Method for preparing uniform and compact carbon coating on surface of carbon fiber

Abstract

The invention relates to a technology for preparing a carbon coating on the surface of carbon fiber, and belongs to the field of composite material preparation. The invention discloses a method for preparing a uniform and compact carbon coating on the surface of carbon fiber. According to the invention, sugar, an amide compound and inorganic salt are used as raw materials, a uniform and compact carbon coating is prepared on the surface of the carbon fiber by using a hydrothermal method, and the coating can protect the carbon fiber in the preparation and use processes of the composite material and improve the combination of the carbon fiber and a matrix material. According to the scheme, an efficient and low-cost preparation scheme is provided for preparation of the carbon fiber surface carbon coating, the morphology, thickness and the like of the coating in the method are easy to control, and the preparation period and cost of a traditional fiber surface carbon coating can be remarkably reduced.

Description

Technical Field

[0001] The technical solution of the present invention relates to a method for preparing a uniform and dense carbon coating on the surface of a carbon fiber, and belongs to the field of composite material preparation. Background Art

[0002] Carbon fiber (C f ) materials are widely used in aerospace, military and high-end automotive industries. f With its high tensile strength, high Young's modulus, low density and excellent chemical resistance, C f There are still many problems in practical applications, such as the performance degradation of fibers due to surface oxidation during preparation and use; f The bonding strength between the fiber and the matrix is ​​too strong or too weak, which affects the toughening effect. f It will not be oxidized during the preparation and use of composite materials, thus avoiding the degradation of fiber performance. In addition, the presence of the coating can improve the bonding properties between the fiber and the matrix material, and increase C f Properties of composite materials.

[0003] At present, the preparation of carbon coating on the surface of carbon fiber is mainly carried out by chemical vapor deposition (CVD), pyrolysis, etc. The coating preparation cycle is long, the process is complex, and the energy consumption is high, which affects the application of carbon coating in carbon fiber composite materials. With the development of the times, renewable resources, especially biomass energy, have always received much attention. Sugar, as a cheap and non-toxic biomass material, can be used to prepare carbon materials with a network structure and uniform distribution. The present invention converts sugar into carbon and uniformly coats it on C f Surface, to achieve C f Effective surface modification can shorten the process cycle and reduce process costs, which is of great significance to the performance improvement of carbon fiber composites. Summary of the invention

[0004] The technical solution of the present invention aims to provide a method for converting sugar into carbon and coating the carbon with C f The solution of forming a dense coating on the surface solves the problem of C f The present invention realizes the controllable preparation of carbon coating through reasonable component and process design, inhibits the influence of gas phase on coating quality during coating preparation, improves coating density, and is conducive to inhibiting damage to carbon fiber during the preparation and use of composite materials, thereby improving the performance of composite materials.

[0005] The present invention is a method for preparing a uniform and dense carbon coating, and the preparation process comprises the following steps: (1) Soak the carbon fiber in anhydrous ethanol and then dry it in vacuum; the density of the carbon fiber used is 0.25g / cm 3 ; (2) dissolving sugar, amide compounds and inorganic salts in water, wherein the mass ratio of sugar to amide compounds in the raw materials is 40:1-1:10, the mass ratio of sugar to water is 1:1-1:50, and the mass ratio of sugar to inorganic salt is 10:1-50:1; The sugar may be one or more of glucose, sucrose, fructose, maltose, lactose and the like. The amide compound can be one or more of N-vinyl caprolactam, N-2,3-trimethyl-2-isopropylbutyramide, 4-chlorothiobenzamide N, N-dimethyloxalamide Dulbecco's modified medium guaramide, 2,4-dihydroxybenzamide caprolactam methyl o-formate benzenesulfonamide, N,N-dimethylformamide, 2,3-dibromopropionamide, 3-amino-N-methylbenzamide, N,N'-methylenebisacrylamide, 2-acrylamide, 2,2-dibromo-3-nitrilopropionamide, N-methyl caprolactam, 5-chloro-2,4-disulfonamidoaniline, N-tert-butylacrylamide, N,N-dimethylsulfonamide, 6-methylnicotinamide sulfonamide, 3-amino-6-methylbenzenesulfonamide, 2-iodoacetamide, N-methylformamide, N-methylacetamide, N,N-diethyl-2-chloroacetamidebenzamide, and 4-methoxybenzamide. The inorganic salt is one or more of aluminum chloride, ferric chloride, sodium chloride, potassium chloride, aluminum nitrate, ferric nitrate, cerium nitrate, and aluminum sulfate; (3) pouring the solution obtained in step (2) into a reaction kettle, and then immersing the carbon fiber obtained in step (1) in the solution; (4) Tighten the reactor and place it in an oven for heat treatment. After the heat treatment is completed, take out the fiber; (5) placing the fiber obtained in step (4) in a vacuum oven to remove moisture; (6) The fiber obtained in step (5) is placed in a tubular furnace and heat treated under a protective atmosphere to finally obtain a carbon fiber with a uniform and dense carbon coating.

