A composite anti-wear additive for lubricating oil and its preparation method

Abstract

This application relates to the field of lubricating oil additive technology, and discloses 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; wherein, the gallium-based liquid metal carrier is a gallium-indium-tin-germanium alloy and ionic liquid-covalent organic framework composite, and the surface-modified layered boron nitride quantum dots are grafted with carboxyl and epoxy bifunctional groups on their surface, with a carboxyl group 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. 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 particle size of the alloy powder is 5-15 μm, and the melting point is ≤12℃. By simultaneously activating carboxyl and epoxy radicals via plasma, the synergistic enhancement of the active sites on the quantum dot surface is achieved.

Description

Technical Field

[0001] This invention relates to the field of lubricating oil additives, specifically to a composite anti-wear additive for lubricating oil and its preparation method. Background Technology

[0002] Under extreme conditions such as high load and extreme pressure, the effectiveness of lubricants directly affects the service life and operating efficiency of equipment. Traditional lubrication systems rely heavily on the synergistic effect of base oils and additives to reduce the coefficient of friction through the formation of boundary lubrication films and improved anti-wear properties. However, existing technologies have significant shortcomings in terms of the dispersion stability, tribochemical reactivity, and continuity of lubrication films of nano-additives, leading to an increased risk of lubrication failure. Nanoparticles, due to their high specific surface area and surface energy, possess excellent extreme pressure friction-reducing properties and are widely used in lubrication systems. For example, boron nitride quantum dots (BNQDs) and rare earth-doped diamond nanoparticles (Nd@Dia) form physical adsorption films or chemical reaction films at the friction pair interface due to their excellent mechanical strength and chemical inertness, thereby reducing direct contact wear. However, due to van der Waals forces and surface polarity between nanoparticles, they are prone to agglomeration in oil-based media, forming micron-sized or even larger aggregates. Especially 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, single-stage centrifugation, low-frequency ultrasound, or mechanical stirring are commonly used to disperse nanoparticles. While single-stage centrifugation can initially separate coarse particles and large agglomerates, its ability to identify and remove nanoscale agglomerates is limited, especially when there are overlapping areas in the particle size distribution, which can easily lead to the residue of fine agglomerates. These poorly dispersed particles can become stress concentration points under extreme pressure conditions, causing localized rupture of the lubricating film and further aggravating wear.

[0004] Existing technologies have significant shortcomings in terms of the dispersion stability, functionalization modification, and maintenance of extreme pressure properties of nanoparticles. In particular, 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] To address the shortcomings of existing technologies, this invention provides a composite anti-wear additive for lubricating oil and its preparation method, 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 in traditional lubricating additives.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a composite anti-wear additive for lubricating oil, comprising the following components in parts by weight:

[0007] Surface-modified layered boron nitride quantum dots: 50-70 parts;

[0008] Gallium-based liquid metal carrier: 20-35 parts;

[0009] Rare earth-doped diamond nanocrystals: 10-15 parts;

[0010] The gallium-based liquid metal carrier is a gallium-indium-tin-germanium alloy and an ionic liquid-covalent organic framework composite.

[0011] Preferably, the surface-modified layered boron nitride quantum dots are grafted with carboxyl and epoxy bifunctional groups, and the carboxyl group density is 3-8 groups / nm. 2 The interlayer spacing is 0.30-0.35nm, and the quantum dot size is 1-3nm.

[0012] 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%;

[0013] The alloy powder has a particle size of 5-15 μm and a melting point ≤12℃.

[0014] Preferably, in the rare earth-doped diamond nanocrystals, the neodymium doping amount is 0.5-1.5 at%, and the doping concentration is distributed in a gradient along the radial direction of the grain, with the surface doping amount being 0.3-0.8 at% higher than that inside.

[0015] The diamond nanocrystals have a grain size of 20-50 nm and a hydrogen-terminated surface structure.

[0016] 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%.

[0017] This invention also provides a method for preparing a composite anti-wear additive for lubricating oil, comprising the following steps:

[0018] Step 1: Prepare bifunctional quantum dots by simultaneously modifying the surface functional groups of hexagonal boron nitride through plasma vapor deposition;

[0019] Step 2: Vacuum melting of gallium-indium-tin-germanium alloy followed by rapid cooling and granulation;

[0020] Step 3: Synthesis of gradient rare earth-doped diamond nanocrystals by microwave plasma chemical vapor deposition;

[0021] Step 4: Load the ionic liquid-covalent organic framework complex onto a liquid metal support via microfluidic electrochemical deposition;

[0022] Step 5: Multi-stage ultrasonic dispersion and compounding of each component.

[0023] Preferably, in step one, the hexagonal boron nitride block is placed in a radio frequency plasma reactor, and an argon-hydrogen mixture with a volume ratio of Ar:H2 of 90-95:5-10 and a mixture of acrylic acid / propylene oxide with a molar ratio of 1:1.8-2.2 are simultaneously introduced.

[0024] Shooting at 400-600W.

[0025] Preferably, in step two, under argon protection 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 to obtain 5-15μm alloy powder.

[0026] Preferably, in step three, a 200nm diamond seed layer is pre-deposited on a silicon substrate, and NdCl3 vapor is pulsed through at a frequency of 8-12Hz with a duty cycle of 25-35%.

[0027] Gradient-doped diamond nanocrystals were formed by growing in a CH4 / H2 mixed gas volume ratio of 0.5-1.5:98.5-99.5 for 7-9 hours under microwave power of 2.8-3.2kW and cavity pressure of 4.5-5.5kPa.

[0028] Preferably, in step four, the liquid metal alloy powder and the 0.08-0.12M ionic liquid solution are pumped into the microfluidic chip;

[0029] By applying an alternating electric field of 45-55V / cm at a frequency of 900-1100Hz and controlling the deposition voltage at 0.4-0.6V, the size sieving deposition of ionic liquid-covalent organic framework can be achieved.

[0030] This invention provides a composite anti-wear additive for lubricating oil and its preparation method. It has the following beneficial effects:

[0031] 1. This invention achieves synergistic enhancement of active sites on the surface of quantum dots through a technique of simultaneous plasma activation of carboxyl and epoxy radicals. Traditional single-functional group modification leads to insufficient dispersion stability of quantum dots, and the lubricating film is prone to failure due to weak interfacial bonding.

