Preparation method and application of liquid-like carbon dot material

Abstract

The present invention relates to a preparation method of a liquid-like carbon dot material, which comprises mixing anhydrous citric acid and an ammonium salt, heating at 160-250°C for 0.5-1 h, adding deionized water to the reaction system, and ultrasonically dispersing for 20-60 min to obtain a mixed solution; adding ethyl acetate in an amount equal to the volume of deionized water to the mixed solution, extracting an organic phase, removing the solvent in the organic phase by rotary evaporation to obtain a crude product; and vacuum drying the crude product at 60-90°C for 24-48 h to obtain a liquid-like carbon dot material. At the same time, the present invention also discloses the application of the liquid-like carbon dot material. The method of the present invention is simple and agglomeration-free, and the obtained liquid-like carbon dot material has good compatibility in lithium-based grease, exhibits good lubrication and anti-wear properties as a lithium-based grease additive, and can be used as a high-performance lubrication and anti-wear additive in the field of lubrication engineering.

Description

Technical Field

[0001] The present invention relates to the technical field of lubricating additives, and in particular to a preparation method and application of a liquid-like carbon dot material. Background Art

[0002] Friction and wear are important causes of energy loss in industrial production, accounting for about 23% each year. Therefore, it is necessary to find suitable lubricating materials for effective lubrication to reduce friction and wear. Carbon dots are a zero-dimensional fluorescent carbon nanomaterial with a quasi-spherical structure and a size of less than 10nm. They have the characteristics of self-repair, high strength, strong interface adsorption, etc. that are superior to traditional lubricating materials. As a nanomaterial, it has the basic role of nanomaterials in the field of lubrication, such as rolling, repairing, polishing, etc., and can repair minor damage to the surface of the friction pair. In addition, a carbon protective film can be formed in the friction area through deposition, which can improve the film-forming ability.

[0003] Nanomaterials such as carbon dots are usually solid at room temperature. Solid materials have the problem of poor compatibility with grease as grease additives and are prone to agglomeration. Liquid-like nanomaterials are fluid at room temperature and can improve the problem of poor compatibility with grease as additives. Compared with solid nanomaterials, liquid-like nanomaterials have lower interaction energy, which can improve the phenomenon of easy agglomeration of nanomaterials to a certain extent. However, liquid-like nanomaterials require long alkyl chain oligomers as a corona and are prepared by covalent grafting and ion exchange methods. The synthesis steps are relatively cumbersome. Then, carbon dot-like ionic liquid materials are prepared by Lewis acid-base reaction of amines with carboxyl groups on the surface of carbon dots. Similar to the structure of ionic liquids, they also exhibit liquid-like behavior at room temperature, but this method still requires two steps. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method for preparing a liquid-like carbon dot material with a simple method and no agglomeration.

[0005] Another technical problem to be solved by the present invention is to provide applications of this type of liquid behavior carbon dot material.

[0006] In order to solve the above problems, the present invention discloses a method for preparing a liquid-like carbon dot material, which is characterized in that: the method comprises mixing anhydrous citric acid and an ammonium salt, heating at 160-250°C for 0.5-1 h, adding deionized water to the reaction system, and ultrasonically dispersing for 20-60 min to obtain a mixed solution; adding ethyl acetate in an amount equal to the volume of deionized water to the mixed solution, extracting an organic phase, removing the solvent in the organic phase by rotary evaporation to obtain a crude product; and vacuum drying the crude product at 60-90°C for 24-48 h to obtain a liquid-like carbon dot material.

[0007] The mass ratio of the anhydrous citric acid, the ammonium salt and the deionized water is 10:1:30 to 10:3:30.

[0008] The ammonium salt refers to one of tetra-n-butylammonium phosphate, tetrabutylammonium chloride and betaine.

[0009] A liquid-like carbon dot material prepared by the method described above.

[0010] The application of a liquid-like carbon dot material as described above is characterized in that the liquid-like carbon dot material is used as an additive in lithium-based grease.

