Fluoroborate modified coal gasification fine slag wave-absorbing agent as well as preparation method and application thereof

Abstract

The invention discloses a fluoborate modified coal gasification fine slag wave-absorbing agent and a preparation method and application thereof, and belongs to the technical field of electromagnetic wave absorbing material preparation.The method comprises the steps that coal gasification fine slag and fluoborate are mixed, a shaping agent is dropwise added, and after even grinding, sieving and dry pressing are conducted, a pressed blank is obtained; and sintering the pressed blank in an inert atmosphere to obtain the fluoborate modified coal gasification fine slag wave-absorbing agent. The method is easy and convenient to operate, high in repeatability and easy to control, recycling of resources is achieved through utilization of the waste coal gasification fine slag, fluoborate is added as a modifier, and through simple mixing, forming and sintering processes, the preparation method is simple, and the preparation cost is low. The prepared fluoborate modified coal gasification fine slag wave-absorbing agent has stronger electromagnetic loss capability and multiple loss mechanisms, so that the coal gasification fine slag is effectively modified, and the problems that the additional value of resource utilization of the coal gasification fine slag is low and the traditional wave-absorbing modification technology is high in cost and serious in pollution are solved; better application prospects are realized in the field of electromagnetic wave absorption.

Description

Technical Field

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

[0002] Coal gasification slag, as a solid waste generated during the coal gasification process, has a huge output and is usually regarded as industrial waste for landfill or simple treatment. It not only occupies a large amount of land resources, but also may cause potential pollution to the environment. Studies have shown that the composition of coal gasification slag not only contains residual carbon with a highly developed pore structure and in the form of irregular particles, but also contains aluminum silicate complexes of calcium, iron, magnesium, etc. Based on its unique physical and chemical properties, coal gasification slag has certain potential utilization value in electromagnetic wave absorption. However, the degree of carbon graphitization in coal gasification slag is low, and the iron-containing minerals mainly exist in an amorphous state, which greatly limits its electromagnetic loss capacity. Therefore, it is urgent to exert the electromagnetic loss capacity of carbon and magnetic iron through modification and sintering, and optimize the synergistic effect of its multiple loss mechanisms.

[0003] At present, the existing modification technologies for the absorption performance of coal gasification fine slag mainly include: acid leaching deashing-functionalization treatment, that is, after removing inorganic minerals through hydrochloric acid, sulfuric acid, etc., carbon-based materials or metal oxides are added through processes such as hydrothermal technology to regulate the electromagnetic wave loss performance, but the acid leaching process is prone to produce a large amount of waste acid pollution; hydrothermal technology uses high temperature and high pressure environment to synthesize nanoparticles in situ and load them on the surface of fine slag. Although it can achieve uniform dispersion, it requires special high-pressure resistant equipment and the reaction cycle is long, and the industrialization cost is high; metal oxide doping technology relies on magnetic compounds such as iron and cobalt to improve its magnetic loss; carbon-based materials such as graphene and carbon nanotubes often face problems such as poor dispersion and complex preparation process when combined with fine slag.

[0004] In view of the problems of low resource utilization and poor electromagnetic wave loss capacity of existing coal gasification fine slag, it is urgently necessary to find a method for modifying coal gasification fine slag to improve its performance and the application of the obtained modified products, so that the coal gasification fine slag can be effectively modified, the high-value resource utilization of coal gasification fine slag can be achieved, and its electromagnetic wave absorption performance can be improved. 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 fluoroborate-modified coal gasification fine slag absorber and its preparation method and application, so as to solve the technical problems of low added value of resource utilization of coal gasification fine slag and high cost and high pollution of traditional absorbing modification technology.

[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 fluoroborate-modified coal gasification fine slag wave absorber, comprising: The coal gasification fine slag is mixed with fluoroborate, and a plasticizer is added dropwise. The mixture is ground evenly, sieved, and dry-pressed to obtain a compact. The compact is sintered in an inert atmosphere to obtain a fluoroborate-modified coal gasification fine slag absorber.

