Method for in-situ preparation of black phosphorus nanoparticles by using pva / paam interpenetrating network hydrogel as micro-reactor and application as wear-resistant additive of lubricating oil

Abstract

This invention relates to the field of oil additives for power generation, specifically a method for in-situ preparation of black phosphorus nanoparticles (BPNPs) using PVA / PAAM interpenetrating network hydrogel as a microreactor and its application as a wear-resistant additive in lubricating oils. The confinement effect of the interpenetrating network hydrogel results in uniform BPNP size and high crystallinity, thus endowing BPNPs with excellent air / water / oil stability, with an oxidation rate of <5% within 7 days. Swelling allows RP / KI to permeate uniformly and be physically embedded in the network. Subsequently, under a nitrogen protective atmosphere, photolysis of iodine ions generates solvated electrons (e). ‑ (aq) restores RP to P ‑ P ‑ The BP crystal nucleus is formed by recombination, and the IPN three-dimensional nanochannels (pore size 30~120nm) confine and inhibit excessive growth of the crystal nucleus. At the same time, the PVA hydroxyl groups and PAAm amide groups passivate the BP surface in situ through hydrogen bonding / coordination, preventing oxidation.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oil additives for electric power, in particular to a method for in-situ preparation of black phosphorus nanoparticles using PVA / PAAM interpenetrating network hydrogel as a micro-reactor and application as a wear-resistant additive for lubricating oil. BACKGROUND

[0002] It has broad application prospects in the fields of aerospace, automobile manufacturing, etc. Especially in high-load, high-contact-pressure friction pairs, such as engine bearings, gears, hydraulic systems, etc., it is expected to replace traditional lubricants and improve the reliability and energy efficiency of equipment. Black phosphorus nanoparticles (BPNP) have a layered structure and abundant surface active sites. During friction, BPNP can be adsorbed on the friction surface to form a thin and uniform lubricating film, thereby reducing the friction coefficient and wear. The surface lone pair electrons of black phosphorus can react with lubricant molecules (such as oleic acid, polyaspartic acid, etc.) to release passivation groups, further enhancing the lubricating effect. At the same time, the interlayer slip of black phosphorus also helps to reduce the shear force of the friction interface.

[0003] Black phosphorus (BP) has a layer-dependent adjustable band gap, low interlayer shear strength (0.03-0.05 GPa), and surface lone pair electrons that easily bond with metals, making it theoretically possible to achieve an ultra-low friction coefficient of ≤0.01 under high contact stress, making it a potential "green" lubricating oil anti-wear additive for the next generation. However, existing mechanical exfoliation, liquid-phase sonication, electrochemical exfoliation, or high-temperature conversion of mineralizers have the following shortcomings: (1) Inert atmosphere, high temperature and pressure, or strong polar organic solvents are required, and the process is complex and energy-intensive; (2) The product size distribution is wide (50 nm-1 μm), and it is easy to agglomerate and settle in base oil, with a storage stability of <72 h; (3) Unpassivated BP rapidly oxidizes to phosphate in the friction heat zone (>150℃), losing its layered lubrication properties; (4) Existing post-modification (dopamine, oleic acid, PEG, etc.) requires multiple centrifugation-freeze-drying-redispersion processes, and the coating layer is easily detached under high-temperature shear, which actually exacerbates abrasive wear.

[0004] Therefore, developing a BPNP preparation strategy that can be generated in-situ at room temperature and pressure, has uniform size, is in-situ passivated on the surface, and can be dispersed in a lubricating oil system immediately after production, has become an urgent need in the field of long-life lubrication for high-precision machinery, electric power equipment, and wind turbine gearboxes. SUMMARY

[0005] In view of the problems in the prior art, the application provides a method for in-situ preparation of black phosphorus nanoparticles by using PVA / PAAM interpenetrating network hydrogel as a microreactor and application thereof as a wear-resistant additive of lubricating oil, which is a simple method for in-situ reduction and exfoliation of high-stability BPNP under normal temperature and pressure and visible light irradiation by using PVA / PAAm interpenetrating network (IPN) hydrogel as a microreactor, a stabilizer and a carrier, and directly applying the BPNP to the field of wear-resistant lubricating oil.

