Magnetic heterojunction tunable two-dimensional friction material and preparation and application thereof

Abstract

The invention discloses a magnetic heterojunction tunable two-dimensional friction material as well as preparation and application thereof. The method comprises the following steps: dissolving a polymer in deionized water, stirring until the polymer is completely dissolved, adding Fe3O4 / MXene coated BN, and stirring until the Fe3O4 / MXene coated BN is uniformly dispersed to obtain a mixed solution; slowly adding the cross-linking agent solution into the mixed solution while stirring to form a uniform polymer coating, and washing the polymer coating with deionized water; the problem that the friction coefficient cannot be reversibly regulated in real time in the prior art is solved. An MXene-coated BN heterojunction two-dimensional material is constructed, Fe3O4 magnetic nanoparticles are introduced to obtain a magnetic heterojunction two-dimensional material, the magnetic heterojunction two-dimensional material is added into a polymer coating, and the deflection angle of the Fe3O4 / MXene-coated BN heterojunction two-dimensional material in the polymer coating is changed through the interaction of an external magnetic field and the Fe3O4 magnetic nanoparticles, so that the friction performance of the material is dynamically regulated and controlled.

Description

Technical Field

[0001] The present invention relates to a Fe3O4 / MXene composite material, and in particular to a magnetic heterojunction tunable two-dimensional friction material as well as its preparation and application. Background Art

[0002] With the growing demand for high-performance friction materials in modern industry, the development of composite materials with low friction coefficients, high wear resistance, and functional tunability has become a research hotspot. Two-dimensional materials, such as MXene and boron nitride (BN), exhibit breakthrough potential in the field of friction interface control due to their unique layered structures, high surface area, high mechanical strength, and excellent physical and chemical properties.

[0003] Traditional research in the field of tribology has primarily focused on the static lubrication mechanisms of materials, primarily aiming to reduce friction and wear by reducing interfacial shear. Traditional two-dimensional friction materials have a fixed friction coefficient. Single two-dimensional materials or simple blends still face functional limitations, limited adjustability, and poor interfacial compatibility in terms of friction performance optimization, functional integration, and interfacial synergy. Dynamic adjustment to operating conditions during application is impossible, and existing technologies have yet to address the real-time, reversible control of the friction coefficient. The key scientific challenge in breaking through the traditional theoretical framework of tribology is to construct a dynamically responsive friction interface control system through the precise combination of two-dimensional materials and functional nanoparticles (e.g., atomic layer deposition and magnetic field-induced self-assembly), thereby achieving a transition from "performance optimization" to "behavioral control" of friction materials. Summary of the Invention

[0004] The purpose of the present invention is to provide a magnetic heterojunction tunable two-dimensional friction material as well as its preparation and application, which solves the problem that the existing technology cannot perform real-time and reversible regulation of the friction coefficient. By using an external magnetic field, the deflection angle of the Fe3O4 / MXene@BN heterojunction in the polymer coating is regulated, thereby affecting the tribological properties and thermal conductivity orientation.

[0005] In order to achieve the above object, the present invention provides a method for preparing a magnetic heterojunction tunable two-dimensional friction material, the method comprising: (1) Dissolve the polymer in deionized water and stir until completely dissolved, add Fe3O4 / MXene@BN, and stir until uniformly dispersed to obtain a mixed solution; The polymer is any one or more of chitosan, sodium alginate, polyacrylic acid, polyvinyl alcohol and polyethylene glycol; the Fe3O4 / MXene@BN is prepared by dispersing MXene@BN in an iron-containing solution, adding a dispersant, adjusting the pH to 11, reacting at 180°C, centrifuging and washing, vacuum drying at 60°C, and annealing at 600°C under inert gas; the iron-containing solution is Fe3+ and Fe 2+ solution, in which Fe 3+ and Fe 2+ The total concentration of Fe is 0.08mol / mL~0.12mol / mL, 3+ and Fe 2+ The amount of the substance is 2:1; the MXene@BN is obtained by mixing MXene and BNNS powder and ball milling under inert gas; the MXene is Ti3C2T x 、Ti2CT x 、Nb2CT x 、V2CT x and Mo2TiC2T x Any one or more of the following.

