Light magnetic control terahertz protective aerogel as well as preparation method and application thereof

Abstract

The invention discloses light magnetic control terahertz protective aerogel as well as a preparation method and application thereof, and particularly relates to the technical field of terahertz protective materials. Comprising the following steps: (1) adding a metal salt, an alkaline reagent and a stabilizer into an organic reagent, uniformly stirring and mixing, and adding a reducing agent to obtain a mixed solution; (2) in a gradient magnetic field, placing the mixed solution in a water bath for reaction to obtain wet gel; and (3) washing the wet gel obtained in the step (2) with a gradient alcohol-water solution, and drying to obtain the product. The'magnetic field 'and the'heat treatment' are synchronously carried out in a reaction container. The magnetic field penetrates through the whole process of metal ion reduction, nucleation, growth and assembly. Due to the synergistic effect, anisotropic growth of the nanowires can be effectively regulated and controlled, the nanowires are promoted to form long chains in an end-to-end connection mode, and finally the oriented metal aerogel is constructed; the cost effectiveness is improved, the flexibility is higher, large-area samples can be prepared, the energy consumption is lower, and the environmental protection property is improved.

Description

Technical Field

[0001] This invention relates to the field of terahertz protective materials technology, specifically to a lightweight magnetron-controlled terahertz protective aerogel, its preparation method, and its application. Background Technology

[0002] Terahertz electromagnetic radiation covers a frequency range of 100-10000 GHz (0.1-10 THz), located between microwaves and infrared radiation. It possesses characteristics such as low photon energy, strong penetration, high spatial resolution, and wide bandwidth. These superior properties provide crucial support for ultra-high-speed communication and detectors, stimulating numerous demands in fields such as radar stealth, biomedical imaging, chemical analysis, spectral analysis, and high-precision sensing. With the increasing number of terahertz devices, electromagnetic interference between devices has become a prominent issue, making the development of terahertz stealth and shielding technologies urgent. For example, current 6G technology (with data transmission rates 100 times that of commercial 5G) is rapidly advancing, and one of its core breakthroughs is the introduction of terahertz waves. However, the electronic chips in 6G devices generate electromagnetic radiation / leakage during high-frequency information exchange, especially in the THz band, which directly threatens human health, information security, and the stable operation of nearby critical components. In addition, high-efficiency, high-sensitivity strong-field terahertz light sources and detectors place higher demands on functionalized terahertz wave protection materials. There is an urgent need to design efficient terahertz protection materials to prevent electromagnetic interference problems in the system.

[0003] Magnetic transition metals, such as iron, cobalt, nickel, and their alloys, have attracted widespread attention due to their high saturation magnetization, favorable magnetic loss, and conduction loss. Aerogels possess characteristics of low density, high specific surface area, and high porosity, which meet the requirements of modern electronic devices for lightweight electromagnetic shielding materials. Meanwhile, metal aerogels, a novel type of aerogel composed of nanostructured metals, exhibit high electrical conductivity, high porosity, and the favorable magnetism of magnetic metals. Therefore, magnetic aerogels are a strong choice for preparing lightweight and efficient electromagnetic shielding materials. Currently published patents use MXene or graphene to prepare aerogels. Compared to metal aerogels, the preparation processes of MXene or graphene are more complex, costly, and prone to oxidation. The inherent magnetic properties of magnetic metals enable the material to effectively attenuate terahertz waves through a magnetic loss mechanism. Magnetic fields can induce the directional alignment of metal nanoparticles or precursors, forming a one-dimensional chain structure. These oriented chains construct continuous conductive and magnetic pathways within the aerogel, achieving excellent terahertz shielding performance through magnetic-dielectric synergy and multiple polarization.

[0004] Among the currently published patents, the main methods for preparing metal aerogels employ a combination of template-based methods and supercritical / freeze-drying. The template-based method may damage the structure during template removal, and the process is cumbersome, potentially limiting the specific surface area and macroscopic size of the final product. Supercritical drying equipment is expensive, requires harsh operating conditions, and carries safety risks. Freeze-drying is extremely slow, requiring prolonged freezing and sublimation (typically several days) to remove the solvent, resulting in low energy efficiency, high production costs, and hindering large-scale production.

[0005] Chinese patent CN120059285A discloses a method for preparing terahertz-controlled conductive aerogel. The main steps involve pouring a mixed precursor dispersion into a mold immersed in liquid nitrogen, subjecting it to bidirectional freezing, and then freeze-drying it to obtain the aerogel. This patent has at least three independent processes, with a freeze-drying time of 48 hours, resulting in a long operation chain and an overall long production cycle. Liquid nitrogen is a consumable resource, further increasing the cost.

