X-ray diffraction is found effective in disclosing the distribution of stresses over the surface of adhesively bonded lap joints when loads well below the yield point are applied. When a pair of 6061-T6 aluminum strips 1/16” or 1/32” thick and 3/4” wide is adhesively bonded in a single lap joint and loaded in tension, maps giving the distribution of the X-ray-measured stresses show the limits of the bonded area with an accuracy about equal to the width (1 mm) cf the irradiated area along the specimen. Attendant bending stresses resulting from the loading are also registered. Stress values can be obtained from the observed diffraction angles by calibration with tensile tests of a single unbonded strip. Similar results are obtained for graphite/epoxy laminates adhesively bonded in a single lap joint to aluminum when diffraction is from the aluminum, but a lower accuracy is obtained when diffraction is from the filled composite.

Another X-ray method was developed for measuring applied (not pre-existing residual) stresses, and for mapping their distribution around a joint. A thin layer of epoxy paint containing a diffracting filler (say aluminum or silver powder) is applied to a specimen and cured. Diffraction from this paint yields shifts in diffraction angle approximately proportional to the magnitude of applied stresses. The limits of the bonded area in single lap joints under load are disclosed. Both methods appear, therefore, to be practicable for mapping the areas that are properly bonded, and presumably also for non-destructive evaluation of bond defects.

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.

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.

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 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.

An improved method for sample preparation and determination of minor elements in catalytic materials by radioisotope induced X-ray fluorescence is presented. The sample preparation is simple and rapid, it utilizes both and internal standard procedure as well as a thin film technique. Synthetic standards are prepared simply by mixing thoroughly the appropriate amounts of the elements of interest as their respective oxides with the matrix and the internal standard. The above standards are used to calculate the relative-fluorescence ratio factors (FJL) for each element of interest relative to the internal standard.

Some of the different types of deviations (sample preparation, standard counting, instrumental, etc) will be shown for typical determinations applying experimental methods. Finally the application of this technique for the determination of Cobalt, Nickel, Molybdenum, Platinum and Palladium in catalytic materials is presented.

The authors previously reported stress measurement in stainless steel by the use of monochromatic Cr-Kβ X-rays and a position sensitive proportional counter. Results indicated that a stress value can be obtained with high precision on account of the subtraction of background and the elimination of αFe(211) peak by Cr-Kα X-rays. The major disadvantage of this method, however, is that the intensity of Kβ X-rays monochromatized is essentially weak and it is complicated to eliminate Kα X-rays for practical use.

A double diffractometric method which allows clean separation of the thermal diffuse contribution from X-ray reflection peaks is demonstrated.

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.

An X-ray fluorescence analysis unit has been automated with a multi-position sample changer, a stepping motor to position the spectrometer, and computer addressable switches to control the selection of crystal, detector, collimator, and beam filter. The unit can be controlled off-line through a Teletype or on-line with a computer. This computer utilizes a multi-user program for the simultaneous operation of the fluorescence analysis unit and two diffractometers. Programming the system for any desired analytical or research procedure is accomplished using an expanded version of BASIC.

Recently synchrotron radiation (SR) sources have been extensively used for the study of materials science. The high intensity of tunable monochromatic X-rays from SR facilitates many types of spectroscopic/ diffraction studies which have otherwise not been possible. Regarding the X-ray fluorescence technique, significant improvement of the minimum detection limit has been performed and has enabled trace element analysis in the order of tens of ppb or 10-12 g.3-8 SR microanalyzers and near surface analysis using grazing incidence geometry are also attractive applications of synchrotron X-ray fluorescence technique. From a point of materials characterization, chemical state analysis is not less important than ordinary element analysis.

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.

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.

One of the most important properties that characterizes alumina is its elemental composition. Although XRF has been applied to the analysis of aluminas for the past three decades, special aluminas have always presented a maj or challenge. Moreover, only recently did it become possible to analyze for light elements such as Na. Two new sample preparation techniques for elemental analysis of aluminas by XRF were developed. One is based on briquetted powders, another involves fused samples. Their advantages and limitations will be presented. In the case of fusion one analytical program was applied to aII types of aluminas, The performance of each method will be discussed.

A comprehensive chart is preserit of the X-ray diffraction effects of gas-and Uquid-like armorphous substances, small particle-size materials, mixtures of amorphous and crystalline compounds, sheetlike crystals, and fibrous materials.

The relationship between the X-ray diagrams and chemical preparations as shown by typical examples from the field of the manufacture of active catalysts cadmium sulfide semiconductors, pour point-depressed lubricants, electroless nickel platings and metal-filled cellulose fibers.

The investigation of thin surface layers formed by chemical reactions required the combination of electron and X-ray diffraction techniques. The usefulness of this combination of methods is demonstrated by a study of black stain formation on cold rolled annealed steel. By identifying the materials in the stain and determining the sequence in which they formed a reaction mechanism between steel surface and annealing-gas can be postulated.

The adsorption of liquids in 2eolites has been a widely studied phenomenon, and with the development of ZSM-5, considerable work has been carried out on this zeolite, However, few articles have been published dealing with changes in the X-ray diffraction patterns when the zeolite pores contain adsorbed molecules. The purpose of this paper is to report changes in the X-ray diffraction pattern of ZSM-5 after mixing it with various organic solvents.

This work began after studies of both deactivated and partially deactivated ZSM-5 catalysts showed that their X-ray diffraction patterns changed in intensities and peak positions after use in microreactor studies. If coke or hydrocarbons were causing the above changes, as postulated, would hydrocarbons adsorbed in ZSM-5 produce the same changes? Simpson and Steinfink showed that the low-angle lines of faujasite decreased in intensity after the adsorption of m-dichlorobenzene.

Both double-crystal and triple-axis x-ray diffraction techniques have been used to study complex SiGe/Si structures. A novel method for measuring the nucleation activation energy of dislocations in strain relaxed SiGe/Si structures is presented to illustrate the usefulness of these techniques.

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.

The effect of sample granularity on diffracted x-ray intensity was evaluated by measuring the 2θ dependence of x-ray fluorescence from various samples. Measurements were made in the symmetric geometry on samples ranging from single crystals to highly absorbing coarse powders. A characteristic shape for the absorption correction was observed. A demonstration of the sensitivity of Rietveld refined site occupation parameters is made on CuAu and Cu50Au44Ni6 alloys refined with and without granularity corrections. These alloys provide a good example of the effect of granularity due to their large linear x-ray absorption coefficients. Sample granularity and refined thermal parameters obtained from the Rietveld analysis were found to be correlated. Without a granularity correction, the refined thermal parameters are too low and can actually become negative in an attempt to compensate for granularity, A general shape for granularity correction can be included in refinement procedures. If no granularity correction is included, data should be restricted to above 30° 2θ, and thermal parameters should be ignored unless extreme precautions are taken to produce <5 (μm particles and high packing densities.