Carbon-ceramic brake disc with composite functional layer and preparation method of carbon-ceramic brake disc

Abstract

The invention relates to the technical field of brake discs, in particular to a carbon-ceramic brake disc with a composite functional layer and a preparation method of the carbon-ceramic brake disc. The problems that a brake disc is insufficient in strength and poor in ablation resistance are solved. The preparation method comprises the following steps: carrying out low-temperature plasma treatment and silicon dioxide sol impregnation on carbon fibers, and inserting a graphene oxide film between woven layers, so as to obtain a carbon fiber preform; primary densification is carried out through pretreatment activation, low-temperature permeation and high-temperature permeation, and two graphitization treatments are combined; siliconizing is carried out through low-pressure permeation, high-pressure strengthening and laser cladding, and secondary densification is carried out through precursor impregnation and cracking; the titanium zirconium silicide-nano aluminum oxide composite layer generated through the embedding process forms a compact oxidation film at high temperature, and the silicon carbide nano crystal whiskers are subjected to chemical vapor deposition, so that the strength and ablation resistance of the prepared carbon ceramic brake disc are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of brake discs, and specifically to a carbon-ceramic brake disc with a composite functional layer and a preparation method thereof. Background Art

[0002] Carbon-ceramic brake discs, with characteristics such as light weight, high specific strength, excellent thermal stability and wear resistance, show broad application prospects in fields such as aerospace, high-speed trains, and high-end automobiles.

[0003] There are mainly two ways for the traditional preparation process of carbon-ceramic brake discs: short-fiber molded carbon-ceramic brake discs and long-fiber carbon-ceramic brake discs. The short-fiber molded carbon-ceramic brake disc uses chopped carbon fibers and resin raw materials to be cured and formed into a blank by heating and molding, and then silicon infiltration is carried out to prepare a carbon-ceramic brake component. The long-fiber carbon-ceramic brake disc uses a three-dimensional needle-punched carbon fiber preform, with a cyclic layering method of one layer of net tire and one layer of non-woven fabric, where the non-woven fabric is used alternately in two directions of 0° and 90°, and in the thickness direction, the whole bundle of fibers is pierced and combined to form a carbon fiber preform. Subsequently, carbon matrix densification is carried out by chemical vapor infiltration (CVI) or precursor infiltration and pyrolysis (PIP), and then high-temperature graphitization treatment is performed on the densified preform, and then silicon infiltration is carried out to prepare a carbon-ceramic brake component. Compared with the short-fiber molded brake disc, the long-fiber carbon-ceramic brake disc is widely used due to its advantages such as high strength and good heat conduction.

[0004] However, when the long-fiber carbon-ceramic brake disc is graphitized, cracks will be generated in the matrix carbon, resulting in silicon carbide entering the fiber surface during the silicon infiltration process, causing irreversible damage to the fibers, thereby reducing the strength of the carbon-ceramic brake disc; in addition, as a brake material, it should have high ablation resistance to reduce the problem of brake failure caused by too fast temperature during braking. Therefore, a carbon-ceramic brake disc with a composite functional layer and a preparation method thereof are proposed to improve the strength and ablation resistance of the carbon-ceramic brake disc. Summary of the Invention

[0005] The purpose of the present invention is to provide a carbon-ceramic brake disc with a composite functional layer and a preparation method thereof. By treating carbon fibers with low-temperature plasma and impregnating them with silica sol, and inserting graphene oxide films between the woven layers, a carbon fiber preform is obtained; primary densification is carried out through pretreatment activation, low-temperature infiltration, and high-temperature infiltration, combined with two graphitization treatments; silicon infiltration is carried out by low-pressure infiltration, high-pressure strengthening, and laser cladding, and secondary densification is carried out by precursor infiltration and pyrolysis; a titanium / zirconium silicide-nanoaluminum oxide composite layer generated by the embedding process forms a dense oxide film at high temperature, and silicon carbide nanowhiskers are chemically vapor deposited, so that the strength and ablation resistance of the prepared carbon-ceramic brake disc are improved.

[0006] To achieve the above object, the present invention provides the following technical solutions: On the one hand, the present invention provides a preparation method of a carbon-ceramic brake disc with a composite functional layer. The preparation method is as follows: The carbon fiber preform is first densified by chemical vapor infiltration to obtain a carbon fiber layer, then subjected to low-temperature graphitization to obtain a low-temperature graphitized layer, and then silicon infiltration is carried out to obtain a silicon carbide layer. The precursor infiltration and pyrolysis process is used for secondary densification and high-temperature graphitization to obtain a high-temperature graphitized layer. Subsequently, an embedding process is used to form a composite functional layer on the surface of the high-temperature graphitized layer. Finally, silicon carbide nanowhiskers are chemically vapor deposited to obtain the carbon-ceramic brake disc; The carbon fiber preform is obtained by subjecting carbon fibers to low-temperature plasma treatment, impregnation with silica sol, gradient temperature drying, and weaving; The first densification includes pretreatment activation and two infiltrations; In the silicon infiltration step, the silicon powder layer is composed of silicon powder and nano-aluminum powder.

[0007] Preferably, the preparation steps of the carbon fiber preform are as follows: The carbon fibers are subjected to low-temperature plasma treatment in an oxygen atmosphere to obtain surface-treated carbon fibers; the vacuum degree of the impregnation tank is pumped to 10 -2 Pa, the surface-treated carbon fibers are immersed in silica sol for 30 min, and during this process, the pressure is increased to 0.5 MPa. Then, supercritical CO2 is used to assist capillary infiltration under the condition of a pressure of 6.5 - 8.2 MPa. Finally, a film is pulled up at a speed of 0.5 mm / s, and it is placed in a constant-temperature oven with a humidity of 40% and a temperature of 25°C. After gelation for 4 - 8 h, gradient temperature drying is carried out, and then it is irradiated with a microwave generator at a power of 500 - 1000 W for 5 min to obtain pretreated carbon fibers; the pretreated carbon fibers are woven. The axial layer adopts a 2.5D weaving method, the radial layer adopts a 3D needle punching weaving method, the crossing angle is controlled at 45°, and a graphene oxide film is inserted between the woven layers. The graphene oxide is reduced to a graphene connection network by microwave radiation to obtain the carbon fiber preform.

