A method for improving high-temperature oxidation resistance of carbon fibers

Abstract

The application relates to the technical field of wave-absorbing materials and mineral material utilization, and discloses a method for improving high-temperature oxidation resistance of carbon fibers, which comprises the following steps: surface modification of pretreated attapulgite fibers by a modifier, then hydroxylation treatment of the carbon fibers by hydrogen peroxide to obtain carbon fibers with a large amount of hydroxyl groups on the surface and greatly increased activity, and then hydrogen transfer reaction of the modified attapulgite fibers and the hydroxylated carbon fibers to realize chemical compounding of the attapulgite fibers and the carbon fibers. The attapulgite can form a uniform, dense and stable coating layer on the surface of the carbon fibers, blocks the transmission channel of oxygen, and further improves the high-temperature oxidation resistance of the carbon fibers. The application uses natural attapulgite fibers as the coating material, adopts a simple chemical grafting method, has simple process, low material cost, avoids complicated process and use of a large amount of solvents, and realizes low-cost and green and environment-friendly preparation of the carbon fiber-attapulgite composite wave-absorbing material.

Description

Technical Field

[0001] This invention relates to the field of microwave absorbing materials and mineral material utilization technology, and in particular to a method for improving the high-temperature oxidation resistance of carbon fibers. Background Technology

[0002] With the rapid development of modern electronics and wireless communication, various electronic and electrical devices have been widely used in various fields, such as communication and navigation, broadcasting and television, high-frequency medical equipment, and household appliances. These devices and products generate a large amount of electromagnetic radiation. Electromagnetic radiation not only causes mutual interference between radiation sources but also pollutes the space in which humans live. When electromagnetic radiation reaches a certain intensity, it can affect the human immune, nervous, and reproductive systems, inducing various diseases. Absorbing materials can absorb or significantly reduce the energy of electromagnetic waves projected onto their surface, thereby reducing electromagnetic interference.

[0003] Carbon fiber is a special fiber composed of carbon elements. Due to its excellent mechanical properties, electrical conductivity, and superior thermal and chemical stability, it has been widely used in structural microwave absorbing materials. Furthermore, carbon fiber has a high dielectric loss, resulting in good microwave absorption performance. Therefore, the preparation of carbon fibers with good overall performance will make it possible for carbon fiber materials to be applied in practice. However, carbon fiber has poor oxidation resistance and cannot withstand high operating temperatures in air, which limits the use of carbon fiber microwave absorbing materials.

[0004] Therefore, surface treatment of carbon fibers to form a dense coating layer on their surface is an effective way to improve their oxidation resistance. Summary of the Invention

[0005] Objective: To address the problems existing in the prior art, this invention provides a method for improving the high-temperature oxidation resistance of carbon fibers. By using natural attapulgite as a surface coating material and carbon fibers as an absorbent, and employing chemical grafting technology, attapulgite fibers are coated onto the surface of the carbon fibers, forming a uniform, dense, and stable coating layer. This layer blocks oxygen transport channels, thereby improving the high-temperature oxidation resistance of the carbon fibers and achieving a low-cost, green, and environmentally friendly preparation of carbon fiber@attapulgite composite materials. This invention avoids complex processes and the use of large amounts of solvents, reducing subsequent processing steps and making it economical and environmentally friendly.

[0006] Technical solution: This invention provides a method for improving the high-temperature oxidation resistance of carbon fibers, comprising the following steps:

[0007] S1: The surface of the pretreated attapulgite fiber was modified with the modifier 3-aminopropyltriethoxysilane;

[0008] S2: Hydroxylation treatment of carbon fibers using hydrogen peroxide solution;

[0009] S3: The attapulgite fibers modified with 3-aminopropyltriethoxysilane obtained in S1 are reacted with the carbon fibers after hydroxylation treatment obtained in S2 to obtain carbon fiber@attapulgite composite material.

[0010] Further, in S1, the volume-to-mass ratio of 3-aminopropyltriethoxysilane to attapulgite fiber is 30-50 mL:2 g.

[0011] Furthermore, in S2, the concentration of the hydrogen peroxide is 10–30 wt%.

