A MoS2-based friction-reducing and wear-resistant composite metal coating material and its preparation method

Abstract

The application discloses a MoS2-based friction-reducing wear-resistant composite metal coating material and a preparation method thereof in the field of metal coating, and forms a double low-friction component through MoS2 and nitrogen-doped carbon graphite material, so that low friction coefficient stability can be realized, and the low friction coefficient stability is far superior to that of traditional metal coating; meanwhile, the metal-metal sulfide composite support phase gives the coating high hardness and high toughness, and the wear rate can be controlled to remain at a low level, so that the core contradiction that traditional coating is poor in wear resistance while reducing friction or is poor in friction reduction while being wear-resistant is solved. In the application, MoS2 is wrapped by a metal phase and nitrogen-doped carbon graphite carbon, so that the contact with water molecules in the air can be reduced, and the friction reduction failure caused by the generation of MoO3 can be avoided; the metal sulfide and the metal element have excellent corrosion resistance, and can prevent corrosive media from penetrating into the coating, so that the service life of the coating is prolonged compared with that of traditional coating under corrosion-wear coupling conditions (such as marine equipment and chemical pipelines).

Description

Technical Field

[0001] This invention belongs to the field of metal coating technology, specifically referring to a friction-reducing and wear-resistant composite metal coating material based on MoS2 and its preparation method. Background Technology

[0002] In industrial manufacturing, aerospace, rail transportation, and energy equipment, friction and wear of mechanical components are core issues leading to equipment failure, shortened lifespan, and increased energy consumption. Approximately 70% of component failures in mechanical systems originate from surface wear, and 30% of energy consumption is used to overcome frictional resistance. Especially under heavy loads, high speeds, high temperatures, or harsh media (such as humid or corrosive environments), traditional metal substrates (such as steel, aluminum alloys, and titanium alloys) have low surface hardness and high coefficients of friction (typically between 0.3 and 0.8), making them prone to adhesive wear, abrasive wear, or fatigue wear, severely restricting equipment reliability and service life. Therefore, developing surface modification technologies that combine low coefficients of friction, high wear resistance, and strong substrate adhesion has become a key direction for solving the industrial friction and wear problem.

[0003] Metal coatings, as a core technology for surface modification, can effectively improve the surface properties of materials by constructing a functional protective layer on the substrate surface. Traditional friction-reducing and wear-resistant metal coatings mainly rely on single metals (such as Cr, Ni, W) or alloys (such as Ni-P, Co-W, Fe-Cr-B). Although they can reduce the risk of abrasive wear by increasing surface hardness, they have drawbacks such as high friction coefficients, poor high-temperature stability, and weak environmental adaptability (e.g., hard chrome coatings are prone to microcrack corrosion in humid environments). For example, in the field of aero-engine bearings, the friction coefficient of traditional Ni-based alloy coatings rises to over 0.4 under operating conditions above 350°C, and the wear rate is 3-5 times higher than at room temperature, making it difficult to meet long-term service requirements. In wind turbine gearboxes, although the Fe-Cr-B coating on the steel substrate surface has high hardness, it is prone to peeling due to interface corrosion in outdoor humid environments, with an average replacement cycle of only 1-2 years and high maintenance costs.

[0004] Molybdenum disulfide (MoS2), a typical layered transition metal sulfide (TMD), possesses excellent friction-reducing properties due to its unique hexagonal layered structure (atoms within the layers are bonded by strong covalent bonds, while those between the layers are connected by weak van der Waals forces). Its interlayer shear force is extremely low, and the coefficient of friction can be as low as 0.02-0.05 in dry environments. Furthermore, it exhibits excellent chemical stability, making it an ideal component for friction reduction. As early as the 1950s, MoS2 was used in solid lubricants (such as grease additives and dry film lubricants). However, pure MoS2 coatings have two major drawbacks: firstly, weak adhesion to the metal substrate, making them prone to peeling under load; and secondly, high environmental sensitivity. In air with humidity >50%, MoS2 readily reacts with water molecules to form MoO3 (a brittle oxide), causing the coefficient of friction to surge to over 0.3 and a sharp decline in wear resistance.

[0005] In existing research on MoS2-based composite coatings, the reported metal substrates mainly include Ni, Co, Cr, Al, and their alloys. Preparation methods cover electroplating, electroless plating, thermal spraying (such as plasma spraying and supersonic flame spraying), physical vapor deposition (PVD, such as magnetron sputtering and arc ion plating), and chemical vapor deposition (CVD). For example, Ni-P-MoS2 composite coatings prepared by electroless plating, by dispersing MoS2 particles in the Ni-P coating, can reduce the coefficient of friction to 0.15-0.2, a reduction of 30%-40% compared to pure Ni-P coatings. However, this method suffers from problems such as uneven MoS2 dispersion and limited coating thickness, making it difficult to meet the requirements of heavy-duty components for thick coatings.

[0006] Furthermore, existing composite coatings share a common problem of insufficient synergy between friction reduction and wear resistance: when the MoS2 content is too high, although it can significantly reduce the coefficient of friction, it leads to a decrease in coating hardness and a deterioration in wear resistance; while when the MoS2 content is too low, the friction reduction effect is not obvious and it cannot perform its core function. At the same time, under corrosion-wear coupled conditions, most metal substrates are prone to electrochemical corrosion, resulting in corrosion products at the coating interface, accelerating coating peeling, and further shortening the component life. Summary of the Invention

[0007] To address the above issues and overcome the shortcomings of existing technologies, this invention provides a MoS2-based friction-reducing and wear-resistant composite metal coating material and its preparation method. By forming dual low-friction components with MoS2 and nitrogen-doped carbon-based graphite materials, a low friction coefficient stability can be achieved, far superior to traditional metal coatings. Simultaneously, the metal-metal sulfide composite support phase endows the coating with high hardness and high toughness, keeping the wear rate controlled at a low level, thus resolving the core contradiction of traditional coatings where friction reduction results in poor wear resistance, and vice versa. In this invention, MoS2 is encapsulated by the metallic phase and nitrogen-doped carbon-based graphite materials, reducing contact with water molecules in the air and preventing friction-reducing failure caused by MoO3 formation. The metal sulfides and elemental metals possess excellent corrosion resistance, preventing corrosive media from penetrating into the coating interior. Under corrosion-wear coupled conditions (such as marine equipment and chemical pipelines), the coating life is extended compared to traditional coatings.

