Quantitative multicomponent analysis of phases by x-ray diffraction still remains one of the most difficult applications of any element or phase spectroscopic method. The level of quality of XRD quantitative analysis is largely in the hands of the operator, but several relatively new methods for processing basic diffraction data are becoming known and more frequently used, including fulltrace (observed and calculated) subtraction methods (Smith et al, 1988), Rietveld procedures (Bish and Howard, 1988; Taylor and Aldridge, 1993), and chemical “apportionment” target-transformation methods (Starks, et al, 1984). In spite of these new advances, the single or multiple peak reference intensity ratio (RIR, or kj) procedure remains a simple and attractive technique for routine quantitative XRD analysis (Schreiner, 1995; Snyder, 1992; Davis, 1992).

Simplified models are “being used, at the College Park Metallurgy Research Center for six popular methods for matrix correction in X-ray analysis, including Lachance-Traill, Lucas-Tooth and Pyne, and Rasberry-Heinrich procedures. A choice of models provides the broader data-handling capability required for processing information obtained by both energy-dispersive and wavelength-dispersive X-ray systems. The selection of model for each problem depends on the system and the availability of standard reference materials. Programming developed at College Park using the simplified models has been formulated for use by analytical chemists with minimal computer training. Some of the considerations involved in developing a versatile computer program for matrix correction will be presented, as well as applications of the procedures to iron-nickel-chromium alloys, aluminum alloys, and low-alloy steels.

Metallic impurities present in crude oils lead to the rapid deactivation of catalysts used in refineries and a drop in the yield of oil products. The determination of these impurities is therefore of primary importance. The conventional and most widely used methods to determine trace metals in oils and petroleum products are chemical analysis methods such as atomic absorption spectrometry (AAS) and inductively coupled plasmaoptical emission spectrometry (ICP-OES). Sample preparation for these methods includes decomposition of the crude sample by dry ashing and combustion of the oil sample followed by chemical treatment of the dry ash residue (ASTM, 1983; Fassel et al., 1976). Major drawbacks of chemical analysis methods are the length of time required to prepare the sample and the possibility of losing trace metallorganic compounds in the form of volatile compounds.

A micro fluorescent X-ray analyzer with a focusing type of spectrometer has been developed to analyze samples of small amounts such as extracted inclusions or precipitates from metals or small areas in samples from 0.1 to 2.0 mm in diameter. This instrument is expected especially to analyze powder samples of small quantity because average values from such samples can be obtained and because surface conditions of the samples scarcely affect the results compared with their effect in electron probs microanalysis. A commercial X-ray tube is combined with a device of slits limiting incident X-rays, a focusing spectrometer with a Rowland circle of 4-in. radius, and a microscope of low magnification for observing the analyzing point on the samples. The wavelength range of the spectrometer with LiF and ADP analyzing crystals is from 1.20 to 9.94 Å, and, therefore, higher elements than aluminum in atomic number can be analyzed. The authors exerted their efforts to obtain the higher X-ray intensities in order to analyze smaller areas. The X-ray intensities obtained are satisfactory, except for light elements. For example, the detected X-ray intensity of pure nickel is 1650 cps with the use of a 0.1-mm diameter specimen, and that of pure sulfur is 52 cps with the use of a 0.1-ramdiameter specimen; however, with a 1-mm-diameter specimen, the intensity of pure nickel is over 5000 cps and that of pure sulfur is 1650 cps. These correspond to the intensities from 20-mm-diameter specimens of those elements when a flat-crystal spectrometer is used. The calibration curve for quantitative analysis generally varies with the sample area under analysis, but the same curves are obtained if the sample area is larger than 1 mm in diameter. Then, powder samples are analyzed quantitatively by using a plastic sample holder of 1-mm diameter and 0.3-mm depth. This instrument has good ability for microanalyzing trace elements by, for example, the ion-exchenge membrane method. The sensitivity represented is nearly 5000 cps/μg for Ni Kα from NiSO4 that is soaked and dried in thin rice paper. Some applications of the micro fluorescent X-ray analyzer to precipitates in steels and corrosion products are reported.

Residual stresses in thin films are important technologically due to their impact on the reliability of these structures. Various techniques are used to measure these stresses, and the results of these techniques do not always agree. In some cases, formation of interphase stresses were postulated to account for such discrepancy, but no definitive microstructural analysis was given. In this study, the residual stress response of evaporated films of 9 1% Al - 9% Hf (atomic %) deposited on 0.4 mm thick (100) Si wafers was studied as a function of thermal treatment. The stresses were measured by radius of curvature and d vs. sin2ψ techniques. Concurrently, the microstructure evolution was tracked using powder diffraction and metallographic techniques. As previously reported in the literature, residual stresses were tensile in all cases for both techniques. However, as expected, the stress results from both techniques did not always agree. The delta between the residual stresses measured by the radius of curvature and d vs. sin2ψ techniques were found to correlate well with the development of a 2nd phase (metastable cubic Al3Hf).

