X-Ray Diffraction Study of Ordering in Two Sigma Phases

1966 ◽  
Vol 10 ◽  
pp. 213-220 ◽  
Author(s):  
R. W. Spor ◽  
H. Claus ◽  
Paul A. Beck
Keyword(s):  
Scintillation Counter ◽  
Pulse Height ◽  
X Ray Diffraction ◽  
Measured Intensity ◽  
Atomic Size ◽  
X Ray ◽  
Line Intensities ◽  
Ordering Schemes ◽  
Intensity Ratios ◽  
Pattern Line

AbstractX-ray powder pattern line intensities were measured for the (Cr, Re)σ and (Re, Fe)σ phases by a step-scanning diffractometer, using CrKα radiation, scintillation counter, and a pulse height analyzer. The measured intensity ratios for all available pairs of adjacent lines were compared by means of a computer with the corresponding calculated intensity ratios based on approximately 1800 different ordering schemes for each alloy. The results showed ordering in both alloys, and indicated that the ordering was based on atomic size. These results are different from those obtained previously by Kasper and Waterstrat (no ordering), and by Ageyev et al. [In (Cr, Re)σ the Cr atoms are preferentially in large coordination number positions.]

Structure Maps and Phase Stability in AlTi3 Alloyed with Rare-Earth Elements

1988 ◽  
Vol 133 ◽  
Author(s):  
C. T. Liu ◽  
J. A. Horton ◽  
D. G. Petitifor
Keyword(s):  
Crystal Structure ◽  
Rare Earth ◽  
Rare Earth Elements ◽  
Solubility Limit ◽  
Size Factor ◽  
X Ray Diffraction ◽  
Atomic Size ◽  
X Ray ◽  
Dependent Parameter ◽  
Rare Earth Additions

ABSTRACTRare-earth elements including Y, Er and Sc were added to AlTi3 for stabilizing the Ll2 ordered crystal structure, as predicted by the AB3 structure map. The crystal structure and phase composition in the AlTi3 alloys were studied by electron microprobe analysis, X-ray diffraction and TEM. The solubility limit of the rare-earth elements were determined and correlated with the atomic size factor. The results obtained so far indicate that rare-earth additions are unable to change the crystal structure of AlTi3 from DO19 to Ll2. The inability to stabilize the Ll2 structure demonstrates the need to characterize the structure map domains with a further period-dependent parameter.

Applications of a Portable Radioisotope X-Ray Fluorescence Spectrometer to Analysis of Minerals and Alloys*

1967 ◽  
Vol 11 ◽  
pp. 249-274 ◽  
Author(s):  
J. R. Rhodes ◽  
T. Furuta
Keyword(s):  
Single Channel ◽  
Scintillation Counter ◽  
Pulse Height ◽  
X Rays ◽  
X Ray ◽  
Scattering Coefficients ◽  
Finite Samples ◽  
Counting Statistics ◽  
Fluorescence Spectrometer ◽  
Sulfur In Coal

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.

An X-Ray Small-Angle Scattering Instrument

1967 ◽  
Vol 11 ◽  
pp. 332-338 ◽  
Author(s):  
Donald M. Koffman
Keyword(s):  
Small Angle ◽  
Scintillation Counter ◽  
Small Angle Scattering ◽  
High Angular Resolution ◽  
X Ray Diffraction ◽  
Multiple Diffraction ◽  
Double Crystal ◽  
X Ray ◽  
Angle Scattering ◽  
Diffraction Patterns

AbstractAn X-ray small-angle scattering instrument is described which is used for recording X-ray diffraction patterns or small-angle X-ray scattering curves in an angular region very close to the direct beam. The measurement of X-ray intensity is accomplished with standard geiger or scintillation counter techniques. The instrument is designed for use with a spot-focus or vertical-line X-ray source, In essence, it is a multiple-reflection double-crystal diffractometer, based on a concept developed by Bonse and Hart, employing two grooved perfect germanium crystals arranged in the parallel position. Multiple diffraction from these crystals produces a monochromated X-ray beam which can be several millimeters wide while still exhibiting extremely high angular resolution. As a result, effective sample volumes can be employed with maximum volume-to-thickness ratios. The principal features of the instrument are discussed with emphasis on the advantages of this device over those employing complex slit systems and film-re cording techniques, Data are presented to illustrate the operation, intensity, and resolution of the unit.

