High-precision homogeneous metal film filter element and preparation method thereof

Abstract

The invention is suitable for the technical field of metal film filter elements, and provides a high-precision homogeneous metal film filter element and a preparation method thereof.The high-precision homogeneous metal film filter element comprises a metal matrix, a metal film layer and a protective layer, the metal film layer is located on the surface of the metal matrix, and the protective layer is located on the surface of the metal film layer; the metal film layer comprises the following raw materials: nano metal powder, modified mannitol, modified nano graphene and nano aluminum oxide, according to the high-precision homogeneous metal film filter element provided by the invention, the dispersity of the nano metal powder is improved by adding the modified mannitol, particle aggregation can be prevented, and uniform pore size distribution of the film layer is ensured; by adding the modified nano graphene, the interface bonding strength between the modified nano graphene and the nano metal powder is improved, the modified graphene can be used as a reinforcing phase in the metal film layer to improve the mechanical property of the film layer, and by adding the nano aluminum oxide particles, the hardness and the wear resistance are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal membrane filters, and particularly relates to a high-precision homogeneous metal membrane filter and a preparation method thereof. Background Art

[0002] A metal membrane filter is a high-precision filtering element made of a metal material through a special process. It is mainly used for achieving high-precision filtration of fluids (such as gases or liquids), can effectively remove impurities, particles, microorganisms, etc. in the fluid, and at the same time maintain good mechanical properties and chemical stability. Due to its unique properties, the metal membrane filter has been widely used in the fields of industry, medical treatment, environmental protection, etc.

[0003] When the existing metal membrane filters are in use, problems such as film layer peeling and mechanical strength decline are likely to occur, affecting the service life and filtration performance of the filters. Summary of the Invention

[0004] The present invention provides a high-precision homogeneous metal membrane filter, aiming to solve the above problems.

[0005] The present invention is implemented as follows. A high-precision homogeneous metal membrane filter includes a metal matrix, a metal film layer, and a protective layer. The metal film layer is located on the surface of the metal matrix, and the protective layer is located on the surface of the metal film layer. Preferably, the thickness of the metal film layer is 0.1 - 2 mm. The metal film layer comprises the following raw materials by weight: 90 - 100 parts of nano metal powder, 5 - 10 parts of modified mannitol, 1 - 2 parts of modified nano graphene, and 1 - 3 parts of nano alumina. The nano metal powder can be nickel, titanium, tantalum, etc.

[0006] Preferably, the metal film layer comprises the following raw materials by weight: 92 - 98 parts of nano metal powder, 6 - 9 parts of modified mannitol, 1.3 - 1.7 parts of modified nano graphene, and 1.5 - 2.5 parts of nano alumina.

[0007] Preferably, the metal film layer comprises the following raw materials by weight: 95 parts of nano metal powder, 7.5 parts of modified mannitol, 1.5 parts of modified nano graphene, and 2 parts of nano alumina.

[0008] Preferably, the protective layer is a multi-layer structure, and the thickness can be 0.5 - 3 mm. From the inside to the outside, it is an alumina layer, an alumina-zirconia gradient layer, and a zirconia layer in sequence. By adopting a gradient material design, the composition and structure of the protective layer gradually change from the inside to the outside to improve the bonding force between the protective layer and the metal film layer and the thermal shock resistance.

[0009] Preferably, the preparation method of the modified mannitol is as follows: Mannitol and polyethylene glycol are added to a reaction kettle in a ratio of 1:1-2, heated and stirred at 160-180 °C for 30-50 min. After the reaction is completed, the water generated during the reaction is discharged under reduced pressure. The modified mannitol is obtained by cooling and crystallization separation. Multiple hydroxyl groups of mannitol react with hydroxyl groups of PEG to form a mannitol-PEG conjugate structure. The introduction of PEG increases the molecular weight and steric hindrance of mannitol, improves its dispersibility and stability, thereby improving the dispersibility of nano metal powder, preventing particle aggregation, ensuring uniform pore size distribution of the film layer. During the deposition process on the metal matrix surface, the modified mannitol can reduce the friction between the film layer and the matrix and improve the adhesion of the film layer.