[0006] Chinese patent CN115725265A discloses a microwave / terahertz wave compatible absorption aerogel and its preparation method. The main steps are: a dispersion of MXene (Ti3C2Tx) nanosheets obtained by etching and ultrasonication using the MILD method is reacted with a homogeneous solution obtained by stirring 3-glycidyloxypropyltrimethoxysilane (A-187) in an oil bath at a certain temperature; subsequently, the solution is cooled to room temperature and then freeze-dried to obtain a covalently bonded MXene three-dimensional porous aerogel. For most metal aerogels, energy-intensive freeze-drying or supercritical drying methods are usually required, and the drying process is complex and time-consuming, which needs to be improved. Summary of the Invention

[0007] The technical problem to be solved by this invention is how to address the high operational complexity, high energy consumption, high cost, and difficulty in large-area preparation of existing metal aerogel preparation methods.

[0008] The present invention solves the above-mentioned technical problems through the following technical means: This invention proposes a method for preparing a lightweight magnetron terahertz protective aerogel, comprising the following steps: (1) Add metal salt, alkaline reagent and stabilizer to organic reagent, stir and mix well, then add reducing agent to obtain mixed solution; (2) The mixture is placed in a water bath under a gradient magnetic field to react and obtain a wet gel; (3) The wet gel obtained in step (2) is washed with a gradient alcohol aqueous solution and dried to obtain the final product.

[0009] Preferably, in step (1), the metal salt is at least one of nickel chloride, cobalt chloride, ferric chloride, nickel nitrate, ferric nitrate, cobalt nitrate, nickel bromide, ferric bromide, and cobalt bromide.

[0010] Further preferred, in step (1), the metal salt is a mixed metal salt in which the molar ratio of cobalt chloride, nickel nitrate and iron bromide is 1~2:1.8~2.5:2~3.

[0011] Preferably, in step (1), the alkaline reagent is at least one of potassium hydroxide, sodium hydroxide, and ammonia.

[0012] Preferably, in step (1), the stabilizer is at least one of chloroplatinic acid, hexadecyltrimethylammonium bromide, and trisodium citrate.

[0013] Preferably, in step (1), the reducing agent is at least one of hydrazine hydrate, sodium borohydride, and ascorbic acid.

[0014] Preferably, in step (1), the molar ratio of metal salt, alkaline reagent, stabilizer and reducing agent is 1:0.5~3:1~4:2~6.

[0015] Further optimization yields a molar ratio of 1:2.3:2.8:4.7 for the metal salt, alkaline reagent, stabilizer, and reducing agent.

[0016] In an alkaline environment, when the stabilizer is trisodium citrate, and the molar ratio of the total molar number of the metal salt to the stabilizer is 1:2~3, the metal ions (Ni) 2+ / Co 2+ / Fe 3+ ) and the carboxyl group (-COO) on the citrate ion - The metal ions (Ni) and hydroxyl groups (-OH) form stable polydentate coordination bonds. When the reducing agent is hydrazine hydrate, the molar ratio of the total molar number of the metal salt to the reducing agent is 1:2~5. The reducing agent provides electrons through the breaking and recombination of covalent bonds, thereby releasing the metal ions (Ni) in the coordination bonds. 2+ Co 2+ Fe 3+ ) reduced to metallic element (Ni) 0 Co 0 Fe 0 ) or alloy nanoparticles.

[0017] Preferably, in step (1), the organic reagent is at least one of ethylene glycol, isopropanol, anhydrous ethanol, and tert-butanol.

[0018] Preferably, in step (1), the mixing method is to mix thoroughly by magnetic stirring for 8 to 15 minutes within a temperature range of 30 to 50°C.

[0019] Preferably, in step (2), the gradient magnetic field is set to have a magnetic induction intensity B between 1 and 3 T, and the magnetic field gradient is... The value of B ranges from 0.68 to 2.24 T / m.

[0020] The origin of the coordinate system is the plane of symmetry of the magnetic field (Z=0). An axial coordinate Z (unit: mm) is established along the direction of the magnetic field. Z is adjustable within the range of 0~400 mm. The water bath device is placed within the coordinate Z range. The magnetic field induction intensity B is controlled from 0.1~3T, and the magnetic field gradient is adjusted accordingly. The size of B ranges from 0.68 to 2.24 T / m. Utilizing the magnetic force generated by the gradient to directionally regulate the metal nanoparticles in the precursor is beneficial for the self-assembly of metal chains into aerogels.

