Composite anti-wear additive for lubricating oil and preparation method of composite anti-wear additive

Abstract

The invention relates to the technical field of lubricating oil additives, and discloses a composite anti-wear additive for lubricating oil, which comprises the following components by mass: 50-70 parts of surface-modified layered boron nitride quantum dots; 20 to 35 parts of a gallium-based liquid metal carrier; 10 to 15 parts of rare earth doped diamond nanocrystals; wherein the gallium-based liquid metal carrier is a gallium-indium-tin-germanium alloy and ionic liquid-covalent organic framework compound, the surface of the surface-modified layered boron nitride quantum dot is grafted with carboxyl and epoxy bifunctional groups, the carboxyl density is 3-8 groups / nm < 2 >, the interlayer spacing is 0.30-0.35 nm, the size of the quantum dot is 1-3 nm, and the quantum dot is a gallium-indium-tin-germanium alloy / ionic liquid-covalent organic framework compound. The gallium-indium-tin-germanium alloy comprises the following components in atomic percent: 64%-66% of Ga, 21%-23% of In, 12%-13% of Sn and 0.4%-0.6% of Ge. The particle size of the alloy powder is 5-15 microns, and the melting point of the alloy powder is smaller than or equal to 12 DEG C. Through the technical scheme of synchronously activating carboxyl and epoxy free radicals through plasmas, synergistic enhancement of active sites on the surfaces of the quantum dots is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of lubricating oil additives, in particular to a composite anti-wear additive for lubricating oil and a preparation method thereof. Background Art

[0002] Under extreme operating conditions such as high loads and extreme pressures, the effectiveness of lubricants directly impacts the service life and operating efficiency of equipment. Traditional lubrication systems rely on the synergistic effects of base oil and additives to reduce friction by forming boundary lubrication films and improving wear resistance. However, existing technologies have significant deficiencies in the dispersion stability, tribochemical reactivity, and lubricant film continuity of nano-additives, leading to an increased risk of lubrication failure. Nanoparticles, due to their high specific surface area and surface energy, exhibit excellent extreme pressure and wear reduction properties and are widely used in lubrication systems. For example, boron nitride quantum dots (BNQDs) and rare earth-doped diamond nanoparticles (Nd@Dia) exhibit excellent mechanical strength and chemical inertness, forming physical adsorption films or chemical reaction films at the friction pair interface, thereby reducing direct contact wear. However, due to van der Waals forces and surface polarity between nanoparticles, they easily agglomerate in oil-based media, forming micron-sized or even larger aggregates. In particular, in the absence of effective dispersion methods, sedimentation and stratification of the dispersion are exacerbated, leading to lubricant failure after prolonged use.

[0003] In existing technologies, nanoparticle dispersion is often achieved through single-stage centrifugation, low-frequency ultrasound, or mechanical agitation. While single-stage centrifugation can initially separate coarse particles and large aggregates, its ability to identify and remove nanoscale aggregates is limited, particularly when there are overlapping regions in the particle size distribution, which can easily lead to the retention of fine aggregates. Under extreme pressure conditions, these poorly dispersed particles can become stress concentration points, causing localized rupture of the lubricating film and further exacerbating wear.

[0004] Existing technologies have significant deficiencies in nanoparticle dispersion stability, functional modification, and extreme pressure performance. Especially under extreme operating conditions, the instability of the dispersion system and the discontinuous formation of the lubricating film become the main factors affecting lubrication performance. Summary of the Invention

[0005] In response to the deficiencies in the prior art, the present invention provides a composite anti-wear additive for lubricating oil and a preparation method thereof, which solves the problems of unstable extreme pressure performance and high-temperature lubrication failure caused by nanoparticle agglomeration, insufficient surface modification and dispersion process defects of traditional lubricating additives.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solutions: A composite anti-wear additive for lubricating oil, comprising the following components in parts by weight: Surface-modified layered boron nitride quantum dots: 50-70 parts; Gallium-based liquid metal carrier: 20-35 parts; Rare earth-doped diamond nanocrystals: 10-15 parts; The gallium-based liquid metal carrier is a gallium-indium-tin-germanium alloy and an ionic liquid-covalent organic framework complex.

[0007] Preferably, the surface of the surface-modified layered boron nitride quantum dots is grafted with carboxyl and epoxy bifunctional groups, and the carboxyl density is 3-8 groups / nm 2 , the interlayer spacing is 0.30-0.35 nm, and the quantum dot size is 1-3 nm.

[0008] Preferably, the atomic percentage composition of the gallium-indium-tin-germanium alloy is: Ga 64-66%, In 21-23%, Sn 12-13%, Ge 0.4-0.6%; The alloy powder has a particle size of 5-15 μm and a melting point of ≤12° C.

[0009] Preferably, the doping amount of neodymium in the rare earth-doped diamond nanocrystal is 0.5-1.5 at%, and the doping concentration is gradient distributed along the radial direction of the grain, with the surface doping amount being 0.3-0.8 at% higher than that in the interior; The diamond nanocrystal has a grain size of 20-50 nm and a surface hydrogen-terminated structure.

[0010] Preferably, in the ionic liquid-covalent organic framework composite, the pore size of the covalent organic framework is 1.0-1.5 nm, and the ionic liquid loading rate is 60-80 wt %.

[0011] The present invention also provides a method for preparing a composite anti-wear additive for lubricating oil, comprising the following steps: Step 1: Synchronously modifying the surface functional groups of hexagonal boron nitride by plasma vapor deposition to prepare bifunctional quantum dots; Step 2: vacuum melting the gallium-indium-tin-germanium alloy and quenching it into granules; Step 3: synthesizing gradient rare earth doped diamond nanocrystals by microwave plasma chemical vapor deposition; Step 4: loading the ionic liquid-covalent organic framework complex onto the liquid metal carrier by microfluidic electrochemical deposition; Step 5: Multi-stage ultrasonic dispersion and compounding of the components.

[0012] Preferably, in the step 1, the hexagonal boron nitride block is placed in a radio frequency plasma reactor, and an argon-hydrogen mixed gas Ar:H2 with a volume ratio of 90-95:5-10 and an acrylic acid / propylene oxide mixed gas with a molar ratio of 1:1.8-2.2 are simultaneously introduced; Shoot at 400-600W.

[0013] Preferably, in the step 2, the temperature is raised to 280-320°C under argon protection with O2≤1ppm, stirred and melted for 1.5-2.5h, then rapidly cooled to -25--15°C at a rate of 800-1200°C / s, and crushed to obtain 5-15μm alloy powder.

