Low-eutectic solvents for friction-induced MoS2 lubricating film formation, their preparation methods, and applications.

Abstract

The application provides a eutectic solvent based on friction-induced generation of MoS2 lubricating film and a preparation method and application thereof, wherein the eutectic solvent comprises a hydrogen bond acceptor, a hydrogen bond donor of a sulfur source and a hydrogen bond donor of a molybdenum source, forms a liquid eutectic solvent at room temperature through hydrogen bond interaction, and the eutectic solvent is chemically reacted under the action of friction-heat to generate a MoS2 lubricating film on a friction interface; the molar ratio of the hydrogen bond acceptor, the hydrogen bond donor of the sulfur source and the hydrogen bond donor of the molybdenum source is 2-8:0.1-1:0.01-1. The application does not need to use a catalyst and a lubricating additive and is independent of consumed friction pair materials, and a MoS2 lubricating film is generated through reaction under friction induction, so that the eutectic solvent of the application can be applied to friction lubrication under harsh working conditions such as high load and high temperature.

Description

Technical Field

[0001] This invention belongs to the field of liquid lubrication technology, and particularly relates to a eutectic solvent based on friction-induced generation of MoS2 lubricating film, its preparation method, and its application. Background Technology

[0002] As high-end equipment faces increasingly complex and demanding operating conditions, traditional lubricants present numerous challenges, such as easy failure under harsh conditions (heavy load, low speed, high temperature, strong impact, etc.), complex synthesis, high cost, corrosiveness to metals, poor compatibility, environmental pollution, and high toxicity. These issues make it difficult to meet the high-performance requirements of equipment for green lubricating materials. To improve the lubrication performance of liquid lubricating materials, additives are mainly introduced into the liquid lubricant. These include solid additives (such as graphene and its derivatives, quantum dots, hexagonal boron nitride (h-BN), transition metal carbides or carbonitrides (MXene), transition metal disulfides (TMDs), metal-organic frameworks (MOFs), and covalent organic frameworks (COFs)). These additives enhance the friction reduction, wear resistance, and load-bearing capacity of the liquid lubricating film through interlaminar shearing, rolling bearings, polishing repair, and film deposition. Liquid additives, such as zinc dialkyl dithiophosphate (ZDDP), molybdenum dialkyl dithiophosphate (MoDTP), and ionic liquids (ILs), react with friction pair materials or functionalized surfaces to form tribochemical reaction films, decompose the additives themselves to form lubrication protection products, and react with added reactants to generate lubrication products. However, introducing friction-reducing and anti-wear additives into liquid lubricants presents several challenges in practical use, including continuous additive consumption, poor compatibility between base oils and additives, difficulty in designing additive molecular structures, cumbersome preparation processes, and high costs. These issues severely limit the service life and application areas of liquid lubricants. Therefore, to meet the complex demands of mechanical operating conditions and the requirements of industrial energy conservation, emission reduction, and environmental protection, the development of self-lubricating, customizable, sustainable, and environmentally friendly lubricating materials is imperative.

[0003] To address the limitations of existing liquid lubricants in lubrication protection design, lubrication strategies utilizing friction-induced in-situ synthesis of solid lubricating films from liquid lubricants have rapidly developed in recent years. These strategies primarily include friction-induced in-situ click chemistry and friction-catalyzed in-situ lubricant degradation. While these methods avoid relying on the direct addition of lubricating additives and do not depend on consuming friction pair materials as reactants to form a lubricating protective film, they share a common problem: they are limited by the use of specific reactants and catalysts, relying on the introduction of solid catalysts to trigger tribochemical reactions for in-situ lubricant film formation. Therefore, the current development direction of liquid lubricating materials lies in how to regulate the mechanochemical reactivity of the lubricant itself through the molecular structure and multi-component design of liquid lubricating materials, without introducing or synthesizing catalysts, reactants, or additives, and without relying on consuming friction pair materials to form a lubricating film. This involves utilizing the friction-thermal coupling effect to directly induce chemical reactions between the components of the liquid lubricant, generating adaptive solid lubricating load-bearing products in situ. The goal is to achieve high-load, adaptive, sustainable, efficient, and intelligent lubrication at the friction interface of key mechanical equipment components under harsh operating conditions.