[0010] Preferably, the preparation method of the modified nano-graphene is as follows: Nano-graphene is oxidized by the Hummers method to generate graphene oxide, and then its conductivity is restored by chemical reduction. The oxidation stage is carried out at 0-5 °C, and the reduction stage is carried out at 80-100 °C. Then, the reduced nano-graphene and polyvinyl alcohol are mixed in a mass ratio of 1:2-4 and added to an ethanol solution with a weight 10-15 times and a mass fraction of 70-80%. The reaction is carried out at 60-80 °C for 2-4 h, and the modified nano-graphene is obtained by filtration, washing and drying. Through the redox process, oxygen-containing functional groups (such as hydroxyl groups and carboxyl groups) are introduced onto the graphene surface to improve its dispersibility and compatibility with the metal matrix. The reduced graphene restores its conductivity while retaining some functional groups, enhancing the binding force with the metal powder. Through the grafting reaction of polyvinyl alcohol, active groups are introduced onto the graphene surface to improve the interfacial bonding strength with the nano metal powder. The modified graphene can be used as a reinforcing phase in the metal film layer to improve the mechanical properties of the film layer.

[0011] The present invention also provides a preparation method of the above-mentioned high-precision homogeneous metal membrane filter element, including the following steps: Using 3D printing technology, a metal matrix with a porous structure is printed, the pore size ranges from 10-100 microns, and the porosity is 30-70%. 3D printing technology can achieve high-precision pore size control; The raw materials of the metal film layer are mixed to obtain a mixture, and the mixture is deposited on the surface of the metal matrix to form a metal film layer; A protective layer is coated on the surface of the metal film layer. The alumina layer can be coated by ALD technology, and the alumina-zirconia gradient layer and zirconia layer are coated by combining sol-gel method and heat treatment to improve the crystallinity and mechanical strength of the protective layer; Cleaning and drying are carried out to obtain the metal membrane filter element, and the drying temperature can be 40-60 °C.

[0012] Preferably, in the process of depositing the mixture on the surface of the metal matrix to form a metal film layer, methods such as magnetron sputtering, chemical vapor deposition or atomic layer deposition are adopted.

[0013] Preferably, before depositing the metal film layer, the metal matrix is placed in a low-temperature plasma device for low-temperature plasma treatment for 10 - 30 min. The power of the low-temperature plasma device is 100 - 500 W, the pressure is 10 - 100 Pa, the gas is argon or oxygen, the gas flow rate is 10 - 50 sccm (standard cubic centimeters per minute). Plasma treatment can clean the surface of the metal matrix, remove oxides and pollutants. Through plasma activation, active groups (such as hydroxyl groups, carboxyl groups, etc.) can be introduced on the metal surface, increasing the surface energy, enhancing the bonding force between the metal film layer and the metal matrix, forming a micro-nano scale rough structure on the metal surface, increasing the surface area, and improving the adhesion of the metal film layer.

[0014] Preferably, after coating a protective layer on the surface of the metal film layer, the product is subjected to a fermentation treatment. The method of the fermentation treatment is as follows: The product is immersed in a culture medium, and Acetobacter xylinum is inoculated into the culture medium at an inoculation amount of 5 - 10%. The fermentation container is placed in a constant-temperature fermentation chamber and fermented at 28 - 30 °C for 3 - 5 d. After the fermentation is completed, the product is taken out. Through the formation of a uniform nano-scale porous structure of bacterial cellulose on the surface of the product during the fermentation process, the filtration pore size is further refined, and the filtration performance is improved. Bacterial cellulose has natural corrosion resistance and can protect the surface of the product. Bacterial cellulose has high strength and toughness and can improve the tensile strength and impact resistance of the metal film. Bacterial cellulose has hydrophilicity and can improve the wettability of the filter element surface, promote the uniform distribution of the liquid on the membrane surface, and improve the filtration efficiency and flux.