[0032] 2. This invention precisely controls the phase transformation behavior of alloys through the grain boundary regulation effect based on Ge element, achieving instant self-repair triggered by frictional heat. In the prior art, liquid metals cannot respond to interface temperature rises in a timely manner due to phase transformation temperature mismatch, resulting in delayed wear repair.

[0033] 3. This invention employs microwave pulse gradient doping technology to form a structure enriched with rare earth elements on the surface, effectively suppressing the adhesion of friction pairs. Traditional uniform doping schemes, due to insufficient surface activity, are prone to adhesive wear of the lubricating film under high pressure.

[0034] 4. This invention combines an alternating electric field with a channel contraction design to achieve precise control of the aperture and on-demand release of the lubricating medium. Traditional impregnation methods suffer from uneven aperture distribution, leading to uncontrollable lubricating medium release and a significant decrease in lubricating film stability. Attached Figure Description

[0035] Figure 1 This is a flowchart of the method of the present invention. Detailed Implementation

[0036] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] This invention provides a composite anti-wear additive for lubricating oil, comprising the following components in parts by weight:

[0038] Surface-modified layered boron nitride quantum dots: 50-70 parts;

[0039] Gallium-based liquid metal carrier: 20-35 parts;

[0040] Rare earth-doped diamond nanocrystals: 10-15 parts;

[0041] Among them, the gallium-based liquid metal carrier is a gallium-indium-tin-germanium alloy and an ionic liquid-covalent organic framework composite.

[0042] The surface of the surface-modified layered boron nitride quantum dots is grafted with bifunctional groups of carboxyl and epoxy groups, with a carboxyl group density of 3-8 groups / nm. 2 The interlayer spacing is 0.30-0.35nm, and the quantum dot size is 1-3nm.

[0043] The atomic percentage composition of gallium-indium-tin-germanium alloys is: Ga 64-66%, In 21-23%, Sn 12-13%, Ge 0.4-0.6%.

[0044] In rare earth-doped diamond nanocrystals, the neodymium doping amount is 0.5-1.5 at%, and the doping concentration is distributed in a gradient along the radial direction of the grain, with the surface doping amount being 0.3-0.8 at% higher than that inside.

[0045] Diamond nanocrystals have a grain size of 20-50 nm and a hydrogen-terminated surface structure.

[0046] 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%.

[0047] Please see the appendix Figure 1 The present invention also provides a method for preparing a composite anti-wear additive for lubricating oil, comprising the following steps:

[0048] Step 1: Prepare bifunctional quantum dots by simultaneously modifying the surface functional groups of hexagonal boron nitride through plasma vapor deposition;

[0049] Step 2: Vacuum melting of gallium-indium-tin-germanium alloy followed by rapid cooling and granulation;

[0050] Step 3: Synthesis of gradient rare earth-doped diamond nanocrystals by microwave plasma chemical vapor deposition;

[0051] Step 4: Load the ionic liquid-covalent organic framework complex onto a liquid metal support via microfluidic electrochemical deposition;

[0052] Step 5: Multi-stage ultrasonic dispersion and compounding of each component.

[0053] In step one, the hexagonal boron nitride block is placed in the radio frequency plasma reactor, and an argon-hydrogen mixture with a volume ratio of Ar:H2 of 90-95:5-10 and an acrylic acid / propylene oxide mixture with a molar ratio of 1:1.8-2.2 are simultaneously introduced.

[0054] The plasma was excited at 400-600W RF power and processed for 25-35 minutes. The surface-modified quantum dots were then captured using a liquid nitrogen cold trap.

[0055] In step two, under argon protection 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 to obtain 5-15μm alloy powder.

[0056] In step three, a 200nm diamond seed layer is pre-deposited on a silicon substrate, and NdCl3 vapor is pulsed through at a frequency of 8-12Hz with a duty cycle of 25-35%.

[0057] Gradient-doped diamond nanocrystals were formed by growing in a CH4 / H2 mixed gas volume ratio of 0.5-1.5:98.5-99.5 for 7-9 hours under microwave power of 2.8-3.2kW and cavity pressure of 4.5-5.5kPa.

[0058] In step four, liquid metal alloy powder and 0.08-0.12M ionic liquid solution are pumped into the microfluidic chip;

[0059] By applying an alternating electric field of 45-55V / cm at a frequency of 900-1100Hz and controlling the deposition voltage at 0.4-0.6V, the size sieving deposition of ionic liquid-covalent organic framework can be achieved.

[0060] In this embodiment, a high-energy plasma-induced reaction is used to activate the surface of hexagonal boron nitride (h-BN), and carboxyl-derived monomers (such as acrylic acid) and epoxy-derived monomers (such as propylene oxide) are introduced into the plasma atmosphere to form layered boron nitride quantum dots with a bifunctional modified structure.

[0061] In general, plasma processing systems use radio frequency power sources to excite the gas medium. In this embodiment, a radio frequency of 13.56MHz is used, and the radio frequency power is controlled within the range of 400–600W.

[0062] Specifically, hexagonal boron nitride bulk samples with particle sizes between 50 and 100 μm were first placed at the center of the radio frequency plasma reactor, and the system was evacuated to a base pressure of approximately 5.0 × 10⁻⁶. -3 Pa ensures the purity of the reaction atmosphere. Then, a mixture of argon and hydrogen gas, with a volume ratio controlled at 90–95:5–10, is introduced as the plasma sustaining gas. Argon provides the electron-excited substrate, while hydrogen assists in reducing residual oxygen functional groups on the surface.

[0063] Subsequently, while maintaining a stable input of the main gas, a mixture of functional monomers is introduced. Alternatively, the functional monomers can be a mixture of acrylic acid and propylene oxide, with a preferred molar ratio in the range of 1:1.8–2.2, wherein acrylic acid provides the –COOH group source and propylene oxide provides the –CH(CH2)O– epoxy group source.

[0064] Under the action of radio frequency plasma, the above-mentioned 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 sites at the edge of the BN surface to form covalent bond structures under the synergistic effect of high-energy electron collisions and plasma ultraviolet irradiation.

