A method for preparing a low-density ultrasonic transducer backing based on thermal expansion

Abstract

The present invention provides a method for preparing a low-density ultrasonic transducer backing based on thermal expansion, the process of which is as follows: 1. Evenly mix the epoxy resin, curing agent and hollow microspheres before curing to obtain a mixed fluid. The hollow microspheres are made of polymer materials. 2. Add the mixed fluid obtained in step 1 to a soft mold that is pressurized and can expand, and heat and cure it at 60°C to 80°C to obtain an ultrasonic transducer backing. The present invention uses a soft mold expansion method to utilize the heating expansion of hollow microspheres during the epoxy resin curing process to occupy the reserved space in the soft mold, and after filling the soft mold, it pushes the soft mold and epoxy resin to expand together, thereby breaking through the density bottleneck of traditional preparation schemes and greatly reducing the density of the transducer backing. In addition, the present invention forms a dense porous structure inside the transducer backing through the expansion of hollow microspheres, which reduces the density while increasing the sound attenuation coefficient of the transducer backing.

Description

Technical Field

[0001] The invention belongs to the technical field of acoustic materials, and in particular relates to a method for preparing a low-density ultrasonic transducer backing based on thermal expansion. Background Art

[0002] Acoustic technology has advanced significantly in recent decades, with transducers widely used in diverse fields such as medical ultrasound, sonar imaging, and nondestructive testing. A transducer consists of a piezoelectric element, a matching layer, a backing layer, and a circuit. The piezoelectric element converts acoustic energy into electrical energy through the piezoelectric effect and the inverse piezoelectric effect. The matching layer is one or more layers of materials with different acoustic impedances bonded to the piezoelectric element. By matching the acoustic impedance, it regulates energy transmission efficiency and broadens the transducer's operating frequency band. The backing layer provides mechanical support for the transducer body and reduces signal smearing by absorbing sound, thereby improving signal bandwidth to a certain extent. Backings can be categorized as high-impedance or low-impedance based on their acoustic impedance. High-impedance backings typically have an acoustic impedance between 10 and 30 MRayl, similar to that of the piezoelectric element material. This results in a higher loss of acoustic energy from the backing, resulting in greater attenuation and shorter interference pulse duration, but also lower sensitivity. Low-impedance backings have an acoustic impedance of less than 10 MRayl, significantly different from that of piezoelectric element materials. They reflect more sound waves and exhibit higher sensitivity, but their acoustic attenuation is weaker than that of high-impedance backings, resulting in longer interference pulse durations. The ideal backing material should have both low acoustic impedance to ensure high sensitivity and a high acoustic attenuation coefficient to minimize interference pulse duration.

[0003] The traditional method for preparing transducer backing materials is to add solid powders (such as tungsten powder, tungsten oxide, hollow microspheres, etc.) to a liquid epoxy resin body, mix them, and cure them at low temperature (around 50°C). However, this method of preparing backing materials has some problems: backing materials made with metal or metal oxide powders as fillers have a large acoustic impedance, usually greater than 2.5 MRayl; when hollow microspheres are used as fillers, as the mass fraction increases, the material mixing tends to be uneven, and the density and sound velocity have limit values. The density is usually greater than 700 kg / m^3, the sound velocity is greater than 1700 m / s, and the acoustic impedance of the backing material is greater than 1.2 MRayl.

[0004] To address these issues, the present invention utilizes a soft mold expansion method. Using a soft mold at high temperature, the expansion volume of the hollow microspheres within is altered by regulating the curing temperature, thereby reducing the density of the backing material and increasing the acoustic attenuation coefficient. This method, while ensuring uniform distribution of the backing material, creates a dense concentration of small pores within the material, resulting in a backing material with lower acoustic impedance and higher acoustic attenuation coefficient. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for preparing a low-density ultrasonic transducer backing based on thermal expansion. By using a soft mold and changing the curing temperature of the backing material, a series of backing materials used in transducers are prepared.

