A carbon ceramic brake pad with a non-dense microcrystalline silicon carbide structure and its preparation method

Abstract

This invention relates to the field of carbon-ceramic brake material technology, specifically to a carbon-ceramic brake pad with a non-dense microcrystalline silicon carbide structure and its preparation method. The carbon-ceramic brake pad is prepared by this method. The method includes the following steps: S1, preparing a 2.5D carbon fiber preform; S2, preparing a carbon / carbon composite; S3, loading reactants into the carbon / carbon composite; S4, subjecting the carbon / carbon composite loaded with reactants to a high-temperature solid-state reaction to synthesize a first preform; S5, repeating steps S3 to S4 to obtain a second preform; S6, applying a liquid-phase silicon infiltration process or a gas-phase silicon infiltration process to the second preform to obtain a third preform; S7, removing free silicon through post-treatment to obtain the carbon-ceramic brake pad. This invention can prepare a carbon-ceramic brake pad with metallurgical bonding and a non-dense microcrystalline silicon carbide structure.

Description

Technical Field

[0001] This invention relates to the field of carbon ceramic brake material technology, specifically to a carbon ceramic brake pad with a non-dense microcrystalline silicon carbide structure and its preparation method. Background Technology

[0002] Carbon ceramic materials possess excellent properties such as high temperature resistance, oxidation resistance, corrosion resistance, and impact resistance, making them widely recognized as the best automotive braking materials. Compared to existing cast iron brake discs paired with resin brake pads, carbon ceramic brake materials offer longer service life, stronger braking performance (such as shorter braking distance and faster braking response), and lighter weight (e.g., carbon ceramic brake discs are more than 50% lighter than cast iron brake discs of the same size).

[0003] Currently, the manufacturing technology of carbon ceramic brake discs is relatively mature. Its structural feature is that it has a large and dense silicon carbide hard phase inside, and its surface usually has a dense silicon carbide hard coating. It is almost not worn during its use and has the entire life cycle of the vehicle.

[0004] However, the usage requirements for carbon-ceramic brake pads, which are paired with carbon-ceramic brake discs, are completely different from those for carbon-ceramic brake discs. During use, they must not cause wear to the carbon-ceramic brake discs. This is because existing carbon-ceramic brake pads have the same or similar structural composition as carbon-ceramic brake discs, namely, they have a large, dense, hard silicon carbide phase (see...). Figure 1 This often leads to problems such as excessive hardness of carbon-ceramic brake pads damaging the carbon-ceramic brake discs, unstable friction coefficients, and excessive noise. Specifically, when carbon-ceramic brake pads, which have large, dense silicon carbide hard phases in their structure, rub against carbon-ceramic brake discs, their hardness is close to that of the discs. This can cause damage to the discs during braking, especially as large, dense silicon carbide particles are ground off the brake pads, forming hard and coarse silicon carbide abrasive grains on the friction surface. These grains cause even more severe abrasive damage to the carbon-ceramic brake discs, resulting in unstable friction coefficients and excessive noise.

[0005] In summary, there is a need to develop a carbon-ceramic brake pad with a non-dense microcrystalline silicon carbide structure and its preparation method to solve the problems of excessive hardness that easily damages the carbon-ceramic brake disc in existing carbon-ceramic brake pads with large, dense silicon carbide hard phases, as well as the hard and coarse silicon carbide abrasive grains formed on the friction surface after large, dense silicon carbide is ground off from the carbon-ceramic brake pad, causing more severe abrasive damage to the carbon-ceramic brake disc, and leading to unstable friction coefficient and excessive noise. Summary of the Invention

[0006] The purpose of this invention is to provide a carbon ceramic brake pad with a non-dense microcrystalline silicon carbide structure and its preparation method. The specific technical solution is as follows:

[0007] In a first aspect, the present invention provides a method for preparing a carbon-ceramic brake pad having a non-dense microcrystalline silicon carbide structure, comprising:

[0008] Step S1: Prepare a 2.5D carbon fiber preform; alternately stack carbon fiber mesh and carbon fiber non-woven fabric, and needle punch to form a 2.5D carbon fiber preform;

[0009] Step S2: Preparation of carbon / carbon composite; pyrolytic carbon is deposited on the 2.5D carbon fiber preform using a chemical vapor infiltration process to form a carbon composite with a density of 1.2~1.5 g / cm³. 3 Carbon / carbon complexes;

[0010] Step S3: The carbon / carbon composite is impregnated in a mixture containing reactants. After impregnation, it is then subjected to heat curing to load reactants into the carbon / carbon composite. The reactants include silicon materials, transition metal oxides, and resinous materials that are cured into the carbon / carbon composite after the heat curing treatment. The resinous materials include at least one of phenolic resin, polyimide resin, and furan resin.

[0011] Step S4: The carbon / carbon composite loaded with the reactants is subjected to a high-temperature solid-state reaction to synthesize a first preform with a non-dense microcrystalline silicon carbide structure; the high-temperature solid-state reaction is carried out under an inert atmosphere, and the reaction temperature is 1200~1450℃, and the reaction time is 0.5~3h.

[0012] Step S5: Repeat steps S3 to S4 until a density of 1.55 to 1.7 g / cm³ is obtained. 3 A second preform having a non-dense microcrystalline silicon carbide structure;

[0013] Step S6: Increase the density of the second preform with a non-dense microcrystalline silicon carbide structure to 1.8~2.1 g / cm³ using a liquid-phase silicon infiltration process or a vapor-phase silicon infiltration process. 3 A third preform with metallurgical bonding and a non-dense microcrystalline silicon carbide structure was obtained.

[0014] Step S7: Post-processing is used to remove free silicon to obtain carbon ceramic brake pads with metallurgical bonding and a non-dense microcrystalline silicon carbide structure.

