A rare earth gypsum board loaded with composite wave absorber and a preparation method thereof
By combining Fe4N-coated ferrite and active flake graphite with carbonized natural bamboo fiber composite microwave absorber and rare earth gypsum matrix, a broadband and high-efficiency rare earth gypsum board was prepared, which solved the problems of narrow bandwidth and environmental pollution of existing building microwave absorbing materials and realized green and environmentally friendly resource utilization.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- TAISHAN GYPSUM (JIANGYIN) CO LTD
- Filing Date
- 2026-04-24
- Publication Date
- 2026-07-14
AI Technical Summary
Existing building wave-absorbing materials have narrow absorption frequency bands, complex manufacturing processes, and high costs. Rare earth gypsum has not been effectively utilized as a resource, leading to environmental pollution.
Rare earth gypsum boards were prepared by combining Fe4N-coated ferrite and active flake graphite with carbonized natural bamboo fiber as a microwave absorber, along with a rare earth gypsum matrix, and through processes such as nitriding and ultrasonic stirring. This process achieved broadband microwave absorption and improved mechanical properties.
It achieves efficient electromagnetic wave absorption in a wide frequency band of 2GHz-18GHz, reduces production costs, improves mechanical properties, reduces environmental pollution, and promotes the resource utilization of rare earth gypsum.
Smart Images
Figure CN122380705A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of green microwave absorbing building materials technology, specifically a rare earth gypsum board loaded with a composite microwave absorbing agent and its preparation method. Background Technology
[0002] The widespread use and high frequency of electronic products such as mobile communications, computers, and home appliances have brought great convenience to people's lives, but have also brought increasingly serious electromagnetic pollution problems. Indoor electromagnetic pollution not only seriously endangers human health, but may also generate electromagnetic interference that damages various electrical equipment in buildings. Therefore, there is an urgent need to develop green electromagnetic absorbing building materials that can be used indoors to effectively reduce electromagnetic radiation and improve the electromagnetic environment of living spaces.
[0003] Adding electromagnetic wave absorbing agents to the cementitious material matrix is a mainstream and feasible method for preparing building electromagnetic wave absorbers. Electromagnetic wave absorbing agents can generally be classified into magnetic loss type and electrical loss type according to their loss mechanism. Ferrites, ultrafine alloy powders, etc., belong to magnetic loss type absorbers, relying on magnetic polarization mechanisms such as hysteresis loss, domain wall resonance, and natural resonance to attenuate and absorb electromagnetic waves. Carbon-based materials such as graphite and carbon black belong to electrical loss type absorbers, mainly relying on relaxation processes such as electronic polarization and molecular polarization of the medium to attenuate and absorb electromagnetic waves. The unique electronic structure of Fe4N endows it with excellent electrical conductivity and saturation magnetization, showing great potential for application in the field of electromagnetic wave absorption. Surface nitriding treatment of ferrite followed by Fe4N coating on the ferrite surface can yield a novel high-magnetic-loss Fe4N-coated ferrite composite absorber.
[0004] Gypsum, as an important building material in the modern construction industry, is widely used in various buildings. How to economically, efficiently, and in large quantities produce gypsum products with excellent electromagnetic absorption properties to meet the strict requirements of electromagnetic radiation and product weight is of great significance to the development of the functional building materials industry.
[0005] Currently, conventional building microwave absorbing materials generally suffer from problems such as narrow absorption bandwidth, complex manufacturing process, and high production cost, making it difficult to meet the needs of large-scale application in the construction field. At the same time, rare earth gypsum, a solid waste generated during rare earth hydrometallurgy, has not yet formed a complete resource utilization system. Long-term accumulation of large quantities will have an adverse impact on the surrounding soil and water environment. However, the rare earth element cerium (Ce) remaining in rare earth gypsum can improve the performance of magnetic loss type microwave absorbing materials, and has a natural advantage in preparing functional gypsum materials.