[0008] Preferably, the first densification step is as follows: The carbon fiber preform is placed in a CVI furnace. First, a mixed gas of hydrogen and argon is introduced, and after the temperature rises to 900°C, it is kept at this temperature for 1 h (to remove surface impurities and activate pores) for pretreatment activation; then, methane is used as the gas source, the pressure is 5 kPa, the furnace temperature is 900°C, and it is kept at this temperature for 50 h for low-temperature infiltration; finally, the gas source is switched to a mixed gas of propyne and methane, and it is heated to 1000 - 1200°C at a pressure of 8 kPa and kept at this temperature for 30 h for high-temperature infiltration to obtain a carbon fiber layer; among them, iron nanoparticles are introduced into the pores of the carbon fiber preform after pretreatment activation.

[0009] Preferably, the low-temperature graphitization temperature is 1600 - 1800 °C, and the low-temperature graphitization holding time is 4 - 10 h; the high-temperature graphitization temperature is 2100 - 2500 °C, and the high-temperature graphitization holding time is 4 - 10 h.

[0010] Preferably, the silicon infiltration step is as follows: bury the low-temperature graphitized layer in the silicon powder layer, lay graphite paper at the bottom of the furnace chamber for oxygen isolation, perform low-pressure infiltration at 1450 °C under normal pressure for 2 h, and introduce argon for protection during the process; then raise the temperature to 1500 - 1700 °C, and apply an axial mechanical pressure of 5 MPa for high-pressure strengthening for 1 - 3 h; then cool down to 1200 °C at a rate of 5 °C / min, and then naturally cool to room temperature; finally, perform laser cladding, with a CO2 laser power of 500 W, a scanning speed of 10 mm / s, and a spot diameter of 0.2 mm to obtain a silicon carbide layer; the thickness of the silicon powder layer is twice the height of the low-temperature graphitized layer; the silicon powder layer is composed of 95 wt% silicon powder and 5 wt% nano-aluminum powder.

[0011] Preferably, the secondary densification step is as follows: mix phenolic resin and polycarbosilane in a mass ratio of 7:3 to obtain the main resin; add 1 - 6 wt% nano-silicon carbide whiskers and 1 wt% boric acid catalyst to the main resin, and add anhydrous ethanol to dilute to a solid content of 40% to obtain a resin solution; place the silicon carbide layer in a vacuum tank, inject the resin solution for impregnation, pressurize to 10 MPa and hold for 2 h, then perform gradient curing, and finally add it to a carbonization furnace for carbonization. Under an argon atmosphere, heat up to 800 °C at a rate of 5 °C / min and hold for 2 h, and then heat up to 1000 - 1500 °C at a rate of 10 °C / min and hold for 1 h; repeat the impregnation, curing, and carbonization processes 3 times to complete the secondary densification; the phenolic resin is converted into glassy carbon, and the polycarbosilane pyrolyzes to generate β-SiC nanoparticles, filling the pores to achieve "carbon + silicon carbide" composite filling; the SiC whiskers penetrate the carbon matrix, and the flexural strength is improved.

[0012] Preferably, the embedding process steps are as follows: place silicon powder and additives in a ball mill, and dry mix for 4 h under an argon atmosphere to obtain embedding powder; lay 0.5 mm thick embedding powder at the bottom of the crucible, put in the high-temperature graphitized layer, fill the powder around to cover it, and cover a graphite felt heat insulation layer on the top. Use a high-temperature sintering furnace for high-temperature sintering, with a temperature of 1500 - 1700 °C, a holding time of 1 - 3 h, and a protective gas of argon. Then cool down to 800 °C at a rate of 8 °C / min, and then naturally cool to room temperature to obtain a composite functional layer; the additives are obtained by mixing titanium dihydride, zirconium silicide, and alumina nanoflakes in a mass ratio of 1 - 10:5 - 15:0.1 - 5; the additives account for 3 - 20 wt% of the silicon powder.

[0013] Preferably, in the chemical vapor deposition of silicon carbide nanowhiskers, the main source gas is methyltrichlorosilane, the carrier gas is hydrogen, and the diluent gas is argon. The volume ratio of the three is 1:15:5; the temperature is 1100 - 1300 °C, the pressure is 2 kPa, and the deposition time is 3 h.

[0014] On the other hand, the present invention provides a carbon-ceramic brake disc with a composite functional layer. The carbon-ceramic brake disc sequentially includes carbon fiber, a low-temperature graphitized layer, a silicon carbide layer, a high-temperature graphitized layer, and a composite functional layer from the inside to the outside; the carbon-ceramic brake disc is prepared by the preparation method of any one of the above.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. By preparing a carbon fiber preform, the strength of the brake disc is improved. Through the low-temperature plasma treatment and silica sol impregnation strategy, a chemically active nano-rough interface is formed on the surface of the carbon fiber, which is more conducive to binding with the substances treated subsequently; supercritical CO2-assisted capillary infiltration realizes the filling of the micro-pores by the sol, and combined with the reduction of the graphene interlayer network driven by microwave irradiation, a multi-dimensional texture framework with nano-micron synergistic strengthening is constructed; the in-situ transformation of the graphene oxide film not only improves the axial compressive strength of the preform, but also optimizes the lateral heat diffusion path through a high-thermal-conductivity network, avoiding fiber brittle fracture caused by local overheating; the composite structure design of 2.5D axial and 3D radial weaving enables the uniform transfer of the load from in-plane to out-of-plane, suppressing the tendency of anisotropic cracking, and simultaneously improving the flexural strength and fatigue life of the matrix.

