A high thermal conductivity and ablation-resistant carbon-ceramic brake disc and its preparation process

Abstract

The present invention relates to the technical field of braking materials, and specifically to a high thermal conductivity and ablation-resistant carbon-ceramic brake disc and its preparation process. The present invention overcomes the disadvantages of poor mechanical properties and poor ablation resistance of existing carbon-ceramic brake discs. The present invention prepares modified polyacrylonitrile-based carbon fibers by using polyacrylonitrile-based short carbon fibers, γ-aminopropyltriethoxysilane, multi-walled carbon nanotubes, nickel sulfate hexahydrate, and ferrous sulfate heptahydrate as raw materials; prepares modified pitch-based carbon fibers by using pitch-based short carbon fibers, nano-silicon carbide, and γ-aminopropyltriethoxysilane as raw materials; prepares modified viscose-based carbon fibers by using viscose-based short carbon fibers and tantalum carbide as raw materials; uses the three modified fibers as raw materials for the reinforcement layer, thermal conductivity layer, and ablation layer; and prepares the carbon-ceramic brake disc through raw material molding, two-stage high-pressure impregnation, densification treatment, interface treatment, heat treatment, and chemical vapor deposition. The carbon-ceramic brake disc has the advantages of strong mechanical properties and strong ablation resistance.

Description

Technical Field

[0001] The present invention relates to the technical field of braking materials, and specifically to a high thermal conductivity and ablation-resistant carbon-ceramic brake disc and its preparation process. Background Technique

[0002] In modern vehicle braking systems, the performance of braking materials directly affects driving safety and handling stability. Currently, the mainstream braking materials include three categories: cast iron, resin-based composites, and carbon-ceramic composites. Cast iron materials occupy the traditional market with the advantages of low cost and mature technology, but they have defects such as high density and obvious thermal fade; resin-based composites optimize the lightweight and anti-thermal attenuation performance through the combination of carbon fiber and resin, but organic matter decomposition is likely to occur at high temperatures, resulting in unstable friction coefficients. As the third-generation braking material, carbon-ceramic brake discs show significant advantages in high-temperature resistance, corrosion resistance, and lightweight through the combination of carbon fiber preforms and silicon carbide ceramics, and are widely used especially in the fields of high-end automobiles and rail transit.

[0003] According to the differences in the preparation processes of carbon fiber preforms, carbon-ceramic brake discs can be divided into two categories: short fiber compression molding type and long fiber weaving type. Short fiber compression molding carbon-ceramic brake discs are prepared by mixing chopped carbon fibers and phenolic resin and molding them by compression, and then through high-temperature carbonization and chemical vapor infiltration processes. They have the characteristics of high production efficiency and controllable cost. However, the random distribution of short fibers leads to more interface defects inside the material, blocking the heat conduction path, and the thermal conductivity is only 60%-70% of that of the long fiber structure. The improvement of fiber continuity in long fiber carbon-ceramic brake discs significantly improves the mechanical properties and thermal conductivity of the material, but the fiber buckling phenomenon in the weaving structure reduces the ablation resistance of the material. Under extreme working conditions above 1200°C, the thermal stress concentration at the fiber-ceramic interface causes local spalling failure.

[0004] In summary, existing carbon-ceramic brake discs still have the disadvantages of poor mechanical properties and poor thermal conductivity. When the braking system works continuously, the heat cannot be quickly dissipated, resulting in a sudden increase in the temperature of the disc surface, triggering the expansion of thermal cracks and the failure of the friction film. In severe cases, it may cause a decline in braking performance or a sudden fracture accident, becoming a potential threat to the safe operation of high-speed transportation vehicles.

[0005] Therefore, a high thermal conductivity and ablation-resistant carbon-ceramic brake disc and its preparation process are proposed. Summary of the Invention

[0006] The object of the present invention is to provide a high thermal conductivity and ablation-resistant carbon-ceramic brake disc and its preparation process. The present invention prepares modified polyacrylonitrile-based carbon fibers by using polyacrylonitrile-based short carbon fibers, γ-aminopropyltriethoxysilane, multi-walled carbon nanotubes, nickel sulfate hexahydrate, and ferrous sulfate heptahydrate as raw materials; prepares modified pitch-based carbon fibers by using pitch-based short carbon fibers, nano-silicon carbide, and γ-aminopropyltriethoxysilane as raw materials; prepares modified viscose-based carbon fibers by using viscose-based short carbon fibers and tantalum carbide as raw materials; uses the three modified fibers as raw materials for the reinforcement layer, thermal conductivity layer, and ablation layer; and prepares the carbon-ceramic brake disc through raw material molding, two-stage high-pressure impregnation, densification treatment, interface treatment, heat treatment, and chemical vapor deposition. The carbon-ceramic brake disc has the advantages of strong mechanical properties and strong ablation resistance.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] On the one hand, the present invention provides a high thermal conductivity and ablation-resistant carbon-ceramic brake disc: calculated by mass, it specifically includes the following components:

[0009] The carbon-ceramic brake disc includes three layers: a reinforcement layer, a thermal conductivity layer, and an ablation layer; the raw materials of the reinforcement layer include: modified polyacrylonitrile-based carbon fibers; the raw materials of the thermal conductivity layer include: modified polyacrylonitrile-based carbon fibers and modified pitch-based carbon fibers; the raw materials of the ablation layer include: modified polyacrylonitrile-based carbon fibers and modified viscose-based carbon fibers;

[0010] The raw materials of the modified polyacrylonitrile-based carbon fibers include: 90-110 parts of polyacrylonitrile-based short carbon fibers, 1-2 parts of γ-aminopropyltriethoxysilane, 5-7 parts of multi-walled carbon nanotubes, 0.5 part of nickel sulfate hexahydrate, and 0.3 part of ferrous sulfate heptahydrate; the raw materials of the modified pitch-based short carbon fibers include: 90-110 parts of pitch-based short carbon fibers, 5-7 parts of nano-silicon carbide, and 1.5-2.5 parts of γ-aminopropyltriethoxysilane; the raw materials of the modified viscose-based carbon fibers include: 90-110 parts of viscose-based short carbon fibers and 3-4 parts of tantalum carbide.