[0015] Optionally, the density of the 2.5D carbon fiber preform is 0.4~0.6 g / cm³. 3 .

[0016] Optionally, the process conditions used in the chemical vapor permeation process include: the carbon source gas includes methane or propane; the carrier gas includes hydrogen or nitrogen; and the carbon source gas and the carrier gas are introduced into the furnace at a flow ratio of 1:1 to 1:1.5 when the furnace temperature reaches 900~1200℃, and the furnace pressure is controlled at 5~15KPa.

[0017] Optionally, the silicon material includes silicon dioxide powder or elemental silicon; the particle size of the silicon dioxide powder is 20-200 nm; the particle size of the elemental silicon is 20-200 nm; the particle size of the transition metal oxide is 20-200 nm; and the transition metal oxide includes any one of iron oxide, cobalt oxide, and nickel oxide.

[0018] Optionally, the impregnation treatment uses a mixture comprising a first solution and a second solution prepared sequentially;

[0019] The preparation steps of the first solution include: first, mixing the silicon material and the transition metal oxide in 1 / 3 to 1 / 2 of the mass of a solvent, and then adding the following sequentially under stirring conditions. -Diaminodiphenyl ether and pyromellitic dianhydride; wherein, the mass of the silicon substance accounts for 4.5% to 10% of the solvent mass in the first solution; the mass of the transition metal oxide accounts for 0.05% to 0.1% of the solvent mass in the first solution; The molar ratio of diaminodiphenyl ether to pyromellitic dianhydride is 100:95~105, and the combined mass of the two accounts for 15%~20% of the solvent mass in the first solution;

[0020] The preparation step of the second solution includes mixing 1 / 2 to 2 / 3 of the mass of the solvent into the first solution; the solvent is N,N-dimethylformamide or N,N-dimethylacetamide;

[0021] The impregnation process includes first impregnating the carbon / carbon composite in the second solution, controlling the impregnation pressure at 0.02~0.06MPa and the impregnation time at 15~60min; then controlling the impregnation pressure to increase to 0.6~0.7MPa and holding the pressure for 1~3h.

[0022] The heat curing process includes a first heat curing process and a second heat curing process; the first heat curing process uses a heating temperature of 80~120℃ and a holding time of 10~30min; the second heat curing process uses a heating temperature of 280~340℃ and a holding time of 5-10min.

[0023] The resin-like substance that is cured and formed in the carbon / carbon composite after the heat curing treatment is the polyimide resin.

[0024] Optionally, the preparation steps of the mixture used in the impregnation treatment include: first diluting the phenolic resin with xylene to a solid content of 20%~30%; then adding the silicon material and the transition metal oxide under stirring conditions; the silicon material accounts for 20%~50% of the solid content of the phenolic resin; and the transition metal oxide accounts for 0.3%~0.6% of the solid content of the phenolic resin.

[0025] The impregnation process includes first impregnating the carbon / carbon composite in the mixture, controlling the impregnation pressure at 0.02~0.06MPa and the impregnation time at 15~60min; then controlling the impregnation pressure to increase to 0.6~0.7MPa and holding the pressure for 1~3h.

[0026] The heat curing process includes a first heat curing process and a second heat curing process; the first heat curing process uses a heating temperature of 60~100℃ and a holding time of 10~30min; the second heat curing process uses a heating temperature of 130~180℃ and a holding time of 20~90min.

[0027] The resinous substance that is cured and formed in the carbon / carbon composite after the heat curing treatment is the phenolic resin.

[0028] Optionally, the preparation steps of the mixture used in the impregnation treatment include: first diluting the furan resin with xylene to a solid content of 20%~30%; then adding the silicon material and the transition metal oxide under stirring conditions; the silicon material accounts for 20%~50% of the solid content of the furan resin; and the transition metal oxide accounts for 0.3%~0.6% of the solid content of the furan resin.

[0029] The impregnation process includes first impregnating the carbon / carbon composite in the mixture, controlling the impregnation pressure at 0.02~0.06MPa and the impregnation time at 15~60min; then controlling the impregnation pressure to increase to 0.6~0.7MPa and holding the pressure for 1~3h.

[0030] The heat curing process includes a first heat curing process and a second heat curing process; the first heat curing process uses a heating temperature of 60~100℃ and a holding time of 10~30min; the second heat curing process uses a heating temperature of 130~180℃ and a holding time of 20~90min.

[0031] The resinous substance that is cured and formed in the carbon / carbon composite after the heat curing treatment is the furan resin.

[0032] Optionally, the process conditions for the liquid phase silicon infiltration process include: the liquid phase silicon infiltration process is carried out in a liquid phase silicon infiltration furnace. First, silicon powder with a mass of 1.5 to 2 times the mass of the second preform is weighed and covered on the second preform; second, the liquid phase silicon infiltration furnace is heated to 1700±20℃ under vacuum and held for 2 to 6 hours.

[0033] The process conditions for the vapor phase silicon infiltration process include: the vapor phase silicon infiltration process is carried out in a vapor phase silicon infiltration furnace. First, a target mass of silicon powder is weighed and placed below the second preform, and a perforated partition with multiple through holes is set between the second preform and the silicon powder. Second, the vapor phase silicon infiltration furnace is heated to 1750±20℃ under vacuum and held for 2~6 hours.

[0034] The target quality of silicon powder is calculated using the following formula:

[0035] Target mass = Volume of the second precast body × (2.0 g / cm³) 3 -Second prefabricated density) × 1.5.

[0036] Optionally, the post-processing includes heat treatment under an inert atmosphere to remove free silicon; the heat treatment uses a heating temperature of 1300~1400℃ and a holding time of 3~6h;

[0037] The post-processing also includes a grinding process on the carbon-ceramic brake pads after removing free silicon.

