CN120644665A

CN120644665A - Preparation method of magnesium-aluminum composite brake pad and brake pad

Info

Publication number: CN120644665A
Application number: CN202510799735.3A
Authority: CN
Inventors: 闫文; 范劲松; 高建文
Original assignee: Shenzhen Ester New Materials Technology Co ltd
Current assignee: Shenzhen Ester New Materials Technology Co ltd
Priority date: 2025-06-16
Filing date: 2025-06-16
Publication date: 2025-09-16

Abstract

The application provides a preparation method of a magnesium-aluminum composite material brake pad and the brake pad, the method comprises the steps of placing a base layer mixture and a wear-resistant layer mixture into a hot press for hot press molding to obtain a blank, wherein the blank comprises 35-55% of Mg, 0.1-0.3% of Mn, 15-30% of Si3N4 and 20-50% of Al, the base layer mixture comprises 6-10% of graphene oxide modified silica aerogel, 60-80% of polybutadiene-acrylonitrile core-shell particle modified phenolic resin, 3-5% of coconut shell powder and 6-10% of carbon fiber, and the blank is subjected to heat treatment to obtain the double-layer brake pad. The magnesium-aluminum composite brake pad prepared by the preparation method has good corrosion resistance, wear resistance and oxidation resistance, and solves the noise problem in high-temperature friction.

Description

Preparation method of magnesium-aluminum composite brake pad and brake pad

Technical Field

The application relates to the technical field of aluminum alloy plates, in particular to a preparation method of a magnesium-aluminum composite material brake pad and the brake pad.

Background

With the increasing perfection of automobile performance and the demand for safety, environmental protection and high efficiency, the automobile has higher requirements for automobile brake control in the running process of the automobile. Shorter braking time, faster cooling rate, shorter braking distance, and better braking experience are brought to people, and the requirements of the masses are met. In brake pad applications, the traditional materials are mostly cast iron, and although the materials have higher heat capacity and wear resistance, the materials are heavy, and the weight of the materials is challenging to the overall weight and comprehensive performance of the vehicle. In addition, cast iron has relatively poor heat dissipation performance at high temperature, and heat is easily accumulated in a long-time braking process, so that the braking performance and the safety are affected.

To overcome the above problems, other alloy materials such as aluminum-based composite materials and the like have been widely studied. However, the composition characteristics of the composite material lead to the complexity of a friction mechanism, so that the problems of high temperature noise generation, cracking of the surface and the like of the composite material brake disc are easy to occur in the friction process. Therefore, there is a need to develop a brake pad or brake pad material suitable for new materials to solve the problems in the prior art.

Disclosure of Invention

The application provides a preparation method of a magnesium-aluminum composite material brake pad and the brake pad, and the magnesium-aluminum composite material brake pad prepared by the preparation method has good corrosion resistance, wear resistance and oxidation resistance, and solves the noise problem in high-temperature friction.

In a first aspect, an embodiment of the present application provides a method for preparing a magnesium-aluminum composite brake pad, where the method includes:

Placing the base layer mixture and the wear-resistant layer mixture into a hot press for hot press molding to obtain a blank, wherein the blank comprises, by mass, 35% -55% of Mg, 0.1% -0.3% of Mn, 15% -30% of Si ₃N₄% of Al and 20% -50% of wear-resistant layer mixture, and the wear-resistant layer mixture comprises, by mass, 6% -10% of graphene oxide modified silica aerogel, 60% -80% of polybutadiene-acrylonitrile core-shell particle modified phenolic resin, 3% -5% of coconut shell powder and 6% -10% of carbon fibers;

And (5) carrying out heat treatment on the blank to obtain the double-layer brake pad.

In some alternative embodiments, the ratio of the thicknesses of the base layer and the wear layer is 1 (0.1-0.2).

In some alternative embodiments, the hot press molding is performed at a pressure of 15-50Mpa, a temperature of 500-800 ℃ and a time of 10-30 min.

In some alternative embodiments, the mass ratio of the polybutadiene-acrylonitrile core-shell particle modified phenolic resin to the graphene oxide modified silica aerogel is 10 (0.8-1.2).

In some alternative embodiments, the heat treatment includes first heating to 500-600C, maintaining for 150-180min, and continuing heating to 700-800C, maintaining for 60-90min.