[0006] In a first aspect, the present invention provides a method for preparing a low-density ultrasonic transducer backing based on thermal expansion, comprising the following steps:

[0007] Step 1: Evenly mix the epoxy resin before curing, the curing agent and the hollow microspheres to obtain a mixed fluid. The hollow microspheres are made of polymer material.

[0008] Step 2: Add the mixed fluid obtained in step 1 into the mold and reserve space required for expansion in the mold; heat the mixed fluid added to the mold at 60° C. to 80° C. to expand and solidify, thereby obtaining an ultrasonic transducer backing.

[0009] Preferably, the volume of the mixed fluid added to the mold in step 2 is 2 / 3 to 3 / 4 of the volume of the mold; the mold is a soft mold that can expand under internal pressure; the material of the soft mold is rubber or silicone.

[0010] Preferably, the mass fraction of the hollow microspheres in the epoxy resin, curing agent and hollow microspheres before curing is less than or equal to 9.1%.

[0011] Preferably, the mass ratio of the epoxy resin, the curing agent and the hollow microspheres before curing is (10-20):(0.1-4):(0.1-2).

[0012] Preferably, the hollow microspheres are made of one or more of polystyrene, phenolic resin, polyurethane, and cured epoxy resin.

[0013] Preferably, the particle size of the hollow microspheres is less than or equal to 15 μm.

[0014] Preferably, the epoxy resin comprises a rigid epoxy resin and a flexible epoxy resin. The Young's modulus of the rigid epoxy resin after curing is greater than that of the flexible epoxy resin after curing. The mass ratio of the rigid epoxy resin to the flexible epoxy resin is (8-15):5.

[0015] Preferably, the Young's modulus of the rigid epoxy resin after curing is 2 GPa (inclusive) to 5 GPa (inclusive); the Young's modulus of the flexible epoxy resin after curing is less than 2 GPa, preferably 1 GPa (inclusive) to 2 GPa (exclusive).

[0016] Preferably, in step 1, the epoxy resin, curing agent and hollow microspheres are mixed uniformly by centrifugation.

[0017] In a second aspect, the present invention provides a method for controlling the acoustic impedance of a transducer backing, comprising the following steps:

[0018] Step 1: Evenly mix the epoxy resin before curing, the curing agent and the hollow microspheres to obtain a mixed fluid. The hollow microspheres are made of polymer material.

[0019] Step 2: Set the target curing temperature based on the target acoustic impedance. The higher the target acoustic impedance, the lower the target curing temperature. The target curing temperature range is 20°C to 80°C.

[0020] Step 3: Add the mixed fluid obtained in step 1 into a soft mold that is pressurized and expandable, and heat and cure it at the target curing temperature obtained in step 2 to obtain an ultrasonic transducer backing.

[0021] Preferably, the target curing temperature is obtained according to the target acoustic impedance and the relationship between the target curing temperature and the target acoustic impedance. The relationship between the target curing temperature and the target acoustic impedance is obtained through experiments.

[0022] In a third aspect, the present invention provides a method for controlling the acoustic attenuation coefficient of a transducer backing, comprising the following steps:

[0023] Step 1: uniformly mixing the epoxy resin before curing, the curing agent and the hollow microspheres to obtain a mixed fluid; the hollow microspheres are made of polymer material;

[0024] Step 2: Set the target curing temperature according to the target sound attenuation coefficient; the larger the target sound attenuation coefficient, the higher the target curing temperature is set; the target curing temperature range is 20°C to 80°C;

[0025] Step 3: Add the mixed fluid obtained in step 1 into a soft mold that is pressurized and expandable, and heat and cure it at the target curing temperature obtained in step 2 to obtain an ultrasonic transducer backing.

[0026] Preferably, the target curing temperature is obtained according to the target acoustic attenuation coefficient and the relationship between the target curing temperature and the target acoustic attenuation coefficient. The relationship between the target curing temperature and the target acoustic attenuation coefficient is obtained through experiments.

