A method for preparing high-density and high-strength carbon materials based on waste carbon-carbon composite materials

Abstract

The present invention discloses a method for preparing high-density and high-strength carbon materials based on waste carbon-carbon composite materials, comprising the following steps: 1) using waste carbon-carbon composite materials as raw materials and mechanically crushing them; 2) subjecting the crushed carbon-carbon waste materials to high-energy ball milling to obtain fine materials with dissociation of carbon fibers and pyrolytic carbon interfaces; 3) coating the waste carbon-carbon fine materials with a phenolic resin alcohol solution; 4) thoroughly mixing the mesophase carbon microspheres with the resin-coated carbon-carbon waste materials, and then subjecting them to cold molding and carbonization treatment to obtain high-density and high-strength carbon materials. The present invention solves the problem of tight interface bonding between carbon fibers and pyrolytic carbon, and achieves nearly 100% recovery of waste carbon-carbon composite materials. The carbon material prepared by the present invention has high density and high strength, low production cost, short preparation cycle, and low requirements for process operation and equipment.

Description

Technical Field

[0001] The present invention belongs to the technical field of carbon material preparation, and relates to a method for preparing a high-density and high-strength carbon material, and in particular to a method for preparing a high-density and high-strength carbon material based on waste carbon-carbon composite materials. Background Art

[0002] Carbon-carbon composites (CCCs) are carbon-based composites composed of carbon fibers or carbon fiber products reinforced with a carbon matrix (pyrolytic carbon, resin carbon, or pitch carbon). They feature low density, high thermal conductivity, low thermal expansion coefficient, and excellent high-temperature mechanical properties, and are widely used in aerospace, photovoltaic, and military applications. In recent years, with the rapid development of my country's aerospace and photovoltaic industries, the consumption of CCCs has steadily increased. This has led to a significant increase in the production and processing of CCCs, including large amounts of waste, including offcuts and scrap. Recycling this waste into high-value-added products has become a critical issue.

[0003] High-density carbon materials, with their excellent mechanical properties, ideal self-lubrication, and superior thermal and electrical conductivity, have found widespread application in fields such as electrolytic aluminum, aerospace, and transportation. Using carbon-carbon composite waste as aggregate to produce high-density carbon materials is a promising option for reproducing high-value-added products. To this end, the first issue that must be addressed is the tight interface between the carbon fibers and pyrolytic carbon in the carbon-carbon waste, making dispersion difficult. Tightly bonded carbon fibers / pyrolytic carbon prevent complete encapsulation by the binder and create excessively large aggregate pores, negatively impacting the product. Currently, screening and oxidation treatment are commonly used solutions. On the one hand, screening reduces recycling rates and can only remove large particles, failing to address the interfacial dispersion of fine particles. On the other hand, oxidation treatment reduces aggregate strength, is costly, and takes a long time to process, making it unsuitable for large-scale industrialization. Secondly, the low density of carbon materials produced from carbon-carbon waste as aggregate must be addressed. The carbon materials produced by CN108395268A and CN114773078A using carbon waste have the problem of low density. Both require a long time of chemical vapor deposition densification, and the density after densification is only 1.3g / cm 3 This undoubtedly increases production costs and time costs. CN114276158A uses carbon waste as raw material to prepare a high-density carbon material. The cost is that the waste needs to be treated with strong acid and alkali, oxidized, and impregnated three times for densification. This process is also not suitable for actual industrial production. Summary of the Invention

[0004] The present invention aims to provide a method for preparing high-density, high-strength carbon materials from recycled waste carbon-carbon composite materials. This method is low-cost, quick, and convenient. The invention proposes a method for preparing high-density, high-strength carbon materials by mechanically shaping the waste carbon-carbon materials to achieve interfacial dissociation between carbon fibers and pyrolytic carbon, and then combining self-sintering with traditional sintering to achieve a single-step carbonization and densification.

[0005] To achieve the above objectives, the present invention provides the following technical solutions:

[0006] The method for preparing high-density and high-strength carbon materials based on recycling waste carbon-carbon composite materials provided by the present invention comprises the following steps:

[0007] Step 1: Mechanically crushing the waste carbon-carbon composite material to obtain waste carbon-carbon coarse material particles;

[0008] Step 2: Using alcohol as a ball milling medium, the waste carbon coarse material particles in step 1 are subjected to high-energy ball milling, and after mechanical shaping, waste carbon fine material particles with dissociation of carbon fibers and pyrolytic carbon are obtained;

[0009] Step 3: adding the waste carbon fine material particles in step 2 to the phenolic resin alcohol solution, stirring thoroughly, and then drying to obtain phenolic resin-coated waste carbon coarse material particles;