In some alternative embodiments, a method of preparing a graphene oxide modified silica aerogel, comprising:

slowly adding graphene oxide dispersion liquid into the hydrolyzed silica sol, wherein the mass ratio of the graphene oxide is 1-10wt%;

dispersing the composite sol in an ammonia water environment, and then standing and aging for 24-48 hours at 35-55 ℃ to strengthen a siloxane network to obtain a composite;

And (3) replacing water in the complex with ethanol in a gradient way, immersing the complex in a trimethylchlorosilane/ethanol mixed solution, reacting at 40-60 ℃ to convert Si-OH groups into Si-CH ₃, and performing supercritical drying to obtain the graphene oxide modified silica aerogel.

In some alternative embodiments, the volume ratio of the trimethylchlorosilane to the ethanol in the trimethylchlorosilane/ethanol mixed solution is (8-10): 100.

In some alternative embodiments, the pH of the aqueous ammonia environment is 8-10.

In some alternative embodiments, a method of preparing a polybutadiene-acrylonitrile core shell particle modified phenolic resin, comprising:

Mixing and stirring phenol and formaldehyde with NaOH according to a molar ratio of 1 (1.2-1.5) to form a prepolymer, wherein the viscosity of the prepolymer is 500-1000cP.

Slowly adding polybutadiene-acrylonitrile core-shell particle emulsion (5-15 wt% of phenolic solid content) into a prepolymer, and stirring, wherein the mass ratio of the prepolymer to the polybutadiene-acrylonitrile core-shell particle emulsion is 100 (5-20), so as to obtain a mixed solution;

Heating to 85-100 ℃, carrying out polycondensation reaction on the phenolic resin, forming chemical bonds between the shell layers of the polybutadiene-acrylonitrile core-shell particles and the phenolic resin, and curing and forming to obtain the butadiene-acrylonitrile core-shell particle modified phenolic resin.

In a second aspect, an embodiment of the present application provides a brake pad, which is manufactured by the method of the first aspect according to a processing model of the brake pad.

The preparation method of the magnesium-aluminum composite material brake pad provided by the embodiment of the application has the advantages that the prepared aluminum alloy substrate comprises aluminum element and Si ₃N₄, so that the aluminum alloy substrate has good hardness and tensile strength, the film layer arranged on the surface of the aluminum alloy substrate has good hardness and tensile strength, the brittleness is small, the aluminum alloy substrate is not easy to wear and corrosion resistant, the film layer is generated in situ, the poor matching property of the aluminum alloy substrate and the film layer is enhanced, the risks of abnormal wear and separation and stripping of the film layer are reduced, the film layer generated in situ is arranged on the surface of the aluminum alloy substrate, the scratch of the aluminum alloy substrate by a hard friction material is reduced, the service life of the brake pad is prolonged, the light weight is realized, the high heat capacity of the traditional cast iron disc absorbs friction heat, the aluminum alloy plate is fast in heat dissipation, the braking performance is improved, the aluminum alloy plate is prepared by using an organic metal adhesive, the aluminum alloy substrate has improved stability, the aluminum alloy substrate and the bonding strength between the aluminum alloy substrate and the film layer is higher, the film layer is generated in situ, the aluminum alloy substrate is protected for a long time, and the wear resistance and the corrosion resistance of the aluminum alloy plate are further improved.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the application and together with the description, serve to explain the principles of the application.

Fig. 1 shows a schematic structural diagram of a magnesium-aluminum composite brake pad according to an embodiment of the present application.

Specific embodiments of the present application have been shown by way of the above drawings and will be described in more detail below. The drawings and the written description are not intended to limit the scope of the inventive concepts in any way, but rather to illustrate the inventive concepts to those skilled in the art by reference to the specific embodiments.

Detailed Description

Each example or embodiment in this specification is described in a progressive manner, each example focusing on differences from other examples.

In the description of the present specification, reference to the terms "one embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the application. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiments or examples. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include at least one such feature. In the description of the present application, the meaning of "plurality" means at least two, for example, two, three, etc., unless specifically defined otherwise.

