Cold mounting

Thermosets with or without fillers are suitable for hot mounting in a mounting press. Thermoplastics are also suitable for this purpose. Thermoplastics do not need to be heated under pressure, but they do need to be subjected to pressure while cooling. Thermosets, which are heated under pressure, can be removed from the press immediately after polymerization has occurred. For a mold diameter of 25 mm, the mounting time lies within the approximate range of 12-15 min. Thermoplastics are not as hard as thermosets. Unlike thermosets, thermoplastics are transparent. 

The temperatures required for hot mounting (150-190°C) do not alter the microstructure of ceramics. However, cracks in the specimen can result from the molding pressure and the rapid temperature drop in cooUng. In such cases, it is best to resort to cold mounting. Fig. 7 shows a chromium oxide coating on steel, in which cracks developed after hot mounting in epoxy resin at a load of 20-30 kN and a diameter of 25 mm, or a pressure of 0.4-0.6 kbar. 

The basic substances used in cold mounting media include epoxy resins and polyester resins (thermosets), as well as acrylates (thermoplastics) that cure exothermically 

Plastic Hard- Rate of Adhesion Resistant Not Thermal 

Thermosets 46 560 Slight to Dilute acids Strong adds 120-150 C 

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The loaded specimens were sectioned at two perpendicular directions as shown in Figure 4. The specimens were then moimted in cold mount, polished with 12 grades of sandpaper and gold-coated to be prepared for SEM photography. 

Hot mounting uses hot-press equipment as shown in Figure 1.18. A specimen is placed in the cylinder of a press and embedded in polymeric powder. The surface to be examined faces the bottom of the cylinder. Then, the specimen and powder are heated at about 150°C under constant pressure for tens of minutes. Heat and pressure enable the powder to bond with the specimen to form a cylinder. Phenolic (bakelite) is the most widely used polymeric powder for hot mounting. Hot mounting is suitable for most metal specimens. However, if the microstructure of the material changes at the mounting temperature, cold mounting should be used. 

Figure 1.19 Cold mounting of specimens (a) place specimens on the bottom of molds supported by clamps and (b) cast resin into the mold. (Reproduced with permission of Struers A/S.)...

After pyrolysis pieces of the resultant char were mounted using Fisher Chemical Co. Quickmount cold-mounting resin, and polished in preparation for scanning electron microscopy. The object was to analyse for sulphur by scanning across selected pyrite sections, and continuing out into the surrounding coal matrix. 

Tables 1 and 2 provide an overview of the properties and possible appUcations of hot and cold mounting media.

Sectioning Diamond wheel low speed Mounting Cold mounting in epoxy ... 

Sectioning Diamond wheel Mounting Cold mounting and vacuum impregnation with epoxy resin ... 

Mounting 1 With cold mounting medium before sectioning, with impregnation of porous ceramic layers ... 

Sectioning Diamond wheel, low speed Mounting In cold mounting medium ... 

Sectioning Step Not applicable Abrasive Grain size Mounting Working surface Cold mounting in epoxy resin Lubricant Load RPM Time and coolant N min ... 

Coating Nickel applied by electroless method, or TiN applied by PVD method Sectioning Diamond wheel Mounting In a cold mounting medium (0.6 mm), low speed ... 

As-cast AlxCoCrFeNi alloys were prepared according to molar ratios of x = 0, 0.25, 0.50, and 1.00 (called C-0, C-0.25, C-0.50, and C-1.00, respectively) in a vacuum arc remelter. Table 1 lists the composition of the alloys. Test specimens were cut in 0.8 cm x 0.8 cm x 0.3 cm and cold-mounted in epoxy with the outside surface from a surface of 0.8 cm x 0.8 cm of specimens. The specimens were subsequently ground and polished with grit 1000 silicon carbide paper, rinsed and dried in preparation for electrochemical tests and weight loss measurements. During determination of the weight loss, six sets of samples were dipped in... 

Cross-sections of the embedded layers were also investigated by SEM. The substrates were cut using a diamond cutting blade about 2-3 mm from the end and mounted into a mixture of cold mounting epoxy resin and an epoxy system (1 1) for metallographic preparation. Cross-sections of the samples were polished with silicon carbide (SiC) grinding papers (180, 500, 1200,2400,4000) and with 1.0 and 0.3 pm of alpha alumina suspension. 

Polarized light microscopy was used to collect photomicrographs from a number of cross-sectioned samples for microstructure evaluation and to determine glass fiber orientations. Some samples were also cold mounted and examined using microscopy. Comparisons were made for filled samples welded to filled samples, unfilled samples welded to unfilled samples, and filled samples welded to unfilled samples for both US-assisted hot plate welding and hot plate welding without US assist. 

Unfilled PP samples were welded to glass-filled PP samples without US assist. Weld strengths were lower than those achieved with the unfilled to unfilled samples and comparable to the glass-filled to glass-filled samples. A representative photo of a cross-sectioned, cold mounted, and polished sample can be seen in Figures 3... 

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