Composite lubricating material for ship main engine in biofuel environment and preparation method thereof

Abstract

The present invention provides a composite lubricating material for a ship main engine in a biofuel environment and a preparation method thereof. The preparation method comprises: first, mixing expanded graphite, attapulgite and an organic solvent and stirring the mixture to obtain a mixed solution; second, ball-milling the mixed solution in a dielectric barrier discharge plasma atmosphere to obtain a suspension; then, standing the suspension for stratification to obtain a supernatant; finally, centrifuging and washing the supernatant to obtain a centrifugal mother liquor, and then drying the centrifugal mother liquor to obtain a graphene / attapulgite composite lubricating material. The present invention utilizes the unique two-dimensional structure and excellent lubricating properties of graphene itself, and combines the hardness and chemical stability of attapulgite to significantly improve the lubricating effect of the lubricating medium under extreme working conditions. In addition, expanded graphite and attapulgite are widely available, with low preparation costs and high economic efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of lubricating materials, and in particular to a composite lubricating material for a ship main engine in a biofuel environment and a preparation method thereof. Background Art

[0002] With growing global awareness of environmental protection and the pursuit of sustainable development, biofuels are increasingly being used in the marine sector as a green energy alternative to traditional fossil fuels. However, the use of marine biofuels poses even more stringent challenges to the lubrication conditions of marine power systems, particularly in the critical cylinder liner-piston ring assembly. Biofuels differ significantly from conventional fuels in terms of chemical composition and physical properties. Biofuels typically contain higher oxygen content, acidic substances, and biodegradation residues, which lead to increased deposits and corrosive substances during combustion. These deposits easily form carbon deposits and sludge on the cylinder liner and piston rings, increasing the viscosity and reducing the fluidity of the lubricant, thereby compromising the lubrication performance of the cylinder liner-piston ring assembly. Furthermore, the high combustion temperature of biofuels increases the temperature of the cylinder liner and piston rings. High temperatures accelerate the oxidation and decomposition of the lubricant, reducing its lubrication performance and service life. Furthermore, high temperatures can cause thermal deformation of the cylinder liner and piston rings, further exacerbating wear and poor lubrication. Therefore, the lubrication conditions of the cylinder liner-piston ring assembly become even more demanding when using marine biofuels. Summary of the Invention

[0003] The purpose of the present invention is to solve the technical problem that the existing lubricating materials have poor lubrication performance in the field of cylinder liner and piston ring of ship main engine under biofuel conditions.

[0004] To solve the above technical problems, the present invention first provides a method for preparing a composite lubricating material for ship main engines in a biofuel environment, comprising:

[0005] S10, mixing expanded graphite, attapulgite and an organic solvent and stirring to obtain a mixed solution;

[0006] S20, ball milling the mixed solution in a dielectric barrier discharge plasma atmosphere to obtain a suspension;

[0007] S30, performing a stratification process on the suspension to obtain a supernatant;

[0008] S40, performing a centrifugal washing treatment on the supernatant to obtain a centrifugal mother liquor, and then drying the centrifugal mother liquor to obtain a graphene / attapulgite composite lubricating material.

[0009] Preferably, before performing step S10, the method further includes: performing thermal expansion pretreatment on the expanded graphite using a box-type resistance furnace.

[0010] Preferably, in the thermal expansion pretreatment, the power of the box-type resistance furnace is 1-5 kW, the heating temperature is 800-1200° C., and the heating time is 30-120 s.

[0011] Preferably, in step S10: the mass ratio of expanded graphite to attapulgite is (1-5):1; the organic solvent is oleic acid, and the volume of the organic solvent is 400-600 ml.

[0012] Preferably, step S20 specifically includes:

[0013] S21, pouring the mixed solution into a ball mill;

[0014] S22, placing the ball mill jar into a plasma-assisted ball milling device having a dielectric barrier discharge plasma atmosphere for assisted ball milling, and then taking out the ball mill jar to obtain a suspension.

[0015] Preferably, the operating parameters of the plasma-assisted ball milling device in step S22 are: vibration frequency of 16 Hz, vibration amplitude of 10 mm, plasma discharge voltage of 23 kV, and current of 1.5 A.

[0016] Preferably, in step S22: the ball milling tank is also filled with an inert gas, and the auxiliary ball milling treatment time is 8 to 15 hours.

[0017] Preferably, in step S30, the time for static stratification treatment is 8 to 20 hours; in step S40, the centrifugal washing speed for centrifugal washing treatment is 3000 to 5000 r / min, the centrifugal washing time is 20 to 60 minutes, and the drying temperature for drying treatment is 80 to 100° C., and the drying time is 18 to 36 hours.

[0018] Correspondingly, the present invention also provides a composite lubricating material for ship main engines in a biofuel environment, which is prepared using any of the above methods for preparing a composite lubricating material for ship main engines in a biofuel environment.

[0019] The beneficial effects of the present invention are as follows: different from the prior art, the present invention provides a composite lubricating material for a ship main engine in a biofuel environment and a preparation method thereof, the preparation method comprising: first, mixing expanded graphite, attapulgite and an organic solvent and stirring to obtain a mixed solution; second, ball milling the mixed solution in a dielectric barrier discharge plasma atmosphere to obtain a suspension; then, standing and stratifying the suspension to obtain a supernatant; finally, centrifuging and washing the supernatant to obtain a centrifuged mother liquor, and then drying the centrifuged mother liquor to obtain a graphene / attapulgite composite lubricating material; the present invention first ball mills the mixed solution containing expanded graphite in a dielectric barrier discharge plasma atmosphere, and due to the synergistic effect of the thermal explosion and activation effect of the plasma and the mechanical ball milling, the mixed solution containing expanded graphite is subjected to a ball milling treatment. The expanded graphite is gradually refined in this process, which is conducive to the formation of thinner graphene; then, the attapulgite component is loaded on the surface of the graphene to form a graphene / attapulgite composite lubricating material; the present invention fully utilizes the unique two-dimensional structure and excellent lubrication properties of graphene itself, and combines the hardness and chemical stability of attapulgite to obtain an excellent lubrication and friction reduction effect, significantly improving the lubrication effect of the lubricating medium under extreme working conditions such as high temperature, heavy load and high speed, and has broad application prospects in the fields of marine equipment, mining machinery, military equipment, etc.; at the same time, the graphene / attapulgite composite lubricating material is prepared by plasma-assisted ball milling, which has a simple process, a short production cycle, and high repeatability, and is conducive to large-scale industrial production. In addition, the prices of expanded graphite and attapulgite are widely available, the preparation cost is low, and the economy is high. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A flow chart of a method for preparing a composite lubricating material for a ship main engine in a biofuel environment provided by an embodiment of the present invention;

[0021] Figure 2 This is a scanning electron microscope image of the graphene / attapulgite composite lubricating material provided in Example 1 of the present invention;

[0022] Figure 3 A Fourier infrared spectrum of the graphene / attapulgite composite lubricating material provided in Example 1 of the present invention;

[0023] Figure 4 A comparison chart of the friction coefficients of the cylinder liner and piston ring in a tribological experiment between the graphene / attapulgite composite lubricating material and the base oil provided in Example 1 of the present invention;

[0024] Figure 5 This is a comparison chart of cylinder liner wear quality of the graphene / attapulgite composite lubricating material and base oil provided in Example 1 of the present invention in tribological experiments. DETAILED DESCRIPTION

[0025] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0026] Currently, marine diesel engines, as the primary source of ship power, are widely used in ocean trade and transportation due to their advantages, including rapid start-up, excellent operating performance, safety and reliability, a wide power range, and mature technology. As the primary means of transport for ocean-going shipping, the operational reliability of marine diesel engines dictates the safety of the vessel. The cylinder liner-piston ring assembly is a core component of marine diesel engines, and its performance significantly impacts the engine's efficiency and service life. However, under extreme operating conditions such as high temperature, high pressure, and high speed, the cylinder liner-piston ring friction pair experiences friction, wear, and thermal expansion, which restricts engine performance and reliability. Furthermore, failures caused by the cylinder liner-piston ring assembly account for a significant proportion of marine mechanical failure statistics. Therefore, improving the mechanical reliability of the cylinder liner-piston ring assembly and reducing its failures are crucial for ensuring the long-term stable operation and performance of marine diesel engines.

