A water-based lubricating fluid for black phosphorus nanosheets and preparation method thereof

Abstract

The present invention discloses a water-based lubricant for black phosphorus nanosheets and a preparation method thereof, comprising the following steps: S1, thoroughly ultrasonically treating black phosphorus nanosheets, citric acid, and anhydrous ethanol in proportion to obtain a uniform mixture to obtain a mixed sample; S2, reacting the mixed sample at a certain temperature, and after the anhydrous ethanol is completely evaporated, obtaining citric acid-modified black phosphorus nanosheets, and using the citric acid-modified black phosphorus nanosheets as a water-based lubricant additive; S3, dissolving the citric acid-modified black phosphorus nanosheets in an aqueous solution of polyethylene glycol, and ultrasonically treating the black phosphorus nanosheets to obtain a water-based lubricant for the black phosphorus nanosheets. The present invention modifies the black phosphorus nanosheets to obtain P-OH bonds, HO-P=O bonds, and P=O bonds on their surfaces, thereby enabling the black phosphorus nanosheets to obtain better lubrication performance as a water-based lubricant additive. Furthermore, an excellent lubrication effect is achieved through the synergistic lubrication effect of the polyethylene glycol and the modified black phosphorus nanosheets in the lubricant.

Description

Technical Field

[0001] The present invention relates to the technical field of black phosphorus nanosheets, and in particular to a water-based lubricating liquid for black phosphorus nanosheets and a preparation method thereof. Background Art

[0002] Currently, commonly used lubrication methods include solid, liquid, and solid-liquid coupled lubrication. Solid lubricants typically have a high coefficient of friction, making heat conduction between friction pairs difficult. Liquid lubricants offer advantages over solid lubricants, such as superior cooling and low pollution. However, their poor lubrication, low viscosity, and corrosion resistance limit their use. Compared to the former two, adding nanomaterials to lubricating fluids to create solid-liquid coupled lubricants can significantly improve lubrication performance. Using black phosphorus nanosheets alone as a water-based lubricant can achieve a low coefficient of friction, and their use as the solid phase in a solid-liquid coupled system has significant potential for application in tribology. Polyethylene glycol-based lubricants also possess high chemical stability, excellent hydrophilicity, and lubricity. The good dispersibility of black phosphorus nanosheets in polyethylene glycol enhances the lubricant's friction reduction and anti-wear capabilities. Using polyethylene glycol as the liquid phase in a solid-liquid coupled system can be used to develop high-performance lubricants.

[0003] Over the past few decades, nanomaterials, such as graphene, nanometal particles, molybdenum disulfide, and hexagonal boron nitride, have been widely and successfully applied in tribology. In recent years, black phosphorus nanosheets, as an emerging two-dimensional material with weak interlayer shear and good anisotropy, have attracted extensive research attention.

[0004] At present, a black phosphorus quantum dot water-based lubricating additive and preparation method (CN116286141A) has been developed, but the friction coefficient test results of the three embodiments of this technology all achieved super-lubricity (friction coefficient less than 0.01). Super-lubricity can provide the friction pair with better friction reduction and anti-wear capabilities.

[0005] Therefore, it is necessary to study new process methods to obtain modified black phosphorus nanosheets. Summary of the Invention

[0006] In order to overcome the above technical problems, the purpose of the present invention is to provide a water-based lubricating fluid and preparation method of black phosphorus nanosheets. By modifying the black phosphorus nanosheets, P-OH bonds, HO-P=O bonds, and P=O bonds are obtained on their surfaces, so that the black phosphorus nanosheets can obtain better lubrication performance as water-based lubricant additives. At the same time, excellent lubrication effect is achieved through the synergistic lubrication effect of polyethylene glycol and modified black phosphorus nanosheets in the lubricating fluid.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is:

[0008] A method for preparing a water-based lubricating liquid for black phosphorus nanosheets comprises the following steps:

[0009] S1. Ultrasonic treatment is performed on black phosphorus nanosheets, citric acid, and anhydrous ethanol in proportion to obtain a mixed sample.

[0010] S2. reacting the mixed sample at a certain temperature to obtain citric acid-modified black phosphorus nanosheets after the anhydrous ethanol is completely evaporated, and using the citric acid-modified black phosphorus nanosheets as a water-based lubricating additive;

[0011] S3. Dissolving the citric acid-modified black phosphorus nanosheets in an aqueous solution of polyethylene glycol, and obtaining a water-based lubricating liquid for the black phosphorus nanosheets by ultrasonic treatment.

[0012] In S1, the black phosphorus nanosheets have a particle size of 10-100 nm. The particle size of the black phosphorus nanosheets plays a crucial role in friction performance. As the particle size decreases, the surface area increases, providing a more uniform friction surface and thus reducing the friction coefficient. However, the smaller the particle size, the greater the production cost. Therefore, selecting the appropriate particle size range is beneficial for balancing process economics and lubrication performance.

[0013] In the S1, the mass ratio of black phosphorus nanosheets, citric acid and anhydrous ethanol is 1:(10-15):(20-30).

[0014] Citric acid itself is rich in hydroxyl groups, and the hydroxyl functional groups adsorbed onto the surface of black phosphorus nanosheets can provide them with excellent lubrication properties. This application adopts a more convenient hydrothermal method, which simplifies the preparation process and reduces costs. The obtained water-based lubricant for hydroxylated black phosphorus nanosheets has a lubrication performance improved by about 132 times compared with the water-based lubricant for original black phosphorus nanosheets.

[0015] In S2, the sample preparation temperature is 70-100°C and the reaction time is 0.5-2h. The black phosphorus nanosheets are oxidized to a certain extent by a hydrothermal method to generate P x O y Low or high temperatures can lead to insufficient or excessive oxidation of the black phosphorus nanosheets, both of which result in poor lubrication. Partially oxidized black phosphorus nanosheets form P=O and P-OH bonds, which can adsorb and retain water molecules. At the same time, the hydroxyl groups of citric acid interact with the surface of the black phosphorus nanosheets, adsorbing them and enhancing their lubricity.

[0016] In S3, the mass ratio of the modified black phosphorus nanosheets to the aqueous solution of polyethylene glycol is 1:(10-50).

[0017] Polyethylene glycol, as an excellent solid-liquid organic phase change material, has high chemical stability, excellent hydrophilicity and lubricity. It has been widely used in high-performance lubricants. However, the lubricating effect of using polyethylene glycol alone as a lubricant is not very ideal. The lubricating performance of polyethylene glycol-based lubricants is extremely dependent on friction-reducing and anti-wear additives. Due to the good dispersibility of black phosphorus nanosheets in polyethylene glycol, the friction-reducing and anti-wear capabilities of polyethylene glycol-based lubricants are enhanced. Compared with pure polyethylene glycol aqueous solution, the lubricating performance of the polyethylene glycol aqueous solution of black phosphorus nanosheets is improved by 200%, and can be used to develop high-performance lubricants.

[0018] In the S3, the molecular weight of polyethylene glycol is (200-1000) g / mol, and the mass ratio of polyethylene glycol to water is 1:(0.1-1).

[0019] The molecular weight and concentration of polyethylene glycol play a key role in the lubricating properties of the lubricant. The molecular weight is proportional to the viscosity. Too high or too low a viscosity will lead to a decrease in the performance of the lubricant.

[0020] A black phosphorus nanosheet water-based lubricant, wherein the friction coefficient of the black phosphorus nanosheet water-based lubricant drops below 0.01 after 470 seconds, and the final friction coefficient stabilizes between 0.004 and 0.01.

[0021] The surface of the black phosphorus nanosheets in the black phosphorus nanosheet water-based lubricating liquid is modified by citric acid, and has P-OH bonds, HO-P=O bonds, and P=O bonds;

[0022] The size of black phosphorus nanosheets is relatively uniform, ranging from 10-100nm. The interlayer shear force and sliding force between black phosphorus nanosheets are weak, which can provide a lower friction coefficient.

