Lubricating oil additive material and preparation method thereof

Abstract

The invention provides a lubricating oil additive material and a preparation method thereof. The preparation method of the lubricating oil additive material comprises the following steps: step a, reacting an alkaline substance with a carbonyl compound, and adding an aromatic compound containing nitrogen and sulfur functional groups or sulfur-containing amino acid as a doping agent in the reaction; step b, separating and purifying a product obtained in the step a to obtain nitrogen and sulfur doped carbon quantum dots; c, mixing the purified nitrogen-sulfur doped carbon quantum dots with a base solution to obtain the lubricating oil additive material.

Description

Technical Field

[0001] This application relates to the field of lubricant additive technology, and more specifically, to a lubricating oil additive material and its preparation method. Background Technology

[0002] Lubricants are widely used in many important sectors and industries, including transportation, manufacturing, power generation, oil and gas, food, and pharmaceuticals. The influential transportation sector currently accounts for nearly 60% of the lubricant market demand and is expected to remain a key contributor to future lubricant applications and development. In this area, vehicle electrification has been identified as an important strategy for meeting future vehicle emission standards.

[0003] Traditional internal combustion engine lubricants primarily focus on load-bearing capacity, while the focus of lubrication for electric vehicles shifts to accommodating higher torque and operating speeds. This shift can be achieved by switching to a lower viscosity base fluid. Besides reducing viscous resistance to accommodate the higher torque and operating speeds of friction components in electric vehicles, lower lubricant viscosity also improves cooling performance. However, as lubrication conditions shift from hydrodynamic lubrication to elastohydrodynamic and boundary lubrication, lowering lubricant viscosity can also lead to more severe surface contact and wear problems. Therefore, reducing lubricant viscosity is an ideal approach and should be combined with more effective anti-wear and friction-reducing additives.

[0004] Currently, the development and application of environmentally friendly lubricants (EALs) have received widespread attention, aiming to find base fluids and additives that are both environmentally friendly and have superior performance. Carbon nanostructures, due to their unique physicochemical properties, are considered potential high-efficiency lubricant additives. However, despite extensive research on the lubricating properties of carbon nanostructures over the past few decades, a comprehensive understanding of the mechanisms by which carbon nanostructures reduce friction and wear remains lacking. To date, most experimental studies on the tribological behavior of functionalized carbon nanostructures have primarily focused on reporting observed friction and wear behaviors without delving into the origins of these observed behaviors. Several speculative lubrication mechanisms have been proposed in the existing literature, but few have actually been studied or verified. Furthermore, although it is presumed that the nanoscale of carbon nanostructures should allow for dispersion via Brownian motion, carbon nanostructures themselves are difficult to disperse and prone to aggregation due to their high surface energy. For this reason, it has been recognized that carbon nanostructures should be functionalized to achieve stable and uniform dispersion in lubricant base fluids. However, aside from improving dispersibility, few studies have attempted to understand how functionalization affects the lubricating properties of nano-additives. Preliminary results indicate that factors such as adsorption properties and the chemical reactivity of surface functional groups are important, but their impact has not yet been systematically studied. All of this makes it difficult to make informed and thoughtful decisions regarding the selection of nanostructures and surface functional groups in future research.

[0005] There is currently no good solution to the above problems, and there is an urgent need to develop new lubricant additives to overcome them. Summary of the Invention

[0006] This application provides a lubricating oil additive material and its preparation method to at least solve the more serious surface contact and wear problems that accompany the reduction of lubricating oil viscosity to accommodate higher torque and operating speed of friction components.

[0007] This invention synthesizes nitrogen-sulfur-doped carbon quantum dots as lubricating oil additives. Specifically, this invention synthesizes two types of nitrogen-sulfur-doped carbon quantum dots: p-aminobenzenesulfonic acid (sNS-CQDs) and L-cystine (lNS-CQDs). The nitrogen-sulfur-doped carbon quantum dots of this invention can significantly improve the tribological properties of lubricating oils, especially their anti-wear and friction-reducing properties under low viscosity conditions. While both sNS-CQDs and L-cystine exhibit excellent effects, the sNS-CQDs additive demonstrates superior wear resistance and friction reduction under various operating conditions.

[0008] According to one aspect of this application, a method for preparing a lubricating oil additive material is provided, comprising:

[0009] Step a: React the alkaline substance with the carbonyl compound, and add an aromatic compound containing nitrogen and sulfur functional groups or a sulfur-containing amino acid as a dopant in the reaction.