[0007] Preferably, the usage ratio of coal gasification fine slag, fluoroborate and plasticizer is 5 g: (0.5-1.6) g: (0.4-0.8) mL.

[0008] Preferably, the fluoroborate is sodium fluoroborate or potassium fluoroborate.

[0009] Preferably, the plasticizer is polyvinyl alcohol.

[0010] Preferably, the sieved particle size is 100 mesh.

[0011] Preferably, the dry pressing conditions are: dry pressing at a pressure of 4-5 MPa for 1-2 minutes.

[0012] Preferably, the inert atmosphere is Ar.

[0013] Preferably, the sintering treatment conditions are: heating to 800-1000°C at a heating rate of 2-5°C / min and keeping the temperature for 2-3h.

[0014] The invention also discloses a fluoroborate modified coal gasification fine slag wave absorbing agent, which is prepared by adopting the preparation method of the fluoroborate modified coal gasification fine slag wave absorbing agent.

[0015] The invention also discloses the use of the fluoroborate modified coal gasification fine slag wave absorbing agent prepared by the above preparation method in the preparation of electromagnetic wave absorbing materials.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The present invention discloses a preparation method of a fluoroborate-modified coal gasification fine slag absorber. Coal gasification fine slag was originally a bulk waste with poor electromagnetic loss capacity. The modification method of the present invention gives it new application value. The introduction of the fluoroborate modifier, during the subsequent sintering process, produces active products and alkaline oxides containing elements such as boron and fluorine through high-temperature decomposition. These substances can destroy the silicate network structure in the fine slag, form low-solubility products, reconstruct the microstructure and structure of the coal gasification fine slag, and optimize the impedance matching between the material and free space. At the same time, fluorine has a strong etching ability and can etch silicon-aluminum minerals, increase surface roughness and defect concentration, and increase the electromagnetic wave absorption interface. In addition, the residual carbon in the fine slag not only improves its graphitization degree at high temperature, effectively enhancing the conductive loss of the system, but also undergoes a carbon thermal reduction reaction during the sintering process to reduce the iron minerals in the fine slag to elemental iron, directly introducing magnetic loss into the system. Therefore, the modified coal gasification slag can synergistically construct a multiple loss mechanism of "interface polarization loss-magnetic loss-conductive loss" to improve its electromagnetic wave absorption efficiency. The preparation method of the present invention is easy to operate, does not require complex equipment and harsh production conditions, and reduces energy consumption and equipment investment in the production process. At the same time, due to the high process repeatability, it can improve production efficiency and reduce production costs, making the modified coal gasification slag absorber more competitive in large-scale production and application. Through simple mixing, molding and sintering processes, the coal gasification slag is effectively modified, and the prepared fluoroborate modified coal gasification slag absorber has excellent electromagnetic wave absorption performance, which provides an effective way to solve the problem of electromagnetic pollution and the resource utilization of coal gasification slag, and has better application prospects in the field of electromagnetic wave absorption.

[0017] Furthermore, sodium fluoroborate, potassium fluoroborate and other fluoroborates, when used as modifiers and introduced into coal gasification slag, can decompose into active products containing sodium, potassium, boron and fluorine during sintering. These active substances can destroy the silicate network structure in the slag, forming low-solubility products, reconstructing the microstructure and structure of the coal gasification slag, and optimizing the impedance matching between the material and free space; at the same time, fluorine has a strong etching ability and can etch silicon-aluminum minerals, increase surface roughness and defect concentration, and increase the electromagnetic wave absorption interface; in addition, the residual carbon in the slag not only improves its graphitization degree at high temperature, effectively enhancing the conductive loss of the system, but also undergoes a carbon thermal reduction reaction during the sintering process to reduce the iron minerals in the slag to elemental iron, directly introducing magnetic loss into the system. Therefore, the modified coal gasification slag can synergistically construct a multiple loss mechanism of "interface polarization loss-magnetic loss-conductive loss" to improve its electromagnetic wave absorption efficiency. Compared to other methods, the introduction of fluoroborates not only simultaneously achieves compositional and structural reconstruction, introduces magnetic losses, and improves conductive losses, but also avoids issues such as acid contamination, the addition of foreign magnetic materials, and complex preparation processes. Based on this, the present invention explores the direct modification of coal gasification slag with fluoroborates, establishing multiple losses and thereby improving its electromagnetic wave absorption properties, thereby achieving high-value resource utilization of coal gasification slag. This research work has important theoretical significance and practical application value.

