A method for preparing a liquid metal-alumina fiber composite conductive material resistant to oxidation at high temperatures

Abstract

The application discloses a preparation method and material of a liquid metal-alumina fiber composite conductive material resistant to oxidation at high temperature and application, and belongs to the technical field of high-temperature conductive composite materials. The application first dissolves and mixes aluminum nitrate nonahydrate and polyvinylpyrrolidone to prepare a spinning solution, and then obtains an alumina fiber net through electrostatic spinning, sintering and water jet reinforcement; then the fiber net is needled with a gallium-based liquid metal at a specific mass ratio to prepare a target composite conductive material. The application uses alumina fibers as a carrier and realizes the conduction of the gallium-based liquid metal, utilizes the characteristics of self-passivation of the liquid metal and formation of a conductive oxide film at high temperature, so that the material can maintain stable conductivity and excellent oxidation resistance in an oxygen environment at 1000 DEG C, and has good mechanical stability. The material preparation process is feasible and the structure is flexible, and the material can be widely applied to the fields of aerospace, heavy industry high-temperature monitoring, metallurgy and high-temperature nuclear reaction monitoring.

Description

Technical Field

[0001] This invention relates to the field of high-temperature conductive composite materials technology, specifically to a liquid metal-alumina fiber composite material with oxidation resistance, high conductivity and suitability for high-temperature oxygen environments, as well as its preparation method and application. Background Technology

[0002] The demand for high-temperature conductive materials is growing in aerospace, metallurgy, nuclear industry, and high-temperature monitoring equipment. While widely used carbon-based conductive materials possess good conductivity, their poor oxidation resistance makes them prone to oxidation failure in oxygen-containing high-temperature environments, leading to a significant decrease in conductivity and making it difficult to maintain long-term stable operation in oxidizing atmospheres above 600°C. Although alloy conductive materials possess some degree of high-temperature stability, they still face problems such as conductivity degradation and structural instability near 1000°C, limiting their application in extreme environments. Summary of the Invention

[0003] Technical issues At temperatures near 1000°C, the conductivity of alloy materials degrades and the structure becomes unstable. Existing alumina-based ceramic fiber composite materials only focus on thermal insulation and have no electrical conductivity, which cannot meet the needs of aerospace and other fields for stable conductive materials in high-temperature and oxygen-containing environments.

[0004] Technical content To address the aforementioned technical problems, this invention develops a novel composite conductive material that combines excellent high-temperature conductivity, oxidation stability, process feasibility, and structural flexibility. This material combines liquid metal with alumina fibers, leveraging the high conductivity and self-passivation properties of the liquid metal, as well as its ability to form a conductive oxide film at high temperatures, to construct a stable conductive composite material suitable for high-temperature oxidizing environments.

[0005] This invention provides a method for preparing a high-temperature resistant liquid metal-alumina fiber composite conductive material, the preparation method comprising the following steps: Aluminum nitrate nonahydrate, polyvinylpyrrolidone, ethanol, and water are mixed and stirred to obtain a spinning solution; The fiber preform is initially spun using an electrospinning device, and then the fiber web is sintered. After sintering, the fiber web is reinforced by hydroentangling to obtain a structurally stable alumina fiber web. Gallium-based liquid metal and reinforced alumina fiber mesh are combined by needle punching to obtain a high-temperature oxidation-resistant liquid metal-alumina fiber composite conductive material.

[0006] Furthermore, the mass ratio of the aluminum nitrate nonahydrate to polyvinylpyrrolidone is 10~50:1.

[0007] Preferably, the mass ratio of aluminum nitrate nonahydrate to polyvinylpyrrolidone is 20-40:1.

[0008] More preferably, the mass ratio of aluminum nitrate nonahydrate to polyvinylpyrrolidone is 25~35:1.

[0009] Furthermore, the mass ratio of ethanol to polyvinylpyrrolidone is 20~50:1.

[0010] Furthermore, the mass ratio of water to polyvinylpyrrolidone is 40~80:1.

[0011] Furthermore, the stirring time is 6-8 hours; after stirring, the mixture is allowed to stand for 30-60 minutes to remove bubbles.

[0012] Furthermore, the diameter of the syringe needle in the electrospinning process is 0.5~0.8mm.

[0013] Furthermore, the syringe propulsion rate for electrospinning is 0.3~0.8 mL / h.

[0014] Furthermore, the electrospinning voltage is 15~25kV, and the distance between the needle and the receiving device is 15~20cm.

[0015] Furthermore, the sintering temperature is 800~1100℃.

