Cd-doped ZIF-62 and preparation method thereof, Cd-doped ZIF-62 / PEEK composite material and preparation method and application thereof

Abstract

The invention relates to the technical field of friction materials, in particular to Cd-doped ZIF-62, a preparation method of the Cd-doped ZIF-62, a Cd-doped ZIF-62 / PEEK composite material and a preparation method and application of the Cd-doped ZIF-62 / PEEK composite material. The invention provides a Cd-doped ZIF-62 which is used as a tribological functional filler and can be applied to a PEEK (Polyether Ether Ketone) material formed by FDM (Fused Deposition Molding). Cd heterojunctions are added to the Cd-doped ZIF-62, so that the melting point and shear strength of ZIF-62 particles are reduced, and when the Cd-doped ZIF-62 is used as a functional filler to be applied to a PEEK matrix, the Cd-doped ZIF-62 particles are easier to decompose due to interlayer shear when the Cd-doped ZIF-62 and bearing steel are subjected to opposite abrasion, so that an anti-friction effect is achieved, formation of a transfer film is promoted, and further anti-friction and anti-wear modification of the PEEK composite material is achieved.

Description

Technical Field

[0001] This invention relates to the field of friction materials technology, and in particular to a Cd-doped ZIF-62 and its preparation method, a Cd-doped ZIF-62 / PEEK composite material and its preparation method and application. Background Technology

[0002] Polyetheretherketone (PEEK), a specialty engineering plastic with excellent tribological properties, is widely used in self-lubricating bearings, speed reducers, guide rails, hinges, and sliding tracks. Using PEEK can further reduce the weight of sliding parts, achieving lightweighting. However, with the rapid development of industrial robots, low-altitude aircraft, and new energy vehicles, more stringent requirements are being placed on the tribological properties of PEEK materials, and single-material PEEK is gradually becoming insufficient to meet these increasingly demanding performance requirements. Meanwhile, PEEK components in these devices are small in size and complex in structure, and given the low melt flow properties of PEEK, they are currently typically produced by extruding preforms followed by machining. This production method has high processing costs and suffers from the inherent material loss problems of subtractive manufacturing. As a mature 3D printing technology, Fused Deposition Modeling (FDM) can produce PEEK devices with fine dimensions and complex structures through in-situ layer-by-layer deposition.

[0003] However, current research on the tribological properties of PEEK composites mainly focuses on PEEK extrusion and injection molding processes. Existing filler modification systems are also largely based on these processes. Therefore, developing PEEK fillers suitable for FDM molding has become an urgent problem to be solved. The inventors previously prepared ZIF-62 / PEEK composites suitable for FDM molding using ZIF-62 as a filler, but the ZIF-62 / PEEK composites exhibited poor tribological properties under high load conditions. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide a Cd-doped ZIF-62 and its preparation method, a Cd-doped ZIF-62 / PEEK composite material and its preparation method and application. The ZIF-62 / PEEK composite material provided by this invention exhibits excellent tribological properties under high load conditions.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a Cd-doped ZIF-62, in which some Zn metal center sites in ZIF-62 are replaced by Cd; the molar substitution rate of Cd in the metal centers of ZIF-62 is 10~40%.

[0006] This invention provides a method for preparing Cd-doped ZIF-62 as described above, comprising the following steps: A zinc source, imidazole, benzimidazole, cadmium source and organic solvent were mixed and a coordination reaction was carried out under ball milling conditions to obtain Cd-doped ZIF-62 with solvent adsorbed. The Cd-doped ZIF-62 with adsorbed solvent was calcined under vacuum to obtain the Cd-doped ZIF-62. The cadmium source is Cd(OAc)2 and CdO, and the molar ratio of Cd(OAc)2 to CdO is 1:8~12; The percentage of the molar amount of Cd in the cadmium source relative to the total molar amount of Cd in the cadmium source and Zn in the zinc source is 10-40%.

[0007] Preferably, the ratio of the total molar amount of Zn in the zinc source and Cd in the cadmium source to the total molar amount of imidazole and benzimidazole is 1:2; the molar ratio of imidazole and benzimidazole is 5~8:1. The zinc source includes zinc hydroxide and zinc acetate; the molar percentage of zinc acetate in the zinc source is 20-40%.

[0008] Preferably, the ball mill rotation speed is 700~1200 r / min; the coordination reaction time is 1~3 h.

