Method for in-situ growth of nano SiO2 on surface of carbon fiber

Abstract

The invention discloses a method for in-situ growth of nano SiO2 on the surface of carbon fiber, which comprises the following steps: (1) soaking carbon fiber in acetone, and then carrying out ultrasonic treatment and washing; immersing the washed carbon fiber into a nitric acid solution for heating treatment, and washing and drying after treatment; (2) dipping the carbon fiber obtained in the step (1) in a KH550 silane coupling agent aqueous solution, and carrying out a reaction at a high temperature; (3) preparing an ethanol water solution containing sodium metasilicate, adding a dispersing agent into the ethanol water solution, heating and stirring, putting the carbon fibers in the step (2) into the solution, introducing CO2 gas into the solution until the pH value of the solution is 7-8, and ending the reaction; and cleaning and drying the reacted carbon fiber to obtain the carbon fiber with nano SiO2 grown in situ. CO2 gas is introduced into a sodium metasilicate solution, so that nano SiO2 particles which are uniformly dispersed and controllable in particle diameter grow on the surfaces of the carbon fibers in situ, the roughness and surface activity of the carbon fibers are improved, the interface bonding performance of the carbon fibers and a geopolymer is effectively improved, the stress transfer degree between a geopolymer matrix and the carbon fibers is enhanced, and the mechanical properties of the carbon fibers are improved. Stress concentration is effectively relieved, material damage is prevented, and the mechanical property of the geopolymer is improved.

Description

Technical Field

[0001] The invention relates to a method for in-situ growth of nano-SiO2 on the surface of carbon fiber. Background Art

[0002] Fibers and nanomaterials are commonly used to enhance the mechanical properties of geopolymers. However, untreated carbon fibers have a smooth and chemically inert surface, resulting in poor interfacial bonding with geopolymers. This limits the fiber's high tensile strength and high modulus properties, thereby weakening the carbon fibers' reinforcing and toughening effects on geopolymers. Therefore, improving the bonding between carbon fibers and the geopolymer matrix is ​​crucial for enhancing geopolymer performance.

[0003] Research has shown that combining carbon fibers with nano-SiO2 can effectively enhance the reinforcement and toughening effects of carbon fibers on geopolymers. Nano-SiO2 can significantly improve the mechanical properties of geopolymers through its filling effect, promoting polycondensation reactions, and refining the microstructure. The combination of carbon fibers and nano-SiO2 can increase the surface roughness and active sites of the carbon fibers, promoting interfacial friction or chemical bonding with the geopolymer matrix, thereby improving the interfacial bonding between the carbon fibers and the geopolymer matrix.

[0004] At present, there are many technologies for grafting nanoparticles on the surface of carbon fibers. However, on the one hand, the existing technologies have high requirements for equipment and processes and high preparation costs. On the other hand, there is a problem that the reinforcing and toughening effect of carbon fibers and nano-SiO2 composites on geopolymers is limited. This may be due to the uneven and weak bonding between the fibers and the nanomaterials. Summary of the Invention

[0005] Purpose of the invention: The purpose of the present invention is to provide a method for in-situ growth of nano-SiO2 on the surface of carbon fiber. The carbon fiber and nano-SiO2 composite material based on this method can greatly improve the reinforcement and toughening effect of geopolymers.

[0006] Technical solution: The method for in-situ growth of nano-SiO2 on the surface of carbon fiber of the present invention comprises the following steps:

[0007] (1) Carbon fiber (CF) degumming and surface oxidation: The carbon fiber was soaked in acetone solution for 24 h, ultrasonically treated for 30 min after soaking, and washed with ethanol and deionized water in sequence; the washed carbon fiber was immersed in nitric acid solution and heated, and then taken out and immediately immersed in deionized water to stop oxidation, washed, and dried;

[0008] (2) Surface hydroxylation: The carbon fiber obtained in step (1) was immersed in a KH550 silane coupling agent aqueous solution, reacted at 60°C for 2 hours, and then rinsed with ethanol to increase the hydroxyl content on the carbon fiber surface;

