A piezoelectrically driven self-biased very low frequency mechanical transmit antenna and method of making the same

Abstract

The application provides a piezoelectric driving self-biased very low frequency mechanical transmitting antenna and a preparation method thereof. The preparation method comprises the following steps: step one, preparing piezoelectric ceramic material; step two, cutting and slotting; step three, pouring resin; step four, cutting layer sheet; step five, packaging; step six, polarization treatment; step seven, preparing adhesive layer; and step eight, hot-pressing compounding. Compared with the existing magnetoelectric antenna, the self-biased very low frequency mechanical transmitting antenna has the characteristics of self-bias, high piezoelectricity, miniaturization, no additional noise source and electromagnetic interference, and the like, has the advantages of high stress transmission efficiency and small ohmic loss, can realize the miniaturization requirement of the magnetoelectric mechanical antenna, is easy to form a large-scale array, improves the magnetic transmitting performance under zero bias, and achieves the low frequency communication effect.

Description

Technical Field

[0001] This invention relates to the field of electromagnetic communication technology, and in particular to a piezoelectrically driven self-biased very low frequency mechanical transmitting antenna and its fabrication method. Background Technology

[0002] With the rapid proliferation of low-power electronic devices and smart sensor devices, the demand for miniaturized antennas in the medical device field has surged. Among them, low-frequency magnetoelectric antennas play a crucial role in implantable medical device applications because they offer miniaturization, lower path loss, and higher efficiency, enabling therapeutic drug delivery, nerve stimulation, and deep body communication. However, these antennas have limitations in bandwidth and cross-medium transmission capabilities, requiring the application of a bias magnetic field to achieve optimal magnetic emission performance. This is mainly because the introduction of a bias magnetic field causes the hysteresis-stretching material to be in an easily magnetized state, thereby improving its stress-magnetization response behavior. In existing research, a pair of permanent magnets or a Helmholtz coil carrying direct current is typically used to provide the required bias magnetic field (H). bias However, the presence of permanent magnets or coils leads to a larger size of the magneto-electromechanical antenna system, additional noise sources, and electromagnetic interference, all of which make it difficult to meet the miniaturization requirements of magneto-electric antennas. Therefore, a novel design is needed to achieve efficient magnetic transmission in the absence of a DC magnetic field.

[0003] Currently, there are two solutions to the problem of magnetic bias in low-frequency magnetoelectric antennas: one is to enhance the magnetic emission intensity under zero bias, and the other is to change the way the magnetic bias is applied. Ultimately, the goal is to improve the magnetization state of the magnetoelectric composite material under zero bias. However, the introduction of a whole magnetic layer into the sample will affect its stress transfer efficiency. Regarding the stress transfer problem of magnetoelectric composite materials, Hwang et al. (Enhancement of Magnetoelectric Conversion Achieved by Optimization of Interfacial Adhesion Layer in Laminate Composites[J].ACSAppl.Mater.Interfaces,2018,10(38):32323-32330) proved through theoretical simulation that the thickness and elastic modulus of the adhesive layer will significantly affect the stress transfer efficiency. However, it is very difficult to directly increase the elastic modulus of the adhesive layer. The cross-linking structure and degree of polymerization inside the adhesive will affect the elastic modulus of the adhesive layer.

[0004] Therefore, there is an urgent need to develop a self-biased very low frequency mechanical transmitting antenna to solve the problems of additional noise sources and stress transmission caused by the external bias magnetic field, to achieve enhanced magnetic emission intensity under zero bias, and to achieve low frequency communication effect. Summary of the Invention

[0005] In view of this, the present invention proposes a self-biased, high-voltage, miniaturized, piezoelectrically driven self-biased very low frequency mechanical transmitting antenna and its fabrication method, which is free from additional noise sources and electromagnetic interference. The self-biased very low frequency mechanical transmitting antenna has high stress transfer efficiency and low ohmic loss, can meet the miniaturization requirements of magneto-electro-mechanical antennas, is easy to array on a large scale, improves magnetic transmission performance under zero bias conditions, and achieves low frequency communication effects.