[0038] In a second aspect, the present invention provides a carbon-ceramic brake pad with a non-dense microcrystalline silicon carbide structure, which is prepared by the method described above for preparing a carbon-ceramic brake pad with a non-dense microcrystalline silicon carbide structure; the particle size of the microcrystalline silicon carbide in the carbon-ceramic brake pad structure is 2~10μm; the flexural strength of the carbon-ceramic brake pad is 100~160 MPa; the hardness of the carbon-ceramic brake pad is 95~120HRR; and the coefficient of friction of the carbon-ceramic brake pad is 0.35~0.60.

[0039] The application of the technical solution of the present invention has at least the following beneficial effects:

[0040] (1) The present invention provides a method for preparing a carbon-ceramic brake pad with a non-dense microcrystalline silicon carbide structure, which can prepare a carbon-ceramic brake pad with metallurgical bonding and a non-dense microcrystalline silicon carbide structure. When rubbing against a carbon-ceramic brake disc, it is not easily cut and peeled off by surface friction. When the surface friction increases to a critical value, the silicon carbide microcrystals of the carbon-ceramic brake pad are cut and peeled off. These fine-grained silicon carbide microcrystals only produce a polishing effect on the friction surface of the carbon-ceramic brake disc, without causing scratches or damage. This also ensures a moderate and stable coefficient of friction and low noise, thus solving the problems of excessive hardness that easily damages the carbon-ceramic brake disc in existing carbon-ceramic brake pads with large, dense silicon carbide hard phases, and the formation of hard and coarse silicon carbide abrasive grains on the friction surface after large, dense silicon carbide is ground off from the carbon-ceramic brake pad, causing more severe abrasive damage to the carbon-ceramic brake disc, and resulting in excessively high coefficient of friction and excessive noise. Specifically:

[0041] This invention prepares a carbon / carbon composite using steps S1-S2. Then, in step S3, the carbon / carbon composite is impregnated and heat-cured before being loaded with reactants. The reactants include silicon, transition metal oxides, and resin-like substances that have been cured into the carbon / carbon composite after the heat-curing treatment. In step S3, the heat-curing treatment evaporates the solvent in the resin and solidifies the resin within the carbon / carbon composite. In step S4, a high-temperature solid-state reaction ensures that the resin-like substances undergo thermal decomposition at high temperatures to form resin carbon. Furthermore, the silicon and transition metal oxides are reduced to silicon and transition metal particles by the resin carbon in the carbon / carbon composite at high temperatures. Further, the resin carbon and silicon are adsorbed onto the surface of the transition metal particles and diffuse into vacancies or interstitial spaces in the transition metal particle lattice, forming saturated MeC. x Si y (Me represents a transition metal; x represents the molar content of carbon; y represents the molar content of silicon.) In solid solutions or compounds, under high temperatures, both Si and C can potentially separate from MeC. x Si ySiC (silicon carbide) crystal nuclei precipitate and react in a solid solution or compound, meaning transition metal particles can promote SiC nucleus formation, increasing the number of SiC nuclei and refining the SiC grains. Furthermore, during the high-temperature solid-state reaction, volume shrinkage creates gaps or pores between SiC grains. Additionally, after the high-temperature solid-state reaction, resin carbon is abundant, becoming intercalated between the silicon carbide grains. Step S4 synthesizes a first preform with a non-dense microcrystalline silicon carbide structure intercalated with abundant resin carbon. Considering that the abundant resin carbon intercalates between silicon carbide grains, resulting in poor metallurgical bonding, this invention employs step S5—repeating steps S3 to S4—to increase the silicon carbide content and the density of the first preform until a density of 1.55–1.7 g / cm³ is obtained. 3 The second preform, possessing a non-dense microcrystalline silicon carbide structure, not only increases the silicon carbide content but also improves the density of the first preform. To enhance the metallurgical bonding between silicon carbide grains, this invention employs a liquid-phase silicon infiltration process or a vapor-phase silicon infiltration process in step S6 to convert all excess resin carbon intercalated between silicon carbide grains in the second preform into silicon carbide, thereby increasing the density to 1.8~2.1 g / cm³. 3 This process enhances the metallurgical bonding between silicon carbide grains, resulting in a third preform with metallurgical bonding and a non-dense microcrystalline silicon carbide structure. Furthermore, the silicon infiltrated using the liquid-phase silicon infiltration process or the gas-phase silicon infiltration process in step S6 will react with the deposited pyrolytic carbon in step S2 to generate silicon carbide, further increasing the silicon carbide content. In this invention, step S7 is used to remove unreacted free silicon, resulting in a carbon-ceramic brake pad with metallurgical bonding and a non-dense microcrystalline silicon carbide structure.

[0042] (2) The carbon-ceramic brake pad prepared by the present invention has metallurgical bonding and a non-dense microcrystalline silicon carbide structure. The microcrystalline silicon carbide in the structure of the carbon-ceramic brake pad has a particle size of 2~10 μm, which shows a good microcrystalline structure. The bending strength of the carbon-ceramic brake pad is 100-160MPa, which indicates that the carbon-ceramic brake pad has excellent structural strength. The hardness of the carbon-ceramic brake pad is 95~120HRR, which avoids damage to the carbon-ceramic brake disc during braking due to excessive hardness. The friction coefficient of the carbon-ceramic brake pad is 0.35~0.60, which is conducive to ensuring a relatively moderate friction coefficient and reducing noise.

[0043] In addition to the objectives, features, and advantages described above, the present invention has other objectives, features, and advantages. The invention will now be described in further detail with reference to the figures. Attached Figure Description

[0044] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0045] Figure 1 The image shows a SEM image of a carbon-ceramic brake pad with a bulk, dense silicon carbide hard phase, as described in the background art.

[0046] Figure 2 This is a SEM image of the carbon ceramic brake pad with a non-dense microcrystalline silicon carbide structure prepared in Example 1. Detailed Implementation

[0047] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention are within the scope of protection of the present invention.

