Advances in the characterization of industrial minerals
The use of minerals by man is as old as the human race. In fact the advancement of human civilization has been intimately associated with the exploitation of raw materials. It is not by chance that the distinction of the main historical eras is based on the type of raw materials used. Hence the passage from the Paleolithic and Neolithic Age to the Bronze Age is characterized by the introduction of basic metals, mainly copper, zinc and tin, to human activities and the Iron Age was marked by the introduction of iron. Since then the use of metals has increased and culminated in the industrial revolution in the mid-eighteenth century which marked the onset of the industrial age in the western world. However, during the past 50 years, although metals were equally important to western economies as they had been previously, the amount of metals extracted annually in western countries has decreased significantly and metal mining activity shifted mainly to third world countries (in Africa, South America, Asia) and Australia, due to economic and environmental constraints. At the same time the role of industrial minerals has become increasingly important for the western economies and today, in developed EU countries, the production of industrial minerals has surpassed by far the production of metals. In some EU countries, metal mining activities have stopped completely. The importance of industrial minerals is expected to increase further in the future.
Electron Microbeam Analysis Techniques used for the Characterization of Industrial Minerals
Published:January 01, 2010
Mark I. Pownceby, Colin M. Macrae, 2010. "Electron Microbeam Analysis Techniques used for the Characterization of Industrial Minerals", Advances in the characterization of industrial minerals, George E. Christidis
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Electron microbeam techniques such as Scanning Electron Microscopy (SEM), Electron Probe Microanalysis (EPMA) and Transmission Electron Microscopy (TEM) are commonly used in the characterization of industrial minerals providing morphological, chemical and structural information down to the atomic scale. The principal advantage of the electron microscope over the light microscope is the much improved resolution, due to the very low wavelength of the energetic electron (<1 Å) compared to the visible light, which is employed in the optical microscope. A key advantage of microbeam instruments is the generation of X-rays from the interaction of electron with the sample thereby allowing both the identification of elements present through observation of the KLM X-ray lines and determination of the elemental composition when matrix affects are taken into consideration.
In this chapter an overview of the two main classes of electron microscopy, scanning and transmission, is presented, including a description of the instrumentation required and a discussion of their similarities and differences. The chapter also includes detailed information regarding the generation, detection and measurement of the various signals within the SEM and EPMA, the two instrument techniques most common to mineralogists. Finally, several case studies highlighting the use of these two electron microbeam techniques in the characterization of industrial minerals are presented. The examples were chosen to both illustrate traditional areas of use and emerging areas of application and include; automated SEM techniques, electron backscattered diffraction, charge contrast and in situ SEM imaging, EPMA mapping techniques, the determination of chemical states in minerals and materials using changes in X-ray peak shape, hyperspectral EPMA, and trace-element speciation using quantitative cathodoluminescence.