[0006] (2) slowly adding the crosslinker solution to the mixed solution while stirring to form a uniform polymer coating, and washing the polymer coating with deionized water; Preferably, the MXene is prepared by the following method: Add lithium fluoride to the hydrochloric acid solution and stir the reaction at 35-45°C. Add the MAX phase and stir the reaction at 35-45°C. Centrifuge several times until the pH of the upper liquid is ≥6. Continue centrifugation until the upper liquid turns black. Centrifuge again 3-5 times, remove the upper liquid, repeat the centrifugation, pre-freeze, and freeze-dry. The MAX phase is any one or more of Ti3AlC2, Ti2AlC, Nb2AlC, V2AlC and Mo2TiAlC2.

[0007] More preferably, the concentration of the hydrochloric acid solution is 9M-12M, and the mass ratio of lithium fluoride to MAX phase is 1:(1.5-2).

[0008] Preferably, the iron-containing solution is a FeCl3 / FeSO4 solution, wherein Fe 3+ and Fe 2+ The total concentration of Fe is 0.08mol / mL~0.12mol / mL, 3+ and Fe 2+ The amount of substance is 2:1, which is to avoid the formation of Fe2O3 impurity phase and ensure the formation of pure phase Fe3O4, and the pH of the solution should be adjusted to 11 during the reaction, which is to ensure that Fe3O4 can nucleate. 3+ and Fe 2+ If the total concentration of Fe is low, the nucleation rate will be slow and the generated particles will be large; if the concentration is high, the nucleation rate will be too fast and the agglomeration will be serious, forming irregular aggregates. 3+ Excess (>2:1) → non-magnetic α-Fe2O3 (hematite) is generated; if Fe2+ Excessive (<2:1) → FeO(OH) (goethite) impurities are generated. If the pH is less than 7, the acidic environment inhibits the formation of Fe3O4; if the pH is 8~10, some Fe 3+ Hydrolysis generates colloids, which hinder Fe 2+ Diffusion, the product contains impurities; if the pH is greater than 11, the particles will dissolve and become uneven in size.

[0009] Preferably, the dispersant is 1 wt% polyvinyl pyrrolidone; the cross-linking agent is any one or more of sodium tripolyphosphate, glutaraldehyde, N,N'-methylenebisacrylamide, boric acid and polyethylene glycol diacrylate.

[0010] Preferably, the BNNS powder is h -BN powder and grinding aid are mixed, ball-milled, and dried.

[0011] More preferably, the h The mass ratio of the BN powder to the grinding aid is 1: (1-10), the rotation speed of the ball mill is 300 rpm / min-500 rpm / min, the ball milling time is 24h-48h, and the ball milling is carried out using zirconia balls, wherein the h The mass ratio of -BN powder to zirconia ball is 1: (50~80).

[0012] Preferably, the mass ratio of the polymer and Fe3O4 / MXene@BN is 3:1; the volume ratio of the crosslinker solution and the mixed solution is 1:9, the concentration of Fe3O4 / MXene@BN in the mixed solution is 1 wt%, and the concentration of the crosslinker solution is 2 wt%; the mass ratio of the MXene to the BNNS powder is 1:1.

[0013] More preferably, the mass ratio of the MXene@BN, the iron-containing solution, and the dispersant is (1-5): (25-30): (10-15). When preparing the Fe3O4 / MXene@BN, after adding the dispersant, the concentration of the MXene@BN is 1 mg / mL-2 mg / mL. The concentration (amount) of MXene@BN should not be too high and should be maintained between 1 mg / mL and 2 mg / mL. Too high a concentration may result in uneven loading of Fe3O4, while too low a concentration may result in too low a sample amount being prepared and an excessive amount of Fe3O4 loaded per unit MXene@BN.

[0014] More preferably, the mass ratio of the MXene@BN, the iron-containing solution, and the dispersant is 1:27.2:11.1.

[0015] The invention provides a magnetic heterojunction tunable two-dimensional friction material prepared by the method.

[0016] The present invention provides an application of the magnetic heterojunction tunable two-dimensional friction material in the field of lubrication.

[0017] The present invention provides Fe3O4 / MXene@BN prepared by the method described above, wherein the MXene@BN heterostructure in the Fe3O4 / MXene@BN serves as a matrix, and Fe3O4 nanoparticles are loaded on the surface, wherein the mass of Fe3O4 is 5%-30% of the mass of Fe3O4 / MXene@BN.

[0018] The magnetic heterojunction tunable two-dimensional friction material of the present invention, as well as its preparation and application, solves the problem of the existing technology that the friction coefficient cannot be adjusted in real time and reversibly, and has the following advantages: 1. The present invention constructs a MXene@BN heterojunction two-dimensional material and introduces Fe3O4 magnetic nanoparticles to obtain a Fe3O4 / MXene@BN magnetic heterojunction two-dimensional material. Adding the material to a polymer coating can obtain a tunable friction material. Through the interaction between an external magnetic field and the Fe3O4 magnetic nanoparticles, the deflection angle of the Fe3O4 / MXene@BN magnetic heterojunction two-dimensional material in the polymer coating is changed by the direction of the magnetic field, thereby dynamically regulating the friction performance of the material.

[0019] 2. The present invention constructs a friction interface control system with dynamic response capability through the precise combination of two-dimensional materials and functional nanoparticles (such as magnetic field-induced self-assembly), which solves the problem of real-time and reversible control of the friction coefficient and provides a new solution for dynamic control of friction performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 These are the XRD patterns of MAX, MXene, MXene@BN and Fe3O4 / MXene@BN in Example 1 of the present invention.

[0021] Figure 2 Schematic diagram of the microstructure of the Fe3O4 / MXene@BN polymer prepared in Example 1 of the present invention.

[0022] Figure 3 Schematic diagram of the change in the deflection angle of the magnetic heterojunction two-dimensional material in the Fe3O4 / MXene@BN polymer coating prepared in Example 1 of the present invention with the direction of the magnetic field.

[0023] Figure 4 This is a graph of the friction coefficient of the Fe3O4 / MXene@BN polymer coating prepared in Example 1 of the present invention when magnetic fields of different angles are applied. DETAILED DESCRIPTION

[0024] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0025] Example 1 A Fe3O4 / Ti3C2T x A method for preparing a @BN composite material, the method comprising: (1) Ti3C2T x Preparation (MAX phase) Use deionized water and concentrated hydrochloric acid with a concentration of 12M to prepare HCl with a concentration of 9M, weigh 3.2g LiF and 2g Ti3AlC2 (abbreviated as MAX), first mix 40mL 9M HCl with 3.2g LiF, stir and react in a 40℃ water bath for 15min, then slowly add Ti3AlC2 powder, add in small amounts and multiple times, each time adding about 0.1g~0.2g, stir and react in a 40℃ water bath for 48h (etching time); after the reaction, transfer the solution to a centrifuge tube for centrifugation at a centrifugal speed of 5000rpm and a centrifugal time of 1min, repeat the centrifugation several times, centrifuge 10~15 times, pour out the supernatant after each centrifugation, add deionized water, shake until pH ≥ 6 and the supernatant turns black, shake and centrifuge 3 times, collect the upper liquid, and obtain Ti3C2T x Solution; Ti3C2T x The solution was pre-frozen for 24 h and freeze-dried in a freeze dryer for 48 h to obtain Ti3C2T x Powder (MXene for short).

[0026] (2) Preparation of BNNS Weigh 2 g of h-BN powder and 80 g of zirconia balls (the ratio of grinding balls with particle sizes of 3 mm and 5 mm is 4:1) into a ball mill, pour in 6 g of isopropanol, and ball mill at 400 rpm / min for 24 h. After ball milling, dry and collect to obtain BNNS powder.

[0027] (3) Ti3C2T x Preparation of @BN The Ti3C2T xThe powder was mixed with the BNNS powder in step 2 at a mass ratio of 1:1, placed in a ball mill, and zirconia balls were added. The ball mill was vacuumed and purged with argon for 5 times, and then ball milled at 600 rpm for 8 h to obtain Ti3C2T x @BN powder (abbreviated as MXene@BN).