At present, the iron casting brake pad is difficult to realize light weight, and the brake pad has the problems of easy surface abrasion, corrosion resistance, high temperature noise generation and the like.

According to research, the structure and the materials of the brake pad are improved, and a preparation method of the magnesium-aluminum composite brake pad is provided, so that the problems of the brake pad are solved.

The embodiment of the application provides a preparation method of a magnesium-aluminum composite material brake pad, which comprises steps 100 to 200.

And 100, placing the base layer mixture and the wear-resistant layer mixture into a hot press for hot press molding to obtain a blank, wherein the blank comprises, by mass, 35% -55% of Mg, 0.1% -0.3% of Mn, 15% -30% of Si ₃N₄% of Al and 20% -50% of wear-resistant layer mixture, and the wear-resistant layer mixture comprises, by mass, 6% -10% of graphene oxide modified silica aerogel, 60% -80% of polybutadiene-acrylonitrile core-shell particle modified phenolic resin, 3% -5% of coconut shell powder and 6% -10% of carbon fiber.

It is understood that the core layer of the polybutadiene-acrylonitrile core-shell particle is formed by polymerizing butadiene monomers, and the shell layer can be formed by polymerizing acrylonitrile and styrene. Polybutadiene-acrylonitrile core-shell particles can be purchased from Zhejiang Xinhui new materials and CW-PBAN series products.

In the step, hydroxyl (-OH) or cyano (-CN) of a PBAN shell layer in the phenolic resin can form hydrogen bond or coordination bond with an oxide layer (Al ₂O₃) on the surface of aluminum (Al), so that interface bonding is enhanced, and carboxyl (-COOH) and epoxy (-O-) on the surface of GO can chemically react with Si-N bond on the surface of Si ₃N₄ to form Si-O-C covalent bond, so that interface strength is improved. The hot pressing process makes the base layer diffuse with the wear-resisting layer, and the strengthened diffusion combination enhances the interface binding force.

And 200, performing heat treatment on the blank to obtain the double-layer brake pad.

According to the embodiment of the application, the wear-resistant layer is arranged on the surface of the base layer, the polybutadiene-acrylonitrile core-shell particle modified phenolic resin in friction resistance can improve better toughness when impacted, reduce noise and abrasion caused in the working process or overheat of the brake pad, and the lubricity of graphene oxide is combined with the abrasive dust containing capacity of aerogel, so that the brake pad can still stably brake at high speed/high load, the driving comfort is improved, and the three-dimensional nano porous structure (aperture 20-50 nm) of the aerogel can effectively attenuate brake vibration energy, further reduce high-frequency noise and reduce the phenomenon of wet whistle.

The polybutadiene-acrylonitrile (PBAN) core-shell particles elastically absorb impact energy, the polybutadiene-acrylonitrile core-shell particle modified phenolic resin with the characteristics of reduced brittle peeling abrasion is improved in toughness while high hardness is maintained, microcrack generation and expansion are inhibited, and the service life of the brake pad is remarkably prolonged.

In the embodiment of the application, the mass content of aluminum, magnesium and manganese in the base layer is precisely controlled, so that the strength and hardness of the material can be obviously improved, the addition of magnesium element improves the hardness and tensile strength of the base layer, and manganese element is beneficial to improving the wear resistance and corrosion resistance of the base layer. The introduction of Si ₃N₄ particles as a reinforcing phase can effectively improve the overall hardness and wear resistance of the material.

In some alternative embodiments, the ratio of the thicknesses of the base layer and the wear layer is 1 (0.1-0.2). The heat conduction effect of the base layer and the heat insulation effect of the wear-resistant layer are smaller than the base layer, heat can be quickly conducted out through the base layer (usually a high-heat-conductivity metal composite material), heat fading is reduced, and the high-temperature stability of the friction coefficient is improved by 10% -15%. The thickness of the wear-resistant layer is too small relative to the base layer, which is easy to cause fracture or failure of the wear-resistant layer, the ratio of the thicknesses of the base layer and the wear-resistant layer is in the range, the wear-resistant layer is thin, the shearing deformation is small, the pressure transmission is more direct, the braking response is more sensitive, in addition, the rigidity of the thin wear-resistant layer (such as 1:0.1) is higher, more high-frequency vibration can be transmitted, and the wear-resistant layer can reduce noise by relying on the elastic damping effect of PBAN core-shell particles (in the wear-resistant layer).