[0018] Furthermore, the ratio of coal gasification slag: fluoroborate: plasticizer is 5g: (0.5-1.6)g: (0.4-0.8)mL, ensuring effective modification of the slag without introducing excessive impurities that could affect material properties. For example, if the amount of modifier is too small, it may not significantly change the microstructure of the slag, resulting in a minimal improvement in microwave absorption performance. However, if the amount of modifier is too large, it may destroy some of the slag's inherent beneficial structures and even increase the material's weight, making it unsuitable for practical applications.

[0019] Furthermore, polyvinyl alcohol, as a plasticizer, helps to fully mix the coal gasification fine slag and the modifier 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.

[0020] Furthermore, after grinding, the material is passed through a 100-mesh sieve and uniform mixing of the materials is achieved through particle size control: on the one hand, the 100-mesh sieve 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; on the other hand, the uniform fine particle system can significantly improve the packing density during dry pressing, reduce the internal porosity and stress concentration of the compact, reduce the risk of cracking, and at the same time increase the specific surface area of the particles, accelerate the material migration and reaction during the sintering process, thereby improving the sintering efficiency and reducing energy consumption. In addition, it can also effectively separate impurities to ensure the purity and performance stability of the sample.

[0021] Furthermore, the press pressure during dry pressing is 4-5 MPa, and the pressure is maintained for 1-2 minutes. These conditions allow the powder sample to form a compact with a certain density and strength. The appropriate pressure and time ensure a compact internal structure, which facilitates atomic diffusion and reaction during the subsequent annealing process and promotes microstructural optimization. Too low a 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.

[0022] Furthermore, sintering in an Ar atmosphere is of great significance. Ar, as an inert gas, can prevent the compact from being oxidized at high temperatures, thus ensuring the purity and stability of the material.

[0023] Furthermore, the annealing treatment is performed at a heating rate of 2-5°C / min, a temperature of 800-1000°C, and a duration of 2-3 hours. These parameters are designed to ensure a thorough reaction between the modifier and the coal gasification slag, forming 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 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 time that is too long may damage the material structure and degrade performance.

[0024] The present invention also discloses a fluoroborate-modified coal gasification slag absorber, produced by the aforementioned preparation method. This absorber achieves high-value resource conversion of coal gasification slag, a major industrial waste, turning waste into valuable resources and reducing the environmental and resource pressures caused by waste accumulation. Furthermore, the modification process is environmentally friendly and avoids pollution from acidic solutions. By utilizing fluoroborate modification and a specialized process, a multi-loss mechanism of "interface polarization loss, magnetic loss, and conductive loss" is synergistically constructed. This enhances interfacial polarization loss, introduces magnetic loss, and increases conductive loss, while simultaneously optimizing impedance matching and significantly improving electromagnetic wave absorption efficiency. The absorber exhibits high absorptivity across a wide frequency band, a stable microstructure, and excellent performance.

