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

Abstract

The invention provides a preparation method of a magnesium-aluminum composite material brake pad and the brake pad. The method comprises the steps that a base layer mixture and a wear-resistant layer mixture are put into a hot press to be subjected to hot press forming, a blank is obtained, and 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 the following chemical components in percentage by mass: 35%-55% of Mg, 0.1%-0.3% of Mn, 15%-30% of Si3N4 and 20%-50% of Al; the wear-resistant layer mixture is prepared from the following chemical components in percentage by mass: 6 to 10 percent of graphene oxide modified silicon dioxide aerogel, 60 to 80 percent of polybutadiene-acrylonitrile core-shell particle modified phenolic resin, 3 to 5 percent of coconut shell powder and 6 to 10 percent of carbon fiber; and the blank is subjected to heat treatment, and the double-layer brake pad is obtained. The magnesium-aluminum composite material brake pad prepared by the preparation method has good corrosion resistance, wear resistance and oxidation resistance, and the problem of noise generation in high-temperature friction is solved.

Description

Technical Field

[0001] The present application relates to the technical field of aluminum alloy plates, and in particular to a preparation method of a magnesium-aluminum composite brake pad and a brake pad. Background Art

[0002] With the increasing improvement of automobile performance and the demand for safety, environmental protection, and efficiency, higher requirements have been placed on automobile braking control during driving. Shorter braking time, faster cooling rate, shorter braking distance, and a better braking experience have become popular demands. In the application of brake pads, cast iron is traditionally used. Although it has high heat capacity and wear resistance, it is heavy, posing a challenge to the overall lightweight and comprehensive performance of the vehicle. In addition, cast iron has relatively poor heat dissipation performance at high temperatures, and heat easily accumulates during long braking processes, thus affecting braking performance and safety.

[0003] To overcome these issues, other alloy materials, such as aluminum-based composites, have been extensively researched. However, the compositional properties of these composites complicate friction mechanisms, making composite brake discs susceptible to high-temperature noise and surface cracking during friction. Therefore, there is an urgent need to develop brake pads or brake pad materials made from these new materials to address the challenges of existing technologies. Summary of the Invention

[0004] The present application provides a preparation method and brake pad of a magnesium-aluminum composite material. 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 caused by high-temperature friction.

[0005] In a first aspect, an embodiment of the present application provides a method for preparing a magnesium-aluminum composite brake pad, the method comprising:

[0006] The base mixture and the wear-resistant layer mixture are placed in a hot press and hot-pressed to obtain a blank, wherein the blank includes a base and a wear-resistant layer provided on at least one side of the base; the base mixture includes 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 includes 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;

[0007] The blank is further heat treated to obtain a double-layer brake pad.

[0008] In some optional embodiments, the ratio of the thickness of the base layer to that of the wear-resistant layer is 1:(0.1-0.2).

[0009] In some optional embodiments, 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.

[0010] In some optional embodiments, the mass ratio of the polybutadiene-acrylonitrile core-shell particles modified phenolic resin to the graphene oxide modified silica aerogel is 10:(0.8-1.2).

[0011] In some optional embodiments, the heat treatment includes first heating the temperature to 500-600° C. and keeping the temperature for 150-180 minutes; then continuing heating the temperature to 700-800° C. and keeping the temperature for 60-90 minutes.

[0012] In some optional embodiments, the method for preparing graphene oxide-modified silica aerogel comprises:

[0013] 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%;

[0014] The composite sol is dispersed in an ammonia environment, and then aged at 35-55°C for 24-48 hours to strengthen the siloxane network to obtain a composite;

[0015] The water in the complex was replaced with ethanol in a gradient manner, and the complex was immersed in a trimethylchlorosilane / ethanol mixture, reacted at 40-60°C to convert the Si-OH groups into Si-CH3, and then supercritically dried to obtain graphene oxide-modified silica aerogel.

[0016] In some optional embodiments, in the trimethylchlorosilane / ethanol mixture, the volume ratio of trimethylchlorosilane to ethanol is (8-10):100.

[0017] In some optional embodiments, the pH of the ammonia environment is 8-10.