[0015] Compared with the prior art, the embodiments of the present application mainly have the following beneficial effects: The high-precision homogeneous metal membrane filter element provided by the present invention improves the mechanical properties and durability of the metal membrane filter element by adding modified mannitol, modified nano-graphene, and nano-aluminum oxide to the raw materials of the metal film layer. By adding modified mannitol, the dispersibility of nano-metal powder is improved, particle aggregation can be prevented, and the pore size distribution of the membrane layer is ensured to be uniform. During the deposition process on the surface of the metal matrix, modified mannitol can reduce the friction between the membrane layer and the matrix and improve the adhesion of the membrane layer. By adding modified nano-graphene, the interfacial bonding strength with nano-metal powder is improved. The modified graphene can be used as a reinforcing phase in the metal film layer to improve the mechanical properties of the membrane layer. By adding nano-aluminum oxide particles, the hardness and wear resistance are improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a flowchart of the preparation of a high-precision homogeneous metal membrane filter element provided by the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0017] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field to which this application belongs; the terms used in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification, claims, and above-mentioned drawings of this application are intended to cover non-exclusive inclusion. The terms "first", "second", etc. in the specification, claims, or above-mentioned drawings of this application are used to distinguish different objects and are not used to describe a specific order.

[0018] Reference to "embodiments" herein means that the specific features, structures, or characteristics described in connection with the embodiments can be included in at least one embodiment of this application. The phrase appears in various places in the specification and does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art will explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments.

[0019] Embodiment 1 An embodiment of the present invention provides a high-precision homogeneous metal membrane filter element, including a metal matrix, a metal membrane layer, and a protective layer. The metal membrane layer is located on the surface of the metal matrix, and the protective layer is located on the surface of the metal membrane layer. Preferably, the thickness of the metal membrane layer is 1 mm. The metal membrane layer includes the following raw materials in parts by weight: 90 parts of nano metal powder, 5 parts of modified mannitol, 1 part of modified nano graphene, and 1 part of nano alumina. The nano metal powder can be nickel, titanium, tantalum, etc., as Figure 1 shown. The preparation method of the metal membrane filter element includes the following steps: Using 3D printing technology, print a metal matrix with a porous structure, the pore diameter ranges from 10 microns, and the porosity is 30%. 3D printing technology can achieve high-precision pore diameter control; Mix the raw materials of the metal membrane layer to obtain a mixture, and deposit the mixture on the surface of the metal matrix to form a metal membrane layer; Coat a protective layer on the surface of the metal membrane layer. The alumina layer can be coated by ALD technology, and the alumina-zirconia gradient layer and zirconia layer can be coated by combining sol-gel method and heat treatment to improve the crystallinity and mechanical strength of the protective layer; Perform cleaning and drying to obtain the metal membrane filter element.

[0020] Preferably, the protective layer is a multi-layer structure, and the thickness can be 0.5 mm. From the inside to the outside, it is an alumina layer, an alumina-zirconia gradient layer, and a zirconia layer in sequence. The gradient material design is adopted to make the composition and structure of the protective layer gradually change from the inside to the outside to improve the bonding force and thermal shock resistance between the protective layer and the metal membrane layer.

[0021] Preferably, the preparation method of the modified mannitol is as follows: Mannitol and polyethylene glycol are added to a reaction kettle in a ratio of 1:1, heated and stirred at 160 °C for 30 min. After the reaction is completed, the water generated during the reaction is discharged under reduced pressure, and the modified mannitol is obtained by separation through steps such as cooling and crystallization.

[0022] Preferably, the preparation method of the modified nano-graphene is as follows: The nano-graphene is oxidized by the Hummers method to generate graphene oxide, and then its conductivity is restored by chemical reduction. The oxidation stage is carried out at 0 °C, and the reduction stage is carried out at 80 °C. Then, the reduced nano-graphene and polyvinyl alcohol are mixed in a mass ratio of 1:2 and added to an ethanol solution with a weight 10 times and a mass fraction of 70%. The reaction is carried out at 60 °C for 2 h, and the modified nano-graphene is obtained by filtration, washing and drying.

[0023] Preferably, in the step of depositing the mixture on the surface of the metal substrate to form a metal film layer, methods such as magnetron sputtering, chemical vapor deposition or atomic layer deposition are used.

[0024] Preferably, before depositing the metal film layer, the metal substrate is placed in a low-temperature plasma device for low-temperature plasma treatment for 10 min. The power of the low-temperature plasma device is 100 W, the pressure is 10 Pa, the gas is argon or oxygen, and the gas flow rate is 10 sccm (standard cubic centimeters per minute).

[0025] Preferably, after coating a protective layer on the surface of the metal film layer, the product is subjected to fermentation treatment. The method of the fermentation treatment is as follows: The product is immersed in a culture medium, and Acetobacter xylinum is inoculated into the culture medium at an inoculation amount of 5%. The fermentation container is placed in a constant-temperature incubator and fermented at 28 °C for 3 d. After the fermentation is completed, the product is taken out.

[0026] Example 2 The embodiment of the present invention provides a high-precision homogeneous metal membrane filter element, including a metal substrate, a metal film layer and a protective layer. The metal film layer is located on the surface of the metal substrate, and the protective layer is located on the surface of the metal film layer. Preferably, the thickness of the metal film layer is 1 mm. The metal film layer includes the following raw materials in parts by weight: 92 parts of nano-metal powder, 6 parts of modified mannitol, 1.3 parts of modified nano-graphene, and 1.5 parts of nano-aluminum oxide. The nano-metal powder can be nickel, titanium, tantalum, etc. As Figure 1 shown, the preparation method of the metal membrane filter element includes the following steps: Using 3D printing technology, a metal substrate with a porous structure is printed, the pore size range is 10 microns, and the porosity is 30%. The 3D printing technology can achieve high-precision pore size control; Mix the raw materials of the metal film layer to obtain a mixed material, and deposit the mixed material on the surface of the metal substrate to form a metal film layer; Coat a protective layer on the surface of the metal film layer. The alumina layer can be coated by ALD technology, and the alumina-zirconia gradient layer and zirconia layer can be coated by combining sol-gel method with heat treatment to improve the crystallinity and mechanical strength of the protective layer; Perform cleaning and drying to obtain a metal film filter element.

[0027] Preferably, the protective layer is a multi-layer structure with a thickness of 0.5 mm. From the inside to the outside, it is an alumina layer, an alumina-zirconia gradient layer, and a zirconia layer. The gradient material design is adopted to make the composition and structure of the protective layer gradually change from the inside to the outside, so as to improve the bonding force and thermal shock resistance between the protective layer and the metal film layer.

[0028] Preferably, the preparation method of the modified mannitol is as follows: Add mannitol and polyethylene glycol into the reaction kettle at a ratio of 1:1, heat and stir at 160 °C for 30 min. After the reaction is completed, reduce the pressure to discharge the water generated during the reaction process, and separate the modified mannitol through steps such as cooling and crystallization.

[0029] Preferably, the preparation method of the modified nano-graphene is as follows: Oxidize nano-graphene by the Hummers method to generate graphene oxide, and then restore its conductivity through chemical reduction. The oxidation stage is carried out at 0 °C, and the reduction stage is carried out at 80 °C. Then, mix the oxidized and reduced nano-graphene with polyvinyl alcohol at a mass ratio of 1:2, add it to an ethanol solution with a weight 10 times and a mass fraction of 70%, react at 60 °C for 2 h, filter, wash and dry to obtain the modified nano-graphene.

[0030] Preferably, in the process of depositing the mixed material on the surface of the metal substrate to form a metal film layer, methods such as magnetron sputtering, chemical vapor deposition or atomic layer deposition are used.

[0031] Preferably, before depositing the metal film layer, put the metal substrate into a low-temperature plasma device for low-temperature plasma treatment for 10 min. The power of the low-temperature plasma device is 100 W, the pressure is 10 Pa, the gas is argon or oxygen, and the gas flow rate is 10 sccm (standard cubic centimeters per minute).

[0032] Preferably, after coating the protective layer on the surface of the metal film layer, perform fermentation treatment on the product. The method of the fermentation treatment is as follows: Immerse the product in the culture medium, inoculate Acetobacter xylinum into the culture medium at an inoculation amount of 5%, put the fermentation container into a constant temperature incubator and ferment at 28 °C for 3 d. After the fermentation is completed, take out the product.

