Surface rough

The roughness of solid surfaces affects wetting owing to two different effects the first is the fact that the actual surface area is increased and the second is pinning of the triple line by sharp edges. 

Apart from scattering, which increases the DR spectral contrast of a film, and the intensity enhancement, a rough surface can give a specific contribution to the IR spectra of an ultrathin film deposited on this surface. As pointed out in Section 3.2.1, under ordinary experimental conditions, a surface polariton on a fiat surface is nonradiative. However, when the surface of an active medium is grated with a spacing a, the x-component of the incident-photon wave vector (Fig. 1.9) becomes [418] 

DETERMINATION OF OPTICAL CONSTANTS OF ISOTROPIC ULTRATHIN FILMS EXPERIMENTAL ERRORS IN REFLECTIVITY MEASUREMENTS 

In this section, only the optical constants of isotropic films determined by the multiwavelength approach in IRRAS will be discussed. The optical constants are assumed to be independent of the film thickness, and any gradient in the optical properties of the substrate (Section 3.5) is ignored. This undoubtedly lowers accuracy of the results. Anisotropic optical constants of a film are more closely related to real-world ultrathin films. At this point, it is worth noting that approaches to measuring isotropic and anisotropic optical constants are conceptually identical An anisotropic material shows a completely identical metallic IRRAS spectrum to the isotropic one if the complex refractive index along the z-direction for the anisotropic material is equal to that for the isotropic one [44]. However, to 

The results of this approach to extracting ri2 v) and fe(v) from the experimental spectra of MgO layers on the surface of Al mirrors are discussed below. 

These layers were deposited by magnetron sputtering on A1 substrates maintained at temperatures of 25° and 250°C. The spectrum obtained by IRRAS for the film deposited at 25°C (Fig. 3.68a) shows an intense vlo absorption band at 725 cm . In the spectrum of the film deposited at 250°C, the maximum of this band is shifted to higher frequencies, and its FWHM is smaller than that in the spectrum of the film obtained at 25°C. The resulting spectral dependences of n2(v) and k2 v) for the MgO layers are presented in Fig. 3.68Z . The optical constants of the layer sputtered on the 250°C substrate are close to those of a MgO crystal. The lower frequency and larger bandwidth of the / 2(v) band suggest an amorphous phase in the layer. 

An important issue is the amplitude of a hydrophobic slip. The observed slip length reached the range 20-100 nm, which is above predictions of the models of a molecular slip. This suggests the apparent slip, such as the gas cushion model, Eq. 2.2. Water glides on air, owing to the large viscosity ratio between water and air (typically a factor of 50). Experimental values of b suggest that the thickness of this layer is below 2 nm. Another scenario of the apparent slip, such as a nanobubble-coated surface, has to be explored in more details. 

An important conclusion is that it is impossible to benefit of such a nanometric slip at separations 0( o.m) and larger, that is, in microfluidic applications. This is why in the discussion of superhydrophobic slippage below we often ignore a slip past hydrophobic solids. However, a hydrophobic slippage is likely of major importance in nanochannels (highly confined hydrophobic pores, biochannels, etc.), where ordinary Poiseuille flow is fully suppressed. 

This issue was recently resolved in the lattice Boltzmann (LB) simulation study,where the hydrod3mamic interaction between a smooth sphere of radius R and a randomly rough plane was studied (as shown in Fig. 2.9). Besides its signiBcance as a geometry of SFA/AFM dynamic force experiments, this allowed one to explore both far- and near-field flows in a single experiment. The measured hydrod5mamic force was smaller than predicted for two smooth surfaces (with the separation deBned at the top 

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The inspection possibility of welds and rough surfaces also under the coating of various foulings, oils, scale, rust etc. without the preliminary preparation. 

No false operations on rough surface of complex shape. 

Figure 6 Fig 4. part inspection with the new desien ofnhotothermal camera only the crack indications can be seen in spite of the rough surface condition (no more false alarms). 

Non Invasive Optical and Digital Metrology of Rough Surfaces. 

When a laser beam eross a rough surface, the scattered light presents an granular aspect, which is call speckle. 

P. Beckmaim and A. Spizziehino, The Scattering of Electromagnetic Waves from Rough Surfaces , Pergamon, London (1963). 

Many of the adsorbents used have rough surfaces they may consist of clusters of very small particles, for example. It appears that the concept of self-similarity or fractal geometry (see Section VII-4C) may be applicable [210,211]. In the case of quenching of emission by a coadsorbed species, Q, some fraction of Q may be hidden from the emitter if Q is a small molecule that can fit into surface regions not accessible to the emitter [211]. 

P. Meakin, Multiple Scattering of Waves in Random Media and Random Rough Surfaces, The Pennsylvania State University Press, State College, PA, 1985. 

The preceding material has been couched in terms of site energy distributions—the implication being that an adsorbent may have chemically different kinds of sites. This is not necessarily the case—if micropores are present (see Section XVII-16) adsorption in such may show an increased Q because the adsorbate experiences interaction with surrounding walls of adsorbent. To a lesser extent this can also be true for a nonporous but very rough surface. 

The currently useful model for dealing with rough surfaces is that of the selfsimilar or fractal surface (see Sections VII-4C and XVI-2B). This approach has been very useful in dealing with the variation of apparent surface area with the size of adsorbate molecules used and with adsorbent particle size. All adsorbate molecules have access to a plane surface, that is, one of fractal dimension 2. For surfaces of Z> > 2, however, there will be regions accessible to small molecules... 

Greenwood J A 1967 On the area of contact between rough surfaces and flats J. Lub. Tech. (ASME) 1 81... 

Detennining the contact area between two rough surfaces is much more difficult than the sphere-on-flat problem and depends upon the moriDhology of the surfaces [9]. One can show, for instance, that for certain distributions of asperity heights the contact can be completely elastic. However, for realistic moriDhologies and macroscopic nonnal forces, the contact region includes areas of both plastic and elastic contact with plastic contact dominating. 

Greenwood J A 1992 Contact of rough surfaces Fundamentals of Friotion Maorosoopio and Miorosoopio Processes (NATO ASI Series E220) eds I L Singer and FI M Pollock (Dordrecht Kluwer) pp 37-56... 

Diazomethane is easily decomposed by rough surfaces for this reason glass apparatus with scratches and also porous pot ( boiling stones ) should not be used. 

Smoothing of Rough Surfaces. The simplest and a very common appHcation of ECM is deburring. An example is given in Eigure 2a, where a plane cathode tool is placed opposite a workpiece. The current densities at the peaks of the surface irregularities ate higher than those elsewhere. The former are therefore removed preferentially, and the workpiece becomes smoothed (8). 

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