[0025] The present invention also discloses the use of the fluoroborate-modified coal gasification slag absorber prepared by the above-mentioned preparation method in the preparation of electromagnetic wave absorbing materials. Its broadband high absorptivity can meet the diverse electromagnetic wave absorption needs of various fields, such as communications and radar, effectively reducing electromagnetic wave reflection and transmission, and significantly improving the electromagnetic environment. Using low-cost coal gasification slag as raw material, with simplified processes and flexible applications, it can be produced in a variety of forms, such as coatings and blocks, to suit different industrial scenarios. This significantly reduces raw material procurement, production, and application costs, and enhances product market competitiveness. This helps reduce the harm of electromagnetic pollution to humans and electronic devices, promotes resource recycling, and aligns with the concept of sustainable development, providing an efficient and economical solution to addressing electromagnetic pollution and resource recycling. The coal gasification slag absorber modified by the present method can effectively absorb electromagnetic waves, reduce electromagnetic radiation intensity, and mitigate electromagnetic interference in the field of absorbing materials. It can be used in electromagnetic shielding for electronic devices, military stealth materials, and other fields. Furthermore, the present method realizes the resource utilization of coal gasification slag, reduces environmental pollution from solid waste, and has significant environmental and economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 XRD comparison patterns of the unmodified coal gasification fine slag disclosed in the comparative example of the present invention, the sodium fluoroborate modified coal gasification fine slag absorber disclosed in Example 1, and the potassium fluoroborate modified coal gasification fine slag absorber disclosed in Example 2; Figure 2 This is an SEM image of the fluoroborate-modified coal gasification fine slag absorber prepared in Example 1 of the present invention; Figure 3 These are reflection loss curves of the unmodified coal gasification slag disclosed in the comparative example of the present invention and the sodium fluoroborate-modified coal gasification slag absorber disclosed in Example 1; wherein (a) is the unmodified coal gasification slag; and (b) is the sodium fluoroborate-modified coal gasification slag absorber disclosed in Example 1. DETAILED DESCRIPTION

[0027] 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.

[0028] 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.

[0029] 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.

[0030] In the present invention, unless otherwise specified, percentages (%) or parts refer to percentages by weight or parts by weight relative to the composition.

[0031] 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.

[0032] 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.

[0033] The "range" disclosed in the present invention is in the form of a lower limit and an upper limit, which can be one or more lower limits, and one or more upper limits, respectively.

[0034] 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.

[0035] In the present invention, unless otherwise specified, each reaction or operation step can be carried out sequentially or in accordance with the sequence. Preferably, the reaction method herein is carried out sequentially.

[0036] 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.

[0037] The present invention provides a method for preparing a fluoroborate-modified coal gasification fine slag wave absorber, comprising the following steps: S1. Coal gasification slag and fluoroborate 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: fluoroborate: polyvinyl alcohol is 5g: (0.5-1.6)g: (0.4-0.8)mL. After grinding, the powder sample is sieved with 100 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 1-2 minutes at a pressure of 4-5 MPa to obtain a compact; S3. Sintering the compact obtained in step S2 under an Ar atmosphere at a heating rate of 2-5°C / min, a temperature of 800-1000°C, and a holding time of 2-3h to obtain a fluoroborate-modified coal gasification fine slag absorber.

[0038] The present invention mixes coal gasification slag with a modifier in a specific ratio, drips polyvinyl alcohol as a plasticizer, and then grinds the mixture 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 a fluoroborate-modified coal gasification slag absorber. The slag is then mixed with paraffin wax in a mass ratio of (30-40):(70-60) to prepare an absorbing sample, and its electromagnetic wave absorption performance is tested. The addition of the modifier and the sintering process impart a composition and structure to the coal gasification slag that is conducive to electromagnetic wave absorption, thereby improving the electromagnetic wave absorption performance of the coal gasification slag. This invention, for the first time, uses fluoroborate as a modifier, combines dry pressing and sintering processes, and prepares a fluoroborate-modified coal gasification slag absorber with excellent electromagnetic wave absorption performance.

[0039] The fluoroborate-modified coal gasification fine slag absorber prepared by the present invention can not only effectively enhance electromagnetic wave absorption, but also realize resource recycling and reuse by utilizing the waste coal gasification fine slag.

