Showing papers in "Langmuir in 1987"

Morphology of flame-generated soot as determined by thermophoretic sampling

Abstract: Description de l'affinement de l'echantillonnage thermophoretique permettant une amelioration de la qualite des informations. Les mesures sont effectuees sur une flamme a diffusion d'ethylene laminaire et asymetrique

Use of nitrogen vs. carbon dioxide in the characterization of activated carbons

Abstract: Etudes de l'adsorption de N 2 (77 K) et de CO 2 (273 et 298 K) sur une serie de charbons actifs, ayant subi differents degres de calcination. Considerations sur la structure microporeuse

Structural analysis of soot agglomerates

Abstract: Etude de la structure des agglomerats de noir de carbone formes par combustion d'acetylene dans un bruleur a diffusion coannulaire

Aqueous biphase formation in polyethylene oxide-inorganic salt systems

Abstract: Diagramme de phase des systemes obtenus avec differents sels (formate, succinate, tartrate, citrate, phosphate, carbonate, sulfate et silicate de sodium, etc.)

Effects of the molecular structure of the interface and continuous phase on solubilization of water in water/oil microemulsions

Abstract: micellar solutions: one may be controlled by a chemorheological process involving actual breakdown and reformation of the entanglement network, presumably by scission and re-formation of the threadlike micelles themselves, and the other by disentanglement due to diffusion of the network chains but without accompanying their breakdown. An important feature of the type I11 behavior is that the mechanism is a single relaxation time process. This result suggests that the relaxation of the entanglement network of the micellar solutions in the type I11 region is due to a chemorheological process independent of the length of the threads rather than to a diffusional process highly dependent on the thread length. The peculiar dependence of 7, on CsCD-' of this chemorheological process of entanglement relaxation should reflect the stability of the threadlike micelles under the given environment. In the micellar solutions with CsCD-' above 1, the micelles are coexisting with excess Nasal. Therefore, scission and reformation of the micelles may happen rather easily by exchange of the CTAB units of the CTAB/NaSal complexes between the threadlike micelles a t the sites of entanglement, where the threadlike micelles can pass through each other with a certain characteristic time (T,,,) reflecting the rate of this process. Scission of the threadlike micelles may also take place, especially in the highly strained portions between entanglement points by the similar mechanism of exchange of the CTAB units with free Nasal molecules in the medium. Since the solubility of CTAB is rather low in the aqueous medium, the exchange rate must be higher; hence the relaxation time is shorter in solutions with a larger excess of Nasal. Although the detailed features of the dependence of 7, on CSCD-'~~ such as seen in Figure 6 cannot be adequately explained at the moment, the general tendency of the Cs and C D dependences of 7, and J,O may be interpreted as discussed above. The type I and type I1 behavior are the results of the onset of entanglement and the fully developed entanglement network as the threadlike micelles are formed with increasing C&-' up to the critical value of approximately 1. On the other hand, the type I11 (Maxwell model) behavior is the result of actual breakdown and re-formation of the entanglement network with the rate dependent on CsCD-1'2 but with the entanglement density being practically constant after CsCD-' exceeds the critical value.

Two-dimensional reaction solvents: surfactant bilayers in the formation of ultrathin films

Abstract: Adsorption d'agent de surface sur de l'alumine. Formation d'«admicelles» suivie d'«adsolubilisation» du styrene dans la couche bimoleculaire. Polymerisation radicalaire du styrene en couches ultraminces

SORPTION AND PACKING OF n-ALKANE MOLECULES IN ZSM-5.

Abstract: Etude de l'adsorption de l'ethane, du propane, de l'hexane et du butane sur la zeolite ZSM-5

Marangoni effects in the spreading of liquid mixtures on a solid

Abstract: The spreading of binary liquid mixtures on Pyrex glass was experimentally studied, qualitatively and quantitatively, for a large number of liquids. The mixtures were classified according to the spreading behavior of the individual components and according to the expected direction of the Marangoni flow, which may be induced by the differences in volatilities and surface tensions between the components. The general trends of the results agree with previously reported data for other solid surfaces. The quantitative measurements led to novel conclusions regarding the rates of spreading of mixtures. Binary mixtures of completely spreading components spread faster than the individual components when the Marangoni flow is expected to coincide with the spreading direction. Spreading of such mixtures is delayed or arrested when the Marangoni flow is expected to oppose spreading, until a sufficient amount of the volatile component evaporates. The spreading rate of mixtures of only one completely spreading component may be insensitive to concentration when the Marangoni flow compensates for a decreased tendency for spreading. Many mixtures of two incompletely spreading components exhibit complete spreading when the Marangoni flow is expected to be in the direction of spreading. The effect of the component concentration is unsymmetric. Small concentrations of the less volatile component induce complete spreading of the mixture, while relatively high concentrations of the volatile liquid are required for the same purpose.

In situ determination of species adsorbed at a solid-liquid interface by quantitative infrared attenuated total reflectance spectrophotometry

Abstract: Donnees theoriques et cas de l'adsorption du chlorure de cetylpyridinium sur de la poudre de seleniure de zinc

Interactions of diatomic molecules with graphite

Abstract: Etude de l'adsorption de CO, O 2 et N 2 sur du graphite, et des interactions existantes en fonction de la temperature