[0048] Example 1:

[0049] A method for preparing a carbon-ceramic brake pad with a non-dense microcrystalline silicon carbide structure, comprising:

[0050] Step S1: Prepare a 2.5D carbon fiber preform; alternately stack carbon fiber mesh and carbon fiber non-woven fabric, and needle-punch in the Z direction to form a 2.5D carbon fiber preform; the needle-punching density is 40 needles / cm. 2 ;

[0051] Step S2: Preparation of carbon / carbon composite; pyrolytic carbon is deposited on the 2.5D carbon fiber preform using a chemical vapor infiltration process to form a carbon composite with a density of 1.2~1.5 g / cm³. 3 (Specifically 1.35±0.05g / cm) 3 Carbon / carbon complexes;

[0052] Step S3: The carbon / carbon composite is impregnated in a mixture containing reactants. After impregnation, it is then subjected to heat curing to load reactants into the carbon / carbon composite. The reactants include silicon materials, transition metal oxides, and resinous materials that are cured into the carbon / carbon composite after the heat curing treatment. The resinous materials include at least one of phenolic resin, polyimide resin, and furan resin, specifically polyimide resin.

[0053] Step S4: The carbon / carbon composite loaded with the reactants is subjected to a high-temperature solid-state reaction to synthesize a first preform with a non-dense microcrystalline silicon carbide structure; the high-temperature solid-state reaction is carried out under an inert atmosphere (such as nitrogen or argon, specifically nitrogen), and the reaction temperature is 1200~1450℃ (specifically 1350℃), and the reaction time is 0.5~3h (specifically 3h).

[0054] Step S5: Repeat steps S3 to S4, specifically repeating 4 times, until a density of 1.55~1.7 g / cm³ is obtained. 3 (Specifically 1.6±0.05g / cm) 3 A second preform having a non-dense microcrystalline silicon carbide structure;

[0055] Step S6: The density of the second preform with a non-dense microcrystalline silicon carbide structure is increased to 1.8~2.1 g / cm³ using a vapor-phase silicon infiltration process. 3 (Specifically 1.9±0.5g / cm) 3 This process yields a third preform with metallurgical bonding and a non-dense microcrystalline silicon carbide structure.

[0056] Step S7: Post-processing is used to remove free silicon to obtain carbon ceramic brake pads with metallurgical bonding and a non-dense microcrystalline silicon carbide structure.

[0057] The density of the 2.5D carbon fiber preform is 0.4~0.6 g / cm³. 3 The preferred concentration is 0.45~0.5 g / cm³. 3 Specifically, it is 0.48 g / cm³. 3 The preferred carbon fiber is T700.

[0058] The process conditions for the chemical vapor infiltration process include: the carbon source gas includes methane or propane (specifically methane); the carrier gas includes hydrogen or nitrogen (specifically hydrogen); and the carbon source gas and the carrier gas are introduced into the furnace at a flow ratio of 1:1.1 when the furnace temperature reaches 900~1200℃ (specifically 1080±60℃), and the furnace pressure is controlled at 5~15KPa (specifically 10KPa).

[0059] The silicon material includes silicon dioxide powder or elemental silicon (specifically silicon dioxide powder); the particle size of the silicon dioxide powder is 20 nm; the particle size of the transition metal oxide is 40 ± 10 nm; the transition metal oxide includes any one of iron oxide, cobalt oxide, and nickel oxide (specifically nickel oxide).

[0060] The impregnation treatment uses a mixture comprising a first solution and a second solution prepared sequentially.

[0061] The preparation steps of the first solution include: first mixing the silicon material and the transition metal oxide in 1 / 2 mass of solvent, and then adding the following sequentially under stirring conditions. -Diaminodiphenyl ether and pyromellitic dianhydride; wherein, the mass of the silicon substance accounts for 4.5%~10% (specifically 8%) of the solvent mass in the first solution; the mass of the transition metal oxide accounts for 0.05%~0.1% (specifically 0.075%) of the solvent mass in the first solution; The molar ratio of diaminodiphenyl ether and the pyromellitic dianhydride is 100:95, and the combined mass of the two accounts for 15% to 20% (specifically 15%) of the solvent mass in the first solution; in the first solution, by -Diaminodiphenyl ether and pyromellitic dianhydride undergo a polymerization reaction to form polyamic acid;

[0062] The preparation steps of the second solution include mixing 1 / 2 by mass of the solvent into the first solution; the solvent is N,N-dimethylformamide; the solvent N,N-dimethylformamide is added in two parts to form the first solution and the second solution, the purpose of which is: 1) to make the first solution contain... - The reaction system formed by diaminodiphenyl ether and pyromellitic dianhydride has a suitable concentration so that the polymerization reaction can form polyamic acid; 2) Dilute the first solution to form a second solution so that the reactants can be more uniformly loaded on the carbon / carbon composite during impregnation treatment;

[0063] The impregnation process includes first impregnating the carbon / carbon composite in the second solution, controlling the impregnation pressure at 0.02~0.06MPa (specifically 0.02MPa) and the impregnation time at 15~60min (specifically 15min); then increasing the impregnation pressure to 0.6~0.7MPa (specifically 0.7MPa) and maintaining the pressure for impregnation time at 1~3h (specifically 3h).

[0064] The heat curing process includes a first heat curing process and a second heat curing process; the first heat curing process uses a heating temperature of 100°C and a holding time of 10 min; the first heat curing process is used to evaporate and remove the solvent N,N-dimethylformamide; the second heat curing process uses a heating temperature of 330°C and a holding time of 5 min; the second heat curing process is used to cause the polyamic acid to dehydrate and condense to form the reactant polyimide resin;

[0065] The resin-like substance that is cured and formed in the carbon / carbon composite after the heat curing treatment is the polyimide resin.