[0028] (4) Fe3O4 / Ti3C2T x Preparation of @BN The Ti3C2T obtained in step 3 x @BN powder 0.1g was dispersed in 80mL of 0.1mol / mL FeCl3 / FeSO4 solution (Fe 3+ and Fe 2+ The total concentration is 0.10 mol / mL, of which Fe 3+ and Fe 2+ The concentration ratio of Fe 3+ and Fe 2+ The concentrations of the two catalysts were 0.067 mol / L and 0.033 mol / L, respectively. 20 mL of 1 wt% PVP was added as a dispersant. Ammonia was added to adjust the pH to 11. The reaction was carried out at 180 °C for 12 h to generate Fe3O4 / MXene@BN with a uniform Fe3O4 coating layer. The obtained Fe3O4 / MXene@BN was centrifuged and washed, vacuum dried at 60 °C, and annealed at 600 °C for 1 h under argon protection to obtain Fe3O4 / Ti3C2T x @BN composite material (abbreviated as Fe3O4 / MXene@BN).

[0029] A magnetic heterojunction tunable two-dimensional friction material (Fe3O4 / Ti3C2T x A method for preparing a BN-based polymer coating, the method comprising: (1) Weigh 0.05 g chitosan powder, dissolve it in 20 mL deionized water, stir for 2 h (until chitosan is completely dissolved), and then add the Fe3O4 / Ti3C2T prepared above. x @BN composite material, stirred and dispersed for 2 h (until uniformly dispersed), and obtained a Fe3O4 / Ti3C2T x @BN mixed solution.

[0030] (2) Prepare a 2 wt% sodium tripolyphosphate solution (crosslinker solution) using sodium tripolyphosphate and deionized water. Slowly add 1 mL of the 2 wt% sodium tripolyphosphate solution to the 1 wt% Fe3O4 / Ti3C2T x@BN mixed solution until a uniform gel is formed, and then washed three times with deionized water to remove unreacted sodium tripolyphosphate to obtain Fe3O4 / Ti3C2T x @BN-based polymer coatings (such as Figure 3 shown).

[0031] like Figure 1 As shown in Figure 1, the XRD patterns of MAX, MXene, MXene@BN and Fe3O4 / MXene@BN in Example 1 of the present invention. Figure 1 It can be seen that the MXene obtained after etching the MAX phase shows an obvious (002) characteristic peak, and other impurity peaks disappear, proving that the etching is successful; after compounding with BN, the (002) peak of BN appears in the sample; and after compounding with Fe3O4, an obvious characteristic peak of Fe3O4 is also obtained.

[0032] like Figure 2 As shown in FIG, the microstructure diagram of the Fe3O4 / MXene@BN polymer prepared in Example 1 of the present invention. Figure 2 It can be seen that the polymer in the hydrogel is in a filamentous structure, Fe3O4 / Ti3C2T x @BN heterojunction two-dimensional materials are interwoven to form a cross-linked network.

[0033] Example 2 A Fe3O4 / Ti3C2T x The preparation method of the @BN composite material is exactly the same as that in Example 1.

[0034] A Fe3O4 / Ti3C2T x The preparation method of the @BN-based polymer coating is basically the same as that of Example 1, except that the chitosan powder is replaced with sodium alginate powder. The specific differences are: In step (1), sodium alginate was dissolved in deionized water to prepare 20 mL of sodium alginate solution with a concentration of 5 wt%, and 0.2 g of the Fe3O4 / Ti3C2T prepared above was added. x @BN composite material, stirred and dispersed for 2 h (until uniformly dispersed), and a Fe3O4 / Ti3C2T3@BN composite material with a concentration of 1 wt% was obtained. x @BN mixed solution.

[0035] In step (2), CaCl2 was dissolved in deionized water to prepare a solution with a concentration of 2 wt% and used as a crosslinking agent; Fe3O4 / Ti3C2T xThe mixed solution of @BN was poured into a mold and immersed in a 2 wt% CaCl2 solution (the amount of CaCl2 solution is not specific, as long as it slightly covers the mold). Cross-linking was performed for 30 min to obtain a gel, which was then washed three times with deionized water to remove unreacted CaCl2. 2+ .

[0036] Compared with Example 1, Example 2 selected different hydrogel materials in order to test the binding properties of Fe3O4 / MXene@BN in different hydrogels. The results showed that Fe3O4 / Ti3C2T x @BN materials can also be used in different hydrogels.

[0037] Example 3 A Fe3O4 / Ti2CT x The preparation method of the @BN composite material is basically the same as that of Example 1, except that: In step (1), Ti3AlC2 was replaced with Ti2AlC, and the etching time was shortened to 24 h. The obtained product was Ti2CT x ; The same operation as in Example 1 was used to prepare Ti2CT x @BN powder and Fe3O4 / Ti2CT x @BN Composites.

