High-thermal-conductivity ablation-resistant carbon ceramic brake disc and preparation process thereof

Abstract

The invention relates to the technical field of brake materials, in particular to a high-thermal-conductivity ablation-resistant carbon ceramic brake disc and a preparation process thereof. The carbon-ceramic brake disc overcomes the defects that an existing carbon-ceramic brake disc is poor in mechanical property and ablation resistance. The preparation method comprises the following steps: preparing modified polyacrylonitrile-based carbon fibers by taking polyacrylonitrile-based short carbon fibers, gamma-aminopropyltriethoxysilane, multiwalled carbon nanotubes, nickel sulfate hexahydrate and ferrous sulfate heptahydrate as raw materials; the preparation method comprises the following steps: preparing modified asphalt-based carbon fibers by taking asphalt-based short carbon fibers, nano silicon carbide and gamma-aminopropyltriethoxysilane as raw materials; preparing modified viscose-based carbon fibers by taking viscose-based chopped carbon fibers and tantalum carbide as raw materials; three modified fibers are used as raw materials of the enhancement layer, the heat conduction layer and the ablation layer; the carbon-ceramic brake disc is prepared through raw material mold pressing, two-stage high-pressure dipping, densification treatment, interface treatment, heat treatment and chemical vapor deposition, and the carbon-ceramic brake disc has the advantages of being high in mechanical property and ablation resistance.

Description

Technical Field

[0001] The invention relates to the technical field of brake materials, and in particular to a high-heat-conductivity, ablation-resistant carbon-ceramic brake disc and a preparation process thereof. Background Art

[0002] In modern vehicle braking systems, the performance of brake materials directly affects driving safety and handling stability. The current mainstream brake materials include cast iron, resin-based composite materials and carbon-ceramic composite materials. 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 decay; resin-based composite materials optimize lightweight and anti-thermal decay performance through the composite of carbon fiber and resin, but organic matter is prone to decomposition at high temperatures, resulting in unstable friction coefficient. As the third-generation brake material, carbon-ceramic brake discs show significant advantages in high temperature resistance, corrosion resistance and lightweight through the composite of carbon fiber preforms and silicon carbide ceramics, and are widely used in high-end automobiles and rail transportation.

[0003] According to the differences in the preparation process of carbon fiber preforms, carbon ceramic brake discs can be divided into two categories: short fiber molded type and long fiber braided type. Short fiber molded carbon ceramic brake discs are made of short-cut carbon fibers and phenolic resin mixed by molding, and are prepared by high-temperature carbonization and chemical vapor infiltration processes. They have the characteristics of high production efficiency and controllable costs, but the random distribution of short fibers leads to many interface defects inside the material, the heat conduction path is blocked, and the thermal conductivity is only 60%-70% of the long fiber structure. The improvement of the fiber continuity of long fiber carbon ceramic brake discs significantly improves the mechanical properties and thermal conductivity of the material, but the fiber buckling phenomenon in the braided structure reduces the material's anti-ablation performance. Under extreme working conditions exceeding 1200°C, the thermal stress at the fiber-ceramic interface is concentrated, resulting in local spalling failure.

[0004] In summary, the existing carbon-ceramic brake discs still have the disadvantages of poor mechanical properties and poor thermal conductivity. When the braking system continues to work, the heat cannot be quickly dissipated, which will cause the disc surface temperature to rise suddenly, causing thermal crack expansion and friction film failure. In severe cases, it may cause braking performance degradation or sudden fracture accidents, becoming a potential threat to the safe operation of high-speed 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 purpose 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 uses polyacrylonitrile-based chopped carbon fibers, γ-aminopropyltriethoxysilane, multi-walled carbon nanotubes, nickel sulfate hexahydrate, and ferrous sulfate heptahydrate as raw materials to prepare modified polyacrylonitrile-based carbon fibers; uses asphalt-based chopped carbon fibers, nano silicon carbide, and γ-aminopropyltriethoxysilane as raw materials to prepare modified asphalt-based carbon fibers; uses viscose-based chopped carbon fibers and tantalum carbide as raw materials to prepare modified viscose-based carbon fibers; uses the three modified fibers as raw materials for the reinforcing layer, the thermal conductive layer, and the ablation layer; and prepares the carbon-ceramic brake disc by 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: On the one hand, the present invention provides a high thermal conductivity and ablation-resistant carbon ceramic brake disc, which specifically includes the following components by weight: The carbon ceramic brake disc includes three layers: a reinforcement layer, a heat-conducting layer, and an ablation layer; the reinforcement layer is made of modified polyacrylonitrile-based carbon fiber; the heat-conducting layer is made of modified polyacrylonitrile-based carbon fiber and modified asphalt-based carbon fiber; the ablation layer is made of modified polyacrylonitrile-based carbon fiber and modified viscose-based carbon fiber; The modified polyacrylonitrile-based carbon fiber raw materials include: 90-110 parts of polyacrylonitrile-based chopped carbon fibers, 1-2 parts of γ-aminopropyltriethoxysilane, 5-7 parts of multi-walled carbon nanotubes, 0.5 parts of nickel sulfate hexahydrate, and 0.3 parts of ferrous sulfate heptahydrate; the modified asphalt-based chopped carbon fiber raw materials include: 90-110 parts of asphalt-based chopped carbon fibers, 5-7 parts of nano-silicon carbide, and 1.5-2.5 parts of γ-aminopropyltriethoxysilane; the modified viscose-based carbon fiber raw materials include: 90-110 parts of viscose-based chopped carbon fibers and 3-4 parts of tantalum carbide.

