A prototype instrument, which provides x-ray powder diffraction and x-ray fluorescence analysis in a compact unit, has been developed to support the needs of NASA for planetary exploration. The instrument uses a 9-watt Fe-anodc x-ray tube and CCD in a fixed geometry for recording powder patterns with a 2θ range of 35°. The fluorescence spectrum for elements below Fe is collected simultaneously with the diffraction data. A shuttered Cd-109 isotopic source with emissions at 22 and 80 keV is used to excite higher energy fluorescence.

The low-energy limit for discriminating single photon events was found to be ∼1.5 keV. Al-K could be distinguished from a pure sample, but the spectrum below 6 keV was degraded by the read noise of the CCD, which introduced spectral artifacts. Diffraction peaks from halite had a FWHM of ∼1°(2θ), with major contributions to the width from the use of slit collimation on the source and the low tilt angle of the sample.

An irradiation of solid samples with x-rays causes an electron emission from the sample surface, owing to photoabsorption. These electrons can be detected under vacuum conditions and are photo, Auger and secondary electrons. Due to inelastic collisions most of these electrons have lost some of their original kinetic energy along the path from the atom of origin to the surface. With nondispersive electron detection the total electron yield (TEY) is observed.

For measurements performed with a tunable x-ray monochromator information on the qualitative composition can be obtained by the following procedure. The photon energy has to be timed from below to above of one of the absorption edges of a given element. In case of its presence in the specimen an increase of the TEY-signal can be observed.

In X-ray fluorescence analysis, the specific secondary radiation intensities of the elements are generated and measured by a spectrometer. Usually, the measured intensities are corrected for instrument drift first, then converted into element concentrations. In routine analysis, the intensity is always affected by the instability of the instrument. Instrumental instability consists of two components: short and long term drift Short-term instability is caused by fluctuations in the ambient laboratory conditions and the instrument's components. Long-term drift is caused by aging of the instrument's components (mainly X-ray tube, crystals, detectors, electronic circuitry) and results in a gradual intensity decrease. For example, the X-ray tube output decreases due to pitting of the target and sublimation of metal on the inside of the window. The quantum efficiency of detectors gradually decreases due to drift in potential supply and changes in ambient pressure and temperature.

Various industries throughout the world require Standard methods for trade of products and referee analysis. Over the past 20-30 years, a number of wet-chemical Standard methods have been developed and are in use. Due to the large number of elements required for analysis in most products, XRF methods have become attractive as techniques to handle many elements simultaneously with a simple single sample preparation. Despite XRF being in daily use in many industries as an ‘in-house’ method, there are relatively few National or International Standard XRF methods.

We discuss the optical principles behind a novel, duMond configuration, beam conditioning monochromator for high resolution X-ray diffraction. The device is capable of being switched extremely rapidly between high intensity and high resolution settings by lateral translation of the elements. It comprises two blocks of silicon each containing two beam channels oriented parallel to and at 17.65° to the (Oil) planes. In the high intensity mode, with the beam making two asymmetric reflections in each block, the angular divergence and dispersion are comparable to that from a symmetric Ge 022 device. The high resolution setting, where the beam makes four symmetric reflections, while comparable in divergence and dispersion with the 044 Ge device, exploits both σ and π polarisations. We report on the performance of the device and show how this compares with predictions using the dynamical theory of diffraction.

We describe the design and application to X-ray diffractometry of a new X-ray detector based on a fast, non-hygroscopic, rare earth scintillator. The detector has a background count of 0.1 c.p.s. and a peak count rate in excess of 3 x 106 c.p.s. A good fit is found to the theoretical curve of measured against real count rate for a paralysable detector with 160 ns dead-time.

An automated computer technique for the indexing of spot or transmission Kikuchi patterns from any crystal structure has been developed. The patterns are recorded from the fluorescence screen of a PHILIPS EM 430 TEM with an integrating, Peltier cooled CCD camera (PULNIX TM 86QN) through a window from outside by replacing the focusing binocular. The frame-grabber board PCLL2 (SPINDLER & HOYER) has a resolution of 8 bit which corresponds to 256 grey levels. To reduce the high range of image contrastj a circular continuous density filter is positioned directly in front of the camera lens.

Scanning x-ray mapping based on energy dispersive x-ray diffraction is a powerful technique for imaging the spatial distributions of crystal texture and elements [1, 2]. Odd-shaped samples can be studied in air at ambient pressure and without special preparation. A schematic drawing of the scanning x-ray apparatus is shown in Figure 1. A “white” radiation x-ray source (PHILIPS generator PW 1830/25 equipped with a fine-focus tungsten tube) rather than characteristic radiation is used. The high density target material gives rise to an intense continuous Bremsstrahlung background. A collimator, consisting of two circular pinhole diaphragms, is attached to the tube and produces an aperture of 0.3° and an effective beam diameter of 50 μm on the sample. The apertures, Δθ, of the primary and secondary beams are not critical, since crystal texture is scarcely sharper than several degrees, and x-ray fluorescence lines are not affected at all by the aperture settings.