[0033] Example 3 An embodiment of the present invention provides a high-precision homogeneous metal membrane filter element, which includes a metal matrix, a metal membrane layer, and a protective layer. The metal membrane layer is located on the surface of the metal matrix, and the protective layer is located on the surface of the metal membrane layer. Preferably, the thickness of the metal membrane layer is 1 mm. The metal membrane layer includes the following raw materials by weight: 95 parts of nano metal powder, 7.5 parts of modified mannitol, 1.5 parts of modified nano graphene, and 2 parts of nano alumina. The nano metal powder can be nickel, titanium, tantalum, etc. As Figure 1 shown, the preparation method of the metal membrane filter element includes the following steps: Using 3D printing technology, a metal matrix with a porous structure is printed, the pore size ranges from 50 microns, and the porosity is 50%. 3D printing technology can achieve high-precision pore size control; Mix the raw materials of the metal membrane layer to obtain a mixture, and deposit the mixture on the surface of the metal matrix to form a metal membrane layer; Coat a protective layer on the surface of the metal membrane layer. The alumina layer can be coated by ALD technology, and the alumina-zirconia gradient layer and zirconia layer can be coated by combining sol-gel method and heat treatment to improve the crystallinity and mechanical strength of the protective layer; Perform cleaning and drying to obtain the metal membrane filter element.

[0034] Preferably, the protective layer is a multi-layer structure, and the thickness can be 0.5 mm. From the inside to the outside, it is an alumina layer, an alumina-zirconia gradient layer, and a zirconia layer. The gradient material design is adopted to make the composition and structure of the protective layer gradually change from the inside to the outside to improve the bonding force and thermal shock resistance between the protective layer and the metal membrane layer.

[0035] Preferably, the preparation method of the modified mannitol is as follows: Add mannitol and polyethylene glycol into the reaction kettle at a ratio of 1:1.5, heat and stir at 170 °C for 40 min. After the reaction is completed, reduce the pressure to discharge the water generated during the reaction process, and separate the modified mannitol through steps such as cooling and crystallization.

[0036] Preferably, the preparation method of the modified nano graphene is as follows: Oxidize the nano graphene by the Hummers method to generate graphene oxide, and then restore its conductivity through chemical reduction. The oxidation stage is carried out at 3 °C, and the reduction stage is carried out at 90 °C. Then, mix the oxidized and reduced nano graphene with polyvinyl alcohol at a mass ratio of 1:3, add it to an ethanol solution with 12 times the weight and a mass fraction of 75%, react at 70 °C for 3 h, filter, wash, and dry to obtain the modified nano graphene.

[0037] Preferably, in the step of depositing the mixture on the surface of the metal matrix to form a metal membrane layer, methods such as magnetron sputtering, chemical vapor deposition, or atomic layer deposition are used.

[0038] Preferably, before depositing the metal film layer, the metal substrate is placed in a low-temperature plasma device for low-temperature plasma treatment for 20 min. The power of the low-temperature plasma device is 300 W, the pressure is 50 Pa, the gas is argon or oxygen, and the gas flow rate is 30 sccm (standard cubic centimeters per minute).

[0039] Preferably, after coating a protective layer on the surface of the metal film layer, the product is subjected to a fermentation treatment. The method of the fermentation treatment is as follows: The product is immersed in a culture medium, and Acetobacter xylinum is inoculated into the culture medium at an inoculation amount of 8%. The fermentation container is placed in a constant-temperature incubator and fermented at 29 °C for 4 d. After the fermentation is completed, the product is taken out.

[0040] Example 4 An embodiment of the present invention provides a high-precision homogeneous metal film filter element, including a metal substrate, a metal film layer, and a protective layer. The metal film layer is located on the surface of the metal substrate, and the protective layer is located on the surface of the metal film layer. Preferably, the thickness of the metal film layer is 1 mm. The metal film layer includes the following raw materials by weight: 98 parts of nano metal powder, 9 parts of modified mannitol, 1.7 parts of modified nano graphene, and 2.5 parts of nano alumina. The nano metal powder can be nickel, titanium, tantalum, etc., as Figure 1 shown. The preparation method of the metal film filter element includes the following steps: Using 3D printing technology, a metal substrate with a porous structure is printed, the pore diameter range is 100 microns, and the porosity is 70%. 3D printing technology can achieve high-precision pore diameter control; The raw materials of the metal film layer are mixed to obtain a mixture, and the mixture is deposited on the surface of the metal substrate to form a metal film layer; A protective layer is coated on the surface of the metal film layer. The alumina layer can be coated by ALD technology, and the alumina-zirconia gradient layer and zirconia layer are coated by combining sol-gel method and heat treatment to improve the crystallinity and mechanical strength of the protective layer; Washing and drying are carried out to obtain the metal film filter element.

