Electron microprobe X-ray emission

The surface of the particles can be studied directly by the use of electron microprobe X-ray emission spectrometry (EMP), electron spectroscopy for chemical analysis (ESCA), Auger electron spectroscopy (AES), and secondary ion-mass spectrometry. Depth-profile analysis determines the variation of chemical composition below the original surface. 

The analysis of metals by X-ray fluorescence has been widely used on geological and sediment samples, either deposited on filters or as thin films. The method can be made quantitative by using geological standards and transition metals can be determined in the 1-5 tg per g range. The surfaces of sediment particles can be examined by the direct use of electron microprobe X-ray emission spectrometry and Auger electron spectroscopy. Although these methods are not particularly sensitive, they can allow the determination of a depth-profile of trace metals within a sediment particle. 

Impurity inclusions and surface defects are a cause of many difficulties to the polymer producer and user. Equipment used for studying these phenomena discussed in Chapter 4 include electron microprobe x-ray emission/spectroscopy, NMR micro-imaging, various forms of surface infrared spectroscopy, e.g., diffusion reflection FTIR, ATR, also photoacoustic spectroscopy and x-ray diffraction - infrared microscopy of individual polymer fibres. Newer techniques such as scanning electron microscopy (SECM), transmission electron microscopy, time of flight secondary ion mass spectrometry (TOFSIMS), laser induced photoelectron ionisation with laser desorption, atomic force microscopy and microthermal analysis are discussed. 

With the electron microprobe. X-ray emission is stimulated on the surface of the sample by a narrow, focused beam of electrons. The resulting X-ray emission is detected and analyzed with either a wavelength or an... 

Electron Microprobe A.na.Iysis, Electron microprobe analysis (ema) is a technique based on x-ray fluorescence from atoms in the near-surface region of a material stimulated by a focused beam of high energy electrons (7—9,30). Essentially, this method is based on electron-induced x-ray emission as opposed to x-ray-induced x-ray emission, which forms the basis of conventional x-ray fluorescence (xrf) spectroscopy (31). The microprobe form of this x-ray fluorescence spectroscopy was first developed by Castaing in 1951 (32), and today is a mature technique. Primary beam electrons with energies of 10—30 keV are used and sample the material to a depth on the order of 1 pm. X-rays from all elements with the exception of H, He, and Li can be detected. 

The x-ray emission electron-microprobe is a sufficiently complex spectrograph system to make naming it a problem. The name used here has been chosen because it emphasizes the three salient characteristics of... 

Fig. 9-14. Schematic diagram of the essential elements of an x-ray emission electron-microprobe. (After Castaing and Guinier, Anal. Chem., 25, 724.)...

For additional information about the x-ray emission electron-microprobe, the reader will do well to consult Birks and Brooks,11 who built a simplified probe that gave satisfactory results. They examined both metallic and nonmetallic materials, the surface of the latter being covered by evaporation with about 50 A of manganese or copper to provide sufficient electrical conductivity. Figure 9-15 illustrates an application... 

The short wavelength of x-rays naturally makes them difficult to focus. Electrons, on the other hand, can rather easily be controlled to give beams a few square microns in cross section, a fact that made possible the x-ray emission electron-microprobe (9.9). Clearly, such a concentrated electron beam striking one side of a suitable thin target can give rise to an x-ray spot on the other, and this spot can be small enough to be regarded as a point source of x-rays. 

The apparatus has also been made into an x-ray emission electron-microprobe (9.9) by replacing the target with a transparent section of a rock or mineral sample. The spot being excited could be located easily by viewing it through the sample with an optical microscope. 

The fine-focus electron optical system of the General Electric X-ray Microscope has been used as the basis for an x-ray emission electron-microprobe.9 10... 

Microprobe, electron-, x-ray emission, 261-265, 292, 294, 295 Microscope, X-ray, General Electric, 294-296... 

X-ray emission electron-microprobe, 261-265, 292, 294, 295 development by Castaing, 261 schematic diagram, 263 simplified, researches of Birks and Brooks with use of, 264, 265 X-ray emission lines, characteristic, chemical influences on, 37-40 effect on analytical-line ratios, 189-191... 

Neutron Activation Analysis X-Ray Fluorescence Particle-Induced X-Ray Emission Particle-Induced Nuclear Reaction Analysis Rutherford Backscattering Spectrometry Spark Source Mass Spectrometry Glow Discharge Mass Spectrometry Electron Microprobe Analysis Laser Microprobe Analysis Secondary Ion Mass Analysis Micro-PIXE... 

There are two principal sources of reliable partitioning data for any trace element glassy volcanic rocks and high temperature experiments. For the reasons outlined above, both sources rely on analytical techniques with high spatial resolution. Typically these are microbeam techniques, such as electron-microprobe (EMPA), laser ablation ICP-MS, ion-microprobe secondary ion mass spectrometry (SIMS) or proton-induced X-ray emission (PIXE). 

Ion beam spectrochemical analysis Auger emission spectroscopy Scanning electron microscopy (SEM) Electron microprobe (EMPA) Particle-induced X-ray emission spectroscopy (PIXE)... 

There are now several different types of machines that are all capable of microanalysis. All have advantages and disadvantages, but the choice of which to use is often governed by expense and availability to a particular institution. Electron probe microanalysis is by far the most popular, but here particle-induced X-ray emission (PIXE), the laser microprobe mass analyzer (LAMMA), electron energy loss spectroscopy (EELS), and secondary ion mass spectrometry (SIMS) are also considered. 

Recently, methods for quantitatively determining the chemical element composition of solid materials by x-ray emission spectroscopy using the electron microprobe have become available. A significant advantage of the electron microprobe, compared with methods for bulk analysis. Is Its capability for rapid analysis of many different mlcron-slze areas of a solid sample. Thus, In a relatively short time, we can obtain several hundred quantitative analyses of the chemical element content of a solid sample. These analyses usually will be different because sample homogeneity Is absent on the micron level. Thus, each chemical analysis Is a linear sum of the chemical elements In the subset of minerals present at that location. Generally, we expect the number of minerals present In a mlcron-slze spot to be less than the total number of minerals In the bulk sample. 

Usually, bulk samples are crushed Co less than 10 mm and split to obtain workable quantities of material. Fractions of these are crushed again so the rock passes a 20 mesh sieve and then is ground to -200 mesh. Portions of this material are taken for XRD and electron microprobe energy dispersive x-ray emission (EDX) analysis. Samples for EDX probe analysis are made into 100-mg pellets at 2000 psl. Before analysis, Che pellets are coated with 100 Co 200 angstroms of carbon. 

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