Bionic liquid lubricant capable of forming multi-layer super-lubricating film on surface of high-roughness steel and preparation method of bionic liquid lubricant

Abstract

The invention discloses a bionic liquid lubricant capable of forming a multilayer super-lubricating film on the surface of high-roughness steel and a preparation method of the bionic liquid lubricant, and relates to the technical field of lubricant formulas and preparation methods, and the bionic liquid lubricant comprises a mixed liquid prepared from water, polyethylene glycol, phytic acid modified graphene oxide and graphene oxide as raw materials. The phytic acid modified graphene oxide and the unmodified graphene oxide are compounded to serve as a synergistic additive, a rapid chemical adsorption layer is constructed through the strong chelation of phytic acid groups and iron ions on the steel surface, and the unmodified graphene oxide is arranged in situ under shear stress to form a low-resistance shear layer; and polyethylene glycol provides a three-dimensional hydrogen bond network supporting layer, and the three layers are coupled to form a multi-layer super-lubricating film structure, so that the purposes that the time is shortened on the surface of the high-roughness engineering steel friction pair, macroscopic super-lubricity is realized, the steady-state friction coefficient is as low as 0.006-0.007, and the bearing capacity breaks through 600 MPa are achieved.

Description

Technical Field

[0001] This invention relates to the technical field of lubricant formulation and preparation methods, specifically to a biomimetic liquid lubricant capable of forming a multilayer super-lubricating film on a high-roughness steel surface and its preparation method. Background Technology

[0002] Friction and wear are key causes of energy loss and component failure in mechanical systems. Liquid superlubricity technology (with a friction coefficient of 0.001 or even lower) is an emerging technology that can significantly reduce friction and wear of friction pairs. Li et al. found that high-hardness ultra-smooth material surfaces (Ra < 10 nm, such as sapphire and silicon nitride) can achieve macroscopic superlubricity under the lubrication of acid groups and polyhydroxy alcohol solutions through the combined action of the Stern layer, hydrogen bond network layer and free bilayer (Langmuir, 2011, 27(15): 9413-9417; Langmuir 2013, 29, 5239-5245.). Subsequently, research revealed that when two-dimensional nanomaterials (such as graphene oxide, black phosphorus, hexagonal boron nitride, and transition metal carbides) are used as lubricating additives, high load-bearing superlubricity at the GPa level can be achieved on high-hardness, ultra-smooth surfaces (Friction, 2023, 11(3): 369-382; NanoResearch, 2025, 18(4): 94907294.), but it is still difficult to achieve high load-bearing superlubricity (final contact stress < 330 MPa) on highly rough engineering steel surfaces (Ra > 30 nm) (Carbon, 2024, 226: 119226; Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2016, 489: 400-406.). This is because two-dimensional nanomaterials are easily sheared off on highly rough surfaces, making it difficult to form a low-shear superlubricating film under high load conditions.

[0003] In nature, biological friction systems (such as articular cartilage and teeth) achieve efficient lubrication through multilayer film structures. Inspired by this, the development of a biomimetic lubricant that forms a multilayer lubricating film with excellent shear resistance on the surface of high-roughness engineering steel, achieving high load-bearing superlubricity, is of great significance for the industrial application of liquid superlubricating systems. Summary of the Invention

[0004] The purpose of this invention is to provide a biomimetic liquid lubricant that can form a multi-layer super-lubricating film on a high-roughness steel surface and its preparation method. By designing a lubricant that can form a multi-layer lubricating film structure, the problem of insufficient super-lubricating load-bearing capacity of existing lubricants on high-roughness engineering steel surfaces can be solved.

[0005] First, embodiments of the present invention provide a biomimetic liquid lubricant capable of forming a multilayer super-lubricating film on a high-roughness steel surface, comprising a mixed liquid prepared from water, polyethylene glycol, phytic acid-modified graphene oxide, and graphene oxide as raw materials.

[0006] This invention uses phytic acid-modified graphene oxide and unmodified graphene oxide as synergistic additives. The strong chelation between phytic acid groups and iron ions on the steel surface constructs a rapid chemical adsorption layer. Unmodified graphene oxide arranges itself in situ under shear stress to form a low-resistance shear layer. Polyethylene glycol provides a three-dimensional hydrogen bond network support layer. The three are coupled to form a multi-layer super-lubricating film structure, achieving macroscopic super-lubricity, a steady-state friction coefficient as low as 0.006~0.007, and a load-bearing capacity exceeding 600 MPa on the friction pair surface of high-roughness engineering steel in a shortened time.

[0007] As an optional implementation, the mass ratio of water, polyethylene glycol, phytic acid-modified graphene oxide, and graphene oxide is 45~55:45~55:0.025~0.0375:0.025~0.0375.

[0008] Secondly, this invention also provides a method for preparing a biomimetic liquid lubricant capable of forming a multilayer super-lubricating film on a high-roughness steel surface, comprising the following steps: S1: Phytic acid-modified graphene oxide powder was prepared by modifying graphene oxide powder. S2: Disperse graphene oxide powder and phytic acid-modified graphene oxide powder in water to obtain a mixed graphene liquid; S3: Polyethylene glycol is added to the mixed graphene liquid and mixed to obtain a lubricant.

