Graphene anti-wear hydraulic oil and preparation method thereof

Abstract

This invention relates to the field of hydraulic oil technology, specifically to a graphene anti-wear hydraulic oil and its preparation method. The graphene anti-wear hydraulic oil, by weight, comprises the following components: base oil, graphene / MoS2 composite additive, zinc dialkyl dithiophosphate, dodecenyl succinate half-ester, hindered phenolic antioxidant, polymethyl methacrylate, benzotriazole derivative, and polysiloxane antifoaming agent; wherein the base oil is polyalphaolefin (PAO6). The graphene anti-wear hydraulic oil provided by this invention improves the stability and anti-wear performance of the solid lubricating film during lubrication, reduces the coefficient of friction, improves the dispersion stability of graphene and MoS2 and the compatibility of the composite in the base oil, and enhances its antioxidant and anti-corrosion protection for metal components of the hydraulic system.

Description

Technical Field

[0001] This invention relates to the field of hydraulic oil technology, specifically to a graphene anti-wear hydraulic oil and its preparation method. Background Technology

[0002] Graphene, a two-dimensional nanomaterial composed of a single layer of carbon atoms, possesses a unique electronic structure and excellent physicochemical properties. Its extremely high strength, excellent thermal conductivity, and good lubrication performance make it a promising candidate for applications in the lubrication field. Introducing graphene into hydraulic oil can significantly improve its anti-wear properties. During friction, graphene can form a robust lubricating film on the metal surface, effectively withstanding high loads and rapidly dissipating the heat generated by friction, reducing lubrication failure caused by localized overheating, thereby reducing wear on metal parts and extending equipment lifespan. Molybdenum disulfide is also a layered compound with excellent lubrication properties; its interlayer slip characteristics enable it to provide low friction characteristics and reduce the coefficient of friction during friction.

[0003] Although graphene and molybdenum disulfide possess excellent anti-wear properties, their dispersion stability in base oils is poor. Due to the strong van der Waals forces between graphene and MoS2 nanosheets, agglomeration is prone to occur, making uniform dispersion in base oils difficult. This agglomeration not only reduces the effective concentration of graphene and MoS2, affecting their anti-wear performance, but may also clog filters, valves, and other components during hydraulic system operation, impacting system performance. Currently, while some studies have attempted to improve the dispersibility of graphene and MoS2 in base oils through surface modification and the addition of dispersants, these methods often suffer from short-lasting dispersion effects and negatively impact other hydraulic oil properties, failing to meet the demands of practical applications. Therefore, this invention proposes a graphene anti-wear hydraulic oil and its preparation method. Summary of the Invention

[0004] This invention proposes a graphene anti-wear hydraulic oil and its preparation method, which improves the stability and anti-wear performance of the solid lubricating film during lubrication and reduces the coefficient of friction; improves the dispersion stability of graphene and MoS2 and the compatibility of the composite in base oil, and enhances its antioxidant and anti-corrosion protection for metal components of hydraulic systems.

[0005] The technical solution of the present invention is as follows: In a first aspect, the present invention provides a graphene anti-wear hydraulic oil, comprising, by weight, the following components: 85-93 parts base oil, 1.0-2.0 parts graphene / MoS2 composite additive, 1.0-2.0 parts zinc dialkyl dithiophosphate, 0.3-0.5 parts dodecenyl succinate half-ester, 0.3-0.8 parts hindered phenolic antioxidant, 2.0-4.0 parts polymethacrylate, 0.05-0.2 parts benzotriazole derivative, and 0.01-0.03 parts polysiloxane antifoaming agent; wherein the base oil is polyalphaolefin PAO6.

[0006] As a further technical solution, the preparation method of the graphene / MoS2 composite additive includes: S1. Few-layer molybdenum disulfide nanosheets were prepared by a hydrothermal method; S2. The few-layer molybdenum disulfide nanosheets and graphene oxide are combined by electrostatic self-assembly and hydrothermal in-situ reduction to obtain a preliminary composite material; S3. The preliminary composite is subjected to ionic liquid intercalation modification, freeze drying, inert atmosphere heat treatment and surface hydrophobication treatment in sequence to obtain graphene / MoS2 composite additive.

[0007] As a further technical solution, the preparation method of few-layer molybdenum disulfide nanosheets by hydrothermal method includes the following steps: dissolving molybdenum source and sulfur source in deionized water and stirring to form a precursor solution; transferring the precursor solution to a high-pressure reactor and hydrothermally reacting it at 180-220℃ for 20-28h; after the reaction is completed, the product is washed and freeze-dried to obtain the few-layer molybdenum disulfide nanosheets.

[0008] As a further technical solution, the molybdenum source is ammonium molybdate, and the sulfur source is thiourea; the molar ratio of the molybdenum source to the sulfur source is 1:3-5; and the concentration of the molybdenum source in the precursor solution is 0.1-0.2 mol / L.

[0009] As a further technical solution, step S2 specifically includes: S2.1, disperse few-layer molybdenum disulfide nanosheets in water, adjust the pH value to 4.5-5.5, and sonicate to form dispersion A; S2.2, Adjust the pH of the graphene oxide dispersion to 8.5-9.5 to obtain dispersion B; S2.3 Under stirring conditions, the dispersion B is slowly added dropwise to the dispersion A. After the addition is complete, stirring is continued for 12-36 hours to complete electrostatic self-assembly. S2.4, A reducing agent is added to the self-assembled mixed system, and a hydrothermal reaction with stepwise heating is carried out. After the reaction is completed, the preliminary complex is obtained by washing.

[0010] As a further technical solution, the concentration of molybdenum disulfide nanosheets in dispersion A is 0.4-0.6 mg / mL; the mass of graphene oxide in dispersion B is 25%-35% of the mass of molybdenum disulfide nanosheets; the reducing agent is L-ascorbic acid, and its addition amount is 4-6 times the mass of graphene oxide; the conditions for the step-heating hydrothermal reaction are: first react at 110-130℃ for 1-3 hours, then increase to 150-170℃ for 3-5 hours, and finally increase to 170-190℃ for 1-3 hours.

[0011] As a further technical solution, step S3 specifically includes: S3.1, the preliminary complex is dispersed in a mixed solvent of ethanol and ionic liquid, and subjected to a solvothermal reaction at 140-160℃ for 6-10 h. After the reaction is completed, the mixture is washed to obtain a wet gel modified by ionic liquid intercalation. S3.2, The product obtained in step S3.1 is subjected to vacuum freeze drying to obtain a fluffy composite dry powder; S3.3, the composite dry powder is heat-treated at 250-350℃ for 1-3 hours under an inert atmosphere; S3.4 The heat-treated powder is subjected to air jet milling and classification, then surface-treated by immersion in an organic solution of long-chain organic acids, and finally vacuum-dried to obtain the final product.

[0012] As a further technical solution, the ionic liquid is 1-butyl-3-methylimidazolium hexafluorophosphate; the volume ratio of ethanol to ionic liquid in the mixed solvent is 8-10:1; The conditions for vacuum freeze drying are: cold trap temperature below -50℃, vacuum degree below 10Pa, and drying time of 24-48h; the inert atmosphere is nitrogen or argon.

[0013] As a further technical solution, the long-chain organic acid is stearic acid; the organic solution is a heptane solution, wherein the mass concentration of stearic acid is 0.8wt%-1.wt%; the soaking treatment temperature is 55-65℃, and the time is 1-3h.

[0014] Secondly, this invention proposes a method for preparing graphene anti-wear hydraulic oil, the steps of which include: (1) The graphene / MoS2 composite additive is mixed with 10%-20% of the base oil by weight, and processed at 70-80°C using a high-speed shear disperser at a speed of 5000-8000 rpm for 30-60 minutes to obtain a pre-dispersed slurry. (2) Heat the remaining base oil to 70-80℃, add the polymethyl methacrylate viscosity index improver, and stir at 200-400 rpm until completely dissolved and dispersed; (3) Add the zinc dialkyl dithiophosphate, dodecenyl succinate half ester, hindered phenolic antioxidant and benzotriazole derivative to the oil in step (2) in sequence. Stir for 10-20 minutes after each additive is added to make it evenly mixed. The mixing temperature is controlled at 70-80℃. (4) Add the pre-dispersed slurry obtained in step (1) to the oil in step (3) and stir at 70-80℃ for 60-90 minutes; (5) Post-treatment and refining: Cool the oil to below 50°C, add the polysiloxane antifoaming agent, and stir for 30 minutes; then filter and vacuum degas the oil in sequence to obtain the graphene anti-wear hydraulic oil.

[0015] The working principle and beneficial effects of this invention are as follows: This invention employs a hydrothermal method to prepare few-layer molybdenum disulfide (MBD) nanosheets, using ammonium molybdate as the molybdenum source and thiourea as the sulfur source to obtain structurally complete MBD nanosheets. MBD nanosheets are then composited with graphene oxide via electrostatic self-assembly and hydrothermal in-situ reduction. By adjusting the pH values ​​of the two dispersions, the MBD nanosheets are made positively charged and the graphene oxide negatively charged, achieving electrostatic self-assembly under stirring to form a uniform composite structure. Subsequently, L-ascorbic acid is added as a reducing agent, and a step-by-step heating hydrothermal reaction is carried out, which helps to gradually reduce the graphene oxide and simultaneously promotes the chemical bonding between MBD and graphene, forming a stable preliminary composite. This composite process enables graphene and MoS2 to be uniformly and tightly bonded at the nanoscale, fully utilizing the excellent load-bearing and thermal conductivity of graphene and the low-friction characteristics of interlayer slippage in MoS2, laying the foundation for constructing a highly efficient solid lubricating film.

[0016] Furthermore, the preliminary composite was modified with an ionic liquid intercalation. 1-Butyl-3-methylimidazolium hexafluorophosphate was selected as the ionic liquid, and it was dispersed with the preliminary composite in a mixed solvent of ethanol and the ionic liquid for a solvothermal reaction. The ionic liquid can intercalate into the interlayer of graphene and MoS2, preventing them from recombinizing, while improving the compatibility of the composite in base oil and enhancing its dispersion stability.

[0017] This invention utilizes a graphene / MoS2 composite additive as the core anti-wear component, constructing a stable and efficient solid lubricating film during lubrication. Graphene's high strength and thermal conductivity enable it to withstand high loads and rapidly dissipate heat generated by friction, reducing lubrication failure caused by localized overheating. The layered structure of MoS2 undergoes interlayer slippage during friction, providing low-friction characteristics and reducing the coefficient of friction. Dialkyl dithiophosphate zinc, a traditional anti-wear agent, works synergistically with the graphene / MoS2 composite additive. On the friction surface, zinc dialkyl dithiophosphate and the nanocomposite additive form a more effective mixed lubricating film, further enhancing anti-wear performance. Simultaneously, it also possesses antioxidant and anti-corrosion properties, protecting metal components in the hydraulic system. Detailed Implementation

[0018] 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.

[0019] In this invention, the thickness of the graphene oxide sheets is less than 3 nm and the sheet diameter is 0.5-2 μm; the CAS number of the polymethyl methacrylate is 9003-21-8.

[0020] Example 1 This embodiment provides a graphene anti-wear hydraulic oil, which, by weight, comprises the following components: base oil: 90 parts of polyalphaolefin PAO6, 1.5 parts of graphene / MoS2 composite additive, 1.5 parts of zinc dialkyl dithiophosphate, 0.4 parts of dodecenyl succinate half-ester, 0.5 parts of hindered phenolic antioxidant T501, 3.0 parts of polymethacrylate, 0.1 parts of benzotriazole derivative TH-551, and 0.02 parts of polysiloxane antifoaming agent T1001; The preparation method of the graphene / MoS2 composite additive includes the following steps: Weigh 2.48 g of ammonium molybdate and 3.04 g of thiourea, dissolve them in 100 mL of deionized water, and stir thoroughly to form a clear precursor solution. Transfer the solution into a 200 mL high-pressure reactor lined with polytetrafluoroethylene. Place the reactor in an oven and carry out a hydrothermal reaction at 200 °C for 24 h. After the reaction is completed, allow it to cool naturally to room temperature. The resulting black product is washed repeatedly by centrifugation with deionized water and ethanol. The washed precipitate is freeze-dried to finally obtain loose black few-layer MoS2 nanosheet powder. 200 mg of MoS2 nanosheets were dispersed in 400 mL of deionized water, and the pH was adjusted to 5.0 with dilute hydrochloric acid. The solution was then sonicated for 2 h to form a homogeneous dispersion A. Separately, 60 mg of graphene oxide was dispersed in 100 mL of water, and the pH was adjusted to 9.0 with ammonia to obtain dispersion B. Dispersion B was slowly added dropwise to dispersion A through a constant-pressure dropping funnel at 500 rpm with magnetic stirring for 1 h. After the addition was complete, stirring was continued at room temperature for 24 h to allow the positively charged MoS2 and negatively charged graphene oxide to fully self-assemble through electrostatic interactions. 300 mg of [unspecified substance] was then added to the above self-assembled mixture. L-ascorbic acid was stirred evenly and then transferred to a high-pressure reactor. A stepwise temperature reduction reaction was carried out: first, the reaction was carried out at 120℃ for 2 hours, then at 160℃ for 4 hours, and finally at 180℃ for 2 hours. After the reaction was completed, the mixture was cooled, centrifuged, and washed several times with deionized water and ethanol to obtain a preliminary composite of reduced graphene oxide (rGO) / MoS2. The preliminary composite was dispersed in a mixed solvent consisting of 90 mL anhydrous ethanol and 10 mL 1-butyl-3-methylimidazolium hexafluorophosphate ionic liquid. The mixture was transferred to an autoclave and subjected to a solvothermal reaction at 150 °C for 8 h. After the reaction, the mixture was washed to obtain a wet gel modified by ionic liquid intercalation. The wet gel was placed in a vacuum freeze dryer with a cold trap temperature of -55 °C and a vacuum of 5 Pa for 36 h to obtain a composite dry powder. The composite dry powder was placed in a tube furnace and heated to 300 °C at a rate of 5 °C / min under argon protection, and then heat-treated at this temperature for 2 h to further improve the crystallinity and stability of the material. The heat-treated powder was then pulverized and classified by an air jet mill to obtain fine powder with uniform particle size distribution. This powder was then immersed in 100 mL of heptane solution containing 1.0 wt% stearic acid and soaked at 60 °C for 2 h. After soaking, the powder was filtered and separated, and then treated at 80 °C and -0.095 °C. After drying under MPa vacuum for 4 hours, a surface-hydrophobic graphene / MoS2 composite additive was finally obtained. The preparation method of graphene anti-wear hydraulic oil in this embodiment includes the following steps: (1) The graphene / MoS2 composite additive and 10% of the base oil PAO6, which accounts for 90 parts of the total base oil, were treated at 75°C using a high-speed shear disperser at a speed of 6000 rpm for 45 minutes to obtain a uniform and stable pre-dispersed slurry. (2) Heat the remaining PAO6 base oil to 75°C, and slowly add polymethyl methacrylate while stirring at 300 rpm, and continue stirring until completely dissolved; (3) Keep the oil temperature at 75°C, and add zinc dialkyl dithiophosphate, dodecenyl succinate half ester, hindered phenolic antioxidant and benzotriazole derivative to the oil in step (2) in sequence. After each addition, stir at 300 rpm for 15 min to ensure thorough mixing. (4) Slowly add the pre-dispersed slurry obtained in step (1) to the oil in step (3); keep the temperature at 75°C and stir at 400 rpm for 75 min; (5) Cool the blended oil to 45°C naturally, add 30 ppm of polysiloxane antifoaming agent, and stir for 30 min. Filter the oil through a filtration system with a 1 μm precision filter bag. Finally, degas the oil under vacuum at 50°C and -0.098 MPa for 1 h to obtain the final product.

[0021] Example 2 This embodiment provides a graphene anti-wear hydraulic oil, which, by weight, comprises the following components: base oil: 85 parts of polyalphaolefin PAO6, 1.0 part of graphene / MoS2 composite additive, 1.0 part of zinc dialkyl dithiophosphate, 0.3 parts of dodecenyl succinate half ester, 0.3 parts of hindered phenolic antioxidant T501, 2.0 parts of polymethacrylate, 0.05 parts of benzotriazole derivative TH-551, and 0.01 parts of polysiloxane antifoaming agent T1001; The preparation methods for graphene / MoS2 composite additives include: 2.48 g of ammonium molybdate and 3.04 g of thiourea were weighed and dissolved in 100 mL of deionized water. The solution was stirred thoroughly to form a clear precursor solution. The solution was transferred into a 200 mL high-pressure reactor lined with polytetrafluoroethylene. The reactor was placed in an oven and subjected to a hydrothermal reaction at 180 °C for 20 h. After the reaction was completed, the mixture was allowed to cool naturally to room temperature. The resulting black product was washed repeatedly by centrifugation with deionized water and ethanol. The washed precipitate was freeze-dried to finally obtain loose black few-layer MoS2 nanosheet powder. 200 mg of MoS2 nanosheets were dispersed in 400 mL of deionized water, and the pH was adjusted to 4.5 with dilute hydrochloric acid. The solution was then sonicated for 2 h to form a uniform dispersion A. Separately, 60 mg of graphene oxide was dispersed in 100 mL of water, and the pH was adjusted to 8.5 with ammonia to obtain dispersion B. Dispersion B was slowly added dropwise to dispersion A under magnetic stirring at 500 rpm for 1 h. After the addition was complete, stirring was continued at room temperature for 12 h to allow the positively charged MoS2 and negatively charged graphene oxide to fully self-assemble through electrostatic interactions. 300 mg of [unspecified substance] was then added to the above self-assembled mixture. L-ascorbic acid was stirred evenly and then transferred to a high-pressure reactor. A stepwise temperature reduction reaction was carried out: the reaction was first carried out at 110℃ for 1 h, then at 150℃ for 3 h, and finally at 170℃ for 1 h. After the reaction was completed, the mixture was cooled, centrifuged, and washed several times with deionized water and ethanol to obtain a preliminary reduced graphene oxide (rGO) / MoS2 composite. The preliminary composite was dispersed in a mixed solvent consisting of 90 mL anhydrous ethanol and 10 mL 1-butyl-3-methylimidazolium hexafluorophosphate ionic liquid. The mixture was transferred to an autoclave and subjected to a solvothermal reaction at 140 °C for 6 h. After the reaction, the mixture was washed to obtain a wet gel modified by ionic liquid intercalation. The wet gel was placed in a vacuum freeze dryer with a cold trap temperature of -50 °C, a vacuum degree of less than 10 Pa, and a drying time of 24 h to obtain a composite dry powder. The composite dry powder was placed in a tube furnace and heated to 300 °C at a rate of 5 °C / min under argon protection, and heat-treated at this temperature for 2 h to further improve the crystallinity and stability of the material. The heat-treated powder was pulverized and classified by an air jet mill to obtain fine powder with uniform particle size distribution. This powder was then immersed in 100 mL of heptane solution containing 0.8 wt% stearic acid and soaked at 55 °C for 1 h. After soaking, the powder was filtered and separated, and then treated at 80 °C and -0.095 °C. After drying under MPa vacuum for 4 hours, a surface-hydrophobic graphene / MoS2 composite additive was finally obtained. The preparation method of graphene anti-wear hydraulic oil in this embodiment is as follows: (1) Mix all the graphene / MoS2 composite additives with PAO6 base oil accounting for 10% of the total weight of the base oil, and process it at 70°C using a high-speed shear disperser at a speed of 5000 rpm for 30 minutes to obtain a pre-dispersed slurry. (2) Heat the remaining base oil to 70°C, add polymethyl methacrylate while stirring, and stir until completely dissolved; (3) Keep the oil temperature at 70°C, and add zinc dialkyl dithiophosphate, dodecenyl succinate half ester, hindered phenolic antioxidant and benzotriazole derivative to the oil in sequence. Stir for 10 minutes after each additive is added to make it evenly mixed. (4) Add the pre-dispersed slurry from step (1) to the oil from step (3) and stir at 70°C for 60 minutes. (5) Cool the oil to below 50°C, add polysiloxane antifoaming agent, and stir for 30 minutes; then filter and degas the oil under vacuum to obtain the finished hydraulic oil.