[0018] In some optional embodiments, the preparation method of polybutadiene-acrylonitrile core-shell particles modified phenolic resin includes:

[0019] Phenol and formaldehyde are mixed with NaOH in a molar ratio of 1: (1.2-1.5) and stirred to form a prepolymer with a viscosity of 500-1000 cP.

[0020] Slowly adding a polybutadiene-acrylonitrile core-shell particle emulsion (5-15 wt% solid content of phenolic acid) 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;

[0021] 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.

[0022] 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.

[0023] The preparation method of the magnesium-aluminum composite brake pad in the embodiment of the present application is that the obtained aluminum alloy matrix includes aluminum element and Si3N4, so that the aluminum alloy matrix has good hardness and tensile strength, and the film layer arranged on the surface of the aluminum alloy matrix has good hardness and tensile strength, low brittleness, not easy to wear and corrosion-resistant; and the film layer is generated in situ, which enhances the compatibility between the aluminum alloy matrix and the film layer, and reduces the risk of abnormal wear and separation and peeling of the film layer; and the in-situ generated film layer is arranged on the surface of the aluminum alloy matrix, which reduces the scratching of the aluminum alloy matrix by hard friction materials, increases the service life of the brake pad, and achieves the purpose of lightweighting at the same time; the high heat capacity of the traditional cast iron disc absorbs friction heat, while the aluminum alloy plate dissipates heat quickly, thereby improving the braking performance; and the aluminum alloy plate uses an organic metal adhesive to make the aluminum alloy matrix, which improves the stability of the aluminum alloy plate, and the bonding strength between the aluminum alloy matrix and the film layer is high, indicating that the film layer is generated in situ and can protect the aluminum alloy matrix for a long time, further improving the wear resistance and corrosion resistance of the aluminum alloy plate. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0025] Figure 1 A schematic structural diagram of a magnesium-aluminum composite brake pad according to an embodiment of the present application is shown.

[0026] The above drawings illustrate specific embodiments of the present application, which will be described in more detail below. These drawings and the textual description are not intended to limit the scope of the present application in any way, but rather to illustrate the concepts of the present application to those skilled in the art by reference to specific embodiments. DETAILED DESCRIPTION

[0027] The various embodiments or implementation schemes in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments.

[0028] Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples" means that a specific feature, structure, material, or characteristic described in conjunction with an embodiment or example is included in at least one embodiment or example of the present application. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0029] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of such features. Throughout the description of this application, "plurality" means at least two, for example, two, three, etc., unless otherwise specifically defined.

[0030] Currently, cast iron brake pads are difficult to lightweight, and they also have problems such as easy surface wear and corrosion resistance, and high temperature-induced noise.

[0031] Research has found that by improving the structure and materials of brake pads, a method for preparing magnesium-aluminum composite brake pads is provided to improve the problems existing in brake pads.

[0032] An embodiment of the present application provides a method for preparing a magnesium-aluminum composite brake pad, the method comprising steps 100 to 200.

[0033] Step 100: Place the base mixture and the wear-resistant layer mixture into a hot press and perform hot pressing to obtain a blank, wherein the blank includes a base and a wear-resistant layer provided on at least one side of the base; the base mixture includes 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 includes 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.

[0034] It is understood that the core layer of the polybutadiene-acrylonitrile core-shell particles is formed by the polymerization of butadiene monomers, and the shell layer can be formed by the polymerization of acrylonitrile and styrene. Polybutadiene-acrylonitrile core-shell particles can be purchased from Zhejiang Xinhui New Materials, CW-PBAN series products.

[0035] During this step, the hydroxyl groups (-OH) in the phenolic resin or the cyano groups (-CN) in the PBAN shell may form hydrogen bonds or coordination bonds with the oxide layer (Al2O3) on the aluminum (Al) surface, strengthening the interfacial bonding. The carboxyl groups (-COOH) and epoxy groups (-O-) on the GO surface can chemically react with the Si-N bonds on the Si3N4 surface to form Si-OC covalent bonds, enhancing interfacial strength. The hot pressing process promotes diffusion between the base layer and the wear-resistant layer. This enhanced diffusion bonding strengthens the interfacial adhesion.