[0011] Preferably, the thicknesses of the reinforcement layer, the thermal conductivity layer, and the ablation layer respectively account for 60%, 30%, and 10% of the carbon-ceramic brake disc; the mass ratio of the polyacrylonitrile-based short carbon fibers to the pitch-based short carbon fibers in the raw materials of the thermal conductivity layer is 6-9:1-4; the mass ratio of the polyacrylonitrile-based short carbon fibers to the modified viscose-based short carbon fibers in the raw materials of the ablation layer is 6-9:1-4.

[0012] On the other hand, the present invention provides a preparation process for a high thermal conductivity and ablation-resistant carbon-ceramic brake disc, which specifically includes the following steps: S1 Using modified polyacrylonitrile-based carbon fiber, modified polyacrylonitrile-based carbon fiber and modified pitch-based carbon fiber, and modified polyacrylonitrile-based carbon fiber and modified viscose-based carbon fiber as raw materials to prepare a reinforcing layer molding compound, a thermal conductivity layer molding compound, and an ablation layer molding compound respectively; S2 Subjecting the reinforcing layer molding compound, the thermal conductivity layer molding compound, and the ablation layer molding compound to three-stage curing to obtain a carbon fiber preform; S3 Subjecting the carbon fiber preform to two-stage high-pressure impregnation to obtain an impregnated blank; S4 Subjecting the impregnated blank to densification treatment to obtain a densified blank; S5 Subjecting the densified blank to interface treatment to obtain a coated blank; S6 Subjecting the coated blank to chemical vapor deposition to obtain a carbon-ceramic brake disc.

[0013] Preferably, the preparation method of the modified polyacrylonitrile-based carbon fiber is as follows: By mass, immerse the polyacrylonitrile-based short carbon fiber into 20 parts of a nitric acid solution with a mass fraction of 68%, add nickel sulfate hexahydrate and ferrous sulfate heptahydrate, and perform ultrasonic treatment at 80 °C at 40 kHz for 1.5 - 2 h to obtain a fiber mixture; Subject the multi-walled carbon nanotubes to plasma treatment, introduce a mixed gas with a volume ratio of argon to oxygen of 4:1, and treat at a power of 300 W for 15 min to obtain activated carbon nanotubes; Immerse the activated carbon nanotubes and the fiber mixture into a solution composed of 1 part of sodium hypophosphite and 20 parts of deionized water, adjust the pH to 8.5, and react at 85 °C for 1 - 1.5 h to obtain a reaction system; Dissolve γ-aminopropyltriethoxysilane in 30 parts of absolute ethanol to prepare a 2.5% solution, mix it with the reaction system and perform ultrasonic treatment for 1 h to obtain modified fibers; Immerse the modified fibers into a 0.6% dispersion prepared from 0.3 part of polyvinylpyrrolidone and 50 parts of absolute ethanol, perform ultrasonic treatment at 40 kHz for 30 min, and then cure at 120 °C for 2 h to obtain the modified polyacrylonitrile-based carbon fiber.

[0014] Preferably, the preparation method of the modified pitch-based carbon fiber is as follows: By mass, immerse the pitch-based short carbon fiber into a mixed solution of 30 parts of nitric acid with a mass fraction of 68% and 10 parts of hydrogen peroxide with a mass fraction of 30%, and perform ultrasonic treatment at 60 °C to obtain pretreated fibers; Dissolve γ-aminopropyltriethoxysilane in absolute ethanol to prepare a solution with a mass fraction of 5%, and react with the pretreated fibers at 55 °C for 4 h to obtain modified fibers; Disperse nano-silicon carbide in 50 parts of deionized water to prepare a 10% mass fraction suspension, assist in impregnation under ultrasonic treatment for 1 h, and then immerse it into a 10% mass fraction solution composed of 3 parts of phenolic resin and 27 parts of acetone, and cure at 100 - 120 °C for 2 - 3 h to obtain the modified pitch-based carbon fiber.

[0015] Preferably, the preparation method of the modified viscose-based carbon fiber is as follows: by mass, immerse the viscose-based chopped carbon fiber into a mixed solution of 15 parts of 68% nitric acid and 5 parts of 30% hydrogen peroxide, and obtain the pretreated fiber after ultrasonic treatment at 70 °C; disperse tantalum carbide nanoparticles and 4 parts of phenolic resin in isopropanol to prepare a coating solution with a mass fraction of 1%, impregnate under vacuum for 0.5 - 1 h, and then cure at 180 - 200 °C for 2 h to obtain the viscose-based carbon fiber.

[0016] Preferably, the two-stage high-pressure impregnation method is as follows: first immerse the carbon fiber preform into the impregnating solution, impregnate at 10 MPa for 1 - 1.5 h to obtain a macroporous filling embryo; heat the macroporous filling embryo to 50 °C and impregnate again at 20 MPa for 1.5 - 2 h to obtain the impregnated embryo.

[0017] Preferably, the preparation method of the impregnating solution is as follows: by mass fraction, dissolve 25 parts of polycarbosilane and 7.5 parts of boron carbide powder in 175 parts of tetrahydrofuran to prepare a mixed impregnating solution with a mass concentration of 15.7%; the preparation method of the carbon fiber preform is as follows: cure the reinforcing layer molding compound at 20 MPa and 120 °C for 1.2 h to obtain the reinforcing layer embryo; lay the heat-conducting layer molding compound on the reinforcing layer embryo and cure at 18 MPa and 120 °C for 0.5 h to obtain the composite embryo; lay the ablation layer molding compound on the composite embryo and cure at 15 MPa and 120 °C for 0.3 h to obtain the carbon fiber preform.

