Water-based lubricant for achieving super-slip under super-high contact pressure, its preparation and application

Abstract

The application discloses a water-based lubricating liquid for realizing super-slip under super-high contact pressure, a preparation method and application thereof. The water-based lubricating liquid comprises a water-based base liquid and functional nanoparticles dispersed in the water-based base liquid; the water-based base liquid comprises water and a polyhydric alcohol; and the functional nanoparticles comprise phosphorus-containing carbon quantum dots. The water-based lubricating liquid provided by the application adopts a technical scheme in which the water-based base liquid is dispersed and combined with the phosphorus-containing carbon quantum dots, a scale can be formed on a friction surface through a tribochemical reaction, a lubricating film formed by adsorption and aggregation of the scale on the friction surface, macro-slip is realized, the macro-slip can be stably realized under super-high contact pressure, the wear of the friction surface can be significantly reduced, and a strong anti-wear effect is achieved; and with the help of the stable super-slip performance, the friction heat caused by a friction pair is also greatly reduced, so that the service life of a component is significantly improved.

Description

Water-based lubricants that achieve super-lubricity under ultra-high contact pressure, their preparation methods and applications Technical Field

[0001] This invention relates to the field of friction lubrication technology, and in particular to a water-based lubricant that achieves super-lubricity under ultra-high contact pressure, its preparation method, and its application. Background Technology

[0002] With the rapid development of marine resource development and engineering equipment, hydraulic technology has been widely used in the shipbuilding industry due to its advantages such as high torque transmission, wide speed range, stable operation, fast response speed, and high degree of automation. Hydraulic fluid not only transmits power but also provides lubrication. Due to limited space on ships, the piping is densely arranged and there are many heat sources. When leaks or ruptures occur in the hydraulic system pipelines, the use of mineral-based hydraulic oil can cause fires or even explosions. To improve the safety of ship hydraulic systems in heat-prone and hazardous areas and reduce the risk of fire, the use and promotion of flame-retardant hydraulic fluids in shipbuilding hydraulic equipment has broad application prospects and high practical value.

[0003] According to ISO 12922 classification, flame-retardant hydraulic fluids mainly include oil-in-water emulsions (HFAE), water-in-oil emulsions (HFB), water-glycol flame-retardant hydraulic fluids (HFC), anhydrous synthetic fluids made from phosphate esters (HFDR), and anhydrous synthetic fluids made from other components (HFDU). Among these types, water-based lubricants are widely used in marine applications due to their excellent biodegradability and low pollution. HFC flame-retardant fluids, in particular, have become ideal working media for hydraulic systems in fire hazard or enclosed locations due to their excellent flame retardancy, lubricity, anti-wear properties, stability, and economy.

[0004] However, the lubricity and anti-wear properties of HFC flame-retardant hydraulic fluids are inferior to those of mineral-based hydraulic oils. This is because water-based lubricants have lower viscosity, poorer film-forming ability, and lower lubricating film strength. Currently, most HFC flame-retardant hydraulic fluids are only suitable for medium and low-pressure hydraulic systems. Furthermore, the poor lubrication performance can lead to high frictional heat generation in equipment, ultimately causing equipment failure. Therefore, there is an urgent need for a technology to improve the lubricity and anti-wear properties of HFC flame-retardant hydraulic fluids.

[0005] In the field of lubricant technology, superlubricity (superlubricity) refers to extremely low friction (e.g., a coefficient of friction less than 0.01), which can significantly reduce wear and energy loss. In existing technologies, superlubricity has been achieved through asymmetric contact between two-dimensional (2D) materials or heterostructures under dry conditions and graphite surfaces lubricated by nanoscale ionic liquids and other lubricants. However, despite ongoing pursuit in industrial applications, achieving superlubricity on a macroscopic scale remains a challenge. For example, Berman et al. achieved macroscopic superlubricity at a diamond-like carbon interface by coiling graphene, but this lubrication system is far from suitable for extreme conditions.

[0006] Achieving macroscopic superlubricity under high loads on common industrial materials such as stainless steel is crucial. Li et al. successfully extended structural superlubricity on steel from the microscopic to the macroscopic by constructing microscopic point contacts on a steel matrix and orienting the two-dimensional material in an oxygen environment. However, this method requires maintaining the layer-by-layer structure of the two-dimensional material in a nitrogen environment, which limits its industrial application. Minimizing wear and energy dissipation during the initial break-in period and achieving stable superlubricity under ultra-high contact pressures (defined as >1 GPa) in steel-to-steel contacts remains a challenge.

[0007] Of course, this challenge is not limited to hydraulic systems; it exists in any lubrication application scenario under ultra-high contact pressure. Summary of the Invention

[0008] To address the shortcomings of existing technologies, the present invention aims to provide a water-based lubricant that achieves super-lubricity under ultra-high contact pressure, its preparation method, and its applications. This solves the technical problem in existing flame-retardant water-based lubricants that struggle to achieve stable super-lubricating properties under ultra-high contact pressure.