[0010] Step b: Separate and purify the product from step a to obtain nitrogen-sulfur-doped carbon quantum dots;

[0011] Step c: Mix the purified nitrogen-sulfur-doped carbon quantum dots with the base liquid to obtain a lubricating oil additive material.

[0012] Furthermore, the dopant is selected from p-aminobenzenesulfonic acid or L-cysteine.

[0013] Furthermore, the alkaline substance is sodium hydroxide, and the carbonyl compound is acetaldehyde.

[0014] Further, in step a, the dopant is dissolved in the carbonyl compound, then an alkaline substance and deionized water are added, and the mixture is stirred for 1 to 3 hours, followed by the addition of hydrochloric acid and stirring for 24 to 48 hours.

[0015] Furthermore, the molar ratio of hydrochloric acid to dopant is 0.7:1 to 1.2:1.

[0016] Furthermore, the molar ratio of the dopant to the carbonyl compound is 1:10 to 1:50, preferably 1:20 to 1:35; the molar ratio of the alkaline substance to the carbonyl compound is 1:2 to 1:10, preferably 1:2 to 1:3; and the volume ratio of the carbonyl compound to deionized water is 1:1 to 1:3, preferably 1:1.5 to 1:2.

[0017] Further, the base fluid is ethylene glycol; preferably, based on the total weight of the lubricating oil additive material, the amount of nitrogen-sulfur doped carbon quantum dots is 0.1 wt% to 0.5 wt%, more preferably 0.2 wt% to 0.4 wt%.

[0018] Further, step b includes filtration, dialysis, and freeze drying.

[0019] Further, in step b, the product of step a is filtered by a vacuum pump to remove the upper precipitate, leaving a clear liquid, which is then transferred to a dialysis bag for dialysis, and then placed in a freeze dryer, vacuumed, and freeze-dried for 30 to 60 hours, preferably 48 hours, to obtain nitrogen-sulfur-doped carbon quantum dots.

[0020] According to another aspect of this application, a lubricating oil additive material is provided, which can be prepared by the above method.

[0021] The lubricant additive material of this invention exhibits excellent tribological properties under various operating conditions, including a significant reduction in the coefficient of friction and a decrease in wear scar diameter. Even under extreme conditions of higher torque and operating speed, it effectively reduces friction and wear, thereby extending service life and improving energy efficiency. Attached Figure Description

[0022] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:

[0023] Figure 1 This is a schematic diagram of the preparation process of sNS-CQDs according to the present invention;

[0024] Figure 2 This is a TEM image of nitrogen-sulfur-doped carbon quantum dots according to the present invention;

[0025] Figure 3 This is an HRTEM image of nitrogen-sulfur-doped carbon quantum dots according to the present invention;

[0026] Figure 4 The friction coefficient curve, average friction coefficient, and average wear scar diameter diagram of lNS-CQDs according to the present invention are shown.

[0027] Figure 5 The friction coefficient curve, average friction coefficient, and average wear scar diameter diagram of sNS-CQDs according to the present invention are shown.

[0028] Figure 6 The image shows a SEM image of the wear scar after lubrication and friction. Detailed Implementation

[0029] To enable those skilled in the art to better understand the present application, the technical solution of the present application will be described more clearly and completely below. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present application.

[0030] It should be noted that the terms "comprising" and "having" and any variations thereof in the specification and claims of this application are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such process, method, product, or device.

[0031] According to an embodiment of this application, a green light-induced stepwise polymerization method is provided, comprising:

[0032] Step a: React the alkaline substance with the carbonyl compound, and add an aromatic compound containing nitrogen and sulfur functional groups or a sulfur-containing amino acid as a dopant in the reaction.

[0033] Step b: Separate and purify the product from step a to obtain nitrogen-sulfur-doped carbon quantum dots;

[0034] Step c: Mix the purified nitrogen-sulfur-doped carbon quantum dots with the base liquid to obtain a lubricating oil additive material.

[0035] The reaction in step a can be carried out at room temperature; the separation and purification in step b can be carried out using methods already available in the prior art; and step c can be performed by sonication for 30 minutes after mixing to obtain a stable lubricant.

[0036] In a preferred embodiment, the dopant is selected from p-aminobenzenesulfonic acid or L-cysteine.