X-ray powder diffraction (XRD) is widely used for qualitative analysis of the phases in multiphase mixtures. To extend the characterization to the level of quantitative analysis (QA) requires solution of many challenging problems such as elimination of preferred orientation (1,2,3); selection of an appropriate reference standard which closely matches the analyte phase in crystallite size, thermal history, stoichiometry etc. (4); effectively collecting the experimental intensities (5,6); and finally, performing the data reduction and analysis.

The desire to solve the last problem in a general way and to incorporate the “best” procedures developed in several laboratories into one package was one of the stimuli for developing the NBS*QUANT82 system of programs. This system is integrally coupled with the data collection system AUTO (6,7).

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.

We have conducted in-situ, real-time x-ray diffraction experiments to probe the dynamic structural changes occurring in copper during loading and then on relaxation. The 331 KαI, KαII peaks were used to monitor the development of elastic strains during loading, and their response during relaxation. The peak width was studied to better understand the structural changes that occur during loading, and more importantly on relaxation, since it is these structural rearrangements that reduce the overall strain in the system and allow the stress to relax.

The results revealed that the structure is highly mobile immediately following the start of stress relaxation. The mobility decreases with time, scales with the magnitude of the applied strain and is highly dependent upon the applied strain rate. In addition, it was apparent that the KαI and KαII peaks do not respond in the same way to the elastic strains and that they also show different structural rearrangements. This suggests an in homogeneous distribution of displacements within the sample.

Techniques of determining spot size and sensitivity of the instrument will be developed. Spot sizes of the order of 5 microns have been obtained with the possibility remaining for improvement- Preliminary sensitivity measurements indicate that micro-microgram quantities of some elements are sufficient to be detected. Difficulties involved in finding desired target areas will be discussed. The inhomogeneities of standard samples used for conventional fluorescense X-ray quantitative analyses precludes their use for microemission techniques at least in some cases. Possible ways of determining homogeneity will be discussed. Analysis which can be performed to advantage may be classed into several categories.

• 1. The changes in composition occurring in grain boundaries can be detected and compared with the base material.

• 2. An inclusion, in a metallic material can be brought under the electron probe and analyzed independently of the base material.

• 3. Changes in composition across a boundary between solid phases can be measured.

• 4. Diffusion coefficients between solid phases may be determined.

• 5. Thickness of thin films and variations in film thickness can be measured.

Examples of the instrument's performance will be given in some of these categories.

To assure an adequate supply of such critical metals as nickel and chromium, extraction procedures must be developed to process low grade domestic sources. In optimizing these procedures it is essential to use suitable analytical procedures to characterize the materials, identify phase transformations, and determine metal and mineral association of the critical metallic elements through all stages of the process. Evaluation of complex sources such as laterites requires special material handling techniques coupled with X-ray diffraction and with optical and SEM analyses of many individual particles. A joint study by the Bureau of Mines and the Denver Research Institute using these procedures has resulted in optimizing a new modification of an extraction process.

An irradiation of solid samples with x-rays causes an electron emission from the sample surface, owing to photoabsorption. These electrons can be detected under vacuum conditions and are photo, Auger and secondary electrons. Due to inelastic collisions most of these electrons have lost some of their original kinetic energy along the path from the atom of origin to the surface. With nondispersive electron detection the total electron yield (TEY) is observed.

For measurements performed with a tunable x-ray monochromator information on the qualitative composition can be obtained by the following procedure. The photon energy has to be timed from below to above of one of the absorption edges of a given element. In case of its presence in the specimen an increase of the TEY-signal can be observed.

Both ammonium chloride and ammonium bromide undergo a transition, with rise in temperature, from an interpenetrating simple cubic (II) to a face-centered cubic (I) lattice at 183 and 137°C, respectively, and both the low- and high-temperature forms give a complete series of solid solutions. We have determined the lattice constants of the high-temperature solids at about 250° as a function of composition, and redetermined the lattice constants of the low-temperature solids at room temperature. The solutions were made by crystallization from water, followed by stirring in contact with mother liquor for at least three weeks at room temperature. Measurements were made with a Norelco- Philips diffractometer and recorder, with Cu Ko. radiation. For the high-temperature work, a simple, inexpensive heating apparatus was developed. The only previous data reported for the high-temperature forms are the lattice constants of the pure components given by Bartlett and Langmuir.

The low-temperature solutions showed negative deviations from Vegard's rule at both ends of the concentration range and a slight positive deviation elsewhere when high-angle data were used. The high-temperature solutions showed marked positive deviations from Vegard's rule over the whole compositions range. Values for the pure components agreed reasonably well with those of Bartlett and Langmuir.

The progress of the change II → I with time was followed for some of the solutions in the neighborhood of the transition temperature in an attempt to reveal the mechanism of the process.

