Graphite and graphene synergistically enhanced cellulose-based self-lubricating composite film and preparation method thereof

Abstract

The invention discloses a graphite and graphene synergistically enhanced cellulose-based self-lubricating composite film and a preparation method thereof.The method comprises the steps that choline chloride and oxalic acid dihydrate are mixed and heated to form a transparent deep eutectic solvent, wood or agricultural waste powder is added into DES, after mixing, the mixture is fully stirred and dissolved at the temperature of 100 DEG C to form brownish black viscous liquid, and the transparent deep eutectic solvent is obtained; adding deionized water for dilution, filtering and washing to obtain a brownish black filter cake; dispersing the brownish black filter cake in deionized water, adding sodium chlorite and acetic acid, stirring at a high temperature, obtaining milky white mixed slurry after the reaction is finished, filtering and washing to obtain a milky white filter cake, dispersing the filter cake and crystalline flake graphite in deionized water, and sequentially performing ultrasonic dispersion and ball milling treatment to obtain a graphite slurry; the preparation method comprises the following steps: preparing a graphite-graphene / cellulose self-lubricating film, sequentially carrying out vacuum filtration and hot pressing treatment on the obtained slurry, and finally drying at room temperature to obtain the graphite-graphene / cellulose self-lubricating film which has the characteristics of high strength and toughness, excellent flexibility, wear resistance and biodegradability.

Description

Technical Field

[0001] The present invention belongs to the technical field of self-lubricating films, and particularly relates to a cellulose-based self-lubricating composite film synergistically reinforced by graphite and graphene and a preparation method thereof. Background Art

[0002] Polymer-based solid self-lubricating materials have attracted extensive attention and been widely used due to their excellent anti-friction and wear-resistant properties, impact resistance, chemical stability, etc., and are commonly used in manufacturing bearings, piston rings, sliding electrical contacts, and parts of medical devices. However, traditional polymer matrix materials still have some inherent defects, which not only have an impact on the environment but also impose an economic burden. The main problems include: (1) Some polymer matrix materials involve the petrochemical industrial chain in the production process, which leads to a large amount of pollutant emissions and dependence on non-renewable resources such as petroleum; (2) The manufacturing cost is high; (3) Traditional polymers are difficult to achieve natural degradation, resulting in higher recycling and treatment costs.

[0003] Cellulose, as one of the most abundant and easily accessible natural polymers in nature, is considered an ideal substitute for preparing high-strength composite materials due to its non-toxic, biodegradable, and low-cost characteristics. Cellulose-based composite materials are gradually becoming strong competitors to non-degradable resin-based materials. However, the insufficient mechanical strength and poor friction durability of pure cellulose matrix materials may lead to more serious wear during the friction process. Summary of the Invention

[0004] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide a cellulose-based self-lubricating composite film synergistically reinforced by graphite and graphene and a preparation method thereof, which solves the problem that the existing single cellulose matrix material does not have high mechanical strength and poor friction durability, and prepares a self-lubricating material with high strength and toughness, excellent flexibility, wear resistance, and biodegradability characteristics.

[0005] The present invention is realized through the following technical solutions:

[0006] A preparation method of a cellulose-based self-lubricating composite film synergistically reinforced by graphite and graphene, comprising the following steps:

[0007] Step 1: Mix choline chloride and oxalic acid dihydrate in a molar ratio of 1:1, heat at 110 °C to form a transparent deep eutectic solvent, add the powder of wood or agricultural waste into the transparent deep eutectic solvent, and by mass ratio, transparent deep eutectic solvent: powder = (10 - 15):1, and fully stir at 100 - 110 °C. After the powder is completely dissolved to form a brownish-black viscous liquid, add deionized water for dilution and filter and wash with water to obtain a brownish-black filter cake;

[0008] Step 2: Disperse 3.5 - 4.2 g of the brownish-black filter cake in 200 mL of deionized water, add 4 - 6 g of sodium chlorite and 2 - 4 mL of acetic acid, stir at 100 - 110 °C. After the reaction, a milky white mixed slurry is obtained. Filter and wash the milky white mixed slurry to obtain a milky white filter cake. Disperse the milky white filter cake and 0.03 - 0.16 g of flake graphite in 120 mL of deionized water, and successively perform ultrasonic dispersion and ball milling to obtain the ball-milled slurry;

[0009] Step 3: Subject the ball-milled slurry to vacuum filtration and hot pressing in sequence, and finally obtain the graphite-graphene / cellulose-based self-lubricating composite film through drying at room temperature.