[0037] In this invention, p-aminobenzenesulfonic acid or L-cysteine ​​is preferred as a dopant. The inventors have discovered that p-aminobenzenesulfonic acid or L-cysteine ​​are not only rich in nitrogen and sulfur elements, but also possess unique chemical structures and properties, enabling them to play a crucial role in the synthesis of carbon quantum dots.

[0038] In a preferred embodiment, the alkaline substance is sodium hydroxide and the carbonyl compound is acetaldehyde.

[0039] During the synthesis of carbon quantum dots, sodium hydroxide, through its strong alkaline properties, can effectively stimulate the breaking and recombination of chemical bonds between molecules, which helps to promote the chemical bonding between functional groups and the carbon quantum dots that are forming, thereby achieving effective doping of nitrogen and sulfur elements.

[0040] Acetaldehyde is the basic carbon source for carbon quantum dots. Under certain reaction conditions, acetaldehyde molecules can decompose and recombine to form the core structure of carbon quantum dots. Moreover, the carbonyl group (C=O) in acetaldehyde is a highly reactive chemical group that readily participates in various chemical reactions, promoting the formation of carbon quantum dots.

[0041] In a preferred embodiment, in step a, the dopant is dissolved in a carbonyl compound, then an alkaline substance and deionized water are added, and the mixture is stirred for 1 to 3 hours, followed by the addition of hydrochloric acid and stirring for 24 to 48 hours.

[0042] In this process, the dopant is fully dissolved and uniformly distributed in the carbonyl compound, and the mixture is continuously stirred for 1 to 3 hours to ensure sufficient contact between the reactants and promote the growth of carbon quantum dots. Typically, but not limitingly, the stirring time is 1, 1.5, 2, 2.5, or 3 hours, or any two of these values. Preferably, the stirring time is 2 hours.

[0043] Then hydrochloric acid is added, preferably dropwise. Stirring for 24 to 48 hours ensures complete reaction and optimal doping of the carbon quantum dots. Prolonged stirring promotes uniform growth of the carbon quantum dots, preventing uneven particle size or aggregation caused by localized supersaturation. Simultaneously, this extended reaction time allows sufficient time for the dopant to engage in deep chemical interactions with the carbon quantum dots, ensuring a uniform distribution of nitrogen and sulfur elements, thereby obtaining carbon quantum dot materials with excellent tribological properties. Typically, but not limitingly, the stirring time is 24, 30, 36, 42, or 48 hours, or any combination of two such values.

[0044] In a preferred embodiment, the molar ratio of hydrochloric acid to dopant is 0.7:1 to 1.2:1.

[0045] The inventors discovered that adding hydrochloric acid within this range is beneficial for achieving effective doping of nitrogen and sulfur elements and improving the final surface properties of carbon quantum dots. If the range is below this, the doping efficiency may be affected, leading to insufficient lubrication performance of the carbon quantum dots. If the range is above this, side reactions unrelated to the reaction objective may occur, affecting the stability and dispersibility of the carbon quantum dots in the lubricating fluid. Typical, but not limiting, molar ratios of hydrochloric acid to dopant are 0.7:1, 0.8:1, 0.9:1, 1:1, 1.1:1, 1.2:1, or any two of these values.

[0046] In a preferred embodiment, the molar ratio of the dopant to the carbonyl compound is 1:10 to 1:50, preferably 1:20 to 1:35; the molar ratio of the alkaline substance to the carbonyl compound is 1:2 to 1:10, preferably 1:2 to 1:3; and the volume ratio of the carbonyl compound to deionized water is 1:1 to 1:3, preferably 1:1.5 to 1:2.

[0047] Typical, but not limiting, molar ratios of dopant to carbonyl compound are 1:10, 1:20, 1:30, 1:40, 1:50, or any two of these ratios. Preferably, the molar ratios are 1:20, 1:25, 1:30, 1:35, or any two of these ratios. Within this range, the growth rate of carbon quantum dots and the uniform distribution of dopant elements can be balanced, while avoiding aggregation or byproduct formation due to excessive dopant.

[0048] Typical, but not limiting, molar ratios of the basic substance to the carbonyl compound are 1:2, 1:5, 1:10, or any combination of two such values. Preferably, the molar ratios are 1:2, 1:2.5, 1:3, or any combination of two such values. This range is favorable for the synthesis of carbon quantum dots.