[0023] The black phosphorus nanosheet water-based lubricating additive can be stably dispersed in a polyethylene glycol aqueous solution, and has a particle size of 10-100 nm.

[0024] Beneficial effects of the present invention:

[0025] (1) The preparation method of the present invention can evenly disperse the modified black phosphorus nanosheets in the aqueous solution of polyethylene glycol through step S3. Good dispersibility will greatly enhance the lubrication effect.

[0026] (2) The modified black phosphorus nanosheets obtained by the preparation method of the present invention are modified to obtain P-OH bonds, HO-P=O bonds, and P=O bonds on their surfaces.

[0027] (2) The black phosphorus nanosheet water-based lubricant of the present invention has excellent lubrication performance under low load conditions, and its friction coefficient is lower than that of an aqueous solution of black phosphorus nanosheets, citric acid and polyethylene glycol or an aqueous solution of black phosphorus nanosheets and citric acid. Citric acid is a common acidic substance, and its existence is often overlooked by those skilled in the art. This substance has abundant hydroxyl groups, which can provide excellent lubrication performance. Compared with the existing technology, step S2 prepares the modified black phosphorus nanosheets by a simple hydrothermal method, which has good economic efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 TEM images of black phosphorus nanosheets, where: (a) a typical TEM image and (b) and (c) are the corresponding magnified images.

[0029] Figure 2 This is a macroscopic image of the dispersion of the modified black phosphorus nanosheets of Example 1 in an aqueous solution of polyethylene glycol.

[0030] Figure 3 This is the Fourier transform infrared spectrum image of the citric acid-modified black phosphorus nanosheets in Example 1.

[0031] Figure 4 The figure is a comparison chart of the friction coefficients of Example 1, Comparative Example 1 and Comparative Example 2. DETAILED DESCRIPTION

[0032] The present invention will be described in further detail below with reference to the accompanying drawings.

[0033] Example 1

[0034] This embodiment provides a method for preparing a water-based lubricating liquid for black phosphorus nanosheets, and the steps are as follows:

[0035] (1) Black phosphorus nanosheets, citric acid, and anhydrous ethanol were fully mixed in a mass ratio of 1:10:20 and ultrasonically treated to achieve uniform mixing;

[0036] (2) The mixed solution of step (1) was reacted in an oven at 100° C. for 1 h, and after the anhydrous ethanol was completely evaporated, citric acid-modified black phosphorus nanosheets were obtained, which were used as a water-based lubricating additive.

[0037] (3) Dissolving the citric acid-modified black phosphorus nanosheets in a 50% by mass polyethylene glycol aqueous solution at a mass ratio of 1:50 to obtain a polyethylene glycol aqueous solution of the citric acid-modified black phosphorus nanosheets.

[0038] The prepared lubricating fluid was tested using a ball-on-disc friction and wear tester. The friction pair was a 6mm diameter Si3N4 ball, with a SiO2 sheet as the disc bottom, a load of 3N, a rotation speed of 146mm / s, and a test time of 1h. After testing, the polyethylene glycol aqueous solution of the citric acid-modified black phosphorus nanosheets prepared in this example had a stable friction coefficient between 0.005 and 0.01 after a run-in time of about 500s. Figure 3 shown.

[0039] Example 2

[0040] The embodiment provides a method for preparing a water-based lubricating liquid of black phosphorus nanosheets, the steps are as follows:

[0041] (1) Black phosphorus nanosheets, citric acid, and anhydrous ethanol were fully mixed in a mass ratio of 1:10:30 and ultrasonically treated to achieve uniform mixing;

[0042] (2) The mixed solution of step (1) was reacted in an oven at 90° C. for 2 h, and after the anhydrous ethanol was completely evaporated, citric acid-modified black phosphorus nanosheets were obtained, which were used as a water-based lubricating additive.

[0043] (3) The citric acid-modified black phosphorus nanosheets were dissolved in a 50% by mass polyethylene glycol aqueous solution at a mass ratio of 1:30 to obtain a polyethylene glycol aqueous solution of the citric acid-modified black phosphorus nanosheets.

