The least-squares method with complete component library spectra is applied to the quantitative analysis of X-ray fluorescence spectral intensities. An approach is outlined for application to the general case of thick homogeneous samples at high counting rates, A simplified approach can be taken with the more specific case represented, by atmospheric particulates collected on filters. The details and sample results of this approach for this specific case are given for an energy dispersive X-ray fluorescence analyzer. The results indicate that the least-squares method as developed and applied here is valid and should prove generally useful to X-ray analysts.

Compositions in the tantalum-carbon system were prepared by carburizing high-purity tantalum wires. The microstructures so produced exhibit regions of a characteristic striated structure identical to those observed by earlier investigators. There are disparities in the literature as to the origin of such structures in the tantalum—carbon system. They have been variously described as “twins,” “striated structure,” “precipitate,” and “structure of unknown origin.” This paper presents conclusive evidence that the structures in question are the result of precipitation on cooling. In addition, a coherent precipitation model is applied in which it is shown that the lattice relationship {0001}Ta2C‖{Klll}TaC can exist with less than 0.5% misfit. This relationship is shown to completely explain the occurrence and characteristic appearance of the observed micro structures. Correlations between chemical analysis, X-ray diffraction results, metallography, and microhardness measurements confirm the proposed precipitation model.

By means of a combined X-ray diffraction and metallographic study, two heretofore unrecognized phases, Zr4Fe and Zr2Fe, have been identified. Approximate verification of this finding has been made by Dr. David Levinson, using microprobe analysis. A tentative revision of the Zr-Fe phase diagram is proposed.

A fundamental quantitative treatment of the heterogeneity effects in X-ray fluorescence has been made. The theory predicts that the grain-size effect appears only in a limited region of grain sizes which depends on the wavelength of the primary radiation and the nature of the compounds in the mixture. With monochromatic radiation, the fluorescence intensity showed increase or decrease by a factor of a few units as grain size is decreased, A factor as large as 12, the theoretical value, has been observed in one particular experiment. Usually the grain-size effect can be eliminated by intensive grinding. For the light elements fine grinding is disastrous if long wavelengths are used. By an appropriate choice of the wavelength it is possible to eliminate the effect even without grinding. The mathematical treatment also predicts, but less rigorously, a grain-size effect in X-ray diffraction.

The effect on the fluorescence intensities by changes in the chemical composition of the grains that contain the fluorescent element is predicted by the theory.

These findings are discussed in relation to the analysis of elements when polychromatic beams are used.

Software is described for complete computer control of residual stress measurements. One program (that incorporates either the two tilt method, the sins| procedure, or the Cohen-Marion technique) has been developed for use with either a normal detector or a position sensitive detector. The operator inputs the desired error in stress and various instrumental parameters that determine systematic errors. The counting strategy to obtain the total error is then determined by the software.

Employing this automated system, an investigation of a parabolic fit to the top of a diffraction profile indicates that a three point fit is satisfactory only for sharp profiles.

In order to convert residual strains measured by x-ray diffraction techniques into residual stresses, appropriate x-ray elastic constants have to be measured. Since these x-ray elastic constants may depend on the metallurgical state, deformation, and entire specimen history, errors in stress values may result if the constants are not measured for representative material states. In the present work, it is shown that in same cases these errors may be large.

Roe's method for deriving the crystallite orientation distribution in a series of generalized spherical harmonics is applied to the analysis of texture in rolled cubic materials. The augmented Jacobi polynomials, which are the basis of the generalized spherical harmonics, have been derived for cubic crystallographic symmetry and orthotopic physical symmetry through the sixteenth order. Truncation of the series expansions at the sixteenth order should permit treatment of textures having a maximum of 17 times random and a minimum angular width at half maximum of 34°. A numerical technique has been developed which permits approximate evaluation of the integral equations from a finite array of data points. The method is illustrated for commercial steels and is used to elucidate the primary recrystalization texture of a decarburized Fe-3%Si alloy.

