Oil-soluble Mo-functionalized graphene composite material as well as preparation method and application thereof

Abstract

The invention discloses an oil-soluble Mo-functionalized graphene composite material as well as a preparation method and application thereof, and belongs to the field of lubricating oil additives. The preparation method comprises the following steps: (1) mixing a Mo-functionalized graphene composite material with an organic solvent, and performing ultrasonic treatment to form a solution A; (2) adding an amine reducing agent into the solution A, carrying out reduction reaction, filtering and washing to obtain a filter cake; and (3) mixing a long-chain organic compound, a coupling agent and a surfactant, performing ultrasonic treatment to form a mixed solution B, performing ultrasonic dispersion on the filter cake into the mixed solution B, and performing heating treatment, cooling, filtering, washing and drying to obtain the oil-soluble Mo-functionalized graphene composite material. Through partial reduction and chemical grafting processes, the Mo-functionalized graphene composite material is subjected to selective reduction firstly, then a coupling agent is utilized to graft a long-chain organic compound to the surface of the composite material, and an oil-soluble group is introduced, so that the dispersion stability and the anti-wear and anti-friction performance in lubricating oil are remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of lubricant additives, and in particular to an oil-soluble Mo@functionalized graphene composite material, its preparation method, and its application. Background Technology

[0002] The information disclosed in the background section of this invention is intended only to enhance the understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] In the mechanical industry, friction and wear are key factors leading to reduced efficiency and shortened lifespan of mechanical equipment. High-performance lubricant additives are an effective means of mitigating friction and wear. Two-dimensional layered materials, such as graphene, are considered highly promising solid lubricants due to their excellent mechanical properties and extremely low coefficient of friction. On the other hand, molybdenum (Mo)-based compounds are another classic class of lubricant additives; they can undergo chemical reactions on friction surfaces to form a protective film with extreme pressure anti-wear properties.

[0004] In existing technologies, research has attempted to combine graphene with molybdenum-based compounds to obtain synergistic lubricating additives. For example, Mo@functionalized graphene composites have been prepared via a solvothermal method. However, the composites obtained by such methods often have residual polar groups such as hydroxyl and carboxyl groups on their surface, resulting in poor compatibility with non-polar lubricating oils. This leads to agglomeration or precipitation, preventing uniform dispersion in the lubricating oil. Consequently, they not only fail to exert a synergistic lubricating effect but may also cause additional wear on the friction pairs due to agglomerated particles. This dispersion stability issue has become a key bottleneck restricting the practical application of Mo@functionalized graphene composites.

[0005] In existing modification technologies, some schemes attempt to introduce oil-soluble groups through physical adsorption. However, the adsorption effect is easily affected by temperature and shear force, and the groups are prone to detachment, making long-term stable dispersion impossible. Other schemes use strong oxidizing modifiers to adjust surface groups, causing molybdenum to oxidize and detach, leading to a decrease in the extreme pressure resistance of the composite material. Therefore, how to achieve stable grafting of oil-soluble groups through chemical modification without damaging the original extreme pressure and anti-wear core structure of Mo@functionalized graphene composites, and solve the dispersion problem in lubricating oil, has become a pressing technical challenge that needs to be overcome. Summary of the Invention

[0006] To overcome the problems of poor dispersion stability and easy agglomeration and precipitation of Mo@functionalized graphene composite materials in lubricating oils in existing technologies, this invention provides an oil-soluble Mo@graphene composite lubricating oil additive, its preparation method, and its application. This invention employs a partial reduction and chemical grafting process to first selectively reduce the functional groups on the surface of the Mo@functionalized graphene composite material. Subsequently, a coupling agent is used to graft long-chain organic compounds onto the surface of the composite material, introducing oil-soluble groups, thereby significantly improving its dispersion stability in lubricating oil and enhancing the anti-wear and friction-reducing properties of the lubricating oil. This method avoids the use of harmful elements such as sulfur, phosphorus, and chlorine, meeting environmental protection requirements, and the process conditions are mild, facilitating large-scale production.

[0007] To achieve the above technical objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a method for preparing an oil-soluble Mo@functionalized graphene composite material, comprising the following steps: (1) Mix Mo@functionalized graphene composite material with an organic solvent and sonicate to form solution A; (2) Add an amine reducing agent to solution A to carry out a reduction reaction, filter, wash, and obtain filter cake; (3) Mix long-chain organic compounds, coupling agents and surfactants, and sonicate to form a mixed solution B. Disperse the filter cake into the mixed solution B by sonication, heat treatment, cooling, filtering, washing and drying to obtain oil-soluble Mo@functionalized graphene composite material.

