ISSN:0049-8246    

DOI:10.1002/xrs.1300230602

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

年代:1994

数据来源: WILEY

摘要:

AbstractRare earth molybdate crystals such as those based on lanthanum, neodymium and some mixed molybdates, grown by the gel method, were analysed for major and trace impurity elemental concentrations using energy‐dispersive X‐ray fluorescence spectrometry in order to understand the characteristics of the material in terms of structural perfection and composition. The method used permits the simultaneous determination of rare earth elements such as La and Nd and also Mo and impurities such as Fe and Zn. Based on the observed concentrations of major elements, it is shown that the formulae so far assumed for some of these composites may be incorrect and may need a major refinement. Monoenergetic X‐rays of 22.1 and 59.6 keV were employed for fluorescence excitation and optimum detection efficiency was obtained for a large number of elements. Pulverized samples mixed with cellulose powder and specimens prepared in the form of pellets were used. The fundamental parameter method was used for the quantitative estimation of elemental concentr

ISSN:0049-8246    

DOI:10.1002/xrs.1300230603

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

年代:1994

数据来源: WILEY

摘要:

AbstractTwo samples of ordinary Portland cement, one consisting of dry powder and the other of hydrated paste 28 days old, were bombarded with protons, resulting in proton‐induced X‐ray emission (PIXE). The X‐ray yield was measured as a function of the exit angle and the differences between the two samples were interpreted by the hypothesis that the pores of the hydrated cement gel form a fractal. The fractal dimension that was calculated is in good agreement with the values found by small‐angle neutron scattering and nuclear magnetic re

ISSN:0049-8246    

DOI:10.1002/xrs.1300230604

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

年代:1994

数据来源: WILEY

摘要:

AbstractA peak‐to‐background method was implemented for standardless electron microprobe analysis of bulk samples and particles. First, a study on the choice of the beam entry point was performed; the region of the particle closest to the detector proved to be the most convenient. Then, a very simple algorithm, which does not require any kind of standard, was developed for particle analysis. This method was tested for glass standard particles and the results were compared with those given by other methods; the proposed standardless approach appeared to yield very satisfactory resu

ISSN:0049-8246    

DOI:10.1002/xrs.1300230605

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

年代:1994

数据来源: WILEY

摘要:

AbstractThe applicability of crystal monochromators, X‐ray mirrors and multilayer configurations as filter elements in the primary beam of a total reflection X‐ray fluorescence spectrometer is discussed. The best compromise between detection limits and multielement capability was found to be a double multilayer arrangement with variable distance between the multilayer mirrors. Two multilayers in combination with the respective control units for multilayer distance, tube height and sample positioning provide a free choice of isolated X‐ray lines and narrow energy bands of the bremsstrahlung continuum. This permits optional excitation energies in one instrument. Using a tungsten anode at 60 kV, three arbitrarily selected energies of 9.7, 20 and 40 keV were applied. The effect of tunable exciting energies was demonstrated by means of a standard multielement sol

ISSN:0049-8246    

DOI:10.1002/xrs.1300230606

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

年代:1994

数据来源: WILEY

摘要:

AbstractThe synchrotron photoionization method was applied to measure L‐subshell fluorescence yields. This method is based on the capability of tuning the energy of the synchrotron photons producing a selective subshell ionization. Three foil samples of Tb, Ho and Yb were irradiated and their characteristic spectra were recorded. Although it was not possible to obtain absolute results for the three ω L 1, ω L 2and ω L 3fluorescence yields, the poorly known ω L 1and ω L 2coefficients were calculated using theoretical values for the well known ω L 3yield. The results are very reliable and agree with reported theoretical and experimental data. These coefficients are valuable information for spectroscopists considering the lack of data for L1‐ and L2‐subshell parameters. Finally, synchrotron radiation has proved to be a useful tool for f

ISSN:0049-8246    

DOI:10.1002/xrs.1300230607

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

年代:1994

数据来源: WILEY

摘要:

AbstractOwing to improvements in impregnation techniques, the impregnation of copper compounds into a zeolite framework to form copper zeolite catalysts results in more uniformly distributed and finer (nanoscale size) copper‐containing particles. In order to determine the oxidation state of copper in a copper zeolite catalyst, a method utilizing the X‐ray absorption‐induced (absorption edge/self‐absorption) effect was developed using electron probe microanalysis. This method can provide oxidation state information that is not possible with traditional quantitative microanalysis owing to the electron beam and specimen interaction volume. The advantages and limitations of this method are di

ISSN:0049-8246    

DOI:10.1002/xrs.1300230608

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

年代:1994

数据来源: WILEY

摘要:

AbstractThe functionality of the computer package AXIL (Analysis of X‐ray spectra by Iterative Least squares), suitable for the evaluation of energy‐dispersive X‐ray spectra, has been extended in a number of ways. First, a background modelling algorithm, based on the use of mutually orthogonal polynomials was introduced to replace the linear or exponential polynomials employed previously. Second, the Gaussian photopeak model employed in previous versions of the program was extended to include the non‐Gaussian parts of the characteristic peaks and related background contributions. Both innovations are shown to improve the performance of the spectrum evaluation procedure. Third, the user‐friendliness of the evaluation program was enhanced (a) by allowing a PC plug‐in MCA card to be directly controlled from within the program and (b) by extending the command‐interface to allow for repeated execution of series of commands by means of control loops. A brief description of these changes is given; as an application, the accurate evaluation of micro‐XRF imag

ISSN:0049-8246    

DOI:10.1002/xrs.1300230609

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

年代:1994

数据来源: WILEY

ISSN:0049-8246    

DOI:10.1002/xrs.1300230610

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

年代:1994

数据来源: WILEY

ISSN:0049-8246    

DOI:10.1002/xrs.1300230611

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

年代:1994

数据来源: WILEY