[0008] To achieve the above objectives, the technical solution adopted by this invention is as follows: This invention proposes a method for preparing a friction-reducing and wear-resistant composite metal coating material based on MoS2, specifically including the following steps:

[0009] A1. Dissolve 3-aminopyrazole in a mixed solution of anhydrous DMF and N,N-dimethylethylenediamine, purge with flowing nitrogen, add anhydrous potassium carbonate and cuprous chloride and mix well, then add 2-bromopyridine and stir continuously until the reaction system is homogeneous. Raise the reaction temperature to reflux reaction. After the reaction is completed, add deionized water to quench, add ethyl acetate to extract, collect the organic phase, wash the organic phase with saturated NaCl aqueous solution, dry the organic phase to remove water, and concentrate by rotary evaporation to obtain intermediate 1.

[0010] A2. Dissolve intermediate 1 prepared in step A1 in anhydrous dichloromethane, transfer to an ice-water bath and stir to cool thoroughly. Slowly add triethylamine and mix evenly. Then add acryloyl chloride dropwise. After the addition is complete, stir in an ice-water bath and transfer to room temperature to continue the reaction for 2-3 hours. Add saturated sodium bicarbonate aqueous solution to quench the reaction. Collect the organic phase and wash it with deionized water, hydrochloric acid aqueous solution and saturated NaCl aqueous solution in sequence. After drying to remove water, concentrate under reduced pressure to obtain intermediate 2.

[0011] A3. Dissolve ammonium heptamolybdate in deionized water, add nitric acid, mix well, transfer to a high-pressure reactor, heat-treat by raising the temperature, after the reaction is complete, cool to room temperature, centrifuge, collect the precipitate, wash with deionized water, freeze-dry, and obtain MoO3 nanomaterials.

[0012] A4. Disperse the MoO3 nanomaterials prepared in step A3 in deionized water, add sodium dodecylbenzenesulfonate, mix evenly, and place under ice-water bath conditions. Add intermediate 2 reaction solution dropwise to the reaction system and stir continuously until the reaction system is homogeneous. Add potassium persulfate aqueous solution, and stir the reaction under ice-water bath conditions for 6-8 hours. Centrifuge, discard the supernatant, wash repeatedly with deionized water and anhydrous ethanol, and freeze-dry to obtain the MoO3 / polymer composite material.

[0013] A5. Disperse the MoO3 / polymer composite material prepared in step A4 in deionized water, add a metal salt aqueous solution, and carry out a complexation reaction at room temperature. After the reaction is completed, centrifuge, discard the supernatant, wash repeatedly with deionized water, and freeze-dry to obtain the metal complexed MoO3 / polymer composite material.

[0014] A6. Take the metal complex MoO3 / polymer composite material and thiourea prepared in step A5 and place them in two quartz boats respectively. Place the quartz boat containing thiourea in the upper part of the tube furnace and place the quartz boat containing the metal complex MoO3 / polymer composite material in the lower part of the tube furnace. Introduce a mixed gas of H2 / Ar into the tube furnace and raise the temperature to carry out the sulfidation reaction. After the reaction is completed, stop heating and allow it to cool naturally to room temperature. Then wash it repeatedly with deionized water and anhydrous ethanol, vacuum dry it, and then ball mill it to obtain the metal coating material.

[0015] Preferably, in step A1, the mass ratio of 3-aminopyrazole to 2-bromopyridine is 1:2.3-2.8;

[0016] Preferably, in step A1, the mass concentration of the 3-aminopyrazole in anhydrous DMF is 0.02-0.03 g / mL;

[0017] Preferably, in step A1, the volume of N,N-dimethylethylenediamine added is 0.5%-0.6% of the volume of anhydrous DMF;

[0018] Preferably, in step A1, the mass ratio of 3-aminopyrazole, anhydrous potassium carbonate, and cuprous chloride is 1:3.5-4.5:0.012-0.018;

[0019] Preferably, in step A1, the reflux reaction temperature is 100-120°C, and the reflux reaction time is 12-18 hours.

[0020] Preferably, in step A2, the mass-to-volume ratio of intermediate 1 to acryloyl chloride is 1.25-1.875 g / mL;

[0021] Preferably, in step A2, the mass-to-volume ratio of intermediate 1 to triethylamine is 0.6-1.0 g / mL;

[0022] Preferably, in step A3, the mass concentration of ammonium heptamolybdate in deionized water is 0.016-0.025 g / mL;

[0023] Preferably, in step A3, the mass-to-volume ratio of ammonium heptamolybdate to nitric acid is 1-1.33 g / mL;

[0024] Preferably, in step A3, the heat treatment temperature is 180-200℃ and the heat treatment time is 18-24h;

[0025] Preferably, in step A4, the mass concentration of the MoO3 nanomaterial in deionized water is 2-2.5 mg / mL;

[0026] Preferably, in step A4, the added mass of sodium dodecylbenzenesulfonate is 5%-10% of the mass of the MoO3 nanomaterial;

[0027] Preferably, in step A4, the preparation method of the intermediate 2 reaction solution specifically includes the following steps: take intermediate 2 and place it in a flask, add 1M hydrochloric acid aqueous solution and anhydrous ethanol, stir evenly and then perform ultrasonic treatment to obtain intermediate 2 reaction solution;

[0028] Preferably, in step A4, the mass-to-volume ratio of intermediate 2 to 1M hydrochloric acid aqueous solution in the intermediate 2 reaction solution is 0.01-0.025 g / mL;

[0029] Preferably, in step A4, the mass-to-volume ratio of intermediate 2 to anhydrous ethanol in the reaction solution of intermediate 2 is 0.1-0.25 g / mL;

[0030] Preferably, in step A4, the mass concentration of potassium persulfate in the potassium persulfate aqueous solution is 6-14 mg / mL;

[0031] Preferably, in step A4, the mass of potassium persulfate added is 28%-30% of the mass of intermediate 2;

[0032] Preferably, in step A5, the mass ratio between the MoO3 / polymer composite material and the metal salt is 3.3-5:1;

[0033] Preferably, in step A5, the mass concentration of the metal salt in the aqueous solution is 4-6 mg / mL; the metal salt includes at least one of copper nitrate, copper sulfate, zinc nitrate, and cobalt nitrate.