[0016] Preferably, the sintering temperature is 850~950℃.

[0017] Furthermore, the hydroentangling process involves spraying water through a needle to rinse the fiber web, thereby compressing and pressurizing the fiber web without damaging its fiber structure; the diameter of the needle is 0.5~0.8mm.

[0018] Furthermore, the gallium-based liquid metal has a melting point of 16°C and is liquid at room temperature.

[0019] Furthermore, the mass ratio of the gallium-based liquid metal to the alumina fiber is 20 to 30:1.

[0020] Preferably, the mass ratio of the gallium-based liquid metal to the alumina fiber is 22 to 27:1.

[0021] Furthermore, the needling frequency in the acupuncture process is 12~36 times / s.

[0022] Furthermore, the needling time in the acupuncture process is 1 to 30 minutes.

[0023] Preferably, the needling frequency in the acupuncture process is 18-36 times / s, and the needling time is 5-25 minutes.

[0024] Specifically, the acupuncture frequency is 18 times / second, and the acupuncture time is 20-25 minutes.

[0025] Specifically, the acupuncture frequency is 21 times / second, and the acupuncture time is 15-25 minutes.

[0026] Specifically, the acupuncture frequency is 24 times / second, and the acupuncture time is 8-15 minutes.

[0027] Specifically, the acupuncture frequency is 27 times / second, and the acupuncture time is 8-15 minutes.

[0028] Specifically, the acupuncture frequency is 30 times / second, and the acupuncture time is 5 to 15 minutes.

[0029] Specifically, the acupuncture frequency is 33 times / second, and the acupuncture time is 5-15 minutes.

[0030] Specifically, the acupuncture frequency is 36 times / second, and the acupuncture time is 5-15 minutes.

[0031] Furthermore, the needle density of the needle-punching process is 90~300 needles / cm². 2 .

[0032] This invention provides a high-temperature resistant liquid metal-alumina fiber composite conductive material prepared as described above.

[0033] The high-temperature resistant liquid metal-alumina fiber composite conductive material provided by this invention has applications in aerospace, high-temperature monitoring in heavy industry, metallurgical industry, and high-temperature nuclear reaction monitoring.

[0034] Beneficial effects (1) The high-temperature antioxidant liquid metal-alumina fiber composite conductive material prepared by this invention combines the high-temperature structural stability of alumina fiber with the high conductivity of gallium-based liquid metal. Utilizing the self-passivation properties of liquid metal and its ability to form a conductive oxide film at high temperatures, it achieves stable conductivity in an oxygen-rich environment at 1000℃. Compared with traditional high-temperature conductive materials, the composite conductive material prepared by this invention has higher and more stable conductivity, excellent antioxidant properties, and can be used in textiles, aerospace, heavy industry high-temperature monitoring, metallurgical industry, and high-temperature nuclear reaction monitoring, greatly expanding its application scenarios and enhancing the material's performance and application value under extreme environments.

[0035] (2) The preparation process of this invention adopts a combination of electrospinning, hydroentangling reinforcement and needle punching. The process is simple and controllable, and the parameters are easy to adjust, combining good process feasibility and structural flexibility. The material also has excellent mechanical stability and oxidation resistance, and can be widely used in extreme high-temperature scenarios such as aerospace, high-temperature monitoring in heavy industry, metallurgical industry and high-temperature nuclear reaction monitoring, which greatly expands the application range of high-temperature conductive materials and improves the reliability and practicality of conductive monitoring in extreme environments. Attached Figure Description

[0036] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein: Figure 1 This is a schematic diagram of the process in Example 1 of the present invention, in which aluminum nitrate nonahydrate and spinning aid polyvinylpyrrolidone are dissolved in a solution of anhydrous ethanol and deionized water, stirred and sonicated, and then allowed to stand to remove air bubbles to obtain a spinning solution. After electrospinning, sintering, hydroentangling, and composite preparation of liquid metal and alumina fiber, a liquid metal-alumina fiber composite conductive material is prepared.

[0037] Figure 2 The diagram shows the conductivity of the liquid metal-alumina fiber composite conductive material prepared in Example 3 and Comparative Example 3 of this invention (blue areas are conductive, red areas are non-conductive, and gray areas have excessive strength loss).

[0038] Figure 3 This is a comparison chart of the conductivity of the raw material ratios of the liquid metal-alumina fiber composite conductive materials prepared in Example 2 and Comparative Example 4 of the present invention.