[0027] Under the conditions of marine biofuels, the lubrication of the cylinder liner-piston ring assembly becomes even more demanding. To ensure the normal operation of the ship's power system and extend the service life of the equipment, more advanced lubrication technologies and high-performance lubricant products are needed to meet the challenges posed by biofuels. One effective measure to address wear of the cylinder liner-piston rings of ship main engines in biofuel environments is to use lubricant additives with enhanced resistance to oxidation, corrosion, and deposits.

[0028] To address the critical lubrication requirements of the cylinder liner-piston ring assembly under marine biofuel conditions, the present invention leverages graphene's advantages, including high mechanical strength, excellent thermal conductivity, high thermal stability, and corrosion resistance, combining appropriate components with graphene to create a more effective composite lubricant additive. The synergistic lubrication between the composite additive materials can further improve lubrication and significantly enhance tribological performance. Attapulgite, a natural silicate mineral with attractive properties such as large surface area, high mechanical strength, and excellent thermal stability, can form a repair layer on the worn surface of the cylinder liner-piston ring assembly, significantly reducing wear.

[0029] The present invention aims to provide a composite lubricating material for marine main engines operating in a biofuel environment and a method for preparing the same. The composite lubricating material has the advantages of good dispersion stability in base oil, the ability to effectively improve the tribological properties of cylinder liners and piston rings, and the simplicity and speed of its preparation process, which allows for repeatable operations and facilitates large-scale production.

[0030] See also Figure 1 , Figure 1 This is a flow chart of a method for preparing a composite lubricating material for a ship main engine in a biofuel environment provided by an embodiment of the present invention; wherein the above-mentioned preparation method specifically includes:

[0031] S10, mixing expanded graphite, attapulgite and an organic solvent and stirring the mixture to obtain a mixed solution.

[0032] Specifically, step S10 further includes:

[0033] First, we offer expanded graphite. Expanded graphite (EG) is a new type of functional carbon material. It's made from natural flake graphite. Under specific conditions, molecules, atoms, ions, or particle clusters are inserted between graphite layers to form graphite intercalation compounds. High-temperature treatment then decomposes and vaporizes the intercalation compounds, causing the graphite to expand significantly along the C-axis between the layers, resulting in a worm-like structure.

[0034] Afterwards, the expanded graphite is subjected to thermal expansion pretreatment using a box-type resistance furnace to increase the interlamellar spacing of the expanded graphite.

[0035] Finally, the expanded graphite, attapulgite and the organic solvent are mixed and stirred to obtain a mixed solution.

[0036] Specifically, the expanded graphite is subjected to thermal expansion pretreatment. Due to the high temperature, a large amount of CO2 and SO2 gases are instantly produced, which increases the interlamellar spacing of the expanded graphite and weakens the van der Waals force between the expanded graphite flakes, which is beneficial to the subsequent preparation of composite lubricating materials.

[0037] Specifically, in thermal expansion pretreatment: the box-type resistance furnace power is 1~5kW, the heating temperature is 800~1200℃, and the heating time is 30~120s; among them, the power of the box-type resistance furnace will affect the heating rate and the time to reach the set temperature; the heating temperature range determines the intensity and effect of the thermal action during the pretreatment process, and the setting of the heating time will affect the degree of treatment and the performance of the product.