[0004] Eutectic solvents (DESs), as a new generation of economical and environmentally friendly designable solvents, are considered an ideal alternative to traditional organic solvents. Eutectic solvents combine two or more substances through hydrogen bond networks to form eutectic liquids with melting points lower than the original components. The environmental friendliness, design flexibility, adjustable performance, excellent lubrication, and biocompatibility of eutectic solvents have led to their widespread application in the field of tribology. In particular, by controlling the structural composition of their hydrogen bond acceptors and hydrogen bond donors, they are widely used as lubricants, lubricating additives, or functionalized nanocomposite lubricating additives. However, from the perspective of existing technologies, the main methods to enhance the lubrication performance of eutectic solvents under harsh conditions such as heavy load and high temperature are: (1) adding lubricating additives to eutectic solvents; (2) controlling the strength of hydrogen bond interactions between hydrogen bond acceptors and donors in eutectic solvents, thereby controlling their viscosity and optimizing their tribological properties; and (3) utilizing the component diversity of eutectic solvents to control the chemical reactions at their friction interfaces. However, these methods still have certain shortcomings, such as the long-term stability of additives in eutectic solvents, the high viscosity which means high energy consumption, and the fact that the formation of the tribochemical reaction film at the tribochemical interface still depends on the consumption of the friction pair to participate in the tribochemical reaction. Summary of the Invention

[0005] To address the problems of existing technologies, this invention provides a eutectic solvent for the friction-induced generation of a MoS2 lubricating film, its preparation method, and its application. This invention does not require the use of catalysts, lubricating additives, or the consumption of friction pair materials, and generates a MoS2 lubricating film through a friction-induced reaction.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows: The first aspect of the present invention provides a eutectic solvent for the friction-induced generation of a MoS2 lubricating film, comprising a hydrogen bond acceptor, a hydrogen bond donor from a sulfur source, and a hydrogen bond donor from a molybdenum source, which forms a eutectic solvent that is liquid at room temperature through hydrogen bond interactions. The eutectic solvent undergoes a chemical reaction under the action of friction and heat to generate a MoS2 lubricating film at the friction interface. The molar ratio of the hydrogen bond acceptor, the hydrogen bond donor of the sulfur source, and the hydrogen bond donor of the molybdenum source is 2-8:0.1-1:0.01-1. Typical non-limiting examples include 6:1:0.05, 4:1:0.05, 4:0.5:0.05, 6:0.5:0.05, 2:0.5:0.05, 2:1:0.05, 4:1:0.05, 4:0.96:0.05, 4:0.48:0.05, 4:0.24:0.05, 2:0.5:0.5, 2:1:0.5, 4:1:0.5, 4:1:1, 6:1:0.5, 6:0.5:0.5, 4:0.5:0.5, etc., as well as any ratio within the range formed by two of these ratios. Preferably, the molar ratio of the hydrogen bond acceptor, the hydrogen bond donor of the sulfur source, and the hydrogen bond donor of the molybdenum source is 2-8:0.1-1:0.01-0.5, or 2-8:0.24-1:0.01-0.5.

[0007] In a preferred embodiment of the present invention, the hydrogen bond acceptor is a quaternary ammonium salt.

[0008] In a preferred embodiment of the present invention, the quaternary ammonium salt is selected from any one or more of betaine, choline chloride, acetylcholine chloride, tetraethylammonium bromide, tetrapropylammonium bromide, tetrabutylammonium bromide, tetraethylammonium chloride, tetrapropylammonium chloride, and tetrabutylammonium chloride.

[0009] In a preferred embodiment of the present invention, the hydrogen bond donor of the sulfur source is selected from any one or more of diallyl disulfide, diallyl thiosulfinate, allyl isothiocyanate, benzyl isothiocyanate, sulforaphane, methionine, cysteine, cystine, alliin, taurine, and lipoic acid.

[0010] In a preferred embodiment of the present invention, the hydrogen bond donor of the molybdenum source is selected from ammonium molybdate and / or molybdate.

[0011] In a preferred embodiment of the present invention, the melting point of the eutectic solvent lubricant is -60 to -40°C.