[0011] Compared with the prior art, the present invention has the following advantages:

[0012] 1. When a solid material is converted into a liquid, the interaction energy between its molecules is reduced. Based on the citric acid carbon dot synthesis system, the present invention introduces ammonium salt materials in the process of preparing carbon dots, which hinders the polymerization reaction of the original citric acid system, reduces the oxygen-containing groups on the surface of the carbon dots, reduces the interaction energy between the carbon dots, and retains part of the ionic structure, so that the carbon dot state changes, thereby effectively solving the agglomeration problem between the carbon dots. At the same time, the ammonium salt can be partially retained around the carbon core to form an ionic structure similar to that of an ionic liquid, and the larger ionic radius makes it exhibit liquid behavior. The lower interaction energy and ionic structure also improve the easy agglomeration problem of the carbon dot material.

[0013] 2. The liquid-like carbon dot material of the present invention exhibits fluidity at room temperature, which improves the poor compatibility of solid nanomaterials as additives with grease and expands the lubrication application prospects of carbon dots as grease additives.

[0014] 3. The present invention only requires one step to complete the reaction, and the synthesis process is simplified compared to other liquid-behavioral nanomaterials.

[0015] 4. The liquid-like carbon dots described in the present invention are used as lithium-based grease additives, exhibiting excellent lubrication and anti-wear properties, can improve the problem of poor compatibility with grease, solve the friction and wear problems during equipment operation, and expand the application of carbon dot materials in the lubrication field. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The specific implementation modes of the present invention are further described in detail below in conjunction with the accompanying drawings.

[0017] Figure 1 Transmission electron microscope photo (a) and particle size distribution diagram (b) of the carbon dots synthesized in Example 2 of the present invention. DETAILED DESCRIPTION

[0018] A method for preparing a liquid-like carbon dot material, the method comprising mixing anhydrous citric acid and an ammonium salt, heating at 160-250°C for 0.5-1 h, adding deionized water to the reaction system, wherein the mass ratio (g / g) of anhydrous citric acid, ammonium salt and deionized water is 10:1:30-10:3:30. Ultrasonic dispersion is performed for 20-60 min to obtain a mixed solution; ethyl acetate equal in volume to deionized water is added to the mixed solution, an organic phase is obtained by extraction, and a crude product is obtained by removing the solvent in the organic phase by rotary evaporation; the crude product is vacuum dried at 60-90°C for 24-48 h to obtain a liquid-like carbon dot material.

[0019] Among them: the ammonium salt refers to one of tetra-n-butylammonium phosphate, tetrabutylammonium chloride and betaine.

[0020] An application of a liquid-like carbon dot material, wherein the liquid-like carbon dot material is used as an additive in lithium-based grease.

[0021] Example 1 A method for preparing a liquid-like carbon dot material, the method comprising: mixing 10 g of anhydrous citric acid and 1 g of tetra-n-butylammonium phosphate, heating at 200 °C for 0.5 h, adding 30 g of deionized water to the reaction system, and ultrasonically dispersing for 30 min to obtain a mixed solution; adding ethyl acetate in an amount equal to the deionized water to the mixed solution, extracting an organic phase, removing the solvent in the organic phase by rotary evaporation to obtain a crude product; and vacuum drying the crude product at 70 °C for 24 h to obtain a liquid-like carbon dot material, recorded as LCDs-1.

[0022] Example 2 A method for preparing a liquid-like behavior carbon dot material, the method comprising mixing 10 g of anhydrous citric acid and 2 g of tetra-n-butylammonium phosphate, heating at 200 ˚C for 0.5 h, adding 30 g of deionized water to the reaction system, and ultrasonically dispersing for 30 min to obtain a mixed solution; adding ethyl acetate in an amount equal to the deionized water to the mixed solution, extracting an organic phase, removing the solvent in the organic phase by rotary evaporation to obtain a crude product; and vacuum drying the crude product at 70 ℃ for 24 h to obtain a liquid-like behavior carbon dot material, recorded as LCDs-2.

[0023] See the attached transmission electron microscope photos and particle size distribution photos of LCDs-2 carbon dots. Figure 1 ,As can be seen from the figure, the carbon dots present a spherical structure without obvious aggregation, and the average particle size is about 3.3 nm.