[0010] Further, the powder of the wood or agricultural waste in Step 1 is specifically wood powder, bamboo powder, wood fiber powder, corn or wheat straw powder, rice husk or peanut shell powder, and various fruit residue powders.

[0011] Further, the stirring time in Step 1 is 2 - 4 h.

[0012] Further, the reaction time in Step 2 is 1 - 2 h.

[0013] Further, the ultrasonic dispersion treatment time in Step 2 is 20 - 30 min.

[0014] Further, the ball milling in Step 2 uses a planetary ball mill, with the rotation speed set at 400 rpm and the ball milling time of 12 - 24 h.

[0015] Further, the hot pressing temperature in Step 3 is 60 °C and the hot pressing time is 6 h.

[0016] A graphite and graphene synergistically reinforced cellulose-based self-lubricating composite film obtained by the above preparation method.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] The present invention combines the graphite exfoliation technology with the dispersion process of the cellulose matrix to obtain a graphite-graphene / cellulose dispersion slurry through one-step wet ball milling. During the ball milling process, the mechanical shear force generated by the friction between the ball milling beads on the graphite surface and the cellulose improves the exfoliation efficiency. Part of the flake graphite is completely exfoliated into graphene nanosheets. The hydrophilic functional groups of cellulose can stably disperse the graphene nanosheets in water, preventing the aggregation of the nanosheets. However, due to the limitations of the ball milling method for exfoliation, there is still unexfoliated graphite in the dispersion, enabling the synergistic effect between graphite and graphene. On the premise of ensuring economic and environmental friendliness, this synergistic effect successfully constructs a composite material system with both environmental friendliness and excellent comprehensive tribological properties. Its self-lubricating and low-wear properties stem from the formation of the graphene lubricating transfer film, the increased load-bearing capacity brought by graphite, and the transfer of surface load by the self-reinforcing structure of cellulose.

[0019] The thin film material prepared by the present invention has excellent flexibility, higher strength and toughness. The strong interaction between graphene, graphite and fibers plays a key role in the high strength and toughness. The hydrogen bonds between cellulose molecules as sacrificial bonds are broken, resulting in the straightening of the bent fibers after macroscopic yielding during stretching, sliding together with the graphene nanosheets and releasing the hidden length, corresponding to the large macroscopic plastic elongation in the tensile stress-strain curve. After the hidden length is exhausted, the fibers are pulled out together with the nanosheets, leading to a large failure strain and high toughness. The interface between the edges of the graphite sheets and the cellulose matrix is hydrogen-bonded, significantly enhancing the load transfer between the graphite sheets.

[0020] The raw materials used in the present invention are abundant in the earth's reserves and low in price. The preparation method is simple and easy to operate, without using any toxic solvents. The whole preparation process is green, environmentally friendly and pollution-free, and can be prepared on a large scale.

[0021] The thin film material prepared by the present invention exhibits excellent environmental friendliness and biological safety. The waste products can be degraded by microorganisms in moist soil, meeting the policy of green environmental protection, and providing an effective method for manufacturing degradable, recyclable and low-cost self-lubricating materials. Description of the Drawings

[0022] Figure 1 It is a TEM image of the graphite structure after wet ball milling exfoliation prepared in Example 4.

[0023] Figure 2 It is a Zeta potential diagram of the slurries prepared in Examples 2, 3, 4 and 5.

[0024] Figure 3 It is a physical image of the graphite-graphene / cellulose self-lubricating thin film prepared in Example 4.

[0025] Figure 4It is the stress-strain curve diagram of the graphite-graphene / cellulose self-lubricating films prepared in Examples 1, 2, 3, 4, and 5.

[0026] Figure 5 It is the SEM morphology diagram of the tensile fracture surface of the graphite-graphene / cellulose self-lubricating film prepared in Example 4.

