Preparation method of solid-waste-based lightweight high-strength ceramsite with electromagnetic shielding function

Abstract

The invention discloses a preparation method of solid-waste-based lightweight high-strength ceramsite with an electromagnetic shielding function, which comprises the following steps: (1) forming a modified liquid by using a Fe < 3 + > source, a transition metal ion source and a mineralization inducer, then adding a surface modifier and a homogeneous precipitator, uniformly mixing, and then adding silicon carbide powder and / or pulverized coal treated by acid liquor into the obtained liquid phase to form a suspension liquid; and reacting to obtain the foaming-crystal orientation coupling agent. (2) preparing a core raw material ball by using the calcium-silicon-magnesium-sulfur-aluminum iron solid waste, an ion doping agent, a fluxing agent and a foaming-crystal orientation coupling agent as raw materials; and (3) preparing slurry by using calcium-silicon-magnesium-sulfur-aluminum iron solid waste and a fluxing agent as raw materials, coating the surface of the core raw material ball with the slurry to form a core-shell type ceramsite blank, and sintering to obtain the solid-waste-based lightweight high-strength ceramsite. The technical bottleneck that light weight, high strength and wave absorbing performance of existing common ceramsite are difficult to consider at the same time is effectively solved, and the electromagnetic shielding effect and the mechanical property of the prepared concrete material are improved.

Description

Technical Field

[0001] This invention relates to the field of special building materials technology, specifically to a method for preparing solid waste-based lightweight high-strength ceramsite with electromagnetic shielding function. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] With the increasing complexity of the current electromagnetic environment and the urgent need for upgraded building functions, electromagnetic shielding building materials have become key materials for ensuring equipment safety, information confidentiality, and human health. Traditional cement-based composite microwave absorbing materials typically add microwave absorbing components such as TiO2, CNTs, graphene, and carbon fibers to cement paste. However, the microwave absorbing agents in cement-based materials suffer from problems such as difficulty in dispersion and deterioration of mechanical properties. Moreover, the volume ratio of cement paste in concrete is less than 30%, leaving the aggregate area without shielding effectiveness, making it difficult to significantly improve the microwave absorption efficiency of concrete. Therefore, endowing aggregates with excellent microwave absorption properties is another key to improving the electromagnetic shielding effectiveness of cement-based materials. Using conductive or magnetic aggregates and constructing porous structures can improve the microwave absorption efficiency of aggregates in cement-based materials. However, surface-coated or high-iron-content aggregates have problems such as weak interfacial transition zones (ITZ) and poor durability. Porous electromagnetic shielding materials such as foamed concrete face the challenge of balancing lightweight and high strength while also exhibiting low microwave absorption efficiency.

[0004] As a lightweight porous aggregate, expanded clay has advantages such as lightweight sound absorption, thermal insulation, earthquake resistance and fire resistance, and is widely used in lightweight aggregate concrete, precast building products, roof insulation and ground backfill. With the continuous expansion of application scenarios, the functionalization of expanded clay refers to the integration of specific functions on the basis of traditional properties through material modification technology. Among them, electromagnetic shielding function is one of the current research frontiers and industrial hotspots. First, the pores inside the expanded clay can allow more electromagnetic waves to enter the interior, thereby improving its impedance matching. Second, the spherical pore walls carrying the wave-absorbing components naturally form microwave resonant cavities, allowing electromagnetic waves to be scattered multiple times inside the expanded clay, thereby achieving efficient attenuation of electromagnetic waves. However, in practice, there are still the following problems: (1) It is difficult to reconcile lightweight, high strength and efficient wave absorption performance. (2) It is difficult to uniformly and firmly load the wave-absorbing components inside the expanded clay and they are easy to desorb and block the pores, thereby destroying the multiple reflection mechanism inside the pores and seriously weakening the wave absorption performance. (3) The interface with cement is fragile and leads to impedance mismatch, highlighting the contradiction between lightweight and durability. Summary of the Invention

[0005] In view of this, the present invention provides a method for preparing lightweight, high-strength ceramsite based on solid waste with electromagnetic shielding function, effectively solving the technical bottleneck of existing ordinary ceramsite in which it is difficult to simultaneously achieve lightweight, high strength, and wave absorption performance, thereby improving the electromagnetic shielding effect and the mechanical properties of the prepared concrete material. Specifically, the technical solution of the present invention is as follows.

[0006] A method for preparing solid waste-based lightweight high-strength ceramsite with electromagnetic shielding function includes the following steps: (1) With Fe 3+ A modified liquid is formed by adding a source of transition metal ions and a mineralization inducer. Then, a surface modifier and a homogeneous precipitant are added and mixed thoroughly. Next, silicon carbide powder and / or coal powder treated with acid are added to the resulting liquid phase to form a suspension. The suspension is heated and stirred to react. After the reaction is completed, the solid product is separated, washed, and dried to obtain the foamed-crystal orientation coupling agent.

[0007] (2) Using calcium, silicon, magnesium, sulfur, aluminum, and iron solid waste, ion dopant, flux, and the foaming-crystal orientation coupling agent as raw materials, mix them evenly and add water to granulate to obtain core raw material balls for later use.