In some alternative embodiments, the hot press molding is performed at a pressure of 15-50Mpa, optionally 43-50 Mpa, at a temperature of 500-800 ℃ for a time of 10-30 min.

The pressure of hot press molding is in the range, gaps of porous components such as carbon fibers and aerogel in the wear-resistant layer can be forcibly filled, the porosity is reduced to be less than 5%, the hardness (Rockwell HRB) is improved, and the Graphene Oxide (GO) sheets are promoted to be oriented to form a continuous lubrication network. The carbon fibers are arranged parallel to the friction surface, the bearing capacity in the surface is improved, the resin fully wraps the PBAN core-shell particles, the coconut shell powder and the like, interface defects are reduced, the pressure of hot press forming is in the range, the metal particles in the base layer are plastically deformed, the density is close to a theoretical value, the porosity is reduced, and the heat conductivity coefficient is improved, for example, to 180W/(m.K). And Mg atoms in the base layer diffuse to the wear-resistant layer to form Mg-O-C chemical bonds, which can be detected by XPS, for example, and improve the interface bonding strength. In addition, the molding pressure ensures that the aerogel pores are not crushed while promoting the resin-filler interface bond.

In some alternative embodiments, the heat treatment includes first heating to 500-600C, maintaining for 150-180min, and continuing heating to 700-800C, maintaining for 60-90min. Heating to 500600 ℃ at first, preserving heat for 150180 minutes, releasing stress and promoting interface reaction, and then continuously heating to 700-800 ℃ to enhance densification degree and tissue stability, so as to obtain the final double-layer brake pad.

It can be understood that the temperature is raised to 500-600 ℃ and kept for 150-180min, which can be referred to as a first stage, the first stage is helpful for stress release and grain rearrangement in the base layer (Mg, al), the interface combination of metal and nonmetal phases (such as Si ₃N₄, graphene oxide aerogel and the like) is promoted, the release of residual volatile substances (such as water and solvent) in the aerogel and phenolic resin is promoted at this stage, and the phenolic resin modified polymer begins to crosslink and solidify to form a thermosetting structure, so that the heat resistance, the wear resistance and the mechanical strength are improved. The temperature is continuously raised to 700-800 ℃, the heat preservation is carried out for 60-90min, the second stage can be used for facilitating the further sintering and densification of the inside of the material, enhancing the mechanical strength, further enhancing the diffusion bonding between metal phases of a base layer, improving the interface bonding strength between a wear-resistant layer and the base layer, in addition, in the range of 700-800 ℃, the carbon material is subjected to partial structure reconstruction, thereby being beneficial to forming a high-orientation and high-strength carbon structure, and partial oxygen-containing functional groups in the graphene oxide are removed, thereby being beneficial to enhancing the heat conductivity and the friction stability.

In some alternative embodiments, the mass ratio of the polybutadiene-acrylonitrile core-shell particle modified phenolic resin to the graphene oxide modified silica aerogel is 10 (0.8-1.2). The polybutadiene-acrylonitrile core-shell particle modified phenolic resin has higher occupation ratio, improves the shock resistance, absorbs vibration through elastic deformation, reduces friction coefficient fluctuation, absorbs high-frequency vibration and reduces noise, aerogel pores store lubricating fragments of graphene oxide, a phenolic resin matrix maintains structural integrity, the hardness of a brake pad is improved, CN in a shell layer of the polybutadiene-acrylonitrile core-shell particle reacts with the phenolic resin, and-COOH of the graphene oxide is bonded with silicon dioxide aerogel to form a three-dimensional reinforced network, so that the bonding force of a base layer and a wear-resistant layer is improved.

In this step, the graphene oxide may be modified with a KH-550 silane coupling agent to react-NH ₂ with-COOH of GO, enhancing interfacial bonding.

In this step, ammonia was added to adjust ph=8-10, and the sol formed a wet gel within 5-20min to accelerate gel network crosslinking. This step can avoid the capillary forces from damaging the aerogel structure during subsequent drying.

In the step, the mixture is kept stand and aged for 24-48 hours at 50-60 ℃ to strengthen a siloxane (Si-O-Si) network.