[0012] Further, in S1, the pretreatment specifically involves soaking the attapulgite fiber in an HCl solution with a concentration of 3 mol / L at 70-80 ℃ for 46-50 h.

[0013] Furthermore, in S2, the specific conditions for the hydroxylation treatment are as follows:

[0014] The reaction temperature is 60–80℃, and the treatment time is 2–6 h.

[0015] Furthermore, in S3, the mass ratio of the attapulgite fiber modified with 3-aminopropyltriethoxysilane to the hydroxylated carbon fiber is 1:6 to 20.

[0016] Furthermore, in S3, the specific conditions for the reaction are as follows:

[0017] The reaction temperature is 40–60℃, the reaction pH is 3–7, and the reaction time is 0.5–2 h.

[0018] The preparation principle of this invention is as follows:

[0019] This invention employs a chemical grafting method to achieve a stable coating of attapulgite fibers on the surface of carbon fibers. First, the pretreated attapulgite fibers are surface-modified using the modifier APTES. The ethoxy groups of APTES react with the silanol groups on the attapulgite surface through condensation to form new covalent bonds. This method can also modify the attapulgite surface with functional groups such as amino groups. Then, the carbon fibers are hydroxylated using a hydrogen peroxide solution, resulting in carbon fibers with a large number of hydroxyl groups and significantly increased activity. By controlling the reaction conditions and process parameters, the APTES-modified attapulgite fibers react with the carbon fibers. The amino groups introduced by APTES undergo hydrogen transfer reactions with the hydroxyl groups on the carbon fiber surface, forming new chemical bonds and achieving a chemical composite of attapulgite and carbon fibers. Because a large number of active hydroxyl groups are uniformly distributed on the carbon fiber surface, the hydrogen transfer reaction sites are also uniformly distributed. Furthermore, the attapulgite and carbon fibers are bonded by chemical bonds. Therefore, attapulgite can form a uniform, dense, and stable coating layer on the carbon fiber surface, resulting in a structurally stable carbon fiber@attapulgite composite material.

[0020] Beneficial effects: Compared with the prior art, the present invention improves the high-temperature oxidation resistance of carbon fibers by preparing a dense coating layer from attapulgite fibers with low conductivity, and has the following advantages:

[0021] 1) Natural attapulgite fiber replaces expensive synthetic raw materials such as silicon carbide. A dense coating layer is prepared using chemical grafting technology. The technology is simple and easy to operate, does not involve the use of a large amount of solvent, reduces subsequent processing, and is economical and environmentally friendly, realizing the low-cost and green preparation of carbon fiber@attapulgite.

[0022] 2) Attapulgite fiber has lower electrical conductivity than carbon fiber. By using chemical grafting technology, attapulgite fiber is coated on the surface of carbon fiber to form a uniform, dense and stable coating layer, which blocks the oxygen transport channel and improves the high-temperature oxidation resistance of carbon fiber.

[0023] 3) Attapulgite fiber itself is also a novel absorber with excellent wave absorption properties. The composite of attapulgite fiber and carbon fiber is expected to generate new loss mechanisms, thereby improving the wave absorption performance of carbon fiber.

[0024] 4) Currently, no domestic or international papers, patents, or other literature have described the use of attapulgite fiber as a coating layer in the coating treatment of carbon fibers. However, the applicant's use of readily available natural attapulgite as a coating layer not only improves the high-temperature oxidation resistance of carbon fibers but also effectively reduces the cost of preparing surface-coated carbon fibers. This successful research on the application of natural mineral material attapulgite fiber in the field of microwave absorption is expected to open up a new area for the application of attapulgite fiber and add value to the in-depth development and utilization of this unique resource in my country. Attached Figure Description

[0025] Figure 1 SEM images of carbon fiber (a), attapulgite fiber (b), carbon fiber@attapulgite-1 (c), carbon fiber@attapulgite-2 (d), and carbon fiber@attapulgite-3 (e).

