bluuebunny/crossref_metadata_2025_split huggingface dataset:
Crystal Distortion Associated with Magnetic Ordering in Alpha Iron Oxide and Manganese Carbonate
Authors: McCain W. S. , Albright D. L. 
Published: March 2019

AbstractThe magnetic crystal disrortion of weakly ferromagnetic α-Fe2O3 was investigated by x-ray diffraction techniques. Here crystal distortion is taken as the temperature dependent changes of lattice constants and thermal expansion coefficients. Moreover, the oxygen position parameter and the carbon-oxygen distance of MnCO3 were determined.The lattice constants and thermal expansion coefficients of α-Fe2O3 were measured from room temperature down to 243°K. The crystal distortion, as measured by the changes in lattice constants, thermal expansion coefficients and axial ratio, was found to be highly anisotropic. The co hexagonal lattice constant was influenced very slightly by magnetic distortion; it changed only by 0.01 percent between room temperature and the Morin temperature of 254°K. On the other hand, the ao lattice constant changes by 0.11 percent between room temperature and the Morin temperature. The thermal expansion coefficients of the lattice constants showed a similar contrast. The co coefficient was found to be independent of temperature from room temperature down to the Morin temperature. However, in the same temperature range, the ao coefficient showed an anomalous increase with decreasing temperature. In addition, the ao coefficient showed an infinite discontinuity at the Morin temperature.The change in the axial ratio with temperature suggests that the net weak ferromagnetic moment of α-Fe2O3 reaches a maximum at 275°K.The oxygen position parameter, x, in MnCO3 as determined from two reflections has a value of 0.2702 ± 0.001. The carbon-oxygen distance as calculated from the lattice constants and the oxygen position parameter is 1.29 ±0.002 Å. This value is another confirmation of the Pauling theory of the resonating carbonate structure.
X-Ray Diffraction Topography
Authors: Bonse U. K. , Hart M. , Newkirk J. B. 
Published: March 2019

AbstractIn recent years, a number of experimental X-ray diffraction techniques have been developed by which a topographical display of the microscopical defects in a crystal can be obtained. This brief review of the most useful of these techniques is intended to summarize the elements of the various methods and to compare their respective features and limitations. Contrary to microradiographic methods, in which image contrast is due entirely to variations in X-ray absorption from point to point in the specimen, X-ray diffraction topography is concerned with point-topoint variations in the directions or the intensities of X-rays that have been diffracted by crystals. From these variations the defect structure of the crystal may be examined. Methods that mainly measure local variations in the direction of the diffracted beam are useful for the detection of gross misorientations such as subgrains or grains (methods of Gui nier and Tennevin, Schulz, Weissmann). Intensity mapping methods are chiefly concerned with individual defects such as dislocations, stacking faults, etc. In both groups there are experimental arrangements with both Laue-case (transmission) and Bragg-case (back reflection) geometry.
A Comparison of Four Slit Apertures for Selected-Area Analysis with the X-Ray Secondary-Emission Spectrometer
Authors: Bertin Eugene P. 
Published: March 2019

AbstractFour types of slit apertures—vertical, horizontal, inclined, and sirtgle-edge—for selected-area analysis with commercial X-ray secondary-emission (fluorescence) spectrometers are described, evaluated, and compared. The vertical and single-edge slits already have been described by the writer and Rizzo. The other two are described here for the first time. The vertical and horizontal slits are secondarybeam apertures; the other two lie in both the primary and secondary beams. AH the slits are mounted on the specimen drawer. No further modification of the spectrometer is required except replacement of the soller collimators with open tunnels or simple slits, and replacement of the flat crystal with a fixed-radius curved crystal to increase sensitivity. The accessories are inexpensive and can be made in even a modest machine shop. They can be installed on or removed from the spectrometer in about 5 min. The accessories are applicable ordy to linear selected areas where composition varies in the direction normal to but not along the line, for example, linear inclusions and sections of plated surfaces, diffusion couples, and interfaces. The four slits were evaluated and compared for resolution, sensitivity, and spectral-line width. Techniques for use, advantages, limitations, and means for improvement are discussed for each of the slits. The horizontal slit is of little value, but each of the others has features which permit analysis of very narrow selected areas for which pinhole apertures would not be sufficiently sensitive. Slit widths as narrow as 0,00012 in. (0.003 mm) have been used in favorable cases. The inclined slit, used with a pulse-height analyzer, is probably the most useful of the four apertures, combining high sensitivity, high resolution, and narrow spectral-line width.
Common Sources of Error in Electron Probe Microanalysis
Authors: Heinrich Kurt F. J. 
Published: March 2019