[0009] As an optional implementation, the modification of graphene oxide described in S1 includes: S11: Graphene oxide is dispersed in water to form a dispersion; S12: Add phytic acid aqueous solution to the dispersion, mix and heat to allow phytic acid to react with graphene oxide; S13: Filter the liquid after the reaction, wash the lower solid layer, and collect the solid. S14: The solid is dried to obtain phytic acid modified graphene oxide powder.

[0010] As an optional implementation, the mass ratio of graphene to water in S11 is 0.018 to 0.023:10.

[0011] As an optional implementation, the concentration of the phytic acid aqueous solution in S12 is 65-75 wt%, and the mass ratio of the phytic acid aqueous solution to graphene oxide is 1-2:1.

[0012] As an optional implementation, the heating in S12 is water bath heating, and the heating temperature is 50~70°C.

[0013] As an optional implementation, the filtration in S13 includes centrifuging the reacted liquid at 10000~13000 r / min for 30~45 min and discarding the supernatant; The washing of the lower solid layer includes washing the lower solid layer with deionized water, then centrifuging again at 10000~13000 r / min for 8~12 min, discarding the supernatant, and repeating the cycle 2~4 times.

[0014] As an optional implementation, the drying temperature in S14 is 50~70°C, and the drying time is 1.5~2.5h.

[0015] As an optional implementation, the graphene oxide in S1 and S2 has a thickness of 0.8–1.2 nm and a sheet diameter of 0.5–4 μm; The polyethylene glycol in S3 has a molecular weight of 8000 to 12000, and the water includes deionized water.

[0016] Compared with the prior art, the embodiments of the present invention have the following advantages and beneficial effects: 1. The biomimetic liquid lubricant provided by this invention can achieve macroscopic superlubricity on the surface of highly rough engineering steel friction pairs, with a short break-in period and a high load-bearing capacity of >600 MPa. This is because: the phytic acid groups on phytic acid-modified graphene oxide have a strong ability to chelate metal ions, forming coordination bonds with iron ions on the steel surface. During lubrication, they can first adsorb onto the stainless steel surface, forming a stable adsorption layer, reducing direct contact between the rough peaks of the friction pair; subsequently, the unmodified graphene oxide reorganizes under shear stress to form a shear layer; in addition, polyethylene glycol can provide a large number of hydrogen bond network layers. During lubrication, the above-mentioned multi-layered lubricating film structure can significantly improve the load-bearing capacity of the lubricating film and reduce friction and wear.

[0017] 2. Applying the biomimetic liquid lubricant prepared in the embodiments of the present invention to a friction pair of engineering steel with a surface roughness Ra > 60 nm can reduce the coefficient of friction to approximately 0.006~0.007 and increase the load-bearing capacity to approximately 600 MPa. Furthermore, the preparation method of the biomimetic liquid lubricant is simple, requires a small amount of nano-additives, has low operating costs, is easy to mass-produce, and is environmentally friendly, avoiding environmental pollution. Currently, macroscopic superlubricity can be achieved on the surface of engineering steel with a load-bearing capacity greater than 300 MPa, and the surface roughness of the engineering steel is approximately 10 nm. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and therefore should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort. In the drawings: Figure 1 This is an atomic force microscope image of phytic acid-modified graphene oxide in Example 1 of the present invention, wherein... Figure 1 a is a three-dimensional morphology image of phytic acid-modified graphene oxide nanosheets. Figure 1 b is a height cross-sectional view of phytic acid-modified graphene oxide nanosheets; Figure 2 This is a graph showing the change in the friction coefficient of the biomimetic liquid lubricant prepared in Example 1 of this invention. Figure 3 This is a laser confocal image of the wear region of the friction pair of the biomimetic liquid lubricant prepared in Example 1 of the present invention, wherein... Figure 3 a is a diagram showing the wear diameter of the friction ball. Figure 3 b is the wear diameter diagram of the friction block; Figure 4 The friction coefficient variation curve of the biomimetic liquid lubricant prepared in Example 4 of this invention is shown. Figure 5 The friction coefficient variation curve of the biomimetic liquid lubricant prepared in Example 5 of this invention; Figure 6 The friction coefficient variation curve of the biomimetic liquid lubricant prepared in Example 6 of this invention; Figure 7 The friction coefficient variation curve of the biomimetic liquid lubricant prepared in Example 7 of this invention; Figure 8 The friction coefficient variation curve of the biomimetic liquid lubricant prepared in Comparative Example 1 is shown. Figure 9 This is a laser confocal image of the wear region of the friction ball obtained by the biomimetic liquid lubricant prepared in Comparative Example 1. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments.