[0010] Step 4: using water as a ball milling medium, ball milling the phenolic resin-coated waste carbon coarse material particles in step 3 to crush and refine them to obtain phenolic resin-coated waste carbon fine material particles;

[0011] Step 5: adding mesocarbon microspheres to phenolic resin-coated waste carbon fine particles according to a preset ratio, fully ball-milling, and drying the water to obtain a mixture of refined phenolic resin-coated waste carbon particles and mesocarbon microspheres;

[0012] Step 6: cold-pressing the mixture obtained in step 5 to obtain a green body;

[0013] Step 7: Under the protection of an inert atmosphere, the green body obtained in step 6 is carbonized to obtain a high-density and high-strength carbon material with carbon waste as aggregate.

[0014] Preferably, in the step 2, the ball milling speed is 800-1000 r / min, and the ball milling time is 1-2 h.

[0015] Preferably, in step three, the mass ratio of waste carbon fine particles to phenolic resin is (11-14):7, and the mass concentration of phenolic resin in the phenolic resin alcohol solution is 0.16 g / ml.

[0016] Preferably, in step 3, the stirring speed is 600-800 r / min and the stirring time is 1-2 h.

[0017] Preferably, in step 4, the ball milling speed is 200-400 r / min, and the ball milling time is 1-2 h.

[0018] Preferably, in step five, the mass of the mesocarbon microspheres accounts for 25%-50% of the total mass of the mesocarbon microspheres and the phenolic resin-coated waste carbon fine material particles.

[0019] Preferably, in step 5, the ball milling speed is 100-200 r / min, and the ball milling time is 1-2 h.

[0020] Preferably, in step six, the molding pressure of the cold molding is 2-10 MPa, and the holding time is 3 minutes.

[0021] Preferably, in step seven, the process parameters of the carbonization treatment are specifically as follows: RT-300°C, time is 3h; 300-800°C, time is 12h; 800-1000°C, time is 2h; 1000-1000°C, time is 1h; 1000-600°C, time is 6.5h; 600°C-RT, natural cooling.

[0022] Principles and beneficial effects of the present invention:

[0023] The present invention uses cuttings and scraps from the production and processing of carbon-carbon composite materials as raw materials, obtains waste carbon-carbon coarse particles after mechanical crushing, and then subjects the waste carbon-carbon coarse particles to high-energy ball milling to obtain micron-sized particles with dissociation of carbon fibers and pyrolytic carbon interfaces. This is conducive to achieving 100% recycling of carbon-carbon waste materials, complete coating of carbon-carbon waste materials with phenolic resin, and reduction of aggregate accumulation pores. Particle refinement is inevitable in the mechanical separation of the interface between carbon fibers and pyrolytic carbon. The increase in the specific surface area of ​​the refined particles leads to an increase in the amount of binder added, thereby reducing the density of the final product. In order to eliminate the negative impact of particle refinement and shorten the preparation cycle, and to achieve the purpose of preparing high-density carbon materials by one-time carbonization, the self-sintering properties of mesophase carbon microspheres are utilized to cooperate with the traditional sintering behavior of resin-coated waste carbon-carbon, thereby achieving the purpose of preparing high-density and high-strength carbon materials based on the recycling of waste carbon-carbon composite materials.

[0024] The method of the invention has the characteristics of 100% carbon waste utilization rate, low production cost, short preparation cycle and low requirements on process operation and equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is an operation flow chart of the present invention;

[0026] Figure 2 is a SEM secondary electron photograph of the carbon-carbon waste after mechanical crushing in Example 1;

[0027] Figure 3 is a SEM secondary electron photograph of the carbon-carbon waste after high-energy ball milling in Example 1;

[0028] Figure 4 is a SEM secondary electron photograph of the carbon-carbon waste after resin coating in Example 1;

[0029] Figure 5 This is a photo of the high-density and high-strength carbon material prepared in Example 1;

[0030] Figure 6 This is a SEM secondary electron photograph of the high-density and high-strength carbon material prepared in Example 1. DETAILED DESCRIPTION

[0031] The technical solutions of the present invention are further described below in conjunction with the embodiments. The following embodiments are intended to better illustrate the present invention, but are not intended to limit the scope of the present invention.

[0032] Example 1

[0033] Step 1: Cut the carbon-carbon composite scraps into pieces of about 2×2×2cm using a cutting machine. 3 The small pieces of waste carbon are separated and the cuttings are collected at the same time. Subsequently, the small pieces and cuttings are put into a mechanical crusher for crushing to obtain waste carbon coarse particles.

