An energy conversion device based on a flexible electromagnetic wave absorbing material and a preparation method thereof

Abstract

The application discloses an energy conversion device based on a flexible electromagnetic wave absorbing material and a preparation method thereof, and belongs to the technical field of composite functional materials. The method is that PBAs precursors are first synthesized, then magnetic nanoparticle@nitrogen-doped carbon is prepared, further pouring is conducted to obtain a flexible composite sheet (magnetic nanoparticle@nitrogen-doped carbon / polymer), finally, an electromagnetic energy-thermal energy-electric energy conversion device is constructed, and thus the energy conversion device is obtained. After electromagnetic wave radiation to the energy conversion device, the electromagnetic wave energy is converted into thermal energy by a magnetic loss introduced by the magnetic nanoparticle, a dipole polarization and a conductance loss introduced by the nitrogen-doped carbon, and an interface polarization between the two. The application can not only solve the increasingly serious electromagnetic radiation and pollution problems, but also recycle and utilize the harmful electromagnetic wave energy and convert the electromagnetic wave energy into electric energy, and can supply energy for wearable electronic equipment.

Description

Technical Field

[0001] This invention relates to an energy conversion device based on flexible electromagnetic wave absorbing material and its preparation method, belonging to the field of composite functional materials technology. Background Technology

[0002] With the widespread application of new-generation information and communication technologies and various electronic products, electromagnetic pollution is becoming increasingly severe. Electromagnetic radiation not only interferes with the normal operation of electronic components but also harms human health. Electromagnetic wave absorbing materials, based on multiple mechanisms such as magnetic and electrical losses, can convert electromagnetic wave energy into heat energy and dissipate it, becoming a key strategy for solving the electromagnetic radiation problem. Meanwhile, with the rapid development of electronic technology, the field of wearable electronic devices has made significant progress, with the integration of various electronic products increasing, showing a trend towards high efficiency, miniaturization, and intelligence. However, the integration of various electronic components not only brings electromagnetic interference and radiation problems but also necessitates the development of lightweight, flexible, and sustainable energy supply devices. Currently, wearable devices generally rely on battery power, which severely restricts their further development and breakthroughs in performance improvement, functional expansion, and application scenario extension, becoming a critical issue that urgently needs to be addressed in this field.

[0003] In existing technologies, many studies address the power supply problem for passive wearable sensors by focusing on the effective utilization of various types of energy in the environment, such as collecting kinetic energy, solar energy, and thermal energy, and further converting them into other forms of energy that can be reused. CN202111122744.7, CN202211042071.9, CN202310972616.4, and CN202210548446.2 propose using triboelectric power generation to continuously power passive devices that monitor human movement or health indicators. However, such energy conversion devices based on mechanical friction have complex internal structures and relatively narrow application scenarios, making it difficult to provide power for passive sensors in a wider range of fields. CN202310583675.2, CN202110775134.0, and CN201910310265.4 focus on converting solar energy into electrical energy to perform charging control operations for related devices. However, this energy supply method is significantly constrained by environmental factors, making it difficult to ensure a stable and continuous power supply in actual use. CN202310969955.7, CN202310090664.0 and ZL201510328818.0 proposed energy storage by boosting voltage after passive radio frequency signal identification and applying it to positioning services or temperature detection. Its drawback is that it can only identify low-frequency signals, and it adopts a contact response mode when detecting temperature, which limits the detection range. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides an energy conversion device based on flexible electromagnetic wave absorbing materials and its fabrication method. By absorbing waves to generate heat and then generating electricity, it can efficiently collect and convert electromagnetic wave energy, and realize its wide application in wearable devices.

[0005] To achieve the above objectives, this invention proposes a method for fabricating an energy conversion device based on a flexible electromagnetic wave absorbing material, the method comprising the following steps:

[0006] 1) Dissolve the ionic compound in dilute hydrochloric acid, and add Na3C6H5O7·2H2O and polyvinylpyrrolidone to form solution A. Dissolve two or more of K3[Fe(CN)6], K4[Fe(CN)6]·3H2O and K3[Co(CN)6] in dilute hydrochloric acid to form solution B. Mix solution A and solution B, and heat the mixture in a water bath to react. After post-processing, the PBA precursor is obtained.

[0007] 2) The PBA precursor was subjected to heat treatment to obtain magnetic nanoparticles@nitrogen-doped carbon;

[0008] 3) The magnetic nanoparticles@nitrogen-doped carbon are added to a polymer solution, and then the mixed solution is poured into a mold to obtain a flexible composite sheet, which is also a flexible electromagnetic wave absorbing material.

[0009] 4) Using the flexible composite sheet as the top layer material, a layer of first thermally conductive silicone grease is coated on the bottom. Then, a copper foil is attached to the lower surface of the thermally conductive silicone grease, and a layer of second thermally conductive silicone grease is filled under the copper foil. A semiconductor thermoelectric generator is set under the second thermally conductive silicone grease to obtain the energy conversion device based on the flexible electromagnetic wave absorbing material.

[0010] According to a preferred embodiment of the present invention, in step 1), the ionic compound is Fe. 3+ Co 2+ Ni 2+ chloride salt compounds, Fe 3+ Co 2+ Ni 2+ nitrate compounds or Fe 3+ Co 2+ Ni 2+ The solution is a sulfate compound, and the ionic compound contains at least two metal elements. Preferably, the concentration of dilute hydrochloric acid in solutions A and B is 0.1–1 mol / L.

[0011] According to a preferred embodiment of the present invention, in step 1), the total concentration of ionic compounds in solution A is 0.01–0.2 mol / L, and the total concentration of K3[Fe(CN)6], K4[Fe(CN)6]·3H2O, and K3[Co(CN)6] in solution B is 0.01–0.2 mol / L. Preferably, the volume ratio of solution A to solution B is 1:1. Preferably, the concentration of Na3C6H5O7·2H2O in solution A is 0.02–0.5 g / mL, and the concentration of polyvinylpyrrolidone in solution A is 0.02–0.5 g / mL.