[0036] In step 200 , the blank is subjected to further heat treatment to obtain a double-layer brake pad.

[0037] According to the embodiments of the present application, a wear-resistant layer is provided on the surface of the base layer, and the polybutadiene-acrylonitrile core-shell particles modified phenolic resin in the friction-resistant layer can improve the toughness when subjected to impact, and reduce the noise and wear caused by the brake pad during operation or overheating; the lubricity of graphene oxide is combined with the wear debris holding capacity of aerogel, so that the brake pad can still maintain stable braking under high speed / high load, thereby improving driving comfort; the three-dimensional nanoporous structure of aerogel (pore diameter 20-50nm) can effectively attenuate brake vibration energy, further reduce high-frequency noise, and reduce the "wet howl" phenomenon.

[0038] Graphene oxide forms an ultra-thin lubricating transfer film during the friction process, reducing direct contact between metals during friction and lowering the wear rate; polybutadiene-acrylonitrile (PBAN) core-shell particles elastically absorb impact energy and reduce brittle spalling wear; polybutadiene-acrylonitrile core-shell particle modified phenolic resin improves toughness while maintaining high hardness, inhibits the generation and expansion of microcracks, and significantly extends the life of the brake pad.

[0039] In the examples of this application, precise control of the mass content of aluminum, magnesium, and manganese in the base layer significantly enhances the material's strength and hardness. The addition of magnesium increases the base layer's hardness and tensile strength, while manganese improves its wear and corrosion resistance. The introduction of Si3N4 particles as a reinforcing phase effectively increases the material's overall hardness and wear resistance.

[0040] In some optional embodiments, the thickness ratio of the base layer to the wear-resistant layer is 1:(0.1-0.2). The base layer's thermal conductivity and the wear-resistant layer's thermal insulation provide benefits. Since the wear-resistant layer is thinner than the base layer, heat can be quickly dissipated through the base layer (typically a highly thermally conductive metal composite material), reducing thermal decay and improving the high-temperature stability of the friction coefficient by 10% to 15%. A wear-resistant layer that is too thin relative to the base layer can easily break or fail. When the thickness ratio of the base layer to the wear-resistant layer is within the aforementioned range, the wear-resistant layer is thin, resulting in less shear deformation, more direct pressure transmission, and a more sensitive braking response. Furthermore, a thin wear-resistant layer (e.g., 1:0.1) is more rigid and can potentially transmit more high-frequency vibrations, which can rely on the elastic damping effect of the PBAN core-shell particles (in the wear-resistant layer) to reduce noise.

[0041] In some optional embodiments, the pressure of the hot pressing molding is 15-50 MPa, optionally 43 to 50 MPa, the temperature is 500 to 800° C., and the time is 10 to 30 minutes.

[0042] Hot pressing pressure within the above range can forcibly fill the gaps between porous components such as carbon fibers and aerogel in the wear-resistant layer, reducing porosity to <5% and improving hardness (Rockwell HRB). It also promotes the oriented alignment of graphene oxide (GO) sheets, forming a continuous lubrication network. It also aligns the carbon fibers parallel to the friction surface, improving in-plane load-bearing capacity. The resin fully encapsulates the PBAN core-shell particles and coconut shell powder, reducing interfacial defects. Hot pressing pressure within the above range plastically deforms the metal particles in the base layer, bringing the density close to the theoretical value, reducing porosity and improving thermal conductivity, for example, to 180 W / (m·K). Mg atoms in the base layer diffuse into the wear-resistant layer, forming Mg-OC chemical bonds, which can be detected, for example, by XPS. These Mg-OC bonds enhance interfacial bonding strength. Furthermore, the molding pressure prevents the aerogel pores from collapsing while promoting interfacial bonding between the resin and filler.

[0043] In some optional embodiments, the heat treatment includes first heating to 500-600°C and holding for 150-180 minutes, then continuing to heat to 700-800°C and holding for 60-90 minutes. The initial heating to 500-600°C and holding for 150-180 minutes can be used to release stress and promote interfacial reaction, followed by further heating to 700-800°C to enhance densification and structural stability, resulting in the final double-layer brake pad.