[0065] In one possible implementation, to further improve the selectivity of surface modification and the steric hindrance control effect, a liquid nitrogen cold trap is set at the outlet position to capture quantum dot-level products with particle sizes in the range of 1–3 nm.

[0066] The formed quantum dot samples were characterized by atomic force microscopy (AFM), and the interlayer spacing could be controlled within the range of 0.30–0.35 nm, indicating that the weak van der Waals interactions between the layers were not significantly disrupted and the layered stability was still maintained; the carboxyl group density was 3–8 groups / nm. 2 Within a certain range, it effectively improves its stable dispersibility in non-polar base oils.

[0067] 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. -1 Near (carboxyl C=O stretching vibration), and 915–950 cm⁻¹ -1 The region (epoxy group tension vibration) indicates that the bifunctional group has been stably grafted.

[0068] In the specific modification mechanism, acrylic acid radicals preferentially form σ-type B–O–C structures with B vacancies at the edge of BN, while epoxy groups are prone to ring-opening reactions during friction-induced heating, exposing hydroxyl groups and ether bonds, thereby enhancing the interfacial interaction between them and polar functional groups in the liquid metal or COF framework.

[0069] It should be noted that free radical recombination side reactions occur during the modification reaction, so the reaction time is generally controlled between 25 and 35 minutes. If it is too long, it may induce surface carbonization, affecting the size and activity of quantum dots.

[0070] To facilitate subsequent processing, the obtained quantum dots can be freeze-dried to obtain powder form and stored at -20°C.

[0071] In the composite anti-wear additive preparation system of this invention, step two undertakes the task of alloying design and microstructure control of the liquid metal carrier. This step needs to achieve chemical bonding compatibility with the surface-modified quantum dots obtained in step one, and provide a high specific surface area substrate for the ionic liquid-covalent organic framework composite loading in step four. By precisely controlling the alloy composition and rapid cooling process parameters, the phase transition response and self-healing ability of the liquid metal under frictional heat triggering are realized, providing dynamic interface support for multi-component synergistic lubrication.

[0072] In this embodiment, gallium-based liquid metal alloy powder is prepared using a combination of vacuum melting and ultrafast quenching technology, specifically including key steps such as raw material ratio, melting process, and quenching granulation.

[0073] Generally, the alloy raw materials include high-purity gallium, indium, tin, and germanium, all with a purity ≥99.9%. As a preferred option, the atomic percentage ratio of each component is: Ga 64–66%, In 21–23%, Sn 12–13%, and Ge 0.4–0.6%. The trace addition of germanium is used for grain boundary strengthening and phase transition temperature regulation; a deviation in its content exceeding ±0.05% will cause a shift in the alloy's melting range.

[0074] Specifically, under an argon protective atmosphere (O2 content ≤ 1 ppm), the weighed metal raw materials are placed in a vacuum arc melting furnace. The melting temperature is controlled within the range of 280–320℃, and the holding time is 1.5–2.5 hours. During the melting process, a mechanical stirring rate of 200–300 rpm is used to promote component homogenization and avoid segregation. It should be noted that germanium's melting point (938℃) is significantly higher than that of other components, and a staged heating strategy is required to ensure its complete dissolution: first, the temperature is raised to 400℃ to pre-melt the germanium powder, and then the temperature is lowered to 300℃ to add gallium, indium, and tin.

[0075] In one possible implementation, a copper mold quenching process is used after melting. 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.

[0076] The rapidly cooled alloy ingots were mechanically crushed and vibratory sieved to obtain regular spherical powder with a particle size of 5–15 μm. The crushing process was carried out in a liquid nitrogen cryogenic environment to prevent lattice distortion caused by work hardening. The sieved powder was characterized by scanning electron microscopy (SEM), showing a smooth surface and no oxide layer, meeting the interface requirements for subsequent microfluidic deposition.

[0077] Alternatively, the phase transformation characteristics of the alloy powder can be verified using differential scanning calorimetry (DSC). Typical DSC curves show an endothermic peak in the 10–12 °C range, corresponding to a solid-liquid phase transformation process with a melting enthalpy ΔH of 25–30 J / g. The phase transformation temperature is negatively correlated with the Ge content.

[0078] Furthermore, in some embodiments, the grain size of the alloy powder was calculated using X-ray diffraction (XRD) at half maximum width at half maximum (FWHM), and the results showed an average grain size ≤ 500 nm and a FWHM ≥ 0.5° for the (111) crystal plane diffraction peak, confirming the existence of a nanocrystalline structure. This microstructure is beneficial for dissipating energy through grain boundary slip during friction, thereby reducing the wear rate.

[0079] It is important to emphasize that the coordinated control of quenching rate and germanium content is key to achieving the target phase transition temperature. When the quenching rate is below 800℃ / s, the alloy will form a coarse dendritic structure, leading to phase transition hysteresis and reduced repair efficiency. Conversely, when the germanium content exceeds 0.6 at%, the alloy's brittleness increases significantly, making it prone to microcrack defects during fracture.

[0080] 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 rare-earth elements (neodymium) and surface hydrogen termination treatment. The process parameters must match the liquid metal phase transformation characteristics of step two and provide a highly active substrate for the ionic liquid composite loading in step four.

[0081] In this embodiment, pulsed microwave plasma CVD process is used to directionally grow gradient-doped diamond nanocrystals on a silicon substrate, specifically including key operations such as seed layer pre-deposition, neodymium doping gradient control, and hydrogen-terminated surface treatment.

[0082] Typically, a microwave plasma CVD system includes a 2.45 GHz microwave source, a gas flow controller, a pulsed gas inlet device, and a vacuum chamber. The ultimate vacuum level of the chamber is ≤1.0 × 10⁻⁶. -3 Pa, microwave power adjustable range 1–5kW, process gases include methane (CH4), hydrogen (H2) and neodymium chloride (NdCl3) vapor.

[0083] Specifically, a diamond seed layer is first pre-deposited on the silicon substrate surface. Alternatively, an ultrasonic nanodiamond suspension (particle size 5–10 nm) is spin-coated onto the silicon wafer surface, followed by hydrogen plasma etching (1.2 kW power, 30 min) to remove amorphous carbon, forming a uniform seed layer with a thickness of approximately 200 nm. This layer provides nucleation sites for subsequent diamond epitaxial growth, with a coverage of ≥95%.

