Composite nanolubricant additive based on ionic liquid precursor and method of making same

Abstract

The application discloses a composite nano-lubricating additive based on an ionic liquid precursor and a preparation method thereof. The composite nano-lubricating additive is composed of a copper sulfide / chitosan composite precursor and a phosphorus-containing ionic liquid; the copper sulfide / chitosan composite precursor comprises chitosan, a soluble copper salt and a sulfur source. The phosphorus-containing ionic liquid of the application penetrates into the deep part of the composite precursor with high specific surface area and porous structure due to low interfacial tension, and the unreacted anion / cation network in the ionic liquid is firmly anchored to the polar groups on the surface of the precursor and copper-based particles through electrostatic attraction and coordination bonds, can produce strong hydrogen bond crosslinking and physical entanglement with the fiber of the soap base thickener of the lubricating grease, inhibit the oil separation phenomenon under high shear extreme pressure conditions, and at the same time, promote the rapid spreading of the additive on the metal surface of the friction pair, form a high-efficiency anti-wear layer with a "grease-film" dynamic repair synergistic effect, and thus prolong the service life of the lubricating grease.

Description

Technical Field

[0001] This invention relates to the field of nanomaterial surface modification and tribology, specifically to a composite nano-lubricating additive based on an ionic liquid precursor and its preparation method. Background Technology

[0002] Introducing phosphorus-containing substances onto the surface of transition metal sulfides or transition metal sulfide nanoparticles can trigger tribochemical reactions during friction, generating a phosphorus-containing tribochemical film with strong boundary protection, thereby further improving the material's friction-reducing and wear-resistant properties. Currently, common methods for achieving surface phosphating are mainly divided into gas-phase phosphating and liquid-phase (aqueous / solvent-phase) phosphating.

[0003] Among these methods, vapor-phase phosphating typically presents significant safety risks and incurs high equipment costs. For instance, patent application CN114150291A discloses a method for surface phosphating transition metal sulfides using PH3 (phosphine) gas or red phosphorus vapor at high temperatures. While this method can achieve relatively deep phosphating, the PH3 and other gases used are highly toxic, flammable, and explosive, placing extremely stringent requirements on the airtightness of the production equipment and the exhaust gas treatment system. More critically, for nanoparticles, the high-temperature vapor-phase deposition environment can easily damage the organic polymer framework in composite nanomaterials, leading to direct carbonization or structural collapse, making it difficult to meet the demands of green, safe, and controllable large-scale industrial production.

[0004] To overcome the risks of gas-phase methods, many studies have turned to milder liquid-phase methods. However, traditional aqueous or inorganic phosphate methods face serious interfacial compatibility defects. For example, patent application CN103881421B proposes a technique for surface treatment of nanoparticles in an aqueous solution of inorganic phosphates (such as sodium phosphate and sodium hypophosphite). Due to the steric hindrance and hydrophobic interfaces within complex nanocomposites, and the high surface tension of inorganic phosphate aqueous solutions, the aqueous solution struggles to effectively penetrate into the deeper layers of the composite system. This results in the modified layer prepared by this method remaining only on the outer surface of the material, creating the illusion of a "surface film with internal voids." Furthermore, the chemical bonds between simple inorganic phosphate groups and the interface are weak, making them prone to peeling off under the high shear forces of the friction pair, leading to rapid lubrication failure.

[0005] Developing a novel phosphating method based on in-situ modification of phosphorus-containing ionic liquids to effectively overcome the penetration resistance of complex nanomaterials, eliminate the defects of high toxicity and high pollution in traditional processes, and construct a firmly bonded and non-detachable phosphorus-containing lubricating protective layer in situ on the material surface and internal interface is a technical problem that urgently needs to be solved in the field of composite nano-lubricating additives. Summary of the Invention