[0016] 2. Through chemical vapor infiltration for primary densification and graphitization treatment, the ablation resistance of the brake disc is improved. Chemical vapor infiltration combined with a two-stage temperature-gas regulation strategy constructs a gradient deposition layer from pyrolytic carbon to graphite-like carbon in the pores of the carbon fiber; the viscous carbon generated by methane cracking at the low temperature stage preferentially coats the fiber bundles to form a buffer interface, and the rigid carbon decomposed from propyne at the high temperature stage further fills the deep pores; and the pre-introduction of iron nanoparticles during primary densification catalyzes the graphitization process in the micro-region, generating a short-range ordered whisker-like structure, which not only buffers the thermal stress but also hinders dislocation slip, endowing the material with creep resistance and thermal shock resistance at high temperatures; subsequently, gradient graphitization promotes the structural rearrangement of the carbon matrix, and the healing of lattice defects and the optimization of grain orientation significantly improve the thermal conductivity isotropy; low-temperature graphitization initially constructs graphite microcrystals, and high-temperature graphitization further improves the structure, increasing the strength of the material. At the same time, in a high-temperature ablation environment, the stable graphite structure can effectively resist thermal shock and thermal erosion, improving the ablation resistance.

[0017] 3. The present invention enhances the strength and ablation resistance of the brake disc through silicon infiltration and subsequent secondary densification treatment. During silicon infiltration, the low-temperature graphitized layer is buried in a specific silicon powder layer, first infiltrated under low pressure and then strengthened under high pressure, so that silicon uniformly infiltrates and reacts with carbon to form silicon carbide. This not only seals the open pores and reduces the oxygen diffusion channels, but also significantly improves the surface abrasion resistance of the abrasive particles due to its high hardness characteristics; laser cladding further optimizes the surface quality and enhances the surface strength; the secondary densification uses the PIP process to introduce nano-SiC whiskers and resin carbon matrix, filling the internal pores of the material and improving the density of the material.

[0018] 4. The present invention enhances the strength and ablation resistance of the brake disc through the embedding process and chemical vapor deposition (CVD) of silicon carbide (SiC) nanowhiskers. The titanium (Ti) zirconium (Zr) silicide-nanoaluminum oxide composite layer formed by the embedding process forms a dense oxide film at high temperatures, and its high melting point and low oxygen permeability actively isolate the external thermal oxygen erosion; the remaining Ti and Zr in the embedding layer form liquid alloy microdroplets, which serve as catalysts for whisker growth. The SiC nanowhiskers grown on the surface through CVD accelerate forced convection heat dissipation by increasing the specific surface area and reduce the actual surface heating temperature; the spatial gradient composite of the two enables the surface layer to have both "rigidity" (erosion resistance) and "toughness" (thermal shock resistance) characteristics. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a process flow chart of a carbon-ceramic brake disc with a composite functional layer and its preparation method according to the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0020] 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.

[0021] Please refer to Figure 1 , the present invention provides a carbon-ceramic brake disc with a composite functional layer and its preparation method. A carbon-ceramic brake disc with a composite functional layer is obtained by preparing a carbon fiber preform and performing primary densification, low-temperature graphitization, silicon infiltration treatment, secondary densification, high-temperature graphitization, embedding treatment, and chemical vapor deposition. The technical solutions are as follows: The substance information involved in the present invention is as follows: Phenolic resin CAS: 9003-35-4; polycarbosilane CAS: 62306-27-8; boric acid CAS: 10043-35-3; anhydrous ethanol CAS: 64-17-5; titanium dihydride CAS: 7704-98-5; zirconium silicide CAS: 12039-90-6; carbon fiber is T800 grade carbon fiber, purchased from Jilin Chemical Fiber Co., Ltd.; silica sol was purchased from Xuancheng Jingrui New Materials Co., Ltd.; graphene oxide film was purchased from Nanjing Xianfeng Nanomaterials Technology Co., Ltd.; silicon powder was purchased from Guangdong Wengjiang Chemical Reagent Co., Ltd.; nano-aluminum powder was purchased from Shanghai Hanlang New Materials Technology Co., Ltd.; nano-silicon carbide whiskers were purchased from Zhejiang Yamei Nano Technology Co., Ltd.; and alumina nanopowder was purchased from Beijing Bailingwei Technology Co., Ltd.

