阅读说明：本技术 一种石墨烯和碳纳米管原位生长共修饰增韧碳纤维的制备方法 (Preparation method of graphene and carbon nanotube in-situ growth co-modified toughened carbon fiber ) 是由 汪训国 张羽丰 李孙平 周燚平 于 2019-11-19 设计创作，主要内容包括：本发明公开了一种石墨烯和碳纳米管原位生长共修饰增韧碳纤维的制备方法,包括以下步骤：(1)碳纤维超声清洗；(2)碳纤维预氧化；(3)预氧化的碳纤维表面生长多孔石墨烯,得表面生长多孔石墨烯的碳纤维；(4)表面生长多孔石墨烯的碳纤维表面原位生长碳纳米管,得到石墨烯/碳纳米管共修饰增韧碳纤维材料。本发明通过在碳纤维表面刻蚀生长多孔石墨烯,一方面为碳纳米管的生长提供了活性位点,解决了碳纤维表面活性位点少,不易于生长碳纳米管的难题,一方面也提高了纤维力学性能。(The invention discloses a preparation method of graphene and carbon nanotube in-situ growth co-modified toughened carbon fibers, which comprises the following steps: (1) ultrasonic cleaning of carbon fibers; (2) pre-oxidizing carbon fibers; (3) growing porous graphene on the surface of the pre-oxidized carbon fiber to obtain the carbon fiber with the porous graphene growing on the surface; (4) and growing a carbon nano tube on the surface of the carbon fiber with the porous graphene growing on the surface in situ to obtain the graphene/carbon nano tube co-modified toughened carbon fiber material. According to the invention, the porous graphene is etched and grown on the surface of the carbon fiber, so that on one hand, an active site is provided for the growth of the carbon nanotube, the problems that the surface of the carbon fiber has few active sites and the carbon nanotube is not easy to grow are solved, and on the other hand, the mechanical property of the fiber is improved.)

1. A preparation method of graphene and carbon nanotube in-situ growth co-modified toughened carbon fibers is characterized by comprising the following steps:

(1) ultrasonic cleaning carbon fibers in water, acetone, isopropanol and ethanol in sequence;

(2) soaking the carbon fiber subjected to ultrasonic cleaning in a mixed solution of nitric acid and sulfuric acid for 0.5-1 hour for pre-oxidation, cleaning and drying to obtain pre-oxidized carbon fiber;

(3) winding and fixing the obtained pre-oxidized carbon fiber on a graphite support, placing the graphite support into a chemical vapor deposition reaction furnace, heating the carbon fiber to 800-fold-1000 ℃ under the protection of Ar atmosphere, and introducing H at a certain flow rate₂Carrying out surface etching for 5-10 min, and cooling in Ar atmosphere to obtain carbon fibers with porous graphene growing on the surfaces;

(4) heating the carbon fiber with the surface growing porous graphene to 700-800 ℃ in a chemical vapor deposition reaction furnace, feeding a prepared carbon nanotube synthetic precursor organic solution from the upper part of a cavity of the chemical vapor deposition reaction furnace through an atomizer, and feeding Ar and H₂The mixed gas is used as carrier gas, the temperature of the cavity of the reaction furnace is controlled at 700-800 ℃, the feeding reaction is carried out for 30-90 min, carbon nanotubes grow on the surface of the carbon fiber with the porous graphene, and the graphene/carbon nanotube co-modified toughened carbon fiber material is prepared after cooling.

2. The method of claim 1, wherein: the carbon fiber is polyacrylonitrile-based carbon fiber.

3. The method of claim 1, wherein: in the step (1), the ultrasonic cleaning time is 10-25min each time.

4. The method of claim 1, wherein: in the step (2), the mixed solution of nitric acid and sulfuric acid is formed by mixing concentrated nitric acid and concentrated sulfuric acid according to the volume ratio of 1:1, wherein the mass concentration of the concentrated nitric acid is 68-75%, and the mass concentration of the concentrated sulfuric acid is 80-98%.

5. The method of claim 1, wherein: in the step (3), the heating rate is 10-20 ℃/min.

6. The method of claim 1, wherein: in step (3), H₂At a flow rate of30-60 mL/min。

7. The method of claim 1, wherein: in the step (4), the carbon nano tube synthesis precursor organic solution is formed by mixing thiophene, ferrocene and xylene according to the mass ratio of 1: 5-10: 50-100.