[0014] Preferably, in step 3, a 200 nm diamond seed layer is pre-deposited on a silicon substrate, and NdCl 3 vapor is pulsed in at a frequency of 8-12 Hz and a duty cycle of 25-35%; Under a microwave power of 2.8-3.2kW and a cavity pressure of 4.5-5.5kPa, the gradient-doped diamond nanocrystals are grown in a CH4 / H2 gas mixture with a volume ratio of 0.5-1.5:98.5-99.5 for 7-9 hours.

[0015] Preferably, in the step 4, the liquid metal alloy powder and the 0.08-0.12M ionic liquid solution are pumped into the microfluidic chip; Apply an alternating electric field of 45-55 V / cm at a frequency of 900-1100 Hz and control the deposition voltage to 0.4-0.6 V to achieve size screening deposition of the ionic liquid-covalent organic framework.

[0016] The present invention provides a composite anti-wear additive for lubricating oil and a preparation method thereof. It has the following beneficial effects: 1. This invention achieves a synergistic enhancement of active sites on the quantum dot surface by simultaneously activating carboxyl and epoxy radicals through plasma. Traditional single-functional group modification results in insufficient dispersion stability of quantum dots, and the lubricating film is prone to failure due to weak interfacial bonding.

[0017] 2. This invention precisely controls the alloy's phase transition behavior through the regulation of Ge-based grain boundaries, achieving instant self-repair triggered by frictional heat. In existing technologies, liquid metals cannot respond to interface temperature rises in a timely manner due to phase transition temperature mismatches, resulting in delayed wear repair.

[0018] 3. This invention uses microwave pulse gradient doping technology to form a surface structure enriched with rare earth elements, effectively suppressing friction pair adhesion. Traditional uniform doping schemes lack surface activity, and the lubricating film is prone to adhesive wear under high pressure.

[0019] 4. This invention combines an alternating electric field with a channel contraction design to achieve precise pore size control and on-demand release of the lubricant. Traditional impregnation methods, due to uneven pore size distribution, result in uncontrollable lubricant release and significantly reduce the stability of the lubricating film. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Flow chart of the method of the present invention. DETAILED DESCRIPTION

[0021] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0022] An embodiment of the present invention provides a composite anti-wear additive for lubricating oil, comprising the following components in parts by weight: Surface-modified layered boron nitride quantum dots: 50-70 parts; Gallium-based liquid metal carrier: 20-35 parts; Rare earth-doped diamond nanocrystals: 10-15 parts; Among them, the gallium-based liquid metal carrier is a gallium-indium-tin-germanium alloy and an ionic liquid-covalent organic framework complex.

[0023] The surface of the surface-modified layered boron nitride quantum dots is grafted with carboxyl and epoxy functional groups, with a carboxyl density of 3-8 groups / nm 2 , the interlayer spacing is 0.30-0.35 nm, and the quantum dot size is 1-3 nm.

[0024] The atomic percentage composition of the gallium-indium-tin-germanium alloy is: Ga 64-66%, In 21-23%, Sn 12-13%, Ge 0.4-0.6%.

[0025] In rare earth-doped diamond nanocrystals, the neodymium doping amount is 0.5-1.5at%, and the doping concentration is gradient distributed along the radial direction of the grain, with the surface doping amount being 0.3-0.8at% higher than that in the interior; The grain size of diamond nanocrystals is 20-50nm, and the surface is a hydrogen-terminated structure.

[0026] In the ionic liquid-covalent organic framework composite, the pore diameter of the covalent organic framework is 1.0-1.5 nm, and the ionic liquid loading rate is 60-80 wt %.

[0027] Please see the attached Figure 1 The present invention also provides a method for preparing a composite anti-wear additive for lubricating oil, comprising the following steps: Step 1: Synchronously modifying the surface functional groups of hexagonal boron nitride by plasma vapor deposition to prepare bifunctional quantum dots; Step 2: vacuum melting the gallium-indium-tin-germanium alloy and quenching it into granules; Step 3: synthesizing gradient rare earth doped diamond nanocrystals by microwave plasma chemical vapor deposition; Step 4: loading the ionic liquid-covalent organic framework complex onto the liquid metal carrier by microfluidic electrochemical deposition; Step 5: Multi-stage ultrasonic dispersion and compounding of the components.

[0028] In step 1, the hexagonal boron nitride block is placed in a radio frequency plasma reactor, and an argon-hydrogen mixed gas Ar:H2 with a volume ratio of 90-95:5-10 and an acrylic acid / propylene oxide mixed gas with a molar ratio of 1:1.8-2.2 are simultaneously introduced; The plasma was excited at 400-600W RF power for 25-35min, and the surface-modified quantum dots were captured by liquid nitrogen cold trap.

[0029] In step 2, under the protection of argon gas with O2≤1ppm, the temperature is raised to 280-320℃, stirred and melted for 1.5-2.5h, and then rapidly cooled to -25~-15℃ at a rate of 800-1200℃ / s, and crushed to obtain 5-15μm alloy powder.

[0030] In step 3, a 200 nm diamond seed layer is pre-deposited on a silicon substrate, and NdCl3 vapor is pulsed in at a frequency of 8-12 Hz and a duty cycle of 25-35%; Under a microwave power of 2.8-3.2kW and a cavity pressure of 4.5-5.5kPa, the gradient-doped diamond nanocrystals are grown in a CH4 / H2 gas mixture with a volume ratio of 0.5-1.5:98.5-99.5 for 7-9 hours.

[0031] In step 4, liquid metal alloy powder and 0.08-0.12M ionic liquid solution are pumped into the microfluidic chip; Apply an alternating electric field of 45-55 V / cm at a frequency of 900-1100 Hz and control the deposition voltage to 0.4-0.6 V to achieve size screening deposition of the ionic liquid-covalent organic framework.

[0032] In this embodiment, hexagonal boron nitride (h-BN) is surface activated by a high-energy plasma-induced reaction, and a carboxyl-derived monomer (such as acrylic acid) and an epoxy-derived monomer (such as propylene oxide) are introduced in a plasma atmosphere to form layered boron nitride quantum dots with a bifunctional modified structure.

[0033] Generally, a plasma processing system uses a radio frequency power source to excite a gas medium. In this embodiment, a radio frequency of 13.56 MHz is used, and the radio frequency power is controlled within a range of 400-600 W.

[0034] Specifically, a bulk sample of hexagonal boron nitride with a particle size of 50–100 μm was first placed in the center of a radio frequency plasma reactor, and the system was evacuated to a base pressure of approximately 5.0×10 -3Pa to ensure the purity of the reaction atmosphere. A mixture of argon and hydrogen is then introduced, with a volume ratio of 90–95:5–10, as the plasma-maintaining gas. Argon provides the electron-excited substrate, while hydrogen assists in reducing residual oxygen functional groups on the surface.

