bluuebunny/crossref_metadata_2025_split huggingface dataset:
An X-Ray Camera for Precision Lattice Parameter Measurements
Authors: Franks A. 
Published: March 2019

AbstractA back-reflection focusing camera has been constructed in which instrumental errors, including those due to uneven film shrinkage, have been eliminated or very much reduced. This has been achieved by employing metrological techniques both in construction and calibration, The temperature of the camera can be controlled to 0.05°C. The form of the specimen is such that horizontal and vertical divergence cause no line shift. The X-ray source is a demountable semimicrofocus tube with an adjustable focus. The radiation is monochromatized by a bent and ground quartz crystal.
A Highly Simplified Multielement Calibration System for Semiquantitative X-Ray
Spectrographic Analysis
Authors: Salmon Merlyn L. 
Published: March 2019

AbstractSemiquantitative results are adequate for the satisfactory solution of many problems involving mineral analyses, andfluorescent X-ray spectrography is gaining more recognition as a satisfactory method for performance of these analyses.Successful applications of the method, in various instances are discussed to demonstrate a system involving minimum s am - pie preparation and the use of instrumental factors in establishing multielement calibration curves.
Integrated X-Ray Diffraction Intensities from Single Crystals
Authors: Chessin Henry 
Published: March 2019

AbstractThe advantages and accuracy of counter equipment for the measurement of the intensity of scattered X-rays from small single crystals are discussed and illustrated. Several precautions necessary to obtain reliable intensity measurements are discussed. The equi-inclination method of inspecting all accessible reflections is treated in detail. The practicality of the stationary crystal method for determining integrated intensities, in principle the most accurate and rapid method, is demonstrated. Suggestions for improving the accuracy and speed of collecting data are made.
Determination of Relative Stability of Urea Complexes from X-Ray Powder Diffraction Data
Authors: Radell Jack , Connolly J.W. 
Published: March 2019

AbstractUrea complexes consist of a channel made up of hydrogen-bonded urea host molecules into which a variety of guest molecules can fit to form a crystalline complex. The urea host can accommodate, one at a time, a variety of guests having the requisite size and shape. The stability of the resulting complex is a function of the properties of the guest molecule. A procedure has been devised which produces pure complex free of any uncomplexed urea or host molecules in solution. The insoluble crystalline complexes formed from the solution of urea and guest molecule in methanol established a dynamic equilibrium. When the crystals of complex are removed from the solution, dissociation to urea and guest occurs to an extent, depending upon the dissociation constant of the complex. If the dissociation constant, KD, is very low, undetectable quantities of uncomplexed urea form along with complex. If the dlissoclation constant is high, extensive amounts of urea form in the presence of complex. Characteristic interplanar spacing s are obtained for a urea complex irrespective of the guest molecule present. The pattern obtained for the hexagonal complex is completely different from the pattern obtained for tetragonal urea. X-ray examination of a homologous series of compounds gives, for each partially dissociated complex, spacings for both urea and complex. The relative intensities of urea and complex spacings permit the estimation of the stability of such a complex compared to that of other homologues.
Twenty Years of Progress in X-Ray Diffraction Techniques
Authors: Guinier Andre 
Published: March 2019

AbstractAlthough no revolutionary advance has been achieved in the last two decades, X-ray diffraction is not to be considered as a quiescent field of physics. Actually many improvements, in theory as well as in experiment, slight by themselves but very numerous, have considerably increased the efficiency of techniques such as the determination of crystal structures, the analysis of crystalline phases, and the applications of X-rays to various problems of the physics of solids. Only the two last points will be dealt with here:1.Crystalline phase analysis. The development of a satisfactory atlas of powder patterns has been too slow, and the data are not yet complete and precise enough to permit a rational utilization of the modern diffractometers. A very interesting new approach is the systematic indexing of the powder patterns which would be possible with computers. In the near future, anyone should be able to analyze a powder at any temperature as an easy routine experiment.2.The study of lattice defects. X-ray techniques are now in competition with electron microscopy, the development of which has been very successful in recent years. Now we have a better understanding of the possibilities of both techniques. X-rays give better results to determine the statistics of an extended disorder even if it is slight (e.g., degrees of order in a solid solution), and the microscope is more powerful for the detection of large but rare defects (e.g., dislocations).
The Lattice Parameters of Iron-Ruthenium Solid-Solution Alloys
Authors: Cotta Leo J. , Gazzara Charles P. 
Published: March 2019

