Influence Of Surface-active Substances Research Articles

Surface effects in micromachining of metals and alloys

Surface effects play an important role in micromachining. Decrease in the metal surface tension under the influence of surface active substances causes the surface to weaken as a barrier and the shear stress and cutting energy to decrease. The effect may be doubled when a bias potential is applied to the test piece. Results obtained from three different materials are presented here. The phenomenon is noticeable when cutting at depths less than 70 μm. The lesser the microcutting depth, the greater is this effect.

Influence of surface-active substances on pertraction of cobalt(II) cations through bulk and emulsion liquid membranes

Pertraction of Co 2+ by di (2-ethylhexyl)phosphoric acid (D2EHPA) in bulk and emulsion liquid membrane systems containing various emulsifiers and surface-active substances has been studied. If no emulsifier was present in a bulk membrane system, initial flux of Co 2+ cations through the feed-membrane solutions interface ( J Fo) was more than six times higher than flux through the stripping-membrane solutions interface ( J Ro), thus the stripping process was much slower than the extraction process. All emulsifiers studied decelerated initial fluxes of Co 2+ ( J Fo and J Ro). Fluxes decreased much more in the presence of polyamine based emulsifiers compared to sorbitan mono-oleate (Span 80), due to more condensed adsorption films created by polyamines at the interfaces. In the presence of polyamines, J Ro decreased more than J Fo and it may indicate that due to larger geometrical dimensions of the Co-D2EHPA complex, its diffusion through a condensed polyamine film was much slower than diffusion of the dimer of protonized D2EHPA. An addition of alkylphenol sulphides to the membrane solution containing polyamine ECA 4360-III accelerated cobalt pertraction ( J Ro). Fluxes were strongly influenced by unknown substances (impurities) present in emulsifiers. Experiments with the emulsion membranes confirmed differences in pertraction found in the bulk membranes systems.

Turbulent flows of solutions of surface-active substances

Not only polymers, but also some surface-active substances have the capacity to reduce the hydrodynamic resistance in the turbulent regime of a fluid. From the point of view of stability against mechanical destruction, the addition of surface-active substances has certain advantages over polymers; in particular, they are capable of recovering their hydrodynamic effectiveness having passed through pumps and local points of resistance [1]. The basic possibility of reducing drag by the addition of surface-active substances was demonstrated in [2–6]. It was later shown that a reduction in the drag of liquids could be achieved only by micelle-forming surface-active substances [5, 7], in solutions of which spherical and platelike micelles, respectively, are formed at the critical concentrationsCm1 andCm2 for micelle formation. The values ofCm1 andCm2 depend both on the molecular structure of the surface-active substances as well as on external factors such as the temperature, the presence in the solution of electrolytes, polar organic substances, and so forth. The connection established in [5, 7] between the reduction in the drag and the value ofCm2 suggests that the reduction in the turbulent friction will also depend on the above factors. It is therefore possible to control processes of turbulent transfer in a fluid as well as the drag. However, this possibility has not been sufficiently studied. In [1–7], the influence of surface-active substances on the drag was investigated. First data on the velocity profiles in solutions of surface-active substances were given in [9, 10]; they are not sufficiently complete. In the present work, we made measurements of the velocity profiles and the turbulence intensity in solutions of surfaceactive substances, and we have calculated the generation of turbulence energy and the dissipation of the energy of the averaged motion. We have studied the influence of electrolytes and the temperature on the reduction in the drag and give the results of full-scale experiments.

Some trends in the influence of surface-active substances on electrode processes

Suggestions for the origin of an additional energy barrier during discharge at high degrees of surface coverage with an adsorbate are expounded. The influence of pH and background anions on the rate of inhibited electrode reactions is discussed. The effects of the inhibition of electrode processes by the adsorption of complexes of reacting ions with addition agents are considered. The main trends in the action of various classes of surface-active substances and their effect on the kinetics of electroreduction of metal ions and technological characteristics of electrocrystallization processes (current efficiency, diffusibility, the structure of cathodic deposits and others) are discussed. The main principles in choosing surface-active substances and background anions for the electrodeposition of metals in electroplating and hydroelectrometallurgy are formulated.

Liquid-liquid interfaces as potentiometric ion-sensors—I: The n-butanol-water interface as indicating sensor for the potentiometric titration of some acids and bases

The property that liquid-liquid interfaces modify their electrical charge as a function of the composition of the two phases in contact has been used to detect the end-points in a series of acid-base titrations in the aqueous phase. Although the titration curves are not classical in shape, the equivalence points can be located if the solutions are not too dilute. Good results for concentrations down to 10 −3 N have been obtained. The electrode has a fast response. The influence of surface-active substances on the titration has also been investigated.