[0049] Typical, but not limiting, volumes of the carbonyl compound to deionized water are 1:1, 1:2, 1:3, or any combination of two such values. Preferably, the volumes of the carbonyl compound to deionized water are 1:1.5, 1:1.75, 1:2, or any combination of two such values. Within this range, reaction efficiency is favorable.

[0050] In a preferred embodiment, the base fluid is ethylene glycol; preferably, based on the total weight of the lubricating oil additive material, the amount of nitrogen-sulfur-doped carbon quantum dots is 0.1 wt% to 0.5 wt%, more preferably 0.2 wt% to 0.4 wt%.

[0051] Ethylene glycol exhibits excellent solubility, effectively dissolving and stabilizing nitrogen-sulfur-doped carbon quantum dots. Furthermore, its high boiling point and low volatility maintain the stability of the reaction system during heating or stirring. Typically, but not limitingly, based on the total weight of the lubricant additive material, the amount of nitrogen-sulfur-doped carbon quantum dots is 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%, or any two of these values. Preferably, the amount of nitrogen-sulfur-doped carbon quantum dots is 0.2 wt%, 0.25 wt%, 0.3 wt%, 0.35 wt%, 0.4 wt%, or any two of these values.

[0052] In a preferred embodiment, step b includes filtration, dialysis, and freeze drying.

[0053] These separation and purification procedures remove insoluble byproducts or impurities generated during the reaction, ensuring high efficiency and high quality in subsequent processing. Filtration can be performed at room temperature (25±5°C) for at least 2 to 4 hours until the supernatant is completely removed, leaving a clear liquid, i.e., a suspension of carbon quantum dots. Dialysis can be performed at room temperature, preferably 25°C, to maintain the stability of the carbon quantum dots. A freeze-drying step is used to convert them into a dry and easily stored powder form.

[0054] In a preferred embodiment, in step b, the product of step a is filtered by a vacuum pump to remove the upper precipitate, leaving a clear liquid, which is then transferred to a dialysis bag for dialysis, and then placed in a freeze dryer, vacuumed, and freeze-dried for 30 to 60 hours, preferably 48 hours, to obtain nitrogen-sulfur-doped carbon quantum dots.

[0055] The vacuum pump can be a water-circulating vacuum pump, which uses negative pressure to force the reaction mixture through a filter medium, effectively separating insoluble solid particles or incompletely dissolved impurities generated during the reaction. Dialysis can further remove small molecule residues in the reaction system, such as unreacted small organic molecules, free dopants, or byproducts, thereby purifying the carbon quantum dots. The preferred dialysis bag pore size is 1 kDa to 10 kDa, a range that effectively removes most small molecule residues while preserving the integrity of the carbon quantum dots. Freeze-drying completely removes moisture and other volatile solvents from the carbon quantum dot suspension using a low-temperature and vacuum environment. For example, freezing at a low temperature of -50°C to -80°C, followed by drying under a high vacuum of below 10 Pa, preferably maintained between 0.06 MPa and 0.08 MPa. Typically, but not limitingly, the freeze-drying time is 30, 40, 50, 60 hours, or any combination of two values, preferably 48 hours. Within this range, moisture in the carbon quantum dots is removed, while reducing structural changes or loss of activity that may occur with prolonged drying.

[0056] The preparation process of this invention is as follows: Figure 1 As shown. Figure 1 This is a schematic diagram of the preparation process of sNS-CQDs according to the present invention. The process of preparing lNS-CQDs according to the present invention is illustrated by replacing p-aminobenzenesulfonic acid with L-cysteine.

[0057] According to an embodiment of this application, a lubricating oil additive material is also provided, which can be prepared by the above method.

[0058] The applicant tested the relevant properties of the lubricating oil additive material of the present invention, and the test method is as follows.

[0059] This invention employs a vertical universal tribological testing machine to test the tribological properties of nitrogen-sulfur-doped carbon quantum dots. Specifically, high load and high speed conditions are adopted: a load of 392 N and a speed of 1450 rpm. The coefficient of friction is measured and recorded in real time using a mechanical sensor within the tribological testing machine. Before testing, both the steel ball and the oil tank are ultrasonically cleaned with petroleum ether for 30 minutes. The test temperature is room temperature (25±5℃), and the experiment is repeated three times under the same conditions to ensure the accuracy of the results. After the friction experiment, the wear scar diameter is measured using an optical microscope, and the three-dimensional morphology of the wear scar is determined using an optical profilometer to analyze the wear condition.