AbstractIn order to reduce the error of quantitative electron probe microanalysis, error sources in the preparation and measurement of specimens and standards must be minimized. These sources of error are described, and literature references for detailed study are given. A critical analysis is made of 150 analytical measurements of binary specimens previously discussed by Poole and Thomas. It is shown that the cases of serious errors reported by these authors are mainly due to poorly characterized or measured specimens and, in. some cases, to the omission of characteristic fluorescence corrections. If these sources of error are eliminated, a much more favorable error distribution can be obtained through relatively simple correction calculations. Further progress in quantitative micro probe analysis is dependent upon measurements under well-controlled conditions and standard materials of experimentally proven microhomogeneity and reliably determined composition.
X-Ray Spectrographs Analysis of Traces in Metals by Preconcentration Techniques
Authors: Davis C. M. , Burke Keith E. , Yanak M. M. 
Published: March 2019

AbstractChemical separation techniques with their roots in classical analysis have been highly developed since the turn of the century. During the last two decades, X-ray spectrography has proven to be a very acceptable method of analysis because of the relative ease and rapidity of measurement of the intensity of characteristic wavelengths, the ready knowledge of the precision of the measurement, the facility of automating the analysis, and the nondestructive nature of the method. When chemical separation techniques are combined with X-ray spectrography, the problem of matrix effects is eliminated and the element being analyzed is substantially concentrated, which affords a means of performing trace element analyses. Published examples of preconcentration followed by X-ray measurement both outside and in the field of metallurgy are cited.
Applications of a Portable Radioisotope X-Ray Fluorescence Spectrometer to Analysis of Minerals and Alloys*
Authors: Rhodes J. R. , Furuta T. 
Published: March 2019

AbstractA portable, battery-operated X-ray fluorescence analyzer weighing 15 lb is described, consisting of a Nal(Tl) scintillation-counter probe and an electronic unit with a single-channel pulse-height analyzer and reversible scaler. Radioisotope X-ray sources are used for excitation of the sample and, where necessary, balanced filters for resolution of neighboring characteristic X-rays. Emphasis has been placed on designing and producing an instrument that is easy and convenient to operate in laboratory, factory, or field conditions and that can equally well be used to measure extended surfaces, such as rock faces, or finite samples in the form of powders, briquettes, or liquids. The feasibility of the following analyses has been studied by using for each determination the appropriate radioisotope source and filters: sulfur in coal; calcium and iron in cement raw mix; copper in copper ores; and vanadium, chromium, molybdenum, and tungsten in steels. Detection limits, based on counting statistics obtained in count times of 10 to 100 sec, range from 0.03% for copper in ores to 0.2% for sulfur in coal. Both matrix absorption and enhancement effects were encountered and were eliminated or reduced substantially by suitable choice of source energy, by the use of nomograms, or by semiempirical correction factors based on attenuation or scattering coefficients.
X-Ray Stress Measurement by the Single-Exposure Technique
Authors: Norton John T. 
Published: March 2019

