Surface Chemical Effects Research Articles

The surface of Venus as revealed by the Venera landings: Part II

Observations of the panoramic photographs transmitted by Veneras 13 and 14 indicate that many visible rock units are layered and that at least a portion of the fine material could be the result of in situ geomorphic disintegration. Chemical and material property experiments indicate that the chemical composition of the material at the landing sites is essentially basaltic, that the bearing strength is minimal (a few kilograms per square centimetre, or a few hundred kilopascals), that the density is less than 1.5 g/cm 3 , that the porosity is very high (>50%), and that the electrical resistivity is very low ( The discussion on the possible geological nature of the surface of Venus presented in Part I (Florensky and others, 1977a) is extended in light of these new data. Six possible origins of the rock units were discussed: (1) surface lava extrusion; (2) igneous intrusion, later exposed by erosion; (3) pyroclastic fall; (4) impact ejection and lithification; (5) sedimentary deposits lithified at depth and later exposed by erosion; and (6) surface metamorphism due to unique Venusian surface conditions. It is concluded that, although none of the above hypotheses can be conclusively proven or disproven, hypothesis 6 is to be advanced to the forefront. This is suggested by (1) the low density and low bearing strength, (2) the presence of layering, (3) the possible presence of sedimentary structures in the rock units, such as cross-bedding and ripple marks, (4) the low electrical resistivity, which may indicate chemical alterations of surface material, and (5) the albedo of the loose, fine material, which is lower than the albedo of the rock units. This again suggests chemical alterations. Within the context of this hypothesis, the rock units are sedimentary or sedimentary-volcanic. Lithification occurred in the past due to surface chemical effects. The rock units, analogous with a similar terrestrial phenomenon, can be referred to as “duricrusts” (with the understanding that the Venusian process is completely different from the terrestrial process). Presently, the rock units are undergoing disintegration, indicating that changes have occurred in the surface conditions at the landing sites.

Clay intercalation catalysts interlayered with rhodium phosphine complexes. Surface effects on the hydrogenation and isomerization of 1-hexene

Clay intercalation catalysts formed by interlayering of Na +-hectorite with rhodium phosphine complexes of the type Rh(NBD)(PPh 3) 2 + and Rh(NBD)(dppe) +, where NBD = norbornadiene and dppe = 1,2-bis(diphenylphosphino)ethane, were examined as catalyst precursors for the hydrogenation-isomerization of 1-hexene in methanol. Relative to reaction under homogeneous solution conditions, the intercalated catalysts exhibit a much lower tendency to isomerize the substrate to the less reactive internal olefin 2-hexene. In the case of Rh(NBD)(PPh 3) 2 +-hectorite, the dramatic dependence of the hexane: 2-hexene product ratio on substrate concentration and water content indicates that the intrinsic Brønsted acidity of partially hydrated Na + ions in the clay interlayers causes the protonic equilibrium between surface intermediates responsible for the isomerization and hydrogenation pathways to be shifted in favor of hydrogenation. Rh(NBD)(dppe) +-hectorite also favors hydrogenation over isomerization relative to homogeneous solution. In this case, however, a catalytically important protonic equilibrium is not involved in the reaction mechanism, and the reaction is insensitive to factors which influence surface acidity. The results demonstrate that surface chemical effects can dramatically alter the catalytic properties of metal complexes immobilized in clay interlayers.

Are theoretical surface chemistry measurements really practical?