[0027] Figure 6 It is the friction coefficient curve diagram of the graphite-graphene / cellulose self-lubricating films prepared in Examples 1, 2, 3, 4, and 5 under the conditions of 3N - 200 rpm - 30 min.

[0028] Figure 7 It is the friction coefficient curve diagram of the film samples prepared in Examples 1 and 4 under the conditions of 3N - 200 rpm - 300 min. Detailed implementation manners

[0029] The following further elaborates on the present invention in conjunction with specific embodiments, which is an explanation rather than a limitation of the present invention.

[0030] Example 1

[0031] A preparation method of a cellulose-based self-lubricating composite film synergistically reinforced by graphite and graphene includes the following steps:

[0032] Step 1: Mix 27.92 g of choline chloride with 25.2 g of oxalic acid dihydrate, heat at 110 °C until a transparent deep eutectic solvent (DES) is formed, add 4 g of poplar powder, and after mixing, heat and stir at 100 °C for 3 h to form a brownish-black viscous liquid. Add 300 mL of deionized water for dilution and filter and wash with water 5 times to obtain a brownish-black filter cake.

[0033] Step 2: Disperse the brownish-black filter cake in 200 mL of deionized water, add 5 g of sodium chlorite and 2.5 mL of acetic acid, and stir at 100 °C for 2 h to obtain a milky white mixed slurry. Filter and wash the mixed slurry 5 times to obtain a milky white solid (cellulose). Disperse the solid substance in 120 mL of deionized water and ultrasonically disperse for 30 min.

[0034] Step 3: Perform vacuum filtration on the obtained slurry, then perform hot pressing molding, and finally obtain a pure cellulose film through drying at room temperature.

[0035] Example 2

[0036] A preparation method of a cellulose-based self-lubricating composite film synergistically reinforced by graphite and graphene includes the following steps:

[0037] Step 1: Mix 27.92 g of choline chloride with 25.2 g of oxalic acid dihydrate, heat at 110 °C until a transparent deep eutectic solvent (DES) is formed, add 4 g of poplar powder, and after mixing, heat and stir at 100 °C for 3 h to form a brownish-black viscous liquid. Add 300 mL of deionized water to dilute and filter and wash with water 5 times to obtain a brownish-black filter cake;

[0038] Step 2: Disperse the brownish-black filter cake in 200 mL of deionized water, add 5 g of sodium chlorite and 2.5 mL of acetic acid, and stir at 100 °C for 2 h to obtain a milky white mixed slurry. Filter and wash the mixed slurry 5 times to obtain a milky white solid (cellulose). Co-disperse the solid material with 0.036 g of flake graphite in 120 mL of deionized water, ultrasonically disperse for 30 min, and mechanically ball mill for 12 h;

[0039] Step 3: Subject the ball-milled slurry to vacuum filtration, then perform hot pressing (6 h), and finally obtain a graphite-graphene / cellulose self-lubricating film by drying at room temperature.

[0040] Example 3

[0041] A preparation method of a graphite and graphene synergistically reinforced cellulose-based self-lubricating composite film, comprising the following steps:

[0042] Step 1: Mix 27.92 g of choline chloride with 25.2 g of oxalic acid dihydrate, heat at 110 °C until a transparent deep eutectic solvent (DES) is formed, add 4 g of poplar powder, and after mixing, heat and stir at 100 °C for 3 h to form a brownish-black viscous liquid. Add 300 mL of deionized water to dilute and filter and wash with water 5 times to obtain a brownish-black filter cake;

[0043] Step 2: Disperse the brownish-black filter cake in 200 mL of deionized water, add 5.5 g of sodium chlorite and 3 mL of acetic acid, and stir at 100 °C for 1.5 h to obtain a milky white mixed slurry. Filter and wash the mixed slurry 5 times to obtain a milky white solid (cellulose). Co-disperse the solid material with 0.074 g of flake graphite in 120 mL of deionized water, ultrasonically disperse for 30 min, and mechanically ball mill for 12 h;

[0044] Step 3: Subject the ball-milled slurry to vacuum filtration, then perform hot pressing (6 h), and finally obtain a graphite-graphene / cellulose self-lubricating film by drying at room temperature.