Suppression of X-Ray Fluorescence Background in X-Ray Powder Diffraction by a Mercuric Iodide Spectrometer

1983 ◽  
Vol 27 ◽  
pp. 307-316
Author(s):  
J. Nissenbaum ◽  
A. Levi ◽  
A. Burger ◽  
M. Schieber ◽  
Z. Burshtein
Keyword(s):  
Powder Diffraction ◽  
Energy Resolution ◽  
Scintillation Counter ◽  
Peak Height ◽  
Maximum Energy ◽  
Mercuric Iodide ◽  
X Ray Diffraction ◽  
X Ray ◽  
Order Of Magnitude ◽  
Diffraction Patterns

AbstractWe have explored the merits of using a Hgl2 spectrometer as a detector in x-ray diffraction systems instead of a proportional gas counter, or a scintillation counter. The full width at half maximum energy resolution of the HgI2 spectrometer used was about 1.1 keV for the CuKα line (8.1 keV), and about 1.5 keV for the MoKα line (17.4 keV), The energy resolution was utilised to eliminate x-ray fluorescence background from powder diffraction spectra. We demonstrate the suppression of Fe x-ray fluorescence in diffraction patterns of ErFe03 obtained with a Cu x-ray tube, and of Y x-ray fluorescence in diffraction patterns of Y2O3 obtained with a Mo x-ray tube. The peak height to background ratios were improved by about an order of magnitude in both cases.

X-Ray Spectrographic Analysis of the 3-d Transition Metal Corrosion Products Using Potassium Bromide Disks*

1963 ◽  
Vol 7 ◽  
pp. 590-597
Author(s):  
L. A. Schluter
Keyword(s):  
Pulse Height ◽  
Weight Ratio ◽  
Internal Standard ◽  
Corrosion Products ◽  
Metal Corrosion ◽  
Small Samples ◽  
Bragg Angle ◽  
X Ray ◽  
Calibration Curves ◽  
Intensity Ratios

AbstractA technique has been developed for quantitative analysis of the major constituents in small samples (less than 0.1 g) of corrosion products found On various missile parts. The technique was developed primarily to aid in interpretation of X-ray diffraction patterns of multicomponent corrosion products. The corrosion sample is mixed with KBr and the mixture is pressed into a disk in the same fashion commonly used in infrared work. The Br Kβ1 line serves as an internal standard. Intensities of the element's Kα line and the internal standard are established by scanning through the appropriate Bragg angle and recording peak heights on a strip-chart recorder. A xenon-filled proportional detector and a pulse-height analyzer were used.The percent of an element is determined by references to calibration curves which relate intensity ratios to weight ratios for the 3-d transition metals. The oxides of the metals were used in the preparation of the calibration curves. The weight ratio vs. intensity ratio relationship is linear over the weight ratio range 0.01 to 0.11. Data were collected using an air path and a helium path; the higher intensity ratios obtained with, the helium path, and the dependence of intensity on atomic number are illustrated. A comparison is made between the intensity ratios in a KBr matrix and in a NaBr matrix. The technique developed requires about 15 min sample preparation time.

Flat Crystal X-Ray Optics

1957 ◽  
Vol 1 ◽  
pp. 193-206 ◽  
Author(s):  
William J. Campbell ◽  
Melvin Leon ◽  
John Thatcher
Keyword(s):  
Wave Length ◽  
Pulse Height ◽  
Line Profiles ◽  
Line Broadening ◽  
Crystal Surfaces ◽  
X Ray ◽  
Line Intensities ◽  
Long Wave ◽  
On Line ◽  
College Park

AbstractAn investigation was undertaken by the Bureau of Mines at College Park, Md., to determine the effect of various combinations of collimators, analyzing crystals and detectors on line intensities, line-to-backgrouhd ratios, and spectral resolution. The research showed that line broadening due to mosaic crystal surfaces was greatly reduced and line splitting from faults was eliminatedby the use of two fine collimators (0.005 inch, spacing, 4 inch length). Line intensities were reduced, but lineto- background ratios arid line profiles were substantially improved with double collimators. Pulse height discrimination resulted in marked improvement in the line-to-background ratio in the long-wave length region, 2 to 10 A, but was much less effective for shorter wave lengths.