[0012] Based on the same inventive concept, a second aspect of the present invention provides a method for preparing a eutectic solvent based on friction-induced generation of a MoS2 lubricating film, comprising the following steps: S1: The hydrogen bond acceptor, the hydrogen bond donor of the sulfur source, and the hydrogen bond donor of the molar source are mixed in a molar ratio and stirred for a preset time at a preset temperature to form a eutectic solvent that is liquid at room temperature through hydrogen bond interactions. S2: Stabilize the product after the process.

[0013] In a preferred embodiment of the present invention, in step S1, the stirring speed is 400-700 rpm, the preset temperature is 50-120℃, and the time is 0.5-36 h. The stirring speed can typically be 400, 500, 600, 700 rpm, etc., or any value within a range formed by two of these values. The temperature can be 50, 60, 70, 80, 90, 100, 110, 120℃, etc., or any value within a range formed by two of these values. The stirring time can be 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 30, 36 h, etc., or any value within a range formed by two of these values.

[0014] For example, hydrogen bond acceptors, hydrogen bond donors from sulfur sources, and hydrogen bond donors from molybdenum sources are mixed in a mixing container according to a molar ratio, and the mixture is placed in an oil bath and stirred at 50-120℃ for 0.5-36 hours at a stirring speed of 400-700 rpm to form a transparent homogeneous liquid.

[0015] In a preferred embodiment of the present invention, the stabilization treatment in step S2 is performed at a temperature of 40-70°C for a time of 1-24 hours. The stabilization temperatures are 40, 50, 60, and 70°C, and any value within a range formed by two of these values. The stabilization times are 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, and 24 hours, and any value within a range formed by two of these values.

[0016] Based on the same inventive concept, the present invention also provides an application of a eutectic solvent based on friction-induced generation of MoS2 lubricating film in the field of friction lubrication, especially in friction lubrication in harsh environments such as high temperature and high load.

[0017] Because the present invention adopts the above technical solution, it has the following advantages and positive effects compared with the prior art: The eutectic solvent provided by this invention, as a friction interface lubricant, does not require catalysts or other additives. Under the action of frictional force-thermal coupling, it converts frictional mechanical energy into chemical energy, stimulating chemical reactions between the components in the eutectic solvent, and generating a molybdenum disulfide lubricating film in situ at the interface, thus providing effective lubrication. This invention overcomes the cumbersome process of traditional lubricants that rely on the use of lubricating additives or catalysts and consume friction pair materials to generate a lubricating film under harsh operating conditions. It directly utilizes friction to induce chemical reactions between the components of the eutectic solvent itself to generate a solid lubricating film in situ. Furthermore, the product yield can be controlled by adjusting the composition of the eutectic solvent. This method is simple, readily available, intelligently controllable, and energy-saving. The results of the examples show that, compared with commercial lubricants, namely polyethylene glycol (PEG 200) and polyalphaolefin (PAO 40), which experience lubrication failure under harsh operating conditions such as high temperature (80 ℃) and high load (2079 N), the eutectic solvent prepared by this invention still possesses excellent friction-reducing and anti-wear properties, with a friction coefficient of 0.064 and a wear scar diameter of 0.77 mm. Attached Figure Description

[0018] Figure 1 The infrared spectrum of the eutectic solvent prepared in Example 1 of this invention; Figure 2 Differential scanning calorimetry (DSC) curves of the eutectic solvents prepared in Examples 1 and 2 of this invention; Figure 3 The friction coefficient variation trends of the eutectic solvent and lubricating oil (PEG 200 and PAO 40) prepared in Examples 1 and 2 of this invention are shown. Figure 4 The wear scar diameter is the diameter of the eutectic solvent prepared in Examples 1 and 2 of this invention when used as a lubricant. Figure 5 The morphology and elemental distribution of the worn surface when the eutectic solvent prepared in Example 1 of this invention is used as a lubricant; Figure 6 The X-ray photoelectron spectrum (XPS) of the worn surface when the eutectic solvent prepared in Example 1 of the present invention is used as a lubricant. Figure 7 The images show the Raman spectra of the worn surfaces when the eutectic solvents prepared in Example 1 and Comparative Example 3 of this invention are used as lubricants. Detailed Implementation