[0039] Figure 4 This is a schematic diagram of the hydroentanglement process in an embodiment of the present invention. Detailed Implementation

[0040] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0041] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0042] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0043] The method for determining the conductivity of the high-temperature resistant liquid metal-alumina fiber composite conductive material is as follows: the liquid metal-alumina fiber composite conductive material is fixed on a ceramic-based heat insulation plate, the liquid metal-alumina fiber composite conductive material is heated by an infrared laser heating device, and the material is connected to an electrochemical workstation using wires for resistance monitoring and data recording.

[0044] The method for determining the conductivity stability of the high-temperature resistant liquid metal-alumina fiber composite conductive material is as follows: The liquid metal-alumina fiber composite conductive material is connected to a power source using a wire, and an electrochemical workstation is connected in series. The material is then energized at 1000°C for an extended period, and the resistance change is observed using the electrochemical workstation. The liquid metal-alumina fiber composite conductive material is subjected to 30 cycles of increasing the temperature from room temperature to 1000°C, and the resistance value is measured at each 1000°C increase to observe its variation.

[0045] The liquid metal used in this invention is gallium-based liquid metal at -16°C.

[0046] Unless otherwise specified, all raw materials used in this invention are commercially available.

[0047] Example 1 This embodiment provides a method for preparing a high-temperature resistant liquid metal-alumina fiber composite conductive material, specifically as follows: (1) Mix aluminum nitrate nonahydrate and polyvinylpyrrolidone evenly, add anhydrous ethanol and deionized water. The mass ratio of aluminum nitrate nonahydrate, polyvinylpyrrolidone, anhydrous ethanol and deionized water in the whole solution is 20:1:28:52. Stir for 6 hours, then ultrasonically diffuse for 30 minutes and let stand to remove bubbles to obtain spinning mother liquor. (2) The fiber web was initially spun using an electrospinning device at 20kV, with a needle-to-receiver distance of 20 cm and a feed rate of 0.5 mL / h. The fiber web was then sintered at 900℃ for 4 h. After sintering, the fiber web was reinforced by spraying water through a 0.8 mm needle with high pressure to obtain a structurally stable alumina fiber web. (3) Gallium-based liquid metal was placed on the surface of the above-mentioned stable alumina fiber mesh (the mass ratio of liquid metal to alumina fiber was 1:30, and the area of ​​the alumina fiber mesh was 10cm×10cm). The composite was carried out by needle punching process with a needle punching frequency of 30 times / s and a needle punching time of 5min. Finally, liquid metal-alumina fiber composite conductive material was prepared.

[0048] Example 2 This embodiment provides a method for preparing a high-temperature resistant liquid metal-alumina fiber composite conductive material, specifically as follows: (1) Mix aluminum nitrate nonahydrate and polyvinylpyrrolidone evenly, add anhydrous ethanol and deionized water. The mass ratio of aluminum nitrate nonahydrate, polyvinylpyrrolidone, anhydrous ethanol and deionized water in the whole solution is 30:1:44:68. Stir for 6 hours, then ultrasonically diffuse for 30 minutes and let stand to remove bubbles to obtain spinning mother liquor. (2) The fiber web was initially spun using an electrospinning device at 20kV, with a needle-to-receiver distance of 20 cm and a feed rate of 0.5 mL / h. The fiber web was then sintered at 900℃ for 4 h. After sintering, the fiber web was reinforced by spraying water through a 0.8 mm needle with high pressure to obtain a structurally stable alumina fiber web. (3) Gallium-based liquid metal was placed on the surface of the above-mentioned stable alumina fiber mesh (the mass ratio of liquid metal to alumina fiber was 1:30, and the area of ​​the alumina fiber mesh was 10cm×10cm). The composite was carried out by needle punching process with a needle punching frequency of 30 times / s and a needle punching time of 5min. Finally, liquid metal-alumina fiber composite conductive material was prepared.

[0049] Example 3 This embodiment provides a method for preparing a high-temperature resistant liquid metal-alumina fiber composite conductive material, specifically as follows: (1) Mix aluminum nitrate nonahydrate and polyvinylpyrrolidone evenly, add anhydrous ethanol and deionized water. The mass ratio of aluminum nitrate nonahydrate, polyvinylpyrrolidone, anhydrous ethanol and deionized water in the whole solution is 30:1:44:68. Stir for 6 hours, then ultrasonically diffuse for 30 minutes and let stand to remove bubbles to obtain spinning mother liquor. (2) The fiber web was initially spun using an electrospinning device at 20kV, with a needle-to-receiver distance of 20 cm and a feed rate of 0.5 mL / h. The fiber web was then sintered at 900℃ for 4 h. After sintering, the fiber web was reinforced by spraying water through a 0.8 mm needle with high pressure to obtain a structurally stable alumina fiber web. (3) Gallium-based liquid metal was placed on the surface of the above-mentioned stable alumina fiber mesh (the mass ratio of liquid metal to alumina fiber was 1:40, and the area of ​​the alumina fiber mesh was 10cm×10cm). The composite was carried out by needle punching process with a needle punching frequency of 30 times / s and a needle punching time of 5min. Finally, liquid metal-alumina fiber composite conductive material was prepared.