[0006] In a first aspect, the present invention provides a method for fabricating a piezoelectrically driven self-biased very low frequency mechanical transmitting antenna, comprising the following steps:

[0007] Step 1: Preparation of piezoelectric ceramic materials

[0008] After the raw materials are prepared and mixed, the piezoelectric ceramic material is obtained through pre-firing, granulation, molding, debinding and sintering.

[0009] Step 2: Cutting and Grooving

[0010] The piezoelectric fiber composite material prepared in step one is cut and slotted.

[0011] Step 3: Pouring Resin

[0012] Resin is poured into the piezoelectric fiber composite material that was grooved in step two, and then cooled.

[0013] Step 4: Cutting the slices

[0014] The cooled product from step three is sliced ​​to obtain piezoelectric fiber sheets.

[0015] Step 5: Packaging

[0016] The piezoelectric fiber sheet from step four is bonded to the interdigitated electrode using an adhesive, and then hot-pressed to obtain a piezoelectric fiber composite material.

[0017] Step Six: Polarization Treatment

[0018] The piezoelectric fiber composite material from step five is subjected to polarization treatment;

[0019] Step 7: Prepare the adhesive layer

[0020] Adhesive filled with magnetic particles;

[0021] Step 8: Hot pressing composite

[0022] A self-biased very low frequency mechanical transmitting antenna was fabricated by hot-pressing the piezoelectric fiber composite material polarized in step six with a magnetostrictive phase using an adhesive layer.

[0023] By employing the above technical solution, this invention fills the adhesive layer between the piezoelectric fiber composite material (MFC) and the magnetostrictive phase (Metglas) with magnetic particles. The high elastic modulus and high remanent magnetization of these magnetic particles provide advantageous conditions for the stress and magnetization states of the magnetostrictive phase. Because the difference in magnetic properties between the magnetic particles in the adhesive layer and the magnetostrictive phase induces an internal magnetic field, the magnetoelectric mechanical antenna with a magnetic gradient structure can achieve self-biasing. Simultaneously, the high elastic modulus and small adhesive layer thickness can improve stress transmission in the strain layer (i.e., the interface between the piezoelectric and magnetostrictive phases). This enhances the magnetic emission intensity of the magnetoelectric mechanical antenna under zero-bias conditions, achieving very low frequency (VLF) communication performance.

[0024] Based on the above technical solutions, preferably, in step one, the preparation of the piezoelectric ceramic material includes the following steps: ball milling ceramic powder, adding a 5% polyvinyl alcohol solution by mass, grinding and granulating, pressing and molding, debinding, sintering, and obtaining the piezoelectric ceramic material.

[0025] Based on the above technical solutions, preferably, the mass ratio of the ceramic powder to the polyvinyl alcohol solution is 10-15:1.

[0026] More preferably, the mass ratio of the ceramic powder to the polyvinyl alcohol solution is 15:1.

[0027] In this invention, the selection of ceramic powder raw materials includes, but is not limited to: lead zirconate titanate ceramic blocks of niobium magnesium zirconate, polyvinylidene fluoride ceramic blocks, or lead zirconate titanate ceramic blocks; the preferred material in this invention is lead zirconate titanate ceramic blocks, which have a particle size of less than 0.12 mm after being crushed.

[0028] Based on the above technical solutions, preferably, the preparation of the piezoelectric ceramic material includes the following steps: zirconate titanate ceramic powder is placed in a crucible, compacted and mixed, then placed in a muffle furnace for pre-firing, and cooled with the furnace to obtain a pre-fired sample. Subsequently, it is ball-milled, a polyvinyl alcohol solution is added, and the mixture is ground and granulated, pressed into shape, debinded, and sintered to obtain the piezoelectric ceramic material.

[0029] More preferably, the selection of the ball milling media includes, but is not limited to, alcohol, with a rotation speed of 200-300 r / min and a time of 10-20 h.

[0030] More preferably, the grinding requirement is to grind until the powder becomes uniform granules that do not easily stick to the wall, and the particle size does not exceed 100 mesh.

[0031] More preferably, the pressure application conditions are: cold isostatic pressure under vacuum conditions, and pressure needs to be applied from all directions.

[0032] More preferably, the green body needs to be buried with powder before sintering, that is, a layer of powder left over after molding is laid around the green body to avoid lead loss.

