A novel coupling method for ultrasonic transducer based on pressureless sintering of nano-Ag

Abstract

The acoustic performance of ultrasonic transducer is directly determined by the coupling between the piezoelectric unit and the medium. At present, the coupling methods of the transducer are relatively single. In this work, a novel ultrasonic transducer coupling method based on pressureless sintering of nano-Ag is reported. The effects of sintering temperature on the micro-morphology and macro-porosity of nano-Ag sintered bulk (i.e. demoulded coupling layer) are systematically investigated. The transducers are design and fabricated by one-time pressureless sintering of nano-Ag paste. The influences of sintering temperature on acoustic performance of the transducers are analysed by experiments in detail. The results show that the number of the pores in the pressureless sintered bulk decrease with the sintering temperature, while the pores size gradually increase. From the perspective of acoustic impedance matching, silver materials have great advantages and universality as the coupling layer between most piezoelectric wafers and steel mediums. The coupling effect of sintered Ag could be improved by increasing the temperature. The best coupling effect could be obtained by sintering at 350 °C, at which the primary echo of the transducer has ideal waveform and bandwidth.

Keywords

• Coupling
• Nano-Ag
• Pressureless sintering
• Structural health monitoring (SHM)
• Ultrasonic transducer