[0008] Preferably, the thicknesses of the reinforcing layer, the thermal conductive layer, and the ablation layer account for 60%, 30%, and 10% of the carbon-ceramic brake disc, respectively; the mass ratio of polyacrylonitrile-based chopped carbon fibers and asphalt-based chopped carbon fibers in the raw materials of the thermal conductive layer is 6-9:1-4; the mass ratio of polyacrylonitrile-based chopped carbon fibers and modified viscose-based chopped carbon fibers in the raw materials of the ablation layer is 6-9:1-4.

[0009] 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 asphalt-based carbon fiber, modified polyacrylonitrile-based carbon fiber and modified viscose-based carbon fiber as raw materials to prepare reinforcement layer molding materials, thermal conductive layer molding materials, and ablation layer molding materials respectively; S2 subjecting the reinforcement layer molding materials, thermal conductive layer molding materials, and ablation layer molding materials 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 embryo; S4 subjecting the impregnated embryo to densification treatment to obtain a densified embryo; S5 subjecting the densified embryo to interface treatment to obtain a coating embryo; S6 subjecting the coating embryo to chemical vapor deposition to obtain a carbon-ceramic brake disc.

[0010] Preferably, the preparation method of modified polyacrylonitrile-based carbon fiber is as follows: by weight, immersing polyacrylonitrile-based chopped carbon fiber in 20 parts by weight of 68% nitric acid solution, adding nickel sulfate hexahydrate and ferrous sulfate heptahydrate, and ultrasonically treating at 80°C and 40kHz for 1.5-2h to obtain a fiber mixture; plasma treating multi-walled carbon nanotubes, passing a mixed gas of argon and oxygen in a volume ratio of 4:1, and treating at a power of 300W for 15min to obtain activated carbon nanotubes; immersing the activated carbon nanotubes and the fiber mixture together The modified carbon fiber was prepared by adding 1 part of sodium hypophosphite and 20 parts of deionized water, adjusting the pH to 8.5, and reacting at 85°C for 1-1.5 hours to obtain a reaction system; γ-aminopropyltriethoxysilane was dissolved in 30 parts of anhydrous ethanol to prepare a 2.5% solution, and the solution was mixed with the reaction system and then ultrasonically treated for 1 hour to obtain a modified fiber; the modified fiber was immersed in a 0.6% dispersion prepared by 0.3 parts of polyvinyl pyrrolidone and 50 parts of anhydrous ethanol, and ultrasonically treated at 40kHz for 30 minutes and then cured at 120°C for 2 hours to obtain a modified polyacrylonitrile-based carbon fiber.

[0011] Preferably, the preparation method of the modified asphalt-based carbon fiber is as follows: by mass, the asphalt-based chopped carbon fiber is immersed in a mixed solution of 30 parts by mass of 68% nitric acid and 10 parts by mass of 30% hydrogen peroxide, and ultrasonically treated at 60°C to obtain pretreated fibers; γ-aminopropyltriethoxysilane is dissolved in anhydrous ethanol to form a 5% solution, and reacted with the pretreated fibers at 55°C for 4 hours to obtain modified fibers; nano-silicon carbide is dispersed in 50 parts of deionized water to form a 10% suspension, and ultrasonically assisted impregnation is performed for 1 hour, and then immersed in a 10% solution of 3 parts of phenolic resin and 27 parts of acetone, and cured at 100-120°C for 2-3 hours to obtain modified asphalt-based carbon fibers.

[0012] Preferably, the preparation method of the modified viscose-based carbon fiber is as follows: by weight, immersing the viscose-based chopped carbon fiber in a mixture of 15 parts by weight of 68% nitric acid and 5 parts by weight of 30% hydrogen peroxide, and ultrasonically treating at 70°C to obtain pretreated fibers; dispersing tantalum carbide nanoparticles and 4 parts of phenolic resin in isopropanol to form a coating liquid with a mass fraction of 1%, immersing under vacuum for 0.5-1h, and then curing at 180-200°C for 2h to obtain viscose-based carbon fibers.

[0013] Preferably, the two-stage high-pressure impregnation method is: first immerse the carbon fiber preform into the impregnation liquid, immerse it at 10MPa for 1-1.5h to obtain a macroporous filling embryo; heat the macroporous filling embryo to 50°C and immerse it again at 20MPa for 1.5-2h to obtain an impregnated embryo.

[0014] Preferably, the preparation method of the impregnation liquid is as follows: by mass fraction, 25 parts of polycarbosilane and 7.5 parts of boron carbide powder are dissolved in 175 parts of tetrahydrofuran to prepare a mixed impregnation liquid with a mass concentration of 15.7%; the preparation method of the carbon fiber preform is as follows: the reinforcement layer molding material is cured at 20MPa and 120°C for 1.2h to obtain a reinforcement layer embryo body; the thermal conductive layer molding material is laid on the reinforcement layer embryo body and cured at 18MPa and 120°C for 0.5h to obtain a composite embryo body; the ablation layer molding material is laid on the composite embryo body and cured at 15MPa and 120°C for 0.3h to obtain a carbon fiber preform.

