Pb/EPOXY Acoustic Impedance Gradient Composite Material Preparation And Acoustic Properties Research

Ultrasound is widely used in military,defense,medical and daily life.Ultrasonic transducer is the main device for producing and receiving ultrasonic wave.In the design and production of ultrasonic transducer,in order to improve the efficiency of launch ultrasonic wave,ultrasonic transducer need matching layer between acoustic emission materials and acoustic load,to meet the demand of the acoustic impedance matching.The materials used to make the matching layer are mainly tungsten(W)or alumina(Al2O3)powder for packing as composite materials.However,the matching layer with W as filler has higher cost,and the range of acoustic impedance of the matching layer with Al2O3 is smaller.In order to overcome the shortcoming of the two common packing,this paper chooses lead powder(Pb)as filler prepared by acoustic impedance gradient composite material because the price is relatively cheap,to meet the demand of the gradient matching layer and the characterization of the acoustic characteristics of Pb matching layer.Because the centrifugal force will be influenced by the kinds and the particle size of the packing,in this paper,the optimization selection is 2 microns particle size of tungsten powder and 5 microns of lead powder as a filler within epoxy resin as matrix,and the 0 to 3 acoustic impedance gradient composites is prepared by the centrifugal method.The effects of particle size and type of packing on the distribution of centrifugal filler in the base are analyzed.The packing gradient distribution of Pb matching layer and W matching layer was measured under different centrifugal parameters.The relation between the density of Pb matching layer and volume ratio is given.The longitudinal wave acoustic characteristics of Pb composites prepared by different centrifugal conditions are measured,and the changes of longitudinal velocity and acoustic impedance are given.The range of longitudinal wave velocity is between 1600 and 2500 m/s.The range of wave acoustic impedance is 4~11 Mrayl.The transverse wave velocity of Pb composites was measured by pulse echo method,and the variation of the transverse wave velocity with volume fraction was obtained,and the transverse wave velocity variation range of Pb matching layer was 700 ~900 m/s.The variation of acoustic impedance with Pb volume fraction in different centrifugal parameters is characterized,and the influence of centrifugal parameters on acoustic impedance distribution is analyzed.The variation range of the wave acoustic impedance is 1~5 MRayl.Use of ultrasonic wave in the interface mode conversion method,based on fast Fourier transform to the collected signals,acoustic attenuation of shear wave is calculated,and analyzes the shear-wave acoustic attenuation law along with the change of Pb volume fraction.In the paper,we prepare the Pb gradient composites for high performance ultrasonic transducer and give the optimum preparation.The relation between volume fraction of Pb and density(acoustic velocity? acoustic impedance and acoustic attenuation of longitudinal wave and transverse wave).We find that the Pb gradient composites are the optimum gradient matching layer of ultrasonic transducer.