[0034] Preferably, in step A5, the stirring speed of the complexation reaction is 500-700 rpm, and the reaction time of the complexation reaction is 3-5 h;

[0035] Preferably, in step A6, the mass ratio between the metal complex MoO3 / polymer composite material and thiourea is 1:1.2-1.5;

[0036] Preferably, in step A6, the reaction temperature of the vulcanization reaction is 300-330℃, the heating rate of the vulcanization reaction is 8-10℃ / min, and the reaction time of the vulcanization reaction is 2-3h.

[0037] The present invention also provides a MoS2-based friction-reducing and wear-resistant composite metal coating material prepared according to the above preparation method.

[0038] The beneficial effects achieved by this invention are as follows:

[0039] This invention provides a MoS2-based friction-reducing and wear-resistant composite metal coating material and its preparation method. This invention utilizes MoS2 and nitrogen-doped carbon-based graphite materials to form a dual low-friction component, achieving low friction coefficient stability far superior to traditional metal coatings. Simultaneously, the metal-metal sulfide composite support phase imparts high hardness and toughness to the coating, maintaining a low wear rate and resolving the core contradiction of traditional coatings where friction reduction is accompanied by poor wear resistance, or vice versa. In this invention, MoS2 is encapsulated by the metal phase and nitrogen-doped carbon-based graphite materials, reducing contact with water molecules in the air and preventing friction-reducing failure caused by MoO3 formation. The metal sulfides and elemental metals possess excellent corrosion resistance, preventing corrosive media from penetrating into the coating. Under corrosion-wear coupled conditions (such as marine equipment and chemical pipelines), the coating life is extended compared to traditional coatings. In this invention, the core function of intermediate 1 is to provide a functional monomer precursor for subsequent polymer synthesis. The conjugated system of pyrazole and pyridine rings in its molecular structure can form polymer chains with a rigid backbone through polymerization reactions in subsequent steps. This rigid polymer framework provides high dispersion support for metals in future metal coatings, enhancing the coating's mechanical strength (such as hardness and resistance to deformation) and preventing wear aggravation due to structural collapse during friction. The nitrogen atom sites in the molecule provide "anchoring points" for subsequent bonding with metal ions and MoO3 nanomaterials, strengthening interfacial adhesion between components and reducing abrasive wear caused by component detachment during friction. This lays the structural foundation for the coating's friction-reducing and wear-resistant properties. The acryloyl double bond introduced in intermediate 2 is a key active site for subsequent polymerization with MoO3 nanomaterials. Through free radical polymerization of the double bond, MoO3 nanomaterials can be "anchored" within the polymer network, preventing further wear. Particles agglomerate in the coating (agglomeration easily leads to stress concentration inside the coating, generating microcracks during friction and aggravating wear). MoO3 nanomaterials are the precursors for subsequent conversion into the core friction-reducing component of MoS2. Its nanoscale dimension has two major advantages: First, in the subsequent polymerization and vulcanization reactions, it can be uniformly dispersed in the polymer matrix and the final coating, avoiding voids inside the coating due to excessive particle size. The MoO3 / polymer composite structure is the key to improving the synergistic effect of coating friction reduction and wear resistance: On the one hand, the polymer network, as a "flexible matrix", can buffer the impact load during the friction process and prevent rigid MoO3 particles from cracking due to stress concentration. At the same time, its dense structure can prevent external abrasive particles from penetrating into the coating and reduce abrasive wear.On the other hand, uniformly dispersed MoO3 nanoparticles, acting as a "hard reinforcing phase," can improve the overall hardness of the polymer matrix (preventing adhesive wear due to excessive softness in the coating). Furthermore, the strong interfacial bonding between MoO3 and the polymer prevents particles from detaching during friction, thus preventing the formation of "secondary abrasive particles." The complexation load of metal ions provides a foundation for the subsequent formation of the "metal support phase." Its core benefits are threefold: First, the uniform dispersion of metal ions in the polymer network prevents metal phase agglomeration (agglomeration easily leads to hardness gradients within the coating, resulting in large differences in local wear rates during friction) during subsequent sulfidation reactions to form the metal phase (such as metal sulfides or elemental metals). This ensures uniform coating hardness, enhances overall wear resistance, and is crucial for the formation of the friction-reducing core component (MoS2) and the wear-resistant support phase (metal phase, graphite-like carbon). These beneficial effects directly determine the final performance of the coating. First, the formation of MoS2 achieves low friction. Layered MoS2 readily undergoes interlayer shear sliding during friction, significantly reducing frictional resistance and adhesive wear. Second, the composite support phase of elemental metal and metal sulfide enhances wear resistance. Elemental metal possesses high toughness, buffering frictional impact, while metal sulfides possess high hardness, resisting abrasive wear. Their synergistic effect gives the coating both toughness and hardness, avoiding a single-phase configuration. Third, the formation of graphite-like carbon further optimizes the friction-reducing effect—the layered structure of graphite-like carbon can form a dual low-friction system with MoS2. Graphite-like carbon can replace MoS2 in reducing friction and improving the coating's environmental adaptability. Fourth, the fine powder after ball milling possesses good dispersibility and flowability, allowing for the formation of a dense coating structure during subsequent coating preparation. This reduces porosity, preventing abrasive intrusion and corrosive media penetration that could exacerbate wear and coating failure. Attached Figure Description

[0040] Figure 1 The COF curves of the metal coating materials prepared in Example 1 and Comparative Examples 1-3 as a function of time are shown.

[0041] Figure 2 The graph shows the results of friction reduction and wear resistance of the metal coating materials prepared in Examples 1-3 and Comparative Examples 1-3.

[0042] Figure 3 The graph shows the wear rate results of the metal coating materials prepared in Examples 1-3 and Comparative Examples 1-3 under different loads.

[0043] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof. Detailed Implementation

[0044] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0045] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those familiar to those skilled in the art. Furthermore, any methods and materials similar to or equivalent to those described herein may be applied to this invention. The preferred embodiments and materials described herein are for illustrative purposes only and do not limit the scope of this application.

[0046] Unless otherwise specified, the experimental methods used in the following examples are conventional methods; unless otherwise specified, the experimental materials and test strains used in the following examples were purchased from commercial channels.