[0044] Example 3

[0045] The embodiment provides a method for preparing a water-based lubricating liquid of black phosphorus nanosheets, the steps are as follows:

[0046] (1) Black phosphorus nanosheets, citric acid, and anhydrous ethanol were fully mixed in a mass ratio of 1:10:25 and ultrasonically treated to achieve uniform mixing;

[0047] (2) The mixed solution of step (1) was reacted in an oven at 80° C. for 1 h, and after the anhydrous ethanol was completely evaporated, citric acid-modified black phosphorus nanosheets were obtained, which were used as a water-based lubricating additive.

[0048] (3) The citric acid-modified black phosphorus nanosheets were dissolved in a 50% by mass polyethylene glycol aqueous solution at a mass ratio of 1:40 to obtain a polyethylene glycol aqueous solution of the citric acid-modified black phosphorus nanosheets.

[0049] Comparative Example 1

[0050] This embodiment provides a method for preparing a water-based lubricating liquid of unmodified black phosphorus nanosheets, the steps of which are as follows:

[0051] (1) Black phosphorus nanosheets, citric acid, and anhydrous ethanol were fully mixed in a mass ratio of 1:10:20 and ultrasonically treated to achieve uniform mixing;

[0052] (2) Under normal temperature conditions, after the anhydrous ethanol in the mixed solution of step (1) is completely evaporated, unmodified black phosphorus nanosheets are obtained, which are used as a water-based lubricating additive.

[0053] (3) Dissolving unmodified black phosphorus nanosheets in a pure aqueous solution at a mass ratio of 1:50 to obtain a mixed aqueous solution of citric acid and black phosphorus nanosheets.

[0054] The prepared lubricating fluid was tested by a ball-on-disc friction and wear tester. The friction pair was a Si3N4 ball with a diameter of 6 mm, and a SiO2 sheet was used as the disc bottom. The load was 3 N, the rotation speed was 146 mm / s, and the test time was 1 hour. After testing, the aqueous solution of citric acid and black phosphorus nanosheets prepared in this comparative example had a stable friction coefficient of about 0.015 after a running-in time of about 1250 seconds. Figure 3 As shown, compared with comparative example 1, the running-in time of embodiment 1 is shortened by about 750s, and the friction coefficient is reduced by 66.7% at the maximum.

[0055] Comparative Example 2

[0056] This embodiment provides a method for preparing a water-based lubricating liquid of unmodified black phosphorus nanosheets, the steps of which are as follows:

[0057] (1) Black phosphorus nanosheets, citric acid, and anhydrous ethanol were fully mixed in a mass ratio of 1:10:20 and ultrasonically treated to achieve uniform mixing;

[0058] (2) Under normal temperature conditions, after the anhydrous ethanol in the mixed solution of step (1) is completely evaporated, unmodified black phosphorus nanosheets are obtained, which are used as a water-based lubricating additive.

[0059] (3) The unmodified black phosphorus nanosheets were dissolved in a 50% by mass polyethylene glycol aqueous solution at a mass ratio of 1:50 to obtain a polyethylene glycol aqueous solution mixed with citric acid and black phosphorus nanosheets. The prepared lubricating fluid was tested by a ball-disc friction and wear tester. The friction pair was a Si3N4 ball with a diameter of 6 mm, with a SiO2 sheet as the disc bottom, a load of 3 N, a rotation speed of 146 mm / s, and a test time of 1 h. After testing, the polyethylene glycol aqueous solution mixed with citric acid and black phosphorus nanosheets prepared in this comparative example had a friction coefficient that stabilized at about 0.02 after a running-in time of about 1600 s, as shown in FIG. Figure 3 As shown, compared with Comparative Example 2, the running-in time of Example 1 is shortened by about 1100 s, and the friction coefficient is reduced by 75% at most.

[0060] Experimental analysis:

[0061] The lubricating fluid of the embodiment of this experiment has good prospect of being implemented and applied.

