Polishing specimen surfaces

Standard metallographic methods [7, 82] are used for grinding and polishing. Large samples are precut with a saw to fit into 1 to 2 inch diam- 

Fiber orientation was studied for different thermoplastic polymers reinforced by short glass fibers, using a special specimen preparation treatment for reflected light microscopy 

In a follow up paper, Mlekusch [92] makes quantitative measurements by image analysis to determine the fiber orientations. In an edited book on the microstructural characterization of fiber reinforced composites [93], polishing was used to determine yam shape and for quantitative image analysis of the composite microstructure using methods found in the earlier editions of this text and by Hemsley [94]. 

Thin sections (about 2-40 )um thick) provide ideal specimens for study using optical nucroscopy. However, some materials are too tough, brittle, or hard to be sectioned by microtomy. In geology thin sections of rocks are commonly made by polishing techniques and this method also works well for polymers that cannot be microtomed because they are too hard at room temperature. 

Applications of the polished thin sectioning method [48] include extrudate cross sections. 

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No elaborate precautions were taken to prevent or control the extent of metal oxidation in the air at room temperature, but much care was taken to assure that a drop of grease-free distilled water would spread spontaneously on each polished specimen surface. Thus, each metal was free of even as little as one hundredth of a monolayer of adsorbed organic contamination when placed in the observation chamber. Since it was impossible to measure the thickness of oxide formed on the metal surface, an oxide of known thickness and structure, a single spinel crystal of pure Fe O, was studied in the same manner as the pure metals. The results were very much like those of the pure iron specimen Yc 0.6% EH was 45 dyn/cm, and at 95%... 

Coal reflectance (ASTM D-2798) is very useful because it indicates several important properties of coal, including determination of the maceral composition of coal, which, in turn, is helpful for the prediction of behavior in processing (Davis, 1978 Davis et al., 1991). Coal reflectance is determined by the relative degree to which a beam of polarized light is reflected from a polished coal surface that has been prepared according to a standard procedure (ASTM D-2797). Samples prepared by this practice are used for microscopical determination of the reflectance of the organic components in a polished specimen of coal (ASTM D-2798) as well as the volume percent of physical components of coal (ASTM D-2799). 

In addition, matrix cracks that severed ligaments between cloths were seen at A T > 600°C in the interior of thermally shocked specimens. The mechanism of formation of these cracks is not clear as thermal shock loading induces mainly high stresses at or near the surface. However, Kastritseas et al. (2004a) observed such cracks on polished parallel surfaces of similar SiC/SiC CMCs as well. Webb et al. (1996) reported that further increases in AT increased the severity of all types of thermal shock damage. 

The Ni-Bi couples were annealed in sealed glass ampoules, filled with high-purity helium (0.25 atm), at 150, 200 and 250°C for 1 to 300 h. Each couple was annealed successively a few times. After each anneal, the specimen surface was examined in the as-received conditions and after mechanical and/or electrolytic polishing. 

The compound layer formed in the transition zone between nickel and bismuth was investigated metallographically, by X-rays and electron probe microanalysis (EPMA). X-ray patterns were taken both from the cross-sections in the planes parallel to the initial Ni-Bi interface (after successive removal of the specimen material and polishing its surface) and the powdered phases using Cu Ka radiation. Two methods of obtaining X-ray patterns were employed. Firstly, X-ray photographs were obtained in a 57.3 mm inner diameter Debye-Scherrer camera. Secondly, use was made of a DRON-3 diffractometer to record X-ray diffractograms. 

The bimetallic steel-aluminium specimens in which the intermetallic layers were thick enough (30 to 40 pm) could easily be fractured along the interface between Layers I and II. After slight mechanical polishing, the surfaces of both parts of the specimen proved to be suitable for X-ray examination, and the first two X-ray patterns were obtained. The cross-sections were then again ground, if necessary, and polished to remove additional portions of the material from their surfaces, and new X-ray patterns were taken. 

Figure 1.23 Sample of specimen surfaces after grinding and polishing with abrasives of different grits and size. (Reproduced with permission of ASM International . Ah Rights Reserved. www.asminternational.org. G.F. Vander Voort, Metallography Principles and Practice, McGraw-Hill, New York. 1984 ASM International .)...

