Silver micro-nanofiber membrane with hollow tubular structure and preparation method thereof

Abstract

The application discloses a silver micro-nanofiber film with a hollow tubular structure and a preparation method thereof, and the preparation method comprises the following steps: dissolving raw materials containing an organic framework material and silver nitrate in an organic solvent to prepare a precursor solution; spinning the precursor solution into fibers; forming a coating structure through ultraviolet irradiation induced pre-phase separation; and forming the hollow tubular structure fibers through calcination reduction of the silver nitrate and decomposition of the organic framework material, and the macroscopic appearance of the fibers is a fiber film or a fiber sponge. Compared with a preparation method of a traditional silver nanofiber material, the preparation method of the flexible silver micro-nanofiber material has the advantages of continuous process production, high yield, good mechanical performance and electromagnetic shielding performance, and is expected to be applied to large-scale electromagnetic shielding material process preparation.

Description

Technical Field

[0001] This invention relates to the fields of materials science and engineering technology, specifically to a silver micro / nanofiber membrane with a hollow tubular structure and its preparation method. Background Technology

[0002] Since the beginning of the 21st century, electronic science and technology have flourished at an unprecedented pace. Today, a variety of lightweight, miniaturized, highly integrated, and flexible portable mobile electronic devices are ubiquitous in human life. However, this has also brought about increasingly serious problems such as electromagnetic radiation pollution, electromagnetic interference with precision instruments, and information leaks. In recent years, a new type of pollution caused by the high degree of electronic integration in human society, known as electromagnetic interference (EMI), has attracted considerable attention. High-performance electromagnetic shielding materials will play an increasingly important role in protecting precision electronic equipment and ensuring human health. Furthermore, special electromagnetic shielding materials that operate across multiple wavelengths are also receiving widespread attention in aerospace, military facilities, and mobile communications.

[0003] To prevent EMI, researchers initially proposed using a paste mixed with metal powders such as silver, copper, iron, and nickel for electromagnetic shielding. However, the poor bonding strength, uneven metal powder distribution, low electromagnetic shielding efficiency, and poor flexibility of this paste severely limited its further development. Furthermore, the electromagnetic shielding performance of these materials is easily affected by macroscopic / microscopic cracks generated during bending and stretching, which means that thin metal film materials cannot effectively meet the electromagnetic shielding requirements of curved surfaces or deformable devices.

[0004] In recent years, researchers both domestically and internationally have developed various thin-film electromagnetic shielding materials based on advanced nanofabrication technologies, including two-dimensional (2D) materials, graphene, carbon nanotubes (CNTs), metal-based materials, and polymer-based composites. These materials possess characteristics such as high electrical conductivity, low density, and excellent flexibility. However, the skin effect inherently limits the minimum thickness of thin-film electromagnetic shielding materials in specific frequency bands. Therefore, an unavoidable contradiction exists between the high efficiency and portability of electromagnetic shielding materials in practical applications. This means that single-layer or few-layer thin-film materials are insufficient to meet the increasingly stringent requirements for flexible electromagnetic shielding applications.

[0005] In summary, the performance and manufacturing process of flexible electromagnetic shielding materials still need further optimization. Summary of the Invention

[0006] The technical problem to be solved by this invention is: how to obtain a fiber material that combines electromagnetic shielding performance and lightweight properties. This invention provides a silver micro / nanofiber membrane with a hollow tubular structure and its preparation method to solve the above problem. The electromagnetic shielding performance and bending resistance of the flexible silver micro / nano hollow tubular fiber prepared therefrom are significantly improved.

[0007] This invention is achieved through the following technical solution:

[0008] A method for preparing a silver micro / nanofiber membrane with a hollow tubular structure includes the following steps:

[0009] A precursor solution is prepared by dissolving raw materials containing organic framework materials and silver nitrate in an organic solvent.

[0010] The precursor solution is spun into fibers;

[0011] Pre-phase separation is induced by ultraviolet light irradiation to form a coated structure; the outer layer of the coated structure is silver particles, and the core is a mixture of organic framework material and silver nitrate.

[0012] Hollow tubular fiber structures are formed by calcining and reducing silver nitrate and decomposing organic framework materials. The macroscopic appearance of the fiber is a fiber film or fiber sponge.

[0013] The outer layer of the coating structure consists of dense silver nanoparticles, while the core is a mixture of organic framework material and silver nitrate. The silver nanoparticles here are silver particles partially reduced by ultraviolet irradiation.

[0014] This invention first prepares a solution containing an organic framework material, silver nitrate, and an organic solvent as a precursor solution. Then, a fiber sample is prepared by spinning technology. Next, the fiber is irradiated with ultraviolet light to induce pre-phase separation and form a coating structure. Finally, the silver nitrate is reduced and the organic framework material is decomposed by high-temperature calcination to form a hollow tubular structure of silver micro / nanofiber material.