[0006] The application is realized by the following technical scheme: The application provides a method for in-situ preparation of black phosphorus nanoparticles by using PVA / PAAM interpenetrating network hydrogel as a microreactor, which comprises the following steps: S1, constructing an IPN hydrogel microreactor: mixing a polyvinyl alcohol solution and an AAm prepolymer solution, injecting into a mold for irradiation, then spraying a glutaraldehyde aqueous solution containing 0.1 M HCl for acetal crosslinking reaction to obtain PVA / PAAm IPN hydrogel; S2, in-situ confined reaction: vacuum drying the PVA / PAAm IPN hydrogel to obtain a reversible collapsed network; immersing the reversible collapsed network in an ethanol-water mixed solution containing red phosphorus and a promoter MKI for swelling at room temperature, then performing a light irradiation reaction under nitrogen protection to obtain an intermediate gel; S3, immersing the intermediate gel in deionized water for impurity removal, then performing mechanical compression or ultrasonic treatment to obtain a crude BPNP solution, and performing filtration, centrifugation, anhydrous ethanol replacement and vacuum drying on the crude BPNP solution to obtain oleophilic BPNP powder.

[0007] Preferably, in S1, the preparation process of the polyvinyl alcohol solution is as follows: PVA with a polymerization degree of 1700-2000 and an alcoholysis degree of greater than or equal to 99% is dissolved in deionized water at 85-95 DEG C to form an 8wt%-12wt% ethylene alcohol solution.

[0008] Preferably, in S1, the preparation process of the AAm prepolymer solution is as follows: acrylamide, a crosslinking agent N,N'-methylene bisacrylamide and a photoinitiator Irgacure 2959 are dissolved in deionized water to form a 15wt%-25wt% prepolymer solution.

[0009] Preferably, in S1, the volume ratio of the polyvinyl alcohol solution to the AAm prepolymer solution is (1:1)-(1:2); the thickness of the injection into the mold is 1-5 mm; during irradiation, 365nm UV light is used for 3-10 min; the concentration of the glutaraldehyde aqueous solution is 1wt%-3wt%; during the acetal crosslinking reaction, the temperature is 25 DEG C and the time is 30-60 min.

[0010] Preferably, in S2, the temperature is 40 DEG C during vacuum drying, and the volume of the PVA / PAAm IPN hydrogel is dried to 50% to 70% of the original volume.

[0011] Preferably, in S2, the ethanol-water mixed solution contains 0.5 to 2 mg / mL of red phosphorus and 0.05 to 0.2 M of the promoter MKI, and the particle size of the red phosphorus is less than 5 mu m. -1

[0012] Preferably, in S2, the wavelength of the visible light used during the light irradiation is 450 to 470 nm, the power density is 50 to 100 mW / cm -2 , and the time is 1 to 6 h.

[0013] Preferably, in S3, the time for the soaking is 12 h, and a filter membrane with a pore size of 0.22 mu m is used during the filtration.

[0014] An oil-wet BPNP powder obtained by a method for in-situ preparation of black phosphorus nanoparticles using a PVA / PAAM interpenetrating network hydrogel as a microreactor, wherein the oil-wet BPNP powder is dispersed in an ester, PAO or mineral base oil, and no sedimentation occurs in 30 days.

[0015] An application of the oil-wet BPNP powder as a wear-resistant additive for lubricating oil.

[0016] Compared with the prior art, the present application has the following beneficial effects: The present application is a method for in-situ preparation of black phosphorus nanoparticles using a PVA / PAAM interpenetrating network hydrogel as a microreactor, wherein the PVA / PAAM interpenetrating network hydrogel is used as a microreactor to prepare high-stability black phosphorus nanoparticles (BPNP).

[0017] The present application uses the confinement effect of the interpenetrating network hydrogel to make the BPNP uniform in size and high in crystallinity, and thus endows the BPNP with excellent air / water / oil stability, with an oxidation rate of less than 5% in 7 days. - (aq) is generated by photolysis of the iodide ions, the RP is reduced to P - , and then P - recombines to form a BP crystal nucleus.

[0018] ​Further, the nitrogen protection is to prevent the oxidation of the phosphorus material in the reaction process, so as to ensure the purity and quality of the final product black phosphorus. The promoter MKI is used as a catalyst to reduce the energy barrier of the conversion of red phosphorus to black phosphorus, improve the conversion rate and reaction rate, and realize the conversion between the two at room temperature.

