Molybdenum disulfide / fluorinated graphene composite lubricating additive and its preparation method

Abstract

This invention discloses a highly wear-resistant molybdenum disulfide / fluorinated graphene composite lubricant additive and its preparation method, comprising the following steps: dispersing an ionic liquid in distilled water, adding molybdenum disulfide to form a mixture, and then sequentially subjecting the mixture to ultrasonic treatment, multiple mechanical crushing treatments, and centrifugation, collecting the supernatant to obtain a molybdenum disulfide dispersion; dispersing an ionic liquid in distilled water, adding fluorinated graphene to form a mixture, then placing the mixture in an autoclave for hydrothermal reaction, followed by centrifugation, collecting the supernatant to obtain a fluorinated graphene dispersion; mixing the molybdenum disulfide dispersion and the fluorinated graphene dispersion at a mass ratio of 1 to 3:1, and ultrasonically treating the mixture to form a molybdenum disulfide / fluorinated graphene composite lubricant additive. The synthesis method of this invention is simple, the raw materials are widely available, the cost is low, and there is no pollution, making it more suitable for industrial promotion and application. The prepared material exhibits excellent stability and high wear resistance.

Description

Technical Field

[0001] This invention belongs to the field of functional materials technology, and relates to composite materials and their preparation methods, specifically to a high wear-resistant molybdenum disulfide / fluorinated graphene composite lubricant additive and its preparation method. Background Technology

[0002] Friction and wear are ubiquitous in daily life. Friction consumes about one-third of the world's primary energy, while wear causes approximately 60% of machine parts to fail. Furthermore, over 50% of mechanical equipment accidents stem from lubrication failure and excessive wear. These factors not only cause wear on surface materials but also directly affect the lifespan of parts, leading to a serious waste of resources and energy.

[0003] Two-dimensional materials have attracted considerable attention due to their thin-layer structure and large specific surface area. The weak interlayer interactions between adjacent atomic layers enable these materials to significantly improve lubricant performance when used as additives. They effectively reduce friction and wear by forming a protective layer on metal surfaces through sliding. When multiple nanomaterials are combined, the resulting synergistic effect not only achieves superlubricity but also improves the corrosion resistance and mechanical properties of contact interfaces.

[0004] Among numerous two-dimensional materials, molybdenum disulfide (MoS2) is one of the most representative transition metal sulfides. Monolayer MoS2 has three atomic planes; the central Mo atomic plane separates the two hexagonal S atoms. The layers are bonded by strong covalent or ionic bonds, while adjacent layers are held together by weak van der Waals forces. Therefore, the interlayer bonds can be easily broken by external forces, resulting in thinner few-layer molybdenum disulfide. It also readily undergoes slippage, exhibiting excellent anti-friction properties, thus giving MoS2 a low coefficient of friction. However, due to its high specific surface area, molybdenum disulfide exhibits a strong tendency to aggregate. This aggregation leads to the formation of large agglomerates, making it difficult to achieve uniform dispersion in a medium.

[0005] Fluorinated graphene (FG) also possesses excellent lubrication properties. As a constituent unit of [CFX]n, FG inherits the advantages of graphene, exhibiting wide interlayer spacing and weak interlayer forces, which can reduce frictional resistance between materials. It can act as an additive in liquid lubricants. Furthermore, the high thermal conductivity of fluorinated graphene can dissipate frictional heat generated during sliding motion. However, the coefficient of friction of fluorinated graphene alone is not low enough on a macroscopic scale, and its lubrication performance is largely constrained by the external environment. Therefore, combining fluorinated graphene with other lubricating materials, through the synergistic effect between different materials, addresses the problems in the friction and wear process, achieving superior tribological performance. Molybdenum disulfide and fluorinated graphene are similar two-dimensional layered nanomaterials. By combining them to form a new heterostructure, interactions occur, achieving synergistic lubrication and obtaining even better performance.

