bluuebunny/crossref_metadata_2025_split huggingface dataset:
High-Temperature Modifications of Thorium Dicarbide
Authors: Gantzel P. K. , Langer S. , Baldwin N. L. , Kester F. L. 
Published: March 2019

AbstractThermal analyses of samples of thorium dicarbide in equilibrium with graphite show arrests which indicate phase transitions at 1427 ± 21°C arid 1481 ± 28°C. These thermal effects have been observed on heating and cooling both in standard thermal analysis and in differential thermal analysis using graphite as a reference material. The microstructure of thorium dicarbide samples shows the characteristic “herringbone” pattern of a material which has undergone a martensitic-type transition.A high-temperature X-ray investigation has revealed that the observed thermal arrests correspond to erystallographic transformations. The monodinic modification found at room temperature is stable to 1427°C, at which temperature a tetragonal modification with a0 = 4.235 ± 0.002Å and c0 = 5.408 ± 0.002Å is formed. At 1481°C, the tetragonal is transformed to cubic with a0 = 5.809 ± 0.002 Å. The best agreement between observed and calculated intensities has been obtained with C-C units of 1.5-Å assumed bond length in space groups P42/mmc and Pa3 for the tetragonal and cubic modifications, respectively.
Escape Peaks in X-Ray Diffractometry*
Authors: Parrish William 
Published: March 2019

AbstractEscape peaks occur when the incident X-ray quantum, energy exceeds the absorption edge energy of the detector element and the resulting X-ray fluorescence is lost from the detector. The most common escape peaks result from 1 K-fluorescence in NaI-scintillation counters and Xe K-, Xe L-, and Kr K-fluorescence in proportional counters. The average pulse amplitude of the escape peak is proportional to the difference of the Energies of the incident and fluorescent X-rays. If the intensity of the escape peak is high as in the case of Mo Kα and a kryptoopreportional counter, and the lower level of the pulse height analyzer is raised to reject the escape peak, the quantum counting efficiency may be reduced by a factor of two. When the pulse height analyzer is set for characteristic incident radiation, escape peaks appear in powder patterns at small diffraction angles. These broad low-intensity peaks are often mistakenly identified as resulting from misalignment, scattering, etc. Each powder reflection can produce its own escape peak which occurs at an angle slightly smaller than the absorption edge of the detector element. In a silicon powder pattern the three strongest reflections produce three resolved escape peaks whose peak intensities are about 4% of their corresponding Cu Kα peaks when the X-ray tube is operated at 50 kV. The escape peak intensities decrease with decreasing X-ray tube voltage and disappear when the voltage is lower than the absorption edge energy of the detector element. Absorption edge peaks observed without the upper level of the pulse height analyzer are similar in appearance, intensity, and diffraction angle to the escape peaks. In complex powder patterns the escape peak pattern is unresolved and may produce a number of very broad peaks.
A Computer Program for Determining Accurate Parameters from Powder Data
Authors: Elliott Rodney P. 
Published: March 2019

AbstractAn IBM 7090 computer program has been written to determine precise lattice parameters for cubic, tetragonal, orthorhombic, and hexagonal systems. Leastsquares analysis is made with data fitted to the equationwhere E is the eccentricity and A. is the absorption-divergence error. The computer program will make the least-squares analysis with neither, either, or both of the error(s) included. Data can then be reprocessed for other combinations of errors. After having determined the lattice parameter(s), on request, the computer program will predict the interplanar spacings, including the errors, so that observed data in the high-angle region may be indexed by comparison. Use of the program indicates that the most consistently reproducible parameters are obtained using only A, the absorption—divergence error.
Modification of Collagen and Nylon Lattices by Resorcinol
Authors: Shaw E. H. , Christensen Alton R. 
Published: March 2019

AbstractBy soaking formalinized rat-tail tendons in 2 M resorcinol, the tendon lattice is expanded equatorially from an interplanar spacing of 11.7 Å to 14.5 Å, indicating a diameter of 7.2 Å for the spiral core of collagen. Resorcinol distorts the lattice of nylon (6:6), converting the normal triclinic cell to an orthorhombic cell whose a and b axes are approximately four times those of the original nylon and whose c axis is reduced from 17.2 to 16.5 Å.
X-Ray Generation by Proton Bombardment
Authors: Sterk Andrew A. 
Published: March 2019