[0015] Compared to traditional methods for preparing silver nanofiber materials, the method for preparing flexible silver micro / nanofiber materials provided by this invention features continuous production and high yield (>150cm). 3 It has advantages such as good mechanical properties and electromagnetic shielding performance, and is expected to be applied to the large-scale electromagnetic shielding material manufacturing process.

[0016] Further optionally, the mass ratio of PVP, silver nitrate, and organic solvent is (0.230-0.260):(1.3-2.0):(1.90-2.30); more preferably (0.245-0.250):(1.4-1.8):(2.10-2.30).

[0017] For example, the masses of PVP, silver nitrate, and acetonitrile are 0.245g to 0.250g, 1.4g to 1.8g, 2.10g to 2.30g, or multiples thereof.

[0018] Further, optionally, the organic framework material includes synthetic polymers and / or natural polymers;

[0019] The synthetic polymer includes one or more of the following: polyacrylonitrile, polyvinylpyrrolidone, polymethyl methacrylate, polyamide, polylactic acid, polyimide, polyethylene oxide, and polyimide dioxime.

[0020] The synthesized polymers include polyacrylonitrile (PAN), polyvinylpyrrolidone (PVP), polymethyl methacrylate (PMMA), polyamide (PA), polylactic acid (PLA), polyimide (PI), polyethylene oxide (PEO), and polyimide dioxime (PIDO), etc.

[0021] Natural polymers, including cellulose, zein, and gelatin; as well as some non-spinnable natural polymers.

[0022] Further optionally, the organic solvent includes one or a combination of acetonitrile, ethanol, and dimethyl sulfoxide.

[0023] Alternatively, the spinning method may employ air-jet spinning or electrospinning techniques, with an ambient humidity of 20% to 60%.

[0024] Further optionally, a drying step is also included; after the fibers are spun into fibers, they are dried and then subjected to ultraviolet light irradiation.

[0025] Further, optionally, the ultraviolet light irradiation parameters include:

[0026] When irradiating with ultraviolet light, the distance between the light source and the sample is 5cm to 15cm; the illuminance near the ultraviolet lamp tube is 300,000 lux to 350,000 lux, and the irradiation distance can be adjusted according to the actual illuminance.

[0027] And / or the irradiation time for each side of the fiber is 20 min to 40 min.

[0028] For example, the preferred distance from the sample to the ultraviolet light irradiation is 10 cm; the total irradiation time is 1 hour, with the fiber irradiated on both sides, and each side irradiated for 30 minutes.

[0029] Setting ultraviolet irradiation parameters is mainly to control the pre-phase separation process of silver nitrate and prevent silver nitrate from being reduced in large quantities.

[0030] Alternatively, the calcination temperature is 210℃~230℃, and the holding time is 1.5h~2.5h;

[0031] During and / or calcination treatment, the heating rate is 1℃ / min to 5℃ / min.

[0032] The present invention designs a calcination temperature. When the calcination temperature is too low, the silver nitrate is not completely reduced, the fiber membrane has low conductivity, and the electromagnetic shielding efficiency and mechanical properties are insufficient. When the calcination temperature is too high, the fiber is over-reduced, the silver particles are too large, which leads to the destruction of the fiber structure and a decrease in flexibility.

[0033] The heating rate designed in this invention is problematic. If the heating rate is too low, it consumes a lot of time; if the heating rate is too high, a large amount of the sample will volatilize during the heating stage, resulting in a small sample area after calcination, which cannot meet the testing requirements. A more preferable heating rate is 1.3℃ / min.

[0034] A silver micro / nanofiber membrane with a hollow tubular structure is described. The macroscopic morphology of the sample is that of a thin film or a sponge. The constituent fibers are hollow tubular fibers composed of silver particles.

[0035] Alternatively, the fiber diameter is 0.5 μm to 3 μm.

[0036] Alternatively, it can be prepared by the above-described method for preparing a silver micro / nanofiber membrane with a hollow tubular structure.

[0037] The present invention has the following advantages and beneficial effects:

[0038] 1. The silver micro / nanofiber membrane with a hollow tubular structure provided by this invention has a fiber surface composed of silver nanoparticles and a hollow interior. This structure allows the fiber to exhibit excellent surface and internal electromagnetic wave reflection capabilities, thus achieving high electromagnetic shielding efficiency. Simultaneously, the fiber structure provides excellent bending mechanical properties, with a conductivity loss of only 5% after thousands of bends. This material, with its high electromagnetic shielding efficiency, has significant research value in fields such as flexible electronics, engineering testing, aerospace, robotics, and the Internet of Things.