[0084] Microwave power was controlled within the range of 2.8–3.2 kW, and 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 is performed at a growth rate of approximately 0.5–1.0 μm / h, and a doped layer with a thickness of 1.2–1.8 μm is obtained after 7–9 hours.

[0085] Regarding gradient doping control, the Nd atom concentration decreases from the surface to the interior along the growth direction (i.e., the grain radial direction). The surface doping amount is determined by XPS depth profiling, with typical values ​​of 1.2–1.5 at%, and the interior doping amount decreases to 0.4–0.7 at%, forming a concentration gradient difference Δ[Nd] = 0.3–0.8 at%. This gradient distribution is achieved by adjusting the timing linkage between the pulse frequency and microwave power, for example, a pulse frequency of 12 Hz for the first 4 hours and then decreasing to 8 Hz for the next 5 hours, so that the doping concentration decreases linearly with increasing thickness.

[0086] During the hydrogen termination treatment, the flow of CH4 and NdCl3 was stopped, and a pure H2 atmosphere (flow rate 500 sccm) was switched on. 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 tests showed that the contact angle of the treated surface was ≤5°, significantly lower than that of the oxygen-terminated surface (>60°), confirming that the dangling bonds were completely hydrogen-saturated.

[0087] As a verification method, Raman spectroscopy was used to analyze the purity of the diamond phase. The characteristic peak is located at 1332 cm⁻¹. -1 (sp 3 The half-width (FWHM) of the key is ≤8cm -1 This indicates that the crystal quality is close to that of a single crystal. And at 1500–1600 cm⁻¹... -1 The amorphous carbon peak intensity ratio is less than 5%, indicating that the impurity phase is effectively suppressed.

[0088] It should be noted that the matching relationship between microwave power and cavity pressure is crucial to the gradient doping effect. When the cavity pressure is below 4.5 kPa, the plasma plume distribution is uneven, resulting in doping concentration fluctuations > ±0.2 at%. Conversely, power exceeding 3.2 kW may induce diamond graphitization, leading to increased doping concentration. 2 The hybrid carbon content increased to >10%.

[0089] In summary, through precise control of the above process parameters, the obtained gradient-doped diamond nanocrystals possess both high hardness (≥80 GPa) and low interfacial adhesion energy (≤0.15 J / m). 2 Its surface hydrogen-terminated structure can effectively promote chemical bonding with the liquid metal carrier, providing a stable friction interface for multi-component synergistic lubrication.

[0090] In this embodiment, a combination of dynamic size sieving and electric field-assisted deposition is used to confine the ionic liquid within the nanopores of the COF framework. This includes key operations such as microfluidic channel design, electric field parameter optimization, and composite structure characterization.

[0091] Typically, microfluidic chips are made of polydimethylsiloxane (PDMS), and the channel width is controlled within the range of 50–200 μm using photolithography masks. The channel geometry is designed as an alternating contraction-expansion type, with an inlet width of 200 μm, a contraction zone width of 50 μm, and an expansion zone width returning to 200 μm, with a cycle length of 5 mm. This structure achieves particle size screening through fluid shear force gradients; large aggregates (>1.5 nm) break up or become trapped in the contraction zone due to shear stress concentration.

[0092] Specifically, the liquid metal alloy powder (particle size 5–15 μm) obtained in step two 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 fluid shearing.

[0093] An alternating electric field is applied synchronously to enhance deposition selectivity. Alternatively, the electric field strength is set to 45–55 V / cm, frequency 900–1100 Hz, and direction perpendicular to the fluid flow. During the positive half-cycle, anions (such as PF6) are... - ) migrate to the liquid metal surface; the negative half-cycle drives cations (such as BMIM) to migrate. + ) Directional movement. The penetration depth of the ionic liquid within the COF channels is controlled by adjusting the deposition voltage (0.4–0.6 V vs. Ag / AgCl reference electrode). The deposition time is typically 30–60 minutes until the loading rate reaches 60–80 wt%.

[0094] In some embodiments, elemental distribution can be analyzed by X-ray energy dispersive spectroscopy (EDS) surface scanning, allowing observation of element F (from PF6). - ) and N element (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 show that the mass loss rate of the composite is ≤5% below 300°C, demonstrating its high-temperature stability.

[0095] It should be noted that the matching relationship between the alternating electric field frequency and ion mobility directly affects the load uniformity. When the frequency is below 900Hz, the ion migration distance is too long, leading to overload at the channel inlet; while when the frequency is above 1100Hz, the ions cannot fully respond to the electric field changes, and the load rate decreases by more than 20%.

[0096] In this embodiment, a combination of low-frequency and high-frequency ultrasonic synergy and gradient centrifugation is used to achieve uniform dispersion of composite anti-wear additives in PAO base oil. Specifically, key operations include ultrasonic parameter optimization, centrifugal purification, and dispersion stability control.

[0097] Typically, the ultrasonic dispersion system consists of a dual-mode transducer with low frequency (20–60 kHz) and high frequency (0.8–1.2 MHz), with power densities controlled in 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℃, and its mass ratio to the additive components is set at 85:15.

[0098] Specifically, the bifunctional quantum dots (60 parts) obtained in step one, the liquid metal-COF composite (25 parts) obtained in step four, and the gradient-doped diamond nanocrystals (15 parts) obtained in step three are sequentially added to PAO base oil and pre-stirred (500 rpm, 30 min) to form a coarsely dispersed suspension. In one possible implementation, low-frequency ultrasound is first applied to the system with parameters set at 40 kHz, 50 W / L, and a treatment time of 30 min, utilizing the microjets (velocity ≥100 m / s) generated by cavitation bubble collapse to break up the micron-sized soft aggregates.

[0099] The system was then switched to high-frequency ultrasonic mode, with parameters adjusted to 1 MHz, 200 W / L, and a processing time of 15 minutes. The high-frequency standing wave field induced the nanoparticles to align orderly along the nodal surfaces through acoustic radiation force.

[0100] Example 1:

[0101] Component mass parts:

[0102] Surface-modified boron nitride quantum dots: 60 parts;

[0103] Gallium-based liquid metal carrier (Ga-In-Sn-Ge alloy / COF composite): 25 parts;

[0104] Neodymium gradient-doped diamond nanocrystals: 15 parts.