[0060] The worn surface of the steel ball was analyzed using the following instruments:

[0061] (1) Scanning electron microscopy (SEM): The surface morphology and elemental distribution of the steel ball were analyzed using a Zeiss SU 8010 scanning electron microscope (SEM) from Germany. Before the test, the test ball was ultrasonically cleaned twice with petroleum ether (60-90℃), each time for about 15 minutes.

[0062] (2) A 3D surface profilometer is an instrument that uses the principle of white light interference for imaging measurement. It is a method to obtain the surface morphology of an object by measuring the interference fringes of the interference light. A beam of broad-spectrum white light is emitted and irradiated onto the surface of the object being measured. The light reflected by the object is then collected, forming a series of interference fringes. The shape and distribution of the interference fringes are related to the height and shape of the object's surface. By analyzing these interference fringes, the three-dimensional morphological information of the object can be obtained.

[0063] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0064] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0065] Example 1

[0066] This embodiment provides a method for preparing a lubricating oil additive material, including the following steps:

[0067] Step a: Dissolve 4 g of p-aminobenzenesulfonic acid in 40 mL of acetaldehyde at room temperature, then add 12 g of NaOH and 70 mL of deionized water and stir for 2 hours. Add 1.5 mL of hydrochloric acid (12 M) dropwise and continue stirring for 24 hours until the solution system is homogeneous.

[0068] Step b: At room temperature, use a water-circulating vacuum pump to filter out the upper precipitate, leaving a clear liquid. Transfer the clear liquid to a dialysis bag for dialysis, then place it in a freeze dryer, apply vacuum, and freeze dry for 48 hours to obtain powdered nitrogen-sulfur-doped carbon quantum dots.

[0069] Step c: Mix the purified nitrogen-sulfur-doped carbon quantum dots with ethylene glycol and sonicate for 30 minutes to obtain a stable lubricating oil additive material. Based on the total weight of the lubricating oil additive material, the amount of nitrogen-sulfur-doped carbon quantum dots is 0.1 wt%.

[0070] exist Figure 2 In the image, left side (a) shows a TEM image (transmission electron microscope) of p-aminobenzenesulfonic acid sNS-CQDs according to Example 1. The TEM image clearly shows that the carbon quantum dots of the present invention maintain ideal small size and high dispersibility, and exhibit excellent morphological distribution and structural uniformity. Figure 3 In the image, leftmost (a) shows an HRTEM (high-resolution transmission electron microscopy) image of p-aminobenzenesulfonic acid sNS-CQDs according to Example 1. The lattice spacing is marked as 0.206 nm, and the clear lattice shows that the dopant atoms are inserted into the lattice rather than simply adsorbed on the surface. The carbon quantum dots of this invention achieve effective doping.

[0071] Example 2

[0072] This embodiment provides a method for preparing a lubricating oil additive material, using the same method as in Example 1, except that the amount of ethylene glycol used in step c is different. Based on the total weight of the lubricating oil additive material, the amount of nitrogen-sulfur-doped carbon quantum dots is 0.2 wt%.

[0073] Example 3

[0074] This embodiment provides a method for preparing a lubricating oil additive material, using the same method as in Example 1, except that the amount of ethylene glycol used in step c is different. Based on the total weight of the lubricating oil additive material, the amount of nitrogen-sulfur-doped carbon quantum dots is 0.3 wt%.

[0075] Example 4

[0076] This embodiment provides a method for preparing a lubricating oil additive material, using the same method as in Example 1, except that the amount of ethylene glycol used in step c is different. Based on the total weight of the lubricating oil additive material, the amount of nitrogen-sulfur-doped carbon quantum dots is 0.4 wt%.

[0077] Example 5

[0078] This embodiment provides a method for preparing a lubricating oil additive material, using the same method as in Example 1, except that the amount of ethylene glycol used in step c is different. Based on the total weight of the lubricating oil additive material, the amount of nitrogen-sulfur-doped carbon quantum dots is 0.5 wt%.

[0079] Example 6

[0080] This embodiment provides a method for preparing a lubricating oil additive material, including the following steps:

[0081] Step a: Dissolve 4 g of L-cysteine ​​in 40 mL of acetaldehyde at room temperature, then add 12 g of NaOH and 70 mL of deionized water and stir for 2 hours. Add 1.5 mL of hydrochloric acid (12 M) dropwise and continue stirring for 24 hours until the solution system is homogeneous.