[0009] To achieve the aforementioned objectives, the technical solution adopted by this invention includes:

[0010] In a first aspect, the present invention provides a water-based lubricant that achieves super-slippery properties under ultra-high contact pressure, comprising an aqueous base fluid and functional nanoparticles dispersed in the aqueous base fluid; the aqueous base fluid comprises water and a polyol; the functional nanoparticles comprise phosphorus-containing carbon quantum dots.

[0011] Secondly, the present invention also provides a method for preparing the above-mentioned water-based lubricating fluid, comprising:

[0012] It provides phosphorus-containing carbon quantum dots, water, and polyols;

[0013] At least enough to mix water and polyol to form an aqueous base solution;

[0014] The phosphorus-containing carbon quantum dots are dispersed into the aqueous base liquid to obtain the aqueous lubricant.

[0015] Thirdly, the present invention also provides the application of the above-mentioned water-based lubricant in lubrication and friction reduction.

[0016] In a specific application, in a fourth aspect, the present invention also provides a friction structure, characterized in that it includes the above-mentioned water-based lubricant and a friction pair, wherein the friction pair is in contact with the water-based lubricant, and the friction interface of the friction pair is lubricated by the water-based lubricant.

[0017] Fifthly, as a further application of the above, the present invention also provides a mechanical hydraulic system containing the above-mentioned friction pair, wherein the water-based lubricant also serves as the power transmission medium of the hydraulic system.

[0018] Based on the above technical solution, compared with the prior art, the beneficial effects of the present invention include at least the following:

[0019] The water-based lubricant provided by this invention adopts a technical solution of water-based base liquid and phosphorus-containing carbon quantum dot dispersion composite, which can form scales on the friction surface through tribochemical reaction, and then accumulate and adsorb to form a lubricating film on the friction surface, thereby achieving macroscopic super-lubricity. Moreover, this macroscopic super-lubricity can be stably achieved under ultra-high contact pressure, which can significantly reduce the wear of the friction surface and play a strong anti-wear role. With the help of stable super-lubricity performance, the frictional heat generated by the friction pair is also greatly reduced, thereby significantly improving the service life of the components.

[0020] The above description is merely an overview of the technical solution of the present invention. In order to enable those skilled in the art to better understand the technical means of this application and to implement it in accordance with the contents of the specification, the preferred embodiments of the present invention are described below in conjunction with detailed drawings. Attached Figure Description

[0021] Figure 1 is a transmission electron microscope image (low magnification) of phosphorus-containing carbon quantum dots provided in a typical embodiment of the present invention;

[0022] Figure 2 is a transmission electron microscope image (high magnification) of phosphorus-containing carbon quantum dots provided in a typical embodiment of the present invention;

[0023] Figure 3 is a friction coefficient curve of a water-based lubricant containing different lubricating additives under the national standard friction test, provided in a typical embodiment and comparative case of the present invention.

[0024] Figure 4 is an optical photograph of the wear scar of a water-based lubricant containing different lubricating additives under the national standard friction test, provided in a typical embodiment and comparative case of the present invention.

[0025] Figure 5 is a statistical chart of the wear scar diameter of water-based lubricants containing different lubricating additives under national standard friction test, provided in a typical embodiment and comparative case of the present invention.

[0026] Figure 6 is a friction coefficient curve of a water-based lubricant containing different concentrations of phosphorus-containing carbon quantum dots under the national standard friction test, provided in a typical embodiment of the present invention.

[0027] Figure 7 is an optical photograph of the wear scar of a water-based lubricant containing different concentrations of phosphorus-carbon quantum dots under a national standard friction test, provided in a typical embodiment of the present invention.

[0028] Figure 8 is a statistical chart of wear scar diameters of water-based lubricants containing different concentrations of phosphorus-containing carbon quantum dots under national standard friction tests, provided in a typical embodiment of the present invention.

[0029] Figure 9 is a comparison of the 3D contours of the wear scars of a water-based lubricant containing phosphorus-carbon quantum dots and a reference sample under national standard friction tests, provided in a typical embodiment of the present invention.

[0030] Figure 10 is a scanning electron microscope image of the wear scars of a water-based lubricant containing different concentrations of phosphorus-containing carbon quantum dots under the national standard friction test, provided in a typical embodiment of the invention.

[0031] Figure 11 is a surface scan of the wear scar X-ray energy dispersive spectroscopy analysis of a water-based lubricant containing phosphorus-carbon quantum dots under national standard friction test, provided in a typical embodiment of the invention.

[0032] Figure 12 is a comparison of the liquid color of a water-based lubricant containing different concentrations of phosphorus-carbon quantum dots before and after a national standard friction test, provided in a typical embodiment of the invention.

[0033] Figure 13 is a curve showing the temperature change of the oil cup in a national standard friction test between a water-based lubricant containing phosphorus-carbon quantum dots and a control sample, provided in a typical embodiment of the invention.

[0034] Figure 14 is an infrared thermal image of the instrument temperature of a water-based lubricant containing phosphorus-carbon quantum dots and a control sample in a national standard friction test, provided in a typical embodiment of the invention.

[0035] Figure 15 shows the friction coefficient curves of two commercial water-based lubricants and the corresponding commercial water-based lubricants containing phosphorus carbon quantum dots provided in a typical embodiment of the present invention under the national standard friction test.

