnitude as typical atomic spacings and because they have comparable energies to those of atomic excitations in solids, both structure and dynamics of matter can be studied via neutron scattering. The High Flux Isotope Reactor (HFIR) provides an intense source of neutrons with which to carry out these measurements. This paper summarizes the available neutron scattering facilities at the HFIR.
Crystal Structure, Short-Range Oxygen Defects, and Water Adsorption in La- and Nd-Modified ZrO2
Authors: Loong C.-K. , Richardson J. W. , Iton L. E. , Ozawa M. 
Published: April 2011

ABSTRACTDoping Rare-earth (RE) elements to ZrO2 helps stabilize the cubic and tetragonal phases and improves resistance to thermal shock and sintering at high temperatures. Since a RE ion has a lower valency (3+) than Zr ion (4+), oxygen vacancies are formed to preserve electroneutrality. We have studied the crystal structure of La0.1Zro.9O1.95 and Nd0.1Zr0.9O1.95 by neutron diffraction and examined the associated oxygen defects by a Fourier transform of the filtered residual diffuse scattering. The hydration process was investigated by inelastic neutron-scattering measurements of the hydrogen vibrational density of states of the surface hydroxyl groups and physisorbed water on these fine powders. We compare the O-H stretch vibrations from samples with only surface hydroxyl groups to multilayer coverage of water molecules. The decreasing energies and increasing widths of the O-H stretch bands with increasing H2O coverage indicate the influence of hydrogen bonding on the motion of water molecules. Similar elastic and inelastic experiments were also performed on a high surface-area pure ZrO2 powder.
Neutron and Raman Spectroscopes of 134 and 134a Hydrofluorocarbons Encaged in Na-X Zeolite
Authors: Udovic T. J. , Nicol J. M. , Cavanagh R. R. , Rush J. J. , Crawford M. K. , Grey C. P. , Corbin D. R. 
Published: April 2011

ABSTRACTInelastic neutron scattering methods were used in conjunction with Raman spectroscopy to probe the vibrational density of states of the hydrofluorocarbons (HFCs) 134 (HF2C-CF2H) and 134a (F3C-CFH2) adsorbed in the cages of dehydrated Na-X zeolite. A comparison of the vibrational spectra of the encaged HFC species with those of their gas-phase analogs indicates that the HFCs adsorb nondissociatively at room temperature and are most likely associated with Na cations in the supercages at the SIII sites. Guest-host interactions are manifested by adsorption-induced perturbations of the gas-phase torsional and C-H stretching vibrations and the presence of additional features presumably due to low-energy whole-molecule vibrations and adsorbate-coupled zeolite framework vibrations. Moreover, although the 134 trans conformer is favored by 5 kJ/mole in the gas phase at 300 K, the gauche conformer seems to be more prevalent in the zeolite at this temperature and below. This suggests that a sizeable fraction of the Na-X adsorption sites provides a stabilizing configuration for the otherwise higher-energy gauche conformation, perhaps due to hydrogen-bonding interactions with the zeolite framework.
Wafer Curvature and Flatness Measurements Using The Magicmirror (Makyoh) Method
Authors: SzabÓ J. , Riesz Ferenc , SzentpÁli B. 
Published: April 2011

ABSTRACTA new method is presented for the measurement of the radii of curvature R of semiconductor wafers using the magic-mirror (Makyoh) technique. A flat mirror is placed beneath the sample, thus a second, “contour” image of the sample is formed beside the Makyoh image. From the ratio of the two image sizes, R can be determined using a set of reference curved mirrors. Model calculations show good agreement with the results. Other examples of assessing of the flatness of semiconductor samples are presented as well.
Critical Thickness for Strained Quantum Wires
Authors: Gosling T. J. , Freund L. B. 
Published: April 2011

ABSTRACTThe stability of strained quantum wires against the propagation of threading dislocations is considered, using a critical thickness criterion due to Matthews and Blakeslee that is extensively used for strained layers. Given first are results for the critical mismatch at which a buried wire of a given thickness becomes susceptible to degradation. It is found that a wire, once buried, is extremely stable, being able to support, without loss of coherency, around five times the lattice mismatch that can be supported by a buried strained layer of the same thickness. It is concluded that if a strained wire contains dislocations then those dislocations must have been introduced during its growth, when the top surface of the wire is exposed. To investigate this, the results of finite element calculations are presented that give the critical relationship between mismatch and thickness during the growth of a triangular quantum wire being deposited in a [110]-oriented V-groove in a patterned (001) substrate. The results may be approximately expressed through an expression of the same form as that derived by Matthews and Blakeslee for a strained layer, but with modified coefficients obtained via the finite element analysis. Contact is made with the limited experimental evidence available.