[0027] The beneficial effects of the present invention are:

[0028] 1. This invention utilizes a soft mold expansion method, leveraging the expansion of hollow microspheres during epoxy resin curing to occupy reserved space within the soft mold. Once the soft mold is filled, the microspheres push both the soft mold and the epoxy resin to expand together, thus overcoming the density bottleneck of traditional preparation methods and significantly reducing the density of the transducer backing. The soft mold can adapt to the varying expansion of the epoxy resin during each process, avoiding uneven top-to-bottom finishes caused by excessive reserved space, or excessive expansion restriction caused by insufficient reserved space.

[0029] 2. The present invention forms a dense porous structure inside the transducer backing by expanding the hollow microspheres, thereby reducing the density and increasing the acoustic attenuation coefficient of the transducer backing.

[0030] 3. The present invention obtains transducer backings with different acoustic impedances and acoustic attenuation coefficients by regulating the curing temperature: the control range of the transducer backing acoustic impedance reaches 0.87 Mrayl to 2.07 Mrayl, and the control range of the acoustic attenuation coefficient reaches 4.41 dB / mm to 16.41 dB / mm. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a density variation diagram of the transducer backing prepared in Examples 1-4 of the present invention.

[0032] Figure 2 This is a diagram showing the sound velocity variation of the transducer backings prepared in Examples 1-4 of the present invention.

[0033] Figure 3 Graph showing the acoustic impedance changes of the transducer backings prepared in Examples 1-4 of the present invention.

[0034] Figure 4 This is a graph showing the change in acoustic attenuation coefficient of the transducer backings prepared in Examples 1-4 of the present invention. DETAILED DESCRIPTION

[0035] The present invention will be further described below with reference to the accompanying drawings.

[0036] Example 1

[0037] A method for preparing an ultrasonic transducer backing comprises the following steps:

[0038] S1. Preliminary mixing of rigid epoxy resin A, flexible epoxy resin B, curing agent, and hollow microspheres with a particle size of 15 μm was performed in a blender at a mass ratio of 10:5:2:0.5, and the mixture was centrifuged and stirred for 1 minute. After the components were fully stirred, a mixed fluid was formed. Rigid epoxy resin A and flexible epoxy resin B use bisphenol A epoxy resin as the main resin component with different Young's modulus. Bisphenol A epoxy resins with different molecular structures have different Young's moduli. The Young's modulus of rigid epoxy resin A after curing is greater than that of flexible epoxy resin B after curing. In this embodiment, the Young's modulus of rigid epoxy resin A after curing is 2 to 5 GPa, and the Poisson's ratio is 0.35 to 0.4. The Young's modulus of flexible epoxy resin B after curing is less than 2 GPa, and the Poisson's ratio is 0.4 to 0.5.

[0039] In some embodiments, the hollow microspheres are made of one or more of polystyrene, phenolic resin, polyurethane, and epoxy resin.

[0040] In some embodiments, the Young's modulus of the rigid epoxy resin A and the flexible epoxy resin B after curing is, for example: (A is 5 GPa, B is 2 GPa), or (A is 4 GPa, B is 1.5 GPa), or (A is 3 GPa, B is 1 GPa), or (A is 2 GPa, B is 1 GPa), or (A is 5 GPa, B is 1 GPa), and other reasonable values ​​may also be taken.

[0041] In some other embodiments, the particle size of the hollow microspheres 5 may also be other values ​​less than 15 μm, such as 14 μm, 13.5 μm, 13 μm, 12.5 μm, 12 μm, 11.5 μm, 11 μm, 10.5 μm, 10 μm, 9.5 μm, 9 μm, 8.5 μm, 8 μm, 7.5 μm, 7 μm, 6.5 μm, 6 μm, or other reasonable values.

[0042] In some other embodiments, the centrifugal stirring time may be other values ​​other than 1 min, such as 2 min, 3 min, 10 min, 15 min, or other time that allows the components to be evenly mixed.

