Solid surface rough

The solid surfaces that one finds are manufactured by different methods sawn, cut, turned, polished, or chemically treated. All of these procedures leave the solid surface rough, in varying degrees. In industry, one finds many methods that can create the roughness. 

Oliver, J. F., Huh, C. and Mason, S. G., An experimental study of some effects of solid surface roughness on wetting. Colloids Surf., 1, 79-104 (1980). 

The requirement that oils adhere to gas-liquid surfaces implies that entry coefficients be positive and that some agency be present that can destabilize any metastable pseudoemulsion films. In the case of air-water-oil pseudoanulsion films, the latter is usually represented by hydrophobic particles adhering to the oil-water surfaces as we describe in Section 4.8. In the case of solids, surface roughness appears to facilitate emergence into air-water surfaces [37], asperities perhaps helping to nucleate rupture of any metastable film separating the solid from the relevant gas-liquid surface (see Section 4.7.4). 

In the context of the structural perturbations at fluid-solid interfaces, it is interesting to investigate the viscosity of thin liquid films. Eaily work on thin-film viscosity by Deijaguin and co-workers used a blow off technique to cause a liquid film to thin. This work showed elevated viscosities for some materials [98] and thin film viscosities lower than the bulk for others [99, 100]. Some controversial issues were raised particularly regarding surface roughness and contact angles in the experiments [101-103]. Entirely different types of data on clays caused Low [104] to conclude that the viscosity of interlayer water in clays is greater than that of bulk water. 

Equations la and lb are for a simple two-phase system such as the air-bulk solid interface. Real materials aren t so simple. They have natural oxides and surface roughness, and consist of deposited or grown multilayered structures in many cases. In these cases each layer and interface can be represented by a 2 x 2 matrix (for isotropic materials), and the overall reflection properties can be calculated by matrix multiplication. The resulting algebraic equations are too complex to invert, and a major consequence is that regression analysis must be used to determine the system s physical parameters. ... 

Actual solid surfaces are always rough at some level and are also generally chemically non-uniform (amorphous vs. crystalline portions of a polymer surface. 

Contact angle, 0, and spreading coefficient for a liquid on a solid surface comparison of spreading coefficient S for a smooth surface with S for a surface of roughness factor r... 

As was shown above (Section 2.2, Eq. 5), Young s equation (Eq. 4) may be derived by considering the small displacement from equilibrium of a sessile drop on a plane surface. If the same derivation is applied to the situation where the solid surface has a roughness factor (Eq. 19) of r, it is readily seen that Eq. 5 becomes [28]... 

Fig. 5. Sessile drop on a rough surface true contact angle BTA and apparent contact angle BTH. Thick curve = surface of solid (s) thin curve = surface of liquid (1) v = vapour. T is the triple point HTR a horizontal AT a tangent to the solid surface BT a tangent to the liquid surface.

It is well established that GGA gives a better description of molecular systems, crystal surfaces and surface-molecule interactions. However, there are cases where the GGA results for solids are in much worse agreement with experiment than the LDA ones (e.g., 3-22 jj has been suggested that the effect of using GGA for solids is roughly equivalent to adding uniform tensile stress, and as a result lattice constants are frequently overestimated. 

The dependence of the C,E curves for a solid metal on the method of electrode surface preparation was reported long ago.10 20 67 70 219-225 in addition to the influence of impurities and faradaic processes, variation in the surface roughness was pointed out as a possible reason for the effect.10 67,70 74 219 For the determination of R it was first proposed to compare the values of C of the solid metal (M) with that of Hg, i.e., R = C-M/c-Hg 10,74.219-221 data at ff=0 for the most dilute solution (usually... 

Daikhin, double layer capacitance of solid at rough electrodes, 52 Debye screening and diffuse layer near the surface, 50... 

Fig. 3.16 Schematic diagram of a model for ultrahydrophobic drag reduction. A combination of surface hy-drophobicity and roughness combine to allow water to stand away from the solid surface. Reprinted from Ou et al. (2004) with permission...

The kj and terms were evaluated from Equation 2 and found to be roughly comparable to the values for naphthalene adsorbed on highly activated alumina (11,30). Generally, the smaller the and values, the more strongly the compound interacts with the surface (29,30). In the future, Equation 2 should be a useful means of comparing various surfaces for RTF in solid-surface phosphorescence analytical work. 

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