One-way controllable sound field transducer of carbon nanotube sponge based on magneto-thermo-acoustic coupling effect

Abstract

The invention provides a one-way controllable sound field transducer of carbon nanotube sponge based on a magneto-thermo-acoustic coupling effect, and belongs to the technical field of transducers. Comprising a three-dimensional carbon nano-porous material serving as a main sound production element, strong magnets located on the two sides of the three-dimensional carbon nano-porous material, and an outer frame used for installing the strong magnets. The sound production element is composed of a piece of carbon nanotube sponge, metal electrodes located at the upper end and the lower end of the carbon nanotube sponge and aluminum oxide mirror surface ceramic insulating rods located at the left end and the right end of the carbon nanotube sponge, and electric signals are connected into the sound production element. According to the invention, thermal sound waves and magnetic sound waves are generated at the same time on the basis of a magnetic-thermal-sound coupling effect and are superposed into new sound waves, so that a wide and flat frequency response is achieved, the high-fidelity performance of the transducer is displayed, and crosstalk and loss of audio signals between traditional piezoelectric transducer elements are avoided; the energy conversion efficiency of the transducer can be improved, and the service life is prolonged.

Description

Technical Field

[0001] The invention belongs to the technical field of transducers and relates to a unidirectional controllable sound field transducer of a carbon nanotube sponge based on magnetothermoacoustic coupling effect. Background Art

[0002] With the continuous advancement of science and technology, acoustic transducers play a vital role in many fields such as medical imaging (Wang Yandong. Modeling study of thermally induced ultrasonic emission of porous silicon [D]; University of Science and Technology of China, 2015.), non-destructive testing (Bowary P., Greenberg B.D. Noninvasive focused ultrasound for neuromodulation: a review [J]. Psychiatric Clinics of North America, 2018, 41(3): 505-514.), and communication technology (Aliev A.E., Mayo NK, Baughman RH, et al. Thermoacoustic excitation of sonarprojector plates by free-standing carbon nanotube sheets [J]. Journal of Physics D: Applied Physics, 2014, 47(35): 355302.). It is urgent for us to study and explore new materials and transduction mechanisms, improve our country's independent innovation capabilities in the industrial chain and supply chain of acoustic transducers, and then achieve curve overtaking, break through the core technology bottleneck, and enhance the ability of our country's scientific and technological system to resist international risks. In addition, the unidirectional controllable emission based on the new unidirectional controllable sound field transducer has great application potential in the field of acoustics, and is expected to provide more efficient and accurate acoustic transduction solutions for medical imaging, non-destructive testing, communication technology and other fields. Therefore, it is of great significance to explore new materials and transduction mechanisms, design a new unidirectional controllable sound field transducer, and improve the performance and application range of acoustic transducers.

[0003] The sound-generating elements of existing acoustic transducers are mainly made of piezoelectric ceramics, piezoelectric crystals or piezoelectric polymers. They generate sound waves that meet the needs by exciting a periodic alternating electric field on the piezoelectric material, which generates mechanical vibrations due to the inverse piezoelectric effect. Traditional acoustic transducers made of piezoelectric materials have four main disadvantages: (1) The frequency response range is narrow (Xu Guang, Wu Peirong, Liu Zhenjun. Power fatigue analysis of high-frequency transducers [J]. Acoustic Technology, 2015, 34(03): 283-286), and they can generally only work near a fixed frequency. (2) The piezoelectric material itself will vibrate during the sound generation process, causing a resonance effect. (3) The signals between components will generate crosstalk and are easily distorted (Tian FH, Liu YM, Ma RL, et al. Properties of PMN-PT single crystal piezoelectric material and its application in underwater acoustic transducer [J]. Applied Acoustics, 2021, 175 (4): 107827.), and the power loss is serious. (4) Traditional acoustic transducers are composed of components such as shell, piezoelectric material, acoustic window matching layer and backing, with complex structure, cumbersome production process and high production cost (Hu HJ, Zhu X., Wang CH, et al. Stretchable ultrasonic transducer arrays for three-dimensional imaging on complex surfaces [J]. Science Advances, 2018, 4 (3): eaar3979.). This means that the existing piezoelectric transducers still have certain limitations, which limits their use scenarios and may not meet the needs in the application of high-intensity, high-frequency and wide-bandwidth ultrasonic signals.