[0039] 2. The continuous preparation process of silver micro / nanofibers provided by this invention, compared with traditional preparation processes, has the advantages of continuous production and high yield (>150cm). 3 It has advantages such as good mechanical properties and electromagnetic shielding performance, and is expected to be applied to the large-scale electromagnetic shielding material manufacturing process. Attached Figure Description

[0040] The accompanying drawings, which are included to provide a further understanding of embodiments of the invention and form part of this application, do not constitute a limitation thereof. In the drawings:

[0041] Figure 1 The flowchart illustrates the preparation process of the silver micro / nanofiber membrane with a hollow tubular structure provided in Embodiment 1 of the present invention.

[0042] Figure 2This is a comparison curve of electromagnetic shielding efficiency (SET) between Embodiment 1 and Comparative Example 1 of the present invention.

[0043] Figure 3 This is a SEM image of the hollow tubular silver micro / nanofiber material provided in Example 1 of the present invention; wherein, Figure 3 'a' represents the original fiber condition. Figure 3 b represents the pre-phase separation case. Figure 3 c represents the case of a phase separation process. Figure 3 d represents the hollow tube silver micro / nanofiber situation.

[0044] Figure 4 These are supplementary graphs for Embodiments 5-8 of the present invention.

[0045] Figure 5 This is a graph showing the test results of the bending resistance of Embodiment 1 of the present invention.

[0046] Figure 6 The thickness measurement SEM image of Example 1 of the present invention. Detailed Implementation

[0047] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0048] Example 1

[0049] This embodiment provides a silver micro / nanofiber membrane with a hollow tubular structure, composed of multiple layers of fibers. The fiber structure is a structure with silver nanoparticles on the surface and a hollow interior. Silver nitrate-containing fibers are pre-separated under ultraviolet light induction and then reduced to silver particles by high-temperature calcination, while simultaneously removing organic matter, forming a hollow tubular fiber structure. The specific preparation method is as follows:

[0050] Step 1: Dissolve 0.248g of PVP powder in 2.14g of acetonitrile solution; then stir at room temperature for at least 30 minutes until completely dissolved to form a colorless solution.

[0051] Step 2: Add 1.6g of silver nitrate solid particles to the solution obtained in Step 1, and stir at room temperature for at least 30 minutes until completely dissolved. The stirring process should be carried out in the dark to obtain a pale yellow transparent solution.

[0052] Step 3: The solution obtained in Step 2 is used to prepare fibers using air-jet spinning technology and then dried in a drying oven at 40°C.

[0053] Step 4: Irradiate the fibers obtained in Step 3 under a UV light source. The distance between the UV light source and the fibers is 10 cm, the illuminance near the UV lamp tube is 300,000 lux, and the irradiation time is 30 min. After irradiation, flip the fibers over and irradiate them again for 30 min. This allows the fibers to enter the pre-phase separation process and form a coating structure. At the same time, a small amount of silver particles are reduced.

[0054] Step 5: Place the fibers obtained in Step 4 into a muffle furnace, set the heating rate to 1.3℃ / min, the calcination temperature to 230℃, and the holding time to 2h.

[0055] Step 6: Encapsulate the sample obtained in Step 5 with silicone, which can be freely cut into the desired shape.

[0056] Example 2

[0057] This embodiment provides a silver micro / nanofiber membrane with a hollow tubular structure, composed of multiple layers of fibers. The fiber structure is a structure with silver nanoparticles on the surface and a hollow interior. Silver nitrate-containing fibers are pre-separated under ultraviolet light induction and then reduced to silver particles by high-temperature calcination, while simultaneously removing organic matter, forming a hollow tubular fiber structure. The specific preparation method is as follows:

[0058] Step 1: Dissolve 0.248g of PVP powder in 2.14g of acetonitrile solution; then stir at room temperature for at least 30 minutes until completely dissolved to form a colorless solution.

[0059] Step 2: Add 1.6g of silver nitrate solid particles to the solution obtained in Step 1, and stir at room temperature for at least 30 minutes until completely dissolved. The stirring process should be carried out in the dark to obtain a pale yellow transparent solution.

[0060] Step 3: The solution obtained in Step 2 is used to prepare fibers using air-jet spinning technology and then dried in a 40°C drying oven.

[0061] Step 4: Irradiate the fibers obtained in Step 3 under a UV light source. The distance between the UV light source and the fibers is 10 cm, the illuminance near the UV lamp tube is 300,000 lux, and the irradiation time is 30 min. After irradiation, flip the fibers over and irradiate them again for 30 min. This allows the fibers to enter the pre-phase separation process and form a coating structure. At the same time, a small amount of silver particles are reduced.