[0018] Preferably, the densification treatment process is as follows: place the impregnated embryo in a hot isostatic press, and treat at 200 MPa and 400 - 450 °C for 30 min to obtain the densified embryo.

[0019] Preferably, the interface treatment method is as follows: evenly spray the yttrium oxide suspension on the surface of the densified embryo, place it in a drying oven at 80 °C for 1 h, and then heat-treat at 300 - 350 °C for 30 min under nitrogen protection to obtain the coated embryo; the preparation method of the yttrium oxide suspension is as follows: by mass fraction, add 1.25 parts of yttrium oxide to 125 parts of absolute ethanol and stir to disperse, and prepare a suspension with a mass concentration of 1%.

[0020] Preferably, the chemical vapor deposition method is as follows: transfer the coated embryo to a deposition furnace, introduce methane at 70 L / h and argon at 30 L / h, and deposit at 1050 - 1150 °C for 8 - 10 h to obtain the carbon-ceramic brake disc.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] 1. In the present invention, a three-dimensional carbon nanotube network is catalytically constructed on the surface of a fiber using a nickel-iron alloy, and interfacial bonding is strengthened by a silane coupling agent to form a metal-carbon nanotube composite reinforcement framework, simultaneously enhancing the flexural strength and thermal conductivity continuity of the fiber body; in the reinforcement layer, this framework forms a rigid support through the interpenetration of phenolic resin, and in the thermal conduction layer, the carbon nanotubes of it and the silicon carbide particles of the pitch-based fiber synergistically accelerate heat transfer through metal heat conduction and solid vibration heat conduction. In the ablation layer, the carbon nanotube network bridged by silane and the tantalum carbide coating of the viscose-based fiber form a high-temperature oxygen diffusion barrier; after the fibers are directionally arranged by gradient pressure molding, the impregnation strengthening process is combined to interlock and penetrate the carbon nanotube network with the pyrolytic carbon matrix, and finally, through multi-level interface coordination, the integrated optimization of mechanical load-bearing, heat conduction, and oxidation resistance erosion is achieved.

[0023] 2. In the present invention, nitric acid-hydrogen peroxide synergistically etches a microgroove structure on the surface of pitch-based carbon fibers, combined with the loading of silicon carbide nanoparticles, significantly enhancing its specific surface area and the density of thermal conduction contact points; in the thermal conduction layer, the modified pitch-based fibers form a synergy of solid vibration heat transfer and electron heat conduction through the silicon carbide particles on the surface and the carbon nanotube network of polyacrylonitrile-based fibers; after the fibers are pretreated by ultrasonic waves and gradient pressure molding, the directionally arranged silicon carbide particles and the resin matrix form an interlocking structure, which not only ensures the interfacial bonding strength between layers but also maintains the continuity of the heat conduction path, improving the thermal conductivity of the carbon-ceramic brake disc.

[0024] 3. In the present invention, a microporous-hydroxy active interface is constructed on the fiber surface based on nitric acid oxidation, and tantalum carbide nanoparticles are deeply embedded in the fiber pores through vacuum impregnation, combined with the stepwise curing of phenolic resin to form a continuous and dense tantalum carbide-carbon composite layer; in the ablation layer, tantalum carbide is preferentially converted into a molten state of tantalum oxide during high-temperature oxidation, and its spontaneous spreading forms a dense glassy oxygen barrier layer. At the same time, the carbon nanotube network of polyacrylonitrile-based fibers anchors the tantalum oxide layer through a mechanical interlocking effect, inhibiting the peeling of the coating caused by high-temperature gas erosion. This design realizes the self-protection function and long-term structural integrity of the ablation layer at extreme temperatures through the dual paths of the intrinsic oxidation resistance of the material and the strengthening of the interface structure.

[0025] 4. In the present invention, the reinforcement layer, thermal conduction layer, and ablation layer are sequentially processed by gradient pressure molding, and the interlayer transition interface is constructed through staged curing to lay the foundation for mechanical load-bearing; high-pressure impregnation strengthening fills the pores deeply with a polycarbosilane-boron carbide mixture through two-stage pressurization, forming a continuous heat conduction network with components such as carbon nanotubes and silicon carbide in the fiber; the yttrium oxide coating constructs a thermal expansion buffer layer on the surface and interpenetrates with the subsequent chemical vapor deposition carbon matrix to form a dense composite interface, achieving the improvement of the comprehensive performance of the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is a schematic structural diagram of the carbon-ceramic brake disc of the present invention;

[0027] In the figure: 1. Ablation layer; 2. Thermal conduction layer; 3. Reinforcement layer. Specific embodiments

[0028] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0029] Please refer to Figure 1 , the present invention provides a high thermal conductivity and ablation-resistant carbon-ceramic brake disc and its preparation process. The technical solutions are as follows:

[0030] Example 1

[0031] By mass, 100 parts of polyacrylonitrile-based short-cut carbon fibers are immersed in 20 parts of a nitric acid solution with a mass fraction of 68%, 0.5 part of nickel sulfate hexahydrate and 0.3 part of ferrous sulfate heptahydrate are added, and ultrasonic treatment is carried out at 80 °C at 40 kHz for 1.5 h to obtain a fiber mixture; 3 parts of multi-walled carbon nanotubes are subjected to plasma treatment, an argon / oxygen mixed gas with a volume ratio of 4:1 is introduced, and treatment is carried out at a power of 300 W for 15 min to obtain activated carbon nanotubes; the activated carbon nanotubes and the fiber mixture are jointly immersed in a 5% aqueous solution containing 1 part of sodium hypophosphite, the pH is adjusted to 8.5, and reaction is carried out at 85 °C for 1 h to obtain a reaction system; 0.8 part of γ-aminopropyltriethoxysilane is dissolved in 30 parts of absolute ethanol to prepare a 2.5% solution, which is mixed with the reaction system and then ultrasonic-treated for 1 h to obtain modified fibers; the modified fibers are immersed in a 0.6% dispersion prepared from 0.3 part of polyvinylpyrrolidone and 50 parts of absolute ethanol, ultrasonic-treated at 40 kHz for 30 min, and then cured at 120 °C for 2 h to obtain modified polyacrylonitrile-based short-cut carbon fibers.

