Surface of mica

Frantz P and Saimeron M 1998 Preparation of mica surfaces for enhanced resoiution and cieaniiness in the surface forces apparatus Tribal. Lett. 5 151-3... 

SFA measurements on mica. Horn et al. [68] studied the deformation of mica surfaces in contact. In these studies, Horn et al. established the applicability of Hertz theory of contact mechanics to non-adhering layered solids by measuring... 

The mechanical instability, jump-in and pull-off phenomenon, can also be observed in a macroscopic system, and both the trajectory and force curves exhibit similar patterns to those in Fig. 6. As a comparison, Fig. 9 shows a force curve obtained from SFA experiments of mica surface separation in diy air [8]. The pattern of the force variation, the... 

If mica-type sites are truly indicative of mica surfaces, and so on for montmoril Ionite etc., then of the clays examined, only the mica could be regarded as pure. The Montana vermiculite contained much montmoril Ionite, the Fithian illite contained mica and montmoril Ionite, the Wyoming bentonite contained some mica,... 

Since the origination of the SFA technique mica has been utilised as a preferred substrate because of the convenience of this substrate. However, the fundamental and practical interest of mica surfaces interactions in liquids and gases is quite limited. It was of great interest to develop a broad range of substrates of various... 

The similarity in the adsorption behavior of krypton on the three kinds of mica surfaces suggests that the adsorption here is primarily due to dispersion forces, with very little contribution from ion-induced dipole forces. The results of Barrer and Stuart (1) for the adsorption of argon on various ion-exchanged forms of faujasite are similar. They found that while calcium, strontium, and lithium faujasite—i.e., the materials containing cations with greater polarizing power—did show heat effects correlatable with ion-induced dipole interactions, no such effects were observed with sodium, potassium, or barium zeolites. With the latter materials, they also concluded that the adsorbed argon possessed appreciable mobility. 

Here, L denotes the length of the capillary. An important advantage of the streaming current measurement is that the surface conductivity does not matter for the calculation (see Equation 5.364), and experimental determination of is not necessary. Similar experiments were performed by Scales et al. to determine the potential of mica surface. 

Boles, J.R. Johnson, S.K. (1984) Influence of mica surfaces on pore water pH. Chem. Geol., 43, 303-317. 

Most SECM measurements are carried out with the sample under a thick liquid layer, and thus the tip must be sheathed in an insulator to achieve high resolution. SECM measurements can also be carried out within a thin layer of water that forms on the surface of a sample in air. In this case very high resolution can be attained using tips without insulation (e.g., the usual W or Pt-Ir STM-type tips) because the tip area is defined by the small part of the tip that touches the liquid layer (34,35). Studies of mica surfaces, polymer films, and some biological samples as described below are possible by this technique. With this mode it is also possible to fabricate small metal structures in polymer films as demonstrated previously (36). High-resolution electrochemical deposition of silver nanostructures on mica surfaces in humid air was also achieved (35). For detailed discussion on SECM applications for fabrication, see Chapter 13. 

Figure 10-16. Interfacial model of mica surfaces covered with adsorbed monolayers of stearic acid.

Ries and Kimball [21] have published micrographs of islands of vertically orientated acid molecules which occur at certain surface pressures in monolayers of fatty acids spread on water. Mathieson[20] examined electron micrographs of replicas of mica surfaces which had been dipped in dilute stearic acid-hexadecane solution he observed that the stearic acid was present on the surface in patches which were of varying lateral extent but only 25 A. thick. He noted in some instances a tendency toward regular alignment of particles of the shadowing metal on the surface of the acid patches. Mathieson suggests these may indicate the presence of Epstein s micelles in the monolayer. 

Pashley and Israelachvili carried out a detailed study of mica surfaces approaching each other through water and dilute electrolyte solutions in an attempt to find hydrate crystal layers. These layers had been inferred from the structure of damp clay, which is known to swell in water and to have a distinct lubricious surface, quite different from normal oxides. In the 1930s such clay had been investigated by the X-ray diffraction method, which showed that the clay plates moved apart in water to distances of 0.25 and 0.55 nm, about the diameter of one or two layers of water molecules, as shown schematically in Fig. 6.15. 

One of the best understood examples is that of mica surfaces, pressed into contact through water, as described in Section 6.6. The plot of force versus separation is not smooth in this case, but shows sharp oscillations as layers of water molecules are squeezed out of the gap between the surfaces. When plotted as an energy diagram, this shows that the surfaces can exist in several metastable adhesive states, depending on how many water layas have been removed, as shown in Fig. 8.7. 

An Influence of Mica Surface on Model Reaction of Reetherification... 

For influence analysis of mica surface on reetherification reaction the scaling approach is used [4], As an example let s consider the reaction in which particles P of a chemical substance diffuse in the medium, containing the randomly located static nonsaturated traps T. By the contact of a particle P with a trap T, the particle disappears. Nonsaturation of a trap means that the reaction P+T->T can repeat itself an infinite number of times. It is usually considered that the concentration of particles and traps is large or the reaction occurs at intersive stirring, and the process can be considered as the classical reaction of the first order. In this case, it is possible to consider that the concentration decay of particles c decreases with time tas [4] ... 

Pzlp = os(z). the wall-molecule distribution function see Chapter 3, Section 3.4). In Figure 6.17a, the density profile at a vapor-liquid interface is represented a relatively smooth density curve is found, which reflects that some molecules are allowed to stick out beyond the limit (in a statistical sense) of the liquid phase. When a hard wall is present, the situation is quite different if it is assumed to be ideally smooth, as in Figure 6.17b, it (along with the liquid molecular interactions) forces the liquid molecules to order into quasi-discrete ordered layers, but this order lasts only for a distance of a few molecular diameters, after which the disordered nature of the liquid prevails. The density at the wall position is zero, and at a distance rjl, a maximum in p is observed, corresponding to the first liquid layer this density, p, is known as the contact value of the density. The midplane density p may or may not approach the bulk density, depending on the wall-wall distance d. Experiments have shown that for water in the presence of mica surfaces, there are about four quasi-ordered water layers, covering a distance of about 1 nm from... 

Figures 1 and 2 show the typical results of our experiments. Based on the Derjaguin approximations, the data obtained from independent experiments (and different contact positions) are summarized as a plot of F/R (with F and R being the force and mean radius of curvature of mica surfaces, rspectively) against the separation between the mica substrates D. The measurements were carried out in toluene at 32 C. The incubation concentrations for both homo-PS (PS233) and PVP-PS (60-60 and 60-90) samples in the apparatus were approximately 3 pg/ml.

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