[0062] Step 5: Place the fibers obtained in Step 4 into a muffle furnace, set the heating rate to 1.3℃ / min, the calcination temperature to 225℃, and the holding time to 2h.

[0063] Step 6: Encapsulate the sample obtained in Step 5 with silicone, which can be freely cut into the desired shape.

[0064] Example 3

[0065] This embodiment provides a silver micro / nanofiber membrane with a hollow tubular structure, composed of multiple layers of fibers. The fiber structure is a structure with silver nanoparticles on the surface and a hollow interior. Silver nitrate-containing fibers are pre-separated under ultraviolet light induction and then reduced to silver particles by high-temperature calcination, while simultaneously removing organic matter, forming a hollow tubular fiber structure. The specific preparation method is as follows:

[0066] Step 1: Dissolve 0.248g of PVP powder in 2.14g of acetonitrile solution; then stir at room temperature for at least 30 minutes until completely dissolved to form a colorless solution.

[0067] Step 2: Add 1.6g of silver nitrate solid particles to the solution obtained in Step 1, and stir at room temperature for at least 30 minutes until completely dissolved. The stirring process should be carried out in the dark to obtain a pale yellow transparent solution.

[0068] Step 3: The solution obtained in Step 2 is used to prepare fibers using air-jet spinning technology and then dried in a 40°C drying oven.

[0069] Step 4: Irradiate the fibers obtained in Step 3 under a UV light source. The distance between the UV light source and the fibers is 10 cm, the illuminance near the UV lamp tube is 300,000 lux, and the irradiation time is 30 min. After irradiation, flip the fibers over and irradiate them again for 30 min. This allows the fibers to enter the pre-phase separation process and form a coating structure. At the same time, a small amount of silver particles are reduced.

[0070] Step 5: Place the fibers obtained in Step 4 into a muffle furnace, set the heating rate to 1.3℃ / min, the calcination temperature to 220℃, and the holding time to 2h.

[0071] Step 6: Encapsulate the sample obtained in Step 5 with silicone, which can be freely cut into the desired shape.

[0072] Example 4

[0073] This embodiment provides a silver micro / nanofiber membrane with a hollow tubular structure, composed of multiple layers of fibers. The fiber structure is a structure with silver nanoparticles on the surface and a hollow interior. Silver nitrate-containing fibers are pre-separated under ultraviolet light induction and then reduced to silver particles by high-temperature calcination, while simultaneously removing organic matter, forming a hollow tubular fiber structure. The specific preparation method is as follows:

[0074] Step 1: Dissolve 0.248g of PVP powder in 2.14g of acetonitrile solution; then stir at room temperature for at least 30 minutes until completely dissolved to form a colorless solution.

[0075] Step 2: Add 1.6g of silver nitrate solid particles to the solution obtained in Step 1, and stir at room temperature for at least 30 minutes until completely dissolved. The stirring process should be carried out in the dark to obtain a pale yellow transparent solution.

[0076] Step 3: The solution obtained in Step 2 is used to prepare fibers using air-jet spinning technology and then dried in a 40°C drying oven.

[0077] Step 4: Irradiate the fibers obtained in Step 3 under a UV light source. The distance between the UV light source and the fibers is 10 cm, the illuminance near the UV lamp tube is 300,000 lux, and the irradiation time is 30 min. After irradiation, flip the fibers over and irradiate them again for 30 min. This allows the fibers to enter the pre-phase separation process and form a coating structure. At the same time, a small amount of silver particles are reduced.

[0078] Step 5: Place the fibers obtained in Step 4 into a muffle furnace, set the heating rate to 1.3℃ / min, the calcination temperature to 215℃, and the holding time to 2h.

[0079] Step 6: Encapsulate the sample obtained in Step 6 with silicone, which can be freely cut into the desired shape.

[0080] Example 5

[0081] This embodiment provides a silver micro / nanofiber membrane with a hollow tubular structure, composed of multiple layers of fibers. The fiber structure is a structure with silver nanoparticles on the surface and a hollow interior. Silver nitrate-containing fibers are pre-separated under ultraviolet light induction and then reduced to silver particles by high-temperature calcination, while simultaneously removing organic matter, forming a hollow tubular fiber structure. The specific preparation method is as follows:

[0082] Step 1: Dissolve 0.248g of PVP powder in 2.14g of acetonitrile solution; then stir at room temperature for at least 30 minutes until completely dissolved to form a colorless solution.

[0083] Step 2: Add 1.6g of silver nitrate solid particles to the solution obtained in Step 1, and stir at room temperature for at least 30 minutes until completely dissolved. The stirring process should be carried out in the dark to obtain a pale yellow transparent solution.