[0012] According to a preferred embodiment of the present invention, in step 1), the temperature range of the water bath heating is 80-100°C, the reaction time is 6-8 hours, and the post-treatment is as follows: after the reaction is completed, the mixture is cooled, the precipitate is collected by centrifugation, washed sequentially with deionized water and anhydrous ethanol, and dried in a vacuum oven to obtain the PBA precursor.

[0013] According to a preferred embodiment of the present invention, the magnetic nanoparticles in the nitrogen-doped carbon obtained in step 2) are Fe 100-a Co a Fe 100-b Ni b or Fe 100-c-d Co c Ni d One of the following, where 10≤a<50, 10≤b<50, 10≤c≤30, and 10≤d≤20.

[0014] According to a preferred embodiment of the present invention, the heat treatment temperature in step 2) is 600–800°C, and the heat treatment time is 2–3 hours; the heat treatment is carried out under a certain atmosphere, which is argon, nitrogen, or a mixture of argon and hydrogen. Preferably, the volume ratio of hydrogen in the mixed gas is 10%.

[0015] According to a preferred embodiment of the present invention, the polymer is one of polyurethane, polyvinyl alcohol, polydimethylsiloxane or polyvinyl butyral; the mass ratio of the magnetic nanoparticles@nitrogen-doped carbon to the polymer is (1:9) to (2:3).

[0016] According to a preferred embodiment of the present invention, in step 3), the magnetic nanoparticles@nitrogen-doped carbon are mixed with a polymer solution, and the sample is dispersed evenly by ultrasonic treatment. Then, the mixture is quickly poured into a mold, mechanically vibrated to fill the mold, and then placed in a vacuum oven to remove air bubbles and dry to form a flexible composite sheet.

[0017] According to a preferred embodiment of the present invention, the flexible composite sheet is composed of magnetic nanoparticles@nitrogen-doped carbon / polymer, and the mass fraction of magnetic nanoparticles@nitrogen-doped carbon in the flexible composite sheet is 10-40 wt.%.

[0018] The present invention also provides an energy conversion device based on a flexible electromagnetic wave absorbing material prepared by the method described above, which is an electromagnetic energy-thermal energy-electric energy conversion device.

[0019] This invention, based on PBA derivatives, designs an electromagnetic wave energy conversion device with wide frequency band, light weight, and excellent flexibility. It is compatible with wearable devices and can be converted into usable electrical energy via a thermoelectric module. By optimizing the ratio of magnetic elements in the PBA derivatives, magnetic loss can be controlled. Magnetic nanoparticles@nitrogen-doped carbon obtained after heat treatment can effectively optimize impedance matching. Constructing a multilayer structure with absorbing sheets, thermally conductive silicone grease, and copper foil not only enables multiple reflections and scattering of electromagnetic waves but also enhances the heat conduction path, directly introducing the converted heat energy into a semiconductor thermoelectric generator and converting it into electrical energy. This energy conversion device based on flexible electromagnetic wave absorbing materials provides an effective solution for utilizing waste and harmful electromagnetic radiation to power passive wearable devices.

[0020] The advantages of this invention compared to the prior art are as follows:

[0021] 1. The Fe involved in this invention 3+ Co 2+ Ni 2+ chloride salt compounds, Fe 3+ Co 2+ Ni 2+ nitrate compounds or Fe 3+ Co 2+ Ni 2+ The magnetic loss contributed by the magnetic properties of two or more metal elements in sulfate compounds plays a significant role. By adjusting the content of metal elements in the aforementioned salt compounds and PBAs, the composition ratio can be controlled, thereby altering the magnetic properties of magnetic nanoparticles and thus allowing for the controllable design of microwave absorption performance.

[0022] 2. The flexible electromagnetic wave absorbing material of this invention combines dielectric and magnetic materials, improving impedance matching. The cross-linking of the three-dimensional spherical carbon network accelerates electron hopping or migration within the material, converting microwave energy into heat energy through lattice collisions. Furthermore, nitrogen and oxygen atoms doped into the carbon framework form numerous defect sites and oxygen-containing functional groups, providing significant dipole and defect losses. Additionally, the heterogeneous interface between the magnetic nanoparticles and the carbon matrix provides interfacial polarization. The magnetic nanoparticles contribute magnetic losses primarily from eddy current effects, natural resonance, and exchange resonance. The synergistic effect of these multiple effects and loss mechanisms significantly enhances electromagnetic wave attenuation.

[0023] 3. In this invention, the prepared flexible composite sheet magnetic nanoparticles@nitrogen-doped carbon / polymer are used as the top layer material, and a multilayer structure of thermally conductive silicone grease-copper foil-thermally conductive silicone grease is constructed. This not only achieves effective loss of electromagnetic waves, but also increases the electromagnetic wave propagation path. Multiple reflections and scattering enhance the attenuation of electromagnetic waves, while better conducting heat for subsequent use. Attached Figure Description

[0024] Figure 1 This is a physical image of the flexible composite sheet magnetic nanoparticles@nitrogen-doped carbon / polymer according to an embodiment of the present invention;

[0025] Figure 2 This is a schematic diagram of an energy conversion device based on flexible electromagnetic wave absorbing material according to an embodiment of the present invention;

[0026] Figure 3 This is a schematic diagram illustrating the connection and application of the electromagnetic wave energy-thermal energy-electric energy conversion device of the present invention. Detailed Implementation

[0027] The present invention will be further described and illustrated below with reference to specific embodiments. The embodiments described are merely examples of the content of this disclosure and do not limit the scope of the invention. The technical features of each embodiment in the present invention can be combined accordingly, provided that there is no mutual conflict.