[0032] By mass, 100 parts of pitch-based short-cut carbon fibers are immersed in a mixed solution of 30 parts of nitric acid with a mass fraction of 68% and 10 parts of hydrogen peroxide with a mass fraction of 30%, and ultrasonic treatment is carried out at 60 °C to obtain pretreated fibers; 1.5 parts of γ-aminopropyltriethoxysilane is dissolved in 30 parts of absolute ethanol to prepare a solution with a mass fraction of 5%, which reacts with the pretreated fibers at 55 °C for 4 h to obtain modified fibers; 5 parts of silicon carbide nanoparticles are dispersed in 50 parts of deionized water to prepare a 10% suspension, ultrasonic-assisted impregnation is carried out for 1 h, and then immersed in a 10% solution prepared from 3 parts of phenolic resin and 27 parts of acetone, and cured at 100 °C for 2 h to obtain modified pitch-based short-cut carbon fibers.

[0033] By mass, 100 parts of viscose-based short carbon fibers are immersed in a mixed solution of 15 parts of 68% nitric acid and 5 parts of 30% hydrogen peroxide, and pretreated fibers are obtained after ultrasonic treatment at 70 °C; 2 parts of tantalum carbide nanoparticles and 4 parts of phenolic resin are dispersed in 394 parts of isopropanol to prepare a coating solution with a mass fraction of 1%, and impregnated at -0.8 MPa for 0.5 h by vacuum impregnation method; the coated fibers are cured at 180 °C for 2 h to obtain viscose-based short carbon fibers.

[0034] S1 Reinforcement layer molding compounds, thermal conductivity layer molding compounds, and ablation layer molding compounds are respectively prepared using 150 parts of modified polyacrylonitrile-based short carbon fibers, 67.5 parts of polyacrylonitrile-based short carbon fibers, 7.5 parts of pitch-based short carbon fibers, 22.5 parts of polyacrylonitrile-based short carbon fibers, and 2.5 parts of viscose-based short carbon fibers as raw materials; the mass ratio of polyacrylonitrile-based short carbon fibers to pitch-based short carbon fibers in the thermal conductivity layer raw materials is 9:1; the mass ratio of polyacrylonitrile-based short carbon fibers to modified viscose-based short carbon fibers in the ablation layer raw materials is 9:1.

[0035] S2 The reinforcement layer molding compound, thermal conductivity layer molding compound, and ablation layer molding compound are subjected to three-stage curing to obtain a carbon fiber preform.

[0036] S3 First, the carbon fiber preform is immersed in the impregnating solution and impregnated at a pressure of 10 MPa for 1.5 h to obtain a macroporous filling blank; the macroporous filling blank is heated to 50 °C and impregnated at a pressure of 20 MPa for 1.5 - 2 h to obtain an impregnated blank.

[0037] The preparation method of the impregnating solution is as follows: 25 parts of polycarbosilane and 7.5 parts of boron carbide are dissolved in 175 parts of tetrahydrofuran to prepare a mixed impregnating solution with a mass concentration of 15.7%; the preparation method of the carbon fiber preform is as follows: the reinforcement layer molding compound is cured at 20 MPa and 120 °C for 1.2 h to obtain a reinforcement layer blank; the thermal conductivity layer molding compound is laid on the reinforcement layer blank and cured at 18 MPa and 120 °C for 0.5 h to obtain a composite blank; the ablation layer molding compound is laid on the composite blank and cured at 15 MPa and 120 °C for 0.3 h to obtain a carbon fiber preform.

[0038] S4 The impregnated blank is placed in a hot isostatic press and treated at 200 MPa and 400 °C for 30 min to obtain a densified blank.

[0039] S5 The yttrium oxide suspension is evenly sprayed on the surface of the densified blank, then placed in a drying oven at 80 °C for 1 h, and then heat-treated at 300 - 350 °C for 30 min under nitrogen protection to obtain a coated blank.

[0040] S6 The coated blank is transferred to a deposition furnace, methane is introduced at 70 L / h and argon is introduced at 30 L / h, and deposited at 1050 - 1150 °C for 8 - 10 h to obtain a carbon-ceramic brake disc.

[0041] The total thickness of the finally prepared carbon-ceramic brake disc is 40 mm, including three layers: a reinforcement layer, a heat-conducting layer, and an ablation layer; the thicknesses of the reinforcement layer, the heat-conducting layer, and the ablation layer respectively account for 60%, 30%, and 10% of the carbon-ceramic brake disc.

[0042] The difference between Example 2 and Example 1 is that in step S1, 150 parts of modified polyacrylonitrile-based short carbon fibers, 45 parts of polyacrylonitrile-based short carbon fibers, 30 parts of pitch-based short carbon fibers, 15 parts of polyacrylonitrile-based short carbon fibers, and 10 parts of viscose-based short carbon fibers are used as raw materials to prepare a reinforcement layer molding compound, a heat-conducting layer molding compound, and an ablation layer molding compound respectively; the mass ratio of polyacrylonitrile-based short carbon fibers to pitch-based short carbon fibers in the raw materials of the heat-conducting layer is 6:4; the mass ratio of polyacrylonitrile-based short carbon fibers to modified viscose-based short carbon fibers in the raw materials of the ablation layer is 6:4, and the other parameters and conditions are the same.