AbstractX-ray techniques employing film recording continue to play an important role in the routine determination of residual stresses in metals, particularly where heavy and bulky specimens are involved. The single-exposure technique in which the two diffraction patterns required are obtained simultaneously in a single X-ray exposure has several practical advantages over the more conventional two-exposure technique for many routine applications. Details of the method are discussed and an analysis is made of the factors influencing the reliability of the stress determination. An apparatus for stress measurement having some unique features is described and a practical application presented, illustrating the use of the single-exposure technique for the determination of the stress constant of a specimen of hardened steel. The specimen was subjected to a series of known stresses in bending, both in tension and compression. The measured diffraction-line displacements were plotted against the applied stress, and a line was fitted to the points by a least-squares calculation. From its slope, the stress constant was determined. The standard deviation of individual stress determinations from the “true” values given by the least-square line was calculated and was in excellent agreement with the value calculated from the errors of measurement. It is concluded that the single-exposure technique with its reduced time required for measurement and less demanding requirement of precise instrumental adjustment provides a reliable and practical method for many routine stress measurement applications.
A Simplified Method of Quantitating Preferred Orientation
Authors: Klenck Michael M. 
Published: March 2019

AbstractQualitative evaluation of preferred orientation in 10-rml Hastelloy N seamless tubing was carried out by obtaining conventional pole figures for several samples with the modified Schulz reflection technique. This established the texture as a (110)[112]. Quantitative determination of this texture was achieved for a large number of samples by a radial traverse of an azimuthally averaged (110) stereographic projection. This was accomplished with a Schulz goniometer by rotating the sample rapidly in its own plane while slowly varying the tilt angle ϕ. The first minimum observed in the resultant pattern approximates the pole density of the randomly oriented component of the sample. A scan obtained from a randomly oriented sample and suitably scaled to match pole density at these minima serves to distinguish the random from the oriented component of the sample. A ratio of the oriented to the random component as a function of the tilt angle ϕ is independent of the instrumental effects of defocusing and absorption. This ratio is proportional to the pole density of the oriented component since the pole density of the random component is a constant by definition. The same constant of proportionality yields a pole density of unity for the random component. Integrating the pole density for die random component over the surface of a reference sphere of unit radius gives the value 4π for the number of randomly oriented poles NR. The number of poles corresponding to the oriented component is obtained by evaluating the integralIn this equation, R(ϕ) is the ratio of the oriented to the random component, Φ is the tilt angle corresponding to the first minimum in the sample scan, and m is a multiplicity factor which compensates for integration over just one 110 face of each grain. Evaluation of this integral may be made by plotting it with the aid of a family of sine curves and measuring the area under the curve.The per cent of volume of the oriented component is then calculated by the relationshipThis method entails about 30min of an analyst's time and 40 to 120 min of machine time, depending on the grain size of the sample. Further information on the angular breadth of the texture may be obtained from the plot of the integrand. This technique is subject to the limitations that the material have a single texture and it must be possible tc prepare the specimens so that a suitably chosen pole figure contains a central concentration of poles which are delineated from other regions of pole concentration by a surrounding minimum in pole density. This is generally not too difficult in the case of sheet textures but requires that the specimen normal be parallel to ths fiber axis for a fiber texture.
Topotactical Relationships Between Hematite α-Fe2O3 and the Magnetite Fe3O4 which is Formed on it by Thermal Decomposition Under Low Oxygen Pressure
Authors: Baro Raymond , Moineau Hervé , Heizmann J. Julien 
Published: March 2019

AbstractThe present work was performed on natural monocrystals from Mexico. All crystals presented well-formed natural faces of indices (01.2), (01.4), (11.3), and (00.1). They were reduced to magnetite in a thermobalance by heating at 1200°C under a pressure of 10−3 torr. The techniques used in the present work were Laue reflection diagrams and pole figures. The magnetite formed on the hematite showed preferential orientations of three different types. The mutual orientations of the two oxides all present a common zone axis for the lattices formed by the oxygen ions.
Crystal Structure Analysis of Niobium-Doped Rutile Single Crystal
Authors: Niizeki Nobukazu 
Published: March 2019

