B4C modified C / C composite material and preparation method thereof

Abstract

The invention belongs to the technical field of functional composite material preparation, and relates to a B4C modified C / C composite material and a preparation method thereof. According to the invention, a B4C neutron shielding material is used as a filler, a carbon fiber preform with a pyrolytic carbon interface layer is placed in B4C slurry, and a centrifugal impregnation process and a multi-time impregnation-curing-carbonization treatment process are adopted, so that the compact modified C / C composite material with uniformly distributed B4C is obtained. According to the method, a traditional slurry vacuum impregnation or pressure impregnation method is replaced, the problem of uneven distribution of B4C in a traditional method is solved, three-dimensional uniform distribution of B4C particles in a matrix is achieved, the process route is simple and easy to popularize, and an innovative solution is provided for material engineering application. Meanwhile, the novel centrifugal impregnation technology is particularly suitable for impregnation of low-density ceramic powder, the permeation and diffusion uniformity effect of slurry particles in the fabric is excellent, and the technology can be expanded to the field of ceramic-based composite material preparation.

Description

Technical Field

[0001] This invention belongs to the field of functional composite material preparation technology, and relates to a B4C modified C / C composite material and its preparation method, specifically to a B4C modified C / C composite material with neutron absorption capability and its preparation method. Background Technology

[0002] Boron-10 (B4C), renowned for its high abundance of the boron-10 isotope (10B), is an important neutron absorbing material. Its high hardness, low density, excellent chemical stability, and extremely high thermal neutron absorption cross-section make it widely used in the nuclear industry. For example, as a control rod in nuclear reactors and a neutron-absorbing shielding material, introducing B4C into metal matrix composites can significantly improve the neutron absorption efficiency of the material. Studies have shown that Al-Si-Mg-B4C composites with a B4C content increasing from 2% to 8% exhibit enhanced thermal neutron shielding performance. Carbon / carbon (C / C) composites are known for their lightweight, high specific strength, and excellent thermal shock resistance. Introducing B4C into C / C composites, combining the advantages of both, aims to develop a novel composite material that combines structural support with highly efficient neutron shielding. This composite material has significant application prospects in nuclear engineering fields such as nuclear waste storage and transport containers.

[0003] Secondly, in the aerospace field, lightweight and high-temperature resistance of materials are crucial. B4C-modified C / C composite materials provide high-temperature structural strength while also withstanding the space radiation environment, making them suitable for radiation shielding or high-temperature components in spacecraft.

[0004] However, in traditional preparation processes (such as vacuum impregnation or pressure impregnation), due to the low density and easy agglomeration of B4C powder, as well as the difference in interfacial properties between B4C and the carbon fiber / matrix, it is difficult to achieve uniform dispersion of B4C particles within the C / C preform. This results in uneven B4C distribution in the composite material, with a large content gradient from the surface to the center, which seriously affects the consistency and reliability of the material's nucleus shielding performance and may introduce local defects, impairing the material's mechanical properties.

[0005] Therefore, developing a preparation method that can achieve three-dimensional uniform dispersion of B4C in a C / C matrix is ​​a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a B4C-modified C / C composite material and its preparation method. This method effectively solves the problem of uneven distribution of B4C particles in the C / C preform through an innovative centrifugal impregnation process. The process is simple and easy to promote.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing B4C modified C / C composite material includes the following steps: (1) Centrifugal impregnation of B4C: Prepare B4C slurry, place the carbon fiber preform with pyrolytic carbon interface layer in the slurry, perform centrifugal impregnation treatment, and obtain a preform containing B4C after drying. (2) Resin impregnation pyrolysis densification: Prepare a resin precursor, impregnate the B4C-containing preform obtained in step (1) with the resin precursor, and then perform curing and carbonization treatment; repeat the impregnation-curing-carbonization treatment process 6-8 times to finally obtain a dense B4C modified C / C composite material.