[0022] Example 1 The carbon fiber was subjected to low-temperature plasma treatment (power 200 W, time 5 min) in an oxygen atmosphere to obtain surface-treated carbon fiber; silica sol was added to the impregnation tank and the vacuum degree was reduced to 10 -2Pa, immerse the surface-treated carbon fiber in it and keep it for 30 min. During this process, pressurize it to 0.5 MPa. Then, use supercritical CO2 (temperature 35 °C) to assist capillary infiltration under the condition of a pressure of 6.5 MPa. Finally, pull it into a film at a pulling speed of 0.5 mm / s. Place it in an incubator with a humidity of 40% and a temperature of 25 °C. After gelation for 4 h, carry out gradient temperature rise drying (40 °C × 2 h → 60 °C × 2 h → 80 °C × 1 h). Then, use a microwave generator to irradiate it at a power of 500 W (2.45 GHz) for 5 min to obtain the pretreated carbon fiber; Weave the pretreated carbon fiber. The axial layer adopts a 2.5D weaving method, and the radial layer adopts a 3D needle punching weaving method. Control the crossing angle to be 45°. And insert a graphene oxide film (thickness 20 μm, area coverage rate 80%) between the woven layers. Reduce graphene oxide to a graphene connection network through microwave radiation to obtain a carbon fiber preform; Place the carbon fiber preform in a CVI furnace. First, introduce a mixed gas of hydrogen and argon (volume ratio of hydrogen to argon is 1:4). After the temperature rises to 900 °C, keep it warm for 1 h for pretreatment activation; Then, use methane as the gas source, with a pressure of 5 kPa and a furnace temperature of 900 °C, and keep it warm for 50 h for low-temperature infiltration; Finally, switch the gas source to a mixed gas of propyne and methane (volume ratio of propyne to methane is 1:9), and raise the temperature to 1000 °C under the condition of 8 kPa and keep it warm for 30 h for high-temperature infiltration to obtain a carbon fiber layer; Among them, introduce iron nanoparticles (10 nm) into the pores of the carbon fiber preform after pretreatment activation; Then, carry out low-temperature graphitization treatment to obtain a low-temperature graphitized layer. The low-temperature graphitization temperature is 1600 °C, and the holding time is 4 h; Bury the low-temperature graphitized layer in a silicon powder layer. Lay a graphite paper at the bottom of the furnace chamber to isolate oxygen (to avoid silicon oxidation). Carry out low-pressure infiltration for 2 h under normal pressure at 1450 °C, and introduce argon for protection during the process; Then, raise the temperature to 1500 °C and apply an axial mechanical pressure of 5 MPa for high-pressure strengthening for 1 h; Then, cool it down to 1200 °C at a rate of 5 °C / min (below the silicon solidification point), and then naturally cool it to room temperature; Finally, carry out laser cladding. The power of the CO2 laser is 500 W, the scanning speed is 10 mm / s, and the spot diameter is 0.2 mm to obtain a silicon carbide layer; The thickness of the silicon powder layer is twice the height of the low-temperature graphitized layer; The silicon powder layer is composed of 95 wt% silicon powder (average particle size is 12.5 μm) and 5 wt% nano-aluminum powder (particle size 50 nm); Mix phenolic resin and polycarbosilane according to a mass ratio of 7:3 to obtain the main resin; Add 1 wt% of nano-silicon carbide whiskers (diameter 50 nm, aspect ratio 20:1) and 1 wt% of boric acid catalyst to it, and add absolute ethanol to dilute it to a solid content of 40% to obtain a resin solution; Place the silicon carbide layer in a vacuum tank (10 -2Pa), impregnate with a resin solution, apply pressure to 10 MPa and hold for 2 h, then carry out gradient curing (pre-curing: 80 °C × 2 h; main curing: 140 °C × 3 h, hot pressing pressure 2 MPa; high-temperature hardening: 180 °C × 1 h, under argon protection), finally add to a carbonization furnace for carbonization, heat up to 800 °C at a rate of 5 °C / min in an argon atmosphere and hold for 2 h, then heat up to 1000 °C at a rate of 10 °C / min and hold for 1 h; repeat the impregnation, curing and carbonization processes 3 times to complete secondary densification; then carry out high-temperature graphitization treatment, the high-temperature graphitization temperature is 2100 °C, and the holding time is 4 h; then place silicon powder and additives in a ball mill and dry mix for 4 h (rotation speed 300 rpm, ball-to-material ratio 5:1) in an argon atmosphere to obtain an embedded powder; lay a 0.5-mm-thick embedded powder at the bottom of the crucible, place it in the high-temperature graphitization layer, fill the surroundings with powder and cover it, and cover the top with a graphite felt heat insulation layer, use a high-temperature sintering furnace for high-temperature sintering, the temperature is 1500 °C, the holding time is 1 h, the protective gas is argon, then cool down to 800 °C at a rate of 8 °C / min, and then naturally cool to room temperature to obtain a composite functional layer; the additives are obtained by mixing titanium dihydride, zirconium silicide and alumina nanoflour in a mass ratio of 1:5:0.1; the additives account for 3 wt% of the silicon powder; finally, carry out chemical vapor deposition (CVD) of silicon carbide nanowhiskers, the main source gas is methyltrichlorosilane, the carrier gas is hydrogen, and the diluent gas is argon, and the volume ratio of the three is 1:15:5; the temperature is 1100 °C, the pressure is 2 kPa, and the deposition time is 3 h to obtain a carbon-ceramic brake disc.

[0023] Examples 2 - 4 Refer to the preparation method and parameter conditions of Example 1, the specific differences are shown in Table 1; the pressure in Table 1 is the pressure during supercritical CO2 treatment when preparing pretreated carbon fibers; the power is the power during microwave generator treatment when preparing pretreated carbon fibers.

[0024] Comparative Example 1 Refer to the preparation method and parameter conditions of Example 1, the difference is that the carbon fibers are not subjected to low-temperature plasma treatment.

[0025] Comparative Example 2 Refer to the preparation method and parameter conditions of Example 1, the difference is that the surface-treated carbon fibers are not impregnated in the silica sol.

[0026] Comparative Example 3 Refer to the preparation method and parameter conditions of Example 1, the difference is that when preparing pretreated carbon fibers, microwave generator irradiation is not used after gradient heating and drying.

[0027] Comparative Example 4 Referring to the preparation method and parameter conditions of Example 1, the difference is that when the pretreated carbon fiber is woven, the graphene oxide film is not inserted between the woven layers.

[0028] Comparative Example 5 Referring to the preparation method and parameter conditions of Example 1, the difference is that supercritical CO2-assisted capillary infiltration is not used during the pretreatment of carbon fiber.

[0029] Experimental Example 1 Strength Test The flexural strength was tested according to the standard of GB / T 6569-2006; the obtained results are shown in Table 1.

