Preparing polished sections for examination

To avoid measurement errors when determining microhardness, sections of ceramic materials must be of high quality and free of relief. The quality of the section can be monitored by the use of an interference microscope or an optical microscope with Die optics. 

Sections of ceramic samples are often subjected to microprobe analyses or SEM examinations with an accessory device for energy-dispersive X-ray analysis. It is essential to avoid the introduction of any elements which are intended to be measured in these examinations or which may have a disruptive influence on them. It is therefore essential to pay special attention to swarf from metal-bonded diamond wheels, composite disks, or disks made of cast iron, lead, copper, or tin, as this swarf may accumulate in pores or in the form of thin surface films. This also applies to swarf from the sample and polish residue, which may remain on the sample after final polishing with alumina, for example. 

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Small polished sections of the reaction products were prepared for reflecting-light microscopy by using Caulk Kadon or Technovit as a mounting medium. Identification of the phases either was undertaken in air or was aided by using oil immersion. In polished sections, depending on the optical properties of the phases examined, identification is often possible when as little as 0.01% of a phase is present. 

For the AIA-SEM analyses, the raw and clean coal samples were prepared by mixing 2 g of the sample with an epoxy resin and casting into molds 1 in. in diameter. The hardened pellets were polished to reveal a cross section and finished by polishing with 0.3-ym alumina powder. Then the pellets were coated with approximately 500 A of carbon to render sample surfaces electrically conductive for examination in the SEM unit. 

If a clinker sample is to be subjected to the extraction, a random sample of 1- to 2-mm crushed clinker particles, taken from the same fraction as previously prepared for polished section examination, is further crushed in a mortar and pestle until all the subsample passes a 75- j,m screen (No. 200 mesh). If acement is to be treated, a random sample of approximately 10 grams is sieved to produce the 45- to 75-pm fraction (325 to 200 mesh) particles left on the 75- j,m screen could be further crushed to pass the screen or, perhaps, studied microscopically to determine belite nest percentage. Sieving, however, is an optional step the main benefit is that it provides a uniformly sized powder promoting a relatively uniform level of focus by removing "boulders" that may interfere with examination and particle manipulation. If sieve confaminafion is a likely problem, one can use disposable nylon with the proper mesh opening. 

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. 

As a result of the whisker agglomerates observed in the 4th and 5th iteration samples, polished sections of selected Iteration 3 samples, which were HIP ed along with 4th and 5th iteration composites in the four HIP runs, were prepared for optical microscopy to examine the degree of whisker dispersion in the composites. Neither whisker agglomerates nor preferred orientations were observed in the... 

Because SEM-AIA is often used to explain behavior under specific processing conditions, samples are prepared in the same size in which they are received. Coal samples with their included mineral matter are prepared for image analysis by mixing samples. of the dry coal with polyethylene powder (as a diluent) and molten carnauba wax in a volume ratio of 1 2 2. Pellets are then cut along the cylindrical axis to expose a vertical cross section of coal and mineral matter and polished using standard petrographic procedures. The surfaces are coated with 150 A of carbon to provide a conductive surface for SEM examination. 

Finally, microscopic examination of samples often requires their preparation as cross sections or thin sections, or by mounting the sample on a glass slide by means of a mounting medium. For preparing thin and cross sections, samples are embedded in a polymer solution. After curing of the polymer, the thin or cross section is obtained by polishing the embedded sample with SiC abrasive disks. Aluminum suspensions or diamond paste are occasionally employed in a final polishing step. 

The metallic layers were examined either by conventional or cross-section TEM in a Jeol 200 Cx microscope. For the cross section preparation a sandwich of two laminates is made, glued face to face with an epoxy, cut in small pieces, mechanically polished, and then ion milled to a final TEM observation thickness. The plane section TEM sample are prepared by dissolving the PET in trifluoroacetic acid for 5 to 10 mn. The area observed, on plane section TEM, for the grain size calculation is close to 0.2 urn. For the adhesion measurements, test pieces consist of aluminum support (1 mm thick) double sided tape (Permacel P-94) PET (12pm) / evaporated aluminum/ ethylene acrylic acid (EAA) copolymer film. These laminates are prepared for the peel test by compression under 1.3 105 N.m2 at 120°C for 10 seconds. The peel test is performed by peeling the EAA copolymer sheet from the laminate in an INSTRON tensile tester at 180° peel angle and 5 cm min peel rate. 

A new technique [204] for studying the progression of densification during the fabrication of composites by CVI has been introduced, which involves the preparation of a carbon-carbon composite and momentarily interrupting the carbon infiltration process (forced flow thermal gradient CVI) at various times to permit the deposition of very thin layers of SiC. Microscopic examination of these layers on a polished cross-section permitted determination... 

The procedure of specimen preparation for microscopic examination is briefly outlined in Section 4.10. After appropriate polishing and etching, the different phases may be distinguished by their appearance. For example, for a two-phase alloy, one phase may appear light and the other phase dark. When only a single phase or solid solution is present, the texture is uniform, except for grain boundaries that may be revealed (Figure 4.15h). 

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