[0006] Patent application CN118048199A discloses a molybdenum disulfide / modified nitrogen-doped graphene composite lubricant and its application. Molybdenum disulfide is modified with an epoxy-containing silane coupling agent, and graphene oxide is modified with an amino-containing silane coupling agent. The modified graphene oxide is then ball-milled with ammonium bicarbonate to obtain modified nitrogen-doped graphene. Subsequently, the modified molybdenum disulfide and modified nitrogen-doped graphene are grafted together to obtain a molybdenum disulfide / modified nitrogen-doped graphene composite lubricant that can be used for solid-liquid lubrication. Although the above invention effectively improves wear resistance, the preparation process easily causes graphene oxide agglomeration, making the preparation process complex. Patent application CN109233177A discloses a molybdenum disulfide / fluorinated graphene-polytetrafluoroethylene composite material, its preparation method, and its application. The composition includes polyvinylpyrrolidone, 4-aminostyrene-grafted polytetrafluoroethylene, and molybdenum disulfide-loaded fluorinated graphene. Although the above inventions effectively improve wear resistance, they use toxic solvents in the preparation process, are not green, environmentally friendly and sustainable, and the preparation process is complicated. Summary of the Invention

[0007] The purpose of this invention is to provide a highly wear-resistant molybdenum disulfide / fluorinated graphene composite material lubricant additive and its preparation method. The preparation process of this invention is simple, pollution-free, and low-cost. The prepared composite material has stable dispersibility and excellent lubrication performance.

[0008] To achieve the above objectives, the present invention provides the following technical solution:

[0009] A highly wear-resistant molybdenum disulfide / fluorinated graphene composite lubricant additive and its preparation method, comprising the following steps:

[0010] Step 1: Weigh 250~350 mg of 1-hexadecyl-3-methylimidazole bromide and add it to 50 mL of deionized water to form an ionic liquid aqueous solution. Add 500 mg of molybdenum disulfide, and then perform ultrasonic dispersion, multiple mechanical crushing and centrifugation treatments. Take the supernatant to obtain a molybdenum disulfide dispersion.

[0011] Step 2: Weigh 350~450 mg of 1-hexadecyl-3-methylimidazole bromide and add it to 50 mL of deionized water. Add 200 mg of fluorinated graphene and disperse it by ultrasonication. Then, put it into an autoclave for hydrothermal reaction to obtain the initial fluorinated graphene suspension. After centrifugation, take the supernatant to obtain the fluorinated graphene dispersion.

[0012] Step 3: Mix molybdenum disulfide dispersion and fluorinated graphene dispersion at a mass ratio of (1~3):1, and ultrasonically treat to form a molybdenum disulfide / fluorinated graphene composite material lubricant additive.

[0013] Furthermore, the ultrasonic dispersion time in step one is 25-30 minutes.

[0014] Furthermore, the total time for the multiple mechanical crushing processes described in step one is 30 to 40 minutes, with each mechanical stripping lasting 10 minutes and an interval of 5 to 10 minutes between each mechanical stripping.

[0015] Furthermore, the centrifugation speed in step one is 2500~3000 rpm, and the centrifugation time is 20~30 min.

[0016] Furthermore, the hydrothermal reaction time in step two is 18-24 hours, and the hydrothermal reaction temperature is 150-200℃.

[0017] Furthermore, the centrifugation speed in step two is 3000~3500 rpm, and the centrifugation time is 20~30 min.

[0018] Furthermore, the ultrasonic treatment time in step three is 30-40 minutes.

[0019] The lubricating additive for the molybdenum disulfide / fluorinated graphene composite material prepared by the above method has a structure in which molybdenum disulfide nanosheets with a lateral size of 100-300 nm are loaded on fluorinated graphene nanosheets with a lateral size of 1.03 μm.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The preparation method of this invention is simple, requiring no extra impurity removal steps, and the solvents used throughout the process are green, environmentally friendly, and pollution-free. Furthermore, the components exhibit excellent dispersibility, stability, and lubrication properties, the process is easy to control, and the preparation cost is low, making it suitable for industrial production. It simply involves using an ionic liquid-assisted in-situ exfoliation method to exfoliate molybdenum disulfide (MoS2) in water. Using amphiphilic ionic liquids (ILs) as a green exfoliating agent not only helps to exfoliate bulk MoS2 into ultrathin MoS2 nanosheets, but also restricts the π-π interactions of the ultrathin MoS2 nanosheets by the ionic liquids (ILs), preventing direct contact between the MoS2 nanosheets and water and preventing aggregation of the ultrathin MoS2 nanosheets in water. The ionic liquid-assisted hydrothermal exfoliation method also exfoliates fluorinated graphene (FG) from bulk fluorinated graphite. Due to the reliable interaction between fluorinated graphene (FG) and ionic liquids (ILs), the non-covalently functionalized fluorinated graphene (FG) nanosheets exhibit good dispersibility in water and organic solvents.