[0028] Example 1

[0029] 1) Synthesis of PBA precursors:

[0030] According to the molar ratio of Fe:Co = 70:30, 0.77363 g of FeCl3·6H2O and 0.87309 g of Co(NO3)2·6H2O were weighed and dissolved in a 0.1 mol / L dilute hydrochloric acid solution. Then, 1.821 g of Na3C6H5O7·2H2O and 2 g of PVP were added sequentially, and the mixture was stirred thoroughly to form solution A. Next, 0.65800 g of K3[Fe(CN)6] and 0.90308 g of K4[Fe(CN)6]·3H2O were weighed and added sequentially to a 0.1 mol / L dilute hydrochloric acid solution, and the mixture was stirred thoroughly to obtain solution B. Solution B was slowly added dropwise to the stirred solution A. After thorough mixing, the mixture was sealed and placed in a water bath at 80°C for 8 hours. After cooling, the precipitate was collected by centrifugation, washed sequentially with deionized water and anhydrous ethanol, and dried in a vacuum oven.

[0031] 2) Preparation of magnetic nanoparticles@nitrogen-doped carbon:

[0032] The sample obtained in step 1) was placed in a tube furnace and heat-treated for 3 hours at a heat treatment temperature of 600℃ and in an inert gas Ar atmosphere, and then cooled to room temperature to obtain the final product.

[0033] 3) Casting flexible composite sheet (magnetic nanoparticles@nitrogen-doped carbon / polyurethane):

[0034] The sample collected in step 2) was added to a polyurethane solution to prepare a composite sheet. 3.072 g of the prepared polyurethane solution was weighed and completely dissolved by ultrasonication. Then, 0.768 g of magnetic nanoparticles@nitrogen-doped carbon was weighed (the final flexible composite sheet contains 20 wt.% magnetic nanoparticles@nitrogen-doped carbon). The sample was ultrasonically dispersed to ensure uniform dispersion, then rapidly poured into a custom mold. After mechanically vibrating to fill the mold, it was placed in a vacuum oven for degassing and defoaming, followed by drying to obtain the flexible composite sheet (magnetic nanoparticles@nitrogen-doped carbon / polyurethane). Figure 1 As shown;

[0035] 4) Construct an electromagnetic energy-thermal energy-electrical energy conversion device:

[0036] Using the flexible composite sheet (magnetic nanoparticles@nitrogen-doped carbon / polyurethane) prepared in step 3) as the top layer material, a layer of thermally conductive silicone grease is coated on the bottom. Next, a copper foil is attached to the lower surface of the thermally conductive silicone grease, and another layer of thermally conductive silicone grease is filled below the copper foil. A semiconductor thermoelectric generator is then placed below the subsequently filled thermally conductive silicone grease, finally producing an electromagnetic wave energy-thermal energy-electric energy conversion device, such as... Figure 2 As shown, a water-cooling device is installed at the bottom of the electromagnetic wave energy-thermal energy-electric energy conversion device to facilitate heat dissipation, and cooling water is used to cool the semiconductor thermoelectric generator.

[0037] The absorption performance of the obtained magnetic nanoparticles@nitrogen-doped carbon samples was tested using the coaxial method, and the results are shown in Table 1. Figure 3 This illustration demonstrates the application of the electromagnetic wave energy-thermal energy-electrical energy conversion device of the present invention, employing... Figure 3 The connection relationship is shown in the diagram. The performance test is carried out. Table 2 shows the output characteristics of the corresponding electromagnetic wave energy-thermal energy-electric energy conversion device constructed with an electromagnetic wave input power of 9W and an irradiation time of 300s. The open circuit voltage (mV) is as a function of frequency.

[0038] Table 1. Microwave absorption properties of magnetic nanoparticles@nitrogen-doped carbon

[0039]

[0040] Table 2. Open-circuit voltage output of the electromagnetic wave energy-thermal energy-electric energy conversion device.

[0041]

[0042] Example 2

[0043] 1) Synthesis of PBA precursors:

[0044] According to the molar ratio of Fe:Co = 90:10, 1.92309 g of Fe(NO3)3·9H2O and 0.23800 g of Co(Cl)2·6H2O were weighed and dissolved in a 0.3 mol / L dilute hydrochloric acid solution. Then, 1.910 g of Na3C6H5O7·2H2O and 2.5 g of PVP were added sequentially, and the mixture was stirred thoroughly to form solution A. Next, 0.22043 g of K3[Fe(CN)6] and 1.50654 g of K4[Fe(CN)6]·3H2O were weighed and added sequentially to a 0.3 mol / L dilute hydrochloric acid solution, and the mixture was stirred thoroughly to obtain solution B. Solution B was slowly added dropwise to the stirred solution A. After thorough mixing, the mixture was sealed and placed in a water bath at 85°C for 8 hours. After cooling, the precipitate was collected by centrifugation, washed sequentially with deionized water and anhydrous ethanol, and dried in a vacuum oven.

[0045] 2) Preparation of magnetic nanoparticles@nitrogen-doped carbon:

[0046] The sample obtained in step 1) was placed in a tube furnace and heat-treated for 3 hours at a heat treatment temperature of 650°C and an inert gas N2 atmosphere, and then cooled to room temperature to obtain the final product.

[0047] 3) Casting flexible composite sheet (magnetic nanoparticles@nitrogen-doped carbon / polyvinyl alcohol):

[0048] The sample collected in step 2) was added to a polyvinyl alcohol solution to prepare a composite sheet. 3.456 g of polyvinyl alcohol was weighed and the solution was prepared. The polyvinyl alcohol was completely dissolved by ultrasonication. Then, 0.384 g of magnetic nanoparticles@nitrogen-doped carbon was weighed (the final mass fraction of magnetic nanoparticles@nitrogen-doped carbon in the flexible composite sheet was 10 wt.%). The sample was ultrasonically treated to ensure uniform dispersion, then quickly poured into a custom mold. After mechanically vibrating to fill the mold, it was placed in a vacuum oven for degassing and defoaming, and then dried to obtain the flexible composite sheet (magnetic nanoparticles@nitrogen-doped carbon / polyvinyl alcohol).

