Novel Nanocomposite Materials for Improving Passive Layers in Air-coupled Ultrasonic Transducer Applications

Recent research has focused on developing air-coupled transducers for use in industrial flow measurement applications. Optimal performance of ultrasonic transducers is only achieved with maximum energy transfer. Unfortunately, the significant acoustic impedance mismatch between the active layer and the load medium (i.e. air) in sensors reduces considerably the effective ultrasonic energy transmission and reception, with most of the energy reflected at the interface. Improved matching layers with an appropriate acoustic impedance and attenuation coefficient as low as possible can significantly improve the power efficiency and sensitivity of devices, decreasing energy loss by scattering. The aim of this research is to evaluate novel acoustic materials for use in a new ultrasonic transducer assembly process involving cost effective advanced manufacturing methods. More efficient and consistent signal shapes could be achieved by substituting current matching layers (e.g. syntactic foams) with new materials. Nanocomposite foams can be obtained via cost effective extrusion/moulding processes where microbubbles are formed inside the polymer when heated above a certain temperature. The reduction in density affects acoustic impedence, ultimately creating light passive layers for ultrasonic applications manufacturable in high volumes.