[0036] Figure 16 is a typical embodiment of the present invention, showing the friction coefficient curves of a water-based lubricant containing phosphorus-carbon quantum dots and the corresponding water-based lubricant under tests with copper and aluminum balls (load, rotation speed and test time are all in accordance with national standards). Detailed Implementation

[0037] In view of the shortcomings of the prior art, the inventors of this invention, through long-term research and extensive practice, have proposed the technical solution of this invention. The following will further explain and illustrate this technical solution, its implementation process, and its principles.

[0038] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and therefore the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0039] This invention provides a water-based lubricant that achieves super-slippery performance under ultra-high contact pressure. The lubricant comprises an aqueous base fluid and functional nanoparticles dispersed in the aqueous base fluid. The aqueous base fluid comprises water and a polyol. The functional nanoparticles comprise phosphorus-containing carbon quantum dots.

[0040] In some embodiments, the method for synthesizing the phosphorus-containing carbon quantum dots includes the following steps:

[0041] Initial carbon quantum dots were prepared using a carbon source via a microwave method.

[0042] The initial carbon quantum dots are phosphated to obtain the phosphorus-containing carbon quantum dots.

[0043] As typical application examples, embodiments of the present invention provide a novel phosphorus-containing carbon quantum dot additive and its preparation method. The carbon quantum dot additive is prepared from glutamic acid as a carbon source via a microwave method. Glutamic acid is prepared into a solution of a certain concentration and synthesized through a microwave reaction, followed by phosphating with phosphoric acid. This phosphorus-containing carbon quantum dot, as a nano-lubricant additive, can be used in water-based lubrication systems and significantly improves the tribological properties of water-based lubricants, such as reducing surface wear and the coefficient of friction in bearing friction. Furthermore, the addition of the phosphorus-containing carbon quantum dot nano-additive also solves the problem of discoloration in water-based hydraulic fluids after friction.

[0044] In some embodiments, the carbon source includes amino acids; the phosphating agent for the phosphating treatment includes a phosphorus-containing acidic substance. Specifically, the amino acid may include, for example, any one of the following: glutamic acid, glycine, alanine, etc. The phosphating agent may be phosphoric acid, or other phosphorus-containing acidic compounds may be used instead.

[0045] In some implementations, the synthesis method specifically includes:

[0046] A solution containing the carbon source is provided, and the solution is subjected to intermittent microwave treatment to obtain a precursor solution containing the initial carbon quantum dots. Intermittent microwave treatment can avoid local overheating of the solution, which is beneficial to improving the heating uniformity and preventing local carbon dots from bonding to form graphite.

[0047] The precursor solution is mixed with the phosphating agent and subjected to a phosphating reaction to obtain the phosphorus-containing carbon quantum dots.

[0048] The concentration of the carbon source in the carbon source solution is 2-20 mg / ml, the total time of the intermittent microwave treatment is 3-10 min, the number of intermittent cycles is 3-20, the duration of a single microwave treatment is 30-60 s, the interval time is 30-120 s, and it is not limited to these, as long as sufficient cooling is ensured, and the microwave power density is 35000-45000 W / L.

[0049] The mass ratio of the phosphating agent to the precursor solution is 1:1 to 1:4, and the phosphating reaction time is 6-12 hours.

[0050] Unless otherwise specified, the reactions exemplified in this invention are all performed at room temperature (e.g., 15-40°C, and in a laboratory environment, generally 20-30°C). However, the reaction system may experience heating, such as microwave heating. This is a natural phenomenon that occurs during the reaction. Although the temperature may change, as long as the above reaction conditions and the ambient temperature are maintained, the reaction can be completed without paying special attention to how the temperature of the reaction system itself changes.

[0051] As a typical application example of the above technical solution, the synthesis step of the phosphorus-containing carbon quantum dots may include, for example:

[0052] (1) The glutamic acid solution was placed in a microwave oven used in the laboratory and reacted under intermittent microwave conditions to obtain a light yellow carbon quantum dot dispersion.

[0053] (2) Add an 85wt% phosphoric acid solution to the carbon quantum dot dispersion and stir magnetically at room temperature.

[0054] (3) The reacted liquid was placed in a dialysis bag (molecular weight 10KD) and dialyzed in deionized water. A phosphorus-containing carbon quantum dot aqueous solution was obtained.

[0055] (4) The phosphorus-containing carbon quantum dot aqueous solution was freeze-dried to obtain phosphorus-containing carbon quantum dot powder.

[0056] Of course, steps (3) and (4) above are steps for extracting solid phosphorus-containing carbon quantum dots from a dispersion, but are not limited to the methods described above. Various other possible methods, such as centrifugation, can also be used to obtain phosphorus-containing carbon quantum dot powder. It is even possible to directly add the phosphorus-containing carbon quantum dot dispersion. The ultimate goal is to form a water-based lubricant with the above-mentioned components and proportions.

