Mica comparison

Fig. III-3. Comparison of Eq. III-18 (solid line) with experimental results for cyclohexane bridges formed between crossed mica cylinders the dashed line is the calculation including Eq. III-20 (from Ref. 19).

The flotation of mica has been correlated to the adhesion force measured from surface force (SFA—see Section VI-4) experiments although, to these authors, it is clear that dynamic effects prevent an absolute comparison [69, 70],... 

In accordance with equation (Bl.20.1). one can plot the so-called surface force parameter, P = F(D) / 2 i R, versus D. This allows comparison of different direct force measurements in temis of intemiolecular potentials fV(D), i.e. independent of a particular contact geometry. Figure B 1.20.2 shows an example of the attractive van der Waals force measured between two curved mica surfaces of radius i 10 nun. 

In the symmetric, three-layer interferometer, only even-order fringes are sensitive to refractive index and it is possible to obtain spectral infonnation of the confined film by comparison of the difierent intensities of odd-and even-order fringes. The absorption spectmm of tliin dye layers between mica was investigated by Muller and Machtle [M, M] using this method. 

Pashley R M and Israelachvili J N 1981 A comparison of surface forces and interfacial properties of mica in purified surfactant solutions Colloids Surf. 2 169-87... 

Many studies have been made of the rates of water evolution from layer-type silicate minerals which contain structural hydroxyl groups (clays and micas). Variations in composition of mineral specimens from different sources hinders comparison of the results of different workers. Furthermore, the small crystallite sizes and poor crystallinity that are features of clays limit and sometimes prevent the collection of ancillary observations (e.g. microscopic examination and diffraction measurements). 

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... 

Figure 1. Comparison of ST2 water-surface interactions computed from Equations 7 or 8 using parameters for the Lennard-Jones 9-3 potential in Table II and the delocalized charge magnitude for smectite and mica surfaces in Table III.

Some data obtained from MCT, SFA, and TFB under similar conditions are compared in Fig. 2.20b. The SFA data were taken from reference [80]. They were obtained with hydrophobized mica surfaces, protein concentration of 0.1 wt%, and ionic strength of 10 mol/1. Data for TFB and MCT led to very similar results. However, comparison with the SFA data demonstrates that the force laws are only qualitatively similar the curves are parallel but the normalized data for liquid-liquid interfaces (TFB and MCT) lie about one decade below those obtained for solid-liquid interfaces (SFA). This result suggests that the proteins exhibit different adsorption abilities and or adopt different conformations at the two types of surfaces. 

To investigate conditions in which unusual luminescence appears, we did comparison with spectra obtained on C6o benzene solution, C60 single crystal, two kinds of crystalline thin films on mica and silicon substrates (Fig. 4). They clearly showed, that the unusual luminescence presents only in FWS. 

Figure 5. Photoluminescence of C film on mica substrate in the immersed in water state and initially dry. Upper spectrum of photoluminescence in single crystal is given for comparison.

Fig. 4. Attractive force law deduced from forces measured between mica surfaces immersed in CTAB solutions. Each point is the difference between the measured force and the expected DLVO interaction. For comparison, from Lifshitz theory calculated van der Waals force-law for two mica surfaces and two hydrocarbon surfaces in water is shown as shaded area. Adapted from Ref. [81]. 1984, with permission from Elsevier.

Morita et al. [34] also used AFM to monitor the aging of the one-layer LB films of alkyl-TCNQ. Fig. 7 depicts AFM images of a (a) fresh (15min after the film deposition) and (b) aged (120 min after the deposition) one-layer LB films of pentadecyl-TCNQ on mica. It can clearly be seen from comparison between the images in Fig. 8(a) and (b) that flat and uniformed domains in the LB film change into smaller and more condensed domains whose sizes are 1 pm in a few hours. Fig. 9(a) shows an AFM image of a one-layer LB film of dodecyl-TCNQ on mica measured 2 days after the film deposition. It is noted that the... 

Comparison of these potentials with those for the terminally anchored chains shows the interaction to be relatively weak. For example, experiments with polystyrene in cyclohexane, which does not adsorb on mica, yielded no detectable forces between mica surfaces because of the polymer (Luckham and Klein, 1985). Indeed, estimates of the potential from Eq. (130) at the experimental conditions fall several orders of magnitude below the detection limit for the instrument. 

Experimental. A Parr model 1221 oxygen bomb calorimeter was modified for isothermal operation and to ensure solution of nitrogen oxides (2). The space between the water jacket and the case was filled with vermiculite (exploded mica) to improve insulation. A flexible 1000-watt heater (Cenco No. 16565-3) was bent in the form of a circle to fit just within the jacket about 1 cm. above the bottom. Heater ends were soldered through the orifices left by removing the hot and cold water valves. A copper-constantan thermocouple and a precision platinum resistance thermometer (Minco model S37-2) were calibrated by comparison with a National Bureau of Standards-calibrated Leeds and Northrup model 8164 platinum resistance thermometer. The thermometer was used to sense the temperature within the calorimeter bucket the thermocouple sensed the jacket temperature. A mercury-in-glass thermoregulator (Philadelphia Scientific Glass model CE-712) was used to control the jacket temperature. 

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