Coal gasification fine slag wave-absorbing agent as well as preparation method and application thereof

Abstract

The invention discloses a coal gasification fine slag wave-absorbing agent as well as a preparation method and application thereof, and belongs to the technical field of preparation of high-frequency electromagnetic wave absorbing materials, the method comprises the following steps: mixing coal gasification fine slag, a modifier and a shaping agent, uniformly grinding, sieving, carrying out dry pressing, and sintering in an argon atmosphere to obtain the coal gasification fine slag wave-absorbing agent; the modifier is tetraborate; the shaping agent is polyvinyl alcohol; after the tetraborate is sintered, B2O3 generated by decomposition reacts with silicate in the coal gasification fine slag to form a glass phase; carbon graphitization and iron elementary substance generation efficiency are directly enhanced through a fluxing effect and a structure reconstruction capability of borate, and a multi-loss mechanism of interface polarization loss-magnetic loss-conductive loss is cooperatively constructed through chemical doping of a borate high-temperature decomposition product and glass phase formation, so that the electromagnetic wave absorption efficiency is improved; modification is completed through three steps of mixing, dry pressing and sintering, and complex equipment and high-pollution processes required by traditional acid leaching, hydrothermal methods or metal doping are avoided.

Description

Technical Field

[0001] The invention belongs to the technical field of preparation of high-frequency electromagnetic wave absorbing materials, and particularly relates to a coal gasification fine slag absorbing agent and a preparation method and application thereof. Background Art

[0002] With the rapid development of modern electronic information technology and national defense science and technology, electromagnetic waves have been widely used in numerous fields, including communications, radar, electronic countermeasures, and medical diagnostics. However, this widespread use of electromagnetic waves has also led to increasingly serious electromagnetic pollution problems. On the one hand, electromagnetic radiation poses potential hazards to human health, such as affecting the nervous, cardiovascular, and reproductive systems. On the other hand, electromagnetic interference can seriously affect the normal operation of electronic equipment, degrade communication quality, and even cause equipment failure, posing a threat to national defense security, aerospace, industrial production, and daily life. Therefore, the development of efficient and environmentally friendly electromagnetic wave absorbing materials to effectively reduce electromagnetic radiation and interference has become a research hotspot and urgent need in the fields of materials science and electromagnetic compatibility. Coal gasification technology plays a vital role in energy conversion and chemical raw material production. The coal gasification process generates a large amount of fine coal gasification slag. As a major industrial solid waste, if this fine slag is not properly and effectively treated and utilized, it not only results in a significant waste of resources but also causes serious pollution to the soil, water, and atmospheric environment. Therefore, how to achieve high-value resource utilization of fine coal gasification slag, turning waste into treasure, is a key issue that needs to be addressed in the field of comprehensive resource utilization. Developing coal gasification slag into materials with specific functions, especially absorbers with electromagnetic wave absorption properties, can not only solve its environmental pollution problem, but also expand its application areas, with important economic, social and environmental benefits.

[0003] Research on electromagnetic wave absorbing materials has made significant progress, with numerous types of absorbing materials being developed, including ferrites, magnetic metals and their alloys, conductive polymers, carbon-based materials, and their composites. These materials absorb and attenuate electromagnetic waves through various loss mechanisms, such as magnetic loss, conductive loss, and dielectric loss. Carbon-based materials, due to their unique electronic structure and excellent electrical conductivity, exhibit significant potential for application in electromagnetic wave absorption. Researchers are continuously improving their electromagnetic wave absorption performance by manipulating surface properties such as pore structure, interlayer spacing, and defects, as well as by combining them with other materials. Coal gasification slag typically contains a certain amount of residual carbon and iron minerals, which contribute to its electromagnetic loss capacity. Some studies have attempted to modify slag through physical or chemical methods to enhance its electromagnetic wave absorption performance. Despite extensive research on electromagnetic wave absorbing materials and the resource utilization of slag, current technologies for preparing absorbers from slag still face numerous challenges, limiting their practical application and widespread adoption. The degree of graphitization of carbon in coal gasification slag is generally insufficient. The degree of graphitization of carbon directly affects its electrical conductivity, which in turn affects the efficiency of electromagnetic wave absorption through the conductive loss mechanism. Carbon materials with low graphitization have poor conductivity and difficulty forming an effective conductive network, resulting in limited conductive loss capacity for electromagnetic waves. Existing methods for increasing the degree of carbon graphitization often require harsh conditions such as high temperature and high pressure, or use complex processes such as chemical vapor deposition. This not only increases production costs but also places high demands on equipment, making large-scale industrial production difficult. The reduction efficiency of iron minerals in coal gasification slag is low. Iron minerals primarily contribute to electromagnetic wave absorption through magnetic loss mechanisms such as hysteresis loss and eddy current loss. However, the iron minerals in coal gasification slag are typically present in an oxidized form, making their reduction to elemental iron difficult, resulting in weak magnetic loss capacity. Existing reduction methods, such as those using reducing gases such as hydrogen and carbon monoxide, are costly and have poor safety issues. Reduction using chemical reducing agents can introduce new impurities, affecting the purity and performance of the material. Furthermore, existing technologies for modifying coal gasification fine slag for wave absorption still face challenges such as complex processes, high equipment requirements, and environmental pollution. For example, while acid leaching can remove some impurities, it produces large amounts of acidic wastewater, causing serious environmental pollution. Hydrothermal methods require high-temperature and high-pressure reactors, impose harsh operating conditions, and incur high equipment costs. While metal doping can introduce new loss mechanisms, the dispersion and stability of the metal elements are difficult to control and may increase the material's density, hindering practical application.

