Solid waste-based high-temperature heat storage material and gradient coating-multi-field synergistic microwave uniform sintering method

Abstract

The invention provides a solid waste-based high-temperature heat storage material and a gradient coating-multi-field synergistic microwave uniform sintering method thereof, and belongs to the technical field of preparation of high-temperature heat storage materials. The method comprises the following steps: adding a polyvinyl alcohol pore-forming agent into a solid waste matrix, carrying out vacuum drying after ball milling, and pressing to obtain a green body; carrying out heat treatment on the green body in a holding furnace through an in-situ reaction synthesis method, and naturally cooling to room temperature to prepare a pre-sintered material; carrying out modification treatment on the surface of the pre-sintered material by adopting Ar / O2 mixed gas plasma, and forming a plasma modified functional layer on the surface of the pre-sintered material; carrying out gradient coating on the surface of the plasma modified functional layer to form an MgO / SiC coating layer; and carrying out microwave sintering treatment on the gradient coated material to obtain the solid-waste-based high-temperature heat storage material. Through the gradient coating layer structural design and in combination with multi-mode microwave field dynamic regulation and control and a temperature-power closed-loop control system, not only is the wave absorbing performance of the material optimized, but also the matching of the microwave penetration depth and the thermal diffusion rate is ensured.

Description

Technical Field

[0001] This disclosure belongs to the field of high-temperature thermal storage material preparation technology, specifically relating to a solid waste-based high-temperature thermal storage material and a gradient coating-multi-field synergistic microwave uniform sintering method. Background Technology

[0002] In the field of preparation of solid waste-based high-temperature thermal storage materials, one of the existing technologies, Chinese patent application CN118026662A, proposes a high-performance microwave ferrite material and its preparation method. The material performance is improved through ion substitution and optimized drying process. However, its focus is mainly on the magnetic properties of the material and the energy consumption of preparation, and the uniformity of energy distribution during microwave heating is not discussed in depth.

[0003] One of the existing technologies, Chinese patent application CN119783482A, focuses on the low-loss design of connectors. Although it performs well in high-frequency and high-power transmission environments, its technical solution is far from the microwave uniform sintering technology of solid waste-based high-temperature thermal storage materials and fails to provide a solution for controlling the microwave absorption performance at the microscale. Summary of the Invention

[0004] This disclosure aims to at least solve one of the technical problems existing in the prior art, and to provide a solid waste-based high-temperature thermal storage material and its gradient coating-multi-field synergistic microwave uniform sintering method.

[0005] One aspect of this disclosure provides a gradient coating-multi-field synergistic microwave uniform sintering method for solid waste-based high-temperature thermal storage materials, comprising: Polyvinyl alcohol pore-forming agent is added to a solid waste matrix, ball milled, vacuum dried, and pressed to obtain a green body; the green body is heat-treated in a heat-insulating furnace by an in-situ reaction synthesis method, and naturally cooled to room temperature to obtain a pre-burned material, which serves as the inner layer. Ar / O2 mixed gas plasma is used to modify the surface of the pre-burned material, forming a plasma-modified functional layer on the surface of the inner layer; A gradient coating of MgO / SiC was formed on the surface of the plasma-modified functional layer using the sol-gel method, which served as the outer layer. Microwave sintering was performed on the gradient-coated material to obtain a solid waste-based high-temperature thermal storage material.

[0006] Optionally, the content of the polyvinyl alcohol pore-forming agent is 5-15 wt% of the solid waste matrix content.

[0007] Optionally, the green body is heat-treated in a holding furnace by in-situ reaction synthesis at a temperature of 350-450°C for 30-50 minutes.

[0008] Optionally, an Ar / O2 mixed gas plasma with a power of 750-850W and a duration of 4-6 minutes is used.

[0009] Optionally, when using the sol-gel method to perform gradient coating on the surface of the plasma-modified functional layer, the coating slurry is coated on the surface of the plasma-modified functional layer in a multi-layer, multi-coating manner to form a multi-layer MgO / SiC coating layer. After drying, a pure SiC outer layer is coated on the multiple MgO / SiC coating layers.

[0010] Optionally, the coating slurry includes MgO and SiC.

[0011] Optionally, during the first coating, the mass ratio of MgO to SiC in the coating slurry is (7-9):1; during the second coating, the mass ratio of MgO to SiC in the coating slurry is (5-7):(3-5); and during the third coating, the mass ratio of MgO to SiC in the coating slurry is (3-5):(5-7).

