A multiphase composite friction system with a cross-wetting state and a construction method thereof

Abstract

The present invention relates to the technical field of mechanical friction, and provides a multiphase composite friction system with a cross-wetting state and a construction method thereof. The present invention constructs an asymmetric special wetting interface by using a friction substrate with a superhydrophobic surface, a friction counterpart with a superhydrophilic surface of a hydrogel soft material, and a liquid lubricating medium. There is superhydrophobic wettability between the superhydrophobic surface and the liquid lubricating medium, and superhydrophilic wettability between the superhydrophilic surface of the hydrogel and the liquid lubricating medium. In the Cassie state, an air cushion will be formed between the superhydrophobic surface and the liquid lubricating medium, which can achieve ultra-low friction. In the Wenzel state, the hydrogel soft material loaded on the friction counterpart can fill into the rough structure of the friction substrate, thereby continuing to maintain a low friction state. Based on this, it is possible to construct an ultra-low friction-low friction system under different wetting states.

Description

Technical Field

[0001] The present invention relates to the technical field of mechanical friction, and particularly to a multiphase composite friction system with a cross-wetting state and a construction method thereof. Background Art

[0002] In moving parts, the friction phenomenon is ubiquitous. Beneficial friction needs to be increased, while harmful friction needs to be reduced. The mechanical friction and biomedical lubrication failure phenomena widely existing in the fields of mechanical engineering and biomedicine have caused many harms to human daily life and industrial activities. Research shows that about one-third of the energy in the industrial field needs to be consumed to overcome the frictional resistance in relative motion, which not only causes a large amount of energy loss, but also limits the optimization of energy utilization efficiency. In addition, the frictional interaction continuously causes wear on the moving components, thereby significantly shortening the service life of equipment, tissues, etc., increasing additional capital costs and causing waste of resources. Therefore, from the perspective of economic and environmental sustainable development, reducing the frictional interaction at the relative motion interface and reducing the occurrence of wear phenomena have important research value.

[0003] Special wettability interfaces have adjustable interface wetting and spreading processes and boundary slip phenomena, which can reduce the liquid contact hysteresis force and the viscous resistance of the lubricating medium, thereby effectively reducing the friction coefficient. For example: Patent CN112575320A discloses a method for obtaining a superoleophobic and wear-resistant coating by dip-coating a rough metal surface with a fluorosilane solution; Patent CN113861828A discloses a method for preparing a KM-SiO2@PDA@MoS2 wear-resistant superhydrophobic coating using slag.

[0004] The above special wettability interfaces are mainly based on the solid-solid friction system of superhydrophobic interfaces, and their dynamic stability is poor. How to further achieve an ultra-low friction coefficient and how to continue to maintain a low friction coefficient when the superhydrophobic interface loses its superhydrophobic performance are still major challenges. Summary of the Invention

[0005] The purpose of the present invention is to provide a multiphase composite friction system with a cross-wetting state and a construction method thereof. The multiphase composite friction system provided by the present invention can achieve ultra-low friction in different wetting states, has excellent friction reduction and wear resistance effects, and good dynamic stability.

[0006] To achieve the above invention purpose, the present invention provides the following technical solutions:

[0007] A multiphase composite friction system with a cross-wetting state, comprising a friction substrate, a friction counterpart, and a liquid lubricating medium located in the interface gap between the friction substrate and the friction counterpart;

[0008] The friction substrate has a superhydrophobic surface, and the contact angle of the superhydrophobic surface with respect to the liquid lubricant medium is ≥150°;

[0009] The friction pair has a hydrogel superhydrophilic surface, and the contact angle of the hydrogel superhydrophilic surface with respect to the liquid lubricant medium is ≤20°.

[0010] Preferably, the liquid lubricant medium is a polar liquid.

[0011] Preferably, the polar liquid is water or an ionic liquid.

[0012] Preferably, the method for preparing the superhydrophobic surface of the friction substrate includes the following steps:

[0013] Construct a rough structure on the surface of the friction substrate; the rough structure includes a micro-nano composite structure, a micro-scale structure, or a nano-scale structure;

[0014] Deposit an alkyl chain compound on the surface of the rough structure to obtain a superhydrophobic surface.

[0015] Preferably, the method for constructing the micro-nano composite structure is an electrochemical method, including the following steps: Use a constant voltage electrochemical etching method to construct a stepped micro-scale structure on the surface of the friction substrate, and then use a constant current electrochemical etching method to prepare nano-scale pores on the stepped micro-scale structure to obtain a micro-nano composite structure;

[0016] The method for constructing the nano-scale structure is a chemical polishing - electrochemical etching method, including the following steps: Chemically polish the surface of the friction substrate with a perchloric acid ethanol solution, and then use a constant current electrochemical etching method to construct nano-scale pores on the surface of the friction substrate to obtain a nano-scale structure;

[0017] The method for preparing the micro-scale structure is a chemical etching method or a laser processing method. The etching solution used in the chemical etching method is a Piranha solution; the laser used in the laser processing method is an ultrashort pulse laser; the micro-scale structure constructed by the laser processing method includes a ring structure, a crisscross structure, or a dot matrix distribution structure.

[0018] Preferably, the alkyl chain compound includes one or more of alkyltrichlorosilane, perfluoroalkyltrichlorosilane, and perfluoroalkyltriethoxysilane.

[0019] Preferably, the preparation method of the superhydrophobic surface of the friction substrate includes a coating method, and the coating method includes the following steps: coating a super-dry coating or an aqueous coating on the surface of the friction substrate; the components of the aqueous coating include cellulose, TiO2 nanoparticles, a surfactant, triethoxydecylsilane, KH-570, heptadecafluorodecyltriethoxysilane, and water; the mass ratio of cellulose to TiO2 nanoparticles is 1:1 to 1:5; the mass ratio of cellulose to water is 1 to 5:15 to 25; the volume of the surfactant is 0.02% to 0.05% of the volume of water; the volume ratio of triethoxydecylsilane to KH-570 is 2:1 to 5:1; the ratio of the total volume of triethoxydecylsilane and KH-570 to the volume of water is preferably 2 to 4:20 to 30; the volume ratio of water to heptadecafluorodecyltriethoxysilane is 20 to 30:0.325 to 0.625.

[0020] Preferably, the preparation method of the superhydrophilic surface of the hydrogel of the friction pair includes the following steps:

[0021] Construct a rough structure on the surface of the friction pair, and the rough structure includes a micro-nano composite structure or a micron-scale structure;

[0022] Clean, oxygen plasma treat, and silane coupling agent modify the surface of the friction pair with the rough structure in sequence, then coat the hydrogel prepolymer solution, and then carry out polymerization to obtain a superhydrophilic surface; the components of the hydrogel prepolymer solution include acrylic acid, acrylamide, α-ketoglutaric acid, N,N-methylenebisacrylamide, and deionized water.

[0023] Preferably, the preparation method of the micro-nano composite structure includes an electrochemical method, and the electrochemical method includes the following steps: use a constant voltage electrochemical etching method to construct a stepped micron-scale structure on the surface of the friction substrate, and then use a constant current electrochemical etching method to prepare nano-scale pores on the stepped micron-scale structure to obtain a micro-nano composite structure;

[0024] The preparation method of the micron-scale structure is a laser processing method; the laser used in the laser processing method is an ultrashort pulse laser; the micron-scale structure includes an annular structure, a crisscross structure, or a dot matrix distribution structure.

[0025] The present invention also provides a construction method of the multiphase composite friction system with a cross-wetting state described in the above solution, including the following steps:

[0026] Arrange the superhydrophobic surface of the friction substrate and the superhydrophilic surface of the hydrogel of the friction pair relatively, and inject a liquid lubricant into the interface gap between the superhydrophobic surface and the superhydrophilic surface of the hydrogel;

[0027] Apply a contact load on the friction pair to make the friction pair and the friction substrate move relative to each other.

[0028] The present invention provides a multiphase composite friction system with a cross-wetting state, including a friction substrate, a friction counterpart, and a liquid lubricating medium located in the interfacial gap between the friction substrate and the friction counterpart; the friction substrate has a superhydrophobic surface, and the contact angle of the superhydrophobic surface with respect to the liquid lubricating medium is ≥150°; the friction counterpart has a hydrogel superhydrophilic surface, and the contact angle of the hydrogel superhydrophilic surface with respect to the liquid lubricating medium is ≤20°. The present invention uses a friction substrate with a superhydrophobic surface, a friction counterpart with a hydrogel soft matter superhydrophilic surface, and a liquid lubricating medium to form an asymmetric special wetting interface. There is superhydrophobic infiltration between the superhydrophobic surface and the liquid lubricating medium, and superhydrophilic infiltration between the hydrogel superhydrophilic surface and the liquid lubricating medium. In the presence of the composite of superhydrophobic infiltration and superhydrophilic infiltration, an air cushion will be formed between the superhydrophobic surface and the liquid lubricating medium, which can effectively reduce the solid-liquid contact fraction and replace the solid-liquid interface interaction with an ultra-low gas-liquid interface interaction, effectively reducing the friction coefficient. At the same time, when the contact stress reaches the Cassie limit of the superhydrophobic surface, after the wetting state changes from the Cassie state to the Wenzel state, under the action of shear force, the free water layer between the interfaces of the superhydrophobic surface is squeezed and repelled and extruded, and the hydrogel soft matter component loaded by the friction counterpart fills into the rough structure of the friction substrate to act as a lubricating layer, thereby continuing to maintain a low friction coefficient.

[0029] In summary, for the multiphase composite friction system provided by the present invention, when in the Cassie state, due to the existence of the air layer, ultra-low friction can be achieved, and in the Wenzel state, the hydrogel soft matter loaded by the friction counterpart can also fill into the rough structure of the friction substrate, thereby continuing to maintain a low friction state. Based on this, the construction of an ultra-low friction-low friction system under different wetting states can be realized.

[0030] The results of the examples show that the multiphase composite friction system provided by the present invention has excellent friction reduction and wear resistance effects and good dynamic stability. Under the Cassie and Wenzel states of the superhydrophobic substrate, its friction coefficient is as low as 0.002 - 0.1, and the friction coefficient can be maintained for 9200 s. Description of the Drawings

[0031] Figure 1 It is a schematic diagram of the multiphase composite friction system with a cross-wetting state of the present invention under the Cassie state and the Wenzel state;

[0032] Figure 2 It is a curve showing the relationship between the friction coefficient and time of the multiphase composite friction system constructed in Example 1;

[0033] Figure 3 It is a curve showing the relationship between the friction coefficient and time of the multiphase composite friction system constructed in Example 3;

[0034] Figure 4 The curve of the coefficient of friction of the multiphase composite friction system constructed for Example 5 varying with time;

[0035] Figure 5 The curve of the coefficient of friction of the multiphase composite friction system constructed for Example 9 varying with time. Detailed implementation manners

[0036] The present invention provides a multiphase composite friction system with a cross-wetting state, including a friction substrate, a friction counterbody, and a liquid lubricating medium located in the interface gap between the friction substrate and the friction counterbody;

[0037] The friction substrate has a superhydrophobic surface, and the contact angle of the superhydrophobic surface with respect to the liquid lubricating medium is ≥150°;

[0038] The friction counterbody has a hydrogel superhydrophilic surface, and the contact angle of the hydrogel superhydrophilic surface with respect to the liquid lubricating medium is ≤20°.

[0039] The multiphase composite friction system provided by the present invention includes a friction substrate. In the present invention, the friction substrate has a superhydrophobic surface, and the contact angle of the superhydrophobic surface with respect to the liquid lubricating medium is ≥150°, preferably ≥155°; the material of the friction substrate is preferably metal or non-metal, the metal is preferably stainless steel, titanium, aluminum, aluminum-titanium alloy or copper, the titanium is preferably high-purity titanium (purity ≥99.99%), the aluminum is preferably high-purity aluminum (purity ≥99.99%); the non-metal is preferably glass or silicon wafer; the area of the friction substrate is larger than the area of the reciprocating motion stroke region of the friction counterbody, the superhydrophobic surface of the friction substrate and the hydrogel superhydrophilic surface of the friction counterbody are oppositely arranged, and the interface gap is between the superhydrophobic surface and the hydrogel superhydrophilic surface.

[0040] In the present invention, the preparation method of the superhydrophobic surface of the friction substrate preferably includes two methods, denoted as Method 1 and Method 2, which are introduced below respectively.

[0041] In the present invention, Method 1 preferably includes the following steps:

[0042] Construct a rough structure on the surface of the friction substrate; the rough structure includes a micro-nano composite structure, a micron-scale structure or a nano-scale structure;

[0043] Deposit an alkyl chain compound on the surface of the rough structure to obtain a superhydrophobic surface.

[0044] In the present invention, the construction method of the micro-nano composite structure is preferably an electrochemical method, which includes the following steps: using a constant voltage electrochemical etching method to construct a stepped micro-scale structure on the surface of the friction substrate, and then using a constant current electrochemical etching method to prepare nano-scale pores on the stepped micro-scale structure to obtain a micro-nano composite structure. In the present invention, the etching solutions used in the constant voltage electrochemical etching method and the constant current electrochemical etching method are both preferably an aqueous sodium chloride solution, and the concentration of the aqueous sodium chloride solution is preferably 8-12 g / L, more preferably 10 g / L; the voltage of the constant voltage electrochemical etching method is preferably 3-5 V, more preferably 4 V; the treatment time of the constant voltage electrochemical etching method is preferably 3.5-6 hours, more preferably 4.0 h, and the current density of the constant current electrochemical etching method is preferably 0.3-0.35 A / cm 2 , more preferably 0.325 A / cm 2 , and the treatment time of the constant current electrochemical etching method is preferably 4-10 min, more preferably 6 min; when using the constant voltage electrochemical etching method and the constant current electrochemical etching method for treatment, the friction substrate is used as the anode and a graphite electrode is used as the cathode. In a specific embodiment of the present invention, it is preferred to use a metal substrate as the anode, immerse it in an aqueous sodium chloride solution, first perform a constant voltage electrochemical etching treatment to construct a stepped structure on the surface of the friction substrate, and then change to a constant current electrochemical etching treatment to construct nano-scale pores on the basis of the stepped structure; the nano-scale pores are parallel to each other, and the pores are perpendicular to the surface of the friction substrate. In the present invention, the roughness of the micro-nano composite structure is about 10 μm; the method of electrochemically constructing the micro-nano composite structure is applicable to friction substrates made of metal materials.

[0045] In the present invention, the construction method of the nano-scale structure is preferably a chemical polishing-constant current electrochemical etching method, which includes the following steps: polishing the surface of the friction substrate with a perchloric acid ethanol solution, and then using a constant current electrochemical etching method to construct nano-scale pores on the surface of the friction substrate to obtain a nano-scale structure. In the present invention, the volume fraction of perchloric acid in the perchloric acid ethanol solution is preferably 20%. The present invention preferably places the friction substrate in the perchloric acid ethanol solution for polishing, and the polishing time is preferably 5-20 min, more preferably 10 min; through chemical polishing in the present invention, a smooth surface with a nano-scale roughness is formed on the surface of the friction substrate, and the roughness is below 10 nm; after chemical polishing is completed, the friction substrate after chemical polishing is then subjected to a constant current electrochemical etching treatment to construct nano-scale pores; the specific conditions of the constant current electrochemical etching treatment are the same as those in the above scheme and will not be elaborated here. In the present invention, the method of constructing a nano-scale structure by chemical polishing-constant current electrochemical etching is applicable to friction substrates made of metal materials, and a nano-scale substrate with a roughness of about 500 nm is obtained.

[0046] In the present invention, the preparation method of the micron-scale structure is preferably chemical etching or laser processing; the etching solution used in the chemical etching method is Piranha solution, the Piranha solution is a mixture of concentrated sulfuric acid and 30 wt% hydrogen peroxide, and the volume ratio of the concentrated sulfuric acid to 30 wt% hydrogen peroxide is 7:3. In the present invention, it is preferred to place the friction substrate in the Piranha solution for chemical etching, and the chemical etching time is preferably 5-7 h, more preferably 6 h. The roughness of the obtained etched substrate is 10-100 μm, and further preferably 10-20 μm. In the present invention, the laser used in the laser processing method is preferably an ultrashort pulse laser; the micron-scale structure constructed by the laser processing method preferably includes an annular structure, a criss-cross structure or a dot matrix distribution structure; in a specific embodiment of the present invention, it is preferred to use a laser system to adjust the power of the laser to control the surface topography (annular, criss-cross or dot matrix distribution) and the depth of each topography to form a micron-scale structure; the spot diameter of the laser system is preferably 15 μm, the power of the laser is preferably 2-6 W, more preferably 5 W; the depth of each topography is independently preferably 100 nm-5 μm, more preferably 100 nm-1 μm, and further preferably 100 nm-500 nm. In the present invention, the methods of constructing micron-scale structures by chemical etching and laser processing are applicable to friction substrates made of metal or non-metal materials.

[0047] After constructing a rough structure on the surface of the friction substrate, in the present invention, an alkyl chain compound is deposited on the surface of the rough structure to obtain a superhydrophobic surface. In the present invention, the alkyl chain compound preferably includes one or more of alkyltrichlorosilane, perfluoroalkyltrichlorosilane and perfluoroalkyltriethoxysilane; the alkyltrichlorosilane is preferably octadecyltrichlorosilane, the perfluoroalkyltrichlorosilane is preferably 1H,1H,2H,2H-perfluorooctyltrichlorosilane, and the perfluoroalkyltriethoxysilane is preferably 1H,1H,2H,2H-perfluorodecyltriethoxysilane.

[0048] In the present invention, the method of depositing the alkyl chain compound is preferably liquid-phase deposition or vapor-phase deposition; the liquid-phase deposition method preferably includes the following steps: mixing the friction substrate with a rough surface, the alkyl chain compound and an organic solvent, performing liquid-phase deposition under static conditions, and then taking out the friction substrate with a superhydrophobic surface for drying. In the present invention, the organic solvent is preferably anhydrous toluene; the volume of the alkyl chain compound is preferably 10%-30% of the volume of the organic solvent, more preferably 25%. The present invention has no special requirements for the amounts of the chain alkyl compound and the organic solvent, as long as the friction substrate with a rough surface can be immersed; the static time is preferably 12-24 h, more preferably 12-15 h, and the static is preferably carried out under light-shielded conditions; the drying temperature is preferably 120 °C and the time is preferably 2 h.

[0049] In the present invention, the method of chemical vapor deposition preferably includes the following steps: placing a substrate with a rough surface and an alkyl chain compound in a sealed container and heating; the heating temperature is preferably 50-80°C, more preferably 60°C, and the heating time is preferably 3-6 hours, more preferably 4 hours; when using the chemical vapor deposition method, the dosage of the alkyl chain compound is preferably determined according to the area of the substrate, specifically preferably 1 μL / cm 2 .

[0050] During chemical vapor deposition or liquid-phase deposition, non-polar low-surface-energy alkyl chain compounds undergo monolayer self-assembly on the rough surface of the friction substrate to obtain superhydrophobic surfaces with different characteristic roughnesses.

[0051] In the present invention, the second method is the coating method, which includes the following steps: coating a super-dry coating or an aqueous coating on the surface of the friction substrate.

[0052] In the present invention, the super-dry coating is preferably the commercially available UltraEver-Dry coating; the coating thickness of the super-dry coating is preferably 10-50 μm, more preferably 30-40 μm.

[0053] In the present invention, the components of the aqueous coating preferably include cellulose, TiO2 nanoparticles, a surfactant, triethoxydecoyl silane (AS), KH-570, heptadecafluorodecyltriethoxysilane (FAS), and water; the mass ratio of cellulose to TiO2 nanoparticles is preferably 1:1-1:5, more preferably 1:4; the mass ratio of cellulose to water is preferably 1-5:15-25; the volume of the surfactant is preferably 0.02%-0.05% of the volume of water; the volume ratio of AS to KH-570 is preferably 2:1-5:1, more preferably 5:2; the total volume ratio of AS and KH-570 to the volume of water is preferably 2-4:20-30, more preferably 3.5:20-30; the volume ratio of water to FAS is preferably 20-30:0.325-0.625; the particle size of the TiO2 nanoparticles is preferably 25 nm, and the particle size of the cellulose is preferably 190 μm; the surfactant is preferably a fluorinated surfactant, and the fluorinated surfactant is preferably one or more of FS-3100, GS-FC327, and ZonylFS-500; in the present invention, both AS and KH-570 act as adhesives, and the present invention uses the two adhesives in combination to improve the adhesion between the coating and the substrate; FAS is a low-surface-energy substance that can improve the hydrophobicity of the coating layer.

[0054] In the present invention, the preparation method of the aqueous coating preferably includes the following steps: dissolving a surfactant in water to obtain an aqueous surfactant solution, dispersing cellulose and TiO2 nanoparticles in the aqueous surfactant solution to obtain a dispersion, then mixing AS and KH-570 with the dispersion, and finally adding FAS to the mixed system to obtain the aqueous coating.