[0006] To address the shortcomings of existing technologies, such as poor interfacial permeability, weak bonding, easy detachment under extreme pressure shear, and the hazards and pollution associated with traditional gas / aqueous phase processes, the present invention aims to provide a composite nano-lubricating additive based on an ionic liquid precursor and its preparation method. This method utilizes a functionalized phosphorus-containing ionic liquid as an "integrated phosphorus source and surface modifier," leveraging its unique molecular wettability and coordination ability to achieve deep phosphating of the material and in-situ construction of an inorganic-organic hybrid lubricating protective layer without damaging the precursor framework.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] This invention relates to a composite nano-lubricant additive based on an ionic liquid precursor, which is composed of a copper sulfide / chitosan composite precursor and a phosphorus-containing ionic liquid in a mass ratio of 1:5~10; the copper sulfide / chitosan composite precursor includes chitosan, soluble copper salt and sulfur source in a mass ratio of 1:0.2~0.3:0.1~0.15.

[0009] Preferably, the soluble copper salt is copper chloride dihydrate or copper sulfate.

[0010] Preferably, the sulfur source is thiourea or sodium sulfide nonahydrate.

[0011] Preferably, the phosphorus-containing ionic liquid is a solution obtained by mixing trihexyl(tetradecyl)phosphine bicyclic (2,4,4-trimethylpentyl)phosphine or 1-butyl-3-methylimidazolium hexafluorophosphate with anhydrous ethanol or acetone at a solid-liquid ratio of 1g:2~3ml.

[0012] The present invention discloses a method for preparing a composite nano-lubricating additive based on an ionic liquid precursor, comprising the following steps:

[0013] S1. Preparation of copper sulfide / chitosan composite precursor: Chitosan powder is dissolved in dilute acetic acid solution and stirred evenly to form a base solution; soluble copper salt and sulfur source are added to the base solution in sequence and stirred evenly to form a mixture; the mixture is placed in a reaction vessel for hydrothermal reaction; after natural cooling, the precipitate is collected and washed with deionized water; the precipitate retained after washing is mixed with deionized water and dispersed to obtain a uniformly dispersed suspension; the suspension is spray-frozen-dried to obtain copper sulfide / chitosan composite precursor powder.

[0014] S2. Place the copper sulfide / chitosan composite precursor powder in a vacuum drying oven for vacuum drying.

[0015] S3. The copper sulfide / chitosan composite precursor powder treated in step S2 is dispersed in a phosphorus-containing ionic liquid, and ultrasonic stirring and magnetic stirring are performed in sequence to carry out in-situ interfacial reaction. Then, it is naturally cooled, centrifuged, the supernatant is discarded, volatile washing solvent is added, ultrasonic stirring is performed again and centrifuged again, and then the washing is repeated 3 to 5 times. Finally, it is vacuum dried at 60 to 80°C for 10 to 12 hours to obtain a composite nano lubricant additive based on the ionic liquid precursor.

[0016] Preferably, the chitosan powder and dilute acetic acid solution are mixed at a solid-liquid ratio of 1g:50ml.

[0017] More preferably, the volume concentration of the dilute acetic acid solution is 1%.

[0018] Preferably, the hydrothermal reaction is carried out at a temperature of 120-160°C for 8-12 hours, the vacuum drying temperature of the copper sulfide / chitosan composite precursor powder is 60-80°C for 12-24 hours, the ultrasonic stirring time is 20-30 minutes, and the magnetic stirring temperature is 90-100°C for 4-8 hours.

[0019] Preferably, the precipitate is mixed with deionized water at a mass ratio of 1:5.

[0020] Preferably, the spray freeze-drying specifically involves spraying the suspension into liquid nitrogen through an atomizing nozzle for primary freezing, and then placing it in a freeze dryer for secondary freezing.

[0021] Preferably, the volatile washing solvent is acetone or anhydrous ethanol.

[0022] The beneficial effects of this invention are as follows:

[0023] 1. Breaking through the interface penetration bottleneck to achieve deep full-surface modification: The core of this invention lies in abandoning the aqueous inorganic phosphate system with high surface tension. By utilizing the low interface tension and "molecular penetrant" properties of phosphorus-containing ionic liquids, the interfacial repulsion of complex nanocomposite structures is effectively overcome. The ionic liquid penetrates deep into the composite precursor with high specific surface area and rich porous structure, achieving comprehensive deep modification from the surface to the interior, avoiding the illusion of "surface film and internal void".