Figure 1.25 Comet tailing generated by polishing on specimen surface (a) bright-held image and (b) Nomarski contrast image. (Reproduced with permission of Struers A/S.)...

We may also use the method of tint etching to produce color contrast in microstructure. Tint etchants, usually acidic, are able to deposit a thin (40-500 nm) film such as an oxide or sulfide on specimen surfaces. Tint etching require a very high-quality polished surface for best results. Tint etching can also be done by heat tinting, a process by which a specimen is heated to a relatively low temperature in air. As it warms, the polished surface is oxidized. The oxidation rate varies with the phase and chemical composition of the specimen. Thus, differences in the thickness of oxidation films on surfaces generate variations in color. Interference colors are obtained once the film reaches a certain thickness. Effectiveness of heat tinting depends on the material of specimens it is effective for alloy steels and other non-ferrous metals and carbides, but not for carbon or low alloy steels. 

After cutting a specimen of AlN/W FGM in the direction of the gradient, we polished the surface to a mirror finish and observed the microstructure by Scanning Electron Microscope. Photo 1 shows the results of backscattered electron image of the microstructure. The black distributed areas are metallic tungsten particles. The dispersed particles are also distributed inside the aluminum nitride crystal grain and grain boundary. 

Specimen surface was polished electrochemically by mixed solution of sulfuric acid and ethyl alcohol (1 3). After polishing, the surface of the specimen was adhered by a film of nitric acid cellulose using acetic acid methyl solution. Specimens were then sealed in the polyethylene sheet and irradiated for 43.2 Ks (12 h) by the atomic reactor in Rikkyo University (thermal neutron = 1.1 x 1010 n/cm2 s) or JRR-4 in JAERI (1.5 x 109 n/cm2 s). After cooling down for 0.61 Ms (7days), the film of nitric acid cellulose was striped off from specimen. Boron distribution in the specimen corresponds to particle-tracks produced on the film of nitric acid cellulose by the interaction between thermal neutron and boron (10B (n,a) 7Li). Using 2.5N-NaOH solution at 303 K, particle-tracks by a-rays produced by thermal neutron with boron were etched for 2.7 ks. Then etched films were washed for 10.8 ks in flowing water. We observed microstructure by optical microscopy and SEM. 

The specimen surface is often prepared before measurement to ensure a reproducible and known surface condition. Metallurgical surface preparation techniques are commonly used, these include wet grinding on silicon carbide abrasive papers, polishing with diamond or alumina media, electropolishing, chemical polishing, pickling or etching. 

Immersion of epoxy-encapsulated materials in polished sections in an anhydrous lightweight oil (preferably odorless) in a wide-mouth glass jar with a screwtop lid effectively minimizes, but does not eliminate, hydration. If the specimen is re-examined microscopically, the oil appearing on the polished surface can be removed with a sonic cleaner containing iso propyl alcohol, followed by a forceful isopropyl alco hoi spray. Dorn and Adams (1983) used Freon in a sonic cleaner to remove residual oil on polished section surfaces. In the writer s experience, oil droplets on a polished section can be removed with a brief application of acetone, followed by an alcohol spray wash, and blow drying. 

The microstructuie of polished specimens (finished with I um diamond paste) was observed by FSEM (GENESIS, INC. USA.) and (.TSE-6460, JEOL INC.) in BSE mode coupled with EDX (EDAX INC. USA.), and the fractured surface was observed in the secondary electron (SE) mode. Only metallic... 

The Vickers hardness of polished CS-SPSed P-SiAlON compacts was measured using a Vickers microhardness tester with a diamond indenter of regular pyramid with an opposite angle of 136°. The experiments were performed under the loads between 0.981 N (0.1kg) and 19.614N (2.0kg) at room temperature. The dwell time for each load was 20 s. An average of at least five readings at different locations of the specimen surfaces was taken for each specimen. The Vickers hardness GPa) was calculated according to Equation 4.4... 

Thicker, opaque specimens are studied by the light that they reflect, either in a specular manner, as from a mirroq or diffusely. Metal specimens, for example, may be polished to a mirror finish and the features of interest differentiated by means of etching. The specimen surface must be arranged to be perpendicular to... 

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