The strain distribution associated with incipient microplasticity and its response to subsequent annealing were studied in smooth and notched silicon crystals. The characterization of plastic and elastic residual strains was carried out by X-ray topography based on PendellBsung Fringe (PF) patterns and was supplemented by X-ray doublecrystal diffractometry and specimen scanning with automatic Bragg angle control (ABAC). It was shown that the sites at or near the surface were preferred sites where, upon mechanical deformation, dislocation sources became activated. Microplastic zones thus formed constrained long-range, residual, elastic strains.

The fluorescent excitation of long-wavelength X-ray spectra is reviewed with respect to X-ray tube target element, inherent filtration, and optimum kilovoltage. A demountable X-ray tube vacuum spectrograph designed for the determination of the light elements is described. Operation of this instrument with both secondary and combined primary—secondary excitation is evaluated. Examples from the literature are cited to show the feasibility of direct electron excitation of longwavelength spectra.

An IBM 1800 time-sharing system is used in our X-ray laboratory to control a four-circle diffractometer for structure research, several powder diffractometers, a pole-figure goniometer and a microdensitometer along with other instruments outside the diffraction area. A survey of the computer system is given and the hardware necessary to automate the diffractometers is discussed. The computer supervision ranges from simple data-logging with a minimum of control to complete control of all actions depending on the diffractometer and the requirements of the experiment. Also described is the use of the computer to process the data and to perform background jobs.

Various sample preparation methods for Energy Dispersive X-ray Fluorescence (EDXRF) analysis of Portland cement were compared in order to evaluate improvement in analytical accuracy and precision. Sample preparation requirements for EDXRF are slightly different than for Wavelength Dispersive X-ray Fluorescence (WDXRF), and the methods commonly used in WDXRF are not optimized for EDXRF. Primarily, the work focuses on techniques for producing a fused sample with the lowest practical concentration of lithium borate flux. Determination of minimum detection limits were made from samples with varying proportions of flux in order to evaluate analytical optimization. Ease and reproducibility of preparation of the sample was also considered.

Last year at this conference we submitted a preliminary report on an X-ray powder diffraction round robin sponsored by the JCPDS-ICDD. This round robin was designed primarily to study the intensities of diffraction lines found by users in routine work. At that time only a portion of the data had been analyzed, and we reported initial findings on the α-Al2O3, and Zn0 /CaCO3 samples. These included studies on counting statistics, resolution, and the effect of software on intensity precision. Since that time, all the data from the round robin has been entered into Lotus 1-2-3 (*) spread-sheets and numerous additional tests have been carried out. This paper discusses some of the more interesting findings. A complete paper on all of the tests performed is in preparation for submission to the "Methods and Practices Manual" published by the JCPDS-ICDD.

Energy-dispersive X-ray techniques can be employed in two different ways for the accurate determination of element concentrations in specimens: (1) spectrometry of fluoresced characteristic X-rays as widely applied in the various modes of the traditional XRF analysis technique, and (2) spectrometry of the energy-differential transmittance of an X-ray continuum at the element-specific absorption-edge energies.

A modern theoretical method using the Fundamental Algorithm to correct for matrix effects in X-Ray Fluorescence (XRF) analysis is described. This powerful quantitative method combines the practical flexibility of influence coefficient concepts and the theoretical exactness of the fundamental parameter technique. This method is in full agreement with the treatment of the physics as proposed by Sherman and can be applied to the analysis of any sample types. It offers the maximum of accuracy limited only by the quality of sample preparation. The special calibration procedure associated with the Fundamental Algorithm is explained. This procedure allows the matching of theoretical formalism to experimental data of each individual laboratory. Finally and obviously, this approach requires a computer program to be applied. Some important guidelines are given to help XRF analysts to select the XRF program appropriate to their needs.

Fracture accidents of engineering structures and machines in operation sometimes result from defects. One of the purposes of fracture analysis are to determine the causes of failure, and to use the information to prevent similar failure accidents. It is important to obtain quantitative analysis from the fracture surface. X-ray diffraction technique as well as Electron Fraotography has been widely used for fracture analysis of engineering structures and machines.