[0026] Figure 2 The static oxidation experimental results are for carbon fiber, carbon fiber@attapulgite-1, carbon fiber@attapulgite-2, and carbon fiber@attapulgite-3. Detailed Implementation

[0027] The present invention will now be described in detail with reference to the embodiments.

[0028] Implementation method 1:

[0029] Attapulgite fibers were activated by soaking in a 3 mol / L HCl solution at 80 °C for 48 h. Then, 2.0 g of the activated attapulgite fibers were surface-modified with 40 mL of a modifier (APTES, 5% v / v). After reacting for 1 h, the fibers were centrifuged, washed, and dried to obtain APTES-modified attapulgite. Next, 12 g of carbon fibers were activated at 60 °C for 2 h using a 20% hydrogen peroxide solution, resulting in carbon fibers with a large number of hydroxyl groups and significantly increased activity. By controlling parameters such as reaction temperature (40 °C), solution pH (3), and reaction time (0.5 h), the APTES-modified attapulgite fibers reacted with the carbon fibers. The amino groups introduced by APTES underwent a hydrogen transfer reaction with the hydroxyl groups on the carbon fiber surface, forming new chemical bonds and achieving a chemical composite of attapulgite fibers and carbon fibers, resulting in a carbon fiber@attapulgite microwave absorbing composite material.

[0030] Implementation Method 2:

[0031] Attapulgite fibers were activated by soaking in a 3 mol / L HCl solution at 80 °C for 48 h. Then, 2.0 g of the activated attapulgite fibers were surface-modified with 40 mL of a modifier (APTES, 5% v / v). After reacting for 1 h, the fibers were centrifuged, washed, and dried to obtain APTES-modified attapulgite. Next, 12 g of carbon fibers were activated at 60 °C for 2 h using a 20% hydrogen peroxide solution, resulting in carbon fibers with a large number of hydroxyl groups and significantly increased activity. By controlling parameters such as reaction temperature (50 °C), solution pH (4), and reaction time (1 h), the APTES-modified attapulgite fibers reacted with the carbon fibers. The amino groups introduced by APTES underwent a hydrogen transfer reaction with the hydroxyl groups on the carbon fiber surface, forming new chemical bonds and achieving a chemical composite of attapulgite fibers and carbon fibers, resulting in a carbon fiber@attapulgite microwave absorbing composite material.

[0032] Implementation Method 3:

[0033] Attapulgite fibers were activated by soaking in a 3 mol / L HCl solution at 80 °C for 48 h. Then, 2.0 g of the activated attapulgite fibers were surface-modified with 40 mL of a modifier (APTES, 5% v / v). After reacting for 1 h, the fibers were centrifuged, washed, and dried to obtain APTES-modified attapulgite. Next, 12 g of carbon fibers were activated at 60 °C for 2 h using a 20% hydrogen peroxide solution, resulting in carbon fibers with a large number of hydroxyl groups and significantly increased activity. By controlling parameters such as reaction temperature (60 °C), solution pH (5), and reaction time (1.5 h), the APTES-modified attapulgite fibers reacted with the carbon fibers. The amino groups introduced by APTES underwent a hydrogen transfer reaction with the hydroxyl groups on the carbon fiber surface, forming new chemical bonds and achieving a chemical composite of attapulgite fibers and carbon fibers, resulting in a carbon fiber@attapulgite microwave absorbing composite material.

[0034] Implementation Method 4:

[0035] Attapulgite fibers were activated by soaking in a 3 mol / L HCl solution at 80 °C for 48 h. Then, 2.0 g of the activated attapulgite fibers were surface-modified with 40 mL of a modifier (APTES, 5% v / v). After reacting for 1 h, the fibers were centrifuged, washed, and dried to obtain APTES-modified attapulgite. Next, 20 g of carbon fibers were activated at 70 °C for 2 h using a 30% hydrogen peroxide solution, resulting in carbon fibers with a large number of hydroxyl groups and significantly increased activity. By controlling parameters such as reaction temperature (60 °C), solution pH (5), and reaction time (1.5 h), the APTES-modified attapulgite fibers reacted with the carbon fibers. The amino groups introduced by APTES underwent a hydrogen transfer reaction with the hydroxyl groups on the carbon fiber surface, forming new chemical bonds and achieving a chemical composite of attapulgite fibers and carbon fibers, resulting in a carbon fiber@attapulgite microwave absorbing composite material.