[0009] (3) In situ growth of nano-SiO2: prepare an ethanol aqueous solution of sodium metasilicate, add dispersant hexadecyltrimethylammonium bromide (CTAB) thereto and heat and stir, put the carbon fiber obtained in step (2) into it, and then introduce CO2 gas to the solution until the pH value is 7-8, terminate the reaction, and age for 1 hour (which can improve the uniformity and stability of the nanoparticles. During the aging process, small particles will gradually dissolve and redeposit on the surface of larger particles, thereby achieving the effect of increasing the particle size and narrowing the particle size distribution); wash the carbon fiber with deionized water and dry it to obtain carbon fiber with in situ growth of nano-SiO2.

[0010] In step (1), the mass volume ratio of the carbon fiber to the acetone solution is 5-6 g / 50 mL.

[0011] In step (1), the concentration of the nitric acid solution is 60-70%, the treatment temperature is 80-100° C., and the treatment time is 1-2 h; and the mass volume ratio of the carbon fiber to the nitric acid solution is 5-6 g / 250 mL.

[0012] In step (2), the mass volume ratio of the carbon fiber to the KH550 silane coupling agent aqueous solution is: 5-6 g / 250 mL; the concentration of the KH550 silane coupling agent aqueous solution is 3-5 wt.%.

[0013] In step (3), the volume ratio of water to ethanol is 8:1 to 12:1; in the solution, the concentration of sodium metasilicate is 0.008 to 0.04 mol / L; the mass volume ratio of CTAB to the solution is 2 to 3 g / 1000 mL, and the mass volume ratio of carbon fiber to the solution is 5 to 6 g / 1000 mL.

[0014] In step (3), the heating temperature is 40-60° C., the stirring speed is 300-500 rpm, and the CO 2 ventilation rate is 100-800 mL / min.

[0015] In step (3), in the carbon fiber with nano-SiO2 grown in situ, the particle size of nano-SiO2 is 20-100nm, and the loading amount of nano-SiO2 is 9-45%.

[0016] The present invention can control the loading amount of SiO2 nanoparticles by controlling the Si(OH)4 monomer concentration (silicon source concentration) in the solution, and can control the particle size of SiO2 nanoparticles by controlling the carbon dioxide introduction rate. The surface roughness of carbon fibers treated with nitric acid increases and active carboxyl groups (-COOH) and hydroxyl groups (-COH) are generated. After further soaking in silane coupling agent KH550, the surface carboxyl groups condense with the amino groups in the silane coupling agent, and the three active -OH groups generated by hydrolysis of the other end of the silane coupling agent are exposed to the outside to achieve hydroxylation of the carbon fiber surface. Carbonic acid generated by the introduction of CO2 into the sodium metasilicate solution catalyzes the polymerization of Si(OH)4 monomers. The active -OH groups on the carbon fiber surface and the hydroxyl groups exposed on the surface of the silane coupling agent attract the Si(OH)4 monomers to rapidly condense and form nuclei, which then gradually grow into nano-SiO2 particles. The nano-SiO2 particles are connected to the carbon fibers through Si-O-Si covalent bonds formed by the silane coupling agent or directly through CO-Si covalent bonds formed with the surface hydroxyl groups. This chemical reaction occurs evenly on the fiber surface, ultimately obtaining a carbon fiber-based in-situ grown nano-SiO2 composite material with uniform particle size and distribution and strong connection. The modified carbon fibers significantly increase in roughness, and the surface nano-SiO2 condenses with the aluminosilicate in the geopolymer to form a more three-dimensional cross-linked structure, improving the interface transition zone and significantly enhancing the bond strength between the carbon fibers and the geopolymer matrix. Consequently, stress in the geopolymer matrix is ​​efficiently transferred to the carbon fibers, alleviating stress concentration in the geopolymer matrix, inhibiting the occurrence and expansion of cracks, preventing material damage, and ultimately improving the mechanical properties of the geopolymer.