A numerical procedure known as the constrained linear inversion method is employed for obtaining the z-profiles of diffraction data from their τ-profiles. The method was first tested with known z-profiles and gave good agreement with the starting z-profiles even with up to 5% random noise introduced into the τ-profile or up to 10% error in specimen thickness. The procedure was then applied to an experimentally obtained strain profile and a non-oscillatory z-profile was calculated. Although the z-profile obtained could not be verified by an independent method, the success of tests with known z-profiles leads to increased confidence in the numerical method described.

Given the vast superiority of synchrotron radiation sources for EXAFS and near-edge measurements, one might assume that conducting such experiments in the laboratory is a waste of time and resources. Upon more careful consideration of the realities of everyday research, however, one can easily see that this is not true. In fact, many people have come to this realization, so much so that a whole conference has been devoted to laboratory EXAFS facilities, their role in research and their relation to synchrotron facilities. The concensus after the conference was that laboratory instruments can and have been developed, with adequate performance for a variety of nontrivial experiments. They usually employ dedicated focusing spectrometers, rotating anode generators and fairly expensive monochromator crystals (see articles in ref. 1 and 2).

Rietveld X-ray powder diffraction (XRD) and uniaxial stress measurement procedures are being evaluated as a means of correlating the crystalline structure properties of zinc-nickel electroplate with observed plating properties. The study is being performed on a suite of six samples of varying composition (6 to 20%Ni) electrodeposited on mild steel. Rietveld refinement of the XRD data (Rietveld, 1969) has been performed on a specially prepared ingot (9%Ni:91%Zn) to determine the structural parameters and relative abundances for the γ(Ni4Zn22), δ(Ni3Zn22) and η(Zn) phases which could possibly be present in the electroplate. Relative phase abundances were verified by Atomic Absorption Spectrometry (AAS) and electron probe microanalysis (EPMA) image mapping techniques.

The structural parameters for the ingot zinc-nickel phases were subsequently used as initial parameters in Rietveld calculations for the six electroplate samples. Structure refinement of the electroplate XRD data was hampered by extremely high preferred orientation and the corresponding lack of quality diffraction peaks. However, Rietveld refinements produced accurate cell dimensions (which correlate linearly with nickel composition), a means of quantifying the degree of preferred orientation, and crystalline phase verification. For residual stress determination, d-sin2ψ plots were produced for each electroplate sample. The plots were found to be linear for Ni < 12%, allowing calculation of residual stress, and distinctly curved for Ni > 12%.

A two-crystal spectrometer employing a Cole polarizer made from a germanium crystal as one of the crystals is described. Experimental tests show that placing the polarizer crystal in the second position markedly improves the degree of plane polarisation, in full agreement with the predictions of the dynamical theory of X-ray diffraction. Tests indicate that the twice-diffracted beam h better than 95% plane polarized. The angular resolving power of the instrument is comparable to that of conventional two-crystal spectrometers. The almost wholly planepolarized monochromatic X-radiation, moreover, permits certain tests to be carried out far more effectively than is possible with partly polarized X-ray beams.

Cemented carbide composites with a WC hard phase and a Co-Ni alloy binder phase have been subjected to monotonic and cyclic deformation and studied using the high resolution General Purpose Powder Diffractometer at the Argonne Intense Pulsed Neutron Source. Upon deformation, relaxation of bulk differential thermal residual stresses, tensile in the binder and compressive in the carbide, is observed to occur as a function of loading mode and plastic strain via shifts in diffraction peak positions. In addition, peak breadth behavior indicates broadening. At low plastic strain this is due primarily to a range of residual stress and at high plastic strain it is attributable to the plastic deformation alone since relaxation is essentially complete. The appropriateness of neutrons is discussed.

As part of a study on the fundamental properties of BeO, the surface area, particle size, and crystallite size of BeO powders prepared from different source materials were measured. The results obtained by means of small-angle X-ray scattering and X-ray line-broadening have been compared with electron micrographs and surface area values by air permeability, nitrogen adsorption, and water-vapor adsorption.