[0044] It can be understood that: first the temperature is raised to 500-600 ° C and kept warm for 150-180 minutes, which can be referred to as the first stage. The first stage helps to release stress and rearrange grains in the base layer (Mg, Al); promotes the interface bonding between metal and non-metal phases (such as Si3N4, graphene oxide aerogel, etc.), and the residual volatile substances (such as water and solvents) in the aerogel and phenolic resin are released in this stage; in this stage, the phenolic resin modified polymer begins to cross-link and cure to form a thermosetting structure, thereby improving heat resistance, wear resistance and mechanical strength. Continuing to heat up to 700-800℃ and keeping warm for 60-90min can be referred to as the second stage. The second stage can promote further sintering and densification inside the material and enhance the mechanical strength; further improve the diffusion bonding between the base metal phases and improve the interface bonding strength between the wear-resistant layer and the base layer; in addition, in the range of 700-800℃, the carbon material undergoes partial structural reconstruction, which is conducive to the formation of highly oriented and high-strength carbon structure; some oxygen-containing functional groups in graphene oxide are removed, which helps to improve thermal conductivity and friction stability.

[0045] In some optional embodiments, the mass ratio of the polybutadiene-acrylonitrile core-shell particles modified with phenolic resin to the graphene oxide modified with silica aerogel is 10:(0.8-1.2). The higher proportion of the polybutadiene-acrylonitrile core-shell particles modified with phenolic resin improves impact resistance. The polybutadiene-acrylonitrile core-shell particles absorb vibrations through elastic deformation, reducing fluctuations in the friction coefficient, absorbing high-frequency vibrations, and reducing noise. The aerogel pores store lubricating fragments of graphene oxide, while the phenolic resin matrix maintains structural integrity, increasing the hardness of the brake pad. The -CN in the shell of the polybutadiene-acrylonitrile core-shell particles reacts with the phenolic resin, and the -COOH of the graphene oxide bonds with the silica aerogel, forming a three-dimensional reinforced network that improves the adhesion between the base layer and the wear-resistant layer.

[0046] In some optional embodiments, the method for preparing graphene oxide-modified silica aerogel comprises:

[0047] 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%;

[0048] The composite sol is dispersed in an ammonia environment, and then aged at 35-55°C for 24-48 hours to strengthen the siloxane network to obtain a composite;

[0049] In this step, graphene oxide can be modified with KH-550 silane coupling agent to allow -NH2 to react with -COOH of GO to enhance the interfacial bonding.

[0050] In this step, ammonia is added to adjust the pH to 8-10, and the sol forms a wet gel within 5-20 minutes to accelerate the crosslinking of the gel network. This step can prevent capillary forces from destroying the aerogel structure during subsequent drying.

[0051] In this step, the siloxane (Si-O-Si) network can be strengthened by aging for 24-48 hours at 50-60°C.

[0052] The water in the complex was replaced with ethanol in a gradient manner, and the complex was immersed in a trimethylchlorosilane / ethanol mixture, reacted at 40-60°C to convert the Si-OH groups into Si-CH3, and then supercritically dried to obtain graphene oxide-modified silica aerogel.

[0053] As an example, a method for preparing graphene oxide-modified silica aerogel includes:

[0054] Tetraethyl orthosilicate (TEOS), ethanol and water were mixed in a molar ratio of 1:4:4, hydrochloric acid was added dropwise to adjust the pH to 2-3, and the mixture was hydrolyzed under magnetic stirring for 1 h.

[0055] Slowly add the graphene oxide dispersion to the hydrolyzed silica sol, wherein the mass proportion of graphene oxide is 1wt%-10wt%, and stir at 60°C for 2h to form a uniform composite sol;

[0056] The composite sol is dispersed in an ammonia environment, and then statically aged for 24-48 hours at 50-60°C to strengthen the siloxane network and obtain a composite;

[0057] The water in the complex was replaced with ethanol gradient, and the complex was immersed in trimethylchlorosilane / ethanol solution with a volume ratio of 1:10. The reaction was carried out at 40-60°C for 24 hours to convert the Si-OH groups into Si-CH3. After supercritical drying, graphene oxide-modified silica aerogel was obtained.