[0057] Regarding the specific composition and proportions of the water-based lubricant, in some embodiments, the polyol includes any one or a combination of two or more of ethylene glycol, diethylene glycol, and polyether polyols; the water-based lubricant also includes a complexing agent and optional functional additives. The complexing agent and / or functional additives include, but are not limited to, lubricating agents, dispersants, and corrosion inhibitors.

[0058] In some embodiments, the water-based lubricant contains 30-33% water by mass and 0.1-1% phosphorus-containing carbon quantum dots by mass; the phosphorus-containing carbon quantum dots have a particle size of 2-5 nm.

[0059] As a typical application of the above technical solution, some embodiments of the present invention illustrate a formulation of a water-based flame-retardant lubricant. The formulation mainly consists of water, ethylene glycol, diethylene glycol, polyether, and related additives. The water-based flame-retardant lubricant provided by the formulation has good extreme environment tolerance, marine corrosion resistance, and environmental friendliness. It can be used at a low temperature of 60°C and has passed the seawater corrosion test (ASTM D665B standard).

[0060] The novel lubricant provided can achieve macroscopic superlubricity under national standard friction tests, and is the highest load pressure (2.3 GPa) that can be achieved for superlubricity reported to date. At the same time, it reduces the wear on the bearing steel surface and plays an anti-wear role. With the help of superlubricity, the frictional heat generated by bearing rotation is significantly reduced (achieving a temperature drop of nearly 1 / 2 compared with the reference sample).

[0061] A more specific formulation of a water-based flame-retardant lubricant comprises water, ethylene glycol, diethylene glycol, and polyether as its main water-based components. Other additives primarily include benzotriazole and compound agent 2300 provided by Fudi Lubrication Technology Co., Ltd. Specifically, the water content is 30-33% by mass; ethylene glycol is 26-30% by mass; polyether (SDN-10D) is 10-15% by mass; diethylene glycol is 15-20% by mass; the corrosion inhibitor benzotriazole is 0.1-0.5% by mass; compound agent 2300 is 6-10% by mass; and phosphorus-containing carbon quantum dots are 0.1-1% by mass.

[0062] In the above and following embodiments, the polyether (SDN-10D) and composite agent 2300 used were provided by Fudi Lubrication Technology Co., Ltd., and composite agent 2300 is a composite formulation lubricant. The composite agent plays a certain role in dispersion and stabilization. At the same time, the composite agent contains corresponding lubricating additives, corrosion inhibitors, defoamers, and other components. These components may also exist in additionally added functional additives, which can also improve lubrication performance and corrosion resistance to a certain extent. The role of these additionally added substances is not the core technical means of this invention, but rather a functional auxiliary reagent added to form the corresponding product. It is an exemplary role and not limited thereto.

[0063] However, in long-term research and development practice, it has been found that many HFC water-based liquids, when combined with the phosphorus-containing carbon quantum dots provided by this invention, can significantly reduce the coefficient of friction under ultra-high contact pressure and achieve super-slippery or "quasi-super-slippery" effects. However, among the many water-based liquids, the water-based liquid formulated by the inventors of this invention has the best super-slippery effect.

[0064] It should be noted that the definition of superlubricity in the above background art is based on the standard under normal contact pressure. However, when under the ultra-high contact pressure in this case, the standard for the coefficient of friction of superlubricity can be appropriately relaxed. For example, under ultra-high contact pressure, a coefficient of friction around 0.01, or even of the same order of magnitude, can still be considered to fall within the scope of superlubricity. Therefore, it should not be considered that the combination of other commercial or other self-made base liquids different from the above-mentioned aqueous base liquids with phosphorus-containing carbon quantum dots is not within the scope of implementation of this invention.

[0065] Corresponding to the composition and proportions of the water-based lubricant described above, this embodiment of the invention also provides a method for preparing a water-based lubricant, which includes the following steps:

[0066] It provides phosphorus-containing carbon quantum dots, water, and polyols.

[0067] At least water and polyol should be mixed to form an aqueous base solution.

[0068] The phosphorus-containing carbon quantum dots are dispersed into the aqueous base liquid to obtain the aqueous lubricant.

[0069] In some embodiments, the polyol includes small molecule alcohols and polyether polyols, and the water-based lubricant also includes a complexing agent and optional functional additives.

[0070] The preparation method specifically includes:

[0071] First, water and polyether polyol are mixed to form a first solution, and then the first solution is mixed with the small molecule alcohol to form the aqueous base liquid.

[0072] Furthermore, the composite agent and functional additives are first added to the aqueous base liquid, and after they are fully dissolved, the phosphorus-containing carbon quantum dots are then added to the liquid phase.

[0073] As some typical application examples of the above technical solutions, the specific implementation steps of the above preparation method may include the following actual steps:

[0074] (1) Mix water and polyether first, and then mix them evenly in a mixer.

[0075] (2) Add ethylene glycol and diethylene glycol to a well-mixed water-polyether system and stir magnetically at room temperature.

[0076] (3) During the magnetic stirring process, add composite agent 2300, benzotriazole and phosphorus-containing carbon quantum dots in sequence and slowly.

[0077] (4) Stir for 24 hours under magnetic stirring to obtain a new type of water-based flame-retardant lubricant.