[0045] Example 4

[0046] A preparation method of a graphite and graphene synergistically reinforced cellulose-based self-lubricating composite film, comprising the following steps:

[0047] Step 1: Mix 27.92 g of choline chloride with 25.2 g of oxalic acid dihydrate, heat at 110 °C until a transparent deep eutectic solvent (DES) is formed, add 4 g of poplar powder, and after mixing, heat and stir at 100 °C for 4 h to form a brownish-black viscous liquid. Add 300 mL of deionized water for dilution and filter and wash with water 5 times to obtain a brownish-black filter cake;

[0048] Step 2: Disperse the brownish-black filter cake in 200 mL of deionized water, add 6 g of sodium chlorite and 3 mL of acetic acid, and stir at 100 °C for 1.5 h to obtain a milky white mixed slurry. Filter and wash the mixed slurry 5 times to obtain a milky white solid (cellulose). Co-disperse the solid material with 0.114 g of flake graphite in 120 mL of deionized water, ultrasonically disperse for 30 min, and mechanically ball mill for 12 h;

[0049] Step 3: Subject the ball-milled slurry to vacuum filtration, then carry out hot pressing (6 h), and finally obtain a graphite-graphene / cellulose self-lubricating film by drying at room temperature.

[0050] Example 5

[0051] A preparation method of a graphite and graphene synergistically reinforced cellulose-based self-lubricating composite film, comprising the following steps:

[0052] Step 1: Mix 27.92 g of choline chloride with 25.2 g of oxalic acid dihydrate, heat at 110 °C until a transparent deep eutectic solvent (DES) is formed, add 4 g of poplar powder, and after mixing, heat and stir at 100 °C for 4 h to form a brownish-black viscous liquid. Add 300 mL of deionized water for dilution and filter and wash with water 5 times to obtain a brownish-black filter cake;

[0053] Step 2: Disperse the brownish-black filter cake in 200 mL of deionized water, add 6 g of sodium chlorite and 3.5 mL of acetic acid, and stir at 100 °C for 2 h to obtain a milky white mixed slurry. Filter and wash the mixed slurry 5 times to obtain a milky white solid (cellulose). Co-disperse the solid material with 0.157 g of flake graphite in 120 mL of deionized water, ultrasonically disperse for 30 min, and mechanically ball mill for 12 h;

[0054] Step 3: Subject the ball-milled slurry to vacuum filtration, then carry out hot pressing (6 h), and finally obtain a graphite-graphene / cellulose self-lubricating film by drying at room temperature.

[0055] In the above examples, in order to ensure the uniformity of the film, the same volume of slurry is used for each vacuum filtration. Examples 1-5 correspond to mass fractions of flake graphite of 0%, 2.5%, 5%, 7.5% and 10% respectively.

[0056] Refer to Figure 1As shown, it is the TEM image of the graphite structure after wet ball milling and exfoliation prepared in Example 4. From Figure 1 (b) and Figure 1 (c), it can be observed that both few-layer graphene and multi-layer graphite structures exist in the prepared graphite-graphene / cellulose dispersion slurry. Figure 1 (a) intuitively shows the coexistence of graphite and graphene in the system. At the same time, the subsequent centrifugation treatment (8000 rpm, 10 min) was carried out on the slurry, and a small amount of deposited graphite particles were also found at the bottom. This coexistence system makes it possible for graphite and graphene to synergistically improve the comprehensive performance of the film.

[0057] Referring to Figure 2 As shown, from left to right are the Zeta potential diagrams of the slurries prepared in Examples 2, 3, 4, and 5. The graphite-graphene / cellulose slurry prepared by the preparation method of the present invention carries more negative charges. The Zeta potential of the slurry prepared in Example 4 is -69.06 mV, and it only increases by 2.36 mV after storing for 100 days, indicating that the system is the most stable at this content. The repulsive force of the negatively charged functional groups in the system contributes to the good dispersion of the slurry and can achieve good processability.