[0058] In some optional embodiments, the volume ratio of trimethylchlorosilane to ethanol in the trimethylchlorosilane / ethanol mixture is (8-10):100. Trimethylchlorosilane (TMCS) converts hydrophilic Si–OH groups on the aerogel skeleton surface into hydrophobic Si–CH3 groups. A higher volume ratio (e.g., 10:100) increases the TMCS concentration in the reaction system, leading to a more complete substitution reaction and enhanced hydrophobicity of the resulting aerogel, significantly suppressing capillary shrinkage and structural collapse during drying.

[0059] In some optional embodiments, the pH of the ammonia environment is 8 to 10. This alkaline environment helps functional groups such as carboxyl and phenolic hydroxyl groups on the surface of graphene oxide to partially dissociate in an alkaline environment, becoming negatively charged. This makes it easier for the graphene oxide to form a stable electrostatic dispersion system in aqueous solution, avoid agglomeration, and enhance its intercalation stability in the silicon-oxygen network. The resulting silica skeleton is relatively "soft" and has a certain degree of toughness. Combined with the two-dimensional support of graphene oxide, it can effectively inhibit structural collapse and cracking.

[0060] In some optional embodiments, the preparation method of polybutadiene-acrylonitrile core-shell particles modified phenolic resin includes:

[0061] Phenol and formaldehyde are mixed with NaOH in a molar ratio of 1:(1.2-1.5) and stirred to form a prepolymer with a viscosity of 500-1000 cP;

[0062] In this step, the reaction temperature is 60-80°C and the stirring time is 40-80 minutes;

[0063] 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;

[0064] The mass ratio of the solid content of phenolic formaldehyde in the prepolymer to the solid content of the polybutadiene-acrylonitrile core-shell particles in the polybutadiene-acrylonitrile core-shell particle emulsion is (5-15):100.

[0065] In this step, the reaction temperature is 60-80°C and the stirring time is 40-80 minutes. KH-550 can be added to the polybutadiene-acrylonitrile core-shell particle emulsion and the prepolymer at 0.5% by weight to improve interfacial bonding. The pH in this step is 8-9 to prevent emulsion demulsification.

[0066] 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 solidified to obtain a butadiene-acrylonitrile core-shell particle modified phenolic resin. The chemical bond may be a bond formed by the reaction of -CN and phenolic hydroxyl groups.

[0067] Curing molding can be achieved by adding 3% to 5% hexamethylenetetramine (curing agent), pouring it into the mold, and step-curing: the curing temperature can be 80 to 100°C / 1 to 2h → 100 to 120°C / 1 to 2h → 140 to 160°C / 1-2h, and the curing pressure is 5-10MPa.

[0068] In some optional embodiments, the base layer includes 15% to 30% Si 3 N 4 based on the total mass of the base layer.

[0069] In this step, the silicon nitride particles can be in the form of dispersed particles. Dispersed particles act as a reinforcing phase, and their effectiveness is limited by interfacial bonding and particle distribution uniformity. The metal material in the base layer forms a thermal conductivity channel, improving overall thermal conductivity and facilitating rapid heat dissipation. The dispersed particles help reduce thermal decay during braking and maintain a stable friction coefficient. The dispersed particles act as a reinforcing phase within the metal material, enhancing friction resistance, reducing heat accumulation, and preventing softening or thermal fatigue failure of the aluminum alloy caused by high temperatures.

[0070] If the proportion of Si3N4 is too high, it will affect the crack initiation and fracture failure of the base layer, and the impact resistance will decrease; an appropriate amount of Si3N4 (20-30%) can improve the connectivity of the thermal conductivity path and enhance the heat dissipation efficiency; and when the Si3N4 content is too high, it is difficult for the metal material to penetrate, resulting in large fluctuations in the quality of the finished product.

[0071] Compared to SiC particles, the Si3N4 of this application is a ceramic material with a clear stoichiometric ratio and stable structure. The structure of SiN is not stable enough, and its performance fluctuates greatly. Si3N4 can still maintain good mechanical properties and a low thermal expansion coefficient at high temperatures, which is particularly important under high-temperature conditions during braking. Amorphous SiN may degrade at high temperatures due to its loose structure. Si3N4 particles can form tiny solid lubrication points in the composite material, which will not break and improve the friction stability during braking. Si3N4 combines well with the metal matrix (such as aluminum alloy), forming a strong interface and improving the overall mechanical strength. SiN with an irregular structure or large fluctuations in composition may lead to poor interface bonding and form defects.