[0021] Preferably, in step (2), the water bath temperature is set to 50~90℃ and the reaction time is 0.5~3h.

[0022] Preferably, in step (3), the gradient concentration is set to a volume fraction of 30% (V / V), 50% (V / V), 70% (V / V), 90% (V / V), and 100% (V / V).

[0023] Preferably, in step (3), the alcohol-water solution refers to one or more of isopropanol, anhydrous ethanol, and tert-butanol.

[0024] Preferably, in step (3), the drying method is to dry the product to constant weight using an oven under normal pressure.

[0025] The present invention also proposes a lightweight magnetron terahertz protective aerogel prepared by the above preparation method.

[0026] This invention also proposes the application of the lightweight magnetron terahertz protective aerogel prepared by the above preparation method in flexible wearable shielding materials, communication base stations, and terahertz communication waveguide components.

[0027] The beneficial effects of this invention are as follows: 1. This invention obtains lightweight and resilient metal aerogels through a one-step method and air drying, which improves cost-effectiveness, flexibility, the ability to prepare large-area samples, lower energy consumption, and environmental friendliness.

[0028] 2. This invention simultaneously applies a magnetic field and heat treatment within a reaction vessel. The magnetic field is present throughout the entire process of metal ion reduction, nucleation, growth, and assembly. This synergistic effect effectively regulates the anisotropic growth of nanowires and promotes their formation of long chains by connecting end-to-end, ultimately constructing an oriented metal aerogel. This densified structure not only enhances the material's mechanical stability but also further improves its shielding effectiveness, making it applicable in fields such as flexible wearable shielding materials, communication base stations, terahertz communication waveguide components, and aerospace equipment.

[0029] 3. This invention utilizes a gradient magnetic field to reduce metal ions and form magnetic nanoparticles. Simultaneously, driven by magnetic force, these magnetic metal nanoparticles grow directionally and connect to form a stable three-dimensional chain network, thereby constructing an ordered microstructure within the aerogel. This method not only enhances the mechanical properties of the aerogel but also endows it with excellent electromagnetic wave absorption and shielding capabilities, achieving the regulation of the aerogel's structure and function.

[0030] 4. The solid framework of the aerogel prepared by this invention is composed of small-sized nanoparticles oriented into nanochains. The aerogel is mostly composed of air (density about 1.29 kg / m³), and the solid metal part (e.g., nickel, density about 8.900 kg / m³) accounts for a very small proportion. Therefore, the overall macroscopic density is very low, thereby achieving the lightweight performance of the electromagnetic protection material in the terahertz band.

[0031] Of course, implementing any product or method of the present invention does not necessarily require achieving all of the advantages described above at the same time. Attached Figure Description

[0032] Figure 1 These are low-magnification (a) and high-magnification (b) scan images of the metal aerogel in Example 1 of the present invention; Figure 2 This is a terahertz shielding performance curve of the metal aerogel in Example 1 of the present invention; Figure 3 Macroscopic diagrams showing (a) resilience and (b) lightweight properties of the metal aerogel in Example 1 of this invention; Figure 4 The images shown are (a) macroscopic and (b) microscopic views of the sample not subjected to magnetic field treatment in Comparative Example 1 of this invention. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Unless otherwise defined, the technical terms used below have the same meaning as understood by those skilled in the art.

[0034] Unless otherwise specified, the test materials and reagents used in the following examples are commercially available or prepared by known methods.

[0035] Unless otherwise specified, all techniques or conditions described in the embodiments can be performed in accordance with the techniques or conditions described in the literature in this field or in the product manual. Unless otherwise specified, the quantitative experiments in the following embodiments are all repeated three times or more, and the results are averaged.

[0036] Example 1: This embodiment prepares a lightweight magnetron terahertz protective aerogel, including the following steps: Step 1: Weigh out cobalt chloride, nickel nitrate, and ferric bromide metal salts (molar ratio 1.5:2.3:2.7), and dissolve them in 100 mL of ethylene glycol. Mix thoroughly at 30 °C by magnetic stirring for 10 min. Add hydrazine hydrate reducing agent to obtain a mixed solution. The molar ratio of the metal salts (cobalt chloride, nickel nitrate, ferric bromide), alkaline reagent (potassium hydroxide), stabilizer (trisodium citrate), and reducing agent (hydrazine hydrate) is 1:2.3:2.8:4.7.

[0037] Step 2: The mixture obtained in Step 1 is ultrasonically stirred for 60 seconds and placed in a magnetic field with a magnetic induction intensity B of 2T and a magnetic field gradient. A wet gel was obtained by reacting a sample at a position with a size of 1.31 T / m in a 90°C water bath for 2 hours.

