Passive materials for high frequency piezocomposite ultrasonic transducers

High frequency ultrasound is receiving increased attention for medical imaging in areas such as ophthalmology and dermatology. Recent advances in the manufacture of fine scale piezocomposite materials mean there is great potential for commercial transducers far superior to conventional devices currently in clinical use. \nThis Thesis reports the fabrication and characterisation of passive materials suitable for use in high frequency piezocomposite transducer devices. Epoxy composites have been fabricated using tungsten and alumina as filler material with volume fractions up to 0.4. Acoustic impedance and attenuation has been determined for different filler volume fractions to provide data for modelling to aid transducer design and also determine the filler volume fraction required to provide optimal results. Acoustic impedance values of 3-15MRayl were measured for the materials made in this work and the influence of filler particle size and shape is also discussed. \nPiezocomposite transducers have been constructed using material developed in this work and compared to devices made with more conventional passive materials. In addition to the fabrication of the composite samples for characterisation a process for incorporating material into transducers is described showing how the fabrication can be a part of the transducer construction resulting in an efficient and neat package.