[0019] Addressing the issue that existing lubricants and eutectic solvents rely on catalysts, reactants, or additives under harsh operating conditions, and suffer from the in-situ formation of a lubricating film due to the consumption of friction pair materials, this invention aims to provide a eutectic solvent that generates a molybdenum disulfide lubricating film in situ based on friction-induced chemical reactions between its components. This eutectic solvent, used as a lubricating material at the friction interface, requires no catalysts or additives. Under the action of frictional force-thermal coupling, it converts frictional mechanical energy into chemical energy, stimulating chemical reactions between the components in the eutectic solvent to generate a molybdenum disulfide lubricating film in situ at the interface, thus providing effective lubrication. It is particularly suitable for lubrication under harsh operating conditions. Compared to directly adding molybdenum disulfide to the eutectic solvent, it exhibits superior friction-reducing and anti-wear properties under harsh conditions because: 1. Molybdenum disulfide nanomaterials are added to eutectic solvents, but molybdenum disulfide nanoparticles are prone to agglomeration. Even with the addition of dispersants and other additives to inhibit molybdenum disulfide agglomeration, although agglomeration can be temporarily suppressed, the local high temperature and shear force during the friction process can still cause the dispersant molecules to desorb or decompose, leading to secondary agglomeration of MoS2 at the friction interface and abrasive wear. In contrast, the MoS2 generated in situ at the friction interface in this application can be well dispersed at the friction interface and exert the lubricating effect of MoS2. 2. The MoS2 generated in situ in this application has a high bonding strength with the friction pair base and can be well deposited on the friction interface, avoiding the peeling failure of premixed MoS2 due to physical adsorption. 3. The eutectic solvent containing sulfur and molybdenum hydrogen bond donors in this application is continuously transported to the damaged interface during the friction process, generating molybdenum disulfide as needed to repair the worn area in real time; while a certain amount of MoS2 added to the eutectic solvent from the outside is consumed and cannot be regenerated, causing the lubricating film to be quickly depleted and cannot be regenerated. 4. In terms of adaptability, the eutectic solvent with hydrogen bond donors of sulfur and molybdenum sources can generate molybdenum disulfide in situ as needed according to the changes in complex alternating friction conditions (load, temperature and rotation speed), and can better dynamically adapt to the friction interface; while exogenously added molybdenum disulfide is difficult to respond in a timely manner at the friction interface according to complex and variable service conditions.

[0020] The following detailed description, in conjunction with the accompanying drawings and specific embodiments, provides a eutectic solvent for the friction-induced generation of a MoS2 lubricating film, its preparation method, and its applications. The advantages and features of the present invention will become clearer from the following description. Example 1

[0021] (1) Weigh out tetrabutylammonium chloride (monohydrate), thioctic acid and ammonium molybdate in a molar ratio of 4:0.96:0.05 and place them in a round-bottom flask, and seal the mouth of the flask with a sealing film; (2) Place the round-bottom flask containing tetrabutylammonium chloride (monohydrate), thioctic acid and ammonium molybdate from step (1) into an oil bath and stir at 80°C for 10 hours at a stirring speed of 400 rpm to form a transparent homogeneous liquid. (3) The transparent homogeneous liquid obtained in step (2) was placed into a 20 mL glass bottle and placed in a 50 °C drying oven for stabilization treatment for 4 h. After cooling to room temperature, the eutectic solvent was finally obtained and denoted as DES1, which was used for subsequent friction experiments. Example 2

[0022] The molar ratios of tetrabutylammonium chloride (monohydrate), thioctic acid, and ammonium molybdate were adjusted to 4:0.48:0.05 and 4:0.24:0.05, respectively. The remaining steps were the same as in Example 1, resulting in DES lubricating materials with different molar ratios, which were designated as DES2 and DES3 for subsequent friction experiments. Example 3