[0078] The above steps yielded a novel water-based flame-retardant lubricant with high-pressure super-lubricating properties, which was constructed by using phosphorus-containing carbon quantum dots as a novel lubricating additive in conjunction with a water-ethylene glycol hydraulic fluid system. This water-based lubricant also possesses corrosion resistance, extreme environment adaptability and environmental friendliness, as well as, most importantly, high-pressure super-lubricating properties.

[0079] It is important to note that water and polyether must first be mixed using a mixer with strong shearing and stirring. All components should be added slowly and sequentially. A simple one-step mixing process can easily lead to unevenness in the final lubricant. Furthermore, if composite agent 2300 is added together with phosphorus-containing carbon quantum dots, there is a possibility of agglomeration. Therefore, the next component should be added only after the previous one has dispersed evenly. Thus, the order of raw material addition is crucial for preparing a uniform water-based flame-retardant lubricant. If the lubricant has an uneven component distribution, such as polyether agglomeration or phosphorus-containing carbon quantum dot segregation, stable superlubricity may not be achieved. Of course, the implementation is not limited to strictly controlling the above addition order; alternative techniques can be used to achieve a uniform component distribution.

[0080] Correspondingly, the embodiments of the present invention also provide the application of the water-based lubricant provided in any of the above embodiments in lubrication and friction reduction.

[0081] For example, in a specific application, the present invention also provides a friction structure, which includes a water-based lubricant and a friction pair provided in any of the above embodiments, wherein the friction pair is in contact with the water-based lubricant and the friction interface of the friction pair is lubricated by the water-based lubricant.

[0082] In some implementations, the contact pressure at the friction interface is above 1 GPa.

[0083] In some embodiments, at least one friction surface of the friction interface is made of steel. Mechanistically, phosphorus in phosphorus-containing carbon quantum dots reacts most readily with iron in steel through tribochemical reactions. Corresponding experiments show that superlubricity, let alone sustained and stable superlubricity, is almost impossible to achieve on other iron-free friction pairs. This is likely related to the tribochemical reactions during the friction process, which necessitates that the surfaces of the friction pair be primarily composed of iron.

[0084] In some implementations, the friction structure is part of a mechanical-hydraulic system, and the water-based lubricant also serves as the power transmission medium in the mechanical-hydraulic system.

[0085] The embodiments of the present invention can also be understood as providing a separate mechanical hydraulic system, which includes the above-mentioned friction structure, and the water-based lubricant also serves as a power transmission medium. In some fields, it is customarily referred to as hydraulic fluid, but functionally, it plays both the role of power transmission and lubrication. The present invention still mainly utilizes its excellent lubrication characteristics.

[0086] This hydraulic system, for example, is a combination of a piston and a cylinder, in which hydraulic fluid is pushed by the piston to transmit power, and at the same time, the hydraulic fluid can lubricate the friction surfaces between the piston and the cylinder.

[0087] It should be noted that the above-mentioned application of hydraulic fluid is a preferred application of the embodiments of the present invention. However, the novel water-based lubricant provided by the present invention is not limited to the application of hydraulic fluid. Other friction reduction applications in mechanical fields can also apply the technical concept provided by the present invention and should all fall within the protection scope of the present invention.

[0088] The technical solution of the present invention will be further described in detail below through several embodiments and in conjunction with the accompanying drawings. However, the selected embodiments are only for illustrating the present invention and do not limit the scope of the present invention.

[0089] Example 1

[0090] Example 1 illustrates the specific preparation process of phosphorus-containing carbon quantum dots, including the following steps:

[0091] Prepare an aqueous solution of glutamic acid with a concentration of 15 mg / ml. Then, place the prepared glutamic acid solution in a laboratory microwave oven and microwave it for 6 minutes at a power of 700W. Use intermittent microwave treatment, removing and cooling for 2 minutes after each 1 minute of microwave treatment. Repeat this process 6 times to finally obtain a pale yellow carbon quantum dot dispersion.

[0092] An 85wt% phosphoric acid solution was added to the carbon quantum dot dispersion at a mass ratio of half that of the above carbon quantum dot dispersion, and the mixture was magnetically stirred at room temperature for 10 hours.

[0093] The resulting solution was placed in a dialysis bag with a molecular weight of 10 KD and dialyzed in deionized water for 72 hours (with the water changed every 6 hours) to obtain a phosphorus-containing carbon quantum dot aqueous solution. The phosphorus-containing carbon quantum dot aqueous solution was then freeze-dried (frozen in liquid nitrogen and then placed in a freeze dryer) to obtain phosphorus-containing carbon quantum dot powder.

[0094] Phosphorus-containing carbon quantum dot powder was dispersed in ethanol to obtain a phosphorus-containing carbon dot dispersion. The dispersion was dropped onto a copper grid for transmission electron microscopy and dried. The morphology of the obtained phosphorus-containing carbon quantum dots was observed using a transmission electron microscope. The results are shown in Figures 1 and 2. It can be observed that the obtained phosphorus-containing carbon quantum dots have good dispersion ability and the particle size distribution is about 2-5 nm.