[0009] Preferably, the vacuum calcination temperature is 250~350℃ and the time is 0.5~2 h.

[0010] The present invention provides a Cd-doped ZIF-62 / PEEK composite material, comprising 90-99% PEEK and 1-10% Cd-doped ZIF-62 by mass percentage.

[0011] This invention provides a method for preparing the Cd-doped ZIF-62 / PEEK composite material described above, comprising the following steps: PEEK and Cd-doped ZIF-62 were mixed to obtain a mixed powder; The mixed powder is extruded to obtain a composite filament; The composite filament was 3D printed to obtain the Cd-doped ZIF-62 / PEEK composite material.

[0012] Preferably, the 3D printing parameters include: nozzle temperature of 400~450℃, base plate temperature of 120~250℃, cavity temperature of 120~250℃, nozzle diameter of 0.2~0.4 mm, printing speed of 20~40 mm / s, layer height of 0.2 mm, and infill density of 100%.

[0013] Preferably, the extrusion molding parameters include: from the tail to the head direction, the temperature of zone one is 320°C, the temperature of zone two is 370°C, the temperature of zone three is 360°C, and the temperature of the head is 355°C.

[0014] This invention provides the application of the Cd-doped ZIF-62 / PEEK composite material prepared by the above-described method in friction materials.

[0015] This invention provides a Cd-doped ZIF-62 as a tribological functional filler applicable to FDM-molded PEEK materials. By adding Cd heterojunctions, the Cd-doped ZIF-62 lowers the melting point and shear strength of the ZIF-62 particles. When used as a functional filler in a PEEK matrix, it is more prone to interlaminar shear decomposition during friction with bearing steel, thus reducing friction and promoting the formation of a transfer film, further achieving friction-reducing and wear-resistant modification of the PEEK composite material.

[0016] This invention proposes that by modifying ZIF-62 with Cd doping, while ensuring the extrusion-melt deposition molding of PEEK, the modified ZIF-62 filler particles can be added in a large proportion of less than 10 wt%, which solves the technical problem that the amount of traditional ZIF-62 added to the PEEK matrix is ​​low (generally not exceeding 3%) due to the limitations of the molding process.

[0017] The Cd-doped ZIF-62 of this invention is used in the preparation of PEEK materials. The resulting Cd-doped ZIF-62 / PEEK composite material exhibits superior tribological properties under high load conditions, which can further broaden the application of PEEK materials in industrial robots, low-altitude aircraft, new energy vehicles and other fields. Attached Figure Description

[0018] Figure 1 A schematic diagram of the tetrahedral structure of Cd-doped ZIF-62; Figure 2 SEM image of Cd-doped ZIF-62 prepared in Example 1; Figure 3 SEM image of undoped ZIF-62; Figure 4 XRD pattern of Cd-doped ZIF-62; Figure 5 SEM image of the wear surface of the 3D-printed Cd-doped ZIF-62 / PEEK composite material in Example 1; Figure 6 This is a SEM image of the dual transfer film after the wear test in Example 1. Detailed Implementation

[0019] The present invention provides a Cd-doped ZIF-62, wherein some Zn metal center sites in ZIF-62 are replaced by Cd; the molar substitution rate of Cd in the metal center of ZIF-62 is 10~40%, and in specific embodiments it can be 10%, 15%, 20%, 25%, 30%, 35% or 40%, with the most preferred being 20%.

[0020] Figure 1 This is a schematic diagram of the tetrahedral structure of Cd-doped ZIF-62.

[0021] In this invention, ZIF-62 is a metal-organic framework (MOF) compound composed of zinc ions (Zn). 2+ The zinc (Zn) metal center is linked to two imidazole ligands (typically imidazole (Im) and benzimidazole (BIm)) via coordinate bonds, forming a three-dimensional porous structure. The metal center is zinc (Zn), and the organic ligands are imidazole (Im) and benzimidazole (BIm). Each Zn... 2+ It forms tetrahedral coordination with the nitrogen atom of imidazole ligands, with each nitrogen atom of imidazole or benzimidazole ligand having a Zn atom. 2+ Coordination occurs, with the nitrogen atom at the other end of the ligand bonded to another Zn atom. 2+ This forms an extended three-dimensional network, with alternating connections of ligands creating four- or six-membered ring channels. The Cd-doped ZIF-62 provided by this invention involves partial replacement of zinc ions with cadmium ions, while still maintaining the ZIF-62 crystal structure.