[0022] The molybdenum disulfide / fluorinated graphene composite lubricant additive prepared in this invention exhibits excellent stable dispersibility, superior self-lubricating properties, and high wear resistance. The few-layer molybdenum disulfide nanosheets endow the composite with excellent self-lubricating properties; the CF bonds in the fluorinated graphene facilitate slippage between FG layers, reducing frictional resistance and improving the lubrication performance of the composite. Uniformly loading molybdenum disulfide nanosheets onto the fluorinated graphene nanosheets effectively ensures the dispersion of molybdenum disulfide on the fluorinated graphene surface, inhibiting the agglomeration tendency of the molybdenum disulfide nanosheets. Simultaneously, chemical bonds are formed between the F atoms on the fluorinated graphene surface and the S atoms of molybdenum disulfide. These chemical bonds enhance the mutual attraction between the two and promote their uniform dispersion, contributing to better frictional performance and reducing localized wear and friction. Fluorinated graphene possesses excellent thermal conductivity, which can promptly transfer heat during the friction process, reducing the generation of frictional heat. Attached Figure Description

[0023] Figure 1 The images show the XRD patterns of the molybdenum disulfide, fluorinated graphene, and composite material stripped from Example 1.

[0024] Figure 2 Raman diagrams of the molybdenum disulfide, fluorinated graphene, and composite material stripped in Example 1;

[0025] Figure 3 The Zeta potential diagrams are for the lubricating additives of the molybdenum disulfide / fluorinated graphene composite material prepared in Example 1, placed for different times.

[0026] Figure 4 The friction coefficient curves of the molybdenum disulfide / fluorinated graphene composite lubricating additives prepared in Examples 1-3 under pure water friction environment are shown.

[0027] Figure 5 The friction coefficient curves of the molybdenum disulfide / fluorinated graphene composite lubricating additives prepared in Examples 1-3 under oil friction environment are shown.

[0028] Figure 6 The graph shows the coefficient of friction of the molybdenum disulfide / fluorinated graphene composite lubricant additives prepared in Examples 1-3 under artificial seawater friction environment. Detailed Implementation

[0029] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0030] Example 1: The preparation method of a high wear-resistant molybdenum disulfide / fluorinated graphene composite lubricant is as follows:

[0031] Step 1: Weigh 250 mg of 1-hexadecyl-3-methylimidazole bromide and add it to 50 mL of deionized water to form an ionic liquid aqueous solution. Add 500 mg of molybdenum disulfide, then perform ultrasonic dispersion for 30 min, followed by multiple mechanical crushing treatments for a total time of 30 min. Each mechanical exfoliation lasts for 10 min, with an interval of 5 min between each mechanical exfoliation. Finally, centrifuge at 3000 rpm for 20 min to remove the unexfoliated molybdenum disulfide nanosheets. Take the supernatant through a pipette to obtain the molybdenum disulfide dispersion.

[0032] Step 2: Weigh 350 mg of 1-hexadecyl-3-methylimidazole bromide and add it to 50 mL of deionized water. Add 200 mg of fluorinated graphite and ultrasonically disperse for 30 min. Then, place it in an autoclave and carry out hydrothermal reaction at 150 °C for 24 h to obtain the initial fluorinated graphene suspension. Finally, centrifuge at 3000 rpm for 30 min to remove the unpeeled fluorinated graphite ([CFX]n) flakes. Take the supernatant through a pipette to obtain the fluorinated graphene dispersion.

[0033] Step 3: Mix molybdenum disulfide dispersion and fluorinated graphene dispersion at a mass ratio of 1:1, and sonicate for 30 minutes to form a molybdenum disulfide / fluorinated graphene composite lubricant additive.