AbstractThe principles and concepts of surface chemistry can be of enormous aid in the application of surfactant chemicals to practical cleaning and foaming problems. The use of surfactants for foam stability was seen to be dependent on rheological properties of the foam (bulk and surface viscosity) and to the energetics of the adsorbed surfactant monolayer (area/surfactant molecule, monolayer clasticity modulus, rate of monolayer spreading and rate of surfactant adsorption into the interface). From these principles, an equation predicting foam volume in the presence or absence of soil was derived and found to be in good agreement with experiment. In detergency, the performance was dictated by the thermodynamic work of adhesion between the soil and substrate. The adhesion was a function of surface properties (soil/water interfacial tension and soil/water/substrate). The role of agitation in detergency was shown to be that energy which was needed to overcome the adhesive bond between soil and substrate. The implicit form of the agitation term was discussed (dependent on substrate configuration, agitator system geometry and mechanics) but not explicitly deduced. The role of interfacial tension was discussed in relation to foam stability and detergency. In both applications, low interfacial tension is beneficial to performance. However, because other surface chemical effects play a role in performance in detergency and foam stability, it was noted that interfacial tension is not the sole correlating parameter with performance. The situations in which low interfacial tension is not sufficient to give improved detergency and foam stability performance were delineated. A possible new method of aiding in optimizing oil/surfactant performance also was discussed. Finally, the role of micelles in detergency was examined in light of very recent experimental work which suggests that micelles may be detrimental to detergency and foam stability performance. This study suggests that surfactants which form mesomorphic phases with soil give better performance. Micelles, instead of solubilizing soil in their hydrophobic cores, are said to be competing with the mesomorphic phase formation process, thereby hindering detergency performance. It is suggested by the sheer weight of new theoretical and innovative approaches to surface chemistry applied to detergency and foam stability performance that “theoretical surface chemistry measurements really (are) practical!”

Corona discharge-induced surface chemical effects on II-VI compounds

Negative corona charging of CdS and ZnSe leads to a significant change in their surface composition. Utilizing x-ray photoelectron spectroscopy and Auger electron spectroscopy, it is found that the primary interaction occurs between oxygen and group-VI surface atoms. In contrast to other oxidation penomena, no oxygen bonded to group-II surface atoms is detected. The results demonstrate for the first time that the electronic processes involved in electrophotography are accompanied by significant and irreversible chemical reactions of the surface exposed to negative corona discharges.

Peel Strength of Silica Reinforced Natural Rubber-Polyethylene Laminates

Abstract The adhesion in silica reinforced natural rubber-polyethylene laminates, made by injection molding without an intermediate adhesive layer, has been examined by means of peel tests. The strength of adhesion was found to depend on the particle size of the silica and on the physical properties of the rubber samples. An influence of the magnitude of the coefficient of thermal expansion above the glass transition of the rubber samples on the adhesion strength was also noted, but surface chemical effects made little, if any, contribution to adhesion in these systems.

Preliminary Evaluation of a Modified Mueller-Hortig Geometry Negative Ion Source Using a Negative Ion Source Test Facility

A negative sputter-type ion source of the Mueller-Hortig geometry is described which utilizes a positive surface ionization source. Among the ion beams which have been produced are: A1-0.2 ?A; A10--3 ?A; Au--6 ?A; C--25 ?A; C2--20 ?A; Cl--100 ?A; Cu--0.5 ?A; CuO--0.8 ?A; F--40 ?A; I--26 ?A; 0--30 ?A; Pt--3 ?A; S--44 ?A; TaO2--2 ?A. The yields of Cl-, F-, O-, and S- produced from gaseous or high vapor pressure compounds are observed to be sensitively dependent on the metallic surface from which they are generated - indicating an intermediate surface chemical effect. While the source produces very intense beams of the halogens, sulfur, and oxygen and relatively intense beams of the metallic oxides, there appears to be a need for additional surface cesium to ensure maximum negative ion yields from many of the elemental materials.

Surface chemical effect of adsorbed water on quartz

Surface chemical effect of adsorbed water on quartz

The second law of thermodynamics for heterogeneous flow systems—I basic relations and the Curie theorem

The integral form of the second law of thermodynamics is developed for heterogeneous systems and from it are obtained the local forms for continuous phases and on the phase boundary. By combining these results with the corresponding forms of the first law and with valid thermodynamic intensive relations, expressions are obtained for the irreversible rates of increase of entropy for these cases. The irreversibility rate on the phase boundary is then analysed in detail in several equivalent variants and is found to consist of a sum of products of generalized driving forces and corresponding fluxes of the transport processes occurring there, i.e. surface chemical reaction, interphase energy and mass transfers and surface frictional effects. An analysis of this expression assuming that each flux is a linear homogeneous function of all the driving forces under conditions of cylindrical isotropy on the boundary shows that Curie's theorem is essentially fulfilled and that the basic inequality for the irreversible rate of production of entropy splits into several inequalities, one for each tensorial order of the transport processes. The cases of surface chemical reaction and surface frictional effects are analysed in some detail. The effect of shifts in entropy zero point values and the analysis of surface isotropy are presented in appendices.