[0023] (1) Weigh out betaine, methionine and ammonium molybdate in a molar ratio of 2:0.5:0.05 and place them in a round-bottom flask, and seal the mouth of the flask with sealing film. (2) Place the round-bottom flask containing betaine, methionine and ammonium molybdate from step (1) in an oil bath and stir at 120 °C for 10 h at a stirring speed of 400 rpm to form a transparent homogeneous liquid. (3) The transparent homogeneous liquid obtained in step (2) is placed into a 20mL glass bottle and placed in a 50℃ drying oven for stabilization treatment for 4h. After cooling to room temperature, a eutectic solvent is finally obtained. Example 4

[0024] The molar ratios of betaine, methionine, and ammonium molybdate were adjusted to 2:1:0.05, 4:1:0.05, and 4:1:0.1, respectively. The remaining steps were the same as in Example 3, resulting in DES lubricating materials with different molar ratios. Example 5

[0025] (1) Weigh out tetrapropylammonium chloride, methionine and ammonium molybdate in a molar ratio of 6:1:0.05 and place them in a round-bottom flask, and seal the mouth of the flask with a sealing film. (2) Place the round-bottom flask containing tetrapropylammonium chloride, methionine and ammonium molybdate from step (1) in an oil bath and stir at 100 °C for 10 h at a stirring speed of 700 rpm to form a transparent homogeneous liquid. (3) The transparent homogeneous liquid obtained in step (2) is placed into a 20mL glass bottle and placed in a 50℃ drying oven for stabilization treatment for 4h. After cooling to room temperature, a eutectic solvent is finally obtained. Example 6

[0026] The molar ratios of tetrapropylammonium chloride, methionine, and ammonium molybdate were adjusted to 6:0.5:0.05, 4:1:0.05, and 4:0.5:0.05, with the remaining steps being the same as in Example 5, to obtain DES lubricating materials with different molar ratios.

[0027] Comparative Example 1 To more fully describe the tribological properties of the eutectic solvent lubricant on steel surfaces, a conventional polar lubricant, PEG200, was used as a reference sample for subsequent test experiments, thereby better demonstrating the excellent friction-reducing and anti-wear properties of the prepared eutectic solvent.

[0028] Comparative Example 2 To more fully describe the tribological properties of the eutectic solvent lubricant on steel surfaces, a conventional non-polar lubricating oil, PAO40, was used as a reference sample for subsequent test experiments, thereby better demonstrating the excellent friction-reducing and anti-wear properties of the prepared eutectic solvent.

[0029] Comparative Example 3 According to the molar ratio of 4:2:0.02, tetrabutylammonium chloride (monohydrate), lipoic acid and ammonium molybdate were weighed and placed in a round-bottom flask, and the mouth of the flask was sealed with sealing film. A round-bottom flask containing tetrabutylammonium chloride (monohydrate), lipoic acid and ammonium molybdate was placed in an oil bath and stirred at 80°C for 10 hours at a stirring speed of 400 rpm to form a transparent homogeneous liquid. The obtained transparent homogeneous liquid was placed in a 20 mL glass bottle and placed in a 50 °C drying oven for stabilization treatment for 4 h. After cooling to room temperature, a eutectic solvent was finally obtained, which was used for subsequent friction experiments.

[0030] Figure 1 The infrared spectrum of the eutectic solvent prepared in Example 1 is shown below. Figure 1 It can be seen from this that at 3405cm -1 The broad peak at 1688 cm⁻¹ is a characteristic of eutectic solvents, which is attributed to the hydrogen bonding between chlorine in tetrabutylammonium chloride and lipoic acid and ammonium molybdate. This is also reflected in the carbonyl group in lipoic acid. -1 Towards 1716 cm -1 The shift, combined with the infrared spectrum of ammonium molybdate at 3175 cm⁻¹ -1 It belongs to NH4 + The stretching vibration peak of the NH bond and the 1400 cm⁻¹ peak -1 The peaks originating from the NH stretching vibrations are respectively directed towards 3405 cm⁻¹. -1 1463cm -1The shift at this point further confirms the hydrogen bond interaction between the hydrogen bond acceptor and donor in the eutectic solvent, and also proves the successful preparation of the eutectic solvent. MoS2 was not prepared at this time.