[0024] 2. Specific Anchoring, Constructing a Highly Binding Hybrid Lubricating Interface: The ionic liquid not only acts as a phosphorus source, reacting under mild conditions to provide phosphorus, but its incompletely reacted anion / cation network can also be firmly anchored to the polar groups (such as chitosan amino groups) and copper-based particles on the precursor surface through electrostatic attraction and coordination bonds. Especially when the material of this invention is used as a grease additive, the polar network of this hybrid surface can generate strong hydrogen bond crosslinking and physical entanglement with the soap-based thickener fibers in the grease. This specific interaction not only significantly improves the colloidal stability and mechanical stability of the grease system and suppresses oil separation under high shear extreme pressure conditions, but also promotes the rapid spread of the additive on the metal surface of the friction pair, forming a highly efficient anti-wear layer with a dynamic repair synergistic effect of "grease-film," thereby extending the service life of the grease in harsh environments by several times.

[0025] 3. The process is green and safe, and has strong applicability: This invention completely eliminates flammable, explosive, and highly toxic gaseous phosphorus sources, and also avoids the generation of phosphorus-containing wastewater; the core ionic liquid modification process has extremely low volatility, excellent thermal stability, and mild reaction conditions, making it suitable for various copper-based nanomaterials, perfectly matching the development trend of green chemistry. Attached Figure Description

[0026] Figure 1 This is a schematic diagram illustrating the working mechanism of the preparation method of the present invention.

[0027] Figure 2 The image shows the microstructure of the composite nano-lubricant additive based on an ionic liquid precursor prepared in Example 1 of this invention under a transmission electron microscope.

[0028] Figure 3 The energy dispersive X-ray spectral elemental mapping diagram of the composite nano-lubricating additive based on ionic liquid precursor prepared in Example 1 of the present invention.

[0029] Figure 4 Comparative images of ball wear scars after four-ball friction and wear tests using the products prepared in Example 1, Comparative Example 1, and Comparative Example 2 as additives. Detailed Implementation

[0030] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0031] like Figure 1As shown, the composite nano-lubricant additive based on the ionic liquid precursor consists of a copper sulfide / chitosan composite precursor and a phosphorus-containing ionic liquid in a mass ratio of 1:5~10. The copper sulfide / chitosan composite precursor includes chitosan, a soluble copper salt, and a sulfur source in a mass ratio of 1:0.2~0.3:0.1~0.15. The soluble copper salt is copper chloride or copper sulfate, the sulfur source is thiourea or sodium sulfide nonahydrate, and the phosphorus-containing ionic liquid is a solution obtained by mixing trihexyl(tetradecyl)phosphine bicyclo(2,4,4-trimethylpentyl)phosphine or 1-butyl-3-methylimidazolium hexafluorophosphate with anhydrous ethanol or acetone at a solid-liquid ratio of 1g:2~3ml.

[0032] The following examples illustrate the preparation method of composite nano-lubricating additives based on ionic liquid precursors, and the performance of the composite nano-lubricating additives based on ionic liquid precursors prepared by the present invention is analyzed by comparison with comparative examples.

[0033] Example 1

[0034] This embodiment provides a method for preparing a composite nano-lubricating additive based on an ionic liquid precursor, comprising the following steps:

[0035] S1. Weigh 2.0 g of chitosan with a degree of deacetylation of 90% and dissolve it in 100 mL of a 1% (v / v) dilute acetic acid aqueous solution. Stir magnetically for 3 hours at room temperature to form a uniform and transparent base solution. Add 0.5 g of copper chloride dihydrate to the base solution and stir for 1.5 hours. Then, add dropwise 50 mL of a sulfur source solution with a thiourea concentration of 5 g / L (containing 0.25 g of thiourea) to maintain the mass ratio of chitosan, copper chloride dihydrate, and thiourea at 1:0.25:0.125, and stir until homogeneous to form a mixture. Transfer the mixture to a reactor and perform a hydrothermal reaction at 140°C for 10 hours. After natural cooling, collect the precipitate and wash it with deionized water to remove residual impurities. Mix the remaining precipitate with deionized water at a mass ratio of 1:5 and disperse to obtain a uniformly dispersed suspension. The suspension was sprayed into liquid nitrogen through an atomizing nozzle and frozen into microdroplets using spray freeze-drying technology. The microdroplets were then placed in a freeze dryer and frozen at -50°C and a vacuum of 5 Pa for 48 hours. Free water was removed by the sublimation of ice, thus obtaining a copper sulfide / chitosan composite precursor powder with high specific surface area and rich porous structure.

