Most position sensitive proportional counters (PSPCs) currently used in X-ray diffraction experiments have a dead time longer than 5 μs. Though such PSPCs are useful in measuring weak diffraction diagrams, a faster counter is needed to detect strong X-ray diagrams produced with synchrotron radiation sources. The long dead time of PSPCs using a charge division position read-out is due to the slow analog division circuit plus analog-to-digital converter employed in the present system. A fast processor can be built utilising two high-speed ADCs to digitize voltage signals from the detector, followed by a digital divider to compute position of detected photons. The present paper describes the design of such a processor and some preliminary testings of its performances.

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.

The residual stress produced by surface and cylindrical grinding was measured by a position sensitive proportional counter. In medium carbon steels the residual stress depends largely on the grinding conditions. For a gentle cylindrical grinding compressive stress was observed, but for a rough grinding tensile stress was present in the workpiece.

Several examples of time-resolved X-ray powder diffraction studies with linear position-sensitive proportional counters (PSPC) are described. The changing patterns are recorded by spectrum multiplexing in a multichannel counter device. The time resolution for single processes is limited to seconds or tenths of seconds mainly because of the counting statistics of the observed peaks. Repetitive processes, however, where the interesting peaks can be accumulated over a large number of periods, permit much higher time resolution. It is finally determined by the timing of a detected X-ray quantum. Using a continuous beam source like a conventional X-ray tube the incidence of a photon into the PSPC can be timed with an accuracy of 20 ns (fwhm). A pulsed synchrotron radiation source, like a storage ring, will be able to define this resolution to its pulse duration, which is less than 200 ps.

Before approaching those limits this paper presents the high temperature phase transformations in iron for different steel specimens as an example of single processes. It also discusses domain-wall effects and electrostriction in ferroelectric perovskites as a function of polarization at frequencies of up to 10 Hz, and elastic lattice distortions of a steel sheet vibrating at about 200 Hz. The timing limit of 20 ns for the PSPC detection system was measured at the storage ring DORIS at DESY, Hamburg.

The mining industry uses coring as a standard method for the evaluation of ore deposits. Since coring is costly and time-consuming, increasing attention has been given to logging techniques capable of providing information about the orebody, thus allowing replacement of at least part of a coring program. An evaluation of the feasibility and potential for application of a variety of borehole logging techniques(l) concluded that X-ray diffraction (XRD) is one of the promising techniques for borehole assay, along with neutron activation analysis, X-ray fluorescence, photoluminescence, and infrared spectroscopy.

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.

A vertical scanning single crystal diffractometer with graphite monochromator and narrow divergent beam controlled by an IBM Series/1 computer was used to study crystal damage in the ion-implanted garnet films including strain effects induced by multi-implantation processes as a function of the types of ions, their energies and doses, growth and annealing temperatures.

The life of a rolling bearing is predominantly determined by the contact stress between the rolling elements (ball and roller) and the raceway of inner and outer rings. The contact stress is calculated by assuming Hertzian stress distribution. The maximum Hertzian contact stress Pmax usually ranges from 2000 to 3000 MPa in actual service of rolling bearings. These figures are rather large compared to the compressive yield strength of hardened bearing steel (σys = 2000 MPa). Therefore plastic deformation sometimes occurs under the raceway, creating residual compressive stress. Several investigators have so far reported about the residual stress due to rolling contact. There were, however, few who referred to the residual stress in used bearings and application of residual stress measurement to failure analysis.

Two metal foils, one pure plutonium and the other being a solid solution of 6.5 a/o gallium In plutonium, were examined, in-situ, by X-ray diffraction techniques while under pressure. The purpose was to determine the compression and compressibility of these materials as a function of pressure and to identify the products of any transformation that may occur due to the action of applied pressures.

X-ray diffraction is found effective in disclosing the distribution of stresses over the surface of adhesively bonded lap joints when loads well below the yield point are applied. When a pair of 6061-T6 aluminum strips 1/16” or 1/32” thick and 3/4” wide is adhesively bonded in a single lap joint and loaded in tension, maps giving the distribution of the X-ray-measured stresses show the limits of the bonded area with an accuracy about equal to the width (1 mm) cf the irradiated area along the specimen. Attendant bending stresses resulting from the loading are also registered. Stress values can be obtained from the observed diffraction angles by calibration with tensile tests of a single unbonded strip. Similar results are obtained for graphite/epoxy laminates adhesively bonded in a single lap joint to aluminum when diffraction is from the aluminum, but a lower accuracy is obtained when diffraction is from the filled composite.

Another X-ray method was developed for measuring applied (not pre-existing residual) stresses, and for mapping their distribution around a joint. A thin layer of epoxy paint containing a diffracting filler (say aluminum or silver powder) is applied to a specimen and cured. Diffraction from this paint yields shifts in diffraction angle approximately proportional to the magnitude of applied stresses. The limits of the bonded area in single lap joints under load are disclosed. Both methods appear, therefore, to be practicable for mapping the areas that are properly bonded, and presumably also for non-destructive evaluation of bond defects.

