[B._Beckhoff,_et_al.]_Handbook_of_Practical_X-Ray_(b-ok.org).pdf

Coefficients have been derived for high accuracy

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coefficients have been derived for high accuracy analysis and wider applicable correction equations. Rousseau [73] showed comparative figures of measured and calculated X-ray intensities and applied them to the correction equations developed by Claisse and Quintin [74] and Criss and Birks [70]. Furthermore, Rigaku Industrial Corporation.. tried to compare the mea- sured intensity with calculated intensities based on its own developed funda- mental parameter method. Using the primary X-ray distribution from the end window X-ray tube, precisely matching calibration curves were obtained. Us- ing these curves, direct quantitative analysis was then carried out by iterative computer algorithms without the need of matrix correction equations. The analytical results for high alloy analysis are shown in the following section. 1.4.2 Quantitative Analysis of Heat-Resistant and High-Temperature Alloys Gould [75] summarized metal analysis with X-ray spectrochemical analysis. In this section, matrix correction and some segregation influencing analytical accuracy are discussed in detail. Abbott who was the first developer of a commercial X-ray fluorescence spectrometer, presented a strip chart record of high alloy steel (16-25-6) shown in Fig. 1.5 [17]. Compared to modern equipment, his spectrometer gave much weaker intensities and poorer spectral resolutions due to adoption of a Geiger counter and a NaCl analyzing crystal. Figure 1.6 is a spectrum of NBS 1155 high alloy steel measured with a modern instrument, which equips a scintil- lation counter and a LiF analyzing crystal. Since the fluorescent intensities and spectral resolution are sufficiently high for practical applications, the dif- ference between these two pictures exhibits the historical progress of 50-years development. As pointed out by Abbott, the X-ray method is well suited for analyz- ing heat-resistant and high temperature alloys which consist of nickel, cobalt, iron, and chromium as major constituents, and low concentrations of vari- ous other elements. Because the concentrations of the constituent elements influence the metallurgical properties of high temperature and heat-resistant alloys, high precision is required in quantitative determination. In order to review the analytical accuracy of numerous reports, a comparison parame- ter is introduced, defined as the root mean square between chemical analysis and non-corrected or corrected X-ray values (abbreviated as RMS-difference). Studies of RMS-differences were performed and are shown in Table 1.3.
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20 T. Arai 14 15 16 17 18 19 20 21 22 23 24 25 100 1000 10000 Ni K b 1 , Cu K a Ni K a Fe K b 1 , Co K a Fe K a Cr K b 1 , Mn K a Cr K a Counts per min. q NaCl(200) ( ) Fig. 1.5. Spectrum of 16-25-6 alloy taken by Abbott [17] 45 50 55 60 65 70 75 0.1 1 10 100 1000 Ni K b 1 Cu K a Co K b 1 Ni K a Fe K b 1 Co K a Mn K b 1 Fe K a Cr K b 1 Mn K a Cr K a x 10 3 counts per second 2 q LiF(200) ( ) Fig. 1.6. Sepctrum of NBS 1155 taken by using Rigaku ZSX 100e Rickenbach [76] showed the precision and accuracy of nickel and chromium analysis. The measured precision of nickel and chromium in an A286 metal
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