Lattice parameters, obtained by least-squares refinement of data from calibrated Guinier powder patterns, are compared in an effort to establish procedures for obtaining reproducible 2θ values with Guiniertype focusing camera techniques. The calibration procedure is discussed and a method of calculation to reduce loss of precision is proposed. Effects of particle size and crushing are also discussed as well as some sources of error such as use of only selected calibrant lines, film background, and mutual interference of powder lines.

Computational methods for determining precision lattice parameters based on extrapolation, lattice refinement, least squares and trial and error indexing, with intermediate corrections for peak positions using external and internal standards, have been evaluated with respect to the ICDD published values for zincite. Lattice parameters can be routinely determined to an accuracy of one part in ten thousand without the use of external or internal standards, by using computational extrapolation on data with a well aligned and maintained diffractometer. Lattice refinement determination of lattice parameters was only effective, with respect to the ICDD values, when used in conjunction with external and internal Standards. Least squares yielded results with low standard deviations, but the use of standards did not reduce the refined sample displacement or zero angle errors, and gave an increased error in lattice parameters with respect to the ICDD values. The trial and error indexing, which can only be used with peak positions corrected with respect to both external and internal standards, gave relatively low de Wolff and Smith-Snyder figures of merit, but nevertheless yielded lattice parameters of the highest accuracy of one part in twelve thousand, with respect to the ICDD values.

A novel windowless sample preparation method is described which allows for X-ray fluorescence analysis of light elements (Z = 13 to 20) in coal or oil-tar pitches, asphalts and other bituminous compounds. The article also discusses blending and spiking of pitches with suitable organometallic compounds in order to prepare a range of trace-element calibration standards. The general instrumental conditions, recommended peak counting times and detection limits are also discussed.

Fluorescent X-ray spectrographic analyses have been made for the oxides Fe2O3 caO, MgO, K2O, TiO2, and MnO on samples of amphibolite rock. In addition, the above oxides and SiO2 and Al2O3 have been determined in a suite of constituent hornblendes from these rocks.

Classical wet chemical analyses of materials of the same minera logical composition as the samples are used to establish the working curves. This eliminates the necessity for Internal standardization or other treatment of the samples. The only sample preparation involves extremely fine grinding before analysis.

Precision of the analyses is equivalent to, or better than, that achieved by wet chemical methods.

Developments during the past few years in solid-state radiation detectors and low-noise electronics employing field-effect transistors operated at cryogenic temperatures have resulted in the availability of high-resolution energy-dispersive spectrometers for a variety of applications in x-ray spectrometry. Using pulseamplitude analysis techniques, these spectrometers make it possible to obtain multi-elemental analyses on a routine laboratory basis employing x-ray fluorescence techniques. The combination of these spectrometers with small, inexpensive on-line computer data systems makes It possible to obtain rapid on-line qualitative and quantitative analysis of samples in the laboratory and in special field applications. A general review of the present state of development in detectors, electronics and on-line data systems will be presented together with descriptions of applications of such equipment in the laboratory.

The detection limit of the proportional counter spectrometer is determined by the low-energy background caused by the wall effect. The choice of the filling gas of the proportional counter has been studied to minimize the background. Detection limits (3σ) for different elements have been calculated. Theoretical results have been compared with the experimental value obtained with Cd-109 and Am-24l excitation. The results are applied to the analysis of metal concentrations in oil samples and mapping the contents of zinc in the bark of living trees with a portable XRF-analyzer.

There are several methods for the measurement of retained austenite in steels, which influences mechanical behavior and corrosion resistance of steels. Among them, X-ray diffraction methods using a wide angle goniometer or X-ray stress analyzer are commonly used because the methods are non-destructive, giving useful information about residual stress or lattice strain as well.

The use of conventional θ/2θ diffraction methods for the characterization of polycrystalline thin films is not in general a satisfactory technique due to the relatively deep penetration of x-ray photons in most materials. Glancing incidence diffraction (GID) can compensate for the penetration problems inherent in the θ/2θ geometry. Parallel beam geometry has been developed in conjunction with GID to eliminate the focusing aberrations encountered when performing these types of measurements. During the past yearwe developed a parallel beam attachment which we have successfully configured to a number of systems.