AbstractDetermination of the atomic sites for the doped niobium atoms by the X-ray diffraction method has been undertaken to obtain the structural basis for the understanding of semiconductive behavior of crystals. Diffraction intensities were measured with spherical samples ground from the undoped and doped (4 mol. %) TiO2 single-crystal rods grown by the flame-fusion method. Measurements were carried out by an automatic single-crystal diffractometer and observed intensities were corrected for Lp and absorption factors. The total number of the independent (hk0) reflections was 45 with Mo Kα. radiation. Structure factors were calculated on the baiis of the following atomic arrangement: titanium at equipoint (2a) of space group P42/mnm, O at (4f) with x = 0.306, and an isoatomic temperature factor B = 0.70 were used. Reliability factor R for the undoped rutile was 0.037 without further refinement. For the doped crystal, an R-yalue of 0.053 was obtained for the substitutional model, where niobium was assumed to be at x = 0, y = 0. The R value was 0.125 for the interstitial model, where niobium was assumed to be at x = ½, y = 0. The difference Fourier map was obtained by subtracting the electron density distribution in a Fourier map of the undoped crystal from that ot the doped crystal. Since the intensity measurements were done only on a relative scale, the two Fourier maps were normalized so as to give an identical number of electrons under the oxygen peak. The resulting map revealed a small peak only at the location x = 0, y = 0. It could be concluded that niobium atoms enter the titanium sites substitutionally, at least in rather heavily doped crystals. Further work on the refinement of the doped structure is in progress.
The Al FeBe4 Intermetallic Phase in Beryllium
Authors: Brower I. , Roberts E. C. , Bosworth T. J. 
Published: March 2019

AbstractX-ray diffracfion analysis has been used to determine the nature and relative concentration of the phases present in diffusion welded joints of fairly high purity beryllium. The analyses were done in conjunction with the major objective of the work which was to correlate the types and amounts of phases in the weld joint with the weld processing variables.The beryllium used contained less than one percent by weight of alloying elements. Those elements present in major amounts were aluminum, less than 0.10 weight percent (less than 0.033 atom percent)and iron, less than 0.15 weight percent (less than 0.023 atom percent).A phase concentration technique was used to obtain the quantities of phases required for positive identification. X-ray powder patterns obtained from the residues provided detailed diffraction data of which those for the phase Al Fe Be4, are of particular interest. These data are compared with the findings of other research investigations.Experimental procedures are discussed in detail and a summary of the test results in included.
The Effects of Self-Irradiation on the Lattice of 238 (80%)PuO2.III
Authors: Roof R. B. 
Published: March 2019

AbstractThe results of the fourth year of observations on the effects of self-irradiation on the lattice of 238(80%)PuO2 confirm the predictions derived from previous observations. Namely, the lattice constant continues to decrease with time but at a slower rate indicating an approach to equilibrium. Very small reductions are also noted in the half-width of the diffraction lines.
A Review of X-Ray Diffraction Methods for Diffusion Studies
Authors: Carpenter J. A. , Tenney D. R. 
Published: March 2019

AbstractX-ray diffraction methods for studying solid-state diffusion are reviewed. Because of the lack of penetration, such methods are suited for diffusion zones spanning only a few microns. Most involve analyses of one, or more, (hkl) “band” of intensities spread in 2θ as a result of the corresponding lattice parameter spread associated with compositional inhomogeneities. Further, many are non-destructive, making it possible to follow the progression of diffusion with time in the same specimen.
An Experimental Evaluation of the Atomic Number Effect
Authors: Parobek L. , Brown J. D. 
Published: March 2019