[0072] 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.

[0073] In some optional embodiments, the surface Vickers hardness of the wear-resistant layer is 1120 HV to 1300 HV, and the bonding strength between the aluminum alloy substrate and the film layer is 50 to 72 MPa.

[0074] In some optional embodiments, the mechanical properties of the brake pad meet the following requirements: longitudinal elongation of 12% to 16%, transverse elongation of 8% to 14%, and compressive strength at break of 580 MPa to 620 MPa; optionally, longitudinal elongation of 11% to 15%, transverse elongation of 9% to 13%, and compressive strength at break of 560 MPa to 590 MPa. The yield strength is 140 MPa to 200 MPa; the tensile strength is 300 MPa to 360 MPa; the hardness of the brake pad is 260 HV to 330 HV, the maximum friction coefficient is 0.5, and the end strain is ≤ 0.13%.

[0075] Brake pads can be made from a variety of raw materials, deslagging with argon gas, and die-cast according to the processing model of the brake pad. Powder spraying / painting can also be used for molding.

[0076] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and is not to be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used that do not specify the manufacturer are conventional products that can be obtained commercially.

[0077] Example 1

[0078] The present invention provides a method for preparing a magnesium-aluminum composite brake pad, the method comprising:

[0079] The base mixture and the wear-resistant layer mixture are placed in a hot press and hot-pressed to obtain a blank, wherein the blank includes a base and a wear-resistant layer arranged on at least one side of the base; the base mixture includes the following chemical components in 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 includes the following chemical components in 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 ratio of the thickness of the base and the wear-resistant layer is 1:0.2; the hot pressing pressure is 42 MPa, the temperature is 750°C, and the time is 180 minutes. The preparation method of graphene oxide-modified silica aerogel includes: slowly adding a graphene oxide dispersion to a hydrolyzed silica sol, wherein the mass ratio of graphene oxide to the hydrolyzed silica sol is 8 wt%; dispersing the composite sol in an ammonia environment, followed by aging at 50°C for 36 hours to strengthen the siloxane network, thereby obtaining a composite; the ammonia environment has a pH of 9. Water in the composite is replaced with a gradient of ethanol, and the composite is immersed in a trimethylchlorosilane / ethanol mixture, reacting at 50°C to convert Si-OH groups to Si-CH3. The composite is then supercritically dried to obtain the graphene oxide-modified silica aerogel, wherein the volume ratio of trimethylchlorosilane to ethanol in the trimethylchlorosilane / ethanol mixture is 10:100.

[0080] Among them, the preparation method of polybutadiene-acrylonitrile core-shell particle modified phenolic resin includes: mixing phenol and formaldehyde in a molar ratio of 1:1.5 with 0.5 mole of NaOH and stirring to form a prepolymer, the viscosity of the prepolymer is 800 cP; slowly adding polybutadiene-acrylonitrile core-shell particle emulsion to the prepolymer and stirring, the mass ratio of the prepolymer to the polybutadiene-acrylonitrile core-shell particle emulsion is 100:20, to obtain a mixed solution; heating to 90°C to cause a condensation reaction of the phenolic resin and to form a chemical bond between the shell layer of the polybutadiene-acrylonitrile core-shell particle and the phenolic resin, and then curing and molding to obtain the polybutadiene-acrylonitrile core-shell particle modified phenolic resin.

[0081] The blank is further heat-treated to obtain a double-layer brake pad, wherein the heat treatment includes first heating to 580° C. and keeping the temperature for 160 minutes; then heating to 750° C. and keeping the temperature for 65 minutes.

[0082] Example 2-Example 3

[0083] The difference between this embodiment and embodiment 1 is that the chemical composition content of the base layer is different, as shown in Table 1.

[0084] Examples 4 to 6

[0085] The difference between this embodiment and embodiment 1 is that the chemical composition content of the wear-resistant layer is different, as shown in Table 2.

