摘要:

In this work we describe the stability of positively charged polystyrene particles dispersed in aqueous binary mixtures (50% v/v) of methanol, ethanol, 1-propanol and 2-propanol. Rate constants for rapid coagulation are found to be 20-50% of those predicted by the Smoluchowski theory. The dependence of W (stability factor) on ionic strength and liquid composition has been compared with the predictions of DLVO theory.

ISSN:0193-2691    

DOI:10.1080/01932699408943540

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Hydrolysis and condensation of monomolecular alkyloxysilane films by the Langmuir technique is presented. Octadecyltrimethoxysilane formed monolayers on aqueous subphases with different properties depending on the bulk pH. At pH 1 a solid condensed film was directly formed with a molecular area of 23 Å2and a surface pressure/surface area variation similar to that on non-ionized stearic acid. At pH 5.6 and 11 several phase transitions were observed during the compression of the monolayer with a final collapse at a molecular area of 20 Å2. Relaxation measurements confirmed the stability of the films for longer than 12 hours at different surface pressures below a critical value.

ISSN:0193-2691    

DOI:10.1080/01932699408943541

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Using earlier results, as well as our own experiments, we have shown the existence of an optimum frequency in a demulsification process utilizing an AC electric field. Within a frequency range of 20 Ha to 100KHz we have determined voltage curves with different insulation and emulsions, these demonstrate why demulsification by means of an AC field is more efficient than that of a DC field. By analyzing the data obtained in measurement of dielectric properties of the system, we found that fmis about the same ofomegap instead of fp. To go Into it seriously, we concluded that the optimum condition is Tm=Tp, at which resonance occurs in the system and hence it promotes coalescence.

ISSN:0193-2691    

DOI:10.1080/01932699408943542

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Silica nanoparticles have been synthesized in AOT/decane/ammorium hydroxide reverse microemulsions via-base-catalyzed hydrolysis of tetraethoxysilano (TEOS). The effect of inter-micellar exchange has been investigated by conducting the synthesis experiments in the presence of benzyl alcohol (BA), an additive which is known to act as a cosurfactant at the water/oil interface, increasing the inter-micellar exchange rates. Larger, more monodisperse particles are formed at higher benzyl alcohol concentrations. Furthermore, the presence of high concentrations of benzyl alcohol (BA/AOT molar ratios larger than 1.5) promotes phase separation, probably due to the combined effects of the high benzyl alcohol content and the presence of ethanol (a product of the TEOS hydrolysis reaction). The effects of benzyl alcohol concentration on particle size and size distribution have been attributed to the inhibition of nucleation by fast rearrangement of hydrolyzed TEOS species.

ISSN:0193-2691    

DOI:10.1080/01932699408943543

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The micellar solution of two cationic surfactants cetyltrimethyl-ammonium bromide (CTAB) and tetradecyltrimethylammonium bromide (TTAB) mixtures was investigated. Their miscibility was determined by measuring the surface tension of the aqueous solution of the mixtures at variable composition.

ISSN:0193-2691    

DOI:10.1080/01932699408943544

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Submicron organic particles are produced by precipitation in an emulsion. The poorly water soluble organic substance is dissolved in a non-polar solvent. This solution is dispersed in an aqueous phase in the presence of emulsifier. When the non-polar solvent is removed by evaporation, the organic substance precipitates and one particle is formed in each emulsion droplet. Experimental work are here reported on the rate and the influence of the evaporation rate on the formation of cholesteryl acetate particles. An introductory theoretical analysis of the conditions experienced by each droplet during the evaporation is given.

ISSN:0193-2691    

DOI:10.1080/01932699408943545

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

ISSN:0193-2691    

DOI:10.1080/01932699408943546

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

ISSN:0193-2691    

DOI:10.1080/01932699408943547

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor