Composite nano lubricating oil additive and preparation method thereof

Abstract

The invention relates to the technical field of nano materials, in particular to a preparation method of a composite nano lubricating oil additive, which is prepared from the following raw materials in parts by weight: 85 to 92 parts of composite nano particles, 6 to 8 parts of dispersing agent, 4 to 6 parts of extreme pressure anti-wear agent, 2 to 4 parts of antioxidant, 0.5 to 3 parts of nano copper powder, 0.3 to 0.8 part of oleic acid, 1 to 2 parts of clearing agent and 0.2 to 0.4 part of defoaming agent. According to the invention, cracks are filled through physical filling of nano copper powder, corrosion is inhibited, self-repairing is realized, in addition, the composite nanoparticles are uniformly dispersed through strong chelation of lanthanum ions and oleic acid carboxyl, sulfydryl on the surfaces of the composite nanoparticles can further react with metal oxide to generate a ferrous sulfide film, and the self-repairing effect is improved. And a self-repairing network with complementary functions is formed with a copper sulfide film of the nano copper powder, and the self-repairing function is enhanced through cooperation of multiple mechanisms.

Description

Technical Field

[0001] This invention relates to the field of nanomaterials technology, specifically to a method for preparing a composite nano-lubricant additive. Background Technology

[0002] The core function of lubricating oil is to ensure the efficient operation of equipment through its properties such as friction reduction, wear resistance, and oxidation resistance. Traditional lubricating oils rely solely on base oils and conventional additives. Under extreme operating conditions, equipment is prone to micro-cracks and wear pits. If these are not repaired in time, they may lead to equipment failure or even accidents. Therefore, in recent years, the field of lubricating oil additives has been researching additives with self-healing functions, enabling them to actively fill defects and inhibit deterioration in the early stages of damage to the friction pair surface.

[0003] In existing technologies, self-healing lubricant additives rely on a single component with a limited repair mechanism, making it difficult to simultaneously address both physical scratches and chemical corrosion. Furthermore, the synergistic effect between components in composite systems is weak, resulting in low repair efficiency. Therefore, this invention provides a composite nano-lubricant additive and its preparation method. Summary of the Invention

[0004] The purpose of this invention is to provide a composite nano lubricant additive and its preparation method. The composite nano lubricant additive prepared by this invention has better self-healing properties and anti-wear ability.

[0005] To achieve the above objectives, the present invention provides the following technical solution: In a first aspect, the present invention provides a composite nano lubricant additive, comprising the following raw materials in parts by weight: 85-92 parts composite nanoparticles, 6-8 parts dispersant, 4-6 parts extreme pressure anti-wear agent, 2-4 parts antioxidant, 0.5-3 parts nano copper powder, 0.3-0.8 parts oleic acid, 1-2 parts detergent, and 0.2-0.4 parts defoamer; Furthermore, the nano-copper powder is pretreated before preparing the composite nano-lubricating oil additive; Furthermore, the composite nanoparticles are modified with lanthanum before being used to prepare the composite nano lubricant additive.

[0006] Further, the preparation method of the composite nanoparticles is as follows: Aqueous dispersion of mercapto-grafted graphene oxide, dispersion of tungsten diselenide nanosheets, organic molybdenum, nano-titanium dioxide, boron nitride nanosheets, and mineral microparticles are mixed in a volume ratio of 100:50:10:5:10:8 and mechanically stirred for 3 hours to obtain a mixed dispersion. The mixed dispersion is transferred to a centrifuge tube and centrifuged at 3000 rpm for 15 minutes. The bottom precipitate is collected and washed twice with an equal volume of deionized water. After washing, the precipitate is dried in a vacuum oven at 50-70℃ for 2 hours to obtain composite nanoparticles, wherein the mineral microparticles are talc powder with a particle size of 4-6 μm, and the nano-titanium dioxide has a particle size of 50-80 nm.

[0007] Furthermore, the preparation method of the thiol-grafted graphene oxide aqueous dispersion is as follows: (1) Sodium nitrate, natural flake graphite and 98% concentrated sulfuric acid were mixed in a mass ratio of 1:2:50 and stirred in an ice bath at 0°C for 1 hour to obtain a mixed solution; (2) Potassium permanganate was slowly added to the mixture and stirred at 35°C for 2 hours. The mixture was then transferred to an oil bath and heated to 95°C for 1.5 hours. After cooling, deionized water was slowly added to dilute the mixture. A 30% hydrogen peroxide solution was added dropwise until the conductivity of the solution was less than 100 μS / cm to obtain a suspension. The mass of potassium permanganate was 260-300% of the mass of natural flake graphite, and the volume of deionized water was 100-150% of the volume of concentrated sulfuric acid. (3) After filtration of the suspension, the filter residue is washed alternately with 5% hydrochloric acid and deionized water until the hydrogen peroxide concentration is less than 0.1%. The filter residue is dispersed in N-methylpyrrolidone at a solid-liquid ratio of 1:(50-100), KH-580 is added, and the reaction is carried out at 80℃ under nitrogen protection for 4h to obtain mercapto-grafted graphene oxide. The mass concentration of N-methylpyrrolidone is 1mg / mL, and the mass of KH-580 is 5-10% of the mass of the filter residue. (4) Place the mercapto-grafted graphene oxide in a freeze dryer, pre-freeze it to -45°C and keep it for 2 hours, then decompose and dry it for 12 hours under vacuum of 10-20 Pa and temperature of 25°C to obtain mercapto-grafted graphene oxide powder. (5) Add graphene oxide powder to deionized water at a solid-liquid ratio of 1:1 and ultrasonically disperse for 2 hours to obtain a mercapto-grafted graphene oxide aqueous dispersion.

[0008] Further, the preparation method of the tungsten diselenide nanosheet dispersion is as follows: tungsten diselenide particles are mixed with N-methylpyrrolidone, and sodium dodecyl sulfate is added simultaneously. The mixture is placed in an ultrasonic cleaner, with intermittent operation set to pause for 2 seconds every 5 seconds, and ultrasonic treatment at 300W and 40kHz for 6 hours. After ultrasonic treatment, the mixture is transferred to a centrifuge tube and centrifuged at 1000rpm for 30 minutes. The supernatant is then collected to obtain the tungsten diselenide nanosheet dispersion. The particle size of the tungsten diselenide particles is 1-5mm, the solid-liquid ratio of tungsten diselenide particles to N-methylpyrrolidone is 1:(45-55), and the mass ratio of tungsten diselenide particles to sodium dodecyl sulfate is 1:(8-12).

[0009] Further, the method for modifying the composite nanoparticles with lanthanum is as follows: the composite nanoparticles are added to a lanthanum nitrate aqueous solution at a solid-liquid ratio of 1:(2-3), stirred at 60°C for 2 hours to load lanthanum ions onto the surface of the composite nanoparticles, washed with anhydrous ethanol until the conductivity of the washing solution is less than 10 μS / cm, and then placed in a vacuum oven and dried under vacuum at 60°C to obtain lanthanum-modified composite nanoparticles, wherein the mass concentration of lanthanum in the lanthanum nitrate aqueous solution is 0.5-1 g / L.

[0010] Further, the method for preparing oleic acid is as follows: thiomaleic anhydride-grafted tallow and sodium hydroxide are added to deionized water and stirred at 80°C for 2 hours to obtain a saponified liquid. Hot water of 2-3 times the volume of the saponified liquid is added to the liquid, and the pH is adjusted to 3 with hydrochloric acid. The aqueous phase is removed by filtration, and the crude fatty acid product is transferred to a round-bottom flask. A straight condenser and a vacuum pump are connected, and vacuum distillation is performed at 20 Pa and 220°C. The fraction distilled at 220°C is collected to obtain oleic acid. The mass ratio of thiomaleic anhydride-grafted tallow to deionized water is 1:(2-3), and the mass ratio of thiomaleic anhydride-grafted tallow to sodium hydroxide is (7-8):1.

[0011] Furthermore, the preparation method of the thiomaleic anhydride-grafted tallow is as follows: tallow and thiomaleic anhydride are mixed at a mass ratio of 1:(0.1-0.2), and reacted at 120-150℃ under nitrogen protection for 2-3 hours to obtain thiomaleic anhydride-grafted tallow.

[0012] Furthermore, the method for pretreating the nano-copper powder is as follows: add the nano-copper powder to anhydrous ethanol at a solid-liquid ratio of 1:(10-20), set the ultrasonic dispersion to 300W and 40kHz for 30min, filter the residue and wash it twice with 2 times the volume of anhydrous ethanol, and vacuum dry it at 60℃ for 2h, wherein the particle size of the nano-copper powder is 10nm.

[0013] Furthermore, the dispersant is polyisobutylene succinimide, the extreme pressure anti-wear agent is zinc dialkyl dithiophosphate, the antioxidant is antioxidant 5057, and the detergent is magnesium petroleum sulfonate.

[0014] Secondly, the present invention provides a method for preparing a composite nano-lubricating oil additive, comprising the following steps: S1: Add the composite nanoparticles to anhydrous ethanol and ultrasonically disperse for 30 min, wherein the volume of anhydrous ethanol is 5-10 times that of the composite nanoparticles. S2: Add dispersant to the product obtained in S1 and stir at 60°C for 2 hours; S3: Add oleic acid to the product obtained in S2 and continue stirring for 1 hour; S4: Add extreme pressure anti-wear agent, antioxidant, detergent and defoamer to the product obtained in S3, and stir at 40°C for 1 hour; S5: Add the pretreated nano-copper powder to the product obtained in S4, and ultrasonically disperse it at 300W and 40kHz for 30min. S6: Transfer the product obtained in S5 to a rotary evaporator, set to 80℃, 100 rpm, and 0.08 MPa to remove ethanol by rotary evaporation, and obtain the composite nano lubricant additive.

[0015] Compared with the prior art, the beneficial effects of the present invention are: 1. In this invention, composite nanoparticles are uniformly dispersed through the strong chelation between lanthanum ions and oleic acid carboxyl groups. The thiol groups on their surface can further react with metal oxides to generate ferrous sulfide film, forming a self-healing network that complements the copper sulfide film of the nano-copper powder. In addition, the nano-copper powder physically fills and seals cracks and inhibits corrosion, thus achieving self-healing. Multiple mechanisms work together to enhance the self-healing function.

[0016] 2. In this invention, the adsorption stability at the friction interface is enhanced by lanthanum-modified composite nanoparticles to improve the anti-wear effect. Furthermore, the composite structure of mercapto-grafted graphene oxide and tungsten diselenide provides a continuous solid lubricating film for anti-wear. At the same time, the pretreated nano-copper powder further fills the friction defects and enhances the anti-wear properties of the additive.

[0017] 3. In this invention, a uniform positive charge layer is formed on the surface of composite nanoparticles modified with lanthanum. The electrostatic repulsion between the particles prevents them from getting close to each other. The oleophilicity of the nano copper powder is improved after pretreatment, which adjusts the particle interface state, so that the base oil and nanoparticles repel each other. In addition, the thiol groups have strong compatibility with the dispersant, further isolating the particles from agglomeration. Attached Figure Description

[0018] Figure 1 The flowchart illustrates a composite nano lubricant additive and its preparation method. Detailed Implementation

[0019] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0020] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings.

[0021] A composite nano lubricant additive comprises the following raw materials in parts by weight: 85-92 parts composite nanoparticles, 6-8 parts dispersant, 4-6 parts extreme pressure anti-wear agent, 2-4 parts antioxidant, 0.5-3 parts nano copper powder, 0.3-0.8 parts oleic acid, 1-2 parts detergent, and 0.2-0.4 parts defoamer; In this embodiment, the nano-copper powder is pretreated before the preparation of the composite nano-lubricating oil additive; In this embodiment, the composite nanoparticles were modified with lanthanum before the preparation of the composite nano lubricant additive.

[0022] In this embodiment, the composite nanoparticles are prepared as follows: A water dispersion of thiol-grafted graphene oxide, a dispersion of tungsten diselenide nanosheets, organic molybdenum, nano-titanium dioxide, boron nitride nanosheets, and mineral powder are mixed at a volume ratio of 100:50:10:5:10:8 and mechanically stirred for 3 hours to obtain a mixed dispersion. The mixed dispersion is transferred to a centrifuge tube and centrifuged at 3000 rpm for 15 minutes. The bottom precipitate is collected and washed twice with an equal volume of deionized water. After washing, the precipitate is dried in a vacuum oven at 50-70℃ for 2 hours to obtain composite nanoparticles. The mineral powder is talc powder with a particle size of 4-6 μm, and the nano-titanium dioxide has a particle size of 50-80 nm. Boron nitride nanosheets were purchased from Shanghai Xiaohuang Nanotechnology Co., Ltd.

[0023] In this embodiment, the preparation method of the mercapto-grafted graphene oxide aqueous dispersion is as follows: (1) Sodium nitrate, natural flake graphite and 98% concentrated sulfuric acid were mixed in a mass ratio of 1:2:50 and stirred in an ice bath at 0°C for 1 hour to obtain a mixed solution; (2) Potassium permanganate was slowly added to the mixture and stirred at 35°C for 2 hours. The mixture was then transferred to an oil bath and heated to 95°C for 1.5 hours. After cooling, deionized water was slowly added to dilute the mixture. A 30% hydrogen peroxide solution was added dropwise until the conductivity of the solution was less than 100 μS / cm to obtain a suspension. The mass of potassium permanganate was 260-300% of the mass of natural flake graphite, and the volume of deionized water was 100-150% of the volume of concentrated sulfuric acid. (3) After filtration of the suspension, the filter residue is washed alternately with 5% hydrochloric acid and deionized water until the hydrogen peroxide concentration is less than 0.1%. The filter residue is dispersed in N-methylpyrrolidone at a solid-liquid ratio of 1:(50-100), KH-580 is added, and the reaction is carried out at 80℃ under nitrogen protection for 4h to obtain mercapto-grafted graphene oxide. The mass concentration of N-methylpyrrolidone is 1mg / mL, and the mass of KH-580 is 5-10% of the mass of the filter residue. (4) Place the mercapto-grafted graphene oxide in a freeze dryer, pre-freeze it to -45°C and keep it for 2 hours, then decompose and dry it for 12 hours under vacuum of 10-20 Pa and temperature of 25°C to obtain mercapto-grafted graphene oxide powder. (5) Add graphene oxide powder to deionized water at a solid-liquid ratio of 1:1 and ultrasonically disperse for 2 hours to obtain a mercapto-grafted graphene oxide aqueous dispersion.

[0024] In this embodiment, the preparation method of tungsten diselenide nanosheet dispersion is as follows: tungsten diselenide particles are mixed with N-methylpyrrolidone, and sodium dodecyl sulfate is added simultaneously. The mixture is placed in an ultrasonic cleaner, with intermittent operation set to pause for 2 seconds every 5 seconds, and ultrasonic treatment at 300W and 40kHz for 6 hours. After ultrasonic treatment, the mixture is transferred to a centrifuge tube and centrifuged at 1000rpm for 30 minutes. The supernatant is then collected to obtain tungsten diselenide nanosheet dispersion. The particle size of tungsten diselenide particles is 1-5mm, the solid-liquid ratio of tungsten diselenide particles to N-methylpyrrolidone is 1:(45-55), and the mass ratio of tungsten diselenide particles to sodium dodecyl sulfate is 1:(8-12).

[0025] In this embodiment, the method for modifying the composite nanoparticles with lanthanum is as follows: the composite nanoparticles are added to a lanthanum nitrate aqueous solution at a solid-liquid ratio of 1:(2-3), and stirred at 60°C for 2 hours to load lanthanum ions onto the surface of the composite nanoparticles. The nanoparticles are then washed with anhydrous ethanol until the conductivity of the washing solution is less than 10 μS / cm. After washing, the composite nanoparticles are placed in a vacuum oven and dried under vacuum at 60°C to obtain lanthanum-modified composite nanoparticles. The mass concentration of lanthanum in the lanthanum nitrate aqueous solution is 0.5-1 g / L.

[0026] In this embodiment, the preparation method of oleic acid is as follows: thiomaleic anhydride-grafted tallow and sodium hydroxide are added to deionized water and stirred at 80°C for 2 hours to obtain a saponified liquid. Hot water with a volume of 2-3 times that of the saponified liquid is added to the liquid, and the pH is adjusted to 3 with hydrochloric acid. The aqueous phase is removed by filtration, and the crude fatty acid product is transferred to a round-bottom flask. A straight condenser and a vacuum pump are connected, and the vacuum degree is set to 20 Pa and the temperature is 220°C for vacuum distillation. The fraction at 220°C is collected to obtain oleic acid. The mass ratio of thiomaleic anhydride-grafted tallow to deionized water is 1:(2-3), and the mass ratio of thiomaleic anhydride-grafted tallow to sodium hydroxide is (7-8):1.

[0027] In this embodiment, the preparation method of thiomaleic anhydride-grafted tallow is as follows: tallow and thiomaleic anhydride are mixed at a mass ratio of 1:(0.1-0.2), and reacted at 120-150℃ under nitrogen protection for 2-3 hours to obtain thiomaleic anhydride-grafted tallow.

[0028] In this embodiment, the method for pretreatment of nano copper powder is as follows: nano copper powder is added to anhydrous ethanol at a solid-liquid ratio of 1:(10-20), ultrasonically dispersed at 300W and 40kHz for 30min, and the filter residue is washed twice with 2 times the volume of anhydrous ethanol after filtration and vacuum dried at 60℃ for 2h. The particle size of the nano copper powder is 10nm.

[0029] In some embodiments, the dispersant is polyisobutylene succinimide, the extreme pressure anti-wear agent is zinc dialkyl dithiophosphate, the antioxidant is antioxidant 5057, and the detergent is magnesium petroleum sulfonate.

[0030] In this embodiment, the preparation method of the composite nano lubricant additive includes the following steps: S1: Add the composite nanoparticles to anhydrous ethanol and ultrasonically disperse for 30 min, wherein the volume of anhydrous ethanol is 5-10 times that of the composite nanoparticles. S2: Add dispersant to the product obtained in S1 and stir at 60°C for 2 hours; S3: Add oleic acid to the product obtained in S2 and continue stirring for 1 hour; S4: Add extreme pressure anti-wear agent, antioxidant, detergent and defoamer to the product obtained in S3, and stir at 40°C for 1 hour; S5: Add the pretreated nano-copper powder to the product obtained in S4, and ultrasonically disperse it at 300W and 40kHz for 30min. S6: Transfer the product obtained in S5 to a rotary evaporator, set to 80℃, 100 rpm, and 0.08 MPa to remove ethanol by rotary evaporation, and obtain the composite nano lubricant additive.

[0031] Based on the foregoing embodiments, the inventors also conducted the following sets of experiments: It should be noted that all raw materials used in the following experiments are commercially available.

[0032] Experiment 1: Prepare the following raw materials by weight: 85 parts composite nanoparticles, 6 parts dispersant, 4 parts extreme pressure anti-wear agent, 2 parts antioxidant, 0.5 parts nano copper powder, 0.3 parts oleic acid, 1 part detergent, and 0.2 parts defoamer; Preparation of thiol-grafted graphene oxide aqueous dispersion: (1) Sodium nitrate, natural flake graphite and 98% concentrated sulfuric acid were mixed in a mass ratio of 1:2:50 and stirred in an ice bath at 0°C for 1 hour to obtain a mixed solution; (2) Potassium permanganate was slowly added to the mixture and stirred at 35°C for 2 hours. The mixture was then transferred to an oil bath and heated to 95°C for 1.5 hours. After cooling, deionized water was slowly added to dilute the mixture. A 30% hydrogen peroxide solution was added dropwise until the conductivity of the solution was less than 100 μS / cm, resulting in a suspension. The mass of potassium permanganate was 260% of the mass of natural flake graphite, and the volume of deionized water was 100% of the volume of concentrated sulfuric acid. (3) After the suspension was filtered, the filter residue was washed alternately with 5% hydrochloric acid and deionized water until the hydrogen peroxide concentration was less than 0.1%. The filter residue was dispersed in N-methylpyrrolidone at a solid-liquid ratio of 1:50. KH-580 was added, and the reaction was carried out at 80°C under nitrogen protection for 4 hours to obtain mercapto-grafted graphene oxide. The mass concentration of N-methylpyrrolidone was 1 mg / mL, and the mass of KH-580 was 5% of the mass of the filter residue. (4) Place the mercapto-grafted graphene oxide in a freeze dryer, pre-freeze it to -45°C and keep it for 2 hours, and then decompose and dry it for 12 hours under vacuum of 10 Pa and temperature of 25°C to obtain mercapto-grafted graphene oxide powder. (5) Add graphene oxide powder to deionized water at a solid-liquid ratio of 1:1 and ultrasonically disperse for 2 hours to obtain a mercapto-grafted graphene oxide aqueous dispersion.

[0033] Preparation of tungsten diselenide nanosheet dispersion: Tungsten diselenide particles were mixed with N-methylpyrrolidone, and sodium dodecyl sulfate was added simultaneously. The mixture was placed in an ultrasonic cleaner and operated intermittently for 5 seconds with a 2-second pause. The mixture was ultrasonically treated at 300W and 40kHz for 6 hours. After ultrasonic treatment, the mixture was transferred to a centrifuge tube and centrifuged at 1000rpm for 30 minutes. The supernatant was collected to obtain the tungsten diselenide nanosheet dispersion. The particle size of the tungsten diselenide particles was 1 mm, the solid-liquid ratio of tungsten diselenide particles to N-methylpyrrolidone was 1:45, and the mass ratio of tungsten diselenide particles to sodium dodecyl sulfate was 1:8.

[0034] Preparation of composite nanoparticles: Aqueous dispersion of thiol-grafted graphene oxide, dispersion of tungsten diselenide nanosheets, organic molybdenum, nano-titanium dioxide, boron nitride nanosheets, and mineral powder were mixed at a volume ratio of 100:50:10:5:10:8 and mechanically stirred for 3 hours to obtain a mixed dispersion. The mixed dispersion was transferred to a centrifuge tube and centrifuged at 3000 rpm for 15 minutes. The bottom precipitate was collected and washed twice with an equal volume of deionized water. After washing, the precipitate was dried in a vacuum oven at 50°C for 2 hours to obtain composite nanoparticles, wherein the mineral powder was talc powder with a particle size of 4 μm and the nano-titanium dioxide had a particle size of 50 nm.

[0035] The composite nanoparticles were modified with lanthanum: the composite nanoparticles were added to a lanthanum nitrate aqueous solution at a solid-liquid ratio of 1:2 and stirred at 60°C for 2 hours to load lanthanum ions onto the surface of the composite nanoparticles. The nanoparticles were washed with anhydrous ethanol until the conductivity of the washing solution was less than 10 μS / cm. After washing, the composite nanoparticles were placed in a vacuum oven and dried under vacuum at 60°C to obtain lanthanum-modified composite nanoparticles. The mass concentration of lanthanum in the lanthanum nitrate aqueous solution was 0.5 g / L.

[0036] Preparation of thiomaleic anhydride-grafted tallow: Tallow and thiomaleic anhydride were mixed at a mass ratio of 1:0.1 and reacted at 120°C under nitrogen protection for 2 hours to obtain thiomaleic anhydride-grafted tallow.

[0037] Preparation of oleic acid: Thiomaleic anhydride-grafted tallow and sodium hydroxide were added to deionized water and stirred at 80°C for 2 hours to obtain a saponified solution. Hot water with a volume twice that of the saponified solution was added to the solution, and the pH was adjusted to 3 with hydrochloric acid. The aqueous phase was removed by filtration, and the crude fatty acid product was transferred to a round-bottom flask. A straight condenser and a vacuum pump were connected, and the flask was distilled under reduced pressure at a vacuum of 20 Pa and 220°C. The fraction distilled at 220°C was collected to obtain oleic acid. The mass ratio of thiomaleic anhydride-grafted tallow to deionized water was 1:2, and the mass ratio of thiomaleic anhydride-grafted tallow to sodium hydroxide was 7:1.

[0038] Pretreatment of nano-copper powder: Add nano-copper powder to anhydrous ethanol at a solid-liquid ratio of 1:10, and ultrasonically disperse at 300W and 40kHz for 30min. After filtration, wash the filter residue twice with 2 times the volume of anhydrous ethanol, and vacuum dry at 60℃ for 2h. The particle size of the nano-copper powder is 10nm.

[0039] Preparation of composite nano lubricant additives: S1: Add the composite nanoparticles to anhydrous ethanol and ultrasonically disperse for 30 min, wherein the volume of anhydrous ethanol is 5 times that of the composite nanoparticles. S2: Add dispersant to the product obtained in S1 and stir at 60°C for 2 hours; S3: Add oleic acid to the product obtained in S2 and continue stirring for 1 hour; S4: Add extreme pressure anti-wear agent, antioxidant, detergent and defoamer to the product obtained in S3, and stir at 40°C for 1 hour; S5: Add the pretreated nano-copper powder to the product obtained in S4, and ultrasonically disperse it at 300W and 40kHz for 30min. S6: Transfer the product obtained in S5 to a rotary evaporator, set to 80℃, 100 rpm, and 0.08 MPa to remove ethanol by rotary evaporation, and obtain the composite nano lubricant additive.

[0040] Experiment 2: Prepare the following raw materials by weight: 88 parts composite nanoparticles, 7 parts dispersant, 5 parts extreme pressure anti-wear agent, 3 parts antioxidant, 2 parts nano copper powder, 0.5 parts oleic acid, 1.5 parts detergent, and 0.3 parts defoamer; Preparation of thiol-grafted graphene oxide aqueous dispersion: (1) Sodium nitrate, natural flake graphite and 98% concentrated sulfuric acid were mixed in a mass ratio of 1:2:50 and stirred in an ice bath at 0°C for 1 hour to obtain a mixed solution; (2) Potassium permanganate was slowly added to the mixture and stirred at 35°C for 2 hours. The mixture was then transferred to an oil bath and heated to 95°C for 1.5 hours. After cooling, deionized water was slowly added to dilute the mixture. A 30% hydrogen peroxide solution was added dropwise until the conductivity of the solution was less than 100 μS / cm, resulting in a suspension. The mass of potassium permanganate was 280% of the mass of natural flake graphite, and the volume of deionized water was 125% of the volume of concentrated sulfuric acid. (3) After the suspension was filtered, the filter residue was washed alternately with 5% hydrochloric acid and deionized water until the hydrogen peroxide concentration was less than 0.1%. The filter residue was dispersed in N-methylpyrrolidone at a solid-liquid ratio of 1:75. KH-580 was added, and the reaction was carried out at 80°C under nitrogen protection for 4 hours to obtain mercapto-grafted graphene oxide. The mass concentration of N-methylpyrrolidone was 1 mg / mL, and the mass of KH-580 was 7.5% of the mass of the filter residue. (4) Place the mercapto-grafted graphene oxide in a freeze dryer, pre-freeze it to -45°C and keep it for 2 hours, and then desorb and dry it for 12 hours under vacuum of 15 Pa and temperature of 25°C to obtain mercapto-grafted graphene oxide powder. (5) Add graphene oxide powder to deionized water at a solid-liquid ratio of 1:1 and ultrasonically disperse for 2 hours to obtain a mercapto-grafted graphene oxide aqueous dispersion.

[0041] Preparation of tungsten diselenide nanosheet dispersion: Tungsten diselenide particles were mixed with N-methylpyrrolidone, and sodium dodecyl sulfate was added simultaneously. The mixture was placed in an ultrasonic cleaner and operated intermittently for 5 seconds with a 2-second pause. The mixture was ultrasonically treated at 300W and 40kHz for 6 hours. After ultrasonic treatment, the mixture was transferred to a centrifuge tube and centrifuged at 1000rpm for 30 minutes. The supernatant was collected to obtain the tungsten diselenide nanosheet dispersion. The particle size of the tungsten diselenide particles was 3mm, the solid-liquid ratio of tungsten diselenide particles to N-methylpyrrolidone was 1:50, and the mass ratio of tungsten diselenide particles to sodium dodecyl sulfate was 1:10.

[0042] Preparation of composite nanoparticles: Aqueous dispersion of thiol-grafted graphene oxide, dispersion of tungsten diselenide nanosheets, organic molybdenum, nano-titanium dioxide, boron nitride nanosheets, and mineral powder were mixed at a volume ratio of 100:50:10:5:10:8 and mechanically stirred for 3 hours to obtain a mixed dispersion. The mixed dispersion was transferred to a centrifuge tube and centrifuged at 3000 rpm for 15 minutes. The bottom precipitate was collected and washed twice with an equal volume of deionized water. After washing, the precipitate was dried in a vacuum oven at 60°C for 2 hours to obtain composite nanoparticles, wherein the mineral powder was talc powder with a particle size of 5 μm and the nano-titanium dioxide had a particle size of 65 nm.

[0043] The composite nanoparticles were modified with lanthanum: the composite nanoparticles were added to an aqueous solution of lanthanum nitrate at a solid-liquid ratio of 1:2.5 and stirred at 60°C for 2 hours to load lanthanum ions onto the surface of the composite nanoparticles. The nanoparticles were washed with anhydrous ethanol until the conductivity of the washing solution was less than 10 μS / cm. After washing, the composite nanoparticles were placed in a vacuum oven and dried under vacuum at 60°C to obtain lanthanum-modified composite nanoparticles. The mass concentration of lanthanum in the aqueous solution of lanthanum nitrate was 0.75 g / L.

[0044] Preparation of thiomaleic anhydride-grafted tallow: Tallow and thiomaleic anhydride were mixed at a mass ratio of 1:0.15 and reacted at 135℃ under nitrogen protection for 2.5 h to obtain thiomaleic anhydride-grafted tallow.

[0045] Preparation of oleic acid: Thiomaleic anhydride-grafted tallow and sodium hydroxide were added to deionized water and stirred at 80°C for 2 hours to obtain a saponified solution. Hot water with a volume of 2.5 times that of the saponified solution was added to the solution, and the pH was adjusted to 3 with hydrochloric acid. The aqueous phase was removed by filtration, and the crude fatty acid product was transferred to a round-bottom flask. A straight condenser and a vacuum pump were connected, and the flask was distilled under reduced pressure at a vacuum degree of 20 Pa and a temperature of 220°C. The fraction distilled at 220°C was collected to obtain oleic acid. The mass ratio of thiomaleic anhydride-grafted tallow to deionized water was 1:2.5, and the mass ratio of thiomaleic anhydride-grafted tallow to sodium hydroxide was 7.5:1.

[0046] Pretreatment of nano-copper powder: Add nano-copper powder to anhydrous ethanol at a solid-liquid ratio of 1:15, and ultrasonically disperse at 300W and 40kHz for 30min. After filtration, wash the filter residue twice with 2 times the volume of anhydrous ethanol, and vacuum dry at 60℃ for 2h. The particle size of the nano-copper powder is 10nm.

[0047] Preparation of composite nano lubricant additives: S1: Add the composite nanoparticles to anhydrous ethanol and ultrasonically disperse for 30 min, wherein the volume of anhydrous ethanol is 7.5 times that of the composite nanoparticles. S2: Add dispersant to the product obtained in S1 and stir at 60°C for 2 hours; S3: Add oleic acid to the product obtained in S2 and continue stirring for 1 hour; S4: Add extreme pressure anti-wear agent, antioxidant, detergent and defoamer to the product obtained in S3, and stir at 40°C for 1 hour; S5: Add the pretreated nano-copper powder to the product obtained in S4, and ultrasonically disperse it at 300W and 40kHz for 30min. S6: Transfer the product obtained in S5 to a rotary evaporator, set to 80℃, 100 rpm, and 0.08 MPa to remove ethanol by rotary evaporation, and obtain the composite nano lubricant additive.

[0048] Experiment 3: Prepare the following raw materials by weight: 92 parts composite nanoparticles, 8 parts dispersant, 6 parts extreme pressure anti-wear agent, 4 parts antioxidant, 3 parts nano copper powder, 0.8 parts oleic acid, 2 parts detergent, and 0.4 parts defoamer; Preparation of thiol-grafted graphene oxide aqueous dispersion: (1) Sodium nitrate, natural flake graphite and 98% concentrated sulfuric acid were mixed in a mass ratio of 1:2:50 and stirred in an ice bath at 0°C for 1 hour to obtain a mixed solution; (2) Potassium permanganate was slowly added to the mixture and stirred at 35°C for 2 hours. The mixture was then transferred to an oil bath and heated to 95°C for 1.5 hours. After cooling, deionized water was slowly added to dilute the mixture. A 30% hydrogen peroxide solution was added dropwise until the conductivity of the solution was less than 100 μS / cm, resulting in a suspension. The mass of potassium permanganate was 300% of the mass of natural flake graphite, and the volume of deionized water was 150% of the volume of concentrated sulfuric acid. (3) After the suspension was filtered, the filter residue was washed alternately with 5% hydrochloric acid and deionized water until the hydrogen peroxide concentration was less than 0.1%. The filter residue was dispersed in N-methylpyrrolidone at a solid-liquid ratio of 1:100. KH-580 was added, and the reaction was carried out at 80°C under nitrogen protection for 4 hours to obtain mercapto-grafted graphene oxide. The mass concentration of N-methylpyrrolidone was 1 mg / mL, and the mass of KH-580 was 10% of the mass of the filter residue. (4) Place the mercapto-grafted graphene oxide in a freeze dryer, pre-freeze it to -45°C and keep it for 2 hours, and then decompose and dry it for 12 hours under vacuum of 20 Pa and temperature of 25°C to obtain mercapto-grafted graphene oxide powder. (5) Add graphene oxide powder to deionized water at a solid-liquid ratio of 1:1 and ultrasonically disperse for 2 hours to obtain a mercapto-grafted graphene oxide aqueous dispersion.

[0049] Preparation of tungsten diselenide nanosheet dispersion: Tungsten diselenide particles were mixed with N-methylpyrrolidone, and sodium dodecyl sulfate was added simultaneously. The mixture was placed in an ultrasonic cleaner and operated intermittently for 5 seconds with a 2-second pause. The mixture was ultrasonically treated at 300W and 40kHz for 6 hours. After ultrasonic treatment, the mixture was transferred to a centrifuge tube and centrifuged at 1000rpm for 30 minutes. The supernatant was collected to obtain the tungsten diselenide nanosheet dispersion. The particle size of the tungsten diselenide particles was 5 mm, the solid-liquid ratio of tungsten diselenide particles to N-methylpyrrolidone was 1:55, and the mass ratio of tungsten diselenide particles to sodium dodecyl sulfate was 1:12.

[0050] Preparation of composite nanoparticles: Aqueous dispersion of thiol-grafted graphene oxide, dispersion of tungsten diselenide nanosheets, organic molybdenum, nano-titanium dioxide, boron nitride nanosheets, and mineral powder were mixed at a volume ratio of 100:50:10:5:10:8 and mechanically stirred for 3 hours to obtain a mixed dispersion. The mixed dispersion was transferred to a centrifuge tube and centrifuged at 3000 rpm for 15 minutes. The bottom precipitate was collected and washed twice with an equal volume of deionized water. After washing, the precipitate was dried in a vacuum oven at 70°C for 2 hours to obtain composite nanoparticles. The mineral powder was talc powder with a particle size of 6 μm, and the nano-titanium dioxide had a particle size of 80 nm.

[0051] The composite nanoparticles were modified with lanthanum: the composite nanoparticles were added to a lanthanum nitrate aqueous solution at a solid-liquid ratio of 1:3 and stirred at 60°C for 2 hours to load lanthanum ions onto the surface of the composite nanoparticles. The nanoparticles were washed with anhydrous ethanol until the conductivity of the washing solution was less than 10 μS / cm. After washing, the composite nanoparticles were placed in a vacuum oven and dried under vacuum at 60°C to obtain lanthanum-modified composite nanoparticles. The mass concentration of lanthanum in the lanthanum nitrate aqueous solution was 1 g / L.

[0052] Preparation of thiomaleic anhydride-grafted tallow: Tallow and thiomaleic anhydride were mixed at a mass ratio of 1:0.2 and reacted at 150°C under nitrogen protection for 3 hours to obtain thiomaleic anhydride-grafted tallow.

[0053] Preparation of oleic acid: Thiomaleic anhydride-grafted tallow and sodium hydroxide were added to deionized water and stirred at 80°C for 2 hours to obtain a saponified solution. Three times the volume of hot water was added to the saponified solution, and the pH was adjusted to 3 with hydrochloric acid. The aqueous phase was removed by filtration, and the crude fatty acid product was transferred to a round-bottom flask. A straight condenser and a vacuum pump were connected, and the flask was distilled under reduced pressure at a vacuum degree of 20 Pa and a temperature of 220°C. The fraction distilled at 220°C was collected to obtain oleic acid. The mass ratio of thiomaleic anhydride-grafted tallow to deionized water was 1:3, and the mass ratio of thiomaleic anhydride-grafted tallow to sodium hydroxide was 8:1.

[0054] Pretreatment of nano-copper powder: Add nano-copper powder to anhydrous ethanol at a solid-liquid ratio of 1:20, and ultrasonically disperse at 300W and 40kHz for 30min. After filtration, wash the filter residue twice with 2 times the volume of anhydrous ethanol, and vacuum dry at 60℃ for 2h. The particle size of the nano-copper powder is 10nm.

[0055] Preparation of composite nano lubricant additives: S1: Add the composite nanoparticles to anhydrous ethanol and ultrasonically disperse for 30 min, wherein the volume of anhydrous ethanol is 10 times that of the composite nanoparticles. S2: Add dispersant to the product obtained in S1 and stir at 60°C for 2 hours; S3: Add oleic acid to the product obtained in S2 and continue stirring for 1 hour; S4: Add extreme pressure anti-wear agent, antioxidant, detergent and defoamer to the product obtained in S3, and stir at 40°C for 1 hour; S5: Add the pretreated nano-copper powder to the product obtained in S4, and ultrasonically disperse it at 300W and 40kHz for 30min. S6: Transfer the product obtained in S5 to a rotary evaporator, set to 80℃, 100 rpm, and 0.08 MPa to remove ethanol by rotary evaporation, and obtain the composite nano lubricant additive.

