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ASTM E1508 – 12a
Working distance is measured in the microscope; its accuracy depends on the method used to measure it and the specimen position. The intensity of such X rays is proportional to the mass fraction of that element in the specimen. Precision and Bias Higher count rates can be achieved by lowering the shaping time on the system ampli?
On the MA alloy, the reproducibility among laboratories was much less than that of the standards technique R in Table 4. To the extent that this number of replicate analyses averages out the effects of precision, the remaining error may be attributed to bias. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the risk of infringement of such rights, are entirely their own responsibility.
Two approaches to this problem commonly used in commercial systems are background modeling and digital? Both sets of data are reported, and the standardized operating parameters are listed in Table 1.
For example, trace element analysis is sensitive to background subtraction because the computer is looking for a small peak above the continuum. Each of the specimens was analyzed with a lithium-drifted silicon detector using a set of standardized operating parameters after an initial round-robin wherein parameters were selected by each participant.
It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. Practice E is used to analyze the round-robin data for consistency and calculates intralaboratory repeatability and interlaboratory reproducibility statistics.
The number of X-ray photons that reach the detector is a function of the solid angle and take-off angle, including the effect of specimen and detector tilt. The beam current must remain stable throughout the analysis, because the counts collected are directly proportional to the beam current. The differences in the results each produces are usually much less than the precision of the analysis. Sr SR r R Nickel 9. Or, if the standardless technique is used, then a pure net intensity is required.
ASTM E – 12a Standard Guide for Quantitative Analysis by Energy-Dispersive Spectroscopy
The s count speci? This standard is subject to revision at any time by the responsible technical committee and must be e11508 every? These approach the problem of asrm correction using more fundamental physics and sometimes combine the effects of Z and A into one, but they too require a set of fundamental parameters optimized to each program.
Software is usually available to calibrate the EDS system, and one should consult the system manual zstm the details of operation. If standards are used, they must be collected under the identical geometrical conditions as the unknowns. All distances must be in the same units. Two methods in common use are 1 the method of overlap factors and 2 the method of multiple least squares.
If the voltage measured in this manner is much lower than the voltage setting, it may be an indication that the specimen is charging.
Nevertheless, metals do not make good standards for nonmetals, and vice versa. Requiring set parameters had little effect on the repeatability but aztm the reproducibility for chromium and iron, but not for nickel. Whichever method is used, all elements present must be speci? Often aluminum and copper are used, and sometimes both the K and L lines of copper are used.
This material was chosen as a routine analysis for iron, chromium, and nickel. If the stoichiometry of compounds containing light elements is known, then calculation by stoichiometry is the most accurate method. For materials such as minerals and ceramics, which contain light elements that s1508, of low atomic number15 kV is usually a good compromise.
Clearly, for a given overall counting time, the relative precision associated with major elements is greater than for minor or trace elements, insofar as there are necessarily fewer counts in minor peaks. EDS detectors do not resolve all peaks. e15088
When analyzing hard and soft X rays in the same specimen, analyses at two voltages may be necessary. It should also be of similar composition awtm thickness between the standards and the unknowns. These errors arise from the different ways various systems generate the pure element intensities, rather than from differences in ZAF or phi-rho-z matrix corrections. For the most accurate analysis, standards and unknowns should be coated at the same time to assure equal coating thicknesses.
For a more detailed treatment of the subject, see Goldstein, et al.