[0030] Table 1 Strength Tests of Examples 1-4 and Comparative Examples 1-5 As can be seen from Table 1, in Examples 1-4, through the low-temperature plasma treatment and silica sol impregnation strategy, a chemically active nano-rough interface is formed on the carbon fiber surface, which is more conducive to binding with the substances in subsequent treatments; supercritical CO2-assisted capillary infiltration realizes the filling of micro-pores by the sol, and combined with the reduction of the graphene interlayer network driven by microwave irradiation, a multi-dimensional texture framework with nano-micro synergistic strengthening is constructed; the in-situ transformation of the graphene oxide film not only improves the axial compressive strength of the preform, but also optimizes the lateral heat diffusion path through the high thermal conductivity network, avoiding fiber brittle fracture caused by local overheating; the composite structure design of 2.5D axial and 3D radial weaving enables uniform load transfer from in-plane to out-of-plane, inhibits the tendency of anisotropic cracking, and synchronously improves the flexural strength and fatigue life of the matrix. In Example 3, when the pressure is 7.5 MPa, the gelation time is 6 h, and the power is 800 W, the best flexural strength of the brake disc prepared is 224 MPa. In Comparative Example 1, the carbon fiber was not subjected to low-temperature plasma treatment, the fiber surface was inert and lacked sufficient polar functional groups and nano-rough structures, the wettability of the fiber with the silica sol and the subsequent carbon matrix decreased significantly, the interfacial bonding force weakened, and the flexural strength decreased significantly due to interfacial debonding. In Comparative Example 2, the surface-treated carbon fiber was not impregnated in the silica sol, and the carbon fiber preform could not form a pore strengthening structure filled with silica sol, and the flexural strength decreased due to the increase in porosity and local stress concentration. In Comparative Example 3, when preparing the pretreated carbon fiber, after gradient heating and drying, the microwave generator was not used for irradiation, resulting in the graphene oxide film remaining in the insulating flake state, unable to form a continuous three-dimensional conductive and thermal network of graphene, lacking strong interfacial connection of graphene between layers, and weakening the hindrance to crack propagation. In Comparative Example 4, when weaving the pretreated carbon fiber, the graphene oxide film was not inserted between the woven layers, and the layers only relied on mechanical interlocking of the fibers, unable to form chemical bonding and a nano-scale toughening network, and cracks at the two-phase interface were prone to spread along the layers, resulting in plane delamination fracture. In Comparative Example 5, when pretreating the carbon fiber, supercritical CO2-assisted capillary infiltration was not used, resulting in the sol only accumulating on the surface, with closed pores or unfilled areas remaining inside, and there was a discontinuous transition zone at the fiber-matrix interface, and the carbon matrix was weakly bonded to the fiber after formation.

[0031] Examples 5-7 Referring to the preparation method and parameter conditions of Example 3, the specific differences are shown in Table 2.

[0032] Comparative Example 6 Referring to the preparation method and parameter conditions of Example 3, the difference is that during the first densification, no pre-activation treatment was carried out.

[0033] Comparative Example 7 Referring to the preparation method and parameter conditions of Example 3, the difference is that during the first densification, no low-temperature infiltration was carried out.

[0034] Comparative Example 8 Referring to the preparation method and parameter conditions of Example 3, the difference is that during the first densification, high-temperature infiltration was not carried out.

[0035] Comparative Example 9 Referring to the preparation method and parameter conditions of Example 3, the difference is that during the first densification, iron nanoparticles were not introduced into the pores of the carbon fiber preform after pretreatment activation.

[0036] Comparative Example 10 Referring to the preparation method and parameter conditions of Example 3, the difference is that during the first densification, low-temperature infiltration was carried out after high-temperature infiltration.

[0037] Comparative Example 11 Referring to the preparation method and parameter conditions of Example 3, the difference is that high-temperature graphitization treatment was not carried out.

[0038] Experimental Example 2 Ablation Resistance Performance Test Referring to the standard of ASTM E285-80 (2002) to test the ablation resistance performance; the obtained results are shown in Table 2.

[0039] Table 2 Ablation Resistance Performance Test of Example 3, Examples 5-7 and Comparative Examples 6-11 As can be seen from Table 2, in Examples 3 and 5-7, chemical vapor infiltration combined with a two-stage temperature-gas regulation strategy was used to construct a gradient deposition layer from pyrolytic carbon to graphitic carbon in the pores of carbon fibers. The viscous carbon generated by methane cracking at the low temperature stage preferentially coated the fiber bundles to form a buffer interface, and the rigid carbon decomposed from propyne at the high temperature stage further filled the deep pores. Moreover, the pre-introduction of iron nanoparticles during the first densification catalyzed the graphitization process in the microregions, generating a short-range ordered whisker-like structure, which not only buffered the thermal stress but also hindered the dislocation slip, endowing the material with creep resistance and thermal shock resistance at high temperatures. Subsequently, low-temperature graphitization preliminarily constructed graphite microcrystals, and high-temperature graphitization further improved the structure, enhancing the strength of the material. At the same time, in a high-temperature ablation environment, the stable graphite structure could effectively resist thermal shock and thermal erosion, improving the ablation resistance performance. In Example 5, when the high-temperature infiltration temperature was 1050 °C, the low-temperature graphitization temperature was 1700 °C for 6 h, and the high-temperature graphitization temperature was 2200 °C for 6 h, the prepared brake disc had the best ablation resistance performance, and the ablation amount was 0.050. In Comparative Example 6, during the first densification, no pre-activation treatment was carried out, and the surface impurities blocked the pore entrances, resulting in hindered subsequent gas-phase infiltration deposition. As a result, there were unfilled micropores / cracks in the matrix layer, the fiber and the pyrolytic carbon matrix were loosely combined, forming a weak chemical bonding interface, which was easily oxidized and degraded at high temperatures, reducing the ablation resistance performance. In Comparative Example 7, during the first densification, no low-temperature infiltration was carried out, and the methane low-temperature infiltration layer was missing, unable to form a viscous buffer carbon / nano-graphite transition layer. The high-temperature oxidation rate and the degree of surface spalling were aggravated, and the ablation rate increased. In Comparative Example 8, during the first densification, no high-temperature infiltration was carried out, and the carbon fiber matrix only contained the soft pyrolytic carbon formed by low-temperature methane cracking, without forming a rigid carbon skeleton. The low-temperature carbon layer was porous and loose, and the oxidation medium was easily penetrated to the fiber core region, resulting in a decrease in the ablation resistance performance. In Comparative Example 9, during the first densification, iron nanoparticles were not introduced into the pores of the carbon fiber preform after pre-treatment activation, and the catalytic graphitization effect of the iron particles in the pores was lost, increasing the oxidation rate of the carbon matrix and reducing the ablation resistance performance. In Comparative Example 10, during the first densification, high-temperature infiltration was carried out first and then low-temperature infiltration. The outer layer was a rigid high-temperature carbon layer, and the inner layer was a ductile low-temperature carbon layer. The difference in the expansion coefficients caused internal stress cracks. The outer hard material was more likely to peel off from the flexible inner layer during thermal cycling. After the loose inner layer was exposed, it became a rapid oxygen diffusion channel, accelerating the overall oxidation damage. In Comparative Example 11, no high-temperature graphitization treatment was carried out, and the carbon matrix remained in the low-temperature graphitization stage, unable to form a highly oriented graphite lattice. The low-order carbon matrix had poor antioxidant and thermal conductivity capabilities, and the local temperature increased sharply. The oxidation rate of the material increased significantly at high temperatures, and the ablation rate increased.