[0008] Further, in step (1), the carbon fiber preform adopts a needle-punched structure, the fiber volume content is 30%~40% (preferably 30%~35%), and the average fiber diameter is 7μm; the thickness of the pyrolytic carbon interface layer is 50~300nm (preferably 100~200nm); the pyrolytic carbon interface layer is prepared by chemical vapor infiltration process, using one or two of Ar and N2 as carrier gas and dilution gas, and one or two of natural gas and C3H8 as gas phase precursor, with a gas phase precursor concentration of 10%~50% (preferably 15%~30%); the deposition temperature is 900~950℃, and the deposition time is 30~100h.

[0009] Further, in step (1), the B4C slurry preparation method is as follows: B4C powder, anhydrous ethanol and dispersant are mixed and ball-milled; the particle size of the B4C powder is 50~200nm (preferably 50~100nm), and the B4C content is 3~15% (preferably 5~10%); the type of dispersant is one of polyethyleneimine (PEI), polyethylene glycol (PEG) and polyoxymethylene (PMA); the mass ratio of anhydrous ethanol to dispersant is 1000~2000:1 (preferably 1000~1500:1); the ball milling medium is zirconium oxide, the ball diameter is 3~8mm (preferably 5~8mm), the ball-to-material volume ratio is 3:1, the ball milling speed is 200~600 rpm (preferably 300~400 rpm), and the ball milling time is 10~50h (preferably 10~12h).

[0010] Further, in step (1), the centrifugal impregnation treatment is performed with a rotation speed of 500~1000r / min (preferably 500~800r / min) and an impregnation time of 1~3h (preferably 1~1.5h); the drying temperature is 100-120℃ and the drying time is 5~20h.

[0011] Further, in step (2), the resin precursor is prepared by mixing and stirring a thermosetting resin and a curing agent for 0.5 to 2 hours. The thermosetting resin is phenolic resin or furfuryl ketone resin, and the curing agent is one of hexamethylenetetramine, benzenesulfonic acid and oxalic acid. The amount of curing agent added is 0.2 to 1% (preferably 0.5 to 0.8%) of the resin mass.

[0012] Further, in step (2), the impregnation process conditions are as follows: first, vacuum is applied to 10~50Pa (preferably 10~20Pa) and maintained for 3~5h (preferably 5h), then pressure is applied to 6~10MPa (preferably 6~7MPa) and maintained for 3~5h (preferably 5h). The curing temperature is 150~180℃ (preferably 170~180℃), and the curing time is 10~15h (preferably 12~15h). The carbonization temperature is 1000~1200℃ (preferably 1100~1200℃), the heating rate is 1~3℃ / min (preferably 1~2℃ / min), and the carbonization time is 1~2h (preferably 2h).

[0013] Further, in step (2), after each impregnation-curing-carbonization treatment, the weight gain rate of the preform containing B4C is detected. When the weight gain rate is less than 1.5%, the graphitization process is carried out. The graphitization process conditions are: temperature 1900~2200℃ (preferably 1900~2000℃), heating rate 0.05~2℃ / min (preferably 0.5~1℃ / min), and holding time 2~3h (preferably 2h).

[0014] A B4C-modified C / C composite material prepared according to the above preparation method, with a composite material density ≥ 1.7 g / cm³. 3 The B4C content in the composite material is 3~8wt%, and the B4C is evenly distributed from the surface to the center of the material.

[0015] Effective gain Compared with the prior art, the present invention has the following significant advantages: (1) High uniformity of distribution: The centrifugal impregnation process is adopted, which uses centrifugal force to drive the B4C slurry to penetrate deeply into the interior of the carbon fiber preform. This fundamentally solves the problem of uneven distribution caused by B4C particle agglomeration and density difference in the traditional vacuum or pressure impregnation method, and realizes the three-dimensional uniform dispersion of B4C in the C / C matrix.

[0016] (2) Simple and efficient process: The process route is clear, the operation is simple, the equipment requirements are lower than those of traditional high pressure impregnation, and it is easy to achieve large-scale production and promotion.

