ISSN:0049-8246    

DOI:10.1002/xrs.1300150402

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractA Monte Carlo simulation has been developed to describe the incoherent and coherent scatter processes for the complex geometry of a secondary target energy‐dispersive x‐ray fluorescence system. Photons are followed from the x‐ray tube anode until the detection of scattered secondary target photons in the active Si layer of the detector. The program quantitatively shows the broadening of the incoherent scatter peak with increasing atomic number, and it models the incoherent peak shape adequately. The incoherent‐to‐coherent scatter intensity ratios obtained differ by 10–30% from the theoretical values, while their dependence on the sample atomic number corresponds to that expected

ISSN:0049-8246    

DOI:10.1002/xrs.1300150403

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractXANES (x‐ray absorption near edge structure) in the vicinity of the K absorption edge of cobalt has been studied for two bivalent cobalt polymers, viz. cobalt(II) azelaic acid bis(phenylhydrazide) and cobalt(II) sebacic acid bis(2,4‐dinitrophenylhydrazide), using a bent crystal x‐ray spectrograph of the Cauchois type. This study helped in the determination of the average bond lengths in the two compounds. The study of the chemical shifts and the edge widths throws some light on the relative covalency in these comp

ISSN:0049-8246    

DOI:10.1002/xrs.1300150404

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractA simple model of the x‐ray Kα emission spectrum of copper metal has been proved to fit the experimental distribution curve of diffracted intensity fairly well, after correcting for profile distortion due to the spectrometer geometry and the diffraction process. Each Kα line can be described by a doublet of overlapping dispersion curves of different height and width. Although the physical relevance of the model is not clear at present, the simple analytical expression of the spectrum may be useful for some problems in x‐ray diffracto

ISSN:0049-8246    

DOI:10.1002/xrs.1300150405

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractA systematic study has been made of the line shapes of x‐ray fluorescence spectra obtained with a conventional spectrometer using various analysing crystals and experimental conditions. It was found that each component of the K and L spectra can be closely matched by the sum of an asymmetric Gaussian and Lorentzian, namely the pseudo‐Voigt function. Analysis of spectra in the 0.4–3 Å range showed that profile shapes are functions of 2θ, the analysing crystal and the collimating system, but nearly independent of chemical state, specimen thickness and operating voltage. For a fixed analysing crystal and collimator, larger values of 2θ exhibited lower Gaussian content and higher asymmetry. Using an LiF (200) crystal, spectra obtained for 2θ°<20° were found to be pure Gaussian and symmetric, indicating the dominance of the instrumental effects. As 2θ increased, the Lorentzian component or the spectral effects emerged and the shapes became asymmetric. The analysing crystal has a pronounced effect on the experimental profile shapes. Use of a graphite (002) instead of an LiF (200) crystal yielded profiles three times wider and with twice the Lorentzian content. The differences between PET and LiF crystals were smaller. The accuracy achieved in using the pseudo. Voigt function to describe the experimental XRF spectra demonstrates the convenience and effectiveness of the function in obtaining precise fluorescence intensities, especially in the case of poor counting statistics and

ISSN:0049-8246    

DOI:10.1002/xrs.1300150406

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractIntercomparison of fundamental parameter interelement correction methods is extended to include α‐coefficient algorithms in which the coefficients are calculated from fundamental parameters. Several of these methods are intercompared, including a comprehensive α‐coefficient algorithm recently proposed by Lachance. Results of the analysis of alloys, pressed cements and fused specimens are pres

ISSN:0049-8246    

DOI:10.1002/xrs.1300150407

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractIn Monte Carlo simulation of energy‐dispersive x‐ray fluorescence analysers, one must account for both x‐ray scattering effects and photoelectric absorption. To access the required random values of differential coherent and incoherent scattering angles, two‐variable cubic spline representations of the appropriate cumulative distribution functions are developed and their use is demonstrated. In this approach the scattering angle is taken to be the dependent variable while the two independent variables are the x‐ray energy and the normalized cross‐sections.Cubic spline coefficients for the elements from sodium to nickel have been obtained for x‐ray energies from 1 to 150 keV for all scattering angles for both coherent and incoherent scattering. Compared with the commonly used method of numerically integrating tabular values of coherent and incoherent cross‐sections to produce a table of values for subsequent interpolation, use of cubic spline representations gives a 90% reduction in storage space and a 25–80% reduction in the amount of computer time required f

ISSN:0049-8246    

DOI:10.1002/xrs.1300150408

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractThe rapid rise in the popularity of the McCrone Micronizing Mill for sample preparation in routine quantitative analytical x‐ray powder diffractometry (XRPD) has led to the present examination of material obtained with the device and a comparison with material produced by the widely used Tema Mill. Specimens of α‐quartz, prepared for a range of milling times under wet‐ and dry‐grinding conditions, were assessed according to their particle size distributions and XRPD integrated intensities. Particle size distributions were measured using a sedimentation technique. Changes in XRPD integrated intensity with milling treatment have been used to derive amorphous content indices representing the change in estimated intensity attributed to milling. The results show that the McCrone Mill can produce XRPD specimens of α‐quartz for assay work which adequately satisfy particle size criteria. Powders obtained by wet‐milling with the McCrone device are more acceptable for XRPD work than those prepared by dry‐milling, and both are clearly superior to powders produced with the Tema Mill under the dry‐grinding conditions conside

ISSN:0049-8246    

DOI:10.1002/xrs.1300150409

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractThe object of this paper is to outline the principle of the fundamental influence coefficient method and emphasize its utilization for the accurate x‐ray fluorescence analysis of compact or diluted specimens.For any given composition, effective coefficients, as defined by Tertian's identities, can be derived from the calculation of the theoretical fluorescence intensities, as used in the fundamental parameter approach. The importance of a careful selection of theoretical data is underlined. These include the fundamental parameters, i.e. essentially the mass absorption coefficients and the excitation factors, and the instrumental characteristics, namely the spectral intensity distribution of the x‐ray tube and the geometric factor of the spectrometer. All of these data are still under investigation and the accuracy of their determination is being assessed. The effective coefficients are inserted in a comparison standard algorithm, a practice which compensates for the residual uncertainties affecting some of the parameters. In fact, and in terms of concentration ranges, the compensation limits are fairly large and can be extended, if necessary, by recurrence procedures. A special correction algorithm, similar to the basic one, but based on ‘modified’ coefficients, is used for the analysis of diluted specimens. A suitable computer program and its accessories are defined and their use is illustrated by a variety of practical applications including the analysis of stainless steels, high‐temperature alloys, non‐ferrous alloys (bronzes) and, as an example of fused specimens, cement. The characteristic of the fundamental coefficient method is that it combines the theoretical exactness of the fundamental parameter approach with the flexibility of the usual Lachance‐Traill formulation, thus allowing any given analytical problem, whether complex or comparatively simple, to be studied and solved in agreement with the actual degree of difficulty and the accu

ISSN:0049-8246    

DOI:10.1002/xrs.1300150410

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractA method for improving the determination of cobalt as a minor element in steel specimens is reported. A line overlap correction for the contribution of the Fe Kβ background on the Co Kα peak plus inter‐element matrix corrections is necessary in the determination of Co when standards of varying matrix compositions are used. Co was determined in several NBS SRM steels and values were found that agreed with the certificate values to within 5% relative error in the range 0.005–0.40 wt‐%

ISSN:0049-8246    

DOI:10.1002/xrs.1300150411

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY