Nano-fluid lubricating liquid suitable for near-zero wear of engineering steel surface as well as preparation method and application of nano-fluid lubricating liquid

Abstract

The invention relates to the technical field of friction lubrication, in particular to nano-fluid lubricating liquid suitable for near-zero wear of the surface of engineering steel as well as a preparation method and application of the nano-fluid lubricating liquid. The nanofluid lubricating liquid provided by the invention is of a core-shell structure, the core of the nanofluid lubricating liquid is an inorganic nanomaterial, and the shell of the nanofluid lubricating liquid is a flexible organic long chain; the flexible organic long chain is formed by covalent bonding of organosilane and polyethyleneimine; the flexible organic long chain is grafted on the surface of the inorganic nano material through the organosilane. The nano-fluid lubricating liquid provided by the invention has low friction coefficient, ultralow wear and high bearing capacity when being applied to the surface of engineering steel, and shows a wide application prospect.

Description

Technical Field

[0001] This invention relates to the field of friction lubrication technology, and in particular to a nanofluid lubricant suitable for near-zero wear on engineering steel surfaces, its preparation method, and its application. Background Technology

[0002] Component wear is a common and serious problem during the operation of mechanical equipment, severely impacting not only the safety and reliability of the equipment but also leading to decreased energy efficiency and economic losses. The rational application and continuous innovation of lubricating materials provide an important path to address this tribological challenge. Currently, widely used lubricants mainly fall into two categories: liquid lubricants and solid lubricants. However, each has significant limitations: while liquid lubricants possess excellent fluidity, they are prone to leakage and contamination, and their lubrication performance easily deteriorates or even fails under harsh operating conditions; solid lubricants, although highly stable, often struggle to achieve real-time repair and rapid replenishment after wear, resulting in limited service life. Therefore, developing a novel lubricating material that combines the advantages of both liquid and solid lubricants has become an urgent direction to meet current high-performance lubrication needs.

[0003] Nanofluids are a novel type of organic-inorganic hybrid nanomaterial that exhibits liquid flow characteristics even under normal temperature and pressure conditions and without solvents. They possess diverse structural combinations, room temperature flow, zero vapor pressure, good dispersion stability, and compatibility. Their basic structure consists of a core and a shell: theoretically, the core can be composed of zero-dimensional nanoparticles, one-dimensional nanofibers, two-dimensional nanosheets, or macromolecular materials; the shell is an organic bilayer. The inner layer of this organic bilayer, called the "neck layer," is covalently anchored to the core structure, connecting the inner nanomaterials to the outer organic molecules; the outer layer, called the "crown layer," is grafted onto the inner molecules via ionic or covalent bonds and primarily provides the flow medium.

[0004] As a functional lubricating material, nanofluids have attracted widespread interest in the field of tribology, but there are no reports of nanofluids suitable for near-zero wear on engineering steel surfaces. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a nanofluid lubricant suitable for near-zero wear on engineering steel surfaces, its preparation method, and its application. The nanofluid lubricant provided by this invention maintains near-zero wear behavior even under high load conditions.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a nanofluid lubricant with a core-shell structure. The core of the nanofluid lubricant is an inorganic nanomaterial, and the outer shell is a flexible organic long chain. The flexible organic long chain is formed by covalent bonding of organosilane and polyethyleneimine. The flexible organic long chain is grafted onto the surface of the inorganic nanomaterial through the organosilane.

[0007] Preferably, the inorganic nanomaterial content in the nanofluid lubricant is 0.5% to 5.5% by mass.

[0008] Preferably, the inorganic nanomaterials include graphene oxide, layered double hydroxides, few-layer or monolayer Ti3C2T x One or more of MXene nanosheets, nano-silica, nano-iron oxide, nano-titanium oxide, nano-zirconia, and nano-zinc oxide.

[0009] Preferably, the organosilane comprises one or more of γ-glycidoxypropyltrimethoxysilane, 3-(trihydroxysilyl)-propanesulfonic acid, dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium chloride, tetradecyldimethyl[3-(trimethoxysilyl)propyl]ammonium chloride, and monosodium salt of 3-(trihydroxysilyl)propylmethylphosphonic acid.

[0010] Preferably, the relative molecular mass of the polyethyleneimine is 600 to 10000.

[0011] The present invention provides a method for preparing the nanofluid lubricant described above, comprising the following steps: dissolving organosilane and polyethyleneimine in an alcohol solvent for a covalent bonding reaction, and then removing the alcohol solvent to obtain a flexible organic long-chain material; An aqueous dispersion of an inorganic nanomaterial rich in hydroxyl groups on its surface is mixed with the organic long-chain material, and after a dehydration condensation reaction, water is removed to obtain the nanofluid lubricant.

[0012] Preferably, the covalent bonding reaction is carried out at a temperature of 30-80°C for 8-12 hours.

[0013] Preferably, the dehydration condensation reaction is carried out at a temperature of 30-80°C for 8-12 hours.

[0014] This invention provides the application of the nanofluid lubricant described in the above-described scheme or the nanofluid lubricant prepared by the preparation method described in the above-described scheme in the field of friction lubrication.

[0015] Preferably, the friction lubrication field includes engineering steel for friction reduction and wear resistance.

[0016] This invention provides a nanofluid lubricant with a core-shell structure. The core of the nanofluid lubricant is an inorganic nanomaterial, and the outer shell is a flexible organic long chain. The flexible organic long chain is formed by covalent bonding of organosilane and polyethyleneimine. The flexible organic long chain is grafted onto the surface of the inorganic nanomaterial through the organosilane. In the nanofluid lubricant, the inorganic nanomaterial can significantly enhance the friction reduction and anti-wear properties of the lubricant, while the flexible organic long chain endows the lubricant with good fluidity and dispersion stability. The nanofluid lubricant combines the advantages of both solid and liquid lubricants. The inventors unexpectedly discovered that the nanofluid lubricant developed using polyethyleneimine as the coronal layer exhibits excellent lubrication performance in the field of tribology, realizing the expansion of the application of nanofluid technology in tribology, especially providing an effective lubrication solution for near-zero wear on engineering steel surfaces.

[0017] Data from the embodiments show that when the nanofluid lubricant provided by this invention is applied to an engineering steel friction pair, under friction conditions of 150 N (Hertz contact pressure of 2.46 GPa) and 30 min, the average coefficient of friction is 0.068~0.116, and there are no obvious wear marks on the surface of the friction pair. Even in a continuous friction experiment lasting up to 150 min, the average coefficient of friction of the nanofluid lubricant is 0.069, and the wear rate is only 1.32 × 10⁻⁶. -10 mm 3 ·N -1 ·m -1 Furthermore, when the nanofluid lubricant provided by this invention is applied to friction pairs on engineering steel, it exhibits excellent friction-reducing properties under different load (150~300N), temperature (25~125℃), and frequency (15~55Hz) conditions. In summary, the nanofluid lubricant provided by this invention demonstrates a low coefficient of friction, ultra-low wear, and high load-bearing capacity in its application on engineering steel surfaces, showing broad application prospects.

[0018] The present invention also provides a method for preparing the nanofluid lubricant described in the above technical solution, which is simple to operate and the process is economical and environmentally friendly. Attached Figure Description

[0019] Figure 1 Friction curves obtained by applying the nanofluid lubricant prepared in Example 1 and Comparative Examples 1-3 to engineering steel friction pairs at 150 N for 30 min. Figure 2 The wear trace optical micrographs obtained by applying the nanofluid lubricant prepared in Example 1 and Comparative Examples 1-3 to engineering steel friction pairs at 150 N for 30 min are shown. Figure 3The nanofluid lubricant prepared in Example 1 was applied to an engineering steel friction pair. The friction curve and wear trace optical micrograph were obtained by testing at 150N and 150min. Detailed Implementation

[0020] This invention provides a nanofluid lubricant with a core-shell structure. The core of the nanofluid lubricant is an inorganic nanomaterial, and the outer shell is a flexible organic long chain. The flexible organic long chain is formed by covalent bonding of organosilane and polyethyleneimine. The flexible organic long chain is grafted onto the surface of the inorganic nanomaterial through the organosilane.

[0021] In this invention, the inorganic nanomaterial content in the nanofluid lubricant is preferably 0.5-5.5% by mass, more preferably 2-4%, and in specific embodiments it can be 2%, 2.2%, 2.4%, 2.6%, 2.8%, 3%, 3.2%, 3.4%, 3.6%, 3.8% or 4%; the balance is the mass of the outer shell.

[0022] In this invention, the inorganic nanomaterial preferably includes graphene oxide, layered double hydroxides, few-layer or single-layer Ti3C2T. x One or more of MXene nanosheets, nano-silica, nano-iron oxide, nano-titanium oxide, nano-zirconia, and nano-zinc oxide are further optimized to form graphene oxide. This invention does not specifically limit the type of the layered double hydroxide; any layered double hydroxide well-known in the art that can be used in nanofluid lubricants is acceptable, specifically, nickel-aluminum layered double hydroxides. In this invention, the above-mentioned inorganic nanomaterials are all nanomaterials with surface-rich hydroxyl groups (inherent in the material). The inorganic nanomaterials are specifically bonded to the organosilane through Si-O bonds.

[0023] In this invention, the organosilane is used as a neck layer material; the organosilane preferably includes one or more of γ-glycidoxypropyltrimethoxysilane (KH560), 3-(trihydroxysilyl)-propanesulfonic acid, dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium chloride, tetradecyldimethyl[3-(trimethoxysilyl)propyl]ammonium chloride, and monosodium salt of 3-(trihydroxysilyl)propylmethylphosphonic acid, and more preferably KH560.

[0024] In this invention, the polyethyleneimine is used as the coronal layer material; the relative molecular mass of the polyethyleneimine is preferably 600-10000, specifically 600, 800, 1000, 1800, 2000, 3000, 4000, 5000, 6000, 7000, 8000, 9000, or 10000, and more preferably 1800. When the relative molecular mass of the polyethyleneimine is 1800, the obtained nanofluid lubricant exhibits superior friction-reducing and anti-wear properties.

[0025] In this invention, the nanofluid lubricant is a covalent nanofluid. Specifically, an organosilane and polyethyleneimine are formed through covalent bonding; for example, when the organosilane is KH560, the epoxy group of KH560 undergoes a ring-opening reaction with the amino group of polyethyleneimine to form a covalent bond. The flexible organic long chain is grafted onto the surface of the inorganic nanomaterial via the organosilane, specifically through Si-O bonds.

[0026] In the aforementioned nanofluid lubricant, inorganic nanomaterials significantly enhance the friction-reducing and anti-wear properties of the lubricant, while flexible organic long chains impart good fluidity and dispersion stability. This invention uses polyethyleneimine as the coronal layer material, resulting in a nanofluid lubricant with superior tribological properties compared to other coronal layer materials.

[0027] The nanofluid lubricant provided by this invention exhibits excellent tribological properties on engineering steel substrates, specifically in the following aspects: First, it has strong load-bearing capacity, demonstrating excellent friction reduction and anti-wear performance under high load conditions of 150 N (Hertz contact pressure of 2.46 GPa); second, it maintains good lubrication performance during high load (150 N, Hertz contact pressure of 2.46 GPa) and long-term (150 min) friction tests; third, it possesses good lubrication performance at a relatively high test frequency (55 Hz); and fourth, it maintains excellent friction reduction and anti-wear performance at a relatively high temperature (125 °C). In summary, the nanofluid lubricant of this invention exhibits excellent tribological properties, achieving ultra-low wear behavior on engineering steel substrates under complex environments, and possesses strong load-bearing capacity. This is of great significance for the research and application of nanofluids in the field of tribology, and also has broad application prospects in the field of friction lubrication.

[0028] The present invention provides a method for preparing the nanofluid lubricant described above, comprising the following steps: dissolving organosilane and polyethyleneimine in an alcohol solvent for a covalent bonding reaction, and then removing the alcohol solvent to obtain a flexible organic long-chain material; An aqueous dispersion of an inorganic nanomaterial rich in hydroxyl groups on its surface is mixed with the organic long-chain material, and after a dehydration condensation reaction, water is removed to obtain the nanofluid lubricant.

[0029] Unless otherwise specified, all raw materials used in this invention are commercially available products well known in the art.

[0030] This invention involves dissolving organosilanes and polyethyleneimine in an alcohol solvent for a covalent bonding reaction, followed by removing the alcohol solvent to obtain a flexible organic long-chain material.

[0031] In this invention, the alcohol solvent preferably includes ethanol, more preferably anhydrous ethanol. There are no special requirements for the amount of alcohol solvent used in this invention, as long as it is sufficient to completely dissolve the organosilane and polyethyleneimine. In this invention, the molar ratio of the organosilane and polyethyleneimine is preferably 1:(1~10), and in specific embodiments it can be 1:1, 1:2, 1:3, 1:3.8, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, or 1:10.

[0032] In this invention, the temperature of the covalent bonding reaction is preferably 30-80°C, and in specific embodiments, it can be 30°C, 40°C, 50°C, 55°C, 60°C, 70°C, or 80°C; the time of the covalent bonding reaction is preferably 8-12 hours, and in specific embodiments, it can be 8 hours, 9 hours, 10 hours, 11 hours, or 12 hours. In this invention, the covalent bonding reaction is preferably carried out under stirring conditions, and the stirring speed is preferably 300-800 rpm, and in specific embodiments, it can be 300 rpm, 400 rpm, 500 rpm, 600 rpm, 700 rpm, or 800 rpm. During the covalent bonding reaction, the amino group of polyethyleneimine chemically bonds with the organosilane.

[0033] In this invention, the removal of the alcohol solvent preferably includes: sequentially subjecting the reacted system to rotary evaporation and vacuum drying. The rotary evaporation temperature is preferably 75°C; the rotary evaporation time is not specifically limited in this invention, as long as the alcohol solvent is completely removed. In this invention, the vacuum drying temperature is preferably 50~80°C, and in specific embodiments, it can be 50°C, 55°C, 60°C, 65°C, 70°C, or 80°C; the vacuum drying time is preferably 12~24 hours, and in specific embodiments, it can be 12 hours, 14 hours, 16 hours, 18 hours, 20 hours, 22 hours, or 24 hours; the vacuum degree is preferably 10~133 Pa, and in specific embodiments, it can be 10 Pa, 20 Pa, 30 Pa, 40 Pa, 50 Pa, 60 Pa, 70 Pa, 80 Pa, 90 Pa, 100 Pa, 110 Pa, 120 Pa, 130 Pa, or 133 Pa.

[0034] After obtaining the flexible organic long-chain material, the present invention mixes the aqueous dispersion of the inorganic nanomaterial rich in hydroxyl groups on the surface with the organic long-chain material, performs a dehydration condensation reaction and removes water to obtain the nanofluid lubricant.

[0035] The present invention does not impose special requirements on the concentration of the aqueous dispersion of the inorganic nanomaterial with hydroxyl-rich surface, as long as it can disperse the inorganic nanomaterial with hydroxyl-rich surface evenly. In the embodiments of the present invention, the mass concentration of the dispersion is specifically 5%.

[0036] In this invention, the temperature of the dehydration condensation reaction is preferably 30-80°C, and in specific embodiments, it can be 30°C, 40°C, 50°C, 55°C, 60°C, 70°C, or 80°C; the time of the dehydration condensation reaction is preferably 8-12 hours, and in specific embodiments, it can be 8 hours, 9 hours, 10 hours, 11 hours, or 12 hours. In this invention, the dehydration condensation reaction is preferably carried out under stirring conditions, and the stirring speed is preferably 300-800 rpm, and in specific embodiments, it can be 300 rpm, 400 rpm, 500 rpm, 600 rpm, 700 rpm, or 800 rpm. In this invention, the dehydration condensation reaction is preferably carried out under a protective atmosphere; the protective atmosphere preferably includes a nitrogen atmosphere. During the dehydration condensation reaction of this invention, the hydroxyl groups of the inorganic nanomaterial undergo dehydration condensation with the organosilane structure in the flexible organic long chain to form Si-O bonds.

[0037] In this invention, the dehydration preferably includes: sequentially subjecting the reacted system to rotary evaporation and vacuum drying. The rotary evaporation temperature is preferably 75°C; the rotary evaporation time is not specifically limited, as long as the alcohol solvent is completely removed. In this invention, the vacuum drying temperature is preferably 50-80°C, and in specific embodiments, it can be 50°C, 55°C, 60°C, 65°C, 70°C, or 80°C; the vacuum drying time is preferably 12-24 hours, and in specific embodiments, it can be 12 hours, 14 hours, 16 hours, 18 hours, 20 hours, 22 hours, or 24 hours; the vacuum degree is preferably 10-133 Pa, and in specific embodiments, it can be 10 Pa, 20 Pa, 30 Pa, 40 Pa, 50 Pa, 60 Pa, 70 Pa, 80 Pa, 90 Pa, 100 Pa, 110 Pa, 120 Pa, 130 Pa, or 133 Pa.

[0038] The preparation method provided by this invention is simple and easy to operate, economical and environmentally friendly, and has broad application prospects.

[0039] The present invention also provides the application of the nanofluid lubricant described in the above technical solution or the nanofluid lubricant prepared by the preparation method described in the above technical solution in the field of lubrication.

[0040] The present invention does not impose specific limitations on the application of the nanofluid lubricant; those skilled in the art can set it according to actual needs.

[0041] In this invention, the friction lubrication field preferably includes engineering steel for friction reduction and wear resistance.

[0042] The following detailed description, in conjunction with embodiments, illustrates the nanofluid lubricant suitable for near-zero wear on engineering steel surfaces, its preparation method, and its application. However, these descriptions should not be construed as limiting the scope of protection of this invention.

[0043] Example 1 A nanofluid lubricant suitable for near-zero wear on engineering steel surfaces is prepared using the following steps: (1) Preparation of flexible organic long-chain material: organosilane γ-glycidoxypropyltrimethoxysilane (KH560) was used as the neck layer material and polyethyleneimine (PEI, Mw=1800) was used as the coronal layer material. 0.236 g of neck layer material and 8.9 g of coronal layer material (the molar ratio of KH560 to PEI was 1:3.8) were added to 25 mL of anhydrous ethanol and magnetically stirred at 500 rpm for 12 h at 55 °C. Then the solvent was removed by rotary evaporation at 75 °C and dried in a vacuum drying oven at 100 Pa and 80 °C for 24 h to obtain a covalently bonded flexible organic long-chain material, denoted as KH560-PEI.

[0044] (2) Preparation of nanofluid lubricant: A 5% (w / w) aqueous dispersion of graphene oxide nanosheets was ultrasonically treated for 30 min and then added to the flexible organic long-chain material in step (1). Nitrogen gas was introduced, and the mixture was magnetically stirred at 500 rpm for 12 h at 40 °C. Then, the solvent was removed by rotary evaporation at 75 °C, and the mixture was dried in a vacuum drying oven at 100 Pa and 80 °C for 24 h to obtain the nanofluid lubricant, denoted as GO NFs. The mass of graphene oxide nanosheets accounted for 3% of the total mass of graphene oxide and flexible organic long-chain material.

[0045] Example 2 A nanofluid lubricant suitable for near-zero wear on engineering steel surfaces is prepared using the following steps: (1) Preparation of flexible organic long-chain materials: organosilane γ-glycidyl etheroxypropyltrimethoxysilane (KH560) was used as the neck layer material and polyethyleneimine (PEI, Mw=600) was used as the coronal layer material. 0.708 g of neck layer material and 9.1 g of coronal layer material (the molar ratio of KH560 to PEI was 1:3.8) were added to 25 mL of anhydrous ethanol and magnetically stirred at 500 rpm for 12 h at 55 °C. Then the solvent was removed by rotary evaporation at 75 °C and dried in a vacuum drying oven at 100 Pa and 80 °C for 24 h to obtain covalently bonded flexible organic long-chain materials.

[0046] (2) Preparation of nanofluid lubricant: A 5% (w / w) aqueous dispersion of graphene oxide nanosheets was ultrasonically treated for 30 min and then added to the flexible organic long-chain material in step (1). Nitrogen gas was introduced, and the mixture was magnetically stirred at 500 rpm for 12 h at 40 °C. Then, the solvent was removed by rotary evaporation at 75 °C, and the mixture was dried in a vacuum drying oven at 100 Pa and 80 °C for 24 h to obtain the nanofluid lubricant, denoted as GO NFs-PEI. 0.6K The mass of graphene oxide nanosheets accounts for 3% of the total mass of graphene oxide and flexible organic long-chain materials.

[0047] Example 3 A nanofluid lubricant suitable for near-zero wear on engineering steel surfaces is prepared using the following steps: (1) Preparation of flexible organic long-chain materials: organosilane γ-glycidoxypropyltrimethoxysilane (KH560) was used as the neck layer material and polyethyleneimine (PEI, Mw=10000) was used as the coronal layer material. 0.059 g of neck layer material and 12.5 g of coronal layer material (the molar ratio of KH560 to PEI was 1:3.8) were added to 25 mL of anhydrous ethanol and magnetically stirred at 500 rpm for 12 h at 55 °C. Then the solvent was removed by rotary evaporation at 75 °C and dried in a vacuum drying oven at 100 Pa and 80 °C for 24 h to obtain covalently bonded flexible organic long-chain materials.

[0048] (2) Preparation of nanofluid lubricant: A 5% (w / w) aqueous dispersion of graphene oxide nanosheets was ultrasonically treated for 30 min and then added to the flexible organic long-chain material in step (1). Nitrogen gas was introduced, and the mixture was magnetically stirred at 500 rpm for 12 h at 40 °C. Then, the solvent was removed by rotary evaporation at 75 °C, and the mixture was dried in a vacuum drying oven at 100 Pa and 80 °C for 24 h to obtain the nanofluid lubricant, denoted as GO NFs-PEI. 10K The mass of graphene oxide nanosheets accounts for 3% of the total mass of graphene oxide and flexible organic long-chain materials.

[0049] Example 4 A nanofluid lubricant suitable for near-zero wear on engineering steel surfaces is prepared using the following steps: (1) The preparation of flexible organic long-chain materials is the same as in Example 1.

[0050] (2) Preparation of nanofluid lubricant: An aqueous dispersion of 5% by mass of nano-silica particles was ultrasonically treated for 30 min and then added to the flexible organic long-chain material in step (1). Nitrogen gas was introduced, and the mixture was magnetically stirred at 500 rpm for 12 h at 40 °C. Then, the solvent was removed by rotary evaporation at 75 °C, and the mixture was dried in a vacuum drying oven at 100 Pa and 80 °C for 24 h to obtain the nanofluid lubricant, denoted as SiO2NFs. The mass of the nano-silica particles accounted for 3% of the total mass of the nano-silica and the flexible organic long-chain material.

[0051] Example 5 A nanofluid lubricant suitable for near-zero wear on engineering steel surfaces is prepared using the following steps: (1) The preparation of flexible organic long-chain materials is the same as in Example 1.

[0052] (2) Preparation of nanofluid lubricant: A 5% (w / w) aqueous dispersion of nickel-aluminum layered double hydroxide nanosheets was ultrasonically treated for 30 min and then added to the flexible organic long-chain material in step (1). Nitrogen gas was introduced, and the mixture was magnetically stirred at 500 rpm for 12 h at 40 °C. Then, the solvent was removed by rotary evaporation at 75 °C, and the mixture was dried in a vacuum drying oven at 100 Pa and 80 °C for 24 h to obtain the nanofluid lubricant, denoted as LDH NFs. The mass of the layered double hydroxide accounted for 3% of the total mass of the layered double hydroxide and the flexible organic long-chain material.

[0053] Comparative Example 1 To more fully describe the tribological properties of the nanofluid lubricant on the contact surface of engineering steel, a graphene oxide nanosheet-polyethyleneimine blend was prepared: a 5% (w / w) aqueous dispersion of graphene oxide nanosheets was added to polyethyleneimine (PEI, Mw=1800) material, nitrogen gas was introduced, and the mixture was magnetically stirred at 500 rpm for 12 h at 40 °C. The solvent was then removed by rotary evaporation at 75 °C, and the mixture was dried in a vacuum drying oven at 100 Pa and 80 °C for 24 h to obtain the graphene oxide nanosheet-polyethyleneimine blend, denoted as GO-PEI. The mass of the graphene oxide nanosheets accounted for 3% of the total mass of the graphene oxide nanosheets and polyethyleneimine material.

[0054] Comparative Example 2 To more fully describe the tribological properties of the nanofluid lubricant on the contact surface of engineering steel, the flexible organic long-chain material KH560-PEI from Example 1 was used as a reference sample for tribological testing, thereby better illustrating the low friction and near-zero wear performance of the nanofluid lubricant on the contact surface of engineering steel.

[0055] Comparative Example 3 To more fully describe the tribological properties of the nanofluid lubricant on the contact surface of engineering steel, a commercially available base oil, PAO, was used as a reference sample for tribological testing, thereby better illustrating the low friction and near-zero wear performance of the nanofluid lubricant on the contact surface of engineering steel.

[0056] Comparative Example 4 To more fully illustrate the role of PEI, tribological tests were conducted using polyetheramine, the most commonly used coronal material in the field, as a reference sample. This demonstrates that PEI, as a nanofluid lubricant developed for the coronal layer, exhibits superior lubrication performance in the field of tribology.

[0057] (1) Preparation of flexible organic long-chain materials: Using organosilane KH560 as the neck layer material and polyetheramine (M2070) as the crown layer material, 0.236 g of neck layer material and 10.22 g of crown layer material (the molar ratio of KH560 to M2070 is 1:3.8) were added to 25 mL of anhydrous ethanol, and the mixture was magnetically stirred at 500 rpm for 12 h at 55 °C. Then, the solvent was removed by rotary evaporation at 75 °C, and the mixture was dried in a vacuum drying oven at 100 Pa and 80 °C for 24 h to obtain covalently bonded flexible organic long-chain materials.

[0058] (2) The preparation of the nanofluid lubricant is the same as in Example 1, and is denoted as GO NFs-M2070.

[0059] Test Example 1 The tribological properties of the nanofluid lubricant obtained in Example 1 and Comparative Examples 1-4 were tested using an SRV-V friction testing machine in a reciprocating mode. The upper friction pair used steel balls (AISI 52100, HRC = 60 ± 2, D = 10 mm), and the lower friction pair used a cylindrical steel disc (AISI 52100, HRC = 60 ± 2, 24 mm × 7.9 mm). Before and after testing, the upper and lower friction pairs were cleaned with anhydrous ethanol and allowed to dry before being installed on the friction testing machine. The nanofluid lubricant from Examples 1 and Comparative Examples 1-4 was applied to the cylindrical steel disc of the lower friction pair using a dropper, and tribological testing was performed. The test conditions were: load 150 N (Hertz contact pressure 2.46 GPa), stroke 1 mm, frequency 25 Hz, time 30 min, and temperature 25 °C. The friction coefficient curve and wear scar width were recorded. The results are as follows: Figure 1 , Figure 2 As shown in Table 1.

[0060] Figure 1 Friction curves obtained by testing the nanofluid lubricant prepared in Example 1 and Comparative Examples 1-3 on engineering steel friction pairs at 150 N for 30 min. Figure 2 Here are the corresponding optical micrographs of the wear marks; from Figure 1 and Figure 2 It can be seen that the nanofluid lubricant GO NFs obtained in Example 1 has excellent friction reduction and anti-wear properties, and there are no obvious wear marks on the steel substrate surface, exhibiting significant ultra-low wear behavior.

[0061] Table 1. Comparison of tribological properties of the lubricants obtained in Example 1 and Comparative Examples 1-4

[0062] As shown in Table 1, the average friction coefficients of the nanofluid lubricant prepared in Example 1 and Comparative Examples 1-4 in the 30-minute friction and wear test were 0.068, 0.114, 0.117, 0.102, and 0.097, respectively. The engineering steel substrate surface after lubrication in Example 1 showed almost zero wear. Compared to the conventional base oil PAO used in the comparative examples (average friction coefficient of 0.102, wear scar diameter of 341 μm), the average friction coefficient of GO NFs was significantly reduced, especially the surface wear of the engineering steel substrate, further demonstrating the excellent tribological properties of the nanofluid lubricant prepared in Example 1.

[0063] Test Example 2 The difference from Test Example 1 is that the time was extended to 150 minutes, and the sample was only the nanofluid lubricant obtained in Example 1. The results are as follows: Figure 3 As shown. Figure 3 The nanofluid lubricant prepared in Example 1 was applied to an engineering steel friction pair. Friction curves and wear trace optical micrographs were obtained after testing at 150 N for 150 min. Figure 3 It can be seen that the average friction coefficient is 0.069 and the wear scar diameter of the steel disc is 341 μm.

[0064] Test Example 3 The average friction coefficient of the nanofluid lubricant obtained in Example 1 was studied at different temperatures. The method was the same as in Example 1, and the test conditions were: load 150N, stroke 1mm, frequency 25Hz, and time 30min, except that the temperature was adjusted to 25℃, 50℃, 75℃, 100℃, and 125℃ respectively. The results are shown in Table 2.

[0065] Table 2. Average friction coefficient of the nanofluid lubricant obtained in Example 1 at different temperatures.

[0066] As shown in Table 2, the average friction coefficient of GO NFs gradually increases within the temperature range of 25~125℃. When the temperature rises to 125℃, the average friction coefficient increases to 0.114, but it is still at a low level, indicating that GO NFs have excellent lubrication performance.

[0067] Test Example 4 The average friction coefficient of the nanofluid lubricant obtained in Example 1 was studied at different frequencies using the same method as in Example 1. The test conditions were: load 150 N, stroke 1 mm, time 30 min, and temperature 25 °C, with the frequency adjusted to 15 Hz, 25 Hz, 35 Hz, 45 Hz, and 55 Hz respectively. The results are shown in Table 3.

[0068] Table 3. Average friction coefficient of the nanofluid lubricant obtained in Example 1 at different frequencies.

[0069] As shown in Table 3, GO NFs exhibit a low average coefficient of friction within the test frequency range of 15–55 Hz. The average coefficient of friction fluctuates slightly with increasing frequency, but does not show a clear monotonic upward or downward trend. Even at a test frequency of 55 Hz, the average coefficient of friction is only 0.073, demonstrating excellent tribological properties.

[0070] Test Example 5 Examples 1-5 were tested for average friction coefficient according to Test Example 1. The test conditions were: load 150N, stroke 1mm, time 30min, and temperature 25℃. The results are shown in Table 4.

[0071] Table 4 Comparison of tribological properties of the lubricants obtained in Examples 1-5

[0072] As can be seen from Table 4, Examples 1-5 all exhibited significant near-zero wear behavior on the steel substrate surface, with wear rates all reaching 10%. -10 The order of magnitude; among them, Example 1 has a more significant advantage over Examples 2-5 in both average friction coefficient and wear rate, indicating that GO NFs is a high-performance lubricant with excellent tribological properties.

[0073] In summary, the nanofluid lubricant provided by this invention can significantly reduce the coefficient of friction, effectively suppress wear on the surface of engineering steel friction pairs, and achieve long-lasting and stable near-zero wear on the steel substrate surface under high loads and various working conditions, demonstrating excellent tribological properties.

[0074] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A nanofluid lubricant with a core-shell structure, characterized in that, The core of the nanofluid lubricant is an inorganic nanomaterial, and the outer shell is a flexible organic long chain; the flexible organic long chain is formed by covalent bonding of organosilane and polyethyleneimine; the flexible organic long chain is grafted onto the surface of the inorganic nanomaterial through the organosilane.

2. The nanofluid lubricant according to claim 1, characterized in that, The inorganic nanomaterials in the nanofluid lubricant contain 0.5% to 5.5% by mass.

3. The nanofluid lubricant according to claim 1 or 2, characterized in that, The inorganic nanomaterials include graphene oxide, layered double hydroxides, and few-layer or monolayer Ti3C2T. x One or more of MXene nanosheets, nano-silica, nano-iron oxide, nano-titanium oxide, nano-zirconia, and nano-zinc oxide.

4. The nanofluid lubricant according to claim 1, characterized in that, The organosilanes include one or more of γ-glycidoxypropyltrimethoxysilane, 3-(trihydroxysilyl)propanesulfonic acid, dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium chloride, tetradecyldimethyl[3-(trimethoxysilyl)propyl]ammonium chloride, and monosodium salt of 3-(trihydroxysilyl)propylmethylphosphonic acid.

5. The nanofluid lubricant according to claim 1, characterized in that, The relative molecular mass of the polyethyleneimine is 600~10000.

6. The method for preparing the nanofluid lubricant according to any one of claims 1 to 5, characterized in that, The process includes the following steps: dissolving organosilane and polyethyleneimine in an alcohol solvent to carry out a covalent bonding reaction, then removing the alcohol solvent to obtain a flexible organic long-chain material; An aqueous dispersion of an inorganic nanomaterial rich in hydroxyl groups on its surface is mixed with the organic long-chain material, and after a dehydration condensation reaction, water is removed to obtain the nanofluid lubricant.

7. The preparation method according to claim 6, characterized in that, The covalent bonding reaction is carried out at a temperature of 30-80℃ for 8-12 hours.

8. The preparation method according to claim 6, characterized in that, The dehydration condensation reaction is carried out at a temperature of 30~80℃ for 8~12 hours.

9. The application of the nanofluid lubricant according to any one of claims 1 to 5 or the nanofluid lubricant prepared by the preparation method according to any one of claims 6 to 8 in the field of friction lubrication.

10. The application according to claim 9, characterized in that, The friction lubrication field includes friction reduction and wear resistance of engineering steel.

Images