[0047] Example 1

[0048] This embodiment provides a method for preparing a friction-reducing and wear-resistant composite metal coating material based on MoS2, specifically including the following steps:

[0049] A1. Flowing nitrogen gas was introduced into the reaction flask to dry and deoxygenate the reaction system. 1.0 g of 3-aminopyrazole was accurately weighed and placed in the reaction flask. 40 mL of anhydrous DMF and 0.2 mL of N,N-dimethylethylenediamine were mixed evenly and added to the reaction flask. The mixture was stirred at 300 rpm until the 3-aminopyrazole was completely dissolved. 3.5 g of anhydrous potassium carbonate and 12 mg of cuprous chloride were accurately weighed and mixed evenly. 2.5 g of 2-bromopyridine was added and the mixture was stirred until the reaction system was homogeneous. The mixture was transferred to an oil bath and heated to 110 °C for reflux reaction. After 15 h, the reaction was completed. Heating was stopped, and the reaction system was cooled to room temperature. Deionized water was added for quenching, and ethyl acetate was added for extraction. The organic phase was collected and washed with saturated NaCl. Anhydrous magnesium sulfate was added to the organic phase to remove water. After filtration, the filtrate was collected and concentrated by vacuum distillation to obtain intermediate 1.

[0050] A2. Take 1.5g of intermediate 1 prepared in step A1 and place it in a dry flask. Add 100mL of anhydrous dichloromethane to completely dissolve intermediate 1 prepared in step A1. Transfer the flask to an ice-water bath and stir at 300rpm for 10min to allow the reaction system to cool fully. Add 1.5mL of triethylamine at a rate of 0.5mL / min and continue stirring for 5min to allow the triethylamine to be fully dispersed in the reaction system. Add 0.8mL of acryloyl chloride slowly at a rate of 1 drop / s to the reaction system through a constant pressure dropping funnel. Stir the reaction in an ice-water bath for 30min. Transfer the reaction system to room temperature and continue stirring for 3h. Add saturated sodium bicarbonate aqueous solution to the reaction system to quench the reaction. After standing and separating the layers, collect the organic phase. Wash the organic phase with deionized water, 1M hydrochloric acid aqueous solution and saturated NaCl aqueous solution in sequence. After collecting the organic phase, add anhydrous magnesium sulfate to dry and remove water. Distill the organic phase under reduced pressure to obtain intermediate 2.

[0051] A3. Dissolve 0.2g of ammonium heptamolybdate in 80mL of deionized water. Add 1.5mL of 68wt / % nitric acid solution to the reaction system. Stir continuously at 400rpm until the reaction system is mixed evenly. Transfer the mixture to a high-pressure reactor lined with polytetrafluoroethylene. Raise the reaction temperature to 180℃ for heat treatment. After 24h, the reaction is complete. After the reaction cools to room temperature, centrifuge at 3000rpm for 15min. Collect the precipitate, wash it with deionized water, and freeze-dry it to obtain MoO3 nanomaterials.

[0052] A4. Add 0.1g of MoO3 nanomaterial and 40mL of deionized water to a flask, add 5mg of sodium dodecylbenzenesulfonate, stir at 400rpm for 10min, then sonicate at 300W for 30min to obtain a MoO3 nanomaterial suspension. Transfer the suspension to an ice-water bath and stir at 400rpm to completely cool the reaction system. Take 0.25g of intermediate 2 and place it in a flask, add 10mL of... 1M hydrochloric acid aqueous solution and 1mL anhydrous ethanol were stirred at 300rpm for 15min and then sonicated at 300W for 15min to obtain intermediate 2 reaction solution. Intermediate 2 reaction solution was added dropwise to MoO3 nanomaterial suspension at a rate of 1 drop / s. After the addition was complete, the mixture was stirred thoroughly at 500rpm for 30min. 70mg potassium persulfate was dissolved in 5mL water to prepare potassium persulfate aqueous solution, which was added to the reaction system. After stirring at 500rpm for 8h, the reaction solution was collected and centrifuged at 8000rpm for 10min. The supernatant was discarded, and the precipitate was washed with deionized water and anhydrous ethanol in sequence. After freeze-drying, MoO3 / polymer composite material was obtained.

[0053] A5. Take 0.2g of the MoO3 / polymer composite material prepared in step A4 and place it in 40mL of deionized water. Sonicate at 500W for 20min. Accurately weigh 50mg of copper nitrate and dissolve it in 10mL of deionized water to obtain a metal salt aqueous solution. Add it to the reaction system and stir at 500rpm at room temperature to carry out the complexation reaction. After the reaction is completed, transfer it to a centrifuge and centrifuge at 8000rpm for 10min. Discard the supernatant, wash the precipitate repeatedly with deionized water, freeze-dry it, and obtain the copper-complexed MoO3 / polymer composite material.

[0054] A6. Take 0.2g of the metal complex MoO3 / polymer composite material prepared in step A5 and place it in a quartz boat, which is then placed downstream of a tube furnace. Take 0.24g of thiourea and place it in a quartz boat, which is then placed upstream of the tube furnace. Introduce a mixed gas of H2 / Ar (H2 to Ar volume ratio of 1:9) into the tube furnace at 100 sccm for 30 min to remove air. Then, increase the reaction temperature to 320℃ at 8℃ / min and hold for 2.5 h. Stop heating and allow the reaction system to cool naturally to room temperature. Wash the product with deionized water and anhydrous ethanol. After vacuum drying at 70℃ for 6 h, transfer it to a planetary ball mill. Add agate balls at a ball-to-material ratio of 15:1 and ball mill at 250 rpm for 1.5 h to obtain the metal coating material.

[0055] This embodiment also provides a MoS2-based friction-reducing and wear-resistant composite metal coating material prepared according to the above method.

[0056] Example 2

[0057] This embodiment provides a method for preparing a friction-reducing and wear-resistant composite metal coating material based on MoS2, specifically including the following steps:

[0058] A1. Flowing nitrogen gas was introduced into the reaction flask to dry and deoxygenate the reaction system. 1.0 g of 3-aminopyrazole was accurately weighed and placed in the reaction flask. 50 mL of anhydrous DMF and 0.25 mL of N,N-dimethylethylenediamine were mixed evenly and added to the reaction flask. The mixture was stirred at 300 rpm until the 3-aminopyrazole was completely dissolved. 4.0 g of anhydrous potassium carbonate and 18 mg of cuprous chloride were accurately weighed and mixed evenly. 2.3 g of 2-bromopyridine was added and the mixture was stirred until the reaction system was homogeneous. The mixture was transferred to an oil bath and heated to 110 °C for reflux reaction. After 15 h, the reaction was completed. Heating was stopped, and the reaction system was cooled to room temperature. Deionized water was added for quenching, and ethyl acetate was added for extraction. The organic phase was collected and washed with saturated NaCl. Anhydrous magnesium sulfate was added to the organic phase to remove water. After filtration, the filtrate was collected and concentrated by vacuum distillation to obtain intermediate 1.