[0006] Therefore, in view of the above situation, there is an urgent need to develop a rare earth gypsum board loaded with composite microwave absorbing agent and its preparation method to overcome the shortcomings in current practical applications. Summary of the Invention
[0007] The purpose of this invention is to provide a rare earth gypsum board loaded with a composite microwave absorbing agent and its preparation method, so as to solve the problems mentioned in the background art.
[0008] To achieve the above objectives, the present invention provides the following technical solution: A rare earth gypsum board loaded with a composite microwave absorbing agent, wherein the raw materials for preparing the gypsum board include rare earth gypsum, composite microwave absorbing agent, binder and water-reducing agent; The rare earth gypsum is cerium-containing waste rare earth gypsum; The composite microwave absorbing agent includes a magnetic loss type composite iron-based microwave absorbing agent and an electrical loss type carbon-based microwave absorbing agent. The magnetic loss type composite iron-based microwave absorbing agent is Fe4N coated ferrite, and the electrical loss type carbon-based microwave absorbing agent includes active flake graphite and carbonized natural bamboo fiber.
[0009] As a further aspect of the present invention: by weight, the raw materials for preparing gypsum board include: 300-400 parts of rare earth gypsum, 20-25 parts of composite iron-based microwave absorber, 20-25 parts of active flake graphite, 15-20 parts of carbonized natural bamboo fiber, 2-5 parts of binder, and 1-2 parts of water-reducing agent.
[0010] As a further aspect of the present invention: the adhesive is a polyvinyl alcohol adhesive, and the water-reducing agent is a polycarboxylate water-reducing agent.
[0011] As a further aspect of the present invention: the Fe4N-coated ferrite is prepared by surface nitriding modification of ferrite powder.
[0012] A method for preparing rare earth gypsum board loaded with the above-mentioned composite microwave absorbing agent includes the following steps: S1: Mix magnetic loss type composite iron-based microwave absorber, active flake graphite and carbonized natural bamboo fiber evenly to obtain composite microwave absorber dry material; The magnetic loss type composite iron-based microwave absorber is Fe4N coated ferrite; S2: Mix the cerium-containing waste rare earth gypsum with the composite microwave absorber dry material evenly, add water to prepare a wet material, then add a binder and a water-reducing agent, and stir evenly to obtain gypsum slurry; S3: The gypsum slurry is molded into shape, and the finished product is obtained after curing and maintenance.
[0013] As a further aspect of the present invention: in step S1, the mixture is carried out by ultrasonic stirring, with an ultrasonic power of 500-800W and a stirring time of 10-20min.
[0014] As a further aspect of the present invention: in step S2, the water-cement ratio of water to solid material is (0.5-0.6):1, and the solid material is the total mass of cerium-containing waste rare earth gypsum and composite microwave absorbing agent dry material.
[0015] As a further aspect of the present invention: in step S2, the cerium-containing waste rare earth gypsum and the composite microwave absorbing agent dry material are mixed by ultrasonic vibration at a frequency of 20-40kHz and a mixing time of 5-15min.
[0016] As a further aspect of the present invention: in step S3, the molding pressure is 0.3-0.8 MPa, and the holding time is 30-60 s.
[0017] As a further aspect of the present invention: in step S3, the curing environment is a temperature of 20±5℃ and a relative humidity of 50±10%, and the curing time is 5-8 days.