[0035] Subsequently, while maintaining a steady flow of the main gas, a mixed gas of functional monomers is introduced. Alternatively, the functional monomer can be a mixture of acrylic acid and propylene oxide, with a preferred molar ratio of 1:1.8–2.2. The acrylic acid provides a source of –COOH groups, while the propylene oxide provides a source of –CH(CH2)O– epoxy groups.

[0036] Under the action of radio frequency plasma, the above monomers undergo in situ dissociation to form highly active free radical species (such as ·COOH, ·OCH2CHCH2, etc.). These free radicals can be directionally grafted to the unsaturated B or N positions on the edge of the BN surface under the synergistic effect of high-energy electron collisions and plasma ultraviolet irradiation to form a covalent bond structure.

[0037] In one possible implementation, in order to further improve the selectivity of surface modification and the steric control effect, a liquid nitrogen cold trap is set at the outlet position to capture quantum dot-level products with a particle size in the range of 1–3 nm.

[0038] The formed quantum dot samples were characterized by atomic force microscopy (AFM), and their interlayer spacing can be controlled in the range of 0.30–0.35 nm, indicating that the weak van der Waals interaction between the layers is not significantly destroyed and the layered stability is still maintained; the carboxyl group density is 3–8 groups / nm 2 range, effectively improving its stable dispersibility in non-polar base oil.

[0039] As an auxiliary analytical method, Fourier transform infrared spectroscopy (FTIR) can be used to confirm the presence of surface grafted groups. The characteristic absorption peak appears at 1720 cm -1 near (carboxyl C=O stretching vibration), and 915–950 cm -1 region (epoxy group strain vibration), indicating that the bifunctional groups have been stably grafted.

[0040] In the specific modification mechanism, acrylic radicals preferentially form σ-type B–O–C structures with B vacancies at the BN edge, while epoxy groups are prone to ring-opening reactions when subjected to friction-induced heating, exposing hydroxyl groups and ether bonds, thereby enhancing the interfacial interaction between them and the polar functional groups in the liquid metal or COF skeleton.

[0041] It should be pointed out that there are free radical recombination side reactions during the modification reaction, so the reaction time is generally controlled between 25-35 minutes. If it is too long, it may induce surface carbonization and affect the size and activity of quantum dots.

[0042] To facilitate subsequent processing, the obtained quantum dots can be freeze-dried to obtain powder form and stored at -20°C.

[0043] In the composite anti-wear additive preparation system of the present invention, step two involves alloying the liquid metal carrier and regulating its microstructure. This step requires chemical bonding compatibility with the surface-modified quantum dots obtained in step one and provides a high-surface-area substrate for the ionic liquid-covalent organic framework composite loading in step four. By precisely controlling the alloy composition and quenching process parameters, the phase change response and self-healing ability of the liquid metal triggered by frictional heat are achieved, providing dynamic interface support for multi-component synergistic lubrication.

[0044] In this embodiment, a gallium-based liquid metal alloy powder is prepared by combining vacuum melting and ultra-fast quenching technology, which specifically includes key steps such as raw material ratio, melting process, and quenching granulation.

[0045] Typically, the alloy raw materials include high-purity gallium, indium, tin, and germanium, all with a purity of ≥99.9%. The preferred atomic percentage ratio of these components is: Ga 64–66%, In 21–23%, Sn 12–13%, and Ge 0.4–0.6%. Germanium is added in trace amounts for grain boundary strengthening and phase transition temperature regulation. A content deviation exceeding ±0.05% will shift the alloy's melting point.

[0046] Specifically, under an argon protective atmosphere (O2 content ≤ 1ppm), the weighed metal raw materials are placed in a vacuum arc melting furnace. The melting temperature is controlled in the range of 280-320℃, and the holding time is 1.5-2.5 hours. During the melting process, a mechanical stirring rate of 200-300rpm is used to promote component homogenization and avoid segregation. It should be noted that the melting point of germanium (938℃) is significantly higher than that of other components, and a staged heating strategy is required to ensure its complete dissolution: first heat it to 400℃ to pre-melt the germanium powder, and then cool it to 300℃ to add gallium, indium, and tin.

[0047] In one possible implementation, a copper mold rapid cooling process is used after smelting. The melt is cooled from the liquid phase to -25 to -15°C at a cooling rate of 800–1200°C / s, forming an amorphous / nanocrystalline composite structure.

[0048] The quenched alloy ingot was mechanically crushed and vibrated to obtain a regularly spherical powder with a particle size of 5–15 μm. The crushing process was performed in liquid nitrogen to prevent lattice distortion caused by work hardening. Scanning electron microscopy (SEM) analysis of the sieved powder revealed a smooth surface with no oxide layer, meeting the interface requirements for subsequent microfluidic deposition.

[0049] Alternatively, the phase transition characteristics of the alloy powder can be verified using differential scanning calorimetry (DSC). A typical DSC curve exhibits an endothermic peak in the 10–12°C range, corresponding to the solid-liquid phase transition, with a melting enthalpy, ΔH, of 25–30 J / g. The phase transition temperature is negatively correlated with the Ge content.

[0050] Furthermore, in some embodiments, the grain size of the alloy powder is calculated using the X-ray diffraction (XRD) half-width method, and the results show that the average grain size is ≤ 500 nm, and the half-width (FWHM) of the (111) plane diffraction peak is ≥ 0.5°, confirming the presence of a nanocrystalline structure. This microstructure is beneficial for dissipating energy through grain boundary sliding during friction, thereby reducing the wear rate.

[0051] It's important to emphasize that the coordinated control of the quenching rate and germanium content is key to achieving the target phase transition temperature. When the quenching rate falls below 800°C / s, the alloy will form a coarse dendritic structure, resulting in delayed phase transition and reduced repair efficiency. When the germanium content exceeds 0.6 at%, the alloy becomes significantly more brittle, and microcracks are more likely to form during the crushing process.

[0052] In the composite anti-wear additive system of this invention, gradient rare earth-doped diamond nanocrystals serve as the core anti-wear phase, requiring both high hardness and low interfacial adhesion. This step utilizes microwave plasma chemical vapor deposition (CVD) technology to achieve a gradient distribution of the rare earth element (neodymium) and a surface hydrogen termination treatment. The process parameters must match the liquid metal phase transition characteristics of step two and provide a highly active substrate for the ionic liquid composite loading in step four.

[0053] In this embodiment, a pulsed microwave plasma CVD process is used to directionally grow gradient-doped diamond nanocrystals on a silicon substrate, which specifically includes key operations such as seed layer pre-deposition, neodymium doping gradient control, and hydrogen termination surface treatment.

[0054] Generally, the microwave plasma CVD system configuration includes a 2.45GHz microwave source, a gas flow controller, a pulse gas inlet device, and a vacuum chamber. The ultimate vacuum degree of the chamber is ≤1.0×10 -3 Pa, the microwave power is adjustable in the range of 1–5 kW, and the process gases include methane (CH4), hydrogen (H2) and neodymium chloride (NdCl3) vapor.

[0055] Specifically, a diamond seed layer is first pre-deposited on the silicon substrate. Alternatively, an ultrasonic nanodiamond suspension (particle size 5–10 nm) is spin-coated onto the silicon wafer surface. A hydrogen plasma etchant (1.2 kW, 30 minutes) removes the amorphous carbon, forming a uniform seed layer approximately 200 nm thick. This layer provides nucleation sites for subsequent diamond epitaxial growth, with a coverage of ≥95%.

[0056] The microwave power was controlled in the range of 2.8–3.2 kW, and the cavity pressure was maintained at 4.5–5.5 kPa. The CH4 / H2 volume ratio in the process gas was set to 0.5–1.5:98.5–99.5, and the total gas flow rate was 200–300 sccm. Under these conditions, diamond nanocrystals <110> Directional epitaxial growth was performed at a rate of approximately 0.5–1.0 μm / h for 7–9 hours to obtain a doped layer with a thickness of 1.2–1.8 μm.

[0057] Regarding gradient doping control, the concentration of neodymium atoms decreases from the surface to the interior along the growth direction (i.e., the radial direction of the grain). The surface doping level, measured by XPS depth profiling, is typically 1.2–1.5 at%. The internal doping level decreases to 0.4–0.7 at%, resulting in a concentration gradient Δ[Nd] of 0.3–0.8 at%. This gradient distribution is achieved by sequentially adjusting the pulse frequency and microwave power, for example, with a pulse frequency of 12 Hz for the first four hours and then 8 Hz for the last five hours, resulting in a linear decrease in doping concentration with increasing thickness.

[0058] During the hydrogen termination treatment, the CH₄ and NdCl₃ atmospheres were discontinued and replaced with a pure H₂ atmosphere (500 sccm). The microwave power was adjusted to 1.0–1.5 kW, and the treatment time was 30–60 minutes. Hydrogen radicals (H*) etched the amorphous carbon on the surface and saturated the dangling bonds, forming a hydrogen-terminated surface. Contact angle measurements showed that the treated surface had a contact angle of ≤5°, significantly lower than that of the oxygen-terminated surface (>60°), confirming that the dangling bonds were fully hydrogen-saturated.

[0059] As a verification method, Raman spectroscopy was used to analyze the phase purity of diamond. The characteristic peak is located at 1332 cm -1 (sp 3 Full width at half maximum (FWHM) ≤ 8 cm -1 , indicating that the crystal quality is close to the single crystal level. -1 The amorphous carbon peak intensity accounts for <5%, indicating that the impurity phase is effectively suppressed.

[0060] It should be pointed out that the matching relationship between microwave power and cavity pressure is crucial to the gradient doping effect. When the cavity pressure is lower than 4.5kPa, the plasma plume is unevenly distributed, resulting in a doping concentration fluctuation of >±0.2at%. When the power exceeds 3.2kW, it may induce the graphitization of diamond, making sp 2 The hybridized carbon content increased to >10%.

[0061] In summary, through the precise control of the above process parameters, the gradient-doped diamond nanocrystals obtained have both high hardness (≥80GPa) and low interfacial adhesion energy (≤0.15J / m 2), whose surface hydrogen-terminated structure can effectively promote chemical bonding with the liquid metal carrier, providing a stable friction interface for multi-component synergistic lubrication.

[0062] In this embodiment, a technique combining dynamic size screening and electric field-assisted deposition is used to confine the ionic liquid within the nanopores of the COF framework, including key operations such as microfluidic channel design, electric field parameter optimization, and complex structure characterization.

[0063] Typically, microfluidic chips are made of polydimethylsiloxane (PDMS), with channel widths controlled within a range of 50–200 μm using photolithographic masks. The channel geometry is designed to alternate between contraction and expansion, with an inlet width of 200 μm, a contraction zone width of 50 μm, and an expansion zone width that recovers to 200 μm, with a cycle length of 5 mm. This structure achieves particle size screening through a fluid shear gradient. Large aggregates (>1.5 nm) are fragmented or retained in the contraction zone due to concentrated shear stress.

[0064] Specifically, the liquid metal alloy powder (particle size 5–15 μm) obtained in step 2 is mixed with a 0.08–0.12 M ionic liquid solution (e.g., [BMIM][PF6]) at a volume ratio of 1:3 to form a suspension. The suspension is pumped into the main channel of the microfluidic chip at a flow rate of 5–10 μL / min. In one possible implementation, the ionic liquid monomers are oriented due to the shear effect of the fluid.

[0065] An alternating electric field is applied synchronously to enhance the deposition selectivity. As an option, the electric field strength is set to 45–55 V / cm, the frequency is 900–1100 Hz, and the direction is perpendicular to the fluid flow. In the positive half cycle, anions (such as PF6 - ) migrates to the liquid metal surface; the negative half-cycle drives the cations (such as BMIM + ) directional migration. The penetration depth of the ionic liquid into the COF pores is controlled by adjusting the deposition voltage (0.4–0.6 V vs. Ag / AgCl reference electrode). Deposition time is typically 30–60 minutes, until a loading of 60–80 wt% is achieved.

[0066] In some embodiments, the element distribution can be analyzed by X-ray energy spectrum (EDS) surface scanning, and F element (from PF6 - ) and N elements (from BMIM + The signal intensity in the COF pore region is 3–5 times higher than that in the bulk solution, indicating preferential loading of the ionic liquid. Furthermore, thermogravimetric analysis (TGA) data showed that the composite had a mass loss of ≤5% below 300°C, demonstrating its high-temperature stability.

[0067] It's important to note that the matching relationship between the alternating electric field frequency and ion mobility directly impacts load uniformity. When the frequency is below 900Hz, the ions migrate too far, leading to overload at the pore entrance. When the frequency is above 1100Hz, the ions are unable to fully respond to the electric field changes, and the load rate drops by >20%.

[0068] In this embodiment, low-frequency-high-frequency ultrasound synergy and gradient centrifugation are used to achieve uniform dispersion of the composite anti-wear additive in the PAO base oil, specifically including key operations such as ultrasound parameter optimization, centrifugal purification, and dispersion stability control.