[0095] Example 2

[0096] Example 1: The preparation process of the novel water-based lubricant is shown below:

[0097] First, mix 30g of water with 15g of polyether (SDN-10D) in a mixer until homogeneous. Then, add 30g of ethylene glycol and 15g of diethylene glycol to the homogeneous water-polyether system and stir magnetically for 12 hours at room temperature.

[0098] After 12 hours, under magnetic stirring, composite agent 2300 (9g), benzotriazole corrosion inhibitor (0.5g), and phosphorus-containing carbon quantum dots prepared in Example 1 (0.5g) were added slowly in sequence. Stirring was continued for 24 hours under magnetic stirring to obtain a novel water-based flame-retardant lubricant.

[0099] The kinematic viscosity and pour point of several novel water-based flame-retardant lubricants were tested. Their kinematic viscosity at 40℃ and 100℃ was measured, and the results are shown in Table 1. The viscosities are 41.8 m² / s and 26.0 m² / s, respectively, with a pour point of 59℃. This indicates that the novel water-based lubricant has good fluidity and is suitable for extremely low ambient temperature conditions.

[0100] Example 3

[0101] This embodiment is basically the same as Embodiment 2, except that:

[0102] The mass of phosphorus-containing carbon quantum dots added was changed to 0.1g and 1g respectively, while the rest of the process and parameters remained unchanged. As shown in Table 1 below, the lubrication performance of the two water-based lubricants was slightly lower than that of the lubricant provided in Example 2, but it still had better lubrication performance. This shows that the new water-based lubricant with a phosphorus-containing carbon quantum dot addition of 0.5wt% has the best lubrication performance.

[0103] Table 1. Test results of kinematic viscosity and pour point of different water-based lubricants

[0104]

[0105]

[0106] The table shows that all the lubricants exhibit good fluidity, with viscosity similar to common water-glycol lubricants. Furthermore, the new lubricant has a pour point of 59°C, indicating its applicability under extremely low temperature conditions.

[0107] Comparative Example 1

[0108] This embodiment is basically the same as Embodiment 2, except that:

[0109] Without adding phosphorus-containing carbon quantum dot lubricant components, and keeping the rest of the process and parameters unchanged, a blank control lubricant without additives was obtained.

[0110] Comparative Example 2

[0111] This embodiment is basically the same as Embodiment 2, except that:

[0112] The phosphorus-containing carbon quantum dot lubricant was replaced with a phosphorus-containing ionic liquid, carbon quantum dots, boron nitride, and graphene, with each component added at a mass of 1g. The rest of the process and parameters remained unchanged.

[0113] Example 4

[0114] This embodiment illustrates the tribological performance testing of the novel water-based lubricant provided in Embodiments 2 and 3 above, as well as the tribological performance testing comparison of samples provided in some comparative examples. In conjunction with the above comparative examples, to compare with phosphorus-containing carbon quantum dots, this embodiment selected several commonly used different lubricating additives for experiments, including phosphorus-containing ionic liquids, carbon quantum dots, boron nitride, and graphene. The amount of these additives added was kept consistent with that of phosphorus-containing carbon quantum dots.

[0115] The tribological properties of the new water-based lubricant were tested using a four-ball friction testing machine. The test conditions were in accordance with the national standard SH / T0762-2005 (load 400N, speed 1200rpm, the initial friction pressure was calculated to be 2.3GPa using the Hertz contact formula and the pressure calculation formula related to the four balls). The wear pattern of the wear scar after friction was analyzed using an optical microscope and laser confocal microscopy.

[0116] As shown in Figure 3, the friction coefficient curves reveal that adding carbon quantum dots or phosphorus-containing carbon quantum dots can reduce the friction coefficient of the lubricant compared to the blank lubricant. However, in the lubricant provided in Comparative Example 2, the addition of phosphorus-containing ionic liquid, boron nitride, and graphene leads to an increase in the friction coefficient. This indicates that most common lubricant additives are ineffective in reducing friction in lubricants. This may be due to the dispersibility of the lubricant in the compound lubricant, or the presence of various functional components in the lubricant, which react on the friction surfaces. This creates surface competition between the added lubricant and the functional components, thus affecting the lubrication effect. Furthermore, it can be observed that phosphorus-containing carbon quantum dots are most effective in reducing the friction coefficient of the lubricant.

[0117] As can be observed from Figures 4 and 5, the wear scar diameter of all lubricants with added additives is smaller than that of the blank lubricant, indicating that the addition of additives is effective in improving the anti-wear performance of the lubricant. Compared with the lubricant reference sample without additives such as ionic liquids and carbon quantum dots, all lubricants with additives such as ionic liquids or carbon quantum dots exhibit superior anti-wear performance.

[0118] Taking all factors into consideration, the introduction of phosphorus-containing carbon quantum dots is beneficial to improving the tribological properties of water-based lubricants. This embodiment also tested the tribological properties of water-based lubricants with different concentrations of phosphorus-containing carbon quantum dots.

