Preparation of thin sections

The supplies needed for creating thin sections (such as lapping disks, sample holders, lapping abrasives, coolants, adhesives, and cloths) can be obtained from the producers of metallographic and petrographic equipment. The standard thin section has a thickness of 20-35 pm. The process of creating a thin section involves seven or eight steps (see Fig. 140). 

Impregnation. Porous samples and delicate materials should be impregnated. This is performed with the same media which will be used to cement the sample to the slide in a later step. The impregnating medium, consisting of epoxy resin or Canada balsam, should have a suitable index of refraction (close to 1.535), allowing the phases to be distinguished from one another by optical methods. In many cases, it is sufficient to simply lay the sample in the mounting medium and then allow capillary forces to 

Sectioning, i.e. separating the sample from the larger piece of material 

Impregnation of porous and brittle samples, when necessary 

Thinning the sample by cutting it after it has been cemented to the slide 

Ultramicrotomy (including cryo-ultramicrotomy) is a standard method for the preparation of ultrathin or semithin sections, as well as very flat surfaces for various microscopic investigations. Improvements in preparation techniques over the last few decades have demonstrated that thin sections of different materials that are free from artifacts can be successfully prepared for EM investigations. Therefore, successful sectioning now depends primarily on the experience of the experimentalist rather than on the instrumentation used [14]. 

Variations of thickness along a single section are connected to properties of the materiai or sectioning procedure. Knife-edge defects produce scratches and can break sections into pieces, as is visible in Fig. 1.42. In electron micrographs, small scratches disturb a good visibility of the structures, as seen in an ultrathin section of HDPE with banded spherulites in Fig. 1.43(a). 

Using crystalline dark-field imaging (only diffracted electrons are allowed to contribute to image formation), visibility of cutting artifacts is suppressed because mass thickness effects do not contribute to the image contrast see Fig. 1.43(b). 

In polymers with hard particles, as in polymer composites, defect knife edges not only initiate scratches in the sections, but also produce larger defects. Hard particles can be scratched and moved together with the knife edge along the section along the surface such defects are seen in Fig. 6.20 in Part II. 

Success in cutting quality with such an oscillating knife is illustrated in Fig. 1.45. A rubber-modified polymer (high-impact polystyrene, HIPS) with so-called salami 

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Conventional bright-field TEM observations of polyolefins often require contrast enhancement, usually by staining with Ru04 or other suitable markers [17]. These accumulate in the amorphous phase, at lamellar surfaces and in cavities, and differential staining can reveal the phase distribution in blends. Staining also hardens the specimens, facilitating preparation of thin sections at room temperature (cryo-sectioning is required for unfixed polyolefins). 

Petrographic Work. Petrographic studies required preparation of thin sections. Briefly, rectangular blocks of material were treated with ethanol to remove water and then infiltered with hard grade LR White resin, a low viscosity resin developed for biological work. Following this, the block was mounted on a petrographic slide and a polished thin section produced (see Bailey and Blackson (26) and Blackson and Bailey (27)). A total of 57 sections were produced in this way, at least 1 from each thinner lithofacies unit and 2 from thicker lithofacies units. 

Equipment needed for microscopy in a cement plant may range from only a polarized-light microscope required for powder mount analysis to sawing, grinding, and polishing equipment necessary for thin-sec-tion and polished-section study. Two somewhat idealized lists of equipment are given in Table 11-1. The "Economy" column in the table contains only the minimum equipment for powder-mount study and polished-section examination. The other column also contains items for preparation of thin sections. 

Brown, L.S., (1) "The Preparation of Thin Sections of Portland Cement for Microscopic Study," 5 pp. (2) "Optical Anomalies in the Microscopic Observation of Portland Cement Clinker," 13 pp. (3) "The Minor Constituents of Portland Cement Clinker, A Preliminary Report," 13 pp. Unpublished reports. Lone Star Cement Corporation, Portland Cement Association Library, Skokie, Illinois, 1936. 

Humphries DW (1992) The Preparation of Thin Sections of Rocks, Minerals, and Ceramics. Oxford Oxford University Press and Royal Microscopical Society. 

The whole procedure from the sample preparation of thin sections of biological tissue by cryo-cutting via the imaging procedure in LA-ICP-MS, including the scanning (line by line) of tissue in the selected brain area of mouse brain by a focused laser beam to measure ion intensities for analyte ions as a function of time and for a final evaluation of data in order to produce... 

Preparation of Thin Sections for Optical Microscopy Assessment... 

The preparation of thin sections by ultramicrotomy, generally after special fixation and staining procedures has been performed. Investigations are carried out by conventional TEM, HEM, or AFM. 

Measurement techniques for MFA are divided into microscopy and X-ray diffraction. Microscopy methods can include polarization microscopy, confocal reflectance microscopy, fluorescence microscopy, as well as electron microscopy in combination with preparation of thin sections and dyeing [Donaldson, 1991 Donaldson et al., 2004 Martz, 1955]. For instance, the technique of polarization microscopy involves rotating the plane of fibers until the bright cell wall becomes dark, the so-called maximum extinction... 

Preparation of Thin Sections of Drosophila for Examination by Transmission Electron Microscopy... 

Optical methods for the study of fine-grained soil minerals were developed early, and many of these early techniques are still in use today. Advancements in the preparation of thin sections have occurred in recent years, and in addition to mineral identification, fabric analyses can now be done more effectively (Brewer [1964], Cady [1965], Jongerius and Heintzberger [1963]). Numerous microscopical studies of the mica component of soils and rocks, concerning the different aspects of soil mineralogy, have been described in the literature (Brewer and... 

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