[0008] (3) Using calcium, silicon, magnesium, sulfur, aluminum and iron solid waste and flux as raw materials, mix them evenly and add water to form a slurry. Then coat the core raw material ball to form a core-shell type ceramic pellet blank. After sintering, solid waste-based lightweight high-strength ceramic pellets are obtained.

[0009] Further, in step (1), the Fe 3+ The molar ratio of the source and the transition metal ion source is 2:1. Optionally, the transition metal ion source includes Ni. 2+ Source, Co 2+ At least one of the following: source, etc.

[0010] Furthermore, the Fe 3+ The source includes at least one of ferric chloride, ferric sulfate, etc. The Ni 2+ The source includes at least one of nickel nitrate, nickel chloride, etc. The Co 2+ The sources include at least one of cobalt nitrate, cobalt chloride, etc.

[0011] Further, in step (1), the mass fraction of the mineralization inducer in the modified liquid is 10-30%. Optionally, in step (1), the mineralization inducer includes at least one of NaCl, KCl, Na2SO4, B2O3, etc.

[0012] Further, in step (1), the surface modifier and Fe 3+The molar ratio of the source and the total transition metal ion source is 1:2~5. Optionally, the surface modifier includes at least one of sodium citrate, sodium tartrate, etc. The surface modifier helps the silicon carbide powder and / or coal powder to become negatively charged, thereby reacting with Fe. 3+ Transition metal ions form stable and soluble complexes, significantly reducing the concentration of free metal ions and achieving ultra-slow-release precipitation.

[0013] Further, in step (1), the homogeneous precipitant and Fe 3+ The molar ratio of the source and the total transition metal ion source is 3~10:1. Optionally, the homogeneous precipitant includes at least one of urea, hexamethylenetetramine, etc. The homogeneous precipitant can achieve homogeneous precipitation by uniformly and slowly increasing the pH value of the entire solution system through its own decomposition, ensuring that precipitation occurs on the particle surface rather than homogeneously nucleating in the solution, so as to form the foaming-crystal orientation coupling agent with spinel nucleation precursor on the surface.

[0014] Further, in step (1), the method of treating silicon carbide powder and / or coal powder with acid includes: placing silicon carbide powder and / or coal powder in acid solution for ultrasonic treatment, separating the silicon carbide powder and / or coal powder after completion, washing and drying to obtain the final product. Optionally, the acid solution includes at least one of nitric acid, hydrofluoric acid, etc.; the ultrasonic treatment time is 1 to 3 hours.

[0015] Further, in step (1), the ratio of the liquid phase to silicon carbide powder and / or coal powder is 5~10mL:1g.

[0016] Furthermore, in step (1), the temperature of the heating and stirring reaction is 90~95℃, and the time is 4~8 hours.

[0017] Furthermore, in step (1), the drying temperature is 100~120℃ and the time is 3~6 hours.

[0018] Further, in step (2), the ratio of the calcium-silicon-magnesium-sulfur-aluminum-iron solid waste, ion dopant, flux, foaming-crystal orientation coupling agent, and water is 100g: 1~3g: 1~2g: 0.5~2.5g: 15~25g. Optionally, the ion dopant includes at least one of the following: electric arc furnace dust, copper slag, zinc slag, neodymium iron boron waste, and waste electrode materials.

[0019] Furthermore, in step (2), the particle size of the core raw material ball is 2~25mm.

[0020] Furthermore, in step (3), the ratio of the calcium, silicon, magnesium, sulfur, aluminum, and iron solid waste, flux, and water is 100g: 1~2g: 20~30g.

[0021] Furthermore, in step (3), the coating layer thickness of the core-shell type ceramsite blank is 0.5~5mm.

[0022] Further, in step (3), the sintering temperature is 1050~1250℃ and the time is 15~30min. Optionally, the heating rate of the sintering process is 5~10℃ / min.

[0023] Furthermore, in steps (2) and (3), the calcium-silicon-magnesium-sulfur-aluminum-iron solid waste includes at least two of the following: steel slag, coal gangue, phosphogypsum, high-magnesium limestone, red mud, and boron mud.

[0024] Furthermore, in step (2), the flux includes at least one of borax, glass powder, potassium feldspar, etc.