[0119] As shown in Figure 6, the amount of phosphorus-containing carbon quantum dots added also affects the lubrication performance of the lubricant. When the addition amount is 0.5 wt%, the lowest coefficient of friction is obtained, and the coefficient of friction is below 0.01 after 1000 seconds, entering a superlubricating state. Calculations of the contact stress between the steel ball friction pair using Hertz's formula show that the initial contact stress is as high as 2.301 GPa. The new lubricant achieved macroscopic superlubricity on the bearing steel surface at 2.301 GPa, which is the highest load reported to achieve superlubricity to date.

[0120] As can be seen from Figures 7 and 8, a lower addition amount can achieve excellent anti-wear performance compared to the lubricant with an addition amount of 1 wt%. Figure 9 compares the 3D profile morphology of wear scars of the blank lubricant and the phosphorus-containing carbon quantum dot lubricant that achieves super-lubricity. It can be found that the addition of phosphorus-containing quantum dots (0.5 wt%) significantly improves the anti-wear performance of the lubricant.

[0121] To achieve the best results, the recommended addition amount of phosphorus-containing carbon quantum dots is 0.1-0.5 wt%. However, this is not the only option. When faced with different composition ratios of aqueous base solutions, the above-mentioned optimal addition amount of phosphorus-containing carbon quantum dots may need to be adjusted accordingly. This parameter can be obtained through conditional experiments.

[0122] Furthermore, as shown in Figure 12, all lubricants with added phosphorus-carbon quantum dots maintained their color before and after friction, while the blank lubricant turned a darker color after friction. This is likely because a large amount of iron filings reacted with various active components in the lubricant during friction. The introduction of phosphorus-carbon quantum dots effectively reduced the generation of iron filings and prevented this reaction. This demonstrates that the introduction of phosphorus-carbon quantum dots, even at extremely low concentrations, can effectively suppress the discoloration of lubricants after friction, thus improving the stability of the lubricant product.

[0123] Example 5

[0124] This embodiment demonstrates the analysis of the lubrication mechanism through the characterization of wear scars using scanning electron microscopy and energy dispersive spectroscopy.

[0125] As shown in Figure 10, the introduction of phosphorus-containing carbon quantum dots resulted in the appearance of more obvious scaly material at the wear scar location, and the amount of scaly material increased with the increase of the amount of phosphorus-containing carbon quantum dots added. From the energy spectrum of Figure 11, it can be found that the main components of these scaly materials are carbon, phosphorus, and oxygen. This proves that these scaly materials are a lubricating film formed by the aggregation and adsorption of phosphorus-containing carbon quantum dots on the friction surface. The formation of these scaly lubricating films comes from the tribochemical reaction between phosphorus-containing carbon quantum dots and the steel surface, which can play a good role in separating the friction surface and thus reducing friction and wear.

[0126] Furthermore, we can see from Figure 10 that when the amount of phosphorus-containing carbon quantum dots added is too small, a lubricating film cannot be effectively formed on the friction surface, while when the amount added is too large, severe scale buildup is formed, which leads to a certain negative lubrication effect.

[0127] Example 6

[0128] This embodiment demonstrates the effective effect of phosphorus-containing carbon quantum dot lubricant on reducing frictional heat. The temperature change of the oil cup in the four-ball friction tester during the friction test of blank lubricant and superlubricant was recorded in real time by a temperature sensor, and the friction process was recorded by infrared thermal imaging.

[0129] As can be seen from Figures 13 and 14, the superlubricity effectively suppresses the generation of frictional heat. Compared with the blank lubricant, the superlubricant containing phosphorus carbon quantum dots only increased in temperature by about 5°C before and after friction, while the temperature rise of the blank lubricant reached nearly 32°C. The superlubricity reduced heat generation by nearly 6 times. This shows that the lubricant provided by this invention can effectively reduce the frictional heat generated during friction, which directly proves the important significance of superlubricity in reducing frictional heat generation.

[0130] Comparative Example 3

[0131] This comparative example shows the friction coefficient curves of commercial water-based lubricants under national standard testing and the friction coefficient curves after introducing phosphorus-containing carbon dots. As can be seen from Figure 15, the friction coefficients of the selected Castrol water-based lubricants are all between 0.05 and 0.1 under national standard testing. After introducing phosphorus-containing carbon dots, the friction coefficient can be effectively reduced, with a significant effect. The friction coefficient can be reduced to below 0.025, but there is still a certain gap compared with the example. Therefore, the super-lubricating system of phosphorus-containing carbon dot water-based lubricant described in this invention currently achieves the best and most stable super-lubricating effect among the modified water-based fluids. Although it also has significant technical effects in other water-based fluids, it may not achieve the best super-lubricating effect.

[0132] However, this does not mean that the combination of phosphorus-containing carbon quantum dots and commercial base liquid provided by this invention cannot achieve the technical effect, especially under ultra-high contact pressure, it has significantly reduced the coefficient of friction and can be considered to be in the category of super-slippery under high pressure; this also shows that although this comparative example is classified as a comparative case, it only represents a suboptimal choice and is still essentially within the scope of implementation of this invention.