[0036] S2. Weigh 2.0g of copper sulfide / chitosan composite precursor powder and place it in a vacuum drying oven. Dry it under vacuum at 80°C for 12 hours to further remove any bound water, trace amounts of residual solvent and other impurities that may remain deep in the pores, ensuring that the surface and internal pores of the precursor are completely dry and in an activated state.

[0037] S3. Weigh 10.0 g of trihexyl(tetradecyl)phosphine bicyclic (2,4,4-trimethylpentyl)phosphine and add it to 30 mL of anhydrous ethanol to prepare a phosphorus-containing ionic liquid. Disperse 2.0 g of copper sulfide / chitosan composite precursor powder, treated in step S2, into the liquid. Then, ultrasonically stir for 30 minutes to promote deep penetration of the phosphorus-containing ionic liquid into the precursor nanostructure. After ultrasonic stirring, continuously stir magnetically at 90°C for 8 hours to ensure sufficient time for the internally penetrated phosphorus-containing ionic liquid to undergo a complete in-situ binding reaction with the precursor framework. Then, allow it to cool naturally, centrifuge, discard the supernatant, add anhydrous ethanol, ultrasonically stir again, and centrifuge again. Repeat the washing process three times, and finally vacuum dry at 60°C for 12 hours to obtain a composite nano-lubricant additive based on the ionic liquid precursor, namely, ionic liquid modified CuS / P.

[0038] Example 2

[0039] S1. Weigh 2.0 g of chitosan with a degree of deacetylation of 90% and dissolve it in 100 mL of a 1% (v / v) dilute acetic acid aqueous solution. Stir magnetically for 3 hours at room temperature to form a uniform and transparent base solution. Add 0.4 g of copper sulfate to the base solution and stir for 1.5 hours. Then, add dropwise 40 mL of a 5 g / L sodium sulfide nonahydrate sulfur source solution (containing 0.20 g of sodium sulfide nonahydrate) to maintain the mass ratio of chitosan, copper sulfate, and sodium sulfide nonahydrate at 1:0.2:0.1, and stir until homogeneous to form a mixture. Transfer the mixture to a reactor and perform a hydrothermal reaction at 120°C for 12 hours. After natural cooling, collect the precipitate and wash it with deionized water to remove residual impurities. Mix the remaining precipitate with deionized water at a mass ratio of 1:5 and disperse to obtain a uniformly dispersed suspension. The suspension was sprayed into liquid nitrogen through an atomizing nozzle and frozen into microdroplets using spray freeze-drying technology. The microdroplets were then placed in a freeze dryer and frozen at -50°C and a vacuum of 5 Pa for 48 hours. Free water was removed by the sublimation of ice, thus obtaining a copper sulfide / chitosan composite precursor powder with high specific surface area and rich porous structure.

[0040] S2. Weigh 2.0g of copper sulfide / chitosan composite precursor powder and place it in a vacuum drying oven. Dry it under vacuum at 60°C for 24 hours to further remove any bound water, trace amounts of residual solvent and other impurities that may remain deep in the pores, ensuring that the surface and internal pores of the precursor are completely dry and in an activated state.