[0031] Figure 2 The DSC curves are for the eutectic solvents obtained in Examples 1, 3, and 5. Based on the DSC curves, it can be determined that the melting points of the prepared eutectic solvents are all around -40°C, far lower than the melting points of the hydrogen bond acceptors and donors. This demonstrates the successful preparation of the eutectic solvents and also indicates that the prepared eutectic solvents can remain liquid over a wide temperature range, possessing the potential to be used as liquid agents.

[0032] Friction performance test: This study demonstrates that tribomechanical properties can induce a reaction in a eutectic solvent and generate a molybdenum disulfide lubricating film in situ, and tests the tribological properties of the prepared eutectic solvent. A four-ball triboelectric wear tester was used, with one steel ball fixed to the spindle end as a friction pair, and three stationary steel balls immersed in lubricant and secured in an oil box as another friction pair. The steel balls used were GCr15 steel balls with a diameter of 12.7 mm and a hardness of 59-61 HRC. The normal load was 2079 N, the temperature was 80 °C, and the time was 1 h. Simultaneously with the in-situ synthesis, the friction coefficient and wear scar diameter of the eutectic solvent lubricant prepared in Example 1 and the two lubricating oils of Comparative Examples 1 and 2 were measured to test the tribological properties of the prepared eutectic solvent.

[0033] Figure 3 The graph shows the friction coefficients of the eutectic solvent prepared in Example 1 and the lubricating oils of Comparative Examples 1 and 2 under harsh high-temperature and heavy-load conditions over time. As can be seen from the graph, the friction coefficients of PEG 200 and PAO 40 lubricating oils rapidly exceeded 0.2 under a load of 2079 N (the maximum protection value of the friction testing machine, at which point the experiment automatically stopped), indicating that the oil film at the friction interface ruptured and lubrication failed. Conversely, the friction coefficient curve of the prepared eutectic solvent was more stable and maintained a lower friction coefficient (approximately 0.06), indicating that the prepared eutectic solvent has superior friction-reducing performance compared to the two common lubricating oils.

[0034] Figure 4 The average wear scar diameter is shown in Figure 1 after a 1-hour friction test at 2079 N using the eutectic solvent prepared in Example 1. Since the two lubricating oils in Comparative Examples 1-2 experienced lubrication failure, the experiment was automatically terminated, and therefore testing their wear scar diameter is meaningless. Figure 4 It can be seen that the wear scar diameter of the prepared eutectic solvent is about 0.77 mm, and it has excellent wear resistance.

[0035] Figure 5The image shows the surface morphology and elemental distribution of the eutectic solvent prepared in Example 1 after a friction experiment. Figure 5 It can be seen that a small number of furrows appear on the worn surface under eutectic solvent lubrication, and the sulfur element signal along the friction direction increases with the increase of the molybdenum element signal, indicating that sulfur and molybdenum in the eutectic solvent undergo a chemical reaction to generate molybdenum-sulfur compounds in situ at the friction interface; in addition, it can be seen that the sulfur element signal along the friction direction does not change with the change of the iron element signal, indicating that the eutectic solvent does not rely on the consumption of the metal friction pair to participate in the tribochemical reaction to generate a protective film.

[0036] Figure 6 The image shows the XPS spectrum of the worn surface after lubrication with the eutectic solvent prepared in Example 1. To further analyze the composition and chemical valence state of the lubricating film formed in situ by the eutectic solvent under friction-induced conditions, XPS tests were performed on the lubricating film on the worn surface. The results show that the eutectic solvent forms a molybdenum disulfide lubricating film in situ under friction-induced conditions.

[0037] Figure 7 Raman spectra of the worn surfaces lubricated with eutectic solvents prepared in Example 1 and Comparative Example 3 (Comparative Example 3 has a different formulation than Example 1, but other conditions are the same; the comparative example is not within the formulation range of this invention) are shown. To further analyze the composition of the friction film formed in situ under friction-induced conditions with different formulations of eutectic solvents, Raman tests were performed on the lubricating film on the worn surfaces. The results showed that the eutectic solvent in Example 1 formed a molybdenum disulfide lubricating film in situ under friction-induced conditions, while the eutectic solvent in Comparative Example 4 formed a friction film mainly composed of iron oxides and iron sulfides under friction-induced conditions, without forming molybdenum disulfide.