[0040] Ordinary coal gasification slag has poor electromagnetic wave absorption performance due to microstructural defects and a single composition, making it difficult to meet actual needs. The present invention introduces a modifier and combines it with a specific process to form a composition and structure that is conducive to electromagnetic wave absorption, thereby improving absorption efficiency.

[0041] Coal gasification slag was originally a bulk waste generated in the industrial production process. Large amounts of accumulation not only occupy land resources, but also may cause potential pollution to the environment. The present invention uses a specific modification method to convert coal gasification slag into an absorbent with excellent electromagnetic wave absorption performance, thereby achieving high-value resource utilization of waste, effectively alleviating the disposal pressure of coal gasification slag, and providing new ideas and methods for the comprehensive management of industrial waste. In the modification process, fluoroborate is used as a modifier, which avoids the harm of acid to the environment compared to other methods that may introduce acid pollution. At the same time, the entire preparation process is simple, reduces the addition of foreign magnetic materials, avoids the environmental pollution problems that may be caused by the addition of complex components, and is in line with the development concept of green environmental protection.

[0042] The decomposition of the fluoroborate modifier during the sintering process produces active products containing elements such as boron and fluorine, as well as alkaline oxides. These products disrupt the silicate network in the fine slag, forming eutectics and reshaping the microstructure and composition of the coal gasification fine slag. This microstructural change results in an uneven charge distribution within the material, which, under the influence of an applied electromagnetic field, easily induces interfacial polarization, thereby enhancing interfacial polarization losses. Furthermore, the strong etching ability of fluorine can etch silicate and aluminum minerals, increasing surface roughness and defect concentration, further increasing the electromagnetic absorption interface and providing more active sites for interfacial polarization, thereby improving interfacial polarization loss efficiency. During the sintering process, residual carbon in the fine slag undergoes a carbothermal reduction reaction, reducing the iron minerals in the slag to elemental iron, directly introducing magnetic losses into the system. The presence of elemental iron imparts magnetic properties to the material, enabling it to interact with electromagnetic waves, converting electromagnetic wave energy into heat through mechanisms such as hysteresis loss and eddy current loss, thereby enhancing the material's electromagnetic absorption properties. At high temperatures, the degree of graphitization of the residual carbon in the fine slag is enhanced, effectively enhancing the system's electrical conductivity. The increased conductivity enables the material to generate a larger induced current under the influence of an electromagnetic field, converting electromagnetic wave energy into heat energy through resistive loss, further improving the material's conductive loss capacity. These three loss mechanisms work synergistically together to significantly improve the electromagnetic wave absorption efficiency of the fluoroborate-modified coal gasification fine slag absorber. During the modification process, the impedance matching between the material and free space is optimized by reconstructing the microscopic composition and structure of the coal gasification fine slag. Good impedance matching can reduce the reflection of electromagnetic waves on the material surface, allowing more electromagnetic waves to enter the material interior, thereby increasing the interaction between electromagnetic waves and the material and improving the electromagnetic wave absorption rate.

[0043] Because the fluoroborate-modified coal gasification fine slag absorber synergistically constructs a multiple loss mechanism of "interface polarization loss-magnetic loss-conductive loss", it can effectively absorb electromagnetic waves in a wider frequency band. Whether it is low-frequency electromagnetic waves, such as electromagnetic interference signals generated by some communication equipment, or high-frequency electromagnetic waves, such as radar waves, the absorber can play a good absorption role and meet the needs of electromagnetic wave absorption frequency bands in different application scenarios. The synergistic effect of multiple loss mechanisms and the optimization of the microstructure make the fluoroborate-modified coal gasification fine slag absorber have a high electromagnetic wave absorption rate. In practical applications, it can effectively reduce the reflection and transmission of electromagnetic waves, convert more electromagnetic wave energy into heat energy or other forms of energy, thereby significantly reducing the impact of electromagnetic waves on the surrounding environment and equipment, and improving the stability of the electromagnetic environment.