[0019] The black phosphorus nanoparticles obtained by the method of in-situ preparation of black phosphorus nanoparticles by PVA / PAAM interpenetrating network hydrogel as a microreactor are in a multi-layer structure, and the particle size is 30-60 nm, which is an ideal specification for wear-resistant additives. The black phosphorus nanoparticles do not contain harmful elements such as sulfur, phosphorus (free), zinc, etc., meet the IEC 60296 transformer oil specification, and can be directly used as anti-wear / reducing friction / self-repairing multifunctional additives for high-end lubricating oil and insulating oil, used in long-life scenarios such as power transformers, wind power gearboxes, nuclear power plant main pump bearings, etc. The base oil object to which the black phosphorus nanoparticles are added as wear-resistant additives is mineral oil, poly-alpha-olefin, synthetic ester or a mixture thereof, and the black phosphorus nanoparticles have good dispersibility in these base oils and do not settle for 30 days. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 The flowchart of the method of in-situ preparation of black phosphorus nanoparticles by PVA / PAAM interpenetrating network hydrogel as a microreactor. DETAILED DESCRIPTION

[0021] The following specific examples illustrate the embodiments of the present application, and those skilled in the art can easily understand other advantages and effects of the present application from the disclosure.

[0022] Exemplary embodiments of the present application will now be described with reference to the accompanying drawings. The present application can, however, be carried out in many different ways, and is not limited to the embodiments described herein, which are provided for the purpose of fully and completely disclosing the present application and to convey the full scope of the present application to those skilled in the art. The terminology used herein is not intended to limit the present application. In the drawings, like reference numerals refer to like elements throughout.

[0023] Unless otherwise defined, the terms (including technical terms) used herein have meanings commonly understood by those skilled in the art. In addition, it is to be understood that the terms defined by commonly used dictionaries are to be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art, and are not to be interpreted in an idealized or overly formal sense.

[0024] The present application will be further described in detail with reference to specific examples, which are intended to explain the present application rather than limit the present application.

[0025] This invention discloses a method for in-situ preparation of black phosphorus nanoparticles using PVA / PAAM interpenetrating network hydrogel as a microreactor, comprising: S1, Constructing IPN hydrogel microreactors: Mix polyvinyl alcohol solution and AAm prepolymer liquid in a volume ratio of (1:1) to (1:2), inject into a mold 1 to 5 mm deep, and irradiate with 365 nm UV light for 3 to 10 min to form the first layer of PAAm network; then spray 1 wt% to 3 wt% of glutaraldehyde aqueous solution containing 0.1 MHCl onto the first layer of PAAm network to carry out acetal crosslinking reaction to obtain PVA / PAAmIPN hydrogel.

[0026] The preparation process of the polyvinyl alcohol solution is as follows: PVA with a degree of polymerization of 1700–2000 and a degree of alcoholysis ≥99% is dissolved in deionized water at 85~95℃ to form an 8wt%~12wt% ethylene alcohol solution.

[0027] The preparation process of AAm prepolymer is as follows: acrylamide, crosslinking agent N,N′-methylenebisacrylamide, and photoinitiator Irgacure 2959 are dissolved in deionized water to form a 15 wt%~25 wt% prepolymer.

[0028] The acetal crosslinking reaction is carried out at a temperature of 25℃ for 30-60 minutes.

[0029] S2, In-situ confined reaction: PVA / PAAmIPN hydrogels were vacuum dried at 40℃ until the volume of the PVA / PAAmIPN hydrogels was 50%~70% of the original volume, resulting in a reversible collapsed network. The vacuum level was -0.08 ~ -0.1 MPa, a typical negative pressure in a chemical laboratory.

[0030] At room temperature, the reversible collapsible network was immersed in an ethanol-water mixture containing red phosphorus and accelerator MKI to swell, and then subjected to a photocatalytic reaction under nitrogen protection to obtain an intermediate gel.

[0031] The ethanol-water mixed solution contains 0.5–2 mg / mL red phosphorus and 0.05–0.2 M of accelerator MKI, with the red phosphorus having a particle size of less than 5 μm. During the photo-irradiation reaction, visible light with a wavelength λ of 450–470 nm and a power density of 50–100 mW / cm⁻² is used for 1–6 hours.

[0032] S3. The intermediate gel was soaked in deionized water for 12 hours to remove impurities. Then, it was mechanically compressed or ultrasonically treated to obtain a crude BPNP solution. The crude BPNP solution was filtered through a filter membrane with a pore size of 0.22µm. After centrifugation, replacement with anhydrous ethanol and vacuum drying, oleophilic BPNP powder was obtained.

[0033] This invention discloses a method for in-situ preparation of black phosphorus nanoparticles using PVA / PAAM interpenetrating network hydrogel as a microreactor. First, the three-dimensional network within the IPN hydrogel forms nano / micro-scale channels and cavities, serving as a natural microreactor. This provides a spatial confinement effect for the subsequent conversion of red phosphorus to black phosphorus, effectively inhibiting the excessive growth and stacking of black phosphorus nanosheets, thus facilitating the acquisition of products with uniform size and good dispersibility. Simultaneously, the PVA / PAAM IPN structure combines the properties of both polymers, giving it excellent hydrophilicity and swelling properties, facilitating the efficient and uniform penetration and loading of red phosphorus into various parts of the gel network. During this process, a preliminary stable network is formed through irradiation crosslinking, and the network structure is further strengthened through the reaction of glutaraldehyde with the hydroxyl groups of PVA. This ensures that the hydrogel maintains structural integrity and mechanical strength during subsequent drying, swelling, reaction, and processing, preventing disintegration.