[0015] Preferably, the densification process is: placing the impregnated embryo body in a hot isostatic press, and processing it at 200 MPa, 400-450° C. for 30 min to obtain a densified embryo body.

[0016] Preferably, the interface treatment method is: after the yttrium oxide suspension is uniformly sprayed on the surface of the densified embryo, it is placed in an 80°C drying oven for treatment for 1 hour, and then heat-treated at 300-350°C for 30 minutes under nitrogen protection to obtain a coated embryo; the preparation method of the yttrium oxide suspension is: by mass fraction, 1.25 parts of yttrium oxide are added to 125 parts of anhydrous ethanol and stirred and dispersed to prepare a suspension with a mass concentration of 1%.

[0017] Preferably, the chemical vapor deposition method is: transferring the coating embryo to a deposition furnace, introducing 70 L / h of methane and 30 L / h of argon, and depositing at 1050-1150° C. for 8-10 hours to obtain a carbon-ceramic brake disc.

[0018] Compared with the prior art, the present invention has the following beneficial effects: 1. In the present invention, nickel-iron alloy is used to catalyze the construction of a three-dimensional carbon nanotube network on the fiber surface, and combined with the interfacial bonding strengthening of a silane coupling agent, a metal-carbon tube composite reinforcement skeleton is formed, and the bending strength and thermal conductivity continuity of the fiber body are simultaneously improved; in the reinforcement layer, the skeleton is interpenetrated by phenolic resin to form a rigid support, and in the thermal conductive layer, its carbon nanotubes and silicon carbide particles of the asphalt-based fiber synergistically accelerate heat transfer through metal thermal conduction and solid vibration thermal conduction, and in the ablation layer, the silane-bridged carbon tube network and the tantalum carbide coating of the viscose-based fiber form a high-temperature oxygen diffusion barrier; after the fibers are directional arranged by gradient pressure molding, the carbon nanotube network and the pyrolytic carbon matrix are interlocked and penetrated in combination with an impregnation strengthening process, and finally the integrated optimization of mechanical bearing, heat conduction and anti-oxidation corrosion is achieved through multi-level interface synergy.

[0019] 2. In the present invention, nitric acid and hydrogen peroxide synergistically etch a micro-groove structure on the surface of asphalt-based carbon fiber, combined with the loading of silicon carbide nanoparticles, significantly improving its specific surface area and thermal contact point density; in the thermal conductive layer, the modified asphalt-based fiber realizes the synergistic enhancement of solid vibration heat transfer and electronic thermal conductivity through the surface silicon carbide particles and the carbon nanotube network of polyacrylonitrile-based fiber; after the fiber is ultrasonically pretreated and gradient pressure molded, its directionally arranged silicon carbide particles and the resin matrix form an interlocking structure, which not only ensures the interlayer interface bonding strength, but also maintains the continuity of the thermal conductive path, thereby improving the thermal conductivity of the carbon-ceramic brake disc.

[0020] 3. In the present invention, a microporous-hydroxyl 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, and a continuous and dense tantalum carbide-carbon composite layer is formed by combining phenolic resin step curing; in the ablation layer, tantalum carbide is preferentially converted into molten tantalum oxide during high-temperature oxidation, which spontaneously spreads to form a dense glassy oxygen barrier layer, and at the same time, the carbon nanotube network of the polyacrylonitrile-based fiber anchors the tantalum oxide layer through a mechanical interlocking effect, inhibiting the peeling of the coating caused by high-temperature airflow scouring. This design achieves the self-protection function and long-term structural integrity of the ablation layer at extreme temperatures through the dual paths of intrinsic material antioxidant properties and interface structure strengthening.

[0021] 4. The present invention uses gradient pressure molding to process the reinforcement layer, the thermal conductive layer and the ablation layer in sequence, and constructs the interlayer transition interface through staged curing to lay the foundation for mechanical bearing; high-pressure impregnation strengthening uses double-stage pressurization to make the polycarbosilane-boron carbide mixed liquid deeply fill the pores, forming a continuous thermal conductive network with the carbon nanotubes, silicon carbide and other components 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, thereby improving the comprehensive performance of the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a schematic diagram of the structure of the carbon-ceramic brake disc of the present invention; In the figure: 1. ablation layer; 2. thermal conductive layer; 3. reinforcement layer. DETAILED DESCRIPTION

[0023] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] See also Figure 1 The present invention provides a high thermal conductivity and ablation-resistant carbon ceramic brake disc and a preparation process thereof. The technical scheme is as follows: Example 1 100 parts of polyacrylonitrile-based chopped carbon fibers were immersed in 20 parts of nitric acid solution with a mass fraction of 68%, 0.5 parts of nickel sulfate hexahydrate and 0.3 parts of ferrous sulfate heptahydrate were added, and the mixture was ultrasonically treated at 80°C and 40kHz for 1.5h to obtain a fiber mixture; 3 parts of multi-walled carbon nanotubes were plasma treated, and a mixed gas of argon / oxygen with a volume ratio of 4:1 was introduced, and the mixture was treated at a power of 300W for 15min to obtain activated carbon nanotubes; the activated carbon nanotubes and the fiber mixture were immersed in a nitric acid solution containing 1 The reaction system was prepared by adjusting the pH value to 8.5 in a 5% aqueous solution of 0.5% sodium hypophosphite, and reacting at 85°C for 1h. 0.8 parts of γ-aminopropyltriethoxysilane was dissolved in 30 parts of anhydrous ethanol to prepare a 2.5% solution, which was mixed with the reaction system and then ultrasonically treated for 1h to obtain modified fibers. The modified fibers were immersed in a 0.6% dispersion prepared by 0.3 parts of polyvinyl pyrrolidone and 50 parts of anhydrous ethanol, ultrasonically treated at 40kHz for 30min, and then cured at 120°C for 2h to obtain modified polyacrylonitrile-based chopped carbon fibers.