[0084] Step 3: The solution obtained in Step 2 is used to prepare fibers using air-jet spinning technology and then dried in a 40°C drying oven.

[0085] Step 4: Irradiate the fibers obtained in Step 3 under a UV light source. The distance between the UV light source and the fibers is 10 cm, the illuminance near the UV lamp tube is 300,000 lux, and the irradiation time is 30 min. After irradiation, flip the fibers over and irradiate them again for 30 min. This allows the fibers to enter the pre-phase separation process and form a coating structure. At the same time, a small amount of silver particles are reduced.

[0086] Step 5: Place the fibers obtained in Step 4 into a muffle furnace, set the heating rate to 1.5℃ / min, the calcination temperature to 230℃, and the holding time to 2h.

[0087] Step 6: Encapsulate the sample obtained in Step 5 with silicone, which can be freely cut into the desired shape.

[0088] Example 6

[0089] This embodiment provides a silver micro / nanofiber membrane with a hollow tubular structure, composed of multiple layers of fibers. The fiber structure is a structure with silver nanoparticles on the surface and a hollow interior. Silver nitrate-containing fibers are pre-separated under ultraviolet light induction and then reduced to silver particles by high-temperature calcination, while simultaneously removing organic matter, forming a hollow tubular fiber structure. The specific preparation method is as follows:

[0090] Step 1: Dissolve 0.248g of PVP powder in 2.14g of acetonitrile solution; then stir at room temperature for at least 30 minutes until completely dissolved to form a colorless solution.

[0091] Step 2: Add 1.6g of silver nitrate solid particles to the solution obtained in Step 1, and stir at room temperature for at least 30 minutes until completely dissolved. The stirring process should be carried out in the dark to obtain a pale yellow transparent solution.

[0092] Step 3: The solution obtained in Step 2 is used to prepare fibers using air-jet spinning technology and then dried in a 40°C drying oven.

[0093] Step 4: Irradiate the fibers obtained in Step 3 under a UV light source. The distance between the UV light source and the fibers is 10 cm, the illuminance near the UV lamp tube is 300,000 lux, and the irradiation time is 30 min. After irradiation, flip the fibers over and irradiate them again for 30 min. This allows the fibers to enter the pre-phase separation process and form a coating structure. At the same time, a small amount of silver particles are reduced.

[0094] Step 5: Place the fibers obtained in Step 4 into a muffle furnace, set the heating rate to 1.7℃ / min, the calcination temperature to 230℃, and the holding time to 2h.

[0095] Step 6: Encapsulate the sample obtained in Step 5 with silicone, which can be freely cut into the desired shape.

[0096] Example 7

[0097] This embodiment provides a silver micro / nanofiber membrane with a hollow tubular structure, composed of multiple layers of fibers. The fiber structure is a structure with silver nanoparticles on the surface and a hollow interior. Silver nitrate-containing fibers are pre-separated under ultraviolet light induction and then reduced to silver particles by high-temperature calcination, while simultaneously removing organic matter, forming a hollow tubular fiber structure. The specific preparation method is as follows:

[0098] Step 1: Dissolve 0.248g of PVP powder in 2.14g of acetonitrile solution; then stir at room temperature for at least 30 minutes until completely dissolved to form a colorless solution.

[0099] Step 2: Add 1.6g of silver nitrate solid particles to the solution obtained in Step 1, and stir at room temperature for at least 30 minutes until completely dissolved. The stirring process should be carried out in the dark to obtain a pale yellow transparent solution.

[0100] Step 3: The solution obtained in Step 2 is used to prepare fibers using air-jet spinning technology and then dried in a 40°C drying oven.

[0101] Step 4: Irradiate the fibers obtained in Step 3 under a UV light source. The distance between the UV light source and the fibers is 10 cm, the illuminance near the UV lamp tube is 300,000 lux, and the irradiation time is 30 min. After irradiation, flip the fibers over and irradiate them again for 30 min. This allows the fibers to enter the pre-phase separation process and form a coating structure. At the same time, a small amount of silver particles are reduced.

[0102] Step 5: Place the fibers obtained in Step 4 into a muffle furnace, set the heating rate to 2.0℃ / min, the calcination temperature to 230℃, and the holding time to 2h.

[0103] Step 6: Encapsulate the sample obtained in Step 6 with silicone, which can be freely cut into the desired shape.

