ASTM E1508 PDF

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Standard Guide for Quantitative Analysis by Energy-Dispersive Spectroscopy

If you feel that your comments have not received a fair hearing you should make your views known to the ASTM Committee on Standards, at the address shown below. There are many potential sources of bias, but the effect of each is hard to predict. If the stoichiometry of compounds containing wstm elements is known, then calculation by stoichiometry is the most accurate method.

For the most accurate analysis, standards and unknowns should be coated at the same time to assure equal coating thicknesses. If the results are comparable, the standardless method may be used for specimens of composition similar to those on which it was validated.

For the alloy MAthe average was 3. Higher count rates can be achieved by lowering the shaping time on the system ampli? More accurate interaction volumes can be computed by Monte Carlo computer methods to generate random electron trajectories, but Eq 1 provides a reasonable estimate for astn purposes.

These conditions include the accelerating voltage, take-off angle and tilt, and the analytical line KLM used. In energy-dispersive spectroscopy, X rays from the specimen are detected by a solid-state spectrometer that converts them to electrical pulses proportional to the characteristic X-ray energies. To ensure reproducible zstm, calibration should be checked periodically.

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When analyzing hard and soft X rays in the same specimen, analyses at two voltages may be necessary. For example, trace element analysis is sensitive to background subtraction because the computer is looking for a small peak above the continuum.

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. If the specimen is tilted such that the beam is not perpendicular to the specimen surface, an effective take-off angle is used. And even though the average errors compared with the reference composition Table 5 are not great, they are probably the result of positive and negative errors among laboratories canceling each other.

Consequently, one would expect the most improvement using a phi-rho-z method in light element analysis. Longer counting times and increased beam current produce more counts. A spectrum from pure aluminum could be collected followed by pure copper in the same spectrum. Two approaches to this problem commonly used in commercial systems are background modeling and digital? It includes both methods that use standards as well as standardless methods, and it discusses the precision and accuracy that one can expect from the technique.

A superscript epsilon e indicates an editorial change since the last revision or reapproval. The EDS values are the average of? The inherent precision of the EDS method is controlled by counting statistics.

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If the specimen is inhomogeneous at the micrometre level, then a truly quantitative analysis is not possible, and a bulk technique such as X-ray? Lowering the beam current to lower the count rate usually eliminates the problem. Accordingly, before routinely using a standardless method for aetm analysis, it is important to validate the method for a particular class of materials by comparing it against analysis with standards or against a completely different quantitative technique, such as X-ray?

It was not possible to specify all of these conditions because some are inherent to the system used. Originally approved in It covers atm range of energies up to the aztm of the electron beam.

It should also be of similar composition and thickness between the standards and the unknowns.

ASTM E – 12 Standard Guide for Quantitative Analysis by Energy-Dispersive Spectroscopy

A second round-robin test program, which required the use of a standard accelerating voltage, detector dead time, take-off angle, and acquisition time, was also initiated.

Requiring set parameters had little effect on the repeatability but improved the reproducibility for chromium and iron, but not for nickel. Historical Version s – view previous versions of standard. If the unknown and standard were identical, each of these factors would equal one. However, most matrix correction programs are sufficiently accurate to permit the use of pure element standards.