Research On Preparation Of Acoustic Materials Based On 3D Printing Technology

Ultrasonic transducer,as the carrier of ultrasonic transmission,reception,and conversion between ultrasonic and electrical signals,is the core device in the ultrasonic imaging and detection system.In order to improve the performance parameters such as the bandwidth and sensitivity of the ultrasonic transducer,in addition to optimizing the electrical properties of the piezoelectric layer,the design of passive acoustic functional materials such as matching layer and backing layer also play an important role in improving the performance of the ultrasonic transducer.The piezoelectric layer usually does not match the acoustic impedance of the propagation medium(such as tissue,air and water),resulting in low acoustic energy transmission efficiency,thereby reducing the sensitivity and bandwidth of the ultrasonic transducer.The matching layer has the characteristics of high sound energy transmission,which can effectively solve the problem of low sound energy transmission efficiency.The backing layer is used to absorb the ultrasonic waves propagating backward from the piezoelectric layer,thereby increasing the bandwidth of the ultrasonic transducer.Therefore,the design of acoustic materials such as matching layer and backing layer has become a research hotspot in this field in recent years.The 3D printing technology has the characteristics of fast forming,high precision and moldless forming,which has been gradually applied in the manufacturing field.In this subject,in order to improve the performance of the ultrasonic transducer,simplify the manufacturing process of the matching layer and the backing layer,the preparation of acoustic materials such as matching layer and backing layer by light curing technology are studied in the following three aspects:(1)Alumina/low viscosity photosensitive resin matching layer.Determine the technical parameters of light curing molding and study the influence of alumina volume fraction(5-25%)on the performance parameters of the matching layer.When the volume fraction of alumina increases,the density of alumina/photosensitive resin also increases,showing a linear proportional relationship,and the change range is 1.25?1.86 g/cm~3.The density of alumina(3.98 g/cm~3)is higher than that of photosensitive resin(1.14 g/cm~3),so the density of matching layer increases with the volume fraction of alumina.The sound velocity decreases first and then increases,and the range is 2410?2650 m/s.When the volume fraction of alumina is 15%,the minimum value is 2410 m/s.The acoustic impedance is increasing,and its variation range is 3.15?4.93 MRaly.The acoustic impedance is determined by the density mainly because the sound velocity of the matching layer does not change obviously.Therefore,the change rule of acoustic impedance is consistent with the change rule of density,showing a linear proportional relationship.The acoustic attenuation coefficient first increases and then decreases,and the variation range is 2.54?3.59 dB/mm.When the volume fraction of alumina is 15%,the maximum value is 3.59 dB/mm.(2)Ferroalloy/high viscosity photosensitive resin backing.The backing layers with different volume fractions of ferroalloys(5-25%)were prepared by light-curing molding technology,and the changing laws of the performance parameters of the backing layer were studied.With the increase of the volume fraction of ferroalloy,the density of ferroalloy/photosensitive resin increases linearly with the range of 1.86?2.54 g/cm~3.The speed of sound presents a rule of change that first increases,then decreases,and then increases,and the overall trend is downward,with a range of change from 1762 to 2080 m/s.The acoustic impedance has a linear proportional relationship with a range of 3.75?4.60MRayl.The sound attenuation coefficient presents a changing law that first increases,then decreases and then increases,with an overall upward trend,and its variation range is 4.55?8.63 dB/mm.PiezoCAD was used to simulate the prepared alumina/photosensitive resin matching layer and ferroalloy/photosensitive resin backing layer to study its influence on the PZT-5H ultrasonic transducer with a center frequency of 2.5 MHz.Compared with the ultrasonic transducer without matching layer,the bandwidth of the alumina/photosensitive resin matching layer transducer has been increased from 25.86%to 44.02%.The backing layer was replaced with a backing layer with a ferroalloy volume fraction of 25%for simulation.The bandwidth of the ultrasonic transducer is increased from 44.02%to 55.19%.(3)The samples with through hole(diameter:0.8 mm;spacing:1.2 mm)and conical structure(bottom radius:0.4 mm,height:1.3 mm)were printed by UV curing technology.Study the influence of different fillers on its acoustic performance.The results show that the acoustic attenuation coefficient of tungsten powder photosensitive resin with through-hole structure is increased by 7.18 dB/mm from 3.93 dB/mm compared with that of tungsten powder/photosensitive resin without through-hole structure.The cone-shaped samples were prepared by light-curing molding technology,and the cone-shaped samples were filled with70%silver powder/epoxy resin by centrifugation.Compared with the silver powder/epoxy resin sample prepared by centrifugal method,the sound attenuation coefficient of the conical silver powder/epoxy resin sample decreased from 8.9 dB/mm to 7.6 dB/mm.