In view of the importance of obtaining optimum conditions for the X-ray fluorescence analysis of light elements, an investigation has been made of the effects of varying the X-ray tube target, the target take-off angle, the tube voltage, and the tube window thickness. The effects of these parameters have been observed by measurement of the intensity of fluorescence of two light elements using the Ray max 60 demountable tube and vacuum path spectrometer. The results obtained are compared with those given by theoretical calculations based on consideration of the relevant parameters; good qualitative agreement has been obtained. It is shown that a high primary X-ray intensity is obtained with a high target take-off angle, a low angle of incidence of the electron beam on the target, and an optimum setting of tube voltage. It is further shown that the most suitable target to use for the fluorescence analysis of light elements is markedly dependent on the thickness of the X-ray tube window.

A procedure to obtain analytical models for the elemental X-ray pulse-height distribution libraries necessary in the library least-squares analysis of energy-dispersive x-ray fluorescence spectra is outlined. This is accomplished by first obtaining the response function of Si(Li) detectors for incident photons in the energy range of interest. Subsequently this response function is used to generate the desired elemental library standards for use in the least-squares analysis of spectra, or it can be used directly within a least-squares computer program, thus eliminating the large amount of computer storage required for the standards.

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.

Many of the operational problems encountered in the utilization of coal can be attributed to the inorganic constituents in coal. These problems depend upon the quantity and association of the inorganic components in the coal, the combustion conditions, and the combustion or gasification system, geometry. Thus the mineral concentrations and organie associations within a coal must be determined to predict the properties and behavior of the inorganic constituents of coal during combustion and utilization.

The ability to predict fatigue failure has long eluded scientists and engineers. Because they can be applied nondestructively, X-ray diffraction methods have been employed to measure fatigue induced lattice misorientation, lattice strain, residual stress and subgrain formation. The changes in the X-ray patterns, however, were found to be restricted principally to the very early and late fractions of the fatigue life. Their invariance during the intermediate portion of the life has hampered the evaluation of cumulative fatigue damage and prediction of ultimate failure.

The primary difference between previous investigations and our recent X-ray diffraction studies is the emphasis we placed on characterizing both the surface and subsurface response to fatigue. By evaluating the prefracture damage with depth from the specimen surface a more reliable procedure for failure estimation emerged.

The electron-pro be analyzer has been developed in a period of thirteen years to a point where several different instruments are commercially available and about one hundred are already in use. At the present time it is possible to analyze volumes of about 1 μ3 at the surface of a specimen for elements above sodium in the periodic table with a concentration sensitivity of the order of 0.1-0.01%. New developments in the field include efforts to extend the range of Z to lower atomic numbers and to increase the spatial resolution of the method so that smaller volumes niay be analyzed. Progress in the analysis of the light elements centers at present mainly on the use of nondispersive detectors and. computer techniques for the resolution of overlapping pulse-height distributions. With such methods qualitative detection of elements down to beryllium has been achieved in the presence of their near neighbors. Efforts to increase the spatial resolution of the probe have led to the use of thin specimens which are partially transparent to electrons. Partly as a consequence of this approach, apparatus has been developed in which an electron microscope with facilities for selected area diffraction has been combined with an electron-probe analyser. The ever-widening range of application of the electron-pro be technique has inevitably disclosed problems in the interpretation of quantitative data, and it is clear that at the present time more information on the process of X-ray production by electrons is required before semi-empirical methods can be entirely eliminated. Examples of the use of the method in metallurgical and mineralogical studies illustrate some of the current trends in the refinement of measurement technique and interpretation of experimental data.

The substructures of a bet a-quenched and a recrystallized form of high-purity uranium were measured by a method based on statistical fluctuations in X-ray diffraction intensity. For these measurements, Warren's statistical equation for determining grain size was modified to make the equation applicable to materials with high absorption coefficients or moderate-to-large grain size ( > 20 microns) or both, since many metals fall into this category, and to allow for defocusing of the X-ray beam which occurs as a natural consequence of the experiment.

The beta-quenched uranium was found to have numerous subgrains with a range of misorientation angles that was smaller and larger than the limits of the X-ray measurements (Ω = 10−4 to 10−2 steradians). The presence of the large subgrains was corroborated by optical microscopy. The presence of very small subgrains was corroborated by transmission electron microscopy which showed 0.1- to 1-micron subgrains relatively free of dislocations bounded by dense dislocation networks, and by micro Laue diffraction patterns (30-micron beam diameter) which showed partial rings similar to a powder pattern.

