Conductive two-dimensional material functionalized complexing urea-based lubricating grease as well as preparation method and application thereof

Abstract

The invention discloses conductive two-dimensional material functionalized complexing urea-based lubricating grease as well as a preparation method and application thereof. The urea-based lubricating grease comprises a urea-group-containing oil-soluble single-layer conductive two-dimensional material and polyurea lubricating grease, wherein the ureido-containing oil-soluble single-layer conductive two-dimensional material is obtained by performing amination modification on a conductive two-dimensional material of which the surface of a few-layer nanosheet layer contains hydroxyl, and then reacting with alkyl isocyanate to form ureido. The problems that in the prior art, a functional additive is mechanically mixed into lubricating grease, stability is poor, and the electric corrosion risk is increased are solved, stable dispersion can be achieved, agglomeration is avoided, the remarkable friction reducing and wear resisting effects are achieved, and the low resistance and electric corrosion protection effects are achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of grease materials, and specifically relates to a conductive two-dimensional material functionalized complex urea-based grease, and a preparation method and application thereof. Background Art

[0002] With the advancement of science and technology, electric drive systems in new energy vehicles are characterized by high voltage, high power, high frequency, and high speed. This means that the grease used in electric drive systems faces higher shaft voltages, making the bearing oil film more susceptible to breakdown. Furthermore, high speeds, high power, and shaft currents cause bearings to operate at higher temperatures, leading to rapid failure due to electrothermal damage. Therefore, the risk of electrocorrosion in electric drive systems of new energy vehicles has increased dramatically, and particular attention must be paid to the risk of electrocorrosion in the gearbox-side bearings.

[0003] As a solution for preventing and controlling bearing electrocorrosion, insulating coatings or ceramic bearings are currently commonly used. The purpose is to avoid bearing electrocorrosion through insulation blocking. This requires changing the bearing design and is costly. It is commonly used in fields such as wind power, while in the field of new energy vehicles, it is more hoped to reduce costs by using conductive grease.

[0004] Studies have shown that electrical conductivity is more effective than electrical insulation in preventing electrical damage. Conductive greases, by creating current paths and reducing current density in contact areas, are superior to non-conductive greases in preventing electrical pitting in motor bearings. Conductive materials, such as carbon materials (graphite, carbon nanotubes, graphene), metals, and metal oxides, have been used as additives. However, at higher concentrations, conductive materials tend to increase mechanical wear, leading to deterioration in lubrication and wear resistance. Therefore, selecting a material with excellent electrical conductivity and lubrication properties is crucial.

[0005] The advantage of MXene as an additive lies in its layered structure and weak interlayer interaction, which enables it to form a uniform and continuous friction film in the lubricant, thereby effectively improving the friction performance of the material. At the same time, it does not contain harmful elements such as sulfur and phosphorus, which meets environmental protection requirements. However, Ti3C2T x It is the most widely used type in the MXene family and has excellent hydrophilicity. According to previous reports, Ti3C2T x The concentration in organic solvents is usually less than 0.5 mg / mL. When dispersed in non-polar oils (such as PAO), its stability is even lower, and local agglomeration is difficult to avoid during the material preparation process, which makes Ti3C2T x Not suitable as an additive for PAO-based polyurea greases.

[0006] Existing grease technology focuses on the relationship between base greases (such as lithium-based greases, urea-based greases, and bentonite-based greases) and additives, with research focused on reducing and preventing wear. Researchers working on conductive greases have also simply mechanically incorporated functional additives into the grease to improve its electrical conductivity. In this traditional grease formulation, the thickener (polyurea grease) and additives are completely separate, meaning they interact as independent components in the frictional interaction. While this approach appears to be rapid and effective in improving specific functionalities, it has led to significant misunderstandings in current research: first, whether the stable dispersion of additives in the grease system can be guaranteed, and second, the impact of thickeners (which comprise a significant proportion of the grease) on improving lubrication performance is often overlooked, severely hindering the development of high-performance greases. Furthermore, the lack of interaction between thickeners and conductive additives leads to insufficient stability, resulting in a sharp decline in grease stability and conductivity over long periods of operation. Furthermore, when conductive particles agglomerate and degrade, the conductive fillers, acting as mechanical impurities, further increase the risk of electrical corrosion in bearings. In addition, the thickener of traditional conductive grease mainly plays a thickening role. The main components of the lubricating oil film are precipitated oil and additives. The oil film formed without the participation of the thickener is relatively weak.