[0043] In some other embodiments, the centrifugal stirring speed may be 10,000 r / min, 12,000 r / min, 15,000 r / min, or other reasonable speeds that can uniformly mix the components.

[0044] In some other embodiments, centrifugal stirring can be replaced by other methods to promote mixing, as long as the components can be mixed evenly.

[0045] In some other embodiments, under the condition that the mass fraction of hollow microspheres is less than or equal to 9.1%, the mass ratio of rigid epoxy resin A, flexible epoxy resin B, curing agent, and particle size of 15 μm can be other reasonable ratios other than 10:5:2:0.5, for example: 10:1:0.1:0.1, 10:10:4:2, 10:5:2:1, 10:5:2:0.5, 10:5:2:0.5, 10:8:2:0.5.

[0046] In some other embodiments, the flexible epoxy resin B may not be used, that is, only the rigid epoxy resin A, the curing agent, and the epoxy resin with a particle size of 15 μm are mixed according to a set mass ratio.

[0047] S2. The resulting mixed fluid is introduced into a soft mold and placed in an oven, where it is heated at a constant temperature of 50°C for 4 hours for curing. The volume of the mixed fluid introduced into the soft mold is 2 / 3 to 3 / 4 of the initial volume of the soft mold, so that there is space in the soft mold for the expansion of the mixed fluid. At the same time, the soft mold itself can also expand under internal pressure. During the heating and curing process of the mixed fluid, the hollow microspheres expand, causing the mixed fluid to have an expansion trend. The expanded mixed fluid can occupy the space reserved in the soft mold, and after filling the internal space of the soft mold, it squeezes the soft mold from the inside out, causing the soft mold to expand together, meeting the expansion requirements of the mixed fluid. During this process, the density of the mixed fluid decreases. Using a soft mold allows the mold to adapt to the differences in the amount of expansion of the mixed fluid in each processing, avoiding the problem of uneven top and bottom of the finished product due to too much reserved space, or avoiding the problem of excessive obstruction of expansion due to too little reserved space.

[0048] In some embodiments, the soft mold is made of rubber or silicone.

[0049] S3. Take out the solidified product from the soft mold and place it under a grinder to process it to a specified thickness to obtain a transducer backing.

[0050] The performance of the transducer backing obtained in this embodiment was tested, and the performance indicators obtained were as follows: density was 855 kg / m 3 , the sound velocity is 2185m / s, the acoustic impedance is 1.83MRayl, and the acoustic attenuation is 4.89dB / mm.

[0051] Example 2

[0052] A method for preparing an ultrasonic transducer backing comprises the following steps:

[0053] S1. Preliminary mixing of rigid epoxy resin A, flexible epoxy resin B, curing agent, and hollow microspheres with a particle size of 15 μm is carried out in a blender at a mass ratio of 10:5:2:0.5, and centrifugal stirring for 1 minute. After the components are fully stirred, a mixed fluid is formed. Rigid epoxy resin A and flexible epoxy resin B use bisphenol A epoxy resin as the main resin component with different Young's moduli. The Young's modulus of rigid epoxy resin A after curing is greater than that of flexible epoxy resin B after curing. In this embodiment, the Young's modulus of rigid epoxy resin A after curing is 2 to 5 GPa, and the Poisson's ratio is 0.35 to 0.4. The Young's modulus of flexible epoxy resin B after curing is less than 2 GPa, and the Poisson's ratio is 0.4 to 0.5.

[0054] S2. The obtained mixed fluid is introduced into a soft mold and then placed in an oven, and heated at a constant temperature of 60° C. for 4 hours to solidify.

[0055] S3. Take out the solidified product from the mold and place it under a grinder to be processed to a specified thickness to obtain a transducer backing.

[0056] The performance indicators of the obtained transducer backing are as follows: density of 585kg / m^3, sound velocity of 2060m / s, acoustic impedance of 1.20MRayl, and acoustic attenuation of 9.08dB / mm.

