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

Abstract

The application provides a one-way controllable sound field transducer based on a carbon nanotube sponge and a magneto-thermo-acoustic coupling effect, and belongs to the technical field of transducers.The one-way controllable sound field transducer comprises a three-dimensional carbon nanometer porous material as a main sound emitting element, strong magnet blocks located at two sides of the three-dimensional carbon nanometer porous material, and an outer frame for mounting the strong magnet blocks; the sound emitting element is composed of a carbon nanotube sponge, metal electrodes located at upper and lower ends of the carbon nanotube sponge, and alumina mirror ceramic insulating rods located at left and right ends of the carbon nanotube sponge, and an electric signal is connected to the sound emitting element.The application simultaneously generates thermo-acoustic waves and magnetic acoustic waves based on the magneto-thermo-acoustic coupling effect, and the thermo-acoustic waves and the magnetic acoustic waves are superimposed into new acoustic waves, so that the one-way controllable sound field transducer has a wide and flat frequency response, exhibits high fidelity performance of the transducer, avoids crosstalk and loss of audio signals between traditional piezoelectric transducer elements, and can improve energy conversion efficiency of the transducer and improve service life.

Description

Technical Field

[0001] This invention belongs to the field of transducer technology and relates to a unidirectional controllable acoustic field transducer based on carbon nanotube sponge with magnetothermal-acoustic coupling effect. Background Technology

[0002] With the continuous advancement of science and technology, acoustic transducers play a crucial role in many fields, including medical imaging (Wang Yandong. Modeling study of thermally induced ultrasonic emission in 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): 355-302.). There is an urgent need for us to research and explore new materials and transduction mechanisms to improve my country's independent innovation capabilities in the acoustic transducer industry chain and supply chain, thereby achieving a leapfrog development, breaking through core technology bottlenecks, and enhancing the ability of my country's science and technology system to withstand international risks. Furthermore, unidirectional controllable emission based on novel unidirectional controllable sound field transducers has enormous application potential in the acoustic field, and is expected to provide more efficient and accurate acoustic transduction solutions for fields such as medical imaging, non-destructive testing, and communication technology. Therefore, exploring new materials and transduction mechanisms, designing a novel unidirectional controllable sound field transducer, and improving the performance and application range of acoustic transducers are of great significance.

[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 requirements by exciting a periodic alternating electric field on the piezoelectric material and generating mechanical vibrations due to the inverse piezoelectric effect. Traditional acoustic transducers made of piezoelectric materials have four main disadvantages: (1) Narrow frequency response range (Xu Guang, Wu Peirong, Liu Zhenjun. Power fatigue analysis of high-frequency transducers [J]. Acoustics Technology, 2015, 34(03):283-286), and generally can only work near a fixed frequency. (2) The piezoelectric material itself vibrates during the sound generation process, causing a resonance effect. (3) Crosstalk can occur between components, which is prone to distortion (Tian FH, Liu YM, Ma RL, et al. Properties of PMN-PTsingle crystal piezoelectric material and its application in underwateracoustic transducer[J]. Applied Acoustics, 2021, 175(4): 107827.), and power loss is severe. (4) Traditional acoustic transducers are composed of components such as shell, piezoelectric material, acoustic window matching layer and backing, which are complex in structure, cumbersome in production process and high in manufacturing 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 existing piezoelectric transducers still have certain limitations, which restricts their application scenarios and may not meet the requirements in the application of high-intensity, high-frequency and wide-bandwidth ultrasonic signals.