Measurement of Residual Stress Distribution of Ground Silicon Nitride by Glancing Incidence X-ray Diffraction Technique

1995 ◽  
Vol 39 ◽  
pp. 331-338
Author(s):  
Yoshihisa Sakaida ◽  
Keisuke Tanaka ◽  
Shintaro Harada
Keyword(s):  
Residual Stress ◽  
Surface Layer ◽  
Stress Distribution ◽  
Stress Measurement ◽  
Scintillation Counter ◽  
Ground Surface ◽  
Residual Stress Distribution ◽  
X Ray Diffraction ◽  
X Ray ◽  
Very High

A new method of X-ray stress measurement was proposed to estimate non-destructively the steep residual stress distribution in the surface layer of ground Si3N4. We assumed an exponential decrement of the residual stress near the ground surface, and derived a formula for the lattice strain as a function of sin2Ψ. In the experiments, the diffraction angles were measured on the ground surface for a widest possible range of sin2ѱ using an Ω-goniometer. In order to measure the diffraction angle at very high sin η values, a scintillation counter was located on the -η side and an incident X-ray beam impinged on the ground surface with a very low angle from the +η side using the glancing incidence X-ray diffraction technique. A strong non-linearity was found in the 20-sin2ѱ diagrams especially at very high ѱ -angles. From the analysis of non-linearity, the stress distribution in the surface layer was determined. Tine residual stress took the maximum compression of 2 GPa at a depth of about 0.5 μm from the surface, and then diminished to zero at about 25 μm in depth. In the close vicinity of the ground surface, the compressive residual stress was relieved because of both the surface roughness and microcracking induced during the grinding process.

A Technique for Studying Coprecipitated Chromia-Alumina Catalysts by X-Ray Diffraction

1960 ◽  
Vol 4 ◽  
pp. 117-129
Author(s):  
W. L. Kehl
Keyword(s):  
Background Radiation ◽  
Pulse Height ◽  
Chromium Concentration ◽  
White Background ◽  
X Ray Diffraction ◽  
Pulse Height Analyzer ◽  
X Ray ◽  
Gas Proportional Counter ◽  
Diffraction Patterns ◽  
Alumina Catalysts

AbstractA diffractometer equipped with a gas proportional counter and pulse-height analyzer provides a very satisfactory means of recording the X-ray diffraction patterns of chromium-containing materials with Cu Kα radiation. The fluorescent chromium K radiation can be rejected along with much of the white background radiation without appreciable loss of Cu Kα intensity, and the advantages of copper over chromium or molybdenum radiation can be fully utilized. This is illustrated by an X-ray diffraction study of coprecipitated chromia-alumina catalysts, in which the chromium concentration varies between 0 and 37 w, %. At each chromium concentration the precipitate was studied in the washed and dried state, as well as after calcination at 500, 750, and 1400°C. X-ray diffraction patterns are presented to show the phase transformations and sample inhomogenelties that were observed.

Instrumentation for X-Ray Diffraction Studies of Highly Radioactive Samples

1958 ◽  
Vol 2 ◽  
pp. 107-115
Author(s):  
Vincent G. Scotti ◽  
James I. Mueller ◽  
John J. Little
Keyword(s):  
Radiation Damage ◽  
Gamma Ray ◽  
Pulse Height ◽  
Fission Products ◽  
Analytical Tool ◽  
Nuclear Engineering ◽  
X Ray Diffraction ◽  
X Ray ◽  
Background Ratio ◽  
Gamma Ray Irradiation

AbstractWith the advent of nuclear engineering, x-ray diffraction has become an important analytical tool in the study of radiation damage due to neutron and gamma-ray irradiation. The materials under study in this work have rdioactive levels up to 40 R/hr. at 17 centimeters combined β and γ. The activity of the various samples under study may be due to (n, γ) reactions or fission products or both.Data are presented to illustrate the use of sample shielding, detector shielding pulse height discrimination and the combination of all three aids in an effort to attain the most favorable peak to background ratio.

Formation of Ni57Zr20Ti22Pb1 Amorphous Powders by Mechanical Alloying

2007 ◽  
Vol 539-543 ◽  
pp. 2767-2772
Author(s):  
Pee Yew Lee ◽  
S.S. Hung ◽  
Jason S.C. Jang ◽  
Giin Shan Chen
Keyword(s):  
Thermal Stability ◽  
Supercooled Liquid ◽  
Supercooled Liquid Region ◽  
Liquid Region ◽  
X Ray Diffraction ◽  
Mechanically Alloyed ◽  
Atomic Size ◽  
X Ray ◽  
Amorphous Powders ◽  
Thermal Stability Of

In the current study, the amorphization behavior of mechanically alloyed Ni57Zr20Ti22Pb1 powder was examined in details. The conventional X-ray diffraction results confirm that the fully amorphous powders formed after 5 hours of milling. The thermal stability of the Ni57Zr20Ti22Pb1 amorphous powders was investigated by differential scanning calorimeter (DSC). As the results demonstrated, the glass transition temperature (Tg) and the crystallization temperature (Tx) are 760 K and 850 K, respectively. The supercooled liquid region is 90 K. The appearance of wide supercooled liquid region may be mainly due to the Pb additions which cause the increasing differences in atomic size of mechanically alloyed Ni57Zr20Ti22Pb1 powders.

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