[0041] Preferably, the protective layer is a multi-layer structure, and the thickness can be 0.5 mm. From the inside to the outside, it is an alumina layer, an alumina-zirconia gradient layer, and a zirconia layer. The gradient material design is adopted to make the composition and structure of the protective layer gradually change from the inside to the outside to improve the bonding force and thermal shock resistance between the protective layer and the metal film layer.

[0042] Preferably, the preparation method of the modified mannitol is as follows: Mannitol and polyethylene glycol are added to a reaction kettle in a ratio of 1:2, heated and stirred at 180 °C for 50 min. After the reaction is completed, the water generated during the reaction is discharged under reduced pressure, and the modified mannitol is separated by steps such as cooling and crystallization.

[0043] Preferably, the preparation method of the modified nano-graphene is as follows: The nano-graphene is oxidized by the Hummers method to generate graphene oxide, and then its conductivity is restored by chemical reduction. The oxidation stage is carried out at 5 °C, and the reduction stage is carried out at 100 °C. Then, the reduced nano-graphene and polyvinyl alcohol are mixed at a mass ratio of 1:4 and added to an ethanol solution with 15 times the weight and a mass fraction of 80%. The reaction is carried out at 80 °C for 4 h, and then filtered, washed and dried to obtain the modified nano-graphene.

[0044] Preferably, in the step of depositing the mixture on the surface of the metal substrate to form a metal film layer, magnetron sputtering, chemical vapor deposition or atomic layer deposition is used.

[0045] Preferably, before depositing the metal film layer, the metal substrate is put into a low-temperature plasma device for low-temperature plasma treatment for 30 min. The power of the low-temperature plasma device is 500 W, the pressure is 100 Pa, the gas is argon or oxygen, and the gas flow rate is 50 sccm (standard cubic centimeters per minute).

[0046] Preferably, after coating the protective layer on the surface of the metal film layer, the product is subjected to fermentation treatment. The method of fermentation treatment is as follows: The product is immersed in a culture medium, and Acetobacter xylinum is inoculated into the culture medium at an inoculation amount of 10%. The fermentation container is placed in a constant-temperature incubator and fermented at 30 °C for 5 d. After fermentation, the product is taken out.

[0047] Example 5 An embodiment of the present invention provides a high-precision homogeneous metal film filter element, which includes a metal substrate, a metal film layer and a protective layer. The metal film layer is located on the surface of the metal substrate, and the protective layer is located on the surface of the metal film layer. Preferably, the thickness of the metal film layer is 1 mm. The metal film layer includes the following raw materials by weight: 100 parts of nano-metal powder, 10 parts of modified mannitol, 2 parts of modified nano-graphene, and 3 parts of nano-aluminum oxide. The nano-metal powder can be nickel, titanium, tantalum, etc. As Figure 1 shown, the preparation method of the metal film filter element includes the following steps: Using 3D printing technology, a metal substrate with a porous structure is printed, the pore diameter ranges from 100 microns, and the porosity is 70%. The 3D printing technology can achieve high-precision pore diameter control; Mix the raw materials of the metal film layer to obtain a mixture, and deposit the mixture on the surface of the metal substrate to form a metal film layer; Coat a protective layer on the surface of the metal film layer. The alumina layer can be coated by ALD technology, and the alumina-zirconia gradient layer and zirconia layer are coated by combining sol-gel method and heat treatment to improve the crystallinity and mechanical strength of the protective layer; Wash and dry to obtain the metal film filter element.

[0048] Preferably, the protective layer is a multi-layer structure with a thickness of 0.5 mm. From the inside to the outside, it is an alumina layer, an alumina-zirconia gradient layer, and a zirconia layer. The gradient material design is adopted to make the composition and structure of the protective layer gradually change from the inside to the outside, so as to improve the bonding force between the protective layer and the metal film layer and the thermal shock resistance.

[0049] Preferably, the preparation method of the modified mannitol is as follows: Add mannitol and polyethylene glycol into the reaction kettle at a ratio of 1:2, heat and stir at 180 °C for 50 min. After the reaction is completed, reduce the pressure to discharge the water generated during the reaction process, and separate the modified mannitol through steps such as cooling and crystallization.