[0004] Carbon nanotube sponges (Aliev AE, Mayo NK, De Andrade MJ, et al. Alternative nanostructures for thermophones[J].ACS Nano,2015,9(5):4743-4756.) have extremely low specific heat capacity per unit area. When driven by a DC biased AC signal, they can rapidly generate heat energy and release it into the surrounding medium, causing the surrounding environment to expand and contract, thereby generating corresponding thermoacoustic waves. In addition, carbon nanotube sponges are elastic, high specific surface area, and high porosity sponge-like macroscopic carbon nanotube materials formed by the overlapping and assembly of countless multi-walled carbon nanotubes. They are self-supporting, easy to cut, and have good flexibility. Their shape and size can be cut and manufactured according to actual requirements. In a static magnetic field environment, when a DC biased AC signal is applied to a carbon nanotube sponge, it will be forced to vibrate due to the Ampere force. This vibration further causes the surrounding environment to periodically expand and contract, thereby exciting corresponding magnetoacoustic waves. The application of magnetothermal-acoustic coupling allows for precise control of the emission direction and intensity of the sound field, improving the controllability and flexibility of the transducer. Therefore, based on the excellent thermoacoustic and mechanical properties of carbon nanotube sponges, this study aims to develop a unidirectional controllable sound field transducer using carbon nanotube sponges with magnetothermal-acoustic coupling, breaking through the technical barriers of traditional sound field transducers and achieving directional emission and efficient conversion of sound waves. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a unidirectional controllable sound field transducer based on the magnetothermal-acoustic coupling effect of carbon nanotube sponge. This transducer can generate ultrasonic waves in the frequency range of 1Hz-100kHz, achieving a variable frequency function. By utilizing the excellent mechanical and electrical properties of carbon nanotube sponge and combining them with the magnetothermal-acoustic coupling effect, the energy conversion efficiency of the transducer is significantly improved, realizing unidirectional controllable emission of the sound field.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A unidirectional controllable sound field transducer based on the magnetothermal-acoustic coupling effect of carbon nanotube sponge is disclosed. The transducer includes a three-dimensional porous carbon nanomaterial as the main sound-generating element, strong magnets located on both sides of the porous carbon nanomaterial, and an acrylic outer frame 8 for mounting the magnets. Specifically:

[0008] The sound-generating element consists of a carbon nanotube sponge 1, metal electrodes at its top and bottom ends, and alumina mirror ceramic insulating rods at its left and right ends. The metal electrodes include a first metal electrode 2 and a second metal electrode 3, each connected to an insulated wire for connecting to external devices or a power source. The alumina mirror ceramic insulating rods include a first alumina mirror ceramic insulating rod 6 and a second alumina mirror ceramic insulating rod 7, which work in conjunction 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 gate structure to provide static magnetic field environment conditions.

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

[0011] Furthermore, the electrical signal is a DC-biased AC signal, ensuring that the magnetoacoustic and thermoacoustic waves generated by the unidirectional controllable sound field transducer are superimposed. 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.

[0012] Furthermore, the strong magnet block is a rare-earth magnet, specifically a neodymium iron boron magnet. While maintaining strong magnetism, the magnet is relatively small in size and lightweight. The distance between the strong magnet and the carbon nanotube sponge 1 is 1.5 cm.

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

[0014] Furthermore, the carbon nanotube sponge 1 is an elastic, high specific surface area, and high porosity sponge-like macroscopic carbon nanotube material formed by the overlapping and assembly of multiple multi-walled carbon nanotubes. It has a three-dimensional porous structure and possesses excellent electrical and mechanical properties. It can achieve independent support, and 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. After connecting the electrodes with ultraviolet photosensitive conductive adhesive, the insulating wires are soldered to the electrodes.

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

[0017] Furthermore, the alumina mirror ceramic insulating rod is a material with insulation and high-temperature stability, and its volume resistivity is 10 Ω·cm. 14 For ohmmeter, the selected material diameter is 2 mm, but the actual 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 attached to the left and right sides of the carbon nanotube sponge.

[0019] Furthermore, the method of using a soldering iron to solder insulated wires to metal electrodes includes various types of solder materials such as tin-lead alloy solder, antimony-added solder, cadmium-added solder, silver-added solder, and copper-added solder.

[0020] The beneficial effects of this invention are as follows:

[0021] (1) Compared with traditional acoustic transducers, the novel unidirectional controllable sound field transducer of carbon nanotube sponge is based on the magnetothermal-acoustic coupling effect, which generates thermoacoustic waves and magnetoacoustic waves at the same time, superimposed into new sound waves. It has a wide and flat frequency response, demonstrating the high fidelity performance of the transducer and avoiding the crosstalk and loss of audio signals between components of traditional high-voltage electric transducers.