[0044] Fluoborate-modified coal gasification fine slag absorbers can be prepared into electromagnetic wave absorbing materials in a variety of ways according to different application requirements. For example, they can be compounded with matrix materials such as resins to make coating materials, which can be applied to electronic equipment housings, building walls, etc. to achieve effective shielding and absorption of electromagnetic waves; they can also be prepared into block materials and used in special environments such as electromagnetic wave absorption darkrooms and microwave darkrooms to provide a good non-reflective environment for electromagnetic testing and research. This flexible application method enables the absorber to adapt to different industrial scenarios and application requirements, further improving its cost-effectiveness. The application of fluoroborate-modified coal gasification fine slag absorbers can effectively absorb and attenuate electromagnetic waves, reduce the harm of electromagnetic radiation to the human body and interference with surrounding electronic equipment, protect the ecological environment and human health, and meet the requirements of sustainable development.

[0045] The present invention discloses a fluoroborate-modified coal gasification slag absorber, and its preparation method and application, aiming to solve the problems of low added value of resource utilization of coal gasification slag and high cost and pollution of traditional absorbing modification technology. The present invention uses coal gasification slag as raw material, adds fluoroborate as a modifier, mixes and grinds, and then dry-presses and shapes it. During sintering, it decomposes into active products containing boron, fluorine, etc., which can destroy the silicate network structure, form low-solvent products, reconstruct the microstructure and structure, and optimize impedance matching. In addition, fluorine can etch silicon-aluminum minerals and increase the electromagnetic wave absorption interface. At the same time, the residual carbon graphitizes at high temperature to enhance the conductive loss, and also generates iron element through carbon thermal reduction reaction to introduce magnetic loss. The modified coal gasification slag synergistically constructs the multiple loss mechanism of "interface polarization loss-magnetic loss-conductive loss" to improve the electromagnetic wave absorption efficiency. This method does not require strong acids, strong bases or precious metals, and the process is simple, realizing the transformation of coal gasification slag from solid waste to high-performance absorbing material. The resulting material can be used in fields such as electromagnetic shielding and stealth coatings, providing a sustainable solution for solid waste resource utilization and electromagnetic pollution control. Its simple preparation method and excellent electromagnetic wave absorption properties have broad application prospects in the field of absorbing materials.

[0046] 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.

[0047] Example 1 A method for preparing a fluoroborate-modified coal gasification fine slag absorber comprises: Weigh 5 g of coal gasification slag and 1.0 g of sodium fluoroborate, 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.

[0048] The compact was then sintered in an Ar atmosphere, heated at a heating rate of 2°C / min, and kept at 900°C for 2h to obtain a sodium fluoroborate modified coal gasification fine slag absorber.

[0049] Obvious diffraction peaks of Fe and CaF2 appear in the coal gasification fine slag modified by sodium fluoroborate. The appearance of these peaks indicates that the modification promotes the formation or growth of these phases and improves their crystallinity.

[0050] Example 2 A method for preparing a fluoroborate-modified coal gasification fine slag absorber comprises: Weigh 5 g of coal gasification slag and 1.0 g of potassium fluoroborate, 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.

[0051] The compact was then sintered in an Ar atmosphere, heated at a heating rate of 2°C / min, and kept at 900°C for 2 h to obtain potassium fluoroborate-modified coal gasification fine slag.

[0052] The diffraction peaks of Fe and GaF2 also appear in the coal gasification fine slag modified by potassium fluoroborate, which shows that fluoroboric acid plays a major role in the modification process. However, the crystallinity of Fe is low, indicating that the introduction of sodium fluoroborate has a better reduction effect on iron minerals in the fine slag than potassium fluoroborate.

