Macroscopic topography, surface

The presence of an oriented oxide and the type of orientation are determined to a marked extent by the nature of the metal surface. Two factors in particular, the presence or absence of contaminating materials and the topography of the metal surface, have a very strong influence on the oxide formation. The presence of a contaminant in many cases leads to the formation of a randomly oriented polycrystalline oxide rather than an oriented one. A faceted or terraced surface can lead to the formation of orientations which are different from those found on a macroscopically smooth surface. It is obviously important to have well prepared and characterized surfaces if epitaxial studies are to have any real meaning. Despite this, there has been a notable lack of attention to this point and some authors have made no indication at all of the nature of the metal surface. 

Figure 16.6 Macroscopic surface topography and domain pattern taken from an epitaxial PZT...

More recently, ordered ultradense arrays in block copolymer films have been obtained over macroscopic distances using faceted surfaces of commercially available single-crystal sapphire substrates [152]. The self-assembly overrides substrate defects and uses the topography only as a guide to the orientation of the arrays. 

TEM observations were performed in the as-received and deformed samples in order to reveal the effects of microstructure on the fatigue response of the studied alloy. Fracture surfaces of the deformed fatigue test specimens were comprehensively examined in a scanning electron microscope (JEOL JSM6500F) equipped with field emission gun to determine the macroscopic fracture mode and characterize the fine-scale topography and microscopic mechanisms governing fatigue fracture. 

Macroscopic Appearance of Fracture Surfaces. The most striking observations (Table III) of fracture surface topography are the occurrences of stress-whitening and extensive plastic deformation at the higher water contents, and the occurrence of arrest lines at high values of AK. 

It is apparent that macroscopic as well as microscopic topography may affect osteoblast differentiation and mineralization. In a recent study by Groessner-Schrieber and Tuan [1992], osteoblast growth, differentiation, and synthesis of matrix and mineralized nodules were observed on rough, textured, or porous coated titanium surfaces. It may be possible therefore, not only to optimize the interactions of host tissues with implant surfaces during the Phase I tissue responses but also to influence the overall bone responses to biomechanical forces during the remodeling phase (Phase II) of tissue responses. 

In terms of the XPS investigation, the intensity ratio Ti(2pKoxide)/Ti(2pXmetal) (a sensitive measure of oxide film thickness) and the ratio C(ls)/Ti(2p) (a sensitive function of the self-assembly coverage) depend on the distribution of local slopes of the surface relative to the mean (macroscopic) surface plane (Figure 13). The SLA surface topography profiles are too complex to be used directly within the XPS model. Therefore, the assumption was made that a mean slope may be a reasonable first approximation to be introduced as a parameter in both intensity ratios mentioned above. 

The starting point of molecular simulation methods is - as in the density functional theory - the well-defined microscopic description of the system studied. This macroscopic (molecular) specification includes (1) the equations of statistical thermodynamics describing the fluid/fluid and solid/fluid interactions, and (2) the molecular model of solid adsorbent. This model should take into account all possible and reliable information on the solids, most of which can be developed from various modern surface science techniques [417]. For instance, some important data on the bulk crystalline structures are given by the X-ray diffraction or neutron diffraction, but the scanning tunelling microscopy is a valuable source of information on the topography of a surface solid. For solving... 

Wenzel [15] considered the true area of a rough surface A (which takes into account all the surface topography, peaks and valleys) and the projected area A (the macroscopic or apparent area). A roughness factor r can be defined as... 

The use of DIC in the study of polymers is particularly well suited to situations such as etched surfaces (see sections 10.3.2.2 and 10.4.2.3), which are macroscopically flat but which nevertheless contain fine topographic details [45]. However, the direct examination of polymer surfaces in reflection is not always entirely straightforward because of the low reflectivity exhibited by many systems. It is therefore often desirable to evaporate or sputter a reflective metallic coating on to the specimen surface prior to examination. While this improves the reflectivity of the sample it also has another less obvious benefit. In low-absorbance systems, the illumination may be reflected back into the objective lens not only from the surface of the specimen, but also from other boundaries within the sample. Particularly at low magnifications, where the depth of field may be considerable in comparison with the size of the surface features, such subsurface effects may give a false impression of the sample topography. 

Figure 4. The three main substrate classes (a) smooth surfaces on which surface molecules have a definite orientational distribution (represented surface obtained on a rubbed polyimide film [52]) (b) interpenetrable surfaces of dangling chains (c) topographies (represented grooved surface) with a favorable (left) and unfavorable director field R. In all cases, a is the macroscopic anchoring direction.

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