[0041] S3. Weigh 20.0 g of 1-butyl-3-methylimidazolium hexafluorophosphate and add it to 40 mL of acetone to prepare a phosphorus-containing ionic liquid. Disperse 2.0 g of copper sulfide / chitosan composite precursor powder (treated in step S2) into the liquid. Then, ultrasonically stir for 20 minutes to promote deep penetration of the phosphorus-containing ionic liquid into the precursor nanostructure. After ultrasonic stirring, continuously stir magnetically at 100°C for 4 hours to ensure sufficient time for the internally penetrated phosphorus-containing ionic liquid to undergo a complete in-situ binding reaction with the precursor framework. Then, allow it to cool naturally, centrifuge, discard the supernatant, add acetone, ultrasonically stir again, and centrifuge again. Repeat the washing process four times. Finally, vacuum dry at 80°C for 10 hours to obtain a composite nano-lubricant additive based on the ionic liquid precursor.

[0042] Example 3

[0043] S1. Weigh 2.0 g of chitosan with a degree of deacetylation of 90% and dissolve it in 100 mL of a 1% (v / v) dilute acetic acid aqueous solution. Stir magnetically for 3 hours at room temperature to form a uniform and transparent base solution. Add 0.6 g of copper sulfate to the base solution and stir for 1.5 hours. Then, add dropwise 60 mL of a thiourea source solution with a concentration of 5 g / L (containing 0.30 g of thiourea) to maintain the mass ratio of chitosan, copper sulfate, and thiourea at 1:0.3:0.15, and stir until homogeneous to form a mixture. Transfer the mixture to a reactor and perform a hydrothermal reaction at 160°C for 8 hours. After natural cooling, collect the precipitate and wash it with deionized water to remove residual impurities. Mix the remaining precipitate with deionized water at a mass ratio of 1:5 and disperse to obtain a uniformly dispersed suspension. The suspension was sprayed into liquid nitrogen through an atomizing nozzle and frozen into microdroplets using spray freeze-drying technology. The microdroplets were then placed in a freeze dryer and frozen at -50°C and a vacuum of 5 Pa for 48 hours. Free water was removed by the sublimation of ice, thus obtaining a copper sulfide / chitosan composite precursor powder with high specific surface area and rich porous structure.

[0044] S2. Weigh 2.0g of copper sulfide / chitosan composite precursor powder and place it in a vacuum drying oven. Dry it at 70°C for 18 hours to further remove any bound water, trace amounts of residual solvent and other impurities that may remain deep in the pores, ensuring that the surface and internal pores of the precursor are completely dry and in an activated state.

[0045] S3. Weigh 16.0 g of trihexyl(tetradecyl)phosphine bicyclic (2,4,4-trimethylpentyl)phosphine and add it to 35 mL of anhydrous ethanol to prepare a phosphorus-containing ionic liquid. Disperse 2.0 g of copper sulfide / chitosan composite precursor powder, treated in step S2, into the liquid. Then, ultrasonically stir for 25 minutes to promote deep penetration of the phosphorus-containing ionic liquid into the nanostructure. After ultrasonic stirring, continuously stir magnetically at 95°C for 6 hours to ensure sufficient time for the internally penetrated phosphorus-containing ionic liquid to undergo a complete in-situ binding reaction with the precursor framework. Then, allow it to cool naturally, centrifuge, discard the supernatant, add anhydrous ethanol, ultrasonically stir again, and centrifuge again. Repeat the washing process 5 times. Finally, vacuum dry at 70°C for 11 hours to obtain a composite nano-lubricant additive based on the ionic liquid precursor.

[0046] Comparative Example 1

[0047] The difference between this comparative example and Example 1 is that step S1 is not performed, and the copper sulfide / chitosan composite precursor powder is replaced with nano copper oxide (CuO) precursor, that is, nano copper oxide (CuO) is directly selected as the precursor, and the final product is obtained by in-situ modification with phosphorus-containing ionic liquid, namely ionic liquid modified CuO / P.

[0048] This comparative example aims to verify the applicability and performance improvement effect of the in-situ modification process of phosphorus-containing ionic liquid of the present invention on different types of copper-based precursors.