[0004] In order to solve the technical problem that coal gasification fine slag has weak electromagnetic loss capacity due to insufficient carbon graphitization and low iron mineral reduction efficiency, it is urgently necessary to find a modification method that is simple in process, low in cost, environmentally friendly and can effectively improve the electromagnetic wave absorption performance of coal gasification fine slag, effectively improve the electromagnetic wave absorption performance of coal gasification fine slag, realize its high-value resource utilization, and provide a new way to solve the electromagnetic pollution problem and the environmental pollution problem of coal gasification fine slag. Summary of the Invention

[0005] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a coal gasification fine slag absorber and its preparation method and application, so as to solve the technical problem of weak electromagnetic loss capacity of coal gasification fine slag due to insufficient carbon graphitization and low iron mineral reduction efficiency. Through the fluxing effect and structural reconstruction ability of borate, the carbon graphitization and iron element generation efficiency are directly enhanced, and through the chemical doping and glass phase formation of the high-temperature decomposition products of borate, the conductive loss and magnetic loss mechanisms are synergistically optimized.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions: The present invention discloses a method for preparing a coal gasification fine slag wave absorber, comprising: The coal gasification fine slag, the modifier and the plasticizer are mixed, ground evenly, sieved, dry pressed, and sintered in an argon atmosphere to obtain the coal gasification fine slag absorber; The modifier is tetraborate; the plasticizer is polyvinyl alcohol; After the tetraborate is sintered, the decomposed B2O3 reacts with the silicate in the coal gasification fine slag to form a glass phase.

[0007] Preferably, the usage ratio of coal gasification fine slag, modifier and plasticizer is 5g: (0.8-1.4)g: (0.2-1.0)mL.

[0008] Preferably, the tetraborate is sodium tetraborate or potassium tetraborate; and the sieved particle size is 80-120 mesh.

[0009] Preferably, the dry pressing pressure is 3-6 MPa.

[0010] Preferably, the dry pressing time is 1 to 3 minutes.

[0011] Preferably, the heating rate of the sintering process is 1-10°C / min.

[0012] Preferably, the sintering temperature is 800-900°C.

[0013] Preferably, the sintering treatment time is 1 to 3 hours.

[0014] The invention also discloses a coal gasification fine slag wave absorbing agent, which is prepared by adopting the above-mentioned method for preparing the coal gasification fine slag wave absorbing agent.