Small-angle scattering data were analyzed to yield particle size distribution curves as well as surface areas for various calcined BeO samples. Line-broadening measurements were made to determine mean crystallite dimensions of these same materials. By using both photographic film and automatic recording techniques, crystallite sizes from about 50 to over 5000 A were estimated. The rate of growth of BeO crystals from beryllium hydroxide, beryllium sulfate, and beryllium oxalate source materials has been followed by these complementary techniques.

In this paper, the application of recently developed x-ray diffraction techniques to the characterization of thin epitaxial films will be discussed. The double-crystal diffractometer, with high resolution in the non-dispersive arrangement, enables the materials scientist to study epitaxial systems having a very small mismatch with high precision. A key part of the characterization of an epitaxial film is the determination of the strain tensor by measuring lattice spacing! in various directions The determination of strain and composition profiles in ion-implanted films, epitaxial layers and superlattices by rocking-curve analysis will also be reviewed. Grazingincidence diffraction, an emerging new technique, can be used to obtain structural details parallel to the interface on films with thicknesses ranging down to a few atomic layers. The synchroton has now become increasingly available as a powerful source of x radiation which will facilitate the application of conventional and grazing-incidence diffraction to ultra-thin films.

Recent developments in position sensitive detectors (PSD's), solid state power and computer technologies make it possible to design accurate instruments for in-situ stress measurement. Such instruments require compromises in the interests of portability, size and speed stiich may limit accuracy and/or versatility. Furthermore, extraction of a stress tensor from X-ray data is not always straightforward and considerable research is required before an instrument for X-ray stress measurement can be treated as a “black box” to be given to an uneducated operator.

The development of a new instrument for in-situ stress measurement is described in this paper. It was conceived as a field instrument with two position-sensitive proportional counters (PSPC's) for use in the single exposure mode (SET), and incorporates precise angular qontrol of the incident X-ray beam and data analysis to eliminate irregular Bragg peaks owing to coarse grain structure, An experimental instrument was built tc test the concept (1).

Energy dispersive X-ray fluorescence (EDXRF) spectrometry has been applied to the high speed analysis of uranium ore for the purpose of grading and sorting truckloads of ore at the mine. The system is able to analyze uranium ore in less than 60 seconds with uranium levels ranging from < 0.005% to > 5% U3O8. Precision at the 2σ level for 200 ppm ore is better than 10% relative. Good agreement is obtained with wet chemical results in a large variety of rock matrices.

Sampling is a necessary part of the chemical analysis of particulate matter where the objective is to characterize bulk properties since it is usually undesirable or impossible to test an entire lot. The sample must be a miniature replica of the bulk material at least in respect to those features being tested. In other words, the sample must be representative to permit extrapolation from the sample to the bulk.

There is error associated with sampling particulate material, but this sampling error is only one component of the total error associated with an analytical result. Sample preparation and determination of the property being tested are two other major sources of error, These three errors combine as the squares of their standard deviations, i.e., their variances, to produce the total analytical error. Very often, sampling error is the largest of the three and, therefore, contributes a disproportionately large share to the total error.

Basic lead azides are obtained by the slow thermal decomposition of PbN6 at temperatures up to 200°C in oxygen, argon, and air containing varying amounts of moisture. The decomposition diagrams show several stages due to the formation of different phases, two of which have been separated. One phase can be identified as a tetragonal deformed cubic lattice. Further slow decompositions of the basic lead azide at 250°C lead to tetragonal lead oxide. The structure of the other isolated phase Is of lower symmetry and has not yet been classified. The results of this investigation are also compared with the work of previous investigators.

There is a veritable renaissance occurring in x-ray imaging. X-ray imaging by radiography has been a highly developed technology in medicine and industry for many years. However, high resolution imaging has not generally been practical because sources have been relatively dim and diffuse, optical elements have been nonexistant for most applications, and detectors have been slow and of low resolution. Materials analysis needs have therefore gone unmet. Rapid progress is now taking place because we are able to exploit developments in microelectronics and related material fabrication techniques, and because of the availability of intense x-ray sources.