[0034] X-ray diffraction (XRD) analysis was performed on the molybdenum disulfide, fluorinated graphene, and their composite materials exfoliated in Example 1 to observe the crystal information and elemental composition of the samples, such as... Figure 1As shown, the diffraction peaks at diffraction angles of 14.3° and 56.8° correspond to the (002) and (110) crystal planes of molybdenum disulfide. The diffraction peaks at diffraction angles of 14.1° and 41° correspond to the (001) and (100) crystal planes of fluorinated graphene. It can be seen that the characteristic diffraction peaks of both molybdenum disulfide and fluorinated graphene appear in the XRD pattern of the molybdenum disulfide / fluorinated graphene nanocomposite material, indicating that the composite is composed of these two substances.

[0035] Raman spectroscopy analysis was performed on the molybdenum disulfide, fluorinated graphene, and their composite materials exfoliated in Example 1, such as... Figure 2 As shown, the Raman spectrum of the composite material can be observed at 373 cm⁻¹. -1 and 406cm -1 The characteristic peaks that appear correspond to the A1g and E2g characteristic peaks of molybdenum disulfide. At 1355 cm⁻¹ -1 and 1590cm -1 The characteristic peaks correspond to the D and G peaks of F-fluorinated graphene. It can be seen that the characteristic peaks of both molybdenum disulfide and fluorinated graphene appear in the Raman spectrum of the molybdenum disulfide / fluorinated graphene nanocomposite, indicating that the composite consists of these two substances.

[0036] The changes in the Zeta potential of the composite material prepared in Example 1 were observed after being placed for different periods of time. Figure 3 As shown, the absolute value of the Zeta potential of the static dispersion exceeds 25 mV, indicating that the composite material has good dispersion stability.

[0037] Example 2: The preparation method of a high wear-resistant molybdenum disulfide / fluorinated graphene composite lubricant is as follows:

[0038] Step 1: Weigh 300 mg of 1-hexadecyl-3-methylimidazole bromide and add it to 50 mL of deionized water to form an ionic liquid aqueous solution. Add 500 mg of molybdenum disulfide, then perform ultrasonic dispersion for 25 min, followed by multiple mechanical crushing treatments for a total time of 40 min. Each mechanical exfoliation lasts for 10 min, with an 8 min interval between each mechanical exfoliation. Finally, centrifuge at 2500 rpm for 30 min to remove the unexfoliated molybdenum disulfide nanosheets. Take the supernatant through a pipette to obtain the molybdenum disulfide dispersion.

[0039] Step 2: Weigh 400 mg of 1-hexadecyl-3-methylimidazole bromide and add it to 50 mL of deionized water. Add 200 mg of fluorinated graphite and ultrasonically disperse for 30 min. Then, place it in an autoclave and carry out hydrothermal reaction at 200 °C for 18 h to obtain the initial fluorinated graphene suspension. Finally, centrifuge at 3500 rpm for 20 min to remove the unpeeled fluorinated graphite ([CFX]n) sheets. Take the supernatant through a pipette to obtain the fluorinated graphene dispersion.

[0040] Step 3: Mix molybdenum disulfide dispersion and fluorinated graphene dispersion at a mass ratio of 2:1, and sonicate for 40 minutes to form a molybdenum disulfide / fluorinated graphene composite lubricant additive.

[0041] Example 3: A method for preparing a highly wear-resistant molybdenum disulfide / fluorinated graphene composite lubricant additive is as follows:

[0042] Step 1: Weigh 350 mg of 1-hexadecyl-3-methylimidazole bromide and add it to 50 mL of deionized water to form an ionic liquid aqueous solution. Add 500 mg of molybdenum disulfide, then perform ultrasonic dispersion for 28 min, followed by multiple mechanical crushing treatments for a total time of 35 min. Each mechanical exfoliation lasts for 10 min, with a 10 min interval between each mechanical exfoliation. Finally, centrifuge at 2600 rpm for 28 min to remove the unexfoliated molybdenum disulfide nanosheets. Take the supernatant through a pipette to obtain the molybdenum disulfide dispersion.