[0017] The present invention increases the roughness and surface activity of carbon fibers by introducing CO2 gas into a sodium metasilicate solution to in-situ grow uniformly dispersed nano-SiO2 particles with controllable particle diameter on the carbon fiber surface, thereby effectively improving the interfacial bonding performance between the carbon fibers and the geopolymer, enhancing the degree of stress transfer between the geopolymer matrix and the carbon fibers, effectively alleviating stress concentration, preventing material damage, and improving the mechanical properties of the geopolymer.

[0018] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: in the carbon fiber and nano-SiO2 composite material prepared by the method of the present invention, the in-situ grown nano-SiO2 is covalently bonded to the carbon fiber through a chemical reaction, so the nano-SiO2 particles are not easy to fall off; the carbon fiber modified with nano-SiO2 can not only achieve better intercalation with the geopolymer by increasing the roughness and friction, but the nano-SiO2 firmly grown on the carbon fiber can also participate in the geopolymer reaction to produce gel, and the gel fills the gap between the carbon fiber and the geopolymer, further improving the bonding performance of the interface between the two, thereby being able to better play the reinforcing and toughening effect of the carbon fiber on the geopolymer. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a scanning electron microscope image of unmodified carbon fiber;

[0020] Figure 2 This is a scanning electron microscope image of the in-situ grown nano-SiO2 on a carbon fiber substrate obtained in Example 1;

[0021] Figure 3 This is a partially enlarged scanning electron microscope image of the in-situ grown nano-SiO2 on the carbon fiber substrate obtained in Example 1;

[0022] Figure 4 This is a Fourier transform infrared spectrum of the carbon fiber-based in-situ grown nano-SiO2 and carbon fiber obtained in Example 1;

[0023] Figure 5 This is a scanning electron microscope image of the geopolymer mortar obtained in Comparative Example 2 at 28 days of age;

[0024] Figure 6 This is a scanning electron microscope image of the geopolymer mortar obtained in Example 1 at 28 days of age; DETAILED DESCRIPTION

[0025] Example 1

[0026] The method for in-situ growth of nano-SiO2 on the surface of carbon fiber of the present invention comprises the following steps:

[0027] (1) Carbon fiber degumming and surface oxidation: 5 g of carbon fiber was soaked in 50 mL of acetone for 24 h, ultrasonically treated for 30 min after soaking, and washed with ethanol and deionized water in sequence; the washed carbon fiber was immersed in 250 mL of 60 wt.% nitric acid solution and heated to 80 ° C for 2 h. After the end, the carbon fiber was taken out and immediately immersed in deionized water to stop oxidation and washed clean, and then fully dried in an oven at 80 ° C;

[0028] (2) Surface hydroxylation: The carbon fibers obtained in step (1) were immersed in 250 mL of a 3 wt.% aqueous solution of KH550 silane coupling agent and reacted at 60° C. for 2 h to increase the surface hydroxyl content. After the reaction, the carbon fibers were washed with ethanol three times.

[0029] (3) In situ growth of nano-SiO2: 1000 mL of an ethanol aqueous solution with a concentration of 0.008 mol / L sodium metasilicate was prepared, with a water-to-alcohol ratio of 8:1. 2 g of CTAB was added thereto and heated with stirring at 40°C and a stirring speed of 500 rpm. The carbon fiber obtained in step (2) was placed in the above solution and stirred evenly. CO2 gas was introduced at a rate of 300 mL / min until the solution pH reached 7-8, the reaction was terminated, and the solution was aged for 1 h. After the reaction, the carbon fiber was washed three times with deionized water and dried at 110°C to obtain carbon fiber-based in situ grown nano-SiO2 (abbreviated as INS@CF).

[0030] In the carbon fiber with in-situ grown nano-SiO2, the particle size of the nano-SiO2 is 40-50 nm and the loading amount is 9.6%.