[0066] The process conditions for the vapor phase silicon infiltration process include: the vapor phase silicon infiltration process is carried out in a vapor phase silicon infiltration furnace. First, a target mass of silicon powder is weighed and placed below the second preform, and a perforated partition with multiple through holes is set between the second preform and the silicon powder. Second, the vapor phase silicon infiltration furnace is heated to 1750±20℃ under vacuum and held for 3 hours.

[0067] The target quality of silicon powder is calculated using the following formula:

[0068] Target mass = Volume of the second precast body × (2.0 g / cm³) 3 -Second preform density) × 1.5 = Second preform volume × 0.4 g / cm³ 3 ×1.5.

[0069] The post-treatment includes heating in an inert atmosphere (such as nitrogen or argon, specifically nitrogen) to remove free silicon; the heating temperature used in the heating treatment is 1300~1400℃ (specifically 1350℃), and the holding time is 6h.

[0070] The post-processing also includes a grinding process on the carbon-ceramic brake pads after removing free silicon; specifically, a grinding machine is used to grind the surface of the carbon-ceramic brake pads.

[0071] Samples of the carbon-ceramic brake pad with a non-dense microcrystalline silicon carbide structure prepared in Example 1 were subjected to scanning electron microscopy (SEM). The test results are shown below. Figure 2 .Depend on Figure 2 It is known that the particle size of the microcrystalline silicon carbide in the carbon-ceramic brake pad structure is 2~10 μm (e.g., Figure 2 The microcrystalline silicon carbide grains shown are 8.77 μm and 8.73 μm in size. The silicon carbide grains are tightly connected but also contain some pores, indicating a non-dense metallurgical bond. Deposited pyrolytic carbon (i.e., Figure 2 Substance B in the text) and carbon fiber (i.e. Figure 2 The presence of substance A in the sample indicates that a non-dense metallurgically bonded microcrystalline carbon ceramic material has been successfully prepared.

[0072] Example 2:

[0073] Unlike Example 1, a liquid-phase silicon infiltration process is used in step S6. The process conditions for the liquid-phase silicon infiltration process include: the liquid-phase silicon infiltration process is carried out in a liquid-phase silicon infiltration furnace. First, silicon powder with a mass of 1.5 to 2 times (specifically 1.5 times) the mass of the second preform is weighed and covered on the second preform; second, the liquid-phase silicon infiltration furnace is heated to 1700±20°C under vacuum and held at that temperature for 2 to 6 hours (specifically 3 hours).

[0074] Example 3:

[0075] Unlike Example 1, the high-temperature solid-phase reaction in step S4 uses a reaction temperature of 1200°C and a reaction time of 3 hours.

[0076] Example 4:

[0077] Unlike Example 1, the high-temperature solid-phase reaction in step S4 uses a reaction temperature of 1450°C and a reaction time of 0.5 h.

[0078] Example 5:

[0079] Unlike Example 1, the preparation steps of the mixture used in the impregnation treatment include: first, diluting the phenolic resin with xylene to a solid content of 20%~30% (specifically 20%); then, adding the silicon material and the transition metal oxide under stirring conditions; the mass of the silicon material accounts for 20%~50% (specifically 50%) of the solid content of the phenolic resin; and the mass of the transition metal accounts for 0.3%~0.6% (specifically 0.5%) of the solid content of the phenolic resin.

[0080] The impregnation process includes first impregnating the carbon / carbon composite in the mixed solution, controlling the impregnation pressure at 0.02~0.06MPa (specifically 0.02MPa) and the impregnation time at 15~60min (specifically 15min); then increasing the impregnation pressure to 0.6~0.7MPa (specifically 0.7MPa) and maintaining the pressure for impregnation time at 1~3h (specifically 3h).

[0081] The heat curing process includes a first heat curing process and a second heat curing process; the first heat curing process uses a heating temperature of 60~100℃ (specifically 100℃) and a holding time of 10~30min (specifically 20min); the second heat curing process uses a heating temperature of 130~180℃ (specifically 180℃) and a holding time of 20~90min (specifically 30min).

[0082] The resinous substance that is cured and formed in the carbon / carbon composite after the heat curing treatment is the phenolic resin.

[0083] Example 6:

[0084] Unlike Example 1, the preparation steps of the mixture used in the impregnation treatment include: first, diluting the furan resin with xylene to a solid content of 20%~30% (specifically 30%); then, adding the silicon material and the transition metal oxide under stirring conditions; the mass of the silicon material accounts for 20%~50% (specifically 50%) of the solid content of the furan resin; and the mass of the transition metal oxide accounts for 0.3%~0.6% (specifically 0.5%) of the solid content of the furan resin.

[0085] The impregnation process includes first impregnating the carbon / carbon composite in the mixed solution, controlling the impregnation pressure at 0.02~0.06MPa (specifically 0.02MPa) and the impregnation time at 15~60min (specifically 15min); then increasing the impregnation pressure to 0.6~0.7MPa (specifically 0.7MPa) and maintaining the pressure for impregnation time at 1~3h (specifically 3h).

[0086] The heat curing process includes a first heat curing process and a second heat curing process; the first heat curing process uses a heating temperature of 60~100℃ (specifically 100℃) and a holding time of 10~30min (specifically 20min); the second heat curing process uses a heating temperature of 130~180℃ (specifically 180℃) and a holding time of 20~90min (specifically 30min).

[0087] The resinous substance that is cured and formed in the carbon / carbon composite after the heat curing treatment is the furan resin.

[0088] Comparative Example 1:

[0089] Unlike Example 1, step S5 is omitted.

[0090] Comparative Example 2:

[0091] Unlike Example 1, step S6 is omitted.

[0092] The carbon-ceramic brake pads prepared in Examples 1-6 and Comparative Examples 1-2 were sampled and subjected to density testing, bending strength testing, hardness testing, and friction and wear performance testing, respectively. The test results are shown in Table 1.

