Liquid film formation

FIG. 6.2 Illustrations of liquid film formation, contact angle, and measurement of contact angle (a) a wire loop with a slide wire on which a liquid film might be formed and stretched by an applied force F. (b) profile of a three-phase (solid, liquid, gas) boundary that defines the contact angle 0. (c) the tilted plate method for measuring contact angles. 

The Bailey and Watkins study shows that continuous liquid film formation is favoured by interfacial reactivity due to mutual solubility or to formation of intermetallics. This correlation between film stability and reactivity is due to several reasons ... 

Forcada, M.L. 1993. Instability in a system of two interacting liquid films Formation of liquid bridges between solid surfaces. J. Chem. Phys. 98(1) 638—643. 

Drums used for packing storage should be cleaned free of foreign material that may chemically attack packing or stick to packing surfaces and later inhibit liquid film formation, or cause undesirable effects (e.g., foaming). Oversized containers are hazardous to workers lifting them, and should be avoided. 

M. P. Fard, N. Ashgriz, J. Mostaghimi, L. A. Prociw, T. C. J. Hu, Modeling liquid film formation and breakup in an industrial spray nozzle, ILASS America, 15th Annual Conference on Liquid Atomization and Spray Systems, May 14—17, 2002, Madison, Wisconsin. 

Figure 21.8 Selected structures of vinyliir i szolium-based ionic liquids used for cross-linked ionic liquid film formation of capillary GC column walls.

Forsyth M, Neil WC, Howlett PC, Macfarlane DR, Hinton BRW, Rocher N, Kemp TF, Smith ME (2009) New insights into the fundamental chemical nature of ionic liquid film formation on magnesium alloy surfaces. ACS Appl Mater Interfaces 1(5) 1045-1052. doi 10.1021/ am900023j... 

Thus, the UGAL model gives additional possibilities for studying the adsorption kinetics of gaseous and liquid film formation. 

Foulk CW, Miller JN. (1931) Experimental evidence in support of the balanced-layer theory of liquid film formation. Ind Enjf Chem 23 1283. 

A general prerequisite for the existence of a stable interface between two phases is that the free energy of formation of the interface be positive were it negative or zero, fluctuations would lead to complete dispersion of one phase in another. As implied, thermodynamics constitutes an important discipline within the general subject. It is one in which surface area joins the usual extensive quantities of mass and volume and in which surface tension and surface composition join the usual intensive quantities of pressure, temperature, and bulk composition. The thermodynamic functions of free energy, enthalpy and entropy can be defined for an interface as well as for a bulk portion of matter. Chapters II and ni are based on a rich history of thermodynamic studies of the liquid interface. The phase behavior of liquid films enters in Chapter IV, and the electrical potential and charge are added as thermodynamic variables in Chapter V. 

Finally, in yet another variant, the sample liquid stream and the gas flow are brought together at a shaped nozzle into which the liquid flows (parallel-path nebulizer). Again, the intersection of liquid film and gas flow leads to the formation of an aerosol. Obstruction of the sample flow by formation of deposits is not a problem, and the devices are easily constructed from plastics, making them robust and cheap. 

If no wave formations are present, analysis of behavior of the liquid-film mass transfer as developed by Hatta and Katori [J. Soc. Chem. Ind., 37, 280B (1934)] indicates that... 

The theory of seaweed formation does not only apply to solidification processes but in fact to the completely different phenomenon of a wettingdewetting transition. To be precise, this applies to the so-called partial wetting scenario, where a thin liquid film may coexist with a dry surface on the same substrate. These equations are equivalent to the one-sided model of diffusional growth with an effective diffusion coefficient which depends on the viscosity and on the thermodynamical properties of the thin film. 

Figure 9-6T. (Top) Cascade Mini-Ring, (metal and plastic). Originally used by permission of Mass Transfer, Inc., now, Glitsch, Inc. (middle and bottom) Elevation and plan views of Ballast rings (right) and Cascade Mini-Rings (left). Note how high aspect ratio of former permits occlusion of interior surfaces. Low aspect ratio of Cascade Mini-Rings, on the other hand, favors orientation that exposes internal surfaces for excellent film formation, intimate mixing, and gas-liquid contact. Used by permission of Glitsch, Inc. Bull. 345.