[0031] Example 2

[0032] The method for in-situ growth of nano-SiO2 on the surface of carbon fiber of the present invention comprises the following steps:

[0033] (1) Carbon fiber degumming and surface oxidation: 5 g of carbon fiber was soaked in 50 mL of acetone for 24 h, ultrasonically treated for 30 min after soaking, and washed with ethanol and deionized water in sequence; the washed carbon fiber was immersed in 250 mL of 60 wt.% nitric acid solution and heated to 80 ° C for 2 h. After the end, the carbon fiber was taken out and immediately immersed in deionized water to stop oxidation and washed clean, and then fully dried in an oven at 80 ° C;

[0034] (2) Surface hydroxylation: The carbon fibers obtained in step (1) were immersed in 250 mL of a 3 wt.% aqueous solution of KH550 silane coupling agent and reacted at 60° C. for 2 h to increase the surface hydroxyl content. After the reaction, the carbon fibers were washed with ethanol three times.

[0035] (3) In situ growth of nano-SiO2: prepare 1000 mL of ethanol aqueous solution with a concentration of 0.024 mol / L sodium metasilicate and a water-to-alcohol ratio of 8:1, add 2 g of CTAB and heat with stirring at 40°C and a stirring speed of 500 rpm; take the carbon fiber obtained in step (2) and put it into the solution and stir it evenly, introduce CO2 gas at a rate of 300 mL / min until the solution pH is 7-8, terminate the reaction, and age for 1 hour; after the reaction, the carbon fiber is washed three times with deionized water and dried at 110°C to obtain carbon fiber-based in situ grown nano-SiO2.

[0036] In the carbon fiber with in-situ grown nano-SiO2, the particle size of the nano-SiO2 is 40-50 nm, and the loading amount is 28.2%.

[0037] Example 3

[0038] The method for in-situ growth of nano-SiO2 on the surface of carbon fiber of the present invention comprises the following steps:

[0039] (1) Carbon fiber degumming and surface oxidation: 5 g of carbon fiber was soaked in 50 mL of acetone for 24 h, ultrasonically treated for 30 min after soaking, and washed with ethanol and deionized water in sequence; the washed carbon fiber was immersed in 250 mL of 60 wt.% nitric acid solution and heated to 80 ° C for 2 h. After the end, the carbon fiber was taken out and immediately immersed in deionized water to stop oxidation and washed clean, and then fully dried in an oven at 80 ° C;

[0040] (2) Surface hydroxylation: The carbon fibers obtained in step (1) were immersed in 250 mL of a 3 wt.% aqueous solution of KH550 silane coupling agent and reacted at 60° C. for 2 h to increase the surface hydroxyl content. After the reaction, the carbon fibers were washed with ethanol three times.

[0041] (3) In situ growth of nano-SiO2: prepare 1000 mL of ethanol aqueous solution with a concentration of 0.04 mol / L sodium metasilicate and a water-to-alcohol ratio of 8:1, add 2 g of CTAB and heat with stirring at 40°C and a stirring speed of 500 rpm; take the carbon fiber obtained in step (2) and put it into the solution and stir it evenly, introduce CO2 gas at a rate of 300 mL / min until the solution pH is 7-8, terminate the reaction, and age for 1 hour; after the reaction, the carbon fiber is washed three times with deionized water and dried at 110°C to obtain carbon fiber-based in situ grown nano-SiO2.

[0042] In the carbon fiber with in-situ growth of nano-SiO2, the particle size of the nano-SiO2 is 40-50 nm, and the loading amount is 42.5%.

[0043] Example 4

[0044] The method for in-situ growth of nano-SiO2 on the surface of carbon fiber of the present invention comprises the following steps:

[0045] (1) Carbon fiber degumming and surface oxidation: 5 g of carbon fiber was soaked in 50 mL of acetone for 24 h, ultrasonically treated for 30 min after soaking, and washed with ethanol and deionized water in sequence; the washed carbon fiber was immersed in 250 mL of 60 wt.% nitric acid solution and heated to 80 ° C for 2 h. After the end, the carbon fiber was taken out and immediately immersed in deionized water to stop oxidation and washed clean, and then fully dried in an oven at 80 ° C;

[0046] (2) Surface hydroxylation: The carbon fibers obtained in step (1) were immersed in 250 mL of a 3 wt.% aqueous solution of KH550 silane coupling agent and reacted at 60° C. for 2 h to increase the surface hydroxyl content. After the reaction, the carbon fibers were washed with ethanol three times.