[0049] 4) Construct an electromagnetic wave energy-thermal energy-electric energy conversion device:

[0050] The flexible composite sheet (magnetic nanoparticles@nitrogen-doped carbon / polyvinyl alcohol) prepared in step 3) is used as the top layer material. A layer of thermally conductive silicone grease is coated on the bottom. Then, a copper foil is attached to the lower surface of the thermally conductive silicone grease. A layer of thermally conductive silicone grease is filled under the copper foil. A semiconductor thermoelectric generator is placed under the filled thermally conductive silicone grease. Finally, an electromagnetic wave energy-thermal energy-electric energy conversion device is obtained.

[0051] The obtained magnetic nanoparticles@nitrogen-doped carbon samples were tested for microwave absorption performance using the coaxial method, and the results are shown in Table 3. Table 4 shows the open-circuit voltage (mV) of the corresponding electromagnetic wave energy-thermal energy-electric energy conversion device constructed under an electromagnetic wave input power of 9W and an irradiation time of 300s as a function of frequency.

[0052] Table 3. Microwave absorption properties of magnetic nanoparticles@nitrogen-doped carbon

[0053]

[0054] Table 4. Open-circuit voltage output of the electromagnetic wave energy-thermal energy-electric energy conversion device

[0055]

[0056] Example 3

[0057] 1) Synthesis of PBA precursors:

[0058] According to the molar ratio of Fe:Co = 55:45, 0.38682 g of FeCl3·6H2O and 1.30964 g of Co(NO3)2·6H2O were weighed and dissolved in a 0.5 mol / L dilute hydrochloric acid solution. Then, 1.700 g of Na3C6H5O7·2H2O and 1.5 g of PVP were added sequentially, and the mixture was stirred thoroughly to form solution A. Next, 0.98700 g of K3[Fe(CN)6] and 0.45154 g of K4[Fe(CN)6]·3H2O were weighed and added sequentially to a 0.5 mol / L dilute hydrochloric acid solution, and the mixture was stirred thoroughly to obtain solution B. Solution B was slowly added dropwise to the stirred solution A. After thorough mixing, the mixture was sealed and placed in a water bath at 90°C for 7 hours. After cooling, the precipitate was collected by centrifugation, washed sequentially with deionized water and anhydrous ethanol, and dried in a vacuum oven.

[0059] 2) Preparation of magnetic nanoparticles@nitrogen-doped carbon:

[0060] The sample obtained in step 1) was placed in a tube furnace and heat-treated for 2.5 hours at a heat treatment temperature of 700℃ in a mixed gas atmosphere of Ar / H2 (10 vol% H2). The sample was then cooled to room temperature to obtain the final product.

[0061] 3) Casting flexible composite sheet (magnetic nanoparticles@nitrogen-doped carbon / polydimethylsiloxane):

[0062] The sample collected in step 2) was added to a polydimethylsiloxane solution to prepare a composite sheet. 2.688 g of polydimethylsiloxane was weighed and the solution was prepared. The polydimethylsiloxane was completely dissolved by ultrasonication. Then, 1.152 g of magnetic nanoparticles@nitrogen-doped carbon was weighed (the final mass fraction of magnetic nanoparticles@nitrogen-doped carbon in the flexible composite sheet was 30 wt.%). The sample was ultrasonically treated to ensure uniform dispersion, then quickly poured into a custom mold. After mechanically vibrating to fill the mold, it was placed in a vacuum oven for degassing and defoaming, and then dried to obtain the flexible composite sheet (magnetic nanoparticles@nitrogen-doped carbon / polydimethylsiloxane).

[0063] 4) Construct an electromagnetic energy-thermal energy-electrical energy conversion device:

[0064] The flexible composite sheet (magnetic nanoparticles@nitrogen-doped carbon / polydimethylsiloxane) prepared in step 3) is used as the top layer material. A layer of thermally conductive silicone grease is coated on the bottom. Then, a copper foil is attached to the lower surface of the thermally conductive silicone grease. A layer of thermally conductive silicone grease is filled under the copper foil. A semiconductor thermoelectric generator is placed under the filled thermally conductive silicone grease. Finally, an electromagnetic wave energy-thermal energy-electric energy conversion device is obtained.

[0065] The obtained magnetic nanoparticles@nitrogen-doped carbon samples were tested for microwave absorption performance using the coaxial method, and the results are shown in Table 5. Table 6 shows the open-circuit voltage (mV) of the corresponding electromagnetic wave energy-thermal energy-electric energy conversion device constructed under an electromagnetic wave input power of 9W and an irradiation time of 300s as a function of frequency.

[0066] Table 5. Microwave absorption properties of magnetic nanoparticles@nitrogen-doped carbon

[0067]

[0068] Table 6. Open-circuit voltage output of the electromagnetic wave energy-thermal energy-electric energy conversion device.

[0069]

[0070] Example 4

[0071] 1) Synthesis of PBA precursors:

[0072] According to the molar ratio of Fe:Ni = 75:25, 1.34535 g of Fe(NO3)3·9H2O and 0.65713 g of Ni(SO4)2·6H2O were weighed and dissolved in a 0.7 mol / L dilute hydrochloric acid solution. Then, 1.865 g of Na3C6H5O7·2H2O and 2 g of PVP were added sequentially, and the mixture was stirred thoroughly to form solution A. Next, 0.54943 g of K3[Fe(CN)6] and 1.05500 g of K4[Fe(CN)6]·3H2O were weighed and added sequentially to the 0.7 mol / L dilute hydrochloric acid solution, and the mixture was stirred thoroughly to obtain solution B. Solution B was slowly added dropwise to the stirred solution A. After thorough mixing, the mixture was sealed and placed in a water bath at 80°C for 6 hours. After cooling, the precipitate was collected by centrifugation, washed sequentially with deionized water and anhydrous ethanol, and dried in a vacuum oven.

[0073] 2) Preparation of magnetic nanoparticles@nitrogen-doped carbon:

[0074] The sample obtained in step 1) was placed in a tube furnace and heat-treated at a heat treatment temperature of 700℃ and in an inert gas Ar atmosphere for 2 hours, and then cooled to room temperature to obtain the final product.