[0069] Typically, the ultrasonic dispersion system consists of a dual-mode transducer: a low-frequency (20–60 kHz) and a high-frequency (0.8–1.2 MHz) transducer. Power densities are controlled within the ranges of 50–100 W / L and 150–250 W / L, respectively. The dispersion medium is PAO6 base oil, with a viscosity of approximately 30–35 mPa·s at 40°C. The mass ratio of the base oil to the additive component is set at 85:15.

[0070] Specifically, the bifunctional quantum dots (60 parts) obtained in step 1, the liquid metal-COF composite (25 parts) obtained in step 4, and the gradient-doped diamond nanocrystals (15 parts) obtained in step 3 were sequentially added to a PAO base oil and pre-stirred (500 rpm, 30 minutes) to form a coarsely dispersed suspension. In one possible implementation, low-frequency ultrasound (40 kHz, 50 W / L, and a treatment time of 30 minutes) was first applied to the system. Microjets (velocity ≥ 100 m / s) generated by the collapse of cavitation bubbles were used to break up micron-sized soft aggregates.

[0071] The system then switched to high-frequency ultrasound mode, adjusting the parameters to 1 MHz, 200 W / L, and a treatment time of 15 minutes. The high-frequency standing wave field, through the action of acoustic radiation forces, induced the nanoparticles to align in an orderly manner along the nodal planes.

[0072] Example 1: Component mass fraction: Surface modified boron nitride quantum dots: 60 parts; Gallium-based liquid metal carrier (Ga-In-Sn-Ge alloy / COF composite): 25 parts; Neodymium gradient doped diamond nanocrystals: 15 parts.

[0073] Key points of preparation process: BN quantum dot synthesis: 500W plasma treatment for 30min (Ar / H2+acrylic acid / propylene oxide mixture) to obtain 1.5-2.5nm quantum dots.

[0074] Liquid metal alloy: Ga65%, In22%, Sn12.5%, Ge0.5% (atomic ratio), rapidly cooled to -20°C at 1000°C / s, and granulated to obtain 8-12μm powder.

[0075] Nd@Dia synthesis: microwave CVD pulse doping (10 Hz, 30% duty cycle), surface Nd 1.2 at%.

[0076] Composite dispersion: 40kHz+1MHz multi-stage ultrasonic treatment, D50=65nm after gradient centrifugation.

[0077] Example 2: Component mass fraction: Surface modified boron nitride quantum dots: 70 parts; Gallium-based liquid metal carrier: 20 parts; Neodymium gradient doped diamond nanocrystals: 10 parts.

[0078] Performance optimized design: High BN quantum dot content (70 parts): By increasing the proportion of quantum dots, the interlayer slip lubrication mechanism is enhanced, making it suitable for low-load and high-speed working conditions.

[0079] Process adjustment: The carboxyl group density of quantum dots is increased to 7 groups / nm 2 (plasma power 550W); The liquid metal quenching rate is increased to 1200℃ / s, and the particle size is refined to 5-8μm; The dispersion process increased the high-frequency ultrasound duration to 20 min (1 MHz, 220 W / L).

[0080] Measured data: Friction coefficient: 0.032 (1000rpm, 50N load); Wear spot diameter: 0.12 mm (33% lower than that of Example 1).

[0081] Example 3: Component mass fraction: Surface modified boron nitride quantum dots: 50 parts; Gallium-based liquid metal carrier: 35 parts; Neodymium gradient-doped diamond nanocrystals: 15 parts; Performance optimized design: High liquid metal content (35 parts): Enhances adaptability to heavy-load conditions by increasing the proportion of self-repairing carriers, making it suitable for impact load scenarios.

[0082] Process adjustment: The liquid metal Ge content is increased to 0.6at%, and the phase transition temperature is 11.8℃; The surface doping level of Nd@Dia was increased to 1.5at%, and the grain size was compressed to 20-30nm; The COF pore size was compressed to 1.0 nm (microfluidic channel width 180 → 40 → 180 μm).

[0083] Measured data: Extreme pressure performance PB value: 2600N (18% higher than that of Example 1); 200℃ high temperature wear rate: 3.2×10 -6 mm 3 / N·m (meets aviation lubricant standards).

[0084] Example 4: Component mass fraction: Surface modified boron nitride quantum dots: 55 parts; Gallium-based liquid metal carrier: 30 parts; Neodymium gradient-doped diamond nanocrystals: 15 parts; BN quantum dot / liquid metal synergy: Balances lubrication and self-healing functions through a 55:30 ratio, suitable for wide temperature range (-30 to 180°C) scenarios.

[0085] Process innovation: The quantum dot interlayer spacing was expanded to 0.35 nm (by adjusting the plasma treatment gas ratio); The proportion of liquid metal COF loaded with ionic liquid increased to 80wt%; Dispersive centrifugation adds a low-temperature (4°C) sedimentation separation step.

[0086] Performance highlights: -30℃ low temperature starting friction coefficient: 0.055 (conventional additives>0.1); 180℃ high temperature durability: continuous lubrication time>8h (ASTMD5800).

[0087] Comparative Example 1: Compared with Example 1, the difference is that the surface-modified boron nitride quantum dots are removed, the proportions of the remaining components are adjusted to 40 parts of liquid metal carrier and 15 parts of Nd@Dia, and the other preparation conditions are the same.

[0088] Comparative Example 2: Compared with Example 1, the difference is that: no plasma treatment is performed, and unmodified hexagonal boron nitride nanosheets (size 200-500 nm, no functional group) are directly used, and the other preparation conditions are the same.

[0089] Comparative Example 3: Compared with Example 1, the difference is that the addition amount of BN quantum dots is increased to 80 parts, the proportions of the other components are adjusted to 80 parts of BN, 20 parts of liquid metal carrier, and 10 parts of Nd@Dia, and the other preparation conditions are the same.

[0090] Comparative Example 4: Compared with Example 1, the difference is that the Ge content in the liquid metal carrier is reduced to 0.2%, and the other alloy components are the same as the preparation conditions.

[0091] Comparative Example 5: Compared with Example 1, the difference is that the rapid cooling process is cancelled, the alloy melt is cooled naturally (cooling rate <50° C. / s), and the other preparation conditions are the same.

[0092] Comparative Example 6: Compared with Example 1, the difference is that Nd@Dia is replaced by undoped nanodiamond (particle size 20-50 nm), and the proportions of other components are the same as the preparation conditions.

[0093] Comparative Example 7: Compared with Example 1, the difference is that the pulse doping process is cancelled, NdCl3 vapor is continuously introduced (without gradient distribution), and the other preparation conditions are the same.

[0094] Comparative Example 8: Compared with Example 1, the difference is that the COF pore diameter is increased to 1.8 nm, and the other preparation conditions are the same.

[0095] Comparative Example 9: Compared with Example 1, the difference is that the ionic liquid-covalent organic framework complex is removed and the unloaded liquid metal alloy powder is directly used. The other preparation conditions are the same.

[0096] Comparative Example 10: Compared with Example 1, the difference is that the conventional impregnation method is used to load the ionic liquid (not microfluidic dynamic screening), and the other preparation conditions are the same.

[0097] Test Example 1: Experimental equipment and materials Friction tester: SRV-IVOptimol; Lubricant component detection: Agilent 1260 Infinity II HPLC; Test samples: lubricating oils prepared in Example 1, Comparative Example 1, Comparative Example 6, and Comparative Example 9 (added in an amount of 2 wt %); Dual parts: GCr15 bearing steel ball (Φ10mm) and disc (Φ24mm×7.9mm).

[0098] Experimental procedures Sample pretreatment: Each lubricating oil sample was placed in a 60°C thermostat for 24 h to eliminate bubbles; The steel ball and steel disk were ultrasonically cleaned with petroleum ether and acetone for 15 min respectively, and then stored in a desiccating dish after drying.

[0099] Friction test parameter settings: Normal load: 1000±10N; Temperature: 150 ± 2 °C (heating rate 5 °C / min); Frequency: 50Hz (stroke 1mm); Test duration: 120 minutes (the first 10 minutes are the running-in phase, and the data collection interval is 5 minutes).

[0100] Wear spot morphology analysis: After the test, the steel pan was cleaned three times with petroleum ether; Lubricant consumption detection: The residual lubricating oil after the test was collected and filtered through a 0.22 μm filter membrane; HPLC conditions: C18 column (4.6 × 250 mm), mobile phase acetonitrile / water (70:30), flow rate 1 mL / min, detection wavelength 210 nm; The consumption was calculated by the characteristic peak area of ionic liquid (calibration curve R 2 =0.998).

[0101] Data recording specifications: The friction coefficient is the average value of the data in the last 110 minutes (excluding the running-in period); The wear spot diameter was measured three times and the average value was taken, and the error bar represents ±1σ; The lubricant consumption rate is calculated as (initial amount - residual amount) / time.

[0102] Table 1 Test Example 1: Core component function verification experimental data According to Table 1 above, we can see that: This experiment revealed the synergistic lubrication mechanism of multi-scale materials in composite anti-wear additives by systematically removing core functional components. When the surface-modified boron nitride quantum dots were removed, the friction coefficient increased significantly to 0.085, and large-scale adhesion and peeling occurred on the wear spot surface, which was directly related to the interruption of the interlayer slip effect caused by the loss of quantum dots. 2The epoxy groups (with an interlayer spacing of 0.33 nm) originally form a stable dispersion through directional adsorption between the carboxyl groups and the base oil hydrogen bond. Simultaneously, the epoxy groups, stimulated by frictional heat, undergo a ring-opening reaction with the hydroxyl groups on the metal surface, forming a covalently bonded protective film. Without this mechanism, the continuity of the lubricating film is disrupted, and direct metal-to-metal contact causes severe adhesive wear.

[0103] Substituting gradient-doped diamond nanocrystals (Comparative Example 6) increased the friction coefficient to 0.063. While the diamond surface electronic state is manipulated to reduce adhesion energy with the mating metal, the highly reactive carbon dangling bonds on the undoped diamond surface directly induce interfacial chemical adsorption, leading to increased adhesion torque between the friction pairs. Furthermore, the loss of the ultra-low contact angle (<5°) of the hydrogen-terminated surface further weakens the wetting and spreading ability of the lubricant on the diamond surface.

[0104] The removal of the ionic liquid-covalent organic framework complex (Comparative Example 9) caused the lubricant consumption rate to surge to 7.2 μg / min, and a large amount of oxidized debris was detected at the edge of the wear spot. The 1.3 nm pore size of the COF framework originally limited the sudden release of the ionic liquid through the molecular sieving effect, and its π-π stacking structure also inhibited the oxidation of the liquid metal (XPS showed that the Ga2O3 content in Comparative Example 9 increased by 3 times). After losing the COF confinement, the ionic liquid was quickly depleted in the early stages of friction and could not form a continuous lubricating film. At the same time, the hard debris produced by the oxidation of the liquid metal exacerbated the three-body wear, confirming the indivisibility of the component linkage in the claims.

[0105] Test Example 2: Experimental equipment and materials High temperature friction testing machine: CETRUMT-3; Surface analysis equipment: ThermoScientific K-AlphaXPS, FEITalos F200XTEM; Pore size analysis: Micromeritics 3FlexBET analyzer; Test samples: lubricating oils prepared in Example 1, Comparative Example 2, Comparative Example 5, Comparative Example 7, and Comparative Example 10; Special fixture: customized high temperature sealed chamber (temperature resistant to 300℃).

[0106] Experimental procedures High temperature durability test: Set the initial temperature to 80°C, increase the temperature to 180°C at a gradient of 20°C / 10min, and maintain the final temperature for 4 hours; The normal load is constant at 800N, the reciprocating frequency is 30Hz, and the stroke is 2mm; The friction coefficient was collected every 10 min, and the temperature-friction coefficient evolution curve was recorded.

[0107] Plasma treatment validation: The unmodified BN nanosheets of Comparative Example 2 were tested under the same experimental conditions; After the test, the friction interface deposits were scraped off and XPS was used to detect the shift of B1s, N1s, and O1s peak positions; The intensity change of the C=O bonding peak (288.6 eV) of the BN quantum dots in comparative example 1.

[0108] Liquid metal phase change analysis: The slowly cooled alloy of Comparative Example 5 was prepared Disc, DSC test (-30~50℃, rate 10℃ / min); Tribothermal imaging (FLIRA65 infrared camera) was performed simultaneously to capture the starting temperature of the phase change.

[0109] Gradient doping structure verification: The uniformly doped diamond of Comparative Example 7 was made into ultrathin slices (<50 nm); TEM-EDS line scanning (step size 2 nm) was used to detect the radial distribution curve of Nd element; Comparative Example 1 has a gradient distribution (1.2 at% on the surface → 0.8 at% on the interior).

[0110] Verification of microfluidic screening effect: The conventional impregnation sample of Example 10 was subjected to a BET test and a pore size distribution histogram was drawn; The full width at half maximum (FWHM) of the pore size distribution of the COF of Comparative Example 1.