[0059] A2. Take 1.5g of intermediate 1 prepared in step A1 and place it in a dry flask. Add 90mL of anhydrous dichloromethane to completely dissolve intermediate 1 prepared in step A1. Transfer the flask to an ice-water bath and stir at 300rpm for 10min to allow the reaction system to cool fully. Add 2.0mL of triethylamine at a rate of 0.5mL / min and continue stirring for 5min to allow the triethylamine to be fully dispersed in the reaction system. Add 1.0mL of acryloyl chloride slowly to the reaction system at a rate of 1 drop / s through a constant pressure dropping funnel. Stir the reaction in an ice-water bath for 30min and then transfer the flask to room temperature and continue stirring for 2.5h. Add saturated sodium bicarbonate aqueous solution to the reaction system to quench the reaction. After standing and separating the layers, collect the organic phase and wash it successively with deionized water, 1M hydrochloric acid aqueous solution and saturated NaCl aqueous solution. After collecting the organic phase, add anhydrous magnesium sulfate to dry and remove water. Distill the organic phase under reduced pressure to obtain intermediate 2.

[0060] A3. Dissolve 0.2g of ammonium heptamolybdate in 100mL of deionized water. Add 1.8mL of 68wt / % nitric acid solution to the reaction system. Stir continuously at 400rpm until the reaction system is mixed evenly. Transfer the mixture to a high-pressure reactor lined with polytetrafluoroethylene. Raise the reaction temperature to 200℃ for heat treatment. After 18h, the reaction is complete. After the reaction cools to room temperature, centrifuge at 3000rpm for 15min. Collect the precipitate, wash it with deionized water, and freeze-dry it to obtain MoO3 nanomaterials.

[0061] A4. Add 0.1g of MoO3 nanomaterial and 50mL of deionized water to a flask, add 8mg of sodium dodecylbenzenesulfonate, stir at 400rpm for 10min, then sonicate at 300W for 30min to obtain a MoO3 nanomaterial suspension. Transfer the suspension to an ice-water bath and stir at 400rpm to completely cool the reaction system. Take 0.1g of intermediate 2 and place it in a flask, add 10mL of... 1M hydrochloric acid aqueous solution and 1mL anhydrous ethanol were stirred at 300rpm for 15min and then sonicated at 300W for 15min to obtain intermediate 2 reaction solution. Intermediate 2 reaction solution was added dropwise to MoO3 nanomaterial suspension at a rate of 1 drop / s. After the addition was complete, the mixture was stirred thoroughly at 500rpm for 30min. 30mg potassium persulfate was dissolved in 5mL water to prepare potassium persulfate aqueous solution, which was added to the reaction system. After stirring at 500rpm for 8h, the reaction solution was collected and centrifuged at 8000rpm for 10min. The supernatant was discarded, and the precipitate was washed with deionized water and anhydrous ethanol in sequence. After freeze-drying, MoO3 / polymer composite material was obtained.

[0062] A5. Take 0.2g of the MoO3 / polymer composite material prepared in step A4 and place it in 50mL of deionized water. Sonicate at 500W for 20min. Accurately weigh 60mg of zinc nitrate and dissolve it in 10mL of deionized water to obtain a metal salt aqueous solution. Add it to the reaction system and stir at 600rpm at room temperature to carry out the complexation reaction. After the reaction is completed, transfer it to a centrifuge and centrifuge at 8000rpm for 10min. Discard the supernatant, wash the precipitate repeatedly with deionized water, freeze-dry it, and obtain the zinc complexed MoO3 / polymer composite material.

[0063] A6. Take 0.2g of the metal complex MoO3 / polymer composite material prepared in step A5 and place it in a quartz boat, which is then placed downstream of a tube furnace. Take 0.27g of thiourea and place it in a quartz boat, which is then placed upstream of the tube furnace. Introduce a mixed gas of H2 / Ar (H2 to Ar volume ratio of 1:9) into the tube furnace at 100 sccm for 30 min to remove air. Then, increase the reaction temperature to 330℃ at 9℃ / min and hold for 2 h. Stop heating and allow the reaction system to cool naturally to room temperature. Wash the product with deionized water and anhydrous ethanol. After vacuum drying at 70℃ for 6 h, transfer it to a planetary ball mill. Add agate balls at a ball-to-material ratio of 15:1 and ball mill at 250 rpm for 1.5 h to obtain the metal coating material.

[0064] This embodiment also provides a MoS2-based friction-reducing and wear-resistant composite metal coating material prepared according to the above method.

[0065] Example 3

[0066] This embodiment provides a method for preparing a friction-reducing and wear-resistant composite metal coating material based on MoS2, specifically including the following steps:

[0067] A1. Flowing nitrogen gas was introduced into the reaction flask to dry and deoxygenate the reaction system. 1.0 g of 3-aminopyrazole was accurately weighed and placed in the reaction flask. 33 mL of anhydrous DMF and 0.2 mL of N,N-dimethylethylenediamine were mixed evenly and added to the reaction flask. The mixture was stirred at 300 rpm until the 3-aminopyrazole was completely dissolved. 4.5 g of anhydrous potassium carbonate and 15 mg of cuprous chloride were accurately weighed and mixed evenly. 2.8 g of 2-bromopyridine was added and the mixture was stirred until the reaction system was homogeneous. The mixture was transferred to an oil bath and heated to 110 °C for reflux reaction. After 15 h, the reaction was completed. Heating was stopped, and the reaction system was cooled to room temperature. Deionized water was added for quenching, and ethyl acetate was added for extraction. The organic phase was collected and washed with saturated NaCl. Anhydrous magnesium sulfate was added to the organic phase to remove water. After filtration, the filtrate was collected and concentrated by vacuum distillation to obtain intermediate 1.