[0022] (2) The unidirectional controllable acoustic field transducer of carbon nanotube sponge is based on the thermo-induced sound effect. The thermo-sound wave generated by the transducer is symmetrical about the carbon nanotube sponge itself. Under the magneto-sound vibration effect, the magneto-sound wave generated by the transducer due to the magneto-sound effect should be symmetrical about the center of the carbon nanotube sponge transducer. The waveform in the positive direction is the same as the waveform of the thermo-sound wave, and the waveform in the negative direction is opposite to the waveform of the thermo-sound wave. Based on the acoustic wave characteristics of thermo-sound and magneto-sound of the carbon nanotube sponge body, a single transducer device emits thermo-sound and magneto-sound at the same time and superimposes them, thereby realizing unidirectional sound transmission with enhanced positive sound pressure and weakened negative sound pressure, and improving the energy conversion efficiency of the transducer.

[0023] (3) Unlike the rigid piezoelectric materials of traditional piezoelectric transducers, carbon nanotube sponges have excellent flexibility, super elasticity (can recover its original shape at 90% strain) and high strength (can withstand 12MPa pressure at 90% strain), so they can fit surfaces of any shape and roughness.

[0024] (4) The three-dimensional carbon nanotube sponge has a better heat dissipation capacity, which allows the heat generated by the carbon nanotube sponge to be quickly discharged when it is working, reducing the surface temperature. Furthermore, the heat dissipation capacity of the sponge is further improved through magnetoacoustic vibration, thereby increasing the service life of the unidirectional controllable acoustic field transducer of the carbon nanotube sponge. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of a unidirectional controllable acoustic field transducer for carbon nanotube sponges.

[0026] Figure 2 Comparison of surface temperatures when two types of carbon nanotube sponge acoustic transducers generate 60dB sound waves. Figure 2 (a) in the figure is a carbon nanotube sponge acoustic transducer with magnetothermal-acoustic coupling effect; Figure 2 (b) in the figure is a carbon nanotube sponge thermoacoustic transducer with thermoacoustic coupling effect.

[0027] Figure 3 The sound pressure frequency response curve of a unidirectional controllable sound field transducer for carbon nanotube sponge.

[0028] Figure 4 The image shows the stable sound pressure response of a unidirectional controllable acoustic field transducer for carbon nanotube sponges.

[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 outer frame; 9 First strong magnet block; 10 Second strong magnet block. Detailed Implementation

[0030] The present invention will be further described below with reference to specific embodiments.

[0031] Figure 1A schematic diagram of the sound-generating element structure of a unidirectional controllable sound field transducer based on carbon nanotube sponge is shown. The sound-generating 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 novel unidirectional controllable sound field transducer based on carbon nanotube sponge includes a sound-generating element, an acrylic plate outer frame 8, and first and second strong magnet blocks 9 and 10 located on both sides of it. The carbon nanotube sponge 1 is connected to a first metal electrode 2 and a second metal electrode 3 at both ends, respectively. A first wire 4 is welded to the first metal electrode 2, and a second wire 5 is welded to the second metal electrode 3. The first alumina mirror ceramic insulating rod 6 and 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. An acrylic plate frame 6 and a first strong magnet block 9 and a second strong magnet block 10 are respectively pasted on both sides of the carbon nanotube sponge 1, so that the first metal electrode 2, the second metal electrode 3, 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-generating element through the first wire 4 and the second wire 5, so that the novel unidirectional controllable sound field transducer of the carbon nanotube sponge outputs unidirectional sound transmission with enhanced positive sound pressure and weakened negative sound pressure, thereby improving the output sound pressure intensity of the transducer.