AbstractSome of the characteristics of X-ray generation by proton bombardment are described. With work still in progress, it has been proven that this method is particularly suitable for soft X-rays >10 Å. Excitation efficiencies equal or excel electron excitation efficiencies, while the resulting spectrum consists of a single characteristic radiation line, but with complete absence of bremsstrahlung. Experimental results, the design of an instrument, and some applications are discussed.
A Compilation of Beta-Ray Stimulated X-Ray Spectra
Authors: Preuss L. E. , Collins H. , Wilson E. R. 
Published: March 2019

AbstractThe photons resulting from the interaction of beta particles and matter have a certain complexity of origin; but the spectrum is made up, in large part, of two primary components, one of these being the white radiation continuum produced by the external bremsstrahlung mechanism of beta acceleration at the target atom. The second fraction consists of the characteristic K and L X-rays of the target atom. Published beta-excited X-ray spectra are centered about a small fraction of the available pure beta emitters and a restricted group of target materials. Furthermore, intercomparisons between references are difficult, due to an infinite variety of source and detector parameters influencing the data.This laboratory has begun a comprehensive reference compilation of these spectra, done on a comparative basis and simplified and standardized for sensible cataloging and easy reproduction of the experimental design. The prime purpose is to make available coherent data for many beta-excited X-ray sources in which beta activities, target geometries, and other critical parameters are known, controlled, and constant. Spectral sets for given source-target combinations may, therefore, be intercompared, and application of the beta-excited X-ray may be made with the best possible source-target atom combination.The spectra are studied by three proportional counters (operating down to the 1 kV energy range) and two standard scintillation crystals, accumulated in a 256-channel analyzer, and are presented in sets (representing one beta source-target combination) consisting of a minimum of eight spectra, six of which represent the most critical transmission target geometry.Examples of the cataloging of the spectral sets, for the mixture, apposition, and compound isotopic X-ray sources, are presented.
An Instrument for Soft X-Ray Selected-Area Microdiffraction*
Authors: Pattee H. H. 
Published: March 2019

AbstractAn instrument for soft X-ray selected-area microd infraction has been constructed fulfilling the principles of optimum intensity for given specimen size and resolution, and permitting direct visual beam focusing and alignment for specimen sizes in the 1-10 μ region. The X-ray source is a modified, two-lens, microfocus tube manufactured by Canal Industrial Corporation supplemented by a camera, specimen stage, and incident-light microscope. Target-to-film distance may be adjusted from 50 μ to several millimeters which allows the use of wavelengths as long as Al K radiation in air. The use of soft radiation for microsamples simplifies the collimation requirements and permits shorter specimen-to-film distance for a given resolution. Collimating apertures are punched in foil with etched tungsten points or with the microfocus electron beam. Results confirm the prediction that microsamples do not require excessive exposure times using optimum geometry for source size and camera dimensions.
Some Notes on Ultrasoft X-Ray Fluorescence Analysis—10 to 100 Å Region*
Authors: Henke Burton L. 
Published: March 2019

AbstractMethods and instrumentation have heen developed for the extension of X-ray fluorescence analysis into the light element region, magnesium through beryllium. Examples of current values for the minimum detectable limits for these elements and associated instrumental parameters are presented. Some specific techniques are described for the use of an ultrasoft X-ray vacuum spectrograph, for the development of large d-spacing multilayer analyzers, and for the construction of thin window systems.
Preliminary Studies on the Characterization of Solution-Grown ADP Crystals
Authors: Deslattes Richard D. , Torgesen John L. , Paretzkin Boris , Horton Avery T. 
Published: March 2019