8. The method of claim 1, wherein: in the step (4), the temperature of the feed inlet of the atomizer is controlled at 300-400 ℃.

9. The method of claim 1, wherein: in the step (4), the feeding speed of the carbon nanotube synthetic precursor organic solution is 100-.

10. The method of claim 1, wherein: in step (4), Ar and H₂Is 1: 1.

Technical Field

The invention relates to the technical field of carbon fiber production, in particular to a preparation method of graphene and carbon nanotube in-situ growth co-modified toughened carbon fiber.

Background

Carbon fiber is a special fiber composed of carbon elements. Has the characteristics of high temperature resistance, friction resistance, electric conduction, heat conduction, corrosion resistance and the like, and is an ideal reinforcement of the composite material. However, the surface of the carbon fiber belongs to a graphite disordered layer structure, and the microcrystals are oriented in order and have high inertia and are not easy to combine with a resin matrix, so that the interface bonding property of the reinforced composite material is poor, and the reinforcing effect of the carbon fiber reinforced phase is difficult to realize. On the other hand, the inherent brittleness of the highly crosslinked three-dimensional network matrix formed in the epoxy curing process causes the problems of insufficient toughness, low shear strength, easy fracture, easy delamination, low impact damage resistance and the like, and the application of the high-performance carbon fiber composite material is always hindered. Therefore, the proper surface modification of the carbon fiber, the increase of the specific surface area and the roughness of the fiber, the introduction of the active functional group and the improvement of the delamination resistance and the shear fracture toughness of the carbon fiber composite material have very important significance.

The traditional carbon fiber modification method, such as coating graphene oxide, graphene, carbon nanotubes and the like on the surface, mainly comprises the technological means of solution impregnation, surface coating, electrophoretic deposition, chemical vapor deposition and the like.

① the traditional carbon fiber has poor surface wettability, is not easy to combine with resin matrix and has insufficient mechanical properties such as shear strength and the like;

② the carbon fiber has less surface active sites, is not easy to grow carbon nanotubes and needs surface treatment;

③ the method for growing carbon nano-tube on the surface of carbon fiber includes such steps as diffusing catalyst particles in the carbon fiber to destroy the microcrystal structure on the surface of carbon fiber, increasing the number of defects and decreasing the mechanical strength, and physical combination between them, resulting in low binding force, easy dropping off, low stress transfer power and limited effect on improving the mechanical performance of carbon fiber.

CN 103225203 a discloses a method for preparing a carbon fiber-graphene oxide-carbon nanotube multi-scale reinforcement, in which a carbon nanotube grows in situ after the surface of a carbon fiber is coated and modified by graphene oxide to prepare the multi-scale reinforcement. It has the following disadvantages: the graphene oxide is coated on the carbon fibers by an impregnation method to grow the carbon nanotubes, so that the bonding force between the graphene oxide and the carbon fibers is weak, and the graphene oxide and the carbon nanotubes are easy to fall off; the method adopts the mode of processing graphene oxide and then growing the carbon nano tube on the surface, so that the active sites for the growth of the carbon nano tube are few, and the growth of the carbon nano tube is not facilitated. The catalyst loaded carbon nanotube growth by soaking in nickel nitrate solution may cause the catalyst to penetrate into the carbon fiber material resulting in a decrease in strength.

Disclosure of Invention

The invention aims to provide a preparation method of graphene and carbon nanotube in-situ growth co-modified toughened carbon fibers.

The technical scheme adopted by the invention for solving the technical problems is as follows:

a preparation method of graphene and carbon nanotube in-situ growth co-modified toughened carbon fibers comprises the following steps:

(1) ultrasonic cleaning carbon fibers in water, acetone, isopropanol and ethanol in sequence;

(2) soaking the carbon fiber subjected to ultrasonic cleaning in a mixed solution of nitric acid and sulfuric acid for 0.5-1 hour for pre-oxidation, cleaning and drying to obtain pre-oxidized carbon fiber;

(3) winding and fixing the obtained pre-oxidized carbon fiber on a graphite support, placing the graphite support into a chemical vapor deposition reaction furnace, heating the carbon fiber to 800-fold-1000 ℃ under the protection of Ar atmosphere, and introducing H at a certain flow rate₂Carrying out surface etching for 5-10 min, and cooling in Ar atmosphere to obtain carbon fibers with porous graphene growing on the surfaces;