[0040] Examples 8-10 Referring to the preparation method and parameter conditions of Example 5, the specific differences are shown in Table 3; the temperature in Table 3 is the temperature of the second temperature rise during carbonization for the second densification.

[0041] Table 3 Specific preparation parameters of Examples 8 - 10 Comparative Example 12 Referring to the preparation method and parameter conditions of Example 5, the difference is that during the silicon infiltration treatment, low - pressure infiltration is not carried out.

[0042] Comparative Example 13 Referring to the preparation method and parameter conditions of Example 5, the difference is that during the silicon infiltration treatment, high - pressure strengthening is not carried out.

[0043] Comparative Example 14 Referring to the preparation method and parameter conditions of Example 5, the difference is that during the silicon infiltration treatment, laser cladding is not carried out.

[0044] Comparative Example 15 Referring to the preparation method and parameter conditions of Example 5, the difference is that secondary densification is not carried out.

[0045] Comparative Example 16 Referring to the preparation method and parameter conditions of Example 5, the difference is that during the secondary densification, the main resin is only phenolic resin.

[0046] Comparative Example 17 Referring to the preparation method and parameter conditions of Example 5, the difference is that during the secondary densification, nano - silicon carbide whiskers are not added to the resin solution.

[0047] Comparative Example 18 Referring to the preparation method and parameter conditions of Example 5, the difference is that during the secondary densification, the impregnation, curing, and carbonization processes are only carried out once.

[0048] Experimental Example 3 Friction coefficient, strength, and ablation resistance performance test The friction coefficient is tested according to the standard of ISO 26867:2009; the flexural strength is tested according to the standard of GB / T 6569 - 2006; the ablation resistance performance is tested according to the standard of ASTM E285 - 80 (2002); the obtained results are shown in Table 4; within the range of 0.3 - 0.5, the larger the friction coefficient, the better, and when the friction coefficient exceeds 0.5, it will bring negative effects.

[0049] Table 4 Friction coefficient, strength, and ablation resistance performance test of Example 5, Examples 8 - 10, and Comparative Examples 12 - 18 As can be seen from Table 3 and Table 4, in Examples 5 and 8 - 10, during silicon infiltration, the low - temperature graphitized layer was buried in a specific silicon powder layer, first infiltrated under low pressure and then strengthened under high pressure, enabling silicon to uniformly infiltrate and react with carbon to form silicon carbide. This not only seals the open pores and reduces the oxygen diffusion channels, but also significantly improves the surface abrasive wear resistance due to its high hardness characteristics; laser cladding further optimizes the surface quality and enhances the surface strength; the secondary densification uses the PIP process to introduce nano - SiC whiskers and resin carbon matrix, filling the internal pores of the material, increasing the material density, and improving the ablation performance. In Example 8, when the high - pressure strengthening temperature is 1600 °C, the time is 2 h, the nano - silicon carbide whisker dosage is 3 wt%, and the temperature of the second heating during carbonization for secondary densification is 1200 °C, the performance of the brake disc prepared is the best, with a friction coefficient of 0.42, a flexural strength of 231 MPa, and an ablation amount of 0.039%. In Comparative Example 12, during silicon infiltration treatment, low - pressure infiltration was not carried out, and the insufficient infiltration of silicon led to a discontinuous silicon carbide layer on the surface, a decrease in hardness, and easy occurrence of abrasive wear during friction; the unclosed pores became stress concentration sources, weakening the fiber - matrix interface bonding and reducing the flexural strength; the oxidation channels were not closed, and oxygen rapidly diffused along the pores to the interior, increasing the ablation rate. In Comparative Example 13, during silicon infiltration treatment, high - pressure strengthening was not carried out, and the residual carbon matrix that was not fully reacted peeled off preferentially during the wear process, forming abrasive particles to accelerate surface damage; the lack of high - pressure made it impossible for silicon to completely fill the pores between fiber bundles and layers, and cracks were prone to expand along the unreacted carbon area; moreover, the absence of the SiC layer allowed oxygen to directly erode the carbon matrix, and a continuous molten SiO2 protective film could not be formed on the ablation surface. In Comparative Example 14, during silicon infiltration treatment, laser cladding was not carried out, and the uncladded SiC layer was porous, and micro - cracks caused adhesive wear; the surface compressive capacity was insufficient, and stress was easily concentrated at the bottom layer, resulting in a decrease in flexural strength; moreover, there were micro - cracks in the uncladded silicon carbide layer, and the oxidized molten silicon was easily lost at high temperatures, with poor surface thermal shock resistance and an increased ablation rate. In Comparative Example 15, secondary densification was not carried out, and the porosity was still relatively high after primary densification, resulting in the expansion of micro - cracks and the shedding of particles during friction, forming a "self - wear" effect; the bending load was borne by the brittle carbon skeleton, and the fracture toughness and flexural strength decreased; the residual pores became oxidation channels, and the oxidation rate of the carbon matrix increased significantly. In Comparative Example 16, during secondary densification, the brittle glassy carbon matrix was prone to crumbling and the number of abrasive particles increased; the absence of the SiC phase made the matrix a pure carbon structure, with a strength weaker than that of the carbon - SiC mixed phase; moreover, the high - temperature oxidation resistance of SiC was lost, and the surface carbon layer oxidized rapidly at high temperatures. In Comparative Example 17, during secondary densification, nano - silicon carbide whiskers were not added to the resin solution, the crack deflection and bridging effects of the whiskers disappeared, and the wear scar depth increased; the matrix without whisker reinforcement was prone to brittle fracture, and the flexural strength decreased; the thermal conductivity strengthening effect of the whisker network was absent, and the local accumulation of frictional heat led to the expansion of thermal stress cracks, accelerating the fragmentation rate of the ablation surface.In Comparative Example 18, during the secondary densification, the impregnation, curing, and carbonization processes were only carried out once, resulting in a relatively high porosity and insufficient surface densification, which led to a decline in the performance of the brake disc.

