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X-Ray Diffraction Study of the Internal Structure of Supercooled Water

Description: From Summary: "A Bragg X-ray spectrometer equipped with a volume-sensitive Geiger counter and Soller slits and employing filtered molybdenum Ka radiation was used to obtain a set of diffracted intensity curves as a Punction of angle for supercooled water. Diffracted intensity curves in the temperature region of 21 to -16 C were obtained. The minimum between the two main diffraction peaks deepened continuously with lowering temperature, indicating a gradual change in the internal structure of the water. No discontinuity in this trend was noted at the melting point. The internal structure of supercooled water was concluded to become progressively more ice-like as the temperature is lowered."
Date: October 1951
Creator: Dorsch, Robert G. & Boyd, Bemrose
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department

Nondestructive Measurement of Residual and Enforced Stresses by Means of X-Ray Diffraction 1: Correlated Abstract of the Literature

Description: Note presenting a study of the stress measurements by means of the x-ray diffraction method, which have found considerable application in solving both commercial and laboratory problems. Two problems related to x-ray diffraction are studied and a literature review is conducted.
Date: September 1945
Creator: Sachs, George; Smith, Charles S.; Lubahn, Jack D.; Davis, Gordon E. & Ebert, Lynn J.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department

X-Ray Diffraction Investigation of Minor Phases of 20 High-Temperature Alloys

Description: Report presenting the use of x-ray diffraction methods to identify the minor phases present in 20 high-temperature alloys in current use. The minor phases were noted in seven of the 20 alloys. A description of the relation of the alloys to one another and their chemical properties are provided.
Date: July 1948
Creator: Rosenbaum, B. M.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department

Surprising Coordination Geometry Differences in Ce(IV)- and Pu(IV)-Maltol Complexes

Description: As part of a study to characterize the detailed coordination behavior of Pu(IV), single crystal X-ray diffraction structures have been determined for Pu(IV) and Ce(IV) complexes with the naturally-occurring ligand maltol (3-hydroxy-2-methyl-pyran-4-one) and its derivative bromomaltol (5-bromo-3-hydroxy-2-methyl-pyran-4-one). Although Ce(IV) is generally accepted as a structural analog for Pu(IV), and the maltol complexes of these two metals are isostructural, the corresponding bromomaltol complexes are strikingly different with respect to ligand orientation about the metal ion: All complexes exhibit trigonal dodecahedral coordination geometry but the Ce(IV)-bromomaltol complex displays an uncommon ligand arrangement not mirrored in the Pu(IV) complex, although the two metal species are generally accepted to be structural analogs.
Date: February 12, 2008
Creator: Laboratory, Lawrence Berkeley National; Raymond, Kenneth; Szigethy, Geza; Xu, Jide; Gorden, Anne E.V.; Teat, Simon J. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department

Incorporating Electrochemistry and X-ray Diffraction Experiments Into an Undergraduate Instrumental Analysis Course

Description: Experiments were designed for an undergraduate instrumental analysis laboratory course, two in X-ray diffraction and two in electrochemistry. Those techniques were chosen due their underrepresentation in the Journal of Chemical Education. Paint samples (experiment 1) and pennies (experiment 2) were characterized using x-ray diffraction to teach students how to identify different metals and compounds in a sample. in the third experiment, copper from a penny was used to perform stripping analyses at different deposition times. As the deposition time increases, the current of the stripping peak also increases. the area under the stripping peak gives the number of coulombs passed, which allows students to calculate the mass of copper deposited on the electrode surface. the fourth experiment was on the effects of variable scan rates on a chemical system. This type of experiment gives valuable mechanistic information about the chemical system being studied.
Date: May 2012
Creator: Molina, Cathy
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries

Nondestructive Measurement of Residual and Enforced Stresses by Means of X-Ray Diffraction 2: Some Applications to Aircraft Problems

Description: Note presenting tests on the use of x-ray diffraction methods for determining surface stress distributions in notched tensile bars and in the vicinity of a welded joint in aircraft steel tubing. Data on the effects of stress and degree of notching on the principal stresses and stress-concentration factors for flat notched tensile-test specimens were obtained.
Date: November 1945
Creator: Sachs, George; Smith, Charles S.; Lubahn, Jack D.; Davis, Gordon E. & Ebert, Lynn J.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department

X-Ray Diffraction by Bent Crystal Lamellae

Description: Note presenting an overview of bent crystal lamellae, which may consist of individual blocks, spaced somewhat irregularly and with a mutual angular disorientation. In this case, the x-ray intensities of the individual blocks will simply be added. A study was done to determine if there was any difference between diffraction by a bent lamella and by an array of irregularly spaced blocks arranged in a circle.
Date: September 1951
Creator: Ekstein, Hans
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department

Table of Interplanar Spacings for Crystal-Structure Determinations by X-Ray Diffraction With Molybdenum, Copper, Cobalt, Iron, and Chromium Radiations