[0025] Compared with the prior art, the technical solution of the present invention has at least the following beneficial effects: First, this invention treats silicon carbide powder and / or coal powder with acid to form more hydroxyl (-OH) groups on the surface of the silicon carbide powder and / or coal powder particles, improving interfacial compatibility and dispersion uniformity. Then, using the treated silicon carbide powder and / or coal powder as a carrier, this invention prepares a foaming-crystal orientation coupling agent with a surface composed of a mixed metal hydroxide or basic salt and a mineralization inducer, forming spinel nucleating agent precursors. Core raw material balls are then prepared using this agent. During the subsequent calcination process, the mineralization inducer in the foaming-crystal orientation coupling agent primarily acts as a "binder," enhancing the thermal bonding between the foaming agent particles and the nucleating agent precursor. The gas generated by the decomposition of silicon carbide powder and / or coal powder particles in the foaming-crystal orientation coupling agent expands from the inside out to form pores. This pushes away the molten spinel nucleating agent precursor wrapped around the surface of the silicon carbide powder and / or coal powder particles, and "coats" it onto the formed pore walls. This achieves in-situ forced dispersion and adhesion of the precursor on the pore walls, ensuring that each pore formation point is tightly surrounded by induced active crystal nuclei, resulting in a more uniform spatial distribution and higher directional growth induction efficiency. During the sintering process, the precursor can induce the in-situ formation of high-entropy spinel ferrite crystal nuclei on the pore walls. Simultaneously, since the mineralization inducing agent has already melted to form a low-viscosity liquid phase below the spinel formation temperature, it can significantly enhance ion diffusion. Molten salt ions selectively adsorb onto the {110} / {100} side of the spinel ferrite crystal nuclei through electrostatic attraction and coordination site occupancy, inhibiting their lateral expansion and thus forcing the crystal nuclei to mainly grow along the {110} / {100} side. <111> The axial growth of the crystal face preferentially forms a pyramidal cone-shaped structure. Furthermore, during sintering, the temperature at the pore wall is higher than at the pore center, and the spinel nucleus concentration is highest at the pore wall. This temperature and concentration gradient further drives the spinel crystals to grow inwards perpendicular to the pore wall surface, promoting the formation of this unique pyramidal cone morphology. Electromagnetic waves form resonant cavities between the cone-shaped grains, resulting in multiple reflections and scattering, significantly extending the propagation path of the electromagnetic waves. This allows for sufficient contact between the electromagnetic waves and the absorbing components of the spinel-type ferrite, achieving efficient attenuation and significantly improving electromagnetic loss efficiency. In addition, the ion dopant can modulate the lattice structure and magnetic domain characteristics of the spinel-type ferrite through ion substitution, further enhancing its magnetic loss performance.

[0026] Secondly, the solid waste-based lightweight high-strength ceramsite of this invention adopts a core-shell structure, simultaneously constructing a functional shell layer of "highly active porous calcium sulfoaluminate phase + α-Fe2O3" on the surface of the "high magnetic loss ceramsite microwave absorbing core". Specifically, the calcium sulfoaluminate phase of the low-dielectric matrix and its pore structure optimize impedance matching, while α-Fe2O3 itself generates polarization relaxation loss. Furthermore, the heterogeneous interface between α-Fe2O3 and the calcium sulfoaluminate phase generates additional interfacial polarization loss, achieving preliminary dielectric loss for electromagnetic wave incidence. The microwave absorbing ceramsite prepared by this invention has a unique cubic close-packed AB2O4 crystal structure, with a framework density significantly higher than the framework or chain structure of the silica-alumina mineral phase in traditional ceramsite. This high-symmetry, high-bond-energy structure endows it with intrinsic high hardness and high strength, significantly improving the densification and integrity of the ceramsite pore walls. Furthermore, the high hydration activity of the calcium sulfoaluminate mineral phase can enhance the interfacial bonding force and interfacial size between the surface of the ceramsite and the cement matrix, significantly improving the mechanical properties of the prepared cement-based materials. It fundamentally overcomes the various defects caused by traditional external absorbing components, achieving all-round three-dimensional high-efficiency wave absorption of the ceramsite body and significantly optimizing impedance matching characteristics. It solves the technical bottlenecks of ordinary ceramsite being lightweight, high-strength, and having wave absorption performance that are difficult to balance, as well as the difficulty of uniformly and firmly loading traditional wave absorbing components, which are prone to falling off and clogging pores, thus improving the electromagnetic shielding effect. Attached Figure Description

[0027] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0028] Figure 1 The image shows a sample of the foamed-crystal coupling agent prepared in Example 1 below.

[0029] Figure 2 The image shows a sample of lightweight, high-strength ceramsite based on solid waste prepared in Example 1 below. Detailed Implementation

[0030] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods in the following embodiments, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer.

[0031] Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as those skilled in the art. All reagents and raw materials used in this invention are readily available through conventional means, and unless otherwise specified, they shall be used in accordance with conventional methods in the art or as per the product instructions.

[0032] Furthermore, any methods and materials similar to or equivalent to those described herein can be applied to the method of this invention. The technical solution of this invention will now be further described in conjunction with the accompanying drawings and specific embodiments.

[0033] Example 1: A method for preparing solid waste-based lightweight high-strength ceramsite with electromagnetic shielding function includes the following steps: (1) Silicon carbide powder (particle size distribution between 0.6 and 1.0 μm) was placed in 2.5 mol / L nitric acid at a ratio of 1 g: 10 mL and ultrasonically treated for 2 hours. After completion, the silicon carbide powder was filtered out, washed with water to remove residual acid, and then dried to obtain pretreated silicon carbide powder for later use.