[0007] For example, Chinese patents with patent application numbers CN202310300477.0, CN201710932491.7, and CN202410232203.7, as well as papers Lubrication Science. 2022;34:182–195, TribologyInternational 191 (2024) 109137, and Tribology International 186 (2023) 108565, etc., improve the conductivity of grease by adding conductive ion salts, conductive graphite, conductive polymers, or MXene to the base grease, and study its antistatic effect and tribology under current. However, these works did not consider whether its dispersion is stable and were not used in the prevention and control of bearing electrocorrosion.

[0008] It should be noted that the information disclosed in the above background technology section is only used to enhance the understanding of the background of the present disclosure, and therefore may include information that does not constitute prior art known to ordinary technicians in the field. Summary of the Invention

[0009] The purpose of the present invention is to provide a conductive two-dimensional material functionalized complex urea-based grease and its preparation method and application, which solves the problems of poor stability and increased risk of electrolytic corrosion caused by mechanically mixing functional additives into grease. It can be stably dispersed and not agglomerated, has significant friction reduction and anti-wear effects, and also has low resistance and electrolytic corrosion protection effects.

[0010] In order to achieve the above-mentioned objectives, the present invention provides a conductive two-dimensional material functionalized complex urea-based grease, which comprises: an oil-soluble single-layer conductive two-dimensional material containing a urea group and a polyurea grease; wherein the oil-soluble single-layer conductive two-dimensional material containing a urea group is obtained by amino-modifying a conductive two-dimensional material containing hydroxyl groups on the surface of a few-layer nanosheet, and then reacting it with an alkyl isocyanate to form a urea group.

[0011] Preferably, the oil-soluble single-layer conductive two-dimensional material containing urea groups is obtained by reacting a conductive two-dimensional material containing hydroxyl groups on the surface of a few-layer nanosheet with KH550 to achieve amino modification on the surface of the conductive two-dimensional material containing hydroxyl groups on the surface of the few-layer nanosheet, and then reacting with octadecyl isocyanate to form a urea group.

[0012] Preferably, the polyurea grease is a polyurea grease having a thickener mass fraction of 8%; or / and, in the polyurea grease, the thickener is a polyurea formed by the reaction of 4,4'-methylenebis(phenyl isocyanate) with cyclohexylamine and octadecylamine; or / and, in the polyurea grease, the base oil comprises any one or more of PAO8, PAO10 and PAO20; or / and, the conductive two-dimensional material is selected from GO, rGO, Ti3C2T x 、V2CT x 、Nb2CT x 、Ti2CT x and Mo2CT x Any one or two or more of the following.

[0013] Preferably, the mass fraction of the urea-containing oil-soluble single-layer conductive two-dimensional material is 0.1-2.0 wt%.

[0014] A second object of the present invention is to provide a method for preparing the conductive two-dimensional material functionalized complex urea-based grease, the method comprising: (1) Preparation of oil-soluble single-layer conductive two-dimensional materials containing urea groups The aminosilane is mixed in an alcohol-water mixed solution under alkaline conditions, and an aqueous solution of a conductive two-dimensional material containing hydroxyl groups on the surface of a few nanosheets is added, and the mixture is reacted under reflux. After the reaction is completed, the conductive two-dimensional material modified by amino group is post-treated to obtain the conductive two-dimensional material modified by amino group, and the conductive two-dimensional material modified by amino group is dispersed in water to obtain an aqueous solution of the conductive two-dimensional material modified by amino group; Alkyl isocyanate is dissolved in dichloromethane and gradually added to an aqueous solution of an amino-modified conductive two-dimensional material to form a microemulsion, providing a large amount of two-phase interface. The reaction is stirred at room temperature, and the -CNO group in the alkyl isocyanate reacts with the -NH2 group in the amino-modified conductive two-dimensional material. After the reaction is completed, the dichloromethane solution of the oil-soluble single-layer conductive two-dimensional material containing urea groups is separated by liquid-liquid separation. (2) Preparation of conductive two-dimensional material functionalized complex urea-based grease A dichloromethane solution of an oil-soluble single-layer conductive two-dimensional material containing urea groups is added to the polyurea grease, and the mixture is stirred at 50-60°C and mixed evenly. After the reaction is completed, the dichloromethane solvent is removed, and the conductive two-dimensional material functionalized complex urea-based grease is obtained after grinding.