Description: "For a simple diffraction pattern, the time required to calculate interplanar distances from measurements of the pattern is not excessive. If more than a few lines are present, however, or if several patterns are to be studied, it is very advantageous to have available a table giving interplanar spacings directly in terms of the linear measurements made on the film of the lines appearing on the diffraction pattern. The preparation of the table given here was undertaken when the expansion of research activities involving X-ray diffraction techniques indicated that such a table would greatly decrease the time required to analyze diffraction patterns" (p. 1).
Date: October 1945
Creator: Kittel, J. Howard
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department

Multiple-Film Back-Reflection Camera for Atomic Strain Studies

Description: Note presenting the application of a new back-reflection X-ray diffraction technique, which was developed through use of a multiple-film camera containing four parallel films separated by known distances. Diffraction angles were calculated by determining the change in radius of the diffraction ring from film to film. A multiple-film-technique analysis and a conventional-method analysis of the same X-ray strain data indicated that a more detailed analysis of atomic strain could be obtained from the multiple-film technique.
Date: November 1950
Creator: Marmo, Anthony B.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department

X-ray diffraction characterization of suspended structures for MEMS applications

Description: Mechanical stress control is becoming one of the major challenges for the future of micro and nanotechnologies. Micro scanning X-ray diffraction is one of the promising techniques that allows stress characterization in such complex structures at sub micron scales. Two types of MEMS structure have been studied: a bilayer cantilever composed of a gold film deposited on poly-silicon and a boron doped silicon bridge. X-ray diffraction results are discussed in view of numerical simulation experiments.
Date: September 15, 2005
Creator: Goudeau, P.; Tamura, N.; Lavelle, B.; Rigo, S.; Masri, T.; Bosseboeuf, A. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department

Crystal Splitting in the Growth of Bi2S3

Description: Novel Bi{sub 2}S{sub 3} nanostructures with a sheaf-like morphology are obtained via reaction of bismuth acetate-oleic acid complex with elemental sulfur in 1-octadecence. We propose these structures form by the splitting crystal growth mechanism, which is known to account for the morphology some mineral crystals assume in nature. By controlling the synthetic parameters, different forms of splitting, analogous to observed in minerals, are obtained in our case of Bi{sub 2}S{sub 3}. These new and complex Bi{sub 2}S{sub 3} nanostructures are characterized by TEM, SEM, XRD and ED.
Date: June 15, 2006
Creator: Tang, Jing & Alivisatos, A. Paul
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department

Effects of Fe spin transition on the elasticity of (Mg,Fe)O magnesiow�ustites and implications for the seismological properties of the Earth's lower mantle

Description: High-pressure x-ray diffraction of (Mg{sub 0.8}Fe{sub 0.2})O at room temperature reveals a discontinuity in the bulk modulus at 40 ({+-}5) GPa, similar pressure at which an electronic spin-pairing transition of Fe{sup 2+} is also observed. In the x-ray diffraction experiments the transition is completed only at 80 GPa, possibly reflecting lack of equilibration. Combining recent measurements, we document anomalies in the compression curve of Mg-rich magnesiowuestites that are manifestations of the spin transition. The best fit to a third order Birch-Murnaghan equation for the low-spin phase of magnesiowuestite with 17-20 mol% FeO yields bulk modulus K{sub T0} = 190 ({+-}150) GPa, pressure derivative ({partial_derivative}K{sub T}/{partial_derivative}){sub T0} = 4.6 ({+-}2.7) and unit-cell volume V{sub 0} = 71 ({+-}5) {angstrom}{sup 3}, consistent with past estimates of the ionic radius of octahedrally-coordinated low-spin Fe{sup 2+} in oxides. A sharp spin transition at lower-mantle depths between 1100 and 1900 km (40-80 GPa) would cause a unit-cell volume decrease ({Delta}{nu}{sub {phi}}) of 3.7 ({+-}0.8) to 2.0 ({+-}0.2) percent and bulk sound velocity increase ({Delta}{nu}{sub {phi}}) of 8.1 ({+-}6-1.7) percent ({nu}{sub {phi}} = {radical}K{sub s}/{rho}). Even in the absence of a visible seismic discontinuity, we expect the Fe-spin transition to imply a correction to current compositional models of the lower mantle, with up to 10 mol percent increase of magnesiowuestite being required to match the seismological data.
Date: August 29, 2006
Creator: Speziale, S; Lee, V E; Clark, S M; Lin, J F; Pasternak, M P & Jeanloz, R
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department

Phase Identification of Seismic Borehole Samples

Description: This report documents the phase identification results obtained by x-ray diffraction (XRD) analysis of samples taken from borehole C4998 drilled at the Waste Treatment Plant (WTP) on the Hanford Site (REF). XRD samples were taken from fractures and vesicles or are minerals of interest at areas of interest within the basalt formations cored. The samples were powder mounted and analyzed. Search-match software was used to select the best match from the ICDD mineral database based on peak locations and intensities.
Date: November 1, 2006
Creator: Crum, Jarrod V. & Riley, Brian J.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department

