The back reflection x-ray divergent beam technique is examined as a tool for studying elastic strains. In particular, a method of calculating interplanar spacings using a least squares fit of experimental "conic" coordinates to Newman's general equation for back reflection (J. Appl. Cryst. 3 (1970) 191) is described. Using this technique, interplanar spacings can be obtained from partial conies. To determine the precision of this method an unstrained silicon single crystal is studied, and the errors associated with determining its interplanar spacings are discussed. The technique is then applied to elastically strained silicon and the results compared to theoretical predictions. It is shown that strains down to 2 × 10−5 are readily measured on high angle planes in silicon.

Residual stresses are expected to lead to a linear dependence of the interplanar spacing, d, on sin2ψ (where ψ is the sample tilt) and the stress can be obtained from the slope of this line, As a result of the linear dependence a two-tilt method is often employed to obtain the stress. However, when a specimen is subjected to extensive plastic deformation large deviations from a straight line can occur and a two-point method can lead to an erroneous stress determination. The results reported here show that: (1) this is more likely to occur in homogeneous materials than in multiphase materials (2) the oscillations follow closely the variation in peak intensity due to texture (3) the oscillations are caused by microstresses which are due to an "orientation" effect as suggested by Weidemann,

A simple, easy-to-use procedure has been developed and tested to correct the data and obtain the correct macrostress.

The effect of temperature on nucleation and growth of Ti3Al precipitates in two Ti-Al alloys was determined using sensitive X-ray diffraction techniques. The X-ray peaks arising from the ordered Ti3Al phase were compared with the fundamental peaks of the matrix. Peak broadening due to particle size resulted from the small Ti3Al precipitates and this was analysed using Fourier methods to determine a mean particle size and particle size distribution. The two alloys used for this investigation were Ti-8.5 wt.% Al and Ti-8%Al-1%Mo-1%V (8-1-1) alloy. The precipitate size in Ti-8.5 wt% Al was considerably more dependent on temperature than the precipitate size in 8-1-1 alloy, achieving a size of 190Å after 20 hrs at 650°C. The solvus temperature for precipitation was the same for both alloys, vis, 675°C to 700°C. These results compare favorably with transmission electron microscopy of thin foils prepared from the same samples.

The use of incomplete pole figures results in the loss of orthogonality relations among the associated Legendre functions, and necessitates explicitly evaluating integrals of products of these functions. The required indefinite integrals of associated Legendre functions and their products have been evaluated for cubic crystallographic symmetry and orthotropic physical symmetry through sixteenth order.

The solution has been particularized for {200}, {222}, and {110} back-reflection pole figures, where data are confined to the region not exceeding 60 degrees from the sheet normal direction.

Data obtained from a sample of low—manganese steel sheet are used to illustrate the method, and results are compared to those obtained using complete pole figures obtained with a composite sample of the same material.

The method described makes it possible to study crystallite orientation distribution as a function of distance from the sheet surface, by a series of pole figure measurements on the surface after successive material removals by polishing and etching.

The polymorphism of an homologous series of highly purified mixed triglycerides has been studied using powder and single crystal X-ray diffraction techniques, in conjunction with thermal analysis and infrared spectroscopy. From thermal analysis, three polymorphs were identified. Single crystals of the most stable polymorph were obtained for two members of the series, 2-acetodimyristin (14-2-14) and 2-acetodipalmitin (16-2-16). Their unit-cell and sub-cell dimensions were used to interpret the powder data, and to provide preliminary general information about the crystal packing for this polymorph. Of the two other polymorphs identified, the first one (obtained by rapid cooling of the melt) is disordered, and transforms on standing, to a second, unstable intermediate polymorph. Infrared spectroscopy showed that for at least two of the three polymorphs, the long chain acyl groups of the triglycerides are in a parallel packing arrangement.

Current methods of measuring bone mineral content In vitro are either inaccurate or measure density in non-intuitive units. A recently developed system overcomes these difficulties by utilizing the Compton scattering of photons from bone. Two sources of monoenergetic photons with related properties are required. The range includes energetic x-rays and low energy gamma rays. This study analyzes a number of the possible nuclide source combinations, and reports experimental results accomplished with a 153Gd-170-Tm combination. In vitro measurement of the density of ox bones by this method agreed with Archimedean measurements within three percent.