[0020] Therefore, the detailed description of the embodiments of the present invention provided below is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0021] This invention provides a method for preparing a biomimetic liquid lubricant capable of forming a multilayer superlubricating film on a high-roughness steel surface (Ra > 60 nm), comprising the following: (1) Preparation of phytic acid modified graphene oxide Step 1: Disperse graphene oxide in water using ultrasound, with a mass ratio of graphene oxide to water of 0.018–0.023:10. Sonicate for 25–35 min to form a dispersion. Step 2: Add 65-75 wt% phytic acid aqueous solution to the dispersion, with the mass ratio of phytic acid aqueous solution to graphene oxide being 1-2:1, and continue ultrasonic treatment for 25-35 min; Step 3: Heat the solution obtained in Step 2 in a water bath at a temperature of 50-70℃, while simultaneously stirring with a mechanical magnetic force for 2-4 hours at a speed of 300-700 r / min, so that the phytic acid and graphene oxide can react fully.

[0022] Step 4: Centrifuge the solution obtained in Step 3 at 10,000-13,000 r / min for 30-45 min, discard the supernatant, wash the lower solid with deionized water, and then centrifuge again under the same conditions for 8-12 min, discard the supernatant, and repeat this cycle 2-4 times to wash away excess phytic acid and avoid the lubricant having too low a pH and corroding the metal. Step 5: Dry the precipitate obtained in Step 4 at a temperature of 50-70℃ for 1.5-2.5 hours to obtain phytic acid-modified graphene oxide powder.

[0023] (2) Preparation of biomimetic liquid lubricant Step 1: Disperse the above phytic acid modified graphene oxide powder in water at a mass ratio of 0.025-0.0375:45-55, mix and then sonicate for 10-30 minutes until uniformly dispersed to obtain a dispersed liquid; Step 2: Add graphene oxide powder to the liquid in Step 1. The mass ratio of graphene oxide to water is 0.025-0.0375:45-55. Disperse the mixture by ultrasonication for 10-30 min. Step 3: Add polyethylene glycol to the liquid from Step 2, with a polyethylene glycol to water mass ratio of 4.5-5.5:4.5-5.5. Stir mechanically and magnetically for 0.8-2 hours at a stirring speed of 300-700 r / min, and then sonicate for 10-30 minutes to obtain a biomimetic liquid lubricant.

[0024] Preferably, the graphene oxide has a thickness of 0.8–1.2 nm and a sheet diameter of 0.5–4 μm; the polyethylene glycol has a molecular weight of 8000–12000; and the water includes deionized water.

[0025] Example 1: This embodiment of the invention provides a method for preparing a biomimetic liquid lubricant capable of forming a multilayer super-lubricating film on a high-roughness steel surface, comprising the following: (1) Preparation of phytic acid modified graphene oxide Step 1: Disperse graphene oxide in water using ultrasound at a mass ratio of 0.02:10. Sonicate for 30 min to form a dispersion. Step 2: Add 70wt% phytic acid aqueous solution to the dispersion, with a mass ratio of phytic acid aqueous solution to graphene oxide of 1:1, and continue ultrasonic treatment for 30 min. Step 3: The solution obtained in Step 2 is heated in a water bath at 70°C, and simultaneously mechanically and magnetically stirred for 3 hours at a speed of 600 r / min to ensure that phytic acid and graphene oxide react fully.

[0026] Step 4: Centrifuge the solution obtained in Step 3 at 12000 r / min for 40 min, discard the supernatant, wash the lower solid with deionized water, and then centrifuge again for 10 min under the same conditions, discard the supernatant, and repeat this cycle 3 times to wash away excess phytic acid and avoid the lubricant having too low a pH and corroding the metal. Step 5: The precipitate obtained in Step 4 is dried at a temperature of 60℃ for 2 hours to obtain phytic acid modified graphene oxide powder.

[0027] The prepared phytic acid-modified graphene oxide powder was scanned, and the scanning results are as follows: Figure 1 As shown, by Figure 1 It can be seen that phytic acid was successfully grafted onto the surface of graphene oxide, and the modified nanosheets have good exfoliation state and dispersion stability.

[0028] (2) Preparation of biomimetic liquid lubricant Step 1: Disperse the above phytic acid modified graphene oxide powder in water at a mass ratio of 0.0375:50, mix and then sonicate for 20 min until uniformly dispersed to obtain a dispersion solution; Step 2: Add graphene oxide powder to the liquid in Step 1. The mass ratio of graphene oxide to water is 0.0375:50. Disperse the mixture by ultrasonication for 30 min. Step 3: Add polyethylene glycol to the liquid from Step 2, with a polyethylene glycol to water mass ratio of 1:1. Stir mechanically and magnetically for 1 hour at a stirring speed of 500 r / min, and then sonicate for 20 minutes to obtain a biomimetic liquid lubricant.