The recrystallized uranium had no misorientation within the grains greater than 5.5 × 10−3 steradians. In contrast to the beta-quenched case, no subgrains were found either by transmission electron microscopy (TEM) or micro Laue diffraction patterns. The TEM micrographs showed a uniform distribution of dislocation networks. Since no other substructural elements were observed, the dislocations are believed to be the cause of the misorientation within the grains for solid angles of less than 5 × 10−3 steradiflns.

These preliminary experiments show that the statistical method may be used in conjunction with transmission electron microscopy and micro Laue diffraction for the study of substructure. The statistical method gives quantitative data on “bulk” specimens that can be given a meaningful interpretation with the aid of the other techniques.

Two methods are described for computing multielement x-ray absorption corrections for aerosol samples collected in IPC-1478 and Whatman 4l filters. The first relies on scatter peak intensities and scattering cross sections to estimate the mass of light elements (Z < l4) in the sample. This mass is used -with the measured heavy element (Z ≥l4) masses to iteratively compute sample absorption corrections. The second method utilizes a linear function of ln(μ) vs. ln(E) determined from the scatter peak ratios and estimates sample mass from the scatter peak intensities. Both methods assume a homogeneous depth distribution of aerosol in a fraction of the front of the filters, and the assumption is evaluated with respect to an exponential aerosol depth distribution. Penetration depths for various real, synthetic and liquid aerosols were measured.

Elemental analyses of geologic materials were obtained using X-ray microfluorescence combined with simultaneous elemental digital mapping. The analytical results corroborate the information obtained by electron and optical microscopy methods. Zoned garnet and ore deposit specimens were analyzed and compared to information obtained from other analytical methods. The penetrating nature of the X-ray beam using this method provides elemental information from beneath the sample surface. The combination of this depth information with the surface information supplied by electron microscopy provides a more complete analysis of the sample than is possible with each technique alone. Minimal or no sample preparation along with the ability to examine materials in air enhances the microfluorescence and digital mapping analysis technique.

Standard X-ray fluorescence spectrogmphs are capable of measuring elements in areas as small as ⅛-in. diameter, while an electron mitroprobe specialises in areas less than 10 μ. Frequently, a sample of an intermediate size (0.1 mm to 2 mm) requires analysis, so an attachment was designed for Philips Electronics Company equipment. Reasons for its design, sensitivity of the system, and several metallurgical examples showing its versatility are discussed in the report.

The mass absorption coefficient is a useful parameter for quantitative characterization of materials. If the chemical composition of a sample is known, the mass absorption coefficient can be calculated directly. However, the mass absorption coefficient must be determined empirically if the chemical composition is unknown. Traditional methods for determining the mass absorption coefficient involve measuring the transmission of monochromatic X-rays through a sample of known thickness and density. Reynolds (1963,1967), however, proposed a method for determining the mass absorption coefficient by measuring the Compton or inelastic X-ray scattering from a sample using Mo radiation on an X-ray fluorescence spectrometer (XRF). With the recent advances in solid-state detectors/electronics for use with conventional powder diffractometers, it is now possible to readily determine mass absorption coefficients during routine X-ray diffraction (XRD) analyses.

Using Cu Kα radiation and Reynolds’ method on a Siemens D-500 diffractometer fitted with a Kevex Si(Li) solid-state detector, we have measured the mass absorption coefficients of a suite of minerals and pure chemical compounds ranging in μ/ρ from graphite to Fe-metal (μ/ρ = 4.6-308 using Cu Kα radiation) to ±4.0% (lσ). The relationship between the known mass absorption coefficient and the inverse count rate is linear with a correlation coefficient of 0.997. Using mass absorption coefficients, phase abundances can be determined during quantitative XRD analysis without requiring the use of an internal standard, even when an amorphous component is present.

Previous work on modification of the collagen lattice, presented at these meetings, has served to confirm the Ramachandran proposal for the structure of this important protein, together with information on the lengths and tensile strengths of these bonds, including hydrogen bonds, hydrophobe bonds, and Vander Waals attractions. Rat tail tendons were suspended in 2 M aqueous solutions of dimethylsulfoxide, acetone, trimethylamineoxide and 1,4-cyclohexanedione, all of which showed evidence of ligation by expansion of the collagen lattice and refinement of the 100 spot in the x-ray diffraction pattern run by rotation on the collagen fiber axis. In the case of trimethylamineoxide and cyclohexanedione, oriented crystallization also occurred, with the long direction of the molecule in the plane perpendicular to the fiber axis of collagen. With the monofunctional ligands, the -C=0 group forms a hydrogen bond to the N-H group in the Ramachandran standard revised model, leaving the methyl groups to form the hydrophobe bond.