[0036] Implementation Method 5:

[0037] Attapulgite fibers were activated by soaking in a 3 mol / L HCl solution at 80 °C for 48 h. Then, 2.0 g of the activated attapulgite fibers were surface-modified with 40 mL of a modifier (APTES, 5% v / v). After reacting for 1 h, the fibers were centrifuged, washed, and dried to obtain APTES-modified attapulgite. Next, 20 g of carbon fibers were activated at 70 °C with a 30% hydrogen peroxide solution for 2 h, resulting in carbon fibers with a large number of hydroxyl groups and significantly increased activity. By controlling parameters such as reaction temperature (50 °C), solution pH (4), and reaction time (1 h), the APTES-modified attapulgite fibers reacted with the carbon fibers. The amino groups introduced by APTES underwent a hydrogen transfer reaction with the hydroxyl groups on the carbon fiber surface, forming new chemical bonds and achieving a chemical composite of attapulgite fibers and carbon fibers, resulting in a carbon fiber@attapulgite microwave absorbing composite material.

[0038] Implementation method 6:

[0039] Attapulgite fibers were activated by soaking in a 3 mol / L HCl solution at 80 °C for 48 h. Then, 2.0 g of the activated attapulgite fibers were surface-modified with 40 mL of a modifier (APTES, 5% v / v). After reacting for 1 h, the fibers were centrifuged, washed, and dried to obtain APTES-modified attapulgite. Next, 20 g of carbon fibers were activated at 70 °C for 4 h using a 20% hydrogen peroxide solution, resulting in carbon fibers with a large number of hydroxyl groups and significantly increased activity. By controlling parameters such as reaction temperature (40 °C), solution pH (4), and reaction time (0.5 h), the APTES-modified attapulgite fibers reacted with the carbon fibers. The amino groups introduced by APTES underwent a hydrogen transfer reaction with the hydroxyl groups on the carbon fiber surface, forming new chemical bonds and achieving a chemical composite of attapulgite fibers and carbon fibers, resulting in a carbon fiber@attapulgite microwave absorbing composite material, denoted as carbon fiber@attapulgite-1.

[0040] Implementation Method 7:

[0041] Attapulgite fibers were activated by soaking in a 3 mol / L HCl solution at 80 °C for 48 h. Then, 2.0 g of the activated attapulgite fibers were surface-modified with 40 mL of a modifier (APTES, 5% v / v). After reacting for 1 h, the fibers were centrifuged, washed, and dried to obtain APTES-modified attapulgite. Next, 20 g of carbon fibers were activated at 70 °C for 4 h using a 20% hydrogen peroxide solution, resulting in carbon fibers with a large number of hydroxyl groups and significantly increased activity. By controlling parameters such as reaction temperature (40 °C), solution pH (4), and reaction time (1 h), the APTES-modified attapulgite fibers reacted with the carbon fibers. The amino groups introduced by APTES underwent a hydrogen transfer reaction with the hydroxyl groups on the carbon fiber surface, forming new chemical bonds and achieving a chemical composite of attapulgite fibers and carbon fibers, resulting in a carbon fiber@attapulgite microwave absorbing composite material, denoted as carbon fiber@attapulgite-2.

[0042] Implementation Method 8:

[0043] Attapulgite fibers were activated by soaking in a 3 mol / L HCl solution at 80 °C for 48 h. Then, 2.0 g of the activated attapulgite fibers were surface-modified with 40 mL of a modifier (APTES, 5% v / v). After reacting for 1 h, the fibers were centrifuged, washed, and dried to obtain APTES-modified attapulgite. Next, 20 g of carbon fibers were activated at 70 °C for 4 h using a 20% hydrogen peroxide solution, resulting in carbon fibers with a large number of hydroxyl groups and significantly increased activity. By controlling parameters such as reaction temperature (40 °C), solution pH (4), and reaction time (1.5 h), the APTES-modified attapulgite fibers reacted with the carbon fibers. The amino groups introduced by APTES underwent a hydrogen transfer reaction with the hydroxyl groups on the carbon fiber surface, forming new chemical bonds and achieving a chemical composite of attapulgite fibers and carbon fibers, resulting in a carbon fiber@attapulgite microwave absorbing composite material, denoted as carbon fiber@attapulgite-3.

