Pitch densified carbon-carbon composites and methods of making the same

Abstract

The application discloses pitch densification carbon-carbon composite material and a preparation method thereof. The preparation method comprises the following steps: pitch high-pressure impregnation is carried out on a carbon fiber preform or a low-density carbon-carbon composite material; a non-placed surface of the impregnated material is sequentially covered with polyurea, solidified, and covered with a heat-resistant thermosetting adhesive, and then solidified; and finally, heating carbonization and high-temperature graphitization treatment are carried out. The application can significantly improve the densification efficiency of pitch densification carbon-carbon composite material, and the quality, uniformity and stability of the obtained product, and reduce the production cost.

Description

Technical Field

[0001] This invention relates to the technical field of carbon-carbon composite materials, and particularly to a method for preparing carbon-carbon composite materials by asphalt densification. Background Technology

[0002] Asphalt is widely available and inexpensive. It has a high residual carbon rate after high temperature, and the asphalt carbon obtained after carbonization has a higher degree of graphitization than pyrolytic carbon obtained by pyrolysis or resin carbon obtained by resin carbonization. Asphalt is increasingly used in the preparation of carbon-carbon composite materials, especially in the treatment of carbon-carbon composite materials to enhance density, i.e., densification treatment.

[0003] Currently, when using asphalt for densification of carbon-carbon composites, to ensure the densification effect, the methods often involve chemical modification of the asphalt or high-temperature, high-pressure impregnation of unmodified asphalt. However, among these methods, chemical modification is costly, inefficient, and the modified material is difficult to reuse. While high-temperature, high-pressure impregnation addresses this issue because asphalt's physical properties are similar to thermoplastic resins; when the temperature exceeds the asphalt's softening point, the viscosity decreases rapidly with increasing temperature. This causes most of the impregnated asphalt in the preform or carbon-carbon composite to flow out during carbonization, resulting in poor densification. To improve this, some existing technologies repeat the asphalt impregnation and carbonization process multiple times. However, this significantly increases production costs, reduces the uniformity of the material's structure and properties, and increases the difficulty of controlling material quality stability. Summary of the Invention

[0004] To address the aforementioned problems in the prior art, the present invention aims to provide a novel method for preparing carbon-carbon composite materials using asphalt densification. This method can significantly improve the densification efficiency, the quality, structural uniformity, and stability of the resulting product, while reducing production costs.

[0005] The technical solution of the present invention is as follows:

[0006] A method for preparing an asphalt-densified carbon-carbon composite material, comprising:

[0007] (1) The carbon fiber preform or low-density carbon-carbon composite material is impregnated with pitch by vacuum-assisted high-pressure impregnation to obtain the first composite material.

[0008] (2) Using one outer surface of the first composite material as the placement surface, polyurea is used to cover all other surfaces of the first composite material except the placement surface, and after curing, a second composite material is obtained.

[0009] (3) The entire surface of the second composite material covered with polyurea is further covered with a thermosetting high-temperature resistant adhesive to obtain a third composite material;

[0010] (4) Place the third composite material with its surface facing down, and then heat it until the thermosetting high-temperature resistant adhesive is cured to obtain the fourth composite material;

[0011] (5) Place the fourth composite material with its surface facing upwards, and then heat and carbonize it in an inert atmosphere to obtain the fifth composite material;

[0012] (6) The fifth composite material is subjected to high-temperature graphitization treatment to obtain a carbon-carbon composite material with asphalt densification.

[0013] In the above technical solution of the present invention, polyurea is first coated onto a portion of the surface of the asphalt-impregnated carbon fiber preform or porous carbon-carbon composite material, followed by a thermosetting high-temperature resistant adhesive. Polyurea significantly improves the bonding strength, coating quality, and processing efficiency between the thermosetting high-temperature resistant adhesive and the asphalt. After combining with the thermosetting high-temperature resistant adhesive, a stable, continuous shell resistant to 450°C can be formed on the asphalt surface, effectively preventing asphalt outflow during the carbonization stage, thus improving asphalt utilization efficiency and carbon yield. Furthermore, after carbonization and high-temperature graphitization treatment, both polyurea and the thermosetting high-temperature resistant adhesive retain only carbon elements, eliminating the need for physical removal or chemical purification.

[0014] According to some preferred embodiments of the present invention, the preparation method further includes: testing the density of the composite material obtained by heating and carbonization; if the density reaches the set requirement, then performing the high-temperature graphitization treatment; otherwise, repeating steps (1) to (5) several times until the density reaches the set requirement.