[0015] The present invention also discloses the use of the coal gasification fine slag absorber prepared by the above-mentioned preparation method in the preparation of 5G base station absorbing patches, stealth drone coatings or medical equipment shielding covers.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The present invention discloses a method for preparing a coal gasification fine slag absorber. The method uses coal gasification fine slag as a raw material, adds borates such as sodium tetraborate as a modifier, and cooperates with polyvinyl alcohol as a plasticizer. The polyvinyl alcohol as a plasticizer helps the coal gasification fine slag and the modifier to be fully mixed during the grinding process, and can ensure the molding quality of the green compact in the subsequent dry pressing step, so that the green compact has a certain strength and stability, which is conducive to the smooth progress of the subsequent annealing treatment. The coal gasification fine slag absorber is finally prepared through mixed grinding, dry pressing, and inert atmosphere sintering treatment. Ar, as an inert gas, can prevent the green compact from being oxidized at high temperatures, thereby ensuring the purity and stability of the material. The electromagnetic wave absorption performance and application of the coal gasification fine slag are effectively improved and expanded. As a multifunctional modifier, borate has continuous glass forming ability, chemical doping activity and fluxing effect during high-temperature sintering, which can achieve structural optimization, interface regulation and phase reconstruction of the fine slag. Taking sodium tetraborate-modified coal gasification slag as an example, active substances such as sodium oxide generated by pyrolysis during sintering disrupt the silicate network, forming eutectics, reconstructing the microstructure, and optimizing impedance matching. High-temperature graphitization of residual carbon in the slag enhances conductive loss, while carbon-thermal reduction to elemental iron introduces magnetic loss. The modified slag establishes a multi-loss mechanism: interfacial polarization loss, magnetic loss, and conductive loss, enhancing its electromagnetic absorption efficiency. Discarded coal gasification slag is transformed into a high-quality absorbing material, enabling resource recycling. The preparation method presented here is simple, requires minimal equipment, and is suitable for industrial production. The resulting modified coal gasification slag absorber can be used in the field of absorbing materials, helping to address electromagnetic pollution and promote sustainable development in the industry. Coal gasification slag, once a bulk waste with poor electromagnetic loss performance, has been given new application value through the modification method presented here. The B2O3 generated by borate decomposition reacts with silicates to form a glassy phase, optimizing the impedance matching between the material surface and free space and reducing electromagnetic reflection. The introduction of Fe element absorbs electromagnetic waves through hysteresis loss and eddy current loss. In addition, the residual carbon in the fine slag not only improves its degree of graphitization at high temperature, but also forms a continuous conductive network of graphitized carbon, effectively enhancing the conductive loss of the system. In addition, a carbon thermal reduction reaction occurs during the sintering process to reduce the iron minerals in the fine slag to iron element, directly introducing magnetic loss into the system. The present invention directly enhances the efficiency of carbon graphitization and iron element generation through the fluxing effect and structural reconstruction ability of borates, and synergistically optimizes the conductive loss and magnetic loss mechanisms through the chemical doping and glass phase formation of the high-temperature decomposition products of borates. In response to the common problems of carbon structure destruction, poor metal stability, and complex processes in existing coal gasification fine slag absorption modification technologies, borate modification technology, with its unique high-temperature activity and interface control capabilities, provides a new path to break through the above bottlenecks. As a multifunctional modifier, borate exhibits continuous glass-forming ability, chemical doping activity, and fluxing effect during high-temperature sintering, which can simultaneously achieve structural optimization, interface control, and phase reconstruction of carbon-based materials, providing an innovative approach for the preparation of high-performance absorbing materials.The method of the present invention is simple and easy to operate. The modification is completed in three steps of mixing, dry pressing and sintering, avoiding the complex equipment and high-pollution processes required by traditional acid leaching, hydrothermal methods or metal doping (such as no need for strong acid treatment or high-pressure reactors). The prepared modified coal gasification fine slag absorber has excellent electromagnetic wave absorption performance, providing an effective way to solve the problem of electromagnetic pollution and resource utilization of coal gasification fine slag.

[0017] Furthermore, taking sodium tetraborate as an example, it is introduced as a modifier into coal gasification slag. During sintering, the active substances such as sodium oxide and boron trioxide produced by pyrolysis can destroy the silicate network structure in the slag, forming low-solvent products, reconstructing the microstructure and structure of the coal gasification slag, and optimizing the impedance matching between the material and free space. In addition, the residual carbon in the slag not only increases its degree of graphitization at high temperatures, effectively enhancing the conductive loss of the system, but also undergoes a carbothermal reduction reaction during the sintering process, reducing the iron minerals in the slag to elemental iron, directly introducing magnetic losses into the system.

[0018] Furthermore, the ratio of coal gasification fine slag, modifier, and plasticizer is 5g:(0.8-1.4)g:(0.2-1.0)mL. This avoids insufficient borate, which can lead to discontinuous glass phase formation, and prevents excessive borate from introducing impurities. This ensures effective modification of the coal gasification fine slag without introducing excessive impurities that could affect material properties. For example, when the modifier dosage is too low, it may not significantly change the microstructure of the coal gasification fine slag, resulting in a lack of significant improvement in microwave absorption performance. Excessive dosage may destroy some of the original beneficial structures of the fine slag and even increase the weight of the material, which is not conducive to practical application. The appropriate amount of plasticizer ensures the strength of the compact. Exceeding this range can lead to insufficient bonding or plasticizer residue that affects sintering.

[0019] Furthermore, after grinding, the particles are sieved through 80-120 mesh to ensure particle fluidity, reduce the cracking rate of the green compacts, and achieve uniform mixing of materials through particle size control: on the one hand, the 80-120 mesh screen can remove coarse particles that are not fully ground, so that the gasification fine slag and the modifier are fully in contact at the microscopic level; the uniform fine particle system can significantly improve the packing density during dry pressing, reduce the internal porosity and stress concentration of the green compacts, reduce the risk of cracking, and at the same time increase the specific surface area of the particles, accelerate the migration and reaction of materials during the sintering process, thereby improving the sintering efficiency and reducing energy consumption. In addition, it can effectively separate impurities to ensure the purity and performance stability of the sample.

[0020] Furthermore, during dry pressing, the press pressure is maintained at 3–6 MPa, with the pressure maintained for 1–3 minutes. This prevents excessive pressure from causing internal stress concentration within the compact, effectively removes inter-powder gas, and reduces sintering porosity. These conditions allow the powder sample to form a compact with a certain density and strength. Appropriate pressure and time ensure a compact internal structure, facilitating atomic diffusion and reaction during subsequent annealing, and promoting microstructural optimization. Excessively low pressure results in insufficient compact density and a loose structure, hindering the modification reaction. Excessive pressure can lead to internal defects such as cracks, which also affect material properties.