[0050] Comparative Example 1 The difference between this comparative example and Example 1 is that the mass ratio of aluminum nitrate nonahydrate and polyvinylpyrrolidone in step (1) is adjusted to 10:1, 20:1, 30:1, 40:1, and 50:1 to prepare the liquid metal-alumina fiber composite conductive material of this comparative example.

[0051] The mechanical properties of the iron powder-induced thermochromic polydimethylsiloxane fibers prepared in Example 1 and Comparative Example 1 were measured, and the results are shown in Table 1.

[0052] Table 1 Comparison of mechanical properties of alumina fibers prepared with different mass ratios

[0053] Note: Poor means almost no adsorption; Very poor means weak adsorption and poor interfacial binding; Good means good adsorption that meets basic requirements; Fairly good means relatively good adsorption and stable interfacial binding; Excellent means excellent adsorption that completely covers the fiber and has a tight interfacial binding.

[0054] As can be seen from the table, when the mass ratio of aluminum nitrate nonahydrate to PVP is between 20:1 and 40:1, the alumina fibers produced by electrospinning exhibit better performance, with a bulk density of 3.2 g / cm³. 3 The following materials exhibit good porosity. The porosity is highest when the mass ratio is 30:1. Excessive or insufficient PVP content reduces porosity and strength, and the porosity of the fibers directly affects the adsorption effect of alumina fibers on liquid metals, thus impacting subsequent composite processes.

[0055] Comparative Example 2 The difference between this comparative example and Example 2 is that the sintering temperatures of the green alumina fibers in step (2) were adjusted to 700℃, 750℃, 800℃, 850℃, 900℃, 950℃, 1000℃, and 1100℃, respectively, to prepare liquid metal-alumina fiber composite conductive materials.

[0056] The electromagnetic induction heating properties of the iron powder-induced thermochromic polydimethylsiloxane fibers prepared in Example 2 and Comparative Example 2 were measured, as shown in Table 2.

[0057] Table 2 Comparison of mechanical properties of alumina fibers prepared at different sintering temperature ratios

[0058] Note: Poor means almost no adsorption; Very poor means weak adsorption and poor interfacial binding; Good means good adsorption that meets basic requirements; Fairly good means relatively good adsorption and stable interfacial binding; Excellent means excellent adsorption that completely covers the fiber and has a tight interfacial binding.

[0059] As shown in Table 2, a sintering temperature of 900℃ yields the best results. Higher sintering temperatures result in higher porosity of the alumina fibers, but a decrease in strength. This is because excessively high sintering temperatures affect the internal structure of the alumina fibers, leading to a decrease in mechanical properties while simultaneously increasing porosity. To obtain high-quality alumina fibers, it is best to preserve a larger porosity before the mechanical properties deteriorate. Therefore, the optimal sintering temperature is 900℃.

[0060] Comparative Example 3 The difference between this comparative example and Example 3 is that the needle punching frequency in step (3) is adjusted to 12, 15, 18, 21, 24, 27, 30, 33, 36 times / s and the needle punching time is adjusted to 1, 2, 3, 5, 8, 10, 15, 20, 25, 30 min, respectively, to prepare liquid metal-alumina fiber composite conductive material.

[0061] The conductivity of the liquid metal-alumina fiber composite conductive materials prepared in Example 3 and Comparative Example 3 was measured, and the results are as follows: Figure 2 As shown.

[0062] from Figure 2 As can be seen, with the increase of the needle punching frequency, the preparation time is shorter. However, as the needle punching frequency and time increase, the overall strength of the composite material decreases. The red background in the figure represents the process range without stable conductivity, the blue background represents the process range with stable conductivity, and the gray background represents the process range where the strength decreases significantly due to excessive needle punching frequency and time. When the needle punching frequency is 30 times / s and the needle punching time is shortened to 5 minutes, the prepared liquid metal-alumina fiber composite conductive material has the highest efficiency, while also possessing the strength characteristics of general alumina fibers.

