Water-based lubricating liquid of black phosphorus nanosheet and preparation method of water-based lubricating liquid

Abstract

The invention discloses a water-based lubricating liquid of black phosphorus nanosheets and a preparation method. The preparation method comprises the following steps: S1, carrying out sufficient ultrasonic treatment on the black phosphorus nanosheets, citric acid and absolute ethyl alcohol in proportion, and uniformly mixing to obtain a mixed sample; s2, the mixed sample is subjected to a reaction at a certain temperature, citric acid modified black phosphorus nanosheets are obtained after absolute ethyl alcohol is completely evaporated, and the citric acid modified black phosphorus nanosheets serve as a water-based lubricating additive; and S3, dissolving the citric acid modified black phosphorus nanosheet in an aqueous solution of polyethylene glycol, and carrying out ultrasonic treatment to obtain the water-based lubricating liquid of the black phosphorus nanosheet. According to the invention, the black phosphorus nanosheet is modified, and a P-OH bond, a HO-P = O bond and a P = O bond are obtained on the surface of the black phosphorus nanosheet after modification, so that the black phosphorus nanosheet as a water-based lubricant additive can obtain better lubricating performance, and meanwhile, an excellent lubricating effect is obtained through the synergistic lubricating effect of polyethylene glycol and the modified black phosphorus nanosheet in the lubricating liquid.

Description

Technical Field

[0001] The 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] The commonly used lubrication methods at present include: solid, liquid and solid-liquid coupling lubrication methods. Generally, the friction coefficient of solid lubricants is large, and heat conduction between friction pairs is difficult; liquid lubricants have other advantages such as better cooling and low pollution compared to solid lubricants. However, their poor lubrication performance, low viscosity and corrosion resistance limit their use. Compared with the first two, adding nanomaterials to the lubricant to make solid-liquid coupling lubricants will greatly improve the lubrication performance. Simply using black phosphorus nanosheets water-based lubricants can obtain a lower friction coefficient, and using it as a solid phase in a solid-liquid coupling system has great application potential in the field of tribology; at the same time, polyethylene glycol-based lubricants have high chemical stability, excellent hydrophilicity and lubricity. Due to the good dispersibility of black phosphorus nanosheets in polyethylene glycol, the friction reduction and anti-wear ability of the lubricant are enhanced. Using polyethylene glycol as the liquid phase in a solid-liquid coupling system can be used to develop high-performance lubricants.

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

[0004] At present, a black phosphorus quantum dot water-based lubricating additive and preparation method (CN116286141A) have been developed, but the friction coefficient test results of the three embodiments of this technology all achieve super-lubricity (friction coefficient less than 0.01). The 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 liquid of black phosphorus nanosheets and a preparation method thereof. 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 obtained through the synergistic lubrication effect of polyethylene glycol and modified black phosphorus nanosheets in the lubricating liquid.

[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 of 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 by mixing them uniformly;

[0010] S2, reacting the mixed sample at a certain temperature, and obtaining 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 particle size of the black phosphorus nanosheet is 10-100 nm. The particle size of the black phosphorus nanosheet plays a crucial role in the friction performance. As the particle size decreases, the surface area increases, because it provides a more uniform friction surface, thereby reducing the friction coefficient; however, the smaller the particle size, the greater the preparation cost, so choosing a suitable particle size range is conducive to balancing the economic efficiency of the process and the lubrication effect.

[0013] In 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 the original black phosphorus nanosheets.

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

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

[0017] As an excellent solid-liquid organic phase change material, polyethylene glycol has high chemical stability, excellent hydrophilicity and lubricity. It has been widely used in high-performance lubricants. However, the lubricating effect of 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 polyethylene glycol aqueous solution of black phosphorus nanosheets is improved by 200%, which can be used to develop high-performance lubricants.

[0018] In 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. If the viscosity is too high or too low, the performance of the lubricant will be reduced.

[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 is stabilized between 0.004 and 0.01.

[0021] The surface of the black phosphorus nanosheets in the black phosphorus nanosheet water-based lubricant 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 an aqueous solution of polyethylene glycol, 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 improve 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 has a lower friction coefficient than 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 technicians in this field. The 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 economy. 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 of Example 1.

[0031] Figure 4 It 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 further described in detail below in conjunction with the accompanying drawings.

