Electron microprobe energy-dispersive analysis

Multivariate Analysts of Electron Microprobe-Energy Dispersive X-ray Chemical Element Spectra for Quantitative Mineralogical Analysis of Oil Shales... 

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. 

The failure analysis can be done using a judicious combination of several methods such as visual examination, metallography, microscopy, electron microprobe, energy dispersive X-ray analysis, X-ray diffraction methods for determining residual stress in the sample, surface analytical techniques to determine the nature and composition of surface deposits and finite element analysis modeling. 

As indicated in Fig. 7.2, X-rays are among the by-products in an electron microscope. Already at the beginning of this century, people knew that matter emits X-rays when it is bombarded with electrons. The explanation of the phenomenon came with the development of quantum mechanics. Nowadays, it is the basis for determining composition on the submicron scale and, with still increasing spatial resolution, is used in the technique referred to as Electron Microprobe Analysis (EMA), Electron Probe Microanalysis (EPMA) or Energy Dispersive Analysis of X-rays (EDAX, EDX) [21]. 

K. F.J. (1968) Solid-state energy-dispersion spectrometer for electron-microprobe X-ray analysis. 

As illustrated by Fig. 10.4, an electron microscope offers additional possibilities for analyzing the sample. Diffraction patterns (spots from a single-crystal particle and rings from a collection of randomly oriented particles) enable one to identify crystallographic phases as in XRD. Emitted X-rays are characteristic for an element and allow for a determination of the chemical composition of a selected part of the sample (typical dimension 10 nm). This technique is called electron microprobe analysis (EMA, EPMA) or, referring to the usual mode of detection, energy dispersive analysis of X-rays (EDAX or EDX). Also the Auger electrons carry information on sample composition, as do the loss electrons. The latter are potentially informative on the low Z elements, which have a low efficiency for X-ray fluorescence. 

Modes of occurrence of the elements in coal can be determined using a variety of procedures. Perhaps the most effective method is the use of scanning electron microscopy-energy dispersive X-ray analysis (SEM-EDX). This method can detect and analyze minerals as small as 1 pm in diameter (Figure 14). The SEM-EDX also provides useful information on the textural relationships of the minerals. Other microbeam techniques, such as the electron microprobe analyzer, ion microprobe, laser mass analyzer, and transmission electron microscopy, have also been used to determine modes of occurrence of elements in coal. 

Elemental chemical analysis provides information regarding the formulation and coloring oxides of glazes and glasses. Energy-dispersive x-ray fluorescence spectrometry is very convenient. However, using this technique the analysis for elements of low atomic numbers is quite difficult, even when vacuum or helium paths are used. The electron-beam microprobe has proven to be an extremely useful tool for this purpose (106). Emission spectroscopy and activation analysis have also been appHed successfully in these studies (101). 

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). 

This chapter summarizes results obtained during the past 5 years, on the design, preparation and study of titanium and vanadium compounds as candidate precursors to TiC, TiN, VC, and VN. The study of the precursor molecules was conducted through several steps. After their synthesis, thermoanalytical studies (TG-DTA), coupled to simultaneous mass spectroscopic (MS) analysis of the decomposition gases, were carried out to determine their suitability as precursors. CVD experiments were then conducted and were followed by characterization of the deposits by scanning electron microscopy (SEM) energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and electron microprobe analysis with wavelength dispersion spectroscopy (EPMA-WDS). 

Effects of Chemical Purity. Zirconia tubes from five different sources were analyzed at Pennsylvania State University using scanning electron microscopy, plasma emission spectroscopy, energy dispersive X-ray spectroscopy, and electron beam microprobe analysis. The sources for the tubes included several commercially available tubes as well as tubes fabricated by the Pennsylvania State University Ceramics Department. 

Electron microprobe analysis (EMA, EPMA) Energy dispersive X-ray analysis (EDX, EDAX) Field emission microscopy (FEM)... 

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. 

A Tracor Northern quantitative energy-dispersive X-ray analysis system with solid-state detectors was used for the electron microprobe measurements. The method is based on electron microbeam point analyses on a maceral level (18, 19) The emitted characteristic X-ray fluorescence radiation is used to quantify sulfur. Other elements of interest, such as iron and calcium, are monitored simultaneously to ensure that only the organic sulfur component is characterized. The measured... 

The data presented in Table V were obtained by energy-dispersive X-ray analysis using an electron microprobe. The method is based on monitoring the sulfur content of an organic maceral (in this case, vitrinite), which is not associated with any cations, as an index of the organic sulfur... 

The analysis of corrosion scale or product may be done by wet chemical methods such as spectrophotometry or atomic absorption spectrophotometry in cases where the removal of corrosion scale is permitted, or by surface analytical techniques such as X-ray photoelectron spectroscopy, Auger electron spectroscopy, electron microprobe analysis, by energy dispersive X-ray analysis in the case of samples which need to be preserved. 

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