As one example, a method of preparing a graphene oxide modified silica aerogel, comprising:

mixing Tetraethoxysilane (TEOS), ethanol and water according to a molar ratio of 1:4:4, dropwise adding hydrochloric acid to adjust pH=2-3, and magnetically stirring for 1h for hydrolysis.

Slowly adding graphene oxide dispersion liquid into the hydrolyzed silica sol, wherein the mass ratio of the graphene oxide is 1-10wt%, and stirring for 2h at 60 ℃ to form uniform composite sol;

Dispersing the composite sol in an ammonia water environment, and then standing and ageing for 24-48 hours at 50-60 ℃ to strengthen a siloxane network to obtain a composite;

And (3) replacing water in the complex by ethanol gradient, immersing the complex in a trimethylchlorosilane/ethanol solution with the volume ratio of 1:10, reacting for 24 hours at 40-60 ℃ to convert Si-OH groups into Si-CH ₃, and performing supercritical drying to obtain the graphene oxide modified silica aerogel.

In some alternative embodiments, the volume ratio of the trimethylchlorosilane to the ethanol in the trimethylchlorosilane/ethanol mixed solution is (8-10): 100. The function of Trimethylchlorosilane (TMCS) is to convert hydrophilic Si-OH groups on the surface of the aerogel backbone into hydrophobic Si-CH ₃ groups. The higher the volume ratio (e.g., 10:100), the greater the TMCS concentration in the reaction system, the more complete the substitution reaction, and the enhanced hydrophobicity of the final aerogel formed, which can significantly inhibit capillary shrinkage and structural collapse during drying.

In some alternative embodiments, the pH of the aqueous ammonia environment is 8-10. The alkaline environment is favorable for the graphene oxide surface to contain carboxyl, phenolic hydroxyl and other functional groups, and the graphene oxide surface is partially dissociated and negatively charged in the alkaline environment, so that a stable electrostatic dispersion system is easier to form in an aqueous solution, agglomeration is avoided, the chimeric stability of the graphene oxide in a silica network is improved, the formed silica framework is relatively soft, has certain toughness, and can effectively inhibit structural collapse and chapping by matching with the two-dimensional supporting function of graphene oxide.

Mixing phenol and formaldehyde according to a molar ratio of 1 (1.2-1.5) with NaOH and stirring to form a prepolymer, wherein the viscosity of the prepolymer is 500-1000cP;

in the step, the reaction temperature is 60-80 ℃, and the stirring time is 40-80min;

slowly adding the polybutadiene-acrylonitrile core-shell particle emulsion into the prepolymer, and stirring, wherein the mass ratio of the prepolymer to the polybutadiene-acrylonitrile core-shell particle emulsion is 100 (5-20), so as to obtain a mixed solution;

The mass ratio between the phenolic solid content in the prepolymer and the solid content of the polybutadiene-acrylonitrile core-shell particle emulsion and the polybutadiene-acrylonitrile core-shell particle is (5-15): 100.

In this step, the reaction temperature is 60-80 ℃ and the stirring time is 40-80min, and 0.5% KH-550 of the total mass of the polybutadiene-acrylonitrile core-shell particle emulsion and the prepolymer can be added to improve the interface bonding. In this step, ph=8-9, and emulsion breaking can be avoided.

Heating to 85-100 ℃, carrying out polycondensation reaction on the phenolic resin, forming chemical bonds between the shell layers of the polybutadiene-acrylonitrile core-shell particles and the phenolic resin, and curing and forming to obtain the butadiene-acrylonitrile core-shell particle modified phenolic resin. The chemical bond may be a bond formed by the reaction of-CN with a phenolic hydroxyl group.

The curing molding can be carried out by adding 3% -5% of hexamethylenetetramine (curing agent), pouring into a mold, and step curing, wherein the curing temperature can be 80-100 ℃ per 1-2h, 100-120 ℃ per 1-2h, 140-160 ℃ per 1-2h, and the curing pressure is 5-10MPa.

In some alternative embodiments, the base layer comprises 15% -30% Si ₃N₄ based on the total mass of the base layer.

