Among the limitations of the classical methods for measuring stresses by X-ray diffraction, the existence of stress gradients constitutes a particularly delicate problem. On the theoretical plane, this problem has been tackled by Dölle, Hauk and Cohen. These authors showed that whilst the gradients of the shear stresses σ13 and σ23+ are relatively easy to bring to the fore, as their presence is reflected in an opening out of the curves for 2θ ϕ ψ =f (sin2ψ), those of the direct stresses σ11, σ22 an σ33 are very difficult to detect. In the latter case it is demonstrated that even when the gradients attain very high values, the curves of 2θ ϕ ψ =f (sin2ψ) remain practically linear. This may invite one to apply the classical sin2ψ law, with the result that the stress values so determined do not correspond with the real mechanical state of the surface of the specimen.

An X-ray fluorescence analysis unit has been designed and built especially for the measurement of certain mineral elements in individual biological tissue sections. Such a section may contain in the neighborhood of 10-10 grams of an element of interest, in a concentration in the range of 1-100 p.p.m.

The unit consists of a special high-power X-ray tube with a builtin interchangeable secondary radiator, which irradiates the speciman with the characteristic lines of the radiator element) and a proportional counter and pulse-height analyzer system, which provides analysis of the X-ray spectrum emitted by the specimen. Because the emitted spectrum is greatly simplified by the use of an appropriate radiator element, a diffracting crystal can be omitted, permitting a great increase in absolute sensitivity.

The system is feasible only because of two peculiarities of our biological specimens: they are so thin that matrix effects are negligible, and they consist essentially of a few mineral elements in a light matrix.

Design considerations, calibration procedures, procedures for the analysis of the observed proportional counter pulse-height spectra and results to date will be discussed.

A highly oriented pyroliiic graphite crystal is commonly used as a monochromator for X-ray diffraction and fluorescence analysis (l)-(6). Improvements in the monocliromator performance is desired to increase the range of practical applications.

A new method for the collection and analysis of high temperature Guinier x-ray data has been devised at The Dow Chemical Co. This technique can be used to monitor various types of structural transformation and thermal expansions up to 900°C. The thermal expansions of α-Al2O3 and two TiO2 structures, anatase and rutile, have been characterized for their use as high temperature internal standards.

A procedure and program are described for rapid, economical and simple production of fully quantitative, multi-element analyses from energy dispersive microprobe data. Methods are outlined for background shaping and scaling, comprehensive overlap correction, and adjustment for instrumental drift. Program facilities include the output of all coefficients required, built-in standard data, the option to use default standards when no working standards have been measured, and the ability to respecify standards during data processing.

This report will describe scientific activity in XRF as well as some practical application topics for Japan and China.

A PDF 15/40 computer wich ADC and CAMAC interfaces is used to control data collection apparatus, acquire data, and reduce data to determine the elemental composition of aerosol samples. The background is subtracted from each energy spectrum, peak centers are located automatically using a Gaussian correlation technique, peak multiplets are resolved with Gaussian fits, peak energies are compared with entries in a table of x-ray lines for possible identification, multiple identification of peaks and line interferences are resolved, and the elemental amounts are determined from the areas of the Gaussian fits.

A series of nanostructured Fe/Ag metal films were produced at various substrate temperatures to determine their magnetic characteristics. The magnetic coercivity was found to increase with the diffracting-particle size which is process controlled. The films produced at low substrate temperature (<200°C) consisted of small metallic clusters of Ag (<100 Å). As the substrate temperature was increased, the films exhibited increased crystallinity and larger diffracting-particle size. The position of the maximum in the particlesize distribution function and the width of the function increased with substrate temperature.

Magnesium has been shown to have a marked effect upon preprecipitation processes occurring in aluminum-13 wt.% zinc alloys containing 0.025, 0.098, 0.17, 0.19, 0.23, and 0.27 wt.% magnesium. X-ray small-angle scattering and resistance measurements have been used to monitor the rate of growth of Guinier-Preston zones in quenched foils and wires. The following results have been obtained: (a) small additions of magnesium noticeably decrease the rate of growth of G-P zones but the final zone size reached in the magnesium containing alloys is generally larger than in Al-Zn alloys quenched and aged under identical conditions; (b) the general pattern of preprecipitation found in Al-Zn alloys is not seriously changed by these small additions of magnesium; (c) the dependence of the rate of preprecipitation on quenching temperature is shown to be a function of magnesium content and aging temperature; (d) the dependence of the rate of preprecipitation on aging temperature is influenced by the range of aging temperature, magnesium content, and the quenching temperature.

