Research On Acoustic Impedance Gradient Materials And Its Application In Ultrasonic Probe

Since the concept of functionally gradient materials was put forward, it became one of the key study field in material science. Especially in terms of acoustic materials, such as under water acoustic absorption material, wave-absorbing material, functionally gradient materials had got very ideal research achievement. Numerous studies showed that the materials, whose acoustic impedance is continuous and gradient changed, can significantly improve the effect of acoustic impedance matching on the heterogeneous interface, leading to more acoustic wave getting into the interior of the material and doing energy attenuation. Compared with the traditional homogeneous materials, acoustic impedance gradient materials had better properties of acoustic impedance matching and sound absorption.Ultrasonic testing technology is one of the most widely used non-destructive testing technology in the industry, lots of research are also focused on ultrasonic testing. In fact, the testing process is completed by a variety of ultrasonic testing equipments, while ultrasonic probe is one of the most critical. Usually an ultrasonic probe consists of piezoelectric crystal plate, protective film, wedge, backing, tuning coil and cable conductor. The studies of ultrasonic probes are mainly about the above aspects.Based on the previous study, we improved and optimized the process of preparing acoustic impedance gradient materials by coated particles sedimentation method. Based on study results of powder properties(density and particle size), phenolic resin content, it achieved to quantitatively control the end face acoustic impedance of the material. Sedimentation fluid viscosity’s effect on properties and structure of prepared acoustic impedance gradient materials are also studied. In order to test the effect of impedance matching and absorption, the gradient materials is applied to the ultrasonic probe as backing structure. By connecting the matching circuit, we explored the of ultrasonic probe trial process, analyzed the effect of adhesive backing and matching circuit on performance of the ultrasonic probe, and the trial ultrasonic probe were compared with domestic commercial probe.The results show that the preparation process of gradient materials described in this paper is feasible and stable, and this method has the characteristics of large acoustic impedance gradient range and quantitatively controllable of acoustic impedance in end face. Meanwhile, the results of scanning electron microscopy prove that gradient materials prepared by this process have internal high density and less porosity. Moreover, within certain range, the higher the viscosity of the liquid sedimentation, the more desirable gradient effect of sample particles inside and it has the best value for the sedimentation. Powder characteristics and resin content have a great effect on the acoustic impedance. By adjusting the experimental parameters, the gradient materials can meet technical requirements of the ultrasonic probe backing. After connecting matching circuit, the trial production ultrasonic probe can satisfy to actual detect level, part of the performance parameters are superior to domestic commercial probe. However to achieve better results, it needs further research and optimization of process.