[0075] 3) Casting flexible composite sheet (magnetic nanoparticles@nitrogen-doped carbon / polyvinyl butyral):

[0076] The sample collected in step 2) was added to a polyvinyl butyral solution to prepare a composite sheet. 3.072 g of polyvinyl butyral was weighed and the solution was prepared. The polyvinyl butyral was completely dissolved by ultrasonication. Then, 0.768 g of magnetic nanoparticles@nitrogen-doped carbon was weighed (the final mass fraction of magnetic nanoparticles@nitrogen-doped carbon in the flexible composite sheet was 20 wt.%). The sample was ultrasonically treated to ensure uniform dispersion, then quickly poured into a custom mold. After mechanically vibrating to fill the mold, it was placed in a vacuum oven for degassing and defoaming, and then dried to obtain the flexible composite sheet (magnetic nanoparticles@nitrogen-doped carbon / polyvinyl butyral).

[0077] 4) Construct an electromagnetic wave energy-thermal energy-electric energy conversion device:

[0078] The flexible composite sheet (magnetic nanoparticles@nitrogen-doped carbon / polyvinyl butyral) prepared in step 3) is used as the top layer material. A layer of thermally conductive silicone grease is coated on the bottom. Then, a copper foil is attached to the lower surface of the thermally conductive silicone grease. A layer of thermally conductive silicone grease is filled under the copper foil. A semiconductor thermoelectric generator is placed under the filled thermally conductive silicone grease. Finally, an electromagnetic wave energy-thermal energy-electric energy conversion device is obtained.

[0079] The obtained magnetic nanoparticles@nitrogen-doped carbon samples were tested for microwave absorption performance using the coaxial method, and the results are shown in Table 7. Table 8 shows the open-circuit voltage (mV) of the corresponding electromagnetic wave energy-thermal energy-electric energy conversion device constructed under an electromagnetic wave input power of 9W and an irradiation time of 300s as a function of frequency.

[0080] Table 7. Microwave absorption properties of magnetic nanoparticles@nitrogen-doped carbon

[0081]

[0082] Table 8. Open-circuit voltage output of the electromagnetic wave energy-thermal energy-electric energy conversion device.

[0083]

[0084] Example 5

[0085] 1) Synthesis of PBA precursors:

[0086] According to the molar ratio of Fe:Ni = 90:10, 1.28758 g of FeCl3·6H2O and 0.23769 g of Ni(Cl)2·6H2O were weighed and dissolved in a 0.9 mol / L dilute hydrochloric acid solution. Then, 2 g of Na3C6H5O7·2H2O and 3 g of PVP were added sequentially, and the mixture was stirred thoroughly to form solution A. Next, 0.22043 g of K3[Fe(CN)6] and 1.50654 g of K4[Fe(CN)6]·3H2O were weighed and added sequentially to a 0.9 mol / L dilute hydrochloric acid solution, and the mixture was stirred thoroughly to obtain solution B. Solution B was slowly added dropwise to the stirred solution A. After thorough mixing, the mixture was sealed and placed in a water bath at 100°C for 6 hours. After cooling, the precipitate was collected by centrifugation, washed sequentially with deionized water and anhydrous ethanol, and dried in a vacuum oven.

[0087] 2) Preparation of magnetic nanoparticles@nitrogen-doped carbon:

[0088] The sample obtained in step 1) was placed in a tube furnace and heat-treated at a heat treatment temperature of 800℃ and an inert gas N2 atmosphere for 2.5 hours, and then cooled to room temperature to obtain the final product.

[0089] 3) Casting flexible composite sheet (magnetic nanoparticles@nitrogen-doped carbon / polyurethane):

[0090] The sample collected in step 2) was added to a polyurethane solution to prepare a composite sheet. 3.456 g of polyurethane was weighed and the prepared solution was dissolved completely by ultrasonication. Then, 0.384 g of magnetic nanoparticles@nitrogen-doped carbon was weighed (the final flexible composite sheet contains 10 wt.% magnetic nanoparticles@nitrogen-doped carbon). The sample was ultrasonically treated to ensure uniform dispersion, then quickly poured into a custom mold. After mechanically vibrating to fill the mold, it was placed in a vacuum oven for degassing and defoaming, and then dried to obtain the flexible composite sheet (magnetic nanoparticles@nitrogen-doped carbon / polyurethane).

[0091] 4) Construct an electromagnetic wave energy-thermal energy-electric energy conversion device:

[0092] The flexible composite sheet (magnetic nanoparticles@nitrogen-doped carbon / polyurethane) prepared in step 3) is used as the top layer material. A layer of thermally conductive silicone grease is coated on the bottom. Then, a copper foil is attached to the lower surface of the thermally conductive silicone grease. A layer of thermally conductive silicone grease is filled under the copper foil. A semiconductor thermoelectric generator is placed under the filled thermally conductive silicone grease. Finally, an electromagnetic wave energy-thermal energy-electric energy conversion device is obtained.

[0093] The obtained magnetic nanoparticles@nitrogen-doped carbon samples were tested for microwave absorption performance using the coaxial method, and the results are shown in Table 9. Table 10 shows the open-circuit voltage (mV) of the corresponding electromagnetic wave energy-thermal energy-electric energy conversion device constructed under an electromagnetic wave input power of 9W and an irradiation time of 300s as a function of frequency.