[0050] Preferably, the preparation method of the modified nano-graphene is as follows: Oxidize nano-graphene by the Hummers method to generate graphene oxide, and then restore its conductivity through chemical reduction. The oxidation stage is carried out at 5 °C, and the reduction stage is carried out at 100 °C. Then, mix the oxidized and reduced nano-graphene with polyvinyl alcohol at a mass ratio of 1:4 and add it to an ethanol solution with a weight 15 times and a mass fraction of 80%. React at 80 °C for 4 h, filter, wash and dry to obtain the modified nano-graphene.

[0051] Preferably, in the step of depositing a metal film layer on the surface of the metal matrix from the mixture, methods such as magnetron sputtering, chemical vapor deposition or atomic layer deposition are used.

[0052] Preferably, before depositing the metal film layer, put the metal matrix into a low-temperature plasma device for low-temperature plasma treatment for 30 min. The power of the low-temperature plasma device is 500 W, the pressure is 100 Pa, the gas is argon or oxygen, and the gas flow rate is 50 sccm (standard cubic centimeters per minute).

[0053] Preferably, after coating the protective layer on the surface of the metal film layer, ferment the product. The method of the fermentation treatment is as follows: Immerse the product in the culture medium, inoculate Acetobacter xylinum into the culture medium at an inoculation amount of 10%, put the fermentation container into a constant-temperature fermentation box and ferment at 30 °C for 5 d. After the fermentation is completed, take out the product.

[0054] Comparative Example 1: The difference from Example 3 is that it does not contain modified mannitol.

[0055] Comparative Example 2: The difference from Example 3 is that the modified mannitol is replaced with ordinary mannitol.

[0056] Comparative Example 3: The difference from Example 3 is that the modified graphene is replaced with ordinary graphene.

[0057] Comparative Example 4: The difference from Example 3 is that modified mannitol is replaced by ordinary mannitol and modified graphene is replaced by ordinary graphene.

[0058] Comparative Example 5: The difference from Example 3 is that the product is not subjected to fermentation treatment.

[0059] Performance tests were carried out on the metal membrane filters of Examples 1-5 and Comparative Examples 1-5.

[0060] 1. Tensile strength test Test method: Tensile test.

[0061] Standard: ISO 6892-1: Metallic materials - Tensile testing.

[0062] ASTM E8 / E8M: Standard test methods for tension testing of metallic materials.

[0063] Equipment: Universal material testing machine.

[0064] Steps: Prepare standard tensile specimens (such as dumbbell-shaped specimens, with a gauge length of 50 mm, a width of 10 mm, and a thickness of 1 mm); fix the specimens in the fixtures of the testing machine; apply tensile force at a constant rate (usually 1 mm / min) until the specimens break; record the maximum tensile force and the elongation at break, and calculate the tensile strength (maximum tensile force / cross-sectional area).

[0065] 2. Filtration accuracy test Test method: Particle retention rate test.

[0066] Standard: ISO 16889: Hydraulic fluid power - Filter elements - Methods for evaluating filtration performance.

[0067] ASTM F795: Test method for particle retention of filter elements.

[0068] Equipment: Particle counter, filtration test device.

[0069] Steps: Prepare a standard particle suspension (such as a latex particle suspension with a particle size of 0.1 µm), install the metal membrane filter in the filtration test device, filter the suspension at a constant pressure (0.1 MPa), measure the particle concentration in the filtrate using a particle counter, and calculate the retention rate.

[0070] The test results are shown in Table 1 below: As can be seen from the above results, the metal membrane filter element prepared by the present invention has good mechanical properties and filtration performance. By adding modified mannitol and modified nano-graphene to the metal membrane layer, the two have a synergistic effect, which can further improve its performance. By fermenting the product, a bacterial cellulose layer is formed, and a uniform nano-porous structure is formed on the surface of the product, further refining the filtration pore size and improving the filtration performance. Bacterial cellulose has natural corrosion resistance and can protect the surface of the product. Bacterial cellulose has high strength and toughness, which can improve the tensile strength and impact resistance of the metal membrane. Bacterial cellulose has hydrophilicity, which can improve the wettability of the filter element surface, promote the uniform distribution of liquid on the membrane surface, and improve the filtration efficiency and flux.

[0071] It should be noted that for the foregoing embodiments, for the sake of simple description, they are all expressed as a series of action combinations. However, those skilled in the art should know that the present invention is not limited by the described action sequence, because according to the present invention, some steps may be performed in other sequences or simultaneously. Secondly, those skilled in the art should also know that the embodiments described in the specification are all preferred embodiments, and the actions and modules involved are not necessarily essential to the present invention.