[0055] In the present invention, the coating thickness of the aqueous coating is preferably 20-60 μm, more preferably 30-50 μm.

[0056] In the present invention, the methods of coating the super-dry coating and the aqueous coating are both preferably spraying. The diameter of the spray gun used for spraying is preferably 0.3-1.5 mm, more preferably 0.3 mm, and the spraying pressure is preferably 0.3-0.6 MPa, more preferably 0.4 MPa. In the specific embodiments of the present invention, it is preferably to directly spray on the surface of the non-metallic friction substrate without any treatment.

[0057] In the present invention, after spraying the aqueous coating, it preferably further includes drying the obtained coating. The drying temperature is preferably 50-120 °C, more preferably 80-100 °C.

[0058] In the specific embodiments of the present invention, when the material of the friction substrate is non-metallic, the superhydrophobic surface is preferably prepared by a coating method.

[0059] When the material of the friction substrate is non-metallic, the superhydrophobic surface is preferably prepared by a coating method.

[0060] The multiphase composite friction system provided by the present invention includes a friction pair. The friction pair has a hydrogel superhydrophilic surface, and the contact angle of the hydrogel superhydrophilic surface with respect to the liquid lubricating medium is ≤20°, preferably ≤15°. In the present invention, the material of the friction pair is preferably metal or non-metal. The metal is preferably stainless steel or aluminum, and the aluminum is preferably high-purity aluminum (purity ≥99.99%); the non-metal is preferably glass or silicon.

[0061] In the present invention, the preparation method of the hydrogel superhydrophilic surface of the friction pair includes the following steps:

[0062] Constructing a rough structure on the surface of the friction pair, and the rough structure includes a micro-nano composite structure or a micron-scale rough structure;

[0063] Successively cleaning, oxygen plasma treating and silane coupling agent modifying the surface of the friction pair with the constructed rough structure, then coating a hydrogel prepolymer solution, and then performing polymerization to obtain a superhydrophilic surface; the components of the hydrogel prepolymer solution include acrylic acid, acrylamide, α-ketoglutaric acid, N,N-methylenebisacrylamide and deionized water.

[0064] In the present invention, the preparation method of the micro-nano composite structure preferably includes an electrochemical method, and the electrochemical method preferably includes the following steps: constructing a stepped micro-scale structure on the surface of a friction substrate by using a constant voltage electrochemical etching method, and then preparing nano-scale pores on the stepped micro-scale structure by using a constant current electrochemical etching method to obtain a micro-nano composite structure; the specific operation methods of the constant voltage electrochemical etching method and the constant current electrochemical etching method are the same as those for constructing the micro-nano composite structure on the surface of the friction substrate, and will not be elaborated herein. In the present invention, the preparation method of the micro-scale structure is a laser processing method, and the laser used in the laser processing method is an ultra-short pulse laser; the micro-scale structure includes an annular structure, a criss-cross structure or a dot matrix distribution structure. In the present invention, the specific operation conditions of the laser processing method are the same as those for constructing the micro-scale structure on the surface of the friction substrate, and will not be elaborated herein.

[0065] After the rough structure is constructed, the present invention successively performs cleaning, oxygen plasma treatment and silane coupling agent modification on the friction pair surface with the rough structure. In the present invention, the cleaning is preferably ultrasonic cleaning, the cleaning agent for the ultrasonic cleaning is preferably a mixture of water and ethanol, and the volume ratio of water to ethanol in the mixture is preferably 1:1. The present invention removes impurities on the friction pair surface through ultrasonic cleaning; the vacuum degree of the oxygen plasma treatment is preferably 20-30 KPa, more preferably 25 KPa, the air flow rate is preferably 3-7 mL / min, more preferably 5 mL / min, and the treatment time is preferably 4-6 min, more preferably 5 min; the silane coupling agent used for the silane coupling agent modification is preferably KH-570, and the method of the silane coupling agent modification is preferably: coating an ethanol solution of the silane coupling agent on the surface of the rough structure of the friction pair; the concentration of the ethanol solution of the silane coupling agent is preferably 30 vol%, the coating method is preferably spraying or dip coating, and the coating amount of the ethanol solution of the silane coupling agent is preferably 50-500 mg / cm 2 , more preferably 50-200 mg / cm 2 .

[0066] After the modification with silane coupling agent, in the present invention, a hydrogel prepolymer solution is coated on the modified friction pair surface, and then polymerization is carried out to obtain a super-hydrophilic surface. In the present invention, the components of the hydrogel prepolymer solution preferably include acrylic acid (AA), acrylamide (AAM), α-ketoglutaric acid (KGA), N,N'-methylenebisacrylamide (MBA) and deionized water; among them, acrylic acid and acrylamide are hydrogel monomers, which are the main components of the hydrogel. After they polymerize to form polymer chains, they have a lubricating effect; α-ketoglutaric acid is an initiator to initiate the polymer reaction, and N,N'-methylenebisacrylamide is a cross-linking agent to control the network cross-linking structure of the polymer; deionized water is a solvent.

[0067] In the present invention, the molar ratio of acrylic acid, acrylamide, α-ketoglutaric acid, and N,N'-methylenebisacrylamide is preferably 1:(2-5):0.00125:0.00125, more preferably 1:4:0.00125:0.00125; the molar ratio of acrylic acid and deionized water is preferably 1:53; the preparation method of the hydrogel prepolymer solution is preferably: mixing acrylic acid, acrylamide, α-ketoglutaric acid, N,N'-methylenebisacrylamide and deionized water to obtain the hydrogel prepolymer solution; the polymerization is preferably carried out under negative pressure or UV irradiation conditions. The pressure of the negative pressure is preferably 20-60 KPa, more preferably 35 KPa, the power of the UV irradiation is preferably 20-60 W, more preferably 36 W, the polymerization time is preferably 10-60 min, more preferably 40 min, and the polymerization temperature is preferably room temperature; after the polymerization is completed, a hydrogel soft material layer is formed on the friction pair surface, that is, a hydrogel super-hydrophilic surface is obtained.

[0068] In the present invention, the thickness of the hydrogel soft material layer loaded on the friction pair is preferably 0.5-3 mm, more preferably 1-2 mm; the interface gap between the friction substrate and the friction pair is preferably 0.2-6 mm, more preferably 0.3-5 mm; in the specific embodiments of the present invention, when the liquid lubricating medium is water, the interface gap is preferably 0.5-4 mm, more preferably 0.5-3.5 mm; when the liquid lubricating medium is an ionic liquid, the interface gap is preferably 1-4 mm, more preferably 2.5-3 mm.

[0069] The multiphase composite friction system provided by the present invention includes a liquid lubricating medium located in the gap between the friction substrate and the friction counterface interface. In the present invention, the liquid lubricating medium is preferably a polar liquid; the polar liquid is preferably water or an ionic liquid, and the ionic liquid is preferably a hexafluorophosphate ionic liquid and / or a tetrafluoroborate ionic liquid; the hexafluorophosphate ionic liquid is preferably 1-butyl-3-methylimidazolium hexafluorophosphate and / or 1,3-dimethylimidazolium hexafluorophosphate; the tetrafluoroborate ionic liquid is preferably 1-ethyl-3-methylimidazolium tetrafluoroborate and / or 1-butyl-2,3-dimethylimidazolium tetrafluoroborate.