[0033] Based on the above technical solutions, preferably, in step two, the depth of the groove is about 4 / 5 of the ceramic material.

[0034] Based on the above technical solutions, preferably, the casting resin specifically includes: ultrasonically cleaning the product in step two, adding adhesive under vacuum, venting, and cooling.

[0035] In this invention, the elastic modulus of the adhesive is greater than 3 GPa, and its specific selection includes, but is not limited to, epoxy resin, acrylate, silicone, rubber or other flexible insulating materials; epoxy resin is preferred in this invention.

[0036] More preferably, before pouring the resin, the epoxy resin should be placed in a 60°C drying oven for 15 minutes to increase its fluidity.

[0037] More preferably, the amount of epoxy resin added is positively correlated with the volume of the ceramic block, and its volume percentage is 30%.

[0038] Based on the above technical solutions, preferably, in step four, the thickness of the sheet is generally 0.3 mm, the length is 10 cm, and the width is 2 cm.

[0039] Based on the above technical solutions, preferably, the amount of adhesive used is about 0.5 to 1.0 g, the purpose of which is to make the adhesive evenly coated on the piezoelectric fiber sheet.

[0040] Based on the above technical solutions, preferably, the polarization conditions are 1.5 to 3.5 kV / mm.

[0041] Based on the above technical solutions, preferably, the use of magnetic particles to fill the adhesive layer specifically includes:

[0042] Magnetic particles with a volume fraction of 10-50% are added to epoxy resin, stirred under heating conditions, amine curing agent is added, and ultrasonic treatment is performed to obtain the adhesive layer.

[0043] In this invention, the magnetic particles are selected from materials with an elastic modulus of 10 GPa to 100 GPa, a remanent magnetization of 10 to 200 emu / g, and a particle size of 1 to 5 μm. The selection of magnetic particles in this invention includes, but is not limited to, Terfenol-D powder or cobalt ferrite particles, with Terfenol-D powder being preferred.

[0044] By employing the above technical solution, the addition of Terfenol-D powder in the adhesive layer and the setting of its volume fraction can adjust the magnitude of the internal bias magnetic field of the mechanical antenna and the elastic modulus of the epoxy adhesive layer. For Terfenol-D powder, excessively large particle sizes make it difficult to fill and affect interfacial bonding, while excessively small particle sizes lead to agglomeration and poor dispersion. Therefore, its particle size is controlled to be 1–5 μm. Furthermore, when the volume fraction of Terfenol-D powder is below 10%, the magnetic emission intensity under zero bias is very weak; when the volume fraction of Terfenol-D powder exceeds 50%, it may lead to uneven filler dispersion and poor interfacial bonding quality, resulting in a decrease in performance.

[0045] In this invention, the elastic modulus of the adhesive layer filled with Terfenol-D powder is 3 GPa to 10 GPa, and the thickness is 0.15 to 0.4 μm.

[0046] By adopting the above technical solution, the magnetic emission effect of the low elastic modulus adhesive layer will be reduced, and the adhesive layer of this thickness will have a better stress transmission effect and better magnetic emission performance.

[0047] Based on the above technical solutions, preferably, the conditions for hot-pressing composite are set as follows: pressure 2-20 MPa, temperature 50-100℃, and curing time 5-30 min.

[0048] By adopting the above technical solutions, the interfacial bonding state of composite materials and the degree of cross-linking and curing of adhesives can be significantly improved, thereby affecting the stress transmission and magnetic emission performance of magnetoelectric composite materials.

[0049] Secondly, the present invention relates to a piezoelectrically driven self-biased very low frequency mechanical transmitting antenna prepared by the above method, wherein the self-biased very low frequency mechanical transmitting antenna comprises, from the inside to the outside: a piezoelectric phase, an adhesive layer and a magnetostrictive phase; the piezoelectric phase and the magnetostrictive phase are connected through the adhesive layer.

[0050] Based on the above technical solutions, preferably, the material selection of the magnetostrictive phase includes, but is not limited to, magnetic amorphous alloys, and the magnetostrictive phase of the present invention is preferably Metglas.