[0017] (3) Excellent and consistent performance: The prepared composite material not only has high density (≥1.7 g / cm³), but also has excellent and consistent performance.3 Furthermore, the B4C content is controllable and uniformly distributed, ensuring the uniformity and reliability of the material's neutron absorption performance and mechanical properties.

[0018] (4) Strong technical versatility: This centrifugal impregnation technology is particularly suitable for the uniform introduction of low-density ceramic powder into porous preforms and can be extended to the preparation of other ceramic matrix composites. Attached Figure Description

[0019] Figure 1 This is a process flow diagram of the preparation method of the present invention.

[0020] Figure 2 The diagram shows a comparison of the bending strength-displacement curves of the materials obtained in the examples and comparative examples.

[0021] Figure 3 The image shows a comparison of the XRD patterns of samples taken from the central region of the materials obtained in the examples and comparative examples.

[0022] Figure 4 The image is a scanning electron microscope (SEM) image of the B4C modified C / C composite material prepared in Example 1. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. The following embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0024] Example 1 The process flow diagram of the preparation method of this invention is as follows: Figure 1 As shown, the details are as follows: (1) Centrifugal impregnation of B4C: A B4C slurry with an average particle size of 80 nm, anhydrous ethanol, and dispersant polyethyleneimine (PEI) powder (molecular weight 1800, particle size <0.5 mm) was prepared, with a content of approximately 4 wt%. The mass ratio of anhydrous ethanol to dispersant was 1000:1. Zirconia balls with a diameter of 5 mm were added at a ball-to-material volume ratio of 3:1, and the mixture was ball-milled at 400 rpm for 10 h. A needle-punched carbon fiber preform (purchased from Jiangsu Tianniao High-Tech Co., Ltd.) with dimensions of 50mm×50mm×50mm, a fiber (average diameter 7μm) volume content of 32%, and a 100nm thick pyrolytic carbon layer on its surface (the pyrolytic carbon layer was obtained on the fiber surface through a chemical vapor infiltration process using Ar or N2 as the carrier gas and dilution gas, and natural gas or C3H8 as the gaseous precursor, with a gas concentration of 15%; deposition temperature 950℃, deposition time 80h) was immersed in the above slurry. The container was placed in a centrifuge and centrifuged at 800r / min for 1.2h. The preform was then removed and dried at 100℃ for 10h to obtain a preform containing B4C.

[0025] (2) Resin impregnation, pyrolysis, and densification: Phenolic resin (produced by Shandong Shengquan Chemical) was mixed with 1 wt% hexamethylenetetramine curing agent, and stirred for 1 h to obtain a resin precursor. The preform obtained in step (1) was placed in a vacuum-pressure impregnation furnace (vacuum-pressure impregnation furnace, manufactured by Jiangsu Wangda Special Equipment Manufacturing Co., Ltd.), and a vacuum was drawn to 10 Pa and maintained for 3 h. Then, the resin precursor was slowly injected until the preform was completely impregnated. Nitrogen gas was introduced to pressurize to 6 MPa and the pressure was maintained for 5 h to complete the impregnation. After removal, it was cured at 170℃ for 10 h, and then carbonized at 1℃ / min under vacuum to 1150℃ for 1 h. This is one "impregnation-curing-carbonization" cycle, which was repeated. After each cycle, the weight was weighed. When the weight gain rate of a single cycle was less than 1.5%, graphitization treatment was performed at 0.5℃ / min under nitrogen protection, and the temperature was maintained for 2 h. Then the cycle was continued. In this embodiment, the weight gain rate was 1.4% when the fifth cycle was performed. After one graphitization treatment, two more cycles were performed, for a total of seven cycles, and finally the B4C modified C / C composite material was obtained.

[0026] Comparative Example 1 The only difference between this comparative example and Example 1 is step (1): the centrifugal impregnation step is omitted, and the carbon fiber preform and the ball-milled B4C slurry are placed in a container and impregnated for 3 hours under a vacuum of 10 Pa. The remaining steps and parameters are exactly the same as in Example 1.