[0015] Preferably, the aminosilane comprises: KH550; or / and, the alkaline conditions are adjusted with ammonia water; or / and, the alkyl isocyanate comprises: octadecyl isocyanate; or / and, the amount of KH550 and the conductive two-dimensional material containing hydroxyl groups on the surface of the few-layer nanosheet is in the ratio of 1 mL:1200 mg; or / and, in the preparation of the amino-modified conductive two-dimensional material, the volume ratio of water to ethanol is 1:1; or / and, the reflux temperature is 70°C.

[0016] Preferably, the mass fraction of the urea-containing oil-soluble single-layer conductive two-dimensional material is 0.1~2.0 wt%; or / and, the polyurea grease is a polyurea grease with a thickener mass fraction of 8%; or / and, the preparation method of the polyurea grease comprises: adding 4,4'-methylenebis(phenyl isocyanate) to PAO8, and continuously stirring at 60~70 ° C until completely dissolved to obtain a mixture A; adding cyclohexylamine and octadecylamine to the base oil, and stirring thoroughly at 80~90 ° C to obtain a uniform mixture B; quickly adding mixture B to mixture A and reacting at 90 ° C, then heating the reaction system to 110~120 ° C and maintaining at this temperature, then raising the temperature to 140~150 ° C and maintaining it, and after the reaction is completed, rapidly cooling and grinding to obtain polyurea grease.

[0017] More preferably, the mass ratio of the 4,4'-methylenebis(phenyl isocyanate), cyclohexylamine and octadecylamine is 171-172:137-138:91-92; or / and, the 4,4'-methylenebis(phenyl isocyanate) is added to PAO8, and the mass ratio of the 4,4'-methylenebis(phenyl isocyanate) to PAO8 is 190-191:2300; or / and, cyclohexylamine and octadecylamine are added to the base oil, and the mass ratio of the base oil to cyclohexylamine and octadecylamine is 2300:137-138:91-92; or / and, the base oil comprises: any one or more of PAO8, PAO10 and PAO20.

[0018] Preferably, the conductive two-dimensional material containing hydroxyl groups on the surface of the few-layer nanosheet is selected from the few-layer nanosheet Ti3C2T x , the few-layer nanosheet Ti3C2T xThe preparation method comprises: slowly adding Ti3AlC2 powder to a mixed solution of LiF and HCl, stirring at 35 ° C, and obtaining an etched Ti3C2T x The solution was centrifuged several times until the pH of the supernatant was close to 7; the precipitate was then collected, washed with ethanol, ultrasonically dispersed, centrifuged, and the precipitate was resuspended in water and centrifuged to obtain a few-layer nanosheet Ti3C2T x aqueous solution.

[0019] The third object of the present invention is to provide the application of the conductive two-dimensional material functionalized complex urea-based grease in bearings.