Influence of Surface Active Substances and Preparation Conditions on the Properties of AgI

Influence of Surface Active Substances and Preparation Conditions on the Properties of AgI

Influence of surface-active substances on fine milling of quartzite

Surface-active substances accelerate fine milling of quartzite appreciably in a periodic-action ball mill.

The wear of oxide ceramics under the influence of surface-active substances. (in German) : B. Frisch, Ber. Deut. Keram. Ges., 44 (1967) 584–591; 12 figs., 31 refs.

The wear of oxide ceramics under the influence of surface-active substances. (in German) : B. Frisch, Ber. Deut. Keram. Ges., 44 (1967) 584–591; 12 figs., 31 refs.

The influence of surface active substances on alveolar mechanics in the respiratory distress syndrome.

The influence of surface active substances on alveolar mechanics in the respiratory distress syndrome.

Influence of surface-active substances on the evaporation of fine water drops

1. A method was developed and the possibility of studying the rate of evaporation of small individual drops, which show a decrease in radius from 3–4 to 1μ during evaporation, was demonstrated. 2. Comparative experiments were conducted on the influence of certain relatively nonvolatile surface-active substances in various concentrations upon the rate of evaporation of water drops. 3. The presence of surface-active substances slows down the evaporation of water drops substantially more than that calculated according to the decrease in the vapor tension above the solutions according to Raoult's law for the same concentrations. 4. It was hypothesized that the deceleration of the evaporation of drops is a consequence of a change in the coefficient of evaporation on account of coating of the drop with a monolayer of the surface-active substance.

The inhibiting effect of foreign particles in the electrodeposition of nickel

1. The dependence of the overvoltage upon the pH of the solution in the electrodeposition of nickel from a sulfate solution passes through a maximum and is related to the redistribution of the rates of liberation of nickel and hydrogen. 2. At high temperatures (180°), the current yield of nickel is 100%, and the overvoltage does not depend upon the pH of the solution. 3. The influence of surface-active substances (thiourea) upon the overvoltage and quality of the precipitates, observed at low temperatures, is absent at high temperatures. 4. It is hypothesized that the cause of the high polarization of nickel is the adsorption of foreign substances upon the electrode surface during electrolysis.

Influence of surface-active substances on depolarization kinetics

The previously described “depolarization kinetics” is being used for studying the surface activity of surfactants. The surface activity of a few pH Depolarization kinetics has been used for studying the surface activity of a few surfactants. The rate of depolarization is enhanced (time for first an

The influence of surface‐active substances on the growth of acid‐fast bacteria

The influence of surface‐active substances on the growth of acid‐fast bacteria

Solvation in Dispersed Systems. XII. Influence of Surface-Active Substances on the Structure of Rubber Fractions

Abstract We have previously shown that the addition of nitrogen-containing compounds to sols of butadiene polymers results in the development of colloidal structures. To explain the mechanism of this action, the effect of adding similar compounds to fractions of crude rubber of varying degrees of aggregation was studied. These active substances, when dissolved either in low molecular weight fractions of the polymer or in a mutual dispersing medium, become adsorbed on the rubber micelles, change the equilibrium between the fractions, and modify the properties of the colloid. The molecular nature of the dispersing medium has a marked effect on the interaction between the polymer and the active substances. The data obtained by us are shown in Table I.

On the influence of surface active substances upon the imbibition of plant tissues

On the influence of surface active substances upon the imbibition of plant tissues

The effect of surface active substances on the diffusion of water through membranes

According to the investigations of Jacques Loeb, the diffusion of water through membranes is a linear function of the solute, as would be expected according to the law of van't Hoff, only if the concentration of the salt solution is greater than M/16. In lesser concentrations than this the so-called “initial rate” of diffusion is represented by a curve having a maximum corresponding to a concentration varying from M/512 to M/256. If the concentration becomes greater the rate of diffusion decreases until a concentration of M/16 is reached. The experiments of Loeb, and of Bethe and Toropoff seem to indicate the identity of electro-osmosis and free osmosis in low concentrations, and in this way furnish the explanation of the influence of electrolytes on the rate of diffusion by the difference of effect of the ions on the quantity of charge on the Helmholtz double layer on the capillary walls. Grumbach has shown that surface active substances exert an influence on capillary electric forces and consequently on the diffusion potential. Our own investigations are concerned with the influence of surface active substances on the capillary kinetic phenomena. Collodion sacs of 50 cc. capacity were attached to upright manometer tubes of 2 mm. diameter. The sacs were made on the inside of a 50 cc. Erlenmeyer flask, coated twice with 4 per cent collodion, and dried for one-half hour after the first coating, and 4 to 5 hours after the second. The sacs were filled with electrolytes of M/32 concentration immersed in distilled water. In the case of a given electrolyte the manometer readings obtained with different sacs were relatively constant. Having established the normal rate of diffusion, the sacs were treated by filling them with solutions of surface active substances.