[0008] In step (1), ultrasonic treatment can break the agglomeration of Mo@functionalized graphene composite material, so that it can be uniformly dispersed in organic solvent, providing a homogeneous environment for subsequent reduction reaction; the reduction reaction in step (2) selectively converts the carboxyl groups on the surface of the composite material into amino groups, while retaining the stable chemical bond between Mo and graphene, providing reaction sites for subsequent grafting of long-chain groups; in step (3), heating treatment promotes the chemical bonding between long-chain organic compounds and functional groups on the surface of the composite material through coupling agent, and with the dispersing effect of surfactant, introduces long carbon chain structure, thereby giving the composite material excellent oil solubility and dispersion stability.

[0009] In one or more embodiments, the organic solvent is selected from at least one of acetone, methyl ethyl ketone, cyclohexanone, carbon tetrachloride, phenol, N,N-dimethylformamide, tetrahydrofuran, or dimethyl sulfoxide.

[0010] In one or more embodiments, the amine reducing agent is selected from at least one of ammonium formate, ammonium acetate, ammonium oxalate, or ammonium chloride. These amine reducing agents are all weakly acidic ammonium salts, exhibiting mild and selective reduction reactions that convert only the carboxyl groups on the surface of the composite material into amino groups. They do not disrupt the covalent bonds between Mo and graphene, nor do they affect the extreme pressure resistance of Mo.

[0011] In one or more embodiments, the surfactant is selected from at least one of triethylamine, dodecylamine, hexadecylamine, hexadecyltrimethylammonium bromide, or N,N-dimethylformamide. The surfactant can be adsorbed onto the surface of the composite material through electrostatic adsorption or hydrophobic interaction, preventing particle agglomeration during grafting and synergistically interacting with long-chain organic compounds to enhance the coverage of grafted groups on the composite material surface.

[0012] In one or more embodiments, the long-chain organic compound is selected from at least one of octadecylamine, di-n-hexylamine, oleic acid, stearic acid, coconut oil, cinnamyl alcohol, n-heptyl alcohol, n-octanol, tetrahydrofurfuryl alcohol, or coconut oil diethanolamide. These long-chain organic compounds all contain active functional groups such as hydroxyl, amino, or ester groups, which can chemically bond with the amino and residual hydroxyl groups generated by reduction on the surface of the composite material. Their long-chain alkyl groups can significantly improve the oil solubility of the composite material.

[0013] In one or more embodiments, the coupling agent is selected from trimethyl orthoformate and triethyl orthoformate. The coupling agent can act as a bridge to connect the functional groups on the surface of the composite material with the long-chain organic compound, improve the conversion rate and grafting stability of the grafting reaction, and prevent the long-chain groups from falling off during the friction process.

[0014] In one or more embodiments, the mass ratio of the Mo@functionalized graphene composite material, organic solvent, amine reducing agent, surfactant, long-chain organic compound and coupling agent is 1:400-500:1-10:5-500:1-15:0.5-10; Preferably, the mass ratio of the Mo@functionalized graphene composite material, organic solvent, amine reducing agent, surfactant, long-chain organic compound and coupling agent is 1:500:2-3:20-300:1-5:1-8; More preferably, the mass ratio of the Mo@functionalized graphene composite material, organic solvent, amine reducing agent, surfactant, long-chain organic compound, and coupling agent is 1:500:2:250:2:2. Under these conditions, this mass ratio range ensures that each component works fully, achieving efficient reduction and grafting. In one or more embodiments, in step (2), the reduction reaction temperature is 80-100℃ and the reduction reaction time is 1-4h; Preferably, the reduction reaction temperature is 90-95℃ and the reduction reaction time is 2-4h. Under these conditions, the temperature and time range can ensure that the carboxyl group is efficiently reduced to amino group, while avoiding high temperature causing structural damage or functional group degradation of the composite material, thus preserving sufficient reaction sites for subsequent grafting.

[0015] Alternatively, in step (3), the temperature of the heat treatment is 60℃-120℃, and the heat treatment time is 2-10h; Preferably, the heat treatment temperature is 80℃-100℃, and the heat treatment time is 4-8 hours. Under these conditions, this heating range can activate the coupling agent and functional group reaction, promote the grafting of long-chain organic compounds through chemical bonds, and at the same time avoid excessive temperature leading to long-chain decomposition or a decrease in the performance of the composite material.

[0016] Secondly, the present invention provides an oil-soluble Mo@functionalized graphene composite material prepared by the above preparation method.

[0017] Thirdly, the present invention provides the application of the above-mentioned oil-soluble Mo@functionalized graphene composite material in the field of friction and wear industry.