[0056] Comparative Example 1: The difference between this comparative example and Experiment 1 is as follows: This comparative example does not contain composite nanoparticles.

[0057] Comparative Example 2: The difference between this comparative example and Experiment 1 is as follows: This comparative example does not contain thiol-grafted graphene oxide.

[0058] Comparative Example 3: The difference between this comparative example and Experiment 1 is that: This comparative example does not contain tungsten diselenide nanosheets.

[0059] Comparative Example 4: The difference between this comparative example and Experiment 1 is as follows: This comparative example does not contain nano copper powder.

[0060] Performance testing: The composite nano lubricant additives prepared in Experiments 1, 2, 3, Comparative Examples 1, 2, 3, and 4 were subjected to performance testing. The test data are recorded in the table below:

[0061] In the performance test, the self-healing performance test was conducted using a ball-and-disc friction and wear tester. First, the steel disc was pre-treated with wear in additive-free base oil to form wear pits with a diameter of 1.0 mm and a depth of 5 μm. Then, lubricating oil containing 1% composite nano lubricating oil additive was added. The test was conducted for 2 hours under a load of 200 N and a speed of 1000 r / min. The change in the depth of the wear pits was measured using a white light interferometer. The greater the decrease in depth, the better the self-healing performance.

[0062] Abrasion resistance testing was conducted in accordance with SH / T 0204-1992, and dispersion stability testing was conducted in accordance with GB / T 6533-2012.

[0063] The self-healing performance test results of the composite nano lubricant additives prepared in Experiment 1, Experiment 2, Experiment 3, Comparative Example 1, Comparative Example 2, Comparative Example 3 and Comparative Example 4 were 3.4μm, 3.7μm, 3.5μm, 1.2μm, 1.8μm, 2.4μm and 2.7μm, respectively.

[0064] The anti-wear test results of the composite nano lubricant additives prepared in Experiment 1, Experiment 2, Experiment 3, Comparative Example 1, Comparative Example 2, Comparative Example 3 and Comparative Example 4 were 0.38 mm, 0.35 mm, 0.36 mm, 0.64 mm, 0.50 mm, 0.57 mm and 0.41 mm, respectively.

[0065] The dispersion stability test results of the composite nano lubricant additives prepared in Experiment 1, Experiment 2, Experiment 3, Comparative Example 1, Comparative Example 2, Comparative Example 3 and Comparative Example 4 were 11 mg, 8 mg, 10 mg, 26 mg, 20 mg, 15 mg and 19 mg, respectively.

[0066] It is evident that the self-healing properties, anti-wear properties, and dispersion stability of the composite nano-lubricant additives prepared in Comparative Examples 1, 2, 3, and 4 are all lower than those in Experiments 1, 2, and 3; this indicates that: After being modified with lanthanum, the lanthanum ions of the composite nanoparticles can form stable coordination bonds with active sites such as hydroxyl and carboxyl groups on the friction surface, enhancing the adsorption strength of the particles at the friction interface and preventing lubrication failure caused by particle detachment. At the same time, the high activity of lanthanum ions promotes the formation of stable chemical bonds between the particles and the metal surface, filling wear depressions and achieving self-repair. Thiol-grafted graphene oxide forms a strong interfacial bond with tungsten diselenide nanosheets through thiol groups, preventing structural dissociation of the composite particles during long-term friction. The synergistic effect of the sheet-like and layered structures of the two forms a continuous and dense solid lubricating film, effectively reducing the coefficient of friction and further enhancing the anti-wear effect. The thiol groups can react chemically with the metal surface to form a tightly bonded repair layer substrate, providing support for the adhesion of other repair components and improving the overall self-repair capability. In addition, the uniform positive charge on the surface brought by lanthanum modification and the enhanced compatibility of thiol grafting with dispersants can effectively reduce the tendency of particle aggregation and help the dispersant to be uniformly adsorbed on the surface of the composite nanoparticles. After pretreatment, the nano-copper powder not only improves its dispersibility but also significantly enhances its surface oleophilicity and uniform charge distribution. It can form a stable dispersion system with composite nanoparticles that repel each other, avoiding agglomeration between heterogeneous particles and reducing the amount of deposits after centrifugation. At the same time, by improving dispersion stability, it improves the synergistic effect of each component to a certain extent, and enhances the wear resistance and self-healing ability of the additive.

[0067] By comparing and analyzing the relevant data in the table, it can be seen that the composite nano-lubricant additive prepared by this invention not only has good self-healing properties, but also good anti-wear properties and dispersion stability. This indicates that the composite nano-lubricant additive and its preparation method provided by this invention have a broader market prospect and are more suitable for widespread application.

[0068] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. 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 one or more embodiments or examples.

[0069] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A composite nano-lubricant additive, characterized in that, The raw materials include the following parts by weight: 85-92 parts composite nanoparticles, 6-8 parts dispersant, 4-6 parts extreme pressure anti-wear agent, 2-4 parts antioxidant, 0.5-3 parts nano copper powder, 0.3-0.8 parts oleic acid, 1-2 parts detergent, and 0.2-0.4 parts defoamer; The nano-copper powder is pretreated before the preparation of the composite nano-lubricating oil additive. The composite nanoparticles were modified with lanthanum before the preparation of the composite nano lubricating oil additive. The defoamer used is GPE100.

2. The composite nano-lubricant additive according to claim 1, characterized in that, The method for preparing the composite nanoparticles is as follows: A water dispersion of thiol-grafted graphene oxide, a dispersion of tungsten diselenide nanosheets, organic molybdenum, nano-titanium dioxide, boron nitride nanosheets, and mineral powder are mixed in a volume ratio of 100:50:10:5:10:8 and mechanically stirred for 3 hours to obtain a mixed dispersion. The mixed dispersion is then transferred to a centrifuge tube and centrifuged at 3000 rpm for 15 minutes. The bottom precipitate is collected and washed twice with an equal volume of deionized water. After washing, the precipitate is dried in a vacuum oven at 50-70℃ for 2 hours to obtain composite nanoparticles. The mineral powder is talc powder with a particle size of 4-6 μm, and the nano-titanium dioxide has a particle size of 50-80 nm.