[0029] The tribological properties of the biomimetic liquid lubricant were tested using a ball-and-disc friction and wear testing machine (UMT Tribolab). The upper friction pair consisted of a 10 mm diameter 440C ball, and the lower friction pair consisted of a 440C block. The reciprocating friction test was set with a load of 10 N, a sliding frequency of 4 Hz, a sliding distance of 4 mm, and a test time of 30 min. The coefficient of friction variation of the biomimetic liquid lubricant prepared in this embodiment is shown below. Figure 2 As shown, the friction coefficient decreases to 0.01 in approximately 110 s, achieving macroscopic superlubricity, and the final friction coefficient is approximately 0.0065. The wear region of the friction pair was observed using a laser confocal microscope, and the results are as follows... Figure 3 As shown, the wear diameter of the upper sample on the grinding ball is 145 μm, and that of the lower sample is 143 μm. The calculated final contact stress reaches 602 MPa, indicating that the biomimetic liquid lubricant achieves high load-bearing capacity while rapidly entering superlubricity.

[0030] Example 2: This embodiment of the invention provides a method for preparing a biomimetic liquid lubricant capable of forming a multilayer super-lubricating film on a high-roughness steel surface, comprising the following: (1) Preparation of phytic acid modified graphene oxide Step 1: Disperse graphene oxide in water using ultrasound at a mass ratio of 0.018:10 and sonicate for 25 min to form a dispersion. Step 2: Add 65 wt% phytic acid aqueous solution to the dispersion, with a phytic acid aqueous solution to graphene oxide mass ratio of 1.5:1, and continue ultrasonic treatment for 2 min; Step 3: The solution obtained in Step 2 is heated in a water bath at 50°C, and simultaneously mechanically and magnetically stirred for 4 hours at a speed of 300 r / min to ensure that phytic acid and graphene oxide react fully.

[0031] Step 4: Centrifuge the solution obtained in Step 3 at 10000 r / min for 40 min, discard the supernatant, wash the lower solid with deionized water, and then centrifuge again under the same conditions for 8 min, discard the supernatant, and repeat this cycle twice to wash away excess phytic acid and avoid the lubricant having too low a pH and corroding the metal. Step 5: The precipitate obtained in Step 4 is dried at a temperature of 50°C for 2.5 hours to obtain phytic acid-modified graphene oxide powder.

[0032] (2) Preparation of biomimetic liquid lubricant Step 1: Disperse the above phytic acid modified graphene oxide powder in water at a mass ratio of 0.025:55, mix and then sonicate for 10 min until uniformly dispersed to obtain a dispersed liquid; Step 2: Add graphene oxide powder to the liquid in Step 1. The mass ratio of graphene oxide to water is 0.025:55. Disperse the mixture ultrasonically for 10 min. Step 3: Add polyethylene glycol to the liquid from Step 2, with a polyethylene glycol to water mass ratio of 45:55. Stir mechanically and magnetically for 0.8 hours at a stirring speed of 300 r / min, and then sonicate for 30 minutes to obtain a biomimetic liquid lubricant.

[0033] The tribological properties of the biomimetic liquid lubricant were tested using a ball-and-disc tribolab. The upper friction pair consisted of a 10 mm diameter 440C ball, and the lower friction pair consisted of a 440C block. The reciprocating friction test was set with a load of 10 N, a sliding frequency of 4 Hz, a sliding distance of 4 mm, and a test time of 30 min. The biomimetic liquid lubricant prepared in this embodiment of the invention exhibits a coefficient of friction below 0.01, achieving macroscopic superlubricity, but its load-bearing capacity is lower than that of Example 1.

[0034] Example 3: This embodiment of the invention provides a method for preparing a biomimetic liquid lubricant capable of forming a multilayer super-lubricating film on a high-roughness steel surface, comprising the following: (1) Preparation of phytic acid modified graphene oxide Step 1: Disperse graphene oxide in water using ultrasound at a mass ratio of 0.023:10 and sonicate for 35 min to form a dispersion. Step 2: Add 75wt% phytic acid aqueous solution to the dispersion, with a mass ratio of phytic acid aqueous solution to graphene oxide of 2:1, and continue ultrasonic treatment for 35 min; Step 3: The solution obtained in Step 2 is heated in a water bath at 60°C, and simultaneously mechanically and magnetically stirred for 2 hours at a speed of 700 r / min to ensure that phytic acid and graphene oxide react fully.

[0035] Step 4: Centrifuge the solution obtained in Step 3 at 13000 r / min for 30 min, discard the supernatant, wash the lower solid with deionized water, and then centrifuge again under the same conditions for 12 min, discard the supernatant, and repeat this cycle 4 times to wash away excess phytic acid and avoid the lubricant pH being too low and corroding the metal. Step 5: The precipitate obtained in Step 4 is dried at a temperature of 70°C for 1.5 hours to obtain phytic acid-modified graphene oxide powder.

[0036] (2) Preparation of biomimetic liquid lubricant Step 1: Disperse the above phytic acid modified graphene oxide powder in water at a mass ratio of 0.0375:45, mix and then sonicate for 30 min until uniformly dispersed to obtain a dispersed liquid; Step 2: Add graphene oxide powder to the liquid in Step 1. The mass ratio of graphene oxide to water is 0.0375:45. Disperse the mixture ultrasonically for 20 min. Step 3: Add polyethylene glycol to the liquid from Step 2, with a polyethylene glycol to water mass ratio of 55:45. Stir mechanically and magnetically for 2 hours at a stirring speed of 700 r / min, and then sonicate for 10 minutes to obtain a biomimetic liquid lubricant.