[0104] Example 8

[0105] This embodiment provides a silver micro / nanofiber membrane with a hollow tubular structure, composed of multiple layers of fibers. The fiber structure is a structure with silver nanoparticles on the surface and a hollow interior. Silver nitrate-containing fibers are pre-separated under ultraviolet light induction and then reduced to silver particles by high-temperature calcination, while simultaneously removing organic matter, forming a hollow tubular fiber structure. The specific preparation method is as follows:

[0106] Step 1: Dissolve 0.248g of PVP powder in 2.14g of acetonitrile solution; then stir at room temperature for at least 30 minutes until completely dissolved to form a colorless solution.

[0107] Step 2: Add 1.6g of silver nitrate solid particles to the solution obtained in Step 1, and stir at room temperature for at least 30 minutes until completely dissolved. The stirring process should be carried out in the dark to obtain a pale yellow transparent solution.

[0108] Step 3: The solution obtained in Step 2 is used to prepare fibers using air-jet spinning technology and then dried in a 40°C drying oven.

[0109] Step 4: Irradiate the fibers obtained in Step 3 under a UV light source. The distance between the UV light source and the fibers is 10 cm, the illuminance near the UV lamp tube is 300,000 lux, and the irradiation time is 30 min. After irradiation, flip the fibers over and irradiate them again for 30 min. This allows the fibers to enter the pre-phase separation process and form a coating structure. At the same time, a small amount of silver particles are reduced.

[0110] Step 5: Place the fibers obtained in Step 4 into a muffle furnace, set the heating rate to 2.5℃ / min, the calcination temperature to 230℃, and the holding time to 2h.

[0111] Step 6: Encapsulate the sample obtained in Step 5 with silicone, which can be freely cut into the desired shape.

[0112] Example 9

[0113] This embodiment provides a silver micro / nanofiber membrane with a hollow tubular structure, composed of multiple layers of fibers. The fiber structure is a structure with silver nanoparticles on the surface and a hollow interior. Silver nitrate-containing fibers are pre-separated under ultraviolet light induction and then reduced to silver particles by high-temperature calcination, while simultaneously removing organic matter, forming a hollow tubular fiber structure. The specific preparation method is as follows:

[0114] Step 1: Dissolve 0.230g of PVP powder in 1.90g of acetonitrile solution; then stir at room temperature for at least 30 minutes until completely dissolved to form a colorless solution.

[0115] Step 2: Add 1.3g of silver nitrate solid particles to the solution obtained in Step 1, and stir at room temperature for at least 30 minutes until completely dissolved. The stirring process should be carried out in the dark to obtain a pale yellow transparent solution.

[0116] Step 3: The solution obtained in Step 2 is used to prepare fibers using air-jet spinning technology and then dried in a 40°C drying oven.

[0117] Step 4: Irradiate the fibers obtained in Step 3 under a UV light source. The distance between the UV light source and the fibers is 10 cm, the illuminance near the UV lamp tube is 300,000 lux, and the irradiation time is 30 min. After irradiation, flip the fibers over and irradiate them again for 30 min. This allows the fibers to enter the pre-phase separation process and form a coating structure. At the same time, a small amount of silver particles are reduced.

[0118] Step 5: Place the fibers obtained in Step 4 into a muffle furnace, set the heating rate to 1.3℃ / min, the calcination temperature to 220℃, and the holding time to 2h.

[0119] Step 6: Encapsulate the sample obtained in Step 5 with silicone, which can be freely cut into the desired shape.

[0120] Example 10

[0121] This embodiment provides a silver micro / nanofiber membrane with a hollow tubular structure, composed of multiple layers of fibers. The fiber structure is a structure with silver nanoparticles on the surface and a hollow interior. Silver nitrate-containing fibers are pre-separated under ultraviolet light induction and then reduced to silver particles by high-temperature calcination, while simultaneously removing organic matter, forming a hollow tubular fiber structure. The specific preparation method is as follows:

[0122] Step 1: Dissolve 0.248g of PVP powder in 2.18g of acetonitrile solution; then stir at room temperature for at least 30 minutes until completely dissolved to form a colorless solution.

[0123] Step 2: Add 1.7g of silver nitrate solid particles to the solution obtained in Step 1, and stir at room temperature for at least 30 minutes until completely dissolved. The stirring process should be carried out in the dark to obtain a pale yellow transparent solution.

[0124] Step 3: The solution obtained in Step 2 is used to prepare fibers using air-jet spinning technology and then dried in a 40°C drying oven.

[0125] Step 4: Irradiate the fibers obtained in Step 3 under a UV light source. The distance between the UV light source and the fibers is 10 cm, the illuminance near the UV lamp tube is 300,000 lux, and the irradiation time is 30 min. After irradiation, flip the fibers over and irradiate them again for 30 min. This allows the fibers to enter the pre-phase separation process and form a coating structure. At the same time, a small amount of silver particles are reduced.