[0057] Example 3

[0058] A method for preparing an ultrasonic transducer backing comprises the following steps:

[0059] S1. Preliminary mixing of rigid epoxy resin A, flexible epoxy resin B, curing agent, and hollow microspheres with a particle size of 15 μm is carried out in a blender at a mass ratio of 10:5:2:0.5, and centrifugal stirring for 1 minute. After the components are fully stirred, a mixed fluid is formed. Rigid epoxy resin A and flexible epoxy resin B use bisphenol A epoxy resin as the main resin component with different Young's moduli. The Young's modulus of rigid epoxy resin A after curing is greater than that of flexible epoxy resin B after curing. In this embodiment, the Young's modulus of rigid epoxy resin A after curing is 2 to 5 GPa, and the Poisson's ratio is 0.35 to 0.4. The Young's modulus of flexible epoxy resin B after curing is less than 2 GPa, and the Poisson's ratio is 0.4 to 0.5.

[0060] S2. The obtained mixed fluid is introduced into a soft mold and then placed in an oven, and heated at a constant temperature of 70° C. for 4 hours to solidify.

[0061] S3. Take out the solidified product from the mold and place it under a grinder to be processed to a specified thickness to obtain a transducer backing.

[0062] The performance indicators of the obtained transducer backing are as follows: density of 522kg / m^3, sound velocity of 1909m / s, acoustic impedance of 0.99MRayl, and acoustic attenuation of 12.48dB / mm.

[0063] Example 4

[0064] A method for preparing an ultrasonic transducer backing comprises the following steps:

[0065] S1. Preliminary mixing of rigid epoxy resin A, flexible epoxy resin B, curing agent, and hollow microspheres with a particle size of 15 μm is carried out in a blender at a mass ratio of 10:5:2:0.5, and centrifugal stirring for 1 minute. After the components are fully stirred, a mixed fluid is formed. Rigid epoxy resin A and flexible epoxy resin B use bisphenol A epoxy resin as the main resin component with different Young's moduli. The Young's modulus of rigid epoxy resin A after curing is greater than that of flexible epoxy resin B after curing. In this embodiment, the Young's modulus of rigid epoxy resin A after curing is 2 to 5 GPa, and the Poisson's ratio is 0.35 to 0.4. The Young's modulus of flexible epoxy resin B after curing is less than 2 GPa, and the Poisson's ratio is 0.4 to 0.5.

[0066] S2. The obtained mixed fluid is introduced into a soft mold and then placed in an oven, and heated at a constant temperature of 80° C. for 4 hours to solidify.

[0067] S3. Take out the solidified product from the mold and place it under a grinder to be processed to a specified thickness to obtain a transducer backing.

[0068] The performance indicators of the obtained transducer backing are as follows: density of 480kg / m^3, sound velocity of 1820m / s, acoustic impedance of 0.87MRayl, and acoustic attenuation of 16.41dB / mm.

[0069] Comparative Example 1

[0070] A method for preparing an ultrasonic transducer backing comprises the following steps:

[0071] S1. Preliminary mixing of rigid epoxy resin A, flexible epoxy resin B, curing agent, and hollow microspheres with a particle size of 15 μm is carried out in a blender at a mass ratio of 10:5:2:0.5, and centrifugal stirring for 1 minute. After the components are fully stirred, a mixed fluid is formed. Rigid epoxy resin A and flexible epoxy resin B use bisphenol A epoxy resin as the main resin component with different Young's moduli. The Young's modulus of rigid epoxy resin A after curing is greater than that of flexible epoxy resin B after curing. In this embodiment, the Young's modulus of rigid epoxy resin A after curing is 2 to 5 GPa, and the Poisson's ratio is 0.35 to 0.4. The Young's modulus of flexible epoxy resin B after curing is less than 2 GPa, and the Poisson's ratio is 0.4 to 0.5.

[0072] S2. The obtained mixed fluid is introduced into a soft mold and allowed to stand at room temperature for 12 hours to solidify.