[0034] (2) Fe 3+ A source of Fe (ferric chloride), a transition metal ion source (nickel chloride), and a mineralization inducer (Na₂SO₄ powder) are added to water and stirred until fully dissolved to form a modified solution, wherein: the Fe 3+ The molar ratio of the source and the transition metal ion source is 2:1, and the mass fraction of the mineralization inducer in the modified solution is 15%. Then, a surface modifier (sodium citrate) and a homogeneous precipitant (urea) are added to the modified solution and stirred until fully dissolved, wherein: the surface modifier and Fe... 3+ The molar ratio of the source and the total transition metal ion source is 1:3, and the homogeneous precipitant and Fe 3+ The molar ratio of the source and the total transition metal ion source is 5:1. Then, the pretreated silicon carbide powder is added to the obtained liquid phase at a ratio of 8 mL:1 g and ultrasonically dispersed for 10 min to obtain a suspension. The suspension is then heated to 90°C and continuously stirred for 8 hours. After the reaction is complete, the solid product is filtered out, washed with water, and then dried at 110°C for 4 hours to obtain the foamed-crystal alignment coupling agent (e.g., ...). Figure 1 (As shown), for later use.

[0035] (3) According to the ratio of calcium, silicon, magnesium, sulfur, aluminum, and iron solid waste (composed of steel slag and boron mud in a mass ratio of 7g:3g), ion dopant (copper slag), flux (borax), foaming-crystal coupling agent described in this embodiment, and water = 100g:2.5g:1.5g:2g:20g, the calcium, silicon, magnesium, sulfur, aluminum, and iron solid waste, ion dopant, flux, and foaming-crystal coupling agent are first ground in a planetary ball mill until the residue on an 80μm square hole sieve is 5%. Then, the obtained powder is mixed with the water and granulated by a disc granulator to obtain core raw material balls with a particle size distribution between 10 and 20mm, which are then set aside.

[0036] (4) According to the ratio of calcium, silicon, magnesium, sulfur, aluminum, and iron solid waste (composed of steel slag, phosphogypsum, and fly ash in a mass ratio of 6.5g:1.5g:2.0g), flux (borax), and water = 100g:1.5g:26g, the calcium, silicon, magnesium, sulfur, aluminum, and iron solid waste and flux are first ground in a planetary ball mill until the residue on an 80μm square hole sieve is 5%. Then, the obtained powder is mixed with the water and stirred evenly to form a slurry. Then, the core raw material ball and the slurry are fed into a disc granulator and continuously rolled, so that the slurry coats the surface of the core raw material ball to form a core-shell type ceramsite embryo, with a coating layer thickness of 2mm. After completion, the ceramsite embryo is first heated to 80℃ in a rotary dryer and dried for 1 hour. The obtained ceramsite pellets are then placed in a heating furnace and heated at a rate of 10℃ / min to 1150℃ for 20 minutes. After heating, the pellets are cooled to room temperature to obtain solid waste-based lightweight high-strength ceramsite (e.g., ...). Figure 2 (As shown).

[0037] Performance Testing: (I) The compressive strength of the solid waste-based lightweight high-strength ceramsite prepared in this embodiment was tested according to GB / T 17431.2-2010 "Lightweight Aggregates and Their Test Methods Part 2: Test Methods". (II) The bulk density of the solid waste-based lightweight high-strength ceramsite was tested according to GB / T 17431.1-2022 "Lightweight Aggregates and Their Test Methods Part 1: Apparent Density and Porosity". (III) The minimum reflection loss (RL) of the solid waste-based lightweight high-strength ceramsite in the 2~18GHz frequency band was tested according to GJB 2038A-201 "Test Method for Reflectivity of Radar Absorbing Materials". min The electromagnetic shielding effect was measured by the effective absorption bandwidth (EAB, RL value < 10dB). The test results of each performance sub-table are shown below: cylinder compressive strength = 10.5MPa, bulk density = 710.6kg / m³. 3 RL min =-49.65dB, EAB=12.5GHz.

[0038] Example 2: A method for preparing solid waste-based lightweight high-strength ceramsite with electromagnetic shielding function includes the following steps: (1) Silicon carbide powder (particle size distribution between 0.6 and 1.0 μm) was placed in 3 mol / L nitric acid at a ratio of 1 g: 10 mL and ultrasonically treated for 1 hour. After completion, the silicon carbide powder was filtered out, washed with water to remove residual acid, and then dried to obtain pretreated silicon carbide powder for later use.

[0039] (2) Fe 3+ A source of Fe (ferric chloride), a transition metal ion source (cobalt chloride), and a mineralization inducer (Na₂SO₄ powder) are added to water and stirred until fully dissolved to form a modified solution, wherein: the Fe3+ The molar ratio of the source and the transition metal ion source is 2:1, and the mass fraction of the mineralization inducer in the modified solution is 10%. Then, a surface modifier (sodium citrate) and a homogeneous precipitant (urea) are added to the modified solution and stirred until fully dissolved, wherein: the surface modifier and Fe... 3+ The molar ratio of the source and the total transition metal ion source is 1:2, and the homogeneous precipitant and Fe... 3+ The molar ratio of the source and the total transition metal ion source is 3:1. Then, the pretreated silicon carbide powder is added to the obtained liquid phase at a ratio of 5 mL: 1 g and ultrasonically dispersed for 10 min to obtain a suspension. The suspension is then heated to 95°C and continuously stirred for 4 hours. After the reaction is complete, the solid product is filtered out, washed with water, and then dried at 100°C for 6 hours to obtain the foamed-crystal alignment coupling agent for later use.