[0018] Compared with the prior art, the beneficial effects of the present invention are: This invention prepares Fe4N-coated ferrite as a magnetically depleted composite iron-based microwave absorber through nitriding treatment. The ordered solid solution Fe4N has excellent oxidation resistance, ultra-high saturation magnetization, and dielectric constant. By using a simple nitriding process to coat Fe4N onto the ferrite surface, the prepared composite iron-based microwave absorber can obtain higher microwave absorption performance, especially good low-frequency absorption characteristics. At the same time, the rare earth element Ce in waste rare earth gypsum can further improve the magnetic loss effect of the composite iron-based microwave absorber. This invention combines two types of dielectric loss carbon-based microwave absorbers, namely active flake graphite and natural bamboo fiber, with a composite iron-based microwave absorber. This combination can leverage the synergistic effect of the two different loss mechanisms, tune the impedance matching of the materials, and achieve effective electromagnetic wave absorption in a wide frequency band of 2GHz-18GHz. Microwave-activated flake graphite possesses excellent mechanical, thermal, and electrical properties, while carbonized natural bamboo fiber exhibits flexibility, multiple interface polarization, ease of composite formation, and lightweight characteristics. The combination of these two materials not only promotes the dispersion of magnetic media, thereby enhancing the magnetic coupling interaction of the composite microwave absorber, but also effectively improves the mechanical properties of rare earth gypsum board. The resulting gypsum board exhibits stable structural dimensions, excellent appearance quality, good flame retardancy and fire resistance, and is safe and reliable, fully meeting the requirements for use in building decorative panels. The rare earth gypsum board of the present invention uses Ce-containing waste rare earth gypsum generated during the rare earth hydrometallurgical process as the base material. It can not only give full play to the advantage of Ce in solid waste in enhancing the magnetic loss of composite iron-based microwave absorbers, but also save natural mineral gypsum resources, significantly reduce the raw material production cost, and avoid the pollution of the surrounding ecological environment caused by the long-term accumulation of rare earth gypsum, thus promoting the formation of a complete resource utilization system. The composite microwave absorber and other fillers used in this invention are all safe and non-toxic, with a wide range of raw material sources and good compatibility with gypsum matrix. The resulting gypsum board has excellent processing performance, high production efficiency, and is green and environmentally friendly throughout the entire process, which is in line with the development requirements of environmental protection and circular economy and the functional development direction of traditional gypsum materials. Attached Figure Description
[0019] Figure 1 This is a flowchart illustrating the preparation method of rare earth gypsum board loaded with composite microwave absorbing agent in an embodiment of the present invention. Detailed Implementation
[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0021] The specific implementation of the present invention will be described in detail below with reference to specific embodiments.
[0022] Please see Figure 1 The present invention provides a rare earth gypsum board loaded with composite microwave absorbing agent and its preparation method. By combining magnetic loss type and electrical loss type microwave absorbing agent in a synergistic manner, and combining the characteristics of Ce-containing rare earth gypsum matrix, it achieves broadband and high-efficiency microwave absorption performance, and at the same time realizes the high-value resource utilization of rare earth metallurgical solid waste.
[0023] The rare earth gypsum board loaded with composite microwave absorbing agent is prepared from raw materials including rare earth gypsum, composite iron-based microwave absorbing agent, active flake graphite, natural bamboo fiber, binder, and water-reducing agent; wherein the mass content of each component is as follows: rare earth gypsum 300-400 parts, composite iron-based microwave absorbing agent 20-25 parts, active flake graphite 20-25 parts, natural bamboo fiber 15-20 parts, PVA binder 2-5 parts, and polycarboxylate water-reducing agent 1-2 parts.
[0024] The composite microwave absorbing agent is composed of a magnetic loss type composite iron-based microwave absorbing agent and two electrical loss type carbon-based microwave absorbing agents. Through the synergistic effect of different loss mechanisms and the impedance matching of the material, it achieves effective absorption of electromagnetic waves in a wide frequency range, solving the problem of narrow absorption bandwidth of existing building microwave absorbing materials.
[0025] The composite iron-based microwave absorbing agent is Fe4N-coated ferrite, which belongs to the magnetic loss type microwave absorbing agent. Its preparation method is as follows: First, the ferrite powder is ground to a fineness of 50-60μm, and then placed in a nitriding furnace preheated to 500℃. The surface modification of the ferrite powder is completed by holding it in a nitrogen-containing atmosphere for 40-50 minutes. The powder is then air-cooled to room temperature with the furnace to obtain the composite iron-based microwave absorbing agent with Fe4N coating.