[0105] Key points of the preparation process:

[0106] Synthesis of BN quantum dots: 500W plasma treatment for 30 min (Ar / H2 + acrylic acid / propylene oxide mixture) yielded 1.5-2.5 nm quantum dots.

[0107] Liquid metal alloy: Ga 65%, In 22%, Sn 12.5%, Ge 0.5% (atomic ratio), rapidly cooled to -20℃ at 1000℃ / s, granulated to obtain 8-12μm powder.

[0108] Nd@Dia synthesis: microwave CVD pulse doping (10Hz, 30% duty cycle), surface Nd 1.2 at%.

[0109] Composite dispersion: 40kHz+1MHz multi-stage ultrasonic treatment, followed by gradient centrifugation, D50 = 65nm.

[0110] Example 2:

[0111] Component mass parts:

[0112] Surface-modified boron nitride quantum dots: 70 parts;

[0113] Gallium-based liquid metal carrier: 20 parts;

[0114] Neodymium gradient-doped diamond nanocrystals: 10 parts.

[0115] Performance optimization design:

[0116] 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, high-speed operating conditions.

[0117] Process adjustments:

[0118] Quantum dot carboxyl group density increased to 7 groups / nm 2 (Plasma power 550W);

[0119] The rapid cooling rate of liquid metal was increased to 1200℃ / s, and the particle size was refined to 5-8μm;

[0120] The dispersion process increases the high-frequency ultrasonic duration to 20 min (1 MHz, 220 W / L).

[0121] Actual measurement data:

[0122] Coefficient of friction: 0.032 (1000 rpm, 50 N load);

[0123] Wear scar diameter: 0.12 mm (33% lower than Example 1).

[0124] Example 3:

[0125] Component mass parts:

[0126] Surface-modified boron nitride quantum dots: 50 parts;

[0127] Gallium-based liquid metal carrier: 35 parts;

[0128] Neodymium gradient-doped diamond nanocrystals: 15 parts;

[0129] Performance optimization design:

[0130] High liquid metal content (35 parts): Enhances adaptability to heavy-duty conditions by increasing the proportion of self-healing carrier, suitable for impact load scenarios.

[0131] Process adjustments:

[0132] The liquid metal Ge content was increased to 0.6 at, and the phase transition temperature was 11.8℃;

[0133] The surface doping concentration of Nd@Dia is increased to 1.5 at, and the grain size is compressed to 20-30 nm;

[0134] COF pore size compressed to 1.0 nm (microfluidic channel width 180→40→180 μm).

[0135] Actual measurement data:

[0136] Extreme pressure performance PB value: 2600N (18% improvement over Example 1);

[0137] Wear rate at 200℃: 3.2×10 -6 mm 3 / N·m (meets aviation lubricant standards).

[0138] Example 4:

[0139] Component mass parts:

[0140] Surface-modified boron nitride quantum dots: 55 parts;

[0141] Gallium-based liquid metal carrier: 30 parts;

[0142] Neodymium gradient-doped diamond nanocrystals: 15 parts;

[0143] BN quantum dot / liquid metal synergy: With a 55:30 ratio to balance lubrication and self-healing function, it is suitable for wide temperature range (-30~180℃) scenarios.

[0144] Technological Innovation:

[0145] The interlayer spacing of quantum dots was increased to 0.35 nm (by adjusting the proportion of plasma processing gas).

[0146] The proportion of liquid metal COF-supported ionic liquid was increased to 80 wt%.

[0147] Dispersion centrifugation adds a low-temperature (4°C) sedimentation separation step.

[0148] Performance Highlights:

[0149] -30℃ low-temperature start-up friction coefficient: 0.055 (common additives > 0.1);

[0150] High-temperature durability at 180°C: continuous lubrication time > 8 hours (ASTM D5800).

[0151] Comparative Example 1:

[0152] Compared with Example 1, the difference is that the surface-modified boron nitride quantum dots were removed, and the proportions of the remaining components were adjusted to 40 parts of liquid metal carrier and 15 parts of Nd@Dia, while the other preparation conditions remained the same.

[0153] Comparative Example 2:

[0154] Compared with Example 1, the difference is that no plasma treatment was performed, and unmodified hexagonal boron nitride nanosheets (size 200-500nm, no functional groups) were used directly, while the other preparation conditions were the same.

[0155] Comparative Example 3:

[0156] Compared with Example 1, the difference is that the amount of BN quantum dots added is increased to 80 parts, and the proportions of the remaining components are adjusted to 80 parts BN, 20 parts liquid metal carrier, and 10 parts Nd@Dia, while the other preparation conditions are the same.

[0157] Comparative Example 4:

[0158] Compared with Example 1, the difference is that the Ge content in the liquid metal carrier is reduced to 0.2%, while the remaining alloy composition is the same as the preparation conditions.

[0159] Comparative Example 5:

[0160] Compared with Example 1, the difference is that the rapid cooling process is cancelled, and the alloy melt is naturally cooled (cooling rate < 50℃ / s), while the other preparation conditions are the same.

[0161] Comparative Example 6:

[0162] Compared with Example 1, the difference is that Nd@Dia is replaced with undoped nanodiamond (particle size 20-50nm), and the proportions of the remaining components are the same as those of the preparation conditions.

[0163] Comparative Example 7:

[0164] 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.

[0165] Comparative Example 8:

[0166] Compared with Example 1, the difference is that the COF pore size is increased to 1.8 nm, while the other preparation conditions are the same.

[0167] Comparative Example 9:

[0168] Compared with Example 1, the difference is that the ionic liquid-covalent organic framework complex is removed, and unloaded liquid metal alloy powder is used directly, while the other preparation conditions are the same.

[0169] Comparative Example 10:

[0170] Compared with Example 1, the difference is that the ionic liquid was loaded using a conventional impregnation method (non-microfluidic dynamic sieving), while the other preparation conditions were the same.

[0171] Test Example 1:

[0172] Experimental equipment and materials

[0173] Friction testing machine: SRV-IVOptimol;

[0174] Lubricant composition analysis: Agilent 1260 Infinity II HPLC;

[0175] Test samples: Lubricating oils prepared in Example 1, Comparative Example 1, Comparative Example 6, and Comparative Example 9 (addition amount 2wt%);

[0176] Matching components: GCr15 bearing steel balls (Φ10mm) and disc (Φ24mm×7.9mm).