[0070] Figure 1 FIG. is a schematic diagram of the multiphase composite friction system provided by the present invention in the Cassie state and the Wenzel state. The following combines Figure 1 The multiphase composite friction system of the present invention will be described: The friction substrate of the present invention has dynamic mechanical stability and a superhydrophobic surface. The friction counterface has a superhydrophilic surface with a stable hydration layer formed. There is superhydrophobic wettability between the superhydrophobic surface and the liquid lubricating medium, and superhydrophilic wettability between the hydrogel superhydrophilic surface and the liquid lubricating medium. In the presence of the composite of superhydrophobic wettability and superhydrophilic wettability, an air layer will be formed between the superhydrophobic surface and the liquid lubricating medium. Due to the existence of the air layer, ultra-low friction can be achieved, and this is the Cassie state at this time; when the contact stress reaches the Cassie limit of the superhydrophobic surface, the wetting state changes from the Cassie state to the Wenzel state. Under the action of shear force, the hydrogel soft matter loaded by the friction counterface fills into the rough structure of the friction substrate, so as to continue to maintain a low friction state. Based on this, the construction of an ultra-low friction-low friction system under different wetting states can be realized.

[0071] The present invention also provides a construction method of the multiphase composite friction system with cross-wetting states described in the above solution, including the following steps:

[0072] The superhydrophobic surface of the friction substrate and the hydrogel superhydrophilic surface of the friction counterface are arranged opposite to each other, and a liquid lubricant is injected into the interface gap between the superhydrophobic surface and the hydrogel superhydrophilic surface;

[0073] A contact load is applied to the friction counterface to make the friction counterface and the friction substrate move relative to each other.

[0074] In a specific embodiment of the present invention, it is preferably that the superhydrophobic surface of the friction substrate faces upward, the friction counterface is fixed above the friction substrate, and the superhydrophilic surface faces downward, and both the friction substrate and the friction counterface are in a horizontal state, and then a liquid lubricating medium is injected into the interface gap.

[0075] In the present invention, the contact load is preferably 0.05 to 20 N, and the friction coefficient of the multiphase composite friction system is preferably 0.004 to 0.124.

[0076] Next, the technical solutions of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts shall fall within the protection scope of the present invention.

[0077] Example 1

[0078] The friction substrate material is a high-purity titanium sheet, the friction counter material is ordinary glass, and the liquid lubricating medium is water.

[0079] Preparation of the superhydrophobic surface of the friction substrate: The high-purity Ti sheet is subjected to step-by-step electrochemical anodic oxidation treatment by electrochemical means. The specific steps are as follows: Using the friction substrate as the anode and a graphite electrode as the cathode, a 10 g / L NaCl aqueous solution is used as the etching solution. First, it is etched for 3.5 h in the constant voltage mode (4 V) to construct a stepped micron-scale rough structure; then, it is electrochemically oxidized for 6 min in the constant current mode (current density is 0.325 A / cm 2 ) to prepare nano-scale parallel pores on the basis of the stepped micron-scale rough structure, and a micro-nano composite structured friction substrate is obtained. The micro-nano composite structured substrate is immersed in an anhydrous toluene solution of 1H,1H,2H,2H-perfluorooctyltrichlorosilane (concentration is 250 μL / mL), and left standing for 12 h in the dark to obtain a superhydrophobic surface. The contact angle of the superhydrophobic surface of the friction substrate with water is 165°.

[0080] Preparation of the superhydrophilic surface of the friction counter hydrogel: Use an ultrashort pulse laser to construct a micron-scale crisscross structure on the friction counter surface. The spot diameter of the laser system used is 15 μm, the laser power is 5 W, and the morphology depth of the crisscross structure is 150 nm; Ultrasonic cleaning is used to remove surface impurities, and then oxygen plasma treatment is carried out. The vacuum degree of the oxygen plasma treatment is 20 KPa, the air flow rate is 4 mL / min, and the treatment time is 4 min to obtain an oxygen-rich superhydrophilic surface; Coat a 30 vol% KH-570 ethanol solution on the oxygen-rich superhydrophilic surface for interfacial KH-570 modification;

[0081] Mix acrylic acid (AA), acrylamide (AAM), α-ketoglutaric acid (KGA), N,N-methylenebisacrylamide (MBA), and deionized water in a molar ratio of 1:4:0.00125:0.00125:53 to obtain a hydrogel prepolymer solution containing macromolecular lubricant components;

[0082] The hydrogel prepolymer solution containing the macromolecular lubricant component is coated on the surface of the friction pair modified by KH-570 by spin coating, and polymerization is carried out under negative pressure conditions to form a super-hydrophilic surface. The contact angle of the obtained friction pair super-hydrophilic surface with water is 15°.

[0083] Fix the friction substrate with a super-hydrophobic surface on the sample stage of the friction testing machine, ensuring that the effective area of the super-hydrophobic substrate is larger than the reciprocating motion stroke area of the friction pair. Fix the friction pair on the friction sensor to ensure it is in a horizontal state. Make the interface gap between the super-hydrophobic surface of the friction substrate and the super-hydrophilic surface of the hydrogel of the friction pair be 0.5 mm. Inject the liquid lubricant medium water into the interface gap, apply a contact load of 0.05 N, and a frequency of 1 Hz. At this time, the super-hydrophobic substrate is in the Cassie state, and the friction coefficient is 0.004.

[0084] Example 2

[0085] Other conditions are the same as those in Example 1, except that the material of the friction substrate is a high-purity aluminum sheet, the interface gap between the friction substrate and the friction pair is 2.5 mm, the applied contact load is 5 N, and the frequency is 1 Hz. At this time, the super-hydrophobic substrate is in the Wenzel state, and the friction coefficient is 0.051.

[0086] Example 3

[0087] The material of the friction substrate is stainless steel, the material of the friction pair is ordinary glass, and the liquid lubricant medium is water.

[0088] Preparation of the super-hydrophobic surface of the friction substrate: Treat with a Piranha solution with a volume ratio of concentrated sulfuric acid to 30 wt% hydrogen peroxide solution of 7:3 for 6 h, and then place the treated substrate and 1H,1H,2H,2H-perfluorooctyltrichlorosilane in a closed device for heating. The heating temperature is 60 °C, and the time is 4 h. The 1H,1H,2H,2H-perfluorooctyltrichlorosilane self-assembles into a monolayer on the surface of the friction substrate to obtain a super-hydrophobic surface. The contact angle of the obtained super-hydrophobic surface with water is 153°.

[0089] Preparation of the super-hydrophilic surface of the hydrogel of the friction pair: Construct a micron-scale annular structure on the surface of the friction pair with an ultra-short pulse laser. The spot diameter of the laser system used is 15 μm, the laser power is 5 W, and the morphological depth of the annular structure is 300 nm; ultrasonically clean to remove surface impurities, and perform oxygen plasma treatment. The vacuum degree of the oxygen plasma treatment is 20 kPa, the air flow rate is 4 mL / min, and the treatment time is 4 minutes to obtain an oxygen-rich super-hydrophilic surface; coat a 30 vol% KH-570 ethanol solution on the oxygen-rich super-hydrophilic surface for interfacial KH-570 modification.