[0015] According to some preferred embodiments of the present invention, the asphalt is selected from one or more of high-temperature coal tar pitch, mesophase asphalt and modified coal tar pitch with a softening point of 80 to 180°C.

[0016] According to some preferred embodiments of the present invention, the density of the carbon fiber preform is 0.10–0.60 g / cm³. 3 .

[0017] According to some preferred embodiments of the present invention, the density of the low-density carbon-carbon composite material is 0.6–1.4 g / cm³. 3 .

[0018] According to some preferred embodiments of the present invention, the impregnation temperature is 200-300°C and the impregnation pressure is 2.0-5.0 MPa.

[0019] According to some preferred embodiments of the present invention, the thermosetting high-temperature resistant adhesive comprises a thermosetting resin selected from phenolic resins and / or furan resins.

[0020] According to some preferred embodiments of the present invention, the thermosetting high-temperature resistant adhesive further includes a modifier and a diluent, wherein the modifier is selected from high-temperature coal tar pitch powder and / or mesophase coal tar pitch powder, and the diluent is selected from methanol and / or ethanol.

[0021] According to some preferred embodiments of the present invention, in the thermosetting high-temperature resistant adhesive, the mass ratio of the thermosetting resin, the modifier and the diluent is 100:(2-10):(0-25).

[0022] According to some preferred embodiments of the present invention, the polyurea has a coating thickness of 0.05 to 0.2 mm.

[0023] According to some preferred embodiments of the present invention, the coating thickness of the thermosetting high-temperature resistant adhesive is 0.6 to 1.5 mm.

[0024] According to some preferred embodiments of the present invention, the carbonization treatment temperature is 800-1000℃, and the heating rate in the heating range of 400℃-450℃ is ≤10℃ / h.

[0025] According to some preferred embodiments of the present invention, the temperature of the high-temperature graphitization treatment is 1800-2500°C.

[0026] This invention further provides a carbon-carbon composite material for asphalt densification prepared according to the above-described preparation method. The density of this composite material is 1.3–1.8 g / cm³. 3 .

[0027] This invention can significantly reduce the number of cycles of asphalt impregnation and carbonization in traditional asphalt impregnation and densification methods, save asphalt usage, reduce production energy consumption and carbon emissions, and obtain a denser carbon-carbon composite material with more uniform internal and external density. Attached Figure Description

[0028] Figure 1 SEM images of the interior (a) and edge (b) of the densified flat carbon-carbon composite material obtained in Example 1;

[0029] Figure 2 The image shows the actual carbon-ceramic brake disc made of carbon-carbon composite material obtained in Example 4.

[0030] Figure 3 SEM images of the interior (a) and edge (b) of the densified carbon-carbon composite material obtained in Comparative Example 1. Detailed Implementation

[0031] The technical solutions of the present invention will be further described below with reference to the embodiments and accompanying drawings. The embodiments described below are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0032] Example 1

[0033] The following steps are used to prepare dense, flat carbon-carbon composite materials in batches:

[0034] (1) The bulk density is 0.40 g / cm³. 3 Flat carbon fiber preforms were subjected to vacuum-assisted high-pressure impregnation with asphalt to obtain composite material A, wherein the impregnation pressure was 2.0 MPa, the impregnation temperature was 210℃, the asphalt was high-temperature coal tar pitch with a softening point of 108℃~120℃, and its quinoline insoluble content was ≤4.0% and coking value was ≥54%.

[0035] (2) Using one horizontal surface of composite material A as the placement surface, apply a layer of polyurea to all surfaces of composite material A except the placement surface using Aier New Material D460 polyurea primer. After coating, place the material in a 50℃ forced-air oven for 15 minutes and then remove it to obtain composite material B.

[0036] (3) Apply thermosetting phenolic adhesive twice to the entire surface of composite material B that has been coated with polyurea primer, with each application having a coating thickness of 0.3–0.5 mm, to obtain composite material C; wherein, the thermosetting phenolic adhesive is Shandong Shengquan... The product is obtained by mixing 6% by mass of 200-mesh high-temperature asphalt powder and 12% by mass of ethanol into PF9501B thermosetting high-viscosity phenolic resin.

[0037] (4) With its surface facing down, place composite material C in a forced-air drying oven and treat it at 200℃ for 2 hours to obtain composite material D;

[0038] (5) With its surface facing up, place the composite material D into a carbonization furnace and heat it to 900℃ for 4 hours for carbonization treatment. The heating rate between 400℃ and 450℃ is 6.5℃ / h to obtain composite material E.