[0082] Step b: At room temperature, use a water-circulating vacuum pump to filter out the upper precipitate, leaving a clear liquid. Transfer the clear liquid to a dialysis bag for dialysis, then place it in a freeze dryer, apply vacuum, and freeze dry for 48 hours to obtain powdered nitrogen-sulfur-doped carbon quantum dots.

[0083] Step c: Mix the purified nitrogen-sulfur-doped carbon quantum dots with ethylene glycol and sonicate for 30 minutes to obtain a stable lubricating oil additive material. Based on the total weight of the lubricating oil additive material, the amount of nitrogen-sulfur-doped carbon quantum dots is 0.1 wt%.

[0084] exist Figure 2 In the image, right side (b) shows a TEM image of L-cystine lNS-CQDs according to Example 6. The TEM image clearly shows that the carbon quantum dots of the present invention maintain ideal small size and high dispersibility, and exhibit excellent morphological distribution and structural uniformity. Figure 3 In the image, right side (b) shows an HRTEM image of L-cystine lNS-CQDs according to Example 6. The lattice spacing is marked as 0.197 nm, and the clear lattice shows that the dopant atoms are inserted into the lattice rather than simply adsorbed on the surface. The carbon quantum dots of this invention achieve effective doping.

[0085] Example 7

[0086] This embodiment provides a method for preparing a lubricating oil additive material, using the same method as in Example 6, except that the amount of ethylene glycol used in step c is different. Based on the total weight of the lubricating oil additive material, the amount of nitrogen-sulfur-doped carbon quantum dots is 0.2 wt%.

[0087] Example 8

[0088] This embodiment provides a method for preparing a lubricating oil additive material, using the same method as in Example 6, except that the amount of ethylene glycol used in step c is different. Based on the total weight of the lubricating oil additive material, the amount of nitrogen-sulfur-doped carbon quantum dots is 0.3 wt%.

[0089] Example 9

[0090] This embodiment provides a method for preparing a lubricating oil additive material, using the same method as in Example 6, except that the amount of ethylene glycol used in step c is different. Based on the total weight of the lubricating oil additive material, the amount of nitrogen-sulfur-doped carbon quantum dots is 0.4 wt%.

[0091] Example 10

[0092] This embodiment provides a method for preparing a lubricating oil additive material, using the same method as in Example 6, except that the amount of ethylene glycol used in step c is different. Based on the total weight of the lubricating oil additive material, the amount of nitrogen-sulfur-doped carbon quantum dots is 0.5 wt%.

[0093] Comparative Example 1

[0094] Only ethylene glycol-based liquid is used, without adding the nitrogen-sulfur-doped carbon quantum dots of the present invention.

[0095] exist Figure 4 In the middle, the left figure shows the friction coefficient curves of lNS-CQDs of Examples 6-10 and the ethylene glycol-based liquid of Comparative Example 1 according to the present invention; the right figure shows the average friction coefficient and average wear scar diameter.

[0096] exist Figure 5 In the figure, the left figure shows the friction coefficient curves of sNS-CQDs of Examples 1-5 and the ethylene glycol-based liquid of Comparative Example 1 according to the present invention; the right figure shows the average friction coefficient and average wear scar diameter.

[0097] Figure 4 and Figure 5 The values ​​were measured using the aforementioned measurement method under conditions of a load of 392 N, a rotation speed of 1450 rpm, and a time of 60 min. The "blank" in the left graph and the additive concentration of "0.0" in the right graph both correspond to Comparative Example 1.

[0098] Friction test results showed that the 0.5 wt% L-cystine (lNS-CQDs) additive achieved the maximum friction reduction effect, decreasing the average coefficient of friction by 69.7% and the wear scar diameter by 20.1%. Furthermore, the friction reduction effect increased with increasing carbon quantum dot additive content. The 0.2 wt% p-aminobenzenesulfonic acid (sNS-CQDs) additive achieved the maximum friction reduction effect, decreasing the average coefficient of friction by 75.4% and the wear scar diameter by 25.8%.

[0099] This invention selected 0.2 wt% p-aminobenzenesulfonic acid sNS-CQDs additive and conducted friction experiments for different time lengths of 1200s, 2400s and 3600s. The results showed that wear mainly occurred in the first 1200s. In the later stage of friction, due to the tribochemical reaction of sNS-CQDs additive molecules during the friction process, a tribochemical film was formed, which greatly reduced the wear.