[0022] Example 3 This embodiment provides a graphene anti-wear hydraulic oil, which, by weight, comprises the following components: base oil: 93 parts of polyalphaolefin PAO6, 2.0 parts of graphene / MoS2 composite additive, 2.0 parts of zinc dialkyl dithiophosphate, 0.5 parts of dodecenyl succinate half-ester, 0.8 parts of hindered phenolic antioxidant T501, 4.0 parts of polymethacrylate, 0.2 parts of benzotriazole derivative TH-551, and 0.03 parts of polysiloxane antifoaming agent T1001; The preparation methods of graphene-based anti-wear additives include: 2.48 g of ammonium molybdate and 3.04 g of thiourea were weighed and dissolved in 100 mL of deionized water. The solution was stirred thoroughly to form a clear precursor solution. The solution was transferred into a 200 mL high-pressure reactor lined with polytetrafluoroethylene. The reactor was placed in an oven and subjected to a hydrothermal reaction at 220 °C for 28 h. After the reaction was completed, the mixture was allowed to cool naturally to room temperature. The resulting black product was washed repeatedly by centrifugation with deionized water and ethanol. The precipitate after washing was freeze-dried to finally obtain loose black few-layer MoS2 nanosheet powder. 200 mg of MoS2 nanosheets were dispersed in 400 mL of deionized water, and the pH was adjusted to 5.5 with dilute hydrochloric acid. The solution was sonicated for 2 h to form a uniform dispersion A. Separately, 60 mg of graphene oxide was dispersed in 100 mL of water, and the pH was adjusted to 9.5 with ammonia to obtain dispersion B. Dispersion B was slowly added dropwise to dispersion A under magnetic stirring at 500 rpm for 1 h. After the addition was complete, stirring was continued at room temperature for 36 h to allow the positively charged MoS2 and negatively charged graphene oxide to fully self-assemble through electrostatic interactions. 300 mg of [unspecified substance] was added to the above self-assembled mixture. mgL-ascorbic acid was stirred evenly and then transferred to a high-pressure reactor. A stepwise temperature-increasing reduction reaction was carried out: first, the reaction was carried out at 130℃ for 3 hours, then at 170℃ for 5 hours, and finally at 190℃ for 3 hours. After the reaction was completed, the mixture was cooled, centrifuged, and washed several times with deionized water and ethanol to obtain a preliminary composite of reduced graphene oxide (rGO) / MoS2. The preliminary composite was dispersed in a mixed solvent consisting of 90 mL anhydrous ethanol and 10 mL 1-butyl-3-methylimidazolium hexafluorophosphate ionic liquid. The mixture was transferred to an autoclave and subjected to a solvothermal reaction at 160 °C for 10 h. After the reaction, the mixture was washed to obtain a wet gel modified by ionic liquid intercalation. The wet gel was placed in a vacuum freeze dryer with a cold trap temperature of -50 °C, a vacuum degree of less than 10 Pa, and a drying time of 48 h to obtain a composite dry powder. The composite dry powder was placed in a tube furnace and heated to 350 °C at a rate of 5 °C / min under argon protection, and heat-treated at this temperature for 3 h to further improve the crystallinity and stability of the material. The heat-treated powder was pulverized and classified by an air jet mill to obtain fine powder with uniform particle size distribution. This powder was then immersed in 100 mL of heptane solution containing 1.2 wt% stearic acid and soaked at 55 °C for 1 h. After soaking, the powder was filtered and separated, and then treated at 80 °C and -0.095 °C. After drying under MPa vacuum for 4 hours, a surface-hydrophobic graphene / MoS2 composite additive was finally obtained. The preparation method of graphene anti-wear hydraulic oil in this embodiment is as follows: (1) Mix all the graphene / MoS2 composite additives with PAO6 base oil accounting for 20% of the total weight of the base oil, and process it at 80°C using a high-speed shear disperser at a speed of 8000 rpm for 60 minutes to obtain a pre-dispersed slurry. (2) Heat the remaining base oil to 80°C, add polymethyl methacrylate while stirring, and stir until completely dissolved; (3) Keep the oil temperature at 80°C, and add zinc dialkyl dithiophosphate, dodecenyl succinate half ester, hindered phenolic antioxidant and benzotriazole derivative to the oil in sequence. Stir for 20 minutes after each additive is added to make it evenly mixed. (4) Add the pre-dispersed slurry from step (1) to the oil from step (3) and stir at 80°C for 90 minutes. (5) Cool the oil to below 50°C, add polysiloxane antifoaming agent, and stir for 30 minutes; then filter and vacuum degas the oil to obtain the finished hydraulic oil. It should be noted that, unless otherwise explained, all aspects of Examples 2 and 3 are the same as those in Example 1.