[0032] The carbon nanotube sponge 1 is an elastic, high specific surface area, and high porosity macroscopic material composed of countless multi-walled carbon nanotubes interconnected and assembled. It possesses excellent electrical and mechanical properties, enabling independent support. The appropriate size can be selected according to specific needs; in this example, the selected carbon nanotube sponge is 1 cm long, 1 cm wide, and 2 mm thick. The first metal electrode 2 and the second metal electrode 3 can both be made of materials with good conductivity and high-temperature stability, such as copper, zinc, iron, or aluminum electrodes. They are fixedly connected to the carbon nanotube sponge 1 using ultraviolet photosensitive adhesive (VG352). Under ultraviolet irradiation, the adhesive absorbs ultraviolet light and generates active free radicals or cations, initiating monomer polymerization and cross-linking chemical reactions, causing the adhesive to transform from liquid to solid within seconds. It exhibits high viscosity, moisture resistance, high temperature resistance, and impact resistance, making it suitable for bonding materials such as glass, plastics, metals, and ceramics. The conductive material of the epoxy conductive adhesive is nano-scale ultrafine silver powder with a volume resistivity of less than 10 Ω·cm. -3The operating temperature is -40°C to 150°C. The first conductor 4 and the second conductor 5 are made of insulating material on the outside and metal on the inside. The insulating conductors are soldered to electrodes 2 and 3 using a soldering iron. Various solder materials can be selected, including tin-lead alloy solder, antimony-added solder, cadmium-added solder, silver-added solder, and copper-added solder. The signal is transmitted to the sound-generating element through the first conductor 4. The first alumina mirror ceramic insulating rod 6 and B7 are materials with good insulation and high-temperature stability, and their volume resistivity is 10 ohms. 14 Ohm-meter. The strong magnet blocks A9 and B10 are rare-earth strong magnets, professionally known as neodymium iron boron magnets. While maintaining strong magnetism, the strong magnets are relatively small in size and light in weight. In this example, the selected dimensions are 2 cm long, 1 cm wide, and 5 mm thick. The distance between the strong magnets and the carbon nanotube sponge 1 is 1.5 cm, and the magnetic induction intensity generated at the carbon nanotube sponge is 1.5 millitalas.

[0033] In this embodiment of the 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 static magnetic field controlled by the strong magnet block is 6 millitalas, and the structural size is not limited, and can be selected according to actual needs. Ultraviolet photosensitive adhesive (VG352) and epoxy conductive adhesive (K-856) are evenly applied to the connection points between electrodes 2 and 3 and the carbon nanotube film 1. Then, the first metal electrode 2, the second metal electrode 3, and the carbon nanotube film 1 are aligned, joined together, and pressed firmly to achieve a fixed connection between the metal electrodes and the sponge. The first wire 4 and the second wire 5 are soldered onto the first metal electrode 2 and the second metal electrode 3 respectively using a soldering iron.

[0034] In this embodiment, the temperature rise of the novel unidirectional controllable acoustic field transducer of the carbon nanotube sponge under normal conditions was tested according to GB / T 5170.2-2008. The ambient temperature was 21.5 degrees Celsius, the input power was 1.76 watts, the sound 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+), the highest surface temperature of the carbon nanotube sponge after 5 minutes of power-on was measured to be 65.6 degrees Celsius. In the comparative example, with the strong magnet removed and only considering the thermoacoustic effect, the highest surface temperature of the carbon nanotube sponge after 5 minutes of power-on, under the same sound pressure level of 60 dB, was 113.9 degrees Celsius. The surface temperature of the unidirectional controllable acoustic field transducer is lower during operation.