[0038] A Fe3O4 / Ti2CT x The preparation method of the BN-based polymer coating is basically the same as that in Example 1. x @BN composite material replaced with Fe3O4 / Ti2CT x @BN composite materials, the specific differences are: (1) Weigh 0.05 g of chitosan powder, dissolve it in 20 mL of deionized water, stir for 2 h (until the chitosan is completely dissolved), and then add 0.2 g of Fe3O4 / Ti2CT prepared above. x @BN composite material, stirred and dispersed for 2 h (until uniformly dispersed), and a Fe3O4 / Ti2CT with a concentration of 1 wt% was obtained. x @BN mixed solution.

[0039] (2) Prepare a 2 wt% sodium tripolyphosphate solution using sodium tripolyphosphate and deionized water. Slowly add 1 mL of the 2 wt% sodium tripolyphosphate solution to the 1 wt% Fe3O4 / Ti2CT x @BN mixed solution until a uniform gel is formed, and then washed three times with deionized water to remove unreacted sodium tripolyphosphate to obtain Fe3O4 / Ti2CT x@BN-based polymer coating.

[0040] Compared with Example 1, Example 3 selected different MXene materials and prepared different Fe3O4 / MXene@BN materials. The results demonstrated the feasibility of composites of different MXene materials with BN.

[0041] Comparative Example 1 (Prior Art) A TiO2 / Ti3C2T x A method for preparing a Fe3O4 layered composite material, the method comprising: 200 mesh Ti3AlC2 was dispersed in HF solution (50% wt%) and stirred continuously at 60℃ for 48h. The suspension was centrifuged and rinsed with deionized water to obtain MXene suspension. FeCl3·6H2O and NaHCO3 were dissolved in deionized water with vigorous stirring. Vitamin C aqueous solution (Fe 3+ and vitamin C in a molar ratio of 1:6) to obtain a Fe-containing 3+ Mixture of MXene suspension and Fe 3+ The mixture was transferred to a Teflon-lined autoclave and hydrothermally treated at 150 °C for 5 h; finally, the product was dried in a vacuum oven at 60 °C for 24 h.

[0042] Compared with the prior art in comparative example 1, the method of etching Ti3AlC2 using HCl / LiF system in embodiment 1 of the present invention is safer, and the Ti3C2T2O3 ...4O3O4O3O3O3O3O3O3O3O4O3O3O3O3O3O3O3O4O3O3O3O3O3O3O3O4O3O3O3O3O3O3O4O3O3O3O3O3O3O4O3O4O3 x The nanosheets have a smaller size and number of layers, and have more sites when loaded with Fe3O4 nanoparticles; MXene and BN are composited to form a heterojunction structure, and after loading Fe3O4 nanoparticles, the Fe3O4 / MXene@BN heterojunction material is obtained, whose friction performance can be regulated by an external magnetic field.

[0043] Comparative Example 2 (Prior Art) A method for preparing MXene@Fe3O4 composite microspheres, the method comprising: FeCl3 and FeSO4 were dissolved in deionized water to prepare a solution, and then the mixture was transferred to a three-necked flask, stirred vigorously at 45℃, and NaOH solution was added. The temperature was raised to 80℃ and the reaction was kept at this temperature for 50 min. Finally, the product was washed to neutrality and dispersed in deionized water. The solid content was measured for later use. Ti3AlC2 was etched using HCl / LiF system to obtain Ti3C2T x Nanosheet dispersion, Ti3C2T x The nanosheet dispersion was added with KOH solution and shaken at 30 °C for five days, then washed with water until neutral and freeze-dried to obtain Ti3C2T xnanofibers; finally, Ti3C2T x Nanofibers and iron acetylacetonate were dispersed and dissolved in benzyl alcohol, mechanically stirred, and the temperature was raised to 190 °C and maintained for 3 h. The product was washed three times with anhydrous ethanol to separate and then vacuum dried to obtain MXene@Fe3O4 composite nanofibers.

[0044] Compared with Comparative Example 2, Example 1 of the present invention has streamlined steps and simple operation: Example 1 of the present invention uses a MXene nanosheet dispersion as an intermediate raw material during the preparation process, which can better retain the two-dimensional structure of the MXene@BN heterojunction, has excellent lubricity, and has better performance in the lubrication field.