[0040] (3) According to the ratio of calcium-silicon-magnesium-sulfur-aluminum-iron solid waste (composed of coal gangue and boron mud in a mass ratio of 6.8g:3.2g), ion dopant (copper slag), flux (glass powder), foaming-crystal coupling agent described in this embodiment, and water = 100g:3g:2g:2.5g:25g, the calcium-silicon-magnesium-sulfur-aluminum-iron solid waste, ion dopant, flux, and foaming-crystal coupling agent are first ground in a planetary ball mill until the residue on an 80μm square hole sieve is 5%. Then, the obtained powder is mixed with the water and granulated by a disc granulator to obtain core raw material balls with a particle size distribution between 10 and 20mm, which are then set aside.

[0041] (4) According to the ratio of calcium-silicon-magnesium-sulfur-aluminum-iron solid waste (composed of coal gangue, phosphogypsum, and fly ash in a mass ratio of 6.7g:1.5g:1.8g), flux (glass powder), and water = 100g:2g:30g, the calcium-silicon-magnesium-sulfur-aluminum-iron solid waste and flux are first ground in a planetary ball mill until the residue on an 80μm square hole sieve is 5%. Then, the obtained powder is mixed with the water and stirred evenly to form a slurry. Then, the core raw material ball and the slurry are fed into a disc granulator and continuously rolled, so that the slurry coats the surface of the core raw material ball to form a core-shell type ceramsite embryo, with a coating layer thickness of 3mm. After completion, the ceramsite embryo is heated to 80℃ and dried in a rotary dryer for 1.5 hours. The obtained ceramsite pellets are then placed in a heating furnace and heated at a rate of 10℃ / min to 1250℃ for 15 minutes. After the heating is completed, the pellets are cooled to room temperature to obtain solid waste-based lightweight high-strength ceramsite.

[0042] Performance Testing: The compressive strength, bulk density, and absorption loss in the 2-18 GHz frequency band of the solid waste-based lightweight high-strength ceramsite prepared in this embodiment were tested using the same method as in Example 1 above. The test results are as follows: compressive strength = 9.3 MPa, bulk density = 680.2 kg / m³3 RL min =-45.32dB, EAB=11.8GHz.

[0043] Example 3: A method for preparing solid waste-based lightweight high-strength ceramsite with electromagnetic shielding function includes the following steps: (1) Coal powder (particle size distribution between 0.5 and 0.8 μm) was placed in 2 mol / L hydrofluoric acid and ultrasonically treated for 3 hours at a ratio of 1 g: 10 mL. After completion, the silicon carbide powder was filtered out, washed with water to remove residual acid, and then dried to obtain pretreated silicon carbide powder for later use.

[0044] (2) Fe 3+ A source of Fe (ferric sulfate), a transition metal ion source (nickel nitrate), and a mineralization inducer (NaCl powder) are added to water and stirred until fully dissolved to form a modified solution, wherein: the Fe... 3+ The molar ratio of the source and the transition metal ion source is 2:1, and the mass fraction of the mineralization inducer in the modified solution is 30%. Then, a surface modifier (sodium tartrate) and a homogeneous precipitant (hexamethylenetetramine) are added to the modified solution and stirred until fully dissolved, wherein: the surface modifier and Fe... 3+ The molar ratio of the source and the total transition metal ion source is 1:5, and the homogeneous precipitant and Fe 3+ The molar ratio of the source and the total transition metal ion source is 10:1. Then, the pretreated silicon carbide powder is added to the obtained liquid phase at a ratio of 10 mL: 1 g and ultrasonically dispersed for 10 min to obtain a suspension. The suspension is then heated to 95°C and continuously stirred for 4 hours. After the reaction is complete, the solid product is filtered out, washed with water, and then dried at 120°C for 3 hours to obtain the foamed-crystal alignment coupling agent for later use.

[0045] (3) According to the ratio of calcium, silicon, magnesium, sulfur, aluminum, and iron solid waste (composed of coal gangue and boron mud in a mass ratio of 6.8g:3.2g), ion dopant (zinc slag), flux (borax), foaming-crystal coupling agent described in this embodiment, and water = 100g:1g:1g:0.5g:15g, the calcium, silicon, magnesium, sulfur, aluminum, and iron solid waste, ion dopant, flux, and foaming-crystal coupling agent are first ground in a planetary ball mill until the residue on an 80μm square hole sieve is 5%. Then, the obtained powder is mixed with the water and granulated by a disc granulator to obtain core raw material balls with a particle size distribution between 15 and 25mm, which are then set aside.