AbstractLarge single crystals of ammonium dihydrogen phosphate (ADP) have been grown from solutions of reagent grade materials by means of precisely controlled temperature programs. We have studied the perfection of these crystals by means of double-crystal rocking curves and diffraction topographs. In the course of this study, effects associated with various techniques of sectioning and polishing specimens from these crystals were examined. A combination of string sawing and chemical polishing procedures produced specimens exhibiting the best diffraction characteristics. Results obtained from surfaces so prepared are tentatively taken as being characteristic of the bulk crystal and may be interpreted in terms of longrange strain fields and imaging of both emergent and nonemergent dislocations. In some specimens, regions of 1 cm2 or more have been found to be free of defect images and to have uniform reflectance.The perfection of some specimen pairs and the intrinsic properties of certain reflections suggest their possible application to spectroscopic problems. Some crystal pairs cut parallel to (101) planes have exhibited physical resolving powers of 104 at 8.3 Å; others cut for the 600 reflection have given 4 x 105 at 1,5 Å, These crystals deteriorate on exposure to moist laboratory air and preservation techniques had to be employed.
The Diffraction of X-Rays by Multilayer Stearate Soap Films
Authors: Ehlert Ralph C. 
Published: March 2019

AbstractThe diffraction of X-rays by multilayer stearate soap films has been studied as a function of (a) the number of diffracting layers and (b) the bivalent metal present. Both “Y” and “X” type structures have been built and analyzed with Al and C Kα radiation. The measured diffraction efficiency is compared with that predicted theoretically and with that obtained from a single crystal such as potassium acid phthalate.
A Study of Homogeneity of Solid Solutions of Cadmium Sulfide and Cadmium Selenide by X-Ray Fluorescence*
Authors: Chan Frank L. , Brooks Donald A. 
Published: March 2019

AbstractThe homogeneity of solid solutions of cadmium selenide and cadmium sulfide has been investigated. Crystals of the solid solutions having different selenium contents were grown in the Aerospace Research Laboratories by the conventional methods as described in the earlier conferences. The composition of these solid solutions were analyzed chemically for their selenium content by a procedure perfected in the Aerospace Research Laboratories.Crystals in the form of lumps were cut to optimum size suitable to be inserted into the commercially available sample holder. The selenium content of these crystals was ascertained by scanning the samples with stationary colljmators of small aperture. The spectrograph used for the present study was operated at 75 KVP and 50 mA. The target tube was constructed of molybdenum. The results from the chemical method were used to correlate the counts per second obtained from the X-ray spectrograph.
The Determination of Calcium in Uranium Ore Concentrates by X-Ray Fluorescence
Authors: Knoke D. R. , Waldron H. F. 
Published: March 2019

AbstractSince the advent of vacuum and helium path X-ray spectrometers, and flow proportional counters, the determination of low-atomic-number elements by X-ray fluorescence has become relatively common for light-element matrices. However, there are no reports in the literature on the determination of the low atomic-number elements in a rnatrix approaching that of uranium. This paper describes the successful application of the vacuum path X-ray spectrometer for the determination of calcium in the range of 0.03 to 1.75% (on a U3O3 basis) in uranium ore concentrates. The procedure provides a 50% saving in analyst time, with no sacrifice of accuracy or precision, compared to the chemical method previously used. With a chromium target tube, the intensity of the calcium radiation is quite sufficient for accurate analyses even though the samples contain approximately 80% uranium. The heavy uranium matrix actually serves to minimize any absorption or enhancement effects that would normally be expected from the large number of impurities that are present in widely varied concentrations.Samples are prepared by dissolving 1.8 g of concentrate in 10.0 g of Na2B4O7 at 1050°C and casting into a disk on a polished aluminum plate. The advantages of this preparation compared to the use of pelletised powders will be discussed. The Ca Kα-to-U Mγ ratio is used to minimize the1 effect of instrumental and sample variations and to provide a linear relation with respect to the calcium concentration on a U3O8 basis. Calibration standards are prepared by the addition of CaHPO4 to either pure U3O8 or a uranium ore concentrate of low residual calcium. Data obtained during routine application of this procedure will be presented.
X-Ray Fluorescence in Cotton Modification Research
Authors: Mitcham Donald , Piccolo Biagio , Tripp Verne W. , T. O’Connor Robert 
Published: March 2019