[0038] In the embodiment of the present invention, in step S10: the mass ratio of expanded graphite to attapulgite is (1-5):1; the organic solvent is oleic acid, and the volume of the organic solvent is 400-600 ml.

[0039] Specifically, attapulgite is a natural silicate mineral with attractive characteristics such as large surface area, high mechanical strength, and good thermal stability. In the wear inhibition of cylinder liner-piston ring, it can form a repair layer on its wear surface and significantly reduce the wear amount.

[0040] Specifically, expanded graphite has the characteristics of looseness, porosity and strong adsorption; attapulgite also has good adsorption performance and ion exchange properties; the mass ratio of expanded graphite to attapulgite is (1~5):1, which can optimize the overall lubrication performance of the composite lubricating material.

[0041] Specifically, the organic solvent serves as a ball milling medium, which not only allows the graphene surface to load more attapulgite material, but also plays a role in surface organic modification of the prepared graphene / attapulgite composite material, thereby enhancing its dispersion stability in the lubricating oil.

[0042] S20, ball milling the mixed solution in a dielectric barrier discharge plasma atmosphere to obtain a suspension.

[0043] Specifically, step S20 further includes:

[0044] S21, pouring the mixed solution into a ball mill;

[0045] S22, placing the ball mill jar into a plasma-assisted ball milling device having a dielectric barrier discharge plasma atmosphere for assisted ball milling, and then taking out the ball mill jar to obtain a suspension.

[0046] Preferably, the operating parameters of the plasma-assisted ball milling device in step S22 are: vibration frequency of 16 Hz, vibration amplitude of 10 mm, plasma discharge voltage of 23 kV, and current of 1.5 A.

[0047] Preferably, in step S22: the ball milling tank is also filled with an inert gas, and the auxiliary ball milling treatment time is 8 to 15 hours.

[0048] Specifically, in the process of preparing composite lubricating materials using a plasma-assisted ball milling device, due to the synergistic effect of the plasma's thermal explosion and activation effect and mechanical ball milling, the expanded graphite is gradually refined during this process, which is conducive to the formation of thinner graphene.

[0049] S30, performing a stratification process on the suspension to obtain a supernatant.

[0050] Specifically, step S30 further includes:

[0051] The suspension is subjected to a stratification treatment for 8 to 20 hours to obtain an upper clear liquid and a lower precipitate, wherein the lower precipitate is solid impurities.

[0052] S40, performing a centrifugal washing treatment on the supernatant to obtain a centrifugal mother liquor, and then drying the centrifugal mother liquor to obtain a graphene / attapulgite composite lubricating material.

[0053] Specifically, step S40 further includes:

[0054] First, the supernatant is centrifuged and washed in a centrifuge to obtain a centrifugal mother liquor and a centrifugal precipitate, wherein the centrifugal precipitate includes excess reactants and unexfoliated graphite; wherein the centrifugal washing process is performed at a centrifugal washing speed of 3000-5000 r / min and a centrifugal washing time of 20-60 min;

[0055] Secondly, the centrifugal mother liquor is dried to obtain a graphene / attapulgite composite lubricating material; wherein the drying temperature for the drying treatment is 80-100° C., and the drying time is 18-36 hours.

[0056] Correspondingly, the present invention also provides a composite lubricating material for ship main engines in a biofuel environment, which is prepared using any of the above methods for preparing a composite lubricating material for ship main engines in a biofuel environment.

[0057] Specifically, the graphene / attapulgite composite lubricating material and preparation method thereof provided by the embodiments of the present invention have the following advantages:

[0058] The preparation method of the present invention prepares the graphene / attapulgite composite lubricating material through plasma-assisted ball milling, has a simple process, a short production cycle, high repeatability, and is conducive to large-scale industrial production.

[0059] In the preparation method of the present invention, before synthesizing graphene with attapulgite loaded on its surface, the expandable graphite is subjected to high-temperature heat treatment, which is beneficial to increasing the interlamellar spacing and facilitating the subsequent introduction of attapulgite on its surface without introducing material defects.

[0060] The composite lubricating material for marine engines, prepared according to an embodiment of the present invention, loads the attapulgite component onto its surface during plasma-assisted ball milling without disrupting the ordered graphite structure. The graphene sheets are continuously exfoliated during the milling process. Furthermore, the use of oleic acid as a milling medium not only increases the loading of attapulgite onto the graphene surface but also provides surface organic modification for the prepared graphene / attapulgite composite, enhancing its dispersion stability in lubricating oil.

[0061] The composite lubricating material for ship main engines in a biofuel environment prepared according to an embodiment of the present invention fully utilizes the unique two-dimensional structure and excellent lubrication properties of graphene itself, and at the same time combines the hardness and chemical stability of attapulgite to achieve excellent lubrication and friction reduction effects, significantly improving the lubrication effect of the lubricating medium under extreme working conditions such as high temperature, heavy load and high speed, and has broad application prospects in the fields of marine equipment, mining machinery, military equipment, etc.

[0062] The technical solution of the present invention will now be further described with reference to specific embodiments.

[0063] Example 1:

[0064] This embodiment 1 provides a method for preparing a composite lubricating material for a ship main engine in a biofuel environment. The preparation method and application steps are as follows:

[0065] Step 1: heating expandable graphite in a box-type resistance furnace to obtain expanded graphite, wherein the box-type resistance furnace has a power of 4 kW, a temperature of 1000° C., and a heating time of 60 s;

[0066] Step 2: uniformly mix expanded graphite and attapulgite with 500 ml of oleic acid in a mass ratio of 4:1 to obtain a mixed solution;

[0067] Step 3, pouring the mixed solution obtained in step 2 into a ball mill;

[0068] Step 4: Place the ball milling jar prepared in step 3 into a dielectric barrier discharge plasma for assisted ball milling. At the same time, the ball milling jar is filled with 0.1 MPa of high-purity argon as a protective gas. The ball milling time is 10 h. The vibration frequency of the plasma-assisted ball milling device is 16 Hz, the vibration amplitude is 10 mm, the plasma discharge voltage is 23 kV, and the current is 1.5 A.

[0069] Step 5: After the ball milling in step 4 is completed, the suspension in the ball mill is taken out;

[0070] Step 6: let the suspension obtained in step 5 stand for 10 hours to obtain a supernatant;

[0071] Step 7: taking out the supernatant after standing in step 6, and centrifuging the supernatant three times in a centrifuge to remove excess reactants and unexfoliated graphite, wherein the centrifugal washing speed is 4000 r / min and the centrifugal washing time is 30 minutes;

[0072] Step eight, drying the solution obtained after washing in step seven in a drying oven at 90° C. for 24 hours to obtain a graphene / attapulgite composite lubricating material.

[0073] See also Figure 2 , Figure 2This is a scanning electron microscope image of the graphene / attapulgite composite lubricating material provided in Example 1 of the present invention; Figure 2 It can be seen that the graphene / attapulgite composite lubricating material provided in Example 1 of the present invention has a large amount of lamellar graphene material and is loaded with attapulgite on the surface. The two present a two-dimensional form and are stacked and entangled with each other to form a layered structure.

[0074] See also Figure 3 , Figure 3 The Fourier infrared spectrum of the graphene / attapulgite composite lubricating material provided in Example 1 of the present invention; Figure 3 It can be seen that the stretching vibrations of -CH3 and -CH2 in the figure come from oleic acid, indicating that oleic acid successfully modified the surface of graphene / attapulgite composite materials as a ball milling medium and surface modifier; the bending vibrations of C=C and CC groups come from expanded graphite, and the stretching vibrations of Si-O-Si, Si-O-Mg and Si-O-Al all come from attapulgite.

[0075] Specifically, a cylinder liner-piston ring friction test was performed on the graphene / attapulgite composite lubricating material provided in Example 1 of the present invention, and the specific steps are as follows:

[0076] (1) Graphene / attapulgite composite lubricating materials with different mass fractions were uniformly dispersed in base oil by ultrasonic and magnetic stirring, and base oil without additives was used as a control.