[0021] Furthermore, the sintering process should be conducted at a heating rate of 1-10°C / min, a temperature of 800-900°C, and a duration of 1-3 hours to allow the modifier to fully react with the coal gasification slag to form a stable absorbing structure. A heating rate that is too fast may cause thermal stress within the material, damaging the microstructure. A temperature that is too low or a sintering time that is too short may result in an incomplete modification reaction and fail to achieve ideal absorbing performance. A temperature that is too high or a sintering time that is too long may damage the material structure and degrade performance.

[0022] Furthermore, the sintering temperature is 800-900°C for 1-3 hours. Maintaining the sintering temperature within this range provides optimal energy conditions for the reaction between the modifier (such as a borate, such as sodium tetraborate) and the coal gasification fine slag. Within this temperature range, the borate can fully exert its continuous glass-forming ability, chemical doping activity, and fluxing effect, effectively disrupting the silicate network structure in the coal gasification fine slag to form a eutectic, thereby reconstructing the microstructure and optimizing the physical phase. This temperature also facilitates the graphitization of residual carbon in the slag, increasing its degree of graphitization and enhancing the system's conductive loss performance. It also promotes the carbothermal reduction reaction, reducing the iron minerals in the slag to elemental iron, introducing a magnetic loss mechanism, and thus comprehensively improving the electromagnetic wave absorption performance of the coal gasification fine slag absorber. This ensures that various reactions between the coal gasification fine slag and the modifier proceed fully, such as the reaction between the borate and silicate, the graphitization of residual carbon, and the carbothermal reduction reaction. Sufficient time allows the reactants to contact, diffuse, and react with each other, forming a stable phase and microstructure, thereby optimizing the electromagnetic wave absorption performance of the coal gasification fine slag. If the sintering time is too short, the reaction may not be complete, resulting in poor modification effect; while a longer time can allow for a more complete reaction, it will increase production costs and reduce production efficiency.

[0023] The present invention also discloses a coal gasification fine slag absorber prepared by the above-mentioned preparation method. After borate modification and preparation process optimization, the coal gasification fine slag absorber extends the electromagnetic wave propagation path and increases the interaction sites by regulating the pore structure and grain size morphology; the glass phase optimizes impedance matching and strengthens interface polarization, and the magnetic phase introduces a magnetic loss mechanism and optimizes the distribution; residual carbon is graphitized to construct a continuous conductive network, and the conductive phase and the insulating phase work together and utilize the seepage effect to enhance the loss; the complex dielectric constant and complex magnetic permeability are synergistically regulated to achieve broadband matching, while improving the surface and internal impedance characteristics and reducing electromagnetic wave reflection. These structural performance optimizations work synergistically to significantly improve its electromagnetic wave absorption performance and expand its application potential in multiple fields.

[0024] The present invention also discloses the use of the coal gasification fine slag absorber produced by the above-mentioned preparation method in the preparation of 5G base station absorbing patches, stealth drone coatings, or medical equipment shielding covers. In 5G base stations, the absorbing patches can effectively absorb electromagnetic radiation generated by the base station, reducing electromagnetic pollution to the surrounding environment. In the field of stealth drones, the coating can reduce the drone's radar cross-sectional area, improving its stealth performance. In medical equipment, the shielding cover can prevent external electromagnetic interference from affecting the normal operation of the equipment, ensuring the safety and accuracy of the medical equipment. The application of this absorber in 5G base stations, stealth drones, and medical equipment can help address electromagnetic pollution issues and improve the performance and reliability of the equipment. With the rapid development of electronic technology, electromagnetic pollution is becoming increasingly serious, posing a potential threat to human health and equipment operation. The use of this coal gasification fine slag absorber provides an effective way to address these issues and promotes technological progress and sustainable development in related industries. The coal gasification fine slag modified by the present method has broad application prospects in the field of absorbing materials. It can effectively absorb electromagnetic waves, reduce the intensity of electromagnetic radiation, and reduce electromagnetic interference. It can be used in electromagnetic shielding of electronic equipment, military stealth materials, and other fields. At the same time, the method of the present invention realizes the high-value utilization of coal gasification fine slag, reduces the pollution of solid waste to the environment, and has significant environmental and economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 XRD comparison patterns of the unmodified coal gasification fine slag disclosed in the comparative example of the present invention, the sodium tetraborate modified coal gasification fine slag absorber disclosed in Example 1, and the potassium tetraborate modified coal gasification fine slag absorber disclosed in Example 2; Figure 2 This is an SEM image of the coal gasification fine slag absorber prepared in Example 1 of the present invention; Figure 3These are reflection loss curves of the unmodified coal gasification slag disclosed in the comparative example of the present invention and the coal gasification slag absorber disclosed in Example 1; wherein (a) is the unmodified coal gasification slag; and (b) is the coal gasification slag absorber disclosed in Example 1. DETAILED DESCRIPTION

[0026] The technical solution of the present invention will be described clearly and completely below. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0027] In the present invention, unless otherwise specified, all the embodiments and preferred implementation methods mentioned herein can be combined with each other to form a new technical solution.