[0177] Experimental steps

[0178] Sample pretreatment:

[0179] Each lubricating oil sample was left to stand in a 60℃ constant temperature oven for 24 hours to eliminate air bubbles;

[0180] The steel ball and steel disc were ultrasonically cleaned with petroleum ether and acetone for 15 minutes in sequence, and then dried and stored in a desiccator.

[0181] Friction test parameter settings:

[0182] Normal load: 1000±10N;

[0183] Temperature: 150±2℃ (heating rate 5℃ / min);

[0184] Frequency: 50Hz (stroke 1mm);

[0185] Test duration: 120 minutes (the first 10 minutes are the break-in phase, with data collection intervals of 5 minutes).

[0186] Analysis of wear scar morphology:

[0187] After the test, the steel disc was cleaned three times with petroleum ether;

[0188] Lubricant consumption detection:

[0189] The residual lubricating oil after the test was collected and filtered through a 0.22μm filter membrane;

[0190] HPLC conditions: C18 column (4.6×250mm), mobile phase acetonitrile / water (70:30), flow rate 1mL / min, detection wavelength 210nm;

[0191] Consumption was calculated using the characteristic peak area of ​​the ionic liquid (calibration curve R). 2 =0.998).

[0192] Data recording guidelines:

[0193] The friction coefficient is the average value of the data in the last 110 minutes (excluding the break-in period);

[0194] The wear scar diameter was measured three times and the average value was taken. The error bar represents ±1σ.

[0195] The lubricant consumption rate is calculated as (initial amount - residual amount) / time.

[0196] Table 1 Test Example 1: Experimental Data for Functional Verification of Core Components

[0197]

[0198]

[0199] According to Table 1 above:

[0200] 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 significantly increased to 0.085, and large-area adhesion and delamination appeared on the wear scar surface. This is directly related to the interruption of the interlayer slip effect caused by the absence of quantum dots. Bifunctionalized BN quantum dots (carboxyl group density 5.2 groups / nm) 2 The interlayer spacing (0.33 nm) could originally form a stable dispersion through directional adsorption via hydrogen bonds between carboxyl groups and base oil. Simultaneously, under frictional heat, the epoxy groups undergo a ring-opening reaction with the hydroxyl groups on the metal surface, generating a covalently bonded protective film. Without this mechanism, the continuity of the lubricating film is disrupted, leading to direct metal-to-metal contact and severe adhesive wear.

[0201] The replacement of diamond nanocrystals with gradient doped material (Comparative Example 6) increased the friction coefficient to 0.063. Originally, this was achieved by controlling the electronic states of the diamond surface to reduce the adhesion energy with the mating metal. However, the highly active carbon dangling bonds on the undoped diamond surface directly induced interfacial chemisorption, leading to an increase in the adhesive torque between the friction pairs. Furthermore, the lack of an ultra-low contact angle (<5°) at the hydrogen-terminated surface further weakened the wetting and spreading ability of the lubricating medium on the diamond surface.

[0202] The removal of the ionic liquid-covalent organic framework complex (Comparative Example 9) resulted in a sharp increase in lubricant consumption rate to 7.2 μg / min, with a large amount of oxidized wear debris detected at the edge of the wear scar. The 1.3 nm pore size of the COF framework originally limited the burst release of the ionic liquid through molecular sieving effect, and its π-π stacking structure also inhibited the oxidation of the liquid metal (XPS showed a 3-fold increase in Ga2O3 content in Comparative Example 9). After losing the COF confinement, the ionic liquid was rapidly depleted in the early stages of friction, failing to form a sustained lubricating film. At the same time, the hard wear debris generated by the oxidation of the liquid metal exacerbated the three-body wear, confirming the indivisibility of the component linkages in the claims.

[0203] Test Example 2:

[0204] Experimental equipment and materials

[0205] High-temperature friction testing machine: CETRUMT-3;

[0206] Surface analysis equipment: Thermo Scientific K-Alpha XPS, FE I Talos F200 XTEM;

[0207] Pore ​​size analysis: Micromeritics 3 FlexBET analyzer;

[0208] Test samples: Lubricating oils prepared in Example 1, Comparative Example 2, Comparative Example 5, Comparative Example 7, and Comparative Example 10;

[0209] Special fixture: Custom-made high-temperature sealed cavity (temperature resistant to 300℃).

[0210] Experimental steps

[0211] High-temperature durability test:

[0212] Set the initial temperature to 80℃, and increase it to 180℃ in a gradient of 20℃ / 10min, and maintain the final temperature for 4 hours.

[0213] The normal load is constant at 800N, the reciprocating frequency is 30Hz, and the stroke is 2mm.

[0214] The friction coefficient was collected every 10 minutes, and the temperature-friction coefficient evolution curve was recorded.

[0215] Plasma processing verification:

[0216] Unmodified BN nanosheets from Comparative Example 2 were tested under the same experimental conditions.

[0217] After the experiment, the deposits at the friction interface were scraped off, and the peak shifts of B1s, N1s, and O1s were detected by XPS.

[0218] Changes in the intensity of the C=O bonding peak (288.6 eV) of the BN quantum dot in Comparative Example 1.

[0219] Liquid metal phase transition analysis:

[0220] Made from a slow-cooling alloy of proportion 5 Discs, DSC test (-30~50℃, rate 10℃ / min);

[0221] Simultaneous tribothermography (FLIRA65 infrared camera) was performed to capture the phase transition initiation temperature point.

[0222] Gradient doping structure verification:

[0223] Ultrathin slices (<50 nm) were made from uniformly doped diamond in Comparative Example 7;

[0224] TEM-EDS line scanning (2nm step size) to detect the radial distribution curve of Nd element;

[0225] Gradient distribution compared to Example 1 (surface 1.2 at% → interior 0.8 at%).

[0226] Microfluidic sieving effect verification:

[0227] BET tests were performed on the conventional impregnated samples of Comparative Example 10, and histograms of pore size distribution were plotted.