[0043] Step 2: Weigh 450 mg of 1-hexadecyl-3-methylimidazole bromide and add it to 50 mL of deionized water. Add 200 mg of fluorinated graphene and ultrasonically disperse for 30 min. Then, place it in an autoclave and carry out hydrothermal reaction at 160 °C for 20 h to obtain the initial fluorinated graphene suspension. Finally, centrifuge at 3200 rpm for 26 min to remove the unpeeled fluorinated graphene ([CFX]n) flakes. Take the supernatant through a pipette to obtain the fluorinated graphene dispersion.

[0044] Step 3: Mix molybdenum disulfide dispersion and fluorinated graphene dispersion at a mass ratio of 3:1, and sonicate for 35 minutes to form a molybdenum disulfide / fluorinated graphene composite lubricant additive.

[0045] After freeze-drying the composite materials prepared in Examples 1-3, the change in the friction coefficient of the molybdenum disulfide / fluorinated graphene composite lubricant over time was observed in frictional environments of pure water, oil, and artificial seawater.

[0046] like Figure 4As shown, in a pure water environment, the average coefficients of friction of the molybdenum disulfide / fluorinated graphene composite lubricating additives prepared in Examples 1-3 were 0.098, 0.096, and 0.099, respectively. Figure 5 As shown, under PAO 4 base oil conditions, the average friction coefficients of the molybdenum disulfide / fluorinated graphene composite lubricating additives prepared in Examples 1-3 were 0.0364, 0.0127, and 0.0296, respectively. Figure 6 As shown, in a seawater environment, the average friction coefficients of the molybdenum disulfide / fluorinated graphene composite lubricating additives prepared in Examples 1-3 were 0.1398, 0.0953, and 0.1108, respectively. The friction coefficients of the prepared molybdenum disulfide / fluorinated graphene composite lubricating additives showed a trend of first decreasing and then increasing with the increase of the amount of molybdenum disulfide dispersion added.

[0047] Due to the synergistic effect between molybdenum disulfide and fluorinated graphene, a tribochemical reaction occurs, forming a protective film that reduces friction and wear. The weak van der Waals forces and easy shearing between the friction films improve the lubrication performance of the friction pair. When the ratio of molybdenum disulfide dispersion to fluorinated graphene dispersion is 3:1, excess molybdenum disulfide nanosheets agglomerate on the friction surface, leading to an increased coefficient of friction. However, compared with the absence of the molybdenum disulfide / fluorinated graphene composite lubricant, the coefficient of friction is reduced by 76%, 80%, and 63% in pure water, oil, and artificial seawater environments, respectively. This indicates that the composite material has excellent lubrication properties and can effectively reduce friction and wear.

[0048] Example 4: The preparation method of a high wear-resistant molybdenum disulfide / fluorinated graphene composite lubricant is as follows:

[0049] Step 1: Weigh 300 mg of 1-hexadecyl-3-methylimidazole bromide and add it to 50 mL of deionized water to form an ionic liquid aqueous solution. Add 500 mg of molybdenum disulfide, then perform ultrasonic dispersion for 26 min, followed by multiple mechanical crushing treatments for a total time of 30 min. Each mechanical exfoliation lasts for 10 min, with a 10 min interval between each mechanical exfoliation. Finally, centrifuge at 2800 rpm for 25 min to remove the unexfoliated molybdenum disulfide nanosheets. Take the supernatant through a pipette to obtain the molybdenum disulfide dispersion.

[0050] Step 2: Weigh 400 mg of 1-hexadecyl-3-methylimidazole bromide and add it to 50 mL of deionized water. Add 200 mg of fluorinated graphite and ultrasonically disperse for 30 min. Then, place it in an autoclave and carry out a hydrothermal reaction at 180 °C for 22 h to obtain the initial fluorinated graphene suspension. Finally, centrifuge at 3400 rpm for 24 min to remove the unpeeled fluorinated graphite ([CFX]n) sheets. Take the supernatant through a pipette to obtain the fluorinated graphene dispersion.

[0051] Step 3: Mix molybdenum disulfide dispersion and fluorinated graphene dispersion at a mass ratio of 1.5:1, and sonicate for 32 minutes to form a molybdenum disulfide / fluorinated graphene composite lubricant additive.