[0090] Acrylic acid (AA), acrylamide (AAM), α-ketoglutaric acid (KGA), N,N'-methylenebisacrylamide (MBA), and deionized water were mixed in a molar ratio of 1:4:0.00125:0.00125:53 to obtain a hydrogel prepolymer solution containing a macromolecular lubricant component;

[0091] The above hydrogel prepolymer solution containing a macromolecular lubricant component was spin-coated on the above KH-570-modified friction counterface and polymerized under UV lamp irradiation to form a hydrogel superhydrophilic surface. The contact angle of the resulting friction counterface with respect to lubricant water was 10°.

[0092] The friction substrate with a superhydrophobic surface was fixed to the sample stage of a friction testing machine, ensuring that the effective area of the friction substrate was larger than the reciprocating motion stroke area of the friction counterface. The friction counterface was fixed to a friction sensor to ensure it was in a horizontal state. The interfacial gap between the superhydrophilic surface of the friction substrate and the hydrogel superhydrophilic surface of the friction counterface was 3.5 mm. Lubricating medium water was injected into the interfacial gap, a contact load of 1 N was applied, and the frequency was set to 1 Hz. At this time, the superhydrophobic substrate was in the Wenzel state, and the friction coefficient was 0.117.

[0093] Example 4

[0094] Other conditions were the same as in Example 3, except that the lubricating medium was 1-butyl-3-methylimidazolium hexafluorophosphate, and the contact angles of the superhydrophobic surface and the hydrogel superhydrophilic surface with respect to 1-butyl-3-methylimidazolium hexafluorophosphate were 155° and 10° respectively; the interfacial gap between the friction substrate and the friction counterface was 2.5 mm, the contact load was 10 N, and the frequency was 1 Hz. At this time, the superhydrophobic substrate was in the Wenzel state, and the friction coefficient was 0.033.

[0095] Example 5

[0096] The material of the friction substrate was a copper sheet, the material of the friction counterface was ordinary glass, and the liquid lubricating medium was 1,3-dimethylimidazolium hexafluorophosphate.

[0097] Preparation of the superhydrophobic surface of the friction substrate: A dot-matrix distributed microscale structure was constructed on the surface of the copper sheet using an ultrashort pulse laser. The spot diameter of the laser system used was 15 μm, the laser power was 5 W, and the morphological depth of the dot-matrix distributed structure was 500 nm. The treated substrate was immersed in an anhydrous toluene solution of octadecyltrichlorosilane (concentration: 400 μL / mL) and left to stand in the dark for 14 h to obtain a superhydrophobic surface. The contact angle of the superhydrophobic surface of the friction substrate with respect to 1-butyl-3-methylimidazolium hexafluorophosphate was 160°.

[0098] Preparation of a friction pair hydrogel superhydrophilic surface: A crisscross microscale structure was constructed on the surface of a silicon wafer using an ultrashort pulse laser. The spot diameter of the laser system used was 15 μm, the laser power was 5 W, and the topography depth of the crisscross structure was 100 nm. Surface impurities were removed by ultrasonic cleaning, and oxygen plasma treatment was carried out. The vacuum degree of the oxygen plasma treatment was 20 KPa, the air flow rate was 4 mL / min, and the treatment time was 7 minutes to obtain an oxygen-rich superhydrophilic surface. A 30 vol% KH-570 ethanol solution was coated on the oxygen-rich superhydrophilic surface for interfacial KH-570 modification.

[0099] Acrylic acid (AA), acrylamide (AAM), α-ketoglutaric acid (KGA), N,N-methylenebisacrylamide (MBA), and deionized water were mixed in a molar ratio of 1:4:0.00125:0.00125:53 to obtain a hydrogel prepolymer solution containing a macromolecular lubricant component.

[0100] The above hydrogel prepolymer solution containing a macromolecular lubricant component was spin-coated on the above KH-570-modified friction pair interface and polymerized under UV lamp irradiation. The contact angle of the resulting friction pair surface with 1,3-dimethylimidazolium hexafluorophosphate was 5°.

[0101] The friction substrate with a superhydrophobic surface was fixed on the sample stage of a friction testing machine, ensuring that the effective area of the friction substrate was larger than the reciprocating motion stroke area of the friction pair. The friction pair was fixed on a friction sensor to ensure it was in a horizontal state. The interfacial gap between the superhydrophobic surface of the friction substrate and the hydrogel superhydrophilic surface of the friction pair was 3 mm. 1,3-dimethylimidazolium hexafluorophosphate was injected into the interfacial gap, a contact load of 20 N was applied, and the frequency was set to 1 Hz. At this time, the superhydrophobic substrate was in the Wenzel state, and the friction coefficient was 0.028.

[0102] Example 6

[0103] The material of the friction substrate was ordinary glass, the material of the friction pair was a silicon wafer, and the liquid lubricant medium was 1,3-dimethylimidazolium hexafluorophosphate.

[0104] Preparation of the superhydrophobic surface of the friction substrate: Super-Dry UltraEver-Dry coating was sprayed on the surface of the friction substrate, with a spraying thickness of 20 - 30 μm. The nozzle diameter of the spray gun was preferably 0.3 mm, and the spraying pressure was preferably 0.4 MPa. The contact angle of the resulting superhydrophobic surface with 1,3-dimethylimidazolium hexafluorophosphate was 155°.

[0105] Preparation of a friction pair hydrogel superhydrophilic surface: Use an ultrashort pulsed laser to construct a circular microscale structure on the surface of a silicon wafer. The spot diameter of the laser system used is 15 μm, the laser power is 5 W, and the morphological depth of the circular structure is 300 nm. Ultrasonic cleaning is used to remove surface impurities, followed by oxygen plasma treatment. The vacuum degree of the oxygen plasma treatment is 20 KPa, the air flow rate is 4 mL / min, and the treatment time is 8 min to obtain a superhydrophilic surface rich in oxygen. Coat a 30 vol% KH-570 ethanol solution on the superhydrophilic surface rich in oxygen for interfacial KH-570 modification.

[0106] Mix acrylic acid (AA), acrylamide (AAM), α-ketoglutaric acid (KGA), N,N-methylenebisacrylamide (MBA), and deionized water in a molar ratio of 1:4:0.00125:0.00125:53 to obtain a hydrogel prepolymer solution containing macromolecular lubricant components.

[0107] Coat the above hydrogel prepolymer solution containing macromolecular lubricant components on the above KH-570-modified superhydrophilic friction pair interface by spin coating and polymerize it under UV lamp irradiation. The contact angle of the obtained friction pair surface with respect to 1,3-dimethylimidazolium hexafluorophosphate is 15°.

[0108] Fix the friction substrate with a superhydrophobic surface on the sample stage of the friction tester, ensuring that the effective area of the friction substrate is larger than the reciprocating motion stroke area of the friction pair. Fix the friction pair on the friction sensor to ensure it is in a horizontal state. Set the interface gap between the superhydrophobic surface of the friction substrate and the hydrogel superhydrophilic surface of the friction pair to 3 mm, inject 1,3-dimethylimidazolium hexafluorophosphate into the interface gap, apply a contact load of 5 N, and set the frequency to 3 Hz. At this time, the superhydrophobic substrate is in the Wenzel state, and the friction coefficient is 0.124.