[0043] The difference between Example 3 and Example 1 is that in step S1, 150 parts of modified polyacrylonitrile-based short carbon fibers, 52.5 parts of polyacrylonitrile-based short carbon fibers, 22.5 parts of pitch-based short carbon fibers, 17.5 parts of polyacrylonitrile-based short carbon fibers, and 7.5 parts of viscose-based short carbon fibers are used as raw materials to prepare a reinforcement layer molding compound, a heat-conducting layer molding compound, and an ablation layer molding compound respectively; the mass ratio of polyacrylonitrile-based short carbon fibers to pitch-based short carbon fibers in the raw materials of the heat-conducting layer is 7:3; the mass ratio of polyacrylonitrile-based short carbon fibers to modified viscose-based short carbon fibers in the raw materials of the ablation layer is 7:3, and the other parameters and conditions are the same.

[0044] The difference between Example 4 and Example 3 is that the dosages of each component are different when preparing the modified polyacrylonitrile-based carbon fiber: 100 parts of polyacrylonitrile-based short carbon fibers, 1.5 parts of γ-aminopropyltriethoxysilane, and 6 parts of multi-walled carbon nanotubes; the dosages of each component are different when preparing the pitch-based short carbon fiber: 100 parts of pitch-based short carbon fibers, 6 parts of nano-silicon carbide, and 2 parts of γ-aminopropyltriethoxysilane; the dosages of each component are different when preparing the viscose-based short carbon fiber: 100 parts of viscose-based short carbon fibers and 3 parts of tantalum carbide, and the other parameters and conditions are the same.

[0045] The difference between Example 5 and Example 3 is that the dosages of each component are different when preparing the modified polyacrylonitrile-based carbon fiber: 110 parts of polyacrylonitrile-based short carbon fibers, 2 parts of γ-aminopropyltriethoxysilane, and 7 parts of multi-walled carbon nanotubes; the dosages of each component are different when preparing the pitch-based short carbon fiber: 110 parts of pitch-based short carbon fibers, 7 parts of nano-silicon carbide, and 2.5 parts of γ-aminopropyltriethoxysilane; the dosages of each component are different when preparing the viscose-based short carbon fiber: 110 parts of viscose-based short carbon fibers and 4 parts of tantalum carbide, and the other parameters and conditions are the same.

[0046] Example 6 is different from Example 3 in that the amounts of each component are different when preparing the modified polyacrylonitrile-based carbon fiber. There are 100 parts of polyacrylonitrile-based short carbon fibers, 2 parts of γ-aminopropyltriethoxysilane, and 7 parts of multi-walled carbon nanotubes; the amounts of each component are different when preparing the pitch-based short carbon fiber. There are 100 parts of pitch-based short carbon fibers, 7 parts of nano-silicon carbide, and 2.5 parts of γ-aminopropyltriethoxysilane; the amounts of each component are different when preparing the viscose-based short carbon fiber. There are 100 parts of viscose-based short carbon fibers and 4 parts of tantalum carbide, and the remaining parameters and conditions are the same.

[0047] Examples 7-18 are different from Example 6 in that the ultrasonic treatment time is different and the reaction time of the activated carbon nanotube and fiber mixture is different when preparing the modified polyacrylonitrile-based carbon fiber; the curing time and curing temperature are different after impregnation when preparing the modified pitch-based carbon fiber; the impregnation time under vacuum and the curing temperature are different when preparing the modified viscose-based carbon fiber. The specific parameters are shown in Table 1.

[0048] Table 1 Parameter Table of Examples 6-18

[0049]

[0050] Example 19 is different from Example 17 in that the impregnation time at 10 MPa is 1.25 h and the impregnation time at 20 MPa is 1.75 h in the high-pressure impregnation process; the treatment temperature is 425 °C in the densification step; the heat treatment temperature is 325 °C in the interface treatment step; the deposition temperature is 1100 °C and the deposition time is 9 h in the chemical vapor deposition step.

[0051] Example 20 is different from Example 17 in that the impregnation time at 10 MPa is 1.5 h and the impregnation time at 20 MPa is 2 h in the high-pressure impregnation process; the treatment temperature is 450 °C in the densification step; the heat treatment temperature is 350 °C in the interface treatment step; the deposition temperature is 1150 °C and the deposition time is 10 h in the chemical vapor deposition step.

[0052] Comparative Example 1 is different from Example 1 in that the polyacrylonitrile-based short carbon fiber is not modified, and commercially available polyacrylonitrile-based carbon fiber is used, and the remaining parameters and conditions are the same.

[0053] Comparative Example 2 is different from Example 1 in that nickel sulfate hexahydrate and ferrous sulfate heptahydrate are not used when preparing the modified polyacrylonitrile-based carbon fiber, and the remaining parameters and conditions are the same.

[0054] Comparative Example 3 is different from Example 1 in that γ-aminopropyltriethoxysilane is not added when preparing the modified polyacrylonitrile-based carbon fiber, and the remaining parameters and conditions are the same.

[0055] Comparative Example 4 is different from Example 1 in that when preparing the modified polyacrylonitrile-based carbon fiber, multi-walled carbon nanotubes are not added, and the remaining parameters and conditions are the same.

[0056] Comparative Example 5 is different from Example 1 in that when preparing the modified polyacrylonitrile-based carbon fiber, the multi-walled carbon nanotubes are not subjected to plasma treatment, and the remaining parameters and conditions are the same.

[0057] Comparative Example 6 is different from Example 1 in that the pitch-based short carbon fibers are not subjected to modification treatment, and the remaining parameters and conditions are the same.

[0058] Comparative Example 7 is different from Example 1 in that when preparing the modified pitch-based carbon fiber, the pretreatment step is omitted, and the remaining parameters and conditions are the same.

[0059] Comparative Example 8 is different from Example 1 in that when preparing the modified pitch-based carbon fiber, nano-silicon carbide is not added, and the remaining parameters and conditions are the same.