[0022] This invention provides a method for preparing Cd-doped ZIF-62 as described above, comprising the following steps: A zinc source, imidazole, benzimidazole, cadmium source and organic solvent were mixed and a coordination reaction was carried out under ball milling conditions to obtain Cd-doped ZIF-62 with solvent adsorbed. The Cd-doped ZIF-62 with adsorbed solvent was calcined under vacuum to obtain the Cd-doped ZIF-62. The cadmium source is Cd(OAc)2 and CdO, and the molar ratio of Cd(OAc)2 to CdO is 1:8~12; The percentage of the molar amount of Cd in the cadmium source relative to the total molar amount of Cd in the cadmium source and Zn in the zinc source is 10-40%.

[0023] Unless otherwise specified, all raw materials used in this invention are commercially available products well known in the art.

[0024] This invention involves mixing a zinc source, imidazole, benzimidazole, Cd(OAc)2, CdO, and an organic solvent, and then performing a coordination reaction under ball milling conditions to obtain Cd-doped ZIF-62 with adsorbed solvent.

[0025] In this invention, the zinc source preferably includes zinc hydroxide and zinc acetate; the zinc acetate is further preferably Zn(OAc)2•2H2O; the molar percentage of zinc acetate in the zinc source is preferably 20~40%, and in specific embodiments it can be 20%, 25%, 30%, 35% or 40%, with the most preferred being 30%.

[0026] In this invention, the cadmium source is Cd(OAc)2 and CdO, and the molar ratio of Cd(OAc)2 to CdO is 1:8 to 12. In specific embodiments, it can be 1:8, 1:9, 1:10, 1:11, or 1:12. The Cd(OAc)2 is preferably Cd(OAc)2•2H2O.

[0027] In this invention, the ratio of the total molar amount of Zn in the zinc source and Cd in the cadmium source to the total molar amount of imidazole and benzimidazole is preferably 1:2; the molar ratio of imidazole and benzimidazole is preferably 5 to 8:1, and in specific embodiments it can be 5:1, 6:1, 7:1 or 8:1.

[0028] In this invention, the molar amount of Cd in the cadmium source accounts for 10-40% of the total molar amount of Cd in the cadmium source and Zn in the zinc source. In specific embodiments, it can be 10%, 10.88% (Example 3), 15%, 20%, 21.56% (Examples 1-2), 25%, 30%, 35% or 40%.

[0029] In this invention, the organic solvent preferably includes N-methylpyrrolidone. In this invention, the preferred ratio of the zinc source to the organic solvent is 2-10 g: 1-10 mL.

[0030] In this invention, the ball milling speed is preferably 700~1200 r / min, and in specific embodiments it can be 700, 800, 900, 1000, 1100 or 1200 r / min; the coordination reaction time is preferably 1~3 h, and in specific embodiments it can be 1, 1.5, 2, 2.5 or 3 h.

[0031] This invention uses CdO to ensure that Cd is doped into the ZIF-62 lattice to form stable Cd-doped ZIF-62, rather than a physical mixture of Cd and ZIF-62. Because the raw material system is weakly acidic, during ball milling, CdO slowly dissolves, releasing cadmium ions that replace zinc in ZIF-62 to form Cd-doped ZIF-62. Furthermore, during the coordination reaction, organic solvents are adsorbed and coordinated within the pores of the Cd-doped ZIF-62.

[0032] After the coordination reaction is completed, the present invention preferably uses ethanol to filter and wash the product, and then places the washed product in an oven at 100°C for 6 h to dry it, thereby obtaining Cd-doped ZIF-62 with solvent adsorbed.

[0033] After obtaining Cd-doped ZIF-62 with adsorbed solvent, the present invention performs vacuum calcination on the Cd-doped ZIF-62 with adsorbed solvent to obtain the Cd-doped ZIF-62.

[0034] Before vacuum calcination, the present invention preferably involves repeatedly evacuating and degassing the calcination chamber followed by nitrogen purging. This repeated evacuation and nitrogen purging ensures complete removal of O2 from the chamber, improving the thermal stability of Cd-doped ZIF-62. In an embodiment of the present invention, this process is specifically repeated three times.

[0035] In this invention, the vacuum calcination temperature is preferably 250~350℃, and in specific embodiments it can be 250, 280, 300, 320 or 350℃; the vacuum calcination time is preferably 0.5~2 h, and in specific embodiments it can be 0.5, 1, 1.5 or 2 h. This invention utilizes vacuum calcination to remove the organic solvent adsorbed by Cd-doped ZIF-62. If it is not removed, Cd-doped ZIF-62 cannot be formed when used for 3D printing.