[0004] The specific heat capacity per unit area of ​​carbon nanotube sponge (Aliev AE, Mayo NK, De Andrade MJ, et al. Alternative nanostructures for thermophones [J]. ACS Nano, 2015, 9 (5): 4743-4756.) is extremely low. When driven by a DC biased AC signal, it can quickly generate heat energy and release it to the surrounding medium, causing the surrounding medium to expand and contract and generate corresponding thermoacoustic waves. In addition, the carbon nanotube sponge is an elastic, high specific surface area, and high porosity sponge-like carbon nanotube macroscopic material formed by countless multi-walled carbon nanotubes overlapped and assembled with each other. It is self-supporting, easy to cut, and has good flexibility. Its shape and size can be cut and manufactured according to actual requirements. In a static magnetic field environment, when a DC biased AC signal acts on the carbon nanotube sponge, it will produce forced vibrations due to the action of the Ampere force. This vibration further causes the surrounding medium to expand and contract periodically, thereby exciting corresponding magnetoacoustic waves. The application of magnetothermoacoustic coupling effect enables the emission direction and intensity of the sound field to be precisely controlled, improving the controllability and flexibility of the transducer. Therefore, based on the excellent thermoacoustic and mechanical properties of carbon nanotube sponge, the study of the unidirectional controllable sound field transducer of carbon nanotube sponge with magnetothermoacoustic coupling effect aims to break the technical barriers of traditional sound field transducers and realize the directional emission and efficient conversion of sound waves. Summary of the invention

[0005] In view of the problems existing in the prior art, the present invention provides a unidirectional controllable sound field transducer of carbon nanotube sponge based on the magnetothermal acoustic coupling effect. The transducer can generate ultrasonic waves in the frequency range of 1Hz-100kHz to achieve the effect of variable frequency. The transducer utilizes the excellent mechanical and electrical properties of carbon nanotube sponge and combines the magnetothermal acoustic coupling effect to significantly improve the energy conversion efficiency of the transducer and realize unidirectional controllable emission of the sound field.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] A one-way controllable sound field transducer of a carbon nanotube sponge based on the magneto-thermo-acoustic coupling effect, the one-way controllable sound field transducer comprises a three-dimensional carbon nanoporous material as the main sound-generating element, and strong magnet blocks located on both sides of the three-dimensional carbon nanoporous material, and an acrylic plate outer frame 8 for mounting the strong magnet. Specifically:

[0008] The sound-generating element is composed of a carbon nanotube sponge 1, metal electrodes at the upper and lower ends thereof, and alumina mirror ceramic insulating rods at the left and right ends thereof. The metal electrodes include a first metal electrode 2 and a second metal electrode 3, each of which is connected to an insulated wire, and the wire is used to connect an external device or a power supply. The alumina mirror ceramic insulating rod includes a first alumina mirror ceramic insulating rod 6 and a second alumina mirror ceramic insulating rod 7, and the alumina mirror ceramic insulating rod cooperates with the metal electrodes to fix the carbon nanotube sponge.

[0009] The strong magnet blocks include a first strong magnet block 9 and a second strong magnet block 10, which are symmetrically placed on both sides of the carbon nanotube sponge 1 and fixed on both sides of the acrylic plate outer frame 8 of the door-shaped structure to provide static magnetic field environment conditions.

[0010] The electrical signal is connected to the sound-generating element through an insulated wire at one end and flows out from the wire at the other end, ensuring that the direction of the magnetic field is perpendicular to the direction of the current. When the electrical signal flows through the carbon nanotube sponge 1 through the metal electrode, the surface of the carbon nanotube sponge 1 rapidly produces temperature changes and forced vibrations, causing the surrounding medium to expand and contract, thereby generating thermal sound waves and magneto-sound waves respectively. The two sound waves are superimposed to achieve unidirectional propagation of sound waves with a controllable sound field.

[0011] Furthermore, the electrical signal is a DC biased AC signal, which ensures that the magnetic sound and thermal sound of the unidirectional controllable sound field transducer produce a single-frequency sound wave for superposition. The DC biased AC signal is connected to the sound-emitting element through one of the wires via a metal electrode, and then output through another wire via another metal electrode.