[0228] The half-width at half-peak (FWHM) of the COF pore size distribution in Comparative Example 1.

[0229] Table 2 Test Example 2: Experimental Data for Verification of Key Process Parameters

[0230]

[0231] According to Table 2 above:

[0232] This experiment reveals the mechanism by which key process parameters regulate the microstructure and tribological properties of materials. When the plasma bifunctional modification process was removed, the carboxyl group density of boron nitride quantum dots plummeted to 1.8 groups / nm. 2 (The peak intensity of XPSO1s decreased by 34.7%), indicating that insufficient epoxy grafting rate weakened the hydrogen bonding between quantum dots and base oil. Unmodified BN nanosheets (Comparative Example 2) exhibited disordered stacking during high-temperature friction, with the interlayer spacing compressed from 0.33 nm to 0.28 nm, losing their intercalation lubrication function and widening the friction coefficient fluctuation range to 0.051-0.089. This drastic fluctuation is directly related to the alternating "adhesion-sliding" behavior of the friction interface, confirming the decisive role of plasma-synchronous modification technology in the stability of the quantum dot interface.

[0233] The absence of a rapid cooling process on a liquid metal carrier (Comparative Example 5) led to grain coarsening in the alloy, with the average size increasing from 8-12 μm to 25 μm and the phase transformation temperature rising to 16.2 °C. DSC curves showed a decrease in the phase transformation enthalpy to 18 J / g (compared to 28 J / g in Example 1), resulting in a decline in the response efficiency of frictional heat-triggered self-healing. Infrared thermography revealed that when the temperature of local hot spots exceeded 180 °C, the slowly cooled alloy remained solid and could not fill the wear pits through liquid-phase mass transfer. This phase transformation hysteresis is closely related to the rapid cooling rate (800-1200 °C / s) in the claims, which inhibits grain boundary segregation, allowing the Ga-In-Sn-Ge alloy to maintain uniform solid solution characteristics at the microscale.

[0234] The absence of microfluidic dynamic sieving technology (Comparative Example 10) broadened the COF pore size distribution to 0.55-0.79 nm (BET full width at half maximum 0.67 nm), and reduced the ionic liquid loading from 72% to 45%. Conventional impregnation methods, lacking electric field-induced size selectivity, resulted in the partial retention of ionic liquid molecules (such as [BMIM]). + Approximately 1.2 nm in diameter was mechanically trapped outside the COF channels. HPLC analysis showed that the lubricating medium in Comparative Example 10 was consumed at 62% within the first 30 minutes of the experiment, while the sustained-release curve of Example 1 showed a linear increase (total consumption of 21%). This difference is directly related to the electrophoretic effect induced by the alternating electric field (50 V / cm, 1 kHz) in the microfluidic process—charged ionic liquid monomers undergo a sieving-enrichment cycle in the periodically contracting channels (200→50→200 μm), ultimately achieving precise loading with pore size matching. This is the physical basis for the realization of the "ionic liquid-covalent organic framework complex" function in the claims.

[0235] Test Example 3:

[0236] Experimental equipment and materials;

[0237] Laser particle size analyzer: Malvern Mastersizer 3000 (UK);

[0238] Differential Scanning Calorimeter (DSC): TA Instruments Q2000;

[0239] Impact and friction testing machine: Cameron-Plint TE77 (simulates impact load);

[0240] Test sample:

[0241] Example 1 (Standard Parameters);

[0242] Comparative Example 3 (80 samples of BN quantum dots);

[0243] Comparative Example 4 (Ge content 0.2%);

[0244] Comparative Example 8 (COF pore size 1.8 nm);

[0245] Experimental steps

[0246] Dispersion stability test:

[0247] Each lubricating oil sample was continuously shaken in a 25℃ constant temperature shaker (200rpm) for 24 hours;

[0248] After standing for 0h, 24h, and 72h, the D50 / D90 values ​​were measured using a laser particle size analyzer (the average of the three measurements was taken).

[0249] Record the sedimentation and stratification phenomenon after standing for 72 hours (visual observation + centrifuge tube calibration).

[0250] Phase transition behavior analysis:

[0251] Liquid metal alloy powder (Comparative Example 4, Example 1) was used to prepare φ5mm thin sheets;

[0252] DSC test parameters: -20℃→50℃, heating rate 5℃ / min, nitrogen protection (50mL / min); compare phase change onset temperature, peak temperature and phase change enthalpy ΔH.

[0253] Extreme operating condition simulation test:

[0254] The impact load was set to 2000N (5 cycles, 10s interval), and the temperature was 200℃.

[0255] Material of mating components: cemented carbide ball (WC-Co, HV1800) and cast iron disc;

[0256] After testing, the diameter of the wear scar was measured (3-point measurement method), and the surface peeling was observed by SEM.

[0257] COF pore size exceeding limit verification:

[0258] N2 adsorption-desorption test (BET method) was performed on the COF complex of Comparative Example 8;

[0259] Analyze the pore size distribution curve and calculate the average pore size and most probable pore size. Auxiliary equipment: constant temperature oscillator (dispersion stability test), high temperature vacuum furnace (200℃ pretreatment).

[0260] Experimental steps:

[0261] Dispersion stability test:

[0262] Each lubricating oil sample was continuously shaken in a 25℃ constant temperature shaker (200rpm) for 24 hours;

[0263] After standing for 0h, 24h, and 72h, the D50 / D90 values ​​were measured using a laser particle size analyzer (the average of the three measurements was taken); the sedimentation stratification phenomenon after standing for 72h was recorded (visual observation + centrifuge tube calibration observation).

[0264] Phase transition behavior analysis:

[0265] Prepared from liquid metal alloy powder (Comparative Example 4, Example 1) thin slices;

[0266] DSC test parameters: -20℃→50℃, heating rate 5℃ / min, nitrogen protection (50mL / min); compare phase change onset temperature, peak temperature and phase change enthalpy ΔH.

[0267] Extreme operating condition simulation test:

[0268] The impact load was set to 2000N (5 cycles, 10s interval), and the temperature was 200℃.

[0269] Material of mating components: cemented carbide ball (WC-Co, HV1800) and cast iron disc;

[0270] After testing, the diameter of the wear scar was measured (3-point measurement method), and the surface peeling was observed by SEM.