[0012] Optionally, the thickness of each coating layer is 180-220 nm, and the total thickness of the multi-layer coating is 1100-1300 nm.

[0013] Optionally, when performing microwave sintering on the gradient-coated material, the sintering process parameters are as follows: under an argon protective atmosphere, the temperature is programmed to rise to 1450-1550°C at a rate of 80-120°C / min, and held at this temperature for 20-40 min; wherein, a dual-frequency microwave source is used for microwave sintering during the sintering process, with frequencies of 2.45 GHz and 5.8 GHz, respectively.

[0014] In another aspect of this disclosure, a solid waste-based high-temperature thermal storage material is provided, which is prepared by the method described above.

[0015] This disclosure proposes a solid waste-based high-temperature thermal storage material and its gradient coating-multi-field synergistic microwave uniform sintering method, comprising: adding a polyvinyl alcohol pore-forming agent to a solid waste matrix, ball milling, vacuum drying, and pressing to obtain a green body; heat-treating the green body in a holding furnace using an in-situ reaction synthesis method, and naturally cooling to room temperature to obtain a pre-sintered material as the inner layer; modifying the surface of the pre-sintered material using Ar / O2 mixed gas plasma to form a plasma-modified functional layer on the surface of the inner layer; performing gradient coating on the surface of the plasma-modified functional layer using a sol-gel method to form a MgO / SiC coating layer as the outer layer; and performing microwave sintering on the gradient-coated material to obtain the solid waste-based high-temperature thermal storage material. This disclosure, through gradient coating layer structure design, combined with multi-mode microwave field dynamic control and a temperature-power closed-loop control system, not only optimizes the microwave absorption performance of the material but also ensures the matching of microwave penetration depth and thermal diffusion rate, thereby solving the problem of uneven energy distribution in the microwave heating process of solid waste-based high-temperature thermal storage materials. Attached Figure Description

[0016] Figure 1 The flowchart is a specific embodiment of the gradient coating-multi-field synergistic microwave uniform sintering method for solid waste-based high-temperature thermal storage materials disclosed herein. Figure 2 This is a schematic diagram of the gradient coating-multi-field synergistic microwave uniform sintering method for solid waste-based high-temperature thermal storage materials according to a specific embodiment of this disclosure. Figure 3 A schematic diagram of a multi-field coordinated microwave uniform sintering system according to a specific embodiment of this disclosure; Figure 4 This is a schematic diagram of the structure of the solid waste-based high-temperature thermal storage material according to a specific embodiment of this disclosure. Detailed Implementation

[0017] To enable those skilled in the art to better understand the technical solutions of this disclosure, the disclosure will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain this disclosure and represent a part of the embodiments of this disclosure, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this disclosure without creative effort are within the protection scope of this disclosure.

[0018] like Figure 1 and Figure 2 As shown, one aspect of this disclosure provides a gradient coating-multi-field synergistic microwave uniform sintering method S100 for solid waste-based high-temperature thermal storage materials, specifically including the following steps S110~S140: S110. Polyvinyl alcohol pore-forming agent is added to the solid waste matrix, ball milled and vacuum dried, and pressed to obtain a green body; the green body is heat-treated in a heat-insulating furnace by in-situ reaction synthesis and naturally cooled to room temperature to obtain a pre-burned material, which serves as the inner layer.

[0019] In step S110, the solid waste matrix serves as the matrix of the material. The solid waste matrix can be coal powder, tailings, or steel slag, etc.

[0020] In step S110, polyvinyl alcohol (PVA) is used as a pore-forming agent to create pores inside the material, thus giving the inner layer a porous structure. The content of the polyvinyl alcohol pore-forming agent is 5-15 wt% of the solid waste matrix content. When the pore-forming agent is within this range, it helps to balance the porosity and material strength, ensuring thermal storage performance.

[0021] In step S110, the green body is heat-treated in a holding furnace at a temperature of 350-450℃ for 30-50 minutes by in-situ reaction synthesis. S120: The surface of the pre-burned material is modified by Ar / O2 mixed gas plasma, forming a plasma-modified functional layer on the surface of the inner layer.

[0022] In step S120, the power of the Ar / O2 mixed gas plasma is 750-850W, and the time is 4-6min.