[0034] Step 2: Weigh 200g of the coarse waste carbon particles from Step 1, divide them into four equal portions, and place them into four zirconia ball mills. Simultaneously, inject 60ml of alcohol into each mill. Set the ball mill speed to 1000 rpm and mill for 2 hours, running for 15 minutes and pausing for 5 minutes. The milled waste carbon fines were then dried in a 70°C oven to constant weight, yielding waste carbon fines with dissociated carbon fibers and pyrolytic carbon at the interface.

[0035] Step 3: Add 20g of waste carbon fine particles in batches to 67mL of a 0.16g / mL phenolic resin alcohol solution while stirring. Stir the mixture for 2 hours using a magnetic stirrer at 800 rpm. Place the stirred slurry in a 65°C oven to dry the alcohol, obtaining phenolic resin-coated waste carbon coarse particles.

[0036] Step 4: Weigh 30g of phenolic resin-coated waste carbon coarse particles, divide them into two equal parts, and place them into two corundum ball mills. Add 40ml of water. Set the ball mill speed to 400r / min and mill for 2 hours to obtain phenolic resin-coated waste carbon fine particles. Then, add 15g of mesophase carbon microspheres to each corundum ball mill, reduce the ball mill speed to 100r / min, and mill for 2 hours. Place the thoroughly stirred phenolic resin-coated waste carbon and mesophase carbon microspheres in a 75°C oven to dry out the moisture, obtaining a mixture of refined phenolic resin-coated waste carbon particles and mesophase carbon microspheres.

[0037] Step 5: Place the mixture obtained in step 4 into a stainless steel mold with a size of 40×60mm. 2 The material is then placed in a flat vulcanizer for cold compression molding at a pressure of 2-10 MPa and a holding time of 3 minutes. After pressure relief, a high-density, high-strength carbon green body is obtained.

[0038] Step 6: Place the green body obtained in Step 5 in a high-temperature tube furnace and purge with inert gas for 15 minutes. Carbonization is then performed under the protection of the inert gas. The carbonization process parameters are as follows: RT-300°C for 3 hours; 300-800°C for 12 hours; 800-1000°C for 2 hours; 1000-1000°C for 1 hour; 1000-600°C for 6.5 hours; 600°C-RT, followed by natural cooling. The result is a high-density, high-strength carbon material.

[0039] The SEM secondary electron photo of the waste carbon coarse material particles prepared in step 1 of this embodiment is as follows: Figure 2 As shown. Figure 2 It can be seen that the carbon fibers in the waste carbon coarse material particles are tightly combined with the pyrolytic carbon, and a large amount of carbon fibers are in the shape of bamboo rafts under the influence of the pyrolytic carbon.

[0040] The SEM secondary electron photo of the waste carbon fine particles prepared in step 2 of this embodiment is as follows: Figure 3 As shown. Figure 3 It can be seen that after high-energy ball milling, the pyrolytic carbon and carbon fiber have been completely separated, and the particles have become micron-sized.

[0041] The SEM secondary electron photograph of the waste carbon fine material particles coated with phenolic resin prepared in step 4 of this embodiment is as follows: Figure 4 As shown. Figure 4 It can be seen that the phenolic resin can completely cover the dissociated carbon fibers and pyrolytic carbon, i.e., carbon-carbon waste.

[0042] The macroscopic photograph of the high-density and high-strength carbon material prepared in this embodiment is shown in FIG. Figure 5 As shown. Figure 5It can be seen that the high-density and high-strength carbon material samples prepared based on the recycling of waste carbon-carbon composite materials are complete.

[0043] The SEM secondary electron photograph of the microstructure of the high-density and high-strength carbon material prepared in this embodiment is as follows: Figure 6 As shown. Figure 6 It can be seen that the high-density and high-strength carbon materials prepared based on the recycling of waste carbon-carbon composite materials have a relatively dense structure.

[0044] The density of the high-density and high-strength carbon material prepared in this embodiment is 1.50 g / cm 3 , open porosity is 20.1%, compressive strength is 122.24MPa, resistivity is 8.41mΩ·cm, and conductivity is 11890.61S / m.

[0045] Example 2

[0046] Step 1: Same as step 1 in Example 1.

[0047] Step 2: Weigh 200g of the coarse waste carbon particles from Step 1, divide them into four equal portions, and place them into four zirconia ball mills. Simultaneously, inject 60ml of alcohol into each mill. Set the ball mill speed to 900 rpm and mill for 1.5 hours at a rate of 15-minute runs and 5-minute pauses. The milled waste carbon fines are then dried in a 70°C oven to constant weight, yielding waste carbon fines with dissociated carbon fibers and pyrolytic carbon at the interface.