AbstractThe application of X-ray fluorescence to the qualitative and quantitative analysis of chemically modified cotton textile materials is described. The scope and flexibility of the technique have permitted the determination of more than 20 elements with, greatly reduced elapsed time compared with the corresponding spectroscopic or wet methods. Precautions to be observed in preparing standards are discussed. Results of the analysis of typical modifications and their significance in the development of cottons for specific uses are described.
Observations of G-P Zone Reversion in Al-Zn-Mg Alloys by Small-Angle X-Ray Scattering and Transmission Electron Microscopy
Authors: Gould R. W. , Starke E. A. 
Published: March 2019

AbstractA study of the reversion process in Al-Zn-Mg alloys has been made using small-angle X-ray scattering and transmission electron microscopy techniques. The rate and mode of Guinier-Preston zone dissolutions was investigated as a function of magnesium content, prior zone radius, and reversion temperature. Results indicate that in this system the reversion process is characterized by the preferential dissolution of the smallest G-P zones present after cold aging with a corresponding decrease in the volume fraction of zones. The amount of reversion at a specific temperature is dependent on magnesium content, however, the rate of reversion is independent of magnesium content.
The Structure of the γ′-Phase in Nickel-Base Superalloys
Authors: Rosen S. , Sprang P. G. 
Published: March 2019

AbstractPresent day nickel-base superalloys are hardened in part by the precipitation of a phase which has variously been identified as Ni3Al, Ni3(Al, Ti) and γ′. X-ray diffraction techniques which include precision lattice parameter measurements, intensity measurements, and phase identification are used to define the structural and chemical relationships upon which this phase is based.These relationships are developed from the following considerations: crystal chemistry and atomic size factors which relate binary Cu3Au-type T3B phases (e.g., Ni3Al) and ternary Perovskite-type T3BC2 carbide phases (e.g., Y3AlC), the determination of the number and kind of atoms in the unit cell of Ni3Al and certain ternary phases, the crystallographic relationship between the structure of Y3C and Y3AlC, and phase relations in certain quarternary alloys.From these considerations it is shown that the γ′ phase may best be characterized as a Peiovskite-type carbide phase having the chemical formula TsBCx. A model of the γ′ structure is presented which indicates the position of the various atomic constituents based upon whether they are T or B elements. (An atomic component is considered of the T type if it is capable of substituting for nickel in 3, of the B type if it can replace the aluminum. The essential features of this model are: T and B elements form an ordered T3B lattice of the Cu3Au type ; carbon atoms are located only in octahedral holes in the centers of the Cu3Au-type cells thereby establishing Perovskite-type T3BC3 unit cells; the effective size of T and B atoms in the T3BC3 unit cell is the same: hyperstoichiometric alloys, (ratio of B atoms to T atoms greater than one) will contain B atoms at face-centered positions in addition to a small amount of equilibrium vacant sites; in all alloys aluminum will preferentially occupy the cube corners of the unit cell ; the amount of carbon which is soluble in T3BC3; at any particular temperature is determined both by the distribution of the elements which are carbide-formers and the elements manganese, iron and cobalt. This model accounts for microstructural changes which occur in some nickel-base superalloys as a function of temperature and composition.
Crystallographic Studies of NH4Cl—NH4Br Solid Solutions
Authors: Callanan Jane Edmund , Smith Norman O. 
Published: March 2019

AbstractBoth ammonium chloride and ammonium bromide undergo a transition, with rise in temperature, from an interpenetrating simple cubic (II) to a face-centered cubic (I) lattice at 183 and 137°C, respectively, and both the low- and high-temperature forms give a complete series of solid solutions. We have determined the lattice constants of the high-temperature solids at about 250° as a function of composition, and redetermined the lattice constants of the low-temperature solids at room temperature. The solutions were made by crystallization from water, followed by stirring in contact with mother liquor for at least three weeks at room temperature. Measurements were made with a Norelco- Philips diffractometer and recorder, with Cu Ko. radiation. For the high-temperature work, a simple, inexpensive heating apparatus was developed. The only previous data reported for the high-temperature forms are the lattice constants of the pure components given by Bartlett and Langmuir.The low-temperature solutions showed negative deviations from Vegard's rule at both ends of the concentration range and a slight positive deviation elsewhere when high-angle data were used. The high-temperature solutions showed marked positive deviations from Vegard's rule over the whole compositions range. Values for the pure components agreed reasonably well with those of Bartlett and Langmuir.The progress of the change II → I with time was followed for some of the solutions in the neighborhood of the transition temperature in an attempt to reveal the mechanism of the process.
Chemical Bonding and the Sulfur K X-Ray Spectrum
Authors: Wilbur D. W. , Gofman J. W. 
Published: March 2019