[0126] Step 5: Place the fibers obtained in Step 4 into a muffle furnace, set the heating rate to 1.3℃ / min, the calcination temperature to 220℃, and the holding time to 2h.

[0127] Step 6: Encapsulate the sample obtained in Step 5 with silicone, which can be freely cut into the desired shape.

[0128] Example 11

[0129] This embodiment provides a silver micro / nanofiber membrane with a hollow tubular structure, composed of multiple layers of fibers. The fiber structure is a structure with silver nanoparticles on the surface and a hollow interior. Silver nitrate-containing fibers are pre-separated under ultraviolet light induction and then reduced to silver particles by high-temperature calcination, while simultaneously removing organic matter, forming a hollow tubular fiber structure. The specific preparation method is as follows:

[0130] Step 1: Dissolve 0.260g of PVP powder in 2.30g of acetonitrile solution; then stir at room temperature for at least 30 minutes until completely dissolved to form a colorless solution.

[0131] Step 2: Add 2.0g of silver nitrate solid particles to the solution obtained in Step 1, and stir at room temperature for at least 30 minutes until completely dissolved. The stirring process should be carried out in the dark to obtain a pale yellow transparent solution.

[0132] Step 3: The solution obtained in Step 2 is used to prepare fibers using air-jet spinning technology and then dried in a 40°C drying oven.

[0133] Step 4: Irradiate the fibers obtained in Step 3 under a UV light source. The distance between the UV light source and the fibers is 10 cm, the illuminance near the UV lamp tube is 300,000 lux, and the irradiation time is 30 min. After irradiation, flip the fibers over and irradiate them again for 30 min. This allows the fibers to enter the pre-phase separation process and form a coating structure. At the same time, a small amount of silver particles are reduced.

[0134] Step 5: Place the fibers obtained in Step 4 into a muffle furnace, set the heating rate to 1.3℃ / min, the calcination temperature to 220℃, and the holding time to 2h.

[0135] Step 6: Encapsulate the sample obtained in Step 5 with silicone, which can be freely cut into the desired shape.

[0136] Example 12

[0137] This embodiment provides a silver micro / nanofiber membrane with a hollow tubular structure, composed of multiple layers of fibers. The fiber structure is a structure with silver nanoparticles on the surface and a hollow interior. Silver nitrate-containing fibers are pre-separated under ultraviolet light induction and then reduced to silver particles by high-temperature calcination, while simultaneously removing organic matter, forming a hollow tubular fiber structure. The specific preparation method is as follows:

[0138] Step 1: Dissolve 0.248g of PVP powder in 2.14g of acetonitrile solution; then stir at room temperature for at least 30 minutes until completely dissolved to form a colorless solution.

[0139] Step 2: Add 1.6g of silver nitrate solid particles to the solution obtained in Step 1, and stir at room temperature for at least 30 minutes until completely dissolved. The stirring process should be carried out in the dark to obtain a pale yellow transparent solution.

[0140] Step 3: The solution obtained in Step 2 is used to prepare fibers using electrospinning technology and then dried in a drying oven at 40°C.

[0141] Step 4: Irradiate the fibers obtained in Step 3 under a UV light source. The distance between the UV light source and the fibers is 10 cm, the illuminance near the UV lamp tube is 300,000 lux, and the irradiation time is 30 min. After irradiation, flip the fibers over and irradiate them again for 30 min. This allows the fibers to enter the pre-phase separation process and form a coating structure. At the same time, a small amount of silver particles are reduced.

[0142] Step 5: Place the fibers obtained in Step 4 into a muffle furnace, set the heating rate to 1.3℃ / min, the calcination temperature to 230℃, and the holding time to 2h.

[0143] Step 6: Encapsulate the sample obtained in Step 5 with silicone, which can be freely cut into the desired shape.

[0144] Comparative Example 1

[0145] This comparative example provides a conventional ultraviolet silver nanofiber material with a surface composed of silver nanoparticles. The silver particles are formed by reducing silver nitrate fibers to silver particles under ultraviolet light irradiation, and the electromagnetic shielding efficiency is 5 dB. The specific preparation method is shown below:

[0146] Step 1: Dissolve 0.248g of PVP powder in 2.14g of acetonitrile solution; then stir at room temperature for at least 30 minutes until completely dissolved to form a colorless solution.

[0147] Step 2: Add 1.6g of silver nitrate solid particles to the solution obtained in Step 1, and stir at room temperature for at least 30 minutes until completely dissolved. The stirring process should be carried out in the dark to obtain a pale yellow transparent solution.

[0148] Step 3: Add 50 μL of FS3100 to the solution obtained in Step 2 and stir for 30 min to obtain the precursor solution.

