Ultrasonic characterization of alumina/silicone-rubber composites for acoustical applications

Abstract

Silicone rubber has been used commonly as a material for an acoustic lens in medical ultrasonic probes. In order to achieve the desired properties for an acoustic lens, i.e., acoustic impedance close that of, and wave velocity lower than that of, human body, different materials have been considered as fillers or dopants to be dispersed in silicone rubber. A micromechanics-based analysis has revealed that silicone-rubber composites can have the desired acoustical properties with a certainamount of dispersed alumina particles. In this study, the ultrasonic wave propagation characteristics of alumina-particle-dispersed silicone-rubber composites fabricated with different particle concentrations and average particle radii were investigated experimentally. Namely, the velocity and attenuation coefficient of longitudinal wave in the alumina/silicone-rubber composites were evaluated at the frequency of 5 MHz by the spectral analysis of the reflected waves obtained in the immersion measurement. The experimental results have shown that the acoustic impedance and the wave velocity desired for an acoustic lens can be achieved by the alumina particle concentration as predicted by the micromechanics-based analysis. The influence of the particle radius on the acoustical properties of the composite has also been examined.