[0038] Step 3: The wet gel obtained in Step 2 is washed repeatedly with isopropanol at volume fractions of 30% (V / V), 50% (V / V), 70% (V / V), 90% (V / V), and 100% (V / V) (to remove unreacted reducing agents and other impurities), and then dried at atmospheric pressure (i.e., one atmosphere) (to constant weight) to obtain a metal chain oriented self-assembled aerogel.

[0039] like Figure 1 The images shown are low-magnification and high-magnification scans of the metal aerogel in Example 1. From (a) the low-magnification scan, it can be seen that the aerogel has an ordered microstructure, which gives it good resilience. From (b) the high-magnification scan, it can be seen that the metal particles are chained together in a predetermined direction.

[0040] like Figure 2 The shielding performance of the aerogel in Example 1 is shown in the terahertz 0~1.5THz frequency range. The shielding performance can reach 78.43dB at a frequency of 0.95THz.

[0041] like Figure 3 The image shows the tests on the resilience and lightweight properties of the aerogel in Example 1. (a) shows that the aerogel can rebound to its original state after being subjected to pressure. (b) shows that the aerogel can stand upright on foxtail grass, demonstrating its lightweight properties.

[0042] Example 2: This embodiment prepares a lightweight magnetron terahertz protective aerogel, including the following steps: Step 1: Dissolve cobalt chloride, chloroplatinic acid, and sodium hydroxide in 100 mL of ethylene glycol. Mix thoroughly at 30 °C by magnetic stirring for 15 min. Add ascorbic acid reducing agent to obtain a mixed solution. The molar ratio of metal salt (cobalt chloride), alkaline reagent (sodium hydroxide), stabilizer (chloroplatinic acid), and reducing agent (ascorbic acid) is 1:0.5:1:2.

[0043] Step 2: The mixture obtained in Step 1 is ultrasonically stirred for 60 seconds and placed in a magnetic field with a magnetic induction intensity B of 3T and a magnetic field gradient. A wet gel was obtained by reacting a sample at a position with a size of 2.24 T / m in a water bath at 90°C for 1.0 h.

[0044] Step 3: The wet gel obtained in Step 2 is washed multiple times with anhydrous ethanol at volume fractions of 30% (V / V), 50% (V / V), 70% (V / V), 90% (V / V), and 100% (V / V), and then dried at atmospheric pressure (i.e., one atmosphere) (to constant weight) to obtain a metal chain oriented self-assembled aerogel.

[0045] Example 3: This embodiment prepares a lightweight magnetron terahertz protective aerogel, including the following steps: Step 1: Dissolve nickel chloride, trisodium citrate, and sodium hydroxide in 100 mL of ethylene glycol. Mix thoroughly at 45 °C by magnetic stirring for 8 min. Add sodium borohydride as a reducing agent to obtain a mixed solution. The molar ratio of the metal salt (nickel chloride), alkaline reagent (sodium hydroxide), stabilizer (trisodium citrate), and reducing agent (sodium borohydride) is 1:3:4:6.

[0046] Step 2: The mixture obtained in Step 1 is ultrasonically stirred for 60 seconds and placed in a magnetic field with a magnetic induction intensity B of 1T and a magnetic field gradient. A wet gel was obtained by reacting a sample at a position with a size of 0.68 T / m in a water bath at 70°C for 3 hours.

[0047] Step 3: The wet gel obtained in Step 2 is washed repeatedly with isopropanol at volume fractions of 30% (V / V), 50% (V / V), 70% (V / V), 90% (V / V), and 100% (V / V) (to remove unreacted reducing agents and other impurities), and then dried at atmospheric pressure (i.e., one atmosphere) (to constant weight) to obtain a metal chain oriented self-assembled aerogel.

[0048] Comparative Example 1: This comparative example prepared an aerogel, including the following steps: The difference between this comparative example and Example 1 is that in step two, the mixture was not placed in a magnetic field.

[0049] like Figure 4 The images shown are (a) macroscopic and (b) microscopic images of the sample in Comparative Example 1 of this invention that was not subjected to magnetic field treatment. Without external guidance, the metal nanoparticles disperse and settle at a rate much faster than they form a cohesive network. Therefore, a loose black precipitate forms at the bottom of the container, failing to form a stable three-dimensional aerogel structure. This demonstrates that gradient magnetic field treatment facilitates the orientation and self-assembly of metal particles into an aerogel.