[0036] The present invention provides a Cd-doped ZIF-62 / PEEK composite material, comprising 90-99% PEEK and 1-10% Cd-doped ZIF-62 by mass percentage.

[0037] In a specific embodiment, the content of Cd-doped ZIF-62 in the Cd-doped ZIF-62 / PEEK composite material can be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10%, with the balance being PEEK.

[0038] This invention provides a method for preparing the Cd-doped ZIF-62 / PEEK composite material described above, comprising the following steps: PEEK and Cd-doped ZIF-62 were mixed to obtain a mixed powder; The mixed powder is extruded to obtain a composite filament; The composite filament was 3D printed to obtain the Cd-doped ZIF-62 / PEEK composite material.

[0039] This invention mixes PEEK and Cd-doped ZIF-62 to obtain a mixed powder.

[0040] In this invention, the mixing is preferably mechanical mixing, and the mechanical mixing is preferably carried out in a high-speed mixer. This invention does not specifically limit the parameters of the mechanical mixing, as long as the two materials can be mixed evenly.

[0041] After mixing, the present invention preferably further includes drying; the drying temperature is preferably 80~120℃, specifically 80℃, 90℃, 100℃, 110℃ or 120℃; the drying time is preferably 12~36h, specifically 12h, 18h, 24h, 30h or 36h.

[0042] After obtaining the mixed powder, the present invention extrudes the mixed powder to form a composite filament.

[0043] In this invention, the extrusion molding parameters preferably include: from the tail to the head, the temperature in zone one is 320°C, the temperature in zone two is 370°C, the temperature in zone three is 360°C, and the head temperature is 355°C. In this invention, the extrusion molding is preferably performed under a protective atmosphere, which preferably includes nitrogen. In this invention, the extrusion molding is preferably performed in a twin-screw extruder. In this invention, the diameter of the composite filament is preferably 1.75 ± 0.1 mm.

[0044] After the extrusion molding, the present invention preferably further includes: drying the obtained extrudate to obtain the composite filament. In the present invention, the drying temperature is preferably 90~130℃, specifically 90, 100, 110, 120 or 130℃; the drying time is preferably 9~13h, specifically 9, 10, 11 or 12h; the drying is preferably carried out in a drying oven.

[0045] After obtaining the composite filament, the present invention performs 3D printing on the composite filament to obtain the Cd-doped ZIF-62 / PEEK composite material.

[0046] In this invention, the 3D printing is preferably FDM. The preferred parameters for the 3D printing include: nozzle temperature of 400-450°C, base plate temperature of 120-250°C, cavity temperature of 120-250°C, nozzle diameter of 0.2-0.4 mm, printing speed of 20-40 mm / s, layer height of 0.2 mm, and infill density of 100%. In specific embodiments, the nozzle temperature can be 400, 410, 420, 430, 440, or 450°C; the base plate temperature can be 120, 150, 180, 200, 220, or 250°C; the cavity temperature can be 120, 150, 180, 200, 220, or 250°C; the nozzle diameter can be 0.2, 0.3, or 0.4 mm; and the printing speed can be 20, 25, 30, 35, or 40 mm / s.

[0047] This invention provides the application of the Cd-doped ZIF-62 / PEEK composite material described in the above-described scheme or the Cd-doped ZIF-62 / PEEK composite material prepared by the above-described preparation method in friction materials.

[0048] The following detailed descriptions, in conjunction with embodiments, illustrate the Cd-doped ZIF-62 and its preparation method, the Cd-doped ZIF-62 / PEEK composite material and its preparation method, and its applications. However, these descriptions should not be construed as limiting the scope of protection of this invention.

[0049] Example 1: (1) Synthesis of Cd-doped ZIF-62 2.784 g Zn(OH)₂, 2.64 g Zn(OAc)₂•2H₂O, 0.268 g Cd(OAc)₂•2H₂O, 1.284 g CdO, 5.955 g imidazole, 1.475 g benzimidazole, and 5 mL N-methylpyrrolidone were weighed using an analytical balance and added to an agate jar. The jar was then placed in a planetary ball mill and ground at 800 r / min for 2 h. After grinding, the product was collected and washed with ethanol by vacuum filtration. Finally, the washed product was dried in an oven at 100 °C for 6 h to obtain Cd-doped ZIF-62.