[0051] Based on the above technical solutions, preferably, two holes are opened on one side of the piezoelectric phase, and the two holes are used to connect external wires to apply an external DC electric field.

[0052] By adopting the above technical solution, the piezoelectric phase is used as the excitation source, and the external wire generates resonance through the inverse piezoelectric effect to drive the ferromagnetic material to vibrate, which can convert electrical energy into mechanical energy and then into magnetic field energy.

[0053] The self-biased very low frequency mechanical transmitting antenna provided by this invention has the following advantages over the prior art:

[0054] (1) Compared with existing magnetoelectric antennas, the self-biased very low frequency mechanical transmitting antenna of the present invention has the characteristics of self-biasing, high voltage, miniaturization, no additional noise source and electromagnetic interference, and has the advantages of high stress transmission efficiency and low ohmic loss. It can meet the miniaturization requirements of magnetoelectric mechanical antennas, is easy to array on a large scale, improves the zero-biased magnetic transmission performance, and achieves low frequency communication effect.

[0055] (2) The self-biased very low frequency mechanical transmitting antenna of the present invention can obtain an internal magnetic gradient structure by introducing magnetic particles in the adhesive layer, which brings about a self-biasing effect and solves the problem of additional noise sources and electromagnetic interference from the external bias magnetic field.

[0056] (3) The self-biased very low frequency mechanical transmitting antenna of the present invention uses an epoxy adhesive layer with high elastic modulus, which can improve the stress transmission between the piezoelectric phase and the magnetostrictive phase, and solves the problem that the thickness and elastic modulus of the adhesive layer will significantly affect the stress transmission efficiency.

[0057] (4) The self-biased very low frequency mechanical transmitting antenna of the present invention is driven by piezoelectric resonance, and has the characteristics of low ohmic loss and high efficiency. It can meet the need for miniaturization of magneto-electro-mechanical antenna, is easy to form large-scale arrays, improves magnetic transmission performance, and achieves low frequency communication effect. Attached Figure Description

[0058] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0059] Figure 1 A process flow diagram for fabricating the self-biased very low frequency mechanical transmitting antenna of this invention;

[0060] Figure 2 This is a structural diagram of the self-biased very low frequency mechanical transmitting antenna prepared according to the present invention.

[0061] Figure 3 The magnetic emission intensity diagrams of M-0, M-1, M-2, and M-3 under zero bias in various embodiments of the present invention are shown.

[0062] Figure 4 The graph shows the variation of magnetic emission intensity of M-0, M-1, M-2, and M-3 with voltage under zero bias in various embodiments of the present invention.

[0063] Figure 5This is a graph showing the variation of magnetic emission intensity with frequency for embodiments M-0 and M-3 of the present invention;

[0064] Figure 6 This is a comparison diagram of the changes in magnetic emission intensity as a function of magnetic field direction for embodiments M-0 and M-3 of the present invention under zero bias.

[0065] Figure 7 This is a signal modulation diagram of embodiment M-3 of the present invention. Detailed Implementation

[0066] In practice, the inventors discovered that existing magneto-electro-mechanical antennas typically have the following problems:

[0067] (1) The existence of existing permanent magnets or coils will lead to problems such as large size of magneto-electro-mechanical antenna systems, additional noise sources and electromagnetic interference, which are difficult to meet the needs of miniaturization of magneto-electro-electric antennas.

[0068] (2) From the perspective of stress transmission, the low elastic modulus of the adhesive layer of the magnetoelectric composite material will affect its magnetic emission performance.

[0069] (3) Low-frequency magnetoelectric antennas have limitations in terms of bandwidth and cross-medium transmission capability.

[0070] To solve the above-mentioned technical problems, the inventors conducted further research and came up with this invention.

[0071] This invention fabricates a self-biased very low frequency (VLF) mechanical transmitting antenna. This antenna utilizes magnetic particles with high elastic modulus and high remanent magnetization, filled in the adhesive layer between a piezoelectric fiber composite (MFC) and a magnetostrictive phase, providing favorable conditions for the stress and magnetization states of the magnetostrictive phase. Furthermore, the difference in magnetic properties between the magnetic particles in the adhesive layer and the magnetostrictive phase induces an internal magnetic field, generating a magnetic gradient structure, thus enabling self-biasing. Simultaneously, the high elastic modulus and small adhesive layer thickness enhance stress transfer between the piezoelectric and magnetostrictive phases, thereby improving the magnetic emission intensity of the magnetoelectric mechanical antenna under zero-bias conditions and achieving VLF communication performance.