[0068] A2. Take 1.5g of intermediate 1 prepared in step A1 and place it in a dry flask. Add 75mL of anhydrous dichloromethane to completely dissolve intermediate 1 prepared in step A1. Transfer the flask to an ice-water bath and stir at 300rpm for 10min to allow the reaction system to cool fully. Add 2.5mL of triethylamine at a rate of 0.5mL / min and continue stirring for 5min to allow the triethylamine to be fully dispersed in the reaction system. Add 1.2mL of acryloyl chloride slowly to the reaction system at a rate of 1 drop / s through a constant pressure dropping funnel. Stir the reaction in an ice-water bath for 30min. Transfer the reaction to room temperature and continue stirring for 2h. Add saturated sodium bicarbonate aqueous solution to the reaction system to quench the reaction. After standing and separating the layers, collect the organic phase. Wash the organic phase with deionized water, 1M hydrochloric acid aqueous solution and saturated NaCl aqueous solution in sequence. After collecting the organic phase, add anhydrous magnesium sulfate to dry and remove water. Distill the organic phase under reduced pressure to obtain intermediate 2.

[0069] A3. Dissolve 0.2g of ammonium heptamolybdate in 120mL of deionized water. Add 2.0mL of 68wt / % nitric acid solution to the reaction system. Stir continuously at 400rpm until the reaction system is mixed evenly. Transfer the mixture to a high-pressure reactor lined with polytetrafluoroethylene. Raise the reaction temperature to 190℃ for heat treatment. After 21h, the reaction is complete. After the reaction cools to room temperature, centrifuge at 3000rpm for 15min. Collect the precipitate, wash it with deionized water, and freeze-dry it to obtain MoO3 nanomaterials.

[0070] A4. Add 0.1g of MoO3 nanomaterial and 40mL of deionized water to a flask, add 10mg of sodium dodecylbenzenesulfonate, stir at 400rpm for 10min, then sonicate at 300W for 30min to obtain a MoO3 nanomaterial suspension. Transfer the suspension to an ice-water bath and stir at 400rpm to completely cool the reaction system. Take 0.18g of intermediate 2 and place it in a flask, add 10mL of... 1M hydrochloric acid aqueous solution and 1mL anhydrous ethanol were stirred at 300rpm for 15min and then sonicated at 300W for 15min to obtain intermediate 2 reaction solution. Intermediate 2 reaction solution was added dropwise to MoO3 nanomaterial suspension at a rate of 1 drop / s. After the addition was complete, the mixture was stirred thoroughly at 500rpm for 30min. 52mg potassium persulfate was dissolved in 5mL water to prepare potassium persulfate aqueous solution, which was added to the reaction system. After stirring at 500rpm for 8h, the reaction solution was collected and centrifuged at 8000rpm for 10min. The supernatant was discarded, and the precipitate was washed with deionized water and anhydrous ethanol in sequence. After freeze-drying, MoO3 / polymer composite material was obtained.

[0071] A5. Take 0.2g of the MoO3 / polymer composite material prepared in step A4 and place it in 60mL of deionized water. Sonicate at 500W for 20min. Accurately weigh 40mg of cobalt nitrate and dissolve it in 10mL of deionized water to obtain a metal salt aqueous solution. Add it to the reaction system and stir at 700rpm at room temperature to carry out the complexation reaction. After the reaction is completed, transfer it to a centrifuge and centrifuge at 8000rpm for 10min. Discard the supernatant, wash the precipitate repeatedly with deionized water, freeze-dry it, and obtain the cobalt complexed MoO3 / polymer composite material.

[0072] A6. Take 0.2g of the metal complex MoO3 / polymer composite material prepared in step A5 and place it in a quartz boat, which is then placed downstream of a tube furnace. Take 0.30g of thiourea and place it in a quartz boat, which is then placed upstream of the tube furnace. Introduce a mixed gas of H2 / Ar (H2 to Ar volume ratio of 1:9) into the tube furnace at 100 sccm for 30 min to remove air. Then, increase the reaction temperature to 300℃ at 10℃ / min and hold for 3 h. Stop heating and allow the reaction system to cool naturally to room temperature. Wash the product with deionized water and anhydrous ethanol. After vacuum drying at 70℃ for 6 h, transfer it to a planetary ball mill. Add agate balls at a ball-to-material ratio of 15:1 and ball mill at 250 rpm for 1.5 h to obtain the metal coating material.

[0073] This embodiment also provides a MoS2-based friction-reducing and wear-resistant composite metal coating material prepared according to the above method.

[0074] Comparative Example 1

[0075] This comparative example provides a metal coating material and its preparation method. The only difference between this example and Example 1 is that the preparation method of the metal coating material does not include steps A1 and A2. In step A4, intermediate 2 is replaced with methyl methacrylate in the same mass ratio. The remaining components and their contents are the same as in Example 1.

[0076] Comparative Example 2

[0077] This comparative example provides a metal coating material and its preparation method. The only difference between this example and Example 1 is that the preparation method of the metal coating material does not include steps A1 and A2. In step A4, intermediate 2 is replaced with methacrylamide in the same mass ratio. The remaining components and their contents are the same as in Example 1.

[0078] Comparative Example 3

[0079] This comparative example provides a metal coating material and its preparation method. The only difference between this example and Example 1 is that the preparation method of the metal coating material does not include step S5. In step S6, the copper complexed MoO3 / polymer composite material is used in the same mass ratio as in Example 1, while the other components and their contents are the same.

[0080] Application examples

[0081] This example demonstrates cold spraying treatment of the metal coating materials prepared in Examples 1-3 and Comparative Examples 1-3:

[0082] 1. Sample preparation:

[0083] Substrate pretreatment process: 304 stainless steel sheet (size 50mm×25mm×1mm) is selected, with an initial surface roughness Ra≈1.6μm.

[0084] Degreasing: Immerse a stainless steel sheet (e.g., 304, size 50mm×25mm×1mm) in anhydrous ethanol or acetone and ultrasonically clean for 20 minutes (power 400W) to remove surface oil and dust.

[0085] Surface roughening: 80-mesh white corundum was used for sandblasting (sandblasting pressure 0.6MPa, distance 20cm) to achieve a surface roughness Ra of 2.5~5μm for the substrate;

[0086] Drying and preparation: Immediately after sandblasting, blow away any residual sand particles on the surface with compressed air, and then dry with 100°C forced air for 5 minutes to avoid surface oxidation or residual moisture affecting the bonding.