AbstractThe lattice parameters of iron-ruthenium solid-solution alloys of 0.10, 0.20, 0.50, 0.75, 1.50, 2.25, and 3.00 wt, % ruthenium have been determined at 310°K using a Philips back-reflection focusing camera and annealed-powder specimens.
Precision Lattice-Parameter Determination by Double-Scanning Diffractometry
Authors: King H. W. , Vassamillet L. F. 
Published: March 2019

AbstractThe availability of counter-tube diffractometers which can scan both sides of the direct beam makes it possible to locate the zero-angle position by comparing peak positions measured on either side of the beam. These diffractometers may thus be used to determine accurate lattice parameters without the need of a calibrating substance. The feasibility of this method is explored by determining the lattice parameters of pure silver, and the limits of accuracy are discussed.
The Determination of Crystallite Size and Size Distribution from Broadened X-Ray Diffraction Lines
Authors: Quinn H. F. , Cherin P. 
Published: March 2019

AbstractMagnesium oxide crystallites having mean dimensions in the range of 25–1000 A can be prepared by controlled thermal decomposition of the carbonate.Following some earlier investigations of Birks and Friedman, we have determined the mean size and size distribution of several such MgO samples from the broadened X-ray diffraction lines which they exhibit. Contrary to the procedure of the above investigators, the harmonic analysis due to Stokes has been used to correct for instrumental broadening and values of mean-size and size-distribution functions obtained from the Fourier coefficients by the methods of Warren and Averbach.The results obtained are compared with average sizes and distributions obtained by direct examination of the samples in an electron microscope.A composite sample has been prepared by mixing known quantities of the sample previously studied. The distribution function obtained by harmonic analysis of one diffraction line of the composite sample is compared with the function calculated from the distributions of its components.Conclusions are drawn concerning the significance of the results obtained by the Warren technique: in particular, the average sizes obtained by this method are compared with those given by the approximate method used by Birks and Friedman.
X-Ray Studies on the Formation of Basic Lead Azides
Authors: Reitzner Bruno , Abel James E. 
Published: March 2019

AbstractThe reaction between solid lead azide and lead oxide at different molar ratios yields two phases of basic lead azide of the type xPb(N3)2·yPbO with different azide content. The first phase was identified as xPb(N3)2·PbO, investigation of the second phase is still under way. The results up to the present time suggest that the formula for this phase is between Pb(N3)2·2PbO and Pb(N3)2·3PbO, probably 2Pb(N3)2·5PbO. The reaction is catalyzed by traces of water. The formulas of the two lead azide phases are established by X-ray analysts. The phases are identical with those found previously when lead azide was thermally decomposed in atmospheres containing water.
Problems in the Temperature Calibration of an X-Ray Diffractometer Furnace*
Authors: Mauer F.A. , Bolz L.H. 
Published: March 2019

AbstractTests were carried out with an X-ray diffractometer furnace to determine the temperature variations from point to point in the specimen and the correction to be applied to thermocouple readings. It was found that, under the conditions of the tests, temperature corrections depend on the preparation and properties of the sample. Calibration curves for two standards are given to illustrate this point, and suggestions for improving temperature measurements are made.
Thermal Expansion of Alpha-Alumina
Authors: Campbell William J. , Grain Clark 
Published: March 2019