[0063] Comparative Example 4 The difference between this comparative example and Example 3 is that the mass ratio of liquid metal to alumina fiber in step (2) is adjusted to 1:20, 1:30, 1:40, 1:50, and 1:60, respectively, to prepare a liquid metal-alumina fiber composite conductive material.

[0064] The conductivity of the liquid metal-alumina fiber composite conductive materials prepared in Example 2 and Comparative Example 4 was measured, and the results are as follows: Figure 3 As shown.

[0065] from Figure 3 As can be seen, with the increase of the proportion of liquid metal, the ratio of alumina fiber to liquid metal stabilizes at about 1:25, and the conductivity of the liquid metal-alumina fiber composite conductive material stabilizes at 2~3 S / m.

[0066] In summary, this invention discloses a liquid metal-alumina fiber composite material, its preparation method, and its applications. The material uses alumina fibers as a carrier, with a gallium-based liquid metal coating on the surface, and achieves three-dimensional interpenetrating composite bonding through a needle-punching process. The material maintains excellent electrical conductivity even in an oxygen-rich environment at 1000℃, and possesses good oxidation resistance and mechanical stability. This material is suitable for extreme environments such as high-temperature sensors and aerospace monitoring, and has significant industrial application value.

[0067] It should be noted that 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 preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for preparing a high-temperature oxidation-resistant liquid metal-alumina fiber composite conductive material, characterized in that, The preparation method includes the following steps: A spinning solution is prepared by mixing and stirring aluminum nitrate nonahydrate, polyvinylpyrrolidone, ethanol and water; the mass ratio of aluminum nitrate nonahydrate to polyvinylpyrrolidone is 10~50:

1. The fiber preform is initially spun using an electrospinning device, and then the fiber web is sintered. After sintering, the fiber web is reinforced by hydroentangling to obtain a structurally stable alumina fiber web. The sintering temperature is 850~950℃. Gallium-based liquid metal and reinforced alumina fiber mesh are composited via needle punching to obtain a high-temperature oxidation-resistant liquid metal-alumina fiber composite conductive material. The mass ratio of gallium-based liquid metal to alumina fiber is 20-30:

1. The needle punching process involves a needle punching frequency of 18-36 times / s, a needle punching time of 5-25 minutes, and a needle punching density of 90-300 needles / cm². 2 .

2. The preparation method according to claim 1, characterized in that, The mass ratio of aluminum nitrate nonahydrate to polyvinylpyrrolidone is 20~40:

1.

3. The preparation method according to claim 1, characterized in that, The mass ratio of ethanol to polyvinylpyrrolidone is 20-50:1; the mass ratio of water to polyvinylpyrrolidone is 40-80:

1.

4. The preparation method according to claim 1, characterized in that, The syringe needle diameter for electrospinning is 0.5~0.8mm, and the syringe injection rate is 0.3~0.8mL / h; the electrospinning voltage is 15~25kV, and the distance between the needle and the receiving device is 15~20cm.

5. The preparation method according to claim 1, characterized in that, The hydroentanglement is achieved by spraying high-pressure water through a needle tip to rinse the fiber web. The diameter of the needle tip is 0.5~0.8mm.

6. The preparation method according to claim 1, characterized in that, The mass ratio of the liquid metal to the alumina fiber is 22 to 27:

1.

7. The preparation method according to claim 1, characterized in that, When the acupuncture frequency is 18 times / s, the acupuncture time is 20-25 minutes; when the acupuncture frequency is 21 times / s, the acupuncture time is 15-25 minutes; when the acupuncture frequency is 24 times / s, the acupuncture time is 8-15 minutes; when the acupuncture frequency is 27 times / s, the acupuncture time is 8-15 minutes; when the acupuncture frequency is 30 times / s, the acupuncture time is 5-15 minutes; when the acupuncture frequency is 33 times / s, the acupuncture time is 5-15 minutes; when the acupuncture frequency is 36 times / s, the acupuncture time is 5-15 minutes.

8. A liquid metal-alumina fiber composite conductive material resistant to oxidation at high temperatures, characterized in that, The liquid metal-alumina fiber composite conductive material is prepared by the method according to any one of claims 1 to 7.

9. The high-temperature resistant liquid metal-alumina fiber composite conductive material as described in claim 8 is used in aerospace, high-temperature monitoring in heavy industry, metallurgical industry, and high-temperature nuclear reaction monitoring.

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