[0006] In step (1), the ethanol soaking time is 0.1-24h, and the drying temperature is 0-100°C.

[0007] In step (2), the constant temperature stirring temperature is 0-95° C., and the constant temperature stirring speed is 10-8000 r / min.

[0008] In step (4), the heat treatment temperature is 100-300°C, and the insulation time is 0.1-24h.

[0009] In step (5), the drying temperature is 20-100° C. and the drying time is 0.1-24 h.

[0010] In step (6), the heat treatment atmosphere is argon, the heating rate is 0.1-10°C / min, the heat treatment temperature is 300-1200°C, and the heat treatment time is 0.1-24h.

[0011] A uniform and dense carbon coating on the surface of a carbon fiber is prepared by the method for preparing the uniform and dense carbon coating on the surface of a carbon fiber, and the carbon coating is a coating formed by converting sugar into carbon.

[0012] Application of a carbon fiber with a uniform carbon coating: It can be applied to the field of carbon fiber composite materials to prepare high-performance carbon fiber composite materials.

[0013] The uniform and dense carbon coating on the surface of the carbon fiber prepared by the present invention is realized by coating the carbon coating prepared by sugar on the carbon fiber through a simple hydrothermal method. Due to the protective effect of the carbon layer, it is expected that the carbon fiber will be protected from damage caused by oxidation or interfacial reaction during the preparation and use of the carbon fiber composite material, and the damage to the carbon fiber will reduce the performance of the carbon fiber composite material. In addition, the carbon layer is formed by countless small carbon balls gathered on the fiber surface. This unique microstructure can effectively increase the bonding force between carbon and the matrix material, and significantly improve the performance of the carbon fiber composite material.

[0014] In the present invention, the essence of the sugar-carbon conversion method is the continuous dehydration of sugar, that is, sugar solution-sugar gel-caramel-carbon. The temperature for generating caramel is above 140°C. Therefore, in order to prepare a uniform and dense carbon coating, it is necessary to control the dehydration process. Compared with the prior art, the technical solution of the present invention has the advantage of converting sugar into carbon by hydrothermal method, which solves the problems of low density and uneven carbon coating in the existing sugar-carbon conversion method. In the traditional method, the reaction container is usually a beaker, and the heating device is usually an oven or a water bath. As the temperature gradually increases, the water fixed in the gel network evaporates rapidly, causing the gel to foam, and finally generating a loose porous structure of carbon. This type of carbon is difficult to be effectively wrapped in C f This technology uses a reactor for hydrothermal reaction. The closed and high-pressure environment in the reactor makes it difficult for water molecules to escape, which is conducive to the formation of dense and uniform caramel and wrapping it in C f The surface of the fiber is finally heat treated to form a dense and uniform carbon coating. This solution has simple equipment, short preparation cycle, low cost, and is a good choice for C f The efficient preparation of surface carbon coatings introduces new ideas and solutions. DETAILED DESCRIPTION

[0015] The present invention will be further described below in conjunction with the embodiments.

[0016] The scope of the present invention is not limited to the following embodiments. Those skilled in the art will appreciate that various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention.

[0017] The instruments, reagents, and materials involved in the following examples, unless otherwise specified, are all conventional instruments, reagents, and materials available in the prior art and can be obtained through regular commercial channels. The experimental methods, detection methods, etc. involved in the following examples, unless otherwise specified, are all conventional experimental methods and detection methods available in the prior art.

[0018] Example 1: (1) Soak the carbon fiber in anhydrous ethanol for 4 hours, take it out and dry it in vacuum at a drying temperature of 70°C; (2) Dissolve glucose, 2-acrylamide, N,N-methylenebisacrylamide and KCl in water, and stir at 70°C and 1400 r / min for 2 h until uniform, to form a precursor solution, wherein the mass ratio of glucose to amide compound is 8:1, the mass ratio of glucose to water is 1:15, and the mass ratio of sugar to inorganic salt is 20:1; (3) pouring the solution obtained in step (2) into a reaction kettle, and then immersing the carbon fiber obtained in step (1) in the solution. After the fiber is fully immersed, tighten the reaction kettle and place it in an oven for heat treatment at 200°C for 10 hours; (4) After the heat treatment, the fiber is taken out and placed in an oven at 70°C for 6 hours to form a carbon fiber wrapped with a caramel layer; (5) The fiber obtained in step (4) is placed in a tubular furnace and heated to 800°C at a rate of 10°C / min for heat treatment for 1 hour in an argon atmosphere to obtain a carbon fiber with a uniform carbon coating.

[0019] The obtained carbon fiber with uniform carbon coating is shown in FIG1 : SEM photo of the carbon fiber with uniform carbon coating obtained in Example 1.