This paper reviews several procedures for the removal of instrumental contributions from measured x-ray diffraction profiles, including: direct convolution, unconstrained and constrained deconvolution, an iterative technique, and a maximum entropy method (MEM) which we have adapted to x-ray diffraction profile analysis. Decorevolutions using the maximum entropy approach were found to be the most robust with simulated profiles which included Poisson-distributed noise and uncertainties in the instrument profile function (IPF). The MEM procedure is illustrated by application to the analysis for domain size and microstrain carried out on the four calcined α-alumina candidate materials for Standard Reference Material (SRM) 676 (a quantitative analysis standard for I/Ic determinations), along with the certified material. Williamson-Hall plots of these data were problematic with respect to interpretation of the microstrain, indicating that the line profile standard, SRM 660 (LaB6), exhibits a small amount of strain broadening, particularly at high 2θ angle. The domain sizes for all but one of the test materials were much smaller than the crystallite (particle) size; indicating the presence of low angle grain boundaries.

In the “double-Voigt” approach, an exact Voigt function describes both size- and strainbroadened profiles. The lattice strain is defined in terms of physically credible mean-square strain averageid over a distance in the diffracting domains. Analysis of Fourier coefficients in a harmonic approximation for strain coefficients leads to the Warren-Averbach method for the separation of size and strain contributions to diffraction line broadening. The model is introduced in the Rietveld refinement program in the foliowing way: Line widths are modeled with only four parameters in the isotropic case. Varied parameters are both surface- and volumeweighted domain sizes and root-mean-square strains averaged over two distances. Refined parameters determine the physically broadened Voigt line profile. Instrumental Voigt line profile parameters are added to obtain the observed (Voigt) line profile. To speed computation, the corresponding pseudo-Voigt function is calculated and used as a fitting function in refinement. This approach allows for both fast computer code and accurate modeling in terms of physically identifiable parameters.

Methods for detecting and modeling micro-crystallinity are discussed in view of determining the systematic effects produced on powder diffraction patterns by both sample features and instrumentation. The mathematical theory of x-ray powder diffraction is the appropriate developmental base for defining micro-crystallinity models in terms of structural ohservables, as well as the “mean equivalent lattice” in terms of computational approximations. Such a theory indicates the way to detect micro-crystallinity accurately and precisely within the limits of the approximations.

Measurements have been carried out on a natural magnetite sample and reported here.

Metal carbonyls are important for chemical vapor deposition (CVD) of metals and alloys and formation of high surface area metallic particles which have potential applications as catalysts. Rhodium carbonyl [Rh6(CO)16] produces high surface area metallic particles whose structure has been reported as monoclinic (I2/a) with lattice dimensions, a=17.00(±0.03)Å, b=9.78(±0.02)Å, c=17.53(±0.03)Å and β=121°45' ± 30' at room temperature. Generally, metal carbonyl crystals dissociate under vacuum as carbonyl gas and decompose to metallic crystals and carbon monoxide at higher temperatures. However, the behavior of rhodium carbonyl crystals is different; they decompose directly to metallic rhodium without the formation of rhodium carbonyl gas in vacuum. Several residual fine grains of rhodium metal are found after the decomposition in vacuum at relatively low temperatures. The metallic samples of rhodium were obtained from vapor pressure experiments using torsion Knudsen-effusion apparatus. X-ray diffraction analyses performed on these grains showed severely broadened Bragg reflections indicative of small particle size and/or lattice microstrain. In this study, a comparison of lattice strains and domain sizes obtained by integral breadth and Fourier methods has been made. In addition a comparison of the lattice strains and domain sizes has been made between the Cauchy, Gaussian, Cauchy-Gaussian and Aqua integral breadth methods.

The fracture toughness test was conducted on γ + α2 two-phase TiAl alloys with lamellar, duplex and near-y structures. The x-ray fractographic technique was applied to the fracture, surfaces. The plastic zone size my was determined on the basis of the distributions of the residual stress and the half-value breadth beneath the fracture surfaces. Although the fracture mode shows microstructure dependence, ωγ is related to the fracture toughness value KIC and the yield stress σY as:

where α is 0.13.