The State of Metal Ion in Aqueous Solutions and its Surface Chemical Effects. III. Rheological Study for the Effect of Metal Ions on the Monolayer of Stearic Acid

Abstract The effect of metallic ions on the monolayer of stearic acid was studied by the rheologi-cal method. (1) It was shown that the development of visco-elastic property of the film is closely correlated with the formation of metal soap. Result obtained by the rheological measurement enables us to classify the metal ions into three groups; Li, Ca, Sr and Ba belong to the 1st, showing the formation of the condensed solid film and the rheological behavior of Voigt model; Th, Fe, Al, Co, Cu and Zn, the 2nd, exhibiting the formation of the expanded solid film and the rheological behavior of Maxwell model; Na, K, Rb and NH4, the 3rd, forming no solid film. These results were discussed in relation to the phenomena observed in the studies of the metal ion monolayer interaction, the adsorption of ion on the built-up film and the effect of ion on the wettability of a solid surface. These phenomena could be correlated with the formation of simple soap or complex metal ion-monolayer aggregate, the 1st and 3rd resulting in the former and the 2nd, in the latter. (2) It was frequently observed for the interacted film with the ions of the 2nd group that the area of solidification is larger than the limiting area estimated from the surface pressure-area curve, while in the case of the film with the ions of 1st group the values of both area coincide with each other. (3) It was shown that the monolayer of stearic acid, spread on the substrate containing ferric hydroxide sol, formed an expanded solid film. (4) It was shown for Co and Sr ions that the strength of interacted film is a measure of film-bound ion.

The State of Metal Ion in Aqueous Solutions and its Surface Chemical Effect. II. Uptake of Metal Ions from Aqueous Solutions by Stearic Acid Monolayer

Abstract It has been attempted to determine the binding ratio of strontium and cobalt atoms in the monolayer of stearic acid spread on aqueous strontium and cobalt solutions, respectively, containing radioactive cations. The number of strontium atoms bound to one molecule of stearic acid increased with increasing pH of substrate solution as well as concentration of strontium ion in it. Tentative explanation was made by assuming interaction between strontium and stearate ions. A theoretical formula based on ioniza-tions of stearic acid, strontium hydroxide, and strontium stearate proved to support the validity of this presumption. A similar explanation was also made for interaction between monolayer of stearic acid and substrate solution containing cobaltous chloride of pH less than 6.5, where the monolayer showed no expansion but rather a small condensation, while the number of bound Co atoms per one molecule of stearic acid increased with increasing pH up to 0.5. At pH 7–9, remarkably expanded and compressible films were obtained and the binding ratio reached a maximum value of unity. Films thus formed were considered to consist of stearate ions and polymer ions of cobalt which may exist as aggregates in the solution. Co-existing ammonia used as a pH-adjusting agent of the solution of cobaltous chloride resulted in exaggeration of these effects. It might be attributed to co-ordination of ammonia molecules towards Co atoms.

The State of Metal Ion in Aqueous Solutions and Its Surface Chemical Effects. I. Cobalt lon-Stearic Acid Monolayer Interaction

Abstract The presence of aggregates of cobalt ion in the alkaline solution of 10−3 mol./l. CoCl2 was shown by the measurement of self-diffusion coefficients. Large expansion and high rigidity of the stearic acid monolayer caused by cobalt ion in the alkaline solution were accounted for by the interaction of stearate ion in the monolayer with the aggregates of cobalt ion in the solution, resulting in the formation of two-dimensional network structure in the film. This idea was confirmed by the effect of aging of the substrate solution and also by the action of complex-forming agents such as ammonium oxalate and sodium citrate on the monolayer-ion interaction.