3. The composite nano-lubricant additive according to claim 2, characterized in that, The preparation method of the thiol-grafted graphene oxide aqueous dispersion is as follows: (1) Sodium nitrate, natural flake graphite and 98% concentrated sulfuric acid were mixed in a mass ratio of 1:2:50 and stirred in an ice bath at 0°C for 1 hour to obtain a mixed solution; (2) Potassium permanganate was slowly added to the mixture and stirred at 35°C for 2 hours. The mixture was then transferred to an oil bath and heated to 95°C for 1.5 hours. After cooling, deionized water was slowly added to dilute the mixture. A 30% hydrogen peroxide solution was added dropwise until the conductivity of the solution was less than 100 μS / cm to obtain a suspension. The mass of potassium permanganate was 260-300% of the mass of natural flake graphite, and the volume of deionized water was 100-150% of the volume of concentrated sulfuric acid. (3) After filtration of the suspension, the filter residue is washed alternately with 5% hydrochloric acid and deionized water until the hydrogen peroxide concentration is less than 0.1%. The filter residue is dispersed in N-methylpyrrolidone at a solid-liquid ratio of 1:(50-100), KH-580 is added, and the reaction is carried out at 80℃ under nitrogen protection for 4h to obtain mercapto-grafted graphene oxide. The mass concentration of N-methylpyrrolidone is 1mg / mL, and the mass of KH-580 is 5-10% of the mass of the filter residue. (4) Place the mercapto-grafted graphene oxide in a freeze dryer, pre-freeze it to -45°C and keep it for 2 hours, then decompose and dry it for 12 hours under vacuum of 10-20 Pa and temperature of 25°C to obtain mercapto-grafted graphene oxide powder. (5) Add graphene oxide powder to deionized water at a solid-liquid ratio of 1:1 and ultrasonically disperse for 2 hours to obtain a mercapto-grafted graphene oxide aqueous dispersion.

4. The composite nano lubricant additive according to claim 2, characterized in that, The preparation method of the tungsten diselenide nanosheet dispersion is as follows: tungsten diselenide particles are mixed with N-methylpyrrolidone, and sodium dodecyl sulfate is added simultaneously. The mixture is placed in an ultrasonic cleaner, with a 5-second working pause followed by a 2-second intermittent working cycle. The mixture is ultrasonically treated at 300W and 40kHz for 6 hours. After ultrasonic treatment, the mixture is transferred to a centrifuge tube and centrifuged at 1000rpm for 30 minutes. The supernatant is then collected to obtain the tungsten diselenide nanosheet dispersion. The particle size of the tungsten diselenide particles is 1-5mm, the solid-liquid ratio of tungsten diselenide particles to N-methylpyrrolidone is 1:(45-55), and the mass ratio of tungsten diselenide particles to sodium dodecyl sulfate is 1:(8-12).

5. The composite nano-lubricant additive according to claim 1, characterized in that, The method for modifying the composite nanoparticles with lanthanum is as follows: the composite nanoparticles are added to a lanthanum nitrate aqueous solution at a solid-liquid ratio of 1:(2-3), and stirred at 60°C for 2 hours to load lanthanum ions onto the surface of the composite nanoparticles. The nanoparticles are then washed with anhydrous ethanol until the conductivity of the washing solution is less than 10 μS / cm. After washing, the composite nanoparticles are placed in a vacuum oven and dried under vacuum at 60°C to obtain lanthanum-modified composite nanoparticles. The mass concentration of lanthanum in the lanthanum nitrate aqueous solution is 0.5-1 g / L.

6. The composite nano-lubricant additive according to claim 1, characterized in that, The method for preparing oleic acid is as follows: thiomaleic anhydride-grafted tallow and sodium hydroxide are added to deionized water and stirred at 80°C for 2 hours to obtain a saponified liquid. Hot water of 2-3 times the volume of the saponified liquid is added to the liquid, and the pH is adjusted to 3 with hydrochloric acid. The aqueous phase is removed by filtration, and the crude fatty acid product is transferred to a round-bottom flask. A straight condenser and a vacuum pump are connected, and the flask is distilled at a vacuum of 20 Pa and 220°C. The fraction distilled at 220°C is collected to obtain oleic acid. The mass ratio of thiomaleic anhydride-grafted tallow to deionized water is 1:(2-3), and the mass ratio of thiomaleic anhydride-grafted tallow to sodium hydroxide is (7-8):

1.

7. The composite nano lubricant additive according to claim 6, characterized in that, The preparation method of the thiomaleic anhydride-grafted tallow is as follows: tallow and thiomaleic anhydride are mixed at a mass ratio of 1:(0.1-0.2), and reacted at 120-150℃ under nitrogen protection for 2-3 hours to obtain thiomaleic anhydride-grafted tallow.

8. The composite nano-lubricant additive according to claim 1, characterized in that, The method for pretreating the nano-copper powder is as follows: add the nano-copper powder to anhydrous ethanol at a solid-liquid ratio of 1:(10-20), set the ultrasonic dispersion to 300W and 40kHz for 30min, filter the residue and wash it twice with 2 times the volume of anhydrous ethanol, and vacuum dry it at 60℃ for 2h. The particle size of the nano-copper powder is 10nm.

9. The composite nano-lubricant additive according to claim 1, characterized in that, The dispersant is polyisobutylene succinimide, the extreme pressure anti-wear agent is zinc dialkyl dithiophosphate, the antioxidant is antioxidant 5057, and the detergent is magnesium petroleum sulfonate.

10. The method for preparing the composite nano-lubricating oil additive according to any one of claims 1-9, characterized in that, Includes the following steps: S1: Add the composite nanoparticles to anhydrous ethanol and ultrasonically disperse for 30 min, wherein the volume of anhydrous ethanol is 5-10 times that of the composite nanoparticles. S2: Add dispersant to the product obtained in S1 and stir at 60°C for 2 hours; S3: Add oleic acid to the product obtained in S2 and continue stirring for 1 hour; S4: Add extreme pressure anti-wear agent, antioxidant, detergent and defoamer to the product obtained in S3, and stir at 40°C for 1 hour; S5: Add the pretreated nano-copper powder to the product obtained in S4, and ultrasonically disperse it at 300W and 40kHz for 30min. S6: Transfer the product obtained in S5 to a rotary evaporator, set to 80℃, 100 rpm, and 0.08 MPa to remove ethanol by rotary evaporation, and obtain the composite nano lubricant additive.

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