Experimental Study of Sound Attenuation in Quasi-Monodisperse Emulsions

Very narrow size distribution oil-in-water emulsions have been prepared by using a recently proposed selective creaming method. The emulsions have been characterized by static and dynamic light scattering measurements. The ultrasonic absorption of the emulsions has been measured with an acoustic interferometer at frequencies between 0.5 and 10 MHz for a wide range of concentrations and droplets sizes. The comparison of the experimental results with existing theories shows an excellent agreement at oil volume fractions up to 0.15. The discrepancy between theory and experiments observed at higher volume fractions is attributed to thermal interactions between droplets for which a semi-quantitative model is proposed. Rdsumd. Des 6mulsions d'huile dans l'eau pr6sentant une distribution en taille trbs 6troite ont 6t6 pr6par6es gr£ce h une m6thode r6cemment propos6e, fondle sur le cr6mage s61ectif des gouttelettes. Ces 6mulsions ont 6t6 caract6ris6es par diffusion statique et dynamique de la lumibre. L'abiorption ultrasonore des 6mulsions a 6t6 mesur6e h l'aide d'un interf6rombtre acous- tique h des fr6quences comprises entre 0,5 et 10 MHz pour une large gamme de concentrations et de dimensions des gouttelettes. L'accord des rdsultats expdrimentaux avec les thdories existantes est excellent pour les fractions volumiques en huile infdrieures h IS ~. L'dcart entre thdorie et expdrience qui apparait aux fractions volumiques plus dlevdes est attribud aux interactions thermiques entre gouttelettes, pour lesquelles un modAle semi-quantitatif est proposd.