[0100] Figure 6 SEM images of wear scars after lubrication and friction are shown. Figure 6 In the figures, (a) is a SEM image of the wear scar after friction using the ethylene glycol-based lubricant of Comparative Example 1. Without adding any doped carbon quantum dots, using only ethylene glycol as the lubricant leaves a distinct wear scar morphology on the friction surface. (b) is a SEM image of the wear scar after friction using p-aminobenzenesulfonic acid sNS-CQDs of Example 1. It can be seen that the presence of sNS-CQDs improves lubrication performance and significantly reduces the size and depth of the wear scar. (c) is a SEM image of the wear scar after friction using L-cysteine ​​lNS-CQDs of Example 6. It can be seen that the presence of lNS-CQDs also improves lubrication performance and significantly reduces the size and depth of the wear scar.

[0101] By analyzing the friction coefficient curve ( Figure 4 and Figure 5 ) and SEM images of the wear marks ( Figure 6 Analysis of the two types of nitrogen-sulfur-doped carbon quantum dots shows that both have good wear resistance and friction reduction effects as lubricant additives.

[0102] Using the preparation method provided in this invention, two types of nitrogen-sulfur-doped carbon quantum dots, namely aminobenzenesulfonic acid sNS-CQDs and L-cystine lNS-CQDs, are innovatively synthesized, thereby obtaining novel lubricating oil additive materials that can significantly improve lubrication performance and exhibit excellent friction reduction and anti-wear properties under different working conditions.

[0103] The above description is only a preferred embodiment of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of this application, and these improvements and modifications should also be considered within the scope of protection of this application.

Claims

1. A method for preparing a lubricating oil additive material, characterized in that, The method includes: Step a: React an alkaline substance with a carbonyl compound, and add an aromatic compound containing nitrogen and sulfur functional groups or a sulfur-containing amino acid as a dopant in the reaction. Step b: Separate and purify the product from step a to obtain nitrogen-sulfur-doped carbon quantum dots; Step c: Mix the purified nitrogen-sulfur-doped carbon quantum dots with the base liquid to obtain the lubricating oil additive material.

2. The method according to claim 1, characterized in that, The dopant is selected from p-aminobenzenesulfonic acid or L-cysteine.

3. The method according to claim 1 or 2, characterized in that, The alkaline substance is sodium hydroxide, and the carbonyl compound is acetaldehyde.

4. The method according to claim 1 or 2, characterized in that, In step a, the dopant is dissolved in the carbonyl compound, then the alkaline substance and deionized water are added, and the mixture is stirred for 1 to 3 hours. Then hydrochloric acid is added, and the mixture is stirred for 24 to 48 hours.

5. The method according to claim 4, characterized in that, The molar ratio of hydrochloric acid to the dopant is from 0.7:1 to 1.2:

1.

6. The method according to claim 1 or 2, characterized in that, The molar ratio of the dopant to the carbonyl compound is 1:10 to 1:50, preferably 1:20 to 1:35; the molar ratio of the alkaline substance to the carbonyl compound is 1:2 to 1:10, preferably 1:2 to 1:3; the volume ratio of the carbonyl compound to the deionized water is 1:1 to 1:3, preferably 1:1.5 to 1:

2.

7. The method according to claim 1 or 2, characterized in that, The base liquid is ethylene glycol; preferably, based on the total weight of the lubricating oil additive material, the amount of nitrogen-sulfur-doped carbon quantum dots is 0.1 wt% to 0.5 wt%, more preferably 0.2 wt% to 0.4 wt%.

8. The method according to claim 1 or 2, characterized in that, Step b includes filtration, dialysis, and freeze drying.

9. The method according to claim 1 or 2, characterized in that, In step b, the product of step a is filtered using a vacuum pump to remove the upper precipitate, leaving a clear liquid, which is then transferred to a dialysis bag for dialysis. After dialysis, the liquid is placed in a freeze dryer, vacuumed, and freeze-dried for 30 to 60 hours, preferably 48 hours, to obtain the nitrogen-sulfur-doped carbon quantum dots.

10. A lubricating oil additive material, characterized in that, The lubricating oil additive material is prepared by the method according to any one of claims 1 to 9.

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