[0093] The density test method is as follows: process it into a standard sample block of 50×50×25 mm, weigh it with an electronic balance, and calculate the density by dividing the mass by the volume.

[0094] The bending strength test method is as follows: The bending strength test is completed according to the test method of "GB / T 40398.2-2021 Carbon-Carbon Composite Carbon Materials Test Methods Part 2: Bending Performance Test".

[0095] The hardness test method is as follows: The HRR value of carbon ceramic brake pads is measured according to "GB / T 5766-2023 Rockwell Hardness Test Method for Friction Materials".

[0096] The friction and wear performance test method is as follows: A LINK 3900 brake test bench is used, according to SAE-J2522. TM According to the 2023 SURFACE VEHICLE RECOMMENDED PRACTICE test standard, the effective radius of a carbon ceramic brake disc is 107 mm, the piston diameter is 55 mm, and the actual moment of inertia is 57 kg·m. 2 The friction and wear characteristics were tested under the conditions of a wheel load of 600 kg and a tire radius of 308 mm.

[0097] Table 1 Test Results

[0098]

[0099] As shown in Table 1, compared with Comparative Example 1, the carbon ceramic brake pads prepared by Examples 1 to 6 of the present invention have lower density, higher bending strength, lower hardness, lower wear thickness, and moderate nominal and minimum friction coefficients; among which, the difference between the nominal and minimum friction coefficients is small. This is because in Comparative Example 1, step S5 was omitted, meaning only step S3 was used once. This resulted in less resinous material and transition metal oxides solidified in the carbon / carbon composite. Using only step S4 once resulted in less microcrystalline silicon carbide formed through high-temperature solid-state reaction in the carbon / carbon composite. This resulted in more and larger pores remaining in the carbon / carbon composite, leading to rapid silicon atom infiltration into the carbon / carbon composite during the vapor-phase silicon infiltration process in step S6. Besides reacting with the small amount of resin carbon that did not form microcrystalline silicon carbide in step S4, many more silicon atoms contacted and reacted with the vapor-deposited pyrolytic carbon in the carbon / carbon composite, easily forming a large, dense hard silicon carbide phase. Some silicon atoms that did not contact carbon remained encapsulated within the hard silicon carbide phase as elemental silicon. Elemental silicon has a melting point of 1414℃, lower than silicon carbide's 2700℃, leading to an increase in the density of the carbon-ceramic brake pad. The carbon-ceramic brake pads exhibit several drawbacks: increased hardness and decreased high-temperature stability. Because they contain large, dense silicon carbide hard phases and residual silicon, large, high-hardness silicon carbide abrasive particles are easily generated during braking, leading to severe abrasive wear. Furthermore, the high temperatures generated by microscopic point contact during braking can soften or even melt elemental silicon, causing adhesive wear and severe thermal decay of the friction coefficient. Therefore, the friction and wear performance test results show a higher nominal friction coefficient, a lower minimum friction coefficient, and a greater wear thickness. The surface of the carbon-ceramic brake disc also shows obvious ploughing scratches. Additionally, during the vapor-phase silicon infiltration process in step S6, besides reacting with a small amount of resin carbon and vapor-deposited pyrolytic carbon, some infiltrated silicon atoms react with the carbon fibers after the vapor-deposited pyrolytic carbon on the outer layer of the carbon fibers has been completely reacted with the silicon atoms, damaging the carbon fiber structure and thus reducing the bending strength of the carbon-ceramic brake pads.

[0100] In Examples 1-6 of this invention, step S5 is used, which repeats steps S3-S4 to further increase the content of microcrystalline SiC in the carbon / carbon composite and the excess resin carbon trapped between silicon carbide grains. Combined with the vapor-phase silicon infiltration process in step S6, all the excess resin carbon trapped between silicon carbide grains is converted into silicon carbide, resulting in a relatively increased density of the prepared carbon-ceramic brake pad. However, the prepared carbon-ceramic brake pad has a non-dense microcrystalline silicon carbide structure, thus exhibiting lower density and lower hardness. In addition, the conversion of all excess resin carbon trapped between silicon carbide grains into silicon carbide enhances the metallurgical bonding between silicon carbide grains, giving the carbon-ceramic brake pad a stronger metallurgical bonding force. Because the carbon-ceramic brake pad prepared in Examples 1-6... The brake pads have a non-dense microcrystalline silicon carbide structure and strong metallurgical bonding, resulting in low wear thickness and moderate nominal and minimum friction coefficients. Furthermore, due to step S5, the content of microcrystalline silicon carbide and excess resin carbon in the carbon / carbon composite increases, reducing the number and size of remaining pores in the composite. This slows down the infiltration rate and amount of silicon atoms. The infiltrated silicon atoms can react with more excess resin carbon and then with the vapor-deposited carbon on the outer layer of the carbon fiber. At this point, the infiltrated silicon atoms are essentially consumed, reducing the probability of a reaction between silicon atoms and the carbon fiber, thus preventing damage to the carbon fiber structure and resulting in higher flexural strength.

[0101] Compared to Comparative Example 2, the carbon-ceramic brake pads prepared in Examples 1-6 of this invention exhibit higher density, higher bending strength, higher hardness, lower wear rate, and higher nominal and minimum friction coefficients; the difference between the nominal and minimum friction coefficients is relatively small. This is because Comparative Example 2 did not employ the vapor-phase silicon infiltration process in step S6, resulting in the excess resin carbon embedded between silicon carbide grains failing to convert into silicon carbide. This leads to a decrease in the density, hardness, and nominal and minimum friction coefficients of the prepared carbon-ceramic brake pads. Furthermore, the inability to convert the excess resin carbon between silicon carbide grains into silicon carbide weakens the metallurgical bonding between the silicon carbide grains, thereby reducing the bending strength and increasing the wear thickness of the carbon-ceramic brake pads. Although the wear thickness of the carbon-ceramic brake pads increased in Comparative Example 2, the silicon carbide microcrystals that were cut and detached only polished the friction surface of the carbon-ceramic brake disc, without causing scratches or damage. Therefore, there was no significant damage to the carbon-ceramic brake disc.