[0037] The tribological properties of the biomimetic liquid lubricant were tested using a ball-and-disc tribolab. The upper friction pair consisted of a 10 mm diameter 440C ball, and the lower friction pair consisted of a 440C block. The reciprocating friction test was set with a load of 10 N, a sliding frequency of 4 Hz, a sliding distance of 4 mm, and a test time of 30 min. The biomimetic liquid lubricant prepared in this embodiment of the invention exhibits a coefficient of friction below 0.01, achieving macroscopic superlubricity, but its load-bearing capacity is lower than that of Example 1.

[0038] Example 4: This embodiment of the invention provides a method for preparing a biomimetic liquid lubricant that can form a multilayer super-lubricating film on a high-roughness steel surface. The difference from Example 1 is that in “(1) Preparation of phytic acid modified graphene oxide”, the mass ratio of phytic acid aqueous solution to graphene oxide is 3:1, and the other steps remain unchanged.

[0039] The tribological properties of the biomimetic liquid lubricant were tested using a ball-and-disc friction and wear testing machine (UMT Tribolab). The upper friction pair consisted of a 10 mm diameter 440C ball, and the lower friction pair consisted of a 440C block. The reciprocating friction test was set with a load of 10 N, a sliding frequency of 4 Hz, a sliding distance of 4 mm, and a test time of 30 min. The coefficient of friction variation curve of the biomimetic liquid lubricant prepared in this embodiment is shown below. Figure 4As shown, the friction coefficient drops to 0.01 in about 200 s, achieving macroscopic superlubricity, and the final friction coefficient is about 0.007, with the final contact stress reaching 537 MPa.

[0040] Therefore, it can be seen that in Example 4, the excessive amount of phytic acid used in the surface modification of graphene oxide resulted in too many phytic acid groups on the surface of the phytic acid-modified graphene oxide, leading to stronger interlayer hydrogen bonding and greater shear force, which is not conducive to achieving superlubricity. Ultimately, the break-in period was extended to 200 s (compared to only 110 s in Example 1), and the load-bearing capacity decreased.

[0041] Example 5: This embodiment of the invention provides a method for preparing a biomimetic liquid lubricant that can form a multilayer super-lubricating film on a high-roughness steel surface. The difference from Example 1 is that in “(2) Preparation of biomimetic liquid lubricant”, the above-mentioned phytic acid modified graphene oxide powder is dispersed in water at a mass ratio of 0.0625:50; the mass ratio of graphene oxide to water is 0.0125:50, and the remaining steps remain unchanged.

[0042] The tribological properties of the biomimetic liquid lubricant were tested using a ball-and-disc friction and wear testing machine (UMT Tribolab). The upper friction pair consisted of 10 mm diameter 440C balls, and the lower friction pair consisted of 440C blocks. The reciprocating friction test was set with a load of 10 N, a sliding frequency of 4 Hz, a sliding distance of 4 mm, and a test time of 30 min. The coefficient of friction variation curve of the biomimetic liquid lubricant prepared in this embodiment is shown in the figure below. Figure 5 As shown, the friction coefficient drops to 0.01 in about 280 s, achieving macroscopic superlubricity, and the final friction coefficient is about 0.008, with the final contact stress reaching 566 MPa.

[0043] As can be seen, in Example 5, due to the excessive amount of modified graphene oxide and the insufficient amount of graphene oxide, the interlayer interaction of the graphene lubricating layer was too strong, and the shear force was high, resulting in a significantly prolonged break-in period of 280 s (Example 1 only required 110 s), a slight increase in the coefficient of friction, and a final load-bearing capacity of 566 MPa, which was 6% lower than that of Example 1 (602 MPa).

[0044] Example 6: This embodiment of the invention provides a method for preparing a biomimetic liquid lubricant that can form a multilayer super-lubricating film on a high-roughness steel surface. The difference from Example 1 is that in “(1) Preparation of phytic acid modified graphene oxide”, the mass ratio of phytic acid aqueous solution to graphene oxide is 0.5:1, while the other steps remain unchanged.

[0045] The tribological properties of the biomimetic liquid lubricant were tested using a ball-and-disc friction and wear testing machine (UMT Tribolab). The upper friction pair consisted of a 10 mm diameter 440C ball, and the lower friction pair consisted of a 440C block. The reciprocating friction test was set with a load of 10 N, a sliding frequency of 3 Hz, a sliding distance of 4 mm, and a test time of 15 min. The coefficient of friction variation curve of the biomimetic liquid lubricant prepared in this embodiment is shown in the figure below. Figure 6 As shown, the friction coefficient drops to 0.01 in about 410 s, achieving macroscopic superlubricity, and the final friction coefficient is about 0.008, with the final contact stress reaching 480 MPa.