This paper summarizes experiences available for the measurement of lattice strains in different materials with different wavelengths to evaluate stresses by means of X-rays. The recommendations given are based on previous statements. Some principles of fundamentals of X-ray physics for the recording of interference lines with Ω and ψ-diffractometers are dealt with. Methods applicable for the determination of the peak position of the interference lines, the assessment of linear and non-linear lattice strain distributions, and tine calculation of stresses are outlined. For iron, aluminium, copper, nickel and titanium the constants for practical X-ray stress evaluation (XSE) and the parameters of measurement are tabled.

X-ray Microfluorescence (XRMF) analysis uses a finely collimated beam of X-rays to excite fluorescent radiation in a sample (Nichols & Ryon 1986). Characteristic fluorescent radiation emanating from the small interaction volume element is acquired using an energy dispersive detector placed in close proximity to the sample. The signal from the detector is processed using a computer-based multi-channel analyzer.

XRMF imaging is accomplished by translating the sample through the small X-ray beam in a step or continuous raster mode. As the sample is translated, a pixel by pixel X-ray intensity image is formed for each chemical element in the sample. The resulting digitized image information for each element is stored for subsequent processing and/or display. The images, in the form of elemental maps representing identical areas, may be displayed and color coded by element and/or intensity and then overlayed for spatial correlation.

The present study of parameters affecting the performance of an X-ray microfluorescence system has shown how such systems use X-ray beams with effective spot sizes less than 100 micrometers to bridge the gap in analytical capabilities between predominately surface micro analytical techniques such as SEM/EDX and bulk analytical methods such as standard XRF analysis. The combination of XRMF spectroscopy with digital imaging allows chemical information to be obtained and mapped from surface layers as well as from layers or structures beneath the sample surface. Simultaneously, it provides valuable high resolution chemical information in a readily interpreted visual form which displays the homogeneity within a given layer or structure. XRMF systems retain the advantages of minimal sample preparation, non-destructive analysis and high sensitivity inherent to XRF methods.

From measurements of the shift in wavelength with chemical combination, it appears there is very little transfer of charge between the metal and nonmetal atoms for the Group-IV transition-metal carbides and diborides. For Group-VI transition-metal carbides and beyond, there appears to be a definite transfer of charge from the carbon to the metal atom. The bonding in the Group-IV transitionmetal carbides is largely co valent, and metallic for the Group-IV transition-metal diborides. A comparison of shapes of emission bands with crystal structure indicates that, in general, NaCl-type structures have symmetrical peaks with narrow bandwidths compared to hexagonal structure, which have asymmetrical peaks, broad bandwidths, and long tails to the bottom of the bands.

In the field of material analysis and characterization interest has considerably shifted over the last few decades from bulk to surface and very thin film problems. At the present state a wide range of surface analytical techniques - such as x-ray photoelectron (XPS), Auger electron (AES), secondary ion mass (SIMS), ion scattering (ISS) spectroscopies - have become available but every one of them exhibits specific analytical features and information content. Within the context of this paper the main parameter to be considered is the information depth i.e the layer thickness from which the majority of information-bearing particles escape and hence are detected. For XPS and AES, this parameter is associated with the mean-free path of photoelectrans or Auger electrons and typically is in the range from 0.5 to 4 nm. In SIMS the ejected secondary ions are emitted from the outer 2 or 3 atomic layers (i.e. from about 1 nm) while the single-collision binary process occuring in ISS is restricted to atoms from the top most atomic layer (0.2-0.3 nm).

Results are shown for O and F K emission lines from several oxide and fluoride compounds. The spectra are examined for both structure and wavelength. Excitation of the spectra is by both electrons and X-rays. The emission spectra from several oxygen- and fluorine-bearing gases and the influence of the composition of the diffracting crystal on the shape of the observed oxygen spectra are also discussed. Curved crystals of potassium acid phthalate and lead stearate, and a thin-window flow proportional counter, are used to obtain the results.

Methods 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.

The physical meaning of non-linearities in “d” vs. sin2ψ lines, encountered in X-ray measurements of surface residual stresses in polycrystalline materials is investigated. It is shown that when oscillations are present in any one reflection, switching to another reflection to obtain a straight line in “d“ vs. sin2.ψ is feasible only under very special conditions. We also discuss the effect of “quasi-homogeneous” strain distributions and investigate the effects of ψ-range on the accuracy of X-ray residual stress measurements when ψ-splitting” is present. A new geometric error is also discussed that can not be detected by the “annealed powder” method often used for alignment.