[0050] Comparative Example 2: This comparative example prepared an aerogel, including the following steps: The difference between this comparative example and Example 1 is that in step two, the mixture is placed in a magnetic field with a magnetic induction intensity B of 7T and a magnetic field gradient. The position B has a size of 3.73 T / m. Due to the excessive magnetic field gradient, the migration of metal particles was aggravated, causing the particles to aggregate and grow into large particles, which destroyed the nanoporous structure and failed to form a stable three-dimensional aerogel structure.

[0051] Comparative Example 3: This comparative example prepared an aerogel, including the following steps: The difference between this comparative example and Example 1 is that in step two, the mixture is placed in a magnetic field with a magnetic induction intensity B of 0.5T and a magnetic field gradient. In a 90℃ water bath with a magnetic field strength of 0.4 T / m, the metal particles were not sufficiently guided by the small magnetic field gradient, thus failing to form a three-dimensional aerogel structure.

[0052] Comparative Example 4: This comparative example prepared an aerogel, including the following steps: The difference between this comparative example and Example 1 is that in step one, the molar ratio of metal salt, alkaline reagent, stabilizer, and reducing agent in the mixture is 1:0.4:0.5:4.7. Insufficient alkaline reagent and stabilizer prevent the long-term stable dispersion of a large number of nanoparticles. After particle formation, they easily aggregate and settle, rather than forming a uniform, self-supporting network structure. A highly stable metal aerogel was not successfully prepared.

[0053] Comparative Example 5: This comparative example prepared an aerogel, including the following steps: The difference between this comparative example and Example 1 is that in step two, the water bath temperature is set to 40°C and the reaction time is 6 hours. If the temperature is too low, the kinetic energy barrier for the reduction of metal ions by hydrazine hydrate is high, resulting in an extremely slow reaction rate and making it difficult to generate the product.

[0054] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a lightweight magnetron-controlled terahertz protective aerogel, characterized in that, Includes the following steps: (1) Add metal salt, alkaline reagent and stabilizer to organic reagent, stir and mix well, then add reducing agent to obtain mixed solution; (2) The mixture is placed in a water bath under a gradient magnetic field to react and obtain a wet gel; (3) The wet gel obtained in step (2) is washed with a gradient alcohol aqueous solution and dried to obtain the final product.

2. The preparation method according to claim 1, characterized in that, In step (1), the metal salt is at least one of nickel chloride, cobalt chloride, ferric chloride, nickel nitrate, ferric nitrate, cobalt nitrate, nickel bromide, ferric bromide, and cobalt bromide. More preferably, the metal salt is a mixed metal salt in which the molar ratio of cobalt chloride, nickel nitrate, and ferric bromide is 1~2:1.8~2.5:2~3.

3. The preparation method according to claim 1, characterized in that, In step (1), the alkaline reagent is at least one of potassium hydroxide, sodium hydroxide, and ammonia water; the stabilizer is at least one of chloroplatinic acid, hexadecyltrimethylammonium bromide, and trisodium citrate; and the reducing agent is at least one of ascorbic acid, hydrazine hydrate, and sodium borohydride.

4. The preparation method according to claim 1, characterized in that, In step (1), the molar ratio of metal salt, alkaline reagent, stabilizer and reducing agent is 1:0.5~3:1~4:2~6.

5. The preparation method according to claim 1, characterized in that, In step (1), the organic reagent is at least one of ethylene glycol, isopropanol, anhydrous ethanol, and tert-butanol; the mixing method is to mix thoroughly by magnetic stirring for 8 to 15 minutes within a temperature range of 30 to 50°C.

6. The preparation method according to claim 1, characterized in that, In step (2), the gradient magnetic field is set to have a magnetic induction intensity B between 1 and 3 T, and the magnetic field gradient is... The size of B is 0.68~2.24T / m; the water bath temperature is set to 50~90℃, and the reaction time is 0.5~3h.

7. The preparation method according to claim 1, characterized in that, In step (3), the gradient concentrations are set to volume fractions of 30% (V / V), 50% (V / V), 70% (V / V), 90% (V / V), and 100% (V / V); the alcohol-water solution refers to at least one of isopropanol, anhydrous ethanol, and tert-butanol.

8. The preparation method according to claim 1, characterized in that, In step (3), the drying method is to dry the product to constant weight in an oven under normal pressure.

9. The lightweight magnetron terahertz protective aerogel prepared by the preparation method according to any one of claims 1-8.

10. The application of the lightweight magnetically controlled terahertz protective aerogel as described in claim 9 in flexible wearable shielding materials, communication base stations, and terahertz communication waveguide components.

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