[0046] (4) According to the ratio of calcium-silicon-magnesium-sulfur-aluminum-iron solid waste (composed of coal gangue, phosphogypsum, and fly ash in a mass ratio of 6.7g:1.5g:1.8g), flux (borax), and water = 100g:1g:20g, the calcium-silicon-magnesium-sulfur-aluminum-iron solid waste and flux are first ground in a planetary ball mill until the residue on an 80μm square hole sieve is 5%. Then, the obtained powder is mixed with the water and stirred evenly to form a slurry. Then, the core raw material ball and the slurry are fed into a disc granulator and continuously rolled, so that the slurry coats the surface of the core raw material ball to form a core-shell type ceramsite embryo, with a coating layer thickness of 1mm. After completion, the ceramsite embryo is first heated to 80℃ in a rotary dryer and dried for 1 hour. The obtained ceramsite pellets are then placed in a heating furnace and heated at a rate of 5℃ / min to 1050℃ for 30 minutes. After the heating is completed, the pellets are cooled to room temperature to obtain solid waste-based lightweight high-strength ceramsite.

[0047] Performance Testing: The compressive strength, bulk density, and absorption loss in the 2-18 GHz frequency band of the solid waste-based lightweight high-strength ceramsite prepared in this embodiment were tested using the same method as in Example 1 above. The test results are as follows: compressive strength = 9.8 MPa, bulk density = 703.6 kg / m³ 3 RL min =-47.28dB, EAB=12.1GHz.

[0048] Example 4: A method for preparing solid waste-based lightweight high-strength ceramsite with electromagnetic shielding function includes the following steps: (1) According to the ratio of calcium, silicon, magnesium, sulfur, aluminum, and iron solid waste (composed of steel slag and boron mud in a mass ratio of 7g:3g), ion dopant (copper slag), flux (borax), and water = 100g: 2.5g: 1.5g: 20g, the calcium, silicon, magnesium, sulfur, aluminum, and iron solid waste, ion dopant, and flux are first ground in a planetary ball mill until the residue on an 80μm square hole sieve is 5%. Then, the obtained powder is mixed with the water and granulated by a disc granulator to obtain core raw material balls with a particle size distribution between 10 and 20mm, which are then set aside.

[0049] (2) According to the ratio of calcium-silicon-magnesium-sulfur-aluminum-iron solid waste (composed of steel slag: phosphogypsum: fly ash in a mass ratio of 6.5g: 1.5g: 2.0g), flux (borax), and water = 100g: 1.5g: 26g, the calcium-silicon-magnesium-sulfur-aluminum-iron solid waste and flux are first ground in a planetary ball mill until the residue on an 80μm square hole sieve is 5%. Then, the obtained powder is mixed with the water and stirred evenly to form a slurry. Then, the core raw material ball and the slurry are fed into a disc granulator and continuously rolled, so that the slurry coats the surface of the core raw material ball to form a core-shell type ceramsite embryo, with a coating layer thickness of 2mm. After completion, the ceramsite embryo is first heated to 80℃ in a rotary dryer and dried for 1 hour. The obtained ceramsite pellets are then placed in a heating furnace and heated at a rate of 10℃ / min to 1150℃ for 20 minutes. After the heating is completed, the pellets are cooled to room temperature to obtain solid waste-based lightweight high-strength ceramsite.

[0050] Performance Testing: The compressive strength, bulk density, and absorption loss in the 2-18 GHz frequency band of the solid waste-based lightweight high-strength ceramsite prepared in this embodiment were tested using the same method as in Example 1 above. The test results are as follows: compressive strength = 30.2 MPa, bulk density 3120.5 kg / m³ 3 RL min =-19.32dB, EAB=2.8GHz.

[0051] Example 5: A method for preparing solid waste-based lightweight high-strength ceramsite with electromagnetic shielding function includes the following steps: (1) Coal powder (particle size distribution between 0.5 and 0.8 μm) was placed in 2 mol / L hydrofluoric acid and ultrasonically treated for 3 hours at a ratio of 1 g: 10 mL. After completion, the silicon carbide powder was filtered out, washed with water to remove residual acid, and then dried to obtain pretreated silicon carbide powder for later use.

[0052] (2) According to the ratio of calcium-silicon-magnesium-sulfur-aluminum-iron solid waste (composed of coal gangue and boron mud in a mass ratio of 6.8g:3.2g), ion dopant (zinc slag), flux (borax), the pretreated silicon carbide powder described in this embodiment, and water = 100g:1g:1g:0.5g:15g, the calcium-silicon-magnesium-sulfur-aluminum-iron solid waste, ion dopant, flux, and pretreated silicon carbide powder are first ground in a planetary ball mill until the residue on an 80μm square hole sieve is 5%. Then, the obtained powder is mixed with the water and granulated by a disc granulator to obtain core raw material balls with a particle size distribution between 15 and 25 mm, which are then set aside.