[0058] Referring to Figure 3 As shown, it is the physical diagram of the graphite-graphene / cellulose self-lubricating film prepared in Example 4, showing its bendability and rollability. Among them, Figure 3 (a) shows the size information of the graphite-graphene / cellulose self-lubricating film prepared by the present invention. From Figure 3 (b) and Figure 3 (c), it can be seen that the graphite-graphene / cellulose film has good foldability and is easy to fold into a complex small boat without showing any signs of damage. The foldability of the composite film is attributed to the combined action of cellulose and graphene. Cellulose itself is a flexible matrix, and during the folding or bending process, the hydrogen bond network of cellulose absorbs most of the deformation energy, while graphene disperses the remaining stress through sheet slip and bending, avoiding damage caused by stress concentration, and endowing the film with excellent flexibility and the ability to resist mechanical deformation.

[0059] Referring to Figure 4 As shown, it is the stress-strain curve diagram of the graphite-graphene / cellulose self-lubricating films prepared in Examples 1, 2, 3, 4, and 5. From Figure 4It can be clearly seen that the tensile strength of the film is the highest when the mass fraction of flake graphite is 5% (Example 3), followed by 7.5% (Example 4). The high tensile strength is attributed to the stable dispersion slurry that enables graphene to be uniformly filled in the fiber skeleton network. During the vacuum filtration self-assembly process, the liquid flow induces the directional stacking of substances to form a stable hierarchical structure. In this hierarchical structure, the graphene sheets are arranged orderly, which can effectively bear the externally applied stress and transfer the stress to the cellulose matrix, thus forming a stable stress transfer path, which plays a positive role in improving the mechanical properties of the composite material.

[0060] Refer to Figure 5 As shown, it is the SEM morphology diagram of the tensile fracture surface of the graphite-graphene / cellulose self-lubricating film prepared in Example 4. It can be clearly seen from the figure that the film presents a dense layered structure. It can also be observed that a small amount of cellulose, graphene nanosheets are pulled out, and unpeeled graphite particles. The strong interaction between graphene, graphite and fibers plays a key role in high strength and toughness. The hydrogen bonds between cellulose molecules as sacrificial bonds are broken, resulting in the straightening of the bent fibers after macroscopic yield during stretching. They slide together with the graphene nanosheets and release their hidden lengths, corresponding to the macroscopic large plastic elongation in the tensile stress-strain curve. After the hidden length is exhausted, the fibers are pulled out together with the nanosheets, resulting in a large failure strain and high toughness.

[0061] Refer to Figure 6 As shown, it is the friction coefficient curve diagram of the graphite-graphene / cellulose self-lubricating films prepared in Examples 1, 2, 3, 4, and 5 under the conditions of 3N - 200 rpm - 30 min. The inset is the morphology diagram of the wear scar under the optical microscope. It can be seen from the figure that under dry friction conditions, the graphite-graphene / cellulose film has a lower friction coefficient than the pure cellulose film, and at the same time, the wear on the film surface is reduced. It can be determined from the figure that the optimal mass ratio of flake graphite to cellulose is 7.5% (Example 4). This phenomenon can be attributed to the positive effect of the excellent dispersion stability of the slurry at 7.5% content on the tribological properties of the film.

[0062] Refer to Figure 7 As shown, it is the friction coefficient curve diagram of the film samples prepared in Examples 1 and 4 under the conditions of 3N - 200 rpm - 300 min. It can be seen from the figure that the dense surface structure of the graphite-graphene / cellulose film and the synergistic effect of graphite and graphene in the system make it remain stable under long-term wear, and the friction coefficient also tends to be stable, significantly lower than that of the pure cellulose film.

[0063] Example 6

[0064] A preparation method of a graphite and graphene co-reinforced cellulose-based self-lubricating composite film, comprising the following steps:

[0065] Step 1: Mix choline chloride and oxalic acid dihydrate in a molar ratio of 1:1, heat at 110 °C to form a transparent eutectic solvent, add bamboo powder into the transparent eutectic solvent, by mass ratio, transparent eutectic solvent: powder = 10:1, and stir thoroughly at 102 °C for 2 h. After the powder is completely dissolved to form a brownish-black viscous liquid, add deionized water for dilution and filter and wash with water to obtain a brownish-black filter cake;

