Controllable acoustic properties of tungsten-epoxy composites prepared using a shaker-type ball milling process

Abstract

Tungsten-epoxy composites are often applied as backing layer substrates in piezoelectric-based ultrasonic transducers. Control of its acoustic impedance is crucial to customize the specifications of fabricated ultrasonic transducers, especially for biomedical transducers that necessitate low acoustic impedance (<10 Mrayl). This study investigates the influences of the tungsten-to-epoxy loading ratio on its composite acoustic impedance, which the preparation using a ball milling method with different tungsten-epoxy weight ratios of 1:1 to 10:1 and a uniform particle size of 1 μm. Important acoustic parameters such as phase velocity, acoustical impedance, and damping were evaluated. The results show a clear correlation between the weight ratio of tungsten to epoxy and the acoustic behavior of the composites. As the weight ratio increased from 1:1 to 10:1, the phase velocity and acoustic impedance steadily decreased from 2200 to 1400 m/s and 8.31 to 2.30 Mrayl, respectively. At the same time, the composites showed a gradual increase in damping with increasing weight ratios. These results underscore the significant influence of tungsten particle loading on the acoustic properties of tungsten-epoxy composites. In summary, tungsten-epoxy composite acoustic impedance below 10 Mrayl is tunable by controlling tungsten particle contents in the epoxy matrix, facilitated by the application of a ball milling technique that results in tungsten-epoxy composites that meet the criteria for an effective backing layer in piezoelectric ultrasonic transducers. This study underscores the potential to improve the acoustic properties of these composites by precisely tuning the weight ratio, thereby contributing to the development of superior composites for ultrasound.