[0053] (3) According to the ratio of calcium-silicon-magnesium-sulfur-aluminum-iron solid waste (composed of coal gangue, phosphogypsum, and fly ash in a mass ratio of 6.7g:1.5g:1.8g), flux (borax), and water = 100g:1g:20g, the calcium-silicon-magnesium-sulfur-aluminum-iron solid waste and flux are first ground in a planetary ball mill until the residue on an 80μm square hole sieve is 5%. Then, the obtained powder is mixed with the water and stirred evenly to form a slurry. Then, the core raw material ball and the slurry are fed into a disc granulator and continuously rolled, so that the slurry coats the surface of the core raw material ball to form a core-shell type ceramsite embryo, with a coating layer thickness of 1mm. After completion, the ceramsite embryo is first heated to 80℃ in a rotary dryer and dried for 1 hour. The obtained ceramsite pellets are then placed in a heating furnace and heated at a rate of 5℃ / min to 1050℃ for 30 minutes. After the heating is completed, the pellets are cooled to room temperature to obtain solid waste-based lightweight high-strength ceramsite.

[0054] Performance Testing: The compressive strength, bulk density, and absorption loss in the 2-18 GHz frequency band of the solid waste-based lightweight high-strength ceramsite prepared in this embodiment were tested using the same method as in Example 1 above. The test results are as follows: compressive strength = 8.9 MPa, bulk density 687.5 kg / m³. 3 RL min =-26.42dB, EAB=6.5GHz.

[0055] Example 6: A method for preparing lightweight, high-strength ceramsite based on solid waste with electromagnetic shielding function includes the following steps: According to the ratio of calcium-silicon-magnesium-sulfur-aluminum-iron solid waste (composed of coal gangue and boron mud in a mass ratio of 6.8g:3.2g), ion dopant (copper slag), flux (glass powder), foaming-crystal coupling agent from Example 2 above, and water = 100g:3g:2g:2.5g:25g, the calcium-silicon-magnesium-sulfur-aluminum-iron solid waste, ion dopant, flux, and foaming-crystal coupling agent are first ground in a planetary ball mill until the residue on an 80μm square-hole sieve is 5%. Then, the obtained powder is mixed with water and granulated using a disc granulator to obtain raw material balls with a particle size distribution between 10 and 20 mm. The raw material balls are then dried in a rotary dryer at 80°C for 1.5 hours. The obtained ceramsite pellets are then placed in a heating furnace and heated at a rate of 10℃ / min to 1250℃ for 15 minutes. After the heating is completed, the pellets are cooled to room temperature to obtain solid waste-based lightweight high-strength ceramsite.

[0056] Performance Testing: The compressive strength, bulk density, and absorption loss in the 2-18 GHz frequency band of the solid waste-based lightweight high-strength ceramsite prepared in this embodiment were tested using the same method as in Example 1 above. The test results are as follows: compressive strength = 11.1 MPa, bulk density = 734.5 kg / m³ 3, RLmin=-37.03dB, EAB=8.7GHz.

[0057] Example 7: A method for preparing solid waste-based lightweight high-strength ceramsite with electromagnetic shielding function is the same as in Example 1 above, except that the foaming-crystal coupling agent in this example is prepared using the following steps: (1) Silicon carbide powder (particle size distribution between 0.6 and 1.0 μm) was placed in 2.5 mol / L nitric acid at a ratio of 1 g: 10 mL and ultrasonically treated for 2 hours. After completion, the silicon carbide powder was filtered out, washed with water to remove residual acid, and then dried to obtain pretreated silicon carbide powder for later use.

[0058] (2) Fe 3+ A source of Fe (ferric chloride) and a transition metal ion source (nickel chloride) are added to water and stirred until fully dissolved to form a modified solution, wherein: the Fe 3+ The molar ratio of the source and the transition metal ion source is 2:1. Then, a surface modifier (sodium citrate) and a homogeneous precipitant (urea) are added to the modified solution and stirred until fully dissolved, wherein: the surface modifier and Fe... 3+ The molar ratio of the source and the total transition metal ion source is 1:3, and the homogeneous precipitant and Fe 3+ The molar ratio of the source and the total transition metal ion source is 5:1. Then, the pretreated silicon carbide powder is added to the obtained liquid phase at a ratio of 8 mL: 1 g and ultrasonically dispersed for 10 min to obtain a suspension. The suspension is then heated to 90 °C and stirred continuously for 8 hours. After the reaction is complete, the solid product is filtered out, washed with water, and then dried at 110 °C for 4 hours to obtain the foamed-crystal coupling agent.

[0059] Performance Testing: The compressive strength, bulk density, and absorption loss in the 2-18 GHz frequency band of the solid waste-based lightweight high-strength ceramsite prepared in this embodiment were tested using the same method as in Example 1 above. The test results are as follows: compressive strength = 10.9 MPa, bulk density 723.5 kg / m³ 3 RL min =-37.34dB, EAB=8.8GHz.

