WDX analysis

Elemental analysis can also be performed on SEM samples using x-ray spectrometer attachments [55], The techniques are known as energy dispersive x-ray (EDX) analysis and wavelength dispersive x-ray (WDX) analysis and require installation of a detector in the sample chamber. 

Recent developments, such as the windowless EDX detector, have allowed the light element range to be extended down to C. Automated WDX spectrometers with computer control of the operating parameters are now available, such as the Microspec WDX-2A system. This considerably simplifies WDX analysis. The ideal system, however, requires both an EDX and WDX system mounted on the microscope simultaneously. This would permit the rapid determination of the elements present with the EDX system, and a detailed analysis of these elements using the WDX spectrometer. Combined EDX/WDX systems have already been developed where components of the hardware are shared, such as a computer to perform corrections on the measured data for atomic number, absorption, and fluorescence effects. These corrections are necessary when performing quantitative analysis. 

The scanning electron microscope (SEM) (XL30 PHILIPS) was used to characterize the surface morphology of deposits. The wavelength-dispersive X-ray (WDX) analysis( 3PC, Microspec Ltd., USA) was used to exist metallic particles over surface Cu-Ni-P alloy plated fabrics. 

If local materials analysis or concentration profiles are necessary, EDX analysis can be carried out as dot, line, or area analysis. In some cases, wavelength-dispersive X-ray (WDX) analysis can also be conducted, for example, to verify whether a phase consists of minimal amounts of Cr, or whether the Cr Kai Hne overlaps with the La L/32 line from the cathode material. 

The most popular and powerful method of local and almost nondestructive chemical analysis is electron probe microanalysis (EPMA), based on the excitation of characteristic X-rays by a finely focused electron beam. Actually this method combines several techniques [energy dispersive X-ray (EDX), wave dispersive X-ray (WDX) analysis etc.]. In any case the best results can be achieved by using carefully prepared preanalyzed standard samples (for example, single crystals with a defined composition). 

Electron Probe Microanalysis, EPMA, as performed in an electron microprobe combines EDS and WDX to give quantitative compositional analysis in the reflection mode from solid surfaces together with the morphological imaging of SEM. The spatial resolution is restricted by the interaction volume below the surface, varying from about 0.2 pm to 5 pm. Flat samples are needed for the best quantitative accuracy. Compositional mapping over a 100 x 100 micron area can be done in 15 minutes for major components Z> 11), several hours for minor components, and about 10 hours for trace elements. 

TGA/DTA combined thermogravimetry / differential thermal analysis WDX wavelength-dispersive X-ray diffraction... 

Within this technique, we include EDX (energy dispersive x-ray analysis), WDX (wavelength dispersive x-ray analysis), and XRF (x-ray fluorescence analysis). In all of these, x-rays emitted from a sample are analyzed. In one case, they are created by bombarding the sample with x-rays (XRF), and in the others, they are created by high energy electron beam as in an SEM (EDX, WDX). 

PIXE is the analogue to EDX/WDX (energy/wave dispersive analysis of X-rays) done with electron microprobes. Elements in the sample are identified by the characteristic X-rays emitted during MeV particle bombardment. PIXE is not well suited for fluorine detection because of the low energy of the corresponding X-rays. However, it is often performed simultaneously with other ion beam techniques and gives very valuable information on the bulk composition and other trace element concentrations in the sample. 

Other analytical methods can also be applied for the detection of F in archaeological artefacts, especially when it is possible to take a sample or to perform microdestructive analysis. These are namely the electron microprobe with a wavelength-dispersive detector (WDX), secondary ion mass spectrometry (SIMS), X-ray fluorescence analysis under vacuum (XRF), transmission electron or scanning electron microscopy coupled with an energy-dispersive detector equipped with an ultrathin window (TEM/SEM-EDX). Fluorine can also be measured by means of classical potentiometry using an ion-selective electrode or ion chromatography. 

Electron microprobe WDX Yes mm or im sample Metallisation Surface analysis Some hundreds of nm 0.5wt.%... 

Figure 5.(a) Typical mass spectra of a 0.9 im borophosphoro silica glass (b) weight % concentrations of B and P compared with chemical analysis, EDX and WDX at various diboran flow rates. 

There are, however, three main limitations of EDX spectrometers. The resolution of characteristic peaks is poorer than with WDX spectrometers, and the background is higher. Furthermore, the efficiency of the normal Li-doped Si detector with an 8 / m thick Be window falls off dramatically for elements of low atomic number Z thus, only x-rays from Na (Z = 11) and heavier atoms can be detected. Windowless detectors are available, which can detect light elements such as B (Z = 5), but their use is not free of complications for quantitative analysis. 

The other type of X-ray analysis system used with SEMs today is the wavelength spectrometer, illustrated in Fig. 5. Here the selective diffraction properties of a crystal in conjunction with a proportional counter detector is used to sort out the radiation according to wavelength. With suitable crystals, this system allows the analysis of all elements from Be-U. In addition to allowing the detection of light element radiation, the WDX spectrometer provides superior elemental discrimination compared to an EDX system. 

Electron probe microanalysis (EPMA), X-ray analysis (energy dispersive, EDX, or wavelength dispersive, WDX), and X-ray fluorescence spectroscopy (XRF) are... 

An SEM is usually equipped with an X-ray detector (allowing energy dispersive analysis of X-rays, EDX or wavelength dispersive analysis, WDX). Thus, the characteristic signal X-ray emission of a particular element can be displayed on the imaging screen, and the distribution of different elements on a surface can be readily obtained. Figure 1.26 reveals the origin of particles on a polymer surface with the help of EDX. 

Surface analyses, such as with X-ray photoelectron spectroscopy (XPS = ESCA), scanning electron microscopy (SEM), and dispersive X-ray analysis (EDX, WDX) are discussed in Section 17.7 because they are used routinely in characterizing vinyl composites. They are also useful in other connections, such as changes to vinyl surfaces from weathering or exposure to aggressive media. Fourier transform infrared (FTIR) analysis is also discussed in Section 17.7. 

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