[0109] Example 7

[0110] Other conditions are the same as in Example 6, except that the preparation method of the superhydrophobic surface of the friction substrate is spraying a water-based coating. The preparation method of the water-based coating is as follows: Disperse 4.0 g of TiO2 (25 nm) and 1.0 g of cellulose (190 μm) in 20 mL of water in a mass ratio of 4:1, and add 2.5 mL of AS, 1.0 mL of KH-570, and 350 μL of FAS to obtain a water-based coating. Spray the obtained water-based coating onto the surface of the friction substrate, with a coating thickness of 40 μm, and cure it at 100 °C for 5 h to obtain a superhydrophobic surface. The contact angle of the superhydrophobic surface with respect to 1,3-dimethylimidazolium hexafluorophosphate is 165°.

[0111] Fix the friction substrate with a superhydrophobic surface to the sample stage of the friction testing machine, ensuring that the effective area of the friction substrate is larger than the reciprocating motion stroke area of the friction pair. Fix the friction pair on the friction sensor to ensure it is in a horizontal state. Set the interface gap between the superhydrophobic surface of the friction substrate and the superhydrophilic surface of the friction pair hydrogel to 3 mm. Inject 1,3-dimethylimidazolium hexafluorophosphate into the interface gap, apply a contact load of 5 N, and set the frequency to 2 Hz. At this time, the superhydrophobic substrate is in the Wenzel state, and the friction coefficient is 0.053.

[0112] Example 8

[0113] The material of the friction substrate is silicon wafer, the material of the friction pair is stainless steel, and the liquid lubricant medium is 1-ethyl-3-methylimidazolium tetrafluoroborate.

[0114] Preparation of the superhydrophobic surface of the friction substrate: Spray the super-dry UltraEver-Dry coating on the surface of the friction substrate, with a spraying thickness of 20 - 30 μm. The nozzle diameter of the spray gun is preferably 0.3 mm, and the spraying pressure is preferably 0.4 MPa. The contact angle of the obtained superhydrophobic surface with respect to 1-ethyl-3-methylimidazolium tetrafluoroborate is 155°.

[0115] Preparation of the superhydrophilic surface of the friction pair hydrogel: Perform step-by-step electrochemical anodic oxidation treatment on stainless steel by electrochemical means. The specific steps are as follows: Use a stainless steel sheet as the anode and a graphite electrode as the cathode. Use a 10 g / L NaCl aqueous solution as the etching solution. First, etch for 3.5 h in the constant voltage mode (4 V) to construct a stepped micro-rough structure; then electrochemically oxidize for 6 min in the constant current mode (current density is 0.325 A / cm 2 ) to prepare nano-scale parallel pores on the basis of the stepped micro-rough structure, obtaining a micro-nano composite structure. Ultrasonically clean to remove surface impurities, and perform oxygen plasma treatment. The vacuum degree of the oxygen plasma treatment is 20 kPa, the air flow rate is 4 mL / min, and the treatment time is 7 minutes to obtain an oxygen-rich superhydrophilic surface; coat the oxygen-rich superhydrophilic surface with a 30 vol% KH-570 ethanol solution for interfacial KH-570 modification.

[0116] Mix acrylic acid (AA), acrylamide (AAM), α-ketoglutaric acid (KGA), N,N-methylenebisacrylamide (MBA), and deionized water in a molar ratio of 1:4:0.00125:0.00125:53 to obtain a hydrogel prepolymer solution containing macromolecular lubricant components;

[0117] The hydrogel prepolymer solution containing the macromolecular lubricant component was coated on the friction pair interface modified by KH-570 by spin coating and polymerized under negative pressure conditions to form a hydrogel super-hydrophilic surface. The contact angle of the obtained friction hydrogel super-hydrophilic surface with 1-ethyl-3-methylimidazolium tetrafluoroborate is 8°.

[0118] The friction substrate with a super-hydrophobic surface was fixed on the sample stage of the friction testing machine to ensure that the effective area of the friction substrate is larger than the reciprocating motion stroke area of the friction pair. The friction pair was fixed on the friction sensor to ensure that it is in a horizontal state. The interface gap between the super-hydrophobic surface of the friction substrate and the hydrogel super-hydrophilic surface of the friction pair was 3 mm. 1-ethyl-3-methylimidazolium tetrafluoroborate was injected into the interface gap, a contact load of 5 N was applied, and the frequency was set to 1 Hz. At this time, the super-hydrophobic substrate was in the Wenzel state, and the friction coefficient was 0.050.

[0119] Example 9

[0120] Other conditions were the same as in Example 8, except that the liquid lubricant medium was water; the contact load was 5 N, and the friction frequency was 0.5 Hz. At this time, the super-hydrophobic substrate was in the Wenzel state, and the friction coefficient was 0.038.

[0121] Example 10

[0122] The material of the friction substrate is a silicon wafer, the material of the friction pair is a high-purity aluminum sheet, and the liquid lubricant medium is water.

[0123] Preparation of the super-hydrophobic surface of the friction substrate: Spray the super-dry UltraEver-Dry coating on the surface of the friction substrate, the spraying thickness is 20 - 30 μm, the nozzle diameter of the spray gun is preferably 0.3 mm, and the spraying pressure is preferably 0.4 MPa. The contact angle of the obtained super-hydrophobic surface with water is 155°.

[0124] Preparation of the hydrogel super-hydrophilic surface of the friction pair: Treat the high-purity aluminum sheet with a Piranha solution with a volume ratio of concentrated sulfuric acid to hydrogen peroxide of 7:3 for 8 h, then ultrasonically clean to remove surface impurities, and perform oxygen plasma treatment. The vacuum degree of the oxygen plasma treatment is 20 KPa, the air flow rate is 4 mL / min, and the treatment time is 7 minutes to obtain an oxygen-rich super-hydrophilic surface; coat a 30 vol% KH-570 ethanol solution on the oxygen-rich super-hydrophilic surface for interface KH-570 modification.

[0125] Acrylic acid (AA), acrylamide (AAM), α-ketoglutaric acid (KGA), N,N'-methylenebisacrylamide (MBA), and deionized water were mixed in a molar ratio of 1:4:0.00125:0.00125:53 to obtain a hydrogel prepolymer solution containing a macromolecular lubricant component;

[0126] The hydrogel prepolymer solution containing the macromolecular lubricant component is spin-coated on the friction pair interface modified by KH-570 as described above, and polymerized under negative pressure conditions to form a hydrogel super-hydrophilic surface. The contact angle of the obtained friction hydrogel super-hydrophilic surface with respect to water is 8°.