[0271] COF pore size exceeding limit verification:

[0272] N2 adsorption-desorption test (BET method) was performed on the COF complex of Comparative Example 8;

[0273] Analyze the pore size distribution curve and calculate the average pore size and the most probable pore size.

[0274] Table 3 Test Case 3: Boundary Validation Experimental Data (Irregular Simulation)

[0275]

[0276]

[0277] According to Table 3 above:

[0278] This experiment verified the critical necessity of component ratios and process parameters by exceeding the parameter boundaries defined in the claims. When the amount of boron nitride quantum dots added increased to 80 parts (Comparative Example 3), laser particle size analysis showed that the D90 value reached 285 nm, far exceeding the 150 nm upper limit defined in the claims. Excessive BN quantum dots exceeded the functional group grafting capacity of the plasma modification process, leading to an increase in the proportion of unmodified surface, and the agglomeration behavior was dominated by van der Waals forces between particles. During friction, these agglomerates were embedded in the contact interface as hard third-body abrasive particles, triggering the failure mode dominated by abrasive wear. Under impact load, the wear scar diameter increased to 0.53 mm (0.24 mm in Example 1). SEM observation showed that the wear surface had furrows with a depth >5 μm, which was directly related to the complete loss of the interlayer slip mechanism of BN quantum dots.

[0279] The liquid metal alloy with Ge content reduced to 0.2% (Comparative Example 4) exhibited significant deterioration in grain boundary stability. DSC curves showed that its phase transformation temperature increased to 17.8℃, and the phase transformation enthalpy decreased to 14 J / g (compared to 28 J / g in Example 1). This change stemmed from a weakening of the grain boundary pinning effect of Ge—Ge atoms were unable to effectively suppress grain coarsening in the Ga-In-Sn alloy during rapid cooling, with the average grain size increasing from 8-12 μm to 22 μm. Tribothermography revealed that the alloy remained solid at an interface temperature of 160℃, unable to fill the wear pits through liquid-phase mass transfer. After losing its dynamic self-healing ability, localized material transfer occurred on the wear scar surface (EDS detected Fe content > 12 at%) in the mating part, confirming the crucial role of Ge content (0.4-0.6%) in maintaining the metastable alloy structure.

[0280] The expansion of COF pore size to 1.8 nm (Comparative Example 8) disrupted the sustained-release kinetics of ionic liquids. BET data showed that the pore size distribution broadened to 0.8–2.2 nm, affecting the release kinetics of some ionic liquid monomers (such as [BMIM]). + The 1.2 nm diameter pore size rapidly released lubricant at the initial stage of friction, with 68% of the lubricant consumed after 30 minutes of testing. This sudden release behavior caused the friction coefficient to fluctuate drastically between 0.025 and 0.062, while in Example 1, due to the molecular sieving effect of the 1.3 nm pore size, the ionic liquid exhibited linear slow release (total consumption 21%). Without pore size control, the π-π stacking structure of the COF framework could not effectively block oxygen diffusion, and XPS detected a 2.3-fold increase in Ga2O3 content on the liquid metal surface. The accumulation of oxidized wear debris further exacerbated three-body wear; after the impact test, spalling pits up to 8 μm deep appeared at the edge of the wear scar, revealing the irreplaceable role of the 1.0-1.5 nm COF pore size in maintaining the stability of the lubrication system.

[0281] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A complex antiwear additive for lubricating oils, characterized in that, The components include the following quality parts: 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 composite; The surface of the surface-modified layered boron nitride quantum dots 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, and the quantum dot size is 1-3 nm; In the rare earth doped diamond nanocrystals, the doping amount of neodymium is 0.5-1.5at%, and the doping concentration is gradiently distributed along the grain diameter, with the surface doping amount being 0.3-0.8at% higher than the internal doping amount; The grain size of the diamond nanocrystals is 20-50nm, and the surface is hydrogen-terminated structure; The preparation method of the surface modified layered boron nitride quantum dots includes the following steps: Put the hexagonal boron nitride bulk into a radio frequency plasma reactor, and synchronously introduce argon-hydrogen mixed gas Ar:H2 with a volume ratio of 90-95:5-10 and acrylic acid / propylene oxide mixed gas with a molar ratio of 1:1.8-2.2; Excite the plasma under a radio frequency power of 400-600W for 25-35min, and capture the surface modified quantum dots by a liquid nitrogen cold trap; The preparation method of the rare earth doped diamond nanocrystals includes the following steps: Pre-deposit a 200nm diamond seed layer on a silicon substrate, pulse-in NdCl3 vapor with a frequency of 8-12Hz 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, grow the gradient doped diamond nanocrystals by using CH4 / H2 mixed gas with a volume ratio of 0.5-1.5:98.5-99.5 for 7-9h.

2. A complex anti-wear additive for lubricating oils according to claim 1, characterized in that, The atomic percentage composition of the gallium-indium-tin-germanium alloy is: Ga64-66%, In21-23%, Sn12-13%, and Ge0.4-0.6%.

3. A complex anti-wear additive for lubricating oils according to claim 1, characterized in that, In the ionic liquid-covalent organic framework composite, the pore size of the covalent organic framework is 1.0-1.5nm, and the ionic liquid loading rate is 60-80wt%.

4. A process for the preparation of a complex antiwear additive for lubricating oils according to any one of claims 1 to 3, characterized in that, The steps include: Step one: synchronously modify the surface functional groups of hexagonal boron nitride by plasma vapor deposition to prepare bifunctional quantum dots; Step two: vacuum smelt the gallium-indium-tin-germanium alloy and rapidly cool it to form granules; Step three: synthesize gradient rare earth doped diamond nanocrystals by microwave plasma chemical vapor deposition; Step four: load the ionic liquid-covalent organic framework composite on the liquid metal carrier by microfluidic electrochemical deposition; Step five: multi-stage ultrasonic dispersion to compound each component.

5. The method for preparing a composite anti-wear additive for lubricating oil according to claim 4, characterized in that, In step two, under argon protection O2≤1ppm, heat to 280-320℃, stir and melt for 1.5-2.5h, then rapidly cool to -25~-15℃ at a rate of 800-1200℃ / s, and break to obtain 5-15μm alloy powder.

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

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