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Thin film balance

To overcome these limitations, the porous plate technique, also called Mysels cell , was introduced by Mysels [446, 769]. It was further improved by Exerowa and [Pg.198]

In equilibrium, the disjoining pressure IT in the flat part of the film is equal to the capillary pressure at the rim [771] IT = P. Balancing all forces for the setup and assuming complete wetting of the glass frit by the solution, one obtains [Pg.199]

P xt is the external reference pressure, is the radius of the glass capillary, is the contact angle formed between the liquid and the wall of the capillary, and H is the [Pg.199]

/ is the observed reflected intensity at a certain film thickness. By measuring the maximum and minimum intensities during thinning and correctly counting the number of multiples of k/4 still left - the final thin film of interest will be less than A./4 thick - one obtains the film thickness. [Pg.200]

For real systems, we do not have a homogeneous water film but surfactant layers at both interfaces. These layers can be accounted for by correcting h with a three-layer model derived by Duyvis [773]. The total film thicJcness is calculated from [Pg.200]


Thin-film balance apparatus, 12 7 Thin-film composite membranes, 21 633 Thin-film deposition, laser ablation for, 24 740... [Pg.945]

The interaction between the two gas-liquid interfaces across a foam film can directly be measured by a thin-film balance (TFB) [571-573], A single thin foam film is formed in a hole drilled through a porous glass plate (Fig. 12.19). The plate, and therefore the liquid in the foam, is connected to a reservoir with a constant reference pressure Pr by a capillary tube. The film holder is placed into a closed cell. A constant pressure Pg is applied to the gas in the... [Pg.274]

Surface Forces. Surface forces can be measured with thin film balances where freely suspended horizontal films are submitted to controlled pressures. If the film drainage has been smooth enough, so that no early rupture has occurred, a regime where interactions between the two sides of the film become significant can be attained this is in a thickness region of about 100 nm and less. Typical interactions are van der Waals forces (attractive) and electrostatic forces (repulsive). Short range forces (steric, hydration) are also present. [Pg.136]

Measurements of it as a function of h may be performed using thin-film balances of this type [7, 12, 13, 24]. To the extent that the disjoining pressure arises from electrostatic forces, there will be an obvious influence of electrolyte concentration. For very thin films (>1000 A), the disjoining pressure is very important. But for thicker films, wetter foams, the factors discussed previously are more important. [Pg.174]

The apparatus used for studying thin liquid films is schematically depicted in Fig. 6. This device, commonly known as a thin-film balance, allows drainage patterns of single foam, emulsion, or wetting films to be recorded. The film is formed in a specially constructed cell that is placed on the state of an inverted microscope. The reflected light from the film is split into two parts, one directed to a CCD camera and another to a fiber-optic probe tip located in the microscope eyepiece. The radius of the tip is only about 20... [Pg.313]

Figure 6 Schematic representation of the main components of a typical thin-film balance... Figure 6 Schematic representation of the main components of a typical thin-film balance...
By using the thin-film balance developed by Schedud-luko and Exerowa (6), the drainage of foam films has been extensively studied. The apparatus employed is shown in Figure 2.16. [Pg.37]

Figure 2.16. The thin-film balance method used for evaluating the stability and drainage of foam films (a) schematic representation of the geometry of films in a foam, which occurs in the measuring cell of the Scheludko-Exerowa system (b) schematic of the set-up used for studying microscopic thin aqueous films (c) a typical interferogram of photocurrent versus time of drainage for the thinning process (adapted from ref. (6)), with permission from Elsevier Science... Figure 2.16. The thin-film balance method used for evaluating the stability and drainage of foam films (a) schematic representation of the geometry of films in a foam, which occurs in the measuring cell of the Scheludko-Exerowa system (b) schematic of the set-up used for studying microscopic thin aqueous films (c) a typical interferogram of photocurrent versus time of drainage for the thinning process (adapted from ref. (6)), with permission from Elsevier Science...
First, we note that a force versus distance curve may be obtained in two fundamentally different ways. The force can be controlled and the resulting separation measured. This is the principle used in the thin film balance. Alternatively, the distance can be controlled and the resulting force determined, and this is the method utilized in the SFA, AFM and MASIF approaches. The methodology used in these latter techniques does, however, differ in several important respects. Perhaps the most fundamental difference is how the force and the surface separation are determined. [Pg.385]

Thin-Film Balance (TFB) Foam, emulsion and wetting... [Pg.417]

Due to the flexibility of fluid interfaces, the mechanical techniques used in the surface-force instruments cannot generally be applied. Instead, the forces in a thin-liquid film can be balanced by an applied capillary pressure, which is at the origin of the technique referred to as the Thin-Film Balance (TFB). The general concept was first realized by Derjaguin and Obuchov when they... [Pg.417]

Figure 21.4. Cross-sectional view of typical film-holders used in the thin-film balance (a) Scheludko cell (b) porous disc holder (from ref (11))... Figure 21.4. Cross-sectional view of typical film-holders used in the thin-film balance (a) Scheludko cell (b) porous disc holder (from ref (11))...
Figure 21.5. Schematic of the pressure cell and film holder for a typical thin-film balance. The film can be optically interrogated from above and/or below (from ref. (11))... Figure 21.5. Schematic of the pressure cell and film holder for a typical thin-film balance. The film can be optically interrogated from above and/or below (from ref. (11))...
Engel, J. H. Alivisatos, A. P., Postsynthetic doping control of nanocrystal thin films Balancing space charge to improve photovoltaic efficiency. Chem. Mater. 2013,26, 153-162. [Pg.179]