[0049] Comparative Example 2

[0050] Steps S1 and S2 are the same as in Example 1, that is, the copper sulfide / chitosan composite precursor of Example 1 is used; Step S3 is as follows: 2.0g of copper sulfide / chitosan composite precursor powder after step S2 is weighed and dispersed in 100ml of 10% sodium hexametaphosphate aqueous solution. Then, it is ultrasonically stirred for 30 minutes, then magnetically stirred continuously at 90°C for 8 hours, then naturally cooled, centrifuged, the supernatant is discarded, anhydrous ethanol is added, ultrasonically stirred again and centrifuged again, then washed 3 times, and finally vacuum dried at 60°C for 12 hours to obtain the final product, that is, the traditional inorganic aqueous phase preparation of CuS / P.

[0051] This comparative example uses a traditional inorganic aqueous phosphate modification method to prepare additives, aiming to demonstrate the superiority of the process of this invention in overcoming interfacial resistance and improving extreme pressure lubrication performance.

[0052] like Figure 2As shown, the microstructure of the composite nano-lubricant additive based on the ionic liquid precursor prepared in Example 1 was observed by transmission electron microscopy (TEM). The results showed that the composite nanomaterial exhibited a regular spherical or near-spherical porous structure, with monomer particle sizes distributed between 100 and 200 nanometers, and the framework network showed no collapse, proving that the mild phosphorus-containing ionic liquid modification process did not damage the original framework of the precursor. Figure 3 As shown, combined with energy dispersive X-ray spectroscopy (EDS) elemental mapping analysis, it can be observed that the three characteristic elements, phosphorus (P), sulfur (S), and copper (Cu), exhibit a highly uniform distribution throughout the entire spherical or near-spherical porous structure, both inside and on its outer surface. This confirms that the low interfacial tension of the phosphorus-containing ionic liquid in this invention can effectively overcome the resistance of the hydrophobic interface, acting as a "molecular penetrant" to penetrate deep into the precursor, achieving comprehensive, deep, and uniform surface modification from the surface to the interior.

[0053] This invention compares the anti-wear and friction-reducing properties of three lubricants obtained by adding the products prepared in Example 1, Comparative Example 1, and Comparative Example 2 as additives to polyalphaolefin (PAO) base oil through a four-ball friction and wear test. The ball material used in the test was GCr15 steel, and the material of the parts rubbing against the balls was also GCr15 steel. The optical microscope microscopic comparison of the ball wear scars after the four-ball friction and wear test of the three lubricants is shown below. Figure 4As shown, the lubricant using the additive (ionic liquid modified CuS / P) of Example 1 of this invention exhibits excellent extreme pressure anti-wear performance. Its corresponding ball wear scar surface is the smoothest and the wear scar diameter is the smallest (only 587.2 μm). This indicates that in-situ modification with phosphorus-containing ionic liquid has a greater advantage in friction reduction and anti-wear than traditional inorganic aqueous phosphate modification. It utilizes the low interfacial tension of ionic liquid to achieve comprehensive deep modification from the surface to the interior, and constructs a hybrid lubrication interface with stronger chemical bonding and less prone to peeling under high shear force of friction pair. The ionic liquid modified CuO / P of Comparative Example 1 still has a significant performance improvement compared to the unmodified material of Comparative Example 2. This strongly demonstrates that the in-situ modification process with phosphorus-containing ionic liquid can significantly improve and dominate the lubrication performance of the material, showing strong process universality. In contrast, Comparative Example 2 (CuS / P prepared by traditional inorganic aqueous phase), which also uses copper sulfide / chitosan composite precursors but is modified with traditional inorganic aqueous phosphate, has the largest wear scar diameter and a large number of rough and extremely deep mechanical grooves on the surface of the wear scars. The core reason for this phenomenon is that due to the extremely high surface tension of the aqueous system, the modifier is unable to overcome the steric hindrance and hydrophobic interface resistance inside the precursor, which prevents the phosphorus source from penetrating into the deep interior of the composite system. Only a weak inorganic phosphate adsorption layer is formed on the outer surface of the material. The chemical bonding force between the inorganic phosphate and the interface is weak, presenting a non-uniform modification state of "surface film and internal vacancy". The physical adsorption film formed is very easy to peel off under the high shear force of the friction pair, resulting in rapid lubrication failure and inability to provide stable and long-term boundary protection. The comparison clearly shows that the hybrid lubrication interface constructed in situ through the phosphorus-containing ionic liquid modification process has unparalleled advantages over traditional aqueous phosphate modification technology in terms of bonding strength, anti-detachment ability, and anti-wear and friction reduction performance under harsh working conditions.