[0023] The plasma treatment in this embodiment activates the surface through high-energy bombardment and chemical reaction, introduces active groups (such as hydroxyl groups and oxygen-containing functional groups), increases surface roughness, and may form a thin oxide film or composite phase, forming a gradient process layer. This improves the chemical activity and physical adsorption capacity of the inner surface, enhances the interfacial bonding with the subsequent coating layer, and optimizes microwave absorption performance.

[0024] S130. A gradient coating of MgO / SiC is formed on the surface of the plasma-modified functional layer using the sol-gel method, which serves as the outer layer.

[0025] In step S130, when performing gradient coating on the surface of the plasma-modified functional layer using the sol-gel method, a multi-layer, multi-coating method is employed to coat the coating slurry onto the surface of the plasma-modified functional layer, forming a multi-layer coating. After drying, a pure SiC outer layer is coated onto multiple coating layers. That is, the coating slurry is first coated onto the surface of the plasma-modified functional layer and dried to form the first coating layer. The coating slurry is then coated onto the first coating layer and dried to form the second coating layer, and so on, to form a multi-layer coating.

[0026] It should be noted that the coating slurry in this embodiment includes MgO and SiC. The relative mass ratio of these two components can be adjusted according to actual needs, and different content ratios can be adjusted for different coating layers. For example, in the first coating, the mass ratio of MgO to SiC in the coating slurry is (7-9):1, preferably 8:1; in the second coating, the mass ratio is (5-7):(3-5), preferably 6:4; and in the third coating, the mass ratio is (3-5):(5-7), preferably 4:6. The above ratios, through gradient design, transition from high MgO content to high SiC content, optimizing microwave absorption and thermal stability, resulting in a 45% improvement in microwave absorption efficiency of the material over a wide frequency band (1-10 GHz). It should be understood that in other preferred embodiments, other coating times and other mass ratios can also be selected, for example, six or more coating processes, without specific limitations.

[0027] It should be further noted that this embodiment does not specifically limit the thickness of the coating layer. For example, the thickness of each coating layer is in the range of 180-220nm, preferably 200nm, and the total thickness of multiple coating layers is in the range of 1100-1300nm, preferably 1200nm. This thickness range is optimized through simulation and experiment to ensure that the microwave penetration depth matches the thermal diffusion rate and achieve uniform sintering. Of course, coating layers of other thicknesses can be set according to actual needs.

[0028] In this embodiment, forming an MgO / SiC coating layer helps to improve the thermal stability and microwave absorption efficiency of the material. Furthermore, through this gradient coating, the microwave absorption efficiency of the material can be increased by 45% over a wide frequency band (1-10 GHz), while the sintering temperature is reduced by 200-300°C and energy consumption is reduced by 40%.

[0029] S140. Microwave sintering is performed on the gradient-coated material to obtain a solid waste-based high-temperature thermal storage material.

[0030] like Figure 3 As shown, in step S140, the solid waste-based high-temperature thermal storage material with a gradient coating structure prepared in the above steps is subjected to microwave sintering, wherein... Figure 3 The label 1 indicates a dual-frequency microwave source (2.45GHz + 5.8GHz), providing microwave energy at different frequencies (2.45GHz and 5.8GHz) for coordinated heating. Figure 3 The label 2 in the figure indicates a waveguide conversion system (TEM wave → circularly polarized wave). Figure 3 The label 3 indicates a metal finger tube (extended microwave field mapping range). Figure 3The number 4 in the figure represents a metal sheet (for constructing holographic metamaterial structures). Figure 3 The number 5 in the text indicates the filler material (such as carbon nanotubes). Figure 3 The number 6 in the designation indicates a high-precision temperature sensor. Figure 3 The number 7 in the diagram represents the AI ​​intelligent control system. Based on the above processing device, the sintering process parameters are as follows: under an argon protective atmosphere, the temperature is programmed to rise to 1450-1550°C at a rate of 80-120°C / min, and held at this temperature for 20-40 minutes; during the sintering process, dual-frequency microwave sources work together, with frequencies of 2.45GHz (power adjustable range 0-5kW) and 5.8GHz (power adjustable range 0-3kW), respectively, and the power ratio of the two sources is dynamically adjusted by the intelligent control system according to the sintering stage.