[0025] By mass, 100 parts of asphalt-based chopped carbon fibers were immersed in a mixed solution of 30 parts of 68% nitric acid and 10 parts of 30% hydrogen peroxide, and ultrasonically treated at 60°C to obtain pretreated fibers; 1.5 parts of γ-aminopropyltriethoxysilane were dissolved in 30 parts of anhydrous ethanol to form a 5% solution, and reacted with the pretreated fibers at 55°C for 4 hours to obtain modified fibers; 5 parts of silicon carbide nanoparticles were dispersed in 50 parts of deionized water to form a 10% suspension, which was ultrasonically assisted impregnated for 1 hour, and then immersed in a 10% solution of 3 parts of phenolic resin and 27 parts of acetone, and cured at 100°C for 2 hours to obtain modified asphalt-based chopped carbon fibers.

[0026] 100 parts by mass of viscose-based chopped carbon fibers were immersed in a mixture of 15 parts by mass of 68% nitric acid and 5 parts by mass of 30% hydrogen peroxide, and ultrasonically treated at 70°C to obtain pretreated fibers; 2 parts of tantalum carbide nanoparticles and 4 parts of phenolic resin were dispersed in 394 parts of isopropanol to form a coating solution with a mass fraction of 1%, and the solution was impregnated at -0.8 MPa for 0.5 h by vacuum impregnation method; the coated fibers were cured at 180°C for 2 h to obtain viscose-based chopped carbon fibers.

[0027] S1 uses 150 parts of modified polyacrylonitrile-based chopped carbon fibers, 67.5 parts of polyacrylonitrile-based chopped carbon fibers and 7.5 parts of asphalt-based chopped carbon fibers, 22.5 parts of polyacrylonitrile-based chopped carbon fibers and 2.5 parts of viscose-based chopped carbon fibers as raw materials to prepare reinforcement layer molding materials, thermal conductive layer molding materials and ablation layer molding materials respectively; the mass ratio of polyacrylonitrile-based chopped carbon fibers and asphalt-based chopped carbon fibers in the thermal conductive layer raw materials is 9:1; the mass ratio of polyacrylonitrile-based chopped carbon fibers and modified viscose-based chopped carbon fibers in the ablation layer raw materials is 9:1.

[0028] S2 obtains a carbon fiber preform by curing the reinforcement layer molding material, the heat conduction layer molding material, and the ablation layer molding material in three stages; S3: first immerse the carbon fiber preform into the impregnation liquid, and impregnate it at a pressure of 10 MPa for 1.5 hours to obtain a macroporous filling embryo; heat the macroporous filling embryo to 50 degrees Celsius and impregnate it at a pressure of 20 MPa for 1.5-2 hours to obtain an impregnated embryo; The preparation method of the impregnation liquid 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 impregnation liquid with a mass concentration of 15.7%; the preparation method of the carbon fiber preform is as follows: the reinforcement layer molding material is cured at 20MPa and 120°C for 1.2h to obtain a reinforcement layer embryo body; the thermal conductive layer molding material is laid on the reinforcement layer embryo body and cured at 18MPa and 120°C for 0.5h to obtain a composite embryo body; the ablation layer molding material is laid on the composite embryo body and cured at 15MPa and 120°C for 0.3h to obtain a carbon fiber preform.

[0029] S4: placing the impregnated embryo body in a hot isostatic press and processing it at 200 MPa and 400° C. for 30 min to obtain a densified embryo body.

[0030] S5: Evenly spray the yttrium oxide suspension on the surface of the densified embryo body and place it in a drying oven at 80°C for 1 hour, and then heat treat it at 300-350°C for 30 minutes under nitrogen protection to obtain a coated embryo body.

[0031] S6: Transfer the coated body to a deposition furnace, introduce 70 L / h of methane and 30 L / h of argon, and deposit at 1050-1150° C. for 8-10 hours to obtain a carbon-ceramic brake disc.

[0032] The final carbon-ceramic brake disc has a total thickness of 40 mm and includes three layers: a reinforcing layer, a thermal conductive layer, and an ablation layer; the thicknesses of the reinforcing layer, the thermal conductive layer, and the ablation layer account for 60%, 30%, and 10% of the carbon-ceramic brake disc, respectively.