[0012] Furthermore, the strong magnet block is a rare earth strong magnet, specifically a neodymium iron boron magnet, which has a relatively small volume and light weight while maintaining strong magnetism. The distance between the strong magnet and the carbon nanotube sponge 1 is 1.5 cm.

[0013] Furthermore, the surfaces where the two strong magnet blocks are located and the surfaces where the two metal electrodes are located are perpendicular to each other in space, ensuring that the direction of the magnetic field and the direction of the current are perpendicular to each other, and together constitute a unidirectional controllable sound field transducer of the carbon nanotube sponge with magnetothermal acoustic coupling effect.

[0014] Furthermore, the carbon nanotube sponge 1 is a sponge-like carbon nanotube macroscopic material with elasticity, high specific surface area, and high porosity ratio formed by lap-assembling a plurality of multi-walled carbon nanotubes. It has a three-dimensional porous structure. The carbon nanotube sponge has excellent electrical and mechanical properties and can achieve independent support. The appropriate size can be selected according to specific needs.

[0015] Furthermore, the metal electrodes are connected to both ends of the carbon nanotube sponge 1, and after the electrodes are connected using ultraviolet light-sensitive conductive adhesive, the insulated wires are fixed to the electrodes by soldering.

[0016] Furthermore, the metal electrode can be selected from materials with good conductivity and high temperature stability, such as copper electrode, zinc electrode, iron electrode, and aluminum electrode.

[0017] Furthermore, the alumina mirror ceramic insulating rod is a material with insulation and high temperature stability, and its volume resistance is 10 14 Ohm meter, the selected material diameter is 2 mm, and the actual selected diameter can be determined according to actual needs.

[0018] Furthermore, the first alumina mirror ceramic insulating rod 6 and the second alumina mirror ceramic insulating rod 7 are arranged vertically and adhered to the left and right sides of the carbon nanotube sponge.

[0019] Furthermore, the insulated wire and the metal electrode are welded by using an electric soldering iron tool, and the solder materials available include tin-lead alloy solder, antimony-added solder, cadmium-added solder, silver-added solder, copper-added solder and other types.

[0020] The beneficial effects of the present invention are:

[0021] (1) Compared with traditional acoustic transducers, the new unidirectional controllable sound field transducer of carbon nanotube sponge is based on the magnetothermal-acoustic coupling effect, which simultaneously generates thermal acoustic waves and magnetic acoustic waves, superimposed into new sound waves, has a wide and flat frequency response, demonstrates the high-fidelity performance of the transducer, and avoids the crosstalk and loss of audio signals between traditional piezoelectric transducer elements.

[0022] (2) The unidirectional controllable acoustic field transducer of the carbon nanotube sponge is based on the thermoacoustic effect. The thermoacoustic waves generated by the transducer are symmetrical about the carbon nanotube sponge itself. Under the magnetoacoustic vibration effect, the magnetoacoustic waves generated by the transducer due to the magnetoacoustic effect should be symmetrical about the center of the carbon nanotube sponge transducer. The waveform in the forward direction is the same as that of the thermoacoustic wave, and the waveform in the reverse direction is opposite to that of the thermoacoustic wave. Based on the acoustic wave characteristics of thermoacoustics and magnetoacoustics utilized by the carbon nanotube sponge body, a single transducer device emits thermoacoustics and magnetoacoustics at the same time and superimposes them, thereby achieving unidirectional sound transmission with enhanced forward sound pressure and weakened reverse sound pressure, thereby improving the energy conversion efficiency of the transducer.

[0023] (3) Unlike the rigid piezoelectric materials of traditional piezoelectric transducers, carbon nanotube sponge has excellent flexibility, superelasticity (can return to its original shape at 90% strain), and high strength (can withstand a pressure of 12 MPa at 90% strain), so it can conform to surfaces of any shape and roughness.

[0024] (4) The three-dimensional carbon nanotube sponge has a better heat dissipation ability, so that the heat generated by the carbon nanotube sponge can be quickly discharged when it is working, reducing the surface temperature, and further improving the heat dissipation ability of the sponge through magnetoacoustic vibration, thereby increasing the service life of the carbon nanotube sponge's unidirectional controllable sound field transducer. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Schematic diagram of the unidirectional controllable acoustic field transducer of carbon nanotube sponge.