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.

A prototype Environmental Monitoring Device (EMD) has been developed as a simple means for inexpensive, routine determination of site severities. The EMD is a cartridge that can be connected to an inexpensive pumping unit to collect an atmospheric sample. The field procedures are extremely simple and have been done routinely by individuals with no chemical training. Four filters within the cartridge selectively react with and permanently trap pollutants from the air drawn through the cartridge. The first filter collects particulates. The second is o-tolidine impregnated Whatman #41 filter paper to collect gaseous chlorine species. Silver nitrate impregnated paper collects reactive sulfur gases, and the fourth filter paper is impregnated with sodium hydroxide to react with and collect sulfur dioxide. After atmospheric sampling, the cartridges are returned via mail to a central analytical lab. Procedures have been developed for easy and rapid determination of the quantities of pollutants on the filters by energy dispersive X-ray fluorescence. Laboratory and field measurements from a number of locations within the IBM Corporation have been made and will be reported. The EMD approach is providing a large data base on indoor atmospheric pollutants that could affect electronic equipment. The approach could easily be extended to numerous other applications.

Rapid changes in methods of energy production and utilization are occurring in California, as elsewhere. The affects of such changes upon atmospheric aerosols have been monitored since January, 1973, as part of the continuing study of California aerosols undertaken by U.C. Davis for the California Air Resources Board. A primary goal of the program is to identify aerosol sources in detail, thus allowing energy related components to be isolated and evaluated at many locations throughout the state.

Use of ion-excited x-ray emission as the major (although not exclusive) method of elemental analysis is well suited to this program for a number of reasons. Among them include; 1. The sensitivity allows particle-sized aerosol samples to be easily collected, 2. The low cost (under $6, per sample) allows many samples to be run within a fixed budget, 3, The large number of elements seen in the average sample allows source identification by element to element to weather correlations. In addition, the samples are suitable for light element analysis by alpha scattering, for elements H through Cl, thus allowing an inventory to be made of all the aerosol mass in the atmosphere within the size range of the sampler.

The St. Louis aerosol was sampled during the period 16-22 August 1973 simultaneously at two locations using cascade impactors for sequential 12-hour samples. The six particle size fractions of each sampling were individually analyzed using PIXE for elements from S to Br and beyond and for heavy elements including Pb which permitted time variations of concentrations and particle size distributions to be followed and related to meteorological changes during the sampling period. In addition, the data were compared with average levels of the elements in coastal north Florida and maritime Bermuda as well as at a third St. Louis site. From this it appeared that some of the concentrations in St. Louis were at natural levels whereas others appeared to be higher and linked to air pollution sources. These relationships and others in this study may lead to criteria for distinguishing between pollutants and natural background in urban aerosols.

Proton scattering quantitative elemental analysis is examined as a complement to proton induced X-ray emission analysis for air particulate samples. Both methods are absolute, non-destructive, and are suitable for use on samples up to about 1 mg/cm2 in areal density. Characteristics of the method are discussed and examples of aerosol spectra are presented.

Pure standards of molybdenum disulfide, silver, and calcium silicide particles 0.5 μm in diameter and larger, were used to obtain calibration curves for size effect on x-ray intensities. The decrease in intensity with size follows a straight line down to about 3 μm. For the smaller sizes the intensities decrease exponentially. Good agreement has been found between curves calculated using simplified models of diffusion volumes intercepted by the particles and curves of measured x-ray intensities.

The intensity versus size was plotted as a percentage of the intensity of a flat, infinite standard. Therefore, the number of counts measured for a sample of known size can be converted to the intensity it would have if it were an infinite surface. These values can then be plugged into existing computer programs for quantitative analysis. Samples of atmospheric aerosols were analyzed by using these calibration curves.

A procedure is described for making self absorption corrections for x-ray fluorescence analysis of ambient air aerosols which are collected in two size ranges with a dichotomous sampler. Calculations for fine particles are based on the assumption of a uniform layer of accumulated deposit which has an exponentially decreasing depth profile within a membrane filter. Coarse particles are treated as spheres with a log normal mass distribution which is subject to modification by the sampling device. An average attenuation and the associated uncertainty is deduced for coarse particles by considering a wide variety of possible chemical compositions.