[0094] Table 9. Microwave absorption properties of magnetic nanoparticles@nitrogen-doped carbon

[0095]

[0096] Table 10 Open-circuit voltage output of the electromagnetic wave energy-thermal energy-electric energy conversion device

[0097]

[0098] Example 6

[0099] 1) Synthesis of PBA precursors:

[0100] According to the molar ratio of Fe:Ni = 52:48, 0.30837 g of FeCl3·6H2O and 1.14091 g of Ni(Cl)2·6H2O were weighed and dissolved in a 1.0 mol / L dilute hydrochloric acid solution. Then, 1.764 g of Na3C6H5O7·2H2O and 1 g of PVP were added sequentially, and the mixture was stirred thoroughly to form solution A. Next, 1.05280 g of K3[Fe(CN)6] and 0.36292 g of K4[Fe(CN)6]·3H2O were weighed and added sequentially to a 1.0 mol / L dilute hydrochloric acid solution, and the mixture was stirred thoroughly to obtain solution B. Solution B was slowly added dropwise to the stirred solution A. After thorough mixing, the mixture was sealed and placed in a water bath at 85°C for 7 hours. After cooling, the precipitate was collected by centrifugation, washed sequentially with deionized water and anhydrous ethanol, and dried in a vacuum oven.

[0101] 2) Preparation of magnetic nanoparticles@nitrogen-doped carbon:

[0102] The sample obtained in step 1) was placed in a tube furnace and heat-treated for 3 hours at a heat treatment temperature of 650°C in a mixed gas atmosphere of Ar / H2 (10 vol% H2). The sample was then cooled to room temperature to obtain the final product.

[0103] 3) Casting flexible composite sheet (magnetic nanoparticles@nitrogen-doped carbon / polyvinyl alcohol):

[0104] The sample collected in step 2) was added to a polyvinyl alcohol solution to prepare a composite sheet. 2.688 g of polyvinyl alcohol was weighed and the solution was prepared. The polyvinyl alcohol was completely dissolved by ultrasonication. Then, 1.152 g of magnetic nanoparticles@nitrogen-doped carbon was weighed (the final mass fraction of magnetic nanoparticles@nitrogen-doped carbon in the flexible composite sheet was 30 wt.%). The sample was ultrasonically treated to ensure uniform dispersion, then quickly poured into a custom mold. After mechanically vibrating to fill the mold, it was placed in a vacuum oven for degassing and defoaming, and then dried to obtain the flexible composite sheet (magnetic nanoparticles@nitrogen-doped carbon / polyvinyl alcohol).

[0105] 4) Construct an electromagnetic wave energy-thermal energy-electric energy conversion device:

[0106] The flexible composite sheet (magnetic nanoparticles@nitrogen-doped carbon / polyvinyl alcohol) prepared in step 3) is used as the top layer material. A layer of thermally conductive silicone grease is coated on the bottom. Then, a copper foil is attached to the lower surface of the thermally conductive silicone grease. A layer of thermally conductive silicone grease is filled under the copper foil. A semiconductor thermoelectric generator is placed under the filled thermally conductive silicone grease. Finally, an electromagnetic wave energy-thermal energy-electric energy conversion device is obtained.

[0107] The obtained magnetic nanoparticles@nitrogen-doped carbon samples were tested for microwave absorption performance using the coaxial method, and the results are shown in Table 11. Table 12 shows the open-circuit voltage (mV) of the corresponding electromagnetic wave energy-thermal energy-electric energy conversion device constructed under an electromagnetic wave input power of 9W and an irradiation time of 300s as a function of frequency.

[0108] Table 11 Microwave absorption properties of magnetic nanoparticles@nitrogen-doped carbon

[0109]

[0110] Table 12 Open-circuit voltage output of the electromagnetic wave energy-thermal energy-electric energy conversion device

[0111]

[0112] Example 7

[0113] 1) Synthesis of PBA precursors:

[0114] According to the molar ratio of Fe:Co:Ni = 60:20:20, 0.51395 g of FeCl3·6H2O, 0.47600 g of Co(Cl)2·6H2O, and 0.47538 g of Ni(Cl)2·6H2O were weighed and dissolved in a 0.5 mol / L dilute hydrochloric acid solution. Then, 2 g of Na3C6H5O7·2H2O and 2 g of PVP were added sequentially, and the mixture was stirred thoroughly to form solution A. Next, 0.87843 g of K3[Fe(CN)6] and 0.60346 g of K4[Fe(CN)6]·3H2O were weighed and added sequentially to the 0.5 mol / L dilute hydrochloric acid solution, and the mixture was stirred thoroughly to obtain solution B. Solution B was slowly added dropwise to the stirred solution A, and after thorough mixing, the mixture was sealed and placed in a water bath at 80°C for 8 hours. After cooling, the precipitate was collected by centrifugation, washed successively with deionized water and anhydrous ethanol, and then dried in a vacuum oven.

[0115] 2) Preparation of magnetic nanoparticles@nitrogen-doped carbon:

[0116] The sample obtained in step 1) was placed in a tube furnace and heat-treated for 3 hours at a heat treatment temperature of 600℃ and in an inert gas Ar atmosphere, and then cooled to room temperature to obtain the final product.

[0117] 3) Casting flexible composite sheet (magnetic nanoparticles@nitrogen-doped carbon / polyurethane):

[0118] The sample collected in step 2) was added to a polyurethane solution to prepare a composite sheet. 3.072 g of polyurethane was weighed and the prepared solution was completely dissolved by ultrasonication. Then, 0.768 g of magnetic nanoparticles@nitrogen-doped carbon was weighed (the final flexible composite sheet contains 20 wt.% magnetic nanoparticles@nitrogen-doped carbon). The sample was ultrasonically dispersed to ensure uniform dispersion, then quickly poured into a custom mold. After mechanically vibrating to fill the mold, it was placed in a vacuum oven for degassing and defoaming, and then dried to obtain the flexible composite sheet (magnetic nanoparticles@nitrogen-doped carbon / polyurethane).

[0119] 4) Construct an electromagnetic wave energy-thermal energy-electric energy conversion device:

[0120] The flexible composite sheet (magnetic nanoparticles@nitrogen-doped carbon / polyurethane) prepared in step 3) is used as the top layer material. A layer of thermally conductive silicone grease is coated on the bottom. Then, a copper foil is attached to the lower surface of the thermally conductive silicone grease. A layer of thermally conductive silicone grease is filled under the copper foil. A semiconductor thermoelectric generator is placed under the filled thermally conductive silicone grease. Finally, an electromagnetic wave energy-thermal energy-electric energy conversion device is obtained.