[0034] Secondly, vacuum drying causes the hydrogel network to collapse, significantly reducing its volume. When the dried gel is then immersed in the precursor solution, the gel rapidly swells, drawing reactants such as red phosphorus and accelerators into the network. This achieves high concentration and uniform loading of reactants within the gel matrix, improving raw material utilization and reaction efficiency. Under light and with the aid of accelerators, the loaded red phosphorus transforms into black phosphorus within the spatial confinement of the gel network. This not only controls the nucleation and growth of black phosphorus but also prevents the aggregation of the generated black phosphorus nanoparticles.

[0035] Next, soluble impurities are removed by soaking, and then the hydrogel carrier is destroyed by mechanical compression or ultrasonic treatment to release the encapsulated BPNPs. Then, large particles and unconverted red phosphorus are gradually separated and removed by filtration, centrifugation, solvent replacement and drying to achieve size-based purification of the product.

[0036] In summary, the method disclosed in this invention uses hydrogel as the reaction medium and adopts room temperature light irradiation reaction, avoiding the traditional black phosphorus preparation method. The entire process is at room temperature and pressure, and uses an aqueous phase system, making it green and safe.

[0037] This invention also discloses a method for preparing lipophilic BPNP powder in situ using PVA / PAAM interpenetrating network hydrogel as a microreactor. The lipophilic BPNP powder is dispersed in esters, PAO or mineral base oils and shows no sedimentation after 30 days.

[0038] This invention also discloses the application of lipophilic BPNP powder as a wear-resistant additive for lubricating oil. Specifically, 0.03 wt% to 0.1 wt% of lipophilic BPNP is added to 150N base oil and ultrasonicated for 10 minutes to obtain a transparent dispersion. The base oil is selected from mineral oil, polyα-olefin, synthetic ester, or mixtures thereof.

[0039] Example 1 S1, Dissolve 10g PVA in 90mL of deionized water and stir at 95℃ for 2h to obtain a polyvinyl alcohol solution; Dissolve 20g AAM, 0.03g MBAA, and 0.2g Irgacure 2959 in 80mL of water to obtain AAM prepolymer solution; The polyvinyl alcohol solution and AAm prepolymer were mixed and then injected into a 2 mm thick mold. The mixture was cured by irradiation with 65 nm UV light for 5 min, and then immediately sprayed with 2 wt% GA (containing 0.1 M HCl) solution. The mixture was reacted at 25 °C for 45 min to obtain PVA / PAAmIPN hydrogel.

[0040] S2, the dried and collapsed gel was immersed in an ethanol / water solution containing 1 mg / mL-1 RP and 0.1 MKI, swollen at 25 °C for 8 h, and then dissolved under a N2 atmosphere at 60 mW / cm -2 Irradiate with blue light for 4 hours to obtain an intermediate gel.

[0041] S3, the intermediate gel is washed with water, sonicated and filtered to obtain a BPNP aqueous dispersion; the BPNP aqueous dispersion is centrifuged, replaced with ethanol and dried to obtain lipophilic BPNP powder.

[0042] The lipophilic BPNP powder obtained in Example 1 was subjected to relevant tests: The lipophilic BPNP powder was dissolved in 150N base oil to prepare a 0.05wt% lubricating dispersion, and relevant test experiments were conducted: In the copper strip corrosion test, its copper strip corrosion was ASTM D130 1a grade; in the four-ball machine test, the PB value increased by 42% and the wear scar diameter decreased by 38%; in the 120℃, 192h oxidation tube test (ASTM D2272), the induction period was extended by 1.8 times and the amount of sludge was reduced by 70%.

[0043] Example 2 The BPNP powder obtained in Example 1 was added to PAO40 synthetic hydrocarbon oil to prepare a 0.08 wt% lubricating dispersion, which was used on a 2.5MW wind turbine gearbox test bench (GB / T 19936.1). After 200 hours of full-load operation, the area of ​​micro-pitting on the gear tooth surface was reduced by 85% compared with the blank, the oil temperature was reduced by 6℃, and the concentration of large abrasive particles (>10 µm) decreased by 88% according to ferrography.