[0018] Compared with the prior art, the present invention has achieved the following beneficial effects: (1) This invention utilizes the existing carboxyl, hydroxyl, and sulfur-containing groups on the surface of Mo@functionalized graphene composite materials as reaction sites through a two-step method of partial reduction and chemical grafting. First, amine reducing agents are used to convert some carboxyl groups into amino groups and sulfoxy groups into hydroxyl groups. This step not only changes the types of surface functional groups but also increases the number of active sites (hydroxyl groups) that can be used for subsequent grafting reactions. Subsequently, coupling agents are used to promote the reaction between long-chain organic compounds and these active sites (especially the newly generated hydroxyl and amino groups), and long-chain alkyl and other oil-soluble groups are firmly grafted onto the surface of the composite material through chemical bonding. This method fundamentally changes the surface properties of the composite material, transforming it from hydrophilic and oleophobic to oleophilic and hydrophobic, thereby achieving long-term stable dispersion in lubricating oil base oil and effectively solving the technical bottleneck of easy agglomeration and sedimentation of existing Mo@functionalized graphene composite materials.

[0019] (2) A stable molybdenum disulfide reinforcement layer is generated in situ on the surface of the friction pair in the form of chemical bonds through the tribochemical reaction of molybdenum. Functionalized graphene is also fixed on the friction pair or the molybdenum disulfide reinforcement layer in the form of chemical bonds, forming a stable double-layer synergistic anti-wear and friction-reducing structure between the friction pairs, thereby improving the anti-wear and friction-reducing performance of the lubricant under harsh working conditions such as high speed, high temperature, and high load.

[0020] (3) The modification strategy of this invention has a high degree of selectivity. The entire reaction process mainly targets the functional groups composed of carbon, oxygen, sulfur and other elements on the surface of the composite material, without involving or destroying the molybdenum element that has been stably bonded to graphene through chemical bonds. This design ensures that the core anti-wear and friction-reducing components of the composite material, the layered structure of the molybdenum compound and graphene, are completely preserved after modification. Therefore, the oil-soluble product obtained in the end has both excellent dispersibility and maintains the excellent extreme pressure anti-wear and friction-reducing properties of the original Mo@functionalized graphene composite material, achieving a unity of dispersibility and functionality.

[0021] (4) The amine reducing agents, long-chain organic compounds and coupling agents used in this invention do not introduce harmful elements such as sulfur, phosphorus and chlorine, which meets environmental protection requirements. At the same time, by precisely controlling the mass ratio between each reactant, reaction temperature and time and other parameters, the number and chain length of the oil-soluble groups grafted on the surface can be effectively controlled, thereby optimizing the oil solubility of the final product. The process is highly controllable and suitable for large-scale production. Attached Figure Description

[0022] The accompanying drawings, which form part of this specification, are used to provide a further understanding of the invention. The illustrative embodiments and descriptions of the invention are used to explain the invention and do not constitute an undue limitation thereof. Obviously, those skilled in the art can obtain other drawings based on these drawings without any inventive effort.

[0023] Figure 1 These are the infrared spectra of the oil-soluble Mo@functionalized graphene composite materials prepared in Examples 1-8 of this invention; Figure 2 This is a scanning electron microscope image of the Mo@functionalized graphene composite material prepared in Example 1 of this invention; Figure 3 This is an EDS elemental analysis surface scan of the Mo@functionalized graphene composite material prepared in Example 1 of this invention; Figure 4 This is a schematic diagram of the dispersion state of the oil-soluble Mo@functionalized graphene composite material prepared in Example 3 of the present invention. Detailed Implementation It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0024] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0025] To enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments. Specific conditions are not specified in the embodiments; they are performed according to conventional conditions or conditions recommended by the manufacturer. Components used, unless otherwise specified, are all commercially available conventional products.

[0026] Preparation Example 1 This invention prepares Mo@functionalized graphene composite materials via a solvothermal method: 2 ml of Tween 80 solution was mixed with 8 ml of N,N-dimethylformamide to prepare solution A with a Tween 80 concentration of 20%. Then, 20 mg of monolayer carboxylated graphene was dispersed in solution A and sonicated for 30 min to form a suspension. 190 mg of ammonium molybdate tetrahydrate and 90 mg of thiourea were added sequentially to the prepared suspension, and sonication was continued for another 30 min. The resulting mixture was transferred to a high-pressure reactor and reacted at 200 °C for 8 h. After natural cooling to room temperature, a black viscous liquid was obtained. Finally, the mixture was washed three times with anhydrous ethanol and three times with deionized water, and then vacuum dried to obtain a black powdery Mo@functionalized graphene composite material.

[0027] Figure 2 This is a scanning electron microscope image of the Mo@functionalized graphene composite material prepared in Preparation Example 1 of this invention.

[0028] Figure 3 This is an EDS elemental analysis surface scan of the Mo@functionalized graphene composite material prepared in Preparation Example 1 of this invention. The elemental content of the Mo@functionalized graphene composite material obtained in Preparation Example 1 was analyzed, and the results are shown in Table 1.

[0029] Table 1. Elemental content analysis data of Preparation Example 1

[0030] The following examples and comparative examples all use the Mo@functionalized graphene composite material prepared in Preparation Example 1.

[0031] Example 1 Weigh 1 part of Mo@functionalized graphene composite material, add 500 parts of N,N-dimethylformamide, and ultrasonically mix to form solution A; while stirring, add 2 parts of reducing agent ammonium chloride, react at 90℃ for 2 hours, filter, wash 3 times with ethanol, and wash 3 times with deionized water to obtain filter cake; separately take 2 parts of octadecylamine, 2 parts of trimethyl orthoformate, and 250 parts of N,N-dimethylformamide, and ultrasonically mix for 15 minutes to form mixed solution B; transfer the filter cake into mixed solution B, ultrasonically disperse for 30 minutes, transfer to a high-pressure reactor, react at 100℃ for 4 hours, cool naturally, filter, wash, and dry at 120℃ to obtain oil-soluble solid product.

[0032] Structural characterization: such as Figure 1 As shown, infrared spectroscopy characterization revealed that at 2849 cm⁻¹... -1 and 2919cm -1 They respectively show the CH stretching vibration absorption peaks of the long-chain alkyl (octadecylamine) structure; at 1647 cm⁻¹ -1 The absorption peak at 1462 cm⁻¹ shows the C=O stretching vibration of the amide group introduced after the modification of the Mo@functionalized graphene composite material; -1 An absorption peak for the long-chain fatty acid -CH2 bending vibration appears at 717 cm⁻¹; -1 The presence of long-chain aliphatic hydrocarbon -(CH2)n- segments (n>4) in the vicinity of the oil-soluble organic functional group indicates that octadecylamine was successfully incorporated into the Mo@functionalized graphene composite material.

[0033] Dispersion performance: When the obtained oil-soluble Mo@functionalized graphene composite material was added to the lubricating oil base oil PAO-100 at an addition amount of 10 ppm, its dispersion stability was greater than 8 months.

[0034] Example 2 Weigh 1 part of Mo@functionalized graphene composite material, add 500 parts of N,N-dimethylformamide, and ultrasonically mix to form solution A; while stirring, add 2 parts of reducing agent ammonium formate, react at 90℃ for 2h, filter, wash 3 times with ethanol, and wash 3 times with deionized water to obtain filter cake; separately take 2 parts of octadecylamine, 2 parts of trimethyl orthoformate, and 250 parts of N,N-dimethylformamide, and ultrasonically mix for 15min to form mixed solution B; transfer the filter cake into mixed solution B, ultrasonically disperse for 30min, transfer to a high-pressure reactor, react at 100℃ for 6h, cool naturally, filter, wash, and dry at 120℃ to obtain oil-soluble solid product.

[0035] Structural characterization: such as Figure 1 As shown, infrared spectroscopy characterization revealed that at 2847 cm⁻¹... -1 and 2916cm -1 They respectively show the CH stretching vibration absorption peaks of the long-chain alkyl (octadecylamine) structure; at 1670 cm⁻¹-1 The absorption peak at 1453 cm⁻¹ shows the C=O stretching vibration of the amide group introduced after the modification of the Mo@functionalized graphene composite material; -1 An absorption peak for the long-chain fatty acid -CH2 bending vibration appears at 713 cm⁻¹; -1 The presence of long-chain aliphatic hydrocarbon -(CH2)n- segments (n>4) in the vicinity of the oil-soluble organic functional group indicates that octadecylamine was successfully incorporated into the Mo@functionalized graphene composite material.

[0036] Dispersion performance: When the obtained oil-soluble Mo@functionalized graphene composite material was added to the lubricating oil base oil PAO-100 at an addition amount of 10 ppm, its dispersion stability was greater than 6 months.

[0037] Example 3 Weigh 1 part of Mo@functionalized graphene composite material, add 500 parts of N,N-dimethylformamide, and ultrasonically mix to form solution A; while stirring, add 2 parts of reducing agent ammonium chloride, react at 90℃ for 4 hours, filter, wash 3 times with ethanol, and wash 3 times with deionized water to obtain filter cake; separately take 2 parts of octadecylamine, 2 parts of trimethyl orthoformate, and 250 parts of N,N-dimethylformamide, and ultrasonically mix for 15 minutes to form mixed solution B; transfer the filter cake into mixed solution B, ultrasonically disperse for 30 minutes, transfer to a high-pressure reactor, react at 80℃ for 8 hours, cool naturally, filter, wash, and dry at 120℃ to obtain oil-soluble solid product.

[0038] Structural characterization: such as Figure 1 As shown, infrared spectroscopy characterization revealed that at 2848 cm⁻¹... -1 and 2917cm -1 They respectively show the CH stretching vibration absorption peaks of the long-chain alkyl (octadecylamine) structure; at 1663 cm⁻¹ -1 The absorption peak at 1448 cm⁻¹ shows the C=O stretching vibration of the amide group introduced after the modification of the Mo@functionalized graphene composite material; -1 An absorption peak for the -CH2 bending vibration of long-chain fatty acids appears at 720 cm⁻¹; -1 The presence of long-chain aliphatic hydrocarbon -(CH2)n- segments (n>4) in the vicinity of the oil-soluble organic functional group indicates that octadecylamine was successfully incorporated into the Mo@functionalized graphene composite material.

[0039] Dispersion performance: The obtained oil-soluble Mo@functionalized graphene composite material was added to the lubricating oil base oil PAO-100 at a dosage of 10 ppm. Figure 4 As shown, the dispersion remained stable even after standing for 10 months, indicating that its dispersion stability was greater than 10 months.

[0040] Example 4 Weigh 1 part of Mo@functionalized graphene composite material, add 500 parts of N,N-dimethylformamide, and ultrasonically mix to form solution A; while stirring, add 2 parts of reducing agent ammonium chloride, react at 95℃ for 2 hours, filter, wash 3 times with ethanol, and wash 3 times with deionized water to obtain filter cake; separately take 2 parts of coconut oil, 2 parts of trimethyl orthoformate, and 250 parts of N,N-dimethylformamide, and ultrasonically mix for 15 minutes to form mixed solution B; transfer the filter cake into mixed solution B, ultrasonically disperse for 30 minutes, transfer to a high-pressure reactor, react at 100℃ for 8 hours, cool naturally, filter, wash, and dry at 120℃ to obtain oil-soluble solid product.

[0041] Structural characterization: such as Figure 1 As shown, at 2917cm -1 and 2848cm -1 The absorption peaks in the vicinity mainly originate from the stretching vibration mode of the methylene CH in coconut oil; at 1700 cm⁻¹ -1 The absorption peaks in the vicinity mainly originate from the carbonyl C=O stretching vibration mode of acids and esters, possibly from residual carboxyl groups or esterification products on the surface of oil-soluble Mo@functionalized graphene composites; the absorption peak at 1462 cm⁻¹... -1 An absorption peak for the long-chain fatty acid -CH2 bending vibration appears at 723 cm⁻¹. -1 The peak at this location is an out-of-plane bending vibration absorption peak of CH on -(CH2)n-, which is a typical characteristic of oil-soluble organic functional groups. This indicates that coconut oil has been successfully incorporated into the Mo@functionalized graphene composite material.

[0042] Dispersion performance: When the obtained oil-soluble Mo@functionalized graphene composite material was added to the lubricating oil base oil PAO-100 at an addition amount of 10 ppm, its dispersion stability was greater than 8 months.

[0043] Example 5 Weigh 1 part of Mo@functionalized graphene composite material, add 500 parts of N,N-dimethylformamide, and ultrasonically mix to form solution A; while stirring, add 2 parts of reducing agent ammonium chloride, react at 90℃ for 3 hours, filter, wash 3 times with ethanol, and wash 3 times with deionized water to obtain filter cake; separately take 2 parts of coconut oil, 2 parts of triethyl orthoformate, and 250 parts of N,N-dimethylformamide, and ultrasonically mix for 15 minutes to form mixed solution B; transfer the filter cake into mixed solution B, ultrasonically disperse for 30 minutes, transfer to a high-pressure reactor, react at 120℃ for 4 hours, cool naturally, filter, wash, and dry at 120℃ to obtain oil-soluble solid product.

[0044] Structural characterization: such as Figure 1 As shown, infrared spectroscopy characterization revealed that at 2850 cm⁻¹... -1 and 2921cm -1The absorption peaks for the CH stretching vibrations of the long-chain alkyl (coconut oil) structure are shown respectively; at 1723 cm⁻¹ -1 and 1646cm -1 The absorption peak at 1462 cm⁻¹ shows the C=O stretching vibration in the acid and ester structures of the introduced triethyl orthoformate; -1 An absorption peak for the -CH2 bending vibration of long-chain fatty acids appears at 718 cm⁻¹. -1 The peak at this location is an out-of-plane bending vibration absorption peak of CH on -(CH2)n-, which is a typical characteristic of oil-soluble organic functional groups. This indicates that coconut oil has been successfully incorporated into the Mo@functionalized graphene composite material.

[0045] Dispersion performance: When the obtained oil-soluble Mo@functionalized graphene composite material was added to the lubricating oil base oil PAO-100 at an addition amount of 10 ppm, its dispersion stability was greater than 6 months.

[0046] Example 6 Weigh 1 part of Mo@functionalized graphene composite material, add 500 parts of N,N-dimethylformamide, and ultrasonically mix to form solution A; while stirring, add 2 parts of reducing agent ammonium formate, react at 95℃ for 2 hours, filter, wash 3 times with ethanol, and wash 3 times with deionized water to obtain filter cake; separately take 2 parts of coconut oil, 2 parts of trimethyl orthoformate, and 250 parts of N,N-dimethylformamide, and ultrasonically mix for 15 minutes to form mixed solution B; transfer the filter cake into mixed solution B, ultrasonically disperse for 30 minutes, transfer to a high-pressure reactor, react at 100℃ for 4 hours, cool naturally, filter, wash, and dry at 120℃ to obtain oil-soluble solid product.

[0047] Structural characterization: such as Figure 1 As shown, infrared spectroscopy characterization revealed that at 2840 cm⁻¹... -1 and 2918cm -1 The absorption peaks at 1716 cm⁻¹ show the CH stretching vibration of the long-chain alkyl (coconut oil) structure. -1 and 1647cm -1 The absorption peak at 1384 cm⁻¹ shows the C=O stretching vibration in the acid and ester structures of the introduced trimethyl orthoformate; -1 An absorption peak for the -CH2 bending vibration of long-chain fatty acids appears at 720 cm⁻¹. 1 The peak at this location is an out-of-plane bending vibration absorption peak of CH on -(CH2)n-, which is a typical characteristic of oil-soluble organic functional groups. This indicates that coconut oil has been successfully incorporated into the Mo@functionalized graphene composite material.

[0048] Dispersion performance: When the obtained oil-soluble Mo@functionalized graphene composite material was added to the lubricating oil base oil PAO-100 at an addition amount of 10 ppm, its dispersion stability was greater than 6 months.

[0049] Example 7 Weigh 1 part of Mo@functionalized graphene composite material, add 500 parts of tetrahydrofuran, and ultrasonically mix to form solution A; while stirring, add 2 parts of reducing agent ammonium formate, react at 90℃ for 2h, filter, wash 3 times with ethanol, and wash 3 times with deionized water to obtain filter cake; separately take 2 parts of octadecylamine, 2 parts of trimethyl orthoformate, and 250 parts of N,N-dimethylformamide, and ultrasonically mix for 15min to form mixed solution B; transfer the filter cake into mixed solution B, ultrasonically disperse for 30min, transfer to a high-pressure reactor, react at 100℃ for 6h, cool naturally, filter, wash, and dry at 120℃ to obtain oil-soluble solid product.

[0050] Structural characterization: such as Figure 1 As shown, infrared spectroscopy characterization revealed that at 2849 cm⁻¹... -1 and 2919cm -1 They respectively show the CH stretching vibration absorption peaks of the long-chain alkyl (octadecylamine) structure; at 1670 cm⁻¹ -1 The absorption peak at 1453 cm⁻¹ shows the C=O stretching vibration in the acid and ester structures of the introduced trimethyl orthoformate; -1 An absorption peak for the -CH2 bending vibration of long-chain fatty acids appears at 713 cm⁻¹. 1 The peak at this location is an out-of-plane bending vibration absorption peak on the CH group at -(CH2)n-, which is typical of oil-soluble organic functional groups. This indicates that octadecylamine was successfully incorporated into the Mo@functionalized graphene composite material.

[0051] Dispersion performance: When the obtained oil-soluble Mo@functionalized graphene composite material was added to the lubricating oil base oil PAO-100 at an addition amount of 10 ppm, its dispersion stability was greater than 6 months.

[0052] Example 8 Weigh 1 part of Mo@functionalized graphene composite material, add 500 parts of N,N-dimethylformamide, and ultrasonically mix to form solution A; while stirring, add 2 parts of reducing agent ammonium acetate, react at 90℃ for 2 hours, filter, wash 3 times with ethanol, and wash 3 times with deionized water to obtain filter cake; separately take 2 parts of octadecylamine, 2 parts of trimethyl orthoformate, and 250 parts of N,N-dimethylformamide, and ultrasonically mix for 15 minutes to form mixed solution B; transfer the filter cake into mixed solution B, ultrasonically disperse for 30 minutes, transfer to a high-pressure reactor, react at 100℃ for 4 hours, cool naturally, filter, wash, and dry at 120℃ to obtain oil-soluble solid product.

[0053] Structural characterization: such as Figure 1 As shown, infrared spectroscopy characterization revealed that at 2848 cm⁻¹... -1 and 2918cm-1 They respectively show the CH stretching vibration absorption peaks of the long-chain alkyl (octadecylamine) structure; at 1647 cm⁻¹ -1 The absorption peak at 1462 cm⁻¹ shows the C=O stretching vibration in the acid and ester structures of the introduced trimethyl orthoformate; -1 An absorption peak for the -CH2 bending vibration of long-chain fatty acids appears at 713 cm⁻¹. 1 The peak at this location is an out-of-plane bending vibration absorption peak on the CH group at -(CH2)n-, which is typical of oil-soluble organic functional groups. This indicates that octadecylamine was successfully incorporated into the Mo@functionalized graphene composite material.