[0121] The obtained magnetic nanoparticles@nitrogen-doped carbon samples were tested for microwave absorption performance using the coaxial method, and the results are shown in Table 13. Table 14 shows the open-circuit voltage (mV) of the corresponding electromagnetic wave energy-thermal energy-electric energy conversion device constructed under an electromagnetic wave input power of 9W and an irradiation time of 300s as a function of frequency.

[0122] Table 13 Microwave absorption properties of magnetic nanoparticles@nitrogen-doped carbon

[0123]

[0124] Table 14 Open-circuit voltage output of the electromagnetic wave energy-thermal energy-electric energy conversion device

[0125]

[0126] Example 8

[0127] 1) Synthesis of PBA precursors:

[0128] According to the molar ratio of Fe:Co:Ni = 70:20:10, 1.15547 g of Fe(NO3)3·9H2O, 0.58206 g of Co(NO3)2·6H2O, and 0.26285 g of Ni(SO4)2·6H2O were weighed and dissolved in a 0.1 mol / L dilute hydrochloric acid solution. Then, 2 g of Na3C6H5O7·2H2O and 1.5 g of PVP were added sequentially, and the mixture was stirred thoroughly to form solution A. Next, 0.65800 g of K3[Fe(CN)6] and 0.90308 g of K4[Fe(CN)6]·3H2O were weighed and added sequentially to a 0.1 mol / L dilute hydrochloric acid solution, and the mixture was stirred thoroughly to obtain solution B. Solution B was slowly added dropwise to the stirred solution A, and after thorough mixing, the mixture was sealed and placed in a water bath at 90°C for 7 hours. After cooling, the precipitate was collected by centrifugation, washed successively with deionized water and anhydrous ethanol, and then dried in a vacuum oven.

[0129] 2) Preparation of magnetic nanoparticles@nitrogen-doped carbon:

[0130] The sample obtained in step 1) was placed in a tube furnace and heat-treated at a heat treatment temperature of 700℃ and an inert gas N2 atmosphere for 2.5 hours, and then cooled to room temperature to obtain the final product.

[0131] 3) Casting flexible composite sheet (magnetic nanoparticles@nitrogen-doped carbon / polyurethane):

[0132] The sample collected in step 2) was added to a polyurethane solution to prepare a composite sheet. 2.688 g of polyurethane was weighed and the prepared solution was dissolved completely by ultrasonication. Then, 1.152 g of magnetic nanoparticles@nitrogen-doped carbon was weighed (the final flexible composite sheet contains 30 wt.% magnetic nanoparticles@nitrogen-doped carbon). The sample was ultrasonically treated to ensure uniform dispersion, then quickly poured into a custom mold. After mechanically vibrating to fill the mold, it was placed in a vacuum oven for degassing and defoaming, and then dried to obtain the flexible composite sheet (magnetic nanoparticles@nitrogen-doped carbon / polyurethane).

[0133] 4) Construct an electromagnetic wave energy-thermal energy-electric energy conversion device:

[0134] The flexible composite sheet (magnetic nanoparticles@nitrogen-doped carbon / polyurethane) prepared in step 3) is used as the top layer material. A layer of thermally conductive silicone grease is coated on the bottom. Then, a copper foil is attached to the lower surface of the thermally conductive silicone grease. A layer of thermally conductive silicone grease is filled under the copper foil. A semiconductor thermoelectric generator is placed under the filled thermally conductive silicone grease. Finally, an electromagnetic wave energy-thermal energy-electric energy conversion device is obtained.

[0135] The obtained magnetic nanoparticles@nitrogen-doped carbon samples were tested for microwave absorption performance using the coaxial method, and the results are shown in Table 15. Table 16 shows the open-circuit voltage (mV) of the corresponding electromagnetic wave energy-thermal energy-electric energy conversion device constructed under an electromagnetic wave input power of 9W and an irradiation time of 300s as a function of frequency.

[0136] Table 15 Microwave absorption properties of magnetic nanoparticles@nitrogen-doped carbon

[0137]

[0138] Table 16 Open-circuit voltage output of the electromagnetic wave energy-thermal energy-electric energy conversion device

[0139]

[0140] Example 9

[0141] 1) Synthesis of PBA precursors:

[0142] According to the molar ratio of Fe:Co:Ni = 70:10:20, 1.15547 g of Fe(NO3)3·9H2O, 0.29103 g of Co(NO3)2·6H2O, and 0.52570 g of Ni(SO4)2·6H2O were weighed and dissolved in a 1 mol / L dilute hydrochloric acid solution. Then, 2 g of Na3C6H5O7·2H2O and 2.5 g of PVP were added sequentially, and the mixture was stirred thoroughly to form solution A. Next, 0.65800 g of K3[Fe(CN)6] and 0.90308 g of K4[Fe(CN)6]·3H2O were weighed and added sequentially to a 1 mol / L dilute hydrochloric acid solution, and the mixture was stirred thoroughly to obtain solution B. Solution B was slowly added dropwise to the stirred solution A, and after thorough mixing, the mixture was sealed and placed in a water bath at 100°C for 6 hours. After cooling, the precipitate was collected by centrifugation, washed successively with deionized water and anhydrous ethanol, and then dried in a vacuum oven.

[0143] 2) Preparation of magnetic nanoparticles@nitrogen-doped carbon:

[0144] The sample obtained in step 1) was placed in a tube furnace and heat-treated for 2 hours at a heat treatment temperature of 800℃ in a mixed gas atmosphere of Ar / H2 (10 vol% H2). The sample was then cooled to room temperature to obtain the final product.