[0031] It should be noted that the specific optimization of the microwave sintering process in this embodiment is as follows: Based on the waveguide conversion system, a rectangular waveguide is used to convert the microwaves of the above frequency into TEM waves, which are then converted into circularly polarized waves through the dielectric plate to achieve multi-mode synergistic heating.

[0032] Furthermore, the multimode cavity is coupled to a circular waveguide, which provides multiple mode distribution schemes. The mode tuner dynamically switches between TE_{mn} and TM_{mn} modes at a frequency of 1-5Hz. The superposition of the field strengths of the two modes achieves the combined effect of the magnetic field and the electric field.

[0033] Furthermore, by inserting metal finger tubes (3-5mm in diameter, with a programmable moving speed of 10-50mm / s) into the cavity, the "pinned" antenna can improve the mapping range of the microwave field, and by continuously changing its position, different boundary conditions and radiation states can be obtained, thereby achieving a wider absorption bandwidth.

[0034] Furthermore, a holographic metamaterial structure can be constructed by combining a thin metal sheet (0.1-0.5 mm thick) inside the cavity with a metal finger tube, forming a wide-bandwidth, high-Q, and tunable electromagnetic field, achieving near-perfect absorption in the microwave continuous band (1 THz).

[0035] Furthermore, by filling the cavity structure with materials of different dielectric constants, such as fibrous silica with a dielectric constant of 3-5 and carbon nanotubes with a dielectric constant of 100-300, the distribution of the electromagnetic field inside the cavity can be changed.

[0036] Furthermore, the temperature field distribution is monitored in real time by eight sets of high-precision infrared temperature sensors (measurement accuracy ±2°C, sampling frequency 10Hz) arranged around the cavity, and the data is fed back to the AI ​​intelligent control system.

[0037] Furthermore, based on finite element simulation and artificial intelligence optimization algorithms, the cavity structure and the loaded microwave mode are iteratively optimized. The microwave output power is adjusted in real time through PID control algorithm (proportional coefficient 0.8-1.2, integral time 0.5-1.5 min, derivative time 0.1-0.3 min) to ensure that the surface temperature difference of the sintered body is less than 15°C, so as to achieve the best microwave absorption effect.

[0038] In this embodiment, multi-mode synergistic heating is achieved through the coordinated use of dual-frequency microwave sources. Furthermore, an asymmetric resonant cavity design, combined with metal finger tubes and metal sheets to form a holographic material structure, enables a wide-bandwidth, high-Q electromagnetic field. This asymmetric resonant cavity design further improves energy conversion efficiency, giving the method of this disclosure advantages in high efficiency and low cost in industrial applications. Additionally, real-time control of the microwave mode and cavity structure using AI optimization algorithms, combined with a high-precision temperature sensor, ensures closed-loop control and uniform sintering. In summary, this disclosure achieves near-perfect absorption in the 1THz microwave continuous band with an absorption rate >99% through multi-physics field synergistic optimization, solving the problem of uneven energy distribution in solid waste materials during the sintering process.

[0039] This disclosure proposes a gradient coating-multi-field synergistic microwave uniform sintering method for solid waste-based high-temperature thermal storage materials. Specifically, it employs a plasma-modified gradient coating-enhanced "inner layer-transition layer-outer layer" sandwich structure. Through in-situ nano-sizing, gradient coating, and microwave sintering, it achieves strong microwave absorption characteristics of high-dielectric-loss solid waste slurry over a wide wavelength range, with adjustable admittance loss and dielectric constant, ultimately yielding solid waste-based ceramic materials with excellent dielectric properties. In other words, this disclosure aims to achieve uniform heating of solid waste-based materials during microwave sintering through innovative material design and multi-physics field synergistic control, filling the gaps in existing technologies regarding "microscopic-scale microwave absorption control" and "multi-physics field synergy."

[0040] Another aspect of this disclosure is to provide a solid waste-based high-temperature thermal storage material, which is prepared by the method described above. For details of the process, please refer to the above description, which will not be repeated here.

[0041] like Figure 4 As shown, the solid waste-based high-temperature thermal storage material of this embodiment includes an inner layer 10, a transition layer 9, and an outer layer 8 from the inside out. The inner layer 10 is a solid waste matrix, the transition layer 9 is a plasma-modified functional layer, and the outer layer 8 is a MgO / SiC coating layer, which is a multi-layer stacked structure.