[0023] Example 4 Based on Example 1, adjustments were made. The difference from Example 1 is that the solvothermal reaction step of ionic liquid intercalation modification was omitted in the preparation of the graphene MoS2 composite additive; otherwise, it is the same as Example 1. The preparation method of the graphene-MoS2 composite additive is as follows: according to steps S1 and S2 of Example 1, a preliminary reduced graphene oxide (rGO) / MoS2 composite is prepared; without performing the solvothermal reaction of ionic liquid intercalation modification in Example 1, the preliminary composite is directly subjected to vacuum freeze-drying (under the same conditions as Example 1) to obtain composite dry powder; the subsequent heat treatment (300℃, 2h), air jet milling, stearic acid surface treatment (1.0 wt%, 60℃, 2h) and drying steps are the same as in Example 1, and finally a composite additive without ionic liquid intercalation is obtained.

[0024] Example 5 Based on Example 1, adjustments were made. Unlike Example 1, the graphene / MoS2 composite additive was prepared by simple physical grinding and blending of reduced graphene oxide and MoS2 nanosheets without electrostatic self-assembly and hydrothermal reduction composite; otherwise, it was the same as Example 1. The preparation method of graphene / MoS2 composite additive is as follows: following step S1 of Example 1, few-layer MoS2 nanosheet powder is prepared; following steps 1-3 of Comparative Example 2, reduced graphene oxide (rGO) powder is prepared; the two powders are placed in a mortar at a mass ratio (rGO:MoS2 = 60mg:200mg) and thoroughly ground and mixed for 30min; the physically mixed powder is dispersed in a mixed solvent consisting of 90 mL of anhydrous ethanol and 10 mL of 1-butyl-3-methylimidazolium hexafluorophosphate; the subsequent solvothermal reaction (150℃, 8h), freeze drying, heat treatment (300℃, 2h), pulverization and stearic acid surface treatment (1.0 wt%, 60℃, 2h) steps are the same as in Example 1, and finally a physically blended additive is obtained.

[0025] Comparative Example 1 The method is based on Example 1, but with adjustments. Unlike Example 1, no graphene / MoS2 composite additive is added; otherwise, it is the same as Example 1.

[0026] Comparative Example 2 The method is based on Example 1, but with adjustments. The difference from Example 1 is that the functional component in the graphene / MoS2 composite additive is a single reduced graphene oxide (rGO), which is not combined with MoS2; otherwise, it is the same as Example 1. The method for preparing single reduced graphene oxide is as follows: 60 mg of graphene oxide is weighed and dispersed in 100 mL of deionized water, and the pH value is adjusted to 9.0 with ammonia. 300 mg of L-ascorbic acid is added to the above dispersion, stirred evenly, and then transferred to a high-pressure reactor for hydrothermal reduction reaction at 120°C for 2 h. After the reaction is completed, the mixture is cooled, centrifuged and washed to obtain reduced graphene oxide (rGO) precipitate. The rGO precipitate is dispersed in a mixed solvent consisting of 90 mL of anhydrous ethanol and 10 mL of 1-butyl-3-methylimidazolium hexafluorophosphate. The subsequent solvothermal reaction (150°C; 8 h), freeze drying, heat treatment (300°C; 2 h), pulverization and stearic acid surface treatment (1.0 wt%; 60°C; 2 h) steps are the same as in Example 1, and finally a single graphene additive is obtained.

[0027] Comparative Example 3 The method is based on Example 1, but with some adjustments. The difference from Example 1 is that the functional component in the graphene / MoS2 composite additive is a single MoS2 nanosheet, which is not composited with graphene; otherwise, it is the same as Example 1. The method for preparing single MoS2 nanosheets is as follows: following step S1 of Example 1, few-layer MoS2 nanosheet powder is prepared; 200 mg of MoS2 nanosheet powder is weighed and directly dispersed in a mixed solvent consisting of 90 mL of anhydrous ethanol and 10 mL of 1-butyl-3-methylimidazolium hexafluorophosphate; the subsequent solvothermal reaction (150℃; 8h), freeze drying, heat treatment (300℃; 2h), pulverization and stearic acid surface treatment (1.0 wt%; 60℃; 2h) steps are the same as in Example 1, and finally a single MoS2 additive is obtained.

[0028] Comparative Example 4 The following adjustments were made based on Example 1, except that 1.5 parts of zinc dialkyl dithiophosphate were replaced with an equal part by mass of zinc dialkyl dithiocarbamate; the rest were the same as in Example 1.