[0020] Comparative Example 1: A method for preparing a carbon fiber with a uniform carbon coating, wherein the steps are substantially the same as those of Example 1, except that the amount of KCl introduced is 1%. The obtained carbon fiber with a uniform carbon coating is shown in FIG2: SEM photo of the carbon fiber with a uniform carbon coating obtained in Comparative Example 1.

[0021] Comparative Example 2: A method for preparing a carbon fiber with a uniform carbon coating, wherein the steps are substantially the same as those of Example 1, except that the amount of KCl introduced is 2%. The obtained carbon fiber with a uniform carbon coating is shown in FIG3 : SEM photo of the carbon fiber with a uniform carbon coating obtained in Comparative Example 2.

[0022] Although the present invention has been illustrated and described with specific embodiments, it will be appreciated that many other changes and modifications may be made without departing from the spirit and scope of the present invention. Therefore, it is intended to include all such changes and modifications within the scope of the present invention in the appended claims.

Claims

1. A method for preparing a uniform and dense carbon coating on the surface of a carbon fiber, characterized in that: The following steps are involved: (1) Immerse the carbon fiber in anhydrous ethanol for pretreatment, and then place it in an oven for vacuum drying; (2) dissolving sugar, amide compound and inorganic salt in water and stirring at a constant temperature to form a precursor solution; (3) pouring the solution obtained in step (2) into a high-pressure reaction vessel, and then immersing the carbon fiber obtained in step (1) in the solution; (4) Tighten the high-pressure reaction vessel, perform heat treatment at a certain temperature, and take out the fiber after the heat treatment; (5) placing the fiber obtained in step (4) in an oven for vacuum drying; (6) The fiber obtained in step (5) is placed in a tubular furnace and heat-treated under a protective atmosphere to finally obtain a carbon fiber with a uniform carbon coating.

2. A method for preparing a uniform and dense carbon coating on the surface of a carbon fiber as claimed in claim 1, characterized in that: The sugar in step (2) can be one or more of glucose, sucrose, fructose, maltose, lactose, etc.; the amide compound can be N-vinyl caprolactam, N-2,3-trimethyl-2-isopropylbutyramide, 4-chlorothiobenzamide N, N-dimethyloxalamide Dulbecco's modified medium glutamine amide, 2,4-dihydroxybenzamide caprolactam methyl o-formate benzenesulfonamide, N,N-dimethylformamide, 2,3-dibromopropionamide, 3-amino-N-methylbenzamide, N,N'-methylenebisacrylamide, 2-acrylamide, 2,2-dibromo-3-nitrilopropionamide , N-methylcaprolactam, 5-chloro-2,4-disulfonamidoaniline, N-tert-butylacrylamide, N,N-dimethylsulfonamide, 6-methylnicotinamidesulfonamide, 3-amino-6-methylbenzenesulfonamide, 2-iodoacetamide, N-methylformamide, N-methylacetamide, N,N-diethyl-2-chloroacetamidebenzamide, 4-methoxybenzamide or more; the inorganic salt is one or more of aluminum chloride, ferric chloride, sodium chloride, potassium chloride, aluminum nitrate, ferric nitrate, cerium nitrate, and aluminum sulfate; the sugar, amide compound and inorganic salt are dissolved in water, and the constant temperature stirring temperature is 0-95 ° C, the stirring rate is 10-8000 r / min, and the stirring time is 0.1-24 h; The mass ratio of sugar to amide compounds in the raw materials is 40:1~1:10, the mass ratio of sugar to water is 1:1~1:50, and the mass ratio of sugar to inorganic salt is 10:1~50:

1.

3. A method for preparing a uniform and dense carbon coating on the surface of a carbon fiber as claimed in claim 1, characterized in that: In step (3), the high-pressure reaction vessel can provide a high-pressure environment greater than 1 atmosphere for the reaction solution during the reaction process.

4. A method for preparing a uniform and dense carbon coating on the surface of a carbon fiber as claimed in claim 1, characterized in that: In step (1), the carbon fiber is immersed in ethanol for 0.1-24 h and then taken out and dried at a temperature of 0-100 °C.

5. A method for preparing a uniform and dense carbon coating on the surface of a carbon fiber as claimed in claim 1, characterized in that: In step (4), the temperature of the oven is 100-300°C, and the holding time is 0.1-24 h.

6. A method for preparing a uniform and dense carbon coating on the surface of a carbon fiber as claimed in claim 1, characterized in that: In step (5), the drying temperature is 20-100°C and the drying time is 0.1-24 h.

7. A method for preparing a uniform and dense carbon coating on the surface of carbon fiber according to claim 1, characterized in that: In step (6), the heat treatment atmosphere is argon, nitrogen, helium or a mixture thereof, the heating rate is 0.1-10 °C / min, the heat treatment temperature is 300-1200 °C, and the heat treatment time is 0.1-24 h.

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