[0047] (3) In situ growth of nano-SiO2: prepare 1000 mL of ethanol aqueous solution with a concentration of 0.008 mol / L sodium metasilicate and a water-to-alcohol ratio of 8:1, add 2 g of CTAB and heat with stirring at a heating temperature of 40°C and a stirring speed of 500 rpm; take the carbon fiber obtained in step (2) and put it into the solution and stir it evenly, introduce CO2 gas at a rate of 800 mL / min until the solution pH is 7-8, terminate the reaction, and age for 1 hour; after the reaction, the carbon fiber is washed three times with deionized water and dried at 110°C to obtain carbon fiber-based in situ grown nano-SiO2.

[0048] In the carbon fiber with in-situ grown nano-SiO2, the particle size of the nano-SiO2 is not greater than 20 nm, and the loading amount is 9.6%.

[0049] Example 5

[0050] The method for in-situ growth of nano-SiO2 on the surface of carbon fiber of the present invention comprises the following steps:

[0051] (1) Carbon fiber degumming and surface oxidation: 5 g of carbon fiber was soaked in 50 mL of acetone for 24 h, ultrasonically treated for 30 min after soaking, and washed with ethanol and deionized water in sequence; the washed carbon fiber was immersed in 250 mL of 60 wt.% nitric acid solution and heated to 80 ° C for 2 h. After the end, the carbon fiber was taken out and immediately immersed in deionized water to stop oxidation and washed clean, and then fully dried in an oven at 80 ° C;

[0052] (2) Surface hydroxylation: The carbon fibers obtained in step (1) were immersed in 250 mL of a 3 wt.% aqueous solution of KH550 silane coupling agent and reacted at 60° C. for 2 h to increase the surface hydroxyl content. After the reaction, the carbon fibers were washed with ethanol three times.

[0053] (3) In situ growth of nano-SiO2: prepare 1000 mL of ethanol aqueous solution with a concentration of 0.008 mol / L sodium metasilicate and a water-to-alcohol ratio of 8:1, add 2 g of CTAB and heat with stirring at 40°C and a stirring speed of 500 rpm; take the carbon fiber obtained in step (2) and put it into the solution and stir it evenly, introduce CO2 gas at a rate of 100 mL / min until the solution pH is 7-8, terminate the reaction, and age for 1 hour; after the reaction, the carbon fiber is washed three times with deionized water and dried at 110°C to obtain carbon fiber-based in situ grown nano-SiO2.

[0054] In the carbon fiber with in-situ grown nano-SiO2, the particle size of the nano-SiO2 is not less than 100 nm, and the loading amount is 9.6%.

[0055] The carbon fiber-based in-situ grown nano-SiO2 prepared in Example 1 was incorporated into the geopolymer cementitious material to prepare modified carbon fiber geopolymer mortar specimens, with the dosage set at 0.3%, 0.6% and 0.9% of the volume of the geopolymer slurry. The carbon fiber-based in-situ grown nano-SiO2 prepared in Examples 2 to 5 was incorporated into the geopolymer cementitious material to prepare modified carbon fiber geopolymer mortar specimens, with the dosage set at 0.6% of the volume of the geopolymer slurry. The geopolymer slurry mix ratio (mass ratio) was sand: slag powder: fly ash: activator: water = 1.13:0.5:0.5:0.33:0.26. After the geopolymer slurry was prepared according to the above mix ratio, the corresponding carbon fiber was added in the above dosage. The compressive and flexural strength of the mortar were tested in accordance with GB / T 17671-2021 "Test Method for Strength of Cement Mortar".

[0056] Comparative Example 1

[0057] Geopolymer cement mortar was prepared according to the above mix ratio without adding carbon fiber.

[0058] Comparative Example 2

[0059] Geopolymer cement mortar was prepared according to the above mix ratio, using unmodified carbon fiber, with the carbon fiber content being 0.3%, 0.6% and 0.9% of the mortar volume.