[0029] Experimental Example: The graphene anti-wear hydraulic oils prepared in Examples 1-5 and Comparative Examples 1-4 were tested as follows; Wear resistance test: according to NB / SH / T 0189-2017; parameters: 75℃ temperature, 1200r / min rotation speed, 1h time, 300N load; Copper strip corrosion test: According to GB / T 5096-2017, the test temperature is 120℃ and the test time is 3h; Field Application Testing: To evaluate the actual long-term anti-wear and comprehensive protection performance of different hydraulic oil formulations, tests were conducted in a mining transport fleet operating under harsh conditions. Nine different oils were treated as independent groups, with each group added to the hydraulic systems (including vane pumps, piston pumps, and gear pumps) of three identical mining trucks, creating parallel replicates. All vehicles operated continuously for three months under the same load and operating environment. At the end of the maintenance cycle, the hydraulic systems of all vehicles underwent an open-pack inspection, with a focus on evaluating the surface wear condition of key friction pairs in the core hydraulic pumps.

[0030] The results are shown in Table 1 below: Table 1

[0031] Based on the above, Examples 1-3 exhibit the best performance, demonstrating that the nanocomposite structure formed by graphene and MoS2 through electrostatic self-assembly and stepwise hydrothermal reduction can play a synergistic role in lubrication. Graphene provides excellent load-bearing and thermal conductivity, while MoS2 provides low-friction characteristics for interlayer slippage; the combination of the two constructs a stable and efficient solid lubricating film. In rigorous field tests at mines, the friction pairs of the three hydraulic pumps (vane pump, piston pump, and gear pump) remained "smooth with no visible wear." This confirms that the composite additive system has a universal and long-lasting protective effect on different types of hydraulic pumps (sliding friction and rolling friction), meeting the needs of complex working conditions. Furthermore, the copper sheet corrosion rating reached 1a or 1b, indicating good compatibility between the benzotriazole derivative in the formulation and the composite additive system, effectively protecting copper alloy components.

[0032] Example 4 omits the ionic liquid intercalation step, which is crucial for improving the dispersion stability and anti-wear properties of the composite additive. Without this step, the wear scar diameter increases to 0.45 mm, resulting in a performance decrease. The ionic liquid not only prevents the recombination of graphene and MoS2 but also improves its compatibility in base oils, ensuring the long-term stable function of the nanomaterials.

[0033] Example 5 uses physical blending instead of electrostatic self-assembly, which is a key process for achieving uniform and compact nanoscale composites of graphene and MoS2. Simple physical blending cannot form a stable heterostructure, resulting in a significant reduction in the synergistic effect. The wear resistance (0.52 mm) is significantly worse than in Example 1, and "very slight friction marks" were also observed in field tests.

[0034] Comparative Example 1 did not include the graphene / MoS2 composite additive, which is a core component for improving the anti-wear performance of hydraulic oil. Relying solely on traditional additives (such as zinc dialkyl dithiophosphate), the anti-wear performance was the worst (0.68 mm), and field wear was the most pronounced. This highlights the irreplaceable role of nanomaterial additives in modern high-performance hydraulic oils.

[0035] Comparative Example 2, using only graphene, and Comparative Example 3, using only MoS2, disrupted the synergistic effect of the graphene-MoS2 composite. While single graphene (Comparative Example 2) exhibited some wear resistance (0.48 mm), it showed severe scratches and wear in field tests, and the copper sheet corrosion worsened (level 2b), indicating that single graphene's protection under extreme pressure was incomplete and may have interfered with corrosion inhibition. Single MoS2 (Comparative Example 3) showed better wear resistance (0.58 mm) than traditional oil but was far inferior to the composite system. Field wear was also significant. Both examples performed worse than any of the other examples, strongly demonstrating the superiority of the composite structure.

[0036] Comparative Example 4 involved replacing the primary anti-wear agent. In this composite additive system, zinc dialkyl dithiophosphate (ZDDP) is a traditional anti-wear agent with better synergistic effects with graphene / MoS2. Replacing it with zinc dialkyl dithiocarbamate resulted in a decrease in anti-wear performance (0.55 mm), and uniform wear was observed in the field. This indicates that ZDDP may form a more effective mixed lubricating film with the nanocomposite additives on the friction surface.

[0037] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A graphene-based anti-wear hydraulic oil, characterized in that, By weight, it comprises the following components: 85-93 parts base oil, 1.0-2.0 parts graphene / MoS2 composite additive, 1.0-2.0 parts zinc dialkyl dithiophosphate, 0.3-0.5 parts dodecenyl succinate half ester, 0.3-0.8 parts hindered phenolic antioxidant, 2.0-4.0 parts polymethacrylate, 0.05-0.2 parts benzotriazole derivative, and 0.01-0.03 parts polysiloxane antifoaming agent; wherein the base oil is polyalphaolefin PAO6.

2. The graphene anti-wear hydraulic oil according to claim 1, characterized in that, The preparation method of the graphene / MoS2 composite additive includes the following steps: S1. Few-layer molybdenum disulfide nanosheets were prepared by a hydrothermal method; S2. The few-layer molybdenum disulfide nanosheets and graphene oxide are combined by electrostatic self-assembly and hydrothermal in-situ reduction to obtain a preliminary composite material; S3. The preliminary composite is subjected to ionic liquid intercalation modification, freeze drying, inert atmosphere heat treatment and surface hydrophobication treatment in sequence to obtain graphene / MoS2 composite additive.