[0033] Example 2 differs from Example 1 in that, in step S1, 150 parts of modified polyacrylonitrile-based chopped carbon fibers, 45 parts of polyacrylonitrile-based chopped carbon fibers and 30 parts of asphalt-based chopped carbon fibers, 15 parts of polyacrylonitrile-based chopped carbon fibers and 10 parts of viscose-based chopped carbon fibers are used as raw materials to prepare reinforcement layer molding materials, thermal conductive layer molding materials and ablation layer molding materials respectively; the mass ratio of polyacrylonitrile-based chopped carbon fibers and asphalt-based chopped carbon fibers in the thermal conductive layer raw material is 6:4; the mass ratio of polyacrylonitrile-based chopped carbon fibers and modified viscose-based chopped carbon fibers in the ablation layer raw material is 6:4, and other parameters and conditions are the same.

[0034] Example 3 differs from Example 1 in that, in step S1, 150 parts of modified polyacrylonitrile-based chopped carbon fibers, 52.5 parts of polyacrylonitrile-based chopped carbon fibers and 22.5 parts of asphalt-based chopped carbon fibers, 17.5 parts of polyacrylonitrile-based chopped carbon fibers and 7.5 parts of viscose-based chopped carbon fibers are used as raw materials to prepare reinforcement layer molding materials, thermal conductive layer molding materials and ablation layer molding materials respectively; the mass ratio of polyacrylonitrile-based chopped carbon fibers and asphalt-based chopped carbon fibers in the thermal conductive layer raw material is 7:3; the mass ratio of polyacrylonitrile-based chopped carbon fibers and modified viscose-based chopped carbon fibers in the ablation layer raw material is 7:3, and other parameters and conditions are the same.

[0035] Example 4 differs from Example 3 in that the amounts of the components used in preparing modified polyacrylonitrile-based carbon fibers are different, namely, 100 parts of polyacrylonitrile-based chopped carbon fibers, 1.5 parts of γ-aminopropyltriethoxysilane, and 6 parts of multi-walled carbon nanotubes; the amounts of the components used in preparing asphalt-based chopped carbon fibers are different, namely, 100 parts of asphalt-based chopped carbon fibers, 6 parts of nano-silicon carbide, and 2 parts of γ-aminopropyltriethoxysilane; the amounts of the components used in preparing viscose-based chopped carbon fibers are different, namely, 100 parts of viscose-based chopped carbon fibers and 3 parts of tantalum carbide, and the other parameters and conditions are the same.

[0036] Example 5 is different from Example 3 in that the amounts of the components used in preparing modified polyacrylonitrile-based carbon fibers are different, namely, 110 parts of polyacrylonitrile-based chopped carbon fibers, 2 parts of γ-aminopropyltriethoxysilane, and 7 parts of multi-walled carbon nanotubes; the amounts of the components used in preparing asphalt-based chopped carbon fibers are different, namely, 110 parts of asphalt-based chopped carbon fibers, 7 parts of nano-silicon carbide, and 2.5 parts of γ-aminopropyltriethoxysilane; the amounts of the components used in preparing viscose-based chopped carbon fibers are different, namely, 110 parts of viscose-based chopped carbon fibers and 4 parts of tantalum carbide, and the other parameters and conditions are the same.

[0037] Example 6 is different from Example 3 in that the amounts of the components used in preparing modified polyacrylonitrile-based carbon fibers are different, namely, 100 parts of polyacrylonitrile-based chopped carbon fibers, 2 parts of γ-aminopropyltriethoxysilane, and 7 parts of multi-walled carbon nanotubes; the amounts of the components used in preparing asphalt-based chopped carbon fibers are different, namely, 100 parts of asphalt-based chopped carbon fibers, 7 parts of nano-silicon carbide, and 2.5 parts of γ-aminopropyltriethoxysilane; the amounts of the components used in preparing viscose-based chopped carbon fibers are different, namely, 100 parts of viscose-based chopped carbon fibers and 4 parts of tantalum carbide, and the other parameters and conditions are the same.

[0038] The difference between Examples 7-18 and Example 6 is that the ultrasonic treatment time and the reaction time of activated carbon nanotubes and fiber mixture are different when preparing modified polyacrylonitrile-based carbon fibers; the curing time and curing temperature after impregnation are different when preparing modified asphalt-based carbon fibers; and the impregnation time and curing temperature under vacuum are different when preparing modified viscose-based carbon fibers. The specific parameters are shown in Table 1.

[0039] Table 1 Parameters of Examples 6-18 Example 19 differs from Example 17 in that the immersion time at 10 MPa in the high-pressure immersion process is 1.25 h, and the immersion time at 20 MPa is 1.75 h; the treatment temperature in the densification step is 425°C; the heat treatment temperature in the interface treatment step is 325°C; the deposition temperature in the chemical vapor deposition step is 1100°C and the deposition time is 9 h.

[0040] The difference between Example 20 and Example 17 is that in the high-pressure impregnation process, the immersion time at 10 MPa is 1.5 h, and the immersion time at 20 MPa is 2 h; the treatment temperature in the densification step is 450°C; the heat treatment temperature in the interface treatment step is 350°C; the deposition temperature in the chemical vapor deposition step is 1150°C and the deposition time is 10 h.

[0041] Comparative Example 1 is different from Example 1 in that the polyacrylonitrile-based chopped carbon fibers are not modified, and commercially available polyacrylonitrile-based carbon fibers are used, and the other parameters and conditions are the same.

[0042] Comparative Example 2 is different from Example 1 in that nickel sulfate hexahydrate and ferrous sulfate heptahydrate are not used in preparing modified polyacrylonitrile-based carbon fibers, and other parameters and conditions are the same.