[0077] (2) Common materials used in ship diesel engine cylinder liners and piston rings were used to make samples. The cylinder liner samples were processed into disc samples with a size of Φ38.1mm×8mm and polished with sandpaper until the friction surface roughness Ra was about 0.8μm. The piston ring samples were processed into cylindrical pin samples with a nominal size of Φ6.36mm and a length of 16mm. Reciprocating tribology experiments were carried out using an Rtec friction and wear tester. The Rtec friction and wear tester is a new generation of friction and wear testing equipment developed by a professional tribology team in the United States and a team of optical / semiconductor testing experts in Silicon Valley.

[0078] (3) The friction and wear behavior of the cylinder liner-piston ring friction pair was investigated using two operating conditions: low and high loads of 50 N (1.57 MPa) and 100 N (3.15 MPa) and two low and high reciprocating frequencies (1 and 3 Hz). The experiments were conducted indoors, and each experiment lasted for 1 h. Before the start of the test, the experimental lubricant containing various concentrations of BNNs / Cu additives was dripped onto the cylinder liner specimens. The friction coefficient was continuously recorded by an Rtec friction and wear tester at a recording frequency of 0.01 s / time. After the friction test, all cylinder liner specimens were cleaned with anhydrous ethanol and weighed using a precision analytical balance.

[0079] Specifically, the cylinder liner-piston ring tribology test results using base oil as lubricant are shown in Table 1:

[0080] Table 1 Tribological test results of cylinder liner and piston ring under base oil lubrication

[0081]

[0082] Specifically, the cylinder liner-piston ring tribology test results of the graphene / attapulgite composite lubricating material provided in Example 1 of the present invention as a lubricant are shown in Table 2:

[0083] Table 2 Tribological test results of cylinder liner and piston ring under lubrication of graphene / attapulgite composite material provided in Example 1 of the present invention

[0084]

[0085] See also Figure 4 , Figure 4 A comparison chart of the friction coefficients of the cylinder liner and piston ring in a tribological experiment between the graphene / attapulgite composite lubricating material and the base oil provided in Example 1 of the present invention; Figure 4 It can be seen that the graphene / attapulgite composite lubricating material provided in Example 1 of the present invention can significantly reduce the friction coefficient of the cylinder liner-piston ring compared to the base oil as a lubricating oil additive.

[0086] See also Figure 5 , Figure 5 A comparison chart of cylinder liner wear quality between the graphene / attapulgite composite lubricating material and the base oil in a tribological experiment provided by Example 1 of the present invention; Figure 5 It can be seen that the graphene / attapulgite composite lubricating material provided in Example 1 of the present invention can significantly reduce the wear quality of the cylinder liner compared to the base oil as a lubricating oil additive.

[0087] The method for preparing the composite lubricating material for ship main engines in an oleic acid-modified biofuel environment obtained in Example 1 of the present invention has the advantages of simple process, easy operation, low cost, and high purity of the prepared product. The obtained graphene-loaded attapulgite composite material has good lubrication and friction reduction effects and can be applied to the automotive industry, aerospace and other fields.