In this step, the silicon nitride particles may be in the form of dispersed particles, which may act as a reinforcing phase, and the reinforcing effect is limited by interfacial bonding and uniformity of particle distribution. The metal material in the base layer can form a heat conduction channel to improve the overall heat conductivity and facilitate rapid heat dissipation, the dispersed particles are favorable for reducing the heat fading effect during braking, maintaining the stable friction coefficient, enhancing the phase of the dispersed particles in the metal material, improving the friction resistance, reducing the heat aggregation and preventing the aluminum alloy from softening or losing efficacy due to high temperature.

Si ₃N₄ is excessively high in proportion, crack initiation and fracture failure of a base layer can be affected, impact resistance is reduced, a proper amount of Si ₃N₄ (20-30%) can improve connectivity of a thermal conduction path and heat dissipation efficiency, and when the content of Si ₃N₄ is excessively high, metal materials are difficult to permeate, so that quality fluctuation of a finished product is large.

Compared with SiC particles, the Si ₃N₄ is a ceramic material with definite stoichiometric ratio and stable structure, the SiN has an unstable structure and large performance fluctuation, the Si ₃N₄ can still keep good mechanical property and low thermal expansion coefficient at high temperature, which is particularly important under high-temperature working conditions in the braking process, amorphous SiN can generate performance degradation at high temperature due to loose structure, the particles of Si ₃N₄ can form tiny solid lubrication points in the composite material, the particles cannot be broken, the friction stability in the braking process is improved, the Si ₃N₄ is well combined with a metal matrix (such as aluminum alloy), a firm interface can be formed, and the integral mechanical strength is improved. SiN with irregular structure or large component fluctuation may cause poor interface bonding and defect formation.

In some alternative embodiments, the surface vickers hardness of the wear layer is 1120HV to 1300HV and the bond strength between the aluminum alloy matrix and the film layer is 50 to 72MPa.

In some alternative embodiments, the mechanical properties of the brake pad meet the requirements of 12% -16% of longitudinal elongation, 8% -14% of transverse elongation, 580-620 MPa of fracture compression strength, and optionally 11% -15% of longitudinal elongation, 9% -13% of transverse elongation and 560-630 MPa of fracture compression strength. The yield strength of the brake pad is 140-200 mpa, the tensile strength is 300-360 mpa, the hardness of the brake pad is 260-330 hv, the maximum friction coefficient is 0.5, and the end strain is less than or equal to 0.13%.

The brake pad can utilize multiple raw materials, carries out argon deslagging, and carries out die casting processing according to a processing model of the brake pad. Powder/paint spraying molding may also be performed.

Hereinafter, embodiments of the present application are described. The following examples are illustrative only and are not to be construed as limiting the application. The examples are not to be construed as limiting the specific techniques or conditions described in the literature in this field or as per the specifications of the product. The reagents or apparatus used were conventional products commercially available without the manufacturer's attention.

Example 1

The embodiment of the application provides a preparation method of a magnesium-aluminum composite material brake pad, which comprises the following steps:

The base layer mixture and the wear-resistant layer mixture are placed into a hot press for hot press molding, so as to obtain a blank, wherein the blank comprises a base layer and a wear-resistant layer arranged on at least one side of the base layer, the base layer mixture comprises, by mass, 35% -55% of Mg, 0.1% -0.3% of Mn, 15% -30% of Si ₃N₄ and 20% -50% of Al, the wear-resistant layer mixture comprises, by mass, 6% -10% of graphene oxide modified silica aerogel, 60% -80% of polybutadiene-acrylonitrile core-shell particle modified phenolic resin, 3% -5% of coconut shell powder and 6% -10% of carbon fibers, the thickness ratio of the base layer to the wear-resistant layer is 1:0.2, the hot press molding pressure is 42MPa, and the hot press molding temperature is 750 ℃ and the time is 180min. The preparation method of the graphene oxide modified silica aerogel comprises the steps of slowly adding graphene oxide dispersion liquid into hydrolytic silica sol, wherein the mass ratio of graphene oxide to the hydrolytic silica sol is 8wt%, dispersing the composite sol in an ammonia water environment, standing and ageing at 50 ℃ for 36 hours to strengthen a siloxane network, and obtaining a composite, wherein the pH of the ammonia water environment is 9. The water in the complex is replaced by ethanol in a gradient way, the complex is immersed in a trimethylchlorosilane/ethanol mixed solution, the trimethylchlorosilane/ethanol mixed solution is reacted at 50 ℃ to convert Si-OH groups into Si-CH ₃, and the graphene oxide modified silica aerogel is obtained through supercritical drying, wherein the volume ratio of the trimethylchlorosilane to the ethanol is 10:100.