[0028] In the present invention, unless otherwise specified, all technical features and preferred features mentioned herein can be combined with each other to form a new technical solution.

[0029] In the present invention, unless otherwise specified, percentages (%) or parts refer to percentages by weight or parts by weight relative to the composition.

[0030] In the present invention, unless otherwise specified, the components involved or their preferred components can be combined with each other to form a new technical solution.

[0031] In this disclosure, unless otherwise specified, the numerical range "a-b" is an abbreviation for any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "6-22" indicates that all real numbers between "6-22" are listed herein, and "6-22" is merely an abbreviation for these numerical combinations.

[0032] The "range" disclosed in the present invention is in the form of lower limit and upper limit, which can be one or more lower limits, and one or more upper limits respectively.

[0033] In the present invention, the term "and / or" used herein refers to any combination and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0034] In the present invention, unless otherwise specified, each reaction or operation step can be carried out sequentially or in accordance with the order. Preferably, the reaction method herein is carried out sequentially.

[0035] Unless otherwise indicated, the professional and scientific terms used herein are the same as those familiar to those skilled in the art. In addition, any method or material similar or equivalent to the described content can also be applied to the present invention.

[0036] The present invention provides a method for preparing a coal gasification fine slag wave absorber, comprising the following steps: S1. Coal gasification slag and borate are mixed and ground to obtain a powder sample. Polyvinyl alcohol is added dropwise as a plasticizer during grinding. The amount ratio of coal gasification slag: borate: polyvinyl alcohol is 5g: (0.8-1.4)g: (0.2-1.0)mL. After grinding, the powder sample is sieved through 80-120 mesh to ensure that the coal gasification slag and the modifier are fully mixed. S2. Place the uniform powder obtained in step S1 in a press and dry-press for 1-3 minutes at a pressure of 3-6 MPa to obtain a compact; S3. Sintering the compact obtained in step S2 under an Ar atmosphere at a heating rate of 1-10°C / min, a temperature of 800-900°C, and a holding time of 1-3h to obtain a coal gasification fine slag absorber.

[0037] The present invention provides a method for preparing a coal gasification slag absorber. The method comprises mixing coal gasification slag with a modifier in a specific ratio, adding polyvinyl alcohol as a plasticizer, and then grinding to prepare a uniform powder. The powder is dry-pressed in a press to obtain a compact. The compact is sintered in an Ar atmosphere to obtain the coal gasification slag absorber. The coal gasification slag absorber is then mixed with paraffin wax in a mass ratio of (30-40):(70-60) to test its electromagnetic wave absorption performance. The addition of the modifier and the sintering process effectively improve the composition and structure of the coal gasification slag, thereby enhancing its electromagnetic wave absorption performance. This method, for the first time, utilizes borate as a modifier, combined with dry pressing and sintering processes, to prepare a modified coal gasification slag absorber with excellent electromagnetic wave absorption performance. The modified coal gasification slag absorber prepared by the present invention can effectively enhance electromagnetic wave absorption and, by utilizing waste coal gasification slag, achieves resource recycling.

[0038] The modified coal gasification fine slag absorber disclosed in the present invention, as well as its preparation method and application, is dedicated to solving the problem of low added value of coal gasification fine slag applications and developing high-performance absorbing materials. Ordinary coal gasification fine slag has poor electromagnetic wave absorption performance due to its microstructural defects and single composition, making it difficult to meet actual needs. The present invention introduces a modifier and cooperates with a specific process to form a microstructure that is conducive to electromagnetic wave absorption in the coal gasification fine slag, thereby improving the absorption efficiency. Coal gasification fine slag is used as raw material, sodium tetraborate and other borates are added as modifiers, and polyvinyl alcohol plasticizer is used. The coal gasification fine slag absorber is finally prepared by mixed grinding, dry pressing, and inert atmosphere sintering. As a multifunctional modifier, borate can achieve structural optimization, interface regulation and phase reconstruction of fine slag due to its continuous glass forming ability, chemical doping activity and fluxing effect during high-temperature sintering. Taking the sodium tetraborate-modified coal gasification fine slag as an example, the active substances such as sodium oxide produced by pyrolysis during sintering destroy the silicate network, forming a low-solubility product, reconstructing the microstructure and optimizing the impedance matching; the high-temperature graphitization of the residual carbon in the fine slag enhances the conductive loss, and the carbon thermal reduction generates iron to introduce magnetic loss. The modified coal gasification fine slag constructs a multiple loss mechanism of "interface polarization loss-magnetic loss-conductive loss", which improves the electromagnetic wave absorption efficiency of the fine slag. In this way, the discarded coal gasification fine slag is transformed into a high-quality absorbing material, realizing resource recycling. The preparation method of the present invention is simple, has low equipment requirements, and is suitable for industrial production. The prepared modified coal gasification fine slag absorber can be used in the field of absorbing materials, helping to solve the problem of electromagnetic pollution and promote the sustainable development of the industry.

