Surfaces roughness factor

In NiV intermetallics, Ni has been identified as providing the active sites, and it has been found that the as-prepared materials are less active because they are partially passivated by surface oxides. A treatment with HF greatly improves the activity, which is mainly related to the formation of a surface porous layer enriched with Ni as proven by AES analysis (Fig. 31). However, when NiV and Raney Ni are compared, for both the activity has been found to vary proportionally to the surface roughness factor, but the specific activity is much higher for NiV [542]. This indicates that synergetic effects are real in this case this recalls the observations made in the cases of Ni—Mo and Ni—Mo-Cd solid solutions [141, 518]. 

Table 2.7. Surface roughness factor for biogenic carbonates and ratios of surface roughness factors versus specific surface area ratios (Walter and Morse, 1984b).

Manurung s observed results than those from the equation of Thorley et al., [Eqs. (80) or (81), and (3) or (83)]. However, for coal particles which were rough and irregular, Manurung found it necessary to introduce a surface-roughness factor and a shape factor in Eq. (81) in order to obtain agreement between predicted and observed results ... 

If a theoretical random slice is cut through a network like that in Fig. 14, the cross section produced will show pore spaces exposed amongst the solid support. Figure 16 illustrates how such a sliced section appears for five degrees of randomness (with a surface roughness factor of 0.2) for the instance where the pores are relatively uniform in diameter, obeying... 

What are the virtues of these emerging photoelectrode materials The first is related to their enormous surface area. Consider that the 3D structure is built up of close-packed spheres of radius, r. Then ignoring the void space, the specific area. As (area/volume) is given by 3/r [205]. For r = 10 nm, Ag is on the order of 10 cm , and for a 1 cm film of 1 pm thickness, this value corresponds to an internal sxtrface area of 100 cm (i.e. a surface roughness factor of 100). Clearly, this becomes important if we want the electrolyte redox species to be adsorbed on the electrode surface (see following). Alternatively, a large amount of sensitization dye can be adsorbed onto the support semiconductor although this dye sensitization approach is not considered... 

The Rh electrode is more difficult to roughen, even by applying the square-wave potential procedure described for Pt. It is of special interest that Rh is very easily roughened by applying a square-wave current. This method is also very effective for producing a Pt electrode of low surface area, for example, with a surface roughness factor down to 3 to 5, but with high SERS activity, however, the selection of the current and frequency are very different from those for Rh. 

Fig. 47 Dependence of static state current (i) and the integrated intensity of the Raman band on the electrode potential in 1.0 mol 1 CH3OH and 1.0 mol 1 H2SO4 during the electrooxidation of methanol on a rough platinum surface (roughness factor 200).

The WenzeP equation relates the contact angle of a water drop upon a rough solid surface (Fig. 5), 0, with that upon a smooth surface, through the nondimensional surface roughness factor, Rf > equal to the ratio of the surface area to its flat projection ... 

---