During this decade, several influence-coefficient algorithms have been published which utilize fundamental parameter equations to correct interelement effects in bulk samples. The Comprehensive Algorithm of Lachance (COLA) is one such algorithm and is used in the program NBSGSC(l). Another COLA-based computer program called FLY-FPM has been developed in China by one of the authors (L. Feng). Using FLY-FPM as a starting point, we developed a new COLA-based program as part of a Cooperative Research Agreement with Kevex Instruments. This program was designed for use with x-ray spectrometers that employ both tube and secondary targets for excitation. For direct tube excitation, the NIST tube spectral distribution algorithm is used in this program (2). For secondary target excitation, the radiation is usually treated as being monochromatic, and fundamental parameter expressions are formulated with this in mind.

XRF and Ion mfcroprobe analyses of fossils of known and uncertain provenance from the Lower-Middle Pleistocene locality of Kanjera. Kenya, are reported. The goal of this study was to develop a nondestructive technique of provenancixig fossils, which could be applied to the Kanjera sample. The fossils of known provenance were collected in the excavations of the 1987 Smithsonian Expedition. Three fossils of uncertain provenance, two specimens of Theropithecus oswaldi and a hominid fossil, were analyzed as test cases.

Both qualitative and quantitative XRF analyses of Kanjera fossils were carried out. In the qualitative analysis, the elemental peak areas from each fossil's XRF spectrum were calculated and normalized to the peak area of the incoherently scattered radiation. Results of the analysis showed that fossils from the Lower-Middle Pleistocene Kanjera Beds, for the most part, had higher levels of yttrium (Y) and zirconium (Zr) than those of the younger Apoko (Ap) Bed. black cotton soil (BCS) and modem bones (MD). The relative concentrations of uranium (U) v strontium (Sri and thorium (Th) were diagnostic of the Kanjera Bed of origin. These findings were confirmed by quantitative XRF and ion microprobe analyses of a subsample of Kanjera fossils. The T. oswaldi and hominid fossils had trace element concentrations suggestive of K2 and BCS provenances, respectively. These findings provide a framework for the qualitative XRF provenancing of other surface collected fossils from the locality.

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.

The amphibole mineral, cummingtonite-grunerite, has been used as a tracer for taconite tailings discharged into Western Lake Superior. The discovery of many asbestiform amphibole fibers in the tailings and Western Lake Superior water lead to concern over fiber concentrations in municipal water supplies using this water. This concern was based on the association between human asbestos exposure and increased rates of cancer of the gastrointestinal tract and peritoneum. An x-ray diffraction external standard technique has been developed for rapid, inexpensive, semi-quantitative determinations of amphibole mass concentration in water. The average amphibole mass concentrations for different Western Lake Superior water intakes compare very well with the average electron microscope fiber counts for the same samples. Daily amphibole analysis of the Duluth water supply indicates an average amphibole concentration of 0.19 milligrams per liter.

Energy dispersive X-ray fluorescence (EDXRF) analysis is finding increasing application in field assay of soils and stream sediments for geochemical prospecting; in borehole logging and core analysis for formation evaluation in mine control, and in on stream analysis for process control.

The analytical capability of the method is determined by the choice of source, the energy of the exciting radiation and the energy resolution of the detector. The nature of the samples, their atomic number and concentration are also important. However, the most dominant constraints on limits of detection are often imposed by the environment at the region of measurement: by the borehole condition, the nature of the rock face or the form of the particulates and stability of the fluid in a process stream.

The electron probe microanalyzer has found numerous applications in physical metallurgy. Some recent problems which have been studied with the microanalyzer constructed by the author at the California Institute of Technology include (1) determination of the penetration of chromium in chromized iron, (2) determinations of the concentration of nickel in taenite bands occurring in a fragment of meteorite from Canyon Diablo, (3) identification of intermediate phases in the as-cast structure of an alloy of titanium and copper, (4) identification of phases in the titanium—silver binary system, (5) determination of concentration fluctuations in a gold—copper alloy resulting from slow solidification, and (6) determination of the diffusion profile of nickel in single crystal sapphire.