[0044] Figure 1 SEM images of carbon fiber (a), attapulgite fiber (b), carbon fiber@attapulgite-1 (c), carbon fiber@attapulgite-2 (d), and carbon fiber@attapulgite-3 (e). From Figure 1 (a) It can be seen that the carbon fiber diameter is around 10 μm, and the surface has uniformly distributed grooves and wrinkles. This structure provides favorable conditions for the coating of attapulgite fibers on the carbon fiber surface. Figure 1 (b) It can be seen that attapulgite is a uniformly dispersed fibrous mineral material with a diameter between 20-70 nm and a length between 1-5 μm. Figure 1 As shown in (c)-(e), attapulgite fibers have been successfully coated on the surface of carbon fibers, and with the increase of reaction time, the amount of attapulgite coating increases, and the resulting coating layer is denser and more uniform.

[0045] Figure 2 The static oxidation test results are presented for carbon fiber, carbon fiber@attapulgite-1, carbon fiber@attapulgite-2, and carbon fiber@attapulgite-3. According to the static oxidation experiment, the carbon fiber was kept at 600 ℃ for 2 h, and the oxidation weight loss rate was calculated to evaluate the high-temperature oxidation resistance of the carbon fiber. All samples were dried at 100 ℃ for 4 h before testing. The oxidation weight loss rate was calculated according to the following formula: In the formula, m0 represents the mass before static oxidation, and m1 represents the mass after static oxidation. The static oxidation experiment results show that the weight loss rate of the carbon fiber@attapulgite composite material in air is reduced, indicating that the high-temperature oxidation resistance of the composite material is improved. Furthermore, the oxidation resistance increases with the increase of the coating thickness.

[0046] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent transformations or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for improving the high-temperature oxidation resistance of carbon fibers, characterized in that, Includes the following steps: S1: The surface of the pretreated attapulgite fiber was modified with the modifier 3-aminopropyltriethoxysilane; S2: Hydroxylation treatment of carbon fibers using hydrogen peroxide solution; S3: The attapulgite fibers modified with 3-aminopropyltriethoxysilane obtained in S1 are reacted with the carbon fibers after hydroxylation treatment obtained in S2 to obtain carbon fiber@attapulgite composite material; the specific conditions of the reaction are: reaction temperature of 40℃, reaction pH of 4, and reaction time of 1 to 1.5 h. In the carbon fiber@attapulgite composite material, attapulgite fibers coat the surface of the carbon fiber, forming a uniform, dense, and stable coating layer that blocks the oxygen transport channel.

2. The method for improving the high-temperature oxidation resistance of carbon fibers according to claim 1, characterized in that: In S1, the volume-to-mass ratio of 3-aminopropyltriethoxysilane to attapulgite fiber is 30-50 mL:2 g.

3. The method for improving the high-temperature oxidation resistance of carbon fibers according to claim 1, characterized in that: In S2, the concentration of hydrogen peroxide is 10–30 wt%.

4. The method for improving the high-temperature oxidation resistance of carbon fiber according to claim 1, characterized in that: In S1, the pretreatment specifically involves soaking the attapulgite fiber in an HCl solution with a concentration of 3 mol / L at 70-80 ℃ for 46-50 h.

5. The method for improving the high-temperature oxidation resistance of carbon fibers according to claim 1, characterized in that: In S2, the specific conditions for the hydroxylation treatment are as follows: The reaction temperature is 60–80℃, and the treatment time is 2–6 h.

6. The method for improving the high-temperature oxidation resistance of carbon fibers according to claim 1, characterized in that: In S3, the mass ratio of the attapulgite fiber modified with 3-aminopropyltriethoxysilane to the carbon fiber after hydroxylation treatment is 1:6 to 20.

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