Separating overlapped peaks is a part of many x-ray diffraction analyses, for example, polymer crystallinity. Natta [1] defined a method for polypropylene in 1957. His method was computerized at the Hercules Research Center in 1960 with an automatic “curve follower” which punched paper tape for the computer. A later method deviated fTom Natta's method by approximating the amorphous curve with a fixed shape and a height chosen to best fit the diffraction data from 2θ = 7.5 through 10. degrees. Neither of these methods worked on “smectic” polymer samples, i.e., composed of very small crystallites. Also, a different computer program was used for each different polymer, so a general purpose computer program was developed using a peak profile method. This method has been used en polymer mixtures and copolymers of ethylene, propylene, and butene; and on cellulose, modified cellulose, and catalysts. The selection of a profile function is discussed in the next section. In later sections, the background, the fitting procedure, and computer input and output are discussed.

The intensities of x-rays scattered by amorphous Fe80P13C7 and Fe40Ni40P14B6 samples have been measured as a function of photon energies E at fixed scattering angles 2θi using a Li-drifted Si detector and polychromatic x-rays generated by a 50KV full-wave rectified generator. The coherently scattered intensity per atom was calculated for free-standing samples as well as samples contained in a Be or pyrolytic graphite cell, after the evaluation of the energy dependence of the primary beam spectrum by an iterative process. The interference functions were then calculated from the data obtained in transmission and reflection, and compared with those measured with the conventional variable 2θ technique. Good agreement between energy-dispersive diffraction (also called variable wavelength technique) and variable 2θ diffraction was observed in all cases.

Quantitative phase analysis by X-ray diffraction (QTXRD) has been an established tool of analytical chemistry for more than four decades. Despite its age, this tool remains ascendant as the only universally applicable method for determining the manner in which elements are combined into crystalline phases in multiphase solids. QTXRD is entering its second renaissance. The first came with the introduction of the counter diffractometer in the late 1940's. The specimen preparation and data collection processes were exacting and tedious, but reasonably accurate analyses could be obtained. The second came with the introduction of computer controlled diffractometers, whose software packages include QTXRD routines, in the late 1970's. With the tedium of data collection and analysis greatly reduced, we can expect even more widespread adoption of this tool in the general analytical laboratory.

Accurate phase characterization of the alteration products of rad-waste requires the separation and identification of scattered individual grains from among the bulk product. These grains are typically 5 to 100 μm in size. Bulk x-ray powder diffraction will normally not detect these minor phases, and even if the phase can be detected, it often may not be identifiable. The use of the Gandolfi technique with the individual particle not only facilitates the identification, but also allows the assignment of the identification to the specific grain.

Intermediate aluminum oxides (aluminas) have broad X-ray diffraction (XRD) peaks. Many of the phases have similar XRD patterns with overlapping of major peaks. To characterize a multi-component alumina mixture several regions of multiple overlapping peaks are examined. Each region is integrated to a single sum without regard for individual peaks. The integrated regions are applied to various ratio functions obtained from single component standards. By using an iterative technique, the functions converge to yield weight fractions for up to six alumina phases.

The mathematical description of an X-ray peak, diffracted from a powder or polycrystalline material, using physically meaningful parameters has been of interest for many years. With the popularity of computers, this need to characterize a diffraction peak has intensified.

A key problem which persists is how to describe the instrumental diffracted profile and therefore the observed diffracted characteristic peak with subsequent combinations of Kα doublets and mixed overlapping peaks. Many attempts have been made at finding a “true“ function to fit the observed diffracted peak; however, a practical solution has yet to be found.

A special purpose, automated, four circle goniometer arrangement has been developed for the rapid orientation of large specimens of single crystal turbine hardware. This system rapidly establishes the complete orientation of these large components and generates a fully documented stereographic projection. The system is also capable of generating detailed information on crystal quality including rocking curves in several dimensions. X, Y translational capability of the specimen makes it possible to characterize crystallographic defects such as sub-grain boundaries.

On-line X-ray fluorescence analysis is used in the mineral processing industry to monitor the composition of the solids contained in various slurry streams. This study compares wavelength dispersive and energy dispersive techniques by using a slurry recirculation system employing both an X-ray tube excitation-wavelength dispersive system, and an isotope-excitation energy dispersive system. The results showed the less costly energy dispersive system yields accurate information that can be used to control milling operations.

An on-stream XRF analysis system for monitoring the concentrations of the elements in float process slurries is described. The system consists of multiple XRF stations monitored by a central computer. The stations utilize high resolution Si(Li) detectors and radioisotope x-ray sources for stability and for good separation of adjacent elements such as Cu and Zn. Results obtained from an on-stream slurry analysis of Copper and Lead Tails and Copper and Lead Concentrates are presented and these are compared to assay lab results.

Mercuric iodide HgI2 room temperature solid state radiation spectrometers having 4% energy resolution at 100 KeV detected the x-ray fluorescence (XRF) of the K shell of intermediate and high Z elements. The excitation of the K shells which emit XRF more energetic than 60 KeV was achieved with 7mCi collimated 57Co and for XRF less energetic than 60 KeV the excitation was done with a 10mCi 241Am source. The K shell XRF spectra of a 1:1 mixture of U and Th, and also of the single elements of Au, Tb, Ba, Ag, Mo, and Rb are shown. The results prove the feasibility of developing mercuric iodide portable XRF spectrometers which operate at room temperature and which have a wide range of geochemical and industrial applications.