[0038] In summary, the eutectic solvent of this invention, composed of hydrogen bond acceptors, sulfur-containing hydrogen bond donors, and molybdenum-containing hydrogen bond donors, regulates the chemical projection activity between hydrogen bond acceptors and donors by adjusting the appropriate ratio, promoting the reaction between hydrogen bond acceptors and donors at the friction interface, thereby avoiding dependence on additional catalysts or complex additives. Furthermore, the eutectic solvent of this invention cannot synthesize MoS2 under static conditions because the high reaction energy barrier and strong hydrogen bond network confine the reactants; however, the friction process, through mechanochemical mechanisms including generating local flash temperature and high pressure to decompose and release active sulfur and reduce the molybdenum source, can disrupt the original hydrogen bond network in the eutectic solvent to release reactants, and may catalyze nucleation at the friction metal interface, thus overcoming kinetic limitations and achieving instantaneous synthesis and deposition of MoS2. Therefore, the eutectic solvent of this invention does not require any catalysts or additives, and can only synthesize MoS2 under friction-induced conditions, exhibiting low friction and excellent anti-wear performance even under harsh operating conditions.

[0039] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to the above embodiments. Even if various changes are made to the present invention, if these changes fall within the scope of the claims of the present invention and their equivalents, they shall still fall within the protection scope of the present invention.

Claims

1. A eutectic solvent based on friction-induced formation of a MoS2 lubricating film, characterized in that, The system includes hydrogen bond acceptors, hydrogen bond donors from sulfur sources, and hydrogen bond donors from molybdenum sources. These hydrogen bond donors interact to form a eutectic solvent that is liquid at room temperature. The eutectic solvent undergoes a chemical reaction under frictional-thermal action to generate a MoS2 lubricating film at the frictional interface. The molar ratio of the hydrogen bond acceptor, the hydrogen bond donor of the sulfur source, and the hydrogen bond donor of the molybdenum source is 2-8:0.1-1:0.01-1; The hydrogen bond acceptor is a quaternary ammonium salt; The hydrogen bond donor of the sulfur source is selected from any one or more of diallyl disulfide, diallyl thiosulfinate, allyl isothiocyanate, benzyl isothiocyanate, sulforaphane, methionine, cysteine, cystine, alliin, taurine, and lipoic acid. The hydrogen bond donor of the molybdenum source is selected from ammonium molybdate and / or molybdate.

2. The eutectic solvent based on friction-induced formation of a MoS2 lubricating film according to claim 1, characterized in that, The quaternary ammonium salt is selected from any one or more of betaine, choline chloride, acetylcholine chloride, tetraethylammonium bromide, tetrapropylammonium bromide, tetrabutylammonium bromide, tetraethylammonium chloride, tetrapropylammonium chloride, and tetrabutylammonium chloride.

3. The eutectic solvent based on friction-induced formation of a MoS2 lubricating film according to claim 1, characterized in that, The melting point of the eutectic solvent lubricant is -60 to -40°C.

4. A method for preparing a eutectic solvent based on friction-induced formation of a MoS2 lubricating film according to any one of claims 1-3, characterized in that, Includes the following steps: S1: The hydrogen bond acceptor, the hydrogen bond donor of the sulfur source, and the hydrogen bond donor of the molar source are mixed in a molar ratio and stirred for a preset time at a preset temperature to form a eutectic solvent that is liquid at room temperature through hydrogen bond interactions. S2: Stabilize the product after the process.

5. The method for preparing a eutectic solvent based on friction-induced formation of a MoS2 lubricating film according to claim 4, characterized in that, In step S1, the stirring speed is 400-700 rpm, the preset temperature is 50-120℃, and the time is 0.5-36 h.

6. The method for preparing a eutectic solvent based on friction-induced formation of a MoS2 lubricating film according to claim 4, characterized in that, The stabilization treatment in step S2 is carried out at a temperature of 40-70℃ for 1-24 hours.

7. The application of a eutectic solvent based on friction-induced formation of a MoS2 lubricating film according to any one of claims 1-3 in the field of friction lubrication.

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