In X-ray diffraction techniques intensity of radiation is an important factor. In addition, when high resolution is required, the usual collimating system restricts the width of focus that can be effectively used. Accordingly, a prime requirement is that the target loading shall be high to give the greatest possible brilliance at the focus. An X-ray unit designed to achieve these qualities will be described. Its use with a spectrometer and with a number of cameras for differing crystallographic studies will be illustrated.

The tube operates with alternative electron guns, one of them to provide a circular focus of 40 microns in diameter and the other to provide a line focus of 1.4 millimeters in length and 0. 1 millimeter in width.

In the measurement of residual stresses in hardened carbon steels by X-ray diffraction the principal difficulty encountered is determining the precise location of the broad diffraction lines. Christenson and RowlandM have proposed a workable technique, but it entails a complicated correction calculation. A simplified correction procedure, based on theoretical considerations, will be described which shortens the time required to obtain accurate data and cuts the time required for calculation to a fraction of that required for the previous method.

It can be shown that the asymmetry of the broad diffraction lines in the back reflection region is largely due to 6 dependent intensity factors. Thus, the proposed correction procedure uses a multiplicative correction to peak intensity which includes all significant geometrical and absorption factors. The line position is then determined accurately as the axis of a parabola fitted to the corrected data. Since the data is taken in the vicinity of the peak, the time required to obtain accurate data is reduced and furthermore it is possible to determine residual stresses in as-quenched steel even though the structure is tetragonal.

Examples of the type of stresses measured and the correlation between this new method and that of Christenson and Rowland will be presented.

In view of present difficulties encountered in met alio graphic methods of phase analysis of titanium and its alloys, the possibility of utilizing integrated X-ray intensities for phase analysis was investigated. Power Formula variables were calculated for titanium, and relative areas of three alpha and one beta peak were determined. Recorded X-ray intensities were obtained from a large number of titanium specimens. The recorded intensities were analyzed and the results compared with those from metallographic analysis. The errors in the method arising from the nature of titanium, texture and peak overlapping, were studied and where possible, compensated for by adjusting the method of measurement and calculation.

The amount of kyanite in samples obtained from magnetic and density separations of a kyanite ore was established by a quantitative X-ray diffraction procedure employing an internal standard. The accuracy of the results at low kyanite levels was improved by adding pure kyanite to the samples, analyzing these mixtures and extrapolating back to the lower level. The results were verified by X-ray diffraction analyses of synthetic mixtures containing amounts of kyanite approximately equal to that indicated in the ore samples. The percentage of error is estimated to be ±3per cent of the amount present in the range of 20 to 80 per cent kyanite.

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 identification of phases in solid steel specimens is subject to well known limitations. With suitable techniques, however, phases present in exceedingly small amounts can be isolated and identified. The work to be described is represented by three main stages.

• 1. The techniques of isolation. The aim has been simplicity with the maximum efficiency of separation. Simple open and closed type cells are used and a few selected electrolytes for different conditions.

• 2. The second stage is the identification of the separated particles. The X-ray photographs do, however, provide a considerable amount of other data which are often as important as the identity of the constituents. Thus, information can be obtained about the shape and size of particles and lattice spacing changes in solid solution phases. A supplementary determination of the solid solution content of the matrix is often useful.

• 3. The third stage involves the interpretation of the results in relation to the strength and other properties of the steel or alloy. Here such questions arise as the effects of particular carbides or intermetallic phases, solid solution hardening and the times involved in various reactions and their relation to creep, etc.

A number of examples are given and some limitations noted.

In making quantitative X-ray diffraction studies of quantities such as lattice parameters one generally treats the measured quantity as existing at the sample surface. In X-ray residual stress analyses; large lattice parameter gradients as a function of depth below the sample surface are sometimes encountered and the measured stress (as obtained from, these parameter measurements) is affected toy the fact that the X-ray beam penetrates the sample. In order to accurately evaluate residual stress as a function of depth, it is necessary to consider the "depth of penetration" of the X-ray beam.

The authors have treated this problem by considering the measured stress as an average weighted over the depths from which the diffracted information emanates. By using the observed lattice-parameter gradient as a first approximation, it is possible to set up a theoretical expression for the measured stress with the actual stress at the surface as the only unknown. By equating this to the measured value, it is possible to solve for the value at the surface and thus obtain an equation for the variation of lattice parameter as a function of depth. This process may be used reiteratively to improve the accuracy of the approximation. A specific example of the use of this equation will be presented.

Work at the Detroit Arsenal has shown that techniques similar to those employed for the determination of pole figures of metals can be utilized for studying organic materials such a a stretched rubber latex. The rubber, when stretched, forms a preferred orientation pattern which is proportional in intensity to the degree of elongation, and which can be used to plot a pole figure.

A Geiger-counter spectrometer was used to study samples of rubber stretched 600 to 1000 per cent. Using a transmission technique, the specimens were tilted to the impinging X-ray beam in five degree increments while rotating through 360 degrees to allow the measurement of the diffracted beam from the selected atomic planes at various angles within the specimen. The intensities of the diffracted beam at these angles were plotted on a stereographic net to form the pole figures of the (002) and (012) planes of the stretched rubber. The geometry of the sample arrangements permitted the outer portion of the pole figure to be plotted from alpha angle 0 degrees to alpha angle 45 degrees.