[0060] Comparative Example 3

[0061] Geopolymer cement mortar was prepared according to the above-mentioned mix ratio, and nano-SiO2 modified carbon fiber prepared by the existing sol-gel method was used (the preparation path refers to patent CN202110243494.6), and the carbon fiber content was 0.3%, 0.6% and 0.9% of the mortar volume.

[0062] The carbon fiber-based in-situ grown nano-SiO2 obtained in Examples 1 to 5 was characterized and tested as follows:

[0063] Figure 1 This is a scanning electron microscope image of unmodified carbon fiber. Figure 2 This is a scanning electron microscope image of the in-situ grown nano-SiO2 on the carbon fiber substrate obtained in Example 1. Figure 3 This is a partially enlarged scanning electron microscope image of the in-situ grown nano-SiO2 on the carbon fiber substrate obtained in Example 1. Figure 4 The Fourier transform infrared spectrum of the carbon fiber-based in-situ grown nano-SiO2 and carbon fiber obtained in Example 1. The surface of the unmodified carbon fiber is smooth, and there are lines along the fiber direction ( Figure 1 There is a large amount of nano-scale SiO2 evenly distributed on the surface of the carbon fiber-based in-situ grown nano-SiO2 prepared by the method of the present invention ( Figure 2 and Figure 3In the Fourier transform infrared spectrum, the spectra of carbon fiber-based in-situ grown nano-SiO2 and carbon fiber are obviously different. -1 A new broad absorption peak of hydroxyl group appears at 1194 cm -1 A new Si-OC absorption peak appeared at 1095 cm -1 The emergence of a new Si-O-Si absorption peak indicates that the nano-SiO2 is covalently bonded to the carbon fiber surface. The method of the present invention can in situ grow nano-SiO2 particles connected by chemical covalent bonds on the carbon fiber surface. By controlling the silicon source concentration and the CO2 ventilation rate, the controllable preparation of carbon fiber-based in situ grown nano-SiO2 can be achieved. The parameters of carbon fiber-based in situ grown nano-SiO2 obtained in Examples 1 to 5 are shown in Table 1 below:

[0064] Table 1 is the parameters of carbon fiber-based in-situ grown nano-SiO2 obtained in Examples 1 to 5

[0065] serial number <![CDATA[Particle diameter of nano-SiO2 / nm]]> <![CDATA[Growth amount of nano-SiO2 / %]]> Example 1 40～50 9.6 Example 2 40～50 28.2 Example 3 40～50 42.5 Example 4 ≤20 9.6 Example 5 ≥100 9.6

[0066] The flexural strength of the geopolymer mortars obtained in Examples 1 to 5 and Comparative Examples 1 to 3 was tested, and the results are shown in Table 2:

[0067] Table 2 shows the flexural strength of the polymer mortars obtained in Examples 1 to 5 and Comparative Examples 1 to 3.

[0068]

[0069] The geopolymer mortars of Examples 1 to 5 were doped with carbon fiber-based in-situ grown nano-SiO2 prepared by the present invention. Comparative Example 1 was a geopolymer mortar without carbon fiber doping, Comparative Example 2 was doped with unmodified CF, and Comparative Example 3 was doped with nano-SiO2 modified carbon fiber prepared by the sol-gel method. As shown in Table 2, compared with Comparative Example 1, the 28d flexural strength of Example 1 increased by 40.3%, 53.7%, and 49.3% at 0.3%, 0.6%, and 0.9% volume dosages, respectively. The 28d flexural strength of Comparative Example 2 increased by 19.4%, 23.9%, and 23.9% at 0.3%, 0.6%, and 0.9% volume dosages, respectively. The 28d flexural strength of Comparative Example 3 increased by 32.8%, 47.8%, and 44.8% at 0.3%, 0.6%, and 0.9% volume dosages, respectively. The carbon fiber-based in-situ grown nano-SiO2 prepared by the present invention and the nano-SiO2 modified carbon fiber prepared by the sol-gel method have better effects on improving the flexural strength of geopolymer mortar than unmodified carbon fiber, and the carbon fiber-based in-situ grown nano-SiO2 prepared by the present invention has a more significant effect on improving the flexural strength of geopolymer than the nano-SiO2 modified carbon fiber prepared by the sol-gel method.