[0149] Step 4: The solution obtained in Step 3 is used to prepare fibers using air-jet spinning technology and then dried in a 40°C drying oven.

[0150] Step 5: Place the fibers obtained in Step 4 under a UV light source, with a distance of 10 cm between the UV light source and the fibers, an illuminance of 300,000 lux near the UV lamp tube, and an irradiation time of 2 hours; after irradiation, flip the fibers over and irradiate them again for 2 hours to reduce the silver particles.

[0151] Step 6: Encapsulate the sample obtained in Step 5 with silicone.

[0152] I. Performance Testing Methods

[0153] 1. Electromagnetic shielding efficiency test method: The test is conducted using a vector network analyzer, and the results are calculated from the S-parameters.

[0154] The calculation formula is:

[0155]

[0156]

[0157]

[0158] 2. Resistance measurement method: Use a multimeter with the probes spaced 1cm apart to measure the resistance value of the sample.

[0159] 3. Bending resistance test method: A flexible electronic tester, combined with an electrochemical workstation and a computer, was used to test the change in current signal during cyclic bending. The data was processed into a curve of resistance change rate versus bending times. Measurement parameters: 0-100°, 20° / s.

[0160] II. Performance Test Results

[0161] In this invention, the electromagnetic shielding efficiency of the silver micro-nanofiber materials obtained in Example 1 and Comparative Example 1 was tested, and the results were as follows: Figure 1 The electromagnetic shielding efficiency (SET) curve is shown, and the electromagnetic shielding efficiency, the ratio of the sample area after calcination to that before calcination, and the resistance value of the 1cm sample are summarized in Table 1 below.

[0162] It can be seen that the electromagnetic shielding material obtained by combining ultraviolet reduction and calcination processes has a significantly improved electromagnetic shielding efficiency compared to the sensing material obtained by traditional ultraviolet processing, thereby improving the overall performance of the material; at the same time, the silver nitrate content also affects the resistance, and this range is adjustable.

[0163] Table 1 shows the test results of electromagnetic shielding efficiency, remaining area ratio, resistance value, and film thickness of the samples provided in the examples and comparative examples.

[0164]

[0165]

[0166] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a silver micro / nanofiber membrane with a hollow tubular structure, characterized in that, Includes the following steps: A precursor solution is prepared by dissolving raw materials containing organic framework materials and silver nitrate in an organic solvent; the precursor solution is then spun into fibers. Pre-phase separation is induced by ultraviolet light irradiation to form a coated structure. The outer layer of the coated structure consists of silver particles, and the core is a mixture of organic framework material and silver nitrate. The silver particles here are partially reduced by ultraviolet light irradiation. Hollow tubular fiber structure is formed by calcination reduction of silver nitrate and decomposition of organic framework material. Its macroscopic appearance is a fiber film or fiber sponge. The ultraviolet light irradiation parameters include: the distance from the light source to the sample is 5 cm to 15 cm, the illuminance near the ultraviolet lamp tube is 300,000 lux to 350,000 lux, and the irradiation time for each side of the fiber is 20 min to 40 min.

2. The method for preparing a silver micro / nanofiber membrane with a hollow tubular structure according to claim 1, characterized in that, The organic framework material includes synthetic polymers and / or natural polymers; the synthetic polymers include one or more combinations of polyacrylonitrile, polyvinylpyrrolidone, polymethyl methacrylate, polyamide, polylactic acid, polyimide, polyethylene oxide, and polyimide dioxime; and the organic solvents include one or more combinations of acetonitrile, ethanol, and dimethyl sulfoxide.

3. The method for preparing a silver micro / nanofiber membrane with a hollow tubular structure according to claim 1, characterized in that, The spinning method employs either air-jet spinning or electrospinning technology, with an ambient humidity of 20% to 60%.

4. The method for preparing a silver micro / nanofiber membrane with a hollow tubular structure according to claim 1, characterized in that, It also includes a drying step; after the fibers are spun into fibers, they are dried and then subjected to ultraviolet light irradiation.

5. A method for preparing a silver micro / nanofiber membrane with a hollow tubular structure according to any one of claims 1 to 4, characterized in that, The calcination temperature is 210℃~230℃, and the holding time is 1.5h~2.5h; during the calcination treatment, the heating rate is 1℃ / min~5℃ / min.

6. A silver micro / nanofiber membrane with a hollow tubular structure prepared by the preparation method described in claim 5, characterized in that, The sample has a macroscopic morphology of a thin film or sponge, and the constituent fibers are hollow tubular fibers composed of silver particles.

7. A silver micro / nanofiber membrane with a hollow tubular structure according to claim 6, characterized in that, The fiber diameter is 0.5μm to 3μm.

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