(4) heating the carbon fiber with the surface growing porous graphene to 700-800 ℃ in a chemical vapor deposition reaction furnace, feeding a prepared carbon nanotube synthetic precursor organic solution from the upper part of a cavity of the chemical vapor deposition reaction furnace through an atomizer, and feeding Ar and H₂The mixed gas is carrier gas, the temperature of the cavity of the reaction furnace is controlled at 700 ℃ and 800 DEG CFeeding and reacting for 30-90 min, growing carbon nanotubes on the surface of the carbon fiber on which the porous graphene grows, and cooling to prepare the graphene/carbon nanotube co-modified toughened carbon fiber material.

According to the method, graphene grows in situ on the surface of the carbon fiber, so that a porous graphene surface layer structure which is uniformly distributed is formed on the surface of the carbon fiber, hole sites of the porous structure can be used as active sites for growth of carbon nanotubes, and the provided vacancies (active sites) are more uniform in macroscopical view and more controllable in quantity by controlling the hydrogen flow rate and the etching time.

According to the invention, when the carbon nano tube grows, the catalyst is not loaded on the carbon fiber in advance, but the catalyst is loaded while growing in a spraying manner, so that the contact time of the catalyst and the carbon fiber is greatly reduced, the catalyst can be effectively prevented from permeating into the carbon fiber, and the internal structure of the carbon fiber is damaged, thereby reducing the strength. The method for growing the carbon fiber on the upper side of the carbon fiber by spraying without loading a catalyst in advance is mainly realized by improving the organic solution of the carbon nanotube synthetic precursor, and the core is that thiophene is used as a catalyst promoter.

The carbon fiber is polyacrylonitrile-based carbon fiber.

In the step (1), the ultrasonic cleaning time is 10-25min each time.

In the step (2), the mixed solution of nitric acid and sulfuric acid is formed by mixing concentrated nitric acid and concentrated sulfuric acid according to the volume ratio of 1:1, wherein the mass concentration of the concentrated nitric acid is 68-75%, and the mass concentration of the concentrated sulfuric acid is 80-98%.

In the step (3), the heating rate is 10-20 ℃/min.

In step (3), H₂The flow rate is 30-60 mL/min.

In the step (4), the carbon nano tube synthesis precursor organic solution is formed by mixing thiophene, ferrocene and xylene according to the mass ratio of 1: 5-10: 50-100. Xylene is used as solvent and carbon source, ferrocene is used as catalyst precursor, and thiophene is used as catalyst promoter.

In the step (4), the temperature of the feed inlet of the atomizer is controlled at 300-400 ℃.

In the step (4), the feeding speed of the carbon nanotube synthetic precursor organic solution is 100-.

In step (4), Ar and H₂Is 1: 1.

The invention has the beneficial effects that:

① solves the problems of poor surface wettability, difficult combination with resin matrix, and insufficient mechanical properties such as shear strength of the traditional carbon fiber;

② porous graphene is etched and grown on the surface of the carbon fiber, so that on one hand, active sites are provided for the growth of the carbon nanotubes, the problem that the carbon nanotubes are not easy to grow due to few active sites on the surface of the carbon fiber is solved, and on the other hand, the mechanical property of the fiber is improved;

③ the method adopts improved floating catalyst method (compared with traditional floating method, adding catalyst promoter, optimizing proportion) to grow carbon nanometer tube in situ, compared with common solution dipping method, surface coating method, etc., the method greatly reduces contact time between catalyst and carbon fiber, can effectively prevent catalyst from permeating into carbon fiber, damages internal structure of carbon fiber and reduces strength, and the two are combined by chemical bond, and the binding force is strong and not easy to fall off.

Drawings

FIG. 1 is a process flow diagram of the present invention.

Detailed Description

The technical solution of the present invention will be further specifically described below by way of specific examples.

In the present invention, the raw materials and equipment used are commercially available or commonly used in the art, unless otherwise specified. The methods in the following examples are conventional in the art unless otherwise specified.

The reaction cavity used in the invention is a vertical chemical vapor deposition reaction furnace, can resist the temperature of over 1200 ℃, a feed inlet and an air inlet are arranged above the cavity, an air outlet and a discharge outlet are arranged below the cavity, and an annular graphite frame can be arranged in the middle section of the cavity.