[0062] By observing the macroscopic image of the lubricating fluid in Example 1, it can be found that the modified black phosphorus nanosheets have good dispersibility in the aqueous solution of polyethylene glycol, and there is no obvious precipitation at the bottom. Figure 1 It can be observed that the size of black phosphorus nanosheets is in the range of 10-100nm; Figure 2 It can be observed that the modified black phosphorus nanosheets can be evenly dispersed in the lubricating fluid through the ultrasonic treatment in step S3; Figure 3 It can be observed that after the black phosphorus nanosheets were modified with citric acid, obvious peaks of P-OH bonds, HO-P=O bonds, and P=O bonds appeared. These functional groups significantly improved the lubrication performance of the black phosphorus nanosheets. The P=O and P-OH bonds formed during the modification process can adsorb and retain water molecules on the surface of the black phosphorus nanosheets, helping to achieve and maintain a low friction coefficient. The low friction coefficient is also attributed to the excellent dispersibility of the black phosphorus nanosheets in the aqueous solution of polyethylene glycol. The synergistic effect of these factors greatly enhances the friction reduction and anti-wear ability of the lubricant; from the attached Figure 4 It can be observed that compared with Comparative Examples 1 and 2, Example 1 can provide excellent super-lubricity and greatly improve the anti-friction and anti-wear capabilities of the lubricant. The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art who, within the technical scope disclosed by the present invention, can make equivalent substitutions or modifications based on the technical solutions and inventive concepts of the present invention shall be covered by the scope of protection of the present invention.

Claims

1. A method for preparing a water-based lubricating liquid of black phosphorus nanosheets, characterized in that: The following steps are involved: S1. Ultrasonic treatment is performed on black phosphorus nanosheets, citric acid, and anhydrous ethanol in proportion to obtain a mixed sample. S2. reacting the mixed sample at a certain temperature to obtain citric acid-modified black phosphorus nanosheets after the anhydrous ethanol is completely evaporated, and using the citric acid-modified black phosphorus nanosheets as a water-based lubricating additive; S3, dissolving the citric acid-modified black phosphorus nanosheets in an aqueous solution of polyethylene glycol, and obtaining a water-based lubricating liquid for the black phosphorus nanosheets by ultrasonic treatment; In S1, the mass ratio of black phosphorus nanosheets, citric acid and anhydrous ethanol is 1: (10-15): (20-30); In S2, the sample preparation temperature is 70-100°C and the reaction time is 0.5-2h; In the S3, the mass ratio of the modified black phosphorus nanosheets to the aqueous solution of polyethylene glycol is 1:(10-50).

2. The method for preparing a water-based lubricating liquid of black phosphorus nanosheets according to claim 1, characterized in that: In the S1, the particle size of the black phosphorus nanosheets is 10-100 nm.

3. The method for preparing a water-based lubricating liquid of black phosphorus nanosheets according to claim 1, characterized in that: In the S3, the molecular weight of polyethylene glycol is (200-1000) g / mol, and the mass ratio of polyethylene glycol to water is 1:(0.1-1).

4. A black phosphorus nanosheet water-based lubricating liquid prepared according to the method according to any one of claims 1 to 3, characterized in that: The friction coefficient of the black phosphorus nanosheet water-based lubricant dropped below 0.01 after 470 seconds, and finally stabilized between 0.004 and 0.

01.

5. The black phosphorus nanosheet water-based lubricating fluid according to claim 4, characterized in that: The surface of the black phosphorus nanosheets in the black phosphorus nanosheet water-based lubricating liquid is modified with citric acid, and has P-OH bonds, HO-P=O bonds, and P=O bonds; The size of black phosphorus nanosheets is relatively uniform, ranging from 10 to 100 nm. The interlayer shear force and slip force between black phosphorus nanosheets are weak, which can provide a lower friction coefficient. The black phosphorus nanosheet water-based lubricating additive can be stably dispersed in an aqueous solution of polyethylene glycol.

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