Petrographic microscopy

Characterization. Ceramic bodies are characterized by density, mass, and physical dimensions. Other common techniques employed in characterizing include x-ray diffraction (XRD) and electron or petrographic microscopy to determine crystal species, stmcture, and size (100). Microscopy (qv) can be used to determine chemical constitution, crystal morphology, and pore size and morphology as well. Mercury porosknetry and gas adsorption are used to characterize pore size, pore size distribution, and surface area (100). A variety of techniques can be employed to characterize bulk chemical composition and the physical characteristics of a powder (100,101). 

Studies of the inorganics in cotton dust have incorporated the use of a wide variety of techniques. These include X-ray fluorescence spectroscopy, atomic absorption spectroscopy, electron microscopy, energy dispersive analysis of X-rays, X-ray diffraction, atomic absorption spectroscopy, neutron activation analysis and petrographic microscopy. It is necessary to use a wide array of techniques since no single technique will permit the measurement of all trace elements. Steindard chemical techniques to determine the ash content of samples and of various extracts have also been used. In most of these studies the ash fraction has been considered to be a reasonably accurate measure of the inorganic content. 

Hersh and coworkers (16) examined electrostatic precipitator samples using petrographic microscopy. The minerals along with their chemical formula eind mode of occurrence are given in Table VIII. Kaolinite and limonite were by far the most abundant minerals detected. 

Crystallization of the homogeneous glasses was performed in a vertical tube furnace with a controlled atmosphere (002/ 2 with a total flow rate of 200 ml per min.). This is tne same atmosphere used in the ash fusion test ( ). The quenched sample was analyzed by petrographic microscopy, powder X-ray diffraction and chemical analysis (to determine the ferrous/total iron ratio) using the method of Hey (2). 

In the held, beachrock sections were located and sampled. Subsequentiy the rocks were thin-sectioned. Traditional petrographic microscopy studies of the samples included the texture of the rock, composition of particles, and cement, and pore types. 

Resistivity measurement showed large increases after treatment, to over 200 kfl cm in the field and 5 kO cm on untreated lab specimens to 30 kO cm after treatment on specimens vacuum saturated with distilled water. Petrographic microscopy showed the treatment to block pores, especially close to the steel reducing transport of water, oxygen and chloride ions. This is possibly due to redistribution of calcium hydroxide. There was also an improvement in freeze/thaw resistance (Buenfeld and Broomfield, 1994). 

Figure 2.2. Grog temper of a ceramic in Northern France - petrographic microscopy on thin section ( C2RMF - photo A. Leclaire)...

A variety of instmmental techniques may be used to determine mineral content. Typically the coal sample is prepared by low temperature ashing to remove the organic material. Then one or more of the techniques of x-ray diffraction, infrared spectroscopy, differential thermal analysis, electron microscopy, and petrographic analysis may be employed (7). 

England, B.M. Mikka, R.A. Bagnall, B.J. Petrographic Characterization of Coal Using Automatic Image Analysis, J. Microscopy. 1979, 116, 329-336. 

This investigation relied on petrographic analysis of polished sections using reflected light and the scanning electron microscopy (SEM) and electron microprobe (EPMA) analyses to identify minerals and to document the distribution of gold. The mineralized zone is coincident with a distinct bleached alteration zone that contains fine- to coarse-grained, subhedral arsenopyrite and pyrite in quartz-carbonate veins. 

X-ray diffractograms (Fig. 4) and petrographic analyses (scanning electron microscopy also used for estimating the surface roughness and micro-heterogeneity of samples) indicate the presence of diverse silicates and oxides on the surface and in the bulk of the vitrocrystalline samples. In addition to the nearly ubiquitous quartz, other minerals were found in several samples gehlenite, albite, diopside, portlandite, pyroxenes... 

Petrographic data consist of light photomicrographs, electron micrographs, x-ray microanalyses, and observations on size and distribution of pyrite crystals. Light microscopy was carried out on all 57 sections, while electron microscopy and x-ray microanalysis were carried out on two sections, one from the Avery site (depth 210 cm) and one from the Barataria site (depth 106 cm). Micrographs and x-ray microanalysis of iron sulfides are shown in Figures 9 and 10, respectively. 

Petrographically, Spannagel flowstone and stalagmites are composed of coarsely crystalline, columnar calcite indicating slow precipitation rates (e.g., Frisia et al., 2000). Lamination is rare in these samples, although faint laminae of possible annual origin were identified in thin section by epifluorescence microscopy. Postdepositional alteration is confined to macroscopic dissolution features, while there is little evidence of in-situ recrystallization in our samples. 

Standard petrographical and mineralogical techniques, including optical and cathodoluminescence (CL) microscopy. X-ray diffraction (XRD) and electron microprobe analysis (EPMA), were used to characterize detrital and diagenetic minerals and textural relationships. Thin sections were half stained with K-Fe cyanide for rapid identification... 

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