[0024] Example 3 A method for preparing a liquid-like carbon dot material, the method comprising: mixing 10 g of anhydrous citric acid and 3 g of tetra-n-butylammonium phosphate, heating at 200 °C for 0.5 h, adding 30 g of deionized water to the reaction system, and ultrasonically dispersing for 30 min to obtain a mixed solution; adding ethyl acetate in an amount equal to the deionized water to the mixed solution, extracting an organic phase, removing the solvent in the organic phase by rotary evaporation to obtain a crude product; and vacuum drying the crude product at 80 °C for 24 h to obtain a liquid-like carbon dot material, recorded as LCDs-3.

[0025] Example 4 A method for preparing a liquid-like carbon dot material, the method comprising mixing 10 g of anhydrous citric acid and 1 g of tetrabutylammonium chloride, heating at 180 °C for 1 h, adding 30 g of deionized water to the reaction system, and ultrasonically dispersing for 30 min to obtain a mixed solution; adding ethyl acetate in an amount equal to the deionized water to the mixed solution, extracting an organic phase, removing the solvent in the organic phase by rotary evaporation to obtain a crude product; and vacuum drying the crude product at 80 °C for 36 h to obtain a liquid-like carbon dot material, recorded as LCDs-4.

[0026] Example 5 A method for preparing a liquid-like behavior carbon dot material, the method comprising mixing 10 g of anhydrous citric acid and 1 g of betaine, heating at 210 °C for 0.5 h, adding 30 g of deionized water to the reaction system, and ultrasonically dispersing for 30 min to obtain a mixed solution; adding ethyl acetate in an amount equal to the deionized water to the mixed solution, extracting an organic phase, removing the solvent in the organic phase by rotary evaporation to obtain a crude product; and vacuum drying the crude product at 70 °C for 24 h to obtain a liquid-like behavior carbon dot material, recorded as LCDs-5.

[0027] Tribological performance test of liquid-like carbon dot materials as lithium-based grease additives:

[0028] LCDs-2 synthesized in Example 2 was selected as the performance research object, and its lubricating and anti-wear performance as a lithium-based grease additive was investigated using a four-ball friction and wear tester. The addition amount was 0.5% to 1%.

[0029] The load was 392 N, the temperature was 75 °C, the speed was 1200 r / min, the experimental time was 60 min, and the ball used in the experiment was GCr15 steel ball. After the friction experiment, the wear spot diameter was measured using an optical microscope. The friction test results are shown in Table 1.

[0030] Table 1 Comparison of average friction coefficient and wear spot diameter of base grease and base grease containing LCDs-2

[0031]

[0032] It can be seen from Table 1 that, compared with the base grease, LCDs-2 as an additive significantly reduces the friction coefficient and wear spot diameter of the base grease, showing excellent tribological properties.

[0033] In summary, the liquid-like behavior carbon dot material of the present invention has good compatibility in lithium-based grease, and exhibits good lubrication and anti-wear properties as a lithium-based grease additive, and can be used as a high-performance lubrication and anti-wear additive in the field of lubrication engineering.

Claims

1. A method for preparing a liquid-like carbon dot material, characterized in that: The method comprises the steps of mixing anhydrous citric acid and an ammonium salt, heating at 160-250°C for 0.5-1 h, adding deionized water to the reaction system, and ultrasonically dispersing the mixture for 20-60 min to obtain a mixed solution; adding ethyl acetate in an amount equal to the deionized water to the mixed solution, extracting an organic phase, and removing the solvent in the organic phase by rotary evaporation to obtain a crude product; vacuum drying the crude product at 60-90°C for 24-48 h to obtain a liquid-like carbon dot material; the ammonium salt is one of tetra-n-butylammonium phosphate, tetrabutylammonium chloride, and betaine.

2. The method for preparing a liquid-like carbon dot material according to claim 1, characterized in that: The mass ratio of the anhydrous citric acid, the ammonium salt and the deionized water is 10:1:30 to 10:3:

30.

3. A liquid-like carbon dot material prepared by the method as described in claim 1 or 2.

4. The use of a liquid-like carbon dot material as claimed in claim 3, characterized in that: This type of liquid-behaving carbon dot material is used as an additive in lithium-based grease.

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