[0027] Example 2 This embodiment is consistent with step (1) of the centrifugal impregnation method of B4C in Embodiment 1; Step (2) Resin impregnation, pyrolysis, and densification: Furfuryl ketone resin was mixed with 0.5 wt% benzenesulfonic acid curing agent and stirred for 1.5 h to obtain a resin precursor. The impregnation, curing, and carbonization parameters were the same as in Example 1. A total of 6 cycles were performed, and graphitization treatment was carried out after the 4th cycle (under the same conditions as in Example 1) to finally obtain the B4C modified C / C composite material.

[0028] Comparative Example 2 The only difference between the comparative example and Example 2 is step (1): the centrifugal impregnation step is omitted, and the carbon fiber preform is immersed in the ball-milled B4C slurry at normal pressure for 3 hours. The remaining steps and parameters are exactly the same as in Example 2.

[0029] Example 3 The difference between this embodiment and the centrifugal impregnation method of B4C in step (1) of embodiment 1 is that the solid content of the slurry is changed to 6wt%, while other parameters are the same; step (2) is completely the same as step (2) of embodiment 1.

[0030] Comparative Example 3 The only difference between this comparative example and Example 3 is step (1): the centrifugal impregnation step is omitted, and the carbon fiber preform and the ball-milled B4C slurry are placed in a pressure vessel (vacuum-pressure impregnation furnace, manufactured by Jiangsu Wangda Special Equipment Manufacturing Co., Ltd.) and impregnated at 5MPa for 3 hours. The remaining steps and parameters are exactly the same as in Example 1.

[0031] The material properties of the examples and comparative examples are compared in Table 1.

[0032] Table 1 Performance Comparison

[0033] In the table: Design B4C content %: refers to the percentage of boron by mass in the final material; Surface area B4C content %: refers to the percentage of B4C by mass in the area 1 mm deep from the surface; Central area B4C content %: refers to the percentage of B4C by mass in the area 24-25 mm deep from the surface; Overall B4C content %: refers to the percentage of B4C by mass in all areas; All the above content values ​​are average values ​​obtained after testing multiple points within the specified area.

[0034] Note: The testing standards refer to the following standards: ASTM C559 (material density), ASTM C1233 (boron content), ASTM C1341 (material flexural strength), and ASTM C1470 (coefficient of thermal expansion).

[0035] As shown in Table 1, the boron content in the central region of the materials from Examples 1, 2, and 3, which utilize the centrifugal impregnation process of this invention, is very close to that in the surface region, and the uniformity of distribution is far superior to that of the samples impregnated using traditional vacuum impregnation (Comparative Example 1), atmospheric pressure immersion (Comparative Example 2), and high pressure impregnation (Comparative Example 3). This indicates that centrifugal force effectively promotes the penetration of B4C slurry into the core of the preform. Simultaneously, the flexural strength of the materials from these examples is slightly higher than that of the comparative examples, demonstrating that a uniform microstructure is beneficial for improving mechanical properties.

[0036] Combination Figures 2-4 The test results can further verify that the bending load-displacement curve of the material in the example is superior. Figure 2 This indicates that it has better toughness; the characteristic peak intensity of B4C in the XRD pattern of the central region is significantly higher than that of the comparative example ( Figure 3 SEM images show that B4C particles are well dispersed in the carbon matrix with no significant agglomeration. Figure 4 ).

[0037] In summary, this invention successfully prepared a B4C-modified C / C composite material with uniform B4C distribution and excellent performance through a centrifugal impregnation process, effectively solving the problems mentioned in the background art.