AbstractHigh-temperature X-ray diffractometer measurements by the Bureau showed that alpha-alumina expands anisotropically with expansion parallel to the c axis approximately 10% greater than that parallel to the a axis. Thermal-expansion characteristics of four different alumina samples were determined up to 1200°C; the results are presented in both tabular and graphical form. The combined random and systematic errors in the measurements are considered less than 3% above 500°C and approximately 2% at 1000°C. No differences in expansion were observed between the samples or between the heating and cooling cycles.Critical evaluation of the literature showed that published values for thermal-expansion coefficients of single crystals vary over a range of 40% (relative values) and disagreement concerning whether expansion of alpha-alumina is isotropic or anisotropic. Systematic and experimental errors were found to be the principal factor for the variation in results, rather than differences in measuring techniques or in samples.Published values for polycrystalline aggregates also varied. Two laboratories reported values 20–30% lower than those of the Bureau of Mines, but two other laboratories agree with the Bureau within 3–5% above 500°C.
Some Considerations on the Excitation Efficiency in X-Ray Spectrochemical Analysis
Authors: Schreiber H. 
Published: March 2019

AbstractMost considerations of excitation conditions either have ignored the target material of the X-ray tube and the resulting spectrum of the primary X-ray beam or have dealt with it in very general terms, making a few broad assumptions regarding its effect on the final result. This is quite understandable since any attempt to handle the quantitative relationship between the primary spectrum and the resulting fluorescent spectrum results in extremely complex and unwieldy mathematical expressions. However, with the number of different primary sources now available, it is possible to evaluate these complex expressions in terms of actual data and permit more reliable values to be placed on the relative contributions of the components in the primary spectrum.A discussion is included of results obtained with X-ray tubes with chromium, molybdenum, tungsten, and platinum targets together with a few typical applications to actual X-ray spectrochemical procedures. Also discussed are the other variables which play a part in the excitation of fluorescent X-ray spectra, such as the primary X-ray tube voltage and the window of the X-ray tube.
The Application of X-Rays to the Analysis of Container Glass
Authors: Laning Stephen H. 
Published: March 2019

AbstractContainer glass, which is derived from the fusion of sand, sodium carbonate, limestone or dolomite, and feldspar, along with small amounts of colorants, reducing agents, and other modifiers, offers quite a challenge to the analyst, whether it be by conventional wet-chemical methods or by modern instrumentation. An analysis for 12 elements, which would take many days by standard wet methods, can now be done in 3–4 hr for a single sample, or 2 hr when analyzed in groups of three or more samples.X-ray procedures have been developed and calibration curves obtained for SiO2, CaO, MgO, K2O, Al2O3, Cr2O3, Mn2O3, Fe2O3, CoO, BaO,TiO2, SrO, ZrO2, As2O5, and SO3 In glass. With a gravimetric determination of Na2O added to the elements determined by Xray, the total should approach 100%. An analysis Is considered satisfactory if the combined determinations total within ±0.3% of 100%. Various X-ray procedures and matrix effects shall be discussed.
On-Line Type X-Ray Emission Analyzer Systems
Authors: Furbee A.D. 
Published: March 2019

AbstractThis paper describes equipment and performance characteristics of an X-ray emission analyzer designed specifically for continuous, 24-hr on-line process chemical analysis and control. Analysis of elements from Mg (12) upward in the periodic chart are generally feasible.The basic instrument is a multichannel spectrometer with provision for the simultaneous analysis of up to six elements. Either curved or flat crystals may be used as dictated by the particular application for which it is intended. X-ray detection is accomplished with flow proportional, sealed proportional, and scintillation detectors with both counter tube gas and electronic discrimination against undesired X-rays. The instrument is designed for excellent stability with provision for either automatic or simple manual standardization for long-term drift. A helium atmosphere is used for light elements, and through great care in spectrometer head design consumption is limited to 1 ft3/hr. A number of sample-presenting apparatus have been designed as companions to the basic equipment, including a continuous automatic powder, slurry, and liquid presenter. The powder presenter is particularly adaptable Co continuous analysis of materials which are finely ground (e.g., -200 mesh), whereas the slurry presenter is adaptable to continuous monitoring of solutions or finely ground particles in a slurry state. Readout is available as a d-c signal suitable for strip-chart recorders, voltmeters, data loggers, computers, and control. Digital readout and print out are also available. Performance tests in both the laboratory and field indicate an instrument suitable for on-line process use in a wide variety of industries, including cement, steel, mining, petroleum, and chemicals.
Application of X-Ray Fluorescence Analysis to Process Control
Authors: Bernstein F. 
Published: March 2019