[0026] Figure 2 This is a comparison of the surface temperatures of two carbon nanotube sponge acoustic transducers when they generate 60dB sound waves; Figure 2 (a) is a diagram of a carbon nanotube sponge acoustic transducer with magnetothermal acoustic coupling effect; Figure 2 (b) is a diagram of a carbon nanotube sponge thermoacoustic transducer with thermoacoustic coupling effect.

[0027] Figure 3 This is the sound pressure frequency response curve of the unidirectional controllable sound field transducer of carbon nanotube sponge.

[0028] Figure 4 This is the stable sound pressure response diagram of the unidirectional controllable sound field transducer of carbon nanotube sponge.

[0029] In the figure: 1 carbon nanotube sponge; 2 first metal electrode; 3 second metal electrode; 4 first wire; 5 second wire; 6 first alumina mirror ceramic insulating rod; 7 second alumina mirror ceramic insulating rod; 8 acrylic plate frame; 9 first strong magnet block; 10 second strong magnet block. DETAILED DESCRIPTION

[0030] The present invention is further described below in conjunction with specific embodiments.

[0031] Figure 1A schematic diagram of the structure of a sound element of a one-way controllable sound field transducer of a carbon nanotube sponge is shown. The schematic diagram of the structure of a one-way controllable sound field transducer of a carbon nanotube sponge is shown. The sound element includes a layer of carbon nanotube sponge 1, a first metal electrode 2 and a second metal electrode 3, a first wire 4 and a second wire 5, a first alumina mirror ceramic insulating rod 6 and a second alumina mirror ceramic insulating rod 7. The new one-way controllable sound field transducer of carbon nanotube sponge includes a sound element, an acrylic plate frame 8 and first and second strong magnet blocks 9 and 10 located on both sides thereof. The two ends of the carbon nanotube sponge 1 are respectively connected to the first metal electrode 2 and the second metal electrode 3; the first wire 4 is connected to the first metal electrode 2 by welding, and the second wire 5 is connected to the second metal electrode 3 by welding, and the first alumina mirror ceramic insulating rod 6, the second alumina mirror ceramic insulating rod 7 are fixed to the first metal electrode 2, the second metal electrode 3 and the carbon nanotube sponge 1; the acrylic plate outer frame 6 and the first strong magnet block 9 and the second strong magnet block 10 are respectively pasted on both sides of the carbon nanotube sponge 1, and the first metal electrode 2, the second metal electrode 3 and the first strong magnet block 9 and the second strong magnet block 10 are all perpendicular to each other; the signal is connected to the sound element through the first wire 4 and the second wire 5, and then the new unidirectional controllable sound field transducer of the carbon nanotube sponge outputs unidirectional sound transmission with forward sound pressure enhancement and reverse sound pressure weakening, thereby improving the output sound pressure intensity of the transducer.

[0032] The carbon nanotube sponge 1 is a sponge-like carbon nanotube macroscopic material with elasticity, high specific surface area and high porosity ratio formed by countless multi-walled carbon nanotubes overlapped and assembled. The carbon nanotube sponge has excellent electrical and mechanical properties and can achieve independent support. According to your needs, choose the appropriate size. The size of the carbon nanotube sponge selected in this example is 1 cm long, 1 cm wide and 2 mm thick. The first metal electrode 2 and the second metal electrode 3 can be made of copper electrode, zinc electrode, iron electrode, aluminum electrode and other materials with good conductivity and high temperature stability. They are fixedly connected with the carbon nanotube sponge 1 using ultraviolet photosensitive glue (VG352). After absorbing ultraviolet light under ultraviolet irradiation, active free radicals or cations are generated, which trigger monomer polymerization and cross-linking chemical reactions, so that the adhesive is converted from liquid to solid within a few seconds. It has high viscosity, moisture resistance, high temperature resistance and impact resistance, and is suitable for bonding glass, plastic, metal, ceramic and other materials. The conductive material of the epoxy conductive adhesive is nano-scale ultrafine silver powder with a volume resistivity of less than 10 -3Ohmmeter, operating temperature -40 degrees Celsius - 150 degrees Celsius. The first wire 4 and the second wire 5 are made of insulating materials on the outside and metal materials on the inside. The insulated wires are respectively welded to the electrodes 2 and 3 by electric soldering iron tools. The optional soldering materials include tin-lead alloy solder, antimony solder, cadmium solder, silver solder, copper solder and other types. The signal is connected to the sound element through the first wire 4. The first alumina mirror ceramic insulating rod 6 and B7 are insulating and high temperature stable materials, and their volume resistivity is 10 14 Ohm meter. The strong magnet block A9 and the strong magnet block B10 are rare earth strong magnets, professionally called neodymium iron boron magnets. While maintaining strong magnetism, the strong magnets are relatively small in size and light in weight. The size selected in this example is 2 cm long, 1 cm wide, and 5 mm thick. The distance between the strong magnet and the carbon nanotube sponge 1 is 1.5 cm, and the magnetic induction intensity generated at the carbon nanotube sponge is 1.5 millitesla.