[0050] Subsequently, the adsorbed and coordinated organic solvents in the pores of Cd-doped ZIF-62 were further removed by high-temperature vacuum calcination. Specifically, the dried Cd-doped ZIF-62 was placed in a high-temperature vacuum oven. The oven was repeatedly degassed and purged with nitrogen three times using a vacuum pump to ensure complete removal of O2. The oven temperature was then further heated to 300°C, and vacuum calcination was performed for 1 hour to completely desorb the adsorbed gases and release the coordinated NMP.

[0051] (2) Preparation of Cd-doped ZIF-62 / PEEK composite material 6 g of Cd-doped ZIF-62 was weighed using an analytical balance and added to a high-speed mixer along with 94 g of PEEK for thorough mechanical mixing. The mixture was then dried at 100°C. Under nitrogen protection, the mixture was extruded into filaments using a twin-screw extruder, yielding filaments with a diameter of 1.75 ± 0.1 mm. The temperature settings for each zone of the extruder were as follows: Zone 1: 320°C, Zone 2: 370°C, Zone 3: 360°C, and Die Head Zone 1: 355°C. Through these steps, Cd-doped ZIF-62 / PEEK composite filaments were obtained. Subsequently, the filaments were dried in a 100°C drying oven for 12 hours. Samples were then printed using a fused deposition modeling (FDM) 3D printer. The parameters set during the printing process are as follows: nozzle temperature 440℃, substrate temperature 200℃, cavity temperature 200℃, nozzle diameter 0.2 mm, printing speed 20 mm / s, layer height 0.2 mm, and infill density 100%. The final material obtained is a Cd-doped ZIF-62 / PEEK composite material.

[0052] Example 2: (1) Synthesis of Cd-doped ZIF-62 Same as Example 1.

[0053] (2) Preparation of Cd-doped ZIF-62 / PEEK composite material 2 g of Cd-doped ZIF-62 was weighed using an analytical balance and added to a high-speed mixer along with 98 g of PEEK for thorough mechanical mixing. The mixture was then dried at 100°C. Under nitrogen protection, the mixture was extruded into filaments using a twin-screw extruder, yielding filaments with a diameter of 1.75 ± 0.1 mm. The temperature settings for each zone of the extruder were as follows: Zone 1: 320°C, Zone 2: 370°C, Zone 3: 360°C, and Die Head Zone 1: 355°C. Through these steps, Cd-doped ZIF-62 / PEEK composite filaments were obtained. Subsequently, the filaments were dried in a 100°C drying oven for 12 hours. Samples were then printed using a fused deposition modeling (FDM) 3D printer. The parameters set during the printing process are as follows: nozzle temperature 440℃, substrate temperature 200℃, cavity temperature 200℃, nozzle diameter 0.2 mm, printing speed 20 mm / s, layer height 0.2 mm, and fill density 100%. The final material obtained is a Cd-doped ZIF-62 / PEEK composite material.

[0054] Example 3: (1) Synthesis of Cd-doped ZIF-62 First, using an analytical balance, 3.132 g Zn(OH)₂, 2.97 g Zn(OAc)₂•2H₂O, 0.134 g Cd(OAc)₂•2H₂O, 0.642 g CdO, 5.955 g imidazole, 1.475 g benzimidazole, and 5 mL N-methylpyrrolidone were weighed and added to an agate jar. The jar was then placed in a planetary ball mill and ground at 800 r / min for 2 h. After grinding, the product was collected and washed with ethanol by vacuum filtration. Finally, the washed product was dried in an oven at 100℃ for 6 h to obtain Cd-doped ZIF-62.

[0055] Subsequently, the adsorbed and coordinated organic solvents in the pores of Cd-doped ZIF-62 were further removed by high-temperature vacuum calcination. Specifically, the dried Cd-doped ZIF-62 was placed in a high-temperature vacuum oven. The oven was repeatedly degassed and purged with nitrogen three times using a vacuum pump to ensure complete removal of O2. The oven temperature was then further heated to 300°C, and vacuum calcination was performed for 1 hour to completely desorb the adsorbed gases and release the coordinated NMP.