[0053] Example 3 A method for preparing a fluoroborate-modified coal gasification fine slag absorber comprises: Weigh 5 g of coal gasification slag and 1.5 g of sodium fluoroborate, 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.

[0054] The compact was then sintered in an Ar atmosphere, heated at a heating rate of 2°C / min, and kept at 900°C for 2 h to obtain sodium fluoroborate-modified coal gasification fine slag.

[0055] Increasing the amount of sodium fluoroborate introduced, the F-containing active substances produced during sintering have a more significant etching effect on the fine slag.

[0056] Example 4 A method for preparing a fluoroborate-modified coal gasification fine slag absorber comprises: Weigh 5 g of coal gasification slag and 1.0 g of sodium fluoroborate, 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.

[0057] The compact was then sintered in an Ar atmosphere, heated at a heating rate of 2°C / min, and kept at 800°C for 2 h to obtain sodium fluoroborate-modified coal gasification fine slag.

[0058] 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.

[0059] Example 5 A method for preparing a fluoroborate-modified coal gasification fine slag absorber comprises: Weigh 5 g of coal gasification slag and 0.5 g of sodium fluoroborate, 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 0.4 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 4 MPa for 1 min to obtain a compact.

[0060] The compact was then sintered in an Ar atmosphere, heated at a heating rate of 3°C / min, and kept at 850°C for 2 h to obtain sodium fluoroborate-modified coal gasification fine slag.

[0061] Example 6 A method for preparing a fluoroborate-modified coal gasification fine slag absorber comprises: Weigh 5 g of coal gasification slag and 1.2 g of sodium fluoroborate, 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 0.6 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 4.5 MPa for 1.5 minutes to obtain a compact.

[0062] The compact was then sintered in an Ar atmosphere, heated at a heating rate of 4°C / min, and kept at 950°C for 2.5 h to obtain sodium fluoroborate-modified coal gasification fine slag.

[0063] Example 7 A method for preparing a fluoroborate-modified coal gasification fine slag absorber comprises: Weigh 5 g of coal gasification slag and 1.6 g of sodium fluoroborate, 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 0.8 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 4 MPa for 1 min to obtain a compact.

[0064] The compact was then sintered in an Ar atmosphere, heated at a heating rate of 5°C / min, and kept at 1000°C for 3 h to obtain sodium fluoroborate-modified coal gasification fine slag.

[0065] 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.

[0066] Figure 1 Comparative XRD patterns of the unmodified coal gasification slag disclosed in the comparative example of the present invention, the sodium fluoborate-modified coal gasification slag absorber disclosed in Example 1, and the potassium fluoborate-modified coal gasification slag absorber disclosed in Example 2 are shown. As can be seen from the figure, diffraction peaks for elemental Fe and CaF2 appear in both fluoborate-modified coal gasification slags. The appearance of these peaks indicates that the modification promotes the formation or growth of these phases, suggesting that fluoboric acid plays a primary role in the modification process. Furthermore, the crystallinity of elemental Fe in the sodium fluoborate-modified slag is higher, indicating that it is more effective in reducing iron minerals in the slag than potassium fluoborate.

[0067] Figure 2This is an SEM image of the fluoroborate-modified coal gasification fine slag absorber prepared in Example 1 of the present invention. As can be seen from the figure, the surface of the fluoroborate-modified coal gasification fine slag absorber exhibits obvious roughening characteristics, with a large number of irregular etched pits, micro-nanoscale protrusions and interconnected porous structures, and the surface morphology is complex and porous. The formation of this microstructure is due to the etching effect of the fluorine element released by the fluoroborate during the sintering process on the silica-alumina mineral, and the reconstruction of the fine slag surface during the formation of the low-melting melt. The rough and porous surface not only significantly increases the specific surface area of the material, providing more incident interfaces and scattering paths for electromagnetic waves, but also enhances the interface polarization loss effect by introducing a large number of defects.