[0072] See attached document Figure 1 As shown, the process flow for fabricating a self-biased very low frequency mechanical transmitting antenna according to the present invention specifically includes the following steps:

[0073] Step 1: Preparation of piezoelectric ceramic materials

[0074] After the raw materials are prepared and mixed, the piezoelectric ceramic material is obtained through pre-firing, granulation, molding, debinding and sintering.

[0075] Step 2: Cutting and Grooving

[0076] The piezoelectric fiber composite material prepared in step one is cut and slotted.

[0077] Step 3: Pouring Resin

[0078] Resin is poured into the piezoelectric fiber composite material that was grooved in step two, and then cooled.

[0079] Step 4: Cutting the slices

[0080] The cooled product from step three is sliced ​​to obtain piezoelectric fiber sheets.

[0081] Step 5: Packaging

[0082] The piezoelectric fiber sheet from step four is bonded to the interdigitated electrode using an adhesive, and then hot-pressed to obtain a piezoelectric fiber composite material.

[0083] Step Six: Polarization Treatment

[0084] The piezoelectric fiber composite material from step five is subjected to polarization treatment;

[0085] Step 7: Prepare the adhesive layer

[0086] The adhesive layer is filled with magnetic particles;

[0087] Step 8: Hot pressing composite

[0088] By hot-pressing the piezoelectric fiber composite material polarized in step six with a magnetostrictive phase using an adhesive layer, a self-biased very low frequency mechanical transmitting antenna was fabricated, the structure of which is shown in the attached figure. Figure 2 As shown.

[0089] In this invention, the preparation of piezoelectric fiber composite material (MFC), namely the specific operations of steps one to five, are carried out in accordance with the piezoelectric fiber composite structure layer disclosed in Chinese Patent CN201510907240.4. The relevant content of this invention is only summarized.

[0090] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0091] The present invention will be further described below with reference to specific embodiments. The scope of protection of the present invention is not limited to the following embodiments. Unless otherwise specified, the main materials involved in the embodiments are conventional commercially available products.

[0092] Example 1

[0093] This embodiment provides a method for fabricating a very low frequency mechanical transmitting antenna, including the following steps:

[0094] Lead zirconate titanate (PZT) powder was thoroughly mixed and pre-fired using ball milling and sieving techniques. The pre-fired blocks were crushed and placed in a ball mill jar. A 5 wt% polyvinyl alcohol (PVA) solution was added to the dried particles, and the mixture was ground until the powder became uniform and did not easily adhere to the mill walls. After passing through a 100-mesh sieve, ceramic powder was obtained. The PZT piezoelectric ceramic powder was then flattened and further degassed using hot pressing technology. Following debinding and high-temperature sintering, PZT piezoelectric ceramic blocks were obtained. After cleaning and drying, the blocks were cut to obtain piezoelectric fiber arrays (fiber length 100 mm, width 0.6 mm, spacing 0.3 mm). Epoxy resin was poured into the arrays, and after complete solidification, layers (length 100 mm, width 20 mm, thickness 0.3 mm) were cut. Two mirror-symmetrical interdigitated electrodes were then encapsulated. The piezoelectric phase polarization conditions were 3 kV / mm and an 80°C oil bath. The desired MFC was then obtained.

[0095] The Metglas film was cut into sheets 100 mm long and 20 mm wide. An amine curing agent (Westsystem 206) was added to the epoxy resin (Westsystem 105), and the mixture was stirred under heating for a period of time to reduce viscosity. Afterward, it was ultrasonically treated for 10 minutes. The epoxy resin was then scraped onto the MFC and Metglas films with a blade and bonded together. Finally, the Metglas / MFC laminate was compacted in a hot press at 2 MPa and cured at 60°C for 15 minutes to obtain the magneto-electro-mechanical antenna, denoted as M-0.

