EDAX Methods Research Articles

Ion−beam analysis of corrosion films on 316 steel

Ion backscattering at MeV energies, coupled with nuclear reaction analysis, has been used to determine quantitatively the composition of complex corrosion films produced by the exposure of 316 stainless−steel specimens to a variety of alkaline solutions. The oxygen content as a function of depth, up to about 2 μ, and the trace heavy metal content were determined by helium backscattering at 2.9 MeV. The lithium content was measured by means of the Li7 (p,α) reaction at Ep = 3 MeV, with a calibration achieved by comparison with LiNbO3. It is shown how much more valuable such ion−beam techniques become when combined with microscopic examination using SEM, EDAX, and optical methods. In this way, for example, the variation in composition with depth has been correlated with oxide thickness. The advantages of this form of analysis for other corrosion problems will be described.

Enhancement of EDAX Spectra from TEM and SEM Analysis

The attachment of EDAX systems to the TEM and SEM makes possible the microanalysis of features observed in the high magnification images. In general the interpretation of the resulting spectra is very straightforward, with qualitative identification of the major and minor elements present requiring only reference to a simple chart, and semiquantitative estimation of concentration possible by direct comparison of peak heights. True quantitative analysis requires more complex mathematics and/or standards but this is not generally the aim of most SEM and TEM users.There is one class of problems for which the direct interpretation of the recorded EDAX spectrum can be difficult, especially for the operator not highly trained in EDAX methods. This is the case of very low total count rates, typically encountered with low concentrations of elements in organic matrices and/or with low total specimen mass as encountered with thin sections.

An Integrated System for Elemental X-Ray Analysis of Materials

The use of energy dispersive analysis of x-rays (EDAX method) is now well entrenched in the electron column field(l), where more scanning electron microscopes have been fitted with EDAX instrumentation than all of the conventional (wavelength-dispersive spectrometer) microprobes ever made. The principle advantage of the EDAX approach for the SEM user is the efficiency of detection, which permits its use at the low power levels of the SEM. In addition, the simultaneous analysis of the entire spectrum and the lack of focusing restrictions that permits analysis of rough samples are important advantages.