[0052] Example 5: A method for preparing a highly wear-resistant molybdenum disulfide / fluorinated graphene composite lubricant additive is as follows:

[0053] Step 1: Weigh 300 mg of 1-hexadecyl-3-methylimidazole bromide and add it to 50 mL of deionized water to form an ionic liquid aqueous solution. Add 500 mg of molybdenum disulfide, then perform ultrasonic dispersion for 30 min, followed by multiple mechanical crushing treatments for a total time of 40 min. Each mechanical exfoliation lasts for 10 min, with an interval of 5 min between each mechanical exfoliation. Finally, centrifuge at 3000 rpm for 20 min to remove the unexfoliated molybdenum disulfide nanosheets. Take the supernatant through a pipette to obtain the molybdenum disulfide dispersion.

[0054] Step 2: Weigh 400 mg of 1-hexadecyl-3-methylimidazole bromide and add it to 50 mL of deionized water. Add 200 mg of fluorinated graphite and ultrasonically disperse for 30 min. Then, place it in an autoclave and carry out hydrothermal reaction at 170 °C for 24 h to obtain the initial fluorinated graphene suspension. Finally, centrifuge at 3000 rpm for 25 min to remove the unpeeled fluorinated graphite ([CFX]n) sheets. Take the supernatant through a pipette to obtain the fluorinated graphene dispersion.

[0055] Step 3: Mix molybdenum disulfide dispersion and fluorinated graphene dispersion at a mass ratio of 2.5:1, and sonicate for 38 minutes to form a molybdenum disulfide / fluorinated graphene composite lubricant additive.

Claims

1. A method for preparing a highly wear-resistant molybdenum disulfide / fluorinated graphene composite lubricant additive, characterized in that, Includes the following steps: Step 1: Weigh 250~350 mg of 1-hexadecyl-3-methylimidazole bromide and add it to 50 mL of deionized water to form an ionic liquid aqueous solution. Add 500 mg of molybdenum disulfide, and then perform ultrasonic dispersion, multiple mechanical crushing and centrifugation treatments. Take the supernatant to obtain a molybdenum disulfide dispersion. Step 2: Weigh 350-450 mg of 1-hexadecyl-3-methylimidazole bromide and add it to 50 mL of deionized water. Add 200 mg of fluorinated graphene and disperse it by ultrasonication. Then, place it in an autoclave for hydrothermal reaction. The hydrothermal reaction time is 18-24 h and the hydrothermal reaction temperature is 150-200℃ to obtain the initial fluorinated graphene suspension. After centrifugation, take the supernatant to obtain the fluorinated graphene dispersion. Step 3: Mix molybdenum disulfide dispersion and fluorinated graphene dispersion at a mass ratio of (1~3):1, and ultrasonically treat to form a molybdenum disulfide / fluorinated graphene composite material lubricant additive.

2. The method for preparing a high-wear-resistant molybdenum disulfide / fluorinated graphene composite lubricant additive according to claim 1, characterized in that, The ultrasonic dispersion time in step one is 25~30 minutes.

3. The method for preparing a high-wear-resistant molybdenum disulfide / fluorinated graphene composite lubricant additive according to claim 1, characterized in that, The total time for the multiple mechanical crushing processes described in step one is 30-40 minutes, with each mechanical stripping lasting 10 minutes and an interval of 5-10 minutes between each mechanical stripping.

4. The method for preparing a high-wear-resistant molybdenum disulfide / fluorinated graphene composite lubricant additive according to claim 1, characterized in that, The centrifugation process in step one is carried out at a speed of 2500~3000 rpm for 20~30 min.

5. The method for preparing a high-wear-resistant molybdenum disulfide / fluorinated graphene composite lubricant additive according to claim 1, characterized in that, The centrifugation process in step two is carried out at a speed of 3000~3500 rpm for 20~30 min.

6. The method for preparing a high-wear-resistant molybdenum disulfide / fluorinated graphene composite lubricant additive according to claim 1, characterized in that, The ultrasonic treatment in step three takes 30-40 minutes.

7. The high wear-resistant molybdenum disulfide / fluorinated graphene composite lubricant additive prepared by the preparation method according to any one of claims 1-6, characterized in that, The structure of the molybdenum disulfide / fluorinated graphene composite lubricant additive is that molybdenum disulfide nanosheets with a lateral size of 100-300 nm are loaded on fluorinated graphene nanosheets with a lateral size of 1.03 μm.

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