[0046] Therefore, it can be seen that in Example 6, due to the insufficient amount of phytic acid and the reduction of the sliding frequency to 3 Hz, there were too few phytic acid groups on the surface of the phytic acid-modified graphene oxide, resulting in insufficient bonding ability of the adsorption layer and weakened hydrodynamic pressure effect. This led to a prolonged break-in period of 410 s (compared to only 110 s in Example 1), and a slight increase in the coefficient of friction. The decrease in load-bearing capacity is attributed to the fact that high loads easily cause shear failure in the unstable adsorption layer.

[0047] Example 7: This embodiment of the invention provides a method for preparing a biomimetic liquid lubricant that can form a multilayer super-lubricating film on a high-roughness steel surface. The difference from Example 1 is that in “(2) Preparation of biomimetic liquid lubricant”, the above-mentioned phytic acid modified graphene oxide powder is dispersed in water at a mass ratio of 0.0075:50; the mass ratio of graphene oxide to water is 0.0675:50, and the remaining steps remain unchanged.

[0048] The tribological properties of the biomimetic liquid lubricant were tested using a ball-and-disc friction and wear testing machine (UMT Tribolab). The upper friction pair consisted of a 10 mm diameter 440C ball, and the lower friction pair consisted of a 440C block. The reciprocating friction test was set with a load of 10 N, a sliding frequency of 3 Hz, a sliding distance of 4 mm, and a test time of 15 min. The coefficient of friction variation curve of the biomimetic liquid lubricant prepared in this embodiment is shown in the figure below. Figure 7 As shown, the friction coefficient drops to 0.01 in about 330 s, achieving macroscopic superlubricity, and the final friction coefficient is about 0.007, with the final contact stress reaching 517 MPa.

[0049] As can be seen, in Example 7, due to the insufficient amount of modified graphene oxide and the excessive amount of unmodified graphene oxide, the insufficient number of phytic acid groups led to the delayed formation of the chemical adsorption layer on the steel surface. Combined with the 3 Hz condition, this resulted in a weakened hydrodynamic pressure effect, and the break-in period was as long as 330 s (compared to only 110 s in Example 1). The load-bearing capacity was reduced to 517 MPa (a 14% decrease compared to Example 1).

[0050] Example 8: This embodiment of the invention provides a method for preparing a biomimetic liquid lubricant that can form a multilayer super-lubricating film on a high-roughness steel surface. The difference from Example 1 is that in “(2) Preparation of biomimetic liquid lubricant”, the mass ratio of polyethylene glycol to water is 3:4, and the other steps remain unchanged.

[0051] The tribological properties of the biomimetic liquid lubricant were tested using a ball-and-disc tribolab. The upper friction pair consisted of a 10 mm diameter 440C ball, and the lower friction pair consisted of a 440C block. The reciprocating friction test was set with a load of 10 N, a sliding frequency of 4 Hz, a sliding distance of 4 mm, and a test time of 30 min. The biomimetic liquid lubricant prepared in this embodiment of the invention exhibits a coefficient of friction below 0.01, achieving macroscopic superlubricity, but its load-bearing capacity is lower than that of Examples 1-3.

[0052] Therefore, it can be seen that in Example 8, due to the low content of polyethylene glycol, a sufficiently strong hydrogen bond network could not be constructed, and the reduced viscosity of the lubricant led to a weakening of the hydrodynamic effect, which mainly resulted in a certain degree of deterioration in the load-bearing capacity.

[0053] Example 9: This embodiment of the invention provides a method for preparing a biomimetic liquid lubricant that can form a multilayer super-lubricating film on a high-roughness steel surface. The difference from Example 1 is that in “(2) Preparation of biomimetic liquid lubricant”, the mass ratio of polyethylene glycol to water is 4:3, and the other steps remain unchanged.

[0054] The tribological properties of the biomimetic liquid lubricant were tested using a ball-and-disc tribolab (UMT Tribolab). The upper friction pair consisted of a 10 mm diameter 440C ball, and the lower friction pair consisted of a 440C block. The reciprocating friction test was set with a load of 10 N, a sliding frequency of 4 Hz, a sliding distance of 4 mm, and a test time of 30 min. The biomimetic liquid lubricant prepared in this embodiment of the invention ultimately reduced its coefficient of friction to below 0.01, achieving macroscopic superlubricity, but the coefficient of friction was higher than in Examples 1-3, and the final contact stress was reduced.

[0055] It can be seen that in Example 8, the high content of polyethylene glycol increased the solution viscosity and the shear force of the lubricating film, resulting in a certain degree of deterioration in the coefficient of friction and load-bearing capacity.

[0056] Comparative Example 1: A method for preparing a lubricant is provided, which differs from Example 1 in that the mass ratio of water to phytic acid-modified graphene oxide is 50:0.075, and it does not contain unmodified graphene oxide, while the remaining steps remain unchanged.

[0057] Using the same detection method as in Example 1, the friction coefficient variation curve is shown in the figure below. Figure 8As shown, the friction coefficient decreases to 0.01 in approximately 310 s, achieving macroscopic superlubricity, and the final friction coefficient is approximately 0.007. The wear region of the friction pair was observed using a laser confocal microscope, and the results are as follows... Figure 9 As shown, the wear diameter of the upper sample on the grinding ball is 157 μm, and the calculated final contact stress reaches 518 MPa.

