Preparation method of near-zero expansion carbon-based composite material

Abstract

The invention provides a preparation method of a near-zero-expansion carbon-based composite material, which comprises the following steps: selecting mesophase pitch-based carbon fiber to prepare a fiber preform, carrying out ultrahigh-temperature graphitization treatment on the preform, preparing a carbon coating layer on the surface of the fiber, introducing SiO2 gel by a sol-gel process, and carrying out carbon thermal reduction reaction to generate SiC nanowires, thereby obtaining the near-zero-expansion carbon-based composite material. According to the preparation method, the composite material is subjected to multi-round densification by adopting a precursor impregnation-pyrolysis (PIP) process, and finally, the density of the composite material is further improved by adopting a hot isostatic pressing (HIP) process, so that the obtained carbon-based composite material has the characteristics of high rigidity and near-zero expansion, and can meet the application requirements of spatial high-stability structural materials.

Description

Technical Field

[0001] The invention belongs to the field of preparation of composite materials, and in particular relates to a method for preparing a near-zero expansion carbon-based composite material. Background Art

[0002] Space remote sensing technology plays an increasingly important role in many fields such as geographic surveying and mapping, resource investigation, and ocean surveillance. With the demand for ultra-high-precision observation, space cameras, as the core equipment for space observation, are developing in the direction of lightweight and large-caliber. The service performance of key components such as optical components and supporting structures has become the key to achieving ultra-long-distance and ultra-high-precision observation of space cameras. Compared with other application environments, the working environment faced by space optomechanical structural components is more complex, mainly including temperature changes, mechanical vibrations, space radiation, and space atomic oxygen impact. In order to ensure ultra-high resolution imaging of space cameras, space optomechanical structural materials must ensure ultra-high dimensional and load-bearing stability in such a harsh service environment, that is, the material is required to have both high modulus (>150GPa) and near-zero expansion (<5×10 -7 / K) characteristics.

[0003] Compared with traditional near-zero expansion structural materials in space, such as alloy materials and resin-based composite materials, carbon-based composite materials have the advantages of low expansion, low density, strong designability, and stable physical / chemical properties. They have become the first choice and hot spot for near-zero expansion structural materials in space. The coordinated regulation of mechanical / thermal properties of composite materials can be achieved through the design of factors such as material composition, structure, and preparation process. However, at present, the linear expansion coefficient of traditional carbon-based composite materials is still difficult to meet the application technical indicators, and the regulation of thermal expansion performance often sacrifices the mechanical properties of the material. The materials often have problems such as insufficient modulus and high porosity. Summary of the invention

[0004] In order to solve the problems existing in the above-mentioned carbon-based composites, a method for preparing high-rigidity near-zero expansion carbon-based composites is proposed. This method uses mesophase asphalt-based carbon fibers as reinforcements, introduces SiC nanowires into the preform, and then uses SiC components as matrix modification. By adjusting the relative content of matrix carbon and SiC components, the preparation of high-rigidity near-zero expansion composites is achieved.

[0005] The above-mentioned purpose of the present invention is mainly achieved through the following technical solutions:

[0006] A method for preparing a near-zero expansion carbon-based composite material comprises the following steps:

[0007] (1) weaving mesophase pitch-based carbon fibers into a preform, and then graphitizing the preform;

[0008] (2) subjecting the preform obtained in step (1) to carbon source precursor impregnation-cracking, introducing matrix carbon, and obtaining a C / C intermediate;

[0009] (3) The C / C intermediate obtained in step (2) is immersed in silica sol and then dried in air to obtain C / C-SiO 2 Intermediates;

[0010] (4) The C / C-SiO obtained in step (3) 2 The intermediate is placed in a high temperature treatment furnace to grow SiC nanowires to obtain C / C-SiC nw Intermediates;

[0011] (5) Using polycarbosilane as a ceramic precursor, the C / C-SiC obtained in step (4) is treated by a precursor impregnation-cracking process. nw The intermediates undergo multiple rounds of densification;

[0012] (6) Using hot isostatic pressing to densify the C / C-SiC obtained in step (5) nw The intermediate is subjected to multiple rounds of impregnation-carbonization sealing treatment to obtain a near-zero expansion carbon-based composite material.