[0070] Figure 5This is a scanning electron microscope image of the geopolymer mortar obtained in Comparative Example 2 at 28 days old. Figure 6 This is a scanning electron microscope image of the polymer mortar obtained in Example 1 at 28 days of age ( Figure 5 and Figure 6 The corresponding carbon fiber content is 6%). Figure 5 It can be seen that the surface of unmodified carbon fiber is smooth and the bonding surface with geopolymer slurry is not tight. Figure 6 It can be seen that the nano-SiO2 on the surface of the carbon fiber-based in-situ grown nano-SiO2 reacts with the geopolymer to generate C(N)-ASH gel, which adheres to the carbon fiber surface. This improves the interface transition zone between the carbon fiber and the geopolymer matrix, making the in-situ grown nano-SiO2 on the carbon fiber-based in-situ grown nano-SiO2 and the geopolymer bond more tightly. Therefore, the stress exerted on the geopolymer matrix can be efficiently transferred to the carbon fiber, which can alleviate stress concentration in the geopolymer matrix, inhibit the occurrence and expansion of cracks, prevent material damage, and thus improve the mechanical properties of the geopolymer.

Claims

1. A method for in-situ growth of nano-SiO2 on the surface of carbon fiber, characterized in that: The steps include: (1) soaking the carbon fiber in acetone, ultrasonically treating and washing the carbon fiber after soaking; immersing the washed carbon fiber in a nitric acid solution for heating treatment, washing and drying the carbon fiber after treatment; (2) immersing the carbon fiber obtained in step (1) in an aqueous solution of a KH550 silane coupling agent and reacting the mixture at a high temperature; (3) preparing an ethanol aqueous solution containing sodium metasilicate, adding a dispersant thereto and heating and stirring, placing the carbon fiber of step (2) into the above solution and introducing CO2 gas into the solution until the pH value of the solution is 7-8, and terminating the reaction; washing and drying the carbon fiber after the reaction to obtain a carbon fiber with in-situ growth of nano-SiO2.

2. The method according to claim 1, wherein: In step (1), the mass volume ratio of the carbon fiber to acetone is 5-6 g / 50 mL.

3. The method according to claim 1, wherein: In step (1), the concentration of the nitric acid solution is 60% to 70%, the treatment temperature is 80 to 100° C., and the treatment time is 1 to 2 hours.

4. The method according to claim 3, wherein: The mass volume ratio of carbon fiber to nitric acid solution is 5-6 g / 250 mL.

5. The method according to claim 1, wherein: In step (2), the concentration of the KH550 silane coupling agent aqueous solution is 3-5 wt.%; the mass volume ratio of the carbon fiber to the KH550 silane coupling agent aqueous solution is: 5-6 g / 250 mL.

6. The method according to claim 1, wherein: In step (2), the reaction temperature is 60-65° C., and the reaction time is 2-3 h.

7. The method according to claim 1, wherein: In step (3), the water-to-alcohol ratio of the ethanol aqueous solution is 8:1 to 12:1; and in the solution, the concentration of sodium metasilicate is 0.008 to 0.040 mol / L.

8. The method according to claim 1, wherein: In step (3), the dispersant is hexadecyltrimethylammonium bromide, the mass volume ratio of hexadecyltrimethylammonium bromide to the solution is: 2-3 g / 1000 mL, and the mass volume ratio of carbon fiber to the solution is: 5-6 g / 1000 mL.

9. The method according to claim 1, wherein: In step (3), the heating temperature is 40-60° C., the stirring speed is 300-500 rpm, and the CO 2 ventilation rate is 100-800 mL / min.

10. The method according to claim 1, wherein: In step (3), in the carbon fiber with nano-SiO2 grown in situ, the particle size of nano-SiO2 is 20-100nm, and the loading amount of nano-SiO2 is 9-45%.

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