[0054] Dispersion performance: When the obtained oil-soluble Mo@functionalized graphene composite material was added to the lubricating oil base oil PAO-100 at an addition amount of 10 ppm, its dispersion stability was greater than 4 months.

[0055] Comparative Example 1 2 ml of Tween 80 solution was mixed with 8 ml of N,N-dimethylformamide to prepare solution A with a Tween 80 concentration of 20%. Then, 20 mg of monolayer graphene oxide was dispersed in solution A and sonicated for 30 min to form a suspension. 190 mg of ammonium molybdate tetrahydrate and 90 mg of thiourea were added sequentially to the prepared suspension, and sonication was continued for another 30 min. The resulting mixture was transferred to a high-pressure reactor and reacted at 200 °C for 10 h followed by 8 h. After natural cooling to room temperature, a black viscous liquid was obtained. Finally, the mixture was washed three times with anhydrous ethanol and three times with deionized water, and then vacuum dried to obtain the unmodified Mo@functionalized graphene composite material.

[0056] Dispersion performance: One part of unmodified Mo@functionalized graphene composite material was added directly to PAO-100 lubricating oil base oil at a dosage of 10 ppm. The dispersion stability in PAO-100 was less than 1 week, with obvious agglomeration and precipitation.

[0057] Comparative Example 2 One part of Mo@functionalized graphene composite material was mixed with 500 parts of N,N-dimethylformamide and ultrasonically dissolved to form a solution. Then, 50 parts of oleic acid were added, and the mixture was stirred for 2 hours before being filtered, washed, and dried.

[0058] Dispersion performance: The obtained product was added to the lubricating oil base oil PAO-100 at a dosage of 10 ppm. In the initial stage, the product had a certain degree of dispersibility in the lubricating oil base oil, but over time (about 1 month), agglomeration and precipitation gradually occurred, and the dispersion stability was poor.

[0059] Comparative Example 3 The difference between this comparative example and Example 1 is that no reducing agent ammonium chloride is added in this comparative example, while the other preparation methods are the same as in Example 1.

[0060] Dispersion performance: The obtained product was added to PAO-100 lubricating oil base oil at a dosage of 10 ppm. The dispersion stability in PAO-100 was less than half a month, with obvious agglomeration and precipitation.

[0061] Comparative Example 4 The difference between this comparative example and Example 1 is that this comparative example does not contain the coupling agent trimethyl orthoformate, while the other preparation methods are the same as in Example 1.

[0062] Dispersion performance: The obtained product was added to PAO-100 lubricating oil base oil at a dosage of 10 ppm. The dispersion stability in PAO-100 was less than 1 month, with obvious agglomeration and precipitation.

[0063] Comparative Example 5 The difference between this comparative example and Example 1 is that the surfactant N,N-dimethylformamide is not added in this comparative example, but the other preparation methods are the same as in Example 1.

[0064] Dispersion performance: The obtained product was added to PAO-100 lubricating oil base oil at a dosage of 10 ppm. The dispersion stability in PAO-100 was less than 2 months, with obvious agglomeration and precipitation.

[0065] Comparative Example 6 The difference between this comparative example and Example 1 is that this comparative example does not contain the long-chain organic compound octadecylamine, while the other preparation methods are the same as in Example 1.

[0066] Dispersion performance: The obtained product was added to PAO-100 lubricating oil base at a dosage of 10 ppm. The dispersion stability in PAO-100 was less than 1 week, with obvious agglomeration and precipitation.

[0067] Comparative Example 7 Weigh 1 part of Mo@functionalized graphene composite material, add 500 parts of N,N-dimethylformamide, and ultrasonically mix to form solution A; weigh 2 parts of reducing agent ammonium chloride, 2 parts of octadecylamine, 2 parts of trimethyl orthoformate, and 250 parts of N,N-dimethylformamide, and ultrasonically mix for 15 min to form mixed solution B; mix solution A and mixed solution B, ultrasonically disperse for 30 min, transfer to a high-pressure reactor, react at 100℃ for 4 h, cool naturally, filter, wash, and dry at 120℃ to obtain an oil-soluble solid product.

[0068] Dispersion performance: The obtained product was added to the lubricating oil base oil PAO-100 at a dosage of 10 ppm. The dispersion stability in PAO-100 was less than 3 months.

[0069] The dispersion stability of Examples 1-8 was greater than 4 months, with Example 3 showing the best performance, achieving a dispersion stability of greater than 10 months. This indicates that the oil-soluble Mo@functionalized graphene composite material obtained by the method of this invention exhibits excellent long-term dispersion stability in the lubricating oil base PAO-100. This demonstrates that this invention successfully grafts long-chain organic compounds onto Mo@functionalized graphene through the synergistic effect of reduction reaction, coupling agent, and surfactant, imparting oil solubility and thus preventing aggregation. In contrast, the dispersion stability of Comparative Examples 1-7 was significantly lower than that of the Examples.