[0039] (6) The composite material E was graphitized at 2100℃ for 3 hours to obtain a denser flat carbon-carbon composite material.

[0040] The bulk density of the resulting densified flat carbon-carbon composite material was tested to be 0.82–0.90 g / cm³. 3 The average bulk density is 0.86 g / cm³. 3The charcoal yield was 48-53%, with an average yield of 51.1%.

[0041] The microstructure of the resulting denser plate-shaped carbon-carbon composite material was characterized, and SEM images of the interior (a) and edge (b) of the material are attached. Figure 1 As shown, it can be seen that inside the carbon-carbon composite material, asphalt is stacked in layers in sheet form between the carbon fiber individual fibers, and the gaps between the individual fibers are basically filled with asphalt; at the edge of the carbon-carbon composite material, most of the gaps between the individual fibers in the SEM field of view are also filled with asphalt, with only a few isolated carbon fibers at the very edge.

[0042] Example 2

[0043] The densified flat carbon-carbon composite material was prepared by the following steps:

[0044] (1) The bulk density is 0.45 g / cm³. 3 Flat carbon fiber preforms were subjected to vacuum-assisted high-pressure impregnation with asphalt to obtain composite material A. The impregnation pressure was 3.6 MPa, the impregnation temperature was 230℃, and the asphalt used was modified impregnated coal tar pitch with a softening point of 105~115℃, and its quinoline insoluble content was ≤2.0% and coking value was ≥50%.

[0045] (2) Using a horizontal surface of composite material A as the placement surface, apply two coats of Langke WXPUA-901 high temperature and wear resistant polyurea spray to all surfaces of composite material A except the placement surface, and allow it to cure naturally to obtain composite material B.

[0046] (3) Apply furan adhesive to all surfaces of the polyurea primer that have been sprayed on composite material B three times, with each application having a thickness of 0.2 to 0.3 mm, to obtain composite material C; wherein, the furan adhesive is obtained by uniformly mixing 15% by mass of high-temperature coal tar pitch powder with an average particle size of 150 mesh into Huibo XLZ500 furan resin.

[0047] (4) With its surface facing down, composite material C is placed in a carbonization furnace and treated at 220°C for 3 hours to obtain composite material D;

[0048] (5) With its surface facing up, the composite material D is flipped over and heated to 850℃ for carbonization treatment for 4 hours. The heating rate between 400℃ and 450℃ is 5℃ / h to obtain composite material E.

[0049] (6) Treat composite material E as the flat carbon fiber preform of step (1) and repeat the treatment of steps (1) to (4) three times.

[0050] (7) The processed composite material obtained in step (6) is subjected to high-temperature graphitization treatment at 2400℃ for 2 hours to obtain a denser flat carbon-carbon composite material.

[0051] The bulk density of the resulting densified flat carbon-carbon composite material was tested to be 1.65 g / cm³. 3 .

[0052] Example 3

[0053] The following steps are used to prepare a thermal insulation cylinder for a carbon-carbon composite material:

[0054] (1) A bulk density of approximately 0.90 g / cm³ was obtained through natural gas chemical vapor infiltration (CVI) densification treatment. 3 Carbon-carbon composite material insulation cylinder;

[0055] (2) Vacuum-assisted high-pressure impregnation of medium-temperature asphalt was performed on the obtained carbon-carbon composite insulation cylinder to obtain composite insulation cylinder A. The impregnation temperature was 240℃, the impregnation pressure was 1.6MPa, and the medium-temperature asphalt used was high-purity impregnation low-ash asphalt of Shandong coal series with a softening point of 80℃~95℃.

[0056] (3) Using the outer circumferential arc surface of 1 / 6 of the composite material insulation cylinder A as the placement surface, use the Aier New Material D460 polyurea primer roller to coat all surfaces of the composite material insulation cylinder A except the placement surface with polyurea, and obtain the composite material insulation cylinder B after natural surface drying.

[0057] (4) Apply high-temperature adhesive twice to the entire surface of the polyurea primer already sprayed on the composite insulation cylinder B, with each application having a thickness of 0.2 to 0.3 mm, to obtain the composite insulation cylinder C; wherein, the high-temperature adhesive is obtained by dissolving Yushiju PF-YSJ-2180M phenolic resin powder in 20 wt% ethanol and then adding 10% by mass of high-temperature asphalt powder with an average particle size of 400 mesh and mixing evenly.