[0072] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the protection scope of the invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all embodiments. Based on these embodiments, all other embodiments obtained by those of ordinary skill in the art without creative work belong to the scope of protection of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art can still, without conflict, make combinations, additions, deletions or other adjustments to the features in the embodiments of the present invention according to the situation without creative work, so as to obtain different technical solutions that do not essentially depart from the concept of the present invention, and these technical solutions also belong to the scope of protection of the present invention.

Claims

1. A high-precision homogeneous metal membrane filter element, characterized in that: It includes a metal substrate, a metal film layer and a protective layer. The metal film layer is located on the surface of the metal substrate, the protective layer is located on the surface of the metal film layer, and the metal film layer includes the following raw materials in parts by weight: 90-100 parts of nano metal powder, 5-10 parts of modified mannitol, 1-2 parts of modified nano graphene, and 1-3 parts of nano alumina.

2. The high-precision homogeneous metal membrane filter element according to claim 1, characterized in that: The metal film layer comprises the following raw materials in parts by weight: 92-98 parts of nano metal powder, 6-9 parts of modified mannitol, 1.3-1.7 parts of modified nano graphene, and 1.5-2.5 parts of nano alumina.

3. The high-precision homogeneous metal membrane filter element according to claim 2, characterized in that: The metal film layer comprises the following raw materials in parts by weight: 95 parts of nano metal powder, 7.5 parts of modified mannitol, 1.5 parts of modified nano graphene, and 2 parts of nano alumina.

4. The high-precision homogeneous metal membrane filter element according to claim 1, characterized in that: The protective layer is a multi-layer structure, which includes an aluminum oxide layer, an aluminum oxide-zirconia gradient layer, and a zirconium oxide layer from the inside to the outside.

5. The high-precision homogeneous metal membrane filter element according to claim 1, characterized in that: The preparation method of the modified mannitol is as follows: mannitol and polyethylene glycol are added into a reaction kettle at a ratio of 1:1-2, heated and stirred at 160-180° C., reacted for 30-50 minutes, and after the reaction is completed, the water generated during the reaction is discharged under reduced pressure, and the modified mannitol is obtained by cooling and crystallization separation.

6. The high-precision homogeneous metal membrane filter element according to claim 1, characterized in that: The preparation method of the modified nanographene is as follows: oxidizing the nanographene by the Hummers method to generate graphene oxide, and then restoring its conductivity by chemical reduction, the oxidation stage is carried out at 0-5°C, and the reduction stage is carried out at 80-100°C, and then the oxidized and reduced nanographene is mixed with polyvinyl alcohol in a mass ratio of 1:2-4, and then added to an ethanol solution with 10-15 times the weight and a mass fraction of 70-80%, reacting at 60-80°C for 2-4h, filtering, washing and drying to obtain the modified nanographene.

7. The method for preparing a high-precision homogeneous metal membrane filter element according to any one of claims 1 to 6, characterized in that: The steps include: Using 3D printing technology, a metal matrix with a porous structure is printed; The raw materials of the metal film layer are mixed to obtain a mixture, and the mixture is deposited on the surface of the metal substrate to form a metal film layer; Coating a protective layer on the surface of the metal film layer; The metal membrane filter element is obtained by washing and drying.

8. The method for preparing a high-precision homogeneous metal membrane filter element according to claim 7, characterized in that: The method of depositing the mixed material on the surface of the metal substrate to form a metal film layer adopts magnetron sputtering, chemical vapor deposition or atomic layer deposition.

9. The method for preparing a high-precision homogeneous metal membrane filter element according to claim 7, characterized in that: Before depositing the metal film layer, the metal substrate is placed in a low-temperature plasma device for low-temperature plasma treatment for 10-30 minutes.

10. The high-precision homogeneous metal membrane filter element according to claim 7, characterized in that: After the protective layer is coated on the surface of the metal film layer, the product is fermented. The fermentation method is as follows: the product is immersed in a culture medium, 5-10% of the Acetobacter xylinum is inoculated into the culture medium, the fermentation container is placed in a constant temperature fermentation box and fermented at 28-30°C for 3-5 days. After the fermentation is completed, the product is taken out.

Images