By utilizing the total reflecting properties of x-rays inside glass capillary tubes, intensive fine- or microbeams of x-rays can be attained. By using a conventional x-ray tube in combination with capillary technique, microbeams with a diameter of a few μm and with an intensity sufficient for trace elements, analyses have been achieved. By moving the sample, lineand areascan can be performed and trace element information can be directly superimposed on a micrograph from a built-in optical microscope.

The background of the capillary technique is reviewed and an EDXRF microbeam spectrometer for trace elements is described. Examples of applications for the microbeam spectrometer are given.

In X-ray diffraction and wavelength dispersive X-ray fluorescence, it is necessary to determine the intensity of a coherently diffracted X-ray peak with respect to its position, two-theta. To accomplish this, most X-ray diffractometers are provided with a scanning goniometer mounted X-ray detector that scans the angular two-theta region of interest and obtains X-ray Intensity as a function of time and therefore two-theta.

The peak angle 2θp is one of the most commonly measured parameters in powder diffractometry, but there is little understanding of the extent to which the instrument affects this measurement. The majority of theoretical and experimental studies of the effects of instrumental aberrations have been based on the peak centroid 29c. In this investigation we have examined the extent to which peak angles in a conventional powder diffractometer shift for different combinations of divergence slit, Soller slits and receiving slit. The line profile standard SRM 660 (LaB6) was used to generate instrument profiles and X-ray data were collected from a diffractometer fitted with a fine focus Cu X-ray tube and a graphite post-monochromator set for CuKa. The effect of the instrument is greatest at low angles, but shifts arising from axial divergence can also be detected above 2θ=120°. Below 2θ = 40° changing the divergence slits from 0.3° to 1.0°, or removing one of the Soller slits, can move 2θp by up to 0.025°.

Reference intensity ratios (RIRs) with zincite (ZnO) as the internal standard have been measured and calculated for key phases in coal combustion solid residuals. Detailed comparisons of measured and calculated corundum RIRs (converted from zincite RIRs), and literature I/Ic values led to the conclusion that for best results, laboratory measured values must be used. Using measured zincite RIRs and standard mixtures of important crystalline phases, a protocol for routine semi-quantitative analysis has been developed. The need to grind under ethanol to minimize decomposition of hydrated phases was demonstrated. An unusual procedure employing mixed peak and integrated intensities in the RIR of one key phase, ettringite (Ca6Al2(SO4)3(OH)12-26H2O), has been adopted for this protocol.

We have developed a technique to determine the dissolved solid components of water and other liquids by Energy- Dispersive X-Ray Fluorescence (EDXRF) spectrometry. The liquid samples are presented to the spectrometer as small dried spots of the residue remaining after evaporation of the liquid. The dried residues are mounted on thin plastic films cemented to 35 mm plastic slide mounts. Elements from sodium through uranium are detected with detection limits less than one nanogram in favorable cases. Precision of the measurement is better than 2 % relative in favorable cases for secondary-target excitation, and is typically 5 to 10 % for direct excitation given the geometry of the instrument. Detection limits are as low as a part per billion relative to the original liquid for solutions whose total dissolved solid content is 1000 part per million or less.

Grazing-incidence X-ray analysis techniques which are commonly used for the nondestructive characterization of surfaces and thin films are reviewed. The X-ray reflectivity technicue is used to study surface uniformity and oxidation, layer thickness and density, interface roughness and diffusion, etc. The grazing-incidence in-plane diffraction technique is used to determine in-plane crystallography of epitaxial films. The grazing-incidence asymmetric-Bragg diffraction is used for surface phase identification and structural depth profiling determination of polycrystalline films. Typical examples to illustrate the types of information that can be obtained by the techniques are presented.

X-ray work in the 10 to 400 Å range usually requires, for maximum sensitivity, new methods of X-ray generation, analysis, and detection. A comparative survey includes X-ray generation by fluorescence, electron bombardment, and proton bombardment. Dispersive analysis with crystals and gratings is described. Finally, window less photoelectric multipliers are evaluated as X-ray detectors.

Results show that typical efficiences range from 10−4 to 10−2 photons/electron or photons/proton, with the latter value as a practical upper limit. An efficiency of 8.5% has been measured for a KAP crystal covering the wavelength range up to 25 Å, while an original gold-plated grating lias a maximum measured efficiency of 20%. Counter efficiency may range from 1 to 50%, depending on wavelength. Total efficiency for a grating-type spectrometer in the 20 to 400 Å range has been measured to 2 × 105 photons/cm2-count.