[0013] The preform structure in step (1) comprises at least one of two-dimensional plying, ply stitching, suturing or fine weaving puncture, and the fiber volume fraction is 20-60%.

[0014] The graphitization treatment temperature in step (1) is 2300-3200° C., and the insulation time is 0.5-2 h.

[0015] In step (2), the carbon source precursor is furfural resin, coal tar pitch, mesophase pitch or phenolic resin, and the volume fraction of the introduced matrix carbon is 20-60%.

[0016] The maximum reaction temperature in step (2) is 700-1000°C.

[0017] The solid content of the silica sol in step (3) is 20-40%, the immersion time is 8-24 hours, the drying temperature is 80-120° C., and the insulation time is 8-16 hours.

[0018] In step (4), the treatment temperature is 1450-1550° C. and the insulation time is 0.5-2 h.

[0019] In step (5), the number of cycles of the precursor impregnation-cracking process is 5 to 15.

[0020] In step (6), the impregnation-carbonization sealing treatment process is cycled 2 to 7 times.

[0021] Compared with the prior art, the present invention has at least the following beneficial effects:

[0022] (1) The present invention achieves the preparation of materials with near-zero expansion characteristics by optimizing the preform design and matrix composition, while taking into account the high modulus characteristics, and the material has high density, thereby ensuring the ultra-high dimensional stability of the material under specific service environments.

[0023] (2) The process adopted by the present invention is highly mature and can realize the controllable introduction of SiC components and C components in the matrix according to the material performance requirements. It is suitable for the preparation of large-sized special-shaped components and can meet the preparation of large-sized components of space optical systems with different requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a flow chart of a method for preparing a near-zero expansion carbon-based composite material according to the present invention;

[0025] Figure 2 This is a scanning electron microscope image of SiC nanowires prepared in Example 1 of the present invention;

[0026] Figure 3 This is a local scanning electron microscope image of the near-zero expansion carbon-based composite material of Example 1 of the present invention;

[0027] Figure 4 This is a local scanning electron microscope image of the near-zero expansion carbon-based composite material of Example 2 of the present invention. DETAILED DESCRIPTION

[0028] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments:

[0029] like Figure 1 The flowchart of the preparation method of a near-zero expansion carbon-based composite material of the present invention is shown, which comprises the following steps:

[0030] (1) weaving mesophase pitch-based carbon fibers into a preform, and then graphitizing the preform;

[0031] (2) subjecting the preform obtained in step (1) to carbon source precursor impregnation-cracking, introducing matrix carbon, and obtaining a C / C intermediate;

[0032] (3) The C / C intermediate obtained in step (2) is immersed in silica sol and then dried in air to obtain C / C-SiO 2 Intermediates;

[0033] (4) The C / C-SiO obtained in step (3) 2 The intermediate is placed in a high temperature treatment furnace to grow SiC nanowires to obtain C / C-SiC nw Intermediates;

[0034] (5) Using polycarbosilane as a ceramic precursor, the C / C-SiC obtained in step (4) is treated by a precursor impregnation-cracking process. nw The intermediates undergo multiple rounds of densification;

[0035] (6) A hot isostatic pressing process is used to perform multiple rounds of impregnation-carbonization sealing treatment to obtain a near-zero expansion carbon-based composite material.

[0036] Example 1

[0037] In this embodiment, a preform of a ply stitched structure is used, and the fiber volume fraction is about 46%. The preform is subjected to ultrahigh temperature graphitization treatment by keeping the temperature at 2800°C for 1 hour. The matrix carbon is introduced into the preform using the mesophase pitch as the carbon source to make the volume fraction reach 30%. The preform is immersed in a silica sol with a solid content of 20% at normal pressure for 12 hours, kept at 80°C for 12 hours, and slowly dried to obtain C / C-SiO 2 The intermediate was placed in a high temperature heat treatment furnace under argon atmosphere and kept at 1550°C for 2 hours for full reaction. Figure 2 Shown is a scanning electron microscope image of the prepared SiC nanowires, which were then densified through 10 rounds of precursor impregnation-cracking process and finally 7 rounds of HIP process. Figure 3 The following is a local SEM image of the composite material, showing that it has a high density and no obvious pores. The average linear expansion coefficient of the composite material in the XY direction measured within -50 to 80°C is 1.2×10 -7 / K, and the tensile modulus at room temperature is 198GPa.