[0060] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing solid waste-based lightweight high-strength ceramsite with electromagnetic shielding function, characterized in that, Includes the following steps: (1) With Fe 3+ A modified liquid is formed by adding a source of transition metal ions and a mineralization inducer. Then, a surface modifier and a homogeneous precipitant are added and mixed. Acid-treated silicon carbide powder and / or coal powder are added to the obtained liquid phase to form a suspension. The suspension is heated and stirred to react. After the reaction is completed, the solid product is separated, washed, and dried to obtain the foamed-crystal orientation coupling agent. (2) Using calcium, silicon, magnesium, sulfur, aluminum, and iron solid waste, ion dopant, flux, and the foaming-crystal orientation coupling agent as raw materials, mix them evenly and then add water to granulate to obtain core raw material balls for later use; (3) Using calcium, silicon, magnesium, sulfur, aluminum and iron solid waste and flux as raw materials, mix them and add water to form a slurry. Then coat the core raw material ball to form a core-shell type ceramic pellet blank. After sintering, solid waste-based lightweight high-strength ceramic pellets are obtained.

2. The method for preparing solid waste-based lightweight high-strength ceramsite with electromagnetic shielding function according to claim 1, characterized in that, In step (1), the Fe 3+ The molar ratio of the source and the transition metal ion source is 2:1; Optionally, further, the Fe 3+ The source includes at least one of ferric chloride and ferric sulfate; Optionally, in step (1), the transition metal ion source includes Ni. 2+ Source, Co 2+ At least one of the sources; Optionally, the Ni 2+ The sources include at least one of nickel nitrate and nickel chloride; Optionally, the Co 2+ The source includes at least one of cobalt nitrate and cobalt chloride.

3. The method for preparing solid waste-based lightweight high-strength ceramsite with electromagnetic shielding function according to claim 1, characterized in that, In step (1), the mass fraction of the mineralization inducer in the modified liquid is 10-30%; Optionally, in step (1), the mineralization inducer includes at least one of NaCl, KCl, Na2SO4, and B2O3.

4. The method for preparing solid waste-based lightweight high-strength ceramsite with electromagnetic shielding function according to claim 1, characterized in that, In step (1), the surface modifier and Fe 3+ The molar ratio of the source and the total transition metal ion source is 1:2~5; Optionally, in step (1), the surface modifier includes at least one of sodium citrate and sodium tartrate.

5. The method for preparing solid waste-based lightweight high-strength ceramsite with electromagnetic shielding function according to claim 1, characterized in that, In step (1), the homogeneous precipitant and Fe 3+ The molar ratio of the source and the total transition metal ion source is 3~10:1; Optionally, in step (1), the homogeneous precipitant includes at least one of urea and hexamethylenetetramine.

6. The method for preparing solid waste-based lightweight high-strength ceramsite with electromagnetic shielding function according to claim 1, characterized in that, In step (1), the method of treating silicon carbide powder and / or coal powder with acid includes: placing silicon carbide powder and / or coal powder in acid solution for ultrasonic treatment, separating the silicon carbide powder and / or coal powder after completion, washing and drying to obtain the product; Optionally, the acid solution includes at least one of nitric acid and hydrofluoric acid; Optionally, the ultrasonic treatment time is 1 to 3 hours.

7. The method for preparing solid waste-based lightweight high-strength ceramsite with electromagnetic shielding function according to claim 1, characterized in that, In step (1), the ratio of the liquid phase to silicon carbide powder and / or coal powder is 5~10mL:1g; Optionally, in step (1), the temperature of the heating and stirring reaction is 90~95℃ and the time is 4~8 hours; Optionally, in step (1), the drying temperature is 100~120℃ and the time is 3~6 hours.

8. The method for preparing solid waste-based lightweight high-strength ceramsite with electromagnetic shielding function according to claim 1, characterized in that, In step (2), the ratio of the calcium, silicon, magnesium, sulfur, aluminum, and iron solid waste, ion dopant, flux, foaming-crystal orientation coupling agent, and water is 100g: 1~3g: 1~2g: 0.5~2.5g: 15~25g; Optionally, in step (2), the ion dopant includes at least one of the following: electric arc furnace dust, copper slag, zinc slag, neodymium iron boron waste, and waste electrode materials; Optionally, in step (2), the particle size of the core raw material ball is 2~25mm.

9. The method for preparing solid waste-based lightweight high-strength ceramsite with electromagnetic shielding function according to claim 1, characterized in that, In step (3), the ratio of calcium, silicon, magnesium, sulfur, aluminum, and iron solid waste, flux, and water is 100g: 1~2g: 20~30g; Optionally, in step (3), the coating layer thickness of the core-shell type ceramsite blank is 10~20mm; Optionally, in step (3), the sintering temperature is 1050~1250℃ and the time is 15~30min.

10. The method for preparing solid waste-based lightweight high-strength ceramsite with electromagnetic shielding function according to any one of claims 1-9, characterized in that, In steps (2) and (3), the calcium-silicon-magnesium-sulfur-aluminum-iron solid waste includes at least two of the following: steel slag, coal gangue, phosphogypsum, high-magnesium limestone, red mud, and boron mud. Optionally, in steps (2) and (3), the flux includes at least one of borax, glass powder, and potassium feldspar.

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