[0043] Comparative Example 3 is different from Example 1 in that γ-aminopropyltriethoxysilane is not added when preparing modified polyacrylonitrile-based carbon fibers, and other parameters and conditions are the same.

[0044] Comparative Example 4 is different from Example 1 in that, when preparing the modified polyacrylonitrile-based carbon fiber, no multi-walled carbon nanotubes are added, and the other parameters and conditions are the same.

[0045] Comparative Example 5 is different from Example 1 in that, when preparing modified polyacrylonitrile-based carbon fibers, the multi-walled carbon nanotubes are not subjected to plasma treatment, and the other parameters and conditions are the same.

[0046] Comparative Example 6 is different from Example 1 in that the asphalt-based chopped carbon fibers are not modified, and other parameters and conditions are the same.

[0047] Comparative Example 7 is different from Example 1 in that the pretreatment step is omitted when preparing the modified asphalt-based carbon fiber, and the other parameters and conditions are the same.

[0048] Comparative Example 8 is different from Example 1 in that nano-silicon carbide is not added when preparing the modified asphalt-based carbon fiber, and the other parameters and conditions are the same.

[0049] Comparative Example 9 is different from Example 1 in that the viscose-based chopped carbon fibers are not subjected to modification treatment, and other parameters and conditions are the same.

[0050] The difference between Comparative Example 10 and Example 1 is that when preparing the modified viscose-based carbon fiber, the pretreatment step is omitted, and the other parameters and conditions are the same.

[0051] Comparative Example 11 is different from Example 1 in that, when preparing the carbon-ceramic brake disc, the high-pressure impregnation stage is only performed at a pressure of 20 MPa for 2 h, and the other parameters and conditions are the same.

[0052] Comparative Example 12 is different from Example 1 in that boron carbide is not used when preparing the carbon-ceramic brake disc, and the other parameters and conditions are the same.

[0053] Comparative Example 13 is different from Example 1 in that yttrium oxide coating is not performed when preparing the carbon-ceramic brake disc, and other parameters and conditions are the same.

[0054] The difference between Comparative Example 14 and Example 1 is that when preparing the carbon-ceramic brake disc, the raw materials for preparing the reinforcement layer, the heat-conducting layer and the ablation layer are all modified polyacrylonitrile-based carbon fibers.

[0055] The difference between Comparative Example 15 and Example 1 is that when preparing the carbon-ceramic brake disc, the raw materials for preparing the reinforcement layer, the heat-conducting layer and the ablation layer are all modified asphalt-based carbon fibers.

[0056] The difference between Comparative Example 16 and Example 1 is that when preparing the carbon-ceramic brake disc, the raw materials for preparing the reinforcement layer, the heat-conducting layer and the ablation layer are all modified viscose-based carbon fibers.

[0057] Test Example 1 Comprehensive Performance Test Test objects: carbon-ceramic brake discs prepared in Examples 1-6, Example 17, Examples 19-20 and Comparative Examples 11-16.

[0058] 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.

[0059] Table 2 Comprehensive performance test results 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.

[0060] Test Example 2 Mechanical Properties Test Test object: carbon ceramic brake discs prepared in Examples 6-10 and Comparative Examples 1 and 3.

[0061] Test method: refer to test example 1. The final test results are shown in Table 3.

[0062] Table 3 Mechanical properties test results Comparative Example 1: The polyacrylonitrile-based carbon fiber is not modified, and the surface lacks a three-dimensional carbon nanotube network generated by nickel-iron alloy catalysis, resulting in only physical bonding between the fiber and the resin matrix. The lack of chemical bonding of the silane coupling agent greatly reduces the interfacial bonding strength, and the interlaminar shear performance deteriorates after carbonization. The disappearance of the metal-carbon tube composite skeleton significantly reduces the fiber's bending resistance, and the stress cannot be effectively dispersed through the three-dimensional network. Comparative Example 3: No silane coupling agent is added to make the carbon nanotube and fiber interface have no covalent bond connection, and only rely on van der Waals force for bonding. Microcracks are easily generated and expanded at the interface, and the interlaminar shear strength is significantly reduced due to the slip effect. Although the metal skeleton is partially retained, the interface defects lead to a decrease in stress transfer efficiency.

[0063] Test Example 3 Thermal Conductivity Test Test objects: carbon ceramic brake discs prepared in Examples 11-14, Comparative Example 2, and Comparative Examples 4-8.

[0064] Test method: refer to test example 1. The final test results are shown in Table 4.