[0056] (2) Preparation of Cd-doped ZIF-62 / PEEK composite material 6 g of Cd-doped ZIF-62 was weighed using an analytical balance and added to a high-speed mixer along with 94 g of PEEK for thorough mechanical mixing. The mixture was then dried at 100°C. Under nitrogen protection, the mixture was extruded into filaments using a twin-screw extruder, yielding filaments with a diameter of 1.75 ± 0.1 mm. The temperature settings for each zone of the extruder were as follows: Zone 1: 320°C, Zone 2: 370°C, Zone 3: 360°C, and Die Head Zone 1: 355°C. Through these steps, Cd-doped ZIF-62 / PEEK composite filaments were obtained. Subsequently, the filaments were dried in a 100°C drying oven for 9–13 hours. Samples were then printed using a fused deposition modeling (FDM) 3D printer. The parameters set during the printing process are as follows: nozzle temperature 440℃, substrate temperature 200℃, cavity temperature 200℃, nozzle diameter 0.2-0.4 mm, printing speed 20-40 mm / s, layer height 0.2 mm, and fill density 100%. The final material obtained is a Cd-doped ZIF-62 / PEEK composite material.

[0057] Comparative Example 1: (1) Synthesis of Cd-doped ZIF-62 First, using an analytical balance, 1.74 g Zn(OH)₂, 1.65 g Zn(OAc)₂•2H₂O, 0.67 g Cd(OAc)₂•2H₂O, 3.21 g CdO, 5.955 g imidazole, 1.475 g benzimidazole, and 5 mL N-methylpyrrolidone were weighed and added to an agate jar. The jar was then placed in a planetary ball mill and ground at 800 r / min for 2 h. After grinding, the product was collected and washed with ethanol by vacuum filtration. Finally, the washed product was dried in an oven at 100 °C for 6 h to obtain Cd-doped ZIF-62. The molar amount of Cd in the cadmium source accounted for 52.37% of the total molar amount of Cd in the cadmium source and Zn in the zinc source.

[0058] Subsequently, the adsorbed and coordinated organic solvents in the pores of Cd-doped ZIF-62 were further removed by high-temperature vacuum calcination. Specifically, the dried Cd-doped ZIF-62 was placed in a high-temperature vacuum oven. The oven was repeatedly degassed and purged with nitrogen three times using a vacuum pump to ensure complete removal of O2. The oven temperature was then further heated to 300°C, and vacuum calcination was performed for 1 hour to completely desorb the adsorbed gases and release the coordinated NMP.

[0059] (2) Preparation of Cd-doped ZIF-62 / PEEK composite material 6 g of Cd-doped ZIF-62 was weighed using an analytical balance and added to a high-speed mixer along with 94 g of PEEK for thorough mechanical mixing. The mixture was then dried at 100°C. Under nitrogen protection, the mixture was extruded into filaments using a twin-screw extruder, yielding filaments with a diameter of 1.75 ± 0.1 mm. The temperature settings for each zone of the extruder were as follows: Zone 1: 320°C, Zone 2: 370°C, Zone 3: 360°C, and Die Head Zone 1: 355°C. Through these steps, Cd-doped ZIF-62 / PEEK composite filaments were obtained. Subsequently, the filaments were dried in a 100°C drying oven for 12 hours. Samples were then printed using a fused deposition modeling (FDM) 3D printer. The parameters set during the printing process are as follows: nozzle temperature 440℃, substrate temperature 200℃, cavity temperature 200℃, nozzle diameter 0.2 mm, printing speed 20 mm / s, layer height 0.2 mm, and fill density 100%. The final material obtained is a Cd-doped ZIF-62 / PEEK composite material.

[0060] Comparative Example 2: (1) Preparation of PEEK polymer by fused deposition modeling 100 g of PEEK was weighed using an analytical balance and dried at 100°C. Under nitrogen protection, the mixture was extruded into filaments using a twin-screw extruder, yielding filaments with a diameter of 1.75 ± 0.1 mm. The extruder temperatures were set as follows: Zone 1: 320°C, Zone 2: 370°C, Zone 3: 360°C, and Die Head Zone 1: 355°C. This process yielded PEEK filaments. The filaments were then dried in a 100°C oven for 12 hours. A fused deposition modeling (FDM) 3D printer was used to print the sample. The printing parameters were set as follows: nozzle temperature 440°C, base plate temperature 200°C, cavity temperature 200°C, nozzle diameter 0.2 mm, printing speed 20 mm / s, layer height 0.2 mm, and infill density 100%. The final material obtained was PEEK material.