[0096] Example 2

[0097] This embodiment provides a method for fabricating a self-biased magneto-electro-mechanical antenna, the steps of which are as follows:

[0098] Lead zirconate titanate (PZT) powder was thoroughly mixed and pre-fired using ball milling and sieving techniques. The pre-fired blocks were crushed and placed in a ball mill jar. A 5 wt% polyvinyl alcohol (PVA) solution was added to the dried particles, and the mixture was ground until the powder became uniform and did not easily adhere to the mill walls. After passing through a 100-mesh sieve, ceramic powder was obtained. The PZT piezoelectric ceramic powder was then flattened and further degassed using hot pressing technology. Following debinding and high-temperature sintering, PZT piezoelectric ceramic blocks were obtained. After cleaning and drying, the blocks were cut to obtain piezoelectric fiber arrays (fiber length 100 mm, width 0.6 mm, spacing 0.3 mm). Epoxy resin was poured into the arrays, and after complete solidification, layers (length 100 mm, width 20 mm, thickness 0.3 mm) were cut. Two mirror-symmetrical interdigitated electrodes were then encapsulated. The piezoelectric phase polarization conditions were 3 kV / mm and an 80°C oil bath. The desired MFC was then obtained.

[0099] The Metglas film was cut into sheets 100 mm long and 20 mm wide. Terfenol-D powder was added to epoxy resin (West system 105) to form a 10 vol% Terfenol-D / epoxy resin mixture. The mixture was stirred under heating for a period of time to reduce viscosity and promote the dispersion of Terfenol-D powder in the epoxy resin. Then, an amine curing agent (West system 206) was added, and the mixture was ultrasonically treated for 10 minutes. The 10 vol% Terfenol-D / epoxy resin mixture was then scraped onto the MFC and Metglas films using a blade, and the two were bonded together. Finally, the Metglas / MFC laminate was compacted in a hot press at 2 MPa and cured at 60°C for 15 minutes to obtain a self-biased magneto-mechanical antenna, denoted as M-1.

[0100] Example 3

[0101] This embodiment provides a method for fabricating a self-biased magneto-electro-mechanical antenna, the steps of which are as follows:

[0102] Lead zirconate titanate (PZT) powder was thoroughly mixed and pre-fired using ball milling and sieving techniques. The pre-fired blocks were crushed and placed in a ball mill jar. A 5 wt% polyvinyl alcohol (PVA) solution was added to the dried particles, and the mixture was ground until the powder became uniform and did not easily adhere to the mill walls. After passing through a 100-mesh sieve, ceramic powder was obtained. The PZT piezoelectric ceramic powder was then flattened and further degassed using hot pressing technology. Following debinding and high-temperature sintering, PZT piezoelectric ceramic blocks were obtained. After cleaning and drying, the blocks were cut to obtain piezoelectric fiber arrays (fiber length 100 mm, width 0.6 mm, spacing 0.3 mm). Epoxy resin was poured into the arrays, and after complete solidification, layers (length 100 mm, width 20 mm, thickness 0.3 mm) were cut. Two mirror-symmetrical interdigitated electrodes were then encapsulated. The piezoelectric phase polarization conditions were 3 kV / mm and an 80°C oil bath. The desired MFC was then obtained.

[0103] The Metglas film was cut into sheets 100 mm long and 20 mm wide. Terfenol-D powder was added to epoxy resin (West system 105) to form a 30 vol% Terfenol-D / epoxy resin mixture. The mixture was stirred under heating for a period of time to reduce viscosity and promote the dispersion of Terfenol-D powder in the epoxy resin. Then, an amine curing agent (West system 206) was added, and the mixture was ultrasonically treated for 10 minutes. The 30 vol% Terfenol-D / epoxy resin mixture was then scraped onto the MFC and Metglas films using a blade, and the two were bonded together. Finally, the Metglas / MFC laminate was compacted in a hot press at 4 MPa and cured at 70°C for 20 minutes to obtain a self-biased magneto-electromechanical antenna, denoted as M-2.