[0065] Table 4 Thermal conductivity test results After omitting the nickel-iron catalyst in Comparative Example 2, the carbon nanotubes cannot grow in situ on the fiber surface, but only loosely adhere. The metal heat conduction channel is broken, resulting in local accumulation of heat, and the overall thermal conductivity structure cannot be formed. Comparative Example 4 lacks a three-dimensional thermal conductivity network of carbon nanotubes, and heat transfer depends only on the inherent thermal conductivity of the resin matrix and carbon fiber. The thermal conduction path is broken and cannot be synergistically strengthened. In Comparative Example 5, the unactivated carbon nanotubes are severely agglomerated due to insufficient surface functional groups, forming a local thermal resistance barrier, and the deterioration of dispersibility leads to a reduction in the effective thermal conduction area. In Comparative Example 6, the asphalt-based fiber is not modified, lacks the acid-etched high specific surface area structure and silicon carbide, the solid vibration heat transfer path is interrupted, the thermal conductive layer relies only on the electronic heat transfer of the polyacrylonitrile-based carbon tube, the synergistic effect disappears, the heat scattering at the interface is aggravated, and the overall thermal conductivity efficiency is reduced. Comparative Example 7 omits the nitric acid-hydrogen peroxide pretreatment, resulting in the loss of the micro-groove structure on the fiber surface, the mechanical interlocking of the silicon carbide particles is not strong, the thermal resistance of the particle and fiber interface increases, the vibration heat transfer path is blocked, and the thermal conduction efficiency of the thermal conductive layer decreases. In Comparative Example 8, the lack of silicon carbide particles makes the thermal conductive layer rely only on the single heat transfer mechanism of the carbon nanotube network, lacking the synergistic effect of solid vibration heat transfer. The heat stays in the resin matrix for a longer time, and the discontinuous heat conduction path leads to a decrease in the overall thermal conductivity.

[0066] Test Example 4 Ablation resistance test Test object: carbon ceramic brake discs prepared in Examples 15-18 and Comparative Examples 9-10.

[0067] Test method: refer to Test Example 1. The final test results are shown in Table 5.

[0068] Table 5 Ablation test results Comparative Example 9 uses unmodified viscose-based chopped fibers, and there are no tantalum carbide particles that are not embedded in the treated fiber pores, so that the oxygen diffusion channel of the carbon-ceramic brake disc is not blocked at high temperatures. The ablation layer lacks a dense glass barrier layer formed by molten tantalum oxide, the oxidation reaction rate increases sharply, and the material's anti-ablation ability is seriously deteriorated. Comparative Example 10 is not pretreated, resulting in tantalum carbide particles only loosely attached to the surface and unable to deeply fill the fiber pores. After the phenolic resin is cured, the particles are unevenly distributed, the high-temperature tantalum oxide layer has poor continuity, the oxygen diffusion rate is accelerated, and the ablation protection function fails.

[0069] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A high thermal conductivity and ablation resistant carbon ceramic brake disc, characterized by: Calculated by mass, it specifically includes the following components: The carbon ceramic brake disc comprises three layers: a reinforcement layer, a heat conducting layer, and an ablation layer; the reinforcement layer raw material comprises: modified polyacrylonitrile-based carbon fiber; the heat conducting layer raw material comprises: modified polyacrylonitrile-based carbon fiber and modified asphalt-based carbon fiber; the ablation layer raw material comprises: modified polyacrylonitrile-based carbon fiber and modified viscose-based carbon fiber; The modified polyacrylonitrile-based carbon fiber raw material includes: 90-110 parts of polyacrylonitrile-based chopped carbon fibers, 1-2 parts of γ-aminopropyltriethoxysilane, 5-7 parts of multi-walled carbon nanotubes, 0.5 parts of nickel sulfate hexahydrate, and 0.3 parts of ferrous sulfate heptahydrate; the modified asphalt-based chopped carbon fiber raw material includes: 90-110 parts of asphalt-based chopped carbon fibers, 5-7 parts of nano-silicon carbide, and 1.5-2.5 parts of γ-aminopropyltriethoxysilane; the modified viscose-based carbon fiber raw material includes: 90-110 parts of viscose-based chopped carbon fibers and 3-4 parts of tantalum carbide.

2. The high thermal conductivity and ablation-resistant carbon-ceramic brake disc according to claim 1, characterized in that: The thicknesses of the reinforcing layer, the thermal conductive layer, and the ablation layer account for 60%, 30%, and 10% of the carbon-ceramic brake disc, respectively; the mass ratio of the modified polyacrylonitrile-based carbon fiber and the modified asphalt-based carbon fiber in the raw material of the thermal conductive layer is 6-9:1-4; the mass ratio of the modified polyacrylonitrile-based carbon fiber and the modified viscose-based carbon fiber in the raw material of the ablation layer is 6-9:1-4.

3. A process for preparing a high thermal conductivity and ablation-resistant carbon-ceramic brake disc as claimed in claim 1, characterized in that: Specifically, the method comprises the following steps: S1, using modified polyacrylonitrile-based carbon fiber, modified polyacrylonitrile-based carbon fiber and modified asphalt-based carbon fiber, modified polyacrylonitrile-based carbon fiber and modified viscose-based carbon fiber as raw materials to prepare reinforcing layer molding materials, thermal conductive layer molding materials and ablative layer molding materials respectively; S2, subjecting the reinforcing layer molding materials, the thermal conductive layer molding materials and the ablative layer molding materials 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 embryo; S4, subjecting the impregnated embryo to densification treatment to obtain a densified embryo; S5, subjecting the densified embryo to interface treatment to obtain a coating embryo; S6, subjecting the coating embryo to chemical vapor deposition to obtain the carbon-ceramic brake disc.