[0061] Comparative Example 3: (1) Synthesis of ZIF-62 First, 3.48 g Zn(OH)₂, 3.3 g Zn(OAc)₂•2H₂O, 5.955 g imidazole, 1.475 g benzimidazole, and 5 mL N-methylpyrrolidone (NMP) were weighed using an analytical balance and added to an agate jar. The jar was then placed in a planetary ball mill and ground at 800 r / min for 2 h. After grinding, the product was collected and washed with ethanol using vacuum filtration. Finally, the washed product was dried in an oven at 100℃ for 6 h to obtain ZIF-62.

[0062] Subsequently, the adsorbed and coordinated organic solvents in the pores of ZIF-62 were further removed by high-temperature vacuum calcination. Specifically, the dried ZIF-62 was placed in a high-temperature vacuum oven. The oven was repeatedly degassed and purged with nitrogen three times using a vacuum pump in a dual-row tube phase vacuum oven to ensure complete removal of O2. The oven temperature was then further heated to 300°C, and vacuum calcination was carried out for 1 hour to completely desorb the adsorbed gas and release the coordinated NMP.

[0063] (2) Preparation of ZIF-62 / PEEK composite material 2 g of ZIF-62 was weighed using an analytical balance and added to a high-speed mixer along with 98 g of PEEK for thorough mechanical mixing. The mixture was then dried at 100°C. Under nitrogen protection, the mixture was extruded into filaments using a twin-screw extruder, yielding filaments with a diameter of 1.75 ± 0.1 mm. The temperature settings for each zone of the extruder were as follows: Zone 1: 320°C, Zone 2: 370°C, Zone 3: 360°C, and Die Head Zone 1: 355°C. Through these steps, Cd-doped ZIF-62 / PEEK composite filaments were obtained. The filaments were then dried in a 100°C drying oven for 12 hours. Samples were then printed using a fused deposition modeling (FDM) 3D printer. The printing parameters were as follows: nozzle temperature: 440°C, base plate temperature: 200°C, cavity temperature: 200°C, nozzle diameter: 0.2 mm, printing speed: 20 mm / s, layer height: 0.2 mm, and infill density: 100%. The final material obtained is the ZIF-62 / PEEK composite material.

[0064] Comparative Example 4 Using an analytical balance, 2.784 g Zn(OH)₂, 2.64 g Zn(OAc)₂•2H₂O, 2.948 g Cd(OAc)₂•2H₂O, 5.955 g imidazole, 1.475 g benzimidazole, and 5 mL N-methylpyrrolidone were weighed and added to an agate jar. The jar was then placed on a planetary ball mill and ground at 800 r / min for 2 h. After grinding, the product was collected and washed with ethanol by vacuum filtration.

[0065] The product clearly shows two substances, a pale yellow and a white one. Significant stratification also occurred during the filtration process. This can be attributed to the high solubility of Cd(OAc)₂•2H₂O in the reaction system and the excessively high molar concentration of Cd in the initial stage of the ball milling reaction.

[0066] Tribological property testing The tribological properties of the samples prepared in Examples 1-4 and Comparative Examples 1-3 were tested according to ASTM G99-2. Specifically, a pin-disc contact mode was used, and the experimental conditions were set as follows: load 64 N and speed 1 m / s.

[0067] Table 1 Performance indicators of the embodiments and comparative examples

[0068] As shown in Table 1, compared with the ZIF-62 / PEEK composite material of Comparative Example 3 and the PEEK material of Comparative Example 2, the Cd-doped ZIF-62 / PEEK composite material prepared in this invention exhibits superior friction reduction and wear resistance. Furthermore, in Comparative Example 1, the excessively high molar substitution rate of Cd at the metal center in ZIF-62 led to a decrease in the wear resistance of the final Cd-doped ZIF-62 / PEEK composite material.

[0069] Structural characterization The Cd-doped ZIF-62 prepared in Example 1 was observed by scanning electron microscopy (SEM), and the results are as follows: Figure 2 As shown. By Figure 2 It can be seen that Cd-doped ZIF-62 has typical crystal structure with a particle size of 50~100 nm, compared to undoped ZIF-62 (1~3 μm). Figure 3 The particle size decreased significantly, which is due to the change in the material's crystallization behavior after Cd addition. The XRD pattern of Cd-doped ZIF-62 is shown below. Figure 4 As shown, the characteristic diffraction peaks of the material shift by less than 0.5° compared to the standard pattern, which should be attributed to the change in the lattice size caused by the introduction of Cd. Smaller particle size is more conducive to the dispersion performance of Cd-doped ZIF-62 in composite materials, and further endows the ZIF-62 / PEEK composite material with better tribological properties.