[0048] Step 3: Add 26g of waste carbon fine particles in batches to 87.5mL of a 0.16g / mL phenolic resin alcohol solution, stirring continuously. Stir the mixture at 700 rpm using a magnetic stirrer for 1.5 hours. Place the stirred slurry in a 65°C oven to dry the alcohol, obtaining phenolic resin-coated waste carbon coarse particles.

[0049] Step 4: Weigh 39g of phenolic resin-coated waste carbon coarse particles, divide them into two equal parts, and place them into two corundum ball mills, injecting 40ml of water at the same time. Set the ball mill speed to 300r / min and mill for 1.5h to obtain phenolic resin-coated waste carbon fine particles; then add 10.5g of mesophase carbon microspheres to each corundum ball mill, reduce the ball mill speed to 150r / min, and mill for 1.5h. Place the thoroughly stirred phenolic resin-coated waste carbon and mesophase carbon microspheres in a 75℃ oven to dry out the moisture to obtain a mixture of refined phenolic resin-coated waste carbon particles and mesophase carbon microspheres.

[0050] Step 5: Same as step 5 in Example 1.

[0051] Step 6: Same as step 6 in Example 1.

[0052] The density of the high-density and high-strength carbon material prepared in this example is 1.42 g / cm 3 , open porosity is 25.7%, compressive strength is 109.74MPa, resistivity is 9.20mΩ·cm, and conductivity is 10869.56S / m.

[0053] Example 3

[0054] Step 1: Same as step 1 in Example 1.

[0055] Step 2: Weigh 200g of the coarse waste carbon particles from Step 1, divide them into four equal portions, and place them into four zirconia ball mills. Simultaneously, inject 60ml of alcohol into each mill. Set the ball mill speed to 800 rpm and mill for 1 hour, running for 15 minutes and pausing for 5 minutes. The milled waste carbon fines are then dried in a 70°C oven to constant weight, yielding waste carbon fines with dissociated carbon fibers and pyrolytic carbon at the interface.

[0056] Step 3: Add 30g of waste carbon fine particles in batches to 101mL of a 0.16g / ml phenolic resin alcohol solution while stirring. Stir the mixture at 600 rpm on a magnetic stirrer for 1 hour. Place the stirred slurry in a 65°C oven to dry the alcohol, obtaining phenolic resin-coated waste carbon coarse particles.

[0057] Step 4: Weigh 45g of phenolic resin-coated waste carbon coarse particles, divide them into two equal parts, and place them into two corundum ball mills. Add 40ml of water. Set the ball mill speed to 200r / min and mill for 1 hour to obtain phenolic resin-coated waste carbon fine particles. Then, add 7.5g of mesophase carbon microspheres to each corundum ball mill, reduce the ball mill speed to 100r / min, and mill for 1 hour. Place the thoroughly stirred phenolic resin-coated waste carbon and mesophase carbon microspheres in a 75°C oven to dry out the moisture, obtaining a mixture of refined phenolic resin-coated waste carbon particles and mesophase carbon microspheres.

[0058] Step 5: Same as step 5 in Example 1.

[0059] Step 6: Same as step 6 in Example 1.

[0060] The density of the high-density and high-strength carbon material prepared in this example is 1.37 g / cm 3 , open porosity is 28.6%, compressive strength is 98.07MPa, resistivity is 9.94mΩ·cm, and conductivity is 10060.36S / m.

[0061] Comparative Example 1

[0062] Step 1: Same as step 1 in Example 3.

[0063] Step 2: This step is different from Step 2 in Example 3, except that the ball milling time is 1 h, and other conditions are the same.

[0064] Step 3: Add 38g of waste carbon fine particles in batches to 128mL of a 0.16g / mL phenolic resin alcohol solution while stirring. Stir the mixture at 600 rpm on a magnetic stirrer for 1 hour. Place the stirred slurry in a 65°C oven to dry the alcohol, obtaining phenolic resin-coated waste carbon coarse particles.

[0065] Step 4: Weigh 57g of phenolic resin-coated waste carbon coarse particles, divide them into two equal parts, and place them into two corundum ball mills, injecting 40ml of water at the same time. Set the ball mill speed to 200r / min and mill for 1 hour to obtain phenolic resin-coated waste carbon fine particles; then add 1.5g of mesophase carbon microspheres to each corundum ball mill, reduce the ball mill speed to 100r / min, and mill for 1 hour. Place the thoroughly stirred phenolic resin-coated waste carbon and mesophase carbon microspheres in a 75℃ oven to dry out the moisture to obtain a mixture of refined phenolic resin-coated waste carbon particles and mesophase carbon microspheres.