[0104] Example 4

[0105] This embodiment provides a method for fabricating a self-biased magneto-electro-mechanical antenna, the steps of which are as follows:

[0106] Lead zirconate titanate (PZT) powder was thoroughly mixed and pre-fired using ball milling and sieving techniques. The pre-fired blocks were crushed and placed in a ball mill jar. A 5 wt% polyvinyl alcohol (PVA) solution was added to the dried particles, and the mixture was ground until the powder became uniform and did not easily adhere to the mill walls. After passing through a 100-mesh sieve, ceramic powder was obtained. The PZT piezoelectric ceramic powder was then flattened and further degassed using hot pressing technology. Following debinding and high-temperature sintering, PZT piezoelectric ceramic blocks were obtained. After cleaning and drying, the blocks were cut to obtain piezoelectric fiber arrays (fiber length 100 mm, width 0.6 mm, spacing 0.3 mm). Epoxy resin was poured into the arrays, and after complete solidification, layers (length 100 mm, width 20 mm, thickness 0.3 mm) were cut. Two mirror-symmetrical interdigitated electrodes were then encapsulated. The piezoelectric phase polarization conditions were 3 kV / mm and an 80°C oil bath. The desired MFC was then obtained.

[0107] The Metglas film was cut into sheets 100 mm long and 20 mm wide. A certain amount of Terfenol-D powder was added to epoxy resin (West system 105) to form a 50 vol% Terfenol-D / epoxy resin mixture. The mixture was stirred under heating for a period of time to reduce viscosity and promote the dispersion of Terfenol-D powder in the epoxy resin. Then, an amine curing agent (West system 206) was added, and the mixture was ultrasonically treated for 10 minutes. The 50 vol% Terfenol-D / epoxy resin mixture was then scraped onto the MFC and Metglas films with a blade and bonded together. Finally, the Metglas / MFC laminate was compacted in a hot press at 8 MPa and cured at 80°C for 25 minutes to obtain a self-biased magneto-mechanical antenna, denoted as M-3.

[0108] The magnetic emission performance of the above embodiments 1 to 4 was tested, specifically referring to the literature (Magneto-Mechano-Electric Antenna for Portable VLF Transmission[J].Adv.Elect.Mater,2023,9(7):2300096), including: using a lock-in amplifier (SR830, Stanford Research Systems, USA) to measure the magnetic emission intensity of the magnetoelectric composite material as a function of frequency under an unbiased magnetic field, and testing the change of magnetic emission intensity with voltage. In this part, a self-made coil was used as a long-distance receiver to capture the radiation signals in various magnetic directions.

[0109] The digital data transmission detection of the above embodiments 1 to 4, specifically referring to the literature (Bias-free VeryLow Frequency Magnetoelectric Antenna[J]. Appl. Phys. Lett, 2023, 122(26):262901), includes: using a function generator to convert the binary bit stream into an ASK signal, and then amplifying it through a power amplifier; using a loop antenna to measure the magnetic radiation signal and demodulating it through a computer.

[0110] Test results as follows Figures 3-7 As shown.

[0111] Depend on Figure 3 It can be seen that, compared with M-0, samples M-1, M-2, and M-3 with magnetic gradient structures exhibit superior magnetic emission performance under zero bias. Among them, M-3 has the best magnetic emission intensity, which is 2.8 times that of M-0. This is attributed to the appropriate amount of magnetic particles providing better internal magnetic field and interface bonding, facilitating the realization of the self-biasing effect.

[0112] Depend on Figure 4 It can be seen that, compared with M-0, the M-1, M-2 and M-3 samples with magnetic gradient structures have greater power output at the same voltage under zero bias, with M-3 having the best output.

[0113] Depend on Figure 5 It can be seen that M-0 and M-3 have the best magnetic emission intensity around 13kHz, which can meet the very low frequency communication range, and M-3 has a greater magnetic emission intensity.

[0114] Depend on Figure 6 It can be seen that when a coil is used to receive signals at 40cm, M-0 and M-3 have the greatest radiation intensity at 0° and 180°, respectively, and M-3 has better directionality.

[0115] Depend on Figure 7 It can be seen that for digital signal transmission using M-3, the 1Hz binary bitstream is converted into an ASK modulated signal and loaded at the antenna's resonant frequency. After demodulation and low-pass filtering, the measurement signal is successfully converted back into the original bitstream without distortion, thus achieving very low frequency communication.