[0020] The conductive two-dimensional material functionalized complex urea-based grease of the present invention, and its preparation method and application, solve the problems of poor stability and increased risk of galvanic corrosion caused by mechanically mixing functional additives into grease. It has the following advantages: (1) The present invention combines a single layer of conductive two-dimensional materials (such as GO, rGO, Ti3C2T x 、V2CT x 、Nb2CT x 、Ti2CT x 、Mo2CT x ) modification, amino-modification (using aminosilane) on the surface of the single-layer conductive two-dimensional material and reaction with alkyl isocyanate with a long alkyl chain, so that the single-layer conductive two-dimensional material has hydrophobic properties, and the obtained oil-soluble single-layer conductive two-dimensional material containing urea groups can be stably dispersed in base oil and grease without agglomeration. The conductive two-dimensional material functionalized complex urea-based grease obtained by compounding with polyurea grease has significant wear reduction and anti-wear effects, as well as low resistance and electrical corrosion protection effects; (2) The present invention combines a urea-containing oil-soluble single-layer conductive two-dimensional material with a polyurea grease. The two materials contain homologous urea groups and can be effectively combined organically through hydrogen bonding to form a multifunctional complex thickening system in which the additive and thickener molecules act together, thereby increasing the stability of the material. (3) The present invention adjusts the oil-soluble Ti3C2T x The ratio of Ti3C2T to polyurea grease (0.1%~2%) forms a eutectic hydrogen bond thickening system with excellent lubrication performance and conductivity. x The formation of urea-based lubrication system is also conducive to the rapid dissipation of heat in grease. The thickened grease releases Ti3C2T xNanosheets can fully exert their load-bearing and lubricating functions, and the interlayers are easy to shear, forming a unique nanostructured friction film with excellent anti-friction and anti-wear properties. In the SRV friction test, it showed a wear-reducing and anti-wear effect. In the interface resistance ECR test, it showed low contact resistance. In the bearing bench test, Ti3C2T x The composite urea-based thickening system forms a conductive oil film, which can significantly prevent galvanic corrosion damage at extremely low concentrations;

[0021] (4) The present invention utilizes the difference in reaction rates among -NH3, H2O, and -CNO groups, and adds an aqueous solution of an amino-modified single-layer conductive two-dimensional material to a dichloromethane solution containing an alkyl isocyanate to form a microemulsion, providing a large amount of two-phase interface. The reactivity of -CNO with -NH3 is 1000 times that of water. By cleverly utilizing the microinterface reaction with low reactivity, an oil-soluble, urea-containing single-layer conductive two-dimensional material is successfully synthesized. The material is used as a complexing thickener. By adjusting the content of the prepared complexing thickener and interacting with the polyurea grease thickener, a conductive two-dimensional material functionalized urea-based multi-hydrogen bond thickening system is developed; (5) The process preparation method of the present invention is novel and can effectively improve the oil solubility modification of single-layer conductive materials. x The modification method is not suitable for the modification of few-layer non-polar two-dimensional materials. This method has a wide applicability and can be extended to all other two-dimensional sheet materials to introduce urea groups and perform oil-soluble modification at the same time. It is also suitable for the introduction of urea groups and oil-soluble modification of other materials containing -OH on the surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram of the principle of modifying a single-layer conductive two-dimensional material according to the present invention.

[0023] Figure 2 Ti3C2T x Dispersion state diagram of dispersion in PAO base oil; the left side is before modification and the right side is after modification.

[0024] Figure 3 Graph showing the coefficient of friction of the comparative example and Example 3 of the present invention.

[0025] Figure 4 Graphs of interface resistance of the comparative example and Example 3 of the present invention.

[0026] Figure 5 The figures are diagrams showing the electrical corrosion of the bearings of Comparative Example (a) and Example 3 (b) of the present invention under an AC electric field; the following are partial enlarged views of (a) and (b).

[0027] Figure 6The optical interference diagram of the ball-on-disk oil film thickness of the urea-based grease of the embodiment of the present invention and the comparative example at 15N and 1000 mm / s. DETAILED DESCRIPTION

[0028] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0029] Note: If specific conditions are not specified in the examples, the experiments were conducted under conventional conditions or those recommended by the manufacturer. Instruments used without manufacturer information are commercially available. Raw materials and reagents used without manufacturer information are commercially available or can be prepared by known methods.

[0030] Throughout this disclosure, all features, such as values, amounts, amounts, and concentrations, specified in numerical ranges or percentage ranges are provided for simplicity and convenience only. Accordingly, the description of numerical ranges or percentage ranges should be considered to encompass and specifically disclose all possible subranges and individual values ​​within those ranges (including integers and fractions).