[0026] Through the above-mentioned nitriding process, Fe4N is coated on the ferrite surface. The unique electronic structure of Fe4N endows it with excellent electrical conductivity and saturation magnetization, enabling the prepared composite iron-based microwave absorber to obtain higher microwave absorption performance, especially good low-frequency absorption characteristics. At the same time, the preparation process is simple and controllable, requires no complex equipment, and is easy to scale up for industrial production.
[0027] The active flake graphite is an electrically depleting carbon-based microwave absorber, and its surface has been pre-treated with microwave activation. The microwave-activated flake graphite possesses excellent mechanical, thermal, and electrical properties. On one hand, it can achieve dielectric loss of electromagnetic waves through electronic polarization and molecular polarization relaxation processes; on the other hand, it can promote the uniform dispersion of magnetic media, enhance the magnetic coupling interaction of the composite microwave absorber, and effectively improve the mechanical properties and dimensional stability of the gypsum board.
[0028] The natural bamboo fiber is an electrically lossy carbon-based microwave absorber, and the bamboo fiber has undergone pre-carbonization treatment. The carbonized natural bamboo fiber possesses characteristics such as flexibility, multiple interface polarization, easy composite properties, and lightweight. When combined with active flake graphite, it can synergistically optimize the dielectric constant of the material, further enhancing dielectric loss capacity. Simultaneously, it improves the flexural and impact resistance of gypsum board, reduces the product's water absorption rate, and enhances long-term stability.
[0029] The rare earth gypsum mentioned is a Ce-containing waste rare earth gypsum produced during my country's rare earth hydrometallurgical process. Using this industrial solid waste as the matrix raw material for gypsum board can, on the one hand, utilize the residual rare earth element Ce to enhance the magnetic loss effect of composite iron-based microwave absorbers on electromagnetic radiation, further improving the overall microwave absorption performance of the material; on the other hand, it can achieve green and high-value utilization of solid waste, avoid soil and water pollution caused by long-term accumulation of rare earth gypsum, and significantly reduce raw material costs, which is in line with the development requirements of environmental protection and circular economy.
[0030] The PVA adhesive is a polyvinyl alcohol adhesive, which can improve the interfacial bonding performance between various raw material components, improve the molding performance of gypsum slurry, and ensure the structural integrity and mechanical strength of gypsum board after curing. The polycarboxylate superplasticizer can effectively reduce the water-cement ratio of gypsum slurry, improve the workability and fluidity of slurry, ensure the density of gypsum board after molding, reduce the water absorption rate of the product, and improve water resistance and long-term use stability.
[0031] Furthermore, the preparation method of the rare earth gypsum board loaded with composite microwave absorbing agent according to the present invention includes the following steps: S1: Weigh the composite iron-based microwave absorber, active flake graphite and natural bamboo fiber in the indicated mass fractions, and mix them evenly by ultrasonic stirring to obtain the dry composite absorber material. In this step, the ultrasonic stirring power can be selected as 500-800W, and the stirring time is 10-20 minutes to ensure that the three microwave absorbing agent components are fully dispersed and mixed evenly, so as to avoid uneven microwave absorption performance in subsequent products.
[0032] By premixing different types of absorbing agents evenly in this step, it can be ensured that the absorbing agents can be evenly dispersed in the matrix when mixed with the gypsum matrix later, so as to give full play to the synergistic absorbing effect of the multi-components.
[0033] S2: Weigh rare earth gypsum powder and composite absorbent dry material according to the preset mass ratio, mix them evenly, add an appropriate amount of water to the mixture according to the water-cement ratio of 0.5-0.6:1 to make wet material, then add PVA binder and polycarboxylate superplasticizer in sequence, stir evenly to obtain mixed rare earth gypsum slurry.