[0116] In summary, the self-biased magneto-electro-mechanical antenna with a magnetic gradient structure prepared in this invention not only exhibits excellent performance in terms of magnetic emission intensity and power output, but also demonstrates significant advantages in very low frequency (VLF) communication applications. This provides important theoretical basis and technical support for the development of novel magneto-electric composite materials and their applications in wireless communication and other fields.

[0117] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for fabricating a piezoelectrically driven self-biased very low frequency mechanical transmitting antenna, characterized in that, The preparation method includes the following steps: Step 1: Preparation of piezoelectric ceramic materials After the raw materials are prepared and mixed, the piezoelectric ceramic material is obtained through pre-firing, granulation, molding, debinding and sintering. Step 2: Cutting and Grooving The piezoelectric fiber composite material prepared in step one is cut and slotted. Step 3: Pouring Resin Resin is poured into the piezoelectric fiber composite material that was grooved in step two, and then cooled. Step 4: Cutting the slices The cooled product from step three is sliced ​​to obtain piezoelectric fiber sheets. Step 5: Packaging The piezoelectric fiber sheet from step four is bonded to the interdigitated electrode using an adhesive, and then hot-pressed to obtain a piezoelectric fiber composite material. Step Six: Polarization Treatment The piezoelectric fiber composite material from step five is subjected to polarization treatment; Step 7: Prepare the adhesive layer The adhesive layer is filled with magnetic particles; wherein, the magnetic particles are used with a volume fraction of 10~50%, and the magnetic particles are Terfenol-D powder or cobalt ferrite particles. Step 8: Hot pressing composite A self-biased very low frequency mechanical transmitting antenna was fabricated by hot-pressing the piezoelectric fiber composite material polarized in step six with a magnetostrictive phase using an adhesive layer.

2. The preparation method according to claim 1, characterized in that, In step one, the preparation of piezoelectric ceramic material includes the following steps: ball milling ceramic powder, adding a 5% polyvinyl alcohol solution, grinding and granulating, pressing and molding, debinding, sintering, and obtaining piezoelectric ceramic material.

3. The preparation method according to claim 2, characterized in that, The mass ratio of ceramic powder to the polyvinyl alcohol solution is 10~15:

1.

4. The preparation method according to claim 1, characterized in that, In step three, resin casting specifically includes: ultrasonically cleaning the product from step two, adding adhesive under vacuum, venting, and cooling; the elastic modulus of the adhesive is greater than 3 GPa.

5. The preparation method according to claim 1, characterized in that, In step six, the polarization conditions are 1.5~3.5 kV / mm.

6. The preparation method according to claim 1, characterized in that, Step seven, the step of filling the adhesive layer with magnetic particles, specifically includes: Magnetic particles with a volume fraction of 10-50% are added to the adhesive, stirred under heating conditions, amine curing agent is added, and ultrasonic treatment is performed to obtain the adhesive layer. The magnetic particles have an elastic modulus of 10 GPa to 100 GPa, a remanent magnetization of 10 to 200 emu / g, and a particle size of 1 to 5 μm.

7. The preparation method according to claim 1, characterized in that, In step eight, the hot-pressing composite conditions are set as follows: pressure 2~20 MPa, temperature 50~100 ℃, curing time 5~30 min.

8. A piezoelectrically driven, self-biased very low frequency mechanical transmitting antenna, characterized in that, The self-biased very low frequency mechanical transmitting antenna is prepared by the method described in any one of claims 1 to 7.

9. The piezoelectrically driven self-biased very low frequency mechanical transmitting antenna as described in claim 8, characterized in that, The self-biased very low frequency mechanical transmitting antenna comprises, from the inside out: a piezoelectric fiber composite material, an adhesive layer, and a magnetostrictive phase; the piezoelectric fiber composite material and the magnetostrictive phase are connected through the adhesive layer.

10. The piezoelectrically driven self-biased very low frequency mechanical transmitting antenna as described in claim 9, characterized in that, The piezoelectric fiber composite material has two holes on one side for connecting external wires to apply an external DC electric field.

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