[0031] The features described in this disclosure may be combined in any manner, and as long as there are no conflicts between the combinations of these features, all possible combinations should be considered within the scope of this specification. Each feature disclosed in this specification may be replaced by any alternative feature that provides the same, equivalent, or similar purpose. Therefore, unless otherwise specified, the features disclosed are merely general examples of equivalent or similar features.

[0032] Examples 1 to 4 A Ti3C2T x Functionalized complex urea-based grease, the preparation method of which comprises: (1) Ti3C2T x Preparation of few-layer nanosheets: Stir 1.6 g of LiF and 20 mL of 9 M HCl solution in a polyphenylene ether beaker to ensure thorough mixing. Subsequently, slowly add 1 g of Ti3AlC2 powder and stir in a 35 °C water bath for 24 h to obtain the etched Ti3C2T xThe solution was divided into two 50 mL centrifuge tubes. Centrifuged at 3500 rpm, water was added and centrifuged repeatedly until the pH of the supernatant was close to 7. The precipitate was then collected, washed with excess ethanol, and ultrasonically dispersed for 2 h using a 300W ultrasonic processor. Subsequently, the dispersion was centrifuged at 10000 rpm for 10 minutes to collect the precipitate. The precipitate was resuspended in 40 mL of deionized water and centrifuged at 3500 rpm for 10 minutes. Ti3C2T x The few nanosheets are on the upper part, and the unreacted multilayers are precipitated to obtain the upper black Ti3C2T x The aqueous solution was prepared with deionized water to a concentration of 20 mg / mL Ti3C2T x aqueous solution.

[0033] (2) Oil-soluble single-layer Ti3C2T containing urea groups x Preparation In order to prepare oil-soluble Ti3C2T x First, the material was amino-modified. 1 mL of KH550 was added to a mixture of 200 mL of deionized water and ethanol (the volume ratio of water to ethanol was 1:1). Next, 3 mL of ammonia water was added and the mixture was stirred magnetically until it was completely homogeneous. After it was completely dissolved, 60 mL of the Ti3C2T prepared above was added. x The aqueous solution was added to the prepared KH550 solution and refluxed at 70 °C for 24 h. The resulting suspension was then centrifuged at 5000 rpm and washed five times with deionized water to ensure complete removal of unreacted KH550. The precipitated Ti3C2T x -NH3 was dispersed in 100mL of aqueous solution and stored.

[0034] Then, 2 mL of octadecyl isocyanate solution was added to 100 mL of dichloromethane and gradually added to 100 mL of Ti3C2T x -NH3 aqueous solution, and magnetic stirring was performed at room temperature for 1 hour to ensure that Ti3C2T x The oil-soluble Ti3C2T x The dichloromethane dispersion was washed several times with a mixture of dichloromethane and ethanol by centrifugation (8000 rpm, 10 min) to remove any residual isocyanate and water by-products. x Dispersed in dichloromethane at a concentration of 50 mg / mL.

[0035] (3) Ti3C2T x Preparation of functionalized complex urea-based grease 171.5 g of MDI (4,4'-methylenebis(phenyl isocyanate)) was added to a 5.00 L stainless steel reactor containing 2300.00 g of PAO8 (hydrogenated polydecene) and stirred continuously at 60–70°C until completely dissolved, yielding Mixture A. Similarly, 137.1 g of cyclohexylamine (CA) and 91.4 g of octadecylamine (OA) were added to 2300.00 g of PAO8 base oil and stirred thoroughly at 80–90°C to yield a homogeneous Mixture B. Mixture B was then rapidly added to Mixture A and allowed to react at 90°C for 1 hour. The reaction system was then heated to 110–120°C and maintained at this temperature for 1 hour, during which time an additional 2 mL of CA was added to remove excess MDI. The temperature was then raised to 140–150°C and maintained for 30 minutes. After rapid cooling and grinding on a three-roll mill, a polyurea grease with an 8% thickener mass fraction was obtained.