[0039] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0040] Example 1 A method for preparing a coal gasification fine slag absorber comprises the following steps: Weigh 5 g of coal gasification slag and 1.0 g of sodium tetraborate, place them together in an agate mortar, mix and grind them, and then sieve them through 100 mesh to ensure that the coal gasification slag and the modifier are fully mixed. During the grinding process, add 0.5 mL of polyvinyl alcohol as a plasticizer; The mixed powder was dry-pressed and shaped using a press, and the press was maintained at a pressure of 5 MPa for 2 minutes to obtain a compact.

[0041] The compact was then sintered in an Ar atmosphere at a heating rate of 2°C / min and kept at 900°C for 2h to obtain a coal gasification fine slag absorber.

[0042] Obvious diffraction peaks of Fe, Ca(Mg,Al)(Si,Al)2O6 and SiO2 appear in the coal gasification fine slag absorber modified by sodium tetraborate. The appearance of these peaks indicates that the modification promotes the formation or growth of these phases, thereby improving their crystallinity.

[0043] Example 2 A method for preparing a coal gasification fine slag absorber comprises the following steps: Weigh 5 g of coal gasification slag and 1.0 g of potassium tetraborate, place them together in an agate mortar, mix and grind them, and then sieve them through 100 mesh to ensure that the coal gasification slag and the modifier are fully mixed. During the grinding process, add 0.5 mL of polyvinyl alcohol as a plasticizer; The mixed powder was dry-pressed and shaped using a press, and the press was maintained at a pressure of 5 MPa for 2 minutes to obtain a compact.

[0044] The compact was then sintered in an Ar atmosphere at a heating rate of 2°C / min and kept at 900°C for 2h to obtain a coal gasification fine slag absorber.

[0045] The potassium tetraborate-modified coal gasification slag absorber also exhibits diffraction peaks for elemental Fe, Ca(Mg,Al)(Si,Al)2O6, and SiO2, indicating that boric acid plays a primary role in the modification process. Furthermore, compared to sodium tetraborate, the crystallinity of elemental Fe in the potassium tetraborate-modified slag is lower, while the crystallinity of SiO2 is higher, indicating that the introduction of the two borate modifiers has different effects on the composition and structure of the modified slag.

[0046] Example 3 A method for preparing a coal gasification fine slag absorber comprises the following steps: Weigh 5 g of coal gasification slag and 1.4 g of sodium tetraborate, place them together in an agate mortar, mix and grind them, and then sieve them through 100 mesh to ensure that the coal gasification slag and the modifier are fully mixed. During the grinding process, add 0.5 mL of polyvinyl alcohol as a plasticizer; The mixed powder was dry-pressed and shaped using a press, and the press was maintained at a pressure of 5 MPa for 2 minutes to obtain a compact.

[0047] The compact was then sintered in an Ar atmosphere at a heating rate of 2°C / min and kept at 900°C for 2h to obtain a coal gasification fine slag absorber.

[0048] With increasing the amount of modifier introduced, some impurity peaks appear in the modified coal gasification fine slag absorber, and the crystallinity of Fe element, Ca(Mg,Al)(Si,Al)2O6 and SiO2 is low. This indicates that excessive modifier triggers new side reactions and generates impurity phases. At the same time, excessive ions are incorporated into the lattice, which destroys the order of the lattice and causes lattice distortion.

[0049] Example 4 A method for preparing a coal gasification fine slag absorber comprises the following steps: Weigh 5 g of coal gasification slag and 1.0 g of sodium tetraborate, place them together in an agate mortar, mix and grind them, and then sieve them through 100 mesh to ensure that the coal gasification slag and the modifier are fully mixed. During the grinding process, add 0.5 mL of polyvinyl alcohol as a plasticizer; The mixed powder was dry-pressed and shaped using a press, and the press was maintained at a pressure of 5 MPa for 2 minutes to obtain a compact.

[0050] The compact was then sintered in an Ar atmosphere at a heating rate of 2°C / min and kept at 800°C for 2h to obtain a coal gasification fine slag absorber.

[0051] The crystallinity of Fe in the modified fine slag is low, which indicates that the rate of carbothermal reduction reaction is slow and the degree of progress is insufficient at this sintering temperature.

[0052] Example 5 A method for preparing a coal gasification fine slag absorber comprises the following steps: Weigh 5 g of coal gasification slag and 0.8 g of sodium tetraborate, place them together in an agate mortar, mix and grind them, and then sieve them through 100 mesh to ensure that the coal gasification slag and the modifier are fully mixed. During the grinding process, add 0.2 mL of polyvinyl alcohol as a plasticizer; The mixed powder was dry-pressed and shaped using a press, and the press was maintained at a pressure of 3 MPa for 3 minutes to obtain a compact.