[0050] Examples 11 - 13 Referring to the preparation method and parameter conditions of Example 8, the specific differences are shown in Table 5; the mass ratio of the three in Table 5 is the mass ratio of titanium dihydride, zirconium silicide, and alumina nanoflour.

[0051] Table 5 Specific preparation parameters of Examples 11 - 13 Comparative Example 19 Referring to the preparation method and parameter conditions of Example 8, the difference is that the chemical vapor deposition (CVD) silicon carbide nanowhisker treatment was not carried out.

[0052] Comparative Example 20 Referring to the preparation method and parameter conditions of Example 8, the difference is that the embedding powder consists only of silicon powder.

[0053] Comparative Example 21 Referring to the preparation method and parameter conditions of Example 8, the difference is that the embedding powder consists only of 90wt% silicon powder and 10wt% titanium dihydride.

[0054] Experimental Example 4 Strength and ablation resistance performance test The flexural strength was tested according to the standard of GB / T 6569 - 2006; the shear strength was tested according to the standard of GB / T 40388 - 2021; the ablation resistance performance was tested according to the standard of ASTM E285 - 80 (2002); the obtained results are shown in Table 6.

[0055] Table 6 Strength and ablation resistance performance test of Example 8, Examples 11 - 13, and Comparative Examples 19 - 21 As can be seen from Table 5 and Table 6, in Examples 8, 11 - 13, the ablation resistance of the brake disc is improved by the embedding process and chemical vapor deposition (CVD) of silicon carbide (SiC) nanowhiskers. The titanium zirconium silicide - nanoaluminum oxide composite layer formed by the embedding process forms a dense oxide film at high temperatures. Its high melting point and low oxygen permeability actively isolate the external thermal oxygen erosion; the residual Ti and Zr in the embedding layer form liquid alloy micro - droplets, which act as catalysts for whisker growth. The SiC nanowhiskers grown on the surface by CVD accelerate the forced - convection heat dissipation by increasing the specific surface area, reducing the actual surface heating temperature. In Example 12, when the high - temperature sintering temperature is 1600 °C, the time is 2 h, the mass ratio of titanium hydride, zirconium silicide, and alumina nanopowder is 6:12.5:3.1, the additive dosage is 12 wt%, and the CVD temperature is 1250 °C, the performance of the prepared brake disc is the best, with a flexural strength of 236 MPa, an interlaminar shear strength of 29 MPa, and an ablation amount of 0.030%. In Comparative Example 19, the chemical vapor deposition (CVD) of silicon carbide nanowhiskers was not carried out. The absence of nanowhiskers causes the material to lose the ability of crack bridging and deflection. The crack rapidly propagates along the fiber - matrix interface, resulting in a decrease in flexural strength; the lack of the three - dimensional network anchoring effect of whiskers reduces the interfacial bonding strength; and the high - temperature oxidation resistance and thermal - conductivity strengthening effect of nano - SiC whiskers are absent, and a stable oxide layer cannot be formed after surface ablation. In Comparative Example 20, the embedding powder consists only of silicon powder. The silicon powder reacts alone to form pure SiC, but the lack of additive catalysis leads to incomplete reaction. The residual silicon forms a soft phase, intensifying stress concentration and resulting in a decrease in flexural strength; the silicon infiltration is uneven, and a loose SiC region is formed in the fiber - bundle gap, reducing the interlaminar shear strength. Moreover, the pores become oxygen diffusion channels, and local spalling is likely to occur on the ablated surface, shortening the ablation - resistant life. In Comparative Example 21, the embedding powder consists only of 90 wt% silicon powder and 10 wt% titanium hydride. The titanium hydride decomposes at high temperatures to generate Ti and release H2. The escaping H2 forms micropores, reducing the matrix density and decreasing the flexural strength; the brittle interface in the Ti - Si reaction region hinders the transfer of shear stress; the Ti - Si compound generates a TiO2 - SiO2 mixed oxide at high temperatures, but TiO2 is easily evaporated in a high - temperature plasma environment, and the stability of the surface protective layer is poor, increasing the ablation rate.

