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Non-wetting liquids

Hint the pressure needed to force a non-wetting liquid into a parallel-sided cavity of thickness t is given by... [Pg.156]

R. Yershalmi-Rozen, J. Klein, L. J. Fetters. Suppression of rupture in thin non-wetting liquid films. Science 262 793-795, 1994. [Pg.629]

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. [Pg.195]

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. [Pg.176]

Figure 2.7 Schematic diagram of the shape of a meniscus for wetting and non-wetting liquids. 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... [Pg.28]

The total accessible pore volume may be measured by the amount of adsorbate at the saturation pressure of the adsorptive, calculated as liquid volume, provided the adsorption on the external surface can be neglected or can be evaluated. The accessible pore volume may be different for molecules of different sizes. A method which is not subject to the effect of the external surface is the determination of the dead space by means of a non-sorbable gas (normally helium) in conjunction with the determination of the bulk volume of the adsorbent by means of a non-wetting liquid or by geometrical measurements. [Pg.368]

The WIT is based on the capillary depression of non-wetting liquids at the membrane surfaces. To overcome these negative capillary forces, a certain pressure gradient is required. This pressure gradient depends among other things on the pore size. This is generally known as the water penetration point (WPP). The WPP depends on... [Pg.213]

In this book, a contact angle of less than 90° will identify a wetting liquid, while a greater value will identify a non-wetting liquid. If the contact angle is zero, the liquid will be considered to be perfectly wetting (see also Table 1.1 in Section 1.4.1). [Pg.7]

For any cavity with a / value higher than / , d((5Fs) / d(<51) will be positive whatever the value of 1, so the cavity will not be infiltrated by the liquid. Equation (1.39) shows that composite interfaces can be produced only for non-wetting liquids and very rough surfaces. [Pg.35]

The work of immersion Wj is a thermodynamic quantity that describes any process of infiltration of liquids into porous media, for instance fabrication of composites by liquid routes, liquid state sintering or infiltration of refractories by molten metals or salts. In the example of Figure 1.36, at a depth z, any porosity (assumed cylindrical and open) of radius r larger than (—2<7Lvcos0)/(pgz) will be infiltrated by the non-wetting liquid, while for smaller porosities no infiltration will occur. [Pg.51]

Figure 3.17. Common shape of an experimental curve of variations in the force exerted on a cylindrical solid during its immersion-emersion in a non-wetting liquid plotted as a function of the depth of immersion of the solid. The translation rate of the solid is supposed to be infinitely slow. From... Figure 3.17. Common shape of an experimental curve of variations in the force exerted on a cylindrical solid during its immersion-emersion in a non-wetting liquid plotted as a function of the depth of immersion of the solid. The translation rate of the solid is supposed to be infinitely slow. From...
For non-wetting liquids, the measurement of the height of the meniscus z is difficult to perform by an optical technique. In this case, one can use the method developed by Rivollet (1986) based on the non-linear parts of the f(zb) curve corresponding to the situation where the meniscus is connected to the solid base (part A-C of Figure 3.17). The f(zb) curve is obtained by solving equations (3.19) and (3.20) with zb = z. The value of yLV is then determined by fitting the calculated curve to the experimental one. [Pg.136]

The process depends on a liquid metal flowing over surfaces to form a fillet between components and into the gap between the components, and then solidifying to form a permanent bond. Thus it is essential that the braze experiences high temperature capillary attraction. Without such attraction, solid braze material placed between components will flow out of the gap, sweat , when it melts. Any residue of non-wetting liquid that remains within the gap will not conform to the microscopic features of the component surfaces but form an array of voids, as illustrated schematically in Figure 10.1, that is mechanically deleterious and should be avoided if at all possible. The size of such voids can be decreased if an external pressure is used to confine a non-wetting liquid braze into a gap but cannot eliminate them because the pressure needed to shrink voids increases as they become smaller. [Pg.348]

Interfaces can exhibit both physical and chemical flaws, as exemplified by the presence of small voids in the valleys of roughened surfaces brought into contact with a non-wetting liquid (0 > 90°), or retained islands of unwettable oxide on the surfaces of metal components or of surface contaminants on both metal and ceramic components. Such flaws can have detrimental effects on mechanical properties because at the very least their presence decreases the bonded area. Thus the mechanical preparation and cleaning of component surfaces are crucially important steps of the brazing process. [Pg.375]