[0036] Finally, a certain amount of oil-soluble Ti3C2T was added to the 8% polyurea grease. x The mixture was stirred at 50-60 °C for 10 minutes to ensure uniform mixing and remove the dichloromethane solvent. After three times of processing on a three-roll mill, the oil-soluble Ti3C2T x Ti3C2T with mass fractions of 0.1 wt%, 0.3 wt%, 0.5 wt%, 1.0 wt% and 2.0 wt% x The functionalized complex urea-based greases are named M-0.1, M-0.3, M-0.5, M-1.0, and M-2.0, corresponding to Example 1, Example 2, Example 3, Example 4, and Example 5, respectively.

[0037] Comparative Example It is basically the same as Example 1, except that: Without adding oil-soluble Ti3C2T x The polyurea grease with a thickening mass fraction of 8% was named M-0.0.

[0038] Experimental Example 1 Dispersion Stability Test The unmodified Ti3C2T prepared in the example x Few-layer nanosheets and oil-soluble monolayer Ti3C2T containing urea groups x Dispersed in PAO8 base oil for 48 hours, the results are shown in Figure 2 .

[0039] like Figure 2 As shown, it is Ti3C2T x The dispersion state of Ti3C2T in PAO base oil is shown on the left before modification and on the right after modification.x It can be stably dispersed in PAO, therefore, it has better dispersion stability during compounding with polyurea grease.

[0040] Experimental Example 2 Tribological Performance Test Tribological properties were evaluated over a 1 mm stroke using an SRV-V reciprocating friction and wear tester (Optimal Oil, Germany). The disc dimensions were 24 × 8 mm, with a surface roughness (Ra) of approximately 11 nm. The test conditions were: a load of 200 N, a frequency of 25 Hz, and a temperature of 50°C.

[0041] Table 1 shows the average friction coefficient and average wear volume of the examples and comparative examples of the present invention. like Figure 3 The friction coefficient diagrams of the comparative example and embodiment 3 of the present invention are shown in FIG. Figure 3 As can be seen from Table 1, the friction coefficient and wear volume of the embodiment of the present invention are lower than those of the comparative example, which is more obvious in the wear volume. The wear volume of Example 3 is reduced by 90.87% compared with the comparative example, which proves that the prepared Ti3C2T x The complex urea-based thickening system has excellent friction reduction and anti-wear effects.

[0042] like Figure 4 As shown, the interface resistance diagram of the comparative example and embodiment 3 of the present invention is shown. Figure 4 It can be found that in the SRV-V reciprocating friction and wear tester, the interface resistance of the comparative example is almost zero in the initial stage of friction because the friction lubricating film has not yet formed and is in direct contact. As the friction time increases and the lubricating film is formed, the interface resistance increases. However, the Ti3C2T x Functionalized complex urea grease is still conductive after forming a lubricating oil film after long-term friction, and the interface resistance is stable and close to 0, which proves that the Ti3C2T x Complex urea-based grease has the effect of reducing friction and resisting wear, and can also form a low interfacial resistance oil film.

[0043] Experimental Example 3: Bearing electrical corrosion protection performance test The bearing electrocorrosion test was conducted on a test bench independently developed by the Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences. The bearing size used was 25 mm × 52 mm × 15 mm. The experimental conditions included 2 mL Ti3C2T x The complex urea-based grease was evenly applied to the bearing track contact area. The bearing speed was 3000 rpm, the applied alternating voltage was 11-14 V, the constant current was 23-24 A, and the running time was 6 hours.

[0044] like Figure 5 The following are the electrical corrosion conditions of the bearings of the comparative example (a) and embodiment 3 (b) of the present invention under AC electric field. Figure 5 As can be seen in the comparative example, when the electric field accumulates on both sides of the oil film and reaches sufficient strength to penetrate the oil film, a tip discharge occurs, forming a burn pit. Due to the uneven distribution, the damaged area is more likely to discharge repeatedly at the same location. Therefore, when the rotor rotates at high speed, the bearing undergoes a continuous charge-discharge breakdown process, forming a washboard pattern. In Example 3, the electrical corrosion resistance is significantly improved, and the current is in the on-state during operation, which effectively reduces the electrical corrosion of the bearing.