The preparation method of the polybutadiene-acrylonitrile core-shell particle modified phenolic resin comprises the steps of mixing and stirring phenol and formaldehyde with NaOH in an amount of 0.5 mol according to a mol ratio of 1:1.5 to form a prepolymer, wherein the viscosity of the prepolymer is 800cP, slowly adding the polybutadiene-acrylonitrile core-shell particle emulsion into the prepolymer, stirring, enabling the mass ratio of the prepolymer to the polybutadiene-acrylonitrile core-shell particle emulsion to be 100:20, obtaining a mixed solution, heating to 90 ℃, enabling the phenolic resin to undergo a polycondensation reaction, enabling a shell layer of the polybutadiene-acrylonitrile core-shell particle to form a chemical bond with the phenolic resin, and curing and forming to obtain the butadiene-acrylonitrile core-shell particle modified phenolic resin.

And carrying out heat treatment on the blank to obtain the double-layer brake pad, wherein the heat treatment comprises heating to 580 ℃ and preserving heat for 160min, and continuously heating to 750 ℃ and preserving heat for 65min.

Example 2-example 3

This example differs from example 1 in that the chemical composition content of the base layer is different as shown in Table 1.

Examples 4 to 6

This example differs from example 1 in that the chemical composition content of the wear-resistant layer is different as shown in table 2.

Example 7

The difference between this example and example 1 is that the hot press molding pressure is 30MPa, the temperature is 780 ℃ and the time is 20min.

Example 8

The difference between this example and example 1 is that the hot press molding pressure was 50MPa, the temperature was 800℃and the time was 15 minutes.

EXAMPLE 9

This example differs from example 1 in that the viscosity of the prepolymer is 900cP and the mass ratio of the prepolymer to the polybutadiene-acrylonitrile core-shell particle emulsion is 100:18 by slowly adding the polybutadiene-acrylonitrile core-shell particle emulsion to the prepolymer and stirring.

Example 10

The present example is different from example 1 in that the mass ratio of graphene oxide to hydrolyzed silica sol is 10wt%.

EXAMPLE 11

The present example is different from example 1 in that the mass ratio of graphene oxide to hydrolyzed silica sol is 4wt%.

Comparative example 1

This comparative example differs from example 1 in that the chemical component content of the base layer is different as shown in Table 1.

Comparative example 2

This comparative example differs from example 1 in that the silicon nitride particles in the base layer are SiC.

Comparative example 3

This comparative example differs from example 1 in that the chemical composition content of the abrasion resistant layer is different as shown in table 1.

Comparative example 4

This comparative example differs from example 1 in that the base layer of example 1 was used to make a brake pad without providing a wear layer.

Table 1 base layer chemical composition weight percent/wt% of the brake pad of the example

Numbering device	Mg	Si₃N₄	Mn	Al
					Example 1	42	28	0.2	29.8
Example 2	35	29	0.3	35.7
					Example 3	55	30	0.15	14.85
Comparative example 1	20	13	0.2	66.8

Table 2 weight percent/wt% of the wear layer chemistry of the brake pad of the example

Test part

The brake pads prepared in the above examples and comparative examples were subjected to the following performance tests:

the bending strength is tested according to GB/T9341-2008, the bonding strength of the base layer and the wear-resistant layer can be tested according to GB/T32971-2016 'scratch test method for measuring bonding strength of thin film on metal substrate', the friction coefficient is tested according to GB/T5763-2018, the abrasion rate is tested according to GB/T5763-2018, the sound absorption coefficient is tested by adopting an AWA6128A standing wave tube sound absorption coefficient tester, heat treatment is carried out for 500 hours at 300 ℃, and the heat resistance is inspected, and the test results are shown in Table 3.