[0066] Step 5: Same as step 5 in Example 3.

[0067] Step 6: Same as step 6 in Example 3.

[0068] The density of the high-density and high-strength carbon material prepared in this comparative example is 1.21 g / cm 3 , open porosity is 36.7%, compressive strength is 40.59MPa, resistivity is 13.33mΩ·cm, and conductivity is 7501.87S / m.

[0069] Comparative Example 2

[0070] Step 1: Same as step 1 of comparative example 1.

[0071] Step 2: Same as step 2 of comparative example 1.

[0072] Step 3: Add 50g of waste carbon fine particles in batches to 168mL of a 0.16g / mL phenolic resin alcohol solution, stirring continuously. Stir the mixture at 600 rpm on a magnetic stirrer for 1 hour. Place the stirred slurry in a 65°C oven to dry the alcohol, obtaining phenolic resin-coated waste carbon coarse particles.

[0073] Step 4: Weigh 75g of phenolic resin-coated waste carbon particles, divide them into two equal parts, and place them into two corundum ball mills. Add 40ml of water and set the ball mill speed to 200 rpm. Mill for 1 hour, then dry the mixture in a 75°C oven to obtain the refined phenolic resin-coated waste carbon.

[0074] Step 5: Place the refined phenolic resin coated carbon waste into a stainless steel mold with a size of 40×60mm 2 The material is then placed in a flat vulcanizer for cold compression molding at a pressure of 2-10 MPa and a holding time of 3 minutes. After pressure relief, a high-density, high-strength carbon green body is obtained.

[0075] Step 6: Same as step 6 in Example 3.

[0076] The density of the high-density and high-strength carbon material prepared in this embodiment is 1.12 g / cm 3 , open porosity is 43.3%, compressive strength is 28.65MPa, resistivity is 17.74mΩ·cm, and conductivity is 5636.98S / m.

Claims

1. A method for preparing high-density and high-strength carbon materials based on recycling waste carbon-carbon composite materials, comprising the following steps: Step 1: Mechanically crushing the waste carbon-carbon composite material to obtain waste carbon-carbon coarse material particles; Step 2: Using alcohol as a ball milling medium, the waste carbon coarse material particles in step 1 are subjected to high-energy ball milling, and after mechanical shaping, waste carbon fine material particles with dissociation of carbon fibers and pyrolytic carbon are obtained; Step 3: adding the waste carbon fine material particles in step 2 to the phenolic resin alcohol solution, stirring thoroughly, and then drying to obtain phenolic resin-coated waste carbon coarse material particles; Step 4: using water as a ball milling medium, ball milling the phenolic resin-coated waste carbon coarse material particles in step 3 to crush and refine them to obtain phenolic resin-coated waste carbon fine material particles; Step 5: adding mesocarbon microspheres to phenolic resin-coated waste carbon fine particles according to a preset ratio, fully ball-milling, and drying the water to obtain a mixture of refined phenolic resin-coated waste carbon particles and mesocarbon microspheres; Step 6: cold-pressing the mixture obtained in step 5 to obtain a green body; Step 7: Carbonizing the green body obtained in step 6 under inert atmosphere to obtain a high-density and high-strength carbon material with carbon waste as aggregate; In the step 2, the ball milling speed is 800-1000 r / min, and the ball milling time is 1-2h; In step 5, the mass of the mesocarbon microspheres accounts for 25%-50% of the total mass of the mesocarbon microspheres and the phenolic resin-coated waste carbon fine material particles.

2. The method according to claim 1, characterized in that In the step 3, the mass ratio of the waste carbon fine particles to the phenolic resin is (11-14):7, and the mass concentration of the phenolic resin in the phenolic resin alcohol solution is 0.16 g / ml.

3. The method according to claim 1, characterized in that In the step 3, the stirring speed is 600-800 r / min and the stirring time is 1-2 h.

4. The method according to claim 1, wherein In the step 4, the ball milling speed is 200-400 r / min, and the ball milling time is 1-2 h.

5. The method according to claim 1, wherein In the step 5, the ball milling speed is 100-200 r / min, and the ball milling time is 1-2 h.

6. The method according to claim 1, characterized in that In step six, the molding pressure of the cold molding is 2-10 MPa, and the holding time is 3 minutes.

7. The method according to claim 1, characterized in that In step seven, the process parameters of the carbonization treatment are specifically as follows: RT-300°C, time is 3h; 300-800°C, time is 12h; 800-1000°C, time is 2h; 1000-1000°C, time is 1h; 1000-600°C, time is 6.5h; 600°C-RT, natural cooling.

Images