[0045] Comparative Example 3 (Prior Art) A method for preparing a MXene / CNT@Fe3O4 three-dimensional conductive composite material, the method comprising: Ti3AlC2 was etched using HF to obtain Ti3C2T x Nanosheet suspension (Ti3C2T x MXene suspension); carboxylated multi-walled carbon nanotubes (MWCNTs-COOH) were dispersed in deionized water to prepare a uniform dispersion of MWCNTs-COOH, and then FeCl3·6H2O and FeCl2·4H2O were added to the solution, stirred and mixed for 1 hour, and ultrasonicated for 30 minutes. Subsequently, dilute ammonia was gradually added to adjust the pH value of the solution to 12, and the reaction was stirred at 65°C for 2 hours. After the reaction, the CNT@Fe3O4 flocculated precipitate was separated by a magnet and washed with deionized water several times until it reached neutrality, and then dried and ground; CNT@Fe3O4 powder was mixed with polypyrrolidone dispersant, ground evenly, poured into deionized water, stirred, ultrasonicated and centrifuged to obtain CNT@Fe3O4 dispersion, and Ti3C2T x The MXene suspension and CNT@Fe3O4 dispersion were thoroughly mixed and stirred for 2 h, and then ultrasonicated for 1 h to form a MXene / CNT@Fe3O4 (MCFe) solution.

[0046] Compared with Comparative Example 3 (loading Fe3O4 nanoparticles onto CNTs), Example 1 of the present invention composites BN and MXene to prepare a MXene@BN heterojunction two-dimensional material, and then loads Fe3O4 nanoparticles on the heterojunction to better achieve magnetically controlled angle regulation of friction performance. However, the carbon nanotubes in Comparative Example 3 cannot achieve angle regulation with MXene to regulate the friction coefficient.

[0047] Experimental Example 1 Friction Test The friction test was carried out using a reciprocating friction machine with the following parameters: load 0.5 N, frequency 1 Hz, motion stroke 5 mm, 304 stainless steel balls with a diameter of 6 mm for the dual balls, ambient temperature 25 ± 1 °C, air humidity 25 ± 5%, and the permanent magnet was fixed on the Fe3O4 / Ti3C2T prepared in Example 1. x @BN-based polymer coatings are surrounded by a magnetic field (such as Figure 3 As shown in the figure), and the direction of the magnetic field is adjusted during the test, the friction coefficient evolves as shown in the figure Figure 4 shown.

[0048] like Figure 3 As shown in FIG, a schematic diagram of the change in the deflection angle of the magnetic heterojunction two-dimensional material in the Fe3O4 / MXene@BN polymer coating prepared in Example 1 of the present invention with the direction of the magnetic field. Figure 3 It can be seen that an external magnetic field is applied outside the hydrogel by a permanent magnet, and the state of Fe3O4 / MXene@BN in the hydrogel is changed by changing the deflection angle of the permanent magnet, thereby affecting the friction performance of the coating.

[0049] like Figure 4 As shown in FIG, the friction coefficient of the Fe3O4 / MXene@BN polymer coating prepared in Example 1 is applied with magnetic fields of different angles. Figure 4 It can be seen that the friction coefficient of the coating shows different sizes at different deflection angles of Fe3O4 / MXene@BN, and generally shows a parabolic trend with the change of angle. The friction coefficient is the smallest when the Fe3O4 / MXene@BN two-dimensional material is parallel to the friction surface (0° and 180°), and the friction coefficient is the largest when it is perpendicular to the friction surface (90°).

[0050] Compared with the prior art in Comparative Examples 1 to 3, Examples 1 to 3 of the present invention design a Fe3O4 / MXene@BN magnetic heterojunction two-dimensional material different from that in Comparative Examples 1 to 3, such as Figure 1 The XRD data in Figure 1 characterize the Fe3O4 / Ti3C2T x @BN; and different from the actual application in Comparative Examples 1 to 3, Examples 1 to 3 of the present invention combine Fe3O4 / MXene@BN magnetic heterojunction two-dimensional materials with hydrogel materials to prepare coating materials, and apply them to the field of lubrication, thereby achieving tunable friction.

