Electron energy dispersive-spectroscopy

A scanning electron microscope can also be equipped with additional instmmentation for electron-excited x-ray analysis (9). In many systems, this is performed in the mode known as energy dispersive x-ray analysis (edx). Other common acronyms for this method are eds for energy dispersive spectroscopy or edax for energy dispersive analysis of x-rays. 

The incoming electron beam interacts with the sample to produce a number of signals that are subsequently detectable and useful for analysis. They are X-ray emission, which can be detected either by Energy Dispersive Spectroscopy, EDS, or by Wavelength Dispersive Spectroscopy, WDS visible or UV emission, which is known as Cathodoluminescence, CL and Auger Electron Emission, which is the basis of Auger Electron Spectroscopy discussed in Chapter 5. Finally, the incoming... 

In recent years there is a growing interest in the study of vibrational properties of both clean and adsorbate covered surfaces of metals. For several years two complementary experimental methods have been used to measure the dispersion relations of surface phonons on different crystal faces. These are the scattering of thermal helium beams" and the high-resolution electron-energy-loss-spectroscopy. ... 

Catalysts were characterized using SEM (Hitachi S-4800, operated at 15 keV for secondary electron imaging and energy dispersive spectroscopy (EDS)), XRD (Bruker D4 Endeavor with Cu K radiation operated at 40 kV and 40 mA), TEM (Tecnai S-20, operated at 200 keV) and temperature-programmed reduction (TPR). Table 1 lists BET surface area for the selected catalysts. 

Firstly, the energy losses of the incident electrons which produce the inner shell excitations may be detected as peaks in electron energy loss spectroscopy (EELS). The elecrons transmitted by the specimen are dispersed in a magnetic field spectrometer and the peaks, due to K, L and other shell excitations giving energy losses in the range of 0-2000eV, may be detected and measured. 

Secondly, the characteristic X-rays, emitted as the electrons displaced from the inner shells of the atoms are replaced, can be detected by use of an energy-sensitive detector placed close to the specimen. An account of the application of both the energy dispersive spectroscopy (EDS) of the emitted X-rays and EELS to the... 

EPMA is a technique for chemically analysing small selected areas of solid samples, in which X-rays are excited by a focused electron beam. Spatial distribution of specific elements can be recorded as two-dimensional X-ray maps using either energy dispersive spectroscopy (EDS) or... 

Table 5.2 Summary of selected analytical methods for molecular environmental geochemistry. AAS Atomic absorption spectroscopy AFM Atomic force microscopy (also known as SFM) CT Computerized tomography EDS Energy dispersive spectrometry. EELS Electron energy loss spectroscopy EM Electron microscopy EPR Electron paramagnetic resonance (also known as ESR) ESR Electron spin resonance (also known as EPR) EXAFS Extended X-ray absorption fine structure FUR Fourier transform infrared FIR-TEM Fligh-resolution transmission electron microscopy ICP-AES Inductively-coupled plasma atomic emission spectrometry ICP-MS Inductively-coupled plasma mass spectrometry. Reproduced by permission of American Geophysical Union. O Day PA (1999) Molecular environmental geochemistry. Rev Geophysics 37 249-274. Copyright 1999 American Geophysical Union...

Although a number of secondary minerals have been predicted to form in weathered CCB materials, few have been positively identified by physical characterization methods. Secondary phases in CCB materials may be difficult or impossible to characterize due to their low abundance and small particle size. Conventional mineral identification methods such as X-ray diffraction (XRD) analysis fail to identify secondary phases that are less than 1-5% by weight of the CCB or are X-ray amorphous. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM), coupled with energy dispersive spectroscopy (EDS), can often identify phases not seen by XRD. Additional analytical methods used to characterize trace secondary phases include infrared (IR) spectroscopy, electron microprobe (EMP) analysis, differential thermal analysis (DTA), and various synchrotron radiation techniques (e.g., micro-XRD, X-ray absorption near-eidge spectroscopy [XANES], X-ray absorption fine-structure [XAFSJ). 

Kamiya et al. [83] evaluated particulate contamination in 199 samples of admixed and un-admixed parenteral nutrition solution bags from 10 hospitals in Japan. Seven samples were used as controls since they had not been mixed with ampoules or vials (un-admixed samples). Size and number of particles were measured using a particle counter, and the identification of elements was carried out by scanning electron microscopy coupled to energy dispersion spectroscopy. The authors collected the residual volume of the samples (10-60 mL) after their usage. The results are presented in Table 40. 

FIGURE 19 Identification of two types of particles by scanning electron microscopy coupled to energy dispersion spectroscopy (a) suggests glass particles (b) suggests rubber particles [83]. 

Local chemical composition from areas less than 1 nm in diameter can be measured by energy dispersive X-ray spectroscopy (EDS) or electron energy loss spectroscopy (EELS). Such spectroscopic information may be presented in 2D maps showing the spatial element distribution in the specimen (13). Furthermore, information about the local density of unoccupied electron states of a specific element can be extracted from EELS data and used to estimate the oxidation state and the local coordination geometry of the excited atoms (14). In some favorable cases, electronic structure information with a resolution of about 1 eV from individual atomic columns has been attained (15,16). Recent developments of monochromators and spectrometers have brought the resolution down to 0.1 eV (17,18), and this capability may offer new opportunities to determine relationships between electronic structure information, the atomic arrangements and the catalytic activities of solids. 

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