[0058] (5) With its surface facing down, place the composite material insulation cylinder C on the arc-shaped wooden fixture in the forced-air drying oven and treat it at 160℃ for 4 hours to obtain the composite material insulation cylinder D.

[0059] (6) With its surface facing up, place the composite material insulation cylinder D on the arc-shaped steel fixture in the carbonization furnace, introduce nitrogen gas, and heat it to 1000℃ for carbonization treatment for 2.5h, wherein the heating rate between 400℃ and 450℃ is 4℃ / h; to obtain the composite material insulation cylinder E.

[0060] (7) The composite material insulation cylinder E is treated at 2300℃ for 3 hours to obtain a carbon-carbon composite thermal insulation cylinder.

[0061] Tests showed that the bulk density of the carbon-carbon composite material in the thermal insulation cylinder for this thermal field is no less than 1.25 g / cm³. 3 .

[0062] Example 4

[0063] Carbon-ceramic brake discs made of carbon-carbon composite materials are prepared by the following steps:

[0064] (1) A bulk density of approximately 1.0 g / cm³ was obtained through natural gas CVI densification treatment. 3 Carbon-carbon composite material disk;

[0065] (2) Vacuum-assisted high-pressure impregnation of the obtained carbon-carbon composite disk with mesophase pitch was carried out to obtain composite disk A. The impregnation temperature was 280℃, the impregnation pressure was 2.0MPa, and the pitch used was Baowu mesophase pitch MP-1, which had a softening point of 155℃~175℃.

[0066] (3) Using any disk plane of composite material disk A as the placement surface, apply polyurea twice to all surfaces of composite material disk A except the placement surface using Langke WXPUA-901 high temperature and wear resistant polyurea. After natural curing, composite material disk B is obtained.

[0067] (4) Apply thermosetting boron phenolic adhesive 3-5 times to the entire surface of the composite material disk B that has been coated with polyurea primer, with a total thickness of approximately 1.2 mm, to obtain composite material C; wherein, the thermosetting boron phenolic adhesive is made from Shandong Shengquan... PF9506 is obtained by mixing 5% by mass of 400-mesh mesophase pitch powder and 6% by mass of methanol with boron phenolic resin for ablation resistance.

[0068] (5) With its surface facing down, place the composite material disk C into a forced-air drying oven and heat it to 180℃ for 2 hours to obtain the composite material disk D.

[0069] (6) With its surface facing up, place the composite material disk D into the carbonization furnace, introduce nitrogen gas, and heat it to 900℃ for carbonization treatment for 3 hours. The heating rate between 400℃ and 450℃ is 5℃ / h; thus, the composite material disk E is obtained.

[0070] (7) Treat the composite material disk E as the carbon-carbon composite material disk in step (2) and repeat the process of steps (2) to (6) once.

[0071] (8) The processed composite material disk obtained in step (7) is subjected to high temperature treatment at 2100℃ for 3.5 hours to obtain the following result. Figure 2 The carbon-ceramic brake disc shown is made of carbon-carbon composite material.

[0072] From the appendix Figure 2 It can be seen that the black carbon is densely and uniformly distributed throughout the entire carbon-carbon composite disk, with no CVI-densified hard lumps on the surface. Furthermore, nine Φ30*30 cylinders were cut from the carbon-carbon composite disk. Testing showed that their average bulk density was approximately 1.45 g / cm³, with a coefficient of variation ≤3%; their average porosity was approximately 19%, with a coefficient of variation ≤2%.

[0073] Comparative Example

[0074] The following steps are used to prepare dense, flat carbon-carbon composite materials in batches:

[0075] (1) The bulk density is 0.40 g / cm³. 3 Flat carbon fiber preforms were subjected to vacuum-assisted high-pressure impregnation with asphalt to obtain composite material A, wherein the impregnation pressure was 2.0 MPa, the impregnation temperature was 210℃, the asphalt was high-temperature coal tar pitch with a softening point of 108℃~120℃, and its quinoline insoluble content was ≤4.0% and coking value was ≥54%.

[0076] (2) Place composite material A into a carbonization furnace, introduce nitrogen gas, and heat to 900℃ for carbonization treatment for 4 hours. The heating rate between 400 and 450℃ is 6.5℃ / h to obtain composite material B.

[0077] (3) The composite material B was graphitized at 2100℃ for 3 hours to obtain a denser flat carbon-carbon composite material.

