Hydrophobic surfaces contact angle

The Attachment of Air Bubbles. Particles are carried upward and are held in the froth if air bubbles can be attached to them. The adhesion of bubbles is only possible if the particle surface is sufficiently hydrophobic. The contact angle (see Appendix Chapter 4) is an important variable related to the adhesion of bubbles to solid surfaces. As shown in Fig. A.4.1, Chapter 4, and by Youngs Equation (Eq. A.4.3, Chapter 4)... 

The problem here consists in listing the material parameters because, in activated sludge, they fluctuate strongly (much in contrast to ore flotation). Surely, the degree of hydrophobicity (wettability) of the particle surface (contact angle, ) will be of importance. Furthermore, the pH value, the concentration of the flocculant (poly-electrolyte), cF, the portion of solids, [Pg.30]

In most fuel cell operations, humidified gases are used to ensure proper membrane hydration. Hence, the ability to remove liquid water becomes the primary concern of GDL selection. PTEE is often used to increase the GDL hydrophobic-ity. Contact angle is commonly used to measure the hydrophobicity (typically in the range between 120 and 140°). However, Gurau et al. suggested that external contact angle measurements were more indicative of the GDL surface roughness than the capillary forces in the GDL pores (which reflects the real measurement of water removal capacity). They presented a new method for... 

Generally, oilfield emulsions are most often W/O with the surface-active emulsifiers residing in the crude-oil continuous phase. According to the Bancroft rule (109) the phase for which the emulsifiers are most soluble is the continuous phase. The emulsifiers possess some degree of polarity which attracts them to the water phase. Solid emulsifiers would be very fine particles in a state of incipient flocculation (110). The emulsifiers may be one or more of the following solids whieh are partially hydrophobic with contact angle (9>90°), polar asphaltenes and resins with some partial insolubility indueed by solvents which dilute the crude oils, or metalloporphyrins integrated within the asphaltenes (24, 25). 

Hydrophilic/hydrophobic (HL/HB) patterning means creating adjacent areas of different contact angles. This is achieved by manipulating the surface chemistries or topographies, or both. At least one chemistry needs to be hydrophilic (water contact angle <90 ) and at least one chemistry needs to be hydrophobic (water contact angle >90°). 

Finally, when the BDD is removed from the CVD diamond reactor, it is hydrogen (H-) terminated, which also confers hydrophobic properties on the surface. Contact angles of 90 have been measured using water [34]. The question of how long the hydrogen termination lasts, especially after oxidative electrochemical treatment [4,17], is an important one to consider therefore at the minimum, simple contact angle verification before and after experiment is a necessary and important measurement to make. 

F. 5 Reduced compressibility, pk TK, of water in a planar nanopore of width D = 1.64 nm as a function of surface contact angle, 0c SPC/E water [53, 66, 119], Contact angle of chemically homogeneous pore walls was varied through surface chemistry (circles at 0c = 135, 93, or 69 ), or by applying electric field across a hydrophobic pore (squares at 114 and 129 )... 

The term represents the surface energy of the solid substrate, and it is important for determining how a liquid droplet wets the solid surface. If the surface is hydrophobic, the contact angle of a droplet is larger. Hydrophilicity is indicated by smaller contact angles and higher solid surface energy [37, 38]. 

Remarkably, an apparent mass loss is found for the second immersion cycle (Adv-fdc-2) reflective of a hydrophobic surface (0adv2 = 106°). Now, water-hydrogen bonding interactions are stronger than water-surface interactions and water resists wetting the surface. Contact angles measured by drop profile analysis are close to those observed for DCA. 

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