Claims

1. A method for preparing B4C modified C / C composite material, characterized in that, Includes the following steps: (1) Centrifugal impregnation of B4C: Prepare B4C slurry, place the carbon fiber preform with pyrolytic carbon interface layer in the slurry, perform centrifugal impregnation treatment, and obtain a preform containing B4C after drying. (2) Resin impregnation, pyrolysis and densification: Prepare a resin precursor, impregnate the preform containing B4C obtained in step (1) with the resin precursor, and then perform curing and carbonization treatment. Repeat the impregnation-curing-carbonization process 6-8 times to finally obtain a dense B4C modified C / C composite material.

2. The preparation method according to claim 1, characterized in that: In step (1), the carbon fiber preform adopts a needle-punched structure, with a fiber volume content of 30%~40% (preferably 30%~35%) and an average fiber diameter of 7μm; the thickness of the pyrolytic carbon interface layer is 50~300nm (preferably 100~200nm); the pyrolytic carbon interface layer is prepared by chemical vapor infiltration process, using one or two of Ar and N2 as carrier gas and dilution gas, and one or two of natural gas and C3H8 as gas phase precursor, with a gas phase precursor concentration of 10%~50% (preferably 15%~30%); the deposition temperature is 900~950℃, and the deposition time is 30~100h.

3. The preparation method according to claim 1, characterized in that: In step (1), the B4C slurry preparation method is as follows: B4C powder, anhydrous ethanol, and dispersant are mixed and ball-milled; the particle size of the B4C powder is 50~200nm (preferably 50~100nm), and the B4C content is 3~15% (preferably 5~10%); the type of dispersant is one of polyethyleneimine (PEI), polyethylene glycol (PEG), and polyoxymethylene (PMA); the mass ratio of anhydrous ethanol to dispersant is 1000~2000:1 (preferably 1000~1500:1); the ball milling media is zirconium oxide, the ball diameter is 3~8mm (preferably 5~8mm), the ball-to-material volume ratio is 3:1, the ball milling speed is 200~600 rpm (preferably 300~400 rpm), and the ball milling time is 10~50h (preferably 10~12h).

4. The preparation method according to claim 1, characterized in that: In step (1), the centrifugal impregnation treatment is carried out at a speed of 500~1000 r / min (preferably 500~800 r / min) and an impregnation time of 1~3 h (preferably 1~1.5 h); the drying temperature is 100-120℃ and the drying time is 5~20 h.

5. The preparation method according to claim 1, characterized in that: In step (2), the resin precursor is prepared by mixing and stirring a thermosetting resin and a curing agent for 0.5 to 2 hours. The thermosetting resin is phenolic resin or furfural resin, and the curing agent is one of hexamethylenetetramine, benzenesulfonic acid and oxalic acid. The amount of curing agent added is 0.2 to 1% (preferably 0.5 to 0.8%) of the resin mass.

6. The preparation method according to claim 1, characterized in that: In step (2), the impregnation process conditions are as follows: first, vacuum is applied to 10~50Pa (preferably 10~20Pa) and maintained for 3~5h (preferably 5h), then pressure is applied to 6~10MPa (preferably 6~7MPa) and maintained for 3~5h (preferably 5h). The curing temperature is 150~180℃ (preferably 170~180℃), and the curing time is 10~15h (preferably 12~15h). The carbonization temperature is 1000~1200℃ (preferably 1100~1200℃), the heating rate is 1~3℃ / min (preferably 1~2℃ / min), and the carbonization time is 1~2h (preferably 2h).

7. The preparation method according to claim 1, characterized in that: In step (2), after each impregnation-curing-carbonization treatment, the weight gain rate of the preform containing B4C is detected. When the weight gain rate is less than 1.5%, the graphitization process is carried out. The graphitization process conditions are: temperature 1900~2200℃ (preferably 1900~2000℃), heating rate 0.05~2℃ / min (preferably 0.5~1℃ / min), and holding time 2~3h (preferably 2h).

8. A B4C-modified C / C composite material prepared according to any one of claims 1-7, characterized in that: The density of the composite material is ≥1.7 g / cm³. 3 The B4C content in the composite material is 3~8wt%, and the B4C is evenly distributed from the surface to the center of the material.

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