[0060] Comparative Example 9 is different from Example 1 in that the viscose-based short carbon fibers are not subjected to modification treatment, and the remaining parameters and conditions are the same.

[0061] Comparative Example 10 is different from Example 1 in that when preparing the modified viscose-based carbon fiber, the pretreatment step is omitted, and the remaining parameters and conditions are the same.

[0062] Comparative Example 11 is different from Example 1 in that when preparing the carbon-ceramic brake disc, the high-pressure impregnation stage is only impregnated at 20 MPa for 2 h, and the remaining parameters and conditions are the same.

[0063] Comparative Example 12 is different from Example 1 in that when preparing the carbon-ceramic brake disc, boron carbide is not used, and the remaining parameters and conditions are the same.

[0064] Comparative Example 13 is different from Example 1 in that when preparing the carbon-ceramic brake disc, the coating of yttrium oxide is not carried out, and the remaining parameters and conditions are the same.

[0065] Comparative Example 14 is different from Example 1 in that when preparing the carbon-ceramic brake disc, all the raw materials for preparing the reinforcing layer, heat-conducting layer, and ablation layer are modified polyacrylonitrile-based carbon fibers.

[0066] Comparative Example 15 is different from Example 1 in that when preparing the carbon-ceramic brake disc, all the raw materials for preparing the reinforcing layer, heat-conducting layer, and ablation layer are modified pitch-based carbon fibers.

[0067] Comparative Example 16 is different from Example 1 in that when preparing the carbon-ceramic brake disc, all the raw materials for preparing the reinforcing layer, heat-conducting layer, and ablation layer are modified viscose-based carbon fibers.

[0068] Test Example 1 Comprehensive Performance Test

[0069] Test objects: carbon-ceramic brake discs prepared in Examples 1-6, Example 17, Examples 19-20 and Comparative Examples 11-16.

[0070] Test method: Refer to GB / T 6569-2006 standard for testing bending strength; refer to GB / T 40388-2021 standard for testing shear strength; refer to ASTM E1461 standard for testing thermal conductivity; refer to ASTM E285-80 (2002) standard for testing ablation resistance. The final test results are shown in Table 2.

[0071] Table 2 Comprehensive performance test results

[0072]

[0073] By optimizing the ratio of various components and the overall process, it can be seen that the performance of the carbon ceramic brake disc prepared in Example 20 is in the optimal state. In Comparative Example 11, only a single-stage high-pressure impregnation results in insufficient pore filling, a decrease in the interlocking rate between the carbon nanotube network and the matrix, and a break in the heat conduction path that leads to heat accumulation. At the same time, the unfilled micropores become oxidation erosion channels, and the mechanical and ablation resistance properties deteriorate simultaneously. In Comparative Example 12, the lack of boron carbide makes it impossible for the impregnation liquid to form a continuous heat conduction network, and the brittleness of polycarbosilane increases after curing alone. The scattering of heat at the pores is aggravated, the interlayer shear strength decreases due to the embrittlement of the matrix, and the oxidation erosion accelerates along the weak interface. In Comparative Example 13, the lack of yttrium oxide coating leads to a mismatch in the interfacial thermal expansion coefficient, and microcracks are generated between the chemical vapor deposited carbon matrix and the embryo. High-temperature oxygen diffuses rapidly along the cracks, the ablation protection function fails, and the increase in interfacial thermal resistance weakens the thermal conductivity efficiency. Comparative Example 14: The fully modified polyacrylonitrile-based fiber system has optimized mechanical properties, but the thermal conductivity gradient design is destroyed. The thermal conductive layer lacks other substances for synergistic heat transfer, and the heat conduction capacity is reduced; the ablation layer has no tantalum carbide protection, which leads to aggravated oxidation corrosion. Comparative Example 15: The fully modified asphalt-based fiber lacks a carbon nanotube network, and the thermal conductivity relies on a single mechanism of silicon carbide, which reduces efficiency; the reinforcement layer has no three-dimensional metal skeleton support, the bending strength is reduced, and the deterioration of the ablation layer performance further weakens the overall stability. Comparative Example 16: The mechanical properties of the fully modified viscose-based fiber system only rely on the resin matrix, the interface bonding is fragile, the thermal conductivity path is broken, resulting in heat accumulation, the ablation layer is fully functional, but the structural imbalance accelerates oxidation corrosion, and the overall performance is reduced.

[0074] Test Example 2 Mechanical Properties Test

[0075] Test object: carbon ceramic brake discs prepared in Examples 6-10 and Comparative Examples 1 and 3.

[0076] Test method: refer to test example 1. The final test results are shown in Table 3.

[0077] Table 3 Table of Mechanical Property Test Results

[0078]

[0079] In Comparative Example 1, the polyacrylonitrile-based carbon fiber was not modified, and the surface lacked the three-dimensional carbon nanotube network generated by nickel-iron alloy catalysis. As a result, only physical bonding relied between the fiber and the resin matrix, and the lack of chemical bonding of the silane coupling agent greatly reduced the interfacial bonding strength, and the interlaminar shear performance deteriorated after carbonization. The disappearance of the metal-carbon tube composite skeleton significantly decreased the bending resistance of the fiber, and the stress could not be effectively dispersed through the three-dimensional network. In Comparative Example 3, the absence of the silane coupling agent resulted in no covalent bond connection between the carbon nanotubes and the fiber, and they were only combined by van der Waals forces. Microcracks were easily generated and propagated at the interface, and the interlaminar shear strength was significantly reduced due to the slip effect. Although part of the metal skeleton remained, the interfacial defects led to a decrease in the stress transfer efficiency.

[0080] Test Example 3 Thermal Conductivity Test

[0081] Test Object: The carbon-ceramic brake discs prepared in Examples 11-14, Comparative Example 2, and Comparative Examples 4-8.

[0082] Test Method: Refer to Test Example 1. The final test results are shown in Table 4.