[0070] Test case 1. Comparison of friction coefficient and wear volume of oil-soluble Mo@functionalized graphene composite materials: Using PAO-8 lubricating oil as a blank, the composite materials obtained in Examples 1-8 and Comparative Examples 1-7 were diluted 10,000 times with PAO-8 lubricating oil and subjected to friction tests using a UMT-5 friction and wear testing machine. The test parameters were: load 5N, contact stress 835MPa, oil temperature 25℃, and test duration 30min.

[0071] Table 1. Test results of friction coefficient and wear volume.

[0072] The results are shown in Table 1. As can be seen from the results in Table 1, Embodiment 1 of the present invention... The oil-soluble Mo@functionalized graphene composite material obtained in step 8 exhibits excellent friction-reducing and anti-wear effects. The friction coefficient of the blank PAO-8 lubricating oil is 0.0947, and the wear volume is 2287 μm. 3 In contrast, the coefficients of friction for Examples 1-8 ranged from 0.0843 to 0.0890, and the wear volumes ranged from 721 to 896 μm. 3 This indicates that the composite material of the present invention can effectively reduce the coefficient of friction by more than 10% and reduce the wear volume by more than 60%, wherein Example 3 (coefficient of friction 0.0843, wear volume 721 μm) 3 The control group (1-7) demonstrated optimal performance. However, the anti-wear effects of the control groups (1-7) were significantly lower than those of the control group (example 1).

[0073] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing an oil-soluble Mo@functionalized graphene composite material, characterized in that, Includes the following steps: (1) Mix Mo@functionalized graphene composite material with an organic solvent and sonicate to form solution A; (2) Add an amine reducing agent to solution A to carry out a reduction reaction, filter, wash, and obtain filter cake; (3) Mix long-chain organic compounds, coupling agents and surfactants, and sonicate to form a mixed solution B. Disperse the filter cake into the mixed solution B by sonication, heat treatment, cooling, filtering, washing and drying to obtain oil-soluble Mo@functionalized graphene composite material.

2. The preparation method according to claim 1, characterized in that, The organic solvent is selected from at least one of acetone, methyl ethyl ketone, cyclohexanone, carbon tetrachloride, phenol, N,N-dimethylformamide, tetrahydrofuran, or dimethyl sulfoxide.

3. The preparation method according to claim 1, characterized in that, The amine reducing agent is selected from at least one of ammonium formate, ammonium acetate, ammonium oxalate, or ammonium chloride.

4. The preparation method according to claim 1, characterized in that, The surfactant is selected from at least one of triethylamine, dodecylamine, hexadecylamine, hexadecyltrimethylammonium bromide, or N,N-dimethylformamide.

5. The preparation method according to claim 1, characterized in that, The long-chain organic compound is selected from at least one of octadecylamine, di-n-hexylamine, oleic acid, stearic acid, coconut oil, cinnamyl alcohol, n-heptyl alcohol, n-octanol, tetrahydrofurfuryl alcohol, or coconut oil diethanolamide.

6. The preparation method according to claim 1, characterized in that, The coupling agent is selected from trimethyl orthoformate and triethyl orthoformate.

7. The preparation method according to claim 1, characterized in that, The mass ratio of the Mo@functionalized graphene composite material, organic solvent, amine reducing agent, surfactant, long-chain organic compound and coupling agent is 1:400-500:1-10:5-500:1-15:0.5-10; Preferably, the mass ratio of the Mo@functionalized graphene composite material, organic solvent, amine reducing agent, surfactant, long-chain organic compound and coupling agent is 1:500:2-3:20-300:1-5:1-8; More preferably, the mass ratio of the Mo@functionalized graphene composite material, organic solvent, amine reducing agent, surfactant, long-chain organic compound and coupling agent is 1:500:2:250:2:

2.

8. The preparation method according to claim 1, characterized in that, In step (2), the reduction reaction temperature is 80-100℃ and the reduction reaction time is 1-4h; Preferably, the reduction reaction temperature is 90-95℃ and the reduction reaction time is 2-4h; Alternatively, in step (3), the temperature of the heat treatment is 60℃-120℃, and the heat treatment time is 2-10h; Preferably, the heating treatment temperature is 80℃-100℃, and the heating treatment time is 4-8h.

9. The oil-soluble Mo@functionalized graphene composite material prepared by the preparation method according to any one of claims 1 to 8.

10. The application of the oil-soluble Mo@functionalized graphene composite material as described in claim 9 in the field of tribology and wear.

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