Films of II-VI compounds have been prepared by vacuum technique for the determination of their thicknesses. Some difficulties have been experienced in preparing good quality films- The positron of the substrate in the vacuum chamber, the rate of deposition, and the temperature of sublimation are some of the factors influencing the quality of these films. For instance, films of cadmium sulfide could be prepared in the usual yellow or orange color or in colors ranging from brown to black, depending on the conditions enumerated. For energy conversion, a film of proper thickness is one of the requirements for aerospace application. Among the various methods used for the determination of the thickness of these films, X-ray fluorescence can be performed rapidly and nondestructively. After determination of thickness by the X-ray fluorescence method, the samples can be used for other determinations and for energy conversion without their efficiency's having been affected. Other physical and chemical methods have been worked out. Comparison of these methods with the X-ray fluorescence method is made. Procedures and results are presented.

A modular x-ray and electron beam system has been constructed to accomplish most standard types of x-ray analysis automatically. The system includes a vertical powder diffractometer, a vacuum spectrograph, a four-axis single-crystal diffractometer and an electron microprobe with four spectrometers. The system is controlled by a single computer with auxilliary drum storage. The powder diffractometer has automatic goniometer drive, automatic sample changing with computer cataloging of samples and automatic variable divergence slit. The x-ray spectrograph is a standard unit with added 100 KV capability, automated goniometer drive, eight or 32 position sample changer, six-analyzing-crystal changer, collimator changer, and detector changer. All functions including sample number cataloguing are computer controlled. The four-axis single crystal diffractometer has all functions computer controlled and includes peak search option. The electron microprobe/scanning electron microscope has all spectrometers, x, y, z stage motions and sample changer controlled by computer. X-Ray channels, beam current and sample current are automatically read-out. Control of probe functions and correction of mechanical errors in stage operation, are aided by a digital beam scanner with a light pen. Counting channels and computer interfacing are modular, and channel components are interchangable by the operator. Computer hardware may be expanded and the software is modular. Any combination of instruments up to eight may be operated.

The computer operates all instruments simultaneously in a time-sharing mode. Programs consist of operating system programs, individual instrument programs and data processing programs. The operating system drives all x-ray hardware, fetches programs and data from the drum, allocates data storage, queues final results for printing and performs other necessary executive functions. For qualitative analysis, spectra for each instrument are collected automatically in several modes and are stored on the drum. A variety of methods are used to remove background, strip unwanted peaks and find peak position and intensity. A.S.T.M. diffraction, spectrographic and special files are maintained on the drum. Quantitative analysis is executed automatically using a version of "MAGIC" on the electron microprobe and a multiple linear regression method for the spectrograph and diffractometer.

The use of the computer controlled powder diffractometer for the qualitative and quantitative analysis of multi phase powder mixtures is becoming relatively common place, and we ourselves have described in some detail the hardware and software components of typical systems 1,2) of which the AFD 3600 is the latest version 3). Although great success has been achieved in the use of the minicomputer for machine control, data acquisition and display, plus some degree of data workup, less success has been gained in search/matching of unknown powder patterns, although computer programs have been available for a number of years which utilize relatively large computers for automatic search/matching e.g. 4,5) the success with which these programs have been applied has been somewhat disappointing. Much of the difficulty arises from the marginal quality of data in the JCPDS index and from uncertainties in the accuracy of the experimental patterns.

A general computer program has been written in basic Fortran language and tested for computing average particle size, strain, and particle size distribution according to the Fourier method of B. E. Warren.

The program provides such optional features as input data and Fourier coefficient print out, automatic background correction, the choice of fixed count or fixed time input mode, the synthesized diffraction peaks deconvoluted with respect to the instrumental diffraction peak, and a variable amplification range of particle Size. Included in the analysis is a polynomial fitting procedure for the scattering factor. The authors have attempted to write this computer program to be as self-explanatory as possible for general applicability. This program is available on request.

This Fourier analysis program has been tested using known distribution functions, and has been used for measuring average particle size, particle size and strain distribution in heattreated boron-doped graphite samples.

The total reflection x-ray fluorescence (TXRF) method of analyzing elemental contents Is based on the small angle irradiation of thin samples placed on a total reflecting backing with a narrow photon beam. Two instrumental problems are to be solved here. The first is to form the narrow beam with a small angular deviation. The usual way to solve this problem is to use collimators with small solid angles. These angles must be less than the critical angle for x-ray total reflection, which, in the energy range 10 - 20 keV has an order of magnitude around 10−3 rad.