High frequency properties of passive materials for ultrasonic transducers

The acoustic properties of passive materials for ultrasonic transducers hav e been measured at room temperature in the frequency range from 25 to 65 MH z using ultrasonic spectroscopy. These materials include alumina/EPO-TEK 30 1 composites and tungsten/EPO-TEK 301 composites. Experimental results show ed that the acoustic impedance of the composites monotonically increased wi th the volume fraction of the particle filler, which is in agreement with t he Denavey model. The attenuation, however, peaked between 7 and 9% volume fraction of particle filler. Far comparison, several other passive material s were also fabricated and measured. The results suggest that materials tha t possess a higher attenuation also appear to have a larger velocity disper sion.