[0053] The compact was then sintered in an Ar atmosphere at a heating rate of 1°C / min and kept at 860°C for 1 h to obtain a coal gasification fine slag absorber.

[0054] Example 6 A method for preparing a coal gasification fine slag absorber comprises the following steps: Weigh 5 g of coal gasification slag and 0.9 g of sodium tetraborate, place them together in an agate mortar, mix and grind them, and then sieve them through 100 mesh to ensure that the coal gasification slag and the modifier are fully mixed. During the grinding process, add 0.7 mL of polyvinyl alcohol as a plasticizer; The mixed powder was dry-pressed and shaped using a press, and the press was maintained at a pressure of 5.5 MPa for 2.5 minutes to obtain a compact.

[0055] The compact was then sintered in an Ar atmosphere at a heating rate of 4°C / min and kept at 840°C for 2.5 h to obtain a coal gasification fine slag absorber.

[0056] Example 7 A method for preparing a coal gasification fine slag absorber comprises the following steps: Weigh 5 g of coal gasification slag and 1.2 g of sodium tetraborate, place them together in an agate mortar, mix and grind, and then sieve through 100 mesh to ensure that the coal gasification slag and the modifier are fully mixed. During the grinding process, add 1.0 mL of polyvinyl alcohol as a plasticizer; The mixed powder was dry-pressed and shaped using a press, and the press was maintained at a pressure of 6 MPa for 1 min to obtain a compact.

[0057] The compact was then sintered in an Ar atmosphere at a heating rate of 10°C / min and kept at 820°C for 3 h to obtain a coal gasification fine slag absorber.

[0058] Comparative Example A method for preparing unmodified coal gasification fine slag, comprising: 5 g of coal gasification fine slag was weighed and placed in an agate mortar for grinding, and then sieved through 100 mesh to obtain unmodified coal gasification fine slag.

[0059] Figure 1 The XRD comparison patterns of the unmodified coal gasification fine slag disclosed in the comparative example of the present invention, the sodium tetraborate modified coal gasification fine slag absorber disclosed in Example 1, and the potassium tetraborate modified coal gasification fine slag absorber disclosed in Example 2 are shown in FIG. 1 . As can be seen from the figure, the unmodified coal gasification fine slag spectrum mainly presents amorphous diffraction characteristics, with only a small amount of weak crystalline peaks corresponding to silicate minerals and SiO2, and no Fe elemental diffraction peaks are detected, indicating that the degree of carbon graphitization in the original fine slag is low and the iron minerals exist in an oxidized state. The sodium tetraborate modified fine slag has strong Fe elemental diffraction peaks at 2θ=44.6°, 65.1°, and 82.4°, and the crystalline peak intensities of Ca(Mg,Al)(Si,Al)2O6 and SiO2 are significantly enhanced, indicating that the active substances decomposed by sodium tetraborate during the sintering process promote the carbothermal reduction reaction, reducing the iron minerals to Fe The diffraction peak intensity of Fe element in the fine slag modified with potassium tetraborate is slightly lower than that in the sample modified with sodium tetraborate, but the crystallization peak of SiO2 is stronger and the peak of Ca (Mg,Al)(Si,Al)2O6 is sharper, which reflects the different effects of different borates on the crystallinity of the phase. Overall, the modified samples provide a material basis for the construction of magnetic loss, conductive loss and interface polarization loss mechanisms due to the generation of Fe element and the reconstruction of silicate structure.

[0060] Figure 2This is an SEM image of the coal gasification slag absorber prepared in Example 1 of the present invention. As can be seen from the image, the surface of the modified coal gasification slag absorber forms a continuous glassy matrix, within which are evenly distributed particles with particle sizes of approximately 5 to 10 μm, namely, elemental iron and silicate crystalline phases. Nanoscale pores exist between the particles, with pore sizes ranging from approximately 50 to 200 nm. The glassy phase has a smooth surface and forms a clear interface with the granular phase, with fine cracks and wrinkles visible at the interface. This microstructure not only makes the overall structure more dense and uniform by filling the intergranular gaps with the glassy phase, but also extends the propagation path of electromagnetic waves within the material through the retained pores. Furthermore, the presence of numerous interfaces increases the number of sites for interfacial polarization loss. This, corroborated by the formation of the glassy phase and elemental iron in XRD analysis, demonstrates that the optimized microstructure of the material after borate modification provides a structural foundation for multiple loss mechanisms.