[0034] In this step, the rare earth gypsum powder and the dry composite absorbent are mixed by ultrasonic vibration at a frequency of 20-40kHz for 5-15 minutes to ensure uniform mixing of the solid components. Water is added in batches while stirring to avoid agglomeration and clumping of the slurry.
[0035] This step involves thoroughly mixing the premixed composite microwave absorber with the rare earth gypsum matrix, while simultaneously adding binders and water-reducing agents to optimize the slurry's workability, providing a stable foundation for subsequent molding and curing.
[0036] S3: Pour the above mixed rare earth gypsum slurry into the gypsum board molding mold and press it into shape. After curing at room temperature, demold and cure until absolutely dry to obtain rare earth gypsum board loaded with composite microwave absorbing agent.
[0037] In this step, the molding pressure is 0.3-0.8MPa, the holding time is 30-60s, the room temperature curing time is 12-24h, the curing environment is a standard environment with a temperature of 20±5℃ and a relative humidity of 50±10%, and the curing time is 5-8 days to ensure that the gypsum board is fully hydrated and hardened to achieve the designed mechanical properties and structural stability.
[0038] The rare earth gypsum board loaded with composite microwave absorbing agent prepared by the above method has excellent electromagnetic wave absorption performance in the 2GHz-18GHz frequency band. It also has good mechanical properties, low water absorption rate and excellent flame retardant and fire resistant properties. It is suitable for interior decoration boards of various buildings and can effectively absorb electromagnetic radiation in buildings and improve the electromagnetic environment of human living. Example 1:
[0039] This embodiment provides a rare earth gypsum board loaded with a composite microwave absorbing agent. The raw materials used in its preparation are composed of the following components by mass: 300 parts rare earth gypsum, 20 parts composite iron-based microwave absorbing agent, 20 parts active flake graphite, 15 parts natural bamboo fiber, 2 parts PVA binder, and 1 part polycarboxylate superplasticizer.
[0040] The preparation method of the composite iron-based microwave absorbing agent used in this embodiment is as follows: first, the ferrite powder is ground to a fineness of 50μm, then placed in a nitriding furnace preheated to 500℃, and kept at a nitrogen atmosphere for 40 minutes to complete the surface modification of the ferrite powder. Then, it is air-cooled to room temperature with the furnace to obtain a composite iron-based microwave absorbing agent with Fe4N coated on the surface.
[0041] The surface microwave activation treatment method for the active flake graphite used in this embodiment is as follows: the flake graphite is placed under microwave treatment conditions of 2400MHz and 500W for 15 minutes, and then naturally cooled to room temperature to obtain active flake graphite.
[0042] The pre-carbonization treatment method of natural bamboo fiber used in this embodiment is as follows: natural bamboo fiber is placed in a carbonization furnace and kept at 120°C for 30 minutes in a carbon-containing atmosphere, and then cooled to room temperature with the furnace to complete the carbonization treatment of bamboo fiber.
[0043] The rare-earth gypsum board loaded with composite microwave absorbing agent in this embodiment is prepared by the following steps: According to the above mass proportions, weigh 20 parts of the pre-prepared composite iron-based microwave absorber, 20 parts of the active flake graphite and 15 parts of the natural bamboo fiber, and ultrasonically stir at 600W power for 15 minutes to mix evenly, and obtain 55 parts of the dry composite absorber. Weigh 300 parts of rare earth gypsum powder according to the above-mentioned mass ratio, add 55 parts of the prepared composite absorbent dry material, and mix with ultrasonic vibration at a frequency of 30kHz for 10 minutes until uniform; add 213 parts of water in batches to the mixture according to a water-cement ratio of 0.6:1, while mechanically stirring, and stir until a uniform wet material is formed; then add 2 parts of PVA binder and 1 part of polycarboxylate superplasticizer in sequence, and continue to stir until uniform to obtain mixed rare earth gypsum slurry; The above-mentioned mixed rare earth gypsum slurry was poured into a gypsum board molding mold, pressed and shaped under a pressure of 0.5 MPa for 40 seconds, and then demolded after curing at room temperature for 24 hours. The gypsum board was then placed in a standard environment with a temperature of 20°C and a relative humidity of 50% for 7 days until it was completely dry, thus obtaining the rare earth gypsum board loaded with composite microwave absorbing agent of this embodiment.