[0045] Ti3C2T x The composite urea-based thickening system forms a conductive oil film. Compared with the polyurea-based ester, the system has a certain content of Ti3C2T x In Example 3, Ti3C2T x No electrolytic stripes appeared in the system, proving that the Ti3C2T prepared by this method x Complex urea-based grease has obvious galvanic corrosion protection effect.

[0046] Experimental Example 4 Oil Film Thickness Analysis An optical ball-on-disc tribometer was used for testing, employing red (approximately 640 nm) and green (approximately 525 nm) laser sources. Urea-based greases prepared in the examples or comparative examples of the present invention were applied to the contact surface between a sphere and a spherical track. The elastohydrodynamic lubrication (EHL) contact area was observed using a microscope. Interference images were captured using a high-speed CCD camera, and the lubricant film thickness was measured using dual-wavelength interferometric intensity modulation (DIIM) technology.

[0047] like Figure 6 The figure shows the optical interference diagram of the ball-on-disk oil film thickness of the urea-based grease of the embodiment of the present invention and the comparative example under 15N and 1000 mm / s. It can be seen that since the comparative example polyurea-based grease forms a thin, non-conductive oil film, it is particularly easy to be broken down in the presence of an electric field. x As the content of Ti3C2T increases, the total thickness of the oil film also increases. This trend may be due to the fact that x It tends to adsorb on the contact surface and form a boundary film. In addition, Ti3C2T x With the hydrogen bond interaction between Ti3C2T x With the increase of content, the modified Ti3C2T with urea groups x It tends to adsorb on the contact surface and may carry polyurea thickener molecules, thereby increasing the thickness of the oil film.

[0048] Although the present invention has been described in detail through the above preferred embodiments, it should be understood that the above description is not intended to limit the present invention. After reading the above description, various modifications and substitutions of the present invention will become apparent to those skilled in the art. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A conductive two-dimensional material functionalized complex urea-based grease, characterized in that: The urea-based grease comprises: an oil-soluble single-layer conductive two-dimensional material containing a urea group and a polyurea grease; The oil-soluble single-layer conductive two-dimensional material containing urea groups is obtained by amino-modifying a conductive two-dimensional material containing hydroxyl groups on the surface of a few-layer nanosheet layer, and then reacting the material with alkyl isocyanate to form a urea group.

2. The conductive two-dimensional material functionalized complex urea-based grease according to claim 1, characterized in that: The oil-soluble single-layer conductive two-dimensional material containing urea groups is obtained by reacting a conductive two-dimensional material containing hydroxyl groups on the surface of a few-layer nanosheet with KH550 to achieve amino modification on the surface of the conductive two-dimensional material, and then reacting with octadecyl isocyanate to form a urea group.

3. The conductive two-dimensional material functionalized complex urea-based grease according to claim 1, characterized in that: The polyurea grease is a polyurea grease with a thickener mass fraction of 8%; Or / and, in the polyurea grease, the thickener is a polyurea formed by the reaction of 4,4'-methylenebis(phenyl isocyanate) with cyclohexylamine and octadecylamine; Or / and, in the polyurea grease, the base oil comprises: any one or more of PAO8, PAO10 and PAO20; Or / and, the conductive two-dimensional material is selected from GO, rGO, Ti3C2T x 、V2CT x 、Nb2CT x 、Ti2CT x and Mo2CT x Any one or two or more of the following.

4. The conductive two-dimensional material functionalized complex urea-based grease according to any one of claims 1 to 3, characterized in that: The mass fraction of the urea-containing oil-soluble single-layer conductive two-dimensional material is 0.1-2.0 wt%.