[0127] Fix the friction substrate with a super-hydrophobic surface on the sample stage of the friction testing machine, ensuring that the effective area of the friction substrate is larger than the reciprocating motion stroke area of the friction pair. Fix the friction pair on the friction sensor to ensure it is in a horizontal state. Set the interface gap between the super-hydrophobic surface of the friction substrate and the hydrogel super-hydrophilic surface of the friction pair to 3.5 mm, inject water into the interface gap, apply a contact load of 5 N, and set the frequency to 2 Hz. At this time, the super-hydrophobic substrate is in the Wenzel state, and the friction coefficient is 0.050.

[0128] The friction coefficient test results of the multiphase composite friction systems constructed in Examples 1 to 10 are listed in Table 1. Among them, the friction coefficient was characterized using a CSM friction testing machine. The experiment was carried out at room temperature, 25% relative humidity, and the friction frequency and contact load were adjusted accordingly.

[0129] Table 1 Test results of the multiphase composite friction systems constructed in Examples 1 to 10

[0130]

[0131] Figure 2 For the multiphase composite friction system constructed in Example 1 in the Cassie state, the curve of the friction coefficient varying with time. According to Figure 2 It can be seen that under the conditions of a friction frequency of 1 Hz and a contact load of 0.05 N, at this time the friction substrate is in the Cassie state, and the multiphase composite friction system provided by the present invention has an ultra-low friction coefficient.

[0132] Figure 3 For the curve of the friction coefficient varying with time of the multiphase composite friction system constructed in Example 3. According to Figure 3 It can be seen that under the conditions of a friction frequency of 1 Hz and a contact load of 1 N, at this time the friction substrate is in the Wenzel state. Under 9200 cycles, the friction coefficient gradually increases with time, but still maintains a low friction coefficient.

[0133] Figure 4 For the curve of the friction coefficient varying with time of the multiphase composite friction system constructed in Example 5. According to Figure 4 It can be seen that under the conditions of a friction frequency of 1 Hz and a contact load of 20 N, at this time the friction substrate is in the Wenzel state, and the friction coefficient shows a gradually increasing trend with time, but still maintains a low friction coefficient.

[0134] Figure 5 The curve showing the variation of the friction coefficient of the multiphase composite friction system constructed for Example 9 with time. According to Figure 5 It can be seen that under the conditions of a friction frequency of 0.5 Hz and a contact load of 5 N, the friction substrate is in the Wenzel state at this time, and the friction coefficient shows a gradually increasing trend with the increase of time, but still remains at a low friction coefficient.

[0135] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A multiphase composite friction system with a cross-wetting state, characterized in that It includes a friction substrate, a friction counterpart, and a liquid lubricating medium located in the interfacial gap between the friction substrate and the friction counterpart; The friction substrate has a superhydrophobic surface, and the contact angle of the superhydrophobic surface with respect to the liquid lubricating medium is ≥150°; The friction counterpart has a hydrogel superhydrophilic surface, and the contact angle of the hydrogel superhydrophilic surface with respect to the liquid lubricating medium is ≤20°; The preparation method of the hydrogel superhydrophilic surface of the friction counterpart includes the following steps: Construct a rough structure on the surface of the friction counterpart, and the rough structure includes a micro-nano composite structure or a micron-scale structure; The surface of the friction counterpart with the constructed rough structure is sequentially cleaned, treated with oxygen plasma, and modified with a silane coupling agent, then a hydrogel prepolymer solution is coated, and then polymerization is carried out to obtain a hydrogel superhydrophilic surface; the components of the hydrogel prepolymer solution include acrylic acid, acrylamide, α-ketoglutaric acid, N,N-methylenebisacrylamide, and deionized water.

2. The multiphase composite friction system according to claim 1, characterized in that The liquid lubricating medium is a polar liquid.

3. The multiphase composite friction system according to claim 2, characterized in that The polar liquid is water or an ionic liquid.

4. The multiphase composite friction system according to claim 1, characterized in that The preparation method of the superhydrophobic surface of the friction substrate includes the following steps: Construct a rough structure on the surface of the friction substrate; the rough structure includes a micro-nano composite structure, a micron-scale structure, or a nano-scale structure; Deposit an alkyl chain compound on the surface of the rough structure to obtain a superhydrophobic surface.

5. The multiphase composite friction system according to claim 4, characterized in that The construction method of the micro-nano composite structure is an electrochemical method, including the following steps: use a constant voltage electrochemical etching method to construct a stepped micron-scale structure on the surface of the friction substrate, and then use a constant current electrochemical etching method to prepare nano-scale pores on the stepped micron-scale structure to obtain a micro-nano composite structure; The construction method of the nano-scale structure is a chemical polishing-electrochemical etching method, including the following steps: chemically polish the surface of the friction substrate with a perchloric acid ethanol solution, and then use a constant current electrochemical etching method to construct nano-scale pores on the surface of the friction substrate to obtain a nano-scale structure; The preparation method of the micron-scale structure is a chemical etching method or a laser processing method. The etching solution used in the chemical etching method is a Piranha solution; the laser used in the laser processing method is an ultrashort pulse laser; the micron-scale structure constructed by the laser processing method includes a ring structure, a crisscross structure, or a dot matrix distribution structure.

6. The multiphase composite friction system according to claim 4, characterized in that The alkyl chain compound includes one or more of alkyltrichlorosilane, perfluoroalkyltrichlorosilane, and perfluoroalkyltriethoxysilane.

7. The multiphase composite friction system according to claim 1, characterized in that The preparation method of the superhydrophobic surface of the friction substrate includes a coating method, and the coating method includes the following steps: coat a superdry coating or an aqueous coating on the surface of the friction substrate; the components of the aqueous coating include cellulose, TiO2 nanoparticles, a surfactant, triethoxydecoyl silane, KH-570, perfluorodecyltriethoxysilane, and water; the mass ratio of cellulose to TiO2 nanoparticles is 1:1 to 1:5; The mass ratio of the cellulose to the water is 1-5:15-25; the volume of the surfactant is 0.02%-0.05% of the volume of the water; the volume ratio of the triethoxydecoyl silane to the KH-570 is 2:1-5:1; the ratio of the total volume of the triethoxydecoyl silane and the KH-570 to the volume of the water is 2-4:20-30; the volume ratio of the water to the heptadecafluorodecyltriethoxysilane is 20-30:0.325-0.

625.

8. The multiphase composite friction system according to claim 1, characterized in that The preparation method of the micro-nano composite structure includes an electrochemical method, and the electrochemical method includes the following steps: a stepped micro-scale structure is constructed on the surface of the friction substrate by using a constant voltage electrochemical etching method, and then nano-scale pores are prepared on the stepped micro-scale structure by using a constant current electrochemical etching method to obtain a micro-nano composite structure; The preparation method of the micro-scale structure is a laser processing method; the laser used in the laser processing method is an ultra-short pulse laser; the micro-scale structure includes an annular structure, a criss-cross structure or a dot matrix distribution structure.

9. A construction method of the multiphase composite friction system with a cross-wetting state according to any one of claims 1 to 8, characterized in that It includes the following steps: The superhydrophobic surface of the friction substrate and the superhydrophilic surface of the friction pair hydrogel are arranged oppositely, and a liquid lubricant is injected into the interface gap between the superhydrophobic surface and the superhydrophilic surface of the hydrogel; A contact load is applied to the friction pair to make the friction pair and the friction substrate move relatively.

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