[0044] The above description is merely a preferred embodiment of the present invention and is not intended to limit the technical solution of the present invention in any way. Those skilled in the art should understand that, without departing from the spirit and principles of the present invention, the technical solution can be modified and replaced in several simple ways, and these modifications and replacements are all within the scope of protection covered by the claims.

Claims

1. A method for in-situ preparation of black phosphorus nanoparticles using PVA / PAAM interpenetrating network hydrogel as a microreactor, characterized in that, include: S1, Constructing IPN hydrogel microreactors: Mix polyvinyl alcohol solution and AAm prepolymer solution, inject into a mold for irradiation, and then spray with glutaraldehyde aqueous solution containing 0.1 MHCl to carry out acetal crosslinking reaction to obtain PVA / PAAmIPN hydrogel; S2, In-situ confined reaction: Vacuum drying of PVA / PAAmIPN hydrogel yields a reversible collapsed network; at room temperature, the reversible collapsed network is immersed in an ethanol-water mixed solution containing red phosphorus and accelerator MKI for swelling, followed by photoreaction under nitrogen protection to obtain an intermediate gel. S3. The intermediate gel is soaked in deionized water to remove impurities, and then mechanically compressed or ultrasonically treated to obtain a crude BPNP solution. The crude BPNP solution is filtered, centrifuged, replaced with anhydrous ethanol, and vacuum dried to obtain lipophilic BPNP powder.

2. The method for in-situ preparation of black phosphorus nanoparticles using PVA / PAAM interpenetrating network hydrogel as a microreactor according to claim 1, characterized in that, In S1, the preparation process of the polyvinyl alcohol solution is as follows: PVA with a degree of polymerization of 1700–2000 and a degree of alcoholysis ≥99% is dissolved in deionized water at 85~95℃ to form an 8wt%~12wt% ethylene alcohol solution.

3. The method for in-situ preparation of black phosphorus nanoparticles using PVA / PAAM interpenetrating network hydrogel as a microreactor according to claim 1, characterized in that, In S1, the preparation process of the AAm prepolymer solution is as follows: acrylamide, crosslinking agent N,N′-methylenebisacrylamide, and photoinitiator Irgacure 2959 are dissolved in deionized water to form a 15 wt%~25 wt% prepolymer solution.

4. The method for in-situ preparation of black phosphorus nanoparticles using PVA / PAAM interpenetrating network hydrogel as a microreactor according to claim 1, characterized in that, In S1, the volume ratio of polyvinyl alcohol solution to AAm prepolymer liquid is (1:1) to (1:2); the thickness of the injection mold is 1 to 5 mm; during irradiation, 365 nm UV light is used for 3 to 10 min; the concentration of glutaraldehyde aqueous solution is 1 wt% to 3 wt%; during the acetal crosslinking reaction, the temperature is 25℃ and the time is 30 to 60 min.

5. The method for in-situ preparation of black phosphorus nanoparticles using PVA / PAAM interpenetrating network hydrogel as a microreactor according to claim 1, characterized in that, In S2, during vacuum drying, the temperature is 40℃, and the PVA / PAAmIPN hydrogel is dried to 50%~70% of its original volume.

6. The method for in-situ preparation of black phosphorus nanoparticles using PVA / PAAM interpenetrating network hydrogel as a microreactor according to claim 1, characterized in that, In S2, the ethanol-water mixed solution contains 0.5~2 mg / mL -1 The red phosphorus contains 0.05~0.2M of accelerator MKI, and the particle size of the red phosphorus is less than 5μm.

7. The method for in-situ preparation of black phosphorus nanoparticles using PVA / PAAM interpenetrating network hydrogel as a microreactor according to claim 1, characterized in that, In S2, during the photo-irradiation reaction, a wavelength λ of 450~470nm and a power density of 50~100mW / cm² are used. -2 Visible light, for 1 to 6 hours.

8. The method for in-situ preparation of black phosphorus nanoparticles using PVA / PAAM interpenetrating network hydrogel as a microreactor according to claim 1, characterized in that, In S3, the soaking time is 12 hours; a filter membrane with a pore size of 0.22µm is used for filtration.

9. An oleophilic BPNP powder obtained by the method for in-situ preparation of black phosphorus nanoparticles using PVA / PAAM interpenetrating network hydrogel as a microreactor according to any one of claims 1 to 8, characterized in that, The lipophilic BPNP powder was dispersed in esters, PAO or mineral base oils and showed no sedimentation after 30 days.

10. The application of the lipophilic BPNP powder as described in claim 9 as a wear-resistant additive for lubricating oil.

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