[0111] Table 2 Test Example 2: Key process parameter verification experimental data According to Table 2 above, we can see that: This experiment reveals the regulation mechanism of key process parameters on the microstructure and tribological properties of the material. When the plasma dual functional group modification process is cancelled, the carboxyl density of the boron nitride quantum dots drops sharply to 1.8 groups / nm. 2 (XPSO1s peak intensity decreased by 34.7%). The insufficient epoxy grafting rate resulted in a weakening of the hydrogen bonding force between the quantum dots and the base oil. Unmodified BN nanosheets (Comparative Example 2) were disordered during high-temperature friction, with the interlayer spacing compressed from 0.33nm to 0.28nm, losing the intercalation lubrication function, and the friction coefficient fluctuation range expanded to 0.051-0.089. This drastic fluctuation is directly related to the "adhesion-sliding" alternating behavior of the friction interface, confirming the decisive role of the plasma synchronous modification process on the stability of the quantum dot interface.

[0112] The lack of a rapid cooling process for the liquid metal carrier (Comparative Example 5) causes the alloy grains to coarsen, with the average size increasing from 8-12μm to 25μm, and the phase transition temperature rising to 16.2°C. The DSC curve shows that its phase change enthalpy is reduced to 18J / g (28J / g in Example 1), resulting in a decrease in the response efficiency of friction heat triggered self-repair. Infrared thermal imaging captures that when the local hot spot temperature exceeds 180°C, the slowly cooled alloy remains in a solid state and cannot fill the wear pits through liquid phase mass transfer. This phase change hysteresis is closely related to the formation of a metastable structure by the rapid cooling rate (800-1200°C / s) in the claims - ultrafast cooling suppresses grain boundary segregation, allowing the Ga-In-Sn-Ge alloy to maintain a uniform solid solution characteristic at the microscopic scale.

[0113] The absence of the microfluidic dynamic sieving process (Comparative Example 10) widened the COF pore size distribution to 0.55-0.79 nm (BET half-peak width 0.67 nm), and the ionic liquid loading rate dropped from 72% to 45%. The conventional impregnation method lacks the electric field-induced size selectivity, resulting in the partial ionic liquid molecules (such as [BMIM] + Diameter of about 1.2nm) is mechanically trapped outside the COF pores. HPLC detected that the lubricating medium of Comparative Example 10 consumed 62% within the initial 30 minutes of the experiment, while the sustained-release curve of Example 1 showed a linear increase (total consumption 21%). This difference is directly related to the electrophoretic effect caused by the alternating electric field (50V / cm, 1kHz) in the microfluidic process - the charged ionic liquid monomer undergoes a sieving-enrichment cycle in the periodic contraction channel (200→50→200μm), ultimately achieving precise loading with pore size matching. This is the physical basis for the realization of the function of the "ionic liquid-covalent organic framework complex" in the claims.

[0114] Test Example 3: Experimental equipment and materials; Laser particle size analyzer: Malvern Mastersizer 3000 (UK); Differential scanning calorimeter (DSC): TA Instruments Q2000; Impact friction tester: Cameron-PlintTE77 (simulated impact load); Test sample: Example 1 (standard parameters); Comparative Example 3 (80 parts of BN quantum dots); Comparative Example 4 (Ge content 0.2%); Comparative Example 8 (COF pore size 1.8 nm); Experimental procedures Dispersion stability test: Each lubricating oil sample was continuously shaken in a constant temperature shaker (200 rpm) at 25 °C for 24 h; After standing for 0 h, 24 h, and 72 h, the D50 / D90 value was measured by a laser particle size analyzer (the average of 3 measurements was taken); Record the precipitation and stratification phenomenon after standing for 72 hours (visual method + centrifuge tube scale observation).

[0115] Phase change behavior analysis: Liquid metal alloy powder (Comparative Example 4, Example 1) was prepared into φ5 mm thin slices; DSC test parameters: -20℃→50℃, heating rate 5℃ / min, nitrogen protection (50mL / min); compare the phase transition onset temperature, peak temperature and phase transition enthalpy ΔH.

[0116] Extreme working condition simulation test: The impact load was set to 2000 N (5 cycles with an interval of 10 s) and the temperature was set to 200 °C; Materials of mating parts: carbide ball (WC-Co, HV1800) and cast iron disc; After the test, the wear spot diameter was measured (3-point measurement method), and the surface peeling was observed by SEM.

[0117] COF aperture over-limit verification: The COF composite of Comparative Example 8 was subjected to N2 adsorption-desorption test (BET method); Analyze the pore size distribution curve and calculate the average pore size and the most probable pore size. Auxiliary equipment: constant temperature oscillator (dispersion stability test), high temperature vacuum furnace (200℃ pretreatment).

[0118] Experimental steps: Dispersion stability test: Each lubricating oil sample was continuously shaken in a constant temperature shaker (200 rpm) at 25 °C for 24 h; After standing for 0 h, 24 h, and 72 h, the D50 / D90 value was detected by a laser particle size analyzer (the average of 3 measurements was taken); the precipitation and stratification phenomenon after standing for 72 h was recorded (visual method + centrifuge tube scale observation).

[0119] Phase change behavior analysis: Take liquid metal alloy powder (Comparative Example 4, Example 1) to make thin slices; DSC test parameters: -20℃→50℃, heating rate 5℃ / min, nitrogen protection (50mL / min); compare the phase transition onset temperature, peak temperature and phase transition enthalpy ΔH.

[0120] Extreme working condition simulation test: The impact load was set to 2000 N (5 cycles with an interval of 10 s) and the temperature was set to 200 °C; Materials of mating parts: carbide ball (WC-Co, HV1800) and cast iron disc; After the test, the wear spot diameter was measured (3-point measurement method), and the surface peeling was observed by SEM.

[0121] COF aperture over-limit verification: The COF composite of Comparative Example 8 was subjected to N2 adsorption-desorption test (BET method); Analyze the pore size distribution curve and calculate the average pore size and the most probable pore size.

[0122] Table 3 Test Case 3: Boundary Verification Experimental Data (Non-Regular Simulation) According to Table 3 above, we can see that: This experiment verified the critical necessity of component ratios and process parameters by breaking through the parameter boundaries defined in the claims. When the amount of boron nitride quantum dots added was increased to 80 parts (Comparative Example 3), laser particle size detection showed that the D90 value reached 285nm, far exceeding the upper limit of 150nm defined in the claims. Excessive BN quantum dots exceeded the functional group grafting capacity of the plasma modification process, resulting in an increase in the proportion of unmodified surfaces, and the van der Waals force between particles dominated the agglomeration behavior. During the friction process, these agglomerates were embedded in the contact interface as hard third-body abrasives, triggering a failure mode dominated by abrasive wear, and the wear spot diameter expanded to 0.53mm under impact load (0.24mm for Example 1). SEM observations showed that the wear surface was distributed with furrows with a depth of >5μm, which was directly related to the complete loss of the interlayer slip mechanism of BN quantum dots.

