Non-wetting

As a somewhat anecdotal aside, there has been an interesting question as to whether gold is or is not wet by water, with many publications on either side. This history has been reviewed by Smith [119]. The present consensus seems to be that absolutely pure gold is water-wet and that the reports of non wetting are a documentation of the ease with which gold surface becomes contaminated (see Ref. 120, but also 121). The detection and control of surface contaminants has been discussed by White [121] see also Gaines [122]. 

Figure B3.6.3. Sketch of the coarse-grained description of a binary blend in contact with a wall, (a) Composition profile at the wall, (b) Effective interaction g(l) between the interface and the wall. The different potentials correspond to complete wettmg, a first-order wetting transition and the non-wet state (from above to below). In case of a second-order transition there is no double-well structure close to the transition, but g(l) exhibits a single minimum which moves to larger distances as the wetting transition temperature is approached from below, (c) Temperature dependence of the thickness / of the enriclnnent layer at the wall. The jump of the layer thickness indicates a first-order wetting transition. In the case of a conthuious transition the layer thickness would diverge continuously upon approaching from below.

Hint the pressure needed to force a non-wetting liquid into a parallel-sided cavity of thickness t is given by... 

R. Yershalmi-Rozen, J. Klein, L. J. Fetters. Suppression of rupture in thin non-wetting liquid films. Science 262 793-795, 1994. 

Carbon, made non-wetting by passage of current, 527 Carrier lifetime... 

Interpretation for irreducible water saturation assumes that the rock is water-wet or mixed-wet (water-wet during drainage but the pore surfaces contacted by oil becomes oil-wet upon imbibition). If a porous medium is water-wet and a nonwetting fluid displaces the water (drainage), then the non-wetting fluid will first occupy the larger pores and will enter the smaller pores only as the capillary pressure is increased. This process is similar to the accumulation of oil or gas in the pore space of a reservoir. Thus it is of interest to estimate the irreducible water saturation that is retained by capillarity after the hydrocarbon accumulates in an oil or gas reservoir. The FFI is an estimate of the amount of potential hydrocarbon in... 

The solution of these dynamic nonlinear differential equations is considerably more complex than the previous systems considered. In particular, stable solution methods are based on physically realistic multiphase flow functions that have the following properties relative permeability functions are non-negative, monotoni-cally increasing with their respective saturation, and are zero at vanishing saturations, and capillary pressure is monotonically increasing with respect to the saturation of the non-wetting phase. It is necessary that any iterative scheme for estimating the multiphase flow functions retain these characteristics at each step. 

Flow properties of macroemulsions are different from those of non-emulsified phases 19,44). When water droplets are dispersed in a non-wetting oil phase, the relative permeability of the formation to the non-wetting phase decreases. Viscous energy must be expended to deform the emulsified water droplets so that they will pass through pore throats. If viscous forces are insufficient to overcome the capillary forces which hold the water droplet within the pore body, flow channels will become blocked with persistent, non-draining water droplets. As a result, the flow of oil to the wellbore will also be blocked. 

Figure 2.115 shows a schematic representation of the DEMS apparatus. In essence, the electrochemical cell is separated from a mass spectrometer by a porous, non-wetting PTFE membrane of very small pore size. The working electrode is then deposited as a porous metal layer on the thin... 

The lotus-like and honeycomb-like aligned CNT films with a combination of micro- and nanostructures were also reported (Sun et al., 2003 Choi et al., 2003). They all displayed super-hydrophobic properties as shown in Fig. 9.14. The well-aligned CNT-polymer films or coatings have potential on applications such as super-hydrophobic surfaces to textiles, coatings, gene delivery, micro-fluid channels, non-wetting liquid transfer, and so forth. 

Unless otherwise specified, AISI 4140 steel may be used for non-wetted case and gland studs. 

These contact angles can be related to the physical state of the surface. The 100 facet is better wetted than the 111 one because the 100 surface is partly premelted. But, the liquid-like disordered monolayer is too thin to have the properties of the macroscopic liquid, and this "adsorbed liquid layer" coexists with a non-wetting macroscopic liquid. This so-called "incomplete surface melting" has also been observed on a pure single crystal of ice. ... 

It is more tlian probable that these variations in the apparent densities of charcoals are to be ascribed to a difference in the depths of penetration of the hquids. Thus non-wetting liquids such as mercury would not readily penetrate the large macropores in the solid, far less into the micropores (below 100 A. in diameter) which exist in charcoal. We should thus anticipate that when mercury is employed as immersion liquid the charcoal density would be but small. Actually a value of only 0 865 was obtained by Harkins and Ewing. 

Alternative materials may be substituted for liquid temperatures greater than 45 °C (110 ° F) or for other special services Unless otherarise specified, AISI 4140 steel may be used for non-wetted case and gland studs. 

Absorption Isotherm for non- wetting absorbate -absorbent systems. 

Figure 1.5 A non-wetting water droplet on the surface of methylated, hydrophobic silica.

Figure 2.7 Schematic diagram of the shape of a meniscus for wetting and non-wetting liquids.

The second approach to obtaining the surface energies of solids involves the study of wetting and non-wetting liquids on a smooth, clean solid substrate. Let us examine the situation for a non-wetting... 

In water the wetted solid is termed hydrophilic , whereas the non-wetted solid is hydrophobic . Naturally hydrophobic minerals, such as some types of coal, talc and molybdenite are easily separated from the unwanted hydrophilic quartz sand (referred to as gangue ). However, surfactants and oils are usually added as collectors . These compounds adsorb onto the hydrophilic mineral surface and make it hydrophobic. 

In situ ETEM permits direct probing of particle sintering mechanisms and the effect of gas environments on supported metal-particle catalysts under reaction conditions. Here we present some examples of metals supported on non-wetting or irreducible ceramic supports, such as alumina and silica. The experiments are important in understanding metal-support interactions on irreducibe ceramics. 

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