[0102] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for preparing a carbon-ceramic brake pad with a non-dense microcrystalline silicon carbide structure, characterized in that, include: Step S1: Prepare a 2.5D carbon fiber preform; Carbon fiber mesh and carbon fiber non-woven fabric are alternately laminated and needle-punched into a 2.5D carbon fiber preform. Step S2: Preparation of carbon / carbon composite; pyrolytic carbon is deposited on the 2.5D carbon fiber preform using a chemical vapor infiltration process to form a carbon composite with a density of 1.2~1.5 g / cm³. 3 Carbon / carbon complexes; Step S3: The carbon / carbon composite is immersed in a mixture containing reactants. After immersion, it is then subjected to heat curing to load reactants onto the carbon / carbon composite. The immersion process is first controlled at an immersion pressure of 0.02-0.06 MPa for 15-60 min; then the immersion pressure is increased to 0.6-0.7 MPa, and the pressure is maintained for 1-3 h. The reactants include silicon, transition metal oxides, and resins that have been cured into the carbon / carbon composite after the heat curing process. The resins include at least one of phenolic resin, polyimide resin, and furan resin. The silicon includes silicon dioxide powder or elemental silicon. The particle size of the silicon dioxide powder is 20-200 nm. The particle size of the elemental silicon is 20-200 nm. The particle size of the transition metal oxide is 20-200 nm. The transition metal oxide includes any one of iron oxide, cobalt oxide, and nickel oxide. Step S4: The carbon / carbon composite loaded with the reactants is subjected to a high-temperature solid-state reaction to synthesize a first preform with a non-dense microcrystalline silicon carbide structure; the high-temperature solid-state reaction is carried out under an inert atmosphere, and the reaction temperature is 1200~1450℃, and the reaction time is 0.5~3h. Step S5: Repeat steps S3 to S4 until a density of 1.55 to 1.7 g / cm³ is obtained. 3 A second preform having a non-dense microcrystalline silicon carbide structure; Step S6: Increase the density of the second preform with a non-dense microcrystalline silicon carbide structure to 1.8~2.1 g / cm³ using a liquid-phase silicon infiltration process or a vapor-phase silicon infiltration process. 3 A third preform with metallurgical bonding and a non-dense microcrystalline silicon carbide structure was obtained. Step S7: Remove free silicon using post-processing to obtain a carbon-ceramic brake pad with metallurgical bonding and a non-dense microcrystalline silicon carbide structure; the particle size of the microcrystalline silicon carbide in the carbon-ceramic brake pad structure is 2~10μm; the bending strength of the carbon-ceramic brake pad is 100~160 MPa; the hardness of the carbon-ceramic brake pad is 95~120HRR.

2. The method for preparing a carbon ceramic brake pad with a non-dense microcrystalline silicon carbide structure according to claim 1, characterized in that, The density of the 2.5D carbon fiber preform is 0.4~0.6 g / cm³. 3 .

3. The method for preparing a carbon ceramic brake pad with a non-dense microcrystalline silicon carbide structure according to claim 1, characterized in that, The process conditions for the chemical vapor infiltration process include: the carbon source gas includes methane or propane; the carrier gas includes hydrogen or nitrogen; and the carbon source gas and the carrier gas are introduced into the furnace at a flow ratio of 1:1 to 1:1.5 when the furnace temperature reaches 900~1200℃, and the furnace pressure is controlled at 5~15kPa.

4. The method for preparing a carbon ceramic brake pad with a non-dense microcrystalline silicon carbide structure according to any one of claims 1 to 3, characterized in that, The impregnation treatment uses a mixture comprising a first solution and a second solution prepared sequentially. The preparation steps of the first solution include: first, mixing the silicon material and the transition metal oxide in 1 / 3 to 1 / 2 of the mass of solvent; then, under stirring conditions, sequentially adding 4,4'-diaminodiphenyl ether and pyromellitic dianhydride; wherein, the mass of the silicon material accounts for 4.5% to 10% of the mass of the solvent in the first solution; the mass of the transition metal oxide accounts for 0.05% to 0.1% of the mass of the solvent in the first solution; the molar ratio of 4,4'-diaminodiphenyl ether and pyromellitic dianhydride is 100:95 to 105, and the combined mass of the two accounts for 15% to 20% of the mass of the solvent in the first solution; The preparation step of the second solution includes mixing 1 / 2 to 2 / 3 of the mass of the solvent into the first solution; the solvent is N,N-dimethylformamide or N,N-dimethylacetamide; The impregnation process includes first impregnating the carbon / carbon composite in the second solution, controlling the impregnation pressure at 0.02~0.06MPa and the impregnation time at 15~60min; then controlling the impregnation pressure to increase to 0.6~0.7MPa and holding the pressure for 1~3h. The heat curing process includes a first heat curing process and a second heat curing process; the first heat curing process uses a heating temperature of 80~120℃ and a holding time of 10~30min; the second heat curing process uses a heating temperature of 280~340℃ and a holding time of 5-10min. The resin-like substance that is cured and formed in the carbon / carbon composite after the heat curing treatment is the polyimide resin.

