Specimen surfaces, smoothness

Both the indenter and the specimen surfaces should be smooth and homogeneous in order to minimize friction. If the indenter is not smooth, under pressure that is sufficient to cause plastic flow. The specimen will become embossed by the indenter, tending to lock the surfaces. This will induce a large effective friction coefficient. 

Calorimetry requires large areas of interface, which virtually demands powdered solids. We have not considered (yet) the problem of measuring 0 and dd/dT for powders. Solids that are available as large specimens with smooth surfaces (suitable,... 

Because only relatively small variations in cy occur in typical specimens undergoing sintering and diffusional creep (Chapter 16), we prefer to carry out the analyses of surface smoothing, sintering, and diffusional creep in terms of atom diffusion and the diffusion potential using Eq. 3.72. In this approach, the boundary conditions on a can be expressed quite simply.15... 

A combination modification of BuO + MMA (Figure 7, upper) after 1,800 hrs exposure (light/water) results in some longitudinal checks on the specimen surface but overall integrity. A good portion of the exposed surface is still reasonably smooth with very little loss of surface wood elements. 

This now raises the issue of what is the correct value of the / c ratio for any given material. The CIE Technical Committee TC 1-28 published recommendations on how to handle various parameters that can affect the judgments of color differences as CIE Publication 101 [54]. In that study, the parameter that stood out was the effect of surface texture on the judgments of lightness differences. Small differences in lightness can be assessed for specimens with smooth glossy surfaces but not in samples with textured, patterned, or rough surfaces. Thus studies in the literature... 

Before bending tests, all specimens were ground to make the surfaces smooth and to have the same thickness. All specimens were dried at 105 degree Cels, for 48 hours. Water absorption ratio was measured by the difference of weight before and after drying only in the case water curing. 

All the surfaces of extruded specimens were smooth and had no cracks. It indicates all the composites were extrudable. 

Ideally, the specimen surface should be clean and smooth. Dirt and scale, if present, must be removed, but any removal of material must be done by a process... 

For polymers, we can differentiate different sample preparation procedures that aim at providing smooth films or surfaces or at exposing the interior of bulk samples at a specimen surface. 

Experimental results showed that SiC-AIN-Y203 could be fully densified in wide temperature range (1850"C-2000 C), and kept low weight loss around 2% in this range. The surface of specimens remains smooth, indicating that sintering could be done without powder bed. 

As seen in Figure 9.9, the irradiation causes deep as well as shallow pits on the film surface. The implanted ions restrict the uniformity of the columnar growth in both the H+ and LP implanted samples. Due to the uneven growth in 2D direction, deep and shallow pits are developed. On the other hand, the surface smoothness is spoiled due to the defect clusters. However, cavity formation is not observed in either of the implanted specimens. Network dislocations are also not observed. Complete amorphization is also not observed as it is expected. 

Initial specimen light yellow solid, smooth surface, uniformly distributed pores, not crisp. Compressed specimen Surface appeared crim-ple. The compressed specimen is shown as Figure 2. 

The specimen should have parallel and fairly smooth surfaces, so that the friction between the metal plates and the specimen is eliminated. The latter is ensured by coating the specimen surfaces with graphite grease. The deformation in the specimen is measured at regular intervals, typically after 5,10, 20, 40, 80,120, 300, 600, 2400 and 3600 s. 

The shape of the average specimen is such that only rarely can it be directly placed into the diffractometer for analysis, so that special care has to be taken to achieve the random distribution of the crystallites to have meaningful peak intensities. The problems arising in sample preparation are (1) Particle size. The powdered sample must consist of particles smaller than 5 pm. Collection and separation of particles of these dimensions can be effected by sieving, sedimentation, or elutriation. (2) Surface flatness. Special precautions are needed to make the surface smooth and flat, with its plane including the diffractometer axis. If required, common binders, for instance, collodion, paraffin wax, or silicone grease, are applicable. (3) Preferred orientation. When it is necessary to ensure that the particles do not show preferred orientation, mix crushed glass or other amorphous medium with the powder or coat the plane surface of the sample carrier with a film of adhesive that dries at a moderate rate and then dust a layer of powder on the adhesive, polyfvinyl chloride), after it has become tacky. 

The free surfaces of samples are studied using SEM and AFM. The smooth specimen surfaces which are required for this purpose are prepared either by ultramicrotomy or by solution-casting procedures (e.g., spin-coating). The free surface can also be etched by reactive ions via a process known as reactive ion etching (RIE) [49-51], or by using chemicals as in the case of permanganic etching [52-55]. 

Figure 12.13 presents the SEM images of the specimen before and after different composting times. It can be seen that the control specimen surface is smooth except... 

Figure 12.24a-d shows SEM surface images of green composites composted for 0, 5, 10, and 20 days, respectively. It can be seen in Figure 12.24a that the control (0 days) specimen surface is smooth. However, after composting resin erosion can be observed as the fibers get exposed. As a result, the specimen surface becomes... 

A common apparatus used in the paint industry to measure scratch resistance on smooth surfaces and coatings is the Wolff-Wilbom PencU Hardness Test. Using constant pressure and pencils of varying hardness (usually 6B to 6H), the pencil is held at a fixed angle of 45° to the specimen surface and pushed about 6.5 mm away from the operator under a fixed pressure of 7.5N. This test is repeated using softer lead until one is found that will not cut through the coating or indent the surface. 

The major artifacts contributing to uncertainties in PDCE results stem from effects caused by bombardment of nonideal specimens, particularly thick specimens. The ideal thick specimen would be a homogeneous, smooth electrical conductor that does not change during bombardment. Except for rather simple, well-defined layered structures (e.g., surface oxide layers), specimens having compositional variations with depth yield spectra whose analyses can have large inaccuracies. 

Neutron reflectivity measures the variation in concentration normal to the surface of the specimen. This concentration at any depth is averaged over the coherence length of the neutrons (on the order of 1 pm) parallel to the sur ce. Consequendy, no information can be obtained on concentration variadons parallel to the sample surface when measuring reflectivity under specular conditions. More imponantly, however, this mandates that the specimens be as smooth as possible to avoid smearing the concentration profiles. 

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