AbstractA method for measuring the atomic number effect is developed using a sandwich sample technique. The depth distributions of x-ray production, ϕ(ρz) curves, have been measured for a zinc tracer in aluminum, copper, silver and gold matrices at 30, 25, 20 and 15 keV. The ϕ(ρz) curves were measured using a Cambridge Microscan 5 in which the electron beam is normal to the sample surface and the x-ray take-off angle is 75°.Samples of the low concentrations of copper (∼1 Weight %) in aluminum, nickel, silver and gold were prepared. For each alloy system (for example, Cu - Al), three different concentrations of copper were prepared. The intensity ratios from the sample to the pure element (standard) for each system have been plotted against concentration. At such low concentrations of copper the relation between this ratio and concentration is linear. The slopes of the curves have been compared to the equivalent factors obtained as ratios of the area under F(ρz) curves for aluminum, silver and gold to the area under F(ρz) curve for copper, respectively. The F(ρz) curves are obtained from ϕ(ρz) curves; F(ρz) = ϕ(ρz) exp(-μρz csc ψ) where μ is mass absorption coefficient.Comparisons are made between these experimental data and the current methods of calculating the atomic number effect.
Observation of Dislocation in α-Arsenic Single Crystals by X-Ray Diffraction Topography*
Authors: Shetty M. N. , Taylor J. B. , Calvert L. D. 
Published: March 2019

AbstractX-ray diffraction topographs were obtained from large arsenic single crystals. The camera employed copper Kα, radiation from a microfocus tube and an oscillating assembly of Soller slits limited the beam divergence. Reflections of the type (11) and (20) (primitive rhombohedral cell) were used to characterise dislocation Burgers vectors. The technique has been applied to arsenic single crystals grown from the vapour and from the melt. The majority of dislocations were found to belong to Burgers vectors <10>. Comparison has been made between dislocation etch pit patterns on (111) surfaces and X-ray topographs.
A New Method for Fourier Analysis of Shapes of X-Ray Peaks and its Application to Line Broadening and Integrated Intensity Measurements
Authors: Rothman R. L. , Cohen J. B. 
Published: March 2019

AbstractA method of Fourier analysis of x-ray line broadening is presented whereby microstrain, incoherent particle size, and fault probability can be calculated using only first-order peaks. This method can thus be used in studies of catalysts, vapor- and electrodeposits or heavily textured specimens for which second-order peaks are too broad or weak, in cases where the effect of particle size is not the same for all orders of a peak, or for multiphase specimens where overlap of peaks sometimes occurs. Examples of deformed FCG and BCC metals and alloys are presented, with comparisons to the method of multiple orders.One part of the procedure, first demonstrated by Pines and Sirenko, provides for reducing the effects of truncation on the Fourier coefficients. As a result, larger particle sizes can be analyzed and the integrated intensity can be determined more precisely. Application to determinations of volume fraction are given.
A Comprehensive Alpha Coefficient Algorithm
Authors: Lachance G.R. , Claisse F. 
Published: March 2019

AbstractAn algorithm is proposed as a model that describes the intensity concentration relation over a wide concentration range in binary and more complex systems involving absorption and enhancement. All the influence coefficients can be determined from fundamental parameter equations. Terms containing product of two weight fractions are always negligible in pure absorption cases, are often negligible in absorption/weak enhancement cases and are necessary but small in strong absorption/strong enhancement situations.Once the magnitude of the coefficients is known, the range of application of the one- or two-coefficient models can be established with certitude.
Application of the Pixe method in Atmospheric Aerosol Investigations
Authors: Orsini C. Q. , Bouéres L. C. 
Published: March 2019

Investigations of Atmospheric Aerosol Systems (let us abbreviate AAS) have now spread to many laboratories around the world, mainly because of the important role they assume in the air pollution problem.In most cases, the studies on AAS attempt to evaluate the so-called “size-distribution function”, through which the general behavior of such a system is commonly described.
Effect of Chemical State Upon Phosphorus-L2,3 Fluorescence Spectra
Authors: Taniguchi Kazuo 
Published: March 2019

AbstractThe P-L2,3 emission spectra of the phosphorus compounds were obtained using a secondary excitation. We found that the spectra depended upon the chemical state, the main peak of L2,3 emission spectra shifts to a higher energy, and the peak of intensity of higher energy increases with an increase of oxidation number. It should be noted that the phosphorous spectra of the phosphate anions scarcely reveal influences of the phosphate compounds, except that of H3PO4. We concluded that the spectral feature for the phosphorus compounds is influenced by the condition of surrounding atoms but is not influenced by the bond condition.