[0058] As can be seen, in Comparative Example 1, the unmodified graphene oxide was missing, while the phytic acid-modified graphene oxide had increased shear force due to strong interlayer hydrogen bonding, resulting in a significantly prolonged break-in period of 310 s (compared to only 110 s in Example 1). The load-bearing capacity decreased to 518 MPa (a 14% decrease compared to Example 1), and laser confocal microscopy showed that the wear diameter of the friction ball increased to 157 μm (compared to 145 μm in Example 1), representing a 9% increase in wear.

[0059] Comparative Example 2: A method for preparing a lubricant is provided, which differs from Example 1 in that the mass ratio of water to graphene oxide is 50:0.075, and phytic acid-modified graphene oxide is not included, while the remaining steps remain unchanged.

[0060] Using the same testing method as in Example 1, the coefficient of friction decreased to 0.01 in about 410 s, achieving macroscopic superlubricity, and the final coefficient of friction was about 0.007, with the calculated final contact stress reaching 470 MPa.

[0061] As can be seen, Comparative Example 2 lacks modified graphene oxide, resulting in insufficient adsorption capacity of the adsorption layer. Graphene oxide requires a longer time to adsorb onto the surface of the friction pair, leading to a significant extension of the break-in period to 410 s (Example 1 only requires 110 s), and a reduction in load-bearing capacity.

[0062] Comparative Example 3: A method for preparing a lubricant is provided, which differs from Example 1 in that polyethylene glycol is replaced with polypropylene glycol, while the remaining steps remain unchanged.

[0063] Using the same testing method as in Example 1, when polyethylene glycol was replaced with polypropylene glycol, the lubrication system could not achieve macroscopic superlubricity due to the increased viscosity, and therefore its load-bearing capacity was not statistically analyzed.

[0064] Comparative Example 4: A method for preparing a lubricant is provided, which differs from Example 1 in that polyethylene glycol is replaced with ethylene glycol, while the remaining steps remain unchanged.

[0065] Using the same testing method as in Example 1, when polyethylene glycol was replaced with ethylene glycol, the lubrication system could not achieve macroscopic superlubricity under low-speed conditions due to its low viscosity, and therefore its load-bearing capacity was not statistically analyzed.

[0066] Comparative Example 5: An existing lubricant is provided, sourced from "Wear, 2021, 484: 204037.", which is a mixed solution of fructose and ethylene glycol, wherein the mass fraction of ethylene glycol is 50 wt% and the mass fraction of fructose is 50 wt%.

[0067] Comparative Example 6: An existing lubricant is provided, sourced from "Advanced Functional Materials, 2024, 34(9): 2310880.", which is a CA / CQDs-polyethylene glycol-water mixed solution, wherein the mass fraction of polyethylene glycol is 50 wt% and the mass fraction of CA / CQDs as an additive is 0.1 wt%.

[0068] Comparative Example 7: An existing lubricant is provided, sourced from "Carbon, 2024, 226: 119226.", which is a CGQDs-glycerol-water mixture, wherein the mass fraction of glycerol is 70 wt% and the mass fraction of CGQDs as an additive is 0.1 wt%.

[0069] Comparative Examples 1-7 were tested using the same method as in Example 1, and the test results are shown in Table 1: Table 1 project Time required to achieve superlubricity Final coefficient of friction Final contact stress Example 1 110 s 0.0065 602MPa Comparative Example 1 320 s 0.007 518MPa Comparative Example 2 410 s 0.007 470MPa Comparative Example 3 Not superslip / / Comparative Example 4 Not superslip / / Comparative Example 5 60 s 0.0062 410MPa Comparative Example 6 44 s 0.0052 304MPa Comparative Example 7 600 s 0.007 123MPa Comparing Example 1 and Comparative Example 1, it can be seen that when only phytic acid-modified graphene oxide is contained and unmodified graphene oxide is not contained, the phytic acid-modified graphene oxide lacks unmodified graphene oxide, and the shear force of the phytic acid-modified graphene oxide increases due to the strong interlayer hydrogen bonding, resulting in a significantly prolonged break-in period of 310 s (Example 1 only requires 110 s), and the load-bearing capacity decreases to 518 MPa (a 14% decrease compared to Example 1). Laser confocal microscopy shows that the wear diameter of the friction ball increases to 157 μm (Example 1 is 145 μm), and the wear increases by 9%.

[0070] As can be seen from the comparison between Example 1 and Comparative Example 2, when only unmodified graphene oxide is present, Comparative Example 2 lacks modified graphene oxide, resulting in insufficient adsorption capacity of the adsorption layer. Graphene oxide needs a longer time to adsorb onto the surface of the friction pair, which significantly prolongs the break-in period to 410 s (Example 1 only requires 110 s) and reduces the load-bearing capacity.

[0071] As can be seen from the comparison between Example 1 and Comparative Example 3, when polyethylene glycol is replaced with polypropylene glycol (using the same detection method as in Example 1, when polyethylene glycol is replaced with polypropylene glycol, the lubrication system cannot achieve macroscopic super-lubricity due to the increased viscosity, and therefore its load-bearing capacity was not statistically analyzed).