[0056] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood 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 method of a carbon-ceramic brake disc with a composite functional layer, characterized in that: The preparation method is as follows: The carbon fiber preform is densified once by chemical vapor infiltration to obtain a carbon fiber layer, followed by low-temperature graphitization to obtain a low-temperature graphitized layer, then silicon infiltration to obtain a silicon carbide layer, and secondary densification and high-temperature graphitization are carried out by the process of precursor infiltration and pyrolysis to obtain a high-temperature graphitized layer. Subsequently, an embedding process is used to form a composite functional layer on the surface of the high-temperature graphitized layer, and finally, silicon carbide nanowhiskers are chemically vapor deposited to obtain the carbon-ceramic brake disc; The carbon fiber preform is obtained by subjecting carbon fibers to low-temperature plasma treatment, impregnating with silica sol, gradient heating and drying, and weaving; The first densification includes pretreatment activation and two infiltrations; In the silicon infiltration step, the silicon powder layer is composed of silicon powder and nano-aluminum powder.

2. The preparation method of a carbon-ceramic brake disc with a composite functional layer according to claim 1, characterized in that: The preparation steps of the carbon fiber preform are as follows: subject the carbon fiber to the low-temperature plasma treatment in an oxygen atmosphere to obtain surface-treated carbon fiber; evacuate the impregnation tank to a vacuum of 10 -2 Pa, immerse the surface-treated carbon fiber in the silica sol, pressurize to 0.5 MPa during this process, then assist capillary infiltration with supercritical CO2 under the condition of a pressure of 6.5 - 8.2 MPa, finally lift to form a film, place it in an incubator at a temperature of 25 °C, carry out the gradient heating and drying after gelation for 4 - 8 h, and then irradiate with a microwave generator at a power of 500 - 1000 W to obtain pretreated carbon fiber; The pretreated carbon fibers are woven. The axial layer adopts a 2.5D weaving method, the radial layer adopts a 3D needle punching weaving method, the cross angle is controlled at 45°, and a graphene oxide film is inserted between the woven layers to obtain the carbon fiber preform.

3. The preparation method of a carbon-ceramic brake disc with a composite functional layer according to claim 1, characterized in that: The first densification step is as follows: The carbon fiber preform is placed in a chemical vapor infiltration furnace. First, a mixed gas of hydrogen and argon is introduced for the pretreatment activation; then, using methane as the gas source, the pressure is 5 kPa, the furnace temperature is 900 °C, and it is kept warm for 50 h for the low-temperature infiltration; finally, the gas source is switched to a mixed gas of propyne and methane, and it is heated to 1000 - 1200 °C and kept warm for 30 h under the condition of 8 kPa for the high-temperature infiltration to obtain the carbon fiber layer; wherein, iron nanoparticles are introduced into the pores of the carbon fiber preform after the pretreatment activation.

4. The preparation method of a carbon-ceramic brake disc with a composite functional layer according to claim 1, characterized in that: The low-temperature graphitization temperature is 1600 - 1800 °C, and the low-temperature graphitization holding time is 4 - 10 h; the high-temperature graphitization temperature is 2100 - 2500 °C, and the high-temperature graphitization holding time is 4 - 10 h.

5. The preparation method of a carbon-ceramic brake disc with a composite functional layer according to claim 1, characterized in that: The silicon infiltration step is as follows: The low-temperature graphitized layer is buried in the silicon powder layer, graphite paper is laid at the bottom of the furnace chamber, and low-pressure infiltration is carried out for 2 h under normal pressure at 1450 °C, and argon is introduced for protection during the process; then it is heated to 1500 - 1700 °C, and an axial mechanical pressure of 5 MPa is applied for high-pressure strengthening for 1 - 3 h; then it is cooled to 1200 °C, and then naturally cooled to room temperature; finally, laser cladding is carried out to obtain the silicon carbide layer.

6. The preparation method of a carbon-ceramic brake disc with a composite functional layer according to claim 1, characterized in that: The secondary densification step is as follows: Phenolic resin and polycarbosilane are mixed to obtain the main resin; 1 - 6 wt% of nano-silicon carbide whiskers and boric acid catalyst are added thereto, and anhydrous ethanol is added for dilution to obtain a resin solution; the silicon carbide layer is placed in a vacuum tank, and the resin solution is injected for impregnation, pressurized to 10 MPa and kept for 2 h, then gradient curing is carried out, and finally it is added to a carbonization furnace for carbonization. It is heated to 800 °C in an argon atmosphere and kept warm for 2 h, and then heated to 1000 - 1500 °C at a rate of 10 °C / min and kept warm for 1 h; the impregnation, curing, and carbonization processes are repeated 3 times to complete the secondary densification.

7. The preparation method of a carbon-ceramic brake disc with a composite functional layer according to claim 1, characterized in that: The steps of the embedding process are as follows: Put silicon powder and additives into a ball mill, and dry mix them for 4 h in an argon atmosphere to obtain embedding powder; Lay the embedding powder at the bottom of the crucible, put in the high-temperature graphitization layer, and use a high-temperature sintering furnace for high-temperature sintering. The temperature is 1500 - 1700 °C, the heat preservation time is 1 - 3 h, the protective gas is argon, then cool it to 800 °C at a rate of 8 °C / min, and then naturally cool it to room temperature to obtain the composite functional layer; The additive is obtained by mixing titanium dihydride, zirconium silicide, and alumina nanoflour in a mass ratio of 1 - 10:5 - 15:0.1 - 5; The additive accounts for 3 - 20 wt% of the silicon powder.

8. The preparation method of a carbon-ceramic brake disc with a composite functional layer according to claim 1, characterized in that: In the chemical vapor deposition of silicon carbide nanowhiskers, the main source gas is methyltrichlorosilane, the carrier gas is hydrogen, and the diluent gas is argon. The volume ratio of the three is 1:15:5; The temperature is 1100 - 1300 °C, the pressure is 2 kPa, and the deposition time is 3 h.

9. A carbon-ceramic brake disc with a composite functional layer, characterized in that: The carbon-ceramic brake disc from the inside to the outside is successively carbon fiber, low-temperature graphitization layer, silicon carbide layer, high-temperature graphitization layer, and composite functional layer; The carbon-ceramic brake disc is prepared by the preparation method according to any one of claims 1 - 8.

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