[0087] Pretreatment of coating powder: The metal coating materials prepared in Examples 1-3 and Comparative Examples 1-3 were pretreated;

[0088] Particle size control: Adjust the powder particle size to 10~30μm by sieving or ball milling;

[0089] Drying and impurity removal: Place the powder in an 80℃ vacuum drying oven (vacuum degree -0.09~-0.1MPa) for 2 hours to remove adsorbed moisture.

[0090] Cold spray coating core parameter settings:

[0091]

[0092] Post-coating treatment:

[0093] Surface polishing: Use 1000-grit sandpaper for manual or mechanical polishing to reduce the surface roughness Ra of the coating to 0.8~1.2μm;

[0094] Low-temperature annealing: Anneal at 300℃ in an inert atmosphere (N2) for 1 hour.

[0095] Sample specifications: 304 stainless steel substrate (50mm×25mm×1mm), cold spray coating thickness controlled at 80μm.

[0096] Experimental Example 1

[0097] Friction performance tests were conducted on stainless steel samples with cold-sprayed metal coating materials as described in Examples 1-3 and Comparative Examples 1-3. A UMT-5 TriboLab ball-and-disc friction and wear tester was used. GCr15 bearing steel balls (6mm in diameter) with a surface hardness of HRC 60-62 were selected as the mating parts and polished to Ra≤0.02μm. The mating balls were wiped with anhydrous ethanol before each test to avoid cross-contamination.

[0098] Test parameter settings:

[0099]

[0100] Figure 1 The graphs show the COF curves of the metal coating materials prepared in Example 1 and Comparative Examples 1-3 over time. COF (Coefficient of Friction) is a core physical parameter describing the strength of friction between two contacting surfaces. Essentially, it is the ratio of frictional force to the normal pressure between the two surfaces. The stability of COF reflects the service reliability of the coating. In Example 1, the COF is the lowest, stable between 0.095 and 0.105. The nitrogen heterocyclic polymer improves the dispersion of MoS2 and the copper phase, avoiding agglomeration. The interlayer sliding of MoS2 is efficient, and the components are tightly bonded. After cold spraying, the coating is dense and free from abrasive intrusion caused by pores. In Comparative Example 1, the interaction between methyl methacrylate and MoS2 is weak, which also weakens the complexation with metal ions. MoS2 is prone to agglomeration, the metal phase is unevenly dispersed, interlayer sliding is hindered, and the COF increases. In Comparative Example 2, the amide group of methacrylamide forms hydrogen bonds with MoS2, the dispersibility of MoS2 is better than that of Comparative Example 1, and the complexation with the metal is further improved, and the COF is lower than that of Comparative Example 1. In Example 3, the dispersibility of MoS2 is similar to that of Example 1, but it lacks the support of the metal phase.

[0101] Figure 2 The graph shows the friction-reducing and wear-resistant performance results of the metal coating materials prepared in Examples 1-3 and Comparative Examples 1-3. Wear rate reflects the degree of material wear during friction; the lower the value, the stronger the coating's wear resistance. Coefficient of friction (COF) reflects the resistance of the friction interface; the lower the value, the stronger the coating's ability to reduce friction. As shown in the figure, wear resistance is: Example 3 > Example 1 > Example 2. The ionic radius of Co ions (0.0745 nm) is similar to that of Mo. 6+The ion radius (0.062nm) is closer to that of Co, allowing for more uniform doping into the MoS2 lattice, reducing lattice defects, and improving coating density. In contrast, Zn ions have a larger radius (0.074nm, similar to Co but with a different electronic configuration), resulting in slightly poorer dispersion and a slightly higher wear rate. The wear rate in the comparative study was concentrated around 10 nm. -5 ~10 -6 The magnitude is much higher than the 10 in the example. -7 The friction coefficients of the three examples were all in the range of 0.085 to 0.105, which is considered low. The maximum difference was only 0.018, with no significant fluctuations, indicating that the coating interface lubrication or stress buffering capacity was highly consistent. The friction coefficients of the comparative examples were concentrated in the range of 0.110 to 0.165, which is higher than that of the examples (0.085 to 0.105). The friction coefficients of the comparative examples were 1.93 times that of the examples (0.08563), indicating significantly higher friction resistance and insufficient optimization of coating toughness or lubrication.

[0102] Figure 3 The figures show the wear rate results of the metal coating materials prepared in Examples 1-3 and Comparative Examples 1-3 under different loads. The examples maintained a wear rate of 10 N (low load), 30 N (medium load), and 50 N (high load) at all loads. -7 The extremely low wear rate indicates that its surface hardness, shear strength, and compressive strength are superior. Comparative Example 1 has the highest wear rate (5.26E-05 at 10N), suggesting that its coating may have problems such as loose structure, high porosity, or low bonding strength, making it prone to "particle shedding wear" under load and having the worst strength. Although Comparative Examples 2 and 3 are better than Comparative Example 1, their wear rates at 10N have reached 2.33E-06 and 8.14E-06 respectively (7-53 times that of the Example), indicating that their hardness or shear resistance is still far lower than that of the Example and cannot resist slight friction damage under low load.

[0103] 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.

[0104] The present invention and its embodiments have been described above. This description is not restrictive, and the accompanying drawings are only one embodiment of the present invention. The actual application is not limited to this. In conclusion, if those skilled in the art are inspired by this description and design similar methods and embodiments without departing from the spirit of the present invention, they should all fall within the protection scope of the present invention.