[0035] In this embodiment, the acoustic testing of the carbon nanotube sponge unidirectional controllable sound field transducer was conducted according to GB / T 43537-2023. The unidirectional controllable sound field transducer was placed on a fully anechoic experimental platform, i.e., a cuboid experimental box with 8 cm thick sound-absorbing sponge covering all six sides. The output sound pressure of the unidirectional controllable sound field transducer at the front and back sides was measured using an acoustic measuring instrument (B&K8103). The front side is the side with enhanced sound pressure due to the superposition of magnetic and thermal sound, while the back side is the side with weakened sound pressure due to the superposition of magnetic and thermal sound. The input power was 1 watt, and the test point was located 10 mm away from the central axis of the carbon nanotube sponge surface of the unidirectional controllable sound field transducer. Within the frequency range of 16000–19000 Hz, the unidirectional controllable sound field transducer exhibits a sound pressure level (SPL) of over 50 dB in the forward experimental frequency response curve and below 30 dB in the reverse experimental frequency response curve, approximately equal to ambient noise, with a 20 dB difference between the forward and reverse SPL levels. Furthermore, with the input current set to 5 kHz, measurements were taken on the unidirectional controllable sound field transducer for 30 minutes daily at 2 PM, recording data every 5 minutes for seven consecutive days. The transducer maintained excellent acoustic performance throughout the seven days, with an average SPL of 52.5 dB, demonstrating good acoustic response stability. Therefore, the unidirectional controllable sound field transducer based on carbon nanotube sponge can generate ultrasonic waves with a wide frequency range and high SPL, and can achieve unidirectional sound transmission.

[0036] The embodiments described above are merely illustrative of the implementation methods of the present invention, but should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the protection scope of the present invention.

Claims

1. A unidirectional controllable acoustic field transducer based on carbon nanotube sponge with magnetothermal-acoustic coupling effect, characterized in that, The unidirectional controllable sound field transducer includes 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 consists of a carbon nanotube sponge (1), metal electrodes at its upper and lower ends, and alumina mirror ceramic insulating rods at its left and right ends. In the sound-generating element: the metal electrode includes a first metal electrode (2) and a second metal electrode (3). Each metal electrode is connected to an insulated wire. The wire is used to connect to an external device or power supply to provide an electrical signal. The electrical signal is a DC-biased AC signal, which ensures that the magnetoacoustic and thermoacoustic waves generated by the unidirectional controllable sound field transducer are superimposed. The DC-biased AC signal is connected to the sound-generating element through one of the wires via the metal electrode, and then output through another wire via another metal electrode. 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 gate structure to provide static magnetic field environment conditions.

2. The unidirectional controllable acoustic field transducer based on the magnetothermal-acoustic coupling effect of carbon nanotube sponge according to claim 1, characterized in that, The alumina mirror ceramic insulating rod includes a first alumina mirror ceramic insulating rod (6) and a second alumina mirror ceramic insulating rod (7). The alumina mirror ceramic insulating rod is used in conjunction with a metal electrode to fix the carbon nanotube sponge.

3. The unidirectional controllable acoustic field transducer based on the magnetothermal-acoustic coupling effect of carbon nanotube sponge 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 attached to the left and right sides of the carbon nanotube sponge.

4. The unidirectional controllable acoustic field transducer based on the magnetothermal-acoustic coupling effect of carbon nanotube sponge according to claim 1, characterized in that, The strong magnet is a rare earth strong magnet; the distance between the strong magnet and the carbon nanotube sponge (1) is 1.5 cm.

5. A unidirectional controllable acoustic field transducer based on a carbon nanotube sponge with magnetothermal-acoustic coupling effect according to claim 1, characterized in that, The surfaces of the two strong magnet blocks and the two metal electrodes are perpendicular to each other in space, ensuring that the direction of the magnetic field is perpendicular to the direction of the current, together forming a unidirectional controllable acoustic field transducer of carbon nanotube sponge with magnetothermal-acoustic coupling effect.

6. A unidirectional controllable acoustic field transducer based on a carbon nanotube sponge with magnetothermal-acoustic coupling effect according to claim 1, characterized in that, The carbon nanotube sponge (1) is assembled from multiple multi-walled carbon nanotubes connected together.

7. A unidirectional controllable acoustic field transducer based on a carbon nanotube sponge with magnetothermal-acoustic coupling effect according to claim 1, characterized in that, The metal electrode can be made of materials with good conductivity and high-temperature stability, such as copper, zinc, iron, and aluminum electrodes.

8. A unidirectional controllable acoustic field transducer based on a carbon nanotube sponge with magnetothermal-acoustic coupling effect according to claim 1, characterized in that, The outer frame (8) is an acrylic sheet.

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