[0044] The rare earth gypsum board loaded with composite microwave absorbing agent prepared in this embodiment was subjected to performance testing, and the results are as follows: its compressive strength reached 13MPa and its water absorption rate was less than 0.5%; the gypsum board product with a thickness of 20mm had an effective absorption bandwidth of 14.9GHz with a reflectivity of less than -5dB in the 2-18GHz frequency range, showing excellent broadband microwave absorption effect. At the same time, it also has excellent mechanical properties and low water absorption performance, which can meet the requirements for use in building interior decoration panels. Example 2:
[0045] This embodiment provides a rare earth gypsum board loaded with a composite microwave absorbing agent. The raw materials used in its preparation are composed of the following components by mass: 400 parts rare earth gypsum, 25 parts composite iron-based microwave absorbing agent, 25 parts active flake graphite, 20 parts natural bamboo fiber, 5 parts PVA binder, and 2 parts polycarboxylate superplasticizer.
[0046] The preparation method of the composite iron-based microwave absorbing agent used in this embodiment is as follows: first, the ferrite powder is ground to a fineness of 60μm, then placed in a nitriding furnace preheated to 500℃, and kept at a nitrogen atmosphere for 40 minutes to complete the surface modification of the ferrite powder. Then, it is air-cooled to room temperature with the furnace to obtain a composite iron-based microwave absorbing agent with Fe4N coated on the surface.
[0047] The surface microwave activation treatment method for the active flake graphite used in this embodiment is as follows: the flake graphite is placed under microwave conditions of 2400MHz and 600W for 12 minutes, and then naturally cooled to room temperature to obtain active flake graphite.
[0048] The pre-carbonization treatment method of natural bamboo fiber used in this embodiment is as follows: natural bamboo fiber is placed in a carbonization furnace and kept at 140°C for 20 minutes in a carbon-containing atmosphere, and then cooled to room temperature with the furnace to complete the carbonization treatment of bamboo fiber.
[0049] The rare-earth gypsum board loaded with composite microwave absorbing agent in this embodiment is prepared by the following steps: According to the above mass proportions, weigh 25 parts of the pre-prepared composite iron-based microwave absorber, 25 parts of active flake graphite and 20 parts of natural bamboo fiber, and ultrasonically stir at 700W power for 12 minutes to mix evenly, and obtain 70 parts of composite absorber dry material. Weigh 400 parts of rare earth gypsum powder according to the above-mentioned mass ratio, add 70 parts of the prepared composite absorbent dry material, and mix with ultrasonic vibration at a frequency of 35 kHz for 8 minutes until uniform; add 235 parts of water to the mixture in batches according to a water-cement ratio of 0.5:1, while mechanically stirring, and stir until a uniform wet material is formed; then add 5 parts of PVA binder and 2 parts of polycarboxylate superplasticizer in sequence, and continue to stir until uniform to obtain mixed rare earth gypsum slurry; The above-mentioned mixed rare earth gypsum slurry was poured into a gypsum board molding mold, pressed and shaped under a pressure of 0.6 MPa for 50 seconds, and then demolded after curing at room temperature for 24 hours. The gypsum board was then placed in a standard environment with a temperature of 22°C and a relative humidity of 55% for 8 days until it was completely dry, thus obtaining the rare earth gypsum board loaded with composite microwave absorbing agent of this embodiment.