It is now well established that in lithium batteries (including lithium-ion batteries) containing either liquid or polymer electrolytes, the anode is always covered by a passivating layer called the SEI. However, the chemical and electrochemical formation reactions and properties of this layer are as yet not well understood. In this section we discuss the electrode surface and SEI characterizations, film formation reactions (chemical and electrochemical), and other phenomena taking place at the lithium or lithium-alloy anode, and at the Li. C6 anode/electrolyte interface in both liquid and polymer-electrolyte batteries. We focus on the lithium anode but the theoretical considerations are common to all alkali-metal anodes. We address also the initial electrochemical formation steps of the SEI, the role of the solvated-electron rate constant in the selection of SEI-building materials (precursors), and the correlation between SEI properties and battery quality and performance. 

Foam formation in a boiler is primarily a surface active phenomena, whereby a discontinuous gaseous phase of steam, carbon dioxide, and other gas bubbles is dispersed in a continuous liquid phase of BW. Because the largest component of the foam is usually gas, the bubbles generally are separated only by a thin, liquid film composed of several layers of molecules that can slide over each other to provide considerable elasticity. Foaming occurs when these bubbles arrive at a steam-water interface at a rate faster than that at which they can collapse or decay into steam vapor. 

The effect of surface contamination and the wettability between the tube wall and the fluids were also studied experimentally. It has been shown that a stable annular flow and gas slug formation with a stable thin liquid film formed between the tube wall and gas slugs, which appeared at high velocities under carefully treated, clean... 

Surface force apparatus has been applied successfully over the past years for measuring normal surface forces as a function of surface gap or film thickness. The results reveal, for example, that the normal forces acting on confined liquid composed of linear-chain molecules exhibit a periodic oscillation between the attractive and repulsive interactions as one surface continuously approaches to another, which is schematically shown in Fig. 19. The period of the oscillation corresponds precisely to the thickness of a molecular chain, and the oscillation amplitude increases exponentially as the film thickness decreases. This oscillatory solvation force originates from the formation of the layering structure in thin liquid films and the change of the ordered structure with the film thickness. The result provides a convincing example that the SFA can be an effective experimental tool to detect fundamental interactions between the surfaces when the gap decreases to nanometre scale. 

FIG. 10 Formation of a dry patch (zone) in an unstable liquid film on a rigid substrate. 

Internal heat exchange is realized by heat conduction from the microstructured reaction zone to a mini channel heat exchanger, positioned in the rear of the reaction zone [1,3,4], The falling film micro reactor can be equipped, additionally, with an inspection window. This allows a visually check of the quality of film formation and identification of flow misdistribution. Furthermore, photochemical gas/liquid contacting can be carried out, given transparency of the window material for the band range of interest [6], In some cases an inspection window made of silicon was used to allow observation of temperature changes caused by chemical reactions or physical interactions by an IR camera [4, 5]. 

Ohara, P.C. and Gelbart, W.M. (1998) Interplay between hole instability and nanoparticle array formation in ultrathin liquid films. Langmuir, 14 (12), 3418-3424. 

Sodium ignites in fluorine gas but is inert in the liquefied gas [1]. Cold sodium ignites in moist chlorine [2] but may be distilled unchanged in the dry gas [1]. Sodium and liquid bromine appear to be unreactive on prolonged contact [3], but mixtures may be detonated violently by mechanical shock [4]. Finely divided sodium luminesces in bromine vapour [1], Iodine bromide or iodine chloride react slowly with sodium, but mixtures will explode under a hammer-blow [1]. Interaction of iodine pentafluoride with solid sodium is initially vigorous, but soon slows with film-formation, while that with molten sodium is explosively violent... 

Our "superheated liquid-film concept" stands on the thermodynamic basis of (1) equilibrium shifts due to reactive separation under boiling and refluxing conditions and (2) irreversible processes of heat flows through the catalyst layer as well as bubble formation from the catalyst surface. 

---