X-Ray powder diffraction (XRPD) techniques are compatible with studies of the transplutonium elements and their compounds. Only limited amounts of these materials are available for study, and microchemical techniques exist for the preparation of samples suitable for X-ray analysis. The microscale syntheses, systems for annealing/ quenching to bring about phase transformations, and a modified powder diffraction camera are described. Examples of recent and current work are presented to illustrate some specific applications of XRPD to basic, transplutonium element research.

The continuing development in recent years of mercuric iodide room temperature x-ray spectrometers has led to steady improvment in the spectral energy resolution capability of these systems. This has been due largely to the continuing reduction in the electronic noise level of the associated preamplification electronics. It has been demonstrated that a system consisting of a mercuric iodide detector in combination with a pulsed-optical feedback preamplifier provides superior energy resolution performance in x-ray spectrometry in comparison to the other types of preamplification. Previously, results have been reported by us of the energy resolution of such systems with both the detector and input FET of the preamplifier at room temperature and with the input FET cooled by liquid nitrogen and the mercuric iodide x-ray detectors lightly cooled.

Various kinds of compounds containing arsenic have been used in the world as rat poisons, agricultural chemicals and so on. In the field of semiconductor materials, AsH3 is used as a doping gas on silieon-wafer substrates and GaAs is now also investigated as a wafer substrate instead of Si wafer.

As for quantitative analysis of arsenic, atomic absorption spectrometry (AAS) and inductively coupled plasma atomic-emission spectrometry (ICP-AES) have often been used. In these methods, usually, oomplioated pretreatments such as preconcentration and separation have been needed in order to obtain reproducible values for arsenic.

When X-ray residual stresses are determined taking into account the stress gradients within the penetration depth of X-rays, three assumptions have usually been made; 1) the stress gradient is linear in respect to the depth from the specimen surface, 2) the penetration depth of X-rays is a function of Sin2ψ and 3) the strain measured by X-rays corresponds to the average strain weighted on the intensity of the diffracted X-rays. However, the assumption of the penetration depth of X-rays is the reason we sometimes observed noticeable errors which depend on the combination of stress components in the stress tensor.

On-stream X-ray fluorescence analyzers have been available for about 20 years. They have been used with great success and they have made an effective process control possible in many concentrators. They have, however, one severe drawback. Normally the sample that ought to be measured is in slurry form and it would be difficult and expensive to prepare it into more conventional form used in ordinary laboratory practice. The main constituent of slurry is water and normally some kind of plastic film is needed to keep slurry apart from the measuring system at least when the slurry system is malfunctioning. Already these two things are sufficient to set a limit to the lightest element that can be measured with reasonable accuracy and precision. This means that minerals that contain only such low atomic number elements as e.g. Mg, Al, Si and P remain out of reach. Difficulties arise also in cases where the interesting element is not only in the solid material but also in the solution part of the slurry. In great many cases the interesting element occurs in several minerals at the same time which causes certain problems with the accuracy. Fortunately this problem does not set such a basic limitation as a too low Z does unless only one of these minerals is of interest, which may make the whole method worthless.

On the basis of the “column-like” powder model of Warren and Averbach, a profile fitting procedure was devised to obtain microstructural disorder parameters. The interference function

where d is the interplanar distance, λ the wavelength, θ the diffraction angle and N the number of cells within a column, was used to model experimental profiles taking into account the column-like crystallite size and r.m.s. strain distributions. The procedure can be applied both to single peak and to two or more peaks of multiple order of reflection. The method was tested on several samples, also having a bimodal size distribution, and the results compared with those obtained by the well-established Warren-Averbach analysis.

Calibrated powder patterns of a number of high symmetry crystalline materials were recorded in three different Guinier-type focusing cameras. The films were then measured by three different techniques, one visual and two instrumental. Cell parameters were calculated by three different data reduction procedures. The aim of the work was to establish the level of reproducibility for cell parameters obtained in routine work with these instruments.

A theoretical approach of some factors influencing the intensity diffracted by a polycrystalline material at a definite Bragg angle has been confirmed by experimental data obtained with a high-angle Norelco diffractometer. The factors mainly considered are the focusing arrangement of the goniometer which delineates the geometric shape of the volume fraction of the sample being irradiated and the absorption of the latter.

Tests have been performed (a) with quartz mixed in samples covering a large range of absorption coefficients, (b) with two different K radiations using copper and molybdenum targets, (c) with three different angles of beam divergence of 1, ½, and ¼°, respectively, and (d) with the sample packed and leveled in a copper grid with openings of about 350 μ. As this test with copper grids was to demonstrate that each opening was acting like a volume of sample irradiated by a beam of extremely small divergence (0.1°), it also shows that more accuracy in the measurement of the exact Bragg angle can be reached in these conditions as compared to that obtained with conventional sample holders.

A general equation, suitable for qualitative and quantitative analysis when these factors have to be taken into consideration, is proposed.