[0033] In the embodiment of the present invention, the carbon nanotube sponge 1 of the sound-generating element is a square with a side length of 10 mm and a thickness of 2 mm; the first metal electrode 2 and the second metal electrode 3 are made of metal sheets; the first wire 4 and the second wire 5 are both copper insulated wires; the magnetic induction intensity generated by the strong magnet block to control the static magnetic field is 6 millitesla, and the structural size is not limited and is selected according to actual needs. Ultraviolet photosensitive glue (VG352) and epoxy conductive glue (K-856) are evenly applied to the connection between the electrode 2, the electrode 3 and the carbon nanotube film 1, and then the first metal electrode 2, the second metal electrode 3 and the carbon nanotube film 1 are aligned and joined together and compacted to achieve a fixed connection between the metal electrode and the sponge. Use an electric soldering iron to weld the first wire 4 and the second wire 5 to the first metal electrode 2 and the second metal electrode 3 respectively.

[0034] In this embodiment, the temperature rise test of the novel unidirectional controllable acoustic field transducer of the carbon nanotube sponge was carried out under normal conditions according to GB / T 5170.2-2008. The ambient temperature was 21.5 degrees Celsius at room temperature, the input power was 1.76 watts, the acoustic frequency was 20,000 Hz, and the test point was located 10 mm away from the central axis of the carbon nanotube sponge surface. Using an infrared thermal imager (FLUKE TIS55+), it was measured that the surface temperature of the carbon nanotube sponge was 65.6 degrees Celsius at most after 5 minutes of power-on. In the comparative example, the strong magnet block was removed and only the thermoacoustic effect was considered. After 5 minutes of power-on, under the condition of exciting the same sound pressure level of 60dB, the surface temperature of the carbon nanotube sponge was 113.9 degrees Celsius at most. The surface temperature of the unidirectional controllable acoustic field transducer was lower when it was working.

[0035] In this embodiment, the carbon nanotube sponge unidirectional controllable sound field transducer was acoustically tested according to GB / T 43537-2023. The unidirectional controllable sound field transducer was placed in a full anechoic experimental platform, that is, a rectangular experimental box with 8 cm thick anechoic sponges on all six sides. The output sound pressure of the unidirectional controllable sound field transducer on the front and back sides was measured using an acoustic measuring instrument (B&K8103). The front side was the side where the sound pressure was enhanced after the superposition of magnetic sound and thermal sound, and the back side was the side where the sound pressure was weakened after the superposition of magnetic sound and thermal sound. The input power was 1 watt, and the test point was located 10 mm from the central axis of the carbon nanotube sponge surface of the unidirectional controllable sound field transducer. In the frequency range of 16000 to 19000 Hz, the sound pressure level of the one-way controllable sound field transducer in the forward experimental frequency response curve is above 50dB, and the sound pressure level of the frequency response curve in the reverse experiment is below 30dB, which is approximately equal to the ambient noise, and the difference in the sound pressure levels of the front and back sides is 20dB. In addition, the input current is set to 5kHz, and the one-way controllable sound field transducer is measured for 30 minutes at 2 pm every day, and the data is recorded every 5 minutes. The measurement is continuously carried out for seven days. The one-way controllable sound field transducer maintains excellent acoustic performance within seven days, with an average sound pressure level of 52.5dB, and has good acoustic response stability. Therefore, the one-way controllable sound field transducer of the carbon nanotube sponge can generate ultrasonic waves with a wide frequency range and high sound pressure, and can achieve one-way sound transmission.