[0083] Table 4 Table of Thermal Conductivity Test Results

[0084]

[0085] After omitting the nickel-iron catalyst in Comparative Example 2, the carbon nanotubes could not grow in-situ on the fiber surface and only loosely adhered. The fracture of the metal heat conduction channel led to local heat accumulation, and at the same time, a complete heat conduction structure could not be formed as a whole. In Comparative Example 4, the three-dimensional heat conduction network of carbon nanotubes was lacking, and heat transfer only relied on the inherent heat conductivity of the resin matrix and carbon fiber. The heat conduction path was broken and could not be synergistically strengthened. In Comparative Example 5, the unactivated carbon nanotubes severely agglomerated due to insufficient surface functional groups, forming a local thermal resistance barrier. The deterioration of dispersion led to a reduction in the effective heat conduction area. In Comparative Example 6, the pitch-based fiber was not modified, lacking the high specific surface area structure and silicon carbide after acid etching. The solid vibration heat transfer path was interrupted, and the heat conduction layer only relied on the electron heat transfer of the polyacrylonitrile-based carbon tube. The synergistic effect disappeared, and heat scattering at the interface was aggravated, resulting in a reduction in the overall heat conduction efficiency. In Comparative Example 7, omitting the nitric acid-hydrogen peroxide pretreatment caused the lack of microgroove structure on the fiber surface, the mechanical embedding of silicon carbide particles was not firm, the thermal resistance at the interface between the particles and the fiber increased, the vibration heat transfer path was blocked, and the heat conduction efficiency of the heat conduction layer decreased. In Comparative Example 8, the absence of silicon carbide particles made the heat conduction layer only rely on the single heat transfer mechanism of the carbon nanotube network, lacking the synergistic effect of solid vibration heat transfer. The residence time of heat in the resin matrix was prolonged, and the discontinuous heat conduction path led to a reduction in the overall thermal conductivity.

[0086] Test Example 4 Ablation Resistance Performance Test

[0087] Test Object: The carbon-ceramic brake discs prepared in Examples 15-18 and Comparative Examples 9-10.

[0088] Test Method: Refer to Test Example 1. The final test results are shown in Table 5.

[0089] Table 5 Test Results of Ablation Amount

[0090]

[0091] In Comparative Example 9, unmodified viscose-based short-cut fibers were used, and no tantalum carbide particles were embedded in the pores of the treated fibers, so that the oxygen diffusion channels in the carbon-ceramic brake disc at high temperature were not blocked. The ablation layer lacked a dense glassy barrier layer formed by molten tantalum oxide, and the oxidation reaction rate increased sharply, and the ablation resistance of the material deteriorated seriously. In Comparative Example 10, the lack of pretreatment resulted in the tantalum carbide particles only loosely attached to the surface and unable to deeply fill the fiber pores. After the phenolic resin was cured, the particle distribution was uneven, the continuity of the high-temperature tantalum oxide layer was poor, the oxygen diffusion rate was accelerated, and the ablation protection function failed.

[0092] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A preparation process for a high thermal conductivity and ablation-resistant carbon-ceramic brake disc, characterized in that: Specifically, it includes the following steps: S1: Using modified polyacrylonitrile-based carbon fiber, modified polyacrylonitrile-based carbon fiber and modified pitch-based carbon fiber, and modified polyacrylonitrile-based carbon fiber and modified viscose-based carbon fiber as raw materials respectively to prepare an enhanced layer molding compound, a heat-conducting layer molding compound, and an ablation layer molding compound; S2: Subjecting the enhanced layer molding compound, the heat-conducting layer molding compound, and the ablation layer molding compound to three-stage curing to obtain a carbon fiber preform; S3: Subjecting the carbon fiber preform to two-stage high-pressure impregnation to obtain an impregnated blank; S4: Subjecting the impregnated blank to densification treatment to obtain a densified blank; S5: Subjecting the densified blank to interface treatment to obtain a coated blank; S6: Subjecting the coated blank to chemical vapor deposition to obtain the carbon-ceramic brake disc; By mass, it specifically includes the following components: The carbon-ceramic brake disc includes three layers: an enhanced layer, a heat-conducting layer, and an ablation layer; The raw materials of the enhanced layer include: modified polyacrylonitrile-based carbon fiber; the raw materials of the heat-conducting layer include: the modified polyacrylonitrile-based carbon fiber and modified pitch-based carbon fiber; the raw materials of the ablation layer include: the modified polyacrylonitrile-based carbon fiber and modified viscose-based carbon fiber; The raw materials of the modified polyacrylonitrile-based carbon fiber include: 90-110 parts of polyacrylonitrile-based chopped carbon fiber, 1-2 parts of γ-aminopropyltriethoxysilane, 5-7 parts of multi-walled carbon nanotubes, 0.5 part of nickel sulfate hexahydrate, and 0.3 part of ferrous sulfate heptahydrate; the raw materials of the modified pitch-based chopped carbon fiber include: 90-110 parts of pitch-based chopped carbon fiber, 5-7 parts of nano-silicon carbide, and 1.5-2.5 parts of γ-aminopropyltriethoxysilane; the raw materials of the modified viscose-based carbon fiber include: 90-110 parts of viscose-based chopped carbon fiber and 3-4 parts of tantalum carbide.

2. The preparation process of a highly thermally conductive and ablative-resistant carbon-ceramic brake disc according to claim 1, characterized in that: The thicknesses of the enhanced layer, the heat-conducting layer, and the ablation layer respectively account for 60%, 30%, and 10% of the carbon-ceramic brake disc; the mass ratio of the modified polyacrylonitrile-based carbon fiber to the modified pitch-based carbon fiber in the raw materials of the heat-conducting layer is 6-9:1-4; the mass ratio of the modified polyacrylonitrile-based carbon fiber to the modified viscose-based carbon fiber in the raw materials of the ablation layer is 6-9:1-4.

