Showing papers in "Advances in x-ray analysis in 1988"

Applications of a laboratory x-ray microprobe to materials analysis

Abstract: In this paper, some additional beam characterization experiments will be discussed. Also, applications to several types of materials will be demonstrated

Separation of the Macro- and Micro-Stresses in Plastically Deformed 1080 Steel

Abstract: : The stress tensors were measured with x-ray diffraction in both the ferrite and cementite phases of a 1080 steel specimen deformed in uniaxial tension. The macro- and micro-stresses were separated for all the components of the stress tensors. All the components except the hydrostatic components of the micro-stresses could be determined without an accurate value of the unstressed lattice parameter. Tensile stresses were found in the cementite and compressive stresses in the ferrite along the deformation direction. The tensile stresses in the cementite were quite large.

Chemical Constraints in Quantitative X-ray Powder Diffraction for Mineral Analysis of the Sand/Silt Fractions of Sedimentary Rocks

Abstract: Quantitative X-ray powder diffraction using the complete digitized diffraction pattern has proved to be an effective approach to improving the accuracy of the analysis of complex mineral mixtures, provided representative reference patterns and accurate Reference Intensity Ratio (RIR) factors arc available for each component phase. However, chemical and structural variability of common rock-forming minerals may complicate the pattern fitting approach. A method has been developed which utilizes X-ray fluorescence chemistry of an unknown and realistic compositional ranges for component phases as constraints on the quantitative XRD analysis without significant compromise of the pattern fit. This unique approach no only yields accurate weight fractions, but also provides indications of the specific compositions of each phase present in the mixture.

An Improved Fusion Technique for Major-Element Rock Analysis by XRF

Abstract: A new apparatus and technique are described for borate flux fusion of rocks for x-ray fluorescence analysis. The method yields homogeneous, strain-free glass discs with flat, smooth surfaces that do not require polishing. The technique is adapted from several previous methods but has advantages over each in terms of sample uniformity, quality of the discs, or capital cost. The ignited rock powder is fused with flux over a burner mounted on a stock laboratory mixer, and is cast into a solid flat, polished Pt-Au mold. The very effective mixing action ensures homogeneity An oxidizing atmosphere, which is necessary to prevent loss of iron to the crucibles, is maintained by injecting air during fusion. There is no significant loss of alkali metals during fusion, and negligible loss of flux. Duplicate samples of several rock types show excellent reproducibility, approaching counting statistical errors, for 10 major elements.

Texture Analysis of Thin Films and Surface Layers by Low Incidence Angle X-ray Diffraction

Abstract: We have shown that it is possible to obtain the texture of a thin film by low incidence X-ray texture goniometry. The intensity correction and the correction of the location of the information have been checked and correspond to the theory

Application of a new solid state x-ray camera to stress measurement

Abstract: In the present contribution a versatile and lightweight solid state X-ray camera system, MEXSTRESS, is applied to stress measurement. This new camera unifies the desirable features of the traditional camera and diffractometer techniques into one single equipment

Residual Stress Measurement of Silicon Nitride and Silicon Carbide by X-Ray Diffraction Using Gaussian Curve Method

Abstract: The residual stress induced by grinding or some thermal treatment has a large effect on the strength of ceramics. The X-ray technique can be used to nondestructively measure the residual stress in small areas on the surface of polycrystalline materials. The X-ray stress measurement is based on. the continuum mechanics for macroscopically isotropic polycrystalline materials. In this method, the stress value is calculated selectively from strains of a particular diffraction plane in the grains which are favorably oriented for the diffraction. In general, however, the elastic constants of a single crystal depend on the plane of the lattice, since a single crystal is anisotropic, The behavior of the deformation of individual crystals in the aggregate of polycrystalline materials under applied stress has not yet been solved successfully. Therefore, the stress constant and elastic constants for a particular diffracting plane should be determined experimentally in order to determine the residual stress accurately by X-ray diffraction.