A technique is described for the study of the early stages of precipitation hardening in single-crystalline and poly crystalline copperberyllium alloys. Since no trace of the equilibrium precipitate responsible for hardening can be detected by ordinary X-ray or metallographic techniques prior to the onset of overaging, the described method is based on the changes produced in the matrix as the result of the formation of aggregates along preferred lattice planes. Such formations produce accommodation strains in the matrix lattice which, can be detected as a change in the intensity and angular range of matrix reflection.

An interpretation of the age hardening sequence in a copper - beryllium, alloy after isothermal annealing is presented in terms of fundamental transformations.

Carbon blacks were oxidized by gaseous and wet oxidation techniques. Graphite was oxidized by potassium chlorate dissolved in mixed nitric and sulphuric acids. The resulting oxidized carbon blacks contain 5 to 20% oxygen, 1% or higher hydrogen, and the rest carbon. The oxidized graphite was heated to 200°C at which temperature it explosively forms a material that is very similar to carbon black. The exploded material contains 15% oxygen and the rest carbon. The X-ray work attempts to present a picture of the structure of these materials in terms of per cent disorganized matter, size of crystallites, distribution of thickness of crystallites, and the interplanar distance, according to the methods of Rosalind Franklin and of L. E. Alexander and E. C. Sommer.

The North American Philips G-M Counting Attachment for use with a Weissenberg camera was modified to achieve greater accuracy and speed in measuring integrated diffraction intensities. The shape, size and divergence of the primary beam was changed to obtain a larger and more reproducible number of counts. The oscillating mechanism was simplified and made more convenient. The receiving slit was enlarged so as to yield integrated intensities which were not affected by the diffraction peak shape. The accuracy and precision of the apparatus was determined by measuring the intensities of equivalent reflections from an ideally shaped crystal of nickel dimethyl glyoxime and by measuring the diffraction intensities from a parameterless structure such as sodium chloride. Very few calculation's are necessary in order to make the proper instrument settings as the necessary angles are read directly from a Weissenberg diffraction pattern.

An investigation was undertaken by the Bureau of Mines at College Park, Md., to determine the effect of various combinations of collimators, analyzing crystals and detectors on line intensities, line-to-backgrouhd ratios, and spectral resolution. The research showed that line broadening due to mosaic crystal surfaces was greatly reduced and line splitting from faults was eliminatedby the use of two fine collimators (0.005 inch, spacing, 4 inch length). Line intensities were reduced, but lineto- background ratios arid line profiles were substantially improved with double collimators. Pulse height discrimination resulted in marked improvement in the line-to-background ratio in the long-wave length region, 2 to 10 A, but was much less effective for shorter wave lengths.

The Microemission X-ray Spectrograph is the result of the consolidation of the fine focus electron optics employed in the X-ray microscope, and the spectrograph goniometer used in fluorescent X-ray analysis.

The electron beam, 5 microns in diameter, directly bombards the sample under study. The beam is focused using a three element electrostatic lens system.

Provisions are made for continuous sample viewing with light optics. Sample manipulation, provides for complete coverage of a sample one-half inch in diameter.

The characteristic X-rays generated at the sample are allowed to pass through a beryllium window and fall on the analyzing crystal.

The curved crystal diffracts the characteristic X-ray wavelengths and refocuses them at the bilateral slit ahead of the detector. The goniometer may either be hand operated or motor driven through the various 2 θ angles. Electron beam currents are regulated by controlling filament power oscillator output. Signals are fed through a preamplifier into a rate me ter and recorder or into a high speed sealer which may be set to count for accurate preset periods of time. Samples may be investigated either by complete spectrum analysis of a single point on the sample or by determining concentration changes of a particular element by moving the sample across the electron beam.

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.

A rigorous solution is developed for the correlation of the composition of mixable specimens and the fluorescent X-radiation emitted by the elements in the specimen. The instrumental modifications and treatment of the specimens are derived from the fundamental fluorescence equation.

The resultant dilution formula contains measurable quantities only. No calibration curve is required.

The theory is illustrated by some experimental data confirming the equations.

A method of specific arithmetic corrections for absorption and enhancement interelement effects has been developed, with particular reference to the quantitative determination of mixtures of tantalum, columbium, iron, and titanium oxides. The combined oxides of these elements are prepared chemically from liquid, powder, or metallic samples; weight percantages are determined by reference to calibration and intensity correction curves relating fluorescent intensity to concentration and sample matrix. Tantalum, columbium, iron, or titanium oxide from 0.01 to 100% concentration can be determined with a reproducibility of 1% of the amount present at the 50% concentration and 10% of the amount present at the 1 or 0, 1% level. X-ray analytical time required averages less than 10 minutes per determination. The corrections which have been established are universally applicable to combinations of these four oxides which may be obtained by chemical treatment from such materials as columbite or tantalite ores, tantalum or columbium metalSj and titanium alloys. The method of arithmetic corrections for interelement effects is general in nature and may be applied to the determination of other elements in complex matrices.

This paper outlines a rapid method for the determination of uranium dioxide in stainless steel by direct X-ray fluorescence analysis after chemical solution of the sample in perchloric acid. A scintillation counter is used to detect the intensity of the radiation. Modifications in the apparatus needed to insure stabilization of the counter are described. Strontium is used as internal indicator. The determination of uranium is unaffected by the presence of large amounts of iron, chromium or nickel at the dilutions described. The counting time for four pairs of counts (uranium and strontium) is about 12 minutes.

A standard deviation corresponding to one-half to one per cent of the uranium dioxide present was observed on synthetic samples ranging from 15 to 25% uranium dioxide.