AbstractThe application of X-ray fluorescence-analysis methods to process control is discussed. Various methods of sample preparation are reviewed and compared. The use of the direct sampling technique is discussed and consideration is given to the effects of particle size on precision and accuracy of analytical results. The mechanism of these effects if presented, and some general principles concerning the relationship of fluorescent intensities and particle sizes of pure materials and mixtures are derived. Examples of particle-size effects in cement and mining applications are illustrated.
Electron-Probe X-Ray Spectrograph: Design, Evaluation, and Application
Authors: Brown J. D. , Thatcher J. W. , Campbell W. J. 
Published: March 2019

AbstractThe Bureau of Mines purchased the electron optics, vacuum system, and sample stage assembly for the electron-probe X-ray spectrograph and designed and built the two reflection and two transmission scanning curved-crystal spectrometers. The reflection spectrometers were placed in a vacuum chamber for measurements of long-wavelength X-radiation. Operational characteristics of this spectrograph were determined. A low-alloy stainless-steel sample containing 5 wt. % depleted uranium and a stainless-steel sample containing 20 wt. % gadolinium were analyzed.
Indexing of Powder Diffraction Patterns
Authors: de Wolff P. M. 
Published: March 2019

AbstractDespite the advances of the electron mtcrodiflraction technique, the determination of unit cells of microcrystalline compounds still depends in many cases on the interpretation of the X-ray powder pattern. The feasibility of this interpretation depends strongly un the precision of the data, the present-day level of which is far from its physical limit. It could be improved by application of monochromators in diflractometry. Some possible methods are discussed. With regard to interpretation, a survey of existing methods is given (Lipson, Ito, de Wolff, Szoldos). Some of these techniques are suitable for computers, at least in the initial phase of the procedure. This is illustrated by application of a zone-finding program for the complete solution of a given pattern. Finally, the influence of impurities and other disturbing factors is discussed.
Helium Path Diffractometry and its Application to Determination of Retained Austenite and Macrostress in Steel
Authors: McCune Robert A. 
Published: March 2019

AbstractThe helium X-ray path has long been used, in spectrography to increase the intensity of the long-wavelength X-rays. The same principle has been applied to diflractometry. Up to threefold intensity increase is observed with chromium Ka radiation with very little increase In background. The peak to background ratio, therefore, is Improved by almost the same factor as the increase in intensity. Application of the technique is illustrated by analysis of gauge block steel for retained austcnite and macrostress.
Precision X-Ray Diffractometry using Powder Specimens*
Authors: Vassamillet L. F. , King H. W. 
Published: March 2019

AbstractThe counter tube diffractometer method for determining d spacings is often rejected for precision work because of lack of information concerning the nature and significance of the inherent errors. Errors concerned with the geometry of the method, the nature of the X-ray source, and the technique of collecting data have all been analyzed previously in some detail. The findings of these analyses, which are scattered throughout the literature, are reviewed briefly. Errors arising from imperfections in the instrument and misalignment of the X-ray source with respect to the diffractometev have been studied experimentally. The results are presented and discussed in terms of the resultant error in the determination of the lattice parameter of a cubic crystal. Errors determined both analytically and empirically are discussed in relation to the extrapolation procedures commonly used for diffractometers. It is shown that, depending on the construction of the instrument, the effect of imperfections in the gears may almost double the error in the final extrapolated value of a lattice parameter.
Practical Applications of Filters in X-Ray Spectrography
Authors: Salmon Merlyn L. 
Published: March 2019