The interaction between drops has been studied experimentally with different techniques [731]. The most important technique for studying interfacial forces across thin films is the thin film balance [699,732]. In fact, a whole class of thin film balances have been developed. They are described in detail in Sections 7.4 and 7.6. In another technique, two drops at the end of two capillaries are moved toward each other [733] or one drop is moved toward a planar interface [734]. The process is observed by optical microscopy. Direct force measurements have become possible with the atomic force microscope by attaching tiny oil drops to AFM cantilevers [270, 696]. Recently, such drops have also been produced in microfluidic channels [735]. [Pg.189]

Drainage, interstitial forces, and rupture of thin liquid films are the topic of this chapter. We start by introducing the concept of the disjoining pressure. Then, we describe the drainage of liquid in thin films. Here, we distinguish between vertical films, in which gravitation dictates the direction of the flow, and horizontal films. After introducing thin film balance as the main device to measure forces across liquid... [Pg.191]

The direct measurement of the disjoining pressure as a function of film thickness can be achieved by the thin film balance introduced by Derjaguin et al. [91] and Scheludko and Exerowa [768]. The principle of this so-called Scheludko cell is shown in Figure 7.6. The film is formed within a ring with 2—4 mm diameter. A small hole at the side of the ring allows to draw Uquid from the film and thus adjust and measure the capillary pressure applied. The film thickness is deduced via optical interferometry. Almost exclusively aqueous solutions are studied. Originally, the thin film balance was constructed to measure the force across foam films. Modified versions are also used to measure forces across emulsion films [732, 734]. [Pg.198]

Figure 7.6 Schematic of thin film balance cells. Figure 7.6 Schematic of thin film balance cells.
Figure 7.7 Schematic of a thin film balance. The gas pressure P inside the sealed chamber can be adjusted via the syringe relative to the external reference pressure Pext to enforce... Figure 7.7 Schematic of a thin film balance. The gas pressure P inside the sealed chamber can be adjusted via the syringe relative to the external reference pressure Pext to enforce...
A complete setup of a thin film balance is shown in Figure 7.7. The holder with the film is placed inside a sealed chamber, which contains the same solution as the film for equilibration at the bottom. The holder has been saturated with the solution of interest by immersing it before mounting for several hours. The free end of the capillary tube is exposed to a reference pressure, which in the simplest case is just ambient pressure. The capillary pressure in the film spanning the hole can be controlled by varying the pressure inside the sealed chamber. A simple way to do this with high precision is to coimect to the chamber a syringe pump that is driven by a micrometer screw and measure the chamber pressure with a pressure transducer. [Pg.199]

The situation of the thin film balance is shown in Figure 7.8. We denote the radius of the meniscus by r, as a reminiscence on the bubble-bubble interaction. The general equation describing the shape of the interfaces is a generalized Laplace... [Pg.202]

Figure 7.9 Thickness of two aqueous foam films versus the concentration of added salt. In one classical experiment (o), carried out by Scheludko and Exerowa [444], a thin film balance was used to study an aqueous solution containing saponin plus different... Figure 7.9 Thickness of two aqueous foam films versus the concentration of added salt. In one classical experiment (o), carried out by Scheludko and Exerowa [444], a thin film balance was used to study an aqueous solution containing saponin plus different...
Figure 7.10 Photo of an aqueous foam film in a thin film balance with a hole diameter of 1 mm. The film was stabilized with a mixture of commercial alkyl polyglycosides (APC) with alkyl chain lengths of 12 and 14 carbon atoms at a concentration four times lower than the CMC. In addition, a positively charged polymer poly (diallyl dimethyl ammonium chloride)... Figure 7.10 Photo of an aqueous foam film in a thin film balance with a hole diameter of 1 mm. The film was stabilized with a mixture of commercial alkyl polyglycosides (APC) with alkyl chain lengths of 12 and 14 carbon atoms at a concentration four times lower than the CMC. In addition, a positively charged polymer poly (diallyl dimethyl ammonium chloride)...
Figure 7.14 Schematic of a thin film balance. A capilla of radius Is moved close to the planar surface. Gas Is pressed through the capilla with a pressure AP. Between the end... Figure 7.14 Schematic of a thin film balance. A capilla of radius Is moved close to the planar surface. Gas Is pressed through the capilla with a pressure AP. Between the end...

See other pages where Thin film balance is mentioned: [Pg.53]    [Pg.54]    [Pg.127]    [Pg.162]    [Pg.311]    [Pg.313]    [Pg.313]    [Pg.314]    [Pg.324]    [Pg.385]    [Pg.415]    [Pg.417]    [Pg.417]    [Pg.423]    [Pg.636]    [Pg.198]    [Pg.199]    [Pg.204]    [Pg.211]   
See also in sourсe #XX -- [ Pg.276 ]

See also in sourсe #XX -- [ Pg.198 , Pg.199 , Pg.200 , Pg.203 , Pg.212 ]




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