[0145] 3) Casting flexible composite sheet (magnetic nanoparticles@nitrogen-doped carbon / polyurethane):

[0146] The sample collected in step 2) was added to a polyurethane solution to prepare a composite sheet. 2.304 g of polyurethane was weighed and the prepared solution was dissolved completely by ultrasonication. Then, 1.536 g of magnetic nanoparticles@nitrogen-doped carbon was weighed (the final flexible composite sheet contains 40 wt.% magnetic nanoparticles@nitrogen-doped carbon). The sample was ultrasonically treated to ensure uniform dispersion, then quickly poured into a custom mold. After mechanically vibrating to fill the mold, it was placed in a vacuum oven for degassing and defoaming, and then dried to obtain the flexible composite sheet (magnetic nanoparticles@nitrogen-doped carbon / polyurethane).

[0147] 4) Construct an electromagnetic wave energy-thermal energy-electric energy conversion device:

[0148] The flexible composite sheet (magnetic nanoparticles@nitrogen-doped carbon / polyurethane) prepared in step 3) is used as the top layer material. A layer of thermally conductive silicone grease is coated on the bottom. Then, a copper foil is attached to the lower surface of the thermally conductive silicone grease. A layer of thermally conductive silicone grease is filled under the copper foil. A semiconductor thermoelectric generator is placed under the filled thermally conductive silicone grease. Finally, an electromagnetic wave energy-thermal energy-electric energy conversion device is obtained.

[0149] The obtained magnetic nanoparticles@nitrogen-doped carbon samples were tested for microwave absorption performance using the coaxial method, and the results are shown in Table 17. Table 18 shows the open-circuit voltage (mV) of the corresponding electromagnetic wave energy-thermal energy-electric energy conversion device constructed under an electromagnetic wave input power of 9W and an irradiation time of 300s as a function of frequency.

[0150] Table 17 Microwave absorption properties of magnetic nanoparticles@nitrogen-doped carbon

[0151]

[0152] Table 18 Open-circuit voltage output of the electromagnetic wave energy-thermal energy-electric energy conversion device

[0153]

[0154] The above-described embodiments are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. 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 scope of protection of the present invention.

Claims

1. A method for fabricating an energy conversion device based on a flexible electromagnetic wave absorbing material, characterized in that, Includes the following steps: 1) Dissolve the ionic compound in dilute hydrochloric acid, and add Na3C6H5O7·2H2O and polyvinylpyrrolidone to form solution A. Dissolve two or more of K3[Fe(CN)6], K4[Fe(CN)6]·3H2O, and K3[Co(CN)6] in dilute hydrochloric acid to form solution B. Mix solutions A and B, and after thorough mixing, heat the mixture in a water bath to react. Post-processing yields the PBA precursor; the ionic compound is Fe 3+ Co 2+ Ni 2+ chloride salt compounds, Fe 3+ Co 2+ Ni 2+ nitrate compounds or Fe 3+ Co 2+ Ni 2+ The sulfate compound, and the ionic compound contains at least two metal elements; the concentration of dilute hydrochloric acid in solutions A and B is 0.1~1 mol / L; 2) The PBA precursor is subjected to heat treatment to obtain magnetic nanoparticles@nitrogen-doped carbon; the heat treatment temperature is 600~800 ℃ and the heat treatment time is 2~3 hours; the heat treatment is carried out in an atmosphere of argon, nitrogen, or a mixture of argon and hydrogen. 3) The magnetic nanoparticles@nitrogen-doped carbon are added to a polymer solution, and then the mixed solution is poured into a mold to obtain a flexible composite sheet; the mass fraction of the magnetic nanoparticles@nitrogen-doped carbon in the flexible composite sheet is 10~40 wt.%. 4) Using the flexible composite sheet as the top layer material, a layer of first thermally conductive silicone grease is coated on the bottom. Then, a copper foil is attached to the lower surface of the thermally conductive silicone grease, and a layer of second thermally conductive silicone grease is filled under the copper foil. A semiconductor thermoelectric generator is set under the second thermally conductive silicone grease to obtain the energy conversion device based on the flexible electromagnetic wave absorbing material.

2. The preparation method according to claim 1, characterized in that, In step 1), the total concentration of ionic compounds in solution A is 0.01~0.2 mol / L, and the total concentration of K3[Fe(CN)6], K4[Fe(CN)6]·3H2O, and K3[Co(CN)6] in solution B is 0.01~0.2 mol / L; the volume ratio of solution A to solution B is 1:1; the concentration of Na3C6H5O7·2H2O in solution A is 0.02~0.5 g / mL, and the concentration of polyvinylpyrrolidone in solution A is 0.02~0.5 g / mL.

3. The preparation method according to claim 1, characterized in that, In step 1), the water bath heating temperature range is 80~100 ℃, the reaction time is 6~8 hours, and the post-treatment is as follows: after the reaction is completed, the mixture is cooled, the precipitate is collected by centrifugation, washed with deionized water and anhydrous ethanol in sequence, and dried in a vacuum oven to obtain the PBA precursor.

4. The preparation method according to claim 1, characterized in that, Step 2) The magnetic nanoparticles obtained in nitrogen-doped carbon are Fe 100-a Co a Fe 100-b Ni b or Fe 100-c-d Co c Ni d One of the following, where 10≤a<50, 10≤b<50, 10≤c≤30, and 10≤d≤20.

5. The preparation method according to claim 1, characterized in that, In step 2), the volume ratio of hydrogen in the mixed gas is 10%.

6. The preparation method according to claim 1, characterized in that, In step 3), the polymer is one of polyurethane, polyvinyl alcohol, polydimethylsiloxane or polyvinyl butyral; the mass ratio of the magnetic nanoparticles@nitrogen-doped carbon to the polymer is (1:9) to (2:3).

7. The preparation method according to claim 1, characterized in that, In step 3), the magnetic nanoparticles@nitrogen-doped carbon are mixed with a polymer solution, and the sample is dispersed evenly by ultrasonic treatment. Then, it is quickly poured into a mold, mechanically vibrated to fill the mold, and then placed in a vacuum oven to remove air bubbles and dry to form a flexible composite sheet.

8. An energy conversion device based on a flexible electromagnetic wave absorbing material prepared by the method of any one of claims 1-7.

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