AbstractApplications of filters are routine and useful techniques in X-ray diffraction and.can also be useful in X-ray spectrography to improve analytical results with very simple procedures. Fankuchen demonstrated the use of filters over the window of the X-ray tube to minimize background from the target element and/or elements in other components of the X-ray tube in research programs at the X-ray- Laboratory, Metallurgy Division, Denver Research Institute during the summer of 1952. This general procedure has been adapted to routine analyses by modification of the spectrograph to provide for movement of filters in and out of position between the window of the X-ray tube and the sample while the instrument is in operation. Placement of filters in the X-ray beam path of the spectrograph between the sample and the analyzing crystal is also a useful procedure to reduce interferences by elements exhibiting lines at closely adjacent wavelengths.
Iron Oxide Determination by X-Ray Fluorescence for In-Process Control of Solid Propellant and Premixes
Authors: Lamborn Reuel E. , Sorenson Foster J. 
Published: March 2019

AbstractFinely divided iron oxide is used as a burning-rate catalyst in several solid rocket propellants. The concentration is critical and must be accurately determined as a quality control point before the propeltant is cast in the motor case and cured, in addition to the iron oxide, the propellant used for ignition of the Air Force Minuteman first stage contains a polymeric binder system, a solid oxidizer, and a metal powder. This composition makes it difficult to determine accurately the iron content by wet methods in the time available daring the propellant processing cycle. The use of X-ray fluorescence has been investigated as a means of satisfying the analysis time requirements while meeting the prescribed accuracy of ±1% of the amount of iron oxide present. Procedures for preparing test specimens have been developed and instrument operation conditions chosen which yield satisfactory precision. When ten specimens from each of three premixes were analyzed for iron content, the observed within-mix mean relative standard deviation was 0.28%; for propellant analyzed under the same conditions, the mean relative standard deviation was 0.35%. Factors affecting mix-to-mix accuracy, such as particle size and shape and interelement absorption and enhancement effects, have been investigated. Accuracy is adequate for in-process control of the iron oxide level in the premix, but further work is required before satisfactory control of propellant is achieved.
A Qualitative X-Ray Examination of the Structure of Fiberglass Under Static Tensile Loading
Authors: Materne H. P. 
Published: March 2019

AbstractA series of four types of glasses was supplied for investigation. Six individual filaments of each glass (each filament ranged between 7 and 10 μ in diameter) were extracted and the ultimate tensile strength determined for each. The ultimate average tensile strength was then used in the determination of the tensile load applicable to the investigation.Two methods of examination were used—the Laue and a modified rotation camera. The results of the investigation seem to indicate that a reconstructive transformation in three of the four glasses studied was in process. These results have not been confirmed, due to time limitations. In the case of the E glass investigated, a series of rings were faintly produced after 15 days under 35% of the ultimate average tensile strength. These rings, actually egg-shaped ovals, appeared at 15, 20, and 30 mm from the point of contact of the incident beam. In the other modified E glass and in the YM-31A (BeO) glass, the egg-shaped configuration did not appear in the rotation camera, but did appear in the Laue examination as a semioriented series of spots.
Precipitation of MgF2 in LiF*
Authors: Lilley E. , Newkirk J. B. 
Published: March 2019

AbstractThe structural aspects of the precipitation of MgFa in LiF have been studied in LiF crystals containing up to 3 wt. % MgFs. The precipitate particles appear to be rodlike, having a sawtooth morphology. The rods lie in two directions on matrix planes which are close to but not precisely {111}LIF.The lattice orientation relationship between MgF2 and LiF has been established by X-ray techniques as(111)LIF‖(100)MgF2Laue photographs of slowly cooled crystals show diffuse X-ray scattering effects which are associated with the precipitation process.Excellent matching of atoms at the interfaces between the precipitate and matrix is postulated on the basis of a hard-sphere atomic model. The results suggest that phase coherency obtains during the early stages of growth, and that growth is controlled by dislocation interfaces.Rapid quenching retains all MgF2 in solution. Upon subsequent aging a transition structure forms which is based essentially on the LiF lattice but with a cell size of 8.20 Å, roughly double that of LiF. With further aging the transition structure is replaced by the normal MgF2 tetragonal structure.