[0066] Step 2: Disperse 3.5 g of the brownish-black filter cake in 200 mL of deionized water, add 4 g of sodium chlorite and 2 mL of acetic acid, stir at 102 °C for 1 h. After the reaction, a milky white mixed slurry is obtained. Filter and wash the milky white mixed slurry to obtain a milky white filter cake. Disperse the milky white filter cake and 0.03 g of flake graphite in 120 mL of deionized water, and perform ultrasonic dispersion and ball milling in sequence. After ultrasonic dispersion for 20 min, use a planetary ball mill, set the rotation speed to 400 rpm, and the ball milling time to 16 h to obtain the ball-milled slurry;

[0067] Step 3: Perform vacuum filtration and hot pressing on the ball-milled slurry in sequence. The hot pressing temperature is 60 °C and the hot pressing time is 6 h. Finally, obtain the graphite-graphene / cellulose-based self-lubricating composite film by drying at room temperature.

[0068] Example 7

[0069] A preparation method of a graphite and graphene co-reinforced cellulose-based self-lubricating composite film, comprising the following steps:

[0070] Step 1: Mix choline chloride and oxalic acid dihydrate in a molar ratio of 1:1, heat at 110 °C to form a transparent eutectic solvent, add peanut shell powder into the transparent eutectic solvent, by mass ratio, transparent eutectic solvent: powder = 15:1, and stir thoroughly at 110 °C for 3.5 h. After the powder is completely dissolved to form a brownish-black viscous liquid, add deionized water for dilution and filter and wash with water to obtain a brownish-black filter cake;

[0071] Step 2: Disperse 4.2 g of the brownish-black filter cake in 200 mL of deionized water, add 6 g of sodium chlorite and 4 mL of acetic acid, stir at 110 °C for 1.8 h. After the reaction, a milky white mixed slurry is obtained. Filter and wash the milky white mixed slurry to obtain a milky white filter cake. Disperse the milky white filter cake and 0.16 g of flake graphite in 120 mL of deionized water, and perform ultrasonic dispersion and ball milling in sequence. After ultrasonic dispersion for 28 min, use a planetary ball mill, set the rotation speed to 400 rpm, and the ball milling time to 24 h to obtain the ball-milled slurry;

[0072] Step 3: Subject the ball-milled slurry to vacuum filtration and hot pressing in sequence. The hot pressing temperature is 60°C and the hot pressing time is 6 h. Finally, a graphite-graphene / cellulose-based self-lubricating composite film is obtained through drying at room temperature.

[0073] Example 8

[0074] A preparation method of a graphite and graphene synergistically reinforced cellulose-based self-lubricating composite film includes the following steps:

[0075] Step 1: Mix choline chloride and oxalic acid dihydrate at a molar ratio of 1:1, heat at 110°C to form a transparent eutectic solvent. Add wood fiber powder into the transparent eutectic solvent. By mass ratio, the transparent eutectic solvent: powder = 12:1. Stir well at 105°C for 2.5 h. After the powder is completely dissolved to form a brownish-black viscous liquid, add deionized water for dilution and filter and wash with water to obtain a brownish-black filter cake.

[0076] Step 2: Disperse 3.7 g of the brownish-black filter cake in 200 mL of deionized water, add 4.5 g of sodium chlorite and 3 mL of acetic acid, stir at 105°C, react for 1.2 h. After the reaction, a milky white mixed slurry is obtained. Filter and wash the milky white mixed slurry to obtain a milky white filter cake. Disperse the milky white filter cake and 0.095 g of flake graphite in 120 mL of deionized water, and perform ultrasonic dispersion and ball milling in sequence. After ultrasonic dispersion for 22 min, use a planetary ball mill, set the rotation speed at 400 rpm, and the ball milling time at 20 h to obtain the ball-milled slurry.

[0077] Step 3: Subject the ball-milled slurry to vacuum filtration and hot pressing in sequence. The hot pressing temperature is 60°C and the hot pressing time is 6 h. Finally, a graphite-graphene / cellulose-based self-lubricating composite film is obtained through drying at room temperature.

[0078] Example 9

[0079] A preparation method of a graphite and graphene synergistically reinforced cellulose-based self-lubricating composite film includes the following steps:

[0080] Step 1: Mix choline chloride and oxalic acid dihydrate at a molar ratio of 1:1, heat at 110°C to form a transparent eutectic solvent. Add rice husk powder into the transparent eutectic solvent. By mass ratio, the transparent eutectic solvent: powder = 14:1. Stir well at 108°C for 4 h. After the powder is completely dissolved to form a brownish-black viscous liquid, add deionized water for dilution and filter and wash with water to obtain a brownish-black filter cake.