[0042] The preparation method of solid waste-based high-temperature thermal storage materials will be further explained below with reference to specific embodiments: Example 1 Using coal powder as the matrix, polyvinyl alcohol (PVA, 10wt%) pore-forming agent is added, ball-milled, vacuum dried, and pressed to obtain green body; The pre-burned material was prepared by in-situ reaction synthesis and heat treatment at 400°C in a holding furnace for 40 minutes, followed by natural cooling to room temperature, and used as the inner layer. The surface of the pre-burned material was modified by Ar / O2 mixed gas plasma with a power of 800W and a treatment time of 5min to form a plasma-modified functional layer as a transition layer. A gradient coating was applied to the surface of plasma-modified pre-calcined material using a sol-gel method. The outer layer was formed through six coating processes: the first coating consisted of a slurry with 80 wt% MgO and 20 wt% SiC; the second coating consisted of a slurry with an MgO / SiC ratio of 60:40; the third coating consisted of a slurry with an MgO / SiC ratio of 40:60; and the subsequent fourth to sixth coatings consisted of pure SiC slurry. The thickness of each layer after drying was controlled to approximately 200 nm, resulting in a total gradient coating layer thickness of approximately 1200 nm, forming the outer layer.

[0043] from Figure 4 As shown in the schematic diagram, the total thickness of the gradient coating layer is approximately 1200 nm, within which good impedance matching can be achieved.

[0044] The solid waste-based high-temperature thermal storage material with a gradient coating structure prepared through the above steps was subjected to microwave sintering. The sintering process parameters were as follows: under an argon protective atmosphere, the temperature was programmed to rise to 1500°C at a rate of 100°C / min and held at that temperature for 30 min. Simultaneously, a dual-frequency microwave source was used in synergy during the sintering process, with frequencies of 2.45 GHz and 5.8 GHz, respectively.

[0045] It should be noted that the multi-field synergistic microwave sintering process used in this embodiment is described above. Furthermore, the thermal conductivity of the solid waste-based high-temperature thermal storage material with a gradient coating structure was tested at room temperature. An AT-CMPT8019 thermal conductivity meter was used to measure the change in thermal conductivity of the sample with temperature. The sample was a 10mm diameter cylindrical part. The instrument used steady-state DC heating, and the sample was firmly connected to the copper column via indium tin solder. The upper end of the sample was connected to the power supply and fuse via a copper column with a heating source to prevent excessive current from burning out the sample or the instrument. Argon gas was introduced to accelerate convective heat transfer on the sample surface. Before measurement, the pressure was adjusted to keep the sample at a constant temperature for more than 12 hours to ensure there was no temperature gradient inside the sample, and then the measurement began. The temperature sensor was placed 10mm from the bottom of the sample. The applied AC current amplitude was 0.25A and the frequency was 19.84kHz. The thermal shock stability of the solid waste-based high-temperature thermal storage material with a gradient coating structure at 1800°C under normal pressure was tested. The resistivity of the sample at room temperature was measured using a NETZS2299 resistivity meter. The sample was placed in a quartz crucible, and a small amount of anhydrous ethanol was added to prevent melting. The sample was then heated, and samples were taken at regular intervals. This process was repeated three times. According to Table 1, the resistivity of the sample remained essentially unchanged after three thermal shocks, with a thermal stability retention rate >95%, indicating good thermal shock stability. The microwave absorptivity obtained using the method in Example 1 was 95-99%, and the energy consumption was 450-500 kWh / t.

[0046] Comparative Example 1 The conventional sintering material preparation process in this example is as follows: using the same coal powder as in Example 1 as the matrix, 10 wt% polyvinyl alcohol (PVA) pore-forming agent is added. After ball milling, vacuum drying, and pressing to obtain a green body, without plasma surface modification and gradient coating, it is directly placed in a conventional muffle furnace and heated to 1600°C at a rate of 10°C / min in an air atmosphere and held for 60 minutes, followed by natural cooling to obtain the final product.

[0047] As shown in Table 1, the sample strength decreased by 30% after three thermal shocks, the microwave absorption rate was 60-70%, the sintering temperature was 1500-1600°C, and the energy consumption was 850-950 kWh / t.

[0048] In summary, the microwave absorption rate is increased by 40-65% compared to traditional sintered materials. The sintering temperature is 1200-1300℃, which reduces the microwave absorption rate by 200-300℃ compared to traditional sintered materials, and energy consumption is also significantly reduced. Furthermore, the thermal conductivity and porosity are also increased.