The intensity of Compton scattering, Fe, and Ca chatacteristic radiation can be used to estimate the amount of ash in coal by Xray fluorescence spectroscopy. Mo, W, and Cr radiation were used to study a suite of New Mexico coals, and the best results were obtained with Mo and W X-ray tubes. If the actual concentrations of Fe2O3 and CaO and the mass absorption coefficient, μ*, at the Compton wavelength of scattered Mo K radiation can be determined, the regression equation:

%Ash - 24.2μ* - 6.28(%Fe2O3) - 1.96(%CaO) - 3.4

estimates the ash content with an average error of 0.5% ash at 0.71Å.

An active recording x-ray crystal spectrometer for extended x-ray absorption fine structure (EXAFS) has been built using a position sensitive detector of the self scanning photodiode array (SSPA) type. The SSPA detector has energy and position sensitivity for x-rays. The spectrometer was applied to the measurement for EXAFS of the several compounds in foil, powder and liquid states. The spectra can be obtained rapidly, and compare very well with other methods. We found that the SSPA detector is very useful for the measurement of EXAFS.

It is important to establish precision and accuracy of an X-ray diffraction (XRD) residual stress measurement procedure in order to compare capabilities of instrumentation and techniques, as well as to provide confidence limits for experimental data. There is no broadly acceptable method for establishment of precision and accuracy. This paper describes a proposed approach and one which is used at The Pennsylvania State University.

One impediment to the measurement of precision and accuracy is that no standard specimen with a known residual stress level is available. Proposed standard specimens have been abandoned for various reasons, including the concern for stability of the original stress condition and the existence of stress gradients, i.e., stress inhomogeneity, in the specimens. However, there is one type of specimen which has been accepted by ASTM as an alignment and zero residual stress confirmation standard. That type of specimen is a powdered sample of metal or ceramic which provides XRD peaks in the vicinity of the Bragg angle in which residual stress measurements are to be performed.

Some researchers tend to report detector counting statistics as the uncertainty of stress measurement but such statistical scatter accounts for only one part of uncertainty in precision and accuracy. The total uncertainty is best determined directly through repeated residual stress measurements performed by removal and readdressing the test specimen or through a repetition of measurements under predictably changing conditions.

This paper describes results from the use of powder specimens to establish the repeatability of measurements with a portable instrument after removal and readdressing of the specimens. Also, results showing the uncertainty of the measured stress change in specimens subjected to known loads are discussed.

A versatile double-crystal X-ray spectrometer has been developed for the precise measurement of X-ray diffraction line widths to tenths of seconds. The device can be employed in either the parallel or antiparallel arrangement for rocking curve studies and can also be used in anomalous X-ray transmission experiments with nearly perfect crystals.

A detailed description of the instrument is given as well as some results concerning the Darwin theory of X-ray diffraction line widths and Borrmann effects.

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.

Analysis of sample composition and/or thickness in a routine, process-control or monitoring environment generally requires rapid turn-around time with minimal sample handling. X-ray Fluorescence (XRF) is well-suited for these kinds of analyses and has been applied to various bulk and thin sample applications (1-7). This technique is rapid, precise, non-destructive, and requires minimal sample handling.

X-ray Fluorescence is generally considered a secondary analysis technique, that is, instrumentation must be calibrated using known standards before unknown samples may be analyzed (quantitative analysis). Continuing work on standardless approaches, particularly for Energy-Dispersive XRF (EOXRF) systems, relax this requirement for some samples but the large share of XRF analyses still require calibration with standards. A number of mathematical and non-matheraatical techniques have been devised to calibrate XRF measurements for many different sample types (1,2,8,9).

Recrystallization and grain growth of 99.998% aluminum were studied by methods combining metallographic techniques with x-ray microscopy and diffraction analysis. The recrystallked grains were shown to be the product of preferential subgrain growth whereby subgrains subtending large disoriciitation angles with respect to their neighbors exhibited the highest velocity of growth. The recrystallized grains emerging from the deformed matriv showed at first a high degree of lattice perfection, but incurred growth accidents during the growth process. Values for the mean strain-free energy of the deformed matrix surrounding the growing subgrains were obtained from the kinetics of subgrain growth.