[0051] Although the present invention has been described in detail through the above preferred embodiments, it should be understood that the above description is not intended to limit the present invention. After reading the above description, various modifications and substitutions of the present invention will become apparent to those skilled in the art. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A method for preparing a magnetic heterojunction tunable two-dimensional friction material, characterized in that: The method includes: (1) Dissolve the polymer in deionized water and stir until completely dissolved, add Fe3O4 / MXene@BN, and stir until uniformly dispersed to obtain a mixed solution; (2) slowly adding the crosslinker solution to the mixed solution while stirring to form a uniform polymer coating, and washing the polymer coating with deionized water; The polymer is any one or more of chitosan, sodium alginate, polyacrylic acid, polyvinyl alcohol and polyethylene glycol; The Fe3O4 / MXene@BN is prepared by dispersing MXene@BN in an iron-containing solution, adding a dispersant, adjusting the pH to 11, reacting at 180°C, centrifuging and washing, vacuum drying at 60°C, and annealing at 600°C under inert gas. The iron-containing solution contains Fe 3+ and Fe 2+ solution, in which Fe 3+ and Fe 2+ The total concentration of Fe is 0.08mol / mL~0.12mol / mL, 3+ and Fe 2+ The amount of the substance is 2:1; after adding the dispersant, the concentration of the MXene@BN is 1 mg / mL~2 mg / mL; The MXene@BN is obtained by mixing MXene and BNNS powders and ball milling under inert gas; The MXene is Ti3C2T x 、Ti2CT x 、Nb2CT x 、V2CT x and Mo2TiC2T x Any one or more of the following.

2. The method according to claim 1, characterized in that The MXene is prepared by the following method: Add lithium fluoride to the hydrochloric acid solution and stir the reaction at 35-45°C. Add the MAX phase and stir the reaction at 35-45°C. Centrifuge several times until the pH of the upper liquid is ≥6. Continue centrifugation until the upper liquid turns black. Centrifuge again 3-5 times, remove the upper liquid, repeat the centrifugation, pre-freeze, and freeze-dry. The MAX phase is any one or more of Ti3AlC2, Ti2AlC, Nb2AlC, V2AlC and Mo2TiAlC2.

3. The method according to claim 2, characterized in that The concentration of the hydrochloric acid solution is 9M-12M, and the mass ratio of lithium fluoride to MAX phase is 1:(1.5-2).

4. The method according to claim 1, wherein The iron-containing solution is prepared from FeCl3·6H2O and FeSO4·7H2O; the dispersant is 1 wt% polyvinyl pyrrolidone; and the crosslinking agent is any one or more of sodium tripolyphosphate, glutaraldehyde, N,N'-methylenebisacrylamide, boric acid and polyethylene glycol diacrylate.

5. The method according to claim 1, characterized in that The BNNS powder is made of h -BN powder and grinding aid are mixed, ball-milled, and dried.

6. The method according to claim 5, characterized in that described h The mass ratio of the BN powder to the grinding aid is 1: (1-10), the rotation speed of the ball mill is 300 rpm / min-500 rpm / min, the ball milling time is 24h-48h, and the ball milling is carried out using zirconia balls, wherein the h The mass ratio of -BN powder to zirconia ball is 1: (50~80).

7. The method according to claim 1, characterized in that The mass ratio of the polymer and Fe3O4 / MXene@BN is 3:1; the volume ratio of the crosslinker solution to the mixed solution is 1:9, the concentration of Fe3O4 / MXene@BN in the mixed solution is 1wt%, and the concentration of the crosslinker solution is 2wt%; the mass ratio of the MXene@BN, the iron-containing solution, and the dispersant is (1-5):(25-30):(10-15); and the mass ratio of the MXene to BNNS powder is 1:

1.

8. A magnetic heterojunction tunable two-dimensional friction material prepared by the method according to any one of claims 1 to 7.

9. Application of the magnetic heterojunction tunable two-dimensional friction material according to claim 8 in the field of lubrication.

10. A Fe3O4 / MXene@BN prepared by the method according to any one of claims 1 to 7, wherein the MXene@BN heterostructure in the Fe3O4 / MXene@BN serves as a matrix and Fe3O4 nanoparticles are loaded on the surface, wherein the mass of Fe3O4 is 5% to 30% of the mass of the Fe3O4 / MXene@BN.

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