[0078] The bulk density of the resulting densified flat carbon-carbon composite material was tested to be 0.73–0.78 g / cm³. 3 The average bulk density is 0.72 g / cm³. 3 The charcoal yield was 40-43%, with an average yield of 41.6%.

[0079] As can be seen, Comparative Example 1 used the same preform, asphalt and impregnation, carbonization and high-temperature graphitization process as Example 1, but the average density of the denser flat carbon-carbon composite material obtained in Example 1 increased by 19.4% and the average carbon yield increased by 22.8%.

[0080] Furthermore, the microstructure of the obtained denser planar carbon-carbon composite material was characterized, and the SEM images of the interior (a) and edge (b) of the material are attached. Figure 3 As shown, it can be seen that the gaps between the individual fibers inside the carbon-carbon composite material are also basically filled with bitumen, but the filling rate is worse than that of Example 1; at the edge of the carbon-carbon composite material, almost no bitumen filling is visible in the SEM field of view, and almost all of them are bare carbon fibers. The bitumen at the edge of the carbon-carbon composite material is almost completely lost during the carbonization process.

[0081] It should be noted that the above descriptions are merely preferred embodiments of the present invention and should not limit the scope of protection of the technical solutions of the present invention. Any modifications made to the technical solutions described in the foregoing embodiments, or equivalent substitutions of technical features, by those skilled in the art within the spirit and principles of the present invention, should be included within the scope of protection of the present invention.

Claims

1. A method for preparing an asphalt-densified carbon-carbon composite material, characterized in that, It includes: (1) The carbon fiber preform or low-density carbon-carbon composite material is impregnated with pitch by vacuum-assisted high-pressure impregnation to obtain the first composite material. (2) Using one outer surface of the first composite material as the placement surface, polyurea is used to cover all other surfaces of the first composite material except the placement surface, and after curing, a second composite material is obtained. (3) The entire surface of the second composite material covered with polyurea is further covered with a thermosetting high-temperature resistant adhesive to obtain a third composite material; (4) Place the third composite material with its surface facing down, and then heat it until the thermosetting high-temperature resistant adhesive is cured to obtain the fourth composite material; (5) Place the fourth composite material with its horizontal surface facing upward, and then heat it in an inert atmosphere to carbonize it, thereby obtaining the fifth composite material. (6) The fifth composite material is subjected to high-temperature graphitization treatment to obtain a carbon-carbon composite material with asphalt densification.

2. The preparation method according to claim 1, characterized in that, It also includes: testing the density of the composite material obtained by heating and carbonization; if the density meets the set requirements, then performing the high-temperature graphitization treatment; otherwise, repeating steps (1) to (5) several times until the density meets the set requirements.

3. The preparation method according to claim 1, characterized in that, in, The asphalt is selected from one or more of high-temperature coal tar pitch, mesophase asphalt, and modified coal tar pitch with a softening point of 80–180℃; and / or, the density of the carbon fiber preform is 0.10–0.60 g / cm³. 3 ; and / or, the density of the low-density carbon-carbon composite material is 0.6–1.4 g / cm³. 3 .

4. The preparation method according to claim 1, characterized in that, The impregnation temperature is 200–300°C, and the impregnation pressure is 2.0–5.0 MPa.

5. The preparation method according to claim 1, characterized in that, The thermosetting high-temperature resistant adhesive includes a thermosetting resin, which is selected from phenolic resin and / or furan resin.

6. The preparation method according to claim 5, characterized in that, The thermosetting high-temperature resistant adhesive further includes a modifier and a diluent, wherein the modifier is selected from high-temperature coal tar pitch powder and / or mesophase coal tar pitch powder, and the diluent is selected from methanol and / or ethanol.

7. The preparation method according to claim 6, characterized in that, In the thermosetting high-temperature resistant adhesive, the mass ratio of the thermosetting resin, modifier and diluent is 100:(2-10):(0-25).

8. The preparation method according to claim 1, characterized in that, The polyurea has a coating thickness of 0.05–0.2 mm; and / or the thermosetting high-temperature resistant adhesive has a coating thickness of 0.6–1.5 mm.

9. The preparation method according to claim 1, characterized in that, The carbonization treatment temperature is 800–1000℃, and the heating rate in the heating range of 400℃–450℃ is ≤10℃ / h; and / or, the high-temperature graphitization treatment temperature is 1800–2500℃.

10. The asphalt-densified carbon-carbon composite material prepared by the preparation method according to any one of claims 1-9.

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