[0038] Example 2

[0039] In this embodiment, a preform of a ply stitched structure is used, and the fiber volume fraction is about 45%. After being kept at 3100°C for 0.5h, the preform is densified with phenolic resin, and the matrix carbon volume fraction reaches 50%. Silica sol with a solid content of 30% is impregnated at normal pressure for 8h and then kept at 120°C for 10h to obtain C / C-SiO 2 The intermediate was then heated to 1550℃ for 1.5h in a high temperature heat treatment furnace under argon protection to complete the preparation of SiC nanowires. Five rounds of densification were performed through precursor impregnation-cracking, and finally four rounds of HIP process were performed. Figure 4 The following is a local SEM image of the composite material. The average linear expansion coefficient of the composite material in the XY direction was measured at -50 to 80°C to be -3.2×10 -7 / K, and the tensile modulus at room temperature is 210GPa.

[0040] The above description is only the best specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

[0041] The contents not described in detail in the specification of the present invention belong to the common knowledge of the professionals in this field.

Claims

1. A method for preparing a near-zero expansion carbon-based composite material, characterized in that: The following steps are involved: (1) weaving mesophase pitch-based carbon fibers into a preform, and then graphitizing the preform; (2) subjecting the preform obtained in step (1) to carbon source precursor impregnation-cracking, introducing matrix carbon, and obtaining a C / C intermediate; (3) immersing the C / C intermediate obtained in step (2) in silica sol and drying in air to obtain a C / C-SiO2 intermediate; (4) placing the C / C-SiO2 intermediate obtained in step (3) in a high temperature treatment furnace to grow SiC nanowires to obtain C / C-SiC nw Intermediates; (5) Using polycarbosilane as a ceramic precursor, the C / C-SiC obtained in step (4) is treated by a precursor impregnation-cracking process. nw The intermediates undergo multiple rounds of densification; (6) Using hot isostatic pressing to densify the C / C-SiC obtained in step (5) nw The intermediate is subjected to multiple rounds of impregnation-carbonization sealing treatment to obtain a near-zero expansion carbon-based composite material.

2. The method for preparing a near-zero expansion carbon-based composite material according to claim 1, characterized in that: The preform structure in step (1) comprises at least one of two-dimensional plying, ply stitching, suturing or fine weaving puncture, and the fiber volume fraction is 20-60%.

3. The method for preparing a near-zero expansion carbon-based composite material according to claim 1, characterized in that: The graphitization treatment temperature in step (1) is 2300-3200° C., and the insulation time is 0.5-2 h.

4. The method for preparing a near-zero expansion carbon-based composite material according to claim 1, characterized in that: In step (2), the carbon source precursor is furfural resin, coal tar pitch, mesophase pitch or phenolic resin, and the volume fraction of the introduced matrix carbon is 20-60%.

5. The method for preparing a near-zero expansion carbon-based composite material according to claim 1, characterized in that: The maximum reaction temperature in step (2) is 700-1000°C.

6. The method for preparing a near-zero expansion carbon-based composite material according to claim 1, characterized in that: The solid content of the silica sol in step (3) is 20-40%, the immersion time is 8-24 hours, the drying temperature is 80-120° C., and the insulation time is 8-16 hours.

7. The method for preparing a near-zero expansion carbon-based composite material according to claim 1, characterized in that: In step (4), the treatment temperature is 1450-1550° C. and the insulation time is 0.5-2 h.

8. The method for preparing a near-zero expansion carbon-based composite material according to claim 1, characterized in that: In step (5), the number of cycles of the precursor impregnation-cracking process is 5 to 15.

9. The method for preparing a near-zero expansion carbon-based composite material according to claim 1, characterized in that: In step (6), the impregnation-carbonization sealing treatment process is cycled 2 to 7 times.

10. A near-zero expansion carbon-based composite material, characterized in that: Prepared according to the preparation method according to any one of claims 1 to 9.

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