[0086] Example 7

[0087] The difference between this embodiment and embodiment 1 is that the pressure of hot pressing is 30 MPa, the temperature is 780° C., and the time is 20 min.

[0088] Example 8

[0089] The difference between this embodiment and embodiment 1 is that the hot pressing pressure is 50 MPa, the temperature is 800° C., and the time is 15 minutes.

[0090] Implementation 9

[0091] The difference between this embodiment and embodiment 1 is that the viscosity of the prepolymer is 900 cP; the polybutadiene-acrylonitrile core-shell particle emulsion is slowly added to the prepolymer and stirred, and the mass ratio of the prepolymer to the polybutadiene-acrylonitrile core-shell particle emulsion is 100:18.

[0092] Implementation 10

[0093] The difference between this embodiment and embodiment 1 is that the mass proportion of graphene oxide to the hydrolyzed silica sol is 10 wt %.

[0094] Implementation 11

[0095] The difference between this embodiment and embodiment 1 is that the mass proportion of graphene oxide to the hydrolyzed silica sol is 4 wt %.

[0096] Comparative Example 1

[0097] The difference between this comparative example and Example 1 is that the chemical composition content of the base layer is different, as shown in Table 1.

[0098] Comparative Example 2

[0099] The difference between this comparative example and Example 1 is that the silicon nitride particles in the base layer are SiC.

[0100] Comparative Example 3

[0101] The difference between this comparative example and Example 1 is that the chemical composition content of the wear-resistant layer is different, as shown in Table 1.

[0102] Comparative Example 4

[0103] The difference between this comparative example and Example 1 is that the brake pad is prepared using the base layer of Example 1, and no wear-resistant layer is provided.

[0104] Table 1 Chemical composition of the base layer of the brake pad according to the embodiment of the present invention (weight percentage / wt.%)

[0105] serial number Mg <![CDATA[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

[0106] Table 2 Chemical composition of the wear-resistant layer of the brake pad according to the embodiment of the invention (weight percentage / wt.%)

[0107]

[0108] Test section

[0109] The brake pads prepared in the above embodiments and comparative examples were subjected to the following performance tests:

[0110] The bending strength is tested in accordance with GB / T9341-2008; the bonding strength of the base layer and the wear-resistant layer can be tested in accordance with GB / T32971-2016 "Determination of the bonding strength of thin films on metal substrates - Scratch test method"; the friction coefficient is tested in accordance with GB / T5763-2018; the wear rate is tested in accordance with GB / T5763-2018; the sound absorption coefficient is measured using an AWA6128A standing wave tube sound absorption coefficient tester; the heat resistance is examined by heat treatment at 300°C for 500h; the test results are shown in Table 3.

[0111] Table 3

[0112]

[0113] Figure 1The schematic diagram of the structure of the magnesium-aluminum composite brake pad according to the embodiment of the present application is shown. As can be seen from the figure, the magnesium-aluminum composite brake pad prepared in this embodiment can be used in a brake assembly for braking.

[0114] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions 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: The base mixture and the wear-resistant layer mixture are placed in a hot press and hot-pressed to obtain a blank, wherein the blank includes a base and a wear-resistant layer provided on at least one side of the base; the base mixture includes 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 includes 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, characterized in that 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 hot pressing molding is performed at a pressure of 15-50 MPa, a temperature of 500 to 800° C., and a time of 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 heating the temperature to 700-800° C. and keeping the temperature for 60-90 minutes.

6. The method according to claim 1, characterized in that The method for preparing 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 complex was replaced with ethanol in a gradient manner, and the complex was immersed in a trimethylchlorosilane / ethanol mixture, reacted at 40-60°C to convert the Si-OH groups into Si-CH3, and then supercritically dried to obtain graphene oxide-modified silica aerogel.

7. The method according to claim 6, characterized in that In the trimethylsilyl chloride / ethanol mixed solution, the volume ratio of trimethylsilyl chloride to ethanol is (8-10):

100.

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

9. The method according to claim 1, characterized in that 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: According to the processing model of the brake pad, it is manufactured by the method described in any one of claims 1-9.

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