[0036] The above-described embodiments merely express the implementation methods of the present invention, but they cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that for those skilled in the art, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A unidirectional controllable acoustic field transducer of carbon nanotube sponge based on magneto-thermo-acoustic coupling effect, characterized in that: The one-way controllable sound field transducer comprises a three-dimensional carbon nanoporous material as the main sound-generating element, strong magnet blocks located on both sides of the three-dimensional carbon nanoporous material, and an outer frame (8) for mounting the strong magnets; The sound-generating element is composed of a piece of carbon nanotube sponge (1), metal electrodes located at the upper and lower ends thereof, and alumina mirror ceramic insulating rods located at the left and right ends thereof.

2. The one-way controllable acoustic field transducer of carbon nanotube sponge based on magneto-thermo-acoustic coupling effect according to claim 1, characterized in that: In the sound-generating element: the metal electrode comprises a first metal electrode (2) and a second metal electrode (3), each metal electrode is connected to an insulating wire, and the wire is used to connect to an external device or a power supply to provide an electrical signal; the alumina mirror ceramic insulating rod comprises a first alumina mirror ceramic insulating rod (6) and a second alumina mirror ceramic insulating rod (7), and the alumina mirror ceramic insulating rod cooperates with the metal electrode to fix the carbon nanotube sponge.

3. The one-way controllable acoustic field transducer of carbon nanotube sponge based on magneto-thermo-acoustic coupling effect according to claim 2, characterized in that: The electrical signal is a DC biased AC signal, which ensures that the magnetic sound and thermal sound of the unidirectional controllable sound field transducer produce a single-frequency sound wave for superposition. The DC biased AC signal is connected to the sound-generating element through one of the wires via a metal electrode, and then output through another wire via another metal electrode.

4. The one-way controllable acoustic field transducer of carbon nanotube sponge based on magneto-thermo-acoustic coupling effect according to claim 2, characterized in that: The first alumina mirror ceramic insulating rod (6) and the second alumina mirror ceramic insulating rod (7) are arranged vertically and adhere to the left and right sides of the carbon nanotube sponge.

5. The one-way controllable acoustic field transducer of carbon nanotube sponge based on magneto-thermo-acoustic coupling effect according to claim 1, characterized in that: The strong magnet blocks include a first strong magnet block (9) and a second strong magnet block (10), which are symmetrically placed on both sides of the carbon nanotube sponge (1) and fixed on both sides of the acrylic plate outer frame (8) of the door-shaped structure to provide static magnetic field environment conditions.

6. The one-way controllable acoustic field transducer of carbon nanotube sponge based on magneto-thermo-acoustic coupling effect according to claim 1, characterized in that: The strong magnet block is a rare earth strong magnet; the distance between the strong magnet and the carbon nanotube sponge (1) is 1.5 cm.

7. The one-way controllable acoustic field transducer of carbon nanotube sponge based on magneto-thermo-acoustic coupling effect according to claim 1, characterized in that: The surfaces where the two strong magnet blocks are located and the surfaces where the two metal electrodes are located are perpendicular to each other in space, ensuring that the direction of the magnetic field and the direction of the current are perpendicular to each other, and together constitute a unidirectional controllable sound field transducer of the carbon nanotube sponge with magneto-thermo-acoustic coupling effect.

8. The one-way controllable acoustic field transducer of carbon nanotube sponge based on magneto-thermo-acoustic coupling effect according to claim 1, characterized in that: The carbon nanotube sponge (1) is assembled by overlapping a plurality of multi-walled carbon nanotubes.

9. The one-way controllable acoustic field transducer of carbon nanotube sponge based on magneto-thermo-acoustic coupling effect according to claim 1, characterized in that: The metal electrode can be selected from materials with good conductivity and high temperature stability, such as copper electrode, zinc electrode, iron electrode, and aluminum electrode.

10. The one-way controllable acoustic field transducer of carbon nanotube sponge based on magneto-thermo-acoustic coupling effect according to claim 1, It is characterized in that The outer frame (8) is an acrylic plate.

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