[0133] Comparative Example 4

[0134] This comparative example demonstrates the lubrication effects of lubricating fluid and phosphorus-carbon quantum dot-containing lubricating fluid on different friction pairs. As shown in Figure 16, the lubrication performance of the lubricating fluid and the phosphorus-carbon quantum dot-containing lubricating fluid were tested on copper and aluminum balls. The friction coefficient curves show that the friction coefficient of the lubricating fluid on the copper ball is around 0.07-0.08, while the introduction of phosphorus-carbon quantum dots has a reverse effect on the friction of the copper ball, with the friction coefficient rising to around 0.1. This may be because the surface of the copper ball is relatively soft, and the introduction of phosphorus-carbon dots actually damages the surface of the copper ball, thus leading to an increase in the friction coefficient. The lubricating fluid itself has a poor lubrication effect on the aluminum ball. It can be seen that the friction coefficient of the lubricating fluid on the aluminum ball fluctuates greatly, and friction failure occurs after more than 2000 seconds. Although the introduction of phosphorus-carbon dots prolongs the time to friction failure to some extent, the friction coefficient still increases sharply within 1 hour. This further demonstrates the unsuitability of water-based lubricating fluid + phosphorus-carbon dots in the aluminum ball system.

[0135] This fully demonstrates that the tribochemical reaction between phosphorus-containing carbon dots and the iron components in the steel ball is the key to achieving superlubricity. Therefore, water-based lubricants with phosphorus-containing carbon dots are more suitable for achieving stable superlubricity in steel ball systems.

[0136] Based on the above embodiments and comparative examples, it is clear that the water-based lubricant provided in the embodiments of the present invention adopts a technical solution of water-based base liquid and phosphorus-containing carbon quantum dot dispersion composite, which can form scales on the friction surface through tribochemical reaction, and then accumulate and adsorb to form a lubricating film on the friction surface, thereby achieving macroscopic superlubricity. Moreover, this macroscopic superlubricity can be stably achieved under ultra-high contact pressure, which can significantly reduce the wear of the friction surface and play a strong anti-wear role. With the help of stable superlubricity performance, the frictional heat generated by the friction pair is also greatly reduced, thereby significantly improving the service life of the components.

[0137] It should be understood that the above embodiments are merely illustrative of the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A friction structure that achieves super-lubricity under ultra-high contact pressure, characterized in that, The system includes a water-based lubricant and a friction pair. The friction pair is in contact with the water-based lubricant, and the friction interface of the friction pair is lubricated by the water-based lubricant. At least one friction surface of the friction interface is made of steel, and the contact pressure of the friction interface is above 1 GPa. The water-based lubricant includes an aqueous base liquid and functional nanoparticles dispersed in the aqueous base liquid. The aqueous base liquid includes water and a polyol. The functional nanoparticles include phosphorus-containing carbon quantum dots. The polyol includes polyether polyols and small molecule alcohols. The small molecule alcohol includes any one or a combination of two of ethylene glycol and diethylene glycol. The water-based lubricant also includes any one or a combination of two or more of lubricating agents, dispersants, and anti-corrosion additives. The phosphorus-containing carbon quantum dots form scales on a friction surface through a tribochemical reaction, and then aggregate and adsorb on the friction surface to form a lubricating film. The synthesis method of the phosphorus-containing carbon quantum dots includes: preparing initial carbon quantum dots using a carbon source via a microwave method; phosphating the initial carbon quantum dots to obtain the phosphorus-containing carbon quantum dots; the preparation method of the water-based lubricant specifically includes: first mixing water with a polyether polyol to form a first solution, then mixing the first solution with the small molecule alcohol to form the water-based base liquid; and first adding any one or more combinations of lubricating aids, dispersants, and anti-corrosion additives to the water-based base liquid, dissolving it completely, and then adding and dispersing the phosphorus-containing carbon quantum dots into the liquid phase to obtain the water-based lubricant.

2. The friction structure according to claim 1, characterized in that, The carbon source includes amino acids; the phosphating agent used in the phosphating treatment includes phosphorus-containing acidic substances.

3. The friction structure according to claim 2, characterized in that, The synthesis method specifically includes: providing a solution of the carbon source and subjecting the solution to intermittent microwave treatment to obtain a precursor solution containing the initial carbon quantum dots; mixing the precursor solution with the phosphating agent and performing a phosphating reaction to obtain the phosphorus-containing carbon quantum dots; wherein the concentration of the carbon source in the carbon source solution is 2-20 mg / ml, the total time of the intermittent microwave treatment is 3-10 min, the number of intermittent cycles is 3-20, the duration of a single microwave treatment is 30-60 s, and the microwave power density is 35000-45000 W / L; the mass ratio of the phosphating agent to the precursor solution is 1:1-1:4, and the phosphating reaction time is 6-12 h.

4. The friction structure according to claim 1, characterized in that, The water-based lubricant contains 20-44% water by mass and 0.1-1% phosphorus-containing carbon quantum dots by mass; the particle size of the phosphorus-containing carbon quantum dots is 2-5 nm.

5. The application of the friction structure according to any one of claims 1-4 in lubrication and friction reduction.

6. The application according to claim 5, characterized in that, The friction structure belongs to a mechanical hydraulic system, and the water-based lubricant also serves as the power transmission medium in the mechanical hydraulic system.

Images