[0072] As can be seen from the comparison between Example 1 and Comparative Example 4, when polyethylene glycol is replaced with ethylene glycol, the same detection method as in Example 1 is used. When polyethylene glycol is replaced with ethylene glycol, due to the low viscosity, the lubrication system cannot achieve macroscopic super-lubricity under low-speed conditions, and therefore its load-bearing capacity is not statistically analyzed.

[0073] Comparative Example 5 (fructose / ethylene glycol) achieved superlubricity rapidly within 60 s and had a slightly better coefficient of friction (0.0062), but its load-bearing capacity of 410 MPa remained low, attributed to insufficient shear resistance of the adsorption layer. Comparative Example 6 (CA / CQDs quantum dots) achieved superlubricity rapidly within 44 s and had a slightly better coefficient of friction (0.0052), but its load-bearing capacity of 304 MPa remained low, attributed to insufficient shear resistance of the adsorption layer. Comparative Example 7 (CGQDs-glycerol) achieved superlubricity only within 600 s and had a load-bearing capacity of only 123 MPa, exhibiting the worst performance, attributed to the high viscosity of glycerol and insufficient shear resistance of the adsorption layer. Although all three existing technologies can achieve macroscopic superlubricity, their load-bearing capacity drops sharply by 50-80% compared to Example 1 (602 MPa). The core reason lies in the absence of the synergistic architecture of chemisorption layer + low-resistance shear layer + three-dimensional hydrogen bond network found in the embodiments of this invention.

[0074] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. 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 biomimetic liquid lubricant capable of forming a multilayer superlubricating film on a high roughness steel surface, characterized in that, The mixed liquid is prepared from water, polyethylene glycol, phytic acid modified graphene oxide and graphene oxide.

2. The biomimetic liquid lubricant capable of forming a multilayer superlubricating film on a high roughness steel surface according to claim 1, characterized in that, The mass ratio of the water, polyethylene glycol, phytic acid modified graphene oxide and graphene oxide is 45-55:45-55:0.025-0.0375:0.025-0.0375.

3. A method for preparing a biomimetic liquid lubricant capable of forming a multilayer superlubricating film on a high-roughness steel surface as claimed in claim 1 or 2, characterized in that, The method comprises the following steps: S1: modifying graphene oxide powder to obtain phytic acid modified graphene oxide powder; S2: dispersing graphene oxide powder and the phytic acid modified graphene oxide powder into water to obtain a mixed graphene liquid; S3: adding polyethylene glycol into the mixed graphene liquid to obtain a lubricant after mixing.

4. A method of preparing a biomimetic liquid lubricant capable of forming a multilayer superlubricating film on a high roughness steel surface according to claim 3, characterized in that, The modification of the graphene oxide in S1 comprises: S11: dispersing graphene oxide into water to form a dispersion liquid; S12: adding an aqueous phytic acid solution into the dispersion liquid, mixing and then heating to make the phytic acid react with the graphene oxide; S13: filtering the reacted liquid, washing the lower solid and then collecting the solid; S14: drying the solid to obtain the phytic acid modified graphene oxide powder.

5. A method of preparing a biomimetic liquid lubricant capable of forming a multilayer superlubricating film on a high roughness steel surface according to claim 4, characterized in that, In S11, the mass ratio of graphene and water is 0.018-0.023:

10.

6. The biomimetic liquid lubricant capable of forming a multilayer superlubricating film on a high roughness steel surface according to claim 4, characterized in that, In S12, the concentration of the aqueous phytic acid solution is 65-75wt%, and the mass ratio of the aqueous phytic acid solution to graphene oxide is 1-2:

1.

7. A method of preparing a biomimetic liquid lubricant capable of forming a multilayer superlubricating film on a high roughness steel surface according to claim 4, characterized in that, The heating in S12 is water bath heating, and the heating temperature is 50-70℃.

8. A method of preparing a biomimetic liquid lubricant capable of forming a multilayer superlubricating film on a high roughness steel surface according to claim 4, characterized in that, The filtering in S13 comprises centrifuging the reacted liquid at 10000-13000 r / min for 30-45 min and then discarding the supernatant; The washing of the lower solid comprises washing the lower solid with deionized water, then centrifuging again at 10000-13000 r / min for 8-12 min, discarding the supernatant, and repeating the cycle 2-4 times.

9. A method of preparing a biomimetic liquid lubricant capable of forming a multilayer superlubricating film on a high roughness steel surface according to claim 4, characterized in that, The drying temperature in S14 is 50-70℃, and the drying time is 1.5-2.5h.

10. A method of preparing a biomimetic liquid lubricant capable of forming a multilayer superlubricating film on a high roughness steel surface according to claim 3, characterized in that, The thickness of the graphene oxide in S1 and S2 is 0.8-1.2 nm, and the flake diameter is 0.5-4 μm; The molecular weight of the polyethylene glycol in S3 is 8000-12000, and the water comprises deionized water.

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