[0033] Example 1

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

[0035] (1) mixing black phosphorus nanosheets, citric acid and anhydrous ethanol in a mass ratio of 1:10:20 and performing ultrasonic treatment to make the mixture uniform;

[0036] (2) The mixed solution of step (1) is reacted in an oven at 100° C. for 1 hour, and after the anhydrous ethanol is completely evaporated, citric acid-modified black phosphorus nanosheets are obtained, which are 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 liquid was tested by a ball-disc friction and wear tester, with a friction pair of 6 mm diameter Si3N4 balls, SiO2 sheets as the disc bottom, a load of 3N, a rotation speed of 146 mm / s, and a test time of 1 h. After testing, the polyethylene glycol aqueous solution of the citric acid-modified black phosphorus nanosheets prepared in this embodiment stabilized the friction coefficient between 0.005 and 0.01 after a running-in time of about 500 s. 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) mixing black phosphorus nanosheets, citric acid and anhydrous ethanol in a mass ratio of 1:10:30 and performing ultrasonic treatment to make the mixture uniform;

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

[0043] (3) Dissolving the citric acid-modified black phosphorus nanosheets 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 make the mixture uniform;

[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) Dissolving the citric acid-modified black phosphorus nanosheets 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 are as follows:

[0051] (1) mixing black phosphorus nanosheets, citric acid and anhydrous ethanol in a mass ratio of 1:10:20 and performing ultrasonic treatment to make the mixture uniform;

[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-disc friction and wear tester, with a friction pair of 6mm diameter Si3N4 balls, SiO2 sheets as the disc bottom, a load of 3N, a rotation speed of 146mm / s, and a test time of 1h. After testing, the aqueous solution of citric acid and black phosphorus nanosheets prepared in this comparative example stabilized the friction coefficient at about 0.015 after a running-in time of about 1250s. Figure 3 As shown, compared with comparative example 1, the running-in time of embodiment 1 is shortened by about 750 s, 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 are as follows:

[0057] (1) mixing black phosphorus nanosheets, citric acid and anhydrous ethanol in a mass ratio of 1:10:20 and performing ultrasonic treatment to make the mixture uniform;

[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 liquid was tested by a ball-disc friction and wear tester. The friction pair was a Si3N4 ball with a diameter of 6 mm, a SiO2 sheet as the disc bottom, a load of 3N, 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 stabilized at about 0.02 after a running-in time of about 1600 s. Figure 3 As shown, compared with comparative example 2, the running-in time of embodiment 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 for feasible application.

[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 through the ultrasonic treatment in step S3, the modified black phosphorus nanosheets can be evenly dispersed in the lubricating liquid; 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, which helps to achieve and maintain a low friction coefficient. At the same time, 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 anti-friction and anti-wear capabilities 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-slip performance and greatly improve the anti-friction and anti-wear capabilities of the lubricant. The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the art can make equivalent replacements or changes according to the technical solutions and inventive concepts of the present invention within the technical scope disclosed by the present invention, which should be covered within the protection scope of the present invention.

Claims

1. A method for preparing a water-based lubricating liquid for black phosphorus nanosheets, It is 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 by mixing them uniformly; S2, reacting the mixed sample at a certain temperature, and obtaining 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.

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

3. A method for preparing a water-based lubricating liquid of black phosphorus nanosheets according to claim 1, It is characterized in that In S1, the mass ratio of black phosphorus nanosheets, citric acid and anhydrous ethanol is 1:(10-15):(20-30).

4. The method for preparing a water-based lubricating liquid of black phosphorus nanosheets according to claim 1, It is characterized in that In S2, the sample preparation temperature is 70-100°C, and the reaction time is 0.5-2h.

5. The method for preparing a water-based lubricating liquid of black phosphorus nanosheets according to claim 1, It is characterized in that In S3, the mass ratio of the modified black phosphorus nanosheets to the aqueous solution of polyethylene glycol is 1:(10-50).

6. The method for preparing a water-based lubricating liquid of black phosphorus nanosheets according to claim 1, It is characterized in that In 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).

7. A black phosphorus nanosheet water-based lubricating liquid prepared according to any one of claims 1 to 6, It is 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.

8. The black phosphorus nanosheet water-based lubricating liquid according to claim 7, It is characterized in that The surface of the black phosphorus nanosheets in the black phosphorus nanosheet water-based lubricant is modified by 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 sliding 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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