AbstractAn investigation has been made of the relative Kβ intensities in different chemical states of the sulfur atom using the Kα lines, with appropriate corrections, to provide the intensity standards. Both inorganic and organic compounds were included in the study. The data for each compound appear to be reliable to about ± 0.5%, while the whole series of compounds shows a variation greater than 20% in the corrected Kβ/Kα ratios. Energies were also measured, particularly the Kα energies, and their shifts were studied relative to the Kβ, intensity shifts. The work was done with a plane, single-crystal, helium-path spectrometer with proportional counter and pulse-height analysis for detection. The results are indicative of the usefulness of the method both in clarifying an uncertain chemical state and in studying the electronic structure of the bonded atom.
Determination of Interatomic Distances from X-Ray Absorption Fine Structure
Authors: Lytle F. W. 
Published: March 2019

AbstractA pragmatic, easily applied theory of the extended X-ray absorption fine structure found on the high-energy side of absorption edges is developed. This simple model can be successfully applied to determinations of interatomic distances, and it accounts for differences in Kronig structure on different absorption edges in the same material. Quantitative agreement with experimental data is good.
Matrix and Particle Size Effects in Analyses of Light Elements, Zinc Through Oxygen, by Soft X-Ray Spectrometry
Authors: Madlem K. W. 
Published: March 2019

AbstractWith the development of soft X-ray sources by Henke, it is now possible to extend the range of quantitative analyses by X-ray spectrometry into the very light element range (magnesium through, boron). Techniques of specimen preparation, recognized as one of the most critical aspects of quantitative X-ray analysis in the heavier elemental ranges, present new problems, especially with the physically and chemically heterogeneous materials encountered in mineral and rock analysis. This paper presents the results of new tests extended into the light and very light element range. It is shown that most of the problems previously found are intensified as lower atomic number elements are considered; conditions of the specimen surface are critical and require precise control of particle size. In addition, significant absorption by relatively heavier elemental constituents, either in a separate phase or within the same phase, causes poor precision and is difficult to predict. Thus, the combination of matrix absorption within and between discrete phases, combined with the difficulty of grinding different phases to a uniform particle size, suggests that fusion techniques are required for hest precision. Without fusion, both scatter and bias are introduced through non-linear calibrations, with each calibration dependent upon specimen composition and particle size. It is concluded that only with nearly uniform specimens, where gross deviations are to be checked (e.g., process control) can ground rock powders be used with success in light element analyses.
Use of the Soft X-Ray Spectrograph and the Electron-Probe Microanalyzer for Determination of Elements Carbon Through Iron in Minerals and Rocks
Authors: Baird A. K. , Zenger D. H. 
Published: March 2019

AbstractThe major elements m common rocks are of low atomic number, but analyses of high precision are possible by soft X-ray spectrography if several grams of rock sample are available. The electron-probe microanalyzer is shown to complement this established method by permitting analyses of particles as small as 1 μ in diameter. This paper describes applications of these methods to the analysis of the major and minor elements of silicate, carbonate, and phosphate minerals and rocks.Elements of particular interest are as follows : carbon in particles enclosed in carbonate rocks; oxygen, as the major constituent of the specimens; phosphorus in phosphatic nodules and apatites; manganese and iron, as colorations in fossil shells; and the group oxygen, sodium, magnesium, aluminum, silicon, potassium, calcium, and iron as complex segregations and zonations within single crystals of several mineral phases.If the bulk composition of a rock is known, and also the chemistry of the constituent minerals, it is possible to compute quantitative minéralogie analyses of high precision. Thus, the combined use of soft X-ray spectrography and electronprobe microanalysis can provide quantitative chemical and mineralogicat information on the earth's crust on all scales from thousands of square miles (by means of appropriate sampling) down to the scale of 1 μ.