[0081] Step 2: Disperse 3.9 g of the brownish-black filter cake in 200 mL of deionized water, add 5.5 g of sodium chlorite and 3.5 mL of acetic acid, stir at 108 °C for 1.4 h. After the reaction, a milky white mixed slurry is obtained. Filter and wash the milky white mixed slurry to obtain a milky white filter cake. Disperse the milky white filter cake and 0.13 g of flake graphite in 120 mL of deionized water, and successively carry out ultrasonic dispersion and ball milling treatment. After ultrasonic dispersion for 26 min, use a planetary ball mill, set the rotation speed to 400 rpm, and the ball milling time to 22 h to obtain the ball-milled slurry;

[0082] Step 3: Carry out vacuum filtration treatment and hot pressing on the ball-milled slurry successively. The hot pressing temperature is 60 °C, and the hot pressing time is 6 h. Finally, a graphite-graphene / cellulose-based self-lubricating composite film is obtained by drying at room temperature.

Claims

1. A method for preparing a cellulose-based self-lubricating composite film synergistically reinforced by graphite and graphene, characterized in that: The following steps are involved: Step 1, choline chloride and oxalic acid dihydrate are mixed in a molar ratio of 1:1, heated at 110°C to form a transparent low eutectic solvent, wood or agricultural waste powder is added to the transparent low eutectic solvent, and the mass ratio of transparent low eutectic solvent: powder is (10-15):1, and fully stirred at 100-110°C, after the powder is completely dissolved to form a brown-black viscous liquid, deionized water is added to dilute and filtered and washed to obtain a brown-black filter cake; Step 2, dispersing 3.5-4.2g of the brown-black filter cake in 200mL of deionized water, adding 4-6g of sodium chlorite and 2-4mL of acetic acid, stirring at 100-110°C, and obtaining a milky white mixed slurry after the reaction is completed. The milky white mixed slurry is filtered and washed with water to obtain a milky white filter cake, and the milky white filter cake and 0.03-0.16g of flake graphite are co-dispersed in 120mL of deionized water, and ultrasonic dispersion and ball milling are performed in sequence to obtain a ball-milled slurry; Step 3: subjecting the ball-milled slurry to vacuum filtration treatment and hot pressing molding in sequence, and finally drying at room temperature to obtain a graphite-graphene / cellulose-based self-lubricating composite film.

2. The method for preparing a cellulose-based self-lubricating composite film synergistically reinforced by graphite and graphene according to claim 1, characterized in that: The wood or agricultural waste powder in step 1 is specifically wood powder, bamboo powder, wood fiber powder, corn or wheat straw powder, rice husk or peanut shell powder and various fruit residue powders.

3. The method for preparing a cellulose-based self-lubricating composite film synergistically reinforced by graphite and graphene according to claim 1, characterized in that: The stirring time described in step 1 is 2-4h.

4. The method for preparing a cellulose-based self-lubricating composite film synergistically reinforced by graphite and graphene according to claim 1, characterized in that: The reaction time described in step 2 is 1-2 h.

5. The method for preparing a cellulose-based self-lubricating composite film synergistically reinforced by graphite and graphene according to claim 1, characterized in that: The ultrasonic dispersion treatment time described in step 2 is 20-30 minutes.

6. The method for preparing a cellulose-based self-lubricating composite film synergistically reinforced by graphite and graphene according to claim 1, characterized in that: The ball milling treatment described in step 2 uses a planetary ball mill, the rotation speed is set to 400 rpm, and the ball milling time is 12-24 hours.

7. The method for preparing a cellulose-based self-lubricating composite film synergistically reinforced by graphite and graphene according to claim 1, characterized in that: The hot pressing temperature described in step 3 is 60° C. and the hot pressing time is 6 hours.

8. A cellulose-based self-lubricating composite film synergistically reinforced with graphite and graphene obtained by the preparation method according to any one of claims 1 to 7.

Images