Wetting contact angles

From what you know about wetting, contact angles, and spread monolayers, explain why a Langmuir-Blodgett layer will deposit as a F type if there are nonpolar fatty acids, yet will switch to a Z-type deposition if bipolar alcohols or amines are added (see Refs. 175, 176). What defines the critical contact angle for the deposition change ... 

The wetting (contact) angle method is used for solid surfaces. If a gas bubble sticks to a metal surface, then the individual interfacial tensions are distributed as shown in Fig. 4.11. It holds at equilibrium that... 

Initially, when the protein layer is still wet, contact angles close to (P are obtained. As drying proceeds, there will be a quick increase in contact angle, and then a plateau angle (0) will be reached (typically within 60 min). 

Figure 3.7 Illustration of capillary rise with a wetting contact angle.

Figure 3.8 Illustrations of the Wilhelmy plate (upper) and du Nouy ring (lower) surface tension methods. Both illustrations are for wetting contact angles.

Figure 3.9 Illustration of the drop weight/volume surface tension method (shown here for a wetting contact angle).

The capillary pressure P depends significantly on the wetting contact angle... 

T aking into account the fact that deoxidation of solid metals is very difficult at low temperatures, it is usual to observe non-wetting contact angles for insoluble metal/metal systems. 

J/m2 and should wet SiC surfaces. This prediction is not confirmed by experimental results obtained in the systematic studies performed by Naidich and Nevodnik (1969) and by Nogi and Ogino (1988), which show large non-wetting contact angles for all metals that have a negligible or a weak reactivity with SiC (Table 7.3). The reasons for this disagreement are discussed in the next Section. 

The Cr3C2 is wettable (see Table 7.10) and as a result, low wetting contact angles can be achieved by Cu-Cr alloys (Figure 7.18). However, this reaction layer is not protective and Cu penetrates the grain boundaries of the SiC substrate far from the interface to react and form graphite (Landry and Eustathopoulos unpublished, Xiao and Derby 1998). 

Literature data for the wetting behaviour of low or moderate melting point metals on AIN in a high vacuum are reported on Table 7.7. Large non-wetting contact angles are observed, usually in the range 130-150° (it is noteworthy that... 

FIGURE 5.4.1 Calculated printed line width as a function of wetting contact angle, assuming a small cylindrical liquid pattern. Square data points and the optical micrographs show measurements of printed Ag nanoparticles ink on surfaces that show different water contact angle. (From Street, R.A. et ah. Mater. Today 9, il- il, 2006. With permission.)... 

Adsorption (as well as chemisorption) processes can lead to a drastic change of the surface nature, i.e. its hydrophilisation or hydrophobisation (oleophilisation). A criterion of the surface nature is the wetting contact angle 0. When a drop of a liquid is applied on a solid surface, then three different interfaces are formed (Fig. 6.1) with the corresponding tensions Ysg Tig and ysi. 

Beginning from the fifties of the last century, the investigation of the behavior of solid electrodes came into the foreground. The available methods, for instance, wetting (contact) angle method, the measurement of differential capacity, were far from furnishing reliable data in the case of solid electrodes. 

In view of the foregoing discussion, it is clear that good wetting (contact angle of adhesive against adherend, 6 O ") is a requirement (but not necessarily a... 

Fundamentals of Wetting, Contact Angle, and Adsorption As the number of moles remains unchanged. 

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