[0070] Scanning electron microscopy was used to observe the worn surface of the 3D-printed Cd-doped ZIF-62 / PEEK composite material from Example 1. The results are shown in the figure. Figure 5 .from Figure 5 It can be observed that the Cd-doped ZIF-62 particles further increase in size on the wear surface through melting and enrichment, forming a micro-protrusion structure. Furthermore, the wear surface is smooth and flat, without the fine grooves caused by ZIF-62 release. After aggregation, the ZIF-62 and PEEK interface have good interaction forces, further firmly embedding into the matrix surface. In this process, the Cd-doped ZIF-62 particles act like carbon fibers, mainly bearing the load between the composite material and the metal pair during friction and wear, effectively reducing the scratching effect of the micro-protrusions on the metal pair surface, and further improving the tribological properties of the composite material.

[0071] Figure 6Scanning electron microscope (SEM) images of the transfer film on the metal-pair surface are presented, clearly showing that the original grooved and flat areas of the friction material are uniformly and continuously covered by the transfer film. This is attributed to the coating effect of Cd-doped ZIF-62 as a carbon fiber-like reinforcing filler on the metal-pair surface. During the friction and wear process, the Cd-doped ZIF-62 melts under the promotion of frictional heat and shear, further promoting the transfer of the PEEK matrix to the metal-pair, and ultimately forming a uniform and continuous transfer film.

[0072] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A Cd-doped ZIF-62, characterized in that, In ZIF-62, some Zn metal centers are replaced by Cd; the molar substitution rate of Cd in the metal centers of ZIF-62 is 10-40%.

2. The method for preparing Cd-doped ZIF-62 according to claim 1, characterized in that, Includes the following steps: A zinc source, imidazole, benzimidazole, cadmium source and organic solvent were mixed and a coordination reaction was carried out under ball milling conditions to obtain Cd-doped ZIF-62 with solvent adsorbed. The Cd-doped ZIF-62 with adsorbed solvent was calcined under vacuum to obtain the Cd-doped ZIF-62. The cadmium source is Cd(OAc)2 and CdO, and the molar ratio of Cd(OAc)2 to CdO is 1:8~12; The percentage of the molar amount of Cd in the cadmium source relative to the total molar amount of Cd in the cadmium source and Zn in the zinc source is 10-40%.

3. The preparation method according to claim 2, characterized in that, The ratio of the total molar amount of Zn in the zinc source and Cd in the cadmium source to the total molar amount of imidazole and benzimidazole is 1:2; the molar ratio of imidazole and benzimidazole is 5~8:

1. The zinc source includes zinc hydroxide and zinc acetate; the molar percentage of zinc acetate in the zinc source is 20-40%.

4. The preparation method according to claim 2, characterized in that, The ball milling speed is 700~1200 r / min; the coordination reaction time is 1~3 h.

5. The preparation method according to claim 2, characterized in that, The vacuum calcination temperature is 250~350℃, and the time is 0.5~2 h.

6. A Cd-doped ZIF-62 / PEEK composite material, characterized in that, It contains 90-99% PEEK and 1-10% Cd-doped ZIF-62 by mass percentage.

7. The method for preparing the Cd-doped ZIF-62 / PEEK composite material according to claim 6, characterized in that, Includes the following steps: PEEK and Cd-doped ZIF-62 were mixed to obtain a mixed powder; The mixed powder is extruded to obtain a composite filament; The composite filament was 3D printed to obtain the Cd-doped ZIF-62 / PEEK composite material.

8. The preparation method according to claim 7, characterized in that, The parameters for 3D printing include: nozzle temperature of 400~450℃, base plate temperature of 120~250℃, cavity temperature of 120~250℃, nozzle diameter of 0.2~0.4 mm, printing speed of 20~40 mm / s, layer height of 0.2 mm, and infill density of 100%.

9. The preparation method according to claim 7, characterized in that, The parameters for the extrusion molding include: from the tail to the head, the temperature of zone one is 320°C, the temperature of zone two is 370°C, the temperature of zone three is 360°C, and the temperature of the head is 355°C.

10. The application of the Cd-doped ZIF-62 / PEEK composite material according to claim 6 or the Cd-doped ZIF-62 / PEEK composite material prepared by the preparation method according to any one of claims 7 to 9 in friction materials.

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