X-ray Diffraction Studies of Polycrystalline Thin Films Using Glancing Angle Diffractometry

Abstract: It is the purpose of this paper to contrast a number of methods for the measurement of polycrystalline thin films

Standard deviations in x-ray stress and elastic constants due to counting statistics

Abstract: X-ray diffraction can be used to nondestructively measure residual stress of polycrystalline materials. In x-ray stress measurement, it is important to determine a stress constant experimentally in order to measure the stress accurately. However, every value measured by x-ray diffraction has statistical errors arising from counting statistics. The equations for calculating the standard deviations of the stress constant and elastic constants measured by x-rays are derived analytically in order to ascertain the reproducibility of the measured values

X-ray Diffraction Analysis of High Tc Superconducting Thin Films

Abstract: X-ray diffraction techniques have been used for the structure characterization of Y-Ba-Cu-O and Tl-Ca-Ba-Cu-O thin films. A powder diffraction analysis of Y-Ba-Cu-O films showed that the films deposited at 650°C on Si are polycrystalline and have an orthorhambic structure similar to that of the YBa2Cu3O7 bulk superconductors. In addition to the conventional powder diffraction technique, both the rocking curve and the grazing incidence diffraction methods were used to characterize a YBa2Cu3O7 film on (110) SrTiO3 substrate. Results showed that the film was epitaxially grown and aligned with its substrate in a true epitaxy. Phase identification and line broadening analyses of Tl-Ca-Ba-Cu-O films showed that the films are comprised of one or more superconducting phases and probably contain stacking faults.

Effect of plastic deformations on oscillations in d vs. sin2ψ plots

Abstract: In a previous paper, we modeled the effect of elastic incompatilility on the «d» vs. sin 2 ψ from Cu 311 planes. In the present study, the model is expanded to accommodate the effect of local plastic yielding within grains in the diffracting volume. The effects of such yielding on the oscillatory behavior in «d» vs. sin 2 ψ are investigated

Elastic Constants of Alloys Measured with Neutron Diffraction

Abstract: Elastic constants as a function of crystallographic direction have been measured in polycrystalline alloy samples of 17-4PH stainless steel, Ni-CR-FE, and Ti-6%AI-4%V using a neutron diffraction technique. The results compare best with the constant stress model of Reuss. It is demonstrated that measurements of stress can be made sampling the bulk of the material using neutrons with an accuracy comparable to more conventional x-ray methods

Modern alloy analysis and identification with a portable x-ray analyzer

Abstract: A field portable, microprocessor controlled, fully user-programmable x-ray analyzed is described for fast, reliable, on-site, positive alloy identification and assay. Applications are reviewed and include examples to show the superior performance of the instrument in such difficult cases as sulfur in carbon steels, and titanium and nickel in stainless steels. Discussion of the unique alloy identification scheme and its underlying principles is followed by examples of applications illustrating the capabilities of the instrument in distinguishing, in 5 seconds, alloys of closely similar compositions such as stainless steels 303, 304 and 321, and 410 and 416

X-ray Diffractometric Determination of Lattice Misfit Between γ and γ' Phases in Ni-Base Superalloys: Conventional X-ray Source vs. Synchrotron Radiation

Abstract: The lattice misfits between γ and γ' phases in Ni-base superalloys (single crystal) were accurately determined for filings of specimens by using both a conventional X-ray tube focusing diffractometer(CXRFD) and a synchrotron-radiation parallel beam X-ray diffractometer (SRPXRD). All reflection peaks measured with the CXRFD were in a cluster of overlapping peaks because of the very small differences in the lattice parameters of both phases and the instrumental broadening due to X-ray optics including the spectral distribution of Xray source such as CuKα doublet. The deconvolution method was applied to remove the instrumental broadening from the peaks measured with the CXRFD. The window functions for the deconvolution method were calculated from CuKα doublet reflection of Si standard by a nonlinear least-square method. The instrumental broadening of SRPXRD was much smaller than that of CXRFD since the monochromatic X-rays produced single peak profiles and constant profile shape over a wide 2θ range. A profile fitting with a pseudo-Voigt function was used to determine 2θ angles to 0.0005 deg. for the synchrotron powder data. The peak angle and shape reflected from γ' phases in γ-matrix and those fron electrochemically extracted γ'-phase were significantly different.