Claims

1. A composite nano-lubricant additive based on an ionic liquid precursor, characterized in that: It is composed of a copper sulfide / chitosan composite precursor with a mass ratio of 1:5~10 and a phosphorus-containing ionic liquid; the copper sulfide / chitosan composite precursor includes chitosan, soluble copper salt and sulfur source with a mass ratio of 1:0.2~0.3:0.1~0.

15.

2. The composite nano-lubricant additive based on an ionic liquid precursor according to claim 1, characterized in that: The soluble copper salt is copper chloride dihydrate or copper sulfate.

3. The composite nano-lubricant additive based on an ionic liquid precursor according to claim 1, characterized in that: The sulfur source is thiourea or sodium sulfide nonahydrate.

4. The composite nano-lubricant additive based on an ionic liquid precursor according to claim 1, characterized in that: The phosphorus-containing ionic liquid is a solution obtained by mixing trihexyl (tetradecyl)phosphine bicyclic (2,4,4-trimethylpentyl)phosphine or 1-butyl-3-methylimidazolium hexafluorophosphate with anhydrous ethanol or acetone at a solid-liquid ratio of 1g:2~3ml.

5. The method for preparing the composite nano-lubricating additive based on the ionic liquid precursor according to any one of claims 1 to 4, characterized in that: Includes the following steps: S1. Preparation of copper sulfide / chitosan composite precursor: Chitosan powder was dissolved in dilute acetic acid solution and stirred evenly to form a base solution; soluble copper salt and sulfur source were added to the base solution in sequence and stirred evenly to form a mixture; the mixture was placed in a reaction vessel for hydrothermal reaction; after natural cooling, the precipitate was collected and washed with deionized water; the precipitate retained after washing was mixed with deionized water and dispersed to obtain a uniformly dispersed suspension; the suspension was spray-frozen-dried to obtain copper sulfide / chitosan composite precursor powder; S2. Place the copper sulfide / chitosan composite precursor powder in a vacuum drying oven for vacuum drying; S3. The copper sulfide / chitosan composite precursor powder treated in step S2 is dispersed in a phosphorus-containing ionic liquid, and ultrasonic stirring and magnetic stirring are performed in sequence to carry out in-situ interfacial reaction. Then, it is naturally cooled, centrifuged, the supernatant is discarded, volatile washing solvent is added, ultrasonic stirring is performed again and centrifuged again, and then the washing is repeated 3 to 5 times. Finally, it is vacuum dried at 60 to 80°C for 10 to 12 hours to obtain a composite nano lubricant additive based on the ionic liquid precursor.

6. The method for preparing the composite nano-lubricating additive based on the ionic liquid precursor according to claim 5, characterized in that: The chitosan powder and dilute acetic acid solution were mixed at a solid-liquid ratio of 1g:50ml.

7. The preparation method of the composite nano-lubricating additive based on the ionic liquid precursor according to claim 6, characterized in that: The volume concentration of the dilute acetic acid solution is 1%.

8. The method for preparing the composite nano-lubricating additive based on the ionic liquid precursor according to claim 5, characterized in that: The hydrothermal reaction is carried out at a temperature of 120-160°C for 8-12 hours, the vacuum drying temperature of the copper sulfide / chitosan composite precursor powder is 60-80°C for 12-24 hours, the ultrasonic stirring time is 20-30 minutes, and the magnetic stirring temperature is 90-100°C for 4-8 hours.

9. The method for preparing the composite nano-lubricating additive based on the ionic liquid precursor according to claim 5, characterized in that: The precipitate was mixed with deionized water at a mass ratio of 1:

5.

10. The method for preparing the composite nano-lubricating additive based on the ionic liquid precursor according to claim 5, characterized in that: The volatile washing solvent is acetone or anhydrous ethanol.

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