The process of equilibration of the tetradecane-water interface in the presence of sodium hexadecane-benzene sulfonate is studied using intensive atomistic molecular dynamics simulations. Starting as an initial point with all of the surfactants at the interface, it is obtained that the equilibration time of the interface (several microseconds) is orders of magnitude higher than previously reported simulated times. There is strong evidence that this slow equilibration process is due to the aggregation of surfactants molecules on the interface. To determine this fact, temporal evolution of interfacial tension and interfacial formation energy are studied and their temporal variations are correlated with cluster formation. To study cluster evolution, the mean cluster size and the probability that a molecule of surfactant chosen at random is free are obtained as a function of time. Cluster size distribution is estimated, and it is observed that some of the molecules remain free, whereas the rest agglomerate. Additionally, the temporal evolution of the interfacial thickness and the structure of the surfactant molecules on the interface are studied. It is observed how this structure depends on whether the molecules agglomerate or not.

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The synergism of mixtures of anionic and non-ionic surfactants adsorbed at the water/alkane interface was studied using mesoscopic Dissipative Particle Dynamic simulations. The effect of the mixtures of sodium m, p-exylbenzenesulfonate and sodium m, p-octylbenzenesulfonate with the nonionic surfactant lauryl alcohol polyoxyethylene (9) ether on the surface tension of the water/alkane interface was explored. Alkane scanning curves for n-alkanes from hexane to tetradecane are reported. Our results suggest that dissolution of lauryl alcohol polyoxyethylene (9) ether in the hydrocarbon phase is the origin of this behavior. For the sodium m, p-octylbenzenesulfonate case, the mixture with lauryl alcohol polyoxyethylene (9) ether induces a synergism for alkanes with low carbon number. A moderate lipophilic behavior of the mixture was observed for hexane and as a result 95% of the mixture stays at the interface forming a really compact layer at the interface. Additionally, increase on the carbon number alkane produces an increase in the hydrophilic behavior of lauryl alcohol polyoxyethylene (9) ether inducing higher interfacial tension values.

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Raman spectroscopic studies were performed to identify the nature of the carboncontaining phases in nano-(ZrC,ZrO2)/C composites. The nano-ZrO2/C composites were prepared in a tube furnace by heat-treatment of zirconium-loaded sulfonated styrenedivinylbenzene resins between 1000 and 1400 °C. The plasma processing of a nano-ZrO2/C sample in inert or reducing atmosphere resulted in nano-(ZrC,ZrO2)/C composites. The Raman spectra of the nano-ZrO2/C samples show that the ratio of the amorphous carbon / graphitic components decreases, whereas the fraction of distorted graphite structures increases with increasing reaction temperature and time. This can be attributed to the formation of new graphene edges by the condensation of the polyene content in the amorphous carbon. The ratio of the amorphous carbon practically does not change if the plasma treatment was performed under inert (Ar+He) atmosphere. In contrast, under reducing (Ar+H2) atmosphere, the amorphous carbon almost completely crystallizes into graphite. The ratio of the defective / regular graphite structures and the change of the thickness or separation of the graphene (monolayer carbon) sheets are higher under inert than reducing plasma conditions. We found no catalytic effect of ZrC on the graphite crystallization under inert plasma conditions, but in the presence of H2, ZrC may catalyze the graphitization process. Raman studies on … Raman studies on … Raman studies on … Raman studies on … nanosized nanosized nanosized nanosized----ZrO ZrO ZrO ZrO2 2 2 2/ / / /C C C C and nanosized and nanosized and nanosized and nanosized----( ( ( (ZrC ZrC ZrC ZrC, , , , ZrO ZrO ZrO ZrO2 2 2 2)/ )/ )/