In the last decade, a variety of microporous and mesoporous materials have been developed for applications in catalysis, chromatography and adsorption. Great attention has been paid to the control of (i) pore surface chemistry and (ii) textural properties such as pore size distribution, pore size and shape. Recently, a new field of applications for these materials has been highlighted [1-3] by forcing a non-wetting liquid to invade a porous solid by means of an external pressure, mechanical energy can be converted to interfacial energy. The capillary pressure, Pc p, required for pore intrusion can be written from the Laplace-Washbum relation,... [Pg.197]

In porosimetry, the penetration of a non wetting liquid in the pores is only possible with the action of an external force (applied pressure), this force countering the resistance created by the surface tension of the liquid. The liquid penetrates a pore with a radius under a pressure... [Pg.29]

The bulk density of materials was measured by Hg pycnometry from independent measurements of the mass and the volume of monolithic samples. The geometrical volume of the sample is determined fi om the weight difiference between a flask (calibrated volume) filled up with mercmy and the same flask filled up with the sample and mercury. As mercury is a non-wetting liquid and as no pressure is exerted, mercury does not enter in the porosity of the sample or crush it. [Pg.605]

True density is determined on a finely ground sample pycnometrically bulk density of regular shapes is determined by weighing and measuring the dimensions or by means of volumeters using non-wetting liquids that do not penetrate into open pores (e.g, mercury). [Pg.360]

Eor meso- and macro-pore materials, the Laplace [24] equation has also been applied for the determination of pore size distribution with the assumption that the pores are cylindrical, resulting in the equality of the two radii of curvature in the Laplace equation. In practice, the penetration of a non-wetting liquid such as mercury into the pores at a specific pressure is related to the pore radius through the following equation, with the assumption that all pores are equally accessible... [Pg.51]

In this method, mercury (which is a non-wetting liquid) is forced into the pores of a dry sample. For each applied pressure, the volume of mercury entering the sample porous structure is determined very accurately (e.g. by measuring the variation of capacity induced by the reduction in height of the Hg column connected to the measuring cell). The relationship between pressure P and pore radius rp is given by the modified Laplace equation (Washburn equation)... [Pg.78]

In parallel with mercury porosimetry in which a non wetting liquid is used, we can mention the suction porosimetry in which a wetting liquid like water (0 <0 < Jc/2) is held within the porous solid [5]. In this case the Laplace equation predicts that it will experience a reduced hydrostatic pressure, inversely proportional to the radius of pores in which menisci are formed. The lower limit of pore size accessible to this technique is around a few tens of microns. [Pg.78]

Fig. 6.40. A flat coated film of non-wetting liquid (a) usually greater than 1 pm thick can dewet if a disturbance thins the film (b) to the extent (ordinarily less than 1 pm) that the effect of conjoining force is to dewet (c) the solid substrate. (After Kheshgi and Scriven [73].)... Fig. 6.40. A flat coated film of non-wetting liquid (a) usually greater than 1 pm thick can dewet if a disturbance thins the film (b) to the extent (ordinarily less than 1 pm) that the effect of conjoining force is to dewet (c) the solid substrate. (After Kheshgi and Scriven [73].)...
Fig. 6.41. Disjoining pressure profiles of a wetting liquid film (a) and a non-wetting liquid film (b). Fig. 6.41. Disjoining pressure profiles of a wetting liquid film (a) and a non-wetting liquid film (b).
A more detailed characterization of the pore-size characteristics of AGM can be obtained with the mercury intrusion technique. This is based on the principle that the external pressure required to force a non-wetting liquid into a pore against the opposing force of surface tension depends on the pore size. The technique is widely employed to characterize porous materials, and provides data on pore diameter, pore-size distribution, and pore volume. Some caution must be apphed in interpreting the results, however, because of the assumptions that are made concerning cylindrical pores, contact angle, and the surface tension of mercury. [Pg.172]

The better the liquid wets the capillary walls, the higher its rise at a given value of oLG. In the case of a non-wetting liquid (0>9O°), the meniscus is convex, and the pressure in the fluid under it is increased, as compared to that under the flat interface, resulting in capillary lowering. [Pg.37]


See other pages where Non-wetting liquids is mentioned: [Pg.373]    [Pg.386]    [Pg.300]    [Pg.43]    [Pg.17]    [Pg.86]    [Pg.157]    [Pg.28]    [Pg.33]    [Pg.132]    [Pg.132]    [Pg.137]    [Pg.138]    [Pg.138]    [Pg.140]    [Pg.401]    [Pg.341]    [Pg.103]    [Pg.232]    [Pg.235]    [Pg.189]    [Pg.87]    [Pg.286]   
See also in sourсe #XX -- [ Pg.91 , Pg.93 ]

See also in sourсe #XX -- [ Pg.13 ]




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