[0088] In summary, different from the prior art, the present invention provides a composite lubricating material for ship main engines in a biofuel environment and a preparation method thereof, the preparation method comprising: first, mixing expanded graphite, attapulgite and an organic solvent and stirring to obtain a mixed solution; secondly, ball milling the mixed solution in a dielectric barrier discharge plasma atmosphere to obtain a suspension; thereafter, subjecting the suspension to a static stratification process to obtain a supernatant; finally, subjecting the supernatant to a centrifugal washing process to obtain a centrifugal mother liquor, and then drying the centrifugal mother liquor to obtain a graphene / attapulgite composite lubricating material; the present invention firstly ball mills the mixed solution containing expanded graphite in a dielectric barrier discharge plasma atmosphere, and due to the synergistic effect of the thermal explosion and activation effect of the plasma and the mechanical ball milling, the expanded graphite is The ink is gradually refined in this process, which is conducive to the formation of thinner graphene; then, the attapulgite component is loaded on the surface of the graphene to form a graphene / attapulgite composite lubricating material; the present invention fully utilizes the unique two-dimensional structure and excellent lubrication properties of graphene itself, and combines the hardness and chemical stability of attapulgite to obtain excellent lubrication and friction reduction effects, significantly improving the lubrication effect of the lubricating medium under extreme working conditions such as high temperature, heavy load and high speed, and has broad application prospects in the fields of marine equipment, mining machinery, military equipment, etc.; at the same time, the graphene / attapulgite composite lubricating material is prepared by plasma-assisted ball milling, which has a simple process, a short production cycle, and high repeatability, and is conducive to large-scale industrial production. In addition, expanded graphite and attapulgite are widely available, with low preparation costs and high economic efficiency.

[0089] It should be noted that the above embodiments all belong to the same inventive concept, and the description of each embodiment has its own focus. For any details not described in individual embodiments, reference may be made to the description in other embodiments.

[0090] The above embodiments merely illustrate the implementation methods of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art could make various modifications and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A method for preparing a composite lubricating material for a ship main engine in a biofuel environment, characterized in that: include: S10, mixing expanded graphite, attapulgite and an organic solvent and stirring to obtain a mixed solution; S20, ball milling the mixed solution in a dielectric barrier discharge plasma atmosphere to obtain a suspension; S30, performing a stratification process on the suspension to obtain a supernatant; S40, performing a centrifugal washing treatment on the supernatant to obtain a centrifugal mother liquor, and then drying the centrifugal mother liquor to obtain a graphene / attapulgite composite lubricating material; Wherein, in step S10: the mass ratio of expanded graphite to attapulgite is (1-5):1; the organic solvent is oleic acid, and the volume of the organic solvent is 400-600 ml; Step S20 specifically includes: S21, pouring the mixed solution into a ball mill; S22, placing the ball mill jar in a plasma-assisted ball milling device with a dielectric barrier discharge plasma atmosphere for assisted ball milling, and then taking out the ball mill jar to obtain a suspension; the operating parameters of the plasma-assisted ball milling device are: vibration frequency of 16 Hz, vibration amplitude of 10 mm, plasma discharge voltage of 23 kV, and current of 1.5 A.

2. The method for preparing a composite lubricating material for a ship main engine in a biofuel environment according to claim 1, characterized in that: Before performing the step S10, the method further includes: performing thermal expansion pretreatment on the expanded graphite using a box-type resistance furnace.

3. The method for preparing a composite lubricating material for a ship main engine in a biofuel environment according to claim 2, characterized in that: In the thermal expansion pretreatment, the power of the box-type resistance furnace is 1-5 kW, the heating temperature is 800-1200° C., and the heating time is 30-120 seconds.

4. The method for preparing a composite lubricating material for a ship main engine in a biofuel environment according to claim 1, characterized in that: In step S22: the ball milling jar is also filled with inert gas, and the auxiliary ball milling treatment time is 8 to 15 hours.

5. The method for preparing a composite lubricating material for a ship main engine in a biofuel environment according to claim 1, characterized in that: In step S30, the time for the static stratification treatment is 8 to 20 hours; in step S40, the centrifugal washing speed for the centrifugal washing treatment is 3000 to 5000 r / min, the centrifugal washing time is 20 to 60 minutes, the drying temperature for the drying treatment is 80 to 100°C, and the drying time is 18 to 36 hours.

6. A composite lubricating material for ship main engines in a biofuel environment, characterized in that: The composite lubricating material for ship main engines in a biofuel environment is prepared by the preparation method of the composite lubricating material for ship main engines in a biofuel environment according to any one of claims 1 to 5.

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