[0050] The rare earth gypsum board loaded with composite microwave absorbing agent prepared in this embodiment was subjected to performance testing, and the results are as follows: its compressive strength reached 14MPa and its water absorption rate was less than 0.5%; the gypsum board product with a thickness of 20mm had an effective absorption bandwidth of 15.6GHz with a reflectivity of less than -5dB in the 2-18GHz frequency range, showing a significant broadband and efficient microwave absorption effect, while also possessing superior mechanical properties, which can meet the high standard requirements for use in interior decorative panels of various functional buildings.
[0051] It should be noted that, in this invention, although the specification describes the embodiments, not every embodiment contains only one independent technical solution. This way of describing the specification is only for clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.
Claims
1. A rare-earth gypsum board loaded with a composite microwave absorbing agent, characterized in that, The raw materials for preparing gypsum board include rare earth gypsum, composite microwave absorber, binder and water-reducing agent; The rare earth gypsum is cerium-containing waste rare earth gypsum; The composite microwave absorbing agent includes a magnetic loss type composite iron-based microwave absorbing agent and an electrical loss type carbon-based microwave absorbing agent. The magnetic loss type composite iron-based microwave absorbing agent is Fe4N coated ferrite, and the electrical loss type carbon-based microwave absorbing agent includes active flake graphite and carbonized natural bamboo fiber.
2. The rare earth gypsum board loaded with composite microwave absorbing agent according to claim 1, characterized in that, By weight, the raw materials for preparing gypsum board include: 300-400 parts rare earth gypsum, 20-25 parts composite iron-based microwave absorber, 20-25 parts active flake graphite, 15-20 parts carbonized natural bamboo fiber, 2-5 parts binder, and 1-2 parts water-reducing agent.
3. The rare earth gypsum board loaded with composite microwave absorbing agent according to claim 2, characterized in that, The adhesive is a polyvinyl alcohol adhesive, and the water-reducing agent is a polycarboxylate water-reducing agent.
4. The rare earth gypsum board loaded with composite microwave absorbing agent according to claim 1, characterized in that, The Fe4N-coated ferrite was prepared by surface nitriding modification of ferrite powder.
5. A method for preparing a rare earth gypsum board loaded with a composite microwave absorbing agent as described in claim 1, characterized in that, Includes the following steps: S1: Mix magnetic loss type composite iron-based microwave absorber, active flake graphite and carbonized natural bamboo fiber evenly to obtain composite microwave absorber dry material; The magnetic loss type composite iron-based microwave absorber is Fe4N coated ferrite; S2: Mix the cerium-containing waste rare earth gypsum with the composite microwave absorber dry material evenly, add water to prepare a wet material, then add a binder and a water-reducing agent, and stir evenly to obtain gypsum slurry; S3: The gypsum slurry is molded into shape, and the finished product is obtained after curing and maintenance.
6. The method for preparing rare earth gypsum board loaded with composite microwave absorbing agent according to claim 5, characterized in that, In step S1, the mixture is stirred using ultrasonic stirring with an ultrasonic power of 500-800W and a stirring time of 10-20min.
7. The method for preparing rare earth gypsum board loaded with composite microwave absorbing agent according to claim 5, characterized in that, In step S2, the water-cement ratio of water to solid material is (0.5-0.6):1, and the solid material is the total mass of cerium-containing waste rare earth gypsum and composite microwave absorbing agent dry material.
8. The method for preparing rare earth gypsum board loaded with composite microwave absorbing agent according to claim 5, characterized in that, In step S2, the cerium-containing waste rare earth gypsum and the composite microwave absorbing agent dry material are mixed by ultrasonic vibration at a frequency of 20-40kHz for a time of 5-15min.
9. The method for preparing rare earth gypsum board loaded with composite microwave absorbing agent according to claim 5, characterized in that, In step S3, the compression molding pressure is 0.3-0.8 MPa, and the holding time is 30-60 s.
10. The method for preparing rare earth gypsum board loaded with composite microwave absorbing agent according to claim 5, characterized in that, In step S3, the curing environment is a temperature of 20±5℃ and a relative humidity of 50±10%, and the curing time is 5-8 days.