[0068] Figure 3 The following graphs show the reflection loss of the unmodified coal gasification slag (Comparative Example) and the sodium fluoborate-modified coal gasification slag absorber (Example 1). (a) shows the unmodified coal gasification slag; (b) shows the sodium fluoborate-modified coal gasification slag absorber (Example 1). The graphs show that the unmodified coal gasification slag has very weak electromagnetic wave absorption within the 2-18 GHz frequency band, with reflection loss values exceeding -10 dB at most frequencies. Only slight absorption occurs at certain frequencies, with the lowest reflection loss being approximately -15 dB, failing to meet practical absorption requirements. The sodium fluoborate-modified coal gasification slag absorber, however, exhibits significantly improved absorption performance, with significantly reduced reflection loss and stronger electromagnetic wave absorption across a wide frequency band. In particular, the reflection loss reaches -47.75 dB at specific frequencies. Furthermore, the effective absorption band (reflection loss ≤ -10 dB) is significantly broadened, covering a wider frequency range. This shows that the fluoroborate-modified absorber effectively improves the absorption efficiency and frequency band adaptability of electromagnetic waves by constructing a multiple loss mechanism of "interface polarization loss-magnetic loss-conductive loss", verifying the significant effect of this modification method in enhancing the material's absorption performance.

[0069] In summary, the present invention presents a method for preparing and applying a fluoborate-modified coal gasification slag absorber. Using coal gasification slag as the base raw material and adding fluoborate as a modifier, this method not only achieves waste resource recycling and reuse but also improves electromagnetic wave absorption efficiency. The application of dry pressing and annealing processes, combined with precise parameter control, produces an absorber with excellent electromagnetic wave absorption performance, combining the advantages of both raw materials and processes. This simple process allows the preparation of high-performance electromagnetic wave absorbing materials, demonstrating broad application prospects in the fields of electromagnetic shielding and absorbing materials.

[0070] 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 fluoroborate modified coal gasification fine slag absorber, characterized in that: include: The coal gasification fine slag is mixed with fluoroborate, and a plasticizer is added dropwise. The mixture is ground evenly, sieved, and dry-pressed to obtain a compact. The compact is sintered in an inert atmosphere to obtain a fluoroborate-modified coal gasification fine slag absorber.

2. The method for preparing the fluoroborate modified coal gasification fine slag absorber according to claim 1, characterized in that: The usage ratio of the coal gasification fine slag, fluoroborate and plasticizer is 5g: (0.5-1.6)g: (0.4-0.8)mL.

3. The method for preparing the fluoroborate modified coal gasification fine slag absorber according to claim 1, characterized in that: The fluoroborate is sodium fluoroborate or potassium fluoroborate.

4. The method for preparing the fluoroborate modified coal gasification fine slag absorber according to claim 1, characterized in that: The plasticizer is polyvinyl alcohol.

5. The method for preparing the fluoroborate modified coal gasification fine slag absorber according to claim 1, characterized in that: The sieved particle size is 100 mesh.

6. The method for preparing the fluoroborate modified coal gasification fine slag absorber according to claim 1, characterized in that: The dry pressing conditions are: dry pressing at a pressure of 4-5 MPa for 1-2 minutes.

7. The method for preparing the fluoroborate modified coal gasification fine slag absorber according to claim 1, characterized in that: The inert atmosphere is Ar.

8. The method for preparing the fluoroborate modified coal gasification fine slag absorber according to claim 1, characterized in that: The sintering conditions are as follows: heating to 800-1000°C at a heating rate of 2-5°C / min and keeping the temperature for 2-3 hours.

9. A fluoroborate modified coal gasification fine slag absorber, characterized in that: The fluoroborate-modified coal gasification fine slag absorber is prepared by the preparation method of any one of claims 1 to 8.

10. Use of the fluoroborate-modified coal gasification fine slag absorber prepared by the preparation method according to any one of claims 1 to 8 in the preparation of electromagnetic wave absorbing materials.

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