3. The graphene anti-wear hydraulic oil according to claim 2, characterized in that, The preparation steps of the hydrothermal method for preparing few-layer molybdenum disulfide nanosheets include: dissolving a molybdenum source and a sulfur source in deionized water and stirring to form a precursor solution; transferring the precursor solution to a high-pressure reactor and hydrothermally reacting it at 180-220℃ for 20-28 hours; after the reaction is completed, the product is washed and freeze-dried to obtain the few-layer molybdenum disulfide nanosheets.

4. The graphene anti-wear hydraulic oil according to claim 3, characterized in that, The molybdenum source is ammonium molybdate, and the sulfur source is thiourea; the molar ratio of the molybdenum source to the sulfur source is 1:3-5; the concentration of the molybdenum source in the precursor solution is 0.1-0.2 mol / L.

5. The graphene anti-wear hydraulic oil according to claim 2, characterized in that, Step S2 specifically includes: S2.1, disperse few-layer molybdenum disulfide nanosheets in water, adjust the pH value to 4.5-5.5, and sonicate to form dispersion A; S2.2, Adjust the pH of the graphene oxide dispersion to 8.5-9.5 to obtain dispersion B; S2.3 Under stirring conditions, the dispersion B is slowly added dropwise to the dispersion A. After the addition is complete, stirring is continued for 12-36 hours to complete electrostatic self-assembly. S2.4, A reducing agent is added to the self-assembled mixed system, and a hydrothermal reaction with stepwise heating is carried out. After the reaction is completed, the preliminary complex is obtained by washing.

6. The graphene anti-wear hydraulic oil according to claim 5, characterized in that, The concentration of molybdenum disulfide nanosheets in dispersion A is 0.4-0.6 mg / mL; the mass of graphene oxide in dispersion B is 25%-35% of the mass of molybdenum disulfide nanosheets; the reducing agent is L-ascorbic acid, and its addition amount is 4-6 times the mass of graphene oxide; the conditions for the stepped heating hydrothermal reaction are: first react at 110-130℃ for 1-3 hours, then increase to 150-170℃ for 3-5 hours, and finally increase to 170-190℃ for 1-3 hours.

7. The graphene anti-wear hydraulic oil according to claim 2, characterized in that, Step S3 specifically includes: S3.1, the preliminary complex is dispersed in a mixed solvent of ethanol and ionic liquid, and subjected to a solvothermal reaction at 140-160℃ for 6-10 h. After the reaction is completed, the mixture is washed to obtain a wet gel modified by ionic liquid intercalation. S3.2, The product obtained in step S3.1 is subjected to vacuum freeze drying to obtain a fluffy composite dry powder; S3.3, the composite dry powder is heat-treated at 250-350℃ for 1-3 hours under an inert atmosphere; S3.4 The heat-treated powder is subjected to air jet milling and classification, then surface-treated by immersion in an organic solution of long-chain organic acids, and finally vacuum-dried to obtain the final product.

8. The graphene anti-wear hydraulic oil according to claim 7, characterized in that, The ionic liquid is 1-butyl-3-methylimidazolium hexafluorophosphate; the volume ratio of ethanol to ionic liquid in the mixed solvent is 8-10:1; The conditions for vacuum freeze drying are: cold trap temperature below -50℃, vacuum degree below 10 Pa, and drying time of 24-48h; the inert atmosphere is nitrogen or argon.

9. The graphene anti-wear hydraulic oil according to claim 7, characterized in that, The long-chain organic acid is stearic acid; the organic solution is a heptane solution, wherein the mass concentration of stearic acid is 0.8wt%-1.2wt%; the soaking treatment temperature is 55-65℃ and the time is 1-3h.

10. A method for preparing graphene anti-wear hydraulic oil according to any one of claims 1-9, characterized in that the step include: (1) The graphene / MoS2 composite additive is mixed with 10%-20% of the base oil by weight, and processed at 70-80°C using a high-speed shear disperser at a speed of 5000-8000 rpm for 30-60 minutes to obtain a pre-dispersed slurry. (2) Heat the remaining base oil to 70-80℃, add the polymethyl methacrylate viscosity index improver, and stir at 200-400 rpm until completely dissolved and dispersed; (3) Add the zinc dialkyl dithiophosphate, dodecenyl succinate half ester, hindered phenolic antioxidant and benzotriazole derivative to the oil in step (2) in sequence. Stir for 10-20 minutes after each additive is added to make it evenly mixed. The mixing temperature is controlled at 70-80℃. (4) Add the pre-dispersed slurry obtained in step (1) to the oil in step (3) and stir at 70-80℃ for 60-90 minutes; (5) Post-treatment and refining: Cool the oil to below 50°C, add the polysiloxane antifoaming agent, and stir for 30 minutes; then filter and vacuum degas the oil in sequence to obtain the graphene anti-wear hydraulic oil.

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