4. The preparation process of the high thermal conductivity and ablation-resistant carbon-ceramic brake disc according to claim 3 is characterized in that: The preparation method of the modified polyacrylonitrile-based carbon fiber is as follows: by weight, immersing the polyacrylonitrile-based chopped carbon fiber in 20 parts of a nitric acid solution with a mass fraction of 68%, adding nickel sulfate hexahydrate and ferrous sulfate heptahydrate, and ultrasonically treating at 80°C and 40kHz for 1.5-2h to obtain a fiber mixed solution; plasma treating multi-walled carbon nanotubes, passing a mixed gas with a volume ratio of argon and oxygen of 4:1, and treating at a power of 300W for 15min to obtain activated carbon nanotubes; immersing the activated carbon nanotubes and the fiber mixed solution in a The pH value of a solution composed of 1 part of sodium hypophosphite and 20 parts of deionized water is adjusted to 8.5, and the reaction is carried out at 85° C. for 1-1.5 hours to obtain a reaction system; γ-aminopropyltriethoxysilane is dissolved in 30 parts of anhydrous ethanol to prepare a 2.5% solution, which is mixed with the reaction system and then subjected to ultrasonic treatment for 1 hour to obtain a modified fiber; the modified fiber is immersed in a 0.6% dispersion prepared by 0.3 parts of polyvinyl pyrrolidone and 50 parts of anhydrous ethanol, subjected to ultrasonic treatment at 40 kHz for 30 minutes, and then cured at 120° C. for 2 hours to obtain the modified polyacrylonitrile-based carbon fiber.

5. The preparation process of the high thermal conductivity and ablation-resistant carbon-ceramic brake disc according to claim 3 is characterized in that: The preparation method of the modified asphalt-based carbon fiber is as follows: by weight, immersing the asphalt-based chopped carbon fiber in a mixed solution of 30 parts by weight of 68% nitric acid and 10 parts by weight of 30% hydrogen peroxide, and ultrasonically treating the mixed solution at 60° C. to obtain pretreated fibers; dissolving γ-aminopropyltriethoxysilane in anhydrous ethanol to form a 5% by weight solution, and reacting the pretreated fibers at 55° C. for 4 hours to obtain modified fibers; dispersing nano-silicon carbide in 50 parts by weight of deionized water to form a 10% by weight suspension, assisted by ultrasonic immersion for 1 hour, and then immersing the mixed solution in a 10% by weight solution of 3 parts by weight of phenolic resin and 27 parts by weight of acetone, and curing the mixed solution at 100-120° C. for 2-3 hours to obtain modified asphalt-based carbon fibers.

6. The process for preparing the high thermal conductivity and ablation-resistant carbon-ceramic brake disc according to claim 3 is characterized in that: The preparation method of the modified viscose-based carbon fiber is as follows: by weight, immersing the viscose-based chopped carbon fiber in a mixed solution of 15 parts by weight of 68% nitric acid and 5 parts by weight of 30% hydrogen peroxide, and ultrasonically treating the mixture at 70°C to obtain pretreated fibers; dispersing tantalum carbide nanoparticles and 4 parts of phenolic resin in isopropanol to form a coating solution with a weight fraction of 1%, immersing the mixture under vacuum for 0.5-1h, and then curing the mixture at 180-200°C for 2h to obtain the viscose-based carbon fiber.

7. The preparation process of the high thermal conductivity and ablation-resistant carbon-ceramic brake disc according to claim 3 is characterized by: The two-stage high-pressure impregnation method is: firstly immersing the carbon fiber preform into an impregnation liquid, and immersing it at 10 MPa for 1-1.5 hours to obtain a macroporous filling embryo; heating the macroporous filling embryo to 50° C. and immersing it again at 20 MPa for 1.5-2 hours to obtain the impregnated embryo; The preparation method of the impregnation liquid 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 impregnation liquid with a mass concentration of 15.7%; the preparation method of the carbon fiber preform is as follows: the reinforcement layer molding material is cured at 20MPa and 120°C for 1.2h to obtain a reinforcement layer embryo; a thermal conductive layer molding material is laid on the reinforcement layer embryo and cured at 18MPa and 120°C for 0.5h to obtain a composite embryo; an ablation layer molding material is laid on the composite embryo and cured at 15MPa and 120°C for 0.3h to obtain the carbon fiber preform.

8. The process for preparing the high thermal conductivity and ablation-resistant carbon-ceramic brake disc according to claim 3 is characterized in that: The densification treatment process is: placing the impregnated embryo body in a hot isostatic press, and treating it at 200 MPa and 400-450° C. for 30 minutes to obtain the densified embryo body.

9. The process for preparing the high thermal conductivity and ablation-resistant carbon-ceramic brake disc according to claim 3 is characterized in that: The interface treatment method is: after uniformly spraying the yttrium oxide suspension on the surface of the densified embryo, the embryo is placed in an 80°C drying oven for treatment for 1 hour, and then heat-treated at 300-350°C for 30 minutes under nitrogen protection to obtain the coated embryo; the preparation method of the yttrium oxide suspension is: by mass fraction, 1.25 parts of yttrium oxide are added to 125 parts of anhydrous ethanol and stirred and dispersed to prepare the yttrium oxide suspension with a mass concentration of 1%.

10. The process for preparing the high thermal conductivity and ablation-resistant carbon-ceramic brake disc according to claim 3, characterized in that: The chemical vapor deposition method is: transferring the coating embryo to a deposition furnace, introducing 70 L / h of methane and 30 L / h of argon, and depositing at 1050-1150° C. for 8-10 hours to obtain the carbon ceramic brake disc.

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