Research is being conducted on low energy x-ray and electron physics and application in the 100-1000 eV region. Work on the optimization of fluorescence analysis for light elements, including the development of efficient dispersive systems as the multilayer analysers of the Langmuir-Blodgett type, has been continued. Along with the ultrasoft x-ray program has been one on photoelectron and Auger electron spectroscopy. An evaluation of the application of low energy electron spectroscopy for surface characterization is being made.

Mercuric iodide (HgI2) with high atomic numbers of 80 and 53 for the components, and wide bandgap (2.1 eV) has been considered a potentially useful material for gamma ray spectroscopy for the last number of years. Considerable effort by numerous groups has been directed toward purification and growth of large single crystals of this material. Even with continuing improvement, however, the material is still characterized by good electron transport properties and only modest to poor hole transport behavior. Interesting results nevertheless have been reported in mid-range gamma ray spectroscopy using “up to millimeter thick sections of HgI2. One question always asked is: has the fundamental of lattice scattering etc. been reached in increasing hole transport behavior in this material? There is interesting speculation at this time that this may not be so.

X-ray diffraction observation of metal fractures provides fracture analysists with useful information on the mechanisms and mechanical conditions of fracturing. This method is called “X-ray fractography” and has been developed especially in Japan as a new engineering tool for fracture analysis.

In the present paper, X-ray fractography is applied to fracture surfaces of ductile cast iron (JIS FCD 60) which are widely used as machine parts. The fracture toughness tests were conducted at ambient and low temperatures by using compact tension (CT) specimens with blunt notches and three-point bending (TPB) specimens with fatigue pre-cracks. The line broadening of X-ray diffraction profiles was measured on and beneath fracture surfaces of fracture toughness specimens.

Recently there has been a growing interest in the field of X-Ray MicroFluorescence (XRMF) for analyzing small areas (with sizes greater than about 10 microns diameter). Several recent papers have described prototype systems for this kind of analysis, with particular emphasis on the elemental imaging applications. However, the technique of small-area XRF analysis is not new. For example, Bertin gives an excellent review of much of the earlier work (up to the late 1960s), which used a variety of focusing (with curved crystals) or collimation techniques. Several wavelength dispersive spectrometer systems were modified for small-spot analysis. One of the earliest spectrometers was the X-ray Milliprobe developed by Adler and Axelrod, which employed curved crystals.

Methods of quantitative electron probe analysis using empirical working curves have achieved only partial success because of variations in instrument design, analysis conditions, and homogeneity of standards. These problems have been solved for X-ray fluorescence analysis, but many of the more successful empirical methods cannot be used in electron probe analysis; instead, a more theoretical approach is indicated. In electron probe analysis quantitative results can be achieved with only pure elements as standards provided (1) the analysis conditions are carefully selected, (2) the observed intensities can be corrected to obtain the primary intensity actually produced in the specimen, and (3) the relationship of the primary intensity and concentration can be calculated. While present methods of making some of the corrections required improvement and a “universal” theory for relating the primary X-ray intensities to the concentrations still does not exist, the success achieved with this approach indicates that it should be used to the fullest extent before resorting to calibration curves. Moreover, as information is accumulated, the number of cases requiring the use of calibration curves should diminish, so that eventually it may be possible to perform quantitative analysis in any system with only pure elements as standards,

The synthesis of a new family of aluminophosphate-based molecular sieves containing pores defined by 18 tetrahedrally linked atoms has been described by Davis et al at Virginia Polytechnic Institute (VPI). This development reprsents the first reposted synthesis of a moleoular sieve with pores larger than those defined by 12 tetrahedrally linked atoms. This material has been shown to readily absorb triisopropyl benzene and exhibits a pore size distribution, determined from, its argon adsorption isotherm, which suggests the existence of molecular sieve pores larger than those found in known molecular sieves. Confirmation of a pore defined by 18 tetrahedrally linked aluminum and phosphorus atoms was accomplished by crystallographic structure determination using X-ray powder diffraction data. Single crystal methods were impossible due to an inability to synthesize crystals of suitable size. Details of the structure determination are reported in this work.