[0073] S3. Take out the solidified product from the mold and place it under a grinder to be processed to a specified thickness to obtain a transducer backing.

[0074] The performance indicators of the obtained transducer backing are as follows: density of 948 kg / m^3, sound velocity of 2185 m / s, acoustic impedance of 2.07 MRayl, and acoustic attenuation of 4.41 dB / mm.

[0075] The difference between the above-mentioned Examples 1 to 4 and Comparative Example 1 is that the curing temperature during the preparation process is different; the density, sound velocity, acoustic impedance and acoustic attenuation of the transducer backing obtained in Examples 1 to 4 and Comparative Example 1 change with temperature as shown in FIG. Figures 1 to 4 Shown: From Figure 1 It can be seen that the density of the backing material obtained after high temperature expansion is 948kg / m 3 Reduced to 480kg / m 3 , the density decreases significantly; from Figure 2 It can be seen that the sound velocity in the backing material produced after high-temperature expansion is significantly reduced. Since acoustic impedance = density × sound velocity, a higher curing temperature simultaneously reduces both density and sound velocity, indicating that adjusting the curing temperature can achieve the desired angular amplitude of the backing acoustic impedance.

[0076] from Figure 3 and Figure 4 It can be seen that the acoustic impedance and acoustic attenuation coefficient of the transducer backing material obtained at different curing temperatures have a large variation range. Therefore, the acoustic impedance and acoustic attenuation coefficient of the obtained acoustic transducer backing can be changed by adjusting the curing temperature, thereby achieving effective regulation of the acoustic impedance and acoustic attenuation coefficient.

[0077] Example 5

[0078] A method for controlling the acoustic impedance of a transducer backing comprises the following steps:

[0079] S1. Preliminarily mix rigid epoxy resin A, flexible epoxy resin B, curing agent, and hollow microspheres with a particle size of 15 μm. Place in a blender and centrifuge for 1 minute. After all components are thoroughly stirred, a mixed fluid is formed.

[0080] S2. Set the target curing temperature based on the target acoustic impedance. The higher the target acoustic impedance, the lower the target curing temperature. The target curing temperature range is 20°C to 80°C. The relationship between the target acoustic impedance and the target curing temperature is obtained using a numerical relationship curve or numerical relationship table. The numerical relationship table is obtained through preliminary experiments; the numerical relationship curve is obtained by fitting the obtained discrete values ​​through preliminary experiments.

[0081] S3. The mixed fluid obtained in step S1 is introduced into the soft mold and then placed in an oven. According to the target curing temperature set in step S2, the mixed fluid is heated at a constant temperature for 4 hours to solidify the mixed fluid.

[0082] S4. The cured product in the mold is taken out and placed under a grinder for processing to a specified thickness to obtain a transducer backing with a target acoustic impedance.

[0083] Example 6

[0084] A method for controlling the acoustic attenuation coefficient of a transducer backing comprises the following steps:

[0085] S1. Preliminarily mix rigid epoxy resin A, flexible epoxy resin B, curing agent, and hollow microspheres with a particle size of 15 μm. Place in a blender and centrifuge for 1 minute. After all components are thoroughly stirred, a mixed fluid is formed.

[0086] S2. Set the target curing temperature based on the target acoustic attenuation coefficient. The higher the target acoustic attenuation coefficient, the higher the target curing temperature. The target curing temperature range is 20°C to 80°C. The relationship between the target acoustic attenuation coefficient and the target curing temperature is obtained using a numerical relationship curve or numerical relationship table. The numerical relationship table is obtained through preliminary experiments; the numerical relationship curve is obtained by fitting the obtained discrete values ​​through preliminary experiments.

[0087] S3. The mixed fluid obtained in step S1 is introduced into the soft mold and then placed in an oven. According to the target curing temperature set in step S2, the mixed fluid is heated at a constant temperature for 4 hours to solidify the mixed fluid.