New materials in the Al-Zn-Mg-Cu-La alloy system have been proposed for improving corrosion resistance in a study by Kishi et al, because Lanthanum, La, has a storage capability for hydrogen. Hydrogen is a problem in the stress corrosion cracking (SCC) growth mechanism. Zinc, Zn, Magnesium, Mg, and Copper, Cu, in the alloy have influenced the extrusion, strength and other properties; however, in the case of putting this material to use, it is also necessary to evaluate it from the viewpoint of fracture mechanics. The stress intensity factor, K, obtained from fracture mechanics is a necessary parameter for the evaluation of various materials.

The first part of this study deals with the measurement of fatigue crack growth in the Al-Zn-Mg-Cu-La alloy system. The second part evaluates the fracture surface obtained from tests of these materials by the application of x-ray fractography.

X-ray diffraction observation of the material internal structure beneath fracture surfaces provide fracture analysis with useful information to investigate the conditions and mechanisms of fracture. X-ray fractography is a generic name given to this technique.

In the present study, X-ray fractography was applied to fatigue fracture surfaces of austenitic stainless steel (AISI 304) which consisted of solution treatment. The fatigue tests were carried out on compact tension (CT) specimens. The plastic strain on the fracture surface was estimated from measuring the line broadening of X-ray diffraction profiles. The line broadening of X-ray diffraction profiles was measured on and beneath fatigue fracture surfaces. The depth of the plastic zone left on fracture surfaces was evaluated from the line broadening. The results are discussed on the basis of fracture mechanics.

Sleeve coldworking (SCW) is a mechanical process used in the aircraft industry to strengthen fastener holes of structural parts. By cold-expanding the holes, compressive residual stresses and a high dislocation density are introduced around the holes, the effect of which is to counteract the initiation and propagation of fatigue cracks and thus increase the fatigue life of the parts. The knowledge of residual stress due to SCW is therefore crucial for assessing the fatigue properties of a treated part. In this study, residual stresses were investigated, by employing neutron and X-ray diffraction methods, in a lug specimen that was sleeve coldworked and fatigued.

The specimen had been used for testing the influence of the SCW process on fatigue life and crack propagation behaviour under constant amplitude or variable amplitude cyclic loading.

The various machine parts made of fine ceramics are usually finished by grinding. The X-ray elastic constants in ground ceramics are measured by the X-ray diffraction method, as a result a measurement error can occur. The cause of the error is the stress gradient in the material produced by the grinding. In the case of material in which a stress gradient is present, X-ray stress measurement data show non-linear 2θφψ- sin2ψ diagrams. Until now, the X-ray stress measurement by the sin2ψ method makes use of effectively linear 2θφψ - sin2ψ diagrams. In the case of 2θφψ - sin2ψ diagrams showing non-linear behavior, however, good analysis method are generally not available.

Ion implantation is known to increase the lifetime of cutting tools. Current theories are the increase in lifetime is caused by an increase in the residual stress, or by work hardening of the surface associated with the implantation. In this work the effect of ion implantation on the residual stress in titanium nitride coatings made by the standard industrial methods of chemical and physical vapor deposition (CVD and PVD) is studied. It is found in the as-received condition (unimplanted), the residual stress levels are near zero for CVD materials and highly compressive, of the order of 6 GPa, for PVD materials. Ion implantation has no effect on the residual stress: in the coatings made by CVD. Nitrogen does increase the compressive residual stress by some 10% in the near surface regions of PVD coatings, while nickel-titanium dual metal ion implantation does not have any effect. It appears that the lifetime increase is not associated with residual stress effects.

Recently aluminum nitride (A1N) has been intensively studied as a promising material for production of hybrid integrated circuit substrates because of its high thermal conductivity, high fjexural strength, and nontoxic nature. The estimated theoretical value of its thermal conductivity at room temperature is 320 W/mK, but it is strongly degraded by the introduction of oxygen. The measured values vary from 30 to 260 W/mK, Therefore, in production of this material the reduction of oxygen contamination is of paramount importance.

X-ray scattering is a powerful analytical tool for evaluation of phase structure in crystallizable polymers blends. Our group has been studying crystallization kinetics and micro structure development in binary polymer blends using real-time small angle X-ray scattering (SAXS). Here we describe our research on blends of a crystallizable polymer, poly(burylene terephthalate), PBT, with an amorphous polymer, polycarbonate), PC. In prior studies, we used the same crystalline polymer blended with amorphous polyarylate, PAr. The PBT/PAr system was shown to be inisciblu at all compositions in the melt state. In the present case, PBT/PC blends are not believed to be miscible in the melt. This study was undertaken to determine whether the PBT crystallization kinetics were affected by the presence of low molecular weight PC. This is part of a larger study to investigate the effects of different molecular weights on partial miscibility and on structure development in binary polymer blends.