[0049] Table 1 Performance comparison between Example 1 and Comparative Example 1

[0050] This disclosure proposes a solid waste-based high-temperature thermal storage material and its gradient coating-multi-field synergistic microwave uniform sintering method, which has the following advantages compared with the prior art: First, this disclosure, through the gradient coating layer structure design, combined with multi-mode microwave field dynamic control and temperature-power closed-loop control system, not only optimizes the microwave absorption performance of the material, but also ensures the matching of microwave penetration depth and thermal diffusion rate, thereby solving the problems of uneven energy distribution of solid waste-based high-temperature thermal storage materials during microwave heating, and the easy generation of pores, uneven density, and interface reactions in high dielectric constant solid waste during sintering.

[0051] Secondly, the gradient coating structure of the solid waste-based high-temperature thermal storage material disclosed herein can significantly improve the microwave absorption performance of solid waste-based ceramics and expand the absorption bandwidth, thereby achieving high absorption efficiency over a wide frequency band.

[0052] Third, the gradient coating structure of the solid waste-based high-temperature thermal storage material disclosed herein can be used for microwave heating sintering of any inorganic non-metallic matrix with only simple adjustments to the powder particle size and ratio, and has good industrial applicability.

[0053] It is understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of this disclosure, and this disclosure is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and substance of this disclosure, and these modifications and improvements are also considered to be within the scope of protection of this disclosure.

Claims

1. A gradient coating-multi-field synergistic microwave uniform sintering method for solid waste-based high-temperature thermal storage materials, characterized in that, include: Polyvinyl alcohol pore-forming agent is added to a solid waste matrix, ball milled, vacuum dried, and pressed to obtain a green body; the green body is heat-treated in a heat-insulating furnace by an in-situ reaction synthesis method, and naturally cooled to room temperature to obtain a pre-burned material, which serves as the inner layer. Ar / O2 mixed gas plasma is used to modify the surface of the pre-burned material, forming a plasma-modified functional layer on the surface of the inner layer; A gradient coating of MgO / SiC was formed on the surface of the plasma-modified functional layer using the sol-gel method, which served as the outer layer. Microwave sintering was performed on the gradient-coated material to obtain a solid waste-based high-temperature thermal storage material.

2. The method according to claim 1, characterized in that, The content of the polyvinyl alcohol pore-forming agent is 5-15 wt% of the solid waste matrix content.

3. The method according to claim 1, characterized in that, The green body is heat-treated in a holding furnace at a temperature of 350-450℃ for 30-50 minutes via in-situ reaction synthesis.

4. The method according to claim 1, characterized in that, The power of the Ar / O2 mixed gas plasma is 750-850W, and the time is 4-6 minutes.

5. The method according to claim 1, characterized in that, When performing gradient coating on the surface of plasma-modified functional layers using the sol-gel method, the coating slurry is coated onto the surface of the plasma-modified functional layers in a multi-layer, multi-coating manner to form a multi-layer MgO / SiC coating layer. After drying, a pure SiC outer layer is coated onto the multiple MgO / SiC coating layers.

6. The method according to claim 5, characterized in that, The coating slurry comprises MgO and SiC.

7. The method according to claim 5, characterized in that, During the first coating, the mass ratio of MgO to SiC in the coating slurry was (7-9):

1. During the second coating, the mass ratio of MgO to SiC in the coating slurry was (5-7):(3-5). During the third coating, the mass ratio of MgO to SiC in the coating slurry was (3-5):(5-7).

8. The method according to claim 5, characterized in that, Each coating layer has a thickness of 180-220 nm, and the total thickness of the multi-layer coating is 1100-1300 nm.

9. The method according to claim 1, characterized in that, When performing microwave sintering on gradient-coated materials, the sintering process parameters are as follows: under an argon protective atmosphere, the temperature is programmed to rise to 1450-1550°C at a rate of 80-120°C / min, and held at this temperature for 20-40 min; where, During the sintering process, a dual-frequency microwave source was used for microwave sintering treatment, with frequencies of 2.45 GHz and 5.8 GHz, respectively.

10. A solid waste-based high-temperature thermal storage material, characterized in that, The solid waste-based high-temperature thermal storage material is prepared by the method described in any one of claims 1-9.

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