[0088] S4. The cured product in the mold is taken out and placed under a grinder for processing to a specified thickness to obtain a transducer backing with a target sound attenuation coefficient.

Claims

1. A method for preparing a low-density ultrasonic transducer backing based on thermal expansion, characterized in that: The following steps are involved: Step 1: uniformly mixing an epoxy resin before curing, a curing agent, and hollow microspheres to obtain a mixed fluid; wherein the hollow microspheres are made of a polymer material; the mass fraction of the hollow microspheres in the epoxy resin before curing, the curing agent, and the hollow microspheres is less than or equal to 9.1%; and the particle size of the hollow microspheres is less than or equal to 15 μm; Step 2: Add the mixed fluid obtained in step 1 into a mold, and reserve space required for expansion in the mold; heat the mixed fluid added to the mold at 60° C. to 80° C. to expand and solidify, thereby obtaining an ultrasonic transducer backing; The volume of the mixed fluid added to the mold in step 2 is 2 / 3 to 3 / 4 of the volume of the mold; the mold is a soft mold that can expand under internal pressure; the material of the soft mold is rubber or silicone.

2. The method for preparing a low-density ultrasonic transducer backing based on thermal expansion according to claim 1, characterized in that: The hollow microspheres are made of one or more materials selected from polystyrene, phenolic resin, polyurethane and cured epoxy resin.

3. The method for preparing a low-density ultrasonic transducer backing based on thermal expansion according to claim 1, characterized in that: The epoxy resin comprises a rigid epoxy resin and a flexible epoxy resin; the Young's modulus of the rigid epoxy resin after curing is greater than the Young's modulus of the flexible epoxy resin after curing; and the mass ratio of the rigid epoxy resin to the flexible epoxy resin is (8-15):

5.

4. The method for preparing a low-density ultrasonic transducer backing based on thermal expansion according to claim 3, characterized in that: The Young's modulus of the rigid epoxy resin after curing is 2 GPa to 5 GPa; the Young's modulus of the flexible epoxy resin after curing is less than 2 GPa.

5. The method for preparing a low-density ultrasonic transducer backing based on thermal expansion according to claim 1, characterized in that: In step 1, the epoxy resin, curing agent and hollow microspheres are mixed uniformly by centrifugation.

6. A method for controlling the acoustic impedance of a transducer backing, characterized in that: The following steps are involved: Step 1: uniformly mixing an epoxy resin before curing, a curing agent, and hollow microspheres to obtain a mixed fluid; wherein the hollow microspheres are made of a polymer material; the mass fraction of the hollow microspheres in the epoxy resin before curing, the curing agent, and the hollow microspheres is less than or equal to 9.1%; and the particle size of the hollow microspheres is less than or equal to 15 μm; Step 2: Set the target curing temperature according to the target acoustic impedance; the larger the target acoustic impedance, the lower the target curing temperature; the target curing temperature range is 60°C to 80°C; Step 3: Add the mixed fluid obtained in step 1 into a soft mold that is pressurized and expandable, and heat and cure it at the target curing temperature obtained in step 2 to obtain an ultrasonic transducer backing.

7. A method for controlling the acoustic attenuation coefficient of a transducer backing, characterized in that: The following steps are involved: Step 1: uniformly mixing an epoxy resin before curing, a curing agent, and hollow microspheres to obtain a mixed fluid; wherein the hollow microspheres are made of a polymer material; the mass fraction of the hollow microspheres in the epoxy resin before curing, the curing agent, and the hollow microspheres is less than or equal to 9.1%; and the particle size of the hollow microspheres is less than or equal to 15 μm; Step 2: Set the target curing temperature according to the target sound attenuation coefficient; the larger the target sound attenuation coefficient, the higher the target curing temperature is set; the target curing temperature range is 60°C to 80°C; Step 3: Add the mixed fluid obtained in step 1 into a soft mold that is pressurized and expandable, and heat and cure it at the target curing temperature obtained in step 2 to obtain an ultrasonic transducer backing.

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