[0061] Figure 3 The graphs show the reflection loss of the unmodified coal gasification slag disclosed in the comparative example of the present invention and the coal gasification slag absorber disclosed in Example 1; (a) shows the unmodified coal gasification slag; (b) shows the coal gasification slag absorber disclosed in Example 1; as can be seen from the graph, the reflection loss value of the unmodified coal gasification slag is generally higher than -10 dB in the frequency range of 2 to 18 GHz, and only a weak absorption peak appears in the range of 10 to 12 GHz, with the lowest being about -15 dB. The effective absorption bandwidth is less than 2 GHz, and the absorption performance is poor; while the modified sample shows significant absorption capacity in the frequency band of 8 to 16 GHz, with the lowest reflection loss reaching -48.6 dB (at 12 GHz), and the effective absorption bandwidth extends to 8 GHz (7.5 to 15.5 GHz, RL≤-10 dB), covering the commonly used high-frequency communication bands such as the X-band (8 to 12 GHz) and the Ku-band (12 to 18 GHz). The above data show that through borate modification and sintering treatment, the electromagnetic wave absorption efficiency of the material is effectively improved, and the absorption peak depth and effective bandwidth are better than those of the unmodified sample. This is due to the synergistic effect of the magnetic loss of the iron element, the polarization loss of the high-crystallinity carbon and the glass phase interface, and the conductive loss formed in the modified material. It verifies the optimization effect of the method of the present invention on the absorption performance of coal gasification fine slag, and meets the demand for broadband and high-efficiency absorbing materials in practical applications.

[0062] In summary, the present invention provides a coal gasification fine slag absorber and its preparation method and application, which uses coal gasification fine slag as the basic raw material and selects the addition of borate as a modifier, which not only realizes the recycling and reuse of waste resources, but also broadens the effective absorption band and improves the absorption efficiency by improving the microstructure of the material. The application of dry pressing shaping and sintering process, combined with precise parameter control, prepares a modified coal gasification fine slag absorber with excellent electromagnetic wave absorption performance, combining the common advantages of raw materials and processes. The addition of tetraborate modifier decomposes at high temperature in the subsequent sintering process to produce active substances such as alkaline oxides and boron trioxide, which can destroy the silicate network structure in the coal gasification fine slag, form low eutectic, reconstruct the microscopic composition and structure of the coal gasification fine slag, and optimize the impedance matching between the material and free space. Based on the above composition and structural optimization, the modified coal gasification fine slag can synergistically construct a multiple loss mechanism of "interface polarization loss-magnetic loss-conductive loss" to improve its electromagnetic wave absorption efficiency. Combining the above composition and structure optimization, the modified coal gasification fine slag can synergistically construct a multiple loss mechanism of "interface polarization loss-magnetic loss-conductive loss" to improve its electromagnetic wave absorption efficiency. Compared with other methods, by introducing tetraborate, not only can the reconstruction of composition and structure, the introduction of magnetic loss, and the improvement of conductive loss be achieved simultaneously, but it also avoids problems such as acid pollution, the addition of foreign magnetic materials, and complex preparation process. Based on this, tetraborate is directly used to modify coal gasification fine slag to establish multiple losses, thereby improving its electromagnetic wave absorption performance, so as to realize the high-value resource utilization of coal gasification fine slag. The electromagnetic wave absorption material with good performance is prepared through a simple process, which shows broad application prospects in the field of absorbing materials.

[0063] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a coal gasification fine slag absorber, characterized in that: include: The coal gasification fine slag, the modifier and the plasticizer are mixed, ground evenly, sieved, dry pressed, and sintered in an argon atmosphere to obtain the coal gasification fine slag absorber; The modifier is tetraborate; the plasticizer is polyvinyl alcohol; After the tetraborate is sintered, the decomposed B2O3 reacts with the silicate in the coal gasification fine slag to form a glass phase.

2. The method for preparing the coal gasification fine slag absorber according to claim 1, characterized in that: The usage ratio of the coal gasification fine slag, the modifier and the plasticizer is 5g: (0.8-1.4)g: (0.2-1.0)mL.

3. The method for preparing the coal gasification fine slag absorber according to claim 1, characterized in that: The tetraborate is sodium tetraborate or potassium tetraborate; and the sieved particle size is 80-120 mesh.

4. The method for preparing the coal gasification fine slag absorber according to claim 1, characterized in that: The dry pressing pressure is 3~6Mpa.

5. The method for preparing the coal gasification fine slag absorber according to claim 1, characterized in that: The dry pressing time is 1 to 3 minutes.

6. The method for preparing the coal gasification fine slag absorber according to claim 1, characterized in that: The heating rate of the sintering process is 1-10°C / min.

7. The method for preparing the coal gasification fine slag absorber according to claim 1, characterized in that: The sintering temperature is 800-900°C.

8. The method for preparing the coal gasification fine slag absorber according to claim 1, characterized in that: The sintering time is 1 to 3 hours.

9. A coal gasification fine slag absorber, characterized in that: The invention discloses a coal gasification fine slag absorber prepared by the method for preparing the coal gasification fine slag absorber according to any one of claims 1 to 8.

10. Use of the coal gasification fine slag absorber prepared by the preparation method according to any one of claims 1 to 8 in the preparation of 5G base station absorbing patches, stealth drone coatings or medical equipment shielding covers.

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