5. The method for preparing the conductive two-dimensional material functionalized complex urea-based grease according to any one of claims 1 to 4, characterized in that: The method includes: (1) Preparation of oil-soluble single-layer conductive two-dimensional materials containing urea groups The aminosilane is mixed in an alcohol-water mixed solution under alkaline conditions, and an aqueous solution of a conductive two-dimensional material containing hydroxyl groups on the surface of a few nanosheets is added, and the mixture is reacted under reflux. After the reaction is completed, the conductive two-dimensional material modified by amino group is post-treated to obtain the conductive two-dimensional material modified by amino group, and the conductive two-dimensional material modified by amino group is dispersed in water to obtain an aqueous solution of the conductive two-dimensional material modified by amino group; Alkyl isocyanate is dissolved in dichloromethane and gradually added to an aqueous solution of an amino-modified conductive two-dimensional material to form a microemulsion, providing a large amount of two-phase interface. The reaction is stirred at room temperature, and the -CNO group in the alkyl isocyanate reacts with the -NH2 group in the amino-modified conductive two-dimensional material. After the reaction is completed, the dichloromethane solution of the oil-soluble single-layer conductive two-dimensional material containing urea groups is separated by liquid-liquid separation. (2) Preparation of conductive two-dimensional material functionalized complex urea-based grease A dichloromethane solution of an oil-soluble single-layer conductive two-dimensional material containing urea groups is added to the polyurea grease, and the mixture is stirred at 50-60°C and mixed evenly. After the reaction is completed, the dichloromethane solvent is removed, and the conductive two-dimensional material functionalized complex urea-based grease is obtained after grinding.

6. The preparation method according to claim 5, characterized in that The aminosilane comprises: KH550; or / and, the alkaline condition is adjusted by using aqueous ammonia; or / and, the alkyl isocyanate comprises: octadecyl isocyanate; Or / and, the amount of the KH550 and the conductive two-dimensional material containing hydroxyl groups on the surface of the few-layer nanosheet is 1 mL: 1200 mg; Or / and, in the preparation of the amino-modified conductive two-dimensional material, the volume ratio of water to ethanol is 1:1; Or / and, the reflux temperature is 70°C.

7. The preparation method according to claim 5, characterized in that The mass fraction of the oil-soluble single-layer conductive two-dimensional material containing urea groups is 0.1-2.0 wt%; Or / and, the polyurea grease is a polyurea grease with a thickener mass fraction of 8%; Or / and, the preparation method of the polyurea grease comprises: 4, 4'-methylenebis(phenyl isocyanate) was added to PAO8 and stirred continuously at 60-70°C until completely dissolved to obtain mixture A. Cyclohexylamine and octadecylamine were added to the base oil and stirred thoroughly at 80-90°C to obtain a uniform mixture B. Mixture B was quickly added to mixture A and reacted at 90°C. The reaction system was then heated to 110-120°C and maintained at this temperature. The temperature was then increased to 140-150°C and maintained. After the reaction was completed, the mixture was rapidly cooled and ground to obtain a polyurea grease.

8. The preparation method according to claim 7, characterized in that The mass ratio of the 4,4'-methylenebis(phenyl isocyanate), cyclohexylamine and octadecylamine is 171-172:137-138:91-92; or / and, the 4,4'-methylenebis(phenyl isocyanate) is added to PAO8, the mass ratio of the 4,4'-methylenebis(phenyl isocyanate) to PAO8 being 171-172:2300; or / and, cyclohexylamine and octadecylamine are added to the base oil, and the mass ratio of the base oil to the cyclohexylamine and octadecylamine is 2300:137-138:91-92; Or / and, the base oil comprises: any one or two or more of PAO8, PAO10 and PAO20.

9. The preparation method according to claim 5, characterized in that The conductive two-dimensional material containing hydroxyl groups on the surface of the few-layer nanosheet is selected from the few-layer nanosheet Ti3C2T x , the few-layer nanosheet Ti3C2T x A preparation method comprising: Ti3AlC2 powder was slowly added to the mixed solution of LiF and HCl and stirred at 35 °C to obtain the etched Ti3C2T x The solution was centrifuged several times until the pH of the supernatant was close to 7; The precipitate was then collected, washed with ethanol, ultrasonically dispersed, and centrifuged. The precipitate was resuspended in water and centrifuged to obtain a few-layer nanosheet Ti3C2T x aqueous solution.

10. Use of the conductive two-dimensional material functionalized complex urea-based grease according to any one of claims 1 to 4 in bearings.

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