Claims

1. A method for preparing a friction-reducing and wear-resistant composite metal coating material based on MoS2, characterized in that: Specifically, the following steps are included: A1. Dissolve 3-aminopyrazole in a mixed solution of anhydrous DMF and N,N-dimethylethylenediamine, purge with flowing nitrogen, add anhydrous potassium carbonate and cuprous chloride and mix well, then add 2-bromopyridine and stir continuously until the reaction system is homogeneous. Raise the reaction temperature to reflux reaction. After the reaction is completed, add deionized water to quench, add ethyl acetate to extract, collect the organic phase, wash the organic phase with saturated NaCl aqueous solution, dry the organic phase to remove water, and concentrate by rotary evaporation to obtain intermediate 1. A2. Dissolve intermediate 1 prepared in step A1 in anhydrous dichloromethane, transfer to an ice-water bath and stir to cool thoroughly. Slowly add triethylamine and mix evenly. Then add acryloyl chloride dropwise. After the addition is complete, stir in an ice-water bath and transfer to room temperature to continue the reaction for 2-3 hours. Add saturated sodium bicarbonate aqueous solution to quench the reaction. Collect the organic phase and wash it with deionized water, hydrochloric acid aqueous solution and saturated NaCl aqueous solution in sequence. After drying to remove water, concentrate under reduced pressure to obtain intermediate 2. A3. Dissolve ammonium heptamolybdate in deionized water, add nitric acid, mix well, transfer to a high-pressure reactor, heat-treat by raising the temperature, after the reaction is complete, cool to room temperature, centrifuge, collect the precipitate, wash with deionized water, freeze-dry, and obtain MoO3 nanomaterials. A4. Disperse the MoO3 nanomaterials prepared in step A3 in deionized water, add sodium dodecylbenzenesulfonate, mix evenly, and place under ice-water bath conditions. Add intermediate 2 reaction solution dropwise to the reaction system and stir continuously until the reaction system is homogeneous. Add potassium persulfate aqueous solution, and stir the reaction under ice-water bath conditions for 6-8 hours. Centrifuge, discard the supernatant, wash repeatedly with deionized water and anhydrous ethanol, and freeze-dry to obtain the MoO3 / polymer composite material. A5. Disperse the MoO3 / polymer composite material prepared in step A4 in deionized water, add a metal salt aqueous solution, and carry out a complexation reaction at room temperature. After the reaction is completed, centrifuge, discard the supernatant, wash repeatedly with deionized water, and freeze-dry to obtain the metal complexed MoO3 / polymer composite material. A6. Take the metal complex MoO3 / polymer composite material and thiourea prepared in step A5 and place them in two quartz boats respectively. Place the quartz boat containing thiourea upstream of the tube furnace and the quartz boat containing the metal complex MoO3 / polymer composite material downstream of the tube furnace. Introduce a mixed gas of H2 / Ar into the tube furnace and raise the temperature to carry out the sulfidation reaction. After the reaction is completed, stop heating and allow it to cool naturally to room temperature. Then, wash it repeatedly with deionized water and anhydrous ethanol, vacuum dry it, and then ball mill it to obtain the metal coating material.

2. The method for preparing a MoS2-based friction-reducing and wear-resistant composite metal coating material according to claim 1, characterized in that: In step A1, the mass ratio of 3-aminopyrazole to 2-bromopyridine is 1:2.3-2.8; the mass concentration of 3-aminopyrazole in anhydrous DMF is 0.02-0.03 g / mL; and the mass ratio of 3-aminopyrazole, anhydrous potassium carbonate, and cuprous chloride is 1:3.5-4.5:0.012-0.

018.

3. The method for preparing a MoS2-based friction-reducing and wear-resistant composite metal coating material according to claim 2, characterized in that: In step A1, the volume of N,N-dimethylethylenediamine added is 0.5%-0.6% of the volume of anhydrous DMF; in step A1, the reflux reaction temperature is 100-120℃, and the reflux reaction time is 12-18h.

4. The method for preparing a MoS2-based friction-reducing and wear-resistant composite metal coating material according to claim 3, characterized in that: In step A2, the mass-to-volume ratio of intermediate 1 to acryloyl chloride is 1.25-1.875 g / mL; the mass-to-volume ratio of intermediate 1 to triethylamine is 0.6-1.0 g / mL.

5. The method for preparing a MoS2-based friction-reducing and wear-resistant composite metal coating material according to claim 4, characterized in that: In step A3, the mass concentration of ammonium heptamolybdate in deionized water is 0.016-0.025 g / mL; the mass-to-volume ratio of ammonium heptamolybdate to nitric acid is 1-1.33 g / mL; the heat treatment temperature is 180-200℃, and the heat treatment time is 18-24 h.

6. The method for preparing a MoS2-based friction-reducing and wear-resistant composite metal coating material according to claim 5, characterized in that: In step A4, the mass concentration of the MoO3 nanomaterial in deionized water is 2-2.5 mg / mL; the added mass of sodium dodecylbenzenesulfonate is 5%-10% of the mass of the MoO3 nanomaterial; the mass concentration of potassium persulfate in the potassium persulfate aqueous solution is 6-14 mg / mL; and the added mass of potassium persulfate is 28%-30% of the mass of intermediate 2.

7. The method for preparing a MoS2-based friction-reducing and wear-resistant composite metal coating material according to claim 6, characterized in that: In step A4, the preparation method of the intermediate 2 reaction solution specifically includes the following steps: intermediate 2 is placed in a flask, 1M hydrochloric acid aqueous solution and anhydrous ethanol are added, stirred evenly and then ultrasonically treated to obtain intermediate 2 reaction solution; in the intermediate 2 reaction solution, the mass-volume ratio of intermediate 2 to 1M hydrochloric acid aqueous solution is 0.01-0.025 g / mL; in the intermediate 2 reaction solution, the mass-volume ratio of intermediate 2 to anhydrous ethanol is 0.1-0.25 g / mL.

8. The method for preparing a MoS2-based friction-reducing and wear-resistant composite metal coating material according to claim 7, characterized in that: In step A5, the mass ratio between the MoO3 / polymer composite material and the metal salt is 3.3-5:1; the mass concentration of the metal salt in the aqueous solution is 4-6 mg / mL; the metal salt includes at least one of copper nitrate, copper sulfate, zinc nitrate, and cobalt nitrate; the stirring speed of the complexation reaction is 500-700 rpm, and the reaction time of the complexation reaction is 3-5 h.

9. The method for preparing a MoS2-based friction-reducing and wear-resistant composite metal coating material according to claim 8, characterized in that: In step A6, the mass ratio between the metal complex MoO3 / polymer composite material and thiourea is 1:1.2-1.5; the reaction temperature of the vulcanization reaction is 300-330℃, the heating rate of the vulcanization reaction is 8-10℃ / min, and the reaction time of the vulcanization reaction is 2-3h.

10. A MoS2-based friction-reducing and wear-resistant composite metal coating material, characterized in that: It is prepared by the preparation method according to any one of claims 1-9.

Images