TABLE 3 Table 3

Fig. 1 shows a schematic structural diagram of a magnesium-aluminum composite brake pad according to an embodiment of the present application. As can be seen from the figure, the magnesium-aluminum composite brake pad prepared by the embodiment can be used for a brake assembly and used for braking.

It should be noted that the above embodiments are merely for illustrating the technical solution of the present application and not for limiting the same, and although the present application has been described in detail with reference to the above embodiments, it should be understood by those skilled in the art that the technical solution described in the above embodiments may be modified or some or all of the technical features may be equivalently replaced, and these modifications or substitutions do not make the essence of the corresponding technical solution deviate from the scope of the technical solution of the embodiments of the present application.

Claims

1. A method for preparing a magnesium-aluminum composite brake pad, characterized in that the method comprises:

Placing a base mixture and a wear-resistant layer mixture into a hot press and hot-pressing to obtain a blank, wherein the blank comprises a base and a wear-resistant layer disposed on at least one side of the base; the base mixture comprises the following chemical components by mass percentage: Mg: 35% to 55%, Mn: 0.1% to 0.3%, _Si3N4 : ₁₅ % to 30%, Al: 20% to 50%; the wear-resistant layer mixture comprises the following chemical components by mass percentage: 6% to 10% graphene oxide modified silica aerogel, 60% to 80% polybutadiene-acrylonitrile core-shell particle modified phenolic resin, 3% to 5% coconut shell powder, and 6% to 10% carbon fiber;

The blank is further subjected to heat treatment to obtain a double-layer brake pad.

2 . The method according to claim 1 , wherein the ratio of the thickness of the base layer to the thickness of the wear-resistant layer is 1:(0.1-0.2).

3. The method according to claim 1, characterized in that the pressure of the hot pressing molding is 15-50 MPa, the temperature is 500 to 800°C, and the time is 10 to 30 minutes.

4 . The method according to claim 1 , wherein the mass ratio of the polybutadiene-acrylonitrile core-shell particle modified phenolic resin to the graphene oxide modified silica aerogel is 10:(0.8-1.2).

5. The method according to claim 1, characterized in that the heat treatment comprises first heating the temperature to 500-600°C and keeping the temperature for 150-180 minutes; then continuing to heat the temperature to 700-800°C and keeping the temperature for 60-90 minutes.

6. The method according to claim 1, wherein the preparation method of the graphene oxide modified silica aerogel comprises:

Slowly adding the graphene oxide dispersion to the hydrolyzed silica sol, wherein the mass proportion of the graphene oxide is 1 wt% to 10 wt%;

Dispersing the composite sol in an ammonia environment, and then aging at 35-55° C. for 24-48 hours to strengthen the siloxane network to obtain a composite;

The water in the composite was replaced with ethanol in a gradient manner, and the composite was immersed in a trimethylsilyl chloride/ethanol mixture, reacted at 40-60° C. to convert Si-OH groups into Si-CH ₃ , and subjected to supercritical drying to obtain graphene oxide-modified silica aerogel.

7. The method according to claim 6, characterized in that in the trimethylchlorosilane/ethanol mixture, the volume ratio of trimethylchlorosilane to ethanol is (8-10):100.

8. The method according to claim 6, characterized in that the pH of the environment of the ammonia water is 8-10.

9. The method according to claim 1, wherein the preparation method of the polybutadiene-acrylonitrile core-shell particle modified phenolic resin comprises:

Phenol and formaldehyde are mixed with NaOH in a molar ratio of 1:(1.2-1.5) and stirred to form a prepolymer having a viscosity of 500-1000 cP;

Slowly adding the polybutadiene-acrylonitrile core-shell particle emulsion to the prepolymer and stirring, wherein the mass ratio of the prepolymer to the polybutadiene-acrylonitrile core-shell particle emulsion is 100:(5-20), to obtain a mixed solution;

The temperature is raised to 85-100° C. to cause a polycondensation reaction of the phenolic resin and to form a chemical bond between the shell layer of the polybutadiene-acrylonitrile core-shell particles and the phenolic resin, and then solidification is performed to obtain a butadiene-acrylonitrile core-shell particle modified phenolic resin.

10. A brake pad, characterized in that it is manufactured by the method according to any one of claims 1 to 9 according to a processing model of the brake pad.