[0123] The liquid metal alloy with Ge content reduced to 0.2% (Comparative Example 4) showed significant degradation of grain boundary stability. The DSC curve showed that its phase transition temperature rose to 17.8°C, and the phase transition enthalpy decreased to 14 J / g (28 J / g in Example 1). This change is due to the weakening of the grain boundary pinning effect of the Ge element - Ge atoms cannot effectively suppress the grain coarsening of the Ga-In-Sn alloy during the rapid cooling process, and the average grain size increases from 8-12 μm to 22 μm. Friction thermal imaging shows that when the interface temperature reaches 160°C, the alloy remains solid and cannot fill the wear pits through liquid phase mass transfer. After losing the dynamic self-healing ability, local material transfer occurs on the surface of the wear spot (EDS detects that the Fe element content of the counterpart is >12 at%), which confirms the key role of the Ge content of 0.4-0.6% in maintaining the metastable alloy structure.

[0124] The expansion of COF pore size to 1.8 nm (Comparative Example 8) disrupts the kinetic balance of sustained release of ionic liquids. BET data show that the pore size distribution widens to 0.8-2.2 nm, making some ionic liquid monomers (such as [BMIM] + Diameter 1.2nm) is released quickly at the beginning of friction, and the lubricating medium consumption has reached 68% after 30 minutes of testing. This sudden release behavior causes the friction coefficient to fluctuate violently between 0.025-0.062, while in Example 1, due to the molecular sieving effect of the 1.3nm pore size, the ionic liquid is linearly released (total consumption 21%). After losing pore size control, the π-π stacking structure of the COF framework is also unable to effectively block oxygen diffusion. XPS detected that the Ga2O3 content on the liquid metal surface increased by 2.3 times. The accumulation of oxidized wear debris further aggravated the three-body wear. After the impact test, peeling pits with a depth of 8μm appeared on the edge of the wear spot, revealing the irreplaceable nature of the COF pore size of 1.0-1.5nm in the claims for maintaining the stability of the lubrication system.

[0125] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A composite anti-wear additive for lubricating oil, characterized in that: The composition comprises the following components in parts by weight: Surface-modified layered boron nitride quantum dots: 50-70 parts; Gallium-based liquid metal carrier: 20-35 parts; Rare earth-doped diamond nanocrystals: 10-15 parts; The gallium-based liquid metal carrier is a gallium-indium-tin-germanium alloy and an ionic liquid-covalent organic framework complex.

2. The composite anti-wear additive for lubricating oil according to claim 1, characterized in that: The surface of the surface-modified layered boron nitride quantum dots is grafted with carboxyl and epoxy bifunctional groups, and the carboxyl density is 3-8 groups / nm 2 , the interlayer spacing is 0.30-0.35 nm, and the quantum dot size is 1-3 nm.

3. The composite anti-wear additive for lubricating oil according to claim 1, characterized in that: The atomic percentage composition of the gallium-indium-tin-germanium alloy is: Ga 64-66%, In 21-23%, Sn 12-13%, Ge 0.4-0.6%.

4. The composite anti-wear additive for lubricating oil according to claim 1, characterized in that: In the rare earth-doped diamond nanocrystal, the doping amount of neodymium is 0.5-1.5at%, and the doping concentration is gradient distributed along the radial direction of the grain, with the surface doping amount being 0.3-0.8at% higher than that in the interior; The diamond nanocrystal has a grain size of 20-50 nm and a surface hydrogen-terminated structure.

5. The composite anti-wear additive for lubricating oil according to claim 1, characterized in that: In the ionic liquid-covalent organic framework composite, the pore diameter of the covalent organic framework is 1.0-1.5 nm, and the ionic liquid loading rate is 60-80 wt %.

6. A method for preparing a composite anti-wear additive for lubricating oil, according to the composite anti-wear additive for lubricating oil according to any one of claims 1 to 5, characterized in that: The following steps are involved: Step 1: Synchronously modifying the surface functional groups of hexagonal boron nitride by plasma vapor deposition to prepare bifunctional quantum dots; Step 2: vacuum melting the gallium-indium-tin-germanium alloy and quenching it into granules; Step 3: synthesizing gradient rare earth doped diamond nanocrystals by microwave plasma chemical vapor deposition; Step 4: loading the ionic liquid-covalent organic framework complex onto the liquid metal carrier by microfluidic electrochemical deposition; Step 5: Multi-stage ultrasonic dispersion and compounding of the components.

7. The method for preparing a composite anti-wear additive for lubricating oil according to claim 6, characterized in that: In the step 1, the hexagonal boron nitride block is placed in a radio frequency plasma reactor, and an argon-hydrogen mixed gas Ar:H2 volume ratio of 90-95:5-10 and an acrylic acid / propylene oxide mixed gas molar ratio of 1:1.8-2.2 are simultaneously introduced; The plasma was excited at 400-600W RF power for 25-35min, and the surface-modified quantum dots were captured by liquid nitrogen cold trap.

8. The method for preparing a composite anti-wear additive for lubricating oil according to claim 6, characterized in that: In the step 2, the temperature is raised to 280-320° C. under argon protection with O2≤1ppm, stirred and melted for 1.5-2.5 hours, and then rapidly cooled to -25 to -15° C. at a rate of 800-1200° C. / s, and crushed to obtain 5-15 μm alloy powder.

9. The method for preparing a composite anti-wear additive for lubricating oil according to claim 6, characterized in that: In the step 3, a 200 nm diamond seed layer is pre-deposited on a silicon substrate, and NdCl3 vapor is pulsed in at a frequency of 8-12 Hz and a duty cycle of 25-35%; Under a microwave power of 2.8-3.2kW and a cavity pressure of 4.5-5.5kPa, the gradient-doped diamond nanocrystals are grown in a CH4 / H2 gas mixture with a volume ratio of 0.5-1.5:98.5-99.5 for 7-9 hours.

10. The method for preparing a composite anti-wear additive for lubricating oil according to claim 6, characterized in that: In the step 4, the liquid metal alloy powder and the 0.08-0.12M ionic liquid solution are pumped into the microfluidic chip; Apply an alternating electric field of 45-55 V / cm at a frequency of 900-1100 Hz and control the deposition voltage to 0.4-0.6 V to achieve size screening deposition of the ionic liquid-covalent organic framework.

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