Amorphous clusters in Co implanted ZnO induced by boron pre-implantation

Description: We demonstrate the formation of superparamagnetic/ferromagnetic regions within ZnO(0001) single crystals sequently implanted with B and Co. While the pre-implantation with B plays a minor role for the electrical transport properties, its presence leads to the formation of amorphous phases. Moreover, B acts strongly reducing on the implanted Co. Thus, the origin of the ferromagnetic ordering in local clusters with large Co concentration is itinerant d-electrons as in the case of metallic Co. The metallic amorphous phases are non-detectable by common X-ray diffraction.
Date: February 9, 2009
Creator: Potzger, K.; Shalimov, A.; Zhou, S.; Schmidt, H.; Mucklich, A.; Helm, M. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department

Three-Dimensional Imaging of Nanoscale Materials by Uisng Coherent X-Rays

Description: X-ray crystallography is currently the primary methodology used to determine the 3D structure of materials and macromolecules. However, many nanostructures, disordered materials, biomaterials, hybrid materials and biological specimens are noncrystalline and, hence, their structures are not accessible by X-ray crystallography. Probing these structures therefore requires the employment of different approaches. A very promising technique currently under rapid development is X-ray diffraction microscopy (or lensless imaging), in which the coherent X-ray diffraction pattern of a noncrystalline specimen is measured and then directly phased to obtain a high-resolution image. Through the DOE support over the past three years, we have applied X-ray diffraction microscopy to quantitative imaging of GaN quantum dot particles, and revealed the internal GaN-Ga2O3 core shell structure in three dimensions. By exploiting the abrupt change in the scattering cross-section near electronic resonances, we carried out the first experimental demonstration of resonant X-ray diffraction microscopy for element specific imaging. We performed nondestructive and quantitative imaging of buried Bi structures inside a Si crystal by directly phasing coherent X-ray diffraction patterns acquired below and above the Bi M5 edge. We have also applied X-ray diffraction microscopy to nondestructive imaging of mineral crystals inside biological composite materials - intramuscular fish bone - at the nanometer scale resolution. We identified mineral crystals in collagen fibrils at different stages of mineralization and proposed a dynamic mechanism to account for the nucleation and growth of mineral crystals in the collagen matrix. In addition, we have also discovered a novel 3D imaging modality, denoted ankylography, which allows for complete 3D structure determination without the necessity of sample titling or scanning. We showed that when the diffraction pattern of a finite object is sampled at a sufficiently fine scale on the Ewald sphere, the 3D structure of the object is determined by the 2D spherical pattern. We ...
Date: April 18, 2011
Creator: Miao, Jianwei
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department

Multitechnique Analysis of the Lattice Structures of Highly Siliceous Zeolites

Description: The combined use of high-resolution solid state NMR techniques (both 1D and 2D) with synchrotron-based powder x-ray diffraction studies yields detailed information on the lattice structures of highly siliceous zeolites. The two methods are complementary, the former probing short range ordering and structures while the latter is sensitive to long range orderings and periodicities.
Date: August 26, 1999
Creator: Fyfe, C. A.; Gies, H.; Kokotailo, G. T.; Feng, Y.; Strobl, H.; Marler, B. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department

Determination of mineral abundances in samples from the Exploratory Studies Facility, Yucca Mountain, Nevada, using x-ray diffraction

Description: Tuff samples collected from the Exploratory Studies Facility (ESF) were X-rayed to estimate relative mineral abundances. X-ray analysis was performed on sub-samples of specimens collected from both the Single Heater Test (SHT) and Drift Scale Heater Test (MT) that were used for thermomechanical measurements, as well as samples collected from cores retrieved from boreholes in the Drift Scale Test Area. The abundance of minerals that could affect the behavior of the host rock at repository relevant temperatures is of particular interest. These minerals include cristobalite, which undergoes a phase transition and volume change at elevated temperature (-250 {degree}C), and smectite and clinoptilolite that can dehydrate at elevated temperature with accompanying volume reduction. In addition, the spatial distribution of Si02 polymorphs and secondary minerals may provide evidence for deducing past fluid pathways. The mineral abundances tabulated here include data reported previously in three milestone reports but reanalyzed, as well as previously unreported data.
Date: January 13, 1998
Creator: Roberts, S. & Viani, B.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department

Direct Observation of the alpha-epsilon Transition in Shock-compressed Iron via Nanosecond X-ray Diffraction

Description: In-situ x-ray diffraction studies of iron under shock conditions confirm unambiguously a phase change from the bcc ({alpha}) to hcp ({var_epsilon}) structure. Previous identification of this transition in shock-loaded iron has been inferred from the correlation between shock wave-profile analyses and static high-pressure x-ray measurements. This correlation is intrinsically limited because dynamic loading can markedly affect the structural modifications of solids. The in-situ measurements are consistent with a uniaxial collapse along the [001] direction and shuffling of alternate (110) planes of atoms, and in good agreement with large-scale non-equilibrium molecular dynamics simulations.
Date: March 21, 2005
Creator: Kalantar, D. H.; Belak, J. F.; Collins, G. W.; Colvin, J. D.; Davies, H. M.; Eggert, J. H. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department