3. The preparation process of a high thermal conductivity and ablation resistant carbon-ceramic brake disc according to claim 1, characterized in that: The preparation method of the modified polyacrylonitrile-based carbon fiber is as follows: by mass, immerse the polyacrylonitrile-based chopped carbon fiber into 20 parts of a nitric acid solution with a mass fraction of 68%, add nickel sulfate hexahydrate and ferrous sulfate heptahydrate, and perform ultrasonic treatment at 80 °C for 1.5 - 2 h at 40 kHz to obtain a fiber mixture; perform plasma treatment on the multi-walled carbon nanotubes, introduce a mixed gas with a volume ratio of argon to oxygen of 4:1, and treat at a power of 300 W for 15 min to obtain activated carbon nanotubes; immerse the activated carbon nanotubes and the fiber mixture into a solution composed of 1 part of sodium hypophosphite and 20 parts of deionized water, adjust the pH to 8.5, and react at 85 °C for 1 - 1.5 h to obtain a reaction system; dissolve γ-aminopropyltriethoxysilane in 30 parts of absolute ethanol to prepare a 2.5% solution, mix it with the reaction system and perform ultrasonic treatment for 1 h to obtain modified fibers; immerse the modified fibers into a 0.6% dispersion prepared from 0.3 part of polyvinylpyrrolidone and 50 parts of absolute ethanol, perform ultrasonic treatment at 40 kHz for 30 min, and then cure at 120 °C for 2 h to obtain the modified polyacrylonitrile-based carbon fiber.

4. The preparation process of the high thermal conductivity and ablation-resistant carbon-ceramic brake disc according to claim 1, characterized in that: The preparation method of the modified pitch-based carbon fiber is as follows: by mass, immerse the pitch-based chopped carbon fiber into a mixed solution of 30 parts of nitric acid with a mass fraction of 68% and 10 parts of hydrogen peroxide with a mass fraction of 30%, and perform ultrasonic treatment at 60 °C to obtain pretreated fibers; dissolve γ-aminopropyltriethoxysilane in absolute ethanol to prepare a solution with a mass fraction of 5%, and react with the pretreated fibers at 55 °C for 4 h to obtain modified fibers; disperse nano silicon carbide in 50 parts of deionized water to prepare a suspension with a mass fraction of 10%, assist in impregnation under ultrasonic waves for 1 h, and then immerse it into a 10% solution composed of 3 parts of phenolic resin and 27 parts of acetone, and cure at 100 - 120 °C for 2 - 3 h to obtain the modified pitch-based carbon fiber.

5. The preparation process of a high thermal conductivity and ablation-resistant carbon-ceramic brake disc according to claim 1, characterized in that: The preparation method of the modified viscose-based carbon fiber is as follows: by mass, immerse the viscose-based chopped carbon fiber into a mixed solution of 15 parts of nitric acid with a mass fraction of 68% and 5 parts of hydrogen peroxide with a mass fraction of 30%, and perform ultrasonic treatment at 70 °C to obtain pretreated fibers; disperse tantalum carbide nanoparticles and 4 parts of phenolic resin in isopropanol to prepare a coating solution with a mass fraction of 1%, impregnate under vacuum for 0.5 - 1 h, and then cure at 180 - 200 °C for 2 h to obtain the viscose-based carbon fiber.

6. The preparation process of a high thermal conductivity and ablation-resistant carbon-ceramic brake disc according to claim 1, characterized in that: The method of two-stage high-pressure impregnation is as follows: first immerse the carbon fiber preform into the impregnating solution, impregnate at 10 MPa for 1 - 1.5 h to obtain a macroporous filling embryo; heat the macroporous filling embryo to 50 °C and impregnate again at 20 MPa for 1.5 - 2 h to obtain the impregnated embryo; The preparation method of the impregnating solution is as follows: by mass fraction, 25 parts of polycarbosilane and 7.5 parts of boron carbide are dissolved in 175 parts of tetrahydrofuran to prepare a mixed impregnating solution with a mass concentration of 15.7%; the preparation method of the carbon fiber preform is as follows: the reinforcing layer molding compound is cured at 20 MPa and 120 °C for 1.2 h to obtain a reinforcing layer embryo; the heat-conducting layer molding compound is laid on the reinforcing layer embryo and cured at 18 MPa and 120 °C for 0.5 h to obtain a composite embryo; the ablation layer molding compound is laid on the composite embryo and cured at 15 MPa and 120 °C for 0.3 h to obtain the carbon fiber preform.

7. The preparation process of a high thermal conductivity and ablation-resistant carbon-ceramic brake disc according to claim 1, characterized in that: The densification treatment process is as follows: the impregnated embryo is placed in a hot isostatic press and treated at 200 MPa and 400 - 450 °C for 30 min to obtain the densified embryo.

8. The preparation process of a high thermal conductivity and ablation-resistant carbon-ceramic brake disc according to claim 1, characterized in that: The interface treatment method is as follows: yttrium oxide suspension is evenly sprayed on the surface of the densified embryo and then placed in an 80 °C drying oven for 1 h, and then heat-treated at 300 - 350 °C for 30 min under nitrogen protection to obtain the coated embryo; the preparation method of the yttrium oxide suspension is as follows: by mass fraction, 1.25 parts of yttrium oxide are added to 125 parts of absolute ethanol and stirred and dispersed to prepare the yttrium oxide suspension with a mass concentration of 1%.

9. The preparation process of a high thermal conductivity and ablative-resistant carbon-ceramic brake disc according to claim 1, characterized in that: The chemical vapor deposition method is as follows: the coated embryo is transferred to a deposition furnace, methane is introduced at 70 L / h and argon is introduced at 30 L / h, and deposition is carried out at 1050 - 1150 °C for 8 - 10 h to obtain the carbon-ceramic brake disc.

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