5. The method for preparing a carbon ceramic brake pad with a non-dense microcrystalline silicon carbide structure according to any one of claims 1 to 3, characterized in that, The preparation steps of the mixture used in the impregnation treatment include: first, diluting the phenolic resin with xylene to a solid content of 20%~30%; then, adding the silicon material and the transition metal oxide under stirring conditions; the silicon material accounts for 20%~50% of the solid content of the phenolic resin; and the transition metal oxide accounts for 0.3%~0.6% of the solid content of the phenolic resin. The impregnation process includes first impregnating the carbon / carbon composite in the mixture, controlling the impregnation pressure at 0.02~0.06MPa and the impregnation time at 15~60min; then controlling the impregnation pressure to increase to 0.6~0.7MPa and holding the pressure for 1~3h. The heat curing process includes a first heat curing process and a second heat curing process; the first heat curing process uses a heating temperature of 60~100℃ and a holding time of 10~30min; the second heat curing process uses a heating temperature of 130~180℃ and a holding time of 20~90min. The resinous substance that is cured and formed in the carbon / carbon composite after the heat curing treatment is the phenolic resin.

6. The method for preparing a carbon ceramic brake pad with a non-dense microcrystalline silicon carbide structure according to any one of claims 1 to 3, characterized in that, The preparation steps of the mixture used in the impregnation treatment include: first, diluting the furan resin with xylene to a solid content of 20%~30%; then, adding the silicon material and the transition metal oxide under stirring conditions; the mass of the silicon material accounts for 20%~50% of the solid content of the furan resin; and the mass of the transition metal oxide accounts for 0.3%~0.6% of the solid content of the furan resin. The impregnation process includes first impregnating the carbon / carbon composite in the mixture, controlling the impregnation pressure at 0.02~0.06MPa and the impregnation time at 15~60min; then controlling the impregnation pressure to increase to 0.6~0.7MPa and holding the pressure for 1~3h. The heat curing process includes a first heat curing process and a second heat curing process; the first heat curing process uses a heating temperature of 60~100℃ and a holding time of 10~30min; the second heat curing process uses a heating temperature of 130~180℃ and a holding time of 20~90min. The resinous substance that is cured and formed in the carbon / carbon composite after the heat curing treatment is the furan resin.

7. The method for preparing a carbon ceramic brake pad with a non-dense microcrystalline silicon carbide structure according to claim 4, characterized in that, The process conditions for the liquid phase silicon infiltration process include: the liquid phase silicon infiltration process is carried out in a liquid phase silicon infiltration furnace. First, silicon powder with a mass of 1.5 to 2 times the mass of the second preform is weighed and covered on the second preform. Second, the liquid phase silicon infiltration furnace is heated to 1700±20℃ under vacuum and held for 2 to 6 hours. The process conditions for the vapor phase silicon infiltration process include: the vapor phase silicon infiltration process is carried out in a vapor phase silicon infiltration furnace. First, a target mass of silicon powder is weighed and placed below the second preform, and a perforated partition with multiple through holes is set between the second preform and the silicon powder. Second, the vapor phase silicon infiltration furnace is heated to 1750±20℃ under vacuum and held for 2~6 hours. The target quality of silicon powder is calculated using the following formula: Target mass = Volume of the second precast body × (2.0 g / cm³) 3 -Second prefabricated density) × 1.

5.

8. The method for preparing a carbon ceramic brake pad with a non-dense microcrystalline silicon carbide structure according to claim 5, characterized in that, The process conditions for the liquid phase silicon infiltration process include: the liquid phase silicon infiltration process is carried out in a liquid phase silicon infiltration furnace. First, silicon powder with a mass of 1.5 to 2 times the mass of the second preform is weighed and covered on the second preform. Second, the liquid phase silicon infiltration furnace is heated to 1700±20℃ under vacuum and held for 2 to 6 hours. The process conditions for the vapor phase silicon infiltration process include: the vapor phase silicon infiltration process is carried out in a vapor phase silicon infiltration furnace. First, a target mass of silicon powder is weighed and placed below the second preform, and a perforated partition with multiple through holes is set between the second preform and the silicon powder. Second, the vapor phase silicon infiltration furnace is heated to 1750±20℃ under vacuum and held for 2~6 hours. The target quality of silicon powder is calculated using the following formula: Target mass = Volume of the second precast body × (2.0 g / cm³) 3 -Second prefabricated density) × 1.

5.

9. The method for preparing a carbon ceramic brake pad with a non-dense microcrystalline silicon carbide structure according to claim 6, characterized in that, The process conditions for the liquid phase silicon infiltration process include: the liquid phase silicon infiltration process is carried out in a liquid phase silicon infiltration furnace. First, silicon powder with a mass of 1.5 to 2 times the mass of the second preform is weighed and covered on the second preform. Second, the liquid phase silicon infiltration furnace is heated to 1700±20℃ under vacuum and held for 2 to 6 hours. The process conditions for the vapor phase silicon infiltration process include: the vapor phase silicon infiltration process is carried out in a vapor phase silicon infiltration furnace. First, a target mass of silicon powder is weighed and placed below the second preform, and a perforated partition with multiple through holes is set between the second preform and the silicon powder. Second, the vapor phase silicon infiltration furnace is heated to 1750±20℃ under vacuum and held for 2~6 hours. The target quality of silicon powder is calculated using the following formula: Target mass = Volume of the second precast body × (2.0 g / cm³) 3 -Second prefabricated density) × 1.

5.

10. A method for preparing a carbon ceramic brake pad with a non-dense microcrystalline silicon carbide structure according to any one of claims 7 to 9, characterized in that, The post-processing includes heat treatment under an inert atmosphere to remove free silicon; the heat treatment is performed at a temperature of 1300~1400℃ and a holding time of 3~6h. The post-processing also includes a grinding process on the carbon-ceramic brake pads after removing free silicon.

11. A carbon-ceramic brake pad with a non-dense microcrystalline silicon carbide structure, characterized in that, The carbon-ceramic brake pad with a non-dense microcrystalline silicon carbide structure as described in claim 10 is prepared by means of the method described in claim 10; the friction coefficient of the carbon-ceramic brake pad is 0.35~0.60.

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