The design and application of a newly-developed Siemens multichannel wavelength x-ray fluorescence spectrometer that has been specially adapted to the needs of the Environmental Protection Agency for rapid analysis of particulate samples is described. The system consists of sixteen fixed-wavelength spectrometers which are optimized for sixteen pre-selected elements and a computer-operated scanning channel which is used to determine additional elements that might be desired on a given sample. A minicomputer operates the instrument and custom-designed sample changer and processes the data.

Requirements for standards suitable for air pollution samples and the approaches used for the preparation of thin layer standards are discussed. Sensitivities, detection limits for elements of interest in air pollution, and the relative merits of aerosol filter types for x-ray fluorescence analysis have been determined. The system has been used to measure the elemental composition of a large number of samples from stationary source emissions, mobile sources, and ambient air.

Computer simulation of back reflection Laue patterns now provides the means to plot Laue patterns for any crystal system in any orientation. This capability makes it possible to determine, rapidly and accurately, the orientation of single crystals and large grains in polycrystalline materials even in cases where little or no symmetry is displayed in the Laue photograph. A set of standard Laue patterns is first simulated to cover the stereographic triangle of the crystal being studied. The Laue photograph obtained from the crystal, or grain, is compared with the set of simulated Laue patterns. The pattern most similar to the photograph is used to determine the (HKL) values of three Laue spots. The (HKL) values of these spots and half their angular separations from the x-ray beam, along with the lattice constants, are used by a computer program to calculate the (HKL) value of the crystallographic plane perpendicular to the x-ray beam. A simulated Laue pattern can now be obtained in exactly the same orientation and it can be drawn directly to the scale of the Laue photograph. Thus the validity of the orientation can be easily verified by direct comparison. The (HKL) value of the crystallographic plane perpendicular to the x-ray beam can also be used to plot a stereographic projection of the crystal poles. Therefore, the complete orientation of the crystal can be determined.

Pure cobalt and cobalt-nickel alloys have been plated from simple electrolytic baths with and without additive and with and without ac superimposed upon the dc plating current.

X-ray analysis reveals preferred orientation in the polycrystalline deposits generally and extreme preferred orientation (characterized by [00.2] and [11.0] fiber axes) in the case of those samples obtained with additive-free electrolyte. It is shown that a change in the pH of the bath or the addition of an ac component are equally effective in determining the type of fiber axis in the deposit. The effects on plating texture owing to the use of additive KCNS in the bath are described. Finally, the correlation between the texture and the magnetic properties of the plating Is discussed.

Energy yields in the generafion of monochromatic X-rays by electron bombardment are poor and the utilization of X-rays is even more wasteful, particularly in X-ray diffraction. Only a small stereoangle of radiation issuing from a flat target passes through the collimator of a camera.

An end-window X-ray tube using a conical cavity as a target is more economical, since there is a finite probability of several excitation acts by one electron in the cavity. A major part of the radiation emerges from the tube in a stereoangle of ≈ 0.02 instead of 2π steradian. This and the proximity of the tube focus to the sample are favorable for X-ray diffraction, as will be demonstrated in several examples. The geometry and performance of the tube are also expected to provide a superior replacement for the weak isotopic sources normally used in energy dispersive analysis.

Several versions of the tube, covered by U.S. Patent 3,584,219, H. K. Herglotz and C. D. Reilly, are described. Of particular interesf for X-ray diffraction is a double cavity tube with 2 exit ports. The Iow power consumption of the tubes (35 kV, 1 mA or less) requires only a small power supply. All equipmenf for XRD work including batteries can be accommodated in a suitcase and therefore lends itself to field use by mineralogists, for example, or in materials testing.

Electron optics techniques have been applied to the examination of various evidence materials common to forensic science. Vehicular paint fragments, a common evidence material, possess topographical features suitable for SEM analysis and composition variations in the form of chemically distinct layers and surface contaminant particles which can be characterized using energy dispersive X-ray analysis. The ability to analyze paint samples in terms of both topography and composition presents the potential of an extremely valuable tool for forensic investigators.

Over thirty automotive paint samples from many sources were examined in this study, using either the secondary electron image of the SEM or the SEM image combined with concurrent X-ray analysis by an energy dispersive System. Topographical pictures and X-ray spectra were recorded and comparisons between samples were made. Additional characterization of specimens was attempted through the analysis of individual paint layers.

The data obtained was used to group the paint samples into categories used for identification of the sample source. This information is valuable to several types of criminal investigation.